Thursday, January 31, 2013

Kohama MgFC Technology


"Kohama MgFC Technology" in "Magnesium fuel cell, its anode made of flame-retardant Mg alloy" has been rewritten as below. 
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Kohama MgFC technology may be defined as below.
1. In an MgFC, a negative electrode made of a magnesium alloy containing contains aluminum and calcium, and an electrolytic solution into which magnesium ions emanating from the negative electrode elutes. (←Claim 1)
2. In the MgFC (defined above), the aluminum contained in the magnesium alloy ranges from ≧3 wt% to ≦ 9 wt%, and the calcium contained therein ranges from ≧ 1 wt% to ≦ 3 wt%. (←Claim 2)
3. In the MgFC (defined above), the electrolytic solution is preferably one selected from among sodium chloride solution, sodium hydroxide solution, sodium bicarbonate solution, and sodium percarbonate solution. (←Claim 3)

The magnesium alloy thus composed has at least the following advantageous features.
Feature-1 Kohama MgFC, which uses the flame-retardant magnesium alloy for its negative electrode, successfully solved the self-discharge problem, which is essential to the conventional MgFC.
5 samples having respectively different compositions were prepared. Those samples were immersed in a 18 (wt) % salt water. Weight decreases of those samples were measured.
In the sample 1 (having the magnesium alloy containing 6 wt% of aluminum and 2 wt% of calcium), the magnesium alloy was little eluted into the salt water.
The result shows that where the sample 1 is applied to the negative electrode of the MgFC, no self-discharge will occur in the battery.
Feature-2 1) It has a satisfactory reactivity. 2) It has an ability to control combustion (reaction). The characteristic 1) indicates that it is suitable for the battery material. The characteristic 2) indicates that it is suitable for the industrial material.
Those contradictive characteristics of the magnetic alloy synergically operate to provide an excellent battery material.
The reason why the magnesium alloy has such characteristics:
“The alloy containing aluminum and magnesium has a bilateral structure consisting of two phases, i.e., a metal Mg phase (solid solution) and an Al2Ca compound phase. The compound phase is relatively inactive. The reactivity of the alloy is macroscopically low. The fact is empirically confirmed.
Where the bilateral structure is sufficiently fine, the corrosion reaction (elution reaction is uniform as a whole and gently progresses. The above fact will contribute to the reactivity and the reaction control. It appears that the parent phase of the magnesium alloy having high reactivity and the reaction control by the second phase being inactive cooperate to provide the good performance of the negative electrode.”
Feature-3: The Kohama magnesium alloy is capable of producing electricity of about 80% of the theoretical electric capacity of the magnesium alloy. This is experimentally confirmed.
The theoretical electric capacity of pure magnesium is 2.2Ah/g. The magnesium alloy contains 92 wt% of magnesium, for example.
The electric capacity of the magnesium alloy is 1.63 AH/g.
An experiment was conducted under the following conditions.
Negative electrode: magnesium alloy containing 6 wt% of aluminum and 2 wt% of calcium
Positive electrode current collector: carbon felt
Electrolytic solution: 18 wt% salt water
The experiment results: decreased amount of the magnesium alloy = 0.601g, current amount per 1 g = 1630mAh/g, and electric power = 476mWh/g
Feature-4: The MgFC is capable of producing electricity stably and for a long time.
An experiment was conducted in which an MgFC was manufactured and feeds current to a motor.
In the MgFC,
Negative electrode: magnesium alloy containing 6 wt% of aluminum and 2 wt% of calcium
Positive electrode current collector: carbon felt
Electrolytic solution: 18 wt% salt water
A plate-like magnesium alloy was used. One side of the magnesium alloy plate is covered with a tape, while the other side is exposed to the electrolyte.
The experiment result showed that the MgFC using the magnesium alloy continuously produces electricity more safely and more longer than the MgFC not using the magnesium alloy.
Written based on JPA No. 2012-234799

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