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1.
采用溶胶-凝胶水热法合成了单相黄铁矿结构的FeS2粉晶.用x射线衍射、傅氏变换红外光谱等分析手段对FeS2粉晶进行了表征,以简化的数学模型及相变理论讨论了晶体生长过程.结果表明:FeS2晶粒的生长过程属于相变与扩散的混合机制,符合经时间指数修正的二次方动力学方程,是一个生长速率随时间变化的过程;水热晶化温度高于453 K、反应时间超过18 h且有适量的硫参与反应时,可得到单相的黄铁矿型的FeS2.该过程可分为三个阶段:前期为白铁矿和黄铁矿的成核孕育阶段,中期为FeS2晶核以黄铁矿吞并白铁矿的相变方式逐渐长大的阶段,后期为小晶粒融合而大晶粒继续长大的扩散生长过程. 相似文献
2.
采用溶胶-凝胶方法,在不同的实验条件下获得平均粒径从15到25nm左右的纳米TiO22颗粒.利用这些颗粒制备出的纳米多孔薄膜,应用于染料敏化纳米薄膜太阳电池. 通过x射线 衍射仪分析,得到TiO22颗粒的晶相以及晶粒度大小,用透射电子显微镜观察 了纳米TiO22颗粒的形貌和尺寸.应用于太阳电池的纳米TiO22多 孔膜,经基于布朗诺尔-埃米特-泰 勒(BET)的多层吸附理论的比表面积测试和孔径分布测试,获得了多孔膜的微
关键词:
溶胶-凝胶法
2')" href="#">纳米TiO22
染料敏化
太阳电池 相似文献
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4.
采用溶胶-凝胶法制备了单轴M型锶铁氧体SrFe12-x12-xCrxxO 1919(x=0—1)超细晶粒.实验结果表明, 随掺杂量x的增大,质量饱和磁化强 度σss在x≤04范围内增大,在x=02附近达到极大值.矫顽力Hcc在x<05的范围 内单调降低,这对于用作高密度磁记录材料非常有利.当x≤04时,样品是单相结构, 在 x=06以后出现非磁性相α-Fe22O3<
关键词:
锶铁氧体
3+')" href="#">Cr3+3+
结构
磁性 相似文献
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6.
讨论了采用溶胶-凝胶法经由先驱物钛酸四异丙脂水解而制备的纳米TiO2粉末的 结构相变 ,并讨论了该纳米粉末的生长动力学机理.结果表明,水解pH值为0.9,当高压釜热处理温度 <503K时,粉末晶粒度增长较为缓慢,而当热处理温度>503K时,粉末粒度明显长大.应用 相变理论计算出了纳米TiO2颗粒的两阶段的生长激活能,分别是18.5kJ/mol和5 9.7kJ/mol .XRD物相分析表明,高压釜热处理温度达到503K时,样品就开始发生锐钛矿到金红石相的结 构相变,到543K就基本实现了这一结构相变,使得这一相变温度比其他文献中报道的又降低 了许多.
关键词:
2')" href="#">纳米TiO2
溶胶_凝胶法
结构相变
晶粒生长动力学 相似文献
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8.
以Ti4040Zr4040Ni2020合金为研究对象,用铜 模吸铸法制备出直径为3mm的致密单相准晶棒,通过维氏显微硬度测定和单向压缩实验方 法研究了该合金的室温力学性能 .结果表明:Ti4040Zr4040Ni2020准晶具有良好 的弹性变形能力,室温弹性应 变可达125%.同时,它具有相对高的室温硬度(约55GPa),是普通Ti合金的15倍.T i4040
关键词:
准晶
Ti-Zr-Ni合金
解理断裂 相似文献
9.
采用溶胶-凝胶法在石英玻璃衬底上用旋涂法制备了未掺杂、掺杂钇和掺杂镧的TiO2薄膜样品,对样品在700—1100 ℃范围内进行退火处理,并对样品的拉曼光谱进行了分析.分析表明:随着退火温度的升高,未掺杂TiO2薄膜发生了从锐钛矿相经混相最终向金红石相的转换,掺杂钇和掺杂镧对TiO2薄膜的晶相转换起阻碍作用,掺杂镧的阻碍作用更强;稀土掺杂能使TiO2薄膜晶粒细化,并使晶粒内部应力增大从而阻碍晶格振动,掺杂镧比掺杂钇的效果
关键词:
2薄膜')" href="#">TiO2薄膜
稀土掺杂
拉曼光谱
溶胶-凝胶 相似文献
10.
通过熔体快淬方法获得Pr(Fe1-xCox)2合金条带,经过X射线衍射、差示扫描量热计和磁性测量对其结构、磁性和热稳定性进行了研究.发现当Co的含量x大于0.2时才可能获得Pr(Fe,Co)2立方Laves相化合物.对Pr(Fe0.6Co0.4)2合金,在快淬速度为30m/s时,条带由Pr2(Fe,Co)17,Pr(Fe,Co)2和富稀土相组成;在速度为40m/s时,获得了几乎单相的Pr(Fe0.6Co0.4)2化合物,其居里温度为305℃;在速度为45m/s时,除了Pr(Fe0.6Co0.4)2化合物外,还存在少量的非晶相.Pr(Fe0.6Co0.4)2化合物在770℃以上发生分解.用40m/s快淬纳米晶粉胶粘磁体有大的磁致伸缩系数(λ∥-λ⊥=140×10-6)和高的硬磁性能(iHc=398kA/m).
关键词: 相似文献
11.
A knowledge of the concentration of pyrite and marcasite in coals can provide important insight into the genesis of coal deposits. Determinations of the relative amounts of pyrite and marcasite by traditional methods of coal analysis are, however, beset with many difficulties. Using57Fe Mössbauer spectroscopy and a mild chemical treatment with hydrofluoric acid, a technique has been devised for the quantitative determination of the relative concentrations of pyrite and marcasite in samples of whole coals or their low-temperature ashes. The sample preparation procedure is comparable to less accurate methods. Good qualitative agreement has been obtained between ore microscopic and Mössbauer spectroscopic techniques for a series of extensively investigated whole coal samples. 相似文献
12.
拉曼光谱研究天然FeS_2晶须结构及其相变规律 总被引:5,自引:0,他引:5
利用显微激光拉曼技术研究了山西耿庄天然纳-微米FeS2晶须的结构.发现FeS2晶须中有白铁矿和黄铁矿两种结构类型.较粗的藕节状、粗柱状、串珠状等不规则形貌为白铁矿相,直线状、平直、表面光滑的品须为黄铁矿相.耿庄FeS2晶须结晶生长早期以白铁矿相为主,中期是白铁矿和黄铁矿型结构共存,晚期以黄铁矿相为主.晶须生长过程有早期白铁矿结晶向晚期黄铁矿结晶转变的趋势.而且有黄铁矿包覆白铁矿的生长现象.FeS2晶须结构相变规律与形貌、形成时间和成分特点具有关联性. 相似文献
13.
Nanocrystalline FeS2 cathode material of lithium cell was synthesized from cheap materials of FeSO4, Na2S2O3, and sulfur by a hydrothermal process. The scanning electron microscopy analysis showed the obtained material was nano-sized,
about 500 nm. The X-ray powder diffraction analysis showed that the synthetic FeS2 material had two phases of the crystalline structure, pyrite and marcasite. The phase of marcasite seems to have no negative
effect on the electrochemical performance of the material. The synthetic FeS2 showed a significant improvement of electrochemical performance for Li/FeS2 cells. 相似文献
14.
For a natural crystal of marcasite, an energy gap of 0.34 eV and an acceptor level at 0.052 eV are determined from temperature-dependent (53–370 K) electrical resistivity measurements. Magnetic susceptibilities and dielectric constants of marcasite and pyrite are compared in view of the large difference in their energy gaps. 相似文献
15.
The crystal structure, phonon stability, elasticity and electronic properties of four noble metal nitrides (PtN2, IrN2, OsN2 and AuN2) with three structural types (pyrite, marcasite and CoSb2 structure) were studied by first principles calculations. In agreement with experiments and previous theoretical predictions, it is found that the most stable structure for OsN2 is marcasite, for PtN2 is pyrite, and for IrN2 is the CoSb2 structure. It is found that these three compounds are thermodynamically metastable with respect to solid N2 and the metal at zero pressure. The structures are mechanically and dynamically stable. The lowest energy structure of AuN2 is the CoSb2 structure. The formation energy of AuN2 is found to be very high compared to the other three nitrides studied here. This underlies the experimental difficulty in the synthesis of this compound. OsN2 is found to be metallic, while IrN2 and PtN2 are both semiconductors. 相似文献
16.
The magnetic susceptibility, χ, of a natural single crystal of marcasite, FeS2, has been measured between 300K down to 4K. At room temperature χ=0.3×10?5 emu/g and it is temperature independent down to 10K. Below 10K it increases up to 1.3×10?5 emu/g. It is concluded that iron in marcasite is in the Fe2+ low spin state, and that the 6d electrons occupy the t2g ground state. Consequently iron in marcasite (FeS2) is not magnetic in agreement with our Mössbauer spectra recorded at 4.2K in an external magnetic field up to 39.9 kOe. The small value of χ is explained in terms of contributions from ppm impurities. i.e., diamagnetism and Van Vleck paramagnetism. 相似文献
17.
《Journal of Electron Spectroscopy and Related Phenomena》2002,122(1):91-96
S L2,3 and L1 XANES of the polymorph minerals pyrite (FeS2) and marcasite (two different cleavage planes) were measured in total electron yield mode using synchrotron radiation. Small but distinct differences were found in the fine structure of these spectra. Calculations with the FEFF-8 code were performed to reproduce the experimental data. Ex situ UV–ozone oxidation of the samples reveals different reactivity. Sulphate was identified on the pyrite and one marcasite cleavage planes whereas the second plane normal to the first one oxidises with changing quanta of sulphate and sulphite. 相似文献
18.
The electrochemical behavior of a pyrite electrode in a sulfuric acid solution with different concentrations of ferric iron
(Fe3+) was investigated using electrochemical techniques including measurements of open circuit potential, cyclic voltammetry,
Tafel polarization curves and electrochemical impedance spectroscopy (EIS). The results show that the pyrite oxidation process
takes place via a two-step reaction at the interface of the pyrite electrode and the electrolyte, and that a passivation film
composed of elemental sulfur, polysulfides, and metal-deficient sulfide is formed during the process of the first-step reaction.
Ferric iron plays an important role in the dissolution of pyrite by enhancing the direct oxidation. The Tafel polarization
curves indicate that the polarization current of the pyrite electrode increases with an increase in Fe3+ concentration. It has also been shown that the higher concentration of Fe3+, the more easily the pyrite can be transformed into the passivation region. Moreover, the EIS response is found to be sensitive
to changes in Fe3+ concentration. 相似文献
19.
H. Fjellvåg A. Kjekshus T. Chattopadhyay H.D. Hochheimer W. Hönle H.G. Von Schnering 《Physics letters. A》1985,112(8):411-413
Energy dispersive high-pressure powder X-ray experiments have been performed for MnTe2 up to a pressure of 20 GPa. MnTe2 undergoes a discontinuous transformation from the cubic pyrite type structure to the orthorhombic marcasite type structure at 7.0±0.5 GPa upon increasing pressure. The transformation is accompanied by a large reduction in the specific volume (ΔV/V=0.18) which probably reflects different magnetic properties of the two modifications of MnTe2. 相似文献
20.
T.M. Clark B.J. Evans C. Wynter H. Pollak S. Taole D. Radcliffe 《Hyperfine Interactions》1998,112(1-4):227-230
A quantitative determination of the relative marcasite/pyrite contents in virgin coals is possible by means of 57Fe Mössbauer spectroscopy. Complications arise, however, when iron-containing silicates, carbonates, or other salts are present. The application of a mild chemical treatment involving hydrofluoric acid has been employed to remove these Fe-containing phases while leaving the iron-disulfide phases unaffected. Several South African coal samples with non-iron disulfide, Fe-containing phases ranging from 18 to 30 weight percent have been subjected to a hydrofluoric acid leaching at room temperature. The loss of mineral matter with HF leaching correlates well with the mineral matter residue following low temperature ashing. The 57Fe Mössbauer spectra of the resulting coal samples, collected at 297K, indicate that only FeS2 phases are present. The Mössbauer parameters for these samples (0.619 ≤EQ≤0.622 mm s?1; 0.306≤δ≤0.309 mm s?1) indicate the absence of appreciable quantities of marcasite in the coals. These Mössbauer parameters differ slightly, but systematically, from those of pyrite for which a quadrupole splitting of 0.6110 ± 0.0020 mm s?1 has been established. On the basis of previous studies, these increased EQ values suggest the presence of As substitution in the pyrite phases. 57Fe Mössbauer spectra of virgin coals exhibit phase assemblages comparable to those observed by x-ray diffraction (XRD), e.g. pyrite and (Ca,Fe)CO3, even though the presence of pyrite is less definite in the XRD data. 相似文献