共查询到20条相似文献,搜索用时 15 毫秒
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用DTA法和XRD法研究了粒度为63~74μm的硫钨酸铵在氢气中的热分解机理,用Kissinger法、Freeman-Carol法和Coast-Redfern法测得硫钨酸铵热分解反应三个阶段的活化能分别为(53±0.5),(127±0.5),(300±0.8)kJ/mol,反应级数分别为0.8,0.6,1.5.硫钨酸铵在氢气中的热分解分四步进行,即(NH4)2WS4·H2Os→(NH4)2WO4(s)+H2O(g)→WS2(s)+2NH3(g)+H2(g)+2S(1)+H2O(g)→WS2(s)+2NH3(g)+2H2S(g)+H2O(g)→WS2(s)+W(s)+2NH3(g)+2H2S(g)+H2 相似文献
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A computational model for Lagrangian particle tracking for studying dispersion and deposition of particles in a combustor with swirling flow and chemical reaction is developed. The model accounts for the effect of thermophoretic force, as well as the drag and lift forces acting on particles, in addition to the Brownian motion and gravitational sedimentation effects. The mean turbulent gas flow, temperature fields and chemical species concentration in the combustor are evaluated using the stress transport turbulent model of the FLUENT code. The instantaneous fluctuation velocity field is generated by a Gaussian filtered white noise model.
The simulated axial, radial and tangential mean gas velocities are compared with the existing experimental data. Ensembles of particle trajectories are generated and statistically analyzed. The effects of size and initial distribution on particle dispersion and deposition are studied. The particle concentration at different sections are also evaluated and discussed. The results shows that the turbulence dispersion effect is quite important, while the thermophoresis effect is small. 相似文献
The simulated axial, radial and tangential mean gas velocities are compared with the existing experimental data. Ensembles of particle trajectories are generated and statistically analyzed. The effects of size and initial distribution on particle dispersion and deposition are studied. The particle concentration at different sections are also evaluated and discussed. The results shows that the turbulence dispersion effect is quite important, while the thermophoresis effect is small. 相似文献
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Experiments were performed to grind scrap tire peels into fine powders in the cryogenic grinding process. The temperature distribution within a scrap tire peel was calculated by a numerical method of transient heat transfer. The optimal temperature of the compressed air in the vortex mill was also found by experiments and compared with calculated results. Calculations were in good agreements with the corresponding experimental data. The proposed calculating method may be applied in the design of the cryogenic grinding process for recovering the cold-energy stored in the fine powders. 相似文献
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Suspensions of fine particles in either Newtonian or non-Newtonian fluids are often encountered in the physical, engineering, and biological sciences. For example, the manufacture of particle-laden products such as reinforced composites, paints, paper, slurries, and cements involves the processing of particle suspensions. Fine particles become difficult to suspend due to interparticle attraction forces like ver der Waals, capillary, and cohesive forces, which are responsible for converting fine particles into aggregates. These aggregates prevent the particles from being suspended uniformly, hence external forces are essential to break these aggregates. External forces include magnetic fields, electrical fields, acoustic fields, and mechanical vibration, which are useful to break aggregates and suspend particle uniformly. This process is termed homogeneous fluidization. This article presents a comprehensive review of sound-assisted fluidized beds for group C, A, and B and binary materials. Furthermore, this review covers the effect of acoustic field intensity and frequency on minimum fluidization velocity and on bubbling. 相似文献
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氧化铁超微粉相变过程研究 总被引:20,自引:0,他引:20
对用低温PCVD方法制备的氧化铁超微粉从初始生成态到800℃退火后不同阶段的晶化和相变过程进行了较系统的研究。结果表明,初始生成物为β-Fe2O3,退火后逐渐转变为γ-Fe2O3,继而转变为α-F32O3,到800℃形成单一的α-Fe2O3,这些相变和晶化过程是一种缓慢的渐变过程。 相似文献
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本文主要探讨添加不同含量硅微粉对堇青石窑具多晶结构和性能影响,用以说明超细硅微粉能促进固相反应和坯体烧结的依据,从中确定硅微粉适宜的添加量,有助于选择堇青石窑具的较好配方。 相似文献
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溶胶-凝胶法合成PLZT微细粉末 总被引:7,自引:0,他引:7
以金属异丙醇盐为原料,用溶胶-凝胶法令成了PLZT(La/Zr/Ti为9/65/35)微细粉末。研究了pH值、溶剂、干燥过程等工艺条件对胶凝时间和凝胶性能的影响。通过X射线衍射分析,热重及差热分析,研究了由凝胶至PLZT粉末的转变过程以及凝胶结构和焙烧温度对PLZT粉末性能的影响。实验证明,约在520℃凝胶转变为PLZT固溶体;在550℃下焙烧制备的PLZT粉末粒径小于0.2μm。 相似文献
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废瓷粉在日用细瓷釉中的应用 总被引:1,自引:0,他引:1
在日用细瓷釉中大量引入废瓷粉,研究表明,在1350℃左右烧成的废瓷粉的最佳用量为40-50%,且可以改善日用细瓷釉的性质,提高釉面质量。 相似文献
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自蔓延高温合成细晶六硼化钙陶瓷粉末(英文) 总被引:1,自引:1,他引:0
基于Mg–B2O3–CaO原料体系,采用自蔓延高温合成(self-propagating high-temperature synthesis,SHS)和后期酸处理工艺,制备出高纯度、均匀分布、小粒径的立方晶型细晶六硼化钙粉末。分析了Mg–B2O3–CaO自蔓延高温反应体系的燃烧产物成分及反应机理,测量了不同SHS反应物原始坯体成型压力的燃烧温度曲线,探讨了不同镁掺量和不同气氛对燃烧产物成分和形貌的影响。研究了原始坯体成型压力与最终CaB6产物粒径的关系。结果表明:采用氩气保护能抑制镁挥发;合适的原始坯体压力有利于合成分布均匀的细晶CaB6粉末。 相似文献
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E.J. DERHUN J.T. MULVALE THOMAS Z. FAHIDY† 《Chemical Engineering Communications》2013,200(3-6):299-312
An algebraic method of establishing stability conditions in the case of single-metal deposition and the co-deposition of two metals in an electrolytic reactor is presented. The total energy method and Krasovskii's theorem are employed for the construction of appropriate Liapunov functions. 相似文献
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氧化锆粉料中团聚体的结构与强度 总被引:4,自引:1,他引:4
用共沉淀法经不同温度煅烧,制得不同团聚程度的4种含2.5mol%Y2O3的氧化锆粉料。在不同力下等静压成型。用压汞测孔法测定了成型体内孔隙分布。根据孔隙分布由二级分布转变为单级分布来估计粉体中团聚体的强度。实验数据表明:粉料中团聚体强度同煅烧温度有关,并存在团聚强度最低的煅烧温度。 相似文献
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The deposition of particles under the influence of gravity and adhesive interactions with the other deposited particles is examined using computer simulation. A parameter, s, that represents the probability of adhesion or sticking is used for studying the effects of variations in sticking on the resulting microstructure. A range of packing structures is generated between two limiting cases representing complete restructuring (s = 0) and no restructuring (s = 1). The bulk properties of the resulting structures, such as packing density, particle number density, and coordination number, are obtained. Structural correlations are examined through contact networks, radial and angular distribution functions, and diffraction patterns. The results show that local sticking rules have a significant influence on the long-range structure. Rhombic domains and significant long-range correlations are observed for the case of zero sticking probability. The range of correlations drops very sharply with increases in sticking probability, and large elongated voids, oriented in the direction of the external field, are formed with further increases in s. In the limit of perfect sticking, the deposit becomes columnar. The results have important implications to the structure of particle compacts and its influence on sintering of such compacts. 相似文献
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悬浮液粉体含量对电泳沉积羟基磷灰石涂层的影响 总被引:1,自引:0,他引:1
从不同羟基磷灰石(hydroxyapatite,HA)粉体含量的悬浮液中,在钛表面电泳沉积HA涂层.采用扫描电镜、X射线衍射表征涂层的微观形貌及物相组成,通过黏结-拉伸实验测定涂层与基底的结合强度.结果表明:提高悬浮液的HA粉体含量,有助于提高电泳沉积HA涂层的致密性,改善其烧结性能,提高烧结致密化程度;HA涂层致密性的提高,有效地抑制了钛基底表面氧化反应,改善了涂层与基底的界面结合状态,使HA涂层与钛基底的结合强度从悬浮液HA粉体含量为5g/L时的4.54MPa,提高到悬浮液HA粉体含量为20g/L时的19.92MPa. 相似文献
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水热条件下钛酸钡粉体晶粒形成机理 总被引:15,自引:0,他引:15
以圩采用加直流电场水热法制备的BaTiO3粉体体系,测定了反应过程中外直流电场电流和反应反溶液中残 OHJ一。水热反应初期,电流随着反应温度的升高而增大,反应继续进行,电流达到极大值,然后急剧减小。反应温度越高,反应时间越长,反应后溶液里残留的OH量越少。结合粉体物相和晶粒形貌的表征,对水热条件下BaTiO3晶粒的形成机量进行了探讨。在反应初期,随着温度的升高驱物逐渐溶解,体系中导电离子数不断增多 相似文献