2007 Vol. 20, No. 6

The special issue from "The 6th China International Conferenceon Nanoscience and Technology, Chengdu (2007)"
"ZnO ellipsoid-like structures assembled by ZnO nanrods were fabricated from common ZnO whiskers by autoclave tests and pyrolysis integrated method. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, and high resolution transmission electron microscopy studies reveal ZnO ellipsoidal structures are single-crystals and formed from direct oriented attachment of nanorods. Raman and room temperature photoluminescence spectra are also discussed."
"Three-dimensional molecular dynamics simulations of nanometric cutting monocrystalline copper using atomic force microscopy pin tool are conducted to investigate the effect of crystal orientation and corresponding cutting direction on the deformation characteristics. EAM potential and Morse potential are utilized respectively to compute the interactions between workpiece atoms, interactions between workpiece atoms and tool atoms. The results reveal that the nanometric cutting processes are significantly affected by crystal orientation and cutting direction. Along the [110] cutting direction, better quality of chip pattern and smaller workpiece material deformation region can be obtained than along the [100] cutting direction. Cutting the workpiece material (110) crystal orientation, samaller chip volume and smaller subsurface deformed region can be obtained than cutting the workpiece material (100) crystal orientation. The variations of workpiece atoms potential energy in different cutting processes are investigated."
"To improve the performance of traditional cast iron, trance amount of surface modified nanometer SiC powders were added into the melted iron. The microstructures, the mechanical properties, as well as the wear resistance were investigated. The trace addition of SiC nano-powders were active due to the presence of structural defects arising from the treatment, they were eoient in affecting not only the generation and growth of crystals but also change the morphology of graphite. On the other hand, the addition of SiC nanopowders as heterogeneous seedings in the crystallization of liquid metals lead to the changing of supercooling temperature, so the ratio of ferrite and pearlite was changed. The mechanical characteristics and wear resistance were enhanced as a result of the improved graphite shape and changed matrix composition caused by the trace addition of SiC nanopowders (in amounts of about 0.01% mass). The strengthening mechanism and the free gap between powders were also discussed. It is suggested that the tensile strength, toughness, as well as the wear resistance can be improved simultaneously, which indicates the novel strengthening technology by trace addition of nanopowders is promising to extend to large-scale industrial production."
"Sulfur-doped zinc oxide (ZnO) nanowires were successfully synthesized by an electric field-assisted electrochemical deposition in porous anodized aluminum oxide template at room temperature. The structure, morphology, chemical composition and photoluminescence properties of the as-synthesized ZnO:S nanostructures were investigated. X-ray diffraction and the selected area electron diffraction results reveal that the as-ynthesized products are single phase with hexagonal wurtzite structure with a highly preferential orientation in the (101) direction. Transmission electron microscopy observations indicate that the nanowires are niform with an average diameter of 70 nm and length up to several tens of micrometers. X-ray photoelectron pectroscopy further reveals the presence of S in the ZnO nanowires. Room-temperature photoluminescences observed in the sulfur-doped ZnO nanowires which exhibits strong near-band-edge ultraviolet peaks at 378 and 392 nm and weak green emissions at 533 and 507 nm. A blue emission at 456 nm and violet emissions at around 406, 420, and 434 nm were also observed in the PL spectrum for the as-synthesized ZnO:S nanowires. The PL spectrum shows that S-doping had an obvious effect on the luminescence property of typical ZnO nanowires."
"Brenner-LJ potential is adopted to describe the interactivity between diamond and C36 cluster, and the deposition mechanism of multi-C36 on the diamond surface is researched by molecular dynamics simulation. Through simulative experiments the incident energy, incident point, incident posture, incident angle and other factors are analyzed. Studies discover that the minimal deposition threshold is 20 eV and the maximum is 60 eV with the different incident point locations and incident postures of C36 clusters. When the incident angle is not over 60ffi, C36 may roll or slip to the region of smaller bonding energy and then bond. So the bonding probability is raised. Research results show that when incident angle is between 0ffi and 20ffi and incident energy range is from 30 eV to 60 eV, it is the optimal condition of single C36 cluster deposition on diamond (100) crystal plane."
"Ice polishing single silicon wafers with nano-sized Al2O3 abrasives can be known as ice fixed abrasives chemical mechanical polishing (IFA-CMP). TAn abrasive slurry was made of nano-sized Al2O3 particles dispersed in de-ionized water with a surfactant and the slurry was frozen to form an ice polishing pad. Then polishing tests of blanket silicon wafers with the above ice polishing pad were carried out. The morphologies and surface roughness of the polished silicon wafers were observed and examined on an atomic force microscope. The subsurface damage was assessed by means of cross-section transmission electron microscopy. The surface chemical constituents of the polished silicon wafers were characterized using X-ray photoelectron spectroscopy in order to gain insight into the chemical mechanisms in the process. Scratch resistance of the single silicon wafer was measured by nanoscratching using a nanoindenter to explore the mechanical removal mechanism. The results show that a super smooth surface with an average roughness of 0.367 nm is obtained within 1000 nm£1000 nm and there is a perfect silicon diamond structure without any microcracks in the subsurface. The removal of material is dominated by the coactions of ductile regime machining and chemical corrosion. In the end, a model of material removal of IFA-CMP is built."
"Three-dimensional molecular dynamics simulations have been carried out to predict the mechanical properties of a single crystalline copper with different scratching depths and no defects by embedded-atom method potential respectively. The mechanical properties for nanostructure with no defects and machined groove are investigated by various strain rates, scratched depths and scratching directions. Through the visualization technique of atomic coordination number, the onset and movement of defects in workpiece such as dislocations are analyzed under tensile loads. Work-harden formation, recrystallization behavior and the properties of rupturing process of nanostructure are exhibited at the atomic view. The relation between stress and the onset and evolvement of defects in specimen is analyzed for fundamental understanding the mechanical properties of nanostructure."
"The chemomechanical method was used to scribe the silicon surface with a diamond-tipped instrument in the presence of aryldiazonium salt, the silicon and the arenes was connected with covalent bond, and realize simultaneously functionalizing and patterning silicon. This provided experiment basis for building nano-scale functional structure. At first we scribe the silicon with a diamond-tipped instrument in the atmospheric, and get the micro-structure with better surface quality, which was then used as substrate for the next functionalizing and patterning silicon. By the silicon's controlled self-assembly experiments in the solution, the cutting speed, cutting assembly time in accord with the self-assembled monolayers' quality (SAMs), and more parameters suitable for the film growth are obtained. X-ray photoelectron spectroscopy was used to test the self-assembly monolayers, and atomic force microscopy as well as scanning electron microscopy to characterize the surface morphology. Results show that this method can eoiently achieve simultaneously functionalizing and patterning silicon. We also connect the carbon nanotubes to the SAMs, and charatrerize the surface with AFM. This will provide experimental basis for the further study using SAMs to function silicon surface."
"An in situ polymerization process was used to prepare poly (methyl methacrylate) (PMMA)-functionalized carboxyl multi-walled carbon nanotubes using carboxylate carbon nanotubes and methyl methacrylate as reactants and benzoyl peroxide as an initiator agent. The functionalized multi-walled carbon nanotubes were characterized using transmission electron microscope, scanning electron microscope, nuclear magnetic resonance, Fourier transform infrared spectroscopy, thermogravimetric analysis and Raman. The results indicate that the PMMA chains are covalently linked with the surface of carboxylate carbon nanotubes. The surface morphology is controlled by the content of carboxylate carbon nanotubes in the reactants. The PMMA functionalized multi-walled carbon nanotubes are soluble in deuterated chloroform. The storage modulus and tanffi magnitude increase as the content of CCNTs increases up to 0.3%."
"Compositionally graded ferroelectric lead zirconate titanate Pb(Zr1-xTix)O3 (PZT) thin films were grown on Pt/Ti/SiO2/Si substrates by using a sol-gel process. The final structure consists of six layers, up-graded graded films starting from PbZrO3 on the Pt electrode to the top PZT(50) layer, it consists of no Ti, 10%Ti, 20%Ti, 30%Ti, 40%Ti, and 50%Ti respectively. Whereas films with opposite gradient are called down-graded graded films. Structure and dielectric properties of the graded films was investigated by X-ray diffraction, Auger electron spectroscopy and by impedance analysis. The up-graded and down-graded PZT films annealed at 600 o, exhibited the remanent polarization values of 18.0 and 24.2 1C/cm2, respectively. The typical small signal dielectric constants and loss tanffi at a frequency of 100 Hz were 523 and 0.018, 544, and 0.020, respectively, for up-graded and down-graded PZT thin films. The temperature dependence of pyroelectric coeoients of the graded PZT films was measured by a dynamic technique. From 20 o to 82 o, the pyroelectric coeoients of the up-graded and down-graded PZT films up to 374 and 407 1C/m2K, respectively."
"Se/Te alloy and Te nanowires (NWs) with different morphologies were synthesized through a novel, control-lable solution-phase method. Sodium dodecylbenzene sulfonate was employed as a surfactant to control the reaction rate in the synthesis. Through reaction process dynamics control, both "bending" and "V-shaped" Se/Te alloy NWs were controllably produced. The phase structures and morphologies of the Se/Te and Te products were investigated with XRD, TEM, and HRTEM. The formation mechanisms of the NWs were investigated on the basis of the experimental results. The significance of these results lies in the important implications concerning the potential use of these NWs materials for nanoscale electronic devices."
"?Langmuir monolayers and LB films of 4-((s)-2-methylbutoxy)phenyl-(4'-(10-undecen-1-oyloxy)phenyl) methylenimine (MPUOPM) were investigated by ultraviolet-visible, polarized infrared spectroscopy. ?-A isotherms showed well-defined Langmuir monolayers were formed at an air/water interface for the MPUOPM and their mixture with SA. An inflection point at 13 mN/m appeared on the isotherm, which was due to the transition from the monolayer to multilayer. The polarized IR spectra of LB films of MPUOPM had provided new insight into the molecular orientation and structure. In LB films, the tilted angle between the alkyl chain and the normal line of the substrate was 48ffi, the tilted angle between the dipole moment of C=N and the normal line of the substrate was 51ffi. The alkyl chains assumed a trans-zigzag conformation but it included a few gauche conformers. The C=N groups were almost in one plane in the LB films. "
"Self-standing iron nanowires were fabricated at the apex of a tungsten needle tip by electron beam induced deposition. This sharp needle tip which adhered to the nanowire can be moved with a stepping motor and piezo-driving device, and was attached inside a specially designed transmission electron microscope pecimen holder. A copper conductor substrate, with which the approaching nanowires will build up a closed electric circuit, was set on the holder. The tungsten needle tip accompanied with the EBICVD nanowires made contact with the substrate and then a voltage was applied between the two electrodes. Resistivity values of the examined nanowires, by a devised Lock-in-Amplifier circuit, range from 0.1 -m to 10-3 -m. Our investigation might have implications in the fabrication and characterization of nano-electronics device. Precursor with phenanthrene (C4H10) was used and the deposition experiment was done using a scanning electron microscope at room temperature. It was found that the surface structure at the top of the nanorod, such as a small protrusion within only several nanometers scale, has significant influence on the field emission property. An emission current of several tens of nano-ampere flowing through this nanorod could induce resistance heating. In several minutes, this thermal energy could transform the original amorphous carbon into a graphite-like structure embedded with fullerenes. The turn-on voltage of the graphite-like nanorod was about 11 V less than that of the original amorphous case."
"Using Te powder as a tellurium source and Na2S as a sulfur source, core-shell CdTe/CdS NPs were synthesized at 50 oC. UV-visible and photoluminescence (PL) spectra were used to probe the effect of CdS passivation on the CdTe quantum dots. As the thickness of CdS shell increases, there is a red-shift in the optical absorption spectra, as well as the PL spectra. The broadening absorption peaks and PL spectra indicate that the size distributions of CdTe/CdS NPs widen increasingly with the increase of CdS coverage. The PL spectra also show that the fluorescence intensity of CdTe QDs will increase when the particles are covered with CdS shell with ratio of S/Te less than 1.0, otherwise it will decrease if the ratio of S/Te is larger than 1.0. Furthermore, the (CdTe/CdS)@SiO2 particles were prepared using a water-in-oil microemulsion method at room temperature in which hydrolysis of tetraethyl orthosilicate leads to the formation of monodispersed silica nanospheres. The obtained (CdTe/CdS)@SiO2 particles show bright photoluminescence with their fluorescence intensity being enhanced 18.5% compared with that of CdTe NPs. TEM imaging shows that the diameter of these composite particles is 50 nm. These nanoparticles are suitable for biomarker applications since they are much smaller than cellular dimensions."
"Pt/MgO catalysts were prepared by using wet impregnation method. X-ray diffraction, transmission electron microcopy (TEM), electron spectroscopy for chemical analysis, and temperature programmed surface reaction (TPSR) were used to characterize the calcined and used catalysts. Partial Oxidation of Methane (POM) to synthesis gas was carried out in a fixed bed micro-reactor to test the catalytic activity. TEM images revealed that Pt particles have the size of less than 10 nm, the size of the support MgO is about 50-200 nm. At 800 oC, the Pt/MgO catalyst exhibited a very high activity and stability for POM reaction. Both the conversion of methane and selectivities to CO and H2 remained almost constant up to 120 h. The dispersed Pt existed in the metallic state. The state and the dispersion of active Pt and the structure of support MgO were very stable, together with the high ability to resist carbon deposition, made the catalysts show a very high stability for POM under stoichiometric reaction conditions."
"Using magnesium nitrate as Mg source and regularly packed polymethyl methacrylate (PMMA) spheres were synthesized via a combined strategy of emulsifier-free emulsion polymerization and water floating technique as hard template, we fabricated ordered nanoporous magnesium oxide. The synthesized PMMA and MgO samples were characterized by N2 adsorption-desorption, X-ray diffraction, high-resolution scanning electron microscopy, transmission electron microscopy, and selected area electron diffraction. It was observed that the synthesized PMMA spheres possessed a uniform diameter of approximately 284 nm and were in a highly ordered array, and the MgO generated by using the PMMA-templating method exhibited polycrystallinity with three-dimensionally ordered pores. BET surface area of the synthesized MgO sample is 100.7 m2/g, pore volume is 0.46 cm3/g, wall thickness is 4-24 nm, and pore sizes are in the range of 10-120 nm. Such a 3D high-surface-area nanoporous strongly basic MgO is useful in the applications of catalyst supports and acidic gas adsorbents."
"Multi-walled carbon nanotubes (CNTs) were grown on a silicon nanoporous pillar array (Si-NPA) by thermal chemical vapor deposition. Surface morphologies and microstructure of the resultant were studied by a field emission scanning electron microscope, Raman spectrum, transmission electron microscope, and highresolution transmission electron microscopy. The composition of samples was determined by energy dispersive X-ray spectroscopy (EDS). The results showed that a great deal of CNTs, with diameter in the range of 20-70 nm, incorporated with Si-NPA and a large scale nest array of CNTs/Si-NPA (NACNT/Si-NPA) was formed. EDS analysis showed that the composition of carbon nanotubes was carbon. Field emission measurements showed that a current density of 5 mA/cm2 was obtained at an electric field of 4.26 V/1m, with a turn-on field of 1.3 V/1m. The enhancement factor calculated according to the Fowler-Nordheim theory was ?11,000. This excellent field emission performance is attributed to the unique structure and morphology of NACNT/Si-NPA, especially the formation of a nest-shaped carbon nanotube array. A schematic drawing that illustrates the experimental configuration is given. These results indicate that NACNT/Si-NPA might be an ideal candidate cathode for potential applications in flat panel displays."
"Radio frequency magnetron sputtering technique is used to deposit Ba0:65Sr0:35TiO3 (BST) thin films on fused quartz substrates. In order to prepare the high quality BST thin films, the crystallization and microstructure of the films were characterized by X-ray diffraction, field emission scanning electron microscopy and atom force microstructure. The more intense characteristic diffraction peaks and better crystallization can be observed in BST thin films deposited at 600 oC and subsequently annealed at 700 oC. The refractive index of the films is determined from the measured transmission spectra. The dependences of the refractive index on the deposition parameters of BST thin films are different. The refractive index of the films increases with the substrate temperature. At lower sputtering pressure, the refractive index increases from 1.797 to 2.179 with the pressure increase. However, when the pressure increases up to 3.9 Pa, the refractive index instead reduces to 1.860. The oxygen to argon ratio also plays an important effect on the refractive index of the films. It has been found that the refractive index increases with the ratio of oxygen to argon increasing. The refractive index of BST thin films is strongly dependent on the annealing temperature, which also increases as the annealing temperature ascends. In one word, the refractive index of BST thin films is finally affected by the films microstructure and texture."
"catalysts were synthesized by hydrothermal method. The X-ray diffraction result showed that the averageparticle size was in the range of 11-12 nm, which was correspondence to the high-resolution transmission electron microscopy result that the average particle size was about 12 nm. The specific surface area of the NiO-CeO2 binary compounds was in the range of 54-75 m2/g. Also the average particle size of the Bi2O3-CeO2 binary compounds was in the range of 8-11 nm. The oxygen storage capacity of the NiO-CeO2 and Bi2O3-CeO2 binary compounds was investigated under reduction and oxidation conditions. When the Ni and Bi concentration in CeO2 was up to 30%, the OSC values reached 2465 and 2560 1molO/g separately, which indicated that NiO and Bi2O3 compounded CeO2 materials have fine catalysis activity than other cations doped CeO2-based materials and appear to be very promising for practical applications such as OSC materials"
"A new method of TiN/Si3N4 nanocomposite synthesis was described and tested. TiCl4 and SiCl4 used as the starting materials and sodium as the reduction agent were conducted in liquid ammonia respectively. TiCl4 and SiCl4 were reduced simultaneously and titanium nitride/silicon nitride nanocomposite powderswere obtained by in situ co-deposition at temperatures around ~ 45 oC. X-ray diffraction patterns indicate that the product was amorphous and the by-product was sodium chloride. The product powders were heated up to 1600 oC and crystallization to TiN and fi-Si3N4 happened. Due to presence of TiN, the crystallization of silicon nitride in the mixture was later than that of pure silicon nitride. Transmission electron microscopy images show the average size of powders range from 10 nm to 40 nm and scanning electron microscopy images conformed that Ti and Si elements were dispersed uniformly. A green bulk nitride composite containing 20%TiN with the mean grain size of 100-300 nm and fracture toughness of 10.1§1.1 m1=2MPa , was obtained by spark plasma sintering at 1500-1600 oC. The effect of TiN additiven microstructure and mechanical properties of composite bulk was discussed."
"ZnO piezoelectric thin films were prepared on crystal substrate Si(111) by sol-gel technology, then characterized by scanning electron microscopy, X-ray diffraction and atomic force microscopy (AFM). The ZnO films characterized by X-ray diffraction are highly oriented in (002) direction with the growing of the film thickness. The morphologies, roughness and grain size of ZnO film investigated by AFM show that roughness and grain size of ZnO piezoelectric films decrease with the increase of the film thickness. The roughness dimension is 2.188-0.914 nm. The piezoelectric coeocient d33 was investigated with a piezo-response force microscope (PFM). The results show that the piezoelectric coeocient increases with the increase of thickness and (002) orientation. When the force reference is close to surface roughness of the films, the piezoelectric coefficient measured is inaccurate and fluctuates in a large range, but when the force reference is big, the piezoelectric coeocient d33 changes little and ultimately keeps constant at a low frequency."
"Dandelion-like micro-crystallites and long belt-like nanostructures of Sr-V-O materials were synthesized under mild hydrothermal reaction conditions in the presence of mineralizer adipic acid at 220 oC for 60 h and 180 oC for 60 h, respectively. Scanning electron microscopy measurements show that the Sr-V-O micro-crystallites in general consist of well-arranged microrods with the average length of a few hundred micrometers and diameters ranging from 1 1m to 5 1m. The long belt-like nanostructures around 100 nm in width exhibit visible twist and waving in shapes, showing high flexibility in nature. Powder X-ray diffraction and electron diffraction measurements both revealed that these micro-/nanometer materials have an orthorhombic structure with the lattice parameter a=9.694 ?, b=3.687 ?, and c=12.570 ? (space group of Pnma) as reported for fi-SrV2O6 phase. The electron diffraction patterns also indicate that the micro-/nanometer fi-SrV2O6 crystallites preferentially grow along the h010i crystallographic direction. The effects of the hydrothermal treating temperature and chemical compositions ratio of Sr to V on the morphologies of the final products are extensively investigated. A possible crystallite growth mechanism for the micro-pattern formation is proposed based on the systematic analysis of the experiental results."
"Mesoporous TiO2 powder and films with worm-like channels were synthesized by an evaporation-induced self-assembly approach. The as-prepared samples were calcined at different temperature to investigate the effect of calcined temperature on the mesostructure and the photocatalytic activity. Acetaldehyde photodegradation in gas phase was employed to evaluate the photocatalytic activity of mesoporous TiO2. Results showed that all the calcined powder samples exhibited higher photocatalytic activities than that of Degussa P25. The sample calcined at 400 oC, which showed higher activity than other samples, possessed a homogeneous pore diameter of about 6.0 nm and an 11.0 nm crystalline anatase pore wall, as well as large surface area of 117 m2/g. It was speculated that two factors of surface area and crystallinity affected the photocatalytic activity of mesoporous TiO2 photocatalyst. The mesoporous TiO2 films fabricated by spin-coating also had high photocatalytic activities."
"The polyaniline (PANI)-barium ferrite composite with magnetic behavior was synthesized by in situ poly-merization of aniline in the presence of BaFe12O19 nanoparticles of 60-80 nm in diameters. The structure, morphology and magnetic properties of samples were characterized by powder X-ray diffraction, Fourier transform infrared, scanning electron microscopy, transmission electron microscopy and vibrating sample magnetometer technique. The results of spectroanalysis indicated that there was interaction between PANIchains and ferrite particles. The composite exhibited the hysteresis loops of the ferromagnetic nature. The saturated magnetization of composite was 22.2 emu/g and the conductance was 0.069 S/cm."
"A series of 15%Co/Al2O3 catalysts were prepared by incipient wetness impregnation under various calcination conditions (90-500 oC), and were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy experiments (XPS), temperature programmed reduction, and catalytic measurements of hydrogenation of carbon monoxide to long-chained hydrocarbons leading to clean fuels (Fischer-Tropsch synthesis). The results of XPS show the presence of incompletely decomposed cobalt nitrate for catalysts calcined at 90-200 oC, and the presence of Co3O4 for catalysts calcined at 200-500 oC. For the four alumina-supported nano cobalt catalysts with different thermal treatment (200-500 oC), XRD and XPS results illustrated that there were mainly nano Co3O4 crystalite phases of 9-10 nm and the size of cobalt nano-particles did almost not change with the different temperature of thermal treatment. This was different from that of silica-supported cobalt catalysts. The supported cobalt catalyst (CoAp340 sample) calcinated at 340 oC presented a better activity for Fischer Tropsch synthesis to clean fuels, at mild conditions like atmospheric pressure (100 kPa), 1800 mL/g/h and 190 oC; rather than high pressure (2 MPa or more)."
"Strong crystallographic texture and high performance of Nd3:8Dy0:7Pr3:5Fe86Nb1B5 (containing 30% ff-Fe) nanocomposite permanent magnetic material was prepared by direct rapid solidification. X-ray diffraction analysis and magnetic measurement indicated that the ribbons had preferential orientation. The easy magnetization direction switched from perpendicular to the ribbon plane to parallel to the ribbon plane direction as the wheel speed increased from 10 m/s to 30 m/s. The multigrain domains were observed by scan probe microscope (SPM) in the ribbons prepared at wheel speed of 10-30 m/s. The Henkel plots were employed to investigate the interactions of the grains in the samples. A very fine and uniform microstructure with the average grain size about 16 nm was obtained in the sample prepared at wheel speed of 30 m/s. The sample consisted of highly oriented hard magnetic phase (Nd,Dy,Pr)2(Fe,Nb)14B and soft magnetic phase ff-Fe. High performance of Br=1.29 T, Mr/Ms= 0.76 and (BH)max=158.4 kJ/m3 was achieved due to the strong crystallographic texture, fine and homogeneous microstructure and enhancement of the exchange coupling between the soft and hard magnetic phases in this sample. The mechanism of the formation of the crystallographic texture and the multigrain domains was also discussed."
"High-orderly TiO2 nanotube arrays were fabricated by anodic oxidation of pure titanium substrate in organic electrolyte containing fluoride. Different morphological nanotubes of titania were obtained through controlling the different anodization voltages and durations. The length of the longest nanotubes was approximately 60 1m and the length-to-width aspect ratio was about 600. The nanotube layers were then annealed at different temperatures (450, 550, and 650 oC) in air for 2 h. The samples were characterized by scanning electron microscopy, X-ray diffraction (XRD), energy dispersive X-Ray (EDS) and UV-Vis spectrometer. The XRD results demonstrated that the as-anodized samples were amorphous and the structure changed to antanse and rutile when the samples were annealed at higher temperature. The EDS microanalysis indicated the presence of carbon in the TiO2 nanotubes. The result of degradation of methylene blue showed clearly that the photocatalytic activity of C-doped TiO2 nanotubes increased by 10%."
"Vapor-grown carbon nanofibers (VGCNFs) were treated in radio frequency (RF) plasma to activate their surface and thus to improve the compatibility with the matrix in polymer composites. The surface of VGCNFs was modified in atmospheres containing different ratios of O2 and Ar. Fourier transform infrared spectroscopy and thermogravimetric measurement shows that when the O2 content in mixture gases was 5%, C-O and O-H functional groups were produced abundantly in the surface of the VGCNFs. When O2 content increased to 8%, most of the surface of carbon fibers was severely oxidized, resulting in defects in structures of the inner layers of VGCNFs."
"Lead zirconate titanate Pb(Zr0:95Ti0:05)O3 (PZT95/5) antiferroelectric thin films with 300 nm thickness were grown on Pt/Ti/SiO2/Si substrates by a sol-gel method with rapid thermal annealing processing. The X-ray diffraction results showed that the highly (111)-oriented pervoskite PZT95/5 thin films were grown on Pt/Ti/SiO2/Si substrates when annealed at 600-700 oC. Electrical measurements were conducted on PZT95/5 films in metal-ferroelectric-metal capacitor configuration. The PZT95/5 thin films annealed at 600-700 oC showed well-saturated hysteresis loops at an applied voltage of 20 V. At 1 kHz, the dielectric constant and dielectric loss of the films were 519 and 0.028, 677 and 0.029, 987 and 0.025, respectively for the thin films annealed at 600, 650, and 700 oC. The average remanent polarization (Pr) and the coercive electric field (Ec) obtained from the P-E hysteresis loops, were 19.1 1C/cm2 and 135.6 kV/cm, 29.31C/cm2 and 88.57 kV/cm, 45.3 1C/cm2 and 102.1 kV/cm, respectively for PZT95/5 thin films annealed at 600, 650 and 700 oC for 10 min in the oxygen atmosphere. This showed a good ferroelectricity of the prepared PZT95/5 films on Pt/Ti/SiO2/Si substrates by the simple sol-gel processing. The pyroelectric coeocient (p) of antiferroelectric PZT95/5 films was measured by a dynamic technique. At room temperature, the p values of the antiferroelectric PZT95/5 films at 1 kHz were 274, 238, and 212 1C/m2K."
"NbS2 and TaS2 nanostubes were prepared via solid state reaction method, and their tribological properties were studied over a wide range of normal loads and sliding velocities. The size distributions and shapes of sulfides were characterized using transmission electron microscopy and scanning electron microscopy. The results indicated that the NbS2 and TaS2 compounds had tubular structures with the mean diameter of 100 nm and length of 10 mm. The effect of NbS2 and TaS2 nanotubes added in commercial lubricating oil T40, was initially studied using the instrument MS-T3000. The results showed that the antiwear ability of NbS2 and TaS2 as additives was obviously better than that of the normal lubricating oil in ambient conditions. The general frictional properties of the solid lubricant containing TaS2 is better than those of the solid lubricant containing NbS2. The frictional mechanism was discussed."
"Nanogranular Ag/Fe/Ag films were prepared by magnetron sputtering from a silver and an iron target onto glass substrates at room temperature and subsequent in situ annealing. The structural and magnetic properties of the films were investigated as a function of silver layer thickness and annealing temperature. X-ray diffraction shows the Fe(110) peak is formed in all the samples. Vibrating sample magnetometer measurements indicate that the magnetic moments lie well perpendicular to the film plane. Coercivityreaches the maximum in the sample annealed at 500 oC for 30 min with 3 nm Ag layer. A scanning probemicroscope was used to scan surface morphology and magnetic domain structures. In as-deposited samplesthe average grain size and the average roughness is smaller than that the annealing samples. After annealing,the grain size is larger and the contrast of domains increases, but the domain size becomes smaller."
"The deposition of CdO?nH2O on CdTe nanoparticles was studied in an aqueous phase. The CdTe nanocrystals (NCs) were prepared in aqueous solution through the reaction between Cd2+ and NaHTe in the presence of thioglycolic acid as a stabilizer. The molar ratio of the Cd2+ to Te2- in the precursory solution played an important role in the photoluminescence of the ultimate CdTe NCs. The strongest photoluminescence was obtained under 4.0 of [Cd2+]/[Te2-] at pH?8.2. With the optimum dosage of Cd(II) hydrous oxide deposited on the CdTe NCs, the photoluminescence was enhanced greatly. The photoluminescence of these nanocomposites was kept constant in the pH range of 8.0-10.0, but dramatically decreased with an obvious blue-shifted peak while the pH was below 8.0. In addition, the photochemical oxidation of CdTe NCs with cadmium hydrous oxide deposition was markedly inhibited."
"Carbon nanotubes can be used as absorbent materials at the near infared range. In this study, carbon nanotube was treated with surfactant to prevent aggregation, and the acrylate coating of the carbon nanotube was prepared with the carbon nanotube solution and the near infrared reflection properties of the coating were studied. A series of factors influencing the reflectivity of carbon nanotubes/acrylate coatings at 930 nm, such as PVC concentration, the kinds and concentration of the surfactant and size range of the carbon nanotube, were studied. Based on these, the coating procedure was optimized and the carbon nanotubes/acrylate coating was prepared with good absorption properties. The reflectivity is under 0.1% of the coatings and its transmission is below 1.0% at near infrared wavelength of 840-980 nm."
"RuO2/TiO2 films were deposited on float pearls (FP) by the sol-gel-dipping method. The substrates were coated with RuO2/TiO2 precursor sol, air-dried at 120 oC and further heated at 500 oC to obtain the coupled photocatalyst of RuO2/TiO2 films supported on FP (RuO2/TiO2/FP). The structure of coupled photocatalyst was characterized by SEM, XRD, and FT-IR technique, respectively. The results showed TiO2 has anatase structure and doped RuO2 was highly dispersed on the surface of TiO2 particles as amorphous. The average thickness of RuO2/TiO2 films (3 layers) on FP was determined to be about 1 1m. This study was carried out under the following conditions: volume 60 mL, initial concentration of beta-cypermethrin (BEC) 45 mg/L, pH 6.5, amount of RuO2/TiO2/PF 5 g/L, air flow rate 200 mL/min, reaction time 60 min. The degradation rates of BEC are 88.1% (125 W Hg lamp), 82.8% (8 W UV lamp), and 75.1% (8 W solar lamp), respectively. The photocatalytic degradation of BEC was experimentally demonstrated to follow the Langmuir-Hinshelwood kinetic model, and the reaction rate constant (17.5 mg/(L min)) and the adsorption constant (3.486 L/g) were determined, respectively. It was also found that the RuO2/TiO2 /FP photocatalyst has significantly the visible light photoactivity for degradation of BEC."
"?Fluorescence spectra of naked gold nanoparticles, triphenylphosphine stabled gold nanoparticles, and 3-mercaptopropionic acid substituted gold nanoparticles were studied. It was found that fluorescence intensities of gold nanoparticles were highly sensitive to surface molecules. The fluorescence quenching effect of these gold nanoparticles on CdSe nanoparticles was also investigated. This quenching effect was related to the overlap degree between the absorption spectra of gold nanoparticles and the emission spectrum of CdSe nanoparticles, and was surface-dependent as well. "
"The composites of hollow glass microspheres coated with NiFe2O4 nanoparticles were prepared using polyacrylamide gel method. The structural characteristics, morphology and electromagnetic properties of the composite powders with different weight percent of glass microspheres (15%, 40%, and 65%) were obtained by X-ray diffraction, scanning electron microscope, infrared spectroscopy and HP8510 network analyzer. The results indicated that the phase structure of composite powders was the mixtures of nickel ferrite, quartz, and mullite. The peak intensity for nickel ferrite decreased rapidly and for mullite increased remarkably with the increasing amount of microspheres. A pure spinel structure of NiFe2O4 formed on the glass microspheres at 600 oC. A uniform and continuous NiFe2O4-coating was obtained when the content of microspheres was 40%. A great amount of NiFe2O4 particle size is less than 80 nm. The composite with a content of 40% microspheres exhibits better dielectric and magnetic loss properties which are useful to absorb more electromagnetic wave. It can be a kind of good and light electromagnetic wave absorbing material in the X-band."
"Graphite intercalation compounds with CuCl2-FeCl3-H2SO4 were synthesized via a hydrothermal treatment at 150 oC and exfoliation method. The structure and composition of these graphite intercalation compounds were analyzed by means of X-ray diffraction, energy dispersive X-ray and high-resolution transmission electron microscopy. The results demonstrate that the CuCl2-FeCl3-H2SO4 molecules were successfully intercalated into the interlayer of the graphite sheets. The temperature dependence of magnetization was measured from 5 K to 300 K. Two antiferromagnetic transitions of the graphite intercalation compounds were observed at low temperatures. The critical transition temperatures are estimated to be about 50 and 102 K. The related magnetic properties are discussed briefly."
"Nanoparticle ZnO was synthesized in non-aqueous medium. UV adsorption spectra were measured and effective mass model was used to calculate particle size in situ. A technique method named as supersaturation control growth was developed, which dealt with addition of nanoparticle suspension with small size to another suspension with big size. As a result, those small particles completely dissolved and those big ones totally grew because of dissolution degree difference between small particles and the big ones. The particle number of big particle suspension kept being a constant and the growth rate was much higher than Ostwald ripening. Main characteristic of this technique is that size distribution of nanoparticles can be narrowed provided original size difference of two suspension is big enough and original size distribution is not too broad."
"Electrochemical impedance spectroscopy and cyclic voltammetry were used to investigate the effect of various inorganic particles, including titania, alumina, zirconia with particle sizes ranging from nano- to micro-meter on electrochemical properties of the electrolyte used in dye-sensitized solar cell. Adding inorganic particles could improve the ionic transport of I3- in the electrolyte and reduce the electrolyte-electrode transfer resistance, leading to an improvement of the photoelectric conversion efficiency of the devices. It was proposed that the improvement could be attributed to the interfacial effect between the inorganic particles and the electrolyte; ionic conduction paths formed between the solid particles facilitate the diffusion of the I3- in the electrolyte and improve the connection between the electrolyte and the electrode. Combined with a less volatile solvent system and a proper amount of the inorganic particles as the additive, an overall efficiencyof 5.5% for the DSC (1 cm2) with P25 (10%) under 100 mW/cm2 at room temperature was achieved, an improvement of 51% over that without the oxide additive."
"FeNi nanotubes were successfully prepared in pores of anodic aluminium oxide templates by the wetting template method. By varying the deposition conditions and the parameters of the templates, the lengths and the outer as well as the inner diameters of the tubes can be tailored. The FeNi nanotubes and their arrays were characterized by transmission and scanning electron microscopy. Macroscopic magnetic measurements show the FeNi nanotube arrays to have obvious anisotropy, and the easy axis is parallel to the nanotube axis. The magnetic moment distributions in the tube walls and the magnetization reversal mechanism are discussed. Magnetic moments of the FeNi nanotube preferentially lie in the nanotube wall, but the distribution is spatially isotropic. These magnetic behaviours are due to the unique shape of the nanotube."
2007, 20(6): 825-825. doi: 10.1088/1674-0068/20/6/825-825