IR Laser‐Induced Carbothermal Reduction of Silica

Abstract

Pulsed IR-laser irradiation of silica in the presence of gaseous hydrocarbons (benzene or ethyne) results in carbothermal reduction of silica by hydrocarbon decomposition products and allows deposition of amorphous solids which were analyzed by FTIR, Raman, X-ray photoelectron and Auger spectra and by electron microscopy and revealed as nanosized carbon- IntroductionCarbon and silica composites are of increasing importance due to their properties (high electrical conductivity, intercalating capability, high-thermal stability, and corrosion resistance), industrial use as precursors for silicon carbide ceramic [1] and reinforcing components to so-called "green" tires, [2] as well as promising applications as lowcost solar absorbers [3,4] and novel catalytic systems.[5]Nanosized forms of carbon-silica composites and of silicon oxycarbide have received a great deal of attention recently. The former are important for providing intimate contact between and homogeneous distribution of both constituents, which is a prerequisite for high yield of carbothermal reduction [6,7] of silica by carbon to silicon carbide. [1] The nanostructured composites of carbon and silica were prepared by carbonization inside silica pores, [3] using solgel synthesis of silica-carbon precursor composites, [4,8] intercalation and hydrolysis of alkoxysilane in graphite oxide [9,10] and similar mechanochemical approaches, [11] addition of carbon precursor to silica sol solution, [12,13] monomer polymerization during the sol-gel process, [14] thermal decomposition of silicon grease [15] and carbonization of phenylene-silica hybrids.[16] Other methods involve coating fumed silica particles with carbon from pyrolysis of hydrocarbon gas, [1] flame synthesis from ethyne and silicon tetrachloride, [17] and combustion of hexamethyldisiloxane. [18,19] [ Another coexistence form of the three elements is silicon oxycarbide (e.g. refs. [20][21][22][23] ), which is an amorphous material of the general formula SiO x C 4-x and has a silica network structure in which O atoms are substituted by carbon atoms. This inorganic material shows high thermal, chemical, and mechanical stability and can be used as, for example, a catalyst support, lubricant, and in high-temperature coatings. It is also a possible candidate for anode materials of Li-ion batteries.[24] Bulky silicon oxycarbide is accessible by pyrolysis of various siloxanes, [23,24] polyphenylsilsesquioxanes, [22] or sol-gel organosilicon polymers, [20,[25][26][27][28] and thin films of silicon oxycarbide were obtained by oxygen-assisted plasma CVD from polysiloxanes. [29] These represent a useful intermediate [23,25] to bulky silicon carbide. The amorphous silicon oxycarbide structures coexist with free carbon and are known as glassy blends of both constituents.Nanosized silicon oxycarbide or silicon oxide-carbon composites have not been particularly examined so far, although nanosized H-containing Si/C/O/ (polyoxocarbosilane) phases, similar to silicon oxycarbide, were prepared by chemical vapor depositio...

Reactive deposition of laser ablated FeS1−xparticles on a copper surface

“…[15][16][17], and by laser ablation of bulk elemental solids in the presence of a reactive gas (e.g. oxygen, [18][19][20][21] nitrogen, [22][23][24] carbon monoxide, [25][26][27] hydrocarbon, 28,29 or hydrogen sulde 30 ). All these processes are called reactive laser ablation and yield (in the given order) mixed clusters and nanosized products (e.g.…”

IR laser-induced carbothermal reduction of silicon monoxide

“…We note that silicon oxycarbide components in these materials are richer in silicon and have more significant contribution of the Si-C bonds (more pronounced XPS signal of the C 3 SiO structure and more developed infrared n(Si-C) band) than those in the coatings produced through the IR laser-induced carbothermal reduction of silica [31].…”

“…This work is an extension of our previously published work on IR laser-induced carbothermal reduction of silicon dioxide [31]. a standard vacuum-line.…”