KR100840218B1 - Fabrication and using method of oxide powders with high specific surface area by coating with nacl or salt and ball milling - Google Patents

Abstract

A method for preparing oxides is provided to produce economically the oxides having a high specific surface area by a simple production process. A method for preparing oxides having a specific surface area of 13.9 m^2/g includes the steps of: adding any one, or two or more oxides selected from the group comprising niobium oxide, vanadium oxide, aluminum oxide, magnesium oxide, chrome oxide, iron oxide, and manganese oxide to a brine, and drying the admixture in order to coat the surface of the oxide with salt evenly; and adding water to the milled oxide powder to dissolve salt in water, removing the brine to obtain oxide powder, and drying the oxide powder.

Description

Fabrication and Using Method of Oxide Powders with High Specific Surface Area by Coating with NaCl or Salt and Ball Milling by Ball Milling Oxygen or Salt-Coated Oxide }

The present invention relates to a method for producing nanooxides by ball milling a low-cost oxide, more specifically, NaCl or salt is dissolved in water and added to the oxide and dried to uniformly coat NaCl or salt on the oxide surface, Ball milling the NaCl or salt-coated oxide with a ball into a milling container, adding water to the milled powder to dissolve NaCl or salt in water, removing water and drying to obtain an oxide. The present invention relates to a method for producing an oxide having a large specific surface area.

In addition, the present invention relates to the use of the oxide having a large specific surface area prepared by the above method added to the magnesium-based hydrogen storage powder.

Oxide powders have been widely applied to raw materials for sintering structural materials, powders for thermal spraying, raw materials for powder synthesis for electronic materials, and catalysts for increasing hydrogen storage rate in magnesium-based hydrogen storage powders. In particular, the smaller the oxide powder, the larger the specific surface area, the greater the sintering property, the finer the particles, the better the properties of the material, and the higher the wear resistance of the sprayed parts. In particular, in the case of magnesium-based hydrogen storage powder containing niobium oxide, vanadium oxide, aluminum oxide, magnesium oxide, chromium oxide, iron oxide, manganese oxide, etc. It plays an important role in greatly increasing the hydrogen storage rate by acting as a catalyst to promote decomposition. As the specific surface area of the added oxide increases, the hydrogen absorption rate of the magnesium powder increases, so it is very important to develop an oxide having a large specific surface area.

Such oxide powder may be prepared by chemical methods, physical methods and mechanical methods. Chemical preparation methods include a method of preparing nanooxides by adding a precipitating agent to various metal salts, a method of spray-drying an aqueous metal salt solution, followed by oxidative heat treatment, and a sol-gel method using a metal precursor solution as an initial raw material. These methods have the disadvantage that the initial raw material is expensive and harmful components are released during the process because the initial raw material is a precursor solution such as metal salt or metal alkoxide. As a physical method, a high temperature heat treatment furnace is required as a method of oxidizing a metal by heating and evaporating it, and the initial metal price is high and tends to aggregate well between powders during condensation. As a mechanical method, there are methods for manufacturing nanopowders by inserting a few micron to hundreds of micron oxide powder with a ball into a milling vessel and ball milling, but it is easy to manufacture nanopowders having a large specific surface area due to coagulation and pressure welding. Not. In addition, a method of producing nano metal oxides by ball milling and washing with metal chlorides, metal carbonates, metal hydroxides (hydrooxides), metal oxychlorides, metal sulphates, etc. together with NaCl, NaOH and the like, followed by calcination heat treatment at a temperature of about 400 ° C. or more. This is known. However, the above raw materials have a disadvantage that they are more stable than oxide powders, are toxic to various chloride salts, or the like, and promote the corrosion of equipment and have to undergo a complicated process such as a heat treatment process performed in a heat treatment furnace after washing with water to become a stable metal oxide. In addition, when the heat treatment temperature is high, a metal oxide may grow and an oxide powder having a large specific surface area may not be obtained.

The present invention has been made to solve the above problems, inexpensive NaCl or salt is dissolved in water and added to a low-cost oxide and dried to uniformly coat NaCl or salt on the oxide surface and then charged into a milling vessel with a ball It is an object of the present invention to provide a method of economically obtaining an oxide having a large specific surface area by adding water to ball milling and milling powder to dissolve NaCl or salt in water, and then removing and drying water.

Oxide powder manufacturing method having a large specific surface area according to the present invention devised to achieve the above object, the step of dissolving NaCl or salt in water and adding to the oxide and dried to uniformly coat NaCl or salt on the oxide surface; Ball milling the NaCl or salt-coated oxide with a ball into a milling vessel; Adding water to the milled powder to dissolve NaCl or a salt component in water, and then removing water and drying to obtain an oxide having a large specific surface area.

Hereinafter, the present invention will be described in detail.

Oxide powder and NaCl or salt must be used as initial raw materials. In the present invention, the oxide powder used as the initial raw material is niobium oxide (Nb ₂ O ₅ ), vanadium oxide (V ₂ O ₅ ), aluminum oxide (Al ₂ O ₃ ), magnesium oxide (MgO) which are commonly used low-cost oxides. ), Chromium oxide (Cr ₂ O ₃ ), iron oxide (Fe ₂ O ₃ ), manganese oxide (MnO) and the like. Since the average size of these oxides is about 1 μm to about 100 μm, it is preferable to use oxides of this size as the initial raw material of the present invention.

Metal chlorides, metal carbonates, metal hydroxides (hydrooxides), metal oxychlorides, and metal sulfur oxides can also be considered as initial raw materials. It is preferable to use the above-described oxide powder as an initial raw material because there is a disadvantage in that it becomes stable metal oxide only through a process, and an oxide powder having a high specific surface area cannot be obtained when the metal oxide grows at a high heat treatment temperature.

In addition, since NaCl or salt is inexpensive and soluble in water, it should be added to the oxide powder so that it is easy to uniformly coat the oxide surface and prevents agglomeration by pressure welding between the powders during ball milling of the oxide. It is preferable to dissolve NaCl or salt in water, add it to an oxidized powder, and dry it to evaporate moisture so that fine NaCl particles or salt particles are uniformly deposited on the powder surface. If NaCl or salt powder is added directly to the oxide without dissolving in water, milling can not be uniformly added to NaCl or salt, and it is difficult to pulverize the NaCl or salt particles very finely, effectively preventing powder welding.

The amount of NaCl or salt added to the oxide is preferably between 10% by weight and 90% by weight relative to the weight of the oxide. If the added amount of NaCl or salt is less than 10% by weight, it is not possible to effectively prevent the aggregation by the oxide powder by crimping, and when it exceeds 90% by weight, the amount of the oxide powder recovered after milling is uneconomical.

Next, a step of ball milling NaCl or salt-coated oxide is charged with a ball into a milling vessel. The ball milling apparatus may generally be a horizontal ball mill, a planetary ball mill, an attrition ball mill, a SPEX ball mill, or the like. During ball milling, the raw powders between the moving balls or the powders between the balls and the milling vessel are crushed smaller and NaCl or salt particles act to prevent the agglomeration of the powder. In general, the longer the milling time is obtained, the finer particles having a larger specific surface area can be obtained so that the milling time can be adjusted to obtain a desired specific surface area.

Next, it is necessary to add water to the milled powder to dissolve NaCl or salt components in water, remove water, and dry to obtain an oxide. In this process, enough water to dissolve NaCl or salt is added to the milled powder and stirred or sonicated to better dissolve NaCl or salt in water. The powder may then be allowed to settle (settle) or centrifuged to separate the precipitated or centrifuged oxide powder from the water in which NaCl or salt is dissolved. Depending on the situation, NaCl or salt can be completely removed by repeating the above solid-liquid separation several times.

For the recovered powder, it is necessary to dry it to remove residual water. To this end, it may be dried naturally or by heating in a drying furnace. The oxide powder thus prepared has a much larger specific surface area than oxide milled without adding NaCl or salt.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are only intended to illustrate the present invention, it will be apparent to those skilled in the art that the scope of the present invention is not limited to the following examples in accordance with the gist of the present invention.

Example  One

After weighing 15 g of niobium oxide and 15 g of salt so that 50% by weight of niobium oxide (Nb ₂ O ₅ ) and 50% by weight of commercial salt were added, an aqueous solution of this salt dissolved in water was added to 15g of niobium oxide, followed by stirring well. The surface of niobium oxide was then coated with salt by drying. The dried powder was charged into a planetary ball mill container with 680 g of steel balls having a diameter of 9.6 mm, and ball milled for 72 hours at a rotation speed of 250 rpm. After ball milling, the powder and the ball were separated by sieving, and 1000cc of water was added to the sieved powder, and the water was discarded by the sedimentation method after ultrasonic stirring. After adding 1000 cc of water, the niobium oxide powder was completely separated from the salt by dropping the water by sedimentation, and then dried. The niobium oxide powder was obtained.

The dried niobium oxide powder was measured using a specific surface area measuring instrument (Micromeritics ASAP 2000) and the specific surface area thereof was measured to obtain 22.40 m ² / g. This shows a very large specific surface area value as compared with the comparative example as can be seen through the comparative example described below.

Example  2

After weighing 15 g of niobium oxide and 15 g of NaCl to 50 wt% of niobium oxide (Nb ₂ O ₅ ) and 50 wt% of NaCl reagent, an aqueous solution of this NaCl reagent dissolved in water was added to niobium oxide, and other conditions were performed. It carried out similarly to Example 1. The specific surface area of the milled niobium oxide powder was very large at 21.01 m ² / g.

Example  3

Aluminum oxide was used as an initial raw material, and other conditions were the same as in Example 1. The specific surface area of the milled aluminum oxide powder was very large at 20.53 m ² / g.

Example  4

Magnesium oxide was used as an initial raw material, and other conditions were the same as in Example 1. The specific surface area of the milled magnesium oxide powder was 17.19 m ² / g, which was very large.

Example 5

Chromium oxide was used as an initial raw material, and other conditions were the same as in Example 1. The specific surface area of the milled chromium oxide powder was very large at 23.58 m ² / g.

Example  6

Vanadium oxide was used as an initial raw material and the other conditions were the same as in Example 1. The specific surface area of the milled vanadium oxide powder was very large at 27.73 m ² / g.

Example 7

Manganese oxide was used as an initial raw material, and other conditions were the same as in Example 1. The specific surface area of the milled manganese oxide powder was very large at 30.36 m ² / g.

Example  8

The salt was dissolved in water to 90 wt% niobium oxide (Nb ₂ O ₅ ), 10 wt% salt, and the brine was added to niobium oxide, and the other conditions were the same as in Example 1. The specific surface area of the milled niobium oxide powder showed a large value of 13.9 m ² / g.

Example  9

Salt was dissolved in water to 10 wt% niobium oxide (Nb ₂ O ₅ ), 90 wt% salt, and the brine was added to niobium oxide, and the other conditions were the same as in Example 1. The specific surface area of the milled niobium oxide powder was very large at 30.18 m ² / g.

Example  10

Zirconium oxide was used as an initial raw material, and other conditions were the same as in Example 1. The specific surface area of the milled zirconium oxide powder was very large at 19.12 m ² / g.

Comparative example  One

As in Example 1, only 15 g of niobium oxide (Nb ₂ O ₅ ) 100% was charged to a planetary ball mill with 680 g of steel balls and ball milled for 72 hours. Other conditions were the same as in Example 1. The specific surface area of the milled niobium oxide powder showed a small value of 2.89 m ² / g.

Comparative example  2

Only 3.1 g of 100% niobium oxide (Nb ₂ O ₅ ) was charged into a specs ball mill container with 93 g of steel balls and ball milled for 4 hours. Other conditions were the same as in Example 1. The specific surface area of the milled niobium oxide powder showed a small value of 3.05 m ² / g.

Comparative example  3

Only 3.1 g of 100% niobium oxide (Nb ₂ O ₅ ) was charged to a specs ball mill container with 93 g of steel balls and ball milled for 12 hours. Other conditions were the same as in Example 1. The specific surface area of the milled niobium oxide powder showed a small value of 3.10 m ² / g.

Comparative example  4

The salt was dissolved in water so as to be 97% by weight of niobium oxide (Nb ₂ O ₅ ) and 3% by weight of salt, and the brine was added to niobium oxide, and the other conditions were the same as in Example 1. The specific surface area of the milled niobium oxide powder was small at 5.01 m ² / g.

As can be seen in Examples 1 to 10 and Comparative Examples 1 to 4, it can be seen that the specific surface area of the oxide powders obtained by the method according to the present invention described above is high. The high specific surface area of the oxide has the advantage of good sintering properties and good abrasion resistance of the sintered body or the sprayed body. The oxide powder having such a large specific surface area is particularly useful as an additive for increasing the hydrogen absorption rate of the magnesium-based hydrogen storage powder.

In the above description of the preferred embodiment of the present invention, the scope of the present invention is not limited to the conditions of the specific embodiment, and those skilled in the art within the scope of the claims of the present invention Changes may be made as appropriate.

As described above, according to the present invention, an oxide having a large specific surface area can be economically obtained by a simple manufacturing process in which an aqueous solution of NaCl or an aqueous salt solution is added to a low-cost oxide, followed by ball milling and washing. An oxide having a large specific surface area obtained by the above may be particularly useful as an additive to magnesium-based hydrogen storage powders.

Claims (4)

An aqueous solution of NaCl or salt dissolved in water is added to any one or two or more oxides selected from the group consisting of niobium oxide, vanadium oxide, aluminum oxide, magnesium oxide, chromium oxide, iron oxide and manganese oxide and dried on the oxide surface. Coating the salt uniformly, Adding water to the milled oxide powder to dissolve NaCl or salt in water, and then drying the remaining oxide powder by removing the aqueous NaCl solution or salt solution Method for producing an oxide having a specific surface area of 13.9 m ² / g or more comprising a. The method of claim 1, Method of producing an oxide having a specific surface area of 13.9 m ² / g or more, characterized in that the amount of NaCl or salt added to the oxide is between 10% by weight to 90% by weight relative to the weight of the oxide. delete The 13.9 m ² which is characterized by using in addition to the Mg-based alloy powder for hydrogen storage in order to increase the hydrogen rate of reaction of the alloy powder for the prepared oxide, Mg-based hydrogen storage by 1 or claim 2 of the production process Method of using an oxide having a specific surface area of / g or more.