JP5123755B2 - A method for producing highly crystalline metal or metal oxide particles. - Google Patents
A method for producing highly crystalline metal or metal oxide particles. Download PDFInfo
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- JP5123755B2 JP5123755B2 JP2008165353A JP2008165353A JP5123755B2 JP 5123755 B2 JP5123755 B2 JP 5123755B2 JP 2008165353 A JP2008165353 A JP 2008165353A JP 2008165353 A JP2008165353 A JP 2008165353A JP 5123755 B2 JP5123755 B2 JP 5123755B2
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Description
本発明は、結晶性の高い金属粒子又は金属酸化物粒子を製造する方法に関する。 The present invention relates to a method for producing metal particles or metal oxide particles having high crystallinity.
積層セラミックコンデンサは、誘電層と内部電極とを層状に交互に配した積層状態のチップ状コンデンサである。積層セラミックコンデンサは、誘電層となるセラミックのグリーンシート上に、導電性ペーストを用いて内部電極となる導電膜を印刷等によって形成し、導電膜が形成されたグリーンシートを複数積層し、セラミックの加熱可能な温度で加熱して製造される。積層セラミックコンデンサの内部電極の形成には現在ニッケル粉が一般的に使用されている。 A multilayer ceramic capacitor is a chip-shaped capacitor in a laminated state in which dielectric layers and internal electrodes are alternately arranged in layers. A multilayer ceramic capacitor is formed by forming a conductive film as an internal electrode using a conductive paste on a ceramic green sheet as a dielectric layer by printing or the like, and laminating a plurality of green sheets on which the conductive film is formed. It is manufactured by heating at a heatable temperature. Currently, nickel powder is generally used for forming internal electrodes of multilayer ceramic capacitors.
前記の加熱は、一般に還元雰囲気中、９００℃以上で行われる。この加熱においては、グリーンシー卜の焼結に伴う収縮量が、ニッケルの導電膜の収縮量に比べて小さいので、焼結の進行に伴いニッケル膜が途切れて不連続になり、内部電極として機能しなくなるという不都合が生じることがある。この問題の解決を目的として、例えば特許文献１には、特定の粒径及びタップ密度を有するニッケル粉が提案されている。このニッケル粉は、塩化ニッケルのガス及び水素ガスを用いた塩化ニッケルの気相水素還元法によって製造される。同文献によれば、この製造方法は温度が１０００℃付近の高温なので、ニッケルの結晶が大きく成長し、加熱時に過焼結が発生しにくいとされている。 The heating is generally performed at 900 ° C. or higher in a reducing atmosphere. In this heating, the amount of shrinkage accompanying the sintering of the green sheet is smaller than the amount of shrinkage of the nickel conductive film, so as the sintering progresses, the nickel film becomes discontinuous and functions as an internal electrode. The inconvenience of not doing so may occur. For the purpose of solving this problem, for example, Patent Document 1 proposes nickel powder having a specific particle size and tap density. The nickel powder is produced by a nickel chloride gas phase hydrogen reduction method using nickel chloride gas and hydrogen gas. According to this document, since this manufacturing method is performed at a high temperature around 1000 ° C., nickel crystals grow large and oversintering is unlikely to occur during heating.
しかし、この方法では、反応の副生成物として、環境に有害なガスである塩素ガスが発生してしまうので、製造上安全性に大きな注意をはらう必要がある。また、反応装置として真空装置が必要なので、設備が複雑化し、また製造コストが高くなる。更に、得られるニッケル粉の粒径の下限は約１００ｎｍが限界であり、それ以上微粒のニッケル粉を得ることは極めて困難である。 However, in this method, chlorine gas, which is a gas harmful to the environment, is generated as a by-product of the reaction, and thus it is necessary to pay great attention to safety in production. Moreover, since a vacuum apparatus is required as a reaction apparatus, the facilities are complicated and the manufacturing cost is increased. Furthermore, the lower limit of the particle diameter of the obtained nickel powder is about 100 nm, and it is extremely difficult to obtain finer nickel powder.
特許文献１に記載の方法が乾式でのニッケル粉の製造方法であるのに対し、特許文献２には湿式でのニッケル粉の製造方法が記載されている。この方法においては、パラジウムと銀とからなる複合コロイド粒子が分散したコロイド溶液と、還元剤と、アルカリ性物質とを混合して、アルカリ性コロイド溶液を作製し、該アルカリ性コロイド溶液にニッケル塩水溶液を添加して、ニッケル粒子を生成させている。この方法によれば、上述した乾式法に比べて微粒のニッケル粒子が得られるという利点がある。しかし、この湿式法で製造されたニッケル粒子は結晶性が低く、それに起因して、高温での焼結時における収縮量が大きいという問題がある。 Whereas the method described in Patent Document 1 is a dry method for producing nickel powder, Patent Document 2 describes a method for producing wet nickel powder. In this method, a colloidal solution in which composite colloidal particles composed of palladium and silver are dispersed, a reducing agent, and an alkaline substance are mixed to produce an alkaline colloidal solution, and an aqueous nickel salt solution is added to the alkaline colloidal solution. Thus, nickel particles are generated. According to this method, there is an advantage that fine nickel particles can be obtained as compared with the dry method described above. However, the nickel particles produced by this wet method have low crystallinity, and as a result, there is a problem that the amount of shrinkage during sintering at high temperature is large.
上述の技術とは別に、微粒子の製造方法に関し、出願人は先に、完全酸化体又はそれに近い構造を有する錫ドープ酸化インジウム（ＩＴＯ）ナノ粒子の製造方法を提案した（特許文献３参照）。この製造方法においては、完全酸化状態にないＩＴＯナノ粒子の原料粉末を、酸素雰囲気下、ＩＴＯの完全酸化が可能な温度以上でかつＩＴＯ中の錫が昇華する温度未満の温度範囲で瞬間加熱する。この方法によれば、粒子どうしの凝集を防止しつつ各粒子に存在する酸素欠陥を除去することが可能となる。しかし、同文献には、この方法を金属や金属酸化物（完全酸化体）に適用することで、それらの結晶性が高まることについての記載はない。 Apart from the above-described technology, the applicant previously proposed a method for producing tin-doped indium oxide (ITO) nanoparticles having a completely oxidized form or a structure close thereto (see Patent Document 3). In this production method, the raw material powder of ITO nanoparticles that are not in a completely oxidized state is instantaneously heated in an oxygen atmosphere at a temperature that is not less than the temperature at which ITO can be completely oxidized and less than the temperature at which tin in ITO sublimes. . According to this method, it is possible to remove oxygen defects present in each particle while preventing aggregation of the particles. However, this document does not describe that the crystallinity is enhanced by applying this method to metals or metal oxides (completely oxidized products).
本発明の目的は、結晶性が高い微粒子を、安全にかつ経済的に製造し得る方法を提供することにある。 An object of the present invention is to provide a method capable of safely and economically producing fine particles having high crystallinity.
本発明は、金属又は金属酸化物からなる原料微粒子を、加熱ゾーンを有する縦型加熱炉の上部から落下させ、落下した該原料微粒子を該加熱ゾーンにおいて、該原料微粒子に化学反応を生じさせない雰囲気下に、該金属又は金属酸化物のバルク体の融点未満を上限として、０．００１〜１０秒間加熱して、結晶性が高められた微粒子を得ることを特徴とする高結晶性金属又は金属酸化物微粒子の製造方法を提供するものである。 The present invention is an atmosphere in which raw material fine particles made of metal or metal oxide are dropped from the upper part of a vertical heating furnace having a heating zone, and the dropped raw material fine particles are not caused to cause a chemical reaction in the raw material fine particles in the heating zone. A highly crystalline metal or metal oxide characterized by obtaining fine particles having improved crystallinity by heating for 0.001 to 10 seconds, with the upper limit being less than the melting point of the bulk of the metal or metal oxide. The present invention provides a method for producing physical fine particles.
本発明の方法によれば、微粒でかつ高結晶の金属又は金属酸化物の粒子を、安全にかつ経済的に製造することができる。得られた粒子は、粒子どうしの融着の程度が低いので、粉砕や分散処理が非常に容易である。したがって、得られた粒子は、例えば導電性インクを始めとする各種インクの原料として特に有用である。 According to the method of the present invention, fine and highly crystalline metal or metal oxide particles can be produced safely and economically. Since the obtained particles have a low degree of fusion between the particles, pulverization and dispersion treatment are very easy. Therefore, the obtained particles are particularly useful as a raw material for various inks including, for example, conductive inks.
以下本発明を、その好ましい実施形態に基づき図面を参照しながら説明する。図１には、本発明の製造方法を実施するために好適に用いられる装置の一例が示されている。この装置１０は縦型加熱炉１１を基本構成としている。加熱炉１１は筒状であり、その高さ方向の一部に加熱手段１２を備えた加熱ゾーン１３を有している。加熱炉１１内には、該加熱炉１１の高さとほぼ同様の長さを有し、かつ所定の内径を有する管体１４が配置されている。管体１４は、その周囲が上述の加熱手段１２によって取り囲まれている。管体１４としては熱伝導性の低い耐火材料を用いることが、原料微粒子の急速加熱及び急速冷却を首尾良く行う点から好ましい。そのような材料として例えばアルミナを用いることができる。 The present invention will be described below based on preferred embodiments with reference to the drawings. FIG. 1 shows an example of an apparatus suitably used for carrying out the manufacturing method of the present invention. This apparatus 10 has a vertical heating furnace 11 as a basic configuration. The heating furnace 11 has a cylindrical shape, and has a heating zone 13 provided with heating means 12 in a part in the height direction. In the heating furnace 11, a tube body 14 having a length substantially the same as the height of the heating furnace 11 and having a predetermined inner diameter is disposed. The periphery of the tube body 14 is surrounded by the heating means 12 described above. It is preferable to use a refractory material with low thermal conductivity as the tube body 14 from the viewpoint of successful rapid heating and rapid cooling of the raw material fine particles. For example, alumina can be used as such a material.
管体１４はその上下が開孔している。管体１４の上端の開口部は、ホッパー１５に接続されている。ホッパー１５内には、原料微粒子が仕込まれている。ホッパー１５の下端部には電磁フィーダー（図示せず）が取り付けられており、所定量の原料微粒子が管体１４内に投入されるようになっている。また管体１４の上端付近には、ガスの導入口１６が設けられている。図示しないガス源から供給されたガスは導入口１６を通じて管体１４内に導入され、管体１４内を上から下に向けて流通する。 The upper and lower sides of the tube body 14 are open. The opening at the upper end of the tube body 14 is connected to the hopper 15. In the hopper 15, raw material fine particles are charged. An electromagnetic feeder (not shown) is attached to the lower end portion of the hopper 15 so that a predetermined amount of raw material fine particles are introduced into the tube body 14. A gas inlet 16 is provided near the upper end of the tube body 14. A gas supplied from a gas source (not shown) is introduced into the tube body 14 through the inlet 16 and circulates in the tube body 14 from top to bottom.
以上の構成を有する装置１０を用いた本製造方法について説明すると、ホッパー１５内に仕込まれている原料微粒子としては、金属微粒子や金属酸化物微粒子が用いられる。金属微粒子としては、その種類に特に制限はなく、例えば典型金属元素及び遷移金属元素が挙げられる。ただし、アルカリ金属元素は取り扱いに注意を要する。金属酸化物微粒子としては、典型金属元素（ただしアルカリ金属元素は除く）の酸化物及び遷移金属元素の酸化物が挙げられる。金属微粒子の具体例としては、ニッケル、Ｆｅ、Ｃｏ、Ｃｕ、Ｚｎ、Ｓｎ、Ｐｄ、Ａｇ、Ａｕ、Ｐｔ等の微粒子が挙げられる。金属酸化物微粒子の具体例としては、Ｔａ2Ｏ5、ＴｉＯ2、Ｆｅ2Ｏ3、Ｃｏ3Ｏ4、ＮｉＯ、Ｃｕ2Ｏ、ＺｎＯ、Ｇａ2Ｏ3、ＺｒＯ2、Ｉｎ2Ｏ3、ＳｎＯ2、Ｓｂ2Ｏ5、ＷＯ3等が挙げられる。 The production method using the apparatus 10 having the above configuration will be described. As the raw material fine particles charged in the hopper 15, metal fine particles and metal oxide fine particles are used. There is no restriction | limiting in particular as a metal fine particle, For example, a typical metal element and a transition metal element are mentioned. However, care should be taken when handling alkali metal elements. Examples of the metal oxide fine particles include oxides of typical metal elements (excluding alkali metal elements) and oxides of transition metal elements. Specific examples of the metal fine particles include fine particles such as nickel, Fe, Co, Cu, Zn, Sn, Pd, Ag, Au, and Pt. Specific examples of the metal oxide fine particles include Ta 2 O 5 , TiO 2 , Fe 2 O 3 , Co 3 O 4 , NiO, Cu 2 O, ZnO, Ga 2 O 3 , ZrO 2 , In 2 O 3 , SnO. 2 , Sb 2 O 5 , WO 3 and the like.
原料微粒子が金属酸化物である場合、該金属酸化物は、金属水酸化物又は金属炭化物を含酸素雰囲気下で加熱して得られたものであることが好ましい。これによって、金属水酸化物又は金属炭化物からの金属酸化物の製造工程と、該金属酸化物からの目的物の製造工程を、加熱という共通の操作を有する一連の工程とすることが可能となる。このことは、製造効率の向上の点から有利である。 When the raw material fine particles are a metal oxide, the metal oxide is preferably obtained by heating a metal hydroxide or a metal carbide in an oxygen-containing atmosphere. As a result, the production process of the metal oxide from the metal hydroxide or metal carbide and the production process of the target product from the metal oxide can be made into a series of steps having a common operation of heating. . This is advantageous in terms of improving manufacturing efficiency.
原料微粒子の粒径に特に制限はなく、比較的大きな粒径を有するものから、超微粒のものまでを対象とすることができる。特に本実施形態の方法は、加熱に起因する粒子どうしの融着が起こりやすい粒径の粒子、すなわち一次粒子の粒径が２００ｎｍ以下、特に１００ｎｍ以下の微粒子に適用することが有効である。ここで言う「一次粒子の粒径」とは、走査型電子顕微鏡（ＳＥＭ）観察によって測定された、個々の一次粒子の差し渡しの長さの平均値のことである。原料微粒子の粒径の下限値に特に制限はなく、現在の技術で到達可能な超微粒子までを適用の対象とすることができる。 There is no particular limitation on the particle size of the raw material fine particles, and it is possible to target from a relatively large particle size to an ultrafine particle. In particular, the method of the present embodiment is effective when applied to particles having a particle size in which particles are likely to be fused due to heating, that is, primary particles having a particle size of 200 nm or less, particularly 100 nm or less. The term “primary particle size” as used herein refers to the average value of the length of each primary particle measured as measured by scanning electron microscope (SEM) observation. There is no particular limitation on the lower limit of the particle diameter of the raw material fine particles, and ultrafine particles that can be reached with the current technology can be applied.
原料微粒子の形状にも特に制限はない。例えば球状、多面体状、フレーク状、鱗片状、紡錘状、不定形、又はそれらの任意の組合せ等が挙げられる。本実施形態の方法によれば、原料微粒子の形状が目的物である高結晶性微粒子の形状にほぼ受け継がれるので、目的物である高結晶微粒子の具体的な用途に応じて適切な形状を有する原料微粒子を選定すればよい。 The shape of the raw material fine particles is not particularly limited. Examples thereof include a spherical shape, a polyhedral shape, a flake shape, a scale shape, a spindle shape, an indeterminate shape, or any combination thereof. According to the method of the present embodiment, since the shape of the raw material fine particles is almost inherited by the shape of the high crystalline fine particles as the target, it has an appropriate shape according to the specific use of the high crystalline fine particles as the target. The raw material fine particles may be selected.
図１に示す装置１０において、原料微粒子は、一定量ずつ管体１４内に投入される。投入は連続的でもよく、あるいはインターバルをおいた不連続的でもよい。この状態では原料微粒子は室温状態にある。管体１４内に投入された原料微粒子は重力によって自由落下し、加熱ゾーン１３の位置まで到達する。加熱ゾーン１３に備えられている加熱手段１２によって、加熱ゾーン１３は所定温度に加熱されている。管体１４は上述の通り熱伝導性の低い材料から構成されているので、原料微粒子は加熱ゾーン１３に到達して初めて加熱される。つまり急速加熱される。 In the apparatus 10 shown in FIG. 1, the raw material fine particles are introduced into the tube body 14 by a certain amount. The input may be continuous or discontinuous at intervals. In this state, the raw material fine particles are at room temperature. The raw material fine particles introduced into the tube body 14 freely fall by gravity and reach the position of the heating zone 13. The heating zone 13 is heated to a predetermined temperature by the heating means 12 provided in the heating zone 13. Since the tube body 14 is made of a material having low thermal conductivity as described above, the raw material fine particles are heated only after reaching the heating zone 13. That is, it is rapidly heated.
加熱ゾーン１３における加熱によって原料微粒子は、粒子内で原子の規則的な再配置が起こり、それによって結晶性が高くなる。また、結晶粒が成長する。原料微粒子の形状や粒径等の外観に変化を実質的に生じさせることなく該原料微粒子の結晶性を高め、また結晶粒を成長させる観点から、加熱ゾーン１３における加熱温度は、金属又は金属酸化物のバルク体の融点未満を上限として、高ければ高いほど好ましい。本製造方法によって原料微粒子の結晶性が高くなったか否かは、例えば、本製造方法の前後における原料微粒子をＸ線回折測定して、回折ピークのシャープさや、結晶子径の増大によって判断できる。 The raw material fine particles undergo regular rearrangement of atoms within the particles by heating in the heating zone 13, thereby increasing the crystallinity. In addition, crystal grains grow. From the viewpoint of increasing the crystallinity of the raw material fine particles without causing substantial changes in the appearance of the raw material fine particles, the particle size, etc., and growing the crystal grains, the heating temperature in the heating zone 13 is a metal or metal oxide. The upper limit is less than the melting point of the bulk of the product, and the higher the better. Whether or not the crystallinity of the raw material fine particles has been increased by this production method can be determined, for example, by measuring the raw material fine particles before and after the present production method and measuring the sharpness of the diffraction peak or increasing the crystallite diameter.
加熱ゾーン１３における急速加熱の速度は５００〜２００００℃／秒、特に１０００〜１００００℃／秒であることが、原料微粒子どうしの融着を防止する観点から好ましい。加熱時間、すなわち原料微粒子が加熱ゾーン１３を通過するのに要する時間についても、原料微粒子どうしの融着を防止する観点から短時間であることが好ましく、具体的には０．００１〜１０秒、特に０．０１〜１秒であることが好ましい。 The rapid heating speed in the heating zone 13 is preferably 500 to 20000 ° C./second, particularly 1000 to 10,000 ° C./second, from the viewpoint of preventing fusion of the raw material fine particles. The heating time, that is, the time required for the raw material fine particles to pass through the heating zone 13 is preferably a short time from the viewpoint of preventing fusion of the raw material fine particles, specifically 0.001 to 10 seconds, In particular, it is preferably 0.01 to 1 second.
管体１４内に導入されるガスは、加熱中の原料微粒子に対して化学反応を生じさせる成分が管体１４内に入り込むことを防止するために用いられる。このガスとしては、原料微粒子の種類に応じて適切なものが用いられる。本製造方法は、原料微粒子に化学反応を生じさせない雰囲気下に該原料微粒子を加熱して、該原料微粒子の結晶性のみを変化させる方法なので、管体１４内に導入されるガスは、加熱中の原料微粒子に対して化学的に不活性なものが用いられる。原料微粒子が金属微粒子である場合には、ガスとして例えば窒素、ヘリウム、アルゴン等を用いることができる。反応が起こらない条件であれば水素を用いることもできる。原料微粒子が金属酸化物である場合には、ガスとして酸素、窒素、空気、アルゴン、ヘリウム、水素等を用いることができる。 The gas introduced into the tube body 14 is used to prevent components that cause a chemical reaction with the raw material fine particles being heated from entering the tube body 14. As this gas, an appropriate gas is used according to the type of raw material fine particles. Since the present manufacturing method is a method in which only the crystallinity of the raw material fine particles is changed by heating the raw material fine particles in an atmosphere that does not cause a chemical reaction to the raw material fine particles, Those chemically inert to the raw material fine particles are used. When the raw material fine particles are metal fine particles, for example, nitrogen, helium, argon or the like can be used as the gas. Hydrogen can also be used as long as the reaction does not occur. When the raw material fine particles are a metal oxide, oxygen, nitrogen, air, argon, helium, hydrogen, or the like can be used as the gas.
管体１４内は、加熱中の原料微粒子に対して化学的に不活性なガスの雰囲気になっているので、原料微粒子が加熱ゾーン１３に到達しても、化学反応は生じず、原料微粒子の結晶性のみが変化する。つまり、結晶性が高くなり、かつ結晶粒が大きくなる。加熱は、原料微粒子が加熱ゾーン１３内に通過する間だけ行われる。つまり加熱時間が極めて短い瞬間加熱が行われる。その上、原料微粒子は自由落下による流動状態で加熱ゾーン１３を通過する。これらに起因して、原料微粒子の加熱時に粒子どうしが融着することが効果的に防止される。このように、前記の温度範囲に加熱された加熱ゾーン１３を通過するように、原料微粒子を加熱ゾーン１３上から自由落下させ、落下した該原料微粒子を該加熱ゾーン１３において瞬間加熱することで、原料微粒子の形状及び粒径がほぼ維持されたままで、結晶性が向上した微粒子が得られる。なお、加熱ゾーン１３を通過するときの原料微粒子の温度を測定することは極めて困難なので、本製造方法においては、加熱ゾーン１３に備えられている加熱手段１２の温度をもって加熱温度に代えている。 Since the inside of the tube 14 is in an atmosphere of a gas that is chemically inert with respect to the raw material fine particles being heated, even if the raw material fine particles reach the heating zone 13, no chemical reaction occurs. Only the crystallinity changes. That is, crystallinity increases and crystal grains increase. Heating is performed only while the raw material fine particles pass into the heating zone 13. That is, instantaneous heating is performed with a very short heating time. In addition, the raw material fine particles pass through the heating zone 13 in a fluidized state by free fall. Due to these, it is possible to effectively prevent the particles from fusing when the raw material fine particles are heated. Thus, the raw material fine particles are freely dropped from the heating zone 13 so as to pass through the heating zone 13 heated to the above temperature range, and the dropped raw material fine particles are instantaneously heated in the heating zone 13, Fine particles with improved crystallinity can be obtained while maintaining the shape and particle size of the raw material fine particles. In addition, since it is very difficult to measure the temperature of the raw material fine particles when passing through the heating zone 13, in the present manufacturing method, the temperature of the heating means 12 provided in the heating zone 13 is replaced with the heating temperature.
管体１４が熱伝導性の低い材料から構成されていることは上述の通りであるところ、加熱ゾーン１３よりも下側に位置する管体１４は、その熱伝導性の低さに起因してほぼ室温状態になっている。したがって、加熱ゾーン１３を通過した高結晶性微粒子は直ちに室温まで冷却される。つまり急速冷却される。これによって加熱後に高結晶性微粒子どうしが融着することも効果的に防止される。 As described above, the tube body 14 is made of a material having low thermal conductivity. However, the tube body 14 located below the heating zone 13 is caused by its low thermal conductivity. It is almost at room temperature. Therefore, the highly crystalline fine particles that have passed through the heating zone 13 are immediately cooled to room temperature. That is, it is rapidly cooled. This effectively prevents fusion of the highly crystalline fine particles after heating.
以上の説明から明らかなように、本製造方法によれば、上述した特許文献１に記載の方法と異なり、微粒子の製造中に有害ガスが発生することがないので安全である。また、上述した特許文献１に記載の方法と異なり、真空等の特殊な環境が必要ないので、製造装置が複雑にならず、製造コストを抑えることができる。 As is apparent from the above description, according to the present manufacturing method, unlike the method described in Patent Document 1, the harmful gas is not generated during the production of the fine particles, which is safe. Further, unlike the method described in Patent Document 1 described above, a special environment such as a vacuum is not required, so that the manufacturing apparatus is not complicated and the manufacturing cost can be suppressed.
このようにして製造された高結晶性微粒子は、後述する実施例の結果から明らかなように、一次粒子の融着がほとんど生じておらず、粒成長がほとんど認められない。つまり、原料微粒子の粒径が概ね維持されている。また、本方法で製造された高結晶性微粒子は、その製造方法に起因して、一次粒子どうしの凝集の程度が極めて低い、単分散状態に近いものであるか、又は一次粒子どうしが凝集して二次粒子になっていたとしても、一次粒子どうしの凝集力は弱く、容易に解砕又は分散可能な程度にしか凝集していない。したがって、本製造方法で製造された高結晶性微粒子を原料として導電性インクを始めとする各種インク等の塗布液を調製する場合には、該微粒子の分散性が良好になる。 As can be seen from the results of Examples described later, the highly crystalline fine particles produced in this manner hardly cause primary particle fusion, and almost no grain growth is observed. That is, the particle size of the raw material fine particles is generally maintained. Further, the highly crystalline fine particles produced by this method have a very low degree of aggregation between primary particles due to the production method, are close to a monodispersed state, or primary particles are aggregated. Even if they are secondary particles, the cohesive force between the primary particles is weak, and they are only aggregated to such an extent that they can be easily crushed or dispersed. Therefore, when preparing coating liquids such as various inks including conductive ink using the highly crystalline fine particles produced by this production method as a raw material, the dispersibility of the fine particles is improved.
以上、本発明をその好ましい実施形態に基づき説明したが、本発明は前記実施形態に制限されない。例えば図１に示す装置１０においては管体１４に加熱ゾーン１３が１カ所のみ用いられていたが、これに代えて、管体１４の長手方向に沿って不連続に２又は３以上の加熱ゾーンを設けてもよい。 As mentioned above, although this invention was demonstrated based on the preferable embodiment, this invention is not restrict | limited to the said embodiment. For example, in the apparatus 10 shown in FIG. 1, only one heating zone 13 is used for the tube body 14. Instead of this, two or three or more heating zones are discontinuously along the longitudinal direction of the tube body 14. May be provided.
また、前記実施形態においては、管体１４内における原料微粒子の落下方向と、管体１４内に供給されるガスの流通方向が同一方向であったが、これに代えて原料微粒子の落下方向とガスの流通方向を反対にしてもよい。 Moreover, in the said embodiment, although the falling direction of the raw material microparticles | fine-particles in the tubular body 14 and the distribution direction of the gas supplied in the tubular body 14 were the same direction, instead of this, The gas flow direction may be reversed.
以下、実施例により本発明を更に詳細に説明する。しかしながら本発明の範囲は、かかる実施例に制限されない。 Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples.
〔実施例１〕
図１に示す装置１０を用いた。管体１４として全長８００ｍｍ、外径１３ｍｍ、内径９ｍｍのアルミナ管を用いた。このアルミナ管における上から３５０ｍｍの位置を上端として、加熱ヒータ１３を該アルミナ管に取り付けた。加熱ヒータ１３による加熱ゾーンの長さは１００ｍｍとした。加熱ヒータ１３は１２００℃に加熱した。アルミナ管内に上から下に向けて窒素をフローさせた。フローの速度は１００ｍｌ／ｍｉｎとした。この状態下に、電磁フィーダを用いて原料微粒子である金属ニッケル微粒子をアルミナ管内に連続投入した。投入速度は０．５ｇ／ｍｉｎとした。この金属ニッケル微粒子として、三井金属鉱業（株）製のＮＮ−１５０を用いた。金属ニッケル微粒子は、結晶子径が１９ｎｍで、一次粒子の平均粒径が約１５０ｎｍであった。結晶子径は、Ｘ線回折測定を行い、シェラー法によって算出した。金属ニッケル微粒子を、自然落下によって加熱ゾーンを通過させた。これによって金属ニッケル微粒子を瞬間加熱し、高結晶性ニッケル微粒子を得た。そして、アルミナ管の下端部で高結晶性ニッケル微粒子を回収した。回収した高結晶性ニッケル微粒子の一次粒子の平均粒径を測定したところ約１５０ｎｍであり、加熱前と実質的に変化はなかった。このことは、加熱前後の微粒子のＳＥＭ像である図２（ａ）と図２（ｂ）との対比からも明らかである。結晶子径は７２ｎｍであり、加熱前に比べて非常に大きくなった。また、図２（ｂ）に示すＳＥＭ像から明らかなように、回収した高結晶性ニッケル微粒子に融着は観察されなかった。更に、図３に示すＸ線回折測定結果から明らかなように、ニッケル微粒子は加熱によってその結晶性が向上したことが判る。
[Example 1]
The apparatus 10 shown in FIG. 1 was used. An alumina tube having a total length of 800 mm, an outer diameter of 13 mm, and an inner diameter of 9 mm was used as the tube body. The heater 13 was attached to the alumina tube with the upper position at 350 mm from the top of the alumina tube. The length of the heating zone by the heater 13 was 100 mm. The heater 13 was heated to 1200 ° C. Nitrogen was flowed into the alumina tube from top to bottom. The flow rate was 100 ml / min. Under this state, metallic nickel fine particles as raw material fine particles were continuously charged into an alumina tube using an electromagnetic feeder. The charging speed was 0.5 g / min. As the metal nickel fine particles, NN-150 manufactured by Mitsui Metal Mining Co., Ltd. was used. The metal nickel fine particles had a crystallite size of 19 nm and an average primary particle size of about 150 nm. The crystallite diameter was calculated by the Scherrer method after X-ray diffraction measurement. The metal nickel fine particles were passed through the heating zone by natural fall. As a result, the metallic nickel fine particles were instantaneously heated to obtain highly crystalline nickel fine particles. And the high crystalline nickel fine particles were collect | recovered at the lower end part of the alumina tube. The average particle diameter of primary particles of the recovered highly crystalline nickel fine particles was measured and found to be about 150 nm, which was substantially unchanged from that before heating. This is also clear from the comparison between FIG. 2A and FIG. 2B, which are SEM images of the fine particles before and after heating. The crystallite diameter was 72 nm, which was much larger than before heating. Further, as apparent from the SEM image shown in FIG. 2B, no fusion was observed in the recovered highly crystalline nickel fine particles. Furthermore, as is clear from the X-ray diffraction measurement results shown in FIG. 3, it can be seen that the crystallinity of the nickel fine particles was improved by heating.
〔比較例１〕
実施例１で用いた金属ニッケル微粒子（原料微粒子）をるつぼに入れて、電気炉内に設置した。電気炉内に窒素を流通させた状態下に電気炉内を加熱し、１２００℃で１分間保持した。その後室温まで冷却し、電気炉から取り出した。取り出された金属ニッケル微粒子をＳＥＭ観察したところ、粒子どうしの融着が甚だしく、粒子の原形をとどめていなかった。
[Comparative Example 1]
The metal nickel fine particles (raw material fine particles) used in Example 1 were placed in a crucible and placed in an electric furnace. The inside of the electric furnace was heated under a state where nitrogen was circulated in the electric furnace, and held at 1200 ° C. for 1 minute. Thereafter, it was cooled to room temperature and taken out from the electric furnace. When the extracted metallic nickel fine particles were observed with an SEM, the particles were extremely fused and the original shape of the particles was not maintained.
〔実施例２〕
原料微粒子として、三井金属鉱業（株）製のアモルファス状酸化タンタル（Ｔａ2Ｏ5）を用いた。この酸化タンタルは、一次粒子の平均粒径が約２００ｎｍであった。また、アルミナ管内にフローさせるガスとして酸素を用いた。更に、加熱ヒータ１３を１０００℃に加熱した。これら以外は実施例１と同様にして、高結晶性酸化タンタル微粒子を得た。得られた高結晶性酸化タンタル微粒子の一次粒子の平均粒径を測定したところ約２００ｎｍであり、加熱前と実質的に変化はなかった。このことは、加熱前後の微粒子のＳＥＭ像である図４（ａ）と図４（ｂ）との対比からも明らかである。結晶子径は２６ｎｍであり、また、図４（ｂ）に示すＳＥＭ像から明らかなように、回収した高結晶性酸化タンタル微粒子に融着は観察されなかった。更に、図５に示すＸ線回折測定結果から明らかなように、アモルファスピークが消失し、酸化タンタル由来の鋭いピークが観察された。
[Example 2]
As the raw material fine particles, amorphous tantalum oxide (Ta 2 O 5 ) manufactured by Mitsui Metal Mining Co., Ltd. was used. This tantalum oxide had an average primary particle size of about 200 nm. In addition, oxygen was used as a gas to flow into the alumina tube. Furthermore, the heater 13 was heated to 1000 ° C. Except for these, high crystalline tantalum oxide fine particles were obtained in the same manner as in Example 1. The average particle diameter of primary particles of the obtained highly crystalline tantalum oxide fine particles was measured and found to be about 200 nm, which was substantially unchanged from that before heating. This is clear from the comparison between FIG. 4A and FIG. 4B, which are SEM images of the fine particles before and after heating. The crystallite diameter was 26 nm, and as is apparent from the SEM image shown in FIG. 4B, no fusion was observed in the recovered highly crystalline tantalum oxide fine particles. Further, as apparent from the X-ray diffraction measurement result shown in FIG. 5, the amorphous peak disappeared and a sharp peak derived from tantalum oxide was observed.
１０ 製造装置
１１ 縦型加熱炉
１２ 加熱手段
１３ 加熱ゾーン
１４ 管体
１５ ホッパー
DESCRIPTION OF SYMBOLS 10 Manufacturing apparatus 11 Vertical heating furnace 12 Heating means 13 Heating zone 14 Tubing body 15 Hopper
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