Materials Engineering Symposium on Innovation for Industry

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item: Conference-Abstract
Design and development of ultrasonic wave generator using piezoelectric ceramics
(Department of Materials Science and Engineering, 2020-02) Sivanujan, S; Adikary, SU; Abeygunawardane, AAGA
Ultrasonic transducers using piezoelectric materials are popular among researchers because of the efficiency, ease handling, low weight, and small size. In this research, an ultrasonic wave generator using piezoelectric ceramics was designed using mathematical modelling and finite element analysis. Then a prototype was fabricated to compare the performance. Piezoelectric constitutive equation for converse effect and differential equation of spring- mass system with a forcing function were used for mathematical calculation in thickness mode to determine resonant frequency, dimensions of the design and acoustic impedance of matching layer and backing layer. The matching layer transmits the mechanical vibration as ultrasonic wave. To identify optimum parameters of the design, finite element analysis was done. The design resonant frequency and parameters of layers were calculated from solid mechanics and electrostatics for Eigen frequency and Frequency domain studies using 3D model. Transmitting wave frequency in water and air was calculated from acoustic pressure variation, which was obtained as a results of simulation using 2D axisymmetric model. Arduino software was used to feed controlled electric signals to piezoelectric material. Finally a prototype device was developed using Lead Zirconate Titanate (d33 = 400 ×10-12 m/V) as piezoelectric ceramics, Aluminum as matching material and Steel as backing material. Thickness of them are respectively 1.5 mm, 3 mm, and 10 mm. Terminal wires were soldered and all three were merged together using glue gun with polymer binder. Prototype testing was performed with Oscilloscope. The resonance was observed at 75 kHz, 182 kHz, and 232 kHz. Resonance was also confirmed by Impedance - Frequency and Phase - Frequency analysis using LCR measurements.
item: Conference-Abstract
Design/fabrication of bi-axial tensile testing machine and numerical modeling of polymer composite under bi-axial stress state
(Department of Materials Science and Engineering, University of Moratuwa., 2022-11) Arachchi, KADDK; Sandanayaka, SMP; Abeygunawardane, AAGA; Weragoda, VSC; Abeygunawardana, AAGA
In real engineering applications, materials are subjected to different types of loads applied in several directions. Characterizing materials using the Uni-axial tensile testing can be only enough for Isotropic materials. But it is not accurate when testing the Anisotropic materials where the properties vary with different crystallographic orientations. The main scope of this research is to Design & Fabricate the Sri Lankan first ever Bi-Axial Tensile Testing Machine to Characterize Polymer Composites. This study enabled to fabricate a full-scale Bi-Axial Tensile Testing machine for the first time in Sri Lanka. The machine uses four linear actuators which allow cruciform specimen subjected to load from two independent directions. A non contact strain measurement technique using digital Image correlation has been used to measure the strain induced in the specimen. MCalibration – an optimization numerical tool was used to calibrate the best fit material model for the particular application under the biaxial stress state, and a commercial FEA software ABAQUS was used to build and analyze the tested material for its anisotropic nature.
item: Conference-Abstract
Development of a low-cost ceiling material based on local rice husks and waste plastics
(Department of Materials Science and Engineering, 2020-02) Lakmal, TCT; Chathurika, KPI; Udayakumara, SV; Abeygunawardane, AAGA
In the modern world, plastics play a dominant role among all other types of materials. However, not like other materials, plastics take long time to degrade in normal environmental conditions. Plastics used in packaging industry are often discarded to the environment and generates many environmental issues. Due to these issues, past few years many researches focused on recycling and reusing waste plastics. One of the main methods of recycling plastic is making composites. This study was focused to develop a composite material for ceiling sheets using virgin and waste low-density polyethylene and local rice husk. The rice husk- LDPE composite samples were made by using compression moulding techniques after mixing different proportions of rice husk with LDPE. Tensile strength, Flexural strength, swelling, water absorption, Impact strength, hardness and thermal conductivity were checked for all the samples. Results show increasing of hardness, swelling, water absorption and thermal conductivity and reduction of tensile strength, flexural strength, and impact strength with increasing percentage of rice husk. According to the test results, Sample with 20:80 rice husk to LDPE ratio shows better results to use as ceiling materials based on the test results.
item: Conference-Abstract
Development of a method to measure contact angles of sessile droplets to analyze and enhance the surface wettability of nichrome
(Department of Materials Science and Engineering, 2020-02) Kumarasiri, AAAP; Amarasinghe, DAS; Attygalle, D; Abeygunawardane, AAGA
Nichrome (Ni/Cr) alloys are used in many industrial applications due to their better electrical properties and commercial availability. It is a known fact that these alloys are having a surface passivation layer of chromium oxide (Cr2O3). This oxide passivation layer changes the surface tension of the metal surface, therefore, decreases the surface wettability during soldering. This phenomenon is critically addressed in electronic applications because the wettability inhabitancy of nichrome thin films tends to reduce the solderability of the metal. The decrease in solderability will lead to many difficulties such as poor connecting strength of wires and fluctuations of resistance. In this study, two approaches were introduced to enhance the wettability of nichrome alloy surface. In the first approach a liquid salt solution was used in an acidic environment (ZnCl2/HCl) to remove the oxide passivation layer, thereby, to enhance the wettability of the nichrome alloy. Lead-free industrial solder alloy, SN100C (Sn / Cu 0.70% / Ni 0.06% / Ge 0.005%.) was used as the soldering material for this experiment. Solder drops were formed on the Nichrome thin film (With and without treatment of (ZnCl2/HCl) in 325-350°C temperature range. The second approach was an electroplating process to form a thin nickel coat (3 μm) on the nichrome surface. A two-step plating process was carried out. Various plating conditions such as pH- condition, thickness and current density were controlled of the watts bath to obtain the best wettability and adhesion. An experimental setup together with an image processing software was developed to process the image of the solder droplet and measure the contact angles of the nichrome-solder alloy interface. The contact angle measurements were based on the sessile droplet method. The polynomial and ellipse fitting methods were used to digitize the drop shape.The results of the study show that the contact angles of solder droplets were reduced by more than 50 percent after the ZnCl2/HCl treatment. Contact angles can be reduced by more than 60 percent by nickel electroplating. Therefore, the solderability of the nichrome alloy is significantly enhanced by both treatments.
item: Conference-Abstract
Development of a methodology to identify repairable photoreceptor drums
(Department of Materials Science and Engineering, 2020-02) Sampath, WGC; Senarath, GN; Attygalle, D; Abeygunawardane, AAGA
Toner cartridges are discarded due to the degradation of the organic photoconductor while the other parts of the cartridge are in usable condition. This research is focused on developing a method to identify repairable drums. Since the condition of the used drum is unknown, identifying the primary cause for the quality deterioration of xerographic prints is of great importance in repairing these drums.The print quality deterioration can happen due to deterioration of charge transport layer alone,degradation of charge generation layer alone, or occurance of both simultaneously.The damaged charge transport layer could lead to a higher residual potential due to trapped charges in the charge transport layer, and that finally affect the print quality. A locally fabricated setup was used to obtain dark decay curves and photoinduced discharge curves. These curves were then used to identify repairable drums successfully. Furthermore, the wear-out thickness of the charge transport layer was also estimated using the same data. This information was then used to develop a repair methodology for the damaged drums.
item: Conference-Abstract
Development of a piezoresistive pressure sensor using laser scribed graphene
(Department of Materials Science and Engineering, 2020-02) Prabhath, AAN; Perakotuwa, HPTS; Attygalle, D; Abeygunawardane, AAGA
Pressure sensors are often used in applications in the areas of direct pressure sensing in weather instrumentation, aircrafts, automobiles, machinery and Altitude sensing in aircraft, rockets, satellites. Development of piezo resistive commercial pressure sensors is currently restricted to Silicon, Polysilicon thin film, bonded metal foil and sputtered thin film. Properties of graphene shows the potential to develop more accurate and cheaper piezo resistive pressure sensors. This research is focused on the development of such a graphene based pressure sensor for commercial applications. Major steps towards the success of the research was to reduce graphene oxide to graphene from laser scribing method so that chemical reduction steps are omitted and then to design and fabricate a functional pressure sensor. In this research, graphene oxide was synthesized by modified hummers method. The prepared graphene oxide was characterized using FT-IR spectroscopy, XRD, TGA analysis and SEM. The sensors were fabricated using laser reduction of graphene oxide films that were coated on PET (polyethylene terephthalate) substrates. Sensor calibration was done and optimizing steps were taken for better functionality of the sensor. Uniform films of graphene oxide were prepared by drop casting method. Laser reduced graphene oxide has shown an electrical conductivity comparable to chemically reduced graphene oxide. Functionality of the sensor was analyzed after calibration and significant resistance change with applied pressure was observed. Response time of the sensor was coupled with the design of the apparatus used. Laser reduced graphene has shown the potential to design simple, low cost pressure/strain sensors.
item: Conference-Abstract
Development of perovskite structured materials for solar cells
(Department of Materials Science and Engineering, 2020-02) Anuruddha, WAI; Arush, KM; Galhenage, AS; Abeygunawardane, AAGA
Perovskite solar cells have drawn significant attention from the scientists and the industrialists because of the high efficiency. However, the fabrication of high quality film of perovskite material is a very difficult task. In this study methyl ammonium lead iodide perovskite (CH3NH3PbI3) material was synthesized using two step spin coating method, first applying lead iodide (PbI2) and then methyl ammonium iodide (CH3NH3I, MAI). Fabricated films were analyzed by X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM). It is confirmed that the methyl ammonium lead iodide (CH3NH3PbI3) perovskite structured material with average crystal size of 550 nm was formed.The effect of morphological changes with the concentration of MAI was also studied. SEM images show the enhancement of the film quality with decreasing MAI concentrations. Maximum fill factor of 0.32 has been achieved with the lowest MAI concentration (0.1M).
item: Conference-Abstract
Effect of graphene layer thickness on performances of dye-sensitized solar cells
(Department of Materials Science and Engineering, 2020-02) Senaratna, HMA; Madushan, SAD; Galhenage, AS; Abeygunawardane, AAGA
Dye-sensitized solar cells (DSSCs) use platinum electrode as the counter electrode. In this study, to reduce the overall cost of DSSCs, graphene electrodes were fabricated as an alternative to platinum electrode. Graphene electrode was made using electrophoretic deposition method (EPD). The effect of reaction time on the graphene electrode formation was analyzed by keeping the reaction temperature at room temperature (250C) and voltage at a constant value (10 V). With increasing the reaction time increases grapheme layer thickness. DSSCs were also fabricated using the prepared grapheme electrode and the effect of film thickness on the cell performances were studied. The maximum efficiency of 0.61% has been achieved when the grapheme layer thickness is 1.15 μm.
item: Conference-Abstract
Effect of marine environment on corrosion of mild steel
(Department of Materials Science and Engineering, 2020-06) Divanka, JHHT; Dilrukshi, RAS; Guluwita, SP; Abeygunawardane, AAGA
Corrosion is a major problem in steel structures used in marine environments. This project was carried out to investigate the effect of environmental factors in Sri Lankan coastal area for the uniform corrosion rate of mild steel. The results are used to derive an equation for the calculation of the corrosion rate. This project also serves as a part of a large-scale project to create a corrosion map for Sri Lanka. Mild steel samples were exposed to the marine environment for a four month period in Negombo, Moratuwa, Galle and Tangalle. The samples were collected in every two weeks for the analysis of corrosion rate. In addition, passive samples were placed on each place to investigate the Sulphur deposition and Salinity of those areas, and both parameters were measured monthly. Statistical analysis of the data was done to derive the following equation to obtain a relationship of corrosion rate with the environmental conditions such as level of Salinity, Sulphur deposition, cumulative rainfall and temperature. CR=0.245(T)+0.023(SO )+0.034(RF)+0.005(Cl- )-8.435 Where, CR = Corrosion Rate (mg.m-2day-1) T= Temperature (0C) RF= Rainfall (mm.day-1) SO = Sulphur deposition rate (mg.m-2day-1) 2 Cl- - 2 -1 = Chloride deposition rate (mg.m day ) This method has the advantage of assessing the corrosion rate of mild steel, before applications such as structural requirements.
item: Conference-Abstract
Enhance the bond strength between concrete and coated reinforcement steel bars
(Department of Materials Science and Engineering, 2020-02) Silva, WKEL; Dassanayake, DAMP; Guluwita, SP; Abeygunawardane, AAGA
Corrosion of steel bars embedded in reinforced concrete structures reduces the service life and durability of structures causing early failure of structures, which costs significantly for inspection and maintenance of deteriorating structures. Hence, monitoring of reinforcement corrosion is significant for preventing premature failure of structures. Coated rebar is usually used in reinforced concrete structures. However, coated bars reduce friction and thus the bond strength with the concrete. The basic idea behind this project was improving the bond strength between concrete and coated re-bars. Anticorrosive red (Zn3(PO4)2) coating was selected among the available anticorrosive coating in industry by using pull-out test result. Bondability of anticorrosive red was improved by adding various percentage of CaCO3. The pull-out test was used for analyzing the bond strength and salt spray bath method was used for analyzing the corrosion rate. Anticorrosive red with 15% CaCO3 addition gives the optimum bond strength and corrosion resistance to the reinforcement steel bars.
item: Conference-Abstract
Enhancing high temperature stability of asphalt to eliminate corrugation
(Department of Materials Science and Engineering, 2020-02) Kogulan, L; Anojan, MC; Guluwita, SP; Abeygunawardane, AAGA
Asphalt is widely used as the road pavement material. Warmer conditions in tropical countries like Sri Lanka, leads to corrugation of asphalt pavements. The main objective of this research is to enhance the thermal stability of hot mix asphalt to eliminate corrugation. Carbon black (N330) was chosen as the modifier to improve the stability of asphalt at elevated temperature.. Carbon black increases the softening point of the asphalt binder (bitumen) when it mixes with it. Variation of carbon black amount significantly affects the properties of the binder such as consistency, flow behaviors, ductility etc. It was found that carbon black has a better bonding than fine aggregates with asphalts mix. The high temperature (above 65°C) stiffening effect of the asphalt is highly filler dependent. The result shows that, when carbon black is added as the filler (3.8%), stability of the asphalt is increased, and it remains above the required specification limit of road pavement at 70°C temperature.
item: Conference-Abstract
Fabrication of split Hopkinson pressure bar apparatus to study uniaxial high strain rate behavior of aluminium
(Department of Materials Science and Engineering, 2020-06) Rajapakshe, RMSW; Abeygunawardane, AAGA; ; Abeygunawardane, AAGA
There are many high strain rate related application in the world, including vehicle impact, blast welding, ballistic impact etc. Deformation mechanism of high strain rate applications differ from static applications, as a high strain rate application is solely due to stress wave propagation. These high strain rate data are required for safety and structural integrity assessment of structures subjected to dynamic loading. Engineering materials to be used in these applications should be selected irrespective of the deformation behavior witnessed in static uni-axial tensile test. Split Hopkinson Pressure Bar (SHPB) apparatus is used to study high strain rate behavior of different engineering materials (102 s-1 - 104 s-1) under uni-axial loading applications. In this work, compression type SHPB apparatus was fabricated in- house, is consisted of incident bar, transmission bar with properly mounted strain gauges to measure strain under dynamic conditions. The incident bar was impacted using standard single mass pendulum. Incident bar and Transmission bar was made of mild steel and Aluminium was selected as the test sample. Dynamic stress - strain behavior under different strain rates were determined using standard experimental approach associated to SHPB apparatus, followed by classical numerical approach pertinent on uni-axial stress wave propagation theory. The results obtained through SHPB apparatus and theoretical calculations were compared and analyzed. Dynamic Compressive Yield Stress for Aluminium was calculated for different strain rates, and the strain rate sensitivity was clearly witnessed. The results between experimental and theoretical values agreed considerably and spare deviation from the theoretical calculations was identified due to friction of the contact surfaces and wave dispersion effects.
item: Conference-Abstract
Influence of low-amplitude high-frequency pulsed current on the deformation characteristics of low and medium carbon steels
(Department of Materials Science and Engineering, 2020-02) Hendeniya, HMND; Shiranga, WMP; Abeygunawardane, AAGA; De Silva, GIP; Abeygunawardane, AAGA
When electrical pulses are applied to a metal during deformation, the resistance to deformation is dramatically reduced while the plasticity increases significantly. This phenomenon is introduced as electroplasticity. Macroscopic observations of yield stress reduction under current pulsation due to uniaxial tension, creep and stress relaxation is in the center of attention recently. Traditional manufacturing processes such as drawing, and rolling be contingent on the use of heat to reduce the forces associated with the fabricated parts. The high-temperature requirement is potentially leading to stress, warpage, and reduced tolerance control. Therefore, Electrically Assisted Manufacturing is introduced as an effective way of simplifying the fabrication while enhancing end- product properties. The electroplastic deformation of low and medium carbon steels under uniaxial tensile conditions were investigated with respect to the universal uniaxial tensile testing conditions. A significant reduction of yield stress of low and medium carbon steel with different carbon content were observed due to electroplasticity effect. A qualitative and quantitative analysis of yield stress reduction was carried out. Microstructural behavior and morphological aspects of fractured and strained surfaces of low and medium carbon steel specimens were observed. Keywords: Electro plasticity, Electron wind force, Dislocations, Uniaxial tensile test, Electrically assisted manufacturing, Low and medium carbon steel, Plasticity
item: Conference-Abstract
Investigation of thermal and mechanical properties of micro cellulose based composites
(Department of Materials Science and Engineering, 2020-02) Silva, JASR; Maduranga, SMK; Samarasekara, AMPB; Amarasinghe, DAS; Abeygunawardane, AAGA
This research is based on preparation of a composite with Micro Crystalline Cellulose (MCC) and Polypropylene (PP). MCC is hydrophilic and PP is hydrophobic in nature. To avoid less compatibility of these two materials, surface modification was done for MCC. Coconut oil was used as a green surface modifying agent in this research. Transesterification mechanism was used for surface modification. Modified MCC was characterized by using specific techniques to confirmation of surface modification. PP based composites were prepared by varying 1-5 wt%. percentages MCC for both unmodified and modified MCC conditions. Ingredients were blended in an internal mixer. Composites were prepared by pressing compounded mixers using compression molding technique. Mechanical properties and thermal properties of prepared composites were characterized under standards conditions. Tensile test, water absorption test and hardness test were conducted for all prepared composites. Vicat softening temperature (VST), differential thermal analysis and Thermo gravimetric analysis were conducted for all prepared composites according to standards. A mechanical property prediction model was formulated to model the tensile strength and tensile modulus of PP-MCC based composites. Modified Halpin-Tsai equation model was used to predict above mentioned properties. It was observed that the properties of modified MCC-PP composites were higher than the unmodified MCC-PP composites. Results which were obtained from predicted modified Halpin-Tsai model were in good agreement with experimental data. According to the outcomes of this research, biodegradable, eco- friendly and environment- friendly MCC can be used to improve mechanical and thermal properties of PP based composites. Readily available, cheap and environment-friendly coconut oil can be used for MCC surface modification. This developed composite can be used for various engineering applications.
item: Conference-Abstract
Investigation of thermo-mechanical behavior in polymer based mallet compound with graphite
(Department of Materials Science and Engineering, University of Moratuwa., 2021-12) Gunawardhane, HMD; Abhysinghe, IMS; Abeygunawardane, AAGA; Abeygunawardana, AAGA
This research is based on the mixing of vein graphite powder with rubber compound; which is used to produce polymer-based mallets. Based on the records from the industry, normally these mallets have a higher curing time. So, this research aimed in reducing cure time by improving the thermal properties in the compound. The compound was mixed with vein graphite powder at different weight ratios and investigate the mechanical and thermal behavior. The graphite powder was used as a filler and was mixed with rubber compound at 2.5%, 5%, 7.5% and 10%. Under the mechanical properties in the samples, the tensile strength, resiliency, specific gravity, ML and MH were done and checked and analyzed their results. This work includes the behavior of mechanical properties of the compound with increasing graphite percentage up to 10%. Also, thermal conductivity, thermal diffusivity, specific heat capacity, TS2 and TC90 in the samples were investigated under the thermal properties of that sample compounds. Thermal conductivity of the compound was increased and TC90 was the same as the normal sample. Other properties were nearly the same as the normal sample. Hence the curing time of the mallet can be reduced using this modified compound.
item: Conference-Abstract
Mechanical behaviour of Cu-Zr binary metallic glasses: a molecular dynamic simulation study
(Department of Materials Science and Engineering, 2020-02) Gamage, NH; Madhushan, PAC; Sitinamaluwa, HS; Abeygunawardane, AAGA
Metallic glasses (amorphous alloys) have gained increased attention in recent times due to their unique combination of mechanical properties such as high tensile strength, fatigue and wear resistance together with higher toughness values. However, the underlying deformation physics of these materials remain less firmly established as compared with crystalline alloys. One reason is the difficulty of characterization of material structure, as these materials do not have long range order in their atomic arrangements. Material modelling and simulation methods have paved new ways for the advancement of material development, modification and processing. For the study of amorphous materials, atomistic modelling and simulation techniques have proven to be very useful, as these techniques allow a closer look of local atomic environments of these materials. In this research, molecular dynamics simulation is used to analyze mechanical behavior of Cu- Zr binary metallic glasses under tensile forces. Firstly, the relationship of toughness and strength over a range of atomic compositions of Cu-Zr metallic glasses (45 % Zr to 55 % Zr)is analyzed. In addition, the underlying deformation mechanisms of Cu-Zr metallic glasses were investigated. The MD simulations were done using Large-scale Atomic Molecular Massively Parallel Simulator (LAMMPS) and OVITO software is used for visualization and analysis of the simulation results. As this study reveals, both fracture strength and toughness of Cu-Zr alloys are increased with increasing Zr content. Also, the Young's modulus of these alloys are also increased with the increasing Zr content. In-depth analysis of atomic structures suggests that the increasing free volume with increasing Zr content is responsible for high strength and toughness observed in the alloys with higher Zr content.
item: Conference-Abstract
Mechanical characterization of biological soft tissues under tensile loading - experimentation and numerical aspect
(Department of Materials Science and Engineering, University of Moratuwa., 2022-11) Edirisinghe, AD; Weerasuriya, MACS; Abeygunawardane, AAGA; Abeygunawardana, AAGA
For the first time in Sri Lanka, rectus femoris muscle has been used to characterize the mechanical properties of human soft tissues. These properties can be used to synthesis artificial tissue for bio engineering applications; if these biological soft tissues are to be replaced with polymer based biomaterial. Initially, uniaxial tensile test was performed on cadaveric samples obtained from national hospitals with the relevant ethical clearances. The obtained stress vs. strain graphs elucidates hyperelastic behaviour within non damage domain with initial J shape portion. It was also noticed that mechanical properties are highly non homogeneous as stress vs strain curves are different at different locations on the same cadaver. Variation of the “Damage” variable was also calculated to understand the degradation tendency of these biological materials under uniaxial tensile loading. ‘Snudden’ formula was used to obtain shear modulus of these cadaver samples through curve fitting technique. A numerical model was developed using commercially available FEA software ‘ABAQUS’; Based on the best fit analysis for the obtained stress vs stretch ratio graphs; ‘Polynomial Strain Energy Density Function with N=2” was used to simulate the muscle samples. This numerical model also includes damage parameter through the introduction of “Ductile Damage” of FEA and the parameters of the numerical model were all calibrated well with the experimental observation.
item: Conference-Abstract
Optimization of nano-crystalline cellulose formation from cellulose
(Department of Materials Science and Engineering, 2020-02) Weerakkody, KM; Wathsala, KPT; Samarasekara, AMPB; Amarasinghe, DAS; Abeygunawardane, AAGA
This research work is based on the process optimization of nanocellulose extraction from chemically purified cellulose. Cellulose was extracted from rice straws of BG 352 which contains the highest cellulose percentage among other rice species in Sri Lanka. This process included dewaxing, delignification, bleaching, acid hydrolysis, centrifugation, dialysis, sonication and freeze drying. X-ray diffractometer, FTIR, Laser particle size analyzer, SEM, EDX were used to examine & investigate the effect of each chemical treatment on the chemical structure of the extracted cellulose fibers. FTIR was used to compare the chemical structure of untreated and treated fibers. The chemical compositions of fibers including cellulose, hemicelluloses, lignin, and silica were determined by different techniques. The results showed that the cellulose content of the bleached fibers was increased by around 71% compared to the raw materials. XRD analysis concluded the decrement of crystallinity with an increment of the temperature and time of the centrifugation process. The optimum centrifugation conditions were found at 8000 rpm, 10 min 4 times at room temperature for the centrifugation speed and centrifugation time respectively. The optimum dialysis conditions were determined for regenerated cellulose membranes with 12-14 kDa molecular weight cut off (Fisher brand, Pittsburgh, PA) against distilled water for 4 days using a cellulose membrane in distilled water until a constant pH was achieved. The sonication process parameters were optimized as for 3 hours sonication time, 25W 20kHz and amplitude of 50% in an ice bath to avoid overheating, to disperse the nanocrystals for the sonication frequency and sonication time. Finally, the aqueous suspension was freeze-dried in liquid nitrogen to obtain Nano Crystalline Cellulose powder. The dimensions and morphology of the chemically and mechanically extracted nanofibers were investigated by Scanning Electron Microscopy and Laser Particle Size Analyzer. The results of the image analyzer showed that almost 50% of extracted materials are within the range of 64-98 nm and length of several micrometers.
item: Conference-Abstract
Phosphoric acid treated rice husk as a low cost biosorbent for cadmium removal from wastewater
(Department of Materials Science and Engineering, 2020-02) Ranaweera, PB; Madushanka, HM; Udayakumara, SV; Abeygunawardane, AAGA
Heavy metals, a contaminant present in polluted water pose a major threat to humans due to its ability to cause various health risks such as cancers, defective bone mineralization and chronic kidney disease. The most affected areas are developing nations: mainly Asia and South America. Since most of these countries do not have the ability to use expensive water filtration techniques like saltwater desalination or using graphene-based water purifiers, it's essential to come up with a water purifier/filter made of affordable materials. Adsorption behavior of Cadmium ions to phosphoric acid treated rice husk has been studied in this project. Rice husk samples obtained from a local rice mill was cleaned and heat treated initially. Chemical treatment for the rice husk was done by treating with phosphoric acid under uniform conditions. SEM images of the rice husk after treating with phosphoric acid showed significant increase in pores proving the higher efficiency of adsorption due to increased surface area. Artificially contaminated water samples were prepared by diluting a stock solution of Cd2+ ions. Contaminant concentrations in the ppm and ppb range was then filtered by the treated rice husk. Experimental results proved favorable adsorption of Cadmium into phosphoric acid treated rice husk. Ppm range Cd2+ samples had an average adsorption rate of ~30% and the data fitted well for Langmuir and Freundlich isotherms. The highest adsorption percentage was observed in the 100-ppb region with an adsorption rate of ~90%.
item: Conference-Abstract
Prediction of true compressive flow stress of aa 6063 alloy through ultrasonic attenuation
(Department of Materials Science and Engineering, 2020-02) Jurmey, K; Ghimire, NS; Sivahar, V; Abeygunawardana, AAGA; Piyathilake, SAKVM; Abeygunawardane, AAGA
During the compression testing of any material sample, the true compressive flow stress of the material cannot be determined due to the presence of friction between the end surfaces of the specimen and platens (of the compression testing machine) and due to misalignment of the test specimen and platens. Friction causes the barreling of test specimen and material flow at the interface is restrained. However, the material near the mid height position is less restrained by the friction and spreads laterally to a greatest extent. In addition to the compressive stress, a circumferential tensile stress develops as the specimen barrels. Compressive tests are therefore not valid for measurement of bulk elastic or plastic properties of material. The present research work is based on prediction of true compressive flow stress of AA 6063 alloy through ultrasonic attenuation. AA 6063 specimens were compressed to obtain compressive stress and strain. Ultrasonic attenuation coefficient of the each compressed specimens were measured to correlate the variation of stresses with it. Finite Element Analysis (FEA) was performed to validate the frictional and misalignment effects during compression testing and to obtain true compression flow stress. The destructive compression testing method will be eliminated by using nondestructive ultrasonic testing method which is cost effective and time saving.