排序方式: 共有11条查询结果,搜索用时 15 毫秒
1.
用稀土化合物改性的钛系载体催化剂(SN催化剂)进行苯乙烯和丙烯顺序嵌段共聚合(Sequentialblockcopolymerization)的研究.考察了苯乙烯预聚时间、单体比、外加给电子体(EB)、烷基铝浓度、催化剂浓度和聚合温度等条件对共聚合的影响.发现外加酯(EB)降低了共聚合反应催化活性,在EB/Ti摩尔比为5范围内,外酯有助于提高嵌段共聚物(iPS—b—iPP)中PS段和PP段的等规度及增加苯乙烯链节含量.SN型催化剂对苯乙烯一丙烯嵌段共聚合有较高的催化活性,催化效率在100g聚合物/g-Ti以上.共聚物通过溶剂革取分级除去均聚物后,所得嵌段共聚物中苯乙烯链节含量可在15~85mol%之间调节.其结构表征续见第II报. 相似文献
2.
Christoph Peschel Stefan van Wickeren Yves Preibisch Verena Naber Denis Werner Lars Frankenstein Dr. Fabian Horsthemke Prof. Dr. Urs Peuker Prof. Dr. Martin Winter Dr. Sascha Nowak 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(22):e202200485
Herein we report on an analytical study of dry-shredded lithium-ion battery (LIB) materials with unknown composition. Samples from an industrial recycling process were analyzed concerning the elemental composition and (organic) compound speciation. Deep understanding of the base material for LIB recycling was obtained by identification and analysis of transition metal stoichiometry, current collector metals, base electrolyte and electrolyte additive residues, aging marker molecules and polymer binder fingerprints. For reversed engineering purposes, the main electrode and electrolyte chemistries were traced back to pristine materials. Furthermore, possible lifetime application and accompanied aging was evaluated based on target analysis on characteristic molecules described in literature. With this, the reported analytics provided precious information for value estimation of the undefined spent batteries and enabled tailored recycling process deliberations. The comprehensive feedstock characterization shown in this work paves the way for targeted process control in LIB recycling processes. 相似文献
3.
采用微波辅助法制备了氧化铜(CuO)材料,其结晶度好,没有杂质,呈现片层堆叠而成的块状结构.以CuO材料修饰玻碳电极作为工作电极(CuO/GCE),饱和甘汞电极作为参比电极,铂丝电极作为对电极,在碱性条件下对葡萄糖溶液进行电化学性能检测.该传感器对520 nM到2.0 mM浓度范围内的葡萄糖溶液实现了优良的检测性能,灵敏度为2491.362μA·cm-2·mM-1,检测限为216 nM(S/N=3),在2 s内就可以完成反应.丙烯酸等物质对传感器的影响可以忽略,具有良好的抗干扰性. 相似文献
4.
Stroman PW Krause V Frankenstein UN Malisza KL Tomanek B 《Magnetic resonance imaging》2001,19(6):827-831
Blood-oxygen level dependent signal changes in the visual cortex were investigated as a function of echo time with spin-echo and gradient-echo EPI at 1.5 T and 3 T. The linear relationship between the fractional signal change and the echo time was apparent in all cases. Relaxation rate changes determined from the slope of this linear relation agree with published values, intercept values extrapolated to an echo time of zero, however, were 0.66% to 1.0% with spin-echo EPI, and 0.11% to 0.35% with gradient-echo EPI. Spin-echo and gradient-echo EPI can therefore yield similar signal changes at sufficiently short echo times. 相似文献
5.
Characterization of contrast changes in functional MRI of the human spinal cord at 1.5 T 总被引:5,自引:0,他引:5
Stroman PW Krause V Malisza KL Frankenstein UN Tomanek B 《Magnetic resonance imaging》2001,19(6):833-838
Contrast changes observed in functional magnetic resonance imaging in the human spinal cord were investigated with both motor and sensory tasks over a range of echo times. Data were acquired using a single-shot fast spin-echo sequence at 1.5 Tesla. Data were analyzed with two different correlation thresholds and the effects of altering the order of repeated experiments was also investigated. Plots of the fractional signal change as a function of echo time yielded linear functions with slopes corresponding to relaxation rate changes of -0.30 sec(-1) with sensory stimulation and approximately -0.50 sec(-1) with a motor task. However, the fractional signal change extrapolated to an echo time of zero was significantly greater than zero in each case and was roughly 2.5%. This suggests that in addition to the BOLD effect there is a baseline signal change which occurs concomitant to neuronal activation in the spinal cord. 相似文献
6.
Design of novel substituted phthalocyanines; synthesis and fluorescence,DFT, photovoltaic properties
Mehmet Salih AIRTA Derya GÜNG
RDÜ SOLUN Ümit YILDIKO Abdullah
ZKARTAL 《Turkish Journal of Chemistry》2020,44(6):1574
The 4-(2-[3,4-dimethoxyphenoxy] phenoxy) phthalonitrile was synthesized as the starting material of new syntheses. Zinc, copper, and cobalt phthalocyanines were achieved by reaction of starting compound with Zn(CH3COO)2, CuCl2, and CoCl2 metal salts. Basic spectroscopic methods such as nuclear magnetic resonance electronic absorption, mass and infrared spectrometry were used in the structural characterization of the compounds. Absorption, excitation, and emission measurements of the fluorescence zinc phthalocyanine compound were also investigated in THF. Then, structural, energy, and electronic properties for synthesized metallophthalocyanines were determined by quantum chemical calculations, including the DFT method. The bandgap of HOMO and LUMO was determined to be chemically active. Global reactivity (I, A, η, s, μ, χ, ω) and nonlinear properties were studied. In addition, molecular electrostatic potential (MEP) maps were drawn to identify potential reactive regions of metallophthalocyanine (M-Pc) compounds. Photovoltaic performances of phthalocyanine compounds for dye sensitive solar cells were investigated. The solar conversion efficiency of DSSC based on copper, zinc, and cobalt phthalocyanine compounds was 1.69%, 1.35%, and 1.54%, respectively. The compounds have good solubility and show nonlinear optical properties. Zinc phthalocyanine gave fluorescence emission. 相似文献
7.
酶促合成全氟辛酸半乳糖脂 总被引:4,自引:1,他引:4
首次报道了酶促合成含氟糖脂。在IM-60脂肪酶催化下以85%产率得到了全氟辛酸半乳糖脂。 相似文献
8.
Functional magnetic resonance imaging of the human cervical spinal cord with stimulation of different sensory dermatomes 总被引:8,自引:0,他引:8
Functional MR imaging (fMRI) of the cervical spinal cord was carried out in 13 healthy volunteers. A cold stimulus was applied, at different times, to three different sensory dermatome regions overlying the right hand and forearm: the thumb side of the palm, the little finger side of the palm, and the forearm below the elbow. Stimulation of these areas is expected to involve the 6(th), 8(th), and 5(th) cervical spinal cord segments respectively. Whereas true activations are expected to correspond to the region being stimulated, false activations such as arising from noise and motion, are not. The results demonstrate that clustering of active pixels into groups based on their intensity time courses discriminates false activations from true activations. Following clustering, the distribution of activity observed with fMRI matched the expected regions of neuronal activation with the different areas of stimulation on the hand and forearm. 相似文献
9.
10.
In order to study the effect of substitution of Fe3+ by Al3+ and Cr3+ in Li0.5Fe2.5O4 on its structural and magnetic properties, the spinel system Li0.5Al x Cr x Fe2.5?2x O4 (x=0.0, 0.2, 0.4, 0.5, 0.6 and 0.8) has been characterized by X-ray diffraction, high field magnetization, low field ac susceptibility and 57Fe Mossbauer spectroscopy. Contrary to the earlier reports, about 50% of Al3+ is found to occupy the tetrahedral sites. The system exhibits canted spin structure and a central paramagnetic doublet was found superimposed on magnetic sextet in the Mössbauer spectra (x>0.5). 相似文献