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Influence of high-temperature oxidation of SiC powders on curing properties of SiC slurry for digital light processing

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Journal of Advanced Ceramics 2023年第1期12卷 169-181页

作者： Zhang-Ao SHI jia-min wu Zhi-Qiang FANG Yu-Sheng SHI State Key Laboratory of Materials Processing and Die&Mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China Engineering Research Center of Ceramic Materials for Additive Manufacturing Ministry of EducationWuhan 430074China

Fabrication of silicon carbide(SiC)ceramics by digital light processing(DLP)technology is difficult owing to high refractive index and high ultraviolet(UV)absorptivity of SiC *** surface of the SiC powders can be coated with silicon oxide(SiO_(2))with low refractive index and low UV absorptivity via high-temperature oxidation,reducing the loss of UV energy in the DLP process and realizing the DLP preparation of the SiC ***,it is necessary to explore a high-temperature modification process to obtain a better modification effect of the SiC ***,the high-temperature modification behavior of the SiC powders is thoroughly investigated in this *** results show that nano-scale oxide film is formed on the surface of the SiC powders by short-time high-temperature oxidation,effectively reducing the UV absorptivity and the surface refractive index(nʹ)of the SiC *** the oxidation temperature is 1300℃,compared with that of unoxidized SiC powders,the UV absorptivity of oxidized SiC powders decreases from 0.5065 to 0.4654,and a curing depth of SiC slurry increases from 22±4 to 59±4μ***,SiC green bodies are successfully prepared by the DLP with the the oxidized powders,and flexural strength of SiC sintered parts reaches 47.9±2.3 MPa after 3 h of atmospheric sintering at 2000℃without any sintering aid.

关键词： silicon carbide(SiC)powders oxidation modification digital light processing(DLP) ultraviolet(UV)absorptivity curing depth

Shim coil design for Halbach magnet by equivalent magnetic dipole method

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Chinese Physics B 2018年第10期27卷 300-307页

作者： jia-min wu Zheng Xu Pan Guo Jin-Feng Qi Yu-Cheng He State Key Laboratory of Power Transmission Equipment and System Security and New Technology Chongqing UniversityChongqing 400044China School of Physics and Electronic Engineering Chongqing Normal UniversityChongqing 401331China

Low-field nuclear magnetic resonance magnet（2 MHz） is required for rock core analysis. However, due to its low field strength, it is hard to achieve a high uniform B0 field only by using the passive shimming. Therefore, active shimming is necessarily used to further improve uniformity for Halbach magnet. In this work, an equivalent magnetic dipole method is presented for designing shim coils. The minimization of the coil power dissipation is considered as an optimal object to minimize coil heating effect, and the deviation from the target field is selected as a penalty function term. The lsqnonlin optimization toolbox of MATLAB is used to solve the optimization problem. Eight shim coils are obtained in accordance with the contour of the stream function. We simulate each shim coil by ANSYS Maxwell software to verify the validity of the designed coils. Measurement results of the field distribution of these coils are consistent with those of the target *** uniformity of the B0 field is improved from 114.2 ppm to 26.9 ppm after using these shim coils.

关键词： equivalent magnetic dipole method shim coils magnetic resonance Halbach magnet

Preparation and properties of T-ZnO_(w) enhanced BCP scaffolds with double-layer structure by digital light processing

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Journal of Advanced Ceramics 2022年第4期11卷 570-581页

作者： ming-Zhu PAN Shuai-Bin HUA jia-min wu Xi YUAN Ze-Lin DENG Jun XIAO Yu-Sheng SHI State Key Laboratory of Materials Processing and Die&Mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China Engineering Research Center of Ceramic Materials for Additive Manufacturing Ministry of EducationWuhan 430074China Department of Orthopedic Surgery Tongji HospitalTongji Medical CollegeHuazhong University of Science and TechnologyWuhan 430030China

Bone scaffolds require both good bioactivity and mechanical properties to keep shape and promote bone *** this work,T-ZnO_(w) enhanced biphasic calcium phosphate(BCP)scaffolds with triply periodic minimal surface(TPMS)-based double-layer porous structure were fabricated by digital light processing(DLP)with high *** of suspension was first discussed to obtain better printing *** sintering,T-ZnO_(w) reacts with b-tricalcium phosphate(β-TCP)to form Ca_(19)Zn_(2)(PO_(4))14,and inhibits the phase transition toα-*** the content of T-ZnO_(w) increasing from 0 to 2 wt%,the flexural strength increases from 40.9 to 68.5 MPa because the four-needle whiskers can disperse stress,and have the effect of pulling out as well as fracture ***,excessive whiskers will reduce the cure depth,and cause more printing defects,thus reducing the mechanical ***,T-ZnO_(w) accelerates the deposition of apatite,and the sample with 2 wt%T-ZnO_(w) shows the fastest mineralization *** good biocompatibility has been proved by cell proliferation *** confirmed that doping T-ZnO_(w) can improve the mechanical strength of BCP scaffolds,and keep good biological property,which provides a new strategy for better bone repair.

关键词： biphasic calcium phosphate(BCP) T-ZnO_(w) digital light processing(DLP) double-layer structure cure property mechanical strength

Phase evolution and properties of novel Al2O3-based poly-hollow microsphere (PHM) ceramics

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Journal of Advanced Ceramics 2016年第2期5卷 176-182页

作者： jia-min wu Ying CHEN Xiao-Yan ZHANG Qian HUANG Jin-Long YANG Yu-Sheng SHI State Key Laboratory of Materials Processing and Die & Mould Technology School of Materials Science and Engineering Huazhong University of Science and Technology Wuhan 430074 ChinaState Key Laboratory of New Ceramics and Fine Processing School of Materials Science and Engineering Tsinghua University Beijing 100084 China State Key Laboratory of Materials Processing and Die & Mould Technology School of Materials Science and Engineering Huazhong University of Science and Technology Wuhan 430074 China State Key Laboratory of New Ceramics and Fine Processing School of Materials Science and Engineering Tsinghua University Beijing 100084 China

In this paper, novel Al2O3-based poly-hollow microsphere (PHM) ceramics were prepared using Si3N4 and Al2O3 PHMs as pore-forming agents. The effect of Si3N4 and Al2O3 PHMs with different percentages on properties of Al2O3-based PHM ceramics was investigated. Through adjusting percentage of Al2O3 PHMs, Al2O3-based PHM ceramics with enhanced properties are achieved. X-ray diffraction (XRD) results show that main phases of Al2O3-based PHM ceramics vary from beta-SiAlON (z value increases from 2.9 to 4) to Al2O3 with the increase of percentage of Al2O3 PHMs from 10% to 100%. The different phase compositions result in different properties of Al2O3-based PHM ceramics. With the increase of percentage of Al2O3 PHMs, porosity of Al2O3-based PHM ceramics gradually decreases, while their shrinkage, flexural strength, and fracture toughness firstly decrease and then increase. Using different kinds of ceramic PHMs as pore-forming agents, various novel and high-performance porous ceramics could be prepared via optimizing percentage of ceramic PHMs in the future.

关键词： porous ceramics poly-hollow microsphere (PHM) pore-forming agent phase evolution mechanical properties

Preparation of porous Si_(3)N_(4) ceramics via tailoring solid loading of Si_(3)N_(4) slurry and Si_(3)N_(4) poly‐hollow microsphere content

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Journal of Advanced Ceramics 2015年第4期4卷 260-266页

作者： jia-min wu Xiao-Yan ZHANG Jie XU Ke GAN jia-Lu LI Chen-Hui LI Jin-Long YANG Yu-Sheng SHI State Key Laboratory of Materials Processing and Die&Mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China State Key Laboratory of New Ceramic and Fine Processing School of Materials Science and EngineeringTsinghua UniversityBeijing 100084China

Porous Si_(3)N_(4) ceramics were prepared by aqueous gelcasting using Si_(3)N_(4) poly-hollow microspheres(PHMs)as pore-forming *** effects of solid loading of Si_(3)N_(4) slurry and Si_(3)N_(4) PHM content on the properties of porous Si_(3)N_(4) ceramics were ***β-Si_(3)N_(4) phase is observed in porous Si_(3)N_(4) ceramics,and Si_(3)N_(4) PHMs distribute uniformly both in Si_(3)N_(4) green samples and porous Si_(3)N_(4) *** show that solid loading of Si_(3)N_(4) slurry and Si_(3)N_(4) PHM content could considerably influence the properties of porous Si_(3)N_(4) *** the increase of solid loading of Si_(3)N_(4) slurry(decrease of Si_(3)N_(4) PHM content),the distributing state of Si_(3)N_(4) PHMs changes from contacting with each other to just embedding in the matrix,thus their porosity decreases,while their shrinkage,flexural strength,and fracture toughness increase.

关键词： porous Si_(3)N_(4)ceramics Si_(3)N_(4)poly-hollow microspheres(PHMs) solid loading aqueous gelcasting mechanical properties

Microstructure and properties of silica-based ceramic cores by laser powder bed fusion combined with vacuum infiltration

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Journal of Materials Science & Technology 2023年第26期157卷 71-79页

作者： Jie Zhang jia-min wu Heng Liu Wen Zheng Chun-Sheng Ye Shi-Feng Wen Chun-Ze Yan Yu-Sheng Shi State Key Laboratory of Materials Processing and Die&Mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China Engineering Research Center of Ceramic Materials for Additive Manufacturing Ministry of EducationWuhan 430074China

The silica-based ceramic core has attracted much attention in the preparation of hollow blades due to its great *** 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 *** infiltrated silica promoted the generation of liquid phase in sintering,thereby promoting the removal of pores and the connection of ***,the dispersed ZrSiO_(4) grains prevented the viscous flow of the liquid phase,thereby increasing the ***_(4) grains could hinder the propagation of cracks due to their high *** 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 ***,high-temperature flexural strength reached 13.90 ***,the pre-sintering process could greatly improve the mechanical properties of silica-based ceramic cores prepared by LPBF-VI technology.

关键词： Silica-based ceramic cores Laser powder bed fusion ZrSiO_(4) Pre-sintering Vacuum infiltration

Study of 0.9Al_2O_3–0.1TiO_2 ceramics prepared by a novel DCC-HVCI method

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Journal of Advanced Ceramics 2018年第2期7卷 152-159页

作者： jia-min wu Huan XIAO Meng-Yue LIU Ying CHEN Yi-Xin MA Li-Jin CHENG Yu-Sheng SHI State Key Laboratory of Materials Processing and Die & Mould Technology School of Materials Science and EngineeringHuazhong University of Science and Technology

In this paper, in-situ coagulation of 0.9Al_2O_3–0.1TiO_2 suspension and microwave dielectric properties of 0.9Al_2O_3–0.1TiO_2 ceramics prepared by a novel direct coagulation casting via high valence counter ions(DCC-HVCI) method were proposed. The 0.9Al_2O_3–0.1TiO_2 suspension could be coagulated via controlled release of calcium ions from calcium iodate at an elevated temperature. The influence of tri-ammonium citrate(TAC) content, solid loading, and calcium iodate content on the rheological properties of the suspension was investigated. In addition, the influence of coagulation temperature on coagulation time and properties of green bodies was also studied. It was found that the stable 0.9Al_2O_3–0.1TiO_2 suspension could be successfully prepared by adding 0.3 wt% TAC and adjusting pH value to 10–12 at room temperature. 0.9Al_2O_3–0.1TiO_2 green bodies with uniform microstructures were coagulated by adding 8.0 g/L calcium iodate after treating at 70 ℃ for 1 h. 0.9Al_2O_3–0.1TiO_2 ceramics, sintered at 1500 ℃ for 4 h and annealed at 1100 ℃ for 5 h, showed uniform microstructures with density of 3.62±0.02 g/cm^3. The microwave dielectric properties of 0.9Al_2O_3–0.1TiO_2 ceramics prepared by DCC-HVCI method were: ε_r = 11.26±0.06, Q×f = 11569± 629 GHz, τ_t = 0.93±0.60 ppm/℃. The DCC-HVCI method is a novel and promising route without binder removal process to prepare complex-shaped microwave dielectric ceramics with uniform microstructures and good microwave dielectric properties.

关键词： rheological properties microwave dielectric properties 0.9Al2O3–0.1TiO2 DCC-HVCI

Emerging theories and technologies on computational imaging

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Frontiers of Information Technology & Electronic Engineering 2017年第9期18卷 1207-1221页

作者： Xue-mei HU jia-min wu Jin-li SUO Qiong-hai DAI Department of Automation Tsinghua University Beijing 100084 China Zhcjiang Future Technology Institute Jiaxing 314000 China

Computational imaging describes the whole imaging process from the perspective of light transport and information transmission, features traditional optical computing capabilities, and assists in breaking through the limitations of visual information recording. Progress in computational imaging promotes the development of diverse basic and applied disciplines. In this review, we provide an overview of the fundamental principles and methods in computational imaging, the history of this field, and the important roles that it plays in the development of science. We review the most recent and promising advances in computational imaging, from the perspective of different dimensions of visual signals, including spatial dimension, temporal dimension, angular dimension, spectral dimension, and phase. We also discuss some topics worth studying for future developments in computational imaging.

关键词： Computational imaging Multi-scale and multi-dimensional Super-resolution Femto-photography 3D reconstruction Hyperspectral imaging

Influence of Al_(2)0_(3) content on mechanical properties of silica-based ceramic cores prepared by stereolithography

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Journal of Advanced Ceramics 2021年第6期10卷 1381-1388页

作者： Wen ZHENG jia-min wu Shuang CHEN Chang-Shun WANG Chun-Lei LIU Shuai-Bin HUA Kang-Bo YU Jie ZHANG Jing-Xian ZHANG Yu-Sheng SHI State Key Laboratory of Materials Processing and Die&Mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China Engineering Research Center of Ceramic Materials for Additive Manufacturing Ministry of EducationWuhan 430074China State Key Laboratory of High Performance Ceramics and Superfine Microstructure Shanghai Institute of CeramicsChinese Academy of SciencesShanghai 200050China

Silica ceramic cores have played an important part in the manufacture of hollow blades due to their excellent chemical stability and moderate high-temperature mechanical *** this study,silica-based ceramics were prepared with Al_(2)0_(3) addition by stereolithography,and the influence of Al_(2)0_(3) content on mechanical properties of the silica-based ceramics was *** Al_(2)0_(3) in silica-based ceramics can improve the mechanical properties by playing a role as a seed for the crystallization of fused silica into *** a result,with the increase of Al_(2)0_(3) content,the linear shrinkage of the silica-based ceramics first decreased and then increased,while the room-temperature flexural strength and the high-temperature flexural strength first increased and then *** the Al_(2)0_(3) content increased to 1.0 vol%,the linear shrinkage was reduced to 1.64%because of the blocked viscous flow caused by Al_(2)0_(3).Meanwhile,the room-temperature flexural strength and the high-temperature flexural strength were improved to 20.38 and 21.43 MPa with 1.0 vol%Al_(2)0_(3),respectively,due to the increased a-cristobalite and P-cristobalite ***,using the optimal content of Al_(2)0_(3) in silica-based ceramics can provide excellent mechanical properties,which are suitable for the application of ceramic cores in the manufacturing of hollow blades.

关键词： silica ceramic core stereolithography AI2O3 mechanical properties hollow blades