π-ELECTRON CONTENTS OF RINGS IN THE DOUBLE-HEXAGONAL-CHAIN HOMOLOGOUS SERIES (PYRENE,ANTHANTHRENE AND OTHER ACENOACENES)

Abstract

Recently three methods for calculating the π-electron content of rings of benzenoid hydrocarbons were put forward: one based on the consideration of Kekuléstructural formulas, and the other two based on an analogous treatment of the Clar aromatic sextet formulas. These three methods are applied to the homologous series consisting of two condensed acene chains (whose first members are pyrene, anthanthrene, peri-naphthacenonaphthacene, …), leading to basically identical results. In contrast to acenes (in which the partition of π-electrons into rings is uniform), in the double-hexagonal-chain species the partition of π-electrons is highly non-uniform. The electron content monotonically decreases, in opposite directions, along the two acene chains, being maximal in the least annelated rings. Some other generally valid regularities in the π-electron properties of the double–hexagonal–chain benzenoids are also pointed out.     

6150小六角工具钢丝生产工艺探讨

介绍6150小六角工具钢丝的化学成分、产品特性及用途。传统的6150小六角工具钢丝生产存在的问题:设备产能低,钢丝盘重小,效率低;采用石灰涂层预处理工艺不利于拉拔;再结晶退火温度高、能耗大,使产品硬度低。针对这些问题,对原料规格、酸洗参数、拉丝模具锥度进行优选,采用机械剥皮、保护罩式炉低温退火、磷化、连续拉拔设备和工艺,减少了生产周期,生产的钢丝光亮、无脱碳现象。     

Catalytic Reduction of Nitrogen Oxides in Automotive Exhaust Containing Excess Oxygen by NOx Storage-Reduction Catalyst

Automotive catalyst technology is now faced with very difficult problems. As a result of automakers' efforts to produce more efficient and lower-emission vehicles, lean-burn gasoline engines have been introduced into the market. While these are much more efficient than the conventional engines, the NOx removal has become significantly more difficult. After enormous efforts, we succeeded to solve the problem by inventing a new class of catalyst. Here, our challenge to develop the new catalyst that stores and then reduces NOx is described. The catalyst made it possible for emissions of lean-burn engines to meet the strict NOx regulations.     

正六边形超高层建筑横风向气弹效应研究

为研究正六边形超高层建筑横风向风致响应和气动阻尼比,开展了一系列多自由度气弹模型风洞试验。测量模型顶部风致位移和加速度响应,基于随机减量法识别了横风向气动阻尼比。结果表明,在顶角迎风时,正六边形超高层建筑易于出现大幅涡振现象,在立面迎风时没有出现涡振现象。顶角迎风时,横风向气动阻尼比随折算风速增大呈现出“先增大到最大正值、再迅速转为最小负值,再平稳回升到零值附近”完整过程。而立面迎风时,横风向气动阻尼比与折算风速近似呈线性关系。最后,建立横风向气动阻尼比的经验评估公式。相关研究可为正六边形超高层建筑的抗风设计和规范完善提供参考。     

Enhanced magnetodielectric properties of Co2Z ferrite ceramics for ultrahigh frequency applications achieved via Cr3+ ion doping

Phase formation, microstructure, magnetic properties, and dielectric properties of Ba_1.5Sr_1.5Co₂Fe₍₂₃−_x)Cr_xO₄₁ (0.0 ≤ x ≤ 1.0) ceramics, in which Fe³⁺ ions were substituted by Cr³⁺ ions, were systematically investigated. X-ray diffraction results reveal that Z-type hexagonal ferrite was formed by sintering at 1250 °C, and Cr³⁺ ions successfully enter lattice without destroying crystal structure. Analysis of the microstructure reveals that Cr³⁺ ion doping has significant effect on crystal micromorphology. Samples with x = 0.4 have the most homogeneous micromorphology and the highest sintering density of 5.12 g/cm³. In addition, under the influence of external magnetic field, all samples exhibit typical soft magnetic character and hysteresis characteristics, with saturation magnetization up to 63.86 emu/g (x = 0.6). Particularly, compared with undoped sample, Cr-doped samples have outstanding magnetic–dielectric properties. Firstly, with increasing Cr³⁺ amount, real part of the permeability (μ′) reaches the maximum value of 10.70 at x = 0.4, while cutoff frequency exceeds 2 GHz, and Snoek constant reaches ∼19.50 GHz. Furthermore, due to more homogeneous microstructure, samples with x = 0.4 have low magnetic loss and can maintain high quality factor (Q) over a broad frequency range. Moreover, real part of the permittivity (ε′) reaches the maximum value of 16.90 at x = 0.6, and dielectric loss remains lower than 0.013 for frequencies below 0.7 GHz. Consequently, magnetic–dielectric materials prepared in this work are expected to have extensive application prospects for ultrahigh-frequency devices.     

炭材料中的组织

炭材料的基本结构单元是各向异性碳六角层面。基于择优取向的图型，炭材料中的纳米大小的组织（纳米组织）可发为沿面、轴向点的取向以及任意取向。从这种纳米组织的分类可以容易地了解到为什么炭材料能有如此多的形态，层片、纤维、球和不规则的粒子，以及为什么有如此宽广的性质。文中还简要地介绍了表征这些纳米组织的主要技术。     

Growth and Optical Properties of Quantized CdS Crystallites in TEOS Silica Xerogels

Quantized CdS crystallite-doped tetraethylorthosilicate (TEOS) silica xerogels are prepared by the sol-gel method. In this method, cadmium acetate [Cd(CH₃COO)₂2H₂O]-doped TEOS alcogel is formed by the hydrolysis and polycondensation of ethanolic TEOS in the presence of hydrochloric acid (HCl) and ammonium hydroxide (NH₄OH) catalysts and Cd(CH₃COO)₂.2H₂O. The CdS crystallites are formed in the alcogel by the reaction of Cd(CH₃COO)₂.2H₂O present in the gel and methanolic sodium sulfide (Na₂S), which is added over the alcogel. The effect of CdS/TEOS, EtOH/TEOS, S/Cd molar ratios, and temperature on the optical properties and CdS crystallite sizes in the xerogels are studied. A blue shift is observed in optical absorption spectra by decreasing the CdS/TEOS molar ratio from 2 × 10^–2 to 1 × 10^–4. It is observed that the crystallite size is increased from 1.6 to 3.4 nm by increasing the EtOH/TEOS molar ratio from 2 to 20, respectively, for a constant CdS/TEOS molar ratio of 5 × 10^–4. Emission spectra of xerogels are measured and found that the emission peak maxima shifted toward lower energies (higher wavelengths) by increasing the CdS/TEOS molar ratio in the xerogels. It is known from the X-ray diffraction (XRD) measurements of CdS-doped xerogels that the CdS crystallite structure in the xerogels is hexagonal wurtzite. The crystallite sizes were calculated from the XRD patterns and tight bonding calculations. There is a significant change in the color and size of CdS crystallite in the xerogels with a variation in temperature from 200 to 400°C.     

BaMnZnCoTi—W型铁氧体微波吸收特性的研究

对用Co2 + 、Ti4 + 置换Fe3 + 的BaMnZn -W型铁氧体的制备和微波吸收性能进行了分析研究 ,发现涂层厚为 1.0 6mm在 7.0～ 12 .0GHz频率范围内有 3个损耗吸收峰 ,峰值最高达 3 4dB以上 ;同时测量了复数磁导率 μ～( =μ′ -jμ″) ,复介电常数ε～( =ε′ -jε″) ,求出了磁损耗角正切tgδm 和介电损耗角正切tgδe,初步分析了 3个损耗吸收峰可能产生的机制。比较了在相同工艺条件下 ,随Co2 + 、Ti4 + 含量增加 ,铁氧体的吸收频率特性和涂层厚度的关系。     

Isobutane/2-butene alkylation on faujasite-type zeolites (H EMT and H FAU)

The alkylation of isobutane with 2-butene on hexagonal (protonated form = H EMT, investigated, for the first time on this reaction) and cubic faujasite (protonated form = H FAU) with Si/Al ratios of 3.5 was studied at 80°C and compared with the results obtained for a cerium exchanged Y zeolite (Ce Y). The alkylate composition consisted of 90% and about 80% C₈ paraffins for H EMT and H FAU/Ce Y, respectively. Within the C₈ fractions the three trimethylpentanes (TMP) 2,2,4-, 2,3,3- and 2,3,4-TMP were the dominating product compounds in all tests, whereas a higher content of dimethylhexanes (DMH) was observed for the H FAU and Ce Y. However, among the four trimethylpentanes 2,3,3,-TMP and 2,3,4-TMP were always the main compounds formed. Oligomerization was favoured only by the H FAU and Ce Y, with a strong increase of C₈ olefins after about one third of the observed reaction time. On the contrary, H EMT exhibited much less formation of C₈ olefins (and on a constant level) even after 300 min reaction time. The deactivated samples showed only formation of non-aromatic coke. The differences in the product pattern were attributed to the slightly larger size of the second type of supercage in EMT and to the stronger Bronsted acid sites in the hexagonal faujasite.Dedicated to Professor Dr. Martin Klessinger on the occasion of his 60th birthday.     

纳米晶金刚石的爆炸合成及超微金刚石的应用

爆炸合成的金刚万中存在一种具有纳米级亚晶的金刚石织构，它是由石墨经固态无扩散相变而成的，具有明显择优取向的纤维状组织。除常见的立方金刚石外，还存在一种六方金刚石，二者常共生于一个晶粒中。六方金刚石也是超硬材料之一，经碎化后的纳米级金刚石超微粉，是磁头、电接触头等耐磨性能要求高的材料中的良好的强化相。