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1 – 10 of over 4000S.M. El‐Sawy, I.M. Morsi and F.A. Abdel‐Mohdy
Three different methods have been studied to prepare silver powder pigments in order to find out the most suitable product for application in conductive paints. X‐ray analysis…
Abstract
Three different methods have been studied to prepare silver powder pigments in order to find out the most suitable product for application in conductive paints. X‐ray analysis, specific gravity, pH value, water solubility, oil absorption, particle size distribution, and particle shape of the prepared silver powders were measured and compared with a commercial pigment. It was found that two of the three grades of silver powders have more suitable properties for application as conductive pigments.
M. Umiński and L.M. Saija
A comparison of the difference in chemical nature of re‐dispersible polymer powders useful for the modification of cement based compositions is made. Core‐shell acrylic lattices…
Abstract
A comparison of the difference in chemical nature of re‐dispersible polymer powders useful for the modification of cement based compositions is made. Core‐shell acrylic lattices synthesised by multi‐step sequential polymerisation are formulated and spray‐dried to obtain re‐dispersible powders. The heterogeneous acrylic copolymers prepared are characterised by excellent re‐dispersibility, high chemical stability and good application properties.
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İdris Tuğrul Gülenç, Mingwen Bai, Ria L. Mitchell, Iain Todd and Beverley J. Inkson
Current methods for the preparation of composite powder feedstock for selective laser melting (SLM) rely on costly nanoparticles or yield inconsistent powder morphology. This…
Abstract
Purpose
Current methods for the preparation of composite powder feedstock for selective laser melting (SLM) rely on costly nanoparticles or yield inconsistent powder morphology. This study aims to develop a cost-effective Ti6Al4V-carbon feedstock, which preserves the parent Ti6Al4V particle’s flowability, and produces in situ TiC-reinforced Ti6Al4V composites with superior traits.
Design/methodology/approach
Ti6Al4V particles were directly mixed with graphite flakes in a planetary ball mill. This composite powder feedstock was used to manufacture in situ TiC-Ti6Al4V composites using various energy densities. Relative porosity, microstructure and hardness of the composites were evaluated for different SLM processing parameters.
Findings
Homogeneously carbon-coated Ti6Al4V particles were produced by direct mixing. After SLM processing, in situ grown 100–500 nm size TiC nanoparticles were distributed within the α-martensite Ti6Al4V matrix. The formation of TiC particles refines the Ti6Al4V β grain size. Relative density varied between 96.4% and 99.5% depending on the processing parameters. Hatch distance, exposure time and point distance were all effective on relative porosity change, whereas only exposure time and point distance were effective on hardness change.
Originality/value
This work introduces a novel, cost-effective powder feedstock preparation method for SLM manufacture of Ti6Al4V-TiC composites. The in situ SLM composites achieved in this study have high relative density values, well-dispersed TiC nanoparticles and increased hardness. In addition, the feedstock preparation method can be readily adapted for various matrix and reinforcement materials in future studies.
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Junchao Li, Ran Yan, Yanan Yang and Feng Xie
The purpose of this study was to prepare water-based binders, which aimed to avoid printhead blockage and to improve dimensional accuracy of inkjet 3D printing (3DP) technology…
Abstract
Purpose
The purpose of this study was to prepare water-based binders, which aimed to avoid printhead blockage and to improve dimensional accuracy of inkjet 3D printing (3DP) technology, and a feasible algorithm of full-color printing was realized.
Design/methodology/approach
A self-developed color 3D printer was made by using a piezoelectric printhead of Epson Dx-5. Several water-based binders and corresponding gypsum composite powders were prepared, and the optimum binder-powder assembly was then determined through elementary adhesive testing and roller paving testing. Full-color printing was implemented based on halftoning algorithms that used different threshold matrices for different ink channels, and the performances of various algorithms were evaluated in terms of both subjective and objective indices.
Findings
The optimum binder-powder assembly can solve the jamming problem of printhead and realize agreeable dimensional accuracy with the relative error less than 2.5% owing to the satisfying boundary diffusion control ability. And the determined halftone algorithm was verified to be agreeable for 3D color printing.
Originality/value
The prepared approach of water-based binders and gypsum composite powders can be applied to similar 3DP systems even if different materials are introduced. And the used halftone algorithms provide feasible guidelines to the implementation of 3D full-color printing.
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K.M. Fan, W.L. Cheung and I. Gibson
This paper aims to study the effects of solid additives and compounding processes on the selective laser sintering (SLS) behavior of composite powders.
Abstract
Purpose
This paper aims to study the effects of solid additives and compounding processes on the selective laser sintering (SLS) behavior of composite powders.
Design/methodology/approach
Composite powders were prepared from TrueForm™ acrylic‐styrene co‐polymer and SiO2 powder. Dry mixing and melt extrusion were used as the blending processes to produce the composite powders. Some SiO2 powder was ground and treated with silane coupling agent before blending to study the effects of particle size and surface treatment of the filler, respectively. The temperature of the powder bed was monitored using an infrared thermometer. The fusion behaviors of the powders were investigated in situ using an optical microscope and the sintered specimens were examined by scanning electron microscopy.
Findings
For a given volume fraction of the filler, reducing its particle size will hinder fusion between the polymer particles and weaken the sintered specimens. Surface treatment of the filler by silane coupling agent had little effect on the morphology of the sintered specimens; however, it slightly improved their strength. The blending method plays an important role in the sintering behavior of the composite powders. Although melt blending improved the polymer‐to‐polymer contact between the composite powder particles, the high‐resultant viscosity of the material adversely affected the densification of the powder bed, leading to a highly porous structure of the sintered specimens.
Research limitations/implications
The sintering experiments were conducted in ambient conditions using a laser engraving machine instead of a commercial SLS machine with atmospheric control. The temperature gradient within the powder bed was expected to be higher than that in normal SLS processes.
Practical implications
The SLS behavior of a composite powder not only depends on its composition but also on the powder preparation method or powder morphology.
Originality/value
This paper provides some useful information for future development of composite powders for SLS applications.
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Djamila Olivier, Salvador Borros and Guillermo Reyes
A structured customer-driven and integrative methodology to develop materials is described. The proposed methodology is aimed to drive analysis and prioritization of the multiple…
Abstract
Purpose
A structured customer-driven and integrative methodology to develop materials is described. The proposed methodology is aimed to drive analysis and prioritization of the multiple variables involved in a new application case for 3D printing, which involves the development of a new alumina-starch-based powder.
Design/methodology/approach
The development of new powder mixture designed for 3D printing of refractory supports for metal casting moulds is presented. The quality function deployment (QFD) method was applied. Inputs for QFD analysis were found using total quality management tools. Using this approach, six process and material variables were considered to drive a prioritization analysis using a Plackett-Burman Design of Experiment (DOE) array. As performance parameter, compressive resistance was measured and assessed.
Findings
QFD analysis delivered standardized procedures, irrelevant factors and target values for intermediate step parameters. Sintering parameters were found to be the most influencing over compressive resistance.
Research limitations/implications
The methodology was based upon a materials development case for 3D printing.
Practical implications
Knowing in advance the influence of every affecting factor of the process provides a closer control on variability of final part properties, which is a key issue to launch parts into industrial applications. Quality planning and documentation in advanced is the basis for all the quality system of the new additive manufacturing (AM) process to be created.
Originality/value
Procedures for quality planning and control were proposed. This study, as methodological research, intends to introduce industrial engineering practices and quality management routines for AM material/process developers.
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Agnieszka Chmielewska, Bartlomiej Adam Wysocki, Elżbieta Gadalińska, Eric MacDonald, Bogusława Adamczyk-Cieślak, David Dean and Wojciech Świeszkowski
The purpose of this paper is to investigate the effect of remelting each layer on the homogeneity of nickel-titanium (NiTi) parts fabricated from elemental nickel and titanium…
Abstract
Purpose
The purpose of this paper is to investigate the effect of remelting each layer on the homogeneity of nickel-titanium (NiTi) parts fabricated from elemental nickel and titanium powders using laser powder bed fusion (LPBF). In addition, the influence of manufacturing parameters and different melting strategies, including multiple cycles of remelting, on printability and macro defects, such as pore and crack formation, have been investigated.
Design/methodology/approach
An LPBF process was used to manufacture NiTi alloy from elementally blended powders and was evaluated with the use of a remelting scanning strategy to improve the homogeneity of fabricated specimens. Furthermore, both single melt and up to two remeltings were used.
Findings
The results indicate that remelting can be beneficial for density improvement as well as chemical and phase composition homogenization. Backscattered electron mode in scanning electron microscope showed a reduction in the presence of unmixed Ni and Ti elemental powders in response to increasing the number of remelts. The microhardness values of NiTi parts for the different numbers of melts studied were similar and ranged from 487 to 495 HV. Nevertheless, it was observed that measurement error decreases as the number of remelts increases, suggesting an increase in chemical and phase composition homogeneity. However, X-ray diffraction analysis revealed the presence of multiple phases regardless of the number of melt runs.
Originality/value
For the first time, to the best of the authors’ knowledge, elementally blended NiTi powders were fabricated via LPBF using remelting scanning strategies.
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Gurminder Singh and Pulak Mohan Pandey
The purpose of this study is to study the mechanical, tribological and electrical properties of the copper-graphene (Cu-Gn) composites fabricated by a novel rapid tooling…
Abstract
Purpose
The purpose of this study is to study the mechanical, tribological and electrical properties of the copper-graphene (Cu-Gn) composites fabricated by a novel rapid tooling technique consist of three-dimensional printing and ultrasonic-assisted pressureless sintering (UAPS).
Design/methodology/approach
Four different Cu-Gn compositions with 0.25, 0.5, 1 and 1.5 per cent of graphene were fabricated using an amalgamation of three-dimensional printing and UAPS. The polymer 3d printed parts were used to prepare mould cavity and later the UAPS process was used to sinter Cu-Gn powder to acquire free-form shape. The density, hardness, wear rate, coefficient of friction and electrical conductivity were evaluated for the different compositions of graphene and compared with the pure copper. Besides, the comparison was performed with the conventional method.
Findings
Cu-Gn composites revealed excellent wear properties due to higher hardness, and the lubrication provided by the graphene. The electrical conductivity of the fabricated Cu-Gn composites started increasing initially but decreased afterwards with increasing the content of graphene. The UAPS fabricated composites outperformed the conventional method manufactured samples with better properties such as density, hardness, wear rate, coefficient of friction and electrical conductivity due to homogeneous mixing of metal particles and graphene.
Originality/value
The fabrication of Cu-Gn composite freeform shapes was found to be difficult using conventional methods. The novel technique using a combination of polymer three-dimensional printing and UAPS as rapid tooling was introduced for the fabrication of freeform shapes of Cu-Gn composites and mechanical, tribological and electrical properties were studied. The method can be used to fabricate optimized complex Cu-Gn structures with improved wear and electrical applications.
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Bibo Yao, Zhenhua Li, Baoren Teng and Jing Liu
Laser powder bed fusion (LPBF) can be used to fabricate complex extrusion die without the limitation of structures. Layer-by-layer processing leads to differences in…
Abstract
Purpose
Laser powder bed fusion (LPBF) can be used to fabricate complex extrusion die without the limitation of structures. Layer-by-layer processing leads to differences in microstructures and wear properties. This study aims to investigate the microstructure evolution and effects of tungsten carbide (WC) on the wear properties of LPBF-printed 18Ni300.
Design/methodology/approach
Economical spherical granulation-sintering-deoxygenation (GSD) WC-reinforced 18Ni300 steel matrix composites were produced by LPBF from powder mixtures of WC and 18Ni300. The effects of WC contents on anisotropic microstructures and wear properties of the composites were investigated.
Findings
The relative density is more than 99% for all the composites except 25% WC/18Ni300 composite. The grain sizes distributed on the top cross-section are smaller than those on the side cross-section. After adding WC particles, more high-angle grain boundaries and larger Schmid factor generate, and deformed grains decrease. With increasing WC contents, the hardness first decreases and then increases but the wear volume loss decreases. The side cross-section of the composite has higher hardness and better wear resistance. The 18Ni300 exhibits adhesive wear accompanying with abrasive wear, while plowing and fatigue wear are the predominant wear mechanisms of the composites.
Originality/value
Economical spherical GSD WC particles can be used to improve the wear resistance. The novel WC/18Ni300 composites are suitable for the application under the abrasive wear condition with low stress.
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Abstract
Purpose
The purpose of this paper is to report a new method, the dissolution‐precipitation process, to prepare nylon‐coated metal powders for the indirect selective laser sintering (SLS) process.
Design/methodology/approach
The nylon‐12 coated carbon steel powders were prepared by the dissolution‐precipitation process. The powder characteristics are examined by scanning electron microscope (SEM) and laser diffraction particle size analysis. The effect of the applied laser energy density on the three‐point bend strength and dimensional accuracy of the SLS specimens are studied. The influence of nylon‐12 content on the bend strength are also investigated.
Findings
The SEM and laser diffraction particle size analysis results indicate that the steel particles are well coated by nylon‐12 resin. The bend strength of the SLS specimens increases with increasing the applied energy density until it reaches a maximum value, and then further increasing energy density will cause the decrease in the bend strength. The bend strength of the SLS specimens increases with increasing the nylon‐12 content over the investigated range. The dimensional errors in the X‐Y‐and Z‐directions are all increased with the increase in energy density.
Research limitations/implications
This paper only concerns the preparation and SLS of the coated powders. Further investigations are planned into post‐processing, such as binder decomposition and high‐temperature sintering, of the green parts made from the coated powders.
Originality/value
This paper provides a useful method for preparing nylon‐coated metal powders for making metal parts by the indirect SLS process.
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