Li4SiO4 Powder Research Articles

Additive manufacturing of high-quality tritium breeding pebbles using ceramic precursors

In this study, the fabrication of advanced lithium orthosilicate (Li4SiO4) ceramic tritium breeding pebbles through photopolymerization using ceramic precursors (i.e., SiO2 and Li2CO3) is reported for the first time. The pebbles exhibit excellent mechanical and physical properties. Through optimization of manufacturing parameters and a geometrical correction model to compensate printing deviations, the printing accuracy of the pebbles was enhanced. The resulting pebbles had a diameter of approximately 1 mm, a sphericity of 1.01, a uniformly distributed pore structure, a phase purity > 95%, and a satisfying relative density reaching 91.39%. The average crush load 25.7 ± 0.3 N, surpassed that achieved by previously reported methods. Furthermore, the thermal conductivity was enhanced compared to that of solid-phase synthesized Li4SiO4 powder, facilitating the tritium release process for fusion applications. This study may serve as a guidance for designing appropriate ceramic breeders, providing a cost-effective approach applicable to produce other high-precision ceramic components with complex compositions.

Carbon Capture Performance Enhancement of Solid State Synthesized Li4SiO4 Powders by Using Different Kind Steel Slags as SiO2 Source

The potential of lithium orthosilicate (Li4SiO4) as a material to capture carbon dioxide (CO2) is being explored due to its excellent capture capability and thermal stability. Currently, a significant portion of the world's energy needs are met through the burning of fossil fuels, which leads to an increase in atmospheric CO2 and contributes to global warming. While fossil fuels will remain the primary source of energy for several more years, it is crucial to develop cost-effective and environmentally friendly technology for large-scale CO2 capture and storage before its release into the atmosphere in order to mitigate the associated greenhouse effect. This study focuses on optimizing the synthesis of lithium orthosilicate using a solid-state method to enhance CO2 capture. The research involves assessing the key characteristics of the synthesized material that improve CO2 capture efficiency. The starting materials used for comparison include lithium carbonate (Li2CO3), BF (blast furnace), BOF (blast oxygen furnace) and EAF (electric arc furnace) slags, and pure reagents of silicon dioxide (SiO2). The effect of process conditions, such as synthesis temperatures ranging from 850 to 950°C and varying holding times of 4, 6, 8, and 10 hours in a muffle furnace, were studied and compared. X-ray diffraction (XRD) analysis was performed to characterize the samples and slags. CO2 capture performance of the samples were evaluated in thermobalance test under 92 vol% CO2 (N2 balance) gas concentration at 600°C. As to conclude, carbon dioxide capturing sorbent material was produced by utilizing the slags generated as a by-product in steel production. Thus, considering the principles of circular economy, a material defined as waste was used as raw material for the production of another product used for lowering atmospheric CO2 levels.

Solution combustion synthesis derived Li4SiO4 for post-combustion carbon capture

ABSTRACT Lithium-based sorbents are considered as promising candidates for post-combustion carbon capture because of their superior stability compared to CaO. In the present study, Li4SiO4 powders were synthesized by Solution Combustion Synthesis (SCS) technique using LiNO3 as lithium source, TEOS as silicon source and citric acid as the fuel. CO2 sorption tests were carried out for the synthesized samples and, powder prepared at 650°C during 4 h, which has 17 µm of particle size, 5.2 m2 g−1 of specific surface area, 85.2% Li4SiO4 phase purity with 97 nm of crystallite size showed a sorption performance as 29.5 wt% CO2 uptake value, in thermobalance test under 92 vol% CO2 (N2 balance) gas concentration at 600°C. The sample had a CO2 uptake value of 21.4 wt% under 20 vol% CO2 concentration which was chosen to simulate industrial off-gas conditions. Also, the same sample showed a good cyclic durability during the sorption/desorption tests. The sample maintained its cyclic CO2 uptake capability range between 21 and 24 wt% for 15 cycles.

High efficiency CO2 sorption property of Li4SiO4 sorbent pebbles via a simple rolling ball method

At present, the Li4SiO4 sorbents have been getting widespread attention for mitigating the release of CO2 gas owing to its stable cyclic property, higher capturing ability, and lower regeneration temperatures. In this work, a facile rolling ball method is first proposed to fabricate Li4SiO4 sorbent pebbles, which overcomes the low production efficiency, poor adsorption stability, and high production cost adopted in the previous literature. In the rolling ball process, the spray granulation process was involved to decrease the specific surface area of ceramic powder, which makes it easier for powder self-agglomerate to form pebbles via the centrifugal force with the assistance of PVA polymer solution. Moreover, the phase composition, the specific surface area, the shaping principle, and the microstructure of Li4SiO4 sorbent pebbles were studied, respectively. The result shows that the Li4SiO4 pebbles sintered at 900 °C for 2 h present a superior comprehensive performance with a homogeneous diameter of 1.2 mm, good sphericity of 0.95, high crushing load of 65 N, and suitable porosity of 6.28 %. Compared with Li4SiO4 powder, the spherical pebbles performed superior CO2 adsorption ability (0.304 g CO2/g sorbent) and excellent cyclic stability in a 100% CO2 environment owing to its large number of uniform pores channels produced by binder solution at high temperature. Therefore, the rolling ball process is a potential method for the batch production of Li4SiO4 pebbles to capture CO2 stably in the future.

3D printing of ceramic cellular structures for potential nuclear fusion application

A flexible and integrated design and manufacturing process based on photopolymerization DLP 3D printing technology is proposed to fabricate tritium breeder units that can be used in fusion reactors. Defect-free cellular structures of lithium-enriched Li4SiO4 is manufactured for the first time that can be used to replace the traditional pebble beds configuration to overcome problems resulted from stress concentration and difficulty in packing fraction improvement. As-received large Li4SiO4 powder which is highly sensitive to air and ambient environment is protected and processed in inert glove box for the use in the preparation and optimization of stable photopolymerizable resin-based ceramic slurry suitable for DLP 3D printing. Appropriate debinding and sintering treatments applied result in homogeneous shrinkage and preserved features of the cellular structures, showing benefits for dimension control. The intact structures possess high phase purity and suitable and tailorable effective ‘packing fraction’ for breeding application. Mechanical tests and the obtained results compared with existing works further confirm that the cellular parts prepared in this work have advantageous performance. The unique advantage of flexible control in design and manufacturing of 3D printing may pave a promising way for greater possibilities to engineer novel tailored high-performance tritium breeder structures used in nuclear fusion technology.

CO2 capture properties of Li4SiO4 after aging in air at room temperature

In this study, we evaluated the physicochemical stability of lithium orthosilicate (Li4SiO4) powders after aging in air. Thermogravimetric (TG) analysis in CO2 flow evidences that as-milled Li4SiO4 stored in a closed plastic container in air at Room Temperature (RT) suffers a time progressive CO2 absorption. This carbonation is clearly noticed in the samples with greater specific surface area and depends on two factors: the time of air exposure and the renewal of the air atmosphere in the plastic container, both of them modifying the CO2 capture capacity and kinetics of the material. Specific experiments to analyze the effect of water vapor and carbon dioxide atmospheres on the CO2 capture properties of Li4SiO4 were designed. TG, X-ray diffraction and spectroscopic studies demonstrate that the reaction between as-milled Li4SiO4 and CO2 present in air was promoted by exposure to humidity. In fact, LiOH and LiOH.H2O were formed at the surface of Li4SiO4 during water vapor exposure. These phases enhance the reaction with CO2 from the air to form Li2CO3 at RT before the first carbonation cycle. As a consequence, the CO2 capture capacity of Li4SiO4 in the first carbonation cycle was smaller than the one of Li4SiO4 without water vapor exposure. In opposition, negligible CO2 absorption occurred at RT under CO2 atmosphere. The original properties of Li4SiO4 powders with high specific surface area could be regenerated by heating at 700 °C. Consequently, the storage conditions of Li4SiO4 powders should be considered for their use in different applications.

Hydrogen isotope permeability of reduced activation ferritic/martensitic steel CLF-1 corroded by Li4SiO4

In a solid tritium breeding blanket, Li4SiO4 is in contact with reduced activation ferritic/martensitic (RAFM) steel at high temperatures for years and forms a corrosion layer. The effects of the corrosion layer on the hydrogen isotope permeability of a RAFM steel CLF-1 were thus investigated. X-ray diffraction, secondary ion mass spectroscopy and spherical aberration corrected transmission electron microscopy demonstrated the formation of a three-layered corrosion product, comprising a middle layer of LiFeO2 and an inner layer of LiCrO2. Li4SiO4 powder with the (104) crystal plane orientation was adsorbed on the outermost surface of the CLF-1, forming a nanoscale layer with a thickness of ∼150 nm. Deuterium permeation tests show that the deuterium permeability of the corroded samples was two orders of magnitude higher than that of the blank substrate that was pre-heated for 30 days, but one order of magnitude lower than that of the blank substrate that was not preheated. The CLF-1 corroded for 10 days exhibited the highest deuterium permeation flux. There was a decrease in the deuterium permeability of the steel that corroded for 15 and 30 days; thus, there was a decrease in the permeability with an increase in the corrosion period. By the weighting method and TEM analysis, a cracking and reoxidation process was proposed to explain the decreasing deuterium permeability of CLF-1 during corrosion by Li4SiO4. Our study provides a promising approach for preventing tritium permeation.

Fabrication of efficient and stable Li4SiO4-based sorbent pellets via extrusion-spheronization for cyclic CO2 capture

Li4SiO4 is a promising solid sorbent for high-temperature CO2 capture due to the high and stable CO2 adsorption performance. It is required to possess good mechanical properties in practical fluidized-bed systems and pelletization is necessary. However, pelletization generally results in a large decline in the CO2 uptake or a continuous loss-in-capacity of Li4SiO4 sorbents in cyclic reactions. In this work, three kinds of Li4SiO4 powders were synthesized and screened, and spherical pellets were further prepared via an extrusion-spheronization technique using polyethylene as a pore-former to develop porous microstructure. Then sorbent pellets were systematically tested on the CO2 adsorption performance, compression strength and attrition resistance. Results shows that the pellets modifying with 20 wt% polyethylene reach and stabilize a CO2 sorption capacity of 0.31 g CO2/g sorbent in the whole 40 tested cycles under typical conditions, which is even higher than that in powder form. Moreover, the pellets are observed to have an outstanding compression strength (27.5 MPa after calcination) and an excellent attrition resistance (only 1.01 wt% mass loss in 10 h-attrition test), which are both far more better than sorbents reported in the literature. The simultaneous physiochemical performances indicate that the prepared Li4SiO4 sorbent pellets could be suitable for high temperature CO2 capture in fluidized-bed reactors.

Kinetic study of lithium orthosilicate pellets for high‐temperature chemical heat pumps

AbstractLithium orthosilicate/carbon dioxide/zeolite (Li4SiO4/CO2/zeolite) chemical heat pump (CHP) systems have been discussed for storage and transformation of surplus thermal energy (at ∼650°C) generated from renewable and nuclear energy systems. Tablet forms of Li4SiO4 (referred to as K‐tablets) have been developed with a new pelletizing method for practical application in packed bed CHP reactors. To understand the carbonation and decarbonation mechanisms of K‐tablets, a double‐shell model was suggested and used for explaining experimental results. Isothermal carbonation, decarbonation, and cyclic experiments were conducted under several reaction temperatures for characterization of the K‐tablet. The developed K‐tablet exhibited superior carbonation and decarbonation performance compared to pure Li4SiO4 powder at low temperatures, even when the powder was formed into a tablet shape. The K‐tablet also demonstrated enough durability and a stable reacted conversion value (Δx = 0.75) during cyclic experiments under all temperature. Higher kinetic performances of the K‐tablet than those of pure powder at 650°C and 600°C were also confirmed. The K‐tablet exhibited a high Woutput‐max of 9.82 kW/kg‐tablet at 650°C on the 10th cycle and that value was higher than that of the pure powder (3.25 kW/kg‐Li4SiO4) under the same reaction temperature. The developed K‐tablet has sufficient potential as a CHP material for heat transformation of thermal energy at 600°C to 650°C to >700°C.

Synthesis, kinetic study, and reaction mechanism of Li4SiO4 with CO2 in a slurry bubble column reactor

This study was performed to investigate the synthesis, kinetic and reaction mechanism of Li4SiO4 with CO2 in a slurry bubble column reactor. The Li4SiO4 powder sample was prepared via a solid-state reaction. The sample was characterized via X-ray diffraction (XRD) analysis and verified as a single phase. The median diameter of the sample was measured using the laser diffraction and scattering method as about 20 μm. The synthesized sample was suspended in binary molten carbonate of Li2CO3–K2CO3 having a molar ratio of 38:62. The experimental results show that Li4SiO4 in the slurry bubble column absorbed approximately a stoichiometric amount of CO2. The kinetic study shows that the CO2 reaction behavior on the Li4SiO4 surface was fitted to a double exponential model and the limiting step of the reaction was lithium diffusion. The mass transfer coefficient of CO2 and rate constant of reaction with Li4SiO4 were studied to understand the overall absorption mechanism in the reactor. The resistance for the direct reaction of CO2 on the Li4SiO4 was much smaller than the resistance for the mass transfer of CO2 to the Li4SiO4. We can conclude that the direct contact of CO2 with Li4SiO4 was the main path for the reaction.

Porous extruded-spheronized Li4SiO4 pellets for cyclic CO2 capture

In this work, spherical Li4SiO4 pellets were produced via an extrusion–spheronization technique. This pelletization process caused the destruction of the original porous structure, a reduction of the specific surface area and, thus, a decrease in the CO2 sorption performance. Therefore, a typical pore-forming material of microcrystalline cellulose was employed to modify the inner microstructures of the pellets and thus enhanced the cyclic CO2 sorption capacity. The pellets modified with 20 wt% microcrystalline cellulose exhibited a high capacity of 0.282 g CO2/g sorbent at the 70th cycle, which is even comparable with that of the Li4SiO4 powder. It has been indicated that the performance enhancement is attributed to the increased surface area and enriched porosity. In addition, the sorbent pellets are required to possess excellent mechanical performance for the practical application in the circulating fluidized-bed reactors; therefore, the mechanical properties, i.e., compression strength and anti-attrition performance, were also tested. The results indicated that the Li4SiO4 pellets maintained quite outstanding mechanical performance. The good physicochemical properties of the pellets show that the developed Li4SiO4-based sorbents have promising prospects for high temperature CO2 capture in fluidized-bed systems.

Synthesis, CO2 absorption property and densification of Li4SiO4 powder by glycine-nitrate solution combustion method and its comparison with solid state method

Phase pure Lithium orthosilicate (Li4SiO4) nanopowder was synthesized by solution combustion method using glycine as the fuel and silicic acid as a silica source. The effect of the fuel-to-oxidizer ratio (Φe) (0.6–1.0) in the combustion process and phase evolution was studied. We found that by controlling the fuel-to-oxidizer ratio of the starting solution phase purity can be achieved at 700 °C. Li4SiO4 powder was also prepared by solid state method and phase purity was achieved at 800 °C. The surface area, powder morphology, sintering behavior and CO2 capture properties of the Li4SiO4 were investigated. The powder synthesized by solution combustion route showed higher surface area, sinterability and CO2 absorption capacity compared to the solid state route powder. It could be attributed to the nanostructured morphology of the particles. The grain size in the sintered sample could be kept well below 5 μm. The current report provides a novel method to fabricate lithium orthosilicate, and shows promise for application as high temperature CO2 absorption as well as solid breeder in fusion reactor.

Ultrafast Carbon Dioxide Sorption Kinetics Using Lithium Silicate Nanowires.

In this paper, the Li4SiO4 nanowires (NWs) were shown to be promising for CO2 capture with ultrafast kinetics. Specifically, the nanowire powders exhibited an uptake of 0.35 g g-1 of CO2 at an ultrafast adsorption rate of 0.22 g g-1 min-1 at 650-700 °C. Lithium silicate (Li4SiO4) nanowires and nanopowders were synthesized using a "solvo-plasma" technique involving plasma oxidation of silicon precursors mixed with lithium hydroxide. The kinetic parameter values (k) extracted from sorption kinetics obtained using NW powders are 1 order of magnitude higher than those previously reported for the Li4SiO4-CO2 reaction system. The time scales for CO2 sorption using nanowires are approximately 3 min and two orders magnitude faster compared to those obtained using lithium silicate powders with spherical morphologies and aggregates. Furthermore, Li4SiO4 nanowire powders showed reversibility through sorption-desorption cycles indicating their suitability for CO2 capture applications. All of the morphologies of Li4SiO4 powders exhibited a double exponential behavior in the adsorption kinetics indicating two distinct time constants for kinetic and the mass transfer limited regimes.

Preparation of Li4SiO4-xLi2O powders and pebbles for advanced tritium breeders

Li4SiO4 pebbles and Li2O pebbles have been considered as the potential candidates for tritium breeders. Li2O exhibits higher lithium density whereas worse lithium loss and hygroscopicity compared with Li4SiO4. It is anticipated to obtain an advanced breeder by combining Li4SiO4 with Li2O. The coexistence of Li4SiO4 and Li2O powders could not be obtained by solid state reaction using Li2CO3 as lithium source, while the biphasic Li4SiO4-xLi2O (x=0.1, 0.2, 0.3, 0.4) powders were prepared by sol-gel method in this experiment. Meanwhile, the biphasic Li4SiO4-xLi2O pebbles were fabricated by a wet method for the first time. The Li2O aggregated at the grain boundaries and promoted the grain growth of the Li4SiO4. The grain size and the crush load of the Li4SiO4-0.3Li2O pebbles reached 32.3µm and 46.5 N, respectively.

Fabrication of Li4SiO4 pebbles by wet method with modified powders synthesized via sol–gel process

Li4SiO4 pebbles have been recognized as attractive tritium breeder materials in the fusion reactor blanket of international thermonuclear experimental reactor (ITER). In this work, we present a facile method to prepare Li4SiO4 pebbles of high density and sphericity by using a directive wet method with the Li4SiO4 powders synthesized via sol–gel process. The Li4SiO4 powders were prepared with two-step calcinating method, followed by a ball-milling process. Thermal and phase analysis, morphologies and sintering behaviors observations of the pebbles were carried out systematically. Experimental results show that the pure phase powders with white color that prepared by using two-step calcinating method is different from the powders prepared by the traditional direct calcinating method. The subsequent ball milling process proves to be effective to improve the relative density of the sintered body. When sintered at the temperature as low as 850°C for 4h, the favorable Li4SiO4 pebbles with uniform size (∼1mm), good sphericity (1.02), and high density (above 90% T.D.) were fabricated by using a directive wet method. The as-fabricated pebbles hold good potential as tritium breeding materials for blankets.

Synthesis and Characterization of Li4SiO4 Ceramics from Rice Husk Ash by a Solution-Combustion Method

Phase-pure lithium orthosilicate (Li4SiO4) was prepared by a solution-combustion technique using rice husk ash as a silica source. We found that by controlling the citrate-to-metal (C/M) ratio of the solution and the calcination temperature of the as-burnt powder, phase purity can be achieved. The particle size of the Li4SiO4 powder (prepared at a C/M ratio of 1.4) was found to be 100 to 200 nm with a low surface area (1.83 m2/g). It was found that Li4SiO4 powder can be sintered at a temperature as low as 900°C with a density of ∼83% of the theoretical density. Phase stability in the sintered sample was studied. Attempts were made to minimize lithium loss from the sintered specimens. The solution-combustion–derived Li4SiO4 fractured pellets showed narrow pore size distributions with pore diameters in the range 0.2 to 10 μm. Thermal diffusivity was measured using a laser flash method. Thermal conductivity values depend on the density of the sample. An impedance spectroscopy method has been used to characterize the electrical properties of the sintered sample as tritium diffusion is related to Li+ ion conductivity in Li4SiO4.

Synthesis and sintering of Li4SiO4 powder from rice husk ash by solution combustion method and its comparison with solid state method

Phase pure lithium orthosilicate (Li4SiO4) was prepared by the solution – combustion technique as well as solid state method using rice husk ash (RHA) as silica source. It was found that by controlling the metal to citrate ratio of the starting solution, phase pure powder can be prepared at 650°C. Whereas in solid state method, calcination at 800°C was required to achieve phase purity. The particle size of Li4SiO4 powder (prepared at C/M=1.4) was found to be 100–200nm with low surface area (1.83m2/gm). It was found that Li4SiO4 powder can be sintered at a temperature as low as 900°C with a density ∼83% of the theoretical density. In case of solid state method prepared powder, maximum 80% of the theoretical density could be achieved. Phase stability in the sintered sample was studied.

Synthesis of Lithium Orthosilicate by Solution Combustion Technique and Its Microwave Sintering

The present report demonstrates synthesis of Li4SiO4 powder through solution combustion route using silica from rice husk ash (RHA). RHA is cheap agricultural waste and can be easily procured. It is found that phase pure Li4SiO4 powder can be prepared at 650°C. It is also observed that phase purity of the powder depends on metal to fuel ratio of the starting solution. Finally, microwave sintering is carried out to densify the synthesized Li4SiO4 to more than 80% of theoretical density at a temperature 1000°C.

Fabrication of Li4SiO4 Pebbles Using Slurry Droplet Wetting Method for Solid Breeding Material

Lithium orthosilicate (Li4SiO4) pebbles are the primary candidate breeder for the Korean Helium-Cooled Solid Breeder test blanket module because of their superior overall performance qualities such as reasonable lithium atom density, favorable tritium release behavior, low activation property, and chemical stability. The aim of this study is to develop a fabrication method for Li4SiO4 pebbles with high sphericity and stable micro-crystalline structure. Li4SiO4 slurry was prepared by mixing Li4SiO4 powder and polyvinyl alcohol (PVA) solution. The Li4SiO4 gel-spheres were made by dropping slurry mixture into hydrogen peroxide (H2O2) solution. The gel-spheres were floated up to the surface of the H2O2 solution after staying at the bottom for a while and then aged on the surface of the H2O2 solution. The gel-spheres were dried at room temperature and sintered at several temperatures for 4 hours in air atmosphere. The sintered pebbles kept the shape of spheres during the sintering process in spite of shrinkage. Furthermore, the pebbles had relatively high sphericity. Also, the effects of PVA content and sintering temperature on the properties of the Li4SiO4 pebbles were investigated.