Nanoporous Copper-Zinc-Aluminum Shape Memory Alloy and Preparation and Application Thereof

Abstract

The present invention discloses a nanoporous copper-zinc-aluminum shape memory alloy and a preparation method and an application thereof. According to the method, firstly a pure Cu block, a pure Zn block and a pure Al block are proportioned in a certain mass ratio before being smelted to obtain a copper-zinc-aluminum alloy ingot; the obtained copper-zinc-aluminum alloy ingot is melt spun using a copper roller rapid quenching method under vacuum protection to obtain an ultrathin strip CuZnAl master alloy which is then subjected to an etching treatment with a solution containing chloride ions at a temperature of 080 C. for 10300 minutes to obtain a nanoporous Cu/CuZnAl material; and finally the nanoporous CuZnAl material is sealed in a high vacuum quartz tube for a heat treatment to obtain a nanoporous copper-zinc-aluminum shape memory alloy having a superelastic single phase at room temperature. The preparation method according to the present invention is highly controllable and can be used in the industry preparing electrode materials for lithium ion secondary batteries to remarkably improve the cyclic performance of electrode materials.

Claims

1. A preparation method of a nanoporous copper-zinc-aluminum shape memory alloy, comprising the steps of: (1) smelting raw materials of pure Cu, pure Zn and pure Al to prepare a CuZnAl alloy ingot, with a mass ratio of each element in the CuZnAl alloy ingot Cu:Zn:Al=(100XY): X:Y, wherein X is 2635 and Y is 57; (2) melt spinning the CuZnAl alloy ingot obtained in the step (1) using a copper roller rapid quenching method under vacuum protection to obtain an ultrathin strip CuZnAl master alloy; (3) subjecting the ultrathin strip CuZnAl master alloy obtained in the step (2) to an etching treatment in a solution containing chloride ions to obtain a nanoporous Cu/CuZnAl composite material; (4) sealing the nanoporous Cu/CuZnAl composite material obtained in the step (3) in a high vacuum quartz tube for a heat treatment to obtain a nanoporous CuZnAl shape memory alloy having a single phase, the high vacuum quartz tube having a vacuum degree of 110.sup.2510.sup.4 Pa.

2. The preparation method of a nanoporous copper-zinc-aluminum shape memory alloy according to claim 1, wherein the raw materials of pure Cu, pure Zn and pure Al in the step (1) have a purity of 99% or more by mass percentage.

3. The preparation method of a nanoporous copper-zinc-aluminum shape memory alloy according to claim 1, wherein the CuZnAl alloy ingot of the step (1) is prepared by an induction melting method or an arc melting method.

4. The preparation method of a nanoporous copper-zinc-aluminum shape memory alloy according to claim 1, wherein, in the copper roller rapid quenching method of the step (2), a rotational speed of the copper roller is 10004000 rpm, and a vacuum degree under the vacuum protection is 0.110 Pa.

5. The preparation method of a nanoporous copper-zinc-aluminum shape memory alloy according to claim 1, wherein the ultrathin strip CuZnAl master alloy in the step (2) has a thickness of 10200 m and a width of 320 mm.

6. The preparation method of a nanoporous copper-zinc-aluminum shape memory alloy according to claim 1, wherein the solution containing chloride ions in the step (3) is an aqueous solution or an organic solution with a chloride ion concentration of 0.110 wt. %.

7. The preparation method of a nanoporous copper-zinc-aluminum shape memory alloy according to claim 1, wherein the etching treatment in the step (3) is carried out at a temperature of 080 C. for 10300 minutes.

8. The preparation method of a nanoporous copper-zinc-aluminum shape memory alloy according to claim 1, wherein the heat treatment in the step (4) is carried out in a muffle furnace or a tube furnace at a heating temperature of 600900 C. for 0.510 h, and after the heat treatment, the quartz tube is quenched into water before being broken up and cooled.

9. A nanoporous copper-zinc-aluminum shape memory alloy which is prepared by the preparation method according to claim 1.

10. Application of the nanoporous copper-zinc-aluminum shape memory alloy according to claim 9 in secondary battery electrode materials or catalyst carriers.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG. 1 is an X-ray diffraction (XRD) pattern of the original copper-zinc-aluminum thin strip sample in Embodiment 1;

[0031] FIG. 2 is a pore surface morphology of the copper-zinc-aluminum thin strip sample in Embodiment 1 after being subjected to etching for 90 minutes;

[0032] FIG. 3 is an XRD pattern of the copper-zinc-aluminum thin strip sample in Embodiment 1 after being subjected to etching for 90 minutes, high vacuum heat reservation at 850 C. for 3 hours and quenching;

[0033] FIG. 4 is a SEM surface morphology of the copper-zinc-aluminum thin strip sample in Embodiment 1 after being subjected to etching for 90 minutes, high vacuum heat reservation at 850 C. for 3 hours and quenching;

[0034] FIG. 5 shows a DSC curve of the copper-zinc-aluminum thin strip sample of Embodiment 1 after being subjected to etching for 90 minutes, high vacuum heat reservation at 850 C. for 3 hours and quenching;

[0035] FIG. 6 is an XRD pattern of the copper-zinc-aluminum thin strip sample of Embodiment 1 after being subjected to etching for 90 minutes, high vacuum heat reservation at 850 C. for 3 hours, quenching, and electroless tin plating;

[0036] FIG. 7 is a surface morphology of the copper-zinc-aluminum thin strip sample of Embodiment 1 after being subjected to etching for 90 minutes, high vacuum heat reservation at 850 C. for 3 hours, quenching, and electroless tin plating:

[0037] FIG. 8 shows the first three charge and discharge curves of the copper-zinc-aluminum thin strip sample of Embodiment 1 after being subjected to etching for 90 minutes, high vacuum heat reservation at 850 C. for 3 hours, quenching, and electroless tin plating:

[0038] FIG. 9 a surface morphology of the copper-zinc-aluminum thin strip sample in Embodiment 2 after being subjected to etching for 240 minutes, high vacuum heat reservation at 650 C. for 10 hours, and quenching:

[0039] FIG. 10 is a surface morphology of the copper-zinc-aluminum thin strip sample in Embodiment 3 after being subjected to etching for 120 minutes, high vacuum heat reservation at 750 C. for 6 hours, and quenching.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0040] In order to better understand the present invention, it will be further described below in conjunction with the embodiments and the accompanying drawings, but the embodiments of the present invention are not limited thereto.

Embodiment 1

[0041] (1) A pure copper block, a pure zinc block and a pure aluminum block are weighed according to a mass ratio of 60:34:6, and then are subjected to induction melting to obtain a copper-zinc-aluminum alloy ingot.

[0042] (2) The copper-zinc-aluminum alloy ingot obtained in the step (1) is melt spun using a copper roller rapid quenching method under vacuum protection to obtain an ultrathin strip CuZnAl precursor having a phase (with characteristic peaks of 43.2, 62.7 and 79.2 degrees) and a small amount of phase (with characteristic peaks of 43.5, 63.0 and 79.6 degrees), the XRD pattern of which is shown in FIG. 1. For the copper roller rapid quenching, the vacuum degree is 0.1 Pa, the rotational speed of the copper roller is 4000 rpm, the thickness of the strip is 20 m, and the width of the material is 5 mm.

[0043] (3) The ultrathin strip CuZnAl master alloy having both and phases which is obtained in the step (2) is etched in an aqueous solution of ferric chloride hydrochloride having a mass percentage of 5 wt. % (5 wt. % hydrochloric acid, 5 g of ferric chloride per 100 ml) at a temperature of 30 C. for 90 min to obtain a nanoporous Cu/CuZnAl composite material. It can be seen from the SEM of the surface (FIG. 2) that the pore sizes of the nanopores are about 200300 nm.

[0044] (4) The porous Cu/CuZnAl composite material with nanometer-scale pore sizes which is obtained in the step (3) is sealed into a high vacuum quartz tube, and the quartz tube is vacuum pumped by a vacuum system at a vacuum degree on the order of 510.sup.4 Pa. After vacuuming the quartz tube, its mouth is melted by heating to be sealed. The sealed quartz tube is placed in a muffle furnace for a heat treatment at a temperature of 850 C. for a heat holding time of 3 h, and then is quenched into water before being broken up and cooled. The phase structure of the sample after the high vacuum heat treatment at 850 C. has changed significantly, as the phase changes from the former phase dominated by a pure copper phase to a single phase, as shown in FIG. 3. Test results show that, compared with the heat treatment in the Chinese invention patent CN201510974645.X, the heat treatment under high vacuum condition significantly improves diffusion of internal Zn and Al atoms into the porous copper layer so that a single phase is prepared. FIG. 4 shows the surface morphology of the sample after the the high vacuum heat treatment at 850 C., and the pore sizes range from tens of nanometers to hundreds of nanometers. The DSC results (FIG. 5) show that the martensite critical transformation temperature of the sample after the heat treatment at 850 C. is 35 C., further demonstrating that the prepared -CuZnAl has a parent phase at room temperature and has superelasticity. The sample prepared in the Chinese invention patent CN201510974645.X has a low phase content, and accordingly the martensite transformation point cannot be measured by DSC, which means that no martensite transformation occurs, so the whole composite material exhibits almost no superelasticity.

[0045] The prepared nanoporous -CuZnAl shape memory alloy current collector is immersed in an electroless tin plating solution with a composition of NaOH at 2.8 mol/L, SnSO.sub.4 at 0.3 mol/L, NaH.sub.2PO.sub.4 at 0.9 mol/L and Na.sub.3C.sub.6H.sub.5O.sub.7 at 0.6 mol/L for 3 minutes at room temperature to obtain a nanoporous -CuZnAl/Sn composite electrode. The composite electrode after tin plating is washed with deionized water and then dried in a vacuum drying oven for 8 hours. The XRD pattern of the obtained composite negative electrode material (FIG. 6) shows that significant tin diffraction peaks (characteristic peaks of 30.6, 32.0, and 44.9) occur after electroless tin plating. It can be seen from its surface morphology after tin plating (FIG. 7) that some of the small pores are filled with nano-sized tin particles, but the porous structure remains and can serve as a channel for lithium ion diffusion.

[0046] In a glove box, the prepared composite negative electrode material functioning as a positive electrode, PE as a separator, a metal lithium plate as a negative electrode, and ethylene carbonate as an electrolyte are pressed into a button battery having a diameter of 12 mm to compose a half cell. The prepared half cell is tested for charge and discharge performance in a Land battery test system, and the first three charge and discharge curves are shown in FIG. 8, which result is measured on a Land battery test system with specific parameters as follows: the current density is 1 mA/cm.sup.2, and the charge and discharge voltage ranges from 0.01 V to 2 V. As can be seen from the figure, the first capacity reached 1.35 mAh/cm.sup.2, the first Coulombic efficiency is 87.7%, the irreversible capacity after one cycle is only 8.6% of the original capacity, and the capacity remained at 1.18 mAh/cm.sup.2 after ten cycles, that is 87.6% of the initial capacity, showing excellent cycle stability and high capacity. By comparison, in the battery test results of the Chinese invention patent CN01510974645.X, the first Coulombic efficiency is only 60%, the irreversible capacity after one cycle is 36.4%, and the capacity after ten cycles decays to 33.7% of the initial capacity. Therefore, the present invention not only greatly improves the first Coulombic efficiency of the Sn-based negative electrode material of lithium ion batteries, but also significantly improves the cycle performance, which indicates that the single phase nanoporous CuZnAl shape memory alloy prepared by the present invention is a current collector, it has superelasticity at room temperature, can further alleviate the volume expansion of the Sn-based negative electrode material during the cycle, significantly improve the capacity, Coulombic efficiency and cycle performance of lithium ion batteries, and has great application value in the field of lithium or sodium ion batteries.

Embodiment 2

[0047] (1) A pure copper block, a pure zinc block and a pure aluminum block are weighed according to a mass ratio of 61:32:7, and then are subjected to induction melting to obtain is a copper-zinc-aluminum alloy ingot.

[0048] (2) The copper-zinc-aluminum alloy ingot obtained in the step (1) is melt spun using a copper roller rapid quenching method under vacuum protection to obtain an ultrathin strip CuZnAl master alloy having a phase and a small amount of phase. For the copper roller rapid quenching, the vacuum degree is 1 Pa, the rotational speed of the copper roller is 3000 rpm, the thickness of the strip is 40 m, and the width of the material is 10 mm.

[0049] (3) The ultrathin strip CuZnAl master alloy having both and phases which is obtained in the step (2) is etched in an alcohol solution with a chloride ion concentration of 3% at a temperature of 80 C. for 240 min.

[0050] (4) The porous Cu/CuZnAl composite material with nanometer-scale pore sizes which is obtained in the step (3) is sealed into a quartz tube, and the quartz tube is vacuum pumped by a vacuum system at a vacuum degree on the order of 110.sup.3 Pa. After vacuuming the quartz tube, its mouth is melted by heating to be sealed. The sealed quartz tube is placed in a muffle furnace for a heat treatment at a temperature of 650 C. for a heat holding time of 10 h, and then is quenched into water to get cooled. The phase structure of the sample after the high vacuum heat treatment has changed significantly, as the phase changes from the former phase dominated by a pure copper phase to a single phase. FIG. 9 shows the surface morphology of the sample after the heat treatment at 650 C. and the pore sizes are 50500 nm or so. The specific surface area of the sample is measured by BET, wherein heat preservation is first carried out at 200 C. is for 2 h for degassing, which is followed by cooling with liquid nitrogen as a coolant, then an adsorption experiment is conducted, and the result of specific surface area is directly obtained from the instrument measurement data. The test results show that the nanoporous -CuZnAl shape memory alloy prepared by the heat treatment at 650 C. has a specific surface area of as high as 2.988 m.sup.2/g. The high specific surface area facilitates loading more catalyst, and in addition, the porous structure is beneficial to the contact between reactants and catalysts, thereby improving the reaction efficiency. Therefore, the present invention has great advantages in its use as a catalyst carrier.

Embodiment 3

[0051] (1) A pure copper block, a pure zinc block and a pure aluminum block are weighed according to a mass ratio of 60:35:5, and then are subjected to arc melting to obtain a copper-zinc-aluminum alloy ingot.

[0052] (2) The copper-zinc-aluminum alloy ingot obtained in the step (1) is melt spun using a copper roller rapid quenching method under vacuum protection to obtain an ultrathin strip CuZnAl master alloy having a phase and a small amount of phase. For the copper roller rapid quenching, the vacuum degree is 0.5 Pa, the rotational speed of the copper roller is 2000 rpm, the thickness of the strip is 60 m, and the width of the material is 3 mm.

[0053] (3) The ultrathin strip CuZnAl master alloy having both and phases which is obtained in the step (2) is etched in an aqueous hydrochloric acid solution having a chloride ion concentration of 1 wt. % at a temperature of 50 C. for 120 min to obtain a nanoporous Cu/CuZnAl composite material.

[0054] (4) The porous Cu/CuZnAl composite material with nanometer-scale pore sizes which is obtained in the step (3) is sealed into a quartz tube, and the quartz tube is vacuum pumped by a vacuum system at a vacuum degree on the order of 510.sup.3 Pa. After vacuuming the quartz tube, its mouth is melted by heating to be sealed. The sealed quartz tube is placed in a tube furnace for a heat treatment at a temperature of 750 C. for a heat holding time of 6 h, and then is quenched into water before being broken up and cooled. The phase structure of the sample after the high vacuum heat treatment at 750 C. has changed significantly, as the phase changes from the former phase dominated by a pure copper phase to a single phase. FIG. 10 shows the surface morphology of the sample after the high vacuum heat treatment at 750 C. and the pore sizes range from tens of nanometers to hundreds of nanometers.