CN105714173A - Manganese-cobalt-germanium-base alloy magnetic refrigeration material and preparing method thereof - Google Patents

Abstract

The invention relates to a manganese-cobalt-germanium-base alloy magnetic refrigeration material and a preparing method thereof. The molecule general formula of the magnetic refrigeration material is MnCoGe1-xCux, wherein the value of x ranges from 0.005 to 0.05. The manganese-cobalt-germanium-base alloy magnetic refrigeration material is prepared by the following steps that firstly, a manganese material, a cobalt material, a germanium material and a copper material are weighed according to the molar ratio of 1:1:(1-x): x, heating, fusing and even mixing are conducted under the inert gas shielding, and a mixed sample is obtained; and secondly, the mixed sample is taken out, annealing treatment is conducted, and a target product is obtained. Compared with the prior art, the magnetic refrigeration material has the beneficial effects that the magnetic refrigeration material is good in Curie temperature and magnetocaloric effect, the magnetic refrigeration material is a second-order phase change material, the problem of heat stagnation brought by a first-order phase change material is effectively solved, and preparing is simple and feasible.

Description

A kind of manganese cobalt germanium-base alloy magnetic refrigerating material and preparation thereof

Technical field

The present invention relates to the alloy magnetic refrigeration material in a kind of magnetic refrigerating field, especially relate to a kind of manganese cobalt germanium copper Alloy magnetic refrigeration material and preparation thereof.

Background technology

The nearlyest room temperature magnetic refrigerating development is at a low ebb, and tracing it to its cause is that its heat stagnation, magnetic hysteresis are relatively big, temp. controllable width Less with refrigerating capacity, high cost causes；And along with a large amount of of traditional energy consume, the pressure of environmental conservation in addition, The new forms of energy such as development magnetic refrigeration are extremely the most urgent.For traditional vapor compression refrigeration etc., magnetic refrigeration has Efficiency is high, noise is low, floor space is little and in use will not produce the features such as any pollution.Pass through magnetic The magnetothermal effect of material itself realizes refrigeration, will necessarily become the mankind and solve the important way of the energy and environmental problem Footpath.But, compared with other refrigeration modes, the technology of magnetic refrigeration is the most overripened, particularly room temperature magnetic refrigerating Research just ground zero soon, bigger heat stagnation and magnetic hysteresis, and less magnetothermal effect is restriction magnetic refrigeration development Key.Therefore, how to reduce heat stagnation and magnetic hysteresis, nearly near room temperature obtain bigger magnetothermal effect be for a long time with Carry out the problem that people endeavour to solve always, and a key factor of room temperature magnetic refrigerating development is exactly at nearly near room temperature Magnetothermal effect is less, i.e. obtains bigger magnetothermal effect near room temperature.It is known that MnCoGe alloy is allusion quotation The martensitic phase transformation alloy of type, because its significant magnetic characteristic and magnetic heating performance are considered to be a kind of preferably magneto-caloric material One of, the MnCoGe alloy just divided is a simple ferromagnet, has orthogonal TiNiSi structure under room temperature, Curie temperature is at about 345K, at about 650K, MnCoGe alloy can occur one from orthogonal TiNiSi to hexagonal Ni₂The structural phase transition of In.But MnCoGe alloy structure phase transformation occurs mainly in paramagnetic state, and magnetization change is not Greatly, there is no obvious using value.Therefore, for how reducing structural phase transition and the raising of MnCoGe alloy It is the key in the design of nearly room temperature magnetic refrigerating, preparation that nearly room temperature magnetothermal effect carries out studying.

At present, the design of MnCoGe alloy, preparation etc. have been done substantial amounts of detailed research work by home and abroad, Its technical way has three kinds: doping interstitial atom, changes the chemical composition of compound, utilizes transition group atom Substitute.Particularly the replacement of MnCoGe alloy atom is had been achieved for good magnetothermal effect in preparation. But owing to preparation method and material purity etc. limit so that MnCoGe is in the magnetothermal effect of nearly near room temperature at present The most not ideal.This is because, research work currently mainly concentrates on Mn position and the replacement of Co position atom, Although these are operated in nearly near room temperature and have been obtained for giant magnetio-caloric effects, but incident first order phase change is the most special Point: less half-peak breadth and bigger heat stagnation, still without solution.MnCoGe prepared by generally conventional method Base alloy is usually first order phase change material.And first order phase change material is past in the utilization of refrigeration temp. controllable width and magnetothermal effect Toward unsatisfactory, such as Mn_1-xCu_xCoGe, when x=0.085, under the changes of magnetic field of 5T, the isothermal magnetic of alloy Entropy Changes can reach 53.3JKg^-1K^-1But, during alloy phase change, there is bigger heat stagnation and less temp. controllable width. In recent years, second-order phase transistion material is to material science research, including answering of material behavior, new material synthesis and new material With, create material impact.Relevant research it has been shown that MnCoGe alloy is carried out element substitution technology, The MnCoGe alloy competitiveness in magnetic Refrigeration Technique can be promoted.For room temperature magnetic refrigerating, improve refrigeration effect First it is critical only that of rate obtain bigger magnetothermal effect in nearly room temperature, and next has less heat stagnation and bigger adjustable Wen Kuan.And for general material, magnetothermal effect is the biggest, and but meet at the bigger magnetic of nearly room temperature simultaneously Avoiding again bigger heat stagnation while heat effect, this is necessary for improving original technology of preparing, improves the microcosmic of alloy Structure, thus reduce heat stagnation and obtain bigger magnetothermal effect.Along with the further investigation of MnCoGe alloy, make The second-order phase transistion that must prepare nearly room temperature giant magnetio-caloric effects is possibly realized, though having a lot about MnCoGe base both at home and abroad The research of alloy, but still lack the research to the doping of MnCoGe base Ge position.

Summary of the invention

Defect that the purpose of the present invention is contemplated to overcome above-mentioned prior art to exist and provide a kind of manganese cobalt germanio to close Gold magnetic refrigerating material and preparation thereof.

The purpose of the present invention can be achieved through the following technical solutions:

A kind of manganese cobalt germanium-base alloy magnetic refrigerating material, its general molecular formula is MnCoGe_1-xCu_x, wherein, x takes Value scope is 0.005～0.05.

The span of x is 0.01～0.04.

The preparation method of manganese cobalt germanium-base alloy magnetic refrigerating material, comprises the following steps:

(1) weigh and under manganese, cobalt, germanium and copper product, inert gas shielding, add heat fusing mix homogeneously, obtain Biased sample；

(2) biased sample is taken out, annealing, i.e. obtain purpose product.

In step (1), the air pressure of noble gas is 5～15Pa.

In step (2), the processing step of annealing is: first under inert gas shielding, at 800～900 DEG C Annealing 5～10 days, then be placed in the water of 10～30 DEG C annealing, the process time is about about 2min.

Described noble gas is argon.

MnCoGe compound Ge position is mixed by the present invention by have employed the Cu of trace in MnCoGe architecture Miscellaneous, finally prepare MnCoGe_1-xCu_xAlloy magnetic refrigeration material.Find the most afterwards, when Ge replacement is contained by Cu When amount x is 0.01～0.04, Curie temperature (T_C) risen to 363K by 353K, under the changes of magnetic field of 5T, Maximum magnetic entropy variable is: 18.3JKg^-1K^-1, 12.9JKg^-1K^-1, 15.3JKg^-1K^-1, 6.8JKg^-1K^-1, relatively make Cold is: 292.5JKg^-1, 206.9JKg^-1, 260.5JKg^-1, 242.4JKg^-1；With conventional MnCoGe (343K, 5.8JKg^-1K^-1, 227JKg^-1) alloy compares, it will be apparent that improve Curie temperature and the magnetothermal effect of magnetic material.

Compared with prior art, the invention have the advantages that

(1) present invention is by the Ge position doping micro Cu in MnCoGe architecture, and then significantly improves The Curie temperature of magnetic material and magnetothermal effect, and obtained alloy is second-order phase transistion material, effectively avoids The heat stagnation problem that first order phase change material brings.

(2) preparation method is simple, it is easy to accomplish, cheap, application prospect is extensive, can be applicable to relate to system Numerous key areas of the cold national economy with cryogenic technique, such as high-energy physics, cryogenic engineering, Aero-Space, essence Close instrument, petrochemical industry, power industry, superconducting technology, medical apparatus and instruments etc..

Accompanying drawing explanation

Fig. 1 is the magnetic refrigerating material MnCoGe of the present invention_1-xCu_x(x=0.01,0.02,0.03,0.04) room temperature XRD diffraction pattern；

Fig. 2 is the magnetic refrigerating material MnCoGe of the present invention_1-xCu_xSeries alloy is M-T figure when outfield 0.02T；

Fig. 3 is the magnetic refrigerating material MnCoGe of the present invention_1-xCu_xSeries alloy is at the isothermal magnetic of near Curie temperature Change curve；

Fig. 4 is the magnetic refrigerating material MnCoGe of the present invention_1-xCu_xSeries alloy is bent at the Arrott of vicinity of Curie temperatures Line；

Fig. 5 is the magnetic refrigerating material MnCoGe of the present invention_1-xCu_xSeries alloy is respectively in 2T and 5T changes of magnetic field Under isothermal magnetic entropy varied curve；

Fig. 6 is the magnetic refrigerating material MnCoGe of the present invention_1-xCu_xSeries alloy is respectively under 5T changes of magnetic field Maximum magnetic entropy variable and H^2/3Curve.

Detailed description of the invention

The present invention is described in detail with specific embodiment below in conjunction with the accompanying drawings.

Embodiment 1

Weighing purity according to mol ratio 1:1:0.99:0.01 is 99.9%Mn, 99.9%Co, 99.99%Ge, 99.9%Cu, It is placed in vacuum arc furnace melting, specifically before alloy melting, first is evacuated to, less than 5Pa, open with mechanical pump Molecular pump is evacuated to again less than 10^-4Pa, is passed through the high purity argon (99.999%) of air pressure 10Pa, repeats Above operating procedure twice, on fire with 30A electric current, electrode is about 0.5cm with the distance of sample, slowly will Current-modulation 80A is until sample melts completely, then electric current is down to 60A melting half a minute, treats that alloy cooling is right Turning over, melt back four times is to ensure that sample mix is uniform.After taking out cooling, high-purity high temperature resistant quartz glass put into by sample Test tube, utilizes hight atmospheric molecular pumping system to be evacuated to less than 5Pa, is filled with high purity argon (99.999%) and enters Row gas washing, repeats above step three times, sealed silica envelope, puts in stove formula case 850 DEG C of annealing 7 days good to ensure Good degree of crystallinity, takes out sample and makes annealing treatment about 2min in temperature is 15 DEG C of cold water, i.e. obtain purpose product MnCoGe_1-xCu_xAlloy.

Embodiment 2

Except the ratio of mole addition between Mn, Co, Ge and Cu is that in addition to 1:1:0.98:0.02, remaining is homogeneous With.

Embodiment 3

Except the ratio of mole addition between Mn, Co, Ge and Cu is that in addition to 1:1:0.97:0.03, remaining is homogeneous With.

Embodiment 4

Except the ratio of mole addition between Mn, Co, Ge and Cu is that in addition to 1:1:0.96:0.04, remaining is homogeneous With.

The MnCoGe that above-described embodiment 1-4 is prepared_1-xCu_xAlloy detects, MnCoGe_1-xCu_x(x=0.01, 0.02,0.03,0.04) Alloy At Room Temperature XRD diffraction pattern is as it is shown in figure 1, all samples degree of crystallinity is good, in room temperature The main orthogonal thereto TiNiSi structure of lower all samples, has a small amount of hexagonal Ni simultaneously₂In structure.

Fig. 2 is the alloy outer M-T (FC-ZFC) figure after the match at 0.02T, and illustration is the Curie temperature of alloy With the relation of temperature, alloy occurs by the ferromagnetic magnetic phase transition to paramagnetic near Curie temperature, and Curie temperature is by M-T Figure slope variation maximum is tried to achieve, it is known that, along with the increase Curie temperature of Cu doping content is risen to by 353K 363K。

Fig. 3 is prepared alloy isothermal magnetization curve M-H of near Curie temperature under 0～7T magnetic field, by M-H It is relatively big that figure understands near Curie temperature magnetization change, analyzes consistent with M-T.

Fig. 4 is the prepared alloy Arrott curve near Curie temperature, can be seen that institute from Arrott curve Some samples near Curie temperature slope of a curve be on the occasion of, this shows that all samples is equal near Curie temperature There are two grades of magnetic phase transitions, illustrate that all samples all only has less heat stagnation near transformation temperature, effectively avoid one The problem that near level phase transformation, heat stagnation is bigger, improves the utilization ratio of the energy.

Fig. 5 is the isothermal magnetic entropy varied curve under prepared alloy material 2T and 5T changes of magnetic field, second-order phase transistion magnetic The isothermal magnetic entropy of refrigerating material is become and can be obtained by Maxwell equation:

$\mathrm{\Δ}S(H,T)={\∫}_0^H{\left(\frac{\∂M(T,H)}{\∂T}\right)}_{H}dH---\left(1\right)$

The numerical value in (1) in equation can be write as following formula with trapezoidal rule

${\mathrm{\ΔS}}_M(H,T)=\underset{i}{\Σ}\frac{M_i-M_{i+1}}{T_{i+1}-T_i}{\mathrm{\ΔH}}_i---\left(2\right)$

In formula, H is magnetic field intensity；T is for measuring temperature；M_i+1And M_iIt is respectively T_i+1And T_iTime magnetization Intensity.Then, we combine the experimental result of Fig. 3, and utilize (2) formula to calculate this sample at different magnetic field Lower shown isothermal magnetic entropy becomes.Result shows: under the changes of magnetic field of 2T, and maximum isothermal magnetic entropy becomes: 7.05JKg^-1K^-1(x=0.01), 4.96JKg^-1K^-1(x=0.02), 5.84JKg^-1K^-1(x=0.03), 2.87JKg^-1K^-1 (x=0.04), under the changes of magnetic field of 5T, maximum isothermal magnetic entropy becomes: 18.3JKg^-1K^-1(x=0.01), 12.9 JKg^-1K^-1(x=0.02), 15.3JKg^-1K^-1(x=0.03), 6.8JKg^-1K^-1(x=0.04).

Additionally, evaluate the relative refrigerating capacity (RCP) that another important parameter is magneto-caloric material of magnetothermal effect, RCP can It is expressed as

$RCP=-{\mathrm{\ΔS}}_M(H,T)\×\∂T_{FWHM}---\left(3\right)$

For the half-peak breadth corresponding to maximum isothermal magnetic entropy change, according to above formula, we calculate MnCoGe_1-xCu_xWhen RCP is respectively 2T under the conditions of magnetic field changes of alloy: 113.8JKg^-1(x=0.01), 79.4JKg^-1(x=0.02), 99.2JKg^-1(x=0.03), 97.7JKg^-1(x=0.04)；During 5T: 292.5JKg^-1 (x=0.01), 206.9JKg^-1(x=0.02), 260.5JKg^-1(x=0.03), 242.4JKg^-1(x=0.04). Visible, by adjusting the content of the copper in magnetic material, it is possible to better control over the crystal structure of material, effectively Improve Curie temperature and the magnetothermal effect of magnetic material.With conventional MnCoGe (343K, 5.8JKg^-1K^-1, 227JKg^-1) alloy compares, it will be apparent that improve Curie temperature and the magnetothermal effect of magnetic material.And it is obtained Alloy material is second-order phase transistion material, effectively avoids heat stagnation problem.

Fig. 6 is different-alloy maximum magnetic entropy variable respectively under 5T changes of magnetic field and H^2/3Curve, nearest research Show in the case of second-order phase transistion, the maximum magnetic entropy variable of alloy and and H^2/3Present certain linear relationship, as based on The theory of mean field:

${\mathrm{\ΔS}}_M\≥-1.07qR{\left(\frac{{\mathrm{g\μ}}_{B}JH}{k_B{T}_C}\right)}^{2/3}---\left(4\right)$

The magnetic ion number of q every mole in formula, R is gas constant, g Lande factor, the total angular quantum number of J, k_B For Boltzmann constant, as shown in Figure 6 | Δ S_M| with H^2/3Linear, indicate the feature of second-order phase transistion. Consistent with Arrott map analysis result.

Embodiment 5

According to mol ratio 1:1:0.995:0.005 weigh purity be 99.9%Mn, 99.9%Co, 99.99%Ge, 99.9%Cu, is placed in vacuum arc furnace melting, specifically before alloy melting, first is evacuated to be less than with mechanical pump 5Pa, opens molecular pump and is again evacuated to less than 10^-4Pa, is passed through the high purity argon (99.999%) of air pressure 5Pa, Repeating above operating procedure twice, on fire with 30A electric current, electrode is about 0.5cm with the distance of sample, slowly Slowly by current-modulation 80A until sample melts completely, then electric current is down to 60A melting half a minute, treats that alloy is cold But to turning over, melt back four times is to ensure that sample mix is uniform.After taking out cooling, high-purity high temperature resistant quartz put into by sample Teat glass, utilizes hight atmospheric molecular pumping system to be evacuated to less than 5Pa, is filled with high purity argon (99.999%) Carry out gas washing, repeat above step three times, sealed silica envelope, put in stove formula case 800 DEG C of annealing 10 days to protect Demonstrate,prove good degree of crystallinity, take out sample in temperature is 30 DEG C of cold water, makes annealing treatment about 2min, i.e. obtain purpose Product MnCoGe_1-xCu_xAlloy.

Embodiment 6

Weighing purity according to mol ratio 1:1:0.95:0.05 is 99.9%Mn, 99.9%Co, 99.99%Ge, 99.9%Cu, It is placed in vacuum arc furnace melting, specifically before alloy melting, first is evacuated to, less than 5Pa, open with mechanical pump Molecular pump is evacuated to again less than 10^-4Pa, is passed through the high purity argon (99.999%) of air pressure 15Pa, repeats Above operating procedure twice, on fire with 30A electric current, electrode is about 0.5cm with the distance of sample, slowly will Current-modulation 80A is until sample melts completely, then electric current is down to 60A melting half a minute, treats that alloy cooling is right Turning over, melt back four times is to ensure that sample mix is uniform.After taking out cooling, high-purity high temperature resistant quartz glass put into by sample Test tube, utilizes hight atmospheric molecular pumping system to be evacuated to less than 5Pa, is filled with high purity argon (99.999%) and enters Row gas washing, repeats above step three times, sealed silica envelope, puts in stove formula case 900 DEG C of annealing 5 days good to ensure Good degree of crystallinity, takes out sample and makes annealing treatment about 2min in temperature is 10 DEG C of cold water, i.e. obtain purpose product MnCoGe_1-xCu_xAlloy.

The above-mentioned description to embodiment is to be understood that for ease of those skilled in the art and use to send out Bright.These embodiments obviously easily can be made various amendment by person skilled in the art, and at this The General Principle illustrated is applied in other embodiments without through performing creative labour.Therefore, the present invention does not limits In above-described embodiment, those skilled in the art are according to the announcement of the present invention, without departing from changing that scope is made Entering and revise all should be within protection scope of the present invention.

Claims (6)

1. a manganese cobalt germanium-base alloy magnetic refrigerating material, it is characterised in that its general molecular formula is MnCoGe_1-xCu_x, Wherein, the span of x is 0.005～0.05.

A kind of manganese cobalt germanium-base alloy magnetic refrigerating material the most according to claim 1, it is characterised in that x's Span is 0.01～0.04.

3. the preparation method of manganese cobalt germanium-base alloy magnetic refrigerating material as claimed in claim 1 or 2, its feature exists In, comprise the following steps:

(1) 1:1:(1-x in molar ratio): x weighs and adds under manganese, cobalt, germanium and copper product, inert gas shielding Heat fusing mix homogeneously, obtain biased sample；

(2) biased sample is taken out, annealing, i.e. obtain purpose product.

The preparation method of a kind of manganese cobalt germanium-base alloy magnetic refrigerating material the most according to claim 3, its feature Being, in step (1), the air pressure of noble gas is 5～15Pa.

The preparation method of a kind of manganese cobalt germanium-base alloy magnetic refrigerating material the most according to claim 3, its feature Being, in step (2), the processing step of annealing is: first under inert gas shielding, in 800～900 DEG C Lower annealing 5～10 days, then it is placed in the water of 10～30 DEG C annealing.

The preparation method of a kind of manganese cobalt germanium-base alloy magnetic refrigerating material the most according to claim 3, its feature Being, described noble gas is argon.