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In a hybrid coupled wall (HCW), a steel coupling beam with a good shear performance can replace a concrete coupling beam. This is especially applicable for locations in which height restrictions do not permit the use of deep reinforced concrete beams or in which it is not possible to economically develop required capacity, stiffness, or deformation demands with concrete beams. In this study, a new type of connection design with a steel boundary element of hybrid coupled wall (SBE-HCW) was proposed, and a 23-story SBE-HCW structure was analyzed under both gravity and seismic load to examine the seismic performance using ABAQUS. The structural failure process, base shear force, vertex displacement, and damage distribution of core tube were investigated. The analysis results confirmed that the response of specimen exhibited good plastic deformation behavior under seismic, thereby satisfying the demands of seismic ductility design. The connection between the steel coupling beams and the shear walls in the specimen appeared to be intact. The analysis evidence indicated that the proposed connection detailing appeared to be effective.

Organic-inorganic hybrid perovskite materials offer the potential for realization of low-cost and flexible next-generation solar cells fabricated by low-temperature solution processing. Although efficiencies of perovskite solar cells have dramatically improved up to 22.1% within the past 6 years, there is still considerable room for further improvement in device efficiency through development of smooth and large grain size perovskite films. Commonly, the smooth perovskite layers and large grains are alternative to CH3NH3PbI3-xClx. However, the previous one-step fabrication of CH3NH3PbI3-xClx using PbCl2 needs long annealing time. Herein, the active layer, a noncontinuous CH3NH3PbI3-xClx film with micrometre-level crystalline grain, was fabricated using a one-step spin-coating process followed by high-temperature annealing and exhibited an increased efficiency of 9.93%. This finding enables the formation of larger grain size perovskite films and the demonstration of efficient perovskite heterojunction solar cells.

Graphene quantum dots, a kind of advanced carbon material, have become the frontier of condensed matter physics and material science. Here, we develop a plain and cheap preparation of graphene quantum dots by liquid-phase exfoliation of carbon fibers, which were prepared from absorbent cotton through an annealing process at 1000°C. The structure, micro morphology, chemical bond and optical properties of the as-prepared graphene quantum dots were characterized. Results show that the as-prepared graphene quantum dots present a green luminescence and have a narrow size distribution of 3-10 nm.

A novel gas sensor for the determination of formaldehyde was developed based on molecular imprinting technique (MIT). MIT was for the first time used to recognize small organic molecule by our group. The molecular imprinting nanoparticles (MINs) with a small dimension which possess extremely high surface-to-volume ratio were synthesized using imprinting polymerization with formaldehyde as template and Ag-LaFeO3 as substrate material. The structure of the MINs is orthogonal perovskite. And then the MINs were printed onto an alumina tube. Subsequently, a high selectivity molecular imprinting gas sensor for detection of formaldehyde was achieved. At 86°C, the response to 0.5 ppm formaldehyde based on the sensor is 16, and the response is lower than 2 for the other test gases. The response time and recovery time are 55 s and 40 s, respectively.

In this paper,the micro-arc oxidation technology were utilized to fabricated the oxidation coating in order to resolve the corrosion resistance of the Mg-Al-Y alloy. The EDTA-2Na solution was introduced into the electrolyte solution for improving the coating corrosion properties.After the micro-arc oxidation process, phase structural, surface morphology and corrosion resistance of the MAO coating of Mg-Al-Y alloy were performed by XRD, SEM and Potentiodynamic polarisation measurements. The introduce of EDTA-2Na in the electrolyte solution improve the positive potential and reduced the corrosion current, which would improve the corrosion resistance properties of the Mg-Al-Y alloy.

Inthis investigation, the rare-earth oxide Yb2O3 combined with Al2O3served as sintering additives and SiC and B4C powder were applied to fabricate SiC/B4C multiphase ceramics composites by pressureless sintering. The results proved thatcombination of Al2O3 and Yb2O3 sinter additives were effective fordensification of SiC/B4C composites. The influence of oxidation time onthe phase constitution, micro-structure and oxidation behavior of SiC/B4C composites was investigated.Theformation of eutectic phase Yb2Si2O7 phase waswrapped on the SiC surface and it reduced further oxidation of SiC particles.The oxidation kineticcurves followed a parabolic rule.

In this investigation, the rare-earth oxide La2O3 combined with Al2O3 served as sintering additives and commercial α-SiC and B4C powder were applied to fabricate SiC/B4C composites by pressureless sintering. The results proved that combination of Al2O3 and La2O3 sinter additives were effective for densification of SiC/B4C composites. The influence of sinter temperature on the phase constitution, micro-structure and densification behavior of SiC/B4C composites was investigated.

A new gas sensor with high response and selectivity was fabricated by using molecularly imprinted powders (MIPs) which provide special recognition sites to methanol. The MIPs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and fourier transform infrared spectrometer (FT-IR), respectively. The gas sensing properties of MIPs to methanol were investigated. The experimental results indicate that the sensors based on the MIPs show excellent gas sensing properties to methanol vapor, and the properties of the sensor with x=6:10 (x= methyl acrylic acid: LaFeO3, molar ratio) are the best. At the optimal operating temperature of 130°C, the response of the sensor (x=6:10) to 1 ppm methanol is 21, and the response and recovery times are 57 s and 67 s, respectively.

In this paper, the rare-earth oxide Al2O3 combined with La2O3 served as sintering additives and commercial α-SiC powder were applied to fabricate SiC ceramics by pressure-less sintering technology. The results proved that combination of Al2O3 and La2O3 sintering additives was effective for densification of SiC ceramics. The influence of sintered additives content on the phase constitution, microstructure and sintering behavior of the SiC ceramics was detailed. The relative density, lose weight and volume shrinkage rate of SiC ceramics had similar evolvement trend with the increase of sintered aids content. Keywords: Pressure-less Sintering, Mechanical Properties, Sintering Behavior

The network SiC ceramics was prepared by organic foam impregnation and pressure-less sintering technology. The co-continuous SiCn/Mg composites were fabricated by vacuum infiltration methods. The results proved that coarse surface was observed on the surface of SiC network ceramics, which was helpful for interface reaction of metal alloy during impregnation process. The continuous interface can be formed in the SiCn/Mg composites. KF concentration had more important influence on coatings morphologies and polarization behaviors of SiCn/Mg composites during micro-arc oxidation process.Key words: Interpenetrating, Ceramic Coatings, Micro-arc Oxidation

The micro-arc oxidation technology were utilized to fabricated the ceramics coating in order to improve the corrosion resistance of Ti–6Al–4V alloy (TC4). The sodium silicate solution was introduced into the electrolyte solution for increasing the coating properties. The effect of the sodium silicate content on the phase composition, surface morphology and potentiodynamic polarization behavior was investigated. The results showed that the increase of Na2SiO3 concertration was benefit to improve corrosion resistance of the MAO coating of TC4 alloy. Key words: Micro-arc oxidation, Ceramic Coatings, Corrosion Resistance.

In this investigation, the rare-earth oxide Y2O3combined with Al2O3served as sintering additives and commercial α-SiC powder were applied to fabricate Cf/SiC composites by hot-pressing sintering. The results proved that combination of Al2O3and Y2O3sintering additives was effective for densification of Cf/SiC composites. The influence of annealed temperature on the phase constitution, microstructure and mechanical properties of the Cf/SiC composites was detailed. The combination of grain bridging, crack deflection and fiber debonding can improve fracture toughness. Keywords: Pressing sintering, Mechanical Properties, Annealed Treatment

In this paper, the commercial α-SiC powder and bargain price La2O3/Y2O3 additives were utilized to fabricate SiC matrix composites. The influence of the Y2O3/La2O3 molar proportion on the microstructure, mechanical properties of the Cf/SiC composites were researched. The results showed that La2O3/Y2O3 additives could not enhance mechanical properties for the Cf/SiC composites distinctly. The flexural strength for the Cf/SiC composites with different Y2O3/La2O3 proportion was higher than 250MPa. The multi-toughening mechanics including grain bridge, crack deflection and fiber pullout were responsible for improvement of fracture toughness.

The LaFeO 3 modified by silver (Ag–LaFeO 3 ) further modified by single-walled carbon nanotubes (SWCNTs–Ag–LaFeO 3 ) with different weight ratio were prepared using a sol–gel method combined with the microwave chemical synthesis. The phase structures and micro-morphology of SWCNTs–Ag–LaFeO 3 were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM), respectively. Indirect-heating sensors using SWCNTs–Ag–LaFeO 3 sensitive materials were fabricated on an alumina tube with Au electrodes and platinum wires. Gas-sensing characteristic of SWCNTs–Ag–LaFeO 3 to formaldehyde was investigated. It is found that the structure of SWCNTs–Ag–LaFeO 3 is of orthogonal perovskite. The gas-sensing properties of the Ag–LaFeO 3 sample modified by SWCNTs with 0.75% weight ratio (0.75%SWCNTs–Ag–LaFeO 3 ) are the best. The response of 0.75%SWCNTs–Ag–LaFeO 3 powder to 0.5 ppm formaldehyde is 23 at 86 °C. The detect limit to formaldehyde is 0.2 ppm. The response and recovery times are 6 s and 20 s, respectively. Those good properties make them the promising candidates for practical detectors to formaldehyde.

Sapphire single crystal is widely used in many fields because of its excellent properties, as a focus of mechanical test, nanoindentation on sapphire is paid a great deal of attention by researchers. In this manuscript, the maximum load, depth and loading rate effects on the first pop-in event during nanoindentation of sapphire single crystal were discussed, the results indicated that these factors had no effect on the load at which the first pop-in occurred and the extension width of pop-in; the deformation below the first pop-in event was discussed and it could be roughly considered as purely elastic deformation through analyzing.

The gas-sensing properties of silver doped lanthanum ferrite (Ag–LaFeO 3 ) compounds for formaldehyde were investigated in this paper. Ag–LaFeO 3 powders were prepared using sol–gel method combined with microwave chemical synthesis. The powders were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. The formaldehyde gas-sensing characteristics for the sample were examined between 65 °C and 220 °C. The experimental results indicate that the sensor based on the sample Ag–LaFeO 3 shows excellent gas-sensing properties to formaldehyde gas and the operating temperature is very low. At the optimal operating temperature of 90 °C, the response of the sensor based on Ag–LaFeO 3 to 1 ppm formaldehyde is 25, while to other test gases, the response is all lower than 6. With increasing concentration of formaldehyde, the resistance of the sensor based on the sample Ag–LaFeO 3 increases. The response and recovery times for the sample to formaldehyde gas are 65 s and 60 s, respectively.

The gas-sensing properties of zinc doped lanthanum ferrite (Zn-LaFeO3) compounds for formaldehyde were investigated in this paper. Zn-LaFeO3 powders were prepared using sol-gel method combined with microwave chemical synthesis. The powders were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. The formaldehyde gas-sensing characteristics for the sample were examined. The experimental results indicate that the sensor based on the sample Zn-LaFeO3 shows excellent gas-sensing properties to formaldehyde gas. At the optimal operating temperature of 250°C, the sensitivity of the sensor based on LaFe0.7Zn0.3O3 to 100ppm formaldehyde is 38, while to other test gases, the sensitivity is all lower than 20. The response and recovery times for the sample to formaldehyde gas are 100s and 100s, respectively.

The network SiC ceramics was fabricated by combining organic foam impregnation and presureless sintering method. The co-continuous interpenetrating SiC/P20steel composites were fabricated by means of pressureless infiltration technique. The results showed that coarse surface of SiC ceramics with three-dimensional network structure was obtained and observed, which was halpful for the reaction of metal alloy during the impregnation process. The continuous interface could be detected in the SiC/P20steel composites.

The ceramics coating hadobtained by the micro arc oxidation technology in order to resolve thecorrosion resistance of the Mg alloy.The phase composition, surface morphology,gained weight and polarization behavior of the micro arc oxidation coating wasinvestigated in details. After the introduce of the sodiumcitrate in the electrolyte solution, thespecimen had high relatively positive potential and low corrosion current, sodoped sodium citratewould improve the corrosion resistance properties of the Mg alloy .

Our previous study revealed that the gas sensitive property of Silver-modified Lanthanum Ferrite (Ag-LaFeO3) is well, but the operating temperature is still high and the sensitivity also needs to be improved. This work based on our previous study. Ag-LaFeO3 was further modified by the Carbon nanoTubes (CNTs). The Ag-LaFeO3 powder modified with CNTs (CNTs-Ag-LaFeO3) was prepared by a sol-gel method combined with microwave chemical synthesis. The structure and gas-sensing properties were investigated. The results show that the structure of CNTs-Ag-LaFeO3 is of orthogonal perovskite. The sensitivity of 0.75% CNTs-Ag-LaFeO3 powder for 1 ppm formaldehyde is 13 at 86°C. The response and recovery time are 100s and 60s, respectively. Moreover, the sensor also has an obvious response for 1ppm formaldehyde at 58°C.

The ZrC-20vol.%SiCw ultrahigh temperature ceramics with relative density of 99.2% can be prepared by hot pressing at 1900 oC and 30MPa for 60 min. The mechanical properties and microstructure of the composite were studied. The flexural strength and fracture toughness reaches up to 626.17MPa, 5.03 MPa•m1/2, respectively. SEM analysis shows the microstructure of the ZrC-20vol.%SiCw is homogeneous and SiC whiskers are uniformly distributed around the ZrC grains, which inhibit the ZrC grain growth during sintering. The fracture surface of ZrC-20vol.%SiCw reveals a mixture of intergranular and transgranular failure, and SiC whiskers play a remarkable role in improving the strength and toughness of ZrC matrix. The toughening mechanism of the composite is mainly fine-grain strengthening and whisker pull-out.

article i nfo Article history: Zirconia coated carbon fiber for thermal and oxidation protection was prepared through a sol-gel technique. A zirconia sol was synthesized with the zirconium oxychloride, ammonia and polyethylene glycol, each of them acting as the zirconium resource, precipitant and surfactant. The morphology, phase composition and thermal properties of the zirconia coated carbon fiber were evaluated by SEM, EDS, XRD and TG-DTA. The increase of dipping cycles can raise the thickness of the coating, while attaching more ZrO2 crystals on the coating surface. Mass variations of the 3 mol% YSZ and 2 mol% YSZ coated carbon fibers at 800 °C are 20% and 40%, less than the 70% of the uncoated carbon fiber.

The two kinds of the Ti-rich (Ti0.8Zr0.2)B2 and Zr-rich (Zr0.8Ti0.2)B2 permutation solid solutions were formed when hot pressed ZrB2 and TiB2 ceramics. On the base of the empirical electron theory (EET) of solids and molecules, the crystal bond energy of the two solid-solutions was calculated by use of Average Atom Model, Average Cell Model and Real Cell Model. In Real Cell Model, the crystal cell parameters were assumed to be unchanged and changed. The calculation results were compared among the three models. The results showed that the general trend about the deviation electrons of B element is consistent except Real Cell Model when the lattice constant is unchanged. Namely, the number of the deviation electrons in TiB2 is more than that in ZrB2.The maximum error of crystal bond energy calculated by the three models is 38KJ/mol and the relative error is less than 2%.The general trend of the crystal bond energy calculated by the three models is monotonically increased similar to the trend of melting point of these materials. Relatively speaking, the calculation of crystal bond energy calculated by Average Atom Cell Model is simpler and more reasonable.

Chemical vapor deposition (CVD) is an effective method of preparing silicon carbide whiskers or films and chemical vapor infiltration (CVI) can be successfully used as the preparation of SiC composites. In this paper, silicon carbides whiskers were firstly deposited on substrates of RB-SiC by CVD process and then silicon carbide composites were prepared by chemical vapor infiltration in the SiC whiskers in an upright chemical vapor deposition furnace of Φ150mm×450mm with methyltrichloride silicane (MTS) as precursor gas, H2 as carrier gas and Ar as dilute gas. The morphologies of the SiC whiskers grown on RB-SiC substrate and SiC composites infiltrated in SiC whiskers were determined by scanning electron microscope (SEM), and the crystalline phase of the final deposits were confirmed with X-ray diffractometry (XRD) As a result, the curly defects of whiskers decrease with the addition of dilute gas. And by chemical vapor infiltration in SiC whiskers the, SiC composites were successfully prepared. Finally the deposits were determined as β-SiC.

Ultrasonic cavitations can control algal growth. Considering water ecosystem protection and characteristics of ultrasonic technology, low frequency and low power ultrasonic was especially suitable to control algal growth in water bodies. Effects of low-frequency and low-power ultrasonic irradiation on natural blend algal growth were investigated. The algae spices were collected from a fresh water body. It mainly consists of Cyanophyta, Bacillariophyta and Chlorophyta. The results showed that ultrasonic irradiation with frequency of 60KHz, power of 0.24W/cm2 and irradiation time of 1min, inhibited algal growth significantly. Inhibition of ultrasonic irradiation on algal growth enhanced with ultrasonic power increased. Inhibition did not increase again When ultrasonic power exceeds 0.24W/cm2. The effect of algal control was sustainable by ultrasonic irradiation with interval period of 2-4 days.

SiC whisker was introduced into reaction bonded silicon carbide to produce high performances composite by slip casting and reaction sintering. This study aimed at morphology of SiC whisker in the reaction bonded silicon carbide ceramics. The whisker was homogeneously dispersed into SiC/C suspension by ball-milling and ultrasonic dispersion. By chemical etching, the whisker displays the original burl profile on the polished surface of the composite. The raise of whisker fraction leads to an increase of porosity of the green body; and thus a decrease of density of the sintered body. For the specimen with 25 wt.% whisker, the rapid reaction of carbon with excess molten silicon leads to the missing of burl profile on the whisker surface. It is speculated that β-SiC on the whisker surface dissolved in the molten silicon during liquid silicon infiltration.

Adopting domestic polytetrafluoroethylene (PTFE) turning plate as materials, a new isosceles triangle macroporous mesh was designed. The correspond mould and the special fixtures for continuous punching of ultra-thin plastic sheet were successfully developed. The PTFE mesh was manufactured through computer numerically controlled (CNC) punch. In terms of electronic universal testing machines and microcomputer differential thermal balance, mechanical properties and thermostability of the PTFE mesh were studied. The results indicated that the tensile strength of PTFE mesh is 11.98 MPa which is greater than the literature value of 7.77 MPa, and its heat-resisting performance is excellent without decomposition prior to 312 oC.

The constitutive relation of concrete under uniaxial tension and compression is an essential theoretical basis for structural analysis of concrete. Because of the lack of sufficient stiffness for ordinary test device, a stable decline branch of stress-strain curve could not be obtained. The condition of realizing the stress-strain complete curve for concrete uniaxial tension and compression is derived. The experiment device for uniaxial tension and compression was designed and fabricated with increasing stiffness method. Experiments were carried out for concrete with grade C30~C60 and strain rate 10-5/s~10-2/s. The equation for stress-strain curve in the rising branch were obtained and so were the complete stress-strain curve of uniaxial tension and compression under different strain ratio, which provide the theoretical basis for concrete structural analysis.

The nanocrystalline WC-10Co hard alloys with high density (97.5% T.D.) have been prepared by use of mixing and explosion compaction technology and the average crystalline size is less than 100 nm. The microstructure analysis shows that, the particle size of the mixing powders is less than 200nm and that of the explosive compaction billet is even fine about 100nm. If explosive speed of any explosive is either big or small, we can not get density billets because the initial density of mixing powders is too low. If using secondary explosive compaction process (low-speed explosive Ammonium Nitrate 280g + high-speed explosive TNT 200g), we can get about 97% (maximum density of 97.58%) of the theory density of bulk nanocrystalline WC-10Co hard alloys.

The SiC-B4C multi-phase ceramics was fabricated by gas-pressure sintering technology. The rare-earth oxide Al2O3combined with Er2O3/SiO2was served as sintering aids. The results were shown that the combination of Al2O3/Er2O3/SiO2sintering additives were effective for densification of SiC-B4C multi-phase ceramics. The influence of B4C content on the phase constitution, microstructure and densification behavior of the SiC-B4C multi-phase ceramics were detailed. The lose weight and volume shrinkage rate of SiC-B4C multi-phase ceramics had similar evolvement trend when B4C content increased. Keywords: Gas-Pressure Sintering, SiC-B4C multi-phase ceramics, densification behavior.

The SiC network ceramics was prepared by the organic foam impregnation method and presureless sintering technologies. The network interpenetrating co-continuous SiC/Mg composites were fabricated by means of pressureless infiltration technique. The results showed that The coarse surface of the SiC network ceramics was observed in the SiC network ceramics, which was benefit for the reaction of the metal alloy during the impregnation process. The continuous and gradual interface can be found in the SiC/Mg composites. It was demonstrated that better interface structure was helpful for improving the bonding strength. Key words: Network Interpenetrating, Interface , Pressureless infiltration

Silicon carbide prepared by chemical vapor deposition (CVD) is one of the important candidate materials for space mirror and high-power mirror such as laser mirror, because of its superior performances such as low density, high melting point and homogeneity. In this paper, the SiC coatings were deposited on the substrates of reaction bonded silicon carbide (RB-SiC) by CVD process. Then, the morphologies of the deposits were examined with scanning electron microscopy. The crystalline phase of the as-deposited films was confirmed with X-ray diffractometry. And the adhesion between the CVD film and the substrate was rated with scraping method. As a result, the morphologies of the deposits, i.e. whiskers at 1050°C or films at 1100°C, are different from that of the substrate. And the mean diameter of the deposits at 1100°C is larger than that at 1050°C. Furthermore, the crystalline phase of the as-deposited film is determined as β-SiC and the adhesion is firm enough not to be peeled off with the scraping test.

In order to analyze the influences of axial compression ratio and loading speed to the dynamic response and failure mode of RC columns subjected to blast loading, the collapse test for 6 reinforced concrete column models were conducted. Results show that there are three kinds of failure types: shear failure, flexural failure, flexural-shear failure. It tends to failure in shear mode when compression ratio is 0, and tends to failure in flexural or in flexural-shear mode when compression ratio is 0.5 and 0.25 respectively. The peak value of the exerted load and end moment will increase with the increasing of axial compression ratio in the first stage (approximately when compression ratio is less than 0.25) and then will decrease. The peak value of extra axial forces will decrease with the increasing of axial compression ratio.

The constitutive relation of concrete under uniaxial compression is the essential theoretical basis for structural analysis of concrete. Because of lack of sufficient stiffness for ordinarily tester, stable falling branch of stress-strain curve cannot be obtained. The common methods to increase rigidity of loading system include direct and indirect method. The condition of realizing the stress-strain complete curve for concrete uniaxial compression is derived. A set of stiffness experimental equipment is designed by using the indirect method, which has the advantages of simple, dependable and strong adaptability. Experiment shows that stress-strain complete curve of uniaxial compression under different strain rate could be achieved by using this equipment and electro-hydraulic loading system of MTS co. ltd. It will lay foundation for putting forward the stress-strain curve equation of uniaxial tension and compression under considering the effect of strain rate. It can provide theoretical basis for structural analysis of concrete.

The machinability of nickel-based superalloy GH4169 is very poor, the traditional machining of GH4169 using the cutting fluids with the active additives causes environmental and health problems, which is out of the request of the sustainable development strategy. In this paper a new green cutting technology with overheated water vapor as coolants and lubricants was proposed to achieve the aim of green cutting and high productivity. Cutting experiments and tool wear tests using carbide tool YG6 under dry cutting, emulsion and water vapor were performed. The cutting force, cutting temperature, machined surface quality and tool life were investigated; the curve of flank tool wear and relation between tool life and cutting velocity was carried out. The results of experiments indicated that during water vapor condition, the cutting force and cutting temperature was reduced, the machined surface roughness was improved, and the tool life was longed, respectively, and the higher velocity was taken during the some tool wear condition compared to dry cutting. The research results show that green cutting was achieved associated with overheated water vapor cooling and lubricating, at he same time the machined surface quality and production efficiency was increased.

The valence electron structure (VES) of ZrB2 was set up with the bond length difference (BLD) method based on empirical electron theory (EET) of solids and molecules, and there were 43 potential hybridization combinations. Based on the calculation result of the melting point, the 16th hybridization step of Zr atom and fifth hybridization step of B atom are ascertained as the final hybridization combination. Therefore, the covalent electron number and the bonding energy of the strongest bond (the B-B bonds), the theoretical melting point, and the crystal cohesive energy of the ZrB2 compound can be figured out.

In this paper, micrometers long and 20–100nm diameter SiC nanowires had been synthesized in the Cw/SiC composites by annealing treatment. The present work demonstrated that it is possible to fabricate in-situ SiC nanowires toughening Cw/SiC composites. La2O3 had a significant effect on the morphology and distribution of the SiC nanowires in the Cw/SiC composites. The excess lanthanum resulted in the growth of SiC nanowires with an increasing growth rate in the longitudinal direction and a decreasing growth rate in radial direction. The addition of La2O3 would improve the mechanical properties in the room-temperature. The vapor–liquid-solid growth mechanism of the SiC nanowires along direction was proposed. The combination of grain bridging, crack deflection, whisker debonding and SiC nanowires can improve fracture toughness.

In this paper, dense short carbon fiber reinforced silicon carbide matrix composites had been fabricated by hot-pressed (HP) sintering using Al2O3 and La2O3 as sintering additives. The results showed that the combination of Al2O3 and La2O3 system was effective to promote densification of short cut carbon fiber reinforced silicon carbide composites (Cf/SiC). The whisker structure of silicon carbide was formed during the annealed treatment at 2023 K for 1 h. However, it was noted that this structure was not observed in the as-received HP material. The mechanism of forming whisker structure was not clear, but this kind of whisker structure was helpful to improve mechanical properties. The combination of grain bridging, crack deflection and whisker debonding would improve the fracture toughness of the Cf/SiC composites.

Silicon carbide is one of the best materials for satellite mirror and chemical vapor deposition (CVD) is an effective method of preparing SiC whiskers and films. In this paper, SiC whiskers or films were deposited on substrates of RB-SiC in an upright chemical vapor deposition furnace of Φ150mm × 450 mm with methyltrichloride silicane (MTS) as precursor gas and H2 as carrier gas under dilute gases of different H2/Ar ratio and different deposition temperature between 1050°C and 1150°C. The morphology and composition of the CVD-SiC grown on RB-SiC substrate were determined by scanning electron microscope (SEM) and X-ray diffraction (XRD) respectively. As a result, whisker-like, worm-like or ball-like SiC can be respectively obtained dependent on different deposition conditions such as H2/Ar ratio and deposition temperature, and the composition of the productions are determined as β-SiC by XRD. Furthermore, the deposition mechanisms of different morphologies of SiC are introduced.

An experimental investigation is carried out to machine SiC ceramic material through method of high speed plane lapping with fixed abrasive. The results show that the material removal mechanism and the surface roughness are chiefly related to the granularity of abrasive and the lapping pressure for the brittle materials such as SiC ceramic. It is easily realized to machine SiC ceramic material in ductile mode with a high efficiency and a low cost using W3.5 grit under a lapping pressure of 0.1MPa and then a smooth surface with surface roughness of Ra 2.4nm can be achieved.