Hydrogen-absorbing alloy and process for preparing the same

• US 6,153,032 A
• Filed: 05/14/1999
• Issued: 11/28/2000
• Est. Priority Date: 10/03/1996
• Status: Expired due to Term

• Current Assignee: Japan As Represented By Director General of Agency of National Institute of Health, Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Akiba, Etsuo, Iba, Hideki
• Primary Examiner(s): Wyszomierski, George
• Assistant Examiner(s): MORILLO, JANELL COMBS
• Application Number:
  US09/269,880
• Time in Patent Office: 564 Days
• Field of Search: 420/421, 420/424, 420/428, 420/900, 148/538, 148/669, 148/421
• US Class Current: 148/669
• CPC Class Codes: C01B 3/0031 Intermetallic compounds; Metal alloys; Treatment thereof
• CPC Class Codes: C22C 14/00 Alloys based on titanium
• CPC Class Codes: C22C 27/02 Alloys based on vanadium, niobium, or tantalum
• CPC Class Codes: C22C 27/06 Alloys based on chromium
• CPC Class Codes: C22C 30/00 Alloys containing less than 50% by weight of each constituent
• CPC Class Codes: C22F 1/11 of chromium or alloys based thereon
• CPC Class Codes: C22F 1/183 of titanium or alloys based thereon
• CPC Class Codes: Y02E 60/32 Hydrogen storage
• CPC Class Codes: Y10S 420/90 Hydrogen storage

Abstract

A hydrogen-absorbing alloy capable of controlling the very fine structure formed by a spinodal decomposition for improving flatness of an emission equilibrium pressure in a practical temperature/pressure range and excellent in activation and hydrogen absorption/desorption amounts, and a production method thereof. The hydrogen-absorbing alloy has a composition expressed by the general formula Ti_x Cr_y V_z (where each of x, y and z represents an atomic percent and satisfies the relation x+y+z=100), wherein the composition has a body-centered cubic structural phase as a principal phase, the principal phase exists within the range in which the body-centered cubic structure appears and a spinodal decomposition occurs with the exception of a C14 (a typical structure of the Laves phase; a MgZn₂ type crystal structure) mono-phase range, and has a regular periodical structure formed by the spinodal decomposition, and its apparent lattice constant is at least 0.2950 nm but is not greater than 0.3060 nm. The production method of the hydrogen-absorbing alloy comprises conducting a solution heat-treatment at 700 to 1,500° C. for one minute to 100 hours, and a cooling treatment and/or an aging treatment at 350 to 1,200° C. for one minute to 200 hours.

Claims

1. A hydrogen-absorbing alloy having a composition expressed by the general formula Ti_x Cr_y V_z, where each of x, y and z represents an atomic percent and satisfies the relation x+y+z=100, wherein the composition has a body-centered cubic structural phase as a principal phase, said principal phase exists within the range in which said body-centered cubic structure appears and a spinodal decomposition occurs with the exception of a C14 Laves phase, and the spinodal decomposition forms a periodic structure having a spacing of 1.0 mm to 100 nm, and its apparent lattice constant is at least 0.2950 nu but it is not greater than 0.3060 nm.

2. A hydrogen-absorbing alloy according to claim 1, wherein said composition exists within the range encompassed by segments defined by points A, B, C, D, E, F and G in a Ti--Cr--V ternary phase diagram shown in FIG. 1(a).

3. A method for producing a hydrogen-absorbing alloy having a composition expressed by the general formula Ti_x Cr_y V_z, where each of x,y and z represents an atomic percent and satisfies the relation x+y+z=100, wherein the composition has a body-centered cubic structural phase as a principal phase, said principal phase exists within the range in which said body-centered cubic structure appears and a spinodal decomposition occurs with the exception of a C14 Laves phase, and the spinodal decomposition forms a periodic structure having a spacing of 1.0 mm to 100 nm, and its apparent lattice constant is at least 0.2950 nm but it is not greater than 0.3060 nm, comprising the following steps:

melting and casting said Ti--Cr--V ternary alloy into a cast ingot;

applying a solution heat-treatment to said cast ingot at 700 to 1,500°

C. for one minute to 100 hours;

cooling said cast ingot; and

aging said cast ingot at 350 to 1,200°

C. for one minute to 200 hours.

4. A method for producing a hydrogen-absorbing alloy having a composition expressed by the general formula Ti_x Cr_y V_z, where each of x,y and z represents an atomic percent and satisfies the relation x+y+z=100, wherein the composition has a body-centered cubic structural phase as a principal phase, said principal phase exists within the range in which said body-centered cubic structure appears and a spinodal decomposition occurs with the exception of a C14 Laves phase, and the spinodal decomposition forms a periodic structure having a spacing of 1.0 mm to 100 nm, and its apparent lattice constant is at least 0.2950 nm but it is not greater than 0.3060 nm, comprising the following steps:

melting and casting said Ti--Cr--V ternary alloy into a cast ingot;

applying a solution heat-treatment to said cast ingot at 700 to 1,500°

C. for one minute to 100 hours; and

applying an aging treatment to said cast ingot at 350 to 1.200°

C. for one minute to 200 hours.