Amorphous ices amorphization

N2 as adsorbate, was quite similar to that for N2 on a directly prepared and probably amorphous ice powder [35, 141], On the other hand, N2 adsorption on carbon with increasing thickness of preadsorbed methanol decreased steadily—no limiting isotherm was reached [139]. 

Transitions. Samples containing 50 mol % tetrafluoroethylene with ca 92% alternation were quenched in ice water or cooled slowly from the melt to minimise or maximize crystallinity, respectively (19). Internal motions were studied by dynamic mechanical and dielectric measurements, and by nuclear magnetic resonance. The dynamic mechanical behavior showed that the CC relaxation occurs at 110°C in the quenched sample in the slowly cooled sample it is shifted to 135°C. The P relaxation appears near —25°C. The y relaxation at — 120°C in the quenched sample is reduced in peak height in the slowly cooled sample and shifted to a slightly higher temperature. The CC and y relaxations reflect motions in the amorphous regions, whereas the P relaxation occurs in the crystalline regions. The y relaxation at — 120°C in dynamic mechanical measurements at 1 H2 appears at —35°C in dielectric measurements at 10 H2. The temperature of the CC relaxation varies from 145°C at 100 H2 to 170°C at 10 H2. In the mechanical measurement, it is 110°C. There is no evidence for relaxation in the dielectric data. 

The things that we have been talking about so far - metal crystals, amorphous metals, solid solutions, and solid compounds - are all phases. A phase is a region of material that has uniform physical and chemical properties. Water is a phase - any one drop of water is the same as the next. Ice is another phase - one splinter of ice is the same as any other. But the mixture of ice and water in your glass at dinner is not a single phase because its properties vary as you move from water to ice. Ice + water is a two-phase mixture. 

More recently, simulation studies focused on surface melting [198] and on the molecular-scale growth kinetics and its anisotropy at ice-water interfaces [199-204]. Essmann and Geiger [202] compared the simulated structure of vapor-deposited amorphous ice with neutron scattering data and found that the simulated structure is between the structures of high and low density amorphous ice. Nada and Furukawa [204] observed different growth mechanisms for different surfaces, namely layer-by-layer growth kinetics for the basal face and what the authors call a collected-molecule process for the prismatic system. 

To a stirred solution of 5.7 g (0.02 m) of 4-benzyloxy-2-ureidoacetophenone in 100 ml of chloroform is added 3.2 g (0.02 m) of bromine. The mixture is stirred at room temperature for about 45 minutes and the solution is concentrated in vacuo at 25°-30°C. The amorphous residue (hydrobromide selt of 4-benzyloxy-a-bromo-3-ureidoacetophenone) is dissolved in 80 ml of acetonitrile and 98 g (0.06 m) of N-benzyl-N-t-butylamine is added. The mixture is stirred and refluxed for 1.5 hours, then it is cooled toOt in an ice bath. Crystalline N-benzyl-N-t-butylamine hydrobromide is filtered. The filtrate is acidified with ethereal hydrogen chloride. The semicrystalline product is filtered after diluting the mixture with a large excess of ether. Trituration of the product with 60 ml of cold ethanol gives 4-banzyloxy-Of-( N-benzyl-N-t-butylamino)-3-ureidoacetophenone hydrochloride, MP 200°-221°C (decomposition). 

Preparation of Ba-Methyi-17-Hydroxy progesterone 17-Acetate 1 g of 6a-methyl-17a-hy-droxyprogesterone was dissolved in a mixture of 10 ml of acetic acid and 2 ml of acetic anhydride by heating. After solution was effected the mixture was cooled to 15°C, and 0.3 g of p-toluenesulfonic acid was added. After allowing the mixture to stand for a period of 2 /a hours at room temperature, the pink solution was poured into ice water to give an amorphous solid which was recovered by filtration. 

Callisto orbits Jupiter at a distance of 1.9 million kilometres its surface probably consists of silicate materials and water ice. There are only a few small craters (diameter less than a kilometre), but large so-called multi-ring basins are also present. In contrast to previous models, new determinations of the moon s magnetic field suggest the presence of an ocean under the moon s surface. It is unclear where the necessary energy comes from neither the sun s radiation nor tidal friction could explain this phenomenon. Ruiz (2001) suggests that the ice layers are much more closely packed and resistant to heat release than has previously been assumed. He considers it possible that the ice viscosities present can minimize heat radiation to outer space. This example shows the complex physical properties of water up to now, twelve different crystallographic structures and two non-crystalline amorphous forms are known Under the extreme conditions present in outer space, frozen water may well exist in modifications with as yet completely unknown properties. 

The crude acid is dissolved in 500 ml. of petroleum ether at room temperature. The small amount of amorphous solid which may separate is removed by filtration through Supercel, and the filtrate is concentrated under reduced pressure to 300 ml. Chilling to 0-5° yields a first crop of tan crystals which is collected by suction filtration and washed with the minimum amount of ice-cold petroleum ether. Concentration of the mother liquors to 150 ml. and chilling yields a second crop of brownish crystals. The combined crops are dissolved in 300 ml. of petroleum ether, and the light-red solution is chilled to 0-5°. The almost white to light-tan crystals are collected, washed with a small amount of cold petroleum ether, and dried in a vacuum desiccator. There is obtained 51.5—61.5 g. (51-61%) of stearolic acid, m.p. 46-46.5° (Note 5). 

Fig. 1.12. Phase diagram of water - glycerine. On the left hand side the dependence of the phase transition time from the ice temperature is shown At -140 °C, amorphous ice transforms into cubic ice in approx. 10 min (Fig. 8 from [1.98]).

The combination of this knowledge and the results of quick-freezing processes provide a theoretical opportunity to freeze products into a solid, amorphous state. If the freezing velocity is smaller than required for vitrification, but large enough to avoid an equilibrium state, an amorphous mixture will result of hexagonal ice, concentrated solids and UFW. 

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