Chandra S. Ray's research while affiliated with Missouri University of Science and Technology and other places
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Publications (127)
Differential Thermal Analysis was used to calculate the heterogeneous nucleation rates for lithium disilicate glass doped with different concentrations of platinum particles. The lithium disilicate glass was melted with 0.001 and 0.005 wt% platinum and with PtCl4 for the investigation, and compared with the same glass un-doped. Heterogeneous volume...
Mathematical models for the chemical durability–composition relation for 5-component iron phosphate glasses, containing a nuclear waste similar to that of the high sulfate (~17 wt%), high soda (~80 wt%) Hanford AZ 102 LAW, have been developed using statistical analysis. The dissolution rate (DR) in deionized water at 90 °C was used as a representat...
A methodology for determining glass formation in a 5-component iron phosphate base glass system that contained P2O5, Fe2O3, Al2O3, Na2O and SO3 has been developed using a standard 5-component D-Optimal Statistical Mixture Design procedure. This compositional system was selected in order to study the feasibility of vitrifying a high soda (~ 80 wt%),...
a b s t r a c t Iron phosphate glass is a candidate fixation medium for storing radioactive waste. The Department of Energy supported a program to assess the viability of using Fe-phosphate glass for vitrifying low activity waste in a Joule Heated Melter (JHM). In this study, Inconel 693 electrodes were tested in a research-scale joule-heated melte...
The thermal conductivity (K), thermal diffusivity (α), and specific heat capacity (ρc) for a glass prepared from JSC-1A lunar soil simulant were measured using a combination of open photoacoustic cell (OPC) and thermal relaxation techniques. The values of K and α for the JSC-1A glass were (20 ± 3) mW/cmK and (14 ± 2) cm2/s, respectively, and are so...
As space faring nations consider manned and unmanned missions to the Moon, there is a growing need to develop high fidelity lunar regolith simulants that can accurately reproduce the properties and behavior of lunar regolith. Such simulants will be employed to verify the performance of equipment, mechanisms, structures and processes to be used on t...
Because of their high chemical durability and waste loading capacity, iron phosphate glasses are a natural candidate for a nuclear waste disposal medium. We have studied the effects of uranium on the structure of iron phosphate glasses with both neutron and high-energy x-raydiffraction. The results of neutron scattering, which is mostly sensitive t...
The crystallization processes that occur in alkaline earth silicate glasses designed for sealing solid oxide fuel cells (SOFC) have been investigated using differential thermal analysis (DTA) and hot-stage microscopy (HSM). HSM experiments revealed that glass powders with particle sizes <45 mu m crystallized before viscous sintering was complete. T...
The chemical composition of a volcanic ash deposited near Flagstaff, Arizona, USA closely resembles that of the soil from the Maria geological terrain of the Moon. After mining and processing, this volcanic ash was designated as JSC-1A lunar simulant, and made available by NASA to the scientific research community in support of its future explorati...
Various high temperature chemical processes have been developed to extract oxygen and metals from lunar regolith. These processes are tested using terrestrial analogues of the regolith. But all practical terrestrial analogs contain H2O and/or OH–, the presence of which has substantial impact on important system behaviors. We have undertaken studies...
Tools for extracting life-sustaining resources from the moon are needed to support the vision for space exploration. Of particular interest is the production of oxygen for life support and propulsion. On the lunar surface the only practical source for oxygen is the lunar regolith. Described in this paper is an innovative plasma reduction technique...
The return to the moon is providing a number of challenges for development of lunar regolith processing equipment. There are no metal ore deposits as on Earth, no oxygen atmosphere and no readily available water sources on the moon. During the Apollo missions, lunar explorers stayed only a few days on the surface. All materials for environment and...
The structural properties and crystallization behaviour of xNa2O-(100-x)TeO2 (0 <= x <= 33.3, x-% mole fraction) glasses have been investigated by Raman spectroscopy, X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The Raman spectra of glasses show systematic changes in structural units, from TeO4 trigonal bypiramids (tbps) to...
The crystallization kinetics of a solid oxide fuel cell sealing glass were studied using a new isothermal differential thermal analysis (DTA) method. The weight fraction of glass crystallized after an isothermal heat treatment was determined from the DTA crystallization peak area and the crystallization kinetic parameters were determined using the...
A drop shaft experiment was conducted to melt and solidify a glass of 3.5PbO–96.5B2O3 (mol%) composition adhered to a small platinum heating coil (2–3 mm i.d., 5–6 mm long) at the Japan Microgravity Center (JAMIC). The temperature of glass melt recorded during the drop experiment indicates that the phase-separation of this glass mainly happened dur...
The space exploration mission of NASA requires human and robotic presence for long duration beyond the low earth orbit (LEO), especially on Moon and Mars. Developing a human habitat or colony on these planets would require a diverse range of materials, whose applications would range from structural foundations, (human) life support, (electric) powe...
Glasses with the composition 3.5PbO·96.5B2O3 were melted and solidified through drop shaft experiment and ground experiment to explore the phase-separation of the glass under abnormal gravity condition. The composition homogeneity and the microstructure for different samples were compared. Results show that all the samples phase-separated into two...
The new crystalline phase was found in the Na2O·TeO2 system, Na2O·8TeO2, (NT8) was heated at different temperatures for different time and the crystalline phase in the different samples were analyzed. The mechanism of the decomposition for the Na2O·8TeO2 was explored and discussed in detail. Results show that the NT8 is stable below 330°C and will...
Glasses of Li2O·2SiO2 (LS2), and LS2 doped with 0.001wt% platinum (LS2+0.001wt% Pt) compositions were melted, cooled and reheated at controlled rates while levitated (containerless) inside
an electrostatic levitator (ESL) furnace at the NASA Marshall Space Flight Center. The experiments were conducted in vacuum
using spherical, 2.5–3mm diameter, gl...
Results on exploration of making a large variety of different glasses, which are easy to make, have compositions distinguishable from each other, and are easy to be located in a complicated background, is reported. Porous glasses made by leaching a sodium borosilicate glass were used as the starting glass. The porous glasses were soaked in a soluti...
A method is proposed for estimating the critical cooling rate for glass formation and continuous cooling transformation curve (CCT) from isothermal TTT data. The critical cooling rates and CCT curves for a group of lithium disilicate glasses containing different amount of Pt as nucleating agent estimated through this method are compared with the ex...
Experiments conducted up to this time on glass forming melts in the low gravity environment of space show that glasses prepared in low gravity are more chemically homogeneous and more resistant to crystallization than comparable glasses prepared on Earth. This result is somewhat in contradiction to the accepted concept of glass formation for a melt...
Non-isothermal crystallization techniques are frequently used to determine the kinetic parameters for crystallization in glasses. The techniques are experimentally simple and quick, compared with isothermal techniques. However, the analytical models used for non-isothermal data analysis, that were derived from models originally developed for descri...
Iron redox equilibrium, structure and properties were investigated for 40Fe2O3–60P2O5 (mol%) glasses melted at different temperatures. The Fe2+/(Fe2++Fe3+) ratio increased from 17% to 50% as the melting temperature changed from 1150°C to 1400°C. The equilibrium constant, K, for the reaction of Fe3+ being reduced to Fe2+ varied with temperature as l...
In situ resource processing and utilization on planetary bodies is an important and integral part of NASA's space exploration pro-gram. Within this scope and context, our general effort is primarily aimed at developing glass and glass-ceramic type materials using Lunar and Martian soils, and exploring various application potentials of these materia...
Crystallization of a Li2O·2SiO2 (LS2) glass subjected to a uniform hydrostatic pressure of 4.5 and 6GPa was investigated up to a temperature of 750°C. The density of the compressed glass is ∼2% greater at 4.5GPa than 1atm and, depending on the processing temperature, up to 10% greater at 6GPa. Crystal growth rates investigated as a function of temp...
PbO-B2O3 glasses were melted and solidified through drop shaft experiment to explore the phase-separation of the glasses under different gravity conditions. XRD was conducted to determine the phase of samples after phase-separation. The distribution of elements in different samples was compared through EDS analysis and the microstructures were obse...
PbO-B2O3 glasses were melted and solidified through drop shaft experiment to explore the phase-separation of the glasses under different gravity conditions. XRD was conducted to determine the phase of samples after phase-separation. The distribution of elements in different samples was compared through EDS analysis and the microstructures were obse...
A large variety of porous fluorescent glasses were prepared and the concentration of different elements in these glasses was analyzed. The start porous glasses were soaked in a solution containing soluble salts and then heated at 650 °C for 3 h to decompose the salts in the pores into oxides. Fluorescent agents, such as UO3, Eu2O3, were impregnated...
A method is proposed for estimating the critical cooling rate and continuous cooling transformation curve (CCT) from isothermal TTT data of glasses. The critical cooling rates and CCT curves for a group of lithium disilicate glasses containing different amounts of Pt as nucleating agent estimated through this method are compared with the experiment...
The structure of Li 2 O AE 2SiO 2 (LS 2) glass was investigated as a function of pressure and temperature up to 6 GPa and 750 °C, respectively , using XRD, TEM, IR, Raman and NMR spectroscopy. Glass densified at 6 GPa has an average Si–O–Si bond angle $7° lower than that found in glass processed at 4.5 GPa. At 4.5 GPa, lithium disilicate crystalliz...
Iron phosphate glasses are of interest for immobilizing high level nuclear waste (HLW). The high temperature viscosity and AC electrical conductivity of an iron phosphate melt containing 2.8 mass% chrome oxide were investigated in this work. The viscosity of this melt varied from 10 to 50 poise from 1350 to 1150 °C, respectively, while the activati...
A differential thermal analysis (DTA) method has been developed that identifies and distinguishes surface and internal (volume) crystallization in glasses. This method is fast, convenient, and requires only a small quantity of sample, ∼500 mg, to identify the dominant crystallization, surface versus internal, in the glass. In this method, either th...
The drop shaft experiments were conducted at Japan Microgravity Center, whose experimental facility allowed us to study the phase separation of glass for a few seconds either under low or high gravity. In these few seconds, it also allowed us to record the actual temperatures of samples during the melting and solidification of glasses; these temper...
Glass formation from melts of 44 CaO 56Ga2O3(mol%) was investigated under containerless conditions obtained by acoustically stabilized aerodynamic levitation in combination with laser beam heating. The critical cooling rate for glass formation was Rc<100°C/s, much less than values reported in the literature (Rc=550o±120o C/s and ca 350oC/s) for pen...
The chemical durability, and structure of iron phosphate glasses containing 70 wt% of a simulated high level nuclear waste (HLW), doped with different amounts of Cr2O3 were investigated. All of these iron phosphate glassy and crystallized wasteforms possess an outstanding chemical durability as measured by their small dissolution rate (10-9 g/(cm2·...
The chemical durability of iron phosphate (IP) glass containing different contents of high level radioactive nuclear waste (HLW) loading was measured by dissolution rate (DR) method, product consistency test (PCT) and vapor hydration test (VHT). The measurement shows that the IP glass wasteforms containing 65-75 mass% HLW waste loading have excelle...
The density; molar volume; thermal expansion coefficient; dissolution rate in water, HC1, and NaOH; glass transition and crystallization temperatures; and the absorption edge in the ultraviolet-visible and infrared were measured for PbO─BiO1.5─GaO1.5 glasses. The range of compositions investigated was xPbO (100 −(x + y))BiO1.5. yGaO1.5 for x betwee...
NASA's long-term vision for space exploration includes developing human habitats and conducting scientific investigations on planetary bodies, especially on Moon and Mars. To reduce the level of upmass, processing and utilization of planetary in situ resources is recognized as an important element of this vision. Within this scope and context, we h...
The feasibility of preparing glasses and developing glass-ceramic materials that display magnetic characteristics using the simulated compositions of Lunar and Martian regoliths have been demonstrated. The reported results are preliminary at this time, and are part of a larger on-going research activity at the NASA Marshall Space Flight Center (MSF...
In-situ resource processing and utilization on planetary bodies is an important and integral part of NASA's space exploration program. Within this scope and context, our general effort is primarily aimed at developing glass and glass-ceramic type materials using lunar and martian soils, and exploring various applications of these materials for plan...
NASA's new strategic direction includes establishing a self-sufficient, affordable and sale human and robotic presence outside the low earth orbit. Some of the items required for a self-sufficient extra-terrestrial habitat will include materials for power generation (e.g. Si for solar cells) and habitat construction (e.g. Al. Fe, and Ti). In this p...
The nucleation rate (I) versus temperature type of curves for a Na2O2·CaO·3SiO2 (NC2S3) glass doped with 0.1 wt% platinum, 0.5 wt% Ag2O, and 2.0 wt% P2O5 were determined using a previously developed differential thermal analysis (DTA) technique. In this DTA technique, a constant amount of glass sample was nucleated at selected temperatures for a sp...
The rates for nucleation (I) and crystal growth (U) for a lithium disilicate (Li2O·2SiO2, LS2) glass were determined, as a function of temperature, using a new differential thermal analysis (DTA) technique. This technique requires in situ nucleation and crystal-growth heat treatment of a small amount of powdered sample inside the DTA apparatus, whi...
The effect of melting temperature, time, and the type of raw material, NaNO3 or Na2CO3, as a source for Na2O on the glass formation for a Na2O4TeO2(NT4) melt was investigated. Melting with NaNO3 at 750C for a short time (15 min) produced a glass that is slightly more chemically durable and more resistant to crystallization than glasses melted at a...
Glasses based on rare earth oxides and aluminum oxide with 0–20 mol% SiO2 provide a combination of optical properties, mechanical and chemical stability, and process characteristics not available in other oxide materials. Properties of the glasses include: refractive index 1.7–1.8, low dispersion (Abbe number ∼40), high solubility of optically acti...
Chemical durability, glass formation tendency, and other properties of iron alumina phosphate glasses containing 70 wt% of a simulated high level nuclear waste (HLW), doped with different amounts of Cr2O3, have been investigated. All of the iron alumina phosphate glasses had an outstanding chemical durability as measured by their small dissolution...
The non-linear optical performance and structure of TeO2–Nb2O5–ZnO glasses was investigated as a function of ZnO content. The third-order non-linear optical susceptibility (χ(3)) as measured by a Degenerate Four Wave Mixing (DFWM) method, initially increased with increasing ZnO content to about 8.2 × 10−13 esu for a glass containing 2.5 wt% ZnO, an...
A simulated high level waste (HLW) containing 4 mass% chrome oxide, whose overall composition is representative of the high chrome oxide wastes at Hanford WA USA, was easily vitrified in a phosphate glass at temperatures ranging from 1150 °C, for waste loadings of 55 mass%, to 1250 °C for waste loadings of 75 mass%. Even at these high waste loading...
![Figure 9 Plot of [1−(t)] vs. time for the LS 2 glass fiber after...](profile/Signo-Reis-2/publication/4706144/figure/fig3/AS:465331165634560@1487955003171/Plot-of-1-t-vs-time-for-the-LS-2-glass-fiber-after-heating-at-390-BULLET-C-using-a_Q320.jpg)
The deformation and crystallization of Li2O·2SiO2 and Li2O·1.6SiO2 glass fibers subjected to a bending stress were measured as a function of time over the temperature range ∼50 to ∼150°C below the glass transition temperature (T
g). The glass fibers can be permanently deformed at temperatures about 100°C below T
g, and they crystallize significantl...
A recently proposed analytical (DTA) method for estimating the nucleation rates in glasses has been evaluated by comparing experimental data with numerically computed nucleation rates for a model lithium disilicate glass. The time and temperature dependent nucleation rates were predicted using the model and compared with those values from an analys...
IntroductionExperimental ProcedureResultsDiscussionConclusions
Acknowledgment
A new differential thermal analysis (DTA) experimental method has been developed to determine the critical cooling rate for glass formation, R(sub c). The method, which is found especially suitable for melts that, upon cooling, have a small heat of crystallization or a very slow crystallization rate, has been verified using a 38Na2O-62SiO2 (mol%) m...
A simulated sodium bearing waste (SBW) was successfully vitrified in iron phosphate glasses (IPG) at a maximum waste loading of 40 wt% using conventional and cold crucible induction melting (CCIM) techniques. No sulfate segregation or crystalline phases were detectable in the IPG when examined by SEM and XRD. The IPG wasteforms containing 40 wt% SB...
Glass fibers of Li2O · 2SiO2 (LS2) and Li2 O · 1.6SiO2 (LS1.6) compositions were heated near, but below, the glass transition temperature for different times while subjected to a constant bending stress of about 1.2 GPa. The nucleation density and the crystallization tendency, estimated by differential thermal analysis, of a glass sample in the vic...
The atomic structure of iron phosphate glasses containing uranium has been studied by complementary neutron and x-ray scattering techniques. By combining x-ray and neutron structure factors, detailed information about different pair interactions has been obtained. Most of the basic structural features such as coordination numbers and O–O and P–O di...
During the past year, iron phosphate glasses containing the following three types of nuclear waste, as recommended by the Tank Focus Area (TFA) group, have been investigated. (1) a high sodium/sulfate Hanford Low-Activity Waste (LAW) (2) a High Chrome Waste (HCW) at Hanford, and (3) a Sodium Bearing Waste (SBW) at Idaho National Engineering and Env...
The heat capacity (Cp) change in the glass transition region for the xNa2O ·(100−x)TeO2, mol%, glass forming melts with x=7.5, 11.1, 15.0, 20.0 and 25.0 was measured as a function of heating rate (2, 4, 6, 10 and 15 °C/min) using differential scanning calorimetry. The glass transition properties that have been measured and reported in this paper in...
Changes in the heat capacity from the glass state (Cpg) to the supercooled liquid state (Cpl), ΔCp=Cpl−Cpg, the ratio of heat capacities, Cpl/Cpg, width of the glass transition temperature, ΔTg, and activation enthalpy for structural relaxation, , in the glass transition region for the xNa2O–(20−x)R2O–32Fe2O3–48P2O5 (R=K and Cs) mol% glasses, where...
A review of the results from previous low-gravity experiments conducted on glass-forming melts is presented with particular emphasis on nucleation, crystallization, glass formation, and chemical homogeneity fur high-temperature melts in low gravity. A review of this kind is important for)1 understanding the kinetics of glass formation (conversely,...
This flight definition project has the specific objective of investigating the kinetics of nucleation and crystal growth in high temperature inorganic oxide, glass forming melts in microgravity. It is related to one1 of our previous NASA projects that was concerned with glass formation for high temperature containerless melts in microgravity. The p...
The effect of gravity on glass formation and crystallization of the Na2Ocdot;8TeO2 (NT8) and Na2O4TeO2 (NT4) melts were investigated using the low gravity drop shaft at the Japan Microgravity Center (JAMIC). This drop shaft produces a low gravity of –3 g for 10 s during free-fall and about 8 to 10 g for 5 s during deceleration of the capsule. The g...
The local environment around iron ions in iron phosphate glasses of starting batch composition 40Fe2O3–60P2O5 (mol%) melted at varying temperatures or under different melting atmospheres has been investigated using Fe-57 Mössbauer and X-ray absorption fine structure (XAFS) spectroscopies. Mössbauer spectra indicate that all of the glasses contain b...
A new crystallin phase with the composition of Na2O·8TeO2(NT8) was found in the Na2O-TeO2 system and the formation and decomposition of this new crystalline phase was explored. The NT8 crystalline phase is stable at 330°C or below, and decomposes to Na2O·4TeO2 and TeO2 at temperatures higher than 330-340°C. A modification to the phase diagram of th...
A new crystalline phase with the composition of Na(2)O(.)8TeO(2)(NT8) was found in the Na2O-TeO2 system and the formation and decomposition of this new crystalline phase was explored. The NT8 crystalline phase is stable at 330degreesC or below, and decomposes to Na(2)O(.)4TeO(2) and TeO2 at temperatures higher than 330similar to340degreesC. A modif...
A generalized experimental method that uses differential thermal analysis (DTA) has been developed for determining the nucleation rate (I), the crystal growth rate (U), and the concentration of quenched-in nuclei (N
q) in glasses. The method is applicable even for glasses, whose I and U curves (as a function of temperature) overlap to a considerabl...
Glasses of Na2O8TeO2 and Na2O4TeO2 compositions adhered to a small platinum heating coil (2 to 3 mm ID, 5 to 6 mm long) were melted and evaporated in low gravity using the drop shaft at the Japan Microgravity Center (JAMIC). The gravity level attained during the 10 s free fall was in the order of 10–3 g. The species evaporated from the melt in low...
The formation and decomposition of NT8 crystal phase was investigated using differential scanning calorimetry (DSC) and x-ray diffraction analysis (XRD). DSC measurements indicated that all the glasses used in the investigation crystallized at about 330±5 °C. Results suggested that the NT8 phase, which was very stable at 330 °C was not stable at or...
Mechanical and structural properties of sodium (NAFP) and zinc (ZAFP) iron±aluminum±phosphate bulk glass and ®bers have been investigated. Young's modulus of the ®bers was measured by a three-point bending method while the strength was measured by a two-point bending method. In general, the tensile strength of the ZAFP ®bers (4.2±7.2 GPa) was highe...
A crystal growth rate vs. temperature (U vs. T)-type of curve for a Li2O.2SiO2 glass was determined up to a temperature of 690 °C using a differential thermal analysis (DTA) method. As determined from this (U vs. T)-type of curve, the temperature corresponding to the onset of crystal growth was 570±3 °C which is in excellent agreement with the same...
The electrical conductivity of mixed-alkali, sodium and potassium, iron phosphate glasses has been studied in the frequency range from 0.1 Hz to 10 kHz and over a temperature range from 303 to 423 K. The dc conductivity of the alkali-free iron phosphate glasses was 5–10 times higher than that of the single- or mixed-alkali iron phosphate glasses co...
The local structure of iron and uranium ions in a series of iron phosphate glasses with the general composition (40 – x)Fe2O3–xUO2–60P2O5 and (1–x–y)(40Fe2O3–60P2O5)– xUO2–y(Na2O or CaO) was investigated using Fe K-edge and U LIII-edge x-ray absorption fine structure spectroscopy. Replacing Fe2O3 by UO2 in the glass caused more distortion in the co...
The nucleation rate (I), the crystal growth rate (U), and the concentration of quenched in nuclei (Nq) in lithium disilicate (Li2O.2SiO2) and soda-lime-silica (Na2O.2CaO.3SiO2) glasses have been determined using a newly developed differential thermal analysis (DTA) method. This new DTA technique which is faster, less tedious, and requires a smaller...
The electrical relaxation of mixed alkali, sodium and potassium, iron pyrophosphate 20[(1 − x)K2O–xNa2O]–20Fe2O3–60P2O5, (0⩽x⩽1), glasses has been studied in the frequency range from 0.1 Hz to 10 kHz and over the temperature range from 303 to 423 K. The ac conductivity as a function of the temperature was divided into two domains, one where the abs...
Glass formation and properties of iron phosphate glasses containing Na2O and K2O have been investigated to determine the suitability of these glasses for disposing of certain types of nuclear wastes that contain one or more alkali oxides. Two series of glasses of the general composition xK2O–(20−x)Na2O–20Fe2O3–60P2O5 and xK2O–(20−x)Na2O–32Fe2O3–48P...
The structure of vitreous iron phosphates containing up to 35 wt% of one or more common nuclear waste components such as Na2O, Cs2O, SrO, UO2 or Bi2O3 have been investigated using Fe-57 Mössbauer, X-ray absorption, X-ray photoelectron and Raman spectroscopies and high energy X-ray and neutron diffraction techniques. The glass samples investigated w...
The atomic structure of iron phosphate glasses and those containing common high level nuclear waste components such as UO2, Cs2O and Bi2O3 has been investigated using X-ray photoelectron spectroscopy (XPS) and Mössbauer spectroscopy. Oxygen 1s spectra indicate that only 16–26% of the oxygen ions are bridging oxygens (BOs). The addition of waste com...
The effect of melting temperature and time on iron valence, dissolution rate (DR) in deionized water, and crystallization of iron phosphate glasses was investigated using a 40Fe2O3–60P2O5, mol%, batch composition. The concentration of Fe2+ ions in these glasses increased from 17% to 57% as melting temperature increased from 1150°C to 1450°C, but re...
Glasses of Na2 xTe2(x equals 2,4 and 6) compositions were remelted and evaporated while supported by a platinum heater coil in the low gravity drop shaft at the Japan Microgravity Center. The evaporating species from all the melts, which formed a spherical cloud surrounding the melt during the few seconds low gravity time were identified to be amor...
Fe K-edge x-ray absorption fine-structure (XAFS) measurements were performed on glass samples of (Fe3O4)0.3(P2O5)0.7 with various amounts of Na2O or UO2. Near-edge and extended XAFS regions are studied and comparisons are made to several reference compounds. We find that iron in the base glass is ∼25% divalent and that the Fe2+ coordination is pred...
Up to 40 wt% of a simulated high level waste, whose major components were 54.6 wt% Na2O, 14.9 wt% P2O5 and 8.3 wt% Fe2O3, was successfully vitrified into iron phosphate wasteforms whose chemical durability was equivalent to that of borosilicate glass wasteforms. Because of their high fluidity, the iron phosphate wasteforms could be melted in as lit...
The structures and valence states of iron ions in several iron phosphate glasses with batch compositions similar to 40Fe2O3-60P2O5 (mol%) have been investigated using Mössbauer spectroscopy, X-ray absorption fine-structure spectroscopy (XAFS), X-ray photoelectron spectroscopy (XPS), differential thermal (DTA) and thermo-gravimetric (TGA) analysis a...
The nucleation rate (I) versus temperature type of curves for a Na 2O·2CaO·3SiO 2 (NC 2S 3) glass doped with 0.1 wt% platinum, 0.5 wt% Ag 2O, and 2.0 wt% P 2O 5 were determined using a previously developed differential thermal analysis (DTA) technique. In this DTA technique, a constant amount of glass sample was nucleated at selected temperatures f...
The structure of PbO-Bi2O3-Ga2O3 glasses and crystallised compositions were investigated by Raman spectroscopy and x-ray diffraction analysis. The glasses have a network structure composed of three structural units; GaO4 distorted tetrahedra, BiO6 distorted octahedra and PbO4 and/or PbO3 pyramids present next to each other. The Raman spectra of cry...
Citations
... Iron phosphate glasses, in particular the composition of 40Fe 2 O 3 -60P 2 O 5 (mol%), have recently received substantial attention due to their ability to vitrify certain specific radioactive wastes, for example, sulfates, halides, and heavy metals. [1][2][3][4][5] These wastes are known to be poorly soluble in borosilicate glass which is currently approved as a viable and acceptable media for high-level nuclear wastes. [6][7][8] In addition, iron phosphate glasses exhibit other advantages for vitrification, such as excellent chemical durability, 9,10 high waste loading ability, good glass-forming ability, and low melting temperature. ...
![[object Object]](https://i1.rgstatic.net/ii/profile.image/272742767394851-1442038351542_Q64/Va-Samarayanake.jpg)
... In the classical theory, the crystallization process of glass can be divided into a nucleation stage and a crystal growth stage. In a Li 2 O-SiO 2 system, the nucleation rate, I, and crystal growth rate, U, were discussed to control them through differential thermal analysis (DTA) [28,29]. This approach was also applied to the 78Li 2 S•22P 2 S 5 glass-ceramics system, and their sample was totally crystallized (thio-LISICON II analogue) [30]. ...
... Iron phosphate glasses, in particular the composition of 40Fe 2 O 3 -60P 2 O 5 (mol%), have recently received substantial attention due to their ability to vitrify certain specific radioactive wastes, for example, sulfates, halides, and heavy metals. [1][2][3][4][5] These wastes are known to be poorly soluble in borosilicate glass which is currently approved as a viable and acceptable media for high-level nuclear wastes. [6][7][8] In addition, iron phosphate glasses exhibit other advantages for vitrification, such as excellent chemical durability, 9,10 high waste loading ability, good glass-forming ability, and low melting temperature. ...
... The XRD result is shown in Fig. 2. After compaction, most peaks decrease in height, including the main peaks corresponding to pyroxene minerals 39 . It may be attributed to the crushing of small crystals. ...
![[object Object]](https://i1.rgstatic.net/ii/profile.image/278720049893398-1443463446472_Q64/Signo-Reis-2.jpg)
... A simulated Hanford HLW containing 4 wt% Cr 2 O 3 was vitrified at 1150-1250°C in a phosphate glass with waste loadings as high as 75 wt% by simply adding a source of P 2 O 5 . [73][74][75] Even at these high waste-loading levels, the glassy or deliberately crystallized waste forms had an excellent chemical durability measured by PCT and VHT (Table 1), with the best chemical durability achieved when the O/(Si + P) atomic ratio was between 3.5 and 3.8, in agreement with the trends noted in Figure 6. ...
... Related to this, iron-phosphate glass with good chemical durability is able to accept more types of nuclear waste and up to 6 times more nuclear waste per unit volume, compared to borosilicate glasses. 7,8 It is the combination of degradability and control over the rate of the degradation of these materials that makes them so attractive and is driving their development for biomedical use. In this chapter, we focus on their biomedical applications. ...
Reference: Phosphate-Based Glasses
... France and the UK reprocess spent fuel for electric utilities from other countries using the PUREX process to recover uranium ( 235 U) and plutonium ( 239 Pu). Slight modifications to the PUREX process can be made to recover 235 U, 239 Pu, 237 Np, and 99 Tc (if desired) and a number of countries (e.g., France, Japan, China, etc.) are developing solvent extraction processes to recover the minor actinides (Am and Cm) from spent fuel. Elimination of these actinides and fission products from the HLW reduces the long-term radiotoxicity and heat generation from an immobilized waste form once it is entombed in a geological repository. ...
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... Others studies concluded on this dual role of P 2 O 5 depending the composition in SrO-TiO 2 -Al 2 O 3 -SiO 2 -B 2 O 3 system [51]. In addition, in a Na 2 O-2CaO-3SiO 2 glass, addition of 2 wt% of P 2 O 5 enhances glassforming tendency by diminishing nucleation rate [52]. ...
... The peaks at 296 and 355 cm −1 correspond to cation-oxygen vibration modes, and the peak at 601 cm −1 corresponds to the bending vibrations of the Si─O─Si bonds. [25,26] The stretching modes of Si─O bridging stretching bonds are located at 700 cm −1 , while the peaks at 1017 and 1070 cm −1 correspond to the Si─O nonbridging stretching vibrations. [27] The peaks at 296, 355, 700, 1017, and 1070 cm −1 are characteristics of spodumene crystal, [27,28] therefore we deduced that spodumene crystals were formed in types A and B. The Raman spectra of type C modifications closely resemble those of pristine glass, indicating that the material composition of the type C region is approximately the same as that of the LAS glass. ...
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... All assignments were done in accordance with the literature. 25,[28][29][30][31] Symmetric stretching modes of the P-O-P bridging oxygens in Q 1 and Q 2 linkages appear at ∼750 and 630 cm −1 , whereas the stretching vibration of the (P-O) nb in Q 0 tetrahedra is observed at ∼940 cm −1 . The kink at ∼1300 cm −1 is due to P = O stretching mode, and the broad hump at ∼520 cm −1 is due to bending modes of the Q 1 phosphate tetrahedra along with cationic modifiers. ...
