三元溶液共晶DSC实验研究

抑制共晶产生对低温保存非常重要。本文利用差示扫描量热法研究了加低温保护剂(DMSO、乙二醇、 1,2丙二醇、甘油和1,3丁二醇)的NaCl水溶液的共晶行为。得到以5％、10％、15％NaCl水溶液为母液的五种保护剂溶液热流曲线图。研究发现,溶液共晶是过冷、随机过程。低温保护剂有抑制NaCl水溶液共晶的作用。低温保护剂浓度越高, 共晶焓越小,对共晶的抑制作用越大。不同种类保护剂的抑制共晶的能力从强到弱依次是甘油、乙二醇、 DMSO、 1,2 丙二醇和1,3丁二醇。升温过程中,溶液发生共晶反玻璃化现象和玻璃化现象。     

生物材料玻璃化保存液的热分析

在玻璃化超低温保存生物材料的研究中,低温保护剂的热分析对玻璃化溶液的优化和保存方案的选择具有重要的指导意义.本文以渗透性低温保护剂二甲基亚砜和丙二醇以及非渗透性保护剂聚乙烯醇作为研究对象,利用差式扫描量热法对聚乙烯醇/二甲基亚砜/丙二醇体系进行升温和降温实验,考察了体系的结晶特性、玻璃化转变特性、聚乙烯醇的浓度等因素对体系热性能参数的影响.     

差示扫描量热法测定己内酰胺的纯度

采用差示扫描量热（DSC）仪对己内酰胺标准品进行不同条件下的扫描。基于V an＇t Hoff方程,建立了DSC法测定己内酰胺纯度的方法。与气相色谱-卡尔费休法测得的纯度结果相比,偏差不超过0.1%,其重复性相对标准偏差小于0.02%（n=6）。DSC法的准确性和重复性较高,能快速,准确的测定己内酰胺的纯度。     

醇类低温保护剂水溶液过冷和水合性质研究

利用差示扫描量热仪研究了乙二醇、丙三醇、1,3丙二醇、1,3丁二醇和2,3丁二醇水溶液的过冷行为和水合性质,得出了这些性质与线性多元醇溶液浓度的关系.研究发现,在低浓度过冷度与浓度之间没有明显关系;而在中高浓度则具有相似的变化规律,即随着溶液浓度增大而增大.各低温保护剂在水合性质上所表现出的差异性,体现了保护剂的官能团(羟基、甲基)所起到的重要作用.     

添加剂对AP/Al热分解影响的红外光谱与热分析研究

采用傅里叶变换红外吸收光谱(FTIR)和差示扫描量热法(DSC)研究了草酸铵(AO), 碳酸锶(SC)及复配的草酸铵/碳酸锶等添加剂对复合固体推进剂主要组分高氯酸铵(AP)的作用机理。红外分析表明：草酸铵使AP各吸收峰消失的温度延后。碳酸锶在凝聚相中与AP的分解产物高氯酸发生反应生成比较稳定的产物高氯酸锶,IR光谱证实了高氯酸锶的存在。DSC分析结果表明：草酸铵的加入使AP高温阶段的分解放热峰向高温方向移动,但对AP低温阶段的分解放热峰没有影响。碳酸锶的加入使AP两个阶段的分解放热峰均向高温方向移动。草酸铵/碳酸锶的加入,虽然使AP的分解放热峰均向高温方向移动,但是实验发现,在常压下草酸铵/碳酸锶的组合配方没有发挥对AP高温分解的协同作用。基于上述实验探讨了草酸铵和碳酸锶抑制AP分解的作用机理。     

丙三醇浓溶液玻璃化转变与结构松弛参数DSC分析

利用差示扫描量热仪研究了5种高浓度丙三醇水溶液(60%、70%、80%、90%、100%)的玻璃化转变行为,以考察水分含量和升降温速率对其玻璃化转变行为和结构松弛参数的影响.采用4种线性升降温速率(10、15、20、25K/min)获得玻璃化转变的相关参数.利用GordonTaylor方程对玻璃化转变温度的分析结果表明,水对丙三醇增塑常数的计算结果与升降温速率和玻璃化转变温度的读取方法有很大关系.玻璃化转变过程的比热容变化不仅随水分含量的增加而增加,而且与升降温速率也有一定的依赖关系.结构松弛活化能的计算结果表明,随体系水分含量的增加,体系的结构松弛活化能和动力学脆度都逐渐降低.随水分含量的变化,热力学脆度和动力学脆度表现出相反的变化趋势.     

固体材料低温比热测量技术综述

材料低温比热测量对新材料研究和应用具有重要意义,低温比热测量是低温物理研究领域最活跃的研究方向之一。对低温比热测量研究历史作了简单的介绍,对各种低温比热测量方法的原理、应用、发展进行了较全面的综述分析,对超低温、强磁场、放射性样品等特殊情况下比热测量作了讨论。     

热致晶化高反射率SbOx薄膜的结构分析和光学性质

利用直流磁控反应溅射法制备了SbOx薄膜,利用X射线衍射分析仪和光谱仪分别研究了这种薄膜热致晶化的微观结构和光学性质的变化,并通过非晶态薄膜粉末的示差扫描量热实验测出不同加热速度条件下结晶峰温度,研究了这种薄膜的结晶动力学。发现沉积态SbOx薄膜为非晶态,非晶态SbOx薄膜在热致晶化过程中发生了两种变化,分别对应为较低温度下Sb晶体和较高温度下立方Sb2O3相的生成。退火后晶态薄膜中出现了单质Sb和Sb2O3,300℃退火后Sb2O3相含量最大。晶态薄膜的反射率均高于沉积态,在晶态薄膜中200℃退火的薄膜反射率最大。     

食品玻璃化转变温度测量方法的比较

利用差示扫描量热仪用经过退火处理的连续扫描法、不经过退火处理的连续扫描法和分步扫描法,对20％和50％蔗糖水溶液的玻璃化转变温度进行了测量。结果显示,退火处理的连续扫描法测量结果最好,测得蔗糖水溶液的玻璃化转变温度大致为-34．6℃,Tg'不受退火温度和溶液浓度的影响。三种方法测得20％蔗糖水溶液的Tg'的差别不大。退火方法和不退火方法测得50％蔗糖水溶液的Tg'差别很大。用两种不同的连续扫描方法做了几组测新鲜西瓜汁玻璃化转变温度的实验,结果在-42--44℃之间。     

制备低密度pmp泡沫中的热性能研究

在聚－4－甲基－1－戊烯（pmp）低密度泡沫的制备中,利用示差扫描量热分析仪对pmp聚合物在均四甲苯／萘所组成的溶剂／非溶剂二元体系中的凝胶化过程进行在线测量,测定了它的凝胶化范围以及凝胶化温度与冷却速率和pmp在溶剂;非溶剂体系中所占比例的关系。利用热重－示差扫描量热系统对所制备的低密度pmp泡沫的热性能进行了分析,得到了泡沫密度变化对热稳定性等的影响。     

一种可视化DSC装置的设计与校准

设计研制了一种具有可视化功能的差示扫描量热装置,简称可视化DSC装置。该可视化DSC装置能够在差示扫描测量的同时,通过配套使用的显微镜摄像系统对测试样品的微观结构变化进行观察并记录。采用纯水为标准物质,对可视化DSC装置的温度测量与热量测量分别进行了校准,结果表明具有较高的测量稳定性。该可视化DSC装置能同时提供测试样品的热效应数据和微观结构的图像数据,提高了数据获取的同步性与测量结果的准确性。     

Sorption of Organic Solvents in Poly(Dimethyl Siloxane) Membrane. I. Permeant States Quantification using Differential Scanning Calorimetry

The permeant states of various solvents in poly(dimethyl siloxane) (PDMS) film were evaluated using low temperature differential scanning calorirnetry (DSC) on both vapor and liquid penetrants. Water, cyclohexane, benzene, toluene, and m‐xylene may be present in the freezable and nonfreezable state. At low sorption levels, solvents sorbed in PDMS were in the nonfreezable state until a threshold value was reached. Beyond that, the increased solvent sorption values all occurred in a freezable state. The partition pattern between the freezable and nonfreezable states for a vapor penetrant showed an identical trend with that for the liquid penetrant. The maximum nonfreezable amount of solvent in PDMS depended on the solvent's chemical compatibility with the membrane but not on the sorption temperature. Compared with that at 10°C, the higher solvent solubility at 25°C was due to the increase in the freezable solvent content without any change in the maximum nonfreezable content. The permeant states for equilibrium and nonequilibrium samples did not differ from one another.     

New alkali antimonate glasses

Glass formation has been investigated in ternary systems Sb₂O₃-PbO-M₂O in which M is alkali Li, Na and K and antimony oxide is the glass former. Alkali elements were introduced as carbonates. The size of the glass forming region is enlarged as alkali ionic radius increases. Binary Sb₂O₃-M₂O glasses were obtained: (100−x) Sb₂O₃-xLi₂O, (10<x<30), (100−x) Sb₂O₃-xNa₂O, (10<x<70), and (100−x) Sb₂O₃-xK₂O, (10<x<90). In ternary systems, PbO content could reach 60 mol%. Temperatures of glass transition, T_g, onset of crystallization, T_x, and maximum of crystallization, T_p, have been measured using differential scanning calorimetry. Depending on composition, glass transition temperature ranges from 240 to 330 °C. The incorporation of alkali oxide increases T_g while lead oxide has the reverse effect. Thermal stability range (T_x-T_g) was usually between 65 and 266 °C, while no crystallization exotherm was observed in some cases. Density and thermal expansion increases as lead concentration increases. Optical transmission has been measured. The UV cut-off depends on alkali content: samples are yellow and turn green for large K and Na content. These glasses have potential applications as low phonon energy glasses for infrared transmission or active devices.     

Synthesis of Poly(butylene terephthalate)/Attapulgite Nanocomposites by In-Situ Polymerization and Its Crystallization Behavior

Poly(butylene terephthalate) (PBT)/attapulgite (AT) nanocomposites were prepared via in-situ polymerization without pre-modification of AT. By this method, PBT chains were successfully grafted onto the surface of AT, which was confirmed by Fourier transform infrared spectroscopy and thermogravimetric analysis. Scanning electron microscope examination indicated the uniform dispersion of AT nanoparticles in PBT matrix. The crystallization behavior of PBT/AT nanocomposites was investigated by X-ray diffraction patterns, differential scanning calorimetry, and step-scan differential scanning calorimetry. The non-isothermal crystallization processes were analyzed with the Avrami, Ozawa, and Mo methods. Crystallization activation energies of the samples were also determined by the Kissinger method. The results indicated that AT could act as a heterogeneous nucleating agent in PBT crystallization and lead to an acceleration of crystallization, while AT also acted as a physical hindrance to retard the transport of polymer chains to the growing crystals.     

Sorption of Organic Solvents in Poly(Dimethyl Siloxane) Membrane. II. Effect of Sorption on the Polymer Crystals upon Cooling

Polymer crystalline properties in poly(dimethyl siloxane) (PDMS) film after solvation by various solvents was determined using low temperature differential scanning calorimetry (DSC). At various solvent uptake levels, the crystalline thermal properties of the solvated polymer were modified to different extents as revealed by the shifts in crystalline melting point (T_m) and its enthalpy (ΔH_m). Water uptake in PDMS was very limited (<0.01 g/g) and T_m did not significantly change during the sorption process. For toluene and cyclohexane penetrants, T_m moved toward a much lower temperature depending on the sorption levels. At low solvent uptakes, the T_m values decreased linearly with solvent uptakes due to formation of a miscible phase. Beyond a threshold, the T_m remained stable and an additional penetrant fusion peak appeared, implying the onset of a microphase separation phenomenon. The ΔH_m values for the swollen membranes were decreased, with the exception of the water penetrant. This indicates that a lower percentage of polymer chains were involved in the crystalline domain for swollen PDMS.     

Crystallization of Lightly Sulfonated Poly(ethylene terephthalate) Ionomer. I. Isothermal Crystallization from the Melt

Thermal properties and overall rates of isothermal crystallization from the melt of a commercial ionic copolyester (K‐X/SPET) based on poly(ethylene terephthalate) (PET) were analyzed in detail over a composition range from pure PET to a copolymer containing 10.1 mol% of potassium‐neutralized sulfonated PET. For measurements, differential scanning calorimetry (DSC) was used. Copolyesters with the ionic group content of 4.4 mol% or more were unable to crystallize. The isothermal melt crystallization of the copolyesters was analyzed using both the Avrami and the modified Lauritzen‐Hoffman equations. It was found that both the overall rate constant, as well as the Avrami parameter for the primary crystallization stage, varied with the sulfonated unit percentage—but surface free energy and work of folding were practically independent of them. The observed changes in the thermal properties and the kinetic parameters of crystallization were attributed to the comonomer effects and the intermolecular aggregation of the ionic groups.     

Radiation damage by soft β-particles self-irradiation of β-tritiated polystyrene

The effect of self-irradiation of β-tritiated polystyrene under high vacuum at 25°C was studied, and simultaneous random chain scission and cross-linking were observed. Analyses of the gaseous products and the colored polymer residue showed that hydrogen was the only volatile product, while spectroscopic measurements indicated that the coloration was associated with the presence of main-chain double bonds.

G values for hydrogen formation GH₂, cross-linking, G _XL and chain scission, G _CS were obtained as follows: GH₂=0.031; G _CS=0.044; G _XL=0.061. Possible mechanisms of radiation damage are discussed.     

热爆炸临界参数的数值解法

本文提出的热爆炸临界参数的数值解法是一种变分方法.这种方法依据的是文献[1]给出的热爆炸临界参数的一个变分原理。数值计算的结果表明,这种方法是一种简便、经济而又精确度较高的方法。     

Synthesis,structural study and thermal behaviour of a new compound: trirubidium bis(hydrogen sulphate) dihydrogen arsenate Rb3(HSO4)2.5(H2AsO4)0.5

Mixed crystals Rb₃(HSO₄)_2.5(H₂AsO₄)_0.5 have been prepared by slow evaporation from aqueous solution at room temperature. The crystals were characterized by X-ray single analysis, which revealed that Rb₃(HSO₄)_2.5(H₂AsO₄)_0.5 crystallizes in the space group P with lattice parameters: a = 7.471(3) Å; b = 7.636(1) Å; c = 12.193(2) Å; α = 71.91(1)°; β = 73.04(6)° and γ = 88.77(2)°. In this structure, the ordered S(1)O₄ and the disordered S(3)/AsO₄ tetrahedra are connected by O–H..O hydrogen bonds, to a zigzag chains running in the b-direction. These chains are, in turn, bonded to one another by disordered hydrogen bridges O–H..H–O, to give a planar structure, with hydrogen-bonded sheets, laying parallel to (1 0 0). Each disordered tetrahedron is linked to a tetrahedron neighbouring S(2)O₄ by ordered hydrogen bonds. Broader peaks in IR spectrum of the title material support the assumption of disordered structure. Thermal analysis of the superprotonic transition in Rb₃(HSO₄)_2.5(H₂AsO₄)_0.5 showed that the transformation to the high-temperature phase occurs by one-step process at 404 K. Thermal decomposition of this compound takes place at much higher temperatures, with an onset of approximately 473 K.     

MEMORY EFFECT AND CRYSTALLINE STRUCTURE IN POLYAMIDE 11

The memory effect in PA11 films is studied in close relation with the crystalline structure. In polyamide 11, [(CH₂)₁₀–CO–NH] _n , the polarity of the amide group induces hydrogen bonds between chains that are crucial to the crystalline structure and are responsible for the memory effect. During the forming from the melt, the polyamides are sheared, which leads to persistent chain alignments due to hydrogen bonds. In the present work, the crystalline structure of PA11 films has been studied by differential scanning calorimetry and wide angle x-ray scattering. The crystalline structure at room temperature depends on the cooling rate. A quench leads to the smectic δ′ structure, whereas a slow cooling favors the formation of the triclinic α phase in addition to the smectic δ′ phase. This study also shows the influence of an annealing in the melt on the crystalline structure. With increasing annealing time in the melt, the δ phase develops and the δ′ phase progressively vanishes. It seems necessary to maintain PA11 above the melting point for a long time to totally erase the structural evidence of the memory effect.