Non-coated Materials Research Articles

Role of ureteral stent material and coating to prevent ureteral stent related issue: A systematic review and meta analysis.

Ureteral stents require materials that balance bulk and surface properties. Achieving both can be challenging, as ideal bulk properties may not align with optimal surface properties. Thus, researching coatings and biomanufacturing methods for ideal materials is essential. A systematic review and meta-analysis, following PRISMA Guidelines, involved literature searches across five databases: PubMed, Scopus, Embase, ClinicalKey, and Cochrane. From 417 screened articles, eight studies were deemed eligible for qualitative and quantitative analysis. The selected articles underwent bias assessment using ROB Tools 2. The systematic review analyzed 1.356 participants. Findings revealed that firm ureteral stents significantly increased risk of infection, hematuria, and lower body pain. On the contrary, soft stents reduced infection (OR: 0.62; p=0.004), hematuria (OR: 0.60; p<0.001), and lower body pain (OR: 0.63; p=0.0002). However, infection reduction effect was uncertain due to heterogeneity. Coated vs non-coated material analysis found no difference in encrustation (OR: 1.26; p=0.52) or infection (OR: 1.67; p=0.99). Stent firmness did not affect encrustation on double J stent (OR: 0.97; p=0.17). Softer materials like silicone are preferred for ureteral stents to reduce symptoms like hematuria and lower body pain. Coatings like silver nanoparticles and triclosan, while enhancing antimicrobial properties, did not effectively lower infection risk.

Inactivation of SARS-CoV-2 on salt-coated surfaces: an in vitro study

In the COVID-19 pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), face masks have become a very important safety measure against the main route of transmission of the virus: droplets and aerosols. Concerns that masks contaminated with SARS-CoV-2 infectious particles could be a risk for self-contamination have emerged early in the pandemic as well as solutions to mitigate this risk. The coating of masks with sodium chloride, an antiviral and non-hazardous to health chemical, could be an option for reusable masks. To assess the antiviral properties of salt coatings deposited onto common fabrics by spraying and dipping, the present study established an in vitro bioassay using three-dimensional airway epithelial cell cultures and SARS-CoV-2 virus. Virus particles were given directly on salt-coated material, collected, and added to the cell cultures. Infectious virus particles were measured by plaque forming unit assay and in parallel viral genome copies were quantified over time. Relative to noncoated material, the sodium chloride coating significantly reduced virus replication, confirming the effectiveness of the method to prevent fomite contamination with SARS-CoV-2. In addition, the lung epithelia bioassay proved to be suitable for future evaluation of novel antiviral coatings.

Auranofin coated catheters inhibit bacterial and fungal biofilms in a murine subcutaneous model.

Microbe entry through catheter ports can lead to biofilm accumulation and complications from catheter-related bloodstream infection and ultimately require antimicrobial treatment and catheter replacement. Although strides have been made with microbial prevention by applying standardized antiseptic techniques during catheter implantation, both bacterial and fungal microbes can present health risks to already sick individuals. To reduce microbial adhesion, murine and human catheters were coated with polyurethane and auranofin using a dip coating method and compared to non-coated materials. Upon passage of fluid through the coated material in vitro, flow dynamics were not impacted. The unique antimicrobial properties of the coating material auranofin has shown inhibitory activity against bacteria such as Staphylococcus aureus and fungi such as Candida albicans. Auranofin coating on catheters at 10mg/mL reduced C. albicans accumulation in vitro from 2.0 x 108 to 7.8 x 105 CFU for mouse catheters and from 1.6 x 107 to 2.8 x 106 for human catheters, showing an impact to mature biofilms. Assessment of a dual microbe biofilm on auranofin-coated catheters resulted in a 2-log reduction in S. aureus and a 3-log reduction in C. albicans compared to uncoated catheters. In vivo assessment in a murine subcutaneous model demonstrated that catheters coated with 10 mg/mL auranofin reduced independent S. aureus and C. albicans accumulation by 4-log and 1-log, respectively, compared to non-coated catheters. In conclusion, the auranofin-coated catheters demonstrate proficiency at inhibiting multiple pathogens by decreasing S. aureus and C. albicans biofilm accumulation.

Micro structure and wear analysis of multi-layer nitride coating deposited on the austenitic steel

Utilizing the appropriate technology, the surface property must be improved to offset wear loss caused by friction. Hard ceramic coating compounds include titanium nitride (TiN) and titanium aluminium nitride (TiAlN). The cathodic arc deposition method's effects on the stainless steel (SS304) mechanical and wear properties (CAD) Measurements and comparisons are made for the coated samples of the wear rate microstructural study. In the ball-on-disc wear test, the tribological parameters are altered. Compared to different kinds of coatings, The TiN coating offers remarkable mechanical and tribological qualities on the SS316L surface. the microstructure of the wear areas of materials coated with titanium nitrate and aluminium titanium nitride under various loads. Compared to non-coated material, the titanium nitride and aluminium titanium nitride coated materials have high wear resistance.

Reduction of surface charging effects in laser ablation ionisation mass spectrometry through gold coating.

In femtosecond Laser Ablation Ionisation Mass Spectrometry (fs-LIMS) short laser pulses are used to ablate, atomise, and ionise solid sample material shot-by-shot. When ablating non-conductive samples electric charging of the surface can occur. Depending on the geometry of the instrument, the surface charge can influence the spread of the ablation plume and reduce spectral quality. Methods to reduce surface charging were investigated using a non-conductive geological sample and a miniature fs-LIMS system with a co-linear ablation geometry. Pausing five seconds between consecutive laser bursts fired on non-coated material improved the spectral quality by giving surface charges more time to dissipate. However, best mass spectrometric results were achieved after the sample was sputter coated with a thin gold layer, as a conductive sample surface hinders charge build-up. Consequently, gold coating allowed operation of the laser system at much higher laser pulse energies improving sensitivity and reliability. It also removed the need to pause between laser bursts, speeding up the measurement acquisition.

Disinfection of Outdoor Livestock Water Troughs: Effect of TiO2-Based Coatings and UV-A LED

The control of pathogens is of great importance to maintaining safe water quality for animal consumption and reducing the spread of pathogens in the environment and throughout the production chain. Titanium dioxide (TiO2) is an attractive nanoparticle for disinfection purposes because it is easy to use, highly effective under UV radiation and cost effective. The goal of this study was to assess the disinfection effectiveness of TiO2-coated materials (high-density polyethylene, HDPE and stainless steel, SS) and UV-A LED light of non-coated materials, and the impacts of temperature and bacteria concentration in disinfection. Three TiO2 composites, two synthesized and one commercial (namely, TiO2, Ag- TiO2 and P25 TiO2), were assessed for their removal photocatalytic efficiency of methylene blue (10 mg/L). P25 TiO2 showed fast photocatalytic efficiency after two hours of treatment, reaching 98% efficiency after 4 h. The immobilization method M1 (fast cured epoxy) of particles in the material showed the best adhesion to substrates (scale = 4 ASTM D 3359) and for TiO2-coated stainless steel in a pre-disinfection test at a temperature of 32.3 °C and efficiency of 55.2%. There were statistically significant differences in disinfection treatments between of TiO2-coated and non-coated materials under the influence of UV-A LED light (p &lt; 0.05) at a control temperature of 26 °C. The resulting disinfection efficiencies for typical trough materials (coated (C) or non-coated (NC) HDPE; and SS) were ranked as follows: SS-C-Light (100%) &gt; SS-Light (81.4%) &gt; HDPE-C-Light (63.9%) &gt; HDPE-Light (51.3%). High ambient temperature and initial bacteria concentration tended to reduce the disinfection efficiency. The presence of TiO2 on the coated surface was confirmed using a scanning electron microscope (SEM) and energy dispersive X-ray microanalyses (EDS). These results demonstrate the disinfection potential of TiO2-coated materials and UV-A LED light, and thus, they should be considered as valuable alternatives to deal with persistent E. coli contamination of cattle troughs.

In vitro testing of salt coating of fabrics as a potential antiviral agent in reusable face masks

During the coronavirus disease (COVID-19) pandemic, wearing face masks in public spaces became mandatory in most countries. The risk of self-contamination when handling face masks, which was one of the earliest concerns, can be mitigated by adding antiviral coatings to the masks. In the present study, we evaluated the antiviral effectiveness of sodium chloride deposited on a fabric suitable for the manufacturing of reusable cloth masks using techniques adapted to the home environment. We tested eight coating conditions, involving both spraying and dipping methods and three salt dilutions. Influenza A H3N2 virus particles were incubated directly on the salt-coated materials, collected, and added to human 3D airway epithelial cultures. Live virus replication in the epithelia was quantified over time in collected apical washes. Relative to the non-coated material, salt deposits at or above 4.3 mg/cm2 markedly reduced viral replication. However, even for larger quantities of salt, the effectiveness of the coating remained dependent on the crystal size and distribution, which in turn depended on the coating technique. These findings confirm the suitability of salt coating as antiviral protection on cloth masks, but also emphasize that particular attention should be paid to the coating protocol when developing consumer solutions.

Safety assessment of the substance fatty acid-coated nano precipitated calcium carbonate for use in plastic food contact materials.

The EFSA Panel on Food Contact Materials, Enzymes and Processing Aids (CEP) assessed the safety of the substance identified by the applicant as ‘fatty acid‐coated nano precipitated calcium carbonate’. It is intended to be used as a filler in all plastics at up to 5% for contact with acidic food and at up to 40% for contact with all other types of food. Articles made with the substance are intended for long‐term storage over 6 months at room temperature and below. No information was provided on the mechanism of coating as to whether there is chemical modification of the surface and/or physical adsorption. The substance was not properly characterised, either as pristine material or when incorporated into plastic. Contrary to the non‐coated material, data show that the coated material does not dissolve fully and quickly under pH conditions simulating gastrointestinal tract. Surface analysis with electron microscopy of low‐density polyethylene (LDPE) samples before and after migration experiments showed major differences that indicate release of the substance from the surface after the tests with 3% acetic acid and to a lesser extent with 10% ethanol. This is consistent with measurable migrations that were up to 39 mg CaCO3/kg when using an LDPE sample made with 5% of the substance in contact with acetic acid for 64 days at 40°C. The required data on the release of nanoparticles and on the potential toxicity of the substance in nanoform were not provided. Therefore, the Panel could not conclude on the safe use of the substance.

The Effect of Sol-Gel Coatings on the Phosphorus (P) Adsorption Capacity of Calcareous Materials for Use in Water Treatment

(1) Phosphorus (P) removal has proven difficult in decentralized wastewater treatment systems, and P binding material, installed as an external filter, has been proposed for improving P removal. Especially, calcium (Ca)-rich materials have shown promising results. (2) Five calcareous materials were tested with isotherm batch experiments. The material with the highest P adsorption capacity was selected to undergo different Sol-Gel coatings, i.e., different coating dilution ratios (1:10, 1:5, and 1:1) and exposure periods (5, 10, and 15 min). The seven coated materials were evaluated by isotherm experiments. (3) The maximum adsorption capacity (Qmax) was determined by fitting the Langmuir equation. Qmax for the non-coated materials, and ranged from 0.7 (sand) to 35.1 (Catsan) mg P g−1 DW, while the coated materials ranged from 7.8 to 24.7 mg P g−1 DW depending on the coating. Based on the rotated Principal Component Analysis, the most important parameters for Qmax were the texture and the Ca content. (4) Catsan was the most promising material, but when performing a Sol-Gel coating, a trade-off between preserving Qmax and the coating thickness were evident, as the materials with the thinner coating preserved more of the sorption capacity. The development of P binding materials constitutes a useful technology in decentralized wastewater treatment systems.

Ultrasensitive biosensors based on waveguide-coupled long-range surface plasmon resonance (WC-LRSPR) for enhanced fluorescence spectroscopy.

We investigated the coupling phenomenon between plasmonic resonance and waveguide modes through theoretical and experimental parametric analyses on the bimetallic waveguide-coupled long-range surface plasmon resonance (Bi-WCLRSPR) structure. The calculation results indicated that the multi-plasmonic coupling gives rise to the enhanced depth-to-width ratio of the reflection dip compared to that of LRSPR excited using a single set of Ag and Teflon. The optimized thickness of Ag(40 nm)/Teflon(700 nm)/Ag(5 nm)/Au(5 nm) was obtained and generated the highest plasmon intensity enhancement, which was 2.38 folds in comparison to the conventional bimetallic surface plasmon resonance (SPR) configuration (Ag/Au). 17β-Estradiol was used in the fluorescence enhancement experiment by the reflection geometry-based system, wherein the excitation light source was on the side of a WC-LRSPR chip opposite to that of the light detection unit. The phenomenon of surface plasmon-couple emission (SPCE) depends on the number of 17β-estradiol molecule promoters from female sex steroid hormones, which demonstrated a limit of detection (LOD) of 2 pg mL−1 and 1.47-fold fluorescence improvement as compared to the non-coated material on the surface of pristine glass. This enhanced WC-LRSPR can readily find application in fluorescence escalation needed in cases where a weak fluorescence signal is predicted, such as the small volume of liquid containing fluorescent dyes in biological diagnosis.

A combination of interdisciplinary analytical tools for evaluation of multi-layered coatings on medical grade stainless steel for biomedical applications

In this comprehensive study several analytical techniques were used in order to evaluate multi-layered biomedical surface coatings composed of a drug (diclofenac) and a polymer (chitosan). Such a thorough examination is of paramount importance in order to assure safety and prove efficiency of potential biomedical materials already at the in vitro level, hence leading to their potentially faster introduction to clinical trials.For the first time a novel technique based on thermal diffusivity and conductivity measurements (photothermal beam deflection spectroscopy – BDS) was employed in order to analyse in a non-destructive way the thickness of respective layers, together with their thermal diffusivity and conductivity. In addition to attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), BDS confirmed successive surface layers of the prepared coatings. Scanning electron microscopy and atomic force microscopy were used to examine structural information on the macro- and micro/nano-scale, respectively. Surface hydrophobicity was measured with the contact angle analysis, which clearly showed differences in hydrophobicity between coated and non-coated samples. Considering the targeted application of the prepared coatings (as implant in orthopaedic treatments), the in vitro drug release was analysed spectrophotometrically to examine the coatings potential for a controlled drug release. Furthermore, the material was also tested by electrochemical impedance spectroscopy and cyclic polarisation techniques, which were able to detect even minor differences between the performance of the coated and non-coated materials. As the final test, the biocompatibility of the coatings with human osteoblasts was determined.

The effect of urinary Foley catheter substrate material on the antimicrobial potential of calixerene-based molecules.

This study was to investigate the antimicrobial activity of a modified calixarene polymer bound to a silicone substrate in the presence of pathogens associated with catheter infections, Escherichia coli and Proteus mirabilis. The molecule and its constituent parts were studied bound and unbound to silicone substrates to ascertain growth effects. Minimum inhibitory and bactericidal concentrations were determined against E.coli and P. mirabilis. Biofilm growth was studied by immersing silicone discs seeded with either P. mirabilis or E.coli in artificial urine. Biofilms were assessed at 3, 7 and 10days. The coated material reduced bacterial cell density compared to the uncoated samples. Direct and indirect toxicity tests were conducted with a fibroblast cell line (3T3); coated and noncoated silicone samples were seeded with cells (1×104 /cm2 ) and incubated for 72h. Hoechst propidium iodide staining identified delayed toxic effect from the coated and noncoated material leachate in all but the platinum-cured medical-grade silicone, which showed no evident toxicity. The calixerene polymer was determined to be the active part of the coating. Biofilm formation was dramatically reduced in the coated platinum-cured medical-grade silicone samples, but cell viability was reduced on the clinical-grade silicones regardless of coating in contrast to cells seeded on the platinum-cured medical-grade silicone. A delayed toxic response was evident to the extract of the coated and noncoated clinical-grade samples, indicating that the toxic effect is due to the underlying substrate. This study has established that the immobilized molecule enhances the antibacterial and antifouling properties of silicone, without toxicity. It also clearly demonstrates that regardless of coating efficacy, the substrate material has the capacity to disrupt its potency and change the nature of the material coating.

Improving chondrocyte harvests with poly(2-hydroxyethyl methacrylate) coated materials in the preparation for cartilage tissue engineering.

Remarkable advances have been made in cartilage regenerative medicine to cure congenital anomalies including microtia, tissue defects caused by craniofacial injuries, and geriatric diseases such as osteoarthritis. However, those procedures require a substantial quantity of chondrocytes for tissue engineering. Previous studies have required several passages to obtain sufficient cell numbers for three-dimensional and monolayer cultures. Thus, our objective was to improve the quantity of chondrocytes that can be obtained by examining an anti-fouling polyhydrophilic chemical called poly(2-hydroxyethyl methacrylate) (pHEMA). To determine the effectiveness of the chemical, pHEMA solution was applied via dip-coating to centrifuge tubes, serological pipettes, and pipette tips. The cell quantity obtained during standard cell culturing and passaging procedures was measured alongside non-coated materials as a control. A significant 2.2-fold increase of chondrocyte yield was observed after 2 passages when pHEMA was applied to the tubes compared to when non-coated tubes were utilized. The 3-dimensional chondrocyte pellets prepared from the respective cell populations and transplanted into nude mice were histologically and biochemically analyzed. No evidence of difference in matrix production for in vitro and in vivo cultures was found as well as similar proliferation rates and colony formation abilities. The use of pHEMA provides a powerful alternative method for expanding the quantity of chondrocytes harvested and handled during cell isolation and passaging to enhance cartilage tissue engineering.

Chitosan-coated mesoporous MIL-100(Fe) nanoparticles as improved bio-compatible oral nanocarriers

Nanometric biocompatible Metal-Organic Frameworks (nanoMOFs) are promising candidates for drug delivery. Up to now, most studies have targeted the intravenous route, related to pain and severe complications; whereas nanoMOFs for oral administration, a commonly used non-invasive and simpler route, remains however unexplored. We propose here the biofriendly preparation of a suitable oral nanocarrier based on the benchmarked biocompatible mesoporous iron(III) trimesate nanoparticles coated with the bioadhesive polysaccharide chitosan (CS). This method does not hamper the textural/structural properties and the sorption/release abilities of the nanoMOFs upon surface engineering. The interaction between the CS and the nanoparticles has been characterized through a combination of high resolution soft X-ray absorption and computing simulation, while the positive impact of the coating on the colloidal and chemical stability under oral simulated conditions is here demonstrated. Finally, the intestinal barrier bypass capability and biocompatibility of CS-coated nanoMOF have been assessed in vitro, leading to an increased intestinal permeability with respect to the non-coated material, maintaining an optimal biocompatibility. In conclusion, the preservation of the interesting physicochemical features of the CS-coated nanoMOF and their adapted colloidal stability and progressive biodegradation, together with their improved intestinal barrier bypass, make these nanoparticles a promising oral nanocarrier.

Materials for Proton Exchange Membrane water electrolyzer bipolar plates

Titanium based BiPolar Plates (BPPs) are commonly used in Proton Exchange Membrane Water Electrolyzers (PEMWEs) today as they can withstand the harsh operating conditions experienced inside an operating PEM water electrolyzer. In particular, the high anode potential and acidic nature of the PEM is crucial for BPP performance. In this work we expand the investigation of non-coated materials at relevant operating conditions to include molybdenum, 254 SMO, tungsten, AISI 316L, AISI 304L, Inconel 625, niobium and tantalum, in addition to Titanium gr. 2. Pre-designed potentiostatic and potentiodynamic tests at potentials up to 2.0 VSHE were performed in addition to Interfacial Contact Resistance (ICR) and weight loss measurements. Scanning Electron Microscopy (SEM) imaging was conducted to observe morphology changes during the electrochemical tests. Titanium, tantalum and niobium experienced little or no weight change during potentiostatic polarization, while for AISI 304L, AISI 316L and tungsten the measured weight loss was much lower than the weight loss calculated from currents produced. When the potentiostatic test was prolonged for titanium, the ICR was found to increase with time. Auger Electron Spectroscopy measurements confirmed that the increase in ICR for titanium, tantalum and niobium is related to an increased thickness of surface oxides.

Evaluation of mold growth on sugarcane bagasse particleboards in natural exposure and in accelerated test

The objective of this study was to investigate the performance of alternative sugarcane bagasse particle board (BCP) using castor oil polyurethane resin in comparison with commercial medium density wood particle board (MDP) under natural and accelerated test conditions. The particle boards were evaluated after 12 months of exposure to natural weathering in Pirassununga (21.9965° S, 47.4262° W), Brazil and by an accelerated mold growth test under laboratory conditions. The mold growth was quantified according to the Standards ASTM D 3273-12 (2012) and the results were evaluated by statistical analysis through the Proportional Chances Model (PCM). For both materials, the surface coating with castor oil based bi-component polyurethane resin was less colonized than the non-coated materials; independent of the particleboard type. Additionally, the bending test shows that the sugarcane bagasse particle boards presents better performance of module of elasticity (MOR) (7.7 MPa) in comparison with the commercial wood particle boards (3.6 MPa) after exposed to accelerated tests for mold colonization. The surface coating with castor oil based polyurethane resin reduces mold growth, therefore these results support the potential use of this alternative resin both as a binder and as a surface coating in these particulate materials. The particle boards fabricated with sugarcane bagasse and castor oil resin presented similar mold colonization compared to the commercial wood particle boards.

Role of PEO coatings in long-term biodegradation of a Mg alloy

Long-term effect of plasma electrolytic oxidation (PEO) coatings on in vitro corrosion of 3D Mg implant specimens has been investigated in simulated body fluid (SBF). Hydrogen evolution rate in PEO-coated specimens was 35 times lower compared to the non-coated alloy during first 2 weeks of immersion (0.04–0.07mLcm−2d−1) and reached a steady-state rate of 0.3mLcm−2d−1 by week 6 of immersion. Studies of the tribocorrosion behaviour of the PEO-coated alloy disclosed that the coatings rapidly lose their tribocorrosion resistance due to hydration of the coating material and associated drastic decrease of microhardness but exhibit a better tirbocorrosion performance than the non-coated material.

Organosilane Coatings for Ni-Rich High-Voltage Lithium Ion Batteries

One of the more promising cathode materials for high-energy high-voltage lithium ion batteries (LIBs) are Ni-rich layered cathode materials such as LiNixMnyCozO2 (where x + y + z = 1). Although these cathode materials are attractive from a high capacity standpoint, they commonly suffer from poor structural stability at highly delithiated (charged) states leading to poor electrochemical performance.1-3 While incorporation of additives into the electrolyte provides one way to improve cycling performance in LIBs, surface coatings are becoming a widely adopted method to improve the cycling performance of high-voltage cathode materials. More widely investigated coating materials include oxide coatings (Al2O3, TiO2, etc.)4 while comparatively fewer studies have investigated organic monomer or polymer coatings (PEDOT, polyimide, etc.).5 Additionally, the mechanism of the coating interaction with the material is intriguing due to its importance in creating a performance-enhancing coating. In this work, the surface of LiNi0.5Mn0.3Co0.2O2 cathode materials were coated with organosilane reagents to investigate their effect on cell electrochemical performance. The impact of the cathode pretreatment, the weight percentage of organosilane used and the functionality of the organosilane used will be presented. Characterization of the organosilane coating using SEM shows a slight morphological change in the cathode surface while EDX and FTIR confirm the presence of a Si-containing coating. Half cells (Li/ LiNi0.5Mn0.3Co0.2O2) using the organosilane coated cathodes operating in the voltage window of 3.0 - 4.4 V showed similar cycling behavior to that of non-coated material. In conclusion, a new type of organic coating was utilized on Ni-rich cathode materials and this research explores a new type of coating for high voltage cathodes. References 1) Son, I. H.; Park, J. H.; Kwon, S.; Mun, J. and Choi, J. W. Chem. Mat. 2015, 27, 7370-7379. 2) Bak, S.-M.; Hu, E.; Zhou, Y.; Yu, X.; Senanayake, S. D.; Cho, S.-J.; Kim, K.-B.; Chung, K. Y.; Yang, X.-Q. and Nam, K.-W. ACS Appl. Mater. Interfaces 2014, 6, 22594-22601. 3) Lin, F.; Markus, I. M.; Doeff, M. M.; Xin, H. L. Sci. Rep., 2014, 4, 5694. 4) Xu, S.; Jacobs, R. M.; Nguyen, H. M.; Hao, S.; Mahanthappa, M.; Wolverton, C.; Morgan, D. J. Mater. Chem. A, 2015, 3, 17248. 5) Zhang, J.; Lu, Q.; Fang, J.; Wang, J.; Yang, J. and NuLi, Y. ACS Appl. Mater. Interfaces 2014, 6, 17965-17973.

CHARACTERISTICS OF SOLAR THERMAL ABSORBER MATERIALS FOR CROSS ABSORBER DESIGN IN SOLAR AIR COLLECTOR

The solar thermal absorber is an integral component of a solar air collector, especially in determining the overall performance of a solar air thermal system. The type and shape of material will have a direct impact on the operating temperature and thermal energy storage effect of the solar air thermal collector. This paper focused on the investigation of aluminum and stainless steel hollow square rods in terms of their solar thermal absorber performance. Comparisons between different materials and coatings were conducted in order to determine their impact in solar thermal absorber applications. Experiments were conducted on both materials with flat-black coated and non-coated surfaces of aluminum (6063) and stainless steel sets respectively. Both sets were exposed under 585 W/m2 radiation and the temperature response was recorded. A significant improvement was shown to result from the application of flat-black coating against non-coated material, with maximum temperatures of 67.2oC and 48.3oC respectively. It was observed that for the hollow square metal absorber the heating and cooling characteristics can be established by means of the relation between the surface and inner air temperatures of the absorber. This method can assist in temperature profiling of hollow square metal for solar thermal application.

Physical and electrochemical characteristics of carbon content in carbon-coated Li2MnSiO4 for rechargeable lithium batteries

Carbon-coated Li2MnSiO4 powders were synthesized by a citric acid-assisted sol–gel process, and their physical and electrochemical properties were characterized to assess their suitability as a cathode material in lithium-rechargeable batteries. Carbon was coated onto the Li2MnSiO4 particles through the carbonization of polymeric materials that were caused by the addition of citric acid during the sol–gel process. The particle size and electrical conductivity of the Li2MnSiO4 powders were found to be changed by varying the amount of citric acid added during the sol–gel process. XRD analysis showed that the quantity of impurities in Li2MnSiO4 was decreased during the sol–gel process. The carbon coating led to an increase in conductivity and mean particle size by creating an electrical and physical connection between the particles. The discharge capacity of Li2MnSiO4 with over 5 % carbon coating was significantly increased to ~125 mAh g−1 compared to just ~3 mAh g−1 for noncoated material.