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Microstructure and microwave dielectric properties of Ba_(6-3x)Sm_(8+2x)Ti_(18)O_(54) ceramics with various BaxSr_(1-x)TiO_3 additions

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Journal of Rare Earths 2012年第2期30卷 142-145页

作者：周玲玲周洪庆邵辉朱海奎 college of Materials Science and engineering Nanjing University of Technology

The Ba6-3xSm8＋2xTi18O54 （x=2/3） microwave dielectric ceramics were prepared by traditional solid sate reaction technique. The ex-periment was based on the Ba6-3xSm8＋2xTi18O54 （BST） microwave dielectric ceramics doped with a certain amount of Bi2O3, then the effects of BaxSr1-xTiO3 additives on the structure and microwave dielectric properties of Ba6-3xSm8＋2xTi18O54 ceramics were investigated using X-ray diffraction and scanning electron microscopy. In this study, the small amount substitution of Sr for Ba was effective for the microwave dielec-tric properties of BST, especially the τf could be tuned to near zero. The result showed that the BST possessed excellent dielectric properties when the addition of Bi2O3 and BaxSr1-xTiO3 was 1 wt.% respectively： εr=79.6, Q？f=10789 GHz, τf=-1.5 ppm/oC.

关键词： dielectric properties microstructure BaxSr1–xTiO3 rare earths

Regeneration of waste sintered Nd-Fe-B magnets to fabricate anisotropic bonded magnets

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Journal of Rare Earths 2015年第7期33卷 736-739页

作者：李现涛岳明 ZAKOTNIK Miha 刘卫强张东涛左铁镛 college of Materials Science and engineering Beijing University of Technology

The waste sintered Nd-Fe-B magnets were regenerated as magnetic powders via manually crushing （MC） or hydrogen decrepitation （HD） to fabricate anisotropic bonded magnets. Effect of size distribution on the magnetic properties of the regenerated magnetic MC and HD powders was investigated. For the MC powders, as the particle size decreased, the remanence （Br） increased first, and then decreased again, while the coercivity （Hci） dropped monotonically. The powders with particle size in the range of 200-450μm possessed the best magnetic properties ofBr of 1.22 T and Hci of 875.6 kAJm. The corresponding bonded magnet exhibited magnetic properties ofBr of 0.838 T, Hci of 940.9 kA/m, and （BH）max of 91.4 kJ/m^3, respectively. On the other hand, the liD powders with particle size range of 200-450 μm bore the best magnetic properties Of Br of 1.24 T and Hci of 860.4 kA/m. Compared with magnetic properties of the waste magnet, the powders retained 93.9% of Br and 70.0% of Hci, respectively. The bonded magnet produced from HD powders possessed Br of 0.9 T, Hci of 841.4 kA/m, and （BH）max of 111.6 kJ/m^3, indicating its good potential in practical applications.

关键词： regeneration Nd-Fe-B magnet scraps hydrogen decrepitation anisotropic bonded magnets rare earths

SiC nanoparticles reinforced magnesium matrix composites fabricated by ultrasonic method

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中国有色金属学会会刊：英文版 2010年第S3期20卷 1029-1032页

作者：王朝辉王旭东赵宇昕杜文博 college of Materials Science and engineering Beijing University of Technology

SiC nanoparticles reinforced magnesium matrix composites were fabricated by ultrasonic *** AZ91 alloy and SiC nanoparticles with the average diameter of 50 nm were used as the matrix alloy and the reinforcement,*** addition of nanoparticles was 0.1%,0.3%,and 0.5%(mass fraction) of the *** results of microstructural evaluation and mechanical properties indicate that the nanoparticles can be dispersed into magnesium alloys efficiently and uniformly with the aid of ultrasonic *** compared with the matrix alloys,the grains of composites were refined and the mechanical properties of composites were improved *** SEM and DSC analyses show that the SiC nanoparticles can act as the heterogeneous nucleation of α-***,the strengthening mechanism responsible for the composites reinforced with SiC nanoparticles was discussed.

关键词： magnesium matrix composites AZ91 alloy SiC nanoparticles ultrasonic method

Electromigration-induced cracks in Cu/Sn_(3.5)Ag/Cu solder reaction couple at room temperature

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Journal of Semiconductors 2009年第3期30卷 35-38页

作者：何洪文徐广臣郭福 college of Materials Science and engineering Beijing University of Technology

Electromigration （EM） behavior of Cu/Sn3.5Ag/Cu solder reaction couple was investigated with a high current density of 5 × 10^3 A/cm^2 at room temperature. One dimensional structure, copper wire/solder ball/copper wire SRC was designed and fabricated to dissipate the Joule heating induced by the current flow. In addition, thermomigration effect was excluded due to the symmetrical structure of the SRC. The experimental results indicated that micro-cracks initially appeared near the cathode interface between solder matrix and copper substrate after 474 h current stressing. With current stressing time increased, the cracks propagated and extended along the cathode interface. It should be noted that the continuous Cu6Sn5 intermetallic compounds （IMCs） layer both at the anode and at the cathode remained their sizes. Interestingly, tiny cracks appeared at the root of some long columntype Cu6Sn5 at the cathode interface due to the thermal stress.

关键词： electromigration cracks intermetallic compounds thermal stress

Preparation and laser induced damage properties of rare earth doped BAS glass

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Journal of Rare Earths 2008年第2期26卷 220-224页

作者：倪亚茹许仲梓陆春华张焱张其土 college of Materials Science and engineering Nanjing University of Technology

Rare earth doped B2O3-Al2O3-SiO2 glass （RExBAS, x=5, 10, 20; RE=La, Sm） were prepared by solid state reaction method. Optical transmission spectra of such glass were characterized by ultraviolet spectrometers, and 1064 nm laser induced damage performance was investigated through the method of ＂1-on-1＂. The results indicated that there was a strong absorptive peak near 1064 nm in SmxBAS glass, the peak was enhanced with increasing x. While LaxBAS glass was transparent to 1064 nm laser, at the same time, the results of laser induced damage showed that the anti-laser induced damage performance of such glass was strengthened with the addition of rare earth oxide. Furthermore, the laser induced damage threshold （LIDT） of SmxBAS glass was significantly higher than that of LaxBAS glass. Consequently, Sm^3＋ doping was favor in the improvement of anti-laser induced damage performance for BAS glass.

关键词： BAS glass Sm^3+ La^3+ laser induced damage threshold (LIDT) rare earths

Ultrashort optical pulse shaper based on complex-modulated long-period-grating coupler

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Chinese Physics B 2013年第2期22卷 287-290页

作者：董小伟刘文楷 college of Information engineering North China University of Technology

In this paper,we present a novel ultrashort pulse shaper based on complex-modulated long-period-grating coupler（CM-LPGC）.Temporal rectangular waveform with 2-ps full width at half maximum（FWHM） is obtained by transforming the input Gaussian *** of the CM-LPGC-based shaper to various non-ideal excitation conditions and fabricating errors are *** confirm that CM-LPGC is stable and suitable for optical pulse shaping operation.

关键词： ultrafast process optical pulse shaper complex-modulated long-period-grating coupler rectangular waveform

Die wall lubricated warm compaction of iron-based powder metallurgy material

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中国有色金属学会会刊：英文版 2002年第6期12卷 1095-1098页

作者：倪东惠陈维平肖志瑜温利平吴苑标 college of Mechanical engineering South China University of Technology

Lubricant is harmful to the mechanical properties of the sintered materials. Die wall lubrication was applied on warm compaction powder metallurgy in the hope of reducing the concentration level of the admixed lubricant. Iron based samples were prepared by die wall lubricated warm compaction at 175 ℃, using a compacting pressure of 550 MPa. Emulsified polytetrafluoroethylene(PTFE) was used as die wall lubricant. Admixed lubricant concentration ranging from 0 to 0.5% was tested. Extremely low admixed lubricant contents were used. Results show that in addition to the decrease in ejection forces, the green density of the compacts increases with the decrease of admixed lubricant content until it reaches the maximum at 0.06% of lubricant content, then decreases with the decrease of admixed lubricant content. The mechanical properties of the sintered compacts that contain more than 0.06% admixed lubricant are better than those of the samples that contain lesser lubricant. No scoring was observed in all die wall lubricated experiments.

关键词：加热压塑模壁润滑粉末冶金离子基材料

Preparation and performance of CeO_2 hollow spheres and nanoparticles

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Journal of Rare Earths 2016年第3期34卷 295-299页

作者：张问问陈东辉 college of Chemical and Environmental engineering Shanghai Institute of Technology

CeO_2 hollow spheres were synthesized by polystryrene sphere（PS） templates and CeO_2 nanoparticles were prepared by a facile method. The as-obtained products were characterized by scanning electron microscopy（SEM）, N_2 adsorption-desorption, X-ray diffraction（XRD）, Fourier transform infrared spectroscopy（FTIR） and UV-vis diffuse reflectance spectra. The results showed that the structure of the obtained CeO_2 hollow spheres was hollow microsphere with a diameter of 380 nm and the average particle size of CeO_2 nanoparticles was about 1700 nm. The two samples＇ Brunauer-Emmett-Teller（BET） surface area was 67.1 and 37.2 m^2/g. The CeO_2 hollow spheres had a better performance than nanoparticles at UV-shielding because of higher surface area and the structure of hollow sphere.

关键词： CeO2 UV-shielding hollow spheres template Rh B rare earths

Studies on synthesis and fluorescent property of rare earth complexes RE(ABMF)_2AA and copolymers RE(ABMF)_2AA-co-MMA

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Journal of Rare Earths 2009年第1期27卷 28-32页

作者：索全伶吕芳时建伟洪海龙罗吉平 Chemical engineering college Inner Mongolia University of Technology

Four new complexes RE（ABMF）2AA（RE=Sm, Eu, Tb, Dy） were synthesized by the reaction of RECl3·6H2O with acrylic acid（HAA） and 1-（2-furyl）-3-phenyl-1,3-propanedione（ABMF）.The copolymerization of the rare earth complexes with methyl methacrylate was studied by using 2,2-azobis-isobutyronitrile as an *** composition and structure of the four complexes were characterized by elemental analysis, UV-vis and *** glass transition temperature and molecular weight of the copolymers were ***-minescent measurement showed that ligand ABMF could efficiently transfer the energy to Sm^3＋ and Eu^3＋ ions in the complexes and sensitize the luminescence of the rare earth ions, but could not sensitize Tb^3＋ and Dy^3＋ *** a result, both Sm^3＋ and Eu^3＋ complexes emitted the characteristic fluorescence of Sm^3＋ and Eu3＋ ions due to the f-f *** four copolymers could emit strong fluorescence of the rare earth ions.

关键词： ternary rare earth complex synthesis copolymerization fluorescence property