Search results for: nano-micro crystalline diamond coating

Authors: R. Gounina-Allouane, N. Ouali, F. Z. Berrabah, A. Bentaleb

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For a long time, the Gram-positive spore-forming bacteria Bacillus thuringiensis (Bt) has been widely used in biological control against devastating and disease vectors insects. This is due to the insecticidal activity of its crystalline parasporal inclusion (crystals) predominantly comprised of one or more proteins (Cry and Cyt proteins) also called δ-endotoxins, produced during sporulation. The shape and composition of Bt crystals vary among strains and crystalline proteins are extremely varied (more than 475 cry gene were discovered). The insecticidal activity of Bt crystals is very well studied, thus their insecticidal mode of action is well established, however, their antimicrobial effect is largely unknown. The lack of data on the antimicrobial effect of crystalline proteins of Bt and the need for searching new antimicrobial molecules encouraged us to carried out this study. The antibacterial effect of δ-endotoxines produced by two Bt stains; a strain isolated from soil at northern of Algeria (Bt 7.2.B), and a strain isolated from a bioinsecticide (Bacillus thuringiensis var aizawai), activated by proteolysis, was assayed on clinical bacterial strains and ATCC collection ones respectively. Gram positive and negative clinical bacterial strains (Escherichia coli, Klebsiella pneumonaie, Pseudomonas aeruginosa, Staphylococcus aureus) were sensitive to activated Bt 72B endotoxins. Similarly, bacterial strains from ATCC collection (Escherichia coli ATCC 25922, Pseudomonas aerugenosa ATCC 27853, Staphylococcus aureus ATCC 25923) were sensitive to activated B. thuringiensis var aizawai δ-endotoxines. The activated δ-endotoxins were separated by SDS-PAGE.

Keywords: Bacillus thuringiensis, crystals, cry proteins, δ-endotoxins, antibacterial activity

Procedia PDF Downloads 412

Authors: T. Sakamoto, S. Kainuma

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Firstly, in order to examine the influence of the remaining amount of the rust on the coating film durability, the accelerated deterioration tests were carried out. In order to prepare test specimens, uncoated steel plates were corroded by the Salt Spray Test (SST) prior to the accelerated deterioration tests, and then the prepared test specimens were coated by epoxy resin and phthalic acid resin each of which has different gas-barrier performance. As the result, it was confirmed that the under-film corrosion occurred in the area and the adjacency to great quantities of salt exists in the rust, and did not occurred in the specimen which was applied the epoxy resin paint after the surface preparation by the power tool. Secondly, in order to clarify the influence of the corrosive factors on the coating film durability, outdoor exposure tests were conducted for one year on actual steel bridge located at a coastal area. The tests specimens consist of coated corroded plates and the uncoated steel plates, and they were installed on the different structural members of the bridge for one year. From the test results, the uncoated steel plates which were installed on the underside of the member are easily corrosive and had highly correlation with the amount of salt in the rust. On the other hand, the most corrosive under-film steel was the vertical surface of the web plate. Thus, it was confirmed that under-film corrosion rate was not match with corrosion rate of the uncoated steel. Consequently, it is estimated that the main factors of under-film corrosion are gas-barrier property of coating film and corrosive factors such as water vapor and temperature. The salt which significantly corrodes the uncoated steel plate is not directly related to the under-film corrosion.

Keywords: accelerated deterioration test, coating durability, environmental factor, under-film corrosion

Procedia PDF Downloads 339

Authors: Asiful H. Seikh, Jabair A. Mohammed, Ubair A. Samad, Mohammad A. Alam, Saeed M. Al-Zahrani, El-Sayed M. Sherif

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Three coating formulations were fabricated by incorporating different percentages of MIO (micaceous iron oxide ) (1, 2, and wt%) with ball-milled nanocrystalline Al (2 wt%) particles, which was optimized earlier. These coatings were characterized by means of different methods, namely, SEM, TGA, pendulum hardness, scratch test, and nano-indentation. The EIS measurements were carried out to report the effect of adding MIO powder in fabricated coatings on their corrosion behavior in 3.5 wt% NaCl solutions. In order to report the effect of immersion time on the corrosion and degradation of the prepared coatings, the EIS data were also acquired after various exposure periods of time, i.e., 1 h, 7 d, 14 d, 21 d, and 30 d in the test chloride solution. It has been found that the obtained EIS data for the fabricated coatings proved that the presence of 2% MIO provided the highest corrosion resistance amongst all coatings and that effect was recorded after all immersion periods of time. But, the MIO-incorporated coatings have less corrosion resistance than Al based epoxy coatings. It was also shown that with prolonged immersion, the resistance to corrosion declined after 7d, then with a longer period of immersion, i.e. 14 d, 21 d, and 30 d increases the resistance to corrosion by forming oxide products on the coatings surface. The results obtained from both mechanical and electrochemical testing confirmed that the fabricated coating with 2 wt% Al exhibited better hardness and higher resistance to corrosion as compared to coatings with 1 wt% Al and 3 wt% Al.

Keywords: epoxy coatings, nanomaterials, corrosion resistance, EIS, nanoindentation

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Authors: Remzi Şahin, Sadık Ata, Kevser Dincer

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In this study, performance of proton exchange membrane (PEM) fuel cell was experimentally investigated. The efficiency of energy conversion in PEM fuel cells is dependent on the catalytic activities of the catalysts used in the cathode and anode of membrane electrode assemblies. Membrane is considered the heart of PEM fuel cells without which they cannot produce electricity. PEM fuel cell performance increased with coating carbon nanotube (CNT). CNT show a unique combination of stiffness, strength, and tenacity compared to other fiber materials which usually lack one or more of these properties. Two different experiments were performed and the membrane performance has been determined by repeating the two experiments that were done before coating. The purposes of these experiments are the observation of power change due to a temperature change in the same voltage value.

Keywords: carbon nanotube (CNT), proton exchange membrane (PEM), fuel cell, spin method

Procedia PDF Downloads 355

Authors: Yongseok Kim, Jeong-Min Lee, Hyunwoo Song, Junghan Yun, Jungin Byun, Jae-Mean Koo, Chang-Sung Seok

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Thermal barrier coating(TBC) is applied for gas turbine components to protect the components from extremely high temperature condition. Since metallic substrate cannot endure such severe condition of gas turbines, delamination of TBC can cause failure of the system. Thus, delamination life of TBC is one of the most important issues for designing the components operating at high temperature condition. Thermal stress caused by thermally grown oxide(TGO) layer is known as one of the major failure mechanisms of TBC. Thermal stress by TGO mainly occurs at the interface between TGO layer and ceramic top coat layer, and it is strongly influenced by the thickness and shape of TGO layer. In this study, Isothermal oxidation is conducted on coin-type TBC specimens prepared by APS(air plasma spray) method. After the isothermal oxidation at various temperature and time condition, the thickness and shape(rumpling shape) of the TGO is investigated, and the test data is processed by numerical analysis. Finally, the test data is arranged into a mathematical prediction model with two variables(temperature and exposure time) which can predict the thickness and rumpling shape of TGO.

Keywords: thermal barrier coating, thermally grown oxide, thermal stress, isothermal oxidation, numerical analysis

Procedia PDF Downloads 318

Authors: A. M. Pashayev, A. S. Samedov, T. B. Usubaliyev, N. Sh. Yusifov

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Different types of coating technologies are widely used for gas turbine blades. Thermal barrier coatings, consisting of ceramic top coat, thermally grown oxide and a metallic bond coat are used in applications for thermal protection of hot section components in gas turbine engines. Operational characteristics and longevity of high-temperature turbine blades substantially depend on a right choice of composition of the protective thermal barrier coatings. At a choice of composition of a coating and content of the basic elements it is necessary to consider following factors, as minimum distinctions of coefficients of thermal expansions of elements, level of working temperatures and composition of the oxidizing environment, defining the conditions for the formation of protective layers, intensity of diffusive processes and degradation speed of protective properties of elements, extent of influence on the fatigue durability of details during operation, using of elements with high characteristics of thermal stability and satisfactory resilience of gas corrosion, density, hardness, thermal conduction and other physical characteristics. Forecasting and a choice of a thermal barrier coating composition, all above factors at the same time cannot be considered, as some of these characteristics are defined by experimental studies. The implemented studies and investigations show that one of the main failures of coatings used on gas turbine blades is related to not fully taking the physical-chemical features of elements into consideration during the determination of the composition of alloys. It leads to the formation of more difficult spatial structure, composition which also changes chaotically in some interval of concentration that doesn't promote thermal and structural firmness of a coating. For the purpose of increasing the thermal and structural resistant of gas turbine blade coatings is offered a new approach to forecasting of composition on the basis of analysis of physical-chemical characteristics of alloys taking into account the size factor, electron configuration, type of crystal lattices and Darken-Gurry method. As a result, of calculations and experimental investigations is offered the new four-component metallic bond coat on the basis of chrome for the gas turbine blades.

Keywords: gas turbine blades, thermal barrier coating, metallic bond coat, strategic metals, physical-chemical features

Procedia PDF Downloads 285

Authors: S. Mezghani, E. Perrin, J. L. Bodnar, J. Marthe, B. Cauwe, V. Vrabie

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Non contact evaluation of the thickness of paint coatings can be attempted by different destructive and nondestructive methods such as cross-section microscopy, gravimetric mass measurement, magnetic gauges, Eddy current, ultrasound or terahertz. Infrared thermography is a nondestructive and non-invasive method that can be envisaged as a useful tool to measure the surface thickness variations by analyzing the temperature response. In this paper, the thermal quadrupole method for two layered samples heated up with a pulsed excitation is firstly used. By analyzing the thermal responses as a function of thermal properties and thicknesses of both layers, optimal parameters for the excitation source can be identified. Simulations show that a pulsed excitation with duration of ten milliseconds allows to obtain a substrate-independent thermal response. Based on this result, an experimental setup consisting of a near-infrared laser diode and an Infrared camera was next used to evaluate the variation of paint coating thickness between 60 µm and 130 µm on two samples. Results show that the parameters extracted for thermal images are correlated with the estimated thicknesses by the Eddy current methods. The laser pulsed thermography is thus an interesting alternative nondestructive method that can be moreover used for non conductive substrates.

Keywords: non destructive, paint coating, thickness, infrared thermography, laser, heterogeneity

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Authors: A. A. Azemati, H. Hosseini

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By using an adequate paint in buildings, energy consumption can be decreased. In this research, a range of wall paints in different climatic conditions has been investigated to observe its effect on energy consumption. In the current study, the researchers have investigated the effect of different parameters including climatic condition, absorption coefficient, and thermal loads on paint coating. In order to study these effects, heating and cooling loads of a typical building with different color paints have been calculated. The effect of building paint in different climatic condition was studied and a comparison was drawn between paints and painting coats with inorganic micro particles in temperate climate to obtain optimized energy consumption.

Keywords: climate, energy consumption, inorganic, painting coats

Procedia PDF Downloads 266

Authors: Mohamed S. Selim, Nesreen A. Fatthallah, Shimaa A. Higazy, Zhifeng Hao, Ping Jing Mo

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As marine fouling-release (FR) surfaces, two new superhydrophobic nanocomposite series of polydimethylsiloxane (PDMS) loaded with reduced graphene oxide (RGO) and graphene oxide/boehmite nanorods (GO-γ-AlOOH) nanofillers were created. The self-cleaning and antifouling capabilities were modified by controlling the nanofillers' shapes and distribution in the silicone matrix. With an average diameter of 10-20 nm and a length of 200 nm, γ-AlOOH nanorods showed a single crystallinity. RGO was made using a hydrothermal process, whereas GO-γ-AlOOH nanocomposites were made using a chemical deposition method for use as fouling-release coating materials. These nanofillers were disseminated in the silicone matrix using the solution casting method to explore the synergetic effects of graphene-based materials on the surface, mechanical, and FR characteristics. Water contact angle (WCA), scanning electron, and atomic force microscopes were used to investigate the surface's hydrophobicity and antifouling capabilities (SEM and AFM). The roughness, superhydrophobicity, and surface mechanical characteristics of coatings all increased the homogeneity of the nanocomposite dispersion. To examine the antifouling effects of the coating systems, laboratory tests were conducted for 30 days using specified bacteria.PDMS/GO-γ-AlOOH nanorod composite demonstrated superior antibacterial efficacy against several bacterial strains than PDMS/RGO nanocomposite. The high surface area and stabilizing effects of the GO-γ-AlOOH hybrid nanofillers are to blame for this. The biodegradability percentage of the PDMS/GO-γ-AlOOH nanorod composite (3 wt.%) was the lowest (1.6%), while the microbial endurability percentages for gram-positive, gram-negative, and fungi were 86.42%, 97.94%, and 85.97%, respectively. The homogeneity of the GO-γ-AlOOH (3 wt.%) dispersion, which had a WCA of 151° and a rough surface, was the most profound superhydrophobic antifouling nanostructured coating.

Keywords: superhydrophobic nanocomposite, fouling release, nanofillers, surface coating

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Authors: Rawan Aljabbari, Thamer Alomayri, Faisal G. Al-Maqate, Abeer Al Suwat

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For environmentally friendly innovative technologies and a sustainable future, fly ash/TiO₂ thin film nanocomposites are essential. Fly ash will be doped with titanium dioxide in this work in order to better understand its optical characteristics and employ it in semiconductor electrical devices. This study focused on the structure, morphology, and optical properties of fly ash/TiO₂ thin films. The spin-coating technique was used to create thin coatings of fly ash/TiO₂. For the first time, the doping of TiO₂ in the fly ash host at ratios of 1, 2, and 3 wt% was investigated with the thickness of all samples fixed. When compared to undoped thin films, the surface morphology of the doped thin films was improved. The weakly crystalline structure of the doped fly ash films was verified by XRD. The optical bandgap energy of these films was successfully reduced by the TiO₂ doping, going from 3.9 to 3.5 eV. With increasing dopant concentration, the value of Urbach energy is increasing. The optical band gap is clearly in opposition to the disorder. While it considerably improved the optical conductivity to a value of 4.1 x 10^9 s^(-1), it also raised the refractive index and extinction coefficient. Depending on the TiO₂ doping ratio, the transmittance decreased, and the reflection increased. As the TiO₂ concentration rises, the absorption of photon energy rises, and the absorption coefficient of photon energy is reduced. results in their possible use as solar energy and semiconductor materials.

Keywords: fly ash, structural analysis, optical properties, morphology

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Authors: B. Cilek Tatar, G. Sumnu, M. Oztop, E. Ayaz

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Encapsulation protects sensitive food ingredients against heat, oxygen, moisture and pH until they are released to the system. It can mask the unwanted taste of nutrients that are added to the foods for fortification purposes. Cherry laurels (Prunus laurocerasus) contain phenolic compounds which decrease the proneness to several chronic diseases such as types of cancer and cardiovascular diseases. The objective of this research was to study the effects of centrifugation, different coating materials and homogenization methods on microencapsulation of powders obtained from cherry laurels. In this study, maltodextrin and mixture of maltodextrin:whey protein with a ratio of 1:3 (w/w) were chosen as coating materials. Total solid content of coating materials was kept constant as 10% (w/w). Capsules were obtained from powders of freeze-dried cherry laurels through encapsulation process by silent crusher homogenizer or microfluidization. Freeze-dried cherry laurels were core materials and core to coating ratio was chosen as 1:10 by weight. To homogenize the mixture, high speed homogenizer was used at 4000 rpm for 5 min. Then, silent crusher or microfluidizer was used to complete encapsulation process. The mixtures were treated either by silent crusher for 1 min at 75000 rpm or microfluidizer at 50 MPa for 3 passes. Freeze drying for 48 hours was applied to emulsions to obtain capsules in powder form. After these steps, dry capsules were grounded manually into a fine powder. The microcapsules were analyzed for total antioxidant activity with DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging method. Prior to high speed homogenization, the samples were centrifuged (4000 rpm, 1 min). Centrifugation was found to have positive effect on total antioxidant activity of capsules. Microcapsules treated by microfluidizer were found to have higher total antioxidant activities than those treated by silent crusher. It was found that increasing whey protein concentration in coating material (using maltodextrin:whey protein 1:3 mixture) had positive effect on total antioxidant activity for both silent crusher and microfluidization methods. Therefore, capsules prepared by microfluidization of centrifuged mixtures can be selected as the best conditions for encapsulation of cherry laurel powder by considering their total antioxidant activity. In this study, it was shown that capsules prepared by these methods can be recommended to be incorporated into foods in order to enhance their functionality by increasing antioxidant activity.

Keywords: antioxidant activity, cherry laurel, microencapsulation, microfluidization

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Authors: M. Bouzid, A. Djadi, C. Aribi, A. Irekti, B. Bezzazi, F. Halouene

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The nature of materials structuring our health institutions promote the development of germs. The sustainability of nosocomial infections remains significant (12% and 15%). One of the major factors is the portland cement which is brittle and porous. As part of a national plan to fight nosocomial infections, led by the University Hospital of Blida, we opted for a composite coating, application by multilayer model, composed of epoxy-polyester resin as a binder and calcium carbonate as mineral fillers. The application of composite materials reinforce the wall coating of hospital units and eliminates the hospital infectious areas. The resistance to impact, chemicals, raising temperature and to a biologically active environment gives satisfactory results.

Keywords: nosocomial infection, microbial load, composite materials, portland cement

Procedia PDF Downloads 366

Authors: R. Suresh, Pavan Kumar Nimmagadda, Ming Zo Tan, Shane Hart, Sharp Ugwuocha

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Polycrystalline diamond compact (PDC) drill bits are extensively used in the oil and gas industry as well as the mining industry. Industry engineers continually improve upon PDC drill bit designs and hydraulic conditions. Optimized injection nozzles play a key role in improving the drilling performance and efficiency of these ever changing PDC drill bits. In the first part of this study, computational fluid dynamics (CFD) modelling is performed to investigate the hydrodynamic characteristics of drilling fluid flow around the PDC drill bit. An Open-source CFD software – OpenFOAM simulates the flow around the drill bit, based on the field input data. A specifically developed console application integrates the entire CFD process including, domain extraction, meshing, and solving governing equations and post-processing. The results from the OpenFOAM solver are then compared with that of the ANSYS Fluent software. The data from both software programs agree. The second part of the paper describes the parametric study of the PDC drill bit nozzle to determine the effect of parameters such as number of nozzles, nozzle velocity, nozzle radial position and orientations on the flow field characteristics and bit washing patterns. After analyzing a series of nozzle configurations, the best configuration is identified and recommendations are made for modifying the PDC bit design.

Keywords: ANSYS Fluent, computational fluid dynamics, nozzle configuration, OpenFOAM, PDC dill bit

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Authors: S. A. A. Nabeela Nasreen, S. Sundarrajan, S. A. Syed Nizar, Seeram Ramakrishna

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Metal-organic frameworks (MOFs) have attracted considerable interest due to its diverse pore size tunability, fascinating topologies and extensive uses in fields such as catalysis, membrane separation, chemical sensing, etc. Zeolitic imidazolate frameworks (ZIFs) are a class of MOF with porous crystals containing extended three-dimensional structures of tetrahedral metal ions (e.g., Zn) bridged by Imidazolate (Im). Selected ZIFs are used to separate solvent/solvent mixtures. A layer by layer formation of the nanocomposite of Zinc oxide (ZnO) and ZIF on a ceramic support using a solvothermal method was engaged and tested for target solvent/solvent separation. Metal oxide layer was characterized by XRD, SEM, and TEM to confirm the smooth and continuous coating for the separation process. The chemical composition of ZIF films was studied by using X-Ray absorption near-edge structure (XANES) spectroscopy. The obtained ceramic tube with metal oxide and ZIF layer coating were tested for its packing density, thickness, distribution of seed layers and variation of permeation rate of solvent mixture (isopropyl alcohol (IPA)/methyl isobutyl ketone (MIBK). Pervaporation technique was used for the separation to achieve a high permeation rate with separation ratio of > 99.5% of the solvent mixture.

Keywords: metal oxide, membrane, pervaporation, solvothermal, ZIF

Procedia PDF Downloads 171

Authors: Rafik Balti, Mohamed Ben Mansour, Abdellah Arhaliass, Anthony Masse

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Unfortunately, shrimps are highly perishable and they start deteriorating immediately after death owing to their high water content and nutritional components. Currently, there has been an increasing interest in bioactive edible films and coatings to preserve the freshness and quality of foods. In this study, active edible coatings from microalgal exopolysaccharides (EPS) enriched with different concentrations of Red Seaweed Extract (RSE) (0.5, 1 and 1.5 % (w/v)) were developed and their effects on the quality changes of white shrimp during refrigerated storage (4 ± 1 °C) were examined over a period of 8 days. The control and the coated shrimp samples were analyzed periodically for microbiological (total viable bacteria, psychrotrophic bacteria, and enterobacteriaceae counts), chemical (pH, TVB-N, TMA-N, PV, TBARS), textural and sensory characteristics. The results indicated that the coating with a mixture of EPS and RSE could significantly decrease the total volatile basic nitrogen (TVB-N), trimethylamine (TMA) and thiobarbituric acid reactive substances (TBARS) (p < 0.05). With storage, EPS coatings containing RSE at both levels (1 and 1.5 %) were more effective in inhibiting the microbial species studied, specially psychrotrophic bacteria. Also, EPS + RSE coated samples had lower polyphenol oxidase (PPO) activity and lipid oxidation (p < 0.05) toward the end of storage. Textural and color properties of coated shrimp were generally more acceptable. Sensory scores indicated no significant changes in all samples during storage. The obtained results indicate that the edible EPS coating solutions enriched with RSE have noticeable effects on the quality and shelf life of shrimps when compared to control group. Finally, the present work demonstrates the effectiveness of EPS enriched coatings, offering a promising alternative to preserve more better the quality characteristics and to extend the shelf life of shrimp during the refrigerated storage

Keywords: active coating, exopolysaccharides, red seaweed, refrigerated storage, white shrimp

Procedia PDF Downloads 187

Authors: Lei Zhao, Yi Song, Tim Dunne, Jiaxiang (Jason) Ren, Wenhan Yue, Lei Yang, Li Wen, Yu Liu

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Fasting dissolving magnesium (DM) alloy technology has contributed significantly to the “Shale Revolution” in oil and gas industry. This application requires DM downhole tools dissolving initially at a slow rate, rapidly accelerating to a high rate after certain period of operation time (typically 8 h to 2 days), a contradicting requirement that can hardly be addressed by traditional Mg alloying or processing itself. Premature disintegration has been broadly reported in downhole DM tool from field trials. To address this issue, “temporary” thin polymers of various formulations are currently coated onto DM surface to delay its initial dissolving. Due to conveying parts, harsh downhole condition, and high dissolving rate of the base material, the current delay coatings relying on pure polymers are found to perform well only at low temperature (typical < 100 ℃) and parts without sharp edges or corners, as severe geometries prevent high quality thin film coatings from forming effectively. In this study, a coating technology combining Plasma Electrolytic Oxide (PEO) coatings with advanced thin film deposition has been developed, which can delay DM complex parts (with sharp corners) in corrosive fluid at 150 ℃ for over 2 days. Synergistic effects between porous hard PEO coating and chemical inert elastic-polymer sealing leads to its delaying dissolution improvement, and strong chemical/physical bonding between these two layers has been found to play essential role. Microstructure of this advanced coating and compatibility between PEO and various polymer selections has been thoroughly investigated and a model is also proposed to explain its delaying performance. This study could not only benefit oil and gas industry to unplug their High Temperature High Pressure (HTHP) unconventional resources inaccessible before, but also potentially provides a technical route for other industries (e.g., bio-medical, automobile, aerospace) where primer anti-corrosive protection on light Mg alloy is highly demanded.

Keywords: dissolvable magnesium, coating, plasma electrolytic oxide, sealer

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Authors: M. Masar, P. Janota, J. Sedlak, M. Machovsky, I. Kuritka

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Zinc oxide (ZnO) nano crystals assembled porous architecture was prepared by thermal decomposition of zinc oxalate precursor at various temperatures ranging from 400-900°C. The effect of calcining temperature on structure and morphology was examined by scanning electron microscopy (SEM), X-ray diffractometry, thermogravimetry, and BET adsorption analysis. The porous nano crystalline ZnO morphology was developed due to the release of volatile precursor products, while the overall shape of ZnO micro crystals was retained as a legacy of the precursor. The average crystallite size increased with increasing temperature of calcination from approximately 21 nm to 79 nm, while the specific surface area decreased from 30 to 1.7 m2g-1. The photo catalytic performance of prepared ZnO powders was evaluated by degradation of methyl violet 2B, a model compound. The significantly highest photo catalytic activity was achieved with powder calcined at 500°C. This may be attributed to the sufficiently well-developed crystalline arrangement, while the specific surface area is still high enough.

Keywords: ZnO, porous structure, photodegradation, methyl violet

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Authors: Ahmad Alazemi, M. Sherif El-Eskandrany, Mohamad Kishk, Thanyan AlOnaizi, Ahmad Alduweesh, Shorouq Abdullaleel

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Arc melting technique followed by top-down approach, using a high-energy ball milling technique were employed to synthesize nanocrystalline of Cu50(Zr50-xNix)50 (x = 0, 10, 20 and 30 at.%) powder particles. The end-products of the alloy powders obtained after 50 h of the ball milling time were uniform in composition and had spherical-like morphology with an average particle size of 0.75 µm in diameter. The powders, which consisted of nanocrystalline grains with an average grain size of 10 nm in diameter, were used as feedstock materials for double face coating of stainless (SUS304) sheets, using cold spraying process. The coating materials enjoyed nanocrystalline structure and uniform composition. Biofilms were grown on 20-mm2 SUS304 sheets coated coupons inoculated with 1.5 × 108 CFU ml−1 E. coli. Significant biofilm inhibition was recorded in the nanoparticles coated coupons in comparison to non-coated SUS304 coupon. In conclusion, this study demonstrates that formation of biofilms can be significantly inhibited by Cu-based alloys especially in case of high (Ni) content. The inhibition of biofilm formation by nanocrystalline powders of Cu-based provides a practical approach to achieve the inhibition of biofilms formed by an emerging pathogen.

Keywords: biofilm, Cu, E.coli, FE-HRTEM/EDS, nanomaterials, nanocrystalline

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Authors: H. Acar, M. Karakışla, L. Aksu, M. Saçak

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The corrosion protection effect of poly(o-toluidine) (POT) coated on steel 316 electrode was determined in corrosive media such as NaCl, H2SO4 and HCl with the use of Tafel curves and electrochemical impedance spectroscopy techniques. The POT coatings were prepared with cyclic voltammetry technique in aqueous solution of oxalic acid and they were characterized by FTIR and UV-Visible absorption spectroscopy. The Tafel curves revealed that the POT coating provides the most effective protection compared to the bare steel 316 electrode in NaCl as corrosive medium. The results were evaluated based upon data decrease of corrosion current and shift to positive potentials with the increase of number of scans. Electrochemical impedance spectroscopy measurements were found to support Tafel data of POT coating.

Keywords: corrosion, impedance spectroscopy, steel 316, poly(o-toluidine)

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Authors: S. Y. Lin, C. H. Kuan, C. H. She, W. T. Wang

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In this study, ultrasonic assisted machining (UAM) technique is applied in side-surface milling experiment for glass-ceramic workpiece material. The tungsten carbide cutting-tool with diamond coating is used in conjunction with two kinds of cooling/lubrication mediums such as water-soluble (WS) cutting fluid and minimum quantity lubricant (MQL). Full factorial process parameter combinations on the milling experiments are planned to investigate the effect of process parameters on cutting performance. From the experimental results, it tries to search for the better process parameter combination which the edge-indentation and the surface roughness are acceptable. In the machining experiments, ultrasonic oscillator was used to excite a cutting-tool along the radial direction producing a very small amplitude of vibration frequency of 20KHz to assist the machining process. After processing, toolmaker microscope was used to detect the side-surface morphology, edge-indentation and cutting tool wear under different combination of cutting parameters, and analysis and discussion were also conducted for experimental results. The results show that the main leading parameters to edge-indentation of glass ceramic are cutting depth and feed rate. In order to reduce edge-indentation, it needs to use lower cutting depth and feed rate. Water-soluble cutting fluid provides a better cooling effect in the primary cutting area; it may effectively reduce the edge-indentation and improve the surface morphology of the glass ceramic. The use of ultrasonic assisted technique can effectively enhance the surface finish cleanness and reduce cutting tool wear and edge-indentation.

Keywords: glass-ceramic, ultrasonic assisted machining, cutting performance, edge-indentation

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Authors: Wenliang Song, Yu Zhang, Hua Jin, Il Kim

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The self-assembly of the polypeptide (PP) into well-defined structures at different length scales is both biomimetic relevant and fundamentally interesting. Although there are various reports of nanostructures fabricated by the self-assembly of various PPs, directed self-assembly of PP into three-dimensional (3D) hierarchical structure has proven to be difficult, despite their importance for biological applications. Herein, an efficient method has been developed through living polymerization of phenylalanine N-Carboxy anhydride (NCA) towards the linear and cyclic polyphenylalanine, and the new invented swelling methodology can form diverse hierarchical polypeptide crystals. The solvent-dependent self-assembly behaviors of these homopolymers were characterized by high-resolution imaging tools such as atomic force microscopy, transmission electron microscopy, scanning electron microscope. The linear and cyclic polypeptide formed 3D nano hierarchical shapes, such as a sphere, cubic, stratiform and hexagonal star in different solvents. Notably, a crystalline packing model was proposed to explain the formation of 3D nanostructures based on the various diffraction patterns, looking forward to give an insight for their dissimilar shape inflection during the self-assembly process.

Keywords: self-assembly, polypeptide, bio-polymer, crystalline polymer

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Authors: Adriana Souza M. Batista, Cláubia Pereira, Luiz O. Faria

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The irradiation of polymeric materials has received much attention because it can produce diverse changes in chemical structure and physical properties. Thus, studying the chemical and structural changes of polymers is important in practice to achieve optimal conditions for the modification of polymers. The effect of gamma irradiation on the crystalline structure of poly(vinylidene fluoride) (PVDF) has been investigated using differential scanning calorimetry (DSC) and X-ray diffraction techniques (XRD). Gamma irradiation was carried out in atmosphere air with doses between 100 kGy at 3,000 kGy with a Co-60 source. In the melting thermogram of the samples irradiated can be seen a bimodal melting endotherm is detected with two melting temperature. The lower melting temperature is attributed to melting of crystals originally present and the higher melting peak due to melting of crystals reorganized upon heat treatment. These results are consistent with those obtained by XRD technique showing increasing crystallinity with increasing irradiation dose, although the melting latent heat is decreasing.

Keywords: differential scanning calorimetry, gamma irradiation, PVDF, X-ray diffraction technique

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Authors: Abbas Nasir, Xiong Zhang, Sohail Ahmad, Yiping Cui

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Non-polar a-plane AlGaN epilayers of high structural quality have been grown on r-sapphire substrate by using metalorganic chemical vapor deposition (MOCVD). A graded non-polar AlGaN buffer layer with variable aluminium concentration was used to improve the structural quality of the non-polar a-plane AlGaN epilayer. The characterisations were carried out by high-resolution X-ray diffraction (HR-XRD), atomic force microscopy (AFM) and Hall effect measurement. The XRD and AFM results demonstrate that the Al-composition-graded non-polar AlGaN buffer layer significantly improved the crystalline quality and the surface morphology of the top layer. A low root mean square roughness 1.52 nm is obtained from AFM, and relatively low background carrier concentration down to 3.9×  cm^-3 is obtained from Hall effect measurement.

Keywords: non-polar AlGaN epilayer, Al composition-graded AlGaN layer, root mean square, background carrier concentration

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Authors: Chun-Ying Lee, Kun-Hsien Lee, Bor-Wei Wang

Abstract:

The process of post-supercritical CO₂ electroplating uses the electrolyte solution after being mixed with supercritical CO₂ and released to atmospheric pressure. It utilizes the microbubbles that form when oversaturated CO₂ in the electrolyte returns to gaseous state, which gives the similar effect of pulsed electroplating. Under atmospheric pressure, the CO₂ bubbles gradually diffuse. Therefore, the introduction of ultrasound and/or other agitation can potentially excite the CO₂ microbubbles to achieve an electroplated surface of even higher quality. In this study, during the electroplating process, three different modes of agitation: magnetic stirrer agitation, ultrasonic agitation and a combined mode (magnetic + ultrasonic) were applied, respectively, in order to obtain an optimal surface morphology and mechanical properties for the electroplated Ni coating. It is found that the combined agitation mode at a current density of 40 A/dm² achieved the smallest grain size, lower surface roughness, and produced an electroplated Ni layer that achieved hardness of 320 HV, much higher when compared with conventional method, which were usually in the range of 160 to 300 HV. However, at the same time, the electroplating with combined agitation developed a higher internal stress of 320 MPa due to the lower current efficiency of the process and finer grain in the coating. Moreover, a new control methodology for tailoring the coating’s mechanical property through its thickness was demonstrated by the timely introduction of ultrasonic agitation during the electroplating process with post supercritical CO₂ mixed electrolyte.

Keywords: nickel electroplating, micro-bubbles, supercritical carbon dioxide, ultrasonic agitation

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Authors: Tejinder Singh Sidhu

Abstract:

Hot corrosion has been recognized as a severe problem in steam-powered electricity generation plants and industrial waste incinerators as it consumes the material at an unpredictably rapid rate. Consequently, the load-carrying ability of the components reduces quickly, eventually leading to catastrophic failure. The inability to either totally prevent hot corrosion or at least detect it at an early stage has resulted in several accidents, leading to loss of life and/or destruction of infrastructures. A number of countermeasures are currently in use or under investigation to combat hot corrosion, such as using inhibitors, controlling the process parameters, designing a suitable industrial alloy, and depositing protective coatings. However, the protection system to be selected for a particular application must be practical, reliable, and economically viable. Due to the continuously rising cost of the materials as well as increased material requirements, the coating techniques have been given much more importance in recent times. Coatings can add value to products up to 10 times the cost of the coating. Among the different coating techniques, thermal spraying has grown into a well-accepted industrial technology for applying overlay coatings onto the surfaces of engineering components to allow them to function under extreme conditions of wear, erosion-corrosion, high-temperature oxidation, and hot corrosion. In this study, the hot corrosion performances of Ni-20Cr and Cr₃C₂-NiCr coatings developed by High Velocity Oxy-Fuel (HVOF) process have been studied. The coatings were developed on a Fe-based superalloy, and experiments were performed in an actual industrial environment of a coal-fired boiler. The cyclic study was carried out around the platen superheater zone where the temperature was around 1000°C. The study was conducted for 10 cycles, and one cycle was consisting of 100 hours of heating followed by 1 hour of cooling at ambient temperature. Both the coatings deposited on Fe-based superalloy imparted better hot corrosion resistance than the uncoated one. The Ni-20Cr coated superalloy performed better than the Cr₃C₂-NiCr coated in the actual working conditions of the coal fired boiler. It is found that the formation of chromium oxide at the boundaries of Ni-rich splats of the coating blocks the inward permeation of oxygen and other corrosive species to the substrate.

Keywords: hot corrosion, coating, HVOF, oxidation

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Authors: Ueda Honoka, Yasuo Hasegawa, Fumihiro Nishimura, Jae-Ho Kim, Susumu Yonezawa

Abstract:

Aqueous peroxotitanium acid solution prepared from the TiO₂ fluorinated by F₂ gas was used for the TiO₂ coating on glass fibrous filters in this study. The coating of TiO₂ on the surface of glass fibers was carried out at 120℃ and for 15 min ~ 24 h with aqueous peroxotitanium acid solution using a hydrothermal synthesis autoclave reactor. The morphology TiO₂ coating layer was largely dependent on the reaction time, as shown in the results of scanning electron microscopy and energy dispersive X-ray spectroscopy. Increasing the reaction times, the TiO₂ layer on the glass expanded uniformly. Moreover, the surface fluorination of glass fibers can promote the formation of the TiO₂ layer on the surface. The photocatalytic activity of prepared titania-coated glass fibrous filters was investigated by both the degradation test of methylene blue (MB) and the decomposition test of gaseous acetaldehyde. The MB decomposition ratio with fluorinated samples was about 95% for 30 min of UV irradiation time, and it was much higher than that (70%) with the untreated thing. The decomposition ratio (50%) of gaseous acetaldehyde with fluorinated samples was also higher than that (30%) with the untreated thing. Consequently, photocatalytic activity is enhanced by surface fluorination.

Keywords: aqueous peroxotitanium acid solution, titania-coated glass fibrous filters, photocatalytic activity, surface fluorination

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Authors: Kotaro Miura, Makoto Sakamoto, Yuji Tanabe

Abstract:

We focus on internal stress and displacement of an elastic axisymmetric contact problem for indentation of a layer-substrate body. An elastic layer is assumed to be perfectly bonded to an elastic semi-infinite substrate. The elastic layer is smoothly indented with a flat-ended cylindrical indenter. The analytical and exact solutions were obtained by solving an infinite system of simultaneous equations using the method to express a normal contact stress at the upper surface of the elastic layer as an appropriate series. This paper presented the numerical results of internal stress and displacement distributions for hard-coating system with constant values of Poisson’s ratio and the thickness of elastic layer.

Keywords: indentation, contact problem, stress distribution, coating materials, layer-substrate body

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Authors: I. Ruzaina, A. B. Rashid, M. S. Halimahton Zahrah, C. S. Cheow, M. S. Adi

Abstract:

This study was conducted to determine the potential of palm stearin (PS) as edible coating materials for fruits. The palm stearin was blended with 20-80% palm kernel olein (PKOo) and the properties of the blends were evaluated in terms of the slip melting point (SMP), solid fat content (SFC), fatty acid and triacylglycerol compositions (TAG), and polymorphism. Blending of PS with PKOo reduced the SMP, SFC, altered the FAC and TAG composition and changed the crystal polymorphism from β to mixture of β and β′. The changes in the physicochemical properties of PS were due to the replacement of the high melting TAG in PS with medium chain TAG in PKOo. From the analysis, 1:1 and 3:2 were the better PSPKOo blend formulations in slowing down the weight loss, respiration gases and gave better appearance when compared to other PSPKOo blends formulations.

Keywords: guava, palm stearin, palm kernel olein, physicochemical

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Authors: Feyza Tatar, Alime Cengiz, Dilara Sandikçi, Muhammed Dervisoglu, Talip Kahyaoglu

Abstract:

Blueberries are known for their bioactive properties such as high anthocyanin contents, antioxidant activities and potential health benefits. However, anthocyanins are sensitive to environmental conditions during processes. The objective of this study was to evaluate the effects of spray drying conditions on the blueberry microcapsules by Plackett-Burman experimental design. Inlet air temperature (120 and 180°C), feed pump rate (20% and 40%), DE of maltodextrin (6 and 15 DE), coating concentration (10% and 30%) and source of blueberry (Duke and Darrow) were independent variables, tested at high (+1) and low (-1) levels. Encapsulation efficiency (based on total phenol) of blueberry microcapsules was the dependent variable. In addition, anthocyanin content, antioxidant activity, water solubility, water activity and bulk density were measured for blueberry powders. The antioxidant activity of blueberry powders ranged from 72 to 265 mmol Trolox/g and anthocyanin content was changed from 528 to 5500 mg GAE/100g. Encapsulation efficiency was significantly affected (p<0.05) by inlet air temperature and coating concentration. Encapsulation efficiency increased with increasing inlet air temperature and decreasing coating concentration. The highest encapsulation efficiency could be produced by spray drying at 180°C inlet air temperature, 40% pump rate, 6 DE of maltodextrin, 13% maltodextrin concentration and source of duke blueberry.

Keywords: blueberry, microencapsulation, Plackett-Burman design, spray drying

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Authors: M. Bazrafshan, M. B. de Rooij, D. J. Schipper

Abstract:

Frictional hysteresis is the phenomenon in which mechanical contacts are subject to small (compared to contact area) oscillating tangential displacements. In the presence of adhesion at the interface, the contact repulsive force increases leading to a higher static friction force and pre-sliding displacement. This paper proposes a boundary element model (BEM) for the adhesive frictional hysteresis contact at the interface of two contacting bodies of arbitrary geometries. In this model, adhesion is represented by means of a Dugdale approximation of the total work of adhesion at local areas with a very small gap between the two bodies. The frictional contact is divided into sticking and slipping regions in order to take into account the transition from stick to slip (pre-sliding regime). In the pre-sliding regime, the stick and slip regions are defined based on the local values of shear stress and normal pressure. In the studied cases, a fixed normal force is applied to the interface and the friction force varies in such a way to start gross sliding in one direction reciprocally. For the first case, the problem is solved at the smooth interface between a ball and a flat for different values of work of adhesion. It is shown that as the work of adhesion increases, both static friction and pre-sliding distance increase due to the increase in the contact repulsive force. For the second case, the rough interface between a glass ball against a silicon wafer and a DLC (Diamond-Like Carbon) coating is considered. The work of adhesion is assumed to be identical for both interfaces. As adhesion depends on the interface roughness, the corresponding contact repulsive force is different for these interfaces. For the smoother interface, a larger contact repulsive force and consequently, a larger static friction force and pre-sliding distance are observed.

Keywords: boundary element model, frictional hysteresis, adhesion, roughness, pre-sliding

Procedia PDF Downloads 149