The effect of annealing on the deformation behaviour and microstructure of crystallized Mg–23.5Ni (wt.%) alloy

Rapidly solidified amorphous Mg–23.5Ni (wt.%) ribbons were crystallized at 300 and 400 °C for 90 min. After annealing at 300 °C the microstructure was heterogeneous, consisting of rounded eutectic–lamellar domains, which contained magnesium grains smaller than 500 nm. In the case of ribbons annealed at 400 °C the microstructure, however, was homogenous, and composed of well-formed magnesium grains and Mg₂Ni particles. At room temperature both crystallized materials were brittle due to the high volume fraction of Mg₂Ni particles, but they exhibited some ductility with increasing test temperature. Above 200 °C, the microstructure of the ribbons annealed at 300 °C was characterised by the formation of particle free zones during the tensile test. This structure was not observed in the material annealed at 400 °C. Deformation behaviour and changes in the microstructure during plastic flow of both crystallized materials were explained according to grain boundary sliding mechanisms.     

Formation and properties of nitrogen-rich strontium silicon oxynitride glasses

Glass formation in the system Sr–Si–O–N was investigated and properties of obtained glasses evaluated. The glass-forming region was determined for glasses prepared by melting mixtures of Sr metal, SiO₂ and Si₃N₄ powders in Nb crucibles at 1600–1750 °C in nitrogen atmosphere using a radio frequency furnace. The glasses were found to be homogenous, translucent gray to opaque black, and to contain high contents of N (up to 45 e/o) and Sr (up to 36 e/o). The glass transition temperature (790–973 °C), density (2.99–4.07 g/cm³), microhardness (8.10–10.50 GPa), and refractive index (1.65–1.93) are strongly correlated with the amounts of Sr and N. The properties are compared with findings in other oxynitride silicate glass systems.     

The effect of repeated annealing temperature on the structural,optical, and electrical properties of TiO<Subscript>2</Subscript> thin films prepared by dip-coating sol–gel method

In this study, we have studied the effect of repeated annealing temperatures on TiO₂ thin films prepared by dip-coating sol–gel method onto the glasses and silicon substrates. The TiO₂ thin films coated samples were repeatedly annealed in the air at temperatures 100, 200, and 300 °C for 5 min period. The dipping processes were repeated 5 to 10 times in order to increase the thickness of the films and then the TiO₂ thin films were annealed at a fixed temperature of 500 °C for 1 h period. The effect of repeated annealing temperature on the TiO₂ thin films prepared on glass substrate were investigated by means of UV–VIS spectroscopy, X-ray diffraction (XRD), and atomic force microscopy (AFM). It was observed that the thickness, average crystallite size, and average grain size of TiO₂ samples decreased with increasing pre-heating temperature. On the other hand, thickness, average crystallite size, and average grain size of TiO₂ films were increased with increasing number of the layer. Al/TiO₂/p-Si metal–insulator–semiconductor (MIS) structures were obtained from the films prepared on p-type single silicon wafer substrate. Capacitance–voltage (C–V) and conductance–voltage (G/ω–V) measurements of the prepared MIS structures were conducted at room temperature. Series resistance (R _s) and oxide capacitance (C _ox) of each structures were determined by means of the C–V curves.     

Synthesis and characterization of new glasses based on Li<Subscript>2</Subscript>S-P<Subscript>2</Subscript>S<Subscript>5</Subscript>-Sb<Subscript>2</Subscript>S<Subscript>3</Subscript> system

There is great interest in sulfide glasses because of their high lithium ion conductivity. New sulfide glasses based on Li₂S-P₂S₅-Sb₂S₃ system have been synthesized by a classical quenching technique. A summary of thermal and structural characterization is presented. Electrical conductivities of the samples have been determined by Impedance Spectroscopy. The compositions of low lithium content (below 20% mol) have presented low electronic conductivities close to 10⁻⁸ S/cm at room temperature. The compositions of medium lithium content (30–50% mol) have presented mixed ionic-electronic behavior with predominant on ionic conductivity with a maximum values around 10⁻⁶ S/cm for samples up to 50% Li₂S at room temperature. Arrhenius behavior is verified between 25°C and T_g for all glasses with activation energies about 0.55–0.64 eV. A comparative study of conductivities with glasses belonging to the other chalcogenide systems has been undertaken.     

The influence of rapid thermal annealing on electrical and structural properties of Pt/Au Schottky contacts to n-type InP

The electrical and structural properties of Pt/Au Schottky contacts to n-InP have been investigated in the annealing temperature range of 200–500 °C by current–voltage (I–V), capacitance–voltage (C–V), Auger electron spectroscopy (AES) and X-ray diffraction (XRD) measurements. The barrier height of as-deposited Pt/Au Schottky contact is found to be 0.46 eV (I–V) and 0.68 eV (C–V). For the contacts annealed at 300 °C, the barrier height is increased to 0.51 eV (I–V) 0.89 eV (C–V). Further increase in annealing temperature up to 500 °C, the barrier height has been found to decrease to 0.49 eV (I–V) 0.82 eV (C–V) from those values obtained at 300 °C. It has been found that the electrical characteristics are significantly improved for Pt/Au Schottky contacts upon annealing at 300 °C. Based on the Auger electron spectroscopy and X-ray diffraction results, the formation of Pt–In and Au–In intermetallic compounds at the interface may be the reason for the increase of barrier height after annealing at 300 °C for Pt/Au Schottky contacts. From the atomic force microscopy (AFM) results, it is evident that the surface becomes smooth with RMS roughness of 16.91 nm for the Pt/Au Schottky contacts after annealing at 500 °C compared to the 300 °C annealed sample (RMS roughness of 17.33 nm).     

Electrical and structural properties of double metal structure Ni/V Schottky contacts on n-InP after rapid thermal process

The electrical, structural, and surface morphological properties of Ni/V Schottky contacts have been investigated as a function of annealing. The Schottky barrier height value from I–V and C–V measurements for as-deposited Ni/V/n-InP diode is 0.61 eV (I–V) and 0.91 eV (C–V), respectively. It has been observed that the Schottky barrier height decreases with increasing annealing temperature as compared to the as-deposited contact. For the contact annealed at 200 °C, the obtained barrier height decreased to 0.52 eV (I–V) and 0.78 eV (C–V). Further, the annealing temperature increased to 300 and 400 °C, the barrier height slightly increased to 0.58 eV (I–V), 0.82 eV (C–V) and 0.59 eV (I–V), 0.88 eV (C–V). However, after annealing at 500 °C, results then decrease in barrier height to 0.51 eV (I–V) and 0.76 eV (C–V), which is lower than the value obtained for the sample annealed at 200 °C. The Norde method is also employed to extract the barrier height of Ni/V/InP Schottky diode, and the values are 0.68 eV for the as-deposited and 0.56 eV for the contact annealed at 500 °C, which are in good agreement with those obtained by I–V technique. Based on the results of AES and XRD studies, it is concluded that the formation of indium phases at the Ni/V/n-InP interface may be the reason for the increase in the barrier height for the as-deposited contact. The decrease in the barrier height upon annealing at 500 °C may be due to the formation of phosphide phases at the interface. The AFM results showed that there is no significant degradation in the surface morphology (RMS roughness of 0.61 nm) of the contact even after annealing at 500 °C.     

Electrical properties of R<Subscript>2</Subscript>O–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiO<Subscript>2</Subscript> glass–ceramics for anodic bonding

Temperature and frequency dependence on electrical properties (dielectric constant, dielectric loss and conductivity) of Li₂O–Na₂O–K₂O–Al₂O₃–SiO₂(R₂O–Al₂O₃–SiO₂) system glass–ceramics used as anodic bonding materials were discussed. The results showed that the main crystal phase of glass–ceramics was lithium metasilicate (Li₂SiO₃). Compared with the parent glass, both the dielectric constant and dielectric loss of glass–ceramics decreased, the dielectric constant and dielectric loss increased gradually with the increasing of the test temperature from room temperature to 400 °C, Testing frequency (30–300 MHz) had very little influence on the dielectric properties of samples. The electrical conductivity of glass–ceramics showed a trend of first decrease and then increase with the increasing of temperature. The glass–ceramics which has a lower dielectric constant, dielectric loss and better stability under high frequency was obtained after an appropriate heat treatment; it could be used as anodic bonding materials under very high frequency.     

Strontium oxide doped quaternary glasses: effect on structure,degradation and cytocompatibility

This preliminary study focuses on the effect of adding SrO to a Ti-containing quaternary phosphate glass system denoted by P₂O₅–Na₂O–CaO–TiO₂. The following four different glass compositions were manufactured: 0.5P₂O₅–0.17Na₂O–0.03TiO₂–(0.3−x)CaO–xSrO where x = 0, 0.01, 0.03 and 0.05. Structural characterisation revealed glass transition temperatures in the range 427–437°C and the presence of sodium calcium phosphate as the dominant phase in all the glasses. Degradation and ion release studies conducted over a 15-day period revealed that the Sr-containing glasses showed significantly higher degradation and ion release rates than the Sr-free glass. Cytocompatibility studies performed over a 7-day period using MG63 cells showed that the addition of 5 mol% SrO yielded glasses with cell viability nearly equivalent to that observed for quaternary TiO₂ glasses.     

Electrical, structural and morphological characteristics of rapidly annealed Pd/n-InP (100) Schottky structure

The electrical and structural properties of the Pd/InP (100) Schottky barrier diodes have been investigated as a function of annealing temperature by current–voltage (I–V), capacitance–voltage (C–V) and X-ray diffraction (XRD) measurements. The Schottky barrier height of the as-deposited, 100 and 200°C annealed contacts determined from the I–V and C–V measurements are 0.56 and 0.81 eV, 0.57 and 0.81 eV, and 0.58 and 0.82 eV, respectively. However, both the measurements showed that the Schottky barrier height of the Pd/n-InP Schottky contact is increased to 0.59 eV (I–V) and 0.83 eV (C–V) when the contact is annealed at 300°C for 1 min in nitrogen atmosphere. Further Schottky barrier height decreases to 0.57 eV (I–V), 0.71 eV (C–V) and 0.53 eV (I–V), 0.67 eV (C–V) after annealing at 400 and 500°C samples. The result shows that the optimum annealing temperature for the Pd/InP Schottky diode is 300°C. Norde method is also used to determine the barrier height of Pd Schottky contacts and the values are 0.56 eV for the as-deposited contact, 0.57, 0.57, 0.58, 0.57 and 0.54 eV for contacts annealed at 100, 200, 300, 400 and 500°C which are consistent with the values obtained by the I–V measurements. From the atomic force microscopy results, it is evident that the overall surface morphology of the Pd/InP Schottky diode is fairly smooth. Based on the XRD results, the formation of phosphorus-oxygen compounds at the interface may be responsible for the variation in barrier heights observed in Pd/InP Schottky contacts with annealing temperature.     

Effect of aluminum on precipitation hardening in Cu–Ni–Zn alloys

The effect of aluminum on the precipitation hardening of Cu–Ni–Zn alloys with varying aging temperatures and times was investigated in this article, in the hope to achieve better mechanical properties. Vickers hardness, tensile, and electrical conductivity tests were carried out to characterize the properties of the Cu–Ni–Zn alloys with or without an addition of aluminum subjected to different aging treatments. The results show that an addition of 1.2 wt% aluminum can play an influential role in the precipitation hardening of the Cu–Ni–Zn alloys. For example, it can increase the peak hardness from 58 Hv for the solution-treated Cu–10Ni–20Zn alloy to 185 Hv for the solution-treated Cu–10Ni–20Zn–1.2Al alloy during aging at 500 °C. The yield strength, tensile strength, and electrical conductivity of the Cu–10Ni–20Zn–1.2Al alloy subjected to suitable treatments under prior cold-rolled and aged conditions can reach 889 MPa, 918 MPa, and 10.96% IACS, respectively, being much higher than those of the relevant alloy without aluminum and comparable to those of the Cu–Be alloys (C17200 and C17510). According to the transmission electron microscope observations, it was found that formation of nanosized precipitates with the L1₂-type ordered lattice results in precipitation hardening, and an orientation relationship of [011]_\textp//[011]_\textm [011]_{\text{p}}//[011]_{\text{m}} and (100)_\textp//(200)_\textm (100)_{\text{p}}//(200)_{\text{m}} exists between the precipitates and the α-Cu matrix.     

Structural,optical, electrical and morphological properties of ZnTe films deposited by electron beam evaporation

ZnTe films were deposited on glass substrates at different substrate temperatures in the range 30–300 °C. The thickness of the films was about 200 nm. The films exhibited cubic structure with preferential orientation in the (111) direction. Band gap values in the range 2.34–2.26 eV are observed with increase of the substrate temperature. The refractive index values are in the range of 2.55–2.92 for the films deposited at different substrate temperatures. It is observed that the conductivity increases continuously with temperature. Laser Raman studies indicated the presence of peaks at 206.9 and 412.2 cm⁻¹corresponding to the first order and second order LO phonon.     

CuIn(S,Se)2 thin films prepared by selenization and sulfurization of sputtered Cu–In precursors

CuIn(S,Se)₂(CISSe) thin films have been prepared onto soda-lime-glass (SLG) substrates by selenization and sulfurization of magnetron sputtered Cu–In precursors. The results indicate that the properties of the CISSe films are strongly dependent on the post-annealing treatment. After annealing at 400 °C for 20 min, the CISSe films have formed tetragonal (chalcopyrite) crystal structure and the diffraction peaks of the films shift systematically to the left with the temperature varying from 400 °C to 500 °C. EDAX study reveals that the compositions of CISSe films are Cu_0.83In_1.17S_1.67Se_0.3, Cu_0.86In_1.13S_1.61Se_0.4 and Cu_0.82In_1.15S_1.54Se_0.49 after annealing at 400 °C, 450 °C and 500 °C, respectively. The direct optical band gaps of the films slightly decrease from 1.44 ev to 1.32 ev with the increase of the temperature from 400 °C to 500 °C, and the optical absorption coefficient is over 10⁵ cm⁻¹. The films annealed at 400 °C–500 °C are all found to be p-type and the resistivity is almost 10⁻²–10⁻³ Ω cm. The carrier mobility of the film at 500 °C is almost as high as 1.701 cm²/V S.     

Kinetics and mechanisms of converting bioactive borate glasses to hydroxyapatite in aqueous phosphate solution

Borate bioactive glasses are receiving increasing attention as scaffold materials for bone repair and regeneration. In this study, the kinetics and mechanisms of converting three groups of sodium–calcium–borate glasses with varying CaO:B₂O₃ ratio to hydroxyapatite (HA) in 0.25 M K₂HPO₄ solution were investigated at 10–70 °C. Glass disks with the composition 2Na₂O·(2 − x)CaO·(6 + x)B₂O₃ (x = 0, 0.5, and 1.0) were immersed for up to 8 days in the potassium phosphate solution. The conversion kinetics to HA were monitored by measuring the weight loss of the glass, while X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy were used to study structural and compositional changes. All three groups of glasses formed HA on their surfaces, showing that the glasses were bioactive. At 10–37 °C, the conversion kinetics was well fitted by the contracting sphere model. Also, the contracting sphere model has a good fit for the early stage of conversion at 70 °C, whereas a three-dimensional (3D) diffusion model provided a good fit to the data of the later stage. The results of this study provide kinetic and structural data for the design of borate bioactive glasses for potential applications in bone tissue engineering.     

Undoped tin oxide thin films obtained by the sol gel technique,starting from a simple precursor solution

In this work, we report the synthesis and the structural, optical and electrical properties of undoped tin oxide thin films obtained by the sol–gel technique. The films have been prepared from a simpler precursor solution than other ones reported; it is based on stannous chloride (SnCl₂·2H₂O), ethanol, glycerol and triethylamine. The films are deposited on glass slide substrates and sintered at temperatures in the 300–550 °C range, in an open atmosphere. A second thermal treatment in vacuum is made in order to decrease the resistivity of the films. The X-ray diffraction patterns show the tetragonal phase of SnO₂ with a small preferential orientation in the (110) plane. All films show high optical transmission (~85%) and a direct band gap value around of 3.8 eV. The minimum resistivity value, 2 × 10⁻¹ Ohm-cm, is obtained for the films sintered at 300 and 350 °C and thermal treated in vacuum at 500 °C for 1 h. The decrease of the resistivity with the thermal treatment in vacuum is associated with an increase in the oxygen vacancies concentration.     

Evidence for a threshold in the biosolubility of aluminosilicate vitreous fibers

Two series of aluminosilicate glasses have been synthesized with the nominal composition (64 − x) SiO₂–x Al₂O₃–36 Na₂O/CaO with x varying from 9 to 19 mol%. They have been corroded in static conditions in a solution that mimics in a simplified manner the intracellular medium of the lung alveolar macrophages (37 °C, pH 4.6, citric acid). The original and corroded glasses have been studied by ²⁷Al and ²⁹Si MAS NMR. Both series display a sharp increase in the silicon dissolution rate with the alumina content. The glass network dissolves extremely slowly, whereas the release of excess sodium is very fast, for the glasses with low alumina content. On the opposite, the glasses with high alumina content dissolve much more rapidly in a nearly congruent manner. The crossover between the two behaviors occurs for x = 13, which corresponds to 33% of aluminum in the glass-former network. The sharp crossover from slow to fast network dissolution is explained in terms of connectivity of the silica sub-network. Above a certain amount of alumina, the silicon sub-network is no more percolating and the corroded glass breaks up into colloids. The sharpness of the transition and the relatively low alumina content required for fast dissolution are related to a structural feature of the aluminosilicate glasses, namely the aluminum self-avoidance that decreases the connectivity of the silica sub-lattice.     

Effect of solid solution state of zirconium and Al3Zr (L12) precipitates on the recrystallization behavior of Al-0.2 wt.%Zr alloy

Effect of homogenization annealing on the existence form of zirconium in Al-0.2wt.%Zr alloy and effect of various existence form of zirconium on the recrystallization behavior of Al-0.2wt.%Zr cold-rolled (total deformation is 92.8 %) sheet are studied. The results show that large numbers of nearly spherical Al₃Zr (L1₂) nanoparticles precipitated from aluminum matrix after homogenizing at 475 °C for 24 h. Moreover, due to the precipitation of Al₃Zr particles, the hardness and electrical conductivity of the as-cast Al-0.2wt.%Zr alloy is increased from 25.1±0.5 HV 3 and 54.0±0.2 %IACS to 28.6±0.7 HV 3 and 56.2±0.1 %IACS, respectively. Hence, zirconium exists as solid solution state in the as-cast Al-0.2wt.%Zr alloy and metastable Al₃Zr phase in the homogenized alloy. Moreover, the recrystallization temperature of the pure aluminum without addition of zirconium is 300 °C, while the recrystallization temperature of the Al-0.2wt.%Zr alloy without and with homogenization is about 350 °C and 400 °C, respectively. Obviously, the solid solution state of zirconium has certain effect on retarding the recrystallization of aluminum alloy, while the nanometer Al₃Zr particles can inhibit the recrystallization of aluminum alloy effectively and increase the recrystallization temperature remarkably.     

Effect of Bi<Subscript>2</Subscript>O<Subscript>3</Subscript> on the dynamics of Li<Superscript>+</Superscript> ions in Li<Subscript>2</Subscript>O·P<Subscript>2</Subscript>O<Subscript>5</Subscript> glasses

Lithium ion transport has been studied in bismuth lithium phosphate glasses in the frequency range 20 Hz–1 MHz and in the temperature range 423–573 K using impedance spectroscopy. The addition of Bi₂O₃ in Li₂O·P₂O₅ glass is related to the modification of the glass structure and facilitates the Li⁺ ions migration. The ac and dc conductivities, activation energy of the dc conductivity and relaxation frequency are extracted from the impedance spectra. Conductivity of the present glass system is found to be ionic in nature. The electrical response of the glasses has been studied using both conductivity and electric modulus formalisms. A single ‘master curve’ for normalized plots of all the modulus isotherms observed for a given composition indicates the temperature independence of the dynamic processes for ions in these glasses. Nearly identical values of activation energy for dc conduction and for conductivity relaxation time indicate that the ions overcome same energy barrier while conducting and relaxing.     

Ionic mobility and electrical transport in 45ZrF<Subscript>4</Subscript> · 35BiF<Subscript>3</Subscript> · 20MF (M - Li,Na, K) glasses studied by NMR and impedance spectroscopy

The ionic mobility and electrical transport in 45ZrF₄ · 35BiF₃ · 20MF (M - Li, Na, K) glasses have been studied by ⁷Li, ¹⁹F, and ²³Na NMR and impedance spectroscopy at temperatures from 200 to 500 K. In the range 400–440 K, the main kinds of ionic mobility in these glasses are local motions of fluorine-containing groups and lithium ion diffusion. The temperature range where the dominant kind of ion motion in the glasses is fluoride ion diffusion depends on the nature of the M⁺ cation. Above 470 K, the glasses offer rather high ionic conductivity: σ ≥ 10^?5 S/cm.     

Dielectric property and electrical conduction mechanism of ZrO2–TiO2 composite thin films

ZrO₂–TiO₂ composite films were fabricated by radio frequency magnetron sputtering and post annealing in O₂. It was found the films remained amorphous below the annealing temperature of 500 °C. The as-deposited ZrO₂–TiO₂ film has a high dielectric constant of 22, and which increases to 34 after annealing at 400 °C. At low electric field, the dominant conduction mechanisms are Schottky emission for both the as-deposited and the annealed thin films. At high electric field, the conduction mechanism changes to space-charge-limited current and then changes to Poole–Frenkel (PF) emission after annealing at 400 °C.     

Glass formation region and electrical conductivity in the system B2O3-Li2O-Li3PO4

Glass formation region was determined for the B₂O₃-Li₂O-Li₃PO₄ system. Under the present experimental conditions, binary lithium borate glasses could be formed containing a maximum of 27 mol% Li₂O. However, this could be increased to 36 mol% in the ternary system. Electrical conductivity was measured at temperatures ranging from room temperature to 350°C. The temperature dependence of the electrical conductivity of these glasses follows Arrhenius equation. The conductivity increased with increasingly alkali content. Maximum conductivity of the order of 10⁻⁴ ohm⁻¹ cm⁻¹ was obtained with the glass containing about 36 mol% Li₂O at 250°C. Activation energy for conduction also varied with total Li₂O content.