Band 105, Heft 10

Phase equilibria in the “MnO”–Al 2 O 3 –SiO 2 pseudo-ternary system in equilibrium with metallic alloy have been experimentally investigated in the temperature range from 1 423 K to 1 523 K. This study is a part of a broader research program on the phase equilibria in the Al 2 O 3 –CaO–Li 2 O–“MnO”–SiO 2 system, which is of importance to the slags used in a novel pyrometallurgical process for recycling of electric car batteries. The experimental procedures involve equilibration of high purity powder mixtures at high temperatures, rapid quenching, and accurate measurement of phase compositions using electron probe X-ray microanalysis, which allow the slag liquidus temperatures to be determined. This paper is part 1 of a series of two papers and focuses on the improvement of the experimental methodology. A number of elementary reactions taking place in the samples have been identified, including the formation of a tridymite ring around the alloy particles, manganese oxidation and manganese vaporization. This enabled relevant modifications to the experimental methodology to be introduced. The liquidus at 1 423 K, 1 473 K and 1 523 K in the high silica area and the solid solubility data in the tridymite and rhodonite phases have been reported.

The casting process design and production process of a bimetal wear-resistant block using liquid–solid processing are introduced in this paper. The mold-filling and solidification stages of the casting were numerically analyzed and optimized using ProCAST software. By modifying the original process, the shrinkage cavity at the top of the casting was eliminated and a good quality casting was obtained. The results of ultrasonic non-destructive inspection and a cut-open-check indicated that there was no shrinkage cavity in castings produced according to the modified casting process. The cut-open-check and practical applications also indicated that the bond between the matrix and wear-resistant part was very reliable.

Melt flows in the Kyropoulos sapphire growth system include Marangoni convection and buoyancy convection. From the seeding stage to the final growth stage, both the area of the free surface and melt height decrease to zero from initial values, and hence the flow pattern in the melt varies during growth. To study systematically melt convection and its influence on the growth process, a non-dimensional parameter is introduced to denote the relative strength of Marangoni convection to buoyancy convection. Temperature and stream function distributions for the different growth stages are simulated. It is found that Marangoni convection is negligible during the early growth. However, it plays an important role in the late growth. The remelting of the crystal surface starts when Marangoni convection becomes dominant, and thus it may be related to this convection mode. The interface shape is found to be changing during the whole growth process, which reduces the industrial productivity of sapphire. Interface convexity, crystal diameter and the non-dimensional parameter are presented as functions of the melt height. Interface convexity is further described as a function of the non-dimensional parameter. The results are consistent with experimentally observed phenomena.

During the liquid phase sintering process a liquid is formed, penetrates into the pores, causes rearrangement of particles and shrinkage and forms an amorphous and/or crystalline intergranular phase after firing which re-melts upon heating to the same sintering temperature. In this research a method is proposed to alter the intergranular phase to a phase with a melting point higher than the sintering temperature. The hypothesis is based on the shape of the phase diagram and precise control of particle sizes of liquid forming species. Results show that in the CaO–Al 2 O 3 system a liquid is formed at 1 500 °C and it will then change to CaO. Al 2 O 3 with a melting point of more than 1 600 °C. Differential scanning calorimetry analysis shows that the processes of formation of liquid and crystallization of concomitant crystalline phases occur obviously separately in this system. The system CaO–TiO 2 also confirms the hypothesis, although more analytical evidence is needed for the latter.

Laser treatment of pre-prepared titanium alloy surface is carried out and electrochemical response of the treated surface is analyzed. B 4 C particles are located in a carbon film at the workpiece surface prior to the laser treatment process. Morphological and metallurgical changes are examined in the laser treated layer using analytical tools. Potentiodynamic tests are carried out to assess the corrosion rate of the treated surface. It is found that the laser treated surface is free from large-scale asperities such as large size cracks and cavities. Laser treatment significantly improved the corrosion resistance of the surface. The presence of B 4 C particles contributes to microhardness enhancement at the treated surface; however, the particles do not demonstrate any adverse effect on the corrosion resistance of the surface.

In this study, LiCoO 2 is doped with 2 mol.% Cr and Mo in order to determine the effect of these elements on the electrochemical performance. Precursors are synthesized by means of freeze drying. Calcination is applied at 750 °C for 24 h. Doping content and calcination temperature as well as duration are very important for producing impurity-free layered LiCoO 2 . If the doping content is larger than 2 mol.% or when the calcination temperature is decreased to 550 °C, impurity phases are seen. As a result, the sample doped with 2 mol.% Cr has better high charge and discharge rate capability, and cycleability, but discharge capacity is slightly lowered when compared to the undoped sample. Electrochemical impedance spectroscopy results show that surface film resistances of Cr-doped samples are lower than that of the undoped sample.

The inhibition effect of olive leaf extract on corrosion of carbon steel in brine solutions saturated with CO 2 was investigated at 25 °C and 65 °C by means of Tafel polarization, weight loss measurements and Fourier transform infrared spectroscopy. The experimental results reveal that the olive leaf extract has a good inhibition effect on the carbon steel in CO 2 -saturated brine solution at both temperatures. Tafel polarization investigations revealed that olive leaf extract acted as a mixed inhibitor showing anodic and cathodic behavior. The adsorption of olive leaf extract on carbon steel surface obeyed the Langmuir adsorption isotherm. The adsorption thermodynamic parameters indicated the physisorption of olive leaf extract on carbon steel surface was a spontaneous and exothermic process with an increase in entropy. Fourier transform infrared spectroscopy spectra showed types of bonding for olive leaf extract on the carbon steel surface.

The tribological behavior of Fe 3 Al composite with 60 wt.% Fe 3 AlC 0.5 under air and vacuum was studied. The composite exhibited a lower wear rate but somewhat higher friction coefficient under air than vacuum. The wear rates increased and the friction coefficients decreased with increasing the applied load under both conditions. The sub-layer of the worn surface under vacuum suffered from severe plastic deformation. This was not the case under air due to protection by surface oxide films. The dominant wear mechanisms were plastic deformation and adhesion under vacuum and oxidative wear and slight delamination under air.

The effects of burnishing and other conventional machining processes (grinding, reaming, drilling, turning, and honing) on the surface characteristic properties of mild steel were investigated and compared in terms of surface roughness, circularity (roundness), and cylindricity in this study. The effect of these processes on the microstructures was also examined to understand the relationship between the machining process and surface characteristic properties. All surface machining processes were performed under constant depth of cut, cutting speed, and feed rate. The highest hardness was obtained on the burnished surface. Experimental results also showed that the roller burnishing method is the most favorable post-machining process method for obtaining optimum surface topography on mild steel.

In this paper, additional small-scale boundary effects on the free vibration of single-walled carbon nanotubes under various boundary conditions are investigated using an analytical nonlocal Euler-beam model. From the numerical results, it seems that the various beam boundary conditions due to local and nonlocal elasticity are equivalent. For simplicity, local boundary conditions can still be used even for the free end. It is convenient to analyze the vibration of single-walled carbon nanotubes under various types of boundary conditions. In addition, Hamilton's energy function, which can be explicitly expressed by transverse displacement, has also been derived to explain the boundary equivalence of nonlocal and local beams.

Gold nanoparticles (AuNPs) are considered to be ideal drug delivery vehicles for chemotherapeutic molecules due to the bio-inert nature of the colloids. Critical factors which determine the cellular internalization and intracellular localization of AuNPs are nanoparticle size as well as surface charge. Polydisperse AuNPs with a cationic surface charge, rich in primary amines would present multiple covalent molecule attachment loci and would be ideal for the delivery of chemotherapeutics which have multiple intracellular sites of action. In an adapted synthesis method, polydisperse cationic AuNPs were produced which were soluble in aqueous solution and showed high chemical stability. The synthesis was conducted in a comparative manner using polyethyleneimine (PEI) and reduced glutathione (GSH) as AuNP surface passivation ligands. Anisotropic as well as spherical morphologies were observed for the PEI passivated AuNPs, where the morphology was dependent on the ratio of reducing agent to Au 3+ in solution. Only spherical morphologies were observed when GSH was used as the passivation ligand under similar conditions. The surface chemistry of the AuNPs was characterized by means of attenuated total reflectance spectroscopy and elemental composition was determined using energy dispersive X-ray spectroscopy. The PEI AuNPs surface was nitrogen rich, cationic and provided multiple covalent primary amine attachment points for downstream surface tailoring.