Materials Science Forum Vol. 1001

Abstract: Rare earth is a general term for 17 chemical elements with atomic numbers of 21, 39 and 57~71 in group IIIB in the periodic table. Lanthanide complexes can show unique linear emission bands and have very long luminous lifetime. Lanthanide complexes can be used in electroluminous (EL) devices, lasers and light-emitting biosensors in visible and near-infrared spectra. Therefore, it is of great significance to find new lanthanide luminous complexes. The emission peak of rare earth europium complex is mainly located in the characteristic emission wavelength of ⁵D₀→⁷F₂ of Eu³⁺. The emission wavelength is about 613nm, and it shows the fluorescence characteristics of europium ions. In order to further study the subject, this paper will focus on the current research on luminous rare earth complexes-organic complexes centered on Eu³⁺(emission red light). This paper summarizes the luminous principle of rare earth europium and its application in some fields, and expounds the existing problems at present and looks forward to its application prospect in the future.

Abstract: Chain extender plays a significant role in enhancing the final mechanical properties of thermoplastic polyurethane (TPUs) derived from polytetra methylene etherglycol (PTMG) and 4,4-diphenylmethane diisocyanate (MDI). In this research we focused on the effect that mixed chain extender of ethylene glycol (EG) and 1,4-butanediol (BDO) used has on the phase behavior and morphology of high hard block content TPUs. DSC, FTIR, and mechanical testing were mainly used to characterize the morphology and properties of the TPUs materials. Through this work we were able to show that mixed ratio of different chain extenders had dramatic effects on the properties of the TPUs. After mixing EG and BDO, the degree of hydrogen bonding, melting temperature, tensile strength, tear strength, and hardness of TPUs are all reduced, the glass transition temperature is increased. when the mixing ratio is 1: 1 , the elongation at break is increased to 672% . However, when the mixing ratio is n (EG): n (BDO) = 1: 2, the tensile strength is increased to 29.2 MPa, and the elongation at break is reduced to 353%.

Abstract: Using first-principles calculations, we have investigated the adsorption of NH_x (x =1, 2 or 3) on the FeS₂ (100) surface. The adsorption configurations and adsorption energies were determined. Our calculations showed that the NH_x prefers to adsorb on the surface Fe site via N atom. The NH molecule displays the strongest interaction with the FeS₂ (100) surface among the three adsorbates, while NH₃ is bound relatively weak to the surface. The analysis of the density of states (DOS) showed a strong hybridization between N 2p and Fe 3d states, especially for NH and NH₂ adsorption. The NH₃ adsorption at full coverage was found to be less favoured than at partial coverage because of the steric repulsion among the adsorbates, in agreement with the experiment.

Abstract: The one of major impurities in quartz is iron, which has a great impact on the properties of the material and should be be strictly removed in many applications. In this study, a low-energy consumption, simple, fast processing is introduced by combination microwave treatment with different acid leaching. Selective heating of microwaves is used to process quartz, causing local phase changes to improve the purification effect. Acid leaching was used to remove the iron in the quartz matrix. Under optimized conditions, the iron content can be reduced to below 0.167 ppmw with one single purification pass.

Abstract: Al₂O₃/SiC_p composite ceramics with 2 vol%, 5 vol% and 10 vol% SiC nanoparticles additions were hot pressed at 1650 °C. The polished ceramic discs were prepared and indented at high strain rate using a compressed gas gun with tiny tungsten carbide bullets. The microstructure and mechanical properties were obtained to explain the dynamic deformation behavior of Al₂O₃/SiC_p ceramics. Cr³⁺ fluorescence mapping was used to examine the residual stress and plastic deformation induced on the surface of each target. The residual compressive stress area around the crater was evenly distributed, while the greatest plastic deformation was found at the hitting point of the bullet tip. It can be calculated that the high temperature of 1400K may be produced at the instant of the bullet impact and result in large plastic deformation region and low residual stress of the Al₂O₃/SiC_p ceramic.

Abstract: In this paper, Fe-Cr-C hardfacing alloys with different chromium contents (7.5, 15, 20 and 32wt%, respectively) were deposited by PTA welding. Influence of Cr content on the hardfacing alloys was revealed by analyzing the microstructure, microhardness and wear behavior. The results showed that the primary phase changed from M3C to M7C3, and the eutectic phase changed from M7C3 to M23C6 with the addition of Cr content. The Cr content had a great influence on the hardness of the alloy. The higher the Cr content, the higher the hardness. The abrasiveness of the alloy was closely related to the Cr content. The wear resistance of the alloy increased with the addition of Cr content.

Abstract: It is studied that effects of different amounts of steel fiber and glass fiber on the compressive strength, flexural strength, and compression ratio and bond strength of styrene-acrylic emulsion modified mortar under different ages. The results show that the compressive strength, flexural strength and bond strength of mortar increase with the increase of steel fiber content, and the toughness improvement effect is obvious. With the increase of glass fiber content, mortar compressive strength, flexural strength and bond strength first increases and then decreases. Combined with SEM analysis and theoretical calculation to analyze the mechanical strength mechanism of fiber reinforced polymer mortar.

Abstract: (Fe,Ni)₂(P,Si) compounds were synthesized and characterized. Ni substitution in Fe_1.95-xNi_xP_0.7Si_0.3 is found to favor the formation of Fe₂P-type hexagonal structure. The samples appear nearly single phase. Powder oriented in the magnetic field shows a pronounced uniaxial magnetic anisotropy with c axis as the easy axis. Magnetization measurements carried out along and perpendicular to the c crystal axis demonstrate a significant magnetic anisotropy, making these materials potential candidates for permanent magnet applications. We found that (Fe,Ni)₂(P,Si) compound has no remanent magnetic field and coercivity, but it has a large magnetocrystalline anisotropy at room temperature. Therefore, doping Fe₂P type compounds with a small amount of Ni and Si may be a promising way to create new materials with large magnetocrystalline anisotropy at room temperature, and thus rare-earth free permanent magnet.

Abstract: In this study, Thermogravimetry (TG) were used to analyze thermal degradation properties of two kinds of low-molar ratio of the melamine-modified urea-formaldehyde resin (MUF). The MUF was calculated using Kissinger equation and Flynn-Wall-Ozawa equation Resin pyrolysis activation energy. The results showed that the curing time of low mole was longer than that of MUF resin (muf-b), the content of free formaldehyde was lower, and the formaldehyde emission and wet bonding strength of plywood were reduced by 65.79% and 21.90%, respectively. TG test showed that the pyrolysis process of MUF resins with different molar ratios can be divided into three stages: dehydration, rapid pyrolysis and carbonization. At the same heating rate, the weight loss rate, peak conversion rate and carbon residue of the high molar ratio MUF resin (MUF-a) in the fast pyrolysis stage are larger than those of the MUF-b resin. The MUF-a resin pyrolysis activation energy is 166.76 kJ/mol, and the MUF-b resin pyrolysis activation energy is 95.30 kJ/mol. High molar ratio resin has higher pyrolysis activation energy and better thermal stability.