共查询到20条相似文献,搜索用时 15 毫秒
1.
The binary system Li 2CO 3–BaCO 3 was studied by means of differential thermal analysis (DTA), thermogravimetry (TG) and X-ray phase analysis. The composition
of carbonate and CO 2 partial pressure influence on the thermal behavior of carbonate were examined. It was shown that lithium carbonate does not
form the substitutional solid solution with barium carbonate, however the possible formation of diluted interstitial solid
solutions is discussed. Above the melting temperature the mass loss is observed on TG curves. This loss is the result of both
decomposition of lithium carbonate and evaporation of lithium in Li 2CO 3–BaCO 3 system. Increase of CO 2 concentration in surrounding gas atmosphere leads to slower decomposition of lithium carbonate and to increase the melting
point.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
Russian Journal of Applied Chemistry - Quenching method was used to obtain glasses in the system xWO3-(100-x)P2O5 (x = 70, 75, 80, 82 mol %). The electrical conductivity of the compositions was... 相似文献
3.
The solubility of SnO 2(cassiterite) was studied at 23±2?°C as a function of time (7 to 49 days) and pH (0 to 14.5). Steady state concentrations were reached in <7 days. The data were interpreted using the SIT model. The data show that SnO 2(cassiterite) is the stable phase at pH values of ~11.7. These extensive data provided a log? 10 K 0 value of ?64.39±0.30 for the reaction (SnO 2(cassiterite) +2H 2O?Sn 4++4OH ?) and values of 1.86±0.30, ≤?0.62, ?9.20±0.34, and ?20.28±0.34 for the reaction ( $\mathrm{Sn}^{4+} + n\mathrm{H}_{2}\mathrm{O} \rightleftarrows \mathrm{Sn}(\mathrm{OH})_{n}^{4 - n} + n\mathrm{H}^{+}$ ) with values of “ n” equal to 1, 4, 5, and 6 respectively. These thermodynamic hydrolysis constants were used to reinterpret the extensive literature data for SnO 2(am) solubility, which provided a log? 10 K 0 value of ?61.80±0.29 for the reaction (SnO 2(am)+2H 2O?Sn 4++4OH ?). SnO 2(cassiterite) is unstable under highly alkaline conditions (NaOH concentrations >0.003 mol?dm ?3) and transforms to a double salt of SnO 2 and NaOH. Although additional well-focused studies will be required for confirmation, the experimental data in the highly alkaline region (0.003 to 3.5 mol?dm ?3 NaOH) can be well described with log? 10 K 0 of ?5.29±0.35 for the reaction Na 2Sn(OH) 6(s)?Na 2Sn(OH) 6(aq). 相似文献
4.
Cerium ammonium nitrate (CAN) is an expensive and powerful selective oxidant. It has played an important role in organic synthesis. Because it is a single electron oxidant,many organic reactions need large quantities of it. The application of CAN in organic synthesis in the oxidation of alkyl aromatics has so far been limited. In this paper, we wish to report a new method of oxidation of active α-H of aromatic hydrocarbon by CAN/NaBrO 3/H 2O system. Only catalytic amount of CAN was needed in this method and the selectivity was improved as well. 相似文献
6.
Solid-phase reactions in the aluminum–manganese oxide system, including the structural mechanism of the thermal activation of catalysts, were studied at temperatures up to 1100°C. It was found that the solid-phase reaction at 900–1000°C occurred via two pathways because of the diffusion of manganese ions to aluminum oxide and aluminum ions to manganese oxide. Nanoheterogeneous state of the active component, which was observed in the range 25–600°C, is the product of incomplete decomposition of the high-temperature aluminum–manganese phase Mn 2.1 – x
Al 0.9 + x
O 4 (0 x 0.6) with a cubic spinel structure; this phase was equilibrium at the synthesis temperature but metastable below 650°C. 相似文献
7.
A technique to determine the oxygen distribution in high T c superconducting YBa 2Cu 3O 7–x ceramics has been developed which is based on the (n, ) radiography method. The technique enables the non-destructive study of superconducting ceramics as well as monocrystal samples with spatial resolution not worse than 1 m at a relative standard deviation of 1.5%. This technique is used to study the influence of radiation-stimulated diffussion of oxygen on the formation of the superconducting phase in an yttrium ceramic. The oxygen distribution in the samples with a narrow transition (T1 K) and with a transition widened (T10 K) by thermal and thermo-radiative treatment is compared in the experiment. The oxygen distribution radiographs of irradiated and unirradiated samples provide strong evidence for the influence of irradiation on the ordering of superconducting ceramics structure. 相似文献
8.
A terylene membrane which kept pH〉12 in cathode compartment was used to construct a divided cell with a carbon/polytetrafluoroethylene(C/PTFE) O2-fed cathode. The concentrations of hydrogen peroxide (H2O2) and hydroxyl radical (HO^-)in the catholyte were 8.3 mg/L and 2.15 μmol/L, respectivel.y, which were determined by permanganate titration, electron spin resonance (ESR) spectrum and the fluorescence spectra. ;The efficiency of the removal of phenol achieved 100% as a result of these two kinds of stronger oxidizer. 相似文献
9.
Two types of solid electrolytes have reached technological relevance in the field of sodium batteries: ß/ß”-aluminas and NaSICON-type materials. Today, significant attention is paid to room-temperature stationary electricity storage technologies and all-solid-state Na batteries used in combination with these solid electrolytes are an emerging research field besides sodium-ion batteries. In comparison, NaSICON materials can be processed at lower sintering temperatures than the ß/ß”-aluminas and have a similarly attractive ionic conductivity. Since Na 2O−SiO 2−ZrO 2−P 2O 5 ceramics offer wider compositional variability, the series Na 3Zr 3–xSi 2P xO 11.5+x/2 with seven compositions (0≤x≤3) was selected from the quasi-quaternary phase diagram in order to identify the predominant stability region of NaSICON within this series and to explore the full potential of such materials, including the original NaSICON composition of Na 3Zr 2Si 2PO l2 as a reference. Several characterization techniques were used for the purpose of better understanding the relationships between processing and properties of the ceramics. X-ray diffraction analysis revealed that the phase region of NaSICON materials is larger than expected. Moreover, new ceramic NaSICON materials were discovered in the system crystallizing with a monoclinic NaSICON structure (space group C2/c). Impedance spectroscopy was utilized to investigate the ionic conductivity, giving clear evidence for a dependence on crystal symmetry. The monoclinic NaSICON structure showed the highest ionic conductivity with an optimum ionic conductivity of 1.22×10 −3 at 25 °C for the composition Na 3Zr 2Si 2PO 12. As the degree of P 5+ content increases, the total ionic conductivity is initially enhanced until x=1 and then decreases again. Simultaneously, the increasing amount of phosphorus leads a decrease in the sintering temperatures for all samples, which was confirmed by dilatometry measurements. The thermal and microstructural properties of the prepared samples are also evaluated and discussed. 相似文献
10.
Graphene aerogel-supported manganese ferrite (Mn xFe 3−xO 4/GAs) and reduced-graphene oxide/manganese ferrite composite (MnFe 2O 4/rGO) were synthesized and studied as cathode catalysts for oxygen reduction reactions in urea/O 2 fuel cells. MnFe 2O 4/GAs exhibited a 3D framework with a continuous macroporous structure. Among the investigated Fe/Mn ratios, the more positive oxygen reduction onset potential was observed with Fe/Mn=2/1. The half-wave potential of MnFe 2O 4/GAs was considerably more positive than that of MnFe 2O 4/rGO and comparable with that of Pt/C, while the stability of MnFe 2O 4/GAs significantly higher than that of Pt/C. The best urea/O 2 fuel cell performance was also observed with the MnFe 2O 4/GAs. The MnFe 2O 4/GAs exhibited an OCV of 0.713 V and a maximum power density of 1.7 mW cm −2 at 60 °C. Thus, this work shows that 3D structured graphene aerogel-supported MnFe 2O 4 catalysts can be used as an efficient cathode material for alkaline fuel cells. 相似文献
12.
Journal of Thermal Analysis and Calorimetry - Li(CH3CN)4PF6 and Li(C4H10O2)2PF6 complexes are important intermediates created in the synthetic process of high-purity LiPF6 electrolyte via... 相似文献
13.
Applying the TPD-MS with a high sensitivity of determination, the TPD spectrum of surface oxygen of V2O5/SiO2, V2O5-MoO3/SiO2 and V2O6-P2O5/SiO2 catalysts was obtained. The surface oxygen of these catalysts can be divided into three groups according to the desorption temperature. O2- desorbs mainly from 373K. to 423K, O- from 673K to 873K and O2- at above 873K. The activation energy and frequency factor of all the three kinds of oxygen species were calculated. Based on these results, the mechanism of oxygen desorption and the influence of P2O5 and MoO3 on the properties of oxygen supply of V2O5/SiO2 catalst were investigated. MoO3 and a small amount of P2Os increase the number of supplying oxygen and increase the activity of O- species. A large amount of P2O5 increases the number of supplying oxygen and restrains the activity of O- species. 相似文献
14.
Metal-mediated reactions in aqueous media have received considerable attention in the last decade1. Such aqueous reactions offer a number of advantages over conventional organometallic reactions in organic solvent in that they are practically convenient, environmentally benign and do not require strict anhydrous conditions2. In recent years, besides zinc and tin, indium has been found to be the metal of choice for promoting organic reactions in aqueous media3. Indium is considered to be mor… 相似文献
15.
In order to get insight in some of the yet unanswered questions about the formation process of the (Bi,Pb) 2Sr 2Ca 2Cu 3O 10+ superconducting compound, coupled DTA-TG measurements have been performed in parallel with other techniques such as X-ray diffraction, Scanning Electron Microscopy and Energy Dispersive X-ray Microanalysis. The path leading to the formation of the (Bi,Pb) 2Sr 2Ca 2Cu 3O 10+ compound, starting from coprecipitated oxalates powders was studied. The activation energy of some of the involved transformation processes were determined. Relationships between the differences induced in the DTA traces by various sample nominal compositions and the intergranular magnetic properties of the superconductor will be discussed. 相似文献
16.
At a weight ratio of n‐C 5H 11OH/H 2O=50/50, when the total content of sodium dodecyl sulfate (SDS) was less than 6.0%, the ternary mixture of SDS/ n‐C 5H 11OH/H 2O coexisted in two immiscible microemulsions. The distribution and transfer of gatifloxacin (GTFX) between the two phases were studied using UV‐Vis and electrochemistry AC impedance spectra. The results show that GTFX transferred from the upper phase (W/O) to the lower phase (O/W or bicontinuous microemulsion), but a small amount of SDS transferred from the lower phase to the upper phase correspondingly with the increase of the total SDS content at a total GTFX concentration of 1.0×10 ?5 mol/L. The addition of GTFX did not change the structures of the two different phases fundamentally, but resulted in the transfer and redistribution of GTFX and SDS, so the electric properties of the system were changed correspondingly. 相似文献
17.
Optical resolution of racemic 2-(3-chloro-phenyl)-3.4a. 5.6.7.7a-hexahydrocyclopentapyrimidin-4-one with O.O′-dibenzoyl-2R,3R-tartaric acid in an unusual solvent combination, in water-chloroform two phase solvent system was accomplished. During enantiomeric enrichment of the resulted raw base the optically active base can be recovered from the ethanolic mother liquor. 相似文献
18.
A number of ternary complexes of Cu 2+ with thiosemicarbazide (TSC) including [Cu(bpy)(TSC) 2]Cl 2, [Cu( o-phen)(TSC) 2]Cl 2 and [Cu(bpy)(TSC) 2][CuCl 4] [Cu( o-phen)(TSC) 2] [CuCl 4] have been synthesised and characterized. Their reactivities in aqueous and DMF solutions were studied. It was observed that while on coordination to Cu 2+ thiosemicarbazide is converted to thiocyanate in aqueous solution, in DMF solution the thiocyanate is further aerially oxidised to sulfate. In the presence of hydrogen peroxide, oxidation to sulfate is rapid and from the mother liquor we could isolate [(bpy) 2Cu 2(C 2O 4)Cl 2]·H 2O whose structure was determined by X-ray crystallography. X-ray crystal structure of [Cu(bpy)(H 2O) 2SO 4] is also discussed.* 相似文献
19.
This work synthesized and characterized the NOR-RIB 1:1 (mol–mol) cocrystal. During a study of the reagents, Riboflavin (RIB) melted at 304 °C, which is different from the temperature previously reported in the literature (280–290 °C); therefore, this compound was characterized individually. Subsequently, the cocrystal was synthesized with the active pharmaceutical ingredient (API) norfloxacin (NOR) with the RIB coformer, and the mechanochemical synthesis route was adopted. NOR, RIB, and the cocrystal were characterized by thermogravimetry–differential thermal analysis (TG–DTA), differential scanning calorimetry (DSC), DSC coupled to a microscope (photo-DSC), mid-infrared spectroscopy (MIR), and powder X-ray diffraction. The results of thermal analysis showed that the RIB starts decomposition process (260 °C) and then melts (304 °C). The MIR found that beginning at 295 °C, the RIB passes into the form of a decomposition intermediate; therefore, the melting point observed in the DSC curve is related to this decomposition material. The cocrystal presented thermal stability (200 °C) lower than the API (235 °C) and the coformer (260 °C). The DSC curve did not contain a melting peak. The bands at 1726 cm?1 (C=O of the carboxylic acid) for the NOR, and the band at 3326 cm?1 (stretch O–H), among others, were not visible for the cocrystal in the MIR spectrum, indicating interactions in these regions. The X-ray diffractograms showed a new diffraction pattern, which proved the obtainment of a new phase and cocrystal formation. 相似文献
20.
Research on Chemical Intermediates - Substitutional doping of framework heteroatoms in photocatalysis is one of the approaches for harvesting visible light. Tunnel structure potassium antimony... 相似文献
|