scholarly journals Some Peculiarities of Silica Modification Under High Reagent Pressure. I. Methodological Aspects

1995 ◽  
Vol 12 (3) ◽  
pp. 231-238 ◽  
Author(s):  
V.V. Sidorchuk ◽  
V.A. Tertykh ◽  
R. Leboda ◽  
Z. Hubicki
Keyword(s):  
Thermal Analysis ◽  
Surface Reaction ◽  
Silica Surface ◽  
Porous Silica ◽  
Physicochemical Characteristics ◽  
Geometrical Parameters ◽  
Duration Of Treatment ◽  
Preparation Conditions ◽  
Modification Process ◽  
Methodological Aspects

The effect of the following factors on the chemical and geometrical modification of aerosilogel (prepared from aerosil) was studied: the physicochemical characteristics of the modifying reagent pressures, the preparation conditions for the silica surface, the reaction temperature, the reagent pressures, the duration of treatment and the method employed for the modification process. The course of the surface reaction was followed by IR spectroscopy, differential thermal analysis and adsorption. During high-pressure modification, the geometrical parameters of the porous silica structure may be changed.

scholarly journals Kinetic Study of Sodium-Water Surface Reaction by Differential Thermal Analysis

2013 ◽  
Vol 7 (2) ◽  
pp. 79-93 ◽  
Author(s):  
Shin KIKUCHI ◽  
Hiroshi SEINO ◽  
Akikazu KURIHARA ◽  
Hiroyuki OHSHIMA
Keyword(s):  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
Kinetic Study ◽  
Water Surface ◽  
Surface Reaction

Effect of Sodium Ions on the Dielectric Conductivity of Porous Silica in Humid Environments

1990 ◽  
Vol 195 ◽  
Author(s):  
Wanqing Cao ◽  
Rosario Gerhardt ◽  
John B. Wachtman
Keyword(s):  
Relative Humidity ◽  
Silica Surface ◽  
Porous Silica ◽  
Sodium Content ◽  
Silica Gels ◽  
Interfacial Region ◽  
Relaxation Processes ◽  
Sodium Ions ◽  
Frequency Range ◽  
Dielectric Conductivity

ABSTRACTPartially sintered silica gels were immersed in different NaCI solutions to deliberately introduce a small amount of sodium ions ranging from 387 to 9900 ppm. Dielectric measurements were carried out in the frequency range 12 to 107Hz under various relative humidity conditions. Two relaxation processes were observed in the impedance and modulus planes and were assigned to two separate regions in the hydrated silica surface. The top region is expected to be rich in hydrated sodium since its modulus relaxation time depends strongly on the relative humidity as well as the sodium content. The interfacial region is believed to be composed of structured water since its dielectric conductivity is affected mainly by the amount of water adsorbed on the pore surfaces.

Kinetics of competitive adsorption of polystyrene chains at a porous silica surface

Langmuir ◽  
1994 ◽  
Vol 10 (2) ◽  
pp. 538-541 ◽  
Author(s):  
Masami Kawaguchi ◽  
Yoshimasa Sakata ◽  
Sachio Anada ◽  
Tadaya Kato ◽  
Akira Takahashi
Keyword(s):  
Competitive Adsorption ◽  
Silica Surface ◽  
Porous Silica ◽  
Kinetics Of

scholarly journals Quaternary Ammonium Borohydride Adsorption in Mesoporous Silicate MCM-48

2010 ◽  
Vol 1262 ◽  
Author(s):  
Michael Joseph Wolverton ◽  
Luc L. Daemen ◽  
Monika A. Hartl
Keyword(s):  
Organic Cation ◽  
Silica Surface ◽  
Inelastic Neutron Scattering ◽  
Porous Silica ◽  
Inelastic Neutron ◽  
Hydrogen Release ◽  
Hydrogen Density ◽  
Mesoporous Silicate ◽  
Bet Isotherm ◽  
Lower Temperature

AbstractInorganic borohydrides have a high gravimetric hydrogen density but release H2 only under energetically unfavorable conditions. Surface chemistry may help in lowering thermodynamic barriers, but inclusion of inorganic borohydrides in porous silica materials has proved hitherto difficult or impossible. We show that borohydrides with a large organic cation are readily adsorbed inside mesoporous silicates, particularly after surface treatment. Thermal analysis reveals that the decomposition thermodynamics of tetraalkylammonium borohydrides are substantially affected by inclusion in MCM-48. Inelastic neutron scattering (INS) data show that the compounds adsorb on the silica surface. Evidence of pore loading is supplemented by DSC/TGA, XRD, FTIR, and BET isotherm measurements. Mass spectrometry shows significant hydrogen release at lower temperature from adsorbed borohydrides in comparison with the bulk borohydrides. INS data from partially decomposed samples indicates that the decomposition of the cation and anion is likely simultaneous. These data confirm the formation of Si-H bonds on the silica surface upon decomposition of adsorbed tetramethylammonium borohydride.

Understanding surface charge regulation in silica nanopores

2020 ◽  
Vol 22 (27) ◽  
pp. 15373-15380 ◽  
Author(s):  
Jie Yang ◽  
Haiping Su ◽  
Cheng Lian ◽  
Yazhuo Shang ◽  
Honglai Liu ◽  
...  
Keyword(s):  
Surface Charge ◽  
Surface Reaction ◽  
Porous Silica ◽  
Reaction Model ◽  
Charge Regulation ◽  
Surface Reaction Model

The combination of CDFT and surface reaction model captures the charge regulation of porous silica under nanoconfinement.

Reactions of bis(cyclopentadienyl)zirconium dichloride with porous silica surface

2001 ◽  
Vol 183 (3-4) ◽  
pp. 290-300 ◽  
Author(s):  
Minna Kröger-Laukkanen ◽  
Marko Peussa ◽  
Markku Leskelä ◽  
Lauri Niinistö
Keyword(s):  
Silica Surface ◽  
Porous Silica

XPS Study of a New Heterogeneous Ruthenium Catalyst Precursor

1997 ◽  
Vol 51 (12) ◽  
pp. 1807-1813 ◽  
Author(s):  
P. Smet ◽  
F. Verpoort ◽  
G. De Doncker ◽  
A. R. Bossuyt ◽  
L. Fiermans ◽  
...  
Keyword(s):  
Thin Layer ◽  
Photoelectron Spectroscopy ◽  
Surface Reaction ◽  
Silica Surface ◽  
Silicon Single Crystal ◽  
Catalyst Precursor ◽  
X Ray ◽  
Different Types ◽  
Xps Study

The catalyst precursor has been synthesized by modifying the silica surface with ClPPh2 followed by a surface reaction with RuCl3. Supports consisting of a thin layer of SiO2 on a silicon single crystal have been used. Characterization of the different stages in the reaction procedure has been performed by a combination of conventional and angle-resolved X-ray photoelectron spectroscopy (XPS) using RuCl3/P(C6H5)2/SiO2/Si(100) model precursors. Different types of ruthenium centra have been identified.

Methodological Aspects of Prophylactic Drug Trials in Migraine

Cephalalgia ◽  
1981 ◽  
Vol 1 (3) ◽  
pp. 127-141 ◽  
Author(s):  
Jes Olesen ◽  
Annette Æbelholt Krabbe ◽  
Peer Tfelt-Hansen
Keyword(s):  
Crossover Design ◽  
Drug Trials ◽  
Duration Of Treatment ◽  
Time Effects ◽  
Sufficient Power ◽  
Number Of Patients ◽  
Prophylactic Drug ◽  
Headache Diary ◽  
Methodological Aspects ◽  
Clinical Problems

The purpose of this paper is to analyse methodological aspects of prophylactic drug trials in migraine. A study of ferrum quartz in 33 patients provided the necessary data base. Migraine definitions, relation between interval headache and migraine, and a number of other clinical problems are discussed. A headache diary is presented which to a certain extent allows a separation of interval headache and migraine attacks. Virtually all patients with frequent migraine attacks have interval headaches. A statistical model which allows a separation of time effects and treatment effects is presented. The inter-patient variability was much greater than intra-patient variability. This indicates that it will be difficult to obtain sufficient power with a non-crossover design. The relation between duration of treatment periods and the recessary number of patients is shown to be inversely related.

Preparation of silica glass microspheres by sol-gel processing

1991 ◽  
Vol 6 (1) ◽  
pp. 168-174 ◽  
Author(s):  
J.Y. Ding ◽  
D.E. Day
Keyword(s):  
Thermal Analysis ◽  
Nuclear Magnetic Resonance ◽  
Raw Materials ◽  
Sol Gel ◽  
Porous Silica ◽  
Droplet Generator ◽  
Silica Microspheres ◽  
Glass Microspheres ◽  
Sol Gel Process ◽  
Gel Processing

A method for making glass microspheres by the sol-gel process has been developed. Porous silica microspheres were produced at temperatures as low as 500 °C and densified silica microspheres were prepared at 800 °C. The size of the microspheres was controlled by adjusting the feed rate of the raw materials and the frequency of the droplet generator so that uniform spheres were obtained. Glass microspheres prepared by this method were characterized by Nuclear Magnetic Resonance (NMR), Differential Thermal Analysis (DTA), Thermogravimetric Analysis (TGA), and optical microscopy.

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