A gadolinium-containing high-specific-gravity tungsten alloy shielding material, a preparation method thereof and applications thereof

Abstract

The present application relates to a gadolinium-containing high specific gravity tungsten alloy shielding material and a preparation method and application thereof, and the preparation raw material of the gadolinium-containing high specific gravity tungsten alloy shielding material comprises a gadolinium source; the gadolinium source comprises gadolinium oxide and / or surface-modified gadolinium oxide. As a neutron absorption material additive, the gadolinium oxide has a higher boron equivalent than metal boride, that is, the required addition amount of the gadolinium oxide in the shielding material for achieving the same neutron shielding effect is significantly lower than that of the metal boride, and the adverse effect on the mechanical properties of the shielding material can be significantly reduced; from another angle, the allowed addition amount of the gadolinium oxide is significantly higher than that of the metal boride when having the same mechanical properties. Therefore, the shielding material can achieve the combined shielding effect of gamma rays and neutrons, and the microstructure of the shielding material is similar to that of the conventional high specific gravity tungsten alloy material, no new phase is generated, and the shielding material has good mechanical properties, the ultimate tensile strength at room temperature is greater than or equal to 950 MPa, and the elongation after fracture at room temperature is greater than or equal to 15%.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-density alloy materials, and relates to a high-density tungsten alloy shielding material, in particular to a gadolinium-containing high-density tungsten alloy shielding material, and a preparation method and application thereof. Background Art

[0002] Tungsten, due to its high atomic number and high density, is an excellent and highly effective radiation shielding material. Heavy tungsten alloy is a typical metal-matrix composite material composed of the refractory element tungsten and transition metals such as nickel, iron, copper, and cobalt. The tungsten particle reinforcement phase provides the alloy with high density and high elastic modulus, while the transition metal bonding phase provides room-temperature ductility and ease of processing. Heavy tungsten alloy is a key material used in the modern nuclear industry for radiation shielding.

[0003] With the development and advancement of modern science and technology, higher requirements are being placed on nuclear reactor shielding materials in terms of gamma-ray-neutron composite shielding and mechanical properties. Traditional steel or lead shielding is bulky, resulting in poor gamma-ray-neutron composite shielding effectiveness and suboptimal radiation protection for personnel and the environment. Therefore, the development of a new high-density tungsten alloy material that combines gamma-ray-neutron composite shielding effectiveness with excellent mechanical properties is extremely necessary and urgent.

[0004] In order to obtain good neutron shielding performance, it is necessary to add an element with a large neutron absorption cross section, such as boron, to a high-density tungsten alloy, thereby developing a neutron-γ-ray composite shielding material containing high-density tungsten and neutron absorption components. For example, CN114381623A discloses a method for preparing a boron-containing high-density tungsten-based alloy. The method introduces the boron element by partially or completely replacing the original binder phase in the high-density tungsten alloy material with a metal boride sintering aid such as nickel boride, iron boride or expanded chromium. The preparation method comprises the following steps: (1) weighing tungsten powder, metal boride sintering aid and pure metal powder according to weight percentage; (2) mechanically mixing the weighed mixed powder to uniformly disperse the mixed powder; (3) pressing the uniformly dispersed mixed powder into a preform by cold isostatic pressing; (4) subjecting the preform to a two-step liquid phase sintering process in a hydrogen furnace to obtain a boron-containing high-density tungsten-based alloy.

[0005] Although the boron-containing high-density tungsten-based alloy material prepared by the above-mentioned method has the γ-ray-neutron composite shielding effect, the boron-tungsten phase (WB) will be generated during the sintering process of the high-density tungsten alloy material after the addition of boride. x ), boron iron nickel (BFe x Ni y) and other brittle phases, which lead to a decrease in the strength and ductility of the high-density tungsten alloy material, affecting the use and service of the high-density tungsten alloy material with both γ-ray and neutron composite shielding effect; and the boron content in borides such as nickel boride, iron boride, and chromium boride is usually less than 18%. When boron-containing high-density tungsten-based alloy materials are to meet the application requirements of neutron shielding, the amount of boride required is relatively large. The addition of a large amount of boride will further damage the strength and ductility of the high-density tungsten alloy material. Summary of the Invention

[0006] In response to the deficiencies in the prior art, the present invention aims to provide a gadolinium-containing high-density tungsten alloy shielding material, a preparation method thereof, and an application thereof. The gadolinium-containing high-density tungsten alloy shielding material can achieve a composite shielding effect against gamma rays and neutrons. At the same time, the microstructure of the shielding material is similar to that of traditional high-density tungsten alloy materials, and no adverse new phases are generated. The shielding material has good mechanical properties, with an ultimate tensile strength of ≥950 MPa at room temperature and an elongation after fracture of ≥15% at room temperature.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a gadolinium-containing high-density tungsten alloy shielding material. The raw materials for preparing the gadolinium-containing high-density tungsten alloy shielding material include, by weight percentage, 60-85wt% of tungsten, 0.5-5wt% of a gadolinium source, and the remainder of nickel, iron, and unavoidable impurities.

[0009] The gadolinium source includes gadolinium oxide and / or surface-modified gadolinium oxide;

[0010] The surface-modified gadolinium oxide includes gadolinium oxide with a tungsten layer and / or a nickel layer coated on its surface.

[0011] The gadolinium-containing high-density tungsten alloy shielding material provided by the present invention uses gadolinium oxide as a neutron absorbing material. First, when a small amount of gadolinium oxide is added to the high-density tungsten alloy shielding material, it can achieve the effect of dispersion strengthening, namely, refining the grain size and strengthening the grain boundaries. This effect is directly manifested in improved tensile strength and hardness of the material, while possibly slightly impairing the material's ductility. Second, gadolinium has a neutron absorption cross section of 38,300 barns, and the mass content of gadolinium in gadolinium oxide is 86.8%. Gadolinium oxide has a higher equivalent weight than metal borides. That is, to achieve the same neutron shielding effect, the required amount of gadolinium oxide in the shielding material is significantly lower than that of metal borides, which can reduce the adverse effects on the mechanical properties of the shielding material. From another perspective, the allowable amount of gadolinium oxide added to the high-density tungsten alloy material is significantly higher than that of metal borides when having the same mechanical properties. That is, the neutron shielding performance of the gadolinium-containing high-density tungsten alloy with the same mechanical properties is better than that of the high-density tungsten alloy material added with metal borides.

[0012] Therefore, the shielding material can achieve a composite shielding effect against gamma rays and neutrons. At the same time, the microstructure of the shielding material is similar to that of traditional high-density tungsten alloy materials, and will not produce adverse new phases. It has good mechanical properties, with an ultimate tensile strength of ≥950MPa at room temperature and an elongation after break of ≥15% at room temperature.

[0013] In addition, as one of the parallel technical solutions for the gadolinium-containing high-density tungsten alloy shielding material provided in the first aspect of the present invention, the gadolinium source also includes surface-modified gadolinium oxide; the present invention uses surface-modified gadolinium oxide, that is, coating a tungsten layer and / or a nickel layer on the surface of the gadolinium oxide to enable the gadolinium oxide to be uniformly dispersed and not aggregated in the gadolinium-containing high-density tungsten alloy shielding material. On the one hand, it can ensure that the gadolinium-containing high-density tungsten alloy shielding material has a good neutron shielding effect, and on the other hand, it can avoid the adverse effects on the mechanical properties of the gadolinium-containing high-density tungsten alloy shielding material due to uneven dispersion and aggregation of gadolinium oxide.

[0014] Among them, the tungsten layer can increase the specific gravity of gadolinium oxide; the nickel layer can increase the affinity of gadolinium oxide and high-density tungsten alloy. Therefore, as a preferred technical solution, the surface-modified gadolinium oxide includes gadolinium oxide with a tungsten layer and a nickel layer coated on the surface in sequence.

[0015] The present invention sequentially coats a tungsten layer and a nickel layer on the surface of gadolinium oxide to obtain surface-modified gadolinium oxide, wherein the tungsten layer serves as a base layer and the nickel layer serves as a surface layer, thereby improving the affinity between gadolinium oxide and tungsten, and between nickel and iron, thereby facilitating improved uniform dispersion of gadolinium oxide in gadolinium-containing high-density tungsten alloy shielding materials.

[0016] In terms of mass percentage, the raw materials for preparing the gadolinium-containing high-density tungsten alloy shielding material include 60-85wt% of tungsten, for example, 60wt%, 65wt%, 70wt%, 75wt%, 80wt% or 85wt%, but are not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 75wt%-85wt%.

[0017] In terms of weight percentage, the raw materials for preparing the gadolinium-containing high-density tungsten alloy shielding material include 0.5-5wt% of a gadolinium source, for example, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 3wt%, 4wt% or 5wt%, but are not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0018] If the content of the gadolinium source is low, the obtained gadolinium-containing high-density tungsten alloy shielding material cannot exert the neutron shielding effect; and if the content of the gadolinium source is high, it will have an adverse effect on the mechanical properties of the obtained gadolinium-containing high-density tungsten alloy shielding material.

[0019] Preferably, based on the total mass percentage of the gadolinium source being 100 wt%, the mass percentage of the surface-modified gadolinium oxide in the gadolinium source is ≥ 50 wt%, for example, 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt% or 100 wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0020] Preferably, the thickness of the tungsten layer in the surface-modified gadolinium oxide is 1-5 μm, for example, 1 μm, 2 μm, 3 μm, 4 μm or 5 μm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0021] If the tungsten layer in the surface-modified gadolinium oxide is too thin, it will burn through during subsequent processing, failing to improve the affinity of the gadolinium source and hindering uniform dispersion of the gadolinium source. If the tungsten layer in the surface-modified gadolinium oxide is too thick, the overall particle size of the gadolinium source will be too large, affecting mixing uniformity. Therefore, as a preferred embodiment of the present invention, the tungsten layer in the surface-modified gadolinium oxide has a thickness of 1-5 μm.

[0022] Exemplary methods of coating the tungsten layer include chemical vapor deposition and / or physical vapor deposition.

[0023] Preferably, the thickness of the nickel layer in the surface-modified gadolinium oxide is 1-5 μm, for example, 1 μm, 2 μm, 3 μm, 4 μm or 5 μm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0024] If the nickel layer in the surface-modified gadolinium oxide is too thin, it will not improve the affinity of the gadolinium source, hindering its uniform dispersion. If the nickel layer in the surface-modified gadolinium oxide is too thick, it will cause excessive stress in the nickel layer, resulting in poor bonding between the nickel layer and the gadolinium oxide. Therefore, as a preferred embodiment of the present invention, the nickel layer in the surface-modified gadolinium oxide has a thickness of 1-5 μm.

[0025] Exemplary methods of applying the nickel layer include electroplating and / or electroless plating.

[0026] Preferably, the average particle size of the gadolinium oxide is 0.5-5 μm, for example, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm or 5 μm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0027] If the average particle size of gadolinium oxide is too small, it will not be conducive to the uniform dispersion of the gadolinium source in the raw material preparation. If the average particle size of gadolinium oxide is too large, the density of the resulting gadolinium-containing high-density tungsten alloy shielding material will decrease. Therefore, as a preferred embodiment of the present invention, the average particle size of the gadolinium oxide is 0.5-5 μm.

[0028] Preferably, in the raw materials for preparing the gadolinium-containing high-density tungsten alloy shielding material, the source of tungsten is tungsten powder with an average particle size of 1-3.5 μm, for example, it can be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm or 3.5 μm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0029] Preferably, the source of nickel in the raw materials for preparing the gadolinium-containing high-density tungsten alloy shielding material is nickel powder with an average particle size of 2-5 μm, for example, it can be 2 μm, 2.2 μm, 2.5 μm, 3 μm, 3.2 μm, 4 μm, 4.5 μm, 4.7 μm or 5 μm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0030] Preferably, in the raw materials for preparing the gadolinium-containing high-density tungsten alloy shielding material, the source of iron is iron powder with an average particle size of 2.5μm-4.5μm, for example, it can be 2.5μm, 3μm, 3.5μm, 4μm or 4.5μm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0031] In a second aspect, the present invention provides a method for preparing the gadolinium-containing high-density tungsten alloy shielding material according to the first aspect, the preparation method comprising the following steps:

[0032] The raw materials for preparing gadolinium-containing high-density tungsten alloy shielding material are mixed, and cold isostatic pressing, solid-phase sintering and liquid-phase sintering are sequentially performed to obtain a plate sintered blank; the obtained plate sintered blank is heat treated and rolled to obtain the gadolinium-containing high-density tungsten alloy shielding material.

[0033] The preparation method provided in the second aspect of the present invention does not impose any specific restrictions on the mixing method, as long as the raw materials can be mixed evenly.

[0034] The preparation method provided by the present invention adopts a method that combines solid-phase sintering and liquid-phase sintering. Solid-phase sintering can make the plate nearly completely dense, while liquid-phase sintering can prevent the segregation and aggregation of uniformly dispersed gadolinium oxide during liquid-phase sintering, so that the finally prepared gadolinium-containing high-density tungsten alloy shielding material has both good mechanical properties and shielding properties.

[0035] Preferably, the solid phase sintering temperature is 1350-1430°C, for example, 1350°C, 1360°C, 1380°C, 1400°C, 1420°C or 1430°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0036] Preferably, the solid-phase sintering time is 180-360 min, for example, 180 min, 200 min, 240 min, 250 min, 280 min, 300 min, 320 min or 360 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0037] Preferably, the solid phase sintering is performed under oxygen-free conditions.

[0038] Under the solid-phase sintering conditions provided by the present invention, the density of the material after solid-phase sintering can be guaranteed.

[0039] Oxygen-free conditions for solid phase sintering include hydrogen atmosphere or vacuum.

[0040] Preferably, the temperature of the liquid phase sintering is 1450-1550°C, for example, 1450°C, 1480°C, 1500°C, 1520°C or 1550°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0041] Preferably, the liquid phase sintering time is 30-90 min, for example, 30 min, 40 min, 50 min, 60 min, 80 min or 90 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0042] Preferably, the liquid phase sintering is performed in a reducing atmosphere.

[0043] The reducing gas used in the reducing atmosphere of liquid phase sintering includes hydrogen.

[0044] Preferably, the heat treatment temperature is 1000-1300°C, for example, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, 1250°C or 1300°C, but is not limited to the listed resins, and other values ​​not listed within the numerical range are also applicable.

[0045] Preferably, the heat treatment time is 60-180 min, for example, 60 min, 80 min, 100 min, 120 min, 150 min or 180 min, but is not limited to the listed resins, and other values ​​not listed within the numerical range are also applicable.

[0046] Preferably, the heat treatment is carried out under a vacuum degree of ≤10Pa, for example, 1Pa, 3Pa, 5Pa, 8Pa or 10Pa, but is not limited to the listed resins, and other values ​​not listed within the numerical range are also applicable.

[0047] Preferably, the rolling temperature is 500-850°C, for example, 500°C, 600°C, 700°C, 800°C or 850°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0048] Preferably, the pressing amount of a single rolling pass is 2-6 mm, for example, 2 mm, 3 mm, 4 mm, 5 mm or 6 mm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0049] Preferably, the cumulative deformation of the rolling is above 60%.

[0050] In a third aspect, the present invention provides an application of the gadolinium-containing high-density tungsten alloy shielding material described in the first aspect, characterized in that the gadolinium-containing high-density tungsten alloy shielding material is used for gamma-ray-neutron composite shielding.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] (1) The gadolinium-containing high-density tungsten alloy shielding material provided by the present invention uses gadolinium oxide as a neutron absorption material. First, when a small amount of gadolinium oxide is added to the high-density tungsten alloy shielding material, it can play a role in dispersion strengthening, that is, it can refine the grain size and strengthen the grain boundary. This effect is directly manifested in improving the tensile strength and hardness of the material, while slightly damaging the ductility of the material. Secondly, the neutron absorption cross section of gadolinium is 38300 barns, and the mass content of gadolinium in gadolinium oxide is 86.8%. Gadolinium oxide has a higher equivalent than metal boride, that is, when achieving the same neutron shielding effect, the amount of gadolinium oxide required to be added to the shielding material is significantly lower than that of metal boride, which can significantly reduce the adverse effects on the mechanical properties of the shielding material. From another perspective, when having the same mechanical properties, the amount of gadolinium oxide allowed to be added to the high-density tungsten alloy material is significantly higher than that of metal boride, that is, the neutron shielding performance of the gadolinium-containing high-density tungsten alloy with the same mechanical properties is better than that of the high-density tungsten alloy material with added metal boride;

[0053] (2) The preparation method provided by the present invention adopts a method combining solid-phase sintering and liquid-phase sintering. Solid-phase sintering can make the plate nearly completely dense, while liquid-phase sintering can prevent the segregation and aggregation of uniformly dispersed gadolinium oxide during liquid-phase sintering, so that the finally prepared gadolinium-containing high-density tungsten alloy shielding material has both good mechanical properties and shielding properties. DETAILED DESCRIPTION

[0054] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0055] The tungsten powder in the embodiment is of 99.99wt% purity, the nickel powder is of 99.95% purity, the iron powder is of 99.9% purity, and the gadolinium oxide is of 99.9% purity. The above description is only for the purpose of clearly illustrating the technical solutions of the present application, and should not be regarded as a further limitation of the technical solutions of the present application.

[0056] Embodiment 1

[0057] The preparation raw material of the gadolinium-containing high specific gravity tungsten alloy shielding material according to the embodiment comprises, in mass percentage, 75wt% of tungsten powder, 15.75wt% of nickel powder, 6.75wt% of iron powder, and 2.5wt% of gadolinium source.

[0058] The gadolinium source is gadolinium oxide.

[0059] In the preparation raw material, the average particle size of the tungsten powder is 2.8μm, the average particle size of the nickel powder is 3.2μm, the average particle size of the iron powder is 2.5μm, and the average particle size of the gadolinium oxide is 2.1μm.

[0060] The preparation method of the gadolinium-containing high specific gravity tungsten alloy shielding material according to the embodiment comprises the following steps:

[0061] (1) mixing the preparation raw material of the gadolinium-containing high specific gravity tungsten alloy shielding material, and cold isostatic pressing at 200MPa to obtain a plate-shaped green body;

[0062] (2) performing solid phase sintering and liquid phase sintering on the plate-shaped green body obtained in step (1) to obtain a plate sintered body;

[0063] The solid phase sintering is performed in a hydrogen atmosphere at a temperature of 1419℃ for 223min, and the sintered body obtained by the solid phase sintering has a density of 97.3%;

[0064] The liquid phase sintering is performed in a hydrogen atmosphere at a temperature of 1505℃ for 52min to obtain a sintered body with a thickness of 30mm;

[0065] (3) performing heat treatment and rolling on the plate sintered body to obtain the gadolinium-containing high specific gravity tungsten alloy shielding material;

[0066] The heat treatment is performed at a temperature of 1240℃ for 95min under a vacuum degree of 6Pa;

[0067] The rolling is performed at a temperature of 625℃, and the single pass amount of downward pressing is 3.8mm. After 6 passes of rolling, a plate with a thickness of 7.2mm is obtained, and the cumulative deformation amount is 76%.

[0068] Embodiment 2-1

[0069] This embodiment provides a gadolinium-containing high-density tungsten alloy shielding material. Except that the gadolinium source is a combination of gadolinium oxide and surface-modified gadolinium oxide, the rest is the same as that of Example 1.

[0070] Based on the total mass percentage of the gadolinium source being 100 wt %, the mass percentage of the surface-modified gadolinium oxide in the gadolinium source is 50 wt %;

[0071] The surface-modified gadolinium oxide is gadolinium oxide with a tungsten layer coated on its surface. The thickness of the tungsten layer is 3 μm, and the method of coating the tungsten layer is chemical vapor deposition.

[0072] In Examples 2-2 to 2-4, except that the mass percentage of the surface-modified gadolinium oxide in the gadolinium source was changed as shown in Table 1, the rest were the same as in Example 2-1.

[0073] Table 1

[0074] Mass percentage of surface modified gadolinium oxide (wt%) Example 2-1 50 Example 2-2 60 Example 2-3 80 Examples 2-4 100

[0075] Example 3-1

[0076] This embodiment provides a gadolinium-containing high-density tungsten alloy shielding material. Except that the gadolinium source is a combination of gadolinium oxide and surface-modified gadolinium oxide, the rest is the same as that of Example 1.

[0077] Based on the total mass percentage of the gadolinium source being 100 wt %, the mass percentage of the surface-modified gadolinium oxide in the gadolinium source is 50 wt %;

[0078] The surface-modified gadolinium oxide is gadolinium oxide coated with a nickel layer, the thickness of the nickel layer is 3 μm, and the method of coating the nickel layer is electroplating.

[0079] In Examples 3-2 and 3-4, except that the mass percentage of the surface-modified gadolinium oxide in the gadolinium source was changed as shown in Table 2, the rest were the same as in Example 3-1.

[0080] Table 2

[0081] Mass percentage of surface modified gadolinium oxide (wt%) Example 3-1 50 Example 3-2 60 Example 3-3 80 Examples 3-4 100

[0082] Example 4-1

[0083] This embodiment provides a gadolinium-containing high-density tungsten alloy shielding material, which is the same as Example 1 except that the gadolinium source is surface-modified gadolinium oxide.

[0084] The surface-modified gadolinium oxide is a gadolinium oxide whose surface is sequentially coated with a tungsten layer and a nickel layer. In Example 4-1, the thickness of the tungsten layer is 3 μm, and the thickness of the nickel layer is 3 μm. The method of coating the tungsten layer is chemical vapor deposition, and the method of coating the nickel layer is electroplating.

[0085] In Example 4-2 to Example 4-4, except that the thickness of the tungsten layer and the thickness of the nickel layer are changed as shown in Table 3, the rest are the same as Example 4-1.

[0086] Table 3

[0087]

[0088]

[0089] Example 5

[0090] This embodiment provides a gadolinium-containing high-density tungsten alloy shielding material. The raw materials for preparing the gadolinium-containing high-density tungsten alloy shielding material include, by weight percentage: 70 wt% tungsten powder, 18.2 wt% nickel powder, 7.8 wt% iron powder, and 4 wt% gadolinium source.

[0091] The gadolinium source is surface-modified gadolinium oxide;

[0092] The surface-modified gadolinium oxide is a gadolinium oxide having a tungsten layer and a nickel layer sequentially coated on the surface, wherein the thickness of the tungsten layer is 1.6 μm and the thickness of the nickel layer is 3.4 μm; the tungsten layer is coated by chemical vapor deposition, and the nickel layer is coated by electroplating;

[0093] Among the raw materials prepared, the average particle size of tungsten powder is 1.2 μm, the average particle size of nickel powder is 4.7 μm, the average particle size of iron powder is 3.7 μm, and the average particle size of gadolinium oxide is 4.6 μm;

[0094] The preparation method of the gadolinium-containing high-density tungsten alloy shielding material provided in this embodiment includes the following steps:

[0095] (1) mixing raw materials for preparing gadolinium-containing high-density tungsten alloy shielding materials, and cold isostatically pressing at 200 MPa to obtain a plate-shaped green body;

[0096] (2) performing solid-phase sintering and liquid-phase sintering on the plate-shaped green body obtained in step (1) to obtain a plate sintered green body;

[0097] The solid phase sintering is carried out in a hydrogen atmosphere at a temperature of 1401° C. for 274 minutes. The density of the sintered compact obtained by the solid phase sintering is 98.1%.

[0098] The liquid phase sintering is carried out in a hydrogen atmosphere at a temperature of 1471° C. for 77 minutes to obtain a sintered blank with a thickness of 30 mm.

[0099] (3) heat treating and rolling the obtained plate sintered blank to obtain the gadolinium-containing high-density tungsten alloy shielding material;

[0100] The heat treatment was carried out under a vacuum degree of 8 Pa, a temperature of 1175° C., and a time of 120 min;

[0101] The rolling temperature is 512° C., the pressing amount of a single pass is 2.4 mm, and after 9 rolling passes, a plate with a thickness of 8.4 mm is obtained, and the cumulative deformation amount is 72%.

[0102] Example 6

[0103] This embodiment provides a gadolinium-containing high-density tungsten alloy shielding material. The raw materials for preparing the gadolinium-containing high-density tungsten alloy shielding material include, by weight percentage: 80 wt% tungsten powder, 13.3 wt% nickel powder, 5.7 wt% iron powder, and 1 wt% gadolinium source.

[0104] The gadolinium source is surface-modified gadolinium oxide;

[0105] The surface-modified gadolinium oxide is a gadolinium oxide having a tungsten layer and a nickel layer sequentially coated on the surface, wherein the thickness of the tungsten layer is 4.7 μm and the thickness of the nickel layer is 1.3 μm; the tungsten layer is coated by chemical vapor deposition, and the nickel layer is coated by electroplating;

[0106] Among the raw materials prepared, the average particle size of tungsten powder is 3.5 μm, the average particle size of nickel powder is 2.2 μm, the average particle size of iron powder is 4.5 μm, and the average particle size of gadolinium oxide is 1.3 μm;

[0107] The preparation method of the gadolinium-containing high-density tungsten alloy shielding material provided in this embodiment includes the following steps:

[0108] (1) mixing raw materials for preparing gadolinium-containing high-density tungsten alloy shielding materials, and cold isostatically pressing at 200 MPa to obtain a plate-shaped green body;

[0109] (2) performing solid-phase sintering and liquid-phase sintering on the plate-shaped green body obtained in step (1) to obtain a plate sintered green body;

[0110] The solid phase sintering is carried out in a hydrogen atmosphere at a temperature of 1373° C. for 321 minutes. The density of the sintered compact obtained by the solid phase sintering is 98.4%.

[0111] The liquid phase sintering is carried out in a hydrogen atmosphere at a temperature of 1532° C. for 43 minutes to obtain a sintered blank with a thickness of 30 mm.

[0112] (3) heat treating and rolling the obtained plate sintered blank to obtain the gadolinium-containing high-density tungsten alloy shielding material;

[0113] The heat treatment was carried out under a vacuum degree of 3 Pa, a temperature of 1065° C., and a time of 145 min;

[0114] The rolling temperature is 820° C., the pressing amount of a single pass is 4.8 mm, and after four rolling passes, a plate with a thickness of 10.8 mm is obtained, and the cumulative deformation amount is 64%.

[0115] Example 7

[0116] This embodiment provides a gadolinium-containing high-density tungsten alloy shielding material. The raw materials for preparing the gadolinium-containing high-density tungsten alloy shielding material include, by weight percentage: 60 wt% tungsten powder, 24.5 wt% nickel powder, 10.5 wt% iron powder, and 5 wt% gadolinium source.

[0117] The gadolinium source is surface-modified gadolinium oxide;

[0118] The surface-modified gadolinium oxide is a gadolinium oxide having a tungsten layer and a nickel layer sequentially coated on the surface, wherein the thickness of the tungsten layer is 3.3 μm and the thickness of the nickel layer is 2.1 μm; the tungsten layer is coated by chemical vapor deposition, and the nickel layer is coated by electroplating;

[0119] Among the raw materials prepared, the average particle size of tungsten powder is 2.8 μm, the average particle size of nickel powder is 3.2 μm, the average particle size of iron powder is 2.5 μm, and the average particle size of gadolinium oxide is 2.1 μm;

[0120] The preparation method of the gadolinium-containing high-density tungsten alloy shielding material provided in this embodiment includes the following steps:

[0121] (1) mixing raw materials for preparing gadolinium-containing high-density tungsten alloy shielding materials, and cold isostatically pressing at 200 MPa to obtain a plate-shaped green body;

[0122] (2) performing solid-phase sintering and liquid-phase sintering on the plate-shaped green body obtained in step (1) to obtain a plate sintered green body;

[0123] The solid phase sintering is carried out in a hydrogen atmosphere at a temperature of 1350° C. for 360 min. The density of the sintered compact obtained by the solid phase sintering is 97.9%.

[0124] The liquid phase sintering is carried out in a hydrogen atmosphere at a temperature of 1450° C. for 90 minutes to obtain a sintered blank with a thickness of 30 mm.

[0125] (3) heat treating and rolling the obtained plate sintered blank to obtain the gadolinium-containing high-density tungsten alloy shielding material;

[0126] The heat treatment is carried out under the condition of vacuum degree of 6 Pa, temperature of 1000°C and time of 180 min;

[0127] The rolling temperature is 500° C., the pressing amount of a single pass is 2 mm, and after 11 rolling passes, a plate with a thickness of 8 mm is obtained, and the cumulative deformation amount is 73.3%.

[0128] Example 8

[0129] This embodiment provides a gadolinium-containing high-density tungsten alloy shielding material. The raw materials for preparing the gadolinium-containing high-density tungsten alloy shielding material include, by weight percentage: 85 wt% tungsten powder, 10.15 wt% nickel powder, 4.35 wt% iron powder, and 0.5 wt% gadolinium source.

[0130] The gadolinium source is surface-modified gadolinium oxide;

[0131] The surface-modified gadolinium oxide is a gadolinium oxide having a tungsten layer and a nickel layer sequentially coated on the surface, wherein the thickness of the tungsten layer is 3.3 μm and the thickness of the nickel layer is 2.1 μm; the tungsten layer is coated by chemical vapor deposition, and the nickel layer is coated by electroplating;

[0132] Among the raw materials prepared, the average particle size of tungsten powder is 2.8 μm, the average particle size of nickel powder is 3.2 μm, the average particle size of iron powder is 2.5 μm, and the average particle size of gadolinium oxide is 2.1 μm;

[0133] The preparation method of the gadolinium-containing high-density tungsten alloy shielding material provided in this embodiment includes the following steps:

[0134] (1) mixing raw materials for preparing gadolinium-containing high-density tungsten alloy shielding materials, and cold isostatically pressing at 200 MPa to obtain a plate-shaped green body;

[0135] (2) performing solid-phase sintering and liquid-phase sintering on the plate-shaped green body obtained in step (1) to obtain a plate sintered green body;

[0136] The solid phase sintering is carried out in a hydrogen atmosphere at a temperature of 1430° C. for 180 min. The density of the sintered compact obtained by the solid phase sintering is 98.5%.

[0137] The liquid phase sintering is carried out in a hydrogen atmosphere at a temperature of 1550° C. for 30 minutes to obtain a sintered blank with a thickness of 30 mm.

[0138] (3) heat treating and rolling the obtained plate sintered blank to obtain the gadolinium-containing high-density tungsten alloy shielding material;

[0139] The heat treatment is carried out under the condition of vacuum degree of 6 Pa, temperature of 1300°C and time of 60 min;

[0140] The rolling temperature is 850° C., the pressing amount of a single pass is 6 mm, and after four rolling passes, a plate with a thickness of 6 mm is obtained, and the cumulative deformation amount is 80%.

[0141] Comparative Example 1

[0142] This comparative example provides a gadolinium-containing high-density tungsten alloy shielding material. The raw material composition of the gadolinium-containing high-density tungsten alloy shielding material is, by mass percentage, 75 wt% of tungsten powder, 17.22 wt% of nickel powder, 7.38 wt% of iron powder, and 0.4 wt% of gadolinium source. The rest is the same as Example 4-2.

[0143] Comparative Example 2

[0144] This comparative example provides a gadolinium-containing high-density tungsten alloy shielding material. The raw material composition of the gadolinium-containing high-density tungsten alloy shielding material is, by mass percentage, 75 wt% of tungsten powder, 13.65 wt% of nickel powder, 5.85 wt% of iron powder, and 5.5 wt% of gadolinium source. The rest is the same as Example 4-2.

[0145] Comparative Example 3

[0146] This comparative example provides a high-density tungsten alloy shielding material. In terms of mass percentage, the raw material composition of the high-density tungsten alloy shielding material is 75wt% tungsten powder, 17.5wt% nickel powder and 7.5wt% iron powder, and the rest is the same as Example 4-2.

[0147] That is, no gadolinium source was used in this comparative example.

[0148] Comparative Example 4

[0149] This comparative example provides a high-density tungsten alloy shielding material. In addition to the raw material composition of the high-density tungsten alloy shielding material being 75wt% of tungsten powder, 15.75wt% of nickel powder, 6.75wt% of iron powder and 2.5wt% of iron boride, the rest are the same as Example 4-2.

[0150] The iron boride in this comparative example is a single FeB phase, and the average particle size is 2.1 μm.

[0151] Performance Testing

[0152] The density, room temperature tensile strength, elongation after fracture, gamma-ray shielding capability and neutron shielding capability of the shielding materials obtained in the above examples and comparative examples were tested, and the results are shown in Table 4.

[0153] Among them, the density is tested using the Archimedes drainage method with reference to the standard "ASTM B311-2008 Standard Test Method for Density of Powder Metallurgy Materials with Porosity Less than 2%".

[0154] The room temperature tensile strength and elongation after fracture were tested using a universal testing machine with reference to the standard "GB / T 228.1-2010 Tensile tests on metallic materials - Part 1: Test methods at room temperature".

[0155] γ-ray shielding capability: The reference test standard is GBZ / T147-2002 Determination of attenuation performance of X-ray shielding materials. The dosimeter is used to test the material (thickness is 5mm). 60 Equivalent lead weight of Co-radiation source shielding.

[0156] Neutron shielding capability: The reference test standards are GBZ / T147-2002 Determination of attenuation performance of X-ray shielding materials and NPIC-TCL-QSW325D Determination of neutron attenuation performance of materials. 3 The transmittance f of the He neutron detector / secondary instrument test material (thickness is 5 mm) to cadmium neutrons, f = N / N0, where N0 is the cadmium neutron count measured by the cadmium difference method when there is no shielding material, and N is the cadmium neutron count measured by the cadmium difference method when there is shielding material.

[0157] Table 4

[0158]

[0159]

[0160] It can be seen from Example 1 and Examples 5 to 8 in Table 1 that the gadolinium-containing high-density tungsten alloy shielding material provided by the present invention has excellent mechanical properties, and the obtained shielding material can achieve a composite shielding effect against gamma rays and neutrons.

[0161] From the comparison between Example 2-1 and Example 1, it can be seen that when the surface-modified gadolinium oxide is gadolinium oxide with a tungsten layer coated on its surface, adding an appropriate amount of surface-modified gadolinium oxide to the gadolinium source can further improve the performance of the obtained gadolinium-containing high-density tungsten alloy shielding material; and from the comparison between Example 2-1 to Example 2-4, it can be seen that the performance of the gadolinium-containing high-density tungsten alloy shielding material increases with the increase of the content of surface-modified gadolinium oxide in the gadolinium source.

[0162] From the comparison between Example 3-1 and Example 1, it can be seen that when the surface-modified gadolinium oxide is gadolinium oxide coated with a nickel layer, adding an appropriate amount of surface-modified gadolinium oxide to the gadolinium source can further improve the performance of the obtained gadolinium-containing high-density tungsten alloy shielding material; and from the comparison between Example 3-1 and Example 3-4, it can be seen that the performance of the gadolinium-containing high-density tungsten alloy shielding material increases with the increase of the content of surface-modified gadolinium oxide in the gadolinium source.

[0163] Comparison of Example 4-1 with Example 3-1 and Example 2-1 demonstrates that the technical performance of gadolinium oxide with a surface sequentially coated with a tungsten layer and then a nickel layer is superior to that of surface-modified gadolinium oxide coated with only a tungsten layer or a nickel layer. Sequentially providing a tungsten layer and then a nickel layer further enhances the shielding and mechanical properties of the resulting gadolinium-containing, high-density tungsten alloy shielding material. Furthermore, comparison of Examples 4-1 and 4-4 demonstrates that varying the thickness of the tungsten and nickel layers within the required process range can impart excellent mechanical properties to the resulting gadolinium-containing, high-density tungsten alloy shielding material, and that the resulting shielding material can achieve a combined shielding effect against both gamma rays and neutrons.

[0164] Comparison between Comparative Example 1 and Example 4-2 shows that when the gadolinium source content is lower than 0.5 wt %, the neutron shielding capability decreases significantly. Comparison between Comparative Example 2 and Example 4-2 shows that when the gadolinium source content is higher than 5 wt %, the room temperature tensile strength and room temperature elongation after break decrease significantly.

[0165] From the comparison of Comparative Example 3 with Example 1 and Example 4-2, it can be seen that the addition of the gadolinium source is beneficial to improving the room temperature tensile strength and neutron shielding capability of the gadolinium-containing high-density tungsten alloy shielding material; from the comparison of Comparative Example 4 with Example 1 and Example 4-2, it can be seen that the addition of the gadolinium source has a technical effect that is better than that of the boron source.

[0166] In summary, the gadolinium-containing high-density tungsten alloy shielding material provided by the present invention uses gadolinium oxide as a neutron absorption material. First, when a small amount of gadolinium oxide is added to the high-density tungsten alloy shielding material, it can play a role in dispersion strengthening, that is, it can refine the grain size and strengthen the grain boundaries. This effect is directly manifested in improving the tensile strength and hardness of the material, while slightly damaging the ductility of the material. Secondly, the neutron absorption cross section of gadolinium is 38300 barns, and the mass content of gadolinium in gadolinium oxide is 86.8%. Gadolinium oxide has a higher equivalent than metal boride, that is, the amount of gadolinium oxide required to be added to the shielding material to achieve the same neutron shielding effect is significantly lower than that of metal boride, which can be The adverse effects on the mechanical properties of the shielding material are significantly reduced; from another perspective, when having the same mechanical properties, the amount of gadolinium oxide allowed to be added to the high-density tungsten alloy material is significantly higher than that of metal boride, that is, the neutron shielding performance of the high-density tungsten alloy containing gadolinium with the same mechanical properties is better than that of the high-density tungsten alloy material containing metal boride; moreover, the preparation method provided by the present invention adopts a method combining solid-phase sintering and liquid-phase sintering. Solid-phase sintering can make the plate nearly completely dense, while liquid-phase sintering can avoid segregation and aggregation of uniformly dispersed gadolinium oxide during liquid-phase sintering, so that the finally prepared high-density tungsten alloy containing gadolinium has both good mechanical properties and shielding properties.

[0167] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A gadolinium-containing high-density tungsten alloy shielding material, characterized in that: The raw materials for preparing the gadolinium-containing high-density tungsten alloy shielding material include, by weight percentage: 60-85wt% of tungsten, 0.5-5wt% of gadolinium source, and the balance of nickel, iron, and inevitable impurities; The gadolinium source includes gadolinium oxide and / or surface-modified gadolinium oxide; The surface-modified gadolinium oxide includes gadolinium oxide with a tungsten layer and / or a nickel layer coated on its surface.

2. The gadolinium-containing heavy tungsten alloy shielding material according to claim 1, characterized in that: Based on the total mass percentage of the gadolinium source being 100wt%, the mass percentage of the surface-modified gadolinium oxide in the gadolinium source is ≥50wt%.

3. The gadolinium-containing heavy tungsten alloy shielding material according to claim 1, characterized in that: The thickness of the tungsten layer in the surface-modified gadolinium oxide is 1-5 μm.

4. The gadolinium-containing heavy tungsten alloy shielding material according to claim 1, characterized in that: The thickness of the nickel layer in the surface-modified gadolinium oxide is 1-5 μm.

5. The gadolinium-containing heavy tungsten alloy shielding material according to claim 1, characterized in that: The surface-modified gadolinium oxide comprises gadolinium oxide whose surface is sequentially coated with a tungsten layer and a nickel layer.

6. The gadolinium-containing heavy tungsten alloy shielding material according to claim 1, characterized in that: The average particle size of the gadolinium oxide is 0.5-5 μm.

7. A method for preparing the gadolinium-containing high-density tungsten alloy shielding material according to any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: The raw materials for preparing gadolinium-containing high-density tungsten alloy shielding material are mixed, and cold isostatic pressing, solid-phase sintering and liquid-phase sintering are sequentially performed to obtain a plate sintered blank; the obtained plate sintered blank is heat treated and rolled to obtain the gadolinium-containing high-density tungsten alloy shielding material.

8. The preparation method according to claim 7, characterized in that The temperature of the solid phase sintering is 1350-1430°C.

9. The preparation method according to claim 7, characterized in that The solid phase sintering time is 180-360 minutes.

10. The preparation method according to claim 7, characterized in that The solid phase sintering is performed in an oxygen-free condition.

11. The preparation method according to claim 7, characterized in that The temperature of the liquid phase sintering is 1450-1550°C.

12. The preparation method according to claim 7, characterized in that The liquid phase sintering time is 30-90 minutes.

13. The preparation method according to claim 7, characterized in that The liquid phase sintering is performed in a reducing atmosphere.

14. The preparation method according to claim 7, characterized in that The temperature of the heat treatment is 1000-1300°C.

15. The preparation method according to claim 7, characterized in that The heat treatment time is 60-180 minutes.

16. The preparation method according to claim 7, characterized in that The heat treatment is carried out under the condition of vacuum degree ≤10Pa.

17. The preparation method according to claim 7, characterized in that The rolling temperature is 500-850°C.

18. The preparation method according to claim 7, characterized in that The pressing amount of a single rolling pass is 2-6 mm.

19. The preparation method according to claim 7, characterized in that: The cumulative deformation of the rolling is above 60%.

20. An application of the gadolinium-containing high-density tungsten alloy shielding material according to any one of claims 1 to 6, characterized in that: The gadolinium-containing high-density tungsten alloy shielding material is used for gamma ray-neutron composite shielding.

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