Interfacial Phase Formation Research Articles

Toughening of a vacuum diffusion-bonded heterostructured AZ31/WE94/AZ31 alloy by interfacial reinforcement

Heterostructured materials have recently attracted extensive attentions from the materials community due to their superior combination of strength and ductility as compared to the conventional homogeneous counterparts. In the present study, the laminate AZ31/WE94/AZ31 Mg alloy was produced by vacuum diffusion bonding. The post annealing was carried out to improve the mechanical properties of the heterostructured Mg alloy. It is found the elemental diffusion and formation of interfacial phases enhance the interface bonding strength, thereby improving the comprehensive mechanical properties. The laminate sample annealed at 470 °C for 12 h shows a superior mechanical properties with a yield strength, ultimate tensile strength, and elongation of 158 MPa, 212 MPa and 12.9%, respectively. The higher annealing temperature leads to the growth of interfacial phase, which provides preferential nucleation sites for crack initiation and weakens the tensile properties.

Electrolyte matching design for carboxylic acid-based organic K-storage anode

Carboxylic acid-based organic anodes are emerging as sustainable alternatives to traditional inorganic materials for potassium-ion batteries (PIBs), owing to their potential to improve both sustainability and K-storage performance. Herein, a readily available 4-fluorobenzoic acid (4FA) supported on ordered mesoporous carbon (4FA/CMK3) is proposed as a novel K-storage anode material. Importantly, we extensively investigated the compatibility of various electrolytes with the 4FA/CMK3 anode, focusing on electrolytes with tunable solvation structures to optimize electrode/electrolyte interfacial electrochemistry. A significantly decreased amount of free solvent in the optimized ether-based electrolytes compared to conventional ester-based electrolytes provides excellent compatibility with the modified 4FA/CMK3 anode, which promotes the formation of salt anion-derived interfacial phases, thereby improving K-storage performance. As a result, the optimized 4FA/CMK3||KFSI/DME storage system delivered a reversible capacity of 164 mAh/g with Coulombic efficiency above 99.8 % after 500 cycles at high current density of 200 mA/g. These excellent electrochemical properties are attributed to the synergistic effects of 4FA modification and electrolyte solvation structure modulation, which collectively mitigate the dissolution issues of organic actives and improve the cycling life of PIBs. This work presents a novel vision for designing PIBs with high energy density and long cycle life based on carboxylic acid-based organic electrodes.

Toughening and strengthening of Cu-coated carbon nanotubes reinforced AZ61 magnesium matrix nanocomposites by improving interfacial bonding

Interfacial modification without damaging the structure of carbon nanotubes (CNTs) is urgently needed to improve the performance of CNTs reinforced metal matrix nanocomposites. To fabricate CNTs/AZ61 nanocomposite with strong interfacial bonding, copper-coated CNTs (0.15–2.4 vol%) and AZ61 powder were employed through the process of ball milling mixing, vacuum hot pressing and extrusion. The powder and nanocomposites were characterized by HRTEM, SEM, XRD and compressive test to study the distribution of reinforcements, microstructures, interfacial structure and compression behavior. During the high-temperature fabrication process, in-situ interfacial reactions occurred between Cu particles of CNTs and Mg, Al and Zn elements in AZ61 matrix. As a result, the formation of interfacial reaction phases, such as AlCu3, Al2Cu, Cu2Mg, CuMg2, Cu0.61Zn0.39 and MgAl2C2 phases, and their diffused and/or coherent interface significantly strengthen the interfacial bonding. With only 0.15 vol% CNTs, the work of fracture and compression strength of the composite are 40 % and 20 % higher than those of pure AZ61, respectively. The dominating toughening mechanisms are the load transfer role of scattered CNTs and fine-grain effect. The dominating strengthening mechanisms are thermal mismatch and Orowan strengthening.

Enhanced resistive switching of silver copper iodide thin films prepared by interfacial phase formation

Resistive random-access memory (ReRAM), an alternative to conventional charge storage memory, employs the switching of a resistive material between high-resistance and low-resistance states, which can be generated by the formation/dissolution of metal filaments bridging the two electrodes in the cell. Silver iodide (AgI) is a promising solid electrolyte for ReRAM cells, but its application is hindered by poor photostability and low electrical conductivity. Herein, a Cu-substituted β-AgI system, β′-Ag0.7Cu0.3I, was successfully prepared via sequential deposition of a Cu metal layer onto a AgI thin film by a galvanic reaction, which induced the spontaneous incorporation of Cu+ cations into the AgI lattice. Cu substitution at the Cu–AgI heterojunction interface is a novel way to modulate the chemical composition and improve the resistive switching properties of intrinsic polycrystalline AgI thin films. We compared the resistive switching properties of a ReRAM thin film devices based on β′-Ag0.7Cu0.3I with those based on pristine β-AgI. This device exhibited enhanced performance with high ON/OFF ratio (∼104) and low working voltage compared with the β-AgI-based device. These results strongly suggest that binary metal halide materials can serve as simple model systems for the efficient formation of metal filaments and have potential low-cost, low-power memory applications.

Microwave dielectric characterization and thermal analysis of B2O3-La2O3-ZnO glass-ceramic/Al2O3 composites for LTCC applications

High frequency performance and the content of glass are the direct factors affecting the performance of LTCC. In order to reduce the content of glass and improve the performance, we conducted a systematic study on the composition regulation of B2O3-La2O3-ZnO (BLZ) glass. Glass with low softening point is helpful for LTCC to achieve compact structure. DSC shows that the softening point of BLZ glass can be reduced from 580 ℃ to 537 ℃ by adjusting the composition. XRD analysis indicate that the glass and Al2O3 formed ZnAl2O4 interfacial phases. Combined with the thermal shrinkage curve, it can be proved that the softening of glass and the formation of interfacial phases are the reasons for the shrinkage and densification of LTCC. The lowest coefficient of thermal expansion of 2.878 ppm/℃ was obtained, and the minimum loss of LTCC is 0.00277 at 15 Ghz. These properties are making LTCC more suitable for high-frequency applications.

Interfacial reaction and phase formation in Pd/ZrO/Pd/TiO/Pd multilayer stack on silicon substrate: Investigated by ion beam techniques

The influence of the annealing temperature on the stability of the multilayer stack Pd/Zr/Pd/Ti/Pd thin films system, with both Zirconium (Zr) and Titanium (Ti) layers containing oxygen (O), deposited on silicon substrate was investigated. Using the in-situ real-time Rutherford backscattering spectrometry (RBS) analysis, the multilayer stacked thin film systems were linearly heated, at a constant heating rate, from room temperature up to 600 °C and found to be stable up to ∼370 °C whereby the inter-diffusion of Palladium (Pd), from both the third and the fifth layer, towards the forth layer comprising of Ti and O in 2:1 ratio, was observed. Moreover, the Ti, from the Ti–O layer, was found to spread to low and higher channels during Pd diffusion. Above 480 °C the second reaction was observed between Pd and silicon substrate, forming a hexagon silicide phase (Pd2Si) confirmed by X-ray diffraction. The thickness of the Pd2Si layer increased with increasing temperature and its activation energy was estimated to be 2.30 eV, which is about 1.10 eV and 0.65 eV higher than the activation energy of the Pd2Si phase formation at 100 °C and 250 °C, respectively. Therefore, the activation energy of the Pd2Si phase depends on the temperature at which the phase is growing.

Influence of characteristic parameters of SiC reinforcements on mechanical properties of AlSi10Mg matrix composites by powder metallurgy

The bottleneck problems of SiC particles reinforced AlSi10Mg composites (SiC/AlSi10Mg) prepared by traditional casting method, such as composition segregation, interface reaction and coarse microstructure, can be effectively improved by powder metallurgy with lower processing temperature. In this study, the influence of SiC particle size and content on the properties of SiC/AlSi10Mg was systematically analyzed. SiC/AlSi10Mg composites were prepared by planetary ball milling, spark plasma sintering (SPS) and hot extrusion composite preparation process. The obtained composites presents dense microstructure without the formation of interfacial reaction phase. The distribution of micron SiC particles (μm-SiC) in the matrix is relatively uniform, and nano SiC particles (nm-SiC) slightly agglomerates with the increase of the content. The strength of SiC/AlSi10Mg increases with the increase of nm-SiC content, which is mainly attributed to dispersion strengthening, dislocation strengthening and grain refinement strengthening. The strength of SiC/AlSi10Mg hardly changes with the increase of μm-SiC content, but the elongation decreases gradually. The deformation between μm-SiC and AlSi10Mg matrix is not coordinated and μm-SiC cleave the AlSi10Mg matrix. The irregular boundaries of μm-SiC are easy to produce stress concentration during loading, leading to interface cracking or μm-SiC fracture. Therefore, μm-SiC are difficult to play a significant strengthening effect to composites. With the increase of SiC content, the fracture mechanism of composites gradually changes from ductile fracture to brittle fracture in SiC agglomeration region. This study lays a theoretical and experimental foundation for the controllable preparation and performance optimization of high strength and toughness AMCs reinforced by SiC particles.

An unexpected interfacial Mo-rich phase in 2D molybdenum disulfide and 3D gold heterojunctions.

The interface engineering of two-dimensional transition metal dichalcogenides (2D-TMDs) and metals has been regarded as a promising strategy to modulate their outstanding electrical and optoelectronic properties. Chemical Vapour Deposition (CVD) is an effective strategy to regulate the contact interface between TMDs and metals via directly growing 2D TMDs on a 3D metal substrate. Nevertheless, the underlying mechanisms of interfacial phase formation and evolution during TMD growth on a metallic substrate are less known. In this work, we found a 2D non-van der Waals (vdW) Mo-rich phase (MoNSN+1) during thermal sulfidation of a Mo-Au surface alloy to molybdenum disulfide (MoS2) in a S-poor environment. Systematic atomic-scale observations reveal that the periodic Mo and S atomic layers are arranged separating from each other in the non-vdW Mo-rich phase, and the Mo-rich phase preferentially nucleates between outmost 2D MoS2 and a 3D nanostructured Au substrate which possesses copious surface steps and kinks. Theoretical calculations demonstrate that the appearance of the Mo-rich phase with a unique metallic nature causes an n-type contact interface with an ultralow transition energy barrier height. This study may help understand the formation mechanism of the interfacial second phase during the epitaxial growth of 2D-TMDs on 3D nanostructured metals, and provide a new approach to tune the Schottky barrier height by the design of the interfacial phase structure at the heterojunction.

Characteristics of porous SS316L: Influences of the Sn additive on the interfacial phenomena during the pressureless sintering

The interfacial phenomena through the pressureless sintering of porous stainless steel 316L containing Sn additive, and their influence on the sintering behavior, final microstructure and the obtained mechanical properties of the materials were investigated. The powder mixtures contained 0 to 6 wt% Sn were uniaxial cold pressed up to 400 MPa and then, sintered under the nitrogen atmosphere at various temperatures (1250 °C and 1300 °C) for 120 min.The relative densities of the samples were observed to follow an overall decreasing trend. The highest relative density was achieved in sample containing 2 wt% Sn and sintered at 1300 °C. The final phase arrangement mainly included austenite (γ-Fe) in samples sintered at 1250 °C, whereas the Cr-containing ferrite (α-Fe) was the dominant phase in most of the 1300 °C-sintered samples. The sintering behavior of the samples was then analyzed based on the microstructural investigations and phase arrangements, as well as the thermodynamic calculations of the interfacial reactions.It was confirmed that the formation of chromium oxide at the interfaces controls the sintering behavior of the materials. Hence, the higher sintering temperatures were found to promote the formation of the interfacial chromium oxide, thicken the oxide layer and then, postpone neck formation through the atomic diffusion. The presence of Sn, however, was observed to result in improved atomic diffusion through liquid phase sintering. However, the drawn-out of nickel through the liquid tin and the formation of Sn-based interfacial phases were found to negatively affect the neck formation. Through these competitive phenomena, the best combination of mechanical properties was achieved in the samples contained 2 wt% Sn. The fractural investigations, phase analysis, and the semi-quantitative EDS elemental analysis were finally carried out to discuss the obtained mechanical properties as well as compressive strength of the samples.

Preparation of Al2O3 coating on Nb fiber and the effect on interfacial microstructure of Nbf/TiAl composite

Continuous Nb fiber-reinforced TiAl-matrix composites are a potential structural material to satisfy the service requirements in space industry. However, the premature cracking failure is resulted from the brittle reaction products formed at the interface between Nb fiber and TiAl matrix, which accelerates the structural failure of Nb f /TiAl composite. Fortunately, Al 2 O 3 coating could be introduced on the surface of Nb fiber to tackle the problem. In this study, Al 2 O 3 coating was prepared on the surface of Nb fiber by the cathodic plasma electrolytic deposition (CPED) technology, and then the Al 2 O 3 -coated Nb fibers were used to reinforce TiAl alloy by using vacuum hot-pressing sintering. Furthermore, the influence of the Al 2 O 3 coating on the interfacial microstructure of Nb f /TiAl composite after hot-pressing sintering and thermal exposure was studied. The results show that deposition voltage plays a key role in the microstructure of Al 2 O 3 coating on the Nb fiber. As the voltage increases from 200 V to 400 V, the thickness, density and Al 2 O 3 content of the coating increase. Meanwhile, the bonding between Nb fiber and Al 2 O 3 coating is better when the deposition voltage exceeds 350 V, and the components of Al 2 O 3 -coated Nb fibers prepared from fiber to coating are as follows: Nb/Nb 2 O 5 /Nb 2 O 5 + Al 2 O 3 /Al 2 O 3 . The Al 2 O 3 coating can restrain the formation of the interfacial brittle phases including σ-Nb 2 Al and α 2 -Ti 3 Al during hot-pressing sintering process of Nb f /TiAl composite. In addition, the introduction of Al 2 O 3 coating can reduce the defects in interface, as well as avoid the formation of the crisscrossed and deleterious oxides, which improves interfacial oxidation resistance of the Nb f /TiAl composite. • A uniform and dense Al 2 O 3 coating with a thickness of 4–6 μm can be obtained on Nb fiber surface by CPED technology. • Al 2 O 3 coating can prevent the formation of interfacial brittle phases during the preparation of Nb f /TiAl composite. • Al 2 O 3 coating with excellent thermal stability can avoid the formation of crisscross harmful oxides.

Evidence of Delta Phase of Fe in MBE-Grown Thin Epitaxial Films on GaAs

Fe/GaAs is an important system for the study of spin injection behavior that can vary with the nature and interfaces of Fe films. Here, we investigate the effect of interfacial strain on the microstructure, interfaces and phase-formation behavior in epitaxially grown Fe films. To vary the strain, we have characterized Fe films of various thicknesses ranging from 10 to 1000 nm which were grown using molecular beam epitaxy on GaAs (011) and AlGaAs (001) substrates. High resolution X-ray diffraction studies revealed that films with higher thicknesses exhibited an equilibrium α-Fe phase, while the films with less than 10 nm thicknesses indicated the presence of δ-Fe. Transmission electron microscopy revealed the interface for 10-nm-thick films had strain lobes with no interfacial phase formation for films deposited at room temperature. At a higher deposition temperature of 175 °C, similar strain lobes were observed for a 10-nm-thick film. Extended annealing at 200 °C transformed the metastable δ-Fe phase to an equilibrium α-Fe. However, at higher temperature, the interface contained an intermixing layer of (FeAl)GaAs. We demonstrate that the interfacial strain plays a major role in stabilizing the metastable δ-Fe on GaAs.

Impact of Ni-coated carbon fiber on the interfacial (Cu,Ni)6Sn5 growth of Sn-3.5Ag composite solder on Cu substrate during reflow and isothermal aging

In this work, a novel composite solder was fabricated by mechanically incorporating Ni-coated carbon fiber (Ni-CF) into the Sn-3.5Ag solder paste in an effort to improve the overall service capability, where the intermetallic compound (IMC) formation and growth is a fundamental issue for consideration. General findings indicated that the addition of Ni-CF did not significantly impact the processing properties of the base alloy, such as melting temperature and wettability, when the reinforcement fraction was less than 2 wt%. Isothermal aging tests were carried out to study the formation and growth of interfacial IMC layers between the composite solder and Cu substrate. The addition of Ni-CF into Sn-3.5Ag solder could effectively promote the formation of interfacial (Cu, Ni)6Sn5 phase during reflow but retard its growth in the solid-state aging. The addition of 1 wt% Ni-CF was believed to be more effective to restrict and reduce the subsequent growth rate of the IMCs during solid-state aging due to the initial formation of a thicker (Cu, Ni)6Sn5 layer after reflow.

Thermodynamics-driven interfacial engineering of alloy-type anode materials

Alloy-type anodes can enable high specific capacity for Li-ion batteries, but the large volume change during cycling often causes fast-capacity fading. Here, we report a thermodynamically driven grain boundary engineering method to improve alloy-type anodes via the spontaneous formation of 2D interfacial phases (complexions). Notably, the 2.8 at% Bi-doped SnSb achieves improved cycling stability and rate capability, even though it is 99% dense and has a mean crystallite size 2.7× larger than the undoped SnSb reference sample. Cryogenic transmission electron microscopy reveals Bi segregation at grain boundaries. Thermodynamic modeling further suggests the stabilization of a nanoscale liquid-like interfacial phase. Synchrotron transmission X-ray microscopy shows the suppressed intergranular cracking upon cycling with Bi addition. It suggests that the liquid-like interfacial phase serves as a stress relief mechanism for the high volumetric expansion anode via improved grain boundary sliding and Coble creep, akin to room-temperature superplasticity observed in Sn-Bi. • Spontaneously formed liquid-like interfacial phase improves the SnSb-Bi anode • Cryogenic STEM reveals Bi segregation at SnSb grain boundaries • Transmission X-ray microscopy shows the suppressed cracking upon cycling • Liquid-like interfacial phase promotes grain boundary sliding and Coble creep Alloy-type anodes are promising for Li-ion batteries, but the large volume change during electrochemical cycling can cause fast degradation. Yan et al. report a thermodynamics-driven interfacial engineering method to improve alloy-type anodes via the spontaneous formation of liquid-like interfacial phase that promotes room temperature superplasticity to alleviate cracking.

Ab-initio investigation on the interface improvement by doping boron and carbon in LiMn2O4/LiPON all solid state battery

Lithium phosphorous oxynitride (LiPON), since its outstanding electrochemical stability window and negligible electronic conductivity，it is suitable for practical all-solid-state batteries (ASSBs). Besides, elements doping can not only improve interfacial compatibility but also increase ionic conductivity. However, the detailed interfacial structures of LiMn2O4/LiPON and diffusion mechanism of lithium in LiPON based electrolyte are hardly investigated so far. Herein, we examine the electrochemical and chemical stabilities of LiMn2O4-electrode and LiPON-based-electrolyte interfaces by analyzing the thermodynamics of formation of interfacial phases, LiBPON shows high interfacial stability with LiMn2O4. The doping boron atoms in LiPON play a vital role to enlarge Li ion diffusion channel sizes, hence the diffusion barrier of Li in LiBPON is only 0.25 ​eV, which is much smaller than that in the LiPON, leading to Li-ion super ionic conductivity in LiBPON. Through a charge density difference analysis, it suggests the LiO,Li3O and Li2O4 for LiPON, LiBPON and LiCPON will transfer charge to the surrounding matrix, realize the stability of the interface. This work provides a theoretical insight for the application of LiPON based electrolytes in all solid state battery.

Properties and Performance of Electrolyte Supported SOFCs with EB-PVD Gd-Doped Ceria Thin-Films

High temperature solid oxide fuel cell (SOFC) is regarded as a unique electrochemical device to convert the chemical energy of a large diversity of fuels into electricity and heat with high efficiency and low emission. The electrolyte-supported cell (ESC) design is proven to be one of the most feasible SOFC technologies for commercial applications. Thickness reduction of yttria stabilized zirconia (YSZ) electrolyte supports without sacrifice of mechanical strength is favorable for cell performance enhancement.In this work, dense gadolinium-doped ceria (GDC) thin-films with thickness in the range of 0.15-0.5 µm were fabricated as Sr-barrier layers on the cathode side, and as strength-balance and adhesion layer on the anode side by electron beam physical vapor deposition (EB-PVD) method. Replacing the state-of-the-art screen-printed GDC layers, the approach with YSZ substrate sandwiched in between two GDC thin-films was proposed not only to prevent the formation of interfacial secondary phase on the cathode side, but also to increase the overall robustness of ESCs. Investigated by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), it was confirmed that 0.5 µm thick GDC thin-films were effective to suppress the formation of Sr-zirconate phase at the YSZ/GDC interface. In comparison to reference cells with screen-printed GDC layers, higher breaking loads were recorded on the cells with PVD-GDC thin-films by Ring-On-Ring bending tests, showing considerably improved mechanical properties. Current-voltage characteristics and electrochemical impedance spectroscopy demonstrated that the performance of the as-prepared ESCs with GDC thin-films was comparable to the reference cells. Operated at 860 °C, the ESC with 0.5 µm GDC thin-film outperformed other tested cells with 0.15 µm or 0.3 µm GDC layers, and delivered a power density of 0.55 W•cm-2 at a cell voltage of 0.7 V. The results achieved in this work can be considered as step stones for the further development of ESCs with reduced electrolyte thickness, sufficient robustness and improved performance.This work is financially supported by the German Ministry for Economic Affairs and Energy (BMWi) within the framework of the project “Kostenoptimierter Stack und verbessertes Offgrid-System (KOSOS)” with grant number of 03ETB005C.

Active participation of “inert” YSZ substrates on interface formation in [formula omitted]/YSZ heterostructures

The bulk and emerging interface properties of magnetite Fe3O4/YSZ(001) heterostructures grown by pulsed laser deposition are investigated. Fe3O4 thin films (4–38 nm) grow epitaxially in (111) orientation and undergo a Verwey transition at max. TV = 117±0.6K. Surprisingly, the formation of interfacial Fe2O3 phase is observed albeit the quasi-inert properties of yttrium-stabilized zirconia (YSZ). Possible mechanisms include either (i) thermodynamically induced interfacial redox reaction at the YSZ substrate surfaces or (ii) oxygen diffusion from the outside atmosphere, as YSZ is a very good oxygen ion conductor. Hence, substrate-assisted oxygen supply may enable the control of emerging interface functionalities.

Interfacial precipitation in {101¯2} twin boundaries of a Mg-Gd-Zn-Zr alloy

• A novel interfacial precipitate in {10–12} twin boundaries (TBs) is revealed. • Twinning clearly accelerates aging hardening and improves alloy's strength. • Interfacial precipitate mainly formed at BP facets and tilting TBs. Twinning and precipitation play important roles in deformation and strengthening of magnesium alloys. In this work, interfacial precipitation in {10 1 ¯ 2} twin boundaries (TBs) of a cold-stamped Mg−12Gd−1.2Zn−0.4Zr alloy was investigated using atomic-resolution high-angle annular dark-field scanning transmission electron microscopy. Extended periodic segregation of Gd + Zn atoms in the ~86.2° {10 1 ¯ 2} TBs with basal-prismatic facets and in the symmetric tilting TBs (obviously > 86.2°) frequently occurred, resulted in the formation of new interfacial phases, namely β TB ’ having a monoclinic structure in the TBs with two segregation layers and β TB having a tetragonal structure in the TBs with three or more segregation layers. The formation of β TB clearly accelerates peak-aging and improves the alloy's strength.

Microstructure and mechanical properties of short-carbon-fiber/Ti3SiC2 composites

Short-carbon-fibers (Csf) reinforced Ti3SiC2 matrix composites (Csf/Ti3SiC2, the Csf content was 0 vol%, 2 vol%, 5 vol%, and 10 vol%) were fabricated by spark plasma sintering (SPS) using Ti3SiC2 powders and Csf as starting materials at 1300 °C. The effects of Csf addition on the phase compositions, microstructures, and mechanical properties (including hardness, flexural strength (σf), and KIC) of Csf/Ti3SiC2 composites were investigated. The Csf, with bi-layered transition layers, i.e., TiC and SiC layers, were homogeneously distributed in the as-prepared Csf/Ti3SiC2 composites. With the increase of Csf content, the KIC of Csf/Ti3SiC2 composites increased, but the σf decreased, and the Vickers hardness decreased initially and then increased steadily when the Csf content was higher than 2 vol%. These changed performances (hardness, σf, and KIC) could be attributed to the introduction of Csf and the formation of stronger interfacial phases.

Effect of WC addition on the corrosion behavior of powder metallurgy Cu-10SiC in a 3.5 wt% NaCl solution

An experiment was analyzed to examine the corrosion activity of Cu-10SiC alloy reinforced in a 3.5 wt% NaCl aqueous solution with different volume fractions of Tungsten carbide (WC) particulates. The composites were prepared by means of powder metallurgy (PM). It examined the corrosion of unreinforced and strengthened alloy. Electrochemical measurements (potentiostatic testing) exhibited that the thermal conductivity of the composites decreased with an increase in WC weight percentages due to the unstable microgalvanic synchronizing between the reinforcing particles and the Cu10SiC matrix and a reduced possibility of interfacial phase formation. The ANOVA result revealed that deviations in the corrosion resistance of the composites are statistically relevant when the weight percentages of WC particles change. The characteristic impedance between conductivity and free corrosion points increased with an increase in WC volume fraction, as WC cathodically prevents the polymer composites by ritual reduction of the crevice areas against reinforcement particles. Scanning Electron Microscope (SEM) images of the surfaces of the sample pre and post inspection are in conformance with the electrochemical results. In addition, some concessionary corrosion assaults have been identified at WC / matrix integrations and in WC nodes during the composite corrosion process. Therefore, the porosity content of the composite materials was around the same level.

Size dependence of interfacial intermixing in Fe/Si multilayer

Size effect on interface structure in Fe/Si multilayers and interfacial phase formation as a result of thermal annealing and irradiation with high energy heavy ions has been studied, using a combination of x-ray reflectivity and depth-resolved x-ray diffraction measurements. Study using a single sample with two multilayer structures with different bilayer periods allows us to elucidate the size effects keeping the process parameters identical. In conformity with some earlier studies, in the as-deposited multilayer Fe-on-Si interface is more diffused as compared to Si-on-Fe interface. This interfacial asymmetry is found to diminish with increasing layer thicknesses. Furthermore, β-FeSi2 is formed preferentially at Fe-on-Si interface, which again is more pronounced in the low bilayer period structure as compared to the high bilayer period structure. Thermal annealing results in formation of ε-FeSi, which also preferentially forms at the Fe-on-Si interface. Difference in the structure of the interfaces in terms of concentration gradient, interfacial stresses and disorder may contribute to the observed behavior. In contrast, irradiation with heavy ions results in formation of bcc Fe(Si) alloy and β-FeSi2 phase. Intermixing is significantly stronger in the low bilayer period as compared to the high bilayer period structure. The results can be understood in terms of thermal spike model for irradiation induced modifications.