Jaroslav Kupčík

IR laser-induced decomposition of hexamethyldisiloxane for chemical vapour deposition of nano-structured hydrido(methyl)silicone powders

Abstract The infrared laser-induced decomposition of hexamethyldisiloxane with high-fluence laser pulses affords gaseous C1–C2 hydrocarbons, dimethylsilane and trimethylsilane, all of which confirm a multitude of decomposition steps involving cleavage of the strong SiO bond. The process carried out in the absence or presence of hydrogen affords chemical vapour deposition of solid nano-structured hydrido(methyl)silicone powders and represents the first thermal access to these materials from peralkylated siloxane precursor.

Si/C phases from the IR laser-induced decomposition of 1,4-disilabutane

CO 2 laser-induced decomposition of 1,4-disilabutane (DSB) in the gas phase yields gaseous C 1–2 hydrocarbons and RSiH 3 compounds (R=H, CH 3 , C 2 H 5 and C 2 H 3 ), and it represents a convenient process for chemical vapour deposition of thin films composed of Si/C/H, Si/C and Si components.

Decomposition of liquid hexamethyldisiloxane induced by CO2 laser pulse heating of carbon particles

Abstract CO2 laser-induced decomposition of liquid hexamethyldisiloxane (Me3Si)2O with graphite sensitization has been studied. Suspended graphite is used for an effective heterogeneous sensitization due to very efficient absorption of CO2 laser radiation. In the experiments the laser line 10P16 ( ∼948 cm −1 ) coinciding with the absorption minimum of the a ν Si – O band ( 1055 cm −1 ) of (Me3Si)2O is selected for irradiation. This choice allows to avoid radiation losses due to low (5.4×10 −4 Torr −1 cm −1 ) vapor absorption and to ensure the maximum (>100 μm ) penetration depth of the laser radiation into the liquid. The decomposition is a thermal process and can be denoted as pulsed laser thermolysis. A thermodynamic approach is proposed to evaluate the temperature of graphite particles and adjacent liquid layers resulting from the laser pulse heating. It is shown that for a 100 ns laser pulse at fluence of 1 J / cm 2 adjacent liquid layers with a thickness of 0.2 μm can be heated to temperatures in the range of 400–800 ° C . The high (>8 MPa) pressure inside the supercritical liquid layers favors the decomposition. The IR, mass analyses of irradiated liquid samples indicate the formation of linear polystructures as decomposition products.

Organoclays with carbosilane dendrimers containing ammonium or phosphonium groups

New composite materials could reveal attractive capabilities and favourable properties. Herein, we present novel layered nanocomposites consisting of inorganic clay (montmorillonite) and cationic carbosilane dendrimers. A comparative study was performed to evaluate cationic moieties (ammonium or phosphonium) and various generations of dendrimers (first, second and third) and their influence on the characteristics of resulting materials. The target nanocomposites were characterized by XRD, TEM, TGA, IR and MAS NMR. Interestingly, with multivalent dendritic cations, as opposed to monovalent cations, we detected a new connection of cationic species to the inorganic matrix by both ammonium and phosphonium dendrimers. To evaluate the mechanism of thermal degradation of the prepared materials, non-oxidative pyrolysis coupled with analysis of the resulting products by IR and MS was performed. To illustrate the catalytic activity of the as-prepared materials, selected samples were tested as catalysts in the cycloaddition of CO2 with epoxide (allyl glycidyl ether).

Titania aerogels with tailored nano and microstructure: comparison of lyophilization and supercritical drying

Abstract Structure and phase composition of titania aerogels can be substantially influenced simply by the process of drying their parent water colloid suspensions prepared by the reaction of hydrogen peroxide with suspension of precipitates obtained by neutralization of solution of titanyl sulfate with ammonia. Two methods of drying are compared: (1) lyophilization of fast frozen material immersed in liquid nitrogen, and (2) critical point drying using supercritical CO2 under high pressure. Both methods of drying lead to yellow titanium peroxide aerogels consisting of nanometer-sized blocks. While lyophilization leads to foils consisting of nano-sized crystalline nuclei of peroxo-polytitanic acid dispersed in predominantly amorphous material, the critical point drying provides rather bulk highly porous composite consisting of randomly oriented flat nanoparticles (5–10 nm) composed of crystalline anatase and amorphous peroxo-polytitanic acid.

Laser Ablative Deposition of Polymer Films: A Promise for Sensor Fabrication

There is a continuing interest in the use of polymer films as insulating components of sensors; a number of such films have been prepared by polymer sputtering or vacuum deposition processes involving gas phase pyrolysis/photolysis and by plasma decomposition of monomers. An attractive and rather new technique for the deposition of novel polymer films is IR laser ablation of polymers containing polar groups. We have recently studied this process with poly(vinyl chloride) (PVC), poly(vinyl acetate) (PVAc) and poly(vinyl chloride-co-vinyl acetate) P(VC/VAc) to establish its specific features and differences to conventional pyrolysis.

Excimer Laser Preparation of SnO2 and SnO2/TiO2 Nanoparticles

A single pulse of an ArF excimer laser induces efficient oxidation of Sn(CH3)4 and Sn(CH3)4/Ti(Oi-C3H7)4 in the gas phase. The direct deposition of stoichiometric tin dioxide, tin monoxide and mixed tin/titanium dioxide is demonstrated. Structural changes at 300°C and 500°C in both vacuum and air are studied by means of XRD and Raman spectroscopy. Transmission electron microscopy shows that the nanoparticles possess a mean diameter about 40 nm.