Papers by Author: Zheng Yi Fu

Abstract: Nature is a perfect designer in fabricating biomaterials with well-defined and hierarchical nanostructures. Here we report a biomineralization-inspired approach for preparing hierarchical ZnO structure with high UV-light efficiency. The results show that biomacromolecules play an important role on controlling growth and assembly of ZnO nanostructures. It is found that the biomacromolecules favoring the isotropic growth of ZnO at the high concentration.

Abstract: ZnO-based ceramic was densified at low temperature by using PSP as binder. The results showed that phenolic resin filled in the ZnO grain boundary layer. The sample has a well hardness of 0.8 GPa and bending strength of 78 MPa. The effect of temperature on the microstructure and mechanical properties was also investigated. It was found that the samples sintered at 300 °C showed higher density and better mechanical properties.

Abstract: Reliability of indentation method in carbon nanotube reinforced ceramics had been proposed in some works, especially of indentation toughness. In this work the traditional indentation hardness of the Multi-wall carbon Nanotube reinforced alumina composites was studied. It is found that the Vickers hardness and nanoindentation hardness of MWNT reinforced alumina fabricated by SPS decreased from about 20GPa to 16GPa at a critical load force about 1kg. While pure alumina showed a Vickers hardness of 20.6GPa in the whole load force range. When the load force or displacement into surface increasing, continuous recorded hardness, contact stiffness and modulus of the MWNT reinforced alumina showed quite different behavior compared with the pure alumina, especially at middle period of indentation. It was believed that different properties in vertical and horizontal directions of the MWNT were the key. MWNT was compressed and deformed as a soften component in the whole indentation processing. And tensile stress caused by MWNT in composite became significant until an enough strain attained and decreased when a critical stress was over. The results mean the definition of hardness or similar ones seemed need deep description in this type of material.

Abstract: Hierarchical ZrO2 nanorods have recently received considerable attention due to their special physical and chemical properties. However, traditional preparation methods are involved in expensive equipment, complicated process and high production cost. Here we report a simple hydrothermal approach to prepare hierarchical ZrO2 nanorod. The results show that as-synthesized products are composed of many nanorods with 80~150 nm in diameter and 15~20 μm in length. After annealing, the final product was involved into hierarchical monoclinic ZrO2 (m-ZrO2) nanorods, namely, the big nanorod was made up of many small nanorods with 20~30 nm in diameter and 300~500 nm in length. The possible formation mechanism was proposed based on a series of chemical reactions and the natural properties of zirconium.

Abstract: Phytoremediation is the use of vegetation for in situ treatment of contaminated soils, sediments, and water. It is best applied at sites with shallow contamination of metal pollutants. The term “assisted phytoextraction” usually refers to the process of applying a chemical additive to contaminated soil in order to increase the metal uptake by crop plants. In the process of phytoremediation, applying plant growth regulator can promote phytoextraction effects. This paper reviewed the effect of the plant growth regulator for the biological growth, plant transpiration and heavy metal stress. the increase in metal accumulation in upper parts of plant could be related to both the role of PGRs in the enhancement of plant resistance to stress (as toxic metals) and the increase in transpiration rate, i.e. flux of water-soluble soil components and contaminants by the regulation of stomatal opening.

Abstract: Co-doped ZnO nanorods membrane was deposited at glass substrate in a simple chemical water bath. The morphology and crystal structure of the samples were characterized by SEM, TEM and XRD. It is shown that the ZnO rods membrane exhibits an excellent orientation along the c axis. X-ray diffraction study also indicates decrease in the lattice parameter after Co doping. The results of EDS and XPS verify that Co²⁺ is successfully doped into the lattice of nano ZnO rods. 2at% and 5at% Co doped ZnO rods behave stronger UV emission and weaker visible emission.

Abstract: A new type of ZnO/Ag micro hybrid material has been fabricated by a facile wet chemical method using citrate as a crystal growth modifier. The morphology and component of ZnO/Ag hybrid material were characterized by SEM and XRD. It is shown that the platelike crystals connect together by means of embedding. The sample is composed of wurtzite ZnO and face-centered cubic Ag. The results of XPS, UV-Vis and PL spectra verify the electron transfer from Ag to ZnO. The photocatalytic test with Rhodamine B (RhB) as a representative dye pollutant shows that the ZnO/Ag hybrid material exhibits an improved photocatalytic activity.

Abstract: Pulse Current Heating (PCH) process is a new method characteristic with shorter time and lower temperature to the fabrication of materials. In the present paper, the PCH was used to join Cu/Fe. The microstructures of the joined samples were observed by optical microscope, the diffusions of elements near the interfaces were made qualitative and quantitative analyses by Electron Probe Mechanism. Diffusion coefficients of Cu and Fe at PCH and Radiation Heating (RH) joining methods were compared. The results showed that, the transition layer widths were from 5 to 8 μm when the Cu/Fe joined at 750 to 850°C under 5 MPa pressure with holding times 5 or 10 or 15min. Width of the transition layer increase with the increasing of joining temperature and the extension of holding time. The initial interface will move from the Cu side to the Fe one due to the Kirkendall effect. The diffusion coefficients both of Cu and Fe to PCH joining were larger by three orders of magnitude than those of RH joining. The differences between the two methods were analyzed from dynamics and thermodynamics.

Abstract: The addition of h- BN to a polycrystalline Si3N4 was to increase the fracture toughness and other mechanical properties such as flexural strength and hardness of the material. The hot pressed samples were prepared from the mixture of α-Si3N4, AlN, MgO and h-BN. The composite contained from 0 to 2 wt.% BN powder with sintering aids (9% AlN + 3% MgO). The transparency, mechanical properties and microstructure of hot pressed polycrystalline Si3N4-BN composite materials were investigated by UV/VIS spectrophotometer, scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The transparency decreased with increasing the content of h-BN into Si3N4.

Abstract: Ca-α-sialons with low oxygen content were fabricated at 1800°C by hot pressing. The phase and microstructure were characterized by XRD and SEM. The calculated lattice parameter reveals that 20~30% Ca2+ ions still exist in the grain boundary phase of Ca-α′. A large amount of Ca-containing liquid phase efficiently promotes the anisotropic growth of α′ grains in Ca-rich composition. Reinforced only by elongated α′ grains, the fracture toughness of Ca-α′ can reach 4.96 MPa•m1/2.