JP4776910B2 - Nanostructure - Google Patents
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- JP4776910B2 JP4776910B2 JP2004328545A JP2004328545A JP4776910B2 JP 4776910 B2 JP4776910 B2 JP 4776910B2 JP 2004328545 A JP2004328545 A JP 2004328545A JP 2004328545 A JP2004328545 A JP 2004328545A JP 4776910 B2 JP4776910 B2 JP 4776910B2
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本発明は、一次粒子の粒子サイズが小さく、一次粒子同士の接触面積が小さいナノ構造体に関するものである。 The present invention relates to a nanostructure having a small primary particle size and a small contact area between primary particles.
粉体をナノオーダーまで微粒子化すると、表面を占める分子割合が極めて大きくなる為、バルク材料とは全く異なる物性を示す。この性質を各種分野（触媒、電池材料、磁性体、電子回路素子及び生体材料等）で利用する試みが行われている。しかしながら、ナノ粒子は非常に微細であるため、強い凝集性を有し単分散せず、特性を十分発揮できないという問題がある。 When the powder is atomized to nano-order, the proportion of the molecule occupying the surface becomes extremely large, and therefore exhibits completely different physical properties from the bulk material. Attempts have been made to use this property in various fields (catalysts, battery materials, magnetic materials, electronic circuit elements, biomaterials, etc.). However, since the nanoparticles are very fine, there is a problem that they have strong cohesiveness, do not monodisperse, and cannot fully exhibit their characteristics.
これまで、ナノ粒子を分散する技術に関しては多数報告されているが、ナノ粒子を、アルミナなどの無機担体又は樹脂などの高分子担体等の第三固相の表面或いは内部に分散固定化する技術が大多数である。 There have been many reports on the technology for dispersing nanoparticles, but a technology for dispersing and immobilizing nanoparticles on the surface or inside of a third solid phase such as an inorganic carrier such as alumina or a polymer carrier such as resin. Is the majority.
例えば、特開２００３−１１２９２５号公報によれば、マグネタイトのナノ粒子に対して、分子量が１０００以下である表面修飾分子を結合させ、有機溶媒への分散性を向上させ、その分散溶液を支持体表面に塗布・乾燥することにより、分散固定化させている。 For example, according to Japanese Patent Application Laid-Open No. 2003-112925, surface-modified molecules having a molecular weight of 1000 or less are bonded to magnetite nanoparticles to improve dispersibility in an organic solvent, and the dispersion solution is used as a support. It is dispersed and fixed by applying and drying on the surface.
また、特開２００３−２９７６１７号公報によれば、逆ミセル法により、合成したナノ粒子の分散溶液を基板上に素早く滴下・乾燥させ、ナノメートル・スケールで自己組織化的に配列させて構造体を形成している。 Further, according to Japanese Patent Laid-Open No. 2003-297617, a structure in which a dispersion solution of synthesized nanoparticles is quickly dropped and dried on a substrate by a reverse micelle method and arranged in a self-organizing manner on a nanometer scale. Is forming.
一方、特開平１０−２０８２３６号公報によれば、コバルトフェライトのナノ粒子をイオン交換樹脂内部に分散固定化させている。また、特開２００１―３１６５０１によれば、架橋構造を有する高分子中にナノ粒子を分散固定化させている。 On the other hand, according to Japanese Patent Laid-Open No. 10-208236, cobalt ferrite nanoparticles are dispersed and fixed inside an ion exchange resin. Further, according to Japanese Patent Laid-Open No. 2001-316501, nanoparticles are dispersed and fixed in a polymer having a crosslinked structure.
上述したとおり、ナノ粒子を分散するには、第三固相への固定化或いは介在が必要となる。しかし、ナノ粒子が単分散しているとは言い難く、またナノ粒子表面の大部分或いは一部を第三固相が覆っている為、ナノ粒子の性能を最大限に引き出しているとは言い難い。さらに、分散には常に第三固相を必要とするため、用途が限定され、しかも工程も煩雑である。 As described above, in order to disperse the nanoparticles, it is necessary to immobilize or intervene in the third solid phase. However, it is difficult to say that the nanoparticles are monodispersed, and because the third solid phase covers most or part of the surface of the nanoparticles, it is said that the performance of the nanoparticles is maximized. hard. Furthermore, since a third solid phase is always required for dispersion, the application is limited and the process is complicated.
これまで細孔容積やＢＥＴ比表面積を制御することによって高機能性の粒子を製造することが知られている（特許文献１〜４）。 It has been known so far to produce highly functional particles by controlling the pore volume and the BET specific surface area (Patent Documents 1 to 4).
一方、無機化合物粒子粉末の製造方法の一つとして噴霧熱分解法が用いられている。 On the other hand, a spray pyrolysis method is used as one method for producing inorganic compound particle powder.
噴霧熱分解法とは、原料溶液をノズルや超音波によって噴霧して微小液滴とし、該微小液滴の溶媒を蒸発させて熱分解により目的の粒子粉末を得る方法である。 The spray pyrolysis method is a method in which a raw material solution is sprayed by a nozzle or ultrasonic waves to form fine droplets, and the solvent of the fine droplets is evaporated to obtain a target particle powder by thermal decomposition.
従来、噴霧熱分解法によって微細な酸化物又は金属粒子粉末を製造することが知られている（特許文献５及び６）。 Conventionally, it is known to produce fine oxide or metal particle powder by spray pyrolysis (Patent Documents 5 and 6).
ナノ粒子であって、粒子間の接触が少なく、しかも、取り扱いが容易なナノ構造体は現在、最も要求されているところであるが、未だ得られていない。 Nanostructures that are nanoparticles and have little contact between the particles and that are easy to handle are currently in great demand but have not yet been obtained.
即ち、前出特許文献１には、ＢＥＴ比表面積値が大きなアルミナ、チタニア及びジルコニアが記載されているが、一次粒子が十分に小さいとは言い難いものである。 That is, in the aforementioned Patent Document 1, alumina, titania and zirconia having a large BET specific surface area value are described, but it is difficult to say that the primary particles are sufficiently small.
また、前出特許文献２には凝集粒子の平均粒径が０．１〜１０μｍであって、一次粒子の平均粒子径が１０〜１０００ｎｍの酸化チタン粒子粉末が記載されているが、一次粒子が十分に小さいとは言い難いものである。 Further, in the above-mentioned Patent Document 2, a titanium oxide particle powder in which the average particle diameter of the aggregated particles is 0.1 to 10 μm and the average particle diameter of the primary particles is 10 to 1000 nm is described. It is hard to say that it is small enough.
また、前出特許文献３には、皮殻の厚みが２０ｎｍ以下の中空状酸化物粒子粉末が記載されているが、表面状態を変化させることによって高い比表面積を有する粒子とするものであり、一次粒子サイズを制御することについては考慮されていない。 Moreover, in the above-mentioned patent document 3, although the hollow oxide particle powder whose skin thickness is 20 nm or less is described, it is a particle having a high specific surface area by changing the surface state, No consideration is given to controlling the primary particle size.
また、前出特許文献４には無機中空粉体が記載されているが、緻密な被膜を有する中空粒子を得るものであり、一次粒子サイズを制御することについては考慮されていない。 Moreover, although the above-mentioned patent document 4 describes inorganic hollow powder, it is intended to obtain hollow particles having a dense coating and does not consider controlling the primary particle size.
また、前出特許文献５には、中空状の酸化亜鉛粒子が記載されているが、一次粒子サイズが大きく、一次粒子間の接触面積が大きいものである。 Moreover, although the above-mentioned patent document 5 describes hollow zinc oxide particles, the primary particle size is large and the contact area between the primary particles is large.
また、前出特許文献６には、噴霧熱分解法において、原料成分以外の無機化合物を原料溶液に溶解させ、微粒子を得る技術が記載されている。該特許文献６には、無機化合物に低融点物質を用いており、加熱温度を使用する無機化合物の融点以上に設定することによって、原料成分の熱分解により生成する結晶核に無機化合物を液体状態で接触させ、液滴内に生成する複数の結晶核の間隙に該無機化合物が存在して微細な一次粒子が形成するものであり、一次粒子が点接触で存在できるようなナノ構造体については考慮されていない。 Patent Document 6 mentioned above describes a technique for obtaining fine particles by dissolving an inorganic compound other than raw material components in a raw material solution in the spray pyrolysis method. In Patent Document 6, a low-melting-point substance is used for the inorganic compound, and the inorganic compound is in a liquid state in the crystal nucleus generated by thermal decomposition of the raw material components by setting the heating temperature to be equal to or higher than the melting point of the inorganic compound using For nanostructures in which fine inorganic particles are formed by the presence of the inorganic compound in the gaps between a plurality of crystal nuclei generated in a droplet, and the primary particles can exist in point contact. Not considered.
そこで、本発明は、ナノ粒子であって、可及的に粒子間の接触面積が小さく、しかも、取り扱いが容易なナノ構造体を得ることを目的とするものである。 Therefore, an object of the present invention is to obtain a nanostructure which is a nanoparticle and has a contact area between the particles as small as possible and can be easily handled.
本発明者は、上記課題に対して検討を重ねた結果、微細な一次粒子同士を点焼結させ、球体又は薄膜に形成させることで、ナノ粒子の特性を失活させることなく容易に取り扱うことができるナノ構造体を見出し、本発明に至った。
本発明は第三固相を必要とせず、対象となるナノ粒子単独で、その分散化を実現するものであり、革新的技術である。
As a result of repeated investigations on the above problems, the present inventor can easily handle fine primary particles without causing inactivation of the properties of the nanoparticles by spot-sintering them to form spheres or thin films. The present inventors have found a nanostructure that can be used to achieve the present invention.
The present invention does not require a third solid phase, and realizes the dispersion of the target nanoparticles alone, which is an innovative technology.
即ち、本発明は、平均粒子径が１８ｎｍ以下の一次粒子で構成される酸化物からなるナノ構造体であって、該ナノ構造体のＸ線回折から算出した結晶子サイズに対する電子顕微鏡観察から算出した一次粒子径の比（電子顕微鏡観察から算出した一次粒子径／Ｘ線回折から算出した結晶子サイズ）が０．８〜１．２５であって、ＢＥＴ比表面積が６０〜２４０ｍ ２ ／ｇであり、且つ、当該ナノ構造体を１０００℃で２４時間加熱した後のＢＥＴ比表面積が８〜１０５ｍ ２ ／ｇであることを特徴とするナノ構造体である（本発明１）。
That is, the present invention is a nanostructure made of an oxide composed of primary particles having an average particle size of 18 nm or less, and is calculated from observation of an electron microscope with respect to a crystallite size calculated from X-ray diffraction of the nanostructure. What the primary ratio of the particle diameter (crystallite size calculated from the calculated primary particle size / X-ray diffraction from electron microscopy) is 0.8 to 1.25 der, BET specific surface area of 60~240m 2 / g and a, and a nanostructure BET specific surface area after the nanostructure was heated at 1000 ° C. 24 hours and wherein 8~105m 2 / g der Rukoto (present invention 1).
また、本発明は、本発明１において、ナノ構造体の形状は薄膜、球体又はその断片、或いはそれら混合物であることを特徴とするナノ構造体である（本発明２）。 Further, the present invention is the nanostructure according to the present invention 1, wherein the shape of the nanostructure is a thin film, a sphere or a fragment thereof, or a mixture thereof (Invention 2).
また、本発明は、本発明１又は２において、球状ナノ構造体の平均粒径が５０ｎｍ〜２０μｍであることを特徴とするナノ構造体である（本発明３）。 In addition, the present invention is the nanostructure according to the present invention 1 or 2, wherein the spherical nanostructure has an average particle size of 50 nm to 20 μm (present invention 3).
本発明に係るナノ構造体は、単なる凝集体と比べ、表面に位置する分子数の割合が多く表面エネルギーが高いため、一次粒子を構成する化合物の機能が極めて大きく発揮できることが期待できる。また、ナノ構造体を形成しているのでハンドリング性が向上する。 Since the nanostructure according to the present invention has a higher ratio of the number of molecules located on the surface and higher surface energy than a simple aggregate, it can be expected that the function of the compound constituting the primary particles can be exhibited extremely greatly. Moreover, since the nanostructure is formed, handling property is improved.
本発明に係るナノ構造体を構成する一次粒子は３０ｎｍ以下であるので、バルク材料とは全く異なる物性を示すことが期待される。 Since the primary particles constituting the nanostructure according to the present invention are 30 nm or less, it is expected to exhibit completely different physical properties from the bulk material.
また、従来のナノ粒子分散技術では、その殆どが第三固相を必要するため、用途が限定され、しかも工程が非常に煩雑となり、製造コストも割高となる。それに対し、本発明に係るナノ構造体は、第三固相を必要とせず合成したナノ粒子同士を点接触の状態で焼結させることで、その分散化を実現させる。
また、ナノ構造体の粒子形状は薄膜又は球体と作り分けることができるため、所望の形状に任意に製造することができ、従来のような用途制限は受けない。
更に、必要に応じて、第三固相に固定化してもよいが、特に分散処理も必要なく、安易に固定化できる。さらに、工程もシンプルであり、大幅な生産性向上が見込める。
Moreover, since most of the conventional nanoparticle dispersion techniques require a third solid phase, the application is limited, the process becomes very complicated, and the production cost is high. On the other hand, the nanostructure according to the present invention realizes its dispersion by sintering the synthesized nanoparticles in a point contact state without requiring a third solid phase.
In addition, since the particle shape of the nanostructure can be made separately from a thin film or a sphere, it can be arbitrarily manufactured into a desired shape, and is not subject to conventional application restrictions.
Further, if necessary, it may be immobilized on the third solid phase, but it is not particularly necessary to perform a dispersion treatment and can be easily immobilized. In addition, the process is simple and significant productivity improvements can be expected.
また、本発明に係るナノ構造体は、噴霧熱分解法で製造できるので、簡便な製造法であり、工業的生産性に優れるものである。 Moreover, since the nanostructure according to the present invention can be produced by a spray pyrolysis method, it is a simple production method and excellent in industrial productivity.
本発明の構成を詳述すれば次の通りである。 The configuration of the present invention will be described in detail as follows.
本発明に係るナノ構造体を構成する一次粒子の平均粒子径は３０ｎｍ以下である。３０ｎｍを超える場合には、一次粒子が粗大になるため微粒子としての機能が低下する。好ましくは１８ｎｍ以下、より好ましくは１５ｎｍ以下である。またその下限値は０．５ｎｍ程度である。 The average particle diameter of the primary particles constituting the nanostructure according to the present invention is 30 nm or less. If it exceeds 30 nm, the primary particles become coarse, and the function as fine particles is reduced. Preferably it is 18 nm or less, More preferably, it is 15 nm or less. Moreover, the lower limit is about 0.5 nm.
本発明に係るナノ構造体の粒子形状は、中空状もしくは中実状の球体又は薄膜状のいずれか又はそれら混合物である。球体である場合、その一部が欠損した断片であってもよい。なお、中空状とは球体の表層部分にのみ一次粒子が存在する状態であって中実状とは球体の内部にも一次粒子が存在する状態であり、いずれにおいても、粒子間の接触面積は小さく制御できる。 The particle shape of the nanostructure according to the present invention is either a hollow or solid sphere, a thin film, or a mixture thereof. If it is a sphere, it may be a fragment that is partially missing. The hollow shape is a state in which primary particles exist only in the surface layer portion of the sphere, and the solid state is a state in which primary particles exist in the sphere. In any case, the contact area between the particles is small. Can be controlled.
本発明に係るナノ構造体の形状が球体である場合、その平均粒径はハンドリング性を考慮し、０．０５〜２０μｍが好ましい。より好ましくは０．１〜１０μｍである。 When the shape of the nanostructure according to the present invention is a sphere, the average particle size is preferably 0.05 to 20 μm in consideration of handling properties. More preferably, it is 0.1-10 micrometers.
本発明に係るナノ構造体の形状が薄膜である場合、一層又は数層の膜から形成され、その厚みは０．５〜１００ｎｍが好ましい。 When the shape of the nanostructure according to the present invention is a thin film, it is formed of one or several layers, and the thickness is preferably 0.5 to 100 nm.
本発明に係るナノ構造体は、電子顕微鏡観察から算出した一次粒子径とＸ線回折から算出した結晶子サイズとがほぼ同程度であり、Ｘ線回折から算出した結晶子サイズに対する電子顕微鏡観察から算出した一次粒子径の比（電子顕微鏡観察から算出した一次粒子径／Ｘ線回折から算出した結晶子サイズ）が０．８〜１．２５が好ましい。０．８未満の場合には一次粒子が単結晶とは言い難い。より好ましくは０．９〜１．２５である。 In the nanostructure according to the present invention, the primary particle diameter calculated from the electron microscope observation and the crystallite size calculated from the X-ray diffraction are approximately the same, and from the electron microscope observation with respect to the crystallite size calculated from the X-ray diffraction. The ratio of the calculated primary particle diameter (primary particle diameter calculated from electron microscope observation / crystallite size calculated from X-ray diffraction) is preferably 0.8 to 1.25. If it is less than 0.8, it is difficult to say that the primary particles are single crystals. More preferably, it is 0.9-1.25.
本発明に係るナノ構造体のＢＥＴ比表面積値は５０〜６０００ｍ２／ｇが好ましい。 The BET specific surface area value of the nanostructure according to the present invention is preferably 50 to 6000 m 2 / g.
本発明に係るナノ構造体は酸化物、金属又はこれら混合物で構成される。本発明に係るナノ構造体の構成元素は、例えば、Ｔｉ、Ｆｅ、Ｃｅ、Ｚｒ、Ｎｉ、Ｚｎ、Ｃｄ、Ｓｉ、Ｍｇ、Ａｌ、Ｃａ、Ｐｄ、Ａｇ、Ｂａ、Ｃｕ、Ｌｉ、Ｃｏ、Ｌａ、Ｙ、Ｓｒ、Ｍｎ、Ｒｈ、Ｐｔ、Ｎｄ、Ｓｍ、Ｐｂ、Ｃｒ、Ｇａ、Ｓｃが挙げられ、勿論、前記元素の２種以上からなる複合酸化物或いは合金であってもよい。 The nanostructure according to the present invention is composed of an oxide, a metal, or a mixture thereof. The constituent elements of the nanostructure according to the present invention include, for example, Ti, Fe, Ce, Zr, Ni, Zn, Cd, Si, Mg, Al, Ca, Pd, Ag, Ba, Cu, Li, Co, La, Examples include Y, Sr, Mn, Rh, Pt, Nd, Sm, Pb, Cr, Ga, and Sc. Of course, a composite oxide or alloy composed of two or more of the above elements may be used.
次に、本発明に係るナノ構造体の製造法について述べる。 Next, a method for producing a nanostructure according to the present invention will be described.
上記したナノ構造体は、噴霧熱分解法により製造することができる。 The nanostructure described above can be produced by a spray pyrolysis method.
噴霧熱分解法とは、原料塩溶液を噴霧することによって、発生した液滴を高温場（例えば電気炉）に投入し、乾燥・熱分解を起こさせ、目的の微粒子を直接かつ連続的に得る方法である。 The spray pyrolysis method involves spraying a raw salt solution, putting the generated droplets into a high-temperature field (for example, an electric furnace), causing drying and pyrolysis, and directly obtaining the desired fine particles directly. Is the method.
本発明に係るナノ構造体は、ナノ構造体を構成する元素の水溶性塩と、ナノ構造体を構成する元素以外の元素の無機塩（以下、「第三無機塩」という）とを含有する原料水溶液を噴霧することによって、発生した液滴を反応ガスに同伴させて高温場（例えば電気炉）に投入し、乾燥・熱分解を起こさせた後、生成した粒子を回収し、前記第三無機塩のみを水洗・除去することで得られる。 The nanostructure according to the present invention contains a water-soluble salt of an element constituting the nanostructure and an inorganic salt of an element other than the element constituting the nanostructure (hereinafter referred to as “third inorganic salt”). By spraying the raw material aqueous solution, the generated droplets are entrained in the reaction gas, put into a high temperature field (for example, an electric furnace), dried and thermally decomposed, and the generated particles are recovered, and the third It can be obtained by washing and removing only inorganic salts.
本発明に係るナノ構造体を得るためには、原料溶液中にナノ構造体を構成する元素の塩濃度に対し、第三無機塩をモル比で０．５〜６．０倍添加する。第三無機塩の添加量が６．０倍よりも多い場合には、生成した一次粒子の粒界に点在する第三無機塩の結晶粒が大きくなりすぎ、一次粒子同士が点接触することができず、単独で挙動するナノ粒子が生成する。一方、第三無機塩の添加量が０．５倍より少ない場合には、焼結防止効果が薄れ、一次粒子同士が焼結することにより、粗大な一次粒子となる。より好ましくは１．０〜４．０倍である。 In order to obtain the nanostructure according to the present invention, the third inorganic salt is added in a molar ratio of 0.5 to 6.0 times the salt concentration of the elements constituting the nanostructure in the raw material solution. When the added amount of the third inorganic salt is more than 6.0 times, the crystal grains of the third inorganic salt scattered at the grain boundaries of the generated primary particles become too large, and the primary particles are in point contact with each other. Cannot be produced, and nanoparticles that behave independently are generated. On the other hand, when the addition amount of the third inorganic salt is less than 0.5 times, the sintering preventing effect is weakened, and primary particles are sintered to become coarse primary particles. More preferably, it is 1.0 to 4.0 times.
本発明における第三無機塩は、高融点物質であれば、特に限定されるものではない。後工程の水洗を考慮し、また排水処理が比較的安易な硫酸塩、塩化物塩等を用いればよい。例えば、硫酸マグネシウム、硫酸ナトリウム、硫酸カリウム、塩化ナトリウム、塩化カリウム等が挙げられる。 The third inorganic salt in the present invention is not particularly limited as long as it is a high melting point substance. In consideration of subsequent washing with water, sulfates, chloride salts, etc., which are relatively easy to treat waste water, may be used. For example, magnesium sulfate, sodium sulfate, potassium sulfate, sodium chloride, potassium chloride and the like can be mentioned.
本発明においては、ナノ構造体を構成する元素の水溶性塩は、水に対する溶解度の高い硫酸塩、塩化物塩、硝酸塩等を用いればよい。例えば、Ｔｉ、Ｆｅ、Ｃｅ、Ｚｒ、Ｎｉ、Ｚｎ、Ｃｄ、Ｓｉ、Ｍｇ、Ａｌ、Ｃａ、Ｐｄ、Ａｇ、Ｂａ、Ｃｕ、Ｌｉ、Ｃｏ、Ｌａ、Ｙ、Ｓｒ、Ｍｎ、Ｒｈ、Ｐｔ、Ｎｄ、Ｓｍ、Ｐｂ、Ｃｒ、Ｇａ、Ｓｃの硫酸塩、塩化物塩、硝酸塩等が挙げられる。 In the present invention, the water-soluble salt of the element constituting the nanostructure may be a sulfate, chloride salt, nitrate or the like having a high solubility in water. For example, Ti, Fe, Ce, Zr, Ni, Zn, Cd, Si, Mg, Al, Ca, Pd, Ag, Ba, Cu, Li, Co, La, Y, Sr, Mn, Rh, Pt, Nd, Sm, Pb, Cr, Ga, and Sc sulfates, chlorides, nitrates, and the like.
本発明におけるナノ構造体を構成する元素の原料溶液中における塩濃度は０．０１〜５ｍｏｌ／Ｌが望ましい。 As for the salt concentration in the raw material solution of the element which comprises the nanostructure in this invention, 0.01-5 mol / L is desirable.
また、反応ガスは、特に限定されるものではなく、目的とする物質に応じて、酸化性ガス、還元性ガスを用いればよく、例えば、空気、水素等を用いれば、それぞれ酸化物、金属が得られる。 In addition, the reaction gas is not particularly limited, and an oxidizing gas or a reducing gas may be used according to the target substance. For example, if air, hydrogen, or the like is used, an oxide or a metal may be used. can get.
高温場に投入するときの液滴の平均径は１〜１００μｍが望ましい。 The average diameter of the droplets when placed in a high temperature field is preferably 1 to 100 μm.
なお、加熱温度は使用する第三無機塩の融点以下とする。好ましくは７００〜１２００℃の温度範囲である。 In addition, heating temperature shall be below melting | fusing point of the 3rd inorganic salt to be used. Preferably it is the temperature range of 700-1200 degreeC.
本発明に係るナノ構造体を構成する一次粒子径は、第三無機塩の種類及び添加比率、加熱温度を制御することで変化させることができる。 The primary particle diameter constituting the nanostructure according to the present invention can be changed by controlling the type and addition ratio of the third inorganic salt and the heating temperature.
本発明に係るナノ構造体の形状は、加熱温度、炉内滞留時間、溶質濃度及び液滴径を制御することで、作り分けることができる。 The shape of the nanostructure according to the present invention can be made differently by controlling the heating temperature, the residence time in the furnace, the solute concentration, and the droplet diameter.
＜作用＞
従来の噴霧熱分解法では原理上、生成粒子径は出発液滴径及び溶質濃度によって、一義的に決定される。従って、噴霧熱分解法にてナノ粒子を製造しようとした場合、出発液滴の微小化、或いは溶質濃度の希薄化が必要となる。
液滴の微小化技術としては、超音波噴霧方式等が挙げられるが、数μｍが限界であり、故に非現実的な溶質の希薄化が要求される。しかも、前記の液滴微小化技術ではいずれも極少量しか噴霧できず工業的であるとは言い難い。
<Action>
In principle, in the conventional spray pyrolysis method, the generated particle size is uniquely determined by the starting droplet size and the solute concentration. Therefore, when trying to produce nanoparticles by spray pyrolysis, it is necessary to make the starting droplets smaller or dilute the solute concentration.
As a technique for miniaturizing droplets, an ultrasonic spray method or the like can be mentioned, but a few μm is the limit, and therefore, unrealistic solute dilution is required. Moreover, it is difficult to say that any of the above-described droplet miniaturization techniques is industrial because only a very small amount can be sprayed.
一方、従来の噴霧熱分解法の粒子生成メカニズムを詳述すると、まず、溶媒蒸発により溶質核が発生するが、一般的に溶媒の蒸発速度が非常に大きい為、最終的な溶質核は非常に微細となり、熱分解時はこの溶質核（結晶粒）が踏襲される。さらに受熱・焼結が進み、最終的には一つ或いは数個の結晶粒で構成された球状粒子となる。 On the other hand, the particle generation mechanism of the conventional spray pyrolysis method will be described in detail. First, solute nuclei are generated by evaporation of the solvent, but the final solute nuclei are very high because the evaporation rate of the solvent is generally very high. The solute nuclei (crystal grains) are followed during pyrolysis. Further, the heat receiving and sintering proceeds, and finally, spherical particles composed of one or several crystal grains are formed.
本発明では、熱分解直後の微小な結晶粒を粒成長させず、且つ、互いを点焼結させることで、前記課題を達成するというものである。また本発明では、構成する結晶粒（一次粒子）の粒子径は溶質濃度に全く依存しないため、原料溶液の高濃度化が可能となり、著しい生産性向上が期待できる。 In this invention, the said subject is achieved by not carrying out the grain growth of the minute crystal grain immediately after thermal decomposition, and carrying out point sintering of each other. In the present invention, since the particle diameter of the constituting crystal grains (primary particles) does not depend on the solute concentration at all, it is possible to increase the concentration of the raw material solution, and a significant improvement in productivity can be expected.
具体的には、原料溶液に構成元素の熱分解反応に全く関与しない第三無機塩を添加・混合しておくことで、熱分解時、第三無機塩を前記結晶粒界に点在させ、焼結防止効果を持たせるというものである。なお、第三無機塩には水溶性のものを選定し、後段の水洗工程にて、第三無機塩のみ除去する。 Specifically, by adding and mixing a third inorganic salt that does not participate in the thermal decomposition reaction of the constituent elements at all in the raw material solution, the third inorganic salt is scattered at the crystal grain boundaries during the thermal decomposition, This is to give a sintering prevention effect. A water-soluble one is selected as the third inorganic salt, and only the third inorganic salt is removed in the subsequent water washing step.
合成したナノ粒子同士が点焼結し、形成する状態は球体又は薄膜が挙げられるが、合成メカニズムについて本発明者は以下の通り推定している。 The synthesized nanoparticles are point-sintered and formed into a sphere or a thin film. The inventor presumes the synthesis mechanism as follows.
溶媒蒸発は液滴の表面で起こる為、生じる液滴中心方向の濃度勾配により、溶媒及び溶質の移動が起こる。この溶媒及び溶質の移動が溶媒の蒸発速度とほぼ釣合っている場合は、出発液滴の形状、すなわち球状を保ちつつ、十分収縮して、最終的に球体となる。
一方、溶媒の蒸発速度が著しく大きい場合、溶媒及び溶質の移動が追いつかず、液滴表面に乾燥殻が生じる。内部には溶媒が閉じ込められた状態となる。さらに受熱することで、内圧が上昇し、やがて爆裂・破胞し、薄膜となる。これら両者現象を利用することで、薄膜或いは球体を作り分けることが可能となる。
Since solvent evaporation occurs on the surface of the droplet, the concentration gradient in the direction of the center of the droplet causes solvent and solute movement. When the movement of the solvent and the solute is substantially balanced with the evaporation rate of the solvent, the shape of the starting droplet, that is, the spherical shape is maintained, while sufficiently shrinking to finally become a sphere.
On the other hand, when the evaporation rate of the solvent is remarkably large, the movement of the solvent and solute cannot catch up, and a dry shell is formed on the surface of the droplet. The solvent is confined inside. Furthermore, by receiving heat, the internal pressure rises and eventually explodes and ruptures, forming a thin film. By using both of these phenomena, it is possible to make a thin film or a sphere.
なお、本発明では、第三無機塩に高融点物質を使用し、且つ、処理温度を該第三無機塩の融点以下にしてナノ構造体を製造するものであり、前述した特許文献６の反応機構のように、一旦融液状態を介するものではないものと推定している。 In the present invention, a high-melting-point substance is used for the third inorganic salt, and the nanostructure is produced at a treatment temperature equal to or lower than the melting point of the third inorganic salt. It is presumed that, unlike the mechanism, it does not go through the melt state once.
また、本発明に係るナノ構造体は、耐熱性に優れるものである。ナノ構造体を形成していないナノ粒子の場合、強凝集して一次粒子同士の接触面積が増大するのに対し、本発明に係るナノ構造体では、構成する一次粒子同士の接触面は点接触に近い状態であって接触面積が可及的に小さいことにより、接触面での相互拡散による焼結が抑制されているためと本発明者は推定している。 The nanostructure according to the present invention is excellent in heat resistance. In the case of nanoparticles that do not form nanostructures, the contact area between primary particles increases due to strong aggregation, whereas in the nanostructures according to the present invention, the contact surfaces of the primary particles that constitute are point contacts. The present inventor presumes that since the contact area is as small as possible, sintering due to mutual diffusion at the contact surface is suppressed.
なお、本発明に係るナノ構造体は、その形状を種々変化させることができ、その結果、ナノ構造体或いは一次粒子同士の接触状態・耐熱性を制御することができる。
即ち、薄膜状のナノ構造体では、薄膜と薄膜との間で接触面が発生するため、接触面を起点に焼結が進行するものと考えられる。一方、球体のナノ構造体では、球体間では基本的には接触面が小さく、また、数点しか発生しないため、焼結がより抑制できたと考えられる。更に、球体のナノ構造体においては、中実状のナノ構造体では三次元的なネットワークを形成するため、２次元的なネットワークを有する中空状の球体ナノ構造体に比べ、構成する一次粒子一個当りの接点数が増加したことにより、焼結しやすくなるものと推定される。
従って、要求される耐熱性の程度に応じて、ナノ構造体の形状を変化させればよく、耐熱性を求める用途では、ナノ構造体の形状は球体で且つ中空状が適していると考えられる。
In addition, the nanostructure which concerns on this invention can change the shape variously, As a result, the contact state and heat resistance of a nanostructure or primary particles can be controlled.
That is, in the thin-film nanostructure, a contact surface is generated between the thin films, and therefore, it is considered that sintering proceeds from the contact surface. On the other hand, in the spherical nanostructure, the contact surface is basically small between the spheres, and since only a few points are generated, it is considered that the sintering can be further suppressed. Furthermore, in the case of spherical nanostructures, solid nanostructures form a three-dimensional network, so that each primary particle that constitutes the structure is compared to a hollow spherical nanostructure having a two-dimensional network. It is presumed that the increase in the number of contacts makes it easier to sinter.
Therefore, it is sufficient to change the shape of the nanostructure according to the required degree of heat resistance. For applications requiring heat resistance, the shape of the nanostructure is considered to be spherical and hollow. .
一方、中実状の球体ナノ構造体は前記の通り、一次粒子同士が３次元的なネットワークを形成しているので、構造体内部に均斉な細孔が生じるため、吸着材用途にも展開できる可能性がある。 On the other hand, as described above, solid spherical nanostructures form a three-dimensional network between primary particles, and uniform pores are generated inside the structure, which can be used for adsorbent applications. There is sex.
さらに、薄膜状のナノ構造体に関しては、積層・充填させ、熱処理を施せば、構造欠陥のない焼結体と成り得る可能性がある。 Furthermore, regarding a thin-film nanostructure, if it is laminated, filled, and subjected to heat treatment, there is a possibility that it can be a sintered body free from structural defects.
上述したとおり、本発明に係るナノ構造体は、触媒、電極材、充填材、磁性体、電子回路素子及び生体材料等の各種用途への展開は勿論であるが、ナノ構造体の形状を選択すれば、更なる用途展開が期待できる。 As described above, the nanostructure according to the present invention can be used for various applications such as a catalyst, an electrode material, a filler, a magnetic body, an electronic circuit element, and a biomaterial, but the shape of the nanostructure is selected. Then, further application development can be expected.
以下、実施例及び比較例により本発明を具体的に説明する。 Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.
ナノ構造体の一次粒子の平均粒子径は、電子顕微鏡（ＴＥＭ）の観察写真から約２００個の粒径を測定し、その平均値から求めた。ナノ構造体の平均粒径は、電子顕微鏡（ＴＥＭ）の観察写真から同じく約５０個測定し、その平均値から求めた。 The average particle size of the primary particles of the nanostructure was determined from the average value obtained by measuring about 200 particle sizes from an electron microscope (TEM) observation photograph. About 50 average particle diameters of the nanostructures were measured from an electron microscope (TEM) observation photograph, and the average value was obtained from the average value.
ナノ構造体の結晶構造は、「Ｘ線回折装置 ＲＩＮＴ ２２００Ｖ」（理学電機工業（株）製）（管球：Ｃｕ）を使用し、２θが３〜１０５°の範囲で測定して同定した。 The crystal structure of the nanostructure was identified by using “X-ray diffractometer RINT 2200V” (manufactured by Rigaku Denki Kogyo Co., Ltd.) (tube: Cu) and measuring 2θ in the range of 3 to 105 °.
ナノ構造体の結晶子サイズは、測定した回折ピーク曲線から、下記シェラーの式を用いて計算した値で示したものである。 The crystallite size of the nanostructure is indicated by a value calculated from the measured diffraction peak curve using the Scherrer equation below.
結晶子サイズ＝Ｋλ／βｃｏｓθ
但し、β＝装置に起因する機械幅を補正した真の回折ピークの半値幅（ラジアン単位）。
Ｋ＝シェラー定数（＝０．９）。
λ＝Ｘ線の波長（Ｃｕ Ｋα線 ０．１５４２ｎｍ）。
θ＝回折角（各結晶面の回折ピークに対応）。
Crystallite size = Kλ / βcosθ
Where β = half-value width (in radians) of the true diffraction peak corrected for machine width due to the device.
K = Scherrer constant (= 0.9).
λ = wavelength of X-ray (Cu Kα ray 0.1542 nm).
θ = Diffraction angle (corresponding to the diffraction peak of each crystal plane).
ナノ構造体の比表面積はＢＥＴ法で算出した。 The specific surface area of the nanostructure was calculated by the BET method.
ナノ構造体の耐熱性は、雰囲気温度を約１０００℃に設定した電気炉に対象物を約２４時間放置し、その粉末の比表面積値の変動により評価した。
The heat resistance of the nanostructure was evaluated by allowing the object to stand in an electric furnace set to an atmospheric temperature of about 1000 ° C. for about 24 hours and changing the specific surface area of the powder.
（実施例１）
水にオキシ硝酸ジルコニウム、硫酸マグネシウムをそれぞれ０．２、０．４ｍｏｌ／Ｌ溶解させ、これを二流体ノズルにより噴霧し、空気に同伴させ、加熱炉に供給した。加熱炉を出た粒子はバグフィルターにより捕集し、回収した粒子は超音波洗浄及び遠心分離により洗浄後、乾燥させた。
なお、加熱炉には抵抗加熱方式の管状炉を用い、炉心管には内径（Ｄ）７０ｍｍ、有効長さ（Ｌ）１８００ｍｍのセラミック管を用いた。炉温は１０００℃とした。なお、使用した空気流量は全量で４０ＮＬ／ｍｉｎとした。
Example 1
Zirconium oxynitrate and magnesium sulfate were dissolved in water at 0.2 and 0.4 mol / L, respectively, sprayed with a two-fluid nozzle, entrained with air, and supplied to a heating furnace. The particles exiting the heating furnace were collected by a bag filter, and the collected particles were washed by ultrasonic washing and centrifugation and then dried.
A resistance heating type tubular furnace was used as the heating furnace, and a ceramic tube having an inner diameter (D) of 70 mm and an effective length (L) of 1800 mm was used as the core tube. The furnace temperature was 1000 ° C. The air flow rate used was 40 NL / min in total.
得られたナノ構造体はＺｒＯ２であり、電子顕微鏡観察による一次粒子の平均粒子径は８．０ｎｍであってＸ線回折から算出した結晶子サイズは８．５ｎｍであり、一次粒子サイズの比（電子顕微鏡観察から算出した一次粒子径／Ｘ線回折から算出した結晶子サイズ）が０．９４であり、ほぼ同程度であることから、一次粒子が単結晶であるものと推定される。ナノ構造体の平均粒径は０．８μｍであった。電子顕微鏡観察の結果を図１及び２に示す。図１及び２から明らかなとおり、中空状の球体を呈するナノ構造体であった。ＢＥＴ比表面積は１１０．０ｍ２／ｇであった。 The obtained nanostructure was ZrO 2 , the average particle diameter of primary particles by electron microscope observation was 8.0 nm, the crystallite size calculated from X-ray diffraction was 8.5 nm, and the ratio of primary particle sizes Since (primary particle diameter calculated from electron microscope observation / crystallite size calculated from X-ray diffraction) is 0.94, which is approximately the same, it is estimated that the primary particles are single crystals. The average particle size of the nanostructure was 0.8 μm. The results of electron microscope observation are shown in FIGS. As is apparent from FIGS. 1 and 2, the nanostructure was a hollow sphere. The BET specific surface area was 110.0 m 2 / g.
（実施例２）
原料塩を、硝酸セリウム、硫酸マグネシウムをそれぞれ０．２、０．４ｍｏｌ／Ｌとした以外は、前記実施例１と同様にして、ナノ構造体を得た。
(Example 2)
A nanostructure was obtained in the same manner as in Example 1 except that the raw material salt was changed to cerium nitrate and magnesium sulfate of 0.2 and 0.4 mol / L, respectively.
得られたナノ構造体はＣｅＯ２であり、電子顕微鏡観察による一次粒子の平均粒子径は１０．５ｎｍであってＸ線回折から算出した結晶子サイズは１０．０ｎｍであり、一次粒子が単結晶であるものと推定された。ナノ構造体の平均粒径は１．１μｍであった。電子顕微鏡観察の結果、中空状の球体を呈するナノ構造体であった。ＢＥＴ比表面積は６０ｍ２／ｇであった。 The obtained nanostructure is CeO 2 , the average particle diameter of primary particles by electron microscope observation is 10.5 nm, the crystallite size calculated from X-ray diffraction is 10.0 nm, and the primary particles are single crystals. It was estimated that. The average particle size of the nanostructure was 1.1 μm. As a result of electron microscope observation, it was a nanostructure exhibiting a hollow sphere. The BET specific surface area was 60 m 2 / g.
（実施例３）
四塩化チタン、硫酸ナトリウムを０．３ｍｏｌ／Ｌずつ溶解させ、原料溶液を調製し、加熱温度を８００℃とした以外は、前記実施例１と同様にして、ナノ構造体を得た。
(Example 3)
A nanostructure was obtained in the same manner as in Example 1 except that titanium tetrachloride and sodium sulfate were dissolved 0.3 mol / L each to prepare a raw material solution and the heating temperature was set to 800 ° C.
得られたナノ構造体はＴｉＯ２であり、電子顕微鏡観察による一次粒子の平均粒子径は１１．２ｎｍであってＸ線回折から算出した結晶子サイズは１０．５ｎｍであり、一次粒子が単結晶であるものと推定された。ナノ構造体の平均粒径は０．７μｍであった。電子顕微鏡観察の結果、中空状の球体を呈するナノ構造体であった。ＢＥＴ比表面積は１５１ｍ２／ｇであった。 The obtained nanostructure is TiO 2 , the average particle diameter of primary particles by electron microscope observation is 11.2 nm, the crystallite size calculated from X-ray diffraction is 10.5 nm, and the primary particles are single crystals. It was estimated that. The average particle size of the nanostructure was 0.7 μm. As a result of electron microscope observation, it was a nanostructure exhibiting a hollow sphere. The BET specific surface area was 151 m 2 / g.
（実施例４）
硝酸鉄、硫酸ナトリウムをそれぞれ０．２、０．３ｍｏｌ／Ｌずつ溶解させ、原料溶液を調製し、加熱温度を８００℃とした以外は、前記実施例１と同様にして、ナノ構造体を得た。
Example 4
A nanostructure was obtained in the same manner as in Example 1 except that 0.2 and 0.3 mol / L of iron nitrate and sodium sulfate were dissolved to prepare a raw material solution and the heating temperature was 800 ° C. It was.
得られたナノ構造体はＦｅ２Ｏ３であり、電子顕微鏡観察による一次粒子の平均粒子径は１２．５ｎｍであってＸ線回折から算出した結晶子サイズは１３．５ｎｍであり、一次粒子が単結晶であるものと推定された。ナノ構造体の平均粒径は１．３μｍであった。電子顕微鏡観察の結果を図４に示す。図４から明らかなとおり、中空状の球体を呈するナノ構造体であった。ＢＥＴ比表面積は８９ｍ２／ｇであった。 The obtained nanostructure was Fe 2 O 3 , the average particle diameter of primary particles by electron microscope observation was 12.5 nm, the crystallite size calculated from X-ray diffraction was 13.5 nm, and the primary particles were Presumed to be a single crystal. The average particle size of the nanostructure was 1.3 μm. The result of electron microscope observation is shown in FIG. As is clear from FIG. 4, the nanostructure was a hollow sphere. The BET specific surface area was 89 m 2 / g.
（実施例５）
オキシ硝酸ジルコニウム、硫酸マグネシウムをそれぞれ０．１、０．４ｍｏｌ／Ｌ溶解させ、原料溶液を調製し、加熱温度を１０００℃とした以外は、前記実施例１と同様にして、ナノ構造体を得た。
(Example 5)
A nanostructure was obtained in the same manner as in Example 1 except that 0.1 and 0.4 mol / L of zirconium oxynitrate and magnesium sulfate were dissolved to prepare a raw material solution and the heating temperature was 1000 ° C. It was.
得られたナノ構造体はＺｒＯ２であり、電子顕微鏡観察による一次粒子の平均粒子径は８．０ｎｍであってＸ線回折から算出した結晶子サイズは８．５ｎｍであり、一次粒子が単結晶であるものと推定された。ナノ構造体の平均粒径は０．５μｍであった。電子顕微鏡観察の結果を図４及び５に示す。図４及び５から明らかなとおり、中実状の球体を呈するナノ構造体であった。ＢＥＴ比表面積は１０５ｍ２／ｇであった。 The obtained nanostructure is ZrO 2 , the average particle diameter of primary particles by electron microscope observation is 8.0 nm, the crystallite size calculated from X-ray diffraction is 8.5 nm, and the primary particles are single crystals. It was estimated that. The average particle size of the nanostructure was 0.5 μm. The results of electron microscope observation are shown in FIGS. As is clear from FIGS. 4 and 5, the nanostructure was a solid sphere. The BET specific surface area was 105 m 2 / g.
（実施例６）
オキシ硝酸ジルコニウム、硫酸マグネシウムをそれぞれ０．０１、０．０２ｍｏｌ／Ｌ溶解させ、原料溶液を調製し、加熱温度を１０００℃とした以外は、前記実施例１と同様にして、ナノ構造体を得た。
(Example 6)
A nanostructure was obtained in the same manner as in Example 1 except that 0.01 and 0.02 mol / L of zirconium oxynitrate and magnesium sulfate were dissolved to prepare a raw material solution and the heating temperature was set to 1000 ° C. It was.
得られたナノ構造体はＺｒＯ２であり、電子顕微鏡観察による一次粒子の平均粒子径は８．０ｎｍであってＸ線回折から算出した結晶子サイズは８．５ｎｍであり、一次粒子が単結晶であるものと推定された。電子顕微鏡観察の結果を図６に示す。図６から明らかなとおり、薄膜状を呈するナノ構造体であった。ＢＥＴ比表面積は１０７ｍ２／ｇであった。 The obtained nanostructure is ZrO 2 , the average particle diameter of primary particles by electron microscope observation is 8.0 nm, the crystallite size calculated from X-ray diffraction is 8.5 nm, and the primary particles are single crystals. It was estimated that. The result of electron microscope observation is shown in FIG. As is clear from FIG. 6, the nanostructure was in the form of a thin film. The BET specific surface area was 107 m 2 / g.
（実施例７）
硝酸アルミニウム、硫酸ナトリウムをそれぞれ０．３、０．６５ｍｏｌ／Ｌずつ溶解させ、原料溶液を調整し、加熱温度を９００℃とした以外は、前記実施例１と同様にして、ナノ構造体を得た。
(Example 7)
A nanostructure was obtained in the same manner as in Example 1 except that aluminum nitrate and sodium sulfate were dissolved by 0.3 and 0.65 mol / L, respectively, the raw material solution was adjusted, and the heating temperature was set to 900 ° C. It was.
得られたナノ構造体はＡｌ２Ｏ３であり、電子顕微鏡観察による一次粒子の平均粒子径は７．５ｎｍであってＸ線回折から算出した結晶子サイズは６．１ｎｍであり、一次粒子が単結晶であるものと推定された。電子顕微鏡観察の結果を図７に示す。図７から明らかなとおり、中空状を呈するナノ構造体であった。ナノ構造体の平均粒径は０．６μｍであった。ＢＥＴ比表面積は２４０ｍ２／ｇであった。 The obtained nanostructure is Al 2 O 3 , the average particle diameter of primary particles by electron microscope observation is 7.5 nm, the crystallite size calculated from X-ray diffraction is 6.1 nm, and the primary particles are Presumed to be a single crystal. The result of electron microscope observation is shown in FIG. As is clear from FIG. 7, the nanostructure was hollow. The average particle size of the nanostructure was 0.6 μm. The BET specific surface area was 240 m 2 / g.
ただし、ここに得られたナノ構造体は、第三無機塩との固溶体が一部残存している。そこで、より高純度化を必要する場合は、熱分解時の加熱温度を調整して、結晶構造が異なる形態（非晶質など）で生成粒子を取り出し、一旦洗浄した後、通常の静置炉などで再度、加熱処理を行うことによって得ることができる。 However, a part of the solid solution with the third inorganic salt remains in the nanostructure obtained here. Therefore, when higher purity is required, the heating temperature during pyrolysis is adjusted, the generated particles are taken out in a form with a different crystal structure (such as amorphous), washed once, and then a normal stationary furnace, etc. It can be obtained by performing the heat treatment again.
（比較例１）
オキシ硝酸ジルコニウム、硫酸マグネシウムをそれぞれ０．１、０．８ｍｏｌ／Ｌ溶解させ、原料溶液を調製し、加熱温度を１０００℃とした以外は、前記実施例１と同様にして、ナノ粒子を得た。
(Comparative Example 1)
Nanoparticles were obtained in the same manner as in Example 1 except that 0.1 and 0.8 mol / L of zirconium oxynitrate and magnesium sulfate were dissolved to prepare a raw material solution and the heating temperature was 1000 ° C. .
得られたナノ粒子はＺｒＯ２であり、電子顕微鏡観察による一次粒子の平均粒子径は８．０ｎｍであってＸ線回折から算出した結晶子サイズは８．５ｎｍであり、一次粒子が単結晶であるものと推定された。電子顕微鏡観察の結果を図８に示す。図８から明らかなとおり、一次粒子が単独で存在しており、ナノ構造体を形成していなかった。ＢＥＴ比表面積は１０３ｍ２／ｇであった。 The obtained nanoparticles were ZrO 2 , the average particle diameter of primary particles by electron microscope observation was 8.0 nm, the crystallite size calculated from X-ray diffraction was 8.5 nm, and the primary particles were single crystals. It was estimated that there was. The result of electron microscope observation is shown in FIG. As is clear from FIG. 8, the primary particles existed alone and did not form nanostructures. The BET specific surface area was 103 m 2 / g.
実施例及び比較例で得られた粒子の諸特性を表１に示す。 Table 1 shows various characteristics of the particles obtained in Examples and Comparative Examples.
また、図１〜図７から明らかなとおり、ナノ構造体を構成する一次粒子間には空孔（空隙）が存在しているのが確認できた。 Further, as is apparent from FIGS. 1 to 7, it was confirmed that pores (voids) existed between the primary particles constituting the nanostructure.
なお、実施例１〜７及び比較例１で得られた粒子粉末に対し、Ｘ線回折により、結晶構造を同定した結果、いずれも目標酸化物であることを確認した。 In addition, as a result of identifying a crystal structure with respect to the particle powder obtained in Examples 1 to 7 and Comparative Example 1 by X-ray diffraction, it was confirmed that both were target oxides.
また、実施例１、５、６及び比較例１のＢＥＴ比表面積値はほぼ同程度であった。一次粒子はいずれもＺｒＯ２であり、且つ、一次粒子の平均粒子径は同じ約８．０ｎｍである。実施例１、５及び６は種々の形状を呈したナノ構造体を形成しているのにもかかわらず、ＢＥＴ比表面積値が比較例１とほぼ同等である。従って、ナノ構造体における一次粒子同士の接触・焼結面は小さいものであって、限りなく点焼結に近いものであると推定している。 Moreover, the BET specific surface area values of Examples 1, 5, 6 and Comparative Example 1 were almost the same. The primary particles are all ZrO 2 , and the average particle diameter of the primary particles is the same about 8.0 nm. Although Examples 1, 5 and 6 form nanostructures having various shapes, the BET specific surface area values are almost the same as those of Comparative Example 1. Therefore, it is presumed that the contact / sintered surface between the primary particles in the nanostructure is small and is close to point sintering.
さらに、実施例１、５及び６で得られたナノ構造体と比較例１のナノ粒子の耐熱性を比較すると、実施例のナノ構造体はＢＥＴ比表面積の減少幅が小さく、耐熱性に優れることは明らかである。
また、実施例１、５及び６においても、中空状の球体である実施例１が最も耐熱性に優れ、以下、中実状の球体である実施例５、薄膜状である実施例６の順に耐熱性が低下するものであった。
Furthermore, when the heat resistance of the nanostructures obtained in Examples 1, 5 and 6 and the nanoparticles of Comparative Example 1 are compared, the nanostructures of the examples have a small reduction in BET specific surface area and are excellent in heat resistance. It is clear.
Also in Examples 1, 5 and 6, Example 1 which is a hollow sphere has the most excellent heat resistance. Hereinafter, Example 5 which is a solid sphere and Example 6 which is a thin film are heat resistant in this order. The property was lowered.
従来のナノ粒子分散技術では、その殆どが第三固相を必要するため、用途が限定され、しかも工程が非常に煩雑となり、製造コストも割高となる。それに対し、本発明に係るナノ構造体は第三固相を必要とせず、合成したナノ粒子同士を点接触・焼結させることで、その単分散化を実現させる。また、その構造体形状は薄膜或いは球体と作り分けることができる為、従来のような用途制限は受けない。また、必要に応じて、第三固相に固定化してもよいが、特に分散処理も必要なく、安易に固定化できる。さらに、工程もシンプルであり、大幅な生産性向上が見込める。 Most of the conventional nanoparticle dispersion techniques require a third solid phase, so that their applications are limited, the process becomes very complicated, and the production cost is high. On the other hand, the nanostructure according to the present invention does not require a third solid phase, and realizes monodispersion by performing point contact and sintering between the synthesized nanoparticles. Moreover, since the shape of the structure can be made separately from a thin film or a sphere, there are no restrictions on the use as in the prior art. Further, if necessary, it may be immobilized on the third solid phase, but it is not particularly required to be dispersed and can be easily immobilized. In addition, the process is simple and significant productivity improvements can be expected.
Claims (3)
3. The nanostructure according to claim 1, wherein the spherical nanostructure has an average particle diameter of 50 nm to 20 μm.
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