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[en] Ba2.98-xSrxEu0.02MgSi2O8 (x ≤ 0.365) exhibited emission-color change when exposed to the light from a Xe arc-lamp. Blue emission observed from the above phosphors turned purple after the photostimulation because of 608-nm emission centers arising. The degree of the spectral change monotonically decreased with increasing Sr-replacement x, and became undetectable when x exceeded 0.490. This x value coincided with that dividing the structural symmetry between P (Z = 3) and Pm1 (Z = 1). This coincidence indicates that structural distortion caused by B-site Ba2+ ions contributes to the photostimulated emission-color change of the Eu2+-doped glaserite-type alkali-earth magnesium silicates.
[en] Nitrogen contents and isotopic ratios have been determined for three clasts from the enstatite chondrite Abee by stepwise heating. The clasts possess a wide range in nitrogen content, ranging from 254 to 850 ppm, whereas the nitrogen isotopic ratios are nearly identical at delta15N = -29.2 +- 0.6per mille. A refractory inorganic nitrogen-bearing phase contains about 90% of the nitrogen which is released at temperatures of 10000C and above. The stepwise heating experiments suggest the possible existence of two other distinct nitrogen components, released at low (7700C) and high (15000C) temperatures. (orig.)
[en] The morphology and structural form of Tb doped magnesium silicate are reported as a function of the dopant concentration of Tb. The preparation method is described. This includes a sintering step which is time sensitive and an optimum processing time is discussed to improve dosimeter sensitivity. The thermoluminescence spectra are remarkable as they reveal peak shifts in the temperature of the characteristic lines of the Tb dopant. A model related to charge capture by different upper state orbitals of the rare earth transitions is offered. Optically stimulated luminescence data are also included. - Highlights: • Thermoluminescence spectra of terbium doped Mg_2SiO_4 are reported. • Glow peak shifts of the characteristic lines of terbium are reported. • A model related to charge capture by different upper state orbitals of the rare earth transitions is offered.
[en] Complete text of publication follows. Talcum powder is the main raw material of toilet powder.That is with various amounts of asbestos due to different mineral origin. Exposure to asbestos can cause the cancer.In April 2009,asbestos incident was reported by Chinese government,trace asbestos was detected in some foreign brand bath powder product. Talcum powder (3MgO x 4SiO2 x H2O) is magnesium silicate mineral talcum, and its main content is hydrous magnesium silicate, scrubbed with water, dried after through hydrochloric acid treatment, after crushing. In the production technique of talcum powder, the asbestos in talcum powder is called asbestos (acid washed) after hydrochloric acid treatment. Take dried sample and grind and mix with KBr at certain proportion, and make into Oe13mm KBr wafer. IR spectra of chrysotile, asbestos (acid washed) and talcum powder were obtained by this method. 958 cm-1 and 607 cm-1 in the IR spectra of three contrast samples can be characteristic identification peaks of chrysotile. 949 cm-1 and 756 cm-1 are characteristic peaks of asbestos (acid washed),and those peakes can be used for identification. There is mainly SiO2 in tested sample, the broad body of IR strong absorption peak (∼1018 cm-1) conceals the valuable identification area of 1150-850 cm-1. and sample has weak absorption peak at 756 cm-1, Overlap 756 cm-1 peak of sample and IR spectra of asbestos (acid washed), and it is proved that the peak is attributed to asbestos (acid washed).The spectral peak was treated in second derivative and proved that there was one shoulder peak at area 949 cm-1, According to spectral peak at 756 cm-1 and 949 cm-1, it can be concluded that trace of asbestos (acid washed) exist in tested sample. During the quantitative analysis, enlarge 10 times of sample to weigh, prepare 4 standard samples of different contents of asbestos (acid washed), 0.25%, 1.0%, 2.5% and 5% in toilet powder. Draw calibration curve with peak area (A) at 756 cm-1 as vertical coordinate and concentration (C) of asbestos (acid washed) as horizontal coordinate. The linear relation is good within the calibration curve (R=0.9995). The method has the advantages of high sensibility, simple method, rapid test, intuitionistic and reliable results, which is an effective means to detect the existence of asbestos in toilet powder.
[en] The sorption of uranium(VI) from aqueous solutions was investigated using synthesized magnesium silicate hollow spheres as a novel adsorbent. Batch experiments were conducted to study the effects of initial pH, amount of adsorbent, contact time and initial U(VI) concentrations on uranium sorption efficiency. The desorbing of U(VI) and the effect of coexisting ions were also investigated. Kinetic studies showed that the sorption followed a pseudo-second-order kinetic model. The Langmuir sorption isotherm model correlates well with the uranium sorption equilibrium data for the concentration range of 25-400 mg/L. The maximum uranium sorption capacity onto magnesium silicate hollow spheres was estimated to be about 107 mg/g under the experimental conditions. Desorption of uranium was achieved using inorganic acid as the desorbing agent. The practical utility of magnesium silicate hollow spheres for U(VI) uptake was investigated with high salt concentration of intercrystalline brine. This work suggests that magnesium silicate hollow spheres can be used as a highly efficient adsorbent for removal of uranium from aqueous solutions. (author)
[en] Thermoluminescence (TL) properties of Magnesium Ortho silicate (2:1) Mg2SiO4 doped with various concentrations of rare earth (Nd) have been studied. The phosphor material were prepared using standard solid state reaction technique and heated specimens at 1100 ± 20 deg C for two hours. 4% Ammonium chloride was used as flux. The received material was grinded in an agate mortar and pestle. The TL exhibited by the Mg2SiO4 with varying concentration of Nd is interesting in nature. It is interesting to note but as the concentration of Nd increases the peak around 125 deg C TL peak intensity increases. But the hump around 200 deg C resolved as TL peak at 253 deg C with high intensity. (author)
[en] Crystalline spheres of the silicate forsterite (Mg2SiO4), with a mean diameter of around 600 A, were prepared in the laboratory. Their infrared extinction in the region 1100--400 cm-1 was quantitatively measured and the results were compared with the work of other authors and with Mie theory calculations. The extremely sharp spikes predicted by Mie theory were not realized, though agreement with peak positions and integrated absorption strengths was good
[en] Oxygen isotopic compositions have been measured for ten EH chondrites, eight EL chondrites, and nine aubrites. The mean delta O-18 and delta O-17 values are: 5.31 and 2.74, 5.57 and 2.96, 5.24 and 2.70, respectively. Within the EH group, more equilibrated meteorites are fractionated toward higher heavy isotope abundances than the less equilibrated meteorites. Small departures of individual meteorites from a common mass fractionation occur for some of the EH samples. The aubrites may be genetically related to either the EH or EL group or to both. Almost all of the measured isotopic compositions are indistinguishable from the terrestrial oxygen isotope fractionation line, suggesting a genetic relationship among the earth, the moon, and the enstatite meteorites
[en] Nuclear track records in fourteen samples taken from different locations of a cut-slab of the Abee enstatite chondrite were studied to determine its pre-atmospheric mass and to delineate its cosmic ray exposure history. The measured track densities in different samples range from 104 to 106 cm-2. No significant variations in track densities for individual grains from a given location was found. Excess tracks of fissionogenic origin were found near the grain edges, and across cleavage planes in eight enstatite grains out of approx.= 300 grains analysed in the present work. The compaction age of the meteorite could not be obtained due to the absence of suitable oldhamite-enstatite contacts in thick sections. The track data rule out pre-irradiation of any of the analysed samples with shielding less than a few tens of centimeter. The iso-track-density contours on the plane of the slab imply an asymmetric ablation of the Abee chondrite during its atmospheric transit. A spherical body having a radius of approx.= 30 cm closely approximates the pre-atmospheric shape and size of the Abee meteorite. The mass loss during ablation was approx.= 70% of the original mass. (orig.)