Other Nanometal Powders

1) n-Nickel powder (=50nm), nickel-boron alloys amorphous nanopowder (=20nm), n-copper (=90nm) and nickel-copper alloy (=45 nm) were synthesized with the use of chemical reduction methods. Further, the effect of these metals and alloy powders on thermal decomposition of AP was also studied and the data suggest favorable performance [91] that is, the catalytic effects on the thermal decomposition of AP are more pronounced compared with the micron-sized metal powders. 

2) The preparation of n-Ti powder (=21 nm) has also been reported by a novel chemical solution synthetic route  

3) Berger et al. [93] reported preparation of n-Si (=10-100 nm) with the use of induction coupled plasma and scaled-up the process to kilogram level. The results of some formulations made with the use of this n-Si powder and potassium perchlorate prove their superior performance over the corresponding formulations based on micron-sized silicon powder. 

4) The preparation of n-Li (5-30nm) and n-W (10-30nm) powders which possess spherical forms leading to better packing density coupled with higher loadings have also been reported. 

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Aluminium powders are also used for the thermite reaction. This is the reaction traditionally used to weld rail tracks together in situ 2Al(s)+Fe203(s)=2Fe(l) + Al203(s), which produces so much heat that molten iron is produced, but it can also be used to produce other less easily reduced metals, such as Mo, from their oxides. Using nanometer particles dramatically improves performance, and these reactions are used as priming reactions for munitions and in fireworks. 

The possibility to obtain a uniformly dispersed composite powder was shown for the a-Fe-Al203 system where metal particles with an average size of 55 nm were formed in an amorphous/nano alumina matrix.18 Other studies attempting to obtain dense bulk composites based on the sol-gel route using conventional pressure-assisted sintering ( 1400°C and an applied force of 10 MPa) resulted in a coarse microstructure.16 However, if reaching theoretical density is not a necessary requirement, a porous ceramic microstructure containing nanometer-sized metal particles can be used as a catalytic material.19 Certain combinations of composite materials demand... 

Hydrothermal reactions typically produce nanometer-sized particles that can be quenched to form a nanoparticle powder or cross-linked to produce nanocrystalline stmctures (Feng and Xu, 2001). Hydrothermal conditions allow for reduction in solubilities of ionic materials and thus more rapid nucleation and increased ion mobility, resulting in faster growth. Via judicious choice of the hydrothermal conditions, a measure of control can be exerted over the size and morphology of the materials. As mentioned earlier, the viscosity and ionic strength of solvents is a function of the temperature and pressure at which the reaction is carried out. Other experimental parameters, such as the precursor material and the pH, have... 

The method for the study of crystal structure, including mineral composition, is x-ray diffraction. It is a semiquantitative method (Klug and Alexander 1954 Warren 1999) for the study of mineral composition. Powder samples of rocks are studied, and the place of the peaks (in nanometer or diffraction angle) and their relative intensity are observed. The diffractogram is usually compared to that of known substances that can be found in databases (ICDD 2009). In order to accurately quantify the rock samples, x-ray diffraction must be complemented with other quantitative techniques, including chemical analysis (Section 4.1.1), thermal, infrared analyses (Chapter 2, Section 2.1.2) and surface area (Chapter 1, Section 1.3.4.1.5 Section 4.1.3) measurements. 

Compared to conventional solid-state reaction and co-precipitation method [1,2], sol-gel method offer promising approaches for preparing ultrafine, homogeneous, high-purity powders at temperatures far below other required methods. Currently, there are no literatures reporting that nanometer BaTiOj was used as support to prepare catalyst. In this paper, performance of the catalyst with nanometer BaTiO, as support in the reaction of CO2 reforming CH4 to syngas was described. 

A third area of research, which has the potential to revolutionize powder diffraction, is the focusing of X-rays into very small beams ( nanobeams ). Nanoscience and modem synchrotron diffraction are engaged in a synergetic relationship in which on the one hand nanoscience requires nanoscale X-ray beams to probe nanometer size regions of matter and on the other hand, nanolithography tools... 

ITRI has developed and patented processes for preparing and utilizing stable aqueous colloidal sols of tin(IV) oxide and related materials. These products, which contain nanometer-scale particulate tin oxide, are useful precursors for the synthesis of ceramic bodies, powders, and coatings, and may And application in encapsulated pigments, electroconductive materials, catalysts, and transparent tin oxide Aims on glass and other substrates. 

It is apparent from the data that particles of a few nanometers in size can only be made on industrial scale by synthetic methods. On the other hand, these particles are either intentionally or unintentionally aggregated and agglomerated in their powder forms. Thus, for the dispersion of fillers, agglomerate and aggregate size is usually as relevant as the primaiy particle size. Fillers, which are obtained by various milling and classification processes, can also be obtained in the form of small particles, but usually not below 100 nm. 

In general, these methods are used for the production of nanocrystalline powders which may be further compacted via techniques such as hot-pressing [157, 158] or magnetic pulsed compaction [159, 160]. In addition, other types of nanoionic material maybe prepared, such as nanometer-thin films, using techniques including molecular beam epitaxy [161], pulsed laser deposition [162] or spin-coating methods [163]. Novel structures, such as core-shell [164—166] and multi-layered [167, 168] (so-called onion structures) materials, may also be produced in this way. 

It has been reported in the past decade that a substantial enhancement of hydrogen sorption/desorption properties of various hydrides could be achieved by creating nanostructured/nanocomposite materials using mechanical alloying (MA) and/or milling (MM) [7,8], In this context nanostructured/nanocomposite means that each phase present in the individual powder particle of the alloy is in the form of grains with nanometer size. In other words, one powder particle can be considered as a... 

Both the attraction and the ambient forces are mainly dependent on the size x of the powder particle(s). While the surface area of individual particles, the interface at which all binding mechanisms act, decreases with the second power of particle size, volume and consequently also mass, the most important particle properties that result in forces that challenge adhesion and may cause separation of bonds, diminish with the third power of the particle size. Therefore, if the particle size reaches a few micrometers or is in the nanometer range, the natural adhesion forces dominate and particles that contact each other or come into close proximity adhere to one another. This phenomenon can not be economically eliminated, so very fine particles always adhere and form loose agglomerates, which may be desirable (Chapter 5) or undesirable (Chapter 4). 

Gas-phase reactions for the formation of nonoxide powders have been known for a long time. In the last few years many of these routes were reinvestigated and other precursors have been developed. This is mainly because of their potential to yield very fine grained nonoxides, with mean grain sizes in the nanometer range. Routes via the gas phase have also been intensively studied for the direct formation of coatings that is, CVD (chemical vapor deposition). All reaction paths basically considered as a CVD process can be tailored for the formation of powders the processing parameters must be optimized. 

The product of the chemical synthesis for polyacetylene was a freestanding film. In other cases, the product can be a powder of particles of different shapes and sizes from micrometer down to nanometer dimension. 

Yajima [76] was the first to study the preparation of silicon carbide fibers from carbosilanes. These and other SiC-containing polymers were used to produce SiC powders with a crystallite size as small as several nanometers [77, 78]. The advantage ofthe production route from liquid to solid to produce SiC has also attracted attention for SiC film production in microelectronics or as protection layers. In this way, amorphous, polycrystalline films of high purity produced by the dip-coating of substrates in PCS solutions and subsequent pyrolysis in an inert gas atmosphere, have been prepared [115]. 

Most major improvements in performance of Fischer-Tropsch and other catalysts have been achieved through advanced imaging technologies. For example, different types of electron microscopy (Florea et al. 2013 Thomas et al. 2013), X-ray, and neutron powder diffraction (Rozita et al. 2013) facilitate characterization of catalyst particles and the included pores ranging in size from micron to a few nanometers. These advanced tools lend a capability to analyze down to the level of an atom. Further, the same facilitate introduction of efficient promoters and also distribution of smaller catalytic species over greater surface areas. The last feature implies a catalyst with high activity and surface area and should allow higher rates of reaction. 

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