激光熔覆NbC/Ni60合金复合涂层的组织与性能

利用激光熔覆在45钢基体上制备了NbC颗粒增强的Ni60合金复合涂层。结果表明,复合涂层的组织由γ-Ni奥氏体枝晶、枝晶间的共晶、M₂₃C₆、NbC、和少量的CrB相等组成。NbC颗粒是在激光熔覆过程中原位合成的,其形貌为不规则的块状或花瓣状。原位合成NbC颗粒增强的Ni60合金激光熔覆涂层的显微硬度可达HV0.2 1 000左右,相比于纯Ni60合金涂层,复合涂层的显微硬度提高了约38%。并且,通过激光熔覆（Nb+C）/Ni60混合粉末成功修复了2Cr13材质汽蚀的汽轮机叶片。     

Reconfigurable Anisotropic Coatings via Magnetic Field‐Directed Assembly and Translocation of Locking Magnetic Chains

A method for the generation of remotely reconfigurable anisotropic coatings is developed. To form these coatings, locking magnetic nanoparticles (LMNPs) made of a superparamagnetic core and a two‐component polymer shell are employed. Two different polymers form phase‐separated coaxial shells. The outer shell provides repulsive interactions between the LMNPs while the inner shell exerts attractive forces between the particles. Applying a non‐uniform magnetic field, one gathers the particles together, pushing them to come in contact when the internal shells could effectively hold the particles together. When the magnetic field is turned off, the particles remain locked due to these strong interactions between internal shells. The shells are thus made stimuli‐responsive, so this locking can be made reversible and the chains can be disintegrated on demand. In a non‐uniform magnetic field, the assembled chains translocate, bind to the solid substrate and form anisotropic coatings with a “locked” anisotropic structure. The coatings can be constructed, aligned, realigned, degraded, and generated again on demand by changing the magnetic field and particle environment. The mechanism of the coating formation is explained using experimental observations and a theoretical model.     

A Direct Approach to Organic/Inorganic Semiconductor Hybrid Particles via Functionalized Polyfluorene Ligands

Controlled Suzuki–Miyaura coupling polymerization of 7′‐bromo‐9′,9′‐dioctyl‐fluoren‐2′‐yl‐4,4,5,5‐tetramethyl‐[1,3,2]dioxaborolane initiated by bromo(4‐tert‐butoxycarbonylamino‐phenyl)(tri‐tert‐butylphosphine)palladium ( 1 ) or bromo(4‐diethoxyphosphoryl‐phenyl)(tri‐tert‐butylphosphine)palladium ( 2 ) yields functionalized polyfluorenes (M_n = 4 × 10³ g mol^?1, M_w/M_n < 1.2) with a single amine or phosphonic acid, respectively, end‐group. High temperature synthesis of cadmium selenide quantum dots with these functionalized polyfluorenes as stabilizing ligands yields hybrid particles consisting of good quality (e.g. emission full width at half maximum of 30 nm; size distribution σ < 10%) inorganic nanocrystals with polyfluorene attached to the surface, as corroborated by transmission electron microscopy analysis and analytical ultracentrifugation. Sedimentation studies on particle dispersions show that a substantial portion (ca. half) of the phosphonic acid terminated polyfluorene ligands is bound to the inorganic nanocrystals, versus ca. 5% for the amino‐functionalized polyfluorene ligands. Single particle micro‐photoluminescence spectroscopy shows an efficient and complete energy transfer from the polyfluorene layer to the inorganic quantum dot.     

基于各向同性干法刻蚀的大面积悬空Al膜制备

热声传感器随着多孔硅的热致超声发射现象的发现越来越受到关注。热声传感器通过改变器件表面热量而在周围空气中产生交变压力,从而向外发出声波。热声传感器的关键器件是悬空金属薄膜。制备大面积悬空薄膜释放有一定的难度,需要考虑金属薄膜本身的应力与粘附效应。该文提出了两种基于各向同性干法刻蚀的制备金属薄膜的方法,利用XeF2/SF6制备悬空Al膜。由于XeF2与SF6气体刻蚀硅时对于Al有较高的选择比,XeF2对于硅是各向同性刻蚀且有很高的刻蚀速率,而通过设置感应耦合等离子体（ICP）刻蚀机的参数也可利用SF6达到各向同性刻蚀。基于上述特点制备了悬空Al膜,设计相应的制备流程,探索XeF2刻蚀机与ICP刻蚀机合适的刻蚀参数。所制备的悬空Al膜平整、无杂质,具有良好的形貌。     

MEMS Inductor Consisting of Suspended Thick Crystalline Silicon Spiral with Copper Surface Coating

报道了一种由悬浮在玻璃衬底上的表面镀铜平面单晶硅螺线构成的新型MEMS电感,可消除衬底损耗及减小电阻损耗.采用一种硅玻璃键合-深刻蚀成型释放工艺并结合无电镀技术制作该电感,形成厚约40μm的硅螺线,在硅螺线表面镀有高保形厚铜镀层,在铜镀层表面镀有起钝化保护作用的薄镍镀层.该电感的自谐振频率超过15GHz,在11.3GHz下,品质因子达到约40,电感值超过5nH.基于该电感的简化等效电路模型,采用一种特征函数法进行了参数提取,模拟结果与测量结果符合得很好.     

高温氨化合成GaN微晶

分别利用Ga2O3粉末和Ga2O3凝胶作为Ga源,采用NH3为N源,在950℃下,分别将两种反应物与流动的NH3反应20 min合成了GaN微晶。用X射线衍射(XRD)、扫描电子显微镜(SEM)、选择区电子衍射(SAED)对微晶进行结构、形貌的分析,特别是对两种不同途径合成GaN微晶的XRD进行了分析比较。结果表明,当Ga源温度为950℃时两种不同的合成途径均可得到六方纤锌矿结构的GaN单晶颗粒,在氮化温度为850℃和900℃时,利用Ga2O3粉末作为Ga源,仅有少量的Ga2O3转变为GaN;而采用Ga2O3凝胶作为Ga源,在相同的温度下,大部分凝胶经过高温氨化反应均可转化为GaN。     

空气过滤捕集效率影响因素分析及多元关联式的确定

评价空气过滤捕集效率对于提高空气品质及优化过滤运行是非常重要的,但目前过滤捕集效率的计算公式均为隐函数,不便于实际应用,因此,本文采用过滤理论对各种过滤影响因素进行理论计算,然后,采用多元回归分析方法,得出计算过滤捕集效率的显性计算公式,并提出了计算多分散颗粒捕集效率的计算方法,以便于优化选择过滤介质及优化过滤运行参数。     

关于进入工业火焰的煤粉颗粒温升速率的探讨

从传热角度对煤粉微粒进入高温环境的温度变化进行了初探,对沉降试验炉和煤粉炉内的煤颗粒与环境的换热及有关试验进行对照比较,其结果表明热传导是微粒与外界换热的主要形式。针对流化床锅炉的特点及大小不同的煤颗粒的温升速率进行了探讨。