烷烃—芳烃—N—甲酰吗啉体系液—液平衡研究

用液－液平衡釜测定了常压和58．8℃下正庚烷－苯－N－甲酰吧啉（NFM），甲基环已烷－苯－NFM，正庚烷－甲苯－NFM和甲基环已烷－甲苯－NFM4组三元体系的液－液平衡数据，用NRTL和UNIQUAC模型进行了关联，求得了它们的褶点，并对NFM溶剂存在下烷烃相对于芳烃的选择性进行了比较。     

Conversion of N2O to N2 on TiO2(1 1 0)

In this study, we examine the interaction of N₂O with TiO₂(1 1 0) in an effort to better understand the conversion of NO_x species to N₂ over TiO₂-based catalysts. The TiO₂(1 1 0) surface was chosen as a model system because this material is commonly used as a support and because oxygen vacancies on this surface are perhaps the best available models for the role of electronic defects in catalysis. Annealing TiO₂(1 1 0) in vacuum at high temperature (above about 800 K) generates oxygen vacancy sites that are associated with reduced surface cations (Ti³⁺ sites) and that are easily quantified using temperature programmed desorption (TPD) of water. Using TPD, X-ray photoelectron spectroscopy (XPS) and electron energy loss spectroscopy (EELS), we found that the majority of N₂O molecules adsorbed at 90 K on TiO₂(1 1 0) are weakly held and desorb from the surface at 130 K. However, a small fraction of the N₂O molecules exposed to TiO₂(1 1 0) at 90 K decompose to N₂ via one of two channels, both of which are vacancy-mediated. One channel occurs at 90 K, and results in N₂ ejection from the surface and vacancy oxidation. We propose that this channel involves N₂O molecules bound at vacancies with the O-end of the molecule in the vacancy. The second channel results from an adsorbed state of N₂O that decomposes at 170 K to liberate N₂ in the gas phase and deposit oxygen adatoms at non-defect Ti⁴⁺ sites. The presence of these O adatoms is clearly evident in subsequent water TPD measurements. We propose that this channel involves N₂O molecules that are bound at vacancies with the N-end of the molecule in the vacancy, which permits the O-end of the molecule to interact with an adjacent Ti⁴⁺ site. The partitioning between these two channels is roughly 1:1 for adsorption at 90 K, but neither is observed to occur for moderate N₂O exposures at temperatures above 200 K. EELS data indicate that vacancies readily transfer charge to N₂O at 90 K, and this charge transfer facilitates N₂O decomposition. Based on these results, it appears that the decomposition of N₂O to N₂ requires trapping of the molecule at vacancies and that the lifetime of the N₂O–vacancy interaction may be key to the conversion of N₂O to N₂.     

多弧物理气相沉积技术制备（TiAl）N超硬膜

主要介绍采用多弧物理气相沉积（ＰＶＤ）技术研制新型（ＴｉＡｌ）Ｎ超硬膜的工艺技术特点。对其膜层相结构、化学成分、显微组织等方面做了分析研究。结合工业生产实际应用进行了（ＴｉＡｌ）Ｎ与ＴｉＮ涂层刀具切削耐用度对比试验。     

A PRELIMINARY STUDY ON CRACK HEALING BEHAVIOUR OF Si3 N4 /SiC COMPOSITE CERAMICS

Ceramic (Si3 N4 /SiC) composites have been produced by sintering. From the sintered block, three point bend specimens were cut out. A semi-circular crack was made on the centre of the tension surface of the test specimen with the aid of a Vicker's indenter. The diameter of the semi-circular crack was about 60–70  μm. The specimens were subsequently heat treated at 1300°C for 1  h in vacuum, nitrogen or air. The bending strength was measured at room temperature, 800 and 1000°C. The specimens heat treated in air recovered considerably their bending strength at 1000°C, several specimens failed at a location different from the healed crack and their average strength showed the same value of that for smooth specimens. From these results, it is concluded that the recovery in bending strength of a cracked specimen was caused by crack healing.     

Lebensdauervorhersage auf Basis von Finite Elemente Ergebnissen

Fatigue Life Prediction Based on Finite Element Results The ever‐increasing pressure of competition leads to continuously decreasing product development cycle times. Therefore, information about the life time and the dimensioning of machine parts is required already in the early stages of development. Frequently, a weight optimization is desired, which implies that the local stress must come as close as possible to the strength limit for wide regions of the component under concern. This leads to an increasing use of simulation methods in design as well as in testing. For a life time prediction based on stress results from finite element computations, local S/N curves are needed, which frequently have to be deduced from S/N curves obtained from laboratory specimens. In the present contribution, the transferability from specimen S/N curves to component S/N curves is pointed out exemplarily by taking into account the influences of notches, component size, and microstructure of cast aluminum. Based on such S/N curves, which are computed for each material point in the component, the life time may be calculated by taking into account the local stresses and stress gradients obtained from finite element simulations.     

Highly efficient blue organic light‐emitting diode with high color purity using 4,4′‐N,N′‐dicarbazole‐biphyenyl (CBP) doped with 1,4‐bis[2‐(3‐N‐ethylcarbazoryl) vinyl]benzene (BCzVB)

Abstract— An efficient pure blue multilayer organic light‐emitting diode employing 1,4‐bis[2‐(3‐N‐ethylcarbazoryl)vinyl]benzene (BCzVB) doped into 4,4′‐N,N′‐dicarbazole‐biphyenyl (CBP) is reported. The device structure is ITO (indium tin oxide)/TPD (N,N′‐diphenyl‐N,N′‐bis (3‐methylphenyl)‐1,1′biphenyl‐4,4′diamine)/CBP:BCzVB/Alq₃ (tris‐(8‐hydroxy‐quinolinato) aluminum)/Liq (8‐hydroxy‐quinolinato lithium)/Al; here TPD was used as the hole‐transporting layer, CBP as the blue‐emitting host, BCzVB as the blue dopant, Alq₃ as the electron‐transporting layer, Liq as the electron‐injection layer, and Al as the cathode, respectively. A maximum luminance of 8500 cd/m² and a device efficiency of 3.5 cd/A were achieved. The CIE co‐ordinates were x = 0.15, y = 0.16. The electroluminescent spectra reveal a dominant peak at 448 nm and additional peaks at 476 nm with a full width at half maximum of 60 nm. The Föster energy transfer and, especially, carrier trapping models were considered to be the main mechanism for exciton formation on BCzVB molecules under electrical excitation.     

Synthesis and polymerization of anthracene‐based itaconimides

Two new anthracene‐based itaconimides, ie N‐(1‐ and 2‐anthryl) itaconimides, were synthesized by the reaction of aromatic amines with itaconic anhydride, followed by itaconamic acid imidization. The same reaction failed in the case of anthracene‐ring substitution at the position 9′. Radical and thermal polymerization of N‐(1‐ and 2‐anthryl) itaconimides led to polymers with anthracene pendant groups. No self‐polymerization by Diels–Alder cycloaddition of the itaconic function (dienophile) and anthracene nucleus (diene) was observed, as is the case for N‐(anthryl) maleimides and citraconimides. Copyright © 2004 Society of Chemical Industry     

不同结构聚芳醚的H2／N2透过选择性能

研究了一系列聚芳醚的Ｈ２／Ｎ２透过选择性能，详细讨论了温度和结构的系列变化对气体透过性能的影响。结果表明，此系列聚合物Ｈ２和Ｎ２的透过系数与聚合物的自由体积间有较好的线性相关性，通过结构变化以调节聚合物的自由体积，可以有效地控制聚合物的透Ｈ２系数和Ｈ２／Ｎ２选择系数。     

磁共振成像的信噪比：计量方法与影响因素

在临床上研究不同的MRI扫描技术时，必须要用信噪比这个参数来对图像的成像质量进行评价。最大限度地提高信噪比能有效地改善图像质量。本文描述了信噪比的常用计量方法及在临床磁共振成像扫描中选择不同的参数对信噪比的影响。     

Gas-driven hydrogen permeation in the surface-limited regime

Gas-driven permeation of hydrogen through metal membranes in the surface-limited regime (SLR) is analyzed. An analytical solution for the concentration and permeation flux as a function of time is given for permeation through the asymmetric membrane having different conditions on the inlet and outlet sides. The features of the steady state and transient permeation are discussed. Comparison of calculations with an experiment on deuterium permeation through vanadium, which is available from literature, is performed. It has been demonstrated that the parameters, extracted from the measurements of the permeation rate in SLR are very uncertain. Even the calculations with opposite asymmetries can be equally well adjusted to the experiment. Non-zero initial conditions in SLR experiments are additional source of uncertainty. Measurements of the accumulation in a closed volume instead of the permeation rate can seriously mislead in the interpretation of the experiment. Complementary experiments on permeation in two opposite directions and measurements of permeation decay could increase the reliability of the data obtained.