Evaluation of physical–chemical properties and biocompatibility of a microrough and smooth bioactive glass particles

The purpose of this study was to evaluate physical-chemical and biocompatibility characteristics of a simple synthesis and low cost experimental bioactive glass. Physical and chemical properties were analyzed using scanning electron microscopy (SEM), X-ray energy dispersive (EDX), X-ray fluorescence (XRF) and X-ray diffraction (XRD). The biomaterials were subcutaneously implanted into rats, according to the following groups: G1, PerioGlastrade mark; G2, Biograntrade mark, G3, Experimental Bioactive Glass U (BGU) and G4, Control (Sham). After 7, 15, 21, 45, and 60 days, 5 animals/group/period were sacrificed and the subcutaneous tissue was dissected for histological and histometric analysis, considering inflammatory reaction and granulation area, presence of polymorphonuclear (PMN), monuclear (MN) and fibroblast (F) cells. SEM analysis of biomaterials showed irregular particles with different surface characteristics. EDX showed calcium, oxygen, sodium, phosphorus and silicon; XRF revealed silica oxide (SiO(2)), sodium oxide (Na(2)O), calcium oxide (CaO) and phosphorus oxide (P(2)O(5)). XRD indicated non crystalline phase. Measurement of tissue reaction showed similar results among the experimental groups at 45 and 60 days. No difference was found for PMN, MN and F cell counts. All biomaterials exhibited partial resorption. In conclusion, the experimental bioactive glass analyzed showed physical and chemical characteristics similar to the commercially available biomaterials, and was considered biocompatible, being partially reabsorbed in the subcutaneous tissue.     

Evaluation of mechanical and thermal properties of banana–flax based natural fibre composite

Hybrid materials of any kind are the keynote for today’s demands. This paper deals with one of such hybrid composite made of natural fibres namely, banana and flax fibres. The structural build-up is such that one layer of banana fibre is sandwiched between two layers of flax fibres by hand layup method with a volume fraction of 40% using Epoxy resin and HY951 hardener. Glass fibre reinforcement polymer (GFRP) is used for lamination on both sides. This lamination also increases the overall mechanical properties along with better surface properties. The properties of this hybrid composite are determined by testing its tensile, impact, and flexural loads using a Universal testing machine. Thermal properties are analysed and hybrid composites of flax and banana with GFRP have better thermal stability and flame resistance over flax, banana with GFRP single fibre hybrid composites. Morphological analysis is done using Scanning Electron Microscope (SEM). The result of test shows that hybrid composite has far better properties than single fibre glass reinforced composite under impact and flexural loads. However it is found that the hybrid composite have better strength as compared to single fibre composites.     

Structural,mechanical and thermo physical properties of III–V yttrium pnictides with NaCl-structure under high pressure

In the present paper, we have investigated the high-pressure structural phase transition of yttrium pnictides (YX; X = N, P, As and Sb). An extended interaction potential (EIP) model has been developed (including the zero point energy effect in three body interaction potential model). Phase transition pressures are associated with a sudden collapse in volume. The phase transition pressures and associated volume collapses obtained from present potential model show a generally better agreement with available experimental data than others. The elastic constants and their pressure derivatives are also reported. Moreover the thermo physical properties have also been obtained successfully. Our results are in general in good agreement with experimental and theoretical data where available, and provide predictions where they are unavailable.     

Microstructure and mechanical properties of a sand-cast Mg–Nd–Zn alloy

The microstructures and mechanical properties of a sand-cast Mg–Nd–Zn alloy in the as-cast, solution-treated and peak-aged conditions were investigated. The as-cast alloy was comprised of α magnesium matrix and Mg₁₂Nd eutectic compounds. The eutectic compounds dissolved into the matrix and small Zr-containing particles precipitated at grain interiors, due to the solution treatment. After the solution treatment, two kinds of cooling manner, either cooling in air or quenching in water, were employed. It was worth noting that some basal precipitates formed in the matrix during the in-air cooling process after solution treatment, which led to the succedent weak ageing hardening response and low strength in peak-aged condition. The hardness, yield strength, ultimate tensile strength and elongation at room temperature, of the samples in the T61 condition, were HV81, 191 MPa, 258 MPa and 4.2%, respectively. When tensile tested at high temperature, they exhibited serrated flow. Moreover, the casting surface of the tensile testing bar also had a great influence on its mechanical properties.     

Thixoformability of a Mg–Gd–Y magnesium alloy and its mechanical properties

Abstract

A new magnesium alloy with composition of Mg–8·57Gd–3·72Y–0·54Zr (wt-%, GW94) amenable to semisolid forming is presented. A quantitative investigation of its thixoformability in terms of metallurgical parameters in the semisolid state is performed based on Pandat thermodynamic calculation. The optimised working window for thixoforming is from 581 to 605°C, where the volume fraction of liquid does not change significantly with temperature. The alloy is then successfully thixoformed at 600°C, and a typical thixotropic microstructure is obtained. It is shown that significant improvement of mechanical properties is achieved in the thixoformed (TF) GW94 alloy compared to its permanent mould casting counterpart. This is attributed to an obvious decrease in the amount of porosity and fine distribution of the brittle Mg₂₄(Gd,Y)₅ particles in the thixoforming process.     

Microstructure and mechanical properties of medium-carbon ferrite–pearlite steel microalloyed with vanadium

Abstract

Microstructural analysis and mechanical testing have been carried out on medium-carbon steels to which additions of vanadium in the range 0·075–0·6 wt-% were made. The steels were either continuously cooled or isothermally heat treated after austenitization. Vanadium carbide precipitation in the proeutectoid ferrite regions of the microstructure and, more unusually, also in the pearlitic ferrite lamellae, were identified by transmission electron microscopy. Moreover, in both ferrite phases the precipitates are aligned in rows, indicative of interphase precipitation at the austenite/ferrite transformation interface. These observations are discussed in terms of the various mechanisms that have been proposed for the interphase precipitation reaction. In the alloys studied the vanadium additions were found to increase the strength of the steels by up to 100%, but to reduce the ductility and notched impact resistance. The most useful combination of increased strength with reasonable ductility and impact toughness was achieved with an addition of 0·15 wt-% V. The vanadium additions contributed to a number of variations in microstructure and therefore in strengthening mechanisms, but the largest effect was the interphase precipitation strengthening of the ferritic phases. The highest strength levels were achieved in fully pearlitic microstructures with the pearlitic ferrite lamellae strengthened by interphase precipitation of the vanadium carbide.

MST/536     

Effect of ball milling on the physical and mechanical properties of the nanostructured Co–Cr–Mo powders

In the present study, Co-based machining chips (P1) and Co-based atomized alloy (P2) has been processed through planetary ball mill in order to obtain nanostructured materials and also to comprise some their physical and mechanical properties. The processed powders were investigated by X-ray diffraction technique in order to determine several microstructure parameters including phase fractions, the crystallite size and dislocation density. In addition, hardness and morphological changes of the powders were investigated by scanning electron microscopy and microhardness measurements. The results revealed that with increasing milling time, the FCC phase peaks gradually disappeared indicating the FCC to HCP phase transformation. The P1 powder has a lower value of the crystallite size and higher degree of dislocation density and microhardness than that of the P2 powder. The morphological and particle size investigation showed the role of initial HCP phase and chemical composition on the final processed powders. In addition results showed that in the first step of milling the crystallite size for two powders reach to a nanometer size and after 12 h of milling the crystallite size decreases to approximately 27 and 33 nm for P1 and P2 powders, respectively.     

Evaluation of mechanical properties of aluminium alloy–alumina–boron carbide metal matrix composites

This paper deals with the fabrication and mechanical investigation of aluminium alloy, alumina (Al₂O₃) and boron carbide metal matrix composites. Aluminium is the matrix metal having properties like light weight, high strength and ease of machinability. Alumina which has better wear resistance, high strength, hardness and boron carbide which has excellent hardness and fracture toughness are added as reinforcements. Here, the fabrication is done by stir casting which involves mixing the required quantities of additives into stirred molten aluminium. After solidification, the samples are prepared and tested to find the various mechanical properties like tensile, flexural, impact and hardness. The internal structure of the composite is observed using Scanning Electron Microscope (SEM).     

Effect of γ-irradiation on the physical and mechanical properties of chitosan powder

In this study, locally produced chitosan powder was irradiated with pre-determined doses of γ-ray (Co-60) of 10 kGy, 25 kGy, 50 kGy and 100 kGy respectively. The properties of both chitosan powder and the chitosan film were examined and compared with unradiated chitosan. Physical characteristic of the irradiated powder and film was studied using stereo microscope. It was observed that the γ-ray induces a noticeable colour tone intensity change to the chitosan. Further investigation using Fourier Transformed Infrared Spectroscopy (FT-IR) analysis has confirmed that the chain scission reaction was occurred as a result of γ-ray exposure through the depolymerization mechanisms. Interestingly, the degree of deacetylation (DD) of chitosan measured using FT-IR showed a negligible effect due to the exposure of γ-ray radiation. Further investigation on the viscosity average molecular weight (M_v) showed a reduction of M_v from 577 kD of pure chitosan to 458 kD, 242 kD, 159 kD and 106 kD for 10 kGy, 25 kGy, 50 kGy and 100 kGy of γ-radiated chitosan respectively. In addition, the tensile strength and elongation at break showed a similar decreasing trend with increasing dosage of γ-ray.     

Microstructure and mechanical properties of carbon–carbon composites with multilayered pyrocarbon matrix

The effect of matrix microstructure on the mechanical properties of carbon fiber felts infiltrated by isothermal chemical vapor infiltration (CVI) has been studied by optical microscopy, scanning electron microscopy and three-point bending tests. The nonbrittle fracture behavior of the investigated composites is related to multiple crack deflections caused by the interfacial sliding between pyrocarbon layers with a varying texture degree and the delamination microcracking within the highly textured pyrocarbon layer. An increase of the flexural strength is observed by the composite having a multilayered pyrocarbon matrix.     

Effect of polyethylene glycol on the mechanical property, microstructure, thermal stability, and flame resistance of phenol–urea–formaldehyde foams

In this study, polyethylene glycol (PEG) was added to phenol–urea–formaldehyde foam to improve its toughness, and the effects of PEG, with different molecular weights and dosages, on the mechanical property, microstructure, thermal stability, and flame resistance of phenol–urea–formaldehyde foam were studied. The addition of PEG significantly increased the toughness and impact strength and decreased the pulverization rate of the foam. The compression strength of the foam first increased and then decreased with increasing amounts of PEG. When 2 wt% PEGs were added, the compression strength of foams was the highest. The addition of PEG significantly influenced the microstructure of phenol–urea–formaldehyde foams, in which the cell diameter decreased and wall thickness increased with increasing amount and molecular weight of PEG. The addition of PEG also slightly decreased the thermal stability of phenol–urea–formaldehyde foams, and increased the heat release rate, total heat release, and total smoke release of the foams.     

Microstructure and mechanical properties of Mg–Gd–Zr alloys with low gadolinium contents

Mg–xGd–0.6Zr (x = 2, 4, and 6% mass fraction) alloys were synthesized by semi-continuous casting process. The effects of gadolinium content and aging time on microstructures and mechanical properties of the Mg–xGd–0.6Zr alloys were investigated. The results show that the microstructures of the as-cast GKx (x = 2, 4, and 6%) alloys are typical grain structures and no Gd dendritic segregation. In as-cast Mg–6Gd–0.6Zr alloy, the second phases Mg_5.05Gd, Mg₂Gd, and Mg₃Gd will form due to non-equilibrium solidification during the casting process, and these second phases will disappear after hot-extrusion. The residual compressive stress exists in alloys after extrusion and increases with increasing Gd content. The existence of residual compressive stress contributes to the tensile strength. The elongation of all extruded alloys is over 30%, and the ultimate and yield tensile strength of the Mg–6Gd–0.6Zr alloy are 237 and 168 MPa, respectively. After isothermal aging for 10 h, the strength of extruded Mg–6Gd–0.6Zr alloys increases slightly, however, the elongation of alloys rarely decreases. The fracture mechanism of all studied alloys is ductile fracture.     

Microstructure and mechanical properties of Al–Si cast alloy with additions of Zr–V–Ti

The microstructure and tensile properties at temperatures up to 300 °C of an experimental Al–7Si–1Cu–0.5Mg (wt.%) cast alloy with additions of Ti, V and Zr were assessed and compared with those of the commercial A380 grade. The microstructure of both alloys consisted of Al dendrites surrounded by Al–Si eutectic containing, within its structure, the ternary Al–Al₂Cu–Si phase. Whereas the Al₁₅(FeCrMn)₃Si₂ phases were present in the A380 alloy, Ti/Zr/V together with Al and Si phases, Al(ZrTiV)Si, were identified in the experimental alloy. As a result of chemistry modification the experimental alloy achieved from 20% to 40% higher strength and from 1.5 to 5 times higher ductility than the A380 reference grade. The role of chemistry in improving the alloy thermal stability is discussed.     

Evolution of microstructure and mechanical properties of a duplex Mg–Li alloy under extrusion with an increasing ratio

Mg–5Li–2Zn dual phase alloy was prepared and extruded with ratios of 10, 25 and 79. Microstructures were acquired, and Vickers hardness was examined as well as tensile and compressive properties. The results showed that the alloy possessed a low fraction of β-Li phase besides α-Mg phase. The increase of the extrusion ratio decreased the widths of both phases and also the grain size of α-Mg phase, while increased the homogeneity of the extruded alloys. The strengths were almost the same after the alloy was extruded with ratios of 10 and 25, and the alloy extruded with the ratio of 79 presented a higher strength and a lower ductility. Serrated flow appeared during the tension of the alloy extruded with the ratio of 10. In both tensile and compressive strain–stress curves, yield plateaus were more and more invisible with the increase of the extrusion ratio. It seemed that the deforming behavior of the duplex Mg–5Li–2Zn alloy is still of the pattern of hexagonal Mg alloy with little effect of β-Li phase because of its low fraction.     

Thermal and mechanical properties of La–Al–Sb alloys

We fabricated La–Al–Sb alloy by arc melter system and the fabrication conditions were described in detail. Microstructural analyses were performed and it was found that LaSb, Al₁₁La₃ Al₄La, AlLa₃ and Sb phases formed for different heat treatment conditions. The resistivity results showed the metallic and semiconducting type behavior depending on heat treatment temperatures. The thermal-conductivity measurement was performed in the range of 2–300 K and the data were analyzed by the sum of lattice and carrier components. The linear temperature dependence of thermo power indicates metallic type characteristic of the samples. The micro-hardness values of the phases in the samples were analyzed and it was found that there are two different hardness regions in the samples.     

Investigation of the physical–mechanical properties of Eudragit® RS PO/RL PO and their mixtures with common pharmaceutical excipients

Ammonio methacrylate copolymers Eudragit^® RS PO and Eudragit® RL PO have found widespread use as key components in various types of extended release solid dosage forms. The deformation behavior of neat polymers and binary mixes was evaluated using Heckel Analysis, strain rate sensitivity, work of compaction and elastic recovery index. Additionally, the compact forming ability of neat materials and binary mixes were evaluated by analyzing their tabletability, compressibility and compactibility profiles. The Heckel analysis of both polymers exhibited a speed-sensitive deformation behavior typical to plastic materials. The yield values of the binary mixes of the polymers with microcrystalline cellulose revealed a linear relationship with the weight fractions of individual components. The yield values of binary mixes of both the polymers with dibasic calcium phosphate exhibited slight negative deviations from linearity. Both polymers exhibited axial relaxation after ejection typical of viscoelastic materials, as measured by the elastic recovery index values. The work of compaction and the elastic recovery index values of the binary mixtures were found to be linearly related to the weight fractions of the individual components thus, confirming ideal mixing behavior based on the composition. Addition of microcrystalline cellulose to both polymers significantly improved their tabletability and compactibility. The tensile strengths of the compacts prepared with neat materials and binary mixes with microcrystalline cellulose, dibasic calcium phosphate and lactose were the function of their solid fraction and independent of the tableting speeds tested; thus, validating compactibility as a reliable parameter in predicting acceptable tablet properties.     

Mechanical properties of WC-based hardmetals bonded with iron alloys – a review

Growing concerns over the use of cobalt as binder for WC-based hardmetals has directed research efforts towards finding a suitable alternative binder offering comparable or even superior properties than those found in WC–Co hardmetals. Complete substitution of cobalt by iron alloys has been extensively explored in several studies with significant improvements in mechanical properties of WC bonded with Fe alloys when carbon content addition is strictly controlled in powder composition. Asides from the commonly studied hardness and fracture toughness properties, transverse rupture strength property of this composites has also been observed to hold future promise with further development in the microstructural parameters such as porosity during sintering. This article reviews the progress in the mechanical properties of WC–Fe alloys hardmetals.