Local vibration around rare earth ions in alkaline earth fluorosilicate transparent glass and glass ceramics using Eu^(3+) probe

By heat treating the alkaline earth fluorosilicate glass, transparent glass ceramics containing alkaline earth fluoride nanocrystallites were prepared. The luminescence spectra and phonon sideband associated with the Eu^3＋：^5D2→^7F0 in glass and glass ceramics were investigated to analyze the local environment around Eu^3＋. Judd-Ofelt parameters were also calculated from emission spectra, which indicated that the Eu^3＋ ions entered the precipitated CaF2, SrF2, and BaF2 nanocrystallites. Heat treating could not pledge Eu^3＋ ions to coordinate with F^- in the precipitated MgF2 nanocrystallites, owing to the smaller radius of Mg^2＋ than that of Eu^3＋.

Study on rare earth/alkaline earth oxide-doped CeO_2 solid electrolyte

Five types of rare earth/alkaline earth oxide-doped CeO2 superfine-powders were synthesized by a low-temperature combustion technique. The relevant solid electrolyte materials were also sintered by pressureless sintering at different temperatures. The results of X-ray diffraction and transmission electron microscopy showed that the grain size of the powders was approximately 20-30 nm, and rare earth/alkaline earth oxides were completely dissolved into ceria-based solid solution with fluorite structure. The electrical conductivities of the SmzO3-CeO2 system were measured by the ac impedance technique in air at temperatures ranging from 513-900℃. The results indicated that the ionic conductivities of Srno.2oCe0.8Ol.875 solid electrolyte increase with increasing sintering temperature, and the relationship between the conductivities and measuring temperature obeys the An＇henius equation. Then the SmzO3-CeO2 material was further doped with other rare earth/alkaline earth oxide, and the conductivities improve with the effective index.

Oxidation of propane to acrylic acid and acetic acid over alkaline earth-doped Mo-V-Sb-O_x catalysts

Alkaline earth metal （Mg,Ca,Sr and Ba）-doped Mo-V-Sb-O x catalysts,prepared by a dry-up method,have been investigated for their catalytic performance in the oxidation of propane under different reaction conditions.The catalysts have been characterized by N2 adsorption-desorption,temperature-programmed desorption （TPD） of NH3,SEM and XRD.Influence of water vapor on the catalytic performance,particularly on the selectivities to acetic acid and acrylic acid,has also been studied.The selectivity to acrylic acid was improved significantly by the doping of alkaline earth metals to Mo-V-Sb-O x catalysts.The surface acidic sites of the catalyst decreased with the doping of the catalyst with alkaline earth metals,which ultimately was found to be beneficial for obtaining high selectivity to acrylic acid.The catalytic activity and product selectivities were found to be influenced by the reaction temperature,C3H8/O2 ratio and space velocity.A significant improvement in the selectivity to acrylic acid has also been observed by the addition of water vapor in the feed of propane and oxygen in the oxidation of propane.

Surface-treatment of Alkaline Earth Sulfides Based Phosphor

A series of alkaline earth sulfides based phosphors Ca_ 0.8 Sr_ 0.2 S∶Eu 2+ ,Tm 3+ were covered with a layer of protective coating with alkaline earth fluorides by heating the mixture of phosphor and NH_4HF_2 at elevated temperatures. The coatings were characterized by means of XRD and SEM. The optical properties of the coated phosphors and the influences of the coating on their properties have been discussed extensively. The stabilities of the coated and uncoated phosphors have been compared.

Syntheses of Alkaline Earth and Lanthanide Cryptates with Pyridine-Based Group

New alkaline earth metal cryptates [ML]（NO3）2 ·2H2O （M=Ca^2＋, Sr^2＋, Ba^2＋; L = 1, 4,12,15,18, 26, 31, 39, 42, 43, 44-undecaazapentacyclo- [ 13.13.13.1^6,10 .1^20,24 .1^33,37 ]-tetratetraconta -4, 6, 8, 10（44）, 11, 18, 20, 22, 24（43）, 25, 31, 33, 35, 37（42）, 38-pentadecaene） were synthesized by [2 ＋ 3 ] template condensation of tris（2-aminoethyl） amine with 2, 6-diformylpyridine, and then by transmetallation reactions of the calcium cryptate [CaL] （NO3）2·2H2O with corresponding lanthanide ions; three lanthanide cryptates [ LnL] （NO）3·3H2O （Ln = Eu, Gd, Tb） were synthesized and characterized by physical methods. The crystal structure of the terbium cryptate [TbL] （NO）3·3H2O was studied by X-ray analysis. The central atom was coordinated by three pyridyl and six imino nitrogen atoms and exhibited a distorted tricapped trigonal prismatic coordination geometry.

Microcalorimetric study on host-guest complexation of naphtho-15-crown-5 with four ions of alkaline earth metal

Thermodynamic parameters of complexation of naphto- 15-crown-5 with four alkaline earth ions in aqueous media was determined using titration microcalorimetry at 298.15 K. The stability of the complexes, thermal effect and entropy effect of the complexation is discussed on the basis of the guest ions structure and the solvent effect. The stability constants tendency to vary with ion radius was interpreted. Complex of naphtha-15-crown-5 with calcium ion is very stable due to the synergism of static electric interaction and size selectivity between the host and the guest.

Preparations of Pure Alkaline Earth Molybdate Phases from Single Molecular Precursors

The pure phases of alkaline earth molybdates MMoO 4, where M=Mg, Ca, Sr or Ba, were synthesized via the calcination of the related citrato oxomolybdate complexes. The mixed metal oxides can be highly dispersed at the atomic level due to the existence of uniform citrato oxomolybdenum precursors in definite composition. The complexing effect helps to produce the fine-grained oxides with particle size in the ultrafine scale(<100 nm) at heat-treatment temperatures below 500 ℃. The structures of the precursor complexes and the finally heat-treated particles were studied by means of IR, XRD, DSC, DTA and TG techniques. The morphologies of the particles were observed by using the SEM technique. The average particle sizes were calculated to be in the range of 30_50 nm based on X-ray diffraction line-broadening and SEM images, indicating the poor conglomeration of crystallite at low temperatures.

A Novel 3D Polyoxotungstate Constructed from Dawson Polyanions and Alkaline Earth Cations

A novel 3D polyoxotungstate [Ca（H2O）2][Ca（H2O）3]H2[P2W18O62]·9H2O（1） has been synthesized by the conventional aqueous solution method and characterized by IR spectrum,elemental analyses,single-crystal X-ray diffraction and electrochemistry.1 crystallizes in triclinic,space group P1 with a = 12.9077（14）,b = 14.8593（16）,c = 20.023（2）,α = 70.1620（10）,β = 80.8110（10）,γ = 64.3770（10）o,V = 3256.9（6）3,Z = 2,Dc = 4.790 g/cm3,μ = 31.975 mm-1,F（000） = 4080,R = 0.0412,and wR = 0.1039.X-ray single-crystal structural analysis indicates that the molecular structural unit of 1 consists of one saturated Dawson [α-P2W18O62]6-polyanion,one seven-coordinate [Ca（H2O）2]2＋ cation,one eight-coordinate [Ca（H2O）3]2＋ cation,two protons and nine lattice water molecules.Interestingly,adjacent Dawson [α-P2W18O62]6-polyanions are connected by [Ca（H2O）2]2＋ and [Ca（H2O）3]2＋ cations and hydrogen bonding interactions to form a 3D infinite framework.The electrochemistry property of 1 has been studied.

Solvent Extraction of Alkaline Earth Metals with Alkylphosphorus Acids

Solvent extraction equilibria of four main alkaline earth metals(magnesium, calcium, strontium and barium) with di (2-ethylhexyl)phosphoric acid (DEHPA), 2-ethylhexyl phosphonic acidmono-(2-ethylhexyl) esters, di (2, 4, 4-tri-methylpentyl) phosphinicacid and IR spectra of the extracts have been studied. Theselectivity order is dependent on the e/r value and hydration energyof the metal ions. The minor shift of the P→O in IR absorption ofthe alkaline earth metal extracts indicates that the interactionbetween the metal ions and P→O is much weaker for alkaline earthmetals than for transitional metals.

The Influence of Alkaline Earth Elements on Electronic Properties ofα-Si3N4 via DFT Calculation

We used density functional theory(DFT)calculations to study the influence of alkali earth metal element(AE)doping on the crystal structure and electronic band structure ofα-Si3N4.The diversity of atomic radii of alkaline earth metal elements results in structural expansion when they were doped into theα-Si3N4 lattice.Formation energies of the doped structures indicate that dopants prefer to occupy the interstitial site under the nitrogen-deficient environment,while substitute Si under the nitrogen-rich environment,which provides a guide to synthesizingα-Si3N4 with different doping types by controlling nitrogen conditions.For electronic structures,energy levels of the dopants appear in the bottom of the conduction band or the top of the valence band or the forbidden band,which reduces the bandgap ofα-Si3N4.

Syntheses and Characterization of Two New Alkaline Earth Metal-organic Topological Frameworks with 3-Amino-1H-1,2,4-triazole-5-carboxylate

Two new alkaline earth metal coordination polymers constructed from the deriva-tive of 1,2,4-triazole are presented herein,namely,{[Sr（AmTAZAc）2（H2O）]}（1） and {[Ba（AmTAZAc）2（H2O）]}（2）（AmTAZAc = 3-amino-1H-1,2,4-triazole-5-carboxylate）,which have been synthesized by using the layering method and structurally characterized by elemental analysis,IR,and single-crystal X-ray diffraction.Complexes 1 and 2 are isostructural,and both crystallize in the orthorhombic system,space group Fdd2.X-ray structural analysis shows that 1 or 2 has an intriguing 3-D infinite network of（318.438.510） topology based on a 2-D sheet structure of（4,4） net.The result shows that noncovalent interactions play an important role in strengthening the whole structures of the compounds.

OXIDATIVE COUPLING OF METHANE OVER MODIFIED ALKALINE EARTH OXIDES

Methane conversions at lower temperature were studied. The aetivity of Y_2O_3 sample at 823K was fairly high with some formation of C_2H_4 and C_2H_6, the catalysts based on alkaline earth oxides and yttria would give better results. The influences of flux ratio, space velocity, and reaction temperature were also discussed.

Hydrothermal Synthesis and Thermal Decomposition Mechanism of Alkaline Earth Benzoates

Alkaline earth benzoates were synthesized using hydrothermal reaction. The complexes were characterized by elemental analysis, IR, X ray powder diffraction. All of them are monoclinic and have layered structure. The mechanism of thermal decomposition of alkaline earth benzoates was studied by using TG, DTA, IR and gas chromatography mass spectrometry. The thermal decomposition of alkaline earth benzoates in nitrogen proceeded in one or two stages: they decomposed to form MCO 3 (M=Ca,Sr,Ba) or MgO and organic compounds, respectively. The organic compounds obtained from decomposition reaction are mainly benzophenone, triphenylmethane and so on.

Carbon dioxide adsorption behaviors of aluminum-pillared montmorillonite-supported alkaline earth metals

The Al-pillared montmorillonite-supported alkaline earth metal 5M/Al-PILC(PILC = pillared clay, M = Mg, Ca, Sr, and Ba) and x Mg/Al-PILC( x = 1, 3, 5, and 7 wt.%) samples were prepared using an impregnation method. Physical properties of the materials were determined by means of X-ray diffraction(XRD) and N2 adsorption-desorption, and their CO2 adsorption behaviors were investigated using the thermogravimetric analyzer(TG), CO2 temperatureprogrammed desorption(CO2-TPD), and in situ diffuse reflectance infrared transform spectroscopy(in situ-DRIFTS) techniques. It is shown that 5 Mg/Al-PILC possessed the highest CO2 adsorption capacity(2.559 mmol/g). The characterization results indicate that Alpillaring increased the specific surface area of montmorillonite, which was beneficial for the adsorption of CO2. The CO2 adsorption process on the sample was mainly chemical adsorption, and alkalinity was the main factor influencing its adsorption capacity. The alkalinity of the sample was enhanced by loading an appropriate amount of alkaline earth metal, and the adsorbed CO2 was present in the form of bicarbonate and carbonate. In addition, the 5Mg/Al-PILC sample exhibited an excellent regeneration efficiency. We believe that the outcome of this research would provide a good option for developing highly effective CO2 adsorption materials.

Three alkaline earth metal-organic frameworks based on fluorene-containing carboxylates:syntheses,structures and properties

Three metal-organic frameworks,{[Mg_2(MFDA)_2(DMF)_3]·0.5H_2O}_n(1),{[Ca(MFDA)(DMF)(H_2O)]·0.5DMF}_n(2)and[Ca(MFDA)(DMF)_2]_n(3)(DMF=N,N-dimethylformamide)have been synthesized by the solvothermal reactions between the ligand 9,9-dimethylfluorene-2,7-dicarboxylic acid(H_2MFDA)and the corresponding metal salts,respectively.The single crystal X-ray structural analyses reveal that compounds 1-3 display three-dimensional structures based on the M(Ⅱ)-O-C chains.It is interesting that the MFDA ligands in 1-3 have different dihedral angles between the two carboxylate groups ranging from 9.9(1)°to 41.8(2)°.All of compounds exhibit strong ligand-centered blue emissions under UV lights.Their thermal properties have also been studied.

Effects of alkaline earth oxides on precipitation behavior of metallic iron under CO atmosphere

In gaseous reduction of iron ore fines, alkaline earth oxides have profound effects on the precipitation behavior of fresh metal- lic iron on the particle surface. In this work, in situ observation was performed to reveal the influence of alkaline earth oxides on the precipitation morphology and micro-structure variation of fresh metallic iron from microscopic level by simulation of the gas-solid reaction condition on the surface of ore particles. Experimental results indicate that doping MgO in the particle surface can inhibit the reduction of iron oxide and however doping CaO, SrO and BaO promote; all alkaline earth oxides tested in this study can change the precipitation morphology of fresh metallic iron; minimum doping mole fraction of one oxide to inhibit iron whiskers growth （ NAO ） is related to its cation radius （ r：＋ ） and its extranuclear electronic layers（nAD ）, which can be expressed as NAO = 1.3 × 10^-5r^2AD,√nA^2.

Study on sulfur migration in activated carbon adsorption-desorption cycle: Effect of alkali/alkaline earth metals

Activated carbon(AC)has been widely used in the removal of SO_(2) from flue gas owing to its well-developed pore structure and abundant functional groups.Herein,the effect of alkali/alkaline earth metals on sulfur migration was investigated based on the dynamic adsorption and temperature programmed desorption experiment.The adsorption and desorption properties of six types of AC(three commercial and three laboratory-made)were carried out on a fixed-bed experimental device,and the physical and chemical properties of samples were determined by X-ray fluorescence,X-ray diffraction,scanning electron microscopy/energy dispersive X-ray,and X-ray photoelectron spectroscopy analysis.The experimental results showed that the adsorbed SO_(2) cannot be completely desorbed by increasing the regeneration temperature(350-850℃),while the SO_(2) fixed in the AC combines with the Ca-based minerals in the ash to form a stable sulfate.For different samples,higher ash content,higher CaO content in the ash and a more developed pore structure lead to a higher SO_(2) fixation rate.Moreover,the multiple adsorption-desorption cycles experiment showed that the effect of SO_(2) fixation is mainly reflected in the first cycle,after which the adsorption and desorption amount are approximately the same.This study elucidates the effect of alkali/alkaline earth metals on the adsorption-desorption cycle of AC,which provides a deeper understanding of sulfur migration in the AC flue gas desulfurization process.

Low-temperature(NO + O_(2)) adsorption performance of alkaline earth metal-doped C-FDU-15

To improve the removal capacity of NO + O_(2) effectively, the alkaline earth metal-doped order mesoporous carbon(A-C-FDU-15(0.001)(A = Mg, Ca, Sr and Ba)) and Mg-C-FDU-15( x)( x = 0.001-0.003) samples were prepared, and their physicochemical and NO + O_(2) adsorption properties were determined by means of various techniques. The results show that the sequence in(NO + O_(2)) adsorption performance was as follows: Mg-C-FDU-15(0.001)(93.2 mg/g) > Ca-C-FDU-15(0.001)(82.2 mg/g) > Sr-C-FDU-15(0.001)(76.1 mg/g) > Ba-C-FDU-15(0.001)(72.9 mg/g) > C-FDU-15(67.1 mg/g). Among all of the A-C-FDU-15(0.001) samples, Mg-C-FDU-15(0.001) possessed the highest(NO + O_(2)) adsorption capacity(106.2 mg/g). The species of alkaline earth metals and basic sites were important factors determining the adsorption of NO + O_(2) on the A-C-FDU-15( x) samples, and(NO + O_(2)) adsorption on the samples was mainly chemical adsorption. Combined with the results of(NO + O_(2))-temperatureprogrammed desorption((NO + O_(2))-TPD) and in situ diffused reflectance infrared Fourier transform spectroscopy(DRIFTS) characterization, we deduced that there were two main pathways of(NO + O_(2)) adsorption: one was first the conversion of NO and O_(2) to NO_(2) and then part of NO_(2) was converted to NO_(2)^(-) and NO_(3)^(-);and the other was the direct oxidation of NO to NO-2 and NO_(3)^(-).

Effect of rare earth oxides on the properties of bio-soluble alkaline earth silicate fibers

Using natural mineral wollastonite, talc and quartz sands as raw materials, rare earth oxides (La2O3, Nd2O3 and Y2O3) as additives, the bio-soluble alkaline earth silicate fibers were prepared by melting and blowing process. The viscosity of the molten ma-terials, bio-solubility and crystallization behavior of the fiber were investigated. The results indicated that the fiber drawing tempera-ture range could be broadened since the slope of the temperature-viscosity curve decreased with adding rare earth oxide. The addition of rare earth oxide was beneficial to the increase of crystallization temperature by strengthening the network structure of the fiber. The existence of rare earth oxide in the fibers would reduce the solubility of the fibers, which still belonged to bio-soluble fibers.

Catalytic Performance for Oxidative Coupling of Methane over Eu_2O_3 Catalysts Promoted by Alkaline Earth Flourides

The catalytic performance of oxidative coupling of methane(OCM) over Eu 2O 3 catalysts promoted by alkaline earth fluorides was studied The results showed that C 2 hydrocarbon selectivity and yield over the fluoride promoted Eu 2O 3 catalysts were apparently higher than those over pure Eu 2O 3; the OCM performance increased according to the sequence of CaF 2 Eu 2O 3≈BaF 2 Eu 2O 3<SrF 2 Eu 2O 3 under the same conditions XRD experiment indicated that rhombohedral EuOF phase formed in the fresh BaF 2 Eu 2O 3 catalyst, while the exchange of F - and O 2- did not apparently happen in the fresh CaF 2 Eu 2O 3 and SrF 2 Eu 2O 3 catalysts Pyridine TPD and CO 2 TPD measurements found that, after adding SrF 2 to Eu 2O 3, the catalyst surface acidity decreased, whereas the surface basic strength increased slightly, resulting in an improvement in C 2 selectivity and yield