Cu-Zn ferrite nano thin films were deposited from a target of Cu-Zn ferrite onto a sapphire substrate using XeCl excimer laser operating 308 nm with an energy of 225 mJ and a frequency of 30 Hz. Films were deposited f...Cu-Zn ferrite nano thin films were deposited from a target of Cu-Zn ferrite onto a sapphire substrate using XeCl excimer laser operating 308 nm with an energy of 225 mJ and a frequency of 30 Hz. Films were deposited from the target onto sapphire (001) substrates heated to 650℃ in an oxygen atmosphere of 100 mTorr. The laser beam was incident On the target face at an angle of 45°. Studies on crystal structure were done by X-ray diffactometry (XRD). The surface texture, cross-section morphology and grain size was observed by JEOL-JSM-6400 scanning electron microscopy, atomic force microscopy (AFM) and magnetic force microscopy (MFM) [Model DI 3000, Digital instruments].展开更多
The nano-structural Al-doped ZnO thin films of different morphologies deposited on glass substrate were successfully fabricated at substrate temperature of 350 ℃ by an inexpensive spray pyrolysis method. The structur...The nano-structural Al-doped ZnO thin films of different morphologies deposited on glass substrate were successfully fabricated at substrate temperature of 350 ℃ by an inexpensive spray pyrolysis method. The structural, electrical, optical and photoluminescence properties were investigated. X-ray diffraction study revealed the crystalline wurtzite (hexagonal) structure of the films with nano-grains. Scanning electron microscopy (SEM) micrographs indicated the formation of a large variety of nano-structures during film growth. The spectral absorption of the films occurred at the absorption edge of -410 nm. In the present study, the optical band gap energy 3.28 eV of ZnO decreased gradually to 3.05 eV for 4 mol% of AI doping. The deep level activation energy decreased and carrier concentrations increased substantially with increasing doping. Exciting with the energy 3.543 eV (A=350 nm), a narrow and a broad characteristic photoluminescence peaks that correspond to the near band edge (NBE) and deep level emissions (DLE), respectively emerged.展开更多
The investigation on the oxidation behaviour of Si1-xGex alloys (x=0.05, 0.15, and 0.25) is carried out. It is found for the first time that on the oxide film a germanium nano-cap with a thickness of 1.8-2.8nm and a...The investigation on the oxidation behaviour of Si1-xGex alloys (x=0.05, 0.15, and 0.25) is carried out. It is found for the first time that on the oxide film a germanium nano-cap with a thickness of 1.8-2.8nm and a few Ge nanoparticles with diameters ranging from 5.5 nm to 10 nm are formed by the low-temperatu.re laser-assisted dry oxidation of Si1-xGex substrate. A new scanning method on the decline cross-section of the multiple-layer sample is adopted to measure the layer thickness and the composition. Some new peaks in photoluminescence (PL) spectra are discovered, which could be related to the nano-cap and the nano-particles of germanium. A suitable model and several new calculating formulae with the unrestricted Hartree-Fock-Roothaan (UHFR) method and quantum confinement analysis are proposed to interpret the PL spectra and the nano-structure mechanism in the oxide.展开更多
In the present work, osteoblast behavior on a hierarchical micro-/nano-structured titanium surface was investigated. A hi- erarchical hybrid micro-/nano-structured titanium surface topography was produced via Electrol...In the present work, osteoblast behavior on a hierarchical micro-/nano-structured titanium surface was investigated. A hi- erarchical hybrid micro-/nano-structured titanium surface topography was produced via Electrolytic Etching (EE). MG-63 cells were cultured on disks for 2 h to 7 days. The osteoblast response to the hierarchical hybrid micro-/nano-structured titanium surface was evaluated through the osteoblast cell morphology, attachment and proliferation. For comparison, MG-63 cells were also cultured on Sandblasted and Acid-etched (SEA) as well as Machined (M) surfaces respectively. The results show signifi- cant differences in the adhesion rates and proliferation levels of MG-63 cells on EE, SLA, and M surfaces. Both adhesion rate and proliferation level on EE surface are higher than those on SLA and M surfaces. Therefore, we may expect that, comparing with SLA and M surfaces, bone growth on EE surface could be accelerated and bone formation could be promoted at an early stage, which could be applied in the clinical practices for immediate and early-stage loadings.展开更多
Nano-structured SiO2 thin films were prepared on the surface of carbon steel for the first time by LPD. The compositions of the films were analyzed by XPS, and the surface morphology of the thin films were observed b...Nano-structured SiO2 thin films were prepared on the surface of carbon steel for the first time by LPD. The compositions of the films were analyzed by XPS, and the surface morphology of the thin films were observed by AFM. The thin films were constituted by compact particles of SiO2, and there was no Fe in the films. In the process of film forming, the SiO2 colloid particles were deposited or absorbed directly onto the surface of carbon steel substrates that were activated by acid solution containing inhibitor, and corrosion of the substrates was avoided. The nano-structured SiO2 thin films that were prepared had excellent protective efficiency to the carbon steel.展开更多
The initial field electron emission degradation behaviour of original nano-structured sp^2-bonded amorphous carbon films has been observed, which can be attributed to the increase of the work function of the film in t...The initial field electron emission degradation behaviour of original nano-structured sp^2-bonded amorphous carbon films has been observed, which can be attributed to the increase of the work function of the film in the field emission process analysed using a Fowler-Nordheim plot. The possible reason for the change of work function is suggested to be the desorption of hydrogen from the original hydrogen termination film surface due to field emission current-induced local heating. For the explanation of the emission degradation behaviour of the nano-structured sp2-bonded amorphous carbon film, a cluster model with a series of graphite (0001) basal surfaces has been presented, and the theoretical calculations have been performed to investigate work functions of graphite (0001) surfaces with different hydrogen atom and ion chemisorption sites by using first principles method based on density functional theory-local density approximation.展开更多
Cu-Zn-Al alloy of one dimensional nano-structure was prepared and thestructure of obtained nano-material was characterized by transmission electron microscope (TEM). Itwas shown that there are non-linear oscillations ...Cu-Zn-Al alloy of one dimensional nano-structure was prepared and thestructure of obtained nano-material was characterized by transmission electron microscope (TEM). Itwas shown that there are non-linear oscillations on the surface of Cu-Zn-Al alloy and theconsanguineous connection exists between non-linear oscillation and the growth process of onedimensional nano-structure. The diameter of one dimensional nano-structure is about 40 nm, and theratio of length to diameter is over 40. Finally, the growth mechanism of one dimensionalnano-structure was also studied.展开更多
It was reported that due to the non-linear electrical phenomena,the super-saturated arsenic in silicon single crystalline precipitates during post processing at low temperatures to form different structures.The struct...It was reported that due to the non-linear electrical phenomena,the super-saturated arsenic in silicon single crystalline precipitates during post processing at low temperatures to form different structures.The structure with spatial period of 1.7 to 2.3 nm was observed firstly by TEM on the sample.展开更多
Cobalt supported on carbon nanotubes (CNTs)-covered alumina has been recently developed and successfully utilized as a catalyst in Fischer-Tropsch synthesis (FTS). Problems associated with shaping of Co/CNTs into ...Cobalt supported on carbon nanotubes (CNTs)-covered alumina has been recently developed and successfully utilized as a catalyst in Fischer-Tropsch synthesis (FTS). Problems associated with shaping of Co/CNTs into extrudates or pellets as well as catalyst attrition rendered these materials unfavorable for industrial applications. In this investigation regular γ- and nano-structured (N-S) alumina as well as CNTs-covered regular γ- and N-S-alumina supports were impregnated by cobalt nitrate solution to make new cobalt-based catalysts which were also promoted by Ru. The catalysts were characterized and tested in a micro reactor to evaluate their applicability in FTS. γ-Al2O3 was prepared by calcination of bohemite and N-S-Al2O3 was prepared by sol-gel method using aluminum chloride as starting material. Catalyst evaluations indicated that N-S-Al2O3 was superior to regular γ-Al2O3 and that CNTs-covered alumina supports were favored over non-covered ones in terms of activity and heavy hydrocarbon selectivity. These were justified by porosimetric characteristics of the catalysts and existence of CNTs points of view. CNTs-covered catalysts also showed higher wax selectivity and better resistance to deactivation. Furthermore, TPR analysis indicated that the cobalt aluminate phase, which is responsible for the permanent deactivation of alumina supported Co-based catalysts, did not form on alumina supported Co-based catalysts covered with CNTs due to weaker interactions between cobalt and alumina.展开更多
The Brenner-LJ potential is adopted to describe the interaction between C36 clusters and diamond surface, and the deposition mechanism of multi-C36 clusters on the diamond surface is also studied by using the method o...The Brenner-LJ potential is adopted to describe the interaction between C36 clusters and diamond surface, and the deposition mechanism of multi-C36 clusters on the diamond surface is also studied by using the method of molecular dynamics simulation. The simulation results show that the competition effects of two interactions, i.e. the interaction between cluster and cluster and the interaction between cluster and crystal plane, are studied, and then the influence of these competition effects on C36 cluster deposition is analysed. The finding is that when an incident energy is appropriately chosen, C36 clusters can be chemically adsorbed and deposited steadily on the diamond surface in the form of single-layer, and in the deposition process the multi-C36 clusters present a phenomenon of energy transmission. The experimental result shows that at a temperature of 300K, in order to deposit C36 clusters into a steady nanostructured single-layered film, the optimal incident energy is between 10 and 18 eV, if the incident energy is larger than 18 eV, the C36 clusters will be deposited into an island nano-structured film.展开更多
Graphite electrodes were used for the direct current (DC) arc discharge in water. And high-resolution transmission electron microscopy (HRTEM) was used to investigate the products. Based on the experimental phenom...Graphite electrodes were used for the direct current (DC) arc discharge in water. And high-resolution transmission electron microscopy (HRTEM) was used to investigate the products. Based on the experimental phenomena and nano-structure products, arc plasma characteristics in water were analyzed theoretically. Two growth regions and relevant growth modes were proposed to interpret the formation mechanisms of nano-structures by arc discharge in water. Furthermore, liquid nitrogen and cross magnetic field was applied to change the arcing state respectively, and new carbon nano-structures were obtained. Their formation mechanisms were also analyzed correspondingly.展开更多
The field emission (FE) characteristics of nano-structured carbon films (NSCFs) are investigated. The saturation behaviour of the field emission current density found at high electric field E cannot be reasonably ...The field emission (FE) characteristics of nano-structured carbon films (NSCFs) are investigated. The saturation behaviour of the field emission current density found at high electric field E cannot be reasonably explained by the traditional Fowler-Nordheim (F-N) theory. A three-region E model and the curve-fitting method are utilized for discussing the FE characteristics of NSCFs. In the low, high, and middle E regions, the FE mechanism is reasonably explained by a modified F-N model, a corrected space-charge-limited-current (SCLC) model and the joint model of F N and SCLC mechanism, respectively. Moreover, the measured FE data accord well with the results from our corrected theoretical model.展开更多
A nano-structured surface is formed on the pyramid structure of n-type silicon solar cells by size-controlled silver nano-particle assisted etching. Such a nano-structure creates a front average weighted reflectance o...A nano-structured surface is formed on the pyramid structure of n-type silicon solar cells by size-controlled silver nano-particle assisted etching. Such a nano-structure creates a front average weighted reflectance of less than 2.5% in the 300-1200nm range due to the broadband reflection suppression. The sodium hydroxide is used to obtain the low-area surface by post-etching the nano-structure, thus the severe carrier recombination associated with the nano-structured surface could be reduced. After emitter forming, screen printing and firing by means of the industrial fabrication protocol, an 18.3%-efficient nano-structured silicon solar cell with rear emitter is fabricated. The process of fabricating the solar cells matches well with industrial manufacture and shows promising prospects.展开更多
Titanium64 has characteristics well sought after for applications in demanding environments. In general, due to titanium64’s high performance, it is a material which requires careful and well considered machining app...Titanium64 has characteristics well sought after for applications in demanding environments. In general, due to titanium64’s high performance, it is a material which requires careful and well considered machining approaches in order to optimize the process. Nano-structured bainitic steel whilst having different application bases does none the less have similar machining and machinability short comes as that of titanium64. These similar characteristics have been compared and contrasted in this research study using parameters including cutting force, surface texture and metallography. The results tend to indicate that titanium64 has a poorer machinability characteristics compared to nano-structured bainitic steel. However, in terms of achieving greater surface texture characteristics, the nano-structured bainitic steel exhibited an enhanced capacity.展开更多
Periodic Nanostructured anti-reflection coatings (NALs) are a promising option for enhancing transmission of coherent light without inducing scattering. We’ve found that reducing the height of NALs below a critical v...Periodic Nanostructured anti-reflection coatings (NALs) are a promising option for enhancing transmission of coherent light without inducing scattering. We’ve found that reducing the height of NALs below a critical value to enhance mechanical stability can highly reduce the transmission efficiency. Here, using Rigorous Couples Wave Analysis (RCWA), we find the minimum height for over 99% transmission and effect of height on transmission bandwidth. Then, during a one-step plasma etching, two samples with different heights have been generated and their efficiency is evaluated using RCWA.展开更多
The present article reports on characterization studies performed on amorphized nanostructured Al 6063 alloy powder synthesized by mechanical alloying (MA). The as-milled powder was characterized by X-ray diffraction ...The present article reports on characterization studies performed on amorphized nanostructured Al 6063 alloy powder synthesized by mechanical alloying (MA). The as-milled powder was characterized by X-ray diffraction (XRD) for investigating the development of crystallite nature and determining the different phases of the materials present, scanning electron microscope (SEM) was used for in depth morphological study and High Resolution-transmission electron microscope (HR-TEM) was employed to ensure the development of a nano-structured nature of the Al 6063 matrix. In the present work alloyed powder was milled for 20 h and 40 h at 300 rpm;and 20 h at 700 rpm in a hardened stainless steel medium. Using Williamson-Hall equation;crystallite size, lattice strain and lattice parameter of Al 6063 nanostructure alloy powder was estimated with broadening of XRD peaks. XRD results showed that the crystallite size of Al 6063 alloy powder reached 32 and 53 nm after 20 h at 700 rpm and 40 h at 300 rpm respectively.展开更多
BiFe1-xCoxO3 (x = 0, 0.03, 0.05 and 0.1) symbolic as (BFO, BF3CO, BF5CO and BF10CO) in powder form has been prepared by sol-gel technique using ethylenediamine tetraacetic acid (EDTA) as a chelating agent. X-ray diffr...BiFe1-xCoxO3 (x = 0, 0.03, 0.05 and 0.1) symbolic as (BFO, BF3CO, BF5CO and BF10CO) in powder form has been prepared by sol-gel technique using ethylenediamine tetraacetic acid (EDTA) as a chelating agent. X-ray diffraction (XRD) and FTIR analysis showed rhombohedra distorted BiFeO3 structure with compressive lattice distortion induced by the Co substitution at Fe sites. The transmission electron microscope (TEM) shows irregular particles. The additive of cobalt oxide has led to grains refining giving the following crystallite sizes of 18 nm for BF5Co. The scanning electron microscope (SEM) study reveals that the samples morphology shows relatively uniform grain size distribution. The dielectric properties of BiFeO3 nano-particles in the frequency range of 1 up to 5 MHz at RT revealed that the A.C. conductivity of the prepared samples reaches its maximum value in BF5CO. By decreasing BiFeO3 particle size as a result of doping with different Co ion concentrations, an enhancement in magnetization and a simultaneous suppression in current leakage occurred. The remnant magnetization Mr of BiFe1-xCoxO3 (x = 0, 0.03, 0.05, 0.1) ceramics significantly enhanced, which provides potential applications in information storage.展开更多
A number of techniques have been developed to synthesize nanocrystalline bulk materials,including inert-gas condensation and consolidation,electrodeposition,severe plastic deformation,crystallization of amorphous soli...A number of techniques have been developed to synthesize nanocrystalline bulk materials,including inert-gas condensation and consolidation,electrodeposition,severe plastic deformation,crystallization of amorphous solid,surface mechanical attrition,and powder metallurgy.However,it is hard to produce the bulk with controllable nanostructures,especially with the grain sizes controllable in a wide range below 100 nm.In the conventional powder metallurgy,due to the fact that rapid coarsening of the particles ...展开更多
Barium titanate tin oxides BaTi<sub>0.9</sub>Sn<sub>0.1</sub>O<sub>3</sub> referred to as (BTSO) doped with 0.5Er<sup>3+</sup> and co-doped with (0.75 and 1) Yb<sup&g...Barium titanate tin oxides BaTi<sub>0.9</sub>Sn<sub>0.1</sub>O<sub>3</sub> referred to as (BTSO) doped with 0.5Er<sup>3+</sup> and co-doped with (0.75 and 1) Yb<sup>3+</sup> ions, were prepared using a modified sol-gel method and calcinated at 1050<span style="white-space:nowrap;">?</span>C in the air for 4 h. The influence of the selected rare earth element on the structure morphology, dielectric properties behavior was investigated. From TEM micrographs, it has appeared that the particles have a spherical shape with a small size in nanoscale. The average particle size is determined both by TEM and XRD diffraction was found to be in agreement and within the range between 45.9 and 57.7 nm. The effects of Lanthanide incorporation on the evolution of these nano-crystalline structures were followed by XRD and (FTIR). The XRD patterns give rise to a single perovskite phase, while the tetragonality was found to decrease gradually with Er<sup>3+</sup> and Er<sup>3+</sup>/Yb<sup>3+</sup> ions, respectively. FTIR results showed enhancement of the crystallinity and the absence of carbonates upon increasing Yb<sup>3+</sup> ions concentration from 0.75 up to 1 mol%. The dielectric and conductivity properties were found to be enhanced by the nature and the concentration of the lanthanide element (Er<sup>3+</sup>, Yb<sup>3+</sup>) in the BTSO host lattice. The Curie temperature (T<sub>c</sub>) shifted to a lower value from 117 for BTSO: 0.5Er to 93 for BTSO: 0.5Er/1Yb and the permittivity <em>ε’</em> increased from 3972 to 6071, so BTSO: 0.5Er/1Yb good crystalline material candidate for capacitors application due to its higher permittivity.展开更多
Multifunctional photodetectors boost the development of traditional optical communication technology and emerging artificial intelligence fields, such as robotics and autonomous driving. However, the current implement...Multifunctional photodetectors boost the development of traditional optical communication technology and emerging artificial intelligence fields, such as robotics and autonomous driving. However, the current implementation of multifunctional detectors is based on the physical combination of optical lenses, gratings, and multiple photodetectors, the large size and its complex structure hinder the miniaturization, lightweight, and integration of devices. In contrast, perovskite materials have achieved remarkable progress in the field of multifunctional photodetectors due to their diverse crystal structures, simple morphology manipulation, and excellent optoelectronic properties. In this review, we first overview the crystal structures and morphology manipulation techniques of perovskite materials and then summarize the working mechanism and performance parameters of multifunctional photodetectors. Furthermore, the fabrication strategies of multifunctional perovskite photodetectors and their advancements are highlighted, including polarized light detection, spectral detection, angle-sensing detection, and selfpowered detection. Finally, the existing problems of multifunctional detectors and the perspectives of their future development are presented.展开更多
文摘Cu-Zn ferrite nano thin films were deposited from a target of Cu-Zn ferrite onto a sapphire substrate using XeCl excimer laser operating 308 nm with an energy of 225 mJ and a frequency of 30 Hz. Films were deposited from the target onto sapphire (001) substrates heated to 650℃ in an oxygen atmosphere of 100 mTorr. The laser beam was incident On the target face at an angle of 45°. Studies on crystal structure were done by X-ray diffactometry (XRD). The surface texture, cross-section morphology and grain size was observed by JEOL-JSM-6400 scanning electron microscopy, atomic force microscopy (AFM) and magnetic force microscopy (MFM) [Model DI 3000, Digital instruments].
文摘The nano-structural Al-doped ZnO thin films of different morphologies deposited on glass substrate were successfully fabricated at substrate temperature of 350 ℃ by an inexpensive spray pyrolysis method. The structural, electrical, optical and photoluminescence properties were investigated. X-ray diffraction study revealed the crystalline wurtzite (hexagonal) structure of the films with nano-grains. Scanning electron microscopy (SEM) micrographs indicated the formation of a large variety of nano-structures during film growth. The spectral absorption of the films occurred at the absorption edge of -410 nm. In the present study, the optical band gap energy 3.28 eV of ZnO decreased gradually to 3.05 eV for 4 mol% of AI doping. The deep level activation energy decreased and carrier concentrations increased substantially with increasing doping. Exciting with the energy 3.543 eV (A=350 nm), a narrow and a broad characteristic photoluminescence peaks that correspond to the near band edge (NBE) and deep level emissions (DLE), respectively emerged.
基金Project supported by the Natural Science Foundation of Guizhou Province, China (Grant No 3067(2004)).
文摘The investigation on the oxidation behaviour of Si1-xGex alloys (x=0.05, 0.15, and 0.25) is carried out. It is found for the first time that on the oxide film a germanium nano-cap with a thickness of 1.8-2.8nm and a few Ge nanoparticles with diameters ranging from 5.5 nm to 10 nm are formed by the low-temperatu.re laser-assisted dry oxidation of Si1-xGex substrate. A new scanning method on the decline cross-section of the multiple-layer sample is adopted to measure the layer thickness and the composition. Some new peaks in photoluminescence (PL) spectra are discovered, which could be related to the nano-cap and the nano-particles of germanium. A suitable model and several new calculating formulae with the unrestricted Hartree-Fock-Roothaan (UHFR) method and quantum confinement analysis are proposed to interpret the PL spectra and the nano-structure mechanism in the oxide.
文摘In the present work, osteoblast behavior on a hierarchical micro-/nano-structured titanium surface was investigated. A hi- erarchical hybrid micro-/nano-structured titanium surface topography was produced via Electrolytic Etching (EE). MG-63 cells were cultured on disks for 2 h to 7 days. The osteoblast response to the hierarchical hybrid micro-/nano-structured titanium surface was evaluated through the osteoblast cell morphology, attachment and proliferation. For comparison, MG-63 cells were also cultured on Sandblasted and Acid-etched (SEA) as well as Machined (M) surfaces respectively. The results show signifi- cant differences in the adhesion rates and proliferation levels of MG-63 cells on EE, SLA, and M surfaces. Both adhesion rate and proliferation level on EE surface are higher than those on SLA and M surfaces. Therefore, we may expect that, comparing with SLA and M surfaces, bone growth on EE surface could be accelerated and bone formation could be promoted at an early stage, which could be applied in the clinical practices for immediate and early-stage loadings.
文摘Nano-structured SiO2 thin films were prepared on the surface of carbon steel for the first time by LPD. The compositions of the films were analyzed by XPS, and the surface morphology of the thin films were observed by AFM. The thin films were constituted by compact particles of SiO2, and there was no Fe in the films. In the process of film forming, the SiO2 colloid particles were deposited or absorbed directly onto the surface of carbon steel substrates that were activated by acid solution containing inhibitor, and corrosion of the substrates was avoided. The nano-structured SiO2 thin films that were prepared had excellent protective efficiency to the carbon steel.
文摘The initial field electron emission degradation behaviour of original nano-structured sp^2-bonded amorphous carbon films has been observed, which can be attributed to the increase of the work function of the film in the field emission process analysed using a Fowler-Nordheim plot. The possible reason for the change of work function is suggested to be the desorption of hydrogen from the original hydrogen termination film surface due to field emission current-induced local heating. For the explanation of the emission degradation behaviour of the nano-structured sp2-bonded amorphous carbon film, a cluster model with a series of graphite (0001) basal surfaces has been presented, and the theoretical calculations have been performed to investigate work functions of graphite (0001) surfaces with different hydrogen atom and ion chemisorption sites by using first principles method based on density functional theory-local density approximation.
基金This work was financially supported by the National Climbing Programme of China (No. 1999-444)the Natural Science Foundation of Tianjin (No.003805611 and 033610611) the Center of Liuhui Application Mathematics of Nankai University and Tianjin Univers
文摘Cu-Zn-Al alloy of one dimensional nano-structure was prepared and thestructure of obtained nano-material was characterized by transmission electron microscope (TEM). Itwas shown that there are non-linear oscillations on the surface of Cu-Zn-Al alloy and theconsanguineous connection exists between non-linear oscillation and the growth process of onedimensional nano-structure. The diameter of one dimensional nano-structure is about 40 nm, and theratio of length to diameter is over 40. Finally, the growth mechanism of one dimensionalnano-structure was also studied.
文摘It was reported that due to the non-linear electrical phenomena,the super-saturated arsenic in silicon single crystalline precipitates during post processing at low temperatures to form different structures.The structure with spatial period of 1.7 to 2.3 nm was observed firstly by TEM on the sample.
基金supported by the Research and Technology Directorate of National Iranian Oil Company
文摘Cobalt supported on carbon nanotubes (CNTs)-covered alumina has been recently developed and successfully utilized as a catalyst in Fischer-Tropsch synthesis (FTS). Problems associated with shaping of Co/CNTs into extrudates or pellets as well as catalyst attrition rendered these materials unfavorable for industrial applications. In this investigation regular γ- and nano-structured (N-S) alumina as well as CNTs-covered regular γ- and N-S-alumina supports were impregnated by cobalt nitrate solution to make new cobalt-based catalysts which were also promoted by Ru. The catalysts were characterized and tested in a micro reactor to evaluate their applicability in FTS. γ-Al2O3 was prepared by calcination of bohemite and N-S-Al2O3 was prepared by sol-gel method using aluminum chloride as starting material. Catalyst evaluations indicated that N-S-Al2O3 was superior to regular γ-Al2O3 and that CNTs-covered alumina supports were favored over non-covered ones in terms of activity and heavy hydrocarbon selectivity. These were justified by porosimetric characteristics of the catalysts and existence of CNTs points of view. CNTs-covered catalysts also showed higher wax selectivity and better resistance to deactivation. Furthermore, TPR analysis indicated that the cobalt aluminate phase, which is responsible for the permanent deactivation of alumina supported Co-based catalysts, did not form on alumina supported Co-based catalysts covered with CNTs due to weaker interactions between cobalt and alumina.
基金Project supported by New Century Elitist Supporting Program Foundation by the Ministry of Education of China(Contract No NCET-06-0332)the National Natural Science Foundation of China (Grant No 50405011)
文摘The Brenner-LJ potential is adopted to describe the interaction between C36 clusters and diamond surface, and the deposition mechanism of multi-C36 clusters on the diamond surface is also studied by using the method of molecular dynamics simulation. The simulation results show that the competition effects of two interactions, i.e. the interaction between cluster and cluster and the interaction between cluster and crystal plane, are studied, and then the influence of these competition effects on C36 cluster deposition is analysed. The finding is that when an incident energy is appropriately chosen, C36 clusters can be chemically adsorbed and deposited steadily on the diamond surface in the form of single-layer, and in the deposition process the multi-C36 clusters present a phenomenon of energy transmission. The experimental result shows that at a temperature of 300K, in order to deposit C36 clusters into a steady nanostructured single-layered film, the optimal incident energy is between 10 and 18 eV, if the incident energy is larger than 18 eV, the C36 clusters will be deposited into an island nano-structured film.
基金National Natural Science Foundation of China (No.50377030)
文摘Graphite electrodes were used for the direct current (DC) arc discharge in water. And high-resolution transmission electron microscopy (HRTEM) was used to investigate the products. Based on the experimental phenomena and nano-structure products, arc plasma characteristics in water were analyzed theoretically. Two growth regions and relevant growth modes were proposed to interpret the formation mechanisms of nano-structures by arc discharge in water. Furthermore, liquid nitrogen and cross magnetic field was applied to change the arcing state respectively, and new carbon nano-structures were obtained. Their formation mechanisms were also analyzed correspondingly.
基金Project supported by the National Natural Science Foundation of China (Grant No. 11164031)the Scientific Research Foundation for the Returned Overseas Chinese Scholars,Ministry of Education of China (Grant No. (2009)1341)
文摘The field emission (FE) characteristics of nano-structured carbon films (NSCFs) are investigated. The saturation behaviour of the field emission current density found at high electric field E cannot be reasonably explained by the traditional Fowler-Nordheim (F-N) theory. A three-region E model and the curve-fitting method are utilized for discussing the FE characteristics of NSCFs. In the low, high, and middle E regions, the FE mechanism is reasonably explained by a modified F-N model, a corrected space-charge-limited-current (SCLC) model and the joint model of F N and SCLC mechanism, respectively. Moreover, the measured FE data accord well with the results from our corrected theoretical model.
基金Supported by the National Natural Science Foundation of China under Grant No 51532007the Major Projects of Zhejiang Province under Grant No 2013C01037the Foundation of State Key Lab of Silicon Materials
文摘A nano-structured surface is formed on the pyramid structure of n-type silicon solar cells by size-controlled silver nano-particle assisted etching. Such a nano-structure creates a front average weighted reflectance of less than 2.5% in the 300-1200nm range due to the broadband reflection suppression. The sodium hydroxide is used to obtain the low-area surface by post-etching the nano-structure, thus the severe carrier recombination associated with the nano-structured surface could be reduced. After emitter forming, screen printing and firing by means of the industrial fabrication protocol, an 18.3%-efficient nano-structured silicon solar cell with rear emitter is fabricated. The process of fabricating the solar cells matches well with industrial manufacture and shows promising prospects.
文摘Titanium64 has characteristics well sought after for applications in demanding environments. In general, due to titanium64’s high performance, it is a material which requires careful and well considered machining approaches in order to optimize the process. Nano-structured bainitic steel whilst having different application bases does none the less have similar machining and machinability short comes as that of titanium64. These similar characteristics have been compared and contrasted in this research study using parameters including cutting force, surface texture and metallography. The results tend to indicate that titanium64 has a poorer machinability characteristics compared to nano-structured bainitic steel. However, in terms of achieving greater surface texture characteristics, the nano-structured bainitic steel exhibited an enhanced capacity.
文摘Periodic Nanostructured anti-reflection coatings (NALs) are a promising option for enhancing transmission of coherent light without inducing scattering. We’ve found that reducing the height of NALs below a critical value to enhance mechanical stability can highly reduce the transmission efficiency. Here, using Rigorous Couples Wave Analysis (RCWA), we find the minimum height for over 99% transmission and effect of height on transmission bandwidth. Then, during a one-step plasma etching, two samples with different heights have been generated and their efficiency is evaluated using RCWA.
文摘The present article reports on characterization studies performed on amorphized nanostructured Al 6063 alloy powder synthesized by mechanical alloying (MA). The as-milled powder was characterized by X-ray diffraction (XRD) for investigating the development of crystallite nature and determining the different phases of the materials present, scanning electron microscope (SEM) was used for in depth morphological study and High Resolution-transmission electron microscope (HR-TEM) was employed to ensure the development of a nano-structured nature of the Al 6063 matrix. In the present work alloyed powder was milled for 20 h and 40 h at 300 rpm;and 20 h at 700 rpm in a hardened stainless steel medium. Using Williamson-Hall equation;crystallite size, lattice strain and lattice parameter of Al 6063 nanostructure alloy powder was estimated with broadening of XRD peaks. XRD results showed that the crystallite size of Al 6063 alloy powder reached 32 and 53 nm after 20 h at 700 rpm and 40 h at 300 rpm respectively.
文摘BiFe1-xCoxO3 (x = 0, 0.03, 0.05 and 0.1) symbolic as (BFO, BF3CO, BF5CO and BF10CO) in powder form has been prepared by sol-gel technique using ethylenediamine tetraacetic acid (EDTA) as a chelating agent. X-ray diffraction (XRD) and FTIR analysis showed rhombohedra distorted BiFeO3 structure with compressive lattice distortion induced by the Co substitution at Fe sites. The transmission electron microscope (TEM) shows irregular particles. The additive of cobalt oxide has led to grains refining giving the following crystallite sizes of 18 nm for BF5Co. The scanning electron microscope (SEM) study reveals that the samples morphology shows relatively uniform grain size distribution. The dielectric properties of BiFeO3 nano-particles in the frequency range of 1 up to 5 MHz at RT revealed that the A.C. conductivity of the prepared samples reaches its maximum value in BF5CO. By decreasing BiFeO3 particle size as a result of doping with different Co ion concentrations, an enhancement in magnetization and a simultaneous suppression in current leakage occurred. The remnant magnetization Mr of BiFe1-xCoxO3 (x = 0, 0.03, 0.05, 0.1) ceramics significantly enhanced, which provides potential applications in information storage.
文摘A number of techniques have been developed to synthesize nanocrystalline bulk materials,including inert-gas condensation and consolidation,electrodeposition,severe plastic deformation,crystallization of amorphous solid,surface mechanical attrition,and powder metallurgy.However,it is hard to produce the bulk with controllable nanostructures,especially with the grain sizes controllable in a wide range below 100 nm.In the conventional powder metallurgy,due to the fact that rapid coarsening of the particles ...
文摘Barium titanate tin oxides BaTi<sub>0.9</sub>Sn<sub>0.1</sub>O<sub>3</sub> referred to as (BTSO) doped with 0.5Er<sup>3+</sup> and co-doped with (0.75 and 1) Yb<sup>3+</sup> ions, were prepared using a modified sol-gel method and calcinated at 1050<span style="white-space:nowrap;">?</span>C in the air for 4 h. The influence of the selected rare earth element on the structure morphology, dielectric properties behavior was investigated. From TEM micrographs, it has appeared that the particles have a spherical shape with a small size in nanoscale. The average particle size is determined both by TEM and XRD diffraction was found to be in agreement and within the range between 45.9 and 57.7 nm. The effects of Lanthanide incorporation on the evolution of these nano-crystalline structures were followed by XRD and (FTIR). The XRD patterns give rise to a single perovskite phase, while the tetragonality was found to decrease gradually with Er<sup>3+</sup> and Er<sup>3+</sup>/Yb<sup>3+</sup> ions, respectively. FTIR results showed enhancement of the crystallinity and the absence of carbonates upon increasing Yb<sup>3+</sup> ions concentration from 0.75 up to 1 mol%. The dielectric and conductivity properties were found to be enhanced by the nature and the concentration of the lanthanide element (Er<sup>3+</sup>, Yb<sup>3+</sup>) in the BTSO host lattice. The Curie temperature (T<sub>c</sub>) shifted to a lower value from 117 for BTSO: 0.5Er to 93 for BTSO: 0.5Er/1Yb and the permittivity <em>ε’</em> increased from 3972 to 6071, so BTSO: 0.5Er/1Yb good crystalline material candidate for capacitors application due to its higher permittivity.
基金supported financially by the National Key R&D Program of China (Nos. 2018YFA0208501 and 2018YFA0703200)the National Natural Science Foundation of China (NSFC, Nos. 52103236, 91963212, 21875260)Beijing National Laboratory for Molecular Sciences (No. BNLMSCXXM-202005)。
文摘Multifunctional photodetectors boost the development of traditional optical communication technology and emerging artificial intelligence fields, such as robotics and autonomous driving. However, the current implementation of multifunctional detectors is based on the physical combination of optical lenses, gratings, and multiple photodetectors, the large size and its complex structure hinder the miniaturization, lightweight, and integration of devices. In contrast, perovskite materials have achieved remarkable progress in the field of multifunctional photodetectors due to their diverse crystal structures, simple morphology manipulation, and excellent optoelectronic properties. In this review, we first overview the crystal structures and morphology manipulation techniques of perovskite materials and then summarize the working mechanism and performance parameters of multifunctional photodetectors. Furthermore, the fabrication strategies of multifunctional perovskite photodetectors and their advancements are highlighted, including polarized light detection, spectral detection, angle-sensing detection, and selfpowered detection. Finally, the existing problems of multifunctional detectors and the perspectives of their future development are presented.