Abstract
The adoption of additive manufacturing technology is gaining interest for processing precious metals. In this study, the capability of inkjet printing was explored to fabricate macroscopic parts from commercial silver nanoparticle ink (AgNPs). A bespoke JETx® three dimensional (3D) inkjet printing machine was used to print and subsequently sinter up to 1000 layers of AgNPs using an infrared source. Examination of the sample using X-ray computed tomography and scanning electron microscopy revealed the existence of both micro- and nano-scale pores within the structure. Pinning effect, residual surface temperature, insufficient droplet overlap and surface defects were the key factors contributing to the voids. Elemental mapping confirmed the structure to be composed of 87% of silver along with carbon and oxygen. The 750dpi sample showed a 25% reduction in nanopores and 77% lower micro-pores compared to the 600dpi sample. In terms of hardness, the 750dpi sample was 29% harder than the 600dpi sample, showcasing samples with higher print resolution can contribute towards less voids and improved mechanical properties. Thus by demonstrating the possibility to fabricate dense parts from AgNPs using inkjet technology, this study opens a novel route for processing nano-scale particulates and precious metals in 3D.
Highlights
The success of additive manufacturing (AM) in finding a place in mainstream manufacturing is primarily dictated by the added advantages of AM compared to the traditional forming and subtractive methods
Among the seven AM processes classified by the American Society for Testing and Materials (ASTM), VAT photo-polymerisation, material jetting (MJ), material extrusion, powder-bed fusion (PBF) and directed-energy deposition (DED) are the most common
Surface temperature, surface defects, flow behaviour and wettability of the ink on the surface were observed to affect the merging of droplets, leading to voids in the sample
Summary
The success of additive manufacturing (AM) in finding a place in mainstream manufacturing is primarily dictated by the added advantages of AM compared to the traditional forming and subtractive methods. Some of the key advantages of this computer aided design (CAD) driven process include, but are not limited to, (i) freedom of design (ii) the ability to produce near-net shape and end use parts, (iii) reduced time-to-market, (iv) decreased supply-chain, (v) reduced postprocessing requirements in terms of tooling, (vi) high material utilisation rate and (vii) less wastage [1]. PBF and DED are the most widely used methods for processing metals. With recent advancements in material development, PBF technologies, including selective laser melting (SLM), direct metal laser sintering (DMLS) and electron beam melting (EBM), are used to fabricate parts for various automotive, aerospace and biomedical applications. AM is considered as one of the key enablers for processing precious metals
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