The intense blue emitting phosphors Sr2MgSiO5∶Ce 3+ were synthesized by high temperature solid state reaction method,and their luminescence properties were studied.The intense blue-emission band present a peak fixed ...The intense blue emitting phosphors Sr2MgSiO5∶Ce 3+ were synthesized by high temperature solid state reaction method,and their luminescence properties were studied.The intense blue-emission band present a peak fixed at 420 nm,which consists of two peaks located at 408 and 445 nm,respectively.The two peaks are originated from the transition 5d→ 2F 5/2（4f）and 5d→ 2F 7/2（4f）of Ce 3+ ions.The energy level difference value of the two emission bands is 2 038 cm-1,which is consistent with the theoretic value（2 000 cm-1）between the ground state:2F 5/2 and 2F 7/2 of Ce 3+ ions.The excitation spectra extend from 250 to 400 nm and the peak positions around 365 nm.In addition,the effect of the concentration of Ce 3+ ions and the role of charge compensation of different ions to the emission intense were investigated,the experiment results suggest that when the proportion of Ce 3+ ions to Sr2MgSiO5 were 0.03（molar ratio）,the strongest emission was obtained.Li+,Na+,K+ and Cl-ions can all enhance the intensity of the emissions;especially Cl-ions gave the best improvement.展开更多
根据硅镁型红土镍矿中镁硅酸盐存在形式,采用化学沉淀法合成Mg Si O3,通过正交实验考察反应温度、反应时间、液固比和Na OH浓度对Mg Si O3在Na OH亚熔盐体系中的浸出过程的影响,得出优化实验条件为:反应温度为210℃,反应时间为180min,...根据硅镁型红土镍矿中镁硅酸盐存在形式,采用化学沉淀法合成Mg Si O3,通过正交实验考察反应温度、反应时间、液固比和Na OH浓度对Mg Si O3在Na OH亚熔盐体系中的浸出过程的影响,得出优化实验条件为:反应温度为210℃,反应时间为180min,液固比为6:1,Na OH浓度为80%。在优化实验的基础上,采用Raman光谱对反应过程进行在线检测,利用XRD和IR光谱分析反应后的水浸渣结构变化,解析Mg Si O3在Na OH亚熔盐体系中的反应机理。结果表明:在反应过程中,Si O4中的Si—O被破坏,Na OH介入硅酸盐晶格中,其中间产物为Mg2Si O4和Na2Mg Si O4,Mg2+经过碱浸过程可以脱离Si O4阵列,以Mg(OH)2形式从其硅酸盐中得以释放。展开更多
We report the effects of MgSiO3 addition on the crystal growth and characteristics of type-Ib diamonds synthesized in Fe–Ni–C system. The experiments were carried out with pressure at 5.5 GPa, temperature at 1385℃...We report the effects of MgSiO3 addition on the crystal growth and characteristics of type-Ib diamonds synthesized in Fe–Ni–C system. The experiments were carried out with pressure at 5.5 GPa, temperature at 1385℃–1405℃, and duration of 23.1 h. As MgSiO3 increases from 0.0 wt% to 3.0 wt%, the diamond growth temperature increases from1385℃ to 1405℃, the addition of MgSiO3 and the movement of P–T diagram toward the higher temperature direction result in a series of effects to the Fe–Ni–C system and crystal growth. Firstly, it increases the content of metastable recrystallized graphite and accelerates the competition with the carbon source needed for diamond growth, thus causing the decreased crystal growth rate. Diamond crystals exhibit the combination form of {111}, {100}, {113}, and {110}sectors, the decreased {100} and {113} sectors, dominated {111} sector are all attributed to the higher growth rate in [100]direction caused by the synergy of MgSiO3 and the movement of P–T diagram. The higher growth rate in [100] direction also increases the metal catalyst and graphite inclusions and leads to the increase of residual tensile stress on the crystal surface. Accompanying with the high growth rate, a higher dissolution rate along [100] and [113] directions than [111]direction occurs at the microstructure and forms the significantly developed(111) stepped growth layer. In addition to the movement of P–T diagram, the addition of MgSiO3 poisons the catalyst and increases the nitrogen content of diamond from 120 ppm to 227 ppm.展开更多
The equation of state of MgSiO3 perovskite under high pressure and high temperature is simulated using the molecular dynamics method. It was found that the molecular dynamics simulation is very successful in accuratel...The equation of state of MgSiO3 perovskite under high pressure and high temperature is simulated using the molecular dynamics method. It was found that the molecular dynamics simulation is very successful in accurately reproducing the measured molar volumes of MgSiO3 perovskite over a wide range of temperatures and pressures. The simulated equation of state of MgSiO3 perovskite matched experimental data at up to 140GPa at 300K, as well as the fitting data of others and results from the first-principles simulation based on the local density approximation. The simulated equations of state of MgSiO3 perovskite at higher temperatures and higher pressures also correspond to the other calculations. In addition, the volume compression data of MgSiO3 perovskite is simulated up to 120 GPa at 300, 900, 2000 and 3000 K, respectively.展开更多
文摘The intense blue emitting phosphors Sr2MgSiO5∶Ce 3+ were synthesized by high temperature solid state reaction method,and their luminescence properties were studied.The intense blue-emission band present a peak fixed at 420 nm,which consists of two peaks located at 408 and 445 nm,respectively.The two peaks are originated from the transition 5d→ 2F 5/2（4f）and 5d→ 2F 7/2（4f）of Ce 3+ ions.The energy level difference value of the two emission bands is 2 038 cm-1,which is consistent with the theoretic value（2 000 cm-1）between the ground state:2F 5/2 and 2F 7/2 of Ce 3+ ions.The excitation spectra extend from 250 to 400 nm and the peak positions around 365 nm.In addition,the effect of the concentration of Ce 3+ ions and the role of charge compensation of different ions to the emission intense were investigated,the experiment results suggest that when the proportion of Ce 3+ ions to Sr2MgSiO5 were 0.03（molar ratio）,the strongest emission was obtained.Li+,Na+,K+ and Cl-ions can all enhance the intensity of the emissions;especially Cl-ions gave the best improvement.
文摘根据硅镁型红土镍矿中镁硅酸盐存在形式,采用化学沉淀法合成Mg Si O3,通过正交实验考察反应温度、反应时间、液固比和Na OH浓度对Mg Si O3在Na OH亚熔盐体系中的浸出过程的影响,得出优化实验条件为:反应温度为210℃,反应时间为180min,液固比为6:1,Na OH浓度为80%。在优化实验的基础上,采用Raman光谱对反应过程进行在线检测,利用XRD和IR光谱分析反应后的水浸渣结构变化,解析Mg Si O3在Na OH亚熔盐体系中的反应机理。结果表明:在反应过程中,Si O4中的Si—O被破坏,Na OH介入硅酸盐晶格中,其中间产物为Mg2Si O4和Na2Mg Si O4,Mg2+经过碱浸过程可以脱离Si O4阵列,以Mg(OH)2形式从其硅酸盐中得以释放。
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51772120,51872112,and 11804305)the China Postdoctoral Science Foundation(Grant No.2017M622360)the Project of Jilin Science and Technology Development Plan(Grant No.20180201079GX).
文摘We report the effects of MgSiO3 addition on the crystal growth and characteristics of type-Ib diamonds synthesized in Fe–Ni–C system. The experiments were carried out with pressure at 5.5 GPa, temperature at 1385℃–1405℃, and duration of 23.1 h. As MgSiO3 increases from 0.0 wt% to 3.0 wt%, the diamond growth temperature increases from1385℃ to 1405℃, the addition of MgSiO3 and the movement of P–T diagram toward the higher temperature direction result in a series of effects to the Fe–Ni–C system and crystal growth. Firstly, it increases the content of metastable recrystallized graphite and accelerates the competition with the carbon source needed for diamond growth, thus causing the decreased crystal growth rate. Diamond crystals exhibit the combination form of {111}, {100}, {113}, and {110}sectors, the decreased {100} and {113} sectors, dominated {111} sector are all attributed to the higher growth rate in [100]direction caused by the synergy of MgSiO3 and the movement of P–T diagram. The higher growth rate in [100] direction also increases the metal catalyst and graphite inclusions and leads to the increase of residual tensile stress on the crystal surface. Accompanying with the high growth rate, a higher dissolution rate along [100] and [113] directions than [111]direction occurs at the microstructure and forms the significantly developed(111) stepped growth layer. In addition to the movement of P–T diagram, the addition of MgSiO3 poisons the catalyst and increases the nitrogen content of diamond from 120 ppm to 227 ppm.
基金This work was supported by the National Natural Sci- ence Foundation of China, （NSFC No. 10274055）, the Natural Science Foundation of Gansu Province of China （No. 3ZS051-A25-027） and the Natural Science Foundation of Education Department of Gansu Province of China （No. 0410-01）.
文摘The equation of state of MgSiO3 perovskite under high pressure and high temperature is simulated using the molecular dynamics method. It was found that the molecular dynamics simulation is very successful in accurately reproducing the measured molar volumes of MgSiO3 perovskite over a wide range of temperatures and pressures. The simulated equation of state of MgSiO3 perovskite matched experimental data at up to 140GPa at 300K, as well as the fitting data of others and results from the first-principles simulation based on the local density approximation. The simulated equations of state of MgSiO3 perovskite at higher temperatures and higher pressures also correspond to the other calculations. In addition, the volume compression data of MgSiO3 perovskite is simulated up to 120 GPa at 300, 900, 2000 and 3000 K, respectively.
