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Synthesis of Fe_3O_4 nanoparticles by wet milling iron powder in a planetary ball mill

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China Particuology 2007年第5期5卷 357-358页

作者： Ding Chen Song Ni Zhenhua Chen institute for Materials Research Hunan University Changsha 410082 China

Fe3O4 nanoparticles with sizes ranging from 30 to 80 nm were synthesized by wet milling iron powders in a planetary ball mill. The phase composition and the morphologies of the as-synthesized products were measured by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. Nanosized Fe3O4 particles were prepared by wet milling metallic iron powder （-200 mesh, 99%） in a planetary ball mill equipped with stainless steel vials using iron balls under distilled water with a ball-to-powder mass ratio of 50：1 and at a rotation speed of 300 rpm. The use of the iron balls in this method played a key role in Fe3O4 formation. The present technique is simple and the process is easy to carry out.

关键词： Fe3O4 Wet milling Planetary ball mill

Solution of Electromagnetic Wave in Time-Varying Media in two-Dimensional Space

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Chinese Physics Letters 2006年第3期23卷 595-598页

作者：陈丙康张颖高本庆 Department of Electronic Engineering Beijing Institute of Technology Beijing 100081

The analytical solution of gradual change media in two-dimensional free space is studied. Using separation of variables, the solution of electromagnetic wave in time-varying media, which is an exponential function of time, is derived in two-dimensional space. The rationality of the solution is verified indirectly. According to the solution, the figures of the wave are depicted. Based on these figures, the character of the wave in time-varying media is obtained, which shows frequency shift and changes of phase velocity and amplitude.

关键词： PROPAGATION

Influence of zirconium addition on the microstructure and magnetic properties of nanocomposite Nd_(10.1)Fe_(78.2-x)Co_5Zr_xB_(6.7) permanent magnets

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Rare Metals 2007年第3期26卷 218-221页

作者： FENG Shanshan NI Jiansen WANG Zhanyong WU Yisheng ZHOU Bangxin XU Hui institute of Materials Science Shanghai University Shanghai 20007 China

Nanocomposite Nd10.1Fe78.2-xCo5ZrxB6.7 （x= 0, 1.5, 2.5, 2.7, 3, 4） permanent magnets were prepared by melt-spun and annealing. The microstructure and magnetic properties of the permanent magnets were investigated. The resuits reveal that the addition of Zr element significantly reduces the grain size and improves the thermal stability of the amorphous phase. A fme nanocomposite microstructure with an average grain size of about 35 nm can be developed at a wheel speed of 16 m·s^-1 with the content of Zr up to 2.7 at.%. After optimal annealing （710℃ x 4 min）, the magnetic properties of the ***6.7 bonded magnets were achieved as follows： Br= 0.72 T, jHc = 769 kA·m^-1, and （BH）max = 85.0 kJ·m^-3.

关键词： magnetic properties Nd-Fe-B nanocomposite rare earths bonded magnet

Governing of down-shifting processes in LiLaP_4O_(12):Tb^(3+),Yb^(3+) for enhancement of its near-infrared emission

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Journal of Rare Earths 2016年第8期34卷 833-836页

作者： K.Grzeszkiewicz L.Marciniak D.Hreniak institute of Low Temperature and Structure Research Polish Academy of Sciences

Downshifting behavior of the Tb3＋-gb3＋ co-doped nanocrystalline LiLaP4012 powders synthesized by co-precipitation method was presented and discussed. The structural phase purity of obtained material was confirmed by X-ray diffraction （XRD） measurements. Strong enhancement of ytterbium 2 2 - 3＋ F5/2- F7/2 emission intensity was observed with decreasing Tb concentration un- der UV excitation. Dependence of efficiency of energy transfer between dopants on pumping wavelength was investigated due to bet- ter understanding of down-shifting mechanism. It was found that luminescence intensity of Yb3＋ decreased above 10 tool.% dopant con- tent, what was caused by concentration quenching. The power dependence measurements were carried out at 77 and 300 K. The re- sulting slopes had the same value of 1, what indicated the existence of linear down-shifting process, independent of the temperature.

关键词： downshifting LiLaP4O12 rb3+ yb3+ rare earths

Chiral symmetry restoration in excited hadrons and dense matter

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Chinese Physics C 2010年第9期34卷 1212-1217页

作者： L.Ya.Glozman institute for Physics Theoretical Physics BranchUniversity of Graz

We overview two interconnected topics： possible effective restoration of chiral symmetry in highly excited hadrons and possible existence of confined but chirally symmetric matter at low temperatures and high densities.

关键词： chiral symmetry confinement hadrons QCD phase diagram.

Microstructure of Pd_(77.5)Au_6Si_(16.5) Alloy Droplet Solidified in a Drop Tube Process

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Journal of Materials Science & Technology 1996年第5期12卷 385-388页

作者： Liling SUN Qi WU Liwei SUN and Wenkui WANG (institute of Physics, Chinese Academy of Sciences, Beijing 100080, China) institute of Physics Chinese Academy of Sciences Beijing 100080 China

The microstructure development of Pd77.5Au6Si16.5 alloy droplet solidified in a drop tube process was studied. It was found that two distinct microstructures, i.e. (Pd,Au)3Si primary phase and Pd+(Pd,Au)3Si eutectic can be obtained when the droplet diameter is within the range between 2.3~0.4 mm. The morpologies of the (Pd,Au)3Si developed from dendrite trunk-like with single branching only into dendrite cluster-like with ternary branching with the decrease of the droplet diameter. When the droplet diameter is about 0.25 mm, the primary phase (Pd,Au)3Si almost disappears and the microstructure mainly shows Pd+(Pd,Au)3Si eutectic. The morphology of the eutectic transforms from fiber-like to plate-like with the decrease of the droplet diameter in the range between 2.3-0.25 mm. When the droplet diameter is about 0.19 mm, the microstructure is only the single phase of Pd solid solution

关键词： Microstructure of Pd Au6Si Alloy Droplet Solidified in a Drop Tube Process

Transient Appearance of Double Spontaneous-Snakes in EAST H Mode Plasma

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Chinese Physics Letters 2014年第3期31卷 96-98页

作者： XU Li-Qing HU Li-Qun ZHANG Zi-Jun institute of Plasma Physics Chinese Academy of Sciences Hefei 230031

Transient lasting of double spontaneous snakes is observed in energy confinement improved plasma on the EAST tokamak. The destabilization of snakes with superb particle confinement can lower plasma energy confinement and slow plasma toroidal rotation. The non-monotonic q profile with double q=1 surface, slightly above unity in central, is constructed. The prevailing harmonic modes are susceptible to the nearly zero magnetic shear. Finally, the role of anomalous particle transport and the formation of off-axis peaking electron profile on the excitation of double snakes are discussed.

关键词： TOKAMAKS RESEARCH PLASMA (Ionized gases) -- Research PERTURBATION (Quantum dynamics) EXCITATION spectrum PHYSICS research

Accurate Evaluation of Microwave-Leakage-Induced Frequency Shifts in Fountain Clocks

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Chinese Physics Letters 2014年第10期31卷 18-21页

作者：房芳刘昆陈伟亮刘年丰所睿李天初 Time and Frequency Division National Institute of Metrology Beijing 100013

We report theoretical calculations of the transition probability errors introduced by microwave leakage in Cs fountain clocks, which will shift the clock frequency. The results show that the transition probability errors are affected by the Ramsey pulse amplitude, the relative phase between the Ramsey field and the leakage field, and the asymmetry of the leakage fields for the upward and downward passages. This effect is quite different for the leakage fields presenting below the Ramsey cavity and above the Ramsey cavity. The leakage-field-induced frequency shifts of the NIM5 fountain clock in different cases are measured. The results are consistent with the theoretical calculations, and give an accurate evaluation of the leakage-field-induced frequency shifts, as distinguished from other microwave-power-related effects for the first time.

关键词： MICROWAVE measurements STRAY currents FREQUENCY shift keying BLOCH equations (Physics) WAVE functions

Preparation and Characterization of Gd_3Sc_2Ga_3O_(12) Polycrystalline Material by Co-Precipitation Method

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Journal of Rare Earths 2007年第2期25卷 158-162页

作者：邵淑芳张庆礼苏静孙敦陆王召兵殷绍唐 Anhui institute of Optics and Fine Mechanics Chinese Academy of Sciences

Gd3Sc2Ga3O12 polycrystalline material for single crystal growth was prepared with Ga, Gd2O3 and Sc2O3 as starting materials and aqueous ammonia as the precipitator by co-precipitation method. The precursors sintered at various temperatures were characterized by infrared spectra （IR）, X-ray diffractometry （XRD） and transmitted electron microscopy （TEM）. The results showed that pure GSGG phase could be obtained at 900 ℃. The sintered powders were well-dispersed and less-aggregated in the sintered temperature range of 900 - 1000 ℃. XRD and TEM show that the polycrystalline particle sizes of the polycrystalline powders were about 20 - 50 nm. Compared with the method that Ga2O3, Gd2O3 and Sc2O3 were mixed directly and sintered to get polycrystalline materials, the synthesized temperature was lower and sintered time was shorter. Thus co-precipitation was a good method to synthesize GSGG polycrystalline material.

关键词： Gd3Sc2Ga3O12 co-precipitation laser crystal rare earths