Abstract: High-Fluorescence Mn-doped ZnS quantum dots ( QDs) capped with L-Cysteine (L-Cys) were prepared in the aqueous were presented in this paper. The influences of the pH, the doped-quantity of Mn2+ and the storage time on the PL emission of quantum dots were studied. The samples were characterized by means of ultraviolet-visible absorption spectrometry (UV-vis), photoluminescence (PL) emission and infrared spectrometry (FTIR). The results showed that the fluorescence intensity reached the maximum when the pH was 10, the doped-quantity of Mn2+ was 3% and the storage time was about 7 days. The solubility of the quantum dots in the water was excellent. Because of these advantages, it can be used in biological fields, such as biomarkers, cell imaging, and sensor and so on.
Abstract: High-quality CdTe nanocrystals capped by mercaptopropionic acid (MPA) were prepared in aqueous solution, and core-shell CdTe@SiO2 particles were prepared via reverse microemulsion method. The core-shell CdTe@SiO2 particles were fluorescent, monodispersed, and well-separated. The obtained samples were characterized by means of transmission electron microscope (TEM), ultraviolet-visible absorption spectrometry (UV-vis) and photoluminescence (PL) emission. The influence of ionic strength on the PL emission of uncoated CdTe and CdTe/SiO2 composite nanoparticles were investigated thoroughly. Due to the presence of SiO2 shell, CdTe@SiO2 still remained a strong fluorescence at high ionic strength. Because of these advantages, it had broad applications in biological fields, such as biomarkers, cell imaging.
Abstract: Bacterial Cellulose (BC) consisting of hydrophobic ultra-ﬁne ﬁbers was produced by Acetobacter xylinum. Hydroxypropyl bacterial celluloses (HPBC) were synthesized by surface modification of nano-fibrils via hydroxypropylation using two modifier systems, sodium hydroxide/ propylene oxide as system (I) and sodium hydroxide/urea/propylene oxide as system (II) respectively. The equilibrium swelling ratio (ESR) of HPBC was studied. ESR of HPBC obtained from system (I) was significantly higher than that obtained from system (II). The maximum ESR of HPBC was nearly 70 times larger than that of air dried BC and 10 times larger than that of freeze dried BC.
Abstract: TiO nanosheet films were fabricated by magnetron sputtering and followed with the direct in situ hydrothermal method. Without UV irriadiation, the TiO nanosheet surface showed a wetting property of superhydrophilicity. However, after chemisorptions using a self-assembled monolayer of n-CF3(CF2)7CH2CH2Si(OC2H5)3, the wetting property of the film can be changed from superhydrophilicity to superhydrophobicity. Based on the FESEM, XRD, XPS analysis, the mechanism of the wetting bahavior was proposed.
Abstract: NiO nanoparticles were successfully prepared by decomposing the predecessor bis(glycinato)nickel(II)dihydrate in the presence of oleylamine and triphenylphosphine (TPP), and different approaches including Fourier transforms infrared spectrometry(FT-IR), X-ray diffraction(XRD) and transmission electron microscopy (TEM) were used to characterize the NiO nanoparticles. Meanwhile, the effects of TPP concentration and reaction time on the size and yield of NiO nanoparticles derived from precursors were thoroughly investigated in this paper. The analysis results indicated that the prepared NiO nanoparticles were found spherical in shape and demonstrated weak agglomeration. They had generally high purity and a fine crystal phase of cubic syngony. Furthermore, the effects of the TPP concentration and reaction time on the size and yield of NiO nanoparticles are very crucial, higher concentration of TPP would results in reduction of both the mean size and yield of NiO particles. However both yields and particles size of NiO nanoparticles continuously increased as increasing reaction time, after more than 60 minutes, the size and yield of NiO nanoparticles kept hardly change.
Abstract: To develop a new bearing material with promising tribological properties, low cost and without harmful elements, the TiB2 particle-reinforced Al-10Sn matrix composites were fabricated by Mixed Salt Reaction synthesis process. The solidification microstructure of the composites was investigated by optical microscope and scanning electron microscope. The results indicate that the grains of α-Al matrix are fine, the TiB2 particle size is less than 1.5μm, and the agglomeration of TiB2 particles is mainly present at the boundary of α-Al phase, where the mechanical mixture of TiB2 and β-Sn was observed. The oil lubricated sliding friction tests of composites and matrix alloy were conducted on a small thrust ring versus disc friction testing machine under different loads. The results indicate that, at low load (200N), both of composites and matrix alloy have a conspicuous running-in period and exhibit a better antifriction property with the coefficient of friction (hereafter COF) being 0.017 and 0.015, respectively. However, at high load (400N), the COF of composites and matrix alloy is approximately 0.080 and 0.17, with the frictional temperature being 58°C and 75°C, respectively. The composites exhibit higher bearing capacity and excellent antifriction
Abstract: Weld distortion and residual stresses are two major issues in the fabrication process. Numerical techniques are being tried out to accurately predict the structural integrity of the welding. Interpass time in the multipass welding is an important parameter which influences the weld distortion and residual stresses. In this study two pass tungsten inert gas (TIG) welding of 6 mm mild steel plates has been analyzed using Finite element analysis (FEA) software Sysweld and parametric study is conducted with different interpass time. The temperature distribution, distortion and residual stresses are calculated using three dimensional finite element model (FEM) considering phase transformations in the material. The transient thermo-metallurgical analysis followed by elasto-plastic analysis is carried out using temperature dependent and phase dependent material properties. The material deposition in the multipass welding is numerically simulated using chewing gum method, where dummy phase and dummy material are assigned for the element activation. The phase proportions are calculated by assigning suitable phase kinetics parameter extracted from continuous cooling transformation (CCT) diagram of a given material. Experiments are conducted for validation after given edge preparation and using same material as filler wire. The FEM analysis is carried out for eight cases with different time interval between passes, starting from 30 s to 240 s in the steps of 30 s. FEM results are verified with experimentally measured values. It is found that the time interval between passes has less influence on the residual stresses but significantly affects the distortion and phase proportion due to the first pass preheating effect on second pass and second pass postheating effect on first pass.
Abstract: To increase the magnetic performance of multi-wall carbon nanotubes (MWCNTs)/Fe3O4 nanocomposites, Fe3O4-polymer-MWCNTs with a novel nanostructure was prepared by in-situ method. The low molecular weight poly (acrylic acid) was grafted on the surface of acid-oxidized MWCNTs, forming numerous carboxyl groups from the original hydroxyl groups on the surface of acid-treated MWCNTs. And then, the ferric and ferrous ions would be adsorbed on the surface of PAA-g-MWCNTs through the electrostatic interaction. At last, the ammonia solution was added into the above solution to form Fe3O4 nanoparticles on the surface of MWCNTs through hydrothermal treatment. The experimental results showed that large quantities of Fe3O4 nanoparticles were coated on the surface of PAA-g-MWCNTs via in-situ method and our products possessed high magnetic saturation and magnetic sensitivity.
Abstract: In this paper，according to the shell theory , model are developed to predict delamination damage in the drilling process. Finally, we will get theoretical delamination factor and complete the prediction of the delamination damage area. The known references didn’t find similar model of predicting delamination damage. Therefore, it is new method. With the drilling process experimental contrast，the model is more effective for the prediction of delamination of the carbon fiber composite materials.