An investigation of the effect of SiC particle size on Cu–SiC composites

In this study mechanical properties of copper were enhanced by adding 1 wt.%, 2 wt.%, 3 wt.% and 5 wt.% SiC particles into the matrix. SiC particles of having 1 μm, 5 μm and 30 μm sizes were used as reinforcement. Composite samples were produced by powder metallurgy method and sintering was performed in an open atmospheric furnace at 700 °C for 2 h. Optical and SEM studies showed that the distribution of the reinforced particle was uniform. XRD analysis indicated that the dominant components in the sintered composites were Cu and SiC. Relative density and electrical conductivity of the composites decreased with increasing the amount of SiC and increased with increasing SiC particle size. Hardness of the composites increased with both amount and the particle size of SiC particles. A maximum relative density of 98% and electrical conductivity of 96% IACS were obtained for Cu–1 wt.% SiC with 30 μm particle size.     

The effect of Ta on structure and magnetic properties in Fe–N films

Microstructure and magnetic properties of Fe–Ta–N alloy films near the eutatic composition were studied. The four systematic alloy films with different Ta content were prepared by reactive sputtering. The dependence of structures and magnetic properties on Ta and annealing were investigated by VSM and X-ray diffraction. It is found that Ta atoms replace Fe in α-Fe lattice and have strong affinity for nitrogen, which inhibits the formation of γ-Fe₄N phase in Fe–Ta–N films. The TaN phase precipitates in grain boundaries and suppresses the growth of α-Fe(N) crystalline during annealing. Coercivity varies with the change of microstructure.     

The effect of Zr on the microstructure and tensile properties of hot-extruded Al–Mg2Si composite

This work was carried out to investigate the effect of different amounts of Zr on the microstructure and tensile properties of homogenized and hot extruded Al-15% Mg₂Si composite using optical microscopy and scanning electron microscopy (SEM). The results showed that Zr addition has no significant effect on the morphology of both primary and eutectic Mg₂Si phase in as-cast condition. But, applying homogenizing and extrusion processes changed the morphology of Mg₂Si phases from irregular to a more spherical shape. Further results demonstrated that the average size of primary Mg₂Si decreases with the addition of Zr up to 0.1% from 56 μm to 24 μm in hot-extruded condition. As the mount of Zr increased up to 0.1 wt.%, ultimate tensile strength (UTS) and elongation values were also increased from 160 MPa and 3.2% to 292 MPa and 9.5%, respectively. Fracture surface examinations revealed a transition from brittle fracture mode in as-cast composite to ductile fracture in hot-extruded Zr-modified specimens. This can be attributed to the changes in size and morphology of Mg₂Si intermetallic and porosity content.     

Study of the martensitic transformation in NiTi–epoxy smart composite and its effect on the overall behavior

In this work, the effect of wire phase transformation on the overall thermo-mechanical behavior of NiTi–epoxy composites has been investigated. The shape memory wire received in as drawn condition was subjected to three heat treatments which results to different transformation characteristics. Composite specimens were manufactured by casting followed by curing and post curing process. The mechanical behavior of samples has been determined using standard tensile test. The effect of wire volume fraction and test temperature was investigated as well.It is found that the martensitic transformation occurring in the wire affects the mechanical behavior of the composite specimens. In this way, using the wire with higher transformation stress improves the composite tensile strength. This is achieved either by increasing the test temperature or by using the wires heat treated at lower temperatures. From the experimental results, the martensitic transformation can change the debonding mode. It seems that on the constraint of matrix, the transformation occurs simultaneously at several points in wires that result in regular debonded/undebonded pattern.     

The effect of strontium on the mechanical properties of aluminum–silicon alloy

Technical Physics Letters - We have studied the influence of strontium additives on the microstructure and mechanical properties of an aluminum alloy with 15 wt % silicon prepared by directional...     

Computational study of the effect of core–skin structure on the mechanical properties of carbon nanofibers

Journal of Materials Science - The effect of the core–skin structure on the mechanical properties of carbon nanofibers is investigated in large-scale molecular dynamics simulations of tensile...     

The effect of rare earth CeO2 on microstructure and properties of in situ TiC/Al–Si composite

In this work, CeO₂ is investigated as an additive for in situ preparation of TiC/Al–Si composite using exothermal dispersion (XD)+casting technology. Experimental results show that CeO₂ at high temperature exhibits the same function as Ce, which is a kind of good modificator. When 0.5 wt.% CeO₂ additive is added, the microstructure of eutectic silicon is significantly changed (the size is greatly reduced). Meanwhile, the amount of TiC particles is increased and the size is reduced. Compared with the composite without added CeO₂, the hardness value (HB) value, tensile strength and tensile elongation are greatly increased. However, under dry sliding friction test, weight loss of the composite is not significantly changed.     

The effect of acid mixture on the structure of sol–gel PZT fibers

Author's previous studies [J. Am. Ceram. Soc., in press] showed that the acidification of the precursor solution controls the strength and length of sol–gel PZT fibers. Two acids, acetic acid (CH₃COOH) and methacrylic acid (C₄H₆O₂), were studied. C₄H₆O₂ produced longer fibers with small cracks, while CH₃COOH produced shorter and denser fibers. In order to take advantage of the opposite effect of each of these acids, mixtures of acetic and methacrylic acid are used in this work to obtain longer and dense fibers. The effect of the ratio of CH₃COOH/C₄H₆O₂ mixture on the precursors' chemical structure, crystalline phase formation and microstructure of PZT fibers is investigated and discussed. Long and almost crack-free PZT fibers are obtained for a 1/2 ratio of CH₃COOH/C₄H₆O₂.     

The effect of thermal cycles on the mechanical properties of fiber–metal laminates

The effect of thermal-shock cycles on the mechanical properties of fiber–metal laminates (FMLs) has been evaluated. FML plates were composed by two AA2024 Al sheets (1.6 mm thick) and one composite ply formed by two layers of unidirectional glass fiber epoxy prepreg and two layers of epoxy adhesive tape of glass fiber reinforced epoxy adhesive. The set was manufactured by hand layup and typical vacuum bag technique. The curing cycle was in autoclave at 125 ± 5 °C for 90 min and an autoclave pressure of 400 kPa. FML coupons taken from the manufactured plate were submitted to temperature variations between −50 and +80 °C, with a fast transition between these temperatures. Tensile and interlaminar shear strength were evaluated on samples after 1000 and 2000 cycles, and compared to nonexposed samples. 2000 Cycles corresponds to typical C Check interval for commercial aircraft maintenance programs. It was observed that the thermal-shock cycles did not result in significant microstructural changes on the FML, particularly on the composite ply. Similarly, no appreciable effect on the mechanical properties of FML was observed by the thermal-shock cycles.     

The effect of partially stabilized zirconia on the mechanical properties of the hydroxyapatite–polyethylene composites

The effect of partially stabilized zirconia (PSZ) on the mechanical properties of the hydroxyapatite-high density polyethylene composites was studied by investigating the effect of hydroxyapatite and the simultaneous effect of hydroxyapatite and PSZ volume fractions on fracture strength, modulus of elasticity, and absorbed energy in the composite samples. The results showed a decrease in fracture strength, and absorbed energy with an increase in the volume fraction of hydroxyapatite content in the hydroxyapatite-polyethylene samples. Partial replacement of hydroxyapatite with PSZ particles was beneficial in the improvement of both the fracture strength and failure energy values in the composite samples. A transition from ductile to brittle behavior was observed as the volume fraction of ceramic filler particles increased in the samples.     

The effect of high-temperature heat-treatment on the strength of C/C–SiC joints

Joining of carbon fiber reinforced C–SiC dual matrix composite (denoted by C/C–SiC) is critical for its aeronautical and astronautical applications. Joining of C/C–SiC has been realized through a reaction joining process using boron-modified phenolic resin with micro-size B₄C and nano-size SiO₂ powder additives. The effect of the heat-treatment temperature on the retained strength of the joints, calculated by dividing the strength of the heat-treated joints by the strength of the joints before heat-treatment, was studied. The maximum retained strength of the joints is as high as 96.0% after the heat-treatment at 1200 °C for 30 min in vacuum, indicating good heat resistance of the joints. The thickness of the interlayer of the joint after the heat-treatment is about 18 μm and it is uniform and densified. There are no obvious cracks or pores at the interfaces. During the heat-treatment, carbon, oxygen, silicon, and boron diffuse at the interfacial area. The interlayer is composed of B₄C, SiO₂, glassy carbon, amorphous B₂O₃, and borosilicate glass. SiC appears in the interlayer of the joint heat-treated at 1400 °C for 30 min in vacuum. The addition of B₄C and SiO₂ powders contributes to the densification of the interlayer, the bonding at the interfaces and the heat resistance of the joints.     

The effect of solution temperature on the microstructure and tensile properties of Al–15%Mg2Si composite

The effect of different solution temperatures has been investigated on the microstructure and tensile properties of in situ Al–Mg₂Si composite specimens were subjected to solutionizing at different temperatures of 300 °C, 350 °C, 400 °C, 450 °C, 500 °C, 550 °C and 580 °C for holding time of 4 h followed by quenching. The microstructural studies of the polished and etched samples by scanning electron microscopy (SEM) in the solution condition indicated that the increase in the temperature changes the morphology of both the primary and secondary Mg₂Si phases. Solutionizing led to the dissolution of the Mg₂Si particles and changed their morphology. Tensile test results indicated that ultimate tensile strength (UTS) gradually decreased upon solutionizing from 300 to 550 °C while further increase in the temperature followed by a sharp decrease in UTS up to 580 °C solutionizing temperature. It was found that the elongation has become three times greater in comparison to the as-cast state. Elongation results showed an increase up to 500 °C and then reduced temperatures of 550 and 580 °C. Fractographic analysis revealed a cellular nature for the fracture surface. On the cellular fracture surface, the features of both brittle and ductile fracture were present simultaneously. As a result of solution treatment the potential sites for stress concentration and crack initiation areas were reduced due to softening of the sharp corners and break up of eutectic network respectively, while increase in the number of fine dimples rendered the nature of fracture to ductile and also increased elongation.     

The effect of molybdenum on optical properties of ZnO nanoparticles in Ultraviolet–Visible region

Zn_1?xMo_xO (x = 0.0, 0.01, 0.03, and 0.05) nanoparticles (NPs) are synthesized by using gelatin, via the sol-gel method. A calcination temperature of 600 °C is maintained for 2 h. The influence of molybdenum concentration on the structural and optical properties of these NPs is demonstrated. Synthesized NPs are characterized using X-ray diffraction (XRD), UV–vis spectroscopy, and transmission electron microscopy (TEM). XRD patterns reveal the crystallite nature of samples that exist in the hexagonal wurtzite phase. TEM images manifest the existence of nearly spherically-shaped NPs. The UV–vis spectroscopy results showed that the absorption edge of ZnO nanoparticles is red-shifted by adding molybdenum. Finally, the optical parameters of the refractive index and permittivity of the synthesized samples were calculated using Kramers-Kronig relations using the UV–vis spectra.     

The effect of silicon on the structure and mechanical properties of an α+Β titanium alloy

Titanium 4 wt% Al-4 wt% Mo-2 wt% Sn containing 0, 0.25 and 0.5 wt% Si has been solution-treated in the + phase field at 900 C. The microstructures obtained at room temperature after cooling from 900 C at various rates have been determined using transmission electron microscopy and the partitioning of the elements between the phases has been established using X-ray energy dispersive analysis on the thin foils. The degree of partitioning increases with decreasing cooling rate: aluminium partitions to the -phase, molybdenum and silicon to the -phase and tin remains uniformly distributed. Silicon is found to inhibit the partitioning of molybdenum: this has a profound effect on the stability of the -phase and the resultant microstructure. In quenched material containing transformed , substantial age hardening can be obtained in the range 350 to 600 C and is associated with precipitation within the orthorhombic martensite phase, possibly occurring via a spinodal mechanism. Silicon has little effect on the microstructure of air-cooled samples but contributes to high-temperature strength via dynamic strain ageing.     

The effect of γ-irradiation on the optical properties of polyoxymethylene compacts

The effects of -irradiation on the optical properties of polyoxymethylene (POM) compacts are studied at room temperature. A UV-visible spectrometer is used to study the optical absorbency in the wavelength range 200–1100 nm. The optical energy of both direct and indirect transitions as well as the energy band tail E is determined as a function of exposure dose. The results obtained showed that the POM compacts became brittle as the -radiation dose reaches 5 Mrad. In the meanwhile, the wavelength of the optical band tail g increases to a maximum at 2 Mrad and the energy band tail E reaches 5 eV at the same dose. Both direct and indirect energies of transition decrease with the irradiation dose. The results can be explained on the basis of -irradiation-induced changes due to cross-linking in the POM.     

The effect of rapid solidification on the structure, decomposition behavior, electrical and mechanical properties of the Sn–Cd binary alloys

A group of rapidly solidified Sn–Cd alloys has been prepared by a melt-spinning technique. X-ray diffraction, microstructure, and differential thermal analysis have been carried out. Youngs modulus and internal friction have been measured, and the temperature dependence of resistivity has been evaluated. The results show a modification in both the microstructure and decomposition behavior. Also, an interesting connection between Youngs modulus and the axial ratio (c/a) of the unit cell of the -Sn was found in which Youngs modulus increases by increasing the axial ratio (c/a). It was found also that the internal friction increases on increasing the Cd concentration.     

The effect of zinc oxide–phosphate core–shell pigments on the properties of blend rubber composites

In this work the rheological, physico-mechanical, thermal and morphology studies were performed on a blend of EPDM/SBR (ethylene propylene diene monomer/styrene butadiene rubber) (50/50) loaded with a new prepared core–shell pigment based on a core of zinc oxide which presents the major component of the prepared pigment (≈90%) covered with a shell of phosphate, this shell comprises only about (≈10%). The new pigments were added in different concentration to the rubber blend and were compared to blends pigmented with commercial zinc oxide and zinc phosphate. The results showed that the new pigments exhibited better rheometric, and physico-mechanical properties. In addition, these prepared pigments showed decrease of equilibrium swelling in toluene solvent and increase in crosslink density for EPDM/SBR blend. The efficiency of prepared core–shell pigments were also evaluated by studying the surface morphology (SEM) and thermal properties TGA (thermal gravimetric analysis). The prepared pigments loading of 10 phr (parts per hundred parts of rubber) showed the optimum properties of EPDM/SBR blend than rubber loaded with higher concentration of the commercial pigments, which indicated that the new core–shell pigment is more economic with better performance than commercial zinc oxide and phosphates individually.     

The influence of multiscale fillers on the rheological and mechanical properties of carbon-nanotube–silica-reinforced epoxy composite

Multiscale fillers were fabricated through synthesis of carbon nanotubes (CNTs) on silica microparticles by the use of chemical vapor deposition. Three types of catalyst precursors with different concentrations and reaction times were investigated to find the optimal conditions for CNT synthesis. The produced multiscale fillers of CNT–silica were incorporated within epoxy resin to fabricate a multiscale composite. Rheological analysis and tensile and impact tests were performed to study the effect of fillers on the structural properties of composites. The rheological results demonstrated a similar viscous behavior between CNT–silica suspensions and epoxy, which implies that there was no critical increase of viscosity. Significant improvements in the elastic modulus and tensile and impact strength were achieved for epoxy matrix filled with the optimal fraction of multiscale fillers. The reinforcing efficiency of multiscale fillers was evaluated by comparing the results of micromechanical models with experimental data.