Friday, August 5, 2011

Diamond: Natural & Synthetic

Natural Diamonds

Picture 1. Natural Diamond stone

Natural Diamonds are called so because it is originate from under the ground. Natural diamonds were formed many years ago, the quantities of natural diamonds are limited and the defects are frequent. This is the reason why the most big and clear natural diamonds are so rare and the price is so expensive. Only 20% of natural diamonds are gemstones, others of them are good only for industrial use as cutting tools or abrasives. Natural diamonds are further classified into four categories which depend on the type and amount of impurities in them.

There are: Type Ia, type Ib, type IIa, type IIb.

Type I diamonds is the most common class which contain nitrogen atoms as their main impurity, commonly at a concentration of 0.1%-0.2%.

Picture 2 Natural Diamond type Ia
Type Ia: This is the most common type of diamonds. This type of diamond contains 0.3% of nitrogen and 98% of all natural diamonds are this type. Nitrogen atoms are present as pairs or small groups called aggregates. They are either light yellow or brown in color because they absorb blue light.

Picture 3 Natural Diamond type Ib

Type Ib:
Very few natural diamonds are this type but nearly all synthetic industrial diamonds are. They contain 0.05% of nitrogen but the impurities are more diffuse. Nitrogen atoms are present as isolated atoms. They are in yellow, orange, green or brown color.

Type II diamonds have no measurable nitrogen impurities. The crystals as found tend to be large and irregular in shape. Type II diamonds were formed under extremely high pressure for long time periods.

Picture 4 Natural Diamond type IIa

Type IIa: This type contains little nitrogen and is almost free from all forms of impurities. This type is very rare in nature. This is the purest form of diamond and is generally colorless. It also have the highest thermal conductivity.

Picture 5 Natural Diamond type IIb

Type IIb: This type is a rare type of natural diamond and contains very little amount of nitrogen. Type IIb diamonds contain significant boron impurities. The diamonds of this type are bluish in color and amounts for 0.1% of all the diamonds taken together.

Synthetic Industrial Diamond

Picture 6 Synthetic Industrial Diamond powder

Synthetic industrial diamonds are produced by the method of High Pressure High Temperature Synthesis (HPHT). Such diamonds are also called as lab-created because of their origination. They are nothing less than true diamonds. Under the HPHT process, graphite and catalysts are subject to tremendous hydraulic pressure and at the same time are exposed to high temperature for few hours. After this process, the graphite automatically converts to diamond. Diamonds so produced are small in size and is the best used to cutting and grinding equipments but their quality is so inferior that they can hardly be considered as gemstones. The diamonds produce can be in many colors such as clear white, yellow, brown, blue, green and orange.

Hence, these diamonds are categories with industrial utility. Synthetic industrial diamonds are used in abrasives, in cutting and polishing tools in heat sinks. Besides that, synthetic industrial diamonds also use in electronic application such as high-power switches at power stations, high frequency field-effect transistors and light-emitting diodes. Synthetic industrial diamonds also become the most popular material for optical windows in high-power CO2 lasers and gyrotrons because of its unique combination of thermal and chemical stability, low thermal expansion and high optical transparency in a wide spectral range.

Thin Film Diamond