Gaurav Tripathi and Pulak Mohan Pandey
Topologically ordered functionally graded composite (TOFGC) biodegradable materials are needed in the field of metallic degradable implants, as they degrade over a period of time…
Abstract
Purpose
Topologically ordered functionally graded composite (TOFGC) biodegradable materials are needed in the field of metallic degradable implants, as they degrade over a period of time avoiding the necessity of another surgery for implant removal. Also, their rate of degradation can be tailored to match the requirement of the patient. These biomaterials also have the functionality to assist bone growth and eliminate stress shielding in orthopaedic implants.
Design/methodology/approach
In this study, TOFGC biomaterials were developed for the first time using additive manufacturing, pressureless microwave sintering and casting methods, and their cytocompatibility, hemocompatibility and in vitro degradation evaluations were done. Also, pure dense iron and iron scaffolds were included in the study, for the comparison of results with the iron-hydroxyapatite-zinc functionally graded composite biomaterial.
Findings
The maximum weight loss and corrosion rate were found to be 6.98% and 2.38 mmpy, respectively, in the immersion test and electrochemical test for Fe-3.5HAp-54Zn biomaterial. Zinc-infiltrated composite biomaterials exhibited excellent cytocompatibility and hemocompatibility as compared to pure dense iron and iron scaffolds. A comparative analysis was conducted, taking into account relevant literature, and it was determined that the fabricated iron-hydroxyapatite-zinc biomaterial demonstrated desirable degradation and biological characteristics, customized to meet the specific requirements of bone tissue engineering applications.
Originality/value
TOFGC iron-hydroxyapatite-zinc biomaterial has been fabricated for the first time using the developed novel methodology and their degradation and biological characterizations were performed.
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To achieve high working speed and high positional accuracy, the weight of a robot arm must be reduced.
Marco Montani, Ali Gökhan Demir, Ehsan Mostaed, Maurizio Vedani and Barbara Previtali
This paper aims to investigate the processability by selective laser melting (SLM) of materials of potential interest for innovative biodegradable implants, pure Fe and pure Zn…
Abstract
Purpose
This paper aims to investigate the processability by selective laser melting (SLM) of materials of potential interest for innovative biodegradable implants, pure Fe and pure Zn. The processability of these materials is evaluated with a more established counterpart in permanent implants, stainless steel. In particular, the processing conditions were studied to reduce porosity due to incomplete fusion of the powder.
Design/methodology/approach
In the first phase of the experiments, SLM of AISI 316L was studied through design of experiments method. The study was used to identify the significant parameters in the experimental range and estimate the fluence ranges for pure Fe and pure Zn using the lumped heat capacity model. In the second phase, SLM of pure Fe and pure Zn were studied using estimated fluence ranges. In the final phase, best conditions were characterized for mechanical properties.
Findings
The results showed that complete melting of AISI 316L and pure Fe could be readily achieved, whereas laser melting generated a foam-like porous structure in Zn samples. The mechanical properties of laser melt implant materials were compared to as-cast and rolled counterparts. Laser melted AISI 316L showed superior mechanical performance compared to as-cast and rolled material, whereas Fe showed mechanical performance similar to rolled mild steel. Despite 12 per cent apparent porosity, laser melted Zn exhibited superior mechanical properties compared to as-cast and wrought material because of reduced grain size.
Originality/value
The paper provides key processing knowledge on the SLM processability of new biodegradable metals, namely, pure Fe, which has been studied sparingly, and pure Zn, on which no previous work is available. The results prefigure the production of new biodegradable metallic implants with superior mechanical properties compared to their polymeric counterparts and with improved degradation rates compared to magnesium alloys, the reference material for biodegradable metals.
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Juliána Drábiková, Stanislava Fintová, Jakub Tkacz, Pavel Doležal and Jaromír Wasserbauer
The purpose of this paper is to compare electrochemical corrosion characteristics of conventional and unconventional fluoride conversion coating prepared on magnesium alloy.
Abstract
Purpose
The purpose of this paper is to compare electrochemical corrosion characteristics of conventional and unconventional fluoride conversion coating prepared on magnesium alloy.
Design/methodology/approach
The chemical reaction of AZ61 with 38 wt.% hydrofluoric acid (HF) for 24 h was used as a conventional way of fluoride conversion coating preparation. The unconventionally prepared coating was created in Na[BF4] salt melt at 450°C for 2 h. Morphology and chemical composition of prepared fluoride conversion coatings were studied with scanning electron microscopy and energy-dispersive X-ray spectroscopy. Electrochemical corrosion characteristics of the coatings were analyzed in Hank’s solution using potentiodynamic tests.
Findings
Both the coating preparation ways resulted in the creation of uniform conversion coatings with the same thickness (1.3 ± 0.1 μm). Some defects were observed on the coatings surface; however, the defects did not reach the AZ61 surface. Electrochemical tests performed in Hank’s solution at 37°C showed an improvement of corrosion resistance of AZ61 treated with fluoride conversion coatings when compared to the untreated material. Unconventionally prepared coating reached better electrochemical corrosion characteristics when compared to the conventionally prepared coating.
Originality/value
Electrochemical corrosion characteristics of AZ61 magnesium alloy can be improved with fluoride conversion coatings. Two methods are used in the literature for the coatings preparation. The conventional method is based on dipping of the coated material to the HF, and the unconventional method lies in dipping of the sample to the Na[BF4] salt melt. The main purpose of the present study is to analyze the conventionally and unconventionally prepared coatings in terms of chemical analysis, morphology and material corrosion protection (electrochemical corrosion characteristics), while the data are not provided in the literature, according to the authors’ knowledge. Very similar coatings were prepared using both the methods from the morphological and chemical composition point of view. However, unconventionally prepared coating created in Na[BF4] salt melt reached better electrochemical corrosion characteristics compared to the coating prepared in HF.
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Kexin Liu, Shuhan Meng, Yi Zhang, Peng Zhou, Tao Zhang and Fuhui Wang
The purpose of this paper is to investigate the effect of plasma electrolytic oxidation (PEO) coatings and sealed PEO coatings on the corrosion resistance and cytocompatibility of…
Abstract
Purpose
The purpose of this paper is to investigate the effect of plasma electrolytic oxidation (PEO) coatings and sealed PEO coatings on the corrosion resistance and cytocompatibility of a novel Mg-1Zn-0.45Ca alloy in simulated body fluid (SBF).
Design/methodology/approach
The microstructure, corrosion resistance and cytocompatibility of PEO coatings and phosphate conversion-treated PEO coatings were investigated and was compared with the bare Mg alloy.
Findings
The hot-extruded Mg-Zn-Ca alloy exhibit inhomogeneous microstructure and suffered from localized corrosion in the SBF. The PEO coating after phosphate conversion treatment offers enhanced protectiveness to the Mg alloy within an immersion period of up to 60 days, which is significantly improved compared with the performance of the PEO-coated Mg alloy, but the cytocompatibility was slightly decreased.
Originality/value
This work offers new perspective in balancing the protectiveness and cytocompatibility of bio-materials.
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Cui Tan, Juncen Zhou and Qing Li
The aim of this paper is to predict the in-vivo degradation behaviour of Mg-based implants through in-vitro immersion test.
Abstract
Purpose
The aim of this paper is to predict the in-vivo degradation behaviour of Mg-based implants through in-vitro immersion test.
Design/methodology/approach
A novel placement mode arming to mimic the in-vivo situation was investigated in this work. Specimens were mounted on bones and then immersed in dynamic Hank’s solution.
Findings
The degradation behaviour of the specimen’s two sides is unequal. The bottom side which clings to the bone was isolated from solution in the early stage. During the late immersion period, there was crevice corrosion appearing on the bottom side. Weight loss and mechanical properties of specimens were also affected by the placement mode.
Research limitations/implications
Placement mode reported here have guiding significance for degradation behaviour of bio-implants in the clinical study.
Social implications
Placement mode reported here have guiding significance for degradation behaviour of bio-implants in the clinical study.
Originality/value
A novel placement mode arming to mimic the in-vivo situation was investigated in this work, which was better fit the actual in vivo immersion situation.
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Zhenlei Yang, Yuzhou Du, Bo Ma, Qian Wang and Chao Yang
The purpose of this study is to campare the corrosion behavior of Az91 films and bulk sample, in the objective to provide reference for the corrosion resistance improvement of Mg…
Abstract
Purpose
The purpose of this study is to campare the corrosion behavior of Az91 films and bulk sample, in the objective to provide reference for the corrosion resistance improvement of Mg alloys.
Design/methodology/approach
AZ91 films with various thickness values are produced by magnetron sputtering technique, and the corrosion behavior was characterized by immersion tests and electrochemical measurements.
Findings
The AZ91 films exhibited a preferred orientation with basal planes parallel to the surface and increased densification with the increase of thickness, and a superior corrosion resistance for the AZ91 films compared with the bulk sample.
Originality/value
The preferred (0002) basal planes in AZ91 films benefited the corrosion resistance and the nanoscale AZ91 films facilitated the development of a dense passivation film. Consequently, AZ91 film exhibited a superior corrosion resistance.
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Consumer theory and research are generally founded on the assumption that observed behaviour is mediated by intrapersonal events. This pervasive view now threatens to impede…
Abstract
Consumer theory and research are generally founded on the assumption that observed behaviour is mediated by intrapersonal events. This pervasive view now threatens to impede theoretical development by precluding the establishment of models based on alternative assumptions. Following Feyerabend's advocacy of the active interplay of tenaciously held, incommensurable theories as an essential component of scientific progress, this article examines the relevance to consumer theory of radical behaviourism, which accords explanatory power exclusively to the environmental consequences of behaviour, denying causative significance to intrapersonal processes and events.
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The purpose of this study is to propose a methodological approach for modeling catastrophic consequences caused by black swan events, based on complexity science, and framed on…
Abstract
Purpose
The purpose of this study is to propose a methodological approach for modeling catastrophic consequences caused by black swan events, based on complexity science, and framed on Feyerabend’s anarchistic theory of knowledge. An empirical application is presented to illustrate the proposed approach.
Design/methodology/approach
Thom’s nonlinear differential equations of morphogenesis are used to develop a theoretical model of the impact of catastrophes on international business (IB). The model is then estimated using real-world data on the performance of multinational airlines during the SARS-CoV-2 (COVID-19) pandemic.
Findings
The catastrophe model exhibits a remarkable capability to simultaneously capture complex linear and nonlinear relationships. Through empirical estimations and simulations, this approach enables the analysis of IB phenomena under normal conditions, as well as during black swan events.
Originality/value
To the best of the author’s knowledge, this study is the first attempt to estimate the impact of black swan events in IB using a catastrophe model grounded in complexity theory. The proposed model successfully integrates the abrupt and profound effects of catastrophes on multinational corporations, offering a critical perspective on the theoretical and practical use of complexity science in IB.