Sen Chen

Behaviour of a binary particle system under the effects of simultaneous vertical vibration and rotation

We performed experiments to investigate the effects of simultaneous vertical vibration and rotation (around a vertical axis) on a binary particle system. In particular, the effects of vibration frequency f, dimensionless acceleration Γ, rotation angle velocity ω, and the total mass m of the particle system on the final separation results are investigated. The system exhibited transitional Brazilian Nut (BN) separation patterns in both the vertical and axial directions. The coupling of vertical and axial separation mechanisms determined the final spatial separation state. We defined the vertical and axial separation parameters λz and λr between −1 for Complete Reversed BN (RBN) and 1 for Complete BN to describe the separation states quantitatively. These experiments suggested that when no rotation is applied, the system exhibits mono-directional relations with f and Γ mainly. BN tendency is enhanced when f increases at a constant Γ, but is reduced when Γ increases at a constant f, and vice versa. When ω increases at constant f and Γ, the value of λz first rises as a result of enhanced BN tendency and then drops in response to vertical rotation. As ω increases, the surface of the particle mixture becomes hollow, and the λz–ω curve is partly dispersed. After the hollow touches the container bottom, the curve becomes fully dispersed. ω, f, Γ, and m all have significant effects on the final vertical and axial separation patterns. Stronger vibration generally increases RBN/Axial RBN, whereas stronger rotation helps form BN/Axial BN. We also established a geometrical model of the separation states to study the effect of ω, f, Γ, and m on the final separation results in delicate mathematical descriptions. This model agreed well with the experimental outcomes.

Boron diffusion in bcc-Fe studied by first-principles calculations*

The diffusion mechanism of boron in bcc-Fe has been studied by first-principles calculations. The diffusion coefficients of the interstitial mechanism, the B–monovacancy complex mechanism, and the B–divacancy complex mechanism have been calculated. The calculated diffusion coefficient of the interstitial mechanism is D0 = 1.05 × 10−7 exp (−0.75 eV/kT) m2 s−1, while the diffusion coefficients of the B–monovacancy and the B–divacancy complex mechanisms are D1 = 1.22 × 10−6 f1 exp (−2.27 eV/kT) m2 s−1 and D2 ≈ 8.36 × 10−6 exp (−4.81 eV/kT) m2 s−1, respectively. The results indicate that the dominant diffusion mechanism in bcc-Fe is the interstitial mechanism through an octahedral interstitial site instead of the complex mechanism. The calculated diffusion coefficient is in accordance with the reported experiment results measured in Fe–3%Si–B alloy (bcc structure). Since the non-equilibrium segregation of boron is based on the diffusion of the complexes as suggested by the theory, our calculation reasonably explains why the non-equilibrium segregation of boron is not observed in bcc-Fe in experiments.

Moisture conversion and migration in single-wheat kernel during isothermal drying process by LF-NMR

Abstract Conversion among different moisture-binding types of single Hebei wheat kernels during isothermal drying processing at 60 °C was studied by low field nuclear magnetic resonance (LF-NMR), and moisture migration was studied by MRI. Water inside wheat kernels exists in four types: chemically combined water (T21), strong bound water (T22), loosely bound water (T23), and free water (T24). A new method to obtain the contents of different moisture-binding types is forwarded according to the transverse relaxation time distribution curve of dried wheat kernels. Moisture conversion inside wheat kernels during drying occurs mainly through the following mechanisms: high-temperature drives T24 to diffuse to lower moisture areas and transform into other moisture-binding types, and moisture-gradient drives T22 to transform into T24. The drying process can be divided into two stages. Moisture migrates from endosperm to epidermis during drying. As the drying rate of the wheat kernel significantly decreases, the drying conditions and parameters need to be adjusted to improve the drying rate while ensuring the quality of wheat kernels.

The Morphologies and Adhesion of Ceramic Films on CLAM Steel Substrates for Nuclear Fusion Applications

In the dual-function lithium-lead test blanket module (DFLL-TBM) thin and durable coatings with a large tritium permeation reduction factor (PRF) and high resistivity are usually used to segregate the structural wall from the liquid Li-Pb. Al2 O3 , Cr2 O3 , SiC, Er2 O3 , et al. are considered as the promising functional coating materials for DFLL-TBM. Due to the thermal expansion coefficients and lattice constants of ceramic and metal materials are quite different, the mechanical properties of ceramic coatings on metal substrates can be reduced by poor adhesion. In this study, Al2 O3 , Cr2 O3 , SiC, Er2 O3 films were fabricated on China low activation martensitic (CLAM) steel substrates by magnetron sputtering. Atomic force microscope (AFM) was used to study the surface morphologies of ceramic films. The adhesion strength of the films, deposited on CLAM steel, was also studied by scratch test. Results indicate that the surface of SiC films is smoother than the others. While the surface morphologies of Al2 O3 , Cr2 O3 , Er2 O3 films are similar. The critical load of SiC film, with a minimum value, is about 12.0 mN, while the critical load of Al2 O3 reaches about 16.4 mN.Copyright

Dielectric Properties of Er-Doped HfTiO Films for High-K Gate Stacks

HfTiErO and HfTiO thin films (∼50nm), as potential replacements for traditional SiO2 gate dielectric materials, were prepared on n-Si (100) substrates by radio frequency magnetron sputtering. The dielectric characteristics of HfTiErO were compared with those of HfTiO. The structure of HfTiErO was analyzed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The growth of HfTiErO and HfTiO were observed by field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). Experimental results indicate that as the Er content increases, the dielectric constant (k) can increase to the maximum (∼20.2) and then decrease. In comparison with HfTiO, HfTiErO films (the atomic ratio of Hf:Ti:Er was 1:0.16:0.10) can exhibit a higher relative permittivity (increasing by 54% compared with HfTiO), a smoother interface, a better surface microscopy and a lower interface trap density in C-V curves.Copyright

Sputtering Power on Electrical Characteristics of Er,Ti Co-Doped HfO2 Films

Er,Ti co-doped HfO2 films, as candidate of the gate dielectric material for CMOS technology, were deposited on n-Si (100) by radio frequency magnetron sputtering. The dielectric characteristics of the films were compared with different sputtering powers. The surface morphology of HfTiErO was observed by atomic force microscopy (AFM). The thickness of the films was determined by SGC-10 film calibrator. The results show that the growth rate nearly has a linear increase with the sputtering power rising, the film with sputtering power 40W, 100W or 120W has better surface topography, the sputtering power of 60W and 80W leads to better interfacial and electrical properties. The results of the present work indicate that 60W is the optimal condition for preparing the HfTiErO film.Copyright

Effect of magnetic yoke on magnetic field distribution and intercepting effect of multi‐channel cascading magnet arrays

‘Magnetic‐Sieve’ possesses a potential use in oxygen separation. The effect of a magnetic yoke on magnetic field distribution and intercepting effect of multi‐channel cascading magnet arrays in a ‘Magnetic‐Sieve’ configuration is studied by ANSYS finite element software. The multi‐channel cascading magnet arrays consist of cuboid neodymium‐iron‐boron permanent magnets. The size of the magnets is W×H = 38 mm×5 mm, and the clearance between two adjacent magnets is 1 mm. The results show that the intercepting effect tends to decrease from the central channel to the most lateral channels in multi‐channel cascading magnet arrays. Compared with the simulation result of two magnets, the central magnetic inductions of the center channel and the most lateral channels in the multi‐channel cascading magnet array including 14 magnets decrease respectively 10% and 31%, and the intercepting effects of the center channel and the most lateral channels decrease 19% and 60%, respectively. When the magnetic yoke is added on...