The present invention relates to fabricating a metal compound; more particularly, relates to obtaining a high-quality Mg (magnesium)-based eutectic alloy or metal compound through a simple smelting method and obtaining ah highly-purified γ-phase hydrogen storage alloy through vaporing extra Mg in the eutectic alloy.
Following the industrial revolution, pollution and energy resource become problems. Hence, now, hydrogen catches researchers' eyes as an abundant, economical and environmental-protected energy source.
To use hydrogen as an energy source, the problems on storage and transportation have to be solved. Take USA as an example. There is about 50% of funds spending on hydrogen storage researches. However, traditional hydrogen storage is expansive and not safe. An alternative hydrogen storage solution is an urgent need.
It is known that some metals absorb and diffuse hydrogen. It means that the metals absorb hydrogen to become hydrides and the hydrides diffuse hydrogen to return back to the original metals. Such metals include Fe (iron)-Ti (titanium) alloy, La (lanthanum)-Ni (nickel) alloy, Mg—Ni alloy, which are new hydrogen storage alloys found in years of 60s and 70s. Yet, there are still some problems a bout these hydrogen storage alloys:
(1) Some alloys, like Mg2Ni alloy, are not produced through simply smelting and cooling with a proper rate.
(2) Some alloys have their good performances only when they are in a crystalline state. Hence, if they are glass alloys or amorphous alloys, they have to be put in a vacuum environment to be processed with an annealing through a high heat and/or a high pressure even for several times, so that crystals are obtained for activating those hydrogen storage alloys on absorbing and diffusing hydrogen. These processes increase difficulties.
(3) General crystalline metal hydrides break into pieces or even powders after absorbing and diffusing hydrogen for times, which raises problems on heat transmittance and hydrogen absorbing capability.
(4) When those metal hydrides are put in the air, oxides may produce. Then, even when those metal hydrides are crystalline, they have to be activated for absorbing hydrogen, which requires heating under a high temperature and a high pressure for several times. It means that, each time such an alloy is exposed in the air, it has to be reactivated again.
In the above hydrogen storage alloys, hydrogen storage alloys having a rare earth element or an iron element, like La—Ni alloy and Fe—Ti alloy, do not absorb much hydrogen, which is smaller than 400 mA·h/g. They are not qualified to a specific energy for an electrical vehicle. Hence, for finding hydrogen storage alloys having high energy, researches are mostly centered on Mg-based alloys and vanadium alloys.
A highly-purified Mg element has a high hydrogen absorption. A Mg—H compound (MgH2) contains 7.6 weight percents of hydrogen; however, it requires 330 Celsius degrees high to diffuse the hydrogen. Moreover, Mg takes time to absorb hydrogen and even takes hours to diffuse the hydrogen, which makes it difficult to be applied in vehicles.
In Mg-based binary element hydrogen storage alloys, like those having an element of Ni, Fe, Al, Ti and La, the most effective one is a γ-phase Mg—Ni alloy, which has a good hydrogen absorbing and diffusing capability. However, as is said above, it is not fabricated through simple smelting and cooling. For fabricating Mg-based hydrogen storage alloys, methods generally used include: arc melting, combustion synthesis, powder metallurgy, laminate rolling, mechanical alloying and a rotation-cylinder method (RCM). These methods have disadvantages on high cost, long time expanse and low production. In addition, during the fabricating procedure, a γ-phase Mg—Ni alloy is hard to be obtained because of an impurity of Mg—Ni eutectic alloy easily mixed within.
In U.S. Pat. No. 6,277,170, “Nanocrystalline Ni-based alloys”, ball milling is used to obtain a highly-purified γ-phase Mg—Ni alloy. A pure Mg powder and a pure Ni powder are firstly obtained for ball milling for several hours. After milling for 26 hours, Mg—Ni alloy appears, whose diffraction peaks still don't match those peaks on a diffraction diagram of a standard Mg—Ni alloy. After 66 hours, a Mg—Ni alloy whose diffraction peaks match those peaks on the diffraction diagram of the standard Mg—Ni alloy is finally obtained. However, the whole procedure takes time; and the ball milling devices are damaged heavily after a long time of use, whose cost is not reduced easily.
In U.S. Pat. No. 6,647,166, “Electrochromic materials, devices and process of making”, controls by changes of a material in absorbing and diffusing hydrogen are used and one of such materials is a Mg—Ni alloy film. Two layers of the film is sputtered in a vacuum environment; then is annealed under 125° C. with a protecting gas of nitride. Although a Mg—Ni alloy is obtained, its amount is too small and it takes time; and the film is not made of a highly-purified Mg—Ni alloy.
In U.S. Pat. No. 5,506,069, No. 5616432, etc., fast solidifying methods of jet casting, melt spinning, planar flow casting and a gas atomization are revealed for making Mg—Ni alloys. Yet their contents are not effectively controlled. And their atomic ratio ranges from 1:1 to 2:1, which means highly-purified Mg—Ni alloys are not obtained.
The RCM method is revealed in Journal of Alloys and Compounds, 2002. The method is mainly used for fabricating a composite material; and is further applied in smelting an alloy having two elements of two very different melting points. Hence, it is used to fabricating Mg—Ni alloy. Yet, Mg has only 1 wt % to 10 wt % in the alloy, so they are still far from highly-purified Mg—Ni alloys.
To obtain a highly-purified γ-phase Mg—Ni alloy ball milling is usually used to obtain a Mg-based hydrogen storage metal compound. With a ball milling mechanical device, only at most tens grams of Mg—Ni alloy is obtained within 24 to 48 hours. Besides, the alloy may be easily polluted and poisoned after a long time of ball milling
Furthermore, some researches focus on adding a third element for improving hydrogen absorbing and diffusing capabilities. For example, TiNi is added to Mg in an RCM method as an activator to improve hydrogen absorbing and diffusing capabilities (Tae-Whan Hong, Materials Science Forum, Vols. 486-487, May 2005, pp. 586-589). Or, Mg powder and Ni powder are added with Fe and graphite in a mechanical ball milling which shows a better hydrogen absorbing and diffusing capabilities than the Mg—Ni alloy (E. Grigorova, et. al., International Journal of Hydrogen Energy, 30 (2005), 1099-1105).
Likewise, the alloys are not so pure and the productions are low and not time saving. Even when the third element is added, these defects still exist. Hence, the prior arts do not fulfill all users' requests on actual use.
The main purpose of the present invention is to effectively obtain a pure metal alloy in a short time, where the metal alloy contains elements having big differences in vapor pressures.
The second purpose of the present invention is to continuously and abundantly produce the metal alloy for saving cost with a device which is sealed in a general way and is adjustable and controllable in temperature and time.
The third purpose of the present invention is to obtain alloy bulks with any elements through an easy producing process.
The fourth purpose of the present invention is to obtain an easy operation and control in a smelting environment of a confined space under an atmosphere protected with an inert gas, where no vacuum device is required.
To achieve the above purposes, the present invention is a method of fabricating a metal compound through smelting with a vaporized purification, where a metal compound is obtained through steps of: (a) obtaining a mixed material to be smelted for obtaining a liquid state of the mixed material; (b) obtaining a ratio, a size and a type of an initial phase of the smelted mixed material by controlling a phase formation of a biphasic region through processes of heating, soaking and/or cooling for obtaining an eutectic alloy; and (c) controlling separation statuses of the components in the initial phase having different vapor pressures during a vaporized purification to obtain a metal compound, where a high-quality Mg-based eutectic alloy or metal compound is obtained with a low cost under a mass production. Accordingly, a novel method of fabricating a metal compound through smelting with a vaporized purification is obtained.
The present invention will be better understood from the following detailed descriptions of the preferred embodiments according to the present invention, taken in con junction with the accompanying drawings, in which
The following descriptions of the preferred embodiments are provided to understand the features and the structures of the present invention.
Please refer to
(a) A mixed material is heated until a liquid state of at least an element in the mixed material is obtained, where the mixed material at least comprises an element having a relatively higher vapor pressure and another element having a relatively lower vapor pressure; and each of the elements is a 1A group element, a 2A group element, a 3A group element, a 4A group element, a 5A group element, a transitional element or a rare earth element.
(b) The mixed material is smelted to a pure liquid state or a liquid-solid-mixed state. Then a combination of heating, soaking and/or cooling is processed during a phase formation in the biphasic region to control a ratio, a size and a type of an initial phase, where the phase formation is processed with a mixture of an 8A element gas, nitrogen (N2) argon (Ar), sulfur hexafluoride (SF6) and/or carbon dioxide (CO2); and the cooling is a furnace cooling, an air cooling, a water cooling or an oil quenching.
(c) After the initial phase obtains the requested ratio, size and type, another combination of heating, soaking and/or cooling is processed. A separation of an element or a compound having a different vapor pressure in the initial phase is controlled in the vaporized purification to obtain a metal compound having a high purity, like a hydrogen storage alloy in a γ phase. Therein, the metal compound is obtained through a peritectic reaction or an eutectic reaction; the metal compound is a mixture of at least a primary phase, an eutectic phase, or a primary phase together with an eutectic phase; the initial phase obtained after the vaporized purification comprises at least two requested compound; and another heating, soaking and/or cooling is processed after the vaporized purification for a solid solution or a phase transformation in a micro-structure.
In the above steps, the processes of the smelting in step (a), the phase formation in step (b) and the vaporized purification in step (c) use a mixture of at least a gas as a reacting gas or a protecting gas, where the gas is an 8A element gas, nitrogen (N2) argon (Ar), sulfur hexafluoride (SF6) or carbon dioxide (CO2). A manual agitation, a mechanical agitation or a gas agitation is added in the steps for: (i) speeding up melting an element into the liquid state of the mixed material; (ii) improving an uniformity of the mixed material in a liquid-solid-mixed state; and (iii) changing a state of a forming phase to obtain a change in a reaction ratio or a volatilization ratio. During the agitation, a trace element is further added, which is a 1A element, a 2A element, a 3A element, a 4A element, a 5A element, a transitional element or a rare earth element; or, a metal or non-metal oxide having a higher melting point or a lower vapor pressure than the forming phase is added.
In the other hand, during the vaporized purification, the vapored element is collected to be fabricated into powder or is directed to be reacted with other element for a by-product.
Through the present invention, a great amount, a bout 1 to 5 kilograms (kg), of Mg2Ni hydrogen storage alloy (Mg/Mg2Ni) or Mg2Ni metal compound (Mg2Ni) having a high purity is obtained in 2 to 5 hours through an easy, low-cost and mass production.
(a1) As shown in
(b1) After obtaining a uniformity through the agitation, the smelted mixed material is cooled down [13] to a temperature between 510 and 650° C. in a biphasic region; and is soaked [14] for 40 minutes (m in) to an hour in the biphasic region. Then an alloy bulk of an initial alloy (Mg2Ni) and an eutectic alloy (Mg+Mg2Ni) are obtained through cooling [15]. Therein, extra Mg is left after reaction when cooling down the temperature; a product of an eutectic Mg/Mg2Ni alloy is obtained through smelting; and, an eutectic product of Mg2Ni and Mg2Ni2 or another one of Mg2Ni, Mg2Ni2 and Ni is thus impossible.
(c1) The alloy bulk is taken out to be heated [16] to a Mg vaporing temperature around 700° C. in a closed furnace; and the closed furnace is added with a vapor guiding device. Mg element in the alloy bulk is vapored [17] to control an amount of Mg left in the eutectic alloy. Then the alloy bulk after being vapored is cooled down [18] to be taken out so that a Mg—Ni alloy is obtained. The extra Mg element in the eutectic alloy is thus separated to obtain a Mg—Ni alloy having a high purity, where the closed furnace is a heating furnace.
The final Mg—Ni alloy is processed with an X-ray diffractor (XRD). Peaks on a diagram thus obtained matches peaks data of a Mg—Ni alloy stored in the JCPD database, which shows the obtained alloy bulk consists of a Mg—Ni alloy. For further knowing a combinational ratio of the alloy bulk, the alloy bulk is processed through an analysis with an electron probe microanalyzer (EMPA). After a multipoint comparison, an atomic combinational ratio of Mg to Ni is 67.3 to 32.7, which shows a highly-purified Mg—Ni alloy is obtained successfully.
As shown in
(a2) As shown in
(b2) After obtaining a uniformity through the agitation, the smelted mixed material is cooled down [23] to a temperature between 510 and 650° C. in a biphasic region; and is soaked [24] for 40 min to an hour in the biphasic region. Then an alloy bulk of an initial alloy and an eutectic alloy are obtained. Therein, extra Mg is left after reaction when cooling down the temperature; thus, a product of an eutectic alloy of Mg/Mg2Ni is obtained through smelting; and, an eutectic product of Mg2Ni and Mg2Ni2 or one of Mg2Ni, Mg2Ni2 and Ni is impossible.
(c2) The alloy bulk is taken out to be heated [25] to a vaporing temperature around 700° C. in a closed furnace and is soaked for 2 hours where the closed furnace is added with a vapor guiding device. The vapor guiding device is opened to fully exhaust the vapored [26] extra Mg element to prevent from danger. And the vapor guiding device controls an amount of Mg vapor exhausted to obtain a Mg rate left in the eutectic alloy. The alloy bulk is then cooled down [27] to be taken out after being vapored so that a Mg—Ni alloy having a high purity is obtained, where the closed furnace is a heating furnace.
The final Mg—Ni alloy is processed with an X-ray diffractor (XRD), which shows a Mg—Ni alloy is obtained through the present invention.
(a3) As shown in
(b3) After obtaining a uniformity through an agitation, the smelted mixed material is cooled down [33] to 750° C. for a slow stepped cooling [34]. The temperature is cooled down 10° C. each time to be soaked for 10 min, where Mg—Ni alloy is formed and extra Mg is vapored to be exhausted during the 10 min. When the temperature has reached 510° C. through the slow stepped cooling [34], the temperature is directly cooled down [35] to a room temperature.
The final Mg—Ni alloy is processed with an X-ray diffractor (XRD), which shows a highly purified Mg—Ni alloy is obtained through the present invention.
(a4) As shown in
(b2) Then the smelted mixed material is cooled down to a temperature between 510 and 650° C. in a biphasic region; and is soaked [24] for 40 min to an hour in the biphasic region. After cooling down to a room temperature, an alloy bulk of an eutectic alloy are obtained.
(c4) The alloy bulk is taken out to be heated to a vaporing temperature around 700° C. in a closed furnace and is soaked for a period of time, where the closed furnace is added with a vapor guiding device. The vapor guiding device is opened to fully exhaust the vapored extra Mg element to prevent from danger. The alloy bulk is then cooled down to be taken out, where the closed furnace is a heating furnace.
The final alloy bulk is processed through an EPMA analysis and an inductively coupled plasma (IC P) analysis, which show Al is fully mixed in the alloy bulk and a Mg/Mg2Ni/Al compound is obtained through the present invention.
(a5) A mixture of Mg, Ni and copper (Cu) having a ratio of 55 wt %:43 wt %:2 wt % is put in a stainless-steel crucible which is sealed with a refractory mud or other soft ceramics and is filled with argon as a protecting gas. Then the sealed crucible is heated to a melting point of Mg, Ni and Cu around 800° C. to be smelted into a liquid state with an agitation for obtaining a uniformity. Therein, the protecting gas can further be an 8A element gas, N2, Ar, SF6 or CO2; and the gas can be a reacting gas.
(b5) Then the smelted mixed material is cooled down to a temperature between 510 and 650° C. in a biphasic region; and is soaked for 40 min to an hour in the biphasic region. After cooling down to a room temperature, an alloy bulk of an eutectic alloy are obtained.
(c5) The alloy bulk is taken out to be heated to a vaporing temperature around 700° C. in a closed furnace and is soaked for a period of time, where the closed furnace is added with a vapor guiding device. The vapor guiding device is opened to fully exhaust the vapored extra Mg element to prevent from danger. The alloy bulk is then cooled down to be taken out, where the closed furnace is a heating furnace.
The final alloy bulk is processed through an EPMA analysis and an ICP analysis, which show Cu is fully mixed in the alloy bulk and a Mg/Mg2Ni/Cu compound is obtained through the present invention.
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The final alloy bulk is processed with an XRD, which shows a Mg—Si alloy is obtained through the present invention.
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The final alloy bulk is processed with an XRD, which shows a Mg—Sn alloy is obtained through the present invention.
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To sum up, the present invention is a method of fabricating a metal compound through smelting with a vaporized purification, where, through a simple smelting method, a high-quality Mg-based eutectic alloy or metal compound is obtained; and through vaporing extra Mg in the eutectic alloy, a highly-purified γ-phase hydrogen storage alloy is obtained.
The preferred embodiments herein disclosed are not intended to unnecessarily limit the scope of the invention. Therefore, simple modifications or variations belonging to the equivalent of the scope of the claims and the instructions disclosed herein for a patent are all within the scope of the present invention.
Number | Date | Country | Kind |
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096104675 | Feb 2007 | TW | national |