Advanced Materials Research Vol. 900

Abstract: Al-Ti-B master alloy is an efficient and practical aluminum grain refiner. This paper studies the effect of process parameter on the Second Phase Particles distributions and shape in Al-Ti-B Master Alloys by casting of pure titanium particale method. Emphatically studied three factors of feeding order, superheating temperature and reaction time , then the reasonable process parameters are put forward.

Abstract: This paper reviews several main modification methods of Al-Ti-B master alloy, including high-intensity ultrasound, equal channel angular pressing, conform, and electromagnetic stirring. Attention is directed to the principles and characteristics of various methods, as well as the researches related to Al-Ti-B master alloy. This review also indicates the existing problems of the technology, and the development direction of the modification of Al-Ti-B master alloy in the future.

Abstract: In this paper, the solution and some propagation characteristics of waves inside a rectangular waveguide in the time-varying media are presented. The separation of variables method is used to get a closed form solution i.e. accurate expression for TE mode when the permittivity of media changes with respect to time. It is clearly shown that both the amplitude and frequency of the waves in rectangular waveguide change with respect to time in time-varying permittivity.

Abstract: Lead-free 0.996(Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃-0.004BiYO₃ [BCZT-BY] ceramics were prepared by the conventional solid-state sintering method. By means of XRD, SEM, and quasi-static d₃₃ meter etc., the effect of sintering temperature on the microstructure, piezoelectric and dielectric properties of BCZT-BY ceramics were investigated. All the ceramics possess a pure perovskite structure, indicating that Bi³⁺ and Y³⁺ are incorporated into Ba_0.85Ca_0.15Ti_0.9Zr_0.1O₃ lattices to form a solid solution. The results show that the ceramics sintered at 1420°C exhibit the optimum electrical properties: d₃₃ = 130 pC/N, k_p = 18.2 %, ε_r = 4225, and tan δ = 1.95%, respectively.

Abstract: The processing methods, strengthening methods, water-proof coating procedures, and some ways to improve the transmission of microwaves have been reviewed in relation to fused silica ceramics and their composites for radome applications. Fused silica ceramics are characterized by a residual porosity (up to 18%), low dielectric constant (3.06-3.32), low loss tangent (0.00053-0.0065), excellent thermal properties, but low mechanical strength (37-65 MPa). To achieve higher mechanical strength and better transmission efficiency, new randome materials would be those engineered composites consisting, for instance, of a dense layer-porous core structure, a continuous fiber reinforcement, a multilayered structure, and/or frequency selective surface (FSS) layer (s)/metamaterials.

Abstract: In this paper, the sorts, mechanical property, strengthening and toughening mechanism of ceramic cutting tool materials were summarized in the present study, especially the Si3N4 based nanocomposite and Al2O3 based ceramic cutting tool materials. The problems to be solved in the field were suggested. It would act as the foundation in the future research of ceramic cutting tool materials.

Abstract: The PTCR characteristics of (Ba_1-xSm_x)TiO₃ (BSMT) with different donor-doped concentration (x) sintered in a reducing atmosphere and reoxidized in air are investigated. The results reveal that the room temperature resistivity (ρ_RT) of the semiconducting BSMT ceramics first decreases and then increases with increasing of the x values, especially when x is 0.004, the semiconducting BSMT ceramics reoxidized at 850oC for 1 h after sintering at 1300 °C for 30 min in a reducing atmosphere achieve a lower room temperature resisitivity of 82.6 Ωcm. in addition, the doped 0.1 mol% Sm³⁺ BSMT samples fired at 1300 °C for 30 min in air exhibit remarkable PTCR effect with a resistance jumping ratio of 3.4 orders magnitude; moreover, a lower ρ_RT of the BSMT specimens sintered in a reducing atmosphere is obtained.

Abstract: The effects of in-situ TiB₂ particle fabricated from Al-Ti-B system via the self-propagating high-temperature synthesis (SHS) reaction technology on microstructure and mechanical properties of Mg-Sn-Zn-Al alloy were investigated. The results indicate that the size of the Mg₂Sn and α-Mg+Mg₃₂(Al,Zn)₄₉ phase becomes coarser with the increasing content of Al-Ti-B preform, meanwhile the amount of eutectic α-Mg+Mg₃₂(Al,Zn)₄₉ phase increases too. The addition of Al-Ti-B is favorable toward promoting the strength of composites, but deteriorates elongation. The resulting as-extruded composite material with 4 wt.% Al-Ti-B preform exhibits good overall mechanical properties with an ultimate tensile strength of 291 MPa and an elongation over 2 %.

Abstract: Organosilicon-modified acrylate resin was successfully prepared by solution polymerization and the effect of content of silica sol and silane coupling agent (KH570) on the resistance to water, acid, alkali and aging, the polymerization mechanism, structure were studied,respectively. The results showed that: compared with the properties of resistance to water, acid, alkali and aging of pure acrylate resin, to some extent, those of organosilicon-modified acrylate resin had been improved a lot. The properties of resistance to water, acid, alkali and aging increased at first and then decreased with the increase of the content of organosilicon. Especially, the comprehensive performance of composite resin was relatively excellent when the content of silica sol and KH570 was 5% and 5.1%, respectively.

Abstract: Several kinds of functional particles modified epoxy multilayer composite, which were constituted with lead acrylate/erbium oxide/epoxy and tungsten oxide/erbium oxide/epoxy layer by layer, were successfully prepared. The shielding properties under different γ-ray were tested and discussed in detail. Multilayer composite exhibited higher shielding ability to lower energy γ-ray. The radiation shielding rates of four samples were all above 80% when the energy of γ-ray was about 79.9 keV. The results also revealed that stacking sequence of layer with different functional particles will affect their radiation shielding ability when the energy of γ-ray was low.