scholarly journals Synthesis of Silica Membranes by Chemical Vapor Deposition Using a Dimethyldimethoxysilane Precursor

Membranes ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 50 ◽  
Author(s):  
S. Ted Oyama ◽  
Haruki Aono ◽  
Atsushi Takagaki ◽  
Takashi Sugawara ◽  
Ryuji Kikuchi

Silica-based membranes prepared by chemical vapor deposition of tetraethylorthosilicate (TEOS) on γ-alumina overlayers are known to be effective for hydrogen separation and are attractive for membrane reactor applications for hydrogen-producing reactions. In this study, the synthesis of the membranes was improved by simplifying the deposition of the intermediate γ-alumina layers and by using the precursor, dimethyldimethoxysilane (DMDMOS). In the placement of the γ-alumina layers, earlier work in our laboratory employed four to five dipping-calcining cycles of boehmite sol precursors to produce high H2 selectivities, but this took considerable time. In the present study, only two cycles were needed, even for a macro-porous support, through the use of finer boehmite precursor particle sizes. Using the simplified fabrication process, silica-alumina composite membranes with H2 permeance > 10−7 mol m−2 s−1 Pa−1 and H2/N2 selectivity >100 were successfully synthesized. In addition, the use of the silica precursor, DMDMOS, further improved the H2 permeance without compromising the H2/N2 selectivity. Pure DMDMOS membranes proved to be unstable against hydrothermal conditions, but the addition of aluminum tri-sec-butoxide (ATSB) improved the stability just like for conventional TEOS membranes.

1996 ◽  
Vol 429 ◽  
Author(s):  
G. Lucovsky ◽  
H. Niimi ◽  
K. Koh

AbstractThe incorporation of bonded nitrogen into ultra thin SiO2 gate dielectrics has become an important technology issue. Nitrogen atoms bonded in the immediate vicinity of the Si-SiO2 interface improve device reliability in n-channel field effect transistors. N- atom incorporation at the monolayer concentration range has been achieved by remote plasma assisted oxidation in N2O at 300°C. The incorporation mechanism and the stability of bonded-N are discussed.


Membranes ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 11
Author(s):  
Takayuki Nagano ◽  
Koji Sato ◽  
Koichi Kawahara

An amorphous silicon carbide (SiC) membrane was synthesized by counter-diffusion chemical vapor deposition (CDCVD) using silacyclobutane (SCB) at 788 K. The SiC membrane on a Ni-γ-alumina (Al2O3) α-coated Al2O3 porous support possessed a H2 permeance of 1.2 × 10−7 mol·m−2·s−1·Pa−1 and an excellent H2/CO2 selectivity of 2600 at 673 K. The intermittent action of H2 reaction gas supply and vacuum inside porous support was very effective to supply source gas inside mesoporous intermediate layer. A SiC active layer was formed inside the Ni-γ-Al2O3 intermediate layer. The thermal expansion coefficient mismatch between the SiC active layer and Ni-γ-Al2O3-coated α-Al2O3 porous support was eased by the low decomposition temperature of the SiC source and the membrane structure.


2002 ◽  
Vol 17 (2) ◽  
pp. 367-375 ◽  
Author(s):  
A. Grill ◽  
S. Guilley ◽  
V. Patel ◽  
K. Babich

Germanium- and carbon-based films were deposited by plasma-enhanced chemical vapor deposition from tetramethylgermane (TMGe) with additions of oxygen, hydrogen, or argon. The index of refraction, extinction coefficient, and optical gap and Fourier transform infrared spectra of the films were measured as well as their stability in regular ambiance. It was found that the films deposited from pure TMGe were stable in time only if deposited at a negative bias above −250 V direct current. Films deposited at a bias of −150 V direct current could be stabilized by significant additions of oxygen to the plasma and complete stabilization was achieved at O2/TMGe ratios larger than 3 in the gas feed when GeOx films containing small amounts of C and H were obtained. Additions of hydrogen or argon to TMGe had only slight effects in improving the stability off the films.


Nanoscale ◽  
2021 ◽  
Vol 13 (39) ◽  
pp. 16629-16640
Author(s):  
Yao-Pang Chang ◽  
Wei-Bang Li ◽  
Yueh-Chiang Yang ◽  
Hsueh-Lung Lu ◽  
Ming-Fa Lin ◽  
...  

Adjusting the orientation of the sapphire substrate to align the gas flow direction in the NaCl-assisted CVD process can improve the stability of monolayer WS2.


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