Au/Ni/Al/Ti/AlxGa1-xN/GaN和Au/Pt/Al/Ti/AlxGa1-xN/GaN欧姆接触研究

研究并对比了Ti/Al/Ni/Au和Ti/Al/Pt/Au多层金属膜与未掺杂的Al0 .2 2 Ga0 .78N/GaN(i AlGaN/GaN)异质结构之间的欧姆接触性质。在退火温度低于 70 0℃时 ,两种接触样品上都不能得到欧姆接触。随着退火温度的升高 ,85 0℃快速退火后 ,在Ti/Al/Ni/Au接触上获得了 1.2 6×10 - 6 Ω·cm2 的比接触电阻率 ,在Ti/Al/Pt/Au接触上获得了 1.97× 10 - 5Ω·cm2 的比接触电阻率。研究结果表明 ,金属与半导体接触界面和Al0 .2 2 Ga0 .78N异质结构界面载流子沟道之间适当的势垒的存在对高质量欧姆接触的形成起重要作用 ,势垒的宽度取决于退火温度以及退火的具体进程。对Ti/Al/Ni/Au和Ti/Al/Pt/Au欧姆接触比接触电阻率的差异进行了解释。     

Effect of metal doping into Ce0.5Zr0.5O2 on catalytic activity of MnOx/Ce0.5–xZr0.5–xM0.2xOy/Al2O3 for benzene combustion

The research investigated the effect of doping two metals separately or together into Ce0.5Zr0.5O2 on the catalytic activity of MnOx/Ce0.5-xZr0.5-xM0.2xOy/Al2O3 （M=Y, Mn, Y and Mn） for catalytic combustion of benzene. The prepared catalysts were characterized by X-ray diffraction （XRD）, surface area analysis, oxygen storage capacity （OSC）, and H2-temperature programmed reduction （H2-TPR）. Catalytic test was performed on a conventional fixed bed flow reactor. The characterization results revealed that Y and Mn ions entered into the ceria-zirconia mixed oxides framework, which improved the textural properties and greatly promoted the MnOx dispersion on the support surface. The complete conversion temperature of benzene on MnOx/Ce0.4Zr0.4Y0.1Mn0.1Oy/Al2O3 was 563 K, and the selectivity of carbon dioxides was 99%. This catalyst could be applied in a wide range of GHSV and wide concentration condition, showing great potential for application.     

Superconducting Transition Temperature in YBa2Cu4O8/La2/3 Ca1/3 MnO3 / YBa2 Cu4O8 Heterostructure

YBa2Cu4O8/La2/3 Ca1/3 MnO3/YBa2Cu4O8 （ Y-124/LCMO/Y- 124） heterostructure was prepared by facing-target sputtering technique. The oscillatory superconducting transition temperature was observed when the thickness of LCMO d L is larger than critical thickness d L^CR. The metal-insulator transition temperature can only be detected at d L 〉 d L^CR. The dependence on the spacer layer in LCMO/Y-124 systems suggests strongly the interplay of ferromagnetic and superconducting couplings.     

Sm1+xBa2-xCu3Oy固溶体

用X射线衍射及氧含量分析法测定了Sm_1+xBa_2-xCu₃O_y固溶区域为0 ≤ x ≤ 0.4。当x<0.25时,Sm_1+xBa_2-xCu₃O_y属正交晶系;x=0.25时,发生从正交到四方的相变;在整个固溶区域内,T_c随x的增加而下降,直至淬灭。同时探讨了Sm_1+xBa_2-xCu₃O_y化合物在不同的淬火温度、氧含量与晶体结构、超导电性的关系。     

Bi2O3-BaO-SiO2-RxOy玻璃的结构及其封接性能

研究了Bi₂O₃-BaO-SiO₂-R_xO_y玻璃体系的结构及封接性能.应用密度泛函理论计算获得了Bi₂O₃在SiO₂玻璃网络中的能量最优结构,从理论上确定了铋作为网络中间体最可能以[BiO₃]形式存在,并讨论了Ba²⁺、Al³⁺等在玻璃中的作用及其存在的可能结构.结果表明,该玻璃的热膨胀系数在50~530℃温度为11×10^-6 K^-1,与氧化钇稳定氧化锆(热膨胀系数10.2×10^-6 K^-1)电解质和不锈钢SUS430(热膨胀系数11.3×10^-6 K^-1)合金连接体相匹配.对玻璃粉体进行物相分析表明,该硅酸盐玻璃为非晶体,与理论分析相一致.将氧化钇稳定氧化锆电解质和SUS430合金连接体用Bi-Ba-Si-O玻璃在高温下进行封接实验,结果说明三相界面结合紧密,气密性良好.实验选定的Bi-Ba-Si-O玻璃材料基本满足固体氧化物燃料电池对封接材料的要求.     

热压烧结制备Li3/8Sr7/16Ta3/4Hf1/4O3钙钛矿型固体电解质

采用热压烧结制备了Li_3/8Sr_7/16Ta_3/4Hf_1/4O₃钙钛矿型固体电解质, 研究了不同烧结方式对样品性能的影响。通过X射线衍射仪表征材料的晶体结构, 扫描电子显微镜观察组织形貌, 交流阻抗仪测试电化学性能。结果表明:样品为立方KTaO₃相, 热压烧结成功合成了钙钛矿结构固体电解质, 相对于常压烧结, 热压烧结制备的样品孔隙更少, 晶粒之间结合更加紧密, 致密度高达94.0%, 离子电导率为4.33×10-4S·cm(T=298K).      

LiNi1/3Co1/3Mn1/3O2正极材料的合成与性能

采用共沉淀-高温固相法制备LiNi_1/3Mn_1/3Co_1/3O₂正极材料,利用XRD和SEM对所制试样的晶体结构和形貌进行表征,研究了烧结温度对材料电化学性能的影响.结果表明,焙烧温度为850 ℃制备的材料具有较好电化学性能,在25 ℃,电压范围为2.75~4.2 V,1 C充电6 C放电下首次放电比容量为124.2 mAh/g,50次循环后容量保持率为95.2 %.      

固相反应合成La1-xSrxMnO3的机理

以La₂O₃,MnO₂和SrCO₃为原料,通过固相反应合成SOFC的阴极粉料LSM,利用XRD,TGA/DTA热分析仪等现代分析仪器研究了该材料的反应历程.结果发现,实验过程首先出现了La₂SrO_x相,并在350～1000℃的较大范围内一直存在,到800℃时才出现LaMnO₃.通过分析研究,反应过程先是La₂O₃+SrCO₃→La₂SrO_x+CO₂,然后为La₂O₃+MnO₂→LaMnO₃,,最后发生La₂SrO_x和LaMnO₃向La_1-xSr_xMnO₃转化.这一结果与人们一致公认的反应历程,即先发生La₂O₃+MnO₂→LaMnO₃,然后是LaMnO₃+SrCO₃→La_1-xSr_xMnO₃有较大差异.     

Ni/Co比例对LiCoxNi1-xO2电化学性能的影响

采用固相反应法合成了一系列LiCo_xNi_1-xO₂（0≤x≤1）材料,用XRD和电化学实验方法研究了Co³⁺取代Ni³⁺对LiNiO₂材料电化学性能的影响.结果表明,当Ni/Co比例为8:2时材料具有最好电化学性能,比容量可以达到170～180mAh/g,并且具有好的抗过充性能.     

Effect of Zn Doping on Transport Properties of La2/3 Sr1/3 Mn1 - x Znx O3 Films

La2/3 Sr1/3 Mn1-x ZnxO3films （x =0.05, 0.1,0.3, and 0.5） were prepared using magnetron sputtering method, and the effect of Zn doping on transport properties of the films was studied. An analysis of X-ray diffraction showed that the main phase of the bulk target was orthorhombic and the films had better epitaxial character. It was found that the films with x =0.05 and x =0.1 exhibited typical insulator-metal transition. No transition of the films with x≥0.3 was observed and the dominant transport was variable-range hopping due to observable secondary phase ZnO. These could be attributed to the Zn doping effect on manganites.     

锂过量对钙钛矿型Li3/8Sr7/16Ta3/4Hf1/4O3固体电解质性能的影响

固相烧结法合成钙钛矿型Li_3/8Sr_7/16Ta_3/4Hf_1/4O₃(LSTH) 固体电解质材料,制备过程中分别加入过量的碳酸锂,质量分数分别为(0~30 %).通过XRD、SEM、ICP-OES以及EIS测试,表征不同锂过量LSTH固体电解质材料成相、显微形貌以及室温电导率的影响.实验结果表明,配料时,过量一定质量百分数的碳酸锂,能够有效减少烧结过程中因锂挥发而生成的SrTa₂O₆杂相,提高样品密度和室温电导率.样品最佳锂过量质量百分数为20 %,20 %锂过量样品1 300 ℃烧结10 h为钙钛矿纯相,密度6.5 g/cm3,室温电导率达到3.12×10-4 S/cm.      

锂离子电池正极材料LiNi1/3Co1/3Mn1/3O2研究进展

介绍了比容量高、循环性能优异、成本较低的LiNil/3Co1/3Mnl/3O2正极材料近年来在合成技术及其掺杂改性、表面修饰等方面所取得的成果和进展,并对其未来的发展趋势进行了展望。     

射频溅射Fe1-xNix/Cu超晶格的结构与磁性

应用射频溅射技术制备了面心立方结构的Fe_1-xNi_x/Cu(x=0.26~0.54)金属超晶格.Mgo单晶衬底的采用以及在面心立方结构的Cu上实施外延等措施保证了在Ni质量分数低至0.26时Fe-Ni合金层仍保持了良好的面心立方的晶体结构,而且直到液氦温区这种面心立方结构仍是稳定的.磁性测量表明,当Fe-Ni合金层的Ni质量分数低至接近因瓦合金成分(x=0.35)时,其饱含磁矩呈下降趋势,即表现出偏离Slater-Pauling规律的倾向.同时,面心立方结构的Fe-Ni合金层的饱合磁矩有很强的温度依赖性,表明面心立方结构的Fe-Ni合金中饱含磁矩对Slater-Pauling规律的偏离与所谓的马氏体预相变无关,而与合金中Fe-Fe原子对的反铁磁性耦合有关.     

Antigenic drift between the haemagglutinin of the Hong Kong influenza strains A/Aichi/2/68 and A/Victoria/3/75

A DNA copy of the gene coding for the influenza A/Aichi/2/68 haemagglutinin protein was cloned in the plasmid pBR322 and the complete nucleotide sequence determined. Comparison of this primary structure and the deduced amino acid sequence with the haemagglutinin gene and protein of strains belonging to the same (H3) subtype and to different subtypes, of both human (H2) and avian (Hav1) origin, documents further at the molecular level the two independent modes of antigenic variation of the virus--drift and shift.     

Index/Volume 14/1975

Abstract

A microscopic study has been made of the dissolution of lead and copper sulphides from blast furnace mattes by bioleaching.

The results of the experiments demonstrate the preferential corrosion sites and the degradation of the surface of the sulphides caused by the oxidation catalyzed by bacteria (Tiobacillus ferrooxidans). This degradation of the solid leads to its breakdown and increases the reaction surface.

In addition, it is shown that a two-stage bioleaching treatment (800 h retention time) is required to achieve at least 80% copper extraction.     

Catalytic combustion of diesel soot over K2NiF4-type oxides La2-xKxCuO4

Nanostructure K2NiF4 type oxides La2-xKxCuO4 complex oxides were prepared using the Sol-Gel method, characterized by X-Ray Diffraction （XRD）, Fourier Transform Infrared （FT-IR）, and Scanning Electron Microscopy （SEM）. The catalytic activity for soot combustion was evaluated by the Temperature-Programmed Reaction （TPO） technique. The results demonstrated that the substitution quality of K^＋ for La^3＋ at the A-site would increase the catalytic activities of La2-xKxCuO4 for soot combustion greatly; the substitution quality affected the structure and catalytic activity obviously. The La1.8K0.2CuO4 complex oxides with tetrahedral structures had the best catalytic activity for soot combustion, and the ignition temperature of soot combustion was lowered from 490 to 320 ℃.