Synthetic Diamond in Tools - Report Example

SYNTHETIC DIAMOND IN TOOLS Name: Course: Professor: Institution: Date: Introduction For a period of years, it has been found that impurities in natural diamonds are linked to the variations in wear rate of the cutting edge but these has been reduced by the use of synthetic diamond especially where the control on the impurities is important. It is a more predictable and more controllable tool material. The synthetic diamonds tools cost are generally much higher than that of the natural diamond tools. They have most desirable properties in a cutting tool material. It is strong and hard making it able to deform other materials. Its brittleness makes machining with diamonds less than desirable in all applications. It has high elastic modulus compared to tool steel that results in high specific stiffness allowing the tool to withstand high force and less tool deformation. Precision machining is maintained by the smaller cutting edge deformation of diamonds (Dischler & Wild, 2013). It can maintain strength even at high temperatures though it can convert to graphite at a higher temperature. Synthetic Diamonds Synthetic diamond is also known by two other names; cultured diamond or cultivated diamond. This type of diamond is produced artificially as opposed to natural diamonds which are created through geological processes. They possess the same atomic structure, physical properties and chemical composition that real diamonds have. The diamond is also known as CVD diamond or HPHT diamond after the two common production methods referred to the chemical vapour deposition and high-pressure high-temperature crystal formation methods respectively. The manufacturing process is done entirely under manually controlled temperature and pressure in a laboratory setting. The USA Federal Trade Commission has indicated that the alternative terms of laboratory-created, laboratory grown and [manufacturer-name]-created would more clearly communicate the stones nature. These diamonds are being put to use for their effectiveness as heat sinks in the semiconductor business and also for their physical features which make them well-suited in the production and manufacture of cutting tools putting emphasis on their industrial use rather than just as a piece of jewelry (Sergio, 2002). Most of the industrial applications of these material is based on hardness, a property that makes it suitable for cutting and machine tools. Drill bits, saws and diamond powder abrasives make use of this ability of diamond. The micrometre-sized grains is normally the common form of diamond in cutting tools. This type of diamond is the one referred industrially as polycrystalline diamond. Polycrystalline diamond tools are applied in the cutting and mining industry. Processing and Synthesising Of Synthetic Diamonds There are several methods used to synthesis or process the synthetic diamonds. Here are the two main methods discussed. 1. HPHT-High Pressure and High Temperature It is the original method that uses high pressure and high temperature. The process involves large presses that can weigh hundreds of tonnes to produce the pressure of 5 Gpa at 1500degrees centigrade. It offers a significant degree of control over the quality and geometry of diamond obtained. The method is excellent for the industrial-scale production of synthetic diamonds. This process replicates the natural one by putting very high temperatures and pressures on carbon. Recently companies have fine-tuned the process. A belt is usually used, and anvils bring the required pressure and a heating current then the steel bands maintains the internal pressure needed. HPHT is better suited for industrial synthetic diamond production and involves combining graphite into a diamond. HPHT Growth Process There are three main press designs that are used to supply the pressure and temperature needed in the production of synthetic diamond: They are the belt press, the cubic press and the split sphere. Diamond seeds are placed at the bottom of the press. The internal part of the press is heated above 1400 degrees resulting to the melting of the solvent metal. The product dissolves the high purity carbon source and is then transported to the small diamond seeds that precipitate, forming a large synthetic diamond. Advantages of HPHT Growth Process i. It is cheaper ii. Uses few ingredients to produce more diamonds Impacts of HPHT Process on Synthetic Diamond’s Structures HPHT process produces a molecular structure that makes the material the world’s most versatile material. Most synthetic diamonds are produced as grit or small crystals. It can be cut into gems and different colours can be produced. Flawless diamond results when there is no large and visible inclusions (Sergio, 2002). Impacts of HPHT Process on Synthetic Diamond’s Properties Mechanical properties Hardness: Exceptionally hard and it’s very low coefficient of friction also manufactured to have an ultra-fine edge for extreme precision. Electronic properties: Contains a low dielectric constant and loss, a wide electronic band gap and a high electric carrier mobility. Acoustic properties: The diamonds provided the complex geometric shapes with the right thickness. Electrochemical properties: It is chemically and biologically inert and can survive chemical, physical and radioactive environments that would destroy lesser material. Thermal properties: Provides the highest known thermal conductivity. Optical properties: Synthetic diamond has a wide spectral band of any known material. Extending from ultraviolet to infrared and the millimetre-wave to microwave band. 2. CVD- Chemical Vapour Deposition Process It is a method whereby synthetic diamonds can be grown from a hydrocarbon gas mixture. There were early reports of gem-quality CVD synthetic diamonds that were greeted with lots of scepticism and were not verified until years later. In the fall of 1980s, scientists with highly advanced understanding of this technique discovered how to grow the diamond using this process. The CVD process does not require high pressures as the growth of the diamonds occurs at pressures under 27kPa.This process creates carbon plasma over a substance onto which the carbonic atoms get deposited on to form a diamond. This production method is less costly because it works with low pressure and moderate temperature which requires less expensive equipment. The vacuum chamber contains only some hydrogen and carbon, colourless crystals can be grown. The production process involves i. Substrate preparation The preparation process is characterized by: Feeding varying amounts of gases to the chamber and energizing them. Choosing appropriate material and its crystallographic orientation. Cleaning, often with diamond powder to abrade a non-diamond d substrate. ii. Growth The chamber materials get etched off by plasma and can incorporate into the growing diamond. The silica windows are either avoided or removed from the substrate because they can cause silicon contamination to the diamonds. The addition of ppm levels of nitrogen has been used to modify the texture and morphology of polycrystalline films, increase the growth rate and eventually weaken the grain boundaries. The substrate temperature is usually about 800 degrees centigrade. Gases of carbon, typical methane and hydrogen with a standard ratio of 1:99. Hydrogen is important because it selectively etches off non-diamond carbon. Advantages of the CVD- Chemical Vapour Deposition Process i. Ability to grow diamonds over large areas and on various substrates ii. Excellent control over chemical impurities iii. Diamonds can be grown on all kinds of substrates iv. They spread over a large area that in turn helps in producing larger diamonds Impacts of CVD on Synthetic Diamonds Structure Diamonds have grains like woods because of the way they crystallize and because they grow differently in nature. The grain of synthetic diamonds is different because of being grown in the lab. The physical structure of the synthetic diamond is not visible different from the natural diamond. Its molecular structure makes it most versatile super material. The synthetic diamonds also have edge sharpness. Impacts of CVD Process on Synthetic Diamonds Properties Mechanical properties: The exceptional hardness of this diamond, very low coefficient of friction and also manufactured to have an ultra-fine edge for very high precision. Optical properties: Contains a wide spectral band-width extending from UV to infrared and the millimetre-wave to microwave band. Thermal properties: Synthetic diamonds exhibit highest known resistance to thermal shock and highest thermal conductivity which is about four times higher than copper. They also have low thermal expansion. Electrochemical properties: These diamonds provide efficient oxidation of organic and inorganic compounds. They are also chemically and biologically inert thereby allowing them to be used in extreme physical, chemical and radioactive environments. Electronic properties: CVD diamonds possess high electrical carrier mobility, good electrical insulator properties, low dielectric constant and loss and wide electronic band gap meaning they can carry low current under high voltages. Acoustic properties: Synthetic diamonds contain excellent acoustic properties that aid the CVD diamond tweeters to achieve frequencies of 70 kHz, resulting to an exceptional clear and transparent sound production. Properties of Synthetic Diamonds and Its Improvement and Role to the Technology Associated With It 1. Mechanical Properties Synthetic diamond is exceptional hard and i has very low coefficient of friction and thus of greater advantage to mechanical applications. These extends the tools life, reduces the operating costs, time and carbon footprints. Another extreme hard form of synthetic diamond is the polycrystalline diamond (PDC) which is used as a material in the production of oil and gas drills. This material copes well with those extreme conditions and its used provides significant economic benefits to rig drilling operators. The diamond can also be manufactured to have an ultra-fine edge for extreme precision. This feature has played a far better role in the field of surgery medicine. It has seen the production and its usage as a surgical scalpel in ophthalmic and neurosurgery (Trent, 2013). Many positive changes have been experienced in the oil and gas drilling industry through the usage of tools made from the synthetic diamonds. Economic benefits to the operators. These diamonds can be used to polish, cut and wear away any material including other diamonds Their tools do not require indexing (rotating) to keep their wear flats from growing too large or too fast, the operator no longer has to stop production so as to get the tool indexed to reduce the growth of wearing flats .These has reduced down time and increased productivity. The diamond tools can be marked at the factory with diamond depth lines to allow the operator forecast its life and change worn tools at the beginning of large productions therefore avoiding unnecessary production interruptions (Konstanty, 2011). 2. Optical Properties Synthetic diamonds possess a wide spectral band of any known material. This extends from ultraviolet to infrared and the millimetre-wave microwave band then combined with its thermal and mechanical properties this makes it the ideal ‘window’ material for industrial, R&D, defence and laser application especially in the production of laser optic where the diamond provides optimum exit of carbon (IV) oxide lasers. 3. Thermal Properties The diamond possess the highest known thermal conductivity that is four times higher than copper. This property makes it the ideal material for thermal management applications that require optimum performance. They make an outstanding contribution to all types of electronic and electrical applications where build-up heat or energy can tamper with delicate circuitry or severely impair its performance. One of the most successful applications of this metal in this field was like a ‘heat sink’ for sensitive components used in the telecommunications field in microelectronic devices. 4. Electrochemical Properties Synthetic diamond is biologically and chemically inert and can survive in severely chemical, physical and radioactive environments that would destroy lesser materials. The Element Six investment has resulted in successful applications of a synthetic diamond based product in industrial and water treatment. The diamond anodes enable ozone to be produced on an agreeable scale that is suitable for restaurants homes hospitals and hotels more efficiently and reliably than any other technology available. 5. Electronic Properties Synthetic diamond has a low dielectric constant and loss, a wide electronic band gap and a high electrical carrier mobility all of which allow its use in advanced medical applications that includes therapy for eye cancer patients where synthetic diamond based radiation detectors ensure the delivery of correct dosage to target just the tissue infected by cancer and not to include any healthy tissue around it. A synthetic diamond is used in solid state particle detectors at the Large Hadron Collider at CERN in Switzerland, producing the needed level of ultra-fast, radiation-tolerant sensors capable of measuring proton collisions every 25 nanoseconds. Some of the developed Electronic applications of synthetic diamond are high-power switches at power stations, light-emitting diodes and high-frequency field-effect transistors. Quantum physicists at Harvard University are currently using the highest purity of synthetic diamonds from Element Six to provide synthetic diamond-based quantum computer technology that could enable faster processing and secured communication. The extreme properties of this rock as a semiconductor, combined with its inherent thermal properties are also making the significant contribution in the search to unlock secrets of Big Bang. 6. Acoustic Properties Synthetic diamonds tweeters are used by Bower and Wilkins in their flagship 800 series loudspeaker range. Element Six has perfected the recent technology to grow CVD diamond into complex geometrical shapes at the correct thickness so as to produce domes that have outstanding acoustic properties. Properties of the Material That Detract From Its Use and Highlight Any Alternatives That Are Appearing In Research or In the Market Place The properties of synthetic diamond rely entirely on the facts of the manufacturing methods. 1. Mechanical properties of the synthetic diamonds used in tools With time the diamond coat wears off, scientists have been working to make them even tougher. Researchers led by Yongjun Tian and Quan Huang at Yanshann University in China, has made synthetic diamonds that are harder, meaning they are less prone to deformation and breaking more than both a long lasting operational tool. For surgical cases, diamond like carbon coating on aluminium alloy based surgical instruments is investigated. These can be a better alternative to synthetic diamonds material and it has been used successfully in the medical environment to improve surgery such as cholecystectomy (Konstanty, 2011). 2. Thermal Properties Synthetic diamond tools have higher melting point of 4000Fc, even so it contains thermal limitation of oxidising at temperatures above 600Fc into carbon-dioxide, reacts with the iron group of metals at temperatures above 700Fc and cannot be used to grind steel or titanium alloys if temperature exceeds 700fc. The synthetic diamond possess the highest known thermal conductivity that is four times higher than copper. Recently alternative methods have been achieved by depositing of copper and aluminium metals to enhance thermal capabilities. CBN (cubic boron nitride) has a higher thermal resistance than diamond even at temperatures exceeding 800fC and its thermal conductivity four and a half times better than copper in a closer competition with diamonds. It has same crystal structure as diamond though the boron-nitrogen bonds replace the carbon-carbon bond in diamond which makes it reactive at high temperatures. A better alternative to diamonds (Sergio, 2002). 3. Acoustic properties The domes are extremely fragile and have the thickness of only tens of microns. Bowers and Wilkins through pushing the frontiers of innovation have come up with a synthetic tweeter dome that extends high-frequency response thus improving the quality of sound production. 4. Electronic properties CVD diamonds films are polycrystalline and contain grain boundaries that reduce the lifetime and mobility of carriers. Active devices have been demonstrated using homoepitaxially-grown diamonds. Alternative patterning methods include selective nucleation or laser ablation. Target material determines the type of device to be made suggesting the possibility of faster computers. References Dischler, B. & Wild, C., 2013. Low-Pressure Synthetic Diamond: Manufacturing and Applications. 1st ed. London: Springer. Konstanty, J., 2011. Powder metallurgy Diamond Tools. 1st ed. London: Elsevier Science . Sergio, F., 2002. Synthesis of diamond. journal of materials chemestry, 12(9), pp. 24-55. Trent, E. M., 2013. Metal Cutting. 3rd ed. London: Butterworth-Heinemann. Read More