氟硅酸铵氨化制备纳米二氧化硅的实验研究

实验以氟硅酸铵和氨水为原料,通过化学沉淀法制备纳米二氧化硅粉体。考察了表面活性剂、反应温度、物料配比等不同工艺条件对纳米二氧化硅粉体的粒度分布、反应收率等的影响。实验结果表明:分散剂十二烷基苯磺酸钠可以有效改善粉体粒度的分布;综合考虑二氧化硅粉体的粒度、反应收率、反应效率和生产成本,确定氟硅酸铵氨化制备二氧化硅的反应温度为常温、反应时间为60 min、物料配比(氟硅酸铵与氨水物质的量比)为1∶4.8、氨水的加料速度为96 m L/min、搅拌速度为200~300 r/min。     

表面活性剂存在下四氯化硅水解制备二氧化硅

多晶硅生产中主要副产物四氯化硅副产量大、腐蚀性强、难以安全处理。笔者以四氯化硅为原料,在表面活性剂存在下制备二氧化硅。研究了物料比例、反应温度、加料速率等因素对产品比表面及产率的影响,采用红外光谱仪、X射线衍射仪、比表面积测定仪和扫描电子显微镜对晶体结构、比表面积、产品的形貌进行了表征。结果表明,采用质量浓度0.5 g/L的十二烷基苯磺酸钠(SDBS)溶液为反应底物、四氯化硅加入量为1.5 mol/L(底物)、反应温度为45℃、加料速率为0.35 mol/h,反应混合物具有较好的过滤性能,并可得到粒径分布窄的二氧化硅产品,产品收率可达80%。     

四氯化硅气相水解制备超细白炭黑工艺的研究

本文以四氯化硅为原料,采用气相水解法制备超细白炭黑新工艺.探讨了四氯化硅通气速率、硅酸钠含量及反应温度等因素对产物理化性能的影响.结果表明,较优工艺条件为四氯化硅通气速率150 mL/min,硅酸钠含量13％,反应温度70℃.该工艺条件下所得产物为无定形结构超细白炭黑,其吸油值2.57 mL/g,比表面积115.49m2/g,二氧化硅含量(干基)99.06％,表观密度0.11 g/mL,粒径(d50)6.5μm.     

撞击流反应器制取纳米钛酸钡

在浸没循环撞击流反应器中，以四氯化钛、氯化钡和草酸为原料，采用沉淀法制取纳米钛酸钡，并对产品进行了透射电子显微镜（TEM）表征。通过均匀实验设计，研究了反应温度、加料时间、反应后陈化时间及钡钛物质的量比等因素对产品粒径的影响；初步确定了制备纳米钛酸钡适宜的工艺条件为：反应温度75℃，陈化时间200min，加料时间20min，反应物中钡与钛的物质的量比1．01。制取的钛酸钡产品经TEM表征，其形状皆为球状，具有沉淀法制取的钛酸钡的典型粉体特征，在适宜工艺条件下制取的产品平均粒径为60nm。     

超级电容器电极材料二氧化锰的合成和性能研究

高锰酸钾和硫酸锰混合液,在高压反应釜内通过不同的水热时间合成了纳米级α-二氧化锰。借助X射线衍射（XRD）、扫描电镜（SEM）和比表面积（BET法）分析手段,对样品的结构和性能进行了表征。研究结果表明：水热时间为9 h的样品,扫描电镜检测结果显示,合成的粉体是纳米粉体,粒径为50～60 nm;X射线衍射检测结果表明,合成的粉体为α-二氧化锰;合成粉体的比表面积达到53.66 m2/g。以该二氧化锰为工作电极、饱和甘汞电极（SCE）为参比电极、铂丝电极为辅助电极的三电极体系中,以1 mol/L的硫酸钠溶液为电解液,通过循环伏安和计时电位法研究电化学行为,结果表明：在电位窗口为0～0.8 V（相对于饱和甘汞电极）、扫描速度为2 mV/s时,其比电容达到76 F/g,循环伏安曲线接近于矩形。     

新型阻燃剂硅酸三(2,3-二溴丙基)三溴苯酯的合成与应用

以三溴苯酚、四氯化硅及2,3-二溴丙醇为主要原料合成新型硅、溴协同高效阻燃剂硅酸三（2,3-二溴丙基）三溴苯酯(STTE),探讨了加料顺序、溶剂、反应温度、反应时间及物质的量比等对产率的影响,并采用傅里叶变换红外光谱、核磁共振谱仪和极限氧指数仪等分析手段对产物的分子结构及性能进行了表征。结果表明,使用20份STTE作为阻燃剂时,聚氯乙烯（PVC）的极限氧指数达到395 %,具有良好的增塑、成炭和防熔融滴落效果。     

超微细粉末二氧化硅的新制法

在甲苯溶剂中用正丁醇处理四氯化硅制取超微细粉末二氧化硅。产品比表面积200—700m~2/g。反应温度和四氯化硅浓度是主要影响因素。添加乙醇和水可以加速反应。     

伊利石合成磷酸硅铝分子筛及其表征

采用碱熔活化方法对伊利石进行活化,系统地考察了煅烧温度、煅烧时间、矿物粒度、矿碱质量比等条件对伊利石活化的影响;以活化伊利石为主要硅、铝源,采用水热法合成磷酸硅铝分子筛（SAPO-11）,系统地考察模板剂种类、模板剂用量、投料硅铝物质的量比、晶化温度等合成条件对产物结构和性质的影响。利用X射线衍射（XRD）、N₂吸附-脱附、扫描电镜（SEM）和透射电镜（TEM）等分析手段对活化产物和合成的分子筛进行了分析表征,结果表明,伊利石的最佳碱熔活化条件为煅烧温度为800 ℃、煅烧时间为90 min、伊利石矿粒径为75 μm、矿碱质量比为1∶0.8,经活化后伊利石的晶型结构基本完全被破坏,活化产物主要是高活性的低聚合态硅铝酸盐,化学反应活性较高;在原料配比为n（三氧化二铝）∶n（五氧化二磷）∶n（模板剂）∶n（二氧化硅）∶n（水）=1∶1∶1∶0.5∶50、水热晶化温度为190 ℃、晶化时间为24 h时成功合成结晶度较高的纯相SAPO-11分子筛,合成的SAPO-11分子筛具有较大的比表面积,样品主要由粒径为1~3 μm的椭球状颗粒组成,该合成方法丰富了磷酸硅铝（SAPO）分子筛的原料来源,拓展了中国伊利石的高附加值利用途径。     

Pechini溶胶-凝胶法制备超细二氧化硅

以乙醇和去离子水为溶剂,以正硅酸乙酯为原料,柠檬酸为络合剂,采用Pechini溶胶-凝胶法制备了超细二氧化硅粉体,采用热分析（TG-DTG、DSC）、X射线衍射（XRD）分析、傅里叶红外光谱（FT-IR）分析、场发射扫描电镜（FESEM）分析等对二氧化硅粉体制备过程中的物理化学变化进行了研究。结果表明：1 000 ℃以下煅烧所得二氧化硅粉体均为非晶相,pH影响了煅烧过程中有机物的降解燃烧;煅烧温度为500 ℃时,所得二氧化硅纳米粉体的粒径约为10 nm;煅烧温度升高至600 ℃时,粉体团聚严重,晶粒尺寸增大至20 nm。     

对二乙氨基苯甲醛合成工艺研究

探讨了用苯作溶剂,利用维斯迈尔反应（Vilsmeier）合成对二乙氨基苯甲醛的工艺,用苯代替DMF作溶剂,苯可循环利用,降低生产成本,减少环境污染.采用本法合成的产品纯度高,原料利用充分.通过正交试验,考察了原料配比、加料次序、加料速度等对反应收率的影响,得到了最佳工艺条件,为工业生产提供了可靠的依据.     

硅粉氮化输送床内气固反应过程数值模拟

以单个硅颗粒氮化反应缩核模型为基础,本文建立了硅颗粒在输送床内反应、辐射与对流传热耦合的数学模型,并借助CFD软件FLUENT对输送床内能质传输过程进行了数值模拟,分析了输送床壁面温度、氮气流量、预热温度、硅粉粒径等因素对输送床内温度场和硅粉氮化率的影响。在数值计算域内将单个颗粒反应过程转化为颗粒群整体反应过程,实时监测颗粒粒径及未反应硅颗粒粒径,为数值模拟颗粒流反应提供一种新思路。当壁面温度高于1723K时,输送床内会出现一高温区加速硅粉氮化反应;反应温度越高、颗粒粒径越小,氮化过程越剧烈,硅粉到达完全氮化所需时间越短。模型表明为使粒径为2.5μm的硅粉达到完全氮化且输送床内最高温度不超过氮化硅的分解温度2173K,应控制输送床壁面温度在1773K,氮化时间在170s以上,预热温度在1273K,粉气质量比为0.2,稀释剂比例为0.5~1。     

酸浸工艺脱除微硅粉杂质离子及其对热碱溶解过程的强化

针对热碱溶解微硅粉制备水玻璃的过程中存在Si转化率较低的问题,提出了采用酸浸预处理的方法脱除微硅粉中的金属杂质,强化其热碱溶出过程,以提高Si的转化率。本研究通过采用X射线荧光仪(XRF)、冷场发射扫描电子显微镜与能谱分析仪(SEM-EDS)、X射线衍射仪(XRD)以及滴定分析检测方法,研究了酸种类、酸浓度、反应温度、固液比、反应时间对金属杂质浸出率的影响和酸浸工艺对微硅粉热碱溶出过程的强化作用,得出适宜的酸浸条件:HCl浓度2mol/L、反应温度60℃、固液比1:(6～8)、反应时间40～60min。在碱溶出过程初期,酸浸处理后的微硅粉中SiO₂的溶出率由46.62%增至61.91%,得到了显著提高。结果表明:酸浸预处理对微硅粉的碱溶过程起到很好的强化作用,提高了Si的转化率,这将在增大微硅粉利用率的同时也有利于满足工业水玻璃[Na₂O·(2.5～3)SiO₂]对模数的要求。     

Thermodynamic,hydrodynamic, particle dynamic,and experimental analyses of silica nanoparticles synthesis in diffusion flame

Using silicon tetrachloride as a precursor, the silica nanoparticles (NPs) were synthesized in the diffusion flame of air and liquid petrol gas (LPG). Different effects on flame shape and temperature, silicon tetrachloride conversion, major gas‐phase compositions, and diameter of silica NPs were obtained via thermodynamic, hydrodynamic, or particle‐dynamic approaches. The size of silica NPs decreased with the increasing air‐flow rate, increased with the increasing LPG flow rate, and increased obviously with the increasing evaporator temperature. The size of the synthesized silica NPs is about 25–30 nm at an optimal condition.     

Effect of process parameters on the production of nanocrystalline silicon carbide from water glass

Nanocrystalline silicon carbide was synthesized from the precursor prepared by spray drying slurry of water glass and carbon black. The effect of process parameters, such as reaction temperature, reaction time and carbon content, on phase evolution, crystallite size and specific surface of the resulting samples were characterized by XRD, SEM and BET. The results show the powder produced in this process has a very fine crystallite size and high specific area and the reaction can be completed at 1550 °C for 2 h when the C/Si ratio is 5 or larger. In addition, the powder is of high purity, because sodium oxide in the precursor can be eliminated by the escape of sodium at high temperature. It is a simple and cost-efficient method to synthesize nanocrystalline silicon carbide using cheap and abundant water glass as silicon source.     

Preparation of nano-sized silicon carbide powder using thermal plasma

Nano-sized silicon carbide (SiC) powder was prepared by thermal plasma process using silicon tetrachloride (SiCl₄) and methane (CH₄). The synthesized powder was characterized by X-ray diffraction pattern, scanning electron microscopy, transmission electron microscopy, FT-IR spectroscopy and particle size analyzer. The powder was dominated by β-SiC including some of α-SiC and free carbon species. The quality of the powder was varied with process conditions such as the molar ratio of H/Si and C/Si, and collecting positions. It was known that the conversion to SiC was mainly affected by the addition of hydrogen gas because it promoted the decomposition and reduction of SiCL. CH₄ was easily decomposed to carbon species for the formation of SiC as well as removal of impure oxygen, but excessive carbon suppressed the formation of crystalline SiC and resulted in the solid carbon contamination. The optimum ratio of H/Si was approx. 26 and that of C/Si was 1.1. For collecting positions, the powder collected at the vessel and filter was preferable to that at the reaction tube. The average size of the powder synthesized was estimated to be below 100 nm and uniform in distribution.     

四氯化硅液相鼓泡法制备纳米白炭黑工艺研究

以多晶硅副产物四氯化硅为原料,氨水为中和剂,十二烷基苯磺酸钠为改性剂,在水-醇-氨体系中利用液相鼓泡法制备纳米白炭黑,并采用IR、XRD、SEM、TEM对纳米白炭黑晶体结构、形貌、分散性及粒径进行表征。研究了醇水比、氨水用量、分散剂种类及用量、双氧水加入量等因素对纳米白炭黑分散性及粒径的影响。纳米白炭黑最佳制备工艺条件：体系总体积为70 mL,V（水）∶V（醇）∶V（氨）=38∶15∶12,六偏磷酸钠加入量为1.5%（质量分数）,双氧水用量为5 mL。IR、XRD表征结果表明产品为无定形二氧化硅;SEM、TEM表征结果表明纳米白炭黑粒径约100 nm且分散较好。     

轻烧粉氨气法制备氢氧化镁阻燃剂的研究

以除硫酸根后的轻烧粉精制液为原料,氨气为沉淀剂,在无表面活性剂条件下制备阻燃剂型氢氧化镁。采用X射线衍射仪（XRD）、扫描电镜（SEM）和激光粒度仪对产品进行表征。实验研究了通氨速率、反应温度对氢氧化镁产品形貌和粒度的影响,在较优的反应温度和通氨速率条件下考察了纯晶种加入量对产品的影响。实验结果表明,在纯晶种加入量为3%（质量分数）、氨气流量为300 mL/min、沉镁温度为90 ℃为制备阻燃剂型氢氧化镁的最佳条件,在此条件下产品的粒径D50=1.2 μm,比表面积（BET）为6.3 m2/g,转化率达到81.2%。     

氟化物包覆对镁铝合金与水催化反应效率的影响

为了提高镁铝合金与水的反应效率,采用氟化物对镁铝合金粉进行表面包覆,利用扫描电镜、X射线衍射仪和粒度分析仪对合金粉与高温水反应产物进行表征,对比研究了高温下不同比例的氟化物对镁铝合金与水催化反应效率的影响。结果表明,包覆氟化物的镁铝合金与高温水反应产物的粒径减小,分散性明显改善;固相燃烧产物中主要包含Al_2MgO_4、MgO和Al,表明Al未完全反应;合金粉包覆氟化物后铝的反应效率明显提高,其中,包覆质量分数2%氟橡胶和2%有机氟化物的合金粉反应效率高达89.7%,与未包覆样品相比提高了14.6%。     

Powder metallurgy magnesium composite with magnesium silicide in using rice husk silica particles

By using the solid-state reaction of rice husk silica particles with magnesium powder, P/M magnesium based composites dispersed with the magnesium silicide (Mg₂Si) and magnesium oxide (MgO) were fabricated. High-purity silica particles were originated from rice husks, one of the major agricultural wastes, via the citric acid leaching treatment and combustion in air. The effects of the silica particle characteristics such as size, crystalline and porous structures, on the reactivity of silica and magnesium to synthesize Mg₂Si intermetallics were discussed. As the results by DTA and XRD analysis, finer silica particles were more effective for the solid-state reaction at low temperature due to the increase of their surface area contacted with magnesium powder. Amorphous silica was also more useful for this reaction than the crystalline one. The reactivity of rice husk silica was superior to that of the conventional mineral silica particles not only because of its amorphous structure but also the larger specific surface area due to their pore structures. In the case of the green compact of the elemental mixture of silica particles and Mg powder, the silica particle size was not effective on the reactivity because the coarse particles were fractured into fine ones by cold compaction. The distribution of Mg₂Si intermetallics of magnesium powder composites consolidated by SPS process was investigated by XRD and SEM-EDS analysis. When the sintering temperature was over the exothermic temperature of the mixture in the DTA profile, the synthesis of Mg₂Si completely occurred during sintering. The sinterability of the elemental mixture powder was improved when employing the amorphous rice husk silica particles. The density and hardness of their composites sintered over the ignition temperature of the DTA profile were remarkably high because of the good densification by the high reactivity and the distribution of Mg₂Si hard compounds.