Ting YU
,
Zexaing SHEN
材料科学技术（英）
Metal oxide nanostructures (CuO, Co3O4, ZnO and α-Fe2O3) have been successfully fabricated by a simple and efficient method: heating the appropriate metals in air at low temperatures ranging from 200 to 400℃. The chemical composition, morphology and crystallinity of the nanostructures have been characterized by micro-Raman spectroscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Two mechanisms: vapor-solid and surface diffusion play dominant roles in the growth of metal oxide nanostructures starting with low melting point metals (Zn and Cu) and high melting point metals (Fe and Co), respectively. With sharp ends and large aspect ratio, the metal oxide nanostructures exhibit impressive field-induced electron emission properties, indicating their potentials as future electron source and displays. The water wettability and anti-wettability properties of iron oxide nanoflakes were also discussed in this work.
关键词:
Metal oxide
,
oxide
,
nanostructures
,
field
,
emiss
Physica B-Condensed Matter
The EPR parameters D, g(parallel-to) and DELTAg (=g(parallel-to) - g(perpendicular-to)) for Ni2+ in an Al2O3 crystal have been studied by using the high-order perturbation formulas and the parameters based on the optical absorption spectrum. From the study, one can find that to reach a good fit between calculated and observed EPR parameters, the Ni2+ ion is required to move 0.05 angstrom from the exact site of the replaced Al3+ ion and to be closer to the midway plane between the oxygen layers. The reasonableness of this displacement is discussed.
关键词:
field
Communications in Theoretical Physics
In this paper, we establish an effective medium approximation (EMA) for effective conductivity of nonlinear composite media. As an example, we consider a two-dimensional composite medium with a cylindrical inclusion embedded in a homogeneous host, both the host and the inclusion having nonlinear current-voltage constitutive relations, and apply the perturbation expansion method to derive its analytic series solution. Using the nonlinear EMA we derive the formulae of the first-, the third- and the fifth-order effective conductivities, which are valid for nonlinear composite media with middle concentration of inclusion.
关键词:
field
罗执
,
张杨
,
赵愈亮
,
张卫文
中国有色金属学报
将压力场和超声场复合作用于铝合金的凝固过程,并对比分析无外场、单一外场(压力场、超声场)和复合场的作用效果.采用定量金相分析、扫描电镜、电子探针等手段研究压力场、超声场以及压力和超声复合场作用下Al-5.0Cu-1.0Fe合金的显微组织和显微硬度.结果表明:分别施加50 MPa压力场和800 W超声场均能减少α(Al)二次枝晶间距,细化并分散富铁相和θ(Al2Cu)相,同时改变富铁相的形貌,使针状的Al7Cu2Fe相转变成汉字状的富铁相Al6(CuFe);同时复合场比单一外场能更大程度地细化α(Al)二次枝晶间距、富铁相和θ(Al2Cu)相;单独施加压力50 MPa比单独施加800 W的超声更能够有效减少缩松,但同时施加压力和超声时效果最佳;同时施加压力和超声场时可获得最高的α(Al)基体显微硬度.对复合场的作用效果进行初步探讨,这是超声场的空化效应以及声流效应和压力场的压力效应共同作用的结果.
关键词:
Al-5.0Cu-1.0Fe合金
,
超声场
,
压力场
,
富铁相
,
显微组织
,
显微硬度
刘佳
,
杨仁波
,
邓湘云
,
李德军
,
张小龙
,
王传方
,
王依山
,
杨学良
,
王晓慧
,
李龙土
功能材料
100nm是介于微米晶和纳米晶之间的重要临界尺寸,研究了平均晶粒尺寸为100nm的钛酸钡（BTO）陶瓷的微结构和铁电性能,分析了测试温度和外加电场对纳米晶钛酸钡陶瓷铁电性的影响。与超细纳米晶BTO陶瓷不同的是,100nm BTO陶瓷主要以四方相形式存在的;介电温谱显示,正交到四方相的相变具有典型的弥散特征,低温时介电损耗〈0.02。此外,铁电性能测试表明,100nm BTO陶瓷具有良好的铁电滞后特征,随着电场的增加,能量损耗密度、剩余极化强度和矫顽场均增加;随着温度的升高,陶瓷的铁电性在逐渐减弱,高于居里温度时由铁电相转为顺电相,铁电性消失。实验结果表明,100nm BTO陶瓷的铁电性与测试温度和外加电场有着密切的关系。
关键词:
铁电性
,
纳米晶钛酸钡陶瓷
,
温度
,
电场
张彩军
,
吕达
,
乔士宾
,
顾克井
,
肖鹏程
钢铁钒钛
doi:10.7513/j.issn.1004-7638.2016.03.024
用水力模型和数值模拟方法对高拉速下镀锡板单流中间包流场特性进行研究.水力学模型采用脉冲响应法测定RTD曲线,分析中间包内流动模式;数值模拟应用Fluent商业软件对中间包流场和夹杂物进行模拟分析,并确定优化方案.优化方案中间包钢液平均停留时间由340.7 s增加到545.3 s,增加了60.1％;死区体积比Vd由46.0％降至13.6％,比原方案降低了70.4％;中间包内显微夹杂物和外来夹杂物的去除率大幅提高.
关键词:
中间包
,
流场
,
镀锡板
,
高拉速
,
水力模型
,
数值模拟
付欣欣
,
胡荣
,
王智宇
材料导报
为了在水相体系制备尺寸均一、形貌可控的锐钛矿型纳米TiO2颗粒,研究了钛源、溶液pH值、反应温度对TiO2晶体结构的影响.通过对样品进行XRD、TEM表征,发现形成锐钛矿型TiO2的最佳实验条件为:硫酸钛作为钛源、硝酸浓度为0.14 mol/L、反应温度60℃.硝酸浓度低、反应温度高有利于锐钛矿型TiO2的形成,反之则利于金红石的形成.通过在锐钛矿形成过程中施加外场作用,即紫外光和超声波,探究外场对其形貌的影响.结果表明:无外场作用时,生成的锐钛矿为纺锤状,尺寸为20～30 nm;施加紫外光4h之后,形状为近球状,尺寸约为10nm;施加超声波之后,形状仍为纺锤状,且尺寸无变化.造成TiO2形貌变化的主要原因是,在成核-长大过程中,紫外光可以抑制[001]晶向的生长速度,且时间越长,这种抑制作用越明显,当作用时间为4h时,[001]晶向的生长得到明显的抑制,使得纳米晶由纺锤状变为近似球形.因此,在TiO2的合成过程中可以通过施加外场作用对其形貌进行调控.
关键词:
TiO2
,
外场
,
形貌
