Papers by Author: Feng Qin

Abstract: In this contribution, hard/soft latex blends were prepared by mixing proportionable non-crosslinkable hard and self-crosslinkable soft latices. The stability and mechanical properties of latex blends were comparatively studied with the neat latex with high glass transition temperature (T_g). It was found that the calcium ion stability of the latex blends is better than neat hard latex. In addition, the stress at break decreased with the increasing of φ_s (mass fraction of soft particle in latex blends) and the break elongation increased when φ_s below 0.8. Meanwhile, the value of tensile stress and break elongation of the hard latex film with coalescing agent, DPnB, additive is between that of the latex blends film with 60% and 70% soft particle. The study on viscoelasticity of the latex films demonstrated that this composite latex can be considered as phase separation blend involving a soft phase filled with hard spheres. The results indicate that the soft latex can serve as the substitution of coalescing agents in water-based ink industry to obtain low or zero VOC ink, without compromise on properties.

Abstract: In this paper we have characterized the performance of a vertical metalorganic chemical vapor deposition (MOCVD) reactor used for deposition of ZnO thin films. The equations of the mathematical model are solved numerically using a control-volume-based finite difference method. A two-dimensional model is put forward to study the dependence of the growth rate on the inlet flow rate and susceptor temperature. The mass-fraction distribution of the reactants has been studied as a function of the position above the substrate, which shows that gas phase pre-reaction in our reactor is well confined. The simulation results are useful for the practical growth of ZnO.

Abstract: The morphology evolution of ZnO films grown on sapphire (0001) by MOCVD have been studied as a function of buffer growth time and temperature by means of atomic-force microscope (AFM), x-ray diffractions (XRD) and optical microscopy. When the buffer growth temperature decreased to 450°C, the surface became smooth greatly, indicating the transition from typical 3D island growth to quasi-2D growth mode. As the buffer growth time exceeds 5min, the micron-sized pit-like features are formed. It is due to the lack of stabilization of adatoms under the “etching” action of ionized O2/Ar during high temperature buffer annealing