共查询到20条相似文献,搜索用时 15 毫秒
1.
G.N. KustovaYu.A. Chesalov L.M. PlyasovaI.Yu. Моlinа A.I. Nizovskii 《Vibrational Spectroscopy》2011,55(2):235-240
Vibrational spectra of polycrystalline WO3 hydrates and polymorphs were measured and analyzed. The effect of sampling techniques on IR spectra has been demonstrated. The phase transition into triclinic polymorph (C52 h → C1i) has been revealed for the sample of monoclinic WO3 prepared as KBr pellet. Using the deuteration method in situ has shown that cubic WO3 is non-stoichiometric oxide stabilized by residual OH groups of WO3·H2O precursor. 相似文献
2.
M. Maczka W. Paraguassu P.T.C. Freire F.E.A. Melo 《Journal of solid state chemistry》2004,177(6):2002-2006
A high-pressure Raman scattering study of the tungstate Al2(WO4)3 is presented. This study showed the onset of two reversible phase transitions at 0.28±0.07 and 2.8±0.1 GPa. The pressure evolution of Raman bands provides strong evidences that both the transitions involve rotations/tilts of nearly rigid tungstate tetrahedra and that the structure of the stable phase in the 0.28-2.8 GPa range may be the same as the structure of the ambient pressure, low-temperature monoclinic (C2h5) ferroelastic phase of Al2(WO4)3. 相似文献
3.
Reactions of interactions at the WO3|In2O3 and WO3|In6WO12 heterophase reaction interfaces, whose main product is In2(WO4)3, are studied by electrochemical methods for the first time ever. Due to a far greater n type conductance inherent in the initial substances, the reactions are a model object for the development of methodology
of the electrochemical approach. Both reactions are discovered to proceed at the expense of the transport of components of
WO3 and no evidence is discovered for the contribution of In3+ into diffusion and migration. Consisted data are obtained between the polarity of a spontaneously generated reaction difference
of potentials and the direction of the field that accelerates the reaction: the current that is passed through electrochemical
cells accelerates the reactions exclusively at the (−)-potential of a brick of WO3. A difference is discovered between the charge and mass transport paths—spontaneous and field-induced mass transport of WO3 or its components occurs via heterophase interfaces and adjacent areas and does not touch upon the In2(WO4)3 grains. Shown is the antibatic character of the behavior exhibited by dependences of identical properties of cells (potential
drop across a cell) following a change in the dc polarity. A possible role of a reactionless electrosurface transport of WO3 in the mechanism of reaction and evolution of electrochemical properties of model electrochemical cells is demonstrated.
The obtained data may or may not testify in favor of a hypothesis that presumes a prevailing role of the {WO4}2− mobility in the In2(WO4)3 structure.
Original Russian Text ? A.Ya. Neiman, T.E. Kulikova, 2007, published in Elektrokhimiya, 2007, Vol. 43, No. 6, pp. 714–726.
Based on the report delivered at the 8th International Meeting on Fundamental Problems of Solid-State Ionics, Chernogolovka
(Russia), 2006. 相似文献
4.
Matrix isolation has been combined with infrared spectroscopy to study the reaction chemistry of CrCl2O2 with (CH3)2O and (CH3)2CO. Very similar results were obtained with twin jet and room temperature merged jet deposition, indicating that the initial product forms on the surface of the matrix during deposition, not in the deposition lines prior to matrix condensation. The initial product in both systems was identified as the 1:1 complex between the two reagents, with a structure in which the oxygen atom of the base donates electron density to the Cr center. A number of perturbed vibrational modes of both subunits were observed; for the bases, these modes were vibrations involving the oxygen atom. Hg arc irradiation of the CrCl2O2·O(CH3)2 complex led to growth of a secondary product that is tentatively identified as Cl2CrO(OCH3)2. The CrCl2O2·OC(CH3)2 complex was not photosensitive, and no rearrangements were observed. 相似文献
5.
The origin of the signal seen in response to glucose in a polyaniline|glucose oxidase system is explored by immittance spectroscopy, by comparing data from an equivalent circuit model and the parameters obtained from a solution of the faradaic branch of the frequency dispersion for a coupled chemical—electrochemical reaction mechanism. It was shown that an RC subcircuit in the equivalent circuit model was sensitive to peroxide concentration, and the interaction of peroxide with polyaniline at potentials where it either oxidised or reduced the polyaniline was discussed. This information was used to compare the data obtained in a bulk and entrapped glucose oxidaselglucose system, and it was seen that the origin of the response could not be fully attributed to peroxide interaction in the latter case. Under anaerobic conditions with entrapped enzyme, it was proposed that a complex between the gluconolactone product of the enzyme reaction and the polymer leads to a more conducting polymer, with inherent charge compensation, and this results in the observed enhanced current signal. 相似文献
6.
Microdifferential thermal analysis (μ-DTA), X-ray diffraction (XRD) and infrared (IR) spectroscopy were used for the first time to investigate the liquidus and solidus relations in the KPO3–Y(PO3)3 system. The only compound observed within the system was KY(PO3)4 melting incongruently at 1033 K. An eutectic appears at 13.5 mol% Y(PO3)3 at 935 K, the peritectic occurs at 1033 K and the phase transition for potassium polyphosphate KPO3 was observed at 725 K. Three monoclinic allotropic phases of the single crystals were obtained. KY(PO3)4 polyphosphate has the P21 space group with lattice parameters: a=7.183(4) Å, b=8.351(6) Å, c=7.983(3) Å, β=91.75(3)° and Z=2 is isostructural with KNd(PO3)4. The second allotropic form of KY(PO3)4 belongs to the P21/n space group with lattice parameters: a=10.835(3) Å, b=9.003(2) Å, c=10.314(1) Å, β=106.09(7)° and Z=4 and is isostructural with TlNd(PO3)4. The IR absorption spectra of the two forms show a chain polyphosphates structure. The last modification of KYP4O12 crystallizes in the C2/c space group with lattice parameters: a=7.825(3) Å, b=12.537(4) Å, c=10.584(2) Å, β=110.22(7)° and Z=4 is isostructural with RbNdP4O12 and contains cyclic anions. The methods of chemical preparations, the determination of crystallographic data and IR spectra for these compounds are reported. 相似文献
7.
WO3/C hybrid material as a highly active catalyst support for formic acid electrooxidation 总被引:1,自引:0,他引:1
Zhonghua Zhang Yunjie Huang Junjie Ge Changpeng Liu Tianhong Lu Wei Xing 《Electrochemistry communications》2008,10(8):1113-1116
The hybrid material based on WO3 and Vulcan XC-72R carbon has been used as the support of Pd nanocatalysts. The resultant Pd–WO3/C catalysts in a large range of WO3 content exhibit excellent catalytic activity and stability for formic acid electrooxidation. The great improvement in the catalytic performance is attributed to the uniform dispersion of Pd with less particle sizes on the WO3/C support and the hydrogen spillover effect which greatly accelerates the dehydrogenation of HCOOH on Pd. 相似文献
8.
Anhydrous monoaryllead triacetates ArPb(OAc)3 (Ar = Ph, p-Tolyl, o-Tolyl, 2,5-Xylyl; OAc = OCOMe) were prepared by arylation of Pb(OAc)4 with ArSn(C4H9-n)3 in the presence of Hg(OCOCF3)2. The procedure was adapted for the synthesis of diaryllead diacetates Ar2Pb(OAc)2 (Ar = Ph, p-Tolyl, o-Tolyl, p-ClC6H4, o-ClC6H4) and afforded products with higher purity than other procedures. The crystal structures of PhPb(OAc)3, Ph2Pb(OAc)2 and (o-Tolyl)2Pb(OAc)2 were determined by X-ray diffraction. PhPb(OAc)3 and (o-Tolyl)2Pb(OAc)2 are monomeric. The pentagonal bipyramid around Pb in PhPb(OAc)3, like the trapezoidal bipyramid around Pb in (o-Tolyl)2Pb(OAc)2, is heavily distorted, the OAc groups being unsymmetrically chelating. Lead in Ph2Pb(OAc)2 is in a distorted octahedral environment. One OAc group is bridging, linking the molecular units to infinite chains, the other OAc group is symmetrically chelating. IR, 1H, 13C and 207Pb NMR spectroscopic data are reported. The structures of p-TolPb(OAc)3, o-TolPb(OAc)3 and 2,5-XylPb(OAc)3 are inferred to be similar to that of PhPb(OAc)3, and the structure of (o-ClC6H4)2Pb(OAc)2 is inferred to be similar to that of (o-Tolyl)2Pb(OAc)2. 相似文献
9.
六方相WO3纳米带的制备与表征 总被引:1,自引:1,他引:0
以Na2WO4、K2SO4和H2C2O4为原料,采用两步水热合成法制备了六方相WO3纳米带.首先,在探索pH值、K2SO4加入量、反应温度和时间以及表面活性剂等因素对WO3纳米带的前驱物钨酸盐形貌的影响后,给出了前驱物钨酸盐纳米带的合成条件,并讨论了纳米带的形成机理;然后,在180℃的水热条件下对前驱物再处理48 h获得六方相WO3纳米带.测试结果表明,WO3纳米带的形貌保持较好,宽度在100~300 nm间,长度可达数微米,沿纳米带长轴方向为[001]方向. 相似文献
10.
L. Schriver-Mazzuoli J. M. Coanga A. Schriver P. Ehrenfreund 《Vibrational Spectroscopy》2002,30(2):245-257
Fourier transform infrared reflection spectroscopy (incidence angle of 5°) was used to characterize thin films of dimethyl ether (DME) and of mixtures containing water and DME between 10 and 160 K under a pressure of 10−7 mbar. Solid DME has two solid phases: an amorphous phase which is obtained below 65 K and a crystalline phase >65 K. From 90 K, DME begins to sublimate with surface binding energy of 20±2 kJ mol−1. Vibrational spectrum of DME trapped in water ice remains nearly unchanged from 30 to 120 K. Between 120 and 130 K, a large part of DME is released and strong changes in the frequencies and the profile of the absorptions of DME are observed. This behavior suggests the formation of clathrate hydrate. Below 120 K, the trapped DME is hydrogen-bonded to water molecules. 相似文献
11.
《Journal of Molecular Structure》1998,450(1-3):179-192
The spectroscopic properties of Er3+ doped KY(WO4)2 and Ho3+ doped KYb(WO4)2 single crystals are reported and related to their X-ray structures. The experimental data include a survey of electronic absorption and emission features as well as vibrational IR and Raman spectra made in the polarized light. The effect of the random distribution of the monovalent and trivalent cations as well as intermolecular interactions between the tungstate anions are discussed. 相似文献
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葡萄糖发酵液D-核糖含量的高效液相色谱分析 总被引:3,自引:0,他引:3
D-核糖在生命科学研究领域十分重要,在医药、食品、饲料等工业部门广泛应用,近年来,D-核糖可通过D-葡萄糖在莽草酸营养缺陷型突变株菌种^[1]存在下,经发酵制得,目前国内葡萄糖发酵液中该糖含量分析仍采用苔黑酚光度法,此法没有对发酵液中种种上糖类化合物预先分离,选择性差,得到的是各种糖经合物总含量分析结果,糖类化合物测定的高效液相色谱法有衍生法[2] ,但比较繁琐,近年RI检测器应用于糖类分析日益增多[3,4],但用于葡萄糖发酵液中D-核糖分析尚未见报道,本文采用高效液相色谱法分析葡萄糖发酵液D-核糖含量,并获得良好结果。 相似文献
14.
以离子液体1-丁基-3-甲基咪唑四氟硼酸盐(BMIMBF4)为电解质,采用循环伏安法(CV)、计时电流法(CP)、原位傅里叶变换红外光谱(in situ FTIRS)法等手段研究了对甲氧基甲苯(p-MT)在铂电极上的电氧化行为.实验结果表明:对甲氧基甲苯在离子液体中的电化学氧化反应是受扩散控制的四电子不可逆过程,估算了其扩散系数D=3.4×10-7cm2.s-1,主要电氧化产物为茴香醛,加入适量的水或适当提高温度有利于电氧化反应向生成相应醛的方向进行. 相似文献
15.
Magnesia-supported tungsta catalysts have been prepared by impregnation, with different tungsta contents and calcined at different temperatures in air. All samples are active for propan-2-ol dehydrogenation above 473 K, and selective towards acetone formation. At low W content, acetone is further oxidized. The behavior has been related to the W-containing phases existing in the samples. 相似文献
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18.
Nandini Garg Vinod Panchal Surinder M. Sharma 《Journal of solid state chemistry》2005,178(4):998-1002
The high pressure behavior of aluminum tungstate [Al2(WO4)3] has been investigated up to ∼18 GPa with the help of Raman scattering studies. Our results confirm the recent observations of two reversible phase transitions below 3 GPa. In addition, we find that this compound undergoes two more phase transitions at ∼5.3 and ∼6 GPa before transforming irreversibly to an amorphous phase at ∼14 GPa. 相似文献
19.
Berta Nogueiro Estevinho Amélia Ferraz Fernando Rocha Lúcia Santos Arminda Alves 《Journal of separation science》2009,32(18):3116-3125
The determination of glucose and other carbohydrates is the most widespread chemical analysis that is performed within the industries of food, beverage, forage, biomass, pulp and paper, pharmaceuticals among others. Besides that, sugar refineries need to control their products, by‐products and effluents, and furthermore, glucose in the sucrose refining process, is considered an impurity, which shall be controlled. Being HPLC the most currently instrumental technique used for glucose analysis, the evaporative light scattering detector (ELSD) offers advantages (sensitivity, possibility for operating in gradient mode) over the also used refractive index detector. In this work, an HPLC‐ELSD methodology was optimised and validated, aiming the estimate of the uncertainty associated with the results at low levels of concentration of glucose to be measured. Linearity of the response was obtained in the range of glucose concentrations from 20 to 300 mg/L, with an analysis time of 10 min. The global uncertainty was estimated accordingly to the bottom‐up approach used by Eurachem. It was 13% on average for concentrations from 100 to 300 mg/L. For lower concentrations, uncertainty increased significantly up to 30% in the vicinity of the LOD of the method. 相似文献
20.
Michael D. Hoops 《Journal of Molecular Structure》2007,826(1):36-47
The matrix isolation technique, combined with infrared spectroscopy, has been used to characterize the products of the photochemical reactions of cyclohexane and cyclohexene with CrCl2O2. While initial twin jet deposition of the reagents led to no visible changes in the recorded spectra, strong product bands were noted following irradiation with light of λ > 300 nm. The irradiation was shown to lead to oxygen atom transfer, forming complexes between cyclic alcohol derivatives and CrCl2O, although complexes between ring expansion products and CrCl2O could not be ruled out. This latter result could arise from C-C bond activation and oxygen atom insertion into a C-C bond. For the cyclohexene system, the cyclohexanone-CrCl2O complex was also observed. The identification of the complexes was further supported by isotopic labeling (2H) and by density functional calculations at the B3LYP/6-311G++(d,2p) level. 相似文献