The dehydroaramatization of methane over W-supported ZSM-5 with varying degrees of Li+ ion-exchanged catalysts was studied with and without oxygen at 1073 K and atmospheric pressure. Catalyst activity and stability we...The dehydroaramatization of methane over W-supported ZSM-5 with varying degrees of Li+ ion-exchanged catalysts was studied with and without oxygen at 1073 K and atmospheric pressure. Catalyst activity and stability were found to be influenced by the catalyst acidity related to Bronsted acid sites and by the presence of oxygen in the feed. The NH3-TPD and FTIR-pyridine results demonstrated that partially exchanged of H+ ions by Li+ into the W/HZSM-5 catalysts could be used to control the amount of strong acid sites on the catalyst surface. Without oxygen, the 3WHLi-Z (5:1) catalyst that has strong acid sites equal to nearly 74% of the original strong acid sites in the parent HZSM-5 exhibited the highest methane conversion and selectivity towards aromatics. However, the catalyst deactivated in a five hour period. In the presence of oxygen, the catalyst activity and stability could be improved further. The results of this study revealed that a suitable amount of strong Bronsted acid sites as well as oxygen addition in the feed increased the catalyst activity and stability. The 3WHLi-Z(5:1) catalyst exhibited improved performance in the dehydroaromatization of methane.展开更多
An experimental investigation of the saturation ion current densities （Jions） in hydrogen inductively coupled plasma （ICP） produced by a large-power （2-32 kW） radio frequency （RF） generator is reported, then s...An experimental investigation of the saturation ion current densities （Jions） in hydrogen inductively coupled plasma （ICP） produced by a large-power （2-32 kW） radio frequency （RF） generator is reported, then some reasonable explanations are given out. With the increase of RF power, the experimental results show three stages： in the first stage （2-14 kW）, the electron temperature will rise with the increase of RF power in the ICP, thus, the Jions increases continually as the electron temperature rises in the ICP. In the second stage （14 20 kW）, as some H- ions lead to the mutual neutralization （MN）, the slope of Jio^s variation firstly decreases then increases. In the third stage （20-32 kW）, both the electronic detachment （ED） and the associative detachment （AD） in the ICP result in the destruction of H- ions, therefore, the increased amplitude of the Jions in the third stage is weaker than the one in the first stage. In addition, with the equivalent transformer model, we successfully Explain that the Jions at different radial locations in ICP has the same rule. Finally, it is found that the Jions has nothing to do with the outer/inner puffing gas pressure ratio, which is attributed to the high-speed movement of hydrogen molecules.展开更多
Radiation-induced defect annealing in He<sup>+</sup> ion-implanted 4H-SiC via H<sup>+</sup> ion irradiation is investigated by Raman spectroscopy. There are 4H-SiC wafers irradiated with 230 ke...Radiation-induced defect annealing in He<sup>+</sup> ion-implanted 4H-SiC via H<sup>+</sup> ion irradiation is investigated by Raman spectroscopy. There are 4H-SiC wafers irradiated with 230 keV He<sup>+</sup> ions with fluences ranging from cm<sup>−2</sup> to cm<sup>−2</sup> at room temperature. The post-implantation samples are irradiated by 260 keV H<sup>+</sup> ions at a fluence of cm<sup>−2</sup> at room temperature. The intensities of Raman lines decrease after He implantation, while they increase after H irradiation. The experimental results present that the magnitude of Raman line increment is related to the concentration of pre-existing defects formed by He implantation. A strong new peak located near 966 cm<sup>−1</sup>, which is assigned to 3C-SiC LO () phonon, is found in the He-implanted sample with a fluence of cm<sup>−2</sup> followed by H irradiation. However, for the He-implanted sample with a fluence of cm<sup>−2</sup> followed by H irradiation, no 3C-SiC phonon vibrations are found. The detailed reason for H irradiation-induced phase transformation in the He-implanted 4H-SiC is discussed.展开更多
The negative ion yields φ (H?) and the neutral atom yields φ (H) of 0.6, 0.9, 1.2, 1.6 and 1.8 MeV H+ projectiles traversing various carbon foils have been measured. The experimental results showed that neither φ(H...The negative ion yields φ (H?) and the neutral atom yields φ (H) of 0.6, 0.9, 1.2, 1.6 and 1.8 MeV H+ projectiles traversing various carbon foils have been measured. The experimental results showed that neither φ(H?) nor φ(H) varies with the dwell time ^ at the same energy. φ(H)is larger than φ(H?) by about 3–4 orders of magnitude. The charge exchanging between H+ ions and carbon foils was analyzed. It can be seen that the charge exchange is the most basic process. The experience formula of σc/σl has been gotten.展开更多
The accelerator complex of the China Spallation Neutron Source (CSNS) consists of a H- linear accelerator (linac) and a rapid cycling synchrotron (RCS). The linac contains a Penning surface H- ion source. The designed...The accelerator complex of the China Spallation Neutron Source (CSNS) consists of a H- linear accelerator (linac) and a rapid cycling synchrotron (RCS). The linac contains a Penning surface H- ion source. The designed energy and the beam current of the source are 50 keV and 20 mA respectively, with a normalized root mean square (norm. rms.) emittance of 0.2π mm mrad. The manufactures and tests of the discharge chamber are in great progress. The construction of H- ion source test stand has been completed, and the operation of the source is also in progress. Stable H- ion beams with energy of 50 keV and current up to 50 mA are attained. Emittance measurement for the H- beam is being prepared.展开更多
A penning plasma surface H- ion source test stand for the CSNS has just been constructed at the IHEP. In order to achieve a safe and reliable system, nearly all devices of the ion source are designed to have the capab...A penning plasma surface H- ion source test stand for the CSNS has just been constructed at the IHEP. In order to achieve a safe and reliable system, nearly all devices of the ion source are designed to have the capability of both local and remote operation function. The control system consists of PLCs and EPICS real-time software tools separately serving device control and monitoring, PLC integration and OPI support. This paper summarizes the hardware and software implementation satisfying the requirements of the ion source control system.展开更多
文摘The dehydroaramatization of methane over W-supported ZSM-5 with varying degrees of Li+ ion-exchanged catalysts was studied with and without oxygen at 1073 K and atmospheric pressure. Catalyst activity and stability were found to be influenced by the catalyst acidity related to Bronsted acid sites and by the presence of oxygen in the feed. The NH3-TPD and FTIR-pyridine results demonstrated that partially exchanged of H+ ions by Li+ into the W/HZSM-5 catalysts could be used to control the amount of strong acid sites on the catalyst surface. Without oxygen, the 3WHLi-Z (5:1) catalyst that has strong acid sites equal to nearly 74% of the original strong acid sites in the parent HZSM-5 exhibited the highest methane conversion and selectivity towards aromatics. However, the catalyst deactivated in a five hour period. In the presence of oxygen, the catalyst activity and stability could be improved further. The results of this study revealed that a suitable amount of strong Bronsted acid sites as well as oxygen addition in the feed increased the catalyst activity and stability. The 3WHLi-Z(5:1) catalyst exhibited improved performance in the dehydroaromatization of methane.
基金supported by the National Magnetic Confinement Fusion Science Program of China(Nos.2011GB108011 and 2010GB103001)the Major International(Regional)Project Cooperation and Exchanges of China(No.11320101005)the Startup Fund from Fuzhou University(No.510071)
文摘An experimental investigation of the saturation ion current densities （Jions） in hydrogen inductively coupled plasma （ICP） produced by a large-power （2-32 kW） radio frequency （RF） generator is reported, then some reasonable explanations are given out. With the increase of RF power, the experimental results show three stages： in the first stage （2-14 kW）, the electron temperature will rise with the increase of RF power in the ICP, thus, the Jions increases continually as the electron temperature rises in the ICP. In the second stage （14 20 kW）, as some H- ions lead to the mutual neutralization （MN）, the slope of Jio^s variation firstly decreases then increases. In the third stage （20-32 kW）, both the electronic detachment （ED） and the associative detachment （AD） in the ICP result in the destruction of H- ions, therefore, the increased amplitude of the Jions in the third stage is weaker than the one in the first stage. In addition, with the equivalent transformer model, we successfully Explain that the Jions at different radial locations in ICP has the same rule. Finally, it is found that the Jions has nothing to do with the outer/inner puffing gas pressure ratio, which is attributed to the high-speed movement of hydrogen molecules.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11005130,11475229 and 91026002the Strategic Priority Research Program of Chinese Academy of Sciences under Grant No XDA03010301
文摘Radiation-induced defect annealing in He<sup>+</sup> ion-implanted 4H-SiC via H<sup>+</sup> ion irradiation is investigated by Raman spectroscopy. There are 4H-SiC wafers irradiated with 230 keV He<sup>+</sup> ions with fluences ranging from cm<sup>−2</sup> to cm<sup>−2</sup> at room temperature. The post-implantation samples are irradiated by 260 keV H<sup>+</sup> ions at a fluence of cm<sup>−2</sup> at room temperature. The intensities of Raman lines decrease after He implantation, while they increase after H irradiation. The experimental results present that the magnitude of Raman line increment is related to the concentration of pre-existing defects formed by He implantation. A strong new peak located near 966 cm<sup>−1</sup>, which is assigned to 3C-SiC LO () phonon, is found in the He-implanted sample with a fluence of cm<sup>−2</sup> followed by H irradiation. However, for the He-implanted sample with a fluence of cm<sup>−2</sup> followed by H irradiation, no 3C-SiC phonon vibrations are found. The detailed reason for H irradiation-induced phase transformation in the He-implanted 4H-SiC is discussed.
基金This work was supported by the National Natural Science Foundation of China (Grant Nos. 19735004, 19975033, 19975034).
文摘The negative ion yields φ (H?) and the neutral atom yields φ (H) of 0.6, 0.9, 1.2, 1.6 and 1.8 MeV H+ projectiles traversing various carbon foils have been measured. The experimental results showed that neither φ(H?) nor φ(H) varies with the dwell time ^ at the same energy. φ(H)is larger than φ(H?) by about 3–4 orders of magnitude. The charge exchanging between H+ ions and carbon foils was analyzed. It can be seen that the charge exchange is the most basic process. The experience formula of σc/σl has been gotten.
文摘The accelerator complex of the China Spallation Neutron Source (CSNS) consists of a H- linear accelerator (linac) and a rapid cycling synchrotron (RCS). The linac contains a Penning surface H- ion source. The designed energy and the beam current of the source are 50 keV and 20 mA respectively, with a normalized root mean square (norm. rms.) emittance of 0.2π mm mrad. The manufactures and tests of the discharge chamber are in great progress. The construction of H- ion source test stand has been completed, and the operation of the source is also in progress. Stable H- ion beams with energy of 50 keV and current up to 50 mA are attained. Emittance measurement for the H- beam is being prepared.
文摘A penning plasma surface H- ion source test stand for the CSNS has just been constructed at the IHEP. In order to achieve a safe and reliable system, nearly all devices of the ion source are designed to have the capability of both local and remote operation function. The control system consists of PLCs and EPICS real-time software tools separately serving device control and monitoring, PLC integration and OPI support. This paper summarizes the hardware and software implementation satisfying the requirements of the ion source control system.
