Mechanical properties of a degradable phosphate glass fibre reinforced polymer composite for internal fracture fixation

This paper reports on the mechanical properties and pH upon degradation of phosphate glass fibre reinforced methacrylate-modified oligolactide. Phosphate glass fibres of the composition 51.04 P₂O₅–21.42 CaO–25.51 Na₂O–2.03 SiO₂ (mol%) were produced by a crucible spinning technique. Fibres were embedded into a matrix of a degradable organic polymer network based on methacrylate-modified oligolactide; samples with and without addition of CaCO₃ for pH control were produced. pH during degradation in physiological NaCl solution could be increased to up to 6.5 by addition of 20 wt.% calcium carbonate to the fibre composites. pH in Tris buffer solution was about 7.11. Mechanical properties of dry specimens were investigated during 3-point bending tests and gave elastic moduli in the range of cortical bone (15 to 20 GPa). However, addition of calcium carbonate decreased tensile strength of the fibre composites and resulted in brittle fracture behaviour, while CaCO₃-free composites showed a fibrous fracture mode. Control of pH and degradation is a requirement for obtaining a fracture fixation device with degradation properties matching in vivo requirements. Results show that addition of CaCO₃ is suitable for controlling the pH during degradation of metaphosphate glass polymer composites.     

Structural and optical properties of chlorinated plasma polymers

Amorphous hydrogenated chlorinated carbon (a-C:H:Cl) films were produced by the plasma polymerization of chloroform–acetylene–argon mixtures in a radiofrequency plasma enhanced chemical vapor deposition system. The main parameter of interest was the proportion of chloroform in the feed, R_C, which was varied from 0 to 80%. Deposition rates of 80 nm min^? 1 were typical for the chlorinated films. Infrared reflection–absorption spectroscopy revealed the presence of C–Cl groups in all the films produced with chloroform in the feed. X-ray photoelectron spectroscopy confirmed this finding, and revealed a saturation of the chlorine content at ~ 47 at.% for R_C ≥ 40%. The refractive index and optical gap, E₀₄, of the films were roughly in the 1.6 to 1.7, and the 2.8 to 3.7 eV range. These values were calculated from transmission ultraviolet–visible-near infrared spectra. Chlorination leads to an increase in the water surface contact angle from ~ 40° to ~ 77°.     

Li4Ti5O12/Li3SbO4/C composite anode for high rate lithium-ion batteries

Nanocrystalline Li₄Ti₅O₁₂/Li₃SbO₄/C composite-prepared by mechanical ball-milling of Li₄Ti₅O₁₂ (synthesized by aqueous combustion), Li₃SbO₄ (synthesized by solid state method) and activated carbon, has been investigated as anode in lithium-ion coin cells and compared to pristine Li₄Ti₅O₁₂. Galvanostatic charge–discharge measurements in the potential window of 0.05–2.0 V show three plateau regions corresponding to Li insertion/extraction in the composite: a large flat plateau at ~ 1.52/1.59 V, followed by a second plateau at ~ 0.75/1.1 V and a sloppy tail at ~ 0.4/0.6 V. While the plateaus at ~ 0.4/0.6 V and ~ 1.52/1.59 V correspond to Li₄Ti₅O₁₂, the other one at ~ 0.75/1.1 V corresponds to Li₃SbO₄. At a high rate of ~ 15 C, the capacity for Li₄Ti₅O₁₂/Li₃SbO₄/C composite is found to be 105 mAhg^?1 retaining ~ 78% of its initial capacity compared to only 58 mAhg^?1 (~ 27% of the initial capacity) at 14 C for pristine Li₄Ti₅O₁₂ up to 100 cycles. Thus, such composite material might find application in lithium-ion batteries requiring high rate of charge and discharge.     

Novel,simple and reproducible method for preparation of composite hierarchal porous structure scaffolds

Demand to develop a simple and adaptable method for preparation the hierarchical porous scaffolds for bone tissue regeneration is ever increasing. This study presents a novel and reproducible method for preparing the scaffolds with pores structure spanning from nano, micro to macro scale. A macroporous Sr-Hardystonite (Sr–Ca₂ZnSi₂O₇, Sr–HT) scaffold with the average pore size of ~ 1200 μm and porosity of ~ 95% was prepared using polymer sponge method. The struts of the scaffold were coated with a viscous paste consisted of salt (NaCl) particles and polycaprolactone (PCL) to provide a layer with thickness of ~ 300–800 μm. A hierarchical porous scaffold was obtained with macro, micro and nanopores in the range of 400–900 μm, 1–120 μm and 40–290 nm, after salt leaching process. These scales could be easily adjusted based on the starting foam physical characteristics, salt particle size, viscosity of the paste and salt/PCL weight ratio.     

Structure property relation of hybrid biocomposites based on jute,viscose and polypropylene: The effect of the fibre content and the length on the fracture toughness and the fatigue properties

In the present study, the extent of jute and viscose fibre breakage during the extrusion process on the fracture toughness and the fatigue properties was investigated. The composite materials were manufactured using direct long fibre thermoplastic (D-LFT) extrusion, followed by compression moulding. The fracture toughness (K_IC) and the fracture energy (G_IC) of the PP–J30 composites were significantly improved (133% and 514%, respectively) with the addition of 10 wt% viscose fibres, indicating hindered crack propagation. The addition of viscose fibres resulted in three times higher fatigue life compared with that of the unmodified jute composites. Further, with the addition of (2 wt%) MAPP, the PP–J30–V10 resulted in a higher average viscose fibre length of 8.1 mm, and the fracture toughness and fracture energy increased from 9.1 to 10.0 MPa m^1/2 and 28.9 to 31.2 kJ/m², respectively. Similarly, the fatigue life increased 51% compared with the PP–J30–V10, thus demonstrating the increased work energy due to hindrance of the propagation of cracks.     

Controlled retting of hemp fibres: Effect of hydrothermal pre-treatment and enzymatic retting on the mechanical properties of unidirectional hemp/epoxy composites

The objective of this work was to investigate the use of hydrothermal pre-treatment and enzymatic retting to remove non-cellulosic compounds and thus improve the mechanical properties of hemp fibre/epoxy composites. Hydrothermal pre-treatment at 100 kPa and 121 °C combined with enzymatic retting produced fibres with the highest ultimate tensile strength (UTS) of 780 MPa. Compared to untreated fibres, this combined treatment exhibited a positive effect on the mechanical properties of hemp fibre/epoxy composites, resulting in high quality composites with low porosity factor (α_pf) of 0.08. Traditional field retting produced composites with the poorest mechanical properties and the highest α_pf of 0.16. Hydrothermal pretreatment at 100 kPa and subsequent enzymatic retting resulted in hemp fibre composites with the highest UTS of 325 MPa, and stiffness of 38 GPa with 50% fibre volume content, which was 31% and 41% higher, respectively, compared to field retted fibres.     

Ti/SiO2 composite fabricated by powder metallurgy for orthopedic implant

Titanium/silica (Ti/SiO₂) composites are fabricated using powder metallurgy (P/M). Nanoscale biocompatible SiO₂ particles are selected as reinforcement for the Ti/SiO₂ composite to enhance its biocompatibility and strength, especially when with high porosity. Effects of the SiO₂ particle addition and sintering temperature on mechanical properties of the Ti/SiO₂ composites are investigated. The results indicate that the mechanical property of Ti/SiO₂ composites sintered at 1100 °C are better than those at 900 and 1000 °C. The strength of the Ti/SiO₂ composites is significantly higher than that of pure titanium. The composite with the SiO₂ content of 2 wt% sintered at 1100 °C for 4 h shows an appropriate mechanical property with a relative density of 96.5%, a compressive strength of 1566 MPa and good plasticity (an ultimate strain of 15.96%). In vitro results reveal that the Ti/SiO₂ composite possesses excellent biocompatibility and cell adhesion. Osteoblast-like cells grow and spread well on the surfaces of the Ti/SiO₂ composites. The Ti/SiO₂ composite is a promising material for great potential used as an orthopedic implant material.     

Fabrication of novel composites of ZnO-nanoparticles and magadiite

Novel composites of ZnO-nanoparticles and magadiite were successfully prepared by a simple ion-exchange technique in an aqueous suspension of magadiite (Na₂Si₁₄O₂₉·nH₂O) and Zn(NO₃)₂. The TEM and STEM measurements showed that the composites have a structure in which ZnO-nanoparticles with relatively uniform particle sizes are well dispersed within the interlaminar spaces of the magadiite matrix. The particle sizes of the ZnO-nanoparticles were found to depend on the heat-treatment temperature; the average particle sizes are ~ 2.6, ~ 2.8, ~ 4.4 and ~ 4.6 nm, respectively, for the temperatures of 40, 180, 300 and 600 °C. It was also found that the ZnO nanoparticles crystallize and form a single-crystalline particle when the temperature exceeds ~ 300 °C.     

Microstructure and properties of the Si3N4/silica aerogel composites fabricated by the sol–gel method via ambient pressure drying

Si₃N₄ particle reinforced silica aerogel composites have been fabricated by the sol–gel method via ambient pressure drying. The microstructure and mechanical, thermal insulation and dielectric properties of the composites were investigated. The effect of the Si₃N₄ content on the microstructure and properties were also clarified. The results indicate that the obtained mesoporous composites exhibit low thermal conductivity (0.024–0.072 Wm^− 1 K^− 1), low dielectric constant (1.55–1.85) and low loss tangent (0.005–0.007). As the Si₃N₄ content increased from 5 to 20 vol.%, the compressive strength and the flexural strength of the composites increased from 3.21 to 12.05 MPa and from 0.36 to 2.45 MPa, respectively. The obtained composites exhibit considerable promise in wave transparency and thermal insulation functional integration applications.     

Novel photoluminescent mesogenic Schiff-base ligands bearing [N4O4] donors and their bimetallic Zn(II) complexes

Novel photoluminescent salicylaldimine ligands condensed from 3^/, 3^/, 4^/, 4^/-tetraminobiphenyl and 4-substituted long alkoxy salicylaldehyde possessing two sets of tetradentate [N₂O₂] donor site and their binuclear zinc(II) complexes have been synthesized. The mesogenic and photophysical properties were investigated. The compounds were characterized by FT-IR, ¹H and ¹³C NMR, UV–vis, elemental analyses, solution electrical conductivity measurements and FAB mass spectrometry. The mesomorphic behavior of these compounds was probed by differential scanning calorimetry and polarized optical microscopy. The ligand with six carbon chain length showed monotropic nematic mesomorphism at 128° C. However, the ligand with alkoxy tail of carbon length 12 showed enantiotropic SmC phase. The complexes are devoid of any mesomorphism. The low molar conductance values in CH₂Cl₂ indicate that the complexes are non-electrolytes. At 330 nm excitation, the ligand emits green light at ~ 516 nm (Φ = 30%) and ~ 549 nm (Φ = 16%) in solution and solid state, respectively. At similar excitation wavelength, the complexes exhibit blue light in solution at ~ 452 nm (Φ = 20%) and green light in solid state ~ 555 nm (Φ = 11%). The DFT calculations were performed using DMol3 program at BLYP/DNP level to ascertain the stable electronic structure of the complex.     

Microstructure and mechanical properties of carbon fiber reinforced multilayered (PyC–SiC)n matrix composites

Carbon fiber reinforced multilayered (PyC–SiC)_n matrix (C/(PyC–SiC)_n) composites were prepared by isothermal chemical vapor infiltration. The phase compositions, microstructures and mechanical properties of the composites were investigated. The results show that the multilayered matrix consists of alternate layers of PyC and β-SiC deposited on carbon fibers. The flexural strength and toughness of C/(PyC–SiC)_n composites with a density of 1.43 g/cm³ are 204.4 MPa and 3028 kJ/m³ respectively, which are 63.4% and 133.3% higher than those of carbon/carbon composites with a density of 1.75 g/cm³. The enhanced mechanical properties of C/(PyC–SiC)_n composites are attributed to the presence of multilayered (PyC–SiC)_n matrix. Cracks deflect and propagate at both fiber/matrix and PyC–SiC interfaces resulting in a step-like fracture mode, which is conducive to fracture energy dissipation. These results demonstrate that the C/(PyC–SiC)_n composite is a promising structural material with low density and high flexural strength and toughness.     

Functionally graded hydroxyapatite-alumina-zirconia biocomposite: Synergy of toughness and biocompatibility

Functionally Gradient Materials (FGM) are considered as a novel concept to implement graded functionality that otherwise cannot be achieved by conventional homogeneous materials. For biomedical applications, an ideal combination of bioactivity on the material surface as well as good physical property (strength/toughness/hardness) of the bulk is required in a designed FGM structure. In this perspective, the present work aims at providing a smooth gradation of functionality (enhanced toughening of the bulk, and retained biocompatibility of the surface) in a spark plasma processed hydroxyapatite-alumina-zirconia (HAp-Al₂O₃-YSZ) FGM bio-composite. In the current work HAp (fracture toughness ~ 1.5 MPa.m^1/2) and YSZ (fracture toughness ~ 6.2 MPa.m^1/2) are coupled with a transition layer of Al₂O₃ allowing minimum gradient of mechanical properties (especially the fracture toughness ~ 3.5 MPa.m^1/2). The in vitro cyto-compatibilty of HAp-Al₂O₃-YSZ FGM was evaluated using L929 fibroblast cells and Saos-2 Osteoblast cells for their adhesion and growth. From analysis of the cell viability data, it is evident that FGM supports good cell proliferation after 2, 3, 4 days culture. The measured variation in hardness, fracture toughness and cellular adhesion across the cross section confirmed the smooth transition achieved for the FGM (HAp-Al₂O₃-YSZ) nanocomposite, i.e. enhanced bulk toughness combined with unrestricted surface bioactivity. Therefore, such designed biomaterials can serve as potential bone implants.     

Crystallization and hardening of Zr-40 at.% Cu thin film metallic glass: Effects of isothermal annealing

Effects of isothermal annealing on structural relaxation, crystallization and mechanical behavior of Zr-40 at.% Cu thin film metallic glass (TFMG) are reported. Two annealing temperatures have been chosen in the supercooled liquid region (ΔT) and one below the glass transition temperature (T_g). During annealing the free volume decreased and nanocrystals nucleated into the matrix. Results show that the nanocrystalline CuZr₂ intermetallic phase precipitates in the glassy matrix with respect to the annealing temperature and duration. When annealed below T_g, the structural relaxation induces a slight improvement of the mechanical properties with a hardness and Young's modulus variation of about 2.5% and 9.0% compared with the as-deposited values. At higher temperatures, it is shown that hardness increases of about 5.5% and 25.0% after a heat treatment of 60 min at 350 °C and 380 °C, respectively. The elastic modulus follows a time dependent increase from ~ 100 GPa (as-deposited) up to ~ 105 GPa after a one-hour annealing at 350 °C and ~ 125 GPa at 380 °C, respectively.     

Microstructures,mechanical and cytocompatibility of degradable Mg–Zn based orthopedic biomaterials

The Mg–1Zn–xSr (x = 0.2, 0.5, 0.8 and 1 wt.%) alloys have been prepared by zone purifying solidification followed by backward extrusion (BE). The grain size was reduced and the hardness was improved with the increased concentration of strontium (Sr) after backward extrusion. The BE–Mg–1Zn–0.8Sr alloy was mostly composed of fine precipitates (MgZn and Mg₁₇Sr₂) and Mg matrix. At the same time, the mechanical properties of BE–Mg–Zn–Sr alloys were increased with the increment of strontium, which were strongly associated with fine average grain size and homogeneous secondary precipitates. The degradation rate is significantly increased when Sr content is over 0.8 wt.%. The homogenous degradation rate is achieved. The degradation products show good biocompatibility evaluated by MTT method using L929 cell line. It is demonstrated that the micro-alloying element of Sr is a potential approach to develop novel Mg–Zn based biomaterials.     

Characterisation of micro-sized and nano-sized tungsten oxide-epoxy composites for radiation shielding of diagnostic X-rays

Characteristics of X-ray transmissions were investigated for epoxy composites filled with 2–10 vol% WO₃ loadings using synchrotron X-ray absorption spectroscopy (XAS) at 10–40 keV. The results obtained were used to determine the equivalent X-ray energies for the operating X-ray tube voltages of mammography and radiology machines. The results confirmed the superior attenuation ability of nano-sized WO₃-epoxy composites in the energy range of 10–25 keV when compared to their micro-sized counterparts. However, at higher synchrotron radiation energies (i.e., 30–40 keV), the X-ray transmission characteristics were similar with no apparent size effect for both nano-sized and micro-sized WO₃-epoxy composites. The equivalent X-ray energies for the operating X-ray tube voltages of the mammography unit (25–49 kV) were in the range of 15–25 keV. Similarly, for a radiology unit operating at 40–60 kV, the equivalent energy range was 25–40 keV, and for operating voltages greater than 60 kV (i.e., 70–100 kV), the equivalent energy was in excess of 40 keV. The mechanical properties of epoxy composites increased initially with an increase in the filler loading but a further increase in the WO₃ loading resulted in deterioration of flexural strength, modulus and hardness.     

Y2O3–Nd2O3 double stabilized ZrO2–TiCN nanocomposites

Yttria-neodymia double stabilized ZrO₂-based nanocomposites with 40 vol% electrical conductive TiCN were fully densified by means of pulsed electric current sintering (PECS) in the 1400–1500 °C range. The Y₂O₃ stabilizer content was fixed at 1 mol% whereas the Nd₂O₃ co-stabilizer content was varied between 0.75 and 2 mol% in order to optimise the mechanical properties. The mechanical (Vickers hardness, fracture toughness and bending strength), electrical (electrical resistivity) and microstructural properties were investigated and the hydrothermal stability in steam at 200 °C was assessed.The nanocomposites with 1–1.75 mol% Nd₂O₃, PECS at 1400 or 1450 °C, have an excellent fracture toughness of 8 MPa m^1/2, although the grain size of both ZrO₂ and TiCN phases after densification is in the 100 ± 30 nm range. Moreover, the composites combine a hardness of about 13 GPa, a bending strength of 1.1–1.3 GPa with a low electrical resistivity (1.6–2.2 × 10^?5 Ω m) allowing electrical discharge machining. The hydrothermal stability of the double stabilizer nanocomposites was higher than for yttria-stabilized ZrO₂-based composites with the same overall stabilizer content.     

Characterization of the thermo-mechanical behaviour of Hemp fibres intended for the manufacturing of high performance composites

In this paper, the thermo-mechanical behaviour of hemp fibres (Cannabis sativa L.) is investigated by means of a dynamic mechanical analyser. Experiments were performed at a frequency of 1 Hz, over the temperature range between 20 °C and 220 °C. When a periodic stress is applied to an elementary fibre, an increase in its rigidity and a decrease in its damping capacity are observed. These changes in its mechanical properties tend to stabilize after an identified number of cycles, thus providing evidence of an “adaptation” phenomenon. This specific mechanical behaviour certainly involves biochemical and/or structural modifications, such as microfibril reorientation, in the material’s organisation. In addition, the behaviour of hemp fibres is affected by temperature, which acts not only as an activation factor, but also as a degradation factor with respect to the visco-elastic properties of the fibres. The rigidity and endurance of the fibres are highly affected by thermal treatment at temperatures above 150 °C, and up to 180 °C. Taking these results into account, polypropylene–hemp fibre composites were manufactured using a specific processing cycle. By respecting the integrity of the fibres during manufacturing, it is found that with such composites, comparatively high performance can be achieved with some specific mechanical properties. This is highly encouraging for applications requiring high mechanical performance.     

Microstructure,thermooxidation and mechanical behavior of a novel highly linear,vitamin E stabilized,UHMWPE

A novel, vitamin E-stabilized, medical grade ultra-high molecular polyethylene, MG003 (DSM Biomedical; The Netherlands), has been very recently introduced for use in total joint replacements. This homopolymer resin features average molecular weight similar to that of conventional GUR 1050 resin (5.5–6*10⁶ g/mol), but a higher degree of linearity. The aim of this study was to characterize the microstructure, thermal and thermooxidation properties as well as the mechanical behavior of this novel MG003 resin before and after gamma irradiation in air to 90 kGy. For this purpose, a combination of experimental techniques were performed including differential scanning calorimetry (DSC), thermogravimetry (TG), transmission electron microscopy (TEM), X-Ray Diffraction, electron paramagnetic resonance (EPR), and uniaxial tensile tests. As-consolidated MG003 materials exhibited higher crystalline contents (~ 62%), transition temperatures (~ 140 °C), crystal thickness (~ 36 nm), yield stress (~ 25 MPa) and elastic modulus (~ 400 MPa) than GUR 1050 controls (55%, 136 °C, 27 nm, 19 MPa, and 353 MPa, respectively). Irradiation produced similar changes in both MG003 and GUR 1050 materials, specifically increased crystallinity (63% and 60%, respectively), crystal thickness (39 nm and 30 nm), yield stress (27 MPa and 21 MPa), but, above of all, loss of elongation to breakage (down to 442 and 469%, respectively). Thermogravimetric and EPR results suggest comparable susceptibilities to oxidation for both MG003 and GUR 1050 polyethylenes. Based on the present findings, MG003 appears as a promising alternative medical grade polyethylene and it may satisfactorily contribute to the performance of total joint replacements.     

Mechanical properties and microstructure of spark plasma sintered nanostructured p-type SiGe thermoelectric alloys

SiGe based thermoelectric (TE) materials have been employed for the past four decades for power generation in radio-isotope thermoelectric generators (RTG). Recently “nanostructuring” has resulted in significantly increasing the figure-of-merit (ZT) of both n and p-type of SiGe and thus nanostructured Si₈₀Ge₂₀ alloys are evolving as a potential replacement for their conventional bulk counterparts in designing efficient RTGs. However, apart from ZT, their mechanical properties are equally important for the long term reliability of their TE modules. Thus, we report the mechanical properties of p-type nanostructured Si₈₀Ge₂₀ alloys, which were synthesized employing spark plasma sintering of mechanically alloyed nanopowders of its constituent elements with 1.2% boron doping. Nanostructured p-type Si₈₀Ge₂₀ alloys exhibited a hardness of ~ 9 ± 0.1 GPa, an elastic modulus of ~ 135 ± 1.9 GPa, a compressive strength of 108 ± 0.2 MPa, and fracture toughness of ~ 1.66 ± 0.04 MPa√m with a thermal shock resistance value of 391 ± 21 Wm^− 1. This combination of good mechanical properties coupled with higher reported ZT of nanostructured p-type Si₈₀Ge₂₀ alloys are rendered to be a potential material for power generation applications, compared to its bulk counterpart.     

Influence of La2O3 nanoparticle additions on microstructure,wetting, and tensile characteristics of Sn–Ag–Cu alloy

In this study, the effect of La₂O₃ nanoparticles (0, 0.01, 0.03, 0.05 and 0.1 wt.%) has been investigated in Sn–3.0Ag–0.5Cu (SAC-305) alloy. The various soldering properties have been tested, such as wettability, microstructural evolution, intermetallic compound formation, micro-hardness, tensile strength, and fracture analysis of tensile tested samples. La₂O₃ nanoparticles are added in the Sn–3.0Ag–0.5Cu alloy by mechanical mixing of powders and melting. The structural and morphological features of the samples are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and electron probe micro-analyzer (EPMA). The experimental results indicate that the best combination of microstructural, wetting and tensile properties is obtained at 0.05 wt.% La₂O₃ in the solder matrix. The sample reinforced with 0.05 wt.% La₂O₃ i.e., SAC-0.05 La2O3 exhibits ~ 18% increase in microhardness, ~ 26% increase in the ultimate tensile strength (UTS), and ~ 14% elongation due to the adsorption of high surface energy of La₂O₃ nanoparticles in the matrix.