CaO Powder Research Articles

High Temperature Oxidation Behavior of Mg-6%Al-1%Zn-1%CaO Alloys

The magnesium-base AZ61 alloy was cast while adding 1% CaO powder into the melt. It was hot extruded, and oxidized at 550-650℃ in air in order to study its microstructure and oxidation behavior. Initially added CaO powder reacted with Al in the melt to Al₂Ca particles that aligned along the extrusion direction. The formed Al₂Ca particles increased the oxidation resistance through forming the superficial CaO scale at the upper part of the thin MgO oxide scale.

Part Ι: Effects of two-stage heat treatment on densification, microstructural features and dielectric properties of CaO–MgO–SiO2 glass-ceramics with ZrO2 nucleating agents

Densification, microstructures and dielectric properties of CaO–MgO–SiO2 glass-ceramics were investigated with ZrO2 nucleating agent using two-stage heat treatment in the low temperature co-fired ceramic (LTCC) method. The amorphous cullet (abbreviated as CMSZ glass) was synthesized by mixing CaO, MgO, and SiO2 powders with ZrO2 nucleating agent, which were melted at 1500°C before the quenching process. The results show that CMSZ glasses annealed below the critical nucleation temperature (Tcn) and sintered at 950°C exhibit obvious bloating phenomena. On the other hand, CMSZ glasses annealed above Tcn demonstrate that zirconia nucleation occurs at the first-stage heat treatment (annealing). The second-stage heat treatment (sintering) is characterized by the rapid crystal growth of CaMgSi2O6 phase around the ZrO2 crystallites, indicating growth of nuclei over the critical size above Tcn. Moreover, specimens fabricated using two-stage heat treatment and annealed above Tcn exhibit appropriate microwave dielectric properties and high mechanical strength.

Proton Conducting ZrO2-1.6P2O5 Electrolyte Hybridized with ZnO-2P2O5 for Intermediate Temperature Fuel Cells

In recent years, fuel cells have been attracting much attention as clean energy sources with the progress of global warming. However, a large amount of platinum was required as a catalyst for the fuel cells operating at a low temperature range (~ 80°C) because not only the catalyst was poisoned by carbon monoxide but also platinum has insufficient activity for an oxygen reduction reaction. Intermediate temperature full cells (ITFC) operating at 150 to 300°C are one of the solutions that reduce the amount of platinum. We reported that ZrO2-1.6P2O5 electrolytes have a high proton conductivity in the temperature range of 150 to 300°C and that the performance of water resistance, as well as gas barrier property, was improved by the hybridization with proton conductive ZnO-2P2O5 glass. In this study, we report on the preparation and characterization of silane-treated ZrO2-1.6P2O5 electrolytes hybridized with ZnO-2P2O5 glass electrolyte. A ZrO2-1.6P2O5 electrolyte (abbreviated as EL) was synthesized by mixing (NH4) 2HPO4 and ZrCl2O·8H2O at a stoichiometric ratio, followed by a heat-treatment at 500°C for 45 min under 10 mol% H2O. CaO doped ZnO-2P2O5 glass powders (abbreviated as ZnO-2P2O5 + 0.3 M CaO) were prepared via the following process: After Zn powder was dissolved in 86 wt% phosphoric acid at various stoichiometric ratio, A CaO powder was added in the solution to be 0.3 mol/L with respect to the volume of the phosphoric acid. The suspension melted at 900°C was quenched by pressing on a copper plate at 300°C to vitrify the sample. The NaCl powder was grinded by a ball milling with pottery balls (10 mm in diameter) and classified by sieving. The glass powders was mixed with the milled a NaCl powder (55 vol%) and pressed into a pellet (12 mm in diameter) at 340 MPa, followed by a heat-treatment at 300°C for 30 min. The pellet was immersed in 300 mL of ultra-pure water to produce a porous glass matrix by removing the NaCl particles in the pellet (denoted as ZnO-2P2O5 + 0.3 M CaO) -EL (NaCl particle diameter)). The porous glass matrix was immersed in 1 wt% octadecyltrichlorosilane-toluene solution for 3 min, followed by the injection of 1 mL of the solution into the glass matrix on a filter bottle with an aspirator. The silane-treated porous glass matrix was filled with EL-86 wt% phosphoric acid suspension on a filter bottle with an aspirator. Then, the pellet was again immersed in the 1 wt% octadecyltrichlorosilane-toluene solution for 3 min (added -SP to a sample name). The proton conductivity of the hybrid electrolytes was measured by an AC impedance analyzer (HP-4192A, Yokogawa) with two-terminal configuration. The water resistance of the electrolyte was calculated from the change of pH in 200 mL Milli-Q water. The hydrogen gas permeability of the electrolytes was measured by gas chromatography (GC-8A, Shimadzu). Fig. 1 shows the result of water resistance tests for the electrolytes. The initial rate of dissolution for silane-treated samples using powders(φ=76 μm and 9.7 μm) were 4.12×10-8 mol cm-2 s-1 and 8.28×10-8 mol cm-2 s-1, respectively. These values are 30 and 43 times smaller than those of untreated ones; the silane-treated sample using NaCl (φ=76 μm) powder showed 64 times higher water resistance than that of EL. Acknowledgement:This study was partially supported by a Grant-in-Aid for Young Scientists (B) (No. 26820321) from Japan Society for the Promotion of Science. Figure 1

Improvement of the performance of encapsulated CaO and active carbon powders for rapeseed oil methanolysis to fatty acid methyl esters under condensed light irradiation

The performance of capsulated CaO and active carbon powders for rapeseed oil methanolysis to obtain fatty acid methyl esters (FAME) under light irradiation was improved by inserting a condenser lens between the reactor and light source. Capsule breakage was greatly increased by the condenser lens because the lens increased the temperature inside the capsule dramatically. Consequently, a low FAME yield of 46.9% was obtained with the CaO (100mg/mL)-active carbon (2.0mg/mL)-loaded capsules after 6h. Therefore, the effect of the irradiation power and active carbon loading on the final FAME yield was investigated. Decreasing the active carbon loadings from 2.0 to 0.1mg/mL reduced the capsule breakage, which affected the final FAME yields. The decrease in the irradiation power from 3.6 to 0.6W also affected the capsule breakage. An active carbon loading of 0.5mg/mL and an irradiation power of 3.6W gave the highest FAME yield (90%) after 6h at 308K. Under these conditions, the FAME phase only contained 0.37% Ca from the charged CaO catalyst with a capsule breakage of 53%.

Low-cost Ce1-xSmx(Fe, Co, Ti)12 alloys for permanent magnets

Ce1-xSmxFe9Co2Ti alloys based on the ThMn12-type crystal structure have been synthesized via melt-spinning of prefabricated alloys and via mechanochemical processing of CeO2- Sm2O3- Fe2O3-TiO2- Co - Ca - CaO powder mixtures. Coercive fields up to 0.8 kOe and 2.1 kOe were obtained in annealed melt-spun alloys with x = 0 and x = 0.5, respectively. Submicron, partially anisotropic particles collected after the mechanochemical synthesis for x = 0.5 and x = 1 exhibited coercivity (energy product) of 1.8 kOe (5.4 MGOe) and 5.8 kOe (9.9 MGOe), respectively. The low magnetic anisotropy field of CeFe9Co2Ti alloy requires at least a partial Sm-substitution for Ce in order to develop a reasonably high coercivity.

Solid-State Synthesis of Calcium Carbide by Using 2.45 GHz Microwave Reactor

A simple solid-state method has been described for the synthesis of CaC2 from CaO and graphite powders by using a 2.45 GHz microwave reactor. The reaction mechanism of CaC2 formation in the microwave environment is explained and compared with that of the conventional method. The whole microwave process completed within 180 min because of efficient coupling of microwaves with graphite powder. X-ray diffraction quantitative analysis results revealed 71.8% CaC2 formation at 1700 °C for 30 min of microwave exposure, whereas conventional heat treatment at 1700 °C for 30 min showed 14.1% CaC2 and 1750 °C for 60 min showed 62.8% CaC2. The X-ray photoelectron spectroscopy quantitative chemical state analysis based on C 1s spectra indicated 54.02% CaC2 in microwave heat-treated samples and 30.75% CaC2 in conventional heat-treated samples. The preliminary experimental results suggest that synthesis of CaC2 by microwave reactor is fast because of rapid volumetric heating.

New pyrometallurgical process of EAF dust treatment with CaO addition

The non-carbothermic zinc pyrometallurgical processing of electric arc furnace (EAF) dust was investigated on a laboratory scale. The main objective of this process was to convert highly stable zinc ferrite (ZnFe2O4), which accounts for more than half of total zinc in the EAF dust, into ZnO and Ca2Fe2O5 by CaO addition. The EAF dust was mixed with CaO powder in various ratios, pressed into pellets, and heated in a muffle furnace in air at temperatures ranging from 700 to 1100°C for a predetermined holding time. All ZnFe2O4 was transformed into ZnO and Ca2Fe2O5 at a minimum temperature of 900°C within 1 h when sufficient CaO to achieve a Ca/Fe molar ratio of 1.1 was added. However, at higher temperatures, excess CaO beyond the stoichiometric ratio was required because it was consumed by reactions leading to the formation of compounds other than ZnFe2O4. The evaporation of halides and heavy metals in the EAF dust was also studied. These components could be preferentially volatilized into the gas phase at 1100°C when CaO was added.

Cement/CaO-modified iron ore as oxygen carrier for chemical looping combustion of coal

Chemical looping combustion (CLC) of solid fuels is considered as a potential technology to reduce the energy penalty and the cost for CO2 capture. However, the low efficiency of carbon conversion and gasification products conversion is a big concern for the in-situ gasification chemical looping combustion (IG-CLC) process with the low-cost natural iron ore as an oxygen carrier. This paper evaluates the enhanced fuel conversion with a new CaO-modified iron ore as oxygen carrier during the continuous coal CLC in a 1kWth reactor. Both CaO-mixed iron ore and cement/CaO-combined iron ore were tested. The effect of oxygen carrier on the gaseous products was evaluated in the fuel reactor temperature range of 880–980°C. The samples of oxygen carrier were characterized using BET, SEM–EDX and XRD. The results indicate that compared with the pure iron ore oxygen carrier, the utilization of both CaO-mixed iron ore and the cement/CaO-combined iron ore could efficiently enhance coal conversion and gaseous conversion in the fuel reactor. However, when the CaO-mixed iron ore was used, some CaO powder due to the attrition during continuous operation adhered to the particle surface of iron ore. The Ca-containing compounds, i.e., potential eutectic of a low melting point caused sintering on the particle surface of iron ore. As a result, it caused the reactivity deterioration of oxygen carrier at a high fuel reactor temperature. To avoid the occurrence of sintering on the particle surface of the oxygen carrier, an improvement of cement/CaO-combined iron ore as oxygen carrier was proposed. A stable structure of Ca2Al2SiO7 was formed during the calcination process of the cement/CaO-combined iron ore. The sintering resistance of the iron ore was improved and the oxygen carrier after experiments maintained the porous structure. Reactivity deterioration of the combined oxygen carrier did not occur during the 5h continuous operation even at the fuel reactor temperature of 980°C. Overall, the Cement/CaO-combined iron ore is a competitive oxygen carrier in the coal CLC process.

Sintering kinetics of nanometric calcium oxide in vacuum atmosphere

A recent application for nanometric CaO powder is its use as a spallation target material for the production of isotope beams at CERN. The stability of the nanostructure at high operation temperatures is a crucial feature to provide stable and improved isotope release rates. Prior to operation, sintering studies under thermal conditions similar to those of the target operation are required to establish the microstructural evolution due to coarsening and densification processes. This knowledge enables the identification of the limiting temperatures for the target operation, ensuring a stable nanostructure for higher and constant isotope release rates.In this study, nanometric CaO powder with 58m2g−1 of specific surface area was obtained from vacuum decomposition of calcium carbonate at 800°C. The microstructure evolution of porous powder compacts was investigated under vacuum atmosphere, from 1000 to 1250°C, for holding times from 3 to 600min. For temperatures higher than 1000°C, a significant surface area reduction was observed, accompanied by porosity decrease. The morphological analysis of the pore evolution revealed a differential sintering of the porous compacts, mainly occurring inside the aggregates. The kinetic analysis of the surface area reduction pointed to aggregate shrinkage controlled by volume diffusion with surface diffusion as an underlying mechanism for lower temperatures.

Cyclic CO2 capture characteristics of a pellet derived from sol-gel CaO powder with Ca12Al14O33 support

A novel calcium-based pellet was prepared by extrusion of sol-gel CaO powder and cement with high aluminum-based content. Limestone was used for comparison. The cyclic CO2 capture performance and carbonation kinetics of the sorbents were investigated in a thermogravimetric analyzer (TGA). The changes in phase and microstructure were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Brunauer Emmet Teller (BET) surface area, respectively. The results indicate that the pellet consisted of CaO and Ca12Al14O33 after initial calcination. Limestone reactivity decreased dramatically with the increase in the cycle number, whereas the pellet showed a relatively stable cyclic CO2 capture performance with high reactivity. The CO2 capture capacity of the pellet achieved 0.43 g CO2/g sorbent after 50 cycles at 650 °C and 850 °C for carbonation and calcination, respectively. Moreover, the pellet obtained fast carbonation rates with slight decay after multiple cycles. The porous microstructure of the pellet contributed to the high reactivity of the sorbent during high temperature reactions, and the support material of Ca12Al14O33, enhanced the cyclic durability of the calcium-based sorbents.

A High-Energy Ball Milling as a Useful Technique for the Synthesis of CaCu3Ti4O12Electroceramics

Synthesis of CaCu3Ti4O12 Electroceramics P. Dulian,W. Bik, Cz. Kajtoch and K. Wieczorek-Ciurowa Cracow University of Technology, Faculty of Chemical Engineering and Technology, Warszawska 24, 31-155 Krakow, Poland Pedagogical University, Institute of Physics, Podchori»ych 2, 30-084 Krakow, Poland This paper shows that CaCu3Ti4O12 (CCTO) can be synthesized through the high-energy ball milling of CaO, CuO and TiO2 powders. The dielectric characterization of CCTO obtained mechanochemically as well as, for comparison, by a high-temperature method is presented. Moreover, it is illustrated that zirconium oxide in contrast to a metallic iron generated during milling processes improves the properties of CCTO in terms of ceramic capacitors.

Hydrothermal synthesis of tobermorite nanowires from porcelain stone

A facile and efficient hydrothermal process was explored to obtain tobermorite nanowires using porcelain stone and CaO powders as raw materials. The as-synthesised nanowires have a diameter of 50–100 nm and a length of tens of micrometres under conditions of a porcelain stone/CaO weight ratio of 3, a water/solid weight ratio of 22, a reaction temperature of 240°C and a reaction time of 24 h. The results indicate that the weight ratio of porcelain stone/CaO and hydrothermal temperature play important roles regarding the morphology and structure of tobermorite. Furthermore, a possible growth mechanism of the tobermorite nanowires is proposed. This approach might open up a simple and economic route to prepare tobermorite nanowires using inexpensive porcelain stone as the silicon source.

Study on Desulfurization Abilities of Some Commonly Used Desulfurization Agents

The desulfurization abilities of some commonly used agents, namely fluidized CaO, CaC2, commercial‐CaO, Mg, MgO, CaO · MgO, and mixtures of commercial‐CaO–Mg were studied and compared under the same experimental conditions in a laboratory furnace at 1773 K. The desulfurization mechanisms of CaO · MgO, commercial‐CaO, and mixtures of commercial‐CaO and Mg were also studied. While fluidized CaO showed the best performance, commercial‐CaO mixed with 20 mass% Mg achieved the second best desulfurization. Mg‐granules performed slightly better than CaC2 and commercial‐CaO, but somewhat less satisfactory compared to fluidized CaO and commercial‐CaO–Mg mixtures. Since only the CaO portion in CaO · MgO functioned to take up sulfur, additional 70% mass had to be added to achieve the same desulfurization level. The poor ability of commercial‐CaO in comparison to fluidized CaO powder was due to both its less reactive surface and agglomeration of the particles.

The Wear Behavior of In-Situ Al–AlN Metal Matrix Composites

Al–AlN composites are synthesized using NH4Cl + CaO powder as a nitrogenation precursor in the melt of pure aluminum. In-situ formation of AlN to varying volume fraction is attempted using different proportion of NH4Cl + CaO precursor into the aluminum melt held at 700 °C. Mechanical properties of synthesized metal matrix composites are evaluated for different volume fraction and distribution of AlN particles in aluminum matrix. Agglomeration of AlN is noticed with increasing precursor addition and synthesis time into the aluminum matrix. Due to heterogeneous distribution of AlN particles in aluminum matrix, marginal changes in hardness are observed. Pin on disc, dry sliding wear of metal matrix composites is carried to study wear behavior of synthesized composites. Composite with good dispersion of AlN particulates has shown higher hardness and wear resistance. Present paper discusses wear behavior of composites with different weight fraction of AlN tested under load and sliding distance as wear parameters. The shearing mechanism of agglomerate due to friction and its correlation with the wear loss is also highlighted in the present paper.

Refractory dopant-incorporated CaO from waste eggshell as sustainable sorbent for CO2 capture: Experimental and kinetic studies

This work investigates the development of dopant-stabilized CaO-based sorbents for CO2 capture and studies the kinetics of the carbonation reaction. Eggshell as biogenesis calcium waste was calcined to obtain low cost CaO powder. Several refractory dopants (Ti, Al, Cu and Zi) were then incorporated within the CaO matrix to prepare robust sorbents. The CO2 capture performance of the developed sorbents was assessed in some calcination–carbonation cycles performed in Thermogravimetric analyzer (TGA). Among the developed sorbents, Zr-doped CaO exhibited superior performance and durability, where a conversion of around 88% could be sustained within 20 cycles. To have an insight into the rate controlling mechanism and fundamental concept of activation energy, kinetic study was performed on the carbonation reaction of the Zr-doped CaO sorbent. Kinetic results based on the shrinking core model suggested that the carbonation mechanism was controlled by a combination of resistances arising from diffusion of CO2 through the carbonate layer and its chemical reaction at the CaO–CaCO3 interface. The intrinsic and diffusional activation energies were obtained as 39.4 and 46.5kJ/mol, respectively.

Transesterification of rapeseed oil with methanol using CaO and active carbon powders encapsulated microcapsule under the light irradiation

Transesterification of rapeseed oil with methanol to fatty acid methyl ester (FAME) was conducted using microcapsules loaded with CaO catalyst and active carbon powder under the light irradiation. About 80% of FAME yield was obtained after 6h of reaction with keeping the temperature of reactant mixture (rapeseed oil, methanol, and tetrahydrofuran (THF)) at 308K. This is probably because encapsulated active carbon powder in the microcapsule absorbed the near-infrared and visible ranges of irradiated light, and then transferred the heat inside the microcapsule which leads to higher temperature of inside microcapsule than that of reaction media/bulk. The results of ICP analyses for both FAME and glycerol phases showed that the amount of leached Ca species was significantly reduced due to lower reaction temperature and microcapsule usage. XRD patterns of tested catalysts indicated that the formation of calcium diglyceroxide phase during the transesterification was remarkably retarded for the case of CaO-active carbon-loaded microcapsule in contrast to a conventional process with CaO powder. This light-driven transesterification of rapeseed oil with methanol using catalyst-loaded microcapsule is promising system owing to high FAME yield and low amount of Ca species leaching into FAME phase.

Investigation of cosmic-ray muon induced processes by the MIREDO facility

The MIREDO (Muon Induced Rare Event Dynamic Observatory) spectrometer system is primarily developed for the study of cosmic muon induced processes in different materials. Exploration of such interactions can be important for ultra-low background experiments. The system is based on the 100% relative efficiency ultra-low-background HPGe spectrometer. With the addition of two plastic scintillators and a fast-slow coincidence circuit, the coincidence events between the plastic detectors and the HPGe spectrometer have been investigated. First results derived for a CaO powder sample, placed in a Marinelli beaker, are presented and discussed.

Operational test of micro-oven for 48Ca beam

In order to supply a high-intensity and stable (48)Ca beam from the RIKEN 18-GHz electron cyclotron resonance ion source, we are conducting operational tests of a micro-oven. A mixture of CaO and Al powders is placed into the crucible of the micro-oven and heated to produce metallic calcium by a reductive reaction. The successful production of a calcium beam was confirmed. In addition, we reduced the material consumption rate by using a so-called "hot liner," and we enhanced the beam intensity by applying a negative voltage bias to the micro-oven, the effect of which is similar to the effect of a "biased disk."

Kinetics of sunflower and used vegetable oil methanolysis catalyzed by CaO·ZnO

The kinetics of heterogeneous methanolysis of sunflower oil and used vegetable oil were studied at different temperatures, ranging from 60 to 96°C using CaO·ZnO as catalyst (2wt% on the basis of oil) and methanol to oil molar ratio of 10:1. Heterogeneous CaO·ZnO catalyst was synthesized by mechanochemical treatment of CaO and ZnO powder mixture with the addition of water necessary for the formation of corresponding mixed hydroxides, and their calcination at 700°C in air. It was shown that kinetics of overall process could be described as pseudo-first order reaction. For the sunflower oil methanolysis at 60 and 70°C, the rate of process at the beginning of biodiesel synthesis was limited by triglycerides mass transfer to the catalyst surface, and after that it is governed by the rate of chemical reaction at catalyst surface. At higher temperatures the influence of mass transfer resistance is almost negligible implying that the rate of chemical reaction determines the overall kinetic of biodiesel synthesis. In the case of used vegetable oil, the influence of mass transfer resistance was not observed either at higher or lower temperature. The kinetic model that describes the whole process well was proposed, and it comprises both the triglycerides mass transfer and chemical reaction controlled regime. The overall volumetric mass transfer coefficient was defined, assuming that it depends on the conversion of triglycerides.

Synthesis of glycerol carbonate from glycerol and dimethyl carbonate over the extruded CaO-based catalyst

The extruded CaO-based catalysts are prepared and used for the synthesis of glycerol carbonate from glycerol and dimethyl carbonate. The effects of binders (diatomite, kaolin, and activated alumina), pore-forming agents (polyacrylamide, activated carbon, and polyethylene glycol), and calcination temperatures (700°C, 800°C, and 900°C) on the catalytic activity and stability of the catalyst are investigated. XRD, FT-IR, BET, and SEM are used for the characterization of the prepared catalyst. It is found that the stability of CaO catalyst can be increased by extruding it using activated alumina as the binder and using polyacrylamide, or activated carbon, or polyethylene glycol as the pore forming agent. Under the CaO/binder mass ratio of 3:1, calcination temperature of 800°C, and reaction temperature of 80°C, the glycerol conversion and glycerol carbonate yield for the fresh CaO/Al2O3(polya, 3) catalyst can reach 95.39% and 90.57%, respectively. At the fifth recycling, the glycerol conversion and glycerol carbonate yield for the recovered CaO/Al2O3(polya, 3) catalyst still can reach 65.47% and 62.53%, respectively, which are far higher than for CaO powder catalyst. The extruded catalyst also has a certain water-resistance performance. The catalyst characterization shows the active site of the extruded CaO-based catalyst is CaO. The extruded catalyst not only has higher surface area, higher pore volume, and larger pore diameter, but also higher mechanical strength, and can be used for the industrial process for producing glycerol carbonate.