治理铬渣的两个关键

铬渣中存在的酸溶性六价铬是解毒效果能否持久的关键，而铬渣中游离氧化镁消化是利用铬渣作建筑材料时必须高度重视的问题，论述了湿法解毒、高温解毒和非熔融的综合利用法等方法，对铬盐行业的铬渣治理有指导作用。     

Lipid hydrolysis and oxidation on the surface of milled rice

The changes in milled rice FFA content and composition and in conjugated diene (CD) content and bacterial, yeast, and mold counts were determined at 24, 37, and 50°C and 70% RH over 50 d. There was a rapid rate of FFA formation during the first few days of storage, which was optimal at 37°C, but that slowed after 2, 4, and 5 d at 37, 24, and 50°C, respectively. There was a second increase in FFA after about day 12 that increased with increasing temperature, indicating nonlipase hydrolysis. Linoleic and oleic acids were the main components of the total FFA produced on the surface of milled rice. The pattern of CD development followed that of FFA increase. Bacterial growth correlated with increased FFA levels after 12 d of storage, suggesting that bacterial lipase rather than bran lipase may be responsible for rice lipid hydrolysis     

Free energy calculations of the mutation of Ile96 -> Ala in barnase: contributions to the difference in stability

Free energy calculations were carried out to determine the relativeunfolding free energy of the Ile96 wild type and Ala96 mutantbarnases. The total calculated free energies suggest that substitutionof Ile96 with Ala destabilizes barnase by 3.9 kcal/mol, whichis in good agreement with the independently determined experimentalvalues of 4.0 and 3.3 kcal/mol and a previous simulation. However,a decomposition of the free energy finds the dominant contributionsto this free energy arising from the noncovalent Interactionsbetween the perturbed group and distant residues of barnasein the sequence and water molecules and only a very small contributionfrom covalent interactions. This is in contrast to the previoussimulation, using the dual topology methodology, which produceda decomposition with an {small tilde}60% free energy contributionfrom changes in covalent interactions. The use of the singletopology employed in the present calculations and the dual topologyemployed in the previous study are analyzed in order to understandthe contrast between the present results and the results ofthe previous study.     

铜锡合金的电动势热力学研究

在温度７００℃，组成０≤Ｘｓｎ≤０．２８的范围内，对固体Ｃｕ—Ｓｎ合金的α、β相的电池电动势测量研究表明，在固态高温相区，采用一固体电解质构成电池后，通过电动势测量，来获取热力学函数仍是一可靠方法。从锡活度的测定，体系的相对偏摩尔过剩自由能被确定。体系同理想混合行为的偏差可归结为在本质上是合金组份之间的互相作用，主要表现为在合金组成时的变形贡献和电子相互作用两个方面。     

取代基及分子量对非离子型纤维素醚表面特性的影响

根据Washburn的浸渍理论(Penetration Theory)和van Oss-Good- Chaudhury的组合理论(Combining Theory)及应用柱状灯芯技术(Column Wicking Technique),对几种非离子型纤维素醚,如甲基纤维素、羟丙基纤维素和羟丙基甲基纤维素的表面特性进行了测试。由于这些纤维素醚的取代基、取代度和分子量不同,所以它们的表面能及其组成部分有着明显的差异。数据说明,非离子型纤维素醚Lewis碱大于Lewis酸,表面自由能的主要成分是Lifshitz-van der Waals力。羟丙基的表面能及其成分都大于羟甲基。而在相同取代基和取代度的前提下,羟丙基纤维素的表面自由能正比于分子量;而羟丙基甲基纤维素的表面自由能则正比于取代度,反比于分子量。实验还发现非离子型纤维素醚中的取代基羟丙基和羟丙基甲基的表面能似乎都大于纤维素的表面能,而实验证明所测试得出的纤维素的表面能及其成分的数据是与文献所吻合的。     

Investigation of free volume,interfacial, and toughening behavior for cyanate ester/bentonite nanocomposites by positron annihilation

Effects of filler on microstructure and toughening behavior of cyanate ester (CE)/bentonite (BT) nanocomposites with different content of BT have been studied by positron annihilation lifetime spectroscopy, X‐ray diffraction, transmission electron microscopy, dynamic mechanical analysis, etc. The interesting results found by PALS indicate that the size and concentration of the free volume holes and the apparent free volume fraction increased with increasing the content of BT, which indicates that adding nano‐layers to thermosetting materials can lead to the high crosslinking density structure “looser.” The experimental results reveal that the increases in size of free volume holes and apparent free volume fraction are related to the increasing conversion of cure reaction. On the other hand, the mechanism of toughening (by adding the nano‐clay to the thermosetting material) has been discussed by combining free volume and interfacial property. It is shown that, for the high crosslinking thermosetting material‐based nanocomposites, both the property of free volume and dispersion state of nano‐layers are the two key factors in determining toughening property. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1509–1515, 2006     

Free‐radical grafting of acrylic acid onto isotactic polypropylene using styrene as a comonomer in supercritical carbon dioxide

Free‐radical grafting of acrylic acid (AAc) onto isotactic polypropylene (iPP) using styrene (St) as a comonomer in supercritical carbon dioxide (SCCO₂) medium was studied. The effects of temperature and pressure of reaction on functionalization degree (grafting degree of AAc) of the products were analyzed. The increase of reaction temperature increases the diffusion of monomers and radicals in the disperse reaction system of SCCO₂. In addition, the increase of temperature accelerates the decomposition rate of 2,2′‐azobisisobutyronitrile (AIBN), thus promoting grafting reaction. It was also observed that functionalization degree of the products decreases with the increase of pressure of SCCO₂ in the range of experiment. The effects of comonomer St on the functionalization degree of the products were investigated. The AAc graft degree of the resulting polymer was drastically higher in the present of St. It reached a maximum when the mass ratio of St and AAc was about 0.7 : 1. Because AAc is not sufficiently reactive toward iPP macroradicals, it would be helpful to use a second monomer that can react with them much faster than AAc. St preferentially reacts with the iPP macroradicals to form more stable styrene macroradicals, which then copolymerize with AAc to form branches. The highest functionalization degree was obtained when the AIBN was 0.75 wt %. When the initiator was used excessively, the functionalization degree decreased because of severe chain degradation of the iPP backbone. The morphologies of pure iPP and grafted iPP are different under the polarizing optical microscope. The diameter of the pure iPP spherulites is 20–38 μ and that of the grafted iPP spherulites is reduced with the increase of the functionalization degree of the products. This is proposed to be because the polar grafts formed during the reaction would have a tendency to associate in the hydrophobic PP environment. This might preserve some of the local crystalline order that existed during the reaction in the swollen iPP phase. It can be proven by a DSC cooling investigation that the crystallization temperature increased as the functionalization degree increased. This is proposed to be because the side‐chain of grafting polymer helps to bring about the heterogeneous nucleation in grafting polymer. Therefore, a large number of nuclei can emerge to a lesser supercooling degree. It can be also proven that the percent crystallization decreased as the functionalization degree increased, probably due to the grafted branches, which disrupted the regularity of the chain structure and increased the spacing between the chains. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2203–2210, 2004     

Morphologies and dynamic mechanical properties of core‐shell emulsifier‐free latexes and their copolymers for P(BA/MMA)/P(MMA/BA) and P(BA/MMA)/PSt systems in the presence of AHPS

Different poly(methyl methacrylate/n‐butyl acrylate)/poly(n‐butyl acrylate/methyl methacrylate) [P(BA/MMA)/P(MMA/BA)] and poly(n‐butyl acrylate/methyl methacrylate)/polystyrene [P(BA/MMA)/PSt] core‐shell structured latexes were prepared by emulsifier‐free emulsion polymerization in the presence of hydrophilic monomer 3‐allyloxy‐2‐hydroxyl‐propanesulfonic salt (AHPS). The particle morphologies of the final latexes and dynamic mechanical properties of the copolymers from final latexes were investigated in detail. With the addition of AHPS, a latex of stable and high‐solid content (60 wt %) was prepared. The diameters of the latex particles are ～0.26 μm for the P(BA/MMA)/P(MMA/BA) system and 0.22–0.24 μm for the P(BA/MMA)/PSt system. All copolymers from the final latexes are two‐phase structure polymers, shown as two glass transition temperatures (T_gs) on dynamic mechanical analysis spectra. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3078–3084, 2002     

具有纳米结构的TiO_2纤维光催化氧化活性

研究了具有纳米结构,高比表面的锐钛矿TiO2纤维在光催化降解苯酚体系中的氧化性能,发现其活性与P25相当;通过加羟基自由基猝灭剂证实了羟基自由基(HO.)对苯酚降解的贡献;而通过加空穴猝灭剂则观察到明显的空穴(h )效应。并通过K I氧化反应进一步研究了催化剂表面上的空穴效应,结果表明,TiO2纤维上的光生空穴比P25稳定,其空穴量子产率是后者的3.3倍。