Materials Definition and 989 Threads

Why do radioactive materials decay in half-lifes exponential decay and not over mean time, i.e. like a Bell Curve

Hi. So, I took the general GRE the other day and did crappy on the Quant. This worries me. I'm applying to Materials Engineering PhD programs soon. I'd like to get some opinions of how deep of a ditch I've dug for grad school, or how much this retracts from the rest of my credentials. Do I stand...

So I'm currently a senior undergraduate nuclear engineer at a respected university and I've been considering getting my Ph.D for a while now. I'm having difficulty deciding on a specific research area, however. I'd like my research, optimally, to be applicable outside the nuclear sector as well...

Hello, Around 18 months ago I did a search on buying mete materials & came up with numerous results. This time I searched & found nothing. So I am posting this to find out where (on the internet) I could purchase meta materials. I am searching for a meta material 3 to 4 inches in diameter with...

I have read that Young's Modulus, like spring constant, is a measure of stiffness (how hard it is to deform a material). Though apparently, Young's Modulus is a way of doing so that applies only to the material and not its shape, where a spring constant value depends on the dimensions of the...

Hi PF, As you all may know, the densest naturally occurring material is Osmium, which is 22.59 g/cm3...but it also costs $100/g. Is there any manmade dense material that is 25 g/cm3 and under $1/g? I know lead is the "dense" material to buy in bulk, but even that is only 11 g/cm3. Any help...

I need to cool a slow moving small flow of hydroponic plant water, at most 1000 ppm nutrients, with a pH of typically around 6. I'd like to use aluminum or copper heat sink directly in that fluid stream to drop temp 10 or 20 degrees F down to 50-60F neighborhood. My concern is I don't want...

Any suggestion?

I recently got my B.S. in Physics and began applying to various entry-level analytical jobs. An investment management firm is going to give me a 3 hour test online. The subjects are as follows: Brokerage Firm Case Study Excel Data Proofing Logic I feel comfortable self studying vlook ups and...

I am a high school student experimenting with the Verdet constant of materials and how it affects the polarization of light in magneto-rotation. I have trouble acquiring the proper materials for this experiment. Here is what I have so far: -AC/DC Power Supply -Gaussmeter -Optical laser under...

Hello, I am wondering if getting a mechanical or materials PhD will grant me more access to industrial automotive research opportunities. I understand the difference between materials and mechanical, but I am wondering if there's greater opportunity in materials research related to automotive...

Hi everyone, first time poster here, I'm studying for a Materials exam, one of my weakest subjects and this question is causing me a lot of pain: Beryllium (Be) is a HCP metal with an atomic weight of 9 g mol-1 , an atomic radius of 0.112nm and a density of 1850 kg m-3 . Calculate its c/a ratio...

Hello Forum, Thermochromic materials , either LC or leuco dyes, change color with a change in temperature. They are commonly available and not expensive. Photochromic materials, instead, change color when illuminated by UV light (clear to color or viceversa?). Considering that light (visible...

More specifically, if I have a 100 degree F hot rock in an insulated box with reflective sides and I want it to radiate it's heat away to cooler outer space at night through its open top, what type of material or film could I cover the box with that would assure no air passed in or out, but that...

Has anybody used thin RF absorbing sheets or tiles to attenuate RF radiation off of PCB assemblies? I've seen it used many years ago, and I have a 5GHz application that I'd like to try an absorbing sheet on. The PCBA is a few cm on a side, and the sheet or sheets would be applied directly on...

Could a polymer that acts like a photoresist (either positive or negative) also be a thermoplastic. Do you have any ideas on what polymer/mechanisms could be used to achieve this?

Good evening. I've got stuck in this question from my book of Mechanics of Materials by Beer and Johnston about torsion. The allowable shearing stress is 15 ksi in the 1.5-in.-diameter steel rod AB and 8 ksi in the 1.8-in.-diameter brass rod BC. Neglecting the effect of stress concentrations...

I know it is many threads here about this topic and I've read most of them. But I have next questions, next step :) 1) (Summary) Does it true that composition and structure drive an energy levels of electron and it absorbs such wavelengths which correspond to jump to upper (not implicitly...

Why are some materials behave more like black-bodies than others? What does it mean a "perfect" radiator and absorber? All objects give off 100% of the heat energy given to them eventually if they are at the same temperature as their environment...right?

Dear all, Interested in change phase, I would like to set a simulation to understand the multiphysics phenomena of heat storage in a shell and tube tank between hot water as the heat transfer fluid and a PCM ( phase change material) using the commercial CFD software Fluent. The purpose is to...

This unfinished high rise condo/hotel in gulf of Thailand has been in incomplete state for about 3 years. How long can the materials last in terms of the project being completed ?

Does anyone know of any optically transparent (and preferably thin) piezoelectric materials I could use for a science fair project converting pressure on the glass of touch screens to electrical energy?

For any rod Poisson's ratio should be same i.e. 0.5 (we get this ans if we find (dr/r) / (dl/l) ) assuming that volume of rod always remains constant... But why it is not so ? We have different ratios for different materials..

Hello again PF! I was accepted to an REU for this summer. I was just hoping to get some nuggets of good advice for what to do to be successful. Only thing I keep telling myself is to work HARD so I can make a good impression and hopefully contribute to a successful project. Any good advice...

We will be racing a 55g model F1 car on the 28th of April in the F1 in Schools national finals however at the regional finals we came across a problem. The car traveled 24 meters in 1.1 seconds but broke on impact with the towel used to stop the car at the end of the race. We need to find a...

Hi, I understand stress, strain but when it moves on to 3 dimension anisotropic materials using tensors and stiffness matrices I get confused with einstein's notation. can someone please help me out in this regard to undrstand how stiffness and compliance matrices get reduced for monoclinic...

Homework Statement This problem propped in my head yesterday related to a project I'm working on (not homework, I'm not in school, but I thought this was the best place for it) and I just can't figure out how to crack it! If we have a large plate made up of nxn smaller plates, what is the...

We are trying to come up with a frame for a drone (4' in diameter) that could withstand the pressure and high winds of a super cell. I can't say much more on it at the moment until the project is complete but I would like to know if there are any non-conductive materials that could withstand...

Hello everyone, I am currently enrolled in a Materials Engineering course, but I recently found out that I might be allowed to switch to Biomaterials Engineering, which sounds a bit more appealing to me, since, at the moment, I am interested in a career in the pharmaceutical sector. However...

Hi I've started the simulation of a vcsel structure with lumerical software. I've got a problem in solution mode I don't know how i can define the quantum wells materials and features for the software .. Let me give you an example of its structure : As the example says i have to use 7 layers in...

Can Magnetically inclined materials (possibly non magnetic) be superheated beyond their phase changing point while exposed in an intense magnetic field then while still under perhaps greater Mag field until cooled; affect atomic magnetic orientation and/or alignment of moments and spin...

I will qualify my questions /comments with the fact that I am not a materials science , chemistry, atomic physics, or electrochemical, engineer or scientist. that being said, I am thinking from atomic and material domain perspective that a material such as copper, chromium, nickel, bismuth . . ...

I was wondering what materials will stay most unblemished after the 1000s of centuries of unforeseen wear such as corrosion, salt water, grinding, etc. Materials that are not very rare like gold or silver. I have looked into it and so far I've come across titanium, stainless steel, and their...

Hi PF, As you may know, is the the elasticity/stiffness tensor for isotropic and homogeneous materials characterized by two independant material parameters (λ and μ) and is given by the bellow representation. C_{ijkl} = \lambda\delta_{ij}\delta_{kl} + \mu(\delta_{ik}\delta_{jl} +...

Is carbon nanotube the only material found that would make a faster and more efficient computer or are there other materials or methods found that would make a faster computer as well? Here is an article on carbon nanotube

In griffith's introduction to electrodynamics, he goes over dispersion/absorption using the oscillating electron model. I understand the theory but I am confused about how it relates to how materials appear to us. He says that the material will be practically opaque in the frequency range with...

I am trying to find out what material that cowhide or vulcanized rubber will bounce off the most? (High school student working on a patent, so really not too experienced with materials engineering.)

Hi, About elastic and plastic materials: All materials exhibit elastic deformation up to a certain limit, beyond which they exhibit plastic deformation. Some materials, such as plasticine, have extremely tiny elastic regions, so we call them 'plastic materials'. Some, like rubber, have large...

This system consists of a shaft that is connected to a motor that is rotating at 200rpm. The whole shaft consists of two gears. The input power of the system is 500W. Is there a way i can calculate how exactly i can find the best material for my gears that is able to withstand the input power...

Hello everyone, I have been reading this forums for a while, and today I made an account! Anyway, I am currently a first year Materials Engineering student. Whilst I know it is still very early to start thinking about postgrad, I realized that my interest lies within...

Hey guys I need your helps. Show you as pictures.

What is the material that doesn't diffract x rays ?

Hi, I'm looking for some help regarding heat transfer through some sandwiched materials. We have a pneumatic cylinder with the stainless steel 303 cylinder rod attached to a block of aluminium 6082 t6 50mm high x 40mm wide x 10mm deep. This block is attached to a block of polyurethane, shore...

Hi, I need to run wind tunnel tests on a simple shape which will be made of foam whilst the skin friction is to be negligible. Is there easy ways of cover the model to achieve this ? thanks

Homework Statement Member AD of the timber truss (shown in attachment) is framed into the 100 x 150 mm bottom chord ABC as shown in the insert. Determine the dimension "a" that must be used if the average shearing stress parallel to the grain at the ends of chord ABC is not to exceed 2.25...

Why to calculate the mechanical properties of a material should be used Sigma bands?

Hi all, I have an urgent question.. I am currently applying to materials science PhD, and double majoring in physics and applied math. I haven't had much time to study for my (intro) discrete math course and will likely get a C... I already have a C from sophomore year statistical physics...

I solved the equilibrium equations and found that link BD is in tension while link CE is in compression, but my resulting answers for normal stress were wrong. The solutions show that the cross area to be used for normal stress at links BD and CE should be different. Link BD should incorporate...

I'm an aspiring aerospace engineer. I know that Ada is a language used in many planes today, but I can't find anything to learn about Ada for avionics--I couldn't find books or tutorials. Do any of you guys have any recommendations on how to go about this? I'm very interested in teaching myself...

So, i am trying to decide between materials science or engineering, i understand the difference, and i am preferring engineering due to the better career perspective, specially that i am from a country where research isn't their first priority, but i am still very interesting in research and...