Synthesis and Characterization of Hollow Strontium Carbonate Pompons by Composite Soft Template Method

The hollow strontium carbonate pompons was synthesized for the first time by a controlled reaction precipitation method with sodium dodecyl benzene sulfonate(SDBS)and polyvinyl pyrrolidone(PVP)work together as template.The sampled particles were characterized by scanning electron microscopy(SEM),transmission electron microscopy(TEM),nitrogen adsorption-desorption measurement,X-ray diffraction(XRD),Energy dispersive X-Ray spectroscopy(EDX),Fourier transform infrared spectroscopy(FTIR),Thermogravimetric analysis and differential scanning calorimetry(TGA-DSC),etc.It is shown that the assynthesized hollow strontium carbonate pompons with the size of about 2μm consist of flake-like particles under the optimal reaction conditions.The formation mechanism of hollow strontium carbonate pompons was preliminarily explored.

Strontium Isotope Composition and Characteristic Analysis of Cambrian-Ordovician Carbonate in the Region of Tazhong, Tarim Basin

The research on the trace elements of Ordovician carbonates plays an important part in the whole work on reservoir in Tazhong （塔中 ） area. This paper systematically studies the characteristics and sedimentary settings of Ordovician dolomites in Tazhong area, Tarim basin, and debates their enrichment of mechanisms and different element existing patterns. The study makes use of ICP-MS analysis technology to test the strontium and manganese content of 109 samples from four wells in the Tazhong area, Tarim basin and strontium isotope composition tests have also been done on 25 samples from wells Zhong-1 and Zhong-4 on VG354 solid isotope mass spectrograph. By means of analyzing contents of strontium and manganese elements, doing research on the strontium isotope composition characteristics from wells Zhong-1 and Zhong-4 and comparing the results of strontium analysis to the global Ordovician marine carbonate and its evolution trend, in the combination of sedimentary facies characteristics of isolated wells in this area, we can come to the following cognitions： （1） The marine carbonate strontium isotope curve in the Tazhong area of Tarim basin is consistent to the global evolution trend which is overall descending with time, the direct reason of which is the evolution of paleogeographic environment. The Ordovician paleogeographic environment goes through restricted platform to open platform and then shallow marine shelf in Tazhong area, Tarim basin. Dolomitization is another subordinate reason and the inversion of fluid with high manganese can lead to heavy strontium; （2） The fact that the 87 Sr/86 Sr ratios of the Upper Ordovician in Tazhong area have an apparent mono-decline trend with the time going by, which is similar to the global strontium isotope ratio, is suggesting that the variation of the Upper Ordo- vician sea level is starting, the overall trend of which is the rising of the sea level; （3） Compared to the global seawater strontium ratios, the ^87Sr/^86 Sr ratio of the Lower Ordovician is much high, and ^87Sr/^86Sr ratio of the Lower Ordovician is overall increasing with its maximum value reaching 0. 709 727, the reasons of which are dolomitization, evaporation of the supratidal and the reflux of high manganese haline, those reasons can lead to the increasing amount of the strontium and the rising of the ^87 Sr/^86 Sr ratio; （4） The manganese element content changes little. Dolomitization has little impact on it; （5） Big variation occurs in the strontium values of Ordovician carbonate in the region of Tazhong. Apart from paleogeographic environment and petrography, the factors which can affect the values of strontium are the content of the terrestrial clastics and the diagenesis modification which may result in the further changing of the strontium values.

Carbon and Strontium Isotopes of Late Palaeozoic Marine Carbonates in the Upper Yangtze Platform,Southwest China

238 marine carbonate samples were collected from seven sedimentary sections ofthe entire late Palaeozoic (Permian, Carboniferous and Devonian) in the Upper Yangtze Plat-form, southwest China. Based on the absence of cathodoluminescence and very low Mn (gener-ally<50 ppm) contents of the samples, it is thought that they contain information on the orig-inal sea water geochemistry. The results of isotopic analyses of these samples are presented interms of δ^(13)C and ^(87)Sr/^(86)Sr ratios versus geological time. The strontium data, consistent withother similar data based on samples from North America, Europe, Africa and other areas inAsia, support the notion of a global consistency in strontium isotope composition of marinecarbonates. The strontium data exhibit three intervals of relatively low ^(87)Sr/^(86)Sr ratios in thelate Middle Devonian to early Late Devonian, Early Carboniferous and Early Permian, corre-sponding to global eustatic high sea level stands. The lowest ^(87)Sr/^(86)Sr ratio recorded in theLate Permian was probably caused by substantial basalt eruptions in the Upper Yangtze Plat-form at the time. Three corresponding periods of relatively high δ^(13)C values at roughly the samethe intervals were caused by a relatively high rate of accumulation of organic carbon duringsea level rises at these times. The deposition of coal was probably responsible for the increaseof sea water δ^(13)C at other times. The δ^(13)C values drop dramatically near theDevonian/Carboniferous, Carboniferous/Permian and Permian/Triassic boundaries, con-sistent with other similar data, which further support the notion that geological time boundariesare associated with mass extinction and subsequent rejuvenation.

Identifying the Sources of Solutes in Karst Groundwater in Chongqing,China:a Combined Sulfate and Strontium Isotope Approach

Groundwater from karst subterranean streams is among the world＇s most important sources of drinking water supplies, and the hydrochemical characteristics of karst water are impacted by both natural environment and people. Therefore, the study of hydrochemistry and its solutes＇ sources is very important to ensure the normal function of life support systems. In this paper, thirty-five representative karst groundwater samples were collected from different aquifers （limestone and dolomite） and various land use types in Chongqing to trace the sources of solutes and relative hydrochemical processes. Hydrogeochemical types of karst groundwater in Chongqing were mainly of the Ca-HCO3 type or Ca （Mg）-HCO3 type. However, some hydrochemical types of karst groundwater were the K＋Na＋Ca-SO4 type （G25 site） or Ca-HCO3＋SO4 type （G26 and G14 site）, indicating that the hydrochemistry of these sites might be strongly influenced by anthropogenic activities or unique geological characteristics. The dissolved Sr concentrations of the studied groundwater ranged from 0.57 to 15.06 ~tmmol/L, and the STSr/S6Sr varied from 0.70751 to 0.71627. The j34S-SO42- fell into a range of-6.8%o-21.5%o, with a mean value of 5.6%o. The variations of both 87Sr/S6Sr and Sr values of the groundwater samples indicated that the Sr element was controlled by the weathering of limestone, dolomite and silicate rock. However, the figure of STSr/S6Sr vs. Sr2＋/[K＋＋Na＋] showed that the anthropogenic inputs also obviously contributed to the Sr contents. For tracing the detailed anthropogenic effects, we traced the sources of solutes collected karst groundwater samples in Chongqing according to the j34S value of potential sulfate sources. The variations of both j34S and 1/ SO42- values of the groundwater samples indicated that the atmospheric acid deposition （AAD）, dissolution of gypsum （GD）, oxidation of sulfide mineral （OS） or anthropogenic inputs （SF： sewage or fertilizer） have contributed to solutes in karst groundwater. The influence of oxidation of sulfide mineral, atmospheric acid deposit and anthropogenic inputs to groundwater in Chongqing karst areas was much widespread.

Strontium optical lattice clock at the National Time Service Center

We report the 87Sr optical lattice clock developed at the National Time Service Center. We achieved a closed-loop operation of the optical lattice clock based on 87Sr atoms. The linewidth of the spin-polarized clock peak is 3.9 Hz with a clock laser pulse length of 300 ms, which corresponds to a Fourier-limited linewidth of 3 Hz. The fitting of the in-loop error signal data shows that the instability is approximately 5 × 10 15τ-1/2, affected primarily by the white noise. The fractional frequency difference averages down to 5.7 × 10 ^-17 for an averaging time of 3000 s.

Burning rate and other characteristics of strontium titanate （SrTiO3） supplemented AP/HTPB/Al composite propellants

In a quest of search for a new burning rate modifier for composite propellant, strontium titanate (SrTiO3), a perovskite oxide has been chosen for evaluation in a composite propellant formulation based on its other catalytic applications. Initially, SrTiO3 was characterized for particle size, morphology and material/ phase identification (using XRD). By varying SrTiO3 content in a standard composite propellant, different compositions were prepared and their performance and processing parameters like the end of mix (EOM) viscosity, mechanical properties, density, burning rate, pressure exponent (n-value), etc. were measured. The results reveal that 2% SrTiO3 causes more than 12% enhancement in propellant burning rate (at 70 ksc pressure) in comparison to the standard propellant composition. The pressure exponent also increases to 0.46, whereas the standard composition was having its value as 0.35.

Strontium ferrite powders prepared from oily cold rolling mill sludge by solid-state reaction method

Oily cold rolling mill （CRM） sludge is one of the pollutants emitted by iron and steel plants. Recycling oily CRM sludge can not only reduce pollution but also bring social and environmental benefits. In this study, using oily CRM sludge as sources of iron oxide, the strontium ferrite powders were synthesized in multiple steps including vacuum distillation, magnetic separation, oxidizing roasting, and solidstate reaction. The optimal technological conditions of vacuum distillation and oxidizing roasting were studied carefully. To consider the effects of Fe203/ SrCO3 tool ratio, calcination temperature, milling time and calcination time on magnetic properties of prepared strontium ferrite powders, the orthogonal experimental method was adopted. The maximum saturation magneti- zation （62.6 mA-m2.g-1） of the synthesized strontium ferrite powders was achieved at the Fe203/SrCO3 mol ratio of 6, 5 h milling time, 1250 ~C calcination temperature, and 1 h calcination time. Strontium ferrite powders syn- thesis method not only provides a cheap, high quality raw material for the production of strontium ferrite powders, but also effectively prevents the environmental pollution.

Synthesis,Characterization and Antibacterial Property of Strontium Half and Totally Substituted Hydroxyapatite Nanoparticles

Nanoparticles of hydroxyapatite（HAP）, strontium half substituted hydroxyapatite （SrCaHAP） and strontium totally substituted hydroxyapatite （SrHAP） were prepared by sol-gel-supercritical fluid drying （SCFD） method. The nanoparticles were characterized by element content analysis, FT-IR, XRD and TEM, and the effects of strontium substitution on crystal structure, crystallinity, particle shape and antibacterial properties of the nanoparticles on Escherichia coli, Staphylococcus aureus, Lactobacillus were researched. Results show that strontium can half and totally substitute for calcium and enter the structure of apatite according to the initial atomic ratios of Sr/[Sr＋Ca] as 0.5, 1. The substitution decreases the IR wavenumbers of SrCaHAP and SrHAP, and changes the morphology of the nanoparticles from short rod shaped HAP to needle shaped SrCaHAP, and back to short rod shaped SrHAP. The crystallinity of HAP is higher than that of SrCaHAP, but is lower than that of SrHAP. Moreover, the antibacterial property of SrCaHAP and SrHAP are improved after the calcium is half and totally substituted by strontium.

Roles of crystal defects in the persistent luminescence of Eu^(2+), Dy^(3+) co-doped strontium aluminate based phosphors

The roles of different point defects in persistent luminescence of SrAl2O4：Eu,Dy phosphors were investigated. The research results showed that Dyer plays an important role in the persistent luminescence of SrA1EO4：Eu, Dy phosphors. It can serve as the electron trap of suitable depth for persistent luminescence. V~ does not serve as the electron trap of suitable depth, but its existence can increase the depth of electron traps. There is interaction between the Dy^3＋（ DySr ） and the Eu^2＋（Eu^x Sr ）, and only if the distance between the Dy^3＋（DySr） and the Eu^2＋ （Eu^x Sr） is close enough, the Dyer can work as an effective electron trap. The point defect of V＂ Sr can be hole trap, but the change of its density in crystal matrix does not arouse the obvious change of persistent luminescence.

Association of Urinary Strontium Levels with Pregnancy-induced Hypertension

Pregnancy-induced hypertension(PIH),including gestational hypertension and preeclampsia,accounts for the majority of maternal and perinatal morbidity and mortality.Strontium(Sr)has been recently associated with preeclampsia in a small group of women;however,the role of Sr in PIH is not fully understood and warrants further investigation.In this study,we examined the association between urinary Sr levels and PIH,and assessed the effect of maternal age on the association.Urinary Sr concentrations were measured in 5423 pregnant women before delivery by inductively coupled plasma mass spectrometry(ICP-MS).Logistic regression analysis adjusting for potential confounders was applied to explore the association between Sr and PIH,and to evaluate the Sr-PIH relationship stratified by maternal age.Among the participants,200(3.83%)women were diagnosed with PIH.Compared with non-PIH women,women who developed PIH had lower urinary Sr concentrations(131.26 us.174.98μg/L creatinine,P<0.01).With the natural log-transformed urinary creatinine-standardized Sr concentrations increasing,the risk of PIH decreased significantly[adjusted OR=0.60(95%CI:0.51,0.72)].Furthermore,the significant association of Sr with PIH was found among women under 35 years(P<0.01).Our finding suggested that Sr may play a potential protective role in the pathogenesis of PIH,especially among young pregnant women under 35 years old.

Microstructure of pre-sintered permanent magnetic strontium ferrite powder

The microstructure and characteristics of pre-sintered strontium ferrite powder were investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The present study shows that the pre-sintered strontium ferrite powder is provided with a certain particle size distribution, which results in high-density magnets. The strontium ferrite particle has a laminar hexagonal structure with a size similar to ferrite single domain. Ferric oxide phase due to an incomplete solid phase reaction in the first sintering is discovered, which will deteriorate the magnetic properties of ferrite magnet. In addition, the waste ferrite magnets with needle shape arranging along C axis in good order into the powders are found, which have no negative effects on finished product quality.

First Evaluation and Frequency Measurement of the Strontium Optical Lattice Clock at NIM

An optical lattice clock based on 87Sr is built at National Institute of Metrology （NIM） of China. The systematic frequency shifts of the clock are evaluated with a total uncertainty of 2.3×10-16. To measure its absolute frequency with respect to NIM＇s cesium fountain clock NIM5, the frequency of a flywheel H-maser of NIM5 is transferred to the Sr laboratory through a 50-kin-long fiber. reference frequency of this H-maser, is used for the optical this Sr clock is measured to be 429228004229873.7（1.4）Hz. A fiber optical frequency comb, phase-locked to the frequency measurement. The absolute frequency of

Facile Synthesis of the Magnetic Metal Organic Framework Fe_3O_4@UiO-66-NH_2 for Separation of Strontium

A magnetic metal organic framework（MMOF） was synthesized and used to separate Sr^2＋ in aqueous solution. The shape and structure of prepared Fe3O4@UiO-66-NH2 were characterized, and the absorbed concentration of strontium was determined through inductively coupled plasma mass spectrometry. The results indicated that Fe3O4 and UiO-66-NH2 combined through chemical bonding. The experimental adsorption results for separation of Sr^2＋ in aqueous solution indicated that the adsorption of Sr^2＋ to Fe3O4@UiO-66-NH2 increased drastically from pH 11 to pH 13. The adsorption isotherm model indicated that the adsorption of Sr^2＋ conformed to the Freundlich isotherm model（R2 = 0.9919）. The MMOF thus inherited the superior qualities of magnetic composites and metal organic frameworks, and can easily be separated under an external magnetic field. This MMOF thus has potential applications as a magnetic adsorbent for low level radionuclide （90）Sr.

Comparative Study on the Microstructure and Mechanical Properties of Mg-Li-Al Based Alloys with Yttrium and Strontium Addition

The effects of yttrium and strontium on the microstructure and mechanical properties of Mg- 11Li-3A1 magnesium alloy （LA113） are compared and analyzed. Microstructures and phases of the alloys were studied with optical microscope （OM）, scanning electron microscope （SEM）, X-ray diffractometer （XRD） and energy dispersive spectrometer （EDS）. Mechanical properties of alloys were measured with tensile tester. The results show that yttrium and/or strontium additions produce a strong grain refining effect in LA113 alloy. AI2Y and AI4Sr, etc. phases with different morphologies are verified and exist inside the grain or at the grain boundaries, which directly impact on the mechanical properties of LA113 alloy. The results of tensile tests show that, the as-extruded LA113-1Y-1 Sr alloy obtains the optimal tensile property of which the tensile strength and elongation are 253.56 MPa and 18.12%, the tensile strength is increased by almost 25% compared with the as- extruded LA113 alloy.

Effects of SrO/Al_2O_3 Molar Ratio on the Luminescent Characteristics of Rare-Earth Strontium Aluminate Phosphors

The study on the effects of SrO/Al 2O 3 molar ratio on the crystalline phases and photoluminescence characteristics of strontium aluminate phosphors co-activated with Eu 2+ and Dy 3+ were conducted by X-ray powder diffractometry, fluorescence spectrometer and photometer. The strontium aluminate luminescent materials with different SrO/Al 2O 3 molar ratio emit the visible lights with different color tone after removal of excitation. The peak wavelengths of the emission spectra drift in the direction of short wave, the quantity of Sr 4Al 14O 25 crystalline phase increases and the afterglow time lengthens with the SrO/Al 2O 3 reduction. The results show that when the SrO/Al 2O 3 molar ratio is near 1, the photoluminescence materials have high luminescent intensity, and when it is near 0.75, they have long afterglow time. However, when SrO/Al 2O 3 molar ratio is more than 1, the luminescent materials appear strong alkaline in water solution; when SrO/Al 2O 3 molar ratio is much less than 0.75, the samples need a higher temperature to be sintered.

Strontium chloride-catalyzed one-pot synthesis of 4(3H)-quinazolinones under solvent-free conditions

Strontium chloride was used as an efficient and recyclable catalyst in one-pot condensation of anthranilic acid, ortho esters and amines leading to the formation of 4（3H）-quinazolinone derivatives in good yields at room temperature under solvent-free conditions.

Long Lasting Phosphorescence in Eu^(2+) and Ce^(3+) Co-Doped Strontium Borate Glasses

Long lasting phosphorescence (LLP) was observed in Eu2+, Ce3+ co-doped strontium borate glasses prepared under the reducing atmosphere due to the emission of both Eu2+ and Ce3+. The methods of photoluminescence, thermoluminescence and phosphorescence were used to study the samples, and possible mechanism was suggested. The co-doping of Ce3+ ions poisoned the phosphorescence emission of Eu2+ because of the competition to obtain the trapped electron. The phosphorescence of Ce3+ in the sample decays more quickly than that of Eu2+, which is suggested for the reason that the emission energy of Ce3+ is higher or the distance between Ce3+ and electron traps of the glasses is longer.

Effect of strontium and solidification rate on eutectic grain structure in an Al-13 wt% Si alloy

The influence of strontium addition and solidification rate on eutectic grain structure in a near-eutectic Al-Si alloy was investigated. The characteristic temperature of eutectic nucleation (TN),minimum temperature prior to recalescence (TM),and the growth temperature (TG) during cooling were determined by quantitative thermal analysis. All characteristic temperatures were found to decrease continuously with increasing Sr content and solidification rate. Microstructural analysis also revealed that the eutectic grain size decreases with increasing Sr content and solidi fication rate. Such eutectic grain refinement is attributed to the increased actual under-cooling ahead of the liquid/solid interface during solidification.

TEM observation of sintered permanent magnetic strontium ferrite

Sintered permanent magnetic strontium ferrites were studied using transmission electron microscopy to investigate the microstructure morphology and its correlation with the magnetic properties. The present study shows that the microstructure of sintered permanent magnetic strontium ferrites is an important parameter in determining their magnetic properties. The microstructure morphology in low-performance ferrite magnet is obviously different from high-performance one. The magnetic properties of sintered permanent strontium ferrite depend strongly on the orientation degree of strong magnetic crystals. The presence of ferric oxide phase in ferrite magnet can deteriorate the magnetic properties. Moreover, proper quantities of crystal defects are beneficial to high coercive force due to the fixing of magnetic domain.

Strontium Isotope Compositions of Hydrothermal Barite from the Yonaguni Ⅳ: Insight into Fluid/Sediment Interaction and Barite Crystallization Condition

Hydrothermal barite is a typical low-temperature mineral formed during the mixing of hydrothermal fluid and seawater.Because of its extremely low solubility,barite behaves as a close system after crystallization and preserves the geochemical fingerprint of hydrothermal fluid.In this study,the elemental contents and Sr isotope compositions of hydrothermal barites from the Yonaguni IV were determined using electron microprobe and LA-MC-ICP-MS respectively.On these bases,the fluid/sediment interaction during the hydrothermal circulation and physicochemical condition of barite crystallization were discussed.Results show that the 87 Sr/86 Sr values of hydrothermal barites from the Yonaguni IV are apparently higher than those of the seawater and associated volcanic rocks,indicating the sufficient interaction between the hydrothermal fluid and overlying sediment.Monomineral Sr abundance shows large variations,reflecting the changes in barite growth rate during the fluid mixing.The mineralization condition in the Yonaguni IV was unstable.During the crystallization of barite,hydrothermal fluid and seawater mixed in varying degrees,with the pro-portions of hydrothermal fluid varied from 36%to 72%.The calculated crystallization temperatures range from 109 to 220℃.Sediment plays a critical role during the mineralization process in the Yonaguni IV and incorporation of sediment component into hydrothermal system was prior to barite crystallization and sulfide mineralization.