铝酸钠溶液种分产品粒数分布的数值模拟

为优化铝酸钠溶液种分过程各工艺参数以达到所需产品的粒度分布,采用对数正态分布函数对铝酸钠溶液种分产品粒度分布进行拟合,构建可计算分解过程中粒子总数及各粒径范围内粒数分布的数学模型,并以几何级数方式划分粒径范围进行计算分析.结果表明,初始晶种粒度分布及比表面积大小是影响分解机理及产物粒度组成的重要参数;使用粗晶种时,溶液分解初期主要由二次成核机制控制,而分解后期种分过程是在附聚和晶体长大共同作用下进行的,分解率较低,易细化;初始晶种较细时,种分过程由附聚和晶体长大机制共同控制,分解率提高但所获产品粒度较细.     

氨气法制备氢氧化镁的研究

以硼镁肥精制液硫酸镁为原料,通过氨气法制备花瓣状氢氧化镁.研究搅拌速度、反应温度、氨气流量等因素对氢氧化镁粒径形貌的影响.采用X射线衍射仪（XRD）、扫描电镜（SEM）和激光粒度分布仪等对MH（Mg（OH）2）粉体的晶型、粒度、形貌进行表征.实验结果表明：在大流量氨气条件下,氨气流量为8 333 mL/min时,产品的表观粒径随合成温度的升高而减小.反应温度45℃,氨气流量80 mL/min时,氢氧化镁形貌一致,分散性良好,容易过滤,其产率在80.1%左右.     

均匀橄榄状α-Fe_2O_3胶体粒子成长的动力学分析

本文对硝酸铁的酸性溶液当存在少量草酸时升温水解而生成均匀橄榄状α—Fe_2O_3胶体粒子的动力学进行了分析。按照 Nielsen 时矩(Chronomal)理论,晶体的成长过程符合二级多核层表面反应控制机理,并由此求出速度常数。计算的表面控制过程的活化能值表明,草酸参与了三价铁离子的络合过程。     

阴离子表面活性剂强化铝酸钠溶液种分过程的SEM研究

目的在铝酸钠溶液晶种分解过程中，加入适量的表面活性剂能够强化分解过程，提高分解产物氢氧化铝的粒度和强度．研究表面活性剂强化铝酸钠溶液晶种分解过程的微观作用机理．方法借助扫描电镜分析了种分过程中氢氧化铝晶体的生长．结果加入脂肪酸型阴离子表面活性剂Ⅰ后，晶粒在分解前期急剧增大；脂肪酸型阴离子表面活性剂Ⅰ在试验条件下可以促进某些大颗粒间的附聚．结论分解最终得到的产物粒度与空白样相比明显增大，晶体表面比空白样的晶体表面圆滑致密，因此加入脂肪酸型阴离子表面活性剂后产品的粒度和强度都得到了提高．     

二氧化硫液相浸取低品位软锰矿的动力学

研究了液相中二氧化硫对低品位软锰矿的浸出行为。考察了液相搅拌转速、温度、二氧化硫浓度及pH对锰浸出率的影响,研究了软锰矿粒径及表面元素相对含量随锰浸出率的变化,并对其浸出的动力学模型进行了分析。实验结果表明,搅拌转速为400r/min时可消除外扩散对锰浸出率的影响。锰浸出率随温度、二氧化硫浓度的升高而增大,随pH的增大而减小。当锰浸出率为80%时,软锰矿粒径减小约20%,表面锰含量减小73%,硅元素含量增大18%。动力学研究结果表明,软锰矿的浸出过程为扩散-化学反应混合控制过程,反应的活化能为36.85KJ/mol,二氧化硫浓度、氢离子反应级数分别为1.5595和0.5884。     

硫酸钾晶体生长速率的研究(Ⅰ)

采用流化床对硫酸钾晶体生长速率进行研究。实验表明：硫酸钾晶体生长线速率随溶液过饱和度、粒径增大而加快，与流速关系不大。硫酸钾结晶过程在实验研究范围内，属于表面反应控制。添加剂的加入不但影响晶体的生长速率，还影响其晶习。     

Microstructural evolution and mechanism of grain growth in magnesia ceramics prepared by high pressure and temperature with ultra-high heating rate

The fast densification method of combustion reaction plus quick pressing was adopted to prepare nanocrystalline ceramics.The densification process of magnesia compact with a particle size of 100 nm was investigated,under the applied pressure of up to 170 MPa,and the temperature range of 1740–2080 K with ultra-high heating rate(above 1700 K/min).High-purity magnesia ceramics with a relative density of 98.8%and an average grain size of 120 nm was obtained at 1740 K,and the grain growth during the densification process was effectively restrained.The characteristic morphology of evaporation-condensation was observed in the compact prepared at 2080 K,which revealed the actual process of mass transfer by gas diffusion.Moreover,the investigation on the microstructure evolution and mechanism of grain growth was carried out,on the basis of as-preserved nanocrystalline ceramics.The result indicated that the grain growth of the nanocrystalline MgO was controlled by the mechanism of evaporation-condensation rather than surface diffusion.Furthermore,the pressure had an influence of restraining the grain growth based on solid diffusion and strengthening the effect of gas diffusion with the increasing temperature.Under the particular conditions,there existed an appropriate temperature for the densification of nanocrystalline magnesia,while the excessive temperature would exaggerate grain growth and impede densification.     

复配菌对含蜡原油含蜡量及其黏度作用分析

微生物能改善含蜡原油的流动性,提高运输效率。将已培养的枯草芽孢杆菌6#和铜绿假单胞菌3#按2∶3的体积比复配培养,并优化其生长条件。采用DSC、偏光显微镜、HAKEE流变仪和界面张力仪对复配菌与含蜡原油的作用效果进行分析。经复配菌处理后,含蜡原油的析蜡点降低了2.23 ℃,析蜡高峰点降低了2.71 ℃,原油含蜡量（原油中蜡质量分数）降低51.64%;蜡晶结构发生了明显变化;37 ℃下测得原油表观黏度降低了64.72%;复配菌对液体石蜡的乳化指数为55.39%,液体石蜡培养基的表面张力从79.89 mN/m 降低至38.83 mN/m。与单菌相比,复配菌在除蜡降黏方面效果更为优异,应用前景更为广阔。     

亚磷酸钠的生产工艺及结晶动力学研究

采用酸碱中和法制备亚磷酸钠并利用间歇动态法对亚磷酸钠的结晶动力学进行研究. 借助电位滴定法分析亚磷酸中和过程的跃迁点,确定产物主要为亚磷酸氢二钠. 探讨了中和反应温度、摩尔比和亚磷酸浓度等因素对反应产物的影响. 利用激光粒度分析仪测试产品的粒度体积分数,根据粒数衡算和质量衡算关系经矩量变换法回归得到动力学方程,并探索影响产物晶体粒径的因素. 结果表明:亚磷酸氢二钠生成的优化工艺为控制亚磷酸和氢氧化钠的摩尔比为1∶2,亚磷酸的浓度应控制在8.54 mol/L以下,反应温度对其影响很小;亚磷酸和氢氧化钠很容易形成均匀细小的亚磷酸氢二钠,当粒度大于15 μm后,其晶体的生长与粒度无关,获得了亚磷酸氢二钠成核速率方程和成长速率方程;在亚磷酸氢二钠溶液结晶过程中,在介稳区的中部偏超溶解度曲线的位置加入少量粗晶径的晶种,控制蒸发温度在150 ℃左右,在200 r/min搅拌速度下进行结晶,可以得到晶粒较大的亚磷酸氢二钠晶体.     

Precipitation and growth of titanium nitride during solidification of clean steel

With the help of solidification kinetics, precipitation and growth of TiN have been studied theoretically and the effect of cooling rate on the growth of TiN has been discussed. Through induction electric furnace experiment and electroslag remelting experiment with different cooling rates, the distribution and particle size of TiN were investigated. It is proved that the higher cooling rate is, the smaller the final size of TiN is and the more TiN particles can be found in the steel. That TiN can restrain the growth of columnar crystal and enhance the proportion of equiaxed crystals to refine solidification structure as the heterogeneous nucleation sites of 8-ferrite is confirmed preliminarily. A new method to reduce macrosegregation in continuous cast steel is provided.     

AlCl3/urea类离子液体电沉积铝

类离子液体是近年发展起来的一种新型溶剂,它不仅具有离子液体独特的物理化学性能,还具有合成简单、价格低廉等优点,在电沉积铝技术方面具有广阔的应用前景。但目前相关的作用机制还未明确,而这些对于开发类离子液体电解生产铝和电解精炼铝的新工艺又至关重要。因此,本文以三氯化铝/尿素(AlCl3/urea)类离子液体为电解质,利用电导率仪、黏度计、线性扫描伏安法、场发射电子扫描显微镜(FE-SEM)和X射线衍射仪(XRD)等测试手段研究了AlCl3/urea类离子液体的物理化学性质、铝在电解质中的电化学行为以及铝沉积产物的形貌和物相结构。系统分析AlCl3/urea摩尔比和温度对体系电导率和黏度的影响,研究温度对铝离子析出电位、铝离子还原反应过程动力学、沉积铝形貌和结构的影响规律。结果表明,相同条件下,摩尔比为1.3:1的AlCl3/urea电解质电导率最大,黏度最小,物理化学性质较为优良,且其电导活化能为19.82kJ·mol-1。研究发现升温促进了电荷迁移反应,使得金属铝的析出电位正移,交换电流密度增大,说明较高的温度有利于加快Al(III)离子在铜基体上的还原。FE-SEM结果表明温度的变化对铝沉积产物的表观形貌影响不大,均由不规则的微米块体组成,但对粒径和致密性有一定影响。XRD结果分析表明晶粒的生长方式也受到了温度的影响,但都具有(111)晶面优先取向。     

Grain growth kinetics of SnO<Subscript>2</Subscript> nanocrystals synthesized by precipitation method

Monodispersed spheroidal SnO₂ nanocrystals with the grain size of 8–30 nm were synthesized by the precipitation method using SnCl₄·5H₂O (stannic chloride hydrate) as raw materials. Differential scanning calorimetry/thermogravimetry (DSC/TG), X-ray diffraction (XRD) and transmission electron microscope (TEM) were used to characterize the structure of SnO₂ nanocrystals. The influences of the calcination temperature and time on the lattice constant, the lattice distortion and the grain size of SnO₂ nanocrystals were discussed based on the XRD results. The grain growth kinetics of SnO₂ nanocrystals during calcination process was simulated with a conventional grain growth model which only took into account of diffusion and with a new isothermal model proposed by our group, which took into account of both diffusion and surface reactions. Using conventional model, the grain growth rate constant of SnO₂ crystals is 1.55×10⁴ nm⁵/min with a pre-exponential factor of 5 and an activation energy of 108.62 kJ/mol. Compared with the convention model, the new isothermal model is more realistic in reflecting the grain growth behavior of SnO₂ nanocrystals during the calcination process. This indicates that the grain growth of SnO₂ nanocrystals is controlled by both diffusion and reaction factors, and the effect of surface reactivity on the grain growth of SnO₂ nanocrystals could not be ignored. A combined activation energy estimated with the new isothermal model is 53.46 kJ/mol.     

Effect of tetracarbon additives on gibbsite precipitation from seeded sodium aluminate liquor

Effects of tetracarbon additives, 1-butanol, 1,4-dioxane and tetrahydrofurane on gibbsite precipitation from caustic seeded sodium aluminate liquor were investigated. The additive was charged into supersaturated seeded sodium aluminate liquor, then the precipitation ratio of aluminate liquor in 10 h was evaluated and compared, and the particle size distribution of product was measured. The Mulliken atomic charge of oxygen in the additive molecule was calculated with DMo13 program. The results show that 1-butanol has little effect on gibbsite crystallization, while the precipitation ratios under the effect of 1,4-dioxane and tetrahydrofurane are 1.7% and 3.6% higher than that of the blank, respectively. The agglomeration efficiency of the product is also enhanced obviously by the addition of 1,4-dioxane and tetrahydrofurane. The precipitation ratio is inversely proportional to Mulliken atomic charge of oxygen atom, which implies that functional group in the additive molecule is involved in the gibbsite precipitation process more fundamentally than carbon chain.     

Ambient temperature desulfurizer of nano-ZnO modified with cerium

The compound nano-ZnO modified with Ce was prepared by homogeneous precipitation. IR, XRD and dynamic experiments show that the crystal size of nano-ZnO desulfurizer is decreased after being modified with Ce and its desulfurization activities are improved greatly. When calcined at 270 ℃, Ce distributes evenly on the ZnO particle surface as amorphous state oxides, and the amorphous ZnO · H2O also exists; when the calcining temperature is 570 ℃, the crystal CeO2 separates out and the amorphous structure of zinc oxide disappears, at the same time, the crystal is perfect and its size increases, but the desulfurization activities decrease. The desulfurization product of nano-ZnO modified with Ce was analyzed with XPS. The results show that the adsorption compound of HS, S and ZnS exists on the surface of the desulfurizer.     

溶胶-凝胶法合成二氧化铈纳米晶

用溶胶－凝胶法合成了不同粒径的CeO2纳米晶。XRD分析表明，不同焙烧温度下所合成的CeO2纳米晶均属于立方晶系，空间群为O^5H-FM3M。TEM分析表明，CeO2纳米粒子呈球形，粒度分布集中，粒度随焙烧温度的增加而增大。X射线线宽法计算表明，CeO2纳米粒子越小，晶格畸变越大，晶粒发育越不完整，衍射强度越低。热失重分析表明，热失重率主要受焙烧温度的影响，焙烧时间的影响很小。红外光谱分析表明，纳米CeO2比普通CeO2具有更高的表面活性。     

煤粉粒度对元宝山褐煤燃烧特性的影响

为了给实际工程应用中煤粉粒度的确定提供参考,采用热重分析的方法,研究煤粉粒度对元宝山褐煤燃烧特性的影响.对燃烧热重曲线特征参数分析表明,粒度减小,煤粉着火提前、燃尽时间缩短;粒度减小,可燃指数C和综合燃烧指数S增加,表明煤粉燃烧性能得到改善;用Coats-Redfern方法求解燃烧反应的动力学参数,燃烧反应动力学分析表明,元宝山褐煤的热天平燃烧反应为一级反应;在最大燃烧速度对应温度前后燃烧过程分成两个阶段;粒度减小,各段燃烧反应的表观活化能和质量平均表观活化能均降低.减小煤粉粒度对改善煤粉燃烧性能是有利的.     

硝酸钠晶体接触成核的形成和成长

作者采用显微摄影技术对NaNO_3-H_2O系统中的接触成核现象进行了研究,用一个NaNO_3母晶的(100)晶面靠滑动与玻片进行接触。当母晶在饱和溶液中进行接触时,没有接触核形成,但在过饱和溶液中进行接触时,却形成了接触核。这个研究结果说明,必须有一个生长的晶体表面才能形成晶核,母晶的破碎并非晶核的来源。通过连续摄影测出了晶核的成长速率。每粒单晶的成长速率均不随时间而变,但各晶体的成长速率却有所不同,并发现其成长速率受该晶核的初始尺寸及溶液过冷度(即过饱和度)所影响。用线性回归法处理实验数据,分别关联出了在相同过冷度条件下晶体成长速率与初始尺寸的关系。最后再用最小二乘法关联其在各个过冷度条件下所得的结果,得出了NaNO_3接触成核成长速率的数学模型。     

工业季戊四醇结晶成长速度

针对传统流化床结晶器中工业季戊四醇结晶成长速度低及产品质量和产率不稳定的问题,在新型撞击流结晶器中开展了工业季戊四醇结晶成长速度的研究实验,采用阿伦尼乌斯公式拟合了结晶器中结晶成长速度系数同温度之间的关系,将撞击流结晶器和传统流化床结晶器中工业季戊四醇结晶成长速度进行了对比.研究结果表明:撞击流结晶器中结晶成长速度系数高于流化床中结晶成长速度系数;撞击流结晶器和流化床结晶器中的结晶成长速度系数都随温度的升高而增大;实验结果支持撞击流中强烈的微观混合和压力波动促进结晶成长动力学过程的理论推测.     

单晶铜线材的表面氧化研究

为了解决单晶铜线材在存储过程中的氧化问题,本文通过氧化增重实验,对不同组织、不同纯度铜线材的表面氧化行为进行了研究.结果表明:温度的高低对铜线材的氧化速率起决定性作用,不同铜线材对温度的敏感程度不同.单晶铜的氧化速率低于多晶铜,纯度越高的单晶铜抗氧化性能越好.单晶铜的氧化速率与其晶粒取向有关,生长方向为<100>的单晶铜更容易氧化.铜线材的氧化速率是由Cu2O的生长速度控制的,主要因素是铜离子向外扩散的速率.低纯单晶铜和多晶铜的氧化膜均容易脱落,不能对基体起到应有的保护作用.     

Preparation of spherical cobalt carbonate powder with high tap density

1 INTRODUCTION Cobalt carbonate is an important intermediate products for preparing battery-grade Co3O4 by liquid chemical precipitation-thermal decomposition method[1?5]. The crystallization and density of cobalt carbonate have an immediate effect on electrochemistry performance of Co3O4. So, it is very important to prepare cobalt carbonate with high density and good crystallization. In the process of preparing cobalt carbonate by liquid chemical precipitation method, it is very easy to…