U.S. patent application number 11/819439 was filed with the patent office on 2008-10-02 for method for making lithium aluminide compound in atmospheric environment.
Invention is credited to Te-Chang Tsai, Jun-Yen Uan.
Application Number | 20080237055 11/819439 |
Document ID | / |
Family ID | 39792378 |
Filed Date | 2008-10-02 |
United States Patent
Application |
20080237055 |
Kind Code |
A1 |
Tsai; Te-Chang ; et
al. |
October 2, 2008 |
Method for making lithium aluminide compound in atmospheric
environment
Abstract
A method for making lithium aluminide compound in atmospheric
environment at a working temperature includes accomplishing a
diffusive electrolysis in an electrolyte composed of lithium
chloride, potassium chloride and calcium chloride, exerting a
direct current (voltage) on the electrolyte to reduce the lithium
ions into lithium atoms on the surface of an rotative aluminum
cathode, and subsequently the lithium atoms diffusing into the
aluminum cathode during the electrolysis.
Inventors: |
Tsai; Te-Chang; (Hemei
Township, TW) ; Uan; Jun-Yen; (Tainan City,
TW) |
Correspondence
Address: |
Joe McKinney Muncy
PO Box 1364
Fairfax
VA
22038-1364
US
|
Family ID: |
39792378 |
Appl. No.: |
11/819439 |
Filed: |
June 27, 2007 |
Current U.S.
Class: |
205/338 |
Current CPC
Class: |
C25C 3/02 20130101; C22C
1/002 20130101; C22C 21/00 20130101 |
Class at
Publication: |
205/338 |
International
Class: |
C25B 1/14 20060101
C25B001/14 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 28, 2007 |
TW |
96110901 |
Claims
1. A method for making lithium aluminide compound in an atmospheric
environment, and the method comprising: providing an aluminum
material as a cathode; dipping the cathode into an electrolyte
composed of lithium chloride and potassium chloride; and exerting a
direct current to the electrolyte at a working temperature and
rotating the cathode with a predetermined rotating speed to perform
a diffusive electrolysis, the lithium chloride of the electrolyte
is decomposed and the lithium ions are reduced into lithium atoms
at the surface of cathode, subsequently diffusing into the cathode
to form a lithium aluminide compound during electrolysis.
2. The method of claim 1, wherein the electrolyte essentially
consists of 20.about.45 wt. % lithium chloride, 30.about.60 wt. %
potassium chloride, and less than 5 wt. % calcium chloride.
3. The method of claim 1, wherein the working temperature is kept
within a range of 400.degree. C..about.510.degree. C.
4. The method of claim 1, wherein the predetermined rotating speed
is under 60 rpm.
5. The method of claim 1, wherein the direct current is kept within
a range of 0.02 A.about.0.06 A per unit area of cathode
surface.
6. The method of claim 1, wherein the diffusive electrolysis uses a
graphite material as an anode.
7. The method of claim 1, wherein the composition of the lithium
aluminide compound is within the range of Al-2 wt. % Li.about.Al-50
wt. % Li.
Description
RELATED APPLICATIONS
[0001] The application claims priority to Taiwan Application Serial
Number 96110901, filed Mar. 28, 2007, which is herein incorporated
by reference.
BACKGROUND
[0002] 1. Field of Invention
[0003] The present invention relates to a method for making lithium
aluminide (AlLi) compound. More particularly, the present invention
relates to a method for making lithium aluminide compound in an
atmospheric environment.
[0004] 2. Description of Related Art
[0005] The application of the lithium aluminide compound is limited
because the ingredients of the lithium aluminide compound are
difficult to control. Conventionally, the intermetallic FeLi
compound or intermetallic CuLi compound is prepared by a
ball-grinding method in a chamber with a protective gaseous
environment. The ball-grinding method consumes a lot of energy
resources and time. The ball grinding process forces the metal
powder blend into the lithium granule by mechanical metallurgy.
However, in the case of lithium aluminide compound, both the
aluminum powder and solid lithium are extremely unstable in air, so
that the ball grinding process is not adequate for the preparation
of the lithium aluminide compound.
[0006] The conventional lithium aluminide compound is prepared by
putting solid lithium into an aluminum melt under a layer of flux
or in an argon atmosphere. The above process gets even more
complicated with increasing lithium content in the aluminum alloy
melt. Moreover, solid lithium is extremely unstable in air because
of the air humidity may result in dangerous flash lithium
gasification. A high-frequency induction furnace or a closed
electrical furnaces is needed to melt aluminum-lithium, surrounding
the melt with a protective gas, argon. Therefore, the conventional
process of preparing a lithium-containing alloy is not only
difficult to operate but also expensive.
[0007] Solid lithium is very dangerous during the hauling and
storage period, and the cost cannot be lowered in regions without
lithium ore that relies on importing the lithium from the place of
origin.
SUMMARY
[0008] A method for making lithium aluminide (AlLi) compound in an
atmospheric environment in accordance with the present invention
satisfies the need to lower the danger of conventional processes
and the cost of storing and transporting the solid lithium.
[0009] The method comprises employing an aluminum material as a
cathode and dipping the aluminum cathode into an electrolyte
composed of lithium chloride and potassium chloride. Exerting a
direct current (a voltage) to the electrolyte to decompose the
lithium chloride in the electrolyte and to reduce the lithium ion
on the aluminum cathode at a working temperature, and diffusing the
lithium atoms into the aluminum cathode to obtain a lithium
aluminide compound. During the electrolysis, the aluminum cathode
can be rotated slowly with a predetermined rotating speed, which is
controlled under 60 rpm. The component of the electrolyte, lithium
chloride (LiCl), provides the lithium source for making the lithium
aluminide compound, and potassium chloride (KCL) is employed as a
flux to reduce the temperature and improve the flowability of the
electrolyte. The lithium material is diffused into the aluminum
cathode by a diffusive electrolysis process. The interaction
between the lithium and the aluminum in the electrolyte is shown as
follow:
Anode: 2Cl.sup.-.fwdarw.Cl.sub.2+2e.sup.-
Cathode: Li.sup.++e.sup.-.fwdarw.Li
[0010] The diffusive electrolysis may proceed in an atmospheric
environment to form a lithium aluminide compound within the range
of Al-2 wt. % Li.about.Al-50 wt. % Li, that is, the lithium
concentration of the lithium aluminide compound is within the range
of 2.about.50% by weight. Due to the poor affinity between the
potassium, calcium and the aluminum cathode, the lithium aluminide
compound contains less than 50 ppm of potassium and calcium. Sodium
is a very common impurity in chloride salt and the lithium
aluminide compound contains less than 30 ppm of sodium.
[0011] In conclusion, the embodiment of the present invention
provides a safer and easier way to prepare lithium aluminide
compound. The method employing the aluminum material as a cathode
and dipping the aluminum cathode into the electrolyte composed of
lithium chloride and potassium chloride. The lithium ions of the
electrolyte are reduced into Li atoms on AL cathode. The lithium
atoms simultaneously diffused into the aluminum cathode under a
direct current at a working temperature. The embodiment of the
present invention provides a safer and more convenient way to
transport and store the lithium raw material by employing the
lithium chloride, a stable chemical in atmospheric environment, as
the raw material of the lithium aluminide compound.
[0012] It is to be understood that both the foregoing general
description and the following detailed description are by examples,
and are intended to provide further explanation of the invention as
claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] These and other features, aspects, and advantages of the
present invention will become better understood with regard to the
following description, appended claims, and accompanying drawings
where:
[0014] FIG. 1 is a flowchart of steps in accordance with an
embodiment of the present invention;
[0015] FIG. 2 is an operational cross-section view of a specific
electrolytic bath when the diffusive electrolysis is in progress
therein; and
[0016] FIG. 3 is a sketch of X-ray crystal structures of an
aluminum sheet before and after a diffusive electrolysis
treatment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] Reference will now be made in detail to the present
preferred embodiments of the invention, examples of which are
illustrated in the accompanying drawings. Wherever possible, the
same reference numbers are used in the drawings and the description
to refer to the same or like parts.
[0018] Refer to FIG. 1. FIG. 1 is a flowchart of steps in
accordance with an embodiment of the present invention. The steps
of the embodiment include providing an electrolytic bath with an
electrolyte composed of lithium chloride and potassium chloride.
Employing an aluminum material as a cathode and dipping the
aluminum cathode into the electrolyte. Exerting a direct current
(voltage) to the electrolyte to move the lithium ion in the
electrolyte toward the aluminum cathode at a working temperature.
The lithium ions were reduced into lithium atoms, diffusing the
lithium into the aluminum cathode to obtain a lithium aluminide
compound.
[0019] Refer to FIG. 2. FIG. 2 is an operational cross-section view
of a specific electrolytic bath when the diffusive electrolysis is
in progress therein. An electrolyte 241 is loaded into a container
230 in an atmospheric environment. In accordance with an embodiment
of the invention, the electrolyte 241 essentially consists of
25.about.45% by weight (wt. %) of lithium chloride, 30.about.60% by
weight of potassium chloride, and at least 5 wt. % by weight of
calcium chloride.
[0020] The electrolysis facility 200 possess a double-decked
structure, which comprises an external furnace 210, an alumina
inner 220, and a lid 211 covered on the top of external furnace
210.
[0021] A plank 221 is set in the bottom of the alumina inner 220,
and a container 230 is mounted on the plank 221 wherein the
container 230 is a steel-made container to load the electrolyte
241.
[0022] A heater 250, a thermocouple 260, an anode 242 and a cathode
243 are placed in the container 230, wherein the heater 250 to heat
the electrolyte 241 and the thermocouple 260 is dipped in the
electrolyte 241 to monitor the variation of temperature in the
electrolytic system.
[0023] Portions of the anode 242 and a cathode 243 are dipped into
the electrolyte 241. A cathode rotating member 244 and cathode
rotating member 245 rotates the cathode 243 in a predetermined
speed. In accordance with an embodiment of the invention, an
aluminum material is used as the cathode 243 and the material of
the anode 242 comprises graphite, polymer or alloy material.
[0024] To perform a diffusive electrolysis and diffuse the lithium
material into the cathode 243, the cathode is rotated under 60 rpm
and a direct current with current density of 0.06 A.about.0.02 A
per unit area of the cathode surface (cm.sup.2) is exerted on the
electrolysis system at a working temperature. The lithium aluminide
compound is made from the component of the electrolyte 241, lithium
chloride (LiCl), and the aluminum cathode 243 by performing the
diffusive electrolysis process. The interaction between the lithium
and the aluminum in the electrolyte is shown as follow:
Anode: 2Cl.sup.-.fwdarw.Cl.sub.2+2e.sup.-
Cathode: Li.sup.++e.sup.-.fwdarw.Li
[0025] The electrolyte 241 provides the lithium source from lithium
chloride to form the lithium aluminide compound, and another
component of the electrolyte, potassium chloride (KCL), is employed
as a flux to reduce the temperature and improve the flow rate of
the electrolyte.
[0026] In accordance with an embodiment of the present invention,
the working temperature of the diffusive electrolysis is controlled
within a range of 400.degree. C..about.510.degree. C. When the
electrolyte is treated with the current density of 0.06
A.about.0.02 A per unit area of cathode surface (cm.sup.2) and
between 400.degree. C..about.510.degree. C. temperature at
atmospheric environment, the lithium ion of the electrolyte is
deposed and further diffused into the cathode 243 to form the
lithium aluminide compound with high lithium content within the
range of Al-2 wt. % Li.about.Al-50 wt. % Li. The lithium
concentration of the lithium aluminide compound is within the range
of 2.about.50% by weight.
[0027] Although the electrolyte includes potassium chloride as a
flux, the lithium aluminide compound merely contains less than 50
ppm of potassium as a result of the poor affinity between the
potassium and the aluminum cathode. Sodium is a very common
impurity in chloride salt and the lithium aluminide compound
contains less than 30 ppm of sodium.
[0028] Refer to FIG. 3. FIG. 3 is a sketch of X-ray crystal
structures of an aluminum sheets before and after a diffusive
electrolysis treatment. Portion (A) shows the X-ray diffraction
pattern of an aluminum sheet (before electrolysis). Portion (B)
shows the X-ray diffraction pattern of the cathode after
electrolysis. A diffusive electrolysis treatment were carried out
at 400.degree. C..about.510.degree. C., and the cathode is rotated
with a speed of 2 rpm during the electrolysis. By comparing the
X-ray diffraction pattern of portion (A) with portion (B), the
different X-ray crystal structures of portion (B) can be identified
as the X-ray pattern of Lithium aluminide (AlLi). According to the
above-mentioned, the embodiment of the invention is able to make
lithium aluminide compound with high lithium content in an
atmospheric environment.
[0029] Although the present invention has been described in
considerable detail with reference certain preferred embodiments
thereof, other embodiments are possible. Therefore, the spirit and
scope of the appended claims should not be limited to the
description of the preferred embodiments contained herein.
[0030] It will be apparent to those skilled in the art that various
modifications and variations can be made to the structure of the
present invention without departing from the scope or spirit of the
invention. In view of the foregoing, it is intended that the
present invention cover modifications and variations of this
invention provided they fall within the scope of the following
claims and their equivalents.
* * * * *