碳化硅反射镜轻量化结构优化设计

本文根据某型号碳化硅主反射镜的设计要求,对比了扇形、三角形、六边形轻量化孔对镜体静态、动态性能的影响,选择了综合性能较好的三角形轻量化结构方案,利用有限元方法进行参数建模,将对镜体力学性能和质量影响较大的镜体厚度、面板厚度、筋厚度等结构参数作为设计变量,运用零阶优化方法对镜体结构进行优化设计,得到了轻量化程度高、镜面变形误差完全满足设计要求的碳化硅反射镜体。     

反应烧结碳化硅中碳短纤维的形貌及增强作用

以双峰碳化硅粉末、碳黑、短碳纤维为原料,采用注浆成型、反应烧结法制备了力学性能优异的碳化硅复合材料。研究了硅化反应对碳纤维表面形貌及组分的影响。结果表明：硅化反应在碳纤维表面生成致密β-SiC层,反应过程伴随的体积膨胀增加了纤维表面的粗糙度。混合酸HNO3+HF腐蚀实验表明纤维表面由直径2～5μm的β-SiC晶粒构成。提出了硅化纤维的双层结构模型：外层由微米、亚微米尺度β-SiC晶粒构成,内层由Si–C基团组成的混合物组成。碳短纤维体积分数为30%时,复合材料的弯曲强度、断裂韧性分别达到最大值416 MPa、5.1 MPa?m0.5,相比单一反应烧结碳化硅陶瓷分别提高102%、78%。     

磨削表面损伤对RBSiC弯曲强度的影响

借助X射线衍射方法测量了反应烧结碳化硅(RBSiC)材料的磨削表面的残余应力状态,并根据断裂力学评价了磨削引入的裂纹尺寸,分析了RBSiC的弯曲强度受磨削引入裂纹和残余应力的影响.研究表明,由于磨削过程中与磨削方向有关的机械载荷占主导作用,使磨削后的表面残余应力具有方向依赖性.砂轮轴向进给从0.90μm/s增加到1.35μm/s,磨削表面的残余压应力数值降低,计算得到的磨削引入的裂纹尺寸增大,导致强度下降.     

碳纤维增强碳化硅复合材料的微观结构与界面

利用 Al_2O_3和 Y_2O_3为烧结助剂,通过热压烧结工艺制备了碳纤维增强碳化硅复合材料。结果表明:球磨工艺有助于短切碳纤维的均匀分散。烧结过程中,烧结助剂 Al_2O_3、Y_2O_3之间发生化学反应,促进液相烧结,并形成晶界间的次晶相YAG,有利于提高复合材料的断裂韧性。在较高烧结温度下,碳纤维与烧结助剂以及基体之间反应,形成过强结合界面,纤维性能降低,不利于复合材料力学性能的提高。     

微波协同有机膨润土一体化工艺处理中性红染料废水的研究

分别用阳离子表面活性剂氯化十六烷基吡啶(CPC)、溴化十六烷基三甲铵(CTMAB)与两种膨润土组合，并引入微波于一体化工艺中处理染料废水，采用正交实验选择一种较好组合。通过单因素影响分析，对比研究了微波辐照和常规振荡条件下，CPC有机膨润土合成-废水处理一体化工艺吸附中性红的适宜条件、性能及作用机理；并与振荡条件下活性炭对中性红的脱色效果作比较。结果表明：CPC浓度120Mg／L(28％CEC)，一体化工艺脱色效果明显高于活性炭吸附工艺，微波工艺的处理效果略优于振荡工艺。     

有机膨润土制备及在废水处理中的应用进展

本文综述了有机膨润土的制备原理、方法,有机膨润土在脱色、去除芳香类污染物、重金属离子和有机农药等废水处理领域中的应用研究及前景。     

Design and finite element analysis of lightmass silicon carbide primary mirror

Primary mirror is one of the key components in the space remote sensing system. To minimize the mass of the mirror without compromising its stiffness and decrease the deformation of the mirror surface at the different temperatures are the mainly two objects in the development of the primary mirror. Silicon carbide （SIC）, the most promising optical material, was used as the material of the primary mirror with triangle lightmass structure in a Cassegrain system. By using finite element method, the properties of the SiC mirror were compared with that of the traditional Be mirror and fused silica mirror. The results of static, dynamic and thermo-mechanical analysis indicate that the deformation of the mirror surface caused by temperature field is much bigger than that caused by gravity field. The SiC mirror has the best overall properties, and the SiC material is much suitable for the primary mirror.     

Effects of light-mass structural forms on silicon carbide mirror

To reduce the mass of the mirror, silicon carbide was used as the material and four light-mass structures were designed. The properties of SiC mirror open back structure with triangular cell, open back structure with hexagonal cell, sandwich structure with triangular cell, sandwich structure with hexagonal cell, were analyzed by using finite element method. The results of the static, dynamic, and thermal properties of the four kinds of SiC mirror indicate that the surface figures of the SiC mirrors are all satisfactory with the design requirements. The properties of the mirrors with sandwich structure are better than those with open back structure, except the high cost. And the mirror with triangular cell has better combination properties than the mirror with hexagonal cell. Considering the overall performance and the cost, open back structure with triangular cell is the most suitable for the SiC mirror.     

砌体结构温度裂缝的原因与对策

我校89－1系列教工住宅为6层混合结构,在竣工半年后陆续在房屋的东、西山墙,顶层的内横墙、内外纵墙及屋面板出现裂缝。最大裂缝宽度为1.17mm(外纵墙),最小为0.27mm(屋面板)。以上裂缝,几乎均随温度的升高,裂缝宽度随之加大,"顶层重,下层轻"、"两端重,中间轻"、"向阳重,背阳轻"的特点与规律,是典型的由温度应力产生的裂缝。     

短波接收机数字锁相频率合成器的设计

提出了基于DDS/PLL混合的频率合成器的设计方案,给出了主要的硬件选择,并且对该频率合成器的杂波抑制和相位噪声进行了分析,最后对样机的性能进行了测试,结果表明该频率合成器具有很好的性能,可应用于短波接收机中。