Interfacial Reaction Products Research Articles

Interfacial Characteristic of as-Deformed SiCp-Reinforced Magnesium Matrix Composite

The (submicron + micron) SiCp-reinforced magnesium matrix composite was fabricated by stir casting. After the application of forging and extrusion, the interface between SiCp and Mg in the composite was investigated by transmission electron microscopy. Results show that the interfacial characterization was different at the interfaces of micron-SiCp/Mg and submicron-SiCp/Mg. While most interfaces between micron-SiCp and Mg were clean, the precipitated Mg17Al12 phase as well as dispersedly distributed nano-MgO particles was observed at some interfaces. Unlike the interface between micron-SiCp and Mg, no interfacial reaction product was found at the interface between submicron-SiCp and Mg in the present study. Besides, the specific orientation relationships were found at the interfaces between submicron-SiCp and Mg, which was thought to have developed during hot deformation process. At the fracture surface of the composite, the microcracks were found at the interface between micron-SiCp and Mg, while the interfacial bonding between submicron-SiCp and Mg was very well.

Microstructural evolution at Cu/Sn–Ag–Cu/Cu and Cu/Sn–Ag–Cu/Ni–Au ball grid array interfaces during thermal ageing

The effect of metallization chemistry on the solid state growth kinetics of intermetallics formed in an industrial metallization/solder/metallization arrangement during isothermal ageing has been studied. During isothermal ageing of the Cu/Sn–Ag–Cu/Cu arrangement at temperatures lower than 125°C, Cu was the main mobile element and diffused either through or along interfacial Cu6Sn5 grain boundaries to react with Sn on the solder side of the Cu6Sn5 layer; while for temperatures greater than 125°C, both Cu and Sn were relatively mobile. Isothermal ageing of the Cu/Sn–Ag–Cu/Ni–Au asymmetric arrangement showed a concentration gradient of Ni and Cu across the entire ball in the solder joints leading to an inhomogeneous precipitation of (Cu, Ni)6Sn5 in the vicinity of the Ni metallization. Ni alloying of the interface reaction products also occurred in the vicinity of the Cu metallization, reducing the growth rate of Cu6Sn5 and Cu3Sn by 20% and 70% respectively when compared with symmetric Cu/Sn–Ag–Cu/Cu arrangement. Growth rate studies and microscopy suggested the presence of the Cu6Sn5 η'→η transformation during extended ageing in the region of 150–175°C, which is generally under-reported in these important commercial systems.

Study on Microstructure of Continuous C<sub>f</sub>/Al Composite Material Prepared by Hot Pressing Diffusion Method

Two-dimensional carbon fiber fabric T300 used as reinforcement, Cf/Al composite material was prepared by hot pressing diffusion. Effect of parameters on microstructure of Cf/Al composite material was studied. We found that for aluminum foil used as matrix, hot pressing temperature is 650°C, hot pressing time is 20min, pressure is 30MPa. As a case, interfacial reaction product Al4C3 accounts for 3.6%, and composite material density is 2.44g/cm3. For aluminum powder used as matrix, hot pressing temperature is 620°C, hot pressing time is 35min, pressure is 10MPa. As a case, Al4C3 accounts for 2.8%, and composite material density is 2.58g/cm3. The molding of aluminum powder is much easier than that of aluminum foil. The latter requires higher hot pressing temperature. Interfacial reaction product Al4C3 increases as increasing of hot pressing temperature and pressure.

Interface Remelting of Tungsten Carbide Particles Reinforced Steel Composite

A tungsten carbide particles reinforced steel matrix composite was fabricated by spark plasma sintering(SPS) technique, and then the composite was remelted in a vacuum tube furnace. The effect of remelting temperature on interface reaction was investigated meticulously. The results show that the interface reaction could occur when the matrix was still in solid state, the thickness of interface reaction layer increased with the increasing temperature. The interface reaction product, Fe3W3C, was resulted from the following two step reactions: firstly the reaction 2WC→W2C+C would occur within tungsten carbide particles at 1314℃, then the W2C would react with Fe to produce Fe3W3C at temperatures above1341℃.

Investigation of interfacial reaction product of SiCf/C/Mo/Ti6Al4V composite through Raman spectroscopy

Interfacial reaction products of heat-treated SiCf/C/Mo/Ti6Al4V are studied. Energy dispersive spectrometer (EDS) mapping indicates two sublayers existence in the interface with Si-rich layer 1 next to SiC fiber and C-rich layer 2 next to matrix. Raman line scanning along interface also shows two sublayers with different reaction products, which is consistent with EDS mapping. Si-rich layer 1 is proved mainly Ti5Si3(Cx). C-rich layer 2 is proved mainly TiCx comparing the spectrum with that of TiCx particles in matrix. Peak shifts are also detected, which is possibly due to residual stress or/and microstructural evolution. Existence of SiC and excess carbon throughout the interface is also confirmed by Raman spectroscopy.

Joining of Si3N4 ceramic using PdCo(NiSiB)–V system brazing filler alloy and interfacial reactions

The wettability of V-active PdCo-based alloys on Si3N4 ceramic was studied with the sessile drop method. And the alloy of Pd50.0–Co33.7–Ni4.0–Si2.0–B0.7–V9.6 (wt%), was developed for Si3N4 ceramic joining in the present investigation. The rapidly-solidified brazing foils were fabricated by the alloy Pd50.0–Co33.7–Ni4.0–Si2.0–B0.7–V9.6. The average room-temperature three-point bend strength of the Si3N4/Si3N4 joints brazed at 1453K for 10min was 205.6MPa, and the newly developed braze gives joint strengths of 210.9MPa, 206.6MPa and 80.2MPa at high temperatures of 973K, 1073K and 1173K respectively. The interfacial reaction products in the Si3N4/Si3N4 joint brazed at 1453K for 10min were identified to be VN and Pd2Si by XRD analysis. Based on the XEDS analysis result, the residual brazing alloy existing at the central part of the joint was verified as Co-rich phases, in which the concentration of element Pd was high up to 18.0–19.1at%. The mechanism of the interfacial reactions was discussed. Pd should be a good choice as useful alloying element in newer high-temperature braze candidates for the joining of Si-based ceramics.

Diffusion-Controlled Growth of Oxygen Bubble Evolved from Nanorod-Array TiO2Photoelectrode

Nanorod-array structure gains its popularity in photoelectrode design for water splitting. However, the structure’s effects on solid-liquid interface interaction and reaction product transportation still remain unsolved. Gas bubble generally evolved from photoelectrodes, which provides a starting point for the problem-solving. Based on this, investigations on the gas-evolving photoelectrode are carried out in this paper. By experimental studies of wettability on the photoelectrode nanorod-array surface and oxygen bubble growth from anode, we analyzed the interaction affecting the gas-solid-liquid contact behaviors and product transportation mechanism, which is controlled by diffusion due to the concentration gradient of dissolved gases in the aqueous electrolyte and the microconvection caused by the bubble interface movement. In the end, based on the bubble growth characteristics ofRB(t)~t0.5in the experiment, a model describing the product transport mechanism was presented.

Growth behavior and properties of atomic layer deposited tin oxide on silicon from novel tin(II)acetylacetonate precursor and ozone

In this work, a novel liquid tin(II) precursor, tin(II)acetylacetonate [Sn(acac)2], was used to deposit tin oxide films on Si(100) substrate, using a custom-built hot wall atomic layer deposition (ALD) reactor. Three different oxidizers, water, oxygen, and ozone, were tried. Resulting growth rates were studied as a function of precursor dosage, oxidizer dosage, reactor temperature, and number of ALD cycles. The film growth rate was found to be 0.1 ± 0.01 nm/cycle within the wide ALD temperature window of 175–300 °C using ozone; no film growth was observed with water or oxygen. Characterization methods were used to study the composition, interface quality, crystallinity, microstructure, refractive index, surface morphology, and resistivity of the resulting films. X-ray photoelectron spectra showed the formation of a clean SnOx–Si interface. The resistivity of the SnOx films was calculated to be 0.3 Ω cm. Results of this work demonstrate the possibility of introducing Sn(acac)2 as tin precursor to deposit conducting ALD SnOx thin films on a silicon surface, with clean interface and no formation of undesired SiO2 or other interfacial reaction products, for transparent conducting oxide applications.

Effect of heat treatment on microstructure and thermophysical properties of diamond/2024 Al composites

50% diamond particle (5 μm) reinforced 2024 aluminum matrix (diamond/2024 Al) composites were prepared by pressure infiltration method. Diamond particles were distributed uniformly without any particle clustering, and no apparent porosities or significant casting defects were observed in the composites. The diamond-Al interfaces of as-cast and annealed diamond/2024 Al composites were clean, smooth and free from interfacial reaction product. However, a large number of Al2Cu precipitates were found at diamond-Al interface after aging treatment. Moreover, needle-shaped Al2MgCu precipitates in Al matrix were observed after aging treatment. The coefficient of thermal expansion (CTE) of diamond/2024 Al composites was about 8.5×10−6 °C−1 between 20 and 100 °C, which was compatible with that with chip materials. Annealing treatment showed little effect on thermal expansion behavior, and aging treatment could further decrease the CTE of the composites. The thermal conductivity of obtained diamond/ 2024 Al composites was about 100 W/(m·K), and it was slightly increased after annealing while decreased after aging treatment.

Influence of substrate temperature on structural, morphological and electrical properties of La0.6Sr0.4Co0.2Fe0.8O3 thin films for IT-SOFCs

The crack free, homogeneous, nanocrystalline La0.6Sr0.4Co0.2Fe0.8O3 thin films have been deposited on Ce0.9Gd0.1O1.95 electrolyte by the spray pyrolysis technique. The films with typically 1–2μm thickness, get crystallized on annealing at 800°C. In the present work, the effect of substrate temperature on microstructure, crystallization and conductivity has been systematically studied. The deposition of film at 300°C shows higher in plane electrical conductivity of 26.6Scm−1 with activation energy, Ea=0.23eV. The higher conductivity attributes to uniform, thin and dense microstructure of thin films. No interfacial reaction products between La0.6Sr0.4Co0.2Fe0.8O3 and Ce0.9Gd0.1O1.95 were detected upon annealing at 800°C/4h. The uniformity and porosity distribution as a function of deposition temperature clarified from Scanning Electron micrograph.

Interface Reaction of CNTs/Al Composites Fabricated by High Energy Ball Milling

CNTs/Al composites were fabricated by high energy ball milling. The phase structure and consti- tuent of the preparation process were analyzed. The interface reaction and the formation process of the interface reaction product Al4C3 were discussed by thermodynamics and kinetics. The result shows that no Al4C3 can be found in Al-CNTs composite powders fabricated by high energy ball milling. Al4C3 exists in the inter- face after pressureless sintering. And no appreciable amount of Al4C3 was observed in CNTs/Al composites directly by powder metallurgy. It shows that high energy ball milling can benifit the interface reaction. And the purified CNTs, never milled, is stable in the preparation process of CNTs/Al composites by powder metallurgy.

Joining of Si3N4 to Si3N4 using a AuPd(Co, Ni)–V filler alloy and the interfacial reactions

Au38.0–Pd28.0–Co18.0–Ni7.0–V9.0 (in wt%) alloy was designed as a filler for joining Si3N4. The filler alloy showed a contact angle of 77.2° on Si3N4 ceramic at 1473K. The Si3N4/Si3N4 joint brazed with the rapidly-solidified filler foils at 1443K for 10min exhibits an average three-point bend strength of 320.7MPa at room temperature and the strength values are 217.9MPa and 102.9MPa at 1073K and 1173K respectively. The interfacial reaction products were composed of V2N and Pd2Si, and the elements Co and Ni in the brazing alloy did not participate in the interfacial reactions. The coarse-network-like distribution of refractory Pd2Si compound within the Au–Pd–Co–Ni alloy matrix throughout the joint contributes to the stable high-temperature joint strengths.

Microstructure and Mechanical Propertiesof Ti/Cu-Cr/S20C and Ti/Cu-Ag/S20C Clad Composites

In this study Cu-Ag or Cu-Cr layer was sandwiched by Ti and Fe plates and the three layers of Ti/Cu-8Ag/S20C were clad by High Pressure Torsioning(HPT). The effect of post-HPT heat treatment on the interfacial reaction products and the mechanical performance in Ti/Cu-Ag/S20C and Ti/Cu-Cr/S20C clad material were studied. Cu4Ti3 and Cu4Ti Intremetallic compound layers were observed at the Ti/Cu-Ag and Ti/Cu-Cr interfaces in the clad heat-treated at 500°C where as no intermetallic compounds were observed at the Cu-Ag/S20C and Cu-Cr/S20C interfaces. The strength of as-HPTed Ti/Cu-8Ag/S20C is much higher than that of Ti/Cu-1Cr/S20C. The strengthening mechanism of Cu-Ag deformed severely is the interface and strain hardening in which dislocations are deposited at the Cu/Ag interfaces and can contribute to the strengthening of the clad composite just after HPT processing, rendering the high strength just after processing. In both clad composites, the strength and ductility increased after heat treatment at 350°C, which are likely caused by the enhanced bonding at the interfaces.

Trends in wetting behavior for Ag–CuO braze alloys on Ba0.5Sr0.5Co0.8Fe0.2O(3−δ) at elevated temperatures in air

In the current study, Ag–CuO, a reactive air brazing alloy was evaluated for brazing Ba0.5Sr0.5Co0.8Fe0.2O(3−δ) (BSCF). In situ contact angle tests were performed on BSCF using Ag–CuO binary mixtures at 950 and 1000 °C, and the interfacial microstructures were evaluated. Wetting contact angles (θ < 90°) were obtained at short times at 950 °C, and the contact angles remained constant at 1000 °C for 1, 2, and 8 mol% CuO contents. Microstructural analysis revealed the dissolution of copper oxide into the BSCF matrix to form copper–cobalt–oxygen rich dissolution products along the BSCF grain boundaries. The formation of a thick interfacial reaction product layer and ridging at the sessile drop triple point indicate that the reaction kinetics are very rapid and that it will require careful process control to obtain the desired thin but continuous interfacial product layer.

Silicon dissolution and interfacial characteristics in Si/Al composites fabricated by gas pressure infiltration

The silicon dissolution and interfacial characteristics of Si/Al composites were investigated by microstructure analysis and thermodynamic calculation. A new method of gas pressure infiltration was proposed to fabricate the Si/Al composites with near-net shape. The interfacial characteristics were examined using SEM, TEM, EDS and X-ray Diffraction, especially, silicon particles with reaction products were extracted through the electrochemical etching. The results show that some Si particles have been dissolved and a lot of crusts filled with Al matrix are left. The SiO2 layer in Si/Al composites has three functions: to enhance the interfacial strength by interfacial reactions between Si particles and Al matrix, to serve as barriers to prevent the Si particles from being dissolved by molten Al alloy, and to join Si particles to form Si preform. However, the barriers will not perform these functions when they are damaged. The SiO2 barriers are consumed by molten Al alloy, and the major phase in the interfacial reaction products between the SiO2 barriers and the molten Al is Al2O3, while MgAl2O4 is the minor phase. Furthermore, the reaction of an equation “4Al (L) + 3SiO2 (S) = 2Al2O3 (S) + 3Si (S)”is the dominant interfacial reaction in the Si/Al composites, which is different from the dominant reaction in SiC/Al composites.

Interaction between Two Ni-Base Alloys and Ceramic Moulds

The interfacial reactions between ceramic moulds and DZ417G and DZ125 superalloys were investigated. The microstructure and composition of the interface region were observed by optical microscope, X-ray diffraction and scanning electron microscope with energy dispersive spectroscopy. The results showed that (Al1-xCrx)2O3 solid solution phase with pink color was formed from the dissolution of Cr2O3 and Al2O3 and vapour phase, which was transferred to the reaction surfaces. The reaction layer thicknesses of DZ417G and DZ125 alloys were about in the range of 40-50μm. The interface reaction product between DZ417G alloy and ceramic mould was TiO2 and the product between DZ125 alloy and ceramic mould was HfO2.

Interfacial microstructure of SiCp/Al composite produced by the pressureless infiltration technique

A SiCp/Al composite was fabricated by the pressureless infiltration of an Al–Mg–Si alloy into the pre-oxidized SiC preform at 1000 °C for one hour. The composite fully infiltrated and a homogenous distribution of SiC particles was confirmed. MgAl2O4 was found as the interfacial reaction product, its formation deriving from the reactions: 2Mg+SiO2=2MgO+Si and 2MgO+4Al+3SiO2=2MgAl2O4+3Si. The factors influencing the spontaneous infiltration process were also discussed.

Mechanical Performance of Ti/Cu-8Ag/S20C Clad Composite Processed by High Pressure Torsioning (HPT)

Ti/Cu-8Ag/S20C composite were processed by High Press Torsioning(HPT) and the effect of post-HPT heat treatment on the interfacial reaction products and the mechanical performance were studied. Intremetallic compound layer with the thickness of 11 μm was observed at the interface between Ti and Cu-8Ag for the clad heat-treated at 600°Cfor 24hrs. On the other hand, no intermetallic compounds were observed at the Cu-8Ag/S20C interface. No cracks were observed to be emanated from the corner of the indentation mark on the intremetallic compound layer at the Ti/Cu-8Ag interface, suggesting those intermetallic compounds is not so brittle. The stress-strain curves exhibited two steps in as-HPTed clad samples and those heat-treated at 600°C for 24hrs. The careful examination of the fractured plates revealed that S20C plate fractured first and then Ti and Cu-8Ag layers fractured together, suggesting the bonding strength between two layers is fairly high in the presence of intermetallic layer between Ti and Cu-8Ag layers

Fabrication of diamond/aluminum composites by vacuum hot pressing: Process optimization and thermal properties

Diamond/Al composites were prepared by vacuum hot pressing (VHP) to get high thermal properties. The sintering temperature, pressure and time in the VHP process were optimized. Microstructures, thermal properties, interface reaction product and its effect on the properties of the composites were investigated. The result shows that the sintering temperature and time are key parameters to get high thermal property of the composites. The composites with 20–55vol% diamond sintered at 650°C for 90min under a pressure of 67MPa exhibit thermal conductivities of 320–567W/mK, over 90% of the theoretical predictions by the differential effective medium (DEM) scheme. The high thermal conductivity is attributed to the favorable interface conductance, while the formation of aluminum carbide at diamond–Al interface is found to be negative.

Synthesis and Characterization of Particulate SiC&lt;sub&gt;p&lt;/sub&gt; Reinforced Al-Si-Mg Alloy Composite with Varying Si Content

Amongst the Metal Matrix Composites (MMCs), Al-Si-Mg alloy/ SiCp MMCs are very attractive for their properties. But, the formation of brittle interfacial reaction product, Aluminium carbide has been one of the major concerns when these materials are processed by liquid phase methods. The extent of Aluminium carbide formation depends on various processing parameters such as temperature, wt% of SiCp, particle size of SiCp and chemical composition of the matrix alloy especially Silicon (Si) content. According to recent studies, various difficulties in finding the process parameters to get desirable properties of Al alloy/ SiCp MMCs as desired by the industries. Thus, in the present study thermodynamic &amp; structural estimates in Al alloy/ SiCp MMCs under various process conditions, composition, microstructures were performed. The relatively low cost liquid stir casting technique is used in the production of Al alloy/ SiCp MMCs with varying Silicon content (0–7%) in the alloy matrix using process temperature 710°C. Aluminium carbide layer formation on SiCp surface, Critical Si content for Aluminium carbide separation from SiCp surface, eutectic Si formation, existence of near-dislocation segregation regions after formation of Aluminium carbide on SiCp surface and the equilibrium amount of Si to suppress Aluminium carbide formation were investigated using Transmission electron microscopy (TEM). The separation of Aluminium carbide from SiCp surface was observed after 3% Si. The equilibrium Si content of 7% was found to suppress the formation of Aluminium carbide with thermodynamic model and its significance has been assessed.