Influence of Tb substitution on low-field magnetocaloric effect in Gd5Si1.72Ge2.28 alloy

The lattice parameters, magnetic phase transition, Curie temperature and magnetocaloric properties for (Gd_1−x Tb _x )₅Si_1.72-Ge_2.28 alloys with x = 0, 0.15, 0.20 and 0.25 were investigated by X-ray powder diffractometry and magnetization measurements. The results show that suitable partial substitution of Tb in Gd₅Si_1.72Ge_2.28 compound remains the first-order magnetic-crystallographic transition and enhances the magnetic entropy change, although Tb substitution decreases the Curie temperature (T _C) of the compounds. The magnetic entropy change of (Gd_1−x Tb _x )₅Si_1.72Ge_2.28 alloys retains a large value in the low magnetic field of 1.0 T. The maximum magnetic entropy change for (Gd_0.80Tb_0.20)₅Si_1.72Ge_2.28 alloy in the magnetic field from 0 to 1.0 T reaches 8.7 J/(kg·K), which is nearly 4 times as large as that of (Gd_0.3Dy_0.7)₅Si₄ compound (|ΔS _max| = 2.24 J/(kg·K), T _C = 198 K). Foundation item: Project (50371058) supported by the National Natural Science Foundation of China     

磁致冷材料及技术

磁致冷是一种把磁性材料的磁热效应应用于制冷领域的新技术,它具有高效、节能、无环境污染等优点,可作为气体压缩／膨胀剂制冷的替代技术,受到世界各斩普遍重视,本文概述了磁致冷原理、材料、室温磁致冷技术及磁致冷模型机的工作原理、发展现状及其今后研究的方向。     

Influence on performance and structure of spinel LiMn2O4 for lithium-ion batteries by doping rare-earth Sm

The spinel LiMn₂O₄ used as cathode materials for lithium-ion batteries was synthesized by mechano-chemistry fluid activation process, and modified by doping rare-earth Sm. Thesting of X-ray diffraction, cyclic voltammograms, charge-discharge and SEM was carried out for LiMn₂O₄ cathode materials and the modified materials. The results show that the cathode materials doped rare earth Li _x Mn_2−y Sm _z O₄ (0.95⩽x⩽1.2, 0⩽y⩽0.3, 0⩽z⩽0.2) exhibit standard spinel structure, high reversibility of electrochemistry and excellent properties of charge-discharge. In EC: DMC(1 : 1)+1 mol/L LiPF₆ electrolyte with discharge capacity more than 130 mA · h/g, and its capacity is deteriorated less than 15% after 300 cycles at room temperature and less than 20% after 200 cycles at 55°C. At the same time, Crystal Field Theory was applied to explain the function and mechanism of doped rare earth element. Foundation item: Project (02JJY2081) supported by the Natural Science Foundation of Hunan Province     

Metal magnetic memory testing for early damage assessment in ferromagnetic materials

In order to investigate the physical mechanism of metal magnetic memory testing, both the influences of earth magnetic field and applied stress on magnetic domain structure were discussed. Static tension and fatigue tests for low carbon steel plate specimens were carried out on hydraulic servo testing machine of MTS810 type and magnetic signals were measured during the processes by the type of EMS-2003 instrument. The results indicate that the initial magnetic signals of specimens are different before loading. The magnetic signals curves are transformed from initial random to regular pattern due to the effect of two types of loads. However, the shape and distribution of magnetic signal curves in the elastic region are different from that of plastic region in tension test. While in fatigue test those magnetic signals curves corresponding to different cycles are similar. The H _p(y) value of magnetic signals on the fracture zone increases dramatically at the breaking transient time and positive-negative magnetic poles occur on the two parts of fracture zone. Foundation item: Project(50235030) supported by the National Natural Science Foundation of China     

Synthesis of Ni-Zn ferrite and its microstructure and magnetic properties

1 INTRODUCTION Ni-Zn ferrite with spinel structure is a versatile technological material due to their high-resistivity and low-eddy current losses, particularly suitable for high-frequency applications. Ni-Zn ferrites have been commercially used in recording heads, antennas rods, loading coils, microwave devices and telecommunication applications fields, and so on[1?2]. Ni-Zn ferrites are usually prepared by the conventional ceramic method[3] and the wet-chemical method[4?16]. The cerami…     

Scanner external calibration algorithm based on fixed point in robot remanufacturing system

This paper deals with the scanner exterior calibration algorithm when the scanner is arranged by the robot and the object scanned is fixed on a rotate device in the Robot Remanufacturing System. The method of calibrating the relationship between the scanner coordinate and the robot Tool₀, such as the rotation, R _x , R_y, R_z, and the transformation X, Y, Z is studied. The data of Tool₀ can be directly obtained from the relationship with the robot base-coordinate. So, the coordinate relationship between the scanner coordinate and the robot base coordinate can be easily gotten. This paper explains the basic algorithm theory, computing method, data collecting process and the resulted data in detail. The calibration algorithm is deduced under the orthogonal coordinate. Foundation item: Project (50075086; 50235030) supported by the National Natural Science Foundation of China; Project (413270103) supported by National Basic Research Foundation of China; Project (2000-476) supported by the Ministry of Education for the Outstanding Teachers     

Effect of doped Mn on piezoelectric properties of （Na0.5Bi0.5 ）0.92 Ba0.08 TiO3 lead-free ceramics

Piezoelectric ceramics (Na0.5Bi0.5)0.92Ba0.05TiO3 x%MnCO3(BNBT-Mn, x=0-1.6,mass fraction)were synthesized by conventional solid state reaction. The results show that when the addition of MnCO3 is 0-1.4%, BNBT-Mn ceramics exhibit a single-phase perovskite structure. With the increase of content of MnCO3, piezoelectric constant and electromechanical coupling factor increase rapidly when x is lower than 0.3. Then they both decrease when x is in the range of 0.3 and 1.6. When x=0.3, piezoelectric constant and electromechanical coupling factor reach the maximum value of 160 pC/N and 58.5% respectively, which can improve the temperature stability of BNBT-Mn.     

Structural evolution and stability of mechanically alloyed Fe-Ni nanocrystalline

The structural evolution and stability of Fe100-xNix(x=10, 20, 35, 50) alloys prepared by mechanical alloying were investigated through X-ray diffraction analysis and transmission electron microscopy. The intrinsic conditions of preparation determining phase stability in nanocrystalline were clarified. After being milled for 120 h, the powders of Fe90Ni10 and Fe80Ni20 consist of a single α(bcc) phase, Fe30Ni30 powders are a single γ(fcc), and for Fe65Ni35 powders there is co-existence of α and γ phases. The as-milled Fe80Ni20 powders annealed at 680 ℃ exhibits the stability of high-temperature γ phase at room temperature, which is consistent with the theoretical prediction.     

Magnetostrictive distortion in Pr0.15Tbx Dy0.85-xFe2 polycrystals by X-ray diffraction

The ingots of Pr0.15 Tbx Dy0.85-x Fe2 (x=0.10-0.85) series compounds with a single phase were prepared by a arc melting method. The X-ray diffraction patterns were measured using a Philips X‘pert MPD X-ray diffractometer with a non-ambient sample stage at different temperatures, the magnetostfictive distortion in Pr0.15 Tbx Dy0.85-x Fe2 polycrystals was investigated by X-ray diffraction patterns and the magnetostfiction coefficient λ111 was calculated. The results show when the temperature is raised above the spin reorientation temperature region, a splitting appears in the reflection (440); the λ111 increase with the increasing of Tb content for Pr0.15 Tbx Dy0.85-x Fe2 polycrystals and thefull width at half maximum (FWHM) of the reflection (440) increases gradually with the increasing of Tb content.Moreover, as the FWHM of the reflection (440) decreases gradually with the increasing of temperature, the λ111 decreases slightly with the increasing of temperature at the temperature region of 223 -373 K for Pr0.15 Tb0.3 Dy0.55 Fe2 alloy.     

Life cycle of remanufactured engines

The life cycle index of remanufactured engines was assessed by using the method of life cycle assessment (LCA). A remanufactured engine of a certain domestic brand was taken as researching object. Engine reproducing engineering was investigated from three aspects which were energy, material and environment. The application of LCA on remanufacturing engines was discussed in detail with a practical case. The results indicate that remanufacturing an engine can save 55 kg steels, 8.3 kg aluminum and 113 kW · h electric powers and reduce emissions of 565 kg CO₂, 6.09 kg CO, 1.01 kg NO _x , 3.985 kg SO _x and 288.725 kg solid waste. The remanufacturing of engines possesses great economic value and practicability. Foundation item: Project (50235030) supported by the National Natural Science Foundation of China     

Effects of microstructures on the deformation and fracture behaviors of TiAl-based alloys

The fracture toughnessK _Ic, the tensile deformation and fracture behaviors of different microstructures ofγ-TiAl based alloy, Ti-33Al-3Cr-0.5Mo] were studied at room temperature. It is found that theK _Ic value is lower in the duplex microstructure, and increases with the increase of vol pct of the lamellar microstructure, and that the full lamellar has the highestK _Ic value. Cleavage was the dominant fracture mechanism in the duplex microstructure material. In contrast, for the full lamellar microstructure the high anisotropy of deformation and the large strain discontinuity at grain boundaries resulting in decohesion of grain boundaries are the main fracture processes. Project supported by the National Natural Science Foundation of China and National Advanced Materials Committee of China Synopsis of the first author Chen Xiaoqun, associated professor, born in Jan. 1965, current research fields: physical metallurgy of high-temperature structural intermetallic compounds.     

Oxidation performance of Fe-Al/WC composite coatings produced by high velocity arc spraying

Fe-Al intermetallics with remarkable high-temperature intensity and excellent erosion, high-temperature oxidation and sulfuration resistance are potential low cost high-temperature structural materials. But the room temperature brittleness induces shape difficult and limits its industrial application. The Fe-Al intermetallic coatings were prepared by high velocity arc spraying technology with cored wire on 20G steel, which will not only obviate the problems faced in fabrication of these alloys into useful shapes, but also allow the effective use of their outstanding high-temperature performance. The Fe-Al/WC intermetallic composite coatings were prepared by high velocity arc spraying technology on 20G steel and the oxidation performance of Fe-Al/WC composite coatings was studied by means of thermogrativmetic analyzer at 450, 650 and 800°C. The results demonstrate that the kinetics curve of oxidation at three temperatures approximately follows the logarithmic law. The composition of the oxidized coating is mainly composed of Al₂O₃, Fe₂O₃, Fe₃O₄ and FeO. These phases distribute unevenly. The protective Al₂O₃ film firstly forms and preserves the coatings from further oxidation. Foundation item: Project(50235030) supported by the National Natural Science Foundation of China; Project(98BK014) supported by the Foundation of State Economy Trade Committee of China     

Non-fragile delay-dependent H ∞ control of linear time-delay system with uncertainties in state and control input

The problem of designing a non-fragile delay-dependent H∞ state-feedback controller was investigated for a linear time-delay system with uncertainties in state and control input. First, a recently derived integral inequality method and Lyapunov-Krasovskii stability theory were used to derive new delay-dependent bounded real lemmas for a non-fragile state-feedback controller containing additive or multiplicative uncertainties. They ensure that the closed-loop system is internally stable and has a given H∞ disturbance attenuation level. Then, methods of designing a non-fragile H∞ state feedback controller were presented. No parameters need to be tuned and can be easily determined by solving linear matrix inequalities. Finally, the validity of the proposed methods was demonstrated by a numerical example with the asymptotically stable curves of system state and controller output under the initial condition of x（0）=[1 0 -1]^T and h=0.8 time-delay boundary.     

Synthesis and photophysical and electrochemical properties of new cyclometalated platinum complex containing oxadiazole ligand

A new cyclometalated platinum complex containing 2, 5-bis（naphthalene-1-yl）-1,3,4-oxadiazole ligand was synthesized and characterized. The UV-Vis absorptions and photoluminescent properties of the ligand and its platinum complex were investigated A characteristic metal-ligand charge transfer absorption peak at 439 nm in the UV spectrum and a strong emission peak at 625 nm in the photoluminescence spectrum were observed for this complex in dichloromethane. Cyclic voltammtry （CV） analysis shows that the EHOMO （energy level of the highest occupied molecular orbital） and ELUMO （energy level of the lowest unoccupied molecular orbital） of the platinum complex are about -5.69 and -3.25 eV, respectively, indicating that the oxadiazole-based platinum complex has a potential application in electrophosphorescent devices used as a red-emitting material.     

Optimizing pyrolysis of resin carbon for anode of lithium ion batteries

1INTRODUCTION Lithiumionbatterieshaveattractedworldwide attentionandbeendevelopedrapidlyduetotheirhighenergydensity,goodcharge dischargeper formancesandlongcyclelife[14].Theseoutstand ingpropertiesresultfromtheuseofcarbonmateri alsasanodeinsteadoflithiummetal.However,thespecificcapacityofcarbonmaterialsisfar smallerthanthatoflithiummetal(3670mA·h/g).Muchefforthasbeenfocusedonimprovingca pacityofcarbonanodesduringthepastfew years[57].Recentworkindicatedthatdisorderedcar bons,obtainedbypy…     

Microscopic phase-field simulation for coarsening behavior of L12 and DO22 phases of Ni75Cr x Al25? x alloy

Based on the microscopic phase-field dynamic model and the microelasticity theory, the coarsening behavior of L1₂ and DO₂₂ phases in Ni₇₅Cr _x Al_25−x alloy was simulated. The results show that the initial irregular shaped, randomly distributed L1₂ and DO₂₂ phases are gradually transformed into cuboidal shape with round corner, regularly aligned along directions [100] and [001], and highly preferential selected microstructure is formed during the later stage of precipitation. The elastic field produced by the lattice mismatch between the coherent precipitates and the matrix has a strong influence on the coarsening kinetics, and there is no linear relationship between the cube of the average size of precipitates and the aging time, which does not agree with the results predicted by the classical Lifshitz-Slyozov-Wagner. The coarsening processes of L1₂ and DO₂₂ phases are retarded in elastically constrained system. In the concurrent system of L1₂ and DO₂₂ phases, there are two types of coarsening modes: the migration of antiphase domain boundaries and the interphase Ostwald ripening. Foundation item: Project(50671084) supported by the National Natural Science Foundation of China; Project(20070420218) supported by China Postdoctoral Science Foundation     

Preparation of ITO nano-powders by hydrothermal-calcining process

1 INTRODUCTIONSn-doped In2O3(ITO) is one kind of n-typesemiconductor material[1].It has excellent electro-optical properties , such as electrical conductivityand high transparency under visible light[2],andiswidely used in electronic , transparent electrode ,solar cells and electro-irradiance , especially inscreen display[3 ,4].Recently nearly half of the met-al indium has been used to prepare ITO materialsin the developed countries[5], such as Japan, A-merica ,France and so on.So the…     

Carburization of ferrochromium metals in chromium ore fines containing coal during voluminal reduction by microwave heating

Chromium ore fines containing coal (COFCC) can be rapidly heated by microwave to conduct the voluminal reduction, which lays a foundation of getting sponge ferrochromium powders with a lower content of C. Under the conditions of COFCC with n(O):n(C) (molar ratio) as 1.00:0.84 and n(SiO₂):n(CaO) as 1.00:0.39, the samples were heated by 10 kW microwave power to reach the given temperatures and held for different times respectively. The results show that the low-C-Cr ferrochromium metal phase in the reduced materials forms before the high-C-Cr ferrochromium metal phase does. With increasing temperature the C content of ferrochromium metals is in a positive correlation with the content of Cr. The C content of ferrochromium metal in reduced materials is 0–10.07% with an average value of 4.68%. With the increase of holding time the Cr content in ferrochromium metals is in a negative correlation with the content of C, while the content of Fe changes in the contrary way. In the microwave field the kinetic conditions of carburization are closely related with the temperature of microwave heating, holding time and carbon fitting ratio. Foundation item: Project(50474083) supported by the National Natural Science Foundation of China; Project supported by the Baoshan Iron & Steel Co. Ltd. of China     

Separation of baicalin from Scutellaria Baicalensis Georgi with polyamide

Separation of baicalin from Scutellaria Baicalensis Georgi with polyamide was studied. The adsorption isotherm, kinetic equation and desorption law were investigated by static and dynamic adsorption methods. The results show that the kinetic behavior is mainly controlled by the liquid film diffusion process and obeys the Boyd film diffusion equation. Equilibrium data for the adsorption of baicalin are correlated with Freundlich isotherm equation, i.e. q=3.8Ce2.057, suggesting that the relative capacity of polyamide to baicalin is somewhat small. The desorption results indicate that the baicalin with mass fraction of 33.86% and the least impurities can be obtained by chromatography using 60% ethanol as the eluant at room temperature.     

Synthesis and coloring properties of Cd（S1-xSex） pigments by precipitate-hydrothermal method

Cd（S1-xSex） pigments （red to yellow） were synthesized by precipitate-hydrothermal method. The structure, morphology and hue of the powder were characterized by X-ray diffractometry （XRD）, scanning electron microscopy （SEM）, energy dispersive X-ray spectroscopy （EDAX） and CIE chromaticity. The optimum synthesis conditions were obtained and reaction mechanism was further analyzed as well. The results show that molar ratio of S to Se, pH value and hydrothermal reaction conditions have great effects on the hues of the pigments. Pigments with vivid hues are obtained under the conditions that pH value is about 13.0, hydrothermal reaction condition is at 140 ℃ for 4 h or at 160 ℃ for 6 h. The reaction mechanism is that Se^2- of Cd（S1-xSex） substitutes S^2- of CdS and then forms a continuous solid solution.