The characteristics of PZT suspensions have been studied and fit to stereolithography restraints. On one hand, researches concern the influence of fillers contents, dispersant…
Abstract
The characteristics of PZT suspensions have been studied and fit to stereolithography restraints. On one hand, researches concern the influence of fillers contents, dispersant concentration, temperature and resins nature and amount on suspensions rheological behaviour. On the other hand, the influence of photoinitiator and PZT concentrations, density of energy and nature of the resin on suspension reactivity was investigated. These experiments have led to the choice of two photosensitive suspensions suitable for stereolithography purpose; which use depend on the fillers content. Furthermore, the stereolithography process has been modified owing to the balance between suspensions rheological and photochemical properties in order to shape piezoelectric ceramics. Thanks to these improvements, PZT ceramics/polymer composites dedicated to transducers and medical imaging applications have been fabricated.
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Weizhao Zhou, Dichen Li and Hui Wang
The purpose of this paper is to present a new ceramic suspension to fabricate complex ceramic parts by stereolithography (SL).
Abstract
Purpose
The purpose of this paper is to present a new ceramic suspension to fabricate complex ceramic parts by stereolithography (SL).
Design/methodology/approach
The process consists of preparation of aqueous ceramic suspensions, building ceramic parts, drying, subsequent binder removal, and sintering. Highly concentrated aqueous ceramic suspensions with a suitable viscosity are prepared, then a wet green ceramic part fabricated in a SL machine according to a 3D model is dried in polyethylene glycol. After binder removal sintering in a high temperature‐sintering furnace, a complex ceramic part is obtained.
Findings
The dispersant, volume fraction of ceramic powder and powder diameter could influence the viscosity of suspension. The cured depth is inversely proportional to the scanning speed of laser spot when the laser power keeps a constant and proportional to the concentration of monomer. The penetration depth and critical exposure are 0.27 mm and 231.2 mJ/cm2 from the experimental result of the windowpanes method. A new support structure could prevent the deformation of ceramic part from the suspension and improve the quality of ceramic parts. A complex impeller is fabricated at last.
Research limitations/implications
The dimensional and surface accuracy of ceramic SL should be further investigated.
Originality/value
This paper describes a new aqueous ceramic suspension to produce complex‐shaped ceramic parts by SL.
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Abstract
Purpose
Conventional machining methods for fabricating piezoelectric components such as ultrasound transducer arrays are time-consuming and limited to relatively simple geometries. The purpose of this paper is to develop an additive manufacturing process based on the projection-based stereolithography process for the fabrication of functional piezoelectric devices including ultrasound transducers.
Design/methodology/approach
To overcome the challenges in fabricating viscous and low-photosensitive piezocomposite slurry, the authors developed a projection-based stereolithography process by integrating slurry tape-casting and a sliding motion design. Both green-part fabrication and post-processing processes were studied. A prototype system based on the new manufacturing process was developed for the fabrication of green-parts with complex shapes and small features. The challenges in the sintering process to achieve desired functionality were also discussed.
Findings
The presented additive manufacturing process can achieve relatively dense piezoelectric components (approximately 95 per cent). The related property testing results, including X-ray diffraction, scanning electron microscope, dielectric and ferroelectric properties as well as pulse-echo testing, show that the fabricated piezo-components have good potentials to be used in ultrasound transducers and other sensors/actuators.
Originality/value
A novel bottom-up projection system integrated with tape casting is presented to address the challenges in the piezo-composite fabrication, including small curing depth and viscous ceramic slurry recoating. Compared with other additive manufacturing processes, this method can achieve a thin recoating layer (as small as 10 μm) of piezo-composite slurry and can fabricate green parts using slurries with significantly higher solid loadings. After post processing, the fabricated piezoelectric components become dense and functional.
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Regina Knitter, Werner Bauer, Dieter Göhring and Peter Risthaus
Conventional shaping processes for ceramics are mostly based on a powder‐technological molding process using a negative mold and subsequent thermal compaction. Especially for…
Abstract
Conventional shaping processes for ceramics are mostly based on a powder‐technological molding process using a negative mold and subsequent thermal compaction. Especially for prototypes and small lot series of microcomponents the outlay for molds are the major costing factor. Consequently the use of rapid prototyping (RP) processes can decisively reduce the costs and time in product development of ceramic microcomponents. In spite of the fact, that a large number of freeform fabrication techniques for different materials were developed in recent years, most generative techniques of ceramics still have different drawbacks for the fabrication of prototypes and often exhibit limited resolution compared to those of polymers. The combination of RP techniques such as micro stereolithography and ceramic injection molding in a RP process chain can fill in the gap between the limited applicability of solid freeform fabrication of ceramics and the restricted material properties of polymers.
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A. Touati, S. Corbel and J.P. Corriou
Photolithography allows the fabrication of a solid polymer object through polymerization of a monomer resin by means of a laser source guided according to the data of computer…
Abstract
Photolithography allows the fabrication of a solid polymer object through polymerization of a monomer resin by means of a laser source guided according to the data of computer aided design. However, one drawback of this method is the inaccuracy of the dimensions of the objects related to the shrinkage phenomenon which depends on the polymerization, on the laser flux and on the used sweeping procedure. In this paper, the deformation of an isolated voxel (elementary volume) or a voxel interacting with its neighbor is described. This simulation is based on a kinetic model that takes into account the gel effect and a model of volumetric variation due to the difference of the length of the bonds between the monomer and polymer molecules.
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Pasquale Giungato, Bianca Moramarco, Roberto Leonardo Rana and Caterina Tricase
International outbreak of the SARS-CoV-2 infection has fostered the Italian government to impose the FFP2 protective facial masks in closed environments, including bar…
Abstract
Purpose
International outbreak of the SARS-CoV-2 infection has fostered the Italian government to impose the FFP2 protective facial masks in closed environments, including bar, restaurants and, more in general, in the food sector. Protective facial masks are rocketing, both in mass and in costs, in the food sector imposing efforts in fostering reuse strategies and in the achievement of sustainable development goals. The scope of the present paper is to depict possible strategies in manufacturing and reuse strategies that can reduce the carbon footprint (CF) of such devices.
Design/methodology/approach
To implement circular economy strategies in the protective facial masks supply chain, it was considered significant to move towards a study of the environmental impact of such devices, and therefore a CF study has been performed on an FFP2 facial mask used in the food sector. Different materials besides the mostly used polypropylene (PP) (polyethylene (PE), polycarbonate (PC), poly (lactic acid) (PLA), cotton, polyurethane (PUR), polystyrene (PS) and nylon 6,6) and different sanitisation alternatives as reuse strategies (both laboratory and homemade static oven, ultraviolet germicidal irradiation) readily implemented have been modelled to calculate the CF of a single use of an FFP2 mask.
Findings
The production of textiles in PP, followed by disposal was the main contributor to CF of the single-use FFP2 mask, followed by packaging and transportations. PP and PE were the least impacting, PC, cotton and Nylon 6-6 of the same weight results the worst. PLA has an impact greater than PP and PE obtained from crude oil, followed by PUR and PS. Static laboratory oven obtained an 80.4% reduction of CF with respect to single use PP-made FFP2 mask, whereas homemade oven obtained a similar 82.2% reduction; UV cabinet is the best option, showing an 89.9% reduction.
Research limitations/implications
The key strategies to reduce the environmental impacts of the masks (research for new materials and reuse with sanitisation) should ensure both the retention of filtering capacities and the sanitary sterility of the reused ones. Future developments should include evaluations of textile recycling impacts, using new materials and the evaluation of the life cycle costs of the reused masks.
Practical implications
This paper intends to provide to stakeholders (producers, consumers and policy makers) the tools to choose the best option for producing and reuse environmentally friendly protective facial masks to be used in the food sector, by using both different materials and easily implemented reuse strategies.
Social implications
The reduction of the CF of protective facial masks in the food sector surely will have relevant positive effects on climate change contributing to reach the goals of reducing CO2 emissions. The food sector may promote sustainable practices and attract a niche piece of clients particularly sensible to such themes.
Originality/value
The paper has two major novelties. The first one is the assessment of the CF of a single use of an FFP2 mask made with different materials of the non-woven filtering layers; as the major contribution to the CF of FFP2 masks is related to the non-woven textiles manufacturing, the authors test some other different materials, including PLA. The second is the assessment of the CF of one single use of a sanitised FFP2 mask, using different sanitation technologies as those allowed in bars or restaurants.
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Investigates the dimensions of accounting information prepared foruse in managing non‐corporate pastoral entities in pre‐FederationWestern Victoria and the local, time‐specific…
Abstract
Investigates the dimensions of accounting information prepared for use in managing non‐corporate pastoral entities in pre‐Federation Western Victoria and the local, time‐specific environmental factors which shaped these dimensions. Based on examinations of 23 sets of surviving business records prepared during 1836‐1900, provides evidence of the structure and usage of pastoral accounting information in an unregulated financial reporting environment. Draws conclusions about the likely impact of cultural, legal and political, professional, educational, economic and other factors as key explanatory variables. Also argues a case for lost relevance based on the evidence of accounting change in the closing decades of the nineteenth century.