Addition Of Calcium Research Articles

A Transient Receptor Potential-like Calcium Ion Channel in the Filamentous Fungus Aspergillus nidulans.

Transient Receptor Potential (TRP) proteins constitute a superfamily that encodes transmembrane ion channels with highly diverse permeation and gating properties. Filamentous fungi possess putative TRP channel-encoded genes, but their functions remain elusive. Here, we report that a putative TRP-like calcium channel, trpR, in the filamentous fungus Aspergillus nidulans, performs important roles in conidiation and in adapting to cell wall disruption reagents in a high temperature-induced defect-dependent manner, especially under a calcium-limited culture condition. The genetic and functional relationship between TrpR and the previously identified high-affinity calcium channels CchA/MidA indicates that TrpR has an opposite response to CchA/MidA when reacting to cell wall disruption reagents and in regulating calcium transients. However, a considerable addition of calcium can rescue all the defects that occur in TrpR and CchA/MidA, meaning that calcium is able to bypass the necessary requirement. Nevertheless, the colocalization at the membrane of the Golgi for TrpR and the P-type Golgi Ca2+ ATPase PmrA suggests two channels that may work as ion transporters, transferring Ca2+ from the cytosol into the Golgi apparatus and maintaining cellular calcium homeostasis. Therefore, combined with data for the trpR deletion mutant revealing abnormal cell wall structures, TrpR works as a Golgi membrane calcium ion channel that involves cell wall integration.

Algicidal activity of Aspergillus niger induced by calcium ion as signal molecule on Microcystis aeruginosa

Cyanobacterial blooms pose great threats to water environment safety and human health due to the release of microcystins, and flocculation is an effective way to control cyanobacterial blooms. In this study, Aspergillus niger 7806F3 exhibited high flocculation activity on Microcystis aeruginosa species, and the addition of calcium ion could cause lysis of algal cells. Meanwhile, the combined effect of strain 7806F3 and calcium ion was conducive to reducing extracellular microcystins. The supernatant of strain 7806F3 induced by calcium ion possessed algicidal activity, which could be inhibited by calcium/calmodulin dependent protein kinase (CaMK) inhibitor, suggesting that calcium ion, as signal molecules, can activate CaMK activity, thus regulating a series of algicidal activities. The disturbance induced by 7806F3 and calcium ion on the bacterial community was not obvious, which indicated that the algicidal activity of Aspergillus niger induced by calcium ion cannot significantly affect the bacterial community dynamics. All these results confirm for the first time that calcium ion, as signal molecules, induce the algicidal activity of Aspergillus niger, which can provide a novel choice for controlling cyanobacterial blooms.

Pyrolysis behaviors of model compounds with representative oxygen-containing functional groups in coal over calcium

Calcium has great catalytic potentials to regulate volatiles from low-rank coal pyrolysis to form high-valued products. Due to the complexity of coal structure, it's still no consensus on the catalytic mechanism over calcium catalyst. In this paper, coal-related model compounds with representative O-containing functional groups [1,4-naphthalenedicarboxylic acid, poly (4-vinylphenol) and poly (2,6-dimethyl-1,4-phenylene oxide)] were chosen to study the primary pyrolysis product distribution and composition over calcium components by FTIR, TGA and in-situ pyrolysis vacuum ultraviolet photoionization time-of-flight mass spectrometry. The results show that calcium could be ion-exchanged with the O-containing acidic groups (carboxyl functional group or phenolic hydroxyl group) presented in the model compounds to significantly improve the thermal stability, and the pyrolysis of carboxylic and phenolic compounds in the presence of calcium will not only promote a complex cross-linking reaction for the formation of polymers, but also lead to the formation of ketone compounds. The addition of calcium has no effect on the decomposition modes of ether bond connecting two aromatic rings. In addition, the interaction mode and thermal conversion mechanism between carboxyl groups and calcium component were studied. The benzoic acid, 2-naphthoic acid, anthracene-9-carboxylic acid, and 1-pyrenecarboxylic acid were used to investigate the effect of aromatic ring number on the transformation of carboxyl functional groups under the action of calcium. The results showed that the difference of substitution positions may have a certain effect on the formation of products, but the effect of calcium on the main transformation mechanism of carboxyl functional groups in different aromatic structures is universal.

Calcium monofluoride as a target molecule for determination of organic fluorine in gasoline and its components using high-resolution continuum source flame molecular absorption spectrometry

High-resolution continuum source molecular absorption spectrometry (HR-CS MAS) is widely applied to determine fluorine in various materials, and its graphite furnace option with calcium monofluoride as a target molecule is popular. However, up to now, the idea of using the molecule in flame molecular absorption spectrometry seemed impossible or impractical due to the expected low sensitivity and detectability. The following paper completely changes this view. The CaF molecule has been proven to be an excellent tool for determining organic fluorine in gasoline using flame molecular absorption spectrometry, giving benefits over previously used gallium monofluoride. The following favourable circumstances decide about it: 1) relatively high population of CaF molecules in preferable air-acetylene flame, 2) possibility of using oil calcium “standard” as a source of calcium, which is well dissoluble in both xylene (solvent) and gasoline, 3) extremely good stability of baseline in the used spectrum range, 4) relatively high freedom from spectral and chemical interferences and 5) possibility of summing of many pixels response. The analysis relies on simple sample dilution in xylene, with the addition of oil calcium “standard” to obtain 1500 mg L−1 Ca in measured solutions. Simplified standard addition calibration is used to overcome the effect of variability of samples (various physical properties and combustion characteristics). The signals of four CaF rotational “lines” are summed. The only undesirable spectral effect is a molecular absorption at the second “line” (606.0368 nm), which is attributed to the absorption by the CaOH molecule formed in the flame. The effect can be easily overcome by using the least square background correction, LSBC. The characteristic concentration and the detection limit for solutions are 6 and 0.6 mg L−1, respectively. The detection limit recalculated for the original sample is 2 mg kg−1 in the case of alkalyte, reformate and gasoline, while it is 6 mg kg−1 in the case of volatile isomerizate, mainly due to necessary higher sample dilution. The calibration curve is linear over at least two orders of magnitude. Heptafluorobutanol has been found a suitable standard. The agreement of the results of the proposed method and standard combustion ion chromatography is satisfactory.

Calcium-doped titanium thin films prepared with the assistance of an oxygen ion beam: The effect of Ca content on microstructure, mechanical properties and adhesion

The effect of adding calcium on the microstructural evolution and properties of the Ti-Ca-O system has been investigated. Calcium-doped titanium (Ti-Ca) thin films were prepared by dual electron beam deposition with the assistance of an oxygen ion beam. The films were characterized by glow discharge optical emission spectroscopy (GD-OES), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), to determine the elemental composition, chemical bonds and crystallinity. Oxygen ion assistance produces non-completely oxidized Ti-Ca films. The addition of calcium led to increased formation and stabilization of titanium oxides in the titanium matrix under conditions of oxygen deficiency. Replacement of Ti by Ca in TiO and TiO2 was observed, rather than the formation of a CaO and TiCaO mixture. Compound formation, crystallite growth and lattice expansion with rising Ca concentration induced an increase in mechanical properties (hardness and reduced elastic modulus) and surface roughness. High Ca concentration (5 at%) led to a significant reduction in mechanical properties, and above 1 at% led to a significant reduction in adhesion strength. The Ti-Ca films showed hydrophobic behaviour. The water contact angle followed the increasing trend of Ca concentration and surface roughness. There is a discussion of the changes in the studied properties.

Effects of Exogenous Calcium on Adaptive Growth, Photosynthesis, Ion Homeostasis and Phenolics of Gleditsia sinensis Lam. Plants under Salt Stress

Salinity is the main environmental factor responsible for limited plant growth in many areas of the world. Gleditsia sinensis Lam. is a shelter forest tree species that does not require high-quality soil and can even grow in mild saline soil. This study mainly explored the tolerance of G. sinensis to salt and the effect of exogenous calcium addition on the growth of G. sinensis in a salinized soil. The concentrations of NaCl were set as 0 mmol/L, 100 mmol/L, and 200 mmol/L. Compared with the control, under the NaCl treatment of 200 mmol/L, it was observed that the leaves of G. sinensis turned yellow, the electrical conductivity significantly increased, and the water content and the chlorophyll content significantly decreased, which is probably unfavorable for growth. Our study showed that the addition of 10 mmol/L exogenous calcium chloride under salt stress had a positive effect on the growth and photosynthetic characteristics of G. sinensis. Moreover, the addition of exogenous calcium attenuated the cytotoxicity caused by Na+ under salt stress and promoted the equilibrium of ion homeostasis. More importantly, the addition of exogenous calcium ions was beneficial for the survival of G. sinensis plants on salinized land and the increase of effective active ingredient content including phenolic compounds, which is of direct significance for improving environmental problems such as desertification of saline-alkali land. In conclusion, we investigated the effect of salt treatment on G. sinensis, as well as the positive effects of exogenous calcium on the survival and growth of G. sinensis in salt environment, which provided a scientific basis for the targeted cultivation of G. sinensis in salinized land and the effective utilization of salinized and alkaline land.

Technique of Increasing Calcium Carbonate (CaCO3) in White Shrimp (Litopenaeus vannamei) Feed in Kasetsart University, Bangkok

White shrimp (Litopenaeus vannamei) culture has grown rapidly in Indonesia since early 2000s. White shrimp have stronger resistance to WSSDV attacks, and are euryhaline. In it’s natural habitat, this shrimp was found in waters with a range of 0.5-40 ppt salinity. White shrimp grow optimally at 15-25 ppt salinity, even still suitable at 5 ppt salinity. This capability provides the opportunities to culture these commodities in inland water. White shrimp need inorganic elements or minerals for their living processes. Calcium is one of the main needs of shrimp that is closely related to the development and maintenance of skeletal systems and plays a role in some physiological processes of the body.The requirement for calcium in shrimp is increasing when it is cultivated in fresh water.This Internship aims to find out the technique of adding calcium carbonate (CaCO3) in feed, used for the white shrimp culture in fresh water. In this field practice, the addition of calcium carbonate in a level of 2% refers to the requirement of white shrimp for optimal growth. This was based on the calcium requirements of shrimp in the amount of 1-2%. The method was repelleting, by grinding feed and calcium using mortar and pestle, then filtered to get the smoothest part. Then mix calcium with 10 mL of water and mix it with pellets evenly. Then the mixture is air dried and mashed again and weighed according to the required dose of feed. The addition of calcium in the feed affects the growth of shrimp, because calcium is one of the most important anorganic mineral for the growth and development of exoskeleton, regulates blood clotting, heart rate, kidneys, nerves, the activity of several enzymes, and cell function

Effects of quantity and source of calcium on the behavior of goat milk after heating and acidification

This study investigated changes in the behavior of goat milk protein and physicochemical characteristics of high-pasteurized goat milk and goat milk yogurt during storage caused by calcium chloride and natural milk calcium addition and decalcification. Compared with the control group, the denaturation temperature of goat milk protein dropped in all the treated groups. The addition of both types of calcium accelerated the transition of goat milk protein from β-sheet to β-turn and random coil structure. But opposite results were found in the decalcification process. Compared with calcium chloride, natural milk calcium showed more positive influence on the stability of high-pasteurized milk during storage. The addition of both types of calcium improved significantly the water-holding capacity of yogurt during 7-day storage, and the natural milk calcium dramatically inhibited the post-acidification of yogurt. This study provides a theoretical basis for further study and the development of calcium-based functional goat milk products.

Sodium caseinate hinders chymosin-induced aggregation of caseins in concentrated milk: The role of soluble caseins and calcium ions

Concentrated casein micelle suspensions show an altered balance between the colloidal and soluble phases compared with native skim milk. The objective of this research was to probe the role of such a change on the chymosin-driven destabilization of casein micelles. Skim milk was gently concentrated by osmotic stressing to increase the volume fraction of the micelles while maintaining a constant ionic composition. In situ turbidity measurements demonstrated that the secondary stage of gelation was hindered in the concentrated suspensions. Addition of ionic calcium overcame this inhibition, whereas restoring the original concentration by redilution did not. This work clearly demonstrated that calcium plays a major role in decreasing electrostatic repulsion in casein micelles, but also showed the importance of noncolloidal proteins in altering the gelling functionality of casein micelles in concentrated milk. Additional calcium induces aggregation of these soluble caseins, restoring gelation in concentrates.

Effect of test velocity on the tensile strength of high strength steels using the small punch test in a hydrogen environment

This study aims at evaluating the effect of test velocity associated with the Small Punch Test on the ultimate tensile strength. The velocity factor was investigated on two levels (1.0 μm/s and 0.1 μm/s) based on a single factor design. This design was applied to three high strength steels (AISI 4130 M, 4137 M and 4140) widely used in the oil and gas offshore industry. The tests were performed in a cathodic protection environment, which consisted of a 3.5 wt% NaCl aqueous solution to simulate hydrogen embrittlement. For each material, one specimen in air at the conventional rate (0.02 mm/s) was also tested. An increasing trend was noted toward the susceptibility to hydrogen embrittlement when the test velocity was reduced from 1.0 μm/s to 0.1 μm/s. However, the Analysis of Variance showed that the test velocity factor caused statistically significant effects on the ultimate tensile strength only for 4137 M steel. The distinct behavior shown by the 4137 M, 4130 M and 4140 steels, under the experimental conditions investigated, was attributed to the combination of several factors: test velocity in the investigated H-charged environment; shape and volume fraction of non-metallic inclusion; calcium addition; tensile strength and hardness in air at the as-received condition.

Pyrolysis kinetics and product distribution of α-cellulose: Effect of potassium and calcium impregnation

Cellulose accounts for the largest proportion of lignocellulosic biomass. Herein, experimental and simulation studies are used to deeply understand the kinetic characteristics of the thermal decomposition of α-cellulose. The simulated data is in good agreement with the experimental data in the aspects of the conversion and the conversion rate versus temperature. The decomposition of α-cellulose, mainly occurring at 270–420 °C, induced an apparent activation energy ranging from 175.42 kJ/mol to 197.73 kJ/mol at a conversion of 10–90%. With 0.1–0.2 wt% K or Ca impregnation into the α-cellulose, the mean activation energy for pyrolysis was lowered (from 181.47 kJ/mol (for α-cellulose) to 141.11 kJ/mol (for 0.2 wt% K/α-cellulose) and 159.46 kJ/mol (for 0.1 wt% Ca/α-cellulose)) and higher amounts of liquid and gas products were produced. Furthermore, the addition of potassium and calcium increased the production of lower molecular weight components, such as furfural and its derivatives. The kinetic parameters of the α-cellulose pyrolysis were determined based on a nonlinear least-squares regression of the experimental data assuming first-order kinetics and correlated with the simulated result. The kinetic rate constants indicate that the predominant reaction pathway is from α-cellulose into a liquid product, rather than from α-cellulose into a gas product.

Dietary calcium supplementation promotes the accumulation of intramuscular fat

BackgroundIn the livestock industry, intramuscular fat content is a key factor affecting meat quality. Many studies have shown that dietary calcium supplementation is closely related to lipid metabolism. However, few studies have examined the relationship between dietary calcium supplementation and intramuscular fat accumulation.MethodsHere, we used C2C12 cells, C57BL/6 mice (n = 8) and three-way cross-breeding pigs (Duroc×Landrace×Large white) (n = 10) to study the effect of calcium addition on intramuscular fat accumulation. In vitro, we used calcium chloride to adjust the calcium levels in the medium (2 mmol/L or 3 mmol/L). Then we measured various indicators. In vivo, calcium carbonate was used to regulate calcium levels in feeds (Mice: 0.5% calcium or 1.2% calcium) (Pigs: 0.9% calcium or 1.5% calcium). Then we tested the mice gastrocnemius muscle triglyceride content, pig longissimus dorsi muscle meat quality and lipidomics.ResultsIn vitro, calcium addition (3 mmol/L) had no significant effect on cell proliferation, but promoted the differentiation of C2C12 cells into slow-twitch fibers. Calcium supplementation increased triglyceride accumulation in C2C12 cells. Calcium addition increased the number of mitochondria and also increased the calcium level in the mitochondria and reduced the of key enzymes activity involved in β-oxidation such as acyl-coenzyme A dehydrogenase. Decreasing mitochondrial calcium level can alleviate lipid accumulation induced by calcium addition. In addition, calcium addition also reduced the glycolytic capacity and glycolytic conversion rate of C2C12 cells. In vivo, dietary calcium supplementation (1.2%) promoted the accumulation of triglycerides in the gastrocnemius muscle of mice. Dietary calcium supplementation (1.5%) had no effect on pig weight, but significantly improved the flesh color of the longissimus dorsi muscle, reduced the backfat thickness and increased intramuscular fat content in pigs. Besides, calcium addition had no effect on longissimus dorsi pH, electrical conductivity and shear force.ConclusionsThese results suggest that calcium addition promotes intramuscular fat accumulation by inhibiting the oxidation of fatty acids. These findings provide a new tool for increasing intramuscular fat content and an economical strategy for improving meat quality.

Insights into effect of Ca(OH)2 on pyrolysis behaviors and products distribution of Hongshaquan coal

Pyrolysis is an important approach for the thermochemical transformation of low rank coal. In this work, catalytic effects of Ca(OH)2 on the pyrolysis of coal were investigated by fixed-bed and in-situ pyrolysis time-of-flight mass spectrometry. The catalytic pyrolysis reactivity and chemical structure of coal/chars were analyzed by means of TG, XPS, XRD, FTIR, N2 adsorption/desorption and Ex-situ electron paramagnetic resonance. The results showed that the calcium primarily exists in the form of “Ca-organic” structure in coal, and the loading of calcium could promote the release of gas and water and reduce the yield of char and tar during coal pyrolysis. Moreover, the yields of alkyl benzene, phenols, naphthol, and dihydroxybenzene are significantly different under the condition with or without the calcium addition, and the generation of tar and products distribution have an obvious dependency on calcium compounds in coal. It was demonstrated that the Ca(OH)2 could change the thermal reaction process of oxygen-containing functional groups in coal during pyrolysis process, thereby regulating the distribution of pyrolysis products (tar, gas and char). Calcium species has a significant effect on the thermal conversion of phenols and carboxylic acids structure into tar. Finally, the catalytic process of Ca(OH)2 on the pyrolysis of the coal was discussed.

Role of Calcium/Calcineurin Signalling in Regulating Intracellular Reactive Oxygen Species Homeostasis in Saccharomyces cerevisiae.

The calcium/calcineurin signalling pathway is required for cell survival under various environmental stresses. Using Saccharomyces cerevisiae, we explored the mechanism underlying calcium-regulated homeostasis of intracellular reactive oxygen species (ROS). We found that deletion of acyltransferase Akr1 and C-5 sterol desaturase Erg3 increased the intracellular ROS levels and cell death, and this could be inhibited by the addition of calcium. The hexose transporter Hxt1 and the amino acid permease Agp1 play crucial roles in maintaining intracellular ROS levels, and calcium induced the expression of the HXT1 and AGP1 genes. The cytosolic calcium concentration was decreased in both the akr1Δ and erg3Δ mutants relative to wild-type cells, potentially lowering basal expression of HXT1 and AGP1. Moreover, the calcium/calcineurin signalling pathway also induced the expression of AKR1 and ERG3, indicating that Akr1 and Erg3 might perform functions that help yeast cells to survive under high calcium concentrations. Our results provided mechanistic insight into how calcium regulated intracellular ROS levels in yeast.

Effect of Calcium Level in Feed on Blood Profile of Broiler Chicken

This study aims to determine the effect of calcium supplementation in feed on the blood profile of broilers chickens. This research was conducted in a broiler chicken coop, owned by breeders in Sasi Village, Kefamenanu City District, North Central East District. This research was conducted from July to August 2020. This study used 96 broilers. The method used in this was a completely randomized design consisting of 4 replications and 4 treatments. The treatments given were T0 (control diet), T1 (calcium supplementation 1,00 %), T2 (calcium supplementation 1,50 %), T3 (calcium supplementation 2,00 %). The variables observed in this study were the content of erythrocytes, hemoglobin, and blood leucocytes. The data obtained were analyzed using analysis of variance. Analysis of variance showed that the treatment had no significant effect on erythrocytes, hemoglobin, and leucocytes of broiler chickens. It was concluded that the addition of calcium in feed at different levels did not increase the content of erythrocytes, hemoglobin, and leucocytes of broiler chickens aged 6 weeks.

Hydroxyapatite-based catalysts derived from food waste digestate for efficient glucose isomerization to fructose

Transforming biomass waste into cost-effective catalysts for chemical reactions provides new opportunity for biomass waste valorization. In this work, we examined the possibility of using food waste solid digestate as raw materials for the production of a heterogeneous catalyst for glucose isomerization to fructose, which is one of the important intermediates for the production of platform chemicals, hydrocarbon fuels and synthetic materials from biomass. Hydroxyapatite-based catalysts were obtained from food waste digestate by a coupled hydrothermal-calcination approach. In the hydrothermal treatment process, the addition of exogenous calcium can adjust the alkalinity of the catalyst, which is beneficial to improve the activity of the catalyst. The reaction parameters such as reaction temperature, reaction time and catalyst dosage have also been optimized. The catalyst showed excellent catalytic performance in the glucose isomerization reaction resulting in a high fructose yield of 32.3% with a reaction time of only 20 ​min at 80 ​°C in water. The catalyst can be reused after a simple regeneration without significant activity. This work provides a win-win strategy, which not only solves the problem of the disposal and utilization of digestate, but also expands the synthesis method of the glucose isomerization reaction catalyst.

Respons fisiologis benur udang vaname (Litopenaeus vannamei) terhadap penambahan kalsium selama adaptasi di salinitas rendah

The purpose of this study was to determine the optimum addition of calcium during the adaptation period of white shrimp seed in low salinity media, so the physiological conditions of shrimp still support maximally survival and growth. The research was carried out by using the Completely Randomized Design, i.e., the addition of calcium in freshwater for decreasing water salinity from 20 g L-1 to 0.5 g L-1 as much as 150, 200, 250, 300, and 350 mg L-1, respectively. The freshwater used in the salinity reduction process was based on previous research that included sodium and potassium additions of 75 mg L-1 and 50 mg L-1, respectively. The test animal was a white shrimp stadium PL15 that had been acclimated for 5 days to a medium salinity of 20 g L-1. The results of this study showed that the addition of 300 mg L-1- calcium in freshwater during the adaptation for 96 hours significantly accelerate the achievement of molting time (1360 minutes), suppress the stress levels and metabolism rate (body fluid glucose of 169.80 mg L-1 and oxygen consumption level of 0.95 mg O2 g-1 h-1), and produce the highest survival rate of white shrimp seed (99%).Keywords: adaptation, calcium, low salinity, physiology, white shrimp

The specificities of the circular economy (CE) in the municipal wastewater and sewage sludge sector—local circumstances in Poland

Wastewater treatment plants (WWTPs) have become crucial elements of the regional bioeconomy—mainly through energy (waste to energy) and matter (nutrients–energy–water) recovery as an element of sustainable development of a smart city. In Poland, a decentralized system functioned with 3278 municipal wastewater treatment plants, and less than 80% of the population were connected to public urban wastewater treatment systems. The paper presents the technology selection and implementation of circular economy at WWTPs and the practical approach to challenge of energy-positive and environmentally friendly wastewater and sewage sludge sector. The modernization of technological lines of wastewater treatment has led to a significant improvement in the quality of treated sewage, at the largest WWTPs in Warsaw, Cracow, or Gdansk. Eleven WWTPs produce 34% of the total volume of approximately 337 GWh of electricity from biogas in Poland. The potential of producing electricity from biogas in WWTPs in Poland can be estimated at approximately 700–850 GWh per year. According to the data of the Statistics Poland in Poland, approximately 25% of sewage sludge was used directly in agriculture and for land reclamation. Simultaneously, more than 100 WWTPs produce compost at a high quality. However, only few produce organic/organic-mineral fertilizers, mainly with addition of calcium. Decentralization leads to different technologies used in wastewater treatment plants, and environmental, economic, and social conditions determine the direction of changes and introduction of a circular economy paradigm in the Polish wastewater sector.Graphic abstract

Effect of Calcium Treatment on Inclusions in H08A Welding Rod Steel

The effect of calcium treatment on inclusions in H08A welding rod steel was studied by industrial experiment and using thermodynamics theory. The effects of inclusion composition, morphology, quantity, and size in H08A welding rod steel before and after calcium treatment were studied by metallographic microscope, scanning electron microscope (SEM), and energy dispersive spectrometer (EDS). Thermodynamic studies show that the addition of calcium can form various forms of xCaO·yAl2O3, under the condition that the composition of molten steel remains unchanged, the control of calcium content is the key to generate low melting point calcium-aluminate complex non-metallic inclusions and improve the quality of molten steel. The production practice in steel plant shows that for welding rod steels, the calcium content in a suitable range can meet the requirements of calcium treatment. Effective calcium treatment can not only transform the high melting point Al2O3 inclusions into the low melting point complex non-metallic inclusions between 3CaO·Al2O3 and 12CaO·7Al2O3, but also make the original shape-diversified inclusions into the spherical calcium-aluminate complex non-metallic inclusions. Meanwhile, the total number of inclusions and large-scale inclusions in welding rod steel are reduced, and the inclusions tend to disperse in the steel, which is very conducive to the improvement of steel quality. The results show that the modification path of magnesium aluminate spinel in steel is as follows: Al2O3 → MgO-Al2O3 → MgO-CaO-Al2O3. In addition, calcium treatment can modify MgO-Al2O3 spinel in steel into liquid MgO-CaO-Al2O3 complex non-metallic inclusions with low melting point.

Enhancing the Catalytic Activity of Lanthanum-Ceria Fluorite for Methane Conversion in SOFC

A2B2O7 compounds have unique properties, such as good thermal stability, oxygen mobility, ionic conductivity, etc. Such compounds with tailored compositions exhibit good catalytic properties in a variety of high-temperature reactions, such as reform and oxidative coupling of methane (OCM). An effective catalyst for OCM must have electrophilic oxygen mobility and alkalinity on its surface. A typical A2B2O7 compound that contains a trivalent rare earth metal at site A, such as La, can provide the necessary surface alkalinity for a good OCM catalyst. Previous studies show that La2Ce2O7 (LCO) catalysts perform well in OCM due to the selective mobile oxygen sites, suitable alkaline sites, and high thermal stability. Doping LCO with Ca increases the alkalinity, which can considerably increase selectivity for ethylene in the OCM reaction. We have studied calcium-doped lanthanum ceria materials as a catalytic layer in solid oxide fuel cells reactors for methane conversion to ethylene. We have explored the combustion synthesis to obtain homogeneous La2-xCaxCe2O7 powders with x = 0, 0.25, and 0.50 (LCO, LCa25, and LCa50, respectively). X-ray diffraction (XRD) showed that the calcium addition in LCO formed a single-phase solid solution. The crystalline structure of the synthesized materials is the disordered fluorite-type, as indicated by both XRD and Raman analysis. Raman spectroscopy data evidenced the presence of surface oxygen vacancies on all materials, which may benefit the OCM reaction. SEM images of as-prepared powders obtained evidenced a similar microstructure composed of porous sponge-like agglomerated particles with irregular shape, expected from the combustion synthesis (Fig. 1). Ca-doping changed the sintering behavior by reducing the onset of shrinkage during the sintering process. Impedance spectroscopy data showed increased ionic conductivity with increasing Ca-doping. Such an increase is more evident at high measuring temperature (800 oC) and indicates enhanced oxygen mobility that are expected to contribute to OCM reaction.Figure 1: Scanning electron microscope micrographs of La2-xCaxCe2O7 (x = 0, 0.25, and 0.50) as-prepared powders obtained by combustion method. Figure 1