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Fine-grained NdFeB magnets prepared by low temperature pre-sintering and subsequent hot pressing
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作者 剧锦云 唐旭 +4 位作者 陈仁杰 汪金芝 尹文宗 李东 闫阿儒 《Chinese Physics B》 SCIE EI CAS CSCD 2015年第1期493-497,共5页
Fine-grained Nd10.79Pr2.8Al0.4B7.72Fe78.29 magnets were prepared by low temperature pre-sintering and subsequent hot pressing. The grain size of the magnets is just about 1–3 μm because the low sintering temperature... Fine-grained Nd10.79Pr2.8Al0.4B7.72Fe78.29 magnets were prepared by low temperature pre-sintering and subsequent hot pressing. The grain size of the magnets is just about 1–3 μm because the low sintering temperature results in no grain growth. The orientation degree, microstructure, and magnetic properties were studied. Some grains' easy axes deviate from the orientation direction, possibly due to grain rotation during the hot pressing. By subsequent annealing, the magnetic properties were significantly enhanced. Especially, the squareness of the demagnetization curve was improved greatly.The enhancement of coercivity by annealing can be explained by an improvement of both grain boundaries and magnetic isolation, which decouples the exchange interaction between neighboring grains. 展开更多
关键词 Nd Fe B magnets grain refinement hot press pre-sintering
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Microstructure of pre-sintered permanent magnetic strontium ferrite powder 被引量:2
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作者 YU Hongya LIU Zhengyi ZENG Dechang 《Rare Metals》 SCIE EI CAS CSCD 2006年第z1期572-577,共6页
The microstructure and characteristics of pre-sintered strontium ferrite powder were investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The present study shows that t... The microstructure and characteristics of pre-sintered strontium ferrite powder were investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The present study shows that the pre-sintered strontium ferrite powder is provided with a certain particle size distribution, which results in high-density magnets. The strontium ferrite particle has a laminar hexagonal structure with a size similar to ferrite single domain. Ferric oxide phase due to an incomplete solid phase reaction in the first sintering is discovered, which will deteriorate the magnetic properties of ferrite magnet. In addition, the waste ferrite magnets with needle shape arranging along C axis in good order into the powders are found, which have no negative effects on finished product quality. 展开更多
关键词 pre-sintered permanent magnetic strontium ferrite powder TEM MICROSTRUCTURE particle size
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Design and Performance Analysis of Small Denture Machining Equipment
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作者 雷小宝 谢峰 +2 位作者 廖文和 郑侃 赵吉文 《Journal of Donghua University(English Edition)》 EI CAS 2013年第3期222-227,共6页
The research and application on small denture machining equipment are great breakthrough for modern dental restoration technology. In this paper, a small denture machining equipment made of two spindles with four-axis... The research and application on small denture machining equipment are great breakthrough for modern dental restoration technology. In this paper, a small denture machining equipment made of two spindles with four-axis was designed based on machining characteristics and functional analysis. Position accuracy and re-position accuracy were measured by accuracy instrument. In order to test its machining capacity, some typical microstcucture parts, such as straight channel, hemispherical surface, and molars coronal, were selected for high speed milling. It was obtained that the denture machining equipment met the machining requirements with high quality and efficiency, according to the acquisition and analysis of form and position errors, surface roughness, and 3-D profile. 展开更多
关键词 DENTURE small denture machining equipment high speed milling two spindles with four-axis pre-sintered zirconia ceramics
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Assessment of Elasticity,Plasticity and Resistance to Machining-induced Damage of Porous Pre-sintered Zirconia Using Nanoindentation Techniques
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作者 Abdur-Rasheed Alao Ling Yin 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2016年第5期402-410,共9页
Porous pre-sintered zirconia is subject to white machining during which its elasticity, plasticity and resistance to machining-induced damage determine its machinability and final quality. This study used nanoindentat... Porous pre-sintered zirconia is subject to white machining during which its elasticity, plasticity and resistance to machining-induced damage determine its machinability and final quality. This study used nanoindentation techniques and the Sakai's series elastic and plastic deformation model to extract the resistance to plastic deformation from the plane strain modulus and the contact hardness for presintered zirconia. The modulus and the resistance to plasticity were used to calculate the relative amount of elasticity and plasticity. The fracture energy and the normalized indentation absorbed energy were used to deconvolute the resistance to machining-induced cracking based on the Sakai-Nowak model. All properties were extracted at a 10 mN peak load and loading rates of 0.1-2 mN/s to determine the loading rate effects on these properties. We found that the resistance to plasticity and the resistance to machining-induced cracking were independent of the loading rate (ANOVA, p 〉 0.05). The elastic and plastic displacements depended on the loading rate through power laws. This loading rate-dependent deformation behaviour was explained by the maximum shear stress generated underneath the indenter and the indentation energy. The plastic deformation components and the indentation absorbed energy at all loading rates were higher than the elastic deformation components and the elastic strain energy, respectively. Finally, we established the linkage among the pore structure, indentation behaviour and machinability of pre-sintered zirconia. 展开更多
关键词 Elastic/plastic deformation Loading rate Nanoindentation pre-sintered zirconia Resistance to machining-induced cracking Resistance to plasticity
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Microstructure and properties of silica-based ceramic cores by laser powder bed fusion combined with vacuum infiltration
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作者 Jie Zhang Jia-Min Wu +5 位作者 Heng Liu Wen Zheng Chun-Sheng Ye Shi-Feng Wen Chun-Ze Yan Yu-Sheng Shi 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2023年第26期71-79,共9页
The silica-based ceramic core has attracted much attention in the preparation of hollow blades due to its great leachability.In this paper,the silica-based ceramic cores reinforced with ZrSiO_(4) were prepared by lase... The silica-based ceramic core has attracted much attention in the preparation of hollow blades due to its great leachability.In this paper,the silica-based ceramic cores reinforced with ZrSiO_(4) were prepared by laser powder bed fusion(LPBF)combined with vacuum infiltration(VI).To enhance the infiltration effect,the pre-sintered bodies with high porosity and hydrophilicity were obtained by pre-sintering at 1100℃.Results showed that a large number of silica particles infiltrated into the pre-sintered bodies.The infiltrated silica promoted the generation of liquid phase in sintering,thereby promoting the removal of pores and the connection of grains.Nevertheless,the dispersed ZrSiO_(4) grains prevented the viscous flow of the liquid phase,thereby increasing the porosity.ZrSiO_(4) grains could hinder the propagation of cracks due to their high strength.When the addition of ZrSiO_(4) was 10 wt.%,room-temperature flexural strength of silica-based ceramic cores infiltrated with slurry S1(the mass ratio of silica sol to silica powder was 10:1)reached 17.21 MPa due to the reinforcement of sintering necks.Moreover,high-temperature flexural strength reached 13.90 MPa.Therefore,the pre-sintering process could greatly improve the mechanical properties of silica-based ceramic cores prepared by LPBF-VI technology. 展开更多
关键词 Silica-based ceramic cores Laser powder bed fusion ZrSiO_(4) pre-sintering Vacuum infiltration
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