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1.
Structural characterisation of such bio-objects as fibrinogen solution, yeast cells, wheat seeds and bone tissues has been done using two versions of cryoporometry based on the integral Gibbs-Thomson (IGT) equation for freezing point depression of pore liquids and the measurements by 1H NMR spectroscopy (180-200 < T < 273 K) and the thermally stimulated depolarisation current (TSDC) method (90 < T < 273 K) of structured water. The IGT equation was solved using a self-consisting regularization procedure including the maximum entropy principle applied to the distribution function of pore size (PSD). Both methods give clear pictures of changes in the structural characteristics caused, e.g., by hydration and swelling of wheat seeds and yeast cells, coagulation and interaction of fibrinogen with solid nanoparticles in the aqueous media, and the human bone tissue disease. 相似文献
2.
The TG and DTA curves and diffractograms of powdered CeO2 samples irradiated with a CO2 laser beam with powers of 0.41–1.39 kW/cm2 are presented. The laser treatment induced structural changes and probably generation of a metastable phase. X-ray diffraction coupled with thermal analysis was used to establish the structural modifications in the irradiated samples after heating. 相似文献
3.
Ligia E. Zamora G. A. Perez Alcazar J. M. Greneche S. Suriñach 《Hyperfine Interactions》2006,168(1-3):1057-1063
Fe60Mn10Al20Nb10, (Fe60Mn10Al30)95Nb5 and (Fe60Mn10Al30)90Nb10 ball milled powdered alloys were investigated using X-ray diffraction, Mössbauer spectrometry, thermomagnetic (TGM) and magnetization measurements. We studied the influence of Nb content and of different milling times on the structural and magnetic properties. Two main features can be concluded: (1) the FeAlMn induces a BCC phase whatever the Nb content is, and (2) as both increasing Nb content and milling time give rise to an highly disordered state in conjunction with a decrease of the ferromagnetic behavior. 相似文献
4.
包覆型纳米铜-银双金属粉研究 总被引:21,自引:0,他引:21
目前,导电胶或者电磁波屏蔽涂料用的导电性填料主要有三类,一是铜粉,二是银粉,三是铜-银双金属粉。铜粉具有来源广、价格低廉、导电性好等优点,但其抗氧化性能弱;银粉导电性与抗氧化性好,但其资源日益匮乏。大量的研究试图通过对铜粉进行表面改性来提高其性能。表面改性有两种方法,一是包膜处理,用SiO2溶胶处理铜粉,铜粉抗氧化性能提高,但其表面导电性能大大降低犤1犦;另一类方法是在铜粉表面覆盖一层导电性能与抗氧化性能均佳的银或金而制成双金属粉末犤2~5犦。制取高性能的铜-银双金属粉是该领域的研究重点。目前获得铜-银双金属粉的方… 相似文献
5.
Sm2O3掺杂CeO2纳米粉体的烧结动力学 总被引:2,自引:0,他引:2
对Sm2O3掺杂CeO2纳米粉体的烧结性能进行了研究, 得出等速烧结过程中试样的线收缩率、密度、气孔率随烧结温度的变化规律, 它们随烧结温度的变化均呈"S"型曲线关系, 利用非线性回归了等速烧结过程动力学方程. 结果表明, Sm2O3掺杂CeO2纳米粉体的烧结过程分为3个阶段, 当烧结温度低于1000 ℃时, 线收缩率与密度变化较小, 处于烧结的初期; 在1000~1400 ℃时, 随着烧结温度的升高, 线收缩率与体积密度急剧增大, 材料开始烧结并致密化; 当烧结温度高于1400 ℃时, 线收缩率与体积密度趋于一恒定值, 材料已经致密化. 由归一化速率方程可知, 在T=1225 ℃时, 材料的烧结致密化速率最大. 相似文献
6.
Michele Sacerdoti Maria Chiara Dalconi Barbara Cavicchi Stefano Colonna 《Journal of solid state chemistry》2004,177(6):1781-1788
Sol-gel routes were used to prepare Ta 10 at% and Nb 5 at% and 10 at% doped titania nanosized powders. When fired between 410°C and 850°C the doped titania powders are in the anatase phase; further heating up to 1050°C is required to obtain the rutile phase. The presence of dopant atoms delays the rate of transformation as compared with pure titania powders. Doping also affects the rate of grain growth and increases the conductance response to gas. To better understand the role played by dopant atoms in inhibiting both phase transformation to rutile and grain growth, X-ray Absorption Spectroscopy measurements were performed at the LIII-LI absorption edges of Ta and Nb K absorption edge. Analysis was restricted to the anatase phase because the transformation to rutile phase, obtained by firing at 1050°C, is accompanied by the formation of undesired Ta and Nb oxides (Ta2O5 and Nb2TiO7, respectively). Extended X-ray Absorption Fine Structure and X-ray Absorption Near-Edge Spectroscopy analysis results indicate that in nanostructured anatase both tantalum and niobium atoms substitute Ti cations with +5 valence state. 相似文献
7.
AES depth profiles on ceramic powders (untreated/hydrolyzed/oxidized/ (Al, Y)2O3 coated Si3N4, [BaO, SiO2] coated Al2O3) are feasible on thin, homogeneous layers or m sized agglomerations prepared on an Au foil. By means of the depth profiles one can qualitatively characterize the coating around the particles. Factor analysis of the depth profiles on the differently treated Si3N4 powders suggests the existence of an Si2N2O phase on the oxidized sample.Dedicated to Professor Günther Tölg on the occasion of his 60th birthday 相似文献
8.
Structural and optical properties of 1 at % Al-doped Zn1−xMgxO (x=0–8%) powders prepared by sol–gel method were systematically investigated by means of X-ray diffraction, scanning electron microscopy, ultraviolet–visible absorbance measurement, photoluminescence and Raman scattering spectra. All the powders retained the hexagonal wurtzite structure of ZnO. The band gap and near band emission energies determined from absorbance and photoluminescence spectra increased linearly with increasing Mg content, respectively, which implied that the Mg worked effectively on ZnO band gap engineering, irrespective of Al codoping. However, according to the PL and Raman scattering studies, for the sample of x=8%, the Al doping efficiency was decreased by higher Mg codoping. On the other hand, the effect of Mg codoping on photocatalytic degradation of methylene orange was explored experimentally. The substitution of Mg ions at Zn sites shifted the conduction band toward higher energies and then enhanced the photocatalytic activity, while the incorporation of interstitial Mg ions and decreased Al doping efficiency for higher Mg doping sample (x=8%) reduced the photocatalytic activity. 相似文献
9.
Commonly, sparks emit light according to the well-known black (gray) body radiation. Recently, we reported on color-changing sparks based on erbium powder, which switch their light emission between black body emission (surface combustion) and element-specific emission (vapor phase combustion). Herein, we investigated the spark formation from the adjacent rare-earth elements. The corresponding boiling points are significantly below (Yb, Sm, Tm) or above (Y, Lu) the boiling point of Er. While Yb and Sm evaporate too fast to form longer sparks, Y, Lu and Tm form color-changing sparks with varying length of the element-specific emission phase. The sparks were investigated by time-resolved emission spectroscopy, long-time exposures, and NIR/MIR imaging. The same basic pyrotechnic formulation containing one of these metal powders reveals a strongly differing burning behavior depending on the boiling point of the metal. The burning characteristics change from a green strobe (Yb) to intense colorful crackling (Tm) and finally a sparkling fountain with long-flying sparks (Lu, Y, Er). 相似文献
10.
Nano-crystalline MgNb2O6 was prepared using Mg(NO3)2·6H2O, Nb2O5, HF and citric acid as raw materials by auto-ignition route. The process involves the formation of a viscous gel by thermal dehydration of the citrate-nitrate solution at about 80 ℃. The auto-ignition (at about 200 ℃) of the gel resulted in a high reactivity powder containing intimate blending of MgNbF7 and NbF3. The crystalline phase of MgNb2O6 could be formed easily at 700 ℃, which is 400 ℃ lower than that of common solid-state reaction process. The nano-crystalline MgNb2O6 (~30 nm) powder with good dispersity could be obtained at 850 ℃. 相似文献