Thickness Of Transition Layer Research Articles

Effect of carbon nanotubes and octa-aminopropyl polyhedral oligomeric silsesquioxane on the surface behaviors of carbon fibers and mechanical performance of composites

A kind of carbon fiber/carbon nanotubes/octa-aminopropyl polyhedral oligomeric silsesquioxane (CF/CNTs/POSS for short) reinforcement was prepared by grafting CNTs and OA-POSS to CFs surfaces in order to improve the mechanical properties and interfacial performance. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and contact angle testing and analysis were applied to characterize the carbon fibers surface. Tensile testing, bending testing and interlayer shear strength (ILSS) testing were employed to analyze the mechanical properties of composites. The experimental results of SEM and XPS indicate that CNTs and OA-POSS are grafted uniformly on fibers surface with chemical bonding of NH in CNTs and POSS and COOH on CFs surface. The contact angle test and analysis results show that the surface energy of modified CFs decrease compared with that of the unmodified. Furthermore, the mechanical properties of composites after coating with CNTs and OA-POSS are enhanced effectively. Especially, the properties of composites fabricated by CF/1%CNTs/POSS are significantly improved, because OA-POSS increases the interfacial strength and CNTs increases the thickness of the interfacial transition layer, which both improves the interface defects diffusion of composites. Therefore, CF/CNTs/POSS can improve the performance of the composites by forming interface transition layers.

Research on interface bonding energy of multi-layer model on ZChSnSb/FeSn2/Steel

Abstract Microscopic tests on the interface of ZChSnSb/Steel bimetallic composite specimens were conducted using such methods as SEM, EDS and XRD. The results indicate that the transition layer on FeSn2 could be produced when ZChSnSb was bonded with Steel. Based on test results, the three-layer composite model on ZChSnSb/FeSn2/Steel was constructed, and the model was optimized using Newton-Raphson methods. The formulas on the interface energy of the three-layer composites were deduced, and the interface bonding energy at different temperatures was calculated. The calculated results proved that the optimal bonding temperature of the model is 280 °C and the optimal interlayer thickness of transition layer on FeSn2 at 280 °C is 15.396 A.

The semi-analytical method for damping of tubular transition layer damping structure

To solve the limited vibration consumption of the traditional tubular damping structure (TTDS), the tubular transition layer damping structure (TTLDS) is proposed; Based on viscoelastic materials and theories of thin cylindrical shells, the governing equation, the first order matrix differential equation describing vibration of TTLDS under harmonic excitation, is derived by considering the interaction between all layers and the dissipation caused by the shear deformation for transition layer and damping layer. By using the extended homogeneous capacity precision integration method to solve the control equation, a semi-analytical method for studying the vibration and damping characteristics of TTLDS is given. By way of comparison, the correctness of the method provided in paper is verified. At last, the influence of thickness, material and location of transition layer on damping effect is analyzed. The results show that the change for the thickness or material of the transition layer can make the structural damping effect change greatly, while the change for location of the transition layer plays only a few roles on the structural damping effect.

Designing flexible 2D transition metal carbides with strain-controllable lithium storage

Efficient flexible energy storage systems have received tremendous attention due to their enormous potential applications in self-powering portable electronic devices, including roll-up displays, electronic paper, and "smart" garments outfitted with piezoelectric patches to harvest energy from body movement. Unfortunately, the further development of these technologies faces great challenges due to a lack of ideal electrode materials with the right electrochemical behavior and mechanical properties. MXenes, which exhibit outstanding mechanical properties, hydrophilic surfaces, and high conductivities, have been identified as promising electrode material candidates. In this work, taking 2D transition metal carbides (TMCs) as representatives, we systematically explored several influencing factors, including transition metal species, layer thickness, functional group, and strain on their mechanical properties (e.g., stiffness, flexibility, and strength) and their electrochemical properties (e.g., ionic mobility, equilibrium voltage, and theoretical capacity). Considering potential charge-transfer polarization, we employed a charged electrode model to simulate ionic mobility and found that ionic mobility has a unique dependence on the surface atomic configuration influenced by bond length, valence electron number, functional groups, and strain. Under multiaxial loadings, electrical conductivity, high ionic mobility, low equilibrium voltage with good stability, excellent flexibility, and high theoretical capacity indicate that the bare 2D TMCs have potential to be ideal flexible anode materials, whereas the surface functionalization degrades the transport mobility and increases the equilibrium voltage due to bonding between the nonmetals and Li. These results provide valuable insights for experimental explorations of flexible anode candidates based on 2D TMCs.

Mg concentration profile and its control in the low temperature grown Mg-doped GaN epilayer

In this work, the Cp2Mg flux and growth pressure influence to Mg doping concentration and depth profiles is studied. From the SIMS measurement we found that a transition layer exists at the bottom region of the layer in which the Mg doping concentration changes gradually. The thickness of transition layer decreases with the increases of Mg doping concentration. Through analysis, we found that this is caused by Ga memory effect which the Ga atoms stay residual in MOCVD system will react with Mg source, leading a transition layer formation and improve the growth rate. And the Ga memory effect can be well suppressed by increasing Mg doping concentration and growth pressure and thus get a steep Mg doping at the bottom region of p type layer.

Effect of laser-GTAW hybrid welding heat input on the performance of Mg/Steel butt joint

The most common welding method for Mg/steel dissimilar metals is melt-brazing with lap joints; however, the butt fusion welding of Mg/steel joint remains a challenging task. 1.6mm AZ31B Mg alloy was joined with 1.0mm Q235 steel by using laser-gas tungsten arc welding (GTAW) hybrid butt welding with AZ61 filler metal. The influence of welding heat input on the morphology, interface bonding, mechanical properties and fracture modes of welded joints was systematically analyzed. Resultsshow that laser-GTAW hybrid welding with filling wire can be used to combine high-performance joints and Mg/steel dissimilar metals during butt assembly. The maximum average tensile fracture load of the joints can reach up to 3265N (the load equal to that of steel base metal). The tensile load of the joints decreases with the decrease in heat input. A reaction layer is formed on the welding interface enriched with Al and Mn elements. The morphology of Mg/steel joint and the thickness of interface transition layer are the key factors affecting the properties and fracture mechanism of the welded joint. With the decrease in heat input, the Mg/steel butt joints had three fracture modes, including the fracture on the base metal of steel, Mg weld seam, and Mg/steel interface.

Dissimilar joining of AZ31B magnesium alloy and pure copper via thermo-compensated resistance spot welding

The feasibility of Mg/Cu dissimilar resistance spot welding (RSW) was investigated via a thermo-compensated process. Both physical factors and metallurgical properties of the welds affected the tensile shear properties of the joints. The mechanical properties of the Mg/Cu RSW joints were determined by the competitive relationship between these two factors. The increase in the nugget size with increasing Joule heat input improved the load-bearing ability of the joints. However, at the same time, the microstructure of the nugget transformed from an α-Mg solid solution fusion zone with a thin transition layer into an intermetallic compound (IMC)-enriching fusion zone with a thick transition layer. The mechanical properties of the joints deteriorated, owing to this transformation. All the Mg/Cu RSW samples fractured via interfacial failure (IF) mode and exhibited cleavage features. Although their ductility deteriorated owing to the IMCs, the Mg/Cu thermo-compensated RSW joints exhibited satisfactory tensile shear peak loads (maximum: 2626N), which are comparable to that (2745N) of Mg/Mg RSW joints. A reliable welding lobe suitable for industrial manufacture was obtained, when a welding time and a welding current of 100ms–400ms and 12kA–20kA, respectively, were recommended.

Investigation of Interfacial Layer for Ultrasonic Spot Welded Aluminum to Copper Joints

The bonding formation for ultrasonic welding of dissimilar metals has been shrouded in mystery because of the complex thermomechanical behavior at the bonding interface. We investigated the microstructure and phases at the bonding interface of ultrasonically welded aluminum to copper joints using transmission electron microscopy, and found a ~10 nm thick transition layer composed of amorphous phase and nanocrystallines, which was believed to form the bonding between these two metals in addition to mechanical interlocking observed at a larger scale. Interdiffusion of parent elements (i.e. Al and Cu) was noticed in the amorphous phase, which was mainly driven by plastic deformation in solid state introduced by ultrasonic vibration. High densities of dislocations and stacking faults were also observed in the parent metals close to the transition layer, confirming the effects of severe plastic deformation.

FEM thermal and stress analysis of bonded GaN-on-diamond substrate

A three-dimensional thermal and stress analysis of bonded GaN on diamond substrate is investigated using finite element method. The transition layer thickness, thermal conductivity of transition layer, diamond substrate thickness and the area ratio of diamond and GaN are considered and treated appropriately in the numerical simulation. The maximum channel temperature of GaN is set as a constant value and its corresponding heat power densities under different conditions are calculated to evaluate the influences that the diamond substrate and transition layer have on GaN. The results indicate the existence of transition layer will result in a decrease in the heat power density and the thickness and area of diamond substrate have certain impact on the magnitude of channel temperature and stress distribution. Channel temperature reduces with increasing diamond thickness but with a decreasing trend. The stress is reduced by increasing diamond thickness and the area ratio of diamond and GaN. The study of mechanical and thermal properties of bonded GaN on diamond substrate is useful for optimal designs of efficient heat spreader for GaN HEMT.

Mass transfer performance of water recovery from flue gas of lignite boiler by composite membrane

Membrane technology is a potential way for water recovery from the flue gas of the lignite boiler. Consider the influences of the micro-scale configuration of the membrane and the operating parameters, the physical process was modeled based on the Stefan Maxwell theory, as well as the composite membrane resistance model for numerical simulation. The mass transfer process of flue gas in coating, transition layer and support layer of the composite membrane was analyzed respectively. The theoretical results were both verified by experiments and numerical simulations. The influences of different materials, pressure difference, porosity and transition layer thickness on the water vapor permeation flux were revealed. The results show that the high Henry coefficient and the high selectivity of water vapor have great advantages in the application, and the increase of pressure, porosity and thickness of the transition layer are all beneficial to increase the water vapor flux. Based on the theoretical model, the multi attribute decision making method was employed to provide suggestions for membrane material selection of gas water recycling in the experimental researches as well as in the engineering applications.

Effect of interfacial enhancing on morphology, mechanical, and rheological properties of polypropylene‐ground tire rubber powder blends

ABSTRACTIn this work, polypropylene (PP)‐ground tire rubber (GTR) blends are prepared by means of melt‐extrusion process using a co‐rotating twin screw extruder. The influences of types of compatibilizers and crosslinkers on the interfacial interaction state, mechanical and rheological properties of PP‐GTR blends are investigated systematically. Particularly, quantitative nano mechanic technique of atom force microscope was employed to examine the change in thickness of the interfacial transition layer between PP and GTR phase with variety of compatibilizer and crosslinker types. Results indicated that styrene‐b‐poly(ethylene‐ethylene/propylene)‐b‐polystyrene (SEEPS) and peroxide are optimal compatibilizer and crosslinker for interfacial interaction enhancement, respectively. The resultant PP‐GTR blend possesses tensile strength of 14.5 MPa, elongation at break of 307%, and permanent set of 16%. It was expected that reaction activities of the crosslinker with GTR and SEEPS would have a significant influence on the agglomeration of GTR particles and the interaction between PP and GTR phase. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45354.

Thickness of Transition Layer Effect on Bonding Strength in DLC Film

Make use of PVD technology and ICS-04 ARC PRO coating equipment to prepare three groups of Cr/DLC composite films with different thickness of Cr transition layer based on Hss. Three groups of specimens in the Cr deposition time respectively for 10 mins, 20 mins and 30 mins. After measuring instrument with nondestructive testing, the film’s thickness of three groups of specimens are 0.7μm, 0.8μm and 0.9μm respectively. Measured the bonding strength of three groups of films by indentation method. The results show that the thickness of the film increases linearly with deposition time. The bonding properties improved with the increase of film’s thickness.

Experimental and numerical study of optimum thickness of porous silica transition layer in aeronautic laminated glass

The application of a porous silica (PS) transition layer in an inorganic-organic aeronautic laminated glass can effectively solve the material failure caused by the performance difference of the inorganic-organic materials. The effect of porous silica transition layer thickness on the mechanical and optical properties of laminated glass was investigated. The microstructure of the porous silica transition layer was analyzed by scanning electron microscopy. The film thickness was verified using a step profiler. The failure strength of laminated glass with the porous silica transition layer was tested by a universal testing machine. Finite element modeling of laminated glass with the porous silica transition layer was performed by ANSYS software. Tensile stress between the porous silica and the polyurethane was simulated for different porous silica film thicknesses. Experimental and theoretical results indicated that with the increasing the thickness of the transition film, the failure stress of the laminated glass increased. Improvements in the mechanical properties of the laminated glass are saturation at a PS thickness of approximately 3.8μm.

IMPULSIVELY GENERATED SAUSAGE WAVES IN CORONAL TUBES WITH TRANSVERSALLY CONTINUOUS STRUCTURING

ABSTRACT The frequency dependence of the longitudinal group speeds of trapped sausage waves plays an important role in determining impulsively generated wave trains, which have often been invoked to account for quasi-periodic signals in coronal loops. We examine how the group speeds ( ) depend on angular frequency (ω) for sausage modes in pressureless coronal tubes with continuous transverse density distributions by solving the dispersion relation pertinent to the case where the density inhomogeneity of arbitrary form occurs in a transition layer of arbitrary thickness. We find that in addition to the transverse lengthscale l and density contrast , the group speed behavior also depends on the detailed form of the density inhomogeneity. For parabolic profiles, always decreases with ω first before increasing again, as happens for the much studied top-hat profiles. For linear profiles, however, the behavior of the curves is more complex. When , the curves become monotonical for large values of l. On the other hand, for higher density contrasts, a local maximum exists in addition to a local minimum when coronal tubes are diffuse. With time-dependent computations, we show that the different behavior of group speed curves, the characteristic speeds and in particular, is reflected in the temporal evolution and Morlet spectra of impulsively generated wave trains. We conclude that the observed quasi-periodic wave trains not only can be employed to probe such key parameters as density contrasts and profile steepness, but also have the potential to discriminate between the unknown forms of the transverse density distribution.

Comparison of the structural and corrosion properties of the graphene/SiN(200) coating system deposited on titanium alloy surfaces covered with SiN transition layers

Abstract In this paper, comparative studies of the structural and corrosion properties of SiN/graphene/SiN coating systems with various SiN transition layer thickness have been investigated. The coating systems were formed on Ti6Al4V alloy surfaces. The SiN transition layer thicknesses varied from 100 nm to 300 nm. The thickness of the upper silicon nitride thin film, in all examined cases, was 200 nm. The silicon nitride thin film was deposited using the Plasma Enhanced Chemical Vapour Deposition method. A graphene monolayer was transferred onto the silicon nitride surface using the “PMMA-mediated” method. The structural characteristics of coating systems obtained were examined using Raman spectroscopy, optical profilometry and SEM measurements. The corrosion properties of the coating systems were determined by an analysis of the voltammetric curves. The SiN/graphene/SiN coating system with a 300 nm thick silicon nitride transition layer is characterised by the best structural and corrosion properties of all tested coating systems. In this case, the surface of the top silicon nitride thin film has no holes or flakes, as opposed to the coating systems with 100 nm and 200 nm thick transition layers, in which the upper SiN thin film flaked and dropped off. The value of corrosion current density obtained for this sample was almost two orders of magnitude lower than the current density obtained for the other tested coating systems.

Growth of compressively‐strained GaN films on Si(111) substrates with thick AlGaN transition and AlGaN superlattice buffer layers

AbstractIn this paper, crack‐free GaN films with step‐graded AlGaN transition layer and AlGaN superlattice layer as buffer layers were grown on Si(111) substrate by metal‐organic chemical vapor deposition(MOCVD). The combination of both buffers effectively improves the properties of GaN layer. With the optimization of the buffer structures, high quality compressively‐strained GaN layers with thickness up to 3.6 μm have been obtained on Si(111) substrates (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The Brazing Behavior of Aluminum-Steel Cladding Strip with Pre-Cladded Brazing Layer Used in Air Cooling System of Power Plants

The brazing behavior of 3003 fin assemble with 4343(filler layer)/4A60(transition layer)/08Al(steel layer) brazing sheet (the ratio of filler layer thickness to transition thickness were constant 1:2) were investigated. This study elucidates the brazing results vary with the layer thickness and brazing temperatures. Results showed that keeping the holding time at brazing temperature constant (the holding time of this study was 10 minutes in all brazing progress), under the condition of brazing temperature less than or equal to 580 °C, thinner filler layer led to well formed joint, while thicker filler layer led to defects at brazing joints because of poor mobility. When brazing temperature was up to 600 °C, a thinner transition layer trended to lead to the formation a thick intermetallic compounds layer on the Aluminum-Steel surface. It was inferred that Si diffused from molten filler metal to the interface of transition layer and steel layer and promoted the formation of intermetallic compounds. Furthermore, it was found that in the surface away from brazing joints, with lower Si content, the intermetallic compounds were mainly η (Fe 2Al5 ), while higher Si content region nearby brazing joints trended to form τ 5 (Al 8 Fe 2 Si) and τ 6 (Al 4.5 FeSi). Meanwhile, a transition layer with thickness above 134μm could avoid the formation of intermetallic compound. The optimum brazing process was that temperature range was 590 °C to 595 °C with 10-minutes holding time and the transition layer thickness was suggested to be equal or more than 134μm.

Thermal Stability and Corrosion Resistance of Cr/CrN Multilayer Coatings on Ti6Al4V Alloy

The aim of this work was to investigate thermal stability and corrosion resistance of the Cr/CrN multilayer coatings. For this purpose, multilayer Cr/CrN coating was deposited on Ti6Al4V titanium alloy using PVD vacuum arc method. The Cr/CrN coating has thickness of 5.6 μm and was composed of 16 layers (8 Cr and 8 CrN). The Cr layers has thickness of 0.26 μm and were composed of columnar grains. CrN layer has thickness of 0.32 μm and were characterized by needle-like structure. Because of the potential application of the investigated coatings, thermal stability in temperature range of 300-500°C as well as corrosion behavior during salt fog test were analyzed.The investigation showed that microstructure of Cr/CrN multilayer coating was stable up to 400°C. In this temperature only a slight increase of thickness of transition Cr2N layer was observed. Annealing at temperature of 500°C changed the microstructure of the constituent Cr and CrN layers and caused decrease of their thicknesses due to increase of thickness of Cr2N transition layer. Annealing at 500°C also increased the hardness of Cr/CrN coating. XPS analysis revealed the presence of the CrO3and Cr2O3on the surface after annealing. Cr/CrN multilayer coatings exhibit also excellent corrosion resistant in salt fog test. No corrosion products was observed on the Cr/CrN coating surface after 120 hour of test.

Impact of GaN transition layers in the growth of GaN epitaxial layer on silicon**Project supported by the National Natural Science Foundation of China (Nos. 61474110, 61377020, 61376089, 61223005, 61176126), and the National Science Fund for Distinguished Young Scholars (No. 60925017).

A method for growing GaN epitaxial layer on Si (111) substrate is investigated. Due to the large lattice mismatch between GaN and AlN, GaN grown directly above an AlN buffer layer on the Si substrate turns out to be of poor quality. In this study, a GaN transition layer is grown additionally on the AlN buffer before the GaN epitaxial growth. By changing the growth conditions of the GaN transition layer, we can control the growth and merging of islands and control the transfer time from 3D to 2D growth mode. With this method, the crystalline quality of the GaN epitaxial layer can be improved and the crack density is reduced. Here, we have investigated the impact of a transition layer on the crystalline quality and stress evolution of a GaN epitaxial layer with methods of X-ray diffraction, optical microscopy and in situ reflectivity trace. With the increasing thickness of transition layer, the crack decreases and the crystalline quality is improved. But when the transition layer exceeds a critical thickness, the crystalline quality of the epilayer becomes lower and the crack density increases.

Surface plasmon polaritons at linearly graded semiconductor interfaces.

New results are reported on investigation of dispersion curves for surface plasmon polaritons (SPPs) at an inhomogenously doped semiconductor/dielectric interface whereby the dielectric is represented by the same undoped semiconductor. The doped semiconductor is described by its frequency-dependent permittivity that varies with the depth. It is shown that a transition layer (TL) with a linear change in carrier concentration supports one branch dispersion curve regardless of the TL thickness. The obtained dispersion curves reach a maximum at a finite frequency depending on the TL thickness, and subsequently asymptotically approach the zero frequency in the shortwave limit. Therefore two surface plasmon modes are supported at a given frequency: a long-wave mode with a positive group velocity and a short-wave mode with a negative group velocity. A condition of a zero group velocity can be satisfied by tuning the TL layer. It is shown that the conventional dispersion relation for SPPs at a TL with a zero thickness is an asymptotic solution, and the convergence of real dispersion curves is point-wise instead of an expected uniform convergence.