It is known that restoration of erased engraved identification marks on the engine and the chassis of a car or on a firearm has low success rate. Unlike stamping, engraving on a metal surface leaves no pronounced, permanent subsurface deformation in the crystalline structure, also called dislocation that can be revealed by suitable methods. Hence, the current research work investigated whether metallographic reagents used in the restoration of stamp (compression) marks could be applied to recover engraved marks on steel surfaces and also to establish the sensitivity and effectiveness of some of these reagents for the restoration of the marks. Experiments were conducted by mechanically engraving alphanumeric characters on several steel plates using a computer controlled engraving machine called Gravograph. The markings were later erased from the above steel plates by removing the metal in stages of 0.01 mm through 0.04 mm below the bottom of the engraving. Several plates were thus prepared wherein each one had been abraded to a specific depth. Then eight metallographic reagents were tested on each one of the above erased plates using a swabbing technique. The results had shown that while most of the reagents were able to restore marks up to certain levels of erasure, the reagent 5 g copper sulphate, 60 ml water, 30 ml concentrated ammonium hydroxide and 60 ml concentrated hydrochloric acid restored marks erased to a depth of 0.04 mm below the engraving depth, thus presenting itself the most sensitive reagent. Quite significantly, the above reagent was also able to decipher successfully the original engraved marks that had been erased and engraved with a new number, or obliterated by centre punching. The results of this research work should benefit the forensic practitioners engaged in the serial number recovery on vehicles, firearms and other objects.
This study investigated heat transfer in magnetohydrodynamic (MHD) mixed convection flow of ferrofluid along a vertical channel. The channel with non-uniform wall temperatures was taken in a vertical direction with transverse magnetic field. Water with nanoparticles of magnetite (Fe3O4) was selected as a conventional base fluid. In addition, non-magnetic (Al2O3) aluminium oxide nanoparticles were also used. Comparison between magnetic and magnetite nanoparticles were also conducted. Fluid motion was originated due to buoyancy force together with applied pressure gradient. The problem was modelled in terms of partial differential equations with physical boundary conditions. Analytical solutions were obtained for velocity and temperature. Graphical results were plotted and discussed. It was found that temperature and velocity of ferrofluids depend strongly on viscosity and thermal conductivity together with magnetic field. The results of the present study when compared concurred with published work.
The incorporation of kenaf fiber fillers into a polymer matrix has been pronounced in the past few decades. In this study, the effect of multiwalled carbon nanotubes (MWCNTs) with a short kenaf fiber (20 mesh) with polypropylene (PP) added was investigated. The melt blending process was performed using an internal mixer to produce polymer composites with different filler contents, while the suitability of this melt composite for the injection molding process was evaluated. Thermogravimetric analysis (TGA) was carried out to investigate the thermal stability of the raw materials. Rheological analyses were conducted by varying the temperature, load factor, and filler content. The results demonstrate a non-Newtonian pseudoplastic behavior in all samples with changed kenaf fillers (10 to 40 wt %) and MWCNT contents (1 to 4 wt %), which confirm the suitability of the feedstock for the injection molding process. The addition of MWCNTs had an immense effect on the viscosity and an enormous reduction in the feedstock flow behavior. The main contribution of this work is the comprehensive observation of the rheological characteristics of newly produced short PP/kenaf composites that were altered after MWCNT additions. This study also presented an adverse effect on the composites containing MWCNTs, indicating a hydrophilic property with improved water absorption stability and the low flammability effect of PP/kenaf/MWCNT composites. This PP/kenaf/MWCNT green composite produced through the injection molding technique has great potential to be used as car components in the automotive industry.
With increased awareness on the importance of gloves arising from the COVID-19 pandemic, people are expected to continue using them even after the pandemic recedes. This scenario in a way increased the rubber solid waste disposal problem; therefore, the production of biodegradable gloves may be an option to overcome this problem. However, the need to study the shelf life of biodegradable gloves is crucial before commercialization. There are well-established models to address the failure properties of gloves as stated in the American Society for Testing and Material (ASTM) D7160. In this study, polysaccharide-based material-filled natural rubber latex (PFNRL) gloves, which are biodegradable gloves, were subjected to an accelerated aging process at different temperatures of 50-80 °C for 1-120 days. Prediction models based on Arrhenius and shift factors were used to estimate the shelf life of the PFNRL gloves. Based on the results obtained, the estimated time for the PFNRL gloves to retain 75% of their tensile strength at shelf temperature (30 °C) based on Arrhenius and shift factor models was 2.8 years. Verification on the activation energy based on the shift factor model indicated that the shelf life of PFNRL gloves is 2.9 years, which is only a 3.6% difference. The value obtained is aligned with the requirement in accordance with ASTM D7160, which states that only up to a maximum of 3 years' shelf life is allowed for the gloves under accelerated aging conditions.
In the present study, magnetic oil palm empty fruits bunch cellulose nanofiber (M-OPEFB-CNF) composite was isolated by sol-gel method using cellulose nanofiber (CNF) obtained from oil palm empty fruits bunch (OPEFB) and Fe3O4 as magnetite. Several analytical methods were utilized to characterize the mechanical, chemical, thermal, and morphological properties of the isolated CNF and M-OPEFB-CNF. Subsequently, the isolated M-OPEFB-CNF composite was utilized for the adsorption of Cr(VI) and Cu(II) from aqueous solution with varying parameters, such as pH, adsorbent doses, treatment time, and temperature. Results showed that the M-OPEFB-CNF as an effective bio-sorbent for the removal of Cu(II) and Cr(VI) from aqueous solution. The adsorption isotherm modeling revealed that the Freundlich equation better describes the adsorption of Cu(II) and Cr(VI) on M-OPEFB-CNF composite. The kinetics studies revealed the pseudo-second-order kinetics model was a better-described kinetics model for the removal of Cu(II) and Cr(VI) using M-OPEFB-CNF composite as bio-sorbent. The findings of the present study showed that the M-OPEFB-CNF composite has the potential to be utilized as a bio-sorbent for heavy metals removal.
Microbial fuel cells (MFCs) have a high potential application for simultaneous wastewater treatment and electricity
generation. However, the choice of the electrode material and its design is critical and directly affect their performance.
As an electrode of MFCs, the anode material with surface modifications is an attractive strategy to improve the power
output. In this study, stainless steel (SS) and carbon steel (CS) was chosen as a metal anode, while graphite felt (GF)
was used as a common anode. Heat treatment was performed to convert SS, CS and GF into efficient anodes for MFCs.
The maximum current density and power density of the MFC-SS were achieved up till 762.14 mA/m2
and 827.25 mW/m2
,
respectively, which were higher than MFC-CS (641.95 mA/m2
and 260.14 mW/m2
) and MFC-GF (728.30 mA/m2
and 307.89
mW/m2
). Electrochemical impedance spectroscopy of MFC-SS showed better catalytic activity compared to MFC-CS and
MFC-GF anode, also supported by cyclic voltammetry test.
The mechanical behavior of graphene/polymer interfaces in the graphene-reinforced epoxy nanocomposite is one of the factors that dictates the deformation and damage response of the nanocomposites. In this study, hybrid molecular dynamic (MD) and finite element (FE) simulations of a graphene/polymer nanocomposite are developed to characterize the elastic-damage behavior of graphene/polymer interfaces under a tensile separation condition. The MD results show that the graphene/epoxy interface behaves in the form of elastic-softening exponential regressive law. The FE results verify the adequacy of the cohesive zone model in accurate prediction of the interface damage behavior. The graphene/epoxy cohesive interface is characterized by normal stiffness, tensile strength, and fracture energy of 5 × 10-8 (aPa·nm-1), 9.75 × 10-10 (nm), 2.1 × 10-10 (N·nm-1) respectively, that is followed by an exponential regressive law with the exponent, α = 7.74. It is shown that the commonly assumed bilinear softening law of the cohesive interface could lead up to 55% error in the predicted separation of the interface.
Chitosan/polyvinyl alcohol (Chitosan/PVA) blended film was prepared by direct blend process and solution casting methods.
In order to reduce the swelling ratio and enhance the chemical and mechanical stability, Chitosan/PVA film was crosslinked
with glutaraldehyde in order to produce Chitosan-g-PVA. Bovine serum albumin (BSA) was used as a model protein
to incorporate into the Chitosan-g-PVA. The chemical structure and morphological characteristics of films were studied
by FT-IR and scanning electron microscopy (SEM). Mechanical and physical properties of blended films such as tensile
properties in the dry and wet states, water uptake and water contact angle measurement were characterized. Blending
PVA and chitosan improved strength and flexibility of the films. Crosslinking with glutaraldehyde further improves the
tensile strength and decrease the hydrophilicity of films. BSA immobilized on the Chitosan-g-PVA film was calculated as
BSA encapsulation efficiency.
Ascorbic acid was used for the first time to synthesize cellulose nanoparticles (CNP) extracted from okra mucilage. The physical properties of the CNP including their size distribution, and crystalline structures were investigated. The rheological properties of the cellulose nanofluid (CNF) were compared with the bulk okra mucilage and commercial polymer xanthan. The interfacial properties of the CNF at the interface of oil-water (O/W) system were investigated at different concentrations and temperatures. The effects of the interaction between the electrolyte and ultrasonic were determined. Core flooding experiment was conducted at reservoir condition to justify the effect of the flow behaviour and disperse phase behaviour of CNF on additional oil recovery. The performance of the CNF was compared to conventional EOR chemical. The combined method of ultrasonic, weak-acid hydrolysis and nanoprecipitation were effective in producing spherical and polygonal nanoparticles with a mean diameter of 100 nm, increased yield of 51% and preserved crystallinity respectively. The zeta potential result shows that the CNF was stable, and the surface charge signifies long term stability of the fluid when injected into oil field reservoirs. The CNF, okra and xanthan exhibited shear-thinning and pseudoplastic behaviour. The IFT decreased with increase in concentration of CNF, electrolyte and temperature. The pressure drop data confirmed the stability of CNF at 120°C and the formation of oil bank was enough to increase the oil recovery by 20%. CNF was found to be very effective in mobilizing residual oil at high-temperature high-pressure (HTHP) reservoir condition. The energy and cost estimations have shown that investing in ultrasonic-assisted weak-acid hydrolysis is easier, cost-effective, and can reduce energy consumption making the method economically advantageous compared to conventional methods.
Many studies have shown the remarkable enhancement of thermo-physical properties with the addition of a small quantity of nanoparticles into conventional fluids. However, the long-term stability of the nanofluids, which plays a significant role in enhancing these properties, is hard to achieve, thus limiting the performance of the heat transfer fluids in practical applications. The present paper attempts to highlight various approaches used by researchers in improving and evaluating the stability of thermal fluids and thoroughly explores various factors that contribute to the enhancement of the thermo-physical properties of mono, hybrid, and green nanofluids. There are various methods to maintain the stability of nanofluids, but this paper particularly focuses on the sonication process, pH modification, and the use of surfactant. In addition, the common techniques to evaluate the stability of nanofluids are undertaken by using visual observation, TEM, FESEM, XRD, zeta potential analysis, and UV-Vis spectroscopy. Prior investigations revealed that the type of nanoparticle, particle volume concentration, size and shape of particles, temperature, and base fluids highly influence the thermo-physical properties of nanofluids. In conclusion, this paper summarized the findings and strategies to enhance the stability and factors affecting the thermal conductivity and dynamic viscosity of mono and hybrid of nanofluids towards green nanofluids.
This study presents the electromagnetic (EM) characterization of a multiwalled carbon nanotubes (MWCNT)-silver nanoparticles (AgNP)-reinforced poly(vinyl alcohol) (PVA) hybrid nanocomposite fabricated via the solution mixing technique. Primarily, the structure and morphological properties of the PVA/MWCNT-AgNP hybrid nanocomposite are confirmed by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The complex permittivity (ε*) and permeability (μ*), as well as the electromagnetic scattering parameters are measured using a PNA network analyzer equipped with X-band waveguide. The results showed an enhanced permittivity (ε' ≈ 25) value of the hybrid nanocomposite in the frequency range of 8-12 GHz. However, the permeability decreased to almost zero (μ' ≈ 0.4) since the inclusion of AgNP with an average particle size of 40 nm is not susceptible to magnetization and causes higher magnetic losses (tan δμ) than dielectric losses (tan δε). Remarkably, the hybrid nanocomposite reduced transmission of electromagnetic (EM) wave by nearly 60% in comparison to PVA/MWCNT. This is attributed to the enhanced absorption and reflection at the nanotubes, and metal-dielectric interfaces have induced multiple internal reflections owing to the porous structure of the nanocomposite. The prospect of the PVA/MWCNT-AgNP hybrid nanocomposite is favorable as a thin absorbing material for EM shielding applications.
This paper details analytical research results into a novel geopolymer concrete embedded with glass bubble as its thermal insulating material, fly ash as its precursor material, and a combination of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) as its alkaline activator to form a geopolymer system. The workability, density, compressive strength (per curing days), and water absorption of the sample loaded at 10% glass bubble (loading level determined to satisfy the minimum strength requirement of a load-bearing structure) were 70 mm, 2165 kg/m3, 52.58 MPa (28 days), 54.92 MPa (60 days), and 65.25 MPa (90 days), and 3.73 %, respectively. The thermal conductivity for geopolymer concrete decreased from 1.47 to 1.19 W/mK, while the thermal diffusivity decreased from 1.88 to 1.02 mm2/s due to increased specific heat from 0.96 to 1.73 MJ/m3K. The improved physicomechanical and thermal (insulating) properties resulting from embedding a glass bubble as an insulating material into geopolymer concrete resulted in a viable composite for use in the construction industry.
Fungi of the Trichoderma species are valued industrial enzymes in support of the 'zero-waste' technology to convert agro-industrial biomass into valuable products, i.e. nanocellulose (NC). In this study, an in silico approach using substrate docking and molecular dynamic (MD) simulation was used to predict the order of which the multilayers of cellulosic polymers, i.e. lignin, hemicellulose and cellulose in oil palm leaves (OPL) are degraded by fungal enzymes, endocellulase and exocellulase. The study aimed to establish the catalytic tendencies of the enzymes to optimally degrade the cellulosic components of OPL for high yield production of NC. Energy minimized endocellulase and exocellulase models revealed satisfactory scores of PROCHECK (90.0% and 91.2%), Verify3D (97.23% and 98.85%) and ERRAT (95.24% and 91.00%) assessments. Active site prediction by blind docking, COACH meta-server and multiple sequence alignment indicated the catalytic triads for endocellulase and exocellulase were Ser116-His205-Glu249 and Ser382-Arg124-Asp385, respectively. Binding energy of endocellulase docked with hemicellulose (-6.0 kcal mol-1) was the most favourable followed by lignin (-5.6 kcal mol-1) and cellulose (-4.4 kcal mol-1). Exocellulase, contrarily, bonded favorably with lignin (-8.7 kcal mol-1), closely followed by cellulose (-8.5 kcal mol-1) and hemicellulose (-8.4 kcal mol-1). MDs simulations showed that interactions of complexes, endocellulase-hemicellulose and the exocellulase-cellulose being the most stable. Thus, the findings of the study successfully identified the specific actions of sugar-acting enzymes for NC production. Communicated by Ramaswamy H. Sarma.
Welding parameters obviously determine the joint quality during the resistance spot welding process. This study aimed to investigate the effect of welding current and electrode force on the heat input and the physical and mechanical properties of a SS316L and Ti6Al4V joint with an aluminum interlayer. The weld current values used in this study were 11, 12, and 13 kA, while the electrode force values were 3, 4, and 5 kN. Welding time and holding time remained constant at 30 cycles. The study revealed that, as the welding current and electrode force increased, the generated heat input increased significantly. The highest tensile-shear load was recorded at 8.71 kN using 11 kA of weld current and 3 kN of electrode force. The physical properties examined the formation of a brittle fracture and several weld defects on the high current welded joint. The increase in weld current also increased the weld diameter. The microstructure analysis revealed no phase transformation on the SS316L interface; instead, the significant grain growth occurred. The phase transformation has occurred on the Ti6Al4V interface. The intermetallic compound layer was also investigated in detail using the EDX (Energy Dispersive X-Ray) and XRD (X-Ray Diffraction) analyses. It was also found that both stainless steel and titanium alloy have their own fusion zone, which is indicated by the highest microhardness value.
The learning curve for doing a good qualitative study is steep because qualitative methodologies are often vague and lack explicit steps. We detail the formulation of the grounded theory approach in a study of patients with type 2 diabetes mellitus who made decisions while strategizing their treatment types. This undertaking is to demonstrate how this systematic and yet flexible methods contributed to the understanding of the issue we were investigating. The process from deciding on research objectives and research questions, follow with systematic process for data collection and analysis allows us to generate a substantive theoretical model. By paying critical attention to theoretical saturation, grounded theory approach enabled us to construct all possible explanatory concepts related to decision making in strategizing diabetes treatment. We also describe the challenges throughout the whole research journey, including getting permission to interview patients, gaining the trust of research participants and staying open to the participants’ views.
The fabrication of energy storage EDLC in this work is achieved with the implementation of a conducting chitosan-methylcellulose-NH4NO3-glycerol polymer electrolyte system. The simple solution cast method has been used to prepare the electrolyte. The impedance of the samples was fitted with equivalent circuits to design the circuit diagram. The parameters associated with ion transport are well studied at various plasticizer concentrations. The FTIR investigation has been done on the films to detect the interaction that occurs among plasticizer and polymer electrolyte. To get more insights into ion transport parameters, the FTIR was deconvoluted. The transport properties achieved from both impedance and FTIR are discussed in detail. It was discovered that the transport parameter findings are in good agreement with both impedance and FTIR studies. A sample with high transport properties was characterized for ion dominancy and stability through the TNM and LSV investigations. The dominancy of ions in the electrolyte verified as the tion of the electrolyte is established to be 0.933 whereas it is potentially stable up to 1.87 V. The rechargeability of the EDLC is steady up to 500 cycles. The internal resistance, energy density, and power density of the EDLC at the 1st cycle are 53 ohms, 6.97 Wh/kg, and 1941 W/kg, respectively.
Geopolymer concrete has the potential to replace ordinary Portland cement which can reduce carbon dioxide emission to the environment. The addition of different amounts of steel fibers, as well as different types of end-shape fibers, could alter the performance of geopolymer concrete. The source of aluminosilicate (fly ash) used in the production of geopolymer concrete may lead to a different result. This study focuses on the comparison between Malaysian fly ash geopolymer concrete with the addition of hooked steel fibers and geopolymer concrete with the addition of straight-end steel fibers to the physical and mechanical properties. Malaysian fly ash was first characterized by X-ray fluorescence (XRF) to identify the chemical composition. The sample of steel fiber reinforced geopolymer concrete was produced by mixing fly ash, alkali activators, aggregates, and specific amounts of hook or straight steel fibers. The steel fibers addition for both types of fibers are 0%, 0.5%, 1.0%, 1.5%, and 2.0% by volume percentage. The samples were cured at room temperature. The physical properties (slump, density, and water absorption) of reinforced geopolymer concrete were studied. Meanwhile, a mechanical performance which is compressive, as well as the flexural strength was studied. The results show that the pattern in physical properties of geopolymer concrete for both types of fibers addition is almost similar where the slump is decreased with density and water absorption is increased with the increasing amount of fibers addition. However, the addition of hook steel fiber to the geopolymer concrete produced a lower slump than the addition of straight steel fibers. Meanwhile, the addition of hook steel fiber to the geopolymer concrete shows a higher density and water absorption compared to the sample with the addition of straight steel fibers. However, the difference is not significant. Besides, samples with the addition of hook steel fibers give better performance for compressive and flexural strength compared to the samples with the addition of straight steel fibers where the highest is at 1.0% of fibers addition.
The rapid growth of electronic systems and devices operating within the gigahertz (GHz) frequency range has increased electromagnetic interference. In order to eliminate or reduce the spurious electromagnetic radiation levels more closely in different applications, there is strong research interest in electromagnetic absorber technology. Moreover, there is still a lack of ability to absorb electromagnetic radiation in a broad frequency range using thin thickness. Thus, this study examined the effect of incorporating magnetic and dielectric materials into the polymer matrix for the processing of radar absorbing materials. The experiment evaluated the sample preparation with different weight percentages of multi-walled carbon nanotubes (MWCNT) mixed with Ni0.5Zn0.5Fe2O4 (Nickel-Zinc-Ferrite) loaded into epoxy (P) as a matrix. The prepared samples were analysed by examining the reflectivity measurements in the 8 – 18 GHz frequency range and conducting a morphological study using scanning electron microscopy analyses. The correlation of the results showed that different amounts of MWCNT influenced the performance of the microwave absorber. As the amount of MWCNTs increased, the reflection loss (RL) peak shifted towards a lower frequency range and the trend was similar for all thicknesses. The highest RL was achieved when the content of MWCNTs was 2 wt% with a thickness of 2 mm with an RL of – 14 dB at 16 GHz. The 2.5 GHz bandwidth corresponded to the RL below -10 dB (90% absorption) in the range of 14.5 – 17 GHz. This study showed that the proposed experimental route provided flexible absorbers with suitable absorption values by mixing only 2 wt% of MWCNTs.
A three dimensional (3D) numerical solution of unsteady, Ag-MgO hybrid nanoliquid flow with heat and mass transmission caused by upward/downward moving of wavy spinning disk has been scrutinized. The magnetic field has been also considered. The hybrid nanoliquid has been synthesized in the presence of Ag-MgO nanoparticles. The purpose of the study is to improve the rate of thermal energy transmission for several industrial purposes. The wavy rotating surface increases the heat transmission rate up to 15%, comparatively to the flat surface. The subsequent arrangement of modeled equations is diminished into dimensionless differential equation. The obtained system of equations is further analytically expounded via Homotopy analysis method HAM and the numerical Parametric continuation method (PCM) method has been used for the comparison of the outcomes. The results are graphically presented and discussed. It has been presumed that the geometry of spinning disk positively affects the velocity and thermal energy transmission. The addition of hybrid nanoparticles (silver and magnesium-oxide) significantly improved thermal property of carrier fluid. It uses is more efficacious to overcome low energy transmission. Such as, it provides improvement in thermal performance of carrier fluid, which play important role in power generation, hyperthermia, micro fabrication, air conditioning and metallurgical field.
Recently, many scientists and polymer engineers have been working on eco-friendly materials for starch-based food packaging purposes, which are based on biopolymers, due to the health and environmental issues caused by the non-biodegradable food packaging. However, to maintain food freshness and quality, it is necessary to choose the correct materials and packaging technologies. On the other hand, the starch-based film's biggest flaws are high permeability to water vapor transfer and the ease of spoilage by bacteria and fungi. One of the several possibilities that are being extensively studied is the incorporation of essential oils (EOs) into the packaging material. The EOs used in food packaging films actively prevent inhibition of bacteria and fungi and have a positive effect on food storage. This work intended to present their mechanical and barrier properties, as well as the antimicrobial activity of anti-microbacterial agent reinforced starch composites for extending product shelf life. A better inhibition of zone of antimicrobial activity was observed with higher content of essential oil. Besides that, the mechanical properties of starch-based polymer was slightly decreased for tensile strength as the increasing of essential oil while elongation at break was increased. The increasing of essential oil would cause the reduction of the cohesion forces of polymer chain, creating heterogeneous matrix and subsequently lowering the tensile strength and increasing the elongation (E%) of the films. The present review demonstrated that the use of essential oil represents an interesting alternative for the production of active packaging and for the development of eco-friendly technologies.