Control on Crystal Forms of Ultrafine Barium Carbonate Particles and Study on its Mechanism

Barium carbonate particles were prepared by using homogeneous precipitation method and co-precipitation method respectively. Through adding different crystalline controlling modifiers, Barium carbonate particles in five different shapes including linear, needle-like, pillarlike, sphere-like and dumbbell-like were synthesized. These particles were characterized by SEM and XRD, and their synthetic mechanism was discussed in this paper.

A New Route to the Synthesis of Barium Carbonate Crystals by the Induction of Bacillus Pasteurii

As one of the soil microorganisms, bacillus pasteurii exhibits good urease-produ-cing ability. A novel method is used to prepare BaCO3 crystals by the induction of bacillus pasteurii. The crystals have been characterized by XRD, SEM and FT-IR. X-ray diffraction analysis quantified that the BaCO3 crystals obtained belong to the orthorhombic crystal system. Examination by scanning electron microscopy identified that the BaCO3 crystals have different morphologies under different preparation conditions. FT-IR indicated that surfactant EDTA had great effect on the morphology of BaCO3 crystals. Different morphology crystals had uniform distribution and integral shape. The forming mechanism and influence of EDTA on the morphology of BaCO3 crystals have been discussed.

Study on the Forming Mechanism and Preparation of Different Morphology of Barium Carbonate Crystals with Diethyl Carbonate as Raw Material

Different morphologies of BaCO3 crystals with dendritic structure,spinous sphere structure,and spike-,flower-and rod-like structures were prepared with（C2H5）2CO3 and BaCl2.2H2O as raw materials by homogeneous precipitation method.The crystals have been characterized by SEM,FT-IR and XRD,indicating that the different morphology of BaCO3 crystals belongs to the orthorhombic crystal system with uniform distribution and integral shapes.The effect of reaction conditions and the possible formation mechanism on the morphology of BaCO3 crystals have been discussed.

Simultaneous structure and luminescence property control of barium carbonate nanocrystals through small amount of lanthanide doping

Rare earth doping has been widely applied in many functional nanomaterials with desirable properties and functions,which would have a significant effect on the growth process of the materials.However,the controlling strategy is limited into high concentration of lanthanide doping,which produces concentration quenching of the lanthanide ion luminescence with an increase in the Ln^(3+)concentration,resulting in lowering the fluorescence quantum yield of lanthanide ion.Herein,for the first time,we demonstrate simultaneous control of the structures and luminescence properties of BaCO_3nanocrystals via a small amount of Tb^(3+)doping strategy.In fact,Tb^(3+)would partially occupy Ba^(2+)sites,resulting in the changes to the structures of the BaCO_3nanocrystals,which is primarily determined by charge modulation,including the contributions from the surfaces of crystal nuclei and building blocks.These structurally modified nanocrystals exhibit tunable luminescence properties,thus emerging as potential candidates for photonic devices such as light-emitting diodes and color displays.

An integrated technology for the absorption and utilization of CO_(2)in alkanolamine solution for the preparation of BaCO_(3)in a high-gravity environment

In this study,an integrated technology is proposed for the absorption and utilization of CO_(2)in alkanolamine solution for the preparation of BaCO_(3)in a high-gravity environment.The effects of absorbent type,high-gravity factor,gas/liquid ratio,and initial BaCl2concentration on the absorption rate and amount of CO_(2)and the preparation of BaCO_(3)are investigated.The results reveal that the absorption rate and amount of CO_(2)follow the order of ethyl alkanolamine(MEA)>diethanol amine(DEA)>N-methyldiethanolamine(MDEA),and thus MEA is the most effective absorbent for CO_(2)absorption.The absorption rate and amount of CO_(2)under high gravity are higher than that under normal gravity.Notably,the absorption rate at 75 min under high gravity is approximately 2 times that under normal gravity.This is because the centrifugal force resulting from the high-speed rotation of the packing can greatly increase gas-liquid mass transfer and micromixing.The particle size of BaCO_(3)prepared in the rotating packed bed is in the range of 57.2—89 nm,which is much smaller than that prepared in the bubbling reactor(>100.3 nm),and it also has higher purity(99.6%)and larger specific surface area(14.119 m^(2)·g^(-1)).It is concluded that the high-gravity technology has the potential to increase the absorption and utilization of CO_(2)in alkanolamine solution for the preparation of BaCO_(3).This study provides new insights into carbon emissions reduction and carbon utilization.

Formation of hydrogen in oxidative coupling of methane over BaCO_3 and MgO catalysts

Hydrogen formed in oxidative coupling of methane （OCM） over BaCO3 and MgO catalysts was measured since the data of H2 selectivity were missing almost in all articles published heretofore. It was found that H2 selectivity achieved about 18%, when C2 hydrocarbon＇s selectivity was maintained at 48%-45% over BaCO3 catalyst at the feed molar ratio of CH4/O2 = 4 in temperature range of 780 °C-820 °C. Under similar conditions, H2 selectivity was about 14%-16% over MgO catalyst, with C2 selectivity maintained at 41%-42%. Possible routes for hydrogen formation in OCM reaction were discussed. Effect of addition of alkali metallic ions was also investigated.

Ordered mesoporous Ba CO_3/C-catalyzed synthesis of glycerol carbonate from glycerol and dimethyl carbonate

Ordered mesoporous BaCO3/C composites were synthesized by a multi-component co-assembly method combined with a carbonization process using phenolic resol as carbon source, barium nitrate as barium precursor, and triblock copolymer Pluronic F127 as template. The synthesized materials were characterized by X-ray diffraction, transmission electron microscopy, N2 physical adsorption, thermogravimetric analysis, and temperature-programmed desorption of CO〉 When BaCO3 contents were increased from 9.1 wt% to 44.7 wt%, pore size increased from 3.1 to 4.3 nm and the BET （Brunauer-Emmett-Teller） surface area initially increased to a maximum value of 390 m2 g^-1 （at a BaCO3 content of 18.5 wt%） before subsequently decreasing. BaCO3 was well dispersed in the amorphous carbon framework, and no phase separation was observed. The mesoporous BaCO3/C composites exhibited high catalytic activities toward the transesterification of glycerol and dimethyl carbonate into glycerol carbonate. A glycerol conversion of 97.8% and a glycerol carbonate selectivity of 98.5% were obtained under the optimized reaction conditions.