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聚芳醚酮链扩展单体及单分散齐聚物的分子结构研究 总被引:1,自引:1,他引:0
为了全面表征聚芳醚酮齐聚物及高聚物分子结构,本文合成了系列链扩展单体及单分散齐聚物,以13C NMR对其在DMSO-d6(或DMSO-d6+CDCl3),及H2SO4-d2(或H2SO4)中进行对比研究,表明:它们溶于H2SO4时,分子结构发生明显极化.量子化学计算及动态13C NMR研究表明,极化是H2SO4的正极性磺酸基诱导分子链的氧原子电荷进而诱导芳环电子离域产生的,而非磺化所致.说明极化有普遍意义并提出标题化合物的极化方式,其实际意义明确. 相似文献
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本文使用密度泛函理论(density functional theory, DFT)中的广义梯度近似(generalized gradient approximation, GGA)研究了经碱金属原子Li、过渡金属原子Ti和Fe原子修饰的富勒烯C18B2M(M=Li, Ti, Fe)的储氢性能. 研究发现, C18B2由于B的替代掺杂, 比C20对金属原子具有更高的结合能. 由平均吸附能分析可知: C18B2Li对H2的吸附能力较弱, C18B2Fe对H2的吸附能力过强, 而C18B2Ti对H2的平均吸附能介于0.45-0.59 eV 之间, 介于物理吸附和化学吸附之间 (0.2-0.6 eV), 因此可以实现常温下的可逆储氢. C18B2M(M=Li, Ti, Fe)能够吸附的H2数目最多分别为4, 6和4. 由储氢机理分析可知: C18B2Li主要通过碱金属离子激发的静电场来吸附H2, 而C18B2Ti和C18B2Fe主要通过金属原子与H2之间的Kubas作用来吸附H2. 由于C18B2Ti既有较大的储氢数目, 又可以实现可逆储氢, 因此有望开发成新型纳米储氢材料. 相似文献
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随着石墨烯材料的发现,二维材料被人们广泛认识并逐渐应用,相比于传统二维材料,二维过渡金属碳化物(MXene)的力学、磁学和电学性能更加优异.本文分别利用HF溶液和LiF/HCl溶液刻蚀Ti3AlC2获得了Ti3C2Tx样品,通过电子扫描显微镜(SEM)、X射线光电子能谱(XPS)和气敏特性分析,研究了刻蚀剂对Ti3C2Tx材料结构和气敏性能的影响.材料结构分析表明:HF和LiF/HCl刻蚀剂均对Ti3C2Tx材料具有良好的刻蚀效果;气敏性能结果表明:LiF/HCl刻蚀剂制备的Ti3C2Tx的气敏性能优于HF刻蚀剂,并实现了室温下宽范围、较高灵敏和较高稳定地检测NH3.分析认为:LiF/HCl溶液刻蚀制备的Ti3C2T<... 相似文献
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对高品质单相多晶Bi2Sr2CaCu2O8+δ样品作真空或H2气氛中不同温度下的热处理。由X射线结构分析,其正常态和超导态性质(特别是载流子浓度)的系统测量结果表明:Bi2Sr2CaCu208+δ样品在H2气氛中热处理,其氧的释放可分为两个阶段:一是Bi-O层之间的过量氧原子的逸出,降低系统的载流子浓度,从而调节Tc;二是CuO2面内氧原子的迁移,产生氧空位,使CuO2面内Cu2+的短程二维反铁磁(2D-AFM)有序背景遭到破坏。可以认为:以往文献中报道的Bi2Sr2CaCu2O8+δ超导体的吸氢效应导致Tc的变化,很可能主要的并不是氢原子的电子掺杂行为,而是与吸氢过程中氧含量的变化相联系。
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采用辉光放电技术和等离子体质谱诊断技术,研究了H2/C4H8混合气体等离子体中正离子成分及主要正离子能量随射频功率的变化规律,并分析了H2/C4H8混合气体主要的离解机理和形成过程.研究表明:随着射频功率的增加,碳氢碎片离子的浓度增加,在20 W时达到最大值,25 W后有所减小.当射频功率小于10 W时,H2/C4H8混合气体等离子体中C4H9+相对浓度最大,当功率大于或等于10 W时,C3H3+相对浓度最大.随着射频功率的增大,碳氢碎片离子的能量逐渐增加.对H2/C4H8混合气体等离子体的组成与能量进行的定性分析,将为H2/C4H8混合气体辉光放电聚合物涂层工艺参数优化提供参考. 相似文献
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Bijun Fang Renbing Sun Keitaro Tezuka 《Journal of Physics and Chemistry of Solids》2009,70(5):893-899
Phase pure perovskite (1−x−y)Pb(Ni1/3Nb2/3)O3-xPb(Zn1/3Nb2/3)O3-yPbTiO3 (PNN-PZN-PT) ferroelectric ceramics were prepared by conventional solid-state reaction method via a B-site oxide mixing route. The PNN-PZN-PT ceramics sintered at the optimized condition of 1185 °C for 2 h exhibit high relative density and rather homogenous microstructure. With the increase of PbTiO3 (PT) content, crystal structure and electrical properties of the synthesized PNN-PZN-PT ceramics exhibit successive phase transformation. A morphotropic phase boundary (MPB) is supposed to form in (0.9−x)PNN-0.1PZN-xPT at a region of x=32-36 mol% confirmed by X-ray diffraction (XRD) measurement and dielectric measurement. The MPB composition can be pictured as providing a “bridge” connecting rhombohedral ferroelectric (FE) phase and tetragonal one since crystal structure of the MPB composition is similar to both the rhombohedral and tetragonal lattices. Dielectric response of the sintered PNN-PZN-PT ceramics also exhibits successive phase-transition character. 0.64PNN-0.1PZN-0.26PT exhibits broad, diffused and frequency dependent dielectric peaks indicating a character of diffused FE-paraelectric (PE) phase transition of relaxor ferroelectrics and 0.40PNN-0.1PZN-0.50PT exhibits narrow, sharp and frequency independent dielectric peaks indicating a character of first-order FE-PE phase transition of normal ferroelectrics. The FE-PE phase transition of 0.56PNN-0.1PZN-0.34PT is nearly first-order with some diffused character, which also exhibits the largest value of piezoelectric constant d33 of 462pC/N. 相似文献
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P. Günter R. Sanctuary F. Rohner H. Arend W. Seidenbusch 《Solid State Communications》1981,37(11):883-888
Temperature dependences of the dielectric constants ?i and of the birefringences Δni for light propagation directions along all the three crystallographic axes (i = a, b, c) have been measured between 5 and 350 K. The optical measurements clearly reveal a new phase transition at TL = 75 K, below which the crystal structure is transformed from the ferroelectric Pna21 phase into an unknown low temperature phase, possibly the monoclinic space group P1121. Small peaks in the dielectric constants ?a and ?b have been observed at this transition temperature. 相似文献
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Co3V 2O8 is a spin- 3/2 system on a Kagomé staircase and is known to undergo two magnetic phase transitions between 6 and 11 K. The H-T phase diagram of Co3V 2O8 derived by magnetization measurements on a single crystal is presented. Additionally both ordered magnetic structures were investigated by neutron powder diffraction experiments and solved using Bertaut’s macroscopic theory. For the ferromagnetic phase the magnetic moments of the Co2+ ions were found to be 1.5(3)μB and 2.7(1)μB at 3.5 K along the crystallographic a axis for the (4a) and (8e) sites, respectively. The antiferromagnetic phase exhibits a magnetic cell with a doubled b axis with respect to the nuclear one. The magnetic moments point along the a axis being 1.8(2)μB (4a) and 1.8(1)μB (8e) at 8 K. 相似文献
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We have systematically investigated the doping effect on the Bi2Sr2Ca2Cu3Oy superconductive material. After entering into the crystal lattice, Pb and/or Sb atoms cause not only variations of the temperature condition during the sample preparation process, but also variations of structures and superconductivity. By analyzing the experimental results, we have come to the conclusion that the Pb and/or Sb atoms enter into the Bi-O planes, preferably occupy the sites of Bi ions, regulate the crystal structures and the distribution of oxygen ions in Bi-O planes and nearby lattice sites, thus benefiting the formation of the high-Tc phase and improving the superconductivity. 相似文献
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The electronic structure and magnetic properties of the Heusler compound Co2ScP have been investigated by the generalized gradient approximation based on density functional theory. The results show that the ground state phase of the Co2ScP compound possesses AlCu2Mn-type crystal structure and exhibits half-metallic ferrimagnetism. The total spin moment is 2 μB at the equilibrium lattice constant a0=5.83 Å, which agrees with the Slater–Pauling rule. The spin-up electrons are metallic, but the spin-down bands are semiconductor with a gap of 0.55 eV, and the spin-flip gap is of 0.07 eV. 相似文献
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Magnetic structures and magnetocrystalline anisotropy (MCA) of tetragonal phase Fe3Pt with an L12 atomic ordering in bulk and thin film are investigated by means of the first-principles full-potential linearized augmented plane-wave method. The results obtained predict that the tetragonal phase, in which the tetragonal distortion with (c/a) = 0.95 makes an asymmetry of magnetic properties along the c-axis (out-of-plane) and a-axis (in-plane), has an out-of-plane MCA. In addition, from the thin film calculations, the presence of surface is found to strongly enhance the out-of-plane MCA. 相似文献