In this work, the resistance spot welding (RSW) process was performed to join aluminum alloy and low-alloy carbon steel plates. The macro characteristics including nugget diameters and indentation rates, microstructure and tensile-shear strength of RSW joints were investigated. The results showed that the nugget of the RSW joints comprises a 'bowl' shape nugget on the aluminum side and an elliptical shape nugget on the steel side. Also, the intermetallic compound (IMC) layers containing Fe4Al13 and Fe2Al5 were formed around the aluminum/steel interface with the steel side having a tongue-shape and the aluminum side having a needle-shape. According to metallurgical evaluation and temperature distribution of RSW joints analyzed by the finite element method, the nugget on the aluminum side contained the dendritic grains and equiaxed dendritic grains. The nugget on the steel side consisted of a large amount of bainite and a small amount of coarse lath martensite. The nugget diameters and the indentations rates of RSW joints increased when increasing either welding current or welding time, and decreased when increasing the electrode pressure. The maximum values of nugget diameter and indentation rate of RSW joints were 9.076 mm and 4.144% when using the welding current of 16 kA, welding time of 450 ms and electrode force of 3 kN. In tensile-shear tests, the RSW joints showed a shear-off fracture mode. When increasing the welding current, welding time or electrode force, the tensile-shear strength of RSW joints increased first, and then reached a maximum, and finally decreased. The welding current of 16 kA, the welding time of 300 ms, and the electrode pressure of 3 kN were considered as the optimal welding parameters in the present study which resulted in the maximum tensile-shear strength of 2.24 kN. In addition, the IMC layers of the RSW joints exhibited a uniform and continuous appearance with a thickness of approximately 1.9 μm, and the IMC layer in the central area was thicker than that in the edge area.

通过正交试验法研究了焊接电流、焊接时间和电极压力对热浸镀锌低碳钢板点焊接头抗剪切力的影响规律,并分析最佳焊接工艺参数下点焊接头的微观组织、硬度分布和抗剪切力.结果表明,焊接电流对点焊接头抗剪切力影响最大,最佳焊接工艺参数为:焊接电流13 kA、焊接时间80 ms、电极压力4 kN,在该参数下点焊接头抗剪切力为8.637 kN,熔合区组织主要为板条状马氏体,硬度为320 HV,母材区组织主要为铁素体,硬度为102 HV,热影响区组织为板条状马氏体和铁素体,硬度介于熔合区和母材区之间.

The present research utilized the resistance spot welding process on stainless steel and low carbon steel. The diameters of joint and nugget, microstructure and shearing strength of joints were examined. When increasing the welding current, welding time or clamping force, the diameters of welding joints and nuggets became larger due to the higher heat input and normal load. The shearing strength of joints increased and then decreased with increasing welding current or welding time and decreased with increasing clamping force. For the metallurgical evaluation, it was found that there were five regions around the joint, which consisted of the nugget (austenite and martensite with dendritic structures), coarse heat-affected zone (martensite and pro-eutectoid ferrite), fine heat-affected zone (ferrite and pearlite), base material (ferrite and pearlite) for low carbon steel, and base material (austenite) for stainless steel. In orthogonal tests, it was found that the welding current had the most significant influences on shearing strength, and then welding time and clamping force. Finally, an artificial neural network was established to predict the shearing strength of joints under various welding conditions. The results showed that the shearing strengths predicted by the artificial neural network had good correlation with experimental values. A shearing strength higher than 10000 N could be achieved when welding current was higher than 12.5 kA and welding time was longer than 85 ms. The artificial neural network model has applicable values for predicting the shearing strengths of joints between dissimilar steel plates.

Integration of high quantum yield blue emission and easy film-forming ability in organic emissive materials is challenging. Polycarbosilane (PCS) has received much attention as a model compound owing to its high stability, versatile optical properties, solvability, and film-forming ability; also, anthracene as a star material is the first organic molecule for electroluminescence (EL) devices. Herein, an ingenious strategy was successfully introduced to prepare PCSx with 9-ethylanthracene (referred as 9-EA-PCSx) by a hydrosilylation reaction using 9-vinylanthracene and PCS as starting materials, which transfer efficient energy from -Si-C- bonds to anthracene units. Grafted 9-ethylanthracene with extended pi-conjugation effectively improves optical property, morphological stability, and oxidation and ultraviolet (UV) radiation resistance of PCS. Particularly, 9-EA-PCSh powder displays excellent blue light emission (lambda(max) = 433 nm) with a high quantum yield (up to 80.06%), which is the highest value ever reported for organosilicon polymers to the best of our knowledge. For the first time, such a synergistic effect of PCS with anthracene in this way paves a practical way toward reliable emissive materials capable of forming facile coatings and providing useful low-cost emitting layers in developing foldable organic devices.

Preparation of well-ordered TiO2 films from alkaline solution by liquid phase deposition (LPD) method is still challenging owing to the fact that, in traditional mixing process, several disadvantages exist in controllable homogenous chemical reactions. In this contribution, mixing process in a porous dispersed double T-junction micromixer was designed and investigated using numerical simulation. It is obtained that high mixing intensity can be achieved by micromixer with inlet velocity of 0.6 m s(-1) and microfiltration meshes 10 mu m in size. A micromixing-assisted platform consisted of two syringe pumps and a micromixer was manufactured to efficiently fabricate TiO2 films via mixing of (NH4)(2)TiF6 and CO(NH2)(2) as reactants and fluorine doped tin oxide, F: SnO2 (FTO), conducting glass substrates by LPD in alkaline solutions. The results suggest that surface morphology of TiO2 films fabricated by micromixing can be easily controlled in comparison with that of specimens prepared by traditional stirring mixing process. The dense and well-ordered TiO2 films derived from micromixing have enhanced adhesion strength, high hardness, good hydrophilic and excellent photoelectrochemical properties. Particularly, homogeneous reaction could be inhibited in micromixer and an ideal supersaturation solution would be formed via micromixing treatment, which significantly facilitates the formation of high quality TiO2 films by heterogeneous nucleation on substrate surface. These obtained achievements are expected to promote further application of TiO2 films in a variety of domains including photocatalysis and corrosion protection of metals.

In this contribution, thermodynamic computational calculations firstly carried out on Ar-Si-C-O/Ar-Si-C-O-H database demonstrate that passive oxidation is main reaction of continuous freestanding SiC films in both air and 14%H2O/8%O-2/78%Ar atmospheres. SiC films were subsequently annealed at 1300 degrees C, 1400 degrees C and 1500 degrees C for 1 h in air and O-2-H2O-Ar atmospheres. Results suggest that modulus, hardness and resistivity decrease whereas crystallite size of beta-SiC and a-cristobalite increase with elevated annealing temperature. In particular, hardness of wet oxidized samples is lower than that of air oxidized ones. Additionally, their oxidation kinetics models were also established and verified by annealing at 1200 degrees C in air and wet oxygen for different time from 1 h to 100 h. Oxidation of continuous freestanding SiC films is identified to follow parabolic oxidation kinetics, and water could effectively enhance the oxidation rates. It is revealed that SiO2 layer can protect SiC films from further oxidation, and their thickness increases with prolonged annealing time. In this study, a dense and uniform SiO2 layer with a thickness of 1.1-1.6 mu m was produced for sacrificial and passivation layer based on suitable thermal oxidation process (annealing at 1000 degrees C for 5 h in O-2-H2O-Ar environment). Interestingly, fast diffusion paths in this oxide layer could effectively accelerate oxidation process of SiC films. These obtained achievements would promote further applications of SiC films on microelectromechanical systems (MEMS) devices in harsh environments.

Optical properties and stability of two novel polycarbosilane (PCS) products bearing aryl groups in the main chain synthesized by Grignard reactions were studied. 4-bromostyrene, alpha, alpha'-dibromo-p-xylene and dichloromethylsilane were employed as reactants to yield sigma-pi conjugated PCS with silylene-1,2-diphenyleneethylene-silylene backbone (PCS-SDS) and PCS with silylene-terephthalyidene-silylene backbone (PCS-STS), respectively. Effects of oxidation cross-linking and ultraviolet (UV) radiatimon the luminescence properties were examined. Photoluminescence (PL) spectra exhibit excellent blue light emission (maximum emission peaks at about 422 nm) compared to PCS and the intensity is exactly enhanced due to the insertion of phenyl into the conjugated main chains with Si-C bonds and the combined delocalization of the sigma-sigma* transitions in Si chains and the pi-pi* transitions in the benzene rings. Especially, PCS-SDS with more diphenyl and C=C groups possesses stronger emission intensity, higher quantum yield, better oxidation and UV resistance, and excellent thermal shock behavior below 400 degrees C in comparison with PCS and PCS-STS. Time-resolved PL spectra analysis also indicate that PCS-SDS can maintain longer fluorescence lifetime. These results prove PCS-SDS to be potentially applied to many fields, including but not limited to polymeric semiconducting materials, nonlinearoptics and organic electroluminescence devices. (C) 2016 Elsevier B.V. All rights reserved.

Effects of oxidation cross-linking and sintering additives (TiN, B) on the microstructure formation and heat-resistant performance of freestanding SiC(Ti, B) films synthesized from Ti, B-containing polycarbosilane (TiB-PCS) precursor were investigated. TiB-PCS green films were first cross-linked for 1h, 2h, 3h and 4h, respectively, and then pre-sintered at 950°C. Finally, they were sintered at 1800°C to complete the conversion from organic films to inorganic SiC(Ti, B) films. The results reveal that curing time has a great impact on the uniformity and density of SiC(Ti, B) films. TiB-PCS films cured for 3h yield the best quality SiC(Ti, B) films, which are composed of β-SiC crystals, C clusters, α-SiC nano-crystals, a small amount of TiB2 and B4C. TiB2 and B4C are both steady phases which can inhibit abnormal growth of β-SiC, effectively reduce sintering temperature and help consume excess C from decomposition of amorphous SiOxCy. After high temperature annealing at 1500°C, 1600°C and 1700°C in argon, SiC(Ti, B) films still keep excellent mechanical properties, which makes them attractive candidate materials for microelectromechanical systems (MEMS) used at ultra-high temperatures (exceeding 1500°C).

采用溶胶-凝胶法及浸渍提拉工艺在钠钙玻璃基底表面制备了锐钛矿型TiO2薄膜.利用X射线衍射(XRD)、拉曼(Raman)光谱、扫描电镜(SEM)和原子力显微镜(AFM)对样品物相结构及表面形貌分别进行了表征.分别通过紫外-可见光谱及接触角测试研究了不同聚乙二醇(polyethylene glycol,PEG)用量及其分子质量对薄膜透光性及亲水性的影响.结果表明,经PEG改性后,TiO2薄膜表面出现了纳米尺寸的孔状结构,在可见光区段内具有较高的透光率.当PEG2000用量为1.5g时,TiO2薄膜表面水接触角小于1°,在非紫外光辐照条件下具有最佳的超亲水性.

In this paper, the hydrothermal-assisted liquid phase deposition (HT-LPD) method has been developed to prepare TiO2 films. The crystalline structures and morphologies of as-prepared TiO2 films were analyzed using an X-ray diffractometer (XRD) and scanning electron microscope (SEM). It was found that the HT-LPD TiO2 film showed good crystallinity with preferrred orientation along c-axis. Moreover, the as-prepared TiO2 films consisted of two layers, with the tiny nanoparticles as the underlying layer and the flower-like clusters as the upper layer. The photoelectrochemical measurements revealed that, when illuminated by the white light, the HT-LPD TiO2 films exhibited a more negative photopotential value and an increased photocurrent value with elevated reaction temperature, excepting for the sample prerared at 150 °C. In summary, the TiO2 films prepared by the improved LPD method could be served as the promising photoanode for the photoelectrochemical applications.

Optical properties of aryl-substituted polyphenylcarbosilane (PPCS) and aluminum-containing polyphenylcarbosilane (Al-PPCS) prepared by hydrosilylation polymerization were studied. Polycarbosilane (PCS), aluminum-containing polycarbosilane (Al-PCS) and styrene were employed as reactants to yield sigma-pi conjugated PPCS and Al-PPCS using chloroplatinic acid as catalyst, respectively. Phenyl was directly attached to the conjugated main chains with Si-C bonds. Effects of divinyl benzene cross-linking, oxidation curing and ultraviolet (UV) radiation on the photoluminescence (PL) properties of the samples were examined. PL spectra show strong blue light emission and the intensity of PCS is enhanced by adding the aryl groups and Al atoms. The excellent luminescent properties are attributed to the delocalization of electrons from the a bond to pi system. The hyperbranched Al-PPCS with extended sigma-pi conjugation has an obvious red-shifts PL, high quantum yield, excellent oxidation resistance and good UV resistance performance. Thermal analysis reveals that Al-PPCS can keep structure stability below 400 degrees C under an inert gas atmosphere. The AI-PPCS may have potential applications including organic electroluminescent (EL) devices. 2015 Elsevier B.V. All rights reserved.

The method of producing LED filament lamp filament of the substrate material, to an LED filament lamp. The polypropylene mixed with the polycarbosilane, heated to a molten state, the melt mixing cycle, defoamed spinning membrane, to obtain modified polycarbosilane film former, do not melt pretreatment, calcination and final firing, i.e., from silicon carbide composite film support, after high temperature treatment layer insulating oxide layer SiO upper and lower surfaces of each obtained composite film; partial oxidation of the surface of the composite film layer is etched; composite film after the etching process is fixed on the ceramic sheet, the linear screen alignment is not etched away the oxide layer on the composite film, the silver paste is coated on the side of the screen, with a silver paste to the other side of the blade wiper, the composite film placed in a tube furnace supplied with argon protective gas, heating, LED heat conductive layer prepared on the substrate surface of the composite film, the composite film is then prepared in another heat radiating surface of the LED substrate conductive layer, i.e., to obtain the substrate material LED filament lamp filament.

•Fe-doped TiO2 films were prepared by liquid phase deposition method.•Higher photoelectrochemical response was observed for the Fe-doped TiO2 film.•The sustained anticorrosion behavior for SUS304 stainless steel was observed.

The invention discloses a main-chain aromatic conjugated organic fluorescent material and a preparation method thereof, relating to an organic fluorescent material. The preparation method comprises the steps of adding magnesium powder into an organic solvent, heating for activation under the conditions of magneton stirring and the protection of inert gas, then, adding a bromo-aromatic monomer, cooling a reaction system to the room temperature by using ice water, and reacting under the conditions of magneton stirring and the protection of inert gas to obtain a Grignard solution; adding a methyldichlorosilae monomer into the Grignard solution, reacting under the protection of inert gas, adding an organic alcohol solvent, stirring, filtering, adding n-hexane into filtrate, separating liquid, carrying out spin evaporation on the n-hexane solution under negative pressure, and carrying out vacuum drying to obtain a monomer; and mixing the obtained monomer and a catalyst, heating to react under the protection of inert gas, then, cooling to the room temperature to obtain a faint yellow solid, namely the main-chain aromatic conjugated organic fluorescent material. The oxidative crosslinking resistance, ultraviolet aging resistance and the heat stability of the main-chain aromatic conjugated organic fluorescent material are improved; and the main-chain aromatic conjugated organic fluorescent material has relatively strong fluorescent performance.

Sodium polyacrylate/TiO2 hybrid films that served as photoanodes for cathodic protection application were prepared by liquid phase deposition. Under white-light illumination, the open-circuit potential of the hybrid films coupled with SUS304 stainless steel could shift to a more negative value and offer an effective photogenerated cathodic protection for stainless steel. Moreover, the hybrid films also exhibited stronger photocurrents in both the ultraviolet-light and visible-light regions compared to that of control TiO2 films. In summary, the addition of sodium polyacrylate could greatly improve the photogenerated cathodic protection properties of the liquid-phase-deposited TiO2 films. (C) 2012 Elsevier Ltd. All rights reserved.

The effects of oxygen pick-up and Al atoms on the formation and microstructure of freestanding SiC(Al) films by melt spinning of polyaluminocarbosilane (PACS) precursor were studied. PACS green films were cross-linked for 1h, 2h, 3h and 4h, pre-pyrolyzed at 900°C, respectively. They were continuously pyrolyzed at 1800°C to convert initial PACS into SiC(Al) ceramic films. Results reveal that the strict control of oxygen content during the oxidation curing is essential to produce near-stoichiometric SiC(Al) films. The microstructure of the dense films is a mixture of β-SiC crystals, α-SiC nano-crystals, C clusters and a small amount of Al4O4C and Al4SiC4. Al atoms which play important roles as both sintering aids and grain growth inhibitor are well distributed in the films due to the presence of stable composition and structure. SiC(Al) films with excellent mechanical properties would be attractive candidate materials for MEMS in harsh environments.

In this paper, the ordered mesoporous TiO2 thin films that served as photoanodes for cathodic protection of SUS304 stainless steel (304SS) were prepared through the sol–gel and evaporation-induced self-assembly method. The as-prepared TiO2 thin films were calcined at 350°C and 500°C, and then characterized by scanning electron microscopy (SEM), the small-angle X-ray diffraction (SAXD) as well as the wide-angle X-ray powder diffraction (WAXD). Moreover, the photoelectrochemical properties of the mesoporous TiO2 thin films such as the open circuit potential (OCP), the photocurrent spectra as well as the Tafel polarization curves were also measured. The results showed that the more negative photopotential was observed for the mesoporous TiO2 films compared to the TiO2 films without mesoporous structures. Besides, the mesoporous TiO2 films calcined at 500°C exhibited the more negative photopotential and larger photocurrent than that calcined at 350°C. In conclusion, the mesoporous TiO2 films could provide the effective photogenerated cathodic protection for 304SS.

Optical properties of metal atom-doped polycarbosilane (PCS) which originated from sigma-conjugation effect were studied. Al, Dy, Er and Eu were introduced into PCS by one-pot method to yield polyaluminocarbosilane (PACS), polydysprosiumcarbosilane (PDCS), polyerbiumcarbosilane (PErCS) and polyeuropiumcarbosilane (PECS), respectively. Effects of oxidation curing and ultraviolet (UV) radiation on the photoluminescence (PL) properties of the samples were investigated. PL spectra show strong blue light-emissions and the intensity of PCS is enhanced by adding metal atoms. PACS with extended a-conjugation exhibits an obvious PL red-shift, high intensity, high quantum yield and excellent oxidation resistance as compared with those of others. As treated under UV lamp for 3 h in air, PACS retains good UV resistance performance, owing to the AlOx (x = 4, 5, or 6) groups which effectively extend the sigma-conjugation. The obtained results are expected to have important applications in active sources for electroluminescence (EL) devices, especially suitable for blue emission. (C) 2013 Elsevier B.V. All rights reserved.