JP2009028687A - Method of mechanochemistry treatment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crushing method by a ball mill pulverizer with which pulverizing can be carried out in a short period of time and whose scale up is made easy. <P>SOLUTION: In the method, one or two or more kinds of particulate raw material 52 is fed to the pulverizer equipped with a pulverizing cylinder containing a pulverizing medium 54 and pulverized, to produce a chemically modified article (product) by mechanochemistry treatment. A revolving type pulverizing device generating vibration by revolution is used as the pulverizer. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a method of performing mechanochemistry using a ball mill of granular materials, and more specifically, a ball mill pulverizer including a pulverizing cylinder in which one or more granular materials are charged with a pulverizing medium (ball). The method relates to a method for producing a chemically modified product (product) by pulverizing and subjecting it to mechanochemistry.

  Here, mechanical alloying will be described as an example of mechanochemistry processing.

  Non-Patent Document 1 introduces a technique for synthesizing an alloy by mechanical alloying (MA) using various ball mills.

  Further, “(2) Advantages and disadvantages of mechanical alloying” on pages 103 to 104 of the document 1 includes the following description.

  “One of the features of mechanical alloying is that it can be alloyed in a solid state without melting the raw material. Therefore, there is an advantage that there are few restrictions that were the conventional alloy synthesis methods by melt casting. For example, it is easy to create an alloy with a very large melting point difference such as a niobium-tin alloy or niobium-aluminum alloy, and an alloy with a very large difference in specific gravity such as a cobalt-magnesium alloy. However, it is difficult to create an alloy with a uniform composition because the heavy component sinks down due to the difference in specific gravity and the light component floats upward, but mechanical alloying creates an alloy with a uniform composition that is independent of the specific gravity difference. Alloys of refractory metals such as tungsten and niobium do not dissolve, so they can be easily synthesized, and can dissolve like titanium and magnesium. When highly active metals alloys that would almost react with the crucible material will activity can also be readily synthesized.

  Furthermore, since the formation of amorphous alloys by mechanical alloying was reported by Schwartz et al., Not only amorphous alloys but also heat-sensitive unstable alloys such as nanocrystalline alloys and supersaturated solid solution alloys can be easily synthesized. As a result, mechanical alloying has come to be expected as a means of developing new metal materials. In particular, research on synthesis of amorphous alloys has been actively conducted. According to Schultz, the atomic structure of an amorphous alloy synthesized by mechanical alloying is almost the same as that of an amorphous alloy created by the melt spin method (one of the methods for supercooling a molten alloy). Even without expensive equipment such as a melt spin type ultra-quick solidification device that was necessary for the research of amorphous alloys, the synthesis of amorphous alloys by mechanical alloying has become active.

The disadvantages of mechanical alloying are that the synthesis takes time and that the amount that can be processed at one time by the ball mill is small compared to the grinding operation. Therefore, the cost of alloy synthesis tends to be higher than that of the melt casting method. "
And in the section of “(3) Ball mill used for mechanical alloying” on page 104 of the same document, a schematic diagram (cited as FIG. 1 attached to the present application) is described together with the following description.
“Mechanical alloying mainly uses a stirring ball mill called a high energy ball mill, a planetary ball mill, and a vibration ball mill.” Although it is often possible to synthesize alloys in a relatively short time, it is not suitable for mass production because scale-up is not easy .... Several dozens to hundreds even in low energy ball mills such as a rotating ball mill It takes time and time to synthesize alloys, and a rotating ball mill has the advantages of simple structure, relatively low cost, and easy scale-up. "
In addition, although it does not affect the patentability of this invention, patent document 1 * 2 etc. can be mentioned as related prior art literature.

  Patent Documents 1 and 2 describe “a method for producing heterogeneous composite powder particles (SiC powder) by mechanical alloying using ball milling”. Patent Document 1 further describes that the heterogeneous composite powder particles have a lamellar structure.

  Further, Patent Document 3 proposes a swirling crusher similar to that used in the present invention (centrifugal mill: sometimes referred to as an eccentric mill).

However, in Patent Document 3, mechanical alloying (mechanochemistry processing) is not planned.
Meisei Planning Co., Ltd. “Advanced Grinding Technology and Application” (NTT), 25 September 2005, p103-104 JP 2006-152442 A JP 2004-35327 A Japanese Patent Laid-Open No. 10-34000

  Recently, there has been a demand for the emergence of a pulverization method using a ball mill pulverizer or the like that can be easily scaled up in a short time.

  An object of the present invention is to provide a mechanochemistry processing method using a ball mill pulverizer or the like that can meet the above requirements.

  In order to solve the above-mentioned problems, the present inventors have obtained the following knowledge in the course of making an intensive effort.

  When the granular raw material is pulverized and mechanically alloyed by the swirling method pulverizer having the configuration described in Patent Document 3, as described above, the efficiency that has been most suitable for mechanical alloying is excellent. Compared to a planetary ball mill, a powder composite material by mechanical alloying can be obtained in a shorter time than expected.

  And based on the said knowledge, it came to the method of the mechanochemistry process of the following structure.

A method for producing a chemically modified product (product) by subjecting one or more kinds of granular raw materials to a pulverizer equipped with a pulverization cylinder charged with a pulverization medium and pulverizing and mechanochemistry treatment. ,
As the pulverizer, a swirl type pulverizer that generates vibration by revolution (turning) is used.

  Hereinafter, desirable modes of the present invention will be described.

  An example of the swirl type crusher (eccentric mill) used in the present invention and its principle are shown in FIGS. Here, the case of the single cylinder type is used as an example, but the same applies to the double cylinder type as shown in FIGS.

  The basic configuration is that a (circular) cylindrical pulverization container (pulverization cylinder) 12 filled with a powder medium and an object to be pulverized is swung by a plurality (one pair: two in the example) of cranks (eccentric shafts) 14. (Revolved) The container (grinding cylinder) was filled in such a way as to turn around the origin O of the absolute coordinate system (turning locus L) without rotating itself with respect to the absolute coordinate system. The pulverization medium and the material to be pulverized can be pulverized by generating a centrifugal force (other than the reference numerals are cited from claim 1 of Patent Document 3). In FIG. 3, lowercase letters a, b, c, and d indicate the center positions of the crushing cylinders 12a, 12b, 12c, and 12d, respectively.

  More specifically, it is as follows.

  Each eccentric shaft 14 includes a large-diameter portion (crank arm) 14a and a small-diameter portion (crankshaft) 14b formed at the eccentric positions on both sides of the large-diameter portion.

  The pair of small diameter portions (crankshafts) 14 b are supported by a pair of main bearings (fixed bearings) 18, 18 disposed on the fixed support base 16. A counterweight (balance weight) 20 is attached to each of the small-diameter portions (crankshafts) 14b so that the vibration moment is canceled and vibration is not substantially generated.

  A small-diameter portion (crankshaft) 14 a on one side of each eccentric shaft 14 is connected to a drive motor 24 via a universal shaft joint (universal joint) 22.

  On the other hand, a large bearing (crank arm) 14a of the pair of eccentric shafts 14 is provided with a sub-bearing (floating bearing) 26 that is not fixedly supported. Between the auxiliary bearing boxes 27 and 27 of the auxiliary bearings 26 and 26, a pair of crushing cylinder mounting plates 28 and 28 are stretched in the longitudinal direction of the shaft, and the crushing cylinder 12 is attached to the crushing cylinder mounting plates 28 and 28. It is supposed to be removable. Of course, a crushing cylinder fixing method may be used.

  Further, between the drive motors 24, 24, the drive motors 24, 24 can be rotated synchronously by a timing belt 32 via pulleys 30, 30.

In the above, the ratio between the turning diameter (G) and the pulverizing cylinder inner diameter (D) is appropriately selected from the range of 0.01 <G / D <0.3. These numerical values are based on the assumption that the rotational speed is 500 to 1200 min ⁻¹ , and when the rotational speed is outside these ranges, the G / D range also varies slightly (see FIG. 3).

  Specifically, when the inner diameter of the pulverizing cylinder 12 is 180 mm, for example, the turning diameter (amplitude) is about 1.8 to 54 mm.

  If the turning diameter G is too large compared with the inner diameter D of the grinding cylinder, the centrifugal force (acceleration number) at the time of turning becomes large, and it is necessary to make the eccentric shaft 14 relatively thick (especially the crankshaft 14b) and the counter. The weight 20 also needs to be heavy. Naturally, it becomes difficult to manufacture an eccentric shaft having practical strength. When a material tempered to increase the tensile strength and toughness of the shaft is used, uniform tempering up to the core of the material cannot be performed, resulting in significant distortion at the eccentric part during lathe processing. For this reason, it is necessary to temper and finish the material after roughing. On the other hand, if the turning diameter G is too small compared to the inner diameter D of the pulverizing cylinder, sufficient centrifugal force is not generated at the time of turning, and it becomes difficult to shorten the processing time of the mechanochemistry process on the workpiece.

  The ball mill pulverizer according to the present invention is used for mechanical alloying, and therefore, an air supply means for supplying gas into the pulverization cylinder, and / or a decompression means for reducing the pressure in the pulverization cylinder, and In addition, a pulverizing cylinder temperature control means is provided.

That is, in the mechanical alloying, is often dislike oxide formation, or filled with N ₂ and Ar inert gas to the grinding cylinder, is due to the need or the vacuum state in the milling tube was degassed . In the illustrated example, a gas inlet 12a and a deaeration port (suction port) 12b each connected to a flexible pipe are provided. Reference numeral 12c denotes an open / close lid.

  The reason why the pulverizing cylinder temperature adjusting means is necessary for mechanical alloying is as follows.

  If the temperature is not controlled to the set temperature, it is difficult to control the reaction (alloying), and it is difficult to obtain the required alloy / crystal form (solid solution, phase transfer, etc.). Further, the product (alloy powder) may be contaminated by oxidation or alteration of the container material. In the illustrated example, a heat medium (cooling water) is passed through the jacket 13. The temperature control means can also use the inert gas as a cooling gas.

  Note that the temperature of the crushing cylinder can be detected by using a non-contact type that measures the temperature of the lid of the crushing cylinder using a radiation thermometer, or by using a resistance thermometer to place the temperature measuring part on the lid surface with a heat insulating material. It can be performed by a contact method in which the temperature is measured by covering directly.

  Next, the manufacturing method of the alloy by the mechanical alloying of this invention using the said turning-type grinding | pulverization apparatus is demonstrated.

  First, a granular material based on two or more metals is prepared. As the material of the raw material, nonmetals and ceramics (metal oxides / nitrides, carbides, etc.) can be appropriately combined with metals.

  The granular raw material of the object to be processed is not particularly limited as long as it is granular (including spherical, plate-like, scales, flakes, irregular shapes, etc.), but the average particle size is 100 to 5000 μm, preferably 100 to Use 1500μm.

  Next, the granular material is charged into the pulverizing cylinder 12 through the open / close lid 12 c and charged into the pulverizing cylinder 12 while charging the pulverizing medium. The grinding media are not limited to balls, rods, prisms, tetrahedrons, hexahedrons, octahedrons, etc., but are usually balls. Here, the input amount (filling rate) of the pulverizing medium is 50 to 95%, preferably 65 to 85% of the capacity of the pulverizing cylinder 12 in the case of mechanical alloying. At this time, the diameter of the ball, which is a grinding medium, varies depending on the size of the grinding cylinder, the final product particle size, the particle size of the granular raw material, etc., but is usually 3 to 30 mm (more usually 3 to 13 mm). Select appropriately from the range. In the case of mechanical alloying, the material of the ball is usually made of iron (steel), but may be other alloys or ceramics.

  The pulverizing cylinder is not particularly limited, but is usually liner-lined from the viewpoint of preventing wear. Furthermore, the pulverization cylinder is not limited to a cylinder, and may be a polygonal cylinder (cross-sectional 4-8 octagon).

  Furthermore, the amount of metal granular raw material input varies depending on the type and / or particle size of the raw material and the type and / or material of the grinding medium. For example, when the grinding medium is a ball, 3 to 10% of the volume in the grinding cylinder It sets from the range.

The rotational speed, revolves (turning) in diameter, when the 10~30mm, 500~1800min ^-1, more usually, take 500~1200min ^-1.

  That is, the acceleration number (G) obtained by the following calculation formula is appropriately set within the range of 4 to 72G, preferably more than 10 and 32G, and more preferably 12 to 20G. If the acceleration number is too small, it is difficult to obtain a product having the required particle size. If the acceleration number is too large, the load during operation is too large to be practical.

Acceleration number (G) =
1 / 9.8 (ms ^-2 ) x single amplitude (turning radius) (m) x (2π x frequency (min ^-1 ) x 60 (s ^-1 )) ²
Although the operation time varies depending on the type of alloy required, in the case of the present invention, a particle size of 100 μm or less can be obtained in about 10 minutes as in the examples described later.

  The product (alloy) obtained as described above is usually a batch type, but is discharged from the pulverizing cylinder 12 by gas transportation (usually using an inert gas) as shown in FIG. It can also be collected in the product tank 38.

  That is, an inert gas is fed into the pulverization cylinder 12 by using an air supply device (gas transporter) 34, a product is discharged from the pulverization cylinder 12 with the inert gas pressure, and a product tank is supplied via a cyclone 36. Recover to 38. In addition, 40 is a bag filter and 41 is a suction device (gas transporter). The product may be sucked and discharged from the grinding cylinder 12 by the suction device 41.

  Thus, the manufactured alloy powder is made into a sintered product by sintering or the like as will be described later. For example, a sintered body can be manufactured by pulse current heating in a vacuum or in an inert atmosphere using a firing die 48 including a die 42 and upper and lower punches 44 and 46 as shown in FIG. .

  When the mechanical processing method of the present invention is applied not only to the above mechanical alloying but also to other mechanical chemistry fields as described below, it can be expected that the processing time will be greatly shortened.

    -Metal powder or metal oxide is pulverized in an oxygen atmosphere to adjust the oxide material for sintering.

    ・ Dry milling to crystallize copper phthalonian pigments from β to α (see “Powder and Industry Vol.31.No.12 (1999)” p.58).

・ Mechanochemical desalting treatment of polyvinyl chloride. (See “Journal of Powder Engineering Vol.31.No.44 (2007)” p49)
A mechanical milling process is performed on a mixture of the sulfide-based solid electrolyte material and the LixFeSy material. (Refer to claim 6 of JP 2006-164695 A)

Hereinafter, in order to confirm the effect of the present invention, Examples and Comparative Examples 1 and 2 applied when preparing an Fe ₂ VAl-based sintered body will be described. The Fe ₂ VAl-based sintered body has an excellent Seebeck effect, and is expected as a thermoelectric conversion material for temperature difference power generation utilizing waste heat by utilizing the Seebeck effect.

  The acceleration number of the planetary ball mill is obtained based on the following formula.

Acceleration number (G) = 1 / (9.8ms ^-2 ) x ω ² [D + d (1 + R) ² ] / 2
omega: revolution angular velocity (s ^-1), D: the revolution diameter (m), d: Pot inside diameter (m), R: the gear ratio of the revolution rotation (-), the revolving direction of R by the forward or backward direction The value is positive or negative.

  The raw material particle sizes and compositions used in the examples and comparative examples are as follows.

FeAl (10-100 μm): 0.5165
FeV (100-200 μm): 0.3214
Fe (20-50 μm): 0.1490
Si (30-40 μm): 0.0131
<Example 1>
The specifications and operating conditions of the swirling grinder used in this example are as follows.

Crushing cylinder capacity: 1.38L (98mmφ × 183mm)
Rotation speed: 900min ^-1
Total amplitude (turning diameter): 30mm
Number of acceleration: 13.6G
Grinding medium (ball): 1/2 inch diameter (about 12.7mm), filling rate 80%,
Raw material input: 150 g (bulk specific gravity 0.3, filling rate 100%; grinding medium total void volume ratio)
Operating time: 20h
<Comparative Example 1>
The specifications and operating conditions of the planetary ball mill used in this comparative example are as follows.

Crushing cylinder capacity: 500ml (100mmφ x 75mm depth) x 4
Revolving speed: 180min ^-1 , Revolving diameter: 250mm
Rotation speed: 200min ^-1 , rotation diameter: 100mm
Number of acceleration: 6.8G
Grinding medium (ball): φ10mm: 100 pieces + 2 pieces of φ1 inch (about 24.5mm),
Filling rate: 14%
Raw material input: 30g x 4
Driving time: 200h
<Comparative Example 2>
The specifications and operating conditions of the vibrating ball mill used in this comparative example are as follows.

Crushing cylinder capacity: 3.6L (145mmφ × 220mm)
Rotation speed: 1200min ^-1
Total amplitude: 9mm
Acceleration number: 9.7G
Grinding medium (ball): 1/2 inch diameter (about 12.7mm), filling rate 80%,
Raw material input amount: 300 g (bulk specific gravity 0.3, filling rate 100%; grinding medium total void volume ratio)
Driving time: 25h
Then, the completion of the run, the product of each of Examples and Comparative Examples was taken out from the milling tube: was observed (alloy powder Fe ₂ VAl-based alloy).

  In Example 1, as in Comparative Example 1, aggregated particles close to a spherical shape of about 10 μm with thin pieces (scale pieces) overlapped were obtained. Further, the aggregated particles obtained in Comparative Example 2 also had a particle size of about 10 μm, but unlike Example 1 and Comparative Example 1, they were angular. As described above, in the present invention, it was confirmed that the agglomerated particles having the round shape similar to that of the planetary ball mill can be obtained in a very short time only when the acceleration number is about double. Conventionally, it has been common knowledge to those skilled in the art that the pulverization time for pulverizing to a particle size is approximately proportional to the acceleration number (see Example 1 and Comparative Example 2).

  As will be described later, spherical agglomerated particles with overlapping flakes can obtain superior characteristics as compared to angular agglomerated particles. The reason is considered to be that homogenization (alloying: alloy crystallization) proceeds at a higher level during mechanical alloying.

  Then, pulse current sintering (PCS) was performed under the following conditions using the alloy powder prepared in each of the above Examples and Comparative Examples to prepare a sintered body test piece.

Using a firing mold (made of graphite, firing size: 10 mmφ × 2 mmh), with a degree of vacuum of 20 Pa, a pressing force of 40 MPa, a sintering temperature of 1000 ° C., a sintering time of 3 min, and a heating rate of 100 ° C. min ⁻¹ went.

  The Seebeck coefficient was measured for each specimen thus prepared.

  As a result, as shown in FIG. 8, it was confirmed that in the example, the Seebeck (thermoelectromotive force) characteristic comparable to that obtained when mechanically alloyed with a planetary ball mill (Comparative Example 1) was obtained. . On the other hand, when mechanical alloying is performed with a vibrating ball mill for 25 hours (Comparative Example 2), it can be seen that the Seebeck characteristics are clearly inferior.

  The Seebeck coefficient is measured from the relationship between the thermoelectromotive force generated at both ends of a sample and a temperature difference between the ends of a rod-shaped sample (2 × 2 × 9 mm) in a 100 ° C furnace filled with helium. did.

  It has been experimentally confirmed that the Seebeck coefficient is proportional to the processing time as shown in FIG. 6 when mechanical alloying is performed by a planetary ball mill using raw materials having the same composition.

  That is, by increasing the pulverization (mechanical alloying) time, the particles become finer and the alloy mixing system becomes more uniform, the crystallization is accelerated and the target crystal structure is easily obtained, thereby increasing the Seebeck coefficient. Estimated.

  That is, the principle of mechanical alloying in the present invention is the same as that shown in FIG. 7 in the planetary ball mill, and is considered as follows.

    1) Two or more kinds of metal powders 52 are mixed and formed into flakes while being stretched by the grinding medium (ball) 54.

    2) The flaky powder is stretched while overlapping, forming a fine lamellar texture.

    3) Repeat crushing and bonding to homogenize.

    4) It becomes a non-equilibrium alloy and forms agglomerated grains (flat spheres).

The schematic diagram of “a typical ball mill used for mechanical alloying” described in Non-Patent Document 1 is cited. It is a schematic plane sectional view which shows an example of the turning type crusher used for this invention. It is explanatory drawing of the turning motion of the crushing container in a turning type crusher similarly. It is a flowchart for demonstrating an example of the method of collection | recovery of the product (powder alloy) obtained by the method of this invention. It is a model cross-sectional view of a sintering type used in the pulse current sintering method. It is a graph which shows the relationship between sintering raw material mechanical alloying time and Seebeck coefficient. It is a principle explanatory view of mechanical alloying in a planetary ball mill. It is a graph which shows the measurement result of a Seebeck coefficient about each sintered compact manufactured from the mechanical alloying processing powder of an Example and Comparative Examples 1-2.

Explanation of symbols

12 ... Grinding cylinder (grinding container),
14 ... Eccentric shaft (crank)
14a ... Large diameter part (crank arm)
14b ... Small diameter part (crankshaft)
52 ... Metal powder 54 ... Grinding ball

Claims (6)

A method for producing a chemically modified product (product) by subjecting one or more kinds of granular raw materials to a pulverizer equipped with a pulverization cylinder charged with a pulverization medium and pulverizing and mechanochemistry treatment. ,
A mechanochemistry processing method, characterized in that a swirling crusher that generates vibration by revolution (turning) is used as the grinder.   2. The method of mechanochemistry treatment according to claim 1, wherein the granular raw material is two or more kinds of metals mainly containing metal or a mixture of metal and nonmetal, and an alloy is produced by mechanical alloying. As the granular raw material, one having a particle size of 100 to 1000 μm is used, and the swirl type pulverizer is operated under operating conditions of a rotational speed of 500 to 1800 min ⁻¹ and an acceleration number (G) represented by the following formula is 10 3. The method of mechanochemistry treatment according to claim 2, wherein the inorganic composite material having a particle size of 10 to 100 [mu] m is obtained as a product by using ultra-32G.
Acceleration number (G) =
1 / 9.8 (ms ^-2 ) x single amplitude (turning radius) (m) x (2π x frequency (min ^-1 ) x 60 (s ^-1 )) ²   The mechanochemistry treatment method according to claim 2 or 3, wherein a non-oxidizing atmosphere is provided in the pulverizing cylinder during the pulverization.   A method for producing an alloy, wherein the powdered alloy obtained by the mechanochemistry treatment method according to any one of claims 2 to 4 is a spherical aggregate of pulverized lamellae (flakes). A swirl type ball mill pulverizer comprising a pulverization cylinder and a vibration generator for generating vibration by revolving (turning) the pulverization cylinder,
An air supply means for supplying gas into the pulverization cylinder, and / or a decompression means for reducing the pressure inside the pulverization cylinder, and a pulverization cylinder temperature control means, are characterized by being capable of mechanical alloying. A swivel ball mill.

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