Microstructure and mechanical properties of biodegradable Mg-SiO2 nanocomposite

Conventional metals such as titanium, stainless steel and platinum possess high strength, corrosionresistant and biocompatibility features, therefore, widely used in producing orthopedic implants required during the surgery of fractured bones. However, these materials are not biodegradable and the implants produced by these materials are usually present in the body, even after the healing of the fractured tissue causes infection due to the corrosion of the implant material at the physiological condition. Another drawback of these metallic materials is their high elastic moduli that leads to stress-shielding effect. Therefore, in most cases, a revision surgery is needed to remove the implant and hence causes a lot of inconvenience to the patients. Therefore, it becomes a prime concern to develop a state-of-the-art biodegradable implant material that can maintain the mechanical properties of the bones. In recent years, Magnesium (Mg) and its alloys have attracted significant interest to be potential alternatives to conventional orthopedic implant materials owing to their excellent biodegradable and mechanical properties. This is the lightest metal having a density range from 1.74 to 2.0 g/cc and maintains a great strength-to-weight ratio. Besides, the elastic modulus of magnesium alloys ranging from 41-45 GPa, close to that of cortical bone which would reduce the possibility of stress shielding effect. More importantly, these materials are biodegradable and hence, completely absorbed in the human body after regeneration of the bone tissue. However, Mg is highly corrosive in the biological environment and degraded severely. Therefore, in this study, silica (SiO2) nanoparticle reinforced magnesium (Mg)-based nanocomposites have been developed by powder metallurgy method and the effect of SiO2 on the microstructure and mechanicalproperties have been evaluated. Pure Mg was used as the matrix material while SiO2 nanoparticle with three different weight % was applied as the reinforcement. Pure Mg powder and SiO2 nanoparticle was blended in a planetary ball mill, compacted in a uniaxial hydraulic press and then sintered in a tube furnace to obtain the nanocomposite material. A distinct Mg2Si phase was observed in the microstructure of the nanocomposite. The mechanical properties revealed that the addition of 5% SiO2 significantly increased the microhardness and tensile strength, nevertheless keep the elastic modulus same as the pure Mg. The enhancement of mechanical properties is attributed due to the formation of Mg2Si phase in the nanocomposite

A relationship of porosity and mechanical properties of spark plasma sintered scandia stabilized zirconia thermal barrier coating

Porous ceramic materials are popularly accepted as thermal barrier coatings (TBCs) in insulating gas turbine parts working at high temperatures. In this research, three different types of Scandia stabilized zirconia (ScSZ) systems, a nanometric 10 mol% ScSZ (10-ScSZ), a micrometric 8 mol% ScSZ (8-ScSZ) and a combination of these two powders (10-8-ScSZ) have been developed by Spark Plasma Sintering (SPS) process. Varying SPS parameters, for instance, temperature, pressure and dwell time were applied to develop the different volumes of porosity in the materials. Subsequently, the microstructure of the materials has been studied and mechanical properties have been evaluated. All three materials demonstrate a reduced porosity level at high sintering temperature and pressure. However, the nanometric 10-ScSZ material shows a higher reduction of porosity from 51.8% to 11.1% at 30 MPa pressure and 40.2%–8.5% at 60 MPa pressure within the temperature range of 1000–1200 °C. Besides, the 10-8-ScSZ composite exhibits substantially increased porosity in comparison to its constituent parts. The results also show that the nanometric 10-ScSZ material exhibits a greater mechanical strength including Vickers microhardness of 81 HV, flexural strength of 361 MPa and elastic modulus of 187 GPa at 5% porosity level, as compared to the other two materials. Additionally, it is observed that all the mechanical properties for all three materials consistently decrease with the increase in porosity levels. While compared with the traditional atmospheric plasma spray (APS) processed ceramic coating, the porous ScSZ coating materials exhibit a larger elastic modulus. Therefore, the porous ScSZ developed by the SPS process could be a prospective alternative thermal barrier coating (TBC)

Epoxy based nanocomposite material for automotive application- a short review

The automotive industry is a rapidly growing sector of the economy of most countries. Due to consumer and world population growth, the continuous necessity of a better, safe, and economical transportation approach increases with low emission. Researchers and producers face many challenges in the automobile industry for environmental issues, greenhouse gas emissions, boosting the fuel economy, weight minimization, and maintaining modern automobiles' safety and performance. Several strategies towards developing innovative materials have been introduced to address the challenges and replace heavy metal with lightweight polymer composite. Lightweight polymer composite materials offer great potential for increasing vehicle efficiency, decreased fuel consumption, reduced vehicle weight, and corrosion avoidance perspective than heavier materials. Epoxy as a thermoset polymer added with filler material produces nanocomposite material, which increased mechanical, chemical, electrical, and thermal properties, high compatibility, low cost, and shrinkage played significant roles in this regard. This article summarises the material selection process and the application of lightweight polymer composite materials, especially epoxy nanocomposite material, in the automotive industry

Fabrication and characterization of Al2O3 nanoparticle reinforced aluminium matrix composite via powder metallurgy

In this study, aluminium-aluminium oxide (Al-Al2O3) metal matrix nanocomposites (MMNCs) with the different volume content of Al2O3 reinforcement were prepared. Three different types Al- Al2O3 nanocomposite specimens comprise of 10%, 15% and 20% volume fractions of Al2O3 were fabricated using conventional powder metallurgy (PM) route and their microstructure and mechanical properties were determined. The samples were prepared under 200 kN compaction load and 630 °C sintering temperature. The correlation between microstructure and mechanical properties due to the inclusion of Al2O3 nanoparticles were investigated. The optical micrographs revealed that the Al2O3 nanoparticles are almost uniformly distributed in the Al matrix with good bonding between matrix and reinforcement. Moreover, the mechanical properties including hardness, tensile strength and compressive strength of the nanocomposite increase with increasing volume fraction of the reinforcement. However, the impact strength decreases once the Al2O3 nanoparticles increase in the composite

Influence of glass fiber content on tensile properties of polyamide-polypropylene based polymer blend composites

In recent years, the rapid development of polymer composites is replacing the use of metals and alloys in high performance engineering applications, particularly in automotive and aerospace industries. In this research study, influence of glass fiber (GF) content on tensile properties of polyamide-polypropylene (PA-PP) based blend composites was investigated. Considering, 0%, 3%, 6%, 9% and 12% GF content, PA6-PP-GF composites of five compositions were prepared through injection molding method. In the experiments, tensile tests were performed under strain rate of 5 mm/min for all types of composite specimens. Test results show that tensile properties of composites of five different compositions are influenced by glass fiber content. In general, tensile strength of composite increases gradually with increase in fiber content. On the other hand, tensile modulus increases significantly with increase in fiber content. Experimental data also revealed that yield strength, strength at fracture and strain at break of the composites are influenced by the content of glass fiber. Test data also show that tensile strain at maximum load almost corresponds to the tensile strain at break for all composite specimens

Influence of glass fiber content on tensile properties of polyamide-polypropylene based polymer blend composites

In recent years, the rapid development of polymer composites is replacing the use of metals and alloys in high performance engineering applications, particularly in automotive and aerospace industries. In this research study, influence of glass fiber (GF) content on tensile properties of polyamide-polypropylene (PA-PP) based blend composites was investigated. Considering, 0%, 3%, 6%, 9% and 12% GF content, PA6-PP-GF composites of five compositions were prepared through injection molding method. In the experiments, tensile tests were performed under strain rate of 5 mm/min for all types of composite specimens. Test results show that tensile properties of composites of five different compositions are influenced by glass fiber content. In general, tensile strength of composite increases gradually with increase in fiber content. On the other hand, tensile modulus increases significantly with increase in fiber content. Experimental data also revealed that yield strength, strength at fracture and strain at break of the composites are influenced by the content of glass fiber. Test data also show that tensile strain at maximum load almost corresponds to the tensile strain at break for all composite specimens

Investigation on microstructure and hardness of aluminium-Aluminium oxide functionally graded material

This study investigated the microstructure and hardness of aluminium-aluminium oxide (Al-Al2O3) functionally graded material (FGM). Preparation of metal-ceramic functionally graded material was carried out following powder metallurgy (PM) route. Four-layered aluminium-aluminium oxide (Al-Al2O3) graded composite structure was processed using 0%, 5%, 10% and 15% (from first layer to fourth layer) aluminium oxide as ceramic concentration. A cylindrical steel die was used for the fabrication process of the FGM green compact. The green compact was prepared by applying cold pressing technique using a hydraulic press. The sintering process was implemented at 600 °C sintering temperature and 3 h sintering time using 2-step cycle. Microstructural characterization of the sample was conducted layer by layer using high resolution optical microscopy (OM). Hardness of the sample was also performed layer by layer using Vickers microhardness tester. The obtained results revealed that there is a uniform ceramic particle distribution within the metallic phase. From the microstructural observation it was clear that smooth transition occurred from one layer to next layer and each interface was distinct. It was also observed that there is a steady increase in layer hardness with the increase in ceramic concentration

Investigation of the Fatigue Crack Propagation Behaviour in the Al Alloy/Hybrid MMC Bi-layer Material

In this study, the fatigue crack propagation behaviour in the Al alloy-hybrid MMC bi-material system has been investigated. Three-point bending fatigue test is carried out on the Shimadzu servopulser machine. The plastic replica technique is used to observe the crack growth during cyclic loading. The crack growth rate is analyzed at different stress intensity factor range, ΔK. The experimental results showed that the crack growth decelerates in the MMC layer side and maximum crack retardation occurs on the boundary of the bi-material system. Near the boundary of the bi-material, the crack tip becomes curved, which reduces the crack growth rate in the vicinity of the boundary of the bi-material even at higher ΔK. The particle-matrix interfacial debonding, as well as particle fracture, is observed in the hybrid MMC layer during fatigue loading

Experimental and Numerical Study on the Low Cycle Fatigue Behaviour of a Cast Hybrid Metal Matrix Composites

The low-cycle fatigue (LCF) behavior specially the fracture initiation mechanism in a cast hybrid metal matrix composite (MMC) has been studied experimentally and numerically. Conventional three point bending fatigue test has been carried out and factographic analysis has been conducted to observe the fracture initiation site. Experimental results showed that microcracks in LCF initiated at the particle—matrix interface which was located in the hybrid clustering region. Due to continued fatigue cycling, the interface debonding occurred, created additional secondary microcracks and the microcrack coalesced with other nearby microcracks. As far as the numerical study is concerned, three dimensional (3-D) unit cell models of hybrid MIMC consists of reinforcement clustering and non-clustering regions were developed by using finite element method (FEM). The stress-strain distribution in both the reinforcement clustering and non-clustering regions were analyzed. The numerical results confirmed that the stress concentration occurred on the reinforcement—matrix interfaces located in the clustering region and provide reasonable agreement with the experimental observations

Stress Measurement During Crack Propagation In Metal Matrix Composites Using Micro-Raman Spectroscopy

The measurement of stress in the SiC particles during crack propagation was investigated by micro raman spectroscopy. The experiment was carried out in situ in the Raman spectroscopy. Experimental results showed that cracks due to monotonic loading propagated by the debonding of the particle/matrix interface and particle fracture. A high decrease in stress was observed with the interfacial debonding at the interface and with the particle fracture on the particle. Moreover, the critical tensile stresses for particle-matrix interface debonding and particle fracture developed in hybrid MMC were also estimated during the crack propagation