JP5036443B2 - Photocatalytic material - Google Patents
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- JP5036443B2 JP5036443B2 JP2007199520A JP2007199520A JP5036443B2 JP 5036443 B2 JP5036443 B2 JP 5036443B2 JP 2007199520 A JP2007199520 A JP 2007199520A JP 2007199520 A JP2007199520 A JP 2007199520A JP 5036443 B2 JP5036443 B2 JP 5036443B2
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- 230000001699 photocatalysis Effects 0.000 title claims description 27
- 239000000463 material Substances 0.000 title claims description 23
- 229910052782 aluminium Inorganic materials 0.000 claims description 4
- 229910052733 gallium Inorganic materials 0.000 claims description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 34
- 239000002245 particle Substances 0.000 description 23
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 19
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 18
- 239000000693 micelle Substances 0.000 description 15
- 239000013078 crystal Substances 0.000 description 13
- 239000011941 photocatalyst Substances 0.000 description 13
- 150000002500 ions Chemical class 0.000 description 12
- 239000012071 phase Substances 0.000 description 11
- 235000014413 iron hydroxide Nutrition 0.000 description 9
- NCNCGGDMXMBVIA-UHFFFAOYSA-L iron(ii) hydroxide Chemical compound [OH-].[OH-].[Fe+2] NCNCGGDMXMBVIA-UHFFFAOYSA-L 0.000 description 9
- 239000000377 silicon dioxide Substances 0.000 description 9
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 8
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 8
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 8
- 238000005259 measurement Methods 0.000 description 6
- 239000003795 chemical substances by application Substances 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- 238000000034 method Methods 0.000 description 5
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 4
- 239000008346 aqueous phase Substances 0.000 description 4
- VCJMYUPGQJHHFU-UHFFFAOYSA-N iron(3+);trinitrate Chemical compound [Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VCJMYUPGQJHHFU-UHFFFAOYSA-N 0.000 description 4
- TVMXDCGIABBOFY-UHFFFAOYSA-N octane Chemical compound CCCCCCCC TVMXDCGIABBOFY-UHFFFAOYSA-N 0.000 description 4
- 238000003980 solgel method Methods 0.000 description 4
- 239000010936 titanium Substances 0.000 description 4
- LZZYPRNAOMGNLH-UHFFFAOYSA-M Cetrimonium bromide Chemical compound [Br-].CCCCCCCCCCCCCCCC[N+](C)(C)C LZZYPRNAOMGNLH-UHFFFAOYSA-M 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 3
- 238000011156 evaluation Methods 0.000 description 3
- 239000010419 fine particle Substances 0.000 description 3
- 239000011521 glass Substances 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 229910052738 indium Inorganic materials 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 230000000704 physical effect Effects 0.000 description 3
- 229910052719 titanium Inorganic materials 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 description 2
- 238000003917 TEM image Methods 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 230000005389 magnetism Effects 0.000 description 2
- 230000005415 magnetization Effects 0.000 description 2
- 229910052748 manganese Inorganic materials 0.000 description 2
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 2
- 229910052753 mercury Inorganic materials 0.000 description 2
- VSQYNPJPULBZKU-UHFFFAOYSA-N mercury xenon Chemical compound [Xe].[Hg] VSQYNPJPULBZKU-UHFFFAOYSA-N 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 229910052706 scandium Inorganic materials 0.000 description 2
- 239000004094 surface-active agent Substances 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- 229910052727 yttrium Inorganic materials 0.000 description 2
- 229910052725 zinc Inorganic materials 0.000 description 2
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonium chloride Substances [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 1
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 description 1
- QGZKDVFQNNGYKY-UHFFFAOYSA-N ammonia Natural products N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 1
- 235000011114 ammonium hydroxide Nutrition 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000004332 deodorization Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000006260 foam Substances 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000006864 oxidative decomposition reaction Methods 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 229910000077 silane Inorganic materials 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 239000000779 smoke Substances 0.000 description 1
- 230000001954 sterilising effect Effects 0.000 description 1
- 238000004659 sterilization and disinfection Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
Description
本発明は、光触媒材料に関し、特に特定の結晶構造を有する光触媒材料に関するものである。 The present invention relates to a photocatalytic material, and particularly to a photocatalytic material having a specific crystal structure.
従来、光触媒材料としては、代表的なものとして酸化チタン光触媒が知られている。この酸化チタン光触媒は、光を吸収すると、主に、酸化作用、及び超親水作用を発現する。酸化チタン光触媒の酸化作用は、水を酸素と水素に分解するほど顕著であるので、太陽エネルギーから水素を生成するクリーンエネルギーの循環サイクルの実用化の礎を担う材料として期待されている。また、この酸化作用を利用して、有害物質を分解することにより、殺菌や、脱臭処理を行うこともできる。このような光触媒作用を利用して、光触媒をセラミック多孔体（セラミックフォーム）の表面に担持させてなる光触媒フィルタが、空調機、空気清浄機、分煙機、レンジフード用フィルタや水処理装置等に応用されている（例えば、特許文献１）。 Conventionally, a titanium oxide photocatalyst is known as a typical photocatalyst material. When this titanium oxide photocatalyst absorbs light, it mainly exhibits an oxidizing action and a superhydrophilic action. The oxidation action of the titanium oxide photocatalyst is so prominent that water is decomposed into oxygen and hydrogen. Therefore, the titanium oxide photocatalyst is expected as a material for the practical use of a clean energy circulation cycle that generates hydrogen from solar energy. In addition, sterilization and deodorization treatment can be performed by decomposing harmful substances using this oxidizing action. A photocatalytic filter in which a photocatalyst is supported on the surface of a ceramic porous body (ceramic foam) using such a photocatalytic action is an air conditioner, an air purifier, a smoke separator, a filter for a range hood, a water treatment device, etc. (For example, Patent Document 1).
一方、酸化チタン光触媒の超親水作用は、自動車のバックミラーなどにコーティングすることにより、バックミラーに細かい水滴が付着するのを防止できるので、視認性を向上できるという効果が得られる。また、建物の外壁などにコーティングを施すことによって、雨水により表面が洗浄され、セルフクリーニング効果を得ることができる。 On the other hand, the superhydrophilic action of the titanium oxide photocatalyst can be applied to an automobile rearview mirror or the like to prevent fine water droplets from adhering to the rearview mirror, so that the visibility can be improved. Further, by coating the outer wall of the building or the like, the surface is washed with rainwater, and a self-cleaning effect can be obtained.
このように代表的な酸化チタン光触媒では、種々の用途が試されているだけでなく、今後の用途のさらなる広がりが期待されている。
しかしながら、酸化チタンと似た電子構造を有する光触媒材料は、他にも存在するものの、現時点において顕著な光触媒活性が見当たらない。また、光触媒作用のみならず、他の物性を備えた粒子を提供することができれば、上記したような用途をさらに広げることも期待できる。 However, although there are other photocatalytic materials having an electronic structure similar to titanium oxide, no remarkable photocatalytic activity is found at present. Moreover, if the particle | grains provided with not only a photocatalytic action but another physical property can be provided, it can also anticipate extending the above uses.
そこで本発明は上記した問題点に鑑み、酸化チタン以外の光触媒材料として、光触媒作用のみならず、他の物性を備えた特定の結晶構造を有した光触媒材料を提供することを目的とする。 In view of the above problems, an object of the present invention is to provide a photocatalytic material having a specific crystal structure having not only a photocatalytic action but also other physical properties as a photocatalytic material other than titanium oxide.
そこで、本願発明者らは上記の目的を達成するために材料を種々検討したところ、ε−Ｆｅ２Ｏ３相を主体とする粒子には光触媒作用のみならず、磁気特性をも具備することを知った。 Accordingly, the inventors of the present application have studied various materials in order to achieve the above-described object. As a result, the particles mainly composed of the ε-Fe 2 O 3 phase have not only a photocatalytic action but also magnetic characteristics. Knew.
すなわち、請求項１に係る発明は、一般式ε−Ａ ｘ Ｆｅ ２−ｘ Ｏ ３ （但し、０＜ｘ＜２）を主相とし、前記Ａが、Ａｌ，Ｇａ，及びＩｎの中から選択されるいずれか１種の元素であることを特徴とする。 That is, the invention according to claim 1 has a general formula ε-A x Fe 2−x O 3 (where 0 <x <2) as the main phase, and A is selected from Al, Ga, and In. Any one of the above elements is characterized.
本発明の光触媒材料は、特定の結晶構造（一般式ε−Ｆｅ２Ｏ３）を有する磁性酸化鉄粒子で構成され磁性を発現させることができる。さらに、１種又は２種の元素をＦｅイオンサイトの一部と置換することにより、磁性において熱安定性にすぐれた光触媒材料を得ることができる。 The photocatalytic material of the present invention is composed of magnetic iron oxide particles having a specific crystal structure (general formula ε-Fe 2 O 3 ) and can exhibit magnetism. Further, by substituting one or two kinds of elements with a part of the Fe ion site, a photocatalytic material excellent in thermal stability in magnetism can be obtained.
以下本発明の好適な実施形態について説明する。図１は、本発明に係る光触媒材料の結晶構造であり、一般式：ε−Ｆｅ２Ｏ３で表されるイプシロン型の磁性酸化鉄粒子、又は、ε−Ｆｅ２Ｏ３の前記Ｆｅ３＋イオンサイトの一部が、互いに異なる１種類または２種類の元素と置換された構造を有している。つまり、一般式：ε−ＡｘＦｅ２−ｘＯ３またはε−ＢｙＣｚＦｅ２−ｙ−ｚＯ３と表記される（但し、Ａ、Ｂ、Ｃは、Ｆｅを除く、互いに異なる元素である。）イプシロン型の磁性酸化鉄粒子である。尚、上述の式に記載された元素以外であっても、製造上の不純物等の成分や化合物の含有は許容される。因みに、この磁性酸化鉄粒子は、粒径が１００ｎｍ以下、特に１０ｎｍ〜５０ｎｍのものが好適である。これにより、光の波長よりずっと小さく、光が散乱しないため透明性を高めることができる。
（Ｆｅを除く、１種類または互いに異なる２種類の元素Ａ、Ｂ、Ｃについて）
まず、Ｆｅ３＋イオンサイトの一部と置換された元素が１種類の場合、ε−Ｆｅ２Ｏ３の結晶構造を安定に保つため、Ａとしては、３価の元素を用いることが好ましい。さらにＡとしては、Ａｌ，Ｓｃ，Ｔｉ，Ｖ，Ｃｒ，Ｇａ，Ｉｎ，Ｙから選択される１種の元素を挙げることができる。尚、ｘは、０＜ｘ＜２の範囲であればよい。
Hereinafter, preferred embodiments of the present invention will be described. FIG. 1 is a crystal structure of a photocatalytic material according to the present invention, which is an epsilon-type magnetic iron oxide particle represented by a general formula: ε-Fe 2 O 3 , or the Fe 3+ ion of ε-Fe 2 O 3. A part of the site has a structure in which one or two different elements are substituted. In other words, the general formula: ε-A x Fe 2- x O 3 or denoted as ε-B y C z Fe 2 -y-z O 3 ( where, A, B, C except the Fe, differ from each other Epsilon-type magnetic iron oxide particles. In addition, inclusion of components such as impurities in production and compounds other than the elements described in the above formula is allowed. Incidentally, the magnetic iron oxide particles preferably have a particle size of 100 nm or less, particularly 10 nm to 50 nm. Thereby, since it is much smaller than the wavelength of light and light is not scattered, transparency can be improved.
(About one element or two different elements A, B, and C except for Fe)
First, when one element is substituted for a part of the Fe 3+ ion site, it is preferable to use a trivalent element as A in order to keep the crystal structure of ε-Fe 2 O 3 stable. Furthermore, examples of A include one element selected from Al, Sc, Ti, V, Cr, Ga, In, and Y. Note that x may be in the range of 0 <x <2.
これらの元素のうち、Ａｌ及びＧａは、Ｆｅ３＋イオンサイトの一部であるＦｅ４サイトと置換し、Ｓｃ，Ｔｉ，Ｖ，Ｃｒ，Ｉｎ，及びＹは、Ｆｅ３＋イオンサイトの一部であるＦｅ１サイトと置換する。 Of these elements, Al and Ga replace Fe4 sites that are part of Fe 3+ ion sites, and Sc, Ti, V, Cr, In, and Y are Fe1 that are part of Fe 3+ ion sites. Replace with site.
また、Ｆｅ３＋イオンサイトの一部と置換された元素が互いに異なる２種類で構成される場合、ε−Ｆｅ２Ｏ３の結晶構造を安定に保つため、Ｂとしては４価の元素、Ｃとしては２価の元素を用いることが好ましい。さらにＢとしてはＴｉ、Ｃとしては、Ｃｏ，Ｎｉ，Ｍｎ，Ｃｕ及びＺｎから選択される１種の元素を挙げることができる。尚、ｘ，ｙは、０＜ｘ，ｙ＜１の範囲であればよい。 Further, in the case where the element substituted with a part of the Fe 3+ ion site is composed of two different types, B is a tetravalent element and C is C in order to keep the crystal structure of ε-Fe 2 O 3 stable. Is preferably a divalent element. Further, as B, Ti, and C can include one element selected from Co, Ni, Mn, Cu, and Zn. X and y may be in the range of 0 <x and y <1.
上記Ｂを構成するＴｉは、Ｆｅ３＋イオンサイトの一部であるＦｅ４サイトと置換する。また、上記Ｃを構成するＣｏ，Ｎｉ，Ｍｎ，Ｃｕ及びＺｎは、いずれもＦｅ３＋イオンサイトの一部であるＦｅ１サイトと置換する。 Ti constituting the B substitutes for the Fe4 site which is a part of the Fe3 + ion site. Further, Co, Ni, Mn, Cu and Zn constituting the C are all replaced with Fe1 sites which are part of Fe 3+ ion sites.
尚、当該Ａ、Ｂ、ＣからＦｅを除くのは、当該ε−Ｆｅ２Ｏ３のＦｅ３＋イオンサイトの一部を、１種類または互いに異なる２種類の元素で置換するためである。
（本発明に係る光触媒材料の製造方法）
次に本発明に係る光触媒材料の製造方法の一例について説明する。以下に説明する製造方法は、逆ミセル法とゾル−ゲル法との組み合わせ法によるものである。ここでの逆ミセル法とは、界面活性剤を含んだミセル溶液α（原料ミセル）と、ミセル溶液β（中和剤ミセル）との２種類を混合することによって、ミセル内で水酸化鉄の沈殿反応を進行させる工程をさす。一方、ここでのゾル−ゲル法とは、ミセル内で生成した水酸化鉄微粒子の表面にシリカコートを施す工程をいう。
The reason for removing Fe from A, B, and C is to replace a part of the Fe 3+ ion site of the ε-Fe 2 O 3 with one or two different elements.
(Method for producing photocatalytic material according to the present invention)
Next, an example of the method for producing the photocatalytic material according to the present invention will be described. The manufacturing method described below is based on a combination method of the reverse micelle method and the sol-gel method. Here, the reverse micelle method is a mixture of two kinds of micelle solution α (raw material micelle) containing a surfactant and micelle solution β (neutralizer micelle). It refers to the process of advancing the precipitation reaction. On the other hand, the sol-gel method here refers to a step of applying a silica coat to the surface of iron hydroxide fine particles generated in a micelle.
逆ミセル法とゾル−ゲル法との両方法を組み合わせることで、シリカによる被覆層をもつ水酸化鉄微粒子を得ることが出来る。得られたシリカコートをもつ水酸化鉄微粒子は、液から分離されたあと、所定の温度（７００〜１３００℃の範囲内）で大気雰囲気下での熱処理に供されることにより、単相のε−Ｆｅ２Ｏ３を生成する。 By combining both the reverse micelle method and the sol-gel method, iron hydroxide fine particles having a coating layer of silica can be obtained. The obtained iron hydroxide fine particles having a silica coat are separated from the liquid, and then subjected to a heat treatment in an air atmosphere at a predetermined temperature (in the range of 700 to 1300 ° C.), whereby a single-phase ε to generate a -Fe 2 O 3.
以下、具体例を挙げて説明する。まず、ｎ−オクタンを油相とするミセル溶液αの水相に、硝酸鉄（ＩＩＩ）と界面活性剤（例えば臭化セチルトリメチルアンモニウム（本明細書において、ＣＴＡＢと記載する場合がある。）を溶解する。その際、ＣＴＡＢを効率よく溶解させるため、直鎖のアルコール、例えばブチルアルコールを添加しても差し支えない。ここで、ミセル溶液αの水相に溶解させる硝酸鉄（ＩＩＩ）の一部を、他元素Ａ、Ｂ、Ｃに置き換えることもできる。同じく、ｎ−オクタンを油相とするミセル溶液βの水相にはアンモニア水溶液を用いる。 Hereinafter, a specific example will be described. First, iron (III) nitrate and a surfactant (for example, cetyltrimethylammonium bromide (in this specification, sometimes referred to as CTAB) are added to the aqueous phase of the micelle solution α containing n-octane as the oil phase. In this case, in order to dissolve CTAB efficiently, a linear alcohol such as butyl alcohol may be added, where a part of iron (III) nitrate dissolved in the aqueous phase of the micelle solution α. Can be replaced with other elements A, B, and C. Similarly, an aqueous ammonia solution is used for the aqueous phase of the micelle solution β using n-octane as the oil phase.
尚、ミセル溶液αの水相に形状制御剤として、適量のアルカリ土類元素（Ｂａ、Ｓｒ、Ｃａなど）の硝酸塩を溶解させておくこともできる。この形状制御剤添加を行うことで、単相のε−Ｆｅ２Ｏ３粒子を棒状の形状とすることが出来る。しかし、当該アルカリ土類元素が、生成する結晶の表層部に残存することがある。この場合、残存するアルカリ土類元素の含有量が８質量％を超えなければ、当該形状制御剤が他の物性に与える影響は、それ程強くはない。従って、本発明に係る光触媒材料の原料へは、形状制御剤としてアルカリ土類元素の少なくとも１種を、８質量％以下の量で添加することが出来る。 An appropriate amount of an alkaline earth element (Ba, Sr, Ca, etc.) nitrate may be dissolved in the aqueous phase of the micelle solution α as a shape control agent. By adding this shape control agent, the single-phase ε-Fe 2 O 3 particles can be formed into a rod shape. However, the alkaline earth element may remain in the surface layer portion of the generated crystal. In this case, unless the content of the remaining alkaline earth element exceeds 8% by mass, the influence of the shape control agent on other physical properties is not so strong. Therefore, at least one alkaline earth element as a shape control agent can be added to the raw material of the photocatalytic material according to the present invention in an amount of 8% by mass or less.
ミセル溶液αとβとを混合し、シランを適宜添加することで、ゾル−ゲル法により、得られた棒状、もしくはそれ以外の形状を有する水酸化鉄粒子表面にシリカによる被覆を施す。これらの反応はミセル中で行われており、ミセル内では、ナノオーダーの微細な水酸化鉄粒子の表面において加水分解が起こり、表面がシリカで被覆された粒子を得ることができる。 By mixing the micelle solutions α and β and adding silane appropriately, the surface of the obtained iron hydroxide particles having a rod-like shape or other shapes is coated by silica by a sol-gel method. These reactions are carried out in micelles. In the micelles, hydrolysis occurs on the surface of fine iron hydroxide particles of nano order, and particles whose surfaces are coated with silica can be obtained.
次いで、シリカコーティングされた水酸化鉄粒子を液から分離し、洗浄・乾燥の後、水酸化鉄粒子粉体を得る。得られた粒子粉体を炉内に装入し、空気中で７００〜１３００℃の温度範囲で熱処理（焼成）する。この熱処理により、水酸化鉄粒子はシリカ殻内部での酸化反応により、微細なε−Ｆｅ２Ｏ３粒子が生成する。この酸化反応の際、水酸化鉄粒子がシリカにより被覆されていることが、α−Ｆｅ２Ｏ３やγ−Ｆｅ２Ｏ３ではなく、ε−Ｆｅ２Ｏ３単相が生成するのに寄与していると考えられる。加えて、当該シリカコートは、粒子同士の焼結を防止する作用を果たす。また、上述したように、適量の形状保持剤としてアルカリ土類元素が共存していると、棒状のε−Ｆｅ２Ｏ３単相粒子に成長し易くなる。 Next, the silica-coated iron hydroxide particles are separated from the liquid, and after washing and drying, iron hydroxide particle powder is obtained. The obtained particle powder is placed in a furnace and heat-treated (fired) in the temperature range of 700 to 1300 ° C. in air. By this heat treatment, fine ε-Fe 2 O 3 particles are generated from the iron hydroxide particles by an oxidation reaction inside the silica shell. During this oxidation reaction, the fact that the iron hydroxide particles are coated with silica contributes to the formation of ε-Fe 2 O 3 single phase, not α-Fe 2 O 3 or γ-Fe 2 O 3. it seems to do. In addition, the silica coat serves to prevent sintering of the particles. Further, as described above, when an alkaline earth element coexists as an appropriate amount of the shape retention agent, it becomes easy to grow into rod-like ε-Fe 2 O 3 single phase particles.
このようにして、ε−Ｆｅ２Ｏ３と同じ結晶構造を有しながら、Ｆｅ３＋イオンサイトの一部が置換されたε−ＡｘＦｅ２−ｘＯ３単相粒子や、ε−ＢｙＣｚＦｅ２−ｙ−ｚＯ３単相粒子を合成できる。従って、本発明によれば、磁気特性を備える光触媒材料を提供することができる。
（実施例）
上記した製造方法により、Ｆｅ３＋イオンサイトの一部を前記ＡとしてのＧａと置換して実施例に係る試料を合成した。本実施例に係る試料のＴＥＭ像を図２に示す。この試料に対し、組成分析と、ＶＳＭ（振動試料型磁力計）測定を行った結果を表１に示す。この結果から組成割合を計算したところ、本実施例に係る試料は、ε−Ｇａ０．４７Ｆｅ１．５３Ｏ３であった。
In this way, ε-A x Fe 2-x O 3 single-phase particles in which a part of the Fe 3+ ion site is substituted while having the same crystal structure as ε-Fe 2 O 3, and ε-B y It can be synthesized C z Fe 2-y-z O 3 single phase particle. Therefore, according to the present invention, a photocatalytic material having magnetic properties can be provided.
(Example)
A sample according to the example was synthesized by replacing a part of the Fe 3+ ion site with Ga as A by the manufacturing method described above. A TEM image of the sample according to this example is shown in FIG. Table 1 shows the results of composition analysis and VSM (vibrating sample magnetometer) measurement performed on this sample. When the composition ratio was calculated from this result, the sample according to this example was ε-Ga 0.47 Fe 1.53 O 3 .
Ｘ線回折結晶構造解析の結果を図３に示す。因みに、この試料の結晶構造において、図１に示す各ＦｅサイトのＧａイオン占有率は、Ｆｅ１サイトとＦｅ２サイトが共に０であるのに対し、Ｆｅ３サイトが０．２１、Ｆｅ４サイトが０．７５であった。 The results of X-ray diffraction crystal structure analysis are shown in FIG. Incidentally, in the crystal structure of this sample, the Ga ion occupancy of each Fe site shown in FIG. 1 is 0 for both Fe1 site and Fe2 site, whereas 0.23 for Fe3 site and 0.75 for Fe4 site. Met.
さらに、得られた試料の粒径分布を図４に、ヒステリシスループを図５に示す。さらに、１０［Ｏｅ］の外部磁場のもとでの各温度における磁化を測定した。この測定は、試料を１Ｋ／ｍｉｎの速度で加熱及び冷却しながら磁化を測定した。その結果（図６）、キュリー点（Ｔｃ）は４０８Ｋであった。 Furthermore, the particle size distribution of the obtained sample is shown in FIG. 4, and the hysteresis loop is shown in FIG. Furthermore, magnetization at each temperature under an external magnetic field of 10 [Oe] was measured. In this measurement, the magnetization was measured while heating and cooling the sample at a rate of 1 K / min. As a result (FIG. 6), the Curie point (Tc) was 408K.
次に、上記試料の光触媒活性を、図７に示すように、２−プロパノール（ＩＰＡ）気相酸化分解反応で評価した。５００ｍｌのガラスベッセル内に２５ｍｍφの試料を載置して石英フタで密閉した。密閉した前記ガラスベッセル中に２−プロパノールを充満させ、暗室においてランプ光を照射し、所定時間毎にガラスベッセル中の気体成分をガスクロマトグラフィにより測定した。 Next, the photocatalytic activity of the sample was evaluated by 2-propanol (IPA) gas phase oxidative decomposition reaction as shown in FIG. A 25 mmφ sample was placed in a 500 ml glass vessel and sealed with a quartz lid. The sealed glass vessel was filled with 2-propanol, irradiated with lamp light in a dark room, and gas components in the glass vessel were measured by gas chromatography every predetermined time.
図８はランプ光として水銀灯による紫外光を用いた場合（λ＝３１０〜３７０ｎｍ、４００ｍＷ／ｃｍ２、吸収率＝９８．８％）の測定結果である。尚、２−プロパノールの初期濃度は、２９４ｐｐｍである。図８中、１はＣＯ２、２はアセトン、３は２−プロパノールの濃度をそれぞれ表す。３２時間から９３時間のＣＯ２増加量で計算した量子効率は、１．４×１０−３％であった。 FIG. 8 shows the measurement results when ultraviolet light from a mercury lamp is used as lamp light (λ = 310 to 370 nm, 400 mW / cm 2 , absorptance = 98.8%). The initial concentration of 2-propanol is 294 ppm. In FIG. 8, 1 represents the concentration of CO 2 , 2 represents acetone, and 3 represents the concentration of 2-propanol. The quantum efficiency calculated with the CO 2 increase from 32 hours to 93 hours was 1.4 × 10 −3 %.
また、図９はランプ光として水銀キセノンランプによる可視光を用いた場合（λ＝４３７ｎｍ、３０ｍＷ／ｃｍ２、吸収率＝９８．８％）の結果である。尚、２−プロパノールの初期濃度は、２４７ｐｐｍである。図９中、４はＣＯ２、５はアセトン、６は２−プロパノールの濃度をそれぞれ表す。５６５時間から８５３時間のＣＯ２増加量で計算した量子効率は、２．４×１０−３％であった。この結果から、可視光においても紫外光とほぼ同様の光触媒活性が得られることが分かった。 FIG. 9 shows the results when visible light from a mercury xenon lamp is used as the lamp light (λ = 437 nm, 30 mW / cm 2 , absorptance = 98.8%). The initial concentration of 2-propanol is 247 ppm. In FIG. 9, 4 represents the concentration of CO 2 , 5 represents acetone, and 6 represents the concentration of 2-propanol. The quantum efficiency calculated with the CO 2 increase from 565 hours to 853 hours was 2.4 × 10 −3 %. From this result, it was found that substantially the same photocatalytic activity as that of ultraviolet light can be obtained in visible light.
以上より、ε−Ｆｅ２Ｏ３と同じ結晶構造を有する試料においては、磁気特性のみならず光触媒活性を得ることができることが分かった。 From the above, it was found that a sample having the same crystal structure as ε-Fe 2 O 3 can obtain not only magnetic properties but also photocatalytic activity.
本発明は、本実施形態に限定されるものではなく、本発明の要旨の範囲内で種々の変形実施が可能である。 The present invention is not limited to this embodiment, and various modifications can be made within the scope of the gist of the present invention.
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