模板辅助燃烧合成ZrB_2/Al_2O_3复合纤维及其吸波性能

以ZrO_2纤维为模板,通过铝热还原燃烧法制备了ZrB_2/Al_2O_3复合短纤维,采用X射线衍射与扫描电子显微镜对样品物相组成与微观形貌进行了表征,并用矩形波导法测试样品8.2~12.4 GHz频率范围内的室温复介电常数,根据传输线理论计算不同厚度试样的反射损耗。结果表明:燃烧产物相组成为ZrB_2和Al_2O_3,ZrO_2纤维完全参与了反应,产物保留了ZrO_2原料的纤维形态,但纤维直径增大约1倍;与颗粒状ZrB_2/Al_2O_3复合粉体相比,复合纤维的复介电常数实部与虚部更高,并且表现出更明显的频响特性,掺复合纤维的试样厚度为2.8 mm时吸波性能最佳,有效吸收带宽(RL–10 dB)达到3 GHz,最低反射率为–18.2 dB。     

ZrO_2(Y_2O_3)-Al_2O_3均匀超细粉末的制备新工艺

本文提出了三种制备ZrO_2(Y_2O_3)-Al_2O_3均匀超细活性粉末的工艺:锆、钇、铝的混合盐溶液共沉淀法,铃、钇的混合盐溶液在α-Al_2O_3悬浮液内共沉淀(沉淀包裹法)及ZrO_2(Y_2O_3)、α-Al_2O_3活性粉末在无水乙醇内悬浊混合法。同时,对所制粉末的性能进行了研究对比。结果表明共沉淀法和沉淀包裹法所得粉末的烧结试样具有好的显微结构,ZrO_2和Al_2O_3晶粒尺寸小(0.5μm左右)且分散均匀,ZrO_2的四方相分数高(大于95Vol.%);悬浊混合法稍差。沉淀包裹法与混合法1580℃4h的烧结体密度可达理论密度的96%以上,共沉淀法稍低。     

ZrO_2掺杂对CaO–Al_2O_3–SiO_2系玻璃结构和机械性能的影响

采用熔融冷却法制备ZrO_2掺杂的CaO–Al_2O_3–SiO_2(CAS)系玻璃,通过差热分析仪、紫外可见光分光光度计以及电子万能试验机探讨了ZrO_2掺杂量对玻璃热稳定性、网络结构以及机械性能的影响规律。结果发现:当ZrO_2摩尔分数小于4%时,CAS系玻璃的热学性能更加稳定,光学带隙随着ZrO_2掺杂量的增加而减小,结构更加致密完整,其体积密度、氧原子堆积密度以及弯曲强度均随着ZrO_2含量的增加而上升;当ZrO_2掺杂量超过4%后,该玻璃体系的热学性能、结构稳定性和力学性能均随着ZrO_2含量的增加而出现下降;当ZrO_2掺杂量为4%时,玻璃的光学带隙值达到3.28 e V,析晶温度Tx与玻璃转变温度Tg差值达到230.12℃,同时弯曲强度达到83.67 MPa。适量的掺杂ZrO_2,能够提高氧原子堆积密度、增强其网络结构,从而显著提高玻璃的结构稳定性和机械性能。     

注浆法制备Al_2O_3和Al_2O_3/ZrO_2多层复合材料

为了获得接近理论密度的多层复合材料,注浆是很有前途的工艺方法。从测定Al_2O_3和Al_2O_3/ZrO_2(4％体积ZrO_2)料浆的ξ电位和粘度角度出发,确定了用注浆法制备多层复合材料的条件。同时也报道了用扫描电子显微分析获得的微观结构。     

ZrO_2界面相对3D-Al_2O_3/Al_2O_3复合材料性能的影响

实验主要采用溶胶凝胶法(sol-gel)制备3D-Al_2O_3/Al_2O_3复合材料,并在纤维和基体之间制备ZrO_2界面相,通过三点弯曲实验分析材料的力学性能;通过扫描电镜观察破坏规律。研究表明,所制备的3D-Al_2O_3/Al_2O_3复合材料,其基体的主要成分为α-Al_2O_3,引入ZrO_2界面相的复合材料弯曲强度达到75.2MPa,与无界面相复合材料弯曲强度(62.3 MPa)相比提高了20.7%,无界面相Al_2O_3/Al_2O_3复合材料断口平整,呈现脆性断裂,存在ZrO_2界面相的Al_2O_3/Al_2O_3复合材料断口有大量纤维拔出,表现出类似金属断裂的假塑性断裂特征。     

滑石粉对聚酰亚胺/二氧化锆复合薄膜的影响

本文以PMDA与ODA为原料制得的聚酰亚胺(PI)为研究对象,用溶液法制备不同添加剂含量的聚酰胺酸/滑石粉/二氧化锆(PAA/Talc/ZrO_2)复合溶液,以5℃/min的升温速率从室温升到300℃制备PI复合薄膜。通过偏光显微镜、广角X射线衍射仪、热重分析仪以及万能拉伸试验机对其复合薄膜进行表征及测试。研究结果表明:随着添加剂Talc和ZrO_2的加入,能够诱导聚酰亚胺分子围绕其进行结晶。当Talc和ZrO_2总添加量为3%,Talc和ZrO_2的配比为5∶1时,复合薄膜的综合性能最佳。     

SO_4~(2-)/ZrO_2超细粒子固体超强酸研究

用TEM、BET、Hammett指示刑法、化学分析和正丁烷异构化反应等手段对不同制备方法所得固体超强酸的性质进行了表征。实验结果表明：普通的ZrO_2浸渍H_2SO_4和焙烧后制得的SO_4~(2-)／ZrO_2超强酸粒径<10nm，属超细粒子范畴；以超临界条件制得的超细化ZrO_2晶体为原料制备的SO_4~(2-)／ZrO_2超强酸，可明显提高正丁烧异构化反应稳定性。观察到超细ZrO_2晶体与一般的ZrO_2晶体不同，用稀硫酸浸清处理后其酸强度H0可达到-16．0，且表面硫酸根高于浓度高于用常规方法制备的SO_4~(2-)／ZrO_2超强酸。     

La_2O_3含量对La-Ni/ZrO_2-Al_2O_3催化剂甲烷化性能的影响

采用浸渍法制备了复合氧化物ZrO_2-Al_2O_3,在此基础上采用共浸渍法制备了La-Ni/ZrO_2-Al_2O_3催化剂,考察了催化剂中La2O3含量对催化剂CO甲烷化活性的影响,并利用BET、XRD和TPR对催化剂的物化性能进行了分析。结果表明当La2O3含量为2%~6%(质量分数,下同)时,其在低温和高温时的催化活性均比Ni/ZrO_2-Al_2O_3有一定的提升。另外比较了催化剂4La-Ni/ZrO_2-Al_2O_3和Ni/ZrO_2-Al_2O_3在500℃下连续反应100 h的活性和积碳,结果显示催化剂4La-Ni/ZrO_2-Al_2O_3具有很好的稳定性和优良的抗积碳性能。     

CeO_2-TiO_2-La_2O_3复合烧结助剂对Al_2O_3/ZrO_2复相陶瓷性能影响研究

以氧化锆(3Y-ZrO_2)和氧化铝(Al_2O_3)为主要原料,以CeO_2-TiO_2-La_2O3为烧结助剂,采用常压烧结工艺制备Al_2O_3/ZrO_2复相陶瓷。探讨了配方组成和烧结温度对Al_2O_3/ZrO_2复相陶瓷体积密度、抗弯强度等性能的影响。采用激光粒度仪对氧化铝粉体和氧化锆粉体的粒度大小进行分析,同时采用X-射线衍射仪(XRD)和扫描电镜(SEM)对烧结样品的物相组成和显微结构进行分析。实验结果表明:本实验所采用的氧化铝和氧化锆粉体纯度较高,符合使用要求。当添加剂中TiO_2加入量为2.0%时,Al_2O_3/ZrO_2复相陶瓷在1450℃烧结后的综合性能最佳,其对应的体积密度和抗弯强度分别为3.73g/cm3和353.83MPa。     

溶胶-凝胶法制备Li_2ZrO_3纳米颗粒及其高温二氧化碳吸收性能

通过柠檬酸溶胶-凝胶法制备纳米级锆酸锂(Li_2ZrO_3)材料,利用扫描电子显微镜和X射线衍射仪对Li_2ZrO_3材料的形貌与结构进行表征,利用热重分析仪测试Li_2ZrO_3材料的高温CO_2吸收性能.结果表明,合成的Li_2ZrO_3材料具有良好的高温CO_2吸收性能.在CO_2分压为0.05 MPa、550℃、20min内吸收容量可达20%(质量分数);45 min内可达吸收平衡,平衡吸收量达27%(质量分数).经3次吸收解吸循环后其吸收性能没有明显下降,表明Li_2ZrO_3材料具有良好的稳定性.     

Phase stability and microstructure evolution of MgO-ZrO2 and MgO-6YSZ ceramic fibers

In this work, MgO-ZrO₂ and MgO-6YSZ ceramic fibers were prepared with sol-gel method via electrospinning. Polymorph stability and microstructure evolution of zirconia fibers were fully characterized by X-ray diffraction, Raman spectra, X-ray photoelectron spectroscopy, and Scanning electron microscope. The results indicated that tetragonal zirconia for MgO-ZrO₂ was obtained and cubic zirconia could be fully stabilized for MgO-6YSZ with MgO molar fractions varying from 0.1 to 0.5 at 800°C. Monoclinic phase appeared with MgO molar fractions even up to 0.5 for MgO-ZrO₂ system and partially or fully stabilized zirconia could be achieved for MgO-6YSZ at 1000°C and 1200°C. Grain size was gradually decreased with increasing of MgO content at 800°C both for MgO-ZrO₂ and MgO-6YSZ ceramic fibers. The grain size of both systems increased with MgO molar fractions varying from 0.1 to 0.2 and then decreased at higher contents at 1000°C and 1200°C. A discussion on relationship among MgO state and the phase stability and grain size was presented. This work shows surface excess and solid solution of MgO predominantly controlled the phase stability and microstructure evolution of zirconia fibers.     

Electrospinning Zirconia Fiber From a Suspension

A zirconia suspension containing 5–10 nm size zirconia particles was modified by adding different amounts of polymer solution to enable electrospinning of zirconia fibers from a range of compositions. The electrospun fibers were heat treated at 600° and 1200°C, and analysis of size distribution reveals that zirconia fibers down to about 200 nm in diameter can be prepared in this way, in contrast to other spinning processes, which are able to produce zirconia fibers having diameters ≥3000 nm.     

Electrospun mesoporous zirconia ceramic fibers for catalyst supporting applications

Mesoporous zirconia has been widely used as supporting materials, absorption materials, catalysts and high temperature insulating materials. While seldom has taken a consideration of the mesoporous fiber structure. In the present work, mesoporous zirconia ceramic fibers were fabricated by electrospinning method with CTAB as the template. The thermal decomposition and crystallization process of the mesoporous zirconia fibers were fully studied by TG/DSC, IR spectra and XRD. The highest surface area of the mesoporous zirconia fibers was about 120 m²/g. With mesoporous zirconia fibers as the supporting materials, tungstate supported on zirconia fibers catalyst showed that the specific activity of bromination of phenol red was 1.26 mmol h^?1 g^?1. The results confirmed that zirconia fibers with the mesoporous structure would be a promising candidate as a supporting material.     

氧化锆连续纤维的高温蠕变及其研究方法

氧化锆连续纤维在航空、航天及工业领域中有重要的用途。本文总结了氧化锆连续纤维高温蠕变的基本概念,系统介绍了研究氧化锆纤维高温蠕变的方法及目前氧化锆陶瓷材料高温蠕变性能的研究现状。     

氧化锆料浆性能对其喷雾造粒粉料性质的影响

本文研究了料浆含固量和粘度对其喷雾造粒粉料性质影响。结果表明：氧化锆料浆含固量是喷雾造粒（ＳＤ．）粉料填充密度的主要控制因素，高含固量料浆能得到高填充密度喷雾造粒粉料，且其颗粒显微结构相对致密；随着ＺｒＯ２料浆含固量、粘度增加，喷雾造粒粉料平均粒径增大，粗颗粒含量增多，细颗粒含量减少。     

Novel polymer fibers prepared by electrospinning for use as the pore-former for the anode of solid oxide fuel cell

One-dimensional polyvinyl alcohol (PVA) fibers prepared by electrospinning technique are used as a novel pore-former for the conventional NiO/yttria-stabilized zirconia (YSZ) anodes of solid oxide fuel cell (SOFC). This pore-former forms wire-like pores in the anode substrates, which are beneficial for rapid transport of the fuel and byproduct. The advantage of using this pore-former over the conventional ones (e.g. wheat flour and carbon) is that only a small amount of fibers could generate large amount of continuous pores within the anode for gas transport. In addition the cell with PVA fibers as pore-former for anode exhibits enhanced anode electrocatalytic activity and the cell performance significantly, compared to the cells without pore-former and with wheat flour as pore-former. In this research, an anode-supported SOFC with PVA fibers as pore-former for anode exhibits an open-circuit voltage (OCV) of 1.08 V and maximum power density of 751 mW cm⁻² at 800 °C.     

纳米氧化锆添加量对氧化锆制品性能的影响

在电熔单斜氧化锆原料中添加不同数量的CaO稳定剂,制备部分稳定氧化锆,研究CaO加入量和稳定相数量的关系.在制备的CaO部分稳定氧化锆中添加纳米氧化锆粉体,经过造粒、200 MPa压力成型、干燥、1650 ℃×2 h烧成制得试样.测试试样的物理性能、分析矿物相组成、观察显微结构,研究纳米氧化锆粉体添加量对试样性能的影响.研究结果表明:2Ca-PSZ、3Ca-PSZ、4Ca-PSZ试样中,4Ca-PSZ试样稳定化程度最高;3Ca-PSZ试样显气孔率小,体积密度较大,耐压强度高.在3Ca-PSZ试样中加入纳米氧化锆粉体,随着加入量的增加,试样的显气孔率下降、烧成收缩率增加、耐压强度提高.其中纳米氧化锆粉体添加比例为8wt%时,试样气孔率为9.4%,体积密度为5.08 g/cm3,抗压强度达到381 MPa.与3Ca-PSZ试样相比,气孔率下降40%,体积密度提高5%,耐压强度提高70%.     

铈在介孔氧化锆中的液相移植

利用Ce(NO3) 3·6H2 O溶液与介孔氧化锆原粉在一定pH值的液相中反应 ,将Ce/CeO2 催化剂移植到多孔氧化锆材料中 .用XRD ,TEM ,N2 吸附 -脱附及UV -VIS吸收光谱等手段对产物进行表征 ,结果表明 :铈经Zr—O—Ce键成功地负载于多孔ZrO2 骨架中 ,并且分散于孔表面及孔道中 ,同时保持孔道的有序性及多孔氧化锆较高的比表面积 .     

Cyclic Infiltration of Porous Zirconia Preforms with a Liquid Solution of Mullite Precursor

Composites of mullite and zirconia were fabricated via the cyclic infiltration of porous zirconia-based preforms with a liquid mullite precursor. The maximal amount of mullite precursor that could be infiltrated was dependent primarily on the initial open porosity of the preforms. When a zirconia preform with an initial open porosity of ∼58% was cyclically infiltrated to saturation, the open porosity was reduced to ∼43%, with a median pore diameter of 15 nm. After sintering at a temperature of 1500°C for 2 h, the saturation-infiltrated zirconia preforms could be densified to ∼98% of the theoretical density. In zirconia samples, infiltrated mullite had a tendency to coalesce into large, elongated grains as the sintering temperature was increased. The presence of infiltrated mullite did not have a significant effect on the zirconia grain structure. The distribution of mullite in the samples was nonuniform, and the distribution profiles varied as the number of infiltration cycles varied. Although the sintered density and hardness showed small improvements after saturation infiltration, the fracture toughness did not increase.     

The dual effect of zirconia fiber on the insulation and mechanical performance of the fumed silica-based thermal insulation material

Inorganic fibers and opacifiers are indispensable for improving the strength and high temperature insulation performance of the fumed silica-based thermal insulation material. However, zirconia fiber enhances the strength of the fumed silica-based thermal insulation material and reduces the radiative heat transfer to replace the opacifier. The sample of fumed SiO₂/Al₂O₃ doped with 7% zirconia fiber (FZ7) has a lower density of 0.70 g/cm³ and a high porosity of 75.0%. In addition, the thermal conductivity of FZ7 at 800 °C is 0.077 W/(m·K), which is lower than the sample of fumed SiO₂/Al₂O₃ doped with 7% glass fiber (FG7) and 0.089 W/(m·K) at 800 °C. The effective extinction coefficient of the thermal insulation material containing zirconia fiber is larger than that of the glass fiber by Fourier transform infrared spectroscopy analysis and calculation, indicating that the zirconia fiber has a distinct absorption and scattering effect on infrared radiation to reduce the radiative heat transfer. Therefore, zirconia fiber enhances the strength and decreases the high temperature thermal conductivity of the composites with the dual effect on the insulation and mechanical performance of the fumed silica-based thermal insulation material.