PHASE TRANSITIONS OF WATER AND XENON ADSORBED IN POROUS VYCOR GLASS

1963 ◽  
Vol 41 (12) ◽  
pp. 3095-3107 ◽  
Author(s):  
G. Litvan ◽  
R. McIntosh
Keyword(s):  
Phase Transition ◽  
Capillary Condensation ◽  
Adsorbed Water ◽  
Surface Concentration ◽  
Adsorptive Capacity ◽  
Temperature Cycle ◽  
Length Variation ◽  
Vycor Glass ◽  
Porous Vycor Glass ◽  
Lower Temperature

Measurements of the expansion of porous Vycor glass containing fixed quantities of adsorbed water indicate that in every instance a phase transition starts below −50 °C, with the main change occurring below −160 °C. Two other anomalies of the length variation were observed near −22 °C and −7 °C when the amount of adsorbed water exceeded the value equivalent to two monolayers. The length of the adsorbent after completion of a temperature cycle was different from the initial length. This is thought to be due to damage suffered by the glass and to the fact that the length of the adsorbent is different for adsorption and desorption although the quantity adsorbed may be the same.The phase transition of adsorbed xenon takes place below the normal triple point and is a function of surface concentration as shown by length variations and equilibrium pressures for fixed quantities adsorbed. All transitions are gradual and hysteresis is exhibited by the isosteres. The adsorption isotherms for xenon – Vycor glass show a decreasing adsorptive capacity and a contraction of the hysteresis loop with lower temperature. The inadequacy of the capillary condensation theory of adsorption in relation to these results is discussed.

THE FREEZING OF WATER AND BENZENE IN POROUS VYCOR GLASS

1960 ◽  
Vol 38 (6) ◽  
pp. 958-971 ◽  
Author(s):  
C. Hodgson ◽  
R. McIntosh
Keyword(s):  
Capillary Condensation ◽  
Solid Phase ◽  
Adsorbed Water ◽  
Freezing Process ◽  
Pressure Measurements ◽  
Equilibrium Pressure ◽  
Vycor Glass ◽  
Dimensional Changes ◽  
Porous Vycor Glass

Freezing has been detected in the adsorbed water and benzene of porous Vycor glass at temperatures below that at which the bulk phases freeze. The evidence presented by equilibrium pressure measurements and dimensional changes of the systems is considered in terms of theories of capillary condensation and freezing in cements and soil. Although not all the results can be explained, it is concluded that the freezing process is a gradual one for both adsorbate–adsorbent systems. The evidence further suggests that hysteresis is absent in isotherms if the solid phase has formed.

Small-angle neutron scattering study of adsorbed water in porous Vycor glass: Supercooling phase transition and interfacial structure

1989 ◽  
Vol 39 (1) ◽  
pp. 633-636 ◽  
Author(s):  
M. J. Benham ◽  
J. C. Cook ◽  
J-C. Li ◽  
D. K. Ross ◽  
P. L. Hall ◽  
...  
Keyword(s):  
Phase Transition ◽  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Adsorbed Water ◽  
Interfacial Structure ◽  
Vycor Glass ◽  
Porous Vycor Glass ◽  
Scattering Study ◽  
Neutron Scattering Study

NOTE ON THE DETECTION OF AN APPARENT PHASE TRANSITION OF ADSORBED WATER ON POROUS VYCOR GLASS BY MEASUREMENTS OF DIMENSIONAL CHANGES

1959 ◽  
Vol 37 (8) ◽  
pp. 1278-1280 ◽  
Author(s):  
C. Hodgson ◽  
R. McIntosh
Keyword(s):  
Phase Transition ◽  
Volume Ratio ◽  
Adsorbed Water ◽  
Present Form ◽  
Vycor Glass ◽  
Dimensional Changes ◽  
Porous Vycor Glass ◽  
Moderate Sensitivity ◽  
Length Changes ◽  
A New Technique

A new technique is described for detecting possible phase transitions of adsorbates. The method involves the measurement of length changes of the solid, but only solids for which the surface-to-volume ratio is large could be used with the present form of instrument because of its moderate sensitivity. Using this measurement an apparent phase transition for water adsorbed on porous Vycor glass has been detected at approximately −22 °C.

Small angle neutron scattering studies of adsorbed water in porous Vycor glass

1989 ◽  
Vol 156-157 ◽  
pp. 185-188 ◽  
Author(s):  
J.C. Li ◽  
D.K. Ross ◽  
P.L. Hall ◽  
R.K. Heenan
Keyword(s):  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Adsorbed Water ◽  
Vycor Glass ◽  
Porous Vycor Glass

A Sans Study of Capillary Condensation in Porous Media

1989 ◽  
Vol 166 ◽  
Author(s):  
M.Y. Lin ◽  
S.K. Sinha ◽  
J.S. Huang ◽  
B. Abeles ◽  
J.W. Johnson ◽  
...  
Keyword(s):  
Porous Media ◽  
Porous Structure ◽  
Small Angle ◽  
Structure Factor ◽  
Small Angle Neutron Scattering ◽  
Capillary Condensation ◽  
Distribution Model ◽  
Vycor Glass ◽  
Porous Vycor Glass ◽  
Good Agreement

ABSTRACTWe use small angle neutron scattering (SANS) to study the microstructure of porous Vycor glass and the capillary condensation of fluids in the medium. Using a chord distribution model, we can predict the structure factor measured by SANS. Excellent agreement with the data is obtained. The fitted parameters characterize quantitatively the porous structure before and during the process of condensation, and are in good agreement with isotherm measurements. However, at the latest stages of the process, when all the pores are nearly filled, the model can no longer describe the system.

Length change – adsorption relations for the water – porous glass system to −40 °C

1970 ◽  
Vol 48 (2) ◽  
pp. 287-297 ◽  
Author(s):  
R. F. Feldman
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Low Temperature ◽  
Saturated Vapor Pressure ◽  
Capillary Condensation ◽  
Saturated Vapor ◽  
Length Change ◽  
Adsorptive Capacity ◽  
Volumetric Expansion ◽  
Adsorption Of Water

Adsorption of water has been studied extensively above 0 °C, but the problem of the phase transition of adsorbates in porous materials is presented at temperatures below 0 °C. Experiments that show how phase transitions modify length change – adsorption relationships are described.Adsorption – length change measurements from −40 to −0.5 and isotherms at −20 and −0.5 °C were obtained. In another group of experiments different forms of isosteres were also obtained; the principle that water should be allowed to enter the sample at the low temperature was usually followed.Isotherms and length change – adsorption characteristics below 0 °C are qualitatively similar to those above 0 °C, but a decrease in adsorptive capacity and length change was observed. These results and those obtained from the isosteres lead to the conclusion that capillary condensation and menisci theories are operative and that a solid meniscus exists. It follows therefore that the saturated vapor pressure of frozen adsorbate is greater than that of bulk ice and that its volumetric expansion on freezing is similar to the bulk phase transition. It is shown how these phenomena can predict migration of water and generation of pressure within the porous body when it is subjected to cooling and warming cycles.

ChemInform Abstract: THE PHOTOSENSITIZED ISOMERIZATION OF 2-BUTENES BY SENSITIZERS ADSORBED ON POROUS VYCOR GLASS

1974 ◽  
Vol 5 (49) ◽  
pp. no-no
Author(s):  
KIYOSHI OTSUKA ◽  
AKIRA MORIKAWA
Keyword(s):  
Vycor Glass ◽  
Porous Vycor Glass

scholarly journals Thermal properties of metal-metal bonded Pd(I) complexes supported onto porous Vycor glass

2008 ◽  
Vol 80 (2) ◽  
pp. 263-269
Author(s):  
Iara F. Gimenez ◽  
Oswaldo L. Alves
Keyword(s):  
Solid State ◽  
Thermal Stabilization ◽  
Decomposition Products ◽  
Vycor Glass ◽  
X Ray ◽  
Porous Vycor Glass ◽  
Metal Metal ◽  
Condensed Phosphates ◽  
Diffuse Reflectance Infrared ◽  
Immobilized Complexes

Thermal behavior of the complexes Pd2(dppm)2Cl2, Pd2(dppm)2(SnCl3)Cl and Pd2(dppm)2(SnCl3)2 (dppm = bis[diphenylphosphino(methane)], ((C6H5)2PCH2P(C6H5)2) in the solid state and immobilized onto porous Vycor glass was studied. Similar decomposition mechanisms were observed for the solid and immobilized complexes, with a small thermal stabilization upon immobilization. The decomposition products were characterized by X-ray diffractometry, Raman and diffuse reflectance infrared spectroscopy, which indicated the presence of a mixture of metallic palladium and oxidized species such as PdO,condensed phosphates, SnO2 and SnP2O7. According to X-ray diffractometry, the decomposition products of the immobilized complexes presented higher amounts of PdO than the solid-state residues, probably as an effect of interactions with silanol groups present in the glass surface.

scholarly journals Isomerization ofcis-2-Butene Caused by Electronically-excited Sulfur Dioxide (3B1) Adsorbed on Porous Vycor Glass

1978 ◽  
Vol 51 (2) ◽  
pp. 367-371 ◽  
Author(s):  
Kiyoshi Otsuka ◽  
Masaki Fukaya ◽  
Akira Morikawa
Keyword(s):  
Sulfur Dioxide ◽  
Vycor Glass ◽  
Porous Vycor Glass ◽  
Electronically Excited
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