季铵盐修饰磷钼酸铵纳米微粒的制备、结构表征及摩擦学性能

在醇 -水体系中采用同阴离子共沉淀法制备了季铵盐修饰的 (NH4 ) 3PMo12 O4 0 纳米微粒 ,采用TEM ,XRD ,FTIR ,TGA&DSC等多种分析手段表征了这种纳米微粒的形貌和结构 ,在四球试验机上考察了它们的摩擦学性能。结果表明所合成的杂多化合物具有Keggin骨架结构 ,微粒粒径约 2 0nm ,在有机溶剂中可良好分散 ,作为一类新型润滑油添加剂 ,具有良好的抗磨性能。     

硼酸镧纳米棒的制备及其在植物油中的抗磨减摩性能

以Na2B4O7·10H2O和La(NO3)3·6H2O作原料,油酸作改性剂,采用水热法制备了硼酸镧纳米棒。利用X-衍射仪、FT-IR光谱仪、扫描电镜及能谱仪对其结构进行了表征,采用四球摩擦试验机考察了其在植物油中的抗磨减摩性能,利用扫描电镜观察了钢球表面磨斑的形貌,X射线光电子能谱测定了磨斑的元素组成。结果表明,硼酸镧呈纳米棒结构,其直径为50 nm、长达500 nm。硼酸镧纳米棒能显著提高植物油的抗磨、减摩性能,当添加剂的含量为1wt.%时,植物油的抗磨、减摩性能达到最佳。XPS分析结果表明,在钢球表面形成了一层含油酸的吸附膜和一层含Fe2O3、B2O3和La2O3等物质的润滑膜,这种润滑膜起到了良好的润滑作用。     

PS-TiO2 复合纳米微球的表征及摩擦学行为

采用化学法合成了PS-TiO2复合纳米微球,并对其进行了TEM、 FTIR、 TGA及DSC等分析表征。将这种微球用作润滑油添加剂,在四球试验机上研究了它的减摩抗磨性能,同时又对磨斑表面进行了X射线光电子能谱分析(XPS).研究表明：这种添加剂有良好的抗磨性能,并能在摩擦表面形成由TiO2、 Fe2O3以及有机碎片所组成的边界润滑膜。     

高催化活性Pd-Co3O4/MWCNTs催化剂对甲醇氧化的电催化性能

以Co(NO3)3·6H2O为钴源,聚乙二醇(PEG)20000为表面活性剂,与多壁碳纳米管(MWCNTs)混合后通过水热氧化法成功地合成了表面均匀分布纳米絮状Co3O4的MWCNTs复合物,进一步还原Pd的前驱体而制备得到Pd-Co3O4/MWCNTs复合催化剂.利用扫描电镜(SEM)、透射电镜(TEM)及X射线粉末衍射(XRD)等手段对样品的形貌和晶型结构进行了表征,结果表明Pd纳米粒子为面心立方晶体结构,均匀地分布在Co3O4修饰的MWCNTs表面.用循环伏安法和计时电流法表征结果表明:催化剂Pd-Co3O4/MWCNTs具有较大的电化学活性表面积,在碱性介质中对甲醇氧化具有更高的电催化活性和稳定性.研究结果表明,过渡金属氧化物纳米Co3O4颗粒在提高直接甲醇燃料电池(DMFC)催化性能研究中具有十分重要的作用,是一类很有潜力的载体催化剂.     

快速测定COD最佳催化消解体系研究

通过正交试验 ,确定了测定环境水样中COD的最佳回流消解条件。以CuSO4作催化剂 ,KAl(SO4) 2 Na2 MoO4作助催化剂 ( 0 1 8gCuSO4·5H2 O 0 1 0gKAl(SO4) 2 ·1 2H2 O 0 1 0gNa2 MoO4·2H2 O) ,在H2 SO4 H3PO4体系中可很好地实现对样品的消解。该体系将回流时间由国标法的 2h缩短至 2 0min ,实现了快速测定的目的且大幅度降低测定成本。样品 1 0次平行测定的相对标准偏差为 1 1 % ;加标回收率为 97 7%～ 1 0 3 3% ,均与国标法无显著性差异     

液相烧结碳化硅晶界内氮化反应的研究

碳化硅 ( Si C)由于其高度的共价键结合特性而具有高硬度、耐磨性和高化学稳定性等优异性能而成为热机、高温环境和化学化工等领域的研究应用对象 .碳化硅材料的无压烧结最早是由 Prochazka[1] 实现的 .2 0世纪 80年代初期 ,Omori[2 ] 通过采用氧化物 ( Al2 O3,Y2 O3和稀土氧化物等 )添加剂的手段大大降低了无压烧结的温度 .这些氧化物具有较低的共熔点 ,在高温下易形成液相 ,从而促进了碳化硅的晶粒重排和晶体生长 .2 0世纪 90年代以来 ,氮化物和氧化物的混合添加剂 (如 Al N- Y2 O3) [3]被广泛应用于碳化硅的液相烧结 .这是因为氮在…     

边界润滑条件下石墨与烷基硫代磷酸锌的协同作用

油溶性添加剂与团体润滑剂的相互作用是影响分散在润滑油中固体润滑剂作用的重要因素。本工作在SRV(微振动摩擦磨损)试验机和Falex试验机上考察了边界润滑条件下液体石蜡中石墨与极压抗磨添加剂二烷基二硫代磷酸锌(ZDDP)在摩擦、磨损及承载能力方面的相互影响,并在相同的条件下比较了石墨分别与极压抗磨添加剂磷酸三甲酚基酯(TCP)和二苄基二硫(DBDS)的相互影响。     

表面修饰磷钼酸铵纳米微粒的合成及摩擦学行为研究

在醇-水体系中采用同阴离子共沉淀法合成了季铵盐修饰的(NH4)3PMo12O40纳米微粒,以TEM、 XRD、 FTIR、 TGA、 DSC等多种分析手段表征了这种纳米微粒的形貌和结构,在四球试验机上考察了它们的摩擦学性能.结果表明所合成的杂多化合物具有Keggin骨架结构,微粒粒径约20 nm,在有机溶剂中可良好分散,作为一类新型润滑油添加剂,具有良好的抗磨性能.     

一种高硫的噻二唑衍生物的摩擦学性能研究

合成了一种高硫含羟基和黄原酸的噻二唑衍生物(ESP),利用四球摩擦磨损试验机考察了其在Corda3970基础油中的摩擦磨损性能,表明所合成的添加剂能够有效的提高Corda 3970基础油的极压和抗磨性能,并且在一定的浓度范围内随着浓度的增加,其抗磨减摩性能增加。通过扫描电镜(SEM)分析了钢球表面形貌及元素分布,发现其主导作用的是边界膜中存在S、O、N活性元素,它们形成复合膜是添加剂具有摩擦学性能的主要原因。     

异辛基乙二胺-CF3SO3型质子化离子液体作为液体石蜡添加剂的摩擦学性能

以异辛基乙二胺-CF₃SO₃[HEtHex(TFS)]型质子化离子液体作为钢/钢摩擦副的润滑油添加剂, 考察了不同HEtHex(TFS)含量的液体石蜡(LP)在不同温度和载荷下的摩擦学性能. 通过扫描电子显微镜和X射线能谱仪对钢球表面磨斑的形貌及所含元素进行了分析与表征. 结果表明, 加入HEtHex(TFS)添加剂可明显增大LP的最大无卡咬负荷(P_B)值, 改善LP的减摩抗磨性能. HEtHex(TFS)在LP中添加的最佳质量分数为0.75%, 在25 ℃, 294 N时其减摩效果最好; 在25 ℃, 196 N时其抗磨效果最佳. 元素分析结果表明, 加入HEtHex(TFS)添加剂后在钢球表面形成了一层摩擦保护膜, 从而起到了减摩抗磨的作用.     

Investigation of antioxidant and electron beam radiation effects on the thermal oxidation stability of low-density polyethylene

Effect of various antioxidants on the thermal oxidation stability of LDPE and X-LDPE has been investigated. To achieve this purpose, miscellaneous commercial grade antioxidants such as Irganox 1010, Irganox1076, Irgafos168, Irganox B225, and Chimassorb 944 were selected. Then, formulations based on different content of antioxidant were prepared. The samples were crosslinked by exposure to electron beam irradiation. To assess the thermal oxidation stability of samples, oxidation induction time (OIT) test was accomplished on both the irradiated and unirradiated specimens. Ageing tests were carried out in order to evaluate the thermal oxidation stability of irradiated X-LDPE. The results indicate that Irganox 1010 is the most effective antioxidant amongst the selected ones, concerning thermal oxidation stability of LDPE, before and after aging test.     

Evaluation of thermo-oxidative characteristics of gear oils by different techniques: Effect of antioxidant chemistry

This paper deals with determination of the oxidation stability of gear oils formulated with antioxidants of different chemistries. The oxidation stability has been studied by PDSC, TGA, micro-oxidation, RPVOT and IP 48. The effect of different antioxidants on the thermo-oxidative properties of gear oil is evaluated.     

Structure and thermal stability of PMMA/MMT nanocomposites as denture base material

Poly(methyl methacrylate) (PMMA)/montmorillonite (MMT) nanocomposites were prepared by in situ suspension polymerization. MMT was previously organically modified by three different intercalating agents: methacrylatoethyl trimethyl ammonium chloride (DMC), dodecylamine (12CNH), and hexadecyl allyl ammonium chloride (HADC). The structures of the nanocomposites were investigated by X-ray diffraction and transmission electron microscopy, while the interaction between PMMA and MMT was characterized by Fourier transform infrared spectroscopy. The molecular mass of the extracted PMMA was measured by gel permeation chromatography. The thermal stability of PMMA/MMT nanocomposites was evaluated by thermogravimetric and differential scanning calorimetry. The results indicated that PMMA/MMT nanocomposites were successfully prepared and the interaction between PMMA and MMT of PMMA/MMT–HADC nanocomposites was the strongest. The thermal stability of the nanocomposites was improved and found to be optimal for PMMA/MMT–HADC with T ₁₀ increasing to 304 °C, 52 °C higher than that of neat PMMA.     

氧清除剂用于增强吸热型碳氢燃料热氧化安定性

热氧化安定性是吸热型碳氢燃料贮存和使用过程中评价燃料品质的重要性质之一,反映了喷气燃料在260℃以下组分受溶解氧影响的程度和燃料氧化反应进行的深度。为评价氧清除剂,选用一种实验室自制的吸热型燃料,运用加速氧化法,配合滴定、红外光谱、粒度分布和JFTOT等测试方法对燃料的基础物性和热氧化安定性进行评估,比较了三苯基膦(TPP)、二环己基苯基膦(DCP)和1,2,5-三甲基吡咯(TMP)三种氧清除剂对吸热型碳氢燃料自氧化过程的影响,并确定了测试范围内的最佳添加量。结果显示,三种氧清除剂的添加对燃料的组成和基础物性无明显影响;燃料中的溶解氧浓度随添加量增加不断下降,最大可降低溶氧浓度31.95 mg/m~3;加速氧化后,样品的过氧化值和酸值均不同程度下降;胶团粒径分布趋向于更小粒径方向; JFTOT测试结果均满足国标规定。总体上,氧清除剂的添加均能有效提升燃料的热氧化安定性,三者的最优添加量均为质量分数1.5×10~(-5),作用效果优劣顺序为TMPTPP≈DCP。     

Effect of thermal annealing of poly(3-octylthiophene) films covered stainless steel on corrosion properties

The effect of thermal annealing of poly(3-octylthiophene) (P3OT) coatings on the corrosion inhibition of stainless steel in an NaCl solution was investigated. P3OT was synthesized by direct oxidation of the 3-octylthiophene monomer with ferric chloride (FeCl₃) as oxidant. P3OT films were deposited by drop-casting technique onto 304 stainless steel electrode (304SS). 304SS coated with P3OT films were thermally annealed during 30 h at different temperatures (55°C, 80°C, and 100°C). The corrosion resistance of stainless steel coated with P3OT in 0.5 M NaCl aqueous solution at room temperature was investigated by using potentiodynamic polarization curves, linear polarization resistance, and electrochemical impedance spectroscopy. The results indicated that the thermal treatment at 80°C and 100°C of P3OT films improved the corrosion resistance of the stainless steel in NaCl solution; the speed of corrosion diminished in an order of magnitude with regard to the 304SS. In order to study the temperature effect in the morphology of the coatings before and after the corrosive environment and correlate it with corrosion protection, atomic force microscopy and scanning electron microscopy were used. Morphological study showed that when the films are heated, the grain size increased and a denser surface was obtained, which benefited the barrier properties of the film.     

高超音速推进用吸热型烃类燃烧的热稳定性研究 Ⅱ．添加剂的合成与评价

结合燃料的自氧化机理，指出了抗氧剂，金属减活剂以及清净分散剂三种单元添加剂在燃烧自氧化过程中的抗沉积原理，自行合成了一种新型清净分散剂－聚异丁烯硫磷酸的季戊四醇酯PETPA，对酯化产物用FT－IR和NMR进行了结构分析，给出了合成过程中硫磷化，水解，及本经化阶段的反应历程，考察了三种单元添加剂抗氧剂A，清净分散剂D和金属减活剂M，以及由单元添加剂组成的添加剂包的抗沉积效果，结果表明，抗沉积效果AMD＞MD＞AD＞AM＞D＞M＞A，其中清净分散剂为主要添加剂，三种单元添加剂组成的添加剂包的抗沉积效果最为明显，在RT－3，MCH及THDCPD燃料体系中，沉积量分别减少了87．10％，90．91％和89．12％，PETPA无论是单独还是复合使用其效果均优于聚异丁烯丁二酰亚胺T154。     

Phenolic resin/polyhedral oligomeric silsesquioxane (POSS) composites: Mechanical,ablative, thermal,and flame retardant properties

Three different polyhedral oligomeric silsesquioxanes (POSS), trisilanolphenyl polyhedral oligomeric silsesquioxane (T‐POSS), octaaminophenyl polyhedral oligomeric silsesquioxanes (OAPS), and octaphenyl polyhedral oligomeric silsesquioxanes (OPS) were incorporated into phenolic resin (PR), respectively; PR/POSS composites were successfully prepared, and the properties of PR/POSS composites were studied. The limiting oxygen index (LOI), cone calorimeter, and thermal gravimetric analysis (TGA) were used for the estimation of flame retardancy and thermal stability. Oxyacetylene flame test and flexural strength test were used to study the ablative and mechanical properties of the PR/POSS composites. The results indicated that T‐POSS was more effective in improving the flame retardancy of PR than OAPS or OPS. Meanwhile, compared with pure PR, the second line ablation rates of PR/4% T‐POSS, PR/4% OAPS, and PR/4% OPS were significantly reduced by 53.3%, 61.9%, and 40.0%, respectively. In addition, the thermal stability and flexural strength of PR/4% T‐POSS were significantly higher than that of all other PR composites.     

The Preparation and Properties of Polyurethane/Nano-CeO<Subscript>2</Subscript> Hybrid Aqueous Coating

To improve the ultraviolet resistance and thermal stability of waterborne polyurethane, stable waterborne polyurethane/nano-cerium oxide hybrid dispersions were obtained by adding nano-cerium colloids to previously synthesized waterborne polyurethane dispersions. The dried ceria colloid was characterized by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). The XRD results indicated the prepared CeO₂ was a face-centered cubic structure. The prepared polyurethane/CeO₂ dispersions were studied by dynamic light scattering (DLS), transmission electron microscopy (TEM), UV–Vis spectroscopy and accelerated weathering test. The dried polyurethane/CeO₂ films were characterized using thermogravimetric analysis (TGA). The DLS analysis indicated the particles average diameter of hybrids emulsion was bigger than that of the pure waterborne polyurethane dispersion. TG analysis and accelerated weathering test suggested the hybrid latex films had better thermal stability and mechanical properties than those of the pure waterborne polyurethane. The UV–Vis absorption capacity of the dispersions prepared was increasing with the amount of CeO₂ colloid increased.     

Mechanism of cysteine oxidation by a hydroxyl radical: a theoretical study.

Cysteine oxidation by HO(.) was studied at a high level of ab initio theory in both gas phase and aqueous solution. Potential energy surface scans in the gas phase performed for the model system methanethiol+HO(.) indicate that the reactants can form two intermediate states: a sulfur-oxygen adduct and a hydrogen bound reactant complex. However these states appear to play a minor role in the reaction mechanism as long as they are fast dissociating states. Thus the main reaction channel predicted at the QCISD(T)/6-311+G(2df,2pd) level of theory is the direct hydrogen atom abstraction. The reaction mechanism is not perturbed by solvation which was found to induce only small variations in the Gibbs free energy of different reactant configurations. The larger size reactant system cysteine+HO* was treated by the integrated molecular orbital+molecular orbital (IMOMO) hybrid method mixing the QCISD(T)/6-311+G(2df,2pd) and the UMP2/6-311+G(d,p) levels of theory. The calculated potential energy, enthalpy, and Gibbs free energy barriers are slightly different from those of methanethiol. The method gave a rate constant for cysteine oxidation in aqueous solution, k=2.4 x 10(9) mol(-1) dm(3) s(-1), which is in good agreement with the experimental rate constant. Further analysis showed that the reaction is not very sensitive to hydrogen bonding and electrical polarity of the molecular environment.     

Direct dynamic study on the hydrogen abstraction reaction CH3CN + OH-->CH2CN + H2O

The reaction of acetonitrile with hydroxyl has been studied using the direct ab initio dynamics methods. The geometries, vibrational frequencies of the stationary points, as well as the minimum energy paths were computed at the BHandHLYP and MP2 levels of theory with the 6-311G(d, p) basis set. The energies were further refined at the PMP4/6-311+G(2df, 2pd) and QCISD(T)/6-311+G(2df, 2pd) levels of theory based on the structures optimized at BHandHLYP/6-311G(d, p) and MP2/6-311G(d, p) levels of theory. The Polyrate 8.2 program was employed to predict the thermal rate constants using the canonical variational transition state theory incorporating a small-curvature tunneling correction. The computed rate constants are in good agreement with the available experimental data.