表面微结构防污研究

表面微观结构的开发是目前海洋无毒防污材料的一个重要发展方向,本文主要介绍了防污表面微结构的设计、制备方法以及防污性能评价。     

圆柱表面微结构超精密车削加工技术的探究

超精密加工是衡量一个国家科技和制造水平的重要标志.近年来,我国综合国力和科学技术水平的日渐提升离不开超精密加工技术的发展和进步.文章通过详细分析圆柱表面微结构的超精密车削加工技术,旨在促使科研技术攻关人员关注圆柱表面微结构超精密车削加工技术的发展现状,在不断提高我国机械零部件制造技术水平的同时,促进我国机械制造加工领域...     

浅析表面微结构设计在瓷砖功能化中的应用及发展趋势

传统瓷砖功能化是建筑陶瓷在未来发展的一个重要趋势。材料功能化的主要目的是将材料的表面与基体一起作为系统进行设计,利用表面微观结构的设计,使材料具备材料本身没有而又希望具有的性能。先进材料领域已经在表面微结构设计方面积累了很多经验和成果,但能否将这些技术和科学原理结合并应用到传统建筑陶瓷的配方及工艺体系当中,仍需要很多的研究工作去验证和推动。本文重点讨论了陶瓷砖应用表面微结构设计和构造去实现产品在防滑、抗菌、易清洁三个方面功能化的研究进展,为传统陶瓷砖向多功能性发展提供了一个重要的研发方向。     

单晶硅太阳电池表面绒面制备及其性质研究

单晶硅太阳能电池的表面织构化所形成的陷光效应,可以增强对光的吸收,提高电池的转化效率。本文研究了制绒液主要成分含量、制绒温度以及时间对绒面织构形成的影响。采用扫描电镜分析了试样的表面形貌,分光光度法研究了试样的反射率。通过分析确定了单晶硅太阳电池表面织构化的最佳工艺参数为1.5%wt的NaOH、1.5%wt的Na2SiO3.9H2O和6.5%vol的IPA,反应温度为80℃,反应时间为25min,在此工艺参数下所制得的硅片样品绒面平均反射率为9.85%。     

丙烯酸改性有机硅树脂涂层表面微结构的制备与表征

采用丙烯酸类单体对含可聚合双键的有机硅预聚物进行改性,合成丙烯酸改性有机硅树脂。使用三乙烯四胺固化后,涂层表面形成规律性的微结构形貌,微结构的存在使得改性树脂涂层表面的静态水接触角比纯硅树脂的大,疏水性增强。当有机硅预聚物与丙烯酸类单体含量比为1∶1、丙烯酸类单体中丙烯腈含量为15%~25%时,改性树脂涂层表面微结构形貌规律性较好。海水浸泡实验表明,丙烯酸改性有机硅树脂涂层表面微结构形貌较稳定,且附着力较好,可适应长期海水浸泡环境。     

硅酸钠在太阳能电池单晶硅表面织构化的作用

在单晶硅太阳电池的制备过程中,通常利用晶体硅[100]和[111]不同晶向在碱溶液中各向异性腐蚀特性,在表面形成类似于“金字塔”的绒面结构,使得入射光在硅片表面多次反射,提高入射光吸收效率,可提高单晶硅太阳电池的转换效率。实验探索了一种廉价的硅织构化腐蚀技术,即单独采用Na2SiO3代替传统的氢氧化钠和异丙醇溶液,以减少价格较高的异丙醇的用量,降低成本。不采用异丙醇或其他机械消泡的条件下,用质量分数为5％的Na2SiO3溶液在80℃腐蚀120min,单晶硅片表面可获得最佳反射率为12．56％的减反射绒面。虽然与传统的氢氧化钠和异丙醇溶液效果相比,单独使用Na2SiO3溶液腐蚀单晶硅片表面的反射率和均匀性略差,但在传统的氢氧化钠和异丙醇体系中加入质量分数为0．1％的Na2SiO3也会促进腐蚀反应的进行,获得更加均匀的减反射绒面。     

表面活性剂对材料微结构与光催化性能的调控

为探讨不同性质表面活性剂对材料结构的影响,以4种常用的表面活性剂为模板,在相同的条件下制备出性能各异的铝掺杂二氧化钛（Al-TiO2）粉体材料。并对材料的微结构和组成进行了表征与分析。结果表明,表面活性剂疏水基团所含碳原子数与Al-TiO2粉体的微晶尺寸呈负相关性,与晶格应力呈正相关性。表面活性剂诱导Al3 进入TiO2晶格的质量分数越大,晶格应力越大。Al-TiO2粉体材料的可见光降解吡啶的性能主要是由表面活性剂本身特定的分子结构及其所导致的氧空位浓度大小来决定,而不是能带间隙的宽窄来决定。阴离子表面活性剂对材料的微结构有很大的调控作用,其中SDS为最大;阳离子表面活性剂CTAB次之,两性表面活性剂对材料性能的调控没有优异表现。     

电镀金刚石线切割单晶硅表面损伤研究

首次采用超高速电镀金刚石线切割单晶硅。通过表面分析、拉曼光谱等技术手段研究了金刚石粒度、切割线速度、切割刀数对被切割工件表面粗糙度、表面损伤深度及损伤程度的影响。发现,采用较完整晶形的金刚石,切割刀数越多,被加工工件表面凹坑深度和线痕减少越明显,进而,表面粗糙度获得提高。当随着粒度的减小,表面断裂方式发生了变化,从脆性断裂转变成塑性断裂。切割表面光滑区域以无定形硅为主,线痕明显区域检测到无定形及亚稳态硅,在凹坑内部属于晶态硅。另外,无定形和多晶硅主要取决于线的速度,线的速度越高,无定形和多晶硅越少。     

纳微结构疏水表面结霜过程及抑霜特性

采用静电纺丝法,通过调节电纺母液浓度,制备出7种具有典型微米颗粒结构、微米颗粒/纳米纤维混合结构和纳米纤维结构的疏水表面,实现了纳微结构的表面可控;对表面微观结构进行了表征,测试了其疏水性能;通过表面结霜过程和抑霜性能实验比较,结合表面分形维数分析,研究了纳微结构疏水表面的抑霜特性。结果表明,虽然7种纳微结构疏水表面接触角均在139°~152°之间,具有明显的疏水特性,但其抑霜性能与疏水性能并不呈一致关系;抑霜性能与表面结构密切相关,随着表面结构分形维数的增大而减小。     

石墨烯/镍复合微结构表面的池沸腾传热特性

采用电刷镀和表面改性技术,在紫铜表面制备了纯镍微结构（TS1）、亲水性石墨烯/镍复合微结构（TS2）以及疏水性石墨烯/镍复合微结构（TS3）。采用扫描电镜和接触角测量仪分别对三类微结构的表面形貌和润湿性进行了表征;以去离子水为工质,对三类微结构表面的池沸腾传热特性进行了实验研究,发现含有石墨烯的TS2和TS3较TS1的沸腾传热性能均显著改善,其中,TS3具有最大的传热系数和最高的临界热流密度,与TS1相比,其最大传热系数和临界热流密度分别提高了135%和97%。分析表明,TS3具有复杂三维堆叠微结构,疏水性微结构减小了气泡成核的活化能,增加了核化密度,是传热系数提高的主要因素,同时,三维堆叠微结构增加了受热表面的毛细吸液再润湿能力,是临界热流密度提高的主要机理。     

不同硅片对SBT薄膜结构与性能的影响

采用HPAgilent4294A阻抗分析仪、XRD、TEM等测试方法研究了不同电阻率硅片对Sr0.5Ba0.5TiO3(SBT)薄膜结构与性能的影响.在测试频率为1KHz时,在高阻硅片上生成的SBT薄膜的相对介电常数εr,介质损耗tanδ分别为100.54,0.060,材料的介电性能相对提高,并表现出较好的频散特性;最大εr温度点Tm(居里温度)稍微移向高温.在高阻硅片上制备的SBT薄膜易生成四方钙钛矿结构,薄膜表面无裂纹,孔洞少,比较致密,晶粒的平均粒径均为80nm,分布均匀;晶格条纹间距约为0.296nm,晶界2侧的晶粒取向是随机的.     

电阻率对N型单晶硅电池电性能影响的研究

近年来,P型太阳电池商业化生产效率已趋于稳定,N型太阳电池逐渐走向产业化.基于N+ Np+型铝背结单晶硅太阳电池,研究了电阻率为1 ～5.5 Ω·cm的N型硅衬底材料经过相同工艺后电池性能的差别,可以有效的节省成本.通过选用不同电阻率的N型硅片,经过相同的工艺制备N型单晶硅太阳电池,采用QSSPC、四探针、ECV、恒光源Ⅰ-Ⅴ测试系统对电池的少子寿命、方块电阻、磷元素分布、电性能进行测量.实验结果表明:虽然电池的少子寿命随电阻率的升高而升高,但是在方块电阻、磷元素分布、开路电压Voc、短路电流Isc、填充因子FF、转换效率Eff等方面不同电阻率的电池并无明显差异.     

Effect of Microstructure on the Creep of Siliconized Silicon Carbide

Mechanisms of creep deformation have been investigated for a commercial grade of siliconized carbide containing ≅33%/silicon. Microstructural studies of both tensile and compressive test specimens indicate dislocation damage generation in both the silicon carbide and the silicon phases as a consequence of creep. In the silicon carbide, dislocation damage was normally restricted to contact sites between the silicon carbide grains resulting from high intergranular contact stresses during deformation. Dislocation damage was also observed in the silicon. Although dislocation damage was heavy in some regions of the specimens, most regions of the specimens, most regions were free of dislocations. This result is consistent with the hypothesis that deformations occurs by the motion of clusters of grains during deformation. In tension, creep at high strain rates, 1 × 10⁻⁸_S⁻¹, was accompanied by the formation of cavities at Si/SiC interfaces within the intergranular silicon phase. As cavities were not associated with dislocations, their growth was probably controlled by diffusional processes. Based on observations of the microstructure, a model of deformation is proposed to explain the fact that siliconized silicon carbide creeps faster in tension than in compression, at the same applied stress. The model is based on soil mechanics concepts. It is suggested that creep is controlled by intergranular friction between aggregate particles of the composite.     

反应烧结碳化硅的显微组织及其导电性的研究

研究了液态硅参与下的反应烧结碳化硅的工艺参数、显微组织对其电阻率的影响.随着烧结气氛压力和成型压力增加,反应烧结碳化硅中游离硅量减少,电阻率增加.其烧结机理以碳的溶解及碳化硅的淀析过程为主.     

Microstructure of Silicon Carbide Whiskers Synthesized by Carbothermal Reduction of Silicon Nitride

The microstructure of silicon carbide whiskers synthesized by carbothermal reduction of silicon nitride has been studied using transmission electron microscopy. All of the whiskers examined are single crystals, and grow in the (111) crystallographic direction. Two different forms of stacking faults and microtwins were observed; in one the planar defects are normal to the whisker growth direction, and the other has the defect planes at an angle of about 70° to the growth axis, while both forms of the defects are on the [111] closed-packed planes. Without the addition of catalyst, droplets containing metallic impurities were not found at the tips of the whiskers synthesized by the present process. A core and outer regions were observed in the single-crystal whiskers, which may be evidence that the whiskers were formed by a two-stage mechanism.     

Effect of Microstructure on High-Temperature Compressive Creep of Self-Reinforced Hot-Pressed Silicon Nitride

An experimental self-reinforced hot-pressed silicon nitride was used to examine the effects of microstructure on high-temperature deformation mechanisms during compression testing. At 1575–1625°C, the as-received material exhibited a stress exponent of 1 and appeared to deform by steady-state grain-boundary sliding accommodated by solution-reprecipitation of silicon nitride through the grain-boundary phase. The activation energy was 610 ± 110 kJ/mol. At 1450–1525°C for the as-received material, and at 1525–1600°C for the larger-grained heat-treated samples, the stress exponent was >1. Damage, primarily in the form of pockets of intergranular material at two-grain junctions, was observed in these samples.     

烧结助剂对氮化硅陶瓷显微结构和性能的影响

氮化硅中氮原子和硅原子的自扩散系数很低，致密化所必需的扩散速度和烧结驱动力都很小，在烧结过程中需采用烧结助剂。烧结助剂是影响氮化硅陶瓷的显微结构和性能的关键因素之一。有效的烧结助剂不但可以改善氮化硅陶瓷的显微结构，而且可以提高氮化硅陶瓷的高温性能和抗氧化性能。     

熔融渗硅对石墨材料微观结构及性能的影响

选用四种不同孔隙结构的石墨进行熔融渗硅(简称熔渗)反应,采用扫描电镜、X-射线衍射、压汞、CT等方法表征了熔渗前后材料的微观形貌、物相及孔隙结构。结果表明,熔渗后的材料由石墨、硅及碳化硅三种物相组成,且硅及碳化硅的分布与石墨孔隙结构相关。熔渗后样品孔隙率均<1%,体积密度提高21.08%~35.94%。熔渗后材料强度及模量均有明显提高,强度是原石墨样品的1.7~6.2倍,模量是原石墨样品的2.4~7倍,提高幅度与石墨孔隙结构及晶粒尺寸相关。理论计算结果表明,石墨样品熔渗过程主要受扩散-反应控制。     

Microstructure and Oxidation Behavior of Silicon Carbide Fibers Derived from Polycarbosilane

Polycarbosilane-derived SiC fibers (CG Nicalon, Hi-Nicalon, and Hi-Nicalon type S) were exposed for 1–100 h at 1273–1673 K in air. Oxide layer growth and changes in tensile strength for these fibers were examined after exposure. The three types of SiC fibers decreased in strength as the oxide layer thickness increased. Fracture origins were located near the oxide layer–fiber interface. The Hi-Nicalon type S showed better oxidation resistance than the other polycarbosilane-derived SiC fibers after exposure in air at 1673 K for 10 h. This result was attributed to the nature of the silicon oxide layer on the surface of the SiC fibers.     

High-Temperature Microstructure of a Hot-Pressed Silicon Nitride

The outstanding question as to the microstructure of silicon nitride at temperatures associated with potential high-temperature applications of the material is addressed experimentally by quenching thin (transmission electron microscopy) samples from 1450°C and examining them in the microscope. The morphology of the microstructure is qualitatively unchanged compared to the materials slowly cooled, for example, after hot-pressing, to room temperature. The most significant difference is that the thickness of the intergranular phase is larger, typically 2 to 10 nm, as compared to the ∼ 1 nm observed in the hot-pressed material. In addition there is an apparent increase in the volume fraction of the intergranular phase at the three-grain junctions. On the basis of a number of supporting experiments including both hot-stage transmission electron microscopy (up to 1000°C) and Auger electron spectroscopy of material fractured and examined at 850°C, the change in microstructure is concluded to occur at temperatures above about 1000°C.