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The graphite conductive phase material is used to replace the fine aggregate to prepare the functional conductive concrete, and the concrete matrix can be heated by electricity heating to achieve the purpose of snow melting and ice melting. Resistivity is the main index to measure the electrical conductivity of concrete, which is easily affected by factors such as concrete moisture content and ambient temperature. Tn this paper, graphite, graphite ore and graphite tailings were used as conductive phases to prepare conductive concrete. The mechanical properties of three kinds of graphite conductive phase concrete, the resistivity evolution law and microscopic properties of graphite concrete under different temperatures and water contents were studied, and the conductive mechanism of graphite concrete was analyzed. The results show that the increase of conductive phase content, temperature and water content reduces the resistivity of concrete, and the incorporation of conductive phase reduces the resistivity most significantly. Tn addition, the results of SEM and EDS tests showed that the content of carbon in the concrete matrix increased significantly under different dosage conditions, which verified that the addition of graphite materials could promote the electrical conductivity of concrete, but it would cause holes and micro-cracks in the concrete matrix, which had an adverse effect on the strength of graphite concrete. [ABSTRACT FROM AUTHOR]

Aluminum matrix composites prepared via in-situ synthesis technology weigh the contradiction between strength and plasticity, which is expected to realize the integration of structure and function of aluminum matrix composites. In-situ synthesis of TiB2 particles reinforced aluminum matrix composites has high specific stiffness and modulus, excellent mechanical properties, corrosion resistance, wear resistance and fatigue resistance, which is one of the research hotspots of metal matrix composites in recent years and has broad application prospects in automobile manufacturing, highspeed trains, aerospace and national defense and military fields. In this paper, the characteristics and advantages of three reaction systems, Al-K2TiF6-KBF4 system, Al-TiO2 B2 O3 system and Al-Ti-B system, for in-situ synthesis of TiB2 particles reinforced aluminum matrix are summarized, the research status of the influence of TiB2 particles on the grain size, interfacial bonding and wettability of aluminum matrix is summarized, and the mechanism of TiB2 particles reinforced aluminum composites is discussed. The unsolved problems in this field are summarized, and the potential development space of TiB2 particles reinforced aluminum matrix composites prospected, so as to provide reference for the research and development of in-situ synthesized particles reinforced aluminum matrix composites. [ABSTRACT FROM AUTHOR]

In this paper, five high-entropy alloys, CoCrFeNiSn, Co0.5CrFeNiSn, CoCr0.5FeNiSn, CoCrFe0.5NiSn and CoCrFeNi0.5Sn, were designed and prepared by adding Sn element and changing the content of each element based on CoCrFeNi alloy. Among them, CoCrFeNiSn, Co0.5CrFeNiSn, CoCr0.5FeNiSn and CoCrFe0.5NiSn alloys are composed of FCC phase(black phase) and hexagonal phase(gray phase), and eutectic structure appears in these alloys, especially for CoCrFe0.5NiSn alloy. The CoCrFeNi0.5Sn alloy is composed of FCC (face-centered cubic) phase (black phase) and tetragonal phase(gray phase), and no eutectic structure is observed. By observing the change of eutectic structure volume, it is found that the reduction of Fe element is beneficial to the formation of eutectic structure, and the reduction of Ni element is not conducive. The results of EDS (energy dispersive spectroscopy) analysis showed that Ni and Sn are segregated in the gray phase, and Co, Cr and Fe are segregated in the black phase. In addition, when the content ratio of Ni and Sn in the gray phase is in the range of 1.15 to 1.25, it is favorable for the formation of the hexagonal phase, otherwise the gray phase tends to form the tetragonal phase. This paper has certain reference and guiding significance for the design and development of eutectic high-entropy alloys with HCP structure. [ABSTRACT FROM AUTHOR]

In recent years, nanofibers have excellent properties used in fuel cell materials, which has attracted widespread attention. Electrospinning technology is a low-cost, efficient, controllable, and easy-to-operate fiber preparation method. The micromorphology of the electrode material has a significant impact on cell performance. In this paper, the influencing factors of electrospinning technology are summarized into three categories: internal parameters, process parameters and environmental parameters. The influence of these parameters on the micromorphology of materials as discussed. Furthermore, the fiber structure formed by electrospinning as summarized, with a focus on the performance obtained on different microstructures. In addition, the latest research progress on electrospinning for solid oxide fuel cell materials as summarized. Finally, the development status of composite electrode materials and their microscopic formation mechanism are particularly emphasized' providing research ideas for relevant researchers. [ABSTRACT FROM AUTHOR]

Carbon nanotubes are a new type of material with excellent properties, and their incorporation into cementitious materials can improve the microstructure and durability of the material. This paper reviews the research progress on the effect of nucleation, filling and bridging properties of carbon nanotubes on the microstructure and carbonation resistance of cementitious materials, and discusses the mechanism of the effect of the doping amount, dispersion method and length-to-diameter ratio of carbon nanotubes on the carbonation reaction of cementitious materials. The analysis shows that carbon nanotubes promote the hydration of cement by nucleation, increase the hydration product Ca(OH)2, increase the alkalinity of the matrix and slow down the carbonisation, and optimise the pore structure of the material and the compactness of the interfacial transition zone by combining the filling and bridging effects, inhibit the formation of microcracks and prevent the infiltration of CO2, thus optimising the microstructure of cement-based materials and enhancing their anti-carbonisation properties. Finally, the problems of the current research are analyzed and the prospects of its research are given. [ABSTRACT FROM AUTHOR]

3D printing technology has been significantly developed in the construction field, and in order to address the concrete 3D printing industry to achieve sustainable development, this paper analyzes the causes of deterioration by conducting freezing resistance studies on 3D printed specimens and cast specimens with 0%, 50%, and 100% recycled coarse aggregate（RCA） substitution, combined with electron microscopy scans of the transition zone at the interface of 3D printed recycled coarse aggregate concrete（3DPRAC）. The results showed that the incorporation of RCA in the first 200 freeze-thaw cycles did not significantly reduce the mass and dynamic modulus of 3D printed concrete; after 600 freeze-thaw cycles the 3D printed recycled concrete with 100% RCA incorporation performed better than that with 50% RCA incorporation in the freeze-thaw cycles. Based on the construction characteristics of 3D printed recycled concrete stacked layer by layer, a 3DPRAC pore area concentration distribution model was proposed to reveal the 3DPRAC freeze-thaw damage deterioration mechanism. The established freeze-thaw damage model can better reflect the change pattern of 3DPRAC freeze-resistance performance. [ABSTRACT FROM AUTHOR]

NaC-MgCl2 eutectic salt and α-Al2O3 are selected as phase change material (PCM) and encapsulation material, respectively. Six kinds of NaC-MgCl2 eutectic salt/α-Al2O3 ceramic medium-high temperature composite phase change material (CPCM) with different mass ratios are prepared by spark plasma sintering (SPS) process. The microstructure and thermodynamic properties of CPCM are analyzed by scanning electron microscope (SEM), electron probe micro-analysis (EPMA), X-ray diffraction (XRD), high temperature laser thermal conductivity meter and differential scanning calorimeter-thermogravimetric analyzer (TG-DSC). The changing and discharging rates of CPCM are analyzed by finite element simulation. The results show that after sintered at 550 °C, α-Al2O3 ceramic plays a good role in encapsulation and effectively reduces the weight loss rate of NaC-MgCl2 eutectic salt at high temperature. Compared with NaCl-MgCl2 eutectic salt, the overall thermal conductivity of CPCM is significantly improved, and the phase change time is greatly shortened, indicating that the heat charging and discharging rates of CPCM are significantly improved. The medium-high temperature CPCM has dense microstructure, and the distribution of all elements in CPCM is natively uniform. The distribution of Na and Mg elements is superposition, indicating that there is no chemical reaction between NaCl-MgCl2 eutectic salt and α-Al2O3, and CPCM has good chemical stability. The melting point of NaC-MgCl2 eutectic salt/α-Al2O3 ceramic medium-high temperature CPCM is 408.7 °C, the latent heat of phase transition is 142.6 J/g, and the thermal stability is good at 500-650 °C. This paper provides a novel experimental basis for the preparation and characterization of eutectic salt/ceramic CPCM. [ABSTRACT FROM AUTHOR]

SnO2 pressure-sensitive ceramics is a new type of high-nonlinear ;ind high-gradient press ure-sensitive ceramics. It has good swbility in b0th acidic and alkaline environments, making it ideal for outdoor work. How ever, the comprehensive performance of SnO2 varistor is not comparable to that of mainstream ZnO2 varistor, especially the non-ohmic characteristics need to be further improved. In this paper, based on the basic form ula of SnO2 • CO2 • Nb,O2,• CrO2 different contents of Y1 0O2were added to explo re the SnO2 varistOr with better comprehensive performance through tn1ditional sintering process. The formation mechanism of SnO2 varistor e lectrical characteristics was studied by SEM, E-J, C-V and X-ray diffraction. Results show that when adding O2mol% Y1O2 samples of the electrical properties of the best (voltage gradient of 76:3 v/ mm, leakage current of 10.:3 Y/\/ cm³ nonlinear coefficient of 47.5). This study had important reference value for SnO2 rheost at with high nonlinear and low leakage current. [ABSTRACT FROM AUTHOR]

3D printing technology has the characteristics of not requiring mold and manufacturing cost to be insensitive to the complexity of design, and is suitable for manufacturing complex structure products such as structure-function integration, bionics design, lightweight dot matrix structure, thin wall and the like. However, due to some unavoidable defects in the interior and surface, it is necessary to combine appropriate post-treatment to improve the microstructure and defects of the metal parts. In this paper, the research progress of different post-processing of 3D printing parts from domestic and foreign scholars were summarized from three aspects of microstructure, internal defects and surface defects, and the mainstream direction of future 3D printing post-processing research was analyzed, providing a reference for 3D printing technology to produce more qualified parts. [ABSTRACT FROM AUTHOR]

In this paper, the microstructure of Fe73.3 Cu Nb3 Si133 B9 amorphous ribbons annealed at different temperature and different stress for 60 min was observed by the synchrotron radiation technique. The giant magne-to-impedance ratio and magnetic anisotropy of the corresponding samples were measured by HP4294A impedance analyzer. The results show that under the condition that the annealing temperature was lower than the glass-transition temperature of FeCuNbSiB, the samples were sill amorphous which annealed under different stress, and the shape of giant magneto impedance curve had changed and the wide linear property had appeared. When the stress was 112.1 MPa, the maximum giant magneto impedance ratio of the sample reached 1 818.7%, which was 1.9 times higher than that under free annealing. After fitting the experimental data, it was found that the maximum giant magneto impedance ratio and magnetic isotropy field of the sample were linearly related to the opted stress, and the magnetic inductance sensitivity had a negative exponential relationship with the opted stress. It was found that the magnetic properties of Fe-based alloy ribbons with amorphous structure were sensitive to stress, which could be used as another new direction to study the stress sensitivity of amor-phous nanocrystal alloy materials. [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]

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]

Nickel-based superalloys are widely used in the manufacture of aerospace jet engines and the hottest end parts of various industrial gas turbines due to their high strength, good resistance to oxidation and gas corrosion under high temperature and high pressure conditions. In this paper, firstly, the domestic and international research status of 3D printing nickel-base superalloy parts and simulation by selective laser melting forming technology (SLM) were introduced, and then the mechanical properties and microstructure of nickel-base superalloys by SLM technology and the effects of post-treatment on their microstructure and properties were sum-merized. Secondly, the simulation of the additive manufacturing process was investigated, and its guiding significance to the process was introduced. Finally, the research hotspots in the field of SLM forming nickel-based superalloys and the application of numerical simulation in this field were further introduced. [ABSTRACT FROM AUTHOR]

Tri view of the growth characteristics of microcrystalline silicon thin films which first undergo amorphous transition layer before crystallization, in this paper, it was attempted to prolong the diffusion time of deposited atoms on the growth surface of thiri films by reducing the deposition rate of thin films？ in order to promote grain growth. The results show that the deposition rate decreased with the decrease of gas flow. And as the deposition rate decreased ？ surface roughness decreased obviously and the average grain size improved. Grains which were bigger than 10 nm could be observed in H R T E M photos, which indicated that the decrease of the deposition rate had a great effect on the diffusion of deposited particles on growth surface. At the same time ？ the change rule of minority carrier lifetime agreed with the change rules of the crystallinity and average grain size？ which showed a decisive effect of the microstructure on electrical properties. [ABSTRACT FROM AUTHOR]

In this paper, graphene was synthesized on sapphire substrate by chemical vapor deposition (CVD) method, and the effect of growth time on hydrophobic properties and microstructure of graphene was investigated. Contact-angle meter, Fourier transform infrared spectrometer, Raman spectrometer and field emission scanning electron microscopy were applied to study hydrophobic and microscopic structure of graphene, respectively. It shows that after growing 30 min, maximum contact angle of graphene is 129.96°, it presents hydrophobic properties. Meantime, infrared test shows only carbon-carbon double bonds. Raman analysis also indicates three characteristic peaks of graphene after growing 10-30 min. larger contact angle makes graphene as a potential hydrophobic material, and it can even be a promising superhydrophobic material by its hydrophobic modification. [ABSTRACT FROM AUTHOR]

Vanadium-based hydrogen storage alloys can be introduced lattice defects during ball milling, and the defects can decay the hydrogen storage characteristics. In this paper, the relationships between the micro-strains of V60Ti25Cr3Fe12 alloy powder with average particle size of 100nm to 2μm prepared by ball milling and the hydrogen absorption and desorption properties was studied by XRD, TEM, SEM and PCT. The results show that the ball milling process introduces amorphization, lattice distortions, dislocations, and micro-strains. The function of the milling time (x1) and the micro-strain (y1) of the alloy paticles after heat treatment at 400°C is y1=0.313+0.170 x1-0.00695 x12, and the function of the micro-strains changing rate is y1'=0.170-0.0139 x1. With the increase of milling times, the micro-strains changing rate (y1') decreases linearly. The initial y1' is the maximum y1' (0) (max) = 0.170 (%h-1), thus the micro-strains accumulated rapidly. After milling for 12h, y1'(12) = 0.0032 (%h-1) makes the accumulation of micro-strains tend to be saturated. The milling time increased from 0h to 12h, and the micro-strains increased from 0.313% to 1.354%.The rising of the micro-strains leads to the content of the dihydride (γ-phase) decreases from 65.2% to 13.2%, and the content of the mono-hydride (β-phase) increases from 32.5% to 80.3%, Which results in an effective hydrogen release amount decrease from 1.81 wt% down to 0.58 wt%. The functional relationship of the micro-strains (x2) with the effective hydrogen release amount (y2) and is y2=1.999-1.124 x2. [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]

A safe and stable electro-polished solution containing concentrated sulfuric acid and ethylene glycol was investigated in this paper, which can be used to electro-polish NiTi alloy. The effects of different conditions on the microstructure and surface roughness of the electro-polished samples were investigated by changing the concentration of sulfuric acid, the electro-polishing voltage and temperature. The trend of the corrosion resistance and the radial force about electro-polished samples and the ground samples was investigated as well. The results show that the best electro-polishing condition was 7 mol/L concentrated sulfuric acid, 10 V voltage and 20 °C, respectively, which got the minimum surface roughness (112.9 nm) of the electro-polished samples. While the corrosion resistance could be improved obviously after electro-polishing by forming the passivation layer and the radial force was also controlled effectively by electro-polishing. [ABSTRACT FROM AUTHOR]

The Cr2N films were deposited by hot wire plasma enhanced magnetron sputtering (PEMS) on substrate of 31 6L austenitic stainless steel at different target current density. The effect of target current density on the morphology, phase structures, mechanical properties, adhesion between film and substrate and abrasive resistance of Cr2N films were investigated in this paper. The results showed that the main preferred orientation of the dense columnar Cr2N films was (111), and together existed of WN (101) for the film deposited at the low target current density of 0.132 mA/mm2. With increasing target current density, the deposition rate of the films increased, the nano-hardness and Young's modulus decreased and the adhesion between film and substrate increased. The Rockwell indentation fracture indicated brittle failure of the bonding between the film and substrate. The maximum nano-hardness and modulus of the film deposited at lowest target current density of 0.132 mA/mm² were 33 and 450 GPa, respectively, and the wear resistance was the highest. The maximum adhesion between film and substrate of the film deposited at the highest targets current density of 0.264 mA/mm² was 36.6 N. The hardness and wear resistance of the 31 6L steel were improved significantly after coated with Cr2N films. [ABSTRACT FROM AUTHOR]