Introduction Diamond is commonly known as "diamond", which is what we often call diamond. It is a mineral composed of pure carbon and is also the hardest substance in nature. Since it was confirmed in the 18th century that diamond is composed of pure carbon, people have begun research on artificial diamond. It was only in the 1950s that real success and rapid development were achieved through the advancement of high-pressure research and high-pressure experimental technology. Synthetic diamond is also widely used in various industries and craft industries. In this special topic, the editor will introduce to you the relevant knowledge about artificial diamond and diamond tools.
Contents Uses of artificial diamonds Principles of artificial diamonds Hardness of artificial diamonds Classification of artificial diamond tools Applications of artificial diamond tools The difference between natural diamonds and artificial diamonds How to distinguish artificial diamonds from natural diamonds Artificial diamond brands 1 Uses of artificial diamonds 1. Manufacturing resin bonded grinding tools or grinding tools, etc.
2. Manufacturing metal bonded grinding tools, ceramic bonded grinding tools or grinding tools, etc.
3. Manufacturing general geological drilling bits, semiconductor and non-metal material cutting and processing tools, etc.
4. Manufacturing hard formation geological drill bits, correction tools and non-metallic hard and brittle material processing tools, etc.
5. Resin, ceramic bond grinding tools or grinding, etc.
6. Metal bonded grinding tools and electroplating products. Drilling tools or grinding etc.
7. Cutting, drilling and correction tools, etc.
2 Principle Direct Method of Artificial Diamond
Artificial diamond may use instantaneous static ultra-high pressure and high temperature technology, or dynamic ultra-high pressure and high temperature technology, or a hybrid technology of both, to make graphite and other carbon The raw materials are directly converted into diamond from solid or molten state. The diamond obtained by this method is micron-sized polycrystalline powder.
Medium method
Synthetic diamond uses static ultra-high pressure (50-100kb, 5-10GPa) and high-temperature (1100-3000°C) technology through graphite and other carbonaceous raw materials and Certain metals (alloys) react to form diamond, whose typical crystal states are cube (hexahedron), octahedron, hexa-octahedron and their transition forms. The main one that shows important application value in industry is the static pressure melting method. The output of abrasive-grade artificial diamond obtained by this method has exceeded that of natural diamond. The problems to be further solved are to increase the coarse-grain ratio, increase the conversion rate and improve the crystal quality. The formation of high-quality large-grain single crystal diamond is currently being studied in the laboratory using the static pressure melting method. The seeded epitaxial growth method has produced large single crystals weighing about 1 carat; after slight improvements using general experimental techniques, crystals of about 2 to 4 mm have been obtained. This method is also used to grow and sinter large-grained polycrystalline diamonds, which have found certain applications in industry. The key issue is to further improve the compressive strength, impact strength, wear resistance and wear resistance of this polycrystalline diamond. Heat resistance and other comprehensive properties.
Epitaxial method
Artificial diamond is epitaxially grown on diamond seeds or certain substances that serve as substrates by using the carbon source precipitated during pyrolysis and electrolysis of certain carbon-containing substances. made.
Wurtz reaction method
Let carbon tetrachloride and sodium react at 700°C to generate diamond. But a large amount of graphite will be generated at the same time.
Formation mechanism
There are mainly the following theories: the solvent theory believes that the metal (alloy) used acts as a solvent for carbon; the catalytic theory believes that it is a catalyst; the solid phase The transformation theory emphasizes that graphite crystals do not need to break bonds and disintegrate, and can form diamond crystals after simple deformation. However, the models proposed by these three typical theories often contradict some major experimental phenomena and laws. Therefore, theories such as solvent-catalyst, catalyst-solvent, and melt (solvent) agent-catalyst (referred to as melt medium) have emerged to further explore the role of the metal (alloy) used. Generally speaking, the formation mechanism of artificial diamond is still a complex issue that is still under discussion.
Related Thermodynamics
In "Inorganic Chemistry" co-edited by the three schools (fourth edition, page 236, line 9, starting from the 16th word from the left, it is clearly mentioned:
According to research, the conversion of graphite into diamond under high pressure is exothermic!
3 Artificial diamond hardness is 10 on the Mohs scale and 15 on the new Mohs scale. The hardness is 10000kg/mm2, and the microhardness is 1000 times higher than quartz and 150 times higher than corundum. The hardness of diamond is directional. The hardness of octahedral crystal face is greater than that of rhombic dodecahedron crystal face, and the hardness of rhombic dodecahedral crystal face is greater than that of hexahedral crystal. Surface hardness.
According to the Mohshardness scale, there are 10 levels, and diamond (diamond) is the highest level 10; for example, the hardness of a knife is about 5.5, and that of a copper coin is about 3.5 to 4. , the nail is about 2 to 3, and the glass hardness is 6.
4 Classification of artificial diamond tools 1. According to cutting materials:
1. Building structure cutting: divided into cutting concrete. Used for cutting asphalt and bricks. 2. For cutting stone: divided into cutting granite, marble, sandstone and slate. 3. For cutting decorative ceramic tiles and for cutting glass.
2. According to the manufacturing process:
1. Welding: laser welding products, high-frequency welding products 2. Sintering: cold pressing, hot pressing.
3. According to the machine used: marble machine, angle grinder; road saw, road cutting machine; table saw; stone saw; hand saw; wall saw; high-power flat surface For sawing.
5 Applications of artificial diamond 1. When opening the hole, it should be rotated slowly. After the hole depth reaches 10-15mm, it should be gradually turned into full operation. During the rock drilling process, the drill rod should advance in a straight line according to the hole position design and be located at the center of the hole.
2. When drilling rock, the shaft thrust should be tested reasonably. If the shaft thrust is too small, the machine will rebound, the vibration will increase, and the rock drilling efficiency will decrease; if the shaft thrust is too large, the drill bit will press against the bottom of the hole, causing the machine to operate under overload, which will easily wear parts prematurely and slow down the rock drilling speed.
3. When the rock drill is stuck, the shaft thrust should be reduced to gradually return to normal. If it is invalid, stop the machine immediately. First use a wrench to slowly rotate the drill rod, and then turn on the air pressure to make the drill rod rotate slowly. It is forbidden to knock the drill rod.
4. Observe the powder discharge situation frequently. When the powder discharge is normal, the mud will slowly flow out along the hole; otherwise, the hole must be blown forcefully. If it still doesn't work, you should check the condition of the drill tail of the water hole of the drill, then check the condition of the water needle, and replace the damaged parts.
5. Pay attention to the oil injection reserve and oil output, and adjust the oil injection amount. When operating without oil, it is easy for parts to wear prematurely. When there is too much lubricating oil, it will cause contamination of the working surface.
6. When operating, you should pay attention to the sound of the machine, observe its operation, find problems, and deal with them in time.
7. Pay attention to the working status of the drill and replace it in time if there is any abnormality.
8. When operating an upward rock drill, pay attention to the air supply volume of the air leg to prevent accidents caused by the rock drill swinging up and down. The support point of the air leg must be reliable. Do not hold the machine too tightly and do not ride on the air legs to prevent injury or damage to the machine.
9. Pay attention to the rock condition, avoid perforating along bedding and joint fissures, and prohibit opening holes. Always observe whether there is any danger of roof collapse or fragmentation.
10. Use the hole opening function effectively. In the drilling process, there is an important step in opening the hole, which is completed by reducing the impact pressure and fixing the pushing pressure. The pushing pressure should be as small as possible to facilitate opening holes in very steep rock faces and to avoid bending of the drill pipe.
6 The difference between natural diamond and artificial diamond (1) Difference in solvent. Natural diamond is grown from a silicate solution in which the solubility of carbon is very low, while artificial diamond is grown from a metal melt. Grows from a medium in which the solubility of carbon is much higher than that of silicates. As expressed in the equation: α=ε(1-X2s)-(lnXs+c), "the higher the solubility, the smaller the α value", so that the solid-liquid interface is rough, so for artificial diamond, the growth ratio of facets Expect less.
In the above formula, α——Jackson factor
ε——Orientation factor
Xs——Density of solute in solution
C ——The constant is 1-2.5
(2) The growth temperature of natural diamond (estimated to be 1000-1300°C) is lower than that of artificial diamond (above 1400°C). The lower the growth temperature, the smaller the α value. . Therefore, a rough interface can be expected for synthetic diamond.
(3) The supersaturation degree of artificial diamond when growing is greater than that of natural diamond. Therefore, it can be predicted that the surface of artificial diamond is rough anyway. However, the actual observed artificial diamond shows a rougher surface. Smooth interface.
The morphological differences between natural diamond and artificial diamond, as well as the difference between the theoretically predicted crystal morphology and actual observation, are caused by the different sizes of the growth units.
The difference between the forms of natural diamonds and artificial diamonds can be summarized as follows:
7 How to distinguish artificial diamonds from natural diamonds The editor summarized six tricks to distinguish natural diamonds from artificial diamonds (Soviet diamonds, moss stone), I hope this helps everyone.
The first trick: distinguish hardness. Natural diamonds have a Mohs hardness of 10, Soviet diamonds have a Mohs hardness of 8.5, and mossinite has a Mohs hardness of 9.25.
The second trick: chemical composition. The chemical composition of natural diamonds is carbon, the chemical composition of Soviet diamonds is carbon dioxide, and the chemical composition of mossinite is silicon carbide.
The third trick: thermal probe reaction. Natural diamonds will make a rattling sound, Soviet diamonds will not rattle, and mossite will rattle, which can easily be confused with the real thing.
The fourth trick: conductivity. Natural and Soviet diamonds do not conduct electricity, while mossinite occasionally does.
The fifth tip: optical properties. Natural diamonds have a single refractive index, Soviet diamonds have a single refractive index, and mossinite has a birefringent index.
The sixth trick: observe with a 10x magnifying glass. Natural diamonds are not only polished and smooth, but also have sharp ridges; Soviet diamonds are poorly polished and their ridges are often blunt; while mossite is not only not sharp but also heavy.
8 Synthetic Diamond Brands Industry Recommended Brands Yellow River Whirlwind Zhongnan ZHONGNAN Huajing Diamond Crystal Sun ElementSix Element Liusi Fangda SFD E Xinchang Runfu Nike Funik Zhengzhou Xinya