Sintering mechanism of Cu-9Al alloy prepared from elemental powders

The sintering behavior of Cu-9Al alloys prepared from die pressing of elemental powders was investigated. The experimental results and kinetic analysis showed the formation of three consecutive layers of Al₂Cu, Al₄Cu₉, and AlCu phases, with Al₂Cu appearing first in the initial solid phase sintering stage. A liquid phase formed in the intermediate stage, resulting from the eutectic reaction between Al and Al₂Cu phases at 500 °C, which is 47 °C lower than the equilibrium reaction temperature. Swelling occurred when the liquid phase infiltrated the gaps between the copper particles, leaving pores at the original sites of Al particles and Al₂Cu. In the final stage of sintering, the Al-rich phases (Al₂Cu and AlCu) transformed to Al-poor phases (Al₄Cu₉ and α-Cu) in the temperature range of 500–565 °C. Al₄Cu₉ and α-Cu then transformed to AlCu₃ (β) above the eutectoid reaction temperature (565 °C), whereas AlCu₃ transformed to α-Cu and eutectoid phases (α-Cu + Al₄Cu₉) during cooling. The pure copper transformed to AlCu₃, and the pore volume decreased at 1000 °C. The microstructure study helps manipulate precisely the sintering process of Cu-Al alloys and optimize the microstructure with a high dimensional accuracy.     

液氩探测器的低温PMT性能测试

中国暗物质实验(China dark matter experiment,CDEX)拟使用液氩探测器作为高纯锗探测器的反符合探测器,其使用的光电倍增管(photomultiplier tube,PMT)需能长期稳定地工作在液氩温度(87.3 K)下.PMT在使用前,须掌握其在低温下的性能情况.文章分别在室温和低温环境中测试了ETL 9357FLA型光电倍增管,获得了单光电子响应、暗计数率以及低温环境中运行的稳定性等重要实验结果.通过详细地对比和分析室温和低温环境中PMT的性能表现,确认该型PMT能在低温环境中正常运行.     

从定标粒子理论看溶剂分子参量对液相反应速率的影响

本文在已有工作的基础上,以定标粒子理论为理论基础,以乙酸乙酯在(水 乙醇)和(水 二甲亚砜)两种不同溶剂中的皂化反应为研究对象,对溶剂分子的各种参量对该反应的自由能变的贡献进行了理论计算,并对各参量的影响程度进行了讨论。总的结论与实验结果的一致性较好。     

Enzymatic reduction of fatty acids and acyl-CoAs to long chain aldehydes and alcohols

Summary The properties of enzymatic systems involved in the synthesis of long chain aldehydes and alcohols have been reviewed. Fatty acid and acyl-CoA reductases are widely distributed and generate fatty alcohols for ether lipid and was ester synthesis as well as fatty aldehydes for bacterial bioluminescence. Fatty alcohol is generally the major product of fatty acid reduction in crude or membrane systems, although reductases which release fatty aldehydes as products have also been purified. The reduction of fatty acid proceeds through the ATP-dependent formation of acyl intermediates such as acyl-CoA and acyl protein, followed by reduction to aldehyde and alcohol with NAD(P)H. In most cases, both the rate of fatty acid conversion and acyl chain specificity of the reaction are determined at the level of reduction of the intermediate. The reduction of fatty acids represents the major pathway for the control of the synthesis of fatty aldehydes and alcohols. Several other enzymatic reactions involved in lipid degradation also release fatty aldehydes but do not apear to play an important role in long chain alcohol synthesis.     

微机在变水头流量标准装置中的应用

本文讨论了应用在变水头流量标准装置中的Z-80计算机系统,详述了其硬件设计和软件设计。实践证明,用带有微机的变水头流量标准装置校验电磁流量计所得结果与通常的恒水头流量标准装置一致,说明变水头流量标准装置及微机系统是可行的。     

乳状液膜处理含酚废水的研究

本文报道了在实验室条件下影响液膜法除酚的主要因素及应用液膜处理含酚3000ppm的废水可使废水含酚量降至4ppm以下,除酚率达99.9％。实验结果表明,丁二酰亚胺是一种优良的液膜表面活性剂。     

液晶高聚物PBT

本文综述了液晶聚合物聚对苯撑苯并二噻唑PBT的合成、结构、性能及其应用.其中包含了作者的研究.     

液膜法从川黄连中提取黄连素的研究

本文研究液膜法从川黄连中提取黄连素盐酸盐的实验条件。结果认定,母液pH值为10,膜内盐酸浓度为0.3mol/L,Span-80用量为2%,油内比为2:5,乳水比为1;4时为最佳实验条件。并将实验结果与传统方法进行了对比,证明液膜法具有许多优点,值得采用。     

4′－烷氧基－4－羟基联苯的合成及其液晶行为

报道一系列４′－烷氧基－４－羟基联苯化合物的合成，并对合成方法及影响反应产率的因素进行探讨。通过热台偏光显微镜及差示扫描量热法（ＤＳＣ）对产物进行液晶性质的表征，对所得数据进行了讨论。     

新增稠剂的增稠性能比较

本文测定了我国目前出现的一些新型增稠剂在以ＡＥＳ为主的液体洗涤剂中的增稠性能。对两种氧化脓和尼纳尔的增调性能进行了比较，测定了三类高分子增调剂与尼纳尔的协同增调性能。