Role of Double Oxide Film Defects in the Formal ion ol’ Gas Porosity in Commercial Purity and Sr-containing A1 Alloys

The role of double oxide film （bifilm） defects in the formation of gas porosity in commercial purity and Srcontaining AI alloys was investigated by means of a reduced pressure test （RPT） technique. The liquid metal was poured from a height into a crucible to introduce oxide defects into the melt. The melt was then subjected to different ＂hydrogen addition＂ and ＂holding in liquid state＂ regimes before RPT samples were taken. The RPT samples were then characterized by determining their porosity parameters and examining the internal surfaces of the pores formed in them by scanning electron microscopy. The results indicated oxide defects as the initiation sites for the growth of gas porosity, both in commercial purity and Sr-containing AI alloys. The results also rejected reduction of the surface tension of the melt, increase in the volumetric shrinkage and reduction in interdendritic feeding as the possible causes of an increase in the porosity content of the AI castings modified with strontium. The change in the composition of the oxide layers of double oxide film defects was suggested to be responsible for this behaviour.     

Effect of vibration on behaviour of bifilms in A356 and A357 melts

The effect of applying vibration to a melt on the behaviour of bifilm defects in A356 and A357 melts was studied using a reduced pressure test technique. The results showed that vibrating a melt can have a dual effect on bifilms. This effect depends on the rate of phase transformations that occur in the oxide films. If the transformation occurs fast enough then the vibration would facilitate the formation of bonding between the layers of bifilm defects by causing the atmosphere of the defects to be consumed faster. Otherwise, the vibration might facilitate the diffusion of hydrogen into the atmosphere of the defects, and hence prevent or delay the formation of bonding between the oxide layers.     

制备条件对电致变色氧化镍薄膜特性的影响

在充氧气的真空室内 ,用电子束蒸发NiO粉末颗粒的方法分别以 0 1和 0 8nm/s的淀积速率制备了氧化镍薄膜 ,并在不同的环境中对薄膜进行热处理。研究了薄膜结构和电致变色特性与淀积速率的关系 ,发现以较慢和较快速率淀积的薄膜分别具有NiO晶粒的 (2 0 0 )和 (111)不同择优取向 ,前者致色范围较小 ,后者致色范围较大。还研究了热处理对薄膜的结构、动态致色范围、致色效率 ,以及红外光谱特性的影响 ,发现热处理对薄膜的致色效率影响较小 ,然而对动态致色范围的影响很大。     

电致变色氧化镍薄膜的注入离子及离子注入位置研究

用红外透射率分析方法研究了氧化镍薄膜在原始、致色和消化的红外透射率光谱,用Ｘ－射线衍射方法测量了在ＫＯＨ和ＬｉＣｌＯ４－ＰＣ电解液中致色和消色时,氧化镍多晶薄膜在（１１１）和（２００）方向衍射峰位的移动,分析了注入离子种类和离子注入位置,认为在ＫＯＨ电解液中致色时,注入离子为ＯＨ,离子的注入位置在晶普的间界。在ＬｉＣｌＯ４－ＰＣ电解液中,Ｌｉ＾＋离子的注入位置同样在晶粒的间界。     

Role of porosity defects in metal 3D printing: Formation mechanisms,impacts on properties and mitigation strategies

Metal 3D printing (3DP), a state-of-the-art manufacturing technology that brings the potential to fabricate complex structures at low cost and reduced energy consumption, has been extensively adopted in various industries. However, the porosity defects inherited from the printing process can significantly impede the mechanical properties and weaken the performance of as-printed components, potentially challenging this approach's reliability and reproducibility. The advancement of detection techniques currently opens up a more intuitive and deeper study of porosity defects. Given that, this review systematically states the 'restriction role' of porosity defects in metal 3DP by generalizing the detailed information on porosity defects, including their characterizations, formation and migration mechanisms, and their impacts on the performance of printed parts. Furthermore, feasible porosity mitigation measures are discussed to inspire more advanced methodologies for the next generation of metal 3DP.     

钛膜表面氧气氧化层研究

研究了钼基钛膜表面氧气氧化工艺;用XRD分析了氧气氢化层的物相,其物相随氧化条件而异,含有Ti、TiO2、TiO、Ti2O、Ti3O和Ti6O等多种物相;用XPS研究了氧气氧化层钛的主要价态,其主要价态为 4、 3和 2价;用AES深度剖析研究了氧气氧化层的厚度,并研究了温度、氧气压力和时间对氧气氧化层厚度影响的规律;所有氧气氧化层均不与腐蚀介质发生作用,证明了该氧化层致密连续.     

高频氧等离子体制备氧化铝膜的微结构与光学常数

将真空蒸发沉积的Al膜 ,在一台高频等离子体辉光放电的装置中进行阳极氧化 ,得到了光学和电学性能稳定的Al2 O3 膜。Al膜表面氧化层结构是γ Al2 O3 ,在波长 30 0～ 70 0nm范围内折射率为 1 5 3～ 1 34。文章还对用不同方法制备的Al2 O3 膜的折射率的差异进行了讨论     

钛酸锶钡薄膜中微观结构缺陷及其形成机理

采用脉冲激光沉积方法,在(001)单晶铝酸镧(LaAlO3)衬底上成功制备出钛酸锶钡(Ba0.75Sr0.25TiO3)外延薄膜.利用高分辨电子显微学对其微观结构进行了详细研究,并探讨了其微观结构缺陷的形成机理.研究发现,在钛酸锶钡外延薄膜中存在失配位错和穿透位错,且存在直线型和锯齿型的两种反相畴界.失配位错是由于钛酸锶钡薄膜与LaAlO3单晶衬底之间存在较大的晶格失配形成的,可分解为不全位错;穿透位错可以分解为不全位错伴随有堆垛层错的形成.反相畴界的形成是由于衬底表面存在台阶,直线型反向畴界是由于形核点离台阶处较近产生的,而锯齿型反向畴界是由于形核点离台阶处较远而形成.研究结果可为其它钙钛矿型外延薄膜中微观结构缺陷的形成机理提供理论指导.     

Oxidation Kinetics of (111) Silicon Monocrystal and Morphology of Oxide Film in Dry Oxygen Atmosphere

1. Introduction Thermal oxidation of silicon monocrystalis a very important process in fabricationof metal--oxide--semiconductor (MOS) devices.In recent years it has received great atten-tion. Various proposals for oxidation modeshave been made by different groups.Now most of the authors working in thisfield hold the view that the oxidation rateof silicon obeys a typical parabolic rule,that is, the oxidation reaction is controlledby diffusion. The experimental data inRef. can be taken and a kinetic curve     

溅射气压对HfO_2薄膜结构和光学性能的影响

HfO2薄膜的结构和光学性能与反应溅射时使用的气压有很强的依赖关系。薄膜的晶粒生长取向、生长速率和折射率明显受溅射气压的影响。所有的薄膜均为单斜相,晶粒尺寸在纳米量级。薄膜的折射率在1.92～2.08范围内变化,透过率大于85%。结果表明,这些HfO2薄膜很适宜用作增透膜或者高反膜。此外,通过Tauc公式推出光学带隙在5.150～5.433eV范围内变化,表明样品是良好的绝缘体。     

氢镍电池材料用氧化锆布膜中铁的测试研究

运用N2O-C2H2火焰原子吸收光谱法进行氢镍电池材料用氧化锆布膜中铁的测试研究。介绍了铁的最佳测试条件,对样品的消化处理,以及在测试过程中对样品干扰因素进行了分析。测定样品中铁含量相对标准偏差均小于1.0%(测定次数n=6),加标回收率均在97.0%～98.3%(n=6)范围。该方法具有简便、快速、灵敏度高、重现性好等特点,准确度与精密度均能满足氢镍电池研制工作的要求。     

The Spectral Emissivity of an Oxide Film of Zirconium for Wavelengths of 530 and 650 nm in the Temperature Range from 1450 to 1750 K

The pyrometer method is used to investigate the spectral emissivity of an oxide film of zirconium of a nonstoichiometric composition in the temperature range from 1450 to 1750 K for wavelengths of 530 and 650 nm. The obtained data are used to calculate the color temperature. The results relate to a tetragonal structure of zirconium oxide in the range from 1450 to 1730 K and to a mixture of tetragonal and cubic structures at 1745 K. The sample to be investigated is heated in a high-frequency field of a multiturn cylindrical inductor in an air/argon mixture in a hermetically sealed volume with a volume content of air of 6.2%. The oxide film thickness, estimated by the increment of the sample mass, ranges from 124 to 613 mcm. The estimated error of measurement of the coefficients of spectral emissivity is 10%.     

Thermal Processes During Mechanical Treatment of ZnO and ZnO-TiO2 Powders and their Role in the Formation of Defect Structure

We used electron paramagnetic resonance (EPR) to determine the dependence of the defect structure of zinc oxide powders on the physical characteristics of admixed particles during prolonged mechanical treatment (MT). Our results demonstrate a sequential two-stage thermal process contributing to the defect structure during MT. In the first stage of MT a collective break-up process of individual ZnO particles occurs and the defects are caused by hyper-rapid thermal defects annealing (HRTDA) of the particles. The second stage of defect formation is associated with annealing effects caused by heat accumulation.     

Characterization,Removal and Evaluation of Oxide Film in the Diffusion Bonding of Zr55Cu30Ni5Al10 Bulk Metallic Glass

The composition of oxide film of ZrssCu3oNi5Al10 bulk metallic glass was identified by X-ray photoelectron spectroscopy. In addition, the relatively sound joints of bulk metallic glass without macroscopic deformation were obtained by removing the oxide film before diffusion bonding. The joint interfaces were observed by scanning electron microscopy and atomic force microscopy. The hardness of joints near the interface was higher than that far away from the interface, which is attributed to the difference of structural relaxation. According to the result of micro-focused X-ray diffractometry and transmission electron microscopy, the joints retained the amorphous structure when the holding time is less than 20 min. The surface area fraction of oxide film on the interface of joints was detected by ultrasonic inspection. Moreover, the surface area fraction of oxide film is in excellent agreement with the theoretical value calculated by shear strength. The result indicated that surface oxide film is the dominant barrier on the diffusion bonding of bulk metallic glass rather than low atomic diffusion coefficient.