Metal carbides method

Carbon forms binary compounds with most elements those with metals are considered in this section whilst those with H, the halogens, O, and the chalcogens are discussed in subsequent sections. Alkali metal fullerides and encapsulated (endohedral) metallafullerenes have already been considered (pp. 285, 288 respectively) and met-allacarbohedrenes (metcars) will be dealt with later in this section (p. 300). Silicon carbide is discussed on p. 334. General methods of preparation of metal carbides are ... 

We presented selected results from a new tight-binding total energy method that accurately predicts ground state properties of transition and noble metals, and successfully extended to transition metal carbides. 

A review of the preparation of transition metal carbides and related compounds was published by Windish and Nowotny (1972). The following methods were considered ... 

The various methods of preparation employed to prepare nanoscale clusters include evaporation in inert-gas atmosphere, laser pyrolysis, sputtering techniques, mechanical grinding, plasma techniques and chemical methods (Hadjipanyas Siegel, 1994). In Table 3.5, we list typical materials prepared by inert-gas evaporation, sputtering and chemical methods. Nanoparticles of oxide materials can be prepared by the oxidation of fine metal particles, by spray techniques, by precipitation methods (involving the adjustment of reaction conditions, pH etc) or by the sol-gel method. Nanomaterials based on carbon nanotubes (see Chapter 1) have been prepared. For example, nanorods of metal carbides can be made by the reaction of volatile oxides or halides with the nanotubes (Dai et al., 1995). 

The general methods for the production of the alkali metals are (1) Electrolytic processes involving the electrolysis of (a) the fused hydroxide, or (b) a fused salt— chloride, nitrate, cyanide, etc. (2) Chemical processes involving the reduction of hydroxide, or carbonate, or other salt with carbon, metal carbide, iron, calcium, magnesium, aluminium, etc. W. Spring 5 claims to have reduced a little potassium chloride by passing hydrogen over the salt at a red heat. 

Similar methods are applied by Kuczynski and Landauer (K7) to the diffusion of carbon in metallic carbides, in which a metal-carbon... 

This volume, which is unique in its coverage, provides a general introduction to the properties and nature of transition metal carbides and nitrides, and covers their latest applications in a wide variety of fields. It is directed at both experts and nonexperts in the fields of materials science, solid-state chemistry, physics, ceramics engineering and catalysis. The first chapter provides an overview, with other chapters covering theory of bonding, structure and composition, catalytic properties, physical properties, new methods of preparation, and spectroscopy and microscopy. 

A new method of interpreting Auger electron spectroscopy (AES) sputter profiles of transition metal carbides and nitrides is proposed. It is shown that the chemical information hidden in the shape of the peaks, and usually neglected in depth profiles, can be successfully extracted by factor analysis (FA). The various carbide and nitride phases of model samples were separated by application of FA to the spectra recorded during AES depth profiles. The different chemical states of carbon, nitrogen and metal were clearly identified. 

Transition metal carbides can be used as diffusion barriers like transition metal nitrides in multilayer metallization schemes for integrated circuits. Layers on the order of lOOnm are applied and are produced by sputtering methods. The high chemical stability of these transition metal carbides, especially those of group 4, are exploited to prevent interaction of metal or component layers such as silicon, aluminum, and silicides upon thermal load in production processes. This load would cause electrical or even structural deterioration of the multilayer packages. 

To elucidate the nature of chemical bonding in metal carbides with the NaCl structure, the valence electronic states for TiC and UC have been calculated using the discrete-variational (DV) Xa method. Since relativistic effects on chemical bonding of compounds containing uranium atom become significant, the relativistic Hamiltonian, i.e., the DV-Dirac-Slater method, was used for UC. The results... 

Metallic carbides, nitrides, and oxides are used industrially in many applications their physical properties are also of intrinsic interest. This section pinpoints various preparative techniques and reviews methods of crystal growth for this group of compounds. More detailed discussion is found in the reviews cited and in the references therein. The discussion is confined to binary compounds, M Xi, (M is a cation X = C, N, or O a and b are simple integers) that display metallic properties the very numerous ternaries MoMcXj, (M, M being different cations) cannot be described in this brief presentation. 

The methods for growth of single crystals of metallic carbides are like those for crystalline metallic nitrides however, carbide crystals significantly larger than nitride crystals can be grown. The following techniques are in common use. 

The XRD pattern (Figure 7.18(a)) indicates that the obtained sample is cubic phase TiC, with cell constant a= 4.34A. TEM imaging (Figure 7.18(b)) reveals that it consists of nanoparticles of size 10-20 nm [67]. The co-reduction carburization method may be used to prepare other transition metal carbides. For example, as shown in Reaction (20), nanocrystalline ZrC, size 10-25 nm was synthesized on heating at 550 °C for 12 h [68]. 

In Chapter 8 we described how metal carbides (first mentioned in Section 6-1-4) could serve as precursors to carbyne complexes by way of electrophilic addition. Scheme 10.8 revisits a portion of Scheme 8.12, showing Os-carbide complex 72—with its nucleophilic Ccarbide atom—reacting with methyl triflate or tropylium ion to give alkylidynes 73 and 74, respectively. Comparable reactions occur with the corresponding Ru-carbide complex.87 This method may become more general after the synthesis of additional carbide complexes occurs. 

FELIX is also shown schematically in Fig. 1.19. This method of infrared resonance enhanced multiphoton ionization (IR-REMPI) has been successfully applied to study fullerenes, metal carbide, metal oxide, and metal nitride clusters [126,128-130] as well as metal-adsorbate complexes [131]. 

Early transition metal carbides with high surface area are active catalysts for various reactions such as hydrodenitrogenation(HDN) [1,2], hydrogenation [3,4], Fischer-Tropsch synthesis [5,6], hydrocarbon isomerization [7]. Synthesis of these materials has attracted great attention over the years and a number of procedures have been reported for the preparation of carbides with high surface areas suitable for catalysts. The most commonly employed method is temperature programmed reaction of metal oxide with a mixture of hydrogen and methane, which was developed by Boudart and co-workers [8-10]. 

The SHS/DPIC of diamond- gradually dispersed TiB2/Si cermets was performed. In case of fixing diamond in cermet matrix, there are two methods. One is the physical fixing just like a diamond ring, and the other is the chemical fixing by covalent bond between diamond and metal in the cermet. In this work, we studied the latter system and considered that a metal carbide is very suitable as an interlayer to form the covalent bond.. There are many metals in periodic table to form the metal carbide. However, the... 

In the original work methane was used as the gaseous carbon source. It will now be shown that using ethane as the carbon source results in the formation of metal carbides with higher surface areas than those produced by TPR with methane. Further, the use of ethane allows the carbiding reaction to proceed in a topotactic manner and provides a potential method for synthesising a variety of carbide phases. 

---