不同制备条件对硅酸锆超细粉体水热法合成影响的研究

以正硅酸乙酯(TEOS)和氧氯化锆(ZrOCl_2·8H_2O)为原料,氟化锂为矿化剂,去离子水为溶剂,采用水热法制备硅酸锆粉体。研究了制备工艺中前驱体的Zr/Si摩尔比,前驱体溶液的pH值等因素对硅酸锆粉体合成的影响。并借助X射线衍射(XRD)、扫描电子显微镜(SEM)等测试手段对粉体进行表征。研究结果表明:前驱体中Zr/Si摩尔比影响着硅酸锆粉体的合成率,其最佳摩尔比为1.2∶1。前驱体溶液的pH值对硅酸锆粉体的合成有着重要的影响,pH值为9时最有利于合成硅酸锆粉体,此条件下所得粉体平均粒度大小在500~600 nm。     

硼热/碳热还原反应合成ZrB_2-SiC复合粉体及其抗氧化性能

以锆英石、氧化硼和活性炭为原料,通过硼热/碳热还原合成工艺制备Zr B2-Si C复合粉体。用X射线衍射、场发射扫描电子显微镜和透射电子显微镜研究了Zr B2-Si C复合粉体的物相组成和显微结构。用综合热分析仪研究Zr B2-Si C复合粉体的氧化动力学。结果表明:以锆英石为原料,采用硼热/碳热还原反应工艺,1 500℃反应3 h,合成出纯相Zr B2-Si C复合粉体;复合粉体中,Zr B2呈柱状或颗粒状,Si C则呈晶须状。采用Kissinger法和Ozawa法,计算了Zr B2和Si C的表观活化能,其数值分别为369和211 k J/mol。     

Zr-SBA-15催化苯酚甲醛高选择性合成邻位异构体双酚F

以P₁₂₃为模板剂,正硅酸乙酯为硅源,以硝酸氧锆为锆源,采用水热一步法合成了分子筛催化剂Zr-SBA-15,用XRD、BET、ICP、吡啶FT-IR、NH₃-TPD进行了分析表征,考察了不同Si/Zr摩尔比Zr-SBA-15催化苯酚、甲醛合成双酚F的催化活性,发现当Si/Zr摩尔比为20时催化活性较好。以Si/Zr摩尔比20的Zr-SBA-15为催化剂,在反应温度90℃、酚醛摩尔比30:1、催化剂与甲醛质量比1:1条件下反应240 min,双酚F收率达到83.5%,邻位异构体双酚F选择性高达92.5%,同时还提出了Zr-SBA-15高选择性催化苯酚、甲醛合成邻位异构体双酚F的反应机理。     

Zr-SBA-15催化苯酚甲醛高选择性合成邻位异构体双酚F

以P123为模板剂,正硅酸乙酯为硅源,以硝酸氧锆为锆源,采用水热一步法合成了分子筛催化剂Zr-SBA-15,用XRD、BET、ICP、吡啶FT-IR、NH3-TPD进行了分析表征,考察了不同Si/Zr摩尔比Zr-SBA-15催化苯酚、甲醛合成双酚F的催化活性,发现当Si/Zr摩尔比为20时催化活性较好。以Si/Zr摩尔比20的Zr-SBA-15为催化剂,在反应温度90℃、酚醛摩尔比30:1、催化剂与甲醛质量比1:1条件下反应240 min,双酚F收率达到83.5%,邻位异构体双酚F选择性高达92.5%,同时还提出了Zr-SBA-15高选择性催化苯酚、甲醛合成邻位异构体双酚F的反应机理。     

纳米硅酸锆的合成

利用水热法制备了纳米ZrSiO4粉体，借助XRO，TEM及SEM等研究了ZrSiO4晶粒相组成，粒度和结晶形貌与前驱物Zr和Si的摩尔比，水热反应温度以及反应时间之间的关系，并对ZrSiO4的合成机理进行了实步研究。     

溶胶--凝胶碳热还原法制备硼化锆超细粉体

以氧氯化锆、硼酸、葡萄糖等为原料,在柠檬酸和乙二醇的螯合作用下,采用溶胶--凝胶、碳热还原工艺合成了ZrB2超细粉体。研究了原料配比及合成温度对合成超细粉体的影响。结果表明:不同的B/Zr及C/Zr摩尔比显著影响ZrB2超细粉体的合成,其最佳摩尔比为:n(B)/n(Zr)=2.5,n(C)/n(Zr)=6.5;当热处理温度为1 773K时能够合成纯相的ZrB2超细粉体;1 773K保温2h条件下合成的ZrB2超细粉体的颗粒尺寸为1~2μm,晶粒尺寸为55nm。     

水热法合成Ba(Ti_(0.8)Zr_(0.2))O_3纳米粉体

钛酸钡(BaTiO_3)系列电子材料是一类重要的功能材料,正逐渐向小体积、功能化、大容量方向发展,常采用掺杂改性的方式提高其介电常数及稳定性。本次实验主要以TiCl_4、BaCl_2·2H_2O、ZrOCl_2、NaOH为原料,采用水热合成法制备锆钛酸钡[Ba(Ti_(0.8)Zr_(0.2))O_3,BZT]纳米粉体,并探讨反应温度、Ba/(Ti+Zr)摩尔比以及pH对BZT粉体合成的影响。实验结果表明,在反应温度为220℃,反应时间为4h,Ba/(Ti+Zr)=1.4,且pH为14时制备的BZT粉体物相单一,分散性较好,粒径较小。当提高pH及前驱物的Ba/(Ti+Zr)摩尔比及升高反应温度时,均有利于BZT晶体形成,而且粉体粒径减小。     

一种新型无机-有机硅铝复合絮凝剂的合成与表征

采用硅烷偶联剂γ-氨丙基三乙氧基硅烷作为硅源,与氯化铝在碱性条件下合成新型无机-有机硅铝复合絮凝剂。结果表明,最佳合成条件为：总铝浓度Al_T为0.2 mol/L,Si/Al摩尔比为0.6及碱化度B值为2.0时,合成的絮凝剂依然保持稳定状态。新型无机-有机硅铝复合絮凝剂的pH值与B值和Si/Al摩尔比均存在正相关性;Zeta电位与B值和Si/Al摩尔比均存在负相关性;絮凝剂中的有机组分和无机组分是以共价键结合在一起的;该絮凝剂呈现空间网状的密实结构,吸附架桥性能优越。     

溶胶-凝胶法制备锆铁红色料Ⅰ

本文研究了用溶胶-凝胶法制备锆铁红色料的一系列工艺参数(着色剂的种类及用量、矿化剂种类及用量和Si/Zr比、TEOS预水解时的pH值、加水量和TEOS浓度)。通过正交试验得出:溶胶-凝胶法制备锆铁红色料的最佳着色剂为FeSO4·7H2O,最佳矿化剂为LiCl,理想Si/Zr摩尔比为1:1;并且通过两个单因素实验进一步确定了着色剂最佳用量(x=Fe3+/TEOS,摩尔比)为0.15,矿化剂用量(Li+/TEOS,摩尔比)为0.15。实验结果还表明:pH值为1、加水量(R=H2O/TEOS,摩尔比)为1、TEOS浓度为0.2mol/L时,色料呈色最优。     

双反应室激光诱导气相合成纳米Si/C/N复相粉体及其微波介电特性

用激光诱导气相反应法,以六甲基二硅胺烷(Me3Si)2NH)(MeCH3)为原料,用双反应室激光气相合成纳米粉体装置合成了纳米Si/C/N复相粉体,复相粉体的粒径为20～30nm,纳米粉体的分散性好,无严重团聚.研究了纳米Si/C/N复相粉体在8.2～12.4 GHz的微波介电特性,纳米Si/C/N复相粉体介电常数的实部(ε′)和虚部(ε″)在8.2～12.4 GHz随频率增大而减小,复合材料的ε′和ε″可以通过纳米粉体的含量进行调整,而且介电损耗(tgδ=ε″/ε′)较高,是较为理想的微波吸收材料,计算结果表明经典的有效媒质公式对含纳米Si/C/N复相粉体的复合材料是不适合的.纳米Si/C/N复相粉体中Si,C,N原子周围的化学环境比纯SiC和Si3N4相的混合体要复杂得多,这是导致其性能变化的主要原因.纳米Si/C/N复相粉体中的SiC微晶固溶了大量的N原子,在纳米Si/C/N复相粉体中形成大量的带电缺陷,在电磁场作用下形成极化耗散电流,极化弛豫是其吸收电磁波的主要原因.     

锆掺杂纳米ZSM-5/11共晶分子筛合成

以乙醇锆为锆源、正硅酸乙酯为硅源、四丁基溴化铵为模板剂,采用水热晶化法合成锆掺杂纳米ZSM-5/11共晶分子筛。采用XRD、UV-Vis、TEM和EDX等表征分子筛结构;考察晶化温度、晶化时间、硅锆比和模板剂用量对分子筛形成过程的影响。结果表明,晶化温度180℃、硅锆物质的量比100∶1和晶化时间48 h有利于分子筛晶体的生成。TEM显示合成的锆掺杂纳米ZSM-5/11分子筛为结晶完好的立方体晶体,晶粒长度约200 nm;EDX和UV-Vis证实了锆原子在分子筛中的存在。载金Zr-ZSM-5/11共晶分子筛催化剂在葡萄糖选择性氧化反应中表现出良好的催化活性。     

Up-scalable preparation of nano zirconium carbide powder in liquid polymeric precursor and its pyrolysis mechanism

Nano size ZrC powder was prepared by liquid polymeric precursor method. Zirconium n-butoxide (Zr(OⁿBu)₄) and benzoylacetone (BA) were mixed directly with different molar ratios to synthesize transparent liquid zirconium carbide single-source precursors. The carbon content in the precursor could be changed by adding different amount of BA. X-ray pure ZrC was obtained when the molar ratio of BA/Zr(OⁿBu)₄ was 4.6:1. The viscosity of the precursor was very low (<8 mPa s) without the addition of solvents. Zirconium carbide powders were fabricated by the pyrolysis at 800 °C in argon and subsequent heating at various temperatures in vacuum for carbothermal reduction reaction. The pyrolysis behavior, phase composition and transformation, and microstructure of the as-fabricated ZrC powders were analyzed. The gases of CH₄, CO and CO₂ released due to decomposition and evaporation of the organic component and transformation from ZrO₂ to ZrC during pyrolysis resulted in total 60–70% mass loss. The average grain size of the synthesized X-ray pure ZrC powders was less than 30 nm. Meanwhile, the pyrolysis mechanism of nano zirconium carbide powder was deduced.     

微波法制备磷酸锆的研究

采用氧氯化锆为锆源、氟化铵为络合剂、磷酸为磷源,在低温（〈100℃）和常压条件下,微波辅助加热法在较短时间内制备得到规则的六角形片状结构Zr（HPO4）2·H2O（简写为α-ZrP）晶体。研究了不同反应物浓度下NH4F与ZrOCl2·8H2O摩尔比、磷酸与ZrOCl2·8H2 O摩尔比、反应时间、反应温度等因素对于合成磷酸锆晶体的影响。产物采用XRD、 SEM和FT-IR表征。以罗丹明B为降解对象,可见光下研究所制备磷酸锆的光催化性能。结果表明,当[ Zr^4＋]=0.02 mol/L, NH4 F/Zr=6和P/Zr=40,微波加热温度90℃,反应时间为30 min时制备的磷酸锆具有良好的光催化活性。     

Reactive Hot Pressing of ZrB2–SiC Composites

A ZrB₂–SiC composite was prepared from a mixture of zirconium, silicon, and B₄C via reactive hot pressing. The three-point bending strength was 506 ± 43 MPa, and the fracture toughness was 4.0 MPa·m^1/2. The microstructure of the composite was observed via scanning electron microscopy; the in-situ -formed ZrB₂ and SiC were found in agglomerates with a size that was in the particle-size ranges of the zirconium and silicon starting powders, respectively. A model of the microstructure formation mechanism of the composite was proposed, to explain the features of the phase distributions. It is considered that, in the reactive hot-pressing process, the B and C atoms in B₄C will diffuse into the Zr and Si sites and form ZrB₂ and SiC in situ , respectively. Because the diffusion of Zr and Si atoms is slow, the microstructure (phase distributions) of the obtained composite shows the features of the zirconium and silicon starting powders.     

Properties and reactivity of Zr-incorporated folded sheet mesoporous material for alkylation of anisole using tert-butylalcohol

Zr-incorporated Folded Sheet Mesoporous material (FSM-16) with different Si/Zr ratios = 90, 60, 10 have been synthesized by intercalating kanemite using cetyltrimethylammonium bromide (CTMABr) as the intercalating agent and zirconium sulphate precursors as the zirconium source. The resulting samples were characterized by means of inductively coupled plasma (ICP) technique, XRD, BET, TEM, FT-IR, UV–Vis and a temperature–programmed–desorption (TPD) of pyridine. The effect of the Si/Zr molar ratio on the textural properties of Zr-FSM-16 was investigated. The results reveal that the Zr-FSM-16 was successfully synthesized. The catalytic performance was examined in the vapor phase tert-butylation of anisole with tert-butanol at the temperatures between 423 and 523 K under atmospheric pressure. The results indicate that Zr-FSM-16 (10) was found to be more active than its relatives.The major products are found to be 4-tert-butyl anisole (4-TBA), 2-tert-butyl anisole (2-TBA) and 2,4 di-tert-butyl-anisole (2,4-DTBA). Maximum conversion of anisole is observed at 473 K and decreased after that with increasing temperature. The influence of molar ratio, influence of temperature, weight hourly space velocity (WHSV) and time on stream on the selectivity of products was investigated and the results are discussed.     

水解-共沉淀法制备硅酸锆包裹硫硒化镉色料

利用正硅酸乙酯水解制备的纳米级二氧化硅对共沉淀法制备的氢氧化锆和硫硒化镉悬浊液包覆得前驱体,经高温快速煅烧得到硅酸锆包裹硫硒化镉色料.通过XRD、SEM、激光粒度仪、色差仪等对色料进行表征,考察了硅锆比固定的情况下,煅烧温度、锆镉比对色料粒径、发色效果的影响.研究结果表明当以LiF为矿化剂,Cd:S:Se=4:3:1,Zr:Cd=3:1,Zr:Si=1:1,1050℃煅烧30 min时,制备的硅酸锆包裹硫硒化镉色料a*值高达32.04,粒径D50在2μm附近,为硅酸锆包裹硫硒化镉色料应用于陶瓷喷墨打印技术提供了可能.     

Effect of Si/Zr molar ratio on the sintering and crystallization behavior of zircon ceramics

Zircon (ZrSiO₄) ceramics have been widely used in the field of radioactive waste immobilization and ceramics industry. However, preparation of zircon ceramics suffers from low yield due to the variable Si/Zr molar ratio. Herein, we reported preparation of xSiO₂/ZrSiO₄ (0 ≤ x ≤ 0.3) ceramics using SiO₂ and ZrO₂ as raw materials. The effects of Si/Zr molar ratio and sintering temperature on the phase formation, phase and microstructure evolutions were investigated. The results indicated that zircon formation efficiency increased with increasing Si/Zr molar ratio from 1 to 1.2, while decreased with increasing Si/Zr molar ratio from 1.2 to 1.3. The as-prepared ceramics with Si/Zr molar ratio of 1.1 and 1.2 were single zircon phase, while with Si/Zr molar ratio of 1 and 1.3 exhibited coexistence of zircon and cristobalite phases. The grain growth and compactness can be enhanced by increasing Si/Zr molar ratio. Furthermore, the relative densities increased with increasing Si/Zr molar ratio.     

Synthesis of a soluble preceramic polymer for ZrC using 2-hydroxybenzyl alcohol as carbon source

A preceramic polymer for ZrC was successfully synthesised by chemical reaction between zirconium oxychloride (ZrOCl₂·8H₂O) and 2-Hydroxybenzyl alcohol via a one-pot route. The molecular structure, thermal properties and pyrolysis behaviour of the precursor were investigated. The results indicated that the precursor might be Zr–O–Zr chain polymer with 2-Hydroxybenzyl alcohol as ligand. The precursor was air-stable and exhibited excellent solubility in common organic solvents. The conversions from precursor to ZrC powders were investigated by TG-DTA, X-ray diffraction, Scanning electron microscope, TEM and Raman spectrum. The precursor underwent a thermal decomposition in four steps, and ZrC powders were formed at 1300°C via carbothermal reduction reaction of ZrO₂ and carbon in argon with ceramic yield of 63.0%. The ZrC particles were fine and exhibited irregular polyhedron morphology with average size in the range of 100–300?nm.     

Facile synthesis and morphological study of Si–Zr–C–O fiber felts with high-thermal resistance

The polycarbosilane (PCS) as a ceramic precursor is mainly synthesized using an autoclave and is modified via the reflux method to add organometallic compounds. However, in this study, a zirconium source was added to PCS in order to improve the heat resistance of the polymer-derived SiC fibers using an easy and simple blending method. The zirconium-added PCS solution was spun via electrospinning and converted to Si–Zr–C–O fiber felts at 1300 °C through the processes of curing and pyrolysis. In order to investigate their thermal-degradation behavior, the zirconium added SiC fiber felts were heat-treated at 1500 °C or 1600 °C for 1 h in an Ar atmosphere. The results indicated that the aforementioned felts retained blackness and flexibility, whereas SiC fiber felts deteriorated and were discolored to gray. Moreover, the results confirmed that the growth of crystalline size (approximately calculated via XRD analysis) was significantly inhibited by the presence of zirconium. Therefore, zirconium acetylacetonate as a zirconium source was cross-linked with the PCS structure via the blending method and its role for heat resistance was exhibited at high temperature.     

Co/Mn/Zr复合催化剂催化甲苯液相氧化

以乙酰丙酮锆或乙酸锆与乙酸钴和乙酸锰制备乙酸钴/乙酸锰/乙酰丙酮锆或乙酸锆(Co/Mn/Zr)三元复合催化剂。比较乙酸钴(Co)、乙酸钴/乙酸锰(Co/Mn)和Co/Mn/Zr催化剂体系对甲苯液相氧化反应的催化性能。结果表明:在催化剂中添加Zr可以降低反应温度,提高甲苯转化率和苯甲酸选择性。与乙酸锆相比,采用乙酰丙酮锆制得的Co/Mn/Zr具有较好的催化活性。在Co,Mn和Zr物质的量之比为5 5 1,Co与甲苯的物质的量之比为1 10 000,溶剂乙酸与甲苯质量比为1 2.3,反应温度160℃和反应压力1.4 MPa的条件下反应3 h后,苯甲酸选择性和甲苯转化率分别为80.2%和15.4%。