Isotopically pure diamond

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An isotopical pure diamond is a type of diamond that is composed entirely of one isotope of carbon. Isotopically pure diamonds have been manufactured from either the more common carbon isotope with mass number 12 (abbreviated as 12C) or the less common 13C isotope. Compared to natural diamonds that are composed of a mixture of 12C and 13C isotopes, isotopically pure diamonds possess improved characteristics such as increased thermal conductivity. [1] Thermal conductivity of diamonds is at a minimum when 12C and 13C are in a ratio of 1:1 and reaches a maximum when the composition is 100% 12C or 100% 13C. [1]

Diamond Allotrope of carbon often used as a gemstone

Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. At room temperature and pressure, another solid form of carbon known as graphite is the chemically stable form, but diamond almost never converts to it. Diamond has the highest hardness and thermal conductivity of any natural material, properties that are utilized in major industrial applications such as cutting and polishing tools. They are also the reason that diamond anvil cells can subject materials to pressures found deep in the Earth.

Isotope nuclides having the same atomic number but different mass numbers

Isotopes are variants of a particular chemical element which differ in neutron number, and consequently in nucleon number. All isotopes of a given element have the same number of protons but different numbers of neutrons in each atom.

Carbon Chemical element with atomic number 6

Carbon is a chemical element with symbol C and atomic number 6. It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Three isotopes occur naturally, 12C and 13C being stable, while 14C is a radionuclide, decaying with a half-life of about 5,730 years. Carbon is one of the few elements known since antiquity.

Contents

Manufacture

The isotopes of carbon can be separated in the form of carbon dioxide gas by cascaded chemical exchange reactions with amine carbamate. [2] Such CO2 can be converted to methane and from there to isotopically pure synthetic diamonds. [3] Isotopically enriched diamonds have been synthesized by application of chemical vapor deposition followed by high pressure. [1]

Carbon dioxide chemical compound

Carbon dioxide is a colorless gas with a density about 60% higher than that of dry air. Carbon dioxide consists of a carbon atom covalently double bonded to two oxygen atoms. It occurs naturally in Earth's atmosphere as a trace gas. The current concentration is about 0.04% (410 ppm) by volume, having risen from pre-industrial levels of 280 ppm. Natural sources include volcanoes, hot springs and geysers, and it is freed from carbonate rocks by dissolution in water and acids. Because carbon dioxide is soluble in water, it occurs naturally in groundwater, rivers and lakes, ice caps, glaciers and seawater. It is present in deposits of petroleum and natural gas. Carbon dioxide is odorless at normally encountered concentrations. However, at high concentrations, it has a sharp and acidic odor.

Synthetic diamond diamond produced in an artificial process, as opposed to natural diamonds, which are created by geological processes

A synthetic diamond is a diamond produced by a controlled process, as contrasted with a natural diamond created by geological processes or an imitation diamond made of non-diamond material that appears similar to a diamond. Synthetic diamond is also widely known as HPHT diamond or CVD diamond, after the two common production methods. While the term synthetic may sometimes be associated by consumers with imitation products, synthetic diamonds are made of the same material as natural diamonds—pure carbon, crystallized in an isotropic 3D form. In the United States, the Federal Trade Commission has indicated that the terms laboratory-grown, laboratory-created, and [manufacturer-name]-created "would more clearly communicate the nature of the stone".

Chemical vapor deposition chemical process used in the semiconductor industry to produce thin films

Chemical vapor deposition (CVD) is a deposition method used to produce high quality, high-performance, solid materials, typically under vacuum. The process is often used in the semiconductor industry to produce thin films.

Types

Carbon 12

The 12C isotopically pure, (or in practice 15-fold enrichment of isotopic number, 12 over 13 for carbon) diamond gives a 50% higher thermal conductivity than the already high value of 900-2000 W/(m·K) for a normal diamond, which contains the natural isotopic mixture of 98.9% 12C and 1.1% 13C. This is useful for heat sinks for the semiconductor industry. [4]

The thermal conductivity of a material is a measure of its ability to conduct heat. It is commonly denoted by , , or .

The watt is a unit of power. In the International System of Units (SI) it is defined as a derived unit of 1 joule per second, and is used to quantify the rate of energy transfer. In dimensional analysis, power is described by .

The Kelvin scale is an absolute thermodynamic temperature scale using as its null point absolute zero, the temperature at which all thermal motion ceases in the classical description of thermodynamics. The kelvin is the base unit of temperature in the International System of Units (SI).

Carbon 13

Isotopically pure 13C diamond layers 20 micrometers thick are used as stress sensors due to the advantageous Raman spectroscopy properties of 13C. [5]

Raman spectroscopy spectroscopic technique used to observe vibrational, rotational, and other low-frequency modes in a system

Raman spectroscopy ; named after Indian physicist Sir C. V. Raman) is a spectroscopic technique used to observe vibrational, rotational, and other low-frequency modes in a system. Raman spectroscopy is commonly used in chemistry to provide a structural fingerprint by which molecules can be identified.

Related Research Articles

Boron nitride chemical compound

Boron nitride is a heat and chemically resistant refractory compound of boron and nitrogen with the chemical formula BN. It exists in various crystalline forms that are isoelectronic to a similarly structured carbon lattice. The hexagonal form corresponding to graphite is the most stable and soft among BN polymorphs, and is therefore used as a lubricant and an additive to cosmetic products. The cubic variety analogous to diamond is called c-BN; it is softer than diamond, but its thermal and chemical stability is superior. The rare wurtzite BN modification is similar to lonsdaleite and may even be harder than the cubic form.

Carbon nanotube allotropes of carbon with a cylindrical nanostructure

Carbon nanotubes (CNTs) are allotropes of carbon with a cylindrical nanostructure. These cylindrical carbon molecules have unusual properties, which are valuable for nanotechnology, electronics, optics, and other fields of materials science and technology. Owing to the material's exceptional strength and stiffness, nanotubes have been constructed with a length-to-diameter ratio of up to 132,000,000:1, significantly larger than that for any other material.

Lonsdaleite Hexagonal lattice allotrope of carbon

Lonsdaleite, also called hexagonal diamond in reference to the crystal structure, is an allotrope of carbon with a hexagonal lattice. In nature, it forms when meteorites containing graphite strike the Earth. The great heat and stress of the impact transforms the graphite into diamond, but retains graphite's hexagonal crystal lattice. Lonsdaleite was first identified in 1967 from the Canyon Diablo meteorite, where it occurs as microscopic crystals associated with diamond.

Silicon carbide semiconductor containing silicon and carbon

Silicon carbide (SiC), also known as carborundum, is a semiconductor containing silicon and carbon. It occurs in nature as the extremely rare mineral moissanite. Synthetic SiC powder has been mass-produced since 1893 for use as an abrasive. Grains of silicon carbide can be bonded together by sintering to form very hard ceramics that are widely used in applications requiring high endurance, such as car brakes, car clutches and ceramic plates in bulletproof vests. Electronic applications of silicon carbide such as light-emitting diodes (LEDs) and detectors in early radios were first demonstrated around 1907. SiC is used in semiconductor electronics devices that operate at high temperatures or high voltages, or both. Large single crystals of silicon carbide can be grown by the Lely method and they can be cut into gems known as synthetic moissanite.

Moissanite carbide mineral; polytypes: 10R, 15R, 33R, 5H

Moissanite is naturally occurring silicon carbide and its various crystalline polymorphs. It has the chemical formula SiC and is a rare mineral, discovered by the French chemist Henri Moissan in 1893. Silicon carbide is useful for commercial and industrial applications due to its hardness, optical properties and thermal conductivity. Efforts to synthesize silicon carbide in a laboratory began in the early 1900s.

Carbon-12 (12C) is the more abundant of the two stable isotopes of carbon, amounting to 98.93% of the element carbon; its abundance is due to the triple-alpha process by which it is created in stars. Carbon-12 is of particular importance in its use as the standard from which atomic masses of all nuclides are measured, thus, its atomic mass is exactly 12 daltons by definition. Carbon-12 is composed of 6 protons 6 neutrons and 6 electrons.

Nanoelectromechanical systems devices integrating electrical and mechanical functionality on the nanoscale

Nanoelectromechanical systems (NEMS) are a class of devices integrating electrical and mechanical functionality on the nanoscale. NEMS form the logical next miniaturization step from so-called microelectromechanical systems, or MEMS devices. NEMS typically integrate transistor-like nanoelectronics with mechanical actuators, pumps, or motors, and may thereby form physical, biological, and chemical sensors. The name derives from typical device dimensions in the nanometer range, leading to low mass, high mechanical resonance frequencies, potentially large quantum mechanical effects such as zero point motion, and a high surface-to-volume ratio useful for surface-based sensing mechanisms. Uses include accelerometers, or detectors of chemical substances in the air.

Graphene bi-dimensional crystalline structure of carbon

Graphene is an allotrope (form) of carbon consisting of a single layer of carbon atoms arranged in a hexagonal lattice.

Superhard material

A superhard material is a material with a hardness value exceeding 40 gigapascals (GPa) when measured by the Vickers hardness test. They are highly incompressible solids with high electron density and high bond covalency. As a result of their unique properties, these materials are of great interest in many industrial areas including, but not limited to, abrasives, polishing and cutting tools and wear-resistant and protective coatings.

Material properties of diamond Physical properties of the mineral

Diamond is the allotrope of carbon in which the carbon atoms are arranged in the specific type of cubic lattice called diamond cubic. Diamond is an optically isotropic crystal that is transparent to opaque. Diamond is the hardest naturally occurring material known. Yet, due to important structural weaknesses, diamond's toughness is only fair to good. The precise tensile strength of bulk diamond is unknown, however strength up to 60 GPa has been observed, and it could be as high as 90–100 GPa in the form of nanometer-sized wires or needles ,with a corresponding local maximum tensile elastic strain in excess of 9%. The anisotropy of diamond hardness is carefully considered during diamond cutting. Diamond has a high refractive index (2.417) and moderate dispersion (0.044) properties which give cut diamonds their brilliance. Scientists classify diamonds into four main types according to the nature of crystallographic defects present. Trace impurities substitutionally replacing carbon atoms in a diamond's crystal structure, and in some cases structural defects, are responsible for the wide range of colors seen in diamond. Most diamonds are electrical insulators but extremely efficient thermal conductors. Unlike many other minerals, the specific gravity of diamond crystals (3.52) has rather small variation from diamond to diamond.

Crystallographic defects in diamond

Imperfections in the crystal lattice of diamond are common. Such crystallographic defects in diamond may be the result of lattice irregularities or extrinsic substitutional or interstitial impurities, introduced during or after the diamond growth. The defects affect the material properties of diamond and determine to which type a diamond is assigned; the most dramatic effects are on the diamond color and electrical conductivity, as explained by the electronic band structure.

Second sound is a quantum mechanical phenomenon in which heat transfer occurs by wave-like motion, rather than by the more usual mechanism of diffusion. This leads to a very high thermal conductivity. It is known as "second sound" because the wave motion of heat is similar to the propagation of pressure waves in air (sound).

As the devices continue to shrink further into the sub-100 nm range following the trend predicted by Moore’s law, the topic of thermal properties and transport in such nanoscale devices becomes increasingly important. Display of great potential by nanostructures for thermoelectric applications also motivates the studies of thermal transport in such devices. These fields, however, generate two contradictory demands: high thermal conductivity to deal with heating issues in sub-100 nm devices and low thermal conductivity for thermoelectric applications. These issues can be addressed with phonon engineering, once nanoscale thermal behaviors have been studied and understood.

A nanofluid is a fluid containing nanometer-sized particles, called nanoparticles. These fluids are engineered colloidal suspensions of nanoparticles in a base fluid. The nanoparticles used in nanofluids are typically made of metals, oxides, carbides, or carbon nanotubes. Common base fluids include water, ethylene glycol and oil.

Chemiresistor

A chemiresistor is a material that changes its electrical resistance in response to changes in the nearby chemical environment. Chemiresistors are a class of chemical sensors that rely on the direct chemical interaction between the sensing material and the analyte. The sensing material and the analyte can interact by covalent bonding, hydrogen bonding, or molecular recognition. Several different materials have chemiresistor properties: metal-oxide semiconductors, some conductive polymers, and nanomaterials like graphene, carbon nanotubes and nanoparticles. Typically these materials are used as partially selective sensors in devices like electronic tongues or electronic noses.

References

  1. 1 2 3 Anthony TR, Banholzer; Banholzer, W (April 1992). "Properties of diamond with varying isotopic composition". Diamond and Related Materials. 1 (5–6): 717–726. Bibcode:1992DRM.....1..717A. doi:10.1016/0925-9635(92)90197-V.
  2. ↑ Takeshita K, Ishidaa M (December 2006). "Optimum design of multi-stage isotope separation process by exergy analysis". ECOS 2004 - 17th International Conference on Efficiency, Costs, Optimization, Simulation, and Environmental Impact of Energy on Process Systems. 31 (15): 3097–3107. doi:10.1016/j.energy.2006.04.002.
  3. ↑ Anthony TR, Bradley JC, Horoyski PJ, Thewal ML (November 1996). "Graphite rod precursors for isotopically pure fullerenes and diamond". Carbon. 34 (11): 1323–1328. doi:10.1016/S0008-6223(96)00060-7.
  4. ↑ Bray JW, Anthony TR (February 1991). "On the thermal conductivity of diamond under changes to its isotopic character". Z. Phys. B. 84 (1): 51–57. Bibcode:1991ZPhyB..84...51B. doi:10.1007/BF01453758.
  5. ↑ Qiu W, Velisavljevic N, Baker PA, Vohra YK, Weir ST (June 2004). "Isotopically pure 13C layer as a stress sensor in a diamond anvil cell". Appl. Phys. Lett. 84 (26): 5308–5310. Bibcode:2004ApPhL..84.5308Q. doi:10.1063/1.1766077.
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