Additive Manufacturing(AM)can provide customized parts that conventional techniques fail to deliver.One important parameter in AM is the quality of the parts,as a result of the material extrusion 3D printing(3D-P)proc...Additive Manufacturing(AM)can provide customized parts that conventional techniques fail to deliver.One important parameter in AM is the quality of the parts,as a result of the material extrusion 3D printing(3D-P)procedure.This can be very important in defense-related applications,where optimum performance needs to be guaranteed.The quality of the Polyetherimide 3D-P specimens was examined by considering six control parameters,namely,infill percentage,layer height,deposition angle,travel speed,nozzle,and bed temperature.The quality indicators were the root mean square(Rq)and average(Ra)roughness,porosity,and the actual to nominal dimensional deviation.The examination was performed with optical profilometry,optical microscopy,and micro-computed tomography scanning.The Taguchi design of experiments was applied,with twenty-five runs,five levels for each control parameter,on five replicas.Two additional confirmation runs were conducted,to ensure reliability.Prediction equations were constructed to express the quality indicators in terms of the control parameters.Three modeling approaches were applied to the experimental data,to compare their efficiency,i.e.,Linear Regression Model(LRM),Reduced Quadratic Regression Model,and Quadratic Regression Model(QRM).QRM was the most accurate one,still the differences were not high even considering the simpler LRM model.展开更多
A direct 3D extrusion printing technique was used to produce Ti-TiB filaments and microlattices.The sintering properties of 3D ink extrusion and sintering of in situ Ti-TiB composite structures made from TiH_(2)+TiB_(...A direct 3D extrusion printing technique was used to produce Ti-TiB filaments and microlattices.The sintering properties of 3D ink extrusion and sintering of in situ Ti-TiB composite structures made from TiH_(2)+TiB_(2) ink were investigated.The sintering kinetics of TiH2+TiB2 inks was studied during densification by pressureless sintering at 1050−1200℃ for 4−24 h in Ar.The linear shrinkage,grain size,microhardness,X-ray diffraction(XRD)patterns,and microstructural evolution of the Ti-TiB composite were studied.The sintering temperature had a more pronounced influence than the sintering time on the density of the Ti-TiB composite.There were two kinds of pores,irregular and spherical,caused by the Kirkendall effect and indiffusable gases.The TiB formed by in situ synthesis existed as either separated TiB whiskers(needle-like shapes)or clusters of TiB whiskers.The results of this work could be useful for controlling microporosity through incomplete sintering within filaments,especially for the production of in situ Ti-TiB with high volume fractions of TiB or other composites.展开更多
This study focused on the production of polypropylene(PP)/silver(Ag)composites via additive manufacturing.This study aimed to enhance the quality of medical-grade PP in material extrusion(MEX)three-dimensional printin...This study focused on the production of polypropylene(PP)/silver(Ag)composites via additive manufacturing.This study aimed to enhance the quality of medical-grade PP in material extrusion(MEX)three-dimensional printing(3DP)by improving its mechanical properties while simultaneously adding antibacterial properties.The latter can find extremely important and versatile properties that are applicable in defense and security domains.PP/Ag nanocomposites were prepared using a novel method based on a reaction occurring while mixing appropriate quantities of the starting polymers and additives,namely polyvinylpyrrolidone(PVP)as the matrix material and silver nitrate(AgNO_(3))as the filler.This process produced three-dimensional(3D)printed filaments,which were then used to create specimens for a series of standardized tests.It was found that the mechanical properties of the nanocomposites were enhanced in relation to pristine PP,especially for the PP matrix with various loadings of AgNO_(3)and PVP,such as 5.0 wt%and 2.5 wt%,respectively.The voids,inclusions,and actual-to-nominal dimensions also showed improved results.The 3DP specimens exhibited a more effective biocidal performance against Staphylococcus aureus than Escherichia coli,which developed an inhibition zone only in the case of PP with filler loading percentages of AgNO_(3)and PVP at 10.0 wt%and 5.0 wt%,respectively Compounds possessing such properties can be beneficial for various applications requiring increased mechanical properties and biocidal capabilities,such as in the Defence or medical industries.展开更多
文摘Additive Manufacturing(AM)can provide customized parts that conventional techniques fail to deliver.One important parameter in AM is the quality of the parts,as a result of the material extrusion 3D printing(3D-P)procedure.This can be very important in defense-related applications,where optimum performance needs to be guaranteed.The quality of the Polyetherimide 3D-P specimens was examined by considering six control parameters,namely,infill percentage,layer height,deposition angle,travel speed,nozzle,and bed temperature.The quality indicators were the root mean square(Rq)and average(Ra)roughness,porosity,and the actual to nominal dimensional deviation.The examination was performed with optical profilometry,optical microscopy,and micro-computed tomography scanning.The Taguchi design of experiments was applied,with twenty-five runs,five levels for each control parameter,on five replicas.Two additional confirmation runs were conducted,to ensure reliability.Prediction equations were constructed to express the quality indicators in terms of the control parameters.Three modeling approaches were applied to the experimental data,to compare their efficiency,i.e.,Linear Regression Model(LRM),Reduced Quadratic Regression Model,and Quadratic Regression Model(QRM).QRM was the most accurate one,still the differences were not high even considering the simpler LRM model.
基金Project(201806920003)supported by the China Scholarship CouncilProject(172180)supported by the Swiss National Science FoundationProjects(ECCS-1542205,DMR-1720139)supported by the National Natural Science Foundation,USA。
文摘A direct 3D extrusion printing technique was used to produce Ti-TiB filaments and microlattices.The sintering properties of 3D ink extrusion and sintering of in situ Ti-TiB composite structures made from TiH_(2)+TiB_(2) ink were investigated.The sintering kinetics of TiH2+TiB2 inks was studied during densification by pressureless sintering at 1050−1200℃ for 4−24 h in Ar.The linear shrinkage,grain size,microhardness,X-ray diffraction(XRD)patterns,and microstructural evolution of the Ti-TiB composite were studied.The sintering temperature had a more pronounced influence than the sintering time on the density of the Ti-TiB composite.There were two kinds of pores,irregular and spherical,caused by the Kirkendall effect and indiffusable gases.The TiB formed by in situ synthesis existed as either separated TiB whiskers(needle-like shapes)or clusters of TiB whiskers.The results of this work could be useful for controlling microporosity through incomplete sintering within filaments,especially for the production of in situ Ti-TiB with high volume fractions of TiB or other composites.
文摘This study focused on the production of polypropylene(PP)/silver(Ag)composites via additive manufacturing.This study aimed to enhance the quality of medical-grade PP in material extrusion(MEX)three-dimensional printing(3DP)by improving its mechanical properties while simultaneously adding antibacterial properties.The latter can find extremely important and versatile properties that are applicable in defense and security domains.PP/Ag nanocomposites were prepared using a novel method based on a reaction occurring while mixing appropriate quantities of the starting polymers and additives,namely polyvinylpyrrolidone(PVP)as the matrix material and silver nitrate(AgNO_(3))as the filler.This process produced three-dimensional(3D)printed filaments,which were then used to create specimens for a series of standardized tests.It was found that the mechanical properties of the nanocomposites were enhanced in relation to pristine PP,especially for the PP matrix with various loadings of AgNO_(3)and PVP,such as 5.0 wt%and 2.5 wt%,respectively.The voids,inclusions,and actual-to-nominal dimensions also showed improved results.The 3DP specimens exhibited a more effective biocidal performance against Staphylococcus aureus than Escherichia coli,which developed an inhibition zone only in the case of PP with filler loading percentages of AgNO_(3)and PVP at 10.0 wt%and 5.0 wt%,respectively Compounds possessing such properties can be beneficial for various applications requiring increased mechanical properties and biocidal capabilities,such as in the Defence or medical industries.
