还原气氛烧成Y5V型瓷粉的结构与介电性能

运用SEM、TEM、XRD等手段研究了掺杂组分对钛酸钡基Y5V陶瓷的结构和性能影响.结果表明:由于掺杂组分的存在,烧结情况得到了明显的改进.掺杂钛酸钡陶瓷的烧结包括固-固烧结和液-固烧结.Zr和稀土元素能够扩散进入钛酸钡晶格并促进固-固烧结,SiO2主要聚集在晶界并促进液-固烧结烧结.Nd5 聚集在晶界并促进针状颗粒生成,XRD的结果表明样品中有新相形成.由于掺杂的引入,材料的居里温度向低温方向移动,材料的介温曲线较纯钛酸钡材料的介温曲线更趋平坦.研究的结果还表明,由于在还原气氛中烧结,材料的介电损耗上升.     

Phase diagrams beyond the critical point

Following a path in the usual p‐T‐diagrams of one‐component systems via the supercritical region it seems that one can make a transition from the liquid to the gas phase (and in reverse) without traversing a phase boundary curve, whereas in the sub‐critical region one clearly has to pass a phase boundary curve. To solve this paradox situation, the phase diagrams of one‐component systems are analyzed with respect to the phase transition from the liquid to the gas state in the sub‐ and supercritical range. It is shown that the critical point is not an isolated point or an end point on the phase boundary curve between the gaseous and the liquid phase in a p‐T‐diagram. Instead, it marks on the boundary curve just the transition between the section of a first order phase transition in the sub‐critical range and the section of a second or higher order phase transition in the supercritical range. Thus, the present phase diagrams of one‐component systems are incomplete with respect to the phase boundary curve between liquid and gas in the supercritical region. The result is illustrated using the model of a van der Waals gas.     

聚乙二醇/聚丙烯酰胺相变材料非等温固-固相变动力学

通过在丙烯酰胺聚合反应中加入聚乙二醇的方法制得的聚乙二醇(PEG)/聚丙烯酰胺(PAAm)相变材料具有固-固相转变的性质。对聚乙二醇及五种相变材料分别进行不同速率的非等温DSC测试,采用K iss inger和O zaw a两种动力学模型研究了非等温固-固相变动力学,计算了固-固相变过程的活化能和反应级数,两种方法求得的表观活化能Ea值相一致。     

聚乙二醇/壳聚糖复合物的相变行为及分子间相互作用

应用静态热机械分析(TMA)、差示扫描量热(DSC)和傅立叶转换红外光谱(FT-IR)研究了聚乙二醇(PEG)与壳聚糖(Chitosan)形成复合物的相变行为及分子间的相互作用。结果表明，当复合物中壳聚糖含量高于15％时．复合物表现出固态相转变行为；PEG与Chitosan间存在较强的分子间氢键，束缚和限制了复合物中PEG熔融态的平动自由，致使复合物在高温态下表现出固体化行为。     

Molecular alloys; Status and opportunities

The paper points out the great richness of the organic material and specially of the molecular alloys. Two particular points have been developed : on the one hand, the importance of the preparation method for alloys in the case of compounds with strongly directed intermolecular bonds, on the other hand, the wide diversity presented by the solid-liquid phase diagrams of organic systems, which is mostly linked with solid-solid polymorphism phenomena.     

二元系统分相区的定量预测方法——RO-B_2O_3(R=Mg、Ca、Sr、Ba)系统分相区的预测

本文对应用分相的普适性及定量计算方程来预测分相区进行了分析,认为,对二元系统的分相,只要知道临界点的实验值或临界点附近某两点以上的实验值,就可定量预测出临界点附近的分相区。并用此方法对已知分相区的硼酸盐碱土金属二元系 RO-B_2O_3(R=Mg、Ca、Sr、Ba)的分相区进行了预测验证。结果表明,用本文的方法来预测它们的分相区是可行的。本方法可望用于其它二元系统分相区的预测。     

静电纺丝制备纤维素纳米晶表面接枝聚乙二醇固-固相变纳米纤维

以纤维素纳米晶（CNC）为骨架、聚乙二醇（PEG）为功能性侧链、无毒的草酸为偶联剂,采用了一种绿色的合成方法制备出生物可降解的纤维素纳米晶接枝聚乙二醇共聚物（CNC-g-PEG）,然后通过静电纺丝成功制备出了平均直径约为910 nm的纳米纤维该纳米纤维表现出了优异的固-固相变行为,其相变焓最大可达88.2 J/g,结果表明,该纳米纤维能够作为潜在的固-固相变储能材料。     

HDPE/活性炭颗粒相变材料的制备及其性能研究

以活性炭颗粒(ACG)为骨架材料、高密度聚乙烯(HDPE)为相变材料,采用物理共混法制备了一种固-固相变材料.用扫描电子显微镜、差示扫描量热仪、高温综合热分析仪对所得相变材料进行了表征.结果表明,当ACG质量分数高于15%时,所得复合物宏观上表现为固-固相变;加入活性炭颗粒,可提高材料的热稳定性.     

一种添加蛋白石的固-固相变储能材料的制备及表征

利用天然纳米材料蛋白石(Opal)制备出新型有机-无机体系的聚氨酯/Opal固-固相变储能材料,并通过IR1、H-NMR、DSC、TG、POM、TEM等测试手段对其结构和性能进行表征分析。结果表明,该聚氨酯型相变材料具有较高的相变焓值、适宜的相变温度、热性能稳定和相变过程中不产生液体等特点。同时,加入天然纳米无机材料蛋白石后,结晶性能得到提高。     

A New Version of the Scintillation Phase Procedure

The scintillation phase procedure based on measuring the counting rate of compounds labeled with tritium in a two-layer scintillation cocktail-aqueous solution system was modified. Previously this procedure was used primarily for studying sorption of proteins at the phase boundary. After certain modification, it became applicable to studying the kinetics of sorption and the equilibrium sorption of various compounds at the organic scintillation cocktail-aqueous solution boundary and to evaluating the distribution coefficients of compounds in this system. Two experimental modes are proposed: common two-layer system and drop system. The suitability of these procedures for determining the surface activity and hydrophobicity of organic compounds and for studying the permeability of the molecular layers adsorbed at the phase boundary is discussed.     

Scaled equation of state for Freon-113 near the phase separation boundary

The equation of state of Freon-113 near the phase separation boundary and the behavior of a nonisotropic medium in a gravitational field near the critical point are studied using data on the scattered light intensity.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 39, No. 6, 1084–1089, December, 1980.     

Fabricating highly active mixed phase TiO2 photocatalysts by reactive DC magnetron sputter deposition

Recent work points out the importance of the solid-solid interface in explaining the high photoactivity of mixed phase TiO₂ catalysts. The goal of this research is to probe the structural and functional relationships of the solid-solid interface created by the reactive DC magnetron sputtering of titanium dioxide. We show that sputter deposition provides excellent control of the phase and interface formation. We explored the effects of the process parameters of pressure, oxygen partial pressure, target power, substrate bias (RF), deposition incidence angle, and post annealing treatment on the structural and functional characteristics of the catalysts. We have successfully made pure and mixed phase TiO₂ films. These films were characterized with AFM, SEM, TEM, and XRD to determine surface morphology, phase distribution and phase content. The performance as photocatalytic surfaces was measured and compared (normalized for surface area) to mixed phase TiO₂ fabricated by other methods, including flame hydrolysis powders, and sol-gel deposited TiO₂ films. The sputtered mixed phase materials were far superior to the commercial standard (Degussa P25) and sol-gel TiO₂ as measured by the gas phase oxidation of the air pollutant acetaldehyde under UV illumination. These results demonstrate that reactive DC magnetron sputtering is a powerful tool for investigating the role of the solid-solid interface in influencing photocatalytic activity. In addition, our work illustrates the feasibility of reactive DC magnetron sputtering as a practical commercial technique for manufacturing highly active nanostructured TiO₂ photocatalysts.     

Influence of material flux on the jump relations at a singular interface in a multicomponent solid

Summary. The mass and energy balances for a multicomponent solid, changing its composition by diffusion, are derived both in the bulk and at a moving non-material (singular) interface like a phase boundary. The body is deformable and diffusion of interstitial and substitutional species as well as vacancies is considered. The thermodynamic driving forces and corresponding fluxes are calculated in an interface point derived from the study of the local dissipation. The surface growth terms, as introduced recently by Irschik [1], can be identified via the flux of vacancies.     

聚乙二醇-纤维素接枝物固态相变材料的贮热性能

用化学偶联法,将聚乙二醇(PEG)接枝到纤维素分子链上,制备聚乙二醇-纤维素接枝物。用差示扫描量热(DSC)研究了接枝物的热力学性质。结果表明,PEG-CELL接枝物的相变焓、相变温度与PEG的分子量、PEG的质量百分比有关。当PEG的分子量在2000以下时,制备的接枝物相变焓很低;当PEG的分子量大于4000时。同等分子量情况下,相变焓、相变温度随PEG的质量百分含量减少而下降．所制备的PEG-CELL接枝物为固态相变材料,热滞后性降低,具有很好的热稳定性。     

Role of entropy of fusion in phase transformation and self-diffusion

The present paper discusses the role of the entropy of fusion vis-à-vis the phase transformation characteristics and the self-diffusion behavior of crystalline matrices. The data correlating the entropy of fusion with these properties in metals, alkali halides and some other inorganic compounds are presented and analyzed. It is shown that the occurrence of a solid-solid state phase transformation decreases the magnitude of the entropy of fusion. In addition, the self-diffusion rates within any class of solids scale inversely with the entropy of fusion. The functional relationship of the entropy of fusion vis-a-vis the compressibility and the volume expansion coefficient is also discussed. The conclusion is that the entropy of fusion is not just a physical parameter describing the energy changes associated with the melting. It is, in fact, related in a substantial manner to the bulk properties of the solid and controls the phase transition characteristics and self-diffusion behavior within any group or class of solids in a uniform and consistent manner.     

Numerical Study on the Vortex States of High-T c Superconductors with Point Defects: Novel Phases in the Vortex Liquid Region

Phase diagram of high-T _c vortex states in with point defects is investigated by large-scale Monte Carlo simulations. We find that the first-order boundary between the vortex slush and vortex liquid phases terminates at a critical point, and that there is a step of the specific heat above the critical point as reported experimentally. As the system size increases, this step becomes sharper but smaller, and is associated with a crossover rather than a thermodynamic phase transition.     

On the london model of the intermediate state in current-carrying superconductors

The London picture for the destruction of superconductivity by a current is considered. Equipotential S regions are taken as being placed periodically along the wire, and the magnetic field at the phase boundary is taken to have the critical value. From a solution of the Laplace equation for the electric potential near the contact point of two S regions a relationship between the angular aperture of the conical S region and the period of the structure is found. A numerical solution is given for the phase boundary and for the resistance at large currents. The volume of the S phase is found to be much smaller than that in the original London model. As a consequence the resistance of the wire after destruction of the uniform S state differs from that for the uniform N state by only a few percent.     

Rethinking convective quasi-equilibrium: observational constraints for stochastic convective schemes in climate models

Convective quasi-equilibrium (QE) has for several decades stood as a key postulate for parametrization of the impacts of moist convection at small scales upon the large-scale flow. Departures from QE have motivated stochastic convective parametrization, which in its early stages may be viewed as a sensitivity study. Introducing plausible stochastic terms to modify the existing convective parametrizations can have substantial impact, but, as for so many aspects of convective parametrization, the results are sensitive to details of the assumed processes. We present observational results aimed at helping to constrain convection schemes, with implications for each of conventional, stochastic or 'superparametrization' schemes. The original vision of QE due to Arakawa fares well as a leading approximation, but with a number of updates. Some, like the imperfect connection between the boundary layer and the free troposphere, and the importance of free-tropospheric moisture to buoyancy, are quantitatively important but lie within the framework of ensemble-average convection slaved to the large scale. Observations of critical phenomena associated with a continuous phase transition for precipitation as a function of water vapour and temperature suggest a more substantial revision. While the system's attraction to the critical point is predicted by QE, several fundamental properties of the transition, including high precipitation variance in the critical region, need to be added to the theory. Long-range correlations imply that this variance does not reduce quickly under spatial averaging; scaling associated with this spatial averaging has potential implications for superparametrization. Long tails of the distribution of water vapour create relatively frequent excursions above criticality with associated strong precipitation events.     

Electrothermal properties of perovskite ferroelectric films

The electrothermal properties of the perovskite oxides barium titanate (BTO), lead titanate (PTO), and strontium titanate (STO) are computed near the temperatures of their ferroelectric and/or ferroelastic phase transitions. The computations are performed using a modified 2-4-6 Ginzburg–Landau–Devonshire polynomial as functions of applied electric field and temperature for mechanically free monodomain crystals and for epitaxial thin films subject to perfect lateral clamping. For BTO and PTO, which display weak first-order ferroelectric phase transitions at their Curie points, the application of a bias field exceeding the electrical critical point reduces the dependence of the electrocaloric (EC) response on temperature and automatically reduces its magnitude. Under conditions of perfect lateral clamping, the weak first-order phase change is transformed into second-order phase change. In this instance the electrical critical point is coincident with the Curie temperature and a lower bias field is required to produce a comparable reduction in temperature sensitivity. Comparison of the electrothermal behaviors of BTO and PTO with that computed for STO near the temperature of the second-order ferroelastic phase transition provides insight concerning the EC properties of ferroelectric solid solution systems wherein the Curie temperature and the first-order character of the paraelectric to ferroelectric transition both may change subject to a change in composition. The results illustrate how electrical and mechanical boundary conditions can be adjusted, in conjunction with composition, in altering the EC properties of ferroelectric materials selected for use in a particular temperature range.     

固固相变贮能材料研究现状与进展

本文综述了固固相变贮能材料的研究现状 ,详细讨论了其分类、性能及优缺点 ,展望了该领域的研究发展前景。