Supercooling Phenomena Research Articles

Binary mixtures: CH 3CH 2CONH 2 + (Na, K)/(CNS, ClO 4)

The enthalpy of fusion of propionamide is measured by the DSC method, and liquid—solid equilibrium temperatures are measured for the binary systems CH 3CH 2CONH 2+(Na, K)/(CNS, ClO 4). The cryoscopic thermodynamic constant is compared with the experimental value. It was found that supercooling phenomena in these systems are very limited.

EXAFS study on premelting and supercooling phenomena of gallium

EXAFS spectroscopy and density measurement have been carried out on premelted, melted and supercooled states of gallium. We found a certain premelting phenomenon which is considered as formation of interstitial or Frenkel-type defects besides vacancies.

Supercooling phenomena in binary mixtures of acetamide and inorganic salts

Liquid—solid equilibrium temperatures are measured in binary mixtures of acetamide and inorganic salts [NaClO 4, LiCNS, LiNO 3, CH 3COOLi, Ca(NO 3) 2, (CH 3) 4 NCl, (C 2H 5) 4 NBr]. In some ranges of concentration all these systems (with the exception of CH 3COOLi, R 4NX) exhibit supercooling phenomena and crystallization occurs only through vigorous agitation and in the presence of crystalline nuclei, or does not occur at all, according to the type of salt. A probable explanation is presented on the basis of the trend of Δ T/ν mK vs. m.

Supercooling in SU(5) and temperature dependence of the gauge coupling constant

We discuss the phenomenon of supercooling in the early Universe, when the temperature dependence of the gauge coupling constant in SU(5) is taken into account. We also discuss the effect of temperature dependence of the tunneling parameter ..gamma...

Present and Future Capabilities of Acoustic Levitation and Positioning Devices

ABSTRACTThe techniques of acoustic positioning without the use of resonant cavities have been explored and developed over a number of years and the currently available capabilities are reviewed. The performance and characteristics of these nonresonant acoustic systems are described in regard to containerless processing with emphasis on the low-g environment. This includes manipulation and mixing of liquid drops, super-cooling phenomena, heating to temperatures of 1600°C or higher, rapid cooling solidification, and surface shape control. Some possible applications are measurements of physical properties of substances at high temperatures or of highly reactive specimens, and the formation of unique glasses and alloys of new compositions.

Supercooling phenomenon and water content independence in the overwintering beetle, Coleomegilla maculata

Insect supercooling phenomena observed during overwintering have been coupled with the seasonality of water and nucleator content and feeding behaviour. However, the strength of the conclusion has in most cases rested on presumption and model systems since nucleator content is not readily quantifiable. The ladybird, Coleomegilla maculata is an overwintering adult insect that fasts for weeks before hibernation, does not accumulate identifiable cryoprotectants during cold exposures, and is freezing intolerant. This species would be expected to overwinter with a constancy of ice nucleators subject to relative increases due to winter dehydration and decreases in supercooling ranges. However, acclimatization and laboratory acclimation experiments have demonstrated both temporal and temperature independence of water content while supercooling levels varied substantially. Supercooling ranges were narrow during warm exposures with a unimodal peak at −6·3°C (±0·2 S.E.). Progressive temperature reductions yielded phasic shifts to multimodal ranges until a low temperature peak of −18·4°C (±0·5 S.E.) was attained. Induced feedings of controlled nucleator substances resulted in predictable supercooling variations while ‘nucleator free’ diets yielded results consistent with natural populations.

溶接凝固機構とその組織の特性(第7報)

The changes and the construction mechanism of solidification structure were investigated for the weld metal which had been welded with a moving arc heat source. The materials used were aluminum sheets with different chemical compositions. The conclusions obtained are as follows:(1) The nominal growth rate in the weld metal increases generally as the inward growth proceeds, while the temperature gradient decreases.(2) When the welding is performed in a condition that the bead width is almost the same, the values of the temperature gradient decrease as the welding speed increases. Accordingly the extent of the constitutional supercooling zone in the weld metal increases as the inward growth proceeds and besides the welding speed increases.(3) The columnar crystals develop in the weld metal and under certain circumstances the equiaxed dendrites develop near the center of the weld metal.(4) In the 99.96%- and 99.93%-aluminum sheets, the planar growth is observed near the fusion boundary and afterwards the cellular subgrain is observed. In this case the equiaxed dendrites do not develop.(5) In the commercially pure aluminum sheets, the solidification structure changes from planar to cellular subgrain and cellular dendrite as the inward growth proceeds. The equiaxed dendrites develop near the center of the weld metal when the welding is performed in a high speed.(6) In aluminum alloy sheets, the cellular dendrite is observed even near the fusion boundary and afterwards a lot of equiaxed dendrites develop.(7) The changes of the solidification structure shown in (4), (5) and (6) can be accounted for in terms of the phenomenon of the constitutional supercooling.(8) When the welding is performed in a condition that the bead width is almost the same, it becomes easy for the equiaxed dendrites to develop in the weld metal as the welding speed increases. This phe-nomenon will be accounted for in terms of the extent of the constitutional supercooling zone.

溶接凝固機構とその組織の特性(第1報)

The changes and the construction mechanism of solidification structure were investigated for the weld metal which had been welded with a moving arc heat source. The materials used were aluminum sheets with different chemical compositions. The conclusions obtained are as follows:(1) The nominal growth rate in the weld metal increases generally as the inward growth proceeds, while the temperature gradient decreases.(2) When the welding is performed in a condition that the bead width is almost the same, the values of the temperature gradient decrease as the welding speed increases. Accordingly the extent of the constitutional supercooling zone in the weld metal increases as the inward growth proceeds and besides the welding speed increases.(3) The columnar crystals develop in the weld metal and under certain circumstances the equiaxed dendrites develop near the center of the weld metal.(4) In the 99.96%- and 99.93%-aluminum sheets, the planar growth is observed near the fusion boundary and afterwards the cellular subgrain is observed. In this case the equiaxed dendrites do not develop.(5) In the commercially pure aluminum sheets, the solidification structure changes from planar to cellular subgrain and cellular dendrite as the inward growth proceeds. The equiaxed dendrites develop near the center of the weld metal when the welding is performed in a high speed.(6) In aluminum alloy sheets, the cellular dendrite is observed even near the fusion boundary and afterwards a lot of equiaxed dendrites develop.(7) The changes of the solidification structure shown in (4), (5) and (6) can be accounted for in terms of the phenomenon of the constitutional supercooling.(8) When the welding is performed in a condition that the bead width is almost the same, it becomes easy for the equiaxed dendrites to develop in the weld metal as the welding speed increases. This phe-nomenon will be accounted for in terms of the extent of the constitutional supercooling zone.

Semi-automatic control system for producing constant cooling rates

This control system was designed and is best suited for cooling, at a constant rate, the metal sample block of a differential thermal analysis apparatus used for studying supercooling, melting and solidification phenomena in organic materials. An automatically-controlled flow of liquid refrigerant, passing through a simple heat exchanger, is used to cool the primary liquid circulating continuously in the coil system of the block. The apparatus is also suitable for uniform cooling of a small water or oil bath. For either application, controlled cooling rates of up to about 2° C/min are attainable. Using refrigerated water, control is possible from 95 down to about 10° C depending on the rate, but the range could be extended to lower temperatures by the choice of suitable liquid coolants.

熔融アルミニウム及びその合金の流動性について―二元アルミニウム合金の流動性試験片の顕微鏡組織的研究（第2報）Al-Si系合金

The authors have observed, in the previous paper [this journal, 6 (1942), 27] regarding the running quality of binary aluminium alloys containing silicium up to 15.69%, the following experimental results that the silicium content of the alloy, taking the minimum value of the running quality is between 3% and 4%, and that this content is higher in silicium than the composition of the maximum solidification temperature range and that the running quality of the hyper-eutectic alloy containing 15.69%Si is far more than that of the eutectic alloy. These phenomena could not be explained by using the solidification range theory of the running qaulity of alloys brought forward by A. Portevin and his collaborators. Therefore, the authors have studied the microscopic structures of the cross sections of the running quality test specimens and have confirmed that it is necessary to take into consideration the super-cooling phenomena in the solidification process of molten alloy flowing in the test mould for clarifying the nature of the running quality. Then, the phenomena above mentioned are reasonably explained as follows : the degree of the super-cooling of the hyper-eutectic alloy containing 15.69%Si is far more than that of the eutectic alloy and as the authors have poured the molten alloy into the test mould at about 50° above the liquidus temperature on the equilibrium diagram, the difference between the pouring temperature and the temperature of the primary crystallization of the hypereutectic alloy is more than that of the eutectic alloy. Consequently,the time interval where the perfectly liquid alloy flows in the test mould in the case of the hyper-eutectic alloy is far more than in the case of the eutectic alloy and the length of flow of the former alloy filled up the test mould is longer than that of the latter. The phenomenon that the running quality of the alloy containing silicium between 3% and 4% takes the mimimum value has not been sufficiently clarified by means of the microscopic study only, but it has been suporsed that the degree of the super-cooling of the alloy containing 3% and 4%Si is less than that of the Si 1.6%-alloy, and consequently this phenomenon takes place.