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The electro-acoustic (frequency response) characteristics of the loudspeaker usually be affected by the mechanical properties of the paper diaphragm. The mechanical properties of the diaphragm were improved by modifying the natural fiber. In this work, the structure of Manila hemp fiber and the mechanical properties, electro-acoustic performance of paper diaphragm were discussed on the effects of alkali concentration and treatment time. The surface morphology, crystal structure and chemical composition of Manila hemp fiber treated before and after were characterized by SEM, XRD, FT-IR, TGA. The results showed that the fiber surface roughness increased, and the crystallinity of the fiber increased and then decreased as the alkali concentration or the treatment time increased. The lignin and hemicellulose on the fiber surface were decreased. The thermo-stability of cellulose improved the same time lignin’s decreased. When the alkali concentration was too large or the treatment time was too long, the cellulose will be degraded, the mechanical strength of the diaphragm was affected. The fiber diaphragm has the best mechanical properties and electro-acoustic performance with 5 wt% of the alkali concentration, 3 h of the treatment time. [ABSTRACT FROM AUTHOR]

The continuous upgrading of the automobile industry has put forward higher requirements for the performance and lightweight effect of aluminum alloys. Heat treatment is an effective way to improve the performance of aluminum alloy, but how to obtain the optimal combination of heat treatment process parameters is an urgent problem. In this paper, the influence of heat treatment process parameters (solution temperature, solution time, aging temperature, aging time) on mechanical properties was systematically studied, and the relationship model between mechanical properties and heat treatment process parameters was established. The micromorphology under different process parameters were analyzed by ESDB and SEM. The results show that when the solution temperature was 530 ℃, the solution time was 1 h, the aging temperature was 170 ℃, and the aging time was 6 h, the mechanical property of 6082 aluminum alloy profiles was the best. The yield strength was 313 MPa, the tensile strength was 350 MPa, and the elongation after break was 13.21%. The relationship model between Y value (yield strength, tensile strength, and elongation after fracture) and key process factors was established, in which the solution temperature had the greatest influence. When the solution temperature was 530 ℃, the grain size was the smallest, and the mechanical properties of the precipitated fine Mg2Si phase and Al(FeMnSi) phase were the best, and the tensile fracture was mainly the dimpled fracture. This paper provides theoretical basis and practical guidance for the optimization of heat treatment process parameters of aluminum alloy profiles. [ABSTRACT FROM AUTHOR]

Aerogel materials have broad application prospects in the market of building thermal insulation materials because of their high porosity, strong compression resistance and low thermal conductivity. In this paper, Al2O3-SiO2 aerogel composite thermal insulation materials with different SiO2 content were prepared by sol-gel method using tetraethyl orthosilicate and sec butanol aluminum as raw materials. The effects of SiO2 doping amount on the crystal structure, micro morphology, mechanical properties and thermal conductivity of composite aerogels were studied. The results showed that Al2O3-SiO2 aerogel was mainly composed of polycrystalline boehmite. SiO2 doping inhibited the formation of γ-Al2O3 phase and hindered the occurrence of hydroxyl condensation reaction. H in AlO—H group was replaced by Si, forming a more stable Al—O—Si bond. Al2O3-SiO2 aerogel showed an open porous structure, and the doping of SiO2 improved the pore orientation of the aerogel, reducing the pore size and distributing evenly. With the increase of SiO2 doping, the compressive strength and specific surface area of Al2O3-SiO2 aerogel first increased and then slightly decreased, and the thermal conductivity first decreased and then increased. When the doping amount of SiO2 was 9 mol %, the maximum compressive strength of the aerogel was 40.92 MPa, which was 58.97% higher than that of the undoped aerogel. The maximum specific surface area was 257.33 m²/g, the lowest thermal conductivity was 0.022 W/（m·K）, and the thermal insulation performance was the best. In summary, the optimal doping amount of SiO2 was 9 mol%. [ABSTRACT FROM AUTHOR]

Aiming at the problems of insufficient flexural strength and low durability of cement concrete, this paper prepared concrete with different content of epoxy resin（0%, 3 wt%, 6 wt%, 9 wt%） by using epoxy resin as doping phase, and analyzed the influence of epoxy resin on the mechanical properties, micro appearance and durability of cement concrete. The results show that the doping of epoxy resin accelerates the hydration reaction, reduces the number of cracks and pores, and improves the density of concrete. The compressive strength and flexural strength both increased first and then decreased with the increase of resin doping. The compressive strength and flexural strength of the concrete with 6 wt% epoxy resin doping reached the maximum values of 43.8 and 7.9 Mpa respectively when cured for 28 d, which increased by 18.70% and 29.51% respectively compared with the concrete without resin doping. The chloride ion diffusion coefficient of concrete decreases first and then increases with the increase of resin doping amount. The chloride ion diffusion coefficient of concrete with 6 wt% epoxy resin doping content for 28 d is the lowest of 7.7×10-8 cm/s, and the chloride ion corrosion resistance is the best. When the number of freeze-thaw cycles reaches 80, the concrete with 6 wt% epoxy resin doping has the lowest mass loss rate of-0.13%, the highest relative dynamic elastic modulus of 94.86%, the lowest wear amount of 0.66 kg/m², and the wear amount reduction rate of 46.77%. It has excellent durability. [ABSTRACT FROM AUTHOR]

In this paper, modified cementitious powders with different doping amounts of calcium carbide slag (0,0.5 wt%,1.0 wt% and 1.5 wt%) were prepared with 32.5 grade ordinary portland cement, II grade fly ash and mirabilite as raw materials and industrial waste calcium carbide slag as additive materials. The effects of calcium carbide slag doping on the crystal structure, micro morphology, mechanical properties, setting time and combined water content of modified cementitious powder were analyzed.The results show that the doping of carbide slag doesn’t produce new products, but accelerates the consumption of C2S and C3S and improves the rate of hydration reaction.When the doping amount of carbide slag is 1.0 wt%, the hydration products are most closely combined.With the increase of calcium carbide slag doping, the setting time of the modified cementitious powder gradually decreases, and the compressive strength and chemical binding water content at 28 d first increase and then decrease.When the doping amount of carbide slag is 1.0 wt%, the compressive strength and chemical binding water content at 28 d reach the maximum, which are 2.98 MPa and 6.8% respectively.This is because the addition of appropriate amount of calcium carbide slag accelerates the hydration reaction of cementitious powder, increases its structural compactness, and improves the mechanical properties of cementitious powder.It can be seen that the optimum doping amount of carbide slag is 1.0 wt%. [ABSTRACT FROM AUTHOR]

Al-based particle-reinforced composites have become the focus research around the world due to their unique quality, economic and performance advantages. Powder metallurgy method has the advantages of flexible selection of reinforced particles, accurate and controllable content, and strong designability, which is one of the commonly used methods for preparing particle reinforced Al matrix composites and is favored by many scholars. The present paper firstly gives a brief introduction to the development of Al matrix composites. Secondly, the densification molding technology and sintering process in powder metallurgy process are summarized. Subsequently, the composition design, such as reinforcement type, content, particle size, distribution, etc., interface wettability and its control, the relationship between microstructure characteristics and mechanical properties, and the strengthening mechanism were mainly discussed. Finally, it analyses the problems and challenges faced by powder metallurgical particle-reinforced Al matrix composites and looks forward to their development. [ABSTRACT FROM AUTHOR]

In view of the current research status that the experimental methods to study the effect of solute rare earth on the mechanical properties of steel has not achieved satisfactory results, in this paper, a system research was carried out by means of simulation calculation, and first-principles calculation method based on density functional theory was used to reveal the solid solution mechanism of Ce atoms in α-Fe by solvation energy, geometric structure, electronic structure, and Bader charge. And the mechanical properties of Fe-Ce doped system were calculated in detail. The calculation results of the solvation energy show that Ce can occupy the α-Fe matrix by replacing Fe atoms. In Fe-Ce doped system, Ce atoms lose electrons, resulting in a reduction in the radius of Ce atoms and a polarization effect, which is conducive to the solid solution of Ce in Fe. The calculation results of the mechanical properties of pure Fe and Fe-Ce doped system show that Ce doping reduces the incompressibility, shear strain resistance, rigidity, and Vickers hardness of the system, but improves the toughness and workability of the system. Ce doping leads to a decrease in the strength of the metallic bond of the system, which is the main reason for the decrease in the incompressibility, rigidity and hardness of Fe-Ce doped system. On the other hand, the doping of Ce increases the density of the electron cloud in the system, which is conducive to the improvement of the toughness of the doped system. [ABSTRACT FROM AUTHOR]

Graphene (G)/graphene oxide (GO) has shown promising applications in improving the mechanics and functionality of cement materials with its excellent mechanical, electrical, and thermal conductivity properties. However, these nanomate rials are difficult to disperse in cement-based materials, which limits their practical application in cement-based composites. Tn recent years, researchers have begun to mix fibers with these nanomaterials into cement-based materials, and its dispersion performance has been greatly improved. Tn this paper, the influence of graphene, GO and other fiber mixture on cement-based composite materials is systematically described from five aspects of material dispersion in cement, cement hydration process, mechanical properties, functionality and durability, which has a guiding role in improving the performance of cement-based composite materials in the future. [ABSTRACT FROM AUTHOR]

In this paper, the effect of service conditions at different temperatures ( 77K ~ 77:3 K) on the mechanical properties of entropy alloy in VCoNi was studied. Grain size of VCoNi alloy was adjusted by large deforma tion rolling and short time annealing. The change rule of material mechanical properties was st udied by quasi static tensile test and the internal mechanism was explained by microscopic observation. at 77 K, a large number of twins and twisted dislocations in the material made the alloy have excellent comp rehensive properties. With the increase of experimental temperature from 29:3 K tO 57:3 K, the elongation and mechanic;d properties of the materials remained stable. When the experimental tempen1ture reached :37:3 K, the serneted flow appeared on the stress-strain curve. [ABSTRACT FROM AUTHOR]

In this paper, high purity Ta-Ru alloy was prepared by powder metallurgy hot press sintering. Tantalum ruthenium powder with high purity was mixed in different composition ratio on planetary ball mill, and hot pressed for 3 h at 1 700 ℃ and 20 MPa in vacuum hot pressing sintering furnace. The effect of different Ru contents on the phase composition, microstructure and mechanical properties of Ta-Ru alloys were investigated by XRD, SEM, EDS, tensile strength test and other analytical methods. The results show that, with increasing Ru content, several intermetallic compounds such as TaRu, Ta3Ru, and TaRu4 were successively formed in the alloy. The density and tensile strength of the alloy increased gradually, and the microhardness increased first and then decreased. The fracture mode changed from cleavage fracture to intergranular fracture and ductile fracture. [ABSTRACT FROM AUTHOR]

In this paper, two series of quick-setting 3D printing cement-based materials were prepared with fast hard sulphoaluminate cement and ordinary Portland cement as basic cementing materials, supplemented by water reducing agent, coagulant and volume stabilizer, etc., in order to achieve rapid printing. The experimental results show that the prepared quick-setting 3D printing cement-based material could control the setting time within 5-20 min. The printed specimen had good construction performance with the over all deformation less than 5% and the lowest deformation less than10%. The printed specimen had early and late strength, and the simulated print sample strength loss rate did not exceed 15%, meeting the requirements of architectural 3D printing materials for work performance and mechanical properties. [ABSTRACT FROM AUTHOR]

Polymer cement concrete has become an important part of high-performance concrete research, Tn this paper, a polymer emulsion (styrene-butadiene latex,SBL) was adopted to modify high-performance concrete？ and effects of different additive amounts on basic mechanical properties􀀀 toughness􀀀 autogenous shrinkage and chloride penetration resistance of cement concrete were studied. The results show that the compressive strength of cement concrete modified by SBL decreased with the increase of the content of SBL? while the addition of SBL could greatly improve the splitting tensile strength? flexural strength and toughness of concrete. When SBL addition was 1 5% 􀀀 the enhancement was most obvious􀀀 and the increase of splitting tensile strength and flexural strength was 17.4% and 23,8%,respectively. The toughness index reached its peak at 10% SBL? with the increase of 71.1 The total shrinkage value for 24 h after pouring of the modified cement concrete decreased with the increasing addition of SBL. The total shrinkage decreased by up to 35% at SBL. At the same time, the anti-chloride diffusion ability and anti-permeability performance of modified cement concrete were improved obviously. [ABSTRACT FROM AUTHOR]

Due to high melting point，high strength，strong oxidation resistance and deformation resistance at elevated temperature，refractory metal silicides have attracted extensively attention. In the refractory metal silicides αthe tungsten-silicon binary compounds，where tungsten has the highest melting point，not only have the similar mechanical and physical properties compared to other metal silicides，but also show many other excellent performance characteristics. The theoretical investigation of tungsten-silicon binary compounds was presented by first-principles calculation to fully exploit the potential performance of tungsten-silicon binary compounds. Two prototype structures of WSi2 compounds and three prototype structures of W5Si3 compounds had been taken into account ： a-WSi2 (C40), (3-WSi2 (C l l b) αW5 Si3-prototype structure (D8m)，Cr5B3-prototype structure (D8i) and Mn5 Si3-prototype structure (D88). The formation enthalpies were calculated to analyze the stabilities αand the elastic constants，bulk modulus，shear modulus，tensile modulus，Poisson's ratio，anisotropy factor and Vickers hardness were calculated to obtain the mechanical properties. Otherwise，the total and partial density of states were also calculated to obtain the bonding mechanisms of tungsten-silicon binary compounds. The stability calculation indicated that the stability sequence of the five tungsten-silicon compounds forms the following order ： (3-WSi2 >a-WSi2 > W5 Si3-prototype structure>Mn5 Si3-prototype structure〉Cr5B3-prototype structure，and the results of density of state further verified it. The calculation results of mechanical properties showed that the five stable phases of WSi2 and W5S3 with good shape，toughness and hardness are agreement with the mechanical stability. Among them9 the shape，toughness and hardness of (3-WSi2 are the highest9 while those of Cr5 B3-prototype structure are the lowest. The calculation of elastic constants showed that for a-WSi2， Mn5Si3-prototype structure， W5Si3-prototype structure and Cr5B3-prototype structure， the bondings along [100] and [010] directions are stronger than that along [001] direction，and the [100](010) shear is easier than [100](001) shear. On the contrary，for (3-WSi2，the bondings along [100] and [010] directions are weaker than that along [001] direction，and the [100](010) shear is similar with the [100](001) shear. The results of total and partial density of states exhibited that the bonding mechanisms of these five compounds are all the mixture of strong covalent and certain metal bonds. In this paper，a new idea and theoretical foundation of new materials based on tungsten-silicon binary compounds will be provided. [ABSTRACT FROM AUTHOR]

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