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The existing two-dimensional (2-D) analytical models for rotor eddy current loss (RECL) cannot consider the influence of the three-dimensional (3-D) distribution of the eddy current, so the calculation accuracy is limited. Based on the accurate subdomain method, this article proposes an improved 2-D analytical model for the RECL of high-speed (HS) permanent magnet (PM) motors with sleeve. Based on the load magnetic field, the model considers the influence of stator slotting and time harmonic of each current. The 3-D distribution of the eddy current is considered by expanding the radial component of the flux density axially. The eddy current reaction is considered by introducing the attenuation coefficient. The eddy current distribution on the surface of the PM and the RECL under the load magnetic field are verified by finite element (FE) method. The effect of the PM axial segmentation and thickness of sleeve on the RECL is also analyzed by the proposed analytical model. Finally, the correctness of the analytical model is verified by the loss separation experiment and the C-shape core experiment.

Aiming at the problem of long computation time of finite element analysis (FEA) and poor calculation universality of existing analytical models, this paper proposes a general hybrid analytical model to predict the no-load and load performance of interior permanent magnet motors with any slot-pole combination, where the form of magnet can be V-shape, U-shape or flat-shape. The magnets are equivalent correspondingly according to the rotor structure in the modeling process and the motor can be divided into eight types of subdomains, the no-load and load magnetic field of the motors can be obtained by solving the equations established by boundary conditions, where the nonlinear of core is calculated by local MEC. The proposed model can be used to calculate the air-gap magnetic field, no-load back electromotive force, cogging torque and electromagnetic torque of IPM motors with different rotor topologies. The effectiveness of the proposed model is verified by both FEA and experiments. Compared with FEA, this model can consume less time with the acceptable accuracy, which brings convenience to the design and optimization of related types of motors.

Purpose The specific iron losses of amorphous alloy material are extremely low compared with silicon steel material. The iron losses of motors may reduce by replacing the silicon steel core with an amorphous alloy core. However, one drawback of amorphous alloy material is that the specific iron losses will increase a lot after the motor manufacturing process. This paper aims to study the influences of interlaminar insulator solidifying and annealing on amorphous alloy material. The iron losses of motors made of amorphous alloy and baseline silicon steel sheets are compared and discussed.Design/methodology/approach This paper opted for an exploratory study using the experimental analysis and loss separation methods. Two amorphous alloy cores are produced and tested. The iron losses of motors made of amorphous alloy and silicon steel sheets are calculated and compared based on the measured specific iron losses. Three wound amorphous alloy core samples are made and measured. The iron losses are separated and compared by considering the manufacturing influences.Findings This paper provides empirical insights about what change is brought in amorphous alloy material after manufacturing. The results have shown that, for amorphous alloy cores without the annealing process, the loss increase caused by solidifying is mainly the eddy current loss, while it is mainly the hysteresis loss component for annealed amorphous alloy cores.Originality/value This paper presents for the first time the measured results of manufactured amorphous alloy cores. This paper fulfils the need to manufacture amorphous alloy motors properly for the producers. [ABSTRACT FROM AUTHOR]

Single crystal gold nanorods remain one of the most important and intensively studied anisotropic nanocrystals. The aspect ratio of the nanorods is controlled during the colloidal synthesis using silver nitrate; however, the mechanisms for the underlying control are not well understood. Here, we investigate the growth of gold nanocrystals at the stage where they break symmetry and begin anisotropic growth into nanorods. Using high resolution electron microscopy, we determine directly the size and atomic structure of the nanocrystals at the symmetry breaking point. We find that silver nitrate controls the size of the crystal at which symmetry breaking occurs. The seed crystal undergoes a symmetry breaking event at a critical diameter between 4 and 6 nm that depends upon the [HAuCl4]:[AgNO3] ratio. The smallest diameter for symmetry breaking, ∼4 nm, is observed at the lowest [HAuCl4]:[AgNO3] ratio (i.e., the highest AgNO3concentration) corresponding to the minimum size at which a “truncation” can form, a precursor to a {110} facet. The diameter of the nanocrystal at the symmetry breaking point becomes the width of the nascent nanorod, and this in turn determines the final nanorod width. Surprisingly, the [HAuCl4]:[AgNO3] ratio has little effect on the final nanorod length. Our observations explain why the nanorod aspect ratio is constrained within a limited range. This provides a rational framework for controlling width and aspect ratio in the growth of single crystal gold nanorods.

This work reports on the kinetic control of MnWO4nanoparticles with an aim to achieve the tailored structural properties. Using citric acid as the capping agent, MnWO4nanocrystals were prepared to show particle sizes ranging from 8 to 29 nm under hydrothermal conditions. The grain-growth kinetics for MnWO4nanoparticles was determined to quantitatively follow the equation, D5= (4.59 × 1020)te−17.0/T, where Dis the particle size at given reaction time, t, and reaction temperature, T. Systematic sample characterization using combined techniques of X-ray diffraction, transmission electron microscope, selected area electron diffraction, Barret−Emmett−Teller technique, Fourier transformed infrared spectra, UV−visible diffuse reflectance spectra, and Raman spectra indicates that particle size reduction led to an apparent lattice expansion, which is followed by lowering of lattice symmetry and band gap broadening. Different from the bulk counterparts, new vibration modes were observed in both Infrared and Raman spectra at about 913 and 930 cm−1, respectively, which intensified monotonously with particle size reduction, leading to a picture that MnWO4nanoparticles were terminated by surface disordered layers. All these size-dependent physical properties were closely related to the surface disorder and the relevant absorbates.

CdWO4nanocrystals with controlled particle size and crystallinity were successfully synthesized via a simple hydrothermal method using citric acid as the capping agent. By systematic sample characterization using X-ray powder diffraction, transmission electron microscope, selected area electron diffraction, Barret−Emmett−Teller technique, Fourier transformed infrared spectra, UV−visible diffuse reflectance spectra, and photoluminescence spectra, all as-prepared CdWO4samples were demonstrated to crystallize in a pure-phase of monoclinic wolframite structure. With varying the reaction temperature from 160 to 220 °C, particle size was controlled to grow from 11 to 21 nm. With particle size reduction, CdWO4nanostructure showed a lattice expansion, as is followed by a surprisingly lowered lattice symmetry, band gap broadening, and red-shift of Auvibration mode. Photocatalytic activity of CdWO4nanocrystals was examined by monitoring the degradation of methyl orange dye in an aqueous solution under UV radiation of 254 nm. High crystallinity CdWO4nanostructures with relatively small particle size showed an optimum photocatalytic performance. Consequently, systematic control over semiconductor nanostructures is proved to be useful, in some cases likely general, in achieving the advanced photocatalytic properties for technological uses.

Structural tailoring for dimensionally confined electrical properties is fundamentally important for nanodevices and the relevant technologies. Titanate-based nanotubes were taken as a prototype one-dimensional material to study. First, Na0.96H1.04Ti3O7·3.42H2O nanotubes were prepared by a simple hydrothermal condition, which converted into Na0.036H1.964Ti3O7·3.52H2O nanotubes by a subsequent acidic rinsing. Systematic sample characterization using combined techniques of X-ray diffraction, field emission scanning electron microscopy, high resolution transmission electron microscopy, electron paramagnetic resonance, Fourier transform infrared spectroscopy, elemental analyses, and alternative current impedance indicated that both nanotubes possessed a scrolled trititanate-type structure with the (200) crystal face predominant on the tube surface. With increasing temperature, both nanotubes underwent a continuous dehydration process, which however imposed different impacts on the structures and electrical properties, depending on the types of the nanotubes: (1) the Na0.036H1.964Ti3O7·3.52H2O nanotube converted into anatase-type structure TiO2nanotubes, while the Na0.96H1.04Ti3O7·3.42H2O nanotube kept the trititanate-type tube structure after calcination at 300 °C; (2) both nanotubes exhibited a maximum conductivity at high temperatures, in which Na0.96H1.04Ti3O7·3.42H2O nanotubes are relatively highly conductive, showing a grain conductivity approximately 2 orders of magnitude larger than that of Na0.036H1.964Ti3O7·3.52H2O nanotubes. These observations were interpreted in terms of the defect chemistry, hydration, and the triple conductive species that were confined in the one-dimensional nanostructures. The findings reported in this work may pave the way for titanate-based nanotubes to find a broad class of technological uses for nanodevices.

In typical seed-mediated syntheses of metal nanocrystals, the shape of the nanocrystal is determined largely by the seed nucleation environment and subsequent growth environment (where “environment” refers to the chemical environment, including the surfactant and additives). In this approach, crystallinity is typically determined by the seeds, and surfaces are controlled by the environment(s). However, surface energies, and crystallinity, are both influenced by the choice of environment(s). This limits the permutations of crystallinity and surface facets that can be mixed and matched to generate new nanocrystal morphologies. Here, we control post-seed growth to deliberately incorporate twin planes during the growth stage to deliver new final morphologies, including twinned cubes and bipyramids from single-crystal seeds. The nature and number of twin planes, together with surfactant control of facet growth, define the final nanoparticle morphology. Moreover, by breaking symmetry, the twin planes introduce new facet orientations. This additional mechanism opens new routes for the synthesis of different morphologies and facet orientations.

CdWO4polymorphs are solvothermally synthesized from mixtures of Cd2Cl2and Na2WO4using water as solvent to prepare monoclinic CdWO4, and propylene glycol for tetragonal CdWO4(autoclave, 200 °C, 10 h).