保温条件下过共晶Al-Si合金半固态浆料的组织演变

研究了保温时间和保温温度对电磁搅拌ZL117合金半固态浆料稳定性的影响.试验结果表明：半固态浆料中初生Si的颗粒直径随着保温时间的延长而逐渐增大,但在前15 min内增长速度比较缓慢,15 min后增长较快;随着保温温度的升高而缓慢增大;初生Si的形状系数随着保温时间的延长而变得越来越大,但也在前15 min内变化较为缓慢,15 min后变大速度突然加快;初生Si的形状系数在620 ℃下保温时最小,在610～620 ℃之间随着保温温度的升高而缓慢变小;在620～650 ℃之间随着保温温度的升高而逐渐增加.     

Comparative study of bis-piperidiniummethyl-urea and mono-piperidiniummethyl-urea as volatile corrosion inhibitors for mild steel

Bis-piperidiniummethyl-urea (BPMU) and mono-piperidiniummethyl-urea (MPMU) were developed as novel volatile corrosion inhibitors (VCIs). Their vapor corrosion inhibition property was evaluated by volatile inhibiting sieve test (VIS) and vapor inhibiting ability test (VIA). Volatile weight-loss test in a closed space was used to compare their volatility. Electrochemical impedance spectroscopy of a volatile corrosion inhibitor monitor (VCIM) was applied to study the effect of BPMU and MPMU on the corrosion inhibition of mild steel in thin electrolyte layer. The results show that BPMU has the better protection effect compared with MPMU. Adsorption of BPMU and MPMU on steel surface was investigated by X-ray photoelectron spectroscopy (XPS). It was shown that one BPMU molecule has two N atoms to coordinate with one Fe atom, and that one MPMU molecule has one N atom to coordinate with one Fe atom. The quantum chemical parameters were obtained by PM3 semi-empirical method. BPMU has the smaller HOMO-LUMO energy gap and the smaller net positive charge intensities of 4N and 8N atoms in its molecule.     

消失模样性能对铝合金液充型速度及间隙压力影响的数值计算

采用计算机模拟技术研究了聚苯乙烯模样汽化潜热及发气性对消失模铸造铝合金液充填速度及金属液／模样间隙压力的影响。结果表明，模样汽化潜热与发气性均严重影响铝合金液的充型速度及间隙压力。     

DMTAM光度法同时测定钯和钴

以硫脲作为掩蔽剂,在pH3.75～5.0的HAc—NaAc缓冲介质中,Pd、Co(Ⅱ)和DMTAM均能形成稳定的1∶2型配合物,其表观摩尔吸光系数分别为ε_(Pd)=6.14×10~4,ε_(Co)=6.20×10~4,遵守比尔定律的线性范围分别为Pd0～35μg/25ml,Co0～15μg/25ml。研究了30余种共存离子的影响。可应用于分子筛和矿样中Pd、Co的同时测定。     

渗铝涂层对Ni_3Al－Mo基合金高温氧化的防护作用及机理

采用高活度渗铝工艺在ＩＣ－６（Ｎｉ３Ａｌ－Ｍｏ基）合金表面获得内扩散型渗铝涂层，在氮气环境下对渗铝涂层进行扩散处理．利用光学显微镜、ＳＥＭ、ＥＰＭＡ、ＸＲＤ分析研究了涂层的成分及组织结构，测定表明，涂层中的钼以Ｍｏ３Ａｌ沉淀相的形式存在．等温氧化及循环氧化实验表明，渗铝涂层的抗高温氧化性能明显优于ＩＣ－６合金；保护性的Ａｌ２Ｏ３氧化膜阻止了钼的氧化物的形成，避免了ＩＣ－６合金在循环氧化中出现的ＮｉＭｏＯ４相的多晶型转变，显著改变了合金的抗循环氧化能力；涂层经１０００℃、３００ｈ等温氧化及１０００℃、１００ｈ循环氧化后，未出现β－ＮｉＡｌ相的分解，可认为涂层具有较强的保护作用。     

Simulations of the dielectric constant of bonding materials and field emission properties of CNT cathodes

The effect of the dielectric constant (k) of bonding materials in a screen-printed carbon nanotube (CNT) cathode on the field enhancement factor was investigated for high-efficiency CNT cathodes using the ANSYS software. The values obtained by a simulation study were compared to the experimental results obtained for screen-printed CNT cathodes. The field enhancement factor increased as the dielectric constant decreased, reaching a maximum value at a dielectric constant of 1, the value for a vacuum. The findings indicate that the larger sheet resistance of the bonding materials, after the firing process, can be attributed to the larger emission current of the CNT cathode. From these results, it was concluded that the best bonding materials for screen-printed CNT cathodes should have a low dielectric constant and a high sheet resistance. This finding can be used as criteria for selecting bonding materials for use in CNT pastes for highly efficient CNT cathodes.     

Effect of Powder Injection Location on Ceramic Coatings Properties When Using Plasma Spray

The effect of powder injecting location of the plasma spraying on spraying properties was studied. Three different powder-injecting methods were applied in the experiment. In the first method, the particles were axially injected into the plasma flow from the cathode tip. In the second method, the particles were radially injected into the plasma flow just downstream of the anode arc root inside the anode nozzle. In the third method, the particles were radially injected into the plasma jet at the nozzle exit. The alumina particles with a mean diameter of 20 μm were used to deposit coatings. Spraying properties, such as the deposition efficiency, the melting rate of the powder particles, and the coating quality were investigated. The results show that the spraying with axial particle injecting can heat and melt the powder particles more effectively, produce coatings with better quality, and have higher deposition efficiency. This article is an invited paper selected from presentations at the 2007 International Thermal Spray Conference and has been expanded from the original presentation. It is simultaneously published in Global Coating Solutions, Proceedings of the 2007 International Thermal Spray Conference, Beijing, China, May 14-16, 2007, Basil R. Marple, Margaret M. Hyland, Yuk-Chiu Lau, Chang-Jiu Li, Rogerio S. Lima, and Ghislain Montavon, Ed., ASM International, Materials Park, OH, 2007.     

A comparison between atmospheric water vapour content retrieval methods using MSG2-SEVIRI thermal-IR data

Atmospheric water vapour content (WVC) is a vital parameter in the study of climate change. Various methods have been developed to derive atmospheric WVC from remotely sensed data. In this study, we compared three methods for retrieving atmospheric WVC from thermal infrared data in the Meteosat Second Generation-SEVIRI channels 9 (10.8 μm) and 10 (12.0 ?m). The three methods are (1) the split-window covariance-variance ratio method using a spatial moving window (method 1); (2) the split-window covariance-variance ratio method using a temporal moving window (method 2); and (3) the varying surface temperature method using split-window channel data (method 3). The derived WVC using these three methods was compared to two WVC data sets from European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis data and the MODIS WVC product. Compared with these two data sets, the derived WVC using method 1 performed proved optimal. The valid pixels using methods 1 and 2 are greater than those using method 3. Furthermore, method 2 can be used to retrieve WVC over pixels where method 1 is invalid.