Determination of Natural Logarithm of Diffusion Coefficient and Activation Energy of Thin Layer Drying Process of Ginger Rhizome Slices

This study is an extension of the previous work done with ARS-680 Environmental Chamber. Drying is a complex operation that demands much energy and time. Drying is essentially important for preservation of ginger rhizome. Drying of ginger was modeled, and then the effective diffusion coefficient and activation energy were determined. For this purpose, the experiments were done at six levels of varied temperatures: 10°C, 20°C, 30°C, 40°C, 50°C and 60°C. The values of effective diffusion coefficients obtained in this work for the variously treated ginger rhizomes closely agreed with the average effective diffusion coefficients of other notable authors who determined the drying kinetics and convective heat transfer coefficients of ginger slices.

Influence of holding time on microstructure and shear strength of Mg alloy/steel joint diffusion bonded with Zn-5Al interlayer

The diffusion bonding of AZ31B Mg alloy and Q235 steel was investigated with a Zn-5Al alloy as interlayer and under different holding time ranging from 3 to 1 200 s. The microstructure and phase compositions of bonded joints were characterized by scanning electron microscopy( SEM),energy dispersive spectrometer( EDS) and X-ray diffraction( XRD)methods. The shear strength of Mg alloy/steel joints was measured by tensile tester. It was found that the microstructure of bonded joints evolved dramatically along with the prolongation of holding time. Under the holding time of 3 s,the main part of joint was composed of MgZn_2 phase and dispersed Al-rich solid solution particles. When increased the holding time more than 60 s,the excessive solution of AZ31B into the interfacial reaction area led to the formation of coarse phase and eutectic microstructure,and also the complex Fe-Al and Mg-Al-Zn IMCs at transition layer closed to Q235 steel side. According to the tensile testing characterizations,the joints obtained under holding time of 3 s exhibited the best shear strength of 84 MPa,and the fracture occurred at the intermediary part of joint where the flexible Al-rich solid solution particles could help to impede the microcrack propagations. With prolonging the holding time to 600 s,the shear strength of joints was deteriorated enormously and the fracture position was shifted to the transition layer part closed to Q235 steel.

Diffusion of lanthanum in nanocrystallized surface layer during plasma rare earth nitriding of 3J33B steel

Plasma rare earth nitriding of nanocrystallized surface layer of 3J33B steel at 350 and 410℃ for different time was studied. The microstructure observation and X-ray diffraction（XRD） analysis show that the nitriding layer consists of compound layer （γ′-Fe4N） and diffusion layer （α-Fe）. Lanthanum content profiles in nanocrystallized surface layer were measured using glow discharge spectometry（GDS）. The results show that lanthanum can diffuse into the surface layer of the steel to a large depth. Based on the experimental results mentioned above, the diffusion coefficients and activation energy of lanthanum in γ′ phase are calculated to be 1.03×10 -15 cm2/s （350℃）, 1.75×10 -15 cm2/s （410℃） and 31.313kJ/mol, respectively.

Evolution mechanism of the interfacial reaction layers in the joints of diffusion bonded Mo and Al foils

Mo foil （10 -20 μm in thickness） and Al foil （20 -60 μLm in thickness） were vacuum diffusion bonded at 600 - 640 ~C under 20 MPa for 54 min - 6 h. The joints were examined by scanning electron microscopy （SEM） and energy dispersive spectroscopy （EDS） to study the evolution mechanism of the reaction layers. The results show that Al atoms diffuse into Mo grain boundaries and form reaction products as Mo3Al8, MoAl4 , MoAl5 and MoAl12. The surface oxide film is eroded by the growths of the reaction products that plow into the lamellar texture of Mo grain boundaries. Mo3Al8 layer grows by ＂taking root＂ downwards and transforms into MoAl4 and MoAl5 phases upwards by absorbing Al atoms. MoAl12 layer grows up from MoAl5 layer in the same way. When the supplement of Al atoms ceases, MoAl12 transforms reversely into MoAl5 and MoAl5 into MoAl4 via the loss of Al atoms. However, MoAl4 continues to precipitate from Mo3Als layer. At last, there are MoAl4 and Mo3Al8 remained on the joint interface.

Fast ion diffusion alloy layer facilitating 3D mesh substrate for dendrite-free zinc-ion hybrid capacitors

Although aqueous zinc ion hybrid capacitors have advantageous integration of batteries and supercapacitors,they still suffer from the inherent problems of dendrite growth and interfacial side reactions on Zn anodes.Herein,a universal fast zinc-ion diffusion layer on a three-dimensional(3 D)mesh structure model is demonstrated to effectively improve Zn plating/stripping reversibility.The fast ion diffusion alloy layer accelerates the Zn^(2+)migration in an orderly manner to homogenize Zn^(2+)flux and overcomes the defects of the commercial mesh substrate,effectively avoiding dendrite growth and side reactions.Consequently,the proof-of-concept silver-zinc alloy modified stainless steel mesh delivers superb reversibility with the high coulombic efficiency over 99.4%at 4 mA cm^(-2)after 1600 cycles and excellent reliability of over 830 h at 1 mA cm^(-2),Its feasibility is also evidenced in commercial zinc ion hybrid capacitors with activated carbon as the cathode.This work enriches the fundamental comprehension of fast zinc-ion diffusion layer combined with a 3 D substrate on the Zn deposition and opens a universal approach to design advanced host for Zn electrodes in zinc ion hybrid capacitors.

Modifying element diffusion pathway by transition layer structure in high-entropy alloy particle reinforced Cu matrix composites

The Al0.3CoCrFeNi high-entropy alloy(HEA)particles reinforced Cu matrix composites(CMCs)were fabricated by mechanical alloying and sintering.Transition layer structure was obtained by multi-step ball milling to investigate the related influence on element diffusion behavior and wear properties of CMCs.The results indicate that a new Cu transition layer is generated,and the thickness is about 5μm.Cr element diffuses into the interface via the transition layer,which forms the complex oxide.Because of the structure of Cu transition layer,the diffusion rates of Ni,Co and Fe increase,especially the Ni element.The wear resistance of CMCs is improved by 30%,which is due to the improvement of interface bonding strength,compared with the CMCs without transition layer.This method is applicable to the development of advanced HEA reinforced metallic matrix composites.

Vertical multiple-layer structure of temperature and turbulent diffusivity in the South China Sea

We report field measurements of vertical profiles of the turbulent diffusivity and temperature at different stations in the South China Sea(SCS).Our study shows that the measured turbulent diffusivity follows a power-law distribution with a varying exponent in water layers.Similar multiple-layer scaling regimes were also observed from the temperature fluctuations.Combining turbulent diffusivity and temperature fluctuations,the vertical structure of temperature was revealed.Furthermore,we discussed the temperature profiles in each layer.A constant function of a dimensionless temperature profile was found in water layers that have identical turbulence conditions.Our results reveal the multiple-layer structure of temperature in the SCS.This study contributes to the understanding of the vertical structure of multiple layers in the SCS and provides clues for exploring the physical mechanism for maintaining the temperature structure.

A homogeneous and mechanically stable artificial diffusion layer using rigid-flexible hybrid polymer for high-performance lithium metal batteries

Artificial solid electrolyte interphase(SEI) is promising to inhibit uncontrollable lithium dendrites and enable long cycling stability for lithium metal batteries. However, the essential mechanical stability is limited since organic layers generally have low modulus whereas intrinsic brittleness for inorganic ones remains a great concern. Polymer-based SEIs with rigid and flexible chains in adequate mechanical properties are supposed to address this issue. Herein, a homogeneous and mechanically stable diffusion layer is achieved by blending rigid chains of polyphenylene sulfone(PPSU) with flexible chains of poly(vinylidene fluoride)(PVDF) in a hybrid membrane, enabling uniform diffusion and stabilizing the lithium metal anode. The Li||Cu cell with the protected electrode exhibits a long lifetime more than 450 cycles(0.5 m A cm^(-2), 1.0 m A h cm^(-2))(fourfold longer than the control group) with higher average Coulombic efficiency of 98.7%. Enhanced performances are also observed at Li||Li and full cell configurations. The improved performances are attributed to the controlled morphology and stable interphase, according to scanning electron microscopy(SEM) and electrochemical impedance. This research advances the idea of uniform lithium plating and provides a new insight on how to create a homogeneous and mechanically stable diffusion layer using rigid-flexible polymers.

Implanting a preferential solid electrolyte interphase layer over anode electrode of lithium ion batteries for highly enhanced Li^+ diffusion properties

The lithium-ion batteries are recognized as the most promising energy storage system,but it still does not meet the power requirements of electric vehicle batteries owing to low volumetric energy density with the traditional graphite electrode system.In this study,we report the development of a novel electrode system fabricated by implantation of a solid electrolyte interphase(SEI)layer on the graphite surface.The SEI-implanted graphite electrode is made using a lithium bis(trifluoromethanesulfonyl)imide(LiTFSI)-based electrolyte and cycled with a lithium tetrafluoroborate LiBF4-based electrolyte.This new electrode system shows significantly enhanced electrochemical properties owing to the rapid and efficient diffusion of Li ions through the SEI layer between the electrolyte and electrode.This graphite electrode with its pre-formed SEI layer achieves a reversible capacity of 357 mAh g^-1 at 0.5 C after 50 cycles,which is significantly higher than that of commercial lithium-ion battery systems constructed with LiPF6(312mAh g^-1).The resulting unique electrode system could present a new avenue in SEI research for highperformance lithium-ion batteries.

Screening Effect of the Diffusive Boundary Layer in Sediments of Lake Aha in the Suburbs of Guiyang City, Guizhou Province

The redox cycle of iron and manganese is a major geochemical process at the boundary layers of lake sediments. Lake Aha, which lies in the suburbs of Guiyang City,Guizhou Province, China, is a medium-sized artificial reservoir with seasonally anoxic hypolimnion. Long-term sedimentary accumulation of iron and manganese resulted in their enrichment in the upper sediments. In the anoxic season, Fe2+ and Mn2+, formed by biological oxidation, would diffuse up to overlying waters from sedlments. However, the concentration of Fe2+ increased later and decreased earlier than that of Mn2+. Generally, sulfate reduction occurred at 6 cm below the sediment-water interface. Whereas, in the anoxic season, the reduction reached upper sediments, inhibiting the release of Fe2+. The Fe concentration of anoxic water is quickly decreased from high to low as a result of reduction Of the sulphur system.

Resistance of the diffusive boundary layer to salt release from saline sediments to freshwater

The diffusive boundary layer （DBL） is the zone for matter exchange between surface water and aquatic sediments. To elucidate the influence of DBL on salt release from saline sediments to freshwater, two experiments with or without wind blowing were conducted. According to the experiments, a 3.5 cm DBL is formed above the smoothed sediments at a steady wind field and this thickness is greater than other studies. The observed flux of salt through the DBL is 6% larger than the calculated value from Fick＇ s first law. The results indicate that molecular diffusion is the dominant mechanism for salt transport through the DBL. The presence of DBL suppresses the hydrodynamic enhancement for matter exchange between sediments and overlying water. Therefore, salts in the sediments of a polder reservoir may influence the water quality chronically.

Diffusion bonding of copper alloy to stainless steel with Ni and Cu interlayer

CuAlBe alloy is an attractive shape memory alloy with many important usages in industrial field, in order to spread its range of application it is desirable to be able to join CuAlBe soundly with other metallic materials, for example stainless steel; however the weldability between CuAlBe alloy and stainless steel has never been studied, therefore an experimental investigation of different transition metals was carried out in the diffusion bonding joints of Cu alloys (CuAlBe) to stainless steel (1Cr18Ni9Ti). The microstructure and phase composition of the joint were analyzed by SEM, EPMA and X ray diffraction. The following conclusions have been drawn: 1) The joint strength with Ni interlayer is higher than that with Cu interlayer when the welding parameters are the same; 2) When Ni interlayer is thinner, Al will interact with Ni and Fe, and the intermetallic compounds such as Fe 3Al are formed in the interface, which decreases the strength of the joints; 3) When the bonding temperature is higher, because the diffusion of Cu in Ni is faster than Ni in Cu, a Kirkendall effect occurs, which also decreases the strength of the joints.

Effect of Electric Field-Assisted Diffusion on Surface Layer Structure and Mechanical Properties of Soda-Lime Glasses

Soda-lime glasses were treated by electric field-assisted diffusion（EFAD） process. The mechanical properties and structural evolution on both glass anode and cathode surfaces were investigated, respectively. It was found that the EFAD resulted in the formation of a Na depletion layer on anode surface, which caused the relaxation of the glass anode surface network and the formation of a number of defects. Correspondingly, the hardness and flexural strength declined in anode surface compared to that of the original glass. On the other hand, the EFAD also created a compressive layer on cathode surface, causing the improvement of the hardness and flexural strength on cathode surface. The defected structure could be reconstructed by additional annealing process.

EFFECTS OF TURBULENT COHERENT STRUCTURE ON PLUME DIFFUSION IN ATMOSPHERE BOUNDARY LAYER

The simulation tests of plume diffusion have been carried out in an open water channel,in which a Laser Doppler Velocitymeter,optical concentration measurement and flow visualization technology have been used.Through experiments and theoretical analyses,the effects of environmental wind field,surface roughness and discharge condition of elevated source on plume diffusion have been investigated.The plume dif- fusion mechanism has been elucidated reasonably,based on the turbulent coherent structure theory.

Controlling Diffusion by Varying Width of Layers in Nano Channel

Diffusive dynamics of fluid forming layers of high and low density regions in a nanochannel has been investigated.Diffusion coefficient in direction parallel and perpendicular to the confining wall has been found to show behaviour which is not observed in micro channel or bulk systems.The behaviour of diffusion is found to be controlled by the width of layers formed in nanochannel due to wall and particle interactions.This is an important result as width of layers and hence flow of fluid inside nano pores/tube can be controlled by an external source.

Fractal Analysis of Gas Diffusion Layer in PEM Fuel Cells

The aim of this study is to show how fractal analysis can be effectively used to characterize the texture of porous solids. The materials under study were carbon papers, the backing material of the gas diffusion layer （GDL） in Proton Exchange Membrane Fuel Cell （PEMFC）. The fractal dimensions were calculated by analyzing data from mercury porosimetry. The polytotrafluoroethylene （PTFE） treated carbon paper shows a significantly high fractal dimension value than pare sample, and the high fractal dimension signifies that the physical complexity of the pore surface is enhanced. The fractal dimension can be used as a valid parameter to monitor the textural evolution of the samples as the treatment progresses, as this behaves in a similar way to other textural parameters. The use of fractal analysis in conjunction with the results of classical characterization methods leads to a better understanding of textural modificatious in the processing of materials.

ANALYSIS OF BOUNDARY LAYER SINGULARITYIN A NONLINEAR DIFFUSION PROBLEM

In this paper, the author analyzes the singularity of a boundary layer in a nonlinear diffusion problem. Results show when the limiting solution satisfies the boundary condition, there is no boundary singularity. Otherwise, the boundary layer exists, and its thickness is proportional to epsilon(1/2), here epsilon is a small positive real parameter.

BOUNDARY LAYER AND VANISHING DIFFUSION LIMIT FOR NONLINEAR EVOLUTION EQUATIONS

In this paper, we consider an initial-boundary value problem for some nonlinear evolution equations with damping and diffusion. The main purpose is to investigate the boundary layer effect and the convergence rates as the diffusion parameter α goes to zero.

Ceramic alloying with Ti-N deposition and diffusion of multi-layers by plasma surface alloying technique

High quality TiN multi-layer was obtained on steel substrate by combined technology of plasma glow discharge sputtering, hollow cathode effect and interfacial diffusion. The TiN multi-layer consists of deposition layer and diffusion layer. Its morphology, structure and chemical compositions were analyzed. The microhardness and wear resistance were measured. The results indicate that the diffusion of Ti and N into the substrate leads to a strong interfacial adhesion. The thickness of TiN multi-layer is about 10μm. The strongest diffraction is on the (200) crystal plane of TiN. The surface hardness is about to 2300(HV_ 0.1). The wear resistance of the TiN ceramic alloying multi-layer is excellent and the friction coefficient is low under dry sliding conditions.

A GOOD DIFFUSION LAYER CANDIDATE FOR SHARK

In this paper, a good diffusion layer candidate for SHARK is developed. The diffusion layer presented here is only concerned with 64-bit cipher based on 2-DM diffusion matrixes, which is heavily inspired by James Massey work on the design of SAFER K-64. However, it can be easily extended for a longer size cipher without any extra works and it may serve as a good candidate for other block ciphers.