27,284 research outputs found

    Establishing acceptance criteria for the surface preparation of ships steel structures for coatings protection : diploma thesis

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    Najzastupljenija metoda zaštite brodskih čeličnih konstrukcija od korozije je primjenom premaza, a kvaliteta antikorozivne zaštite jedan je od osnovnih uvjeta za osiguranje dugotrajnosti konstrukcija. U ovom radu određeni su kriteriji prihvatljivosti određenih stupnjeva pripreme površine brodograđevnih limova tipa A za nanošenje sustava premaza. Na uzorke brodograđevnog čelika, koji su pripremljeni na različite stupnjeve čistoće, nanesen je sustav od tri premaza te su ispitana fizikalna, mehanička i antikorozivna svojstva sustava premaza prema važećim HR normama. Također, određene su emisije hlapivih organskih spojeva tijekom postupka antikorozivne zaštite.The most common method of corrosion protection of ship's steel structures is by coatings, and the quality of corrosion protection is one of the basic construction requirements for ensuring its’s longevity. In this paper, the criterion of acceptability of surface preparation degrees of ship-construction steel sheets (type A) before application of protective coating systems was established. A system of three coatings was applied on the surface of ship-construction steels samples which were prepared by different preparation methods and preparation grades. Afterwards physical, mechanical and anticorrosive properties of the protective coating system were tested according to the valid Croatian standards. Also, emissions of volatile organic compounds during the corrosion protection process were determined

    Re-investigating the structure-property relationship of the solid electrolytes Li <sub>3−x</sub>In<sub>1−x</sub>Zr<sub>x</sub>Cl<sub>6</sub> and the impact of In-Zr(iv) substitution

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    Chloride-based solid electrolytes are considered interesting candidates for catholytes in all-solid-state batteries due to their high electrochemical stability, which allows the use of high-voltage cathodes without protective coatings. Aliovalent Zr(iv) substitution is a widely applicable strategy to increase the ionic conductivity of Li3M(iii)Cl6 solid electrolytes. In this study, we investigate how Zr(iv) substitution affects the structure and ion conduction in Li3−xIn1−xZrxCl6 (0 ≤ x ≤ 0.5). Rietveld refinement using both X-ray and neutron diffraction is used to make a structural model based on two sets of scattering contrasts. AC-impedance measurements and solid-state NMR relaxometry measurements at multiple Larmor frequencies are used to study the Li-ion dynamics. In this manner the diffusion mechanism and its correlation with the structure are explored and compared to previous studies, advancing the understanding of these complex and difficult to characterize materials. It is found that the diffusion in Li3InCl6 is most likely anisotropic considering the crystal structure and two distinct jump processes found by solid-state NMR. Zr-substitution improves ionic conductivity by tuning the charge carrier concentration, accompanied by small changes in the crystal structure which affect ion transport on short timescales, likely reducing the anisotropy.RST/Storage of Electrochemical EnergyRID/TS/Instrumenten groe

    Preparation, modification, and clinical application of porous tantalum scaffolds

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    Porous tantalum (Ta) implants have been developed and clinically applied as high-quality implant biomaterials in the orthopedics field because of their excellent corrosion resistance, biocompatibility, osteointegration, and bone conductivity. Porous Ta allows fine bone ingrowth and new bone formation through the inner space because of its high porosity and interconnected pore structure. It contributes to rapid bone integration and long-term stability of osseointegrated implants. Porous Ta has excellent wetting properties and high surface energy, which facilitate the adhesion, proliferation, and mineralization of osteoblasts. Moreover, porous Ta is superior to classical metallic materials in avoiding the stress shielding effect, minimizing the loss of marginal bone, and improving primary stability because of its low elastic modulus and high friction coefficient. Accordingly, the excellent biological and mechanical properties of porous Ta are primarily responsible for its rising clinical translation trend. Over the past 2 decades, advanced fabrication strategies such as emerging manufacturing technologies, surface modification techniques, and patient-oriented designs have remarkably influenced the microstructural characteristic, bioactive performance, and clinical indications of porous Ta scaffolds. The present review offers an overview of the fabrication methods, modification techniques, and orthopedic applications of porous Ta implants

    Multistage Modulation Formation of Hydrophilic–Hydrophobic Boron Carbon Nitride Nanomaterials

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    Boron carbon nitride (BCN) ternary compounds are attractive due to their wide applications in adsorption, catalysis, protective coatings, etc. A simple way is provided to synthesize BCN materials with multistage modulation of hydrophilic–hydrophobic properties. Hydrophilic BCN nanoparticles with a contact angle of 31° and nearly superhydrophobic BCN sheets with a contact angle of 145° are obtained. The participation of a CuO additive in the synthesis process has the role of tuning morphologies, components, and properties of BCN materials. The addition of CuO would improve the hydrophobicity of BCN due to its microstructure with enhanced surface roughness. The interaction between melamine and boric acid on the surface of CuO(111) is investigated by first-principles calculations based on density functional theory (DFT). The tuned BCN materials have different photoelectric properties also, and their performance as photocatalysts has been verified in photocatalytic reactions for hydrogen from water. The achieved uniform hydrophilic BCN nanoparticles and hydrophobic BCN sheets have the potential for further practical applications

    Influence of Short-Pulse Microwave Radiation on Thermochemical Properties Aluminum Micropowder

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    The thermochemical properties of Al micropowder after exposure to microwave irradiation were investigated. The Al micropowder was exposed to microwave irradiation in air with a frequency of 2.85 GHz, a power density of 8 W/cm2, and a pulse duration of 25 ns and 3 µs. The thermochemical parameters of the irradiated metal powders were determined by the method of thermal analysis at the heating in air. It was found that an increase in the duration of microwave pulses and irradiation time leads to the thermal annealing of the metal particles, and the thermal processes of melting and sintering begin to dominate over non-thermal processes. The specific thermal effect of irradiated Al micropowder oxidation increases from 7744 J/g to 10,154 J/g in comparison with the unirradiated powder. The modeling of thermal heating processes of aluminum (Al) micropowder under the action of pulsed microwave radiation has been performed. It is shown that with an increase in the duration of microwave pulses and irradiation time, a significant heating of the Al micropowder occurs, leading to its melting and sintering. The results of modeling on the action of microwave radiation on the Al micropowder were compared with experimental results

    Drug Delivery Applications of Metal-Organic Frameworks (MOFs)

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    There has been substantial progress in the field of metal–organic frameworks (MOFs) and their nanoscale counterparts (NMOFs), in recent years. Their exceptional physicochemical properties are being constantly and actively exploited for various applications such as energy harvesting, gas storage, gas separation, catalysis, etc. Due to their porous framework, large surface area, tunability and easy surface functionalization, MOFs and NMOFs have also emerged as useful tools for biomedical applications, specifically for drug delivery. As drug carriers, they offer high drug loading capacity and controlled release at the target site. This chapter aims to give a panorama of the use of these MOFs as drug delivery agents. A brief overview of the structure and composition of MOFs, along with various methods and techniques to synthesize NMOFs suitable for drug delivery applications are mentioned. In addition, the most commonly employed strategies to associate drugs with these NMOFs are highlighted and methods to characterize them are also briefly discussed. The last section summarizes the applications of MOFs and NMOFs as carriers of therapeutic drugs, biomolecules, and other active agents

    Epoxy as Filler or Matrix for Polymer Composites

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    Epoxy is a widely used polymer because of its ease of processing, high adhesiveness, and high chemical resistance. Epoxy-based composites are commonly used in aerospace, automotive, and marine applications. The epoxy type, function, curing agent, and curing process are discussed in this chapter. Epoxy is used as either a filler or polymer matrix in composite applications. As a filler, the epoxy modification on the fiber is discussed. As a polymer matrix, the epoxy is reinforced by natural and synthetic fibers. The manufacturing process and the fabricated epoxy-based composites’ performance (e.g., mechanical and thermal properties) are investigated. The advantages and disadvantages of epoxy’s function are discussed and summarized. Epoxy modification is an effective approach to improve the composites’ performance

    Corrosion Resistance, Evaluation Methods, and Surface Treatments of Stainless Steels

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    Stainless steels are widely recognized and find applications in many engineering industries and companies due to their excellent properties including high resistance to corrosion as a result of their minimum 10.5% chromium content, exceptional strength and durability, temperature resistance, high recyclability, and easy formability. In the present book chapter, the basic concepts of stainless steel including its applications, classifications, and corrosion properties will first be discussed. Thereafter, their corrosion behaviour will then be explained. The various methods by which the corrosion resistance behaviour can be significantly improved including surface treatments such as coatings/electrodepositions, alloying, mechanical treatment, and others will be discussed in detail

    Environmental Persistence of SARS-CoV-2 and Disinfection of Work Surfaces in View of Pandemic Outbreak of COVID-19

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    Coronavirus disease 2019 (COVID-19) is primarily a respiratory illness, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The pandemic outbreak of SARS-CoV-2 across the world has been responsible for high morbidity and mortality, which emphasizes the role of the environment on virus persistence and propagation to the human population. Since environmental factors may play important roles in viral outbreaks, and the severity of the resulting diseases, it is essential to take into account the role of the environment in the COVID-19 pandemic. The SARS-CoV-2 may survive outside the human body from a few hours to a few days, depending upon environmental conditions, probably due to the relatively fragile envelope of the virus. The shedding and persistence of SARS-CoV-2 in the environment on animate and inanimate objects contributes to the risk of indirect transmission of the virus to healthy individuals, emphasizing the importance of various disinfectants in reducing the viral load on environmental surface and subsequently control of SARS-CoV-2 in the human population
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