共查询到19条相似文献,搜索用时 78 毫秒
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通过对Al和Sn的液态X射线衍射数据的分析,发现Al和Sn的液体结构随温度的变化都存在突变.Al的突变发生在1050—1250 ℃的温度区间内,Sn有两个突变点,一个在800℃左右,另一个在1200℃附近.随着温度的升高,两种液态金属的平均最近邻原子间离r1都呈现减小的趋势.在短程尺度上Sn的液体结构类似于α-Sn的结构.对相关半径rc的物理意义进行了探讨.
关键词: 相似文献
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A nanocrystalline model for microstructures of liquid metals is constructed. According to the nanocrystalline model, the intensity curves of x-ray diffraction (XRD) on liquid Cu, A1 and Al65Cu20Fe15 alloy are derived by broadening the XRD peaks of these metals in some crystal structures. These broadening intensity curves are 相似文献
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液态金属急冷过程中微观结构转变的研究 总被引:2,自引:0,他引:2
本文对液态金属Al在溶态及急冷过程中的微观结构及其转变进行了分子动力学模拟研究。发现在由HA(Honeycut-Andersen)健型指数所确定的双锥体原子团结构的数目随急冷温度变化的关系曲线上存在着二个明显的转变点。第一个点与熟知的玻璃转变温度Tg相吻合;而第二个点则为新发现的低温端相交点Tg2。这一结果为用分子动力学方法从微观层次上研究结构相变过程提供了一条新途径。 相似文献
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针对“液态金属结构与性质”前沿、交叉、抽象的课程特色、围绕学校的办学特色和材料物理专业的人才培养目标,践行“立德树人”根本任务,本文从教材建设、教学过程两大方面介绍液态金属结构与性质课程教学中课程思政的探索与实践。重点介绍了如何结合党中央要求和国家的重大战略部署进行教材建设,充分挖掘教学过程的核心元素,润物无声施教,将思政元素融入液态金属结构与性质课堂教学全过程,总结了通过教学改革,教学过程设计、教学案例遴选等方面的探索和实践。 相似文献
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X射线衍射法测定液态纯铁的密度 总被引:3,自引:0,他引:3
用X射线衍法测试了液态纯铁在1550℃的质量密度,并与文献中的实验结果进行了比较。结果发现,本文计算的密度6.971g/cm^3与文献中的实验结果7.0g/cm^3非常接近,说明本文的计算方法准确、可行。 相似文献
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迄今为止,人们对合金在液相线之上的熔体结构转变过程的认识仍不清晰. 本文运用电阻法、DSC热分析等实验手段,对CuSn60wt%二元合金熔体在升温及保温条件下的结构转变动力学过程进行了研究,并通过相变动力学理论探讨了转变过程的特征与微观物理机制. 分析表明:合金熔体中温度诱导的结构转变过程符合“形核-长大”类型,其动力学过程为自动催化转变模式,其中液相中新结构原子团簇的“形核率”为转变速率的主导控制因素. 相似文献
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迄今为止,人们对合金在液相线之上的熔体结构转变过程的认识仍不清晰. 本文运用电阻法、DSC热分析等实验手段,对CuSn60wt%二元合金熔体在升温及保温条件下的结构转变动力学过程进行了研究,并通过相变动力学理论探讨了转变过程的特征与微观物理机制. 分析表明:合金熔体中温度诱导的结构转变过程符合“形核-长大”类型,其动力学过程为自动催化转变模式,其中液相中新结构原子团簇的“形核率”为转变速率的主导控制因素. 相似文献
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The analytic solution of EIP model in the MSA via the OCP criterion yields temperature dependent results in RPA quite satisfactorily
at high temperatures. The same set of parameters produces low and high angle structural properties. The model can work almost
near to the critical point if the ion-core radius is allowed to vary systematically in the regionρ<2ρ
c,ρ
c being the critical density. The model can also accommodate the general scaling behaviour observed for the structure factors
of liquid alkali metals. 相似文献
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Summary Measured structure factors of liquid alkali metals are examined in the framework of screened pair potential theory. Information
on the main attractive well in the effective pair potential is obtained from the structural data by an approximate method
stemming from an optimized random-phase treatment of the indirect ion-ion attraction. The results are compared with a variety
of theoretical pair potentials in the cases of sodium and potassium, after a test of the method against computer simulation
data on a model for rubidium. Results for the other alkali metals are also given and discussed. The small-angle scattering
region is then examined in considerable detail, with special attention to the possibility of a linear term in a series expansion
of the structure factor at very small momentum transfer. Although sensitivity to both the bare electron-ion coupling and the
local field factor in the screening function is demonstrated and analysed, no linear term of the magnitude reported in recent
X-ray diffraction experiments is found in the present theoretical framework.
Riassunto Il lavoro discute i fattori di struttura misurati nei metalli alcalini liquidi nell'àmbito della teoria di potentiziali di coppia schermati. L'inversione dei dati strutturali permette di ottenere informazioni sulla buca attrattiva nel potenziale, che è confrontata con potenziali teorici dopo un controllo del metodo d'inversione su dati di simulazione. Si analizza quindi il comportamento del fattore di struttura a piccoli numeri d'onda, in relazione all'osservazione di un termine lineare nella figura di diffrazione di raggi X.
Резюме Измеренные структурные факторы жидких щелочных металлов исследуются в рамках теории экранированных парных потенциалов. Из структурных данных получается информация об основной яме притяжения в эффективном парном потенциале. Полученные результаты сравниваются с целым рядом теоретических парных потенциалов в случаях натрия и калия. Предложенный метод проверяется посредством компьютерного моделирования для рубидия. Также приводятся и обсуждаются результаты для других щело ных металлов. Подробно исследуется область малоуглового рассеяния, уделяя особое внимание возможности существования линейного члена в степенном разложении структурного фактора при очень малых передаваемых импульсах. Анализируется чувствительность предложенного подхода в связи с обнаружением линейного члена в экспериментах по дифракции рентгеновских лучей.相似文献
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The static structure factors of liquid alkali metals have been modelled at temperatures close to their melting points and a few higher temperatures using the reverse Monte Carlo (RMC) method. The positions of 5000 atoms in a box, with full periodicity, were altered until the experimental diffraction data of the structure factor agrees with the associated model structure factor within the errors. The model generated is then analysed. The position of the first peak of the pair distribution function g(r) does not show any significant temperature dependence and the mean bond lengths can be approximated within an interval of 3.6–5.3 Å, 4.5–6.6 Å, 4.8–6.7 Å and 5.1–7.3 Å for Na, K, Rb and Cs respectively. The cosine bond distributions show similar trend with the flattening up of the first peak with increase in temperature. In addition, the coordination numbers of these liquid metals are high due to the presence of non-covalent bonding between them. On the average, we surmise that the coordination number decreases with increase in temperature 相似文献
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Xiaolin Zhao Xiufang Bian Changchun Wang Yunfang Li 《Chinese Journal of Physics (Taipei)》2018,56(6):2684-2688
The dynamic viscosity and the liquid structure of Ga98Sn2 alloy melt at different temperatures were measured by a torsional oscillation viscometer and an x-ray diffraction. The viscosity of the liquid Ga98Sn2 alloy increases with decreasing temperature and an obvious turning point is observed on the Arrhenius curve. The breakpoint in Arrhenius plot emerges when the structure of Ga98Sn2 alloy melt is transformed from the high coordinated polyhedron clusters to the low coordinated polyhedron clusters. It is found that the change of the viscosity is a characteristic of microstructure transformation in the alloy melt. 相似文献
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以改进的低频扭摆内耗仪研究了液态PbSn合金连续升温过程的内耗行为.结果表明:合金在液相线以上500—800℃温区内出现内耗峰,其峰温不随频率变化,峰高与升温速率成正比,与振动频率成反比,这与固态相变内耗峰的特征相吻合;合金成分不同,内耗峰峰温不同;非共晶成分合金熔体的内耗曲线上出现次峰.这一现象揭示了PbSn合金熔体随温度可能发生结构转变.对PbSn合金进行差热分析,熔体出现的热效应峰与内耗峰的温区大体对应,进一步揭示熔体的内耗峰可能是由结构转变引起的.
关键词:
液态结构
内耗
Pb-Sn合金 相似文献
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Aurélien Perera 《Molecular physics》2013,111(20):2433-2441