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In this study, a nickel aluminide coating was obtained on CMSX-4 via a chemical vapor aluminizing (CVA) technique. The CVA coating process was carried out for 4 and 6 hours at 1070°C to examine the effects of CVA process time on the properties of the nickel aluminide coating. Heat treatment processes were subsequently applied to nickel aluminide-coated samples for 2 hours at 1050 and 1100°C to examine the effects of heat treatment temperature on the coating. The characterization of coated samples was carried out via SEM, EDS, XRD, GDOES and Vickers hardness analyses. The results showed that the increment in CVA process time induced an increase in inter-diffusion zone thickness due to the increased Ni outward diffusion from the CMSX-4 substrate. The additive layer of the four-hour CVA coating is composed of the δ-Ni2Al3 phase due to the dominance of Al inward diffusion. The phase transformation from δ-Ni2Al3 to the desired β-NiAl was observed in four-hour CVA coating structure subsequent to the heat treatment processes. However, the additive layer of six-hour CVA coating consists of the β-NiAl phase both before and after the heat treatment processes. Heat treatment processes increase the thickness of the coatings because they provide increased Al inward and Ni outward diffusion. The results of the Vickers hardness tests demonstrated that the heat treatment processes cause a decrease in the hardness of the additive layer of the four-hour CVA coating from 754 to 578 HV for heat treatment at 1050°C, and to 522 HV for heat treatment at 1100°C due to phase transformation phenomena.

© 2022 Elsevier LtdSupercapacitors are seemed to be one of the most promising choices as an energy storage system. However, there is still a gap in enhancing its energy density values and cyclic stabilities throughout a facile approach. Herein, it was aimed to propose a facile and effective way to fabricate high-energy supercapacitor electrode material based on reduced graphene oxide (rGO) nanostructure. Bearing this in mind, the bulk rGO powder was irradiated by various beam sources including Co-60, Am-241, Na-22, and Sr-90, and the resultant irradiated rGO samples were utilized as the electrode active material to fabricate symmetrical supercapacitor cells. The irradiated rGO samples were characterized both physicochemically and electrochemically. The physicochemical characterizations revealed that as a consequence of the irradiation, both GO and rGO nanosheets were formed in the resultant powder and the d-spacing of the graphene nanosheets were expanded. The highest electrochemical performance metrics were acquired for Sr-90 irradiated rGO electrode-based supercapacitor cell with the specific capacitance value of 585.44F.g−1 at 0.2 A.g−1, and outstanding capacitance retention performance of 97.14% for the 5000th CV cycles at 200 mV.s−1. Moreover, the energy density and power density values were comparable to other commercial energy storage systems such as lead-acid and nickel-metal hybrid batteries. Hence, it can be speculated that these pioneering breakthroughs could pave the way for cutting-edge high-energy supercapacitors based on rGO-derivatives with superior electrochemical performance metrics, as well as engineering of high-performance rGO-based materials to be employed in various energy applications.

The relationship between diffusion kinetics (interdiffusion coefficients, effective diffusion coefficients and activation energy) of the ion-exchanged float soda lime silicate (SLS) glass in the air and tin surfaces were determined by the Boltzmann-Matano and Green’s function. The compressive stresses generated by ion exchange were discussed from a different viewpoint that compressive stress depth profile gradient (CSG) measurements were performed on both surfaces and analysed in symmetrical depths using FSM 6000LE surface stress metre. This method is easy, practical and non-destructive compared to other methods. Thus, this technical method will importantly result in distinguishing the compressive stress difference of symmetrical depths between air and tin surfaces. The interrelationship among the concentration profiles, CSG and diffusion kinetics of ion-exchanged glasses were evaluated. The results showed that the K+ ion concentration was increased with temperature and time and was always higher on the air surface. Results found will provide a simple guideline for both the process control and the flatness of large-area glasses in strengthening of ion-exchanged SLS float glasses.

In this work, to investigate surface, corrosion and in vitro biological properties of the CuNPs-coated nanotube surfaces, antibacterial, bioactive and biocompatible nanoparticle-coated nanotube surfaces were produced on Ti6Al4V alloys by combined anodic oxidation (AO) and electrodeposition (ED) techniques for implant applications. All surfaces were characterized by SEM, EDX-mapping and -area, XRD, AFM and contact angle measurement techniques. The electrochemical and biological properties such as antibacterial activities, protein adsorption, ALP activity, hemolytic activity and cell viability of the surfaces were investigated in detail. Electrochemical corrosion resistance of CuNPs-coated nanotube surfaces were enhanced respect to uncoated Ti6Al4V alloy under simulated body fluid (SBF) conditions. Antibacterial properties, cell viability and ALP activity of CuNPs-coated nanotube surfaces were improved with compared to uncoated Ti6Al4V alloys. In addition, protein adsorption and hemolytic activity of CuNPs-coated nanotube surfaces were reduced. This work indicates a potential to precisely fabricate an antibacterial, bioactive and biocompatible CuNPs-coated nanotube surfaces on Ti6Al4V to fulfill orthopedic and dental implant needs by using combined AO and ED processes.

In this paper, the electronic stopping power and range calculations of radium-226, thorium-229 and uranium-236 isotopes, which are natural alpha emitters, were performed for the alpha particles in the 200 keV-10 MeV energy range. The effective charge approach based on the Bethe-Bloch theory for the stopping power, the continuous slowing down approach and the Simpson 1/3 method were used for calculation of the range. To this end, new electronic potential energy functions were primarily obtained by using the Lie group method for the target elements. For electronic charge density, relativistic atomic natural orbitals based on Gaussian type orbitals were selected. The results were compared with the existing data sets in the literature. The potential energy curves obtained were irregular at certain distances, but were quite close to that of the multi-atomic target systems. The stripping distances of the target atoms and the corresponding potential energy values were determined from the potential energy functions. It was observed that the stopping power and range values were generally compatible with the SRIM and ICRU 49 data at specific error rates. By adding some correction factors to the calculations, it is predicted that the discrepancies and the error rates may be reduced. The results acquired with this innovative work can be used in the interaction of charged particles with matter, applications related to alpha decay and shielding.

The aim of this study is to determine the mechanical properties differences in between the air and tin surfaces of thin soda-lime silicate float glasses that subjected to ion exchange using KNO3 salt bath. The ion exchange process was carried out at different times and temperatures. Chemically tempered glasses were investigated by means of compressive stress (CS), microhardness measurements, cracking probability, fractographic analysis, and flexural strength. The relationship among these properties was also discussed. The Weibull distributions of the samples were determined for a better understanding of the strength results. The AFM was used to determine the surface roughness. The weight of glass samples was increased gradually with increasing ion exchange time and temperature due to the inter-diffusion of K+–Na+ ions. The fracture load of chemically strengthened glass with ion exchange at 435 °C-8 h showed an increase of ~ 4.4 times that of untreated glass (raw glass), and it was selected as the optimum process conditions. The number of broken pieces was increased by increasing flexural strength, and smaller pieces were obtained with a great deal of branching. The air side always has greater compressive stress than the tin side. The maximum hardness value was reached with ion exchange at 435 °C for 12 h on a tin surface was 8.25 GPa with an increase of ~ 18% with respect to the raw glass. The crack resistance of chemically tempered glasses showed an increase in the range of 410–1290% and 241–1895% for air and tin surfaces, respectively. According to the AFM analysis, surface roughness of the samples after ion exchange did not change dramatically. SEM-EDS analysis revealed that the surface potassium concentration and diffusion depth increase with temperature.

Flooding is a vast problem in many parts of the world, including Europe. It occurs mainly due to extreme weather conditions (e.g. heavy rainfall and snowmelt) and the consequences of flood events can be devastating. Flood risk is mainly defined as a combination of the probability of an event and its potential adverse impacts. Therefore, it covers three major dynamic components: hazard (physical characteristics of a flood event), exposure (people and their physical environment that being exposed to flood), and vulnerability (the elements at risk). Floods are natural phenomena and cannot be fully prevented. However, their risk can be managed and mitigated. For a sound flood risk management and mitigation, a proper risk assessment is needed. First of all, this is attained by a clear understanding of the flood risk dynamics. For instance, human activity may contribute to an increase in flood risk. Anthropogenic climate change causes higher intensity of rainfall and sea level rise and therefore an increase in scale and frequency of the flood events. On the other hand, inappropriate management of risk and structural protection measures may not be very effective for risk reduction. Additionally, due to the growth of number of assets and people within the flood-prone areas, risk increases. To address these issues, the first objective of this thesis is to perform a sensitivity analysis to understand the impacts of changes in each flood risk component on overall risk and further their mutual interactions. A multitude of changes along the risk chain are simulated by regional flood model (RFM) where all processes from atmosphere through catchment and river system to damage mechanisms are taken into consideration. The impacts of changes in risk components are explored by plausible change scenarios for the mesoscale Mulde catchment (sub-basin of the Elbe) in Germany. A proper risk assessment is ensured by the reasonable representation of the real-world flood event. Traditionally, flood risk is assessed by assuming homogeneous return periods of flood peaks throughout the considered catchment. However, in reality, flood events are spatially heterogeneous and therefore traditional assumption misestimates flood risk especially for large regions. In this thesis, two different studies investigate the importance of spatial dependence in large scale flood risk assessment for different spatial scales. In the first one, the “real” spatial dependence of return period of flood damages is represented by continuous risk modelling approach where spatially coherent patterns of hydrological and meteorological controls (i.e. soil moisture and weather patterns) are included. Further the risk estimations under this modelled dependence assumption are compared with two other assumptions on the spatial dependence of return periods of flood damages: complete dependence (homogeneous return periods) and independence (randomly generated heterogeneous return periods) for the Elbe catchment in Germany. The second study represents the “real” spatial dependence by multivariate dependence models. Similar to the first study, the three different assumptions on the spatial dependence of return periods of flood damages are compared, but at national (United Kingdom and Germany) and continental (Europe) scales. Furthermore, the impacts of the different models, tail dependence, and the structural flood protection level on the flood risk under different spatial dependence assumptions are investigated. The outcomes of the sensitivity analysis framework suggest that flood risk can vary dramatically as a result of possible change scenarios. The risk components that have not received much attention (e.g. changes in dike systems and in vulnerability) may mask the influence of climate change that is often investigated component. The results of the spatial dependence research in this thesis further show that the damage under the false assumption of complete dependence is 100 % larger than the damage under the modelled dependence assumption, for the events with return periods greater than approximately 200 years in the Elbe catchment. The complete dependence assumption overestimates the 200-year flood damage, a benchmark indicator for the insurance industry, by 139 %, 188 % and 246 % for the UK, Germany and Europe, respectively. The misestimation of risk under different assumptions can vary from upstream to downstream of the catchment. Besides, tail dependence in the model and flood protection level in the catchments can affect the risk estimation and the differences between different spatial dependence assumptions. In conclusion, the broader consideration of the risk components, which possibly affect the flood risk in a comprehensive way, and the consideration of the spatial dependence of flood return periods are strongly recommended for a better understanding of flood risk and consequently for a sound flood risk management and mitigation., Hochwasser sind ein großes Problem und treten hauptsächlich aufgrund extremer Wetterbedingungen (z. B. starker Regen und Schneeschmelze) auf. Die Folgen von Hochwasserereignissen können verheerend sein. Das Konzept des Hochwasserrisikos beinhaltet die drei Komponenten: Gefahr, Exposition und Vulnerabilität. Hochwasser sind natürliche Phänomene und können nicht sicher verhindert werden. Das Risiko kann jedoch gesteuert und gemindert werden. Für ein solides Hochwasserrisikomanagement und die Minderung des Risikos ist eine ordnungsgemäße Risikobewertung und ein klares Verständnis der Hochwasserrisikodynamik erforderlich. Beispielsweise verursacht der anthropogene Klimawandel eine höhere Intensität der Niederschläge und einen Anstieg des Meeresspiegels und damit eine Zunahme des Ausmaßes und der Häufigkeit von Hochwasserereignissen. Andererseits können unangemessene strukturelle Schutzmaßnahmen, das Anwachsen von Vermögenswerten und eine steigende Anzahl betroffener Personen in den hochwassergefährdeten Gebieten das Risiko erhöhen. Um diese Probleme zu adressieren, besteht ein Ziel dieser Arbeit aus der Durchführung einer Sensitivitätsanalyse, um die Auswirkungen von Änderungen in jeder Hochwasserrisikokomponente auf das Gesamtrisiko und deren Wechselwirkungen untereinander zu verstehen. Eine angemessene Risikobewertung wird auch durch die korrekte k Darstellung des realen Hochwasserereignisses erreicht. Traditionell wird das Hochwasserrisiko bewertet, indem homogene Wiederkehrintervalle von Hochwasserspitzen im gesamten Einzugsgebiet angenommen werden. In der Realität sind Hochwasserereignisse jedoch räumlich heterogen, weshalb die traditionelle Annahme von Homogenität das Hochwasserrisiko insbesondere für große Einzugsgebiete falsch einschätzt. In dieser Arbeit wird die Bedeutung der räumlichen Abhängigkeit bei der Bewertung des Hochwasserrisikos in großem Maßstab in zwei Studien für verschiedene räumliche Skalen untersucht. In der ersten Untersuchung wird die „reale“ räumliche Abhängigkeit durch einen kontinuierlichen Risikomodellierungsansatz dargestellt. Zusätzlich werden die Risikoabschätzungen unter dieser modellierten Abhängigkeitsannahme mit zwei weiteren Annahmen zur räumlichen Abhängigkeit der Wiederkehrintervalle von Hochwasser verglichen: vollständige Abhängigkeit und Unabhängigkeit für das Elbeeinzugsgebiet in Deutschland. Die zweite Studie repräsentiert die „reale“ räumliche Abhängigkeit durch ein copula-basiertes Abhängigkeitsmodell. In ähnlicher Weise werden die drei verschiedenen Annahmen zur räumlichen Abhängigkeit der Wiederkehrintervalle von Hochwasser auf nationaler und kontinentaler Ebene verglichen. Außerdem wird der Einfluss von „Tail-dependences“ im Modell sowie von Hochwasserschutzmaßnahmen auf die räumliche Abhängigkeit untersucht. Die Ergebnisse dieser Arbeit unter Anwendung des Sensitivitätsanalyse-Frameworks zeigen, dass das Hochwasserrisiko aufgrund möglicher Änderungsszenarien dramatisch variieren kann. Der Einfluss des Klimawandels kann durch Änderungen anderer Risikokomponenten (z. B. Änderungen der Deichsysteme und der Vulnerabilität) überdeckt werden. Die Untersuchung zur räumlichen Abhängigkeit zeigen, dass der Schaden unter der Annahme vollständiger Abhängigkeit für Ereignisse mit Wiederkehrintervalle von mehr als ungefähr 200 Jahren im Elbeeinzugsgebiet 100 % größer als der Schaden unter modellierter Abhängigkeit. Die Annahme vollständiger Abhängigkeit überschätzt den 200-jährigen Hochwasserschaden, einen Referenzindikator für die Versicherungsbranche, um 139 %, 188 % und 246 % für Vereinigte Königreich, Deutschland und Europa. Die Fehleinschätzung des Hochwasserrisikos kann unter verschiedenen Annahmen von Abhängigkeit zwischen Oberlauf und Unterlauf eines Einzugsgebietes stark variieren. Zudem können „Tail-dependences“ im Modell sowie der Hochwasserschutz im Einzugsgebiet die Ergebnisse der Risikoabschätzung, unter verschiedenen Annahmen der räumlichen Abhängigkeit, beeinflussen. Abschließend wird eine umfangreiche Berücksichtigung der Risikokomponenten und insbesondere der räumlichen Abhängigkeit von Wiederkehrintervallen stark empfohlen, um das Hochwasserrisiko und damit dessen Management und Minderung besser verstehen zu können.

In this study, boron and lead compounds were coated on amorphous glass. Chemical bath deposition method was used for coating. Films were produced in the baths with pH: 9-12. Some of the produced films were directly analyzed, whereas some of them were analyzed after annealing at 500 degrees C. The characterization of the films was performed by XRD, while surface characterization was performed by SEM and EDX analysis. The study was finalized by performing radioactive analyzes of the films. Am-241 isotopes were used as the radioactive source for Alpha rays, Co-60 for Gamma rays and Sr-90 for Beta rays. According to the results, it was found that the films produced at pH: 9-10 had low optical transmittance but were able to absorb alpha and beta particles considerably. However, despite the high optical permeability of the films produced at pH: 11-12, their absorption of radioactive particles was found to be lower than the others. As a result, it was found that the absorption characteristics of the films produced at baths with different pH depend on the relative rate of boron and lead elements found on the surface.

Bozkurt, Ahmet/0000-0002-3163-0131 WOS: 000433206800017 In this study, we have performed the calculations stopping power, depth dose, and range verification for proton beams using dielectric and Bethe-Bloch theories and FLUKA, Geant4 and MCNPX Monte Carlo codes. In the framework, as analytical studies, Drude model was applied for dielectric theory and effective charge approach with Roothaan-Hartree-Fock charge densities was used in Bethe theory. In the simulations different setup parameters were selected to evaluate the performance of three distinct Monte Carlo codes. The lung and breast tissues were investigated are considered to be related to the most common types of cancer throughout the world. The results were compared with each other and the available data in literature. In addition, the obtained results were verified with prompt gamma range data. In both stopping power values and depth-dose distributions, it was found that the Monte Carlo values give better results compared with the analytical ones while the results that agree best with ICRU data in terms of stopping power are those of the effective charge approach between the analytical methods and of the FLUKA code among the MC packages. In the depth dose distributions of the examined tissues, although the Bragg curves for Monte Carlo almost overlap, the analytical ones show significant deviations that become more pronounce with increasing energy. Verifications with the results of prompt gamma photons were attempted for 100-200 MeV protons which are regarded important for proton therapy. The analytical results are within 2%-5% and the Monte Carlo values are within 0%-2% as compared with those of the prompt gammas.

The goal of this study was to calculate the range values of alpha particles in bone, MS20 tissue substitute, and muscle targets using different approach methods. The range values were calculated using Gauss quadrature, Simpson 1/3, and trapezoidal numerical integration methods in continuous slowing-down approximation (CSDA). Overall, the Gauss quadrature method gave the best CSDA range values for the target materials. These results will be conducive to studies involving the interaction of radiation with biological materials.

A highly well-ordered TiO2 (titanium dioxide) nanotube arrays were prepared at different voltages (20 V, 30 V, 40 V, 50 V, 60 V, 80 V and 100 V) for 60 min on Ti6Al4V (titanium alloy) substrate in the ammonium fluoride-containing ethylene glycol electrolyte by a DC (direct current) power supply through AO (anodic oxidation) technique. The anatase-based TiO2 phases were observed at post-heat treatment although the titanium phase was obtained on TiO2 nanotube surfaces at post-production AO technique. Up to 40 V, the nanotube structures were uniformly distributed and the surface roughness increased. The roughness and thickness of the nanotube surfaces were measured as 7.57 nm – 47.08 nm and 0.18 μm – 0.83 μm, respectively. The nanotube array surfaces indicated hydrophobic properties compared to uncoated titanium surface. The hardness and elastic modulus of plain titanium alloy and TiO2 nanotube surfaces were investigated under a Berkovich indenter by a nanoindentation test device. The elastic modulus values of TiO2 nanotube surfaces were close to bone structure with respect to plain Ti6Al4V substrate. Moreover, hardness values of nanotube surfaces were measured between ~203.7 MPa and ~ 932.2 MPa. The adhesion properties such as critical load of the nanotube surfaces were investigated by micro scratch tester. Adhesion strengths of the nanotube surface were obtained between ~2.2 N and ~4.6 N.

AKTAS, SITKI/0000-0002-9143-6752; Aktug, Salim Levent/0000-0001-7755-0279; DURDU, SALIH/0000-0002-6288-0926; ALTINKOK, ATILGAN/0000-0002-0548-4361 WOS: 000417963600015 In this study, at the first step, the commercial pure zirconium (Zr) was coated by micro arc oxidation (MAO) technique in solution, consisting of calcium acetate and beta-calcium glycerophosphate salt. Then, silver (Ag) thin film layer that had an average thickness of 20 nm was deposited on the MAO coated bioceramic surface by thermal evaporation (TE) technique. The phase structure, surface morphology, elemental composition and wettability of both Ag-coated and uncoated MAO coatings were characterized by powder-XRD and TF-XRD, SEM, EDX-mapping and contact angle goniometer, respectively. The powder and TF-XRD results indicated that cubic-zirconia, calcium zirconate and hydroxyapatite were detected on the surface after MAO and MAO + TE processes. Both coating surfaces were rough and porous. After TE process, Ag was homogeneously distributed on the surface. The Ag-based coated surface was hydrophobic compared to MAO surface. In vitro properties such as bioactivity and anti-bacterial tests of both coatings were investigated by soaking test in simulated body fluid (SBF) and bacterial formation, respectively. The apatite-forming abilities of both coatings were evaluated after soaking in SBF up to 10 days. After soaking process, secondary apatite layer formed on the Ag-based MAO coatings was more homogenous and denser than one on the MAO surface, whereas secondary apatite structure was completely formed on both surfaces. Therefore, the bioactivity of the Ag-based MAO surfaces was significantly improved compared to the uncoated MAO coatings under SBF conditions. For 10 Gram-positive and Gram-negative bacteria, the bacterial adhesion of the Ag-based MAO coatings was considerably reduced compared to plain MAO surface. Scientific and Technological Research Council of Turkey (TUBITAK MAG Project) [113M162] A part of this work (MAO production) was supported by the Scientific and Technological Research Council of Turkey (TUBITAK MAG Project - 113M162).

The goal of this work is to offer an alternative method to the available literature on determining the energy loss of CZTS thin films. For this purpose, thin CZTS film structures were first produced by sol-gel method and then the RBS spectrum was received with RBS detector irradiating this structure with 3.034 MeV proton beams in a microbeam chamber. The energy calibration was implemented to this spectrum, where the it was fitted with SIMNRA program. In the RBS spectrum of the thin film generated, a method for the calculation of energy loss was used for the position and energy width analysis of the corresponding peaks and a polynomial fit was obtained from the stopping power of the CZTS thin film by making certain approaches. Also, the effective charge approach that we used in our previous studies for the stopping power was employed with atomic natural orbitals and it was founded that the results were close to each other at certain error rates. The data obtained from this study will inspire the future studies on the interaction of radiation with matter., Bu çalışmanın amacı, CZTS ince filmlerinin enerji kaybını belirlemek için mevcut literatüre alternatif bir yöntem sunmaktır. Bu amaçla, ince CZTS film yapıları ilkönce sol-gel yöntemiyle üretildi ve daha sonra bu yapı bir mikroışın çemberinde 3.034 MeV protonlarla ışınlanarak RBS detektörüyle RBS spektrumu alındı. SIMNRA programıyla fit edilen bu spektruma enerji kalibrasyonu uygulandı. Üretilen ince filmlerin RBS spektrumunda, ilgili piklerin konum ve enerji genişliği analizinden enerji kaybı hesaplaması için bir yöntem kullanıldı ve belirli yaklaşımlar yaparak CZTS ince filmin durdurma gücünden bir polinom fit elde edildi. Ayrıca, durdurma gücü için önceki çalışmalarda kullandığımız etkin yük yaklaşımı atomik doğal orbitaller ile kullanıldı ve sonuçların belirli hata oranlarında birbirine yakın oldukları bulundu. Bu çalışmadan elde edilen veriler maddeyle radyasyonun etkileşmesi üzerine yapılacak çalışmalara ilham verecektir.

Hydroxyapatite (HA, Ca 10 (PO 4 ) 6 (OH) 2 ) based coatings are used in biomaterial applications and biomedical industrial applications due to its bioactive and biocompatible properties. In this study, commercially pure zirconium was coated in the solution consisting of calcium acetate (CA, (CH 3 COO) 2 Ca)) and β-calcium glycerophosphate (β-Ca-GP, (β-C 3 H 5 (OH 2 )PO 4 Ca)) by micro arc oxidation (MAO) in a single-step process for 1, 10 and 30 min duration times to produce HA-based coatings. The phase structures, surface morphologies, functional groups of molecules, chemical composition of surface and the binding energies of atoms on the coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS), respectively. Zirconium (Zr), monoclinic and cubic zirconium oxide (ZrO 2 ), cubic calcium zirconium oxide (Ca 0.15 Zr 0.85 O 1.85 ), orthorhombic calcium zirconium oxide (CaZrO 3 ) and HA phases on the coatings were detected by XRD analysis. The strongest intensity of crystal HA was also observed in XRD for the coating produced at 30 min. The surface morphologies of coatings produced by MAO method at 1 min have very porous structures because of the existence of micro discharge channels during the process. The surface coatings morphologically have HA microstructure owing to the crystallization of HA particles at 10 min and the existence of growing HA particles in MAO process at 30 min. The HA phase is confirmed by v 3 (PO 4 −3 ) and v s (OH − ) FTIR band assignments in ATR-FTIR and by the binding energies of Ca2p, P2p and O1s in XPS for coating produced at 30 min.

Aktug, Salim Levent/0000-0001-7755-0279; DURDU, SALIH/0000-0002-6288-0926 WOS: 000390967200118 PubMed: 27987655 In the present work, hydroxyapatite (HAP)-based plasma electrolytic oxide (PEO) coatings were produced on zirconium at different current densities in a solution containing calcium acetate and beta-calcium glycerophosphate by a single step. The phase structure, surface morphology, functional groups, thickness and roughness of the coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), eddy current method and surface profilometer, respectively. The phases of cubic-zirconia, calcium zirconate and HAP were detected by XRD. The amount of HAP and calcium zirconate increased with increasing current density. The surface of the coatings was very porous and rough. Moreover, bioactivity and biocompatibility of the coatings were analyzed in vitro immersion simulated body fluid (SBF) and ME (3-(4,5-dimethyl thiazol-2yl)-2,5-diphenyl tetrazolium bromide) assay, hemolysis assay and bacterial formation. The apatite -forming ability of the coatings was evaluated after immersion in SBF up to 28 days. After immersion, the bioactivity of HAP -based coatings on zirconium was greater than the ones of uncoated zirconium and zirconium oxide-based surface. The bioactivity of PEO surface on zirconium was significantly improved under SBF conditions. The bacterial adhesion of the coatings decreased with increasing current density. The bacterial adhesion of the coating produced at 0.370 A/cm(2) was minimum compared to uncoated zirconium coated at 0.260 and 0.292 A/cm(2). The hemocompatibility of HAP-based surfaces was improved by PEO. The cell attachment and proliferation of the PEO coating were better than the one of uncoated zirconium according to MIT assay results. (C) 2016 Elsevier B.V. All rights reserved. Scientific and Technological Research Council of Turkey (TUBITAK MAG)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [113M162, 1001] This work was supported by the code of 1001 of the Scientific and Technological Research Council of Turkey (TUBITAK MAG Project 113M162).

In this study, Ni-B metal matrix composite coatings reinforced with hexagonal boron nitride (hBN) nanoparticles were fabricated on 304L steel substrate with electrochemical deposition method. The volume fraction of hBN was 6-26%. The phase and morphological characteristics were determined via XRD and FE-SEM, respectively. Ni-B/hBN composite coatings were irradiated with Am-241, Sr-90 and Co-60 radioactive sources, which are typical alpha, beta and gamma-ray sources, respectively. Percent absorption rates were acquired according to the hBN volume fractions of each irradiated sample. Accordingly, it was found that the absorption rates also raised as the volume fractions of the hBN in the coating increased. In order to control the findings, stopping power and range values were procured with SRIM and ESTAR databases. Similar to the absorption rate, increasing volume fractions increased the stopping power and decreased the range values. Nuclear radiation shielding properties of metal matrix composite materials are presented here for the first time. This study revealed the importance of Ni-B/hBN composite coatings in terms of radiation shielding properties.

Plasma electrolytic oxidation (PEO) treatment is carried out to improve the mechanical properties of the open-cell aluminum foams. Two different pore densities of open-cell aluminum foams (20 PPI and 40 PPI) were treated in an alkaline solution with a low silicate concentration at different current densities and times. The microstructure and phase composition of samples were investigated by scanning electron microscope (SEM) and X-ray diffraction (XRD) respectively. The coating thickness of the struts was increased with the increasing of treatment time. Ceramic coatings were composed of corundum, gamma alumina, and mullite phases. It was found that the compressive properties of the pore density of 20 PPI composite foams were significantly improved by using PEO treatment.

AKTAS, SITKI/0000-0002-9143-6752; yalcin, emine/0000-0002-5280-5375; DURDU, SALIH/0000-0002-6288-0926; Aktug, Salim Levent/0000-0001-7755-0279 WOS: 000488409900006 Ag (silver)-based bioceramic coatings were fabricated on AZ31 Mg alloy by combining the MAO (micro-arc oxidation) and PVD (physical vapor deposition) methods. As a first step, AZ31 Mg surfaces were coated using MAO using a solution consisting of sodium silicate and potassium hydroxide. As a second step, an Ag layer was accumulated on the MAO surfaces using the PVD method. The XRD patterns thus obtained demonstrated the presences of Mg (magnesium), Si (silicon), M2SiO4 (forsterite) and MgO (periclase) on the Ag-deposited MAO surfaces. The elemental or compound structures of Ag were not detected due to the homogeneous distribution of a trace amount of Ag on the surfaces. Both coatings' surfaces were porous due to the existence of discharge channels. All elements were found to be uniformly distributed across the entirety of the surfaces. The Ag-deposited MAO surfaces were found to have hydrophobic properties with respect to plain MAO surfaces. Newly formed layers consisted of Ca-15(SiO4)(6)(PO4)(2) (calcium silicate phosphate), Ca-3(PO4)(2) (tuite) and Ca-10(PO4)(6)(OH)(2) (hydroxyapatite) as produced on plain MAO and Ag-deposited MAO surfaces by immersion in SBF (simulated body fluid); these layers were more homogeneous on Ag-deposited MAO coatings than ones on plain MAO. Also, for E. coli (Escherichia coli) and S. murus (Staphylococcus moms) bacteria, the numbers of active bacterial colonies on Ag-deposited MAO surfaces were significantly reduced with respect to plain MAO surfaces.

Durdurma gücü, hedef içerisindeki elektronlar ve çekirdeğin Coulomb alanı etkileşmesi nedeniyle yüklü parçacıkların birim uzunluk başına ortalama enerji kaybıdır. Durdurma gücünün atom fiziği, nükleer fizik ve uygulamaları, radyasyon dozimetrisi gibi birçok alanlarda önemli uygulamaları vardır. Bu çalışmanın amacı 1 keV-1 GeV enerjili protonlar için Z=2-54 atom numaralı elementlerin Bethe-Bloch teorisine dayalı etkin yük yaklaşımı yöntemi kullanılarak çarpışma durdurma gücünü hesaplamaktır. Bunun için öncelikle hedef elementlerin etkin yük, etkin ortalama uyarılma enerjileri ve potansiyel enerji fonksiyonları belirlendi. Elektronik yük yoğunluğu için Roothaan-Hartree-Fock atomik dalgafonksiyonları seçildi ve hedef atomların etkin yükünün protonların enerjisiyle değişimi incelendi. Ardından elde edilen hedef atomların etkin yükleri kullanılarak çarpışma durdurma gücü değerleri hesaplandı. Atom numarası ve gelen protonların enerjisi arttıkça etkin yük değerlerinin arttığı görüldü. Durdurma gücü değerlerinin ise atom sayısı arttıkça azaldığı ve durdurma gücüne ait maksimum noktalarının yüksek enerjilere doğru kaydığı belirlendi. Hedef elementlerden karbon atomu için hesaplanan durdurma gücü değerleri literatürde mevcut ICRU 49, SRIM, CasP ve Janni’nin verileriyle karşılaştırıldı. Sonuçların belirli hata oranlarında literatür verileriyle oldukça uygun oldukları gözlendi. Ayrıca bu çalışmada kullanılan etkin yük yaklaşımının 1 MeV’den düşük enerjilerde de kullanılabileceği anlaşıldı., The stopping power is the average energy loss per unit length of charged particles due to the interaction with the Coulomb field of electrons in target and nucleus. Stopping power has important applications in many areas such as atomic physics, nuclear physics and applications, radiation dosimetry. The aim of this study is to calculate the collision stopping power of Z=2-54 atomic elements by using the effective charge approach based on Bethe-Bloch theory for the 1 keV-1 GeV energy protons. For this purpose, the effective charge, effective mean excitation energies and potential energy functions of the target elements were firstly determined. For the electronic charge density, Roothaan-Hartree-Fock atomic wavefunctions were selected and the change of the effective charge of the target atoms with the energy of the protons was examined. Then, the collision stopping power values were calculated by using the obtained effective charges of the target atoms. It was seen that as the atomic number and the energy of the incoming protons increased, effective charge values ascended. It was determined that the stopping power values decreased as the number of atoms increased and the maximum points of stopping power shifted towards high energies. The calculated stopping power values for the carbon atom from the target elements were compared with the data of the ICRU 49, SRIM, CasP and Janni available in the literature. It was observed that the results were quite appropriate with the literature data at certain error rates. In addition, it is understood that the effective charge approach used in this study can be used in energies less than 1 MeV.

AKTAS, SITKI/0000-0002-9143-6752; DURDU, SALIH/0000-0002-6288-0926; Aktug, Salim Levent/0000-0001-7755-0279 WOS: 000468174200009 In this study, porous and rough bioceramic structures were coated on commercial pure Zr by PEO (plasma electrolytic oxidation). Then, Cu was deposited onto the PEO surfaces without any morphological changing by TE (thermal evaporation). Mainly, meta-stable Ca0.15Zr0.85O1.85 (calcium zirconium oxide), cubic-ZrO2 (zirconia) and perovskite-CaZrO3 (calcium zirconate) were observed on the surfaces by powder-XRD (powder X-ray diffraction) and TF-XRD (thin film XRD) analyses as the phases of Zr and Cu-2(P2O7) (copper pyrophosphate) were detected as a trace amount on the Cu-deposited PEO surface. The average thicknesses of the PEO coating and TE layer were measured as approximately 21.8 +/- 2.4 mu m and 20 nm, respectively. The Cu-deposited PEO surfaces indicated superhydrophobic character while the PEO surface exhibited hydrophilic behavior. The apatite-forming abilities on both coatings were evaluated by surface and cross-sectional SEM (scanning electron microscopy) and surface EDS (energy dispersive X-ray spectroscopy)-mapping analyses at post-soaking in SBF (simulated body fluid) up to 10 days. However, apatite formed on the Cu-deposited PEO surfaces was thicker and more homogenous than the PEO surface. Thus, in vitro bioactivity was considerably improved by Cu-deposition on the PEO. In vitro microbial adhesion test of both surfaces was investigated by bacterial adhesions for Gram positive and Gram negative bacteria. The bacterial adhesions on the Cu-deposited PEO surfaces were lower compared to the PEO surfaces for all bacteria types. TUBITAK, TurkeyTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [-113M162] A part of this work (PEO production) was supported by TUBITAK, Turkey (Project Number -113M162).

Aktug, Salim Levent/0000-0001-7755-0279; DURDU, SALIH/0000-0002-6288-0926 WOS: 000365367000029 In this study, AZ31 Mg alloys produced by twin roll casting (TRC) were coated by plasma electrolytic oxidation (PEO) in solution of potassium hydroxide (KOH) and different concentration of sodium metasilicate pentahydrate (Na2SiO3 center dot 5H(2)O) electrolytes at 0.140 A/cm(2) current density for 60 min. The phase structure, morphology, hardness, adhesion strength, surface roughness and wear resistance of the PEO coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), micro-hardness tester, micro-scratch tester, profilometer and tribometer, respectively. The XRD results indicated that Forsterite (Mg2SiO4) and Periclase (MgO) phases were formed on the surface of the coated magnesium alloys. The surface of the coatings is very porous and rough due to the presence of micro-discharges through PEO process. It was seen that the wear rate, hardness and surface roughness of the coatings were increased when the concentration of Na2SiO3 center dot 5H(2)O electrolyte was increased. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved. TUBITAK-MAG projectTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [107M476] This work was supported by the number of 107M476 TUBITAK-MAG project.

AKTAS, SITKI/0000-0002-9143-6752; Aktug, Salim Levent/0000-0001-7755-0279; DURDU, SALIH/0000-0002-6288-0926 WOS: 000437391300053 In this study, as the first step, the bioceramic coatings were fabricated on Zr (commercial pure zirconium) in calcium acetate and beta-calcium glycerophosphate salt-based electrolyte by MAO (micro arc oxidation). And then, as the second step, the Zn (zinc) thin film layer measured an average thickness of 5 nm was coated on the MAO surface by TE (thermal evaporation). The phase composition, surface and cross sectional morphology, elemental composition and wettability of the MAO and Zn-based MAO coatings were analyzed by powder-XRD and TF-XRD, SEM, EDS-mapping and contact angle goniometer, respectively. The phases of cubic-ZrO2, perovskite-CaZrO3 and HA (hydroxyapatite) were observed on the surfaces by powder and TF-XRD analyses. The morphology of the MAO surface was not changed by TE although the chemistry of it was different from the MAO surface. The surfaces of both coatings were porous and rough. The Zn was uniformly deposited through the whole surface. After TE process, the wettability of the surface decreased and the Zn-based surface exhibited superhydrophilicity compared to MAO surface. In vitro bioactivity test of both coatings were investigated by immersion test in SBF (simulated body fluid) up to 10 days. The bone like apatite layer (secondary apatite) on the Zn-based bioceramic surface was compact and uniform compared the one on the MAO surface although it was completely propagated through both surfaces. In vitro anti-bacterial test of both coatings were carried out by microbial adhesion for Gram positive and Gram negative bacteria. It was observed that the microbial adhesions of the Zn-based bioceramic surfaces were lower than ones of the MAO bioceramic surfaces for all Gram-positive and Gram-negative bacteria. Scientific and Technological Research Council of Turkey (TUBITAK MAG Project) [113M162] A part of this work (MAO production) was supported by the Scientific and Technological Research Council of Turkey (TUBITAK MAG Project - 113M162).

Composites of nano-hydroxyapatite (HA) – titania (TiO 2 ) with or without calcium fluoride (CaF 2 ) were synthesized and sintered at 900 °C, 1100 °C, and 1300 °C. The composites were studied to assess the effect of CaF 2 addition on the sinterability, structure, functional groups, morphology and mechanical behavior of the material. The resultant composites were characterized by XRD, ATR-FTIR, SEM and microhardness measurement, respectively. It was seen that the addition of CaF 2 into HA–TiO 2 composites enhanced the densification via reducing the porosity of the composites. The XRD results showed that as the amount of TiO 2 in the composites was increased, transformation of HA into tricalcium phosphate (TCP) was favored due to the formation of calcium titanate (CaTiO 3 ). On the other hand, the addition of CaF 2 into the composites led to the shrinkage of unit cell volume of HA due to the substitution of F − ions into HA and suppressed the decomposition of HA in these composites. Moreover, the addition of CaF 2 also improved the microhardness of the composites.

In this study, hydroxyapatite and calcium apatite-based bio-ceramic composite coatings were produced on Ti6Al4V alloy by plasma electrolytic oxidation (PEO) in the electrolyte consisting of calcium acetate (CA) and β-calcium glycerophosphate (β-Ca-GP) for different treatment times. Coating thickness, phase structure, coating morphology of the cross section, elemental composition, adhesion strength, wear resistance and tribological property of the PEO coatings were analyzed by eddy current method, X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDX mapping), micro scratch tester and tribometer, respectively. The average thickness of the coatings varied from 28 to 52 µm with increasing times. The XRD results indicated that anatase (TiO 2 ), rutile (TiO 2 ), TiP 2 , TCP (Ca 3 (PO 4 ) 2 ), perovskite – CaTiO 3 and hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 ) phases were formed on the Ti6Al4V alloy after PEO. According to the EDS mapping results, uniform Ca and P elemental distributions were observed on the surface of PEO coatings. The adhesion strengths of the PEO coatings enhanced with increasing time. The wear resistances and tribological properties of the PEO coatings were greater than those of the uncoated Ti6Al4V alloys, and they were increased with increased time.

Pure hydroxyapatite (HA), HA and partially stabilized zirconia composites (PSZ) with YF 3 and HA–PSZ composite containing 5 wt% PSZ without YF 3 were sintered in air at 900 °C, 1100 °C and 1300 °C for 1 h. The reactions and transformation of the phases in the composites were determined by X-ray diffraction. All the composites with or without YF 3 showed desirable thermal stability below 1300 °C and besides various amounts of CaZrO 3 , any amount of tri-calcium phosphate (TCP) was not observed. Above 1100 °C, composites with YF 3 showed higher thermal stability than the composites without YF 3 . On the other hand, pure HA started to decompose and TCP was observed at 1300 °C. Composites with YF 3 showed improved thermal stability than the composite containing 5 wt% PSZ without YF 3 and pure HA at lower sintering temperatures such as 900 °C and 1100 °C. However, it was observed that the increasing amount of YF 3 addition caused negative effect on the thermal stability of the composites. 5ZHA composites with YF 3 showed the highest relative density among all of the composites with or without YF 3 .

Pure and cadmium (Cd) doped hydroxyapatites (HA, Ca10(PO4)6(OH)2) were synthesized by a precipitation method from aqueous solutions of Ca(NO3)24·H2O for the former and Cd(NO3)24·H2O for the latter, by using (NH4)2HPO4 as the phosphate source, while pH was kept in the range of 11–12. The effect of incorporation of Cd2+ ions into the structure of HA was investigated after the air sintering at 1100 °C for 1 h. The results indicate that Cd2+ addition into HA yields nearly fully densified products with respect to pure stoichiometric HA. The XRD patterns showed that Cd doping increases the crystallinity of HA. The 2, 4.4, and 8.8 mol% Cd doped HAs had calcium oxide (CaO) impurity phase in their lattice. The CaO phase in the HA structure gradually disappeared with increasing Cd amount, and was replaced with cadmium oxide (CdO) in the CdHA doped with 11 mol% Cd. Cd2+ ion incorporation decreased the a- and c-axis lattice constants and unit cell volume of HA.

Laser monitoring (remote sensing) may be considered as the science of collecting and interpreting information about the atmosphere, earth and sea using sensors on earth, on platforms in our atmosphere (airplanes, balloons) or in space (satellites) without being in direct physical contact with them. Remote sensing by LIDARs (Light Identification Detection and Ranging) has wide applications as technique to probe the Earth's atmosphere, ocean and land surfaces. LIDARs are widely used to get knowledge of spatial and temporal variations in meteorological quantities (e.g. temperature, humidity, clouds and aerosol properties) and to monitor the changes in these quantities on different timescales. Subject of the present work is quite wide. It is rather difficult to perform analysis and to provide full knowledge about existing information. In the present work, in addition to the literature data, the information will be provided also about KA-09 aerosol LIDAR developed at the Marmara Research Centre of TUBITAK (Turkish Scientific and technological Research Council) and also about KA-14 LIDAR developed at the National Aviation Academy of Azerbaijan for remote sensing of contaminations on water surfaces taking place during oil-gas production. The main goal of this paper is to give students insight in different remote sensing instruments and techniques (including their perspectives) that are used for the derivation of meteorological quantities and obtaining the information about water surface.

Aktug, Salim Levent/0000-0001-7755-0279; DURDU, SALIH/0000-0002-6288-0926 WOS: 000406988200016 The bioceramic coatings were formed on zirconium (Zr) at different treatment times such as 5,10 and 15 min in a calcium acetate and beta-calcium glycerophosphate-based electrolyte by a single-step plasma electrolytic oxidation (PEO). The XRD and FTIR confirmed a presence of highly crystalline cubic-ZrO2, perovskite-CaZrO3 and HAP on the surface of Zr. The surface of the coatings was porous and rough due to the existence of micro-sparks through the PEO process. The surface of the coatings produced at long treatment times exhibited a hydrophilic surface compared to the uncoated Zr substrate. The elements of Ca, P and O were homogeneously distributed through on the coated surface. The amount of secondary apatite formed on coated surface after immersion in simulated body fluid (SBF) up to 28 days increased with increasing time. The bioactivity of the coatings was greater than that of the uncoated Zr. The bacterial adhesion to the coated surface decreased considerably compared to the uncoated Zr. MTT analysis showed that a cell viability, a cell attachment and a cell growth for PEO coatings were greater than for the uncoated Zr. As a result, the biological test results show that PEO coatings with different treatment time improve the biocompatibility of the surfaces. (C) 2017 Elsevier B.V. All rights reserved. Scientific and Technological Research Council of Turkey (TUBITAK MAG)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [113M162] A part of this work was supported by the Scientific and Technological Research Council of Turkey (TUBITAK MAG Project - 113M162).

The object of this work is to present the consequences for the stopping power and range values of some human tissues at energies ranging from 1 MeV to 1 GeV and 1–500 MeV, respectively. The considered human tissues are lung, intestine, skin, larynx, breast, bladder, prostate and ovary. In this work, the stopping power is calculated by considering the number of velocity-dependent effective charge and effective mean excitation energies of the target material. We used the Hartree-Fock-Roothaan (HFR) atomic wave function to determine the charge density and the continuous slowing down approximation (CSDA) method for the calculation of the proton range. Electronic stopping power values of tissues results have been compared with the ICRU 44, 46 reports, SRIM, Janni and CasP data over the percent error rate. Range values relate to tissues have compared the range results with the SRIM, FLUKA and Geant4 data. For electronic stopping power results, ICRU, SRIM and Janni's data indicated the best fit with our values at 1–50, 50–250 MeV and 250 MeV–1 GeV, respectively. For range results, the best accordance with the calculated values have been found the SRIM data and the error level is less than 10% in proton therapy. However, greater 30% errors were observed in the 250 MeV and over energies. © 2017 Elsevier Ltd

In this study, AZ31 Mg alloy produced by twin roll casting was coated by a plasma electrolytic oxidation (PEO) in the solution, consisting of Na 2 SiO 3 ·5H 2 O + KOH electrolyte at 0.085 A/cm 2 current density for 15, 30, 45 and 60 min. Thickness of the coated layer, surface morphology, phase structure, hardness, adhesion strength of the layer and wear resistance were analyzed by an eddy current, SEM, XRD, Vickers hardness, micro scratch tester and tribometer, respectively. The average coating thickness ranged from 17 to 56 μm. A number of pores were formed on the coated layer. XRD revealed that Mg 2 SiO 4 (Forsterite) and MgO (Periclase) phases were formed on the surface of the magnesium alloy. Average coating hardness was measured as 660 HV, while the hardness of the magnesium alloy was 72 HV. Adhesion strength of coatings was increased by increasing duration time. Wear resistances of coatings were higher than AZ31 Mg alloy.

In this study, Ti6Al4V alloy was coated in the solution consisting of calcium acetate (CA) and β-calcium glycerophosphate (β-Ca-GP) by plasma electrolytic oxidation (PEO) to produce hydroxyapatite and calcium apatite-based composite used as of bioactive and biocompatible materials in biomedical applications. The phase structures, surface morphologies, functional groups of molecules, chemical compositions of the surfaces and the binding energies of atoms in the coating were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS), respectively. Anatase, rutile, calcium oxide, titanium phosphide, whitlockite, tri-calcium phosphate (TCP), perovskite calcium titanate and hydroxyapatite phases on the coating were detected by XRD analysis. The surface of coatings produced by PEO method has a porous structure. The amount of amorphous hydroxyapatite is the highest value for the coating produced at 5 min in XPS and ATR-FTIR results, whereas the amount of crystalline hydroxyapatite has the highest value for coating produced at 120 min in XRD results.

The commercial pure magnesium was coated by micro arc oxidation method in different aqueous solution, containing sodium silicate and sodium phosphate. Micro arc oxidation process was carried out at 0.060 A/cm(2), 0.085 A/cm(2) and 0.140 A/cm(2) current densities for 30 min. The thickness, phase composition, morphology, hardness, adhesion strength and wear resistance of coatings were analyzed by eddy current, X-ray diffraction (XRD), scanning electron microscope (SEM), micro hardness tester, scratch tester and ball-on disk tribometer, respectively. The average thicknesses of the micro arc oxidized coatings ranged from 27 to 48 mu m for sodium silicate solution and from 45 to 75 mu m for sodium phosphate solution. The dominant phases formed on the pure magnesium were found to be a mixture of spinel Mg2SiO4 (Forsterite) and MgO (Periclase) for sodium silicate solution and Mg-3(PO4)(2) (Farringtonite) and MgO (Periclase) for sodium phosphate solution. The average hardnesses of the micro arc oxidized coatings were between 260 HV and 470 HV for sodium silicate solution and between 175 HV and 260 HV for sodium phosphate solution. Adhesion strengths and wear resistances of coatings produced in sodium silicate solution were higher than those of the ones in sodium phosphate solution due to high hardness of coatings produced in sodium silicate solution. Crown Copyright (C) 2012 Published by Elsevier B. V. All rights reserved.

Tungsten trioxide (WO 3 ) thin films were prepared by thermal evaporation method onto quartz substrates at room temperature. Effect of annealing temperature (from 200 to 800 °C) to morphology, crystallographic structure and electrical properties were investigated. In order to investigate the temperature dependant resistivity properties of the films dark current–voltage measurements were done at the temperatures of 30, 60, 90, 120 and 150 °C. From the AFM pictures it is seen that the increasing annealing temperature causes an increase in grain sizes. At elevated temperatures the grains combine to each other and thus form continuous and homogenous surfaces. From the XRD patterns it was seen that the as-prepared and annealed films at 200, 300, 310 and 320 °C were amorphous. On the other hand at 330 °C and higher temperatures the films were found as in crystallized structures (monoclinic phase). From the current–voltage measurements it was seen that the contacts areohmic and the current increased with increasing temperatures. From the calculated values it was seen that the produced films shows good semiconducting nature.

This article presents an investigation into the possible matching of mechanical properties of a polyimide (PI)–carbon nanotube (CNT) composite system to natural cartilage tissue. Currently used ultrahigh molecular weight polyethylene (UHMWPE) used in total joint replacements presents certain drawbacks due to a mismatch in mechanical and tribological properties with those of a natural bone joint. Natural cartilage tissue is a composite material itself, being composed of collagen fibers, hydrophilic proteoglycan molecules, cells and other constituents. The current investigation attempts to mimic the mechanical and tribological properties of natural cartilage tissue by varying the CNT concentration in a PI matrix. Nanoindentation and pin-on-flat tribological tests were conducted for this purpose. It was found that the coefficient of friction (COF) reached a minimum at a concentration of 0.5% CNT (by volume) when articulated against Ti6Al4V alloy. When articulated against Ti6Al4V alloy in the presence of a lubricant, the minimum COF was obtained at a concentration of 0.2% CNT. The maximum penetration depth under nanoindentation varied with CNT concentration and indicated that the mechanical properties could be tailored to match that of cartilage tissue. A closer investigation into this behavior was carried out using scanning electron, transmission electron, and atomic force microscopy. It was noticed that there is good bonding between the CNTs and polyimide matrix. There was a ductile to brittle transition as the concentration of CNT was increased. Competing interactions between nanotube–matrix and nanotube–nanotube are possible reasons for the deformation and friction behavior identified.

Composites of hydroxyapatite with partially stabilized zirconia with MgO or MgF 2 were pressureless sintered between 1000 °C and 1300 °C. The reactions and transformations of phases were verified by X-ray diffraction. For the hydroxyapatite and zirconia composites with MgO, calcium from the hydroxyapatite diffused into the zirconia phase, and the hydroxyapatite decomposed to tri-calcium phosphate at sintering temperatures higher than 1000 °C. Above about 1200 °C, CaZrO 3 was formed. Composites containing the MgF 2 decomposed slower than the composites with MgO, which was verified by the changes in the lattice volume of the hydroxyapatite left in these composites. Fluorine ions in MgF 2 diffused into hydroxyapatite, which resulted in thermal stability at high sintering temperatures. Composites with MgF 2 had higher hardness than those with MgO. The lowest porosity was found in a composite initially containing 10 wt% partially stabilized zirconia and 5 wt% MgF 2 .

In this study, thick and hard alumina coatings were produced on 6061-T6 Al alloy substrates for different oxidation times and current densities by using of microarc oxidation (MAO) technique in an alkali-silicate electrolytic solution. The influence of oxidation time and current density on the kinetics, phase composition, hardness, surface roughness and structure of the coating were investigated. It is found that the kinetics of coating mainly depends on applied current density and oxidation time. The XRD results revealed that the coatings are composed of mainly α-Al2O3, γ-Al2O3 and mullite phase. The relative ratio of harder and denser α-Al2O3 phase increases with increasing current density and oxidation time. For the same coating time, the position of maximum hardness of coatings moves away from the substrate-coating interface to the coating surface with increasing current density. The surface roughness of coating is a function of coating thickness and increases with increasing deposition time and current density. The surface micro hardness of Al 6061-T6 alloy substrate was increased up to 2200 HV hardness after the coating.

Boronizing was performed by using a solid medium of Ekabor powders at 1073, 1148 and 1223 K for 2, 4 and 8 h. After boronizing, the major dominant phase was found to be Fe2B and the minors were CrB and Ni2B. Boride coating resulted in smooth and dense feature confirmed by optical and SEM. The thickness of boride layer varied from 7 to 87 pm depending on the process time and temperature. Boride layer has a hardness of over 1700 HVN, while the substrate's hardness was about 180 HVN. The growth kinetics of boride layer was found to obey a parabolic rate demonstrating a solid diffusion limited process. The kinetic rates for different process times were plotted by using Arrhenius equation. From this measurement, the activation energy of boride growth for this study was determined as 199 kJ/mol. In addition, the possibility of predicting the iso-thickness of boride layer variation was studied and an empirical relationship between process parameters and boride layer thickness was established. EDS studies showed that Cr concentrated in the coating layer and Ni and Fe concentrated in the substrate. (C) 2008 Elsevier Ltd. All rights reserved.

Composites of hydroxyapatite with cubic zirconia with MgO or MgF2 were pressureless sintered at temperatures from 1000 to 1300 ◦ C. The reactions and transformations of phases were monitored with X-ray diffraction. For the hydroxyapatite and zirconia composites with MgO, calcium diffused from hydroxyapatite into the zirconia, and hydroxyapatite decomposed to tri-calcium phosphate at sintering temperatures higher than 1000 ◦ C. Above about 1200 ◦ C, CaZrO3 was formed. Composites containing the MgF2 decomposed slower than the composites with MgO which was verified by the changes in the lattice volume of the hydroxyapatite left in the composites. Fluorine ions in MgF2 diffused into hydroxyapatite which resulted in thermal stability at high sintering temperatures. Composites with MgF2 had higher hardness than those with MgO. The lowest porosity was found in a composite initially containing 10 wt% cubic zirconia and 5 wt% MgF2. © 2008 Elsevier B.V. All rights reserved.