Name: Yeong Kar Fai MARTIC NO: A148342 Subject: Kkkr2343 Material Engineering

NAME: YEONG KAR FAI
MARTIC NO: A148342

SUBJECT: KKKR2343 MATERIAL ENGINEERING
DIAMOND
In 1772, Antoine Lavoisier used a lens to concentrate the rays of the sun on a diamond in an
atmosphere of oxygen, and showed that the only product of the combustion was carbon dioxide,
proving that diamond is composed of carbon. Later in 1797, Smithson Tennant repeated and
expanded that experiment, by demonstrating that burning diamond and graphite releases the
same amount of gas, he established the chemical equivalence of these substances.
The elements existing in diamond are carbon only (repeating units of carbon). Diamond is a
metastable allotrope of carbon, where the carbon atoms are arranged in a variation of the facecentered cubic crystal structure called a diamond lattice. Diamond is renowned as a material with
superlative physical qualities, most of which originate from the strong covalent bonding between
its atoms. In particular, diamond has the highest hardness and thermal conductivity of any bulk
material. Those properties determine the major industrial application of diamond in cutting and
polishing tools and the scientific applications in diamond knives and diamond anvil cells.
Because of its extremely rigid lattice, it can be contaminated by very few types of impurities,
such as boron and nitrogen. Small amounts of defects or impurities (about one per million of
lattice atoms) color diamond blue (boron), yellow (nitrogen), brown (lattice defects), green
(radiation exposure), purple, pink, orange or red. Diamond also has relatively high optical
dispersion (ability to disperse light of different colors).
What promotes bonding?
The electron configuration of diamond (carbon) is 1s22s22p2. A diamond is a transparent crystal
of tetrahedrally bonded carbon atoms in a covalent network lattice (sp 3) that crystallizes into the
diamond lattice which is a variation of the face centered cubic structure. Diamonds have been
adapted for many uses because of the material's exceptional physical characteristics. Above 1700
C (1973 K / 3583 F) in vacuum or oxygen-free atmosphere, diamond converts to graphite; in

air, transformation starts at ~700 C.
What types of bonds are there?
In diamonds, the bonds form an inflexible three-dimensional lattice, whereas in graphite, the
atoms are tightly bonded into sheets, which can slide easily over one another, making the overall
structure weaker. In a diamond, each carbon atom is surrounded by neighboring four carbon
atoms forming a tetrahedral shaped unit.
What properties are inferred from bonding?
Hardness
Diamond is the hardest known natural material on both the Vickers and the Mohs scale.
Diamond's hardness has been known since antiquity, and is the source of its name. Diamond
hardness depends on its purity, crystalline perfection and orientation: hardness is higher for
flawless, pure crystals oriented to the <111> direction (along the longest diagonal of the cubic
diamond lattice). Therefore, whereas it might be possible to scratch some diamonds with other
materials, such as boron nitride, the hardest diamonds can only be scratched by other diamonds
and nanocrystalline diamond aggregates.
The hardness of diamond contributes to its suitability as a gemstone. Because it can only be
scratched by other diamonds, it maintains its polish extremely well. Unlike many other gems, it
is well-suited to daily wear because of its resistance to scratchingperhaps contributing to its
popularity as the preferred gem in engagement or wedding rings, which are often worn every
day. Diamonds are able to withstand crushing pressures in excess of 600 gigapascals (6 million
atmospheres).
Surface property
Diamonds are naturally lipophilic and hydrophobic, which means the diamonds' surface cannot
be wet by water but can be easily wet and stuck by oil. This property can be utilized to extract
diamonds using oil when making synthetic diamonds. However, when diamond surfaces are
chemically modified with certain ions, they are expected to become so hydrophilic that they can
stabilize multiple layers of water ice at human body temperature.
Color
Diamond has a wide bandgap of 5.5 eV corresponding to the deep ultraviolet wavelength of 225
nanometers. This means pure diamond should transmit visible light and appear as a clear
colorless crystal. Colors in diamond originate from lattice defects and impurities. The diamond
crystal lattice is exceptionally strong and only atoms of nitrogen, boron and hydrogen can be
introduced into diamond during the growth at significant concentrations (up to atomic percents).
Transition metals Ni and Co, which are commonly used for growth of synthetic diamond by
high-pressure high-temperature techniques, have been detected in diamond as individual atoms;
the maximum concentration is 0.01% for Ni and even less for Co. Virtually any element can be
introduced to diamond by ion implantation.
Nitrogen is by far the most common impurity found in gem diamonds and is responsible for the
yellow and brown color in diamonds. Boron is responsible for the blue color. Color in diamond
has two additional sources: irradiation (usually by alpha particles), that causes the color in green
diamonds; and plastic deformation of the diamond crystal lattice. Plastic deformation is the cause
of color in some brown and perhaps pink and red diamonds. In order of rarity, yellow diamond is
followed by brown, colorless, then by blue, green, black, pink, orange, purple, and red. "Black",
or Carbonado, diamonds are not truly black, but rather contain numerous dark inclusions that
give the gems their dark appearance. Colored diamonds contain impurities or structural defects
that cause the coloration, while pure or nearly pure diamonds are transparent and colorless. Most
diamond impurities replace a carbon atom in the crystal lattice, known as a carbon flaw. The
most common impurity, nitrogen, causes a slight to intense yellow coloration depending upon the
type and concentration of nitrogen present. The Gemological Institute of America (GIA)
classifies low saturation yellow and brown diamonds as diamonds in the normal color range, and
applies a grading scale from "D" (colorless) to "Z" (light yellow). Diamonds of a different color,
such as blue, are called fancy colored diamonds, and fall under a different grading scale.

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Name: Yeong Kar Fai MARTIC NO: A148342 Subject: Kkkr2343 Material Engineering

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NAME: YEONG KAR FAI

MARTIC NO: A148342

C (1973 K / 3583 F) in vacuum or oxygen-free atmosphere, diamond converts to graphite; in

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