异质复合结构纳米纤维SnO2/ZnO的制备及其气敏特性研究

采用静电纺丝法制备了多级中空结构的SnO_2纳米纤维,然后将SnO_2纳米纤维置于90℃乙酸锌溶液中,恒温水浴条件下,在SnO_2纳米纤维上生长了ZnO纳米球,形成了异质结构的SnO_2/ZnO复合纳米纤维。分别通过XRD、SEM、EDX和XPS等表征手段对异质复合纳米纤维SnO_2/ZnO材料的结构、形貌及元素含量进行了表征分析。异质结构的SnO_2/ZnO复合纳米纤维保持了SnO_2纳米纤维多级中空的纤维结构,SnO_2纳米纤维长度约为300 nm,依附于SnO_2纤维表面的SnO_2纳米颗粒生长的ZnO纳米球直径为250~300 nm。采用静态气体测试系统对异质复合纳米纤维SnO_2/ZnO气敏元件的气敏性能进行了测试。测试结果表明:异质复合纳米纤维SnO_2/ZnO气敏元件在最佳工作温度350℃下,对(0.5~100)×10-6丙酮具有优异的响应灵敏度、较好的选择性和长期稳定性。异质复合纳米纤维SnO_2/ZnO中存在于ZnO纳米球与SnO_2纳米颗粒间的N-N同型异质结导致复合材料晶界势垒高度的降低,改善了电子与空穴的输运特性,促使SnO_2/ZnO异质复合纳米纤维的吸附能力大大增强,从而改善了SnO_2/ZnO元件的丙酮敏感特性。

Improved AlGaN/GaN HEMTs Grown on Si Substrates Using Stacked AlGaN/AlN Interlayer by MOCVD

AlGaN/GaN high electron mobility transistors(HEMTs)are grown on 2-inch Si(111)substrates by MOCVD.The stacked AlGaN/AlN interlayer with different AlGaN thickness and indium surfactant doped is designed and optimized to relieve the tensile stress during GaN epitaxial growth.The top 1.0μm GaN buffer layer grown on the optimized AlGaN/AlN interlayer shows a crack-free and shining surface.The XRD results show that GaN(002)FWHM is 480arcsec and GaN(102)FWHM is 900arcsec.The AGaN/GaN HEMTs with optimized and nonoptimized AlGaN/AlN interlayer are grown and processed for comparison and the dc and rf characteristics are characterized.For the dc characteristics of the device with optimized AlGaN/AlN interlayer,maximum drain current density I_(dss)of 737mA/mm,peak transconductance G_(m)of 185mS/mm,drain leakage current density Ids of 1.7μA/mm,gate leakage current density I_(gs)of 24.8μA/mm and off-state breakdown voltage VBR of 67V are achieved with L_(g)/W_(g)/L_(g)/L_(g)=1/10/1/1μm.For the small signal rf characteristics of the device with optimized AlGaN/AlN interlayer,current gain cutoff frequency fT of 8.3 GHz and power gain cutoff frequency fmax of 19.9GHz are achieved with L_(g)/W_(g)/L_(g)/L_(g)=1/100/1/1μm.Furthermore,the best rf performance with fT of 14.5 GHz and fmax of 37.3 GHz is achieved with a reduced gate length of 0.7μm.

Syntheses, Structures, Electrochemistry and Magnetic Properties of Two Trinuclear Cyanide-bridged Clusters Based on Tricyanometalate Building Block

The reaction of tricyanometallate precursor, Bu_4N[Fe(Tp)(CN)_3] and(Bu_4N)[(pzTp)Fe(CN)_3](Tp = tris(pyrazolyl)hydroborate, pzTp = tetrakis(pyrazolyl)borate) with Ni(ClO_4).26 H_2O in the presence of the monodentate N-methylimidazole ligand afforded two new cyano-bridged heterobimetallic {Fe2 Ni} trinuclear clusters, {[Fe(Tp)(CN)_3]_2[Ni(Mim)_4]}·8 H_2O(1) and {[Fe(pzTp)(CN)_3]_2[Ni(Mim)_4]}·2 CH_3OH·2H_2O(2). The molecular structure was determined by single-crystal X-ray diffraction. In the two compounds, the FeIII ions were coordinated by three cyanide carbon atoms and three nitrogen atoms of Tp(or pzTp) anions, whereas, the NiII ions were surrounded by two cyanide nitrogen atoms and four nitrogen atoms from four monodentate N-methylimidazole ligands, and they were bridged by tricyanometalate building block to form similar {Fe2Ni} trinuclear clusters. Cyclic voltammetry(CV) measurements indicated that compound 1 exhibited two quasireversible iron-centered reduction processes at –0.71 and –0.17 V and one quasireversible nickel-centered oxidation process at 0.92 V, while compound 2 showed two quasireversible iron-centered reduction processes at –0.66 and –0.09 V and one quasireversible nickel-centered oxidation process at 0.88 V. Magnetic measurements showed that compounds 1 and 2 exhibited strong intrachain ferromagnetic interaction between the low-spin Fe~Ⅲ(S = 1/2) and high-spin Ni~Ⅱ(S = 1) ions.

基于ZnO/NiO纳米异质结构紫外探测器的低温水溶液生长

利用低温水溶液方法制备了ZnO/NiO纳米异质结构,该异质结构主要由ZnO纳米阵列及NiO纳米片状结构层组成,ZnO和NiO纳米材料均由低温水溶液方法生长。同时基于ZnO/NiO纳米异质结构构建了简单的紫外探测器件。研究结果表明,基于上述结构的紫外探测器件具有非常好的紫外响应特性。该方法工艺流程简单、重复性好,具有广阔的应用前景。

“四模块”嵌入下的混合式教学设计与实践——以功能材料专业物理化学基础课程为例

为建设适应新时代要求,突出高阶性、创新性、挑战度的一流本科课程,实现价值引领、能力培养和知识传授的教育教学目标,结合功能材料专业的特点和民族高等院校学生的学情,构建了物理化学基础课程的“四模块、三阶段、两时空、双平台”的混合式教学新模式,重塑了“价值引领模块、基础理论模块、多学科融合模块和虚拟仿真实验模块”的“四模块”内容体系。通过“四模块”嵌入下的混合式教学实践研究,结合学生的课前、课中、课后等学习成绩,多维度评价学习效果,并藉由调查问卷来分析学生对混合式教学的评价,最终研究结果表明学生的个性化自主学习能力有了显著提高、学生运用物理化学理论解决复杂问题的综合能力得到了提升,学生经过刻苦学习获得了素质提高的成就感。