scholarly journals Temperature-Programmed Desorption of Dimethylpyridine Adsorbed on Silica–Alumina Prepared by Chemical Vapor Deposition

1991 ◽  
Vol 64 (3) ◽  
pp. 1005-1007 ◽  
Author(s):  
Satoshi Sato ◽  
Masahiro Tokumitsu ◽  
Toshiaki Sodesawa ◽  
Fumio Nozaki
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Temperature Programmed Desorption ◽  
Silica Alumina ◽  
Temperature Programmed

The Reaction of NH3 With TiN: Implications for CVD

1995 ◽  
Vol 410 ◽  
Author(s):  
Michelle T. Schulberg ◽  
Mark D. Allendorf ◽  
Duane A. Outka
Keyword(s):  
Activation Energy ◽  
Chemical Vapor Deposition ◽  
Reaction Temperature ◽  
Vapor Deposition ◽  
High Probability ◽  
Film Growth ◽  
Chemical Vapor ◽  
Temperature Programmed Desorption ◽  
Surface Sites ◽  
Temperature Programmed

ABSTRACTSince NH3 is an important component of TiN chemical vapor deposition (CVD) processes, understanding the NH3/TiN surface interaction is crucial to developing a model for the overall reaction. Temperature programmed desorption experiments show that NH3 adsorbs molecularly on amorphous TiN surfaces. Chemisorption occurs at only ∼5% of the surface sites, with an activation energy for desorption of 24 kcal/mol. The sticking probability into this state is 0.06 at 100 K. In addition, NH3 adsorbs with high probability into a multilayer state with an activation energy for desorption of 7.3 kcal/mol, similar to that found in other systems. NH3 does not dissociate on TiN. Under CVD conditions, however, the reactivity of NH3 on TiN may increase and surface reactions may play a part in film growth.

Catalyst Support and Pretreatment Effects on Carbon Nanotubes Synthesis by Chemical Vapor Deposition of Methane on Iron over SiO2, Al2O3 or MgO

2009 ◽  
Vol 7 (1) ◽  
Author(s):  
M. Esmaieli ◽  
A. Khodadadi ◽  
Y. Mortazavi
Keyword(s):  
Carbon Nanotubes ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Iron Catalyst ◽  
Supported Catalysts ◽  
Catalyst Support ◽  
Multiwall Carbon Nanotubes ◽  
Chemical Vapor ◽  
Pretreatment Conditions ◽  
Temperature Programmed

In this study we report the effects of support and pretreatment conditions on growth of carbon nanotubes (CNTs) by chemical vapor deposition of methane on iron catalyst supported on MgO, silica or alumina. The iron was impregnated onto the supports, and then the samples were dried, calcined at 550°C and pretreated in either helium or hydrogen up to 1000°C before exposure to methane as a carbon source for CNTs growth. Temperature programmed reduction (TPR) of the fresh catalysts and the ones pre-treated in He and in H2 shows various interactions of the iron with supports at pretreatment conditions. The CNTs are characterized by SEM, Raman, FTIR, and TEM. The IG/ID of Raman spectroscopy are 6.2, 3.8 and 0.7 for the CNTs grown on the MgO, alumina, and silica-supported iron catalysts pretreated in helium, respectively. When the Fe/MgO catalyst is pretreated in hydrogen the IG/ID ratio dramatically reduces to 0.8. A less significant effect of pretreating of the catalysts in hydrogen is observed for silica- and alumina-supported catalysts. RBM peaks of Raman spectra along with TEM results indicate the formation of bundles of 0.8-1.2 nm single-wall as well as multiwall carbon nanotubes on the Fe/MgO catalyst pre-treated in He.

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
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Composite Membranes ◽  
Hydrothermal Conditions ◽  
Porous Support ◽  
Silica Membranes ◽  
Silica Alumina ◽  
Alumina Composite ◽  
The Stability

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.

The Interaction of HCl With polycrystalline β-SiC: Evidence for a Site-Blocking Mechanism for HCl Inhibition of SiC CVD

1995 ◽  
Vol 410 ◽  
Author(s):  
Michelle T. Schulberg ◽  
Mark D. Allendorf ◽  
Duane A. Outka
Keyword(s):  
Vapor Deposition ◽  
Electron Spectroscopy ◽  
Chemical Vapor ◽  
Temperature Programmed Desorption ◽  
Etching Mechanism ◽  
Temperature Programmed ◽  
A Site ◽  
Site Blocking ◽  
Blocking Mechanism ◽  
Initial Sticking

ABSTRACTChlorine-containing precursors are attractive for chemical vapor deposition (CVD) of SiC because they are less hazardous and more economical than silane precursors. The reactivity of HCl, a by-product of these reactions, on SiC is of particular interest because it has been reported that HCl inhibits SiC CVD, but the mechanism for this inhibition has not been identified. In this work the adsorption of HCl on polycrystalline β-SiC was examined with Auger Electron Spectroscopy (AES) and Temperature Programmed Desorption (TPD). HCl adsorbs readily on SiC, with an initial sticking probability of 0.1 at 300 K, and forms a strong bond, with an activation energy for desorption of 64 kcal/mol. The only product detected by TPD is HCl, which desorbs in a peak centered at 1010 K. There are no Si- or C-containing desorption products, demonstrating that HCl does not etch SiC under TPD conditions. These results are consistent with a site-blocking mechanism for HCl inhibition of SiC CVD, but not with an etching mechanism.

scholarly journals Catalytic Chemical Vapor Deposition of Methane to Carbon Nanotubes: Copper Promoted Effect of Ni/MgO Catalysts

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
Wen Yang ◽  
Yanyan Feng ◽  
Wei Chu
Keyword(s):  
Carbon Nanotubes ◽  
Chemical Vapor Deposition ◽  
Calcination Temperature ◽  
Reaction Temperature ◽  
Vapor Deposition ◽  
Sol Gel ◽  
Chemical Vapor ◽  
Growth And Yield ◽  
Calcination Temperatures ◽  
Temperature Programmed

The Ni/MgO and Ni-Cu/MgO catalysts were prepared by sol-gel method and used as the catalysts for synthesis of carbon nanotubes by thermal chemical vapor deposition. The effect of Cu on the carbon yield and structure was investigated, and the effects of calcination temperature and reaction temperature were also investigated. The catalysts and synthesized carbon materials were characterized by temperature programmed reduction (TPR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Results showed that the addition of Cu promoted the reduction of nickel species, subsequently improving the growth and yield of CNTs. Meanwhile, CNTs were synthesized by the Ni/MgO and Ni-Cu/MgO catalysts with various calcination temperatures and reaction temperatures, and results suggested that the obtained CNTs on Ni-Cu/MgO catalyst with the calcination temperature of 500°C and the reaction temperature of 650°C were of the greatest yield and quantity of 927%.

scholarly journals Catalytic Properties of Silica-Alumina Prepared by Chemical Vapor Deposition

1987 ◽  
Vol 16 (8) ◽  
pp. 1535-1536 ◽  
Author(s):  
Satoshi Sato ◽  
Masato Toita ◽  
Yu-Qing Yu ◽  
Toshiaki Sodesawa ◽  
Fumio Nozaki
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Catalytic Properties ◽  
Chemical Vapor ◽  
Silica Alumina
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