JP7470291B2 - Carbide-bonded polycrystalline diamond electrode material - Google Patents
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- 239000010432 diamond Substances 0.000 title claims description 107
- 229910003460 diamond Inorganic materials 0.000 title claims description 105
- 239000007772 electrode material Substances 0.000 title claims description 16
- 239000002245 particle Substances 0.000 claims description 49
- 229910052723 transition metal Inorganic materials 0.000 claims description 23
- 150000003624 transition metals Chemical class 0.000 claims description 17
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 12
- -1 transition metal carbides Chemical class 0.000 claims description 7
- 239000000126 substance Substances 0.000 claims description 3
- 238000005868 electrolysis reaction Methods 0.000 claims description 2
- 239000012779 reinforcing material Substances 0.000 claims 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 22
- 229910052751 metal Inorganic materials 0.000 description 19
- 239000002184 metal Substances 0.000 description 19
- 238000005245 sintering Methods 0.000 description 17
- 239000000463 material Substances 0.000 description 16
- 239000000758 substrate Substances 0.000 description 15
- 238000006243 chemical reaction Methods 0.000 description 14
- 239000010410 layer Substances 0.000 description 14
- 238000000034 method Methods 0.000 description 14
- 239000000843 powder Substances 0.000 description 14
- 239000010955 niobium Substances 0.000 description 12
- 239000010936 titanium Substances 0.000 description 12
- 229910052758 niobium Inorganic materials 0.000 description 10
- 238000004090 dissolution Methods 0.000 description 9
- 239000000047 product Substances 0.000 description 9
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 8
- 230000008569 process Effects 0.000 description 8
- 229910052719 titanium Inorganic materials 0.000 description 7
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 6
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 6
- 239000000203 mixture Substances 0.000 description 6
- 239000006061 abrasive grain Substances 0.000 description 5
- 239000007789 gas Substances 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- 239000011230 binding agent Substances 0.000 description 4
- 239000002775 capsule Substances 0.000 description 4
- 229910017052 cobalt Inorganic materials 0.000 description 4
- 239000010941 cobalt Substances 0.000 description 4
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 4
- 238000005520 cutting process Methods 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 150000002739 metals Chemical class 0.000 description 4
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 3
- 229910052796 boron Inorganic materials 0.000 description 3
- 238000005755 formation reaction Methods 0.000 description 3
- 239000000395 magnesium oxide Substances 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- 229910052715 tantalum Inorganic materials 0.000 description 3
- 229910052726 zirconium Inorganic materials 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 238000005229 chemical vapour deposition Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
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- 239000002994 raw material Substances 0.000 description 2
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- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 2
- MTPVUVINMAGMJL-UHFFFAOYSA-N trimethyl(1,1,2,2,2-pentafluoroethyl)silane Chemical compound C[Si](C)(C)C(F)(F)C(F)(F)F MTPVUVINMAGMJL-UHFFFAOYSA-N 0.000 description 2
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 229910009043 WC-Co Inorganic materials 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 238000010306 acid treatment Methods 0.000 description 1
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 238000005422 blasting Methods 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 150000001639 boron compounds Chemical class 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- NNSIWZRTNZEWMS-UHFFFAOYSA-N cobalt titanium Chemical compound [Ti].[Co] NNSIWZRTNZEWMS-UHFFFAOYSA-N 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
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- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000012805 post-processing Methods 0.000 description 1
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- 239000002356 single layer Substances 0.000 description 1
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- 229910052721 tungsten Inorganic materials 0.000 description 1
Description
本発明はダイヤモンド電極、特にオゾン水発生や様々な規模における汚染水の浄化を目的とした水処理設備用に適する導電性のダイヤモンドを用いた電極素材、並びにその製造方法に関する。 The present invention relates to diamond electrodes, in particular to electrode materials using conductive diamond suitable for use in water treatment facilities for generating ozone water and purifying polluted water on various scales, and to methods for manufacturing the same.
水処理に利用可能な導電性ダイヤモンド電極を得る方法として、シリコンまたはニオブ、タンタルなどの金属基板上に、CVD法によってボロンドープのダイヤモンド膜を形成する方式が広く用いられている。形成された膜の表面は必ずしも平坦でなく、むしろ凹凸のある方が有効表面積が大きく、電極として有利とされ、大きな表面積を得るために、予め基板材料表面にパターンを形成しておく方法も広く採用されている。 A widely used method for obtaining conductive diamond electrodes that can be used in water treatment is to form a boron-doped diamond film on a metal substrate such as silicon or niobium or tantalum using the CVD method. The surface of the film formed is not necessarily flat; rather, unevenness increases the effective surface area and is considered advantageous as an electrode, so a method of forming a pattern on the surface of the substrate material in advance to obtain a large surface area is also widely used.
CVD法によるボロンドープダイヤモンド(BDD)の形成は、高純度のダイヤモンドの形成が可能であり、また形成過程においてもボロンのドープ量を任意に変えることができるメリットを有している。しかし形成反応に長時間を要し、多量のガスを必要とすることから生産性は高くない。 The formation of boron-doped diamond (BDD) using the CVD method has the advantage that it is possible to form high-purity diamond, and the amount of boron doped during the formation process can be changed as desired. However, the formation reaction takes a long time and requires a large amount of gas, so productivity is not high.
ボロンドープダイヤモンドは高圧力・高温を用いた合成反応においても、出発原料中にボロン化合物を添加する方法を用いて砥粒の形で製造されている。高圧力・高温技術はダイヤモンドの粉末を焼結した硬質材料の多結晶ダイヤモンド(PCD)として、我が国においても1962年頃から切削工具素材、耐摩耗材料の製造に用いられている。(特許文献１) Boron-doped diamond is also produced in the form of abrasive grains by adding a boron compound to the starting material in a synthesis reaction using high pressure and high temperature. High pressure and high temperature technology has been used in Japan since around 1962 to produce cutting tool materials and wear-resistant materials, producing polycrystalline diamond (PCD), a hard material made by sintering diamond powder. (Patent Document 1)
工具素材、耐摩耗材料を目指した多結晶ダイヤモンドには、抜群の硬さに加えて靭性の付与も要求されることから、微粉原料を用いた緻密品が要求されている。このことから究極の多結晶ダイヤモンドとして、単結晶ダイヤモンドを超える高い硬度を持つバインダレスのナノ多結晶ダイヤモンドが開発されている。この多結晶は、結合材を含まないため耐熱性が高く、また構成粒子が数十nm と微細であることから、高強度でシャープな刃先の形成が可能になっている。（非特許文献１） Polycrystalline diamond, which is intended to be used as a tool material and wear-resistant material, is required to have not only outstanding hardness but also toughness, so there is a demand for dense products made from fine powder raw materials. For this reason, binderless nano-polycrystalline diamond, which has a hardness exceeding that of single-crystal diamond, has been developed as the ultimate polycrystalline diamond. This polycrystalline diamond has high heat resistance because it does not contain a binder, and the constituent particles are very fine, measuring several tens of nanometers, making it possible to form a high-strength, sharp cutting edge. (Non-Patent Document 1)
一般的な多結晶ダイヤモンドの製造では、焼結助剤としてコバルト系金属が主として用いられ、超高圧力下の高温状態における溶融金属の存在によって、ダイヤモンド粒子の再配列、溶解・析出機構による粒子間の結合、緻密化が進行すると理解されている。 In the general production of polycrystalline diamond, cobalt-based metals are primarily used as sintering aids, and it is understood that the presence of molten metal at high temperatures and under ultra-high pressure promotes rearrangement of diamond particles, bonding between particles through a dissolution and precipitation mechanism, and densification.
コバルト系の焼結助剤金属は、焼結後もダイヤモンド粒子間に残留し、焼結体の緻密性、靭性向上に寄与しているが、高温状態ではダイヤモンドの黒鉛化を促進する逆触媒になることから、高温に曝される用途向けには、粒子間に残留する金属を酸溶解処理によって除去し、ダイヤモンド粒子間の直接結合を維持しつつ、5～30容量％の空孔を持つ焼結体も提案されている。（特許文献２） Cobalt-based sintering aid metals remain between the diamond particles even after sintering, contributing to improved density and toughness of the sintered body, but at high temperatures they become an inverse catalyst that promotes graphitization of diamond. For applications exposed to high temperatures, a sintered body with 5 to 30% voids by volume has been proposed, in which the metal remaining between the particles is removed by acid dissolution treatment, while maintaining the direct bond between the diamond particles. (Patent Document 2)
一方耐熱性の高い焼結体として、結合材に炭化物を用いた多結晶ダイヤモンドも知られており、焼結反応の際に生じた遷移金属炭化物を結合材に用いる先行技術としては、以下の各例が公知である。いずれも切削工具などの素材として、緻密な焼結品の製作を目的としている。 On the other hand, polycrystalline diamond, which uses carbide as a binder, is also known as a highly heat-resistant sintered body, and the following examples are known as prior art that use transition metal carbides produced during the sintering reaction as a binder. All of these are intended to produce dense sintered products as materials for cutting tools, etc.
[1] ダイヤモンド粉体とチタン、ジルコニウム等の金属粉体とを混合し、ダイヤモンド安定領域の高温・高圧条件で金属を溶融し、ダイヤモンドとの反応によって生成した金属炭化物を介してダイヤモンド粉体を固結(焼結)する方法が示されており、焼結温度として最高1950℃の記載がある。（特許文献３） [1] This method involves mixing diamond powder with metal powders such as titanium and zirconium, melting the metal under high temperature and pressure conditions in the diamond stability range, and solidifying (sintering) the diamond powder through the metal carbide produced by the reaction with the diamond. A maximum sintering temperature of 1950°C is listed. (Patent Document 3)
[2] 耐熱性の高い焼結体としては、ホウ素を含有するダイヤモンド粉末を、アルカリ土類金属の炭酸塩を結合材に用いて1600℃以上の高温に曝した焼結体が知られており、耐熱性に加えて放電加工が可能な工具素材になることが示されている。（特許文献４） [2] A known example of a highly heat-resistant sintered body is a sintered body made by exposing boron-containing diamond powder to high temperatures of over 1600°C using an alkaline earth metal carbonate as a binder. It has been shown that this sintered body can be used as a tool material that is heat-resistant and can be used for electric discharge machining. (Patent Document 4)
本発明は導電電極素材の製造において、加圧焼結技術を用いて予め合成された砥粒状の導電性ダイヤモンドを多孔質の一体化品とすることにより、導電電極素材の生産性を高め、併せて電極形状、特性の多様化を可能にすることを課題とする。 The objective of this invention is to increase the productivity of conductive electrode materials by forming a porous, integrated product from pre-synthesized abrasive conductive diamond using pressure sintering technology in the manufacture of conductive electrode materials, while also enabling diversification of electrode shapes and characteristics.
本発明は導電性ダイヤモンドの加圧焼結に際して、焼結促進剤として予めダイヤモンド粒子間に多量の遷移金属を介在させることによって、高温下におけるダイヤモンドと遷移金属との反応によって生じた遷移金属炭化物を介してダイヤモンド粒子を接合すると共に、粒子間隔の広い焼結体を作製し、続く後工程において粒子間に残留する金属を溶出させて多孔質焼結体を得ることを骨子としている。 The gist of the present invention is that when conducting sintering under pressure, a large amount of transition metal is placed between diamond particles as a sintering accelerator in advance, and the diamond particles are joined via the transition metal carbide produced by the reaction between diamond and the transition metal at high temperatures, and a sintered body with wide particle spacing is produced. In a subsequent process, the metal remaining between the particles is dissolved to obtain a porous sintered body.
本発明の主旨は、導電性合成ダイヤモンド粒子を粒子間に空隙を包含せしめて接合一体化させた、多孔質ダイヤモンド集合体で構成されるダイヤモンド電極素材であって、該ダイヤモンド集合体における隣接ダイヤモンド粒子同士がダイヤモンド粒子表面に形成された遷移金属炭化物を介した間接結合によって接合し、かつダイヤモンド集合体全体に対する容積比において20％を超える空隙を有し、さらに分布した空隙が相互に導通して外表面に開口し、水電解操作において、発生ガス及び周囲の水が通過する空間を提供する多結晶ダイヤモンド電極素材にある。
The gist of the present invention is a diamond electrode material composed of a porous diamond aggregate in which conductive synthetic diamond particles are bonded together with voids between them, wherein adjacent diamond particles in the diamond aggregate are indirectly bonded together via transition metal carbides formed on the surfaces of the diamond particles, and the diamond aggregate has voids that account for more than 20% of the volume of the entire diamond aggregate, and the distributed voids are interconnected and open to the outer surface, providing spaces through which generated gas and surrounding water can pass during water electrolysis .
前記の電極素材は以下の各段階を含む工程によって効果的に製造され、従ってこれらの工程もまた本発明の要旨の一面を構成する：
(1) 導電性のバルクダイヤモンド粒子間に遷移金属粉末を配置し、
(2) 全体を加圧加熱処理に供して、ダイヤモンド粒子に接している遷移金属を炭化物に変換すると共に該炭化物を介してダイヤモンド粒子間の接合を行い、
(3) ダイヤモンド粒子間に残留した遷移金属粉末を溶解除去することによって、粒子間に導通した空隙を形成する。
The electrode material is advantageously manufactured by a process which includes the steps of:
(1) Placing transition metal powder between conductive bulk diamond particles;
(2) subjecting the whole to a pressure and heat treatment to convert the transition metal in contact with the diamond particles into carbides and to bond the diamond particles together via the carbides;
(3) The transition metal powder remaining between the diamond particles is dissolved and removed to form conductive voids between the particles.
本発明によれば、高圧力・高温を用いた多結晶ダイヤモンドの製造において、試料の加熱時間は10～20分で十分であり、昇圧・降圧時間を加えても反応サイクルは30分程度であることから、CVD反応に比べて1/10以下の時間で導電電極素材の製造が可能となる。 According to the present invention, in the production of polycrystalline diamond using high pressure and high temperature, the heating time of the sample is sufficient at 10 to 20 minutes, and even if the time for increasing and decreasing the pressure is included, the reaction cycle is about 30 minutes, making it possible to produce conductive electrode materials in less than one-tenth the time required for CVD reactions.
本発明において使用する遷移金属はＴi、Ｚr、Ｈf、Ｎb、Ｔa、Ｍo及びＷが好適で、これらの金属種から選ばれる一種又は複数種を組成又は配合して利用することができる。これらの金属は炭素との化合性が強いため、両材を隣接配置して加熱することにより境界部に炭化物層が形成される。 The transition metals used in the present invention are preferably Ti, Zr, Hf, Nb, Ta, Mo and W, and one or more of these metals can be used in a composition or blend. These metals have a strong affinity with carbon, so a carbide layer is formed at the boundary between the two materials by placing them adjacent to each other and heating them.
本発明の電極素材において、ダイヤモンド粒子間に介在させる遷移金属としては、後工程の酸処理によって溶出させる見地からＴi、Ｚrが適しており、価格の面からＴiが最適である。 In the electrode material of the present invention, Ti and Zr are suitable as transition metals to be interposed between diamond particles from the viewpoint of dissolving them in the acid treatment in the subsequent process, and Ti is the most suitable from the viewpoint of cost.
さらに液相の共存によるダイヤモンド粒子の再配列、ならびに部分的な溶解・析出機構によるダイヤモンド粒子間の直接接合を促進する目的で、これらの遷移金属にコバルトまたはニッケルを添加することもできる。 Cobalt or nickel can also be added to these transition metals to promote rearrangement of diamond particles through the coexistence of a liquid phase, as well as direct bonding between diamond particles through a partial dissolution/precipitation mechanism.
本発明の電極素材の製造において、ダイヤモンド粒子は導電性付与物質としてホウ素を含 有する、いわゆるボロンドープダイヤモンドを使用するのが便利である。このようなダイ ヤモンドは特殊砥粒として市販されており入手が容易である。なお導電性ダイヤモンドとしては窒素、リンをドープした品種も知られており、ボロンドープダイヤと同様に使用することができる。 In the manufacture of the electrode material of the present invention, it is convenient to use diamond particles that contain boron as a conductive material, i.e., so-called boron-doped diamond. Such diamonds are commercially available as special abrasive grains and are easy to obtain. There are also known conductive diamond varieties that are doped with nitrogen and phosphorus, which can be used in the same way as boron-doped diamond.
導電電極素材を目的とした焼結体においては、形状を保ち続けるだけの強度があれば十分であり、ダイヤモンド粒子間に水やガスの通過する空間があり、水に接する面積の大きいことが要求される。このことから原料のダイヤモンド粒子にはメッシュサイズの粗い砥粒を用い、粒子間をその場で形成された遷移金属炭化物を介して接合した多孔質焼結体とすることが望ましい。 For sintered bodies intended as conductive electrode materials, it is sufficient if they are strong enough to maintain their shape, and they are required to have spaces between the diamond particles through which water and gas can pass, and a large surface area in contact with water. For this reason, it is desirable to use coarse mesh-sized abrasive grains as the raw diamond particles, and to create a porous sintered body in which the particles are bonded together via transition metal carbides formed in situ.
このため本発明においては原料のボロンドープダイヤモンド砥粒として400メッシュ(35μm)より粗いサイ ズが用いられるが、特に200メッシュ (75μm)以上とすることが好ましく、100メッシュ (150μm)よりも粗い砥粒を用いて大きな空孔を形成することがより好ましい。 For this reason, in the present invention, boron-doped diamond abrasive grains of a size coarser than 400 mesh (35 μm) are used as the raw material, but it is particularly preferable to use a size of 200 mesh (75 μm) or more, and it is even more preferable to use abrasive grains of a size coarser than 100 mesh (150 μm) to form large pores.
ダイヤモンド(炭素)と遷移金属との反応によって遷移金属炭化物を形成する現象は固相領域においても認められ、1000℃以上で明らかな反応の進行が認められる。従ってダイヤモンド粒子の接合に際して、遷移金属の融点を超える加熱温度を必ずしも必要としない。 The phenomenon of forming transition metal carbides by the reaction between diamond (carbon) and transition metals is observed even in the solid phase region, with the reaction clearly progressing at temperatures above 1000°C. Therefore, when joining diamond particles, it is not necessarily necessary to heat the material to a temperature that exceeds the melting point of the transition metal.
焼結反応はダイヤモンドが熱力学的に安定な高圧領域で実施するのが好ましいが、安定領域は必須要件ではなく、還元雰囲気を用い、反応時間を短くすることで、HIP、ホットプレス、放電プラズマ焼結などの技法も用いることができる。 The sintering reaction is preferably carried out in a high-pressure region where diamond is thermodynamically stable, but the stable region is not a requirement, and techniques such as HIP, hot pressing, and spark plasma sintering can also be used by using a reducing atmosphere and shortening the reaction time.
焼結ダイヤモンド層の平坦度を保つためには、充填ダイヤモンドの基板として遷移金属板やセラミックス板を用いると好都合である。例えば基板材料として遷移金属、特にＴiやＮbを用いた場合、ダイヤモンド粒子と基板との接点では両者の反応で生じた炭化物を介した化学結合によって強力な接合が形成される。即ちダイヤモンド粒子間は、例えばチタン粉とダイヤモンドとの反応で生じた炭化チタンによって固定され、ダイヤモンド粒子と基板との接点では加熱の際に両者の反応によってその場で形成された炭化物を介した化学結合による接合が形成される。 To maintain the flatness of the sintered diamond layer, it is advantageous to use a transition metal plate or a ceramic plate as the substrate for the filled diamond. For example, when a transition metal, especially Ti or Nb, is used as the substrate material, a strong bond is formed at the contact point between the diamond particles and the substrate by chemical bonding via the carbide formed by the reaction between the two. In other words, the diamond particles are fixed together by titanium carbide formed by the reaction between titanium powder and diamond, for example, and at the contact point between the diamond particles and the substrate, a bond is formed by chemical bonding via the carbide formed in situ by the reaction between the two when heated.
遷移金属板を基板材料に用いると、電極面の平坦度が確保されるのに加えて、ダイヤモンド焼結層の補強板としても機能するので，ダイヤモンド層を単一層にまで薄く形成することも可能である。 When a transition metal plate is used as the substrate material, not only does it ensure the flatness of the electrode surface, it also functions as a reinforcing plate for the diamond sintered layer, making it possible to form the diamond layer as thin as a single layer.
焼結反応後にダイヤモンド粒子の隙間に残留した金属は、後工程の塩酸溶解処理によって除くことができる。この際に基板金属の表面からの溶解も生じるが、軽く焼結した遷移金属粉末に比べて溶解速度が遅いことから、板の形で残すことが可能であり、通電用の基板として利用可能である。 Any metal remaining in the gaps between the diamond particles after the sintering reaction can be removed by a subsequent hydrochloric acid dissolution process. During this process, some of the substrate metal dissolves from the surface, but since the dissolution rate is slower than that of lightly sintered transition metal powder, it can be left in the form of a plate, which can be used as a substrate for conducting electricity.
ニオブ、タンタルは殆ど塩酸に溶けないので、基板に最も適した材料と言える。また遷移金属板に代えてＷＣ－Ｃo系超硬合金も用いることができ、この場合さらに超硬合金中のコバルトを塩酸溶解処理の際にダイヤモンド粒子間の残留金属と一緒に溶解除去可能である。 Niobium and tantalum are almost insoluble in hydrochloric acid, making them the most suitable materials for the substrate. WC-Co-based cemented carbide can also be used instead of the transition metal plate, in which case the cobalt in the cemented carbide can be dissolved and removed together with the residual metal between the diamond particles during the hydrochloric acid dissolution process.
ダイヤモンド粒子間の残留金属の除去には、塩酸溶解に代えて電解抽出も用いることができる。この場合、焼結生成物を陽極とし、鉄陰極と組み合わせて希硫酸中で実施できる。大量処理には焼結生成物をまとめてチタンバスケットに入れて電解操作を行うのが有効である。 In place of hydrochloric acid dissolution, electrolytic extraction can also be used to remove residual metal between diamond particles. In this case, the sintered product is used as the anode in combination with an iron cathode in dilute sulfuric acid. For large-scale processing, it is effective to place the sintered product together in a titanium basket and perform the electrolytic operation.
セラミックス系の基板材料としてはマグネシアが好適である。マグネシアは熱伝導率が高く、2800℃という高融点に加えて塩酸に溶解することから、後工程の塩酸溶解処理によってダイヤモンドの粒子間の残留金属と共に除くことができ、ボロンドープダイヤモンドのみで構成された自立導電薄板を得ることができる。 Magnesia is a suitable ceramic substrate material. It has high thermal conductivity, a high melting point of 2800°C, and is soluble in hydrochloric acid. This means that it can be removed together with the residual metal between the diamond particles in a subsequent hydrochloric acid dissolution process, resulting in a self-supporting conductive thin plate made entirely of boron-doped diamond.
電極素材から所定の形状の電極を切り出すのに放電加工を用いる場合には、所定の形状 に切り出してから塩酸溶解処理を行うのが望ましい。 When using electric discharge machining to cut electrodes of a desired shape from electrode material, it is desirable to perform hydrochloric acid dissolution treatment after cutting into the desired shape.
本発明方法においてはダイヤモンド粒子間に残存する焼結助剤金属の溶解除去によって 、表面に導通した空隙の形成による電極材の多孔質化、作用表面積増大が達成される。この多孔質化構造によって作用表面積を大きくすることができ、ガス、水の移動が容易になるのに伴うガス発生効率の上昇、電流密度の低下による電極寿命の向上といった効果が得られる。 In the method of the present invention, the sintering aid metal remaining between the diamond particles is dissolved and removed, forming conductive voids on the surface, making the electrode material porous and increasing the active surface area. This porous structure makes it possible to increase the active surface area, which results in the effects of increasing the gas generation efficiency by facilitating the movement of gas and water, and improving the electrode life by reducing the current density.
前記ダイヤモンド粒子層中に占める空隙の比率はダイヤモンド粒子に混合する焼結助剤の量によって調整可能であるが、空隙のダイヤモンド粒子層に対する相対量(気孔率)は少なくともダイヤモンド粒子層全容積の5％以上とするのが好ましく、20％以上とするのがより好ましい。
The proportion of voids in the diamond particle layer can be adjusted by the amount of sintering aid mixed with the diamond particles , but the relative amount of voids in the diamond particle layer (porosity) is preferably at least 5% of the total volume of the diamond particle layer, and more preferably 20% or more.
次に本発明を実施例によって説明する。なお以下の各例において、カプセルはニオブ薄板製で、厚さ0.15mm、外径63mmのものを用いた。 Next, the present invention will be explained using examples. In each of the following examples, a capsule made of thin niobium plate with a thickness of 0.15 mm and an outer diameter of 63 mm was used.
Ｎbカプセルに、次の充填順序で反応材料を充填して、厚さ約5mmの加圧・加熱試料を製作した。
充填順序(底部から上方へ)
Ｔi基板 厚さ0.5mm
ボロンドープダイヤモンド(BDD) #80/100(180μm)15ｇとＴi粉(45μm以下) 10ｇとの混合粉末
Ｎb薄板(厚さ0.15mm)
The reaction materials were filled into a Nb capsule in the following order to prepare a pressurized and heated sample having a thickness of approximately 5 mm.
Filling order (bottom to top)
Ti substrate, thickness 0.5mm
Mixture of 15g of boron-doped diamond (BDD) #80/100 (180μm) and 10g of Ti powder (45μm or less) Nb thin plate (thickness 0.15mm)
このカプセルを10段重ねて反応室内に充填し、5.5ＧＰa、1350℃の加圧・加熱条件に10分間保持した。
反応生成物はショットブラストにより、周囲のニオブ板を除去し、約2mm厚さのダイヤモンド焼結層が接合したチタン板を回収した。
Ten of these capsules were stacked in layers and packed into a reaction chamber, which was then maintained under pressure and heating conditions of 5.5 GPa and 1350° C. for 10 minutes.
The reaction product was shot blasted to remove the surrounding niobium plate, and the titanium plate bonded with a sintered diamond layer approximately 2 mm thick was recovered.
次いで6Ｎの熱塩酸を用いてダイヤモンド粒子間に残留し、軽く焼結しているチタン粉末を溶解除去した。
顕微鏡観察により、ダイヤモンド粒子が接合して網目構造の組織を呈していることが認められ、焼結物はＸ線回折により、ダイヤモンドと炭化チタンとで構成されていることが確かめられた。
Next, the titanium powder remaining between the diamond particles and lightly sintered was dissolved and removed using 6N hot hydrochloric acid.
Microscopic observation revealed that the diamond particles were bonded together to form a network structure, and X-ray diffraction confirmed that the sintered product was composed of diamond and titanium carbide.
ダイヤモンド粒子間、ならびにダイヤモンド粒子層とチタン基板との結合は共に強固で、ショットブラスト加工においても、研削加工においても剥がれを生じなかった。
容積と質量との測定から、ダイヤモンド層の空隙率は約30％と推定した。
The bonds between the diamond particles and between the diamond particle layer and the titanium substrate were both strong, and no peeling occurred during shot blasting or grinding.
From volume and mass measurements, the porosity of the diamond layer was estimated to be about 30%.
基板として厚さ0.5mmのニオブ板を用いた。ボロンドープダイヤモンド#200/230 (約75μm) 20ｇとＴi粉(45μm以下)10ｇとの混合粉末を充填し、厚さ0.15mmのニオブ板を蓋に用いた。
焼結条件は6ＧＰa、1400℃とし、この圧力温度条件を10分間保持した。
A 0.5 mm thick niobium plate was used as the substrate. A mixture of 20 g of boron-doped diamond #200/230 (approximately 75 μm) and 10 g of Ti powder (45 μm or less) was filled, and a 0.15 mm thick niobium plate was used as the lid.
The sintering conditions were 6 GPa and 1400° C., and these pressure and temperature conditions were maintained for 10 minutes.
回収された焼結品のダイヤモンド層の厚さは2.3mmであった。後処理の塩酸溶解においてニオブ板の寸法変化は認められなかったことから、空隙率の測定精度は高く、22％と見積もられた。 The thickness of the diamond layer on the recovered sintered product was 2.3 mm. Since no dimensional change was observed in the niobium plate during post-processing, when it was dissolved in hydrochloric acid, the measurement accuracy of the porosity was high and it was estimated to be 22%.
基板として厚さ2.5mmのＷＣ－8％Ｃo超硬合金板を用いた。充填混合粉末として、ボロンドープダイヤモンド#200/230 (約75μm) 30ｇ、Ｔi粉(45μm以下) 7ｇ、Ｃo粉(約2μm) 3ｇの混合粉を用いた。焼結条件は5.5ＧＰa、1300℃とし、10分間保持した。 A 2.5 mm thick WC-8%Co cemented carbide plate was used as the substrate. A mixture of 30 g of boron-doped diamond #200/230 (approximately 75 μm), 7 g of Ti powder (45 μm or less), and 3 g of Co powder (approximately 2 μm) was used as the filling mixture powder. The sintering conditions were 5.5 GPa and 1300°C, and the temperature was maintained for 10 minutes.
焼結品のダイヤモンド層の厚さは約3mmであった。研削加工によって超硬合金の厚さを0.5mm以下とした後、塩酸中煮沸によりダイヤモンド粒子間の金属成分を溶解除去した。ダイヤモンド層中の空隙率は約15％と見積もられた。 The thickness of the diamond layer of the sintered product was approximately 3 mm. After grinding to reduce the thickness of the cemented carbide to less than 0.5 mm, the metal components between the diamond particles were dissolved and removed by boiling in hydrochloric acid. The porosity in the diamond layer was estimated to be approximately 15%.
厚さ5mmのマグネシア板上に、ボロンドープダイヤモンド#270/325 (約50μm) 50ｇを、実施例３と同じチタン－コバルト混合粉と組み合わせて充填した。焼結条件は5.5ＧＰa、1300℃とし、10分間保持した。焼結品はショットブラストでカプセル材のニオブ薄板を除いた後、熱塩酸溶解によりダイヤモンド粒子間の残留金属と共にマグネシアも除き、厚さ約5mmで空隙率約10％のボロンドープダイヤモンド自立薄板を得た。 50 g of boron-doped diamond #270/325 (approximately 50 μm) was packed onto a 5 mm thick magnesia plate in combination with the same titanium-cobalt mixed powder as in Example 3. The sintering conditions were 5.5 GPa, 1300°C, and the temperature was maintained for 10 minutes. The sintered product was shot blasted to remove the niobium thin plate capsule material, and then dissolved in hot hydrochloric acid to remove the magnesia along with the residual metal between the diamond particles, resulting in a free-standing boron-doped diamond thin plate with a thickness of approximately 5 mm and a porosity of approximately 10%.
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| JP2005325417A (en) | 2004-05-14 | 2005-11-24 | Sumitomo Electric Ind Ltd | Diamond electrode and production method therefor |
| JP2008133172A (en) | 2006-10-31 | 2008-06-12 | Mitsubishi Materials Corp | Boron-doped diamond sinter and process for producing the same |
| JP2012126605A (en) | 2010-12-15 | 2012-07-05 | Sumitomo Electric Hardmetal Corp | Diamond sintered compact |
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