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排序方式: 共有233条查询结果,搜索用时 943 毫秒
51.
Yiming Niu Xi Liu Yongzhao Wang Song Zhou Zhengang Lv Liyun Zhang Wen Shi Yongwang Li Wei Zhang Dang Sheng Su Bingsen Zhang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(13):4276-4281
Controllable synthesis of well‐defined supported intermetallic catalysts is desirable because of their unique properties in physical chemistry. To accurately pinpoint the evolution of such materials at an atomic‐scale, especially clarification of the initial state under a particular chemical environment, will facilitate rational design and optimal synthesis of such catalysts. The dynamic formation of a ZnO‐supported PdZn catalyst is presented, whereby detailed analyses of in situ transmission electron microscopy, electron energy‐loss spectroscopy, and in situ X‐ray diffraction are combined to form a nanoscale understanding of PdZn phase transitions under realistic catalytic conditions. Remarkably, introduction of atoms (H and Zn in sequence) into the Pd matrix was initially observed. The resultant PdHx is an intermediate phase in the intermetallic formation process. The evolution of PdHx in the PdZn catalyst initializes at the PdHx/ZnO interfaces, and proceeds along the PdHx ?111? direction. 相似文献
52.
By using high resolution solid state nuclear magnetic resonance method, six coal samples coming from four countries were investigated.
Twelve structural parameters of these samples were measured and compared withthose of Chinese coals. Spectral editing experiment
was carried out and15N NMR spectrum was obtained.
Project supported by the National Natural Science Foundation of China (Grant No. 19774068)and the NEDO’s International Joint
Research Program of Japan. 相似文献
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54.
After being treated by mixed acids, single-walled carbon nanotubes (SWNTs) were shortened and had negatively charged groups
on the surface. Positively charged hemoglobin or myoglobin at pH 5.0 was successfully assembled with SWNTs into layer-by-layer
films on solid surfaces, designated as {SWNT/protein}
n
. While only those proteins in the first few bilayers closest to the electrode surface exhibited electroactivity, the {SWNT/protein}
n
films demonstrated a much higher fraction of electroactive proteins and better controllability in film construction compared
with cast films of the proteins and carbon nanotubes. The proteins in the {SWNT/protein}
n
films retained their near-native structure at medium pH. The stable protein film electrode showed good electrocatalytic properties
toward reduction of oxygen and hydrogen peroxide, demonstrating the potential application of the {SWNT/protein}
n
films as a new type of biosensor based on the direct electrochemistry of proteins without using mediators.
Figure Cyclic voltammograms at 0.2 V s−1 in pH 7.0 buffers with different number of bilayers (n) for layer-by-layer {single-walled carbon nanotube/hemoglobin}
n
films. 相似文献
55.
56.
以4,4'-对苯二甲酰二邻苯二甲酸酐(TDPA)为芳二酐单体,对苯二胺(PPD)为芳二胺单体,经低温溶液缩聚制得成膜性能优良的高相对分子质量聚酰胺酸(PAA),再经过热亚胺化制备双酮酐型聚酰亚胺(PI)薄膜。 采用傅里叶变换红外光谱仪(FT-IR)、广角X射线衍射(WAXD)、差示扫描量热仪(DSC)、动态热机械分析仪(DMA)、热重分析仪(TGA)、紫外-可见分光光度计(UV-Vis)及力学性能等技术手段表征了聚酰亚胺膜的结构和性能,考察了不同亚胺化温度对合成的双酮酐型聚酰亚胺膜性能的影响。 结果表明,经程序升温至320 ℃能使PAA热亚胺化基本趋于完成。 PI薄膜为部分有序聚集态结构,玻璃化转变温度(Tg)为298 ℃,具有优异的热性能,热失重温度(T5%)为523 ℃。 拉伸强度达到130 MPa,弹性模量为5.77 GPa。 PI薄膜紫外光透过截止波长为375 nm,在可见光区具有良好的透光性能及耐溶剂性能。 相似文献
57.
MAPO-5分子筛的合成、结构及其性质的研究 总被引:3,自引:0,他引:3
用水热法合成了磷酸镁铝分子筛(MAPO-5),以X射线衍射、电子探针、核磁共振及红外光谱等方法进行了结构分析,并测定了MAPO-5分子筛的晶胞参数、化学组成,同时对分子筛的吸附性能、热稳定性、酸性等进行了研究。证明镁进入了分子筛的骨架。 相似文献
58.
59.
60.
介绍了自行研制的用于动态核极化实验的固体高分辨CP/MAS探头,给出了典型含自由基固体样品的DNP增强高分辨NMR谱.并对动态核极化实验中的技术问题进行了讨论,提出了相应的解决方法. 相似文献