U.S. patent application number 13/110941 was filed with the patent office on 2012-05-31 for lithium-based alloy and method of producing the same.
This patent application is currently assigned to NATIONAL CENTRAL UNIVERSITY. Invention is credited to Chih-Ang CHUNG, Che-Wei HSU, Sheng-Long LEE, Chih-Kuang LIN, Jing-Chie LIN, Yu-Chou TSAI.
Application Number | 20120132035 13/110941 |
Document ID | / |
Family ID | 46125739 |
Filed Date | 2012-05-31 |
United States Patent
Application |
20120132035 |
Kind Code |
A1 |
LEE; Sheng-Long ; et
al. |
May 31, 2012 |
LITHIUM-BASED ALLOY AND METHOD OF PRODUCING THE SAME
Abstract
A lithium (Li)-based alloy and a preparation method thereof are
disclosed, in which the lithium metal is wrapped by a metal foil
with a higher melting point, followed by subjecting to multi-stage
thermal treatment to cast alloy, thereby obtaining the Li-based
alloy with high purity-Li.
Inventors: |
LEE; Sheng-Long; (Taoyuan
County, TW) ; LIN; Chih-Kuang; (Taoyuan County,
TW) ; CHUNG; Chih-Ang; (Taipei City, TW) ;
LIN; Jing-Chie; (Hsinchu City, TW) ; TSAI;
Yu-Chou; (Taoyuan County, TW) ; HSU; Che-Wei;
(Tainan City, TW) |
Assignee: |
NATIONAL CENTRAL UNIVERSITY
TAOYUAN COUNTY
TW
|
Family ID: |
46125739 |
Appl. No.: |
13/110941 |
Filed: |
May 19, 2011 |
Current U.S.
Class: |
75/585 |
Current CPC
Class: |
C22C 1/1036 20130101;
C22C 1/02 20130101; C22C 24/00 20130101; C22F 1/16 20130101 |
Class at
Publication: |
75/585 |
International
Class: |
C22C 1/02 20060101
C22C001/02; C22C 24/00 20060101 C22C024/00; C22C 1/10 20060101
C22C001/10 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 30, 2010 |
TW |
099141471 |
Claims
1. A method of producing lithium-based alloy, comprising: wrapping
lithium metal by using a metal foil for forming a wrapped lithium
metal, wherein the metal foil includes a material of a
high-melting-point metal having a higher melting point than a
melting point of the lithium metal; heating a raw material and the
wrapped lithium metal respectively to a first temperature, wherein
the raw material includes the material of the high-melting-point
metal, and the first temperature is between the melting points of
the metal foil and the lithium metal; mixing the wrapped lithium
metal with the raw material at the first temperature, so as to form
a metal mixture; heating the metal mixture to a second temperature,
wherein the second temperature is higher than the melting point of
the high-melting-point metal, so as to form an molten alloy; mixing
the molten alloy at the second temperature; and cooling down the
alloy for forming a lithium-based alloy, wherein the lithium-based
alloy is a .beta.-phase lithium-based alloy, and the lithium metal
has a weight loss rate of equal to or less than 1 percent.
2. The method of producing lithium-based alloy of claim 1, wherein
the high-melting-point metal comprises at least two different
metals of aluminum, magnesium, manganese, zirconium, zinc,
titanium, scandium, yttrium, copper, silver or any combination
thereof.
3. The method of producing lithium-based alloy of claim 1, wherein
the second temperature is 80.degree. C. to 100.degree. C. higher
than the melting point of the high-melting-point metal.
4. The method of producing lithium-based alloy of claim 1, wherein
the raw material further comprises another metal, and the another
metal includes a material different from the high-melting-point
metal.
5. The method of producing lithium-based alloy of claim 4, wherein
the first temperature is between two lower melting points of the
lithium metal, the high-melting-point metal and the another
metal.
6. The method of producing lithium-based alloy of claim 4, wherein
the second temperature is higher than the highest melting point of
the lithium metal, the high-melting-point metal and the another
metal.
7. The method of producing lithium-based alloy of claim 4, wherein
the second temperature is 80.degree. C. to 100.degree. C. higher
than the highest melting point of the lithium metal, the
high-melting-point metal and the another metal.
8. The method of producing lithium-based alloy of claim 1, wherein
the raw material further comprises a non-metal material.
9. The method of producing lithium-based alloy of claim 8, wherein
the non-metal material comprises silicon.
Description
RELATED APPLICATIONS
[0001] This application claims priority to Taiwan Application
Serial Number 099141471, filed Nov. 30, 2010, which is herein
incorporated by reference.
BACKGROUND
[0002] 1. Field of Invention
[0003] The present invention relates to a lithium (Li)-based alloy
and a method of producing the same. More particularly, the present
invention relates to a lithium (Li)-based alloy with high purity-Li
and a method of producing the same.
[0004] 2. Description of Related Art
[0005] Lithium (Li)-based alloy is generally referred to a
lightweight alloy material including Li. Due to Li with extremely
low density (0.534 g/cm.sup.3), the Li-based alloy has lower
density as compared to other kinds of alloys. Recently, the
Li-based alloy becomes the prime candidate material for designing
lightweight structural devices.
[0006] Typically, vacuum induction melting (VIM) process is
commonly applied to cast the Li-based alloy, and it is generally
divided into forward feed casing process and reverse food casting
process. During the forward feed casing process, low-melting-point
Li is molten in a highly vacuumed chamber of the VIM furnace with
nitrogen gas introduced therein, and then the molten Li is heated
to a higher temperature and added with other higher-melting-point
metal, so as to cast the Li-based alloy. On the contrary, during
the reverse feed casing process, other higher-melting-point metal
is molten in a highly vacuumed chamber of the VIM furnace with
nitrogen gas introduced therein, and then it is added with
low-melting-point Li, so as to cast the Li-based alloy.
[0007] In addition, mechanical alloying process is also applied to
cast the Li-based alloy, in which Li and Al metals are ball milled
for a long period, so as to form .beta.-phase Li--Al alloy (or
.beta.-Li--Al alloy).
[0008] However, it is hardly to avoid the overheating conditions
when using the aforementioned processes. Li is an active element
and has lower melting point and density. During casting alloy in
the conventional processes, the molten Li is easily floated on the
molten Al, so that it hardly prevents the molten Li from being
evaporated in the overheating condition and generating undesired Li
oxides or impurities. Thus, it is more difficult to cast Li--Al
alloy during the conventional processes, and the resulted Li--Al
alloy has low purity Li, oxides and impurities.
[0009] Hence, it is necessary to provide a Li-based alloy and a
method of making the same, thereby overcoming the disadvantages of
evaporation, oxides or impurities of lithium during the
conventional processes such as forward feed casing process, reverse
food casting process and mechanical alloying process.
SUMMARY
[0010] According to an aspect of the invention, a method of
producing lithium (Li)-based alloy is provided. The method of
producing lithium (Li)-based alloy comprises the steps of wrapping
lithium metal by using a metal foil with a higher melting point,
followed by subjecting to multi-stage thermal treatment to cast
alloy, thereby obtaining the Li-based alloy with more uniformly
dispersed and high purity-Li. Since the method can save the total
process time and reduce the occurrence of evaporation, oxides or
impurities of lithium. Therefore, the present method overcomes the
troubles of evaporation, oxides or impurities of lithium during the
conventional processes such as forward feed casing process, reverse
food casting process or mechanical alloying process.
[0011] Moreover, a Li--Al alloy is further provided, which has more
uniformly dispersed and high purity-Li is casted by the
aforementioned method. Therefore, the Li--Al alloy can be applied
on the lightweight structural devices (e.g. materials of sports
equipments or cases of military weapon cases) or composite
hydrogen-storage materials.
[0012] Accordingly, the invention provides a method of producing
Li-based alloy. In an embodiment, a lithium metal is firstly
wrapped by using a metal foil for forming a wrapped lithium metal.
In an example, the metal foil includes a material of a
high-melting-point metal having a higher melting point than a
melting point of the lithium metal.
[0013] Next, a raw material and the wrapped lithium metal are
heated respectively to a first temperature. In an example, the raw
material includes the same material of the high-melting-point metal
as the metal foil, and the first temperature may be between the
melting points of the metal foil and the lithium metal.
[0014] And then, the wrapped lithium metal is mixed with the raw
material at the first temperature, so as to form a metal mixture,
followed by heating the metal mixture to a second temperature, in
which the second temperature is higher than the melting point of
the high-melting-point metal, so as to form an molten alloy.
Afterward, the molten alloy is mixed at the second temperature.
[0015] Subsequently, the alloy is cooled down for forming a
lithium-based alloy, in which the lithium-based alloy is a
.beta.-phase lithium-based alloy, and the lithium metal has a
weight loss rate of equal to or less than 1 percent.
[0016] According to an embodiment of the present invention, the
high-melting-point metal may include but not be limited to
aluminum, magnesium, manganese, zirconium, zinc, titanium,
scandium, yttrium, copper, silver or any combination thereof.
[0017] According to an embodiment of the present invention, the raw
material may further comprise a non-metal material including
silicon.
[0018] According to an embodiment of the present invention, the raw
material may further comprise another metal that includes a
different material from the high-melting-point metal. In an
example, the first temperature may be between two lower melting
points of the lithium metal, the high-melting-point metal and the
another metal. In another example, the second temperature may be
higher than the highest melting point of the lithium metal, the
high-melting-point metal and the another metal.
[0019] According to another aspect of the present invention, a
.beta.-phase Li--Al alloy (or .beta.-Li--Al alloy) is further
provided. In an embodiment, the .beta.-Li--Al alloy may be casted
by any one of the aforementioned methods. In another embodiment,
the .beta.-Li--Al alloy may be applied on the lightweight
structural devices or composite hydrogen storage materials.
[0020] With application of the Li-based alloy and the method of
making the same, the lithium metal is wrapped by using the metal
foil with a higher melting point, followed by subjecting to
multi-stage thermal treatment to cast alloy, thereby obtaining the
Li-based alloy with more uniformly dispersed and high purity-Li.
Since the present method can save the total process time and reduce
the occurrence of evaporation, oxides or impurities of lithium, it
successfully overcomes the troubles of evaporation, oxides or
impurities of lithium during the conventional processes such as
forward feed casing process, reverse food casting process or
mechanical alloying process, thereby being applied on the
lightweight structural devices (e.g. materials of sports equipments
or cases of military weapons) or composite hydrogen storage
materials.
[0021] 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
[0022] The invention can be more fully understood by reading the
following detailed description of the embodiment, with reference
made to the accompanying drawings as follows:
[0023] FIG. 1 depicts a flow chart diagram of the method of
producing a Li-based alloy according to an embodiment of the
invention; and
[0024] FIG. 2 depicts a diagram of a reacting system according to
an embodiment of the invention.
DETAILED DESCRIPTION
[0025] As aforementioned, the present invention provides a Li-based
alloy and a method of producing the same, in which the
low-melting-point lithium metal is wrapped by using metal foil that
is made from a high-melting-point metal having a higher melting
point than lithium (or called as a high-melting-point metal foil).
Following, the wrapped lithium metal is subjected to a multi-stage
thermal treatment to cast alloy, thereby obtaining the Li-based
alloy with more uniformly dispersed and high purity-Li. It should
be clarified that the "Li-based alloy" is referred to a lightweight
alloy material including the lithium metal. The "metal foil" herein
may include but not be limited to a metal film, a metal sheet and
other structural equivalents or alternatives.
Composition of Li-Based Alloy
[0026] In an embodiment, the Li-based alloy may be consisted of two
metal materials such as lithium metal and a high-melting-point
metal. The high-melting-point metal has a higher melting point than
the lithium metal, which may be exemplified as but not limited to
aluminum, magnesium, manganese, zirconium, zinc, titanium,
scandium, yttrium, copper or silver, thereby forming Li--Al,
Li--Mg, Li--Mn, Li--Zr, Li--Zn, Li--Ti, LiSc, Li--Y, Li--Cu or
Li--Ag alloys. In an example, the Li-based may be Li--Al alloy, for
example. In another example, the Li-based alloy may be also a
.beta.-phase Li--Al alloy (or n-Li--Al alloy).
[0027] In another embodiment, at least a third material may be
alternatively added into the Li-based alloy that includes the
aforementioned two metal materials, so as to form a Li-based alloy
that includes at least three components. The third material may be
a metal or non-metal material. When the third material is a metal
material, it may be another high-melting-point metal that is
different from the aforementioned two metal materials or other
metal material. When the third material is a non-metal material, it
may be silicon, for example.
Method of Making Li-Based Alloy
[0028] Since the lithium metal is easily oxidized and evaporated
due to its lower melting point (approximately 180.54.degree. C.),
the present invention is directed to wrap the lithium metal by
using a high-melting-point metal foil, thereby reducing the period
of lithium oxidization and evaporation.
[0029] Reference is made to FIG. 1, which depicts a flow chart
diagram of the method of producing a Li-based alloy according to an
embodiment of the invention. The method 100 may include but not be
limited to a multi-stage thermal treatment to cast alloy.
Hereinafter, the Li-based alloy produced by two components is
firstly exemplified as follows.
[0030] At first, in the step 101, the lithium metal is wrapped by
using a metal foil for forming a wrapped lithium metal. In an
example, a material of the metal foil may be a high-melting-point
metal having a higher melting point than the lithium metal as
exemplified as aforementioned.
[0031] Next, in the step 103 (or a first heating step), a raw
material and the wrapped lithium metal are heated respectively to a
first temperature. In an example, the raw material includes the
same material of the high-melting-point metal as the metal foil,
and the first temperature may be between the melting points of the
metal foil and the lithium metal. Moreover, at the first
temperature, the lithium metal must be molten but the
high-melting-point metal is heated uniformly and close to a
being-molten state, so that the high-melting-point metal can
protect the molten lithium metal from being evaporated and
oxidized. Thus, in an example, the first temperature is higher than
the melting point of the lithium metal but lower than the one of
the high-melting-point metal.
[0032] In another example, when the high-melting-point metal is
aluminum metal that has a melting point of approximately
660.degree. C., the first temperature is about 200.degree. C. to
less than 660.degree. C., or about 630.degree. C. to about
650.degree. C., or alternatively 640.degree. C.
[0033] For the purpose of decreasing the probability of the Li
oxidation, in the step 103, the reacting chamber can be filled with
a protection gas or under vacuum. In an example, when the reacting
chamber is filled with a protection gas, the protection gas may be
nitrogen gas or other inert gases, and an internal pressure may be
more than one atmosphere (atm), for example. In other examples,
when the reaction chamber is under vacuum, the internal pressure
may be less than approximately 10.sup.-2 Torr (i.e. approximately
1.33 Pa), for example.
[0034] In order to reduce the subsequent time of Li oxidation and
evaporation, the step 103 can be carried out in the aforementioned
conditions for about one hour.
[0035] And then, in the step 105, the wrapped lithium metal is
mixed with the raw material at the first temperature, so as to form
a metal mixture. In an example, the pre-heated high-melting-point
metal may be added into the pre-heated wrapped Li metal, for
forming the metal mixture. Following, in the step 107 (or a second
heating step), the metal mixture is heated to a second temperature,
in which the second temperature is higher than the melting point of
the high-melting-point metal, so as to form a molten alloy. For
completely melting the high-melting-point metal and the Li metal to
form the molten alloy, the second temperature is necessarily higher
than the melting point of the high-melting-point metal. According
to an embodiment, the second temperature may be 80.degree. C. to
100.degree. C. higher than the melting point of the
high-melting-point metal.
[0036] Afterward, in the step 109, the molten alloy is mixed well
at the second temperature. Subsequently, in the step 111, the
molten alloy is cooled down for forming a lithium-based alloy. In
an example, the molten alloy may be cooled down to 0.degree. C. to
50.degree. C. approximately.
[0037] Due to the low-melting-point Li metal wrapped with the
high-melting-point metal foil, followed by the multi-stage thermal
treatment to cast alloy, the preset method can produce the Li-based
alloy with more uniformly dispersed and high purity-Li in mass in a
shorter process time (4 to hours approximately), in which the
Li-based alloy is a .beta.-phase lithium-based alloy, and the
lithium metal has a weight loss rate of equal to or less than 1
percent.
[0038] It is worth mentioning that, instead of directly heating to
the second temperature in the prior process, the present method
reduces the difference between the first and second temperatures in
the step 107 because the Li metal contacts with the being-molten
high-melting-point metal prior to contacting with the protecting
gas. Hence, it drastically decreases the probability of the
impurities since the Li metal is hardly to contact with the
impurities in the protecting gas. Moreover, it also reduces the
evaporation time of the Li metal due to the high thermal
treatment.
[0039] Furthermore, the Li-based alloy may be produced by at least
three components, and in this case, the at least three components
may include but be not limited to the Li metal, the
high-melting-point metal and a third material. The third material
may be another metal or a non-metal material.
[0040] In addition, the Li-based alloy produced by the at least
three components may be obtained by using the aforementioned
method. For example, in the step 101, the lithium metal is wrapped
by a metal foil for forming wrapped lithium metal, in which the
metal foil includes a material of the high-melting-point metal.
[0041] Next, in the step 103, the wrapped lithium metal and a raw
material consisting of the high-melting-point metal and the third
material are heated respectively to a first temperature. In an
example, the first temperature may be the first temperature is
between two lower melting points of the lithium metal, the
high-melting-point metal and the third material.
[0042] Following, in the step 107, the second temperature is higher
than the highest melting point of the lithium metal, the
high-melting-point metal and the third material, or the second
temperature may be 80.degree. C. to 100.degree. C. higher than the
highest melting point of the lithium metal, the high-melting-point
metal and the third material.
[0043] It should be supplemented that, during producing the
Li-based alloy with the at least three components, only the Li
metal is wrapped by the high-melting-point metal, but the third
material doesn't be wrapped.
Reacting System for Producing Li-Based Alloy
[0044] Reference will now be made in detail to the present
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.
[0045] In an embodiment, the method of making the Li-based alloy
can be carried out in conventionally reacting system or the
reacting system 200 of FIG. 2. Hereinafter, the reacting system 200
of FIG. 2 is exemplified to clarify this disclosure. Reference is
made to FIG. 2, which depicts a diagram of a reacting system
according to an embodiment of the invention. In an embodiment, the
reacting system 200 of FIG. 2 may be a step-controlled casting
furnace, for example. The aforementioned step 101 may be carried
out in two reacting chambers such as a pre-heat crucible 211 and a
main crucible 212 of the reacting system 200 of FIG. 2, in which
the main crucible 212 is connected to a side of the pre-heat
crucible 211.
[0046] The pre-heat crucible 211 is used for receiving the
high-melting-point metal 218 (e.g. aluminum or at least two
different high-melting-point metals). Heating devices 223 may be
disposed on an outside of the pre-heat crucible 211 for performing
the aforementioned first heating step (e.g. the step 103), for
pre-heating the high-melting-point metal 218 uniformly in the
pre-heat crucible 211 to the first temperature. The main crucible
212 is used for receiving the Li metal 220 wrapped by the
high-melting-point metal foil 219. There are also heating devices
203 disposed on an outside of the main crucible 212 for performing
the multi-stage thermal treatments such as the first heating step
(e.g. the step 103), the second heating step (e.g. the step 107),
the mixing step at the second temperature (e.g. the step 109), the
cooling step (e.g. the step 111) and so on.
[0047] The Li metal has a very lower melting point than the
high-melting-point metal 218, that is to say, it is longer for
heating the high-melting-point metal 218 to the first temperature.
However, during the first heating step, the high-melting-point
metal 218 heated in the pre-heat crucible 211 may generate radiant
heat for melting the Li metal 220 probably. Thus, in an embodiment,
a heat-insulation material, for example, the heat-insulation plate
215 of FIG. 2, may be disposed between the pre-heat crucible 211
and the main crucible 212 of the reacting system 200. The
heat-insulation plate 215 may be made of refractory fibers, so that
it can prevent the heat of the pre-heat crucible 211 from radiating
to the main crucible 212, thereby avoiding the Li metal 220 to melt
too early. Besides, an opening 215a optionally disposed on the
heat-insulation plate 215 may be corresponded to a lowering
position of a mixing bar 214, so that the mixing bar 214 can pass
through the opening 215a and extend into the main crucible 212 for
stirring and mixing the molten alloy.
[0048] When the Li metal 220 wrapped by the high-melting-point
metal foil 219 in the main crucible 212 is heated to the first
temperature by using the heating devices 203, the
high-melting-point metal 218 is also heated uniformly and close to
a being-molten state. In the meanwhile, by using a pushing bar 213
along a direction of an arrow 231, the pre-heated
high-melting-point metal 218 is pushed into the Li metal 220
wrapped by the high-melting-point metal foil 219 in the main
crucible 212, followed by heating to the second temperature by
using the heating devices 203, and allowing both of the
high-melting-point metal 218 and the Li metal 220 wrapped by the
high-melting-point metal foil 219 to form a molten alloy.
[0049] Later, the mixing bar 214 can pass through the opening 215a,
extend into the main crucible 212, stir and mix the molten alloy in
the main crucible 212 along a direction of an arrow 233, so as to
make all components more uniformly. In an example, the mixing bar
214 can be made of a heat-resistant material such as stainless, and
a refractory material can be coated on a surface of the mixing bar
214. In another example, the mixing bar 214 can be disposed above
the main crucible 212 and fixed on a side of the reacting system
200 by using an 0-ring. The mixing bar 214 can be operated along
upward, downward, clockwise or counterclockwise direction for
stirring and mixing the molten alloy uniformly.
[0050] During the cooling step (e.g. the step 111), the molten
alloy can be cooled down naturally for forming the Li-based
alloy.
[0051] Reference is made to FIG. 2 again. In an embodiment, during
performing the aforementioned multi-stage thermal treatment, at
least one gas inlet 216 and a gas outlet 217 can be disposed on a
backside of the reacting system 200, for providing a higher vacuum
environment or an environment filled with the protection gas. In an
example, the gas inlet 216 can be disposed on any position freely
depending on the casting requirements, and it can be connected with
a gas bottle for introducing the protection gas from an opening 205
into the reacting system 200. In this example, a ball valve
(unshown) can be disposed at a connection site of the gas inlet 216
connecting with the reacting system 200, for controlling the
transfer of the protection gas. In another example, the gas outlet
217 can be connected with a mechanical pump (unshown) to vacuum the
inner chamber (e.g. the pre-heated crucible 211 and the main
crucible 212) of the reacting system 200 from an opening 207 for
achieving a vacuum or highly vacuum state. In this example, another
ball valve (unshown) can be also disposed at a connection site of
the gas outlet 217 connecting with the reacting system 200, for
controlling the vacuum degree.
[0052] Since the metal foil with the higher melting point than the
Li metal is used to wrap the Li metal in the present method,
followed by subjecting to the multi-stage thermal treatment to cast
alloy, thereby saving the total process time and drastically reduce
the occurrence of evaporation, oxides or impurities of lithium.
Therefore, the present method successfully overcomes the troubles
of evaporation, oxides or impurities of lithium during the
conventional processes such as forward feed casing process, reverse
food casting process or mechanical alloying process. Moreover, the
Li-based alloy has more uniformly dispersed and high purity-Li,
thereby being applied on the lightweight structural devices (e.g.
materials of sports equipments or cases of military weapons) or
composite hydrogen storage materials.
[0053] Thereinafter, various applications of the Li-based alloy and
the method of making the same will be described in more details
referring to several exemplary embodiments below, while not
intended to be limiting. Thus, one skilled in the art can easily
ascertain the essential characteristics of the present invention
and, without departing from the spirit and scope thereof, can make
various changes and modifications of the invention to adapt it to
various usages and conditions.
EXAMPLE
Preparation of .beta.-Phase Li--Al Alloy
[0054] In this example, the .beta.-phase Li--Al alloy was prepared
by the reacting system 200 of FIG. 2. At first, the aluminum metal
and the lithium metal with the weight ratio of 5:1 were weighted.
The aluminum metal was pre-heated uniformly to the first
temperature, and the first temperature was about 200.degree. C. to
about 660.degree. C., or about 630.degree. C. to about 650.degree.
C., or about 640.degree. C. Meanwhile, the Li metal 220 wrapped by
the high-melting-point metal foil 219 in the main crucible 212 was
also heated uniformly to the first temperature.
[0055] Next, the pre-heated aluminum metal was added into the main
crucible 212, followed by performing the second heating step to the
second temperature. The second temperature was about 740.degree. C.
to about 760.degree. C., or 750.degree. C., for completely melting
the aluminum metal and the Li metal to form the molten alloy.
[0056] Before contacting with the protecting gas, the Li metal
contacted with the being-molten aluminum metal firstly. Hence, it
drastically decreased the probability of the impurities since the
Li metal was hardly to contact with the impurities in the
protecting gas. Moreover, since the aluminum was pre-heated before
being molten, it reduced the heating time of the main crucible 212
and the evaporation time of the Li metal under the high thermal
treatment.
[0057] Afterward, the molten alloy was mixed well at the second
temperature for approximately 10 minutes.
[0058] Subsequently, the molten alloy was cooled down to 0.degree.
C. to 50.degree. C. approximately for forming the .beta.-phase
Li--Al alloy. The aforementioned process time was spent only about
4 to 5 hours.
[0059] The content of the resulted .beta.-phase Li--Al alloy was
further analyzed by a commercially available equipment, for
example, inductively coupled plasma--atomic emission spectrometer
(ICP-AES), for obtaining the result as shown in TAB. 1. According
to the result of TAB. 1, the content of the cast .beta.-phase
Li--Al alloy was very close to the theoretical ratios, and the
total casting process was spent only about 4 to 5 hours.
TABLE-US-00001 TABLE 1 Content of Elements in Li--Al alloy (wt. %)
Li Al Fe Mn Cr O 19.8 80.01 0.10 0.02 0.03 0.04
[0060] It is worth mentioning that, the aluminum foil with the
higher melting point is used to wrap the Li metal in the present
method, followed by subjecting to the multi-stage thermal treatment
to cast alloy, thereby saving the total process time (about 4 to 5
hours) and producing the Li-based alloy with more uniformly
dispersed and high purity-Li in mass. Additionally, the lithium
metal has a weight loss rate of equal to or less than 1 percent.
Therefore, the present method successfully overcomes the troubles
of evaporation, oxides or impurities of lithium during the
conventional processes such as forward feed casing process, reverse
food casting process or mechanical alloying process.
[0061] The resulted Li-based alloy can be applied on any type of
the lightweight structural devices or composite hydrogen storage
materials, which include but not are limited to materials of sports
equipments, cases of military weapons or composite hydrogen storage
materials, rather than describing in detail herein. However, it is
necessarily supplemented that, some technical details such as
specific kinds or ratio of metals, specific processing conditions,
specific equipments and specific analyzing methods are employed as
exemplary embodiments in the present invention, for obtaining and
evaluating the applications of the resulted Li-based alloy.
However, it is not necessary to use all aforementioned details in
all embodiments. As is understood by a person skilled in the art,
the Li-based alloy of the present invention can include other kinds
or ratio of metals, other processing conditions, other equipments
and other analyzing methods rather than limiting to the
aforementioned examples. Moreover, all known structure or devices
familiarly to the person skilled in the art are merely depicted
schematically in the accompanying drawings for illustration
purposes only.
[0062] According to the embodiments of the present invention, the
Li-based alloy and the method of making the same advantageously
include to wrap the lithium metal by using the metal foil with a
higher melting point, followed by subjecting to multi-stage thermal
treatment to cast alloy, thereby obtaining the Li-based alloy with
more uniformly dispersed and high purity-Li. Since the present
method can save the total process time and reduce the occurrence of
evaporation, oxides or impurities of lithium, it can be applied on
the lightweight structural devices (e.g. materials of sports
equipments or cases of military weapons) or composite hydrogen
storage materials.
[0063] As is understood by a person skilled in the art, the
foregoing preferred embodiments of the present invention are
illustrated of the present invention rather than limiting of the
present invention. In view of the foregoing, it is intended to
cover various modifications and similar arrangements included
within the spirit and scope of the appended claims. Therefore, the
scope of which should be accorded the broadest interpretation so as
to encompass all such modifications and similar structure.
* * * * *