Abstract

Ceramics-based additive manufacturing is a complex process and the solidification mechanism and microstructural evolution are currently not fully understood. In this work, Al 2 O 3 single tracks were formed using a customised selective laser melting (SLM) system equipped with a high power diode laser. The effects of laser energy density (LED) on geometry, microstructure and micro-mechanical properties of Al 2 O 3 tracks were investigated. To better understand the solidification mechanism, a transient threedimensional thermal model was developed for predicting the thermal behaviour of the melt pool. The results indicated the use of high LED gave rise to decreased viscosity and surface tension of the molten alumina and led to localised melting of the substrate. Both, in turn, enabled the formation of a continuous solidified track. The solidified tracks were primarily composed of columnar dendrite. When relatively high LED (≥25.7 kJ/m) was applied, equiaxed dendrite appeared along the central line near the 2 track surface. The size of dendritic grains decreased with the decreased LED, attributed to the increased cooling rate at solidification interface. The micro-hardness of the solidified track was found to be inversely proportional to the grain size owning to grain boundary strengthening effect.

No abstract

Abstract

No abstract

Biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) scaffolds have shown great promise for bone tissue engineering applications. The investigation of their hydrolytic degradation is thus essential to understand the effect of hydrolysis on the complex biodegradation behavior of PHBV scaffolds. In this study, we investigated the degradation behavior of high molecular weight PHBV scaffolds manufactured using selective laser sintering (SLS) without using predesigned porous architectures. The manufactured scaffolds have high specific surface areas with great water-uptake abilities. After an incubation of 6 weeks in phosphate-buffered saline solution, the structural integrity of the scaffolds was unaffected. However, a significant decrease in molecular weight ranging from 39% to 46% was found. The measured weight loss was negligible, but their compressive modulus and strength both decreased, likely due to water plasticization. These findings suggest that hydrolytic degradation of PHBV by means of bulk degradation was the predominant mechanism, attributed to their excellent water absorptivity. Overall, the PHBV scaffolds manufactured using SLS exhibited adequate mechanical properties and satisfactory structural integrity after incubation. As a result, the scaffolds have great potential as candidates for bone repair in clinical practice. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 154-162, 2019.

No abstract

Please cite this article as: Mingyuan Lu, Han Huang, Interfacial energy release rates of SiN/GaAs film/substrate systems determined using a cyclic loading dual-indentation method, Thin Solid Films (2015Films ( ), doi: 10.1016Films ( /j.tsf.2015 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT AbstractOur previous study developed a dual-indentation method for testing the interfacial energy release rate, G in , of the SiN/GaAs film/substrate systems. However, for the film/substrate systems with relatively high interfacial toughness, the dual-indentation method was unable to generate interfacial delamination. In this study, a cyclic loading dual-indentation method was proposed, in which the first monotonic loading in the dual-indentation method was replaced by cyclic loading. It was demonstrated that cyclic loading was effective at inducing delamination in relatively "tough" SiN/GaAs interfaces that were unable to be delaminated by dual-indentation method. The G in values obtained from the cyclic loading indentation were in good agreement with those obtained from the dual-indentation method for the less tough interfaces. The delamination mechanism in the cyclic loading indentation was attributed to the hardening effect on the films induced by cyclic loading, permitting sufficient elastic strain energy to be accumulated to initiate the delamination.Key words: Nanoindentation; delamination; cyclic loading; energy release rate A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT IntroductionThe assessment of the adhesion properties of a thin film is imperative to ensure the reliability of the film/substrate system over its life cycles [1]. As a consequence, there is an increasing demand for developing reliable techniques to measure the interfacial adhesion between a film and a substrate. In the past few decades, significant research effort has been directed towards developing approaches to evaluate the adhesion property [1][2][3][4][5][6][7]. Among the available techniques, indentation enables the investigation of interfacial adhesion of a film/substrate system to be undertaken in a controllable manner by generating interfacial cracks on a sufficiently small scale and at a specific site [8].In our previous work, a dual-indentation method was developed to assess the interfacial adhesion of SiN/GaAs film/substrate systems [9]. This method was successfully applied to the SiN/GaAs film/substrate systems with different interfacial properties. The limitation of the dual-indentation approach was that interfacial delamination must be induced during the first ...