Abstract: Zinc is a non-ferrous metal with potential application in orthopaedic implant materials. However, its poor mechanical properties were major challenge to its application. Therefore, this paper studies the mechanical properties of biodegradable Zn-based alloy for biomedical application. Pure zinc powder with varying (0, 1, 2, 3 & 6) wt% of magnesium powders were ball milled using ball-to-powder ratio (B:P) of 10:1 at 350 rpm for 4 hours. The resulting milled powders were compacted and sintered at 300 MPa and 350 °C respectively. Microstructural, phase and mechanical properties analyses were performed following American standard of testing and measurement. The results show that magnesium has influence on the mechanical properties of zinc. The compressive strength, hardness and elastic modulus of 210 ± 8.878 MPa, 76 ± 5.707 HV and 45 ± 11.616 GPa respectively as obtained in Zn-2Mg alloy were optimum and meet the minimum requirement of biodegradable metal for orthopaedics application. These results indicate an increase of 111, 93 and 93% in compressive strength, hardness and elastic modulus respectively as compared to pure zinc. The increase in mechanical properties was adduced to effectiveness of compaction pressure and intermetallic phase formation within the matrix resulting in high dislocation density for improving strength. The study concluded that, Zn-2Mg alloy with optimum mechanical properties can therefore be considered a potential candidate for orthopaedic application.
Abstract: Nanomaterials ferrites have applications in making permanent magnets, high density information devices, color imaging etc. In the present examination, lithium ferrite is synthesized by sol-gel process. The x-ray diffraction (XRD) result shows that the structure of lithium ferrite is monoclinic structure. The average particle size 22 nm is calculated by Scherer formula. The lattice parameters and dislocation density (δ) are calculated from XRD data. Strain (ε) values are evaluated from Williamson – hall plot. The FT-IR study reveals the formation of ferrites showing the significant absorption bands. The VU-VIS spectroscopic data is used to calculate direct and indirect optical band gap (Eg) of 1.57eV and 1.01eV respectively for lithium ferrite by using Tauc plot at the edge of the absorption band. The energy dispersive x-ray analysis spectra showed that the expected elements exist in the material. The magnetic behaviour of the materials studied using vibrating sample magnetometer (VSM).
Abstract: This work studies the effect of thickness on structural
and electrical properties of CuAlS2 thin films grown by two stage
vacuum thermal evaporation technique. CuAlS2 thin films of
thicknesses 50nm, 100nm and 200nm were deposited on suitably
cleaned corning 7059 glass substrate at room temperature (RT). In
the first stage Cu-Al precursors were grown at room temperature by
thermal evaporation and in the second stage Cu-Al precursors were
converted to CuAlS2 thin films by sulfurisation under sulfur
atmosphere at the temperature of 673K. The structural properties of
the films were examined by X-ray diffraction (XRD) technique while
electrical properties of the specimens were studied using four point
probe method. The XRD studies revealed that the films are of
crystalline in nature having tetragonal structure. The variations of the
micro-structural parameters, such as crystallite size (D), dislocation
density ( ), and micro-strain ( ), with film thickness were
investigated. The results showed that the crystallite sizes increase as
the thickness of the film increases. The dislocation density and
micro-strain decreases as the thickness increases. The resistivity ( )
of CuAlS2 film is found to decrease with increase in film thickness,
which is related to the increase of carrier concentration with film
thickness. Thus thicker films exhibit the lowest resistivity and high
carrier concentration, implying these are the most conductive films.
Low electrical resistivity and high carrier concentration are widely
used as the essential components in various optoelectronic devices
such as light-emitting diode and photovoltaic cells.
Abstract: A model to predict the plastic zone size for material
under plane stress condition has been developed and verified
experimentally. The developed model is a function of crack size,
crack angle and material property (dislocation density). Simulation
and validation results show that the model developed show good
agreement with experimental results. Samples of low carbon steel
(0.035%C) with included surface crack angles of 45o, 50o, 60o, 70o
and 90o and crack depths of 2mm and 4mm were subjected to low
strain rate between 0.48 x 10-3 s-1 – 2.38 x 10-3 s-1. The mechanical
properties studied were ductility, tensile strength, modulus of
elasticity, yield strength, yield strain, stress at fracture and fracture
toughness. The experimental study shows that strain rate has no
appreciable effect on the size of plastic zone while crack depth and
crack angle plays an imperative role in determining the size of the
plastic zone of mild steel materials.
Abstract: The microstructure characterization of tempered nanocrystalline bainitic steel is investigated in the present study. It is found that two types of plastic relaxation, dislocation debris and nanotwin, occurs in the displacive transformation due to relatively low transformation temperature and high carbon content. Because most carbon atoms trap in the dislocation, high dislocation density can be sustained during the tempering process. More carbides only can be found in the high tempered temperature due to intense recovery progression.
Abstract: An experimental study is presented on the effect
of microstructural change on the Portevin-Le Chatelier effect
behaviour of Al-2.5%Mg alloy. Tensile tests are performed on
the as received and heat treated (at 400 ºC for 16 hours)
samples for a wide range of strain rates. The serrations
observed in the stress-time curve are investigated from
statistical analysis point of view. Microstructures of the
samples are characterized by optical metallography and X-ray
diffraction. It is found that the excess vacancy generated due
to heat treatment leads to decrease in the strain rate sensitivity
and the increase in the number of stress drop occurrences per
unit time during the PLC effect. The microstructural
parameters like domain size, dislocation density have no
appreciable effect on the PLC effect as far as the statistical
behavior of the serrations is considered.