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首页> 外文期刊>Physical chemistry chemical physics: PCCP >Te glassy water-cubic ice system: a comparative study by X-ray diffraction and differential scanning calorimetry
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Te glassy water-cubic ice system: a comparative study by X-ray diffraction and differential scanning calorimetry

机译：玻璃水立方冰系统：X射线衍射和差示扫描量热法的比较研究

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Mixtures of various ratios of cubic ice and glassy water were obtained by so-called hyperquenching of micrometer-sized water droplets at cooling rates of approx= 10~(6)-10~(7) K s~(-1) on a substrate held at selected temperatures between 130 and 190 K. These samples were characterized by differential scanning calorimetry (DSC) and X-ray diffraction. The minimum deposition temperature to obtain almost entirely vitrified samples is approx= 140 K. Glassy water prepared at this temperature exhibits on heating an endothermic step assignable to a glass -> liquid transition, without the requirement ofr previous annealing. Cubic ice samples obtained by deposition at 160 and 170 K undergo on heating two distinct exothermic processes of comparable intensity. One centered at approx= 230 K is caused by the phase transition to hexagonal ice. The other is centered at approx= 201 K in a sample deposited at 170 K, and it shifts to approx= 170 K, and it shifts to approx= 193 K on deposition at 160 K. The latter process is attributed to the increase in particle size, relief of non-uniform strain and/or healing of different kinds of defects. Since the temperature of this second exotherm depends on the deposition termperature of the sample, it merges on sample deposition at 190 K with the exotherm from the cubic -> hexagonal phase transition. For samples deposited at < = 150 K, the low temperature exotherm merges with the intense exotherm due to glassy water -> cubic ice phase transition. X-ray diffractograms and DSC scans of cubic ice samples of different thermal history show, after annealing at the same temperature of 183 K for 5 min, essentially identical patterns. Likewise, X-raydiffractograms of cubic ice made on heating hyperquenched glassy water or vapor-deposited amorphous solid water up to 183 K are indistinguishable. Cubic ice deposited at 190 K, or annealed at 183 K, contains at most 20% amorphous component which persists up to the cubic to hexagonal ice phase transition. This is in contrast to recent claims of Jenniskens et al. (J. Chem. Phys. 1997, 107, 1232) that cubic ice obtained by heating thin films of vapor-deposited amorphous water contains more than 50% of amorphous, or even liquid, water.
机译：通过在基板上以大约= 10〜（6）-10〜（7）K s〜（-1）的冷却速率对微米级水滴进行所谓的超淬火来获得各种比例的立方冰和玻璃水的混合物。将样品保持在130至190 K之间的选定温度下。通过差示扫描量热法（DSC）和X射线衍射对这些样品进行表征。获得几乎完全玻璃化的样品的最低沉积温度约为= 140K。在该温度下制备的玻璃状水在加热时表现出可归因于玻璃的吸热步骤->液体转变，而无需事先退火。通过在160和170 K下沉积获得的立方冰样品在加热时经历了两个强度相当的不同放热过程。一个以约230 K为中心的现象是由相变到六角形冰引起的。另一个在170 K沉积的样品中位于大约= 201 K的中心，并且偏移到大约= 170 K，在160 K沉积时它偏移到大约= 193K。后一个过程归因于颗粒的增加尺寸，不均匀应变的减轻和/或不同种类缺陷的修复。由于第二个放热的温度取决于样品的沉积温度，因此它在190 K的样品沉积时与立方->六角相变的放热合并。对于以<= 150 K沉积的样品，由于玻璃水->立方冰的相变，低温放热与强烈放热合并。在183 K的相同温度下退火5分钟后，具有不同热历史的立方冰样品的X射线衍射图和DSC扫描显示出基本相同的图案。同样，将超淬火的玻璃状水或气相沉积的无定形固体水加热到183 K时制得的立方冰的X射线衍射图也无法区分。在190 K下沉积或在183 K上退火的立方冰含有至多20％的无定形成分，该成分一直持续到立方到六方冰的相变。这与Jenniskens等人最近的说法相反。 （J.Chem.Phys.1997，107，1232），通过加热汽相沉积的非晶态水的薄膜而获得的立方冰包含超过50％的非晶态或什至液态的水。

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