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Synthesis of Nano-sized Yttria via a Sol-Gel Process Based on Hydrated Yttrium Nitrate and Ethylene Glycol and Its Catalytic Performance for Thermal Decomposition of NH_4ClO_4 被引量:11
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作者 陈伟凡 李凤生 +1 位作者 刘磊力 李永绣 《Journal of Rare Earths》 SCIE EI CAS CSCD 2006年第5期543-548,共6页
Nano-sized yttria particles were synthesized via a non-aqueous sol-gel process based on hydrated yttrium nitrate and ethylene glycol. The effects of the molar ratio of ethylene glycol to yttrium ion and calcination te... Nano-sized yttria particles were synthesized via a non-aqueous sol-gel process based on hydrated yttrium nitrate and ethylene glycol. The effects of the molar ratio of ethylene glycol to yttrium ion and calcination temperature on crystallite size of the products were studied. The catalytic performance of the as-prepared yttria for the ammonium perchlorate (AP) decomposition was investigated by differential scanning calorimetry (DSC). The results indicate that the nano-sized cubic yttria particles with less than 20 nm in average crystallite size can be obtained after 2 h reflux at 70℃, dried at 90 ℃, forming xerogel, and followed by annealing of xerogel for 2 h, and that the addition of the nano-sized yttria to AP incorporates two small exothermic peaks of AP in the temperature ranges of 310 - 350 ℃ and 400 - 470 ℃ into a strong exothermic peak of AP and increases the apparent decomposition heat from 515 to over 1110 J·g^- 1. It is also clear that the temperature of AP decomposition exothermic peak decreases and the apparent decomposition heat of AP increases with the increase of the amount of nano-sized yttria. The fact that the addition of the 5 % nano-sized yttria to AP decreases the temperature of AP exothermic peak to 337.7℃ by reduction of 114.6℃ and increases the apparent decomposition heat from 515 to 1240 J·g^-1, reveals that nano-sized yttria shows strong catalytic property for AP thermal decomposition. 展开更多
关键词 nano-sized yttria ethylene glycol sol-gel ammonium perchlorate thermal decomposition catalytic property rare earths
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NiMo/Al_2O_3 catalyst containing nano-sized zeolite Y for deep hydrodesulfurization and hydrodenitrogenation of diesel 被引量:8
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作者 Hailiang Yin Tongna Zhou Yunqi Liu Yongming Chai Chenguang Liu 《Journal of Natural Gas Chemistry》 EI CAS CSCD 2011年第4期441-448,共8页
Two mixed-matrix NiMo/Al2O3 catalysts containing nano-and micro-sized zeolite Y have been prepared to explore the size effect of zeolite Y particle on the hydrodesulfurization(HDS)and hydrodenitrogenation(HDN)acti... Two mixed-matrix NiMo/Al2O3 catalysts containing nano-and micro-sized zeolite Y have been prepared to explore the size effect of zeolite Y particle on the hydrodesulfurization(HDS)and hydrodenitrogenation(HDN)activities of fluid catalytic cracking(FCC)diesel.They were characterized by SEM,BET,XRD,H2-TPR,NH3-TPD and HRTEM.The results show that the catalyst containing nano-sized zeolite Y possesses larger average pore diameter,higher pore volume,weaker and lesser acid sites,more easily reducible metal phases,shorter MoS2 slabs and more slab layers than the catalyst containing micro-sized zeolite Y.The catalysts were also evaluated with a high-pressure fixed-bed reactor using real FCC diesel as feed.The results display that the catalyst containing nano-sized zeolite Y bears higher HDS and HDN activities and exhibits higher relative rate constant for the removal of total sulfur or nitrogen than the one containing micro-sized zeolite. 展开更多
关键词 zeolite Y nano-sized zeolite micro-sized zeolite HYDRODESULFURIZATION HYDRODENITROGENATION DIESEL
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Synthesis of Neodymium-Doped Yttrium Aluminum Garnet (Nd∶YAG) Nano-Sized Powders by Low Temperature Combustion 被引量:8
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作者 张华山 苏春辉 +1 位作者 韩辉 侯朝霞 《Journal of Rare Earths》 SCIE EI CAS CSCD 2005年第3期304-308,共5页
The homogeneously dispersed, less agglomerated (Nd0.01Y0.99)3Al5O12 nano-sized powders were synthesized by the low temperature combustion (LCS), using Nd2O3, Y2O3, Al(NO3)3·9H2O, ammonia water and citric acid as ... The homogeneously dispersed, less agglomerated (Nd0.01Y0.99)3Al5O12 nano-sized powders were synthesized by the low temperature combustion (LCS), using Nd2O3, Y2O3, Al(NO3)3·9H2O, ammonia water and citric acid as starting materials. This method effectively solves the problems caused by solid-state reaction at high temperature and hard agglomerates brought by the chemical precipitation method. The powders were characterized by TG-DTA, XRD, FT-IR, TEM respectively and the photoluminescence (PL) spectra of (Nd0.01Y0.99)3Al5O12 green and sintered ceramic disks were measured. The results show that the forming temperature of YAG crystal phase is 850 ℃ and YAP crystal phase appearing during the calcinations transforms to pure YAG at 1050 ℃. The particle size of the powders synthesized by the LCS is in a range of 20~50 nm depending on the thermal treatment temperatures. The effectively induced cross section (σin) with the value 4.03×10-19 cm2 of (Nd0.01Y0.99)3Al5O12 ceramics is about 44% higher than that of single crystal. 展开更多
关键词 laser ceramics neodymium-doped yttrium aluminum garnet (Nd∶YAG) nano-sized powders low temperature combustion synthesis (LCS)
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Comparative study of the explosion pressure characteristics of micro- and nano-sized coal dust and methane–coal dust mixtures in a pipe 被引量:5
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作者 Bo Tan Huilin Liu +1 位作者 Bin Xu Tian Wang 《International Journal of Coal Science & Technology》 EI 2020年第1期68-78,共11页
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
关键词 A pipe test apparatus nano-sized Coal dust explosion Methane/coal dust explosion Pressure characteristics
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Synthesis and Characterization of Nano-sized Boron Powder Prepared by Plasma Torch 被引量:4
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作者 黄志军 吴青友 +3 位作者 李祥 尚书勇 戴晓雁 印永祥 《Plasma Science and Technology》 SCIE EI CAS CSCD 2010年第5期577-580,共4页
Hydrogen thermal plasma jet was employed to prepare nano-sized boron powder with hydrogen reduction of BCI3. The maximum yield of nano-sized boron powders was about 50% with the operational conditions of H2/BCl3 of 4.... Hydrogen thermal plasma jet was employed to prepare nano-sized boron powder with hydrogen reduction of BCI3. The maximum yield of nano-sized boron powders was about 50% with the operational conditions of H2/BCl3 of 4.5:1, total feed of 4.9 m3/h, and plasma power of 25 kW. The samples were analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and inductively coupled plasma - mass spectrometry (ICP-MS), inductively coupled plasma - atomic emission spectrometry (ICP-AES), inductive combustion infrared absorption (ICIA) and infrared thermal conductivity of oxygen and nitrogen analyzer (ITCA). The results show that the boron powders have different crystal structures with higher dispersion and purity. The average diameter is about 50 nm, and the purity is 90.29% or so. This new technology can use simple process to produce high quality boron powders, and is feasible for industrial production. 展开更多
关键词 nano-sized boron powder thermal plasma ultra-fine powder
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Effect of deep cryogenic treatment on the formation of nano-sized carbides and the wear behavior of D2 tool steel 被引量:3
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作者 Kamran Amini Amin Akhbarizadeh Sirus Javadpour 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2012年第9期795-799,共5页
The effect of deep cryogenic treatment on the microstructure, hardness, and wear behavior of D2 tool steel was studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffracti... The effect of deep cryogenic treatment on the microstructure, hardness, and wear behavior of D2 tool steel was studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), hardness test, pin-on-disk wear test, and the reciprocating pin-on-fiat wear test. The results show that deep cryogenic treatment eliminates retained austenite, makes a better carbide distribution, and increases the carbide content. Furthermore, some new nano-sized carbides form during the deep cryogenic treatment, thereby increasing the hardness and improving the wear behavior of the samples. 展开更多
关键词 cryogenic treatment tool steel nano-sized carbides wear resistance HARDNESS AUSTENITE
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Effects of nano-sized aluminum on detonation characteristics and metal acceleration for RDX-based aluminized explosive 被引量:3
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作者 Dan-yang Liu Pin Zhao +2 位作者 Serene Hay-Yee Chan Huey Hoon Hng Lang Chen 《Defence Technology(防务技术)》 SCIE EI CAS CSCD 2021年第2期327-337,共11页
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
关键词 nano-sized aluminum Detonation reaction zone Explosive metal acceleration Thermodynamic equilibrium calculation Laser interferometry
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Fabrication of Fine-Grained Si_3N_4-Si_2N_2O Composites by Sintering Amorphous Nano-sized Silicon Nitride Powders 被引量:3
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作者 骆俊廷 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2006年第3期97-99,共3页
Si3N4-Si2N2O composites were fabricated with amorphous nano-sized silicon nitride powders by the liquid phase sintering ( LPS ). The Si2 N2O phase was generated by an in-situ reaction 2 Si3 N4 ( s ) + 1.5 02 ( g... Si3N4-Si2N2O composites were fabricated with amorphous nano-sized silicon nitride powders by the liquid phase sintering ( LPS ). The Si2 N2O phase was generated by an in-situ reaction 2 Si3 N4 ( s ) + 1.5 02 ( g ) = 3 Si2 N2O ( s ) + N2 ( g ) . The content of Si2 N2 O phase up to 60% in the volume was obtained at a sintering temperature of 1 650℃ and reduced when the sintering temperature increased or decreased, indicating the reaction is reversible. The mass loss, relative density and average grain size increased with increasing the sintering temperature. The average grain size was less than 500 nm when the sintering temperature was below 1 700 ℃. The sintering procedure contains a complex crystallization and a phase transition : amorphous silicon nitride→equiaxial α- Si3 N4→ equiaxial β- Si3 N4→ rod- like Si2 N2O→ needle- like β- Si3N4 . Small round-shaped β→ Si3 N4 particles were entrapped in the Si2 N2O grains and a high density of staking faults was situated in the middle of Si2 N2O grains at a sintering temperature of 1 650 ℃. The toughness inereased from 3.5 MPa·m^1/2 at 1 600 ℃ to 7.2 MPa· m^1/2 at 1 800 ℃ . The hardness was as high as 21.5 GPa (Vickers) at 1 600 ℃ . 展开更多
关键词 Si3N4-Si2N2O composite in-situ reaction amorphous nano-sized silicon nitride
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Seed-Assisted Synthesis and Catalytic Performance of Nano-sized ZSM-5 Aggregates in a One-Step Crystallization Process 被引量:2
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作者 Ziyang Wang Yaquan Wang +8 位作者 Chao Sun Aijuan Zhao Cui Wang Xu Zhang Jingjing Zhao Taotao Zhao Wenrong Liu Jiaxin Lu Shuhui Wu 《Transactions of Tianjin University》 EI CAS 2020年第4期292-304,共13页
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
关键词 Hierarchical ZSM-5 nano-sized aggregates Seed-assisted CTAB Toluene alkylation with methanol
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Fluoride-mediated nano-sized high-silica ZSM-5 as an ultrastable catalyst for methanol conversion to propylene 被引量:1
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作者 Junjie Li Min Liu +2 位作者 Xinwen Guo Chengyi Dai Chunshan Song 《Journal of Energy Chemistry》 SCIE EI CAS CSCD 2018年第4期1225-1230,共6页
Fluoride mediated nano-sized ZSM-5 (ZSM-5-F) with a high Si/AI ratio of 181 was fabricated using a seed-induction method and evaluated the catalysis of the methanol to propylene (MTP) reaction. High propylene sele... Fluoride mediated nano-sized ZSM-5 (ZSM-5-F) with a high Si/AI ratio of 181 was fabricated using a seed-induction method and evaluated the catalysis of the methanol to propylene (MTP) reaction. High propylene selectivity (45%) was similar to ZSM-5-OH synthesized via a hydroxide route. However, ZSM- 5-F showed much longer lifetime (305 h) compared with ZSM-5-OH (157 h) in spite of similar crystal size and aluminum content. Characterization by NH3-TPD. Py-IR, OH-IR, SEM, TG-DTA, XRD and 1H MAS NMR techniques indicated that the enhanced catalytic performance of ZSM-S-F is attributed to the fewer structural defects in the form of internal silanol groups and silanol nests. 展开更多
关键词 Fluoride route nano-sized High Si/Al Structural defects MTP
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Enhancing the Deactivation Durability of Nano-sized HZSM-5 for Aromatization by Adjusting its Ratio of Lewis/Brφnsted Acid Sites
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作者 ZhouBoXU HongChenGUO +3 位作者 XiangShengWANG PeiQingZHANG LePingZHAO YongKangHU 《Chinese Chemical Letters》 SCIE CAS CSCD 2004年第9期1123-1126,共4页
Ratio of Lewis/Brfnsted acid sites (Cl/Cb) on the surface of nano-sized HZSM-5 was successfully manipulated by means of steaming and acid leaching. Significant enhancement of the deactivation durability of nano-sized... Ratio of Lewis/Brfnsted acid sites (Cl/Cb) on the surface of nano-sized HZSM-5 was successfully manipulated by means of steaming and acid leaching. Significant enhancement of the deactivation durability of nano-sized HZSM-5 in the aromatization of fluid catalytic cracking (FCC) gasoline olefins seems to be closely related to the increase of Lewis/Brfnsted acid sites ratio. 展开更多
关键词 Lewis acid Brfnsted acid nano-sized HZSM-5 AROMATIZATION gasoline.
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Preparation and Mechanical Properties of Micro- and Nano-sized SiC/Fluoroelastomer Composites
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作者 率志君 刘志刚 +5 位作者 WANG Donghua ZHOU Pan LI Wanyou QIAO Yingjie LIU Ruiliang ZHOU Shi 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2013年第4期658-663,共6页
Microand nano-sized SiC/fluoroelastomer (FKM) composites were prepared by a mechanical mixing method. These composites were first characterized by a rotorless rheometer. Then the effects of micro- and nano-sized SiC... Microand nano-sized SiC/fluoroelastomer (FKM) composites were prepared by a mechanical mixing method. These composites were first characterized by a rotorless rheometer. Then the effects of micro- and nano-sized SiC on hardness, static and dynamic mechanical properties of the composites were investigated. The increasing amount of the SiC filler increased the curing efficiency of the biphenyl curing system, which was evident from the rheometric properties of the resulting composites. The tensile properties of composite increased with the increasing of micro- and nano-sized SiC content. When the micro- and nano-sized SiC content was higher than 20 phr, the composites showed almost unchanged tensile properties. The increasing of the tensile property was mainly attributed to the well dispersed micro- and nano-sized SiC particles characterized by SEM images. Compared to pure FKM, the composites exhibited a higher glass transition temperature and lower tan peak value. 展开更多
关键词 fluoroelastomer (FKM) micro- and nano-sized SiC composites mechanical properties
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Mechanism of expanding swept volume by nano-sized oil-displacement agent
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作者 LEI Qun LUO Jianhui +6 位作者 PENG Baoliang WANG Xiaocong XIAO Peiwen WANG Pingmei HE Lipeng DING Bin GENG Xiangfei 《Petroleum Exploration and Development》 2019年第5期991-997,共7页
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
关键词 nanoparticles nano-sized oil-displacement AGENT WATER FLOODING swept volume WATER molecular hydrogen bonding capillary action
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Combustion and Ball Milled Synthesis of Rare Earth Nano-Sized Ceria Powder
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作者 Ranjan Sen Siddhartha Das Karabi Das 《Materials Sciences and Applications》 2011年第5期416-420,共5页
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
关键词 Ceramics Ball MILLING COMBUSTION Synthesis nano-sized CERIA X-Ray DIFFRACTION
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Nano-sized stationary phase packings retained by single-particle frit for microchip liquid chromatography
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作者 Wangyan Hu Ke Li +2 位作者 Xiangnan Dou Ning Li Xiayan Wang 《Chinese Chemical Letters》 SCIE CAS CSCD 2024年第4期486-489,共4页
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
关键词 nano-size packing Single-particle frit Packed column Microchip LC Chromatographic separation
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Structural,morphological and photoluminescence characterizations of Sm^(3+) doped Y_(2)O_(3) nano-sized phosphors synthesized by ultrasound assisted sol-gel method 被引量:1
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作者 Lyes Lamiri Badis Kahouadji +8 位作者 Mourad Berd Abdelmoumen Abdellatif Lotfi Benchallal Lakhdar Guerbous Salim Ouhenia Abdelhafid Souici Leila Amiour Abdelhalim Zoukel Madani Samah 《Journal of Rare Earths》 SCIE EI CAS CSCD 2023年第1期51-59,共9页
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
关键词 Y_(2)O_(3):Sm^(3+)nano-sized powder Sol-gel method ULTRASOUND Charge transfer PHOTOLUMINESCENCE Rare earths
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MCM-41 supported nano-sized CuO-CeO2 for catalytic combustion of chlorobenzene 被引量:7
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作者 Jie Zheng Zhu Chen +2 位作者 Jianfei Fang Zhuo Wang Shufeng Zuo 《Journal of Rare Earths》 SCIE EI CAS CSCD 2020年第9期933-940,I0001,共9页
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
关键词 CuO-CeO2 MCM-41 nano-sized CHLOROBENZENE Catalytic combustion Rare earths
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Morphology and photocatalytic performance of nano-sized TiO_2 prepared by simple hydrothermal method with different pH values 被引量:7
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作者 Hao Xu Shi-Qi Liu +5 位作者 Shan Zhou Tang-Zhi-Jiu Yuan Xiang Wang Xia Tang Jian Yin Hui-Jin Tao 《Rare Metals》 SCIE EI CAS CSCD 2018年第9期750-758,共9页
pH value is a key factor in the preparation of nano-sized TiO2 with hydrothermal method. Using Ti(SO4)2 as the titanium source, H2O2 as the complexing agent, NaOH and HCl as the pH value regulator, nano- sized TiO2 ... pH value is a key factor in the preparation of nano-sized TiO2 with hydrothermal method. Using Ti(SO4)2 as the titanium source, H2O2 as the complexing agent, NaOH and HCl as the pH value regulator, nano- sized TiO2 powder with various morphologies and sizes was synthesized. Changes in morphology, size and phase type with pH values of samples were characterized by X-ray diffraction (XRD) and transmission electron micro- scopy (TEM) measurements. Results show that under the present preparation conditions, TiO2 powder is an anatase phase with pH value less than 11, but is more likely to be a brookite phase with pH value more than 11. With the increase in pH value from 1 to 11 in hydrothermal envi- ronment, nano-sized anatase TiO2 gradually grows up in all directions. {001 }, { 101 } and { 100} groups of crystal plane are the exposed crystal planes of nano-sized anatase TiO2 for the (004), (101) and (200) facets found in high-reso- lution TEM image. The photocatalytic performance of nano-sized TiO2 with different morphologies was com- pared by measuring their photocatalytic degradation rates for methylene blue under ultraviolet light. Results show that anatase TiO2 prepared under the alkalescenthydrothermal environment (pH = 9, 11) has a better pho- tocatalytic degrading performance. Different sizes and phases of nanoscaled TiO2 powders with different photo- catalytic performances can be prepared by the control of pH value of hydrothermal solutions. 展开更多
关键词 Hydrothermal method pH value ANATASE BROOKITE nano-sized crystal morphology
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Synthesis of Ag_2S nano-sized clusters and their chemical sensitizations in AgCl cubic and {100} tabular microcrystal imaging systems 被引量:4
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作者 LI Zhi1, ZHENG Tong1, CHEN Lijuan1, PENG Bixian1 & YANG Li2 1. Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100101, China 2. Beijing Satellite Manufacturing Factory, Beijing 100080, China 《Science China Chemistry》 SCIE EI CAS 2005年第6期516-522,共7页
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
关键词 SILVER sulfide nano-sized SILVER chloride {100} TABULAR microcrystal chemical sensitization.
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The structural stability in nano-sized crystals of metals 被引量:3
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作者 孟庆平 戎咏华 徐祖耀 《Science China(Technological Sciences)》 SCIE EI CAS 2002年第5期485-494,共10页
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
关键词 phase transformation nano-sized crystal energy of interface CRITICAL size EXCESS volume.
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