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1.
A comparative study of nanolaminate CrN/Mo2N and CrN/W2N as hard and corrosion resistant coatings
Marco Beltrami, Andraž Mavrič, Simone Dal Zilio, Mattia Fanetti, Gregor Kapun, Marco Lazzarino, Orfeo Sbaizero, Miha Čekada, 2013, izvirni znanstveni članek

Opis: Nanolaminate coatings (NLC) consisting of alternated CrN coupled with either cubic tungsten nitride (β-W2N) or molybdenum nitride (γ-Mo2N) were deposited on cold worked tool steel substrates using reactive DC reactive magnetron sputtering for improved mechanical and corrosion resistance. The CrN/γ-Mo2N and CrN/β-W2N nanolaminate systems were found to perform better than the corresponding single-layer systems, with both mechanical and electrochemical properties improving by decreasing the individual layer thickness from 100 to 5 nm. The CrN/β-W2N NLC combined the high hardness value of W2N with the low corrosion current of CrN. The CrN/γ-Mo2N NLC showed synergistic improvements consisting of both higher hardness and lower corrosion currents with respect to the constituent materials alone. The dependence of mechanical and corrosion properties on the bilayer period is discussed in terms of the grain size, residual stresses and texture of the constituent materials and the nanostructured character of the multilayer architecture.
Ključne besede: Nanolayered coatings, Transition metal nitrides, Sputtering, Nanoindentation, Corrosion resistance, Mechanical properties
Objavljeno v RUNG: 12.01.2023; Ogledov: 2065; Prenosov: 0
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2.
Applications of Chitosan as Food Packaging Materials
Patricia Cazón, Manuel Vazquez, 2019, recenzija, prikaz knjige, kritika

Opis: The interest in biopolymers has increased due to the depletion of the fossil fuel reserve and the environmental impact caused by the accumulation of non-biodegradable plastic-based packaging materials. Many biopolymers have been developed from food waste products to reduce this waste and, at the same time, to obtain new food packaging materials. Chitosan is thus an alternative to synthetic polymers, and a raw material for new materials. To assess the suitability of a material as a food packaging material, it is necessary to study their mechanical and permeability properties. Mechanical properties allow to predict the behaviour of films during transportation, handling and storage of packaged foods. Barrier properties play a key role in maintaining the food product quality. Properties values depend on the type of chitosan used. Mechanical and barrier properties of pure chitosan films are suitable for food packaging and active packaging. These properties can be modified by combining chitosan with other components such as plasticizers, other polysaccharides, proteins and lipids. These combinations adapt the properties of the final polymer to the needs of the food to extend its useful life, while maintaining quality properties of the food and the biodegradability of the polymer. Chitosan displays antimicrobial activity against a wide range of foodborne filamentous fungi, yeast, and gram-negative and gram-positive bacteria. This antimicrobial property and film-forming capacity has made chitosan the reference polymer to develop active packaging with the ability to inhibit the growth of microorganisms and improve food safety. Regarding the optical properties, pure chitosan films in the visible range show high transmittance values, being optically transparent films. This is an important parameter related to the acceptability of the films by the consumer. In addition, chitosan-based films exhibit remarkable UV absorbance, which allows to protect food from lipid oxidations induced by UV radiation.
Ključne besede: Film, Mechanical properties, Barrier properties, Antimicrobial, UV protect, Active food packaging
Objavljeno v RUNG: 14.12.2020; Ogledov: 3459; Prenosov: 0
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3.
Mechanical and barrier properties of chitosan combined with other components as food packaging film
Patricia Cazón, Manuel Vazquez, 2019, pregledni znanstveni članek

Opis: Chitosan is an alternative to synthetic polymers for food packaging. The mechanical and barrier properties of pure chitosan films are promising. Chitosan properties can be modified by combining chitosan with other components such as plasticizers, other polysaccharides, proteins and lipids. Here we review mechanical and barrier properties of composite films based on chitosan. The major points are: (1) compared with synthetic plastic films, an important limitation of chitosan-based films is their mechanical properties, especially their capacity to elongation; (2) chitosan is a polymer that allows an easy combination with other polysaccharides, plasticizers, proteins and lipids; (3) this allows to develop mixed components and modify the film properties according to the nature of the food to be packaged.
Ključne besede: Chitosan, Film, Mechanical properties, Barrier properties, Food packaging
Objavljeno v RUNG: 09.12.2020; Ogledov: 3448; Prenosov: 0
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4.
Environmentally Friendly Films Combining Bacterial Cellulose, Chitosan, and Polyvinyl Alcohol: Effect of Water Activity on Barrier, Mechanical, and Optical Properties
Patricia Cazón, Manuel Vazquez, Gonzalo Velazquez, 2019, izvirni znanstveni članek

Opis: The interest in developing new materials intended for food packaging based on bacterial cellulose is growing in the recent years. Flexible and transparent films from bacterial cellulose-chitosan-polyvinyl alcohol have shown excellent UV-barrier properties. However, this composite material interacts with ambient moisture modifying its water activity due to its hydrophilic nature. In this work, an extensive study was carried out to evaluate the changes in the properties of these films as a function of water activity. Moisture adsorption isotherm were described by the GAB method. Results showed the plasticizing effect of water molecules increasing the water vapour permeability of the samples from 1.86·10-12 to 1.17·10-11 g/m·s·Pa, the percentage of elongation from 3.25 to 36.55% and the distance to burst from 0.64 to 5.12 mm. The increase of the water activity dropped the tensile strength values from 74.76 to 38.56 MPa, Young’s modulus values from 3133.46 to 30.71 MPa and burst strength to 703.87 g. The values of the UV-barrier were maintained at the wide range of water activity. Consequently, water molecules do not affect the UV-barrier properties of the films.
Ključne besede: GAB model, moisture adsorption isotherms, plasticization, bacterial cellulose, mechanical properties, UV-barrier properties, moisture content
Objavljeno v RUNG: 09.12.2020; Ogledov: 3384; Prenosov: 0
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5.
Bacterial cellulose films: Evaluation of the water interaction
Patricia Cazón, Gonzalo Velazquez, Manuel Vazquez, 2020, izvirni znanstveni članek

Opis: Bacterial cellulose is a biopolymer that is gaining attention due to its 3D structure, higher purity, porosity and surface area. However, this material can interact with water molecules from the surrounding environment, resulting in alterations of its properties. Hence, the purpose of this study was to analyze the modifications on the mechanical, water vapor permeability and optical properties of bacterial cellulose films as a function of the water activity. Results indicated that water acted as a plasticizer, mainly affecting mechanical and water vapor permeability properties. The moisture adsorption isotherms allowed predicting the moisture content of the bacterial cellulose films at several relative humidity conditions. Values for tensile strength and burst strength ranged from 15.50 to 22.28 MPa and from 145.03–338.10 g, respectively. The elongation and the distance to burst ranged from 1.36 to 3.71 % and from 0.39 to 1.86 mm, respectively. These values increased due to the plasticizing effect of the water molecules. Water vapor permeability values ranged from 1.35·10−12 to 3.13·10-11 g/ m s Pa, showing a significant increase up to 0.48 of water activity. Bacterial cellulose films showed excellent UV-barrier properties in the different water activities evaluated.
Ključne besede: GAB model, Moisture adsorption isotherms, Bacterial cellulose, Mechanical properties, UV-barrier properties
Objavljeno v RUNG: 09.12.2020; Ogledov: 3425; Prenosov: 0
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6.
UV-protecting films based on bacterial cellulose, glycerol and polyvinyl alcohol: effect of water activity on barrier, mechanical and optical properties
Patricia Cazón, Gonzalo Velazquez, Manuel Vazquez, 2020, izvirni znanstveni članek

Opis: Biodegradable films based on bacterial cellulose, glycerol and polyvinyl alcohol are a new alternative to develop food packaging with the capac- ity to retard or inhibit the effect of UV radiation. However, these compounds are sensitive to moisture. Therefore, the purpose of this study was to evaluate the modifications of the mechanical, water vapor permeability and optical properties of these composite films depending on their water activity. Results showed that water molecules acted as a plasticizer agent, modifying the mechanical, water vapor perme- ability and optical properties of the developed films. However, an overplastification process took place at higher activity water, resulting in a weakness of film structure and decreasing drastically the elongation. The transmittance in the UV–VIS light region decreased when the activity water increased. No significant variations were observed in color, trans- parency or opacity properties.
Ključne besede: GAB model, Moisture adsorption isotherms, Plasticization, Bacterial cellulose, Mechanical properties, UV-barrier properties
Objavljeno v RUNG: 09.12.2020; Ogledov: 3226; Prenosov: 97
.pdf Celotno besedilo (552,03 KB)

7.
8.
EVALUATION OF MARINE SEDIMENTS FROM THE PORT OF LUKA KOPER FROM THE ENVIRONMENTAL PERSPECTIVE AND IN TERMS OF THEIR USABILITY IN THE BRICK INDUSTRY
Patrik Baksa, 2016, magistrsko delo

Opis: The majority of the world’s goods are transported over water and dredging is essential for the development of harbors and ports. Therefore, the management of dredged material is a worldwide issue. Due to its chemical and petrographic, mineralogical and homogeneity composition, marine sediments are an appropriate raw material to use in the brick industry. Marine sediments can serve as raw material for the production of clay blocks, roofing and ceramic tiles. Different analyses were carried out in order to determine if the dredged material from the Port of Koper is environmentally friendly and suitable to use in the brick industry. These analyses included: a chemical analysis, a mineralogical analysis, a particle size analysis and a chloride content (Cl-) analysis, and tests of firing in a gradient furnace. Furthermore, tests of mechanical properties, as well as tests of frost-resistance of the samples were carried out. On the basis of primary analyses and samples prepared in a lab, it was established that marine sediments from the Port of Koper without any additives are only conditionally suitable as a source material for producing brick products. In collaboration with Gorica brickworks (Goriške opekarne), a pilot production from a mixture of 60% component B from Gorica brickworks and 40% component A (marine sediments) from the Port of Koper was prepared. Different tests showed the mixture could be appropriate for brick production.
Ključne besede: marine sediments, recycling, clay bricks, chemical analysis, mechanical properties, brick production.
Objavljeno v RUNG: 05.09.2016; Ogledov: 6868; Prenosov: 278
.pdf Celotno besedilo (3,30 MB)

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