Comparison of CMAS corrosion and sintering induced microstructural characteristics of APS thermal barrier coatings

The microstructural features of high-temperature sintered and CaO-MgO-Al₂O₃-SiO₂ (CMAS) corroded air plasma sprayed Y₂O₃ stabilized ZrO₂ (YSZ) thermal barrier coatings (TBCs) under the thermal gradient condition were comparatively studied. As-sprayed YSZ has a lamellar structure and the lamellae are composed of closely aligned columnar crystals. The sintered and the CMAS corroded YSZ coatings maintain the t’-ZrO2 phase as the as-sprayed YSZ coating. The sintered YSZ remains the lamellar structure with reduced interlamellar gaps and grains coarsening. After the CMAS corrosion, the top layer of the YSZ coating keeps its lamellar structure consisting of some columnar grains with the CMAS infiltration into the intergrain gaps and the formation of striped Zr₂Y₂O₇. The typical lamellar structure transforms into more equiaxed grains in the middle and bottom layers of the ceramic coating along with significant infiltration of amorphous CMAS and anorthite formation in the bottom layer owing to the high contents of Ca and Al.     

制造业供应链外包下的高级计划与排程

考察每个客户订单有确定的交付期且外包可用情形下的计划调度问题,提出了制造供应链外包下的高级计划与排程(APS)模型.采用基于遗传算法的方法对该APS模型进行求解.仿真实验中,基于遗传算法的方法有效地解决了APS模型问题,生成了最佳的过程计划(带有外包的加工顺序和机器选择)以及所有订单的排程问题.     

基于正交试验的热障涂层性能变化规律研究

热障涂层广泛应用于燃气轮机、飞机发动机等装备上,其性能直接影响装备的使用寿命。本文采用大气等离子喷涂工艺,在GH4169高温合金表面依次制备NiCoCrAlY金属粘结层和ZrO_2-8%wtY_2O_3陶瓷层。采用扫描电镜和残余应力测试仪对样品的表面形貌、孔隙率以及表面的残余应力进行测试。通过正交试验研究喷涂工艺参数对热障陶瓷层厚度、孔隙率以及残余应力的影响,实验结果表明,对陶瓷层厚度的影响因素从大到小顺序依次为氢气流量,电流,氩气流量,喷涂距离;在相同的制备时间内,陶瓷层的厚度随着电流与氢气流量的增大而明显的增大;随着氩气流量与喷涂距离的增大,陶瓷层的厚度随之减小;对陶瓷层孔隙率的影响因素从大到小顺序依次为喷涂距离,氢气流量,电流,氩气流量。当氩气流量从30 slpm/min增加到40 slpm/min时,氢气流量从5slpm/min增加到10 slpm/min时,孔隙率随之增大;当氩气流量从40 slpm/min增加到50 slpm/min时,氢气流量从10 slpm/min增加到15 slpm/min时,孔隙率随之减小。当喷涂距离从5 mm增加到10 mm时,孔隙率随之减小,而当喷涂距离从10 mm增加到15 mm时,孔隙率急剧升高,而随着电流的增大,孔隙率减小。电流、氢气流量以及氩气流量对涂层残余应力造成很大影响,随着电流以及氢气流量的增大,氩气流量的减小,涂层表面的残余应力急剧上升。     

Hot corrosion behavior of NdYbZr2O7 exposed to V2O5 and Na2SO4 + V2O5 molten salts

In order to evaluate the application prospects of NdYbZr₂O₇ as a novel TBC material, NdYbZr₂O₇ ceramic was synthesized via a solid-state reaction sintering method, and its hot corrosion behavior exposed to V₂O₅ and Na₂SO₄ + V₂O₅ molten salts at 900 °C, 1000 °C, and 1100 °C was comparatively investigated. For the V₂O₅ salt, the primary corrosion products were granular (Nd,Yb)VO₄ as well as cube-like m-ZrO₂. The corrosion layer consisted of two distinct layers, one of which was Zr-rich layer and another was V-rich layer. In the case of Na₂SO₄ + V₂O₅, NaVO₃, as an intermediate product, played an important role in dissolving the NdYbZr₂O₇ ceramic. Herein, the (Nd,Yb)VO₄ exhibited a rod/plate-like morphology, which could be attributed to the synergistic effect of low driving force and low nucleation rate. Since the molten salt infiltration rate was superior to the pore filling rate throughout the hot corrosion, the thickness of corrosion layer increased with the rise of temperature. The hot corrosion mechanisms of NdYbZr₂O₇ ceramic in various molten salts were discussed based on the phase diagram, Lewis acid-base rule and chemical thermodynamics. On this basis, the NdYbZr₂O₇ coating was prepared by atmospheric plasma spray (APS) and it exhibits a higher corrosion resistance compared to YSZ coating.     

黄芪多糖提取工艺研究综述

黄芪 (ＲａｄｉｘＡｓｔｒａｇａｌｉ)为豆科植物蒙古黄芪(Ａｓｔｒａｇａｌｕｓｍｅｍｅｂｒａｎａｃｅｕｓ (Ｆｉｓｈ )Ｂｅｇ .Ｖａｒ.ｍｏｎｇｈｏｌｉｃｕｓ(Ｂｅｇ .)Ｈｓｉａｏ)或膜荚黄芪 (Ａ .ｍｅｍ ｂｒａｎｃｅｕｓ(Ｆｉｓｈ)Ｂｅｇ .)的干燥根。其味甘 ,性微温。具有补气升阳、益卫固表、利尿脱毒、敛疮生肌等功效〔1〕。是一种常见的扶正中药。黄芪多糖 (Ａｓ ｔｒａｇａｌｕｓｐｏｌｙｓａｃｃｈａｒｉｄｓ .ＡＰＳ)是黄芪中重要的天然有效成分。具有促进免疫提高巨噬细胞活性 ,抑制ＥＡＳ、双向调节血糖作用〔2～ 4〕。其分…     

镀锌钢板表面硅烷、铈盐复合膜的制备及耐腐蚀性能研究

先在镀锌钢板表面涂装一层y-氨丙基三乙氧基硅烷（y-APS）膜，然后再在y-APS膜上沉积铈盐转化膜的方法制得复合膜。析氢、碱浸失质量、盐雾实验均说明复合膜的耐腐蚀性明显优于单一铈盐转化膜，且超过某些铬酸盐转化膜。Tafel极化曲线和交流阻抗谱的测定表明复合膜的存在阻碍了锌电化学腐蚀中的阴极还原反应，使电荷转移阻力大增，显著降低了锌的腐蚀速率。经XRD、SEM分析，复合膜中铈盐转化膜的主要成分为CeO2，结构较单一铈盐转化膜更加致密，对基体锌的覆盖度更高。并初步讨论了复合膜的成膜及耐蚀机理。     

Development of Ba-hexaferrite coatings for electromagnetic wave absorption applications

In this research, Ba-hexaferrite coatings for electromagnetic wave absorption applications were deposited by thermal spraying. A suitable powder feedstock was manufactured by blending a BaCO₃ + Fe₂O₃ mixture, which was then agglomerated by spray-drying. The agglomerates were processed by air plasma spraying (APS) without any further treatment or were heat-treated and reactively-sintered to stoichiometric Ba-hexaferrite prior to spraying. As-sprayed coatings were analyzed by Raman spectroscopy and X-ray diffraction (XRD). Whereas the deposition of untreated agglomerates did not result in adequate amounts of crystalline Ba-hexaferrite in the coatings, the APS processing of reactively-sintered agglomerates led to a high content of Ba-hexaferrite and similar magnetic properties to those of Ba-hexaferrite bulk materials.     

真空热处理双粘结层热障涂层抗氧化性能

传统单层结构粘结层热障涂层抗氧化性能不足寿命短,采用超音速火焰喷涂(high velocity oXy-fuel,HVOF)和大气等离子喷涂(atmosphere plasma spray,APS)制备双层结构粘结层,对粘结层进行真空热处理,研究热障涂层的抗氧化性能.结果 显示,经过1050℃×3 h真空热处理,粘结层...     

Size‐resolved fluorescent biological aerosol particle concentrations and occupant emissions in a university classroom

This study is among the first to apply laser‐induced fluorescence to characterize bioaerosols at high time and size resolution in an occupied, common‐use indoor environment. Using an ultraviolet aerodynamic particle sizer, we characterized total and fluorescent biological aerosol particle (FBAP) levels (1–15 μm diameter) in a classroom, sampling with 5‐min resolution continuously during eighteen occupied and eight unoccupied days distributed throughout a one‐year period. A material‐balance model was applied to quantify per‐person FBAP emission rates as a function of particle size. Day‐to‐day and seasonal changes in FBAP number concentration (N_F) values in the classroom were small compared to the variability within a day that was attributable to variable levels of occupancy, occupant activities, and the operational state of the ventilation system. Occupancy conditions characteristic of lecture classes were associated with mean N_F source strengths of 2 × 10⁶ particles/h/person, and 9 × 10⁴ particles per metabolic g CO₂. During transitions between lectures, occupant activity was more vigorous, and estimated mean, per‐person N_F emissions were 0.8 × 10⁶ particles per transition. The observed classroom peak in FBAP size at 3–4 μm is similar to the peak in fluorescent and biological aerosols reported from several studies outdoors.     

DESIGN AND IMPLEMETTATION OF CMOS IMAGE SENSOR

A single Complementary Metal Oxide Semiconductor (CMOS) image sensor based on 0.35 μm process along with its design and implementation is introduced in this paper. The pixel architecture of Active Pixel Sensor (APS) is used in the chip, which comprises a 256×256 pixel array together with column amplifiers, scan array circuits, series interface, control logic and Analog-Digital Converter (ADC). With the use of smart layout design, fill factor of pixel cell is 43%. Moreover, a new method of Dynamic Digital Double Sample (DDDS) which removes Fixed Pattern Noise (FPN) is used.The CMOS image sensor chip is implemented based on the 0.35 μm process of chartered by Multi-Project Wafer (MPW). This chip performs well as expected.