The 3D needled C/SiC brake materials modified with graphite were prepared by a combined process of the chemical vapor infiltration,slurry infiltration and liquid silicon infiltration process.The microstructure and fri...The 3D needled C/SiC brake materials modified with graphite were prepared by a combined process of the chemical vapor infiltration,slurry infiltration and liquid silicon infiltration process.The microstructure and frictional properties of the brake materials were investigated.The density and open porosity of the materials as-received were about(2.1±0.1)g/cm3and(5±1)%,respectively.The brake materials were composed of 59%C,39%SiC,and 2%Si(mass fraction).The content of Si in the C/SiC brake materials modified with graphite was far less than that in the C/SiC brake materials without being modified with graphite,and the Si was dispersed.The braking curve of the 3D needled C/SiC modified with graphite was smooth,which can ensure the smooth and comfortable braking.The frictional properties under wet condition of the 3D needled C/SiC modified with graphite showed no fading.And the linear wear rate of the C/SiC modified with graphite was lower than that of the C/SiC unmodified.展开更多
The C/C composite brake discs were prepared by tri-cylindrical chemical vapor deposition （CVD） process. The optimum processing parameters were as follows： deposition temperature was 830 - 930 ℃, the gas- flow rate...The C/C composite brake discs were prepared by tri-cylindrical chemical vapor deposition （CVD） process. The optimum processing parameters were as follows： deposition temperature was 830 - 930 ℃, the gas- flow rates of N2 and propylene were 4.8 - 5.2 m^3/h and 5.8 - 6.2 m^3/h, respectively, the furnace pressure was 4.5 - 5.5 kPa and the deposition time was 200 h. The effects of processing parameters on the densified rates, thermal-physical property and mechanical performance of C/C composite brake discs were studied. The results show that density, heat conductivity, bend strength and abrasion ratio of the multi-cylindrica brake discs are 1. 02 - 1. 78 g/cm^3 , 31 W/（m·K）, 114 MPa and 7μm/s, respectively, which are approximately similar to those of the singlecylindrical ones. The gas tlow rate has no relation to the number of the cylinder and furnace loading. The utilization ratio of carbon can be improved by multi-cylinder CVD process without changing the characteristics of brake disc.展开更多
Magnesium(Mg)stands out in temporary biomaterial applications due to its biocompatibility,biodegradability,and low Young’s modulus.However,controlling its corrosion through next-generation polymer-based functional co...Magnesium(Mg)stands out in temporary biomaterial applications due to its biocompatibility,biodegradability,and low Young’s modulus.However,controlling its corrosion through next-generation polymer-based functional coatings is crucial due to the rapid degradation behavior of Mg.In this study,the function of 2D lamellar Ti_(3)C_(2)T_(x)(MXene)in Hydroxyapatite(HA)and Halloysite nanotube(HNT)hybrid coatings in biodegradable poly-(lactic acid)(PLA)was investigated.The morphological and structural characterizations of the coatings on Mg were revealed through HRTEM,XPS,SEM-EDX,XRD,FTIR,and contact angle analyses/tests.Electrochemical in vitro corrosion tests(OCP,PDS,and EIS-Nyquist)were conducted for evaluate corrosion resistance under simulated body fluid(SBF)conditions.The bioactivity of the coatings in SBF have been revealed in accordance with the ISO 23,317 standard.Finally,antibacterial disk diffusion tests were conducted to investigate the functional effect of MXene in coatings.It has been determined that the presence of MXene in the coating increased not only surface wettability(131°,85°,77°,and 74°for uncoated,pH,PHH,and PHH/MXene coatings,respectively)but also increased corrosion resistance(1857.850,42.357,1.593,and 0.085×10^(-6),A/cm^(2) for uncoated,pH,PHH,and PHH/MXene coatings,respectively).It has been proven that the in vitro bioactivity of PLA-HA coatings is further enhanced by adding HNT and MXene,along with SEM morphologies after SBF.Finally,2D lamellar MXene-filled coating exhibits antibacterial behavior against both E.coli and S.aureus bacteria.展开更多
We study the coupled flow and heat transfer of power-law nanofluids on a non-isothermal rough rotating disk subjected to a magnetic field.The problem is formulated in terms of specified curvilinear orthogonal coordina...We study the coupled flow and heat transfer of power-law nanofluids on a non-isothermal rough rotating disk subjected to a magnetic field.The problem is formulated in terms of specified curvilinear orthogonal coordinate system.An improved BVP4C algorithm is proposed,and numerical solutions are obtained.The influence of volume fraction,types and shapes of nanoparticles,magnetic field and power-law index on the flow,and heat transfer behavior are discussed.The obtained results show that the power-law exponents(PLE),nanoparticle volume fraction(NVF),and magnetic field inclination angle(MFIA)have almost no effects on velocities in the wave surface direction,but have small or significant effects on the azimuth direction.The NVF has remarkable influences on local Nusselt number(LNN)and friction coefficients(FC)in the radial direction and the azimuth direction(AD).The LNN increases with NVF increasing while FC in AD decreases.The types of nanoparticles,magnetic field strength,and inclination have small effects on LNN,but they have remarkable influences on the friction coefficients with positively correlated heat transfer rate,while the inclination is negatively correlated with heat transfer rate.The size of the nanoparticle shape factor is positively correlated with LNN.展开更多
In current study,the numerical computations of Reiner–Rivlin nanofluid flow through a rotational disk under the influence of thermal radiation and Arrhenius activation energy is considered.For innovative physical sit...In current study,the numerical computations of Reiner–Rivlin nanofluid flow through a rotational disk under the influence of thermal radiation and Arrhenius activation energy is considered.For innovative physical situations,the motile microorganisms are incorporated too.The multiple slip effects are considered in the boundary conditions.The bioconvection of motile microorganism is utilized alongside nanofluids to provide stability to enhanced thermal transportation.The Bioconvection pattern in various nanoparticles accredits novel applications of biotechnology like the synthesis of biological polymers,biosensors,fuel cells,petroleum engineering,and the natural environment.By deploying some suitable similarity transformation functions,the governing partial differential equations(PDEs)of the flow problem are rehabilitated into dimensionless forms.The accomplished ordinary differential equations(ODEs)are solved numerically through the bvp4c scheme via a built-in function in computational MATLAB software.The upshots of some prominent physical and bioconvection parameters including wall slip parameters,thermophoresis parameter,Brownian motion parameter,Reiner–Revlin nanofluid parameter,Prandtl number,Peclet number,Lewis number,bioconvection Lewis number,and the mixed convection parameter against velocity,temperature,nanoparticles concentration,and density of motile microorganism profiles are dichotomized and pondered through graphs and tables.The presented computations show that the velocity profiles are de-escalated by the wall slip parameters while the thermal and solutal fields are upgraded with augmentation in thermophoresis number and wall slip parameters.The presence of thermal radiation enhances the temperature profile of nanofluid.The concentration profile of nanoparticles is boosted by intensification in activation energy.Furthermore,the increasing values of bioconvection Lewis number and Peclet number decay the motile microorganisms’field.展开更多
基金Project(46-QP-2009)supported by the Research Fund of State Key Laboratory of Solidification Processing(NWPU),ChinaProject supported by the Program for Changjiang Scholars and Innovative Research Team in Chinese University
文摘The 3D needled C/SiC brake materials modified with graphite were prepared by a combined process of the chemical vapor infiltration,slurry infiltration and liquid silicon infiltration process.The microstructure and frictional properties of the brake materials were investigated.The density and open porosity of the materials as-received were about(2.1±0.1)g/cm3and(5±1)%,respectively.The brake materials were composed of 59%C,39%SiC,and 2%Si(mass fraction).The content of Si in the C/SiC brake materials modified with graphite was far less than that in the C/SiC brake materials without being modified with graphite,and the Si was dispersed.The braking curve of the 3D needled C/SiC modified with graphite was smooth,which can ensure the smooth and comfortable braking.The frictional properties under wet condition of the 3D needled C/SiC modified with graphite showed no fading.And the linear wear rate of the C/SiC modified with graphite was lower than that of the C/SiC unmodified.
文摘The C/C composite brake discs were prepared by tri-cylindrical chemical vapor deposition （CVD） process. The optimum processing parameters were as follows： deposition temperature was 830 - 930 ℃, the gas- flow rates of N2 and propylene were 4.8 - 5.2 m^3/h and 5.8 - 6.2 m^3/h, respectively, the furnace pressure was 4.5 - 5.5 kPa and the deposition time was 200 h. The effects of processing parameters on the densified rates, thermal-physical property and mechanical performance of C/C composite brake discs were studied. The results show that density, heat conductivity, bend strength and abrasion ratio of the multi-cylindrica brake discs are 1. 02 - 1. 78 g/cm^3 , 31 W/（m·K）, 114 MPa and 7μm/s, respectively, which are approximately similar to those of the singlecylindrical ones. The gas tlow rate has no relation to the number of the cylinder and furnace loading. The utilization ratio of carbon can be improved by multi-cylinder CVD process without changing the characteristics of brake disc.
文摘Magnesium(Mg)stands out in temporary biomaterial applications due to its biocompatibility,biodegradability,and low Young’s modulus.However,controlling its corrosion through next-generation polymer-based functional coatings is crucial due to the rapid degradation behavior of Mg.In this study,the function of 2D lamellar Ti_(3)C_(2)T_(x)(MXene)in Hydroxyapatite(HA)and Halloysite nanotube(HNT)hybrid coatings in biodegradable poly-(lactic acid)(PLA)was investigated.The morphological and structural characterizations of the coatings on Mg were revealed through HRTEM,XPS,SEM-EDX,XRD,FTIR,and contact angle analyses/tests.Electrochemical in vitro corrosion tests(OCP,PDS,and EIS-Nyquist)were conducted for evaluate corrosion resistance under simulated body fluid(SBF)conditions.The bioactivity of the coatings in SBF have been revealed in accordance with the ISO 23,317 standard.Finally,antibacterial disk diffusion tests were conducted to investigate the functional effect of MXene in coatings.It has been determined that the presence of MXene in the coating increased not only surface wettability(131°,85°,77°,and 74°for uncoated,pH,PHH,and PHH/MXene coatings,respectively)but also increased corrosion resistance(1857.850,42.357,1.593,and 0.085×10^(-6),A/cm^(2) for uncoated,pH,PHH,and PHH/MXene coatings,respectively).It has been proven that the in vitro bioactivity of PLA-HA coatings is further enhanced by adding HNT and MXene,along with SEM morphologies after SBF.Finally,2D lamellar MXene-filled coating exhibits antibacterial behavior against both E.coli and S.aureus bacteria.
基金supported by the National Natural Science Foundations of China(Grant No.11772046)。
文摘We study the coupled flow and heat transfer of power-law nanofluids on a non-isothermal rough rotating disk subjected to a magnetic field.The problem is formulated in terms of specified curvilinear orthogonal coordinate system.An improved BVP4C algorithm is proposed,and numerical solutions are obtained.The influence of volume fraction,types and shapes of nanoparticles,magnetic field and power-law index on the flow,and heat transfer behavior are discussed.The obtained results show that the power-law exponents(PLE),nanoparticle volume fraction(NVF),and magnetic field inclination angle(MFIA)have almost no effects on velocities in the wave surface direction,but have small or significant effects on the azimuth direction.The NVF has remarkable influences on local Nusselt number(LNN)and friction coefficients(FC)in the radial direction and the azimuth direction(AD).The LNN increases with NVF increasing while FC in AD decreases.The types of nanoparticles,magnetic field strength,and inclination have small effects on LNN,but they have remarkable influences on the friction coefficients with positively correlated heat transfer rate,while the inclination is negatively correlated with heat transfer rate.The size of the nanoparticle shape factor is positively correlated with LNN.
基金supported by the Government College University,Faisalabad,and Higher Education Commission,Pakistan.
文摘In current study,the numerical computations of Reiner–Rivlin nanofluid flow through a rotational disk under the influence of thermal radiation and Arrhenius activation energy is considered.For innovative physical situations,the motile microorganisms are incorporated too.The multiple slip effects are considered in the boundary conditions.The bioconvection of motile microorganism is utilized alongside nanofluids to provide stability to enhanced thermal transportation.The Bioconvection pattern in various nanoparticles accredits novel applications of biotechnology like the synthesis of biological polymers,biosensors,fuel cells,petroleum engineering,and the natural environment.By deploying some suitable similarity transformation functions,the governing partial differential equations(PDEs)of the flow problem are rehabilitated into dimensionless forms.The accomplished ordinary differential equations(ODEs)are solved numerically through the bvp4c scheme via a built-in function in computational MATLAB software.The upshots of some prominent physical and bioconvection parameters including wall slip parameters,thermophoresis parameter,Brownian motion parameter,Reiner–Revlin nanofluid parameter,Prandtl number,Peclet number,Lewis number,bioconvection Lewis number,and the mixed convection parameter against velocity,temperature,nanoparticles concentration,and density of motile microorganism profiles are dichotomized and pondered through graphs and tables.The presented computations show that the velocity profiles are de-escalated by the wall slip parameters while the thermal and solutal fields are upgraded with augmentation in thermophoresis number and wall slip parameters.The presence of thermal radiation enhances the temperature profile of nanofluid.The concentration profile of nanoparticles is boosted by intensification in activation energy.Furthermore,the increasing values of bioconvection Lewis number and Peclet number decay the motile microorganisms’field.
