共查询到17条相似文献,搜索用时 437 毫秒
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为了研究羟基磷灰石HA纳米微粒对低温保护剂玻璃化性质的影响,利用DSC测量了含有不同粒径(20nm,40nm,60nm)和不同质量浓度(0.1%,0.2%,0.4%,0.8%)HA纳米微粒的PEG-600(50%,w/w)溶液的玻璃化温度。试验结果表明:加入40nm,0.8%HA的PEG-600溶液的玻璃化转变温度最大,熔融温度最小,稳定性也最高。与未加纳米微粒的PEG-600溶液相比,玻璃化转变温度提高了5℃,熔融温度降低了4.5℃,稳定性提高了近30%。加入60nm,0.8%HA的PEG-600溶液的玻璃化转变温度和反玻璃化温度都是最小,而熔融温度最大,稳定性也最低。与未加纳米微粒的PEG-600溶液相比,反玻璃化温度降低了4.5℃,稳定性降低了14%。 相似文献
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HA纳米微粒对PEG-600低温保护剂反玻璃化结晶的影响 总被引:1,自引:0,他引:1
为了研究羟基磷灰石HA纳米微粒对低温保护剂反玻璃化结晶的影响,本文利用DSC和低温显微镜研究了含有不同粒径(20nm、40nm、60nm)和不同质量浓度(0.1%、0.2%、0.4%、0.8%)HA纳米微粒的PEG-600(50%,w/w)溶液反玻璃化过程中的结晶现象.试验结果表明:与未添加纳米微粒的PEG-600溶液相比,加入40nm、0.4%纳米微粒的HA-PEG600溶液的反玻璃化温度升高了7℃;加入20nm、0.4%和40nm、0.8%纳米微粒的HA-PEG600溶液的冰晶生长速率分别降低了35%和提高了50%;纳米低温保护剂溶液的冰晶形貌从大圆形变成了小圆形、枝晶或小圆形中夹带枝晶. 相似文献
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低温纳米复合相变蓄冷材料热物性研究 总被引:4,自引:0,他引:4
低温相变蓄冷的关键是蓄冷材料的开发.本文针对啤酒工艺对冷源温度的要求,选择BaCl2共晶盐水溶液为相变蓄冷材料基液,在基液中添加粒径为20nm的TiO2纳米粒子,形成具有蓄冷功能的纳米复合材料.对其热物性如导热系数、相变潜热、相变温度、过冷度及粘度进行了实验测量和分析.结果表明,在TiO2纳米粒子的质量分数为1%的情况下,纳米复合蓄冷材料的导热系数比基液提高了11.28%,过冷度从3.97℃降为1.21℃,同时粘度增加了21.7%,相变潜热略有降低. 相似文献
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稀土纳米发光材料的燃烧法制备及光谱性质 总被引:7,自引:5,他引:2
用燃烧法制备了不同粒径的La2O3:Eu3 纳米微粒,研究了影响La2O3:Eu3 纳米微粒大小的实验条件,发现粒径大小随甘氨酸(Gly)与稀土离子比例的增大而减小.制备的纳米微粒由谢乐公式计算的粒径尺寸为12~28 nm.测量了样品的高分辨光谱.运用激光选择激发,研究了光谱在不同发光中心上的变化,表面态对于这些变化起着主要作用. 相似文献
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阳离子表面活性剂对液相银纳米微粒吸收光谱的影响 总被引:6,自引:3,他引:3
粒径为20 nm的黄色银纳米微粒在400 nm处有一吸收峰,当加入阳离子表面活性剂(CS)的浓度较低时,A400 nm减小,波长大于400 nm以上的吸收增大且体系的吸收峰发生红;当CS浓度较高时,波长大于400 nm以上的吸收减小,而在400 nm处的吸收增大,体系的吸收峰发生蓝移。研究表明这是由于CS与带负电荷的银纳米存在较强的疏水和静电作用而导致银纳米微粒形貌的改变所致。 相似文献
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We study the slow dynamics of hydration water upon cooling in two different biological aqueous solutions, one containing a molecule of lysozyme and another with trehalose molecules. In particular we test if the glassy behaviour of these solutions fulfils the predictions of the popular Mode Coupling Theory of glassy dynamics. In particular we test the Time Temperature Superposition Principle and the matching of the exponents of the theory. Our results confirm that this theory is able to describe the dynamical behaviour of supercooled water also in non ideal cases as the ones under investigation in the region of mild supercooling. 相似文献
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ABSTRACTThe hydration process of four different cement-based materials at different depths inside the sample was investigated using localised nuclear magnetic resonance relaxation measurements. All the samples are based on white Portland cement (CEM I 42.5 R), with a water-to-cement ratio of 0.5. One sample is a simple cement paste and the other three additionally contain 5% (by mass of cement) silica nanoparticles (50–200?nm size), silanised silica nanoparticles (with silane A 174) or silica fume (80% silica; 0.15?µm average size). The localised transverse relaxation measurements were performed using a single-sided NMR instrument. The relaxation rates were monitored for 48?h during the hydration process at different depths inside the sample. The results showed that the presence of nanoparticles influences not only the speed of hydration overall, but also the homogeneity of the materials. 相似文献
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Huihui Yang Rongjin HuangHao Zhang Laifeng Li Xiangdong XuLihe Qian 《Applied Surface Science》2011,257(9):4129-4132
A plasma polymerization method was used to modify the surfaces of ZnO nanoparticles, and the effects of plasma surface modification on photoluminescence (PL) property of ZnO nanoparticles were studied. High-resolution transmission electron microscopy images revealed that a thin film of vinyl acetate (VAC) polymer layer (∼4 nm) was uniformly deposited on the surfaces of the ZnO nanoparticles. The chemical structure of the polymer layer was identified by Fourier transform infrared (FTIR) experiments. The photoluminescence (PL) intensity of the ZnO nanoparticles was found to be significantly decreased by the deposited plasma films. For the particle of smaller size, the ultrathin film indicated better ultraviolet (UV) shielding ability. 相似文献
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B. I. Kidyarov 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(10):1414-1415
The peculiarities of the crystallization of about 100 solutions of different salts have been experimentally studied. A correlation is established between the maximum attainable supercooling temperature of the solution and the structure of the crystals formed. It is found that the highest supercoolings are characteristic of solutions of acentric crystals. 相似文献
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Kazunori Kadota Atsuko Shimosaka Yoshiyuki Shirakawa Jusuke Hidaka 《Journal of nanoparticle research》2007,9(3):377-387
Ionic motions at solid-liquid interface in supersaturated NaCl solutions have been investigated by molecular dynamics (MD)
simulation for understanding crystal growth processes. The density profile in the vicinity of the interfaces between NaCl(100)
and the supersaturated NaCl solution was calculated. Diffusion coefficients of water molecules in the solution were estimated
as a function of distance from the crystal interface. It turned out that the structure and dynamics of the solution in the
interfaces was different from those of bulk solution owing to electric fields depending on the surface charge. Therefore,
the electric field was applied to the supersaturated solutions and dehydration phenomenon occurring in the process of the
crystal growth was discussed. As the electric field increased, it was observed that the Na+ keeping strongly hydration structure broke out by the electric force. In supersaturated concentration, the solution structure
is significantly different from that of dilution and has a complicated structure with hydration ions and clusters of NaCl.
If the electric fields were applied to the solutions, the breakout of hydration structure was not affected with increasing
the supersaturated ratio. This reason is that the cluster structures are destroyed by the electric force. The situation depends
on the electric field or crystal surface structure. 相似文献
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P. Rodríguez-Fragoso S.A. Tomás J.G. Mendoza-Alvarez O. Zelaya Angel 《Journal of luminescence》2010,130(7):1128-1133
CdS nanoparticles were synthesized by precipitation in aqueous solution using starch as the capping molecule, and the effect of the pH of the solution on the optical absorption, photoluminescence, and size of the nanoparticles was studied. Absorption spectra, obtained by photoacoustic spectroscopy, indicated that the band gap energy of the crystalline nanoparticles decreased from 2.68 eV down to 2.48 eV by increasing the pH of the solution from 9 up to 14. The X-ray diffraction analysis revealed that the CdS nanoparticles were of zinc blende structure, and that the particle size increased from 1.35 nm up to 2.45 nm with increasing pH. In addition, temperature-dependent photoluminescence (PL) measurements of the capped material showed a blue-shift of the emission peak for temperatures higher than 150 K, indicating the influence of starch on the formation of defect levels on the surface of the CdS nanoparticles. 相似文献