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Published in Joseph C. Salamone, Polymeric Materials Encyclopedia, 2020
Transition metal ceramics have potential for applications as electronic, structural, or refractory materials. Such materials can be prepared by pyrolysis of organometallic precursors. Some of these include: TiN from poly(titanium imide), [=Ti-(NR2)2]n; intermediates from ammonolysis of metal (M) halides that give M-nitrides (M = Al, Ti, Nb, etc.); W2C from Cp2(CO2Me)2W2(CO)4; titanium and niobium carbonitrides from titanium and niobium acetylides, respectively; Ti(C,O) powders and fibers that can be synthesized via the modification of polyacrylonitrile with titanium dialkylamides and titanium tetrachloride; TiC/Al2O3, TiN/Al2O3, and AlN/TiN ceramics that can be obtained by pyrolysis of polymers prepared by the reaction between furfuryl alcohol and the products obtained by hydrolyzing a mixture of Ti(O-n-Bu)4 and Al(O-sec-Bu)3; metal-borides, MB2 (M = Ti, Zr, Hf, Nb, Ta) that can be prepared via a polymerprecursor route employing dispersions of metal oxides in the decaborane-dicyanopentane polymers, -[B10H12NC-(CH2)5-CN]x-, or by dispersing metal powders in decaborane- diamine polymers.
Ceramic Fabrication Processes: An Introductory Overview
Published in M. N. Rahaman, Ceramic Processing and Sintering, 2017
While several routes exist for the preparation of polymer precursors to BN and B4C (58–61,73), their usefulness is not clear. However, the reaction between H3B–S(CH3)2 and the silazane product (CH3HSiNH)n formed in the first step of Eq. (1.10) produces borasilazane polymers (molecular weight ~800) that are useful precursors to boron-containing ceramics (74). The polymers are soluble in many common organic solvents and can be processed into fibers. On pyrolysis in argon at 1000°C, polymers (formed with a Si/B reactant ratio of ~2) give a high yield (~90 wt%) of an amorphous ‘‘boron silicon carbon nitride’’ ceramic with a composition of B1.0Si1.9C1.7N2.5. Pyrolysis in NH3 at 1000°C gives a amorphous ‘‘boron silicon nitride’’ ceramic with the composition BSi3N5 with a yield of ~75 wt%. For B4C/BN ceramics, high yield synthesis has been reported from polymer precursors synthesized by the reaction of decaborane (B10H14) with a diamine (e.g., H2NCH2CH2NH2) in an organic solvent (75).
Ceramic Fabrication Processes: An Introductory Overview
Published in Mohamed N. Rahaman, Ceramic Processing, 2017
Several routes exist for the preparation of polymer precursors to BN and B4C [58–61,73]. The reaction between H3BS(CH3)2 and the silazane product, (CH3HSiNH)n, formed in the first step of Equation 1.10, produces borasilazane polymers (molecular weight ~800) that are useful precursors to boron-containing ceramics [74]. The polymers are soluble in many common organic solvents and can be processed into fibers. On pyrolysis in argon at 1000°C, polymers (formed with a Si/B reactant ratio of ~2) give a high yield (~90 wt%) of an amorphous boron–silicon–carbon–nitride ceramic with a composition of B1.0Si1.9C1.7N2.5. Pyrolysis in NH3 at 1000°C gives an amorphous boron–silicon–nitride ceramic with the composition BSi3N5 with a yield of ~75 wt%. For B4C/BN ceramics, high yield synthesis has been reported from polymer precursors synthesized by the reaction of decaborane (B10H14) with a diamine (e.g., H2NCH2CH2NH2) in an organic solvent [75].
Synthesis Of Samarium Oxychloride Nanoplates By Chemical Vapour Deposition
Published in Journal of Experimental Nanoscience, 2019
Yi Chu, Yingjie Xing, H. Q. Xu
We believe the reason for improved two-dimensional growth of SmOCl is H+ ions decomposed from decaborane. Scheme 1 demonstrates the formation of SmOCl nanoplates with and without decaborane. Our method can produce H+ ions timely and ‘in situ’, which is similar to the acidic solution environment for BiOCl nanpolate growth. [6] We find the time to supply decaborane is the key factor to improve the growth of the SmOCl nanoplates. The optimal time for decaborane addition is several minutes earlier than the time of the highest temperature (760 °C). If decaborane is added too early, even if more decaborane is supplied, no benefit effect is observed. This phenomenon indicates that the sublimation and pyrolysis of decaborane should occur in the same period of SmOCl nanoplate growth. According to above growth model, SmOCl nuclei are formed on the substrate during the heating period. In an atmosphere containing enough decaborane at ∼760 °C, SmOCl nuclei adsorb dense decaborane molecules on their surface. The decomposition of decaborane molecules adsorbed on the {100} facets may generate hydrogen ions at the adsorption sites, which play similar role on anisotropic growth as H+ ions in solution.
Energetic aspects of elemental boron: a mini-review
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2022
Okan Icten, Birgul Zumreoglu-Karan
Several routes have been reported to synthesize amorphous BNPs, for potential application as a high energy density fuel. Pyrolysis of decaborane (Bellott et al. 2009) or boron trihalides (Shin et al. 2011) is one of the most applied methods. BNPs have also been synthesized by the ball milling process by coating the particles with a combustion catalyst (Van Devener et al. 2009), a mechanochemical reaction between B2O3 and Mg (Seifolazadeh and Mohammadi 2016), solubilization of B2O3 in hot water followed by freeze-drying (Vignolo et al. 2012), self-propagating high-temperature synthesis Wang et al. 2013), electrolysis of molten borates, or fluoroborates (Zhang et al. 2013) and magnesiothermic reduction reaction (Nersisyan et al. 2015). Coating BNPs with a material to enhance the combustion of either the boron itself or a hydrocarbon carrier fuel appears to be the right approach; however, a detailed analysis of such combustion characteristics is still lacking. On the other hand, the synthesis of crystalline BNPs is a challenge because of the element’s high crystallization temperature. Crystalline boron nanoribbons were obtained by pyrolysis of diborane at 630−750°C and ∼200 mTorr in a quartz tube furnace (Xu et al. 2004). Zhou, Nozaki, and Pi (2017) reported 4–15 nm-sized crystalline BNPs prepared by a nonthermal plasma method. Freestanding boron nanocrystals with tunable sizes were obtained from a radio-frequency initiated plasma of a mixture of B2H6 and Ar gases. The researchers observed that the ignition temperature of BNPs in the air monotonically decreased while the heat released increased as the particle size scaled-down. Recently, Sreedhara et al. (2020) reported cryo-milling preparation of ligand-coated BNPs (<100 nm) to be used in JP10 fuel, and Uspenskii et al. (2020) introduced the ultrasonographic preparation of BNPs (<100 nm) for biomedical (Boron Neutron Capture Therapy, BNCT) applications.