含ZrO2添加剂对方镁石-尖晶石耐火材料力学性能的影响

在方镁石-尖晶石耐火材料中,加入三种不同类型的含ZrO2添加剂,均能明显提高材料的力学性能。经XBD、偏光显微镜及电子探针分析,认为改善性能的机理在于引入ZrO2改善了材料的显微组织结构,并产生了适量微裂纹,强化了基质,从而提高了材料的力学性能。     

含TiO2高炉渣对Sialon结合SiC材料的侵蚀行为

实验考察了含TiO     

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.     

The optimization of the microstructure and phase assemblage of high chromia refractories

The effect of Al₂O₃ and ZrO₂ addition in chromia-based refractories was investigated. The strength of ZrO₂-bearing chromia refractories was greatly enhanced by 4–8 wt% Al₂O₃ additive. In the range of 0–12 wt% ZrO₂ addition, 6 wt% ZrO₂ was most beneficial to the improvement in thermal shock resistance. Corrosion resistance was compared by exposing to three kinds of coal slag with various CaO contents. As the substitution of ZrO₂ for Cr₂O₃ increased, slag penetration increased, particularly in the case of the slag containing ∼16 wt% CaO. Considering the trade-offs between corrosion resistance, thermal shock resistance and mechanical properties, the optimum phase assemblage of high chromia refractories consists of the large granular Cr₂O₃ grains bonded by annular (Cr, Al)₂O₃ grains and well-distributed fine ZrO₂ grains.     

Corrosion behavior of ZrO2-SiO2-Al2O3 refractories in lead silicate glass melts

High-temperature (1200-1350 °C) corrosion of fused-cast ZrO₂-Al₂O₃-SiO₂ (ZAS) refractory contacting lead silicate glass melt (LSG) containing 68.5 wt% PbO was investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), differential scanning calorimetry (DSC), x-ray diffraction (XRD), thickness measurement and Archimedes density measurement. ZAS durability was improved by baddeliyete content and deteriorated with open porosity proportion, corundum percentage and eutectic mixture presence. Diffusion of lead resulted in fusion-temperature lowering of the glassy layers embedded within the ZAS particles. Heating caused viscosity drop across the interface, loosening the inter-connected refractory particles and disrupted the crystalline particles residing adjacent to the refractory exterior. Among three ZAS refractories tested in this research, the most durable material was the one with the utmost baddeliyete amount, the least open porosity and the minimum eutectic mixture.     

Effect of microstructure and mechanical properties on wear behavior of plasma-sprayed Cr2O3-YSZ-SiC coatings

In this study, the microstructure and mechanical properties of the atmospheric plasma-sprayed Cr₂O₃ (C), Cr₂O₃-20YSZ (CZ), and Cr₂O₃-20YSZ-10SiC (CZS) coatings were evaluated and also compared with each other, so as to explain the coatings wear behavior. Microstructural evaluations included X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) equipped with energy dispersive X-ray spectroscopy (EDX) and porosity measurements. Mechanical tests including bonding strength, fracture toughness, and micro-hardness tests were used to advance our understanding of the correlation between the coatings properties and their wear behavior. The sliding wear test was conducted using a ball-on-disk configuration against an alumina counterpart at room temperature. Addition of multimodal YSZ and subsequent SiC reinforcements to the Cr₂O₃ matrix resulted in an increase in the fracture toughness and Vickers micro-hardness, respectively. It was found that the composite coatings had comparable coefficients of friction with pure Cr₂O₃ coatings. When compared with the C coating, the CZ and CZS composite coatings with higher fracture toughness exhibited superior wear resistance. Observation of the wear tracks of the coatings indicated that the lower wear rates of the CZ and CZS coatings were due to the higher plastic deformation of the detached materials. In fact, improvement in the wear resistance of the composite coatings was attributed to a phase transformation toughening mechanism associated with tetragonal zirconia which created more ductile tribofilms during the wear test participated in filling the pores of coatings.     

Improvements on the mechanical properties and thermal shock behaviours of MgO-spinel composite refractories by ZrO2 incorporation

Microstructural features and improvements on the mechanical properties and thermal shock behaviours of MgO-spinel composite refractories with ZrO₂ addition were examined. ZrO₂ incorporation into MgO-spinel led to improvements around ∼1.5-fold ratios on mechanical properties, R_st values and thermal shock results. The basic parameters improving mechanical properties and thermal shock resistance of MgO-spinel-ZrO₂ composite refractories were determined as follows: (i) propagation of microcracks for a short distance by interlinking each other, (ii) stopping or deviation of microcracks when reaching pores or ZrO₂ particles, (iii) concurrent occurrence of mostly intergranular and some transgranular cracks on fracture surfaces, and with the addition of ZrO₂ (iv) the increase in bulk density, and (v) a significant decrease in MgO grain size. The improvements observed in thermo-mechanical properties confirmed that MgO-spinel-ZrO₂ refractories showed a low strength loss and high thermal shock damage resistance at high temperatures, leading to longer service lives for using industrial applications.     

在气化炉中由渗透煤渣引起高铬砖显微结构的改变

对气化条件下渗透的煤渣与耐火材料反应对添加Al2O3和ZrO2的高铬砖显微结构的影响进行了深入研究。氧化铬耐火材料是一种显微结构不均匀的混合体,包括晶粒形状及尺寸、化学成分、致密化程度等。Cr2O3抗渣侵蚀能力与颗粒尺寸和致密化程度有关,颗粒尺寸越大且致密化程度越高,材料的抗侵蚀能力越高。ZrO2没有发生化学变化但它可能会溶解在渣中。对实验室和小规模气化炉用后耐火材料进行分析,均发现相同的反应产物。化学成分和晶相分析同样可以证明在砖和渣界面生成铬的氧化物,Fe慢慢被耗尽。当温度和时间发生变化时,尽管显微结构的变化很难定量分析,但是渣渗透量会随着时间延长和温度升高而增加。     

Effect of ZrO2 on phase transformation of Al2O3

This study investigates the effect of ZrO₂ on phase transformation of alumina. Alumina and alumina–zirconia composite powders were produced by the precipitation method from aluminum sulfate and zirconium sulfate precursors. Precipitates obtained at 15 °C were dried at 80 °C for 72 h, and then calcinated at four different temperatures; 1000 °C, 1100 °C, 1200 °C and 1300 °C for 1 h. Powders calcinated at 1300 °C were pressed uniaxially and sintered at 1600 °C for 1 h. XRD and DSC analyses showed that the presence of zirconia retarded the transformation to α-alumina. SEM studies on the powders calcinated at 1300 °C revealed that both alumina and alumina–zirconia particles were 100–300 nm in size and of near spherical shape. Zirconia additions inhibited abnormal grain growth of alumina and provided homogeneous, equaxied grain structure.     

In situ microstructure characterization of ZrO2 coating at high temperature

Thermal barrier coatings (TBCs) are key materials of turbines for propulsion and power generation. The failure mechanism of TBCs is a crucial problem in scientific community and need to be resolved. Failure of TBCs is a complicated process affected by its own performance, microstructure and service environment. In this study, thermal barrier coatings of ZrO₂ were prepared by plasma spraying method. A SEM with heating system is used to study in situ microstructure change of TBCs at service temperature. Changes in microstructure and interfaces as well as healing and development of cracks are revealed. It is expected that the investigation of the failure mechanism of the TBCs from a microscopic point help to improve service life of the TBCs by providing a reliable basis to solve the failure problem.     

Cr_2O_3对方镁石－尖晶石耐火材料抗渣性的影响

采用电熔镁砂及预合成电熔ＭＡ砂为原料，在高温下烧成方镁石－尖晶石试样，当加入少量铬矿时可提高其热震稳定性及抗渣性。用坩埚法作富ＣａＯ转炉渣对方镁石－尖晶石系耐火材料的侵蚀试验后，采用ＸＲＤ、ＳＥＭ、ＥＤＡＸ、岩相分析等方法分析Ｃｒ_２Ｏ_３对方镁石－尖晶石耐火材料抗渣性的影响。     

The influence of ZrO2 additive on sintering and microstructure of lithium and lithium-titanium-zinc ferrites

The effect of ZrO₂ addition (0–3?wt%) on sintering and microstructure of lithium and lithium-titanium-zinc ferrites was studied. The Vickers hardness and dc electrical resistivity were investigated and discussed in correlation with the structural properties. Ferrite powders with the chemical compositions of LiFe₅O₈ and Li_0.65Fe_1.6Ti_0.5Zn_0.2Mn_0.05O₄ were prepared by the conventional ceramic technique. The synthesized ferrites were doped with various amount of ZrO₂ and then were sintered at 1050?°C for 2?h. Dilatometric studies showed that the zirconia addition affects the densification process of ferrite ceramics so that the shrinkage rate of pressed ferrite powders during their heating decreased with an increase in ZrO₂ content. The bulk density of the sintered ferrites varied slightly as the concentration of the additive was increased from 0 to 2?wt%, while the density of ferrite doped with 3?wt% ZrO₂ significantly decreased. X-ray diffraction and scanning electron microscopy analyses showed that the lattice parameter of ferrites increases and their average grain size decreases as the additive content grows. It was established that small amounts of ZrO₂ additive (up to 2?wt%) improve significantly the hardness and the electrical resistivity of ferrites.     

Cr_2O_3对矾土－尖晶石耐火材料抗渣性的影响

以高铝矾土及预合成电熔ＭＡ砂为原料，制各了矾土－尖晶石耐火材料。对其加入铬精矿后的抗渣性进行了试验。结果表明，少量铬精矿的加入能形成尖晶石固溶体，提高制品的抗渣性能。     

TiO2含量对镁铝钛耐火材料烧结及显微结构的影响

以电熔镁砂、电熔白刚玉、电熔尖晶石、铬精矿及钛白粉为原料制备了镁铝钛试样,研究了加入不同量TiO2(分别为2%、3.5%、4%、4.5%、5%、7%和12.5%)的镁铝钛材料分别在1450℃、1500℃、1550℃、1600℃、1680℃、1750℃保温4~5h后的烧结状况,并对1500℃和1600℃烧后试样进行了SEM、EDAX和XRD分析。结果表明:加入质量分数为3.5%~7%的TiO2就能显著促进镁铝钛试样的烧结,同时改善其抗热震性;当煅烧温度低于1680℃时,随着煅烧温度的升高,试样的烧结程度越好,显气孔率下降,体积密度增加;试样的主晶相为方镁石,基质部分结构致密,气孔少且多呈封闭的圆孔状;基质中主晶相为方镁石,次晶相为尖晶石固溶体、钛酸钙和少量的镁橄榄石,方镁石之间、方镁石和次晶相之间的直接结合利于试样性能的提高。     

Improvement in performance of MgO–CaO refractories by addition of nano-sized ZrO2

MgO–CaO refractories added with different sized ZrO₂ powders were sintered at 1600 °C, the effect of the ZrO₂ powders on performance of MgO–CaO refractories was investigated. The results showed that the densification of the MgO–CaO refractories was appreciably promoted when a small amount of ZrO₂ was added owing to the formation of small size CaZrO₃ facilitated to sintering, and the densification was promoted further with increasing the amount of ZrO₂ due to the volume expansion caused by the reaction of the added ZrO₂ and CaO to form CaZrO₃ in the refractories, and the addition of nano-sized ZrO₂ was more effective. The thermal shock resistance of the MgO–CaO refractories was improved by modification of the microstructure due to the formed CaZrO₃ particles that predominately located on the grain boundaries and triple points in the whole microstructure, and the addition of nano-sized ZrO₂ was more effective attributed to its well dispersion and the critical addition amount was effectively decreased to 6%. The slaking resistance of the MgO–CaO refractories was appreciably improved by addition of ZrO₂ due to its effect on decreasing the amount of free CaO in the refractories, promotion of densification as well as modification of microstructure, the nano-sized ZrO₂ addition was more effective due to its higher activity. The slag corrosion resistance of the MgO–CaO refractories was enhanced by addition of ZrO₂ due to the increase of the viscosity of the liquid phase and thus inhibited further penetration of slag at elevated temperatures.     

烧结温度对漂珠/ZrO2多孔轻质材料性能的影响

以漂珠为成孔材料,以ZrO2为结合剂,采用凝胶注模的方法制备出多孔轻质材料。通过分析材料的微观形貌、物相组成、显气孔率、体积密度、抗弯强度等性能参数,研究了烧结温度1200℃~1500℃对材料性能的影响。结果得出,烧结温度达到1400℃时,漂珠外壳与氧化锆的界面结合不再明显,ZrO2颗粒由点接触扩展到面接触;烧结温度1400℃的试样中锆英石的峰最强,说明漂珠和氧化锆已烧结熔融;1400℃下制备试样的显气孔率最大(68%),体积收缩率(20.8%)最低,而抗弯强度可达7.5MPa;烧结温度控制在1400℃,可使材料处于烧结中期,保证材料的各项性能满足其应用需求。     

ZrB2质与TiB2质耐火材料

介绍了ZrB     

Effect of dispersant content and drying method on ZrO2@Al2O3 multiphase ceramic powders

ZrO₂@Al₂O₃ composite ceramic powders were prepared by solution combustion method with aluminum nitrate (Al (NO₃)₃) and 3?mol% yttria-stabilized tetragonal zirconia polycrystal (3Y- TZP) as the main raw materials, ammonium polyacrylate (PAA-NH₄) as a dispersant, urea (CO (NH₂)₂) as a reducing agent. The effects of PAA-NH₄ concentration and drying method on the microstructure and morphology of the ZrO₂@Al₂O₃ powders were investigated. The results showed that when the concentration of PAA-NH4 was 1.5?wt%, and the molar ratio of Al (NO₃)₃ to CO (NH₂)₂ was 1:2, the ZrO₂@Al₂O₃ powders with uniform grain size and high crystallinity could be synthesized by solution combustion drying method. Additionally, the abnormal growth of 3Y- TZP grain in ZrO₂@Al₂O₃ was suppressed and the crystalline phase transformation trend (t-ZrO₂ to m-ZrO₂) was obviously decreased after sintering at 1600?°C.     

钌助剂对Co/ZrO_2催化剂还原性能的影响

制备了一系列不同钌含量的ZrO2负载的钴基费-托合成催化剂,采用X-射线衍射,H2-程序升温还原分析方法研究了钌助剂对Co-ZrO2催化剂还原性的影响。结果表明,催化剂钴物种主要以Co3O4的形式分散在载体表面。催化剂中加入少量的Ru助剂有利于氧化钴的两步还原和残余硝酸钴的还原,增强了催化剂的还原度。