Organic Light Emitting Diodes with p-Si Anodes and Semitransparent Ce/Au Cathodes

The Ce (x nm)/Au (15 nm) stacked layers were used as semitransparent cathodes in the top-emission organic light emitting devices (TOLEDs) fabricated on a p-type silicon anodes and substrate,where x varies from 4 to 16.The consequence of the Ce layer thickness on transmittance and the device performance were studied when the organic layers NPB (60 nm)/ALQ (60 nm) were kept unchanged,where NPB was N,N'-bis-(1-naphthl)-diphenyl-1,1'-biphenyl-4,4'-diamine,and AlQ is tris-(8-hydroxyquinoline) aluminum.The cathod...     

NPB层嵌入MgF_2超薄层对OLED性能的影响

将MgF2超薄层嵌入有机电致发光器件(OLED)的空穴传输层NPB中,制备了结构为ITO/NPB(10nm)/MgF2(xnm)/NPB(20nm)/Alq3(30nm)/Al(30nm)的一系列OLED。测试结果表明,合适厚度的MgF2可有效降低器件启亮电压,提高器件的发光效率。MgF2厚度为0.5nm的器件启亮电压只有2.3V,较未嵌入MgF2器件降低2V;MgF2厚度为1.0nm的器件最大电流效率达到3.93cd/A,最大光功率效率达到1.58lm/W,较未嵌入MgF2器件分别提高95%和110%。     

Influence of cerium on microstructures and mechanical properties of Al-Zn-Mg-Cu alloys

Effect of element cerium (Ce) on microstructure and mechanical properties of Al-Zn-Mg-Cu alloys has been investigated by transmission electron microscopy (TEM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and hardness test. The results show that addition of Ce can remarkably refine the as-cast grains and eutectic microstructure. A transformation from Mg(Zn,Cu,Al)₂ phase to Al₂CuMg phase is observed during homogenization. Furthermore, the Ce addition introduces changes in the precipitation process and consequently in the age-hardening behavior of the alloy. Microstructural measurements reveal that the addition of Ce promotes the precipitation of η′ phase, but it also partly retards the precipitation of GP zones. The density of precipitates decreases in a certain degree and rod-like η′ precipitates increase when Ce content is from 0.2% to 0.4% (mass fraction).     

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     

Synthesis and properties of the modification of micro-crystal LiMn2−x Al x O4 cathode material for Li-Ion batteries

The micro-single crystal material spinel LiMn2-xAlxO4 was prepared by a sol-gel procedure and modified by alumina; the electrochemical measurements show that the performances and characteristics of modified LiMn2-xAlxO4 electrode material are better than those of LiMn2O4. Hence, the modified LiMn2-xAlxO4 is a good cathode material for lithium batteries. This can be explained that the size of the modified particle is larger than that of unmodified material, so electrons can be easily transported between the particles.     

Synthesis and Characterization of LiCoxMn2-xO4 Cathode Materials

LiCoxMn2.04 cathode materials for lithium ion batteries were synthesized by mechanical activation-solid state reaction at 750 ℃ for 24 h in air atmosphere, and their crystal structure, morphology, element composition and electrochemical performance were characterized with XRD, SEM, ICP-AES and charge-discharge test. The experimental results show that all samples have a single spinel structure, well formed crystal shape and uniformly particle size distribution. The lattice parameters of LiCo Mn2-xO4 decrease and the average oxidation states of manganese ions increase with an increase in Co content. Compared with pure LiMn2O4, the LiCo Mn2xO4 （x=0.03-0.12） samples show a lower special capacity, but their cycling life are improved. The capacity loss of LiCo009Mn191O4 and LiCo0.1Mn1.88O4 is only 1.85% and 0.95%, respectively, after the 20th cycle. The improvement of the cycle performance is attributed to the substitution of Co at the Mn sites in the spinel structure, which suppresses the Jahn-Teller distortion and improves the structural stability.     

Variations in electroluminescence spectra of organic light emitting diodes containing bathocuproine layer

Electroluminescence (EL) of organic light emitting diodes (OLEDs) with a configuration of ITO/TPD/BC/Alq₃/Mg-Ag, where TPD, BC and Alq₃ represent N, N′-diphenyl-N, N′-bis (3-methylphenyl)-1,1′-biphenyl-4,4′-diamine, bathocuproine and tris(8-quinolinolato)aluminum(III), respectively, was investigated in comparison with the photoluminescence (PL) of the individual organic layers. The EL spectra of the OLEDs were found to be much different from the PL spectra of the component multiple layer structure. Each organic layer made its contribution to the light emitted from the OLEDs. Their individual contributions were related to the field distribution across the device, which was in turn dependent on the thickness of each organic layer and the applied bias voltages. Consequently, the EL spectra of the OLEDs were observed to vary as the relative thickness of any organic layer was changed and as the bias voltage was alternated. The variation of the EL spectra of the device resulted in the easiness of achieving variable colors emitted by the device, from blue to green, and then to near white light. Funded by the Scientific Research Foundation for the Returned Overseas Chinese Scholars     

Effects of Si and Ce on the microstructure and hydrogen storage property of Ti<Subscript>26.5</Subscript>Cr<Subscript>20</Subscript>V<Subscript>45</Subscript>Fe<Subscript>8.5</Subscript>Ce<Subscript>0.5</Subscript> alloy

In this paper, the effects of Si and Ce on the microstructure and hydrogen storage property of Ti_26.5Cr₂₀V₄₅Fe_8.5Ce_0.5 alloy were studied, respectively. First of all, effects of Si on the microstructure and hydrogen storage properties of Ti_26.5Cr₂₀(V₄₅Fe_8.5)_1−x Si _x Ce_0.5 (x = 0, 0.5, 1.0, 1.5 and 2.0 at%) alloys were studied by X-ray diffraction, scanning electron microscopy and P-C isotherm measurements. As the Si addition increases, the hydrogen absorption capacities of alloys decrease but the equilibrium pressure increases, due to the formation of Laves phase. Secondly, the effect of Ce on Ti_26.5Cr₂₀ (V₄₅Fe_8.5)_0.98Si₂ alloy was studied. It was found that Ce addition is an effective way to eliminate the effect of Si on the hydrogen storage properties of the alloy. Supported by the National Hi-Tech Research and Development Program of China (“863” Project) (Grant No. 2006AA05Z144)     

The Effect of Bi2O3 on the Structure and Microwave Dielectric Properties of Ba6-3xNd8＋2xTi18O54 System（x=2/3）

The structures and dielectric properties of Ba6-3xNd8＋2xTi18O54 system（x=2/3） doped with different contents of Bi2O3, whose final molecular formula is Ba6-3x（Nd1-yBiy）8＋2xTi18O54 were investigated. It is indicated that the dielectric constant increases greatly whereas Q value（f0=4 GHz） decreases with the increase of Bi2O3 content. However, the temperature coefficient could be controlled below 0±30×10^-6/℃ in the experiment. These phenomena are related to the appearance of a new phase, Bi4Ti3O12, which has high dielectric constant. Also, that Bi^3＋（0.13 nm） substitutes for Nd^3＋（0.099 5 nm） will increase the unit cell volume, which will lead to the enlargement of the octahedron B site occupied by Ti^4＋. So the spontaneous polarization of Ti^4＋ ions will be strengthened. Besides, Bi^3＋ will fill up some vacancies which Ba^2＋ or Nd^3＋ ions leave in two A1 sites and four A2 sites. More positive ions polarize, which also contributes to higher dielectric constant. The samples got with the optimium properties are sintered at 1 200 ℃ for 4 h, when y=0.25, ε≈110, Q≈5 400（f0=4 GHz）, TCC=-4.7×10^-6/℃; When y=0.3, ε≈120, Q≈5 000（f0=4 GHz）, TCC=-24×10^-6/℃.     

Valence Control of Ce Ions in Cerium-substituted Yttrium Iron Garnet

Cerium-substituted yttrium iron garnet( CexY3-xFe5O12, Ce : YIG ) was prepared via coprecipitation. The structure, morphology, valence state and constituent of Ce ions were investigated respectively. X-ray powder diffraction( XRD ) analysis shows that Ce : YIG was of single cubic YIG phase. The result of X-ray photoelectron spectroscopy( XPS ) indicates the Ce ions in Ce : YIG were in the state of trivalence. Scanning electron microscope ( SEM ) demonstrates the conglobatian of Ce : YIG particles about 0.2μm scale. The magnetic properties were studied by a vibrating sample magnetometer (VSM) and the result exhibits that substitution of Ce 3 changes the magnetic parameters of YIG. The effects of doping content of Ce ions and synthesis temperature on valence control were discussed in detail.     

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.     

Thermodynamic assessment of Au-Zr system

1　INTRODUCTIONChemicalvapordeposition (CVD)diamondholdsgreatpromiseinsolvingthermalmanagementprobleminhigh performancemulti chipmodules (MCMs) .However ,thismaterialdoespresentsometechnologi calchallenges ,onebeingthedevelopmentofreliablemetallizationsystems[1] .Thedesirablecharacteristicsofametallizationsystemare goodadhesiontothesubstrate ,lowstress ,goodelectricalconductivityandminimalreactionsatsubsequentprocessingtempera tures (upto 4 0 0℃ ) [2 ] .Goldisusuallychosenasthemetalfor…     

Magnetoresistance plateau in La2/3Ca1/3Bi x Mn1 − x O3 granular system

The effect of doping additional Bi on the magnetoresistance (MR) of La_2/3Ca_1/3B _x Mn_1−x O₃ was investigated. It is found that traditional colossal magnetoresistance (CMR) peak can only be observed in the x<0.05 samples and the peak value decreases with the increase of x, but the x≥0.05 samples show a magnetoresistance plateau above 200 K because of the presence of additional (La,Ca,Bi)-O layers. Moreover, this MR plateau is enhanced for the segregation of the La, Ca, and Bi elements. Funded by the Foundation for the Author of National Excellent Doctoral Dissertation of China (FANEDD) (No. 200233)     

Synthesis and electrochemical properties of Cr-doped Li<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript> cathode materials for lithium-ion batteries

Cr-doped Li₃V₂(PO₄)₃ cathode materials Li₃V_2−x Cr _x (PO₄)₃ were prepared by a carbothermal reduction(CTR) process. The properties of the Cr-doped Li₃V₂(PO₄)₃ were investigated by X-ray diffraction (XRD), scanning electron microscopic (SEM), and electrochemical measurements. Results show that the Cr-doped Li₃V₂(PO₄)₃ has the same monoclinic structure as the undoped Li₃V₂(PO₄)₃, and the particle size of Cr-doped Li₃V₂(PO₄)₃ is smaller than that of the undoped Li₃V₂(PO₄)₃ and the smallest particle size is only about 1 μm. The Cr-doped Li₃V₂(PO₄)₃ samples were investigated on the Li extraction/insertion performances through charge/discharge, cyclic voltammogram (CV), and electrochemical impedance spectra(EIS). The optimal doping content of Cr was that x=0.04 in the Li₃V_2−x Cr _x (PO₄)₃ samples to achieve high discharge capacity and good cyclic stability. The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through the Cr-doping. The improved electrochemical performances of the Cr-doped Li₃V₂(PO₄)₃ cathode materials are attributed to the addition of Cr³⁺ ion by stabilizing the monoclinic structure. Funded by the Guangxi Natural Science Foundation(No. 0832259) and the National Basic Research Program of China (No. 2007CB613607)     

Preparation and electrochemical studies of Y-doped LiVPO<Subscript>4</Subscript>F cathode materials for lithium-ion batteries

Y-doped LiVPO₄F cathode materials were prepared by a carbothermal reduction(CTR) process. The properties of the Y-doped LiVPO₄F samples were investigated by X-ray diffraction (XRD) and electrochemical measurements. XRD studies show that the Y-doped LiVPO₄F samples have the same triclinic structure as the undoped LiVPO₄F. The Li extraction/insertion performances of Y-doped LiVPO₄F samples were investigated through charge/discharge, cyclic voltammogram (CV), and electrochemical impedance spectra(EIS). The optimal doping content of Y is x=0.04 in LiY _x V_1−x PO₄F system. The Y-doped LiVPO₄F samples show a better cyclic ability. The electrode reaction reversibility is enhanced, and the charge transfer resistance is decreased through the Y-doping. The improved electrochemical performances of the Y-doped LiVPO₄F cathode materials are attributed to the addition of Y³⁺ ion by stabilizing the triclinic structure. Funded by the Sponsor Teams for Innovation in the Construction of Talent Highlands in Guangxi Institutions of Higher Learning(GuiJiaoRen [2007]71), Guangxi Natural Science Foundation(No.0832259), the Research Funds of the Guangxi Key Laboratory of Environmental Engineering, Protection and Assessment Program to Sponsor Teams for Innovation in the Construction of Talent Highlands in Guangxi Institutions of Higher Learning(GuiJiaoRen [2007]71)     

Memory characteristics of Au/PZT/BIT/p-Si ferroelectric diode

A ferroelectric memory diode consisting of Au/PZT/BIT/p-Si multilayer configuration has been fabricated by pulsed laser deposition (PLD) technique. The ferroelectric properties and the memory characteristics are investigated. The P-E curve of the PZT/BIT/p-Si films system had an asymmetry saturated hysteresis loop with P, = 15 μC/cm2 and Ec = 48 kV/cm, and the decay in remanent polarization was only 10% after 109 switching cycles, meanwhile the increase in coercive field was 12% . The C-V hysteresis loop and the I-V curve showed a memory effect derived from the ferroelectric polarization of PZT/BIT films, and the current density was 6.7 × 10-8 A/cm2 at a voltage of + 4V. Our diode had nonvolatile and nondestructive memory readout operation. There was a read current disparity of 0.05 μA for logic "1" and logic "0" at a read voltage of + 2V, and the stored logical value ("1" or "0") could be read out in 30 min.     

Synthesis and oxidation behavior of boron-substituted carbon powders by hot filament chemical vapor deposition

Boron-substituted carbon powder, B _x C_1−x with x up to 0.17, has been successfully synthesized by hot filament chemical vapor deposition. The boron concentration in prepared B _x C_1−x samples can be controlled by varying the relative proportions of methane and diborane. X-ray diffraction, transmission electron microscopy, and electron energy loss spectrum confirm the successful synthesis of an amorphous BC₅ compound, which consists of 10–20 nm particles with disk-like morphology. Thermogravimetry measurement shows that BC₅ compound starts to oxidize approximately at 620°C and has a higher oxidation resistance than carbon. Supported by the National Natural Science Foundation of China (Grant Nos. 10474083, 50472051, 50532020, 50672081) and the National Basic Research Program of China (Grant No. 2005CB724400)     

Electrochemical behavior of diverse vanadium ions at modified graphite felt electrode in sulphuric solution

PAN-based graphite felt (PGF) treated in 98% sulphuric acid for 5 h and then kept at 450 ℃ for 2 h was evaluated for their electrochemical performance as electrodes of vanadium redox battery (VRB). Structure and characteristic of treated PAN-based graphite felt (TPGF) were determined by means of Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, Brunauer-Emmett-Teller surface area analysis and VRB test system. The results show that the acid and heat synergistic effect increase the number of —COOH functional groups on the PGF surface, and the PGF is eroded by sulphuric acid oxidation, resulting in the surface area increases from 0.31 m2/g to 0.45 m2/g. The V(Ⅱ)/V(Ⅲ) redox reaction is electrochemically reversible on the TPGF electrode, while the V(Ⅳ)/V(Ⅴ) couple is a quasi reversible process. The diffusion coefficients of the oxidation for V(Ⅳ)/V(Ⅴ) obtained from the scope of peak current Ip vs scan rate v1/2 is 4.4×10-5 cm2/s. The improvement of electrochemical activity for the electrode is mainly ascribed to the increase of the number of —COOH groups on the TPGF, which behaves as active sites catalyzing the vanadium species reactions and accelerating electron transfer reaction and oxygen transfer.     

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…     

Microstructure of a spray deposited intermetallic compound alloy of Ni-Al-Mo system

The microstructure of a spray deposited intermetallic compound alloy of Ni-Al-Mo system(Ni3Al-Mo intermetallic compound alloy) prepared by a spray atomization deposition was studied in detail by using optical metallography,XRD,DTA,SEM,TEM,HREM and computer simulation.The preform consists of uniform and equiaxial grains,ranging from 10-40 μm,with some microporosity.Besides the main phases of the matrix alloy γ' and γ,Ni2Mo and Ni3Mo phases are also found within the γ network.A new Ni enriched phase in the γ phase was identified to have face-centered cubic structure with a lattice constant α=1.09 nm and space group Fm3m.