Carbon hydrothermal synthesis

Other Industrial Applications. High pressures are used industrially for many other specialized appHcations. Apart from mechanical uses in which hydrauhc pressure is used to supply power or to generate Hquid jets for mining minerals or cutting metal sheets and fabrics, most of these other operations are batch processes. Eor example, metallurgical appHcations include isostatic compaction, hot isostatic compaction (HIP), and the hydrostatic extmsion of metals. Other appHcations such as the hydrothermal synthesis of quartz (see Silica, synthetic quartz crystals), or the synthesis of industrial diamonds involve changing the phase of a substance under pressure. In the case of the synthesis of diamonds, conditions of 6 GPa (870,000 psi) and 1500°C are used (see Carbon, diamond, synthetic). 

The two fluids most often studied in supercritical fluid technology, carbon dioxide and water, are the two least expensive of all solvents. Carbon dioxide is nontoxic, nonflammable, and has a near-ambient critical temperature of 31.1°C. CO9 is an environmentally friendly substitute for organic solvents including chlorocarbons and chloroflu-orocarbons. Supercritical water (T = 374°C) is of interest as a substitute for organic solvents to minimize waste in extraction and reaction processes. Additionally, it is used for hydrothermal oxidation of hazardous organic wastes (also called supercritical water oxidation) and hydrothermal synthesis. 

Cancrinites are one of the rarest members of the feldspathoid group, classified as such due to its low silicon content. However, cancrinite is also classified as a zeolite, due to its open pore structure, which confers molecular sieve properties [1], Likewise, variable sodium carbonate and NaOH concentrations in the hydrothermal synthesis of cancrinite could direct the synthesis of the intermediate phase or the disordered cancrinite formation [2], The intermediate phase is described as a phase between cancrinite and sodalite [3], The disordered cancrinite is an intermediate phase which is much closer to the cancrinite structure than sodalite structure [2],... 

Nethravathi, C., et ah, Hydrothermal synthesis of a monoclinic V02 nanotube-graphene hybrid for use as cathode material in lithium ion batteries. Carbon, 2012. 50(13) p. 4839-4846. 

Wang, W. Lu, C. Ni, Y. Su, M. Xu, Z., Hydrothermal synthesis and enhanced photocatalytic activity of flower-like Ti02 on carbon nanotubes. Mater. Lett. 2012,79 11-13. 

Roy, D. M., Eysel, W. and Dinger, D. (1974). Hydrothermal Synthesis of various carbonate containing calcium hydroxyapatite. Mater. Res. Bull., (9) 35-40. 

Matsui, K., Kyotani, T., and Tomita, A. Hydrothermal synthesis of single crystal Ni(OH)2 nanorods in a carbon-coated anodic alumina film. Adv. Mater. 14, 2002 1216-1218. 

Polycrystalline zeolite membranes consist of inter-grown zeolite crystals with no apparent cracks or pinholes (Fig. lA). These films are composed of only zeolite (i.e., there are no non-zeolite components such as amorphous silica or polymer). They are normally supported on a substrate although free-standing films have also been synthesized. Membranes can be prepared on different substrates such as silicon wafer, quartz, porous alumina, carbon, glass, stainless steel (SS), gold, etc. Polycrystalline films are primarily prepared by hydrothermal synthesis methods including in situ crystallization, seeded growth,and vapor transport, " and have potential use in all of the applications discussed in this entry. 

All industrially-produced methanol is made by the catalytic conversion of synthesis gas containing carbon monoxide, carbon dioxide, and hydrogen as the main components. Methanol productivity can be enhanced by synthesis gas enrichment with additional carbon dioxide to a certain limit [14]. However, a C02—rich environment increases catalyst deactivation and shortens its lifetime, and produces water which adversely affects the catalyst matrix stability resulting in crystallite growth via hydrothermal synthesis phenomena [14]. Thus, a special catalyst has been designed to operate under high C02 conditions. This catalyst s crystallites are located on energetically stable sites that... 

The Carbon Black Pearls labeled BP 2000 was supplied by Cabot Corp. 10 g of carbon black pearls (BP-2000) was dried in an oven at 110 °C overnight. In a 200-mL flask, 17.2 g of 40 % tetrabutylammonium hydroxide, 2.5 g of I BO and 15.1 g of ethanol was stirred to obtain a homogeneous solution. The dried carbon black was impregnated with this solution to incipient wetness. After evaporation of ethanol at room temperature for 12 h, carbon particles were impregnated with 19.3 g of tetraethyl orthosilicate. This mixture was left at ambient conditions to hydrolyze overnight. The hydrothermal synthesis was performed in a Teflon-lined autoclave at 180 °C for 72 h. Then the autoclave was cooled, a solid product was filtered and washed with distilled water. Calcination was carried out in a muffle oven at 550 °C for 18 h [86],... 

Carbon nanotubes were purified by reflux with concentrated hydrochloric acid for 24 h. After that 1.0 g of carbon nanotubes was successfully impregnated with 1.0 g of tetrapropylammonium hydroxide (40 wt. %) and 1.0 g of tetraethyl orthosilicate. Samples were digested for 3 h and then heated to an autoclave at 175 °C for 24 h. After the hydrothermal synthesis, the solid phase was filtered, washed with water and ethanol, and dried at 110 °C. The carbon nanotubes were completely removed by calcination in air at 600 °C for 20 h [82J. 

Dozens of methods to synthesize nanotubes, nanowires, and nanorods have been reported that can be found in the references included in Table 1. In addition to the most well known ones, such as hot plasmas, laser ablation, chemical vapor deposition, high temperature solid state and hydrothermal synthesis, fill-ing/coating of carbon nanotubes and similar types of materials, three methods have been developed that enable the synthesis of a wealth of new anisotropic nanoparticles. 

Firstly, a mesoporous silica S , like SBA-15 is impregnated with an organic carbon source [5]. Carbonization of this precursor results in a silica/carbon composite, from which the mesoporous carbon C is obtained by dissolution of the silica. The pores of this carbon are impregnated with a gel for the synthesis of a zeolite which is subsequently submitted to a hydrothermal synthesis yielding a zeolite/carbon composite. Combustion of the carbon and the template molecules should result in mesoporous zeolite Z . 

Other synthesis reactions include hydrothermal techniques, hydrolysis of other calcium phosphates (Monma and Kayima 1987) and sol-gel methods (Masuda et al. 1990). Hydrothermal synthesis is the second most common method and, in comparison to the wet chemical method, is able to produce well-crystallized, compositionally homogeneous apatite (Yoshimura and Suda 1994). In this process, a mixture of calcium carbonate and di-ammonium hydrogen phosphate is subjected to 12,000 psi and heated to 275°C (Roy and Linnehan 1974). A high crystallinity, carbonate substituted HAp is produced by this method. Calcium phosphates that have been hydrolysed to HAp include octacalcium phosphate (Graham and Brown 1996), tricalcium phosphate (Nakahira et al. 1999), and brushite (Monma and Kayima 1987, Fulmer and Brown 1998, Manjubala et al. 2001). The chemical formulas of these and other inorganic compounds are provided in Appendix 1. 

FePt nanorods of high quahty have been produced by decomposition of Fe(CO)5 and reduction of Pt(acac)2 in a confined cyUndiical mesophase consisting of surfactants such as oleic acid and oleyl amine at high concentrations and slow heating (61). Self-assembly of FePt nanorods can be carried out on a silicon wafer by evaporating a hexane dispersion. Hydrothermal synthesis has also been used for self-assembly by precoating the substrate with aluminum metal (62). Under hydrothermal conditions, the aluminum metal transforms to a hydrotalcite-like phase which provides a lattice matched substrate for the growth of oxide nanorods such as ZnO (Fig. 7.12). The substrates can be diverse, flat, or curved, such as silicon, polystyrene beads, carbon nanotube array, etc. 

The size of mesoporous silica MCM-41 can be adjusted by changing the number of carbon atoms in surfactant micelles used in the hydrothermal synthesis. Iwamoto and co-workers have reported photocyclization of diarylethenes 124 in different-sized MCM-41. Only the anti-parallel conformation of open form 124 can undergo cyclization upon irradiation to give closed form 125. The reaction rate of 124 was found to be remarkably dependent on the amount of 124 loaded as well as the pore diameter of MCM-41 s, but be independent of the organic groups on the surface of MCM-41s. °... 

Han, Y. et al. Evaluation of nanostructured carbonated hydroxyapatite coatings formed by a hybrid process of plasma spraying and hydrothermal synthesis. /. Biomed. Mater. Res., 2002,60 511-16. 

Other technological aspects of carbon nanotube synthesis currently under scrutiny include study of the growth mechanism [67,71], attempts to control the diameter [72-74], processes which yield very long CNTs [70,75], optimization of the catalyst composition [76], and improvements in purity [77]. A major area of focus is the production of CNTs at selected sites on a substrate (micropatterning) [78-81]. Other synthetic methods investigated have been (i) a solvothermal route, in which reactants are heated in solution in a sealed autoclave [82,83] (ii) a solid-state metathesis process [84] (iii) a hydrothermal process which produces MWNTs from amorphous carbon [85] and (iv) low-temperature processes [59]. 

In this chapter, we explain why hydrothermal synthesis deserves special consideration and present a review of the current state of the art in hydrothermal synthesis of diamond as a potential future method of making diamond or hard diamond-like sp -carbon. 

Precursor powders of ceramics can be prepared using solids, such as oxides, hydroxides, and carbonates, as starting materials [45-50]. In this case, it is called the solid-state reaction process. The precursor powders can also be synthesized by wet-chemical methods, such as chemical precipitation or co-precipitation [51-59], sol-gel [60, 61], gel combustion [62-65] and hydrothermal synthesis [66-69]. The... 

Eang Y, Gu D, Zou Y, Wu Z, Li E, Che R, Deng Y, Tu B, Zhao D (2010) A low-concentration hydrothermal synthesis of biocompatible ordered mesoporous carbon nanospheres with tunable and uniform size. Angew Chem Int Ed 49 7987-7991... 

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