Composition Of CaO Research Articles

Preparation of A High-Performance Frit Glaze Using High-Potassium Feldspar

In this study, a lead-free transparent frit glaze was fabricated using a high potassium feldspar ore from Northeast China. The effect of the potassium feldspar grade and compositions of CaO and ZnO content on the performance of a block glaze was studied. The study on the effects of the potassium feldspar grade on the molten glaze demonstrated that as the grade of the potassium feldspar in glaze increases, the glaze appearance, gloss, hardness, and thermal stability of the sample become better, and the roughness decreases. CaO and ZnO in glaze have good fusible effects on the performance of melt glaze: the high-temperature viscosity of glaze decreases, and the surface tension and quality of the glaze increase. Moreover, an optimal lead-free frit glaze formula was determined, which provided insight into the production of high-added-value products using complex and refractory potassium feldspar ore.

Influence of Residence Time on Syngas Composition in CaO Enhanced Air–Steam Gasification of Biomass

Influence of Residence Time on Syngas Composition in CaO Enhanced Air–Steam Gasification of Biomass

Gem-Grade Garnet With Metamorphic Origin in the Tiemurt Orogenic-Type Deposit, Chinese Altay Orogen: Texture, Chemistry, and Physicochemical Condition

The Chinese Altay Orogen represents an accretionary collage with episodic subduction-related accretion from the Neoproterozoic to Permian, followed by Triassic continent–continent collision. Reddish gem-grade garnet grains are widespread in Au–Cu–Pb–Zn sulfide deposits of the Chinese Altay Orogen, and how their formation links to regional geological processes such as seafloor sedimentation, magmatic hydrothermal metasomatic, or orogenic metamorphism remains unclear. In this context, we present an integrated set of geological occurrences, mineral texture, and major trace elemental geochemistry of six garnet grains from the representative Tiemurt Cu–Pb–Zn(-Au) deposit. Two categories of garnets, Grt1 and Grt2, are identified in terms of distinct mineral assemblages, textures, and geochemistry. The sub- to euhedral biotite inclusion–rich Grt1 with fine grains of less than 0.3 cm in diameter is intergrown with amphibole, chlorite, and biotite. Comparatively, the euhedral mineral inclusion–poor Grt2 with coarse grains of 0.5–5 cm in diameter is paragenetic with quartz, calcite, chlorite, and biotite. Forty-one EMPA analyses show that Grt1 and Grt2 have similar major elemental compositions of SiO2 (36.2–37.5 wt%), Al2O3 (19.9–20.7 wt%), and CaO (5.3–7.8 wt%) but host variable contents of FeO (31.7–35.9 wt% for Grt1 and 23.0–30.0 wt% for Grt2) and MnO (0.8–3.7 wt% for Grt1 and 4.3–12.7 wt% for Grt2). Both Grt1 (with a chemical formula of Alm49.3–54.6Spe19.7–24.6Gro14.6–18.4Pyr3.7–4.8And3.5–4.9) and Grt2 (Alm57.4–64.4Gro15.5–18.3Spe9.62–19.8Pyr3.8–5.7And1.1–4.4) are plotted into the field close to the end-member of almandine (Fe-Al–garnet). Compared to Grt1, Grt2 displays a Fe-enriched and Mn-depleted trend. Additionally, Mn is enriched in the core but Fe is enriched in the rim on the major elemental profile of Grt1. Regarding the trends of trace elements and REEs, Grt2 is believed to be produced during the detriment and replacement of Grt1 by an intense external metal-rich fluid. In combination with previous fluid inclusion research, the garnet-related fluids are characterized by CO2-rich, mesothermal, mildly acidic, and reduced redox, analogous to metamorphic fluids generated during orogenesis. Collectively, we conclude that the reddish gem-grade garnet crystals in the Chinese Altay Orogen are of metamorphic origin.

Gaseous production kinetics and solid structure analysis during isothermal conversion of biomass pellet under different atmospheres

Isothermal chemical conversion of biomass pellets under the atmospheres of Ar, CO2 and O2 were conducted in this study to explore the effects of atmosphere and temperature on the gaseous releasing process and kinetics, and the structure of the solid char/ash products. Results showed that the gas production was promoted while the solid yield was decreased with the raising temperature. The CO2 reaction with char during gasification process mainly happened after 800 °C that the CO formation lasted for a longer time than pyrolysis. The surface area of char under CO2 atmosphere was increased to 215.57 m2/g with the increased temperature to 800 °C, but it was sharply reduced to 5.10 m2/g when the temperature further raising to 900 °C due to the destroyed carbon skeleton. The CO2 formation was largely promoted with a low activation energy of 11.98 kJ/mol during O2 oxidation process. Compared with the crystal structure of solid residues obtained under Ar and CO2 atmospheres, O2 oxidation process resulted in more complex crystal peaks with the main compositions of SiO2, K2SO4, and CaO. This study should be helpful to further understand the thermal conversion of biomass in a complex reaction atmosphere.

Melting Characteristics of Coal Ash and Properties of Fly Ash to Understand the Slag Formation in the Shell Gasifier.

The flow temperature (FT) of the coal ash from the Liuqiao no. 2 mine in North Anhui Province (C00) is too high (∼1520 °C) to fit the Shell gasifier due to its relatively high content of SiO2 and Al2O3. To solve this problem, a series of coals were blended with C00 with different ratios, and the relations between FT and the ash composition were investigated. The coal ash was analyzed by X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy–EDX to elucidate the mechanism of the improved ash fusion performance and the slag formation in the waste heat boiler of the gasifier. It is shown that FT is relevant to the coal ash compositions as well as the structures formed at high temperatures. The existence of alkaline oxides (CaO, MgO, and Fe2O3) decreases the coal ash FT to a low level. The FT can decrease to <1350 °C to cater to the Shell gasifier by blending C00 and C03 with a mass ratio of 4:6 owing to the plentiful alkaline oxides in C03. The FTIR results indicate that the high flow temperature of C00 is attributed to the formation of mullite at high temperatures. The coal blending with various ratios changes the compositions of CaO, MgO, and Fe2O3, which can form some low-melting-point eutectic compounds with SiO2 and Al2O3 under high temperatures, inhibit the formation of mullite, and thus decrease the ash FT. The coal ash FT was found to have a good linear relation with the ash compositions, which can sever as a reference to the coal blending. According to the model parameters, it is shown that Mg has the most significant promoting effect on the decrease in FT of the coal ash. The caking tendency of fly ash increases with the rising Ca content and an excessive Ca-based fluxing agent used in the coal blending will lead to the aggregation of the Ca-rich clasts around the fly ash particle, resulting in the plugging of the waste heat boiler in the gasifier. Therefore, the Mg-based fluxing agent is more promising to improve the ash fusion performance and reduce the caking tendency of the coal fly ash.

Evaluation of Hydrogenation Kinetics and Life Cycle Assessment on Mg2NiHx-CaO Composites.

Magnesium-based alloys are attractive as hydrogen storage materials due to their lightweight and high absorption, but their high operating temperatures and very slow kinetics are obstacles to practical applications. Therefore, the effect of CaO has improved the hydrogenation kinetics and slowed down the degradation. The Mg2NiHx–CaO composites were prepared by hydrogen-induced mechanical alloying (HIMA). Hydrogenation kinetics was performed by using an Automatic PCT Measuring System and evaluated in the temperature range of 423, 523, and 623 K. As a result of calculating the hydrogen absorption amounts through the hydrogenation kinetics curve, they were calculated as about 0.52 wt%, 1.21 wt%, and 1.59 wt% (Mg2NiHx–10 wt% CaO). In this study, the material environmental aspects of Mg2NiHx–CaO composites were investigated through life cycle assessment (LCA). LCA was performed analyzing the environmental impact characteristics of the manufacturing process by using Gabi software and the Eco-Indicator 99’ and Centrum voor Milieuweten schappen (CML 2001) methodology. As a result, the contents of global warming potential (GWP) and fossil fuels were found to have a higher impact than other impact categories.

Investigation of the Geochemical Composition and Paleo-Depositional Environment of Ubo and Ikpeshi Marble Deposit, Southwestern Nigeria: A Comparative Study

The marble deposits at Ubo and Ikpeshi areas of Edo state, Southwestern Nigeria, were studied in order to determine the major elements and the paleo-depositional environment of the original sediments using standard methods. Results obtained using test of difference between Ubo and Ikpeshi marbles showed that CaO (51.977±0.922 &amp; 54.726±0.23), MgO (3.034±0.829 &amp; 0.499±0.115), Na2O (1.7±0.73 &amp; 0.024±0.008), MgCO3 (6.337±1.734 &amp; 1.034±0.238), Cu (24.589±0.692 &amp; 27.447±0.711), Ni (23.907±0.854 &amp; 30.979±0.494), all for Ubo and Ikpeshi respectively; with Ni showing highest significance with P&lt;0.01. The Ubo marble deposit occurs as a lensoid body within the younger metasedimentary sequence. The major element composition reveal a mean chemical composition of CaO (51.97 and 54.73 %), MgO (3.0 and 0.49 %), SiO2 (0.74 and 0.70%), K2O (0.08 and 0.04%), Na2O (1.70 and 0.02%), Al2O3 (0.75 and 0.25%), Fe2O3 (0.34 and 0.25%), and Loss on Ignition - L.O.I (43.34 and 49.31%) in Ubo and Ikpeshi marbles respectively, which is indicative that the marble samples were all calcitic. The low values of the total alkali content in the marble samples from the two locations indicate that the environment of deposition of the original carbonate materials that metamorphosed into marbles from both locations must have been a shallow, highly saline environment with probably little influx of salty brine water in the basin. Silica was used as an abscissa in these plots because it shows substantial variations among the marbles with most of the linear relationship between silica and the various oxides showing negative correlation, this probably reflects the admixture of the carbonates with chert. The trend of the plots of Na2O + K2O vs. SiO2 for the marbles from both locations show a variation in the salinity.&#x0D; Keywords: Ubo, Ikpeshi, Marble, Marine Environment, Metasedimentary

Structure, and opto-dielectric investigations of Cu2+ -doped calcium bismuth silicate glass ceramics

CuO inclusive silicate glasses are well known for various semiconductor applications. However, there is a lot of demand and necessity of high efficient opto-dielectric materials. In view of this, the glasses of chemical composition (30 – x) CaO + (10) Bi2O3 + (60) SiO2 + (x) CuO have been synthesized and studied for their structural, optical and dielectric characterization techniques. Glassy behaviour of CuO undoped glass and ceramic behaviour of all other CuO doped glasses conformed by structural characterization. The elastic modulus and micro hardness of glass and glass ceramics reveal their inter connected covalent structure. Trap depth parameters (Tm, Eτ, Eδ, Eω & μs) have been determined and analysed under irradiation, and found that 0.3 mol% CuO -doped glass ceramic under 30 kGy of irradiation dose exhibiting better TL output. Dielectric relaxation studies of the glass ceramics suggested that mixed conduction of both ionic and electronic. Observed dielectric results; dielectric constant (εr), dielectric loss (tanφ), temperature region of relaxation (ΔT), low activation energie's for conduction (Ea) and AC Conductivity (σac) suggesting that the glass ceramics are dielectric. Optical band gap (Eo), transition probability (At) and emission cross section (σ) corresponding to the emissive transition 3D1 → 1S0 assessed by optical techniques. All the results suggests that 0.3 mol% CuO -doped glass ceramic is a useful opto-dielectric resource.

Influence of artificial filler made of calcium hydrosilicates of various basicity on the performance characteristics of non-autoclave hardened silicate materials

The work established the nature of the effect of an artificial filler made of calcium hydrosilicates of various basicity on the physical and mechanical properties of non-autoclave silicate composites based on unconventional aluminosilicate raw materials, represented by clay rocks of an unfinished stage of mineral formation. It is determined that the optimal content of an artificial filler of the composition CaO:SiO2 is 1:1 in the raw mixture is in the range of 1–3 wt.%. The available interval makes it possible to vary the composition of the initial mixture and obtain products with the required properties, which is especially important when the material composition of the feedstock fluctuates, as well as in case of violation of the production technology. The rational content of the artificial filler of the composition CaO:SiO2 = 2:1 is 1 wt. %. It is shown that the addition of an artificial filler promotes the formation of a cementitious substance from neoplasms of a higher degree of crystallization, which contributes to an increase in the strength and water resistance of the material. Mathematical models are proposed for the selection and optimization of the compositions of non-autoclave silicate materials based on unconventional aluminosilicate raw materials and modified with an artificial filler represented by calcium hydrosilicates of various basicity to obtain materials with a compressive strength of 18-23 MPa with an average density of finished products of 1750-2000 kg/m3.

Optical and photocatalytic properties of biomimetic cauliflowered Ca2Mn3O8–CaO composite thin films

Inspired from the μ-oxido CaMn4 cluster unit present in the photosystem-II of plant cells, various manganese-based materials, particularly calcium-manganese oxides, have been investigated by the researchers as a new class of catalysts. Herein, we report the synthesis of single source heterobimetallic complex {[CaMn(OAc)(TFA)3(THF)(H2O)2].3THF}n (where OAc ​= ​acetate, TFA ​= ​trifluoroacetate and THF ​= ​tetrahydrofuran) for the deposition of thin films of Ca2Mn3O8–CaO composite on fluorine doped tin oxide (FTO) coated glass substrates at deposition temperatures of 450–550 ​°C via the aerosol assisted chemical vapour deposition (AACVD) method. The complex was characterized by melting point, microanalysis, proton nuclear magnetic resonance (1H NMR), Fourier transformed infra-red (FT-IR) spectroscopy, thermogravimetry (TGA) and single crystal X-ray diffraction. The deposited thin films were analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, energy dispersive X-ray spectroscopy (EDX) and field emission scanning electron microscopy (FESEM) which confirmed the growth of Ca2Mn3O8–CaO composite with high purity and precise stoichiometry. The optical characterization gave direct band gap energies of 2.74, 2.68 and 2.77 ​eV for the Ca2Mn3O8–CaO thin films deposited at 450, 500 and 550 ​°C, respectively. Furthermore, photoelectrochemical studies revealed that the thin film deposited at 500 ​°C showed the photocurrent of 3.75 ​mA ​cm−2 at +0.8 ​V vs. SCE with 1.64% photo-conversion efficiency and 310 ​Ω Rct value, upon illumination with a 150 ​W (100 ​mW ​cm−2) halogen lamp. The improved photocatalytic activity of Ca2Mn3O8–CaO composite was due to the increased photo absorption ability, elevated surface area, and more efficient electron/hole transfer. In addition, this work provides an insight to design the growth of visible light active calcium-manganese based photocatalyst materials for solar energy utilization.

Effect of ball-milling time on chemical property of coconut shell powder

Coconut is one of the abundant agricultural products in Indonesia. Coconut shell is one of the wastes from coconut products that can be used as biocomposite material. The purpose of this study was to find out the effect of ball milling time on the chemical properties of coconut shell powder. X-ray diffraction (XRD) and X-ray fluorescent (XRF) have been used in this study. Coconut shell powder 200 mesh was milled using mechanical ball milling for various milling times (20, 30, and 40 hours) at 350 rpm constant speed. The results of our study using XRD showed that the coconut shell powder contains SiO2, C, Fe2O3, CaO, K2O, and Al2O3. The intensity of the diffraction pattern from our sample increased when the ball-milling time was increased. This implies that the crystallinity of the sample was influenced by the ball-milling time. By using XRF, it was found that the coconut shell powder contains 13.6% of Fe2O3, 25.7% of CaO, 46.1% of K2O, 2.8% of CuO, and 8.2% of P2O5. The percentage composition of Fe2O3 increased from 13.6% for 0 hours milling time to 30.2% after the sample was milled for 20 hours. The percentage composition of Fe2O3 rose to 32.2% for the milling time of 40 hours. However, the percentage compositions of CaO and K2O decrease as the milling time is increased. The percentage composition of P2O5 is independent of milling time. Our results show that the chemical properties of coconut shell powder are influenced by the ball-milling time or particle size of coconut shell powder.

Microstructural Characterization and Microhardness of Leucite Glass-Ceramics Synthesized from Sarawak Sand Reserves.

The purpose of this study was to evaluate the effect of varying the sintering temperature and holding time on the crystallization and microhardness of the SiO2 – Al2O3 –K2O glass system using SiO2 from Sarawak sand reserves. A starting glass composition of SiO2 (from Sarawak sand), Al2O3, K2O, Na2O, CaO, LiO and TiO2 was prepared by conventional melt quenching technique followed by ball milling. The glass powder was pressed under pressure into disk-shaped compacts with 2 mm thicknesses and 14 mm diameters. The samples were then subjected to differing heat treatment schedules of 750°C, 800°C and 850°C with 1, 3 and 6 hours holding times. They were characterized by X-ray Diffraction (XRD), Scanning electron microscopy (SEM) and Vickers microhardness. XRD showed the crystallization of tetragonal leucite with minor secondary sanidine phases. SEM showed the formation irregular shaped and non-uniformly dispersed crystals. The hardness values showed an increasing trend with longer holding time at temperatures of 750°C and 800°C. This pattern was inversed for sintering temperature 850°C. In conclusion, sintering temperatures and holding time combinations influenced the crystallization and microhardness values of leucite glass ceramics produced from Sarawak sand silica.

Optical Properties of Calcium Sodium Phosphate Glasses Doped With Strontium

Strontium doped calcium phosphate sodium oxide glasses are prepared by a conventional melt quenching technique with different concentrations. XRD Spectra reveals that these glasses are amorphous in nature. The absorption spectrum of these glass samples exhibited broad band at about ∼230nm. Optical band gap were determined by drawing Tauc plot. On the basis of the measured values of density, molar volume, optical band gaps and refractive index, properties like Ca2+ ion concentration, electronic polarizabilities, oxide ion polarizabilities, inter ionic distance, polaron radius, molar refraction and optical basicity of glass systems were estimated. All the variation can be attributed to the formation of Non bridging oxygens (NBO) with the increase of CaO composition in the glass network.

Geochemical characteristics and the provenance of aeolian material in the Hexi Corridor Desert, China

The Hexi Corridor Desert is in Gansu Province, northwestern China. The material provenance of desert formation and development is the primary factor of aeolian geomorphology, and it is still not fully understood in the Hexi Corridor Desert. To identify sources of aeolian sand in the formation of dunes in the Hexi Corridor Desert, we investigated 12 sites and collected 70 samples from the dune surface. This study used ratios between Na2O/Al2O3 versus K2O/Al2O3 and SiO2/Al2O3, Ba/Sr versus Rb/Sr and Rb/Sr versus Ce/Sr as well as CaO and Cl composition to identify sediment provenance. CaO was enriched relative to the composition of the upper continental crust (UCC), consistent with a previous study conducted in the Taklamakan and Badain Jaran deserts on adjacent fluvial, lacustrine and gravel deserts, but it differed from one study conducted in the Kumtagh and Tengger deserts. Cl concentrations differed in lacustrine and sand sediments, being higher in lacustrine sediments, followed by sand sediment. Sand sample geochemistry was similar throughout, indicating that sources of sand formation were also similar, which was confirmed by the multidimensional scaling (MDS) and principal component analysis (PCA) methods. Additionally, based on regional topography, the Hexi Corridor acts as a sediment sink not only for sediment from the Qilian Mountains but also for sediment from the Beishan Mountains. The MDS and PCA approaches also indicated that sediment provenance was similar in the Hexi Corridor and the Tengger, Badain Jaran and Kumtagh deserts. Therefore, it can be concluded that dry fluvial deposits, alluvial deposits and lacustrine sediments that combined comprised sand dune provenance were the sources of sand in the Hexi Corridor Desert, and these deposits derived from the Qilian Mountains in the southwest and the Beishan Mountains in the north through alluvial processes.

Bayesian-optimization-guided experimental search of NASICON-type solid electrolytes for all-solid-state Li-ion batteries

Experimental Bayesian optimization for Li ion conductivity in NASICON-type LiZr2(PO4)3.

Time-Dependent Effect of Different Intracanal Medicaments on Dentin Microhardness and Dislocation Resistance of MTA Used During Regenerative Endodontic Treatment

Objectives: This study was designed to measure and compare dentin microhardness and MTA (ProRoot, Dentsply Tulsa Dental, Tulsa, OK) dislocation resistance (DR) used in regenerative endodontic treatment (RET) after application of three different intracanal medication(ICM) for 2,4 and 12 weeks’ time intervals. Material and methods: One-hundred sixty eight human maxillary central incisors were selected for the study. Teeth were cut apically 12 mm below and coronally 2 mm above the cemento-enamel junction. Canals were instrumented up to instrument F5 (ProTaper Universal, Dentsply Maillefer, Ballaigues, Switzerland), then Peeso drills (Mani, Tochigi, Japan) were used from No. 1 up to No. 6 , passing 1 mm beyond the apical foramen to obtain larger root canals. Between every 2 consecutive instruments 2 mL of 2.5% sodium hypochlorite (NaOCl) used for canals irrigation , final flush using 5 mL of 2.5% NaOCl and 5 mL of 17% ethylene-diamine-tetra-acetic acid (EDTA, Sigma) followed by 10 mL of distilled water. Samples were randomly divided according to the type of the ICM used inside the canal into 4 equal groups (n = 42); Group 1: Double antibiotic past(DAP) paste: 1:1 mixture of ciprofloxacin (Cipro 500 mg, Schering Plough, Kenilworth, NJ, USA) and metronidazole (Flagyl 500 mg, Sanofi-Aventis, Tours, France), Group 2: Bioactive glass powders (BAG S53P4) of 60 mol% SiO2, 12 mol% P2O5 and 28 mol% CaO composition were prepared through sol gel processing route, all reagents were purchased from Sigma-Aldrich(Dorset, UK). Group 3: Non-setting Calcium hydroxide (CH) (Merk, Germany) was used, and finally, Group 4(Control): where no ICM was applied. Samples were kept in saline solution for either 2, 4, and 12 weeks, randomly selected samples from each group n=14 at each interval where intracanal medication removed, half of them n=7 were subjected to dentin Vickers microhardness test, in remaining half n=7 MTA (ProRoot, Dentsply Tulsa Dental, Tulsa, OK) placed 4 mm deep into the coronal third of the roots having a 4 mm-long chamber, samples were stored for a week at 37 °C at 100 % humidity to allow the complete setting of MTA, then push-out test was used to measure the dislocation resistance DR of MTA. Collected data were analyzed using a two-way ANOVA followed by Bonferroni’s post-hoc test was used for pair-wise comparisons (P ≤ 0.05). Results: showed that both DAP, CH groups of intracanal medication and time interval had a significant decreasing effect on dentine microhardness and MTA dislocation resistance the DR of MTA (P-value <0.001). While, BAG group`s results revealed significant increase in dentine microhardness and MTA dislocation resistance (P-value <0.001). The time factor displayed a significant effect on dentin microhardness and the DR of MTA (P-value <0.001).Conclusion: Regarding situations in this study, intracanal medications type and duration of application used in root canals disinfection through RET must be carefully chosen to avoid negative effect on dentin microhardness or DR of MTA jeopardizing the success of the treatment. BAG (S53P4) showed promising results, further studies needed to complete investigations about it as intracanal medication in RET.

γ-ray shielding features and crystallization of TiO2 borotellurite glasses

Glasses of composition (60B2O3 –10 Na2O – 20TeO2 – (10-x) CaO) + xTiO2 where x ranged from 0.5 to 3 mol% have been prepared and coded as BTNCT0.0 (x = 0), BTNCT0.5 (x = 0.5), BTNCT 1.0 (x = 1.0), BTNCT2.0 (x = 2.0), and BTNCT3.0 (x = 3.0). Glass transition temperature (Tg) and crystallization temperature (Tc) have been determined for the prepared samples. The addition of small concentration of TiO2 leads to change both of Tg and Tc. The glassy temperature of this glass is about 435 °C and the crystallization temperature at about 505 °C. Heat treatment has done for the glasses to obtain the crystalline phase. This action studied by both XRD, SEM, TEM, and EDAX pictures. Results proved that the glass phase performs as interconnecting amorphous zones between the crystals and the size of crystal grains is changed from 1 μm to 20 μm. The capability of using the investigated glasses as radiation shielding glasses has been evaluated. The mass attenuation coefficient (µ/ρ) has been calculated by using WinXcom software program in the range of 0.01–15 MeV photon energy. The related shielding parameters such as linear attenuation coefficient (µ), half value layer (HVL) and mean free path (MFP) were evaluated and compared with those of commercial γ-ray shielding concrete. Results reveal that the HVL values for all investigated glasses increased except for BTNCT1.0 sample. Thus, BTNCT1.0 glass sample has the lowest HVL compared to other samples.

Calcium-based composites for direct solar-thermal conversion and thermochemical energy storage

Calcium-Looping (CaL) is considered as a promising process for thermochemical energy storage in the 3rd generation Concentrated Solar Power plants using a supercritical carbon dioxide power cycle. Here we propose, for the first time, a novel strategy to directly absorb solar energy using calcium-based composite thermochemical energy storage (TCES) materials. The main novelty lies in the binary metallic element doping of the calcium-based raw materials to enhance their direct interactions with solar radiation photons for light capturing. In particular, the use of the metallic element doping is to form high light-absorbing material for addressing the unfavorable intrinsic optical absorption properties of the calcium carbonate for photon management. A simple and facile sol-gel method was used to synthesize the CaO composites doped with Mn and Fe. Such binary metallic element doping into the calcium-based materials not only boosted the solar absorption but also improved the cycling stability of the TCES material in the integrated CaL-CSP system. The synthetic composites were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The effects of thermochemical cycling on the microstructures and properties of TCES material were investigated. Furthermore, the underlying mechanisms were discussed. The results indicated that the enhancement of the optical absorption for the composites originated from metal oxides of Fe and Mn with high light-absorbing ability. The synergistic effects of small grain size and the reinforced skeleton structures could impede agglomeration and collapse of the composites, thereby improving the cycling stability.

Separation of Cenospheres from Lignite Fly Ash Using Acetone–Water Mixture

This work reports on the separation of cenospheres from lignite fly ash through a wet separation process-the sink-float method. A better quality of cenospheres could be achieved through a physical–chemical approach using an acetone–water mixture as a medium. This work aimed to elucidate the correlation between the structure, morphology, and composition and medium fraction variables, with data for the freshly prepared and the reused mixtures presented for comparison. The work covers a study of the macrocomponent composition of an Fe2O3–SiO2–Al2O3 system, highlighting the pair dependences of SiO2–Al2O3, Al2O3–Fe2O3, and SiO2/Al2O3–Al2O3 and revealing an interesting result in terms of geochemical characteristics categorizing the collected cenosphere fractions separated from high-calcium class C fly ash produced from a lignite coal power plant in Thailand (as magnetic cenospheres). The CaO and SO3 contents increased monotonically with increased water content, particularly for the CaO composition profile, which was found to be similar to the increased carbonate concentration measured from the mixtures after use. The physicochemical properties in terms of the self-association ability of the acetone–water mixing phase is believed to have played an important role in determining the intermolecular interactions and reactivity of ions in the liquid phase, consequently affecting the separation efficiency, recovery yield, and quality of cenospheres.

Solidification of Boron-Containing Ion-Exchange Resins with Aluminosilicate Binder

Solidification of a mixture of ion-exchanger resins (IERs), consisting of a cation exchanger in the sodium form and an anion exchanger in the tetraborate form, using a binder based on calcium aluminate of VGKTs-75-05 grade of the composition CAO·1.64Al2O3 was studied. In solidification with calcium aluminate, the major hydration product responsible for the matrix strength, katoite Ca3(AlO3)2·6H2O, decomposes under the action of B4O72−, which results in low strength of the matrices. To prevent this, IER prior to solidification was treated with a solution of alkaline earth metal (Ca, Sr, Ba) nitrates to decrease the reactivity of B4O2−7 ions as a result of formation of insoluble alkaline earth metal tetraborates. To decrease the 137Cs leaching, a cesiumselective sorbent, diatomite or clinoptilolite, was introduced when performing solidification. The sorbent surface was preliminarily modified with a cationic polymer. Solidification under the above-described conditions allows preparation of aluminate matrices with increased loading with ion-exchange resins. Such matrices meet all the requirements to cemented solid radioactive waste.