原位选择性碳化法制备ZrO2-TiC粉末

利用热力学基本原理分析计算了ＴｉＯ２－ＺｒＯ２－Ｙ２Ｏ３系统的原位选择性碳化条件,确定了原位选择碳化的温度并研究了碳化温度对该系统碳化后的相组成的影响。用含有Ｚｒ＾４＋,Ｔｉ＾４＋,和Ｙ＾３＋的溶液,采用共沉淀法制备了ＴｉＯ２－ＺｒＯ２－Ｙ２Ｏ３超细粉料,然后以蔗糖作为碳化剂,在氩气氛下,分别在１３５０,１４５０,１５５０和１６５０℃进行２ｈ的碳化,然后进行了Ｘ射线衍射分析。     

模板浸渍法制备ZrO2纤维研究

将15 cm×15 cm×1 cm的粘胶纤维模板放入浓度为1、2及3 mol·L^-1的ZrOCl₂溶液,分别在20、40、60℃下浸渍20 h,经过洗涤、离心、干燥得到ZrO₂纤维前驱体,再对前驱体进行600、800、1 000、1 200℃保温2 h热处理制得ZrO₂纤维。研究浸渍温度、浸渍液浓度、热处理温度对ZrO₂纤维形貌和相组成的影响。结果表明,随着浸渍温度由20℃提高到60℃,浸渍液浓度由1 mol·L^-1提高到3 mol·L^-1,纤维横截面微观形貌由扁平状向圆柱状变化,同时纤维的平均直径逐渐增大,说明提高浸渍温度和浸渍液浓度有利于粘胶纤维模板对Zr⁴⁺的吸附。ZrO₂纤维经过热处理后,主要是以单斜相ZrO₂存在。随着热处理温度的增加,ZrO₂纤维晶粒变大,结晶程度增加,同时纤维表面经历由光滑到小晶粒出现再到裂纹出现的转变。     

ZrO2制备方法研究进展

以ZrO₂为活性组分或载体的催化剂,在酚类定向催化转化中具有较高的研究价值。总结了ZrO₂的各种制备方法,包括溶胶-凝胶法、共沉淀法、水热法、表面活性剂辅助法、静电纺丝法、热解法、多元醇还原法、反相微乳法和超临界合成法等。阐述了各种方法的反应原理,详细比较了不同制备方法的优劣,并具体分析了制备方法对催化剂结构及性能的影响。     

用于生产致密陶瓷的ZrO2粉末的制备新方法

微波加热醇盐溶液沉淀法、高浓度溶液的水热分解法、低温水热合成法、酸水解法以及溶胶-凝胶-酸水解法等是最近国内外研制纳米ZrO2微粉的最新方法.这些方法各有特色,与传统方法比较,更科学更合理,是值得推广研究的方法.     

纳米单斜相ZrO2的制备

沉淀法制备了ZrO2,重点考察了煅烧温度ZrO2粉体性质的影响,并用热重法-差示扫描量热法、X-射线衍射和N2物理吸附等手段对粉体进行了测试和表征。结果表明,随煅烧温度的升高,ZrO2的比表面积、平均孔径和孔容大幅度下降,微晶尺寸逐渐增大,单斜相ZrO2的含量增加,四方相的含量减少。1000℃时ZrO2粉体完全以单斜相存在。600℃煅烧2 h制得了单斜相为主的ZrO2粉体,其微晶尺寸为21.6 nm,比表面积为39.2 m2/g、平均孔径为11.7 nm,孔容为0.23 cm3/g。     

ZrO2包覆CaO-MgO-SiO2陶瓷纤维的制备及其性能

为了解决CaO-MgO-SiO2陶瓷纤维在使用过程中析晶、粉化的问题,采用非均相成核法在CaO-MgO-SiO2陶瓷纤维表面制备了ZrO2涂层。用场发射扫描电子显微镜观察ZrO2包覆层,用X射线衍射仪分析800和1 000℃热处理后原始纤维和ZrO2包覆纤维的晶相变化,并检测了二者在模拟肺液中的溶解性能。结果表明:包覆处理后,CaO-MgO-SiO2陶瓷纤维表面形成了一层ZrO2包覆层;ZrO2包覆层的存在可以显著抑制800℃时纤维的析晶,1 000℃时只能抑制纤维中方石英的析出,对其他物相的析晶没有明显抑制作用;ZrO2包覆层的存在降低了纤维在模拟肺液中的早期溶解速率,但对纤维的长期生物可溶性影响不大。     

ZrO2-SiO2 复合气凝胶的制备及其热稳定性研究

为了改善纯ZrO_2气凝胶的高温稳定性,本研究以TEOS为硅源,以硝酸氧锆为锆源,通过滴加环氧丙烷,制备了ZrO_2-SiO_2复合气凝胶,探索了锆硅比例和热处理温度对复合气凝胶结构和性能的影响,结果表明,当锆硅比例为1:1时,制备的复合气凝胶比表面积最大,为551.7 m2/g;1000°C热处理后的比表面积为239.3 m2/g,1200°C热处理后的比表面积为89.5m2/g。与纯ZrO_2气凝胶相比,本研究所制得的ZrO_2-SiO_2复合气凝胶具有更好的热稳定性。     

KOH/ZrO2催化大豆油酯交换制备生物柴油

采用浸渍法制备了二氧化锆负载氢氧化钾固体碱催化剂KOH/ZrO2,在空气中焙烧4 h后,用于大豆油与甲醇的酯交换反应,考察了KOH/ZrO2固体碱催化剂的焙烧温度、醇油摩尔比、催化剂质量分数和反应时间等因素对产品收率的影响。结果表明,催化剂焙烧温度为500℃,KOH负载量为20%,醇油摩尔比为6∶1,催化剂用量为5%,反应时间为3 h时,大豆油酯交换反应转换率为97.73%。     

利用碳模板制备ZrO2亚微米空心球

以水热法合成的单分散碳球为模板,通过无机物前驱体颗粒自组装制备出ZrO2/碳球复合物,采用两步煅烧去除碳球模板,制备出ZrO2亚微米空心球,研究了碳球模板表面改性对空心球结构和性能的影响。借助于X射线衍射、场发射扫描电子显微镜、透射电子显微镜和比表面积分析仪对空心球的组成、形貌和结构进行了表征。结果表明:碳球模板大小均匀,粒径在450nm左右,球表面光滑、形状规则、分散性好;碱处理能有效增加碳球模板表面的官能团数目,改善碳球表面的核电状态和亲水性,进而调控核-壳结构中壳层的厚度;产物空心球由四方相ZrO2组成,随碳球表面改性时间的增加,空心球壁厚逐渐增大,比表面积从104.7m2/g逐渐减小到47.9m2/g。     

ZrO2-CNB复合光催化剂的制备及其性能研究

以四苯基硼化钠和尿素作为原料,通过热聚合法,利用热诱导前驱体发生缩聚反应,合成硼掺杂石墨相氮化碳(CNB)。然后,将ZrO₂与CNB混合均匀,通过煅烧法制备了不同ZrO₂含量的复合光催化剂ZrO₂-CNB。以甲基橙作为降解目标化合物,探究了ZrO₂-CNB的紫外光催化性能,并通过加入各种自由基清除剂,考察了在紫外光照射条件下光催化反应体系中生成的活性物种。研究表明：在所制备的复合光催化剂ZrO₂-CNB中,含有质量分数为0.75%的ZrO₂的ZrO₂-CNB催化剂具有最高的紫外光催化性能;在优化实验条件下,当用紫外光照射反应体系80 min时,以其为催化剂的光催化降解体系对甲基橙的降解率高达85%。ZrO₂-CNB光催化反应机制表明,h⁺和·OH在光催化降解甲基橙反应体系中起到显著作用,特别是h⁺在光催化降解反应过程中起到最主要的作用。     

用冰模板法制备定向结构氧化锆多孔陶瓷

以冰为造孔模板制备氧化锆多孔陶瓷。采用扫描电镜观察微观结构,并测量其气孔率和体积密度。结果表明:经过冷冻干燥工艺及高温烧结后,获得了定向排列的多孔结构。多孔陶瓷的气孔率为29.09%,体积密度为1.37g/cm3。     

Large-scale and ultra-low thermal conductivity of ZrO2 fibrofelt/ZrO2-SiO2 aerogels composites for thermal insulation

The large-scale fibrous/aerogels composites are prepared by using zirconia fibrofelt (ZFF) as skeleton to give high strength and ZrO₂-SiO₂ aerogels (ZSA) as filler to give excellent thermal insulation through vacuum impregnation. The ZFF/ZSA with a low density of 0.302?g/cm³ and a high porosity (89%) exhibits large size of 180?mm in length, 180?mm in width and 25?mm in height which is larger than other fibrous aerogels. Meanwhile, the ZFF/ZSA exhibits high compressive strength of up to 0.17?MPa which is approximately six times higher than that of ZFF (0.028?MPa). The ZFF/ZSA shows a much lower thermal conductivity of 0.0341?W?m^?1 K^?1 at room temperature and 0.0460–0.096?m^?1 K^?1 during 500?°C and 1100?°C which are lower than that of conventional fibrous materials, indicating its excellent thermal insulation property in a wide temperature range, and the thermal insulation mechanism is analyzed. Thus, the large-scale, low density, high strength, and low thermal conductivity of ZFF/ZSA composites show enormous potential application in the fields of architecture, engineering pipes and aerospace for thermal insulation and protection.     

Synthesis of functional gradient BCP/ZrO2 bone substitutes using ZrO2 and BCP nanopowders

BCP/BCP-ZrO₂/ZrO₂ scaffold with a functionally gradient layered structure (FG BCP/ZrO₂) was fabricated by the polymeric sponge replica method and subsequent dipping process. To enhance the compressive strength and bioactive properties of monolithic ZrO₂ scaffold, ZrO₂ and BCP phases were selected as a main frame and surface layer, respectively. The formation of microcracks was significantly decreased by incorporating an intermediate layer consisting of BCP-ZrO₂ phase. The thicknesses of the monolithic ZrO₂, BCP-ZrO₂, and BCP layer were around 10-30 μm, 3-5 μm, and 2-3 μm, respectively. The FG BCP/ZrO₂ scaffold showed highly interconnected pores as well as good material properties, which were 68% porosity and 7.2 MPa of compressive strength. Average pore size of FG BCP/ZrO₂ scaffold was about 220 μm in diameter. From MTT assay and SEM observation of osteoblast-like MG-63 cells, FG BCP/ZrO₂ scaffold showed good cell viability and faster proliferation behavior.     

Preparation and characterization of ZrO2/PES hybrid ultrafiltration membrane with uniform ZrO2 nanoparticles

In current or next-generation reuse systems, the development of new classes of antifouling membranes is needed before viable membrane-based approaches for wastewater reclamation can be achieved. In this study, ZrO₂/PES hybrid ultrafiltration membranes with uniform ZrO₂ nanoparticles were prepared by combining an ion-exchange process with a traditional immersion precipitation process. Hydrous ZrO₂ sol was synthesized by addition of anion-exchange resin in N,N-dimethylformamide solvent containing zirconyl chloride. Homogeneous ZrO₂/PES casting solution was then obtained by dissolving PES polymer in the ZrO₂ sol. The existence and dispersion states of ZrO₂ nanoparticles in the resultant membrane matrix were examined by X-ray photoelectron spectrometer, thermogravimetric analysis, scanning electron microscope and transmission electron microscope. The results indicate that the ZrO₂ nanoparticles were well dispersed throughout the PES matrix and the diameter of the formed nanoparticles was about 5–10 nm. The hydrophilicity of the membranes was determined by measuring the contact angles. The antifouling property was determined by antifouling experiments and atomic force microscopy. The results confirm that the existence of ZrO₂ nanoparticles improves the hydrophilicity and reduces protein adsorption of membranes.     

Microstructural development of sintered ZrO2---CeO2 ceramics

Microstructural development associated with diffusionless phase transformation was investigated in sintered ZrO₂-10–60 mol% CeO₂ ceramics cooled rapidly from a high temperature, using TEM and XRD techniques. The results show that (112) reflections appeared and a domain structure was found in ZrO₂-20–40 mol% CeO₂ samples, which is a result of c-t′ diffusionless transition, while the structure of the ZrO₂-60 mol% CeO₂ sample was fully stabilized zirconia, in which no forbidden reflections of c-ZrO₂ appeared. Finally, plate martensite and lath martensite structure were found in the ZrO₂-10 mol% CeO₂ sample; the former is the tetragonal phase with internal twins and the latter is the twinned monoclinic phase.     

Supersonic atmospheric plasma sprayed ZrO2 and ZrB2-SiC/ZrO2 coatings on Cf/Mg composites for anticorrosion

To improve the corrosion resistance of the carbon fiber reinforced magnesium matrix composites (C_f/Mg composites), ZrO₂ and ZrB₂-SiC/ZrO₂ composite coatings were prepared by supersonic atmospheric plasma spraying (SAPS) on C_f/Mg composites. The microstructure and phase composition of the coatings before and after the corrosion test were investigated. Open circuit potential and potentiodynamic polarization tests were measured at room temperature. Results revealed that the corrosion current density ($i_{\mathit{corr}}$) of the ZrO₂ coated C_f/Mg composites decreased by one order while the ZrB_2-SiC/ZrO₂ coated C_f/Mg composites reduced by two orders. Compared with C_f/Mg composites, the corrosion potential ($E_{\mathit{corr}}$) of the ZrO₂ and ZrB₂-SiC/ZrO₂ coated C_f/Mg composites increased by 220.5?mV and 1021.8?mV respectively, indicating that the ZrB₂-SiC/ZrO₂ composite coatings greatly improve the corrosion resistance of C_f/Mg composites. The uniform distribution of the SiC particles with small grain size in ZrB₂ is responsible for the densification of the coating. The ZrB₂-SiC/ZrO₂ composite coatings provide a barrier for the substrate to impede the entry of Cl^- in the corrosion solution, thus exhibiting a better corrosion resistance than the ZrO₂ coating.     

Effect of ZrO2 content on the mechanical properties and microstructure of HAp/ZrO2 nanocomposites

This paper presents the effect of Zirconia (ZrO₂ =?0, 5, 10, 15, 20 and 25?wt%) on the mechanical properties and micro structural studies of Hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂) (HAp) nano composites. HAp and Zirconia nano composites of 20–40?nm were produced using High Energy Ball milling at 300?rpm for 1?h. X-ray diffraction studies showed that the crystallite and grain size gradually decreased with the increase in ZrO₂ content till 20?wt%, after which there was a sudden raise in both parameters. A dominant ZrO₂ phase was observed in X-ray diffraction studies of sintered samples. Mechanical properties were found to significantly improve on adding 20?wt% of ZrO₂ at 1200?°C. However, the addition of 25?wt% of ZrO₂ powder decreased the mechanical properties of HAp. The reduction could be due to the increase in grain size and dominant smaller particles of ZrO₂. The improved mechanical properties were correlated with the observed micro structural features.     

Mechanical properties of Al2O3/ZrO2 composites

In the present study, both t-phase zirconia and m-phase zirconia particles are incorporated into an alumina matrix. Dense Al₂O₃/(t-ZrO₂+m-ZrO₂) composites were prepared by sintering pressurelessly at 1600 °C. The microstructure of the composites are characterized, the elastic modulus, strength and toughness determined. Because the ZrO₂ inclusions are close to each other in the Al₂O₃ matrix, the yttrium ion originally in t-ZrO₂ particles can diffuse to nearby m-ZrO₂ particles during sintering, and the m-phase zirconia is thus stabilized after sintering. The strength of the Al₂O₃/(t-ZrO₂+m-ZrO₂) composites after surface grinding can reach values as high as 940 MPa, which is roughly three times that of Al₂O₃ alone. The strengthening effect is contributed by microstructural refinement together with the surface compressive stresses induced by grinding. The toughness of alumina is also enhanced by adding both t-phase and m-phase zirconia, which can reach values as high as two times that of Al₂O₃ alone. The toughening effect is attributed mainly to the zirconia t–m phase transformation.     

Laser stereolithography of ZrO2 toughened Al2O3

Ceramic laser stereolithography is a manufacturing process suitable candidate for the production of complex shape technical ceramics. The green ceramic is produced layer by layer through laser polymerisation of UV curable ceramic suspensions. A number of critical issues deserve attention: high solid loading and low viscosity of the suspensions, high UV reactivity, prevention of interlayer delamination in the green and in the sintered body, good mechanical performance. In this work, ZrO₂-reinforced Al₂O₃ components have been obtained from an acrylic modified zircon loaded with alumina powders. The zircon compound is effective as organic photoactivated resin and allows the dispersion of a high volume fraction of Al₂O₃ powder (up to 50 vol.%) while keeping viscosity at reasonable low values. The zircon compound also represents a liquid ceramic precursor that converts to oxide after burning out of the binder. Thank to the good dispersion of the alumina powder in the zircon acrylate, a uniform dispersion of ZrO₂ submicron particles is obtained after pyrolysis. These are located at the grain boundaries between alumina grains. Formation of both monoclinic and tetragonal ZrO₂ occurs as evidenced by XRD. No delamination occurs in bending tests as evidenced by SEM fractography, satisfactory modulus and strength values were concurrently found.