The most widely used metal additive manufacturing processes utilize powder that is spread or fed onto a building platform. Although there are reviews of the literature on some aspects of the powder, many aspects have ...The most widely used metal additive manufacturing processes utilize powder that is spread or fed onto a building platform. Although there are reviews of the literature on some aspects of the powder, many aspects have been under-reviewed or unreviewed. The present work is a review of the literature on these aspects. Articles published in the open literature through the end of February 2022 were collected by consulting highly regarded relevant bibliographic databases, such as Google Scholar and Science Direct. The aspects reviewed were emerging methods of powder production, methods used to improve the quality of a powder after production by a well-established method, influence of variables of well-established powder production methods on powder properties, influence of powder production method on powder properties, and influence of powder reuse on properties of powders of a wide collection of alloys. One key finding was that with regard to powder reuse, the only consistent finding is that it leads to increase in the oxygen content of the powder. Another key finding was that the literature on the aspects of the literature reviewed herein contains many shortcomings and gaps, which suggest potential areas for future research, such as techniques for optimization of process variables for a given combination of metal powder and powder production method and development of methods for production of powders of new/emerging metallic materials.展开更多
The flowability of five kinds of microencapsulation powders,with differentβ-carotene contents and by two alternative particle-forming technologies i.e.spray-drying and starch-catching beadlet technology,was meas- ure...The flowability of five kinds of microencapsulation powders,with differentβ-carotene contents and by two alternative particle-forming technologies i.e.spray-drying and starch-catching beadlet technology,was meas- ured.The actual flow properties of the five powders were compared based on bin-flow test,and three flow indexes (Hausner ratio,repose angle and flow index)were measured.It was found that the repose angle is the most suitable index to reflect the flowability of these powders for the particle properties would not be altered due to compaction or tapping during the measuring process.Particle size and particle size distribution play most important roles in the flowability of these granular materials,which was also influenced by other factors like shape,surface texture,sur- face roughness,etc.Microcapsules with wall material of gelatin and a layer of modified starch absorbed on the sur- face showed excellent flowabilities and good mechanical properties,and they are favorable for tabletting to supply β-carotene.展开更多
The inclination angle of the flake particle has a significant impact on the in-plane thermal conductivity of composites.The graphite flake/Al composites(50 vol%)with different inclination angles were fabricated via fl...The inclination angle of the flake particle has a significant impact on the in-plane thermal conductivity of composites.The graphite flake/Al composites(50 vol%)with different inclination angles were fabricated via flake powder metallurgy,and the results show that with increasing the size of Al particle from 25.6 to 50.7μm,the inclination angle of graphite flake decreases from 7.3°to 4.4°,while the in-plane thermal conductivity of composites increases from 473 to 555 Wm-1 K-1.Based on the rules of mixture,an effective model was established to qualify and quantify the relation between the inclination angle and the in-plane thermal conductivity of the corresponding composites.This model can also be applied to other flake particle-reinforced composites.展开更多
文摘The most widely used metal additive manufacturing processes utilize powder that is spread or fed onto a building platform. Although there are reviews of the literature on some aspects of the powder, many aspects have been under-reviewed or unreviewed. The present work is a review of the literature on these aspects. Articles published in the open literature through the end of February 2022 were collected by consulting highly regarded relevant bibliographic databases, such as Google Scholar and Science Direct. The aspects reviewed were emerging methods of powder production, methods used to improve the quality of a powder after production by a well-established method, influence of variables of well-established powder production methods on powder properties, influence of powder production method on powder properties, and influence of powder reuse on properties of powders of a wide collection of alloys. One key finding was that with regard to powder reuse, the only consistent finding is that it leads to increase in the oxygen content of the powder. Another key finding was that the literature on the aspects of the literature reviewed herein contains many shortcomings and gaps, which suggest potential areas for future research, such as techniques for optimization of process variables for a given combination of metal powder and powder production method and development of methods for production of powders of new/emerging metallic materials.
基金Supported by the National-Natural Science Foundation of China （No.20576118） and National High Technology Research and Development Program of China （863 Program, No.2006AA02Z210）.
文摘The flowability of five kinds of microencapsulation powders,with differentβ-carotene contents and by two alternative particle-forming technologies i.e.spray-drying and starch-catching beadlet technology,was meas- ured.The actual flow properties of the five powders were compared based on bin-flow test,and three flow indexes (Hausner ratio,repose angle and flow index)were measured.It was found that the repose angle is the most suitable index to reflect the flowability of these powders for the particle properties would not be altered due to compaction or tapping during the measuring process.Particle size and particle size distribution play most important roles in the flowability of these granular materials,which was also influenced by other factors like shape,surface texture,sur- face roughness,etc.Microcapsules with wall material of gelatin and a layer of modified starch absorbed on the sur- face showed excellent flowabilities and good mechanical properties,and they are favorable for tabletting to supply β-carotene.
基金financially supported by the National Key Research and Development Program of China(Nos.2018YFB0704400,2017YFB0406100)the National Nature Science Foundation of China(Nos.51671129,51971132,51501111,51471106)
文摘The inclination angle of the flake particle has a significant impact on the in-plane thermal conductivity of composites.The graphite flake/Al composites(50 vol%)with different inclination angles were fabricated via flake powder metallurgy,and the results show that with increasing the size of Al particle from 25.6 to 50.7μm,the inclination angle of graphite flake decreases from 7.3°to 4.4°,while the in-plane thermal conductivity of composites increases from 473 to 555 Wm-1 K-1.Based on the rules of mixture,an effective model was established to qualify and quantify the relation between the inclination angle and the in-plane thermal conductivity of the corresponding composites.This model can also be applied to other flake particle-reinforced composites.
