The effects of Sr TiO_3 on the hydrogen storage properties of MgH_2 have been studied for the first time.The onset dehydrogenation temperature of the MgH_2-10 wt% SrTiO_3 is found to be 275 ℃, which is 55 ℃ lower as...The effects of Sr TiO_3 on the hydrogen storage properties of MgH_2 have been studied for the first time.The onset dehydrogenation temperature of the MgH_2-10 wt% SrTiO_3 is found to be 275 ℃, which is 55 ℃ lower as compared to the as-milled MgH_2. The composite is able to absorb 4.3 wt% of hydrogen in 60 min instead of 1.1 wt% for the as-milled Mg H_2. Meanwhile, the composite is able to release 5.3 wt% of hydrogen in 17 min compared to 1.9 wt% by the as-milled Mg H_2 at 320 ℃. The calculated Eaof the Mg H_2-10 wt% SrTiO_3 is 109 k J/mol, which is 26.3 kJ/mol lower than the calculated Eaof the as-milled MgH_2. The Sr TiO_3 is not decomposed during the ball milling and the re/dehydrogenation processes. The catalytic effect shown by the SrTiO_3 is owing to its ability to change the physical structure of the MgH_2 particles during the ball milling process.展开更多
Acid-base properties of Na-sepiolite and Na-palygorskite were studied by potentiometric titrations at 298 K and two ionic strength I = 0.1 and I = 0.002. Intrinsic constants of deprotonation were calculated by two dif...Acid-base properties of Na-sepiolite and Na-palygorskite were studied by potentiometric titrations at 298 K and two ionic strength I = 0.1 and I = 0.002. Intrinsic constants of deprotonation were calculated by two different methods: a) Stumm method, by extrapolating to zero the function that relates surface charge with the logarithms of apparent acidity constants and b) with MINTEQ program by minimizing the differences between surface H+ concentration data and the values obtained from deprotonation constants proposed according to the Diffuse-Double-Layer Model (DDLM). Hydroxyl groups located at the broken edges of these fibrous clay minerals (SOH) and permanent charge sites (X-) were considered as reactive sites. The determined values of the acid-base constants for Na-sepiolite and Na-palygorskite were intermediate between those for SiO2 and Al2O3, which is in agreement with minerals that contain moderately strong-acidity and weak-acidity surface groups. The SOH groups showed an initial increase (after SOH2+ deprotonation), forming a plateau with a slight de-crease at high pH values (8-9) due to the formation of SO- sites. X- sites ad-sorbed H+, Na+ or Mg2+ ions.展开更多
Viscous aqueous solutions of chitosan and polyvinyl alcohol (PVA) were blended to enhance miscibility and avoid polymer phase separation. The mixtures were drop-casted and air dried to yield composite film materials t...Viscous aqueous solutions of chitosan and polyvinyl alcohol (PVA) were blended to enhance miscibility and avoid polymer phase separation. The mixtures were drop-casted and air dried to yield composite film materials that were characterized by equilibrium water uptake, physical stability in aqueous solution, and thermal stability. Chitosan/PVA blends have greater thermal stability, unique morphology, and reduced solubility in acidic solution, thus extending the useful pH range for chitosan as a sorbent material. The uptake properties of the films was investigated using methylene blue (MB) and a p-nitrophenol (PNP) dyes, where it was found that each single component polymer has greater uptake toward MB than PNP. A direct relationship between film composition (chitosan:PVA) with solution pH and the uptake of MB was observed. The results are in agreement with electrostatic interactions and contributions due to the hydrophobic effect for such composite materials.展开更多
Indaziflam is a new preemergence herbicide for the control of annual grass and broadleaf weeds in various cropping systems including pecan orchards.The objectives of this study were to（1） determine the mobility and ...Indaziflam is a new preemergence herbicide for the control of annual grass and broadleaf weeds in various cropping systems including pecan orchards.The objectives of this study were to（1） determine the mobility and dissipation of indaziflam and（2） evaluate herbicide efficacy in a flood-irrigated pecan orchard in southern New Mexico,USA.Indaziflam was applied at 0,35.5,and 73.1 g/ha in areas with（impacted） and without（unimpacted） tree injury symptoms.Soil samples were collected at 0-15,15-30,and 30-46 cm depths 25,63,90,and 125 days after the first herbicide application.Additional soil samples were collected 4,30,and 55 days after the second application.Indaziflam was detected in soil samples collected at each depth,suggesting movement with irrigation water.Indaziflam concentrations decreased with increasing soil depth and time.Indaziflam mass recoveries were greater in the unimpacted area than in the impacted area after the first and second applications.Dissipation half-lives of indaziflam in the soil ranged from 30 to 85 days for total indaziflam recovered from the entire soil profile after the first and second applications in both areas.The percent weed control was similar in the impacted and unimpacted areas for both rates of indaziflam on 25 and 53 days after application;however,on 90 days after the application,percent weed control was lower in the impacted than unimpacted area.展开更多
基金financially supported by the Ministry of Higher Education Malaysia under the Fundamental Research Grant Scheme (FRGS 59362)
文摘The effects of Sr TiO_3 on the hydrogen storage properties of MgH_2 have been studied for the first time.The onset dehydrogenation temperature of the MgH_2-10 wt% SrTiO_3 is found to be 275 ℃, which is 55 ℃ lower as compared to the as-milled MgH_2. The composite is able to absorb 4.3 wt% of hydrogen in 60 min instead of 1.1 wt% for the as-milled Mg H_2. Meanwhile, the composite is able to release 5.3 wt% of hydrogen in 17 min compared to 1.9 wt% by the as-milled Mg H_2 at 320 ℃. The calculated Eaof the Mg H_2-10 wt% SrTiO_3 is 109 k J/mol, which is 26.3 kJ/mol lower than the calculated Eaof the as-milled MgH_2. The Sr TiO_3 is not decomposed during the ball milling and the re/dehydrogenation processes. The catalytic effect shown by the SrTiO_3 is owing to its ability to change the physical structure of the MgH_2 particles during the ball milling process.
文摘Acid-base properties of Na-sepiolite and Na-palygorskite were studied by potentiometric titrations at 298 K and two ionic strength I = 0.1 and I = 0.002. Intrinsic constants of deprotonation were calculated by two different methods: a) Stumm method, by extrapolating to zero the function that relates surface charge with the logarithms of apparent acidity constants and b) with MINTEQ program by minimizing the differences between surface H+ concentration data and the values obtained from deprotonation constants proposed according to the Diffuse-Double-Layer Model (DDLM). Hydroxyl groups located at the broken edges of these fibrous clay minerals (SOH) and permanent charge sites (X-) were considered as reactive sites. The determined values of the acid-base constants for Na-sepiolite and Na-palygorskite were intermediate between those for SiO2 and Al2O3, which is in agreement with minerals that contain moderately strong-acidity and weak-acidity surface groups. The SOH groups showed an initial increase (after SOH2+ deprotonation), forming a plateau with a slight de-crease at high pH values (8-9) due to the formation of SO- sites. X- sites ad-sorbed H+, Na+ or Mg2+ ions.
文摘Viscous aqueous solutions of chitosan and polyvinyl alcohol (PVA) were blended to enhance miscibility and avoid polymer phase separation. The mixtures were drop-casted and air dried to yield composite film materials that were characterized by equilibrium water uptake, physical stability in aqueous solution, and thermal stability. Chitosan/PVA blends have greater thermal stability, unique morphology, and reduced solubility in acidic solution, thus extending the useful pH range for chitosan as a sorbent material. The uptake properties of the films was investigated using methylene blue (MB) and a p-nitrophenol (PNP) dyes, where it was found that each single component polymer has greater uptake toward MB than PNP. A direct relationship between film composition (chitosan:PVA) with solution pH and the uptake of MB was observed. The results are in agreement with electrostatic interactions and contributions due to the hydrophobic effect for such composite materials.
基金supported by grants from Bayer CropScienceNakayama endowment,New Mexico State University Agricultural Experiment Station,owners of the pecan orchard for support
文摘Indaziflam is a new preemergence herbicide for the control of annual grass and broadleaf weeds in various cropping systems including pecan orchards.The objectives of this study were to（1） determine the mobility and dissipation of indaziflam and（2） evaluate herbicide efficacy in a flood-irrigated pecan orchard in southern New Mexico,USA.Indaziflam was applied at 0,35.5,and 73.1 g/ha in areas with（impacted） and without（unimpacted） tree injury symptoms.Soil samples were collected at 0-15,15-30,and 30-46 cm depths 25,63,90,and 125 days after the first herbicide application.Additional soil samples were collected 4,30,and 55 days after the second application.Indaziflam was detected in soil samples collected at each depth,suggesting movement with irrigation water.Indaziflam concentrations decreased with increasing soil depth and time.Indaziflam mass recoveries were greater in the unimpacted area than in the impacted area after the first and second applications.Dissipation half-lives of indaziflam in the soil ranged from 30 to 85 days for total indaziflam recovered from the entire soil profile after the first and second applications in both areas.The percent weed control was similar in the impacted and unimpacted areas for both rates of indaziflam on 25 and 53 days after application;however,on 90 days after the application,percent weed control was lower in the impacted than unimpacted area.
