Nanocrystalline BaCO 3 was synthesized at ambient temperature by solid state reactions. Phase, particle size and morphology of the prepared nanocrystallite were characterized by XRD and TEM. The crystallite product ha...Nanocrystalline BaCO 3 was synthesized at ambient temperature by solid state reactions. Phase, particle size and morphology of the prepared nanocrystallite were characterized by XRD and TEM. The crystallite product has a size about 30 nm. The effects of a series of reaction conditions on the synthesis of BaCO 3 are studied.展开更多
We investigated the effects of different barium compounds on the thaumasite form of sulphate attack（TSA）resistance of cement-based materials when they were used as admixtures in mortars.Moreover,we analyzed the inhi...We investigated the effects of different barium compounds on the thaumasite form of sulphate attack（TSA）resistance of cement-based materials when they were used as admixtures in mortars.Moreover,we analyzed the inhibition mechanisms within different types of barium salts,namely BaCO_3 and Ba（OH）_2,on the thaumasite formation.The controlcement mortar and mortars with barium salts to cement and limestone weight ratios of 0.5%,1.0%,and 1.5% were immersed in 5%（by weight）MgSO_4 solution at 5 ℃ to mimic TSA.Appearance,mass,and compressive strength of the mortar samples were monitored and measured to assess the generaldegradation extent of these samples.The products of sulphate attack were further analyzed by XRD,FTIR,and SEM,respectively.Experimentalresults show that different degradation extent is evident in allmortars cured in MgSO_4 solution.However,barium salts can greatly inhibit such degradation.Barium in hydroxide form has better effectiveness in protection against TSA than carbonate form,which may be due to their solubility difference in alkaline cement pore solution,and the presence of these barium compounds can reduce the degree of TSA by comparison with the almost completely decomposed controlsamples.展开更多
A pure phase BaCo_(0.5)Fe_(0.5)O_(3–δ)(BCF),which cannot be obtained before,is successfully prepared in this study by using the calcination method with a rapid cooling procedure.The successful preparation of BCF all...A pure phase BaCo_(0.5)Fe_(0.5)O_(3–δ)(BCF),which cannot be obtained before,is successfully prepared in this study by using the calcination method with a rapid cooling procedure.The successful preparation of BCF allows the evaluation of this material as a cathode for proton-conducting solid oxide fuel cells(H-SOFCs)for the first time.An H-SOFC using the BCF cathode achieves an encouraging fuel cell performance of 2012 mW·cm–2 at 700,two℃-fold higher than that of a similar cell using the classical high-performance Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3–δ)(BSCF)cathode.First-principles calculations reveal the mechanism for the performance enhancement,indicating that the new BCF cathode significantly lowers the energy barriers in the oxygen reduction reaction(ORR)compared with the BSCF cathode.Therefore,improved cathode performance and fuel cell output are obtained for the BCF cell.The fuel cell using the BCF cathode also shows excellent long-term stability that can work stably for nearly 900 h without noticeable degradations.The fuel cell performance and long-term stability of the current BCF cell are superior to most of the H-SOFCs reported in previous reports,suggesting that BCF is a promising cathode for H-SOFCs.展开更多
文摘Nanocrystalline BaCO 3 was synthesized at ambient temperature by solid state reactions. Phase, particle size and morphology of the prepared nanocrystallite were characterized by XRD and TEM. The crystallite product has a size about 30 nm. The effects of a series of reaction conditions on the synthesis of BaCO 3 are studied.
基金Funded by the National Natural Science Foundation of China(No.51372076)the Project of Science&Technology Department of Hubei Province(No.2014BCB027)
文摘We investigated the effects of different barium compounds on the thaumasite form of sulphate attack（TSA）resistance of cement-based materials when they were used as admixtures in mortars.Moreover,we analyzed the inhibition mechanisms within different types of barium salts,namely BaCO_3 and Ba（OH）_2,on the thaumasite formation.The controlcement mortar and mortars with barium salts to cement and limestone weight ratios of 0.5%,1.0%,and 1.5% were immersed in 5%（by weight）MgSO_4 solution at 5 ℃ to mimic TSA.Appearance,mass,and compressive strength of the mortar samples were monitored and measured to assess the generaldegradation extent of these samples.The products of sulphate attack were further analyzed by XRD,FTIR,and SEM,respectively.Experimentalresults show that different degradation extent is evident in allmortars cured in MgSO_4 solution.However,barium salts can greatly inhibit such degradation.Barium in hydroxide form has better effectiveness in protection against TSA than carbonate form,which may be due to their solubility difference in alkaline cement pore solution,and the presence of these barium compounds can reduce the degree of TSA by comparison with the almost completely decomposed controlsamples.
基金supported by the National Natural Science Foundation of China(Grant Nos.52272216 and 51972183)the Hundred Youth Talents Program of Hunan,and the Startup Funding for Talents at University of South China.
文摘A pure phase BaCo_(0.5)Fe_(0.5)O_(3–δ)(BCF),which cannot be obtained before,is successfully prepared in this study by using the calcination method with a rapid cooling procedure.The successful preparation of BCF allows the evaluation of this material as a cathode for proton-conducting solid oxide fuel cells(H-SOFCs)for the first time.An H-SOFC using the BCF cathode achieves an encouraging fuel cell performance of 2012 mW·cm–2 at 700,two℃-fold higher than that of a similar cell using the classical high-performance Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3–δ)(BSCF)cathode.First-principles calculations reveal the mechanism for the performance enhancement,indicating that the new BCF cathode significantly lowers the energy barriers in the oxygen reduction reaction(ORR)compared with the BSCF cathode.Therefore,improved cathode performance and fuel cell output are obtained for the BCF cell.The fuel cell using the BCF cathode also shows excellent long-term stability that can work stably for nearly 900 h without noticeable degradations.The fuel cell performance and long-term stability of the current BCF cell are superior to most of the H-SOFCs reported in previous reports,suggesting that BCF is a promising cathode for H-SOFCs.
