SiC薄膜的阻氚性能研究

在不锈钢基体表面用离子束混合技术沉积SiC薄膜,然后用能量为5 keV的H+对其辐照直至剂量达到1×1018/cm2,再用二次离子质谱分析(SIMS)分析H+在SiC薄膜中深度分布和正离子谱,研究薄膜的阻氢性能和阻氢机理;最后采用渗透实验对涂覆在不锈钢基体表面的SiC材料的氚渗透系数进行测试,对其阻氚性能进行验证.结果表明,在不锈钢基材表面涂覆的SiC薄膜具有良好的阻氢性能,可将氚的渗透率降低4个数量级以上,SiC薄膜的阻氢是由于氢与薄膜中的硅、碳悬挂键反应形成诸如C-H、C-H2、C-H3、Si-H、Si-H2和Si-H3引起的.     

离子注入对软金属材料摩擦特性的影响

本工作将银试件作N离子注入。对铝青铜或锡青铜则先真空蒸镀B、Ag、In或Sb膜后作N~+反冲注入。试件在低负载、低转速、干摩擦或高负载、高转速、油润滑条件下作摩擦试验。试验表明大部分注入试件表面的摩擦系数有明显下降。本文对离子注入降低摩擦系数的机理也进行了初步讨论。     

硅基体的金属钼反冲注入

在某基体的表面,真空蒸镀一层其它材料的薄膜,用离子轰击时将引起原子级联碰撞而导致基体原子和薄层原子的混合,特别是在界面区域的混合。所谓反冲注入是指薄层原子在此过程中进入基体的现象。目前,离子束混合已开始应用到半导体器件及金属等材料改性的领域中。     

几种不同元素与45~#钢混合的耐蚀性比较

离子束混合对金属耐蚀性影响的研究已屡见报道。该技术以其固有的特点正引起人们的重视。已有一些报道肯定了它对金属腐蚀研究的作用。 4S~#钢是一种用途广泛的碳素钢。本文用离子束混合技术将Cr、Ti、Mo和Cr+Ni等元素分别引入其基体,企图形成不同的表面新合金,以观察其对基体腐蚀性能的影响。用线性极化法评价各试样在充气的3％NaCl溶液中的腐蚀速率;在0.5mol/1 H_2SO_4和3％NaCl溶液中分别测试了各试样的阳极极化曲线,比较了它们在这两种介质中的电化学行为。     

预处理和溅射工艺参数对锆合金表面TiN涂层膜/基结合强度的影响

为获得高结合强度锆合金表面涂层的制备技术,采用磁控溅射法制备了TiN涂层、划痕法测试了膜/基结合强度,研究了基体预处理表面粗糙度、溅射功率、基体加热温度和基体偏压对锆合金表面TiN涂层膜/基结合强度的影响。实验制备的TiN涂层厚度在5～15 μm范围内、基体预处理表面粗糙度在（0.20±0.03） μm范围内时,溅射功率为500 W及基体加热至300 ℃时涂层均有较好的结合强度。基体偏压为-100 V时涂层在所讨论的4种基体偏压中具有最好的结合强度。结果表明,溅射工艺参数对涂层膜/基结合强度有显著影响,其中影响显著性从大到小依次为基体加热温度、基体偏压、溅射功率、基体预处理表面粗糙度。     

等离子与激光复合热源喷涂WC-CoCr涂层组织性能研究

用等离子束与激光束复合热源喷涂工艺(Laser Hybrid Plasma Spraying,LHPS)在38CrMoAl基体上制备WC-10Co4Cr涂层,对涂层的显微硬度、结合强度、耐滑动摩擦磨损性能进行测试,用光学显微镜、XRD、SEM等方法对涂层的显微组织、相组成、磨损后形貌等测试分析,同时研究激光功率的变化对涂层组织性能影响。结果表明,复合热源喷涂WC-10Co4Cr涂层微观组织与性能随激光功率大小而变化,当激光功率在2100-2500 W时,涂层与基体浸润性好,组织相对致密,结合强度高,摩擦系数低且抗摩擦磨损性能好,其磨损机制为塑性切削与脆性剥落,以脆性剥落为主。     

铬铸铁表面等离子喷涂Ni-Al-WC合金层及组织性能研究

研究了铬铸铁表面等离子喷涂Ni-Al-WC合金层及其组织性能.对喷涂层的化学成分、相组成、显微结构、平均显微硬度、耐磨性及耐蚀性等作了分析.结果表明:喷涂层与基体未完全实现冶金结合,其化学成分、显微组织发生了根本性转变,使表面硬度、耐磨性和耐蚀性得到较大幅度提高.     

铬铸铁表面等离子喷涂Ni-Al-WC合金层及组织性能研究

研究了铬铸铁表面等离子喷涂Ni-Al-WC合金层及其组织性能。对喷涂层的化学成分、相组成、显微结构、平均显微硬度、耐磨性及耐蚀性等作了分析。结果表明：喷涂层与基体未完全实现冶金结合，其化学成分、显微组织发生了根本性转变，使表面硬度、耐磨性和耐蚀性得到较大幅度提高。     

加热去氩处理工艺对离子束混合沉积的C-SiC涂层阻氢性能的影响

利用Ar＋离子束混合技术在不锈钢基体上沉积C-SiC涂层，然后对部分样品进行加热去氩处理（400℃，30min），再用5keV氢离子源辐照样品。通过扫描电镜（SEM）的表面形貌观察、二次离子质谱仪（SIMS）的H与Ar元素深度分布和正离子质谱分析，研究去氩处理对氢离子辐照的C-SiC涂层的形貌和阻氢性能的影响。结果表明，经去氩处理，样品中不锈钢基体内的氢浓度降低了80%，显示出去氩处理的C-SiC涂层具有更高的阻氢性能。研究结果将为该技术应用于不锈钢基体上C-SiC涂层制备工艺的进一步改善提供依据。     

银纳米团簇复合材料的辐射法制备及性能研究

银纳米团簇作为一种新兴的纳米材料，由于其极小的尺寸，表现出独特的物理化学性能，得到了广泛的关注。本文利用辐射技术设计了一种简单有效的银纳米团簇复合材料的制备方法。利用聚丙烯酸类聚合物分子链携带的羧基，通过辐射还原直接获得了银纳米团簇水溶液。基于辐射接枝技术，将聚丙烯酸模板接枝到不同基体材料上得到固体模板。利用固体模板代替水溶性模板材料，实现了银纳米团簇在固体模板上的原位合成，直接得到银纳米团簇复合材料。制备的银纳米团簇及其复合材料依旧保有银纳米团簇光致发光及催化活性，在金属离子检测和催化4-硝基酚还原加氢具有应用潜力。同时，基体材料的结构与银纳米团簇也会形成协同作用，提高银纳米团簇的使用性能。利用辐射技术简化银纳米团簇复合材料的合成路线，对于不同基体材料具有普适性，扩宽了银纳米团簇复合材料的潜在应用领域。     

强脉冲离子束辐照混合的RBS研究

采用卢瑟福背散射(Rutherford backscattering spectroscopy,RBS)方法对强脉冲离子束辐照Ti/Al、Al/Ti和Ni/Ti三组薄膜/衬底体系所形成的混合层进行了研究.在Ni/Ti组合中形成了厚度比离子射程大得多的、混合度较高的梯度混合层.发现熔融态混合的程度不仅取决于两材料在熔融态的表面张力的差别,而且取决于它们熔点的差异.这两个参量较接近的混合程度较好.     

Mechanisms in the ion beam mixing of Al in Si

Ion beam mixing of Al in Si has been studied by implanting 100 keV ⁴⁰Ar⁺ ions into 300 Å Al overlayers on Si substrates. The mixing of the collisionally similar Al and Si atoms was studied with the nuclear resonance broadening technique. It is characterized to be proportional to the square root of ion fluence. The mixing is compared with that of Al in Si due to irradiation with 40 keV ²²Ne⁺ ions studied recently by us. Mechanisms which enhance the observed atomic mixings with about 5 times that expected for ballistic mixing have been studied by Monte Carlo simulation of the collisional cascades. The results indicate the need to revise the present model of the ballistic mixing by focusing more attention to the effect of low-energy impurity—matrix atom collisions.     

Atomic mixing in thin film systems by swift heavy ions

Because of their sensitivity to the electronic energy loss of swift heavy ions, we have investigated the high energy ion beam mixing of oxide layer systems. In this paper we present a summary of the results and first steps towards interpretation and modelling of the observed phenomena. As was also observed in the case of track formation, mixing was found to occur only if the electronic energy loss exceeds a threshold value. The threshold is determined by the less sensitive material, which is a clear hint that both sides of the interface must have been molten, to enable for effective interdiffusion. This interpretation is supported by the estimated interdiffusion constants which indeed lie in the range known for liquid state diffusion.     

离子束混合对铝合金腐蚀行为影响的阳极极化研究

用离子束一次混合、二次混合和氧化处理在LY11硬铝合金基体上形成防护层。在3％NaCl溶液中采用三电极动电位扫描法测定各试样的一次阳极极化和环形极化曲线,比较其自然腐蚀电位、点蚀击穿电位、保护电位、可能点蚀区宽度以及极化电流等电化学参数。发现离子束二次混合形成的富Cr新合金层远优于一次混合或氧化处理的防护层。用RBS分析获得混层合金元素的纵向分布,证明在二次混合情况下,Cr与基体产生了良好的混合。     

Fluid mixing and flow distribution in a primary circuit of a nuclear pressurized water reactor—Validation of CFD codes

The EU project FLOMIX-R was aimed at describing the mixing phenomena relevant for both safety analysis, particularly in steam line break and boron dilution scenarios, and mixing phenomena of interest for economical operation and the structural integrity.This report will focus on the computational fluid dynamics (CFD) code validation. Best practice guidelines (BPG) were applied in all CFD work when choosing computational grid, time step, turbulence models, modelling of internal geometry, boundary conditions, numerical schemes and convergence criteria. The strategy of code validation based on the BPG and a matrix of CFD code validation calculations have been elaborated. CFD calculations have been accomplished for selected experiments with two different CFD codes (CFX, FLUENT). The matrix of benchmark cases contains slug mixing tests simulating the start-up of the first main circulation pump which have been performed with three 1:5 scaled facilities: the Rossendorf coolant mixing model ROCOM, the Vattenfall test facility and a metal mock-up of a VVER-1000 type reactor. Before studying mixing in transients, ROCOM test cases with steady-state flow conditions were considered. Considering buoyancy driven mixing, experimental results on mixing of fluids with density differences obtained at ROCOM and the FORTUM PTS test facility were compared with calculations. Methods for a quantitative comparison between the calculated and measured mixing scalar distributions have been elaborated and applied. Based on the “best practice CFD solutions”, conclusions on the applicability of CFD for turbulent mixing problems in PWR were drawn and recommendations on CFD modelling were given. The results of the CFD calculations are mostly in-between the uncertainty bands of the experiments. Although no fully grid-independent numerical solutions could be obtained, it can be concluded about the suitability of applying CFD methods in engineering applications for turbulent mixing in nuclear reactors.     

包覆工艺对微球形燃料相弥散燃料混合均匀性的影响

针对微球形燃料相颗粒与基体粉末的流动性相差较大、难于混合均匀,建立了一种微球的包覆工艺,并研究了包覆工艺对混合均匀性的影响。采用直径约为100μm的不锈钢微球代替燃料微球,研究结果表明,在微球表面物理包覆一层基体粉末,可增加颗粒表面粗糙度,降低两组元粉末的密度差及颗粒沉降的距离,包覆层还能使颗粒间保持一定的间距,微观上形成连续的基体网络,减少甚至避免发生偏聚,有效地改善了混合均匀性。包覆工艺的最佳参数为:保温温度,76℃;保温时间,6min;黏结剂添加量,1%;粉末粒径,小于25μm。该方法可用于改善(U-Mo)-Al、(U-Mo)-Zr等微球形燃料相弥散燃料的混合均匀性。     

Numerical investigations of thermal mixing performance of a hot gas mixing structure in high-temperature gas-cooled reactor

A numerical simulation study was performed to clarify the thermal mixing characteristics of coolant in the core bottom structure of the high-temperature gas-cooled reactor(HTR). The flow field and temperature field in the hot gas chamber and the hot gas duct of the HTR were obtained based on the commercial computational fluid dynamics(CFD) program. The numerical simulation results showed that the helium flow with different temperatures in the hot gas mixing chamber and the hot gas duct mixed intensively, and the mixing rate of the temperature in the outlet of the hot gas duct reached 98 %. The results indicated many large-scale swirling flow structures and strong turbulence in the hot gas mixing chamber and the entrance of the hot gas duct, which were responsible for the excellent thermal mixing of the hot gas chamber and the hot gas duct. The calculated results showed that the temperature mixing rate of the hot gas chamber decreased only marginally with increasing Reynolds number.     

Ion beam mixing of titanium films on stainless steel

The ion mixing of Ti-steel bilayers with N⁺, Ar⁺, Ti⁺, Kr⁺ and Xe⁺ ions was investigated by means of Rutherford backscattering spectroscopy (RBS). The mixing rates exhibit a linear scaling with the deposited damage energy f_D. No correlation between the properties of the mixing ion and the mixing efficiency was found. The results are compared with the predictions of ballistic and thermal-spike models.     

Simulating the mixing of helium and air by mixing salt water and fresh water in a scaled enclosure

We are attempting to establish scaling laws to simulate the mixing of helium (a simulant for hydrogen) with air in a large-scale enclosure by mixing salt water and fresh water, in a small-scale enclosure. This will allow us to assess the mixing of gases in a nuclear reactor containment using relatively small-scale liquid-mixing experiments. The scope of our current work does not cover the integrated effects of different mechanisms of gas mixing expected to prevail during postulated LOCA (loss-of-coolant accident) scenarios. The work is limited to mixing caused by jet inertia and buoyancy forces. Within this scope, we have identified the dominant scaling laws, and tested them by conducting gas-mixing experiments in a large-scale enclosure and liquid-mixing experiments in a small-scale enclosure. The experimental results demonstrate the validity of the scaling laws.     

Thermal mixing characteristics of helium gas in high-temperature gas-cooled reactor, (I) thermal mixing behavior of helium gas in HTTR

The future high-temperature gas-cooled reactor (HTGR) is now designed in Japan Atomic Energy Agency. The reactor has many merging points of helium gas with different temperatures. It is needed to clear the thermal mixing characteristics of helium gas at the pipe in the HTGR from the viewpoint of structure integrity and temperature control. Previously, the reactor inlet coolant temperature was controlled lower than specific one in the high-temperature engineering test reactor (HTTR) due to lack of mixing of helium gas in the primary cooling system. Now, the control system is improved to use the calculated bulk temperature of reactor inlet helium gas. In this paper, thermal–hydraulic analysis on the primary cooling system of the HTTR was conducted to clarify the thermal mixing behavior of helium gas. As a result, it was confirmed that the thermal mixing behavior is mainly affected by the aspect ratio of annular flow path, and it is needed to consider the mixing characteristics of helium gas at the piping design of the HTGR.