Papers by Keyword: Vitrification

Abstract: Thermosets play an important role in composite processing, adhesive bonding and coating. In all these applications, shrinkage my cause a significant amount of residual stress, leading to distortion, reduced load carrying capacity and cracking. The chemical curing reaction is accompanied by a reduction in volume called “chemical shrinkage”. If curing is performed at elevated temperature, cooling to ambient conditions afterwards is accompanied by “thermal shrinkage” and further shrinkage due to so-called “physical ageing”. A skillful combination of available methods makes it possible to separate chemical shrinkage in the viscous state from shrinkage in the gelled and vitrified state. Modeling of the time-and temperature-dependent properties is the prerequisite for the prediction and control of residual stresses caused by shrinkage in thermoset polymers.

Abstract: Thermoset adhesives convert from liquid to solid due to chemical reactions. Once cured, these adhesives carry the potential to create strong load-bearing joints, resisting even severe detrimental service conditions. In the progress of curing of a thermoset adhesive the viscoelastic properties of the resin and hardener formulation change as the chemical reaction proceeds. Gelation occurs once a continuous 3-dimensional network of polymer chains has been created. After gelation, the microstructure of the resin is fixed and further cure is affected by diffusion limitations [1]. Mastering of the curing kinetics and the physicochemical changes in the transition from the liquid to the solid-state is essential to reliably process adhesives in industrial applications. Rheological experiments in parallel plate configuration have become a well-established practice in investigating viscoelastic properties in the progress of curing. In practice, it has shown to be challenging to access the full range of viscoelastic parameters of thermoset resins with a low initial viscosity from the very beginning of the curing reaction to the post-cure consolidation of the vitrified polymer. This paper will discuss experimental methods and criteria for the viscoelastic analysis of curing thermoset adhesives and present experimental data of the time-, temperature-, and frequency-dependent viscoelastic properties of a curing thermoset epoxy in relation to the features of its time-temperature-transformation-diagram.

Abstract: New techniques for the analysis of complex images were advanced by the example of asurface microrelief of the Fe70Cr15B15 alloys, obtained by the melt-spinning at different linearvelocity of a quenching roller. Proposed techniques are based on the fast Fourier transform of theimage using digital signal processors. The degree of morphological ordering/disordering of ribbonswas determined due to the parameterization of mode spectra by entropy functionals. The best glassforming ability for alloys of the studied composition was obtained at 30 m/s.

Abstract: The effect of sintering temperature on physical properties of Setiu clay sediment was studied. The ceramic samples were prepared via slip casting method, and sintered at different temperatures ranging from 900 to 1100°C, with 2 hours soaking time. Morphologies of ceramic samples were characterized using Tabletop Microscope. Shrinkage was determined from measurement of samples before and after sintering process. A good ceramic sample without warping or cracks obtained after casting process and after sintered at different temperatures. The results show that sintering temperatures greatly influence morphology of samples. As sintering temperature increased the grain boundaries between particles become smoother and compacted while pores shrunk due to the densification behavior. A considerable increased in shrinkage from 5 to 20% were observed with increasing temperature from 900 to 1100°C. As conclusion, Setiu clay sediment are suitable for production ceramic products and 1000°C can be consider the best sintering temperature in terms of quality of products and production costs.

Abstract: FSUE Radon deals with collection, transportation, treatment, conditioning, and interim storage and final disposal of conditioned low-and intermediate-level radioactive wastes (LILW) as well as radiation monitoring, decontamination and environmental remediation of Moscow and Moscow area. Liquid LILW with high salinity is subject to vitrification at the Radon full scale vitrification plant using a cold crucible inductive melting (CCIM) at temperatures of 1150-1200 °C. The bench-scale cold crucible based unit is used for research works and feasibility study on new promising ceramic and glass-ceramic waste forms based on incinerator slag and ash. Solid and liquid organic LILWs are treated in a plasma shaft furnace with liquid slagging at temperatures of 1400-1500 °C. Molten slag is solidified in containers yielding a glass-crystalline material with high chemical durability and strong mechanical integrity suitable for safe long-term storage and disposal in both interim repositories and underground sites. One of the promising methods for LILW treatment is application of thermochemical reactions – self-propagating high-temperature synthesis (SHS) with high energy release which is considered as a potential technology for treatment of spent ion-exchange resins, silts and grounds and some specific wastes.

Abstract: We studied an adsorption method as a technique of collection, and a vitrification method of iodine toward safekeeping. In this study, iodine-adsorptions on magnesium compounds were evaluated, and fixation of iodine into glass was tried. As a result, it was revealed that 1 g of magnesium oxide with high surface area successfully adsorbed 2.23 g of iodine. Iodine-adsorbed magnesium compound was tried to be vitrified with MgO-P₂O₅ glass.

Abstract: Vitrification is considered to be an attractive technology for municipal solid waste incineration. The main components of the vitrified bottom ash slag are SiO₂, CaO, Al₂O₃, Fe₂O₃, Na₂O and MgO, accounting for more than 90% of the total mass. The phase relations and thermodynamic properties of the CaO-Al₂O₃-SiO₂-FeOx-MgO-Na₂O oxide system is highly required, and is of great significance for optimization of vitrification processing and sustainable resource utilization of melting slag. Thermodynamic properties of the vitrified bottom ash slag were investigated in the present work. A study on the phase equilibria of CaO-SiO₂-Na₂O system was carried out with modelling method.

Abstract: Plasma is ionized gas-like substance, comprised by the e-deprived atoms and electron-positron. Plasma possess the characteristics of high energy, high thermal capacity, fast response and electric conversion efficiency, which shows unique advantages and good prospects for the effective disposal of POPs wastes. This paper introduced the basic principle and mechanism of plasma arc technology as a non-combustion technology; reviewed the development of application of plasma technology in the processing of HFC23, organic fluoride industrial waste, phenyl chlorosilane residue, medical waste, printed circuit board, chemical weapons and other hazardous wastes; analyzed the major technical and economic advantages and disadvantages for the plasma technologies in the POPs waste treatment; And corresponding comments and suggestions were proposed to promote the application of plasma technology for POPs waste disposal in China.

Abstract: Heavy metals are one of the important factors that need to be considering for the disposal of sludge incineration ash. Vitrification by melting has been identified as a potentially effective tool that can solidify the heavy metals into the glass matrix structure. In this paper, the characteristics of heavy metals in sludge incineration ash (SIA) were studied by using Community Bureau of Reference (BCR) sequential extraction procedure. Fractions extracted by the BCR sequential procedure were acid soluble/exchangeable, reducible, oxidizable and residual fraction, respectively. The total contents of Cu were the highest, followed by then Zn, Cr and Ni, and the content of Pb was the least. The effects of basicity (CaO/SiO₂) on the solidification efficiency of heavy metals and the leaching toxicity of obtained molten slag were investigated. The molten slags demonstrated strong capacity on the stabilization/ solidification of heavy metals. With the basicity value increasing from 0.4 to 0.8, the solidification efficiency of Cu, Zn, Pb and Ni decreased first and then increased, while that of Cr decreased straightly. The heavy metal leaching test results of the molten slags were far lower than the limits required by the regulatory standard of EPA, confirming the possibility of engineering and construction applications.

Abstract: Promoting of mullite generation has been studied by replacing kaolinite with pyrophyllite because of mullite has excellent strength and thermal shock resistance. Effects of promoting of mullite generation and vitrification by replacing kaolinite with pyrophyllite on the mechanical and thermal properties were investigated. Addition of 45-55% pyrophyllite as a replacement of kaolinite (pyrophyllite (45-55%)-feldspar (30%)-clay (20%)) could vitrify samples (water absorption: 0.05%, bulk density: 2.66g/cm3) and improve the strength (122MPa) of samples fired at 1280°C. In ternary porcelain system, pyrophyllite-feldspar-clay, mullite generation of samples with 50% pyrophyllite reaches about 78.7% and thermal expansion coefficient is 5.4×10-6/K. Beyond 50% pyrophyllite addition, quartz and cristobalite phases increased. And thermal expansion coefficient of samples decreased with increasing of mullite amount.