AC susceptibility and Mossbauer study of Ce3+ ion substituted SrFe12O19 nanohexaferrites

Ce³⁺ ion substituted SrFe₁₂O₁₉, SrFe_12-xCe_xO₁₉ (0.0?≤?x?≤?0.5), nanohexaferrites were fabricated by citrate sol-gel combustion approach. X–ray diffractometry (XRD), Scanning electron microscopy (SEM), Energy dispersive spectroscope (EDX), EDX Elemental mapping, Fourier transform infrared spectroscopy (FT-IR) were used to study the structure and morphology of the samples. AC magnetic susceptibility and ⁵⁷Fe Mossbauer spectroscopy have been operated to examine the hyperfine structure, static and dynamic magnetic properties. The values of variations in line width, quadrupole splitting, hyperfine magnetic field, and isomer shift have been estimated. The impact of Ce-ion substitution on AC magnetic susceptibility properties of Sr-hexaferrite were explored. The AC-susceptibility measurements reveal the frequency dependence of the magnetic responses, indicating strong magnetic interactions among the nanoparticles of the various products. In addition, it is determined that the magnetic interaction between the nanoparticles is weakened in the substituted products, due to the substitution of Fe³⁺ ions by Ce³⁺ ions.     

禁用直接染料的二胺类化合物代用品评介（上）

德国政府规定的118种禁用染料中，直接染料占有65%，其中绝大部分是以联苯胺、联甲苯胺和联大茴香胺等二胺类为中间体合成的，所以用其它无害的二胺类化合物合成的直接染料，是禁用直接染料的主要代用品，是国内外染料厂商近年来研究和开发的热点，文章详尽地列举了六大类二胺类化合物合成的直接染料作为代用染料。     

Ferroelectric Characteristics of Bi 4−x La x Ti 3 O 12 Thin Films Crystallized at Low Temperetures

Recently, Bi 4 m x La x Ti 3 O 12 (BLT) has received much attention because it enables low crystallization temperature with a large remanent polarization. BLT films were prepared using a metal organic decomposition technique followed by a rapid thermal annealing (RTA) and a furnace annealing. The annealing of BLT was performed in the temperature range from 550 to 700C. In particular, BLT film annealed at 600C using the RTA tool and the furnace shows good ferroelectric characteristics. The BLT film annealed at 600C exhibits a large value of remanent polarization (22 w C/cm 2 at 250kV/cm), and a low leakage current density (7 2 10 m 7 A/cm 2 at 250kV/cm), a good endurance characteristics for up to 3.2 2 10 11 cycles at 250kV/cm at 85C. From an accelerated imprint test, the lifetime of hysteresis integrity is estimated to be over 10 years at 85C. In conclusion, BLT is the one of the promising material to achieve the high density FeRAMs.     

Herbicide accumulation and evolution in reservoir sediments

The aim of the present study was to understand the effect of reservoir configurations on sediment pesticide fate. Two dams were selected on the River Garonne, in southwest France: Carbonne and Golfech, both with reservoirs subject to accumulation of herbicide-contaminated sediment. They are situated upstream and downstream respectively of an agricultural and urban area: the Mid-Garonne. The results presented include pesticide concentrations and C/N ratios in the smaller sediment particles (< 2 mm) and values of oxygenation and herbicide concentrations in the water.The dynamic behaviour of sediment in the reservoirs is discussed. The present study shows that the theoretical lifespan (weak remanence in vitro) and the results actually observed in the sediment are conflicting. Pesticide contamination in Carbonne indicates conservation, even accumulation, of herbicide molecules while in Golfech transformation processes clearly dominate. The hydromorphological position of Golfech reservoir, i.e. located at the junction of two rivers with contrasting hydrological regimes and very different oxygenation conditions, leads to accelerated pesticide desorption or degradation. Unfortunately, this configuration is rare.     

Synthesis and polymerization ofgem-methyl-(vinylbenzyl)tetrachlorocyclotriphosphazene

A new styrene-substituted chlorocyclotriphosphazene,gem-methyl(vinylbenzyl) tetrachlorocyclotriphosphazene, has been prepared from vinylbenzylmagnesium chloride and hexachlorocyclotriphosphazene. The organosubstituted chlorocyclotriphosphazene has been used in radical homo- and copolymerization with methyl methacrylate. The reactivity ratios for the MMA copolymerization show a small effect of the phosphazene ring on the olefin reactivity. All these polymers exhibit flame-retardant properties.     

用Hirshfeld电荷预报取代苯胺的logP值

用密度泛函活性理论与方法(DFT/B3LYP)及基组6-31+G(d,p),优化了20种苯胺及其取代苯胺分子的几何结构。结果发现,苯环胺基上N原子的Hirshfeld电荷值(HIR)与其实验油水分配系数(log P)值之间具有良好的线性相关性,普遍比其H原子拟合核静电势电荷(ESP)值以及自然电荷值(NBO)拟合的好。计算了20种未知log P值的取代苯胺化合物胺基的11N原子Hirshfeld电荷值,归入拟合出的最佳线性参数方程式,发现与商业软件ACD/Labs6.0预测得到的多取代苯胺及其衍生物分子的log P预测值非常接近,相对偏差(SD)小于±0.15%.     

单参数法估算取代苯胺的pK_b值

用密度泛函理论方法 DFT/B3LYP与基组6-31+G(d,p),优化了15种苯胺和取代苯胺分子结构,发现苯环氨基上氢原子的自然原子轨道电荷(NBO)值与其实验碱式电离平衡常数(pKb)值之间具有良好的线性相关性,普遍比其原子核静电势电荷(ESP)值拟合较好.计算了17种未知pKb值的取代苯胺化合物的NBO参数,代入拟合出的线性参数方程,发现与流行软件ACD-Labs 6.0检索得到的取代苯胺的pKb实验值非常接近,相对误差(SD)小于±0.1%。     

Coal hydrogasification: Entrained flow bed design-operation and experimental study of hydrogasification characteristics

Coal hydrogasification processes including wire-mesh grid reactor, batch reactor, curie-point pyrolyzer, fixed bed reactor and so on were utilized or developed in laboratory researches. Although the experimental results could help to understand the basic behavior of coal hydrogasification, it was difficult to directly utilize such data for devising a new hydrogasifier. This paper designed a continuous entrained flow bed facility and described the hydrogasification characteristics. This device (15–30 kg/d) mainly consisted of a high-H₂ pressure feed system, a high-temperature tube reactor. The capabilities were shown as follows: the temperature from 700 °C to 850 °C, H₂ pressure from 0.1 MPa to 3.0 MPa, isothermal zone 300–600 mm, feeding rate from 15 to 30 kg/d and water yield was easy to obtained by tar-water separation. The good mass balance on the carbon and weight basis was established by analyzing the product distribution in detail. The results showed the yields of CH₄ and light aromatic hydrocarbons increased through hydrogenation of tar and volatiles, hydrogasification of coal char. Although the small pilot plant had high heat loss through refractory with increasing H₂ pressure, the typical results obtained from the continuous stable operation of the entrained flow bed reactor confirmed the design of new large-scale hydrogasification process was technical feasibility.     

Some substituted polysaccharides as low temperature middle distillate additives

Substituted polysaccharides with different molecular weights (mol. wt 12 000–15 500) were synthesised by reacting aliphatic acid chlorides with different carbon numbers (C₁₂-C₁₈) with dextrin. The resulting polymers were purified and tested as pour point depressants and flow improvers for middle distillates (gas oils). Comparative evaluation of these polysaccharides with some commercial additives showed their good activity, especially as flow improvers.     

Radical copolymerization of maleic anhydride and substituted styrenes by reversible addition-fragmentation chain transfer (RAFT) polymerization

Reversible addition fragmentation transfer (RAFT) copolymerization with benzyl dithiobenzoate (BDTB) as chain transfer agent was used to copolymerize maleic anhydride (MA) with styrene (St) and with the substituted styrenes p-chlorostyrene (pClSt), p-methoxystyrene (pMeOSt) and p-methylstyrene (pMeSt). Kinetic studies indicated that radical copolymerizations proceeded with apparent ‘living’ character, deduced from experiments demonstrating an increase in molar mass with monomer conversion, narrow molar mass distribution and chain extension to form block copolymer. All copolymers were alternating in chain structure as confirmed by determinations of monomer reactivity ratios. The degree of control in the RAFT mechanism and the establishment of the fragmentation equilibrium incorporating MA are discussed for styrene and for p-substituted styrenes, in relation to experimental copolymerizations producing molar masses somewhat higher than expected. For copolymerizations of MA with α-methylstyrene (αMeSt), conventional rather than controlled behaviour was observed, suggesting that the fragmentation equilibrium could be shifted towards the αMeSt propagating radical.