True False - Fill in the blank. If the statement is false, please identify each

Question

True False - Fill in the blank. If the statement is false, please identify each false statements and correct them. Thermoplastic materials are polymers that don't have a melting point and can be sintered. Sintering is similar to melting and is used to transform solid objects to powders. It can be used to make porous as well as fully dense objects and it usually can be accomplished at _________ of the melting temperature. The driving force for sintering is the increase in surface free energy that is caused by the elimination of porosity. Bragg' Law can be used to determine the spacing between atoms in a non-crystalline material. If an x-ray diffraction peak occurs at 60 degrees two theta, the d spacing would be _____________ nm (Assume that the wavelength is 0.154 nm). The (1 1 1) direction is perpendicular to the [1 0 0], [0 1 0], and [0 0 1] planes. The grain boundaries that make up the final micro structures in a sintered powder compact are examples of point defects. It impossible to achieve a complex material micro structure in which the interior grains are small and equiaxed and the exterior grains are larger and anisotropic. Passivation is uncontrolled corrosion that leads to failure in metallic implants. In a metal implant, you can simultaneously achieve higher strength and higher ductility by heat treating the sample to anneal out stresses. Phase diagrams are very useful in determining the types of phases that form when metals are mixed together. Ni and Cu are examples of two metals that can form a complete solid solution just like Pb and Sn and both of these binary phase diagrams show a eutectic and have a eutectic microstructure which is crisscrossed (plaid) pattern. Using a phase diagram for Ni and Cu from your notes, the relative amount of solid and liquid present at a Temperature of 850 C and a composition of 50% Ni is ___________.

Explanation / Answer

1st statement is partially false. Thermoplastics have distinct melting point and vary according their varieties. And they can be sintered

2nd sentence is true.

Sintering process is making porous or powder form of materials without going to melting temperature. Yet the heat is applied but not too much to cross the melting point, other way is using the pressure method.

So the 3rd sentence fill in the blank is below.

The driving force is to decrease surface area and lowering surface free energy. So the 4th sentence is false

The 6th sentence using bragg’s law n = 2d sin, where =0.154nm. =30 and n=1

So d =0.214 nm.

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