CMS和纳米TiO2对氧化铝陶瓷烧结的影响

选用CaO-MgO-SiO2(CMS)和纳米TiO2两种添加剂及其复合来降低氧化铝陶瓷的烧结温度、改善其烧结性能.讨论了烧结助剂配比和掺量、烧结温度对氧化铝陶瓷的相对密度、抗弯强度的影响,利用扫描电子显微镜观察了氧化铝陶瓷的显微结构.研究结果发现:CMS/TiO2质量比为1/1,(CMS+TiO2)质量分数为6%,烧结温度为1450 ℃时,氧化铝陶瓷相对密度为93.07 %,晶粒细小均匀、排列紧密、平均粒径3 μm,抗弯强度达到362.87 MPa.     

La_2O_3增强高性能氧化铝陶瓷制备工艺研究

本文以氧化铝粉、硝酸镧为主要原料,研究了La_2O_3对氧化铝陶瓷显微结构及性能的影响。结果表明:La_2O_3的加入有助于提高氧化铝陶瓷的力学性能,添加0.1wt%La_2O_3的氧化铝陶瓷经1 490℃烧结后具有最佳的力学性能,其抗弯强度和断裂韧性分别达到460.145 MPa、5.26 MPa·m~(1/2),较未添加La_2O_3氧化铝陶瓷的抗弯强度和断裂韧性分别提升了10.67%和1.15%,掺镧氧化铝陶瓷平均晶粒尺寸约为3.5μm,La_2O_3抑制氧化铝陶瓷晶粒长大的效果较为明显。     

以MnO2-TiO2-MgO为添加剂注浆成型低温烧结Al2O3陶瓷

采用注浆成型方法,通过加入MnO2-TiO2-MgO复相添加剂,在1350℃空气气氛中常压烧结,获得了相对密度最大为95.7%的氧化铝陶瓷.研究了MnO2-TiO2-MgO复相添加剂对氧化铝陶瓷显微结构与力学性能的影响.在添加质量分数为3%MnO2,0.5%MgO的情况下,比较添加不同质量分数的TiO2(1.0～3.0%)对氧化铝陶瓷烧结性能的影响.通过对比发现,该复相添加剂能有效降低氧化铝陶瓷的烧结温度,在同一温度下,随着TiO2的增加,烧结体密度也随之增加,强度也有明显差别.结果表明,1350℃下Al2O3+0.5%MgO+3%MnO2+1.5%TiO2体系烧结效果最好,断口为沿晶断裂,无明显气孔,晶粒分布均匀,平均粒径为2μm,无晶粒异常长大现象.烧结体密度达到3.80g/cm3,抗弯强度为243MPa.     

人工关节滑液条件下细晶氧化铝陶瓷摩擦磨损性能

用放电等离子烧结技术制备了2种不同晶粒尺寸(平均晶粒尺寸为0.6μm的细晶氧化铝和2.0μm的粗晶氧化铝)的氧化铝陶瓷。通过往复摩擦磨损实验研究了2种氧化铝陶瓷在人工关节滑液环境下的摩擦学性能和磨损机制。结果表明：相同的摩擦压力和时间条件下(60 N,30 min),细晶粒和粗晶粒氧化铝陶瓷的平均摩擦系数分别为0.245和0.250,细晶粒氧化铝陶瓷耐磨性能优于粗晶粒氧化铝陶瓷,磨损量(20×10–3 mm3)仅为粗晶粒样品的1/2;2种氧化铝陶瓷磨损机制均为摩擦初期的微裂纹控制的晶粒拔出、脆性断裂及后期的塑性变形机制。     

烧结细晶氧化铝陶瓷的新方法

致密的氧化铝陶瓷可用三种方法烧结得到。从SEM照片可看出：样品比较致密,样品的相对密度大于93％．用两步法和两段法烧结得到的氧化铝陶瓷的晶粒尺寸小于400nm,用常规方法烧结得到的氧化铝陶瓷的晶粒尺寸约为650nm。而且,用两步法和两段法烧结时烧结温度低于常规烧结。实验结果表明：两步法和两段法烧结能得到细晶的氧化铝陶瓷。     

超低钠小原晶α氧化铝的陶瓷烧结性能研究

本文详细研究了低钠小原晶α氧化铝的原晶粒度、Na₂O含量、粉体粒度分布以及烧结温度对陶瓷烧结性能的影响。研究结果表明原晶粒度越小、Na₂O含量越低、粉体粒度越细,所得氧化铝陶瓷越致密。以国内某公司的超低钠小原晶α氧化铝(Na₂O含量0.02%,原晶粒度0.2～0.5μm)为原料,将粉体磨至接近原晶粒度,然后通过造粒、干压所得生坯在1600～1620℃下烧结,陶瓷试块烧结密度达到理论烧结密度的99.5%以上,展现出优良的陶瓷烧结性能。     

粉体合成工艺对TiB_2–TiC复相陶瓷微观组织及力学性能的影响

分别以直接法和间接法碳硼热还原工艺合成的TiB_2–TiC复合粉体为原料,采用热压烧结工艺制备了共晶成分的TiB_2–44%TiC(摩尔分数)复相陶瓷,研究了粉体合成工艺和烧结温度对TiB_2–TiC复相陶瓷显微组织和力学性能的影响。结果表明:以直接法合成粉末为原料烧结的TiB_2–TiC复相陶瓷中,TiB_2晶粒多呈棒状、组织细小均匀;而以间接法合成粉末为原料制备的复相陶瓷中TiB_2晶粒多呈等轴状。随着烧结温度的升高,复相陶瓷致密度提高,晶粒长大,但力学性能变化不明显。以直接法合成复合粉末为原料,在烧结温度为2 000℃、压力为30 MPa、保温时间为1 h工艺条件下制备的TiB_2–TiC复相陶瓷综合性能最佳,其致密度、弹性模量、Vickers硬度、抗弯强度和断裂韧性分别为99.9%、537 GPa、19.0 GPa、598 MPa、5.3 MPa·m~(1/2)(压痕法)和11.6 MPa·m1/2(单边切口梁法)。TiB_2–TiC复相陶瓷主要的增韧机制为裂纹偏转和分叉。     

氧化锆增韧氧化铝陶瓷的性能研究

氧化铝陶瓷因其优良的力学性能、电性能、化学稳定性,是目前应用广泛的一种陶瓷材料。文章中先通过溶胶-凝胶法制备出不同摩尔Al/Zr的无定形Zr O2-Al2O3复合粉体。然后,利用SPS烧结技术快速制备复合陶瓷。通过不同烧结温度的探索发现,在升温速率为100℃/min和压力为80 MPa情况下,烧结温度为1600℃,摩尔比Al/Zr=20时,得到致密的复合陶瓷,且力学性能最好,其中维氏硬度为18.6 GPa,断裂韧性为7.6 MPa·m1/2,断裂韧性相对于纯氧化铝陶瓷有了大幅的提升。     

Y3+掺杂对Al2O3陶瓷硬度的影响

本实验主要研究了稀土Y2O3添加量、成形压力和烧结温度等对氧化铝陶瓷的影响.研究结果表明,在Y2O3掺量为0.5wt%、压力20MPa和1 600℃烧成(保温2h)的条件下,Al2O3陶瓷的密度可达3.9g/cm3以上,其硬度也得到了很大程度的提高.微观结构分析表明,添加Y2O3不仅可以细化晶粒,还能抑制氧化铝晶粒的异常长大,使晶粒尺寸均匀而形成致密化结构.     

AlN-Re2O3液相烧结碳化硅

采用非氧化物AlN和Re2O3作为复合烧结助剂(Re2O3-La2O3与Y2O3)进行碳化硅液相烧结得到了致密的烧结体.烧结助剂占原料粉体总质量的20%,其中:AIN与(La0.5Y0.5)2O3的摩尔比为2:1,在30MPa压力下,1850℃保温0.5h热压烧结的碳化硅陶瓷,抗弯强度>800MPa,断裂韧性>8MPa·m1/2,明显高于同组分1 950℃无压烧结0.5h的碳化硅陶瓷的抗弯强度(433.7MPa)和断裂韧性(4.8MPam·m1/2.热压烧结的陶瓷晶粒呈单向生长,断裂模式为沿晶断裂.同组分无压烧结碳化硅陶瓷的显微结构可以观察到核壳结构.     

Al2O3增强ZrO2陶瓷的制备及性能研究

本文采用热分解法制备Al2O3微粉、化学共沉淀法制备(Y,Ce)—ZrO2超细粉,通过适当工艺制备出ZrO2／Al2O3复合陶瓷。经研究发现,添加Al2O3,可抑制ZrO2晶粒的长大,提高基体的强度和韧性。当Al2O3含量达到30%(质量分数)时,复合陶瓷的抗弯强度为986MPa,断裂韧性为13.7MPa*m1／2。材料性能的提高可归结为Al2O3颗粒的弥散增韧和ZrO2陶瓷的相变增韧叠加作用的结果。     

Synthesis and mechanical properties of mullite ceramics with coal gangue and wastes refractory as raw materials

With coal gangue and high alumina refractory solid wastes as raw materials, needle-like mullite powder, with an average diameter of about 1 μm, was synthesized at 1300°C by using the conventional solid-state reaction method. Mullite ceramics were derived from the inexpensive needle-like powder. Phase composition was examined by using X-ray diffraction (XRD), while morphologies of the ceramics were observed by using scanning electron microscopy. The content and distribution of elements in the sintered samples were characterized with energy dispersive spectrometer and X-ray fluorescence spectroscopy. Mechanical properties of the mullite ceramics were studied by using the three-point bending method. The aspect ratio of the needle-like mullite particles was up to 6. The mullite sample sintered at 1500°C for 3 hours had a density of 2.515 g·cm⁻³, which was slightly lower than the theoretical density. Maximum fracture toughness and bending strength of the mullite ceramics were 1.82 MPa·m^1/2 and 71.76 MPa, respectively. This study realizes the resource utilization of gangue and high alumina refractory solid wastes, and the prepared mullite ceramics have good application prospect.     

Effect of the addition of polyvinylpyrrolidone as a pore-former on microstructure and mechanical strength of porous alumina ceramics

The effect of the solvent on the properties of porous alumina ceramics was studied when polyvinylpyrrolidone (PVP) was used as an organic pore-former. In particular, porous alumina ceramics were produced by dry-pressing of mixed PVP–alumina powder; the mixing of PVP and alumina powder was achieved via ball milling using water or acetone as solvent, or dry ball milling. Due to the different solubility of PVP in water and acetone, porous alumina ceramics with different pore structures and mechanical properties were obtained. Because of its cylindrical pores being aligned to some extent, the sample prepared using acetone as solvent exhibited the highest bending strength (140.2 MPa) and Young's modulus (57.4 GPa), which were 1.6 times and 3.4 times higher compared to that prepared without PVP. Moreover, the addition of PVP via wet ball milling led to more uniform dispersion of PVP in alumina, hence limiting the grain growth during sintering process and increasing the grain bonding.     

液相前驱体浸渗工艺引入添加剂制备透明多晶氧化铝陶瓷

以Mg（NO3）2、Y（NO3）3和La（NO3）3为前驱体,采用液相前驱体浸渗工艺将添加剂MgO、Y2O3和La2O3同时引入到预烧氧化铝坯体中,在1830℃、H2气氛下保温2h烧结制备透明多晶氧化铝陶瓷。利用扫描电子显微镜和紫外一可见分光光度计对透明多晶氧化铝陶瓷的显微结构及直线透光率进行表征。结果表明：液相前驱体浸渗工艺提高了添加剂分布的均匀性,采用该工艺制备的透明多晶氧化铝陶瓷显微结构均匀,晶粒尺寸为20～50μm,在波长300～800nm内最高直线透光率达38．7％（λ=800nm,厚度为0．8mm）;而采用传统湿法球磨工艺得到的透明多晶氧化铝陶瓷晶粒尺寸大小不均,在晶界及晶粒内存有残留气孔,最高直线透光率仅为12．3％m=800nm,厚度为0．8mm）。通过液相前驱体浸渗工艺引入添加剂显著提高了透明多晶氧化铝陶瓷的直线透光率。     

Microstructure and Mechanical Properties of Hot-Pressed α-Al2O3-Seeded γ-Alumina Ceramics

High-quality alumina ceramics were fabricated by a hot pressing with MgO and SiO₂ as additives using α-Al₂O₃-seeded nanocrystalline γ-Al₂O₃ powders as the raw material. Densification behavior, microstructure evolution, and mechanical properties of alumina were investigated from 1250°C to 1450°C. The seeded γ-Al₂O₃ sintered to 98% relative density at 1300°C. Obvious grain growth was observed at 1400°C and plate-like grains formed at 1450°C. For the 1350°C hot-pressed alumina ceramics, the grain boundary regions were generally clean. Spinel and mullite formed in the triple-grain junction regions. The bending strength and fracture toughness were 565 MPa and 4.5 MPa·m^1/2, respectively. For the 1300°C sintered alumina ceramics, the corresponding values were 492 MPa and 4.9 MPa·m^1/2.     

Low-temperature sintering of Al2O3 ceramics doped with 4CuO-TiO2-2Nb2O5 composite oxide sintering aid

Dense alumina ceramics doped with 5 wt% 4CuO-TiO₂-2Nb₂O₅ composite sintering aids were obtained at low sintering temperatures of 950∼975 °C. The ceramic sintered at optimal condition shows good microwave dielectric properties (ε_r = 12.7, Q × f = 7400 GHz), high thermal conductivity (18.4 W/m K) and high bending strength (320 MPa). TEM and EDS analysis revealed that amorphous Cu-Ti-Nb-O interfacial films with nanometer thickness formed at the grain boundaries, which could provide paths of mass transportation for densification. Al³⁺ ions may be involved in mass transportation through substitution by Ti³⁺ and Ti⁴⁺ ions near the grain boundary during the sintering process. The accumulation of copper ions at the trigeminal grain boundary was observed. The migration and reaction of copper ions in grain boundaries may also play an important role in promoting mass transportation and low-temperature densification of alumina ceramics.     

Gas permeability and mechanical properties of porous alumina ceramics with unidirectionally aligned pores

Porous alumina ceramics having unidirectionally aligned cylindrical pores were prepared by extrusion method and compared with porous ceramics having randomly distributed pores prepared by conventional method, and their gas permeability and mechanical properties were investigated. SEM micrographs of the porous alumina ceramics prepared by the extrusion method using nylon fibers as the pore former showed excellent orientation of cylindrical pores. The bending strength and Weibull modulus of the extruded porous alumina ceramics with 39% porosity were 156 MPa and 17, respectively. These mechanical properties of extruded samples were higher than those of the conventional porous alumina ceramics. The strength decreased from 156 to 106 MPa with increasing pore size from 8.5 to 38 μm. The gas permeability of the extrusion samples is higher than that of the conventional samples and increased with increasing of porosity and pore size.     

La2O3对镁铝尖晶石透明陶瓷致密化及其性能的影响

镁铝尖晶石透明陶瓷兼具了良好的光学和力学性能,在军、民两用领域有着广泛的实际和潜在应用前景。由于其致密化速率低,在烧结过程中往往需要引入烧结助剂。稀土倍半氧化物熔点高,高温不易挥发,近些年被证实可以促进镁铝尖晶石陶瓷的致密化,但其促烧机理尚不明确。本文以高纯商业化镁铝尖晶石粉体为原料,La₂O₃为烧结助剂,采用无压预烧结合热等静压烧结,制备镁铝尖晶石透明陶瓷,通过XRD、SEM、紫外-可见分光光度计、万能试验机等测试手段对其致密化过程及其力学和光学性能进行表征和分析,研究了La₂O₃对镁铝尖晶石透明陶瓷致密化过程的影响规律和作用机制。结果表明,La₂O₃通过与尖晶石反应或固溶产生晶格畸变,增加缺陷浓度,从而起到促进致密化的作用,一定程度上降低了预烧温度和热等静压温度。对于190 MPa、1 500 ℃热等静压烧结3 h的样品,La₂O₃掺杂可以显著提高紫外区域的透过率;同时,La偏析到晶粒表面,抑制了尖晶石晶粒的生长,从而提高了样品的力学强度。掺杂0.05%(质量分数)La₂O₃样品较未掺的样品,400 nm处透过率从63%提高到81%,弯曲强度从263.7 MPa提高至319.0 MPa,断裂韧性从1.69 MPa·m^1/2提高至1.82 MPa·m^1/2。     

Microstructure and high temperature 4-point bending creep of sol–gel derived mullite ceramics

Four-point bending creep behavior of mullite ceramics with monomodal and bimodal distribution of grain sizes was studied in the temperature range of 1320–1400 °C under the stresses between 40 and 160 MPa. Mullite ceramic with bimodal grain size distribution was prepared using aluminum nitrate nonahydrate as alumina precursor. When γ-Al₂O₃ or boehmite were used as alumina precursors, mullite grains are equiaxial with mean particle size of 0.6 μm for the former and 1.3 μm for the latter alumina precursor. The highest creep rate exhibited the sample with monomodal morphology and grains in size of 0.6 μm, which is about one order of magnitude greater than that for the monomodal morphology but with grains in size of 1.3 μm. The highest activation energy for creep (Q = 742 ± 33 kJ/mol) exhibits mullite with equiaxial grains of 1.3 μm, whereas for sample with smaller equiaxial grains the activation energy is much smaller and similar to mullite ceramics with bimodal grain morphology. Intergranular fracture is predominant near the tension surface, while transgranular more planar fracture is predominant near the compression surface zone.     

添加剂对低温烧结95氧化铝陶瓷性能的影响

采用MnO2-TiO2-CaO-La2O3复相添加剂作为氧化铝陶瓷的烧结助剂,研究了MnO2添加量对95氧化铝陶瓷烧结性能、力学性能和微观结构的影响。结果表明:当配方中MnO2含量为3.0%时,在1550℃烧结温度下制得的氧化铝陶瓷的综合性能最佳,烧结试样的体积密度达到3.76g.cm-3,试样的抗弯强度和洛氏硬度(HRA)分别达到355.22MPa和84.3。