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1.
A ternary phase diagram of the Mn–Te–O system at 950 K has been established in the composition range in and around the MnO–TeO 2 pseudo binary line. Various preparation methods were employed to confirm the co-existence of different ternary phases. The results of these phase equilibration studies were revalidated by the invariancy of partial pressures at constant temperature during high temperature mass spectrometric vaporization experiments. The following three-phase regions have been identified: MnO+Mn 3O 4+Mn 6Te 5O 16 (phase region 1; PH1), Mn 3O 4+Mn 6Te 5O 16+MnTeO 3 (phase region 2; PH2), Mn 3O 4+MnTeO 3+Mn 3TeO 6 (phase region 3; PH3), and MnTeO 3+Mn 2Te 3O 8+Mn 3TeO 6 (phase region 4; PH4). The complex nature of the Mn–Te–O ternary system was revealed by the interesting results obtained by us with regard to preparation of samples and mass spectrometric vaporization experiments. 相似文献
2.
The role of Na 2O- and Li 2O-doping on the thermal decomposition of Co 3O 4 to CoO and the re-oxidation of cobaltous to cobaltic oxide has been investigated using DTA, with controlled rates of heating and cooling, IR and X-ray diffraction spectrometry techniques. The DTA investigation revealed that both Li2O and Na2O increased the thermal stability of Co3O4. However, the effect was much more pronounced in the case of lithium oxide. Doping Co3O4 with 1.5 mole% Li2O was found to prevent any thermal decomposition of cobaltic oxide even by heating at 1100°C. The maximum thermal stabilization effect induced by doping with sodium oxide (4.5 mole%) was 30%. The sodium oxide- and lithium oxide-doping enhanced the reactivity of the produced CoO towards the re-oxidation by O2 yielding Co3O4. The X-ray diffraction and IR spectrometric investigations showed that part of Li2O and Na2O was effectively incorporated in the Co3O4 lattice, affecting the thermal stabilization of the solid, and another part of the dopant oxide interacted with the produced CoO and also with Co3O4 giving a new sodium cobalt compound, and with Co3O4 producing, also, a new lithium cobalt oxide phase. However, the amount of Li2O dissolved in the Co3O4 lattice was greater than that of Na2O. The sudden cooling of doped solids, from 1000°C to room temperature, favoured the formation of the new sodium cobalt oxide compound, and exerted no effect on the production of the new lithium cobalt oxide phase. The characteristic d spacings and IR absorption bands of these new compounds have been determined. The possible mechanisms of dissolution of Li2O and Na2O in cobaltic oxide lattice are discussed. 相似文献
3.
Samples of γ-Mn 2O 3 with various iron contents are obtained by co-precipitation from appropriate amounts of manganese sulphate and ferric nitrate solutions by a concentrated (2.5 N) boiling solution of sodium hydroxide. Thermal analysis, X-ray diffraction and IR spectroscopy of the specimens reveal that the presence of iron in γ-Mn 2O 3 up to 15 to 25 at.% leads to formation of a single phase γ-Mn 2O 3 solid solution, which is partly reduced to Mn 3O 4 around 680 °C and finally transforms to the -Mn 2O 3 phase on heating at or above 950 °C. With increasing iron concentration beyond 25 at.%, the formation of a ferrite phase has been detected in addition to the γ-Mn 2O 3 solid solution. However, this ferrite phase is thermally unstable and breaks down on heating around 600°C. 相似文献
4.
制备一系列包含或不包含铜、钼组分的Ni/γ-Al 2O 3催化剂,并对其进行表征和性能测试。考察了铜、钼负载量,浸渍顺序(包括连续浸渍和共浸渍),反应条件对脂肪酸甲酯加氢脱氧反应性能的影响。根据TG数据,使用过的20Ni-6Cu/γ-Al 2O 3催化剂其热失重小于20Ni/γ-Al 2O 3催化剂,这表明,铜的引入能够有效抑制反应过程中催化剂表面的积炭行为。对于20Ni-6Cu/γ-Al 2O 3和20Ni-6Cu-nMo/γ-Al 2O 3(n=2、5、8和12)催化剂,NH 3-TPD分析结果显示,钼物相的引入对载体γ-Al 2O 3的酸性位有着显著影响,当钼负载量达到5%时,可以观察到一个新的酸位对应于中强酸位。铜和钼修饰过的催化剂其催化性能要高于Ni/γ-Al 2O 3催化剂。从XPS的分析可以看出,催化剂中的铜主要以正二价形式存在,钼主要以正四价和正六价形式存在,而且不同的浸渍顺序会影响催化剂表面活性组分的实际含量。此外,脂肪酸甲酯的转化率和烷烃产品的收率也和所制备出来的催化剂的浸渍顺序有关。在所有的催化剂中,使用连续浸渍(先浸渍镍铜组分、浸渍钼组分)所制备的三金属20Ni-6Cu-5Mo/γ-Al 2O 3催化剂展现了优异的催化性能。在适宜的反应条件下(350 ℃,2.5 MPa,WSHV=2.0 h -1,H 2/oil ratio=1250 mL/mL),脂肪酸甲酯的转化率和烷烃产品的收率分别达到98.4%和94.2%。 相似文献
5.
用X射线粉末衍射法研究了Li 2O-CaO-Gd 2O 3-SiO 2:Eu,Bi发光体系的物相组成随Gd 2O 3含量的变化,探讨了不同硅酸盐物种和结构对Eu 3+和Bi 3+发光特性的影响。结果表明,无Gd 2O 3组分时发光体是β-CaSiO 4多晶体,当Gd 2O 3/SiO 2比超过2.5%时,Ca 2Gd 8(SiO 4) 6O 2和LiGd 9(SiO 4) 6O 2物相逐渐增加,当其成为主要物相时,EU 3+发光呈数倍增强,这2种含钆物相的结构既利于EU 3+的红光发射又利于敏化剂向激活剂传输能量,所形成的固熔体是优良的发光基质材料。 相似文献
6.
以硝酸铋为原料,氨水为沉淀剂,通过液相沉淀法制得前驱体Bi(OH) 3,并将Bi(OH) 3分别在不同温度和时间下焙烧。利用X射线衍射(XRD)、拉曼光谱、热重(TG)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)及紫外-可见漫反射光谱(UV-Vis DRS)详细研究了Bi(OH) 3转变为Bi 2O 3的过程及相变过程中粒子形貌、大小、光吸收性质等。结果表明,前驱体Bi(OH) 3经过焙烧之后,发生了如下的转变过程:Bi(OH) 3→Bi 5O 7NO 3→ β-Bi 2O 3/Bi 5O 7NO 3→ β-Bi 2O 3/Bi 5O 7NO 3/ α-Bi 2O 3→ α-Bi 2O 3,而且转变过程伴随着粒子长大。在上述转变过程中,与Bi 5O 7NO 3向 β-Bi 2O 3转变的过程相比,从 β-Bi 2O 3到 α-Bi 2O 3相变过程更为迅速。此外,以光催化降解罗丹明B(RhB)为模型反应,考察了不同晶相的Bi 2O 3光催化活性,结果表明Bi 5O 7NO 3和 β-Bi 2O 3材料具有优异的光催化性能,而 α-Bi 2O 3具有较低的光催化活性。 相似文献
7.
F.Basile和M.A.Subramanian等人在常压高温下合成出变形的焦绿石化合物Er 2Fe 4/3W 2/3O 7,并用X射线粉末衍射法定出其结构属六方晶系。但对这种化合物的高温高压结构研究未见文献报导。我们在高压高温下进行了这种化合物的多形转变的研究。 相似文献
8.
Gas phase synthesis of methyl tert-butyl ether (MTBE) from methanol and isobutylene has been studied with several heteropolyacids at 303–383 K. It was found that a Dawson-type heteropolyacid, H 6P 2W 18O 62, was much active than Keggin-type heteropolyacids, H nXW 12O 40 (X = P, Si, Ge, B, and Co), and other solid acids such as SO 2−4/ZrO 2, SiO---Al 2O 3 and H-ZSM-5 at 323 K. Since the acid strength of H 6P 2W 18O 62 was weaker than H 3PW 12O 40 and H 4SiW 12O 40, factors other than the acid strength are important for the catalytic activity. Pseudoliquid phase behavior was demonstrated for H 6P 2W 18O 62 and H 3PW 12O 40 by the measurements of the absorption of methanol during the reaction and by the unique pressure dependencies of the rate of synthesis. From the absorption data (the amount and rate), it is concluded that the high catalytic activity of H 6P 2W 18O 62 is brought about by a high-activity state of the pseudoliquid phase in which controlled amounts of molecule are absorbed and the absorption-desorption is rapid. On the other hand, the pseudoliquid phase of H 3PW 12O 40 is in a low-activity state absorbing excessive amounts of molecule. 相似文献
9.
Three hydrated uranyl arsenates, (UO 2) 3(AsO 4) 2 · 11 H 2O, UO 2HAsO 4 · 4 H 2O, and UO 2(H 2AsO 4) 2 · 1 H 2O, have been prepared. The dehydration of these compounds has been studied by thermal analysis. Three crystalline anhydrous uranyl arsenates, (UO 2) 3(AsO 4) 2, (UO 2(AsO 3) 2, have been found. These show melting phenomena and lose arsenic oxide vapour at high temperatures to result, finally, in U 3O 8 at 1500°C in air. The anhydrous compounds have been prepared under isothermal conditions and the strongest X-ray reflections are given. A tentative phase diagram in the composition range UO 3 to As 2O 5 has been constructed. 相似文献
10.
采用高温固相法制备了La_(2.4)Mo_(1.6)O_8∶Yb~(3+),Er~(3+)荧光粉。通过X射线衍射(XRD)和上转换发射光谱对样品进行了相结构和发光性质表征。XRD实验结果表明:合成的样品为面心立方萤石结构(Fm-3m)的La_(2.4)Mo_(1.6)O_8相。在980 nm红外光激发下,La_(2.4)Mo_(1.6)O_8∶Yb~(3+),Er~(3+)荧光粉发出分别来自Er~(3+)离子的~2H1_(1/2)→~4I_(15/2)、~4S_(3/2)→~4I_(15/2)跃迁的绿光(主峰为548和529 nm)和~4F_(9/2)→~4I_(15/2)跃迁的红光(主峰为670 nm)。进一步地,对样品中可能的上转换发光机制进行了讨论。 相似文献
11.
The matrix isolation technique, combined with infrared spectroscopy and theoretical calculations, has been employed to investigate the thermal and photochemical reactions of dimethylsulfoxide (DMSO) with CrCl 2O 2 and OVCl 3. Twin jet codeposition leads to formation and isolation of a photochemically unstable 1:1 complex. The photoproduct in the twin jet DMSO + CrCl 2O 2 experiments is identified as dimethyl sulfone, (CH 3) 2SO 2, interacting with the Cl 2CrO fragment, while in the analogous OVCl 3 reaction, the photoproduct bands were too weak to allow product identification. Merged jet codeposition led to rapid gas phase reaction, and in the case of DMSO + CrCl 2O 2, dimethyl sulfone is formed in high yield. This marks the first demonstration of a gas phase thermal oxygen atom transfer from CrCl 2O 2 to an organic substrate. For the reaction of DMSO with OVCl 3, no volatile products are deposited in the matrix and dimethyl sulfone is not a product. These results support differing pathways for the reactions of CrCl 2O 2 and OVCl 3, a conclusion that is supported by density functional calculations. 相似文献
12.
High-performance solid propellants are very important for the development of modern weapons. Aside from their high energy and high burning rate, safety performance is regarded as the most important factor that should be considered whenever a new solid propellant recipe is formulated. Therefore, exploring a new type of combustion catalyst that can improve both catalytic activity and reduce the sensitivity of the energetic component is significant. Traditionally, transition metals or metal oxides are used as a combustion catalyst for accelerating the thermal decomposition of energetic components. However, the existing problem of these catalysts is the aggregation of particles accompanied by poor surface area. Coupling metal oxides with graphene is a promising approach to obtain a binary composite with stable structure and large specific surface area. In this work, rod-like and granular Fe 2O 3 nanoparticles were synthesized using a hydrothermal method. Then, the two as-prepared Fe 2O 3 nanoparticles were coupled with graphene sheets using an interfacial self-assembly method, which can effectively prevent the aggregation of Fe 2O 3 particles and simultaneously increase the active sites that participate in the reaction. X-ray diffraction and X-ray photoelectron spectroscopy were used to identify the phase states and chemical compositions of the prepared samples. The morphology and internal structures were further demonstrated through scanning electron microscopy, transmission electron microscopy and nitrogen adsorption-desorption tests. Both phase analysis and structure identification indicate that the prepared Fe 2O 3/G has high purity and high surface area. The catalytic performance of the prepared Fe 2O 3 and Fe 2O 3/G in the thermal decomposition of hexanitrohexaazaisowurtzitane (CL-20) was evaluated based on thermal gravimetric analysis-infrared spectroscopy (TGA-IR) and differential scanning calorimetry (DSC) tests. The non-isothermal decomposition kinetics of CL-20, Fe 2O 3/CL-20, and Fe 2O 3/G/CL-20 were further studied by DSC. The results reveal the excellent catalytic activity of Fe 2O 3/G in the thermal decomposition of CL-20, which is attributed to the presence of abundant pore structure and large surface area. The reaction mechanisms of the exothermic decomposition process of CL-20, Fe 2O 3/CL-20, and Fe 2O 3/G/CL-20 were obtained by the logical choice method, and the composites all followed same mechanism function model as CL-20. Through comparison, the rod-like Fe 2O 3 coupled with graphene was found to have the best catalytic activity in the thermal decomposition of CL-20. Thus, the rod-like Fe 2O 3 and its Fe 2O 3/G composite were used to investigate their influence on the impact sensitivity of CL-20 by fall hammer apparatus. The results show that rFe 2O 3/G can effectively decrease the impact sensitivity of CL-20 compared with pure CL-20 and rFe 2O 3/CL-20. Therefore, rFe 2O 3 coupled with graphene not only promotes the thermal decomposition but also improves the safety performance of CL-20. 相似文献
13.
采用灰熔点仪、X射线荧光仪(XRF)研究了无机非金属P2O5对城市污水污泥与烟煤的混烧灰熔融特性的影响,利用X射线衍射仪(XRD)、X射线光电子能谱仪(XPS)研究在各混烧温度下灰中含磷矿物在晶体和非晶体间的演变。结果表明,对于Al_2O_3含量较多且熔点较高的灰样,磷含量的增加可显著降低其灰熔点,P2O5含量在0-4%时影响最大,使其灰熔点降低126℃;但对碱性含量高的灰样的影响较小。低温灰中主要以磷酸铝(AlPO_4)晶体为主,温度升高后,与硬石膏(CaSO_4)等含钙矿物和赤铁矿(Fe_2O_3)反应生成晶体Ca_3(PO_4)_2和玻璃相(Fe_2O_3)_(0.252)(P_2O_5)_(0.748),磷含量增加可使灰中玻璃相(Fe_2O_3)_(0.252)(P_2O_5)_(0.748)增加,是磷降低灰熔点的主要原因。 相似文献
14.
Reaction of the incompletely condensed silsesquioxane derivative Cy 7Si 7O 9(OH) 3 (1) with Ti(OEt) 4 affords the dimeric titanasilsesquioxane [(Cy 7Si 7O 12)Ti(μ-OEt)(EtOH)] 2 (13) in 81% yield. The known titanasilsesquioxane [Cy 7Si 7O 11(OSiMe 3)] 2Ti (18) has been prepared through a modified procedure starting from titanium tetraalkoxides. Novel oxotitanium silsesquioxane derivatives are obtained from reactions of titanocene dihalides with Cy 7Si 7O 9(OH) 2(OSiMe 3) (14). Cp 2TiCl 2 yields dinuclear (μ-O)[{Cy 7Si 7O 11(OSiMe 3)}TiCp] 2 (19), while with Cp *2TiCl 2 the trinuclear titanacycle Cp *2Ti 3O 3[Cy 7Si 7O 11(OSiMe 3)] 2 (20) is obtained. In addition, a new synthetic route to model compounds for titanium catalysts immobilized on silica has been developed. Disilylated Cy 7Si 7O 9(OH)(OSiMe 3) 2 (15) cleanly reacts with the ‘tucked-in’ fulvene complex Cp*Ti(C 5Me 4CH 2) to give the titanium(III) silsesquioxane Cp* 2Ti[Cy 7Si 7O 10(OSiMe 3) 2] (21). In a similar manner treatment of Cp*Ti(C 5Me 4CH 2) with Cy 7Si 7O 9(OH) 2(OSiMe 3) (14) affords the mono(pentamethylcyclopentadienyl) complex Cp*Ti[Cy 7Si 7O 11(OSiMe 3)][Cy 7Si 7O 10-(OH)(OSiMe 3)] (22) which is an advanced model compound for a catalytically active titanium center on a silica surface. The molecular structures of these titanium silsesquioxane derivatives have been determined by X-ray diffraction analyses. 相似文献
15.
A series of fluorinated and one non-fluorinated β-diketonate complexes of oxovanadium IV have been prepared, their gas phase IR spectra examined, vapour pressures determined and their vapour phase thermal decomposition investigated. Decomposition of the fluorinated complexes occurred according to the overall reaction scheme VO(β-diket) 2»VOF 2 + Furanone. The furanones C 5HF 5O 2, C 5H 4F 2O 2 and C 8H 10F 2O 2 were isolated and identified. The non-fluorinated complex gave the parent diketone and a vanadium oxide as its principal products. 相似文献
16.
以N,N,N',N'-四甲基-1,6-己二胺(TMHD)为模板剂,采用水热法在Al 2O 3-P 2O 5-SiO 2体系中合成了SAPO-56分子筛.固定模板剂和水,得到Al-Si-P三元体系相图.当原料物质的量比为0.5 2)/n(M)<0.7(M=SiO2+Al2O3+P2O5),0.152O3)/n(M)<0.4及0.12O5)/n(M)<0.3时,出现SAPO-56合成的纯相区.固定合成凝胶中硅、铝、磷和水的量,模板剂的用量改变对合成影响较大.n(TMHD)/n(P2O5)≥2时,产物是纯SAPO-56.用XRD,SEM,IR,DTA-TG和吸附等方法研究了产物的物化性能.结果表明,SAPO-56分子筛具有较好的热稳定性(骨架坍塌温度为1150℃)和较大的水吸附量(41%).SAPO-56分子筛催化剂对甲醇转化制烯烃反应表现出了良好的催化活性和较高的C2和C3烯烃选择性. 相似文献
17.
使用TiO2、Al2O3以及TiO2-Al2O3复合载体考察了载体对磷化镍催化剂活性相和加氢脱氮性能的影响。不同钛铝原子比的TiO2-Al2O3复合载体采用原位-溶胶凝胶法制备,负载的磷化镍催化剂采用等体积浸渍法和H2原位还原法制备。以喹啉为模型化合物在固定床反应器上对催化剂的加氢脱氮性能进行评价,采用XRD、N2吸附、TEM和H2-TPR等技术对催化剂和载体进行了表征。结果表明,制成的复合载体基本保留了最初引入的γ-Al2O3的孔特征,分散在γ-Al2O3表面的TiO2以锐钛矿晶型存在。不同载体对催化剂的H2还原行为有显著影响,所形成的活性物种也不相同。Al2O3中引入TiO2可以减弱P物种和Al2O3之间的相互作用,有利于Ni2P活性相的生成和催化活性的提高。当Ti/Al的原子比为1∶8时,Ni2P/TiO2-Al2O3催化剂比Ni2P/TiO2、Ni2P/Al2O3催化剂具有更高的加氢脱氮活性。 相似文献
18.
The heat capacities of the tungsten oxides WO 3, W 20O 58, W 18O 49 and WO 2 have been measured over the temperature range 340–999 K using differential scanning calorimetry. The lower oxides were prepared by controlled reduction of WO 3 in H 2/H 2O gas atmospheres. Previous calorimetric work on WO 3 is confirmed in the temperature range 340–800 K, however, significant increases in heat capacity were observed in the range 800–999 K prior to the orthorhombic—tetragonal phase transition. W 20O 58 is shown to behave similarly to WO 3. A high temperture phase change is evident, however, this appears to be complete by 970–990 K. The measured values of heat capacity for W 18O 49 are in close agreement with estimated data for W 18O 49. There is no evidence of any phase transitions for this oxide in the temperature range studied. The heat capacity data for WO 2 confirm previous drop calorimetry measurements and give no evidence of any phase changes for WO 2 in the temperature range 340–990 K. 相似文献
19.
采用分步共沉淀法制备了不同Al 2O 3含量(0%-15% (w))的CuO/Fe 2O 3催化剂, 并进行水煤气变换反应(WGSR)评价测试. 制得的催化剂中含有复合物CuFe 2O 4, 其晶粒尺寸, 氧化还原性质和表面Cu分散通过相应表征手段加以研究. X 射线粉末衍射(XRD), 拉曼(Raman)光谱, N 2物理吸附, N 2O分解和CO 2程序升温脱附(CO 2-TPD)等表征技术说明适量Al 2O 3的加入可以促进尖晶石CuFe 2O 4发生由四方相向立方相的转变, 阻止催化剂中Cu烧结, 增大表面Cu分散, 增加弱碱性位点的数量. 此外, 采用H 2程序升温还原(H 2-TPR)技术探究改性的CuO/Fe 2O 3催化剂的还原性能. 关联结果发现, Al 2O 3掺杂在增大铜物种的耗氢量, 降低其还原温度方面起着重要的作用. 即Al 2O 3的添加促进CuO/Fe 2O 3催化剂中铜铁物种之间的协同作用. 结合活性测试和表征结果,适量的Al 2O 3 (10%(w))改性的催化剂具有较小的Cu颗粒尺寸、较大的Cu分散、较强的还原性能、较多数量的弱碱性位点, 因此具有更好的初始活性和热稳定性. 相似文献
20.
以十二磷钨杂多酸(Tungstophosphoric acid,H_3PW_(12)O_(40))为基体,分别通过普通浸渍法、溶胶凝胶法和超声浸渍法进行了La3+改性作用,合成了三种固体酸催化剂A-LaPW_(12)O_(40)、B-LaPW_(12)O_(40)/Si O2和C-LaPW_(12)O_(40)。采用X射线荧光光谱(XRF)、孔径比表面积测定、X射线粉末衍射(XRD)、透射电镜(TEM)、红外光谱(FT-IR)、热重(TG)、N2吸附-脱附、NH3程序升温脱附(NH3-TPD)、吡啶吸附红外光谱(Py-FTIR)、X射线光电子能谱(XPS)等方法对合成的催化剂进行了表征,并比较了以上催化剂在用于催化以油酸和甲醇为反应物经酯化反应合成生物柴油时的活性和稳定性。结果表明,B-LaPW_(12)O_(40)/Si O2具有最高催化活性,当甲醇与油酸的物质的量比为8∶1,催化剂用量为反应物总质量的2%,反应温度为65℃,反应1 h后,油酸的转化率即高达93%。循环使用B-LaPW_(12)O_(40)/Si O2催化剂六次后,油酸的转化率仍高达86.4%。B-LaPW_(12)O_(40)/Si O2的高催化活性和稳定性可归因于在溶胶凝胶的转化过程中,作为硅源材料的四乙氧基硅(TEOS)易在酸性条件下发生水解反应形成Si O2网络,进而Si O2网络中的硅醇键与H_3PW_(12)O_(40)中的H+发生配位作用,生成具有强静电吸附力的(≡Si-OH2+)(H2PW12O-40)络合物。随着该络合物的形成,促进了La3+在Si O2表面的吸附而堵塞了H_3PW_(12)O_(40)的孔道结构,抑制了H_3PW_(12)O_(40)颗粒在焙烧过程中进一步聚集长大。Si O2将作为载体并以干凝胶状态存在于B-LaPW_(12)O_(40)/Si O2催化剂中,由于Si O2凝胶的高比表面积而使B-LaPW_(12)O_(40)/Si O2具有了较大的比表面积,从H_3PW_(12)O_(40)的1.4 m2/g增加至31.3 m2/g。并且,通过吡啶吸附红外光谱确定B-LaPW_(12)O_(40)/Si O2为Br9nsted-Lewis酸型固体酸,由于Br9nsted酸位易与酯化反应过程中生成的水发生水合反应而失活,因而Lewis酸位的形成有助于减少催化剂的失活现象发生。Lewis酸位的出现可归因于(≡Si-OH2+)(H2PW12O-40)与吸附在其表面的具有强吸电子作用的La3+发生键合作用后生成了LaPW_(12)O_(40)/Si O2。 相似文献
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