Al_2O_3形成合金过渡态氧化行为

综述了亚稳相Al2O3生长和向稳态转变的规律,以及温度、氧化时间、合金元素、表面状态等的影响作用.重点介绍了合金元素特别是活性元素对相转变的影响机制、相转变与膜形成脊状形貌的关系,以及相转变对后续氧化行为的影响等.     

原位合成(Al_2O_3+Al_3Ti)_P/Al复合材料的制备研究

通过对Al-TiO_2-SiO_2体系混合粉末固-液原位合成制备出了(Al_2O_3+Al_3Ti)_P/Al复合材料.利用X射线衍射仪、扫描电镜等方法观察分析了其物相和显微组织形貌.结果表明:原位反应制备的(Al_2O_3+Al_3Ti)_P/Al复合材料,金属间化合物增强相Al_3Ti均匀分布于基体,陶瓷相Al_2O_3颗粒非常细小,弥散分布于基体中,使材料的硬度等性能得到提高.     

水热法制备F/Mn共掺杂SnO2纳米粒子

本文采用水热法制备了具有金红石结构的F-Mn共掺杂SnO2纳米粒子,研究了碱源、pH值、掺杂剂、表面活性剂、煅烧温度对F/Mn共掺杂SnO纳米粒子晶相、微观形貌、分散性和光学性能的影响。采用X射线衍射（XRD）、扫描电镜（SEM）和紫外/可见/近红外分光光度计对F-Mn共掺杂SnO2纳米粒子进行了表征。结果表明,该方法可以获得较高的结晶度、较小的粒径和分散良好的F-Mn共掺杂SnO2纳米粒子。F-Mn共掺杂SnO2涂层具有较好采光的同时有较高的近红外屏蔽性能,其中可见光透过率约为90%,近红外阻隔率约为93%左右。     

Zn、Si共掺杂纳米TiO_2的制备及其光催化性能

采用水热法,以Ti（SO4）2作为前驱体制备出锌、硅单掺杂和共掺杂的二氧化钛纳米晶。分析结果显示锌、硅共掺杂二氧化钛纳米晶的光催化活性高于纯二氧化钛纳米晶和单掺杂的二氧化钛纳米晶;在锌的掺杂量为0.8%、硅的掺杂量为6%时,所获得的二氧化钛纳米晶的光催化活性最佳;锌硅共掺杂二氧化钛纳米晶相对于纯二氧化钛纳米晶和单掺杂的二氧化钛纳米晶,其粒径减小,表面积增加。     

Er掺杂强韧化Al_2O_3/TiAl复合材料

以Ti、Al、TiO2为起始原料,以Er2O3为掺杂剂,原位热压合成了Er掺杂Al2O3/TiAl复合材料。通过XRD、SEM分析及力学性能测试,研究了不同Er2O3引入量对合成Al2O3/TiAl复合材料微观结构和力学性能的影响。结果表明:复合材料主要由TiAl、Ti3 Al、Al2 O3相和少量Al10 Er6 O24相组成,含Er相主要分布在基体相晶界处;掺杂0.01 mol Er2 O3制得的复合材料,经1250℃保温2 h真空热压烧结后表观断裂韧性达到最大值(10.41 MPa.m1/2),经1300℃保温2 h真空热压烧结后弯曲强度达到最大值(456.06 MPa);当Er2O3掺杂量增加到0.02 mol时,复合材料的弯曲强度和表观断裂韧性均呈减小趋势。微观结构分析表明,掺杂0.01 mol Er2O3的复合材料断口毛糙,颗粒尺寸变小,增强相分布较均匀,表明适量的Er2O3掺杂可细化复合材料晶粒尺寸,提高增强颗粒分布均匀度,起到增强增韧的效果。     

无压烧结制备Al_2O_3-TiC复合陶瓷

本文采用无压烧结方法制备Al_2O_3－TiC复合陶瓷，较详细地研究了助烧剂含量、采用的埋粉种类及烧结温度对烧结体致密度的影响，结果表明，当采用助烧剂CaO含量为Al_2O_3量的0．5wt％采用Al_2O_3＋TiC作埋粉时具有较好的促进体系烧结的作用，在1860℃的烧结温度下，烧结体相对密度为98％。     

层压法制备SiC_f/Al_2O_3复合材料的抗弯性能研究

以氧化铝为填料,硅溶胶为粘结剂,碳化硅纤维布为增强纤维,使用层压法制备SiCf/Al2O3复合材料,并对该复合材料做了抗弯性能试验。结果显示,随处理温度的升高,基体缓慢释放出的结合水会对纤维造成氧化损伤,使试样的抗弯性能下降,但是材料始终表现出非脆性断裂行为,这与基体与纤维之间未形成强结合有关;包裹氧化硼玻璃后在空气中对SiCf/Al2O3进行处理后,氧化硼玻璃能有效阻止空气与纤维的接触,防止了纤维在高温下被氧化,分析表明在600、700、800℃保温0.5、1、1.5、2 h后,抗弯强度变化不大。     

Al_2O_3含量对Mo-WC-Co钼合金性能的影响

采用粉末冶金技术制备了Mo-WC-Co合金,利用金相显微镜、XRD、SEM和EDS等手段分析了Al_2O_3添加量对合金组织的影响,并研究Al_2O_3含量对合金硬度及耐磨性的影响。研究表明,Mo-WC-Co合金的晶粒度和孔隙率随着Al_2O_3含量的增加逐渐减小;当Al_2O_3含量为0.2%时合金烧结致密度最高;Al_2O_3含量超过0.2%时合金的硬度趋于平稳但耐磨性下降。     

掺杂方式对Mo-La2O3合金组织和力学性能的影响

分别采用液．固和液．液掺杂方式向钼粉中引入氧化镧，烧结出Mo-La2O3合金，通过扫描电镜和透射电镜观察，研究了不同掺杂方式制备的Mo-La2O3合金中第二相粒子的粒度分布和形貌，分析了第二相粒子在钼基体中的分布规律，检测了钼丝的拉伸性能，通过位错塞积理论讨论了La2O3颗粒形貌和分布对Mo-La2O3拉伸性能的影响机制。结果表明：液．液掺杂方法能够使钼基体中的La2O3粒子均匀分散，细化La2O3粒径；直径0．6mm、液．液掺杂钼丝的拉伸性能优于液-固掺杂钼丝。     

La_2O_3,CeO_2掺杂Sm_2Zr_2O_7陶瓷制备及热物理性能

以Sm_2O_3, La_2O_3, ZrO_2和CeO_2为原料,采用固相反应法制备了(Sm_0.5La_0.5)_2(Zr_0.6Ce_0.4)_2O_7陶瓷.用X射线衍射(XRD),扫描电镜(SEM)研究了样品的相成分和微观组织,用激光脉冲法和推杆法测量了样品的热导率和热膨胀系数.结果表明,所制备的样品具有萤石晶体结构,且组织致密晶界清晰,并具有较低的热导率和满足热障涂层要求的热膨胀系数.     

Al2O3颗粒弥散强化钼合金的显微组织与压缩性能(英文)

采用水热合成法和粉末冶金方法制备Al₂O₃颗粒增强Mo合金,并利用XRD、SEM和TEM对所制备的Mo-Al₂O₃合金的显微组织进行研究。结果表明,Al₂O₃颗粒以稳定的六方相(α-Al₂O₃)形式均匀地分布在Mo基体中,超细α-Al₂O₃颗粒显著细化Mo合金的晶粒尺寸,增加Mo合金位错密度。此外,α-Al₂O₃与Mo晶粒间存在良好的界面结合区,且Al₂O₃颗粒与Mo基体界面存在一定的晶体学关系:[111]_a-Al2O3//[111]_Mo和(112)_a-Al2O3//[111]_Mo。由于二次强化效应和位错强化效...     

Al2O3基复相陶瓷共沉淀-水热法制备研究

用共沉淀-水热法制备Ni／ZrO2／Al2O3复相陶瓷粉体，并对烧结体的力学性能和显微形貌进行了讨论。复相粉体的表征采用高分辩透射电镜（HRTEM）和X射线衍射（XRD）等技术。结果表明：在1．4．丁二醇介质中300℃水热条件下自生压高压釜中反应12h成功制备了Ni／ZrO2／Al2O3复合陶瓷粉体，并且测得复相陶瓷体积密度和断裂韧性。通过场发射扫描电镜观察得到烧结体中t-ZrO2颗粒和Ni颗粒的平均尺寸。     

Shape-controlled synthesis of nanocubic Co3O4 by hydrothermal oxidation method

The nanocubic Co3O4 was synthesized by hydrothermal oxidation method. The effects of cobalt salt, precipitating agent, surfactant, solvent, pH value of the suspension and the amount of oxidant H2O2 on the morphology and structure of Co3O4 were investigated. The Co3O4 powders were characterized by transmission electron microscope and X-my diffraction. The results show that the morphology of Co3O4 is closely dependant on the anion in cobalt salts, but it is not so sensitive to the precipitating agents and solvents. The amount of H2O2 is the key factor to obtain Co3O4 with spinel crystal structure. The optimum synthetic conditions of uniform shape-controlled Co3O4 nanocubes are as follows： Co（CH3COO）2·4H2O as cobalt salt, KOH as precipitating agent, polyethylene glycol with relative molecular mass of about 20 000 as surfactant, water-n-butanol as solvent system, pH value of 8-9, the molar ratio of H2O2 to Co^2＋ above 2.5：1.0, hydrothermal temperature of 160 ℃ and hydrothermal holding time of 10 h. The tap density and apparent density of nanocubic Co3O4 obtained with the average particle size of 20 nm are 1.01 g/cm^3 and 0.70 g/cm^3, respectively.     

ZrB2/Al2O3 composite powders prepared by self-propagating high-temperature synthesis

Self-propagating high-temperature synthesis（SHS） method was used to synthesize ZrB2/Al2O3 composite powders from B2O3-ZrO2-Al system. X-ray diffractometry（XRD） and scanning electron microscopy（SEM） analyses show the presence of ZrB2 and Al2O3 as the primary phases in the composite powders, while the presence of a very small amount of ZrO2 is thought to be unreacted zirconium oxide. Transmission electron microscopy（TEM） and high resolution electron microscopy（HREM） observations of microstructure of the composite powders indicate that the interfaces of ZrB2/Al2O3 bond well without any interracial reaction products. It is proposed that the good interfacial bonding of composite powders results from the ZrB2 particles crystallizing and growing on the Al2O3 particles surface with surface defects acting as nucleation centers.     

Al2O3基复相陶瓷共沉淀-水热法制备研究

用共沉淀-水热法制备Ni/ZrO2/Al2O3复相陶瓷粉体,并对烧结体的力学性能和显微形貌进行了讨论.复相粉体的表征采用高分辩透射电镜(HRTEM)和X射线衍射(XRD)等技术.结果表明:在1.4-丁二醇介质中300℃水热条件下自生压高压釜中反应12h成功制备了Ni/ZrO2/Al2O3复合陶瓷粉体,并且测得复相陶瓷体积密度和断裂韧性.通过场发射扫描电镜观察得到烧结体中t-ZrO2颗粒和Ni颗粒的平均尺寸.     

Preparation and properties of high-strength molybdenum alloy sheets doped with Al_2O_3 particles

The pure molybdenum sheet and the Al_2 O_3-doped molybdenum alloy sheets were prepared by the hydrothermal method and a subsequent powder metallurgy process. The effects of Al_2 O_3 particles addition on the recrystallization temperature, microstructures and properties of the Mo sheets were investigated as the focus. The Al_2 O_3-doped Mo sheets have greater strength than the pure Mo sheet, and the 0.50 wt% Al_2 O_3-doped Mo sheet has the best performance. For the unannealed specimens, the strength increases with the increase in Al_2 O_3 content.Compared with that of pure Mo sheet, the strength of0.50 wt% Al_2 O_3-doped Mo sheet increases by 72%, 54%,73% and 76%, respectively, when annealed at 1000,1100,1200 and 1300 ℃, which is a very obvious reinforcement effect. When lower than 1100 ℃, the elongation of the pure Mo sheet is the best. However, when the annealing temperature is equal to or greater than 1100 ℃,the 0.50 wt% Al_2 O_3-doped Mo sheet obtains the best elongation. Moreover, the Al_2 O_3 addition can greatly improve the recrystallization temperature of molybdenum sheets; for example, the recrystallization temperature of the0.50 wt% Al_2 O_3-doped Mo sheet increases by 200 ℃ at least than that of the pure Mo sheet. Lastly, the strengthening mechanism was discussed.     

Microstructure and mechanical properties of 7075 Al alloy based composites with Al2O3 nanoparticles

A new method was used to fabricate 7075 Al alloy based composites with Al₂O₃ nanoparticles to improve the distribution of particles. In this study, nano-sized particles were fed into the molten alloy through the flow of argon gas, then the Al₂O₃/7075 composites were prepared by solid-liquid mixed casting. The results indicated that the composite samples showed fine microstructure and achieved a homogeneous distribution of particles. Also, it was found that relative to the as-cast 7075 alloy, the Al₂O₃/7075 composites exhibited higher mechanical properties, which is due to the effect of uniform distributed Al₂O₃ nanoparticles reinforcement.     

Photoluminescence properties and synthesis of a PZT mesostructure obtained by the microwave-assisted hydrothermal method

Micro-cube-shaped lead zirconate titanate was synthesized using the microwave-assisted hydrothermal method. Photoluminescence and field emission scanning electron microscopy were used for monitoring the formation of mesocrystals. Based on these results, a growth mechanism was then proposed which involved nanoparticle aggregation, nanoplate self-assembly on specific architecture and the final formation of mesoscopic micro-cube-shaped lead zirconate titanate.     

Preparation of antimony-doped nanoparticles by hydrothermal method

Antimony-doped tin oxide (ATO) nanoparticles were prepared by the mild hydrothermal method at 200℃ using sodium stannate, antimony oxide, sodium hydroxide and sulfuric acid as the starting materials. The doped powders were examined by differential thermal analysis(DTA), X-ray diffractometry(XRD) and transmission electron microscopy(TEM). The doping levels of antimony were determined by volumetric method and iodimetry.The results show that antimony is incorporated into the crystal lattice of tin oxide and the doping levels of antimony in the resulting powders are 2.4%, 4.3%and 5.1%(molar fraction). The mean particle size of ATO nanoparticles is in the range of 25 - 30 nm. The effects of antimony doping level on the crystalline size and crystallinity were also discussed.