Changes In Surface Topography Research Articles

Correlative high-resolution imaging of hydrogen in Mg2Ni hydrogen storage thin films

Nanometer scale imaging of hydrogen in solid materials remains an important challenge for the characterization of advanced materials, such as semiconductors, high-strength metallic alloys, and hydrogen storage materials. Within this work, we demonstrate high-resolution imaging of hydrogen and deuterium within Mg2Ni/Mg2NiH4 hydrogen storage thin films using an in-house developed secondary ion mass spectrometer (SIMS) system attached to a commercially available dual-beam focused ion beam - scanning electron microscope (FIB-SEM) instrument. We further demonstrate a novel approach to measure the size, shape, and distribution of the hydride phase in partially transformed films using laser scanning confocal microscopy (LSCM) to measure surface topography changes from the hydride phase volume expansion. Combining these techniques provides new insights on hydride nucleation and growth within the Mg2NiHx system. Finally, we demonstrate the efficacy of tracking deuterium as a hydrogen analog to reduce the background for SIMS imaging of hydrogen in high-vacuum chambers (∼10−6 mbar).

Guidelines for rail quality selection to increase service life based on wear and fatigue behavior of various wheel and rail materials

The Austrian rail network is very diverse: The lines in the alpine areas have very tight radii while the lines in the flat areas (east and north of Austria) are mainly straight high-speed lines. This leads to different levels of wheel and rail wear. Accordingly, the objective of this study was to experimentally model a laboratory-scale cyclic wheel-rail contact to investigate wear behavior and rolling contact fatigue at different radii (RCF).A novel test system was set up at AC2T research GmbH to reproduce unidirectional loading on a real track. Tribotests were performed with rail (grades R260, R350HT & R400HT) and wheel (grades ER7 & ER9) parts from the field. This newly designed principle is an effective method to characterize the wheel-rail contact. Wear characterization was done after defined testing cycles to detect (i) area loss and (ii) change in surface topography.

Direct observation of the dynamic reconstructed active phase of perovskite LaNiO3 for the oxygen-evolution reaction.

Ni-based transition metal oxides are promising oxygen-evolution reaction (OER) catalysts due to their abundance and high activity. Identification and manipulation of the chemical properties of the real active phase on the catalyst surface is crucial to improve the reaction kinetics and efficiency of the OER. Herein, we used electrochemical-scanning tunnelling microscopy (EC-STM) to directly observe structural dynamics during the OER on LaNiO3 (LNO) epitaxial thin films. Based on comparison of dynamic topographical changes in different compositions of LNO surface termination, we propose that reconstruction of surface morphology originated from transition of Ni species on LNO surface termination during the OER. Furthermore, we showed that the change in surface topography of LNO was induced by Ni(OH)2/NiOOH redox transformation by quantifying STM images. Our findings demonstrate that in situ characterization for visualization and quantification of thin films is very important for revealing the dynamic nature of the interface of catalysts under electrochemical conditions. This strategy is crucial for in-depth understanding of the intrinsic catalytic mechanism of the OER and rational design of high-efficiency electrocatalysts.

MViT-PCD: A Lightweight ViT-Based Network for Martian Surface Topographic Change Detection

Identifying the surface topographic changes accurately plays a vital role in the task of planetary exploration. In this study, a lightweight mobile vision transformer-based planetary image change detection (MViT-PCD) was proposed for monitoring dynamic surface changes using bitemporal images. The mobile vision transformer (MobileViT) was first introduced to make the most of the spatial information available. Subsequently, a multiscale feature differentiation and fusion (MFDF) block was adopted to improve the distinguishability of multilevel contextual information. Moreover, the strategy of information maximization (IM) was integrated to refine the model performance on the heterogeneous dataset. Then, experiments were conducted on the public Martian datasets. Compared with other state-of-the-art (SOTA) methods, the MViT-PCD provides favorable performance, with the highest accuracy of 97.2% and 82.9%, respectively, under the speed of 43.4 frame per second (FPS). Code is available at <uri xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">https://github.com/lynn1023-max/MViTPCD</uri> .

Wear simulation in lubricated contacts considering wear-dependent surface topography changes

Along with friction, wear in lubricated contacts is one of the most essential design criteria. The use of low-viscosity lubricants, as well as changing operating conditions, may lead to the wear-causing operating condition of mixed friction. For wear assessment, in the last decades numerical simulations have been confirmed as a powerful tool. The level of detail of the simulation model has a significant influence on the simulation results. The local wear heights for a hydrodynamic journal bearing under constant operating conditions are calculated numerically. A variant study is used to determine the influence of elastic deformation, cavitation model and the consideration of the wear-dependent surface topography. The surface topography, which is subject to change especially during running-in, is taken into account in the form of wear-dependent asperity contact pressure curves, respectively wear-dependent flow factors. To validate the simulation results, tests were carried out on a rotational tribometer. The results show that the consideration of the wear-dependent surface topography has a significant influence on the wear development and thus the trend evaluated from the experiment can be better assessed.

Multifunctional In-Situ Testing Device for Investigating the Service Performance of Materials

To obtain the change rule of material/structure service performance under complex working conditions, this study developed a material/structure mechanical property testing device with multi-load and multi-physics loading functions. The features of this device include its ability to realize the composite mechanical loading of three loads (tension/compression–bending–torsion), as well as physical field loading, such as current field, magnetic field, and thermal field, to realistically simulate the actual service conditions of materials/structures. To monitor the surface topography change, temperature, and strain distribution of the specimen in real-time, various in-situ monitoring methods, including microscopic imaging, infrared thermal imaging, and digital image correlation method, were integrated into the device. To realize multi-load composite loading, a six-degree-of-freedom parallel drive platform was adopted in the device, and its control system was developed with a distributed double-layer structure to realize the closed-loop control of any combination of load forms. All functional modules of the device were calibrated, and a coaxial calibration method based on a six-dimensional force sensor was proposed. Lastly, several tests were performed to evaluate the effectiveness of the proposed device functions, and the test results revealed the broad application prospects of the device.

An effective laser surface treatment method to reduce biofilm coverage of multiple bacterial species associated with medical device infection

Device associated infection (DAI) is recognized as a worldwide health challenge in total joint replacement (TJR). Bacteria exhibit very strong antibiotic tolerance when they attach to a device and form a biofilm and thus DAI is difficult to treat. In this study, a one-step, clean (no chemicals or additional materials involved) and effective surface engineering approach via laser surface treatment (LST) to tackle the DAI challenge is reported. Commercially pure (CP) Ti were laser-treated in open air using continuous wave (CW) fibre laser. The laser-treated CP Ti was tested against five bacterial species including Gram positive (Staphylococcus aureus and Staphylococcus epidermidis) and Gram negative (Pseudomonas aeruginosa, Escherichia coli and Proteus mirabilis). Live/Dead staining and image analysis results indicated that LST can significantly reduce biofilm coverage of the five tested bacterial species on the CP Ti surfaces. Overall biofilm coverage as a percentage of the surface reduced after laser treatment averaging from 4.24 % to 17.4 %. This meant that relative to the untreated surface, biofilm coverage was reduced after laser treatment, ranging from 84.9 % to 95.6 % across the five species. Furthermore, cytotoxicity results (using MTT assay) showed that the laser-treated CP Ti is non-toxic across both L929 fibroblast and RAW macrophage cell lines. Surface properties after LST were investigated using WLI and AFM (measuring micro-/nano-surface roughness and topography) as well as ToF-SIMS (measuring surface chemistry and oxide thickness), respectively. The cross-sectional microstructure at the surface was imaged using SEM and analysed by XRD, whilst the surface wettability was measured using sessile drop method. To summarise, the reduction of biofilm coverage can be attributed to the favourable changes in surface roughness and topography together with the increased concentration of oxides at the topmost surface after LST.

Influence of surface treatments on the bond strength of metal brackets to CAD/CAM materials and discoloration after various refinishing procedures : Scanning electron microscopy and atomic force microscopy study.

This study evaluated the shear bond strength (SBS) of ametal bracket bonded to three different computer-aided design/computer-aided manufacturing (CAD/CAM) restoration materials pretreated with different surface treatments. In addition, the surface topography and color change of the restorations after debonding with two different tungsten carbide burs were examined. A total of 216plates were cut from three different CAD/CAM blocks, each of which was divided into three subgroups with different pretreatment methods: (1)acid etching, (2)sandblasting, and (3)laser irradiation. Incisor metal brackets were bonded. The SBS test was performed, and the failure types were classified. Then, samples were randomly divided into two subgroups according to the adhesive removal procedure to be used: atungsten carbide bur with 12blades or 24blades (n = 12). Color change was calculated based on the ∆E00, and surface morphology was evaluated via SEM and AFM analysis. The SBS data revealed that the type of CAD/CAM material and the applied surface treatment significantly affected bond strength. The highest SBS values were detected for the Grandio Blocs (VOCO GmbH, Cuxhaven, Germany; 14.3 ± 4.4 MPa), and the lowest was observed for Cerasmart (GC Europe, Leuven, Belgium; 12.0 ± 4.0 MPa). The ∆E00 results demonstrated significant differences only as aresult of the applied surface treatment. The ∆E00 value in all groups was above the 1.77 threshold. CAD/CAM material types and surface treatments affected the bond strength, but the interactions of these factors did not. The chosen surface treatment also significantly affected the ∆E00 after the polishing was done.

Surface modification of nanofibrous polyethersulfone scaffolds with fluorapatite nanoparticles toward improved stem cell behavior and osteogenic activity in vitro

Nanofibrous polyethersulfone (PESf) scaffolds were fabricated by the electrospinning method. The fabricated scaffolds were surface-modified by fluorapatite nanoparticles (FAn) synthesized using Reline deep eutectic solvent (DES). The effect of surface modification on microstructure, wettability, porosity, biodegradation, and absorption of the scaffolds was investigated. Results confirmed the formation of nanofibers with narrow width between 250 and 600 nm and length of a few tens of microns which was roughened by nanoscale spherical FA particles having a particle size in the range of 40–60 nm. Surface modification of PES by FA nanoparticles led to a significant increase in hydrophilicity, roughness, porosity, and biodegradation which in turn resulted in improvement of viability, growth, proliferation, and differentiation of human bone marrow mesenchymal stem cells (hBMMSCs) assessed by MTT, calcium content (biomineralization), alkaline phosphatase (ALP) activity, alizarin red, and acridine orange staining tests. Gene expression test represented a significant increase in expression of ALP, OCN, RUNX-2, ONN, and COL-I in differentiated stem cells which was attributed to the changes in surface topography and releasing bioactive calcium and fluoride ions made by the inclusion of FA nanoparticles. In conclusion, the nanoscale FA particles in the nanofibrous PES scaffolds provided multiple avenues to engineer PES by modification of surface characteristics for favorable cell-surface interactions, biocalcification, and osteogenesis.

Biocompatibility and Surface Integrity of Zirconia Ceramics Treated by Laser-plasma Driven Shock-waves

This is a multi-disciplinary paper focused on the preliminary results of deploying laser shock treatment (LST) to ZrO&lt;sub&gt;2&lt;/sub&gt; ceramics. This work has significance in several industrial sectors for components that will benefit from strengthening. These components are, namely: dental implants; cutting and drawing tools; valves, bearings, pressure vessels, heat exchangers and high-performance scissors and knives, where modification of hard, brittle materials properties such as that of a ZrO&lt;sub&gt;2&lt;/sub&gt;, can yield a performance boost. To elucidate the influence of LST on ZrO&lt;sub&gt;2&lt;/sub&gt; ceramics, an Nd: YAG laser was used, exhibiting (operating at discrete) laser energies of 17 mJ, 85 mJ and 170 mJ, a 2 mm spot size, a pulse repetition rate of 5 Hz and pulse duration of 10 ns was deployed at 532 nm wavelength. Investigation of ZrO&lt;sub&gt;2&lt;/sub&gt; ceramic surface integrity revealed a transition from a crack-free topology to a surface dominated by fractures, as the laser energy increased from 85 mJ to 170 mJ. Residual stresses obtained by incremental hole drilling (IHD) were measured to be tensile in the upper layer and the sub-surface layer. However, compression of -595 MPa was found in the sub-surface of the ZrO&lt;sub&gt;2&lt;/sub&gt; ceramic to a depth of 350 µm after LST, particularly in the transverse direction. Biological analysis metabolic activity measurements, indicated a rise in activity for all samples as the contact time increased (24 h, 3 d and 7 d). The as-received surface revealed a more limited change in metabolism, retaining similar biochemical levels during the first 3 days followed by a slight increase after a week of cultivation, bringing about significant increase in activity in all LST surfaces, relative to the as-received condition. This suggested that a ZrO&lt;sub&gt;2&lt;/sub&gt; LST exhibited enhanced cell response, particularly, after 7 days of contact-time. The overall outcome of this introductory paper, not only showed that ZrO&lt;sub&gt;2&lt;/sub&gt; ceramics, can be laser shock treated/peened, to induce some possible beneficial mechanical and physical effects, microstructural and surface topography changes, but also showed that LST can facilitate improvement in cell response to the ZrO&lt;sub&gt;2&lt;/sub&gt; ceramic. This opens-up, new prospects for treatment of ZrO&lt;sub&gt;2&lt;/sub&gt; based ceramics for biological applications such as tooth implant screws, where avoiding fractures from mechanical loading, strength enhancement, as well as biocompatibility are all important.

Glow discharge plasma stabilization of azo dye on PMMA polymer

The effects of argon gas glow discharge plasma on the surface of DR1 dye-loaded PMMA polymer films are examined in this work. Plasma immobilizes the dye on the surface of polymer without using stabilizers. Argon plasma activates the surface through breaking some bonds and generation of radical sites. It affects the acrylate groups of PMMA leading to covalent bonds between dye and surface of polymer. In addition, plasma treatment and contact with ambient air may result in the creation of new polar components, such as carbonyl and carboxyl compounds and links that enhance the dye attachment to the polymer matrix. Besides, the dye adsorption on the polymer film is impacted by changes in surface topography. Furthermore, plasma modifies the dye conformation, which affects the adherence of the dye to the polymer surface through bringing the dye to the higher energy state. The chemical and topographical modification of dye-loaded PMMA films by plasma are investigated by spectroscopic and AFM methods. Furthermore, aging process was used to confirm dye retention on the polymer film after plasma modification as opposed to dye-loaded polymer film that was left untreated as a reference sample. Finally, investigated method suggests a novel and very affordable technique for fabrication of poly(MMA-co-DR1) copolymer in the form of a homogeneous surface layer.

Kinetics and energetics of pharmacolite mineralization via the classic crystallization pathway

Pharmacolite (CaHAsO4·2H2O) mineralization is an important process controlling arsenate mobility in carbonate areas but is poorly understood in terms of crystallization mechanism and kinetics. The present study intends to investigate pharmacolite formation initiated by heterogenous nucleation through in situ observations of the mineral–water interface. Experiments were performed by exposing gypsum substrate to solutions supersaturated with respect to pharmacolite followed by atomic force microscopy imaging to record changes in surface morphology and topography. The data are used to determine growth mode, step speed, and the rate of step birth. Experimental results show the crystallization is achieved by direction-specific mono-molecular layer growth via 2D surface nucleation or spiral hillock development in accord with the classical crystallization model. Subsequent theoretical analyses allow to determine step energies and kinetic coefficients in major growth directions on (010) and indicate that [001] steps are energetically the most stable and morphologically the most prominent while [100] and [101] steps are controlled either by thermodynamic or kinetics. Gypsum plays an important role in aiding pharmacolite formation through epitaxy as the two minerals share a range of structural commonalities. The notably reduced supersaturation needed in substrate-assisted pharmacolite crystallization relative to bulk solution nucleation suggests gypsum may significantly reduce the energy barrier for the mineralization reactions and hence may find applications in As remediation practice.

Effects on the Titanium Implant Surface by Different Hygiene Instrumentations: A Narrative Review.

Peri-implant disease is usually caused by the accumulation of dental biofilm around the implant, and this biofilm can irradiate the gingiva tissue, which leads to inflammation and, more severely, to a deterioration of the bone structure. There is a concern regarding the removal of biofilm from the implant surface by using different hygiene instruments. Some hygiene instruments may have some effect on the dental implant surface, resulting in roughening or damage to the implant surfaces. This study reviewed the effects of titanium implant surfaces on different hygiene instruments. A literature search was conducted from PubMed, ScienceDirect, and Scopus databases for articles published from 1992 to 2021. A total of 19 full-text papers with keywords of interest that met all the eligibility criteria were selected. Surface roughness was evaluated with a scanning electron microscope and also using a profilometer, laser scanning, scanning probe, and atomic force microscopes. A metal curette produced a roughened surface on the titanium implant, but a plastic curette did not alter the surface. Instrumentation with rubber cups left the surface unchanged and appeared to smoothen the surface, whereas the air-powder abrasive instrumentation altered the surface with the presence of micro pits and pores. A conventional metal ultrasonic scaler showed significant surface topographical changes and scratches on both titanium surfaces, as a diode laser, light-emitting diode (LED), and laser treatment did not show any alteration on the rough and smooth titanium surfaces. Thus, a non-metallic instrument such as a plastic curette, rubber cups, and novel technology including diode laser, LED, and laser treatment is appropriate and can be used for debridement on smooth and machined titanium implant surfaces as well as sandblasted and acid-etched (SLA), titanium plasma-sprayed (TPS), and resorbable blasted media (RBM) surfaces. The use of metallic instruments should be avoided, and it is not recommended.

Energy-dependent film growth of Cu and NiTi from a tilted DC magnetron sputtering source determined by calorimetric probe analysis

Plasma-based processes are key applications in microsystems technology and are mainly used for the deposition and modification of thin films. A strong dependence on used equipment and materials can easily affect plasma processes and results in many differences of process characteristics like energy flow and deposition rates. For a deeper understanding of inclined magnetron-deposited thin films, a passive thermal probe was used to investigate the correlation between the film growth of two commonly used metallic target materials (Cu and Ni 46.8/Ti 53.2) and the energy flow from the plasma to the substrate. The special design of the sputtering system with a fixed angle of 45° between targets and substrate allows homogeneous coating of 200mm wafers with 100mm targets. The passive thermal probe measurements were performed radially across the substrate area for two different magnetron positions. Complementary surface and cross-sectional analysis of the deposited layers by atomic force microscopy, focused ion beam technique, and fracture edge analysis by scanning electron microscopy were performed on thin film samples on silicon substrate to investigate the growth rate and structure of the films. The films deposited in these experiments exhibit randomly oriented crystalline grains and heavily position-dependent change in surface topography and morphology from compact films to columnar growth, for Cu and NiTi respectively.

How Streptococcus mutans Affects the Surface Topography and Electrochemical Behavior of Nanostructured Bulk Ti.

The metabolization of carbohydrates by Streptococcus mutans leads to the formation of lactic acid in the oral cavity, which can consequently accelerate the degradation of dental implants fabricated from commercially available microcrystalline Ti. Microstructure influences surface topography and hence interaction between bacteria cells and Ti surfaces. This work offers the first description of the effect of S. mutans on the surface topography and properties of nanostructured bulk Ti, which is a promising candidate for modern narrow dental implants owing to its superior mechanical strength. It was found that S. mutans incubation resulted in the slight, unexpected decrease of surface nanoroughness, which was previously developed owing to privileged oxidation in areas of closely spaced boundaries. However, despite the changes in nanoscale surface topography, bacteria incubation did not reduce the high level of protection afforded by the oxide layer formed on the nanostructured Ti surface. The results highlight the need–hitherto ignored–to consider Ti microstructure when analyzing its behavior in the presence of carbohydrate-metabolizing bacteria.

Effect of surface finish on the colour anodising of Ti-6Al-4V at various voltages

ABSTRACT In this study, the colour anodising of a Ti-6Al-4V alloy in 0.05 M H3PO4 was investigated in the voltage range of 40–100 V. The Ti-6Al-4V substrates were anodised under two initial surface conditions: ground and unground. By means of ground samples, the native oxide layer was removed before anodising using conventional mechanical grinding techniques. After anodising, the changes in surface chemistry and topography were evaluated by performing Field Emission Scanning Electron Microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Depending on the initial surface finish (ground and unground) and the anodising voltage, different interference colours were obtained on the anodised surfaces. At low anodising voltages, the surfaces displayed relatively compact structures whereas higher voltages resulted in the formation of porosity, cracks, and blisters in both conditions. These changes also influenced the corrosion behaviour. The samples which were ground prior to anodising exhibited higher resistance to corrosion compared to the unground samples.

Machining induced surface integrity behavior of nickel-based superalloy: Effect of lubricating environments

Surface integrity is a critical aspect of machining nickel-based alloys due to their applications in critical components and employment in a harsh environment. The development of sustainable methods for machining difficult-to-cut materials is now of utmost importance because of global environmental concerns, strict policies, and diminishing natural resources. Consequently, different sustainable machining techniques have been developed and utilized for characterizing surface integrity. In the present study, the application of ultrasonically atomized cutting fluid (UAF) has been employed for machining nickel alloys, and its influence on the surface integrity has been evaluated. Moreover, the performance of UAF process has been compared with previously existing machining techniques. The experimental study includes measurement of microhardness, residual stresses, surface topography, chip morphologies, and microstructural changes. The sin2ψ−sin2ψ technique of X-ray diffraction (XRD) is utilized for evaluating residual stresses, whereas microstructural analysis is performed using electron back scattering diffraction (EBSD). It has been found that different lubrication techniques reduces the surface hardening phenomenon by restraining the plastic deformation. Tensile residual stresses have been achieved in dry machining and MQL processes, while flood cooling and UAF processes resulted in compressive residual stresses. MQL and UAF processes have been found to result in less misorientation and grain redistribution as compared to dry and flood cooling. Overall, the UAF process has been found to result in improved surface integrity which enhances the product life and performance.

Surface quality and morphology of NiTiCuZr shape memory alloy machined using thermal-energy processes: an examination of comparative topography

Adding alloying elements like copper (Cu) and zirconium (Zr) to binary NiTi shape memory alloys (NiTiCuZr SMA) raises the martensitic transition temperatures and functional fatigue properties while maintaining high corrosion and wear resistance. Therefore, it is essential to make high-precision SMA components with less damage to be machined into various complex shapes, sizes, and surface topographies to meet the needs of several engineering applications. In this research work, advanced machining processes like wire electrical discharge machining (WEDM) and fiber laser machining were employed to machine NiTiCuZr SMA and study their processing parameters’ effects on the surface roughness, topography changes, and surface hardness. 3D surface topography and surface roughness on the machined surfaces were evaluated through contact and non-contact measurement techniques. The differential scanning calorimetry (DSC) test was conducted on the NiTiCuZr SMA before and after machining to confirm changes in the shape memory properties. When both processes were used at high energy levels, the formation of the resolidified layer and surface defects were more pronounced, increasing surface roughness. DSC curves for heating and cooling profiles show similar transformation temperatures for WEDM and laser machined NiTiCuZr SMA. On comparing two different machining processes, the WEDM process resulted in the Ra (μm) being 28.2% lower, the surface topography was smooth, and the microhardness was 11.9% lower than the samples machined using laser machining. This shows that machining of NiTiCuZr SMA using WEDM gives a better surface finish, reaching a fair decision that WEDM is a better alternative to laser machining.

Methodology improvement of bulk compressive creep test: Deformation measurement and loading rate

Objectives(1) To identify improvements when bulk compressive creep testing of dental resin composite materials to reduce the sensitivity to the surface morphology and parallelism of specimens, to generate more accurate strain (displacement) measurement values. (2) To investigate the effect of loading rate on the creep and recovery behavior under bulk compressive creep test. MethodsCylindrical composite resin specimens were subjected to bulk compressive creep test with conventional and modified methodology (with/without introduction of stainless steel hemisphere and preload process). Furthermore, specimens undertook different loading rates ranging from 1 N/s to 50 N/s. Maximum deformation, creep deformation, permanent set as well as percentage of recovery during the creep and recovery procedure were compared, and surface topography changes before and after preload process was evaluated by laser scanning confocal. Burgers model was used to investigate the effect of improvements to each part of viscoelastic deformation of resin specimens. Results(1) The influence of surface evenness of resin specimens could be reduced by addition of preload process before the bulk compressive creep test resulting in significantly decreased permanent set (p = 0.002), and increased recovery to 91.7 % (p < 0.001). While the standard deviation of maximum deformation, permanent set and percentage of recovery had the smallest values when hemisphere was introduced to loading chain. (2) With increasing loading rate of bulk compressive creep tests, creep deformation increased and this trend became statistically significant when the loading rate reached 50 N/s. SignificanceThe accuracy of deformation measurement during bulk compressive creep test could be improved by means of introducing stainless steel hemisphere to the loading chain, and adding preload process to loading protocol.

Biodegradation study of Polyethylene and PVC using naturally occurring plastic degrading microbes.

One of the most serious man-made concerns today is the ever-increasing amount of plastic waste overwhelming the planet. The worldwide interest in using polymers consistently expanded over the years. Because of the plastic wastes thrown into the environment, outrageously the plastic pollution is increasing. In the present study, degradation of PVC and polyethylene-derived synthetic polymers has been carried out. The fungi and bacteria were isolated from the soil of the plastic waste environment and were used for the biodegradation of plastic films. Successful bacterial candidates for biodegradation were identified after screening. The bacterial strain Sb1 was identified as Bacillus licheniformis and Sb2 as Achromobacter xylosoxidans. The fungal strains Sf.1 and Sf.2 were identified as Aspergillus niger and Aspergillus glaucus, respectively. The degraded polymeric films were critically assessed by following the characterization methods like weight loss, FTIR and SEM. The results indicate that the polymers of polyethylene sample showed 32.2% degradation using bacterial strains and 40% using fungal strains in a time duration of just 4weeks. PVC samples degraded 17 and 32% by fungal strains after 4weeks. The changes in surface topography was confirmed by scanning electron microscopy and the changes in functional groups intensity was observed using the FTIR. Different parameters, varying temperature, pH, and inoculum concentration, were also evaluated, which implied that plastic waste treated by fungal and bacterial strains gives significant (p < 0.05) result in polymer degradation. As a result, the current research gave a scientific justification that bacteria and fungus could be further developed as promising candidates for plastic bioremediation.