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Monochrometer

2012-02-25T20:08:00.001-08:00

A monochrometer is frequently used to measure the spectral response of a light source. The purpose of a monochrometer is to convert a broad light spectral input into a narrow spectral output. Light enters the monochrometer through a slit that directs the input light to the first mirror inside the monochrometer. The firs lens (mirror) collimates the entering light and reflects it into a grating. The groves or line on the grating have a specific spacing that produces constructing and destructing interference of the reflected light from the grating. This process called dispersion separates the different colors of light (wavelengths) in space, reflecting each color at slightly different angles. The second lens (mirror) reflects the disperse light and focus a given light color into the outlet slit, allowing only a narrow band of light to escape the monochrometer. The following diagram illustrates this principle.

It is important to note that the resolution of the monochrometer is dependent on the grating and the outlet slit. The grating geometry and configuration limits the accuracy at which the individual wavelength can be separated in space. The outlet slit limits the how narrow of a band is allowed to escape the monochrometer.

Conjugate Heat Transfer With COMSOL Multiphysics

2012-02-21T21:51:00.001-08:00

Take advantage of this FREE webinar which explores heat transfer analysis in combined fluid and solid systems (conjugate heat transfer) using COMSOL multiphysics.

The webinar is offered on March 28, 2012. Sign up today!

Circuits and Electronics: 6.002x on MITx

2012-02-16T20:30:00.001-08:00

Are you looking to learn or to polish up your Electrical Engineering foundation? Do you want to expand your engineering knowledge and marketability by obtaining a certificate from one of the Top Engineering schools in the world? Or perhaps you just would like to have your name appear in a certificate issued by Massachusetts Institute of technology (MIT)? If you answer YES to one or more of these questions, then this opportunity is for you.

Take advantage of this FREE on-line MIT undergraduate course in Circuits and Electronics. Sign up today! Class starts March 5. Oh, did I mentioned that it is FREE! Check this video for more information.

How does a fluorescent light works

2012-02-15T19:44:00.001-08:00

A fluorescent light consist of a sealed glass tube filled with an inert gas at a low pressure. Inside the glass tube there is a small amount of mercury. On each end of the tube, there is an electrode. The two electrodes are connected to a high voltage AC electrical circuit. A ballast, which is connected to a standard AC voltage circuit, works as a transformer to increase the voltage across the electrodes.

When the lamp is turned on, the high voltage across the electrodes induces the movement of electrons from one electrode to the other. This flow of electrons vaporizes some of the mercury producing mercury gas. When the electrons collide with the mercury gas molecules, electrons on the mercury gas move towards a higher energy level. When the electrons on the mercury gas molecules return to the lower energy state, they release energy: Photons. This electromagnetic radiation emitted from the mercury is mostly ultraviolet and thus not visible to the human eye. A phosphor power coated onto the glass surface of the glass absorbs the emitted UV radiation and emits visible white light.

Reynolds Analogy

2012-02-12T21:21:00.001-08:00

During the later years of the 1800s several of the engineering challenges were related to the steam engines and their applications. One very important component of the steam engine is the Steam Boiler. The Steam boiler is the device in which heat transfer takes place. Several scientists studied and analyzed the heat transfer phenomenon that occurs between a solid and a liquid inter-phase. Up to this point it was known that the rate at which heat is transferred from a surface to a gas or vice versa is proportional to the difference in temperature between the two.

Professor Osborne Reynolds however, questioned the assumption that amount of heat transferred from a solid to a fluid is independent of the fluid motion. Reynolds argued that the cooling effect of wind is very different from the cooling effect of still air and that this effect is so evident that any hypothesis for heat transfer which does not takes fluid motion into account will not be of any accuracy. Reynolds begins to discover that the heat transferred by a fluid from a surface at a different temperature from that of the fluid (Neglecting radiation) is proportional to the internal molecular diffusion of the fluid at and near the surface. Reynolds notes that the rate of internal diffusion is mainly dependent of two things: The natural internal diffusion of the fluid at rest (property of the fluid) and the rate of diffusion caused by fluid currents like eddies (due solely to fluid motion). Professor Osborne then developed a mathematical relationship for the heat transferred to a fluid based on the effect of these two (fluid at rest and fluid motion) Reynolds explains that when a fluid flows in a duct which surface temperature is higher than that of the fluid, there will be a velocity at which after this velocity, the temperature of the emerging gas is constant and independent of the fluid velocity. This velocity, as explained by Reynolds, is the same as that at which the frictional force on the duct due to the fluid motion is proportional to the velocity square. Reynolds then points out that the relationships then for heat transfer and momentum transfer (related to frictional forces) are therefore related and thus presents an analogy between momentum transfer and heat transfer. According to Professor Osborne, the velocity at which this happens is very small and therefore this analogy has a very practical use.

The Reynolds Analogy can be applied to both laminar and turbulent flows since this analogy takes into consideration any fluid movement. However, the analogy becomes even better for turbulent flows since the coefficient of turbulent exchange is larger in those cases making the kinematic viscosity and the thermometric conductivity negligible (This makes a direct proportionality between shearing stresses and heat transfer). For laminar flows, the Reynolds analogy holds better for gases since the kinematic viscosity and the thermal diffusivity are of about the same order. (Making a once again a direct proportionality between shearing stresses ad heat transfer)

The Reynolds Analogy holds true for flows in which the temperature profile and the velocity profile are “similar” (including boundary conditions) and thus the heat and momentum are transported at the same rate. These conditions are met if: 1 the pressure gradient in the direction of the flow is zero, 2 the coefficient of turbulent exchange thermal is equal to the coefficient of turbulent exchange for the momentum (turbulent Prandtl number approximately equal to 1) or 3 if the kinematic viscosity is approximately equal to the thermal diffusivity (Prandtl number is approximately equal to 1). Therefore, for external flow (Laminar or turbulent), the Reynolds analogy holds true since the pressure gradient in the direction of the flow is usually zero. For internal flows, this is not the case, (dp/dx does not equals zero). However, for internal fully developed turbulent flows the pressure and temperature gradient along the flow direction is approximately constant. Therefore for internal, fully developed, turbulent flow, the momentum and heat transfer equation are similar if the conditions 2 and 3 discussed above are met.

Building Human Organs

2012-02-02T21:25:00.001-08:00

Here is an interesting National Geographic documentary about artificially building human organs. This is a great example of how the knowledge that we have learned and gained in all fields of science and engineering have come together to challenge the inner workings of our own body.

Proving that Cp/Cv=Kt/Ks

2012-01-31T20:46:00.001-08:00

Here is the thermodynamic proof that Cp/Cv=Kt/Ks. It is pretty straight forward if you use the cyclic chain rule.

I hope this helps some of you. I know this is a common question that is often asked in Physical Chemistry (P-Chem). If this is helpful and you would like to see the proof for another thermodynamic identity, leave me a comment and let me know!

Molybdenite

2012-01-30T21:38:00.001-08:00

Most us have heard about Silicon and how important Silicon is for generating our indispensable computer electronics. Some of us have even heard about Graphene, the one-atom thick carbon sheets that can possibly solve the issues related to reducing the size of current and future computer chips even further. However, have you heard about Molybdenite yet? Check out this article that explains how Molybdenite might be competing with Silicon and Graphene to be the next generation material for making future computer chips.

Jeep Grand Cherokee vs. Rubicon

2012-01-29T21:30:00.001-08:00

If you are looking for a great off-road car, jeep is always a safe bet. However, you might be wondering if you get the same off road performance out of a new Jeep Grand Cherokee compared to a new Rubicon. Well, I can tell you that both of these vehicles can take you far. However, if you are a serious off-roader, the Rubicon gives you the additional advantage to not only lock your front and rear axle differentials but also to disconnect your sway bar. What does sway bar disconnect mean? Check these following pictures which show how the sway bar disconnect of the Rubicon performs in comparison to the Grand Cherokee.

So, if you are looking for the best off road performance, the Rubicon gives you both sway bar disconnect and axle lock options.

These two options are great for keeping your traction and your wheels on the ground.

A Forward Step For Thermoelectric Materials

2012-01-28T13:09:00.001-08:00

Thermoelectric materials can directly convert heat into electricity as well as electricity into heat. Here is an interesting article review that briefly explains how researchers at RPI developed an easy and inexpensive process to make these materials using clever chemistry and nanostructured components. The full explanation of this work was published in a paper in Nature Materials. In addition to being easier and more cost effective, the new process can also result in higher energy conversion efficiencies. Thermoelectric materials can for example be used to recuperate energy lost in the form of heat (car exhaust for instance) back into useful electrical energy.

ForceEffect By Autodesk

2012-01-26T21:36:00.001-08:00

Here is another great app for your Iphone, Ipod Touch, or Ipad. ForceEffect is a FREE application developed by Autodesk that performs static force calculations (Yes, free-body-diagrams included).

This application is great for engineers at all levels (and architects too!). A static problem carried out by hand can take a significant amount of time. For instance, look at the following example:

While the same problem can be solved using ForceEffect in seconds, check it out:

It even gives you a report with the result summary:

Great app, I highly recommend it, good for checking your homework and brainstorming ideas for new design concepts.

16-Clue Sudoku Proven Not Possible

2012-01-25T21:37:00.001-08:00

Here is an interesting study that proved that a 16-clue Sudoku puzzle is not possible (no unique solution exists). It only took 7.1 million core hours ( Jan 2011 through Dec 2011) on a cluster with 320 compute nodes, and each node had 2 Intel Xeon Hex-core processors with 24GB of RAM. Although this may sound like a brute force simulation, the approach that this group took used a novel algorithm that drastically reduced the computation time, which was previously estimated to be 300,000 years on one computer.

Maple Player for iPad

2012-01-23T21:51:00.001-08:00

Here is a great app for your iPad. Maple Player for iPad is a FREE app that allows viewing and interacting with documents created on desktop Maple. This app basically brings the power of Maple computing to your mobile device. At this moment, the available documents in the app are somewhat limited and restricted to only those provided by Maple Player. However, the possibilities in the future could be endless especially if you could develop and use your own desktop Maple documents on your mobile device. Great work MapleSoft.

Give this app a try. In the mean time, I would like to see this app open for user defined documents as well as availability for the android systems. I wonder if we will be seeing something similar from MathWorks to bring MATLAB computing to the mobile market.

ONE-ON-ONE with Franklin Chang Diaz

2012-01-14T18:17:00.001-08:00

Maria Hinojosa interviews Dr. Franklin Chang Diaz, former NASA astronaut and world known rocket scientist. These are the words of wisdom from a man that has seen and experienced the world in a rather unique way. I really enjoy carefully listening to what Franklin has to tell us and I always find a lot to learn from him.

FC-72 Fluid Properties

2011-12-29T19:15:00.001-08:00

Here is simple excel spreadsheet that can be used to obtain FC-72 fluid properties as a function of temperature. Just change the temperature setting (number in red) and obtain the corresponding fluid properties. Note that not all fluid properties are changing with temperature. Just click on the figure below to download the file.

References:

[1] 3M, 2000, "Fluorinert Electronic Liquid FC-72," 3M Specialty Materials.

[2] Cardenas R., 2011, Submerged Jet Impingement Boiling Thermal Management. PhD Dissertation, Oregon State University, Corvallis, OR, pp. 249-250.

Free Curve Fitting Online

2011-12-04T14:49:00.001-08:00

Need a high quality 2D or 3D curve fit? You can use Excel for 2D curve fits of simple Exponential, Linear, Logarithmic, or Polynomial functions (up to 6^th degree). However, what can you do to curve fit more complex 2D or even 3D functions without doing the coding yourself? Check out www.zunzun.com. This Free online curve fit service offers a broad range of functions to curve fit to in 2D and 3D. Don’t know which function fits your data best? Let the function finder find the best fits for your data and give you your top options. The curve fit results include an extensive statistical report. The curve fit equation is also provided in common source codes languages such as C++, Java, Python, C#, SCILAB, MATLAB, and VBA so that you can easily copy and paste it into your application. You can download all the information resulting from your fit into a single PDF document. Best of all, it is easily accessible online and IT’S FREE! This tool is great for practical and research applications.

FC-72 Viscosity

2011-11-27T14:30:00.001-08:00

Perfluorohexane (C₆F₁₄), more commonly known as FC-72, is a commonly used highly wetting dielectric fluid for electronics cooling applications. This fluid belongs to the Fluorinert^TM line of electronic liquid coolants sold by 3M^TM. As with any coolant, accurate knowledge of the thermo-physical properties of the fluid and their temperature dependence is very important for the design, development, and implementation of heat transfer applications. Fortunately, 3M has provided us with important thermo-physical properties for this fluid [1]. However, the liquid dynamic viscosity as a function of temperature is not explicitly given here (this property is also not available in EES for this particular fluid). I contacted 3M and obtained a mathematical expression that can be used to compute the liquid dynamic viscosity as a function of temperature [2]. I compared the values predicted by this expression with the tabulated value in [1] at 25 ^oC and also with measurements taken by Morgado et al. [3]. This comparison is shown in the figure below:

As the figure shows, the agreement between the 3M equation and the data by Morgado et al. [3] is good with a maximum difference of about 5.7 % at temperatures above 40 ^oC. Note that the variation in dynamic viscosity with temperature is significant and therefore, it must be taken into consideration. For comparison, the figure above also shows the variation of dynamic viscosity of water with temperature [4]. Note that the temperature dependency of the dynamic viscosity is similar for both fluids. This indicates that the temperature variation seen for FC-72 is not uncommon. For the mathematical expression provided by 3M please see reference [2]. For convenience, the table below tabulates the values of liquid kinematic viscosity, liquid density, and liquid dynamic viscosity for FC-72 in 1 ^oC increment from 0 ^oC to 56 ^oC.

T	ν	ρ	μ
[ ^oC ]	[ mm²/s ]	[ kg/m³ ]	[ mPa-s ]
0	0.543	1740.0	0.946
1	0.535	1737.4	0.930
2	0.527	1734.8	0.914
3	0.519	1732.2	0.899
4	0.511	1729.6	0.884
5	0.504	1727.0	0.870
6	0.496	1724.3	0.856
7	0.489	1721.7	0.842
8	0.482	1719.1	0.829
9	0.475	1716.5	0.815
10	0.468	1713.9	0.803
11	0.462	1711.3	0.790
12	0.455	1708.7	0.778
13	0.449	1706.1	0.766
14	0.443	1703.5	0.754
15	0.437	1700.9	0.743
16	0.431	1698.2	0.732
17	0.425	1695.6	0.721
18	0.420	1693.0	0.711
19	0.414	1690.4	0.700
20	0.409	1687.8	0.690
21	0.404	1685.2	0.680
22	0.398	1682.6	0.670
23	0.393	1680.0	0.661
24	0.388	1677.4	0.652
25	0.384	1674.8	0.643
26	0.379	1672.1	0.634
27	0.374	1669.5	0.625
28	0.370	1666.9	0.616
29	0.365	1664.3	0.608
30	0.361	1661.7	0.600
31	0.357	1659.1	0.592
32	0.353	1656.5	0.584
33	0.349	1653.9	0.577
34	0.345	1651.3	0.569
35	0.341	1648.7	0.562
36	0.337	1646.0	0.555
37	0.333	1643.4	0.548
38	0.329	1640.8	0.541
39	0.326	1638.2	0.534
40	0.322	1635.6	0.527
41	0.319	1633.0	0.521
42	0.316	1630.4	0.514
43	0.312	1627.8	0.508
44	0.309	1625.2	0.502
45	0.306	1622.6	0.496
46	0.303	1619.9	0.490
47	0.300	1617.3	0.485
48	0.297	1614.7	0.479
49	0.294	1612.1	0.473
50	0.291	1609.5	0.468
51	0.288	1606.9	0.463
52	0.285	1604.3	0.458
53	0.282	1601.7	0.452
54	0.280	1599.1	0.447
55	0.277	1596.5	0.442
56	0.275	1593.8	0.438

Note: To copy the above table into Excel for example, first copy the table and some text from the previous paragraph into a Word document. From the word document, copy the table and paste it into Excel.

References:

[1] 3M, 2000, "Fluorinert Electronic Liquid FC-72," 3M Specialty Materials.

[2] Cardenas R., 2011, Submerged Jet Impingement Boiling Thermal Management. PhD Dissertation, Oregon State University, Corvallis, OR, pp. 249-250.

[3] Morgado, P., Laginhas, C., M., Lewis, J., B., McCabe, C., Martins, L., F., Filipe, E., J., 2011, “Viscosity of Liquids Perfluoroalkanes and Perfluoroalkylalkane Surfactans,” J. Phys. Chem. B, 2011, 115 (29), pp 9130–9139

[4] Klein, S., A., 2010, "Engineering Equation Solver (EES)," F-Chart Software

Do Siphons Really Suck?

2011-10-11T20:50:00.001-07:00

The fundamental forces involved in a siphon have been a topic of debate for many years. In the past, it was believed that atmospheric pressure is the main force which pushes fluid flow in a siphon and that a siphon cannot “suck” fluid without the aid of atmospheric pressure. However, a recent publication from The School of Chemistry at The University of Nottingham has proven this general belief wrong. Here is a picture of the abstract of the publication.

Click Here for the full publication. If you do not have access to this publication or do not want to spend the time to read it, I recommend watching this video from our Friends at Periodic Videos. This study found that siphons really do suck (a negative pressure is obtained from Bernoulli’s equation) and this is proven by siphoning fluid in a vacuum. The results of this simple experiment are so important than even the Oxford English Dictionary had to fix the definition of the word “Siphon” that they used since the early 1900’s. The study suggests that molecular cohesion and gravity are the main contributing forces for a siphon to work.

Reference:

Boatwright, A., L., Puttick, S., Licence, P., 2011, “Can a Siphon Work In Vacuo?”, Journal of Chemical Education,88 (11), pp. 1547-1550.

Desmos Graphing Calculator

2011-07-02T16:48:00.001-07:00

Need a quick easy way to generate high quality 2D plots. Check out Desmos free online graphing calculator. This is a browser-based web calculator that allows you to easily create 2D plots. It handles Cartesian and Polar coordinates as well as simple implicit equations and summations. The interface is user friendly and quite intuitive. Plot equations within seconds and see how they look even before you attempt to work with them on your next math homework assignment. Best of all, it is FREE! Here are some sample plots that I generated using Desmos free online graphing calculator.

The Spruce Goose

2011-06-05T19:49:00.001-07:00

If you like planes or if you have seen the movie “The Aviator” then you have heard about the Spruce Goose.

The Spruce Goose is the biggest wooden plane/flying-boat ever built and its wingspan is the largest of all planes in history (yes, even larger than a Boeing 747-400).

Because of it size and weight, it took eight 3,000 horse power engines to make it fly.

The Spruce Goose was designed and constructed by Hughes Aircraft Co., and it was only flown once by its designer Howard Hughes. In the movie “The Aviator” this is the large plane that Howard Hughes flies toward the end of the movie.

Often referred as the Hughes Hercules, the Spruce Goose is currently located at the Evergreen Aviation & Space Museum in McMinnville, OR. The design, construction and successful flight of the plane was an important milestone in the aviation industry and for this reason, in 2002 the American Society of Mechanical Engineer (ASME) declared the plane as a Historical Mechanical Engineering Landmark.

For all of you interested, I strongly recommend to go see this plane to get an idea of all the engineering challenges that were overcome to make it fly. If you are a mechanical engineer, this plane is a must see. In addition to the Spruce Goose, the Evergreen Aviation & Space Museum offers a wide range of attractions in aerospace technology and if you are interested you can easily spent an entire day here.

Decay of Isotropic Turbulence in a Box

2011-05-15T19:36:00.001-07:00

A classical example problem in turbulence is that of decay of isotropic turbulence in a box. This problem was proposed by Tennekes and Lumley [1] at the end of chapter 1 and it reads as follow:

I have solved this problem at least twice while studying turbulence and I am sure that many of you have also solved or will solve this problem. Therefore, I decided to post my solution to the problem. For the derivation of an expression for the decay of the kinetic energy as a function of time using the inviscid estimate we have the following:

For Reynolds numbers (Re) less than 10, a viscous dissipation term is used. The value of C in the suggested expression can be found by enforcing the dissipation rate to be continuous at Re=10 :

To derive an expression for the decay of the kinetic energy during the final period of decay, Re<10, we can use the same methodology as used for the initial period of decay, Re>10.

One can use equation (7) to find out the time it takes to enter the final period of decay. The result comes out to be about 19,997 s or about 5.55 hr for the values given (this is also the time at which t*=0). The following semi-log plot shows the decay of turbulent kinetic energy as a function of time as predicted by equation (8) and (18) using the values provided.

The solution of this problem assumes that the wall effects are negligible. At high Re this assumption is correct since the viscous dissipation is much smaller than turbulent dissipation. However, as the Re decreases, the effect of viscous dissipation at the wall becomes important and this is why we are including a final period of decay which includes the effect of the fluid viscosity.

References:

Tennekes, H., Lumley, J., L., 1972, A First Course in Turbulence, MIT Press

Rigoberta Menchú Book

2011-05-02T23:16:00.001-07:00

A few weeks ago I had the opportunity to meet 1992 Nobel Peace Prize winner Rigoberta Menchú Tum. Rigoberta, who was born in Guatemala, is of Mayan Indian descent and over the years she has overcome social, political, educational, and economical buriers to become an active advocate for the rights of the different ethnic groups in America. For all her dedication and hard work, she was also awarded the Prince of Asturias award in 1998. During my visit with her, she signed her book for me and included a short dedication. Here is her note!

Longitudinal Modes in a Laser Resonant Cavity

2011-02-13T00:29:00.001-08:00

A laser can only lase at longitudinal modes which are an integer multiple of half wavelength and that fit within the laser resonant cavity geometry. There are an infinite number of integer multiples of cavity length for any fix length, providing infinite number of possible lasing modes. However, a particular laser gain medium does not have gain at all frequencies, but instead there is a narrow gain profile that describes the gain as a function of longitudinal modes. The resulting laser spectrum corresponds to the set of possible modes that fit within the laser cavity geometry and that fall inside the gain profile of the laser gain medium. Therefore, the light output from a laser cavity is not perfectly monochromatic, but instead there are several modes represented. However, the spacing between the longitudinal modes is so small that for most purposes, laser light is referred as monochromatic light. Nevertheless, it is possible to measure the longitudinal modes from a laser source. Here are some pictures of the equipment that was used in one of my labs to measure these modes from a Helium-Neon Laser (pink color light at approx. 632.8 nm).

Complete Experimental Set-Up on an Optical Table

Piezoelectric Scanning Interferometer

HeNe Laser, Interferometer, Photo-detector, and Some Mirrors

Oscilloscope Reading

As seen in the Oscilloscope picture above, at least three modes were detected, which is more less the number of modes expected for this particular laser which has a typical bandwidth of 1.5 GHz.

It is important to mention that small changes in the laser resonant cavity length, even those caused by thermal expansion or acoustic effects, can result in significant changes in the longitudinal mode characteristics of a laser. Frequency-stabilized lasers actively control the laser cavity length to keep the longitudinal modes at constant frequency.

Here are some more pictures from different angles:

Dryden Drop Tower

2011-01-20T21:58:00.001-08:00

I recently had the opportunity to visit the Dryden Drop Tower located in Portland State University. This facility is a great research resource for investigators looking to study different phenomena in a micro-gravity environment. Several areas of research such as fluid mechanics and heat transfer benefit greatly from drop tower facilities like this one, to further develop our understanding on these important fields. The Dryden Drop Tower is without a doubt a state-of-the-art drop tower facility and it will significantly impact micro-gravity research in the state of Oregon. The tower height is about 31m with an approximate free fall distance of 22.2 m for an anticipated low-gravity time just over 2 seconds. The facility is equipped with a drag shield to reduce the effect of hydrodynamic drag on the experiments and milli-g testing gravity levels are anticipated. The average deceleration for the falling experimental capsule is about 8.5g. This drop tower also includes an automated retrieval system which significantly helps expedite the repetition of experiments. For more information check out these links and make sure to check some of the pictures I have included.

Dryden Drop Tower FAQs

Dryden Drop Tower Website

Major Financial Contributors

Drop Tower seen from above

Drag Shield

Foam Pads + Neon Lights

Tracks

Pneumatics and Data Control

Live Webcam on Network

Fluid Experiment

Retrieval System Motor

Release Mechanism

Braking System

Computer Controls

Micro-Structures on Metal Alloys

2011-01-15T20:26:00.001-08:00

The binary phase diagram for a Cu-Zn alloy is shown in the figure above. A phase diagram of an alloy is a useful tool that allows us to find the relative amount of the phases present and their respective composition for a fixed thermodynamic state of the system at equilibrium. However, the time scales required to achieve thermodynamic equilibrium can be very large (especially at low temperatures). Therefore, non-equilibrium structures are often encountered.

For example, let’s look at the grain micro-structure of four specimens of a copper-42% zinc alloy which have been obtain through different cooling paths.

The first specimen shown above was sand casted from a super heated liquid and was allowed to cool at ambient temperature.

The second specimen shown above was annealed at 800 ˚C for 1 hr and then was quenched rapidly with water.

The third specimen shown above was annealed at 800˚C for 1hr., furnace cooled to 600˚C and then it was water quenched.

The forth specimen shown above was annealed at 800˚C for1hr followed by a slow furnace cooled to room temperature.

From these pictures, one can easily see that the grain micro-structure of an alloy can be very different even though the composition is fixed. This is due to non-equilibrium structures that are captured through heat treatment and rapid cooling of the alloy (as often done in the metal industry). Non-equilibrium structures can significantly affect the properties of metal alloys. Therefore, it is important to understand the kinetics involved in non-equilibrium processes.