The measurement of radiative properties for disperse media has a broad application in high temperature flame combustion diagnosis,nondestructive testing,biomedical imaging and other related fields. Traditional direct measurement methods are mostly to measure the equivalent properties of the specimen,while precise measurements usually need to be obtained by inversion method. Transport-theroy-based reconstruction algorithm can effectively overcome this problem,however,it has a high computational burden and often slowly converging. Therefore,methods that have high accurate and low computation burden are desirable. In this paper,time-domain radiative transfer equation was applied to simulate the photon propagation of the pulse laser in disperse media and then to obtain abundant transmission and reflection signals of media boundary. Sequential quadratic programming algorithm was introduced to inverse the distribution of absorption and scattering coefficient of two -dimensional disperse media. The generalized Gaussian Markov random fields (GGMRF) model was adopted as regularization term to overcome the ill-posed nature of the inverse problem. Simultaneously,to reduce the computation time,the openMP parallel technology is applied to the part of the codes. The reconstruction results show that the SQP algorithm is a promising method to well reconstruct the distribution of absorption and scattering coefficient of two-dimensional disperse media.

A new method was proposed to calculate the key parameters of formaldehyde diffusion within building materials. In addition,the experimental study in different temperature was finished. The experimental results showed that temperature make obvious contribution to formaldehyde diffusion. K_m,C₀ and D_m were obtained by experimental data fitting and the relationship between three key parameters and temperature verify the new method. What's more,the inhibitory effect of formaldehyde concentration was more obvious than promoting effect of temperature on emission rate of formaldehyde. Last but not least,the new procession method proposed in this paper was proved to be feasible and reliable,providing help and reference for dealing with emission parameters of other VOCs.

The wall effect in randomly packed bed with low tube to particle ratio is numerically investigated by coupling discrete element method (DEM) and computational fluid dynamics (CFD). The porosity,characteristics of fluid flow and heat transfer in randomly packed beds are carefully studied,including smooth tube wall model and corrugated tube wall model. Simulation results show that,the wall effect in smooth wall packing with low tube to particle diameter ratio is remarkable. The average velocity of the near tube wall region is higher than inner region,while the average temperature of this region is lower. Besides,the mass flow rate in the range of 0.5d_p near the tube wall is about 46% of the total flow. With corrugated structure,the leakage near the tube wall is suppressed and the mass flow rate decreases to 36%. The heat transfer characteristics and drag coefficient have a slight increase,while the overall heat transfer coefficient is lower than smooth tube wall model.

Bulk polyethylene material is an insulator,whose thermal conductivity could be improved by doping or stretching methods etc,but a single polyethylene chain owns a considerably high thermal conductivity. For polyethylene chains,a detailed calculation is made on the thermal conductivity of original single chain,several chains,torsional chains and stretching chains using equilibrium molecular dynamics methods. Results show that,the thermal conductivity of a single torsional chain decreases slightly,but the thermal conductivity of several chains improves a little when the chains twisted in a particular way. Besides,the thermal conductivity of several chains could achieve a great improvement under stretching loading. Based on above results,a torsional and stretching strand accompanied by better heat-conducting properties is introduced. It has a great significance in guiding the improvement work of the heat conduction of polymer chains under a variety of physical loading.

In this paper,the Realizable k-ε turbulence model is used to simulate the flow and heat transfer mechanism of a corrugated channel. Considering various Re in turbulence regions,the variation of the averaged characteristic number on wall surface (Nu and f) and the local characteristic number along the wall surfaces of the corrugated channel are investigated. The distribution of internal flow and heat transfer parameters in different transverse sections is analyzed. The results show that when Re<7860, Nu of concave wall is larger; when Re>7860, Nu of convex wall is larger; while f on the convex wall is always larger than that on the concave wall. Nu reached two peak values near entrance and exit of the convex wall,moreover,the maximum value in located near the exit. However,a maximum Nu is located near the entrance and a minimum is located near the exit for the concave wall. As for f,steep rising occurs near the exit of the convex wall,while steep rising appears near the entrance of the concave wall. With the increase of Re, v and TKE at all profiles also increase,while T decrease. In addition,v,T and TKE all suddenly increase near the region of convex wall.

The characteristic of cathode water transport in direct methanol fuel cell was investigated using COMSOL Multiphysics,including the effect of the distribution of pressure,velocity,water,oxygen and liquid saturation,as well as diffusion layer under different physical parameters,such as thickness,porosity,size and hydrophobicity. A further mathematical model of diffusion layer with gradient porosity distribution was established to study the effect of porosity gradient and support layer parameters on cell performance and mass transfer. The results show that the diffusion layer with high porosity and thin layer is beneficial to oxygen transfer. The gradient porosity distribution of diffusion layer can reduce oxygen transport resistance,and thus improving the cell performance.

Frosting processes on hydrophilic surface,bare aluminum surface and hydrophobic surface were experimentally investigated. The condensate water droplets freezing,frost layer growth,defrosting and water drainage on different surfaces were studied. The experimental results show that the condensate water droplet shape is spherical segment on hydrophobic surface while irregular shape on hydrophilic surface and bare aluminum surface. The condensate water droplets freezing process is delayed and the height of frost layer grows slower on hydrophobic surface. Frosting process on different surfaces are tend to be the same,when the humid air temperature and cooling surface temperature are low enough. The frost distribution is even on hydrophilic surface and bare aluminum surface compared with the hydrophobic surface; the hydrophilic surface has less residual meltwater,thus frost mass is lower on hydrophilic surface in frosting/defrosting circulation.

Hollow fiber membrane-based dehumification technology is a new process which combines the liquid dehumification technology and membrane separation technology. It prevents the direct contact between the air and solution and thus solve the problem of liquid drop entrainment,which is harmful for human and metal. In this new process,the air and solution is separated. The heat and mass are coupled and exchanged through a selective permeable membrane. In this paper,the application possibility of this new technology in south China is investigated. The module and test condition are designed according to the features of fresh air in south China. A model is established for this model and it is validated via experiment. And the relation of module performance and inlet air flow rate,relative humidity,inlet solution flow rate and temperature are investigated. The heat and mass transfer mechanism in the module is discussed and performance optimization criteria is raised. The result provides basic theory for module design.

The parameter of cooling water has an important effect on heat transfer performance of sodium-potassium alloy thermosiphon (gravity-driven heat pipe). In this study,the effect of cooling water flow rate and temperature on heat transfer performance of a sodium-potassium alloy heat pipe was experimentally studied. The results show that the flow rate of the cooling water presents a significant impact on the outside wall temperature distribution of the heat pipe when it operates under a relative lower flow rates conditions of 4-18 ml·s^-1. But,no further influence of the flow rate is envisioned when the flow rate of the cooling water is more than 18 ml·s^-1. Totally,improvement of the flow rate is beneficial for enhancement of the heat transfer performance of the heat pipe. On the other hand,the temperature of cooling water shows very small impact on the outside wall temperature and heat transfer performance of the sodium-potassium alloy heat pipe.

The leakage of petroleum pipelines has been widely concerned by people and surface transport characteristic of leakage contaminant is the basis of petroleum pipeline leakage detection technology application. This paper established a two-dimensional mathematical-physical model of buried petroleum pipelines leakage,and aimed at the surface transport process of leakage contaminant of buried petroleum pipelines,using the numerical simulation software,it is studied on the effect of different leakage aperture and location for the surface transport characteristic of leakage contaminant of buried petroleum pipelines. The results showed that at the early stage of leakage,the resistance of contaminant is uniform lead to it uniformly transport near areas around with fast speed and gradually decreased in later stage. It would reach the surface faster if the leakage aperture is more larger and the leakage location is more nearer the surface and the surface transport characteristics are more obvious at larger maximum horizontal displacement.

The once-through steam generator which was designed by B & W company was simplified. The flow and heat transfer process in the secondary side under different conditions for the once-through steam generator was numerically simulated based on constant heat flux,and the numerical results were compared with the classic correlations of frictional pressure drop. The results show that Martinelli-Nelson correlation can be used to predict the two-phase frictional pressure drop along with the occurrence of dryout. The frictional pressure drop increases with the increasing steam quality,and the frictional pressure drop gradient obviously increases when the dryout happens. The two-phase frictional pressure drop within the tube increases with the increasing mass flow rate and heat flux,while decreases with the rising operating pressure. The effect of mass flow rate and operating pressure on friction pressure drop is obvious,while the heat flux has little effect on the friction pressure drop.

An air-breathing membraneless microfluidic fuel cell (MMFC) with a three-dimensional graphite felt anode is proposed and simulated. The graphite felt,used as anode catalyst layer as well as diffusion layer of fuel cell,provides more possibility to improve the performance of MMFCs owing to its large porosity. A single-phase,three-dimensional and isothermal steady flow model under acidic electrolyte condition is established for the proposed MMFC with comsol multiphysics. The characteristics of mass transfer and fuel crossover as well as the influence of flow rate of reactants and thickness of the graphite felt on the cell performance are discussed. The results show that comparing with the carbon paper and the carbon cloth flow-through anode,the maximum current density and the maximum power density of the MMFC with a graphite felt anode increased 12% and 50% at the flow rate of 333 μl·min^-1,respectively. The ratio of parasitic current density caused by the fuel crossover to the output current density was 0.86% when the cell voltage is 0.8 V. The current density and power density increase with increasing thickness of graphite felt and reactant flow rate,and then trend to be steady.

Experiments were performed to understand the influence of surface wettability on heat transfer performance of an oscillating heat pipe (OHP),the alkali assistant surface oxidation technique was used to fabricate the surfaces. The surfaces with different wettability were obtained by control the concentration of the reaction solution of sodium hydroxide and ammonium persulfate. Different OHPs were obtained with the surface contact angles(CA) of 0°、33.9°、55.7°、84.3°,respectively. The effect of different degrees of surface wettability on heat transfer performance of oscillating heat pipe was investigated experimentally. The results show that the oscillating frequency and amplitude of the working fluid in the OHP increases as the CA increases. The thermal resistance and temperature difference of OHP decreases as the CA increases. Therefore,heat transfer performance of the OHP was enhanced as the CA increases.

Various factors affecting the water transfer between the anode and cathode of a dual chamber microbial fuel cell (DCMFC) were studied. The results showed that the amount of water transfer increased with the increase of the discharging current; With 1500 mg·L^-1 chemical oxygen demand(COD) and 50 mmol·L^-1 phosphate buffered saline in the anode,50 mmol·L^-1 K₃[Fe(CN)₆] and 50 mmol·L^-1 phosphate buffered saline in the cathode,the amount of water transport between the anode and cathode is 0.045 ml·h^-1 at a discharging current of 5 mA. In addition,the study demonstrated that the concentration difference of the PBS solution between the anode and the cathode,the thickness of the proton exchange membrane have an important influence on the amount of water transfer between the anode and the cathode in the DCMFC.

A new kind of flat plate heat pipe is designed in this article,which uses oxidative dehydration as well as molecular self-assembling method to make hydrophilic and hydrophobic membranes. Membrane's hydrophilicity can be characterized by measuring the contact angle. For hydrophilic membrane,its contact angle is only 9.3°,but that for hydrophobic membrane reaches 153°. Based on the characteristics of the heat pipe after surface modification,four kinds of LED cooling systems are designed for comparison. hot wire method and thermal resistance analysis are used to compare each system's performance. Among theses four cooling systems,the flat plate heat pipe combining with forced convection system has the highest ultimate cooling power,which reaches 55 W.

The delta winglet vortex generators can significantly enhance the heat transfer in tube bank fin heat exchangers with a moderate pressure loss penalty. The height of vortex generator has a great influence on the fluid flow and heat transfer of heat exchanger. The effects of height of delta winglet vortex generators on intensity of secondary flow and heat transfer performance of a circular tube bank fin heat exchanger were investigated numerically. Three different heights of vortex generators 1.5,1.75 and 2.0 mm were studied. The results show that under the same Reynolds number,the values of Nusselt number,friction factor and longitudinal vortex intensity all increase with increasing the height of vortex generators. There is one-to-one correlation between the volume average non-dimensional intensity of secondary flow and Nusselt number for all the cases that studied,but there is no such correlation with the friction factor. To screen the optimal height of vortex generators,an appropriate evaluation criterion JF is used and we obtain that the comprehensive heat transfer performance is best if the height of vortex generators is 1.75 mm for the studied cases.

Sintered nickel porous wick is a key component in the loop heat pipe system,metal powder sintering is a common method to product porous wicks,performance of loop heat pipe will be improved by investigating the effects of sintering parameters on the microstructures and characteristics of wicks. In this paper,sintered nickel porous wicks were fabricated,besides,effects of sintering temperature and time on the microstructure and characteristics of wicks were studied. Sintering temperature changed from 750℃ to 850℃ and sintering time varied in the range of 30-40 min. Results reveal that sintering parameters affect the microstructure and characteristics of wicks obviously. Voidage,average pore size and permeability decreases with increasing sintering temperature and time. Capillary pumping amount and capillary pumping speed are positive to permeability of the wick. Moreover,the microstructure and characteristics of wicks are sensitive to sintering temperature of 750-800℃ and sintering time of 40-50 min.

In the process of ultrasonic antiscaling,the spread of ultrasonic and cavitation effect will be affected by the fluid and ultrasonic parameters,deposition character of crystallization fouling will also be changed. Thus,using the method of the FLUENT software numerical simulation compared with the experimental parameters,the effect of ultrasonic cavitation on CaSO₄ crystallization fouling removal is studied in the different fluid velocity and the ultrasonic frequencies. Results show that under the conditions of the same frequency,increasing velocity of fluid,the removal effect of ultrasonic cavitation on fouling is weakened. The removal rate caused by cavitation effect was brought into the fouling deposition process,and the effect of ultrasonic frequencies on the fouling character was obtained. With the increase of ultrasonic frequencies,fouling net deposition rate and fouling resistance increased.

For heat exchangers operating with low air temperature and high humidity,frost appears on the fin surfaces,which increases the thermal resistance and blocks the air channels. Frosting process on a wavy plate was experimentally investigated. This study focuses on several factors affecting the condensate water droplets freezing process and frost layer growth process,i.e. the cooling surface temperature,the air velocity and the plate structure. The results show that the condensate droplets are smaller and freeze earlier with lower cooling surface temperature. The frost layer grows faster with lower cooling surface temperature and higher air velocity. Compared with flat plates,frost height growth on wavy plates is much slower.

Formaldehyde is a typical volatile organic compound(s) (VOCs) of indoor air pollutants. Surface plasmonic resonance (SPR) photocatalysts can absorb visible light,which allows solar light driven photocatalytic removal of formaldehyde from air to occur at room temperature and ambient pressure. However,very few studies on Au/TiO₂ photocatalyst of SPR for removal of formaldehyde from air are reported,of which the apparent kinetic study is of significance for the design of SPR catalysts and the applications to removal of VOCs pollutants. This paper studies the kinetics of photocatalytic oxidation of formaldehyde over plasmonic Au/TiO₂ under LED visible light. Effects of visible light sources with various wavelengths,light intensity and relative humidity of reaction gas on kinetics of visible-light photocatalytic oxidation of formaldehyde over Au/TiO₂ are investigated. Based on the experimental analyses,the apparent kinetics constant of k(I,H) for the LED visible light driven photocatalytic oxidation of formaldehyde is achieved. It suggests that,under conditions of 13% relative humidity and 38.5 mW·cm^-2 of blue light intensity,the formaldehyde conversion is 77%,almost 5 times that under dark. Under LED irradiations of red,green,blue and white light,the conversions of formaldehyde increases rapidly,slowly,and keeps steady with light intensity. Under the same conditons of light intensity (less than 42 mW·cm^-2) and relative humidity,the conversions of formaldehyde under LED red,green and blue light,are approximate,and the conversion under white light is relatively lower than that of the rest three. At dry condition,the converion of formaldehyde is almost 0. However,at wet condition,the conversions under light or under dark exist (above zero),and that under light is higher than under dark. The conversion as a function of relative humidity behaves similarily under various light sources. The conversion reaches the maximum at 21.9% of relative humidity,followed by almost being steady at 80%. Apparent kinetic parameters k(I)_H,k(H)_I and k(I,H) and the kinetic equations by fitting above data related to red,green,blue and whilte light are achieved and established.

The organic modified montmorillonite was prepared by first and second intercalation modification of Na-montmorillonite,which was used to catalyze the reaction of technical grade oleic acid to prepare dimer acid,and the influence of the catalyst structure and composition on the catalytic performance was analyzed. All the samples were characterized by X-ray diffraction (XRD),Fourier transform-infrared spectroscopy (FTIR),scanning electron microscope (SEM),transmission electron microscopy (TEM),thermogravimetry (TG),and dispersion experiments. The experimental results show that the layer spacing of modified montmorillonite is expanded from 1.48 nm to 3.82 nm,and the original sandwich structure remains unchanged. The surface morphology and internal structure of modified montmorillonite were changed,the surface became loose,the interlayer spacing was enlarged,and the content of intercalation agent was increased. The dispersion experiment showed that the montmorillonite had good dispersion performance in oleic acid after second modification. Under the same conditions,the second intercalation montmorillonite catalytic dimerization reaction of oleic acid,yield of dimer acid was 75.33%,which was 2.14 times higher than that of Na-MMT. Through FTIR,¹H NMR and LC-MS showed that the synthesized product is dimer acid. Thus,it is evident that,the wider the interlayer spacing,the stronger the dispersion,and the better is the catalytic performance,this indicates that increasing the interlayer spacing and lipophilicity of MMT can promote the diffusion and adsorption of unsaturated fatty acids,thereby significantly increasing the yield of dimer acid.

Gas diffusion electrode can enhance mass transfer of CO₂ for CO₂ electrochemical reduction. A carbon felt loaded Sn-graphene gas diffusion electrode for electrochemical reduction of CO₂ to formic acid. Effects of CO₂ reaction condition,electrode thickness,Sn loading and electrolytic potential were studied. The results showed that the performance of CO₂ electrochemical reduction was better under the gas phase CO₂ reaction condition than that under dissolved CO₂ condition. Increasing the electrode thickness or Sn loading within an appropriate range led to an improvement in electrochemical reduction of carbon dioxide to formic acid due to the increase in the gas-liquid-solid three-phase interface. The production of formic acid was raised with the negative shift of the electrolytic potential,while the Faraday efficiency increased at first and then decreased. The average current density of (12.79±1.27)mA·cm^-2 and highest Faraday efficiency of 41.55%±2.50% for electrochemical reduction of carbon dioxide to formic acid were obtained at -1.8 V (vs Ag/AgCl) using the carbon felt electrode with the electrode thickness of 5 mm and Sn loading of 5 mg·cm^-2.

In order to develop better Cu-Au selective OSP (organic solderability preservatives),the procedure and principle of depositing of several selective OSP on printed circuit board(PCB) were studied for the first time. The mechanism of OSP reaction and selective depositing were investigated with UV thickness measure,SEM morphology survey and EDS element-composing analysis. The results indicate that the complexation reaction between substituted benzimidazole derivatives and copper (Ⅰ) compound needs some activation energy. The copper (Ⅱ) ion,ferric (Ⅲ) ion and benzimidazole all can lower this activation energy and have positive catalytic effect,while the zinc (Ⅱ) ion has no such capacity. Employing the catalytic property and no participating in OSP film formation of the ferric ion can endow OSP the selectivity between copper and gold. And no complexation between benzimidazole and gold atom can also be used to make this kind of selectivity as well. The selective OSP containing zinc ion plus pre-treatment process is obviously better than the selective OSP containing ferric ion. The OSP film formation procedure does not change the surface morphology of copper and gold.

The phase and morphological changes of crystalline material during laser internal ablation are studied using molecular dynamics simulations. The atomic images are obtained by recording the velocity and position variation of atoms,stress variation and temperature distribution contour of the materials along the ablation process are charted by statistical physics method and been used to analyze the mechanism of laser ablation. Furthermore,P-T phase diagram are used to study the phase change of the materials in the particular part of the target. The results suggest that only specific laser energy fluence in particular range can induce inside cavity in crystalline material,strong stress wave can be produced during deposition and conversion of laser energy in the target material,and the travel of strong stress wave could lead to separation and explosion of materials in the weld pool and cause structural damage in the depths. Besides,it could be found that the heat affected zone is very small during the laser ablation process by analyzing the temperature distribution contour,and most of the lattice defects caused by the laser energy can recover after the material is cooled,however,there are some scatter schistose defects remained in the crystal lattice.

In order to investigating the effect of heat on quantum dots(QDs)-converted light-emitting diodes(LEDs) and pursuing the excellent performance of QDs-converted LEDs,Quantum dots-mesoporous silica(QDMS) was prepared to mix with phosphor and silica resin,which was packaged onto a blue chip,forming a new type of QDs-converted LED. The light conversion efficiency(LCE) and color rendering index(CRI) of the new QDs-converted LED and traditional phosphor-converted LED were respectively measured and compared. The impact of changing current on the performance of the new type of LED was explored. Finally,the light power of the new type of LED before and after solidification were measured,which was solidified respectively in 100℃ and 60℃. Results suggested that the LCE of the new type of LED reached 110 lm·W^-1,improved by about 56% relative to phosphor-converted LED,CRI attained 96(maximum is 100) and remained above 92 driven by current varing from 20 to 400 mA,which demonstrated that the new type of QDs-converted LED possess obvious advantages compared to the traditional phosphor-converted LED. The decline of the LCE and CRI through solidification of the new type of LED solidified under 60℃ were approximately half of that under 100℃,which revealed that heat transfer must be considered carefully during the fabrication of QDs-converted LED.

Submillimeter single-crystal graphene on copper foils was synthesized by chemical vapor deposition. The influence of cooling rate on hydrogen etching of graphene has been studied by using three different types of cooling method. Methane has been introduced during the cooling process to reduce the etching effect and the etching mechanism has been discussed. The results show that fast cooling by just opening the furnace after graphene growth has the lowest etching effect,while the furnace cooling results in intermediate level of etching,and the slow cooling has the most serious etching. The etching damage reduced after methane is introduced during the cooling process. The crystal quality of open furnace cooling graphene was highly increased,while for the furnace cooling graphene it increased slightly,for the slow cooling graphene,the crystal quality decreased.

Supersonic flow around streamwise-aligned solid cylinder with cylindrical open-cell metal foam insert front is investigated. The fluid field and aero-heating effect inside frontal foam porous region is numerically simulated by single domain method at continuum-scale. The drag characteristic of porous region is added by distributed resistance method. The heat transfer temperature difference between solid and fluid phase is taken into account by employing local thermal non-equilibrium model and the radiation heat transfer of solid phase is calculated using Rosseland approximation. It is found that the installation of certain length of cylindrical open-cell foam in front of solid cylinder can reduce the wave drag and frontal aero-heating effect of the model considerably under simulating airflow condition. Compared with aerodynamic compression effect,the influence of viscous dissipation effect on temperature field is small.

General unsaturated polyester resin (UPR) was synthetised by maleic anhydride,phthalic anhydride and 1,2-propylene glycol. While due to its highly crosslinked structure of rigid benzene ring after curing,it will cause the polymer with slow toughness,high brittleness,flammable and high shrinkage. C₃₆ dimer fatty acid modified styrene polyester resin materials were prepared by using C₃₆ dimer fatty acid,phthalic anhydride,maleic anhydride and 1,2-propylene glycol,styrene as the cross-linking agent,benzoyl peroxide as the initiator. The structure and surface morphology of tensile of resin were characterized by FT-IR and SEM. The study found that the DFA was introduced into the main chain of the resin,and the fracture mode changed from brittle fracture to ductile fracture. In this study,the effects of various mole fractions of DFA on the thermal stability,mechanical properties and solvent resistance of the resin were investigated by TG,DSC,tensile,bending,hardness and solvent resistance test. Study found that when the DFA content is 6% (mole fraction),modified UPR materials contain the best comprehensive performance. The initial thermal decomposition temperature from 147℃ to 201℃,the glass transition temperature reduced from 146.6℃ to 120.7℃. The tensile strength,elongation at break,modulus of elasticity,Shore hardness and bending strength were 7.23,2.90,7.84,1.63 and 5.12 times that unmodified UPR material. And resistance to solvent loss rate were reduced by more than 70%. In conclusion,DFA can be used as a kind of efficient toughening agent,helps to improve the toughness of the styrene polyester resin,and to broaden the scope of application of styrene polyester resin.

Since graphene was made by mechanical exfoliation in 2004,it has attracted great interest due to its unique properties. The growth of graphene directly on insulating substrates without catalyst has emerged as a trend for chemical vapor deposition (CVD)-graphene. This growth method offers an advantage in avoiding the post-growth transfer process. So far,many insulating substrates have been used for graphene growth by CVD,such as Si,sapphire,SiC,and other substrates. In this work,Si,sapphire and SiC substrate were chosen for graphene growth. The surface morphology,defects,crystal quality and electronics characteristic of the samples were characterized by atomic force microscopy (AFM),optic microscopy (OM),Raman spectroscopy,and Hall system. AFM and Raman results showed that 3C-SiC layer could be controlled by Si₃N₄ covered on Si substrate,and 2D-FWHM of material on Si substrate was between 70 cm^-1 and 90 cm^-1,that crystal quality was not as good as material by traditional method. Graphene was grown on a 5.08 cm sapphire substrate,the material surface morphology appeared more flat under the lower growth temperature,while the crystal quality was better under the higher temperature. The carrier mobility is above 1000 cm²·V^-1·s^-1 at room temperature. Compared to epitaxial graphene by Si sublimation,CVD-grown graphene on SiC substrate has a more flat surface morphology,lower defect,better crystal quality,and higher carrier mobility. The highest carrier mobility of CVD-grown graphene on SiC substrate is 4900 cm²·V^-1·s^-1 at room temperature.