Cryogenic fracturing with liquid nitrogen(LN_(2))offers the benefits of reducing the water consumption and adverse environmental impacts induced by water-based fracturing,as well as potentially enhancing the fracture ...Cryogenic fracturing with liquid nitrogen(LN_(2))offers the benefits of reducing the water consumption and adverse environmental impacts induced by water-based fracturing,as well as potentially enhancing the fracture complexity.We performed a series of laboratory experiments to explore the key mechanisms governing the breakdown pressures of shale during cryogenic fracturing.In this study,cylindrical shale samples were pre-conditioned by exposing a borehole to low-temperature LN_(2) for a certain time period,and then,the samples were fractured using gaseous N_(2) under triaxial stress and a high reservoir temperature.The effects of various key parameters on the breakdown pressure were investigated,including the duration of the low-temperature LN_(2) treatment,the confining pressure,the reservoir temperature,and the direction of the shale bedding relative to the borehole axis.The results demonstrate that the injection of low-temperature LN_(2) as a pre-fracturing fluid into a borehole can significantly reduce the breakdown pressure of the shale during subsequent nitrogen fracturing.This reduction in breakdown pressure can be further intensified by increasing the duration of the LN_(2) pre-conditioning.Without LN_(2) pre-conditioning,the breakdown pressure initially increases and then decreases with increasing reservoir temperature.When LN_(2) pre-conditioning is applied,the breakdown pressure keeps decreasing with increasing reservoir temperature.As the confining pressure increased,the breakdown pressure increased linearly in the tests with and without LN_(2) pre-conditioning.The experimental results demonstrate that LN_(2) preconditioning before N_(2) fracturing is a promising waterless fracturing technique that reduces the breakdown pressure and enhances the fracture complexity.展开更多
The delamination of birnessite MnO_(2) into nanosheets by freezing and thawing method was reported here.The proton⁃type birnessite manganese oxide(H⁃birnessite)was added to tetramethylammonium hydroxide(TMAOH)solution...The delamination of birnessite MnO_(2) into nanosheets by freezing and thawing method was reported here.The proton⁃type birnessite manganese oxide(H⁃birnessite)was added to tetramethylammonium hydroxide(TMAOH)solution in a polypropylene tube which was then sealed.Fifty cycles consisting of fast freezing(in liquid nitrogen for 30 s)and thawing(in 70℃ water for 30 min)were operated.The as⁃prepared slurry was characterized by X⁃ray diffraction(XRD)and transmission electron microscope(TEM).The XRD result showed the layered structural H⁃birnessite was delaminated.The TEM result revealed the product had a nanosheet⁃like morphology.Employed as an anode material for lithium⁃ion batteries,MnO_(2) nanosheets as⁃prepared delivered a specific charging capacity of 1040.6 mAh/g after 100 cycles at 100 mA/g.展开更多
Grapevine （Vitis spp.） is an economically important fruit crop worldwide. In Mexico, Sonora State leads the table grape production and exportation to international markets. In this regard, it is important to preserv...Grapevine （Vitis spp.） is an economically important fruit crop worldwide. In Mexico, Sonora State leads the table grape production and exportation to international markets. In this regard, it is important to preserve the grape varieties during long time without phenotypical or genotypical changes. Cryopreservation is a good alternative, although it very often can induce changes in genome and phenotype. In this study, grapevine cv. ＂Flame Seedless＂ axillary buds were cryoprcserved by vitrification using the plant vitrification solution 2 （PVS2） and stored in liquid nitrogen （LN） for one hour, one week and one month, respectively. Genetic stability of buds cryopreserved under all treatments was evaluated using inter-simple sequence repeats （ISSR） markers. Ten ISSR primers were evaluated, but only two primers were possible to amplify distinct and reproducible bands with sizes between 300 bp and 2,000 bp. Different ISSR fragment patterns were recorded in cryopreserved buds as compared with control. These results suggest that cryopreservation by LN and vitrification-cryopreservation affect genetic stability in grapevine.展开更多
In this work, the excess water-stagnation issue in the high current region in direct methanol fuel cells(DMFCs) is resolved by using atomic precision modulated nitrogen-crafted graphene(NG) in the cathode microporous ...In this work, the excess water-stagnation issue in the high current region in direct methanol fuel cells(DMFCs) is resolved by using atomic precision modulated nitrogen-crafted graphene(NG) in the cathode microporous layer by utilizing simplistic,industrial-expansive and ecological strategy. Few-layer 2D-graphene(~2–5 nm thickness) is prepared by bath sonication approach from abundant feedstock-graphite and is treated with nitric acid to yield 1.8 wt.% uniformly dispersed nitrogen containing NG. Specifically, 1:4 weight ratio NG:carbon-black(CB) hybrid architecture, displays 0.252 V in 370 mA cm^(-2) with the peak power density of 93.4 mW cm^(-2), improving cell power density by 45.6% compared with standard one at 60℃ and 1 mol/L methanol/oxygen conditions at ultra-low catalyst loadings and displaying exceptional stability. Atomic insights into NG reveal that interplay between bonding configurations, altered hydrophobic/hydrophilic porosity of graphene(10.6% less wettability from contact angle and 13.1% high electrode porosity measurements) contribute to the better mass-transport-porogenic effect(16.3% high oxygen-permeability), mildly affecting the electron pathway(6.5% reduced in-plane electrical conductivity),overall significantly improving cell performance. Altogether, this work delivers multiple advantages, i.e., the usage of material from facile, sustainable and cost-effective routes, while improving DMFC performance with potential industrial promise.展开更多
基金This work was supported by the National Natural Science Foundation of China(No.51674247)the project for Fundamental Research Funds for the Central Universities(China University of Mining and Technology)under No.2015XKZD06.
文摘Cryogenic fracturing with liquid nitrogen(LN_(2))offers the benefits of reducing the water consumption and adverse environmental impacts induced by water-based fracturing,as well as potentially enhancing the fracture complexity.We performed a series of laboratory experiments to explore the key mechanisms governing the breakdown pressures of shale during cryogenic fracturing.In this study,cylindrical shale samples were pre-conditioned by exposing a borehole to low-temperature LN_(2) for a certain time period,and then,the samples were fractured using gaseous N_(2) under triaxial stress and a high reservoir temperature.The effects of various key parameters on the breakdown pressure were investigated,including the duration of the low-temperature LN_(2) treatment,the confining pressure,the reservoir temperature,and the direction of the shale bedding relative to the borehole axis.The results demonstrate that the injection of low-temperature LN_(2) as a pre-fracturing fluid into a borehole can significantly reduce the breakdown pressure of the shale during subsequent nitrogen fracturing.This reduction in breakdown pressure can be further intensified by increasing the duration of the LN_(2) pre-conditioning.Without LN_(2) pre-conditioning,the breakdown pressure initially increases and then decreases with increasing reservoir temperature.When LN_(2) pre-conditioning is applied,the breakdown pressure keeps decreasing with increasing reservoir temperature.As the confining pressure increased,the breakdown pressure increased linearly in the tests with and without LN_(2) pre-conditioning.The experimental results demonstrate that LN_(2) preconditioning before N_(2) fracturing is a promising waterless fracturing technique that reduces the breakdown pressure and enhances the fracture complexity.
基金Sponsored by the China Postdoctoral Science Foundation(Grant No.2016M592746).
文摘The delamination of birnessite MnO_(2) into nanosheets by freezing and thawing method was reported here.The proton⁃type birnessite manganese oxide(H⁃birnessite)was added to tetramethylammonium hydroxide(TMAOH)solution in a polypropylene tube which was then sealed.Fifty cycles consisting of fast freezing(in liquid nitrogen for 30 s)and thawing(in 70℃ water for 30 min)were operated.The as⁃prepared slurry was characterized by X⁃ray diffraction(XRD)and transmission electron microscope(TEM).The XRD result showed the layered structural H⁃birnessite was delaminated.The TEM result revealed the product had a nanosheet⁃like morphology.Employed as an anode material for lithium⁃ion batteries,MnO_(2) nanosheets as⁃prepared delivered a specific charging capacity of 1040.6 mAh/g after 100 cycles at 100 mA/g.
文摘Grapevine （Vitis spp.） is an economically important fruit crop worldwide. In Mexico, Sonora State leads the table grape production and exportation to international markets. In this regard, it is important to preserve the grape varieties during long time without phenotypical or genotypical changes. Cryopreservation is a good alternative, although it very often can induce changes in genome and phenotype. In this study, grapevine cv. ＂Flame Seedless＂ axillary buds were cryoprcserved by vitrification using the plant vitrification solution 2 （PVS2） and stored in liquid nitrogen （LN） for one hour, one week and one month, respectively. Genetic stability of buds cryopreserved under all treatments was evaluated using inter-simple sequence repeats （ISSR） markers. Ten ISSR primers were evaluated, but only two primers were possible to amplify distinct and reproducible bands with sizes between 300 bp and 2,000 bp. Different ISSR fragment patterns were recorded in cryopreserved buds as compared with control. These results suggest that cryopreservation by LN and vitrification-cryopreservation affect genetic stability in grapevine.
基金supported by China Postdoctoral Science Foundation(Grant No.2019M661749)Six-Talent-Peaks Project in Jiangsu Province(Grant No.2016-XNY-015)+1 种基金the High-Tech Key Laboratory of Zhenjiang City(Grant No.SS2018002)Priority Academic Program Development(PAPD) of Jiangsu Higher Education Institutions。
文摘In this work, the excess water-stagnation issue in the high current region in direct methanol fuel cells(DMFCs) is resolved by using atomic precision modulated nitrogen-crafted graphene(NG) in the cathode microporous layer by utilizing simplistic,industrial-expansive and ecological strategy. Few-layer 2D-graphene(~2–5 nm thickness) is prepared by bath sonication approach from abundant feedstock-graphite and is treated with nitric acid to yield 1.8 wt.% uniformly dispersed nitrogen containing NG. Specifically, 1:4 weight ratio NG:carbon-black(CB) hybrid architecture, displays 0.252 V in 370 mA cm^(-2) with the peak power density of 93.4 mW cm^(-2), improving cell power density by 45.6% compared with standard one at 60℃ and 1 mol/L methanol/oxygen conditions at ultra-low catalyst loadings and displaying exceptional stability. Atomic insights into NG reveal that interplay between bonding configurations, altered hydrophobic/hydrophilic porosity of graphene(10.6% less wettability from contact angle and 13.1% high electrode porosity measurements) contribute to the better mass-transport-porogenic effect(16.3% high oxygen-permeability), mildly affecting the electron pathway(6.5% reduced in-plane electrical conductivity),overall significantly improving cell performance. Altogether, this work delivers multiple advantages, i.e., the usage of material from facile, sustainable and cost-effective routes, while improving DMFC performance with potential industrial promise.
