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.

Diffusion Equations of the Electric Charges and Magnetic Flux

Innovative definitions of the electric and magnetic diffusivities through conducting mediums and innovative diffusion equations of the electric charges and magnetic flux are verified in this article. Such innovations depend on the analogy of the governing laws of diffusion of the thermal, electrical, and magnetic energies and newly defined natures of the electric charges and magnetic flux as energy, or as electromagnetic waves, that have electric and magnetic potentials. The introduced diffusion equations of the electric charges and magnetic flux involve Laplacian operator and the introduced diffusivities. Both equations are applied to determine the electric and magnetic fields in conductors as the heat diffusion equation which is applied to determine the thermal field in steady and unsteady heat diffusion conditions. The use of electric networks for experimental modeling of thermal networks represents sufficient proof of similarity of the diffusion equations of both fields. By analysis of the diffusion phenomena of the three considered modes of energy transfer;the rates of flow of these energies are found to be directly proportional to the gradient of their volumetric concentration, or density, and the proportionality constants in such relations are the diffusivity of each energy. Such analysis leads also to find proportionality relations between the potentials of such energies and their volumetric concentrations. Validity of the introduced diffusion equations is verified by correspondence their solutions to the measurement results of the electric and magnetic fields in microwave ovens.

An Optical Investigation of Silver Nanoclusters Composite Soda-lime Glass Formed by Electric Field Assisted Diffusion

Silver nanoclusters（NCs） embedded in soda-lime glass was synthesized by the electric fieldassisted diffusion（EFAD） and successive annealing. The samples were characterized by UV-Vis absorption spectroscopy, photoluminescence spectroscopy, X-ray photoelectron spectroscopy（XPS）, and lifetime measurements. The experimental results show that the growth of silver clusters is favored by the annealing temperature and dwell time. The as-diffused and annealed glass samples show photoluminescence around 550 nm under UV excitation, which can be associated with the presence of L-center and Ag3~＋ cluster. And the increasing of the annealing temperature and dwell time results in an appearance of the SPR peak and the decreasing of the luminescence intensities because the Ag3~＋ clusters grow up into the Ag nanoparticles.

Quality Evaluation of Diffusion Bonded Joints by Electrical Resistance Measuring and Microscopic Fatigue Testing

Micro-structure related behavior of diffusion bonding joints is a crucial issue in device and reactor fabrication of Micro Chemo Mechanical Systems.However,the previous studies have been focused on the macro mechanical performance of diffusion bonded joint,especially diffusion bonding conditions effects on tensile strength,shearing strength and fatigue strength.The research of interfacial micro-voids and microstructures evolution for failure mechanism has not been carried out for diffusion-bonded joints.An interfacial electrical resistance measuring method is proposed to evaluate the quality of bonded joints and verified by using two-dimensional finite-element simulation.The influences of micro void geometry on increments of resistance are analyzed and the relationship between bonded area fraction and resistance increment is established by theoretical analysis combined with simulated results.Metallographic inspections and micro-hardness testing are conducted near the interface of diffusion bonded joints.For the purpose of identifying the failure mechanisms of the joints,both microscopic tensile and fatigue tests are conducted on the self-developed in-situ microscopic fatigue testing system.Based on the microscopic observations,the mechanism of interfacial failure is addressed.The observation result shows that for 316LSS diffusion-bonded joints,microstructure evolution and effect of micro-voids play a key role in interfacial failure mechanism.Finally,a new life prediction model in terms of the increment of electrical resistance is developed and confirmed by the experimental results.The proposed study is initiated that constituted a primary interfacial failure mechanism on micron scale and provide the life prediction for reliability of components sealed by diffusion bonding.

Electric Field of the Ocean Induced by Diffusion

The equations for gradient of electric field in seawater induced by gradients of salinity, temperature and pressure were developed by means of non-equilibrium thermodynamics. Extrathermodynamic assumptions and accepted chemical model of seawater permit to carry out numerical calculations of electric field caused by diffusion, thermodiffusion and barodiffusion for realistic hydrophysical structure of the ocean. It is shown that contribution of barodiffusion into electric field of the ocean is almost constant (about -3 × 10-7 V/M). This magnitude can be ignored in many cases because it is too small. However natural salinity and temperature gradients significantly impact into electric field of the ocean.

Donnan Electric Potential Dependence of Intraparticle Diffusion of Malachite Green in Single Cation Exchange Resin Particles: A Laser Trapping-Microspectroscopy Study

A laser trapping-microspectroscopy technique combined with excitation energy transfer from a fluorescent cationic dye (Rhodamine B, RB+) to a non-fluorescent cationic dye (Malachite Green, MG+) was employed to study pH effects on the diffusion coefficients of MG+ (D(MG+)) in single cation-exchange resin microparticles with the diameters of 16 μm. When RB+-pre-adsorbed resin particles were soaked in an aqueous MG+ solution, the RB+ fluorescence was quenched gradually with the soaking time. The time course of the quenching efficiency of RB+ by MG+ was then used to evaluate the D(MG+) value in the particle. The D(MG+) value increased from 1.1 × 10-11 to 4.3 × 10-11 cm2.s–1 on going the solu- tion pH value from 9 to 4. The results were explained reasonably by a Donnan electric potential model.

Effect of Electric Current on Diffusion of Aluminum in Ti3AlC2 into Zirconium Alloy

The spark plasma sintering（SPS） method was used to study the mechanism of reaction interface between Zr and Ti3AlC2 with electric current going through it. It was found that electric current greatly reduced the bonding temperature of Zr and Ti3AlC2. By the micro-structure analysis of the interface through SEM/EDS, it was found that Al atoms diffused from the Ti3AlC2 substrate into the Zr side and reacted with Zr to form the Zr-Al compounds at the interface, which is the strengthening mechanism of Ti3AlC2-Zr bonding. The thickness of reaction layers（Zr-Al alloy） was from 0.879 to 13.945 mm depending on different sintering condition. Current direction, heating rate, soaking time, pulse patterns all influenced the diffusion of Al atoms which affected the joining quality of Zr and Ti3AlC2.

Influence of anisotropy on the electrical conductivity and diffusion coefficient of dry K-feldspar： Implications of the mechanism of conduction

The electrical conductivities of single-crystal K-feldspar along three different crystallographic directions are investigated by the Solartron-1260 Impedance/Gain-phase analyzer at 873 K–1223 K and 1.0 GPa–3.0 GPa in a frequency range of 10-1 Hz–106 Hz. The measured electrical conductivity along the ⊥ [001] axis direction decreases with increasing pressure, and the activation energy and activation volume of charge carriers are determined to be 1.04 ± 0.06 e V and 2.51 ± 0.19 cm~3/mole, respectively. The electrical conductivity of K-feldspar is highly anisotropic, and its value along the⊥ [001] axis is approximately three times higher than that along the ⊥ [100] axis. At 2.0 GPa, the diffusion coefficient of ionic potassium is obtained from the electrical conductivity data using the Nernst–Einstein equation. The measured electrical conductivity and calculated diffusion coefficient of potassium suggest that the main conduction mechanism is of ionic conduction, therefore the dominant charge carrier is transferred between normal lattice potassium positions and adjacent interstitial sites along the thermally activated electric field.

Generation of atmospheric pressure diffuse dielectric barrier discharge based on multiple potentials in air

In order to achieve atmospheric pressure diffuse dielectric barrier discharge(DBD) in air, a helical-helical electrode structure with a floating-voltage electrode is proposed in this paper.Results from an electric field distribution simulation indicate that strong electric fields are formed where the helical-contact electrodes’ insulating layers are in contact with each other, as well as near the floating-voltage electrode, which contributes to the production of a large number of seed electrons. The electric field within the air gap is weak(<3?×?106 V m-1), which inhibits the rapid development of electron avalanches and the formation of filament discharge. The experimental result shows that a 3.0 mm width diffuse DBD is generated in air. Moreover, based on the study of the helical-helical electrode with a floating-voltage electrode, a threedimensional electrode structure is presented, and a three-dimensional diffuse discharge is generated in air by adopting this electrode structure. The plasma studied is stable and demonstrates good diffusion characteristics, and therefore has potential applications in the field of exhaust gas treatment and air purification.

Formation of Diffuse and Spark Discharges in Nonuniform Electric Field in Elevated Pressure Gases

Diffuse and spark discharges are formed and studied during breakdowns with nonuniform electric field in nitrogen,air,and argon at elevated pressures and pulse repetition frequency of 400 Hz.Negative-polarity voltage pulses of the amplitude 20 kV,width at the base of 15 ns and rise time of 2 ns are applied to the electrode with a small radius of curvature.In the conditions of generation of runaway electron beams and X-rays,a CCD camera records the time of the diffuse discharge formation and its duration prior to its transition to a spark one.In all three gases,the diffuse discharge is formed during the time not exceeding 1 ns,when the bright spots appear on cathode in argon and air resulting in the beginning of the spark channel propagation.

Spontaneous growth of the reconnection electric field during magnetic reconnection with a guide field:A theoretical model and particle-in-cell simulations

Reconnection electric field is a key element of magnetic reconnection.It quantifies the change of magnetic topology and the dissipation of magnetic energy.In this work,two-dimensional(2D)particle-in-cell(PIC)simulations are performed to study the growth of the reconnection electric field in the electron diffusion region(EDR)during magnetic reconnection with a guide field.At first,a seed electric field is produced due to the excitation of the tearing-mode instability.Then,the reconnection electric field in the EDR,which is dominated by the electron pressure tensor term,suffers a spontaneous growth stage and grows exponentially until it saturates.A theoretical model is also proposed to explain such a kind of growth.The reconnection electric field in the EDR is found to be directly proportional to the electron outflow speed.The time derivative of electron outflow speed is proportional to the reconnection electric field in the EDR because the outflow is formed after the inflow electrons are accelerated by the reconnection electric field in the EDR and then directed away along the outflow direction.This kind of reinforcing process at last leads to the exponential growth of the reconnection electric field in the EDR.

Characteristics and applications of diffuse discharge of water electrode in air

Plasma water treatment technology, which aims to produce strong oxidizing reactive particles that act on the gas-liquid interface by way of discharging, is used to treat the organic pollutants that do not degrade easily in water. This paper presents a diffuse-discharge plasma water treatment method, which is realized by constructing a conical air gap through an uneven medium layer. The proposed method uses water as one electrode, and a dielectric barrier discharge electrode is constructed by using an uneven dielectric. The electric field distribution in the discharge space will be uneven, wherein the long gap electric field will have a smaller intensity, while the short one will have a larger intensity. A diffuse glow discharge is formed in the cavity. With this type of plasma water treatment equipment, a methyl orange solution with a concentration of 10 mg 1-1 was treated, and the removal rate was found to reach 88.96%.

Using Traveltime Tomography to Reconstruct Electrical Conductivity

A new method for reconstructing electrical conductivity distribution from electromagnetic (EM) data by using traveltime tomography is presented in this paper. Diffusive EM fields can be mathematically transformed to wavefields defined in a time like variable. The transform uniquely relates a field satisfying a diffusion equation in time, or in frequency, to an integral of the corresponding wavefield. This paper first transforms numerically calculated transient magnetic fields to wavefields. Traveltime data from a source to the receivers are estimated from the transformed wavefields. Then an iterative reconstruction algorithm is used to obtain the slowness distribution of a medium. This algorithm is an improved ART algorithm taking account of bending ray paths. The slowness distribution is transformed to electrical conductivity distribution according to their relation. The simulation result is presented in this paper.

Bonding interface between TiAl intermetallic compound and Ti under the electric field

TiAl intermetallic compound was synthesized and bonded together with Ti substrate synchronously by using fieldactivated and pressure-assisted synthesis （FAPAS） process. The effect of electric field on the microstructure and growth pattern of the diffusion dissolution layer of TiA1/Ti interface was mainly studied. The microstructure of the diffusion dissolution layer was investigated by optical microscope （OM） and scanning electron microscope （SEM）. The elements distribution of the diffusion dissolution layer was investigated by energy dispersive spectroscopy （EDS）. The results show that a fine and homogeneous grain structure is obtained in sintered TiA1 intermetallic compound. Metallurgical bond is formed at the TiAl/Ti interface. The thickness of diffusion dissolution layer between TiAl and Ti changes with conduction time and current density.

Electric dipolar interaction assisted growth of single crystalline organic thin films

We report on a forest-like-to-desert-like pattern evolution in the growth of an organic thin film observed by using an atomic force microscope. We use a modified diffusion limited aggregation model to simulate the growth process and are able to reproduce the experimental patterns. The energy of electric dipole interaction is calculated and determined to be the driving force for the pattern formation and evolution. Based on these results, single crystalline films are obtained by enhancing the electric dipole interaction while limiting effects of other growth parameters.

Titanium diboride-metals gradient materials prepared by field activated diffusion bonding process

Functionally gradient samples are prepared by getting metal Ni or Cu bonded with Ni-matrix composites reinforced by TiB2 particles by field activated diffusion bonding process. The intermetallic compound of Ni3Al has been applied as a mediate layer in order to reduce residual stress. The microstracture, phase composition of the interfaces between the metal and Ni3Al are determined and the mechanical properties of the gradient materials are characterized. Elemental concentration profiles across the interfaces between layers showed significant diffusion dissolution and formation of firm bonds. Measured micro-hardness values of the sample increased monotonically from the metal substrate to the surface layer of composites. The values for the surface composite layer ranged from about 2 000 HK to 3 300 HK. The results of this investigation demonstrate the feasibility of field activated diffusion bonding process for rapid preparation of FGMs.

Anisotropic WM conductivity reconstruction based on diffusion tensor magnetic resonance imaging: a simulation study

The present study aims to estimate the in vivo anisotropic conductivities of the White Matter (WM) tissues by means of Magnetic Resonance Electrical Impedance Tomography (MREIT) technique. The realistic anisotropic volume conductor model with different conductivity properties (scalp, skull, CSF, gray matter and WM) is constructed based on the Diffusion Tensor Magnetic Resonance Imaging (DT- MRI) from a healthy human subject. The Radius Basic Function (RBF)-MREIT algorithm of using only one magnetic flux density component was applied to evaluate the eigenvalues of the anisotropic WM with target values set according to the DT-MRI data based on the Wolter’s model, which is more physiologically reliable. The numerical simulations study performed on the five-layer realistic human head model showed that the conductivity reconstruction method had higher accuracy and better robustness against noise. The pilot research was used to judge the feasibility, meaningfulness and reliability of the MREIT applied on the electrical impedance tomography of the complicated human head tissues including anisotropic characteristics.

Physics of electron and lithium-ion transport in electrode materials for Li-ion batteries

The physics of ionic and electrical conduction at electrode materials of lithium-ion batteries （LIBs） are briefly sum marized here, besides, we review the current research on ionic and electrical conduction in electrode material incorporating experimental and simulation studies. Commercial LIBs have been widely used in portable electronic devices and are now developed for large-scale applications in hybrid electric vehicles （HEV） and stationary distributed power stations. However, due to the physical limits of the materials, the overall performance of today＇s LIBs does not meet all the requirements for future applications, and the transport problem has been one of the main barriers to further improvement. The electron and Li-ion transport behaviors are important in determining the rate capacity of LIBs.

Simultaneous enhancement of coercivity and electric resistivity of Nd-Fe-B magnets by Pr-Tb-Al-Cu synergistic grain boundary diffusion toward high-temperature motor rotors

To high-power permanent magnetic motors,it is critical for Nd-Fe-B magnets to maintain the desirable coercivity at high-temperature operating conditions.To address this,two approaches have been proven effective:(1)enhancing the room temperature coercivity;(2)reducing the eddy current loss.However,these two items are difficult to be simultaneously achieved.Here,the grain boundary diffusion(GBD)of the Pr-Tb-Al-Cu-based source is applied to enhance the coercivity and electric resistivity at room temperature from 1101 kA m-1 and 2.13×10–6Ωm to 1917 kA m-1 and 2.60×10–6Ωm,and those at 120°C from 384 kA m-1 and 4.31×10–6Ωm to 783 kA m-1 and 4.86×10–6Ωm,respectively.Such optimization is ascribed to the improved formation depth of Tb-rich 2:14:1 shells with large magnetocrystalline anisotropy and the increased intergranular Pr-based oxides with high electric resistivity,induced by the coordination effects of Tb and Pr,as proven by the atomic-scale observations and the first principles calculations.It thus results in the simultaneously improved output power and energy efficiency of the motor because of the combination of magnetic thermal stability enhancement and eddy current loss reduction,as theoretically confirmed by electromagnetic simulation.

Near-seamless joining of Cf/SiC composites using Y_(3)Si_(2)C_(2)via electric field-assisted sintering technique

A novel Y_(3)Si_(2)C_(2)material was synthesized at a relatively low temperature(900℃)using a molten salt method for the first time,and subsequently used as the joining material for carbon fiber reinforced SiC(Cf/SiC)composites.The sound near-seamless joints with no obvious remaining interlayer were obtained at 1600℃using an electric field-assisted sintering technique(FAST).During joining,a liquid phase was formed by the eutectic reaction among Y_(3)Si_(2)C_(2),γ(Y–C)phase,and SiC,followed by the precipitation of SiC particles.The presence of the liquid promoted the sintering of newly formed SiC particles,leading to their complete consolidation with the Cf/SiC matrix.On the other hand,the excess of the liquid was pushed away from the joining area under the effect of a uniaxial pressure of 30 MPa,leading to the formation of the near-seamless joints.The highest shear strength(Ä)of 17.2±2.9 MPa was obtained after being joined at 1600℃for 10 min.The failure of the joints occurred in the Cf/SiC matrix,indicating that the interface was stronger than that of the Cf/SiC matrix.The formation of a near-seamless joint minimizes the mismatch of thermal expansion coefficients and also irradiation-induced swelling,suggesting that the proposed joining strategy can be potentially applied to SiC-based ceramic matrix composites(CMCs)for extreme environmental applications.