CuCrAl和CuCrZr低温液相合成甲醇催化剂的研究

 用络合共沉淀法制备了CuCrAl和CuCrZr复合氧化物液相合成甲醇催化剂，其比表面分别达到119和116m2／g．在5．0～5．5MPa和383K条件下，分别用间歇式和流动式反应釜考察了催化剂的活性和稳定性．结果表明：CuCrAl和CuCrZr的活性均明显高于CuCr；CuCrAl的活性略高于CuCrZr，但甲酸甲酯（MF）的选择性明显低于CuCrZr；两者在12h内未见活性明显下降．甲醇钠在反应过程中部分转化为甲酸钠和NaOH．CuCrAl和CuCrZr有较高的氢解活性可抑制甲醇钠与MF生成甲酸钠，从而有较低的甲酸钠浓度．但是，Al2O3和ZrO2的酸性有利于甲醇脱水，引起甲醇钠水解生成NaOH．溶剂对CuCr基催化剂的活性和选择性有明显影响．对反应机理进行了讨论．     

Nafion化学修饰圆盘预富集-石墨炉 原子吸收联用法对牛血超氧化物歧化酶中铜、锌分布状态的研究

本文研究了Nafion化学修饰钨丝圆盘预富集-石墨炉原子吸收(GFAAS)方法测定牛血超氧化物歧化酶(SOD)中游离态Cu～(2+)及Zn～(2+)的方法,并用GFAAS法直接测定SOD中铜、锌的总量,证实了牛血SOD中金属辅基铜、锌原子个数比为1:1,初步探讨了一定浓度的牛血SOD中Cu～(2+)、Zn～(2+)的表观离解平衡常数。为提高SOD的活性和稳定性的研究,提供了一种有效的方法。     

石墨炉原子吸收法直接测定高温合金中硅

研究了混合基体改进剂，灰北、原子化温度以及共存元素的干扰，采用镧和钙作混合基体改进剂后，硅的灵敏度提高，抗干扰能力增强，可以用石墨炉原子吸收直接测定高温合多中硅。方法特征量为０．２ｎｇ，检出限为２．３μｇ／ｇ，对于含硅量为４００μｇ／ｇ左右的合金样品，相对标准偏差为５％左右，回收率在９０％－１１０％之间。     

Factors affecting the combustion toxicity of polymeric materials

Fire gas toxicity is an essential component of any fire hazard analysis. However, fire toxicity, like flammability, is both scenario and material dependent. A number of different methods exist to assess the fire toxicity, but many of them fail to relate this to a particular fire scenario. Sample thickness alone, in a closed box test such as the NBS Smoke Chamber, is shown to change the fire scenario from well-ventilated to under-ventilated. Data from two flow-through tests, the static tube furnace (NF X 70-100) and the steady state tube furnace (the Purser furnace, BS 7990 and ISO TS 19700) show that there are different patterns of behaviour for different polymers (LDPE, polystyrene, rigid PVC and Nylon 6.6). The predicted toxicities show variation of up to two orders of magnitude with change in fire scenario. They also show change of at least one order of magnitude for different materials in the same fire scenario. Finally, they show that in many cases CO, which is often assumed to be the most, or even the only toxicologically significant fire gas, is of less importance than either HCl, or HCN, when present, and in some cases less important than organo-irritants. Nylon 6.6 shows the highest predicted toxicity, the greatest scenario dependence, and the least sensitivity to different apparatuses, while polystyrene shows the highest sensitivity to the different apparatuses, but the lowest to different fire scenarios. PVC shows high toxicity, mostly due to HCl in the fire effluent, under all fire conditions, and LDPE shows a more progressive increase in toxicity from well-ventilated flaming to both smouldering and under-ventilated flaming.     

Binolam-AlCl: a two-centre catalyst for the synthesis of enantioenriched cyanohydrin O-phosphates

The enantioselective synthesis of cyanohydrin O‐phosphates by using in situ generated bifunctional catalysts (R)‐ or (S)‐3,3′‐bis(diethylaminomethyl)‐1,1′‐binaphthol–aluminium chloride (binolam–AlCl) is reported. The reaction, which can be described as an overall cyano‐O‐phosphorylation of aldehydes, has a wide scope and applicability. Evidence is also provided, including ab initio and DFT calculations, in support of supported by the Lewis acid/Brønsted base (LABB) dual role of the catalyst in inducing first the key enantioselective hydrocyanation, which is then followed by O‐phosphorylation. A brief screening of the synthetic usefulness of the resulting cyanohydrin O‐phosphates unveiles some interesting applications. Among them, chemoselective hydrolysis, reduction and palladium‐catalysed nucleophilic allyl substitution, thereby leading to enantiomerically enriched α‐O‐phosphorylated α‐hydroxy esters, β‐amino alcohols and γ‐cyanoallyl alcohols, respectively. Naturally occurring (?)‐tembamide and (?)‐aegeline are synthesised accordingly.     

Luminescence of Eu~(2 ) in Strontium Aluminum Oxide System with Long Decay Property

Luminescentmaterialshavinglongdecayperi0dhaveat-IIactedmuchinterestduetotheirpotentialwidespreadaPplicati0ns.Recently,alongdecayluminescentp0wderhavingthecomPositionofSrAl2O4activatedwithEu' wasreportedandregardedasthebestcandidateforpracticalaPPlicationbecauseofitsuniqueadVantages0veritsprecursors.l'2Inthispaper,wereportthesynthesisofthelongdecayluminescentpowderandtheinnuence0fthemolarratioofAlt0sr0ntheethessioncolor.Toproducethelundnescentp0wder,amixtureofSrCO3,Al2O3,Eu2O3andsomesol…     

Effect of the polyethylene confinement and topology on its crystallisation within semicrystalline ABC triblock copolymers

The isothermal crystallisation behaviour of the polyethylene block within polystyrene-b-polyethylene-b-poly(ε-caprolactone), SEC, triblock copolymers was studied by differential scanning calorimetry. The morphology was observed by transmission electron microscopy. Melting scans after isothermal crystallisation performed at different times were employed to determine the crystallisation kinetics one step at a time (“isothermal step crystallisation”). Double melting endotherms were observed after isothermal crystallisation and they were interpreted as a result of the melting of two lamellar populations. These arise from the intrinsic short chain branching distribution within the hydrogenated polybutadiene chains that conform the PE blocks and from their location within the copolymer microdomains. The Hoffman-Weeks procedure failed to yield reasonable values for the equilibrium melting point of the PE blocks as a result of the distribution of linear sequences present in these blocks. The results indicate that as the degree of PE confinement increases the Avrami index decreases to values that are even lower than 1, a result that can be explained by the nature of the homogeneous nucleation process that is in between sporadic and instantaneous.     

金属Cu低指数表面熔化行为的分子动力学模

采用Mishin镶嵌原子势, 通过分子动力学方法模拟了金属Cu的低指数表面在不同温度的表面熔化行为, 分析了熔化过程中系统结构组态的变化以及固-液界面迁移情况. 金属Cu的(100)和(110)表面在低于熔点发生预熔化, 而(111)表面存在明显的过热现象. 准液体层的厚度随温度升高而增加, 热稳定性与表面的密排顺序一致, 按(111)、(100)、(110)顺序增大. 当温度高于热力学熔点时, 固液界面的移动速度与温度成正比, 外推得到热力学熔点约为1360～1380 K, 与实验结果1358 K吻合良好. 动力学系数定义为界面移动速度与过热程度的比值, 表现为明显的各向异性: k100=39 cm•s−1•K−1, k110=29 cm•s−1•K−1, k111=20 cm•s−1•K−1. k100与k110之间的比例符合collision-limited理论, (111)密排面有与其它低指数表面不同的熔化方式.