Effect of urea on synthesis of aluminum nitride powders from aluminum nitrate and glucose

1　ＩＮＴＲＯＤＵＣＴＩＯＮＲｅｃｅｎｔｌｙ ,ａｌｕｍｉｎｕｍｎｉｔｒｉｄｅ(ＡｌＮ)ｈａｓａｔｔｒａｃｔｅｄｍｕｃｈａｔｔｅｎｔｉｏｎｉｎａｄｖａｎｃｅｄｍａｔｅｒｉａｌｓｆｏｒｉｔｓｒｅｍａｒｋａｂｌｅｐｒｏｐｅｒ ｔｉｅｓ,ｉｎｃｌｕｄｉｎｇａｈｉｇｈｔｈｅｒｍａｌｃｏｎｄｕｃｔｉｖｉｔｙ(30 2 6 0Ｗ·ｍ- 1·Ｋ- 1ｆｏｒｐｏｌｙｃｒｙｓｔａｌｌｉｎｅｍａｔｅｒｉａｌｓａｎｄ32 0Ｗ·ｍ- 1·Ｋ- 1ｆｏｒｓｉｎｇｌｅｃｒｙｓｔａｌｓ) ,ａｈｉｇｈｅｌｅｃｔｒｉｃａｌｒｅ ｓｉｓｔｉｖｉｔｙ(>10 16Ω·ｍ)…     

缓蚀剂对高压铝箔电蚀特征的影响

利用扫描电镜分析了盐酸+硫酸混合酸电解液中添加适量缓蚀剂聚乙二醇或聚丙烯酸对高压铝箔电解腐蚀后表面形貌与横截面形貌的影响,利用LCR仪与电子天平测试了铝箔比电容与质量失重率。结果表明:缓蚀剂可以改善电解腐蚀后铝箔表面隧道孔孔径的分布,使隧道孔由圆锥状转变为圆柱状,降低隧道孔的并孔团簇现象,这有利于提高铝箔电解腐蚀扩面后的实际表面积;同时铝箔的实际质量失重率明显降低,铝箔的比电容显著增加。     

Adsorption effect of 1‐((2‐hydroxynaphtalen‐1‐yl) (phenyl)methyl)urea on the carbon steel corrosion in hydrochloric acid media

The adsorption effect of 1‐((2‐hydroxynaphtalen‐1‐yl)(phenyl)methyl)urea (HNPU) on corrosion behavior of carbon steel in 1 M hydrochloric acid solution was investigated using weight loss, potentiostatic polarization, and infrared spectroscopy methods. Surface morphology was studied by scanning electron microscopy (SEM). The experimental results, suggest that HNPU inhibited the corrosion of carbon steel in acid solution and the inhibition efficiencies increased as the concentration of the compound in the solution was increased. The calculated inhibition efficiencies from the two investigated methods were in good agreement. Potentiostatic polarization measurements indicate that HNPU acts as a mixed‐type inhibitor. The adsorption of the inhibitor on the carbon steel surface obeys Langmuir adsorption isotherm. The values of activation energy and the thermodynamic parameters, such as adsorption equilibrium constant (K_ads), adsorption free energy (ΔG_ads), adsorption heat (ΔH_ads), and adsorption entropy (ΔS_ads) values were calculated and discussed. The results obtained from infrared spectra, confirmed the adsorption of inhibitor on the alloy surface after immersion in acidic solution containing HNPU. The SEM analysis indicated that there are more lightly corroded and oxidative steel surface for the specimens after immersion in acidic solution containing HNPU than that in blank.     

A study on the effect of coating''s sorption capacity on the porosity in lost foam aluminum alloy casting

Effects of coating constituent, coating density, coating layer thickness and temperature on coating sorption capacity for polystyrene decomposition products have been studied systematically. It has been found that the effect of attapulgite clay on sorption capacity is the largest among coating constituents. The sorption capacity of the coating with 2 %attapulgite clay is elevated by 81%. The relationship between casting porosity and coating sorption capacity has been studied. It has been pointed out that higher coating sorption capacity for polystyrene decomposition products is helpful to decrease the casting porosity. Results also show that the sorption capacity of self- developed HW- 1 coating for polystyrene decomposition products is as good as that of Ashland coating from America.     

高纯超细氧化铝粉末的制备(Ⅲ) --团聚消除的研究

本文对沉淀法制备超细氧化铝粉末过程中的团聚现象进行了研究；利用表面活性剂的起泡性能使颗粒与表面活性剂及空气形成固、液、气三相混合物泡沫，从而使颗粒之间距离增大，同时采用非离子型高分子表面活性剂的稳定作用和空间位阻作用来消除粉末的团聚。通过采用表面活性剂等不同方法消除团聚的比较，发现采用表面活性剂能够有效地消除粉末的团聚并且经济、方便。     

The role that bond coat depletion of aluminum has on the lifetime of APS‐TBC under oxidizing conditions

Bond coat oxidation as well as bond coat depletion of Al are still believed to be a major degradation mechanism with respect to the lifetime of thermal barrier coating (TBC) systems. In this study the top coat lifetime is described as being limited by both bond coat depletion of Al and mechanical failure of the top coat. The empirical results are introduced by considering three spallation cases, namely, Al depletion failure, thermal fatigue failure, and thermal aging failure. Al depletion failure occurs when the Al content within the bond coat reaches a critical value. In this paper bond coat depletion of Al is modeled by considering the diffusion of Al into both the thermally grown oxide (TGO) and substrate. The diffusion model results are compared to Al concentration profiles measured with an electron beam microprobe. These measured results are from oxidized air plasma sprayed TBC systems (APS‐TBC) with vacuum plasma sprayed (VPS) bond coats for exposures up to 5000 h in the temperature range of 950–1100 °C. This paper focuses on the Al depletion failure and how it relates to top coat spallation.     

低价氯化铝分解的热力学分析

对一氯化铝分解得到液态的金属铝和气态的三氯化铝的反应进行了热力学研究,经过热力学计算得到:在常压下,该反应发生的起点温度为1683.31K,当系统压力下降时,该反应的起点温度也会下降,任何压力下,温度越低越有利于本反应的发生;经过计算得到了该反应起点温度与系统压力间的关系.也得到了不同系统压力下反应吉布斯自由能与系统温度间的关系.     

Corrosion and electrochemical behaviors of pure aluminum in novel KOH‐ionic liquid‐water solutions

The corrosion and electrochemical behaviors of pure aluminum in KOH‐ionic liquid‐water solutions with variable volume ratios of water and the ionic liquid 1‐butyl‐3‐methyl imidazolium tetrafluoroborate (BMIMBF₄) were for the first time investigated by means of hydrogen collection, polarization curve, galvanostatic discharge, and electrochemical impedance spectroscopy (EIS). The results of hydrogen collection experiments showed that aluminum has a low corrosion rate in KOH‐BMIMBF₄‐H₂O solutions, and the corrosion rate decreases with increase in BMIMBF₄ content in the electrolytes. The results of electrochemical experiments revealed that aluminum is electrochemically active over a very wide potential window in the KOH‐BMIMBF₄‐H₂O solutions, and its electrochemically kinetic mechanism is similar to that in the corresponding aqueous solution; the increase in KOH and water contents in the electrolytes may improve the anodic dissolution performance of aluminum. It was found that aluminum presents excellent galvanostatic discharge performance in the 2.0 M KOH BMIMBF₄‐H₂O mixed solution with 60% water.     

High temperature DSC study on interfacial reaction of aluminum borate whisker reinforced aluminum alloys

1lNTR0DUCTIONRecently,theceramicwhiskerreinfOrcedmetalshavebeenpaidmoreattentionbecausethesecompositesp0ssessexcellentbehaviorssuchaslowdensity,goodstrength,highspecificstiffnessandspecificmodulus,exce1lentfatigue-resistanceandwear-resistance,andthenwhisker/metalcompositesbecomeanimportantbranchofmetalmatrixcomposites.TheearlydevelopedwhiskerreinforcedmetalaremainlyexpensiveSiCandSi3N4seriescomp0sites,sothatthewideapplicationsofthiskindofcompos-itesarelimited.Atpresent,astateofartwhisker…     

Corrosion mechanism of aluminum alloy by ethylene glycol‐based solution

Corrosion and failure mechanisms on an aluminum (Al) alloy by ethylene glycol base solution have been studied. Extensive crevice corrosion damage and localized scale deposition are clearly observed between the failed Al alloy surface and the rubber hose, in which the leakage of ethylene glycol‐based solution occurred under an actual operating. In addition, many micro‐cracks are found at the rubber hose which is clamped with the Al alloy. The scales on the Al surface appear to be due to the occurrence of Al corrosion, followed by the precipitation of additives of ethylene glycol‐based solution in the crevice between Al alloy and rubber hose. The mechanisms that can account for the crevice corrosion and solution leakage on the Al alloy surface are discussed.     

Electrochemical studies on the effect of (2E)‐3‐amino‐2‐phenylazo‐but‐2‐enenitrile and its derivative on the behaviour of copper in nitric acid

The objective of this work is to provide additional insight on the influence of (2E)‐3‐amino‐2‐phenylazo‐but‐2‐enenitrile and its derivative as corrosion inhibitors for copper in 0.5 M HNO₃. Electrochemical techniques (potentiodynamic polarization, polarization resistance and impedance spectroscopy) as well as weight loss measurements have been employed to study the corrosion inhibition. The investigated compounds have shown inhibition efficiency in 0.5 M HNO₃. Inhibition efficiency of these compounds has been found to vary with the concentrations of the compounds. The adsorption of these compounds on the copper surface from the acid solution has been found to obey Langmuir adsorption isotherm. The results revealed that the compounds are mixed type inhibitors. The effect of temperature on the inhibition efficiency was studied.     

Reaction of boron to transition metal impurities and its effect on conductivity of aluminum

The effects of boron on electrical conductivity of aluminum and the action mechanism have been investigated.The results indicate that,by combining with the trace amounts of transition elements Ti,V and Zr to form two kinds of insoluble borides,boron can significantly improve the electrical conductivity of commercial aluminum.One of the borides contains 54.42% B,13.70% Al and 23.39%(mole fraction) transition elements (including Ti,V,Zr and Fe)and is in the form of fine particles,The other one,in hexagonal shape,contains 78.59% B,14.97%Al and 2.56% (mole fraction)transition elements (including Ti,V and Fe),Neither Cr nor Mn is found in these borides,The conversion of some transition metal impurities from solid solution state to the boride precipitates form leads to a decrease in electrical resistivity,and this decrease constitutes 86.2% of that can be achieved by complete removal of transition element impurities from aluminum melts.     

时效对7055铝合金淬火敏感效应的影响

通过电导率、常温力学性能测试和透射电镜研究了时效对7055铝合金淬火敏感效应的影响。结果表明:合金固溶后慢速淬火时,晶粒内部和晶界上析出大量粗大的η平衡相,基体中的溶质过饱和度及空位浓度大大降低,不利于时效时强化相的均匀弥散析出,导致合金的力学性能下降;双级时效对快速淬火合金的力学性能影响不大,但提高了慢速淬火合金的力学性能,因而一定程度减少了合金的淬火敏感效应;这是因为相对单级时效而言双级时效可使慢速淬火合金中得到更多强化相,分布也更均匀弥散,从而减小空位浓度降低带来的不利影响;在本研究中,100℃,24 h 121℃,24 h是最佳的双级时效制度。     

Nanostructured surface pre‐treatment based on self‐assembled molecules for corrosion protection of Alclad 7475‐T761 aluminum alloy

Coatings based on self‐assembled molecules (SAMs) for corrosion protection of aircraft aluminum alloys have been studied to evaluate their potentialities as replacements to yellow chromate conversion coatings (CCC), due to the toxicity of these leading to environmental problems. In this work, the influence of alkane diphosphonates self‐assembling molecules on the corrosion resistance of the AA7475‐T761 cladded with AA7072 was investigated by electrochemical impedance spectroscopy and cathodic and anodic polarization curves, in naturally aerated 0.5 mol/L Na₂SO₄ aqueous solution, with pH adjusted to 4. Corrosion accelerated experiments (salt spray tests) were also carried out to examine the resistance of the SAM treated samples against corrosion. The results suggested that the development of boehmite (aluminum oxide) layer with incorporation of SAM was beneficial to the corrosion resistance of the tested aluminum alloy. Samples surface treated with SAM or aluminum oxide/SAM (without and with subsequent polyester layer) showed better corrosion resistance results than samples with CCC, indicating that this last type of coating containing hexavalent chromium could be replaced by the environmentally friendly pre‐treatment corresponding to boehmite growth followed by incorporation of SAM.     

铝厂提高电流效率的研究

研究在各项技术条件下 ,如何提高电流效率。通过向电解槽中添加 5 %的氟化镁 ,并且在电解槽上安装盖板 ,这样可控制电解槽温度 ,从而将电解温度降低了 2 0℃。采用以上措施可以节省能量 ,试验的结果也表明电流效率提高了 2 %。