Coal dust explosion accidents often cause substantial property damage and casualties and frequently involve nano-sized coal dust.In order to study the impact of nano-sized coal on coal dust and methane–coal dust expl...Coal dust explosion accidents often cause substantial property damage and casualties and frequently involve nano-sized coal dust.In order to study the impact of nano-sized coal on coal dust and methane–coal dust explosions,a pipe test apparatus was used to analyze the explosion pressure characteristics of five types of micro-nano particle dusts(800 nm,1200 nm,45μm,60μm,and 75μm)at five concentrations(100 g/m3,250 g/m3,500 g/m3,750 g/m3,and 1000 g/m3).The explosion pressure characteristics were closely related to the coal dust particle size and concentration.The maximum explosion pressure,maximum rate of pressure rise,and deflagration index for nano-sized coal dust were larger than for its micro-sized counterpart,indicating that a nano-sized coal dust explosion is more dangerous.The highest deflagration index Kst for coal dust was 13.97 MPa/(m·s),indicating weak explosibility.When 7%methane was added to the air,the maximum deflagration index Kst for methane–coal dust was 42.62 MPa/(m·s),indicating very strong explosibility.This indicates that adding methane to the coal dust mixture substantially increased the hazard grade.展开更多
Two type zirconia(monoclinic and tetragonal phase ZrO_2) carriers were synthesized via hydrothermal route,and nano-sized zirconia supported nickel catalysts were prepared by incipient impregnation then followed therma...Two type zirconia(monoclinic and tetragonal phase ZrO_2) carriers were synthesized via hydrothermal route,and nano-sized zirconia supported nickel catalysts were prepared by incipient impregnation then followed thermal treatment at 300℃ to 500℃,for the CO_2 selective hydrogenation to synthetic natural gas(SNG).The catalysts were characterized by XRD,CO_2-TPD-MS,XPS,TPSR(CH_4,CO_2) techniques.For comparison,the catalyst NZ-W-400(monoclinic) synthesized in water solvent exhibited a better catalytic activity than the catalyst NZ-M-400(tetragonal) prepared in methanol solvent.The catalyst NZ-W-400 displayed more H_2 absorbed sites,more basic sites and a lower temperature of initial CO_2 activation.Then,the thermal treatment of monoclinic ZrO_2 supported nickel precursor was manufactured at three temperature of 350,400,500℃.The TPSR experiments displayed that there were the lower temperature for CO_2 activation and initial conversion(185℃) as well as the lower peak temperature of CH_4 generation(318℃),for the catalyst calcined at 500℃.This sample contained the more basic sites and the higher catalytic activity,evidenced byCO_2-TPD-MS and performance measurement.As for the NZ-W-350 sample,which exhibited the less basic sites and the lower catalytic activity,its initial temperature for CO_2 activation and conversion was higher(214℃) as well as the higher peak temperature of CH_4 formation(382℃).展开更多
Nano-sized aluminum(Nano-Al)powders hold promise in enhancing the total energy of explosives and the metal acceleration ability at the same time.However,the near-detonation zone effects of reaction between Nano-Al wit...Nano-sized aluminum(Nano-Al)powders hold promise in enhancing the total energy of explosives and the metal acceleration ability at the same time.However,the near-detonation zone effects of reaction between Nano-Al with detonation products remain unclear.In this study,the overall reaction process of 170 nm Al with RDX explosive and its effect on detonation characteristics,detonation reaction zone,and the metal acceleration ability were comprehensively investigated through a variety of experiments such as the detonation velocity test,detonation pressure test,explosive/window interface velocity test and confined plate push test using high-resolution laser interferometry.Lithium fluoride(LiF),which has an inert behavior during the explosion,was used as a control to compare the contribution of the reaction of aluminum.A thermochemical approach that took into account the reactivity of aluminum and ensuing detonation products was adopted to calculate the additional energy release by afterburn.Combining the numerical simulations based on the calculated afterburn energy and experimental results,the parameters in the detonation equation of state describing the Nano-Al reaction characteristics were calibrated.This study found that when the 170 nm Al content is from 0%to 15%,every 5%increase of aluminum resulted in about a 1.3%decrease in detonation velocity.Manganin pressure gauge measurement showed no significant enhancement in detonation pressure.The detonation reaction time and reaction zone length of RDX/Al/wax/80/15/5 explosive is 64 ns and 0.47 mm,which is respectively 14%and 8%higher than that of RDX/wax/95/5 explosive(57 ns and 0.39 mm).Explosive/window interface velocity curves show that 170 nm Al mainly reacted with the RDX detonation products after the detonation front.For the recording time of about 10 ms throughout the plate push test duration,the maximum plate velocity and plate acceleration time accelerated by RDX/Al/wax/80/15/5 explosive is 12%and 2.9 ms higher than that of RDX/LiF/wax/80/15/5,respectively,indicating that the aluminum reaction energy significantly increased the metal acceleration time and ability of the explosive.Numerical simulations with JWLM explosive equation of state show that when the detonation products expanded to 2 times the initial volume,over 80%of the aluminum had reacted,implying very high reactivity.These results are significant in attaining a clear understanding of the reaction mechanism of Nano-Al in the development of aluminized explosives.展开更多
Hierarchical nano-sized ZSM-5 aggregates were successfully synthesized via a seed-assisted method in the presence of cetyltrimethylammonium bromide(CTAB)through a facile one-step crystallization process.Commercial ZSM...Hierarchical nano-sized ZSM-5 aggregates were successfully synthesized via a seed-assisted method in the presence of cetyltrimethylammonium bromide(CTAB)through a facile one-step crystallization process.Commercial ZSM-5 zeolites with a SiO2/Al2O3 ratio comparable to that of ZSM-5 products were treated with alkali and used as the seed particles.The influences of crystallization conditions were investigated,and the possible synthesis mechanism was proposed.ZSM-5 zeolites with diff erent amounts of CTAB added were characterized using many techniques and evaluated in toluene alkylation with methanol.The results showed that a trace amount of CTAB signifi cantly promoted the crystallization of ZSM-5 zeolite,with the morphology changing from hexagonal-shape crystals to uniform spherical aggregates.CTAB may act as the structure-directing agent and assemble the primary crystallites to generate hierarchical ZSM-5 aggregates.The ZSM-5 zeolite with the smallest primary particles of 50-80 nm exhibited large specific surface area,abundant mesopores,and the greatest microporosity.The hierarchical nano-sized ZSM-5 aggregate showed higher toluene conversion and a longer lifetime without compromising the selectivity to xylene and p-xylene in toluene alkylation with methanol.展开更多
The effect of expanding swept volume by iNanoW1.0 nanoparticles in ultra-low permeability core was studied by low-field nuclear magnetic resonance(LF-NMR)technology,and the mechanism of expanding swept volume was expl...The effect of expanding swept volume by iNanoW1.0 nanoparticles in ultra-low permeability core was studied by low-field nuclear magnetic resonance(LF-NMR)technology,and the mechanism of expanding swept volume was explained by oxygen spectrum nuclear magnetic resonance(17O-NMR)experiments and capillarity analysis.The results of the LF-NMR experiment show that the nano-sized oil-displacement agent iNanoW1.0 could increase the swept volume by 10%-20%on the basis of conventional water flooding,making water molecules get into the low permeable region with small pores that conventional water flooding could not reach.17O-NMR technique and capillary analysis proved that iNanoW1.0 nanoparticles could weaken the association of hydrogen bonds between water molecules,effectively change the structure of water molecular clusters,and thus increasing the swept volume in the low permeable region.The ability of weakening association of hydrogen bonds between water molecules of iNanoW1.0 nanoparticles increases with its mass fraction and tends to be stable after the mass fraction of 0.1%.展开更多
This paper reports a study on nanocrystalline ceria powder prepared by high energy ball-milling and combustion synthesis methods. The combustion synthesis was carried out using ceric ammonium nitrate as oxidizer and c...This paper reports a study on nanocrystalline ceria powder prepared by high energy ball-milling and combustion synthesis methods. The combustion synthesis was carried out using ceric ammonium nitrate as oxidizer and citric acid, glycine or citric acid plus glycine as fuel. The minimum crystallite size of ceria powder is obtained by combustion synthesis of ceric ammonium nitrate and citric acid. The ceria powder produced by combustion synthesis of ceric ammonium nitrate and citric acid and glycine has less agglomeration of particles than other techniques.展开更多
Modern chromatography is increasingly focused on miniaturization and integration. Compared to conventional liquid chromatography, microfluidic chip liquid chromatography(microchip-LC) has the potential due to its zero...Modern chromatography is increasingly focused on miniaturization and integration. Compared to conventional liquid chromatography, microfluidic chip liquid chromatography(microchip-LC) has the potential due to its zero-dead volume connection and ease of integration. Nano-sized packings have the potential to significantly enhance separation performance in microchip-LC. However, their application has been hindered by packing difficulties. This study presents a method for packing nano-sized silica particles into a microchannel as the stationary phase. The microchip-LC packed column was prepared by combining the weir and the porous silica single-particle as frit to retain the packing particles. A surface tensionbased single-particle picking technique was established to insert porous single-particle frit into glass microchannels. Additionally, we developed a slurry packing method that utilizes air pressure to inject nano-sized packing into the microchannel. Pressure-driven chromatographic separation was performed using this nano-packed column integrated into a glass microchip. The mixture of four PAHs was successfully separated within just 8 min using a 5 mm separation channel length, achieving high theoretical plates(10~6plates/m). Overall, these findings demonstrate the potential of utilizing nano-sized packings for enhancing chromatographic performance in microchip systems.展开更多
Nanosized 1 at% Sm^(3+)doped Y_(2)O_(3)powders were prepared by an ultrasound assisted sol-gel method.Y_(2)O_(3):Sm^(3+)powders crystallize in Y_(2)O_(3)pure cubic phase and XRD analysis shows that the as-used agitati...Nanosized 1 at% Sm^(3+)doped Y_(2)O_(3)powders were prepared by an ultrasound assisted sol-gel method.Y_(2)O_(3):Sm^(3+)powders crystallize in Y_(2)O_(3)pure cubic phase and XRD analysis shows that the as-used agitation protocol affects strongly the crystallite’s shape and mean size.The recorded emission spectra under λ_(em)=600 nm exhibit two absorption bands;the first one is assigned to O^(2-)→Sm^(3+)charge transfer state(CTS) with a maximum absorption at 223 nm,and the second is due to intraconfigurational transition 4f^(5)-4f^(5) of Sm^(3+) with a maximum absorption at 407 nm.The 223 and 407 nm transitions are attributed to characteristics intra-configurational transitions of Sm^(3+).All emission spectra are dominated by reddish/orange luminescence located at 606 nm and assigned to ^(4)G_(5/2)→^(6)H_(7/2) transition.It is found that the photoluminescence intensity of samples obtained under excitation at 407 nm is 60 times smaller than that obtained under 223 nm excitation.Decay time measurements of the ^(4)G_(5/2)→^(6)H_(7/2) luminescence transition indicate that decay time of nano-sized powder is significantly shorter than bulk material one.展开更多
In this paper,MCM-41 was synthesized by a soft template technique and MCM-41 supported CuO-CeO2 nano-sized catalysts with different Cu/Ce molar ratios were prepared by a deposition-precipitation method.N2 adsorption,H...In this paper,MCM-41 was synthesized by a soft template technique and MCM-41 supported CuO-CeO2 nano-sized catalysts with different Cu/Ce molar ratios were prepared by a deposition-precipitation method.N2 adsorption,HRTEM-EDS,H2-TPR,XPS characterization,as well as catalytic activity and durability tests for the catalytic combustion of chlorobenzene(CB)were conducted to explore the relationship between the structure and catalytic performance of the catalysts.It is revealed that cuCe(6:1)/MCM-41 has the highest activity and can completely catalyze the degradation of CB at 260℃.The reasons for the high activity of the catalysts are as follows:MCM-41,a type of mesoporous material which has large pore size and large specific surface area,is suitable as a catalyst carrier.The average diameter of nano-sized CuO and CeO2 particles is about 3-5 nm and adding CeO2 improves the dispersion of active component CuO,which are highly and evenly dispersed on the surface of MCM-41.Characterization results also explain why MCM-41 supported CuO-CeO2 with appropriate proportion can highly enhance the catalytic activity.The reason is that CeO2 acting as an oxygen-rich material can improve the mobility of oxygen species through continuous redox between Ce4^+and Ce3^+,and improve the catalytic performance of CuO for CB combustion.Besides,CuCe(6:1)/MCM-41 also displays good durability for CB combustion,both in the humid condition and in the presence of benzene,making it a promising catalytic material for the elimination of chlorinated VOCs.展开更多
In recent years much attention has been devoted to AgCl emulsion owing to its se-rial advantages and inimitable potential. But in the research of this emulsion a thorny problem remains unsolved till now, which is the ...In recent years much attention has been devoted to AgCl emulsion owing to its se-rial advantages and inimitable potential. But in the research of this emulsion a thorny problem remains unsolved till now, which is the improvement in sensitivity is always accompanied with high fog density. In this work 5 nm Ag2S particles were prepared and used as novel sensitizers in AgCl cubic and {100} tabular microcrystal emulsions. The novel sensitizer shows an effective sensitizing ability for silver chloride emulsion, and it is superior to the traditional Na2S2O3 sensi-tizer because by using it comparatively high sensitivity can be obtained with lower fog density. So the above sensitizing problem is going to be effectively solved. To discover the evolution mechanism of the sensitizer clusters and explain their excellent sensitizing properties, diffuse reflectance spectroscopy (DRS) was used as a probe on the AgCl microcrystal surface.展开更多
The equation of phase equilibria in nano-sized crystal of metals has been established in terms of thermodynamic equilibrium. The thermodynamic parameters are calculated and the critical grain size for the stable high-...The equation of phase equilibria in nano-sized crystal of metals has been established in terms of thermodynamic equilibrium. The thermodynamic parameters are calculated and the critical grain size for the stable high-temperature phase at room temperature is obtained. As an example, the critical grain size of β-Co at room temperature is determined at 35nm when the excess volume is 10%. The result agrees well with the experiment of Katakimi et al. The factors affecting the stability of β-Co are also discussed.展开更多
This paper presents how the combustion performance of nano-sized aluminum(nAl)powder in carbon dioxide are affected by silica. The ignition and combustion performance of nAl powder with silica addition were studied by...This paper presents how the combustion performance of nano-sized aluminum(nAl)powder in carbon dioxide are affected by silica. The ignition and combustion performance of nAl powder with silica addition were studied by a high-temperature tube furnace. An s-type thermocouple and a high-speed motion acquisition instrument were performed to evaluate the ignition temperature, maximum combustion temperature, maximum change of rate of temperature, and combustion propagation speed. The combustion efficiency and combustion products were measured and analyzed by a gas-volumetric method and an X-ray diffraction. The results show that silica added into nAl powder can enhance its maximum combustion temperature and maximum change of rate of temperature, while its ignition temperature increases slightly. The nAl powders with addition of 6.00 wt.% and 12.00 wt.% silica present high combustion propagation speeds, especially for the latter, it has high combustion efficiency. The effect mechanism of silica on the combustion of nAl powder in carbon dioxide was discussed.展开更多
Both HA-CdS and HB-CdS (Hys-CdS, Hys represents HA, HB) complex systems were established according to the dynamics of heterogeneous electron-transfer process ＜0. In these systems, the electron transferring from 1Hys...Both HA-CdS and HB-CdS (Hys-CdS, Hys represents HA, HB) complex systems were established according to the dynamics of heterogeneous electron-transfer process ＜0. In these systems, the electron transferring from 1Hys* to conduction band of CdS is feasible. Determined from the fluorescence quenching, the apparent association constants (Kapp) between Hypocrellin A (HA), Hypocrellin B (HB) and CdS sol. were about 940 (mol/L)-1, 934 (mol/L)-1, respectively. Fluorescence lifetime measurements gave the rate constant for the electron transfer process from 1HA*, 1HB* into conduction band of CdS semiconductor as 5.16×109 s-1, 5.10×109 s-1, respectively. TEMPO (2,2,6,6-tetramethy-1-piperdinyloxy), a stable nitroxide radical, was used in the kinetic study of the reduction reaction taking place on the surface of a CdS colloidal semiconductor, kinetics equation of the reaction was determined with the electron paramagnetic resonance (EPR) method, and the reaction order of TEMPO is zero. When Hys were added, the rate of EPR increased greatly. By comparing rate constants, the Hys-CdS systems were revealed to be about 350 times more efficient than CdS sol. alone in the photoreduction of TEMPO under visi-ble light. It suggests that Hys can be used as efficient sensitizers of a colloidal semiconductor in the application of solar energy.展开更多
1 Results Lithium ion batteries are widely used in many portable devices.However,their power density is not sufficient for use in electric vehicles.One of the most effective methods to improve the power density is the...1 Results Lithium ion batteries are widely used in many portable devices.However,their power density is not sufficient for use in electric vehicles.One of the most effective methods to improve the power density is the use of very fine cathode particles.We investigated new method,excess lithium method,of preparing nano-sized LiCoO2 powders.To begin with,lithium acetate and cobalt acetate are mixed by the molar ratio 9,13 or 21 to 1,uniformly.And the mixture is calcined at 600 ℃ for 6 hours.Finally,obtain...展开更多
This study aimed to evaluate role of nano-sized zinc(Zn)on lactation performance,health status,and mammary permeability of lactating dairy cows.Thirty multiparous dairy cows with similar days in milk(158±43.2)and...This study aimed to evaluate role of nano-sized zinc(Zn)on lactation performance,health status,and mammary permeability of lactating dairy cows.Thirty multiparous dairy cows with similar days in milk(158±43.2)and body weight(694±60.5 kg)were chosen based on parity and milk production and were randomly assigned to 3 treatment groups:basal diet(control,69.6 mg/kg of Zn adequate in Zn requirement),basal diet additional Zn-methionine(Zn-Met,providing 40 mg/kg of Zn),and basal diet additional nano-sized Zn oxide(nZnO,providing 40 mg/kg of Zn).The study lasted for 10 wk,with the first 2 wk as adaptation.Feed intake,milk yield and the related variables,and plasma variables were determined every other week.Blood hematological profiles were determined in the 8 th week of the study.We found that feed intake,milk yield,and milk composition were similar across the 3 groups.The nZnO-and Zn-Met-fed cows had greater milk Zn concentrations in the milk(3.89 mg/L(Zn-Met)and3.93 mg/L(nZnO))and plasma(1.25 mg/L(Zn-Met)and 1.29 mg/L(nZnO))than the control cows(3.79 mg/L in milk and 1.21 mg/L in plasma).The nZnO-fed cows had higher Zn concentrations in plasma but not in milk compared to Zn-Met-fed cows.The Zn appearance in milk was greater in nZnO-fed(area under curve during the first 4 h post-feeding for milk Zn:16.1 mg/L)and Zn-Met-fed cows(15.7 mg/L)than in control cows(15.0 mg/L).During the first 4 h post-feeding,milk to blood Zn ratio was greater in nZnO-fed animals but lower in Zn-Met-fed cows compared with control cows.Oxidative stress-related variables in plasma,blood hematological profiles,and mammary permeability related variables were not different across treatments.In summary,lactation performance,Zn concentrations in milk and plasma,hematological profiles,mammary permeability were similar in cows fed nZnO and Zn-Met.We therefore suggested that nZnO feeding can improve Zn bioavailability without impairing lactation performance,health status,and mammary gland permeability in dairy cows.展开更多
A novel design of micro-aluminum(μAl)powder coated with bi-/tri-component alloy layer,such as:Ni-P and Ni-P-Cu(namely,Al@Ni-P,Al@Ni-P-Cu,respectively),as combustion catalysts,were introduced to release its huge energ...A novel design of micro-aluminum(μAl)powder coated with bi-/tri-component alloy layer,such as:Ni-P and Ni-P-Cu(namely,Al@Ni-P,Al@Ni-P-Cu,respectively),as combustion catalysts,were introduced to release its huge energy inside Al-core and promote rapid pyrolysis of ammonium perchlorate(AP)at a lower temperature in aluminized propellants.The microstructure of Al@Ni-P-Cu demonstrates that a three-layer Ni-P-Cu shell,with the thickness of~100 nm,is uniformly supported byμAl carrier(fuel unit),which has an amorphous surface with a thickness of~2.3 nm(catalytic unit).The peak temperature of AP with the addition of Al@Ni-P-Cu(3.5%)could significantly drop to 316.2℃ at high-temperature thermal decomposition,reduced by 124.3℃,in comparison to that of pure AP with 440.5℃.It illustrated that the introduction of Al@Ni-P-Cu could weaken or even eliminate the obstacle of AP pyrolysis due to its reduction of activation energy with 118.28 kJ/mol.The laser ignition results showed that the ignition delay time of Al@Ni-P-Cu/AP mixture with 78 ms in air is shorter than that of Al@Ni-P/AP(118 ms),decreased by 33.90%.Those astonishing breakthroughs were attributed to the synergistic effects of adequate active sites on amorphous surface and oxidation exothermic reactions(7597.7 J/g)of Al@Ni-P-Cu,resulting in accelerated mass and/or heat transfer rate to catalyze AP pyrolysis and combustion.Moreover,it is believed to provide an alternative Al-based combustion catalyst for propellant designer,to promote the development the propellants toward a higher energy.展开更多
基金This research was supported by the National Key Research and Development Program of China(2016YFC0801800)the National Nature Science Foundation of China(51774291,51864045).
文摘Coal dust explosion accidents often cause substantial property damage and casualties and frequently involve nano-sized coal dust.In order to study the impact of nano-sized coal on coal dust and methane–coal dust explosions,a pipe test apparatus was used to analyze the explosion pressure characteristics of five types of micro-nano particle dusts(800 nm,1200 nm,45μm,60μm,and 75μm)at five concentrations(100 g/m3,250 g/m3,500 g/m3,750 g/m3,and 1000 g/m3).The explosion pressure characteristics were closely related to the coal dust particle size and concentration.The maximum explosion pressure,maximum rate of pressure rise,and deflagration index for nano-sized coal dust were larger than for its micro-sized counterpart,indicating that a nano-sized coal dust explosion is more dangerous.The highest deflagration index Kst for coal dust was 13.97 MPa/(m·s),indicating weak explosibility.When 7%methane was added to the air,the maximum deflagration index Kst for methane–coal dust was 42.62 MPa/(m·s),indicating very strong explosibility.This indicates that adding methane to the coal dust mixture substantially increased the hazard grade.
基金supported by National Natural Science Foundation of China (21476145)
文摘Two type zirconia(monoclinic and tetragonal phase ZrO_2) carriers were synthesized via hydrothermal route,and nano-sized zirconia supported nickel catalysts were prepared by incipient impregnation then followed thermal treatment at 300℃ to 500℃,for the CO_2 selective hydrogenation to synthetic natural gas(SNG).The catalysts were characterized by XRD,CO_2-TPD-MS,XPS,TPSR(CH_4,CO_2) techniques.For comparison,the catalyst NZ-W-400(monoclinic) synthesized in water solvent exhibited a better catalytic activity than the catalyst NZ-M-400(tetragonal) prepared in methanol solvent.The catalyst NZ-W-400 displayed more H_2 absorbed sites,more basic sites and a lower temperature of initial CO_2 activation.Then,the thermal treatment of monoclinic ZrO_2 supported nickel precursor was manufactured at three temperature of 350,400,500℃.The TPSR experiments displayed that there were the lower temperature for CO_2 activation and initial conversion(185℃) as well as the lower peak temperature of CH_4 generation(318℃),for the catalyst calcined at 500℃.This sample contained the more basic sites and the higher catalytic activity,evidenced byCO_2-TPD-MS and performance measurement.As for the NZ-W-350 sample,which exhibited the less basic sites and the lower catalytic activity,its initial temperature for CO_2 activation and conversion was higher(214℃) as well as the higher peak temperature of CH_4 formation(382℃).
基金The authors would like to acknowledge National Natural Science Foundation of China(Grant No.11832006)Open Project of State Key Laboratory of Explosion Science and Technology in Beijing Institute of Technology(Grant No.KFJJ20-04 M)to provide fund for conducting experiments.
文摘Nano-sized aluminum(Nano-Al)powders hold promise in enhancing the total energy of explosives and the metal acceleration ability at the same time.However,the near-detonation zone effects of reaction between Nano-Al with detonation products remain unclear.In this study,the overall reaction process of 170 nm Al with RDX explosive and its effect on detonation characteristics,detonation reaction zone,and the metal acceleration ability were comprehensively investigated through a variety of experiments such as the detonation velocity test,detonation pressure test,explosive/window interface velocity test and confined plate push test using high-resolution laser interferometry.Lithium fluoride(LiF),which has an inert behavior during the explosion,was used as a control to compare the contribution of the reaction of aluminum.A thermochemical approach that took into account the reactivity of aluminum and ensuing detonation products was adopted to calculate the additional energy release by afterburn.Combining the numerical simulations based on the calculated afterburn energy and experimental results,the parameters in the detonation equation of state describing the Nano-Al reaction characteristics were calibrated.This study found that when the 170 nm Al content is from 0%to 15%,every 5%increase of aluminum resulted in about a 1.3%decrease in detonation velocity.Manganin pressure gauge measurement showed no significant enhancement in detonation pressure.The detonation reaction time and reaction zone length of RDX/Al/wax/80/15/5 explosive is 64 ns and 0.47 mm,which is respectively 14%and 8%higher than that of RDX/wax/95/5 explosive(57 ns and 0.39 mm).Explosive/window interface velocity curves show that 170 nm Al mainly reacted with the RDX detonation products after the detonation front.For the recording time of about 10 ms throughout the plate push test duration,the maximum plate velocity and plate acceleration time accelerated by RDX/Al/wax/80/15/5 explosive is 12%and 2.9 ms higher than that of RDX/LiF/wax/80/15/5,respectively,indicating that the aluminum reaction energy significantly increased the metal acceleration time and ability of the explosive.Numerical simulations with JWLM explosive equation of state show that when the detonation products expanded to 2 times the initial volume,over 80%of the aluminum had reacted,implying very high reactivity.These results are significant in attaining a clear understanding of the reaction mechanism of Nano-Al in the development of aluminized explosives.
基金supported by the National Natural Science Foundation of China(No.21276183).
文摘Hierarchical nano-sized ZSM-5 aggregates were successfully synthesized via a seed-assisted method in the presence of cetyltrimethylammonium bromide(CTAB)through a facile one-step crystallization process.Commercial ZSM-5 zeolites with a SiO2/Al2O3 ratio comparable to that of ZSM-5 products were treated with alkali and used as the seed particles.The influences of crystallization conditions were investigated,and the possible synthesis mechanism was proposed.ZSM-5 zeolites with diff erent amounts of CTAB added were characterized using many techniques and evaluated in toluene alkylation with methanol.The results showed that a trace amount of CTAB signifi cantly promoted the crystallization of ZSM-5 zeolite,with the morphology changing from hexagonal-shape crystals to uniform spherical aggregates.CTAB may act as the structure-directing agent and assemble the primary crystallites to generate hierarchical ZSM-5 aggregates.The ZSM-5 zeolite with the smallest primary particles of 50-80 nm exhibited large specific surface area,abundant mesopores,and the greatest microporosity.The hierarchical nano-sized ZSM-5 aggregate showed higher toluene conversion and a longer lifetime without compromising the selectivity to xylene and p-xylene in toluene alkylation with methanol.
基金Supported by the PetroChina Scientifc Research and Technological Development Project(2018A-0907).
文摘The effect of expanding swept volume by iNanoW1.0 nanoparticles in ultra-low permeability core was studied by low-field nuclear magnetic resonance(LF-NMR)technology,and the mechanism of expanding swept volume was explained by oxygen spectrum nuclear magnetic resonance(17O-NMR)experiments and capillarity analysis.The results of the LF-NMR experiment show that the nano-sized oil-displacement agent iNanoW1.0 could increase the swept volume by 10%-20%on the basis of conventional water flooding,making water molecules get into the low permeable region with small pores that conventional water flooding could not reach.17O-NMR technique and capillary analysis proved that iNanoW1.0 nanoparticles could weaken the association of hydrogen bonds between water molecules,effectively change the structure of water molecular clusters,and thus increasing the swept volume in the low permeable region.The ability of weakening association of hydrogen bonds between water molecules of iNanoW1.0 nanoparticles increases with its mass fraction and tends to be stable after the mass fraction of 0.1%.
文摘This paper reports a study on nanocrystalline ceria powder prepared by high energy ball-milling and combustion synthesis methods. The combustion synthesis was carried out using ceric ammonium nitrate as oxidizer and citric acid, glycine or citric acid plus glycine as fuel. The minimum crystallite size of ceria powder is obtained by combustion synthesis of ceric ammonium nitrate and citric acid. The ceria powder produced by combustion synthesis of ceric ammonium nitrate and citric acid and glycine has less agglomeration of particles than other techniques.
基金supported by the National Natural Science Foundation of China (No. 21936001)the Beijing Outstanding Young Scientist Program (No. BJJWZYJH01201910005017)。
文摘Modern chromatography is increasingly focused on miniaturization and integration. Compared to conventional liquid chromatography, microfluidic chip liquid chromatography(microchip-LC) has the potential due to its zero-dead volume connection and ease of integration. Nano-sized packings have the potential to significantly enhance separation performance in microchip-LC. However, their application has been hindered by packing difficulties. This study presents a method for packing nano-sized silica particles into a microchannel as the stationary phase. The microchip-LC packed column was prepared by combining the weir and the porous silica single-particle as frit to retain the packing particles. A surface tensionbased single-particle picking technique was established to insert porous single-particle frit into glass microchannels. Additionally, we developed a slurry packing method that utilizes air pressure to inject nano-sized packing into the microchannel. Pressure-driven chromatographic separation was performed using this nano-packed column integrated into a glass microchip. The mixture of four PAHs was successfully separated within just 8 min using a 5 mm separation channel length, achieving high theoretical plates(10~6plates/m). Overall, these findings demonstrate the potential of utilizing nano-sized packings for enhancing chromatographic performance in microchip systems.
基金supported by Nuclear Research Center of Algiers(CRNA),Department of Laser,Luminescence Laboratory。
文摘Nanosized 1 at% Sm^(3+)doped Y_(2)O_(3)powders were prepared by an ultrasound assisted sol-gel method.Y_(2)O_(3):Sm^(3+)powders crystallize in Y_(2)O_(3)pure cubic phase and XRD analysis shows that the as-used agitation protocol affects strongly the crystallite’s shape and mean size.The recorded emission spectra under λ_(em)=600 nm exhibit two absorption bands;the first one is assigned to O^(2-)→Sm^(3+)charge transfer state(CTS) with a maximum absorption at 223 nm,and the second is due to intraconfigurational transition 4f^(5)-4f^(5) of Sm^(3+) with a maximum absorption at 407 nm.The 223 and 407 nm transitions are attributed to characteristics intra-configurational transitions of Sm^(3+).All emission spectra are dominated by reddish/orange luminescence located at 606 nm and assigned to ^(4)G_(5/2)→^(6)H_(7/2) transition.It is found that the photoluminescence intensity of samples obtained under excitation at 407 nm is 60 times smaller than that obtained under 223 nm excitation.Decay time measurements of the ^(4)G_(5/2)→^(6)H_(7/2) luminescence transition indicate that decay time of nano-sized powder is significantly shorter than bulk material one.
基金Project supported by the National Natural Science Foundation of China(21577094)Zhejiang Public Welfare Technology Research Project(LGG19B070003)the Foundation of Science and Technology of Shaoxing City(2018C10019)。
文摘In this paper,MCM-41 was synthesized by a soft template technique and MCM-41 supported CuO-CeO2 nano-sized catalysts with different Cu/Ce molar ratios were prepared by a deposition-precipitation method.N2 adsorption,HRTEM-EDS,H2-TPR,XPS characterization,as well as catalytic activity and durability tests for the catalytic combustion of chlorobenzene(CB)were conducted to explore the relationship between the structure and catalytic performance of the catalysts.It is revealed that cuCe(6:1)/MCM-41 has the highest activity and can completely catalyze the degradation of CB at 260℃.The reasons for the high activity of the catalysts are as follows:MCM-41,a type of mesoporous material which has large pore size and large specific surface area,is suitable as a catalyst carrier.The average diameter of nano-sized CuO and CeO2 particles is about 3-5 nm and adding CeO2 improves the dispersion of active component CuO,which are highly and evenly dispersed on the surface of MCM-41.Characterization results also explain why MCM-41 supported CuO-CeO2 with appropriate proportion can highly enhance the catalytic activity.The reason is that CeO2 acting as an oxygen-rich material can improve the mobility of oxygen species through continuous redox between Ce4^+and Ce3^+,and improve the catalytic performance of CuO for CB combustion.Besides,CuCe(6:1)/MCM-41 also displays good durability for CB combustion,both in the humid condition and in the presence of benzene,making it a promising catalytic material for the elimination of chlorinated VOCs.
文摘In recent years much attention has been devoted to AgCl emulsion owing to its se-rial advantages and inimitable potential. But in the research of this emulsion a thorny problem remains unsolved till now, which is the improvement in sensitivity is always accompanied with high fog density. In this work 5 nm Ag2S particles were prepared and used as novel sensitizers in AgCl cubic and {100} tabular microcrystal emulsions. The novel sensitizer shows an effective sensitizing ability for silver chloride emulsion, and it is superior to the traditional Na2S2O3 sensi-tizer because by using it comparatively high sensitivity can be obtained with lower fog density. So the above sensitizing problem is going to be effectively solved. To discover the evolution mechanism of the sensitizer clusters and explain their excellent sensitizing properties, diffuse reflectance spectroscopy (DRS) was used as a probe on the AgCl microcrystal surface.
基金This work was supported by the National Natural Science Foundation of China (Grand No. 59971029).
文摘The equation of phase equilibria in nano-sized crystal of metals has been established in terms of thermodynamic equilibrium. The thermodynamic parameters are calculated and the critical grain size for the stable high-temperature phase at room temperature is obtained. As an example, the critical grain size of β-Co at room temperature is determined at 35nm when the excess volume is 10%. The result agrees well with the experiment of Katakimi et al. The factors affecting the stability of β-Co are also discussed.
基金supported by the National Natural Science Foundation of China(Nos.52176099,51376007 and 51806001)the Project of Jiangsu Provincial Six Talent Peak,China(No.JNHB-097)。
文摘This paper presents how the combustion performance of nano-sized aluminum(nAl)powder in carbon dioxide are affected by silica. The ignition and combustion performance of nAl powder with silica addition were studied by a high-temperature tube furnace. An s-type thermocouple and a high-speed motion acquisition instrument were performed to evaluate the ignition temperature, maximum combustion temperature, maximum change of rate of temperature, and combustion propagation speed. The combustion efficiency and combustion products were measured and analyzed by a gas-volumetric method and an X-ray diffraction. The results show that silica added into nAl powder can enhance its maximum combustion temperature and maximum change of rate of temperature, while its ignition temperature increases slightly. The nAl powders with addition of 6.00 wt.% and 12.00 wt.% silica present high combustion propagation speeds, especially for the latter, it has high combustion efficiency. The effect mechanism of silica on the combustion of nAl powder in carbon dioxide was discussed.
基金the National Natural Science Foundation of China (Grant No. 39870221).
文摘Both HA-CdS and HB-CdS (Hys-CdS, Hys represents HA, HB) complex systems were established according to the dynamics of heterogeneous electron-transfer process ＜0. In these systems, the electron transferring from 1Hys* to conduction band of CdS is feasible. Determined from the fluorescence quenching, the apparent association constants (Kapp) between Hypocrellin A (HA), Hypocrellin B (HB) and CdS sol. were about 940 (mol/L)-1, 934 (mol/L)-1, respectively. Fluorescence lifetime measurements gave the rate constant for the electron transfer process from 1HA*, 1HB* into conduction band of CdS semiconductor as 5.16×109 s-1, 5.10×109 s-1, respectively. TEMPO (2,2,6,6-tetramethy-1-piperdinyloxy), a stable nitroxide radical, was used in the kinetic study of the reduction reaction taking place on the surface of a CdS colloidal semiconductor, kinetics equation of the reaction was determined with the electron paramagnetic resonance (EPR) method, and the reaction order of TEMPO is zero. When Hys were added, the rate of EPR increased greatly. By comparing rate constants, the Hys-CdS systems were revealed to be about 350 times more efficient than CdS sol. alone in the photoreduction of TEMPO under visi-ble light. It suggests that Hys can be used as efficient sensitizers of a colloidal semiconductor in the application of solar energy.
文摘1 Results Lithium ion batteries are widely used in many portable devices.However,their power density is not sufficient for use in electric vehicles.One of the most effective methods to improve the power density is the use of very fine cathode particles.We investigated new method,excess lithium method,of preparing nano-sized LiCoO2 powders.To begin with,lithium acetate and cobalt acetate are mixed by the molar ratio 9,13 or 21 to 1,uniformly.And the mixture is calcined at 600 ℃ for 6 hours.Finally,obtain...
基金financially supported by the National Natural Science Foundation of China(31930107)the Fundamental Research Funds for the Central Universities(2021FZZX003-02-06)China Agricultural Research System(No.CARS-36)。
文摘This study aimed to evaluate role of nano-sized zinc(Zn)on lactation performance,health status,and mammary permeability of lactating dairy cows.Thirty multiparous dairy cows with similar days in milk(158±43.2)and body weight(694±60.5 kg)were chosen based on parity and milk production and were randomly assigned to 3 treatment groups:basal diet(control,69.6 mg/kg of Zn adequate in Zn requirement),basal diet additional Zn-methionine(Zn-Met,providing 40 mg/kg of Zn),and basal diet additional nano-sized Zn oxide(nZnO,providing 40 mg/kg of Zn).The study lasted for 10 wk,with the first 2 wk as adaptation.Feed intake,milk yield and the related variables,and plasma variables were determined every other week.Blood hematological profiles were determined in the 8 th week of the study.We found that feed intake,milk yield,and milk composition were similar across the 3 groups.The nZnO-and Zn-Met-fed cows had greater milk Zn concentrations in the milk(3.89 mg/L(Zn-Met)and3.93 mg/L(nZnO))and plasma(1.25 mg/L(Zn-Met)and 1.29 mg/L(nZnO))than the control cows(3.79 mg/L in milk and 1.21 mg/L in plasma).The nZnO-fed cows had higher Zn concentrations in plasma but not in milk compared to Zn-Met-fed cows.The Zn appearance in milk was greater in nZnO-fed(area under curve during the first 4 h post-feeding for milk Zn:16.1 mg/L)and Zn-Met-fed cows(15.7 mg/L)than in control cows(15.0 mg/L).During the first 4 h post-feeding,milk to blood Zn ratio was greater in nZnO-fed animals but lower in Zn-Met-fed cows compared with control cows.Oxidative stress-related variables in plasma,blood hematological profiles,and mammary permeability related variables were not different across treatments.In summary,lactation performance,Zn concentrations in milk and plasma,hematological profiles,mammary permeability were similar in cows fed nZnO and Zn-Met.We therefore suggested that nZnO feeding can improve Zn bioavailability without impairing lactation performance,health status,and mammary gland permeability in dairy cows.
基金supported by the National Natural Science Foundation of China,China(Grant Nos.U20B2018,U21B2086,11972087)。
文摘A novel design of micro-aluminum(μAl)powder coated with bi-/tri-component alloy layer,such as:Ni-P and Ni-P-Cu(namely,Al@Ni-P,Al@Ni-P-Cu,respectively),as combustion catalysts,were introduced to release its huge energy inside Al-core and promote rapid pyrolysis of ammonium perchlorate(AP)at a lower temperature in aluminized propellants.The microstructure of Al@Ni-P-Cu demonstrates that a three-layer Ni-P-Cu shell,with the thickness of~100 nm,is uniformly supported byμAl carrier(fuel unit),which has an amorphous surface with a thickness of~2.3 nm(catalytic unit).The peak temperature of AP with the addition of Al@Ni-P-Cu(3.5%)could significantly drop to 316.2℃ at high-temperature thermal decomposition,reduced by 124.3℃,in comparison to that of pure AP with 440.5℃.It illustrated that the introduction of Al@Ni-P-Cu could weaken or even eliminate the obstacle of AP pyrolysis due to its reduction of activation energy with 118.28 kJ/mol.The laser ignition results showed that the ignition delay time of Al@Ni-P-Cu/AP mixture with 78 ms in air is shorter than that of Al@Ni-P/AP(118 ms),decreased by 33.90%.Those astonishing breakthroughs were attributed to the synergistic effects of adequate active sites on amorphous surface and oxidation exothermic reactions(7597.7 J/g)of Al@Ni-P-Cu,resulting in accelerated mass and/or heat transfer rate to catalyze AP pyrolysis and combustion.Moreover,it is believed to provide an alternative Al-based combustion catalyst for propellant designer,to promote the development the propellants toward a higher energy.
