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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]

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]

Geopolymer is a new green cementitious material, which has many excellent properties in mechanical properties and durability, but also has some shortcomings. It is feasible way to overcome the disadvantages of geopolymer by using the advantages of nano materials. In this paper, the influence of nano materials blending geopolymer on the workability, mechanical properties and durability of the mixture was systematically de scribed. The influence mechanism was summarized and the existing problems of nano modified geopolymer were discussed. The future modification research may include revealing the influence mechanism, focusing on the comp<1tibility and synergy between nano materials and other components, accunnely designing and developing nano core-shell particles suitable for geopolymer reaction system, and quantificationally evaluating the disper sion of nanoparticles in aqueous solution and colloidal environment. Improving the modification effi ciency of nano particles provided a reference for the future research on nano modified geopolymer. [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]

From the perspective of materials research, in this article, the latest developments in equipment and technology of selective electron beam meting process (SEBM), and the published data on the mechanical properties of orthopedic medical materials were reviewed. The technical barriers of current orthopedic medical materials fabricated by SEBM technology alloys were mainly analyzed in detail. Suggestions for further development on biomaterials 3D printing industry were also given at the end of the paper. [ABSTRACT FROM AUTHOR]

Different amounts of PTFE were doped in the process of Cr3+ electroplating to form Cr3+ composite coating. The effects of PTFE particles with different concentrations on the micro-structure and mechanical properties of Cr3+ composite coating were studied in this paper. The micro-structure and mechanical properties of Cr3+ coating were characterized and tested by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), nano-indenter and friction wear testing machine, respectively. The results show that different concentrations of PTFE had significant effects on the micro-structures and mechanical properties of Cr3+ composite coatings. When the concentration of PTFE in the plating solution was 12.5 mL/L, the current density was 35 A/dm², the pH was about 2.0, the temperature was 45 °C, and the deposition time was 20 min, the obtained Cr3+ composite coating had the best comprehensive performance, with the hardness of 6.8 GPa and the lowest friction coefficient value of 0.28. [ABSTRACT FROM AUTHOR]

Wood-plastic composite made of wood processing residues/bamboo charcoal powder/PP was successfully prepared by double screw extruder and injection molding machine. In this paper, the interface adhesion of wood chip and bamboo charcoal powder embedding m wood -plastic composites were studied by scanning electron microscope. The tensile strength, thermodynamis properties, infrared spectra and resistance of composites were tested by electronic universal testing machine, differential thermal analyzer. Fourier infrared spectrometer and resistance measuring instrument. The results showed that when the bamboo charcoal content was 10%-20%, the combination of bamboo charcoal powder and matrix was better. When the bamboo charcoal content increased from 10% to 50%, the tensile strength of the composite decreased from 34.25 to 22.36 MPa, with a decrease of 33.60%, and the elongation decreased from 9.48% to 4.10%, with a decrease of 56.75%, but the elastic modulus of the composite increased from 388.10 to 461.63 MPa, with an increase of 18.95%. In addition, with the increase of bamboo charcoal powder content m a certain range, the water absorption, resistivity and conductivity of the composites increased. [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]

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Coral concrete with coral crumbs as coarse aggregate and coral sand as fine aggregates plays a huge role in solving the shortage of materials in the construction of distant island reefs. This paper began with a scientific measurement analysis of mainstream journals, keywords, scholars and institutions active in coral aggregate concrete research. Then the problems of preparation, mechanical properties, durability and microstructure of coral concrete were summarized, and the shortcomings of coral concrete research were proposed. [ABSTRACT FROM AUTHOR]

In this paper, Ag-15Cu-10Au-2Ni alloy has been fabricated by vacuum induction melting, and the plastic deformation and microstructure, mechanical and electrical properties after heat treatment were investigated. The results show that the Ag-15Cu-10Au-2Ni alloy was mainly composed of silver-rich phase and copper-rich phase, as well as Ni mostly existed in copper-rich phase. The significant strengthening effect could be observed obviously, while the hardness was 201 Hv (90 Hv as cast condition) and the tensile strength was 744 MPa for the 95% deformed alloy. For the specimen annealed at 650 °C for 1 h, the elongation reached 31.8% and the hardness was close to that of the cast condition. The resistivity of the alloy decreased at first and then increased with the increase of annealing temperature. The alloy annealed at 350 °C for 1 h had minimum resistivity (3.98 Ωµ ⋅ cm) due to the emerge of order phase transition after annealing at low temperature region. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) is easily precipitated n high-calcium and high-alkaline cement pastes. In this paper, the dispersion effects of different water-reducing, such as different polycarboxylates (PC1, PC2, PC3), sulfamic acid (A1), and aliphaic (B1), on GO were studied, and the effect different water-reducing on compressive strength, flexural strength and Hudity of GO compounded cement mortar was investigated. The results showed that the mechanical strength of the cement mortar specimens with GO add-on was the largest when the GO content was 0.03%. The compressive strength and lexural strength of the cement mortar sample with GO add-on were increased by 45.26% and 50.66% compared with the blank samples. 28 d compressive strength and flexural strength also increased by 27.24% and 9.3% compared with the blank samples. In terms of fluidity, compared with the blank specimens, except for PC1, several other water reducing agents could make the flow of GO--mixed mortar almost unchanged. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) results of the hardened cement showed that the add-on of PC2 could effectively promote the growth of Aft crystals of the really cement hydration product, and greatly improved the really flexural and compressive strength of the cement mortar. The results of fared spectroscopy (FT--R) and Raman spectroscopy(Raman) showed that the water-reducing PC2 could make GO more disperse n the simulated cement slurry, and the epoxy group in GO could participate in the cement hydration reaction, making a strong interface force between GO and cement hydration products. [ABSTRACT FROM AUTHOR]

The effects of Cu addition on the microstructure, corrosion resistance and mechanical properties of Ni-P-PTFE composite coatings were studied in this paper. The microstructure, corrosion resistance and mechanical properties of the coatings were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), electrochemical workstation, nano-indenter, and friction wear testing machine, respectively. The results show that Cu addition has great influence on the composition, microstructure, corrosion resistance and mechanical properties of Ni-P-PTFE composite coating. With the increase of Cu2+ concentration in the plating solution, Cu content in the coating first increased and then decreased, while the content of Ni, P, and PTFE first decreased and then increased. With the increase of Cu content in the coating, the corrosion resistance and hardness of Ni-Cu-P-PTFE composite coatings improved, while the friction performance decreased. [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]

Carbon nanotube aerogel is a kind of carbon nanotube with dispersed properties. In this paper, carbon nanotube aerogels were prepared by independent research and development. The carbon nanotube aerogels/natural rubber composites were prepared by traditional crafts. The mechanical properties and thermal conductivity of the as-prepared composites were studied. The results suggest that the tensile strength, tear strength and thermal conductivity of the composites are 47%, 52% and 49.9%, respectively higher than those of the carbon black/natural rubber composites, and reveal the good dispersion characteristics and broad application prospects of the carbon nanotube aerogels. [ABSTRACT FROM AUTHOR]