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《自然科学进展(英文版)》2021,31(4):514-520
As a hydrogen storage material, palladium nanoparticle decorated nitrogen doped graphene (Pd/N-rGO) has drawn much attention owing to its high absorption capacity at moderate conditions. However, its hydrogen absorption-desorption cycle performance, which is essential for their practical application, has been rarely studied. In this paper, a simple and convenient high temperature thermal reduction method was used to synthesize nitrogen-doped graphene decorated with Pd nanoparticles (Pd/N-rGO). Taken it as a representative, the hydrogen absorption-desorption cycle performance of Pd/N-rGO was investigated. The results showed that after three cycles the hydrogen storage capacity dropped from 2.9 wt% to 0.8 wt% at 25 °C and 4 MPa pressure. It was found that the palladium nanoparticles shed from Pd/N-RGO sheet after cycle performance test, and then agglomerated. These phenomena will weaken the hydrogen spillover effect, leading to the decrease of hydrogen storage capacity. Meanwhile, decreased defects reduce the hydrogen absorption sites, which will thus deteriorate the hydrogen storage capacity. 相似文献
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依据焊接缺陷评定标准PD6493-8O,CVDA-84,JWES-2805,关于从球罐钻取的深埋夹杂与气孔的实验和金相研究,对于多台球罐最大表面裂纹的断裂力学评定,并鉴于修补这类缺陷占总修补量的70~80%,我们认为放宽气孔与夹杂的验收标准是妥当的 相似文献
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本文通过第一性原理计算在GGA + U 框架下系统地研究了非磁性掺杂剂(Li)和磁性掺杂剂(V)以及相应的点缺陷(VO/VSn)掺杂SnO2基稀磁半导体(DMS)的稳定性、电子结构、键合性质、磁性以及光学性质. 计算得到的形成能结果表明, V元素单掺杂体系比Li元素单掺杂体系更稳定. 其中, VO存在的掺杂体系稳定性更高, 而VSn对掺杂体系的稳定性不利. 磁性分析表明, Li掺杂体系的磁矩大于V掺杂体系的磁矩. 当有点缺陷存在时, VSn的加入显著提高了掺杂体系的磁性, 而VO对非磁性金属元素/磁性金属元素掺杂体系的磁性影响不同:当VO存在于Li掺杂体系时, Li原子周围的O原子自旋极化减少, 因此导致磁矩降低;当V掺杂体系中有VO存在, 磁性不仅来源于V原子的自旋极化, 同时来源于VO周围的O原子的自旋极化,因此磁矩增大. 结合电子结构分析可知, Li掺杂体系的磁性是由O-p和Li-p轨道之间的双交换作用产生的, V掺杂体系的磁性是由O-p和V-d轨道之间的双交换作用产生的. 键合分析发现VO的存在可以提高两种金属掺杂体系键(Li-O和V-O)的共价性. 在可见光区域内, Sn15LiO32和Sn15VO32具有较高的光学透明度. 以上这些结果为非磁性金属元素(Li)和磁性金属元素(V)及相应的点缺陷(VO/VSn)掺杂SnO2在自旋电子器件中的应用提供了新的思路. 相似文献
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钟建刚 《无锡职业技术学院学报》2003,2(4):9-10
由于瓶子的外形很特殊 ,在Pro/ENGINEER软件中进行三维造型设计 ,一般设计人员不易设计出来 ,即使能设计出来 ,瓶子上还存在某些缺陷 ,如 :不光滑、表面有凹坑等 ,实际企业要求设计的瓶子必须与实物一样 ,因而任务艰难 ,如何解决设计中的这类缺陷已成为设计者共同关注的问题。作者经过多次摸索和实践 ,找到了一些解决方法 ,以供大家分享。 相似文献
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李欣 《五邑大学学报(自然科学版)》1995,(2)
设计制造出适用于1511M型织机的自调式送经机构;经试用测试,与原送经机构相比,在减少织物云织、稀密路织疵方面效果显著。 相似文献
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目前非英语专业大学生的写作水平较低,主要存在教学、语言、非语言等几方面的缺陷,可以从课堂教学和课外辅导这两方面加以克服。 相似文献
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Roman Laptev Natalia Pushilina Egor Kashkarov Maxim Syrtanov Ekaterina Stepanova Andrey Koptyug Andrey Lider 《自然科学进展(英文版)》2019,29(4):440-446
The defect microstructure of the samples manufactured from Ti-6Al-4V powder was studied using electron beam melting (EBM) in the beam current range of 17 - 13 mA. The hybrid digital complex combined positron lifetime spectroscopy and coincidence Doppler broadening spectroscopy was used to characterize the defect structure of the materials. The microstructure and defects were also analyzed by transmission electron microscopy. It has been established that the main type of the defects in the EBM manufactured samples is dislocations. According to the conducted measurements and calculations, the dislocation density in the EBM manufactured samples exceeds by two orders the similar value for the cast Ti-6Al-4Valloy. Formation of Ti-Ti-Al nanoscale clusters has been found in the EBM manufactured samples. 相似文献
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