Materials Science Forum Vol. 1033

Abstract: The Sr hexaferrites with chemical formula Sr_0.4La_0.3Ca_0.3Fe_11.85-xGa_xCo_0.15O₁₉ (x = 0.0 — 1.4) were manufactured by traditional ceramic method. The affect of Ga substitution on static magnetic properties and micromorphology of M-type Sr (SrM) hexaferrites have been presented in detail. In accordance with the experiment results, as Ga-substituted content x rises up from 0.0 to 1.4, all SrM hexaferrite samples are magnetoplumbite hexagonal structure. The difference between radius of Fe³⁺ and Ga³⁺ ions leads to the decrease of lattice constants. As the amount of Ga substitution x increases from 0.0 to 1.4, the 4πM_s and 4πM_r presents a trend of increasing, but the H_c shows the opposite trend. K₁ and H_a of all samples are higher than 2.5×10⁵ J/m³ and 21 kOe respectively, which manifests all samples possess the strong uniaxial anisotropy. The materials discussed in this paper possess huge potential in the application of high frequency self-biased microwave devices.

Abstract: In order to increase the energy density of lithium-ion battery, the LiN_i0.8Co_0.1Mn_0.1O₂(NCM811) cathode material with higher Ni content has attracted much attention due to its advantages such as high energy density, low cost. However, there are some bottleneck problems about the NCM811 such as capacity fading, harsh storage conditions, poor thermal stability, poor safety, which limit its large-scale commercial use. This article reviews the urgent problems for NCM811 high nickel ternary materials, briefly describes several common synthesis methods, and focuses on the modification methods, such as element doping, surface coating and special core-shell structure for enhancing the electrochemical performances and explain the modification mechanism. Finally, we prospect the possible research development and commercial application of high nickel ternary material.

Abstract: The properties of colorfastness to crocking and perspiration of sportswear products (OUDIKE, NIKE and an unknown brand bought from the boutique) in Hong Kong marketplace was comparatively investigated in this study. It was found that NIKE performed best in terms of colorfastness to crocking, whereas the unknown brand samples was the best choice in the colorfastness to perspiration.

Abstract: In this study, the quick-dry properties of four popular brands sportswear T-shirts in Hong Kong market, i.e., Nike, Adidas, Laishilong and Columbia, were investigated by Q-max analysis. It was found that all the samples had cooling effect, among which the Laishilong T-shirt had the highest cool feeling. The Nike and Columbia samples showed comparable Q-max behavior, whereas this value for the samples of Adidas was the poorest.

Abstract: Petroleum-based polymers have significantly problems to the environment due to it cannot degrade in the nature. Biopolymer become to interesting materials for replacing these materials for overcome these disadvantages. Here, we intend to study the biocomposite films of polylactic acid (PLA) blend polybutylene succinate (PBS) composited with ZnO nanoparticles. The chemical reaction and the water absorbency of biocomposite films were investigated by FT-IR spectroscopy and swelling ratio, respectively. The FT-IR results showed that the biocomposite films did not have any chemical reactions between polymers chains and ZnO nanoparticles. The swelling ratio of biocomposite films have proportionally with the contact time. The photocatalytic activity of biocomposite film was investigated by the methylene blue degradation in the aqueous solution. It was found that the efficacy of photocatalytic activity increased with increases in the contact time.

Abstract: Diglycidyl ether of bisphenol A (DGEBA) epoxy resin with cycloaliphatic polyamine curing agent was modified with lignin to improve thermal and mechanical properties of of polymer composite. A systematic study of lignin loading, between 5 and 20 phr (per hundred parts resin) as compared to neat epoxy, was conducted for the reinforcement effect of epoxy resin composites. With the as-received lignin having spherical particles of 80 to 100 microns in diameter, the T_g of the epoxy-filler composites increased with a small addition of lignin up to 10 phr. Likewise, the yield stress and stiffness (Young’s modulus) of the epoxy resin-lignin composites significantly increased to a maximum value of 49.32 MPa and 2.75 GPa, respectively, with 10 phr lignin, due to the higher modulus of the filler compared to the bulk epoxy resin. Correspondingly, the storage moduli of the lignin-containing composites also increased upon filler addition up to 10 phr due to the impact of lignin. Conversely, however, the tanδ decreased in intensity with increasing lignin filler content, which reflects the dampening effect due to restricted chain mobility in thepresence of lignin particlesin epoxy systems.

Abstract: In this work, a finite element model based on an improved first-order formulation (IFSDT) is developed to analyze buckling phenomenon in laminated composite beams. The formulation has five independent variables and takes into account thickness stretching. Three-dimensional constitutive equations are employed to define the material properties. The Trefftz criterion is used for the stability analysis. The finite element model is derived from the principle of virtual work with high-order Lagrange polynomials to interpolate the field variables and to prevent shear locking. Numerical results are compared and validated with those available in literature. Furthermore, a parametric study is presented.

Abstract: The precast concrete elements in the construction of buildings are increasingly used due to their better quality control, constructive speed, reduction of the number of workers and less waste of resources compared to conventional construction; for wall applications, to these advantages, the design to ensure thermal comfort requires the improvement of the low thermal insulation of conventional concrete panels. The use of materials with lower thermal conductivity such as Expanded PolyStyrene Beads (EPSB) in lightweight concrete for the construction of precast panels in housing, contributes to improve thermal insulation and the saving operational energy during its operation phase, because the aggregate has a small size, low density and thermal conductivity; applied in higher volumes in concrete, reduces indoor heat loss in cold climates and indoor heat gain in warm climates in housing. The purpose of this research is to study the behavior of lightweight concrete with EPSB for 16%, 26% and 36% addition and evaluate the air-dry density, compressive strength, thermal conductivity, relationship between air-dry density with compressive strength and thermal conductivity. The results indicate that the higher the percentage of EPSB the air-dry density, compressive strength and thermal conductivity decrease; the relationships between air-dry density with compressive strength and thermal conductivity follow a linear trend and are similar.

Abstract: The significant increase in the construction of buildings has led to the appearance of different phenomena that affect the elements that make it up. Due to their large area, in contact with the surface, solid slabs are the most vulnerable to these effects. The appearance of cracks at an early age is one of the most recurrent problems in concrete slabs, which is why it is important to counteract the presence of cracks to improve their mechanical properties to obtain buildings with greater durability. For this, the incorporation of polypropylene fibers has become one of the best alternatives to mitigate the appearance of cracks. In the present investigation, two concrete mixtures reinforced with polypropylene fibers of two lengths will be evaluated and tested for slump, plastic shrinkage, compressive strength and residual flexural strength.

Abstract: In order to solve the problem of workability and durability of concrete caused by poor particle shape and morphology of manufactured sand and high content of stone powder, which leads to crack problems of concrete, the tensile strength, elastic modulus, shrinkage performance and adiabatic temperature rise performance of manufactured sand concrete were studied in this paper. And the cracking risk factor (the reciprocal of the anti cracking safety factor) of the concrete with the special admixtures and the crack resistant functional materials was calculated by according to GB 50496-2018. The experimental results show that the elastic modulus and tensile strength at the age of 28 d of the test concrete are increased from 31.0 GPa to 34.6 GPA and 2.91 MPa to 4.23 MPa, respectively. The shrinkage performance and adiabatic temperature rise of the concrete are reduced from 98 με to 65 με and 38.9°C to 38.4°C, respectively. The risk factors of surface and center crack resistance of mass concrete floor are 0.52 and 0.75, so the concrete under inspection will not crack.