Enhanced Oxidation of Nickel at Room Temperature by Low-energy Oxygen Implantation

The formation of oxide films on pure Ni surfaces by low energy oxygen ion-beam bombardment at room temperature was studied by X-ray photoelectron spectroscopy. Ion-induced oxidation is more efficient in creating thin NiO films on Ni surfaces than oxidation in oxygen atmosphere. The oxide thickness of bombarded samples is related to the penetration depth of oxygen ions in Ni and scales with the dose of implanted oxygen, Φ, as Φ1/6. This type of oxide growth is predicted theoretically for diffusion of Ni cations by doubly charged cation vacancies, which creation and mobility is greatly enhanced by ion-irradiation. This work is licensed under a Creative Commons Attribution 4.0 International License

A New Insight into Coating’s Formation Mechanism Between TiO2 and Alendronate on Titanium Dental Implant

Organophosphorus compounds, like bisphosphonates, drugs for treatment and prevention of bone diseases, have been successfully applied in recent years as bioactive and osseoinductive coatings on dental implants. An integrated experimental-theoretical approach was utilized in this study to clarify the mechanism of bisphosphonate-based coating formation on dental implant surfaces. Experimental validation of the alendronate coating formation on the titanium dental implant surface was carried out by X-ray photoelectron spectroscopy and contact angle measurements. Detailed theoretical simulations of all probable molecular implant surface/alendronate interactions were performed employing quantum chemical calculations at the density functional theory level. The calculated Gibbs free energies of (TiO2)10–alendronate interaction indicate a more spontaneous exergonic process when alendronate molecules interact directly with the titanium surface via two strong bonds, Ti–N and Ti–O, through simultaneous participation common to both phosphonate and amine branches. Additionally, the stability of the alendronate-modified implant during 7 day-immersion in a simulated saliva solution has been investigated by using electrochemical impedance spectroscopy. The alendronate coating was stable during immersion in the artificial saliva solution and acted as an additional barrier on the implant with overall resistivity, R ~ 5.9 MΩ cm2

Surface Functionalisation of Dental Implants with a Composite Coating of Alendronate and Hydrolysed Collagen: DFT and EIS Studies

The success of the osseointegration process depends on the surface characteristics and chemical composition of dental implants. Therefore, the titanium dental implant was functionalised with a composite coating of alendronate and hydrolysed collagen, which are molecules with a positive influence on the bone formation. The results of the quantum chemical calculations at the density functional theory level confirm a spontaneous formation of the composite coating on the titanium implant, ∆G*INT = -8.25 kcal mol-1. The combination of the results of X-ray photoelectron spectroscopy and quantum chemical calculations reveals the structure of the coating. The alendronate molecules dominate in the outer part, while collagen tripeptides prevail in the inner part of the coating. The electrochemical stability and resistivity of the implant modified with the composite coating in a contact with the saliva depends on the chemical nature of alendronate and collagen molecules, as well as their inter- and intramolecular interactions. The formed composite coating provides a 98%-protection to the implant after the 7-day immersion in the artificial saliva. From an application point of view, the composite coating could effectively promote osseointegration and improve the implant’s resistivity in contact with an aggressive environment such as saliva

Multiple exciton generation in 3D ordered networks of Ge quantum wires in alumina matrix

Thin films containing 3D-ordered semiconductor quantum wires offer a great tool to improve the properties of photosensitive devices. In the present work, we investigate the photogenerated current in thin films consisting of an interconnected 3D-ordered network of Ge quantum wires in an alumina matrix. The films are prepared using nitrogen-assisted magnetron sputtering co-deposition of Ge and Al2O3. We demonstrate a strong photocurrent generation in the films, much stronger than in similar films containing Ge quantum dots. The enhanced photocurrent generation is the consequence of the multiple exciton generation and the films’ specific structure that allows for efficient carrier transport. Thin film with the largest nitrogen content showed enhanced performance compared to other thin films with 1.6 excitons created after absorption of a single photon at an energy nearly equal to the double bandgap value. The bandgap value depends on the geometrical properties of the quantum wires, and it is close to the maximum of the solar irradiance in this case. In addition, we show that the multiple exciton generation is the most pronounced at the photon energy values equal to multiple values of the thin film bandgap

Positive socio-economic and ecological effects of biogas production by anaerobic digestion

Glavni proizvod anaerobne digestije je bioplin, koji je obnovljivo gorivo, a sporedni proizvod ovog procesa je digestat, koji se koristi kao gnojivo bogato hranjivim tvarima. Dodatni pozitivni učinci anaerobne digestije su razgradnja organskog otpada te smanjenje neugodnih mirisa i koncentracije patogenih mikroorganizama. Bioplin se uglavnom koristi za proizvodnju električne energije i topline, a u nekim slučajevima se pročišćava da bi se dobio biometan koji se koristi u mreži prirodnog plina, kao gorivo za motore s unutarnjim sagorijevanjem ili kao polazna kemikalija za kemijsku industriju. Zbog svega navedenog, razvoj proizvodnje bioplina ima pozitivne društveno-ekonomske i ekološke učinke. Bioplin proizveden u Hrvatskoj većinom se koristi za proizvodnju električne i toplinske energije u kogeneracijskim postrojenjima. Iako su u Hrvatskoj dostupne različite obnovljive sirovine koje bi se mogle iskoristiti za proizvodnju bioplina, njihov je potencijal do sada bio nedovoljno iskorišten. Kao sirovine za proizvodnju bioplina u nas se pretežno koriste gnojovka i nusproizvodi poljoprivrede, klaonica i prehrambene industrije. Racionalnijim korištenjem zemljišta i razvojem prehrambene industrije mogla bi se povećati količina poljoprivrednih ostataka i nusproizvoda koji nastaju preradom hrane. Usmjeravanjem i poticanjem korištenja ovih nusproizvoda za anaerobnu digestiju može se stimulirati brži razvoj proizvodnje bioplina u Hrvatskoj. Pored mogućeg povećanja vlastite proizvodnje električne energije i goriva, radi se o ekološki povoljnoj tehnologiji koja ima pozitivan društveno-ekonomski učinak.The main product of anaerobic digestion is biogas, which is a renewable fuel, and the by-product of this process is digestate, which is used as a nutrient-rich fertilizer. Additional positive effects of anaerobic digestion are the decomposition of organic waste and the reduction of unpleasant odors and the concentration of pathogenic microorganisms. Biogas is mainly used for the production of electricity and heat, and in some cases it is purified to obtain biomethane which is used in the natural gas network, as a fuel for internal combustion engines or as a starting chemical for the chemical industry. Due to all of the above, the development of biogas production has positive socio-economic and ecological effects. Biogas produced in Croatia is mostly used for the production of electricity and thermal energy at cogeneration plants. Although various renewable raw materials are available in Croatia that could be used for biogas production, their potential has been underutilized until now. Manure and by-products of agriculture, slaughterhouses and the food industry are mainly used as raw materials for the production of biogas in our country. More rational use of land and development of the food industry could increase the amount of agricultural residues and by-products resulting from food processing. Directing and encouraging the use of these by-products for biogas production can stimulate a faster development of biogas production in our Croatia. In addition to the possible increase in own production of electricity and fuel, it is an environmentally friendly technology that has a positive socio-economic effect

Grain-Size-Induced Collapse of Variable Range Hopping and Promotion of Ferromagnetism in Manganite La0.5Ca0.5MnO3

mong transition metal oxides, manganites have attracted significant attention because of colossal magnetoresistance (CMR)- a magnetic field-induced metal–insulator transition close to the Curie temperature. CMR is closely related to the ferromagnetic (FM) metallic phase which strongly competes with the antiferromagnetic (AFM) charge ordered (CO) phase, where conducting electrons localize and create a long range order giving rise to insulator-like behavior. One of the major open questions in manganites is the exact origin of this insulating behavior. Here we report a dc resistivity and magnetization study on manganite La1−xCaxMnO3 ceramic samples with different grain size, at the very boundary between CO/AFM insulating and FM metallic phases x = 0.5. Clear signatures of variable range hopping (VRH) are discerned in resistivity, implying the disorder-induced (Anderson) localization of conducting electrons. A significant increase of disorder associated with the reduction in grain size, however, pushes the system in the opposite direction from the Anderson localization scenario, resulting in a drastic decrease of resistivity, collapse of the VRH, suppression of the CO/AFM phase and growth of an FM contribution. These contradictory results are interpreted within the standard core-shell model and recent theories of Anderson localization of interacting particles

Ta2N3 nanocrystals grown in Al2O3 thin layers

Tantalum nitride nanoparticles (NPs) and cubic bixbyite-type Ta2N3 nanocrystals (NCs) were grown in (Ta–N+Al2O3)/Al2O3 periodic multilayers (MLs) after thermal treatment. The MLs were prepared by magnetron deposition at room temperature and characterized using grazing incidence small-angle X-ray scattering (GISAXS), X-ray reflectivity (XRR), grazing incidence X-ray diffraction (GIXRD), secondary ion mass spectrometry (SIMS) and X-ray photoelectron spectroscopy (XPS). We found amorphous tantalum nitride NPs at 600–800 °C, with a high degree of ordering along the surface normal and short-range ordering within the layers containing tantalum (metallic layers). At an even higher annealing temperature of 900 °C the NPs crystallize in the rare and relatively unexplored Ta2N3 phase. However, the environment, morphology and spatial ordering of the NCs depend on the thickness of the metallic layers. For 12 nm thick metallic layers, the Ta2N3 NCs have an average diameter of 6 nm and they are confined and short-range ordered within the metallic layers. When the metallic layers are thinner, the NCs grow over 20 nm in diameter, show no spatial ordering, while the periodic structure of the ML was completely destroyed. The results presented here demonstrate a self-assembly process of tantalum nitride NPs, the morphological properties of which depend on the preparation conditions. This can be used as a generic procedure to realize highly tunable and designable optical properties of thin films containing transition-metal nitride nanocrystals

Positive socio-economic and ecological effects of biogas production by anaerobic digestion

The main product of anaerobic digestion is biogas, which is a renewable fuel, and the by-product of this process is digestate, which is used as a nutrient-rich fertilizer. Additional positive effects of anaerobic digestion are the decomposition of organic waste and the reduction of unpleasant odors and the concentration of pathogenic microorganisms. Biogas is mainly used for the production of electricity and heat, and in some cases it is purified to obtain biomethane which is used in the natural gas network, as a fuel for internal combustion engines or as a starting chemical for the chemical industry. Due to all of the above, the development of biogas production has positive socio-economic and ecological effects. Biogas produced in Croatia is mostly used for the production of electricity and thermal energy at cogeneration plants. Although various renewable raw materials are available in Croatia that could be used for biogas production, their potential has been underutilized until now. Manure and by-products of agriculture, slaughterhouses and the food industry are mainly used as raw materials for the production of biogas in our country. More rational use of land and development of the food industry could increase the amount of agricultural residues and by-products resulting from food processing. Directing and encouraging the use of these by-products for biogas production can stimulate a faster development of biogas production in our Croatia. In addition to the possible increase in own production of electricity and fuel, it is an environmentally friendly technology that has a positive socio-economic effect

Pozitivni društveno-ekonomski i ekološki učinci proizvodnje bioplina anaerobnom digestijom

Glavni proizvod anaerobne digestije je bioplin, koji je obnovljivo gorivo, a sporedni proizvod ovog procesa je digestat, koji se koristi kao gnojivo bogato hranjivim tvarima. Dodatni pozitivni učinci anaerobne digestije su razgradnja organskog otpada te smanjenje neugodnih mirisa i koncentracije patogenih mikroorganizama. Bioplin se uglavnom koristi za proizvodnju električne energije i topline, a u nekim slučajevima se pročišćava da bi se dobio biometan koji se koristi u mreži prirodnog plina, kao gorivo za motore s unutarnjim sagorijevanjem ili kao polazna kemikalija za kemijsku industriju. Zbog svega navedenog, razvoj proizvodnje bioplina ima pozitivne društveno-ekonomske i ekološke učinke. Bioplin proizveden u Hrvatskoj većinom se koristi za proizvodnju električne i toplinske energije u kogeneracijskim postrojenjima. Iako su u Hrvatskoj dostupne različite obnovljive sirovine koje bi se mogle iskoristiti za proizvodnju bioplina, njihov je potencijal do sada bio nedovoljno iskorišten. Kao sirovine za proizvodnju bioplina u nas se pretežno koriste gnojovka i nusproizvodi poljoprivrede, klaonica i prehrambene industrije. Racionalnijim korištenjem zemljišta i razvojem prehrambene industrije mogla bi se povećati količina poljoprivrednih ostataka i nusproizvoda koji nastaju preradom hrane. Usmjeravanjem i poticanjem korištenja ovih nusproizvoda za anaerobnu digestiju može se stimulirati brži razvoj proizvodnje bioplina u Hrvatskoj. Pored mogućeg povećanja vlastite proizvodnje električne energije i goriva, radi se o ekološki povoljnoj tehnologiji koja ima pozitivan društveno-ekonomski učinak