Isothermal Compressibility of TlInS2–TlPrS2 Alloys

A phase transition in TlIn_{1 – x} Pr _x S₂ (0 <x 0.08) solid solutions was detected at 260–290 K by temperature-dependent isothermal compressibility measurements, in accordance with the thermal expansion data obtained earlier.     

Microwave-assisted sintering of Al–ZrO2 nano-composites

In this project, nano-ZrO₂ particles were dispersed in aluminum powder by a Y-shape mixer. The particle size of ZrO₂ powder was <40 nm and the amount of ZrO₂ reinforcement varies from 3 to 15 %. The mixed powders were compacted. Subsequently the compacted discs were sintered both in the microwave oven and in the conventional muffle furnace. Using microwave-assisted sintering method led to the reduction of sintering time to 15 min. Micro-structural studies of the nano-composites indicated that there is relatively uniform distribution of the reinforcement in the matrix. Aluminum metal matrix nano-composites samples were characterized by micro-hardness measurements, optical microscopy, X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. Mechanical properties reveal that the presence of nano-ZrO₂ particles has improved significantly the strength. The optimum amount of ZrO₂ reinforcement has been determined to be 6 %.     

ZrO2–TiO2Materials

The magnetic, electrical, catalytic, and photocatalytic properties of ZrO₂–TiO₂materials were studied. The ZrO₂–TiO₂system was shown to contain ZrO₂-, TiO₂, and ZrTiO₄-based solid solutions. Procedures for the preparation of high-activity ZrO₂–TiO₂photocatalysts and photostable pigments were developed.     

The effect of ZrO2 and TiO2 on solubility and strength of apatite–mullite glass–ceramics for dental applications

The effect of ZrO₂ and TiO₂ on the chemical and mechanical properties of apatite–mullite glass–ceramics was investigated after sample preparation according to the ISO (2768:2008) recommendations for dental ceramics. All materials were characterized using differential thermal analysis, X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. X-ray fluorescence spectroscopy was used to determine the concentrations of elements present in all materials produced. The chemical solubility test and the biaxial flexural strength (BFS) test were then carried out on all the samples. The best solubility value of 242 ± 61 μg/cm² was obtained when HG1T was heat-treated for 1 h at the glass transition temperature plus 20 °C (T_g + 20 °C) followed by 5 h at 1200 °C. The highest BFS value of 174 ± 38 MPa was achieved when HG1Z and HG1Z+T were heat-treated for 1 h at the T_g + 20 °C followed by 7 h at 1200 °C. The present study has demonstrated that the addition of TiO₂ to the reference composition showed promise in both the glass and heat-treated samples. However, ZrO₂ is an effective agent for developing the solubility or the mechanical properties of an apatite–mullite glass–ceramic separately but does not improve the solubility and the BFS simultaneously.     

Preparation of Ultrafine Tetragonal ZrO2–CeO2Solid Solutions

Nanometer-sized tetragonal Zr_{1 – x} Ce _x O_{2 –} powders were prepared by hydroxide precipitation and sol–gel processing. The effects of gel-aging time and solution concentration on the phase composition and particle size of the powders were studied. The ceramics prepared by sintering ultrafine powders at 1500°C had a density of 6.0 g/cm³, open porosity of 4%, and closed porosity below 1%.     

Mechanical properties and microstructure of ZrO2–SiO2 composite

ZrO2–SiO2 composite powder has been prepared by a wet chemical route using zirconyl chloride and fumed silica as starting materials and subsequently sintered by the hot-pressing method to obtain a ZrO2–SiO2 ceramic. The mechanical properties of the silica matrix have been much increased by the addition of 20 vol% zirconia. The microstructural features of the composite are observed by transmission electron microscopy (TEM) and high-resolution electron microscopy (HREM). The stabilibity of tetragonal zirconia in the matrix is attributed to the particle-size effect, and to the constraint effect of the silica matrix and that of the interphasic reaction layer. The increase in mechanical properties is discussed in relation to the residual stress and the enhanced elastic modulus caused by the incorporated ZrO2 particles.     

Sol-Gel Synthesis and Thermal Evaluation of Cordierite–Zirconia Composites (Ce–ZrO2, Y–Ce–ZrO2)

Cordierite and cordierite–zirconia composites (ceria- and yttria–ceria-stabilized zirconia) were prepared by sol-gel processing for different compositions. The precursor powders of these composites were studied using analytical techniques such as thermogravimetric analysis, differential thermal analysis, X-ray diffraction, and infrared spectroscopy for different temperatures to investigate the crystallization behavior of the material. It was observed that the cordierite–zirconia composite powders are crystallized as -cordierite and tetragonal zirconia when sintered at a temperature above 1200°C in the presence of zircon in the cordierite matrix. Powder morphologies of cordierite–zirconia composites have also been investigated.     

High Selective Etching of Aluminum Alloys In High Plasma Density Reactor

An inductively coupled plasma (ICP) discharge and its etching behaviors for aluminum alloys were investigated in this report. A radio frequency power supply was used for plasma generation. The unique hardware configuration enabled one to control ion energy separately from plasma density. Plasma properties were measured with a Langmuir probe. Electron temperature, plasma potential and plasma density were found to be comparable with those reported from Electron Cyclotron Resonance (ECR) and other types of reactors[1].A mixture of HBr and chlorine gases were used for this aluminum etch study. Experimental matrices were designed with Response Surface Methodology (RSM) to analyze the process trends versus etch parameters, such as source power, bias power and gas composition. An etch rate of 8500A to 9000A per minute was obtained at 5 to 15 mTorr pressure ranges. Anisotropic profiles with high photoresist selectivity (5 to 1) and silicon dioxide selectivity greater than 10 were achieved with HBr addition into chlorine plasma.Bromine-containing chemistry for an aluminum etch in a low pressure ICP discharge showed great potential for use in ULSI fabrication. In addition, the hardware used was very simple and the chamber size was much smaller than other high density plasma sources.     

Calculation of Surface Energy of Metals and Alloys by theElectron Density Functional Method

The surface energy values of (100), (110), (111) surfaces in Ni. Al and ordered alloys NiAl and Ni3Al have been calculated within the framework of methodology based upon the electron density functional method. The results of calculations are in good agreement with the known for pure metals experimental data and in case of Ni3Al allop There is also a good agreement with the results obtained by calculation using the embedded atom method. The investigation has been carried out in this work to show that the surface energy σ of alloys can not be interpreted as an averaged concentration σ of pure metals. For NiAl, the obtained resulsts reveal considerable distinctions in anisotropy of a in comparison to the anisotropy of surface energy in pure matals.     

The role of cementite in the metal dusting of Fe–Cr and Fe–Ni–Cr Alloys

Abstract

Model Fe–25 w/o (weight percent) Cr and Fe–25 Cr–Ni alloys containing 2.5, 5, 10 and 25w/o nickel were exposed to a CO–26H₂–6H₂O (vol. pct) mixture at 680°C under thermal cycling conditions. The supersaturated carbon activity was calculated to be 2.9 (referred to graphite) and M₃C was predicted to form on Fe–25Cr and Fe–25 Cr–2.5 Ni, but not on higher nickel content alloys. Metal dusting occurred on all alloys, accompanied by internal carburisation. Transmission electron microscopy of the dusting deposit showed that much of the carbon consisted of hollow graphite nanotubes. Small, metal-rich particles were found at the carbon filament tips. These were identified as single crystal Fe₃C in the case of Fe–25 Cr, and M₃C, containing low levels of nickel, in the case of Fe–25 Cr–2.5 Ni and Fe–25 Cr–5 Ni. In contrast, the particles found at the filament tips on the higher nickel, two phase, alloys were both M₃C and austenitic Fe–Ni. Strong orientation relationships were determined between the graphite and cementite particles, however, no consistent and clear crystallographic relationship was deduced between the graphite and austenite particles. It is concluded that carbon deposition from the gas is catalysed by both Fe₃C and austenite. Subsequent carbon nanotube growth reflects the orientation relationship between Fe₃C and the graphite.     

Viscosity of Industrially Important Al–Zn Alloys. I-Quasi-eutectic Alloys

Viscosity is a very important property in several fields of materials and metal processing. Many systems are still not fully characterized with regard to their thermophysical property data. In addition, as new alloys are developed or used, viscosity data are necessary to understand the best processing conditions. The data that are available frequently show large discrepancies. The effect of minor constituents is very difficult to model and can have a strong effect on the viscosity. Measurements of the viscosity of Zn–Al alloys, with a quasi-eutectic composition, were performed in the molten state, for temperatures between 690 K and 751 K. The measurements were performed with an oscillating cup viscometer, with an estimated uncertainty of 2 % to 5 %, depending on the alloy. The influence of other minor components, such as Pb, Mn, and Mg, on the viscosity of the alloys is discussed. It was concluded that Pb induces a decrease in viscosity, with Mg having the opposite effect, while the effect of Mn is not significant. All the alloys showed Newtonian behavior in the temperature range studied and a non-Arrhenius temperature dependence of viscosity, as usually found for pure molten metals.     

Process and properties of electroless Ni–Cu–P–ZrO2 nanocomposite coatings

Electroless Ni–Cu–P–ZrO₂ composite coating was successfully obtained on low carbon steel matrix by electroless plating technique. Coatings with different compositions were obtained by varying copper as ternary metal and nano sized zirconium oxide particles so as to obtain elevated corrosion resistant Ni–P coating. Microstructure, crystal structure and composition of deposits were analyzed by SEM, EDX and XRD techniques. The corrosion behavior of the deposits was studied by anodic polarization, Tafel plots and electrochemical impedance spectroscopy (EIS) in 3.5% sodium chloride solution. The ZrO₂ incorporated Ni–P coating showed higher corrosion resistance than plain Ni–P. The introduction of copper metal into Ni–P–ZrO₂ enhanced the protection ability against corrosion. The influence of copper metal and nanoparticles on microhardness of coatings was evaluated.     

The Calculation of Thermodynamic Properties of Ga-Sb Binary Liquid Alloys

In this paper, the activities of componentsof Ga-Sb system have been calculated from itsphase diagram by using computer program CABPD(calculating activities from binary phasediagrams) presented by us in previous paper.The excess free energy of liquid solution canbe expressed as:ΔG_m=X_(Ga)X_(Sb)(4392+17022X_(Sb)-15138X_(Sb)) J/mol In order to verify the reliability ofcalculated results, a discriminant has beenproposed.     

Synthesis of ZnFe2O4–Zn2ZrO4Solid Solutions

Low-temperature plasma synthesis was used to prepare solid solutions ( and ) in the ZnFe₂O₄–Zn₂ZrO₄pseudobinary system. The Zn_{2 – x} Zr_{1 – x} Fe_2x O₄solid solutions were found to have a tetragonal spinel structure (a= 8.607–8.740 Å, c= 8.798–9.120 Å) in the composition range x= 0–0.55 and a cubic spinel structure (a= 8.447–8.539 Å) at x= 0.75–1.0. The tetragonal lattice distortion is attributed to a pseudo-Jahn–Teller effect. The electrical conductivity of the solid solutions shows semiconducting behavior and rises by a few orders of magnitude with increasing Fe³⁺content.     

Preparation and Magnetic Properties of InTe–Cr2Te3 Alloys

InTe–Cr₂Te₃ alloys were prepared and characterized by temperature-dependent magnetic measurements. The results lend support to earlier phase-diagram data indicating the formation of compounds with the compositions In₉Cr₂Te₁₂ and In₂Cr₆Te₁₁. In₉Cr₂Te₁₂ is shown to be a ferromagnet, while In₂Cr₆Te₁₁ has a more complex magnetic structure.     

A Comparison of Surface Tension,Viscosity, and Density of Sn and Sn–Ag Alloys Using Different Measurement Techniques

This work is aimed at comparing several methods for the measurement of physical properties for molten Sn and Sn–Ag alloys, namely, surface tension, density, and viscosity. The method used for viscosity in this work is the modified capillary method. For surface tension and density, the data used for comparison were previously measured using the maximum bubble pressure method and the dilatometer technique, respectively, for four Sn–Ag alloys having (3.8, 32, 55, and 68) at% Ag. The results are compared with those obtained using a new method based on a fluid draining from a crucible under the influence of gravity, designated the Roach–Henein (RH) method. This new method enables the determination of these three physical properties in one set of measurements. Liquid Sn was used as well as two liquid Sn–Ag alloys having (3.8 and 34.6) at% Ag with the RH method. It was determined that the RH method may be used to simultaneously obtain surface tension, viscosity, and density and that the errors associated with these measurements were similar to those obtained using traditional and separate techniques. Comparisons of the measured viscosity and surface tension to those predicted using thermodynamic models will also be presented. Finally a comparison of mixing model predictions with the experimentally measured alloy surface tension and viscosity is also presented.     

Properties of Phases and Alloys of the Mo–Ni–B System in the Ni–MoNi–Mo2NiB2–Ni2B Region

Materials Science - For alloys of the Mo–Ni–B system annealed at subsolidus temperatures (and some as-cast alloys) in the Ni–MoNi–Mo2NiB2–Ni2B region, we study the...