To optimize their Al_(2)O_(3)-SiO_(2) raw materials,anorthite based insulation refractories were prepared by the in-situ sintering process combined with the foaming method after sintering at 1350℃for 3 h,using green ...To optimize their Al_(2)O_(3)-SiO_(2) raw materials,anorthite based insulation refractories were prepared by the in-situ sintering process combined with the foaming method after sintering at 1350℃for 3 h,using green and pollution-free kaolin,kyanite,andalusite and sillimanite as Al_(2)O_(3)-SiO_(2) raw materials,respectively,and industrial CaCO_(3) as the CaO source.Effects of Al_(2)O_(3)-SiO_(2) raw material types on the physical properties,phase composition and microstructure were investigated.The results are as follows.All samples prepared by different Al_(2)O_(3)-SiO_(2) raw materials have hexagonal flake anorthite and a small amount of mullite and corundum.Their bulk density and thermal conductivity decrease in the order of using kaolin,andalusite,kyanite and sillimanite as the Al_(2)O_(3)-SiO_(2) raw material,but their apparent porosity increases.Moreover,in the sample with kaolin,the bonding between anorthite crystals on the pore walls is closer than that of the other samples,which is conducive to increasing the cold crushing strength.The bonding between anorthite crystals on pore walls gradually decreases in the order of using kyanite,andalusite and sillimanite as the Al_(2)O_(3)-SiO_(2) raw material,thus their cold crushing strength decreases accordingly.In comprehensive consideration,the properties of the sample from kyanite are the optimal.Its apparent porosity,thermal conductivity and cold crushing strength are 84.6%,0.141 W·m^(-1)·K^(-1) and 1.89 MPa,respectively.展开更多
Purpose: The study investigated the impact of dietary habits, specifically soda, milk kefir, water kefir, almond milk, and distilled water (control) consumption, on the microhardness of gingiva-coloured composite and ...Purpose: The study investigated the impact of dietary habits, specifically soda, milk kefir, water kefir, almond milk, and distilled water (control) consumption, on the microhardness of gingiva-coloured composite and acrylic denture bases. Methods: Materials included gingiva-coloured composite (Fusion Universal G1), acrylic (Imicryl), and subdivided Procryla group. Subgroups comprised 15 and 30-minute heat polymerized (Pro15, Pro30), and 1 wt% (Pro1Z) and 3 wt% (Pro3Z) zirconium added groups. Immersed in beverages for 1, 7, and 14 days, pH and microhardness were assessed. SEM examined random samples. Statistical analysis used repeated measures ANOVA, and post hoc tests (p Results: The gingiva-coloured composites displayed noteworthy time-associated microhardness changes (p 0.05). Despite variable pH levels in beverages, no substantial group interaction effects were observed (p > 0.05). Initial microhardness rankings shifted after a 14-day immersion. Conclusions: Gingiva-coloured composite exhibited the highest microhardness pre- and post-immersion, followed by Procryla30 and Imicryl groups. .展开更多
This study aims to quantify the susceptibility of granular materials used in pavements to changes in moisture content and propose a correlation model to incorporate this susceptibility into seasonal analyses.The fines...This study aims to quantify the susceptibility of granular materials used in pavements to changes in moisture content and propose a correlation model to incorporate this susceptibility into seasonal analyses.The fines content and the percentage of fractured coarse aggregates were identified as direct indicators of the resilient modulus susceptibility to changes in water content.The results showed that the percentage of fractured coarse aggregates particles(FR)has a more significant impact on the resilient modulus(Er)of crushed granular materials used in pavement construction than the combined indicator of the fines content and sample volumetrics(nf).Crushed granular materials with a higher percentage of fractured coarse aggregates are relatively insensitive to changes in the degree of saturation,but become more sensitive as the fine fraction porosity decreases.An adjusted model was proposed based on the existing formulation,but considers a complex parameter to describe and adjust the sensitivity of base granular materials to variations in moisture content with respect to fabrication charac-teristics,fines content and volumetric properties.The model shows that the variation of Er values is below10%for fully crushed granular materials.However,it reaches approximately±12%for materials with 75%of crushed coarse aggregates andþ40%and-25%for materials with FR=50%.This model could help select good ag-gregates characteristics and adjust grain-size distribution for environments where significant moisture content variations can occur in the pavement system,such as in the Province of Quebec(Canada).As it is based on pa-rameters that can be easily determined or estimated,it also represents a valuable tool for detailed design and analysis that can consider material characteristics.展开更多
The shortage of fresh water in the world has brought upon a serious crisis to human health and economic development.Solar‐driven interfacial photothermal conversion water evaporation including evaporating seawater,la...The shortage of fresh water in the world has brought upon a serious crisis to human health and economic development.Solar‐driven interfacial photothermal conversion water evaporation including evaporating seawater,lake water,or river water has been recognized as an environmentally friendly process for obtaining clean water in a low‐cost way.However,water transport is restricted by itself by solar energy absorption capacity's limits,especially for finite evaporation rates and insufficient working life.Therefore,it is important to seek photothermal conversion materials that can efficiently absorb solar energy and reasonably design solar‐driven interfacial photothermal conversion water evaporation devices.This paper reviews the research progress of carbon‐based photothermal conversion materials and the mechanism for solar‐driven interfacial photothermal conversion water evaporation,as well as the summary of the design and development of the devices.Based on the research progress and achievements of photothermal conversion materials and devices in the fields of seawater desalination and photothermal electric energy generation in recent years,the challenges and opportunities faced by carbon‐based photothermal conversion materials and devices are discussed.The prospect of the practical application of solar‐driven interfacial photothermal conversion evaporation technology is foreseen,and theoretical guidance is provided for the further development of this technology.展开更多
In recent years, additive manufacturing (AM), known as “3D printing”, has experienced exceptional growth thanks to the development of mechatronics and materials science. Fused filament deposition (FDM) manufacturing...In recent years, additive manufacturing (AM), known as “3D printing”, has experienced exceptional growth thanks to the development of mechatronics and materials science. Fused filament deposition (FDM) manufacturing is the most widely used technique in the field of AM, due to low operating and material costs. However, the materials commonly used for this technology are virgin thermoplastics. It is worth noting a considerable amount of waste exists due to failed print and disposable prototypes. In this regard, using green and sustainable materials is essential to limit the impact on the environment. The recycled, bio-based, and blended recycled materials are therefore a potential approach for 3D printing. In contrast, the lack of understanding of the mechanism of interlayer adhesion and the degradation of materials for FDM printing has posed a major challenge for these green materials. This paper provides an overview of the FDM technique and material requirements for 3D printing filaments. The main objective is to highlight the advantages and disadvantages of using recycled, bio-based, and blended materials based on thermoplastics for 3D printing filaments. In this work, solutions to improve the mechanical properties of 3D printing parts before, during, and after the printing process are pointed out. This paper provides an overview on choosing which materials and solutions depend on the specific application purposes. Moreover, research gaps and opportunities are mentioned in the discussion and conclusions sections of this study.展开更多
Material growth and device fabrication of the first 1.3μm quantum well （QW） edge emitting laser diodes in China are reported. Through the optimization of the molecular beam epitaxy （MBE） growth conditions and the...Material growth and device fabrication of the first 1.3μm quantum well （QW） edge emitting laser diodes in China are reported. Through the optimization of the molecular beam epitaxy （MBE） growth conditions and the tuning of the indium and nitrogen composition of the GalnNAs QWs, the emission wavelengths of the QWs can be tuned to 1.3μm. Ridge geometry waveguide laser diodes are fabricated. The lasing wavelength is 1.3μm under continuous current injection at room temperature with threshold current of 1kA/cm^2 for the laser diode structures with the cleaved facet mirrors. The output light power over 30mW is obtained.展开更多
The practical application of magnesium hydride(MgH_(2))was seriously limited by its high desorption temperature and slow desorp-tion kinetics.In this study,a bullet-like catalyst based on vanadium related MOFs(MOFs-V)...The practical application of magnesium hydride(MgH_(2))was seriously limited by its high desorption temperature and slow desorp-tion kinetics.In this study,a bullet-like catalyst based on vanadium related MOFs(MOFs-V)was successfully synthesized and doped with MgH_(2) by ball milling to improve its hydrogen storage performance.Microstructure analysis demonstrated that the as-synthesized MOFs was consisted of V_(2)O_(3) with a bullet-like structure.After adding 7wt%MOFs-V,the initial desorption temperature of MgH_(2) was reduced from 340.0 to 190.6℃.Besides,the MgH_(2)+7wt%MOFs-V composite released 6.4wt%H_(2) within 5 min at 300℃.Hydrogen uptake was started at 60℃under 3200 kPa hydrogen pressure for the 7wt%MOFs-V containing sample.The desorption and absorption apparent activity energies of the MgH_(2)+7wt%MOFs-V composite were calculated to be(98.4±2.9)and(30.3±2.1)kJ·mol^(-1),much lower than(157.5±3.3)and(78.2±3.4)kJ·mol^(−1) for the as-prepared MgH_(2).The MgH_(2)+7wt%MOFs-V composite exhibited superior cyclic property.During the 20 cycles isothermal dehydrogenation and hydrogenation experiments,the hydrogen storage capacity stayed almost unchanged.X-ray diffraction(XRD)and X-ray photoelectron spectrometer(XPS)measurements confirmed the presence of metallic vanadium in the MgH_(2)+7wt%MOFs-V composite,which served as catalytic unit to markedly improve the hydrogen storage properties of Mg/MgH_(2) system.展开更多
In this article,the authors design a speaking unit based on needs analysis following Hutchinson and Waters'(1987) model.First,the rationale in designing this unit is introduced,which involves the teaching approach...In this article,the authors design a speaking unit based on needs analysis following Hutchinson and Waters'(1987) model.First,the rationale in designing this unit is introduced,which involves the teaching approach adopted and relevant theories in organizing the materials.Then,the teaching plan of this speaking unit is provided and some activities are designed to create an authentic and optimal situation for students to practice their speaking skill.展开更多
High performance aluminosilicate based cementitious materials were produced using calcined gangue as one of the major raw materials. The gangue was calcined at 500℃. The main constituent was calcined gangue, fly ash ...High performance aluminosilicate based cementitious materials were produced using calcined gangue as one of the major raw materials. The gangue was calcined at 500℃. The main constituent was calcined gangue, fly ash and slag, while alkali-silicate solutions were used as the diagenetic agent. The structure of gangue-containing aluminosilicate based cementitious materials was studied by the methods of IR, NMR and SEM. The results show that the mechanical properties are affected by the mass ratio between the gangue, slag and fly ash, the kind of activator and additional salt. For 28-day curing time, the compressive strength of the sample with a mass proportion of 2：1：1 （gangue： slag： fly ash） is 58.9 MPa, while the compressive strength of the sample containing 80wt% gangue can still be up to 52.3 MPa. The larger K^＋ favors the formation of large silicate oligomers with which AI（OH）4- prefers to bind. Therefore, in Na-K compounding activator solutions more oligomers exist which result in a stronger compressive strength of aluminosilicate-based cementitious materials than in the case of Na-containing activator. The reasons for this were found through IR and NMR analysis. Glauber＇s salt reduces the 3-day compressive strength of the paste, but increases its 7-day and 28-day compressive strengths.展开更多
Combined with DTG analysis, X-Ray diffraction analysis （XRD） and field emission scanning electron microscopy analysis （FSEM） affiliated with energy dispersive spectrometer analysis （EDS）, the early hydration and...Combined with DTG analysis, X-Ray diffraction analysis （XRD） and field emission scanning electron microscopy analysis （FSEM） affiliated with energy dispersive spectrometer analysis （EDS）, the early hydration and carbonation behavior of cement paste compacts incorporated with 30% of dolomite powder at low water to cement ratio （0.15） was investigated. The results showed that early carbonation curing was capable of developing rapid early strength. It is noted that the carbonation duration should be strictly controlled otherwise subsequent hydration might be hindered. Dolomite powder acted as nuclei of crystallization, resulting in acceleration of products formation and refinement of products crystal size. Therefore, as for cement-based material, it was found that early carbonation could reduce cement dosages to a large extent and promote rapid strength gain resulting from rapid formation of products, supplemental enhancement due to water release in the reaction of carbonation, and formation ofnanometer CaCO3 skeleton network at early age.展开更多
The effect of rare earth (RE) oxide on the microstructure and properties of TiC based cermet/Cu alloy composite hardfacing materials was investigated by using scanning electron microscope (SEM), transmission electron...The effect of rare earth (RE) oxide on the microstructure and properties of TiC based cermet/Cu alloy composite hardfacing materials was investigated by using scanning electron microscope (SEM), transmission electron microscope (TEM), impact test and wear test. The mechanism of RE oxide for improving the phase structure and the impact toughness was also discussed. The experimental results indicate that the microstructure of the matrix can be refined, and the micro-porous defects can be eliminated by adding RE oxide into the composite materials. The polycrystalline and amorphous phase structure is formed at the interface of cermet and matrix metal. The formed structure enhances the conjoint strength of interface. The frictional wear resistance can be improved obviously, although the microhardness of the matrix metal can not be effectively increased by adding RE oxide.展开更多
Sixteen controlled low-strength material( CLSM)mixtures with various cement-to-sand( C/Sa) ratios and water-to-solid( W/So) ratios were prepared using recycled fine aggregate from urban red brick based construction wa...Sixteen controlled low-strength material( CLSM)mixtures with various cement-to-sand( C/Sa) ratios and water-to-solid( W/So) ratios were prepared using recycled fine aggregate from urban red brick based construction waste.The fluidity and bleeding of the fresh CLSM mixtures were measured via the modified test methods, and the hardened CLSM mixtures were then molded to evaluate their compressive strength and durability. The results showthat the fluidity of the fresh CLSM mixtures is 105 to 227 mm with the corresponding bleeding rate of 3. 7% to 15. 5%, which increases with the increase in fluidity. After aging for 28 d,the compressive strength of the hardened CLSM mixtures reaches 1. 15 to 13. 96 M Pa, and their strength can be further enhanced with longer curing ages. Additionally, the strength increases with the increase of the C/Sa ratio, and decreases with the increase of the W/So ratio under the same curing age. Based on the obtained compressive strength, a fitting model for accurately predicting the compressive strength of the CLSM mixtures was established, which takes into account the above two independent variables( C/Sa and W/So ratios).M oreover, the durability of the hardened CLSM mixtures is enhanced for samples with higher C/Sa ratios.展开更多
ZnFe 2O 4 and ZnFe 2O 4 based materials were tested to obtain the electrical conductivity and corrosion resistance in melting bath for aluminum electrolysis. The results proved that adequate additives, such as Ni 2O 3...ZnFe 2O 4 and ZnFe 2O 4 based materials were tested to obtain the electrical conductivity and corrosion resistance in melting bath for aluminum electrolysis. The results proved that adequate additives, such as Ni 2O 3 CuO, Cu, ZnO and CeO 2 would increase the electrical conductivity, and the ZnFe 2O 4 based anodes with these additives were of good corrosion resistance. The current density on anode, the mole ratio of NaF/AlF 3 (MR) and the content of alumina in the bath effect the anode corrosion rate in different way.展开更多
High lattice match growth of InAsSb based materials on GaSb substrates is demonstrated. The present results indicate that a stable substrate temperature and the optimal flux ratios are of critical importance in achiev...High lattice match growth of InAsSb based materials on GaSb substrates is demonstrated. The present results indicate that a stable substrate temperature and the optimal flux ratios are of critical importance in achieving a homogeneous InAsSb based material composition throughout the growth period. The quality of these epilayers is assessed using a high-resolution x-ray diffraction and atomic force microscope. The mismatch between the GaSb substrate and InAsSb alloy achieves almost zero, and the rms surface roughness of InAsSb alloy achieves around 1.7A over an area of 28μm × 28μm. At the same time, the mismatches between GaSb and InAs/InAs0.73Sb0.27 superlattices （SLs） achieve approximately 100 arcsec （75 periods） and zero （300 periods）, with the surface rms roughnesses of InAs/InAs0.73Sb0.27 SLs around 1.8 A （75 periods） and 2.1A （300 periods） over an area of 20 μm×20 μm, respectively. After fabrication and characterization of the devices, the dynamic resistance of the n-barrier-n InAsSb photodetector near zero bias is of the order of 10^6Ω·cm^2. At 77K, the positive-intrinsic-negative photodetectors are demonstrated in InAsSb and InAs/InAsSb SL （75 periods） materials, exhibiting fifty-percent cutoff wavelengths of 3.8μm and 5.1μm, respectively.展开更多
Aiming at the problems of low reliability and complex operation of traditional coin-tap test of composite material,this paper introduces the grey system theory and achieves better performance.The response signals of c...Aiming at the problems of low reliability and complex operation of traditional coin-tap test of composite material,this paper introduces the grey system theory and achieves better performance.The response signals of coin-tap are classified through the grey clustering based on relation analysis,and corresponding improvements are made to the calculation method of the relation degree of nearness.First,the time history of acceleration is taken as the system behavior sequence.The improved correlation calculation method is used to solve the relation degree of nearness between the sequences,and the matrix of degree of grey relation is constructed based on this.Then,the sequence groups are summarized through the matrix,and the response signals of coin-tap are qualitatively classified according to the location of the reference sequence.Finally,the defect detection of composite materials is completed without pre-testing.The test results show that the accuracy of the coin-tap test based on improved grey clustering reaches 100%,which simplifies the operation steps while ensuring the reliability of the coin-tap test results.展开更多
Effects of calcined coal gangue （CG） aggregates treated by the surface thermal activation on the flowability and strength, and paste-CG aggregate interfaces of the cement-based material were investigated. The experi...Effects of calcined coal gangue （CG） aggregates treated by the surface thermal activation on the flowability and strength, and paste-CG aggregate interfaces of the cement-based material were investigated. The experimental results show that the compressive and flexural strength of the cement-based material with the calcined CG aggregates is much higher than that of the material with the natural CG aggregates, but the flowability of the material with calcined CG is significantly reduced with the calcined time. The strength of the material with the calcined CG aggregates only increases little with the calcined time at the same w/c ratio, but is reduced with the calcined time at the same flowability. The CG aggregates calcined by the surface thermal activation obviously overcomes the disadvantages of fully calcined CG.展开更多
To investigate value in use of liquefied wood-based resin applications in molding material, Chinese fir （Cunninghamia lanceolata） and poplar （Populus tomentosa） wood meal were liquefied in phenol. The reactant was...To investigate value in use of liquefied wood-based resin applications in molding material, Chinese fir （Cunninghamia lanceolata） and poplar （Populus tomentosa） wood meal were liquefied in phenol. The reactant was co-condensed with formaldehyde to obtain liquefied wood-based resin. For this paper, we investigated the characterization of the resin and its application in molding material. The result shows that the basic properties of liquefied wood-based resin were satisfactory; the bonding strength of plywood prepared with liquefied Chinese fir and liquefied poplar resin can reach 1.54 and 1.00 MPa, respectively. The compression strengths of the molding material prepared with two kinds of liquefied wood resin were 73.01 and 73.58 MPa, almost the same as that of PF resin molding material. The limiting volume swelling of molding material made with liquefied Chinese resin and liquefied poplar resin were 8.5% and 8.3%, thickness swelling rates of water absorption were 3.3% and 4.2%, and the maximum weight ratios of water absorption were 25.9% and 26.2%, respectively. The soil burial test result shows that the weight loss rate of the molding materials made with liquefied Chinese resin and liquefied poplar resin were 8.3% and 9.1% and that of the PF resin molding material was 7.9%. After the soil internment test, the reduction ratio of compression strength of the two kinds of molding material achieved 16.9% and 17.7%, while that of the PF resin molding material was 15.4%. The test results of wood fungi inoculation on the three surfaces of the molding material indicate the breeding rate of molding material prepared with liquefied Chinese resin and liquefied poplar resin were at level 4 and that of PF resin molding material was at level 1 of the ISO standard.展开更多
The self-healing action of a permeable crystalline coating on the po rous mortar was investigated by two times impermeability test. Moreover, the sel f-healing mechanism of cement-based materials with the permeable cr...The self-healing action of a permeable crystalline coating on the po rous mortar was investigated by two times impermeability test. Moreover, the sel f-healing mechanism of cement-based materials with the permeable crystalline c oating was studied by SEM. The results indicate that the permeable crystalline c oating not only seals the pores and cracks in mortar during its curing process, but also heals the permeable pathway caused by first impermeability test or crac ks produced by freeze-thaw cycles. Therefore, cement-based materials can be im proved by the permeable crystalline coating for the self-healing function. SEM images prove that the self-healing function is realized by generating a great q uantity of non-soluble dendritic crystalline within the pores and cracks, which prevents the penetration of water and other liquids.展开更多
The effects of the component gradient distribution at interface and the fiber gradient distribution on the strength of cement-based materials were studied. The results show that the flexural strength and compressive s...The effects of the component gradient distribution at interface and the fiber gradient distribution on the strength of cement-based materials were studied. The results show that the flexural strength and compressive strength of the mortar and concrete with interface component and fiber gradient distributions are obviously improved. The strengthes of the fiber gradient distributed mortar and concrete (FGDM/C) are higher than those of fiber homogeneously distributed mortar and concrete (FHDM/C). To obtain the same strength, therefore, a smaller fiber volume content in FGDM/C is needed than that in FHDM/C. The results also show that the component gradient distribution of the concrete can be obtained by means of multi-layer vibrating formation.展开更多
To design the high-energy-density Li-ion batteries, the anode materials with high specific capacity haveattracted much attention. In this work, we adopt the first principles calculations to investigate the pos-sibilit...To design the high-energy-density Li-ion batteries, the anode materials with high specific capacity haveattracted much attention. In this work, we adopt the first principles calculations to investigate the pos-sibility of a new two dimensional boron material, named Be, as anode material for Li-ion batteries. Thecalculated results show that the maximum theoretical specific capacity of Bc is 1653mAh g-1 （LiBl.s）.Additionally, the energy barriers of Li ion and Li vacancy diffusion are 330 meV and 110 meV, respec-tively, which imply fast charge and discharge ability for B6 as an anode material. The theoretical findingsreported in this work suggest that BG is a potential candidate as anode material of high-energy-density Li-ion batteries.展开更多
基金This work was supported by the National Natural Science Foundation of China(5180021223)Henan Provice Science&Technology Programs(232102231046 and 232102231051)Cultivation Programme for Yong Backbone Teachers in Henan University to Technology(2142121).
文摘To optimize their Al_(2)O_(3)-SiO_(2) raw materials,anorthite based insulation refractories were prepared by the in-situ sintering process combined with the foaming method after sintering at 1350℃for 3 h,using green and pollution-free kaolin,kyanite,andalusite and sillimanite as Al_(2)O_(3)-SiO_(2) raw materials,respectively,and industrial CaCO_(3) as the CaO source.Effects of Al_(2)O_(3)-SiO_(2) raw material types on the physical properties,phase composition and microstructure were investigated.The results are as follows.All samples prepared by different Al_(2)O_(3)-SiO_(2) raw materials have hexagonal flake anorthite and a small amount of mullite and corundum.Their bulk density and thermal conductivity decrease in the order of using kaolin,andalusite,kyanite and sillimanite as the Al_(2)O_(3)-SiO_(2) raw material,but their apparent porosity increases.Moreover,in the sample with kaolin,the bonding between anorthite crystals on the pore walls is closer than that of the other samples,which is conducive to increasing the cold crushing strength.The bonding between anorthite crystals on pore walls gradually decreases in the order of using kyanite,andalusite and sillimanite as the Al_(2)O_(3)-SiO_(2) raw material,thus their cold crushing strength decreases accordingly.In comprehensive consideration,the properties of the sample from kyanite are the optimal.Its apparent porosity,thermal conductivity and cold crushing strength are 84.6%,0.141 W·m^(-1)·K^(-1) and 1.89 MPa,respectively.
文摘Purpose: The study investigated the impact of dietary habits, specifically soda, milk kefir, water kefir, almond milk, and distilled water (control) consumption, on the microhardness of gingiva-coloured composite and acrylic denture bases. Methods: Materials included gingiva-coloured composite (Fusion Universal G1), acrylic (Imicryl), and subdivided Procryla group. Subgroups comprised 15 and 30-minute heat polymerized (Pro15, Pro30), and 1 wt% (Pro1Z) and 3 wt% (Pro3Z) zirconium added groups. Immersed in beverages for 1, 7, and 14 days, pH and microhardness were assessed. SEM examined random samples. Statistical analysis used repeated measures ANOVA, and post hoc tests (p Results: The gingiva-coloured composites displayed noteworthy time-associated microhardness changes (p 0.05). Despite variable pH levels in beverages, no substantial group interaction effects were observed (p > 0.05). Initial microhardness rankings shifted after a 14-day immersion. Conclusions: Gingiva-coloured composite exhibited the highest microhardness pre- and post-immersion, followed by Procryla30 and Imicryl groups. .
文摘This study aims to quantify the susceptibility of granular materials used in pavements to changes in moisture content and propose a correlation model to incorporate this susceptibility into seasonal analyses.The fines content and the percentage of fractured coarse aggregates were identified as direct indicators of the resilient modulus susceptibility to changes in water content.The results showed that the percentage of fractured coarse aggregates particles(FR)has a more significant impact on the resilient modulus(Er)of crushed granular materials used in pavement construction than the combined indicator of the fines content and sample volumetrics(nf).Crushed granular materials with a higher percentage of fractured coarse aggregates are relatively insensitive to changes in the degree of saturation,but become more sensitive as the fine fraction porosity decreases.An adjusted model was proposed based on the existing formulation,but considers a complex parameter to describe and adjust the sensitivity of base granular materials to variations in moisture content with respect to fabrication charac-teristics,fines content and volumetric properties.The model shows that the variation of Er values is below10%for fully crushed granular materials.However,it reaches approximately±12%for materials with 75%of crushed coarse aggregates andþ40%and-25%for materials with FR=50%.This model could help select good ag-gregates characteristics and adjust grain-size distribution for environments where significant moisture content variations can occur in the pavement system,such as in the Province of Quebec(Canada).As it is based on pa-rameters that can be easily determined or estimated,it also represents a valuable tool for detailed design and analysis that can consider material characteristics.
基金Natural Science Foundation of Shandong Province,Grant/Award Number:ZR2019MB019National Natural Science Foundation of China,Grant/Award Numbers:22075122,52071295Research Foundation for Talented Scholars of Linyi University,Grant/Award Number:Z6122010。
文摘The shortage of fresh water in the world has brought upon a serious crisis to human health and economic development.Solar‐driven interfacial photothermal conversion water evaporation including evaporating seawater,lake water,or river water has been recognized as an environmentally friendly process for obtaining clean water in a low‐cost way.However,water transport is restricted by itself by solar energy absorption capacity's limits,especially for finite evaporation rates and insufficient working life.Therefore,it is important to seek photothermal conversion materials that can efficiently absorb solar energy and reasonably design solar‐driven interfacial photothermal conversion water evaporation devices.This paper reviews the research progress of carbon‐based photothermal conversion materials and the mechanism for solar‐driven interfacial photothermal conversion water evaporation,as well as the summary of the design and development of the devices.Based on the research progress and achievements of photothermal conversion materials and devices in the fields of seawater desalination and photothermal electric energy generation in recent years,the challenges and opportunities faced by carbon‐based photothermal conversion materials and devices are discussed.The prospect of the practical application of solar‐driven interfacial photothermal conversion evaporation technology is foreseen,and theoretical guidance is provided for the further development of this technology.
文摘In recent years, additive manufacturing (AM), known as “3D printing”, has experienced exceptional growth thanks to the development of mechatronics and materials science. Fused filament deposition (FDM) manufacturing is the most widely used technique in the field of AM, due to low operating and material costs. However, the materials commonly used for this technology are virgin thermoplastics. It is worth noting a considerable amount of waste exists due to failed print and disposable prototypes. In this regard, using green and sustainable materials is essential to limit the impact on the environment. The recycled, bio-based, and blended recycled materials are therefore a potential approach for 3D printing. In contrast, the lack of understanding of the mechanism of interlayer adhesion and the degradation of materials for FDM printing has posed a major challenge for these green materials. This paper provides an overview of the FDM technique and material requirements for 3D printing filaments. The main objective is to highlight the advantages and disadvantages of using recycled, bio-based, and blended materials based on thermoplastics for 3D printing filaments. In this work, solutions to improve the mechanical properties of 3D printing parts before, during, and after the printing process are pointed out. This paper provides an overview on choosing which materials and solutions depend on the specific application purposes. Moreover, research gaps and opportunities are mentioned in the discussion and conclusions sections of this study.
文摘Material growth and device fabrication of the first 1.3μm quantum well （QW） edge emitting laser diodes in China are reported. Through the optimization of the molecular beam epitaxy （MBE） growth conditions and the tuning of the indium and nitrogen composition of the GalnNAs QWs, the emission wavelengths of the QWs can be tuned to 1.3μm. Ridge geometry waveguide laser diodes are fabricated. The lasing wavelength is 1.3μm under continuous current injection at room temperature with threshold current of 1kA/cm^2 for the laser diode structures with the cleaved facet mirrors. The output light power over 30mW is obtained.
基金financially supported by the National Natural Science Foundation of China (No. 51801078)the Natural Science Foundation of Jiangsu Province (No. BK20180986)
文摘The practical application of magnesium hydride(MgH_(2))was seriously limited by its high desorption temperature and slow desorp-tion kinetics.In this study,a bullet-like catalyst based on vanadium related MOFs(MOFs-V)was successfully synthesized and doped with MgH_(2) by ball milling to improve its hydrogen storage performance.Microstructure analysis demonstrated that the as-synthesized MOFs was consisted of V_(2)O_(3) with a bullet-like structure.After adding 7wt%MOFs-V,the initial desorption temperature of MgH_(2) was reduced from 340.0 to 190.6℃.Besides,the MgH_(2)+7wt%MOFs-V composite released 6.4wt%H_(2) within 5 min at 300℃.Hydrogen uptake was started at 60℃under 3200 kPa hydrogen pressure for the 7wt%MOFs-V containing sample.The desorption and absorption apparent activity energies of the MgH_(2)+7wt%MOFs-V composite were calculated to be(98.4±2.9)and(30.3±2.1)kJ·mol^(-1),much lower than(157.5±3.3)and(78.2±3.4)kJ·mol^(−1) for the as-prepared MgH_(2).The MgH_(2)+7wt%MOFs-V composite exhibited superior cyclic property.During the 20 cycles isothermal dehydrogenation and hydrogenation experiments,the hydrogen storage capacity stayed almost unchanged.X-ray diffraction(XRD)and X-ray photoelectron spectrometer(XPS)measurements confirmed the presence of metallic vanadium in the MgH_(2)+7wt%MOFs-V composite,which served as catalytic unit to markedly improve the hydrogen storage properties of Mg/MgH_(2) system.
文摘In this article,the authors design a speaking unit based on needs analysis following Hutchinson and Waters'(1987) model.First,the rationale in designing this unit is introduced,which involves the teaching approach adopted and relevant theories in organizing the materials.Then,the teaching plan of this speaking unit is provided and some activities are designed to create an authentic and optimal situation for students to practice their speaking skill.
基金This work was supported by the National High-Tech Research and Development Program of China (No.2003AA332020), the Nation-al Natural Science Foundation of China (No.50474002) and the Key Project of the Ministry of Education of China (No.104231).
文摘High performance aluminosilicate based cementitious materials were produced using calcined gangue as one of the major raw materials. The gangue was calcined at 500℃. The main constituent was calcined gangue, fly ash and slag, while alkali-silicate solutions were used as the diagenetic agent. The structure of gangue-containing aluminosilicate based cementitious materials was studied by the methods of IR, NMR and SEM. The results show that the mechanical properties are affected by the mass ratio between the gangue, slag and fly ash, the kind of activator and additional salt. For 28-day curing time, the compressive strength of the sample with a mass proportion of 2：1：1 （gangue： slag： fly ash） is 58.9 MPa, while the compressive strength of the sample containing 80wt% gangue can still be up to 52.3 MPa. The larger K^＋ favors the formation of large silicate oligomers with which AI（OH）4- prefers to bind. Therefore, in Na-K compounding activator solutions more oligomers exist which result in a stronger compressive strength of aluminosilicate-based cementitious materials than in the case of Na-containing activator. The reasons for this were found through IR and NMR analysis. Glauber＇s salt reduces the 3-day compressive strength of the paste, but increases its 7-day and 28-day compressive strengths.
基金Funded by the National Key Research Program(973 Program)(No.2013CB035901)the National Natural Science Foundation of China(No.51379163)
文摘Combined with DTG analysis, X-Ray diffraction analysis （XRD） and field emission scanning electron microscopy analysis （FSEM） affiliated with energy dispersive spectrometer analysis （EDS）, the early hydration and carbonation behavior of cement paste compacts incorporated with 30% of dolomite powder at low water to cement ratio （0.15） was investigated. The results showed that early carbonation curing was capable of developing rapid early strength. It is noted that the carbonation duration should be strictly controlled otherwise subsequent hydration might be hindered. Dolomite powder acted as nuclei of crystallization, resulting in acceleration of products formation and refinement of products crystal size. Therefore, as for cement-based material, it was found that early carbonation could reduce cement dosages to a large extent and promote rapid strength gain resulting from rapid formation of products, supplemental enhancement due to water release in the reaction of carbonation, and formation ofnanometer CaCO3 skeleton network at early age.
文摘The effect of rare earth (RE) oxide on the microstructure and properties of TiC based cermet/Cu alloy composite hardfacing materials was investigated by using scanning electron microscope (SEM), transmission electron microscope (TEM), impact test and wear test. The mechanism of RE oxide for improving the phase structure and the impact toughness was also discussed. The experimental results indicate that the microstructure of the matrix can be refined, and the micro-porous defects can be eliminated by adding RE oxide into the composite materials. The polycrystalline and amorphous phase structure is formed at the interface of cermet and matrix metal. The formed structure enhances the conjoint strength of interface. The frictional wear resistance can be improved obviously, although the microhardness of the matrix metal can not be effectively increased by adding RE oxide.
基金The National Science and Technology Support Program of China(No.2014BAC07B03)the Science and Technology Project of Transportation Committee of Beijing Government(No.2016-LZJKJ-01-006)the National Natural Science Foundation of China(No.51278016)
文摘Sixteen controlled low-strength material( CLSM)mixtures with various cement-to-sand( C/Sa) ratios and water-to-solid( W/So) ratios were prepared using recycled fine aggregate from urban red brick based construction waste.The fluidity and bleeding of the fresh CLSM mixtures were measured via the modified test methods, and the hardened CLSM mixtures were then molded to evaluate their compressive strength and durability. The results showthat the fluidity of the fresh CLSM mixtures is 105 to 227 mm with the corresponding bleeding rate of 3. 7% to 15. 5%, which increases with the increase in fluidity. After aging for 28 d,the compressive strength of the hardened CLSM mixtures reaches 1. 15 to 13. 96 M Pa, and their strength can be further enhanced with longer curing ages. Additionally, the strength increases with the increase of the C/Sa ratio, and decreases with the increase of the W/So ratio under the same curing age. Based on the obtained compressive strength, a fitting model for accurately predicting the compressive strength of the CLSM mixtures was established, which takes into account the above two independent variables( C/Sa and W/So ratios).M oreover, the durability of the hardened CLSM mixtures is enhanced for samples with higher C/Sa ratios.
文摘ZnFe 2O 4 and ZnFe 2O 4 based materials were tested to obtain the electrical conductivity and corrosion resistance in melting bath for aluminum electrolysis. The results proved that adequate additives, such as Ni 2O 3 CuO, Cu, ZnO and CeO 2 would increase the electrical conductivity, and the ZnFe 2O 4 based anodes with these additives were of good corrosion resistance. The current density on anode, the mole ratio of NaF/AlF 3 (MR) and the content of alumina in the bath effect the anode corrosion rate in different way.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11474248,61176127,61006085,61274013 and 61306013the Key Program for International S&T Cooperation Projects of China under Grant No 2011DFA62380the Ph.D. Programs Foundation of the Ministry of Education of China under Grant No 20105303120002
文摘High lattice match growth of InAsSb based materials on GaSb substrates is demonstrated. The present results indicate that a stable substrate temperature and the optimal flux ratios are of critical importance in achieving a homogeneous InAsSb based material composition throughout the growth period. The quality of these epilayers is assessed using a high-resolution x-ray diffraction and atomic force microscope. The mismatch between the GaSb substrate and InAsSb alloy achieves almost zero, and the rms surface roughness of InAsSb alloy achieves around 1.7A over an area of 28μm × 28μm. At the same time, the mismatches between GaSb and InAs/InAs0.73Sb0.27 superlattices （SLs） achieve approximately 100 arcsec （75 periods） and zero （300 periods）, with the surface rms roughnesses of InAs/InAs0.73Sb0.27 SLs around 1.8 A （75 periods） and 2.1A （300 periods） over an area of 20 μm×20 μm, respectively. After fabrication and characterization of the devices, the dynamic resistance of the n-barrier-n InAsSb photodetector near zero bias is of the order of 10^6Ω·cm^2. At 77K, the positive-intrinsic-negative photodetectors are demonstrated in InAsSb and InAs/InAsSb SL （75 periods） materials, exhibiting fifty-percent cutoff wavelengths of 3.8μm and 5.1μm, respectively.
基金National Key Research and Development Project of China(No.2018YFB1701200)。
文摘Aiming at the problems of low reliability and complex operation of traditional coin-tap test of composite material,this paper introduces the grey system theory and achieves better performance.The response signals of coin-tap are classified through the grey clustering based on relation analysis,and corresponding improvements are made to the calculation method of the relation degree of nearness.First,the time history of acceleration is taken as the system behavior sequence.The improved correlation calculation method is used to solve the relation degree of nearness between the sequences,and the matrix of degree of grey relation is constructed based on this.Then,the sequence groups are summarized through the matrix,and the response signals of coin-tap are qualitatively classified according to the location of the reference sequence.Finally,the defect detection of composite materials is completed without pre-testing.The test results show that the accuracy of the coin-tap test based on improved grey clustering reaches 100%,which simplifies the operation steps while ensuring the reliability of the coin-tap test results.
基金Funded by the Major State Basic Research Development Program of China('973'Project,2001CB610705)
文摘Effects of calcined coal gangue （CG） aggregates treated by the surface thermal activation on the flowability and strength, and paste-CG aggregate interfaces of the cement-based material were investigated. The experimental results show that the compressive and flexural strength of the cement-based material with the calcined CG aggregates is much higher than that of the material with the natural CG aggregates, but the flowability of the material with calcined CG is significantly reduced with the calcined time. The strength of the material with the calcined CG aggregates only increases little with the calcined time at the same w/c ratio, but is reduced with the calcined time at the same flowability. The CG aggregates calcined by the surface thermal activation obviously overcomes the disadvantages of fully calcined CG.
基金This study was financially supported by the National Natural Science Foundation of China （Grant No. 30471351）.
文摘To investigate value in use of liquefied wood-based resin applications in molding material, Chinese fir （Cunninghamia lanceolata） and poplar （Populus tomentosa） wood meal were liquefied in phenol. The reactant was co-condensed with formaldehyde to obtain liquefied wood-based resin. For this paper, we investigated the characterization of the resin and its application in molding material. The result shows that the basic properties of liquefied wood-based resin were satisfactory; the bonding strength of plywood prepared with liquefied Chinese fir and liquefied poplar resin can reach 1.54 and 1.00 MPa, respectively. The compression strengths of the molding material prepared with two kinds of liquefied wood resin were 73.01 and 73.58 MPa, almost the same as that of PF resin molding material. The limiting volume swelling of molding material made with liquefied Chinese resin and liquefied poplar resin were 8.5% and 8.3%, thickness swelling rates of water absorption were 3.3% and 4.2%, and the maximum weight ratios of water absorption were 25.9% and 26.2%, respectively. The soil burial test result shows that the weight loss rate of the molding materials made with liquefied Chinese resin and liquefied poplar resin were 8.3% and 9.1% and that of the PF resin molding material was 7.9%. After the soil internment test, the reduction ratio of compression strength of the two kinds of molding material achieved 16.9% and 17.7%, while that of the PF resin molding material was 15.4%. The test results of wood fungi inoculation on the three surfaces of the molding material indicate the breeding rate of molding material prepared with liquefied Chinese resin and liquefied poplar resin were at level 4 and that of PF resin molding material was at level 1 of the ISO standard.
基金Funded by the Scientific and Technological Project of Hubei Province(2004BCS005)
文摘The self-healing action of a permeable crystalline coating on the po rous mortar was investigated by two times impermeability test. Moreover, the sel f-healing mechanism of cement-based materials with the permeable crystalline c oating was studied by SEM. The results indicate that the permeable crystalline c oating not only seals the pores and cracks in mortar during its curing process, but also heals the permeable pathway caused by first impermeability test or crac ks produced by freeze-thaw cycles. Therefore, cement-based materials can be im proved by the permeable crystalline coating for the self-healing function. SEM images prove that the self-healing function is realized by generating a great q uantity of non-soluble dendritic crystalline within the pores and cracks, which prevents the penetration of water and other liquids.
文摘The effects of the component gradient distribution at interface and the fiber gradient distribution on the strength of cement-based materials were studied. The results show that the flexural strength and compressive strength of the mortar and concrete with interface component and fiber gradient distributions are obviously improved. The strengthes of the fiber gradient distributed mortar and concrete (FGDM/C) are higher than those of fiber homogeneously distributed mortar and concrete (FHDM/C). To obtain the same strength, therefore, a smaller fiber volume content in FGDM/C is needed than that in FHDM/C. The results also show that the component gradient distribution of the concrete can be obtained by means of multi-layer vibrating formation.
基金financially supported by the New Energy Project for Electric Vehicle of National Key Research and Development Program (2016YFB0100200)the National Natural Science Foundation of China (51671004,U1764255)+1 种基金National Postdoctoral Program for Innovative Talents (BX201700001)supported by High-performance Computing Platform of Peking University
文摘To design the high-energy-density Li-ion batteries, the anode materials with high specific capacity haveattracted much attention. In this work, we adopt the first principles calculations to investigate the pos-sibility of a new two dimensional boron material, named Be, as anode material for Li-ion batteries. Thecalculated results show that the maximum theoretical specific capacity of Bc is 1653mAh g-1 （LiBl.s）.Additionally, the energy barriers of Li ion and Li vacancy diffusion are 330 meV and 110 meV, respec-tively, which imply fast charge and discharge ability for B6 as an anode material. The theoretical findingsreported in this work suggest that BG is a potential candidate as anode material of high-energy-density Li-ion batteries.
