Nanocrystalline cellulose (NCC) was used for improving the formaldehyde (HCHO) emission and bonding strength of urea formaldehyde (UF) resin adhesive in fiberboard and plywood. The original NCC was modified by 3-aminopropyltriethoxysilane (APTES) and the wetting property with UF resin adhesive was improved by 26.4%. The UF resin adhesive with modified NCC was characterized by X-ray powder diffraction (XRD), thermogravimetric analysis (TG) and Fourier transform infrared (FT-IR). The crystal region of UF resin adhesive was influenced by NCC and the diffraction intensity of the peak at 2θ = 22.82° was enhanced significantly. The thermal stability of UF resin adhesive with 1.0% modified NCC increased by 4.9%. And modified NCC led hydroxyl groups into the UF resin adhesive. HCHO emission and bonding strength of the UF resin adhesive with modified NCC were tested according to Chinese National Standards GB/T 17657-1999 and GB/T 9846-2004. The HCHO emission of fiberboard and plywood with 1.5% modified NCC decreased by 13.0% and 53.2%, respectively. The bonding strength of fiberboard increased by 158.3% (from 0.12 MPa of control group to 0.31 MPa of fiberboard with 1.5% modified NCC), while 1.5% modified NCC led to a 23.6% increase in the plywood.

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Research into the electrical‐thermal aging properties of cross‐linked polyethylene (XLPE) cable has great significance, because of its wide application. This study conducted accelerated electrical‐thermal aging tests on 10‐kV XLPE cable in order to assess the cable's mechanical and dielectric properties. After being aged by applying 34.8‐kV AC voltage at the four temperatures of 90, 103, 114, and 135°C, the cable samples were taken out in five stages according to the aging time and cut into slices. The slices were conducted experiments to test the breaking elongation, tensile strength, gel content, breakdown voltage, and frequency spectrums of the dielectric constant and dielectric loss. The results demonstrate that the mechanical strength and gel content of XLPE vary greatly under different aging temperatures, a finding that is associated with the crystallization characteristics of the material. The breakdown voltage shows a slight decreasing trend with aging time. The dielectric constant decreases with aging time in high‐frequency areas (103–106 Hz), while the dielectric loss factor increases with aging time at low frequencies (10−2–0 Hz). These two parameters can be used to characterize the degree of aging in cable. Copyright © 2016 John Wiley & Sons, Ltd.

Magnetoelectric voltage tunable inductor (ME-VTI) realizes the modulation of electric field to inductance based on magnetoelectric effect. Compared with other adjustable inductors, it has the advantages of low energy consumption, small volume, large tunability and continuity. However, previous reports on ME-VTI mainly focused on structure and magnetostrictive materials, resulting in the complexity of inductor structure and slight improvement of tunability. This study focuses on the influence of field-induced strain in piezoelectric materials on inductance tunability by constructing a theoretical model. The magnetoelectric laminate of Metglas/ PMN-PT single crystal /Metglas is employed as a magnetic core to design ME-VTI. The tunability is as high as 680% at 1 kHz, which is over 2.4 times larger than that of the Metglas/PZT/Metglas magnetic core. The quality factor of the PMN-PT based ME laminate reaches 15.6, which is 2.8 times higher than that of the PZT-based one. The proposed PMN-PT based ME-VTI provides an alternative approach for developing the integrated and miniaturized devices, and has an important prospect of application in the field of power electronics.

Insulating paper is a traditional insulation material used for transformer insulation. Transformer development is not only limited to small sizes and large capacities, but also limited to insulation life as insulating paper cannot withstand high temperatures. Therefore, recent studies have focused on improving the performance of insulation paper and discovering better insulation materials. In this study, two types of polymeric materials, polycarbonate (PC) and polyester film (PET), were chosen for comparative analysis. In order to test whether these two materials could be used in oil-immersed transformers, the PC and PET were placed in transformer oil for thermal aging at 110°C and 130°C, respectively. The thermal cracking processes and fragmentation mechanisms of the PC, PET, and insulation paper were analyzed using thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), and atomic force microscopy (AFM), as well as their degrees of polymerization and surface morphologies. According to the test results, the initial thermal decomposition temperature of PC and PET are higher than insulation paper and exhibited a better thermal resistance. PC and PET have the potential to substitute insulation paper for large capacity power transformer.