MoSi2对尖晶石制品烧结性能的影响

在尖晶石材料中分别加入3%、5%和10%的MoSi2细粉,分别在1000℃、1200℃、1500℃下烧成,研究了MoSi2对尖晶石材料烧结性能的影响.结果表明(1)在不合镁砂细粉的尖晶石试样中,添加剂MoSi2易发生氧化,生成膨胀系数较大的MoO3,试样容易破碎;(2)同时添加MoSi2和镁砂细粉的尖晶石试样能在较低温度下开始烧结,在1200℃下能达到一定程度的烧结,发生的反应方程式为2MoSi2+7O2+2MgO=2MgMoO4+4SiO2,但MgMoO4在＞1200℃时不稳定,易与Al2O3发生反应,反应方程式为MgMoO4+Al2O3=MoO3+MgAl2O4;(3)过多MoSi2细粉的加入会引起试样较大的体积膨胀.     

矾土基电熔尖晶石对矾土基浇注料性能的影响

为了开发矾土基电熔尖晶石的应用,在矾土骨料、纯铝酸钙水泥、Al2O3微粉、SiO2微粉等原料加入量不变(分别为65%、4%、4%和1%)的条件下,变化矾土基电熔尖晶石的加入量(分别为0、6%、8%、10%和12%)和电熔白刚玉细粉的加入量,研究了矾土基电熔尖晶石对矾土基浇注料常温物理性能、热态抗折强度、抗热震性以及抗渣性的影响。结果表明,与不加矾土基电熔尖晶石的浇注料相比,尖晶石加入量为6%~12%时,浇注料的常温性能相差不大,但热态抗折强度及抗热震性均有所提高,抗渣性有很大改善。     

烧结尖晶石细粉加入量对刚玉-尖晶石浇注料性能的影响

为了改善刚玉-尖晶石浇注料的高温性能,以质量分数分别为10%的15~8 mm的白刚玉、58%的≤8 mm的白刚玉、5%的≤0.08 mm的白刚玉、14%的≤0.045 mm的白刚玉、9%的α-Al2O3微粉、4%的水泥制备了刚玉-尖晶石浇注料。在固定以5%(w)的≤0.048 mm的烧结尖晶石等量替代≤0.045 mm的白刚玉基础上,研究≤0.038 mm的烧结尖晶石等量替代≤0.045 mm的白刚玉的加入量(质量分数分别为1%、3%、5%和7%)对刚玉-尖晶石浇注料性能的影响。结果表明:烧结尖晶石细粉的添加可以改善材料的高温抗折强度和抗热震性能,并且在≤0.038 mm的烧结尖晶石细粉加入量为5%(w)时,试样的高温抗折强度最高,抗热震性最好。分析认为,刚玉在烧结尖晶石细粉中的固溶作用,对试样的高温性能影响较大。     

水泥含量对高纯铝尖晶石自流浇注料性能的影响

以致密刚玉和尖晶石为主要原料,铝镁尖晶石的含量为19%,在颗粒组成(5～0 mm)不变的情况下,研究了水泥含量分别为3%、8%和13%对高纯铝尖晶石自流浇注料性能的影响.结果显示1)随着水泥含量的增加,浇注料的加水量、干燥后致密度和强度均增加,但烧后致密度和强度都下降;2)水泥含量的变化对自流浇注料热态强度的影响不明显;3)随着水泥含量的增加,自流料烧后线变化增加,但水泥含量达到8%以后变化不明显;4)对于LF精炼炉渣,不管水泥的含量多少,自流料都不被渗透,但随水泥含量增加,自流料的抗熔蚀性变差;5)对于转炉钢包渣,随着水泥含量的增加,自流料的抗渗透性增强,抗熔蚀性变差,而渗透与熔蚀量之和减少;6)对于转炉末期渣,随着水泥含量增加,浇注料的抗渗透性增强,抗熔蚀性变差;7)应用相图分析了铝尖晶石浇注料的侵蚀机理,认为渣中Fe2O3或低熔点相CF的增加是渣渗透的主要原因.     

Influence of A‐site nonstoichiometry on the electrical properties of BT‐BMT

A stoichiometric and 2 mol% Ba deficient samples in the formulation 0.5BaTiO₃‐0.5BiMg_1/2Ti_1/2O₃ (BT‐BMT) were processed via a mixed oxide solid‐state route. The deficient sample exhibited a high relative permittivity (2100±15%) over the temperature range 90‐450°C and a low dielectric loss (tanδ < 0.01), maintained up to high temperature (430°C). The samples exhibited intrinsic conduction mechanism and showed an n‐type character. By introducing 2 mol% Ba vacancies, a dramatic influence on the dielectric loss was observed which was mainly associated with the trapping of electrons by barium‐oxygen vacancy pair associated with the intentionally produced cation vacancies. Thus, control of composition by creating deficiency allows fine tuning of the dielectric properties of BT‐BMT ceramics for applications in high‐temperature multilayered ceramic capacitors.     

Influence of doping on magnetic and electromagnetic properties of spinel ferrites

In this study, spinel Ni_0.5Zn_0.5Fe₂O₄ doped with transition metal ions as well as rare-earth ions Ni_0.4Zn_0.4M′_0.2Fe₂O₄ (M′ = Cu, Dy, Gd and Lu) and M″_0.5Zn_0.5Fe₂O₄ (M″ = Ni, Mn and Co) are developed using the sol-gel auto-combustion route, and the role of substitution on electromagnetic properties is investigated. The powder X-ray diffraction accompanied by Rietveld refinement signifies a single-phase spinel ferrite that belongs to Fd-3m space group for all the compositions. Rietveld refinement confirms that doped Cu²⁺, Dy³⁺, Gd³⁺ and Lu³⁺ ions are at random distribution between spinel tetrahedral and spinel octahedral sites against their preferential occupancy. The saturation magnetisation (M_S) of Ni_0.5Zn_0.5Fe₂O₄ (M_S = 50.5 emu/g) increased with partial doping showing M_S = 60.08 emu/g for transition-metal doped Ni_0.4Zn_0.4Cu_0.2Fe₂O₄ and M_S = 109.7 emu/g for rare-earth doped Ni_0.4Zn_0.4Dy_0.2Fe₂O₄, which was the highest among all the doped compositions. Doping enhances the dielectric permittivity of Ni_0.5Zn_0.5Fe₂O₄ from 4.2 to 6.5 for Ni_0.4Zn_0.4Cu_0.2Fe₂O₄ and 7.7 for Ni_0.4Zn_0.4Dy_0.2Fe₂O₄. Further, the reflection coefficient (R_L) of all the doped compositions of Ni_0.4Zn_0.4M′_0.2Fe₂O₄ (M′ = Cu, Dy, Gd and Lu) was less than −8 dB (85% absorption) throughout the frequency band of 8–12 GHz with an optimum material thickness of 3.5 mm. Transition metal ion doped Ni_0.4Zn_0.4Cu_0.2Fe₂O₄ resulted in further improvement of its absorption characteristics of the incident EM waves with reflection coefficient (R_L) less than −10 dB (between 84.15% and 90%) between 10 and 12 GHz at a material thickness of 3.5 mm in the X-band frequency range.     

Influence of inverse spinel structured CuGa2O4 on microwave dielectric properties of normal spinel ZnGa2O4 ceramics

Spinel Zn_1‐xCu_xGa₂O₄ (x = 0‐0.15) ceramics were prepared by the conventional solid‐state method. Only a single phase was indexed in all samples. The continuous lattice contraction of ZnGa₂O₄ unit cell was caused by Cu²⁺ substitution, and the lattice parameter shows a linear correlation with the content of Cu. The refined crystal structure parameters suggest that Cu²⁺ preferentially occupies the octahedron site, and the degree of inversion of Zn_1‐xCu_xGa₂O₄ (x = 0‐0.15) ceramics almost equals to the content of Cu²⁺. The relative intensity of A*_1g mode in Raman spectra confirm that the degree of inversion climbed with the growing content of Cu²⁺. The experimental and theoretical dielectric constant of Zn_1‐xCu_xGa₂O₄ ceramics fit well. Zn_1‐xCu_xGa₂O₄ (x = 0.01) ceramics sintered at 1400°C for 2 h exhibited good microwave dielectric properties, with ε_r = 9.88, Q × f = 131,445 GHz, tanδ = 6.85 × 10^?5, and τ_f = ?60 ppm/°C.     

微孔富镁尖晶石对低碳MgO-C材料性能的影响

分别以微孔富镁尖晶石(5~3和3~1 mm)和电熔镁砂(5~3和3~1 mm)为粗骨料,以<1 mm的电熔镁砂为细骨料,以镁砂粉(≤0.088 mm)、鳞片石墨粉(≤0.088 mm)、金属铝粉(≤0.074 mm)为细粉,以酚醛树脂为结合剂,制备了w(C)=6%的两种低碳MgO-C材料,经220和1 500℃(埋焦炭)热处理后,测定其显气孔率、常温耐压强度、常温抗折强度、加热永久线变化率、抗热震性和抗渣性。结果表明:1)用微孔富镁尖晶石骨料取代普通低碳MgO-C材料中的部分镁砂骨料后,经220和1 500℃热处理后试样的显气孔率均比普通低碳MgO-C试样的大,体积密度均比普通低碳MgO-C试样的小;220℃固化后试样的强度比普通低碳MgO-C试样的小,但1 500℃热处理后试样的强度比普通低碳MgO-C试样的大;1 500℃热处理后试样的加热永久线变化率比普通低碳MgO-C试样的小。2)使用微孔富镁尖晶石骨料代替电熔镁砂骨料能有效提高低碳MgO-C材料的抗热震性,但对低碳MgO-C材料的抗侵蚀性不利。     

Influence of temperature on the phase inversion of chlorinated polypropylene

In this study, the maleic anhydride modified chlorinated polypropylene (MCPP) resin was emulsified by mixed ionic surfactants comprising sodium dodecyl sulfate (SDS) and sulfonated castor oil (SCO). The influence of temperature on the morphology of emulsion was studied through transitional and catastrophic inversion methods. The transitional inversion of emulsion from water‐in‐oil (W/O) to oil‐in‐water (O/W) was triggered by decreasing the temperature and the catastrophic inversion was achieved by increasing the weight fraction of water. The results of transitional and catastrophic inversion both indicated that the phase inversion of “ionic surfactant–MCPP–water” system is easier to trigger at low temperatures than at high temperatures, which could be interpreted by the thermodynamic and hydrodynamic theory. Incomplete phase inversion occurred at low temperatures when the volume of water phase was small and emulsions with small particle size and narrow particle size distribution could only be obtained at an intermediate temperature. These results are of great importance for the preparation of stable polymer emulsions in food, cosmetics and paints industry. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40325.     

无机盐对乳状液稳定性和转相的影响

在进行化学驱油尤其是表面活性剂驱油的过程中,油藏地层水中含有的无机盐离子会对表面活性剂的乳化等性能产生影响。使用0.4%（质量分数）的十二烷基苯磺酸钠（SDBS）作为乳化剂与原油制备了水包油型乳状液,通过向SDBS溶液中加入不同浓度的共13种无机盐,考察了这些无机盐对水包油型乳状液稳定性和转相的影响。实验结果表明：钠盐和钾盐均存在最佳盐质量浓度,在此质量浓度下乳状液稳定性增强,没有引发乳状液转相;二价和三价无机盐不利于乳状液的稳定,其引发乳状液发生转相的能力依次为氧化铝＞氯化铁＞氯化钡＞氯化锶＞氯化钙＞氯化镁;处于最佳盐质量浓度时,弱碱性钠盐可与SDBS产生协同效应,有利于乳状液的稳定。     

镁铝尖晶石原料组成对尖晶石隔热材料性能的影响

分别以Al2O3、MgO质量比为2.554、3.644和5.823的镁铝尖晶石粉71MA、78MA和85MA为主要原料,以聚合氯化铝和镁砂为凝胶体系,采用发泡法制备了尖晶石隔热材料,并研究了料浆性能及尖晶石隔热材料的性能和显微结构。结果表明:用上述3种粉制成的料浆71MA的黏度随时间的延长而增大,料浆78MA和85MA的黏度随时间的延长而减小;随着尖晶石原料中Al2O3含量的提高,1 700℃烧后试样的显气孔率逐渐增大,体积密度、常温耐压强度和常温抗折强度逐渐减小,烧后线收缩率逐渐减小,烧后试样中的气孔形状变得不完整,孔壁结构逐渐疏松;综合考虑料浆性能和烧后试样的性能,富铝适度(Al2O3质量分数76%~80%)的尖晶石原料较适宜采用本工艺来制备尖晶石隔热材料。     

Influence of composition and microstructure on transparency and diffusivity in ion-exchangeable spinel glass-ceramics

Ion-exchangeable, transparent spinel glass-ceramics are presented and discussed here for the first time. To retain transparency with increasing crystallinity, spinel glass-ceramics must have uniform crystallization of small (~9 nm) crystallites, not large spherulitic structures comprised of small crystallites. To obtain such a uniform microstructure, the amount of total nucleating agents (ZrO₂ + TiO₂) in the precursor glass composition must be greater than 5 mol%. With small changes in composition and significant differences in microstructure, the demarcation between transparent and opaque glass-ceramics is distinct as is the decrease in K diffusivity during ion-exchange from the transparent (14.7 microns²/h) to the opaque (11.2 microns²/h) compositions. Understanding how to retain transparency during ceramming and increase diffusivity during chemical strengthening is critical in designing materials for many real-world applications. Ion-exchangeable, transparent spinel glass-ceramics are presented and discussed here for the first time. To retain transparency with increasing crystallinity, spinel glass-ceramics must have uniform crystallization of small (~9 nm) crystallites, not large spherulitic structures comprised of small crystallites. To obtain such a uniform microstructure, the amount of total nucleating agents (ZrO₂ + TiO₂) in the precursor glass composition must be greater than 5 mol%. With small changes in composition and significant differences in microstructure, the demarcation between transparent and opaque glass-ceramics is distinct as is the decrease in K diffusivity during ion-exchange from the transparent (14.7 microns²/h) to the opaque (11.2 microns²/h) compositions. Understanding how to retain transparency during ceramming and increase diffusivity during chemical strengthening is critical in designing materials for many real-world applications.     

Influence of processing route on microstructure and mechanical properties of MgAl2O4 spinel

This paper reports on process dependant microstructural and mechanical properties of MgAl₂O₄ spinel (MAS) ceramics. Two MAS powders with different chemical compositions were synthesized by solid-state reaction of alumina and calcined caustic magnesia at 1400 °C for 1 h. The surface of the as obtained MAS powders was passivated against hydrolysis by coating it with H₃PO₄ and Al(H₂PO₄)₃ species dissolved in ethanol at 80 °C for 24 h. The as protected powders could then be dispersed in aqueous solutions of tetramethylammonium hydroxide (TMAH) and Duramax D-3005 as dispersing agents to obtain stable slurries with 45 vol.% solids loading. The stable aqueous MAS slurries were consolidated by slip casting (SC), gelcasting (GC), hydrolysis assisted solidification (HAS) and hydrolysis induced aqueous gelcasting (GCHAS) routes, fully dried and then sintered for 1 h at 1650 °C. For comparison purposes, dense MAS ceramics were also prepared following a conventional dry-powder pressing (DP) and temperature induced gelation (TIG) routes. All the sintered MAS ceramics were thoroughly characterized for bulk density, apparent porosity, water absorption capacity, SEM microstructure, XRD phase, hardness, 3-point bend strength, and percentage of shrinkage to evaluate the suitability of the processing routes for fabricating defect free components with near-net shape. Among the various techniques employed, the GCHAS was found to be best for fabricating near-net shape MAS ceramics.     

镁铝尖晶石对铝钛渣合成钛酸铝的影响

为降低合成钛酸铝材料的原料成本,以铁合金厂铝钛渣为主要原料,按71.5%(w)铝钛渣和28.5%(w)二氧化钛粉的基础配方,分别外加质量分数1%、2%、3%和4%的添加剂镁铝尖晶石,以聚乙烯醇溶液为结合剂,经湿磨、干燥、机压成型后,分别在1 400、1 450和1 500℃保温2 h合成了钛酸铝材料,然后检测其体积密度和显气孔率,运用XRD和SEM分析物相组成和显微结构,并运用X’Pert Plus软件计算钛酸铝的晶格常数。结果表明:镁铝尖晶石中Mg2+对钛酸铝中Ti4+的置换作用导致钛酸铝的晶格常数增大,晶格发生畸变,从而促进钛酸铝的合成及其烧结;随着合成温度的升高,上述置换作用和促进钛酸铝合成、烧结的效应增强。     

Hyperdense refractories based on magnesia spinel

Conclusions A technology was developed for making hyperdense spinel-based refractories without preliminary synthesis of the spinel.A study of the properties of the refractories showed that in addition to high mechanical properties (_comp=1500–2430 kg/cm², refractoriness under load of about 1800°C), they possessed adequate thermal shock resistance (6–9 air-heat cycles from 1300°C), and a high resistance to the action of alkalis such as caustic soda, sodium adipates, sulfates and sulfides of sodium, which means that they can be recommended for use in conditions subject to the intensive action of these agents.Translated from Ogneupory, No. 8, pp. 34–41, August, 1972.     

Nano-indentation on nickel aluminate spinel and the influence of acid and alkaline attacks on the spinel surface

Nickel aluminate spinel phase was successfully sintered from the thermal reactions between nickel oxide and kaolinite or γ-alumina precursor, to simulate the stabilization mechanism of hazardous metal-bearing waste by ceramic matrix. The product phases were then tested using nano-indentation to obtain their nanohardness and Young's modulus, as a means to evaluate the properties of the product after incorporating the waste material. The results indicate the beneficial effect of forming aluminate spinel phase in the system due to its superior mechanical properties. A higher sintering temperature was found to enhance crystal growth in the spinel phase, together with its nanohardness and modulus. The minimum temperature for fabricating nickel aluminate spinel with a surface property comparable to ceramic materials was found to be 1200 °C, although the initiation of the spinel phase can be achieved at a lower temperature. Nano-indentation experiments performed on the spinel-containing samples leached by strong acid and alkaline solutions reveal the superiority of nickel aluminate spinel in resisting acid and alkaline attack and also suggest a reliable mechanism for hosting hazardous nickel in the crystal structure.