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1.
Effects of heating rate,quartz particle size,viscosity, and form of glass additives on high‐level waste melter feed volume expansion
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SeungMin Lee Bradley J. VanderVeer Pavel Hrma Zachary J. Hilliard Jayven S. Heilman‐Moore Charles C. Bonham Richard Pokorny Derek R. Dixon Michael J. Schweiger Albert A. Kruger 《Journal of the American Ceramic Society》2017,100(2):583-591
Nuclear waste can be vitrified by mixing it with glass‐forming and ‐modifying additives. The resulting feed is charged into an electric glass melter. To comprehend melting behavior of a high‐alumina melter feed, we monitored the volume expansion of pellets in response to heating at different heating rates. The feeds were prepared with different particle sizes of quartz (the major additive component) and with varied silica‐to‐fluxes ratio to investigate the glass melt viscosity effects. Also, we used additional melter feeds with additives premelted into glass frit. The volume of pellets was nearly constant at temperatures <600°C. After a short period of volume shrinkage at ~600°C‐700°C, foam generation produced massive volume expansion. The low heat conductivity of foam hinders the transfer of heat from molten glass to the reacting feed. The extent of foaming increased with faster heating and higher melt viscosity, and decreased with increasing size of quartz particles and fritting of the additives. Volume expansion data are needed for the mathematical modeling of the cold cap. 相似文献
2.
Kai Xu Pavel Hrma Jarrett A. Rice Michael J. Schweiger Brian J. Riley Nicole R. Overman Albert A. Kruger 《Journal of the American Ceramic Society》2016,99(9):2964-2970
The feed‐to‐glass conversion, which comprises complex chemical reactions and phase transitions, occurs in the cold cap during nuclear waste vitrification. To investigate the conversion process, we analyzed heat‐treated samples of a simulated high‐level waste feed using X‐ray diffraction, electron probe microanalysis, leaching tests, and residual anion analysis. Feed dehydration, gas evolution, and borate phase formation occurred at temperatures below 700°C before the emerging glass‐forming melt was completely connected. Above 700°C, intermediate aluminosilicate phases and quartz particles gradually dissolved in the continuous borosilicate melt, which expanded with transient foam. Knowledge of the chemistry and physics of feed‐to‐glass conversion will help us control the conversion path by changing the melter feed makeup to maximize the glass production rate. 相似文献
3.
We investigated , by visual observation and numerical calculations , the foaming behavior of polypropylene within a foam injection mold cavity with the environmentally benign physical blowing agents nitrogen (N2) and carbon dioxide (CO2) . An 85‐ton core‐back injection‐molding machine with temperature and pressure monitoring systems as well as a high‐pressure view cell was used for the investigation . The experiments showed a prominent difference in bubble nucleation and growth between N2 and CO2 injection foaming . Even when the weight concentration of N2 dissolved in polymer was one‐third that of CO2 , N2 injection foaming provided a bubble number density that was 30 times larger and a bubble size that was one‐third smaller compared to CO2 injection foaming . Classical bubble nucleation and growth models developed for batch foaming were employed to analyze these experimental results . The models reasonably explained the differences in injection foaming behavior between N2 and CO2 . It was clearly demonstrated by both experiments and numerical calculations that N2 provides a higher number of bubbles with a smaller bubble size in foam injection molding compared to CO2 as a result of the lower solubility of N2 in the polymer and the larger degree of super‐saturation . POLYM. ENG. SCI., 2011. ©2011 Society of Plastics Engineers 相似文献
4.
Lidia K. Kazantseva Sergey V. Rashchenko 《Journal of the American Ceramic Society》2014,97(6):1743-1749
Lightweight glass‐ceramic material similar to foam glass was obtained at 700°C–800°C directly from alkali‐activated silica clay and zeolitized tuff without preliminary glass preparation. It was characterized by low bulk density of 100–250 kg/m3 and high pore size homogeneity. Chemical processes occurring in alkali‐activated silica clay and zeolitized tuff were studied using X‐ray diffraction, thermal gravimetry, IR‐spectroscopy, and scanning electron microscopy. Pore formation in both compositions is caused by dehydration of hydrated sodium polysilicates (Na2O·mSiO2·nH2O), formed during alkali activation. Additional pore‐forming gas source in alkali‐activated zeolitized tuff is trona, Na3(CO3)(HCO3)·2H2O, formed during interaction between unbound NaOH and CO2 and H2O from air. Influence of mechanical activation of raw materials on chemical processes occurring in alkaline compositions was also studied. 相似文献
5.
David A. Pierce Pavel Hrma José Marcial Brian J. Riley Michael J. Schweiger 《International Journal of Applied Glass Science》2012,3(1):59-68
The selection of raw materials affects the rate of batch-to-glass conversion. In all-electric melters, foam under the batch blanket limits the heat flux from the molten glass, thus slowing the rate of melting. Our study, in which we compare the melting behaviors of three batches formulated to vitrify high-alumina high-level waste, shows that a slowly dissolving refractory component can cause excessive foaming. Faster melting batches with gibbsite [Al(OH)3] or boehmite [AlO(OH)] as an alumina source produced substantially less foaming than a batch with corundum (Al2O3). Although gibbsite and boehmite dissolved below 500°C, corundum was still present in the batch up to 900°C; hence, the glass-forming melt lacked alumina in the batch with corundum. The low viscosity of that batch caused the open pores to close prematurely at 660°C, trapping gases and expanding to foam. This would explain the literature-reported slow melting rate of a batch with corundum, as compared to batches with gibbsite and boehmite. 相似文献
6.
Benjamin P. McCarthy Jaime L. George Derek R. Dixon Michelle Wheeler Derek A. Cutforth Pavel Hrma Diana Linn Jaehun Chun Miroslava Hujova Albert A. Kruger Richard Pokorny 《Journal of the American Ceramic Society》2018,101(11):5020-5029
During the vitrification of radioactive waste in a Joule‐heated melter, aqueous melter feed slurry forms a cold cap, a reacting and melting material, which floats on the surface of the molten glass. The rheological behavior of the feed affects cold cap formation and shape, and is vital for modeling the feed‐to‐melt conversion process. We used slurry feed simulant and fast‐dried slurry solids representing the cold cap to investigate the rheological behavior of the feed as it transforms into glass. Both low‐temperature and high‐temperature rheometry were performed and a new scheme was applied to estimate the feed viscosity. This study shows that the conversion advances in four sequential stages that form distinct regions in the cold cap: (i) a fast‐spreading boiling slurry from which water evaporates, (ii) a porous solid region (viscosity > 108 Pa s) containing reacting solids and molten salts, (iii) a plastic region in which glass‐forming melt connects the refractory solids (~108 to ~106 Pa s), and (iv) a viscous foam layer in which the viscosity drops from ~105 to ~101 Pa s. The implications for the mathematical modeling of the cold cap are discussed. 相似文献
7.
Richard Pokorny Zachary J. Hilliard Derek R. Dixon Michael J. Schweiger Donna P. Guillen Albert A. Kruger Pavel Hrma 《Journal of the American Ceramic Society》2015,98(10):3112-3118
The rate of glass production during vitrification in an all‐electrical melter greatly impacts the cost and schedule of nuclear waste treatment and immobilization. The feed is charged to the melter on the top of the molten glass, where it forms a layer of reacting and melting material, called the cold cap. During the final stages of the batch‐to‐glass conversion process, gases evolved from reactions produce primary foam, the growth and collapse of which controls the glass production rate. The mathematical model of the cold cap was revised to include functional representation of primary foam behavior and to account for the dry cold cap surface. The melting rate is computed as a response to the dependence of the primary foam collapse temperature on the heating rate and melter operating conditions, including the effect of bubbling on the cold cap bottom and top surface temperatures. The simulation results are in good agreement with experimental data from laboratory‐scale and pilot‐scale melter studies. The cold cap model will become part of the full three‐dimensional mathematical model of the waste glass melter. 相似文献
8.
Effect of glass transition temperature and saturation temperature on the solid‐state microcellular foaming of cyclic olefin copolymer
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Effect of glass transition temperature and saturation temperature on the solid‐state microcellular foaming of cyclic olefin copolymer (COC)—including CO2 solubility, diffusivity, cell nucleation, and foam morphology—were investigated in this article. COCs of low Tg (78°C) and high Tg (158°C) were studied. Solubilities are 20–50% higher in high Tg COC than in the low Tg COC across the saturation temperature range. Diffusivities are about 15% higher on average in high Tg COC for temperatures up to 50°C. A much faster increase of diffusivity beyond 50°C is observed in low Tg COC due to it being in the rubbery state. Under similar gas concentration, high Tg COC starts foaming at a higher temperature. And the foam density decreases faster in low Tg COC with foaming temperature. Also, high Tg COC foams show about two orders of magnitude higher cell nucleation density than the low Tg COC foams. The effect of saturation temperature on microcellular foaming can be viewed as the effect of CO2 concentration. Nucleation density increases and cell size decreases exponentially with increasing CO2 concentration. Uniform ultramicrocellular structure with an average cell size of 380 nm was created in high‐Tg COC. A novel hierarchical structure composed of microcells (2.5 μm) and nanocells (cell size 80 nm) on the cell wall was discovered in the very low‐density high‐Tg COC foams. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42226. 相似文献
9.
《Journal of Industrial and Engineering Chemistry》2014,20(5):3089-3095
Using waste LCD glass as a base material helped developed the manufacturing process of the spherical foamed body and its varied functionality. Also, the manufactured spherical foamed body showed great performance as a water treatment media. By mixing 90 wt% of waste LCD glass, 100 parts by weight of glass mixture that has 10 wt% kaolinite as a shaping agent, 1.0 part by weight of carbon foaming agent, and mixture of each 1.5 parts by weight of Na2CO3, CaCO3 and Na2SO4 as foaming agents and the MgO as a parting agent for 10 min of foaming calcination in the rotary kiln at 970–1000 °C, the spherical foamed body can be manufactured effectively. The manufactured spherical foamed body performed as a great water treatment media by showing 70.5% of SS removal efficiency, 56.1% of BOD removal efficiency, 57.5% of COD removal efficiency, 28.6% of denitrification and 49.8% of phosphorous removal. 相似文献
10.
Due to the numerous increase of the building energy consumption and huge volume of industrial wastes produced in China, the development of thermal insulation materials is quite needed. Herein, foam glass ceramic, a kind of thermal insulation materials, was fabricated by using solid wastes high alumina fly ash and waste glass as the main raw materials. First, in this study the proportion scheme of this research was designed by using Factsage 7.1 and the foaming agent was CaSO4. Secondly, the decomposition of calcium sulfate and the influence of process parameters, namely the sintering temperature and the foaming agent additive amount, on the microstructure and mechanical properties of foam glass ceramic were investigated. The experimental results showed that when the proposed foam glass ceramic was sintered at between 1180 and 1220?°C, it exerted excellent macro and micro properties. The optimum parameters were 2% CaSO4 addition and sintering temperature of 1200?°C, and the corresponding bulk density and compress strength values were 0.98?g/cm3 and 9.84?MPa, respectively. Overall these results indicated that the preparation of foam glass ceramic made up a promising strategy for recycling industrial waste into new kind of building insulation materials. 相似文献
11.
《Ceramics International》2021,47(20):28460-28470
Ceramic glass foam/foams (CGF) from two different F-class fly ashes were produced via a well-known simple conventional sintering method using sodium silicate (Na2SiO3) as a foaming and fluxing agent. The research aimed to understand the effects of each fly ash, Na2SiO3 ratio, and sintering conditions on the properties and microstructure to produce a commercial CGF of low thermal conductivity. The chemical composition of fly ash from the thermal power plants of Tunçbilek and Seyitömer were quite similar but had different melting temperatures and microstructures. While the foam structure was successfully obtained at 1100 °C with 30 wt.% Na2SiO3 from Tunçbilek fly ash, a similar structure was obtained at 1150 °C from the Seyitömer fly ash. The effects of Na2SiO3 content and sintering temperature on the properties and microstructure of the CGF from the Tunçbilek fly ash of a lower melting point, in particular, were investigated systematically. The optimal sintering temperatures were determined to be 1200, 1150, and 1100 °C at the highest fly ash ratios of 90, 80 and 70 wt.%, respectively. The CGF were produced with 69.76–75.43% porosity, 0.55–0.69 gr/cm3 bulk density, 3.2–5.35 MPa compressive strength and 0.10–0.21 W/(m K) of low thermal conductivity. XRD results showed that optimal CGF samples mainly contained spinel, quartz and hematite crystal phases and amorphous phase. In this research, a thermal insulation material was successfully produced using an industrial waste completely with a well-known simple method. It is thought that this will contribute beneficially to the environment and the economy. 相似文献
12.
Effect of Sintering Additives on Relative Density and Li‐ion Conductivity of Nb‐Doped Li7La3ZrO12 Solid Electrolyte
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Nataly Carolina Rosero‐Navarro Taira Yamashita Akira Miura Mikio Higuchi Kiyoharu Tadanaga 《Journal of the American Ceramic Society》2017,100(1):276-285
Lithium ion conductors with garnet‐type structure are promising candidates for applications in all solid‐state lithium ion batteries, because these materials present a high chemical stability against Li metal and a rather high Li+ conductivity (10?3–10?4 S/cm). Producing densified Li‐ion conductors by lowering sintering temperature is an important issue, which can achieve high Li conductivity in garnet oxide by preventing the evaporation of lithium and a good Li‐ion conduction in grain boundary between garnet oxides. In this study, we concentrate on the use of sintering additives to enhance densification and microstructure of Li7La3ZrNbO12 at sintering temperature of 900°C. Glasses in the LiO2‐B2O3‐SiO2‐CaO‐Al2O3 (LBSCA) and BaO‐B2O3‐SiO2‐CaO‐Al2O3 (BBSCA) system with low softening temperature (<700°C) were used to modify the grain‐boundary resistance during sintering process. Lithium compounds with low melting point (<850°C) such as LiF, Li2CO3, and LiOH were also studied to improve the rearrangement of grains during the initial and middle stages of sintering. Among these sintering additives, LBSCA and BBSCA were proved to be better sintering additives at reducing the porosity of the pellets and improving connectivity between the grains. Glass additives produced relative densities of 85–92%, whereas those of lithium compounds were 62–77%. Li7La3ZrNbO12 sintered with 4 wt% of LBSCA at 900°C for 10 h achieved a rather high relative density of 85% and total Li‐ion conductivity of 0.8 × 10?4 S/cm at room temperature (30°C). 相似文献
13.
Synthesis and Assessment of a CO2‐Switchable Foaming Agent Used in Drilling Fluids for Underbalanced Drilling
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Junlin Su Wenxin Dong Sulin Zhou Mingyi Deng 《Journal of surfactants and detergents》2018,21(3):375-387
In underbalanced drilling, a switchable foam fluid is essential to reduce the drilling cost. A switchable foaming agent was synthesized by carbonyl–amine condensation and characterized by Fourier transform infrared and 1H nuclear magnetic resonance (NMR) spectroscopy. Thermogravimetric analysis and differential scanning calorimetry showed that the tolerable temperature limit of the surfactant was 128 °C. The effectiveness of CO2/N2 switching was confirmed by analysis of the electrical conductivity and surface tension. Utilizing the foaming agent, 3 different foam systems (unstable, stable, and hard) were designed for drilling after formula optimization. Experimentally, the self‐circulation indicated that the foaming fluids still maintained great foaming performance even after multiple cycles. The experiment also indicated that the suspension of the foam systems was 50–90 times that of water and had a significant resistance to salts (NaCl, CaCl2). Besides, the foam systems found that the suitable foaming temperature was 40–100 °C and that the hard foam system could maintain the foaming performance up to 120 °C. In the oil resistance experiment, the foaming ability of the foam systems decreased obviously above a kerosene content of 5% (w/v), whereas a certain foaming performance still could be ensured below 10% kerosene. 相似文献
14.
Martin B. Østergaard Rasmus R. Petersen Jakob König Michal Bockowski Yuanzheng Yue 《Journal of the American Ceramic Society》2018,101(9):3917-3923
Foam glasses are usually prepared through a chemical approach, that is, by mixing glass powder with foaming agents, and heating the mixture to a temperature above the softening point (106.6 Pa s) of the glass. The foaming agents release gas, enabling expansion of the sintered glass. Here, we use a physical foaming approach to prepare foam glass. First, closed pores filled with inert gases (He, Ar, or N2) are physically introduced into a glass body by sintering cathode ray tube (CRT) panel glass powder at high gas pressure (5‐25 MPa) at 640°C and, then cooled to room temperature. The sintered bodies are subjected to a second heat treatment above the glass transition temperature at atmospheric pressure. This heat treatment causes expansion of the pores due to high internal gas pressure. We found that the foaming ability strongly depends on the gas pressure applied during sintering, and on the kinetic diameters of the gases. The pressure for attaining maximum expansion, that is, lowest density and highest porosity, is found to be around 20 MPa. 相似文献
15.
Jarrett A. Rice Richard Pokorny Michael J. Schweiger Pavel Hrma 《Journal of the American Ceramic Society》2014,97(6):1952-1958
The heat conductivity (λ) and the thermal diffusivity (a) of reacting glass batch, or melter feed, control the heat flux into and within the cold cap, a layer of reacting material floating on the pool of molten glass in an all‐electric continuous waste glass melter. After previously estimating λ of melter feed at temperatures up to 680°C, we focus in this work on the λ(T) function at T > 680°C, at which the feed material becomes foamy. We used a customized experimental setup consisting of a large cylindrical crucible with an assembly of thermocouples, which monitored the evolution of the temperature field while the crucible with feed was heated at a constant rate from room temperature up to 1100°C. Approximating measured temperature profiles by polynomial functions, we used the energy equation to estimate the λ(T) approximation function, which we subsequently optimized using the finite‐volume method combined with least‐squares analysis. The heat conductivity increased as the temperature increased until the feed began to expand into foam, at which point the conductivity dropped. It began to increase again as the foam turned into a bubble‐free glassmelt. We discuss the implications of this behavior for the mathematical modeling of the cold cap. 相似文献
16.
Michelle L. Pantoya Benjamin D. Shaw Elizabeth A. Megas 《Propellants, Explosives, Pyrotechnics》2000,25(1):19-25
Immersion of energetic materials into high‐temperature molten‐salt baths, where the energetic materials decompose, is being considered as a method for their safe destruction. In the present research, behaviors of the high explosives LX‐17 (92.5 wt% 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB), 7.5 wt% KeI‐F 800 plastic binder) and LX‐04 (85 wt% octahydro‐,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine (HMX), 15 wt% Viton A plastic hbinder) were studied when these materials were immersed into molten salt baths. Pressed cylindrical samples initially 6.35 mm in diameter and length were immersed in molten salt baths, and data were taken photographically. Sample decomposition behaviors were observed for varied salt temperatures in a molten LiCl‐NaCl‐KC1 eutectic and then separately in a molten Li2CO3‐Na2CO3‐K2CO3 eutectic. Bath temperatures ranged from 650 to 750°C. General combustion behaviors such as bubble formation characteristics, gas evolution, and sample lifetimes were observed. Results indicated that sample lifetimes decreased as bath temperatures increased, and that the carbonate eutectic increased initial decomposition rates and decreased sample lifetimes relative to the chloride eutectic. 相似文献
17.
《Ceramics International》2021,47(18):26042-26049
The effect of the process atmosphere composition on the foam formation of cathode-ray tube (CRT) glass containing graphite and MnO2 was studied using in situ environmental scanning electron microscopy at high temperature (HT-ESEM). When compared to He+4% H2, O2 or air, water steam facilitates glass grain sintering. This is probably due to the formation of hydroxyl groups at the glass grain surface that locally decrease the glass viscosity. We have shown that increasing the steam pressure from 50 Pa to 750 Pa decreases both sintering and foaming onset temperatures by approximately 100 °C, favouring the formation of closed pores in viscous glass. At high temperature, the presence of water steam or oxygen promotes foam formation, while the presence of a reducing atmosphere (He+4%H2) limits glass melt foaming. A synergetic effect of O2 and H2O on the onset temperature of glass sintering and foam formation is evidenced. 相似文献
18.
A resilient, thermosetting foam system with a bio‐based content of 96 wt % (resulting in 81% of C14) was successfully developed. We implemented a pressurized carbon dioxide foaming process that produces polymeric foams from acrylated epoxidized soybean oil (AESO). A study of the cell dynamics of uncured CO2/ AESO foams proved useful to optimize cure conditions. During collapse, the foam's bulk density increased linearly with time, and the cell size and cell density exhibited power‐law degradation rates. Also, low temperature foaming and cure (i.e. high viscosity) are desirable to minimize foam cell degradation. The AESO was cured with a free‐radical initiator (tert‐butyl peroxy‐2‐ethyl hexanoate, Ti ~ 60°C). Cobalt naphtenate was used as an accelerator to promote quick foam cure at lower temperature (40–50°C). The foam's density was controlled by the carbon dioxide pressure inside the reactor and by the vacuum applied during cure. The viscosity increased linearly during polymerization. The viscosity was proportional to the extent of reaction before gelation, and the cured foam's structure showed a dependence on the time of vacuum application. The average cell size increased and the cell density decreased with foam expansion at a low extent of cure; however, the foam expansion became limited and unhomogeneous with advanced reaction. When vacuum was applied at an intermediate viscosity, samples with densities ~ 0.25 g/cm3 were obtained with small (<1 mm) homogeneous cells. The mechanical properties were promising, with a compressive strength of ~ 1 MPa and a compressive modulus of ~ 20 MPa. The new foams are biocompatible. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
19.
Melter feed viscosity during conversion to glass: Comparison between low‐activity waste and high‐level waste feeds
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Tongan Jin Jaehun Chun Derek R. Dixon Dongsang Kim Jarrod V. Crum Charles C. Bonham Bradley J. VanderVeer Carmen P. Rodriguez Brigitte L. Weese Michael J. Schweiger Albert A. Kruger Pavel Hrma 《Journal of the American Ceramic Society》2018,101(5):1880-1891
During nuclear waste vitrification, a melter feed (a slurry mixture of a nuclear waste and various glass forming and modifying additives) is charged into the melter where undissolved refractory constituents are suspended together with evolved gas bubbles from complex reactions. Knowledge of flow properties of various reacting melter feeds is necessary to understand their unique feed‐to‐glass conversion processes occurring within a floating layer of melter feed called a cold cap. The viscosity of two low‐activity waste (LAW) melter feeds were studied during heating and correlated with volume fractions of undissolved solid phase and gas phase. In contrast to the high‐level waste (HLW) melter feed, the effects of undissolved solid and gas phases play comparable roles and are required to represent the viscosity of LAW melter feeds. This study can help bring physical insights to feed viscosity of reacting melter feeds with different compositions and foaming behavior in nuclear waste vitrification. 相似文献
20.
Sealing Glass‐Ceramics with Near‐Linear Thermal Strain,Part II: Sequence of Crystallization and Phase Stability
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Mark A. Rodriguez James J. M. Griego Steve Dai 《Journal of the American Ceramic Society》2016,99(11):3726-3733
The sequence of crystallization in a recrystallizable lithium silicate sealing glass‐ceramic Li2O–SiO2–Al2O3–K2O–B2O3–P2O5–ZnO was analyzed by in situ high‐temperature X‐ray diffraction (HTXRD). Glass‐ceramic specimens have been subjected to a two‐stage heat‐treatment schedule, including rapid cooling from sealing temperature to a first hold temperature 650°C, followed by heating to a second hold temperature of 810°C. Notable growth and saturation of Quartz was observed at 650°C (first hold). Cristobalite crystallized at the second hold temperature of 810°C, growing from the residual glass rather than converting from the Quartz. The coexistence of quartz and cristobalite resulted in a glass‐ceramic having a near‐linear thermal strain, as opposed to the highly nonlinear glass‐ceramic where the cristobalite is the dominant silica crystalline phase. HTXRD was also performed to analyze the inversion and phase stability of the two types of fully crystallized glass‐ceramics. While the inversion in cristobalite resembles the character of a first‐order displacive phase transformation, i.e., step changes in lattice parameters and thermal hysteresis in the transition temperature, the inversion in quartz appears more diffuse and occurs over a much broader temperature range. Localized tensile stresses on quartz and possible solid‐solution effects have been attributed to the transition behavior of quartz crystals embedded in the glass‐ceramics. 相似文献