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1.
Electrochemical reductive dissolution of Li–Mn–O and Li–Fe–Mn–O spinels and Li + extraction/insertion in these oxides were performed using voltammetry of microparticles. Both electrochemical reactions are
sensitive to the Fe/(Fe+Mn) ratio, specific surface area, Li content in tetrahedral positions, and Mn valence, and can be
used for electrochemical analysis of the homogeneity of the elemental and phase composition of synthetic samples. The peak
potential ( E
P) of the reductive dissolution of the Li–Mn–O spinel is directly proportional to the logarithm of the specific surface area. E
P of Li–Fe–Mn–O spinels is mainly controlled by the Fe/(Fe+Mn) ratio. Li + insertion/extraction can be performed with Mn-rich Li–Fe–Mn–O spinels in aqueous solution under an ambient atmosphere and
it is sensitive to the regularity of the spinel structure, in particularly to the amount of Li in tetrahedral positions and
the Mn valence.
Electronic Publication 相似文献
2.
Bubble points of the HCl–water–isopropanol and the HCl–water–isopropanol–benzene systems and liquid–liquid equilibria (LLE) of the HCl–water–benzene and the HCl–water– isopropanol–benzene systems were measured at 25–85°C and 30–70°C, respectively. The electrolyte nonrandom two-liquid model proposed by Chen et al. [C.-C. Chen, H.I. Britt, J.F. Boston, L.B. Evans, AIChE J. 28 (1982) 588–596] can satisfactorily correlate bubble points and liquid–liquid equilibria of the present mixed-solvent electrolyte systems over the entire range of temperature and concentrations using only binary adjustable parameters. 相似文献
3.
Fundamentally different behavior of Ba–Bi–O (Ba : Bi = 11 : 4, 1 : 1, 2: 3, and 1 : 5 mol/mol) and K nBa mBi m+nO y ( m = n = 1, 2,...; exhibiting superconducting properties with Tc = 28–32 K) oxides and BaO 2 in hydrolysis reactions has been revealed by means of potentiometry and chemical analysis. Products of the oxides treatment with water do not contain H 2O 2, evidencing the absence of peroxide ions in their structure. The perovskite-type barium-bismuth(III) oxides are completely hydrolyzed into Ba(OH) 2 and Bi 2O 3 at room temperature. 相似文献
4.
Cooling a melt of a Bi–Sr–Ca–Cu–O system (Bi:Sr:Ca:Cu = 4:3:3:4 or 2:2:2:4) from 1000°C-1050°C yielded crystals of a new red-colored nonsuperconducting phase, accompanying the superconducting 2212 and 2201 phases. Based on the EPR spectra, it was concluded that copper is univalent in this compound. The new phase has a composition Bi 2.2Sr 1.6Ca 1.3Cu 2O x. The X-ray diffraction pattern has been indexed, and the unit cell parameters of the phase have been determined: space group P2/m, a = 12.93, b = 4.55, c = 10.94 ; = 102.72°. 相似文献
5.
The high nitrogen compound 3,6-bis(1H-1,2,3,4-tetrazol-5-yl-amino)-1,2,4,5-tetrazine and the high energy density material hexanitrohexaazaisowurtzitane (HNIW), were used as substitute of hexogen (RDX) in the composite modified double base (CMDB) propellant formulations, the propellant samples were prepared, the thermal behaviors, nonisothermal reaction kinetics, and thermal safety were carried out, and the eight important parameters were calculated and obtained as the self-accelerating decomposition temperature ( T SADT), thermal ignition temperature ( T TIT), critical temperatures of thermal explosion ( T b), critical temperature of hot-spot initiation ( T cr,hot-spot), characteristic drop height of impact sensitivity ( H 50), critical thermal explosion ambient temperature ( T acr), safety degree ( S d), and thermal explosion probability ( P TE). It shows that the content of HNIW has a large effect on the decomposition reaction mechanism of the CMDB propellant, when the content of HNIW is 10 %, the decomposition reaction are controlled by the random nucleation and subsequent growth ( n = l), and the reaction mechanism obeys Mampel law; but when the content of HNIW is 20 %, the decomposition reaction are controlled by the chemical reaction ( n = 1/4). The mechanism can not be changed by the catalysts, and they just make the apparent activation energy change slightly. For the sample, from BC01 to BC04, the values of T SADT and T TIT making an upward tendency, show the resistivity to heat: BC04 > BC03 > BC02 > BC01; the values of T acr and S d, BC01 are the maximum and BC02 are the minimum, show the heat sensitivity: BC01 > BC03 > BC04 > BC02. For the same radius, the thermal safety of the sphere sample is greater than that of the infinite cylinder one. 相似文献
6.
T– x diagrams of polythermal GeAs–SnAs, GeAs–Sn 4As 3 sections of the Sn–As–Ge system and Sn 4P 3–Sn 4As 3 section of the Sn–As–P system were constructed using the results of X-ray powder diffraction and differential thermal analyses. It was found that the section GeAs–Sn 4As 3 is not quasi-binary due to realization of four-phase peritectic transformation L + SnAs ? GeAs + Sn 4As 3 at the temperature of 834 K. The quasi-binary section GeAs–SnAs represents a phase diagram of the eutectic type with the following coordinates of eutectic reaction: temperature of the eutectic point is 840 K, and composition is 20 mol% GeAs. In the Sn–As–P system, the existence of the solid-solution range indicated as (Sn 4As 3) x (Sn 4P 3) 1?x was defined. The polythermal section Sn 4P 3–Sn 4As 3 is not quasi-binary due to the fact that in the composition range with a high content of tin arsenide discussed section intersects the peritectic part of the three-phase volume (L + SnAs + α) of the ternary diagram. 相似文献
7.
CuAl layered double hydroxide (CuAl-LDH) was synthesized by co-precipitation. Sodium phenyl phosphate (SPP) and sodium dodecyl sulfate (SDS) are used to modify CuAl-LDH for preparing CuAl-(SPP)LDH and CuAl-(SDS)LDH, which were incorporated into epoxy resin (EP) to obtain EP/CuAl-(SPP)LDH and EP/CuAl-(SPP)LDH nanocomposites. The results indicate that SPP and SDS are intercalated into the interlayers of CuAl-LDH, and CuAl-(SPP)LDH has larger layer spacing than CuAl-(SDS)LDH. The thermal stability and flame-retardant performances of EP/CuAl-(SPP)LDH nanocomposites were better than those of EP/CuAl-(SDS)LDH composites. Compared with those of EP/4CuAl-(SDS)LDH nanocomposites, the peak heat release rate (PHRR) of EP/4CuAl-(SPP)LDH nanocomposites is reduced 25.8% and 55.6%, and peak smoke production rate (PSPR) value of EP/4CuAl-(SPP)LDH nanocomposites is reduced 27.6% and 46.2%, value of EP/4CuAl-(SPP)LDH nanocomposites is reduced 27.6% and 46.2%, respectively. The improved flame retardancy and smoke suppression performances of EP/CuAl-(SPP)LDH nanocomposites were attributed to the combination of copper compounds and SPP, promoting the formation of swollen, continuous and compact char layers on the surface of EP nanocomposites during combustion, eventually restraining the decomposition of EP nanocomposites. 相似文献
8.
Rod-shaped amorphous bulk Ni–Cr–Mo-22 at.%Ta-14 at.%Nb–P alloys resistant to concentrated hydrochloric acids were prepared
by copper-mold casting. Alloys of amorphous single phase and mixture of nanocrystalline phases in the amorphous matrix were
all spontaneously passive in 6 and 12 M HCl and were immune to corrosion in 6 M HCl, although the corrosion weight loss was
detected for heterogeneous alloys in 12 M HCl. Spontaneous passivation is due to presence of stable air-formed films in which
chromium was particularly concentrated in addition to enrichment of tantalum and niobium. The angle resolved X-ray photoelectron
spectroscopy revealed that chromium and molybdenum are rich in the inner part of the film. The major molybdenum species is
in the tetravalent state, although penta- and hexavalent state molybdenum is also included. The high corrosion resistance
was interpreted in terms of the high stability of the outer triple oxyhydroxide, Cr 1−x−yTa xNb yO z(OH) 3+2x+2y−2z, and the effective diffusion barrier of the inner Mo 4+ and Cr 3+ oxide layer.
Contribution to the Fall Meeting of the European Materials Research Society, Symposium D: 9th International Symposium on Electrochemical/Chemical
Reactivity of Metastable Materials, Warsaw, 17th-21st September, 2007. 相似文献
9.
The study explored the compatibility between the main product of Portland cement hydration and the main product of the alkali
activation of fly ash: C–S–H and N–A–S–H gels, respectively. Both gels were synthesized with laboratory reagents at different
pH values. Blends of the two were synthesized as well, using the sol–gel procedure. All the gels were characterized with Fourier
transform IR spectroscopy (FTIR). The gels synthesized with this procedure were shown to precipitate together with a silica-rich
gel. In addition, the pH level was found to play a determinant role in both C–S–H and N–A–S–H gel synthesis. The C–S–H gel
is the major phase formed at pH > 11 and N–A–S–H gel for pH > 12. The results relating to the joint synthesis of the two (C–S–H
and N–A–S–H) gels were not conclusive. Technique used for the characterization failed to differentiate between them in the
blended material.
相似文献
10.
Two complex lanthanide(III) transition metal(II) tellurium(IV) oxyhalides, Cu 3Yb 2(TeO 3) 4Cl 4 and Cu 3Yb 3(TeO 3) 4Cl 6 have been synthesized and the crystal structures were determined by single-crystal X-ray diffraction. Both compounds are layered with only weak connections in between the layers. The layers are made up of [YbO 8], [TeO 3] and [CuO xCl y] polyhedra. In both compounds the strong Lewis acid cations Yb 3+ and Te 4+ only form bonds to oxygen while Cu 2+ form bonds to both oxygen and chlorine. This leads the Cl ? ions to be expelled from the bonding volumes of the crystal structures and protrude from the layers. Magnetic susceptibility measurements were performed on a powder sample of Cu 3Yb 2(TeO 3) 4Cl 4. The Curie–Weiss law found at low temperatures indicates a Curie–Weiss temperature of ca. ?5(1) K. However, indication for long-range magnetic ordering could not be observed down to 1.87 K. The two new phases are to the best of our knowledge the first containing all three of Cu, Yb and Te. 相似文献
11.
Doklady Chemistry - Three types of solid solutions of new nickel–cobalt–manganese spinels were synthesized by substitution for manganese cations in oxide Mn3O4:... 相似文献
12.
The crystal structure of a natural sulfide Cu 3,44Ag 0,56Pb 2Bi 6S 13 ( Сmcm, Z = 4, a = 3.973(1) Å, b = 13.370(2) Å, c = 42.182(7) Å, R = 0.059) is determined. The structure has seven cation positions: two of them (Cu and Ag) are in a tetrahedral environment of sulfur atoms; one (Pb), in a special position ( mm2), has a coordination polyhedron in the form of a bicapped trigonal prism; and the other cation positions are surrounded by sulfur atoms forming distorted octahedra. The mirror symmetry plane perpendicular to the c translation causes microtwinning by cutting a layer of trigonal prisms framed by tetrahedron ribbons. These layers are divided by those composed by edge-linked octahedra with a diagonal ribbon of five octahedra ( N = 5). The cation and anion positions are ordered by individual sublattices with pseudohexagonal subcells on the m planes perpendicular to the a translation, which concentrate the positions of all the atoms. Supposedly, this natural sulfide is the previously described (1885) yet unconfirmed alaskaite mineral from the lillianite–heyrovskyite homological series and may be isostructural to the ourayite mineral. 相似文献
13.
Systematic investigation of sol–gel process in the Y–Ba–Cu–O acetate–tartrate system was performed using IR spectroscopy. Different values of synthesis parameters (temperature and duration of inorganic polymerization reactions, evaporation temperature and evaporation time during gelation) were used, and significant influence in some cases on superconducting characteristics of the oxide ceramics of composition YBa 2Cu 4O 8 was observed. Characterization by IR spectroscopy and thermogravimetric analysis, revealed the difference of local homogeneity in the precursor gels prepared under different evaporation regimes during gelation process. In addition, the explanation of the possible hydrolysis and condensation reactions in the sol state has been suggested. 相似文献
14.
A non-commercial Al4Cu0.5Mg alloy has been used for investigating the effects of the elemental Sn additions. Uniaxial die compaction response of the alloys in terms of green density was examined, and the results showed that Sn addition has no effect when compacting conducted under high pressures. In total, 93–95% green density was achieved with an applied pressure of 400 MPa. Thermal events occurring during the sintering of the emerging alloys were studied by using differential scanning calorimetry (DSC). First thermal event on the DSC analysis of the Al4Cu0.5Mg1Sn alloy is the melting of elemental Sn, whereas for Al4Cu0.5Mg alloy, it is the formation of Al–Mg liquid nearly at 450 °C. Also it is clearly seen on the DSC analysis that Sn addition led to an increase in the formation enthalpy of Al–Mg liquid phase. High Sn content and high sintering temperature (620 °C), therefore high liquid-phase content, caused decrease on the mechanical properties due to thick intergranular phases and grain coarsening. Highest transverse rupture strength and hardness values were obtained from Al4Cu0.5Mg0.1Sn alloy sintered at 600 °C and measured as 390 MPa and 73 HB, respectively. 相似文献
16.
Samples of general formulae (AgI) 4?2x(CdI 2) xKI and (AgI) 4?x(CuI) xKI, x = 0–0.4, have been prepared and studied by conductivity measurements, powder X-ray diffraction and DSC techniques. Room temperature XRD reveals the presence of the orthorhombic K 2AgI 3 as the major component in the system. DSC traces show endothermic peaks in the temperature range of 309–330 K, depending on the sample composition. These are attributed to the solid state reaction between AgI and K 2AgI 3 to form the cubic KAg 4I 5. Impedance spectra show the prominence of electrode – electrolyte interface effect which is explained in terms of the high rate of ion migration. Ionic conductivity enhances with the increase of Cd 2+ content, while Cu + contained samples show a decrease in conductivity with increasing Cu + ratio though the ionic conductivity remains higher than that of the pure one. 相似文献
17.
The phase relations in the Pr–Mn–O system were studied by the static method at lowered oxygen pressure in combination with thermal analysis and high-temperature X-ray diffraction. The equilibrium oxygen pressure in dissociation of PrMn 2O 5 and PrMnO 3 was measured, and the thermodynamic characteristics of formation of these compounds from elements were calculated. The Р– Т– х phase diagram of the Pr–Mn–O system was constructed in the “composition–oxygen pressure–temperature” coordinates. 相似文献
18.
The results of the experimental and theoretical studies of the concentration dependence of surface tension of aqueous solutions of the 1,4-dioxane–acetone–water and glycerol–ethanol–water ternary systems were given. The studies were performed by the hanging-drop method on a DSA100 tensiometer. The maximum error of surface tension was 1%. The theoretical models for calculating the surface tension of the ternary systems of organic solutions were analyzed. 相似文献
19.
The density, isothermal compressibility, and thermal expansion coefficient of macroscopically single-phase n-heptane–water–sodium dodecyl sulfate– n-pentanol microemulsions are measured by a precision dilatometric method at 25°C. The internal pressure and molar volume of the investigated microemulsion systems are calculated. It was shown that the bulk properties of direct microemulsions with various contents of the dispersed phase markedly differ. 相似文献
20.
An experimental study of the temperature dependences of the surface tension of liquid high-entropy equiatomic alloys of a Cu–Sn–Bi–In–Pb system is conducted. Measurements are made within the temperature range of t L to 1300°C in the mode of heating and subsequent cooling of a sample. Overcooling of a melt prior to crystallization is detected. The depth of overcooling grows along with the number of components in the melt, while the temperature coefficient of surface tension falls. The experimental results qualitatively interpreted within the concepts of the specific surface entropy of a liquid. 相似文献
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