Advanced Laminated Object Manufacturing (LOM) of SiSiC Ceramics

Carbon sheets were used as a starting material for fabrication of SiSiC composites by advanced LOM. This approach consists of three steps: First a preform was fabricated form phenolic resin coated carbon paper with a LOM-device. Second the preform was turned into a carbon preform by pyrolysis in N2-atmosphere. Third pressureless reactive melt infiltration of silicon into the as fabricated carbon preform, which finally yielded a dense SiSiC composite. SEM analysis revealed a microstructure consisting of uniformly dispersed β-SiC grains in a matrix of silicon. The LOM fabricated material exhibited an average four point bending strength and Youngs modulus of 115 MPa and 165 GPa, respectively.Mechanical Engineerin

Novel hybrid method to additively manufacture denser graphite structures using Binder Jetting.

This study introduces two hybrid processes integrating an additive manufacturing technique with post-processing treatments namely (i) Binder Jetting Printing (BJP) + Cold Isostatic Pressing (CIP) + cycle and (ii) BJP + cycle where cycle refers to a sequence of Impregnation-Drying-Pyrolysis. These two new processes yielded additively manufactured parts with higher density and reduced defects/porosities. As a testbed, we used these new processes to fabricate graphite structures. The samples produced by both methods were compared with each other and benchmarked to the samples produced by (a) BJP alone and (b) Traditional uniaxial pressing like compaction moulding. Various characterisation methods were used to investigate the microstructure and mechanical properties which showed that the porosity of hybrid manufactured samples reduces from 55% to a record 7%. This technological pathway is expected to create a new avalanche of industrial applications that are hitherto unexplored in the arena of hybrid additive manufacturing with BJP method

Ultrasonic tomography of SiC-based materials synthesized by spark plasma sintering of preceramic paper

This paper is devoted to study a structure of SiC-based materials using ultrasonic tomography method. The SiC-based materials were fabricated from preceramic paper using spark plasma sintering (SPS) method. Also as part of the study the Young`s modulus and density of sintered materials were determined and the effect of sintering pressure changing to this parameters value was investigated. The preceramic paper is a composite material including a matrix of organic cellulose fibers and inorganic powder filler (SiC). The sintering temperature and pressure were 2373 K and 20-40 MPa, respectively. The holding time for the sintering process was 10 min. The density of sintered materials was investigated by the hydrostatic weighing method. Ultrasonic tomography was implemented using of single-channel sensor at 10 MHz frequency

Ultrasonic tomography of SiC-based materials synthesized by spark plasma sintering of preceramic paper

This paper is devoted to study a structure of SiC-based materials using ultrasonic tomography method. The SiC-based materials were fabricated from preceramic paper using spark plasma sintering (SPS) method. Also as part of the study the Young's modulus and density of sintered materials were determined and the effect of sintering pressure changing to this parameters value was investigated. The preceramic paper is a composite material including a matrix of organic cellulose fibers and inorganic powder filler (SiC). The sintering temperature and pressure were 2373 K and 20-40 MPa, respectively. The holding time for the sintering process was 10 min. The density of sintered materials was investigated by the hydrostatic weighing method. Ultrasonic tomography was implemented using of single-channel sensor at 10 MHz frequency. © Published under licence by IOP Publishing Ltd.Russian Science Foundation, RSF: 19-19-00192The research was supported by the Russian Science Foundation (grant No. 19-19-00192) as well as b

SiC- and Ti3SiC2-Based Ceramics Synthesis by Spark Plasma Sintering of Preceramic Paper

This paper is devoted to proposing a new approach to the synthesis of SiC- and Ti3SiC2-based ceramics by using of preceramic paper as a feedstock. A preceramic paper with SiC and Ti3SiC2 powder fillers were sintered by spark plasma sintering (SPS) method for holding time 10 minutes under pressure 20-100 MPa. The temperature for the sintering of SiC- and Ti3SiC2-filled paper was 2073-2373 K and 1373-1473 K respectively. The influence of sintering parameters on the materials microstructure was analyzed by scanning electron microscopy. It was revealed that with an increase in pressure from 20 to 100 MPa, the microstructure of the materials becomes denser. It agrees with the results of measuring the density of the sintering materials by the hydrostatic weighting. The determination of Young`s modulus by the acoustic method demonstrates that with the increase of the applied pressure during SPS, Young’s modulus of the synthesized SiC- and Ti3SiC2-ceramics increase

Influence of preceramic paper composition on microstructure and mechanical properties of spark plasma sintered Ti3SiC2-based composites

AbstractThis paper describes the effect of preceramic paper composition on microstructure and mechanical properties of Ti3SiC2-based composites. The preceramic paper with Ti3SiC2-powder filler and different content (from 10 to 40 wt.%) of organic component (cellulose) was prepared. The composites were obtained by spark plasma sintering (SPS) at 50 MPa pressure for 10 min holding time. The sintering temperature was 1473 K. The influence of organic content on microstructure, phase composition, and flexural strength of the sintered materials was analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and mechanical testing, respectively. It was revealed that the microstructure of the sintered materials became more porous with increasing of cellulose content in the paper. XRD analysis showed the presence of Ti3SiC2, TiC and TiSi2 phases in the sintered samples while the content of the Ti3SiC2 phase increase with decreasing of the organic content. The flexural strength changes from 100 (40 wt.%) to 300 MPa (10 wt.% organic binder) that is caused by porosity of the composites

Investigation of process parameter effect on anisotropic properties of 3D printed sand molds

The development of sand mold three-dimensional printing technologies enables the manufacturing of molds without the use of a physical model. However, the effects of the three-dimensional printing process parameters on the mold permeability and strength are not well known, leading the industries to keep old settings until castings have recurring defects. In the present work, the influence of these parameters was experimentally investigated to understand their effect on the mold strength and permeability. Cylindrical and barshaped test specimens were printed to perform, respectively, permeability and bending strength measurements. Experiments were designed to statistically quantify the individual and combined effect of these process parameters. While the binder quantity only affects the mold strength, increasing the recoater speed leads to both greater permeability and reduced strength due to the reduced sand compaction. Recommendations for optimizing some 3D printer settings are proposed to attain predefined mold properties and minimize the anisotropic behavior of the sand mold in regard to both the orientation and the position in the job box

Surface crack healing of polymer-filler derived ceramics

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Processing, Microstructure and Properties of Paper-Derived Porous Al2O3 Substrates

In this work, preceramic papers containing 85 wt% Al2O3 were heat-treated at 1600 °C to obtain paper-derived ceramics. In order to increase the preceramic paper density prior to sintering, the papers were calendered at different roll temperatures and pressures. The influences of the calendering parameters on the microstructure and mechanical properties of the preceramic papers and the paper-derived ceramics were investigated. It was expected that especially the mechanical properties of the papers and derived ceramics would be improved by calendering