Detonation nanodiamond (DND), also known as ultradispersed diamond (UDD), is diamond that originates from a detonation. When an oxygen-deficient explosive mixture of TNT/RDX is detonated in a closed chamber, diamond particles with a diameter of c. 5 nm are formed at the front of the detonation wave in the span of several microseconds.
The diamond yield after detonation crucially depends on the synthesis condition and especially on the heat capacity of the cooling medium in the detonation chamber (water, air, CO2, etc.). The higher the cooling capacity, the larger the diamond yield, which can reach 90%. After the synthesis, diamond is extracted from the soot using high-temperature high-pressure (autoclave) boiling in acid for a long period (ca. 1–2 days). The boiling removes most of the metal contamination, originating from the chamber materials, and non-diamond carbon.
Various measurements, including X-ray diffraction [1] and high-resolution transmission electron microscopy, [2] revealed that the size of the diamond grains in the soot is distributed around 5 nm. The grains are unstable with respect to aggregation and spontaneously form micrometre-sized clusters (see figure above). The adhesion is strong and contacts between a few nano-grains can hold a micrometre-sized cluster attached to a substrate. [2]
Nanosized diamond has extremely large relative surface area. As a result, its surface spontaneously attaches water and hydrocarbon molecules from the ambient atmosphere. [3] However, clean nanodiamond surface can be obtained with appropriate handling. [2]
The detonation nanodiamond grains mostly have diamond cubic lattice and are structurally imperfect. The major defects are multiple twins, as suggested by high-resolution transmission electron microscopy. [2] Despite the carbon source for the diamond synthesis—TNT/RDX explosive mixture—being rich in nitrogen, concentration of paramagnetic nitrogen inside diamond grains is below one part per million (ppm). [1] Paramagnetic nitrogen (neutral nitrogen atoms substituting for carbon in the diamond lattice) is the major form of nitrogen in diamond, and thus the nitrogen content in DND is probably very low.
Diamond nanocrystals can also be synthesized from a suspension of graphite in organic liquid at atmospheric pressure and room temperature using ultrasonic cavitation. The yield is approximately 10%. The cost of nanodiamonds produced by this method are estimated to be competitive with the HPHT process. [4] [5]
An alternative synthesis technique is irradiation of graphite by high-energy laser pulses. The structure and particle size of the obtained diamond is rather similar to that obtained in explosion. In particular, many particles exhibit multiple twinning. [6]
A research group from Case Western Reserve University produced nanodiamonds 2–5 nm in size at near-ambient conditions by a microplasma process. [7] The nanodiamonds are formed directly from a gas and require no surface to grow on.
Commercial products based on nanodiamonds are available for the following applications:
Nanomaterials can shuttle chemotherapy drugs to cells without producing the negative effects of today's delivery agents. Clusters of the nanodiamonds surround the drugs ensuring that they remain separated from healthy cells, preventing unnecessary damage; upon reaching the intended targets, the drugs are released into the cancer cells. The leftover diamonds, hundreds of thousands of which could fit into the eye of a needle, do not induce inflammation in cells once they have done their job. [12] [13]
In 2012 the SKN Company was awarded the Ig Nobel Peace Prize for converting old Russian ammunition into nanodiamonds. [14]
Boron nitride is a thermally 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 but slightly softer than the cubic form.
Chemical vapor deposition (CVD) is a vacuum deposition method used to produce high-quality, and high-performance, solid materials. The process is often used in the semiconductor industry to produce thin films.
β-Carbon nitride (beta-carbon nitride), β-C3N4, is a superhard material predicted to be harder than diamond.
Silicon carbide (SiC), also known as carborundum, is a hard chemical compound containing silicon and carbon. A semiconductor, it occurs in nature as the extremely rare mineral moissanite, but has been mass-produced as a powder and crystal 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. Large single crystals of silicon carbide can be grown by the Lely method and they can be cut into gems known as synthetic moissanite.
Presolar grains are interstellar solid matter in the form of tiny solid grains that originated at a time before the Sun was formed. Presolar stardust grains formed within outflowing and cooling gases from earlier presolar stars.
Lab-grown diamond is diamond that is produced in a controlled technological process. Unlike diamond simulants, synthetic diamonds are composed of the same material as naturally formed diamonds—pure carbon crystallized in an isotropic 3D form—and share identical chemical and physical properties.
Carbon is capable of forming many allotropes due to its valency. Well-known forms of carbon include diamond and graphite. In recent decades, many more allotropes have been discovered and researched, including ball shapes such as buckminsterfullerene and sheets such as graphene. Larger-scale structures of carbon include nanotubes, nanobuds and nanoribbons. Other unusual forms of carbon exist at very high temperatures or extreme pressures. Around 500 hypothetical 3‑periodic allotropes of carbon are known at the present time, according to the Samara Carbon Allotrope Database (SACADA).
In physics, superlubricity is a regime of motion in which friction vanishes or very nearly vanishes. However, a "vanishing" friction level is not clear, which makes the term vague. As an ad hoc definition, a kinetic coefficient of friction less than 0.01 can be adopted. This definition also requires further discussion and clarification.
Amorphous carbon is free, reactive carbon that has no crystalline structure. Amorphous carbon materials may be stabilized by terminating dangling-π bonds with hydrogen. As with other amorphous solids, some short-range order can be observed. Amorphous carbon is often abbreviated to aC for general amorphous carbon, aC:H or HAC for hydrogenated amorphous carbon, or to ta-C for tetrahedral amorphous carbon.
A superhard material is a material with a hardness value exceeding 40 gigapascals (GPa) when measured by the Vickers hardness test. They are virtually 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, disc brakes, and wear-resistant and protective coatings.
Diamond is the allotrope of carbon in which the carbon atoms are arranged in the specific type of cubic lattice called diamond cubic. It is a crystal that is transparent to opaque and which is generally isotropic. Diamond is the hardest naturally occurring material known. Yet, due to important structural brittleness, bulk diamond's toughness is only fair to good. The precise tensile strength of bulk diamond is little known; however, compressive strength up to 60 GPa has been observed, and it could be as high as 90–100 GPa in the form of micro/nanometer-sized wires or needles, with a corresponding 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 that 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 and extremely efficient thermal conductors. Unlike many other minerals, the specific gravity of diamond crystals (3.52) has rather small variation from diamond to diamond.
Imperfections in the crystal lattice of diamond are common. Such defects 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.
Aggregated diamond nanorods, or ADNRs, are a nanocrystalline form of diamond, also known as nanodiamond or hyperdiamond.
Carbon nanofibers (CNFs), vapor grown carbon fibers (VGCFs), or vapor grown carbon nanofibers (VGCNFs) are cylindrical nanostructures with graphene layers arranged as stacked cones, cups or plates. Carbon nanofibers with graphene layers wrapped into perfect cylinders are called carbon nanotubes.
Nanochemistry is an emerging sub-discipline of the chemical and material sciences that deals with the development of new methods for creating nanoscale materials. The term "nanochemistry" was first used by Ozin in 1992 as 'the uses of chemical synthesis to reproducibly afford nanomaterials from the atom "up", contrary to the nanoengineering and nanophysics approach that operates from the bulk "down"'. Nanochemistry focuses on solid-state chemistry that emphasizes synthesis of building blocks that are dependent on size, surface, shape, and defect properties, rather than the actual production of matter. Atomic and molecular properties mainly deal with the degrees of freedom of atoms in the periodic table. However, nanochemistry introduced other degrees of freedom that controls material's behaviors by transformation into solutions. Nanoscale objects exhibit novel material properties, largely as a consequence of their finite small size. Several chemical modifications on nanometer-scaled structures approve size dependent effects.
The nitrogen-vacancy center is one of numerous photoluminescent point defects in diamond. Its most explored and useful properties include its spin-dependent photoluminescence, and its relatively long (millisecond) spin coherence at room temperature. The NV center energy levels are modified by magnetic fields, electric fields, temperature, and strain, which allow it to serve as a sensor of a variety of physical phenomena. Its atomic size and spin properties can form the basis for useful quantum sensors. It has also been explored for applications in quantum computing, quantum simulation, and spintronics.
A microplasma is a plasma of small dimensions, ranging from tens to thousands of micrometers. Microplasmas can be generated at a variety of temperatures and pressures, existing as either thermal or non-thermal plasmas. Non-thermal microplasmas that can maintain their state at standard temperatures and pressures are readily available and accessible to scientists as they can be easily sustained and manipulated under standard conditions. Therefore, they can be employed for commercial, industrial, and medical applications, giving rise to the evolving field of microplasmas.
Nanodiamonds, or diamond nanoparticles, are diamonds with a size below 100 nanometers. They can be produced by impact events such as an explosion or meteoritic impacts. Because of their inexpensive, large-scale synthesis, potential for surface functionalization, and high biocompatibility, nanodiamonds are widely investigated as a potential material in biological and electronic applications and quantum engineering.
Ultra-high-temperature ceramics (UHTCs) are a type of refractory ceramics that can withstand extremely high temperatures without degrading, often above 2,000 °C. They also often have high thermal conductivities and are highly resistant to thermal shock, meaning they can withstand sudden and extreme changes in temperature without cracking or breaking. Chemically, they are usually borides, carbides, nitrides, and oxides of early transition metals.
Although diamonds on Earth are rare, extraterrestrial diamonds are very common. Diamonds small enough that they contain only about 2000 carbon atoms are abundant in meteorites and some of them formed in stars before the Solar System existed. High pressure experiments suggest large amounts of diamonds are formed from methane on the ice giant planets Uranus and Neptune, while some planets in other planetary systems may be almost pure diamond. Diamonds are also found in stars and may have been the first mineral ever to have formed.