CaO Powder Research Articles

Synthesis and Characterization of Nano-Wollastonite from Rice Husk Ash and Limestone

Wollastonite, CaSiO3 material was prepared from rice husk ash, as the source for SiO2 and limestone, source for CaO using sol-gel method. Rice husk ash and CaO powder was mixed together in 100ml distilled water with the rice husk ash/CaO ratios of 45:55 and 40:60. The mixed solution was place in the autoclave and heated at 135°C for 4 hours and calcined at 950°C for 1 and 2 hours. From the XRD results,ratio of 45:55 exhibited that b-wollastonite is the major phase and the minor phase is only contributed by cristoballite and by calcining the mixture for 2hrs would yield better crystallinity. Both of the rice husk ash:CaO ratios produced wollastonite materials in cylinder structures. Wollastonite with nano size grain was obtained for an hour calcination and 2 hrs of calcination would increase the grain size over 100 nm for ratio, 45:55 and 40:60.Therefore in order to get the nano size of wollastonite material, period of calcination process has to be controlled.

Prompt gamma neutron activation analysis for multi-element measurement with series samples

The on-line prompt gamma neutron activation analysis (PGNAA) system is used to measure a series of prepared experimental samples to obtain the prompt characteristic γ-rays of the elements Ca, Fe, Si, Al, Mg and S in the examples of SiO2, Al2O3, MgO, CaO (powder), CaO (block), CaCO3, Fe2O3, Fe3O4 and S. The γ-ray energies are: Si, 3.54 or 4.93 MeV; Ca, 4.42 or 6.42 MeV; S, 5.42 MeV; Fe, 5.92 or 7.63 MeV. Meanwhile, the prompt γ-rays of the main elements are measured in an experiment in which SiO2, Al2O3, MgO, CaO (powder), CaO (block), CaCO3, Fe2O3, Fe3O4 and S are blended to constitute a cement sample. The prompt γ-rays of S will contribute more with increase in S mass, as known from the experiment concerning the prompt γ-ray spectrum for different masses of S.

Radioargon production through the irradiation of calcium oxide

The production of radioargon through the irradiation of CaO was performed in an in-core facility within the The University of Texas at Austin MARK II TRIGA reactor. The major radioargon isotope produced was 37Ar via the 40Ca(n,α)37Ar reaction pathway. The CaO powder was vacuumed sealed in a quartz ampoule. The sample was irradiated in a Cd-lined Al alloy canister for 2 h at 500 kW. After the irradiation, the sample was counted using an HPGe detector five times with increasing count times. 41Ar, 42K, 43K, and 47Ca were detected in the spectra. The induced activities of 37Ar, 39Ar, 41Ar, 42K, 43K, and 47Ca were calculated using a 63-group energy-dependent neutron flux determined utilizing a neutron energy flux profile calculated from a MCNPX model of the TRIGA reactor core. The production ratios generated from the model allowed for the estimation of induced 37Ar and 39Ar activities through the measured induced activities of 41Ar, 42K, 43K, and 47Ca.

Study on the Possibility of Using ZnO for Hot Metal Desulfurization

AbstractThe possibility of using ZnO for desulfurization in hot metal was evaluated. A lab scale experimental setup was designed so that different desulfurizing agents could be added to hot metal for evaluation of their desulfurizing power. The setup had good control of both temperature and the gaseous atmosphere. It also provided stirring of the metal bath with an impeller as well as quenching facility to maintain the metal composition at high temperature. Desulfurization of hot metal using CaO powder showed evidently the applicability of the new setup. On the other hand, additions of ZnO into the hot metal under various experimental conditions showed no effect on desulfurization. The results were in contradiction to the suggestion found in literature. A thorough examination of the thermodynamic data employed by the previous work was carried out. The data used in the literature were found to be subjected to fundamental mistakes. The present experimental results convincingly rule out the possibility of using ZnO as a desulfurization agent.

Research of hydrogen generation by the reaction of Al-based materials with water

Al, CaO and salt powder mixtures are used as the starting materials to prepare the Al-based materials by the mechanical ball-milling method for hydrogen generation. The effects of preparation and reaction parameters on the hydrogen generation are investigated in this paper. With increasing ball milling time, the Al crystallite size is reduced and the reaction activity of Al is improved. But the overlong ball milling time easily causes the oxidation of Al and decreases its hydrogen yield. CaO can provide OH− for the hydrogen generation reaction by hydrolysis. Increasing the NaCl addition can accelerate the activation of Al and promote its hydrogen generation. In the water containing chloride ions and sulfate ions, the hydrogen generation rate is obviously improved. But Mg2+ ions will reduce the hydrogen yield due to its strong affinity to OH−. The maximum hydrogen yield is gained in the water at 30 °C There are some CaO on the surface of Al particle in the Al-based materials, which can improve the air oxidation resistance in air. Storing the Al-based materials in air with relative humidity of 50% at 30 °C for 40 h, the hydrogen yield is still kept at 89%.

Study on the Defluorinated Materials of High Fluoride

In our country, high fluoride containing groundwater is general. Now,there have been some study on fluoride containing groundwater, but MgSO4 is the first use. In this paper,therefore,study a new method for removing fluorine from groundwater with MgSO4 , CaO powder regulate pH, studies the influencing factors of fluorine removal rate, such as pH,temperature and so on, obtain the proper treatment condition:8% MgSO4 solution 10ml, CaO powder regulate pH11,stir 5min at 40°C. Using this method, the concentration of fluorine ion in the groundwater is lower than the national provided drinking water criterion of <1.0mg/L, fluorine removal rate reach 93%.

Separated Sm-Co hard nanoparticles by an optimization of mechanochemical processes

Sm-Co hard nanoparticles have been synthesized by a modified mechanochemical processing. The phases, microstructure, particle sizes and magnetic properties of the synthesized Sm-Co nanoparticles have been investigated. The results showed that the precursors and milling times had great effects on the structure and magnetic properties of the synthesized Sm-Co nanoparticles. It is interesting to find that either Sm2Co7, SmCo5 or Sm2Co17 hard single phases can be obtained by manipulating the amount and ratio of starting materials of Sm2O3 and Co. After the mixture of Sm2O3, Co, Ca, and CaO powders were milled for 2–12 h, no Sm-Co based hard phases was formed, whereas the Sm-Co hard nanocrystallites were formed by a subsequent annealing at 650 °C for 1 h. The maximum coercivities of the synthesized Sm2Co7, SmCo5, and Sm2Co17 were 37.1, 35.5, and 10.8 kOe, respectively. Separated Sm2Co17 nanoparticles were obtained after washing the annealed powder with a solution of acetic acid aqueous solution. The washed Sm2Co17 particles were single crystals and had an average particle size of 81 nm.

Production of CaF<sub>2</sub> by the Destructive Adsorption of Trifluoromethane and a Binary Mixture of Trifluoromethane/ Chlorodifluoromethane with CaO Powder under Air-Flow

Production of CaF<sub>2</sub> by the Destructive Adsorption of Trifluoromethane and a Binary Mixture of Trifluoromethane/ Chlorodifluoromethane with CaO Powder under Air-Flow

Effect of Changes in Sulfur and Oxygen Concentration on Change in Nitrogen Concentration in Liquid Steel during CaO^|^ndash;CaSi Powder Blowing under Reduced Pressure

In this paper, 1500 kg scale experiments of CaSi mixed CaO powder top blowing onto the Al killed steel were carried out under reduced pressure. And the effects of CaSi alloy ratio in the mixture on reactions of desulfurization and nitrogen removal were examined. Aluminum decreasing rate decreased and rate constant of desulfurization and nitrogen removal increased with increasing CaSi mixing ratio to flux. It is supposed from the above that deoxidation and desulfurization reaction can simultaneously occur by blowing the mixture of CaSi and CaO powder and the effect of calcium mixing powder on desulfurization can be explained by promotion of CaO desulfurization and CaS formation. It is suggested that lower oxygen and sulfur activity due to reaction between molten steel and powder with CaSi increased rate constant of nitrogen removal.

Mechanochemically Synthesized CaO ZnO Catalyst For Biodiesel Production

Abstract The transesterification of triglycerides (vegetable oil) with methanol using CaO·ZnO mixed oxides catalyst were conducted to produce FAME (Fatty Acid Methyl Esters, i.e. biodiesel). Catalyst was synthesized by ball milling of CaO and ZnO powder mixture (using molar ratio of Ca and Zn of 1:2 and 1:4) with the addition of water, as well as solely by ball milling (molar ratio of 1:2) of mentioned powders and subsequent. After ball milling prepared mixtures were calcinatied at 700 o C in air atmosphere. The samples of formed catalysts were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. The particle size distribution as well as the base strength using Hammett indicator was determined, too. CaO.ZnO catalysts were used in the methanolysis of sunflower oil, at 60 o C and 1 bar, using molar ratio of sunflower oil to methanol of 1:10 and with 2 wt% of catalyst based on oil weight. All catalysts exhibited good activity in the methanolysis of sunflower oil, with the yield of FAME above 90% after 4 hours of reaction.

Study of the hydration of CaO powder by gas–solid reaction

Hydration of CaO powders by reaction with water vapor has been studied in isothermal and isobaric conditions. Experimental tests were performed within the temperature range of 70 °C–420 °C and with a water vapor pressure from 5 to 160 hPa by means of a thermogravimetric device. Two powders, exhibiting slight differences in their physical properties, were studied. However, for one of the powders and under some temperature and pressure conditions, the reaction is not complete. The difference of behavior between both CaO powders was interpreted by considering the effect of the morphological properties on the mechanism of growth of Ca(OH) 2.

Dispersed Calcium Oxide as a Reversible and Efficient CO2−Sorbent at Intermediate Temperatures

Dispersion of calcium oxide on high surface area γ-Al2O3 creates a stable and reversible CO2−sorbent that overcomes the problems associated with bulk CaO, such as limited long-term stability, slow uptake kinetics, and energy-intensive regeneration. This sorbent is a candidate for the sorption-enhanced hydrogen production via steam reforming and/or water-gas shift reactions. CO2 uptake tests were performed in a 15% CO2/N2 atmosphere to evaluate the efficacy at typical hydrocarbon reformer gas partial pressure. CO2 uptake kinetics and capacities are investigated in TGA studies, while the long-term stability is shown in multicycle experiments. The dispersed CaO is an active sorbent at low temperatures and binds CO2 at 300 °C up to 1.7 times as efficiently as compared to bulk CaO powder. Furthermore, the sorbent can be regenerated in a CO2-free atmosphere at intermediate temperatures between 300 and 650 °C. Multicycle CO2 uptake and release has been tested for 84 cycles at a constant temperature of 650 °C and...

Behaviour of CaO coating of gas atomized Mg powders using mechanical milling process

In order to synthesize a thermally stable Mg powder as a desulfurizer of iron, pure Mg was gas atomized to powders and coated by CaO powders, to produce a thermally stable desulfurizer using a mechanical milling process. Since the effect of desulfurization is dependent on the degree of surface modification, coating behaviours such as the size, morphology and layer thickness were investigated as a function of milling condition. As the milling conducted from 10 min to 30 min, 1 h, 3 h, 6 h, 12 h, CaO particles began to stick on the surface of Mg powders. The layer of CaO formed from 1 h milling was about 17 μm thick and gradually thickened to be 28 μm, 32 μm and 37 μm with increasing the milling time to 3 h, 6 h and 12 h, respectively. The shape of coated powder became more spherical after 1 h milling, being mostly spherical after 6 h. Desulfurization rate and uniformity were evaluated for the various thickness of the coating layer.

Synthesis of Al-AlN metal matrix composites by nitrogenation

Metal matrix composites containing AlN in aluminium matrices is synthesized using NH4Cl and NH4Cl+CaO powders as sources of nitrogen in molten aluminium in the temperature range of 700 1000°C. Active nitrogen dissociated from ammonia at high temperature is used to form AlN. The addition of CaO to NH4Cl is found to have a more pronounced effect as a nitrogenation agent in comparison with NH4Cl. MMCs synthesized at 700°C and 900°C using NH4Cl+CaO showed the highest hardness of 83 Hv100 (814 MPa). The clustering of AlN nanoparticles at few locations indicate insufficient turbulence of the melt during the chemical reactions of powder with aluminium-melt.

Sapphire-SiO<sub>2</sub> Solid-Phase Reaction of Polishing Proving Research

The solid-phase reaction experiment and principle were introduced. 1000# SiO2 micromist and CaO powder were used polishing sapphire, with polishing pressure 7.5kPa，polishing speed 60r/min and 40r/min. The process of polishing was separated every 120 minutes. The surface appearance and roughness will be survey in each part. Non-surface-scratch will be achieved after 600min of polishing. The roughness (Ra) was decreased from 395nm to 7nm. Rmax was decreased from 2.98μm to 0.05μm. Rt was decreased from 3.34μm to 0.05μm. Through the analysis of the experimental data of XRD, kyanite phase map and diffraction pattern fitting degree. The fact that quality of sapphire’s surface was improved by using this approach has been proved.

Effect of Changes in Sulfur and Oxygen Concentration on Change in Nitrogen Concentration in Liquid Steel During CaO Powder Blowing under Reduced Pressure

To examine the change of the rate of nitrogen desorption with sulfur concentration and low oxygen concentration change, the rates of nitrogen desorption from molten steel were measured with the blow of CaO powder or argon gas onto the molten steel through a top lance under the reduced pressure. 15 kg of electrolytic iron was melted molten in a MgO crucible by a high frequency induction furnace and the temperature of the melt was held at 1873K. Aluminum, FeS and other alloying elements were added and composition of molten steel was kept at 0.001–0.19%Al, 0.0007–0.0064%S, 0.002–0.006%N, 0.5%Mn and 0.2%Si. CaO powder was blown onto molten steel with argon gas for 20 min under the reduced pressure of about 670 Pa and metal samples were taken during CaO powder blowing in order to clarified the removal rate of sulfur and nitrogen. The rate constant of desulfurization was maintained during CaO powder blowing, however, the apparent rate constant of nitrogen desorption increased gradually. A mathematical model of nitrogen desorption was presented with the consideration of the chemical reaction of aluminum and sulfur in molten steel with CaO flux, respectively. The calculated nitrogen concentration by the model were in good agreement with the experimental values. It was estimated that the apparent rate constant of nitrogen desorption was increased as a result of decrease of oxygen and sulfur concentration in moleten steel by the reaction between aluminum in molten steel and CaO flux.

Identification and Distribution of Surface Ions in Low Coordination of CaO Powders with Photoluminescence Spectroscopy

Oxide ions in low coordination (O2−LC) play a major role in adsorption and catalysis properties of CaO powders. They also give specific photoluminescence features that could be used to characterize the distribution of these ions at the molecular level, but up to now, the photoluminescence of defective CaO powders was assigned incompletely. In this study, photoluminescence spectra of defective CaO powders prepared in various ways are recorded at 77 K with unprecedented resolution. A new feature is thus evidenced with an excitation at 320 nm and an emission at 490 nm. Combining infrared and photoluminescence spectroscopies, we show that this feature does not originate from remaining hydroxyl groups, but it completes the set of photoluminescence fingerprints of O2−LC ions on CaO. A revisited assignment of this set is proposed, consistent with the dependence of transition energy on coordination numbers. An application example shows how the photoluminescence spectroscopy can be used as an original tool to compare surface morphologies of CaO samples at the molecular level and under in situ conditions.

Discovery of Zr-Al-Ca-O Phase in Zr-Al-Ca-O-N Composites and its Synthesis

Zr-Al-Ca-O-N composites were prepared in N2 atmosphere at 1600 oC with Ca-PSZ and AlN powders as raw materials. Zr-Al-Ca-O phase was synthesized in air atmosphere at 1600 oC with Al2O3, ZrO2 and CaO powders as raw materials. Phase constitution of these composites was investigated by XRD and EDS analyses. The results show that Zr-Al-Ca-O phase exists in Al-CaO-ZrO2-N2 systems ceramic and Zr-Al-Ca-O phase can be synthesized in air atmosphere at high temperature with Al2O3, ZrO2 and CaO powders as raw materials.

Influence of Different Sintering System on the Formation of Tricalcium Aluminate

Several different sintering systems about the formation of C3A ,by mixing CaO and Al2O3 powder, are studied in this experiment. The sample is characterized by glycerol ethanol method, X-ray powder diffraction and TG-DTA. The experimental results show that: reducing the react time cannot boost the formation of C3A, but traditionally electrical heating combined microwave heating can romote the formation of C3A rapidly .In terms of phase equilibria of CaO-Al2O3 system, pure C3A cann’t be synthesized by sintering . Except the samples also contain minor amounts of CA and C12A7.

Surfactant-assisted solvo- or hydrothermal fabrication and characterization of high-surface-area porous calcium carbonate with multiple morphologies

Hexagonally crystallized CaCO 3 materials with flower-like, belt-like, network-like, coralloid, and hexagonal and rectangular parallelepiped morphologies were selectively fabricated using the surfactant (cetyltrimethylammonium bromide, sodium dodecyl sulfate, poly( N-vinyl-2-pyrrolidone or poly(ethylene glycol) (PEG)) mediated solvo- or hydrothermal strategy with CaO powders as Ca source in an oleic acid (OA)/ethanol, OA/ethylene glycol or water solvent, respectively. The as-obtained materials were characterized by means of the techniques, such as X-ray diffraction, thermogravimetric analysis and differential scanning calorimetry, Fourier transform infrared spectroscopy, high-resolution scanning electron microscopy, high-resolution transmission electron microscopy, selected-area electron diffraction, and N 2 adsorption–desorption measurement. It is shown that the morphology of the CaCO 3 product was associated with the nature of surfactant and solvent and solvo- or hydrothermal temperature. The surfactant-free fabricated CaCO 3 particles were cube-like in morphology. The rise in solvo- or hydrothermal temperature favored the enhancement in surface area of the CaCO 3 product. Among the as-fabricated CaCO 3 samples, the one derived hydrothermally with PEG at 240 °C possessed the highest surface area (134 m 2/g). Such a high-surface-area wormhole-like mesoporous CaCO 3 sample could decompose below 800 °C to mesoporous CaO with high surface area (110 m 2/g). This reversible regeneration feature makes the mesoporous calcite useful in gas adsorption and separation as well as catalysis. The possible mechanisms for the multiply morphological CaCO 3 formation have also been discussed.