压痕法研究ZrO2层状复合陶瓷的抗热震性

用压痕法测试了单层和层状两种ZrO2陶瓷材料的抗热震性能.研究结果表明ZrO2层状复合陶瓷的临界热震温差△Tc=400℃,比ZrO2单层陶瓷高出150℃左右,同时还表现出其△Tc与陶瓷厚度无关的优异性质.现场试验结果也证明,ZrO2层状复合陶瓷抵抗1500℃冷热骤变的能力优于ZrO2单层陶瓷.研究认为,界面压应力作用部分或全部抵消了热冲击应力,使裂纹在界面处发生偏转,提高了材料的断裂能和断裂功,导致材料的抗热震性提高.     

Cyclic cold isostatic pressing and improved particle packing of coarse grained oxide ceramics for refractory applications

This study investigated the cold isostatic pressing of coarse grained alumina refractories applying either a cyclic pressure increase or a cycling at maximum pressure. Additionally the effects of the maximum pressure and the particle size distribution on physical, mechanical and thermomechanical properties were analyzed. The cyclic pressure increase resulted in a slightly higher apparent density and lower apparent porosity. A cycling at maximum pressure decreased the median pore size to some extent. Remarkably, an optimized particle size distribution resulted in a lower apparent porosity, lower median pore size and in a higher Young's modulus before and after thermal shock together with a slightly lower relative decrease of the Young's modulus. A higher pressing pressure which decreased the apparent porosity did not affect the Young's modulus. Thus, apparently the optimized particle size distribution improved the particle packing which was associated with a smaller median pore size. This smaller pore size increased the number of pores relative to the total porosity, which then acted as points of crack initiation and crack deflection limiting the length of propagating cracks in case of thermal shock. Thus, tailoring the pore size distribution is a promising starting point to improve the thermomechanical properties of refractories.     

Influence of mullite additions on thermal shock resistance of dense alumina materials. Part 2: Thermal properties and thermal shock behaviour

Abstract

The thermal properties and thermal shock behaviour of homogeneous, fine grained (≈ 0·5–2 µm), dense (≥ 98% of theoretical density) alumina–mullite (5–15 vol.-%) composites have been studied and compared with those of a reference alumina ceramic with similar microstructure. Thermal expansion (25–600°C) thermal diffusivity, and thermal conductivity (25–400°C) were determined and a correlation between these results and microstructural characteristics was established. On the basis of the predicted theoretical relative performance under thermal shock, one of the composites (10 vol.-% mullite) was chosen and the thermal shock behaviour on quenching was compared with that of the reference alumina. A test that accounts for the detrimental effect of mullite on the heat transfer properties of alumina has been proposed. The results obtained agree with the theoretical predictions. In particular, the composite material had a critical temperature increment for failure larger (～ 12%) than that of alumina.     

Ceramic Membranes with Selective Layers Based on SiO2, TiO2, and ZrO2

A technology for producing ultrafiltration ceramic membranes using the sol-gel method has been developed. Experimental lots of membranes with selective layers based on SiO₂, TiO₂, and ZrO₂ are obtained, and their characteristics are investigated.     

Preparation and fine thermal insulation performance of Gd2Zr2O7/ZrO2 composite fibers

Gd₂Zr₂O₇/ZrO₂ (GZC) composite fibers were prepared by electro-spinning method. The XRD, XPS and Raman results showed that there were three crystalline phases, tetragonal phase ZrO₂, cubic phase ZrO₂ and defect fluorite phase Gd₂Zr₂O₇ in GZC composite fibers. GZC fibers remained an intact fiber texture up to 1400 °C according to SEM photographs. The thermal conductivity of GZC fibers was between 0.173 W/(m·K) at 400 °C and 0.309 W/(m·K) at 800 °C, which was lower than that of 7YSZ under the same experimental conditions. The fiber sheet with density about 3.5 g/cm³ has thermal shrinkage less than 3% at 1400 °C. Hence, GZC fibers could be used as refractories for heat protection.     

Al2TiO5添加量对MgO-Al2TiO5复合陶瓷烧结及抗热震性的影响

以纳米MgO粉为原料,选用以纳米Al2O3粉和纳米TiO2粉经1500℃保温3 h烧结制备的Al2TiO5为添加剂,采用固相烧结法经1500℃保温3 h制备了Al2TiO5质量分数分别为0、5%、10%和20%的MgO-Al2TiO5复合陶瓷,并采用XRD、SEM和EDS等研究了Al2TiO5添加量对MgO-Al2TiO5复合陶瓷烧结性能及抗热震性能的影响。结果表明:添加Al2TiO5有利于促进复合陶瓷的烧结,其体积密度和线收缩率随Al2TiO5添加量的增加而增大,当Al2TiO5添加量为20%(w)时,其体积密度和线收缩率分别为3.68 g·cm-3和22.07%;当Al2TiO5添加量为10%(w)时,其抗热震性能最佳。Al2TiO5位于方镁石晶粒交界处,抑制方镁石晶粒生长,阻碍裂纹扩展,使MgO-Al2TiO5复合陶瓷的抗热震性能得到改善。     

ZrO2 对堇青石多孔陶瓷性能和显微结构的影响

以高岭土、滑石和αAl2O3微粉为主要原料,按堇青石的理论组成配料后,外加10%的化学纯活性炭为造孔剂,同时分别外加0、0.25%、0.5%、0.75%和1.0%的分析纯ZrO2,经湿混、干燥、造粒、成型和1340℃保温5h烧成后,制成不同ZrO2含量的堇青石多孔陶瓷,并研究了ZrO2外加量对试样热膨胀系数、显气孔率、吸水率及烧成收缩率的影响,并用XRD和SEM分析了试样的物相组成和断面形貌。结果表明:与未加ZrO2的相比,外加0.25%ZrO2时,试样的热膨胀系数显著降低,但超过0.25%时,热膨胀系数随ZrO2外加量的增加而略有升高;随ZrO2外加量的增加,试样的显气孔率和吸水率逐渐增大,而烧成收缩率降低;与未加ZrO2的试样相比,外加1.0%ZrO的试样内扁平状气孔的数量较多,且气孔在试样内分布较均匀。     

添加TiO_2、ZrO_2对烧结铝铬渣材料性能的影响

为了进一步提高酸洗后铝铬渣烧结块的性能尤其是其抗热震性,取粒度≤0.045 mm的铝铬渣,在浓盐酸中煮沸20 min后,过滤,洗净,干燥,制成酸洗铝铬渣。在酸洗铝铬渣中分别加入4%(w)的钛白粉、锆英石粉或钛白粉-锆英石粉复合粉(钛白粉与锆英石粉的质量比为1 1),经混练、成型、干燥后,在1 500℃保温2 h热处理制成烧结铝铬渣试样,然后检测其体积密度、显气孔率、常温耐压强度、常温抗折强度和抗热震性,并分析其显微结构。结果表明:在酸洗铝铬渣中分别添加钛白粉、锆英石粉或复合添加钛白粉-锆英石粉均可提高烧结铝铬渣试样的致密度、常温强度和抗热震性,其中,添加钛白粉-锆英石粉试样的综合性能提高幅度最大。     

CaO稳定ZrO2耐火材料的相组成和热膨胀

对CaO稳定ZrO2耐火材料的相组成和热膨胀行为进行了研究.重点讨论了三种具有不同相组成的CaO稳定ZrO2材料的热膨胀特性.研究结果表明,通过调整ZrO2的稳定程度,可以优化材料的相组成和热膨胀行为,从而改善材料的抗热震性能,并有望使耐火材料的综合性能得到提高.     

锆硅包膜金红石型钛白粉工艺优化及性能

采用溶胶–凝胶法制备了锆硅包膜金红石型钛白粉。通过正交实验研究了浆液浓度、分散剂用量和Zr O2、Si O2两种包膜剂含量对锆硅包膜金红石型钛白粉的影响,得到了制备锆硅包膜金红石型钛白粉的优化工艺条件。采用Nano-ZS型粒度仪、扫描电子显微镜、透射电子显微镜和能谱仪、Fourier红外光谱仪等测试手段,考察锆硅包膜金红石型钛白粉的效果和包膜机理。结果表明:金红石型钛白粉表面包覆了两层均匀而致密的Zr O2膜和Si O2膜。包膜后金红石型钛白粉的失光率、吸油量和遮盖力都有所下降,白度值增加。同时,证实了这两层膜是以化学键Zr-O-Ti和Si-O-Zr的形式结合在金红石型钛白粉颗粒表面。     

ZrO2/SiO2催化剂的制备及其氧化脱硫性能研究

以己内酰胺-八水氧氯化锆低共熔溶剂为添加组分,采用溶胶-凝胶法合成含锆的硅胶,再经过高温煅烧得到n-ZrO₂/SiO₂ （n=2%,4%,6%） 负载型催化剂。并用红外光谱（FT-IR）、X射线衍射（XRD）、扫描电镜（SEM）、N₂吸附-脱附、X射线光电子能谱（XPS）对其进行结构表征,确定ZrO₂成功负载到SiO₂上。以ZrO₂/SiO₂为催化剂和吸附剂,H₂O₂为氧化剂组成催化氧化脱硫体系,并应用于模拟油脱硫。分别考察了氧化锆负载量、反应温度、氧硫比、催化剂加入量及不同类型的硫化物对脱硫效果的影响。实验结果表明,在反应温度为70℃、n（H₂O₂）/n（S）=4（摩尔比）、4%-ZrO₂/SiO₂的加入量为0.2 g的最佳反应条件下,氧化脱硫体系对二苯并噻吩（DBT）、4,6-二甲基二苯并噻吩（4,6-DMDBT）和苯并噻吩（BT）的脱除率分别为98.7%、93%和65.9%。且4%-ZrO₂/SiO₂回收利用5次后,DBT脱除率仍可达到91.8%。     

ZrO2-莫来石复合耐火材料的反应烧结制备和抗热震性研究

从先进陶瓷精细的制备技术出发 ,以超细ZrSiO4和Al2 O3的反应烧结产物为结合相 ,以粗粒莫来石为骨料 ,制备出ZrO2 -莫来石复合耐火材料。研究了材料的制备工艺、显微结构和力学性能 ,重点探讨了材料的抗热震性。所得ZrO2 -莫来石复合耐火材料同时具有高的致密度 ( >90 % )和优良的抗热震性。     

Coupling copper and hydrogenated TiO2 to bare TiO2 structures for improved photocatalytic performance

Coupling of metals and hydrogenated TiO₂ (HT) to bare TiO₂ may improve synergistically the photocatalytic activity of TiO₂ for pollutant decomposition. Herein, we address this issue by investigating the photocatalytic performances of Cu‐loaded HT (CuHT)/bare TiO₂ (CuHTT) heterojunction nanocomposites for the degradation of harmful n‐butanol under simulated solar light illumination. CuHTT with a CuHT‐to‐TiO₂ composition ratio of 0.1 showed a photocatalytic efficiency exceeding those of four reference photocatalysts, exhibiting the advantages of improved visible light absorption efficiency, charge carrier separation, and adsorption capacity. Increasing the CuHT‐to‐TiO₂ ratio from 0.01 to 0.1 improved the photocatalytic efficiency of CuHTT, whereas a further increase to 0.9 resulted in a decreased photocatalytic efficiency. Moreover, the photocatalytic efficiency improved as relative humidity increased from 20% to 70%, decreasing upon its further increase to 95%. The efficiencies of n‐butanol to CO₂ conversion over CuHTT were lower than the corresponding decomposition efficiencies. Incompletely oxidized CO and three organic vapors (butanal, propanal, and 1‐propanol) were determined as major intermediates. A possible mechanism for CuHTT‐catalyzed photodegradation under simulated solar illumination was proposed.     

Sintering behavior and thermal shock resistance of aluminum titanate (Al2TiO5)-toughened MgO-based ceramics

In order to improve the thermal shock resistance of MgO-based ceramics, aluminum titanate (Al₂TiO₅)-toughened MgO-based ceramics were successfully prepared by solid state sintering at 1450 °C and 1550 °C for 3 h starting from MgO and as-synthesized Al₂TiO₅ powders. The effects of various contents of Al₂TiO₅ second phase on the sintering behavior and thermal shock resistance of MgO-based ceramics were investigated. The sintering behavior of sintered samples was evaluated by comparing the relative density, apparent porosity, bending strength, phase composition as well as microstructure. The thermal shock resistance of sintered samples was characterized by using the residual bending strength after three thermal cycles and thermal expansion coefficient. The obtained samples with 10 wt% Al₂TiO₅, which were sintered at 1550 °C for 3 h, showed the highest relative density, lowest apparent porosity as well as optimum bending strength. In addition, the samples added 15 wt% Al₂TiO₅ at 1550 °C with a dwell time of 3 h were the highest residual bending strength and lowest thermal expansion coefficient. It revealed that the enhancement in thermal shock resistance was ascribed to the reduction of thermal expansion coefficient.     

Influence of TiO2, Cr2O3 and ZrO2 on sintering and machinability of fluorophlogopite glass ceramics

Abstract

The influence of Cr₂O₃, TiO₂ and ZrO₂ on the sintering, crystallisation and machinability of SiO₂–Al₂O₃–MgO–K₂O–B₂O₃–F glasses was investigated. Optimum fluoromica glass ceramic compositions with desirable sintering behaviour and machinability were obtained by addition of titanium and chromium oxides to the base glass. Texture and relative intensity of mica phase I_mica/I_Si were determined by XRD analysis and the particle size distribution of chips was studied by drilling. Microhardness and bending strength were also investigated. The relative intensity of mica phase and microhardness were found to be compatible with the experimental results.