Abstract Félix Bonfils was born in Saint Hippolyte du Fort, France, on 6th March 1831. Little is known of his early life. Family sources indicate he began his professional career by operating his own printing press1. On becoming interested in photography, he produced photographs using the heliogravure process invented by Niépce. In due course, he adopted the collodion wet-plate process, with all its well-known complications and encumbrances. For the landscape photographer lie was to become, the task of moving his equipment from place to place must have been formidable, especially in countries where roads and transport were meagre. 相似文献
In the present investigation, we made an endeavor to fabricate the ZnO nanoparticles and achieved the tunable properties with Nd doping. The Nd-doped ZnO nanoparticles were characterized via X-ray diffraction (XRD), Raman, and X-ray photoelectron spectroscopy (XPS) studies that confirmed the successful doping of Nd ions in the ZnO crystal lattice without amending its hexagonal phase. The particle morphology revealed nearly spherical particles with uniform size distribution. The band gap of these samples was determined using diffuse-reflectance spectra (DRS) and was found to vary from 3.17 to 3.21 eV with increasing Nd concentration. A broad and intense emission band at 1083 nm for Nd doped ZnO nanoparticles is observed and is assigned to corresponding emission transition 4F3/2?→?4I11/2 of Nd3+ ions. Furthermore, the magnetic studies indicate that the Nd doping altered the magnetic behavior of nanocrystalline ZnO particles from diamagnetic to ferromagnetic at 300 K and that the magnetization of these samples decreased with increasing Nd concentration. The tunable optical band gap as well as room-temperature ferromagnetism of these samples may find applications in both optoelectronics and spintronics. 相似文献
The densities of five BMIMBF4 (1-butyl-3-methylimidazolium tetrafluoroborate) + ethanol binary mixtures with compositions of (0.0701, 0.3147, 0.5384, 0.7452,
and 0.9152) mole fraction BMIMBF4 and of pure BMIMBF4 have been measured with a vibrating-tube densimeter. Measurements were performed at temperatures from 298 K to 398 K and
at pressures up to 40 MPa. The total uncertainty of density, temperature, pressure, and concentration measurements were estimated
to be less than 0.1 kg · m−3, 15 mK, 5 kPa, and 10−4, respectively. The uncertainties reported in this article are expanded uncertainties at the 95% confidence level with a coverage
factor of k = 2. The measured densities were used to study derived volumetric properties such as excess, apparent, and partial molar
volumes. It is shown that the values of excess molar volume for BMIMBF4 + ethanol mixtures are negative at all measured temperatures and pressures over the whole concentration range. The effect
of water content on the measured values of density is discussed. The volumetric (excess, apparent, and partial molar volumes)
and structural (direct and total correlation integrals, cluster size) properties of dilute BMIMBF4 + ethanol mixtures were studied in terms of the Krichevskii parameter. The measured densities were used to develop a Tait-type
equation of state. 相似文献
Nickel ferrite NiFe2O4 nanoparticles (NPs) were successfully synthesized by using nickel nitrate, ferric nitrate, citric acid, and ethyl cellulose as a surfactant by a simple sol–gel-assisted combustion method (SACM) and microwave-assisted combustion method (MACM). Structural, morphological, optical, and magnetic properties of the obtained powder were characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), photoluminescence (PL) spectroscopy, and vibrating sample magnetometry (VSM). XRD results show that the resultant powder was pure crystalline with cubic structure. The average crystalline size was found to be 18.8 and 10.2 nm synthesized by SACM and MACM, respectively. FT-IR spectra indicate the type of bonds between Ni–O and Fe–O (metal and oxygen). SEM images show that the morphology of the powder consists of well-defined structure. VSM results showed a ferromagnetic behavior of the sample. Antimicrobial activity of NiFe2O4 nanoparticles was performed. Both sample 1 (SACM) and sample 2 (MACM) show good inhibition in the zone 100 μg/ml. While comparing, sample 2 shows high inhibition than sample 1. 相似文献
The photocatalytic activity of sol–gel synthesized double perovskite type oxides NaEuTi2O6(NETO), NaSmTi2O6 (NSTO), and NaGdTi2O6 (NGTO) powders on degradation of methylene blue (MB) dye was demonstrated for the first time under visible light as well as sunlight irradiation. The obtained samples were characterized by X-ray diffraction, UV–Visible diffuse reflectance spectroscopy and scanning electron microscopy equipped with X-ray energy-dispersion spectrometry. All the three samples have shown photocatalytic activity for degradation of MB under sunlight and visible light irradiation and their photocatalytic activity followed the order of NGTO > NETO > NSTO. The superior activity of NGTO is ascribed to the higher amount of hydroxyl radicals generated in the photocatalytic reaction. 相似文献
Here, the superconducting and AC/DC magnetic properties of REBa2Cu3O7−δ(RE: Eu, Gd, Ho and Er) are investigated in order to understand the inter-granular and intra-granular behavior of these compounds.
These compounds were prepared by standard solid-state reaction route. ErBa2Cu3O7−δ(Er-123) and HoBa2Cu3O7−δ(Ho-123) (consisting of heavier rare earth) show higher orthorhombic splitting in their XRD patterns than those observed for
EuBa2Cu3O7−δ(Eu-123) and GdBa2Cu3O7−δ (Gd-123) (consisting of lighter rare earth). Even though Eu, Gd, Ho and Er are magnetic elements, substitution of these at
Y site in Y-123 does not change the superconducting transition temperature (Tc). Er-123 and Ho-123 exhibit very sharp superconducting transition while Eu-123 and Gd-123 exhibit relatively broad transition
with little hump at the lower part of transition close to the long-range superconducting state with zero resistance. In addition
to that, Eu-123 and Gd-123 show relatively higher normal state resistivity than those of Er-123 and Ho-123. The AC susceptibility
measurements reveal that these compounds possess different strength of inter-granular couplings. The hump in the superconducting
transition of Eu and Gd is not due to the lack of inter-grain couplings in these samples because of having better grain connectivity
in the samples as compared to other rare earth elements in REBa2Cu3O7−δ system. Though intra-grain peak is insensitive to the applied magnetic field, inter-grain peak is sensitive to the applied
magnetic field. 相似文献
RMgPO4:Mn2+ (R?=?Li, Na, and K) phosphors are synthesized by a solid-state reaction method in air. The crystal structures and luminescence properties are investigated. A broad emission band peaking at 638 nm of RMgPO4:Mn2+ (R?=?Li and Na) phosphors with excitation 408 nm is observed in the range of 550–800 nm owing to the 4T1(G) → 6A1 transition of the Mn2+ ion. KMgPO4:Mn2+ phosphor with excitation 416 nm shows a broad emission band peaking at 658 nm in the range of 550–800 nm owing to the 4T1(G) → 6A1 transition of the Mn2+ ion. The optimal Mn2+ ion concentration in RMgPO4:Mn2+ (R?=?Li, Na, and K) phosphors is about 5 mol%. The lifetimes of RMg0.95PO4:0.05Mn2+ (R?=?Li, Na, and K) phosphors is ~6.21, 6.03, and 6.28 ms, respectively. The luminous mechanism is explained by Tanabe-Sugano diagram of Mn2+ ion. 相似文献
Nasicon type compounds of general formula Ca0.5SbMP3O12 (M = Al, Fe, Cr) are prepared by solid-state method. All the compounds crystallize in hexagonal lattice with space group. The IR spectra show characteristic PO4 vibrations. Conductivity studies indicate the presence of charged defects. The Cole-Cole plots of impedance are semicircles
between 150 and 350 °C. The thermal expansion of these samples is studied in the temperature range 25–500 °C. 相似文献
Crystalline α-MoO3 belts consisting of nanosheets stacked along their [010] axes were synthesized via thermal vapor transport of MoO3 powders at elevated temperatures. The MoO3 belts were millimeters in length along their [001] axes and tens to hundreds of micrometers in width along their [100] axes. Mechanical and aqueous exfoliations of the belts to form two-dimensional (2D) nanosheets were processed via the scotch-tape and bovine serum albumin (BSA) assisted methods, respectively. Upon scotch-tape exfoliation, the Raman features of MoO3 exhibited monotonic decreases in intensity as the thickness was gradually fell to approach that of a 2D nanosheet. Most Raman features eventually disappeared when a monolayer nanosheet was produced, except for the Mo–O–Mo stretching mode (Ag) at ~818 cm?1, which was accompanied by mode-softening of up to 5 cm?1. This mode softening, hitherto not reported for 2D α-MoO3 nanosheets, can be attributed to lattice relaxations that are validated here via theoretical density functional perturbation theory calculations. The BSA-assisted exfoliation products exhibited a blueshift in the α-MoO3 nanosheet absorption edge; they also revealed an absorption peak at 3.98 eV that can be attributed to their intrinsic exciton absorptions. These observations, together with the facile synthesis of high-purity α-MoO3 crystals, illuminate the possibility of further 2D α-MoO3 nanosheet production and lattice dynamic studies.
The crystal structure, electronic structure and optical properties of Ba2RETaO6 (RE?=?Y, La, Pr, Sm, Gd) have been studied by first-principles calculation. The calculated lattice parameters are in good agreement with the previously reported values. With increasing the atomic number of RE (i.e., the number of 4f electrons), the energy level of RE 4f bands becomes lower continuously. The relationship between the electronic structure and optical properties is explored based on first-principles calculation. The electron transitions between O 2p states, RE 4f states and Ta 5d states have a key effect on optical properties such as dielectric function, refractive index, absorption coefficient and reflectivity. The phase structures have great influence on the optical properties of Ba2SmTaO6 and Ba2GdTaO6, and the big variation of reflectivity induced from phase transition makes them have potential applications in the infrared radiation protection area. 相似文献
Cobalt substituted strontium ferrites SrCoxFe12?xO19 (x = 0.1, 0.2 and 0.3) were synthesized via sol–gel method and the dried gel obtained was annealed at 800 °C. The powder X-ray diffraction studies helped in the determination of the crystallite size that measured ≈ 12–14 nm. The optical properties of the powdered nanoparticles were determined by means of the UV–Vis absorption spectra of their dispersed solutions in liquid media. Despite these measurements, it was difficult to determine their band gap (Eg) precisely. However, the Kubelka–Munk treatment on the diffuse reflectance spectra of the powdered nanoparticles was used in order to extract their Eg unambiguously. The Co substituted strontium hexaferrites are used for optical studies. The energy band gap for all the ferrite compositions was found to be ≈ 1.46–1.78 eV. The study made on the dielectric behaviour of the substituted SrFe12O19 is also discussed in this paper. 相似文献
The surface tension, density, and viscosity of the Ni-based superalloy CMSX-4® have been determined in the temperature ranges of 1,650–1,850 K, 1,650–1,950 K, and 1,623–1,800 K, respectively. Each property has been measured in parallel by different techniques at different participating laboratories, and the results are compared with the aim to improve the reliability of data and to identify recommended values. The following relationships have been proposed: density-ρ (T) [kg· m?3] = 7,876 ? 1.23(T ? 1,654 K); surface tension-γ (T) [mN·m?1] = 1,773 ? 0.56 (T ? 1, 654 K); viscosity-η (T) [mPa·s] = 8.36 ? 1.82 × 10?2(T ? 1,654 K). For a comparison, surface-tension measurements on the Al-88.6 at% Ni liquid alloy with the same Al-content as the CMSX-4® alloy were also performed. In addition, the surface tension and density have been theoretically evaluated by different models, and subsequently compared with new experimental data as well as with those reported in the literature. The surface-tension experimental data for the liquid CMSX-4® alloy were found to be close to that of the Al-88.6 at% Ni alloy which is consistent with results from the compound formation model (CFM). 相似文献
Ba1?xLaxFe12O19 (x = 0.0, 0.2, 0.4, 0.6) hollow ceramic microspheres (HCMs) have been prepared by combining self-reactive quenching method with heat treatment. Their material parameters, magnetic and microwave absorbing properties were investigated. It was observed that after doping of lanthanum, the material parameters showed a little change except hexagonal crystal disappearing. And the magnetic properties of HCMs were decided by lanthanum content and material parameters. With the lathanum increases from 0.0 to 0.6, the saturation magnetization (Ms) values initially increased, and then decreased sharply to a minimum value, and increased again, moreover, the coercive force (Hc) values were reduced first, and then increased, and decrease to a minimum value. Absorbing properties tests indicate that after La3+-doped, at 2 mm thickness, the effective absorbing band (<?10 dB) was reduced to 4.7, 5 and 4.4 GHz, respectively, the minimum reflectance would decrease in low substituted level (x ≤ 0.4) and increase in high level (x = 0.6), and the frequency shifts to low frequency with the increasing of doping content. In 1.5–3 mm range, with the increasing of thickness, the absorption peak of Ba1?xLaxFe12O19 (x = 0.2, 0.4, 0.6) HCMs shifts to low frequency and the absorption intensity increases, the effective absorbing band can up to 10, 8.1 and 8 GHz, respectively. 相似文献
We have prepared ceramic (La0.8Sr0.2){[Ga0.8–x(Ge0.5Mg0.5)x]Mg0.2}O3–d (LSGGM) (x = 0, 0.1, 0.2, 0.4, 0.6, 0.8) samples by solid-state reactions and studied their phase composition, structure, microstructure, and electrical conductivity. Phase-pure solid solutions have been obtained upon substitution of germanium and magnesium cations for up to 20 at % of the gallium cations. The modified samples have been shown to have high density, optimal microstructure, densely packed grains, and high electrical conductivity at high temperatures. 相似文献
In this paper, we report the structural, magnetic and magnetocaloric properties of Ni-doped La0.67Ba0.33Mn1?xNixO3 (x?=?0, 0.025 and 0.075) manganites. Our compounds were synthesized using the sol–gel method. The structural analysis using Rietveld refinement shows that Ni-doped LaBaMnO3 system crystallizes in the rhombohedral symmetry with \({\text{R}}\bar {3}{\text{c}}\) space group. Magnetization measurements versus temperature in a magnetic applied field of 0.05 T reveal that all the compositions exhibit a transition from a ferromagnetic to paramagnetic phase with increasing temperature. A systematic decrease in the transition temperature is clearly observed upon Ni doping and a near room temperature TC (302 K) is achieved with x?=?0.075 composition. The maximum magnetic entropy change \(\left( { - ~\Delta {\text{S}}_{{\text{M}}}^{{\hbox{max} }}} \right)\) in a magnetic field change of 5 T is found to be 2.12, 2.78 and 1.78 J/kg K for x?=?0, 0.025 and 0.075, respectively. At this value of magnetic field, large relative cooling power values are obtained in our samples, especially for x?=?0.075 (271 J/kg) making it a promising candidate for magnetic refrigeration near room temperature. 相似文献
SrBi2Nb2O9 (SBN) and SrBi2(Nb0.9V0.1)2O9 (SBVN) ceramics were fabricated from the powders consisting of μm sized grains, obtained via the solid state reaction route. V2O5 was found to be an effective microstructure modifier and grain growth truncator for SBN ceramics. X-ray structural studies carried out on SBVN ceramics confirmed the existence of preferential orientation (c-planes) of the grains. V2O5 addition has substantially improved the sinterability of SBN and enabled to achieve high density (95%) which was otherwise difficult in the case of pure SBN. The dielectric properties of SBN ceramics were significantly enhanced by the partial replacement of Nb ions by pentavalent vanadium ions. The complex impedance diagrams of dense SBVN ceramics exhibited only one semicircle indicating a significant contribution from the grains. In contrast, the impedance plots for the porous (density 88%) SBN ceramics show an additional low-frequency semicircle which was attributed to the blocker (pore) size effects. The dielectric behavior of SBN and SBVN ceramics was rationalized using the impedance and modulus data. 相似文献
A microwave assisted hydrothermal method, where the advantages of both microwave and hydrothermal methods are utilized to
synthesize complex fluoride KMF3 (M = Zn, Mn, Co, Fe), materials of technological importance, is proposed. The KMF3 metal fluorides synthesized feature nano-sized particles having well-defined cubic morphologies. The proposed synthesis,
in contrast to the existing synthesis methods is very rapid, economical, and less complex in nature. The structural, thermal,
optical, and chemical properties of synthesized powders are determined by powder X-ray diffraction, scanning and transmission
electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and diffuse reflectance spectra
in the UV–VIS range. 相似文献
Polycrystalline LnTiTaO6 (Ln = Ce, Pr, Sm) compounds were prepared in the solid state ceramic route. The powders were calcined between 1250 °C and
1300 °C and sintered between 1480 °C and 1520 °C. The materials were characterized by XRD and SEM. The dielectric properties
were measured in the frequency range 1 kHz–5 MHz. The absorption spectra and photoluminescence spectra of the samples were
analysed. The materials are useful as gain media in micro lasers because of the optical absorption and photoluminescence. 相似文献
Magnetoelectric (ME) composites consisting of K0.5Na0.5NbO3 (KNN) as ferroelectric phase and CoMn0.2Fe1.8O4 (CMFO) as ferrite phase with general formula (x) CoMn0.2Fe1.8O4–(1???x) K0.5Na0.5NbO3 (x?=?10, 20, 30, 40 and 50 wt%) were synthesized using solid state reaction method. X-ray diffraction analysis asserts the existence of component phases including spinel phase of CMFO and orthorhombic phase of KNN. Field emission scanning electron microscopy has been used for studying the morphology and calculation of average grain size. The temperature dependent dielectric properties including dielectric constant (\(\varepsilon ^{\prime}\)) and dielectric loss (tan δ) at different frequencies has been studied and both are found to increase with incorporation of CMFO. Magnetic hysteresis loops have been measured at temperatures of 300 and 5 K. Variation of magnetization versus temperature has been studied in field cooled and zero field cooled modes. Polarization versus electric field (P–E) hysteresis loops are obtained at room temperature indicating presence of ferroelectric ordering in the composites at room temperature. The remnant polarization (2Pr) and coercive field (2Ec) are found to decrease linearly with incorporation of CMFO. ME voltage coefficient (αME) has been measured. The maximum value of αME is found to be 5.941 mV/cm-Oe for 10% CMFO–90% KNN bulk composite. 相似文献
The synthesis, characterisation, and device performance of a series of cyclopentadithiophene (CPDT)-naphthalenediimide (NDI) donor-acceptor-donor (D-A-D) polymers is reported. The monomers with various alkyl chains are synthesised via direct arylation using palladium complex catalyst. The monomers are then polymerised by oxidative polymerisation using FeCl3 to provide high molecular weight polymers (Mn = 21,800–76,000). The polymer films show deep-red absorption including near-infrared region up to 1100 nm to give optical bandgap of approximately 1.16 eV. The polymers exhibit only n-type semiconducting properties giving the highest electron mobility of 9 × 10-3 cm2 V−1 s−1 in organic field-effect transistors (OFETs). Organic photovoltaic (OPV) devices are fabricated from solutions of the polymers as acceptors and poly(3-hexylthiophene) (P3HT) as a donor. 相似文献