The effect of drying techniques on the microstructure,morphology and pore structure of porous silica gels was studied in the paper.The gels were prepared by using sol-gel process and different drying routes:freeze-dry...The effect of drying techniques on the microstructure,morphology and pore structure of porous silica gels was studied in the paper.The gels were prepared by using sol-gel process and different drying routes:freeze-drying (FD),low pressure drying (LPD),high temperature drying (HTD) and chemical modification & ambient drying (CMD) techniques.Observation under pore distribution and structural properties showed that CMD technique leads to homogenous mesoporous silica material with specific surface area of 745 m2/g,and the average pore size around 20 nm,while LPD and HTD result in loosely packed particles with non-isotropic aggregation pattern.The specific surface areas of LPD and HTD samples are 419 and 513 m2/g respectively,and the pore size distribution of the samples are observed distributing widely in range of 10-100 nm.Freeze drying method is a new but prospective way to prepare mesoporous silica.The specific area of FD sample is around 500 m2/g.By the comparison for the properties of the gels,this paper wants to induce a further interest in finding a proper method to synthesize the porous silica gels for low price use.展开更多
The cross sections of the^(169)Tm(n,2n)^(168)Tm reaction have been measured at incident energies of 12 to 19.8 MeV using the activation technique,relative to the^(93)Nb(n,2n)^(92)mNb reaction.Thulium(Tm)samples were i...The cross sections of the^(169)Tm(n,2n)^(168)Tm reaction have been measured at incident energies of 12 to 19.8 MeV using the activation technique,relative to the^(93)Nb(n,2n)^(92)mNb reaction.Thulium(Tm)samples were irradiated on the surface of a two-ring orientation assembly with neutrons produced from the^(3)H(d,n)^(4)He reaction at the 5SDH-21.7-MV Tandem accelerator in China.Theoretical model calculations were performed.The present data were then compared with previous experimental data and available evaluated data.This study provides more precise nuclear data for improvement of future evaluations.展开更多
Cross-sections for （n, 2n） reactions have been measured on stannum isotopes at the neutron energies of 13.5 to 14.6 MeV using the activation technique. Data are reported for the following reactions： ^112Sn（n, 2n）...Cross-sections for （n, 2n） reactions have been measured on stannum isotopes at the neutron energies of 13.5 to 14.6 MeV using the activation technique. Data are reported for the following reactions： ^112Sn（n, 2n）^111Sn, ^118Sn（n, 2n）^117Sn and ^124Sn（n, 2n）^123mSn. The neutron fluences were determined using the monitor reaction ^93Nb（n, 2n）^92mNb or ^27Al（n, α）^24Na. The results of present work were compared with data published previously.展开更多
Cross-section data of the^(185)Re(n,2n)^(184)mRe,^(185)Re(n,2n)^(184)gRe,^(185)Re(n,α)182m1+m2+gTa,^(187)Re(n,2n)^(186)g,(m)Re,^(187)Re(n,α)^(184)Ta,and^(187)Re(n,p)^(187)W reactions were measured at four neutron en...Cross-section data of the^(185)Re(n,2n)^(184)mRe,^(185)Re(n,2n)^(184)gRe,^(185)Re(n,α)182m1+m2+gTa,^(187)Re(n,2n)^(186)g,(m)Re,^(187)Re(n,α)^(184)Ta,and^(187)Re(n,p)^(187)W reactions were measured at four neutron energies,namely 13.5,14.1,14.4,and 14.8 MeV,by means of the activation technique,relative to the reference cross-section values of the 93Nb(n,2n)92mNb reaction.The neutrons were generated from the T(d,n)4He reaction at the K-400 Neutron Generator at China Academy of Engineering Physics.The inducedγactivities were measured using a high-resolutionγ-ray spectrometer equipped with a coaxial high-purity germanium detector.The excitation functions of the six above-mentioned nuclear reactions at neutron energies from the threshold to 20 MeV were calculated by adopting the nuclear theoretical model program system Talys-1.9 with the relevant parameters properly adjusted.The measured cross sections were analyzed and compared with previous experiments conducted by other researchers,and with the evaluated data of BROND-3.1,ENDF/B-VIII.0,JEFF-3.3,and the theoretical values based on Talys-1.9.The new measured results agree with those of previous experiments and the theoretical excitation curve at the corresponding energies.The theoretical excitation curves based on Talys-1.9 generally match most of experimental data well.展开更多
The cross-section data of the 85Rb(n,2 n)84Rb reaction have been measured with the neutron energies of 12 MeV to 19.8 MeV using the activation technique and the relative method.The 85Rb samples were irradiated on the ...The cross-section data of the 85Rb(n,2 n)84Rb reaction have been measured with the neutron energies of 12 MeV to 19.8 MeV using the activation technique and the relative method.The 85Rb samples were irradiated on the surface of a two-ring orientation assembly with neutrons produced from the 3H(d,n)4He reaction at the 5SDH-21.7-MV Tandem accelerator in China.Theoretical model calculations were performed with the TALYS-1.9 code.The present data were compared with previously obtained experimental data and the available evaluated data.展开更多
基金Sponsored by the National Mega-Project of Scientific & Technical Supporting Programs,Ministry of Science &Technology of China (Grant No.2006BAJ04A04)the Science Foundation of Liaoning Province,China (Grant No. 2008S190)
文摘The effect of drying techniques on the microstructure,morphology and pore structure of porous silica gels was studied in the paper.The gels were prepared by using sol-gel process and different drying routes:freeze-drying (FD),low pressure drying (LPD),high temperature drying (HTD) and chemical modification & ambient drying (CMD) techniques.Observation under pore distribution and structural properties showed that CMD technique leads to homogenous mesoporous silica material with specific surface area of 745 m2/g,and the average pore size around 20 nm,while LPD and HTD result in loosely packed particles with non-isotropic aggregation pattern.The specific surface areas of LPD and HTD samples are 419 and 513 m2/g respectively,and the pore size distribution of the samples are observed distributing widely in range of 10-100 nm.Freeze drying method is a new but prospective way to prepare mesoporous silica.The specific area of FD sample is around 500 m2/g.By the comparison for the properties of the gels,this paper wants to induce a further interest in finding a proper method to synthesize the porous silica gels for low price use.
基金Supported by the National Natural Science Foundation of China(12075216)。
文摘The cross sections of the^(169)Tm(n,2n)^(168)Tm reaction have been measured at incident energies of 12 to 19.8 MeV using the activation technique,relative to the^(93)Nb(n,2n)^(92)mNb reaction.Thulium(Tm)samples were irradiated on the surface of a two-ring orientation assembly with neutrons produced from the^(3)H(d,n)^(4)He reaction at the 5SDH-21.7-MV Tandem accelerator in China.Theoretical model calculations were performed.The present data were then compared with previous experimental data and available evaluated data.This study provides more precise nuclear data for improvement of future evaluations.
基金Supported by Natural Science Foundation of Gansu Province(3ZS042-B25-026)
文摘Cross-sections for （n, 2n） reactions have been measured on stannum isotopes at the neutron energies of 13.5 to 14.6 MeV using the activation technique. Data are reported for the following reactions： ^112Sn（n, 2n）^111Sn, ^118Sn（n, 2n）^117Sn and ^124Sn（n, 2n）^123mSn. The neutron fluences were determined using the monitor reaction ^93Nb（n, 2n）^92mNb or ^27Al（n, α）^24Na. The results of present work were compared with data published previously.
基金Supported by National Natural Science Foundation of China(11605099,11575090)。
文摘Cross-section data of the^(185)Re(n,2n)^(184)mRe,^(185)Re(n,2n)^(184)gRe,^(185)Re(n,α)182m1+m2+gTa,^(187)Re(n,2n)^(186)g,(m)Re,^(187)Re(n,α)^(184)Ta,and^(187)Re(n,p)^(187)W reactions were measured at four neutron energies,namely 13.5,14.1,14.4,and 14.8 MeV,by means of the activation technique,relative to the reference cross-section values of the 93Nb(n,2n)92mNb reaction.The neutrons were generated from the T(d,n)4He reaction at the K-400 Neutron Generator at China Academy of Engineering Physics.The inducedγactivities were measured using a high-resolutionγ-ray spectrometer equipped with a coaxial high-purity germanium detector.The excitation functions of the six above-mentioned nuclear reactions at neutron energies from the threshold to 20 MeV were calculated by adopting the nuclear theoretical model program system Talys-1.9 with the relevant parameters properly adjusted.The measured cross sections were analyzed and compared with previous experiments conducted by other researchers,and with the evaluated data of BROND-3.1,ENDF/B-VIII.0,JEFF-3.3,and the theoretical values based on Talys-1.9.The new measured results agree with those of previous experiments and the theoretical excitation curve at the corresponding energies.The theoretical excitation curves based on Talys-1.9 generally match most of experimental data well.
基金Supported by National Natural Science Foundation of China(11575163)
文摘The cross-section data of the 85Rb(n,2 n)84Rb reaction have been measured with the neutron energies of 12 MeV to 19.8 MeV using the activation technique and the relative method.The 85Rb samples were irradiated on the surface of a two-ring orientation assembly with neutrons produced from the 3H(d,n)4He reaction at the 5SDH-21.7-MV Tandem accelerator in China.Theoretical model calculations were performed with the TALYS-1.9 code.The present data were compared with previously obtained experimental data and the available evaluated data.
