Papers by Keyword: Mean Free Path

Abstract: CBED and EELS are most common methods to determine the thickness of the TEM specimen. In this work, specimen thickness of He-ion irradiated Al is measured respectively by CBED and EELS under 200kV. The helium concentration and the atomic displacement damage level are 2000appm and 0.2dpa, respectively. The CBED results show that the measurements of extinction distance match the calculations of effective extinction distance considering the deviation vector of the crystal. Moreover, it is proven by modeling analysis that He-ion irradiation does not affect the thickness measurements of extinction distance. Compared with CBED, the specimen thickness, measured by EELS, is larger, and may be attributed to the decrease of the zero-loss peak due to a part of elastic scattering electronsloss and the larger inelastic scattering mean free path selected. The EELS measurement error is less than 20%,consistent with the accuracy (about 20%) byK. Iakoubovskiiet al.

Abstract: With manufacturing technology innovation and progress of electronic devices of semiconductors, dimensions of electronic devices get smaller nowadays. There has been processing of 90nm and 20nm in production. With in-depth research, scientists are more and more interested in molecular devices. Since the size of molecular devices is small, electrons transfer by ballistic transport. In semiconductor devices, when the transport distance is at micrometer or smaller sizes, the ballistic transport phenomena of electrons and holes of carriers occur. This transfer form is not affected by lattice defects, doping, and interaction of crystal interfaces. Since there is no interference of these interactions, carrier’s velocity can be faster several times than common electronic devices, resulting in the doubled operating speed of these devices. Although it is difficult to achieve pure ballistic transport, when the size of semiconductor devices is close to the mean free path of carriers, the speed of carriers will still be greatly improved.

Abstract: This paper presents the flying characteristics of air-helium filled hard disk drive for a self-acting two rails flat slider bearing. Numerical scheme based on the finite difference with multi-grid multi-level technique were implemented for the ultra-low flying height sliders. The characteristics of air-helium filled HDD have been examined in this research work. The results shown that the change of flying height is significantly for various fraction of air-helium filled, at various operating conditions such as temperature velocity and mass of slider. Increase of velocity, flying height increase. Increase both the temperature and the mass load, flying height decrease. Increasing of fraction in helium gas, the flying height decreases rapidly for 40% to 60 % of fraction in helium filled. The flying height for air-helium filled magnetic flat slider head equal to 1.3 nm at trailing edge with mass load 12 mN and velocity 20 m/s. The spacing for helium filled hard disk drive is lower than 3 nm when compared with conventional air filled hard disk drive.

Abstract: Mean free path of dislocation motion have a significant effect on mechanical properties because dislocation motion is blocked by eutectics and intermetallics in Al-Si casting alloys. In this study, we proposed a statistical method to evaluate mean free path of dislocation motion by using image processing, and investigated relation between the measured mean free path and mechanical properties of Al-Si casting alloys.

Abstract: The generation of plasmas and the initiation of electrical breakdown are realized by the phenomenon of electrical discharge which is provoked when we apply a sufficient electric field in a gas. Consequently the free charges are accelerated, new charged particles are created and others are destructed. This can be ranged in four phenomena: elastic collision (recombination), attachment, excitation and ionization. The aim of this paper is to study the basic phenomena in an electrical discharge in the case of Oxygen O₂. Monte Carlo Simulation is used to follow the random trajectory of free charges determining in each path many parameters of the discharge. To determinate electrical and physical parameters, we have used the sampling laws. The spatial distributions of space charges (electrons, positive and negative ions) are also obtained. The determination of electrical field depends on distributions of charged particles obtained by solving the Maxwell equations.

Abstract: In order to study the influence of stress ratio and WC grain size, the characteristics of fatigue crack growth were investigated in WC-Co cemented carbides with two different grain sizes of 3 and 6 µm. Fatigue crack growth tests were carried out over a wide range of fatigue crack growth rates covering the threshold stress intensity factor range DKth. It was found that crack growth rate da/dN against stress intensity factor range DK depended on stress ratio R. The crack growth rate plotted in terms of effective stress intensity factor range DKeff still exhibited the effect of microstructure. Fractographic examination revealed brittle fracture at R=0.1 and ductile fracture at R=0.5 in Co binder phase. The amount of Co phase transformation for stress ratio was closely related to fatigue crack growth characteristics.