Preparation,microstructure and magnetic properties of NiZn ferrite thin films by spin spray plating

NiZn ferrite thin fihns were performed on glass substrates of 85 ℃ by spin spray plating method. X-ray diffraction patterns of the films show that the samples have a cubic spinel structure with no extra lines corresponding to any other phases between 75 ℃ and 85 ℃. As the pH value of oxidizing solution increases to 8.3, the saturation magnetization increases to 3.13 × 10^5 A/m and resistivity to 127 m Ω ·cm. Film deposited at pH 7.8 has a smooth surface and definite columnar structure. The large wavy flakes were observed at pH 8.3. The high real part of complex permeability μ′ up to 36.1 and the imaginary part μ″ up to 53.2 were observed at 0.5 GHz by short microstrip line perturbation method. The μ″ of thin film has values higher than 20 at the frequencies between 0.5 GHz and 2 GHz, the film is a promising anti-noise material for high frequency applications,     

Asymptotic analysis of weakly nonlinear and forced oscillations

The restriction ofK-B averaging method is discussed and asymptotic solution of the weakly nonlinear and forced oscillationu″+ω ₀ ² u=εkcosωt−εu ³ is obtained by Struble technique. The conclusion about this oscillation derived with other method is discussed. The results show thatK-B method will break down whena andθ in the zeroth solution of above eqation are not slowly varying functions of timet. The stationary solution of weakly nonlinear oscillation,u″+ω ₀ ² u=εkcosω(ε)t-εu ³ is also analysed. Synopsis of the author Chen Feng, associated professor, born in October 1948, worked on experimental fracture mechanics in Sweden from 1990 to 1995 as a visiting scholar. Major research fields include perturbation and weight function method and its application, experimental mechanics. currently interested in rock fracture mechanics.     

Viscoelastic properties of monodisperse spherical silica suspension

The viscoelastic properties of the suspension of monodisperse spherical silica produced by hydrolysis of tetraethoxysilane in alcohol solvent with ammonia as a catalyst in polyethylene glycol (PEG) were studied. The results show that the SiO2/PEG suspension possesses the reversible shear thinning and shear thickening behaviors. In the shear thinning region, the loss modulus (G″) almost remains unchanged, whereas the storage modulus (G′) decreases. In the shear thickening region, G″ and G′ increase for the formation of the "clusters". The larger G″ over G′ in all the stress studied shows that the system mainly possesses the viscous property, and that the energy dissipated(Ed) is larger than that stored. Ed of this suspension is proportional to the maximum strain (γmax) rising with the exponent of 1.92 under low shear stress; however, in the shear thickening region, Ed is proportional to γmax rising with the exponent of 5.00.     

Critical driving force for martensitic transformation fcc (γ)→hcp(ε) in Fe-Mn-Si shape memory alloys

By the application of Chou's new geometry model and the available data from binary Fe-Mn, Fe-Si and Mn-Si systems, as well as SGTE DATA for lattice stability parameters of three elements from Dinsdale, the Gibbs free energy as a function of temperature of the fcc(γ) and hep(ε) phases in the Fe-Mn-Si system is reevaluated. The relationship between the Neel temperature of the γ phase and concentration of constituents in mole fraction, is fitted and verified by the experimental results. The critical driving force for the martensitic transformation fcc (γ)→ hep (ε), △ G_C~(γ→ε), defined as the free energy difference between γ and ε phases at M_s of various alloys can also be obtained with a known M_s. It is found that the driving force varies with the composition of alloys, e. g. △ G_C~(γ→ε) = - 100.99 J/mol in Fe-27.0Mn-6.0Si and △ G_C~(γ→ε) = - 122.11 J/mol in Fe-26.9Mn-3.37Si. The compositional dependence of critical driving force accorded with the expression formulated by Hsu of 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.     

Rheological properties of konjac glucomannan/SiO<Subscript>2</Subscript>/organic-borate gels

A series of thermoreversible konjac glucomannan gels crosslinked by organic borate were prepared. Required amount of hydrophilic SiO₂ was added into the konjac glucomannan solutions before the crosslinking reaction. The gel network was formed through the crosslinking reaction between borate ions dissociated from organic borate and the cis-diol hydroxyl groups on the mannose units of polysaccharide chains. The rheological properties of the complex gels were studied by dynamic viscoelastic measurement. The gelation kinetics of the complex gels was studied and the critical gelation points of the gels were exactly determined by the Winter-Chambon criterion. The effects of temperature and composite ratio on the shear storage modulus (G′), the loss modulus (G″) and the sol-gel transition points were investigated. Funded by Chinese Natural Science Foundation Committee(No.50673080)     

Experimental Study on Young′s Modulus of Concrete

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Fine structure and interface structure of ion-bombardment nitrided layers

ＧｅｒａｒｄｉｎａｎｄＭｉｃｈｅｌｏｂｓｅｒｖｅｄｔｈｅｉｏｎｎｉｔｒｉｄｅｄｌａｙｅｒｏｆｐｕｒｅｉｒｏｎｗｉｔｈＴＥＭ[1].Ｔｈｅｒｅｓｕｌｔｓｓｈｏｗｅｄｔｈａｔｔｈｅｒｅａｒｅｏｎｌｙｔｗｉｎｓ,ｓｏｗｈｅｔｈｅｒｔｈｅｒｅａｒｅｄｉｓｌｏｃａｔｉｏｎｓａｎｄｗｈａｔｉｓｔｈｅｉｒｃｏｎｆｉｇｕｒａｔｉｏｎａｒｅｎｏｔｑｕｉｔｅｃｌｅａｒ.Ｔｈｅａｕｔｈｏｒｓｈａｖｅｆｏｕｎｄｔｈａｔｔｈｅｒｅａｒｅｖａｃａｎｃｉｅｓｉｎｉｏｎｎｉｔｒｉｄｅｄｌａｙｅｒｓ[2],ｂｕｔｔｈｅｐｒｏｏｆｏｆａｔｏ…     

Experimental measurement and elaborate analysis of strain hardening exponent in tensile deformation

This paper gives a set of formulae for measuring strain hardening exponent n in different typical deforming routes by using experimental parameters p (forming load), v (velocity of cross-head) and / (gauge length of specimen). With them the uniform method for measuring nε(strain hardening exponent at constant strain rate), nv( strain hardening exponent under constant velocity) and np (strain hardening exponent under constant load) is established when ε , v or p is constant distinctively. Furthermore, the deviation among n values via different typical deformation route is analyzed. The results indicate that there exists structural sensitivity under superplastic and plastic deformation. In addition , the experimental results also prove that the values of nε, nv and np obtained with different sets of constant ε , v or p curves are different too, even if the formulae are the same. Thus a more profound understanding of the relation between the experimental results and the mathematic expressions of nε, nv     

Influence of Ni-electrodeposited Pretreatment on Galvanized Coatings of Reactive Steels

Four types of steel sheets containing 0.04%, 0.09%, 0. 14% and 0.36% Si, respectively, were electrodeposited with a nickel layer of 3 tam in thickness and then galvanized in molten Zn at 450℃ for various periods of time. The formation and growth of intermetallic compound layers on the surface of the samples were investigated by SEM and EDS. The experimental results show that the method of Ni-electrodeposited pretreatment can distinctively restrain the over-growth of the galvanized coatings of reactive steels and get eligible coatings with a proper thickness, bright appearance and strong adherence. EDS results indicate that a series of Ni-Zn intermetallic compounds γ′, γ and δ, are first formed on the surface of the samples. With a prolonged immersion time, the F2-Fe-Zn-Ni and δ-Fe-Zn are formed accompanied by the gradual disappearance of γ′, γ and δ2 layer. After a longer immersion time, the lumpy ζ- Fe-Zn occurs between δ and liquid Zn and the F-Fe-Zn does between steel substrate and δ. Subsequently, ζ is in the form of a continuous and compact layer. The method of Ni-electrodeposited pretreatment changes the formation of Fe-Zn intermetallic compounds, which delay the growth of lumpy （and promote the growth of compact δ. Consequently, the abnormal growth of reactive steels is eliminated.     

Effect of intermediate heat treatment temperature on microstructure and notch sensitivity of laser solid formed Inconel 718 superalloy

Inconel 718 superalloys deposited by laser solid forming (LSF) were heat treated with solution treatment,intermediate heat treatment (IHT) and two-stage aging treatment in sequence (SITA heat treatment).The effect of IHT temperature on microstructure,tensile property and notch sensitivity of LSFed Inconel 718 superalloy at 500 ℃ were investigated.As-deposited columnar grains have transformed to equiaxed grains and the grains were refined due to the recrystallization during the SITA heat treatment.It is found that the size and amount of δ phase dispersed at grain boundaries decreased with the increasing of IHT temperature,and δ phase disappeared when the IHT temperature reached 1 020 ℃.The ultimate tensile strength (UTS) and yield strength (YS) of smooth samples increased to a maximum when the IHT temperature reached 980 ℃ and then decreased slightly to a minimum when the IHT temperature was 1 000 ℃,and followed by slight increasing again till the IHT temperature reached 1 020 ℃,resulted from the competition of precipitation strengthening effect of γ″ and γ’ phase and the grain boundary weakening effect caused by the gradual disappearance of δ phase with increasing the IHT temperature.The notch sensitivity factor (qe) decreased but still greater than 1 as the IHT temperature increased,which is attributed to the decrease of the size and amount of δ precipitation.     

Hyers-Ulam-Rassias stability of approximate isometries on restricted domains

Let X and Y be real Banach spaces. The stability of Hyers-Ulam-Rassias approximate isometries on restricted domains S(unbounded or bounded) for into mapping f: S→Y satisfying ‖f(x)-f(y)‖-‖x-y‖≤ε(x,y) for all x,y∈S is studied in case that the target space Y is uniformly convex Banach space of the modulus of convexity of power type q≥2 or Y is the Lq(Ω,,μ) (1＜q＜ ∞) space or Y is a Hilbert space. Furthermore, the stability of approximate isometries for the case that (x,y)=‖x‖p ‖y‖p or (x,y)=‖x-y‖p for p≠1 is investigated.     

Relationship between attachment probability and surface energy in adhesion process of gold particles to oil-carbon agglomerates

1　INTRODUCTIONInflotationfield ,someattentionshavebeenpaidtomodelingtheprocessofflotationinordertoobtainadeepunderstandingofhowamineralparticleisat tachedtoabubble .Schulze[1] analyzedtheelementaryprocessesofflotationintermsofphysico chemistry .Anfrunsetal[2 ] studiedthebubble particleattachmentexperimentallyinthecaseofpotentialflow .Solarietal[3] investigatedtheeffectofbubblesizesonadhesionprobability .Polatetal[4 ] estimatedthetruedistribu tionofflotationrateconstantsforafirst orderkin…     

Crystallization and Electrical Properties of （Ba0.4Pb0.3）Sr0.3TiO3 Thin Film by Pulsed Laser Deposition

（Ba0.4Pb0.3）Sr0.3TiO3 thin films were fabricated via pulsed laser deposition （PLD） technique on Pt/TiO2/SiO2/Si substrate. The crystallization of the films was characterized by XRD and FSEM, and the experimental results suggested deposition parameters, especially the deposition temperature was the key factor in forming the perovskite structure. The dielectric properties of the film deposited with optimized parameters were studied by an Agilent 4294A impedance analyzer at 1 MHz. The dielectric constant was 772, and the loss tangent was 0.006. In addition, the well-shaped hysteresis loop also showed that the film had a well performance in ferroelectric. The saturated polarization P, remnant polarization Pr and coercive field E were about 4.6 μC/cm2, 2.5 μC/cm2 and 23 kV/cm （the coercive voltage is 0.7 V）, respectively. It is suggested the film should be a promising candidate for microwave applications and nonvolatile ferroelectric random access memories （NvFeRAMs）.     

Microwave absorbing properties of high titanium slag

Microwave absorbing properties of high titanium slag were investigated by using microwave cavity perturbation technique. High titanium slag containing more than 90% TiO₂ was prepared by carbothermal reduction of ilmenite. The temperature rise curve of high titanium slag in microwave heating process was obtained. Crystalline compounds of high titanium slag before and after microwave irradiation were obtained and characterized by X-ray diffractometry (XRD). Effects of particle size of high titanium slag and mixtures of high titanium slag with different mass fractions of V₂O₅ on microwave absorbing properties were investigated systematically. The results show that high titanium slag has good microwave absorption property; untreated high titanium slag mainly consists of crystalline compounds of anatase and iron titanium oxide, while the microwave-irradiation treated one is mainly composed of crystalline compounds of rutile and iron titanium oxide. Synthetic anatase is transformed completely into rutile at about 1 050 °C for 20 min under microwave irradiation. High frequency shift and low amplitude of voltage make high titanium slag an ideal microwave absorbent. 180 μm of particle size and 10% mass fraction of V₂O₅ are found to be the optimum conditions for microwave absorption. Foundation item: Project(2007CB613606) supported by the Major State Basic Research and Development Program of China; Project(50734007) supported by the National Natural Science Foundation of China     

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).     

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/℃.     

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.     

Effect of solidification condition on secondary dendrite arm spacing of the A357 alloy under counter-pressure casting

The effect of counter-pressure casting parameters on secondary dendrite arm spacing (SDAS) of A357 alloy under different process parameters was studied. Quartz sand mould with chill can strongly decrease the SDAS. Reduced SDAS close to the mould bottom because of chilling was obtained. Pressure seems to have no apparent effect on the SDAS. In order to obtain casts with UTS ⩾ 320 MPa, SDAS must be less than 55 μm, which means a local cooling rate V _L⩾0.23 °C/s. Funded by the Innovation Fund for Outstanding Scholar of Henan Province(No. 0621000700)     

Synthesis and optophysical properties of blue-emitting iridium （Ⅲ） complex bearing oxadiazole-based picolinic acid derivative

An iridium (III) bis[(4,6-difluorophenyl)pyridinato-N, C²][6-(6′-(4″-(5‴-phenyl-1‴, 3‴, 4‴-oxadiazole- 2‴-yl) phenoxy) hexyloxy picolinate) was synthesized and characterized by ¹H NMR and elementary analysis in order to study the effect of ancillary ligand of the oxadiazole-based picolinic acid derivative on optophysical properties of its iridium complex, and further to obtain an iridium complex with highly-efficient blue emission. The thermal stability, UV absorption and photoluminescent properties of this iridium complex were investigated. Compared with iridium (III) bis[(4,6-difluorophenyl)pyridinato-N, C²](picolinate) reported as a highly-efficient blue electroluminescent material, this iridium complex bearing an oxadiazole-based picolinic acid derivative presents higher thermal stability, more intense UV absorption at 291 nm and similar photoluminescent spectrum peaked at 469 nm. This indicates that tuning ancillary ligand of picolinic acid with an oxadiazole unit can improve the optophysical properties of its iridium complex. Foundation item: Projects(20772101, 50473046) supported by the National Natural Science Foundation of China; Project(2007FJ3017) supported by the Hunan Provincial Science Foundation, China; Project(07C764) supported by the Science Foundation of the Education Department of Hunan Province, China