A new continuous method for kinetic study on conversion coating formation

The kinetics of chromate coating formation and chromium(VI) exchange has been studied by of novel continuous radiotracer method. Comparison has been made with former results obtained by a quasi-continuous procedure and kinetic constants have been determined.     

A radioanalytical study of the chromate conversion coating formed on aluminium

Phosphate/chromate and accelerated chromate coatings were produced on commercially available aluminium. The Cr, P and Fe components of the conversion coatings were determined by radioactive tracer technique. The tracer technique was combined with ion-exchange and film-sectioning methods to determine the chromium (III)/total chromium ratio in the accelerated chromate coating. It was found that during the acidic dissolution of the conversion coating the chromium (III)/total chromium ratio may suffer changes. The filmforming components in the metal/bath interface are supersaturated and deposited onto the aluminium. The identified components of the accelerated chromate coatings are Cr/OH/₃, Cr/OH/CrO₄ and Cr₄[Fe/CN/₆]₃ and the chromium (III)/total chromium ratio was found to be cca. 2/3.     

纳米碳纤维涂层固相微萃取探头的制备及性能分析

采用纳米碳纤维(CNF)作为固相涂层制备了固相微萃取探头(SPME)并进行了评价.该涂层对苯系物(BTX)富集能力强,最高使用温度可达260℃,250℃解析条件下使用50次以上涂层无脱落现象.与活性碳涂层相比,尽管萃取量略小,但其解析时间仅为活性炭的60%,具有更高的精密度和准确度.对BrIX固相微萃取.气相色谱分析结果表明,样品质量浓度在0.1～38.7μg/L范围内与色谱峰面积呈良好线性关系(r=0.9891～0.9940),相对标准偏差为3.9%～5.3%,方法的检出限为2.5×10~(-3)μg/L.     

化学复合镀Ni-P-PTFE镀层的组成分析

近年来化学复合镀技术在工业中应用日益广泛 ,本文运用ＳＥＭ、ＡＥＳ和ＸＰＳ等手段对用化学复合镀制得的Ｎｉ Ｐ ＰＴＦＥ镀层的结构和组分进行了分析 ,并就其耐腐蚀性能与前期得到的Ｎｉ Ｓｎ Ｐ[1 ] 、Ｃｕ Ｓｎ Ｐ[2 ] 、Ｎｉ Ｐ ＣｅＯ2 [3] 、Ｎｉ Ｐ ＳｉＯ2 [4] 镀层进行了比较 ,结果表明 :含量一定的ＰＴＦＥ(聚四氟乙烯 )的共存增强镀层的耐腐蚀性及镀层表面的润滑性。1　实验部分1 1　仪器日产Ｄ/ＭＡＸⅢＡ型Ｘ 射线衍射仪 ,铜靶 ,管压 2 5ｋＶ ,电流 1 0ｍＡ。国产ＪＪＣ 1型润滑湿角测量仪。美国ＰＥＲＫＩＮ ＥＬＭＥＲＰ…     

Development of flame retardant phosphorus- and silicon-containing polybenzoxazines

The copolymerisation of benzoxazine of bisphenol A and diglycidyl ether of (2,5-dihydroxyphenyl)diphenyl phosphine oxide or diglycidyloxymethylphenylsilane has been studied. In all samples the molar ratio of the benzoxazine-epoxy system was varied to achieve different phosphorus or silicon contents. Their thermal, dynamic-mechanical and flame retardant properties were evaluated. The high limiting oxygen index values confirmed that the phosphorus-containing benzoxazine-epoxy resins are effective flame retardants, but no efficiency of silicon on flame retardation was observed.     

The synthesis and study of silicon-containing nanodispersed carbon

Samples of silicon dioxide-modified nanospherical carbon were synthesized by thermooxidative pyrolysis of highly aromatized liquid hydrocarbons with a varied content of organosilicon polymer (polyorganosiloxane). The physicochemical properties of the product synthesized were studied.     

Synthesis and catalytic properties of polynuclear molybdenum silicon-containing carbene complexes

The molybdenum silicon-containing carbene complexes PhMe₂Si—CH=Mo(NAr)(OR)₂ (1), Ph₂Si[CH=Mo(NAr)(OR)₂]₂ (2), and (RO)₂(ArN)Mo=CH—(SiMe₂)₂—CH=Mo(NAr)(OR)₂ (Ar = 2,6-Prⁱ ₂C₆H₃; R = CMe₂CF₃) were synthesized by the reaction of the R′— CH=Mo(NAr)(OR)₂ compounds (R′ = Bu^t or PhMe₂C) with silicon-containing vinyl reagents. The structures of complexes 1 and 2 and the known PhMe₂C—CH=Mo(NAr)(OCMe₂CF₃)₂ compound were established by X-ray diffraction. The catalytic properties of the silicon-containing carbene complexes in homometathesis of hex-1-ene and metathesis polymerization of cyclooctene were studied. The catalytic activity of these complexes and the stereoregularity of the resulting polyoctenamers substantially depend on the nature of the substituent at the carbene carbon atom. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 247–252, February, 2007.     

Effect of flexible units on the properties of silicon-containing phenyleneethynylene hybrid oligomers

New silicon-containing phenyleneethynylene hybrid oligomers P2, P3, and P4 were synthesized via Sonogashira cross-coupling reactions of ethynyl-terminated silazane monomer N,N′-bis(4-ethynylphenyl)-1,1-diphenylsilazane(M1) and corresponding bis-(4-bromo-phenyl)-ended organosilicon unit containing monomers, respectively. These new oligomers were easily soluble in common solvents. The incorporation of flexible organosilicon units in the oligomers leads to blue-shift in both the UV-Vis absorption and fluorescence emission spectra similarly. The results of differential scanning calorimetry(DSC) indicate that the flexible units relieve the rigidity of oligomeric chain and provide favorable conformation for thermal cross-linking reactions. The oligomers show good thermal and thermal-oxidative stability from the thermogravimetric analysis(TGA), with their decomposition temperature at 10% weight loss(T10%) higher than 400 ?C under both nitrogen and air atmosphere.     

Oil coating of hydrophobic surfaces from aqueous media: formation and kinetic study

We perform oil coating of hydrophobic solid surfaces via aqueous media, from emulsions, and under the presence of a shear flow. The principle of such coating is based on the use of a system at the limit of aggregation to give rise to adhesion, with asymmetrical interfaces (oil droplet/water and solid surface/water) in order to favor the oil/surface adhesion in comparison to the oil/oil adhesion. This way, droplets stick to the solid substrate, whereas they are stable and homogeneously dispersed in the bulk. We have realized coatings from two systems of emulsions made of a mixture of hydroxy-terminated silicone oil and classical silicone oil and a mixture of sunflower oil and mineral oil. The kinetics of the coating is described by a Langmuir model where the adhesion between the oil particle and the surface is modeled as a first-order reaction. The resulting coatings are formed of oil droplets uniformly covering the solid surface. The coating density can vary with the nature of the experimental systems.     

Theory of non-dissociative ortho-para conversion on magnetic surfaces

The theory of the non-dissociative ortho-para conversion of a hydrogen molecule on magnetic surfaces is reviewed. The transition probability for the ortho-para conversion is calculated within the lowest order perturbation theory and the expression is obtained in terms of the correlation function or their Fourier transforms (the spectral functions) for the relevant physical quantity. The temperature dependence of the conversion rate is investigated in relation to the properties of the substrate spin systems. Especially the change of conversion rate due to to an onset of long range order in the substrate (Hedvall effect) is discussed within the molecular field approximation for the substrate magnetic system and the refined treatment taking into account the dynamical response of the substrate. The effect of desorption process is carefully examined.     

Preparation and adhesive properties of colored Ti/Zr-based conversion coating on aluminum foil for lithium battery packaging

In this study, an aluminum (Al) foil used for lithium ion battery packaging film was treated with titanium (Ti)/zirconium (Zr) solution containing hexafluorotitanic acid and hexafluorozirconic acid using tannic acid as a colorant and metavanadate as an accelerator, respectively, and a golden conversion coating was successfully deposited on the surface of Al foil. The morphology and composition of the coating were characterized by scanning electron microscopy, energy dispersive spectroscopy, and X-ray photoelectron spectroscopy, and the hydrophilicity was assessed by contact angle measurement. The effect of Ti/Zr treatment on the adhesion properties of Al foil was evaluated by T-peeling test and compared with that of traditional chromate-phosphate treatment. The results show that tannic acid contributes to the formation of the golden coating, and metavanadate accelerates the formation of the conversion coating. The results also indicate that the Ti/Zr-based conversion coating is mainly composed of Al₂O₃, Al (OH)₃, AlF₃, TiO₂/ZrO₂, NH₄VO₃, and V₂O₅. The Ti/Zr treatment cannot only improve the heat-sealing strength, but also the T-peeling strength by approximately 12 times compared with that of untreated Al foil. Thus, Ti/Zr treatment has the potential to replace the traditional chromate conversion treatment.     

Analysis of methane-to-methanol conversion on clean and defective Rh surfaces

We investigate by density-functional theory simulations several elementary reactions associated to direct methane-to-methanol conversion on clean Rh(111) surfaces and on Rh adatoms on Rh(111). Energy barriers and reaction paths have been determined by the nudged elastic band method. The rate-limiting step in the process, C-O bond formation, has higher activation energy than the one for complete methane dehydrogenation. Our analysis enables us to understand the effect of defects on the reactivity and rules out Rh as candidate catalyst for methanol synthesis.     

Influence of the composition and preparation method of molybdenum systems on their oxidizing properties in ethane conversion

Redox conversion of ethane at 600 °C on Mo-containing oxide systems differing in the composition and preparation method was studied. The ethane conversion and the selectivity of the ethylene formation increase in the series of MoO₃ samples supported on SiO₂ (silica gel), TiO₂ (anatase), and alumina. The efficiency of the MoO₃/Al₂O₃ systems increased when HNO₃ was added to a (NH₄)₆Mo₇O₂₄ solution used to impregnate the support, and also when γ-Al₂O₃ was replaced with Al(OH)₃. Gallium oxide additives improve the properties of the MoO₃/Al₂O₃ system, increasing the ethane conversion to 44% at ethylene formation selectivity of more than 96%. The systems under consideration are characterized by high stability and retain their activity after five reaction—regeneration cycles. Based on the data obtained during the reaction of ethane with the Mo systems and in the course of regeneration of the reduced samples with oxygen, the content of active oxygen corresponding to the MoO₃ ? MoO₂ transformation was assessed.

     

Microprinting – a new approach to study competitive structure formation on surfaces

A new approach to the experimental investigation of heterogeneous crystallization on surfaces with molecularly defined structures is demonstrated. Crystallization and competitive dewetting processes of polyethylene on heterogeneous micropatterned surfaces were studied using molecular imprinting techniques for structured chemical modification of surfaces on micrometer scale in laterally defined areas. Examination of spherulitic textures by low‐voltage SEM and AFM shows remarkable differences in spherulite sizes due to surface chemical influences. The results are discussed in terms of a diffusion limited aggregation process which causes the dendritic and spherulitic structures and which is influenced by the dewetting process.     

Stability,composition and properties of Li2FeSiO4 surfaces studied by DFT

Surface structures and energies of the Pmn2₁ polymorph of the electrode material Li₂FeSiO₄ are studied by first-principles calculations using density functional theory. In total, 29 surface terminations of stoichiometric polar and nonpolar slabs were studied. These surfaces were preselected by energy estimation via a model that accounts for bond cutting and additionally for polarity compensation in the case of polar surfaces. The model provides a way to quantify the most important contributions to the surface energy. Furthermore, we analyze the relaxation of surface atoms statistically. This clearly shows that SiO₄ tetrahedra are rather rigid whereas the local environment of Fe and Li can change strongly under relaxation near the surface. We furthermore compare results obtained by generalized gradient approximation (GGA) and GGA+U exchange correlation functionals. Thus, we estimate the thermodynamic equilibrium shape of Li₂FeSiO₄ by the Wulff construction scheme for stoichiometric surfaces obtaining crystallites that are terminated by {110}, {010}, and {001} surfaces.     

镁合金化学转化膜的制备及其性能研究

在磷酸钠-磷酸二氢铵-高锰酸钾体系中对镁合金进行化学转化处理.研究了磷酸钠、磷酸二氢铵、高锰酸钾、温度、时间和添加剂对转化膜性能的影响.通过对转化膜结构、成分及性能的测试评价,得到了性能较好的化学转化溶液配方:Na3PO4为5g·L-1,NH4H2PO4为15 g· L-1,KMnO4为1g· L-1,添加剂(NH4)6 Mo7O24为0.5g·L-1.由SEM可观察到转化膜的表面成“干枯河床”状.XRD和EDS检测表明,膜层的主要成分是Mg,Al12 Mg17和无定形相,膜层表面主要有Mn,Mg,K,O和Al等元素组成.腐蚀实验和电化学测试表明,添加剂能够降低转化膜的腐蚀率,转化膜较基体的腐蚀电位正移了0.73 V,提高了镁合金的耐蚀性.     

Preparation, thermal properties and flame retardancy of phosphorus- and silicon-containing epoxy resins

Phosphorus- and silicon-containing epoxy resins were prepared from (2,5-dihydroxyphenyl)diphenyl phosphine oxide (Gly-HPO), diglycidyloxy methylphenyl silane (DGMPS) and 1,4-bis(glycidyloxydimethyl silyl)-benzene (BGDMSB) as epoxy monomers and diaminodiphenylmethane (DDM), bis(3-aminophenyl)methyl phosphine oxide (BAMPO) and bis(4-aminophenoxy)dimethyl silane (APDS) as curing agents. Epoxy resins with different phosphorus and silicon content were obtained. Their thermal, dynamic mechanical and flame retardant properties were evaluated. The high LOI values confirmed that epoxy resins containing hetero-atoms are effective flame retardants, but a synergistic efficiency of phosphorus and silicon on flame retardation was not observed.     

Preparation and thermal properties of a novel flame-retardant coating

A novel silicone and phosphate modified acrylate (DGTH) was synthesized and characterized by ¹H NMR and FTIR. It was found that DGTH could be cured both by UV radiation and moisture mode with FTIR. The flammability and thermal behavior of the cured film were studied by the limited oxygen index (LOI), thermogravimetric analysis (TG) and real time Fourier transform infrared (RT-FTIR). The LOI value of the cured film is 48 and the TG data shows that the cured film has three characteristic degradation temperature regions, attributing to the decomposition of phosphate and polyurethane to alcohols and isocyanates, thermal pyrolysis of alkyl chains, and decomposition of unstable structures in char, respectively. The RT-FTIR data implies that the degraded products of phosphate form poly(phosphoric acid) further catalyse the breakage of carbonyl groups to form an intumescent char, preventing the samples from further burning.