Experimental Procedures

How to Explain Potentiodynamic Polarization Curve & its Relation to Passivation of Behaviour of Metals

2011-03-29T03:43:00.000-07:00

The concept of passivation has been mentioned earlier in this discussion without a more profound discussion of the characteristics of the phenomena. Passivity is a condition found in some metals and alloys that are capable of resisting corrosion due to the formation of a surface film. These films form under strongly oxidizing conditions or high anodic polarizations. This definition excludes metals possessing a simple barrier film with reduced corrosion at active potential and small anodic polarization. Also, it should be pointed out that insoluble compounds formed by dissolution and re-precipitation are less tenacious and less protective than oxide films formed in situ at the metal surface. This is an exceedingly important characteristic found in several structural metals such as iron, chromium, nickel titanium and aluminium, and its respective alloys being the most noticeable example that of stainless steels.

Figure 1 – Schematic polarization diagram displaying transitions from active corrosion to passive behaviour and to the transpassive state

Metals and alloys that exhibit passive behaviour display a very distinct evolution on the Evans diagram, as exemplified in Figure 1 above. As the potential is increased from the corrosion potential, so the current increases according to normal dissolution behaviour until a critical value (icrit). This point also defines the beginning of stability for passive films, which occurs at potentials higher than Epp (primary passive potential). Beyond this point, the current measured can fall several orders of magnitude to a residual current (ipass). At higher potentials (Et) breakdown of the passive film might occur with an increase in anodic activity, as the metal enters the transpassive state. As always, for self-passivation to occur there must be a cathodic reaction with a nobler potential relative to the anodic reaction and, in this case, superior also to Epp.

One of the strategies employed in the protection of metals is the anodization process. By applying a potential in the passive state (between Epp and transpassivation), and choosing the right media and applied current, it is possible to grow very thick oxide layers to protect the metal surface from oxidation. This constitutes one of the most used techniques in the protection of aluminium alloys. There are several models that try to explain the formation and structure these oxide films; however, much is still uncertain. There are two basic theories: the crystalline oxide model and hydrated polymeric oxide model.

In the crystalline oxide model, as the name implies, passivation depends on the formation of an oxide/hydroxide layer. The exact structure of the oxides is very uncertain and seems to vary from crystalline all the way to completely amorphous. The oxides may contain oxygen and/or hydrogen under several different forms (H+, OH- or H2O), and the number of layers may change according to specific systems as well as the stoichiometry of the oxide.

In polymeric model, on the other hand, water molecules have an important role in passivation as they connect chains of polymeric oxide, whose structure varies from partially crystalline to amorphous.

How to measure grain size using ImageJ software

2009-11-07T08:18:00.000-08:00

copy & paste from http://osdir.com/ml/java.imagej/2006-04/msg00010.html

---------------------------------------------------------------------------------------------------------------

Anneliese writes,

>
> Date: Sat, 1 Apr 2006 14:46:34 +0200
> From: Klughammer GmbH
> Subject: ImageJ and Metallography
>
> Dear users,
>
> has anybody already made some experience with ImageJ and metallography?
>
> I am looking for
>
> - grain size measurement
> - graphite morphology
> - nodularity measurement
> - particle size distribution
>
> Anneliese
>
And Noel replies.
Refer to the following books.
Computer aided Microscopy by John Russ,
Quantitative Stereology by E. E. Underwood,
and the paper by D.C. Sterio 1984 Journal of Microscopy. (the unbiased
estimation of number and sizes of arbitrary particles using the disector, J
microscopy. 134, 127.

Grain size measurement in metallography proves to be difficult because it is
usually next door to impossible to produce a perfect polish and etch which
reveals all boundaries with sufficient difference to the matrix.
Thus thresholding will be incomplete.
Once you have perfect boundaries, then life is easier.
By perfect boundaries I mean black boundaries on a pure white background.
You may measure grain sizes using all three methods easily.
Linear intercept,
Triple point counting,
And area measurement.

Here are some formulae which are commonly used. (From Russ. J.C. Computer
Assisted Microscopy, Plenum Press 1990, isbn 0-306-43410-5.
P 225.
ASTM grain size G
Using intercept method

G=(-6.6457Log[base10](1/PL))-3.298

Where PL is the number of points per unit length, measured in millimeters.

Or if you measure areas of the grain bodies,

(From Russ. J.C. Computer Assisted Microscopy, Plenum Press 1990, isbn
0-306-43410-5.
P 225.
G=(3.22 Log[base10](NA.M^2))-2.95

Where NA is number of grains per unit area on a polished surface at a
magnification M.

If you count the nodes where triple points are then G is got from
(From Russ. J.C. Computer Assisted Microscopy, Plenum Press 1990, isbn
0-306-43410-5.
P 147.

G=(log[base e]((Nodes/2)-1)/Area)/(log[base e](2)) -2.95.

Some investigators have found it quicker to produce a photo, and to trace
the boundaries out manually using a transparent film and a felt pen. The
resulting drawing is then scanned into the computer and processed in ImageJ.
This will be black and white and easily thresholded into a perfectly
segmented binary image. Such an image is the ideal to which your preparation
must aspire.

Otherwise it may be more time consuming.

If your specimens are suitable, and your etching superb, then
it may be possible to produce a perfect image via the image processing tools
in ImageJ.
Techniques to investigate include, thresholding, subtract background, find
edges, skeletonize, erode, dilate, open, close, watershed and so on.
Also useful may be techniques which differentiate between rough and
smooth, or surfaces with different textures.
Each type of material will have its own behaviour, and you must discover
this for yourself.

I have just talked about grains here.
The particle size distribution will be more straightforward, so long as the
particles are easily discriminated from the matrix. Just be careful that the
smallest particles you need to measure are "larger" than the resolution
limit.
The analyze particles menu in ImageJ will be what you use here.

And for Graphite morphology and nodularity, I have no experience.
But I am sure the methods to be used will have the parameters you need and
these will easily be employed in a macro.

Regards
Noel Goldsmith

Noel Goldsmith
Aircraft Forensic Engineering
Air Vehicles Division
DSTO
506 Lorimer Street
Port Melbourne
Vic 3207
AUSTRALIA
Phone (613) 96267538
FAX (613) 96267089
Email noel.goldsmith@xxxxxxxxxxxxxxxxxxx

1 day training session on our new stereomicroscope & metallurgical microscope

2009-09-13T11:38:00.000-07:00

Salam & selamat sejahtera,

Dear colleague, brothers & sisters

Please plan to be at the 1 day training session on our new stereomicroscope & metallurgical microscope (basic unit) that will be held on

Date: 16^th September 2009 (Wednesday)

Time: 10.00 am

Place: Makmal Kubang Gajah (MBG2).

A very experience application specialist from Crest Systems (M) Sdn Bhd will be the speaker and he will share his knowledge on microscope instruments, application using stereomicroscope & metallurgical microscope in material/ metallurgical research and other fields, basic/ advance techniques image analysis and etc.

The topic of training basically covers

i) Streomicroscope (OLYMPUS SZ61TR) – low power scope

ii) Metallurgical microscope (BX51M) – high power scope

iii) CMOS Digital Camera (Moticam 2300)

iv) Basic Image Analysis (Image + 2.0 & Image Adv.)

§ Counting particle and measuring function (linear, area, angle, perimeter, etc)

§ Multilayer version of the same image (each focused at a different position, can be combined produce a single focused image)

§ Image Calibration

Who knows, some of these systems and equipment may be able to solve problems at our lab session, or provide good tools for metallurgical/ materials teaching subject or furthering your R&D activities. Hope to see you there.

Thanks

Note: Postgraduate students or research asst. are also invited

A suggested thesis structure

2009-05-05T06:51:00.000-07:00

The list of contents and chapter headings below is appropriate for some theses. In some cases, one or two of them may be irrelevant. Results and Discussion are usually combined in several chapters of a thesis. Think about the plan of chapters and decide what is best to report your work. Then make a list, in point form, of what will go in each chapter. Try to make this rather detailed, so that you end up with a list of points that corresponds to subsections or even to the paragraphs of your thesis. At this stage, think hard about the logic of the presentation: within chapters, it is often possible to present the ideas in different order, and not all arrangements will be equally easy to follow. If you make a plan of each chapter and section before you sit down to write, the result will probably be clearer and easier to read. It will also be easier to write.

Copyright waiver

Your institution may have a form for this (UNSW does). In any case, this standard page gives the university library the right to publish the work, possibly by microfilm or other medium. (At UNSW, the Postgraduate Student Office will give you a thesis pack with various guide-lines and rules about thesis format. Make sure that you consult that for its formal requirements, as well as this rather informal guide.)

Declaration

Check the wording required by your institution, and whether there is a standard form. Many universities require something like: "I hereby declare that this submission is my own work and that, to the best of my knowledge and belief, it contains no material previously published or written by another person nor material which to a substantial extent has been accepted for the award of any other degree or diploma of the university or other institute of higher learning, except where due acknowledgment has been made in the text. (signature/name/date)"

Title page

This may vary among institutions, but as an example: Title/author/"A thesis submitted for the degree of Doctor of Philosophy in the Faculty of Science/The University of New South Wales"/date.

Abstract

Of all your thesis, this part will be the most widely published and most read because it will be published in Dissertation Abstracts International. It is best written towards the end, but not at the very last minute because you will probably need several drafts. It should be a distillation of the thesis: a concise description of the problem(s) addressed, your method of solving it/them, your results and conclusions. An abstract must be self-contained. Usually they do not contain references. When a reference is necessary, its details should be included in the text of the abstract. Check the word limit. Remember: even though it appears at the beginning, an abstract is not an introduction. It is a résumé of your thesis.

Acknowledgments

Most thesis authors put in a page of thanks to those who have helped them in matters scientific, and also indirectly by providing such essentials as food, education, genes, money, help, advice, friendship etc. If any of your work is collaborative, you should make it quite clear who did which sections.

Table of contents

The introduction starts on page 1, the earlier pages should have roman numerals. It helps to have the subheadings of each chapter, as well as the chapter titles. Remember that the thesis may be used as a reference in the lab, so it helps to be able to find things easily.

Introduction

What is the topic and why is it important? State the problem(s) as simply as you can. Remember that you have been working on this project for a few years, so you will be very close to it. Try to step back mentally and take a broader view of the problem. How does it fit into the broader world of your discipline?

Especially in the introduction, do not overestimate the reader's familiarity with your topic. You are writing for researchers in the general area, but not all of them need be specialists in your particular topic. It may help to imagine such a person---think of some researcher whom you might have met at a conference for your subject, but who was working in a different area. S/he is intelligent, has the same general background, but knows little of the literature or tricks that apply to your particular topic.

The introduction should be interesting. If you bore the reader here, then you are unlikely to revive his/her interest in the materials and methods section. For the first paragraph or two, tradition permits prose that is less dry than the scientific norm. If want to wax lyrical about your topic, here is the place to do it. Try to make the reader want to read the heavy bundle that has arrived uninvited on his/her desk. Go to the library and read several thesis introductions. Did any make you want to read on? Which ones were boring?

This section might go through several drafts to make it read well and logically, while keeping it short. For this section, I think that it is a good idea to ask someone who is not a specialist to read it and to comment. Is it an adequate introduction? Is it easy to follow? There is an argument for writing this section---or least making a major revision of it---towards the end of the thesis writing. Your introduction should tell where the thesis is going, and this may become clearer during the writing.

Literature review

Where did the problem come from? What is already known about this problem? What other methods have been tried to solve it?

Ideally, you will already have much of the hard work done, if you have been keeping up with the literature as you vowed to do three years ago, and if you have made notes about important papers over the years. If you have summarised those papers, then you have some good starting points for the review.

If you didn't keep your literature notes up to date, you can still do something useful: pass on the following advice to any beginning PhD students in your lab and tell them how useful this would have been to you. When you start reading about a topic, you should open a spread sheet file, or at least a word processor file, for your literature review. Of course you write down the title, authors, year, volume and pages. But you also write a summary (anything from a couple of sentences to a couple of pages, depending on the relevance). In other columns of the spread sheet, you can add key words (your own and theirs) and comments about its importance, relevance to you and its quality.

How many papers? How relevant do they have to be before you include them? Well, that is a matter of judgement. On the order of a hundred is reasonable, but it will depend on the field. You are the world expert on the (narrow) topic of your thesis: you must demonstrate this.

A political point: make sure that you do not omit relevant papers by researchers who are like to be your examiners, or by potential employers to whom you might be sending the thesis in the next year or two.

Middle chapters

In some theses, the middle chapters are the journal articles of which the student was major author. There are several disadvantages to this format.

One is that a thesis is both allowed and expected to have more detail than a journal article. For journal articles, one usually has to reduce the number of figures. In many cases, all of the interesting and relevant data can go in the thesis, and not just those which appeared in the journal. The degree of experimental detail is usually greater in a thesis. Relatively often a researcher requests a thesis in order to obtain more detail about how a study was performed.

Another disadvantage is that your journal articles may have some common material in the introduction and the "Materials and Methods" sections.

The exact structure in the middle chapters will vary among theses. In some theses, it is necessary to establish some theory, to describe the experimental techniques, then to report what was done on several different problems or different stages of the problem, and then finally to present a model or a new theory based on the new work. For such a thesis, the chapter headings might be: Theory, Materials and Methods, {first problem}, {second problem}, {third problem}, {proposed theory/model} and then the conclusion chapter. For other theses, it might be appropriate to discuss different techniques in different chapters, rather than to have a single Materials and Methods chapter.

Here follow some comments on the elements Materials and Methods, Theory, Results and discussion which may or may not correspond to thesis chapters.

Materials and Methods

This varies enormously from thesis to thesis, and may be absent in theoretical theses. It should be possible for a competent researcher to reproduce exactly what you have done by following your description. There is a good chance that this test will be applied: sometime after you have left, another researcher will want to do a similar experiment either with your gear, or on a new set-up in a foreign country. Please write for the benefit of that researcher.

In some theses, particularly multi-disciplinary or developmental ones, there may be more than one such chapter. In this case, the different disciplines should be indicated in the chapter titles.

Theory

When you are reporting theoretical work that is not original, you will usually need to include sufficient material to allow the reader to understand the arguments used and their physical bases. Sometimes you will be able to present the theory ab initio, but you should not reproduce two pages of algebra that the reader could find in a standard text. Do not include theory that you are not going to relate to the work you have done.

When writing this section, concentrate at least as much on the physical arguments as on the equations. What do the equations mean? What are the important cases?

When you are reporting your own theoretical work, you must include rather more detail, but you should consider moving lengthy derivations to appendices. Think too about the order and style of presentation: the order in which you did the work may not be the clearest presentation.

Suspense is not necessary in reporting science: you should tell the reader where you are going before you start.

Results and discussion

The results and discussion are very often combined in theses. This is sensible because of the length of a thesis: you may have several chapters of results and, if you wait till they are all presented before you begin discussion, the reader may have difficulty remembering what you are talking about. The division of Results and Discussion material into chapters is usually best done according to subject matter.

Make sure that you have described the conditions which obtained for each set of results. What was held constant? What were the other relevant parameters? Make sure too that you have used appropriate statistical analyses. Where applicable, show measurement errors and standard errors on the graphs. Use appropriate statistical tests.

Take care plotting graphs. The origin and intercepts are often important so, unless the ranges of your data make it impractical, the zeros of one or both scales should usually appear on the graph. You should show error bars on the data, unless the errors are very small. For single measurements, the bars should be your best estimate of the experimental errors in each coordinate. For multiple measurements these should include the standard error in the data. The errors in different data are often different, so, where this is the case, regressions and fits should be weighted (i.e. they should minimize the sum of squares of the differences weighted inversely as the size of the errors.) (A common failing in many simple software packages that draw graphs and do regressions is that they do not treat errors adequately. UNSW student Mike Johnston has written a plotting routine that plots data with error bars and performs weighted least square regressions. It is at http://www.phys.unsw.edu.au/3rdyearlab/graphing/graph.html). You can just 'paste' your data into the input and it generates a .ps file of the graph.

In most cases, your results need discussion. What do they mean? How do they fit into the existing body of knowledge? Are they consistent with current theories? Do they give new insights? Do they suggest new theories or mechanisms?

Try to distance yourself from your usual perspective and look at your work. Do not just ask yourself what it means in terms of the orthodoxy of your own research group, but also how other people in the field might see it. Does it have any implications that do not relate to the questions that you set out to answer?

Final chapter, references and appendices

Conclusions and suggestions for further work

Your abstract should include your conclusions in very brief form, because it must also include some other material. A summary of conclusions is usually longer than the final section of the abstract, and you have the space to be more explicit and more careful with qualifications. You might find it helpful to put your conclusions in point form.

It is often the case with scientific investigations that more questions than answers are produced. Does your work suggest any interesting further avenues? Are there ways in which your work could be improved by future workers? What are the practical implications of your work?

This chapter should usually be reasonably short---a few pages perhaps. As with the introduction, I think that it is a good idea to ask someone who is not a specialist to read this section and to comment.

References (See also under literature review)

It is tempting to omit the titles of the articles cited, and the university allows this, but think of all the times when you have seen a reference in a paper and gone to look it up only to find that it was not helpful after all.

Should you reference web sites and, if so, how? If you cite a journal article or book, the reader can go to a library and check that the cited document and check whether or not it says what you say it did. A web site may disappear, and it may have been updated or changed completely. So references to the web are usually less satisfactory. Nevertheless, there are some very useful and authoritative sources. So, if the rules of your institution permit it, it may be appropriate to cite web sites. (Be cautious, and don't overuse such citations. In particular, don't use a web citation where you could reasonably use a "hard" citation. Remember that your examiners are likely to be older and more conservative.) You should give the URL and also the date you downloaded it. If there is a date on the site itself (last updated on .....) you should included that, too.

Appendices

If there is material that should be in the thesis but which would break up the flow or bore the reader unbearably, include it as an appendix. Some things which are typically included in appendices are: important and original computer programs, data files that are too large to be represented simply in the results chapters, pictures or diagrams of results which are not important enough to keep in the main text.

School of Physics, University of New South Wales, Sydney, Australia.

What is a thesis? For whom is it written? How should it be written?

2009-05-05T06:48:00.000-07:00

Your thesis is a research report. The report concerns a problem or series of problems in your area of research and it should describe what was known about it previously, what you did towards solving it, what you think your results mean, and where or how further progress in the field can be made. Do not carry over your ideas from undergraduate assessment: a thesis is not an answer to an assignment question. One important difference is this: the reader of an assignment is usually the one who has set it. S/he already knows the answer (or one of the answers), not to mention the background, the literature, the assumptions and theories and the strengths and weaknesses of them. The readers of a thesis do not know what the "answer" is. If the thesis is for a PhD, the university requires that it make an original contribution to human knowledge: your research must discover something hitherto unknown.

Obviously your examiners will read the thesis. They will be experts in the general field of your thesis but, on the exact topic of your thesis, you are the world expert. Keep this in mind: you should write to make the topic clear to a reader who has not spent most of the last three years thinking about it.

Your thesis will also be used as a scientific report and consulted by future workers in your laboratory who will want to know, in detail, what you did. Theses are occasionally consulted by people from other institutions, and the library sends microfilm versions if requested (yes, still). More commonly theses are now stored in an entirely digital form. These may be stored as .pdf files on a server at your university. The advantage is that your thesis can be consulted much more easily by researchers around the world. (See e.g. Australian digital thesis project for the digital availability of research theses.) Write with these possibilities in mind.

It is often helpful to have someone other than your adviser(s) read some sections of the thesis, particularly the introduction and conclusion chapters. It may also be appropriate to ask other members of staff to read some sections of the thesis which they may find relevant or of interest, as they may be able to make valuable contributions. In either case, only give them revised versions, so that they do not waste time correcting your grammar, spelling, poor construction or presentation.

How much detail?

The short answer is: rather more than for a scientific paper. Once your thesis has been assessed and your friends have read the first three pages, the only further readers are likely to be people who are seriously doing research in just that area. For example, a future research student might be pursuing the same research and be interested to find out exactly what you did. ("Why doesn't the widget that Bloggs built for her project work any more? Where's the circuit diagram? I'll look up her thesis." "Blow's subroutine doesn't converge in my parameter space! I'll have to look up his thesis." "How did that group in Sydney manage to get that technique to work? I'll order a microfilm of that thesis they cited in their paper.") For important parts of apparatus, you should include workshop drawings, circuit diagrams and computer programs, usually as appendices. (By the way, the intelligible annotation of programs is about as frequent as porcine aviation, but it is far more desirable. You wrote that line of code for a reason: at the end of the line explain what the reason is.) You have probably read the theses of previous students in the lab where you are now working, so you probably know the advantages of a clearly explained, explicit thesis and/or the disadvantages of a vague one.

Make it clear what is yours

If you use a result, observation or generalisation that is not your own, you must usually state where in the scientific literature that result is reported. The only exceptions are cases where every researcher in the field already knows it: dynamics equations need not be followed by a citation of Newton, circuit analysis does not need a reference to Kirchoff. The importance of this practice in science is that it allows the reader to verify your starting position. Physics in particular is said to be a vertical science: results are built upon results which in turn are built upon results etc. Good referencing allows us to check the foundations of your additions to the structure of knowledge in the discipline, or at least to trace them back to a level which we judge to be reliable. Good referencing also tells the reader which parts of the thesis are descriptions of previous knowledge and which parts are your additions to that knowledge. In a thesis, written for the general reader who has little familiarity with the literature of the field, this should be especially clear. It may seem tempting to leave out a reference in the hope that a reader will think that a nice idea or an nice bit of analysis is yours. I advise against this gamble. The reader will probably think: "What a nice idea---I wonder if it's original?". The reader can probably find out via the net or the library.

If you are writing in the passive voice, you must be more careful about attribution than if you are writing in the active voice. "The sample was prepared by heating yttrium..." does not make it clear whether you did this or whether Acme Yttrium did it. "I prepared the sample..." is clear.

Style

The text must be clear. Good grammar and thoughtful writing will make the thesis easier to read. Scientific writing has to be a little formal---more formal than this text. Native English speakers should remember that scientific English is an international language. Slang and informal writing will be harder for a non-native speaker to understand.

Short, simple phrases and words are often better than long ones. Some politicians use "at this point in time" instead of "now" precisely because it takes longer to convey the same meaning. They do not care about elegance or efficient communication. You should. On the other hand, there will be times when you need a complicated sentence because the idea is complicated. If your primary statement requires several qualifications, each of these may need a subordinate clause: "When [qualification], and where [proviso], and if [condition] then [statement]". Some lengthy technical words will also be necessary in many theses, particularly in fields like biochemistry. Do not sacrifice accuracy for the sake of brevity. "Black is white" is simple and catchy. An advertising copy writer would love it. "Objects of very different albedo may be illuminated differently so as to produce similar reflected spectra" is longer and uses less common words, but, compared to the former example, it has the advantage of being true. The longer example would be fine in a physics thesis because English speaking physicists will not have trouble with the words. (A physicist who did not know all of those words would probably be glad to remedy the lacuna either from the context or by consulting a dictionary.)

Sometimes it is easier to present information and arguments as a series of numbered points, rather than as one or more long and awkward paragraphs. A list of points is usually easier to write. You should be careful not to use this presentation too much: your thesis must be a connected, convincing argument, not just a list of facts and observations.

One important stylistic choice is between the active voice and passive voice. The active voice ("I measured the frequency...") is simpler, and it makes clear what you did and what was done by others. The passive voice ("The frequency was measured...") makes it easier to write ungrammatical or awkward sentences. If you use the passive voice, be especially wary of dangling participles. For example, the sentence "After considering all of these possible materials, plutonium was selected" implicitly attributes consciousness to plutonium. This choice is a question of taste: I prefer the active because it is clearer, more logical and makes attribution simple. The only arguments I have ever heard for avoiding the active voice in a thesis are (i) many theses are written in the passive voice, and (ii) some very polite people find the use of "I" immodest. Use the first person singular, not plural, when reporting work that you did yourself: the editorial 'we' may suggest that you had help beyond that listed in your acknowledgments, or it may suggest that you are trying to share any blame. On the other hand, retain plural verbs for "data": "data" is the plural of "datum", and lots of scientists like to preserve the distinction. Just say to yourself "one datum is ..", "these data are.." several times. An excellent and widely used reference for English grammar and style is A Dictionary of Modern English Usage by H.W. Fowler.

Presentation

There is no need for a thesis to be a masterpiece of desk-top publishing. Your time can be more productively spent improving the content than the appearance.

In many cases, a reasonably neat diagram can be drawn by hand faster than with a graphics package, and you can scan it if you want an electronic version. Either is usually satisfactory. A one bit (i.e. black and white), moderate resolution scan of a hand-drawn sketch will be bigger than a line drawing generated on a graphics package, but not huge. While talking about the size of files, we should mention that photographs look pretty but take up a lot of memory. There's another important difference, too. The photographer thought about the camera angle and the focus etc. The person who drew the schematic diagram thought about what components ought to be depicted and the way in which the components of the system interacted with each other. So the numerically small information content of the line drawing may be much more useful information than that in a photograph.

Another note about figures and photographs. In the digital version of your thesis, do not save ordinary photographs or other illustrations as bitmaps, because these take up a lot of memory and are therefore very slow to transfer. Nearly all graphics packages allow you to save in compressed format as .jpg (for photos) or .gif (for diagrams) files. Further, you can save space/speed things up by reducing the number of colours. In vector graphics (as used for drawings), compression is usually unnecessary.

In general, students spend too much time on diagrams---time that could have been spent on examining the arguments, making the explanations clearer, thinking more about the significance and checking for errors in the algebra. The reason, of course, is that drawing is easier than thinking.

I do not think that there is a strong correlation (either way) between length and quality. There is no need to leave big gaps to make the thesis thicker. Readers will not appreciate large amounts of vague or unnecessary text.

Approaching the end

A deadline is very useful in some ways. You must hand in the thesis, even if you think that you need one more draft of that chapter, or someone else's comments on this section, or some other refinement. If you do not have a deadline, or if you are thinking about postponing it, please take note of this: A thesis is a very large work. It cannot be made perfect in a finite time. There will inevitably be things in it that you could have done better. There will be inevitably be some typos. Indeed, by some law related to Murphy's, you will discover one when you first flip open the bound copy. No matter how much you reflect and how many times you proof read it, there will be some things that could be improved. There is no point hoping that the examiners will not notice: many examiners feel obliged to find some examples of improvements (if not outright errors) just to show how thoroughly they have read it. So set yourself a deadline and stick to it. Make it as good as you can in that time, and then hand it in! (In retrospect, there was an advantage in writing a thesis in the days before word processors, spelling checkers and typing programs. Students often paid a typist to produce the final draft and could only afford to do that once.)

How many copies?

Talk to your adviser about this. As well as those for the examiners, the university libraries and yourself, you should make some distribution copies. These copies should be sent to other researchers who are working in your field so that:

they can discover what marvellous work you have been doing before it appears in journals;
they can look up the fine details of methods and results that will or have been published more briefly elsewhere;
they can realise what an excellent researcher you are. This realisation could be useful if a post- doctoral position were available in their labs. soon after your submission, or if they were reviewers of your research/post-doctoral proposal. Even having your name in their bookcases might be an advantage.

Whatever the University's policy on single or double-sided copies, the distribution copies could be double-sided paper, or digital, so that forests and postage accounts are not excessively depleted by the exercise. Your adviser could help you to make up a list of interested and/or potentially useful people for such a mailing list. Your adviser might also help by funding the copies and postage if they are not covered by your scholarship. A CD with your thesis will be cheaper than a paper copy. You don't have to burn them all yourself: companies make multiple copies for several dollars a copy.

The following comment comes from Marilyn Ball of the Australian National University in Canberra: "When I finished writing my thesis, a postdoc wisely told me to give a copy to my parents. I would never have thought of doing that as I just couldn't imagine what they would do with it. I'm very glad to have taken that advice as my parents really appreciated receiving a copy and proudly displayed it for years. (My mother never finished high school and my father worked with trucks - he fixed 'em, built 'em, drove 'em, sold 'em and junked 'em. Nevertheless, they enjoyed having a copy of my thesis.)"

Personal

In the ideal situation, you will be able to spend a large part---perhaps a majority---of your time writing your thesis. This may be bad for your physical and mental health.

Typing

Set up your chair and computer properly. The Health Service, professional keyboard users or perhaps even the school safety officer will be able to supply charts showing recommended relative heights, healthy postures and also exercises that you should do if you spend a lot of time at the keyboard. These last are worthwhile insurance: you do not want the extra hassle of back or neck pain. Try to intersperse long sessions of typing with other tasks, such as reading, drawing, calculating, thinking or doing research.

If you do not touch type, you should learn to do so for the sake of your neck as well as for productivity. There are several good software packages that teach touch typing interactively. If you use one for say 30 minutes a day for a couple of weeks, you will be able to touch type. By the time you finish the thesis, you will be able to touch type quickly and accurately and your six hour investment will have paid for itself. Be careful not to use the typing exercises as a displacement activity.

Exercise

Do not give up exercise for the interim. Lack of exercise makes you feel bad, and you do not need anything else making you feel bad while writing a thesis. 30-60 minutes of exercise per day is probably not time lost from your thesis: I find that if I do not get regular exercise, I sleep less soundly and longer. How about walking to work and home again? (Walk part of the way if your home is distant.) Many people opine that a walk helps them think, or clears the head. You may find that an occasional stroll improves your productivity.

Food

Do not forget to eat, and make an effort to eat healthy food. You should not lose fitness or risk illness at this critical time. Exercise is good for keeping you appetite at a healthy level. I know that you have little time for cooking, but keep a supply of fresh fruit, vegetables and bread. It takes less time to make a sandwich than to go to the local fast food outlet, and you will feel better afterwards.

Drugs

Thesis writers have a long tradition of using coffee as a stimulant and alcohol or marijuana as relaxants. (Use of alcohol and coffee is legal, use of marijuana is not.) Used in moderation, they do not seem to have ill effects on the quality of thesis produced. Excesses, however, are obviously counter-productive: several espressi and you will be buzzing too much to sit down and work; several drinks at night will slow you down next day.

Others

Other people will be sympathetic, but do not take them for granted. Spouses, lovers, family and friends should not be undervalued. Spend some time with them and, when you do, have a good time. Do not spend your time together complaining about your thesis: they already resent the thesis because it is keeping you away from them. If you can find another student writing a thesis, then you may find it therapeutic to complain to each other about advisers and difficulties. S/he need not be in the same discipline as you are.

Coda

Keep going---you're nearly there! Most PhDs will admit that there were times when we thought about reasons for not finishing. But it would be crazy to give up at the writing stage, after years of work on the research, and it would be something to regret for a long time.

Writing a thesis is tough work. One anonymous post doctoral researcher told me: "You should tell everyone that it's going to be unpleasant, that it will mess up their lives, that they will have to give up their friends and their social lives for a while. It's a tough period for almost every student." She's right: it is certainly hard work, it will probably be stressful and you will have to adapt your rhythm to it. It is also an important rite of passage and the satisfaction you will feel afterwards is wonderful. On behalf of scholars everywhere, I wish you good luck!

School of Physics, University of New South Wales, Sydney, Australia.

How to Write a PhD Thesis

2009-05-05T06:43:00.000-07:00

Getting Started

When you are about to begin, writing a thesis seems a long, difficult task. That is because it is a long, difficult task. Fortunately, it will seem less daunting once you have a couple of chapters done. Towards the end, you will even find yourself enjoying it---an enjoyment based on satisfaction in the achievement, pleasure in the improvement in your technical writing, and of course the approaching end. Like many tasks, thesis writing usually seems worst before you begin, so let us look at how you should make a start.

An outline

First make up a thesis outline: several pages containing chapter headings, sub-headings, some figure titles (to indicate which results go where) and perhaps some other notes and comments. There is a section on chapter order and thesis structure at the end of this text. Once you have a list of chapters and, under each chapter heading, a reasonably complete list of things to be reported or explained, you have struck a great blow against writer's block. When you sit down to type, your aim is no longer a thesis---a daunting goal---but something simpler. Your new aim is just to write a paragraph or section about one of your subheadings. It helps to start with an easy one: this gets you into the habit of writing and gives you self-confidence. In an experimental thesis, the Materials and Methods chapter is often the easiest to write – just write down what you did; carefully, formally and in a logical order.

How do you make an outline of a chapter? For most of them, you might try the method that I use for writing papers, and which I learned from my thesis adviser (Stjepan Marcelja): Assemble all the figures that you will use in it and put them in the order that you would use if you were going to explain to someone what they all meant. You might as well rehearse explaining it to someone else---after all you will probably give several talks based on your thesis work. Once you have found the most logical order, note down the key words of your explanation. These key words provide a skeleton for much of your chapter outline.

Once you have an outline, discuss it with your adviser. This step is important: s/he will have useful suggestions, but it also serves notice that s/he can expect a steady flow of chapter drafts that will make high priority demands on his/her time. Once you and your adviser have agreed on a logical structure, s/he will need a copy of this outline for reference when reading the chapters which you will probably present out of order. If you have a co-adviser, discuss the outline with him/her as well, and present all chapters to both advisers for comments.

Organisation

It is encouraging and helpful to start a filing system. Open a word-processor file for each chapter and one for the references. You can put notes in these files, as well as text. While doing something for Chapter n, you will think "Oh I must refer back to/discuss this in Chapter m" and so you put a note to do so in the file for Chapter m. Or you may think of something interesting or relevant for that chapter. When you come to work on Chapter m, the more such notes you have accumulated, the easier it will be to write.

Make a back-up of these files and do so every day at least (depending on the reliability of your computer and the age of your disk drive). Do not keep back-up close to the computer in case the hypothetical thief who fancies your computer decides that s/he could use some disks or membory as well.

A simple way of making a remote back-up is to send it as an email attachment to a consenting email correspondent, preferably one in a different location. You could also send it to yourself. In either case, be careful to dispose of superseded versions so that you don't waste disk space, especially if you have bitmap images or other large files.

You should also have a physical filing system: a collection of folders with chapter numbers on them. This will make you feel good about getting started and also help clean up your desk. Your files will contain not just the plots of results and pages of calculations, but all sorts of old notes, references, calibration curves, suppliers' addresses, specifications, speculations, letters from colleagues etc., which will suddenly strike you as relevant to one chapter or other. Stick them in that folder. Then put all the folders in a box or a filing cabinet. As you write bits and pieces of text, place the hard copy, the figures etc in these folders as well. Touch them and feel their thickness from time to time – ah, the thesis is taking shape.

If any of your data exist only on paper, copy them and keep the copy in a different location. Consider making a copy of your lab book. This has another purpose beyond security: usually the lab book stays in the lab, but you may want a copy for your own future use. Further, scientific ethics require you to keep lab books and original data for at least ten years, and a copy is more likely to be found if two copies exist.

If you haven't already done so, you should archive your electronic data, in an appropriate format. Spreadsheet and word processor files are not suitable for long term storage. Archiving data by Joseph Slater is a good guide.

While you are getting organised, you should deal with any university paperwork. Examiners have to be nominated and they have to agree to serve. Various forms are required by your department and by the university administration. Make sure that the rate limiting step is your production of the thesis, and not some minor bureaucratic problem.

A note about word processors

One of the big FAQs for scientists: is there a word processor, ideally one compatible with MS Word, but which allows you to type mathematical symbols and equations conveniently? One solution is LaTeX, which is powerful, elegant, reliable, fast and free from http://www.latex-project.org/ or http://www.miktex.org/. As far as I know, the only current equation editor for MS Word is slow and awkward. (If anyone knows a way of writing equations in this software without using the mouse, many people including this author would like to hear from you!) Another solution is to use old versions of commercial software. Word 5.1 allows equations to be typed comfortably: it is faster in this respect than LaTeX, with the added advantage of 'what you see is what you get' (WYSIWYG). (If anyone knows how to run Word 5.1 on OSX, please let me know!) A search will find sites that provide discontinued software, but, not knowing whether this is legal or not, I shan't link to them. (I am told that LyX, available free at http://www.lyx.org/, is a convenient front-end to LaTeX that has WYSIWYG. )

Commercial word processors have gradually become bigger, slower, less reliable and more awkward to use as they acquire more features. This is a general feature of commercial software and an important input to the computing industry. If software and operating system performance did not deteriorate, people would not need to buy new computers and profits would fall for makers of both hard- and soft-ware. Software vendors want it to look fancy and obvious in the demo, and they don't really care about its ease, speed and reliability to an expert user because the expert user has already bought it. In our example, it is much faster to type equations and to do formatting with embedded commands because you use your fingers independently rather than your hand and because your fingers don't leave the keyboard. However, click-on menus, although they are slow and cumbersome when typing, look easy to use in the shop.

A timetable

I strongly recommend sitting down with the adviser and making up a timetable for writing it: a list of dates for when you will give the first and second drafts of each chapter to your adviser(s). This structures your time and provides intermediate targets. If you merely aim "to have the whole thing done by [some distant date]", you can deceive yourself and procrastinate more easily. If you have told your adviser that you will deliver a first draft of chapter 3 on Wednesday, it focuses your attention.

You may want to make your timetable into a chart with items that you can check off as you have finished them. This is particularly useful towards the end of the thesis when you find there will be quite a few loose ends here and there.

Iterative solution

Whenever you sit down to write, it is very important to write something. So write something, even if it is just a set of notes or a few paragraphs of text that you would never show to anyone else. It would be nice if clear, precise prose leapt easily from the keyboard, but it usually does not. Most of us find it easier, however, to improve something that is already written than to produce text from nothing. So put down a draft (as rough as you like) for your own purposes, then clean it up for your adviser to read. Word-processors are wonderful in this regard: in the first draft you do not have to start at the beginning, you can leave gaps, you can put in little notes to yourself, and then you can clean it all up later.

Your adviser will expect to read each chapter in draft form. S/he will then return it to you with suggestions and comments. Do not be upset if a chapter---especially the first one you write--- returns covered in red ink (or its electronic equivalent). Your adviser will want your thesis to be as good as possible, because his/her reputation as well as yours is affected. Scientific writing is a difficult art, and it takes a while to learn. As a consequence, there will be many ways in which your first draft can be improved. So take a positive attitude to all the scribbles with which your adviser decorates your text: each comment tells you a way in which you can make your thesis better.

As you write your thesis, your scientific writing is almost certain to improve. Even for native speakers of English who write very well in other styles, one notices an enormous improvement in the first drafts from the first to the last chapter written. The process of writing the thesis is like a course in scientific writing, and in that sense each chapter is like an assignment in which you are taught, but not assessed. Remember, only the final draft is assessed: the more comments your adviser adds to first or second draft, the better.

Before you submit a draft to your adviser, run a spell check so that s/he does not waste time on those. If you have any characteristic grammatical failings, check for them.

School of Physics, University of New South Wales, Sydney, Australia.

Common Etchants for Copper, Nickel and Cobalt: Copper & Alloys

2008-06-22T23:38:00.000-07:00

Composition	Comments
2 5 mL NH₄OH 25 mL water (optional) 25-50 mL H₂O₂ (3%)	General purpose grain contrasts etch for Cu and alloys (produces a flat etch for some alloys). Use fresh, add peroxide last. Use under a hood. Swab specimen 5-45 seconds.
100 mL water 10 g ammonium persulfate orientation.	General purposes etch for Cu and alloys. Immerse or swab for 3-60 seconds. Reveals grain boundaries but is sensitive to crystallographic
100 mL water 3g ammonium persulfate 1mL NH₄OH	General purpose etch for Cu and alloys, particularly Cu-Be alloys.
70 mL water 5 g Fe(NO₃)₃ 25 mL HCI	Excellent general purpose etch, reveals grain boundaries well. Immerse specimen 10-30 seconds

Common Etchants for Iron and Steel

2008-06-19T21:49:00.000-07:00

Composition

Comments

90-99 mL methanol or ethanol

1-10 mL HNO₃

Nital.

Most common etchant for Fe, carbon and alloy steels, cast iron. Reveals alpha grain boundaries and constituents. Excellent for martensitic structures. The 2% solution is most common, 5-10% used for high alloy steels (do not store). Use by immersion or swabbing of sample for up to bout 60 seconds.

1 00 mL ethanol

4 g picric acid

Picral.

Recommended for structures consisting of ferrite and carbide. Does not reveal ferrite grain boundaries. Addition of about 0.5-1% zephiran chloride improves etch rate and uniformity.

100 mL ethanol

5 mL HCI

1 g picric acid

Vilella’s reagent.

Good for ferrite-carbide structures. Produces grain contrast for estimating prior austenite grain size. Results best on martensite tempered at 572-932 °F (300-500 °C). Occasionally reveals prior-austenite grain boundaries in high alloy steels. Outlines constituents in stainless steels. Good for tool steels and martensitic stainless steels.

Saturated aqueous picric acid solution grain plus small amount of a wetting agent

Bechet and Beaujard’s etch,

Most successful etchant for prior-austenite boundaries. Good for martensitic and bainitic steels. Many wetting agents have been used, sodium tridecylbenzene sulfonate is one of most successful (the dodecyl version is easier to obtain and works as well). Use at 20-100 °C. Swab or immerse sample for 2-60 minutes. Etch in ultrasonic cleaner Additions of 0.5g CuCl2 per 100mL solution or about 1% HCI have been used for higher alloy steels to produce etching. Room temperature etching most common. Lightly back polish to remove surface smut.

150 mL water

50 mL HCI

25 mL HNO3

1 g CuCl2

Modified Fry’s reagent.

Used for 18% Ni maraging steels, martensitic and PH stainless steels.

1 00 mL water

25 g NaOH

2 g picric acid

Alkaline sodium picrate.

Best etch for McQuaid-Ehn carburized samples. Darkens cementite. Use boiling for 1-15 minutes or electrolytic at 6 V dc, 0.5 A/in², 30-120 seconds. May reveal prior-austenite grain boundaries in high carbon steels when no apparent grain boundary film is present.

1 00 mL ethanol

100 mL HCI

5 g CuCl₂

Kalling’s no. 2 (“waterless” Kalling’s)

Etch for austenitic and duplex stainless steels. Ferrite attacked readily, carbides unattacked, austenite slightly attacked. Use at 20 °C by immersion or swabbing. Can be stored.

1 5 mL HCI

10 mL acetic acid

5 mL HNO3

2 drops glycerol

Acetic glyceregia. Mix fresh; do not store. Use for high alloy stainless steels.

100 mL water

10 g K₂Fe(CN)₆

10 g KOH or NaOH

Murakami’s reagent.

Usually works better on ferritic stainless grades than on austenitic grades. Use at 20 °C for 7-60 seconds: reveals carbides sigma faintly attacked with etching up to 3 minutes. Use at 80°C (176°F) to boiling for 2-60 minutes: carbides dark, sigma blue (not always attacked), ferrite yellow to yellow-brown, austenite unattacked. Do not always get uniform etching.

100 mL water

1 0 g oxalic acid

Use for stainless steels at 6 V dc. Carbides revealed by etching for 15-30 seconds, grain boundaries after 45-60 seconds, sigma outlined after 6 seconds. 1-3 V also used. Dissolves carbides, sigma strongly attacked, austenite moderately attacked, ferrite unattacked.

100 mL water

20 g NaOH

Used to color ferrite in martensitic, PH or dual-phase stainless steels. Use at 3-5 V dc, 20°C, 5 seconds, stainless steel cathode. Ferrite outlined and colored tan.

40 mL water

60 mL HNO₃

Electrolytic etch to reveal austenite boundaries but not twin boundaries in austenitic stainless steels (304, 316, etc.). Voltage is critical. Pt cathode preferred to stainless steel. Use at 1.4 V dc, 2 minutes.

Commonly Used Etchants for Magnesium and Alloys

2008-06-19T21:08:00.000-07:00

Composition	Comments
25 mL water 75 mL 3-5 ethylene glycol 1 mL HNO3	Glycol etch, general purpose etch for pure Mg and alloys. Swab specimen seconds for F and T6 temper alloys, 1-2 minutes for T4 and 0 temper alloys.
19 mL water 60 mL ethylene glycol 20 mL acetic acid 1 mL HNO3	Acetic glycol etchant for pure Mg and alloys. Swab specimen 1-3 seconds for F and T6 temper alloys, 10 seconds for T4 and 0 temper alloys. Reveals grain boundaries in solution-treated castings and most wrought alloys.
100 mL ethanol 10 mL water 5 g picric acid	For Mg and alloys. Use fresh. Immerse specimen for 15-30 seconds. Produces grain contrast.

Commonly Used Etchants for Aluminum and Alloys

2008-06-19T21:00:00.000-07:00

Composition	Comments
95 mL water 2.5 mL HNO3 1.5 mL HCI 1.0 mL HF	Keller’s reagent, very popular general purpose reagent for Al and Al alloys, except high-Si alloys. Immerse sample 10-20 seconds, wash in warm water. Can follow with a dip in conc. HNO3. Outlines all common constituents, reveals grain structure in certain alloys when used by immersion.
90-100 mL water 0.1-10 mL HF	General-purpose reagent. Attacks FeAl3, other constituents outlined. The 0.5% concentration of HF is very popular.
84 mL water 15.5 mL HNO3 0.5 mL HF 3g CrO3	Graff and Sargent’s etchant, for grain size of 2XXX, 3XXX, 6XXX, and 7XXX wrought alloys. Immerse specimen 20-60 seconds with mild agitation.
1.8% fluoboric acid in water	Barker’s anodizing method for grain structure. Use 0.5-1.5 A/in2, 30-45 V dc. For most alloys and tempers, 20 seconds at 1 A/in2 and 30 V dc at 20 °C is sufficient. Stirring not needed. Rinse in warm water, dry. Use polarized light; sensitive tint helpful.

Hints For Etching

2008-06-19T20:40:00.000-07:00

Many etchants can be used by swabbing or by immersion. Swabbing is preferred for those specimens that form a tight protective oxide on the surface in air, such as Al, Ni, Cr, stainless steels, Nb (Cb), Ti and Zr. However, if the etchant forms a film, as in tint etchants, then immersion must be used as swabbing will keep the film from forming. Keller’s reagent reveals the grain size of certain aluminum alloys by forming a film. This will not occur if the etch is used by swabbing. Many etchants, and their ingredients, do present potential health hazards to the user. ASTM E 2014, Standard Guide on Metallography Laboratory Safety, describes many of the common problems and how to avoid them.

Etching Procedures

2008-06-19T19:51:00.000-07:00

Microscopic examination is usually limited to a maximum magnification of 1000X — the approximate useful limit of the light microscope, unless oil immersion objectives are used. Many image analysis systems use relay lenses that yield higher screen magnifications that may make detection of fine structures easier. However, resolution is not improved beyond the limit of 0.2-0.3-um for the light microscope. Microscopic examination of a properly prepared specimen will clearly reveal structural characteristics such as grain size, segregation, and the shape, size, and distribution of the phases and inclusions that are present. Examination of the microstructure will reveal prior mechanical and thermal treatments give the metal. Many of these microstructural features are measured either according to established image analysis procedures, e.g., ASTM standards, or internally developed methods.

Etching is done by immersion or by swabbing (or electrolytically) with a suitable chemical solution that essentially produces selective corrosion. Swabbing is preferred for those metals and alloys that form a tenacious oxide surface layer with atmospheric exposure such as stainless steels, aluminum, nickel, niobium, and titanium and their alloys. It is best to use surgical grade cotton that will not scratch the polished surface. Etch time varies with etch strength and can only be determined by experience. In general, for high magnification examination the etch depth should be shallow; while for low magnification examination a deeper etch yields better image contrast. Some etchants produce selective results in that only one phase will be attacked or colored. Etchants that reveal grain boundaries are very important for successful determination of the grain size. A vast number of common etchants have been developed and it is displayed in Table 1 after this section.

ETCHING

2008-06-19T19:38:00.000-07:00

Metallographic etching encompasses all processes used to reveal particular structural characteristics of a metal that are not evident in the as-polished condition. Examination of a properly polished specimen before etching may reveal structural aspects such as porosity, cracks, and nonmetallic inclusions. Indeed, certain constituents are best measured by image analysis without etching, because etching will reveal additional, unwanted detail and make detection difficult or impossible. The classic examples are the measurement of inclusions in steels and graphite in cast iron. Of course, inclusions are present in all metals, not just steels. Many intermetallic precipitates and nitrides can be measured effectively in the as-polished condition.

In certain nonferrous alloys that have non-cubic crystallographic structures (such as beryllium, hafnium, magnesium, titanium, uranium and zirconium), grain size can be revealed adequately in the as polished condition using polarized light. Figure (1) shows the microstructure of cold-drawn zirconium viewed in cross-polarized light. This produces grain coloration, rather than a “flat etched” appearance where only the grain boundaries are dark.

Figure 1: Mechanical twins at the surface of hot worked and cold drawn high-purity zirconium viewed with polarized light (200X).

DETERMINATION OF CALCIUM, IRON, MAGNESIUM, MANGANESE, POTASSIUM, AND SODIUM by AAS

2008-06-05T02:51:00.001-07:00

Reagents and Equipment

1. Lanthanum solution: Transfer 140 g of lanthanum oxide (La₂O₃, 99.997 percent pure) into a 2-L beaker. Slowly add 300 mL of concentrated hydrochloric acid, allowing time for the reaction to be completed after each addition of acid. Then, add 200 mL of distilled water. Each 4 mL of the final solution contains approximately 1 g of lanthanum.

2. Manganese stock solution: Transfer 0.3872 g of pure manganese metal into a glass beaker, add 20 mL of hot 8 M nitric acid, and gently boil the nitric acid for several minutes. After the resulting solution has cooled to room temperature, transfer the solution to a 500-mL volumetric flask and dilute to volume with distilled water. The concentration of MnO in this solution is 1,000 m g/mL.

3. Stock multiple-element standard solution: Transfer 0.8924 g of CaCO₃, 0.9435 g of NaCl, 0.7915 g of KCl. and 2.4556 of FeSO₄(NH₄)₂SO_4·6H₂O, (all reagent-grade purity) and 0.3045 g of magnesium ribbon to a 500-mL volumetric flask. (Magnesium ribbon generally is 99 percent magnesium; therefore, the weight of the ribbon includes a 1-percent correction.) Add 50 mL of distilled water and 10 mL of concentrated hydrochloric acid. Boil the dilute acid to dissolve all the constituents. After the solution cools to room temperature, add 50.0 mL of the manganese stock solution (1,000 m g/mL of MnO), dilute to volume with distilled water, and thoroughly mix the final solution. This solution contains the equivalent of 1.00 mg/mL each of Fe₂O₃, CaO, MgO, Na₂O, and K₂O, and 0.1 mg/mL of MnO.

4. Working standard solutions: To six 250-mL volumetric flasks, add 0, 6, 12, 18, 24, and 30 mL of the standard stock solution. Then, add 1.2 g of flux mixture, 5 mL of 8 M nitric acid, and approximately 200 mL of distilled water. Agitate the nitric acid solution to dissolve the flux mixture. Then, add distilled water to make the final volume 250 mL and make the solution homogeneous by vigorous mixing. These six solutions represent a blank and 3-, 6-, 9-, 12-, and 15-percent (equivalent in the sample) standard solutions. For MnO, the same six solutions represent a blank and 0.3-, 0.6-, 0.9-, 1.2-, and 1.5-percent standard solutions.

Procedure for Calcium, Iron, Magnesium, and Manganese

1. Transfer 0.750 mL of blank, sample, and standard solutions into small vials or beakers.

2. Dilute 8 mL of lanthanum solution with 200 mL of distilled water. Add 6.5 mL of this solution to all standards, samples, and blanks.

3. Calibrate the atomic absorption spectrometer by setting the concentration scale to zero for the recommended wavelength (table 16) while the blank solution is nebulized into the flame. Then, set the concentration scale with the 6-percent working standard, and verify this setting with solutions of silicate standards. Directly measure the concentrations of calcium, iron, magnesium, and manganese in each of the samples. Most available atomic absorption spectrometers are suitable for these measurements; the optimum operating conditions for each element usually are discussed in the manual provided with the spectrometer. Importantly, the individual measurements of concentration (or, absorbance) for a sample should be "bracketed" between those of standards because the instrumental responses are usually not linear.

Procedure for Potassium and Sodium

1. Transfer 0.200 mL of blank, sample solutions, working standards, and silicate standards into a small vial or beaker.

2. Dilute 1.2 mL of lanthanum solution with 200 mL of distilled water. Add 5.0 mL of this solution to the blank and to each of the standards and samples.

3. Calibrate the atomic absorption spectrometer using the concentration mode with the 6-percent working standard, and check appropriate silicate standards for known values. Measure directly the concentration of samples.

CONCLUSIONS

Methods based on AAS and spectrophotometry provide accurate determinations of 10 inorganic elements in coal ash. Although not as rapid as X-ray fluorescence (XRF) spectrometry, these methods furnish an approach to determining major oxides in coal ash that is both inexpensive and accurate (table 18). The agreement between our measurements and the NBS-certified concentrations for10 elements in NBS 1633a coal fly ash, demonstrated by data in table 18, is quite acceptable. Results from XRF spectrometry for SiO₂, Al₂O₃, and Fe₂O₃ in ash sample number 1 and for SiO₂ in sample number 7 (table 18) are outside the range covered by the standards used for calibration. Thus, extrapolations beyond this range could introduce error into these determinations.

REFERENCES

Bunting, W.E., 1944, The determination of soluble silica in very low concentrations: Industrial and Engineering Chemistry (analytical ed.), v. 16, p. 612-615.

Parker, C.A., and Goddard, A.P., 1950, The reaction of aluminum ions with alizarin-3-sulfonate, with particular reference to the effect of calcium ions: Analytica Chimica Acta, v. 4, no. 5, p. 517-536.

Shapiro, L., 1975, Rapid analysis of silicate, carbonate, and phosphate rocks: U.S. Geological Survey Bulletin 1401, revised ed., 76 p.

Yoe, J.H., and Armstrong, A.R., 1947, Colorimetric determination of titanium with disodium-1,2-dihydroxybenzene-3,5-disulfonate: Analytical Chemistry, v. 19, p. 100-102.

Sodium (Na+): Perkin Elmer AAnalyst 100 Atomic Absorption Spectrometer

2008-06-05T02:47:00.001-07:00

I) Principle

The ground state sodium atom absorbs light energy at 589.0 nm as it enters the excited state. As the number of sodium atoms in the light path increases, the amount of light absorbed also increases. By measuring the amount of light absorbed, a quantitative determination of the amount of sodium present can be made. 0.5 % lanthanum solution is added to each standard, control and sample to prevent chemical and ionization interference.

II) Preparation of Stock Standard

In a 1000 mL volumetric flask, dissolve 2.5420 g sodium chloride (NaCl) to the mark with deionized water. This standard stock solution is 1000 mg Na⁺/L.

III) Preparation of Reagents

0.5 % Lanthanum Solution

In a 1000 mL volumetric flask, dissolve 13.37 g lanthanum chloride (LaCl₃.7H₂O) to the mark with deionized water.

IV) Analysis Procedure

A) Spike each standard, control and sample 9:10 with 0.5 % Lanthanum Solution (1 part 0.5 % Lanthanum Solution and 9 parts standard, control or sample).

B) Install Na-K hollow cathode lamp. Perkin-Elmer part #N305-0204.

C) Ensure that the correct Default Conditions are entered.

1) Recall Method=2

2) Lamp Current=12

3) Slit=0.2

4) Full Height=Y(Yes)

5) Wavelength(nm)=589.0

6) Int. Time=5.0

7) Replicates=5

8) Cal=1(Nonlinear)

9) Cal=1(Hold)

10) STD1-----

11) Read Delay(sec)=3

D) Use an oxidizing (lean, blue) air-acetylene flame.

E) Calibrate with standards that bracket the sample concentration. Check the calibration curve for drift, accuracy and precision with standards and controls every 20 samples. Correlation coefficient should be greater than or equal to 0.990.

Manganese (Mn): Perkin Elmer AAnalyst 100 Atomic Absorption Spectrometer

2008-06-05T02:45:00.001-07:00

I) Principle

The ground state manganese atom absorbs light energy at 279.5 nm as it enters the excited state. As the number of manganese atoms in the light path increases, the amount of light absorbed also increases. By measuring the amount of light absorbed, a quantitative determination of the amount of magnesium present can be made. 0.5 % lanthanum solution is added to each standard and sample to prevent chemical and ionization interference.

II) Preparation of Stock Standard

Stock standard of 1000 mg Mn/L is purchased commercially. Discard on expiration date.

III) Preparation of Reagents

0.5 % Lanthanum Solution

In a 1000-mL volumetric flask, dissolve 13.37 g lanthanum chloride (LaCl₃.7H₂O) to the mark with deionized water.

IV) Analysis Procedure

A) Dilute each standard and sample 9:10 with 0.5 % Lanthanum Solution (1 part 0.5 % Lanthanum Solution and 9 parts standard or sample).

B) Install a Mn hollow cathode lamp.

C) Ensure that the correct Default Conditions are entered.

1) Recall Method=5

2) Lamp Current=20

3) Slit=0.2

4) Full Height=Y(Yes)

5) Wavelength(nm)=279.5

6) Int. Time=5.0

7) Replicates=5

8) Cal=1(Nonlinear)

9) Cal=1(Hold)

10) STD1____

11) Read Delay(sec)=3

D) Use an oxidizing (lean, blue)air-acetylene flame.

E) Calibrate with standards that bracket the sample concentration. Correlation coefficient should be greater than or equal to 0.990. Check the calibration curve for drift, accuracy and precision with standards and controls every 20 samples.

Perkin Elmer AAnalyst 100 Atomic Absorption Spectrometer: Operating Procedure

2008-06-05T02:40:00.001-07:00

I) Principle

The Perkin Elmer AAnalyst 100 system consists of a high efficiency burner system with a Universal GemTip nebulizer and an atomic absorption spectrometer. The burner system provides the thermal energy necessary to dissociate the chemical compounds, providing free analyte atoms so that atomic absorption occurs. The spectrometer measures the amount of light absorbed at a specific wavelength using a hollow cathode lamp as the primary light source, a monochromator and a detector. A deuterium arc lamp corrects for background absorbance caused by non-atomic species in the atom cloud.

II) Instrument Setup

A) Empty waste container to mark. Add deionized water to drain tubing to ensure that water is present in the drain system float assembly.

B) Drain moisture from air compressor.

1) Unplug compressor.

2) Reduce compressor pressure to nearly zero by opening the pressure release valve and the drain plug located at the bottom of the tank.

3) Close pressure release valve and drain plug.

4) Plug in compressor to restart the motor.

C) Install the appropriate Hollow Cathode Lamp for the analyte to be analyzed.

D) Power AAnalyst 100 and printer ON.

E) Ensure that instrument is in AA mode.

F) Recall Method to be analyzed.

G) Ensure that the correct Default Conditions are entered.

H) Align the Hollow Cathode Lamp.

1) Press Energy.

2) Press Energy a second time if the bar needs to be brought on scale.

3) Adjust the vertical and horizontal lamp adjustment screws to obtain maximum energy.

I) Store Method changes in Parameter Entry, Option, Store and #.

J) Adjust Burner height.

1) Place a white sheet of paper behind the burner to confirm the location of the light beam.

2) Lower the burner head below the light beam with the vertical adjustment knob.

3) Press Cont (Continuous) to display an absorbance value.

4) Press A/Z to Autozero.

5) Raise the burner head with the vertical adjustment knob until the display indicates a slight absorbance (0.002). Slowly lower the head until the display returns to zero. Lower the head an additional quarter turn to complete the adjustment.

K) Ignite flame.

1) Turn Fume Hood switch ON.

2) Open air compressor valve. Set pressure to 50 to 65 psi.

3) Open acetylene gas cylinder valve. Set output pressure to 12 to 14 psi. Replace cylinder when pressure falls to 85 psi to prevent valve and tubing damage from the presence of acetone.

4) Press Gases On/Off. Adjust oxidant flow to 4 Units.

5) Press Gases On/Off. Adjust acetylene gas flow to 2 Units.

6) Press Flame On/Off to turn flame on.

Note: Do not directly view the lamp or flame without protective ultraviolet radiation eyewear.

L) Aspirate deionized water through the burner head several minutes.

M) Adjust Burner Position and Nebulizer.

1) Aspirate a standard with a signal of approximately 0.2 absorbance units.

2) Obtain maximum burner position absorbance by rotating the horizontal and rotational adjustment knobs.

3) Loosen the nebulizer locking ring by turning it clockwise. Slowly turn the nebulizer adjustment knob to obtain maximum absorbance. Lock the knob in place with the locking ring.

Note: An element, such as Magnesium, which is at a wavelength where gases do not absorb is optimal for adjusting the Burner and Nebulizer.

N) Allow 30 minutes to warm-up flame and lamp.

III) Calibration Procedure

A) Calibrate with standards that bracket the sample concentrations.

B) Enter ------ for Std1 in the Default Conditions to obtain absorbance units for each standard. Construct a data regression curve on a computer spreadsheet. Use standard concentrations as the X axis and absorbances as the Y axis.

C) Enter Standard Concentration Values in the Default Conditions to calculate an AAnalyst 100 standard curve.

1) Enter the concentration of the lowest standard for STD1 using significant digits.

2) Enter the concentrations of the other standards of the calibration curve in ascending order and the concentration of the reslope standard.

3) Autozero with the blank before each standard.

4) Aspirate Standard 1, press 0 Calibrate to clear the previous curve. Aspirate the standards in numerical order.

Press standard number and calibrate for each standard.

5) Press Print to print the graph and correlation coefficient.

6) Rerun one or all standards, if necessary. To rerun Standard 3, aspirate standard and press 3 Calibrate.

7) Reslope the standard curve by pressing Reslope after aspirating the designated reslope standard.

D) The correlation coefficient should be greater than or equal to 0.990.

E) Check the calibration curve for drift, accuracy and precision with standards and controls every 20 samples.

IV) Analysis Procedure

A) Autozero with the blank before and after each standard, control and sample.

B) Aspirate sample and press Read. Wait until Read light goes out. Record absorbance or concentration value. Record the five replicate standard deviation. Rerun the sample if the standard deviation is greater than 10% of the sample result.

V) Instrument Shutdown

A) Aspirate 5 % concentrated hydrochloric acid (HCl) for 5 minutes and deionized water for 10 minutes to clean the burner head. Remove the capillary tube from the water.

B) Press Flame On/Off to turn off flame.

C) Close air compressor valve.

D) Close acetylene cylinder valve.

E) Press Gases On/Off three times to bleed the acetylene gas from the lines. The cylinder pressure should drop to zero.

F) Power OFF the AAnalyst 100, the printer and the fume hood.

Magnesium (Mg 2+): Perkin Elmer AAnalyst 100 Atomic Absorption Spectrometer

2008-06-05T02:38:00.001-07:00

I) Principle

The ground state magnesium atom absorbs light energy at 285.2 nm as it enters the excited state. As the number of magnesium atoms in the light path increases, the amount of light absorbed also increases. By measuring the amount of light absorbed, a quantitative determination of the amount of magnesium present can be made. 0.5 % lanthanum solution is added to each standard and sample to prevent chemical and ionization interference.

II) Preparation of Stock Standard

In a 1000-mL volumetric flask, dissolve 8.3632 g magnesium chloride (MgCl₂.6H₂O) to the mark with deionized water. This standard stock solution is

1000 mg Mg²⁺/L.

III) Preparation of Reagents

0.5 % Lanthanum Solution

In a 1000-mL volumetric flask, dissolve 13.37 g lanthanum chloride (LaCl₃.7H₂O) to the mark with deionized water.

IV) Analysis Procedure

A) Dilute each standard and sample 9:10 with 0.5 % Lanthanum Solution (1 part 0.5 % Lanthanum Solution and 9 parts standard or sample).

B) Install a Ca-Mg hollow cathode lamp. Perkin-Elmer part #N305-0202.

C) Ensure that the correct Default Conditions are entered.

1) Recall Method=4

2) Lamp Current=15

3) Slit=0.7

4) Full Height=Y(Yes)

5) Wavelength(nm)=285.2

6) Int. Time=5.0

7) Replicates=5

8) Cal=1(Nonlinear)

9) Cal=1(Hold)

10) STD1____

11) Read Delay(sec)=3

D) Use an oxidizing (lean, blue)air-acetylene flame.

Fwd: Third Announcement

2008-05-28T19:24:00.000-07:00

Dear colleague,

I would like to invite you to submit a paper to the MMC2008, which will be held at Universiti Kebangsaan Malaysia on 3- 4 December 2008 .

MMC 2008 is a national event on metallurgy and related field, and is a continuity of NMC 2007, NMC 2006 and 2004 Metallurgical Conference.

The purpose of this conference is/are to provide national platform for networking between metallurgical local scientists and researchers. To establish an avenue to present ideas and research studies and to share and discuss research findings and disseminate knowledge in the area of metallurgy.

Submitted papers will be published in conference proceeding and selected presented papers will be published in Sains Malaysiana or International Journal of Mechanical and Materials Engineering (cited by Scopus) after normal reviewing procedure. It is my great pleasure if you also can invite your college and postgraduate student to join the conference. In addition, the conference fee is very competitive for the field in the country.

Malaysian Metallurgical
Conference 2008 Secretariat
School of Applied Physics
Faculty of Science and Technology
Universiti Kebangsaan Malaysia
43600 Bangi, Selangor
Tel: 03- 89213873 , 03- 89213404 ,
03- 89213405
Fax: 03- 89213777
Email: metallurgy2008@gmail.com
Website:
http://multimedia.eng.ukm.my/jkmb/mmc2008

Chemical composition of Fly ash by Inductively Coupled Plasma/Mass Spectroscopy (ICP/MS)

2008-05-26T03:24:00.000-07:00

1. Powdered samples were scrapped from each of the four test materials. 100 mg of each powdered sample was weighed and poured into a Teflon screw capped jar (SavillexR).
2. 2 ml concentrated nitric acid (HNO3) was added to each jar and the jars tightly capped.
3. The jars were placed on a hot plate at a temperature of 150°C until the entire samples were dissolved.
4. The solutions were then transferred into separate 125 ml bottles, their jars rinsed thoroughly with water and transferred into appropriate bottles.
5. About 15 ml of water was then added to fill each bottle. The solutions were analyzed using Perkin Elmer Elan 5000 inductively coupled plasma/mass spectrometer (ICP/MS).

6. Using the protocol of internal standardization, about 30 parts per billion (ppb) In, Tb and Bi were added into each sample solution so as to overcome instrumental drift and matrix effect.
7. The high thermal energy and electron rich environment of the ICP resulted in the conversion of most atoms into ions.
8. A quadruple mass spectrometer permitted the detection of ions and each mass in rapid sequence, allowing signals of individual isotopes of an element to be scanned.

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Chemical composition of Fly ash by Inductively Coupled Plasma/Optical Emission Spectroscopy (ICP/OES)

2008-05-26T03:23:00.001-07:00

1. The fly ash sample was totally digested by gently heating 0.25g of the sample in a mixture of HF/HNO3/HClO4 in a Teflon beaker on a hot plate until dry.
2. The residue was then dissolved in 5% HNO3 and topped to 15 ml with deionized water for analysis by Perkin Elmer Optima 3000 DV inductively coupled plasma/optical emission spectrometer (ICP/OES).
3. This was used to determine the major element oxides, with the exception of SiO2, and the larger suite of trace elements. 0.10 g of fly ash sample was also digested with 2.25 ml of a mixture of 9 parts HNO3 with 1 part HCl for 1 hour at 95°C in a boiling water bath and topped to 15 ml with deionized water for analysis by the ICP/OES.
4. This method was used to determine the smaller suite of trace elements.
5. The SiO2 portion was obtained by fusing 0.10 g of the fly ash sample with 1.00 g of lithium metaborate at 1000°C for 1 hour.
6. The residue was dissolved in dilute HNO3 topped to 100 ml with deionized water and then analyzed by the ICP/OES.

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Determining the Amount of Reagent Needed for Solution Preparation

2007-03-20T01:49:00.000-07:00

Before you prepare a solution you must calculate the correct amount of reagent that is to be diluted to make the solution. Several examples of how to make such calculations are given below:

Approximate Dilution of a Concentrated Reagent

What volume concentrated nitric acid is needed for the preparation of 100 mL of 6।0 M HNO3? The calculation is as follows:

Use a graduated cylinder to measure 38 mL of concentrated nitric acid and add this amount to approximately 60 mL of distilled water in a plastic bottle. Mix thoroughly, let the solution cool, then cap and label the container.

Finding the molarity

If the molarity of the reagent is not known, you must find it from the given value of specific gravity and percent composition। For all practical purposes, the specific gravity of a solution is numerically equal to its density। For example, what is the molarity of concentrated nitric acid given that it is 70% HNO3 by mass and has a specific gravity of 1.42?

First, calculate the mass of one liter of solution:

The solution is 70% by mass, so 100 g of solution contains 70 g of pure HNO3. The mass of HNO3 in one liter of concentrated solution is:

To find the number of moles in one liter of solution (the molarity):

===================================================

Quantitative Dilution of a Standard Reagent

A common calculation involved in solution preparation is the one used to make the correct dilution of a more concentrated solution to prepare a new. For example, what volume of 2.00 M HCl solution is needed to prepare a 100-mL solution that is 0.100 M?

The solution is then prepared by pipetting 5.00 mL of 2.00 M HCl solution and diluting it in a 100-mL volumetric flask as described previously.

Preparation of a Solution from a Solid Suppose a you wish to prepare one liter of a 20.0% (w/v) sodium chloride solution. Find the amount of NaCl needed.

"The percentage of mistake in quick decisions is no greater than in long-drawn-out vacillations, and the effect of decisiveness itself makes things go and creates confidence." --Anne O'Hare McCormick

Density and Porosity Measurements

2007-03-19T22:48:00.000-07:00

Note:

This procedure can be used to calculate the density and porosity of alloys and composite materials. For this particular article, I concentrate on metal matrix composite that uses fly ash ceramic particles as reinforcement phase and aluminium alloy A356 as a matrix phase.

The density of raw fly ash used in fabricating the composites was determined. First, a measuring cylinder was filled with distilled water to within 0.5 cm of the 100 ml line. It was placed in a bell jar and evacuated to a pressure of between -86 kPa to -96 kPa until the water stopped bubbling. This removes any entrapped voids. The flask was then removed and filled to the 100 ml mark with distilled water.

The weight of the water filled flask was then recorded as WT2.

15-30 g of fly ash (WT1) was weighed into a flask.

The sample was washed down in the flask with distilled water ensuring that the entire sample is under the water. The flask was filled to within 1-2 cm of the 100 ml line. The setup was then placed under a bell jar and evacuated to a pressure of -86 kPa to -96 kPa until the sample stopped bubbling. It was removed and filled to the 100 ml mark with distilled water.

The weight of the flask with sample and distilled water was then recorded as (WT3).

The density of the fly ash particles was then calculated from equation below. The same procedure was used in determining the bulk density of SiC particles.

The densities of the composites were determined by means of Archimedes’ principle. Archimedes’ principle states that when a body is immersed in a fluid, there is buoyant force acting upward on the body equal to the weight of the displaced fluid. The weight of the displaced fluid equals its volume when water is used (density of water = 1 g/cm3). The volume of water displaced is equal to the volume of the body immersed. All weights were obtained by means of an Ohaus ScoutTM Pro Balance SP2001 equipped with a spring balance. The as-cast material was suspended in air on the spring by means of a thin thread and its weight determined as W1. It was then completely submerged in a beaker of water and the new weight recorded as W2. Its density was then calculated from equation below.

Theoretical calculations, according to the rule of mixtures, were also used to determine the densities of the composites. This was obtained from rule of mixture equation as shown below [1].

where Vr is the weight ratio of fly ash, Pc the density of the composite, Pr is the density of fly ash and Pm the density of the unreinforced A356 alloy.The porosity of the test materials were also calculated from equation shown below [2].

References;

1. Smith, W.F., Hashemi. J. 2006. Foundations of Materials Science and Engineering.4th Ed. McGraw-Hill. New York
2. Indiana University. http://www.geology.iupui.edu/research/SoilsLab/procedures/bulk/Index.htm. Online on March 20, 2007.