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Thermal Expansion Behavior (thermal + expansion_behavior)
Selected AbstractsThermal expansion of organic crystals and precision of calculated crystal density: A survey of Cambridge Crystal DatabaseJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 5 2007Changquan Calvin Sun Abstract True density is a physical property of both fundamental and practical importance to the study of pharmaceutical powders. True density may be calculated from crystal structure. However, precision of such calculated density is not well understood. Furthermore, thermal expansion properties of organic crystals have rarely been characterized. A survey of Cambridge Crystal Database is conducted to assess (1) precision of calculated crystal density from crystal structure; (2) thermal expansion properties of organic crystals. It is shown that calculated crystal density exhibits, on average, a relative standard deviation (RSD) of ,0.4%. It is found that crystal density generally increases linearly with decreasing temperature provided no phase change occurs. Slope of the line, termed thermal density gradient, of organic crystals ranges between 0.04 and 1.74 mg,cm,3,K,1 with an average of ,0.2 mg,cm,3,K,1. It is shown that majority polymorph pairs exhibit significantly different thermal expansion behavior and their density,temperature lines can cross. This likely contributes to the less than perfect prediction of relative stability of polymorphs at ambient temperature using the density rule. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96: 1043,1052, 2007 [source] Phase Relations and Thermal Expansion Studies in the Ceria,Yttria SystemJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2004Sandeep V. Chavan The synthesis, characterization, and bulk and lattice thermal expansions of a series of compounds with general composition Ce1,xYxO2,x/2 (0.0 ,x, 1.0) are reported. The XRD pattern of each product was refined to learn the solid solubility limit and the homogeneity range. The solid solubility limit of YO1.5 in CeO2 lattice, under the conditions of slow cooling from 1400°C, is represented as Ce0.55Y0.45O1.775 (i.e., 45 mol% of YO1.5). The subsequent compositions were biphase. There was no solubility of CeO2 into the lattice of YO1.5. The bulk thermal expansion measurements from ambient to 1123 K, as investigated using a dilatometer, revealed that the ,l (293,1123 K) values, within the homogeneity range, decreased on increased Y3+ content. A similar trend was observed for average lattice thermal expansion coefficient, ,a (293,1473 K), as investigated using high-temperature XRD. No ordered phases were obtained in this system under the used conditions. These studies on Ce1,xYxO2,x/2 (0.0 ,x, 1.0) system can be used to simulate the phase relation and thermal expansion behavior of Pu1,xYxO2,x/2 (0.0 ,x, 1.0), because CeO2 is widely used as a surrogate material for PuO2. [source] Effect of Heat Treatment on the Pore Structure and Drying Shrinkage Behavior of Hydrated Cement PasteJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2002Jeffrey J. Thomas The effect of a short heat treatment on hydrated cement paste has been investigated by measuring the weight and length changes of specimens as they undergo various combinations of heating, drying, and resaturation. Heating a cement paste to 60°C coarsens the capillary pore system, decreases the volume of mesopores, and increases the degree of polymerization of the silicates. In addition, the saturated weight of the paste is permanently decreased by a heat treatment. This weight loss can be explained by conversion of bound hydroxyl groups into liquid water during polymerization of the C-S-H gel phase. These experiments help reconcile and interpret published results describing the properties of cement cured at various temperatures, the effects of a short heat treatment on cement paste, and the thermal expansion behavior of saturated and dry cement paste. [source] Effect of side-chain length of succinic anhydride on coefficient of thermal expansion behavior of epoxy resinsPOLYMER INTERNATIONAL, Issue 11 2006Fan-Long Jin Abstract The effect of an alkenyl side-chain of succinic anhydride (SA) on the thermal behavior and the coefficient of thermal expansion (CTE) of diglycidylether of bisphenol A (DGEBA) epoxy resins was studied. The number of carbons in the side-chain of SA was varied from 6 to 14 and N,N -Dimethylbenzylamine was used as an accelerator. As a result, the reactivity of SA with epoxide groups was decreased on increasing the length of the alkenyl side-chain of SA. The thermal stabilities of cured DGEBA/SA samples were approximately constant with varying alkenyl side-chain of SA. Also, the CTE of the systems was increased as the length of the alkenyl side-chain of SA increased. This could be attributed to the increased motion of the chain segments in the epoxy network structure induced by the longer alkenyl side-chain of SA. The effect of amount anhydride, thermoplastics, and fillers on the CTE of the epoxy resins was also discussed. Copyright © 2006 Society of Chemical Industry [source] Thermal properties of biaxially deformed in situ compositesPOLYMER ENGINEERING & SCIENCE, Issue 8 2004Youngwook P. Seo The thermal properties of biaxially blown poly(etherimide) (PEI) films containing a thermotropic liquid crystalline polymer (TLCP) were studied using differential scanning calorimetry, thermogravimetric analysis, wide-angle X-ray diffraction and dynamic mechanical thermal analysis. The effects of the compatibilizer and thermal annealing on the thermal properties of biaxially oriented TLCP films were investigated. Though the compatibilizer (poly(ester imide)) improved deformation of the TLCP phase (poly ester amide) and adhesion between the matrix and the TLCP phase, which improved mechanical properties, it did not significantly affect the thermal properties of the in situ composite films. The film degradation behavior corroborated the role of the compatibilizer. Since a relatively small amount of TLCP (10 wt%) was added to the matrix and the matrix PEI was amorphous, the effect of annealing on the TLCP structure was not obvious. By the same token, while the effect of the deformation in the circumferential direction (a change in the blow-up ratio) was manifest in mechanical property improvements, its effect on the thermal properties was not obvious. All films showed similar thermal expansion behaviors, regardless of the thermal history and of the compatibilizer addition. Thus, there is an optimum amount of the compatibilizer required to obtain optimal mechanical properties for in situ composite films without causing a deterioration of their thermal properties. Polym. Eng. Sci. 44:1419,1428, 2004. © 2004 Society of Plastics Engineers. [source] | ||||||||||