When were diamond tipped tools invented?

A diamond tool is a cutting tool with diamond grains fixed on the functional parts of the tool via a bonding material or another method. As diamond is a superhard material, diamond tools have many advantages as compared with tools made with common abrasives such as corundum and silicon carbide.

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History

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In Natural History, Pliny wrote "When an adamas is successfully broken it disintegrates into splinters so small as to be scarcely visible. These are much sought after by engravers of gems and are inserted by them into iron tools because they make hollows in the hardest materials without difficulty."[1]

Advantages

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Diamond is one of the hardest natural materials on earth; much harder than corundum and silicon carbide. Diamond also has high strength, good wear resistance, and a low friction coefficient. So when used as an abrasive, it has many obvious advantages over many other common abrasives.

Diamond can be used to make grinding tools, which have the following advantages:

• High grinding efficiency, Low grinding force: Less heat will be generated by the hole in the grinding process. This can decrease or avoid burns and cracks on the surface of the workpiece, and decrease the equipment's wear and energy consumption.
• High wear resistance: Diamond grinding tools' change in dimension is small. This can lead to good grinding quality and high grinding precision.
• Long lifespan, Long dressing period: This can greatly increase the work efficiency, and improve the workers' labor environment and decrease the product's labor intensity.
• Low comprehensive cost: The processing cost of each workpiece is lower.

Categories

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There are thousands of kinds of diamond tools. They can be categorized by their manufacturing methods and their uses.

Categories by manufacturing method

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According to their manufacturing methods or bond types, diamond tools can be categorized to the following way:

• Metal-bonded diamond tools: The tool's bonding material is sintered metal containing diamond grit. The functional parts of the tool are usually diamond segments. These tools include metal-bonded diamond saw blades, diamond grinding cup wheels, diamond core drill bits, etc. For metal-bonded diamond tools, the bond is one of the prime factors when selecting which tool to use for cutting or grinding a specific material, depending on how hard or abrasive the material is. The bond used dictates the rate at which the metallic powders wear down and expose new diamond crystals at the surface, thereby maintaining an abrasive cutting surface. Different bond strengths are achieved by the alloy mix of metallic powders chosen and how much heat and pressure are applied to the sintered segment. The reference material has historically been cobalt, thanks to high diamond retention, ease of processing by hot pressing and adjustable wear rate by admixed bronze[2] or tungstene carbide powders. Due to its high and unstable price and to environmental concerns, alternative systems have been developed based on iron-copper alloys or mixtures, with further metallic and non metallic additions.[3]
• Resin-bonded diamond tools: The tools' bonding material is mainly resin powder. An example of this kind of tool is the resin-bonded diamond polishing pads used in the construction industry.
• Plated diamond tools: These tools are made by fixing the diamonds onto the tool's base via electroplating method or via CVD (Chemical Vapor Deposition) method. They can usually be made to good processing precision.
• Ceramic-bonded diamond tools: The tools' bonding material is usually glass and ceramic powder. This tool usually has the features of good chemical stability, small elastic deformation, but high brittleness, etc.
• Polycrystalline Diamond (PCD): They are normally made by sintering many micro-size single diamond crystals at high temperature and high pressure. PCD has good fracture toughness and good thermal stability, and is used in making geological drill bits.
• Polycrystalline Diamond Composite or Compacts (PDC): They are made by combining some layers of polycrystalline diamonds (PCD) with a layer of cemented carbide liner at high temperature and high pressure. PDC has the advantages of diamond's high wear resistance with carbide's good toughness.
• High-temperature brazed diamond tools: This tool is made by brazing a single layer of diamonds onto the tool via a solder at a temperature of over 900 °C. using vacuum brazing or atmosphere-protected brazing. This tool has several advantages: the solder can hold the diamonds very firmly, the single layer of diamonds' exposed height can be 70%&#;80% of their sizes, and the diamonds can be regularly arranged on the tool.

Categories by use

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If categorized by use, there are diamond grinding tools, diamond cutting tools (e.g., diamond coated twist drill bits), diamond drilling tools, diamond sawing tools (e.g., diamond saw blades), diamond drawing dies, etc.

Applications

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Applicable materials

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Diamond tools are suitable to process the following materials:

• Carbide alloy
• Hard or abrasive non-metallic materials, for example, stone, concrete, asphalt, glass, ceramics, gem stone and semiconductor materials.
• Non-ferrous metals such as aluminium, copper and their alloys, and some soft but tough materials such as rubber and resin.

As diamonds can react with Fe, Co, Ni, Cr, V under the high temperatures generated in the grinding processes, normally diamond tools are not suitable to process steels, including common steels and various tough alloy steels, while the other superhard tool, cubic boron nitride (CBN) tool, is suitable to process steels. The tools made with common abrasives (e.g. corundum and silicon carbide) can also do the task.

Applied domains

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Diamond tools are used in the following domains:

• Geological or project exploration: Diamond geological drill bits, diamond oil drill bits and diamond thin-wall drill bits are often used. The main application of PCD drilling bits is in the oil and natural gas industries and the mining industry.
• Stone processing: Diamond circular saw blades, diamond gang saws, diamond band saws are used to saw marble, granite and other stone blocks. Diamond wire saws are used in stone quarries to exploit raw stone blocks. Shaped diamond tools are used to process stone to a particular shape. Resin-bonded diamond polishing pads are used to polish stone.
• Construction: Medium or small sized diamond saw blades, diamond core drill bits and some diamond grinding or polishing tools are often used in repairing roads, remodeling buildings, and processing building materials.
• Woodworking: Composite laminate flooring is widely used. It is wearable as stone. PCD circular saw blades, profiling cutter, twist drill bits and other diamond tools are used in its processing.
• Auto spare parts processing: PCD and PCBN cutting tools are used to meet the high efficiency and low deviation processing requirements in this domain.
• IT and home appliance products processing: High-precision super-thin diamond cutting wheels are used to cut silicon slices. Resin-bonded diamond grinding wheels are used to process ceramics in optical fiber industry.
• Engineering ceramics processing: Engineering ceramics are widely used in many industries. They have the properties of high toughness, high hardness, high-temperature resistance. High-toughness and durable diamond grinding wheels are developed to process them.
• Carbide tools and other mechanical tools processing: Diamond tools are used to gain high processing precision and efficiency.

Besides what are listed above, there are also other domains where diamond tools are applied, for example, in medicine, Venezuelan scientist Humberto Fernandez Moran invented the diamond knife for use in delicate surgeries in .

Apart from its use as an abrasive due to its high hardness, diamond is also used to make other products for its many other good properties such as high heat-conductivity, low friction coefficient, high chemical stability, high resistivity and high optical performances. These applications include coatings on bearings and CDs, acting as lens and thermistors, making high-voltage switches and sensors, etc.

Diamond dressers consist of single-point or multipoint tools brazed to a steel shank, and used for the trueing and dressing of grinding wheels. The tools come in several types, including: grit impregnated, blade type, crown type, and disc type. The advantages of multipoint over single-point tools are:

1. The whole diamond can be used; in a single-point tool, when the point is blunt the diamond must be reset, and after few resettings the diamond is replaced.
2. Multipoint tools have higher accuracy, especially in form grinding, where blade types are used. Blades consist of elongated diamonds. The thickness is controlled and blades are available in thicknesses from 0.75 to 1.40 millimeters (0.030 to 0.055 in).
3. Grit-type tools are of a tough grade, and can be used for bench grinders.
4. Since small points are used, the diamonds have a cutting edge with natural points, unlike single-point tools, which have brutted points.
5. The cost of multipoint tools is lower, since smaller, less expensive diamonds are used.

Further information on synthetic diamond: Polycrystalline diamond

Polycrystalline diamond (PCD) is formed in a large High Temperature-High Pressure (HT-HP) press, as either a diamond wafer on a backing of carbide, or forming a "vein" of diamond within a carbide wafer or rod.

Most wafers are polished to a mirror finish, then cut with an electrical discharge machining (EDM) tool into smaller, workable segments that are then brazed onto the sawblade, reamer, drill, or other tool. Often they are EDM machined and/or ground an additional time to expose the vein of diamond along the cutting edge. These tools are mostly used for the machining of nonmetallic and nonferrous materials.

The grinding operation is combined with EDM for several reasons. For example, according to Modern Machine Shop,[citation needed] the combination allows a higher material removal rate and is therefore more cost effective. Also, the EDM process slightly affects the surface finish. Grinding is used on the affected area to provide a finer final surface. The Beijing Institute of Electro-Machining[citation needed] attributes a finer shaping and surface geometry to the combination of the two processes into one.

The process itself is accomplished by combining the two elements from each individual process into one grinding wheel. The diamond graphite wheel accomplishes the task of grinding, while the graphite ring around the existing wheel serves as the EDM portion. However, since diamond is not a conductive material, the bonding in the PCD work piece must be ample enough to provide the conductivity necessary for the EDG process to work.

Polycrystalline diamond tools are used extensively in automotive and aerospace industries. They are ideal for speed machining ( surface feet per minute or higher) in tough and abrasive aluminum alloys, and high-abrasion processes such as carbon-fiber drilling and ceramics. The diamond cutting edges make them last for extended periods before replacement is needed. High volume processes, tight tolerances, and highly abrasive processes are ideal for diamond tooling.

Polycrystalline diamond compacts

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In the late s, General Electric pioneered the technology of polycrystalline diamond compacts (PDCs) as a replacement for natural diamonds in drill bits.[4] PDCs have been used to cut through crystalline rock surfaces for extended periods of time in lab environments, and these capabilities have now been implemented in harsh environments throughout the world.

As of August , the U.S. Department of Energy claimed that nearly one-third of the total footage drilled worldwide is being drilled with PDC bits, with a claimed savings of nearly $100,000 per PDC bit as compared to roller-core bits.[5]

Diamond paste and slurry

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Diamond pastes are used for polishing materials that require a mirror finish. They are often used in metallurgical specimens, carbide dies, carbide seals, spectacle glass industry, and for polishing diamonds. Diamond paste is mainly used in industrial requirements for polishing and sharpening metal blades and other metal surfaces. The paste is not just to polish the metal blade but sharpen the cutting edge as well.

Diamond powder deposited through electroplating is used to make files (including nail files) and in small grinding applications.

Single point diamond turning (SPDT) utilizes a solid, flawless diamond as the cutting edge. The single crystalline diamond can be natural or synthetic, and is sharpened to the desired dimensions by mechanical grinding and polishing. The cutting edge of most diamond tools is sharp to tens of nanometers, making it very effective for cutting non-ferrous materials with high resolution. SPDT is a very accurate machining process, used to create finished aspherical and irregular optics without the need for further polishing after completion. The most accurate machine tool in the world, the LODTM, formerly at Lawrence Livermore National Laboratory, had a profile accuracy estimated at 28 nm, while most machines seek a roughness within that deviation.[6]

SPDT is used for optics, for flat surfaces where both surface finish and unusually high dimensional accuracy are required, and when lapping would be uneconomical or impractical.

Diamond saw blades

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For high-speed gas powered cut-off saws, walk-behind saws, handheld grinders, bridge saws, table saws, tile saws, and other types of saws.

Concave blade

For cutting curves in countertops to install sinks or sculpt statues.

Tuck pointers

Thick diamond blades for restoration, involving grinding and replacing mortar.

Crack chasers

Thick V-shaped diamond blades for repairing cracks in concrete.

Diamond tipped grinding cups

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Typically used on hand grinders for grinding concrete or stone.

Diamond tipped core bit or holesaw

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Hollow steel tube with diamond tipped segments for drilling holes through concrete walls in the construction industry, porcelain tiles or granite worktops in the domestic industry, or also used for sample core extractions in the mining industry.

PCD tool insert

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Used in machine tools for machining ceramics and high speed aluminium.

PD tool insert

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Used in turning centers for optics and precision surfaces.

Polishing pads

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Pads with diamond crystals for polishing marble and other fine stone.

Diamond wire cutting

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Wire with diamond crystals for cutting.

Some of the features of Diamond Wire Cutting are:
Non-percussive, fumeless and quiet
Smooth cutting face
Unlimited cutting depth
Horizontal, vertical and angled cutting of circular openings up to mm diameter
Plunge cutting facility which allows blind and rebated openings to be formed
Remote controlled operation for increased safety

Diamond saw chain

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For cutting stone, concrete and brick with a special chainsaw.

See also

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References

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Diamond Tool History

A HISTORICAL OVERVIEW OF DIAMOND USAGE IN THE INDUSTRIAL WORLD

     Diamond, the  most sought-after gemstone in the world, may well also be the world's most versatile engineering material. Diamond is the strongest and hardest known substance, but hardness is not the only superlative property of diamond that makes it important in industry and technology. It also has the highest thermal conductivity of any material at room temperature, has a low-friction surface, and optical transparency. This unique combination of properties cannot be matched by any other material.

     Knowledge of diamonds started in India, where it was first mined. The word most generally used for diamond in Sanskrit is transliterated as vajra, "thunderbolt,"  where the flash of lightning is used as a comparison for the light thrown off by a fine diamond octahedron and a diamond's indomitable hardness. Early descriptions of vajra date to the 4th century BCE which is supported by archaeological evidence. By that date diamond was a valued material. The earliest known reference to diamond is a Sanskrit manuscript, the Arthasastra ("The Lesson of Profit") by Kautiliya, a minister to Chandragupta of the Mauryan dynasty in northern India. The work is dated from 320-296 before the Common Era (BCE). Kautiliya states "(a diamond that is) big, heavy, capable of bearing blows, with symmetrical points, capable of scratching (from the inside) a (glass) vessel (filled with water), revolving like a spindle and brilliantly shining is excellent."

     No diamonds have been found in ancient sites, but holes in ancient beads show diamond's "footprint," cylindrical holes with conspicuous concentric grooves left by a twin-diamond drill. The holes are unlike the marks of any other modern or ancient drilling technique. Beads from sites in Sri Lanka, India, Thailand, Yemen and Egypt show the marks of diamond drills prior to 700 CE and as early as the 4th century BCE in Yemen.

     Chinese interest in diamond was strictly as an engraving or carving tool, primarily for jade, or as a drill for beads and pearls. Chinese writings on diamond refer to "kun wu" and "kin-kang" as jade-cutting knives, the diamond "coming from Rome in iron scribes".

     The presence of diamond in Rome by about 100 CE is established by the writings of Pliny the Elder (23--79 CE), by sapphire engravings, and by talismanic diamond rings. Originally known by the Greek word "adamao", meaning "I tame" or "I subdue", the adjective "adamas" was used in early writings to describe sapphires and corundum, and although there was contact between India and the Mediterranean in ancient times, the timing of the association of  "adamas" with "diamond" has not been established. Pliny the Elder, who died during an eruption of Mount Vesuvius, wrote the encyclopedia "Historia naturalis," a fundamental source of classical information. He states: "The substance that possesses the greatest value, not only among precious stones, but of all human possessions, is adamas; a mineral which for a long time, was known to kings only, and to very few of them... Pliny also discussed diamond fragments: "These particles are held in great request by engravers, who enclose them in iron, and are enabled thereby, with the greatest facility, to cut the very hardest substances known." Roman engraved sapphires, cameos, and intaglios from the first century are undoubtedly the product of diamond engraving points.

     Diamonds were traded out of India by both sea and land routes. Traders employed circuitous trade routes a in an attempt to mask the ultimate source of diamonds, India. For centuries after, rulers of the intervening lands also kept finer diamonds from being carried across their territories, thus diminishing the quantities of diamonds that could reach the Mediterranean region.

     Diamonds disappeared from European history for nearly 1,000 years after the rise of Christianity because the symbolism associated with Roman talismans and Eastern magic made diamond abhorrent to the new religion.  At the same time, Persia and the new Middle Eastern states gained control over much of the trade, and diverted any diamonds from India.

     Diamonds survived conceptually, and in the Middle Ages, medieval treatises called lapidaries presented the qualities of different stones; their power; their efficacy as medicine, poison, or antidote; whether they could reproduce; and sundry other properties. Lapidaries were written until the Age of Enlightenment, in the 18th century.

     One of the earliest diamond-cutting industries is believed to have been in Venice, a trade capital, starting sometime after . Diamond cutting may have arrived in Paris by the late 14th century; for Bruges -- on the diamond trade route -- there is documentation for the technique in .

     The discovery in the s of diamond deposits of unprecedented richness in South Africa changed diamond from a rare gem to one potentially available to anyone who could afford it.

     From the time Smithson Tennant showed that diamond was carbon in , experimenters attempted to synthesize diamond from graphite or lamp black. Although the experiments at high pressure and temperature were in the right direction, for 150 years these attempts were fruitless. The invention of tungsten carbide in the s provided a material that could achieve the pressure containment necessary for growing diamond. Experiments in the s by Harvard professor Percy Bridgman were unsuccessful, but finally in the early s two teams succeeded. The first was led by Baltazar von Platen, at the Allmanna Svenska Elektriska Aktiebolaget (ASEA) Laboratory in Stockholm, Sweden, in . This initial success was neither publicized nor published, and therefore, on February 15, , the General Electric team of Francis Bundy, Tracy Hall, Herbert Strong, and Robert Wentorf claimed credit for the first reproducible transformation of graphite to diamond.

Tracy Hall had this to say when he finally succeeded on December 16, :

"I attempted many hundreds of indirect . . . approaches over a period of about a year but to no avail, and I was becoming discouraged. Then, one wintry morning, I broke open the sample cell after removing it from the Belt. It cleaved near a tantalum disk used to bring in current for resistance heating. My hands began to tremble; my heart beat rapidly; my knees weakened and no longer gave support. My eyes had caught the flashing light from dozens of tiny triangular faces of octahedral crystals that were stuck to the tantalum and I knew that diamonds had finally been made by man. After I had regained my composure, I examined the crystals under a microscope. The largest, about 150 microns across, contained triangular etch and growth pits such as I had observed on natural diamonds. The crystals scratched sapphire and other hard substances, burned in oxygen to give carbon dioxide, and had the density and refractive index of natural diamond. A few days later, an x-ray diffraction pattern unequivocally identified the crystals as diamond."

(Reference: KURT NASSAU, "Gems Made by Man," Gemological Institute of America, Copyright ).

     The device used by GE to synthesize diamond was termed a "belt device" because tungsten carbide rams were driven into a cavity contained by a doubly-tapered carbide cylinder, contained in turn by a steel jacket - termed a belt. Between the rams is a cylinder of graphite - a furnace - containing the material to be raised to high temperature and pressure. Around the furnace assembly and between the anvils and belt is a compressible material to contain the pressure and accept the deformation; it has traditionally been a natural clay called "pipestone clay" for its alternative use in tobacco pipes. A hydraulic press, capable of perhaps 50 tons, drives the rams into the belt cavity, amplifying the force at the interior to high pressure. An electrical current is passed between the rams and through the conductive graphite, which heats in response; the clay acts as a thermal insulator as well as a container for pressure.

     Modern manufacture of synthetic diamonds utilizes these same methods discovered by Mr. Hall. A mixture of graphite and a catalyst (typically nickel) is subjected to a pressure of approximately 1,000,000 pounds per square inch and a temperature of 1,800 °C for a period of approximately 1 hour. During this time diamond crystals nucleate at many sites in the mixture. The mixture is then cooled., then the pressure reduced to atmosphere. The diamond crystals are then separated from the remaining graphite and nickel using an acid wash.

     The separated crystals are sorted by shape, size, and impurities. This process is called grading. A typical production cycle will yield approximately 300 carat. of synthetic industrial diamond of various grades. The larger diamonds are used for sawing concrete, granite, and marble. Smaller diamonds are used in grinding wheels.

     Even though it is more expensive than competing abrasive materials, diamond has proven to be more cost effective in numerous industrial processes because it cuts faster and lasts longer than any rival material. Diamond that does not meet gem-quality standards for color, clarity, size, or shape is used principally as an abrasive, and is termed "industrial diamond." Eighty percent of the diamonds mined annually are used in industry; 4 times that production is grown synthetically for industry - that's a total of over 500 million carats or 100 metric tons. Synthetic industrial is superior to its natural diamond counterpart because it can be produced in unlimited quantities, and, in many cases, its properties can be tailored for specific applications. Consequently, manufactured diamond accounts for more than 90% of the industrial diamond used in the United States.

     Another use for the diamond crystals is to put a layer of diamond on a carbide substrate by again subjecting this to the high temperature high pressure process. This yields a product called polycrystalline diamond compacts (PCD) which are used for oil well drills and cutters for drilling and milling machines.

     Many new products, like compact electronic devices, windows for optical devices in demanding environments, and "no-wear" bearings, such as in the space shuttle, utilize diamond. For these applications, a synthetic form leads the way. This is CVD, so-named for the growth technique chemical vapor deposition. At present the major commercial application for CVD diamond is in thermal management, where diamond heat-spreaders conduct byproduct heat away from a device. The material can be grown with a thermal conductivity close to that of the best natural and high-pressure synthetic diamonds used until now as heat spreaders. Thousands of suitable heat spreaders can be cut from a single wafer of CVD diamond, making for efficient use. A CVD diamond coating on an object can be polished to yield an extremely smooth diamond surface, ideal for high precision and low friction, such as is needed for precision bearings. CVD diamond wafers with high optical transparency are excellent for viewing a wide portion of the electromagnetic spectrum in environments with extreme temperature, corrosiveness, or radiation.

     Because of their transparency, thermal conductivity, or surface properties, diamonds are used in many research instruments as windows. An application of exceptional value in mineral and material science is a small device that generates extremely great pressures in the space between two diamonds - the diamond anvil cell. These devices are used in experiments on the nature of planetary interiors and dense matter, from mimicking Earth's core to producing solid hydrogen. The mechanics of creating high pressure are simple, involving just an application of force onto a small area, but extreme pressure will not be achieved without a material of supreme hardness, incompressibility, and strength - such as diamond. Most materials, steel for example, will deform or break before reaching pressures that exist deep within Earth. Tungsten carbide is better, but diamond is best. By polishing the ends off two fine round brilliant diamonds to a width of a millimeter or so, and carefully and accurately squeezing them together, pressures comparable to the center of Earth - 4,500,000 atmospheres - can be achieved. At these pressures hydrogen transforms into a metal - a state that might exist deep within Jupiter. Research on planetary interiors and dense matter has been advanced greatly by the use of diamond anvil cells, using lasers, optics, and x-rays to probe these small samples to reveal their mysteries. Cruise missiles and smart bombs utilize infrared detectors to seek their targets. Diamond windows can provide a wide band of transparency and resistance to abrasion and heat thereby improving the targeting of such devices.

     Managing heat, particularly in electronics, with large layers of CVD diamond is a rapidly expanding field. One of the most imaginative of these is the three-dimensional multi-chip module, which holds out the promise of an extremely powerful supercomputer. To gain speed, electronics need to be as compact as possible, concentrating waste heat as well. By stacking sandwiches of electronics and CVD diamond, a supercomputer could be made small and cool enough to function. The use of diamonds as radiation detectors, light emitters in electronic displays, and coatings to make surfaces indomitable or unwettable are being researched now. Beyond their imprint as a tool, diamonds will be showing up in more and more products in the future, probably in  home electronics, appliances, and automobiles.

Reference: American Museum of Natural History; US Geological Survey.

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