自蔓延离心熔铸TiB2-(Ti,W)C-TiC陶瓷研究

基于离心热爆反应、难熔液相分离与快速凝固原理,选取(WO3+Al+C)体系辅助(B4C+Ti)反应体系,采用自蔓延离心熔铸工艺可以成功制备出TiB2微纳米晶补强TiC-(Ti,W)C陶瓷基复合材料.将(B4C+Ti)、(WO3+Al+C)两种反应体系依次装填入坩埚中进行SHS离心熔铸实验,发现因W-Ti-C液相动力学粘度的降低、Al2O3液滴迁移路程减小,极大促进Al2O3液滴的Stokes上浮过程,故而显著减小残存于陶瓷基体上的氧化物夹杂含量与尺寸,进而TiB2微纳米片晶诱发的强烈自增韧机制与Al2O3微纳米晶产生的残余应力增韧效应,使得TiB2-(Ti,W)C-TiC陶瓷的弯曲强度、断裂韧性与维氏硬度分别达到(952±25)MPa、(12.6±2.5)MPa·m1/2与(28.6±1.2)GPa.     

Electromagnetic modeling of waveguide amplifier based on Nd<Superscript>3+</Superscript> Si-rich SiO<Subscript>2</Subscript> layers by means of the ADE-FDTD method

By means of ADE-FDTD method, this paper investigates the electromagnetic modelling of a rib-loaded waveguide composed of a Nd³⁺ doped Silicon Rich Silicon Oxide active layer sandwiched between a SiO₂ bottom cladding and a SiO₂ rib. The Auxilliary Differential Equations are the rate equations which govern the levels populations. The Finite Difference Time Domain (FDTD) scheme is used to solve the space and time dependent Maxwell equations which describe the electromagnetic field in a copropagating scheme of both pumping (λ _pump = 488 nm) and signal (λ _signal = 1064 nm) waves. Such systems are characterized by extremely different specific times such as the period of electromagnetic field ~ 10^-15 s and the lifetimes of the electronic levels between ~ 10^-10s and ~ 10^-4 s. The time scaling method is used in addition to specific initial conditions in order to decrease the computational time. We show maps of the Poynting vector along the propagation direction as a function of the silicon nanograin (Si-ng) concentrations. A threshold value of 10²⁴ Si-ng m^-3 is extracted below which the pump wave can propagate so that a signal amplication is possible.     

硅纳米颗粒的制备及其在太阳能电池中的应用

利用HF和AgNO3混合液刻蚀制备出n型硅纳米颗粒,并将其应用到纳米薄膜太阳能电池。结果表明,随着酸刻蚀时间的延长,硅纳米颗粒的尺寸不断减小,当刻蚀时间为35min时,其尺寸平均值为80nm。将n型硅纳米颗粒作为太阳能电池的窗口材料制备出纳米薄膜太阳能电池器件,发现19型硅纳米颗粒尺寸对太阳能电池的光电转换性能也有明显的影响,随着n型硅纳米颗粒尺寸的减小,太阳能电池的光电转化效率不断提高。     

放电等离子烧结制备纳米晶双相耦合(NdDy)11.5(FeCoNb)82.4B6.1致密磁体

使用放电等离子烧结(SPS)制备致密的纳米晶交换耦合Nd_2Fe_(14)B/α-Fe永磁合金.研究烧结温度、时间、压力对合金磁性能和显微组织的影响.结果表明,随温度、压力的升高,密度增大,磁能积增加;但温度过高或时间过长,使得晶粒长大,导致矫顽力降低.在烧结压力为500 MPa,烧结温度为700 ℃保温3 min后,得到密度为7.6 g/cm~3,晶粒细小的致密块体,其磁性能为:B_r=0.81 T,H_(ci) =856 kA·m~(-1),(BH)_m =106 kJ·m~(-3),其晶粒大小约20 nm.     

铱系涂层钛阳极的研究进展

本文简要介绍了涂层钛阳极的发展概况 ;论述了铱系涂层钛阳极的制备工艺及其良好的使用性能和优点。文中重点阐述了几种有代表性、具有广阔应用前景的涂层钛阳极 ,对其制备工艺值得深入地研究。     

Efficient Perovskite Light‐Emitting Diodes Using Polycrystalline Core–Shell‐Mimicked Nanograins

Making small nanograins in polycrystalline organic–inorganic halide perovskite (OIHP) films is critical to improving the luminescent efficiency in perovskite light‐emitting diodes (PeLEDs). 3D polycrystalline OIHPs have fundamental limitations related to exciton binding energy and exciton diffusion length. At the same time, passivating the defects at the grain boundaries is also critical when the grain size becomes smaller. Molecular additives can be incorporated to shield the nanograins to suppress defects at grain boundaries; however, unevenly distributed molecular additives can cause imbalanced charge distribution and inefficient local defect passivation in polycrystalline OIHP films. Here, a kinetically controlled polycrystalline organic‐shielded nanograin (OSN) film with a uniformly distributed organic semiconducting additive (2,2′,2′′‐(1,3,5‐benzinetriyl)‐tris(1‐phenyl‐1‐H‐benzimidazole), TPBI) is developed mimicking core–shell nanoparticles. The OSN film causes improved photophysical and electroluminescent properties with improved light out‐coupling by possessing a low refractive index. Finally, highly improved electroluminescent efficiencies of 21.81% ph el^?1 and 87.35 cd A^?1 are achieved with a half‐sphere lens and four‐time increased half‐lifetime in polycrystalline PeLEDs. This strategy to make homogeneous, defect‐healed polycrystalline core–shell‐mimicked nanograin film with better optical out‐coupling will provide a simple and efficient way to make highly efficient perovskite polycrystal films and their optoelectronics devices.     

高能球磨制备Mo-3%Cu纳米晶复合粉末特性

利用机械合金化法制备出Mo-3%Cu(质量分数,以下同)超细复合粉末,采用X射线衍射、BET氮吸附法和DTA差热分析方法对球磨后的Mo-6%Cu纳米晶复合粉的组织结构变化、表面特性和热稳定性进行了系统的研究.结果表明,高能球磨可以制取纳米晶复合粉末,晶粒内部产生很大的晶格畸变,同时球磨产生的晶体缺陷使原子扩散加快,形成Mo-Cu超饱和固溶体和扩大Mo在粘结相中的溶解度,BET氮吸附结果证实了球磨使粉末产生大量微孔,且比表面、中孔表面和孔径降低.     

Effects of Ribbon Thickness on Structure and Soft Magnetic Properties of a High-Cu-Content FeBCuNb Nanocrystalline Alloy

The effects of ribbon thickness (t) on the structure and magnetic properties of a Fe_82.3B₁₃Cu_1.7Nb₃ alloy in melt-spun and annealed states have been investigated. Increasing the t from 15 to 23 μm changes the structure of the melt-spun ribbons from a single amorphous phase to a composite with dense α-Fe nanograins embedded in the amorphous matrix. The grain size (D_α-Fe) of the α-Fe near the free surface of the ribbon is about 6.7 nm, and it gradually decreases along the cross section toward the wheel-contacted surface. Further increasing the t to 32 μm coarsens the D_α-Fe near the free surface to 15.2 nm and aggravates the D_α-Fe ramp along the cross section. After annealing, the ribbon with t = 15 μm has relatively large α-Fe grains with D_α-Fe > 30 nm, while the thicker ribbons possessing the pre-existing nanograins form a finer nanostructure with D_α-Fe < 16 nm. The structural uniformity of the ribbon with t = 23 μm is better than that of the ribbon with t = 32 μm. The annealed ribbons with t = 23 and 32 μm possess superior soft magnetic properties to the ribbon with t = 15 μm. The ribbon with t = 23 μm exhibits a high saturation magnetic flux density of 1.68 T, low coercivity of 9.6 A/m, and high effective permeability at 1 kHz of 15,000. The ribbon with t = 32 μm has a slightly larger coercivity due to the lower structural uniformity. The formation mechanism of the fine nanostructure for the ribbons with suitable t has been discussed in terms of the competitive growth effect among the pre-existing α-Fe nanograins.     

芳纶纤维Ni-P/Ni-Cu-P双层化学镀的结构与形貌

采用化学镀技术,实现了芳纶纤维表面化学镀Ni-P/Ni-Cu-P的金属化处理,利用SEM、EDS和XRD分别对芳纶纤维原始样品、粗化后、施镀后及剥落层的表面形貌、镀层的成分和物相进行了分析比较,并对镀层的形成机制及剥落原因进行了分析研究。结果表明:经过预处理的芳纶纤维比表面积增大,增加了其亲水性和活性;化学镀Ni-P/Ni-Cu-P后,Ni-P镀层中镍含量降低,磷含量增多,纯镍转化为Ni₃P且伴随有少量的铜的出现,整体镀层中Ni、Cu、P的原子比为8.54:3.66:5.59,镀层中以纯Cu、Cu₃P和Ni₃P为主;另外由于镀层中应力分布不均,以及P在Ni-P/Ni-Cu-P相界面的偏聚,削弱了界面的结合强度,使局部拉应力集中,造成了镀层的剥落;且化学镀铜是依靠镍离子的催化作用形成镀层的。     

基于热力学函数的纳米晶粒长大Cellular Automaton仿真研究

基于纳米晶热力学特性表征函数,将纳米晶热力学性质对晶界迁移的影响引入Cellular Automaton算法,对纳米晶粒长大行为进行了定量化和可视化的仿真研究.模拟结果表明,纳米晶粒长大的动力学与传统粗晶材料不同,在恒温条件下,纳米晶粒的长大指数n不是常数(传统粗晶材料的晶粒长大指数n=2为常数),随纳米晶粒长大过程的进行,n值从1.70至6.59发生变化.作为纳米晶粒长大的驱动力,纳米晶界的过剩自由能与纳米晶粒尺寸的变化直接相关.由于纳米晶材料强烈的小尺寸效应,纳米晶组织的热力学性质较大地影响纳米晶界的结构和能量状态,从而影响纳米晶粒长大的动力学特征.因此,只有结合纳米晶热力学特性的仿真研究才能获得对纳米晶粒长大行为本质性的认识.