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Acetabular cup liners made of ultra‐high molecular weight polyethylene (UHMWPE), in hip implants fail mostly due to wear debris generation and poor wear resistance. Consequently, strengthening UHMWPE becomes essential. The current work exhibits how the addition of 5 vol% carbon nanotubes (CNT) and functionalized carbon nanotubes (fCNT) in UHMWPE (denoted as U) affects the mechanical properties (hardness, elastic modulus) and tribological properties (wear resistance) of biocomposites. To form a composite, powders were mixed using a planetary centrifugal mixer followed by freeze‐drying to disperse‐CNTs, followed by its compression molding at 220°C for 1 h at 10 MPa. With the addition of CNT and fCNT, ≥95% densification was obtained for all samples resulting an increase in hardness and elastic modulus from 74.96 MPa to 168.11 MPa (124%) and 1.65 GPa to 2.96 GPa (79%), respectively, which led to the reduction in wear rate from 12.5 × 10−5 mm3/Nm (U) to 2.5 × 10−5 mm3/Nm (UfCNT). The amount of apatite formation enhanced from U (58.2%) to UfCNT (65.1%) is confirmed via X‐ray diffraction and X‐ray photoelectron spectroscopy. Cell proliferation studies have validated the cytocompatible efficacy of U‐CNT composites with osteoblast‐like MG‐63 cells, making UfCNT as potential material for acetabular cup liners. [ABSTRACT FROM AUTHOR]

Mesoporous silica‐based materials are currently being explored as a new type of bioscaffold for bone regeneration applications. Zinc(Zn) ion incorporation is shown to play an important role in promoting bone regeneration and also providing antimicrobial activity to the scaffold materials. In this work, the role of pore size, geometry, and ordered structure on the Zn loading and release performance of two different mesoporous silica, SBA‐1 and SBA‐15, are compared. Zn loading is varied from 2.5 to 10 wt% for both samples, and its effect on the antibacterial and osteogenic activity is evaluated. Zn loading up to 10 wt% has a negligible effect on the morphology and textural properties of the mesoporous silica samples. The inductively coupled plasma mass spectrometry (ICP‐MS) analysis reveals that SBA‐15 exhibits significantly higher Zn release in Luria‐Bertani (LB) broth as compared to SBA‐1 that is reflected in the higher antibacterial activity of SBA‐15 against both gram‐positive and gram‐negative bacteria. Various assays show that 5 wt% Zn loading is sufficient to produce both bactericidal and inhibitory effects on bacterial cells. The 5 wt% Zn‐loaded samples induce osteogenic differentiation ofavianized bone marow‐derived stromal cells (TVA‐BMSCs) though SBA‐15 samples show better compatibility compared to SBA‐1, suggesting that Zn incorporation can produce sufficient antibacterial effect and osteogenic differentiation of TVA‐BMSCs. [ABSTRACT FROM AUTHOR]

Improving the wear resistance of ultra‐high molecular weight polyethylene (UHMWPE), the gold standard polymer for acetabular component in hip joint arthroplasty, is the most important challenge in joint arthroplasty. The possible ways that have been approached to this challenge are by: (i) engineering multi‐phase that is, both carbonaceous and noncarbonaceous fillers‐based polyethylene composites, which unite the inherent attributes of each element available in the system. The wear rate of carbonaceous composite is nearly 50% lower (5.11–6.69 × 10−5 mm3/Nm) than that of noncarbonaceous composite (10–12.5 × 10−5 mm3/Nm), thus, recognized as a potential reinforcement, and (ii) coupling gamma‐irradiation, which is a mandated sterilization process, with multi‐phase nanocomposite to understand the free radical‐scavenging effect of fillers and improved interfacial adhesion strength between fillers and matrix. After the exposure of gamma‐rays (50–100 kGy), the free radicals formed by bond breakage in both the reinforcements and the matrix recombine to form covalent/Van der Waals bond in the interface. Thus, dramatical improvement in wear resistance of both types of composites with 2–4 times decreased wear rate is observed compared to that of composites under un‐irradiated condition. However, enhancing the interfacial adhesion between two different phases is a major constraint in the design of UHMWPE composites. Many methods such as functionalization of reinforcements, and irradiation on functionalized UHMWPE composites that can be approached to address this constraint are documented in this review. [ABSTRACT FROM AUTHOR]

The engineered role of coarse‐SiC (D50 ≈72 μm) and fine‐SiC (D50 ≈3 μm) particles on the wear damage of zirconium boride (ZrB2) is assessed at different length scales. Monolithic ZrB2 and 20 vol% SiC reinforced ZrB2 with SiC of two different particle sizes are consolidated via spark plasma sintering. Wear tests conducted on sintered samples for examining multi‐length scale performance include fretting (micro‐wear), micro‐scratching (meso‐wear) and ball‐on‐disk (macro‐wear), under dry and unlubricated conditions. The damage assessment and wear mechanism, characterised via scanning electron microscopy and optical profilometry, show Hertzian tensile cracking in all the samples at loads ≥5 N during micro‐scratching. Wear volume, wear rate and coefficient of friction (cof) decreased with SiC reinforcement during macro‐wear. Fine‐SiC reinforced ZrB2 (ZSF) composite showed least cracking at loads ≥5 N owing to its highest fracture toughness (4.6 MPa m1/2) as compared to coarse‐SiC reinforced composite (ZSC, 2.1 MPa m1/2) and monolithic ZrB2 (3.9 MPa m1/2). Hardness of composites increases as compared to ZrB2, and ZSF shows enhanced elastic modulus and fracture toughness. In summary, superiority of ZSF in terms of improved mechanical performance and wear resistance makes it a potential high‐end material for aerospace applications, where particles with high surface impact may cause material deformation and removal. [ABSTRACT FROM AUTHOR]

Polypropylene (PP)‐based composites with reinforcements of CaCO3and rice husk ash (RHA, agricultural waste) are extensively used in textile industry and manufacturing of plastic yarns, tapes, etc. Tribological properties of the PP‐CaCO3‐RHA based composite are studied using constant‐ and progressive‐load scratching. The progressive load scratching depicts a transient‐state interaction, whereas, constant load scratching depicts steady‐state of wear, hence, both modes of scratching are reported to highlight the aspects of damage initiation and damage tolerance on PP‐based composites. The average scratch hardness and toughness of the PP composites improved with reinforcement in both modes of scratching. The reinforcement of 20 wt% RHA and 10 wt% RHA with 10 wt% CaCO3 in PP matrix, marginally improves (0.8%‐1.6%) the wear resistance (wear rate, WR of 12.1‐12.2 mm3 N−1 m−1) during the progressive load scratching compared to that of pure PP (12.3 mm3 N−1 m−1). Poor wear resistance (WR = 12.6 mm3 N−1 m−1) with the addition of 20 wt% CaCO3 in PP matrix during the progressive wear is attributed to poor adhesion (adhesion factor: 0.61) of CaCO3 with PP. Also, an over estimation (3.4‐4.6 times) of wear rate is attributed to high recovery (0.63‐0.77) and the plastic deformation ahead of the scratch tip in the PP‐based composite with viscoelastic nature. High‐wear rate with CaCO3 agglomerate with poor sinterability at 200 °C can be substituted with the strong adhesive nature of RHA (bimodal pore distribution) in PP matrix to achieve optimal hardness, elastic modulus, and scratch resistance. [ABSTRACT FROM AUTHOR]

Hydroxyapatite [Hap, Ca10(PO4)6(OH)2] is one of the most preferred bioceramic material for orthopedic implants and coatings due to its stoichiometric similarities with human hard tissues. However, foreign body implantation inside human body sometimes leads to bacterial film formation over the implant surface causing the implant failure, thereby needing a revision surgery. This study attempts to select the better dopant between zinc (Zn) and cobalt (Co) as per the antibacterial efficacy when doped in Hap. To prepare antibacterial transition‐metal‐doped Hap, Zn and Co are doped in Hap as per the chemical formula Ca10−x Mx(PO4)6(OH)2, (M = Zn or Co and x = 0.24) to improve antibacterial efficacy. Phase and microstructural characterization by Rietveld refinement, scanning electron microscopy (SEM), and Fourier transformation infrared spectroscopy (FT‐IR) confirms the doping. Evaluation of antibacterial activity against E coli reveals that both Zn‐ and Co‐doped Hap shows antibacterial property with the latter being more effective (zone of inhibition ~3 mm more) for the same level of doping. Inductively coupled plasma‐mass spectrometry confirms the presence of ~676 ppb Co+2 and ~303 ppb Zn+2 after leaching. In addition, cytotoxicity assay with NIH3T3 cell line reveals cytocompatibility of both the compositions with either dopant. The effect of spark plasma sintering on densification and mechanical properties of Co‐doped Hap is investigated for the first time and compared with Hap with the same level of Zn doping. It appears that Co‐doped Hap attains higher densification (~7% more) and fracture toughness (~2 times better) as compared to that of Zn‐doped counterpart (densification: 86% and fracture toughness: 0.75 ± 0.12 MPa √m). Thus, this study suggests that Co‐ and Zn‐doped Hap are promising candidates for bone tissue engineering with improved antibacterial properties and in addition, Co‐doped Hap can attain higher density and offer better fracture toughness than that of Hap doped with Zn. [ABSTRACT FROM AUTHOR]

Bone‐tissue engineering mandates the development of multi‐functional bioactive porous hydroxyapatite (HAp) scaffolds. Herein, microwave sintered HAp/ZnO and HAp/Ag composite scaffolds with ≈5–19% porosity are developed using 0–30 vol% graphite as a porogen. The mechanical properties of the porous scaffold are analyzed in detail, revealing that even being more porous, the reinforcement of ZnO (9% porosity, hardness of 2.8 GPa, and toughness of 3.5 MPa.m1/2) has shown to have better hardness and fracture toughness when compared to Ag (5% porosity, hardness of 1.6 GPa, and toughness of 2.6 MPa.m1/2). The flexural strength obtained experimentally are complemented with a finite‐element technique that adopts microstructural features in visualizing the effect of porosity on stress distribution. The antibacterial efficacy and cytocompatibility of these composites are validated by increased metabolic activity and conspicuous cell‐matrix interactions. The anticipation of the results reveal that HAp/ZnO (9% porosity) and HAp/Ag (5% porosity) composites can be used as a potential multi‐functional bone implant scaffolds. [ABSTRACT FROM AUTHOR]

In the current work, contact-mechanics at different length scale is utilized to correlate damage accumulation in TaC-based composites. Upon synergistic reinforcement with silicon carbide (SiC) and carbon nanotubes (CNTs), TaC has shown to reduce the wear rate from 10.5 × 10−7 to 4.1 × 10−7 mm3 N−1 m−1 upon fretting (micro-wear) and from 8.0 to 2.7 mm3 N−1 m−1 upon micro-scratching (meso-wear). Enhancement in the fracture toughness from 2.9 to 10.7 MPam1/2 with reinforcement is attributed to the processing induced defects (such as dislocation, stacking fault etc.) in SiC and strong interfacial bonding of CNTs with TaC, as revealed by transmission electron microscopy (TEM). Delineation of the synergistic contribution of SiC and CNT reinforcement in TaC establishes the wear mechanism to be abrasion (via fretting test), brittle tensile cracking, and fracture (via micro-scratch test). [ABSTRACT FROM AUTHOR]

The effect of replacing Sc2O3 with Yb2O3 on the structural and electrical properties of xYb2O3-(12- x)Sc2O3-88ZrO2 has been investigated. Spark plasma sintering technique is employed to fabricate dense bulk samples from the nano-sized powders. X-ray diffraction and transmission electron microscopy performed on pellets indicate the existence of cubic and rhombohedral phases in 12Sc SZ, and a single cubic phase in all the co-doped compositions. However, Raman spectroscopic studies suggest the presence of a metastable tetragonal t″-phase along with rhombohedral phases in 12Sc SZ, whereas a single cubic phase in all the co-doped compositions. Significant enhancement in the conductivity of grain and grain boundary is observed on replacing Sc2O3 with Yb2O3. In the intermediate temperature range, 1Yb11Sc SZ exhibits the highest, while 12Sc SZ shows the lowest conductivity values, which is attributed to corresponding phases present in that range. Through co-doping with >1 mol% Yb2O3 leads to conductivity decrease, but the value remains higher than that of 12Sc SZ. A sharp conductivity change is observed in 12Sc SZ and 1Yb11Sc SZ samples, which is attributed to partial phase transition as well to the formation of cation-vacancy complexes. In this work, the beneficial effect of Yb2O3 co-doping in 12Sc SZ on the phase and conductivity has been highlighted. [ABSTRACT FROM AUTHOR]

In addressing the issue of prosthetic infection, this work demonstrated the synergistic effect of the application of static magnetic field (SMF) and ferrimagnetic substrate properties on the bactericidal property in vitro. This aspect was studied using hydroxyapatite (HA)-xFe3O4 (x=10, 20, and 40 wt.%) substrates, which have different saturation magnetization properties. During bacteria culture experiments, 100 mT SMF was applied to growth medium (with HA-xFe3O4 substrate) in vitro for 30, 120, and 240 min. A combination of MTT assay, membrane rupture assays, live/dead assay, and fluorescence microscopic analysis showed that the bactericidal effect of SMF increases with the exposure duration as well as increasing Fe3O4 content in biomaterial substrates. Importantly, the synergistic bactericidal effect was found to be independent of bacterial cell type, as similar qualitative trend is measured with both gram negative Escherichia coli (E. coli) and gram positive Staphylococcus aureus ( S. aureus) strains. The reduction in E. coli viability was 83% higher on HA-40 Wt % Fe3O4 composite after 4 h exposure to SMF as compared to nonexposed control. Interestingly, any statistically significant difference in ROS was not observed in bacterial growth medium after magnetic field exposure, indicating the absence of ROS enhancement due to magnetic field. Overall, this study illustrates significant role being played by magnetic substrate compositions towards bactericidal property than by magnetic field exposure alone. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 102B: 524-532, 2014. [ABSTRACT FROM AUTHOR]