JP4071381B2 - Honeycomb filter and manufacturing method thereof - Google Patents

Honeycomb filter and manufacturing method thereof Download PDF

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JP4071381B2
JP4071381B2 JP02295899A JP2295899A JP4071381B2 JP 4071381 B2 JP4071381 B2 JP 4071381B2 JP 02295899 A JP02295899 A JP 02295899A JP 2295899 A JP2295899 A JP 2295899A JP 4071381 B2 JP4071381 B2 JP 4071381B2
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silicon carbide
silica film
sintered body
base material
honeycomb filter
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JP2000218165A (en
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健 二宮
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Ibiden Co Ltd
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Ibiden Co Ltd
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Description

【０００１】
【発明の属する技術分野】
本発明はディーゼルエンジン等の内燃機関における排気ガスを浄化処理するために使用されるハニカムフィルタに係り、詳しくはその強度向上に関する。
【０００２】
【従来の技術】
従来、例えばディーゼルエンジンの排気ガスを浄化するために、耐熱性及び熱伝導性に優れた多孔質炭化珪素焼結体をハニカム状に形成したハニカムフィルタが用いられている。このハニカムフィルタをディーゼルエンジンの排気側に接続し、このフィルタによって排気ガス中のスス（カーボン）,ＮＯｘ及びＨＣ等を酸化分解するようになっている。
【０００３】
このようなハニカムフィルタの破壊強度を向上するためには、炭化珪素の焼成温度及び焼成時間を最適化することにより炭化珪素粒子同士のネック（結合部分）を成長させたり、炭化珪素粒子の粒度分布を最適化することによりネックの数を増加させたりする方法がある。
【０００４】
【発明が解決しようとする課題】
しかしながら、いずれの方法を用いて多孔質炭化珪素焼結体を製造しても、多孔質炭化珪素焼結体の強度の上限があり、さらなる強度の向上を望むことはできない。また、多孔質炭化珪素焼結体よりなるハニカムフィルタには、排気ガス中のパティキュレートの濾過に適した気孔径及び気孔率が存在する。このような気孔径、気孔率を備えた多孔質炭化珪素焼結体を得るためには、炭化珪素粒子の粒度分布や炭化珪素の焼成温度及び焼成時間にも制限が加えられる。
【０００５】
従って、このように製造されたハニカムフィルタの中には十分な強度がないため、捕集されたパティキュレート中のススの燃焼再生時に発生する熱応力に耐え切れず、破壊してしまうものがある。
【０００６】
本発明は上記の事情を考慮してなされたものであって、その目的は多孔質炭化珪素焼結体よりなるハニカムフィルタの強度を向上することができ、極めて簡単な方法によって多孔質炭化珪素焼結体の孔部内面に所望の厚さのシリカ膜を確実に形成することが可能なハニカムフィルタ及びその製造方法を提供することにある。
【０００７】
【課題を解決するための手段】
上記の目的を達成するために、請求項１に記載の発明は、ハニカム状に形成された多孔質炭化珪素焼結体の孔部内面に強度増加用のシリカ膜が形成され、そのシリカ膜を含む多孔質炭化珪素焼結体の酸素濃度は１wt％〜１０wt％としたことを要旨とする。
【０００８】
請求項２に記載の発明は、請求項１に記載のハニカムフィルタにおいて、前記シリカ膜を含む多孔質炭化珪素焼結体中の酸素は炭化珪素粒子の表層部に存在することを要旨とする。
【０００９】
請求項３に記載の発明は、予めハニカム状に形成した多孔質炭化珪素焼結体を酸化雰囲気にて８００℃〜１６００℃で５〜１００時間加熱することにより、この焼結体の孔部内面において前記焼結体の炭化珪素の一部を酸化して強度増加用のシリカ膜を形成するようにしたハニカムフィルタの製造方法を要旨とする。
【００１０】
請求項３に記載の製造方法によってハニカムフィルタを製造すると、多孔質炭化珪素焼結体の孔部内面において、炭化珪素の一部が酸化されて、炭化珪素粒子の表層部にシリカ膜が形成される。シリカ膜を含む多孔質炭化珪素焼結体の酸素濃度は１wt％〜１０wt％の範囲であることが必要である。このシリカ膜によって炭化珪素粒子間のネックが成長するとともに、ネックの結合角度が大きくなってネックの結合端部が滑らかになり、結合強度が向上するとともに、応力集中が緩和され、ハニカムフィルタの破壊強度が向上する。
【００１１】
【発明の実施の形態】
以下、本発明の一実施形態を図面に従って説明する。
図１及び図２に示すように、ハニカムフィルタ１の基材２は高い融点（〜３０００℃）を有する多孔質炭化珪素焼結体によってハニカム状に形成されると共に、全体として四角柱状をなしている。なお、基材２は２０００〜２１００℃の温度で焼結されている。そして、この基材２には軸線方向に平行に延びる多数のガス通過孔３が形成され、各ガス通過孔３の供給側及び排出側のいずれか一端が炭化珪素質の小片４によって交互に封止されている。この基材２において、各ガス通過孔３の内壁面には所定の酸素濃度（１〜１０wt％）を有するシリカ膜が形成されている。
【００１２】
そこで、基材２の製造方法について説明すると、先ず、炭化珪素粉末を主成分とする原料により、公知の方法に従ってハニカム状基材２を焼成する。このとき、図３，４に示すように、基材２における炭化珪素粒子６同士は互いにネック７にて結合しており、炭化珪素粒子６間のネック７の結合角度は小さくネック７の結合端部は先鋭状になっている。従って、この状態で基材２に曲げ荷重が作用すると、ネック７の結合端部に応力が集中する。
【００１３】
そして、この基材２を炭化珪素製の炉に入れ、炉内を空気雰囲気、すなわち酸化雰囲気とするとともに、炉内の温度を５〜１００時間にわたって８００〜１６００℃の範囲の温度に保持する。
【００１４】
この加熱温度が８００℃未満であると、酸化反応が起こり難く、１６００℃を越えると、酸化反応が進みすぎて、シリカ膜が焼結体内部まで形成されて、強度低下を招く。
【００１５】
上記の加熱処理により、図５，６に示すように、各ガス通過孔３の内壁面及び基材２の表面において、炭化珪素粒子６の表層部が酸化され、所定の酸素濃度（１〜１０wt％）のシリカ膜８が形成される。このシリカ膜８によって炭化珪素粒子６間のネック７が成長するとともに、ネック７の結合角度が大きくなってネック７の結合端部が滑らかになる。従って、ネック７の結合強度が向上するとともに、ネック７の結合端部での応力集中が緩和され、基材２の破壊強度が向上する。このシリカ膜の生成量は前記空気量，加熱時間，加熱温度等に依存して変化するため、これらを制御することにより、所望の酸素濃度の均一なシリカ膜８を形成できる。
【００１６】
その後、前記シリカ膜８に、白金に代表される白金族元素やその他の金属元素及びその酸化物等からなる酸化触媒を担持させ、ガス通過孔３の供給側及び排出側のいずれか一端を炭化珪素質の小片４によって交互に封止すれば、内燃機関等の排気ガスを浄化するためのハニカムフィルタ１が形成される。
【００１７】
そして、排気ガスが排気通路５内において、図１に矢印Ａで示すように、その供給側からハニカムフィルタ１内に導入されると、ガス通過孔３間の壁部により、排気ガス中のススやＨＣ等が濾過されると共に、シリカ膜８上の触媒により、燃焼再生される。そして、浄化された排気ガスが矢印Ｂで示すように、ハニカムフィルタ１から排出される。
【００１８】
【実施例】
以下、実施例により本発明をさらに具体的に説明する。
（実施例１）
炭化珪素粉末を主成分とする原料の押出成形加工により、図２において辺Ｌ１，Ｌ２がそれぞれ３３mmの正方形状をなし、図１において長さＬ３が１５０mmの四角柱状をなすハニカム状基材２を形成した。このハニカム基材２において、辺Ｌ１，Ｌ２に沿って正方形状の開口部を有する１８個のガス通過孔３を形成し、ガス通過孔３の開口部の一辺Ｗを１．８mm、壁厚Ｄを０．３６mmに設定した。この基材２を炭化珪素製の炉内に入れ、炉内を空気雰囲気とするとともに、１４００℃で３０時間にわたって加熱した。
【００１９】
その結果、表１に示すように、基材２の重量は１２６．１３５ｇから５．３３１ｇ増加して１３１．４６６ｇとなり、ガス通過孔３の内面全体に、酸素濃度として４．２３wt％のシリカ膜８が形成された。
【００２０】
次に、上記のようにして得られた基材２の破壊荷重をオートグラフを用いて３点曲げ法で測定した。なお、下部スパンは１３５mmとし、ヘッドスピードは０．５mm／分に設定した。シリカ膜８を含む基材２の破壊強度は、図７に示すように約５５０kg／cm2 であった。ちなみに、前記基材２と同様の形状寸法及びほぼ重量を備えシリカ膜を形成していない基材の破壊強度は、図７に示すように３５０kg／cm2 であった。
【００２１】
上記の基材２の圧力損失は、図８に示すように１０．５ＫＰａであった。図９に示すように、このときの気孔径は約８．５μmであり、気孔率は約４４．５％であった。ちなみに、シリカ膜を形成していない基材の圧力損失は９．８ＫＰａであり、このときの気孔径は約９μm、気孔率は約４６％であった。
【００２２】
（実施例２）
実施例１の基材２と同様の形状寸法を備えた多孔質炭化珪素焼結体よりなる基材２を、空気雰囲気の炉内で１４５０℃で９０時間にわたって加熱した。
【００２３】
その結果、表１に示すように、基材２の重量は１２５．１２１ｇから１０．５５２ｇ増加して１３５．６７３ｇとなり、ガス通過孔３の内面全体に、酸素濃度として８．４３wt％のシリカ膜が形成された。
【００２４】
次に、上記のようにして得られた基材２の破壊荷重を実施例１と同様にして測定した。この実施例のシリカ膜８を含む基材２の破壊強度は、図７に示すように約４５０kg／cm2 であった。
【００２５】
上記の基材２の圧力損失は、図８に示すように１２．６ＫＰａであった。図９に示すように、このときの気孔径は約８．１μmであり、気孔率は約４４％であった。
【００２６】
（比較例１）
実施例１の基材２と同様の形状寸法を備えた多孔質炭化珪素焼結体よりなる基材２を、空気雰囲気の炉内で１３００℃で３００時間にわたって加熱した。
【００２７】
その結果、表１に示すように、基材２の重量は１２５．５６２ｇから１６．２５７ｇ増加して１４１．８１９ｇとなり、ガス通過孔３の内面全体に、酸素濃度として１２．９４wt％のシリカ膜が形成された。
【００２８】
次に、上記のようにして得られた基材２の破壊荷重を実施例１と同様にして測定した。この実施例のシリカ膜８を含む基材２の破壊強度は、図７に示すように約４６０kg／cm2 であった。
【００２９】
上記の基材２の圧力損失は、図８に示すように９．９ＫＰａであった。図９に示すように、このときの気孔径は約８．９μmであり、気孔率は約４５．５％であった。
【００３０】
（比較例２）
実施例１の基材２と同様の形状寸法を備えた多孔質炭化珪素焼結体よりなる基材２を、空気雰囲気の炉内で１３００℃で４時間にわたって加熱した。
【００３１】
その結果、表１に示すように、基材２の重量は１２５．４７９ｇから１．００２ｇ増加して１２６．４８１ｇとなり、ガス通過孔３の内面全体に、酸素濃度として０．７９９wt％のシリカ膜が形成された。
【００３２】
次に、上記のようにして得られた基材２の破壊荷重を実施例１と同様にして測定した。この実施例のシリカ膜８を含む基材２の破壊強度は、シリカ膜を形成していない基材の破壊強度３５０kg／cm2 以下であった。
【００３３】
上記の基材２の圧力損失は、図８に示すように１５ＫＰａよりはるかに上回っていた。図９に示すように、このときの気孔径も８μmを下回っており、気孔率は４４％を下回っていた。
【００３４】
【表１】

Figure 0004071381
上記の実施例１，２及び比較例１，２の破壊強度の測定結果に基づいて、図７に示すように基材２の破壊強度と酸素濃度との関係を得ることができる。基材２の酸素濃度が１〜１０wt％の範囲であると、破壊強度は３９０kg／cm2 〜５５０kg／cm2 の範囲となり、シリカ膜が形成されていない基材の破壊強度の１．１１〜１．５７倍の破壊強度を得ることができる。また、基材２の酸素濃度が２〜８wt％の範囲であると、破壊強度は４８０kg／cm2 〜５５０kg／cm2 の範囲となり、シリカ膜が形成されていない基材の破壊強度の１．３７〜１．５７倍の破壊強度を得ることができる。さらに、基材２の酸素濃度が４〜６wt％の範囲であると、破壊強度は５４０kg／cm2 〜５５０kg／cm2 の範囲となり、シリカ膜が形成されていない基材の破壊強度の１．５４〜１．５７倍の破壊強度を得ることができる。
【００３５】
また、実施例１，２及び比較例１，２の圧力損失の測定結果に基づいて図８に示すように基材２の圧力損失と酸素濃度との関係を得ることができる。さらに、実施例１，２及び比較例１，２の気孔径及び気孔率の測定結果に基づいて図９に示すように基材２の気孔径及び気孔率と酸素濃度との関係を得ることができる。図８及び図９に基づいて、基材２の気孔径及び気孔率が低下すればするほど、圧力損失が大きくなることが分かる。
【００３６】
以上のことから、破壊強度を向上しつつ、圧力損失が１５ＫＰａ未満の基材２を得るためには、酸素濃度として１〜１０wt％のシリカ膜８を基材２の炭化珪素粒子の表層部に形成すればよい。また、１〜１０wt％のシリカ膜８は、基材２を酸化雰囲気にて８００℃〜１６００℃で５〜１００時間加熱することにより得ることができる。
【００３７】
また、酸素濃度として２〜８wt％のシリカ膜８を形成した基材２は、シリカ膜が形成されていない基材の破壊強度の１．３７〜１．５７倍の破壊強度を得ることができるとともに、圧力損失を１２．５ＫＰａ未満とすることができ、良好な特性のハニカムフィルタを得ることができる。
【００３８】
さらに、酸素濃度として４〜６wt％のシリカ膜８を形成した基材２は、シリカ膜が形成されていない基材の破壊強度の約１．５倍以上の破壊強度を得ることができるとともに、圧力損失を１２．５ＫＰａ未満とすることができ、より良好な特性のハニカムフィルタを得ることができる。
【００３９】
なお、上記実施形態は次のように変更してもよく、その場合でも同様の作用および効果を得ることができる。
・ 上記実施形態では、基材２は全体として四角柱状に形成したが、円柱状に形成した基材に実施してもよい。
【００４０】
・ 上記実施形態では、基材２を空気雰囲気で加熱することにより炭化珪素粒子を酸化させたが、炭化珪素粒子の酸化はこれに限定されるものではない。
次に、上記実施形態から把握できる他の技術的思想を以下に記載する。
【００４１】
・ 請求項１及び２のいずれか１項に記載のハニカムフィルタにおいて、
前記シリカ膜を含む多孔質炭化珪素焼結体の酸素濃度は２wt％〜８wt％であるハニカムフィルタ。
【００４２】
・ 請求項１及び２のいずれか１項に記載のハニカムフィルタにおいて、
前記シリカ膜を含む多孔質炭化珪素焼結体の酸素濃度は４wt％〜６wt％であるハニカムフィルタ。
【００４３】
【発明の効果】
以上詳述したように、請求項１及び２のいずれかに記載の発明は、ハニカムフィルタの破壊強度を向上することができるという優れた効果を発揮する。
【００４４】
請求項３に記載の発明は、炭化珪素焼結体の強度低下を招くことなく、極めて簡単な方法によって孔部内面に所望のシリカ膜を確実に形成することができるという優れた効果を発揮する。
【図面の簡単な説明】
【図１】本発明の製造方法によって製造されるハニカムフィルタの断面図。
【図２】同じくハニカムフィルタの側面図。
【図３】焼成時の多孔質炭化珪素焼結体を示す模式図。
【図４】同じく焼成時の多孔質炭化珪素焼結体を拡大して示す模式図。
【図５】シリカ膜を形成した多孔質炭化珪素焼結体を示す模式図。
【図６】同じくシリカ膜を形成した多孔質炭化珪素焼結体を拡大して示す模式図。
【図７】多孔質炭化珪素焼結体の破壊強度と酸素濃度との関係を示す線図。
【図８】多孔質炭化珪素焼結体の圧力損失と酸素濃度との関係を示す線図。
【図９】多孔質炭化珪素焼結体の気孔径及び気孔率と酸素濃度との関係を示す線図。
【符号の説明】
２…基材、３…ガス通過孔、６…炭化珪素粒子、７…ネック、８…シリカ膜。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a honeycomb filter used for purifying exhaust gas in an internal combustion engine such as a diesel engine, and more particularly to improvement in strength thereof.
[0002]
[Prior art]
Conventionally, in order to purify, for example, exhaust gas from a diesel engine, a honeycomb filter in which a porous silicon carbide sintered body excellent in heat resistance and thermal conductivity is formed in a honeycomb shape has been used. This honeycomb filter is connected to the exhaust side of a diesel engine, and this filter oxidizes and decomposes soot (carbon), NOx, HC and the like in the exhaust gas.
[0003]
In order to improve the fracture strength of such a honeycomb filter, the necking (bonding portion) between silicon carbide particles is grown by optimizing the firing temperature and firing time of silicon carbide, or the particle size distribution of silicon carbide particles. There is a method of increasing the number of necks by optimizing the above.
[0004]
[Problems to be solved by the invention]
However, even if a porous silicon carbide sintered body is produced using any method, there is an upper limit of the strength of the porous silicon carbide sintered body, and further improvement of the strength cannot be desired. Further, a honeycomb filter made of a porous silicon carbide sintered body has a pore diameter and a porosity suitable for filtering particulates in exhaust gas. In order to obtain a porous silicon carbide sintered body having such a pore diameter and porosity, restrictions are imposed on the particle size distribution of silicon carbide particles, the firing temperature and firing time of silicon carbide.
[0005]
Therefore, some honeycomb filters manufactured in this way do not have sufficient strength, and thus some of them cannot withstand the thermal stress generated during combustion regeneration of the soot in the collected particulates and break down. .
[0006]
The present invention has been made in consideration of the above circumstances, and the object thereof is to improve the strength of a honeycomb filter made of a porous silicon carbide sintered body. An object of the present invention is to provide a honeycomb filter capable of reliably forming a silica film having a desired thickness on the inner surface of a hole of a bonded body and a method for manufacturing the honeycomb filter.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, a silica film for increasing strength is formed on the inner surface of the hole of a porous silicon carbide sintered body formed in a honeycomb shape. The gist is that the oxygen concentration of the porous silicon carbide sintered body to be contained is 1 wt% to 10 wt%.
[0008]
The gist of the invention according to claim 2 is that, in the honeycomb filter according to claim 1, oxygen in the porous silicon carbide sintered body including the silica film exists in a surface layer portion of the silicon carbide particles.
[0009]
According to a third aspect of the present invention, a porous silicon carbide sintered body formed in a honeycomb shape in advance is heated in an oxidizing atmosphere at 800 ° C. to 1600 ° C. for 5 to 100 hours to thereby obtain a hole inner surface of the sintered body. The main point is a method for manufacturing a honeycomb filter in which a part of silicon carbide in the sintered body is oxidized to form a silica film for increasing strength.
[0010]
When a honeycomb filter is manufactured by the manufacturing method according to claim 3, a part of silicon carbide is oxidized on the inner surface of the hole of the porous silicon carbide sintered body, and a silica film is formed on the surface layer portion of the silicon carbide particles. The The oxygen concentration of the porous silicon carbide sintered body including the silica film needs to be in the range of 1 wt% to 10 wt%. This silica film grows the neck between the silicon carbide particles, increases the neck bond angle, smoothes the neck joint end, improves the bond strength, relaxes stress concentration, and destroys the honeycomb filter. Strength is improved.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIGS. 1 and 2, the base material 2 of the honeycomb filter 1 is formed in a honeycomb shape by a porous silicon carbide sintered body having a high melting point (˜3000 ° C.) and has a quadrangular prism shape as a whole. Yes. In addition, the base material 2 is sintered at the temperature of 2000-2100 degreeC. A plurality of gas passage holes 3 extending in parallel to the axial direction are formed in the base material 2, and one end of each gas passage hole 3 on the supply side and the discharge side is alternately sealed with silicon carbide small pieces 4. It has been stopped. In this base material 2, a silica film having a predetermined oxygen concentration (1 to 10 wt%) is formed on the inner wall surface of each gas passage hole 3.
[0012]
Therefore, a method for manufacturing the substrate 2 will be described. First, the honeycomb-shaped substrate 2 is fired with a raw material mainly composed of silicon carbide powder according to a known method. At this time, as shown in FIGS. 3 and 4, the silicon carbide particles 6 in the substrate 2 are bonded to each other at the neck 7, and the bonding angle of the neck 7 between the silicon carbide particles 6 is small, and the bonding end of the neck 7 is The part is sharp. Therefore, when a bending load acts on the base material 2 in this state, stress concentrates on the coupling end portion of the neck 7.
[0013]
And this base material 2 is put into the furnace made from silicon carbide, and while making the inside of an oven into an air atmosphere, ie, an oxidizing atmosphere, the temperature in a furnace is hold | maintained at the temperature of the range of 800-1600 degreeC over 5 to 100 hours.
[0014]
When the heating temperature is less than 800 ° C., the oxidation reaction hardly occurs. When the heating temperature exceeds 1600 ° C., the oxidation reaction proceeds excessively, and the silica film is formed to the inside of the sintered body, resulting in a decrease in strength.
[0015]
5 and 6, the surface layer portion of the silicon carbide particles 6 is oxidized on the inner wall surface of each gas passage hole 3 and the surface of the substrate 2 by the above heat treatment, and a predetermined oxygen concentration (1 to 10 wt. %) Of silica film 8 is formed. The silica film 8 grows the neck 7 between the silicon carbide particles 6 and increases the coupling angle of the neck 7 to make the coupling end of the neck 7 smooth. Therefore, the bond strength of the neck 7 is improved, the stress concentration at the joint end portion of the neck 7 is relaxed, and the breaking strength of the base material 2 is improved. Since the generated amount of the silica film changes depending on the amount of air, the heating time, the heating temperature, and the like, the silica film 8 having a desired oxygen concentration can be formed by controlling these.
[0016]
Thereafter, an oxidation catalyst composed of platinum group elements represented by platinum, other metal elements and oxides thereof is supported on the silica film 8, and either one of the supply side and the discharge side of the gas passage hole 3 is carbonized. By alternately sealing with the silicon small pieces 4, the honeycomb filter 1 for purifying exhaust gas from an internal combustion engine or the like is formed.
[0017]
When exhaust gas is introduced into the honeycomb filter 1 from the supply side in the exhaust passage 5 as indicated by an arrow A in FIG. 1, soot in the exhaust gas is formed by the wall portion between the gas passage holes 3. And HC and the like are filtered and regenerated by the catalyst on the silica film 8. The purified exhaust gas is then discharged from the honeycomb filter 1 as indicated by an arrow B.
[0018]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples.
Example 1
A honeycomb substrate 2 having a square column shape with sides L1 and L2 of 33 mm in FIG. 2 and a length L3 of 150 mm in FIG. Formed. In this honeycomb substrate 2, 18 gas passage holes 3 having square openings are formed along the sides L1 and L2, and one side W of the openings of the gas passage holes 3 is 1.8 mm, and the wall thickness D. Was set to 0.36 mm. This base material 2 was put in a silicon carbide furnace, and the furnace was made into an air atmosphere and heated at 1400 ° C. for 30 hours.
[0019]
As a result, as shown in Table 1, the weight of the substrate 2 increased from 126.135 g to 5.331 g to 131.466 g, and the silica film having an oxygen concentration of 4.23 wt% on the entire inner surface of the gas passage hole 3. 8 was formed.
[0020]
Next, the breaking load of the base material 2 obtained as described above was measured by a three-point bending method using an autograph. The lower span was set to 135 mm, and the head speed was set to 0.5 mm / min. The breaking strength of the substrate 2 including the silica film 8 was about 550 kg / cm 2 as shown in FIG. Incidentally, the breaking strength of the base material having the same shape and size and substantially the same weight as the base material 2 and having no silica film formed thereon was 350 kg / cm 2 as shown in FIG.
[0021]
The pressure loss of the substrate 2 was 10.5 KPa as shown in FIG. As shown in FIG. 9, the pore diameter at this time was about 8.5 μm, and the porosity was about 44.5%. Incidentally, the pressure loss of the base material on which the silica film was not formed was 9.8 KPa, the pore diameter at this time was about 9 μm, and the porosity was about 46%.
[0022]
(Example 2)
The base material 2 made of a porous silicon carbide sintered body having the same shape and dimensions as the base material 2 of Example 1 was heated at 1450 ° C. for 90 hours in a furnace in an air atmosphere.
[0023]
As a result, as shown in Table 1, the weight of the base material 2 increased from 125.121 g to 10.552 g to 135.673 g, and a silica film having an oxygen concentration of 8.43 wt% on the entire inner surface of the gas passage hole 3. Formed.
[0024]
Next, the breaking load of the base material 2 obtained as described above was measured in the same manner as in Example 1. The breaking strength of the substrate 2 including the silica film 8 of this example was about 450 kg / cm 2 as shown in FIG.
[0025]
The pressure loss of the substrate 2 was 12.6 KPa as shown in FIG. As shown in FIG. 9, the pore diameter at this time was about 8.1 μm, and the porosity was about 44%.
[0026]
(Comparative Example 1)
The base material 2 made of a porous silicon carbide sintered body having the same shape and dimensions as the base material 2 of Example 1 was heated in an air atmosphere furnace at 1300 ° C. for 300 hours.
[0027]
As a result, as shown in Table 1, the weight of the base material 2 increased by 16.257 g from 125.562 g to 141.819 g, and a silica film having an oxygen concentration of 12.94 wt% on the entire inner surface of the gas passage hole 3. Formed.
[0028]
Next, the breaking load of the base material 2 obtained as described above was measured in the same manner as in Example 1. The breaking strength of the substrate 2 including the silica film 8 of this example was about 460 kg / cm 2 as shown in FIG.
[0029]
The pressure loss of the substrate 2 was 9.9 KPa as shown in FIG. As shown in FIG. 9, the pore diameter at this time was about 8.9 μm, and the porosity was about 45.5%.
[0030]
(Comparative Example 2)
The base material 2 made of a porous silicon carbide sintered body having the same shape and dimensions as the base material 2 of Example 1 was heated at 1300 ° C. for 4 hours in a furnace in an air atmosphere.
[0031]
As a result, as shown in Table 1, the weight of the base material 2 increased from 125.479 g to 1.002 g to 126.481 g, and a silica film having an oxygen concentration of 0.799 wt% on the entire inner surface of the gas passage hole 3. Formed.
[0032]
Next, the breaking load of the base material 2 obtained as described above was measured in the same manner as in Example 1. The breaking strength of the substrate 2 including the silica film 8 in this example was 350 kg / cm 2 or less of the breaking strength of the substrate not formed with the silica film.
[0033]
The pressure loss of the substrate 2 was much higher than 15 KPa as shown in FIG. As shown in FIG. 9, the pore diameter at this time was also less than 8 μm, and the porosity was less than 44%.
[0034]
[Table 1]
Figure 0004071381
Based on the measurement results of the breaking strengths of Examples 1 and 2 and Comparative Examples 1 and 2, the relationship between the breaking strength of the substrate 2 and the oxygen concentration can be obtained as shown in FIG. When the oxygen concentration of the base material 2 is in the range of 110 wt.%, The breaking strength becomes in the range of 390kg / cm 2 ~550kg / cm 2 , 1.11~ breaking strength of the substrate silica film is not formed 1.57 times the breaking strength can be obtained. Further, when the oxygen concentration of the base material 2 is in the range of 2 to 8 wt%, breaking strength becomes in the range of 480kg / cm 2 ~550kg / cm 2 , the breaking strength of the substrate silica film is not formed 1. A breaking strength of 37 to 1.57 times can be obtained. Further, when the oxygen concentration of the base material 2 is in the range of 4～6Wt%, fracture strength becomes a range of 540kg / cm 2 ~550kg / cm 2 , the breaking strength of the substrate silica film is not formed 1. A breaking strength of 54 to 1.57 times can be obtained.
[0035]
Moreover, based on the measurement result of the pressure loss of Examples 1 and 2 and Comparative Examples 1 and 2, the relationship between the pressure loss and the oxygen concentration of the base material 2 can be obtained as shown in FIG. Furthermore, based on the measurement results of the pore diameter and porosity of Examples 1 and 2 and Comparative Examples 1 and 2, the relationship between the pore diameter and porosity of the substrate 2 and the oxygen concentration can be obtained as shown in FIG. it can. Based on FIG.8 and FIG.9, it turns out that a pressure loss becomes large, so that the pore diameter and porosity of the base material 2 fall.
[0036]
From the above, in order to obtain the base material 2 having a pressure loss of less than 15 KPa while improving the fracture strength, the silica film 8 having an oxygen concentration of 1 to 10 wt% is formed on the surface layer portion of the silicon carbide particles of the base material 2. What is necessary is just to form. Further, the 1-10 wt% silica film 8 can be obtained by heating the substrate 2 at 800 ° C.-1600 ° C. for 5-100 hours in an oxidizing atmosphere.
[0037]
Moreover, the base material 2 in which the silica film 8 having an oxygen concentration of 2 to 8 wt% can obtain a breaking strength of 1.37 to 1.57 times the breaking strength of the base material on which no silica film is formed. At the same time, the pressure loss can be less than 12.5 KPa, and a honeycomb filter having good characteristics can be obtained.
[0038]
Furthermore, the base material 2 on which the silica film 8 having an oxygen concentration of 4 to 6 wt% can obtain a breaking strength of about 1.5 times or more of the breaking strength of the base material on which the silica film is not formed, The pressure loss can be less than 12.5 KPa, and a honeycomb filter with better characteristics can be obtained.
[0039]
In addition, the said embodiment may be changed as follows and the same effect | action and effect can be acquired even in that case.
In the above embodiment, the base material 2 is formed in a quadrangular prism shape as a whole, but may be implemented on a base material formed in a cylindrical shape.
[0040]
In the above embodiment, the silicon carbide particles are oxidized by heating the substrate 2 in an air atmosphere, but the oxidation of the silicon carbide particles is not limited to this.
Next, other technical ideas that can be grasped from the above embodiment will be described below.
[0041]
In the honeycomb filter according to any one of claims 1 and 2,
A honeycomb filter in which the porous silicon carbide sintered body including the silica film has an oxygen concentration of 2 wt% to 8 wt%.
[0042]
In the honeycomb filter according to any one of claims 1 and 2,
A honeycomb filter in which the porous silicon carbide sintered body including the silica film has an oxygen concentration of 4 wt% to 6 wt%.
[0043]
【The invention's effect】
As described above in detail, the invention according to any one of claims 1 and 2 exhibits an excellent effect that the breaking strength of the honeycomb filter can be improved.
[0044]
The invention according to claim 3 exhibits an excellent effect that a desired silica film can be reliably formed on the inner surface of the hole by an extremely simple method without causing a decrease in strength of the silicon carbide sintered body. .
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a honeycomb filter manufactured by the manufacturing method of the present invention.
FIG. 2 is a side view of the honeycomb filter.
FIG. 3 is a schematic view showing a porous silicon carbide sintered body during firing.
FIG. 4 is an enlarged schematic view of a porous silicon carbide sintered body similarly fired.
FIG. 5 is a schematic view showing a porous silicon carbide sintered body on which a silica film is formed.
FIG. 6 is an enlarged schematic view showing a porous silicon carbide sintered body similarly formed with a silica film.
FIG. 7 is a diagram showing a relationship between fracture strength and oxygen concentration of a porous silicon carbide sintered body.
FIG. 8 is a diagram showing the relationship between pressure loss and oxygen concentration of a porous silicon carbide sintered body.
FIG. 9 is a diagram showing the relationship between the pore diameter and porosity of a porous silicon carbide sintered body and the oxygen concentration.
[Explanation of symbols]
2 ... base material, 3 ... gas passage hole, 6 ... silicon carbide particle, 7 ... neck, 8 ... silica film.

Claims (3)

ハニカム状に形成された多孔質炭化珪素焼結体の孔部内面に強度増加用のシリカ膜が形成され、そのシリカ膜を含む多孔質炭化珪素焼結体の酸素濃度は１wt％〜１０wt％であるハニカムフィルタ。A silica film for increasing strength is formed on the inner surface of the hole of the porous silicon carbide sintered body formed in a honeycomb shape, and the oxygen concentration of the porous silicon carbide sintered body including the silica film is 1 wt% to 10 wt%. There is a honeycomb filter. 前記シリカ膜を含む多孔質炭化珪素焼結体中の酸素は炭化珪素粒子の表層部に存在する請求項１に記載のハニカムフィルタ。The honeycomb filter according to claim 1, wherein oxygen in the porous silicon carbide sintered body including the silica film exists in a surface layer portion of the silicon carbide particles. 予めハニカム状に形成した多孔質炭化珪素焼結体を酸化雰囲気にて８００℃〜１６００℃で５〜１００時間加熱することにより、この焼結体の孔部内面において前記焼結体の炭化珪素の一部を酸化して強度増加用のシリカ膜を形成するようにしたハニカムフィルタの製造方法。By heating a porous silicon carbide sintered body formed in a honeycomb shape in advance in an oxidizing atmosphere at 800 ° C. to 1600 ° C. for 5 to 100 hours, A method for manufacturing a honeycomb filter, wherein a silica film for increasing strength is formed by partially oxidizing.
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JP4381011B2 (en) * 2003-03-14 2009-12-09 東京窯業株式会社 Silicon carbide honeycomb structure and ceramic filter using the same
KR100666430B1 (en) 2003-08-12 2007-01-11 니뽄 가이시 가부시키가이샤 Silicon carbide-based catalyst body and method for preparation thereof
WO2006001503A1 (en) 2004-06-25 2006-01-05 Ibiden Co., Ltd. Filter, method for producing same and exhaust purification system
DE102006028636A1 (en) * 2006-06-22 2007-12-27 Robert Bosch Gmbh Filter for purifying a particle-containing gas stream and process for its preparation
JP5228788B2 (en) * 2008-10-21 2013-07-03 住友大阪セメント株式会社 Metal catalyst-supported particles, production method thereof, metal catalyst-supported particle dispersion and catalyst
JPWO2011052676A1 (en) * 2009-10-30 2013-03-21 住友大阪セメント株式会社 Exhaust gas purification device for internal combustion engine
JP2012106223A (en) * 2010-04-09 2012-06-07 Ibiden Co Ltd Honeycomb structure
EP2441741A1 (en) 2010-10-13 2012-04-18 Ibiden Co., Ltd. Honeycomb structured body and exhaust gas purifying apparatus
EP2441513B1 (en) 2010-10-13 2013-08-07 Ibiden Co., Ltd. Honeycomb catalyst body and method for manufacturing honeycomb catalyst body
WO2013145245A1 (en) * 2012-03-29 2013-10-03 イビデン株式会社 Honeycomb structure, honeycomb filter for exhaust gas purification, and exhaust gas purification device
JPWO2013175552A1 (en) * 2012-05-21 2016-01-12 イビデン株式会社 Honeycomb filter, exhaust gas purification device, and exhaust gas purification method
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