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排序方式: 共有729条查询结果,搜索用时 15 毫秒
31.
Egor A. Kapitonov Natalia N. Petrova Vasilii V. Mukhin Leonid A. Nikiforov Vladimir D. Gogolev Ee Le Shim Aitalina A. Okhlopkova Jin-Ho Cho 《Molecules (Basel, Switzerland)》2021,26(4)
The physical and mechanical properties of nitrile–butadiene rubber (NBR) composites with N-cetylpyridinium bromide-carbon black (CPB-CB) were investigated. Addition of 5 parts per hundred rubber (phr) of CPB-CB into NBR improved the tensile strength by 124%, vulcanization rate by 41%, shore hardness by 15%, and decreased the volumetric wear by 7% compared to those of the base rubber-CB composite. 相似文献
32.
In the present investigation, the indentation study on the high-energy ball-milled nanocrystalline Al5Fe2 intermetallic compound has established the inverse Hall–Petch (IHP) behaviour. The structural characterisation of the milled powder particles by X-ray diffraction (XRD) and transmission electron microscopy has shown the evolution of nanocrystalline phase. Micro-indentation measurements have revealed the increase in hardness with decreasing grain size, reaching to a maximum of 9.0 ± 0.3 GPa up to a grain size of 32 ± 4 nm, followed by a decrease. The decrease in hardness with further refinement, an indication of grain size softening, demonstrates the IHP-like behaviour. The deviation from the Hall–Petch behaviour has been discussed using various models based on the dislocations and grain boundary-mediated processes. From the analysis, it appears that the model based on mesocopic grain boundary sliding phenomena is more appropriate to account for the observed grain size softening. 相似文献
33.
The preparation of the cerium and europium co-doped YAG materials as well as the study for their synthesis and emitting mechanism of the energy transfer between Ce3+ and Eu3+ were investigated in the present study. YAG:Ce3+, Eu3+ powders were synthesized using a high-energy ball milling method in different sintering temperature and atmosphere: air and H2/N2. The effects of the synthesis procedure on the crystallinity, morphology, structure, and luminescence spectra were examined by X-ray diffraction, field emission-scanning electron microscopy, and photoluminescence spectroscopy. The europium co-doped YAG:Ce3+ phosphors is improved the chromaticity coordinates. 相似文献
34.
Christian Schumacher Dr. José G. Hernández Prof. Dr. Carsten Bolm 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(38):16499-16502
The formation and regeneration of active CuI species is a fundamental mechanistic step in copper-catalyzed atom transfer radical cyclizations (ATRC). Typically, the presence of the catalytically active CuI species in the reaction mixture is secured by using high CuI catalyst loadings or the addition of complementary reducing agents. In this study it is demonstrated how the piezoelectric properties of barium titanate (BaTiO3) can be harnessed by mechanical ball milling to induce electrical polarization in the strained piezomaterial. This strategy enables the conversion of mechanical energy into electrical energy, leading to the reduction of a CuII precatalyst into the active CuI species in copper-catalyzed mechanochemical solvent-free ATRC reactions. 相似文献
35.
36.
Vnia Andr M. Teresa Duarte Clara S. B. Gomes Mafalda C. Sarragua 《Molecules (Basel, Switzerland)》2022,27(1)
In Portugal, publications with mechanochemical methods date back to 2009, with the report on mechanochemical strategies for the synthesis of metallopharmaceuticals. Since then, mechanochemical applications have grown in Portugal, spanning several fields, mainly crystal engineering and supramolecular chemistry, catalysis, and organic and inorganic chemistry. The area with the most increased development is the synthesis of multicomponent crystal forms, with several groups synthesizing solvates, salts, and cocrystals in which the main objective was to improve physical properties of the active pharmaceutical ingredients. Recently, non-crystalline materials, such as ionic liquids and amorphous solid dispersions, have also been studied using mechanochemical methods. An area that is in expansion is the use of mechanochemical synthesis of bioinspired metal-organic frameworks with an emphasis in antibiotic coordination frameworks. The use of mechanochemistry for catalysis and organic and inorganic synthesis has also grown due to the synthetic advantages, ease of synthesis, scalability, sustainability, and, in the majority of cases, the superior properties of the synthesized materials. It can be easily concluded that mechanochemistry is expanding in Portugal in diverse research areas. 相似文献
37.
Let fs,t(m,n) be the number of (0,1) - matrices of size m x n such that each row has exactly s ones and each column has exactly t ones (sm = nt). How to determine fs,t(m,n)? As R. P. Stanley has observed (Enumerative CombinatoricsⅠ(1997), Example 1.1.3), the determination of fs,t(m, n) is an unsolved problem, except for very small s, t. In this paper the closed formulas for f2,2(n,n), f3,2(m,n), f4,2(m,n) are given. And recursion formulas and generating functions are discussed. 相似文献
38.
Lydia A. Panther Dr. Daniel P. Guest Dr. Andrew McGown Hugo Emerit Dr. Raysa Khan Tareque Dr. Arathy Jose Mr. Chris M. Dadswell Dr. Simon J. Coles Dr. Graham J. Tizzard Dr. Ramón González-Méndez Dr. Charles A. I. Goodall Prof. Mark C. Bagley Prof. John Spencer Dr. Barnaby W. Greenland 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(49):e202201444
Solvent-free synthesis by using a vibratory ball mill (VBM) offers the chance to access new chemical reactivity, whilst reducing solvent waste and minimising reaction times. Herein, we report the core functionalisation of N,N’-bis(2-ethylhexyl)-2,6-dibromo-1,4,5,8-naphthalenetetracarboxylic acid (Br2-NDI) by using Suzuki, Sonogashira and Buchwald–Hartwig coupling reactions. The products of these reactions are important building blocks in many areas of organic electronics including organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs) and organic photovoltaic cells (OPVCs). The reactions proceed in as little as 1 h, use commercially available palladium sources (frequently Pd(OAc)2) and are tolerant to air and atmospheric moisture. Furthermore, the real-world potential of this green VBM protocol is demonstrated by the double Suzuki coupling of a monobromo(NDI) residue to a bis(thiophene) pinacol ester. The resulting dimeric NDI species has been demonstrated to behave as an electron acceptor in functioning OPVCs. 相似文献
39.
原子荧光光谱法测定固体废弃物——氧化皮中的砷 总被引:1,自引:0,他引:1
建立了固体废弃物——氧化皮中砷的测定方法。氧化皮粉末样品经盐酸溶解,在溶液中添加硫脲和抗坏血酸预还原砷,以盐酸(2+98)为载流,硼氢化钠(10g/L)和氢氧化钾(5g/L)混合溶液为还原剂,砷与硼氢化钠、盐酸反应生成砷化氢,砷化氢利用氩气导入石英炉原子化器中原子化,以空心阴极灯为激发光源,测量砷产生的荧光强度。测试氧化皮中砷含量的相对标准偏差为不大于4.8%,检出限为0.12μg/L,回收率为97%~103%,结果准确度较好。方法具有试剂消耗少、快速、检出限低的优点。 相似文献
40.