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91.
The melting process of constrained nylon 6 fibers has been studied to estimate the true melting point of its original crystals.
The melting peak became simpler in shape and shifted to higher temperature with increasing fiber-axis restricting force. When
heating rate, β, was increased, the temperature where the melting curve initially departs from its baseline, Tsm, decreased
steeply in the range of 45 to 60°C min-1, and increased linearly with increasing β above 60°C min-1. By linear extrapolation of Tsm to 0°C min-1, the temperature of ca 190°C was obtained for the melting temperature of the original nylon 6 crystals. This seems to correspond
to the zero-entropy-production melting of the most imperfect crystallites of the nylon 6 fabric.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
92.
Jakubus P. Adamski A. Kurzawa M. Sojka Z. 《Journal of Thermal Analysis and Calorimetry》2003,72(1):299-310
The structure and surface properties of ZrO2 strongly depend on its preparation. In the present work the impact of prolonged aging at basic conditions (pH = 9, T = 100°C, t = 48 h), on the phase composition and textural properties, obtained by calcination of the precipitate, was investigated using
several techniques conjointly (DTA/TG, DSC, XRD, porosimetry). The thermal effects accompanying the ZrO2·xH2O gel formation, the coalescence of the particles and crystallization were evaluated and discussed in terms of the structural
differences between the aged and non-aged samples.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
93.
A. Marotta P. Pernice A. Aronne M. Catauro 《Journal of Thermal Analysis and Calorimetry》1993,40(1):181-188
The non-isothermal devitrification of lithium germanate glasses, examined by DTA and XRD, is reported and discussed. The glass compositions are expressed by the general formula:xLi2O(1?x)GeO2 withx=0.050, 0.125, 0.167, 0.200 and 0.250. All the glasses studied, unlike GeO2 glass, exhibit internal crystal nucleation without the addition of any nucleating agent. The devitrification processes occur in one or more steps. Phases which crystallized at each step are identified and crystallization mechanisms proposed. These crystallization mechanisms are related to structures of the crystallizing phases. Activation energy values as well as those for glass transition temperatures, do not vary linearly with increase in Li2O content but pass through a maximum atx=0.200. 相似文献
94.
早在本世纪初物理化学家们就已观察到,某些物质从其熔融态或溶液中结晶出来时,在某些条件下可形成周期性的宏观结晶条纹[1,2],这就是周期结晶现象,由于这种现象和晶体生长、材料物性以及成矿过程等重要问题紧密相关,很早就引起了人们的重视.近年来有关非平衡非线性系统中自发产生各种时空有序现象(自组织现象)的各种理论(如耗散结构理论)[3]的兴起,重新引起了人们对这类现象的兴趣.八十年代,Iwamoto等先后报道了甲基苄基氨基甲酸酯(MethylMesitylcarbamate)从氯仿溶液[4]和抗坏血酸(AscorbicAcid)从甲醇溶液[5]… 相似文献
95.
Yubin Xue Shun‐Chang Liu Xinsheng Liu Yusi Yang Yimin Zhang Ding‐Jiang Xue Jin‐Song Hu 《中国化学》2020,38(4):356-360
Colloidal quantum dots (CQDs) are attractive absorber materials for high‐efficiency photovoltaics because of their facile solution processing, bandgap tunability due to quantum confinement effect, and multi‐exciton generation. To date, all published performance records for PbS CQDs solar cells have been based on the conventional hot‐injection synthesis method. This method usually requires relatively strict conditions such as high temperature and the utility of expensive source material (pyrophoric bis(trimethylsilyl) sulfide (TMS‐S)), limiting the potential for large‐scale and low‐cost synthesis of PbS CQDs. Here we report a facile room‐temperature synthetic method to produce high‐quality PbS CQDs through inexpensive ionic source materials including Pb(NO3)2 and Na2S in the presence of triethanolamine (TEA) as the stabilizing ligand. The PbS CQDs were successfully prepared with an average particle size of about 5 nm. Solar cells based on the as‐synthesized PbS CQDs show a preliminary power conversion efficiency of 1.82%. This room‐temperature and low‐cost synthesis of PbS CQDs will further benefit the development of solution‐processed CQD solar cells. 相似文献
96.
97.
Păcurariu C. Lazău R. I. Lazău I. Stoleriu Ş. 《Journal of Thermal Analysis and Calorimetry》2007,88(3):641-645
A kinetic study of the crystallization processes was performed for some decorative ceramic glazes in the PbO-SiO2-Na2O-K2O-CaO(BaO)-Al2O3-B2O3 system with addition of 10% TiO2 and ZnO. The crystallization kinetics has been studied in non-isothermal conditions using DTA technique. The apparent activation
energies of the crystallization processes were calculated using the Kissinger method. The main crystalline phase, which provides
the decorative effect, is rutile. This has been identified by X-ray diffraction and it is clearly visible in the optical microscopy
images taken in transmitted light, as needle-like or even prismatic crystals arranged in radial-fibrous aggregates. 相似文献
98.
L. P. Kozeeva M. Yu. Kameneva N. V. Podberezskaya I. G. Vasilieva N. V. Kuratieva D. Yu. Naumov V. A. Nadolinnyi V. E. Fedorov 《Journal of Structural Chemistry》2004,45(2):253-261
Cooling a melt of a Bi–Sr–Ca–Cu–O system (Bi:Sr:Ca:Cu = 4:3:3:4 or 2:2:2:4) from 1000°C-1050°C yielded crystals of a new red-colored nonsuperconducting phase, accompanying the superconducting 2212 and 2201 phases. Based on the EPR spectra, it was concluded that copper is univalent in this compound. The new phase has a composition Bi2.2Sr1.6Ca1.3Cu2Ox. The X-ray diffraction pattern has been indexed, and the unit cell parameters of the phase have been determined: space group P2/m, a = 12.93, b = 4.55, c = 10.94 ; = 102.72°. 相似文献
99.
100.
The morphology and the crystallization behavior of blends of linear low density polyethylene (LLDPE) with an experimental sample of a semiflexible liquid crystalline polymer (SBH 112 by Eniricerche, Italy) have been studied by differential scanning calorimetry (DSC), polarized optical microscopy (POM) and scanning electron microscopy (SEM). The blends possess a two-phase morphology, due to immiscibility of the two components. SEM observations show that dispersion of the minor SBH phase is favored at low (相似文献