Sr_(1-x)Ba_xBi_4Ti_4O_(15)铁电陶瓷性能研究

采用传统固相反应法制备了Sr1–xBaxBi4Ti4O15(x=0～1.0)铁电陶瓷,研究了Ba取代量对其烧结性能和介电性能的影响。结果表明,适量Ba取代促使陶瓷样品烧结温度由1240℃降至1130℃左右,tanδ降至20×10–4,体积电阻率ρv提高一个数量级,同时居里峰显著展宽,居里温度tC下降。当x=0.7时,在1130℃烧结6h获得的陶瓷样品综合介电性能较好:εr≈150,tanδ=53×10–4,ρv=1.7×109Ω·m,tC≈430℃。     

低功耗微型CO_2传感器的研制

制作了一种新型微型结构CO2传感器,该传感器采用Al2O3陶瓷片作为衬底,sol-gel法制备的固体电解质NASICON(sodiumsuperionicconductor)材料为离子导电层,复合碳酸盐Li2CO3-BaCO3(摩尔比为1:1.5)为敏感电极。该传感器在CO2浓度为(500~5000)×10–6体积分数范围内表现出良好的敏感特性,灵敏度达到67.3mV/decade(毫伏/10×10–6体积分数),并且功耗由原来的1.08W降到0.72W。微型元件的响应恢复时间分别为20s和58s。     

回焊炉内氧气体积分数对焊接可靠性的影响

SMT(表面贴装技术)回焊炉工作时,炉中氧气体积分数的差异很大,从100×10–6至10000×10–6不等,在已验证氧气体积分数[(O2)]超过4000×10–6会造成产品不良的前提下,针对500×10–6,1000×10–6,3000×10–6以及4000×10–6这四种不同的氧气体积分数,分别对回焊炉焊接的铜片上的锡焊点进行润湿角、EDS分析,对组装印制电路板(PCBA)上的锡焊点进行X射线、推力、通孔填充量等测试。结果显示,(O2)在4000×10–6以下,元件的焊接可靠性并无明显差异。选择(O2)=4000×10–6可降低回焊炉的氮气用量,节约成本。     

玻璃–氧化硅复合基板材料的制备及性能

以低相对介电常数的硼硅酸盐玻璃粉末和氧化硅粉末为原料,制备了玻璃–氧化硅复合材料。研究了烧结温度和氧化硅含量对复合材料的电学性能和力学性能的影响。结果表明,当氧化硅质量分数为45%时,玻璃–氧化硅复合材料经840℃、2h的烧结后,其εr为3.8,tanδ为4×10–4,ρv为9.8×1011?·cm,抗弯强度σ为30MPa。另外,该复合材料在100~500℃之间的热膨胀系数为(8.0~10.0)×10–6℃–1。     

钇稳定ZrO_2界限电流型微氧氧传感器的设计

从理论和实验角度,对钇稳定ZrO2界限电流型微氧氧传感器的量程与结构设计的关系进行了分析研究。结果显示:被测环境氧摩尔浓度应小于5%,被测环境氧浓度与氧传感器输出极限电流的数值,基本成线性关系;通过(5 000~50000)×10–6;(500~20000)×10–6;(100~10000)×10–6;(50~1000)×10–6四档测量范围的划分以及S/L比的合理设计,可以实现钇稳定ZrO2界限电流型微氧氧传感器对低氧浓度的准确测量。     

占空比和羰基铁含量对镍铁氧体@羰基铁核壳粉体吸波性能的影响

针对镍铁氧体@羰基铁核壳粉体–石蜡复合体系,探讨了占空比和核壳粉体中羰基铁体积分数对其等效介电常数的影响,并预测了其吸波性能。研究结果表明:随着占空比和羰基铁体积分数的提高,复合体系的等效介电常数会有明显的增大;在相同的占空比下,随着羰基铁体积分数的提高,体系反射率有一个先减小后增大的过程,当羰基铁体积分数为30%时,反射率最小,达到–34 dB,吸收峰逐渐向低频移动;当羰基铁体积分数相同时,随着占空比的提高,反射率会逐渐变大,同时吸收峰也会朝低频移动。     

硫脲作还原剂制备二氧化锰及其电化学性能

通过化学液相法,用硫脲作为还原剂和高锰酸钾反应制备了无定形MnO2。用XRD和SEM研究了产物的结构和形貌,用恒流充放电和循环伏安测试考察了MnO2的电化学性能。结果表明:在0.5mol/L的Na2SO4溶液中,电位窗口为0～0.8V、电流密度为1×10–3A/cm2时,首次放电比容量为248F/g,,经过100次循环后比容量保持在232F/g。在(3～5)×10–3A/cm2的电流密度下放电比容量分别为198和182F/g,具有良好的电容特性。     

缓蚀剂对提高腐蚀箔比容的影响

采用硫酸-盐酸体系环保型铝电解电容器用阳极箔腐蚀工艺,在扩孔液中分别加入乙酸、丙酸和乙二酸作为缓蚀剂,结合SEM分析对缓蚀剂在腐蚀扩孔中的缓蚀机理进行了探讨,研究了直流电侵蚀时缓蚀剂对腐蚀箔比容的影响。结果表明:缓蚀剂的引入提高了腐蚀箔比容,当乙酸、丙酸和乙二酸三种缓蚀剂的质量浓度ρ增加到0.5g/L时,所制腐蚀箔比容达到最大值,分别为1.10×10~(–6),1.07×10~(–6)和1.12×10~(–6)F/cm~2。乙二酸的缓蚀效果最好,可使腐蚀箔的比容提高25%以上。     

聚噻吩/WO_3复合纳米材料的制备及气敏性能

采用水合肼法制备WO3粉体,再以无水FeCl3作氧化剂,通过原位化学氧化聚合制备了不同聚噻吩(PTh)掺杂量的PTh/WO3复合纳米材料。并研究了用其制备的气敏元件的气敏性能。结果表明:气敏元件对H2S和NOx有较高的灵敏度和较好的选择性。用质量分数w(PTh)为5%的PTh/WO3复合纳米材料制备的气敏元件,在加热电压为2.25V时,对体积分数φ(NOx)为5×10–6的灵敏度可达77.14;用w(PTh)为20%的PTh/WO3复合纳米材料所制之气敏元件,在加热电压为2.43V时,对φ(H2S)为20×10–6的灵敏度达63.27。     

p型单晶硅涂源掺锰新方法

研究了扩散源的浓度与掺杂后硅材料补偿度之间的关系。以MnCl2·4H2O乙醇溶液为扩散源,涂在初始电阻率为3.8?·cm的p型单晶硅片表面,在高温(1200℃)下掺杂锰后,在室温避光条件下,用SDY—5型双电测四探针仪测样品电阻率ρ。改变扩散源的浓度重复实验,用XRD对扩散后的样品进行分析,结果表明:当硅片表面浓度为23.4×10–8mol/cm2时,扩散后样品体电阻率的径向不均匀度在5%以内,扩散后硅片的补偿度最大。     

单分散钡铁氧体空心粒子的制备研究

以单分散的聚(苯乙烯鄄共鄄丙烯酸)[P(St鄄coA鄄A)]乳胶粒子作为模板粒子,通过其表面羧基与在弱极性溶剂中制得的均匀分散的钡铁氧体前驱物溶胶之间的相互作用,制备了聚苯乙烯/钡铁氧体前驱物核壳复合粒子,再将内核在体积比为1∶1的丙酮和环已烷组成的混合溶剂中溶解而获得单分散钡铁氧体前驱物空心粒子。复合粒子经热处理后得到主晶相为BaFe12O19的钡铁氧体空心粒子。     

核壳型磁性颗粒微波磁导率模拟与实验研究

采用有效媒质理论模拟和实验验证的方法,研究了核壳型磁性颗粒的微波磁导率。结果表明:核壳结构有利于提高微波下颗粒的复磁导率,2GHz时,其实部比氧化后的颗粒提高6%~12%,虚部提高15%~30%。片状椭球形核壳结构优于球形核壳结构,2GHz时,20nm壳层厚的片状颗粒的复磁导率为4.85–1.71i,而同壳层厚的球状颗粒为4.55–1.31i。在核壳结构的颗粒中,壳层厚度薄有利于改善磁导率。     

Synthesis and microstructure of Cd4SiS6/Si composite nanowires

Cd4SiS6/Si composite nanowires are produced through co-thermal evaporation of CdS and Si powders with a small amount of tin sulfide as an additive. A vapor-liquid-solid growth mechanism is proposed for the anisotropic growth of the composite nanowires based on the presence of metallic tin particles at their tip-ends. Both side-by-side and core-shell composite nanowires are obtained. The product is characterized using X-ray powder diffraction and scanning electron microscopy. Detailed structural and chemical analyses of individual composite nanowires are carried out using transmission electron microscopy (TEM), high-resolution TEM (HRTEM), electron diffraction (ED) and energy-dispersive X-ray spectroscopy. Planar defects, including microtwins and stacking faults, are abundant in a Si core, as revealed by HRTEM and selected-area ED. The formation of composite nanowires is discussed in the light of thermodynamic and kinetic aspects.     

Creep Properties of Composite Solders Reinforced with Nano- and Microsized Particles

In the present work the creep properties of Sn37Pb- and Sn0.7Cu-based composite solders reinforced with metallic nano- and microsized Cu and Ag particles have been studied. First, a series of volume percentages of reinforcements were selected to optimize the content of reinforcing particles. Then, the composite solder with optimum volume fraction of reinforcement particles, corresponding to the maximum creep rupture lifetime, was selected to investigate the effect of applied stress and temperature on the creep rupture lifetime of the composite solder joints. In the creep rupture lifetime test, small single-lap tensile-shear joints were adopted. The results indicate that composite solders reinforced with microsized particles exhibit better creep strengthening than composite solders reinforced with nanosized particles, although the mechanical tensile shear strength of composite solder joints reinforced with nanosized particles may be higher than those reinforced with microsized particles. Moreover, the creep strengthening action of the reinforcement particles is more obvious under conditions of lower applied stress or lower test temperature. Strengthening by metallic Cu or Ag reinforcement particles decreases with increasing temperature or applied stress. The Sn0.7Cu-based composite solder reinforced with microsized Ag particles is a low-cost lead-free solder that is easy to process and may have good market potential.     

Enhanced Initial Permeability and Dielectric Constant in a Double- Percolating Ni0.3Zn0.7Fe1.95O4–Ni– Polymer Composite

A novel, three-phase, double-percolating composite with NiZn-ferrite particles and nickel particles embedded in a poly(vinylidene fluoride) matrix is prepared by a simple hot-pressing method. Large ferrite particles in the composite not only act as a magnetic phase, thus endowing the composite with a high initial permeability, but also present (in a high volume fraction) a discrete (non-percolating) phase, confining polymer and metallic particles into a continuous double-percolating structure of low volume fraction. In particular, a large enhancement in both the initial permeability and the dielectric constant of the three-phase composites is observed, which is due mainly to the addition of a small number of nickel particles that act as both magnetic and percolative metallic phases. The dielectric and magnetic behavior observed in the three-phase composites can be explained by effective-medium and percolation theories.     

核壳型铁钴纳米复合材料的制备及其性能

采用多元醇还原工艺和自组装技术,在微米级Fe粉表面包覆纳米Co粒子,一步法制备了一种具有核壳结构的复合磁性微球,用SEM表征了其相组成和形貌,用VSM测试了磁滞回线,初步研究了磁学性能。结果表明:用该法制备的核壳型Fe/Co纳米复合材料表面包覆致密,其比饱和磁化强度和矫顽力介于微米铁粉和纳米钴粉之间。     

Highly sustainable mechanical/electrical resistance switching behaviors via one-dimensional Ag/TiO2 core-shell resistive switchable materials in flexible composite

Composite-based resistance switching random access memory (ReRAM) has great potential for application in flexible and wearable electronics. However, its large operating parameters and low reliability still have some limitations in realizing practical applications, which is derived from its high dependence on the orientation and dispersion of the filler in the composite layer. Here, we proposed a novel composite system that does not depend heavily on the orientation or dispersion of the fillers within the composite film of the ReRAM device. The AgNW/TiO₂ core-shell nanowires inducing superb resistance switching behavior were fabricated. The composite resistance switching (RS) film was prepared by mixing the one-dimensional core-shell particles and poly (vinyl alcohol) (PVA) dielectric matrix. The composite RS film exhibited remarkable resistance switching behavior with extremely low/uniform operating voltage (V_set ~ 0.13 ± 0.013 V, and V_reset ~ −0.10 ± 0.012 V), and the reliable switching behavior was maintained for up to ~200,000 mechanical deformation cycles under 3 mm of bending radius. To evaluate the resistance switching mechanism of the composite-type ReRAM, the structural analysis and device modeling were performed.     

非球形簇团核壳结构粒子的激光散射特性

在冰晶粒子异质核化理论基础上,建立了椭球形、六角平板和六角棱柱3种簇团形核壳结构冰晶粒子模型,利用离散偶极子近似法(DDA)数值计算同一入射波长下,有效尺寸对核壳结构冰晶粒子消光效率、吸收效率和散射效率的影响、中间均匀混合层对核壳结构冰晶粒子散射强度的影响以及Mueller矩阵元素随散射角度的变化情况。数值结果表明:随着有效尺寸的增大,椭球形、六角平板和六角棱柱3种簇团形核壳结构冰晶粒子的消光效率、吸收效率和散射效率随着有效尺寸的增大分别呈现不同的变化趋势;在相等尺寸条件下,散射强度随散射角度的变化情况与粒子形状有密切关系,且相比于椭球形和六角平板两种簇团形核壳结构冰晶粒子,六角棱柱核壳结构冰晶粒子的前向散射强度最大,散射强度随散射角度的变化曲线振荡更明显。根据Mueller矩阵元素随散射角度的分布情况,可以看出六角棱柱簇团形冰晶结构的散射方向最明显,前向散射强度最大,六角平板和六角棱柱簇团形冰晶结构的Mueller矩阵元素相对球形和椭球形在后向散射场区域的偏差更明显。论文的研究结果为进一步分析复杂冰晶粒子的散射特性,开展高空云层中各种复杂几何形状簇团冰晶粒子的散射特性研究和分析提供支持。     

Processing and creep properties of Sn-Cu composite solders with small amounts of nanosized Ag reinforcement additions

In this research, nanosized Ag reinforcement particles were incorporated by mechanical means into a promising lead-free solder, Sn-0.7Cu, in an effort to improve the comprehensive property of the Sn-0.7Cu solder. Wettability, mechanical performance, and creep-rupture life tests were conducted to study the difference between Sn-0.7Cu solder and its composite solder with different Ag reinforcement volume fractions. Experimental results indicated that the composite solders and their joints showed better wettability and mechanical properties, as well as longer creep-rupture lives, than Sn-0.7Cu solder. The composite solder with 1vol.%Ag reinforcement addition exhibited the best comprehensive property as compared to the composite solders with other reinforcement volume fractions. Systematic creep-rupture life tests were conducted on the 1vol.%Ag-reinforced Sn-0.7Cu-based composite solder joints. Significant enhancement of the creep-rupture lives were found in the composite solder joints under different stress and temperature combinations as compared to the Sn-0.7Cu solder joint. Ductile rupture surfaces were exhibited in most of the broken solder joints.