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1.
The data on the thermal decomposition of FeSO4?H2O upon various regimes of heating and gaseous environment prove the formation of intermediate products of the types Fe2O(SO4)2 and FeOHSO4, their stability and amount being determined mainly by temperature and oxygen-reduction potential. This communication aims at presenting results on the synthesis and characterization of Fe2O(SO4)2. The synthesis was carried out using a laboratory thermal equipment operating under isothermal conditions in the temperature range 713–813 K in a gaseous environment either poor in oxygen or containing 100% oxygen. The experimental conditions under which Fe2O(SO4)2 is stable are established. The effect of three basic parameters on the synthesis of Fe2O(SO4)2 is clarified: the oxygen partial pressure, the ratio PH2O/PO2 and the temperature and the mode of heating. Mössbauer spectroscopy and X-ray diffraction data for Fe2O(SO4)2 are presented. 相似文献
2.
A series of Al 2O 3-SnO 2 catalysts with the molar ratio of Al 2O 3 to SnO 2 between 1:0 and 0:1 have been characterized by thermal analysis in reductive conditions, TPR and XRD methods. In the reductive
conditions in temperatures up to about 1000 K, no reduction of the tin component to the metallic form takes place in the binary
gel Al 2O 3-SnO 2. In the temperatures characteristic of the reforming process, only a reduction to SnO occurs in the above binary support.
Thermal analysis of the gels in the reductive conditions and TPR results indicate stabilisation of the tin oxide species even
in the systems of the molar ratio of Al 2O 3 to SnO 2 of 1:1. The metallic tin appears in the binary gel only after its reduction in the hydrogen atmosphere at temperatures close
to ∼1100 K. 相似文献
3.
Fe 2O(SO 4) 2 is a secondary product of the decomposition of FeSO 4⋅H 2O. Part I of this study presents results on the synthesis of Fe 2O(SO 4) 2 in gaseous environment containing either low or high concentration of oxygen. In this paper the existence of differences
between the structures of Fe 2O(SO 4) 2 and Fe 2(SO 4) 3 is proved on the basis of a detailed thermal study of Fe 2O(SO 4) 2 upon dynamic heating (differential thermal analysis) and upon isothermal heating (thermal-analytic balance) in various gaseous
environments as well as by presenting kinetic data on the processes of decomposition of both compounds.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
Thermal decomposition of Bi(SCN) 3, Cd(SCN) 2, Pb(SCN) 2 and Cu(SCN) 2 has been studied. The thermal analysis curves and the diffraction patterns of the solid intermediate and final products of the pyrolysis are presented. The gaseous products of the decomposition (SO 2 and CO 2) were detected and quantitatively determined. Thermal, X-ray and chemical analyses have been used to establish the nature of the reactions occurring at each stage in the decomposition.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
5.
Alumina gels made from the metal alkoxide is known to have high catalyst activity for the selective reduction of NO
x
by hydrocarbons. It is also reported that the fine structure of the gels effects the activity. In this study, the effect of the preparation method on the fine structure and catalyst activity of the gels was investigated. Monolithic gels were obtained by hydrolysis of Al(sec-C 4H 9O) 3. The wet gels were dried at 90°C (xerogels), supercritically dried (aerogels), or dried after immersion in an ethanol solution of methyltrimethoxysilane (modified xerogels). The changes in the microstructure during heating were discussed using the results of TG-DTA, ETA and N 2 adsorption. The ETA curves show the 220Rn-release rate, E, of the samples, previously labelled with 228Th and 224Ra, during heating. The decrease in E of the xerogel at temperatures higher than 400°C indicates a gradual decrease in the surface area and porosity. A remarkable decrease in the BET surface area of the xerogel was found after heat-treating at 500°C. On the other hand, constant E of the aerogels and modified xerogels above 450°C suggests high thermal stability. The pore radii, estimated by BJH method, and the catalyst activities at 500°C of the aerogels and the modified xerogels were higher than those of the xerogels. The temperature range in which the alumina gels are applicable as catalysts was determined. 相似文献
6.
A new compound, Na 2Zn 5(PO 4) 4, was identified in the system ZnONa 2OP 2O 5 and high-quality crystal was obtained by the melt method. The crystal structure of this compound was solved by direct method from single crystal X-ray diffraction data. The structure was then refined anisotropically using a full-matrix least square refinement on F2 and the refinement converged to R1=0.0233 and w R2=0.0544. This compound crystallizes in the orthorhombic system with space group Pbcn, lattice parameters a=10.381(2) Å, b=8.507(1) Å, c=16.568(3) Å and Z=4. The structure is made up of 3D [Zn 5P 4O 16] n2n− covalent framework consisting of [Zn 4P 4O 16] n4n− layers. The powder diffraction pattern of Na 9Zn 21(PO 4) 17 is explained by simulating a theoretical pattern with NaZnPO 4 and Na 2Zn 5(PO 4) 4 in the molar ratio of 1:4 and then by Rietveld refinement of experimental pattern. Na 2Zn 5(PO 4) 4 melts congruently at 855 °C and its conductivity is 5.63×10 −9 S/cm. 相似文献
7.
The termal stabilities of several families of high- T c superconductors (HTSC), as well as the dependence of phase transitions on temperature and stoichiometry, have been studied by X-ray diffraction, DTA, TG and DSC. Experimental results are discussed in the context of decomposition models. 相似文献
8.
The high-pressure behavior of Y 2(WO 4) 3 has been investigated at room temperature by in situ X-ray diffraction and Raman scattering measurements. Both the studies show that beyond ∼3 GPa, this compound smoothly transforms from the ambient orthorhombic phase to a disordered phase. The structural modifications are found to be reversible up to ∼4 GPa but become irreversible at higher pressures. Low pressures of transformation imply that these changes are intrinsic and not due to non-hydrostatic stresses. In addition, the correlation between the stability range of orthorhombic phase and counter cation size supports that this compound has a large field of negative thermal expansion in this family of compounds. 相似文献
9.
Nanocrystalline titania particles doped with ruthenium oxide have been prepared by the homogenous hydrolysis of TiOSO 4 in aqueous solutions in the presence of urea. The synthesized particles were characterized by X-ray diffraction (XRD), Scanning
Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HRTEM), Selected Area Electron Diffraction (SAED)
and Nitrogen adsorption-desorption was used for surface area (BET) and porosity determination (BJH). The photocatalytic activity
of the Ru-doped titania samples were determined by photocatalytic decomposition of Orange II dye in an aqueous slurry during
irradiation at 365 nm and 400 nm wavelengths.
相似文献
10.
在旋涂有球状纳米TiO2薄膜的导电玻璃(ITO)基底上采用循环伏安法(CV)电沉积RuO2作为电催化还原CO2的阴极.采用场发射扫描电子显微镜(FE-SEM)表征了RuO2/TiO2纳米薄膜的形貌,并应用近稳态电位扫描法和计时电流法(i~t)研究了薄膜的电催化CO2性能.结果表明所构建的RuO2/TiO2薄膜中纳米粒子大小均匀、排列致密,且较传统热分解法所得催化剂有更好的电催化性能. 相似文献
11.
The voltammetry of self-assembled monolayers (SAMs) of 7-ferrocenycarbonyloxy-1-heptanethiol (FcCO 2(CH 2) 7SH) has been studied as a function of temperature. Such SAMs are, when oxidised, susceptible to loss of ferrocene via nucleophilic attack, but at temperatures only just above room temperature, there is an accelerated loss of ferrocene from the chain termini, an increase in the capacitance of the layer in its reduced state and a positive shift in the E1/2 value is observed. A comparison between these data and the effects of multiple scans recorded at room temperature suggests that there is a re-orientation, induced at slightly elevated temperatures, which is associated with the ferrocene ester linkage at the chain terminus and which apparently renders ferrocene more susceptible to nucleophilic attack. With the increasing of temperature, the loss of ferrocene (terminal) is accelerated, due to the capacitances and permeability of the SAM layers. The positive shift of the E1/2 value is harder to interpret but may result because the ferrocene is in more intimate contact with the layer and is placed in a more hydrophobic, less polar environment. Other possible influences on the shift of E1/2 are discussed. This work confirms that electroactive terminal groups can provide information on the microenvironment at the SAM/electrolyte interface through variations in current and potential. 相似文献
12.
采用一种新的燃烧合成陶瓷粉末的方法--甘氨酸-硝酸盐法合成中温SOFC所有元件的初始粉体,电池的电解质材料是(CeO 2)x(SmO 1.5) 1-x(x=0.9,0.85,0.8),阳极材料是掺(CeO2)0.8(SmO1.5)0.2(SDC)的NiO,阴极材料是SDC与La0.6Sr0.4Fe0.8Co0.2O3的复合材料.其中以(CeO2)0.9(SmO1.5)0.1为电解质的单电池性能最好,在750℃时短路电流密度为0.5A/cm2,最大功率密度达0.104W/cm2.通过SEM结果分析,掺杂摩尔分数20%SmO1.5的电解质晶界非常明显,而掺杂10%的电解质晶界有很强的融合消失的趋势. 相似文献
13.
通过原位反应法,利用富镍层状金属氧化物LiNi 0.8Co 0.1Mn 0.1O 2(LNCM811)正极材料表面残余的氢氧化锂和碳酸锂,与C 8H 20O 4Ti和(NH 4)H 2PO 4反应,在LNCM811表面原位生成快离子导体LiTi 2(PO 4) 3(LTP)包覆层。这种原位反应的包覆方法有利于移除LNCM811表面有害的残留物氢氧化锂和碳酸锂。而且,获得的LTP均匀包覆层不仅可以有效地抑制LNCM811表面和电解液的直接接触及其副反应,还可以确保充放电循环过程中LNCM811正极材料的快速Li +传导。因此,在LTP包覆层的多重作用下,LTP包覆的LNCM811正极材料具有优异的循环稳定性和倍率性能:在0.2C时,首次放电比容量高达200.6 mAh·g -1,200圈后的可逆容量依然有155.7 mAh·g -1;在2C和5C的高电流密度下,200圈后的可逆容量仍然有126.4和111.9 mAh·g -1。 相似文献
14.
The dehydration of Ca(H 2PO 4) 2·H 2O was examined with simultaneous DTA and TG. This dehydration permitted clearly the apparation of the following phases: Ca(H 2PO 4) 2·0.5H 2O, Ca(H 2PO 4) 2, Ca 3(HP 2O 7) 2, Ca 2HP 3O 10 et Ca(PO 3) 2. The reaction of Ca(H 2PO 4) 2·H 2O and CaSO 4 was also examined with the same technics. It was found that the decomposition of CaSO 4 takes place for relatively low temperature (between 600°C and 800°C). 相似文献
15.
用液相反应-前驱物烧结法制备了Cr 2(WO 4) 3和Cr 2(MoO 4) 3粉体。298~1 073 K的原位粉末X射线衍射数据表明Cr 2(WO 4) 3和Cr 2(MoO 4) 3的晶胞体积随温度的升高而增大, 本征线热膨胀系数分别为(1.274±0.003)×10 -6 K -1和(1.612±0.003)×10 -6 K -1。用热膨胀仪研究了Cr 2(WO 4) 3和Cr 2(MoO 4) 3在静态空气中298~1 073 K范围内热膨胀行为,即开始表现为正热膨胀,随后在相转变点达到最大值,最后表现为负热膨胀,其负热膨胀系数分别为(-7.033±0.014)×10 -6 K -1和(-9.282±0.019)×10 -6 K -1。 相似文献
16.
Randomly oriented ferroelectric BaTiO 3 and (Ba 0.6Sr 0.4) TiO 3 thin films on platinum coated Si (100) were prepared by a sol-gel method. The precursor solutions were derived from barium hydroxide or a mixture of barium/strontium hydroxides dissolved in acetic acid and titanium butoxide. Polarization versus applied voltage hysteresis studies indicated a remanent polarization of 3 µC/cm 2 and a coercive field of 43.4 kV/cm for BaTiO 3 films annealed at 800°C for 1 h. Corresponding parameters for (Ba 0.6Sr 0.4)TiO 3 films annealed at 800°C were found to be 7.2 µC/cm 2 and 102.7 kV/cm, respectively. Microstructural study of the surface morphology of these films indicated grains of less than 0.1 µm in size. The leakage current for (Ba 0.6Sr 0.4)TiO 3 films was found to be two orders of magnitude lower than that for BaTiO 3 films. 相似文献
17.
The interaction energy between two hydrogen molecules near the van der Waals minimum is computed as the sum of the SCF interaction energy of the supermolecule and the so-called Hartree-Fock dispersion energy. The most stable configuration is the perpendicular planar one ( T configuration), this configuration being stable through the first order term. The energy averaged over the four configurations is in agreement with the available experimental data. The perturbative polarization energy is negligible near the van der Waals minimum but it seems that the charge transfer energy must be taken into account. 相似文献
18.
以LiOH·H2O, NH4VO3, NH4H2PO4 和麦芽糖等为原料, 采用水热法合成了碳包覆的磷酸钒锂化合物, 考察了碳含量对材料电化学性能的影响. 利用XRD, TEM, SEM和恒流充放电测试等手段对产物的结构、 形貌和电化学性能进行表征. 结果表明, 在650℃煅烧的样品为单一纯相的单斜晶体结构. 晶体颗粒分布为100~300 nm, 粒度分散均匀, 分散性良好, 无团聚现象, 且在颗粒表面包覆了一层无定形碳, 这有利于改善材料的导电率. 含碳量为10.23%的样品, 在倍率1.0C的电流密度下, 在3.0~4.3 V电压范围内, 样品的首次放电比容量高达118.8 mA·h/g, 循环15圈后放电比容量为115.1 mA·h/g, 容量保持率为96.88%. 相似文献
19.
Gases released during the conversion of NH 4Zr 2(PO 4) 3 to HZr 2(PO 4) 3 were identified using an apparatus in which gases released from a sample placed in a thermogravimetric analyzer were directly introduced to a gas cell of an IR spectrometer. Such acidic gases as N 2O and NO were detected besides the basic NH 3 gas, and their formation mechanism was discussed.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
20.
A new sol-gel route was applied to obtain Y 0.9Er 0.1Al 3(BO 3) 4 crystalline powders and amorphous thin films by using Al(acac) 3, B(OPr i) 3, Y(NO 3) 3·6H 2O, and Er(NO 3) 3·5H 2O as starting materials dissolved in propionic acid and ethyl alcohol mixtures. Our study shows that propionic acid acts as good chelant agent for yttrium and erbium ions while ethyl alcohol allows to dissolve Al(acac) 3. This process makes the resulting sols very stable to obtain homogeneous gels and transparent amorphous thin films. In addition, the propionic acid prevents the sol precipitation, making easy porous- and crack-free thin film depositions. Chemical reactions involved in the complexation were discussed. As-prepared powders and films are amorphous and present a good thermal stability due to their high glass transition (746 °C) and crystallization temperatures (830 °C). This new sol-gel route showed to be adequate to obtain dense and crack-free thin films free of organic and hydroxyl groups that can be considered as promising materials to be used in integrated optical systems. 相似文献
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