Behavior of CaO and Calcium in pure Magnesium

Mg alloys exhibit a number of good properties such as low density, good castability and high specific strength. However, molten Mg and Mg alloys are ignited without the melt protective gases during melting and casting process due to their high reactivity. The purpose of this study is to investigate effects of Ca and CaO on pure Mg through microstructure observation, ignition test and phase analysis. With increasing Ca and CaO contents, the ignition resistance of Ca or CaO added pure Mg is increased and the grains are refined. As results of XRD and EDS, CaO is reduced to Ca in CaO added pure Mg. Mg2Ca phase is formed even in 0.1 wt.%CaO added pure Mg by reduction mechanism, while Mg2Ca phase is formed over 1.35 wt.% Ca added pure Mg.

Effect of CaO and CaCO3 on Reduction Rate of Iron Ore Pellets Containing Carbon

The effect of metallurgical fluxes CaO and CaCO3 on the reduction rate of iron ore pellets containing carbon in nitrogen atmosphere has been studied by a weight-loss thermal balance. The experimental results showed that adding CaO or CaCO3 can promote reduction reaction as the added CaO or CaCO3 probably decrease the apparent activation energy of iron ore concentrate-carbon-CaO or CaCO3 reaction, and the reduction rate constant changes with mass percent of CaO and CaCO3. The kinetic analysis also showed that the rate-controlling step of the reaction is inner gas diffusion.

Corrosion behaviour of as-cast ZK40 with CaO and Y additions

The microstructures of as-cast ZK40,ZK40 with 2%(mass fraction)CaO and ZK40 with 1%(mass fraction)Y were investigated,and the intermetallic phase morphology and the distribution were characterised.By having discrete intermetallic particles at the grain boundaries for the ZK40,the microstructure was modified to a semi-continuous network of intermetallic compounds along the grain boundaries for the ZK40 with CaO or Y additions.The CaO was not found in the microstructure.However,Ca was present in Ca2Mg6Zn3 intermetallic compounds which were formed during casting.Hydrogen evolution and electrochemical impedance spectroscopy tests revealed that the addition of CaO slightly enhanced the corrosion resistance whereas Y had a negative effect on the corrosion resistance of ZK40.Immersion tests showed that severe localised corrosion as well as corrosion along the intermetallic compounds played an important role in the corrosion process of ZK40-Y whereas the localised corrosion was not pronounced for ZK40 or ZK40?CaO alloys.Micro-segregation in theα-Mg matrix was notably higher for the ZK40 alloy compared with the modified alloys.The combination of this effect with a possible formation of a more stable corrosion layer for the ZK40-CaO was attributed as the main reason for an improved corrosion resistance for the ZK40-CaO alloy.

CaO/HZSM-5复合催化剂调控水稻秸秆和PVC共热解产物的协同作用研究

生物质与废旧塑料共热解是实现两者资源化利用的潜在技术之一,不仅能制备高附加值的富烃生物油,还可实现废弃物的洁净资源化利用,减轻环境污染。然而,产物的复杂性限制了共热解技术的进一步应用。本研究以农作废弃物水稻秸秆(RS)和聚氯乙烯塑料(PVC)为研究对象,采用热重-质谱联用仪(TG-MS)和热裂解-气相色谱/质谱联用仪(Py-GC/MS)研究两者单独及共热解特性,并考察CaO和HZSM-5复合催化剂对热解产物的协同调控规律。结果表明,PVC和RS在共热解过程中具有相互作用,促进了芳烃化合物的产生。生物油中烃类化合物的相对含量高达66.78%。其中,芳烃的相对含量达到64.17%。相较于RS单独热解,共热解焦油组分中含氧化合物的含量下降62.05%,有效提高了生物油的氧化稳定性。CaO/HZSM-5复合催化剂相较于CaO、HZSM-5单独催化剂,热解产物油中C4−C10烃类化合物的相对含量分别增加2.81%、5.06%,表现出更好的轻质芳烃选择性。在CaO/HZSM-5复合催化剂协同作用下,生物油中单环芳烃的相对含量为34.34%,大于理论计算值33.03%。而多环芳烃的相对含量为28.21%,小于理论计算值31.22%,表现出较好的单环芳烃选择性。此外,CaO/HZSM-5复合催化剂促进大量氯元素以CaCl2等氯化物的形式固定在半焦中,显著降低了Cl元素的气相释放。

Effect of CaO Impurity on Mullite Formation from SiO_(2) Gel and Al_(2)O_(3) Powders

To broaden the application of SiO_(2) sol-bonded castables,using micro-or nano-Al_(2)O_(3) powder and SiO_(2) gel powder as the main raw materials,the effects of CaO impurity on the formation of mullite by the reaction of Al_(2)O_(3) and SiO_(2) at different temperatures(1350,1400,1500,and 1600℃)in different atmospheres(oxidation atmosphere and reduction atmosphere)were studied.The results show that in the oxidizing atmosphere,the introduction of CaO can promote the formation of mullite.When the temperature increases from 1350℃to 1600℃,the amount of mullite formed gradually increases.In the reducing atmosphere,the introduction of CaO is not conducive to the formation of mullite,and the amount of mullite decreases with the increasing temperature.The smaller the particle size of Al_(2)O_(3),the more easily it reacts with SiO_(2) gel powder to form mullite.

A Brief Analysis of Ranunculaceae Family Resources Based on Yu Tuo Ben Cao

[Objectives]To facilitate the rational use and timely protection of the Tibetan medicinal plant resources to count and reorganize Tibetan medicines recorded in Yu Tuo Ben Cao.[Methods]Based on literature research and data analysis,this paper analyzed the plant genera,and their habitat characteristics and the main types of diseases.[Results]Yu Tuo Ben Cao contains 191 kinds of botanicals,of which Ranunculaceae has the largest number of 11 genera and 25 species,with a wide distribution of habitats and 5 categories,and the main therapeutic efficacy covers 16 fields.[Conclusions]As a part of Yu Tuo Ben Cao,Tibetan medicines of Ranunculaceae have great research value because of their variety,large number,wide distribution,and diverse uses.

Extraction of vanadium from molten vanadium bearing slag by oxidation with pure oxygen in the presence of CaO

A novel process of vanadium extraction from vanadium slag in its molten state was conducted at the laboratory scale by oxidation with pure oxygen in the presence of CaO. The effect of mass ratio of CaO to V2O5 on the recovery of vanadium was studied. The sintered samples were leached by H2SO4 solution and characterized by XRD, XPS, SEM and EDS techniques. Compared with the roasting process, the energy saving effect of the proposed process was also discussed. The results showed that vanadium-rich phases were formed and vanadium mainly existed in the forms of CaV2O5 and Ca2V2O7. The formation mechanism of calcium vanadates in the molten vanadium bearing slag was explained. The XRD and XPS results implied that there was a limit to the oxidation reaction of V(IV) to V(V) under the high temperatures even though oxygen-supply was sufficient. An increase in the CaO content led to an increase in the formation of Ca2V2O7. About 90%of the vanadium recovery was obtained under optimal experiment conditions (mass ratio of CaO to V2O5 of 0.6, particle size 120 to 150μm, leaching temperature 90 °C, leaching time 2 h, H2SO4 concentration 20%, liquid to solid ratio 5:1 mL/g, stirring speed 500 r/min). The energy of 1.85×106 kJ could be saved in every 1000 kg of vanadium bearing slag using the proposed process from the theoretical calculation results. Recovery of vanadium from the molten vanadium bearing slag and utilisation of its heat energy are important not only for saving metal resources, but also for energy saving and emission reduction.

Interfacial reactions between Ti-1100 alloy and CaO crucible during casting process

Ti-1100 alloys were melted in a controlled atmospheric induction furnace equipped with a Ca O crucible. The microstructure, chemical composition, microhardness and metal-crucible interfacial reactions were systematically investigated. The results demonstrate that the primary solidification microstructure in the as-cast alloys was the typical Widmansttten structure. The interactions between crucible and molten alloys are attributed to slight chemical dissolution and weak physical erosion. According to the line scanning analysis, the interfacial layer（α-case） thicknesses of Ti-1100 samples in the bottom and side wall are about 18 and 17 μm, respectively, which are slightly lower than those presented from microhardness tests（25 and 20 μm）. The formation of α-case was caused by interstitial oxygen atoms. The standard Gibbs energy of reaction Ca O（s）=Ca＋O for Ti-1100 alloy was also determined. The equilibrium constant and the interaction parameter between calcium and oxygen were obtained as lg K=-3.14 and eCa O =-3.54.

CaO催化臭氧选择性氧化肉桂中油的研究

粗肉桂油精馏后残留的尾油(也称为肉桂中油)含有肉桂醛和烯烃类化合物。为通过精馏分离肉桂中油中的肉桂醛,实现肉桂中油资源再利用,根据前期研究成果,采用CaO催化臭氧选择性氧化肉桂中油中的烯烃类化合物;采用气相色谱和气相色谱-质谱联用仪(GC-MS)对反应产物进行分析。结果表明,臭氧化反应60 min后,存在于肉桂中油中的10种烯烃类化合物在反应产物中仅检出1种,肉桂醛的相对含量从反应前的56.46%增至80.48%。反应后,GC-MS未检测出烯烃类化合物臭氧化后生成的醛或酮类物质。通过臭氧化可基本清除肉桂中油中的烯烃类化合物,保留肉桂醛。

CaO/LiCl混合固体催化制备碳酸甘油酯及产物结构分析

以新活化的CaO/LiCl为混合催化剂,以碳酸二甲酯和甘油为反应物,制备了碳酸甘油酯。考察反应回流时间和反应物摩尔比对产物纯度和收率的影响,通过气相色谱技术确定了反应最佳时间和最佳摩尔比,采用红外光谱、质谱、核磁共振谱技术表征了产物结构。结果表明,当碳酸二甲酯和甘油的摩尔比为4∶1、催化剂质量分数3.0%、反应时间4 h时,产物纯度最高(97.7%)、收率最好(95.7%);反应时间更短时或摩尔比更低时,甘油转化不完全;通过ChemDraw软件中核磁共振模拟功能对产物结构进行了研究;结合量子化学提出了五元环碳酸甘油酯生成的合理机理。

Densification and sintering dynamics of 10NiO-NiFe_2O_4 composites doped with CaO

The effects of CaO content in the range from 0 to 4.0%, and sintering temperature on the phase composition, relative density and electrical conductivity of 10NiO-NiFe2O4 composites doped with CaO were studied. The results show that there is no change of structure for NiO or NiFe2O4; there is apparent oxygen absorbing and releasing behavior during the heating process in air for 10NiO-NiFe2O4 composites. Introduction of CaO can accelerate the densification of 10NiO-NiFe2O4 composites. The maximum value of relative density is 98.75% for composite doped with 2.0% CaO and sintered at 1 200 ℃, which is beyond about 20% for the undoped composites. The sintering activated energy of sample containing 2% CaO decreases by 15.87 kJ/mol, compared with that of the undoped sample.

Simultaneous CO_(2) capture and thermochemical heat storage by modified carbide slag in coupled calcium looping and CaO/Ca(OH)2 cycles

The simultaneous CO_(2) capture and heat storage performances of the modified carbide slag with byproduct of biodiesel were investigated in the process coupled calcium looping and CaO/Ca(OH)2 thermochemical heat storage using air as the heat transfer fluid.The modified carbide slag with by-product of biodiesel exhibits superior CO_(2) capture and heat storage capacities in the coupled calcium looping and heat storage cycles.The hydration conversion and heat storage density of the modified carbide slag after 30 heat storage cycles are 0.65 mol·mol^(-1) and 1.14 GJ·t^(-1),respectively,which are 1.6 times as high as those of calcined carbide slag.The negative effect of CO_(2) in air as the heat storage fluid on the heat storage capacity of the modified carbide slag is overcome by introducing CO_(2) capture cycles.In addition,the CO_(2) capture reactivity of the modified carbide slag after the multiple calcium looping cycles is enhanced by the introduction of heat storage cycles.By introducing 10 heat storage cycles after the 10th and 15th CO_(2) capture cycles,the CO_(2) capture capacities of the modified carbide slag are subsequently improved by 32%and 43%,respectively.The porous and loose structure of modified carbide slag reduces the diffusion resistances of CO_(2) and steam in the material in the coupled process.The formed CaCO_(3)in the modified carbide slag as a result of air as the heat transfer fluid in heat storage cycles decomposes to regenerate CaO in calcium looping cycles,which improves heat storage capacity.Therefore,the modified carbide slag with by-product of biodiesel seems promising in the coupled calcium looping and CaO/Ca(OH)_(2) heat storage cycles.

Effect of CaO addition on ignition behavior in molten AZ31 and AZ91D Magnesium alloys

Mg alloys have been widely used in automobile and electronic industries because of high specific strength, good castability, etc. However, molten Mg alloys will burn rapidly in air if not protected. To solve this problem, the molten metal should be protected from oxidation by blanketing the surface with flux or protective gases. SF6 gas is widely used for Mg alloys as a cover gas and has proved to be a successful inhibitor. However, the use of SF6 gas is limited because of its high cost and its significant impact on non-global warming potential. Therefore, SF6 gas is being replaced by alternative protection gases. Recent studies show that there has been another attempt by adding CaO into Mg alloys. The aim of this study is to evaluate the effect of CaO on the minimum amount of protective gas, which is necessary not to make ignition in the molten AZ31 and AZ91 Mg alloys.

Relationship between pore structure and hydration activity of CaO from carbide slag

CaO needs to show high activity to be used as Ca-sorbent and slagging agent. Hydration activity is an important characteristic to evaluate the activity of CaO. In this study, carbide slag from polyvinyl chloride(PVC) industry was utilized as precursor for preparing high activity CaO. The roles of crystallite grain, average pore diameter(APD) and volume fraction of pore b 200 nm in diameter(VF200) in hydration activity of CaO from carbide slag(CS-CaO)were respectively investigated. The hydrolysis kinetics model of CaO shows a three-dimensional spherically symmetric diffusion model(D4), which suggests that hydration activity was mainly associated with APD and VF200 of CS-CaO with limited correlation to the crystal size. Specifically, the hydration activity of CS-CaO is increased with increasing VF200, while decreased with increasing APD. Under the invariable calcination temperature,the core–shell structure formed by the addition of graphite or Ca CO3 to CS effectively inhibits the sintering of CS-CaO and improves VF200. Consequently, the hydration activity of CS-CaO increased from 22.79 ℃·min^-1 to27.19 ℃·min^-1 and to 29.27 ℃·min^-1, with addition of 5% graphite or 5% CaCO3 into carbide slag, respectively.

Influence of alkali metal doping on surface properties and catalytic activity/selectivity of CaO catalysts in oxidative coupling of methane

Surface properties （viz. surface area, basicity/base strength distribution, and crystal phases） of alkali metal doped CaO （alkali metal/Ca= 0.1 and 0.4） catalysts and their catalytic activity/selectivity in oxidative coupling of methane （OCM） to higher hydrocarbons at different reaction conditions （viz. temperature, 700 and 750 ℃; CH4/O2 ratio, 4.0 and 8.0 and space velocity, 5140-20550 cm^3 ·g^-1·h^-1） have been investigated. The influence of catalyst calcination temperature on the activity/selectivity has also been investigated. The surface properties （viz. surface area, basicity/base strength distribution） and catalytic activity/selectivity of the alkali metal doped CaO catalysts are strongly influenced by the alkali metal promoter and its concentration in the alkali metal doped CaO catalysts. An addition of alkali metal promoter to CaO results in a large decrease in the surface area but a large increase in the surface basicity （strong basic sites） and the C2＋ selectivity and yield of the catalysts in the OCM process. The activity and selectivity are strongly influenced by the catalyst calcination temperature. No direct relationship between surface basicity and catalytic activity/selectivity has been observed. Among the alkali metal doped CaO catalysts, Na-CaO （Na/Ca = 0.1, before calcination） catalyst （calcined at 750 ℃）, showed best performance （C2＋ selectivity of 68.8% with 24.7% methane conversion）, whereas the poorest performance was shown by the Rb-CaO catalyst in the OCM process.

Effect of Al_(2)O_(3)/CaO on the melting and mineral transformation of Ningdong coal ash

Coal ash melting characteristics has a direct impact on the smooth operation of entrained gasifier.Mineral conversion of coal ash is very significant to be investigated,because the mineral can affect the melting temperature and viscosity under high temperature conditions.In this paper,the effects of different Al2O3/CaO on the mineral conversion,melting temperature and viscosity of Ningdong coal ash are studied by the combination of experiment and simulation.The trend of melting temperature decreases firstly and rises with increasing Al_(2)O_(3)/CaO.The ashmelting point reached to the lowestwhen the ratio is 1.23.XRD and Factsage software are used to analyze crystallization behavior of samples.The results showthat the content of anorthite,albite and corundumincreases and subsequently decreases,while the content of mullite decreases firstly and then rises with increasing Al_(2)O_(3)/CaO.High content with CaO can contribute to form albite and anorthite of low-melting.Besides,high content with Al_(2)O_(3) can tend to produce mullite of high-melting.The results of experimental and simulation are basically the same,which lays a foundation for the melting characteristics of Ningdong coal ash and can provide technical support for the smooth operation of the entrained-gasifier.

Exploring influence of MgO/CaO on crystallization characteristics to understand fluidity of synthetic coal slags

The crystallization has significant influence on fluidity of slag and slag discharge of entrained-flow-bed(EFB) gasifier. The crystallization characteristics and fluidity of five synthetic slags with different MgO/CaO ratios prepared on the basis of the range of oxide contents of Zhundong coal ash were investigated in this study. The results show that with the MgO/CaO ratio increase, the initial crystallization temperature increases, and the main temperature range of crystallization ratio growth moves to higher temperature range gradually which causes Tp25(Tp25is the temperature corresponding to the viscosity of 25 Pa·s)to increase. Mg-rich crystals are formed preferentially than Ca-rich crystals when adding the same amount of MgO and CaO during cooling. The effective slagging operating temperature range decrease from 217 ℃ for the slag with a 0:4 MgO/CaO ratio to 44 ℃ for the slag with a 4:0 MgO/CaO ratio with the MgO/CaO ratio increase. The slags with 2:2 and 1:3 MgO/CaO ratios show similar effective slagging operating temperature range, Tp25and the temperature corresponding to the viscosity of 2 Pa·s.However, compared with the slag with a 1:3 MgO/CaO ratio, the crystallization ratio and rate of slag with a 2:2 MgO/CaO ratio are lower within lower temperature range(1300–1200 ℃), causing its lower critical viscosity temperature and wider actual operating temperature range. Of the five slags, the widest effective slagging operating temperature range and the lowest Tp25of the slag with a 0:4 MgO/CaO ratio due to its low crystallization ratio, and wider actual operating temperature range of the slag with a 2:2 MgO/CaO ratio make the two slags suitable for slag discharge of EFB gasifier.

Synthesis of porous CaO microsphere and its application in catalyzing transesterification reaction for biodiesel

It is hoped to develop a simple and low cost route for preparing the CaO with a novel morphology which can present high catalytic activity in catalyzing transesterification reaction for biodiesel. The porous CaO microsphere was synthesized by calcining spherical CaCO3 precursor which was prepared easily by mixing CaCl2 with Na2CO3. The as-prepared CaO microsphere was characterized by scanning electronic microscopy(SEM), powder X-ray diffractometry(XRD) and N2 adsorption experiment. The results reveal that the synthesized CaO is regular microsphere with many pores in its exterior and interior. The CaO microsphere is applied in catalyzing the transesterification reaction of soybean oil for biodiesel and presents excellent catalytic ability with a transesterification yield of 98.72%. This catalyst could have potential applications in other fields in view of its well-defined morphology, simply synthetic route and low cost.

Combustion Synthesis and Luminescent Properties of CaO: Eu^(3+), M^+ (M=Li, Na, K) Phosphor

Li ^＋ , Na^ ＋ , or K ^＋ co-doped CaO： Eu^3＋ phosphors were prepared by the combustion synthesis method and characterized by X-ray diffraction （XRD）, photoluminescence and photolumi-nescence excitation （PL-PLE） spectra. The experimental results show that, upon excitation with 250 nm xenon light, the emission spectrum of the CaO： Eu^3＋ consists of 4f-4f emission transitions from the 5D0 excited level to the 7FJ （J=1, 2, 3） levels with the mainly electric dipole transition 5D0→7F2 of Eu3＋, indicating that the Eu^3＋ occupies a low symmetry. The charge-transfer band （CTB） shows somewhat red shift with the decreasing ionic radii of co-doped alkali metal ions. The PL and PLE intensities are significantly enhanced, especially the strongest intensity of luminescent is CaO： Eu^3＋, Li ＋ phosphor, when alkali metal ions are incorporated. The strongest peak of emission is slightly shifted from 614 to 593 nm, indicating that the Eu^3＋ ion locates in a symmetric position （Oh） when alkali metal ions are incorporated.

Relationship between alkaloid contents and growth environment of Yimu Cao (Herba Leonuri)

Objective: To study the relationship between alkaloids contents in Chinese traditional drug Yimu Cao (the dried aerial parts of Leonurus artemisia) and its growing environment. Methods: Samples of the drug and the soil at the growing site collected from 5 selected regions. Reference materials were checked and on-the-spot observations were carried out to investigate the growth environment. RP-HPLC was performed to determine the alkaloid contents in the drug. Results: Different regions had different environmental conditions, including climate, soil, vegetation, and so on. No matter barren or fertile the soil at the growing site was, the herb of L. artemisia could grow well, but the contents of alkaloid in the drug varied greatly. The drugs produced in 2 northern regions, where the soil is alkaline, had higher content of alkaloid (about 0.4%) than that produced in southern regions (0.1l%-0.2%), where the soil is acid. Conclusion: The contents of organic matters, effective phosphorus, quick-acting potassium, and the pH value of the growing site soil were the factors correlating with alkaloid contents in the drug, among which the pH value of soil was an important positively correlating factor. The alkaline soils in North benefit the accumulation of alkaloids more than the acid soils in South. The other probable elements affecting the alkaloid contents in Yimu Cao were climate and genetic factors.