151 results about "MAX phases" patented technology

The invention discloses a broadband wave-absorbing material based on an MAX-phase metasurface structure and an impedance matching optimization method of the broadband wave-absorbing material. The wave-absorbing material comprises an MAX-phase ceramic substrate and periodic metasurface structures which are arranged on the surface of the MAX-phase ceramic substrate in an array mode and composed of conductive resonance units. The resonance units are isolated through gaps, an equivalent R1L1C1 series resonance circuit is formed in an electromagnetic field, and a base body is equivalent to a parallel resistor R2. By establishing an equivalent circuit model and optimizing parameters R1, L1, C1 and R2, impedance matching of the wave-absorbing material in a target frequency band can be regulated and controlled, so that the wave-absorbing material at least has an absorption peak of which the reflection loss is less than-10 dB. According to the optimization method, electromagnetic simulation and circuit simulation are combined, optimized circuit parameters are reversely mapped into structure geometric parameters, material preparation is guided, and accurate design and broadband absorption of the wave absorbing performance are achieved.

The invention discloses a silane coupling agent grafted MXene composite material and a preparation method thereof, relates to the technical field of composite materials, and aims to provide a surface modification method to enable the MXene composite material to be in good contact with a PDMS (polydimethylsiloxane) material. The surface modification method comprises the following steps: S1, performing wet chemical etching on an MAX phase material in combination with mechanical stripping to obtain a few-layer MXene dispersion liquid; s2, strong base is added into the few-layer MXene dispersion liquid in the step S1, the PH value of the few-layer MXene dispersion liquid is adjusted, a reaction is conducted in the argon environment, and hydroxyl modified MXene dispersion liquid, namely h-MXene dispersion liquid is obtained; and S3, adding a silane coupling agent and a catalyst into the h-MXene dispersion liquid in the step S2, and reacting in an argon environment to obtain the silane coupling agent grafted MXene composite material.

A hardened alloy composite material comprising an alloy matrix and reinforcing particles dispersed in the alloy matrix, the reinforcing particles having a shell and core structure, wherein the shell and the core have different chemical compositions, and wherein the reinforcing particles are formed by a MAX phase compound and / or a MAB phase compound.

The present invention specifically relates to a copper-based powder metallurgy friction material containing a pretreated MAX phase and its application. The raw materials used in the present invention include pre-burned powder, copper powder, nickel powder, iron powder, tungsten powder, graphite powder, boron carbide powder, and zirconium oxide powder. The raw materials used in the pre-burned powder are composed of copper powder A and Ti2AlN in a mass ratio of copper powder A:Ti2AlN = 1-6:1. The material is prepared by a process of ball milling followed by pre-burning, wherein the ball milling speed is 100-200 r / min and the time is 12-28 hours; the pre-burning temperature is 500-900°C and the time is 140-160 minutes. The preparation method of the product of the present invention includes the preparation of pre-burned powder, mixing, pressing and sintering. The resulting product has high hardness, friction coefficient, friction stability coefficient, compressive strength, and shear strength, and has a low wear rate on the brake disc. The components of the present invention are rationally designed, the process is simple and controllable, and the resulting product has excellent performance and is easy to industrialize and apply.

The invention discloses Si-based MAX phase powder and a preparation method thereof, and belongs to the technical field of ceramic material preparation. The preparation method of the Si-based MAX phase powder comprises the following steps: mixing a transition metal source, polysiloxane, a solvent, a curing agent and a platinum catalyst to obtain a mixed solution; the curing agent is vinyl modified siloxane; heating and curing the mixed solution to obtain a solid precursor; and crushing the solid precursor into powder, and then carrying out pressureless sintering in a protective atmosphere, thereby obtaining the product. According to the method, subsequent ball milling and other procedures are omitted, and impurity introduction to the product is avoided. According to the invention, the operation difficulty is greatly reduced, the production efficiency is improved, the energy consumption is reduced, and large-scale and low-cost production is realized.

The invention discloses metal ceramic MAX-phase composite powder for spraying and a preparation method of the metal ceramic MAX-phase composite powder, and belongs to the field of metal ceramic composite materials. The method comprises the following steps: mixing Ni powder, Cr powder and Cr2AlC nano powder with deionized water, a binder and a dispersant according to a specific ratio, and carrying out wet ball milling to prepare uniform slurry; carrying out spray granulation to obtain primary spherical powder; and finally, carrying out spheroidizing treatment on the primary powder by adopting radio frequency plasma under the protection of inert gas to obtain a final product. The core of the preparation method is that through an optimized two-step process, many limitations in the application aspect of an existing MAX phase material are solved, and the composite powder which is high in sphericity degree, good in flowability, compact in interior and stable in MAX phase component is successfully prepared. The powder can be directly used for thermal spraying, and an ideal raw material is provided for preparing a high-performance MAX-phase metal ceramic coating.

The invention discloses a Ti-Nb-Zr / MAX phase / Cr-C-N multi-layer composite coating bipolar plate and a preparation method thereof. The multi-layer composite coating sequentially comprises a Ti-Nb-Zr alloy transition layer, an MAX phase middle layer and a Cr-C-N nano composite surface layer from inside to outside. According to the Ti-Nb-Zr / MAX phase / Cr-C-N multi-layer composite coating bipolar plate and the preparation method thereof, through the synergistic effect of the Ti-Nb-Zr alloy transition layer, the MAX phase middle layer and the Cr-C-N nano composite surface layer, the comprehensive optimization of the coating performance is realized: the Ti-Nb-Zr alloy transition layer provides excellent matrix adhesive force and stress buffer effect; the MAX-phase intermediate layer provides a main corrosion-resistant barrier and self-repairing capability; the Cr-C-N nano composite surface layer provides low contact resistance and good surface stability; and meanwhile, the interlayer stress is effectively reduced by utilizing the gradient transition region, the bonding strength and long-term stability of the coating are improved, and the comprehensive performance of the multi-layer composite coating bipolar plate is effectively improved.

The invention provides an MAX phase / alumina layered composite ceramic and an in-situ synthesis preparation method thereof, and the method comprises the following steps: respectively preparing an alumina matrix layer and an MAX phase interface layer through a tape casting method, then alternately laminating the alumina matrix layer and the MAX phase interface layer, and finally carrying out hot pressed sintering to obtain a layered composite ceramic product. According to the invention, the layered composite ceramic which takes aluminum oxide as a matrix and MAX-phase ceramic as an interlayer is prepared through an in-situ synthesis technology, so that the effects of great toughening, strength increase without reduction and high damage tolerance are realized, and the fracture mode is converted from brittle fracture of aluminum oxide ceramic to safe stepped fracture. The strength and toughness of the aluminum oxide ceramic are successfully balanced and synergistically improved, and the industrial problem that strength and toughness cannot be both considered in a traditional aluminum oxide ceramic toughening technology is solved.

The invention discloses a preparation method of a medium-entropy MAX phase based on zirconium component regulation and control, which comprises the following steps: 1) material preparation: titanium, vanadium, zirconium, niobium, aluminum and graphite powder are used as raw materials, and the molar ratio of the zirconium element phase in transition metal elements is 8-25%; and 2) sintering: uniformly mixing all the raw materials, and carrying out sintering reaction under the condition of argon Ar protective atmosphere to obtain the medium-entropy MAX phases with different configurations. The controllable preparation of the quaternary medium-entropy MAX phase with brand new element combination is realized by accurately regulating and controlling the molar ratio of the zirconium element in the (Ti, V, Zr, Nb) n + 1AlCn system, and the phase purity is obviously improved; and the medium-entropy MXene material is further prepared by taking the medium-entropy MAX phase as a precursor. The prepared medium-entropy MAX phase has a compact layered structure, and the derived medium-entropy MXene presents an ultrathin and stable two-dimensional lamellar morphology, so that the medium-entropy MXene shows abundant electrochemical active sites and excellent conductivity, and shows good application prospects in many fields.

This invention discloses a coatable, moldable dual-functional coating material for heat protection and stealth, and its preparation method. The coating material is formed from a SiC-based composite ceramic aerogel slurry, a perovskite / MAX phase composite ceramic absorber, and a high-temperature resistant binder. The composite ceramic aerogel slurry is composed of SiC micro / nano-scale aerogel powder, SiC nanowires, and a high-temperature resistant binder; the perovskite ceramic absorber is lanthanum strontium manganese oxide (La). 1‑x Sr x MnO3), lanthanum strontium iron oxide (La) 1‑ x Sr x FeO3), lanthanum strontium cobalt oxide (La) 1‑x Sr x The MAX phase ceramic absorber is Ti3SiC2, and it contains substances such as CoO3. The technology of this invention enables the rapid application of coating materials to the surface of equipment via brushing, enhancing high-temperature radar absorption stealth and thermal protection capabilities, and facilitating the preparation and efficient repair of high-temperature stealth coatings.

This invention proposes a mullite composite brick, its preparation method, and its applications, belonging to the field of refractory materials technology. MXene is prepared by etching the MAX phase with hydrofluoric acid, and Si / Al oxide intercalated MXene is prepared by sol-gel reaction. After modification with polydopamine, intercalated montmorillonite is obtained by adding it to a sodium-based montmorillonite suspension. This intercalated montmorillonite is then uniformly mixed with a binder, high-alumina bauxite, and silicon carbide powder, machine-pressed, and calcined to obtain the mullite composite brick. The mullite composite brick prepared by this invention has good thermal insulation, heat insulation, refractory, and mechanical properties, excellent alkali resistance, improved bonding strength, and extended service life. It also has excellent thermal insulation effect, reduces heat loss, and thus plays a role in energy saving, showing broad application prospects.

In one general approach, a method for fabricating a MXene includes etching a MAX phase for selectively removing an A group element from the MAX phase, thereby forming a multilayer MXene. The multilayer MXene is then intercalated and exfoliated. In another general approach, a method for fabricating a MXene includes contacting a MAX phase with an acid and a fluorophosphate salt in a nonaqueous solvent for selectively removing an A group element from the MAX phase, thereby forming a multilayer MXene. The multilayer MXene is then intercalated and exfoliated.

The application discloses a high-temperature high-strength high-entropy MAX phase bulk material and a preparation method thereof. The high-temperature high-strength high-entropy MAX phase bulk material is expressed as M2AX, M is a combination of any four or more of Ti, Zr, V, Nb and Ta, the atomic percentage of each component in the M sublattice is between 5% and 35%, the sum of the atomic percentages of Zr and V is less than or equal to 16.7%, A is an Al element, and X is a C element. The bulk MAX phase material is prepared by a spark plasma sintering method. The high-temperature high-strength high-entropy MAX material prepared by the application has high purity and excellent mechanical properties at room temperature and high temperature, can be used for preparing high-temperature structural parts under special working conditions, and has a wide application prospect in the high-temperature field.

The invention belongs to the technical field of ceramic materials, and particularly relates to a wide-temperature-range MAX-phase ceramic material and a preparation method thereof. The chemical general formula of the ceramic material is (Ti1-x-yMnxMoy) 3AlC2, the value range of x is greater than or equal to 0.15 and less than or equal to 0.25, the value range of y is greater than or equal to 0.05 and less than or equal to 0.15, and the sum of x and y is 0.3. The preparation method comprises the following steps: weighing titanium powder, manganese powder, molybdenum powder, aluminum powder and graphite powder according to a stoichiometric ratio, and additionally adding 1-3at.% of excessive aluminum powder; and carrying out ball-milling mixing, drying and sieving, and sintering by adopting a two-stage hot pressing sintering process to prepare the MAX phase ceramic material. Through Mo and Mn element solution strengthening, excessive Al adding and two-stage gradient heating sintering processes, the structural stability, the mechanical property and the tribological property of the material in the wide temperature range from the room temperature to 1600 DEG C are remarkably improved.

The invention discloses an in-layer ordered nano layered structure ceramic prepared by a leap-type all-solid-phase reaction and a preparation method thereof, and the preparation method comprises the following steps: mixing commercially purchased Ti2AlC powder and MC (M = Ti, Ta, W) powder according to a standard molar ratio of 1: 1, carrying out ball milling after mixing, and then sintering by adopting a spark plasma sintering furnace to obtain the in-layer ordered nano layered structure ceramic. And after the sintering temperature rises to the set temperature of 1100-1600 DEG C, furnace cooling is carried out, a surface carbonization layer is removed, and the sample Ti2MAlC2 (M = Ti, Ta and W) is obtained. The prepared Ti2MAlC2 (M = Ti, Ta, W) is in-layer ordered nanometer layered structure ceramic, and belongs to 312 phases in MAX phase ceramic. According to the method, the difficulty of multi-component synthesis is remarkably reduced, and a new normal form is developed for MAX phase doping research.

This invention discloses a high-thickness, high-purity MAX phase coating and its preparation method. The method includes: 1. Mixing a metal oxide and a carbon source, followed by high-energy ball milling and spray granulation to prepare spherical precursor powder; 2. Depositing a transition layer on a sandblasted substrate surface using plasma spraying, and then depositing the spherical precursor powder on the transition layer to form a precursor coating; 3. Immersing the substrate with the precursor coating in molten salt for electrolysis, causing the precursor coating to be electro-deoxidized and converted into a MAX phase coating. This invention employs a synergistic process of "plasma spraying-molten salt electrochemical conversion," converting the sprayed precursor coating into a MAX phase coating through in-situ electro-deoxidation in molten salt electrochemistry. This process has high deposition efficiency and avoids the defects of carbon loss, phase decomposition, and oxidation in the coating product when directly thermally spraying MAX materials. It achieves the preparation of a high-thickness, high-purity MAX phase coating, suitable for the field of surface protection.

The invention belongs to the technical field of nuclear energy materials and surface engineering, and particularly relates to application of an MAX phase coating in a lead bismuth environment. The MAX phase coating is deposited on the surface of the structural material, so that the corrosion resistance and wear resistance of the steam generator can be remarkably improved. The result shows that under the conditions that the temperature is 450 DEG C, the normal load is 50N, the displacement amplitude is 75 microns, the vibration frequency is 25Hz and the cycle index is 106, a stable aluminum oxide oxidation layer and a compacted abrasive dust layer can be formed, so that the Ni element is effectively prevented from being dissolved, and the corrosion rate of a structural material is reduced; meanwhile, the abrasion depth of the structural material is reduced by 70% compared with that before protection, the structure is stable, the binding force is high, and the structural material is still kept complete and has no obvious peeling or failure phenomenon even in a long-cycle test.

The application discloses a method for growing a coating on an aluminum surface in situ, aluminum foil, an aluminum-based current collector, an electrode and a battery, wherein the method comprises: covering the surface of metal aluminum or an aluminum alloy with a MXene material, and then performing a heating treatment at a predetermined temperature; the functional groups of the MXene material contain one or more of F, Cl, Br or I. The method provided by the application can form a coating containing a MAX phase material on the surface of aluminum or an aluminum alloy in situ, the MAX phase material is a kind of ceramic, has the advantages of high conductivity and corrosion resistance, and the formed coating improves the corrosion resistance of the surface of aluminum or the aluminum alloy.

The invention discloses a material for an electromagnetic rail gun guide rail and a preparation method and application thereof, and belongs to the technical field of copper-based composite materials. The invention relates to a material for a guide rail of an electromagnetic rail gun. The material comprises a 5-20nm nano precipitated phase dispersed and distributed in a copper matrix; the MXene lamellas are continuously distributed on the grain boundary, and the nanometer MAX phase is distributed in the grain; and the nano precipitated phase, the MXene sheet layer and the nano MAX phase form a continuous reinforced network. The Cu-Ti-Be-Co alloy serves as a matrix, and unification of high strength and high conductivity is achieved through the synergistic effect of nanometer precipitated phase strengthening and MAX and MXene strengthening. The yield strength of the composite material reaches more than 700MPa and the conductivity is greater than or equal to 80% IACS (International Annealed Copper Standard) by regulating and controlling the interface combination of MAX and MXene with a matrix and the size and distribution of a nano precipitated phase, and the composite material is suitable for the fields of high-load electromagnetic guide rails, electromagnetic rail guns and the like.

The invention belongs to the technical field of two-dimensional nano materials, and relates to an MXene material as well as a preparation method and application thereof. The invention provides a novel and efficient MXene material preparation method which is characterized in that a precursor MAX phase material, a chalcogenide element simple substance and an iodine simple substance are mixed and then subjected to a high-temperature reaction in a vacuum environment. According to the method, a chalcogenide and iodine are ingeniously utilized to generate iodide (such as SeI2 or TeI2) with strong oxidizing property in situ at a high temperature, the chalcogenide in a high oxidation state can selectively oxidize A-site atoms (such as Al) in an MAX phase, the A-site atoms are converted into volatile iodide (such as AlI3) and escape from a system, and therefore selective stripping of an A layer is achieved; and a two-dimensional Mn + 1Xn skeleton is formed. Meanwhile, the reduced chalcogenide is directly bonded to the surface of MXene as a terminal group, and the functionalized MXene material with the chalcogenide terminal group (-S,-Se or-Te) is synthesized in one step.

Methods for synthesizing tungsten-based MXenes without using a MAX phase precursor.

The invention discloses a preparation method of a field effect transistor sensor based on nanosheet self-assembly morphology transition metal carbide and detection application of cTnI of the field effect transistor sensor. The preparation method comprises the following steps: step 1, preparing nanosheet self-assembly morphology MXene: step a, etching by taking a TiAlCMAX phase as a raw material; step b, dispersing the etched MXene nanosheets in a CTAB (Cetyltrimethyl Ammonium Bromide) template agent solution, and enabling the etched MXene nanosheets to form a structure in which the nanosheets are vertically arranged on an oil-water interface; c, fixing the three-dimensional network structure on the MXene nanosheet by adopting a freeze drying-confinement annealing method; step d, modifying the MXene material prepared in the step c by using a glutaraldehyde GA cross-linking agent; and 2, preparing the field effect transistor sensor of the nanosheet self-assembly morphology transition metal carbide based on the material prepared in the step 1. The sensor prepared by the invention can realize ultra-sensitive detection of cTnI.

The invention discloses an MAX phase-carbide phase composite interface layer modified carbon fiber and a preparation method thereof, and belongs to the technical field of ceramic-based composite materials and functional coatings, an MAX phase ceramic layer is rapidly constructed on the surface of the carbon fiber through a process of combining precursor solution dipping with transient carbon thermal shock, and the MAX phase-carbide phase composite interface layer modified carbon fiber is obtained. Meanwhile, carbide ceramic can be introduced below the MAX phase to serve as an auxiliary transition layer, the MAX phase is selected from Cr2GaC, Cr2AlC, Zr2AlC, Mn2GaC and Zr3InC2, due to the unique layered structure and high-temperature stability of the MAX phase, the bonding strength and toughness of a carbon fiber interface can be remarkably improved, the thermal mismatch problem of the interface is solved, the material is endowed with excellent conductivity and electrochemical activity, and the material can be used for preparing a high-performance carbon fiber material. The material shows stable performance under high-temperature oxidation, reduction and inert atmospheres, and can be widely applied to high-temperature-resistant composite materials, electrodes and chemical catalyst carriers.

The invention provides a preparation method of a high-heat-resistance and high-wear-resistance aluminum-based composite material, which comprises the following steps: carrying out high-temperature oxidation treatment on MAX-phase ceramic particles to form oxides on the surfaces of the MAX-phase ceramic particles and obtain composite particles with MAX phases as cores and oxides as shells; mixing the composite particles, SiC ceramic particles and aluminum powder to obtain mixed powder; and the mixed powder is sequentially subjected to cold press molding treatment and powder metallurgy sintering treatment, and the aluminum-based composite material is obtained. According to the method, an oxide layer is formed on the surface of the MAX phase ceramic particles through high-temperature oxidation treatment, in the subsequent powder metallurgy sintering treatment process, the MAX phase reacts with Al to generate A13Ti, oxide enters A13Ti crystals, and oxide compounded A13Ti particles are formed; in addition, in-situ A13Ti generated by reaction of MAX and Al can form a low-energy interface with a coherent relationship with an Al matrix, an Al grain boundary can be effectively pinned, grain coarsening and interface degradation caused by high temperature are avoided, and therefore the composite material has high heat resistance.

The invention discloses a long-life corrosion-resistant Al / MAX composite coating as well as a preparation method and application thereof, and belongs to the technical field of protective coatings. The long-life corrosion-resistant Al / MAX composite coating comprises a bottom layer and a surface layer, wherein the bottom layer is composed of at least one bottom layer unit, and each bottom layer unit is composed of an Al layer and an MAX phase layer; in two adjacent bottom layer units, the Al layers and the MAX phase layers are alternately arranged; the surface layer is an Al surface layer; in each bottom layer unit, the thickness ratio of the Al layer to the MAX phase layer is 10: 1 to 30: 1. The long-life corrosion-resistant Al / MAX composite coating has better compactness and uniformity, shows excellent corrosion resistance, and can prolong the service life of parts in a marine environment.

A MAX phase has a layered structure of M(n+1)AXn including a plurality of transition metal layers (where n is a natural number, and n and n+1 represent a number of layers). M includes at least two transition metal elements. X includes nitrogen or carbon. A includes at least a first element and a second element, which are different from each other and selected from a Group 13 element, a Group 14 element, a Group 15 element, and a Group 16 element. A difference in atomic radii of the first element and the second element is greater than or equal to 0.1 Å. A first transition metal layer and a second transition metal layer corresponding to opposite outer layers among the transition metal layers have different compositions so that the MAX phase and a MXene obtained from the MAX phase have an asymmetrical out-of-plane-ordered structure.

The invention discloses a conductive reinforced phase material and an in-situ preparation method thereof, and belongs to the technical field of core electric contact materials for switches. The reinforced phase material is Ti3AlC2-coated Al2O3 and is composed of an inner layer and an outer layer in the coaxial direction, the inner layer is of a hollow cylindrical structure, the component of the inner layer is Ti3AlC2, and the outer layer is an Al2O3 coating layer generated on the surface of the inner layer in situ. The in-situ preparation method comprises the following steps: by taking a carbon nanotube as a template and eutectic molten salt as a carrier, preparing the conductive reinforced phase material with the double-layer concentric cylindrical composite structure through vacuum freeze drying, molten salt shielding reaction and high-temperature and high-pressure oxidation treatment. Compared with an original MAX-phase powder reinforced metal-based electric contact composite material and a commercial metal-based electric contact composite material, the novel material is compounded with conductive metal powder such as silver and copper, the electric conduction and heat conduction performance and the arc erosion resistance of the electric contact composite material can be remarkably enhanced, and the potential of replacing a traditional electric contact material is huge.

The application discloses a method for preparing MXene containing fluorine functional groups by a gas phase method and application, an electrode and a battery thereof, wherein the method uses sulfur hexafluoride gas as an etching agent, the sulfur hexafluoride gas reacts with a MAX phase material to etch the A component in the MAX phase material, and the MXene material is obtained; the MXene material has an accordion-like morphology or a two-dimensional sheet layer morphology; it is found that the SF6 gas can react with the MAX phase material by etching, and it is clear that the SF6 gas first reacts with the A component; based on the finding, by controlling the reaction conditions (time and temperature), the A component in the MAX phase material can be selectively etched, and then the MXene material is obtained, a new etching agent for preparing the MXene is provided, and the preparation technical route of the MXene is expanded. The SF6 gas etching is used to prepare the MXene, the gas is a colorless, odorless, non-toxic and non-combustible stable gas, has high safety, and is suitable for being used as a gas source for industrialized macro-preparation of the MXene material.

The application discloses a Ti3SiC2 MAX phase coating and a preparation method thereof. The preparation method comprises the following steps: depositing a Ti-Si transition layer on the surface of a substrate by using a high-power pulsed magnetron sputtering technology; introducing a carbon hydride; alternately depositing a Ti-Si coating and a Ti-Si-C coating, and the number of times of the alternately depositing is 2-8 times; and performing vacuum annealing treatment on the prepared coating to obtain the Ti3SiC2 MAX phase coating. The Ti-Si coating and the Ti-Si-C coating are alternately deposited by using the high-power pulsed magnetron sputtering technology, the deposited coating can be phase formed at a lower temperature in the subsequent heat treatment process, the generation of impurity phases can be reduced, and the purity of the MAX phase is improved.

The invention belongs to the field of nuclear materials, and particularly relates to a nuclear fuel and a preparation method thereof and a reactor, the nuclear fuel comprises a nitride matrix and an MAX phase material distributed in the nitride matrix; the chemical formula of the MAX phase material is Mn + 1AXn, M is selected from at least one of Ti and Cr, A is selected from at least one of Si and Al, X is selected from C, and n is 1 or 2. According to the nuclear fuel disclosed by the invention, the MAX phase material is introduced into the nitride matrix, and a corrosion-resistant oxide layer is generated in situ by utilizing the MAX phase material to block water permeation, so that the nuclear fuel has the properties of high thermal conductivity, relatively strong water corrosion resistance, steam oxidation resistance and radiation resistance, and can be applied to a light water reactor; the application risk of the existing uranium nitride fuel in the light-water reactor is reduced, and the safety and economy of the reactor are improved.