EFFECT OF METAL-OXIDE DIFFUSION BARRIER ON INTERDIFFUSION OF ELEMENTS BETWEEN COATING AND SUBSTRATE

The effect of LPPS Ni_3Al-Y_2O_3 diffusion barrier layer on interdiffusion of elements between coating and substrate has been investigated.It was found that the retardation of interdiffusion is related to the amount of oxide in the diffusion barrier layer.The retardation is not remark- able when the content of Y_2O_3 is 8 wt-%,whereas the diffusion of Al,Co or Cr has all been notably retarded when the content of Y_2O_3 reaches 30 wt-%.The retardation effect of diffu- sion barrier is different for different elements such as Al,Co or Cr.

Beryllium carbide as diffusion barrier against Cu:First-principles study

Beryllium carbide is used in inertial confinement fusion(ICF)capsule ablation material due to its low atomic number,low opacity,and high melting point properties.We used the method of climbing image nudged elastic band(CINEB)to calculate the diffusion barrier of copper atom in the crystal of beryllium and beryllium carbide.The diffusion barrier of copper atom in crystal beryllium is only 0.79 eV,and the barrier in beryllium carbide is larger than 2.85 eV.The three structures of beryllium carbide:anti-fluorite Be2C,Be2C-Ⅰ,and Be2C-Ⅲhave a good blocking effect to the diffusion of copper atom.Among them,the Be2C-Ⅲstructure has the highest diffusion barrier of 6.09 eV.Our research can provide useful help for studying Cu diffusion barrier materials.

Effect of Pt diffusion barrier layer in Ni/AuGe/Pt/Au on ohmic contact to n-GaAs

The multi-layer metals of Ni/AuGe/Pt/Au with a Pt diffusion barrier layer of ohmic contact to n-GaAs were studied. The surface morphology and ohmic contact resistivity of multi-layer metals were characterized, with and without the Pt diffusion barrier layer for comparison. The SEM and EDS measurements show the Pt diffusion barrier layer can block the interdiffusion of atoms in multi-layer metals, and improve the surface morphology. The TLM results show that the samples with a Pt diffusion barrier layer have uniform ohmic contact resistance, indicating that the Pt diffusion barrier layer can increase the repetition and uniformity of ohmic contact to n-GaAs, and improve the thermal stability and reliability of GaAs-based devices.

Limiting current oxygen sensor based on Y,In co-doped SrTiO_(3)as a dense diffusion barrier layer

A novel dense diffusion barrier material(Y_(x)Sr_(1−x)Ti_(0.9)In_(0.1)O_(3−δ)(x=0.03,0.05,0.07))was prepared by using a sol-gel method.The crystal structure,microstructures,electrical conductivity and ionic conductivity of barrier material were characterized.The results show that the samples exhibit the formation of cubic perovskite structure phase.The increase of Y-doping amount on A-site improved electrical conductivity and sinterability of materials.A limiting current oxygen sensor based on Y_(0.07)Sr_(0.97)Ti_(0.9)In_(0.1)O_(3–δ)as a dense diffusion barrier shows excellent sensing performance.The linear relationship between limiting current logIL and 1000/T can described logIL=4.603,8−3.847,5·1,000/T.At 750°C,0.25%≤x(O_(2))≤5.0%,the linear relationship between limiting current(IL)and oxygen amount(x(O_(2)))can described as I_(L)=7.047,6+3.875,1·x(O_(2)).

Achieving Reliable CoSb_(3) based thermoelectric joints with low contact resistivity using a high-entropy alloy diffusion barrier layer

Skutterudite(SKD)thermoelectric materials have high conversion efficiency,great mechanical proper-ties,and economical practicability in the medium temperature range(500e550C).They need to bejoined with metal electrodes to form a thermoelectric power generation device during application.However,high contact resistivity,severe element diffusion,and large coefficient of thermal expansionmismatch are main obstacles for their applications.To address these issues,a FeCoNiCrMo high-entropyalloy diffusion barrier layer was designed and prepared using an arc smelting method in this paper.Effectof heating temperatures on the microstructure and properties of the bonded joints were investigated.The maximum shear strength was 21.6 Mpa and the corresponding reaction layer thickness,contactresistivity were 3.77 mm,1.8 mUcm2 respectively at 600C,40 MPa,10 min.Shear strength dropped downto 18.8 MPa and the contact resistivity increased to 4.2 mU cm2 after aging for 640 h.Numerical modelwas established and it predicted that the contact resistivity would keep lower than 6.5 mU cm2(300 h,100 days)and 11 mU cm2(8760 h,1 year)and the reaction layer thickness would not exceed 25 mm(2400 h,100 days)and 45 mm(8760 h,1 year).

Effects of Pt diffusion barrier layer on the interface reaction and electric properties of PZT film/Si (111) sample

The effects of the Pt diffusion barrier layer on the interface diffusion and reaction, crystallization, dielectric and ferroelectric properties of the PZT/Si(111) sample have been studied using XPS, AES and XRD techniques. The results indicate that the Pt diffusion barrier layer between the PZT layer and the Si substrate prohibits the formation of TiCx, TiSix and SiO2 species in the PZT layer. The Pt barrier layer also completly interrupts the diffusion of Si from the Si substrate into the PZT layer and impedes the diffusion of oxygen from air to the Si substrate greatly. Although the Pt layer can not prevent completely the diffusion and reaction between oxygen and silicon, it can prevent the formation of a stable SiO2 interface layer on the interface of PZT/Si. The Pt layer reacts with silicon to form PtSix species on the interface of Pt/Si, which can intensify the chemical binding strength between the Pt layer and the Si substrate. To play a good role as a diffusion barrier layer, the Pt barrier layer must be not thinner than 140 nm. The existence of the Pt layer not only promotes the crystallization of PZT layer to form a perovskite phase but also improves dielectric and ferroelectric performances of the PZT layer.

In Situ Reaction Fabrication of a Mixed-Ion/Electron-Conducting Skeleton Toward Stable Lithium Metal Anodes

Lithium metal batteries are emerging as a strong candidate in the future energy storage market due to its extremely high energy density.However,the uncontrollable lithium dendrites and volume change of lithium metal anodes severely hinder its application.In this work,the porous Cu skeleton modified with Cu_(6)Sn_(5)layer is prepared via dealloying brass foil following a facile electroless process.The porous Cu skeleton with large specific surface area and high electronic conductivity effectively reduces the local current density.The Cu_(6)Sn_(5)can react with lithium during the discharge process to form lithiophilic Li_(7)Sn_(2)in situ to promote Li-ions transport and reduce the nucleation energy barrier of lithium to guide the uniform lithium deposition.Therefore,more than 300 cycles at 1 mA cm^(−2)are achieved in the half-cell with an average Coulombic efficiency of 97.5%.The symmetric cell shows a superior cycle life of more than 1000 h at 1 mA cm^(−2)with a small average hysteresis voltage of 16 mV.When coupled with LiFePO_(4)cathode,the full cell also maintains excellent cycling and rate performance.

An in-situ formed ceramic/alloy/ceramic sandwich barrier to resist elements interdiffusion between NiCrAlY coating and a Ni-based superalloy

NiCrAlY coatings are widely applied on various alloy components to enhance oxidation and/or corrosion resistance at high temperatures.However,elements interdiffusion occurs between them due to composition difference.Although various diffusion barriers(DBs)are reported,this problem is still far from completely solved as most ceramic barriers suffer from poor adherence,while the metallic barriers play a limited role.In this study,NiCrAlY coating was deposited onto a second-generation single-crystal superalloy by arc ion plating.A novel simple method is provided to address elements interdiffusion.By pre-oxidation at a moderate temperature,a thin scale of Ni(Co)O forms at the alloy surface.It transforms to be an alumina/NiCoCr alloy/alumina sandwich by an in-situ reaction with the overlaying NiCrAlY coating and the alloy substrate at high service temperatures,which offers good barrier ability in conjunction with strong adhesion.In the presence of such an alumina/alloy/alumina DB,the NiCrAlY coating provides high resistance to oxidation and scale spallation for the alloy substrate.

Search for potential K ion battery cathodes by first principles

An important challenge facing K-ion batteries lies in exploring earth-abundant and safe cathode materials that can provide high capacity with high migration rate of K ions.Here,we propose a simple and efficient method for searching potential K cathode materials with first principles calculations.Our screening is based on combinations of weight capacity,K ion occupation ratio,volume change per K,and valence limit.With this screening method we predicted a series of potential K ions cathodes with favorable electrochemical performance,such as K_(2)VPO_(4)CO_(3)-like structures with 1 D diffusion channels,3 D channel structures K_(2)CoSiO_(4),layered materials KCoO_(2),KCrO_(2),KVF_(4) and K_(5)V_(3)F_(14),and others.These potential cathodes have small volume changes,suitable voltage,and high capacity,with small diffusion barriers.They may be useful in K-ion batteries with high energy density and rate performance.

Preparation and Microstructure of Tantalum Nitride Thin Film by Cathodic Arc Deposition

Tantalum nitride （TAN） thin films are achieved on Si（111） and SS317L substrates by cathodic vacuum arc technique, which is rarely reported in the literature. The crystal structure, composition and surface morphology of the films are characterized by x-ray diffraction （XRD）, x-ray photoelectron spectroscopy （XPS）, auger electron spectroscopy, and atomic force microscopy, respectively. The influence of substrate negative bias on crystal structure, composition, surface morphology of the TaN films is systematically studied. At the substrate bias of 0 V and -50 V, the amorphous TaN film is obtained. As the bias increases to -100 V, cubic TaN phase can be found. Stoichiometric TaN with hexagonal lattice preferred （300） orientation is prepared at a bias of -200 V. Combine the XRD and XPS results, the binding energy value of 23.6eV of Ta 4f（7/2） is contributed to hexagonal TaN. Compared to other techniques, TaN thin films fabricated by cathodic vacuum arc at various substrate biases show different microstructures.

Engineering Sodium Metal Anode with Sodiophilic Bismuthide Penetration for Dendrite-Free and High-Rate Sodium-Ion Battery

Sodium(Na)metal batteries with a high volumetric energy density that can be operated at high rates are highly desirable.However,an uneven Na-ion migration in bulk Na anodes leads to localized deposition/dissolution of sodium during high-rate plating/stripping behaviors,followed by severe dendrite growth and loose stacking.Herein,we engineer the Na hybrid anode with sodiophilic Na_(3)Bi-penetration to develop the abundant phase-boundary ionic transport channels.Compared to intrinsic Na,the reduced adsorption energy and ion-diffusion barrier on Na_(3)Bi ensure even Na^(+)nucleation and rapid Na^(+)migration within the hybrid electrode,leading to uniform deposition and dissolution at high current densities.Furthermore,the bismuthide enables compact Na deposition within the sodiophilic framework during cycling,thus favoring a high volumetric capacity.Consequently,the obtained anode was endowed with a high current density(up to 5 mA∙cm^(−2)),high areal capacity(up to 5 mA∙h∙cm^(−2)),and long-term cycling stability(up to 2800 h at 2 mA∙cm^(−2)).

Interfacial Stress Analysis on Skutterudite-based Thermoelectric Joints under Service Conditions

In thermoelectric(TE)devices,the interfacial reliability greatly influenced devices’durability and power output.For skutterudites(SKD)devices,TE legs and electrodes are bonded together with diffusion barrier layer(DBL).At elevated temperatures,DBL react with SKD matrix or electrode to generate complex interfacial microstructures,which often accompanies evolutions of the thermal,electrical and mechanical properties at the interfaces.In this work,a finite element model containing the interfacial microstructure characteristics based on the experimental results was built to analyze the interfacial stress state in the skutterudite-based TE joints.A single-layer model was applied to screen out the most important parameters of the coefficient of thermal expansion(CTE)and the modulus of DBL on the first principle stress.The multilayer model considering the interfacial microstructures evolution was built to quantitively simulate the stress state of the TE joints at different aging temperatures and time.The simulation results show that the reactive CoSb2 layer is the weakest layer in both SKD/Nb and SKD/Zr joints.And by prolonging the aging time,the thickness of the reaction layer continuously increased,leading to a significant raising of the interfacial stress.The tensile testing results of the SKD/Nb joints match the simulation results well,consolidating accuracy and feasibility of this multilayer model.This study provides an important guidance on the design of DBL to improve the TE joints’mechanical reliability,and a common method to precisely simulate the stress condition in other coating systems.

Improvement of Interfacial Adhesion Strength and Thermal Stability of Cu/p-SiC:H/SiOC:H Film Stack by Plasma Treatment on the Surface of Cu Film

A highly reliable interface of self-aligned barrier CuSiN thin layer between the Cu film and the nano-porous SiC：H （p-SiC：H） capping barrier （k=3.3） has been developed in the present work. With the introduction of self-aligned barrier （SAB） CuSiN between a Cu film and a p-SiC：H capping barrier, the interfacial thermal stability and the adhesion of the Cu/p-SiC：H film are considerably enhanced. A significant improvement of adhesion strength and thermal stability of Cu/p-SiC：H/SiOC：H film stack has been achieved by optimizing the pre-clean step before caplayer deposition and by forming the CuSiN-like phase. This cap layer on the surface of the Cu can provide a more cohesive interface and effectively suppress Cu atom migration as well.

The investigation of ZnO:Al_2O_3/metal composite back reflectors in amorphous silicon germanium thin film solar cells

Different aluminum-doped ZnO （AZO）/metal composite thin films, including AZO/Ag/Al, AZO/Ag/nickelchromium alloy （NiCr）, and AZO/Ag/NiCr/Al, are utilized as the back reflectors of p-i-n amorphous silicon germanium thin film solar cells. NiCr is used as diffusion barrier layer between Ag and Al to prevent mutual diffusion, which increases the short circuit current density of solar cell. NiCr and NiCr/AI layers are used as protective layers of Ag layer against oxidation and sulfurization, the higher efficiency of solar cell is achieved. The experimental results show that the performance of a-SiGe solar cell with AZO/Ag/NiCr/Al back reflector is best. The initial conversion efficiency is achieved to be 8.05%.

Optimal reactions for synthesis of nuclides of element 108

The cross sections for the production of nuclides of element 108 via hot fusion evaporation reactions are studied using a two-parameter Smoluchowski equation. The optimal reactions for the synthesis of new nuclides of element 108 with mass numbers from 266 to 271 are suggested. The macroscopic-microscopic approach predicts a strong deformed shell closure at Z ≈ 108 and N = 162. The synthesis of more nuclides of element 108 is meaningful to the confirmation of the existence of this deformed shell closure.

Magnetic resonance imaging and cell-based neurorestorative therapy after brain injury

Restorative cell-based therapies for experimental brain injury, such as stroke and traumatic brain injury,substantially improve functional outcome. We discuss and review state of the art magnetic resonance imaging methodologies and their applications related to cell-based treatment after brain injury. We focus on the potential of magnetic resonance imaging technique and its associated challenges to obtain useful new information related to cell migration, distribution, and quantitation, as well as vascular and neuronal remodeling in response to cell-based therapy after brain injury. The noninvasive nature of imaging might more readily help with translation of cell-based therapy from the laboratory to the clinic.

Improving cyclic oxidation resistance of Ni_(3)Al-based single crystal superalloy with low-diffusion platinum-modified aluminide coating

A low-diffusion Ni Re Pt Al coating((Ni,Pt)Al outer layer in addition to a Re-rich diffusion barrier layer)was prepared on a Ni_(3)Al-base single crystal(SC)superalloy via electroplating and gaseous aluminizing treatments,wherein the electroplating procedures consisted of the composite deposition of Ni-Re followed by electroplating of Pt.In order to perform a comparison with conventional Ni Al and(Ni,Pt)Al coatings,the cyclic oxidation performance of the Ni Re Pt Al coating was evaluated at 1100 and 1150℃.We observed that the oxidation resistance of the Ni Re Pt Al coating was significantly improved by the greater presence of the residualβ-Ni Al phase in the outer layer and the lesser outward-diffusion of Mo from the substrate.In addition,the coating with the Re-rich diffusion barrier demonstrated a lower extent of interdiffusion into the substrate,where the thickness of the second reaction zone(SRZ)in the substrate alloy decreased by 25%.The mechanisms responsible for improving the oxidation resistance and decreasing the extent of SRZ formation are discussed,in which a particular attention is paid to the inhibition of the outward diffusion of Mo by the Re-based diffusion barrier.

The thermodynamically directed dendrite-free lithium metal batteries on LiZn alloy surface

Metical lithium(Li)is one of the most promising alternatives as an anode in next-generation high energy batteries for its high theoretical specific capacity and low redox potential.However,severe Li dendrite growth leading to poor stability and safety issues hinders its practical implementation.Herein,three-dimensional carbon cloth(CC)with full zinc oxide quantum dots(ZnO QDs)covering is rationally chosen as the substrate for the suppression of Li dendrite.Owing to the spontaneous reaction between ZnO QDs and molten Li,LiZn alloy is formed and covered on CC,which endows substrate with high affinity for Li adsorption and suitable barrier energy for Li diffusion.This thermodynamic regulation on substrate is beneficial for homogeneous Li nucleation and deposition,thus enabling high stability for over 1,900 h at ultrahigh current density of 10 mA∙cm^(−2) in symmetrical cell and delivering superior performance in full batteries.

Enhanced oxidation resistance of Ce by addition of Ga and nanocrystallization

Ce is prone to catastrophic oxidation at room temperature and its oxidation resistance is difficult to be improved by alloying.Herein,we found that the oxidation resistance of active metal Ce can be significantly improved by the addition of 20 at.%Ga.Focused ion beam lift-out technique and scanning transmission electron microscopy analysis disclosed that a discontinuous Ga-rich layer was generated beneath the oxide layer in the coarse-grained Ce-Ga alloy.The Ga-rich layer formed by selective oxidation of Ce acts as a diffusion barrier for Ce outward diffusion and ceases the O/M interfacial reaction when a critical concentration of Ga(75 at.%)is reached.After nanocrystallization,uniform distribution of Ga was achieved.After oxidation,a relatively continuous Ga-rich layer was formed which further enhanced the oxidation resistance.The introduction of noble elements combining with nanocrystallization may provide a novel strategy for the protection of metals with high activity and poor oxidation resistance.

Li-ion transport in solid-state electrolyte of Li_(1-x)Al_(1-x)Si_(2+x)O_(6):an ab initio study

All-solid-state batteries are considered as nextgeneration technology for energy storage due to their high energy density and excellent s afety.However,only a few solid electrolytes exhibit ionic conductivities comparable to liquid electrolytes.Finding low-cost solid electrolytes with high Liion conductivity is in high demand.Based on the ab initio molecular dynamic simulations,the Li^(+)diffusion inβ-LiAISi_(2)O_(6),a type of cost-effective and naturally-available mineral,and its disordered systems Li_(1-x)Al_(1-x)Si_(2+x)O_(6)with-1.0≤x≤0.5 was studied.Our calculations show that the phases of Li_(1-x)Al_(1-x)Si_(2+x)O_(6)with nonzero x all possess much lower diffusion energy barriers than pristine LiAlSi_(2)O_(6).When x is positive,increased concentration of lithium vacancies accelerates the diffusion of Li-ions.When x is negative,additional Li-ions are inserted into structures and co-migration is stimulated among these Li-ions.In particular,the maximal ionic conductivity at 300 K(1.92×10^(-6)S·cm^(-1))is obtained in Li_(2)Al_(2)SiO_(6)(x=-1.0),which is five orders of magnitude larger than that of pristineβ-LiAlSi_(2)O_(6).In addition,the diffusion barrier can be further reduced to 0.38 eV by replacing Si with Ge,and the ionic conductivity for Li_(2)Al_(2)GeO_(6)can reach 3.08×10~(-5)S·cm^(-1)at 300 K.Our work facilitates the understanding of Li+conduction mechanisms in silicatebased electrolytes and the development of cost-effective and high-performance solid-s ate electrolytes.