TiB2粒径对BN-TiB2复相陶瓷致密化和性能的影响

以平均粒径分别为8.1μm和12.2μm的两种TiB2粉末为原料,通过热压烧结方法制备BN–48%（质量分数）TiB2复相陶瓷,研究了TiB2粉末粒径对复相陶瓷致密化和性能的影响。结果表明：平均粒径小的TiB2粉末所制备的复相陶瓷致密化速率更快,致密度更高;在1 850℃烧结1.5 h后,表观相对密度为95.3%,体积...     

Bi2WO6的水热合成及其光催化性能研究

水热法合成了Bi2WO6粉体,并采用XRD、FESEM及UV-Vis分光光度计对样品进行表征,研究了不同合成条件对产物形貌和催化性能的影响.UV-Vis漫反射谱表明产物在紫外和可见光区域均有吸收.样品的光催化性能通过降解RhB溶液来评价.结果表明:180℃,pH=2下合成24h获得的Bi2WO6紫外光催化性能最好,反应速率常数为0.03688/min.还讨论了不同pH值对合成样品催化性能的影响.催化剂的稳定性实验通过180℃,pH=2下合成24h获得的Bi2WO6多次催化实验来评估,结果表明4次循环实验后,样品的催化性能未有明显地衰减.在可见光下照射150min,催化剂对染料的降解率达到38%.     

Kinetics of TiB_2 Grain Growing During HP-Sintering

It was reported that TiB2 gains grew fast during sintering was a main cause for its properties degrading. In this paper the HP-sintering mechanics of TiB2 was studied and the results show that grains grow very fast when the sintering temperature is near 1800℃ . From the sintering dynamics, it can be concluded that grain fast growing results in boundary-transporting processing, during which grain boundary work as fast tunnel for material transporting.     

单相胶的化学组成对莫来石微观结构及红外透波性能的影响

用溶胶-凝胶法制备了质量比m(Al2O3)/m(SiO2)分别为72/28、74/26和76/24(称为样品72/28、样品74/26和样品76/24)不同组成的莫来石单相胶,将单相胶在1 000℃下热处理2h,然后用放电等离子烧结技术分别在1 450、1 500、1 550℃烧结10 min,样品相对密度均可达97%以上.对烧结体的微观结构进行扫描电镜分析,结果表明;随着先驱体组成中SiO2含量降低,长轴晶的形成温度升高.3种样品的红外透波率均随烧结温度的上升而下降,其中样品72/28由于晶粒大小和气孔尺寸均较小,其透波率均高于相应烧结温度的另外两个样品.样品74/26在1 550℃烧结时,由于形成的长轴晶的直径与红外波长相当致使散射损失严重,透波率急剧下降,而样品76/24由于等轴晶的尺寸与红外波长相当,再加上第二相的形成造成的散射,使其透波率均较低.     

SiC含量对机械合金化-热压制备B_4C-SiC复合陶瓷的影响

以B4C、SiC粗粉为原料,采用机械合金化辅助热压烧结工艺,在不添加任何助烧剂的情况下于1950℃制备出致密的B4C-SiC复合陶瓷。通过对烧结样品进行相对密度、维氏硬度、抗弯强度和断裂韧性测试,研究SiC含量对复合陶瓷力学性能的影响;结合XRD、SEM和TEM对样品进行组分和微观结构分析,研究其微观结构与力学性能之间的关系。结果表明:复合陶瓷的相对密度和断裂韧性随SiC含量的增加而增大,当SiC含量为50wt%时获得最大值为96.1%和4.6 MPa·m1/2;复合陶瓷的硬度和抗弯强度随SiC含量的增加呈先增大后减小的趋势,在SiC含量为20wt%时获得最大值25.5 GPa和480 MPa。SiC相均匀分布在B4C基体中使得复合陶瓷具有较高的强度;B4C与SiC之间好的界面相容性以及SiC的高断裂韧性是该B4C基复合陶瓷韧性得到显著提高的原因。     

TiB2陶瓷与Mo金属的燃烧反应焊接

采用燃烧反应工艺焊接了TiB₂陶瓷与金属Mo,对中间反应层生成物进行了XRD物相分析,对焊接界面结合情况进行了电子探针分析。温度和中间层组分对焊接件的抗弯强度和抗剪切强度有一定的影响。分析表明:抗弯强度在焊接温度为1500℃,中间层Mo含量为80wt%时达最大值;在焊接温度为1500℃,中间层组分中含Mo为40wt%时所得焊接件抗剪切强度值达最大。     

直流电弧等离子体制备氮化物纳米粒子

采用直流电弧等离子体设备(自行研制)制备金属氮化物纳米粒子,探讨了直流电弧等离子体条件下(高的热性能、高的化学反应活性、高的冷却速率、可控的气氛)氮化反应机理和金属氮化物纳米粒子的成核、生长机制.研究结果表明:反应温度和过饱和度及反应气体压力是影响成核、生长速率与临界成核半径的主要因素,冷却介质是影响产物粒度的关键因素.调整适当的工艺参数,可制备出平均粒径小于20 nm的AlN和小于80 nm的TiN纳米粒子,粉末粒径分布窄,形貌均匀且无团聚.     

莫来石的低温合成及结构组成变化

以九水硝酸铝和正硅酸乙酯为原料,以无水乙醇为溶剂,用溶胶-凝胶法制备出分子级均匀混合的莫来石前驱体.热重-差示扫描量热、X射线衍射和红外分析结果表明:前驱体在985℃直接由非晶态转化为富铝莫来石晶体,没有经历尖晶石相变过程,随着热处理温度的提高,富铝莫来石逐渐转化为结构为3Al2O3·2SiO2的稳定莫来石.前驱体粉末经1 000℃煅烧4h后,用放电等离子烧结技术在1 450℃烧结10min能制成透明莫来石陶瓷.     

Influence of Fe/Ni/Al additive on the sintering behaviors of TiB<Subscript>2</Subscript> cermets

Fe-Ni-Al mixtures as hot-pressing sintering additive to Titanium diboride (TiB₂) were studied. It is found that liquid alloy formed under high temperature hardly has effects on the densification behaviors of TiB₂-independent. Fe-Ni-Al additive just works as filler between TiB₂ particles and does not change the TiB₂-independent sintering behaviors. Pressing mode has a great effect on the liquid flowing between TiB₂ particles. Multiple-steps pressing mode will give more time and space for the liquid flowing and improve the relative density of TiB₂-Fe-Ni-Al cermet.     

Microstructure and mechanical properties of TiB<Subscript>2</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composites

Effects of Al2O3 and Ni as the additives on the sinterability, microstructure and mechanical properties were systematic studied. The experimental results show that only a relative density about 96.2% of hot-pressing TiB2-30%Al2O3 can be attained due to the plate-like TiB2 particle and its random orientation and excessive Al2O3 grain growth. When sintering temperature is higher than 1 700 ℃, TiB2 grain growth can be found, which obvious improves flexural strength of TiB2 matrix but decreases toughness. It seems that mechanical properties of TiB2-Al2O3 composites are mainly depended on relative density besides grain growth. otherwise, they will be determined by relative density and TiB2 matrix strength together. Anyway, Al2O3 addition can weaken the grain boundary and thus improve the toughness of the materials. A flexural strength of 529 MPa, Vickers hardness of 24.8 GPa and indentation toughness of 4.56 MPa·m1/2 can be achieved inTiB2-30vol% Al2O3.