scholarly journals Fabrics of Icing-Mound and Pingo Ice in Permafrost

1978 ◽  
Vol 20 (84) ◽  
pp. 563-569 ◽  
Author(s):  
W. Alan Gell
Keyword(s):  
Active Layer ◽  
Crystal Size ◽  
Early Growth ◽  
Bulk Water ◽  
Freezing Rate ◽  
Lattice Orientation ◽  
Small Crystals ◽  
Freezing Direction

Abstract Crystallization histories of some ice layers in permafrost are inferred from crystal size, shape, dimensional and lattice orientation, and inclusion patterns. In an icing mound, formed by injection of water beneath frozen active-layer soil, early growth was rapid, indicated by copious small crystals and bubbles, followed by slower growth giving rise to crystals and bubbles elongate parallel to the freezing direction, c-axes were normal to crystal long axes. In a small pingo, bulk water existed temporarily at the freezing interface and freezing was unidirectional. In a larger pingo, variations in freezing rate were inferred. Later flow of ice modifies growth fabrics.

scholarly journals Fabrics of Icing-Mound and Pingo Ice in Permafrost

1978 ◽  
Vol 20 (84) ◽  
pp. 563-569 ◽  
Author(s):  
W. Alan Gell
Keyword(s):  
Active Layer ◽  
Crystal Size ◽  
Early Growth ◽  
Bulk Water ◽  
Freezing Rate ◽  
Lattice Orientation ◽  
Small Crystals ◽  
Freezing Direction

AbstractCrystallization histories of some ice layers in permafrost are inferred from crystal size, shape, dimensional and lattice orientation, and inclusion patterns. In an icing mound, formed by injection of water beneath frozen active-layer soil, early growth was rapid, indicated by copious small crystals and bubbles, followed by slower growth giving rise to crystals and bubbles elongate parallel to the freezing direction, c-axes were normal to crystal long axes. In a small pingo, bulk water existed temporarily at the freezing interface and freezing was unidirectional. In a larger pingo, variations in freezing rate were inferred. Later flow of ice modifies growth fabrics.

Crystal size distribution of benzoic acid at its crystallization from the bulk of vapour phase

1979 ◽  
Vol 44 (7) ◽  
pp. 2165-2172 ◽  
Author(s):  
Jaroslav Vítovec ◽  
Jiří Smolík ◽  
Josef Kugler
Keyword(s):  
Benzoic Acid ◽  
Cooling Rate ◽  
Size Distribution ◽  
Crystal Size ◽  
Vapour Phase ◽  
Crystal Size Distribution ◽  
Water Dispersion ◽  
Small Crystals ◽  
Permeable Walls

Crystal size and their distribution were measured in the crystallizer with gas-permeable walls, at crystallization of benzoic acid vapours from the bulk of vapour phase in the mixture with nitrogen in dependence on concentration (in range from 1.1 to 23 vol.%), temperature (401 to 473 K) and velocity of mixture (0.5 to 6.6 cm/s). At small cooling rate of the mixture the vapours of benzoic acid are condensing in the form of droplets which at continuing cooling solidify. At cooling of the mixture by water dispersion create the needle-shaped crystals. The effect of concentration, temperature and velocity is not profound obviously because by evaporation of water is the mixture rapidly cooled and supersaturated. This results in creation of a large amount of crystal nuclei and thus also of small crystals.

RELATION OF pH TO DRIP FORMATION IN MEAT

1938 ◽  
Vol 16d (9) ◽  
pp. 255-267 ◽  
Author(s):  
L. Sair ◽  
W. H. Cook
Keyword(s):  
Crystal Size ◽  
Protein Denaturation ◽  
Maximum Amount ◽  
The Other ◽  
Absorptive Power ◽  
Small Crystals ◽  
Constant Rate ◽  
Quick Freezing ◽  
Frozen Tissue ◽  
Two Factors

The quantity of drip obtained from meat frozen at a constant rate is affected by the period between slaughter and freezing, and the pH of the tissue. These two factors appear to act independently, and only the latter was studied extensively. In precooled meats the maximum amount of drip was obtained at about pH 5.2, and as the pH increased the net drip decreased to zero at about pH 6.4. Pork, beef and mutton behave similarly both with respect to the form of the drip-pH relation and the quantity of drip exuded at a given acidity. Beef is normally more acid than the other meats tested, and this can account for its greater tendency to drip in commercial practice.Microscopic studies showed that large crystals were always produced by slow-freezing, regardless of the pH of the material. The absence of drip from slowly frozen tissue at pH 6.4 is therefore not due to crystal size, but must be attributed to the greater re-absorbing power of the proteins in this region. Protein denaturation does not affect the quantity of drip obtained when meat is slowly frozen or stored for periods up to three days in the freezing zone. The weak re-absorptive power of the proteins at pH 5.2 must be attributed to their isoelectric condition in this region, rather than to their denaturation. It is only in this isoelectric region that the production of small crystals by quick-freezing will reduce the quantity of drip.

Adsorption Properties of ZSM-5 Zeolites

1998 ◽  
Vol 63 (2) ◽  
pp. 141-154 ◽  
Author(s):  
Pavol Hudec ◽  
Agáta Smiešková ◽  
Zdenek Židek ◽  
Milan Zúbek ◽  
Petr Schneider ◽  
...  
Keyword(s):  
Crystal Size ◽  
Physical Adsorption ◽  
Hysteresis Loops ◽  
Low Pressure ◽  
Adsorption Properties ◽  
Relative Pressure ◽  
Small Crystals ◽  
Bet Method ◽  
Adsorption Of Nitrogen ◽  
Microporous Solids

Adsorption properties determined by physical adsorption of nitrogen for a series of ZSM-5 zeolite samples with various Si/Al ratios and different crystal size were compared. In addition to the BET method, the t-plot method was used to determine the microporosity of samples. Very small crystals of ZSM-5 zeolites, generally below 1 μm, with Si/Al ratio between 14 and 21 exhibit adsorption isotherms typical for purely microporous solids. Samples with Si/Al ratios larger than (about) 95 show low-pressure steps and hysteresis loops and, depending on crystal morphology, also high-pressure hysteresis loops. The low-pressure steps were associated with steps on t-plots which showed two linear parts. Small increase of adsorption up to relative pressure 0.2 is characteristic for samples with Si/Al ratios between 25 and 50.

Synthesis and Characterization of Small Crystals NaY Zeolite with High Silicon

2012 ◽  
Vol 554-556 ◽  
pp. 81-88 ◽  
Author(s):  
Qing Yan Cui ◽  
Ya Song Zhou ◽  
Qiang Wei
Keyword(s):  
Low Temperature ◽  
Crystal Size ◽  
High Surface ◽  
Crystallization Time ◽  
Organic Additives ◽  
Nay Zeolite ◽  
Small Crystals ◽  
Low Temperature Crystallization ◽  
High Silicon ◽  
Temperature Crystallization

Small crystals NaY zeolite with high silicon was successfully synthesized via a two-stage temperature crystallization program, without adding any organic additives. While the effect of low temperature crystallization time and the alkalinity on the crystal size and SiO2/Al2O3 ratio of NaY zeolite were investigated. The as-synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier Transform Infrared (FT-IR) spectroscopy, N2 adsorption, 29Si MAS NMR and thermogravimetric TG measurements. NaY zeolite, with crystal size about 100 nm and SiO2/Al2O3 ratio about 5.3, is obtained. It possesses high surface area and some amount of mecropores, and the decomposition temperature is higher than 1000 °C. The crystal size and SiO2/Al2O3 ratio of as-synthesized NaY zeolite depend on low temperature crystallization time and the alkalinity.

Variation of Lattice Spacing with Thickness of Thin Gold Platelets

1971 ◽  
Vol 29 ◽  
pp. 162-163
Author(s):  
D. C. Smart
Keyword(s):  
Crystal Size ◽  
Lattice Parameter ◽  
Chloroauric Acid ◽  
Research Papers ◽  
Long Period ◽  
Small Crystals ◽  
Parameter Variations ◽  
Subsequent Measurement ◽  
The Subject ◽  
The Many

Variation of lattice parameters with crystal size in very small crystals (generally less than 500 Å in size) has been the subject of many research papers over a long period of time. In principle this method should provide a direct experimental measurement of surface tension but in many cases the reported results are contradictory. This fact has been noted in recent reviews, and the abnormal spacings are now generally regarded with considerable reserve. The many reported contradictions arise from a variety of experimental factors which cannot be discussed here. This paper, however, reports new experiments using a different approach which we believe has eliminated the previous experimental difficulties, and conclusively demonstrates lattice parameter variations associated with surface energy. These experiments consist of the preparation of thin, parallel, clean and nearly perfect platelets of Au and the subsequent measurement of the lattice spacings of these platelets as a function of thickness.The Au platelets were chemically grown by the reduction of chloroauric acid with salicylic acid. Reproducibly clean crystals from 1-5 µ in diameter and ranging in thickness from 80-300 Å were produced.

The influence of crystal size and crystallographic orientation on decomposition in the solid state: sodium and thallous azides

1966 ◽  
Vol 294 (1439) ◽  
pp. 417-436 ◽  
Keyword(s):  
Crystal Size ◽  
Molecular Layer ◽  
High Vacuum ◽  
Crystallographic Direction ◽  
Ultra High Vacuum ◽  
Decomposition Products ◽  
Kinetics Of Decomposition ◽  
Small Crystals ◽  
Kinetics Of ◽  
Scanning Electron

A method of preparing very small crystals of uniform and controlled size has been developed and used to study the decomposition of sodium and of thallous azides. The decomposition is carried out in ultra high vacuum and is coupled with the use of a mass ion spectrometer. The method is a sensitive one and it is possible to follow the kinetics of decomposition of one molecular layer from single crystals which may be only 10 -3 cm 2 in area. The decomposition products are identified by the mass ion spectrometer and the changes in the crystal are observed by scanning electron microscopy. It is shown that the rate of decomposition is proportional to the surface area of the crystals. There is evidence that the decomposition takes place over a surface or interface which moves into the crystal in a preferred crystallographic direction. It is the area of this surface which controls the rate of decomposition.

Modeling of Gas Adsorption Process of a Single Pellet

2011 ◽  
Vol 374-377 ◽  
pp. 1201-1206
Author(s):  
Xiang Jun Liu ◽  
Dan Li Wang
Keyword(s):  
Crystal Size ◽  
Adsorption Process ◽  
Gas Adsorption ◽  
Micro Structure ◽  
N2 Adsorption ◽  
Microporous Material ◽  
Large Numbers ◽  
Single Pellet ◽  
Small Crystals ◽  
5A Zeolite

A commercial zeolite pellet is formed by binding large numbers of small crystals with microporous material. Its Micro-structure has great affects on the gas adsorption process. In this paper, the physical and mathematic models of the adsorption process for a single pellet are established. The N2 adsorption properties in a 5A zeolite pellet are studied. Very detailed results of intra-pellet adsorption process are obtained. The impacts of crystal size, pellet porosity, diffusion coefficient of the binding materials and crystals on the adsorption rate are studied.

scholarly journals Freezing-rate effects on the physical characteristics of basal ice formed by net adfreezing

1991 ◽  
Vol 37 (127) ◽  
pp. 339-347 ◽  
Author(s):  
Bryn Hubbard
Keyword(s):  
Crystal Size ◽  
Empirical Studies ◽  
Individual Characteristics ◽  
Freezing Rate ◽  
Ice Crystal ◽  
Basal Ice ◽  
Rate Effects ◽  
Ice Crystal Size ◽  
Sediment Mixtures ◽  
Cylindrical Reservoir

AbstractA number of theoretical and empirical studies have indicated that many individual characteristics of ice formed by processes of net basal adfreezing may be sensitive to the rate of propagation of the freezing front through the reservoir concerned. The effects of freezing rate on the the stable-isotope chemistry and crystallography of ice, in addition to the disposition and character of included debris and gas are reported. Unidirectional freezing through a cylindrical reservoir containing various water–sediment mixtures has been conducted in the laboratory and the resulting cores analysed for debris and gas disposition and ice-crystal size and fabric. The data lend support to inferences drawn from studies concerned with specific ice properties and an idealized suite of characteristics is developed which may be diagnostic of basal ice formed by net adfreezing.

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