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Sterilization of ultra-high molecular weight polyethylene (UHMWPE) based composites used for acetabular cup liner via UV or gamma-irradiation before surgery is inevitable. Thus, understanding the alteration of mechanical properties and wear resistance of cup liner via irradiation process requires investigation. This paper aims to understand the effect of UV (0.03 J/cm2) and gamma (25 kGy) irradiation on mechanical properties and scratch resistance of compression molded UHMWPE composites reinforced with alumina (Al2O3), hydroxyapatite (HAp) and carbon nanotubes (CNTs). After irradiation, nearly 100% increased crystallinity of polyethylene, due to recrystallization, helped in enhancing the hardness and elastic modulus by ~1.5 times compared to that of as-processed UHMWPE (Hardness: ~70 MPa and Elastic modulus: ~1.25 GPa). The recrystallization was not favored by the presence of nano-reinforcements in irradiated UHMWPE based nanocomposites, and caused deterioration in the mechanical properties. The micro-scratch results revealed the remarkable wear resistance (i.e., 1.5 to 2 times lower wear rate) of irradiated samples than that of as-processed samples. Mouse fibroblast L929 in vitro cell culture test confirmed the cytocompatibility of irradiated samples. This study indicated that the UV and gamma irradiated UHMWPE nanocomposites are the challenging candidates as acetabular cup liner.

Pertaining to real-life applications (by scaling up) of hydroxyapatite (HA)-based materials, herein is a study illustrating the role of carbon nanotube (CNT) reinforcement with ceria (CeO2) and silver (Ag) in HA on titanium alloy (TiAl6V4) substrate, utilizing the plasma-spraying processing technique, is presented. When compared with pure HA coating enhanced hardness (from 2.5 to 5.8 GPa), elastic modulus (from 110 to 171 GPa), and fracture toughness (from 0.7 to 2.2 MPa·m1/2) elicited a reduced wear rate from 55.3 × 10−5 mm3·N−1·m−1 to 2.1 × 10−5 mm3·N−1·m−1 in HA-CNT-CeO2-Ag. Besides, an order of magnitude lower Archard’s wear constant and a 41% decreased shear stress by for HA-CNT-CeO2-Ag coating depicted the effect of higher hardness and modulus of a material to control its wear phenomenon. Antibacterial property of 46% (bactericidal) is ascribed to Ag in addition to CNT-CeO2 in HA. Nonetheless, the composite coating also portrayed exaggerated L929 fibroblast cell growth (4.8 times more than HA), which was visualized as flat and elongated cells with multiple filopodial protrusions. Hence, synthesis of a material with enhanced mechanical integrity resulting in tribological resistance and cytocompatible efficacy was achieved, thereupon making HA-CNT-CeO2-Ag a scalable potent material for real-life load-bearing implantable bio-coating.

In this work, alumina (Al 2 O 3 ) reinforced with zirconia viz., 0, 3, and 8 mol% yttria doped (i.e., ZrO 2 , 3YSZ, and 8YSZ), and 4 wt% carbon nanotube (CNT) are coated on Inconel 718 substrate by atmospheric plasma spraying (APS). Reinforcement by CNT and 3YSZ has led to a substantial enhancement in the fracture toughness from 3.89 MPa m 1/2 (for Al 2 O 3 ) to 5.90 MPa m 1/2 in the reinforced composite. It is observed that CNT has contributed ∼5–12% toughness enhancement, whereas ∼15% contribution to toughening is obtained via tetragonal to monoclinic ( t → m ) transformation of zirconia. Moreover, CNTs not only assist the t → m transformation but also enhance the toughness value of Al 2 O 3 -based thermal barrier coatings (TBC) near to its upper theoretical bound estimated using modified fractal model. Moreover, the effective thermal conductivity is estimated using modified theoretical models embracing the aligning factor of CNT in APS coatings, which unequivocally confirms the superiority of Al 2 O 3 reinforced with 3YSZ and CNT as a potential TBC. [ABSTRACT FROM AUTHOR]