纳米Y-TZP材料烧结过程晶粒生长的分析

分析了无压烧结、热压烧结及SPS烧结过程中晶粒生长的行为及表现活化能．结果表明：在1100～1300℃之间,纳米Y-TZP材料在以上几种烧结条件下的晶粒生长行为不同．无压烧结时晶粒生长较慢,而热压烧结和SPS烧结时晶粒生长较快．对晶粒生长的活化能分析可在一定程度上解释以上现象．分析结果显示：无压烧结的表观活化能为281kJ／mol与纳米Y－TZP材料的晶界扩散活化能相近;热压烧结过程中,由于外压对扩散的促进作用,活化能比无压烧结时略有降低;在SPS烧结过程中,由于外加的脉冲电流能使晶粒表面大大活化,所以活化能与无压烧结相比大幅度下降．     

Al_2O_3/B_4C的致密化机制

初始晶粒尺寸为0.33μm和7.0μm的Al2O3/14%B4C粉末在不同温度烧结,并模拟计算陶瓷粉末烧结过程。通过对比实验结果和计算结果,找出影响材料致密化的机制,讨论晶粒尺寸对扩散机制的影响,并估算出致密化激活能。在实验烧结温度范围内,界面反应被认为是影响Al2O3/B4C粉末致密化过程的主要因素。Al2O3/14%B4C陶瓷的致密化激活能是1820±60KJ.mol-1,这结果很大程度上支持界面反应致密化机制。     

纳米Cu粉末的SPS烧结与晶粒长大行为的研究

为了研究金属材料在放电等离子烧结(SPS)过程中晶粒的长大行为和激活能的变化情况,利用SEM、FESEM、TEM等技术分析测定了纳米Cu粉坯体在SPS过程中组织形貌和晶粒尺寸的变化情况.研究表明:特定的工艺和烧结制度下,应用SPS技术可以得到均匀、致密的组织;脉冲电流的作用使晶粒表面大大活化,晶粒长大激活能大大降低,材料在迅速烧结的同时,晶粒也迅速长大.     

A位Sm掺杂对0.93Na0.5Bi0.5TiO3-0.07BaTiO3陶瓷微结构及电学性能的影响

采用固相反应烧结方法制备了Sm掺杂的[(Na_0.5Bi_0.5)_0.93Ba_0.07]_1-xSm_xTiO₃(BNBST)无铅介电储能陶瓷, 系统研究了Sm掺杂含量对BNBST陶瓷的相结构、微观结构、铁电、介电、储能和交、直流电导的影响。研究结果表明: 制备的陶瓷样品具有单一的钙钛矿结构, Sm掺杂固溶于(Na_0.5Bi_0.5)_0.93Ba_0.07TiO₃基材的晶格A位; 晶粒生长被Sm掺杂抑制, 平均晶粒尺寸在2 μm内, 且均匀致密; Sm掺杂显著降低了剩余极化和矫顽场, 表现出双电滞回线特性, 但饱和极化也略有降低; 储能密度和效率随Sm掺杂量增加先增大后减小, 在x=0.02和电场为70 kV/cm时获得最大储能密度0.70 J/cm³, 其效率为40%; BNBST陶瓷具有明显的弛豫铁电体特征, 其介电常数峰T_m随掺杂量增加而降低且平坦化; BNBST陶瓷的绝缘性有较强的温度依赖性, 300℃以下具有良好的绝缘性。     

微波烧结氧化锌压敏电阻的致密化和晶粒生长

研究了微波烧结的ZnO压敏电阻的致密化和生长动力学, 微波烧结温度从900～1200℃, 保温时间从20min～2h. 研究表明, 微波烧结ZnO压敏电阻的物相组成和传统烧结的样品没有区别; 微波烧结有助于样品的致密化, 并降低致密化温度. 随着烧结温度的升高, 致密化和反致密化作用共同影响样品的密度, 其中Bi的挥发是主要影响因素. 微波烧结ZnO压敏电阻的晶粒生长动力学指数为2.9～3.4, 生长激活能为225kJ/mol, 传统烧结的ZnO压敏电阻的晶粒生长动力学指数为3.6～4.2, 生长激活能为363kJ/mol. 液相Bi₂O₃、尖晶石相和微波的“非热效应”是影响微波烧结ZnO压敏电阻陶瓷晶粒生长的主要因素.     

晶粒尺寸对细晶钛酸钡陶瓷介电、压电和铁电性能的影响

以采用水热法制备的BaTiO₃粉体作为原料, 利用普通烧结法和两步烧结法制备出晶粒尺寸为0.25~10.15 μm的BaTiO₃陶瓷, 研究了晶粒尺寸效应对BaTiO₃陶瓷的介电、压电以及铁电性能的影响。结果表明: BaTiO₃陶瓷的四方相含量随着陶瓷晶粒尺寸的增大而增加; 当晶粒尺寸在1 μm以上时, 室温相对介电常数(ε° )和压电系数(d₃₃)随着晶粒尺寸的减小而增大, 并在晶粒尺寸为1.12 μm时分别达到最大值5628和279 pC/N, 然后两者随着晶粒尺寸的进一步减小而迅速下降。BaTiO₃陶瓷的剩余极化强度P_r随晶粒尺寸的增大而提高, 而矫顽场E_c却呈现出相反的趋势。晶粒尺寸对介电性能和压电性能的影响是由于90°电畴尺寸和晶界数量的变化。晶粒的晶体场和晶粒表面钉扎作用的变化影响了电畴, 进而改变电滞回线。     

烧结工艺对B2O3掺杂Ba1-xSrxTiO3梯度陶瓷介电性能的影响

研究了烧结温度及升温速率对氧化硼(B₂O₃)掺杂钛酸锶钡梯度陶瓷(Ba_1-xSr_xTiO₃,x=0-0.4,步长0.02)的致密化、晶粒尺寸及介电性能的影响.结果表明,随着烧结温度的升高,在氧化硼挥发的同时致密化程度提高,从而居里峰提高且变得尖锐;随着氧化硼含量的增加,晶粒尺寸均匀长大、介电常数和介电损耗都增加;升温速率适中时,掺杂物的挥发、致密化进程及晶粒长大同步完成,梯度陶瓷介电性能才有效提高.此外,钛酸锶钡梯度陶瓷掺杂适量氧化硼明显降低烧结温度,比未掺杂相同成分的陶瓷烧结温度至少降低150℃,且介电损耗明显减小;梯度陶瓷的居里峰温度区间显著展宽,大大降低了该温区的介温系数,可望提高该系列陶瓷元器件精度及稳定性.     

Ce-Y-ZTA 复相陶瓷的微波烧结

系统研究了Ce-Y-ZTA 复相陶瓷批量试样在2. 45GHz, 功率0. 5～ 5kW 连续可调的矩形多模腔内的微波烧结过程及材料性能。实验表明: 通过合理的保温结构和工艺控制, 可实现高稳定性和重复性的微波快速烧结。相对密度达到99%TD。与常规烧结相比, 微波烧结过程只需约2小时, 致密化温度降低50～ 100℃。烧结后材料具有晶粒尺寸细小、均匀的显微结构, 弯曲强度由600M Pa 提高至670M Pa, 同时获得较高断裂韧性值。      

On the sintering kinetics of titania doped ceramic lanthanum chromite

The sintering behaviour of lanthanum chromite with the addition of 1 to 3 wt% TiO₂ was studied. Densification was examined as a function of sintering temperature and TiO₂ concentration. The results showed that pure LaCrO₃ could not be densified to >75% of the theoretical density, while the densities exceeding 90% of the theoretical were achieved with 3 wt% titania addition at 1600° C. Metallographic study reveals a normal grain growth following the rate equationD ²−D ₀ ² =kt. Activation energies both for densification and grain growth have been estimated to be ≈ (80±5) k cal/mole in case of 3 wt% TiO₂ addition.     

微波烧结LiCo1/3Ni1/3Mn1/3O2电磁场与温度场的仿真模拟

分析了微波烧结的原理和特点,利用COMSOL Multi-physics模拟软件对矩形微波炉进行了仿真模拟,研究了微波烧结正极材料LiCo_(1/3)Ni_(1/3)Mn_(1/3)O_2时电磁场与温度场的分布,测量了粉末样品LiCo_(1/3)Ni_(1/3)Mn_(1/3)O_2的介电常数,并与模拟结果相对照.研究表明:微波在烧结LiCo_(1/3)Ni_(1/3)Mn_(1/3)O_2样品时,炉腔内电磁场的分布受到影响,微波炉内表面的电场强度减弱;材料内部温度场的分布不均匀,材料的下半部分温度较高;同时,在仿真模拟计算过程中,求得LiCo_(1/3)Ni_(1/3)Mn_(1/3)O_2在微波中烧结到不同温度时的能量损耗,根据李赫德涅凯法则计算出其对应的相对介电常数,发现在20~620℃,相对介电常数随温度的上升而变大.根据实验测得的复合介电常数,求出对应温度点LiCo_(1/3)Ni_(1/3)Mn_(1/3)O_2的相对介电常数.利用Origin对仿真模拟计算和实验求得的两组相对介电常数数据进行拟合对比,发现实验求得的LiCo_(1/3)Ni_(1/3)Mn_(1/3)O_2的相对介电常数与仿真模拟计算所得数据趋势吻合.     

微波烧结对PLZT陶瓷电学性能的影响

采用部分共沉淀法制备锆钛酸铅镧(PLZT)粉体, 分别用普通马弗炉和微波马弗炉进行烧结成瓷, 对比分析不同烧结方法对PLZT陶瓷的晶体结构、微观形貌和电学性能的影响。结果表明: 微波烧结和常规烧结均成功制备出钙钛矿相PLZT陶瓷。采用微波烧结得到的PLZT陶瓷样品比常规烧结的晶粒细小, 尺寸更均匀, 孔洞较少; 在电学性能相近时, 微波烧结温度远低于常规烧结, 且保温时间远小于常规烧结。在1000℃进行微波烧结, 陶瓷的介电常数ε_r和压电常数d₃₃最大, ε_r为2512, d33为405 pC/N, 此时, 剩余极化强度为16.5 kV/cm, 矫顽场为8.2μC/cm²; 在1250℃常规烧结, 陶瓷的介电常数最大, 为2822, 压电常数最大, 为508 pC/N, 剩余极化强度为21.6 kV/cm, 矫顽场为9.6μC/cm²。     

掺Sr铬酸镧粉体的合成及低温烧结行为研究

通过溶胶-凝胶法制备了La_1-xSr_xCrO₃纳米粉体并实现了低温致密烧结, 用X射线衍射仪、透射电镜、差示扫描量热分析仪和扫描电镜对粉体和烧结体进行分析. 结果表明: 粉体的平均直径<50nm, 当x=0, 0.1时, 粉体为单一的La_1-xSr_xCrO₃, x=0.3时存在第二相SrCrO₄. Sr掺杂使铬酸镧晶格产生畸变, 随Sr含量的增加, 晶格常数逐渐变小. 铬酸镧纳米粉体的烧结分为两个阶段, 1200℃以前的缓慢放热和1350℃左右的较快放热, 分别对应烧结的初期和中期. 依据DSC分析结果制订了烧结工艺, 并在1380℃烧结得到相对密度91％的铬酸镧烧结体.     

Effect of microwave sintering on the microstructure and electrical properties of low-voltage ZnO varistors

Coarse-grained ZnO varistors for low-voltage applications were prepared by microwave sintering technique under different soaking times of 5–150?min. For comparison, a low-voltage ZnO varistor was also prepared through a conventional sintering process. Microwave sintering remarkably enhanced the grain growth rate of ZnO varistors. Average grain size of the sample prepared by microwave sintering in 15?min was about 20?µm, which is similar to the grain size of sample prepared conventionally in 150?min time. In addition to grain growth, an increase in microwave sintering time led to precipitation of zinc titanate (Zn₂TiO₄) on the top surface of samples which sintered for long dwell times. X-ray diffraction and scanning electron microscopy results from different points of the samples declared that precipitation of Zn₂TiO₄ phase is due to the high rate of bismuth evaporation of Bi-rich liquid from top surface and the reaction between remaining titanium ions on the surface with ZnO. The results showed that increasing sintering time from 5 to 150?min increased the grain size from 14 to 33?µm, consequently, the breakdown field decreased from 90 to 27?V/mm, respectively. These changes led to a switch in the varistor application, from low to very low voltage.     

纳米增韧NiFe2O4陶瓷惰性阳极烧结行为与性能的研究

采用粉末冶金法制备NiFe₂O₄纳米粉增韧NiFe₂O₄陶瓷铝电解惰性阳极, 研究了NiFe₂O₄纳米粉添加量对NiFe₂O₄陶瓷惰性阳极烧结行为和材料性能的影响。通过线收缩和SEM对NiFe₂O₄陶瓷的烧结性能和显微结果进行分析。研究结果表明: 随着NiFe₂O₄纳米粉添加量的增加, 烧结收缩程度逐渐增大, 烧结致密化开始温度和烧结初期活化能逐渐降低, 添加量为40%时试样从900℃开始大幅度收缩, 烧结初期表观活化能下降到291.43 kJ/mol。NiFe₂O₄陶瓷惰性阳极的体积密度、抗弯强度和断裂韧性随NiFe₂O₄纳米粉添加量的增加均呈现先上升后下降的变化趋势, 气孔率和静态腐蚀率呈先下降后上升的趋势, 均在30%达到极值, 断裂韧性达到最大值3.12 MPa•m^1/2, 是未添加纳米粉试样的2.14倍。NiFe₂O₄纳米粉的添加能够明显增强晶界结合强度, 降低陶瓷材料气孔率, 从而提高断裂表面能实现增韧作用。     

含有烧结助剂的复相陶瓷材料烧结过程的元胞自动机模拟

基于晶界能和晶界曲率的晶粒生长驱动力理论,建立了含有烧结助剂的复相陶瓷晶粒生长的元胞自动机模型并进行了模拟。结果表明,烧结助剂对晶界有着强烈的钉扎作用,其晶粒生长指数小于未含烧结助剂时的生长指数。模拟结果与制备的含有烧结助剂的Al2O3／TiN复相陶瓷材料微观形貌组织吻合,表明所建立的模型适用于含有烧结助剂的陶瓷材料烧...     

掺ZBS玻璃低温烧结ZnNb2O6微波介质陶瓷的研究

研究了ZnO-B2 O3-SiO2(ZBS)玻璃料对ZnNb2O6微波介质陶瓷烧结特性和介电性能的影响.结果表明,ZBS玻璃料形成的液相加速了颗粒间的传质,促进了烧结,能使ZnNb2O6陶瓷的烧结温度有效地降低至950℃.随着ZBS含量的增加,样品中出现了第二相,且气孔被包裹在晶粒内部难以逃脱出来,导致样品的缺陷和损耗增加,从而降低介电性能.掺杂1%ZBS的ZnNb2O6陶瓷在950℃保温4h,能获得优异的综合介电性能:ε=23.56、Q·f=18482GHz、τf=-28.8×10￣6/℃.     

Experimental and Numerical Studies of Densification and Grain Growth of 8YSZ during Flash Sintering

As a promising sintering technique, flash sintering utilizes high electric fields to achieve rapid densification at low furnace temperatures. Various factors can influence the densification rate during flash sintering, such as ultrahigh heating rates, extra-high sample temperatures, and electric field. However, the determining factor of the densification rate and the key mechanism during densification are still under debate. Herein, the densification and grain growth kinetic during flash sintering of 8 mol% Y₂O₃-stabilized ZrO₂ (8YSZ) is studied experimentally and numerically using finite element method (FEM). The roles of Joule heating and heating rate on the densification are investigated by comparing flash sintering with conventional sintering. An apparently smaller activation energy for the material transport resulting in densification is obtained by flash sintering ($Q_{\mathrm{d}}$ =424 kJ mol⁻¹) compared to the conventional sintering ($Q_{\mathrm{d}}$ = 691 kJ mol⁻¹). In addition, a constitutive model is implemented to study both the densification and the grain growth during flash and conventional sintering. Furthermore, the effect of electrical polarity on the density and the grain size evolution during flash sintering of 8YSZ is also investigated. The simulation results of average density and grain size inhomogeneity agree well with the experimental data.     

无铅压电陶瓷KNN常压烧结及其电学性能

用常压烧结法制备K_0.5Na_0.5NbO₃陶瓷。研究烧结温度与陶瓷密度和电学性能的关系。研究表明在1065℃~1120℃范围内, 温度对陶瓷的密度有显著影响。当烧结温度为1100℃时, 密度达到4.35 g/cm³ (占理论密度的95%); 1100℃烧结的陶瓷表现出最好的电学性能, 压电常数最大118 pC/N, 相对介电常数最大达538, 介电损耗最小仅4.7%, 剩余极化强度为15.37 μC/cm², 矫顽场为13.16 kV/cm。陶瓷样品在206℃从正交结构转变到四方结构, 居里温度为410℃。     

微波烧结SiC颗粒增强铝基复合材料

采用微波烧结的方法,在烧结温度分别为680℃,710℃,740℃,770℃,800℃制备了15％的SiCp／Al复合材料。探讨温度对材料的致密度和力学性能的影响。结果表明：致密度和材料硬度及冲击韧性随温度变化呈马鞍形,在770℃样品的密度和硬度及冲击韧性达到最佳值,分别为2．62g／cm3,42．6MPa,40J／cm2。结论：用微波烧结SiCp／Al复合材料可在短时间内使样品达到烧结致密化,缩短烧结时间,节约能源。     

Densification and Grain-Growth Behavior of Various Amounts of SiO2 Doped 8YSCZ/SiO2 Composites

The effect of SiO₂ addition on densification and grain-growth behavior of 8YSCZ/SiO₂ composites was investigated using high purity 8 mol% yttria-stabilized cubic zirconia powders (8YSCZ) doped with 0, 1, 5, 10 wt% SiO₂. The specimens were sintered at 1400°C for 1 hour. It was seen that the sintered density increased with SiO₂ content up to 1 wt% and further increase in SiO₂ content led to a decrease in density. The enhanced density with increasing SiO₂ content up to 1 wt% could be mainly attributable to liquid phase sintering. For grain growth measurements, the specimens sintered at 1400°C were annealed at 1400, 1500, and 1600°C for 10, 50, and 100 hours. The experimental results showed that the grain growth in 8YSCZ/SiO₂ composites occurred more slowly than that in undoped 8YSCZ. Also, the grain growth rate decreased with increasing SiO₂ content. The grain growth exponent value and the activation energy for undoped 8YSCZ were found to be 2 and 289 kJ/mol, respectively. The addition of SiO₂ raised the grain growth exponent value to 3, and activation energy for the grain growth process was increased from 289 to 420 kJ/mol for the addition of SiO₂ from 0 to 10 wt%.