39results about How to "Mitigate Thermal Mismatch" patented technology

The invention provides a graphite base with a protective coating layer and a preparation method thereof. The invention prepares a silicon carbide coating layer on the surface of the porous graphite base through combining the in-situ chemical gas-phase reaction permeation and the chemical gas-phase deposition two-step method. The preparation method is carried out according to the following steps: placing the a base body of the graphite base in a reaction chamber, introducing SiCl4 gas and H2 gas into the reaction chamber according to the volume ratio that SiCl4/H2 equals to 1/5 to 50 under the condition of the reaction chamber temperature between 1300 and 1600 DEG C and the vacuum between 200 and 500 Pa, wherein the hydrogen flow rate is between 200 and 1000 ml/min, the gas introduction time is between 0.5 and 2 hours, and a primary SiC coating layer is permeated on the base body of the graphite base through the in-situ gas-phase reaction; and then b, introducing CH3SiCl3 gas and H2 gas into the reaction chamber according to the volume ratio that CH3SiCl3/H2 equals to 1/5 to 100, controlling the hydrogen flow rate to be in a range between 200 and 1000 ml/m and the gas introduction time between 1 and 50 hours, and depositing a secondary SiC coating layer outside the surface of the primary SiC coating layer after schizolysis.

The invention discloses a SiC-TaC coating/matrix collaborative modified C/C composite material and its preparation method. The composite material provided by the invention comprises two parts. The portion below the surface of the C/C composite material is the matrix modified portion with the thickness being 0.1-10mm. In addition, carbide in the C/C composite material emerges in gradient distribution. The portion which is deposited on the surface of a carbon material is a coating portion with the thickness being 10-300 microns. The preparation method of the composite material comprises the following steps of: cutting a C/C green body at the density of 0.80g/cm<3>-1.60g/cm<3> into an annular shape or a plate shape, followed by ultrasonic cleaning and drying, placing into a multifunctional CVD furnace, depositing carbide on the surface layer and surface of the C/C green body by controlling deposition parameters, further densifying the green body by the use of pyrolytic carbon so as to obtain the high-density coating/matrix collaborative modified C/C composite material. The main advantages of the invention are as follows: by the penetration of carbide through the surface layer of the C/C composite material, the thermal expansion coefficient of the matrix is raised, the interfacial bonding state is improved, a continuous transition of carbide is formed between the coating and the matrix, and the metallurgical bonding is accomplished between the coating and the matrix.

The invention discloses a method for epitaxial growth of a crack-free high-crystal-quality LED epitaxial layer on a metal gallium nitride composite substrate. The method comprises the steps of performing annealing treatment on the metal GaN (gallium nitride) composite substrate firstly in an N<2> atmosphere at a temperature of 750-850 DEG C at reaction chamber pressure of less than 300torr, and enabling a low-temperature GaN stress release layer with a thickness of 100-300 nanometers to be grown at a low speed of 0.2-1.0 micron/h; then enabling a high-temperature non-doped GaN buffer layer with a thickness of 1-2 microns to be grown at a variable speed linearly changed from 1 micron/h to 3 micron/h in an H<2> atmosphere at a temperature of 950-1,050 DEG C; next, enabling an n type GaN layer with a thickness of 1-2 microns to be grown at a constant growth speed; then enabling a multi-period InGaN/GaN multi-quantum-well active region to be grown in the N<2> atmosphere at a temperature of 750-850 DEG C; and next, enabling a p type AlGaN/GaN superlattice electron barrier layer and a p type GaN layer to be grown in the H<2> atmosphere at a temperature of 950-1,000 DEG C. According to the method, by optimizing parameters of carrier gas, growth temperature, growth speed and the like in the initial growth period of the metal substrate, thermal mismatch between the GaN epitaxial layer and the metal substrate can be effectively relieved to prevent decomposition of the GaN; and the high-quality GaN-based LED epitaxial layer is prepared on the metal substrate.

The invention relates to a high-temperature-resistant long-service-life composite coating on the surface of a carbon/carbon composite material and a preparation method. The (Hf0.25Ta0.25 Zr0.25Ti0.25) B2-SiC-Si/SiC-Si composite anti-oxidation coating is prepared by combining slurry dip-coating with a gas-phase siliconizing technology, a SiC-Si inner coating is used for relieving thermal mismatch between the coating and a base body, an outer layer is (Hf0.25Ta0.25Zr0.25Ti0.25) B2-SiC-Si, high-entropy ceramic is introduced into the outer coating, and a multi-element metal oxide is generated after oxidation, so that the stability of SiO2 at a high temperature is improved, and finally, long-time effective protection of the coating on the C/C composite material at the high temperature is realized. The weight of a (Hf0.25Ta0.25Zr0.25Ti0.25)B2-SiC-Si/SiC-Si composite anti-oxidation coating sample prepared by the preparation method disclosed by the invention is increased by 1.12% after the sample is oxidized for 2000h at the temperature of 1500 DEG C, and the weight of the coating sample is increased by 1.05% after the sample is oxidized for 500h at the temperature of 1700 DEG C.

The invention relates to a connecting device, a gas turbine engine, a connecting piece and a turbine outer ring. The connecting device includes a first component, a second component and connecting pieces. The first component is equipped with annular ribs arranged on the outer circumference of the first component, and each annular rib is equipped with a plurality of first grooves in the circumferential direction; the second component is arranged around the outer circumference of the first component; each connecting piece includes a rod part and a block part; wherein a connecting piece is arranged corresponding to each first groove; and the block part of each connecting piece is placed in the first groove. The connecting device has the advantage of reliable connection, and the gas turbine engine has the advantage of good overall performance.

The invention discloses a method for carrying out spark plasma diffusion bonding on silicon carbide ceramics by adopting a refractory high-entropy alloy interlayer. According to the method, a refractory high-entropy alloy TaxHfZrTi (wherein x is equal to 0.51, Ta (at.%) is equal to 14.225%, and three elements of Hf, Zr and Ti are equal in molar weight) is taken as an interlayer material, and solid-phase diffusion welding is carried out on two SiC ceramic base materials to be welded through an SPS technology, so as to obtain a SiC ceramic welding joint. According to the obtained SiC joint, a high-strength (Ta, Hf, Zr and Ti) C high-entropy ceramic phase is formed on an interface, and brittle silicide with a large thermal expansion coefficient is prevented from being generated by diffusion bonding of SiC ceramic through single refractory metal, so that thermal mismatch of the SiC joint is mitigated, the strength of the joint is improved, the maximum room-temperature shear strength of the joint is up to 326.2+/-9.9 MPa, the hardness of the interlayer is up to 2552.1+/-357.1 HV, and the engineering practical value in a high-temperature environment is high.

The invention discloses a NiCrAlY/NiCrAlY-YSZ/YSZ thermal barrier coating on the surface of a nickel-based alloy. The NiCrAlY/NiCrAlY-YSZ/YSZ thermal barrier coating on the surface of the nickel-basedalloy comprises a NiCrAlY metal coating, a YSZ ceramic coating and a NiCrAlY-YSZ metal ceramic composite coating which are deposited on the surface of a nickel-based alloy in sequence, wherein the NiCrAlY-YSZ metal ceramic composite coating is located between the NiCrAlY metal coating and the YSZ ceramic coating. The invention further discloses a preparation method of the thermal barrier coating.The method comprises the steps of depositing the NiCrAlY coating, the NiCrAlY-YSZ coating and the YSZ coating on the surface of the nickel-based alloy through an electron beam physical vapor deposition method. According to the NiCrAlY/NiCrAlY-YSZ/YSZ thermal barrier coating on the surface of the nickel-based alloy, the thermal expansion coefficient of the NiCrAlY-YSZ metal ceramic composite coating is within the range from the thermal expansion coefficient of the NiCrAlY metal coating to the thermal expansion coefficient of the YSZ ceramic coating. The thermal mismatching performance betweenthe NiCrAlY metal coating and the YSZ ceramic coating is relieved. The thermal shock resistance of the thermal barrier coating is improved. The NiCrAlY/NiCrAlY-YSZ/YSZ thermal barrier coating providedby the invention is simple in process, good in repeatability and easy to operate.

The invention provides an integrated interconnection structure of a self-airtight packaging function module. The integrated interconnection structure comprises the self-airtight packaging function module, a structure switching layer and a system mother board, wherein the self-airtight packaging function module is welded on the system motherboard through the structure switching layer, a heat dissipation micro-channel port of the self-airtight packaging function module is connected to a micro-channel interface of the system motherboard through windowing of the structure switching layer, and theself-airtight packaging function module is in signal interconnection with the system motherboard through a BAG ball. Through the introduction of the metal structure switching layer, the BGA vertical interconnection of high/low-frequency electric signals of the self-airtight packaging function module and interface connection of a built-in micro-channel and a system heat dissipation channel are realized at the same time; high-frequency/low-frequency electrical interconnection and heat dissipation channel interface connection between the function module and an external system are integrally achieved; thermal mismatch between the function module and a system mother board is relieved through optimization of the material of the structure switching layer, the assembly strength is improved by increasing the welding area, and therefore the overall reliability of the system is improved.

The invention discloses a carbon fiber reinforced ceramic matrix composite material and a preparation method thereof, and belongs to the technical field of ceramic matrix composite materials. The composite material comprises a carbon fiber layer containing a carbon interface phase, a SiC-ZrC matrix located on the carbon fiber layer and a SiC layer located on the surface of the SiC-ZrC matrix. The preparation method comprises the following steps: depositing pyrolytic carbon in carbon fiber cloth by adopting a chemical vapor deposition method to obtain a carbon fiber layer containing a carbon interface phase; alternately depositing a SiC layer and a ZrC layer on the obtained sample by adopting a chemical vapor deposition method to obtain a SiC-ZrC matrix, and then depositing a SiC layer on the surface of the matrix by adopting the chemical vapor deposition method to obtain the composite material. The carbon fiber reinforced ceramic matrix composite material provided by the invention is high in density, has good ablation resistance and mechanical properties in a low-temperature environment, and has a wide application prospect in the aspect of ceramic composite material components for high-thrust-ratio aero-engines.

The invention discloses a metal ceramic composite material used at a temperature less than 1,200 DEG C. The material is characterized by comprising the following steps: firstly, weaving mixed metal wires and fibers into a preformed body, permeating a deposited interface layer on the fiber surface of the preformed body by using a CVI (Chemical Vapor Infiltration) method, and further preparing an Sic ceramic matrix by using a CVI technique so as to finally prepare the metal ceramic composite material. The preformed body is formed by weaving mixed carbon fibers with nickel-chromium-nickel-silicon alloy wires; the carbon fibers and the alloy wires can be independently woven, or can be also combined and kneaded into bundles and are subsequently woven; the interface layer consists of carbon or BN (Boron Nitride) adopting a layered structure; the thickness of the carbon interface layer is 0.1-0.3 [mu]m; the thickness of the BN interface layer is 0.3-0.5 [mu]m; the Sic ceramic matrix accounts for 30-50% of the total volume of the composite material. The layered interface layer can be used as a baffle layer, and has the functions of conducting load, deflecting crack and relieving thermal mismatch.

The invention provides a multilayer composite film composed of nanometer titanium layers and a titanium silicon carbide layer. The multilayer composite film is applied as a connecting material for carbon fiber-reinforced carbon composite materials. The invention has the advantages that a strong interface transition layer titanium carbide is formed via a reaction of high-activity metallic titanium layers with carbon in carbon fiber-reinforced carbon composite materials, so thermal expansion mismatch between the carbon fiber-reinforced carbon composite materials and the titanium carbide layer can be effectively alleviated; the reaction is an exothermic reaction, so transient high temperature can be realized, which is beneficial for densification of a connection layer; and the titanium silicon carbide layer can alleviate the collapse failure of a connection interface at a high temperature, compensate for surface defects of the carbon fiber-reinforced carbon composite materials, reduce requirements on surface processing precision of the carbon fiber-reinforced carbon composite materials, improve production efficiency and lower production cost.

The invention provides a composite structure AlN seed crystal for PVT, the AlN seed crystal sequentially comprises an aluminum nitride seed wafer, a back sealing film and an AlN thick film from top to bottom, the two faces of the aluminum nitride seed wafer are polished faces, and the roughness of the back face of the aluminum nitride seed wafer is smaller than 2 nm; the back sealing film is a combination of one or more layers of any one of W, Mo, Ta, WC, TaC, BN and diamond, and is formed on the back surface of the aluminum nitride seed wafer through a coating method; and the AlN thick film covers the back sealing film through a film coating method, and the thickness of the AlN thick film is 0.5-5 mm. The invention provides a method for preparing the composite-structure AlN seed crystal and application of the composite-structure AlN seed crystal in PVT epitaxial growth of an AlN crystal. The density of various defects (cracks, dislocations and air holes) can be effectively reduced, and the crystal growth quality is improved.

The invention provides a semiconductor HEMT device and a manufacturing method thereof. The semiconductor HEMT device comprises: a substrate; a heat conduction layer which is located on the surface of one side of the substrate, and comprises a plurality of supporting structures arranged at intervals and a heat conduction structure, wherein the supporting structures are located on the surface of one side of the substrate; the heat conduction structure is located on the surface, on the same side as the supporting structures, of the substrate, and gaps among the multiple supporting structures are filled with the heat conduction structure; and an insulating layer which covers the surface of the side, back to the substrate, of the heat conduction structure, and further covers the surfaces of the sides, back to the substrate, of the multiple supporting structures, wherein the heat conduction structure is a carbon film. According to the semiconductor HEMT device, through the arrangement of the heat conduction layer, stress concentration caused by thermal mismatch of the device can be reduced, and the possibility of cracking of the device is reduced.

The invention discloses a gallium nitride-based high-electron-mobility transistor and a preparation method thereof, and the gallium nitride-based high-electron-mobility transistor comprises a silicon substrate, and also comprises a dislocation blocking layer, a GaN high-resistance layer, a GaN channel layer, an AlN insertion layer, an AlGaN barrier layer and a GaN cap layer which are sequentially stacked on the silicon substrate. Wherein the dislocation blocking layer comprises n layers of dislocation blocking sub-layers which are arranged in a stacked mode, and each dislocation blocking sub-layer comprises a SiC layer and an Al < x > Ga < 1-x > N layer arranged on the SiC layer. The silicon substrate and the gallium nitride thin film are provided with traditional buffer layers in the prior art, the crystal quality improvement amplitude of the gallium nitride thin film is limited, and a large number of dislocation and defects exist; and the performance of the gallium nitride-based high-electron-mobility transistor is influenced.