Materials Science Forum Vol. 1001

Abstract: Recently, the high Al-added light weight steels are particularly attractive for automotive applications because of their excellent mechanical properties and weight reduction. In this study, the microstructure characteristics and hardness in the resistance spot welding of high Al-added light weight steels were investigated. A Al-added 780MPa steel and Al-added 980MPa steel were used in the present study. For Al-added 780MPa steel the hardness in the weld nugget was higher than that of the base metal, and reduced hardness between the weld nugget and base metal is due to the presence of soft δ-ferrite. For Al-added 980MPa steel the hardness in the welt nugget was lower than that of the base metal due to grain growth.

Abstract: The influence of different acidic medium, including hydrochloric acid, nitric acid and perchloric acid on the absorbance of sodium by flame atomic absorption spectrometry was studied. The results showed that the effects of acidic medium and water on the determination of sodium were as follows: hydrochloric acid > perchloric acid > nitric acid > water. Acid effect changed with the increase of acid concentration, however, the absorbance value of sodium element decreased when the concentration of acid was higher than 1%~2%. This effect was more obvious for high content of sodium. The detection limits, repeatability and recovery of the samples under the three acidic medium were compared. The optimum acid conditions were determined and the sensitivity of the method was improved.

Abstract: This paper introduced the specific application of a new fabricated wall material in building with light steel structure, and studied its structural component, model construction, construction and installation, and analysis and calculation in detail, etc. According to the national and local current national standard specifications, SAP2000 was used to theoretically calculate and analyze the strength, stiffness, stability performance and other and other performance indexes of material structure; and ABAQUS was used to conduct special analysis of joint mechanical properties at key parts of the wall material and steel structure, the Mise stress index was obtained, and all met the requirements after analysis. The results of various indexes show that this new wall material structure has a safe and reliable structural composition and excellent mechanical properties, and the material forms and material quality can be customized, it enriches the application design range of building material architecture and is worth promoting.

Abstract: FSP was applied to the as-cast Al-12.7Si alloy at a traverse speed of 150mm/min and different rotation speeds (700rpm to 1000rpm). The coarse α-Al dendrites and eutectic Si phase can be refined by friction stir process. After FSP, Si particles are homogeneously distributed in the Al matrix with equaixed grains. Tool rotation speed has an effect on the microstructure and mechanical properties of the Al-12.7Si alloy. The size of Si particles decreases and that of the Al matrix grains increases with increase of the rotation speed. The microhardness values of the stir zone increase with increase of rotation speed. With rotation speed increases, the ultimate tensile strength is slightly increased and the elongation is greatly improved.

Abstract: The existing low-frequency magnetic parameter test is mainly based on impedance analysis,Its sample needs to be prepared into a ring,the hard materials are difficult to process into rings for testing. Small piece of material cannot be tested using impedance analysis because it is too small to be cut into a ring for testing. In this paper, the principle of impedance analysis and the basic theory of strip line be used, an empirical formula for the complex permeability of the magnetic bulk thick film material in the 0.1Ghz~0.6GHz frequency band is obtained through design and test by design simulation and physical fixture, it makes the testing of the complex permeability of thick film materials easier due to it avoid damage and ring cutting before testing.

Abstract: The friction and wear experiment employed M-2000 friction and wear tester which friction pair made up of Q235//GCr15 steel, and lubricating oil which contains 3% new N-B-Mo ceramic anti-wear agent was adopted as the medium. The effect of content of new ceramic anti-wear agent on friction and wear property was investigated by using X-Ray diffraction (XRD), optical microscope (OM), et al, and the mechanism of ceramic anti-wear agent was also analyzed. The results showed that in the range of 50-300N load, the friction coefficient is basically related to the size of the load, and the greater the load, the greater the coefficient of friction, the size of the wear rate is not simply increased as the load increases. The wear rate was lowest when the load was 200N. Under this load, the new N-B-Mo ceramic anti-wear agent was generated BN phase which has self-lubricating property at worn surface, reduce the friction coefficient of Q235//GCr15 friction pair and the wear rate of Q235 steel, plays an anti-friction and anti-wear role.

Abstract: In this paper, a novel photoelectrochemical sensor based on doped quantum dots (QDs) under various bias voltages was designed, first, photoelectrochemical sensors were designed for detection of chemical solution concentration. Second, the fabrication processes of doped QDs based sensors were described, third, doped QDs based sensors were tested under different applied potentials and light sources to show different measurement characteristics. From the experimental results, it can be concluded that the doped QDs based sensors designed under-300mV applied potential and 365nm light source show the best performance.

Abstract: Cobalt-free Li-rich Mn-based cathode materials are considered to be the next generation of Li-ion batteries due to low cost, high discharge capacities and high safety feature. However, there are still several serious issues that need to be solved urgently, such as low initial coulombic efficiency, low rate capability, poor cycling performance and voltage fading. Na doping or substitution is introduced to improve the electrochemical performance of Li_1.2Mn_0.6Ni_0.2O₂ cathode material, which is synthesized by sol-gel method. The effect of Na doping or substitution on the morphological, structural and electrochemical properties was systematically studied and analyzed by scanning electron microscope (SEM), X-Ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), cell test system and electrochemical workstation. These results illustrate that lattice layer spacing is enlarged by Na doping or substitution, which is beneficial for the diffusion of Li-ion, and the voltage fading is successfully suppressed. The best electrochemical properties were obtained when Na doping, which is attributed to the stronger structural stability and better reversibility of Li⁺ during the initial charge and discharge process.

Abstract: In this paper, the TiO₂ powder was prepared and the photocatalytic activity was studied. The effects of photocatalytic degradation time, TiO₂ powder dosage and the aging time were examined. The results of XRD analysis revealed that the TiO₂ powders are anatase. The study indicates that TiO₂ powder is a potential material for photocatalytic degradation of dye wastewater.

Abstract: The cast Al-Mg₂Si metal matrix composite was prepared by metal model casting process with rare earth element Nd as the modificator. The effects of modification duration and remelting times on microstructure and mechanical properties of the composite were investicated by optical microscope (OM) and electronic universal testing machine. The results show that, after introducing a proper amount of Nd, both primary and eutectic Mg₂Si in the Al-18 wt.%Mg₂Si composite were well modified. The morphology of primary Mg₂Si is changed from irregular or dendritic to polyhedral shape and the morphology of the eutectic Mg₂Si phase is altered from flake-like to very short fibrous or dot-like. Moreover, the effect is of long-lasting and remelting properties. After the composite is modified for 300 min and remelted by 6 times, its primary and eutectic Mg₂Si structures are still in modification state of small block and slices, and the tensile properties of the composite are not significantly affected.