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Bennett, James

Publications and source records attributed to Bennett, James.

14 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Microstructure and Chemical Composition of Al2O3-, Cr2O3- and MgO-rich Refractories Exposed to Plastic Ashes

Plastics are widely integrated with today’s lifestyle due to their low cost, durability, lightweight, water resistance, and flexibility. However, tremendous plastic waste cause severe threats to the environment. Thus, sustainable recycling of plastic waste is critical, where plastic waste gasification technology with carbon management becomes one of the most effective recycling methods. We simulate the gasification process by exposing the Al2O3-, Cr2O3- and MgO-rich refractories to synthetic plastic ashes at 1500 ℃ for 50 h. A comprehensive study on the microstructure and chemical composition change before/after exposure is conducted using scanning electron microscopy. Meanwhile, the differences among these three refractories after exposure are revealed for quantifying the performance in plastic ashes. Discussion of the results will establish an understanding of the influence of plastic ashes on the microstructure, composition, and phase of different types of refractories, providing insights into designing new refractory materials for future recycling of plastic waste.

Fang, Xiaotian↗
DOE OSTI2022

On the Phase with an Unreported Ternary Composition Found in the P-Pt-Rh System

This work reports a ternary structure in the P-Pt-Rh system, which has a composition not reported in the literature. The structure formed in the Pt-6 wt.% Rh alloy which was partially melted in a P-enriched CO environment near 1000 °C isothermally and non-isothermally as part of the type B thermocouple assembly. A composition and a crystal structure of this phase were investigated by utilizing SEM, EPMA, XRD and TEM techniques to discuss the potential of this structure being a true ternary phase. The EPMA indicated chemistries of the ternary structure from both isothermal and non-isothermal samples were about 23P-52Pt-25Rh (at.%) and, 22P-54Pt-24Rh (at.%) respectively. TEM diffraction patterns identified this ternary structure to be crystalline with a complex non-cubic structure, and confirmed it was not amorphous. Finally, by superimposing the compositions in the ternary phase diagram, it was concluded this phase was not extensions of any binary phases known in the respective binary systems.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Controlled evolution of rare earth phosphate in coal ash slag

Coal ash slag as a waste by-product, is generated from commercial processes that include gasification facilities, power plants, and steelmaking industries. Some is recycled into construction materials, insulation fibers, and used as a soil neutralizer, but the majority is still discarded. Coal ash slag exhibit trace amounts of critical materials including rare earth elements (REEs). An economically viable extraction of REEs from the coal ash would lower the production costs, addressing the availability and environmental concerns. In nature, most REEs exist as phosphate such as monazite but its synthetic evolution in coal ash slag has never been reported. In industrial processes, P may originate from coal, additives, and/or refractory liners. REEs may be extracted by first concentrating REEs into phosphates, sulphide, or fluorides [1], or carbonates [2]. In this work, P-enriched coal ash slag bearing REEs was first melted above 1600 °C, then crystallization behaviors in the melt during controlled cooling was studied. REE phosphate coprecipitated with mullite and hematite with mullite being the first crystal to form on cooling. The REEs were rejected from the molten slag, mullite, and hematite, and tended to segregate only to the phosphate phase with REE concentration as high as 58 wt.% in the structure.

Nakano, Jinichiro↗
DOE OSTI2021

Concentrating rare earth elements to phosphate in molten coal ash by a temperature gradient approach

Synthetic coal ash bearing 560 ppm europium oxide, blended with aluminum phosphate, was heat treated above its melting temperature and crystal evolutions with respect to europium concentration under controlled cooling were studied. The sample in a boat crucible was subjected to a temperature gradient of 100 °C across it to cause zone refining effects on crystallization behaviors in the melt (slag). Post analysis found six mineral phases formed from the melt while europium was only present in calcium phosphate, implying the majority of europium was segregated to the calcium phosphate. Europium concentrations in the calcium phosphate phase tended to be higher at zones with higher temperatures: as high as 7200 ppm, a 13-fold increase from the initial concentration.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2020

Controlled evolution of rare earth phosphate in coal ash slag

Coal ash slag as a waste by-product, is generated from commercial processes that include gasification facilities, power plants, and steelmaking industries. Some is recycled into construction materials, insulation fibers, and used as a soil neutralizer, but the majority is still discarded. Coal ash slag exhibit trace amounts of critical materials including rare earth elements (REEs). An economically viable extraction of REEs from the coal ash would lower the production costs, addressing the availability and environmental concerns. In nature, most REEs exist as phosphate such as monazite but its synthetic evolution in coal ash slag has never been reported. In industrial processes, P may originate from coal, additives, and/or refractory liners. REEs may be extracted by first concentrating REEs into phosphates, sulphide, or fluorides [1], or carbonates [2]. In this work, P-enriched coal ash slag bearing REEs was first melted above 1600 °C, then crystallization behaviors in the melt during controlled cooling was studied. REE phosphate coprecipitated with mullite and hematite with mullite being the first crystal to form on cooling. The REEs were rejected from the molten slag, mullite, and hematite, and tended to segregate only to the phosphate phase with REE concentration as high as 58 wt.% in the structure.

Nakano, Jinichiro↗
NASA NTRS1988

On the secondary instability of Taylor-Goertler vortices to Tollmien-Schlichting waves in fully developed flows

There are many flows of practical importance where both Tollmien-Schlichting waves and Taylor-Goertler vortices are possible causes of transition to turbulence. The effect of fully nonlinear Taylor-Goertler vortices on the growth of small amplitude Tollmien-Schlichting waves is investigated. The basic state considered is the fully developed flow between concentric cylinders driven by an azimuthal pressure gradient. It is hoped that an investigation of this problem will shed light on the more complicated external boundary layer problem where again both modes of instability exist in the presence of concave curvature. The type of Tollmien-Schlichting waves considered have the asymptotic structure of lower branch modes of plane Poiseuille flow. Whilst instabilities at lower Reynolds number are possible, the latter modes are simpler to analyze and more relevant to the boundary layer problem. The effect of fully nonlinear Taylor-Goertler vortices on both two-dimensional and three-dimensional waves is determined. It is shown that, whilst the maximum growth as a function of frequency is not greatly affected, there is a large destabilizing effect over a large range of frequencies.

Bennett, James↗
NASA NTRS1986

On the secondary instability of Taylor-Goertler vortices to Tollmien-Schlichting waves in fully-developed flows

There are many flows of practical importance where both Tollmien-Schlichting waves and Taylor-Goertler vortices are possible causes of transition to turbulence. The effect of fully nonlinear Taylor-Goertler vortices on the growth of small amplitude Tollmien-Schlichting waves is investigated. The basic state considered is the fully developed flow between concentric cylinders driven by an azimuthal pressure gradient. It is hoped that an investigation of this problem will shed light on the more complicated external boundary layer problem where again both modes of instability exist in the presence of concave curvature. The type of Tollmein-Schlichting waves considered have the asymptotic structure of lower branch modes of plane Poisseulle flow. Whilst instabilities at lower Reynolds number are possible, the latter modes are simpler to analyze and more relevant to the boundary layer problem. The effect of fully nonlinear Taylor-Goertler vortices on both two-dimensional and three-dimensional waves is determined. It is shown that, whilst the maximum growth as a function of frequency is not greatly affected, there is a large destabilizing effect over a large range of frequencies.

Bennett, James↗
NASA NTRS1986

Taylor-Goertler instabilities of Tollmien-Schlichting waves and other flows governed by the interactive boundary-layer equations

The Taylor-Goertler vortex instability equations are formulated for steady and unsteady interacting boundary-layer flows. The effective Goertler number is shown to be a function of the wall shape in the boundary layer and the possibility of both steady and unsteady Taylor-Goertler modes exists. As an example the steady flow in a symmetrically constricted channel is considered and it is shown that unstable Goertler vortices exist before the boundary layers at the wall develop the Goldstein singularity discussed by Smith and Daniels (1981). As an example of an unsteady spatially varying basic state, it is considered the instability of high-frequency large-amplitude two- and three-dimensional Tollmien-Schlichting waves in a curved channel. It is shown that they are unstable in the first 'Stokes-layer stage' of the hierarchy of nonlinear states discussed by Smith and Burggraf (1985). This instability of Tollmien-Schlichting waves in an internal flow can occur in the presence of either convex or concave curvature. Some discussion of this instability in external flows is given.

Hall, Philip↗