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881.
本文对合成TiO2一维纳米材料及其有序纳米阵列的阳极氧化法、模板法以及水热法进行了全面而系统的评述,着重介绍了它们的最新研究进展。阳极氧化法能制备牢固负载于基体上的TiO2纳米管阵列,这有助于构筑TiO2纳米结构及其在纳米器件上的应用;与多种制备技术如溶胶-凝胶工艺、电化学沉积以及原子层沉积等相结合,模板法可以合成出多种形貌的TiO2纳米材料如纳米管、纳米线和纳米棒,并可以通过改变所用模板的微观尺寸来调控TiO2一维纳米材料及其有序阵列的微结构参数;水热合成法可以制备出直径小且比表面积大的TiO2纳米管粉末。但从目前看来,该法还不能制备出牢固负载于基体上的有序纳米阵列。文章最后指出了TiO2一维纳米材料及其有序纳米阵列合成中存在的问题及今后发展方向。 相似文献
882.
883.
Jocelyn M. Bouzaid R. L. Frost W. N. Martens 《Journal of Thermal Analysis and Calorimetry》2007,89(2):511-519
The thermal stability and thermal decomposition pathways for synthesized composite iowaite/woodallite have been determined
using thermogravimetry analysis in conjunction with evolved gas mass spectrometry. Dehydration of the hydrotalcites occurred
over a range of 56–70°C. The first dehydroxylation step occurred at around 255°C and, with the substitution of more iron(III)
for chromium(III) this temperature increased to an upper limit of 312°C. This trend was observed throughout all decomposition
steps. The release of carbonate ions as carbon dioxide gas initialised at just above 300°C and was always accompanied by loss
of hydroxyl units as water molecules. The initial loss of the anion in this case the chloride ion was consistently observed
to occur at about 450°C with final traces evolved at 535 to 780°C depending of the Fe:Cr ratio and was detected as HCl (m/z=36). Thus for this to occur, hydroxyl units must have been retained in the structure at temperatures upwards of 750°C. Experimentally
it was found difficult to keep CO2 from reacting with the compounds and in this way the synthesized iowaite-woodallite series somewhat resembled the natural
minerals. 相似文献
884.
Ni-SDC固体氧化物燃料电池阳极的合成和性质 总被引:4,自引:0,他引:4
采用柠檬酸-硝酸盐溶胶-凝胶低温自蔓延燃烧法制备氧化镍(NiO)粉末和Ce0.8Sm0.2O1.9(SDC)粉末,并将NiO与SDC按不同质量比和不同制备工艺制备了固体氧化物燃料电池(SOFC)的阳极前身。再用自组装的还原装置将其在820℃经2.5h还原后,采用四端子法测量其电导率值。分析了阳极片电导率与阳极片微结构、Ni的质量百分数、混合研磨时间及烧结温度之间的关系。结果显示,阳极片的电导率强烈依赖于镍含量和制备工艺。 相似文献
885.
886.
J. Goworek W. Stefaniak Agnieszka Kierys Mariola Iwan 《Journal of Thermal Analysis and Calorimetry》2007,87(1):217-222
Mesoporous silica material of MCM-41 type was synthesized by co-condensation
of highly concentrated octyltriethoxysilane (OTEOS), octadecyltriethoxysilane
(ODTEOS) and tetraethoxysilane (TEOS). The obtained hybrid materials were
characterized using XRD, TG-DSC and low temperature adsorption/desorption
of nitrogen. It was shown that the applied method of synthesis allows to obtain
silica of MCM-41 type with a high degree of hydrocarbon saturation. 相似文献
887.
Nanosized copolymer latex of hydroxypropylmethylcellulose (HPMC) grafted with ethyl acrylate (EA) and dimethylaminoethyl methacrylate
(DMAEMA) has been prepared by acidifying submicron-sized latex particles synthesized by soap-free emulsion graft copolymerization
using potassium persulfate (KPS) as initiator. The effects on the diameter of the latex particles of different conditions,
for example concentration of DMAEMA, amount of HPMC, and ratio of HCl to DMAEMA for acidification, were investigated. It was
found that increasing the mole ratio of HCl to DMAEMA to 1.0 and increasing the DMAEMA content both resulted in a decrease
in particle diameter, whereas increasing the amount of HPMC resulted in larger particle sizes. Measurement by dynamic light
scattering (DLS) revealed the diameter of the latex particles was >200 nm before acidification and <100 nm after acidification.
Evidence of grafting was obtained by use of Fourier transform infrared (FTIR) spectroscopy. Transmission electron microscopy
(TEM) was used to characterize the morphology of the copolymer particles before and after acidification. 相似文献
888.
Two lipids with similar melting ranges but of different composition were analyzed using differential scanning calorimetry and X-ray diffraction. The lipids were processed via extrusion or were tempered at different temperatures; they were analyzed directly after extrusion and after storage at 40°C. Precirol ATO 5® showed high sensitivity to storage time and varied temperature exposure. Extrusion showed only marginal influences on the solid state. Melting peaks were narrower and shifted to higher temperatures in comparison to the untreated powder. Dynasan 114® was more robust, changes in the solid state could only be shown for samples treated above the melting range. Thus, Dynasan 114® is more appropriate for solid lipid extrusion of pharmaceutical products. 相似文献
889.
Fang Fang Zhong Yu Chen Zhi Nan Mei Guang Zhong Yang 《中国化学快报》2007,18(7):849-851
Two novel xanthones, 1,6-dihydroxy-4,5-dimethoxyxanthone (1) and 1,5,6-trihydroxy-7,8-di(3-methyl-2-butenyl)-60,60- dimethylpyrano(20,30:3,4)xanthone (2) were isolated from the bark of Garcinia xanthochymus by normal phase and reverse phase silica gel column chromatography. Their structures were elucidated by spectroscopic methods, especially 2D-NMR techniques. 相似文献
890.
Marta Fernandez-Tarrio Carmen Alvarez-Lorenzo A. Concheiro 《Journal of Thermal Analysis and Calorimetry》2007,87(1):171-178
Tetronic®comprises X-shaped copolymers formed by four poly(propylene oxide) (PPO) andpoly(ethylene oxide) (PEO) block chains bonded to an ethylene diamine centralgroup. Micellization behaviour of three representative Tetronics (T304, T904and T1307) was characterized to gain an insight into the interactions betweenthe copolymer unimers and the state of water in their solutions. The enthalpyof demicellization, recorded at 37°C in an isoperibol microcalorimeter,indicated that the process was in all cases exothermic and the enthalpy rankedin the order T1307≥T904>>T304. Micellization is entropy-driven owing tohydrophobic interactions between the PPO chains.DSC analysisshowed that the crystallization and melting peaks of the free water remainingin T304 and T904 solutions were progressively shifted toward lower temperaturesas the surfactant proportion increased, owing to a colligative effect. Boundwater corresponded to 3 water molecules per EO repeating unit. In the caseof T1307, which has longer PEO chains, a splitting of the melting peak wasobserved, one peak appearing around 0°C due to free water and anotherat –15°C due to interfacial water. As T1307 proportion raised, theenthalpy of the former decreased, whilst the enthalpy of the latter increased.In 40% T1307 solutions, interfacial water overcame the proportion of freewater; there being 1 interfacial and 3 bound water molecules per EO repeatingunit. Gaussian deconvolution of FTIR spectra also enabled to characterizethe evolution of free water as a function of Tetronic proportion. The dependenceof micellization and water interaction behaviour on Tetronics structure shouldbe taken into account to use these copolymers as drug solubilizers and micellarcarriers. 相似文献