Nanodiamonds, characteristics

The light and heavy isotope enrichment in Xe-HL has been interpreted as being due to the p- and r-process, and thus requires an SN origin (Heymann and Dziczkaniec, 1979, 1980 Clayton, 1989). In one model, Xe-H is made by a short neutron burst, with neutron densities intermediate between those characteristic for the r- and s-processes (Clayton, 1989 Howard et al., 1992). Ott (1996) kept the standard r-process but proposed that xenon is separated from iodine and tellurium precursors on a timescale of a few hours after their production. Measurements of tellurium isotopes in nanodiamonds show almost complete absence of the isotopes Te, 22-i26rj,g ... 

However, the particles small dimensions give rise to one of the characteristic structural features of nanodiamond The large portion of surface atoms causes strain within the particles that shows in an altered bonding situation close to the surface. In NMR-examinations, for instance, the carbon atoms on the surface exhibit another chemical shift than those situated in the core of the particle. This is due to the attachment of functional groups or due to sp -hybridized atoms arising from a reconstruction of the surface (Section 5.2.2). 

In addition to the electron microscopic examination, valuable information about the material s structure can also be obtained from the evaluation of spectroscopic data. Analytical methods chiefly reflecting the properties of either the surface or the bulk phase will be considered in this section. This distinction is of particular relevance for nanodiamond as surface properties and bulk characteristics differ in parts significantly here. 

The X-ray diffractogram of nanodiamond exhibits the signals characteristic for the (111)-, (220)-, and (311)-planes of a diamond type lattice at 20= 43.9°, 75.3°, and 91.5° (Table 5.2, Figure 5.19). In comparison to bulk diamond, they show another proportion of intensities and a much larger half width. In some cases even the signals for the (400)- and the (331)-plane are observed, with their intensities being rather weak, though. 

Figure 5.28 Current-voltage characteristic of field emission from a nanodiamond particle on a silicon substrate doped with nitrogen. The turn-on field intensity (attainment of a 0.1 iA current) is 3.2Vpm", and at 5Vpm" a current density of about 95 mAcm" is attained ( Elsevier 2000).

The preparation of composite materials in general is a very important appHca-tion of the mechanical properties of nanodiamond. With many polymers like caoutchouc, polysiloxanes, fluoroelastomers polymethacrylates, epoxy resins, etc., composites with markedly improved mechanical characteristics have already been obtained from the noncovalent incorporation of nanodiamond by simple admixing during polymerization. The modulus of elasticity, the tensile strength, and the maximal elongation of the material all increase upon this modification. Depending on the basic polymer, just 0.1-0.5% (w/w) of nanodiamond are required to achieve this effect (Table 5.3). Polymer films can also be reinforced by the addition of nanodiamond. For a teflon film with ca. 2% of nanodiamond added, for example, friction is reduced at least 20%, and scratches inflicted by mechanical means are only half as deep as in neat teflon. 

Physical properties Nanodiamond stands out for its great hardness and surface conductivity, for field emission characteristics and for the possible fluorescence of defect centers. Spectroscopic examinations revealed both the band structure and the structural properties. 

The physical properties of diamond films largely correspond to those of the macroscopic material. The only significant differences to bulk diamond arise from surface defects and from a possible doping. The spectroscopic properties are employed to characterize the diamond films obtained, to evaluate their quality and, where applicable, to identify defects and impurities. In the following, the main attention will be directed just to those features differing from the bulk properties of diamond. Further aspects are also discussed in Section 5.4 on the physical properties of nanodiamond that shares some characteristics with the so-called ultrananocrystalline diamond in particular. 

Carbon-based polymer nano composites represent an interesting type of advanced materials with structural characteristics that allow them to be applied in a variety of fields. Functionalization of carbon nanomaterials provides homogeneous dispersion and strong interfacial interaction when they are incorporated into polymer matrices. These features confer superior properties to the polymer nanocomposites. This chapter focuses on nanodiamonds, carbon nanotubes and graphene due to their importance as reinforcement fillers in polymer nanocomposites. The most common methods of synthesis and functionalization of these carbon nanomaterials are explained and different techniques of nanocomposite preparation are briefly described. The performance achieved in polymers by the introduction of carbon nanofillers in the mechanical and tribological properties is highlighted, and the hardness and scratching behavior of the nanocomposites are also discussed. 

The outstanding characteristics of PPS make it widely popular in various applications, including electronics and electrical appliances. Nanodiamond acts as an efficient nucleating agent for PPS and promotes its crystallization via heterogeneous nucleation. When the nanoparticle content in the composite was less than 1 wt%, the crystallization temperature increased with increasing nanodiamond content. ... 

Due to its unique physicochemical characteristics, diamond is widely used in industry. Interest in fabrication of artificial diamond crystals, specifically, those obtained by detonation transformation of explosives, was already evinced in the 1940s. Attention was paid to the fact that thermodynamic conditions for the existence of carbon as diamond crystals are realized in the zone of the detonation complex. Nanodiamond powder synthesis and the properties of synthesized materials were studied in numerous works performed at various research centers [1-11]. In subsequent decades, many attempts were undertaken to develop detonation diamond technology. One of these technologies was developed and patented by the Russian Federal Nuclear Center-Zababakhin All-Russian Research Institute of Technical Physics (RFNC-VNIITF). 

Table 2.1 Characteristics of nanodiamond powders obtained by various purification techniques.

The characteristics of nanodiamonds demonstrating their diamondlike (crystalline and molecular) structure include ... 

Nanodiamond powder technology began to be rapidly developed in the mid-1980s. UDD is close to this class of materials by its characteristics. A large body of information on the positive effect of nanofillers on the mechanical properties of various composite materials, polymer composites included, appeared in the patent and technical literature. Still, in spite of UDD evidently being technically... 

This work studied the mechanical characteristics of amorphous plastic styrene acrylonitrile copolymer (SAN). Nanodiamond powder particles (2.5, 5, and 10%) were added to copolymer granules and mixed in a microextruder-type mixer (auger diameter, 9 mm 2rpm, 200°C, mixing time 5 min). Samples of the mixture as extrudates were tested at room temperature on an Instron testing machine. 

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