Advanced Materials Research Vol. 815

Abstract: With the additive agent Ti₃SiC₂, the dry sliding behavior of Cr₃C₂-Ni and Cr₃C₂-Ni-Ti₃SiC₂ composites against GCr15 was investigated with a pin-on-disk tester at 400 °C in air under the load of 200N. Without Ti₃SiC₂, the dynamic coefficient of friction (COF) curves was fluctuated severely. After adding Ti₃SiC₂, the COF was decreased from 0.37 to 0.32, and the initial transition region of dynamic COF curve was shortened. These tribological test results showed that Ti₃SiC₂ was a new kind of solid additive agent with favorable high temperature self-lubricating property, and two possible mechanisms was proposed for its anti-friction ability.

Abstract: The creep behavior of WPCs needs to be addressed when developing and using this kind of materials. In this paper, the creep behavior of WPCs under linear viscoelastic region was investigated at different temperatures and bamboo flours levels. The creep compliance increase with the rise of temperature, the addition of bamboo flour has a positive effect on the creep behavior. Burgers model, Findley power law and TTSP were used to predict the long-term behavior of this kind material. Finely power law can well describe the creep properties of WPCs while Burgers model begins to diverge from measured data at about 100min. The application of TTSP was used to create master curve covered more than 10⁸ from 30-min short-term creep compliance curves.

Abstract: Wood-plastic composite is a kind of viscoelastic materials. This paper presents the dynamic viscoelastic behavior of WPCs at different temperature, frequency and bamboo flours levels. The storage modulus decreased with the rise of temperature, the loss modulus and tanδ increased as temperature increased but decreased after reaching the peak. Frequency had a little influence on storage modulus and loss modulus, but the glass transition temperature increased with the increase of frequency, while the tanδ decreased. The glass transition temperature of this kind WPCs is about 85°C. The addition of bamboo flours had a positive effect on the dynamic viscoelastic behavior. From the results above, the activation energy of the WPCs was measured using an Arrhenius relationship to investigate the interphase between the wood and plastic.

Abstract: Honeycomb absorbing materials were measured using the method of free space in this paper. The reflectance of honeycomb absorbing materials was calculated and simulated, and it was verified based on the measured results. It was demonstrated that this test method was feasible. Through studying on absorbing properties of honeycomb, the results have showed that the radar absorbing properties of honeycomb are related to electromagnetic parameters, as well as thickness of the dip-coatings. With the increase of thickness of the dipping layer, the radar absorbing capability of high frequency and low frequency wave are significantly increased. It is worth noting that the resonance peak moved to the low frequency with the increase of dipping layer thickness. These results are useful for design of honeycomb absorbing materials.

Abstract: onic Polymer Metal Composites (IPMC) is a new kind of electro-active smart material that has many advantages including bending actuation, large displacement, low weight, low driven voltage, low power consumption, flexibility etc. The mechanical characteristic of IPMC is related to ionic polymer membrane, such as thickness, roughening, cation type and so on. In this paper, the actuation principle of IPMC and fabrication technique of Nafion^TM membrane is presented. The performance of IPMC with Nafion membrane pre-treatment, different cation type and thickness are investigated. Experiment results showed that the fabrication process of ionic polymer membrane Nafion change can improve the performance of IPMC effectively.

Abstract: This paper studied the mechanoluminescence of the CaAl₂Si₂O₈:Eu²⁺_x, Dy³⁺_y phosphors. The crystal structure, photoluminescence (PL) and mechanoluminescent intensity of the phosphors were investigated. The emission peak of CaAl₂Si₂O₈: Eu_x²⁺ had a redshift from 418 nm to 428 nm due to the increase of the crystal filed intensity around Eu²⁺ with the increase of Eu²⁺ ion content. The ML (mechanoluminescence) emission of CaAl₂Si₂O₈:Eu_0.01and CaAl₂Si₂O₈:Eu²⁺_0.01, Dy³⁺_0.02 can be seen by the naked eyeswhen compressive loads were appliedon the samples. Whats more, the addition of Dy³⁺can increase the ML intensity of CaAl₂Si₂O₈:Eu_0.01. The ML and PL spectra of the sample CaAl₂Si₂O₈:Eu²⁺_0.01, Dy³⁺_0.02 are identical, located at 428 nm.

Abstract: The broad strong red emission in Pr³⁺ doped MgAl₂O₄ phosphor powders have been synthesized by conventional solid state reaction in air. The temperature dependence of particle size and structural phase were investigated. The intense red emission of the phosphors is observed under 250-350 nm excitation, which cover the spectrum of Ultraviolet. The optimal emission intensity was obtained when Pr doping level was 0.002mol. The lifetime decay curves with different concentrations and a possible mechanism were also studied.

Abstract: After the description of finite element model of three-dimensional heat conduction, the software FLOEFD is used to simulate a components temperature fields under various heat sources, to get the temperature difference curves and to analysis the difference between them. It comes out that when the power of heat source changes as a triangular curve, corresponding temperature difference is lower than that of sinusoidal power curve, but larger than that of constant power; Change rate of temperature difference of triangular power curve is lower than that of sinusoidal and constant power, but larger than that of square power curve. The distinction of temperature difference is caused by the different change-rate of inputting heat; the distinction of changing rate of temperature difference is caused by the different changing rate of heat source power.

Abstract: In order to improve the secondary electron emission coefficient of MgO, we propose to dope Al into MgO. The precursor was obtained by hydrothermal method in the condition of different reaction temperature, different filling volume and different reaction time by using urea, Mg (CH₃COO)₂ and AlCl₃. The Al-doping MgO crystallites powders were obtained by calcining the precursor. The crystal phase and morphology of the products were characterized by XRD and SEM. The results showed that the Al-doping MgO powders were cubic-shaped crystallites. The discharge characteristics of Al-doping MgO powders were tested in a chamber as when the panel was sealed in Ne and 7% Xe at 450 torr. As expected, the discharge voltage of the panel is lower with the Al-doping MgO protective layer than without that.

Abstract: In present work, K₂Y_1-xZr (PO₄)₃:Pr_x³⁺ (0.01x0.05) samples were prepared by solid-state reaction method and their photoluminescence properties were investigated in ultra-violet (UV) and vacuum ultra-violet (VUV) region. The photon cascade luminescence (PCL) of Pr³⁺ had been observed. All the results indicate that, in this Pr³⁺-doped K₂YZr (PO₄)₃ phosphor, even if the ¹S₀ state is higher than the lowest 4f5d energy level, the photon cascade emission (PCE) process for Pr³⁺ still could occur under 147 nm and 234 nm (4f¹5d¹ state) excitation. Therefore, K₂YZr (PO₄)₃ was an ideal host for Pr³⁺ to implement the PCE process successfully.