High-Speed Centrifugal Compaction Process Research Articles

Development of All-ceramic Artificial Teeth Using a High-speed Centrifugal Compaction Process with a 3D Printer

All-ceramic artificial teeth were produced using a high-speed centrifugal compaction process (HCP) combined with a resin shell-mold made by a 3D printer. Slurries of alumina or zirconia fine powders filled the inside and outside of the mold and then rotated at between 7,000 and 11,500 rpm in a centrifuge (HCP buried compaction method). Using this method, crack-free green compacts were produced. The shell-molds were not deformed or broken because the inner and outer pressures generated during the HCP were quasi-balanced. Two methods for mold-releasing, thermal decomposition and mechanical de-molding by hand, were investigated. Thermal decomposition introduced the critical problem of sintering inhibition. To obtain the final products, the compacts were air sintered after being released from the molds. For alumina, green compacts of high packing density (63 %) were sintered homogenously without considerable deformation. For zirconia, the packing density reached approximately 55 % with a density gradient. The zirconia compacts were sintered inhomogeneously, which resulted in a density gradient and deformation. The density gradient and shape deformation of the sintered compacts are discussed.

3D プリンターと高速遠心成形法を組み合わせた ディーゼルノズルの製造－製造プロセスの改良－

A new process method for net-shape formation of diesel nozzles was proposed. Resin cores of tapered spray holes (inwardly larger) were made by a three-dimensional printer, then they were buried in fine (2.6 μm) steel powder compacts by high-speed centrifugal compaction process. The green compacts were heated to eliminate resin cores, resin molds and binders by thermal decomposition, then, sintered at 1473 K. Crack formation during process, which was hardly avoidable by previous studies, were suppressed by changing process parameters especially of thermal decomposition process of resins. Densely and uniformly sintered nozzle tips obtained.

High-speed Centrifugal Compaction Process

High-speed Centrifugal Compaction Process

233 3Dプリンターと高速遠心成形法を組み合わせたセラミックス義歯のオンデマンド製造

233 3Dプリンターと高速遠心成形法を組み合わせたセラミックス義歯のオンデマンド製造

S0410102 3Dプリンターと高速遠心成形法を組み合わせたオールセラミッククス義歯の製造([S041-01]粉末成形とその評価(1),機械材料・材料加工部門)

All-ceramic artificial teeth are made by High-speed Centrifugal Compaction Process (HCP), combined with resin shell mold made by 3D printer. By the process, we can avoid essential problems for on- demand ceramic duplication process, such as shrinkage during sintering, use of high-cost metal dies for high pressure compaction, etc. A shell type resin mold with 0.4 mm thickness is made by UV-hardening 3D printer. The shell is buried in alumina slurry, then compacted by the HCP. The alumina powder is densely compacted (63%) in the mold without breaking or deforming thin walled shell molds, since the applied pressure during the HCP is almost isotropic, that is, no remarkable stress is forced on the molds. The mold is taken off by thermal decomposition in a furnace (N_2 atmosphere). The shape and surface microstructure of sintered compact have good coincidence with that of shell mold, as well as CAD data.

Al2O3 and ZrO2 powders formed by centrifugal compaction using the ultra HCP method

The influence of high speed centrifugal compaction process, the HCP method, on the properties of green compacts and sintered samples of Al2O3 and ZrO2 micropowders was investigated. This method may reduce friction between particles and prevent bridging of particles during compaction. The properties of the sintered materials strongly depend on the conditions of the centrifugal process: i.e. duration, rotation speed, solid content and dispersive liquids. The centrifugal compaction process of powder forming often results in gradient phase composition. An algorithm describing sedimentation of a group of spherical particles of different sizes and of different materials was used. Calculations for Al2O3 and ZrO2 deposition for the real conditions of the high-speed centrifugal compaction process have been carried out using the Barnea–Mizrahi equation. Deposition was carried out using an ultra-centrifuge with rotational speeds of 10,000, 20,000 and 30,000rpm for various pH of dispersive liquids. Pore size and pore size distribution of Al2O3 and ZrO2 green compacts were measured by the mercury porosimetry method. Densities, Young's moduli and Vickers hardness distribution of sintered compacts prepared in various conditions are reported.

S041023 高速遠心成形法によるセラミックス製品のオンデマンド複製プロセスの開発

S041023 高速遠心成形法によるセラミックス製品のオンデマンド複製プロセスの開発

S041024 高速遠心成形法によるコモンレールディーゼル用の微細で複雑な穴配置を持つノズル製造技術の開発

S041024 高速遠心成形法によるコモンレールディーゼル用の微細で複雑な穴配置を持つノズル製造技術の開発

Compacts of Ultra Fine WC Powder by High-Speed Centrifugal Compaction Process and Sintering of them (1st report) -Development of Non-Aqueous Slip of WC-

Compacts of Ultra Fine WC Powder by High-Speed Centrifugal Compaction Process and Sintering of them (1st report) -Development of Non-Aqueous Slip of WC-

Sedimentation Behavior of Mixed Powder Slurry under High-Speed Centrifugal Force

Compaction behavior of two component slurry during High-speed Centrifugal Compaction Process (HCP) was observed. Slight amount of iron oxide powder is mixed into alumina slurry, then the slurry was sedimented in a centrifuge under rotational speed of up to 11,500 rpm. A “Y” letter shaped flow pattern was emerged in the cross section of the compact. The pattern was clearer with higher rotational speed, but indifferent to acceleration rate of rotation. A similar pattern was simulated when we presume bidirectional initial flow in centrifugal field, which indicated that the combination of Corioli’s force and bidirectional flows of powder and dispersing medium caused such flow pattern.

Fabrication of green and sintered bodies prepared by centrifugal compaction process using wet-jet milled slurries

Properties of green and sintered bodies prepared by high-speed centrifugal compaction process (HCP) using wet-jet milled slurries were investigated. At 30 vol.% solids loading, the relative packing density of compacted body prepared from wet-jet milled slurry was 67%. On the other hand, the density of compacted body prepared from ball-milled slurry was 56% at the same loadings. The difference in relative densities of the top and bottom of green bodies prepared from wet-jet milled slurry was decreased to one-third of the ones prepared from ball-milled slurry. Moreover, the linear shrinkage of the sintered bodies prepared from wet-jet milled slurries was almost constant at sintering temperatures above 1400 °C; it was found to be increasing for bodies prepared from ball-milled slurries with increasing sintering temperature. Furthermore, activation energy for grain-growth was estimated. The grain-growth of green bodies prepared from wet-jet milled slurries was promoted at lower-sintering temperatures.

高速遠心成形法による複雑形状品の中子くるみ成形（その２）―ディーゼルエンジン用微細多孔ノズルの製造―

High-Speed Centrifugal Compaction Process (HCP) is a kind of wet compacting method for fine powders suitable for net shape fabrication of complex shape parts with hollow spaces. In the present study, we aim to develop diesel engine fuel injection nozzles using this technique. A plastic core with multiple thin bars (which become nozzle holes) are buried into fine metallic powder compact by the HCP. Then, the core and binder resin in the green compact are thermally decomposed in a vacuum furnace. We developed a proper procedure for de-binding. The de-binded compacts can be sintered uniformly to the relative density of 96 %, having sufficient strength for fuel injection.

樹脂型を高速遠心成形法に用いるオンデマンド焼結製品の製造（その１）

In High-Speed Centrifugal Compaction Process (HCP), powders are prepared as slips and deposited on bottom of molds under huge (10,000 g) centrifugal force to form green compacts. It looks severe process, but the force acting on the mold is less than several tens MPa. Therefore, the HCP is a mild compacting method from a view points of compacting mold. In the present study, we developed plastic compacting mold for the HCP. The hollow shape in the compacting mold is obtaind by selectively dissolving another plastic mold (master mold) buried in it. For releasing green compact from compacting mold, the whole mold is heated and the compacting mold is thermally decomposed. Proper selection of compacting mold resin, filler and binder resin in green compact makes releasing of the compact stress-free. Released compact can be sintered but minute cracks remains there.

Flow Patterns in Green Bodies Made by High-Speed Centrifugal Compaction Process

High-Speed Centrifugal Compaction Process (HCP) is a wet compacting method, in which powders are compacted under a huge centrifugal force. The HCP was well applied to small alumina specimens, but the compact easily cracked when we applied the HCP to other materials. In the present study we clarify the mechanism that introduces such cracks. Firstly, we observed HCP alumina, dyeing with iron oxide powder or by the Immersion Liquid Technique, and found that there was a kind of flow pattern generated during the HCP. A simple simulation also revealed that the formation of such a flow pattern was related to the Colioli’s force in the centrifugal field, and therefore was hard to suppress. Nonetheless, the actual introduction of inhomogeneity along the flow was largely affected by another factor. Die releasing oil was dragged in the flows and formed low density regions along the flow.

Compaction of Ultra-Fine WC Powder by High-Speed Centrifugal Compaction Process

High-Speed Centrifugal Compaction Process (HCP) is one of slip-using compacting method originally developed for processing of oxide ceramics. In this study, we are going to apply the HCP to ultra-fine (0.1 micron) WC powder. Organic liquid of heptane was chosen as dispersing media to avoid possible oxidation of WC. For slip preparation, addition of sorbitan-monostearate (SMS) dramatically improved state of dispersion. The mixing apparatus also was in consideration. The slips mixed by conventional ball mill or turbula mill were scarcely densified by the HCP. Only the slips mixed by high energy planetary ball mill were packed up to 55% by the HCP, and sintered to almost full density at 1673 K without any sintering aids. This sintered compact marked Vickers hardness of Hv 2750 at maximum.

207 高速遠心成形法による複雑形状部品の成形 : 消失性中子を含む成形技術の開発(粉末成形とその評価2)

207 高速遠心成形法による複雑形状部品の成形 : 消失性中子を含む成形技術の開発(粉末成形とその評価2)

高速遠心成形法による複雑形状品の中子くるみ成形(その1)

高速遠心成形法による複雑形状品の中子くるみ成形(その1)

Yttria Partially Stabilized Zirconia Made by High-Speed Centrifugal Compaction Process

Yttria Partially Stabilized Zirconia Made by High-Speed Centrifugal Compaction Process

Net shape formation of sub-micron alumina with reduced flaws by high-speed centrifugal compaction process

A new compacting method for powder materials is presented. High-Speed Centrifugal Compaction Process (HCP) utilizes centrifugal force of about 10,000 g for the compaction. HCP is suitable for net shape compaction of fine sub-micron and nano-powders. HCP possesses a unique compacting mechanism that is different from other colloidal processes including Pressure Casting (PC), and has a number of useful characteristics. HCP has a higher compacting speed than PC, wide applicability for net shape formation, as well as a defect removing function. Because of homogeneous and flawless green microstructure, HCP alumina shows superior sinterability and higher strength and hardness than most of other aluminas.

粉末プロセスの制御と製品の評価 高速遠心成形法による超高強度アルミナの作製と高強度化機構の解明

High-Speed Centrifugal Compaction Process (HCP) is a variety of wet compacting method for fine ceramic powders by using huge centrifugal force of about 10, 000g. The compacting mechanism of the HCP differs from that of slip casting, a conventional wet compaction method, and therefore the HCP possesses a number of unique characteristics such as a higher compacting speed than pressure casting, wide applicability for net shape formation, as well as defect removing function. Because of homogeneous and flawless green microstructure, the HCP alumina shows a superior sinterabiliy and higher strength and hardness than most other alumina. These advantages can be emphasized with a higher centrifugal force.