User:Raleway

Materials Science tests knowledge of the properties and characteristics of metals, ceramics, polymers and composite materials, with a focus on material characterization techniques, intermolecular forces, and surface chemistry.

Rules Review
Each pair of competitors from a team will be allowed 5 front and back pages of cheat sheets. There will a lab section unless listed otherwise, and students must bring safety apparel themselves or be unable to do the lab due to safety concerns. Students will be tested on the field of Materials Science and topics are limited to those listed below, though the scope of each topic is nearly unlimited.

Tips and Tricks
Although some may be astounded by the number of cheat sheets allowed, Materials Science covers a vast amount of knowledge. The extent of each topic is nearly unlimited and you will need to know the topic well and not rely on your cheat sheet for basic knowledge. Graphs are especially important to have, but basic ones explaining concepts should not be required and will only take space. It is recommended to use Google Docs and splitting the page into three columns, and decreasing margins and spacing as far as possible as your printer will allow. Also, although many teams use very different styles for font and size, Times New Roman, size 6, works the best. Also, being dependent on the cheatsheet is a no-no; doing so will make a competitor only as good as the cheat sheet is. However, know the cheat sheet like the back of one's hand- know where each page is and cover it with a screen protector to allow of labeling of special sections, page numbering, and protection from lab work. If unable to always have updated version of cheat sheet and forced to use online version, DO NOT USE the find function- it is a crutch and will only be an impediment to using a cheat sheet.

General Properties of Material Classes
Although this section can be included on the cheat sheet, only the bare-bones should be on it. Most of it should be meomrized, if not all, for easy and fast recall during the test.

Metals
Mechanical properties: [BOLD NEEDED] Stiff, strong, ductile, resistant to fracture, good conductors of electricity and heat and make them lustrous, Fe, Co, Ni have good magnetic properties. 'Diamagnetism:' Present in all materials when they repel magnetic fields(only observed in pure diamagnetic materials). There are no unpaired electrons 'Paramagnetism:' There are unpaired electrons that align their magnetic moments in any direction and when an outside magnetic force is applied, the magnetic moments align themselves in this direction, enhancing it 'Ferromagnetism:' They also have unpaired electrons, but magnetic moments align themselves parallel to each other and to the magnetic field to maintain a lowered state. The magnetic moments line up even if no magnetic field is present. Every ferromagnetic material has its own curie temperature, above which it loses its ferromagnetic properties (occurs in iron, nickel, cobalt and their alloys)

Ceramics
Relatively stiff and strong, hard, brittle, susceptible to fracture, insulative to heat and electricity and more resistant to high temps and harsh conditions than metals and polymers, transparent, translucent, or opaque and some oxide ceramics exhibit magnetic behavior

Polymers
Low density, not as stiff or strong as metals and ceramics, extremely ductile and pliable, chemically inert in a multitude of environments, low electrical conductivity and are not magnetic. Soften or decompose at modest temperatures. The degree of polymerization: The degree of polymerization, or DP, is usually defined as the number of monomeric units in a macromolecule or polymer or oligomer molecule. For a homopolymer, there is only one type of monomeric unit and the number-average degree of polymerization is given by '[Insert equation]' where Mn is the number average molecular weight and M0 is the molecular weight of the monomer unit

Composites
Dependent on constituent parts and usually enhanced with fibers, such as strength and ductility, dependent on fiber length, properties enhanced when fibers are aligned as opposed to randomly ordered, smaller fibers are stronger, matrix should have lower ductility and young’s modulus than fibers, metal matrixes can be used at high temps, ceramic composites are resistant to degradation, but are brittle,carbon-carbon composites have high tensile strength, resistance to creep, fracture toughness, strength, and thermal conductivity, laminar composites have high strength in the 2D plane, sandwich panels core of sandwich panels have low elasticity, lightweight, and high shear strength, and the sheets have to resist tension and compression.

Crystal Structures
Ionic

Covalent:

Crystalline:

Semi-Crystalline:

Amorphous:

Atomic Packing


Face Centered Cubic:

Also known as cubic close packed.

In the FCC cell, atoms are located at each of the 8 corners as well as in the centers of each of the 6 faces.

FCC follows an ABCABC close packing pattern - there are 3 repeating layers, where the atoms of the third layer are located above holes in the first and second layers.

FCC is the most dense of the cubic packing arrangements, with an atomic packing factor of 0.74. Each unit cell contains 4 atoms and has a side length of [math]A = 4R/\sqrt{2}[/math].

Each atom in the FCC matrix has a coordination number of 12.



Body Centered Cubic:

In the BCC cell, atoms are located at each of the 8 corners as well as in the center of the cubic cell.

BCC is less dense than FCC, with an atomic packing factor of 0.68. Each unit cell contains 2 atoms and has a side length of [math]A = 4R/\sqrt{3}[/math].

Each atom in the BCC matrix has a coordination number of 8.



Hexagonal Close Packing:

HCP is another close packed arrangement.

The HCP cell is composed of two hexagons of 6 atoms each, an additional atom in the center of each hexagon, and a triangle of atoms in between the two hexagons.

HCP differs from FCC in that HCP follows an ABAB packing pattern - there are only 2 repeating layers, where the atoms of the third layer are located above the atoms of the first layer, not above gaps.

HCP also has an atomic packing factor of 0.74, the maximum possible. Each unit cell contains 6 atoms and has two parameters, A (side length) and B (height).

Each atom in the HCP matrix has a coordination number of 12.



Simple Cubic:

Simple cubic is a very basic arrangement, only containing atoms at each corner of the unit cell.

SC is the least dense, with an atomic packing factor of 0.52. Each unit cell contains 1 atom and has a side length of [math]A = 2R[/math]

Each atom in the SC matrix has a coordination number of 6.

Atomic Packing Factor (APF):

The atomic packing factor describes the amount of space occupied by atoms.

For example, in the simple cubic packing, each cell has side length 2R and contains 1 atom of radius R.

The volume occupied by the atom is [math](4/3)\pi *R^3[/math], while the total volume is [math](2R)^3 = 8R^2[/math]

The fraction of space occupied by atoms is [math](4/3)\pi *R^3/8R^3[/math] = [pi/6] = 0.524, exactly the amount listed above.

This equation will work for any of the other crystal structures assuming the correct side lengths are used.