Glass formation in the system PbO-PbCl2

The preparation of glasses in the system PbO-PbCl₂ is described. The behaviour of the glass transition temperatures, heat capacities and microhardnesses as a function of glass composition has been investigated. The variations are discussed in terms of the structural features of the glasses.Communication No. 256 from the Solid State and Structure Chemistry Unit.     

Bulk glass formation in the Zr--Ti--Al--Cu--Ni system

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Phase equilibria and glass formation in the AsSe-MnSe system

The phase equilibrium in the AsSe-MnSe system has been studied using physicochemical characterization techniques (differential thermal analysis, X-ray diffraction, microstructural analysis, microhardness tests, and density measurements), and its phase diagram has been mapped out. The system is shown to be a pseudobinary join of the ternary system Mn-As-Se. At AsSe: MnSe = 1: 1, the system contains a compound of composition MnAsSe₂, which melts incongruently at 750°C. The glass-forming region extends to 15 mol % MnSe. We have examined the crystallization behavior of the glasses. Solid AsSe dissolves up to 2 mol % MnSe, and solid MnSe dissolves up to 2.5 mol % AsSe.     

Ceramic flake formation in the aluminosilicate system by plasma spraying

Alumina and aluminosilicate flakes with compositions Al₂O₃, 3Al₂O₃2SiO₂ and Al₂O₃2SiO₂ have been produced from commercial raw materials using a direct current plasma spray process in air. The microstructure and phase constitution of the as-sprayed flakes were examined with optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). Changes in phase constitution of the flakes with heat-treatment were examined using differential thermal analysis (DTA) and XRD of heat-treated samples. The as-sprayed Al₂O₃ flakes consisted of -Al₂O₃ phase plus a minor -Al₂O₃ phase. The -phase could be removed by heat treating the flakes at 1300C for 2 h. The aluminosilicate flakes consisted of 3Al₂O₃:2SiO₂ (mullite) and an amorphous phase which crystallised to 3Al₂O₃:2SiO₂ (mullite) after heat treatment at 1100C for 2 h. These flakes may find applications as high temperature thermal insulation materials.     

Goal-balancing process for goal formation in the fractal manufacturing system

The coordination architecture and mechanisms are proposed for the goal-balancing process (GBP), which is one of the components of goal-formation process (GFP) in the fractal manufacturing system (FrMS). Since each agent in the FrMS generates, achieves and modifies its own goal autonomously during the coordination process with other agents, it is necessary to develop a systematic methodology for the goal-formations in a manufacturing system: GFP takes charge of this methodology, which enables the formation of and the changes in goal through coordination between agents in real-time in the distributed and dynamic systems. The GFP is composed of three sub-processes: the goal-generating process (GGP), the goal-harmonizing process (GHP), and the GBP. The GGP makes and propagates goals for all fractals. The GHP then eliminates or reduces possible conflicts and interferences between goals generated in GGP. The GBP is the post-process of GHP; it refines the fractal's goal, which has been ridded of conflict during the GHP to enhance the global performance of the system, rather than maximizing the performance of each fractal. For the development of the GBP we proposed a mechanism for unit goal-balancing process (UGBP), which is the basic process of GBP that adopts the, fuzzy decision-making, and distributed problem solving approaches.     

Contact mass transfer and phase formation in the Au-Pb system

Contact mass transfer and phase formation processes in the Au-Pb system have been studied by x-ray diffraction, scanning electron microscopy, tunneling electron microscopy, and x-ray microanalysis. The results indicate that dynamic and thermal influences give rise to gold dispersion followed by the formation of intermetallics and eutectic systems.     

Glass formation in the system CaO-Al2O3-CaF2

The formation of glass in the system CaO-Al₂O₃-CaF₂ has been investigated in sealed platinum capsules having about one atmosphere pressure of AlF₃ vapour. Transparent colourless glass could be obtained in the low-fluoride moderate-alumina region of the system (Al₂O₃ 35 to 60%, CaF₂ 0 to 20%). With the concentration of CaF₂ exceeding 20% considerable amount of quench crystals of CaF₂ appeared in the glass. Moderate-alumina low-lime melts containing more than 35% CaF₂ occur in an immiscibility zone. At the low-fluoride periphery of the liquid immiscibility zone a small zone of metastable liquid immiscibility has been found. The results of electron microscopic and infra-red spectroscopic studies of a few selected glasses have been analysed in combination with the molar refractivity data to reflect upon the co-ordination characteristics of aluminium in these glasses.     

Glass formation adjacent to the intermetallic compounds in Cu-Zr binary system

On the contrary to the common belief that glass formation is unfeasible near terminal intermetallic compound due to fast crystallization kinetics, here we present our findings that bulk metallic glasses are readily formed near intermetallic compounds, far away from the traditional region of glass forming near eutectics. While the intermetallic compounds themselves are not possible glass formers, bulk metallic glasses can be quenched compositionally neighboring the intermetallic compounds as close as 0.5 at.%. Taking binary Cu-Zr as a model system, the phenomenon of two optimum glass forming compositions sandwiching the corresponding intermetallic compounds (Cu₅₁Zr₁₄, Cu₁₀Zr₇, CuZr, CuZr₂ and Cu₈Zr₃) is observed consistently. This new scenario of “intermetallic glass” is verified by the thermodynamic principle that the alloy liquids neighboring the intermetallic compounds possess lower Gibbs free energy than that of the compounds themselves. Furthermore, the sluggish crystallization behavior of these liquids provides an additional kinetic explanation.     

Phase formation in the system MgO-Ga2O3-SiO2

Subsolidus phase equilibria in the MgO-Ga₂O₃-SiO₂ system were studied by sintering 18 compositions. A stable gallium analogue of sapphirine and a metastable mullite-like phase were prepared. Ga-sapphirine melts incongruently to MgGa₂O₄ and becomes liquid at 1490 ± 5° C. A diagram showing subsolidus phase compatibility at 1390° C is presented.     

An investigation of the ordered DO19 phase formation in the Ti-Al system

For the Ti-rich, Ti-AI system, the- and- ₂ phase boundaries have been obtained through differential thermal analysis for alloy compositions ranging from 10.2 to 25.2 at% Al (6 to 16 wt% Al). It has been shown that in the above mentioned composition range, a metastable disordered-phase can be quenched in. This metastable then transforms to the ordered ₂(DO)₁₉ phase upon heating and/or isothermal ageing. It has also been observed that the kinetics of this ordering phenomenon is composition dependent.