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ABSTRACTCopper is widely applied however its disadvantages such as low hardness and poor oxidation resistance. TiN coatings are often used industrially for overriding such disadvantages of ferrous components. In this examination the deposition of TiN on Cu substrates is investigated for the first time by pack cementation process with which one or more elements can be deposited simultaneously by gas and solid-state diffusion reactions. This feature makes this process very attractive for industrial use as it is economic and time saving. Microstructural examination of the deposited samples revealed the formation of thick coatings corresponding to Ti–Cu phases. Focusing on the coating surface it was found that a TiN thin layer is formed. This was verified also from hardness measurements which showed that there was a significant increase of the surface hardness. Furthermore, the oxidation resistance of the coated samples has considerably increased as implied from the thermogravimetric measurements.

Copper is widely applied however its disadvantages such as low hardness and poor oxidation resistance. TiN coatings are often used industrially for overriding such disadvantages of ferrous components. In this examination the deposition of TiN on Cu substrates is investigated for the first time by pack cementation process with which one or more elements can be deposited simultaneously by gas and solid-state diffusion reactions. This feature makes this process very attractive for industrial use as it is economic and time saving. Microstructural examination of the deposited samples revealed the formation of thick coatings corresponding to Ti–Cu phases. Focusing on the coating surface it was found that a TiN thin layer is formed. This was verified also from hardness measurements which showed that there was a significant increase of the surface hardness. Furthermore, the oxidation resistance of the coated samples has considerably increased as implied from the thermogravimetric measurements.

The thermal stability and the resistance against oxidation of quaternary compositionally gradient CrAlSiN coatings deposited on steel substrate are investigated by examining their structural, morphological and chemical features before and after oxidation tests, as well as by quantitative thermal analysis. The as-deposited samples exhibit a columnar structure, with each column consisting of nanocrystals as fine as 20 nm. The as-deposited coating is mainly composed of CrxAl1−xN solid solution nanocrystals, which are embedded in an amorphous SiNxmatrix. When exposed to high-temperature dry air environment the coated samples exhibit remarkable stability as they remained intact up to 800°C. Over 800°C, elements from the substrate outdiffused and modified the chemical content of the film, but still remain oxidation-resistant up to 900°C.

The thermal stability and the resistance against oxidation of quaternary compositionally gradient CrAlSiN coatings deposited on steel substrate are investigated by examining their structural, morphological and chemical features before and after oxidation tests, as well as by quantitative thermal analysis. The as-deposited samples exhibit a columnar structure, with each column consisting of nanocrystals as fine as 20 nm. The as-deposited coating is mainly composed of CrxAl1-xN solid solution nanocrystals, which are embedded in an amorphous SiNxmatrix. When exposed to high-temperature dry air environment the coated samples exhibit remarkable stability as they remained intact up to 800°C. Over 800°C, elements from the substrate outdiffused and modified the chemical content of the film, but still remain oxidation-resistant up to 900°C.

In this work, the structure and oxidation behaviour of three different zinc coatings were examined. The coatings were formed with hot dip galvanizing, pack cementation and thermal spray methods. Three different oxidation conditions were selected for the tests, which correspond to low, medium and intensive oxidation conditions. The oxidized samples were examined by scanning electron microscopy and X-ray diffraction. Results showed that the thermal spray coatings are far more susceptible than the others and suffer from extreme oxidation because of the porous net existing in the coating, which provides diffusion paths to oxygen. Hot dip and pack coatings were proved more resistant under the same exposure conditions, mainly due to the presence of different Fe–Zn phases in their structure and their morphological homogeneity.

In this work, the structure and oxidation behaviour of three different zinc coatings were examined. The coatings were formed with hot dip galvanizing, pack cementation and thermal spray methods. Three different oxidation conditions were selected for the tests, which correspond to low, medium and intensive oxidation conditions. The oxidized samples were examined by scanning electron microscopy and X-ray diffraction. Results showed that the thermal spray coatings are far more susceptible than the others and suffer from extreme oxidation because of the porous net existing in the coating, which provides diffusion paths to oxygen. Hot dip and pack coatings were proved more resistant under the same exposure conditions, mainly due to the presence of different Fe–Zn phases in their structure and their morphological homogeneity.

The growth of Mg and Al coatings on copper by pack cementation is examined in this work by investigating the mechanism of the process, the effect of temperature and heating time on the coating structure. The experiments were undertaken at temperatures ranging from 550 to 600°C, while the duration of the process varied from 30 min to 3 h. It was found that the magnesium coatings consist of two phases corresponding to MgCu2and CuMg2. These phases appeared as distinguished layers or mixed with each other, depending on the deposition temperature and duration. On the other hand, the aluminium coatings consist of a single Al4Cu9phase whose thickness increases with deposition time and temperature. Finally, the oxidation resistance was also evaluated by thermogravimetric measurements, which revealed that the coated samples have superior resistance to bare copper, while Al coated coupons had the best performance when exposed in high temperature environment.

n this research, efforts were made to study the modification of microstructure of pure Ni matrices. Modification was attempted using glucose as carburizing medium under a control of heat treatment conditions. Nickel plates were carburized under vacuum conditions at 3800C and 6500C for 3 hours. In order to determine the parameters of the carburizing, thermal properties of glucose along with the thermochemical behavior were examined by Thermogravimetric Analysis (TGA) and Differential Thermal Analysis (DTA). The characterization of the microstructure of the carburized specimens was investigated by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS). For analyzing the effect of temperature treatment on corrosion resistance, electrochemical corrosion tests were conducted. It was observed that the polarization curves for carburized samples at 3800C were shifted to lower corrosion current densities. Consequently, lower corrosion rates were achieved for these samples preventing the formation of extensive corrosion over their surfaces comparing with carburized Nickel substrates at 6500C.

Tin oxide (SnO2) nanowires (NWs) with diameters of 50 nm, lengths up to 100 µm and a tetragonal rutile crystal structure have been grown by low pressure reactive vapour transport on 1 nm Au/Si(001). The free carrier density of the SnO2NWs measured by THz absorption spectroscopy was found to be n= (3.3 ± 0.4) × 1016cm−3. Based on this we have determined the one‐dimensional (1D) sub‐band energies, overall charge distribution and band bending via the self‐consistent solution of the Poisson–Schrödinger equations in cylindrical coordinates and in the effective mass approximation. We find that a high density of 1018–1019cm−3donor‐like defect related states is required to obtain a line density of 0.7 × 109close to the measured value by taking the Fermi level to be situated ≈0.7 eV below the conduction band edge at the surface which gives a surface depletion shell thickness of 15 nm. We discuss the origin of the donor‐like states that are energetically located in the upper half of the energy band gap as determined by ultrafast, time‐resolved absorption–transmission spectroscopy.

AbstractIn this work, the structure and the oxidation resistance of Zn deposited Cu and brass metallic components are examined. The deposition was accomplished with pack cementation chemical deposition. The examination of the samples was performed with electron microscopy and X-ray diffraction analysis. It was found that coatings on Cu substrate consist of two layers with different Zn concentrations, while coatings on brass were single layered with almost constant Zn concentration. The presence of distinct Zn–Cu phases was revealed in both cases. The subjection of the as coated samples together with the uncoated substrates in air at 400°C showed that both Zn coated samples have enhanced resistivity in such atmospheres, as most of the coating remained mostly unoxidised, and the substrates were fully protected. On the contrary, the bare substrates appear to have undergone severe damage as brittle oxides were formed on their surface.

In this work, the structure and the oxidation resistance of Zn deposited Cu and brass metallic components are examined. The deposition was accomplished with pack cementation chemical deposition. The examination of the samples was performed with electron microscopy and X-ray diffraction analysis. It was found that coatings on Cu substrate consist of two layers with different Zn concentrations, while coatings on brass were single layered with almost constant Zn concentration. The presence of distinct Zn–Cu phases was revealed in both cases. The subjection of the as coated samples together with the uncoated substrates in air at 400°C showed that both Zn coated samples have enhanced resistivity in such atmospheres, as most of the coating remained mostly unoxidised, and the substrates were fully protected. On the contrary, the bare substrates appear to have undergone severe damage as brittle oxides were formed on their surface.

Zirconium nitrides (ZrN) coatings have shown better quality in comparison to titanium nitrides (TiN) ones regarding the application in the mechanical processing of aluminum and titanium alloys. This work presents the results from investigation on properties of ZrN-based coatings intended for industrial application. The ZrN and ZrTiN hard coatings in a thickness of (3 5) m were obtained on stainless steel substrates by cathodic arc evaporation method. The coating hardness in the range of 25-32 GPa was evaluated using the Vickers measurement technique. The coating properties were studied in relation to the surface morphology by Atomic force microscopy (AFM) and Scanning electron microscopy (SEM). The analyses showed that the number and size of the macroparticles decrease when N2 pressure increases in the deposition chamber. X-ray diffraction analysis (XRD) was performed to identify the crystallographic structure, preferred orientation and stress of the ZrN coatings.

The effect of CdCl2, NiCl2 and SnCl2 on the morphology and on the structure of hot-dip galvanized coatings was examined with optical microscopy, scanning electron microscopy and X-ray diffraction, when these salts are added in the preflux bath. From this investigation it turned out, that the morphology of the coatings formed after fluxing in a preflux bath containing CdCl2 is very similar to the morphology of the coatings formed in the usual flux, regardless of the concentration of the Cd salt and the solvent used (water or aqueous solution containing 50% ZnCl2.NH4Cl) in the preflux bath. By contrast, Ni enhances the growth of small-sized crystallites of the zeta-phase instead of the columnar growth, and finally it results in reduction of the coating thickness. This phenomenon is likely to be affected by the NiCl2 concentration but not by the solvent used (pure water or aqueous solution containing 50% ZnCl2.NH4Cl). Finally, Sn addition seems to be inert with regard to the coating structure. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Semicontinuous supercritical antisolvent (SAS) precipitation has been employed for the production of micro- and nanoparticles of amoxicillin with controlled size and size distribution. Different mean sizes and size distributions of particles were achieved depending on the parameters of pressure, solution concentration, and organic solvent. The formed particles were spherical, separate, and of size between 0.2 and 1.6 μm. The particles were successfully precipitated from a dimethyl sulfoxide (DMSO) solution and an ethanol/DMSO solution. In our study, high pressures and a coaxial nozzle for the introduction of the organic solution and the SAS were employed, resulting in the increased mixing of the two flows. The precipitated microparticles were analyzed with scanning electron microscopy. X-ray diffraction analysis of amoxicillin microparticles revealed that they become amorphous after SAS treatment. An attempt was made for the explanation of the influence of the different process parameters on the morphology, the mean size, and the size distribution of the precipitated particles.

This paper investigates the feasibility of increasing the wear resistance of cemented carbide tools through micro-blasting of their PVD-coatings. The enhanced and graded film strength properties before and after micro-blasting are determined by means of a FEM-based evaluation of nanoindentation results. The coating topomorphy, induced by micro-blasting, was monitored and correlated to the substrate roughness and film adhesion. The cutting performance of inserts, coated with micro-blasted films, was investigated in milling and explained with the aid of a cutting process FEM simulation. The obtained results reveal a tool life growth through micro-blasting of coatings, deposited on substrates with appropriate roughness characteristics.

Carbon steel samples were galvanized by the hot-dip method in zinc baths containing 0.5 or 1 wt% aluminum, copper, tin, nickel, and/or lead. Bath temperature ranged from 450 to 480 °C. The samples were examined using optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The influence of the alloying elements on the formation of the different phases and on the diffusion process is discussed. In order to study the kinetics and the mechanism of corrosion of these materials, corrosion experiments were carried out in a simulated environment of accelerated atmospheric corrosion conditions, for which a special chamber (Salt Spray Chamber – Alternative Climate Test Chamber) of type SC-450 was used. The corroded samples were examined using optical microscopy, SEM and XRD. Chloride and oxide phases, which penetrated the materials to different depths from the surface, were revealed. Finally, useful conclusions were drawn which help to control the factors of the corrosion behavior of the examined materials in a marine atmosphere. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Bioactive materials develop a strong bond with living tissues through a carbonate-containing hydroxyapatite layer, similar to that of bone. The fabrication of a thin bioactive glass coating on dental ceramics used in metal-ceramic restorations, could provide a bioactive surface, which in combination with a tissue regenerative technique could lead to periodontal tissues attachment. The aim of this study was the in vitro investigation of the surface structure changes of dental ceramics used in metal-ceramic restorations, coated with a bioactive glass heat-treated at 950 °C, after exposure in a simulated body fluid (SBF) under two different soaking conditions. Coating of dental ceramics with a bioactive glass resulted in the formation of a stable and well bonded with the ceramic substrate thin layer. The growth of a well-attached carbonate apatite layer on their surface after immersion in a simulated body fluid is well evidenced under both experimental conditions, although in static environment the rate of apatite growth is constant and the grown layers seem to be more dense and compact compared with the respective layers observed on specimens under dynamic conditions.

Patina layers artificially produced by chemical treatment of copper and bronze were characterized using ion-beam analysis techniques. In order to simulate the corrosion process, the samples were electrochemically treated in 0.5 M Na2SO4 solution at ambient temperature. The corrosion behavior of artificial Cu patina layers prepared on copper and bronze substrates was studied using potentiodynamic, potentiostatic, and cyclic voltammetric techniques. The composition of the patina layers, which mainly consisted of phases corresponding to the minerals cuprite, antlerite, and brochantite, was determined by energy dispersive spectroscopy and scanning electron microscopy was used to examine their surface morphology prior to and after the corrosion tests. A natural patina sample was also investigated in the same way for comparison purposes. Characterization of the untreated and the electrochemically treated samples was also performed by Rutherford backscattering spectroscopy and nuclear reaction analysis techniques. Backscattering of protons and deuterons, as well as the 16O(d,p)17O, 32S(p,p′γ)32S and 63Cu(p,nγ)63Zn nuclear reactions were used for the profiling of oxygen, sulfur, and copper in the patina layers under investigation. The measurements indicate that the composition of the artificially prepared antlerite and brochantite patina layers is very close to that expected stoichiometrically. The antlerite patinas are transformed during the electrochemical treatment in 0.5 M Na2SO4 solution to brochantite, whereas the brochantite patinas seem to remain unchanged.

Patina layers artificially produced by chemical treatment of copper and bronze were characterized using ion-beam analysis techniques. In order to simulate the corrosion process, the samples were electrochemically treated in 0.5 M Na₂SO₄ solution at ambient temperature. The corrosion behavior of artificial Cu patina layers prepared on copper and bronze substrates was studied using potentiodynamic, potentiostatic, and cyclic voltammetric techniques. The composition of the patina layers, which mainly consisted of phases corresponding to the minerals cuprite, antlerite, and brochantite, was determined by energy dispersive spectroscopy and scanning electron microscopy was used to examine their surface morphology prior to and after the corrosion tests. A natural patina sample was also investigated in the same way for comparison purposes. Characterization of the untreated and the electrochemically treated samples was also performed by Rutherford backscattering spectroscopy and nuclear reaction analysis techniques. Backscattering of protons and deuterons, as well as the 16O(d,p)17O, 32S(p,p'γ)32S and 63Cu(p,nγ)63Zn nuclear reactions were used for the profiling of oxygen, sulfur, and copper in the patina layers under investigation. The measurements indicate that the composition of the artificially prepared antlerite and brochantite patina layers is very close to that expected stoichiometrically. The antlerite patinas are transformed during the electrochemical treatment in 0.5 M Na₂SO₄ solution to brochantite, whereas the brochantite patinas seem to remain unchanged.

The mechanism of bonding of bioactive glasses with living tissues has been reported to be associated with the development of a layer consisting of carbonate‐containing hydroxyapatite similar to that of bone on the surface of the materials. This layer is also formed in vitro, in solutions with ion concentrations similar to those of human blood plasma, like SBF (Simulated Body Fluid). The development of HCAp (Hydroxy carbonate apatite) layer on the surface of a commercially available Bioglass® Synthetic Bone Graft Particulate (Perioglas®) after immersion in SBF solution using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) with associated Energy Dispersive Spectroscopy (EDS). PerioGlas® powder with particle size 20‐63μm, pressed in a vacuum press in order to produce pellets. The pellets were soaked in SBF for 12, 18, 24 and 48 hours at 37°C. Results revealed the formation of an amorphous CaO‐P2O5‐ rich layer on the surface of the specimens after 12 hours in the solution and a well crystalline HCAp layer after 24 hours immersion time.

Abstract: Pure HEU-type zeolite (heulandite) crystals were allowed to interact with Sr2+ cations in aqueous solution. The powdered solid experimental products obtained from batch-type sorption experiments, using solutions of Sr2+-concentrations between 10 and 1000 mg/l, were investigated using INAA, RI-XRF and SEM-EDS. The Sr uptake by the mineral which can adequately be described with a Freundlich-type isotherm, varies from 3.14 to 6.22 mg/g. The distribution coefficients increase progressively by decreasing the solutions concentration reaching a value of 1800 ml/g. The investigated zeolite interacts with Sr2+ cations through ion exchange reactions and initial exchangeable Ca2+ cations are replaced into the structural micropores. However, in the best case, only ca. 43% of the theoretical CEC can be covered because of the limited availability of the extra framework Ca2+ cations that can be removed from the lattice under ambient treatment conditions. The XPS investigation of Sr-loaded single crystals indicated that adsorption of Sr2+ cations on the outer surface also occurs while surface precipitation phenomena must be excluded. Similar surface analyses by means of12C-RBS showed that the Sr depth-distribution at near-surface layers is quite homogenous in contrast to a previous relevant study revealing an intense surface Sr-accumulation on a natural Ca-zeolite of different structural characteristics (scolecite).

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