排序方式: 共有394条查询结果,搜索用时 31 毫秒
121.
122.
A fast and accurate method for the determination of precious alloys caratage by Laser Induced Plasma Spectroscopy 总被引:6,自引:0,他引:6
M. Corsi G. Cristoforetti V. Palleschi A. Salvetti E. Tognoni 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(3):373-377
The purpose of this paper is to present a new and efficient technique for precious alloys caratage based on the Laser Induced
Plasma Spectroscopy (LIPS) method. The LIPS analysis can be carried out in few minutes and in an essentially non-destructive
way on samples of arbitrary shape. Experimental results showing the feasibility of the method for fast and precise analysis
of gold jewellery without the need of calibration are presented. Using a new technique of LIPS spectra analysis, recently
developed and patented by the Applied Laser Spectroscopy Laboratory at IFAM, we were able to obtain quantitative information
about all the alloy components, including trace elements at concentration down to the order of 1 ppm. Matrix effects do not
affect the accuracy of the technique.
Received 10 July 2000 and Received in final form 13 November 2000 相似文献
123.
P Dorenbos 《Journal of luminescence》2003,104(4):239-260
fd-excitation, absorption, reflection, and df-emission spectra presented in the literature on Eu2+ in inorganic compounds have been gathered and re-analyzed. Emission wavelength, width of the emission band, absorption wavelength, Stokes shift, and redshift pertaining to Eu2+ in more than 300 different compounds (fluorides, chlorides, bromide, iodides, oxides, sulfides, selenides, and nitrides) are presented. From the data, it is possible to predict for each of the 13 lanthanide ions (La2+, Ce2+, Pr2+, until Yb2+), doped in any of the compounds compiled, the energy of the transition from the 4fn ground state to the first 4fn−15d level and also the energy of df-emission. A brief overview on the relationships between redshift, Stokes shift, and the width of the emission with the type of compound is given. 相似文献
124.
TlGaS2 single crystal doped by paramagnetic Fe3+ ions has been studied by electron paramagnetic resonance (EPR) technique. The fine structure of EPR spectra of paramagnetic Fe3+ ions was observed. The spectra reveal a nearly orthorhombic symmetry of the crystal field (CF) on the Fe3+ ions. Two groups each consisting of four equivalent Fe3+ centers were observed in the EPR spectra. The local symmetry of the crystal field on the Fe3+ centers and CF parameters were determined. Experimental results indicate that the Fe ions substitute Ga at the center of the GaS4 tetrahedrons. The rhombic distortion of the sulfur ligand CF is attributed to the effect of Tl ions located in the trigonal cavities between the tetrahedral complexes. The observed twinning of the resonance lines indicates a presence of two non-equivalent positions of Tl ions that confirms their zigzag alignment in the TlGaS2 crystal structure. 相似文献
125.
Thin films of eight metals with a thickness of 150 nm were deposited on mica substrates by thermal evaporation at various temperatures in a high vacuum. The surface morphology of the metal films was observed by atomic force microscopy (AFM) and the images were characterized quantitatively by a roughness analysis and a bearing analysis (surface height analysis). The films of Au, Ag, Cu, and Al with the high melting points were prepared at homologous temperatures T/Tm = 0.22-0.32, 0.40, and 0.56. The films of In, Sn, Bi, and Pb with the low melting points were prepared at T/Tm = 0.55-0.70, where T and Tm are the absolute temperatures of the mica substrate and the melting point of the metal, respectively. The surface morphology of these metal films was studied based on a structure zone model. The film surfaces of Au, Ag, and Cu prepared at the low temperatures (T/Tm = 0.22-0.24) consist of small round grains with diameters of 30-60 nm and heights of 2-7 nm. The surface heights of these metal films distribute randomly around the surface height at 0 nm and the morphology is caused by self-shadowing during the deposition. The grain size becomes large due to surface diffusion of adatoms and the film surfaces have individual characteristic morphology and roughnesses as T increases. The surface of the Al film becomes very smooth as T increases and the atomically smooth surface is obtained at T/Tm = 0.56-0.67 (250-350 °C). On the other hand, the atomically smooth surface of the Au film is obtained at T/Tm = 0.56 (473 ± 3 °C). The films of In, Sn, Bi, and Pb prepared at T/Tm = 0.55-0.70 also show the individual characteristic surface morphology. 相似文献
126.
CaCu3Ti4O12 ceramics were prepared at the sintering temperatures ranged from 1025 to 1125 °C, and the dielectric characteristics were evaluated together with the microstructures. The giant dielectric constant with the maximum of 53,120 was obtained in CaCu3Ti4O12 ceramics at room temperature and 10 kHz, and strong processing and microstructure dependence of dielectric characteristics of the present ceramics was determined. The precipitation of the dispersed Cu-rich secondary phases of CuO and/or Cu2O and their network structure provided the extrinsic origins of the enhanced giant dielectric response, and the present findings would offer the greater potential for enhancing the giant dielectric constant and controlling the dielectric loss in CaCu3Ti4O12 ceramics by optimizing the microstructures. 相似文献
127.
A multiplex CARS spectrometer based on a cw diode-pumpedQ-switched Nd: YLF laser, a broadband dye-laser and a multichannel spectrum detection system has been constructed. Excellent mode characteristics of the laser beams and high pulse repetition rate (2 kHz) have resulted in good signal-to-noise ratio achieved with a few seconds accumulation time. A 1000 cm–1 wide spectral range is covered in a single CARS spectrum with an expanded bandwidth of the dye laser. A thin-jet sampling method is used in order to avoid the phase-matching limitation. The efficient spectral intensity normalization by the reference (CCl4) nonresonant spectrum and subsequent computer fitting have been implemented. The performance of the system is demonstrated by two different experiments. First, the polarization sensitive measurements (PS-CARS) of cyclohexane show its potential for accurate Raman depolarization ratio determination and for detection of weak (overlapped) Raman bands. Second, the transient resonance CARS measurement of the lowest excited triplet state of all-trans retinal indicate its feasibility to time-resolved CARS spectroscopy of fluorescent excited states. 相似文献
128.
B. Drossel K. Dahmen 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(4):485-496
We report studies of the behaviour of a single driven domain wall in the 2-dimensional non-equilibrium zero temperature random-field
Ising model, closely above the depinning threshold. It is found that even for very weak disorder, the domain wall moves through
the system in percolative fashion. At depinning, the fraction of spins that are flipped by the proceeding avalanche vanishes
with the same exponent as the infinite percolation cluster in percolation theory. With decreasing disorder strength, however, the size of the critical
region decreases. Our numerical simulation data appear to reflect a crossover behaviour to an exponent at zero disorder strength. The conclusions of this paper strongly rely on analytical arguments. A scaling theory in terms
of the disorder strength and the magnetic field is presented that gives the values of all critical exponent except for one,
the value of which is estimated from scaling arguments.
Received: 13 February 1998 / Accepted: 30 March 1998 相似文献
129.
The surface of gloss fired porcelain with and without raw glaze coating was radiated by a CO2 laser working at 10.6 μm, a choice resulted from spectroscopic studies of suspensions made of China. The shine of the untreated sample was defined as the distribution of micro-droplets on the surface. The surface alterations due to laser heating were classified by the diameter of the completely melted surface, the ring of the surface at the threshold of melting, and the size of microscopic cracks. The diameter of the laser treated area was in the range of 3 mm, while the incident laser power and the duration of laser heating were varied between 1 and 10 W and 1-8 min, respectively. The different stages of surface modifications were attributed primarily to the irradiating laser power and proved to be rather insensitive to the duration of the treatment. We have found a range of parameters under which the white China surface coated with raw glaze and followed by laser induced melting exhibited very similar characteristics to the untreated porcelain. This technique seems prosperous for laser assisted reparation of small surface defects of unique China samples after the firing process. 相似文献
130.
The paper briefly reviews the development of domain observation techniques used to study basic properties of electrical steels. A new real-time, dynamic, high magnification domain observation technique is presented as an example of a state-of-the-art system, capable of imaging non-repetitive domain wall motion at power frequencies. Advantages of real-time domain observation over stroboscopic magneto-optic studies are presented and the need for real-time observations in developing future loss theories is proposed. Possible relationships between Barkhausen noise, hysteresis and non-repetitive wall motion in electrical steels are suggested and finally examples of non-repetitive wall motion in other magnetic materials are illustrated. 相似文献