Study on the Growth and Photorefractive Properties of In：Fe：Cu：LiNbO3 Crystals

Fe(0.2 mol%):Cu(0.04 mol%):LiNbO3 crystals with different doping concentration of In3+ (0, 1.0, 2.0, 3.0mol%) were grown by Czochralski method, and then oxidized and reduced. The infrared transmittance spectra of crystals were measured to investigate the location of doping ion and its threshold concentration. The photorefractive properties of the crystals were tested by two beam coupling experiment. The results showed that the threshold concentration of In ions is 2.0～ 3.0 mol% and In ions take the place of NbL 4i+ to form ( In L2i+) before reaching its threshold concentration, and then the location of normal Nb ions. In the (2.0 mol%):Fe:Cu:LiNbO3 crystal with the oxidation treatment having the highest diffraction efficiency (η = 45.8%), the photo-damage resistance threshold value R of In(3.0 mol%):Fe:Cu:LiNbO3 was 3.67×104 W/cm2 which was two orders of magnitude higher than that of Fe:Cu:LiNbO3 crystal (4.30×102 W/cm2). And the photo-damage resistance ability was enhanced by oxidized treatment. The In(2.0～3.0 mol%):Fe:Cu:LiNbO3 crystals with oxidized treatment have the best photorefractive properties.     

Synthesis, Structure and Luminescent Properties of Polymeric Copper(Ⅰ) Halide Complexes Bearing Phosphine and N-donor Bridging Ligands

Three polymeric copper(Ⅰ) halide complexes bearing phosphine and N-donor bridging ligands, [(PPh3)2Cu2(μ-Br)2(μ-4,4'-bipy)]∞ 1 (bipy=bipyridine), [(PPh3)2Cu2(μ-Br)2(μ-bpe)]∞ 2 (bpe=trans-1,2-bis(4-pyridyl)ethene) and [(PPh3)2Cu2(μ-Cl)2(μ-bpe)]∞ 3, were synthesized by the multilayer diffusion method, and the structures were refined by single-crystal X-ray diffraction. Complex 1 crystallizes in triclinic, space group P-1 with a=9.122(3), b=9.322(3), c=13.201(4) (A),α=106.440(4), β=105.965(5), γ=94.167(5)°, V=1021.3(6) (A), Mr=967.62, Z=1,Dc=1.573 g/cm3, F(000)=486,μ=3.111 mm-1, the final R=0.0383 and wR=0.0960 for 2792observed reflections (I ＞ 2σ(Ⅰ)). Complex 2 crystallizes in triclinic, space group P-1 with a=9.420(3), b=10.209(4), c=12.407(4)(A), α=104.136(6), β=108.132(5), γ=95.338(6)°, V=1081.0(7)(A), Mr=496.83, Z=2, Dc=1.526 g/cm3, F(000)=500,μ=2.941 mm-1, the final R=0.0445 and wR=0.1117 for 3251 observed reflections (I＞ 2σ(Ⅰ)). Complex 3 crystallizes in triclinic,space group P-1 with a=8.32(1), b=11.53(2), c=13.94(3)(A), α=109.57(3), β=93.85(3), γ=97.28(3)°, V=1242(4)(A)3, Mr=1074.59, Z=1, Dc=1.436 g/cm3, F(000)=548,μ=1.279 mm-1,the final R=0.0786 and wR=0.1586 for 2266 observed reflections (I ＞ 2σ(Ⅰ)). The complexes exhibit intensive solid-state photoluminescence tentatively assigned to an admixture of triplet intraligand (IL) and metal-to-ligand charge-transfer (MLCT) excited state.     

A Cu(Ⅱ) Complex with IM-MeImz-к2 N,O Mode in [Cu(IM-MeImz)2]·(SCN)2: Synthesis, Crystal Structure and Magnetic Properties

A new copper(Ⅱ) compound with imino nitroxide radicals [Cu(IM-MeImz)2]·(SCN)2 (IM-meImz =2-(5-methylimidazol-4-yl)-4,4,5,5-tetramethyl-2-imidazoline-1-oxyl) has been synthesized and characterized structurally and magnetically. It crystallizes in monoclinic, space group P21/c with a = 9.3604(7), b = 10.3012(7), c = 16.6684(12) (A), β = 105.0290(10)°, V = 1552.25(19)(A)3, C24H34CuN10O2S2, Mr = 622.27, Z = 2, Dc = 1.331 g/cm3, μ(MoKα) = 0.876 mm-1, F(000) =650, the final R = 0.0374 and wR = 0.1079. X-ray analysis demonstrates that the IM-MeImz ligand is coordinated to the copper(Ⅱ) ion as an unusual didentate chelate with a κ2 N(MeImz),O(IM) mode in the complex. The square-planar coordination sites at Cu(Ⅱ) are occupied by two O and two N atoms from the imino nitroxide radicals. The complex molecules are connected as a onedimensional polymer structure by intermolecular interactions. Magnetic measurements show that there are intramolecular antiferromagnetic interactions between the Cu(Ⅱ) ion and radicals.     

制备方法对氧化镁负载的钼钒磷酸铜催化剂结构和催化性能的影响

在乙醇溶液中采用不同的浸渍方法制备了氧化镁负载的钼钒磷酸铜催化剂，利用XRD、IR和BET比表面测定等测试手段对催化剂进行了表征．XRD和IR表征结果表明，负载的钼钒磷酸铜在载体表面均匀分散，而且能够保持Keggin型结构．XRD和BET比表面测定结果说明，经12h浸渍制备的催化剂（H4PMo11VO40-CuO／MgO12H）化学和结构性能发生变化；其它两种方法制备的催化剂（H4PMo11VO40-CuO／MgO和Cu2PMo11VO40／MgO）没有化学和结构性能的变化，而且这两种催化剂具有相近的表征结果，说明两种催化剂具有相似的结构特征，以正己醇氧化脱氢生成正己醛反应评价了催化剂的催化反应性能，结果表明，H4PMo11VO40-CuO／MgO和Cu2PMO11VO40／MgO催化剂显示出比H4PM011VO40-CuO／MgO12H更高的催化反应活性。     

New isomeric states in 152,154,156Nd produced by spontaneous fission of 252Cf

Isomeric states have been observed in fission-fragments produced by spontaneous fission of ²⁵²Cf. These states are found in neutron rich nuclei of different structure and deformations. About 50 isomeric nuclei have been observed using coincidences between γ-rays identified in EUROGAM II and fission fragments detected in photovoltaic cells (SAPhIR). Lifetimes in the range from 20 ns to 2μs have been measured. Presented calculations based on HFB +D1S force on new measured isomeric states in the ^152,154,156Nd show evidence for K-isomers. Received: 3 November 1997 / Revised version: 15 December 1997     

Optical properties and structure of drawn polyethyleneterephtalate-polyethylene films

Films made by coextrusion of polyethyleneterephtalate and low density polyethylene exhibit specular reflection of light when stretched. Unlike the behaviour of films made of pure PET, where specular reflection is rare and does occur at extremely high stretching rates only, PET/LDPE films show specular reflection independent of the stretching rate.A film, containing 70% PET and 30% LDPE, prepared by coextrusion of the two components, has been investigated by scanning electron microscopy, light microscopy and by measuring the optical properties with a spectrophotometer. The (unstretched) as prepared sample has been compared with a sample stretched to =4.The optical measurements show as a result of the stretching a strong decrease of the transmittance and an increase of the remittance. While there is no drastic change of the dispersion (which is only slight), the increase of the refractive index indicates some straininduced crystallization.The scanning electron micrographs show long, needlelike voids and indicate a fractionation of the two components as a result of the stretching. This fractionation has been investigated by heating the samples up under the light microscope: while the stretched sample shows a separation of the components, the unstretched sample does not.Dedicated to Prof. Dr. F. H. Müller.     

NEW MATRIX RESINS FOR GLASS POLYALKENOATES OR GLASS-IONOMERS WITH PENDANT AMINO ACID RESIDUES

The monomers N-acryloyl (AGA) and N-methacryloylglutamic acid (MGA) have been prepared and copolymerized with acrylic acid (AA) and itaconic acid (IA) to make polyelectrolytes for evaluation in glass polyalkenoates or glass-ionomers. It was shown that poly(AA-co-IA-co-AGA) and poly(AA-co-IA-co-MGA), having a monomers ratio, respectively, of 7:3:3 could be formulated with glass powders used in Fuji II (GC America), α-Silver (DMG-Hamburg), α-Fil (DMG-Hamburg) and Ketac-Molar (ESPE, Seefeld, Germany) to produce conventional glass-ionomers with improved compressive strength (CS), flexural strength (FS) and fracture toughness (FT), compared to Fuji II, α-Silver, α-Fil and Ketac-Molar controls. Since MGA is much easier to produce in high yields than AGA, it was important to show that MGA could be used as well as AGA to produce new matrix resins for glass-ionomers. Furthermore, we demonstrated that both the 7:3:3 AGA and MGA copolymers could be reacted with 2-isocyanatoethyl methacrylate (IEM) to produce intermediates useful for formulating visible light-curable (VLC) glass-ionomers with improved CS, FS and FT, compared to two com-mercial VLC materials Fuji II^TM LC and Vitremer^TM Tricure. Here again, it was found that MGA could be used as well as AGA to prepare improved materials. We also demonstrated that poly(AA-co-MGA) could be used to formulate glass-ionomers with improved properties. Further, we demonstrated that small amounts of MGA could be used as a reactive diluent in VLC formulations such as Fuji II^TM LC, Vitremer^TM Tricure, and an experimental VLC formulation to improve their mechanical properties, adhesion to tooth structure, and fluoride release.     

Magic gaps and intruder levels in triaxially superdeformed nuclei

Nuclear shell model calculations based on a modified harmonic-oscillator potential result in amazingly stable triaxial nuclear shapes. Major gaps in the single-particle energy spectra at proton number 71 and neutron number 94 combine constructively at low and intermediate rotational frequencies. At high frequencies, gaps at proton number 72 and neutron number 97 combine in an equally favourable way. The sizes of the gaps may be as large as 35% of the values for the gaps at the classical magic numbers 50 and 82 at spherical shape. The dependence on the positions of the intruder levels in forming the gaps is discussed. Experimentally observed rotational bands in lutetium (Z = 71) and hafnium (Z = 72) appear in isotopes and frequency ranges, which are consistent with the gaps in the theoretical single-particle energy spectra.     

负泊松比材料研究进展

介绍了近年来材料科学的一大热点——负泊松比材料的研究概况，通过讨论负泊松比材料的微观结构与形变机理，阐述了该材料所具有的特殊物理机械性能，并通过与普通材料的性能的比较，指出了此类材料所具有的巨大应用前景和实用价值。     

丙烯基苯化合物改性双马来酰亚胺树脂 Ⅱ.改性树脂的固化及性能

用ＤＳＣ研究了ＢＰＰＤＰＳ改性ＢＭＩ树脂固化反应动力学，获得固化反应级数ｎ＝１．４，活化能Ｅ＝８１．２４ｋＪ／ｍｏｌ，以及树脂的固化工艺：１４０℃，１ｈ；１９０℃，２ｈ；２５０℃，４ｈ。测定了不同配比固化树脂的吸水率、玻璃化温度、热氧化性和弯曲性能，当树脂配比为１．５：１时，固化树脂表现优良的耐热性，特别是在耐热性方面，２３０℃弯曲强度保留达８２．４％，并用Ｆｒｉｅｄｍａｎ法推导出固化树脂的热降解反应活化能为２９０ｋＪ／ｍｏｌ，遵循一级反应。