氧化锆增韧石英陶瓷透波材料的研究

主要研究了通过添加微米级氧化锆来提高石英陶瓷材料的抗弯强度。结果表明,当添加5Wt%的氧化锆时,石英陶瓷的力学性能明显改善,抗弯强度由36.53MPa增至58.95MPa,气孔率下降,而且没有引起石英陶瓷的大量析晶。对引起这种变化的原因进行了分析,并用SEM对材料的微观形貌进行观察,用压汞仪测试材料的气孔率,用X射线衍射对材料的成份进行定性分析。     

氧化锆陶瓷增韧方法的研究进展

本文综述了氧化锆的物理、化学性质、应用性能及改善氧化锆陶瓷韧性的方法,增韧的方法主要有:相变增韧、颗粒增韧、纤维增韧、自增韧、弥散韧化、协同增韧、纳米增韧等。     

非均匀沉淀法制备黑色氧化锆陶瓷

以Y-TZP（氧化钇稳定四方多晶氧化锆）为原料、硝酸锰和硝酸铝为着色剂、PEG2000（聚乙二醇2000）为分散剂,采用非均匀沉淀法制备着色剂/氧化锆复合粉体,经成型、烧结后得到黑色氧化锆陶瓷。采用X射线衍射,扫描电子显微镜、X射线荧光分析和透射电子显微镜等对复合粉体和陶瓷的结构和性能进行表征,结果表明：着色剂/氧化锆...     

气化炉渣合成Ca-α-Sialon-SiC复相陶瓷

利用X射线荧光分析仪、X射线衍射仪、扫描电子显微镜等研究了Texaco气化炉炉渣的化学组成、物相组成和显微结构.以气化炉渣为原料,分别在1 350,1400,1450℃和1 500℃4种氮化温度下碳热还原氮化,利用物相确定和显微结构分析等研究了氮化温度对反应的影响.以1450℃氮化产物为原料,热压制备了Ca-α-sia...     

聚合物模板法制备氧化铝-氧化锆泡沫陶瓷

将发泡聚苯乙烯小球(epispastic polystyrene,EPS)排列成有序的模板,通过离心成型技术制备孔壁致密、孔径均匀的Al2O3-ZrO2泡沫陶瓷.观察了EPS模板的可压缩特性,分析了浆料固相含量对离心成型过程中物质分离现象的影响,研究了不同烧结温度对Al2O3-ZrO2泡沫陶瓷的烧结密度、孔隙率和压缩强度的影响并表征了宏观孔结构和孔壁断面的微观结构.结果表明:用50%(体积分数)固相含量的浆料可制备出孔壁均匀的样品,在样品的不同部位,Al2O3和ZrO2的分布及相对含量基本相同,物质分离现象被很好的抑制.随着烧结温度的从1 450 ℃提高到1 600 ℃,Al2O3-ZrO2泡沫陶瓷的烧结密度增加、孔隙率降低.在1 550 ℃烧结2 h,样品的抗压强度可达2.07 MPa.     

气化炉渣合成Ca-α-Sialon-SiC复相陶瓷

利用X射线荧光分析仪、X射线衍射仪、扫描电子显微镜等研究了Texaco气化炉炉渣的化学组成、物相组成和显微结构。以气化炉渣为原料,分别在1 350,1 400,1 450℃和1 500℃4种氮化温度下碳热还原氮化,利用物相确定和显微结构分析等研究了氮化温度对反应的影响。以1 450℃氮化产物为原料,热压制备了Ca-α-sialon–SiC复相陶瓷,并对此材料的力学性能进行了检测。结果表明:(1)Texaco气化炉炉渣主要化学成分为SiO2,Al2O3,CaO和残余碳,其中大多为玻璃相和无定形物质;(2)低温氮化产物主晶相为β-sialon和Ca-α-sialon,高温氮化产物主晶相为Ca-α-sialon和SiC,提高氮化温度更有利于CaO固溶于sialon形成Ca-α-sialon,在1 450℃碳热还原氮化可合成主要成分为Ca-α-sialon和SiC的复相粉体;(3)随着热压温度的升高,Ca-α-sialon-SiC复相陶瓷致密化程度增加,硬度和断裂韧性均有提高,添加剂对材料的力学性能影响较大,添加3%(质量分数,下同)Y2O3+2%MgO,1 650℃热压制备的复相陶瓷的Vickers硬度可达18 G...     

Y-TZP增韧陶瓷的制备及力学性能

研究了制备工艺和Ｙ２Ｏ３含量对四方多晶氧化锆（ＹＴＺＰ）力学性能的影响，并研究了３ＹＴＺＰ陶瓷的断裂统计、耐热冲击特性。２．５ＹＴＺＰ和３ＹＴＺＰ陶瓷的三点抗弯强度分别为１３６０±１６８ＭＰａ和１０８１±２４３ＭＰａ，Ｗｅｉｂｕｌ模数ｍ分别为８．２７和４．３４；断裂韧性分别为１１．７９ＭＰａ·ｍ１／２和１１．６０ＭＰａ·ｍ１／２。ＹＴＺＰ陶瓷中ＺｒＯ２以四方相与少量的立方相形式存在；压痕裂纹扩展为沿晶和穿晶混合模式。     

利用含钛高炉炉渣制备陶瓷釉料

本实验以含钛高炉炉渣为主要原料制备了具有光催化性能的陶瓷釉料.结果表明,炉渣加入量在33%左右,烧成温度为1200℃时,陶瓷釉料具有较好的光泽度和较高的乳浊性,并具有一定的光催化效率.     

工艺因素对还原气氛下铝热法制备Al203-TiB2复相陶瓷的影响

以铝粉、B2O3粉和TiO2粉为原料,研究了埋炭还原气氛下B2O3加入量、温度和气氛3种工艺因素对铝热还原法制备Al2O3-TiB2复相陶瓷的影响.结果表明(1)在还原气氛下用铝热还原法可以制备Al2O3-TiB2复相陶瓷.(2)原料中B2O3过量,则有9Al2O3@2B2O3相生成.(3)烧成温度在900℃时铝热反应基本未开始;1000℃时有大量TiB2和α-Al2O3相生成,α-Al2O3呈长方柱状,晶粒较大,TiB2分布在α-Al2O3颗粒之间,晶粒细小;1000℃以上时,反应产物的相组成变化不大,但1500℃后,TiB2晶粒较大,尺寸为0.5～3μm.     

Effects of added aluminum chromium slag on the structure and mechanical properties of colored zirconia ceramics

Colored zirconia ceramic samples were prepared via pressureless sintering with yttria-stabilized zirconia as a raw material and aluminum chromium slag (ACS) as an additive. Then, the effects of added ACS (0-15.0 wt%) on the microstructure, phase composition, and mechanical properties of the ceramic were investigated. The addition of ACS changed the apparent color of zirconia ceramics from white to pink, and the color deepened as the ACS content increased. In addition, more pores appeared in the sintered ceramic substrate as the content of ACS increased, and the relative density of samples declined from 97.7% to 91.1% with an increase in ACS content. However, the microhardness and bending strength each reached their maximum values (1887.2 HV and 433.5 MPa, respectively) when the content of ACS was 5.0 wt%. Fracture surface analysis of the samples showed that intergranular fractures were the main features of sintered samples with no added ACS, whereas numerous transgranular fractures occurred in sintered samples to which ACS had been added. The XRD results revealed that the prepared mainly composite ceramics were composed of t-ZrO₂, m-ZrO₂, and chromium-corundum, and the content of the t-ZrO₂ gradually increased as the ACS content increased.     

Ti-Al-C MAX phases by aluminothermic reduction process

A new approach to synthesis of Ti₂AlC-Ti₃AlC₂/Al₂O₃ compounds is developed based on thermite reaction in the TiO₂-Al-C system. The effect of Al excess is also discussed. XRD analysis has proved that this parameter can be used to improve the product purity, i.e., the amount of TiC in the final product. It has also been shown that, with increasing Al excess, the composition of a major MAX phase undergoes a change from Ti₂AlC to Ti₃AlC₂.      

Preparation and properties of porous ceramics from nickel slag by aerogel gelcasting

To further resource industrial solid waste, porous ceramics with high porosity were prepared by a gelcasting method using nickel slag and kaolin as raw materials and hydrophilic nontoxic SiO₂ aerogel as a gelling agent. The effects of nickel slag content, dispersant and solid content on the properties and microstructure of porous ceramics were investigated in detail in terms of density, compressive strength, porosity, phase composition and micromorphology. The results confirmed that a certain amount of nickel slag can effectively improve the porosity of porous ceramics, while the addition of dispersant can promote the flow of the slurry, enhanced the denseness of the raw billet and significantly improved the compressive strength. However, its excessive use had a negative effect on the ceramic density and porosity. At the same time, the solid content played a key role in the performance of porous ceramics prepared by gelcasting, and too much solid content was also not conducive to the generation of pores. When the nickel slag content was 55%, the amount of dispersant was 2%, and the solid content was 60 vol%, the porous ceramic had a better overall performance, the density of the porous ceramic was 510 kg/m³, the compressive strength was 1.3 MPa, and the porosity reached 80.1%. The major crystalline phases of porous ceramics prepared by nickel slag were cordierite and anorthite.     

Mechanically activated aluminothermic reduction of titanium dioxide

Addressed is the effect of ball milling on aluminothermic reduction of TiO₂. In 0.5-h milled 3TiO₂ + Al mixtures, a two-step reaction was found to yield TiAl and Ti₃Al. Upon an increase in the milling time (to 20 h), a one-step reaction yielded TiAl. The activation energy for TiAl formation was 75 kJ mol⁻¹ for 0.5-h milled samples and 33 kJ mol⁻¹ for 20-h milled samples. The article is published in the original.     

Preparation and characterization of porous ceramics from nickel smelting slag and metakaolin

Porous ceramics with high porosity and low bulk density were prepared by using nickel slag and metakaolin as the primary raw materials, glass powder as flux, and SiC as the foaming agent. The content of nickel slag and foaming agent had a significant effect on the bulk density, porosity, and flexural strength of the porous ceramics. The porous ceramics with the best properties were obtained at 1100 °C for 30 min with 50 wt% nickel slag, 40 wt% metakaolin, 10 wt% waste glass, and 0.8 wt% SiC. It had a low bulk density (as low as 245 kg/m³), high flexural strength and compressive strength (0.6 MPa and 1.17 MPa, respectively), and high porosity (about 89.8%). The nickel slag was magnetically separated as well. The density of nickel slag powder could be reduced via magnetic separation, and there was no significant change in the crystal structure of the raw material. Compared with porous ceramics prepared using nickel slag without magnetic separation, ceramics subjected to magnetic separation had lower bulk density, higher porosity, and the same phase composition. This study can be used as an indicator for the application of nickel slag in porous ceramics, which is of great significance in providing a great substitute nickel slag towards recovery and utilization.     

Ultrastrong tough zirconia ceramics by defects-engineering

We report the preparation of a category of ultrastrong tough zirconia ceramics by engineering defects using an oscillatory pressure during pressure assisted sintering. The introduced oscillatory pressure enhances the dynamic grain rearrangement, plastic deformation, mass transportation, and pore removal, leading to the formation of pore-free ceramics characterized by the rich coherent grain boundaries among individual mesocrystalline grains with intragranular quasi-interfaces. As a proof of concept, the pressure required by oscillatory pressure sintering (OPS) for preparing fully dense 3Y-TZP ceramics is significantly reduced, which is just ∼1/5 of that required by hot isostatic pressing. The OPS-prepared 3Y-TZP ceramics reached a record-breaking high bending strength and fracture toughness, being up to 1.8 GPa and 16 MPa·m^1/2, respectively. This success illustrates a universal principle of engineering defects for making breakthrough in exploring other ultrastrong tough ceramics.     

Preparation of high strength foam ceramics from sand shale and steel slag

Foam ceramics with high strength were successfully fabricated by using sand shale and steel slag as the major materials and SiC as foam agent. The influence of raw materials ratio and heat treatment temperatures on crystalline phases, porosity, mechanical properties and pore structures was investigated via XRF, XRD, SEM, DTA-TG, Micro-CT. The results indicate that the raw materials composed of 94 wt% sand shale and 6 wt% steel slag enable the fabrication of foam ceramics possessing strength of 29.98 MPa, bulk density of 0.821 g/cm³, total porosity of 67.22%, closed porosity of 55.27% and thermal conductivity of 0.08 W/(m·K). Micro-CT result shows that the pores with an average size of 267.05 μm are isolated. Pore wall thickness conforms to normal distribution, and it ranges from 18 to 42 μm. The superior property makes it promising high-strength and lightweight material in application fields, including thermal insulation materials and lightweight building materials.     

The toughening mechanism and mechanical properties of graphene-reinforced zirconia ceramics by microwave sintering

ABSTRACT

The graphene/ZrO₂ composites were fabricated by impregnating graphene dispersion into the ZrO₂ ceramic matrix and sintered by microwave, and the microstructure and mechanical properties were investigated. The results showed that the graphene was well dispersed in the ceramic matrix and refined the grain size. The fracture toughness reached 8.62?MPa?m^1/2, confirmed by single-edge notched beam, which was 42% higher than that of the pure ZrO₂. Also, the toughening mechanisms were investigated by micro-hardness testing and showed that a combination of crack deflection, micro-crack and crack bridging increased the fracture toughness.     

Preparation and properties of glass–ceramics derived from blast-furnace slag by a ceramic-sintering process

Glass–ceramics were synthesized using ground blast-furnace slag and potash feldspar additives by a conventional ceramic-sintering route. The results show 5 wt% potash feldspar can enhance the sintering properties of blast-furnace slag glass and the results glass–ceramics have desirable mechanical properties. The main crystalline phase of the obtained glass–ceramic is gehlenite (2CaO·Al₂O₃·SiO₂). A high microhardness of 5.2 GPa and a bending strength higher than 85 MPa as well as a water absorption lower than 0.14% were obtained.     

Preparation of foamed ceramics from steel slag with high calcium and iron content

In this paper, steel slag foamed ceramics were fabricated by using steel slag, kaolin, feldspar, and quartz as main raw materials, and adding SiC as high-temperature foaming agent. The effects of steel slag content and SiC particle size on porosity and mechanical properties of foamed ceramics were researched. Results indicate that when content of steel slag is 40 wt%, and particle size of SiC is 20 µm, foamed ceramics exhibited optimized properties: water absorption rate of 2.59%, total porosity of 55.91%, bulk density of 1.33 g·cm⁻³, and compressive strength of 1.21 MPa. The results show that with the increase of steel slag content, the phase composition of foamed ceramics changes, and foam process is hindered. The increase of steel slag content contributes to the formation of diopside. Fe³⁺, Fe²⁺ in liquid phase enter into diopside by solid solution, the amount of liquid phase decreases. Liquid phase mass transfer slows down, and content of SiC in liquid phase decreases, so that the porosity decreases. At the same steel slag content, different SiC particle size affects the difference between pressure inside the closed pore and surface pressure, thereby the porosity changes.