沉淀法制备纳米氧化铝粉体的新工艺研究

以（NH4）2CO3为沉淀剂，并采用一种高分子分散剂，研制出沉淀法制备纳米氧化铝粉体的新工艺。制备出球形纳米氧化铝粉体，在800℃煅烧得到的颗粒尺寸为5－6nm，在1100℃煅烧得到的颗粒尺寸约为8nm。研究了沉淀pH、溶液浓度、煅烧温度和分散剂用量对纳米氧化铝粉体性能的影响。     

硅灰为原料制备类球形亚微米碳化硅粉体

以硅灰为硅源、葡萄糖为碳源制备粉体先驱体,然后经过炭化和煅烧,制备类球形亚微米碳化硅粉体。实验采用1200、1300、1400、1500℃4种温度煅烧样品,并对产物进行物相、粒度、形貌分析。结果表明:1200℃时,碳热还原反应未发生,硅灰中无定形的二氧化硅转变为结晶形态;剩余三种温度下得到的产物均是3C型碳化硅,在1400℃下能够制备出球形度良好的亚微米碳化硅粉体,其平均粒径约为0.2μm;随着煅烧温度的升高,碳化硅的结晶度增强、粒度变大、球形度变差。     

对甲苯磺酰肼为氮源制备氮掺杂二氧化钛光催化剂

以Ti（SO4）2为前驱物,尿素为沉淀剂,对甲苯磺酰肼为掺杂剂,采用水热沉淀法结合固相反应法制得了锐钛矿相掺氮纳米TiO2粉体。采用XRD对制备的掺氮氧化钛结构进行了表征,以亚甲基蓝为模拟污染物,考察了不同煅烧温度制备的光催化剂在可见光照射下的光催化性能。结果表明,煅烧温度高于120℃时氮可掺进TiO2晶体中,且温度越高,掺氮量越高;煅烧温度为180℃时,氮掺杂TiO2粉体可见光催化活性最强,在波长不低于400nm的可见光作用下,对亚甲基蓝的4h降解率达48.5％。     

沉淀-煅烧法制备锡酸镧

以La（NO）3·6H2O和Na2SnO3·3H2O为原料,分别采用直接沉淀法和氨水沉淀法在室温下制备锡酸镧 （La2Sn2O7）的前驱体产物。对直接沉淀法所得前驱体产物进行热重分析,并对该前驱体不同温度下的煅烧产物进行X射线衍射（XRD）分析,确定最佳煅烧温度为850 ℃,再在此温度下煅烧前驱体制得La2Sn2O7。XRD和扫描电子显微镜（SEM）结果表明,直接沉淀-煅烧法和氨水沉淀-煅烧法制备的La2Sn2O7均为立方晶体结构;采用氨水沉淀-煅烧法,当pH=12时和直接沉淀-煅烧法所得前驱体煅烧产物均为直径约50 nm的类球状颗粒,且颗粒之间基本无团聚。     

化学共沉淀法制备纳米铋掺杂氧化锡的影响因素研究

以SnCl4.5H2O和Bi(NO3)3.5H2O为原料,氨水为沉淀剂,采用化学共沉淀法制备了铋掺杂氧化锡（BTO）纳米粉体,研究了反应温度、滴定终点pH值、铋掺杂量,煅烧温度和分散剂PEG-600对所得的纳米BTO粉体物相、晶粒度和形貌的影响,对粉末的前驱体进行综合热分析（TG-DTA）,用X-射线衍射（XRD）,扫描电镜(SEM)对产物的结构和形貌进行表征,得到共沉淀法制备纳米BTO粉体的最佳条件：反应温度60℃,滴定终点pH值为3,煅烧温度600℃;该条件下制得BTO粉体的电阻率最小为3.48Ω•cm。     

不同煅烧温度下SiO2/TiO2复合粉体的制备与表征

实验以硅酸钠为原料制备比表面积较大的二氧化硅粉体,再以硫酸氧钛为钛源、二氧化硅为载体在一定温度、pH条件下反应制备复合粉体。探讨了不同的煅烧温度对产物的催化性能的影响,并进行了XRD、红外光谱等方面的性能表征。结果表明500℃下煅烧的催化效果最好,对活性大红染料降解率高达99.45%     

熔盐法制备氧化镁粉体及其活性研究

以MgCl2-6H2O、CaCO3和LiCl为原料,采甩熔盐法制备了MgO粉体。通过热重．差示扫描热量计（TG—DSC）、X射线衍射仪（XRD）、场发射扫描电子显微镜（SEM）等手段对反应过程及产物进行了分析和表征,同时采用水解动力学分析法研究了煅烧温度和时间对氧化镁粉体活性的影响。TG-DSC分析表明,650℃时CaCO3可完全反应;XRD分析表朝,450℃保温3h热处理,产物中有MgO生成。650℃保温3h热处理,产物经无水乙醇洗涤后,全部为MgO晶体;SEM分析表明,所制备的氧化镁形貌为颗粒状,形状不规整,大小介于50-250nm之间;水解动力学分析法表明,当温度大于500℃、保温时阕超过3h后,随着热处理温度的升高和时间的延长,MgO粉体活性下降。     

共沉淀法制备Al2O3:Eu红色荧光粉及其发光性能研究

用碳酸氢铵和氨水混合溶液作为复合沉淀剂制备了Al2O3：Eu红色荧光粉体。采用X射线衍射（XED）对粉体制备过程中的相变进行了研究。通过荧光分光光度计分析了Eu掺杂浓度和煅烧温度对Al2O3：Eu粉体发光性能的影响。研究结果表明：采用共沉淀法制备工艺，经过1050℃煅烧4h，可以得到发光强度高的荧光粉体。Eu^3＋离子的最佳掺杂浓度为1mol％，在波长为254nm紫外光激发下，最强的发射波长出现在614nm附近。     

自蔓延法制备ATO纳米导电粉体

采用溶胶-凝胶自蔓延燃烧法,制备了ATO导电粉体.利用TG-DTA对干凝胶的自蔓延燃烧过程进行分析,用XRD和SEM对制备的粉体进行了表征,研究了不同煅烧温度对粉体电阻率的影响.结果表明:干凝胶在282℃达到失重终点,失重率为79.9%.煅烧后的粉体颗粒比较均匀,导电性较好.当煅烧温度为600℃时,导电粉具有最佳导电性...     

化学共沉淀法制备纳米氧化铝粉

以分析纯的硝酸铝和碳酸氢铵为主要原料，采用共沉淀法制备纳米氧化铝粉体，研究反应物的加料顺序和加料速度、表面活性剂种类、溶剂组成、晶种及前驱体的煅烧温度对产物的影响。采用X射线衍射仪分析粉体的物相组成，用谢乐公式计算晶粒尺寸，采用透射电子显微镜观测颗粒形貌。结果表明：原料的加料顺序对产物影响不明显，用PEG6000作表面活性剂，水和乙醇等体积混合液作溶剂，Al(NO₃)₃溶液直接倒入NH₄HCO₃溶液中制得前驱体，当煅烧温度为1135℃煅烧2 h时，制备了粒径为33 nm的α-Al₂O₃粉体，加入晶种后，煅烧温度可降低至1075℃。     

高岭土原位合成高硅铝比小晶粒NaY分子筛

以不同温度焙烧的苏州高岭土为原料,采用原位晶化法合成高硅铝比小晶粒NaY分子筛,考察晶种胶添加量、陈化温度、晶化温度和m(高土)∶m(偏土)对晶化过程和产物性质的影响。结果表明,m(高土)∶m(偏土)=1时,在晶种胶添加质量分数15%、陈化温度90℃和晶化温度100℃条件下,以普通高岭土为原料原位合成NaY样品的相对结晶度约为80%,骨架硅铝比(SiO2与Al2O3物质的量比)为6.4,平均粒径约500nm。调整原料中m(高土)∶m(偏土)可以控制原位晶化样品中的分子筛含量。以细化高岭土为原料合成的NaY分子筛(平均约445nm)粒径小于普通高岭土合成的样品。骨架硅铝比高于6.0的原位晶化样品的骨架坍塌温度高于950℃,具有很高的结构稳定性。     

SiO2/g-C3N4复合粉体制备及其光催化性能

以Stöber法制备出的二氧化硅(SiO₂)微球和三聚氰胺为原料,两者按一定质量比混合后得到前驱体,通过煅烧该前驱体可成功获得SiO₂/g-C₃N₄复合粉体。利用XRD、SEM、UV-Vis和BET等表征手段对获得的复合粉体进行物相组成、形貌、可见光吸收性能以及比表面积大小等进行分析和测试。结果表明,改进的Stöber法制备出的球形SiO₂平均粒径约为200 nm,具有良好的分散性。SiO₂/g-C₃N₄复合粉体中SiO₂含量约为75%(质量分数)时,其比表面积最大,约为23.7 m²/g。同时,以罗丹明B和亚甲基蓝为目标污染物,在可见光照射下,探究了不同g-C₃N₄负载量SiO₂/g-C₃N₄复合粉体的光催化性能。结果表明,随着复合粉体中g-C₃N₄含量的降低,复合粉体的可见光催化活性反而逐渐升高,g-C₃N₄含量约为25%(质量分数)时复合粉体光催化降解罗丹明B和亚甲基蓝效果最好。原因可归结为,复合粉体的强吸附增强了可见光催化性能。     

磁性Fe3O4@SiO2@介孔SiO2空心微球的制备及漆酶固定化

磁性介孔二氧化硅复合材料作为酶固定化载体具有优异的酶固定化性能和良好的磁分离性能,受到国内外学术界广泛关注。本文在自制的β-FeOOH空心微球表面上包覆致密的SiO₂保护层,在酸性条件下以P123为模板剂,十六烷基三甲基溴化铵（CTAB）为辅助导向剂成功制备出了磁性β-FeOOH@SiO₂@介孔SiO₂空心复合微球,最后在还原气氛下煅烧得到Fe₃O₄@SiO₂@介孔SiO₂空心微球。结果表明,所制备的Fe₃O₄@SiO₂@介孔SiO₂微球空心结构未坍塌,具有规整的球形结构,介孔SiO₂壳层（平均厚度约为11nm）均匀地包覆在β-FeOOH@SiO₂中空微球表面。伴随着CTAB量的增加,微球的最可几孔径由4.30nm减小到3.19nm,比表面积从376m²/g升高到640m²/g,孔容从0.36cm³/g升高到0.56cm³/g。复合微球的饱和磁化强度为11.3emu/g,矫顽力为111.5Oe,外加磁场作用下可以实现样品的快速分离,且样品的再分散性良好。当介孔孔径为4.30nm时,Fe₃O₄@SiO₂@介孔SiO₂空心复合微球漆酶固定量高达234mg/g。固定化漆酶在不同pH、温度下的活性显著优于游离酶。     

Ti/Zr复合纳滤膜的制备及其性能

通过聚合溶胶路线制备出稳定的Ti/Zr(摩尔比=1:1)复合溶胶。采用浸浆法,在平均孔径为5～6 nm的片状a-Al₂O₃/g-Al₂O₃载体上制备出完整无缺陷的Ti/Zr复合纳滤膜。详细考察了焙烧温度对Ti/Zr粉体的影响,并考察了Ti/Zr复合纳滤膜的性能。结果表明:在较高烧成温度下(500℃),Ti/Zr粉体依然呈无定形态且保持微孔结构。在400℃烧成温度下制备出孔径为1.49 nm的Ti/Zr复合纳滤膜,该膜的截留分子量(MWCO)为880,纯水通量为4.3 L·m^-2·h^-1·MPa^-1。在pH=6,压力0.8 MPa的条件下,该膜对0.005 mol·L^-1的MgCl₂、CaCl₂的截留率分别为85%和78%。     

热处理温度对低硅含量SiO2微粉固废性能的影响

对回收的w（SiO₂）<85%的低硅含量SiO₂微粉固废进行了不同温度（400、500、600、700、800、900和1 000℃）保温5 h的热处理，并对热处理后的粉体进行了分析。结果表明：随着热处理温度升高，试样逐渐烧结。热处理温度低于800℃时，SiO₂微粉保持原有粒状、球状SiO₂颗粒团聚体结构。但热处理温度为500℃及以下时，团聚体强度较低。热处理温度800℃以上结块严重，并析出方石英相。热处理温度控制在600～800℃可制得具有一定强度，体积密度在0.73～0.95 g·cm^-3的球壳结构的球状粉体，该粉体可以作为轻质原料用在低温保温浇注料，也可以作为其他行业填料。     

用于低损耗特种玻璃熔炼的高纯致密锆英石的研制

以纯度大于99.9%(质量分数)的高纯ZrO₂和SiO₂为原料,少量TiO₂为添加剂,采用高温固相法合成高纯锆英石(ZrSiO₄)粉料。研究温度和反应时间对高纯锆英石合成效率的影响,发现粒度小于50 μm的原料粉末经1 500 ℃反应48 h后,ZrSiO₄相的含量可以达到95.77%(质量分数)。将合成的高纯锆英石粉料球磨并冷等静压成型后,在1 550 ℃高温烧结成高纯致密锆英石砖。高纯致密锆英石中杂质Fe的含量仅为29 μg/g,Cu的含量小于1 μg/g,是普通商用致密锆英石的1/10;对磷酸盐玻璃静态光吸收损耗的影响仅为普通致密锆英石材料的1/3。将这种高纯致密锆英石材料用于激光玻璃窑炉,有助于降低玻璃对1 053 nm激光的损耗,提升激光玻璃的激光性能。     

Effect of post-synthesis hydrothermal treatments on the adsorptive volume of surfactant-templated mesostructures

Ordered aluminosilicate mesostructures of the MCM-41 family having a SiO₂/Al₂O₃ ratio5 were prepared using cetyltrimethylammonium chloride. These mesophases were subsequently exposed to a hydrothermal treatment (110°C for one week at autogeneous pressure). The effects of the hydrothermal treatment were documented by analyzing the samples before and after the treatments by scanning electron microscopy, N₂ sorption for pore volume and pore sizes, powder X-ray diffraction and solid-state, magic-angle-spinning (MAS)-NMR spectroscopy for the ²⁷Al and ²⁹Si nuclei. The post-synthesis hydrothermal treatment increased the mesostructure adsorptive volume by as much as 55% in mesostructures prepared from Na-aluminate (from 0.29 to 0.45 ml/g) and 27% in mesostructures prepared from Al-hydroxide (from 0.44 to 0.56 ml/g) while the average pore diameter remained essentially unchanged.

The post-synthesis hydrothermal treatment caused only small changes in the SiO₂/Al₂O₃ ratio when the source of the aluminum ion was Al-hydroxide (6.4–6.6) and Na-aluminate (5.6–5.8). The crystal symmetry did not change after successive treatments, the unit cell size of the samples prepared from Al-hydroxide increased slightly (5.5–5.7 nm) and the peak width at mid-height changed very little. The mesophases prepared from either source of aluminum showed tetrahedral (T_d) symmetry, as confirmed by ²⁷Al-MAS NMR before the hydrothermal treatment. After two successive hydrothermal treatments, almost all the Al ions show T_d symmetry together with a small population of Al ions in the octahedral (O_h) symmetry. The calcined mesostructures all showed Al ions in T_d and O_h environments.     

Novel Low-Temperature Synthesis of Ferroelectric Neodymium-Doped Bismuth Titanate Nanoparticles

In this study, we report on the synthesis of nanopowders of ferroelectric Bi_3.5Nd_0.5Ti₃O₁₂ ceramic at temperatures below 500°C via a simple chemical method using citric acid as a solvent. The calcined powders were characterized using X-ray diffraction (XRD), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). Heating the as-dried powders in air first leads to crystallization of the Bi₂Ti₂O₇ phase at ∼310°C, followed by crystallization of the perovskite Nd-doped Bi₄Ti₃O₁₂ phase at ∼490°C as suggested by the peaks in the DSC analysis and confirmed by the evolution of phases in XRD patterns of the powders calcined at various temperatures. TEM of particles calcined at 550°C for 1 h in air showed an average particle size of 50–60 nm. The temperature dependence of capacitance of nanopowders calcined at 700°C for 1 h in air showed a Curie temperature of ∼615°C evincing a ferroelectric transition.     

Reactive Cerium(IV) Oxide Powders by the Homogeneous Precipitation Method

CeO₂ powders have been prepared by aging a cerium(III) nitrate solution in the presence of hexamethylenetetramine. Oxidation of Ce³⁺ occurs in the precipitate and the wet precipitate is identified as crystallized CeO₂ before any heat treatment. The cold-pressed powders can be sintered to full density at temperatures as low as 1250°C in just 6 min. Moreover, the sinterability of the powders is insensitive to the calcination temperatures, particle size, or green density. The powders calcined at 850°C with a crystallite size of 600 Å have a sinterability as good as the powders calcined at 450°C with a crystallite size of 145 Å. The mechanisms for direct CeO₂ precipitation and its relation to the excellent sinterability are discussed.     

Preparation and characterization of TiO2–SiO2 nano-composite thin films

TiO₂ nanocrystalline particles dispersed in SiO₂ have been prepared by the sol-gel method using titanium- and silicon-alkoxides as precursors. Nano-composite thin films were formed on the glass substrates by dip-coating technique and heat treated at temperatures up to 500 °C for 1 h. The size of the TiO₂ nanocrystalline particles in the TiO₂–SiO₂ solution ranged from 5 to 8 nm. The crystalline structure of TiO₂ powders was identified as the anatase phase. As the content of SiO₂ increased, the anatase phase tended to be stabilized to higher temperature. TEM results revealed the presence of spherical TiO₂ particles dispersed in a disk-shaped glassy matrix. Photocatalytic activity of the TiO₂–SiO₂ (1:1) thin films showed decomposition of 95% of methylene blue solution in 2 h and a contact angle of 10°. The photocatalytic decomposition of methylene blue increased and the contact angle decreased with the content of TiO₂ phase. TiO₂–SiO₂ with the molar ratio of 1:1 showed a reasonable combination of adhesion, film strength, and the photocatalytic activity.