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421.
Mechanical alloying has been used to produce nanocrystalline samples of Co2CrAl Heusler alloys. The samples were characterized by using different methods. The results indicate that, it is possible to produce L21-Co2CrAl powders after 15 h of ball-milling. The grain size of 15 h ball milled L21-Co2CrAl Heusler phase, calculated by analyzing the XRD peak broadening using Williamson and Hall approach was 14 nm. The estimated magnetic moment per formula unit is ∼2 μB. The obtained magnetic moment is significantly smaller than the theoretical value of 2.96 μB for L21 structure. It seems that an atomic disorder from the crystalline L21-type ordered state and two-phase separation depresses the ferromagnetic ordering in alloy. Also, the effect of annealing on the structural and magnetic properties of ball milled powders was investigated. Two structures were identified for annealed sample, namely L21 and B2. The obtained value for magnetic moment of annealed sample is smaller than the as-milled sample due to the presence of disordered B2 phase and improvement of phase separation. 相似文献
422.
用高能球磨法制备铁与聚苯乙烯纳米复合材料,对其组分采用穆斯堡尔谱和X衍射谱分析,结果表明复合材料中有Fe5C2和Fe2C生成,略有部分Fe氧化.电镜照片表明球磨后复合材料的颗粒平均尺寸约为50nm. 相似文献
423.
424.
Erika Dutkov María Jesús Sayagus Martin Fabin Matej Bal Jaroslav Kov
Jaroslav Kov
Junior Martin Stahorský Marcela Achimovi
ov Zdenka Luk
ov Bujkov 《Molecules (Basel, Switzerland)》2023,28(1)
Copper, antimony and sulfur in elemental form were applied for one-pot solid-state mechanochemical synthesis of skinnerite (Cu3SbS3) in a laboratory mill and an industrial mill. This synthesis was completed after 30 min of milling in the laboratory mill and 120 min in the industrial mill, as corroborated by X-ray diffraction. XRD analysis confirmed the presence of pure monoclinic skinnerite prepared in the laboratory mill and around 76% monoclinic skinnerite, with the secondary phases famatinite (Cu3SbS4; 15%), and tetrahedrite (Cu11.4Sb4S13; 8%), synthesized in the industrial mill. The nanocrystals were agglomerated into micrometer-sized grains in both cases. Both samples were nanocrystalline, as was confirmed with HRTEM. The optical band gap of the Cu3SbS3 prepared in the laboratory mill was determined to be 1.7 eV with UV–Vis spectroscopy. Photocurrent responses verified with I–V measurements under dark and light illumination and Cu3SbS3 nanocrystals showed ~45% enhancement of the photoresponsive current at a forward voltage of 0.6 V. The optical and optoelectrical properties of the skinnerite (Cu3SbS3) prepared via laboratory milling are interesting for photovoltaic applications. 相似文献
425.
借助X射线衍射应力分析仪、球-盘式滑动摩擦磨损试验机以及扫描电子显微镜等工具,考察了已加工表面的残余应力场与X射线衍射线半高宽分布特征,研究了高强度钢工件高速切削强化表面的摩擦学性能,探讨了强化表面的摩擦学性能与表面强化特征指标间的相关性.结果表明:合理的高速切削强化工艺能够有效提高高强度钢材料的滑动摩擦学性能;残余压应力场的作用深度是决定加工表面摩擦学性能的关键强化特征指标;位错密度增加和晶粒细化是提高强化表面耐磨性能的主要因素;高速切削强化表面的主要磨损机理为磨粒磨损、塑变磨损以及疲劳磨损等磨损机理. 相似文献
426.
427.
Prof. Dr. Mohamed Mokhtar Dr. Ghalia Alzhrani Prof. Dr. Elham S. Aazam Prof. Dr. Tamer S. Saleh Dr. Sulaiman Al-Faifi Dr. Subir Panja Prof. Dr. Debabrata Maiti 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(34):8875-8885
Herein, we report the synthesis of nickel-layered double hydroxide amalgamated Y-zeolite (NiLDH@YZ) hybrids and the evaluation of the synergistic effect of various NiLDH@YZ catalysts and mechanochemical agitation on Glaser homocoupling reactions. Nitrogen adsorption-desorption experiments were carried out to estimate the surface area and porosity of NiLDH@YZ hybrids. The basicity and acidity of these hybrids were determined by CO2-TPD and NH3-TPD experiments respectively and this portrayed good acid-base bifunctional feature of the catalysts. The NiLDH@YZ-catalyzed mechanochemical Glaser coupling reaction achieved best yield of 83 % for the 0.5NiLDH@0.5YZ hybrid after 60 min of agitation, which revealed the highest acid-base bifunctional feature compared to all the investigated catalysts. The developed catalyst has proven itself as a robust and effective candidate that can successfully be employed up to four catalytic cycles without significant loss in catalytic activity, under optimized reaction conditions. This work demonstrated a new strategy for C−C bond formation enabled by the synergy between mechanochemistry and heterogeneous catalysis. 相似文献
428.
《Mendeleev Communications》2021,31(5):647-650
Carbon quantum dots (CQDs) with an average diameter of 3 nm, exhibiting blue photoluminescence, have been obtained from commercial conductive carbon black by a cost-effective and straightforward exfoliation method using dry ball milling in the presence of sodium carbonate. As a secondary abrasive medium, sodium carbonate provides effective exfoliation of carbon black with a high degree of CQD graphitization and plays an essential role in the functionalization of CQDs with oxygen groups. Due to the low toxicity of CQDs against HeLa cancer cells (cell viability above 90% at a CQD concentration of 200 μg cm−3) and the ability to penetrate cells and emit blue light, CQDs are possibly suitable for biological imaging of cells. 相似文献
429.
《Mendeleev Communications》2023,33(3):287-301
In response to rising environmental concerns, chemistry is experiencing a considerable change in both concepts and practices to adopt more efficient and sustainable technologies. One of the alternative technologies that offer many advantages over the conventional solution-based techniques is mechanochemistry which utilizes mechanical energy to induce chemical reactions. Despite the fact that mechanochemistry has reached high significance in the creation of advanced materials, such as alloys, ceramics, electrode materials, and nanocomposites, in the field of small molecule synthesis its potential remains largely untapped. This review highlights the opportunities and prospects of different mechanochemical tools in the synthesis of organometallic compounds, including transition metal complexes with N-heterocyclic carbene, arene, and cyclopentadienyl ligands, monometallacyclic and pincer derivatives, as well as main group metal compounds (e.g., allyl complexes and the Grignard reagents). Many important organometallic transformations such as C–H bond metalation, transmetalation, and oxidative addition can be successfully implemented under mechanochemical conditions in a highly productive and energy-saving manner. Furthermore, the postmodification of metal-containing species upon grinding or milling is shown to be a powerful route to both new discrete metal complexes and different supramolecular architectures (metal-containing organic cages, macrocylces, networks). 相似文献