Measurement of electronegativity during the E to H mode transition in a radio frequency inductively coupled Ar/O2 plasma

This paper presents the evolution of the electronegativity with the applied power during the E to H mode transition in a radio frequency(rf)inductively coupled plasma(ICP)in a mixture of Ar and O2.The densities of the negative ion and the electron,as well as their ratio,i.e.,the electronegativity,are measured as a function of the applied power by laser photo-detachment combined with a microwave resonance probe,under different pressures and O2 contents.Meanwhile,the optical emission intensities at Ar 750.4 nm and O 844.6 nm are monitored via a spectrograph.It was found that by increasing the applied power,the electron density and the optical emission intensity show a similar trench,i.e.,they increase abruptly at a threshold power,suggesting that the E to H mode transition occurs.With the increase of the pressure,the negative ion density presents opposite trends in the E-mode and the H-mode,which is related to the difference of the electron density and energy for the two modes.The emission intensities of Ar 750.4 nm and O 844.6 nm monotonously decrease with increasing the pressure or the O2 content,indicating that the density of high-energy electrons,which can excite atoms,is monotonically decreased.This leads to an increase of the negative ion density in the H-mode with increasing the pressure.Besides,as the applied power is increased,the electronegativity shows an abrupt drop during the E-to H-mode transition.

Corrosion Mechanism of Alumina-magnesia Dry Materials for Smelting Manganese/chromium Steel in Coreless Medium Frequency Induction Furnaces

Alumina-magnesia dry materials are widely used in induction furnace linings, but they show different kinds of damage when melting different kinds of alloy steel. In this paper, the chemical composition, phase composition, and microstructure of the post-use dry materials for the working liners melting different kinds of steel were evaluated. Furthermore, the corrosion mechanism of the steel on the furnace lining materials was comprehensively analyzed. The findings reveal a significant ability of the Mn element in the molten steel to diffuse and penetrate into the refractories. Mn oxidizes to form MnO at the steel-refractory interface, and then forms a liquid phase with Al_(2)O_(3). The Cr element is dissolved into corundum and spinel of the refractories, resulting in lattice defects and structural damage of the materials. TiO2reacts with Al_(2)O_(3) to form Al_(2)TiO_(5), which plays a crucial role in preventing crack formation and propagation. Part of Ti4+dissolves into magnesia-alumina(MA), densifying the materials. TiO2also slows down the reaction between the Cr element and refractory components, further improving the corrosion resistance of the materials.

STUDY ON TEMPERATURE FIELD INDUCED IN HIGH FREQUENCY INDUCTION HEATING

A mathematical model was established for the temperature field developed during high frequency induction heating （HFIH） by Maxwell＇s equations. It required solving the coupled equations of the electromagnetic and temperature fields. The numerical simudation was performed using FEMLAB. The comparison of the calculations using the proposed model with experimental results showed a very good correlation. The effects of the heating parameters in high frequency induction such as the distance between the plate and the coil, the applied current, the frequency, and the turns of the coil on the temperature profiles developed in the plate were also discussed using the established model.

Study on GNi-WC25 Coating by High Frequency Induction Cladding

Process and mechanism of high frequency were studied in this paper by means of cold attachment for the preparation of GNi WC25 coating . The results show its special distribution law of eddy current while the magnetic transition temperature and electric resistivity of the coating have been measured .Wear resistance of the high frequency induction coating has an advantage over those of laser cladding coating and oxygen acetylene spraying fusing coating . Moreover , the GNi WC25 coating by high frequency induction cladding has smooth surface and even microstructure.

Nickel-coated Steel Stud to Aluminum Alloy Joints Made by High Frequency Induction Brazing

Nickel-coated 45 steel studs and 6061 aluminum alloy with 4047 A1 alloy foil as filler metal were joined by using high frequency induction brazing. The microstrueture of Fe/A1 brazed joint was studied by means of optical microscopy （OM）, scanning electron microscope （SEM）, energy dispersive X-ray （EDX）, and X-ray diffraction （XRD）. Results showed that 45 steel stud and 6061 aluminum alloy could be successfully joined by high frequency induction brazing with proper processing parameters. The bonding strength of the joint was of the order of 88 MPa. Ni coating on steel stud successfully avoided the generation of Fe-AI intermetallic compound which is brittle by blocking the contact between A1 and Fe. Intermetallic compounds, i e, AI3Ni2, AlmNi0.9 and A10.3Fe3Si0.7 presented in AI side, FeNi and Fe-A1-Ni ternary eutectic structure were formed in Fe side. The micro-hardness in intermetallic compound layer was 313 HV. The joint was brittle fractured in the intermetallic compounds layer of A1 side, where plenty of A13Ni2 intermetallie compounds were distributed continuously.

Interfacial characteristics of high frequency induction brazed Cu and pre-metalized graphite joints

Oxygen-free copper and pre-metalized graphite were brazed using CuNiSnP braze alloy by high frequency induction heating method. Interracial microstructures and reaction phases were analyzed by scanning electron microscopy （SEM） and energy dispersive X-ray spectroscopy （EDS）. The strength and resistance of the joints were tested. It is found that when the brazing parameters are optimized, the structures of the joints are graphite/（Cu,Ni）/Ni（s.s）＋NixPy/Cu3P＋Cu（s.s） （including Sn）＋eutectic structures （Cu3P＋Ni3P＋Cu（s.s）/Cu （s.s）/Cu）. When the temperature increases to 750℃ or the holding time prolongs to 300 s, the eutectie structures disappear and the amount of Cu3P increases. The maximum shear strength of the joints is 5.2 MPa, which fracture at the interface of graphite and metallization. The resistance of the joints is no more than 5 mΩ.

Interface characteristics of Al_2O_3－13%TiO_2 ceramic coatings prepared by laser cladding

Al2O3-13%TiO2 （mass fraction） coatings, prepared by laser cladding on nickel-based alloy, were heated using high frequency induction sources. The coating microstructure and the interface between bond coating and ceramic coating were characterized by SEM, XRD and EDS. The results show that two-layer substructure exists in the ceramic coating： one layer evolving from fully melted region where the sintered grains grow fully; another layer resembling the liquid-phase-sintered structure consisting of three-dimensional net where the melted Al2O3 particles are embedded in the TiO2-rich matrix. The mechanism of the two-layer substructure formation is also explained in terms of the melting and flattening behavior of the powders during laser cladding processing. The spinel compounds NiAl2O4 and acicular compounds Cr2O3 are discovered in the interface between bond coating and ceramic coating. It proves that the chemical reactions in the laser cladding process will significantly enhance the coating adhesion.

The Influence of Endogenous Hormones on Culture Capability of Different Explants in Rice

The endogenous hormones (EHs) content of different explants (anther, young panicle, young embryo and mature embryo) and calli with different culture capability were analyzed by means of high performance liquid chromatography (HPLC). The results showed that the contents and ratio of endogenous hormones were one of the key factors affecting callus induction frequencies (CIF) and green plantlet differentiation frequencies (GPDF). The influence of endogenous hormones of different explants on CIF represented as: Zoatin ribosile (ZR) showed negative effect, indole-3-acetic acid (IAA) did positive effect, and gibberellic acid (GA) did negative effect except for mature embryos. The influence of endogenous hormones on green plantlet differentiation frequency (GPDF) showed: IAA and GA were negative effect; abscisic acid (ABA) and zeatin+ zeatin riboside (Z+ZR) were positive effect. The mixture ratio of endogenous hormones played a role on CIF and GPDF. IAA/Z+ZR had a positive effect on CIF, and there was a notable positive correlation between Z+ZR/ IAA and GPDF, so was between ABA/IAA and GPDF.

Tissue Culture Responses from Different Explants of Rice

Different culture explants, including anther, young panicle, young embryo, and mature embryo, from 19 rice varieties were used for callus induction and green plantlet differentiation. The culture efficiency differed significantly among the four types of explants, and varied from genotype to genotype. Callus induction frequency presented significantly positive correlation each between anther and young panicle, anther and mature embryo, and young panicle and young embryo. Green plantlet differentiation showed no relationship between different types of explants. In addition, no relationship was found between callus induction frequency and green plantlet differentiation frequency.

TIG welding-brazing joint of aluminum to stainless steel with hot wire

TIG welding-brazing process with high frequency induction hot wire technology was presented to create joints between 5A06 aluminum alloy and SUS32! stainless steel using ER1100 filler wire with different temperature. The joints were evaluated by mechanical test and microstructural analyses. The welding procedure using hot fiUer wire （400 ℃ ） significantly increases strength stability by 71% and average value of tensile strength by 30. 8 % of the joints, compared with cold wire. The research of microstructures in interfaces and welded seams reveals that using 400 ℃ hot filler wire can decrease the thickness of intermetallic compounds （ IMCs ） from 6 to 3.5 txm approximately, which is the main reason of mechanical property improvement.

Study on Young Panicle Culture in vitro From Wild Rice of Different Genomes

Researches have been made on young panicle culturein vitro from wild rice of different genomes. Main results are as follows: 1. The induction frequencies of young panicle culturedin vitro from wild rice varied largely a relation to its genome. The optimal induction period of callus is the stamen and pistil differentiation stage of young panicle development. 2. Plantlets were regenerated through two ways: first, culture method, the induced calli were transferred onto differentiation medium; second, regenerate plantlets directly from young panicles of wild rice that were cultured on the differentiation medium. 3. The regeneration rate of green plantlets that obtained through cryopreservated calli inO. meyeriana was 10 times higher than that of control.

Influence of α-Al_2O_3 Micropowder Addition on Properties of Corundum Dry Ramming Mix

In order to improve the service life of corundum lin- ing.for induction Jitrnace, corundum dry ramming mix was prepared using brown corundum, fu.sed magnesia, and α-Al2O3 micropowder as main starting materials, mul the it!fluence of α-Al2O3 micropowder additions （0, 1% , 2%, and 3%, in mass） on properties of corundum dry ramming re.ix was investigated. The results show that after heat treating at 1 600 ~C , with the in-crease of α-Al2O3 addition, the permanent change in di- mensions on heating of the specimens decreases firstly and then increases, bulk density increases, apparent po- rosity decreases, and the crushing strength declines first- Iv and then enhances; when the addition of α-Al2O3 is 2 mass% , the termanent change in dimensions on heating of the specimens i.s relatively small and the crushing .strength decrease.s to 22.8 MPa. The XRD attd SEM reults show that after .firing at 1 600 for 3 h sin, all granular magnesium aluminate spinel form. and is welldistributed, which enhances the density.

Synthesis of Single-Walled Carbon Nanotubes by Induction Thermal Plasma

The production of high quality single-walled carbon nanotubes(SWCNTs)on a bulk scale has been an issue of considerable interest.Recently,it has been demonstrated that high quality SWCNTs can be continuously synthesized on large scale by using induction thermal plasma technology.In this process,the high energy density of the thermal plasma is employed to generate dense vapor-phase precursors for the synthesis of SWCNTs.With the current reactor system,a carbon soot product which contains approximately 40 wt%of SWCNTs can be continuously synthesized at the high production rate of~100 g/h.In this article,our recent research efforts to achieve major advances in this technology are presented.Firstly,the processing parameters involved are examined systematically in order to evaluate their individual inuences on the SWCNT synthesis.Based on these results,the appropriate operating conditions of the induction thermal plasma process for an effective synthesis of SWCNTs are discussed.A characterization study has also been performed on the SWCNTs produced under the optimum processing conditions.Finally,a mathematical model of the process currently under development is described.The model will help us to better understand the synthesis of SWCNTs in the induction plasma process.