Advanced Materials Research Vols. 306-307

Abstract: Cornstalk fibers were modified with surface modification and the properties of cornstalk fiber/gypsum composites was studied. The results showed that mechanical properties of cornstalk fiber/gypsum composites were enhanced by adding unmodified cornstalk fibers, but composites waterproof performance was decreased greatly. Through surface modification on cornstalk fibers, composites mechanical properties were further enhanced, and composites waterproof performance was improved obviously. The mechanism of surface modification was discussed, and the model of interfacial zone between modified cornstalk fiber and gypsum matrix was proposed.

Abstract: A series of organic-vermiculite/polyimide (OVMT/PI) hybrid films were successfully prepared by in situ polymerization using hexadecyltrimethyl ammonium bromide (CTAB) modified vermiculite (VMT) as filler. XRD analysis showed the OVMT were exfoliated in the polymeric matrix below 1.5wt%. The tensile strength and elongation at break increased with the addition of OVMT and up to maximum at 1.5 wt%. The Tgs of the films were nearly 400°C indicating that the incorporation of OVMT did not obviously affect the thermal stability of PI films.

Abstract: In this paper, the prepared LaPO₄/Al₂O₃ composite ceramics were ground by the surface grinding machine. The phase composition and morphology of the coated powders as well as the microstructure of grinding surface of the ceramics were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Scanning electron microscope (SEM), respectively. The results show that the coated powders have a distinct core-shell structure which has a great effect on material’s removal approaches. The main fracture mode is caused by intragranular fracture of layered LaPO₄ rather than the weak interface. Besides, the primary grinding removal mechanism of LaPO₄/Al₂O₃ composite ceramics mainly rise from cracks propagating along the interlayer of LaPO₄.

Abstract: This text have studied the effect of electrical properties of sheet molding compound (SMC), by adding different amount of Aluminum hydroxide powder which was modified by titanate coupling agent. By testing oil absorption value, we can obtain the optimum dosage of coupling agent. The results showed that oil absorption value of the powder can reach minimum when the dosage of coupling agent was 2% .After the modification of aluminum hydroxide powder, the biggest amount of filled powder will increase and the volume resistivity can improve approximately 30%. When the same amount of Aluminum hydroxide powder was added, dielectric constant and dielectric loss of the modified products is less than that of unmodified.

Abstract: A novel model of steady-state sliding wear with electrical current was created, which gives an accurate relational expression of three factors (electrical current, sliding velocity and contact pressure) and wear rate of the pin material. The experiments were carried out on the couple of QCr0.5 against copper-based powder metallurgical materials. The results show that the model is accurate and it is able to clearly show the influence of electrical current, sliding velocity and contact pressure on wear rate of pin.

Abstract: Composite α-PbO₂ coatings with addition of different solid particles were prepared on A1/conductive coating electrodes in 4M NaOH solution with addition of PbO until saturation by electrochemical anode composite electrodeposition technology, doping with different TiO₂ and CeO₂ nanoparticles. The optimum formula and operating condition of the composite electrode material were obtained as follows: adding PbO solid to 4M NaOH until saturation, TiO₂ 15 g/L; CeO₂ 10g/L, temperature 40°C, current density 0.5A/dm², electrodeposition time 4h. On this condition, the PbO₂-(3.77wt%±0.4%)TiO₂-(2.13wt%±0.4%)CeO₂ composite coating can be obtained.

Abstract: M-MCM-41 (M = Al, Cu, Cr, Ti) were synthesized by hydrothermal method and characterized by XRD. Rhodamine B molecules were encapsulated into these mesoporous molecular sieves by impregnation method. Steady fluorescence measurements indicated that doping of Al ions into MCM-41 enhanced largely the fluorescence intensities, but more Al decreased the fluorescence intensities resulting from the formation of Al₂O₃.

Abstract: Powder metallurgy derived microporous Al₂O₃/FeCrWMoV metal ceramic preforms were infiltrated with 60Pb40Sn based solid lubricants to create almost fully dense self-lubrication composites. By means of scanning electron microscope (SEM) and energy dispersive X-ray spectrometer (EDS), it was found that 60Pb40Sn-based solid lubricants are well dispersed and embedded in the Al₂O₃/FeCrWMoV matrix. The friction and wear behaviors of the composites sliding against ZrO₂ ceramic from ambient to 800 °C were investigated using a pin-on-disk wear tester.The results showed that the composites exhibited self-lubricating properties at elevated temperatures up to 700 °C. The friction coefficients of less than 0.27 at 600 °C and wear rates of 6×10⁻⁶ mm³/N m are obtained when rubbing against ZrO₂ ceramic under a normal load of 50 N and a sliding speed of 0.139m/s for 2 hours. The occurrences of lower friction coefficient and plateau in wear rate have been related to the formation of a film of lubricant almost covered entirely the substrate beneath.

Abstract: The isothermal oxidation behaviors at 800-1000°C for 20h in air of bulk Ti₂AlN and Ti₂AlN/TiN were investigated by TG, XRD and SEM coupled with EDS. The oxidation behaviors generally follow the parabolic law. The activation energies of Ti₂AlN and Ti₂AlN/TiN composite are 614.93 KJ∙mol^-1 and 541.35 KJ∙mol^-1 respectively. The antioxidation property of Ti₂AlN/TiN composite is better than Ti₂AlN. Oxidation process of single-phase Ti₂AlN is composed by the outward diffusion of Al³⁺ and Ti⁴⁺, and inward diffusion of oxygen. Oxidation process of Ti₂AlN/TiN composite consists of two parts: firstly, the oxidation of TiN, the oxidation temperature is 500 °C; the second step is the oxidation of Ti₂AlN, carried out mainly in the 800-1000 °C.