Rare earth effect of yttrium on formation and property of Cr2O3 oxide film formed on Co-Cr binary alloy

The isothermal oxidizing kinetics of Co-40Cr alloy and its yttrium ion?implanted samples were studied at 1000 ℃ in air by thermal?gravity analysis (TGA). Scanning electronic microscopy (SEM) was used to examine the Cr2O₃ oxide film's morphology after oxidation. Secondary ion mass spectrum (SIMS) method was used to examine the binding energy change of chromium caused by Y?doping and its influence on formation of Cr2O₃ film. Acoustic emission (AE) method was used in situ to monitor the cracking and spalling of oxide films formed on both samples during oxidizing and subsequent air?cooling stages. Theoretical model simulating the film fracture process was proposed to analyze the acoustic emission spectrum both on time domain and on AE?event number domain. It is found that yttrium ion?implantation can remarkably reduce the isothermal oxidizing rate of Co-40Cr and improve the anti?cracking and anti?spalling properties of Cr2O₃ oxide film. Reasons for the improvement are mainly that the implanted yttrium can reduce the grain size of Cr2O₃ oxide, increase the high temperature plasticity of oxide film, and remarkably reduce the number and size of Cr2O₃/Co-40Cr interfacial defects.     

Rare earth effect of yttrium on formation and property of Cr2O3 oxide film formed on Co-Cr binary alloy

The isothermal oxidizing kinetics of Co-40Cr alloy and its yttrium ion?implanted samples were studied at 1000 ℃ in air by thermal?gravity analysis (TGA). Scanning electronic microscopy (SEM) was used to examine the Cr2O₃ oxide film's morphology after oxidation. Secondary ion mass spectrum (SIMS) method was used to examine the binding energy change of chromium caused by Y?doping and its influence on formation of Cr2O₃ film. Acoustic emission (AE) method was used in situ to monitor the cracking and spalling of oxide films formed on both samples during oxidizing and subsequent air?cooling stages. Theoretical model simulating the film fracture process was proposed to analyze the acoustic emission spectrum both on time domain and on AE?event number domain. It is found that yttrium ion?implantation can remarkably reduce the isothermal oxidizing rate of Co-40Cr and improve the anti?cracking and anti?spalling properties of Cr2O₃ oxide film. Reasons for the improvement are mainly that the implanted yttrium can reduce the grain size of Cr2O₃ oxide, increase the high temperature plasticity of oxide film, and remarkably reduce the number and size of Cr2O₃/Co-40Cr interfacial defects.     

Rare earth effects on high temperature oxidation of pure nickel at 1000 ℃

Isothermal and cyclic oxidation behaviors of pure and yttrium-implanted nickel were studied at 1000 ℃ in air.SEM and TEM were used to examine the oxide scales formed on nickel substrate.It was found that Y-implantation greatly improved the anti-oxidation ability of nickel both in isothermal and cyclic oxidizing experiments.Acoustic emission(AE)technique was used to study the size and number distribution of defects at the oxide/metal interface.Laser Raman microscopy was also used to study the stress status of oxide scales formed on nickel with and without yttrium.The main reason for the improvement in anti-oxidation and adhesion of oxide scale was that Yimplantation greatly reduced the grain size of NiO and lowered the compressive stress within the scale.In the meantime,Y-implantation inhibited ion diffusion rate in the oxide scale and reduced the size and number of interfacial defects,hence remarkably enhanced the adhesion of protective NiO oxide scale formed on nickel substrate.     

Y_2O_3掺杂压制钡钨阴极的制备及发射性能研究

通过溶胶凝胶法制备氧化钇、活性盐和钨均匀混合的前驱粉末,结合氢气高温烧结制备得到稀土氧化物Y2O3掺杂压制钡钨新型阴极材料,并分别测试其热电子发射性能和二次电子发射性能。试验结果表明,采用溶胶凝胶法制备的阴极粉末颗粒分布均匀且细小,在高温烧结过程中有利于活性盐与基体钨之间反应充分,从而形成有利于提高发射的活性物质。发射性能测试结果显示:激活良好的阴极在测试温度1 050℃时的零场电流密度J0为4.18A/cm2;二次电子发射系数随Y2O3含量增加而增大,最大二次电子发射系数δm可以达到2.92。对阴极进行表面分析,激活过程中活性元素Ba、Y和O等从阴极内部向表面扩散,在表面形成均匀分布的发射活性层,促进了阴极的发射。     

钇掺杂对氧化铝膜的热稳定性及其孔结构的影响

以异丙醇铝和Y(NO3)3为主要原料,用溶胶-凝胶法制备掺杂钇的无支撑Al2O3膜,采用XRD、DTA-TG、BET等测试手段分析钇的掺杂对Al2O3膜的物相组成、热稳定性、以及Al2O3膜孔结构在不同煅烧温度时的影响.研究结果表明:掺杂钇能提高γ-Al2O3相向α-Al2O3相的转变温度和Al2O3膜的热稳定性.钇的掺杂也明显了改善了Al2O3膜在高温煅烧中的孔结构参数.     

有序介孔Cr_2O_3-CeO_2的制备与表征

以硝酸铬和硝酸铈作金属源、用介孔氧化硅作硬模板,通过真空辅助浸渍法制备得到高比表面积有序介孔Cr2O3-Ce O2复合氧化物,采用XRD、TEM、UV-Vis和N2吸附-脱附技术表征了样品的物理化学性质.结果表明,经过500℃灼烧处理的样品(meso-Cr-Ce)孔壁晶化度高且虫孔结构发达,比表面积达160 m2/g,平均孔径为7.2 nm,在紫外和可见光区还具有优良的吸光性能.这些特性将使该材料在催化领域特别是光催化领域有着广阔的应用前景.     

Effect of Al2O3 on the viscosity of CaO-SiO2-Al2O3-MgO-Cr2O3 slags

We investigated the effect of Al2O3 content on the viscosity of CaO-SiO2-Al2O3-8wt%MgO-1wt%Cr2O3(mass ratio of CaO/SiO2 is 1.0,and Al2O3 content is 17wt%-29wt%)slags.The results show that the viscosity of the slag increases gradually with increases in the Al2O3 content in the range of 17wt%to 29wt%due to the role of Al2O3 as a network former in the polymerization of the aluminosilicate structure of the slag.With increases in the Al2O3 content from 17wt%to 29wt%,the apparent activation energy of the slags also increases from 180.85 to 210.23 kJ/mol,which is consistent with the variation in the critical temperature.The Fourier-transform infrared spectra indicate that the degree of polymerization of this slag is increased by the addition of Al2O3.The application of Iida’s model for predicting the slag viscosity in the presence of Cr2O3 indicates that the calculated viscosity values fit well with the measured values when both the temperature and Al2O3 content are at relatively low levels,i.e.,the temperature range of 1673 to 1803 K and the Al2O3 content range of 17wt%-29wt%in CaO-SiO2-Al2O3-8wt%MgO-1wt%Cr2O3 slag.     

磁控溅射法制备Er2O3薄膜及其力学性能研究

金属表面纳米化可以明显改善材料表面力学性能,并能对原子的热扩散起到促进作用,本文尝试采用材料表面纳米化技术改善316L不锈钢金属基底与Er₂O₃薄膜相结合的力学性能.对316L不锈钢采用超音速微粒轰击法处理使得基体表面纳米化,之后采用磁控溅射法在表面纳米化和粗晶粒的316L不锈钢基体上沉积Er₂O₃薄膜并进行500℃和700℃的退火.发现薄膜在500℃退火时相结构基本保持稳定,在700℃退火时Er₂O₃薄膜发生明显的单斜相向立方相的转变.利用采用X射线衍射（XRD）、场发射扫描电子显微镜（SEM）和纳米划痕测试对薄膜和基底的结合性能评价.结果表明,700℃退火后的薄膜的要比500℃退火后的薄膜表面裂纹更少,更平整,且证得基底纳米化会使膜基结合性能得到提高.     

Y2O3,La2O3及其混合物对ZrO2陶瓷材料烧结及抗热震性能的影响

以纳米级ZrO2、Y203,La203和黏结剂聚乙烯醇为原料,通过干压成型后烧结,成功制备出稀土增强型ZO2,陶瓷材料,得到其最佳烧结温度为1 450 ℃。先探究了单一稀土对Zx0。的烧结及抗热震性能影响,确定了Y,0。和La,0。的最佳添加量o分别为3%和5% ,然后在总混合稀土添加量o为3%时,探究了Y,0,和La,0,五种不同添加比例对Zx0。的烧结、硬度及抗热震性能影响。结果表明:当Y203和La2O3的质量添加比例为3:1时,制得的ZxO。陶瓷的烧结及抗热震性能最好,此时抗热震次数为15次,硬度为90.2 HRB,密度为5.13 g/ cm''。     

LaCeCuMn/γ-Al2O3纳米稀土催化剂的制备及性能研究

以纳米纤维状γ-Al₂O₃为载体，采用工艺路线简单的浸渍法制备了La_xCe_1-xCuMn纳米稀土催化剂，并应用微反活性评价装置测试了对CO和C₃H₈的氧化活性。利用XRD，TEM，BET等手段，分析了产品的结构和粒子形貌。实验结果表明，催化剂活性组分在载体上分散比较均匀，平均粒径在15～20nm之间，为纳米级催化剂。La物质的量为0.4mol、活性组分质量分数为15.04%时，制得了较为纯净的钙钛矿催化剂，CO和 C₃H₈氧化反应中起燃温度分别可以达到161，186℃，且二者的最终转化率均在99%以上。     

喷丸与ZrO_2/Al_2O_3叠层对Cr_5Mo合金高温氧化性能的影响

采用喷丸处理及溶胶 凝胶工艺涂覆ZrO2/Al2O3叠层对Cr5Mo合金进行了表面处理,研究了不同处理的合金试样在600℃空气中的高温氧化性能。从SEM,XRD及氧化动力学分析结果发现,喷丸处理不能使Cr5Mo合金表面形成保护性的氧化铬膜,反而促进了Cr5Mo合金的高温氧化,其氧化增重与氧化剥落速率最高;ZrO2/Al2O3叠层通过稀土效应改变了氧化膜的生长机制,降低了氧化铬膜的生长速率,促进了合金表面铬的选择氧化,起到了优异的保护作用,大大提高了合金的抗高温氧化性能。     

Reinforcing effect of graphene on the mechanical properties of Al2O3/TiC ceramics

Multilayer graphene (MLG)-reinforced Al2O3/TiC ceramics were fabricated through hot pressing sintering, and the reinforcingef-fect of MLG on the microstructure and mechanical properties of the composites was investigated by experiment and simulation. The simula-tion of dynamic crack initiation and propagation was investigated based on the cohesive zone method. The results show that the composite added with 0.2wt% MLG has excellent flexural strength and high fracture toughness. The major reinforcing mechanisms are the synergistic effect by strong and weak bonding interfaces, MLG pull-out, and grain refinement resulting from the addition of MLG. In addition, the ag-gravating of crack deflection, branching, blunting, and bridging have indispensable contribution to the improvement of the as-designed mate-rials.     

球磨工艺参数对Y2O3和Al2O3混合粉末机械合金化的影响

研究了在机械合金化Y2O3和Al2O3混合粉末的过程中,球磨工艺(球料比、转速、球磨时间)对机械合金化过程的影响。实验结果表明,采用球料比为20∶1,转速为500 r/min,能够获得较高的球磨能量,经10 h机械合金化即可促使Y2O3和Al2O3粉体发生固相反应,合成YAlO3(YAP)。     

Cr3C2颗粒增强型堆焊合金组织与性能分析

对加入Cr3C2的药芯焊丝制备的Cr3C2增强型堆焊合金组织和性能进行了分析。添加Cr3C2的自保护药芯焊丝堆焊工艺性能良好,堆焊表面少飞溅,无裂纹气孔。通过对比实验研究发现,加入Cr3C2的药芯焊丝制备的Cr3C2增强型堆焊合金组织细小,高温冲击韧性明显优于WC颗粒增强型药芯焊丝,合金组织中既有颗粒增强型药芯焊丝堆焊产生的颗粒增强相,又有高铬铸铁型药芯焊丝堆焊产生的高硬度初生碳化物,双重强化机制使堆焊层显微硬度达到含Nb高铬铸铁堆焊层的水平,平均硬度60 HRC以上。     

硅基氧化钆薄膜的生长及结构

采用脉冲激光沉积方法(PLD)在不同温度的Si(100)衬底上制备了Gd2O3栅介质薄膜,利用X射线衍射、X射线反射率以及光电子能谱等方法对它的结构、组成以及价带偏移等进行了研究.结果表明:衬底温度为300℃时,Gd2O3薄膜呈非晶态;当衬底温度为650℃时,形成单斜相的Gd2O3薄膜.XPS和XRR 结果确定其界面主要是由于界面反应形成的钆硅酸盐.通过XPS分析得到Gd2O3与Si之间的价带偏移为(-2.28±0.1)eV.     

Cr, Li, W等添加物对瓷介电容瓷料性能的影响

研究了Cr2O3,Li2CO3,WO3对于0.90(Sr0.54Pb0.26Ca0.20)TiO3-0.1Bi2O3*3.5TiO2为系统的中高压瓷介电容瓷料的介电性能的影响,实验发现掺加Cr2O3对于该瓷料的ε-t曲线有压峰作用;而Li2CO3的掺加有提升ε-t峰作用,介电常数随着掺加量的增加而提高,损耗在45 ℃以下随掺加量的增加而提高;WO3的添加也具有提峰作用,并且同时可以降低高温段ε的温度系数.     

氧对氨在Pt/α-Al2O3催化剂上吸附和解离性能的影响

利用瞬态脉冲技术考察了氨在Pt／Al2O3催化剂表面的吸附、脱附和氧化动力学．结果表明，氨在Pt/Al2O3表面存在两种吸附态：可逆吸附和不可逆吸附．吸附在催化剂表面的氧和体相中的氧促进了氨的分解和氧化．不同的氧物种和反应温度影响产物的分布．体相晶格氧物种是可能形成水的重要因素，而表面氧物种是氯氧化物NO、N2O形成的主要来源．在氧存在的条件下低温有利于氨分解形成N2、N2O，而高温有利于NO的生成．     

Al2 O3和二元碱度对炼钢炉渣中磷酸盐富集机理的综合影响

以六元CaO-SiO2-FeO-P2 O5-Fe2 O3-Al2 O3炼钢渣系为研究对象,结合热力学计算和实验检测,分析( Al2 O3)和二元碱度B综合变化对该六元渣系中磷酸盐富集行为的影响.结果表明：炼钢炉渣中生成游离C2 S含量对磷酸盐富集相nC2 S-C3 P内的( P2 O5)至关重要.该渣系中增加SiO2会降低总的C2 S生成量,增加Al2 O3可促进钙铝黄长石C2 AS相生成,降低游离C2 S ( f-C2 S)的量,进而影响磷酸盐的富集.六元CaO-SiO2-FeO-P2 O5-Fe2 O3-Al2 O3炼钢炉渣获得较好磷酸盐富集程度,渣中二元碱度B和Al2O3含量需满足的耦合关系为：(%Al2O3)=-27.70+21.62B,(Al2O3)<20.0%,B>1.3.     

非晶态合金Co_3B_2稳定结构、组成和电子性质

利用密度泛函理论(DFT)方法,在B3LYP/Lan12dz水平下,对设计出的十几种可能存在的构型分别在二、四重态下进行了全参数优化计算和频率验证,最终获得了6种稳定构型,其中二重态2种,四重态4种。对这些稳定构型的能量、组成和电子性质进行分析,结果表明:团簇Co_3B_2能够稳定存在的几何构型有平面形、三角双锥、单"帽"三角锥和变形四方锥;其中具有单"帽"三角锥结构的构型1~(2)最为稳定;团簇构型随能量的逐渐升高,所占比例逐渐下降,其中构型1~(2)所占比例最大,为27.11%;Co和B原子的电子得失与团簇Co_3B_2构型和重态密切相关;Co原子的3d,4s轨道对原子间成键有较大贡献。     

水合碱金属离子团簇Rb~+(H_2O)_n和Cs~+(H_2O)_n的量子化学研究

应用高水平的从头计算方法QCISD/aug-cc-pVDZ,对气相中的Rb+(H2O)n和Cs+(H2O)n(n=1～6)体系进行研究,优化几何构型,对能量最低的结构,计算结合能和振动频率.结果表明,随着水分子数目的增加,对于Rb+和Cs+,RMO和总结合能有相同的变化趋势;电荷分布显示位于离子上的正电荷逐渐减小,位于氧原子上的负电荷逐渐增大,位于氢原子上的正电荷变化不明显.