The Nature

Diamond

Of

Faculty of engineering

IntroductionDiamond is something superb, the peerless "king of gems"

A diamond is likely the oldest thing you will ever own, probably 3 billion years in age, fully two thirds the age of the Earth. Diamond is a strategic and high-tech super material for our technological society. Diamond is a shape. This exhibition presents the fascinating story of the nature of diamonds

Structure Of Diamond

The crystal structure of diamond is equivalent to a face-centered cubic (FCC) lattice, with a basis of two identical carbon atoms: one at (0, 0, 0) and the other at (1/4, 1/4, 1/4), where the coordinates are given as fractions along the cube sides. This is the same as two interpenetrating FCC lattices, offset from one another along a body diagonal by one-quarter of its length.

The conventional unit cell is cubic (see diagram), with a side length a0 approximately equal to 3.567 Å (0.3567 nm) at room temperature. From this we can derive a few other quantities.

The atomic density is therefore 8/(a03)   8/((3.567×10-10 m)3)   1.76×1029 atoms/m3 ≍ ≍(1.76×1023 atoms/cm3).

The atomic density is therefore 8/(a03)   8/((3.567×10-10 m)3)   1.76×1029 atoms/m3 ≍ ≍(1.76×1023 atoms/cm3).

Chemical PropertiesDiamond is the hardest natural material. It is an exceptional thermal conductor - 4 times better than copper.

it. has an extremely low thermal expansion, is chemically inert with respect to most acids and alkali, and is one of only a few materials with a negative work function (electron affinity). One consequence of the negative electron affinity is that diamonds repel water, but readily accept hydrocarbons such as wax or grease. Diamonds do not conduct electricity well, although some are semiconductors. Diamond has a high specific gravity, Diamond has the highest reflectance and index of refraction of any transparent substances. But colored diamonds, called 'fancies', have been found in all the colors of the rainbow. Boron, which lends a bluish color, and nitrogen, which adds a yellow cast, are common trace impurities. Diamond crystals frequently contain inclusions of other minerals, such as garnet or chromites

للحرارة . استثنائى موصل وهو صالبة الطبيعية المواد أكثر من 4الماسهو أفضل مراتالنحاس

األحماض بمعظم بالمقارنة كيميائيا خامل منخفضوهو حرارى توسع لديه الماسوهذه , ) ( , سالبة اكترونية ألفة عمل تابع ذات قليلة مواد من واحدة وهى والقلويات

أو   الشمع مثل الهيدروكربونات بسهولة تقبل ولكن والمياه الماس تنافر نتيجة السلبية   كأشباه. يعمل بعضهم أن من بالرغم ، جيد بشكل الكهرباء توصل الماسال الشحومإنكسار , انعكاسوقرينة أعلى لديها والماس ، عالى نوعى ثقل لديه الماس موصالت

قوسقزح أنواع جميع فى وجد الملون الماس لكن شفافة مادة أى منالمزرق  اللون يضفي الذي ، البورون ،  ويعتبر

ما   .  كثيرا الماس فى المشتركة الضئيلة الشوائب صفراء يضيفصبغة الذي والنيتروجينأو  األحمر العقيق مثل ، األخرى المعادن من شوائب الماسعلى بلورات تحتوي

الكروميت

Chemical Properties. Diamond is carbon in its most concentrated form. Except for trace impurities like boron and nitrogen, diamond is composed solely of carbon...

But diamond is distinctly different from its close cousins the common mineral graphite and lonsdaleite, both of which are also composed of carbon. Why is diamond the hardest surface known while graphite is exceedingly soft? Why is diamond transparent while graphite is opaque and metallic black? What is it that makes diamond so unique?

        قليل  مقدار باستثناء تركيزا األكثر شكله في كربون . الماسهو،       ,       من عمومته أبناء عن واضحا اختالفا يختلف الماس لكن الكربون من الماسفقط ويتكون

        الكربون من تتألف أيضا وكالهما ولونسدااليت الجرافيت مثل المشتركة  .المعادن       بينما  معروف سطح أصلب الماس لماذا

            الجرافيت  بينما الماسشفاف لماذا جدا؟ لينة الجرافيت         الحد؟  هذا إلى فريدا الماس يجعل الذي ما السوداء؟ والمعدنية معتم

Hardness Diamond is renowned for its hardness. Hardness is the

measure of a substance's resistance to being scratched, and only a diamond can scratch another diamond. Diamond is the hardest substance known.

, و بصالبته الماس يشتهرالمادة مقاومة هى الصالبة , للماس ويمكن للخدشأخرا  ماسا يخدش أن فقطمادة أصلب هو الماس ألنمعروفة

 

Surface properties It repels water, an unusual property for a mineral. Diamond's

strong bonding and carbon composition cause its surface to repel water but to readily accept wax and grease. These two properties provide an effective means of separating diamonds from other minerals that come out of mining operations

.         , ) ( المعادن عن معتادة غير خاصية وهي المياه ينفر الماسيصدبين التنافر يسبب الكربون للماسوتكوين القوى والترابط

.       وهاتين بسهولة والشحوم الشمع يقبل ولكن والمياه سطحهاألخرى المعادن الماسمن لفصل فعالة وسيلة توفر الخاصتين

      التعدين عمليات تأتيمن . التي

Durability Hardness is not the only measure of a mineral's durability--the relative

resistance to fracture is another. diamond has certain planes of weakness along which it can be split.

Diamond is said to have perfect cleavage in four different directions, meaning it will separate neatly along these lines rather than in a jagged or irregular fashion. This is because the diamond crystal has fewer chemical bonds along the plane of its octahedral face than in other directions. Diamond cutters take advantage of cleavage to fashion diamonds efficiently.

Density diamond is much more dense than graphite, which weighs in at only

2.20 grams per cubic centimeter. This comparison offers an important clue to diamond's origin: the fact that diamond's carbon atoms are "squeezed" together tighter than in graphite, which forms near Earth's surface, implies that diamond is formed under high pressure conditions.

refraction Science postulates the speed of light in a vacuum to be about 186,000

miles per second. Light passing through diamond is reduced to about 77,000 miles per

second--near the maximum for any transparent substance.

Electric condition Why does graphite conduct electricity while diamond does not? The

difference in their appearances is one clue. The somewhat metallic luster of graphite announces its capacity to conduct electricity. Metals conduct electricity, while transparent substances, including diamond, are poor electrical conductors. However, rare diamonds, particularly the gray-to-blue ones called type IIB, are semiconductors, and are somewhat conductive.

Thermal condition Diamonds are called "ice" with good reason. Objects feel cold not only

because they are at a lower temperature than our bodies, but also because they can extract or conduct the heat away from us. When you touch a diamond to your lips, it feels ice-cold because it robs your lips of their heat. The capacity of diamond to conduct heat distinguishes it readily from other gems and exceeds that of copper, an excellent thermal conductor, by about 4 times at room temperature. This exceptional property of diamond is increasingly being used for extracting heat from electronic devices to make them smaller and more powerful.

Thermal condition Metals usually conduct heat much better than transparent

substances, because they have loose electrons that act as packets for carrying heat in much the same way they move electricity. Nonmetals conduct heat solely by atomic vibrations, a less efficient mechanism than moving electrons. In diamond, however, vibrational energy travels through the crystal along the strong internal chemical bonds. Thus, diamond's superlative strength provides excellent thermal conduction as well

Diamond vital statistics Composition: C (carbon) Crystallographic Class: Cubic -- hexoctahedral (highest of the symmetries) Space Group: Fd3m -- a = 3.57 A (cell edge) Common Forms {indices}: F Octahedron {111}, cube {100}, dodecahedron {110}, rounded variations Twins: Spinel-law common, yielding the flat triangular "macle" Hardness: 10 Mohs' scale, 56-115 Knoop hardness number (GPa), 10,000 Brooks identer

scale; octahedral face hardest, cube face softest Cleavage: Excellent parallel to octahedron face -- {111} Density: 3.51 g/cm3 (or specific gravity = 3.51) Luster: Adamantine (diamond provides the definition for this kind of luster)

Diamond vital statistics Colors: Colorless, yellow, blue, and many others Refractive Index: 2.4175 (in the yellow light of a sodium lamp) Dispersion: Large (0.044), leading to rainbow colors on refraction Optical Transmission: Transparent over broad spectrum of the electromagnetic spectrum; an

excellent material for optical windows Thermal Conductivity: Superb -- 5-25 Watts/centimeter-degreesC (at 300 K); 4 times greater

than copper, an excellent thermal conductor Electrical Conductivity: 0 to ~ 100 ohm-cm (resistivity at 300 K) -- an insulator

Natural Diamonds Natural diamonds are classified by the type and quantity of

impurities found within them.  

Type Ia - This is the most common type of natural diamond, containing up to 0.3% nitrogen.

Type Ib - Very few natural diamonds are this type (~0.1%), but nearly all synthetic industrial diamonds are. Type Ib diamonds contain up to 500 ppm nitrogen.

Type IIa - This type is very rare in nature. Type IIa diamonds contain so little nitrogen that it isn't readily detected using infrared or ultraviolet absorption methods.

Type IIb - This type is also very rare in nature. Type IIb diamonds contain so little nitrogen (even lower than type IIa) that the crystal is a p-type semiconductor.

Thin Film Diamonds A process called Chemical Vapor Deposition (CVD) may be

used to deposit thin films of polycrystalline diamond. CVD technology makes it possible to put 'zero-wear' coatings on machine parts, use diamond coatings to draw the heat away from electronic components, fashion windows that are transparent over a broad wavelength range, and take advantage of other properties of diamonds

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