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

A Study on Epidural Tramadol Compared with Epidural Fentanyl Combined with Low Dose Bupivacaine for the Control of Metastatic Cancer Pain

Background: Despite advances in the knowledge of pathophysiology of pain and its management, patients continue to suffer from pain in many terminal stage cancer. Tramadol hydrochloride is a weak opioid with analgesic properties, and can be tried for cancer pain management. Objectives: This study was performed to find out the efficacy of the analgesic property of Tramadol through epidural route in cancer patients as an combination with low dose(.125%) Bupivacaine and to compare with Fentanyl, a μ opioid agonist. Methods: 50 Cancer patients with or without previous pain management were randomly allocated to one of the two study regime- Group-A (tramadol 50 mg) and Group-B (Fentanyl 50 mgm) in combination with .125% Bupivacaine. Drugs were administered epidurally 6 hourly, 8 hourly and 12 hourly respectively for the 1st, 2nd and 3rd day. Low dose bupivacaine was added to both groups to enhance quality. Pain scores, blood pressure, respiratory rate, heart rate, side effects and patients' satisfaction score was recorded 6 hourly for 72 hrs. The data yielded from this study were compiled and analyzed by unpaired and paired ‘t' test with 95% confidence limit. A value of P< 0.05 was considered to be significant. ÷ square test was done for some of the data. Results: Pain scores were significantly decreased in both the groups but were not significantly different. The incidence of side effects including nausea and vomiting was found in both the groups and was not significantly different between the two groups. Conclusion: The use of epidural Tramadol in selected cancer pain patients (especially pain in lower abdomen and lower back) may be very useful and is comparable to opioid in certain situations. Key words: Metastatic cancer pain; Epidural tramadol. DOI: 10.3329/bsmmuj.v2i2.4760 BSMMU J 2009; 2(2): 66-7

Challenges in Developing Applications for Aging Populations

Elderly individuals can greatly benefit from the use of computer applications, which can assist in monitoring health conditions, staying in contact with friends and family, and even learning new things. However, developing accessible applications for an elderly user can be a daunting task for developers. Since the advent of the personal computer, the benefits and challenges of developing applications for older adults have been a hot topic of discussion. In this chapter, the authors discuss the various challenges developers who wish to create applications for the elderly computer user face, including age-related impairments, generational differences in computer use, and the hardware constraints mobile devices pose for application developers. Although these challenges are concerning, each can be overcome after being properly identified

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

Diagnosed hematological malignancies in Bangladesh - a retrospective analysis of over 5000 cases from 10 specialized hospitals

Background The global burden from cancer is rising, especially as low-income countries like Bangladesh observe rapid aging. So far, there are no comprehensive descriptions reporting diagnosed cancer group that include hematological malignancies in Bangladesh. Methods This was a multi-center hospital-based retrospective descriptive study of over 5000 confirmed hematological cancer cases in between January 2008 to December 2012. Morphological typing was carried out using the “French American British” classification system. Results A total of 5013 patients aged between 2 to 90 years had been diagnosed with malignant hematological disorders. A 69.2% were males (n = 3468) and 30.8% females (n = 1545), with a male to female ratio of 2.2:1. The overall median age at diagnosis was 42 years. Acute myeloid leukemia was most frequent (28.3%) with a median age of 35 years, followed by chronic myeloid leukemia with 18.2% (median age 40 years), non-Hodgkin lymphoma (16.9%; median age 48 years), acute lymphoblastic leukemia (14.1%; median age 27 years), multiple myeloma (10.5%; median age 55 years), myelodysplastic syndromes (4.5%; median age 57 years) and Hodgkin’s lymphoma (3.9%; median age 36 years). The least common was chronic lymphocytic leukemia (3.7%; median age 60 years). Below the age of 20 years, acute lymphoblastic leukemia was predominant (37.3%), followed by acute myeloid leukemia (34%). Chronic lymphocytic leukemia and multiple myeloma had mostly occurred among older patients, aged 50-over. Conclusions For the first time, our study presents the pattern and distribution of diagnosed hematological cancers in Bangladesh. It shows differences in population distributions as compared to other settings with possibly a lower presence of non-Hodgkin lymphoma. There might be under-reporting of affected women. Further studies are necessary on the epidemiology, genetics and potential environmental risk factors within this rapidly aging country