Bioceramic composites for orthopaedic applications: A comprehensive review of mechanical,biological, and microstructural properties

Bioceramics have been widely utilized for orthopaedic applications in which the biocompatibility and mechanical properties of the materials are vital characteristics to be considered for their clinical use. Till date, extensive studies have been devoted to developing a range of scientific ways for tailoring the microstructure of bioceramics in order to attain the trade-off of mechanical properties and biocompatibility of the final product. Owing to low reactivity, earlier stabilization and longer functional life of bioceramic, the developed implants are capable of replicating the mechanical behaviour of original bone. As the safety of the patient and its ultimate functionality are the ultimate goal of the selected implant material hence, the present literature survey investigates and brings forth the important aspects associated to the mechanical, biological and microstructural characteristics of bioceramics employed in orthopaedic applications. The review paper majorly focuses on effective utilization of various materials as an additive in bioceramics and processing techniques used for enhancement of properties, enabling the use of material in orthopaedic applications. The influence of various additives on the microstructure, mechanical properties and biological performance of developed bioceramics orthopaedic implants has been elaborately discussed. Furthermore, future prospects are proposed to promote further innovations in bioceramics research.     

Microstructure,Thermal, Thermo-mechanical and Fracture Analyses of Hybrid AA2024-SiC Alloy Composites

This research work aims to investigate the inter-correlation between microstructure, thermal (thermal conductivity, thermo-gravimetric analysis), thermo-mechanical (dynamic mechanical analysis) and fracture characteristics of hybrid AA2024-SiC alloy composites fabricated via semi-automatic stir-casting process, as per standard industrial practice. Silicon Carbide (SiC) particulates of varying amount (0–6 wt%; @ step of 2%) were used to reinforce master batch of AA2024 wrought alloy, Silicon Nitride (Si3N4) and graphite particulates. The thermal conductivity and storage-modulus magnitudes of alloy composites have shown diminishing trend with hard SiC reinforcing phase, while material stability, viscous modulus, damping factor and fracture toughness have shown significant improvement. Uniform dispersion and better interfacial adhesion between matrix–reinforcement were observed from metallographic examination. The XRD analysis identified the different phases of the hybrid alloy composites. The trends in variations of physical, mechanical and tribological properties were supported by microstructure analysis, thermal analysis, thermo-mechanical analysis and fracture analysis.     

Hikami-Larkin-Nagaoka (HLN) Treatment of the Magneto-Conductivity of Bi<Subscript>2</Subscript>Te<Subscript>3</Subscript> Topological Insulator

We report the magneto-conductivity analysis at different temperatures under a magnetic field of up to 5 T of a well- characterized Bi₂Te₃ crystal. Details of crystal growth and various physical properties including high linear magneto-resistance are already reported by some of us. To elaborate upon the transport properties of Bi₂Te₃ crystal, the magneto-conductivity is fitted to the known Hikami-Larkin-Nagaoka (HLN) equation and it is found that the conduction mechanism is dominated by both surface-driven weak anti-localization (WAL) and the bulk weak localization (WL) states. The value of HLN equation coefficient (α) signifying the type of localization (WL, WAL or both WL and WAL) falls within the range of ??0.5 to ??1.5. In our case, the low-field (±?0.25 T) fitting of studied crystal exhibited a value of α close to ??0.86 for studied temperatures of up to 50 K, indicating both WAL and WL contributions. The phase coherence length (l_φ) is found to decrease from 98.266 to 40.314 nm with increasing temperature. Summarily, the short letter reports the fact that bulk Bi₂Te₃ follows the HLN equation and quantitative analysis of the same facilitates to know the quality of studied crystal in terms of WAL to WL contributions and thus the surface to bulk conduction ratio.     

Optimum selection of novel developed implant material using hybrid entropy‐PROMETHEE approach

Optimum selection of appropriate biomaterial with unlike properties for the femoral head material is one of the toughest tasks. Therefore, in this article, a series of implant materials for the femoral head by vacuum casting induction furnace containing cobalt‐30chromium (Co‐30Cr) as a base material and three alloying elements (i. e. molybdenum, nickel and tungsten) were developed and evaluated for physical, mechanical and tribological properties. Density, hardness, compressive strength, coefficient of friction and volumetric wear were considered as material selection criterions. The weight of each criterion has been determined by entropy method, while the ranking of the alternatives has been carried out by the preference ranking organization method for enrichment evaluations (PROMETHEE) method. From this ranking results, it is found that the cobalt‐30chromium‐4molybdenum‐1nickel‐2tungsten (Co‐30Cr‐4Mo‐1Ni‐2W) material at given parameters is the best implant material for the femoral head component of hip joint replacement.     

Comparative analysis of wear behavior of garnet and fly ash reinforced Al7075 hybrid composite

Al7075 hybrid composites reinforced with varying weight percentage (0 wt.%, 5 wt.%, 10 wt.%, 15 wt.%) of each of garnet and fly ash were fabricated and characterized for their comparative wear assessment. The sliding wear test was conducted on a reciprocating tribometer in dry medium under the working conditions of applied normal load (2 N, 4 N, 6 N, 8 N), sliding velocities (0.04 m/s, 0.08 m/s, 0.12 m/s, 0.16 m/s), sliding distance (20 m, 40 m, 60 m, 80 m) and working temperature (25 °C, 50 °C, 75 °C, 100 °C). The experiments were performed as per steady‐state condition and Taguchi (L₂₅) orthogonal array design to evaluate specific wear rate of the Al7075 hybrid composites. The finding of results indicated that the wear rate was decreased with the increase in the filler content in both the case of garnet and fly ash reinforced Al7075 hybrid composites. The results from Taguchi experiments suggested that the filler content and load were the most significant factors affecting wear behavior of composites while temperature and sliding distance are the least significant factors. Also, the garnet reinforced Al7075 hybrid composite indicated less specific wear rate as compared to that of fly ash reinforced Al7075 hybrid composite.     

Hydraulic and Thermal Regulation of Coke Batteries with Unidirectional Gas Input and Product Output

The problems arising in the operation of coke battery 3 at Rourkela Steel Plant (India) are considered. The design of coke battery 3 is described. It has an Otto system; the capacity of a single coking chamber is 21.6 m³. Hybrid heating is employed, and heating gas is supplied to the bottom of the chamber. A method is proposed for hydraulic regulation of the coke battery with unidirectional heating-gas input and product output.     

Modified fully utilized design (MFUD) method for stress and displacement constraints

The traditional fully stressed method performs satisfactorily for stress-limited structural design. When this method is extended to include displacement limitations in addition to stress constraints, it is known as the Fully Utilized Design (FUD). Typically, the FUD produces an overdesign, which is the primary limitation of this otherwise elegant method. We have modified FUD in an attempt to alleviate the limitation. This new method, called the Modified Fully Utilized Design (MFUD) method, has been tested successfully on a number of problems that were subjected to multiple loads and had both stress and displacement constraints. The solutions obtained with MFUD compare favourably with the optimum results that can be generated by using non-linear mathematical programming techniques. The MFUD method appears to have alleviated the overdesign condition and offers the simplicity of a direct, fully stressed type of design method that is distinctly different from optimization and optimality criteria formulations. The MFUD method is being developed for practicing engineers who favour traditional design methods rather than methods based on advanced calculus and non-linear mathematical programming techniques. The Integrated Force Method (IFM) was found to be the appropriate analysis tool in the development of the MFUD method. In this paper, the MFUD method and its optimality are examined along with a number of illustrative examples. © 1998 This paper was produced under the auspices of the U.S. Government and it is therefore not subject to copyright in the U.S.     

Effect of Controlled Atmosphere Storage and Chitosan Coating on Quality of Fresh-Cut Jackfruit Bulbs

Fresh-cut jackfruit bulbs were evaluated for quality changes as effect of an additive pretreatment with CaCl₂, ascorbic acid, citric acid, and sodium benzoate followed by chitosan coating. Different types of samples such as pretreated and coated, only pretreated, only coated, and untreated were subjected to controlled atmosphere (CA) storage (3 kPa O₂?+?6 or 3 kPa CO₂; N2 balance) or normal air at 6 °C. CA conditions, pretreatment, as well as chitosan coating in synergy with each other, could significantly minimize the loss in total phenolics and ascorbic acid content of the samples to the levels of around 5% and 17%, respectively, during extended storage up to 50 days. Chitosan coating could also restrict the changes in microbial load. The CA condition of 3 kPa O₂?+?6 kPa CO₂ was found to render higher efficacy in retaining quality attributes of the samples.     

ANALYSIS OF THE EFFECT OF FLOW INTERRUPTIONS ON FED-BATCH FERMENTATION FOR PHB PRODUCTION BY RALSTONIA EUTROPHA IN FINITELY DISPERSED BIOREACTORS

Unlike laboratory-scale bioreactors, large reactors have finite dispersion and are affected by unexpected interruptions in the feed streams. For the optimum level of dispersion determined earlier, the effects of interruptions in the inflow of the carbon (glucose) and nitrogen (NH₄Cl) substrates have been studied for fed-batch fermentation by Ralstonia eutropha to produce poly-β-hydroxybutyrate (PHB). Optimum uninterrupted operation by neural control at dispersion corresponding to Pe = 20 was used as the reference. While glucose stoppage mainly affected cell growth, nitrogen flow suppressed polymer synthesis more strongly. The effects depended also on the time at which the interruptions occurred. These results are interpreted in a metabolic context, emphasizing the complexity of the system and the importance of ‘intelligent’ monitoring and control under disturbed conditions.