脉冲宽度对激光熔覆FeSiB涂层组织与硬度的影响

以FeSiB非晶带材为熔覆材料,采用激光熔覆在低碳钢表面制备高致密度涂层,利用光学显微镜(OM)、X射线衍射仪(XRD)、扫描电子显微镜(SEM)、显微硬度仪等研究不同脉冲宽度对激光熔覆涂层成形、组织特征及硬度的影响。结果表明:随脉冲宽度增大,涂层稀释率升高;裂纹倾向增加,裂纹源萌生由表面到界面处;晶化程度升高,结晶相为α-Fe,Fe_2B和Fe_3Si;熔合区宽度增大,柱状晶沿外延生长趋势更大;显微硬度先增加后减小。当脉冲宽度为3.2ms时,涂层结构致密,无孔洞缺陷,界面呈良好的冶金结合,稀释率低,为23.2%,涂层平均显微硬度达1192HV,约为基材的10倍。     

激光熔覆镍包石墨和石墨烯复合涂层组织和性能分析

采用激光熔覆技术在40CrNi2Si2MoV钢基体表面分别制备镍包石墨和石墨烯复合涂层,测试分析了涂层的物相、微观组织、显微硬度以及摩擦磨损性能。结果表明:激光熔覆涂层主要由γ-Ni、Ni_3B、M_(23)C_6和M_7C_3相组成,均为树枝晶和共晶组织;从熔覆层表面到基体的显微硬度呈现出四个台阶,硬度最高值出现在亚表层;两种涂层均具有较好的减摩性能和耐磨性能。     

TC4钛合金表面激光熔覆NiCrCoAlY-Cr3C2复合涂层的摩擦和高温抗氧化性能

为了提高TC4 钛合金表面摩擦磨损和高温抗氧化性能,以 NiCrCoAlY+20%(质量分数)Cr3 C2 混合粉末作为熔覆粉末,采用激光熔覆技术在TC4 钛合金表面制备NiCrCoAlY-Cr3 C2 复合涂层,利用OM,SEM,XRD,EDS等分析涂层的显微组织和物相组成;采用 HXD-1 000TB 显微硬度计测量涂层显微硬度;采用 MMG-500 三体磨损试验机与 WS-G1 50 智能马弗炉对涂层和基体进行摩擦磨损及高温抗氧化实验.结果表明:利用激光熔覆技术在 TC4 钛合金表面可以制备形貌良好、无裂纹和气孔等缺陷的复合涂层.熔覆区显微组织结构致密,多为针状晶和树枝晶;结合区的显微组织主要由平面晶、胞状晶和树枝晶组成,生成了多种可提高耐磨性和高温抗氧化性的碳化物、氧化物和金属间化合物.复合涂层的最高显微硬度为 1344HV,约为钛合金基体 350HV的 3.8 倍;复合涂层的摩擦因数为0.2～0.3,较钛合金基体的摩擦因数0.6～0.7 明显下降;相同条件下复合涂层的磨损失重为0.00060 g,是钛合金基体磨损失重 0.06508 g 的0.9%;恒温 850 ℃氧化 100 h后复合涂层氧化增重为 6.01 mg·cm－2 ,约为钛合金基体氧化增重 25.10 mg·cm－2的24%.激光熔覆技术有效改善了TC4 钛合金表面的摩擦磨损和高温抗氧化性能.     

稀土含量对活性激光熔覆Fe-Cr-W-Ni-C涂层的组织和磨损性能的影响

采用活性激光熔覆技术,在45钢基体上制备添加质量分数为0.1%～0.4%稀土CeO2的Fe-Cr-W-Ni-C涂层,并研究其物相组成、显微组织、显微硬度、耐磨性能。结果表明:所得高熵合金涂层表面无气孔、裂纹等缺陷,高铝粉煤灰活性剂的加入增大了基体对涂层的稀释作用,使涂层与基体呈良好的冶金结合,高铝粉煤灰可有效增大熔池深宽比,有利于涂层更好地成形;合金涂层主要由α-Fe、γ-Fe组织以及碳化物构成。当RE添加质量分数为0.1%时晶粒细小而弥散,明显起到细晶强化的作用,提高了涂层的硬度和耐磨粒磨损性能,涂层硬度最高可达759 HV,磨损率最低为9.0%。     

镍基熔覆涂层受冲击载荷作用下的性能研究

45钢及1Cr18Ni9Ti表面激光熔覆WFCL-11涂层，研究了激光熔覆涂层与基体界面及表面显微组织和硬度特点，分析在冲击载荷作用下，显微组织、结合性能、硬度变化等特点。发现了不同基材与熔覆材料对结合面性能的影响。     

激光熔覆Fe60Nb20Ti20非晶合金粉末及组织性能研究

采用激光熔覆工艺在45钢表面对Fe60Nb20Ti20非晶合金粉末进行不同工艺参数熔覆试验,获得无裂纹且呈冶金结合的涂层。利用扫描电镜、X射线衍射仪、显微硬度计、摩擦磨损试验机对涂层的微观形貌、组成相、显微硬度和摩擦磨损性能进行分析。结果表明,涂层组织为细小的α-Fe过饱和固溶体等轴晶和少量的非晶相。涂层平均硬度为857HV,为基体材料的4倍,耐磨性也明显优于基体材料。     

激光熔覆法制备Al2O3-TiO2涂层的显微组织与性能研究

采用预置粉末式激光熔覆法在钛合金(Ti-6Al-4V)表面开展了Al_2O_3-13%(质量分数)TiO_2涂层的研究。利用光学显微镜(OM)、扫描电子显微镜(SEM)、X射线衍射分析仪(XRD)和显微硬度计研究了激光熔覆熔池的特征和涂层的显微结构,分析了涂层的成分分布、相组成和显微硬度分布情况。预置粉末激光熔覆制备的Al_2O_3-13%(质量分数)TiO_2涂层界面结合良好,涂层组织均匀,没有明显的裂纹和气孔。激光熔覆涂层表现出明显流线型特征,熔覆层截面分为热影响区、扩散结合区和涂层区。涂层由Ti、AlTi_3、α-Al_2O_3和γ-Al_2O_3等相组成。涂层的显微硬度达到1000~1300HV_(0.3),比基体硬度360~390HV_(0.3)高2倍。     

等离子熔覆Ni—Cr合金涂层的组织与性能研究

采用等离子熔覆技术在40Cr钢基材表面熔覆Ni-Cr合金涂层,研究了熔覆层的组织特征、成分和显微硬度分布特点.结果表明:等离子熔覆层与基体的结合面是由等轴晶构成的,熔覆层与基体呈现良好的冶金结合状态;熔覆层中部分布着沿逆热流方向生长的排列较规则的枝晶组织;熔覆层表层是细小的枝晶组织.能谱分析表明在结合面处Ni,Cr含量发生显著变化,等离子熔覆可以实现低稀释率.熔覆层的显微硬度呈梯度过渡到基体,熔覆层外层硬度值最高,在结合面附近硬度出现显著的变化.     

Q345R表面钛涂层的激光熔覆制备及显微组织研究

本文以采用铜为过渡层、表面激光熔覆钛涂层的Q345R钢板为研究对象,研究了各层凝固组织、结合界面显微组织、元素扩散行为及显微硬度,阐明了两个结合界面处显微组织及元素扩散行为的差异。研究发现,钛层组织为均匀分布的单一柱状树枝晶,与前一条熔覆轨迹交界处为不具备明显方向性的树枝晶,近界面处形成细小而紧密的等轴树枝晶。铜层中部区域的显微组织为典型柱状树枝晶,在铜/钢结合界面铜侧,显微组织表现为垂直于界面的细小树枝晶向细小等轴树枝晶的过渡,细小等轴树枝晶垂直方向的厚度约为20μm。由于激光熔覆过程中强烈的热量影响,钢层存在明显的热影响区,该区域组织发生了重结晶或不完全重结晶,组织由粒状贝氏体、细小的铁素体和珠光体组成。远离界面处组织为典型的铁素体和珠光体组织,呈现带状分布。钛/铜结合界面存在熔合区,并存在显著的元素扩散行为,而铜/钢结合界面不存在熔合区,Cu、Fe元素在铜/钢结合界面处的含量急剧变化,扩散距离约为1～2μm。显微硬度方面,结合界面的硬度实现了两侧材料硬度的过渡,有效避免了界面微裂纹的产生。     

钛合金表面激光熔覆Ni基梯度涂层的研究

为了改善Ti6Al4V钛合金表面耐磨性能和抗高温氧化性能,采用CO2激光在Ti6Al4V钛合金表面进行激光熔覆Ni基梯度涂层试验.利用扫描电镜和显微硬度计等手段分析了熔覆层组织,测试了基体和熔覆层的显微硬度.结果表明,采用适当的工艺参数,可以在钛合金表面获得连续、均匀、无裂纹和气孔的熔覆层.熔覆层组织由树枝晶和晶间共晶组织构成,并与基体形成牢固的冶金结合.由基体到表面,显微硬度过渡平稳,呈明显梯度渐变特征.     

Porous silicon and aluminum co-gettering experiment in p-type multicrystalline silicon substrate

The lifetimes of non-equilibrium minority carriers, which bound with the diffusion length, are considered as two important parameters of the low-quality multicrystalline silicon (mc-Si) substrate. Its value defines the quality of the initial substrate. It is also subjected to change as a result of many high-temperature operations during the device fabrication. Therefore, it is necessary to incorporate certain processing steps that either improve or preserve the electronic quality of the mc-Si substrate. In this study, a novel porous silicon and aluminum co-gettering experiment has been applied as a beneficial approach to improve the electronic quality of the low-resistivity mc-Si substrates. Porous silicon layers were prepared by anodization of the n⁺ silicon region by a simple electrochemical etching process using an aqueous HF-based electrolyte, which leads to the creation of porous silicon microcavities. Besides making porous silicon and aluminum co-gettered samples, both phosphorous and aluminum alloy-gettered samples and reference samples were made. The gettering-induced lifetime enhancement in the test samples was monitored by measuring the lifetime/diffusion length of the test samples using two independent methods such as photoconductivity decay (PCD) measurement and the photocurrent generation method (PCM), respectively. The result in both the measurements has shown a reasonably good agreement with each other. Therefore, it is inferred that the applied co-gettering experiment has a synergetic effect to improve the lifetime of the mc-Si substrate.     

Porous silicon and aluminum co-gettering experiment in p-type multicrystalline silicon substrate

The lifetimes of non-equilibrium minority carriers, which bound with the diffusion length, are considered as two important parameters of the low-quality multicrystalline silicon (mc-Si) substrate. Its value defines the quality of the initial substrate. It is also subjected to change as a result of many high-temperature operations during the device fabrication. Therefore, it is necessary to incorporate certain processing steps that either improve or preserve the electronic quality of the mc-Si substrate. In this study, a novel porous silicon and aluminum co-gettering experiment has been applied as a beneficial approach to improve the electronic quality of the low-resistivity mc-Si substrates. Porous silicon layers were prepared by anodization of the n⁺ silicon region by a simple electrochemical etching process using an aqueous HF-based electrolyte, which leads to the creation of porous silicon microcavities. Besides making porous silicon and aluminum co-gettered samples, both phosphorous and aluminum alloy-gettered samples and reference samples were made. The gettering-induced lifetime enhancement in the test samples was monitored by measuring the lifetime/diffusion length of the test samples using two independent methods such as photoconductivity decay (PCD) measurement and the photocurrent generation method (PCM), respectively. The result in both the measurements has shown a reasonably good agreement with each other. Therefore, it is inferred that the applied co-gettering experiment has a synergetic effect to improve the lifetime of the mc-Si substrate.     

Indentation fatigue in silicon nitride, alumina and silicon carbide ceramics

Repeated indentation fatigue (RIF) experiments conducted on the same spot of different structural ceramics viz. a hot pressed silicon nitride (HPSN), sintered alumina of two different grain sizes viz. 1 μm and 25 μm, and a sintered silicon carbide (SSiC) are reported. The RIF experiments were conducted using a Vicker’s microhardness tester at various loads in the range 1–20 N. Subsequently, the gradual evolution of the damage was characterized using an optical microscope in conjunction with the image analysing technique. The materials were classified in the order of the decreasing resistance against repeated indentation fatigue at the highest applied load of 20 N. It was further shown that there was a strong influence of grain size on the development of resistance against repeated indentation fatigue on the same spot. Finally, the poor performance of the sintered silicon carbide was found out to be linked to its previous thermal history.     

多孔硅对单晶硅少子寿命影响状况的研究

以p型单晶硅片为研究对象,在单晶硅片表面采用化学腐蚀方法制备多孔硅层,通过实验选取制备多孔硅的最佳工艺条件,采用SEM观察多孔硅表面形貌,以及用微波光电导法测试少子寿命的变化情况。结果表明,在相同的腐蚀溶液配比条件下腐蚀11min得到的多孔硅层的表面形貌最好,孔隙率最大。在850℃下热处理150min时样品少子寿命的提高达到最大,不同腐蚀时间的样品少子寿命提高程度不同,腐蚀11min的样品少子寿命提高最大,约有10%左右。多孔层的形成伴随着弹性机械应力的出现,引起多孔层-硅基底界面处产生弹性变形,这有利于缺陷和金属杂质在界面处富集。另外,多孔硅仍具有晶体结构,但其表面方向上的晶格参数要比初始硅的晶格参数大,也有利于金属杂质向多孔层迁移。     

Laser annealing of silicon

In recent years laser processing has attracted much attention in view of its potential use in basic solid-state and material science research as well as in new processing technologies. The dominant feature of laser processing being the deposition of large amounts of energy (a few J/cm²) over very short time scales (a few tens of nanoseconds), it leads to melting of surface layers of solid followed by rapid resolidification. In this article, a few basic consequences of such laser-induced phenomena in silicon are reviewed.     

超高真空电子束蒸发在多孔硅上外延单晶硅

采用超高越空电子束蒸发的方法在用阳极氧化制备的多孔硅衬底上外延单晶硅,研究了不同多孔硅衬底对外延质量的影响。采用高能电子衍射表征外延层的晶体结构,截面透射电镜上材料的微结构,原子力镜表征外延层表面的粗糙度,卢瑟福背散射／沟道表征外延层晶体质量,扩展电阻表征材料的电学性能。一系列的测试结果表明对在5mA／cm^2电流密度下阳极氧化10min形成的多孔硅衬底,可用超高真空电子束蒸发的方法外延出质量良好的单晶硅。     

Light-emitting porous silicon

Although porous silicon has been known for more than 35 years, only in 1990 was it recognized that porous silicon shows an increased bandgap and efficient room-temperature photoluminescence in the visible. This paper will give an overview of porous silicon research, with special emphasis on the formation mechanism of microporous silicon in terms of a depletion of holes in the porous region due to quantum confinement and the understanding of the origin of the visible luminescence. The status of research on electroluminescent and other devices based on porous silicon will be discussed, as well as results for other luminescent forms of nanocrystalline silicon.     

熔析结晶法提纯硅工艺研究进展

随着光伏产业的快速发展,对太阳能级硅原材料的需求不断增加。熔析结晶法作为一种冶金硅提纯的新工艺越来越受到重视。熔析结晶法是利用冶金硅中杂质元素的偏析行为,选择适当的熔析介质,使杂质元素从冶金硅中偏析到熔析介质中,进而获得高纯硅的方法。详细介绍了Al-Si、Sn-Si、Cu-Si、Fe-Si和Ca-Si等熔析体系对冶金硅提纯的研究现状,比较了各种介质体系的优缺点。同时针对熔析结晶法提纯硅存在的问题提出了一些建议。     

高阻硅掩膜选择性生长多孔硅阵列

介绍一种在低阻P型硅衬底上用氢离子注入技术形成局部高阻硅掩膜,用电化学腐蚀选择性生长多孔硅微阵列的工艺流程。结果证明,用高阻硅掩膜选择性生长多孔硅具有很好的掩蔽效果,生成的多孔硅阵列的有序性和完整性良好。     

纳米微粒母料--有机硅/无机硅纳米复合物

在纳米微粒制备过程中,把纳米微粒分散在基体中,形成纳米微粒母料,既防止了纳米材料可能对环境造成的污染,又解决了纳米材料应用时的团聚问题,为收集、保存和运输纳米颗粒提供了一条安全、行之有效的途径.