Thermal manifestations and nanoindentation of bone cements for orthopaedic surgery

Improving of bone cements properties is possible by research of variables influencing exothermal behaviour and mechanical properties. Paper deals with exothermal behaviour experimental evaluation of bone cements used for medical purposes. Specimens were prepared by a conventional manual mixing technique. The work addresses primary risk factor associated with application of bone cement to femoral canal. Different size samples of bone cement has been created with diameter d = 2; 5;12,5 mm fixed in dentacryl. As an experimental material, Palacos R+G high viscosity, radiopaque bone cement containing Gentamicin and Radiopaque bone cement Antibiotic Simplex with Tobramycin, was used. Thermal effect during exothermic polymerisation was measured with period I minute. Evaluated factors were mass and thickness of bone cement. Significant influence of bone cement mass on temperature has been found

Thermal manifestations and nanoindentation of bone cements for orthopaedic surgery

Improving of bone cements properties is possible by research of variables influencing exothermal behaviour and mechanical properties. Paper deals with exothermal behaviour experimental evaluation of bone cements used for medical purposes. Specimens were prepared by a conventional manual mixing technique. The work addresses primary risk factor associated with application of bone cement to femoral canal. Different size samples of bone cement has been created with diameter d = 2; 5;12,5 mm fixed in dentacryl. As an experimental material, Palacos R+G high viscosity, radiopaque bone cement containing Gentamicin and Radiopaque bone cement Antibiotic Simplex with Tobramycin, was used. Thermal effect during exothermic polymerisation was measured with period I minute. Evaluated factors were mass and thickness of bone cement. Significant influence of bone cement mass on temperature has been found

Experimental in-vitro bone cements disintegration with ultrasonic pulsating water jet for revision arthroplasty

The paper deals with the study of using the selective property of ultrasonic pulsating water jet for the disintegration of the interface created by bone cement between cemented femoral stem and trabecular bone tissue as a potential technique for revision arthroplasty. Six types of commercial bone cements based on Polymethyl Methacrylate were used for investigation. The cements were mixed using the DePuy - SmartMix (R) CTS / vacuum mixing bowl. Mechanical properties of hardened bone cements were determined by nanoindentation. The bone cement samples were disintegrated using the pulsating water jet technology. The water pressure varied between 8 divided by 20 MPa. A circular nozzle with an orifice diameter of 0,7 mm was used for water jetting. The stand-off distance from the target material was 2 mm and the traverse speed 1 mm/s. The volume of material removal and depth of created traces were measured by MicroProf FRT optical profilometer. The results positively support an assumption that pulsating water jet has a potential to be a suitable technique for the quick and safe disintegration of bone cement during revision arthroplasty

Flash spark plasma sintering of UHTCs

During the five year XMat research project supported by EPSRC (Engineering and Physical Sciences Research Council, UK) at Queen Mary we developed a novel sintering technique called Flash Spark Plasma Sintering (FSPS[1]) which is particularly suitable for the ultrarapid (a few seconds) consolidation of UHTCs. As in the case of incandescent lamps, flash sintering techniques use localized Joule heating developed within the consolidating particles using typically a die-less configuration. Heating rates are extreme (104–106 °C/min), and the sintering temperature is therefore reached extremely rapidly. The research covered mostly metallic conductors (ZrB2[2], HfB2,TiB2) and semiconductors (B4C, SiC and their composites). The talk will summarize the joint XMat team efforts to: -Identify the FSPS consolidation mechanism using modelling and transmission electron microscopy, -Characterise the structural properties for the bulk materials and redefine the structure-property relationships of FSPSed materials Please click Additional Files below to see the full abstract

Mechanical and electrical properties of Al2O3-CNT nanocomposites

This work describes the microstructure, indentation toughness and electrical conductivity of alumina-carbon black and alumina-carbon nanotubes nanocomposites prepared by spark plasma sintering. Materials have been studied by SEM, Vickers indentation technique and two-point electrical conductivity measurement. The addition of 5 % CNTs increased the indentation toughness from 3.24 MPa m(1/2) to 4.14 MPa m(1/2). The electrical conductivity of alumina-CNT nanocomposites is approximately ten times higher in comparison to the alumina-carbon black nanocomposites due to the fibrous nature and high aspect ratio of CNTs

Wear damage mechanisms in 3Y-TZP ceramics

Tribological behaviour of two 3Y-TZP materials (polycrystalline zirconia stabilized by 3% of yttria) with different heat treatments (i.e. different grain size) has been studied using ball-on-disc technique in dry conditions at different sliding speeds. The wear regimes as a function of speed have been identified. The wear damage increased significantly with increasing sliding speed. The mild-to-severe wear transition occurred at the wear rate of ~10-5 mm3/mN which is in accordance with literature data. The wear damage micromechanisms corresponding to various degrees of wear have been studied and are discussed in detail. It has been found that at the low wear regime both materials behave identically, under more severe conditions, however, the material with finer grains exhibited better wear resistance.Peer ReviewedPostprint (published version

Wear resistance of Al2O3–CNT ceramic nanocomposites at room and high temperatures

This work describes the microstructure, indentation toughness, room and high temperature tribological properties of alumina–carbon nanotubes nanocomposites with various contents of carbon nanotubes prepared by spark plasma sintering. Materials have been studied by SEM, TEM, Vickers indentation technique on the microhardness and nanohardness testers and, by high temperature ball-on-disk tribometer. The microstructure, CNT dispersion, and fracture surface were studied and wearing mechanisms: fiber pull-out, CNT crushing and formation of transferred film were identified. The addition of 5% CNTs increased the indentation toughness from 3.24 MPa m1/2 to 4.14 MPa m1/2. The coefficient of friction of alumina–CNT nanocomposites is approximately three times lower in comparison to the alumina monolithic material due to the lubricating effect of carbon nanotubes during sliding

Wear damage mechanisms in 3Y-TZP ceramics

Tribological behaviour of two 3Y-TZP materials (polycrystalline zirconia stabilized by 3% of yttria) with different heat treatments (i.e. different grain size) has been studied using ball-on-disc technique in dry conditions at different sliding speeds. The wear regimes as a function of speed have been identified. The wear damage increased significantly with increasing sliding speed. The mild-to-severe wear transition occurred at the wear rate of ~10-5 mm3/mN which is in accordance with literature data. The wear damage micromechanisms corresponding to various degrees of wear have been studied and are discussed in detail. It has been found that at the low wear regime both materials behave identically, under more severe conditions, however, the material with finer grains exhibited better wear resistance.Peer Reviewe

Mechanical properties and thermal shock behaviour of an alumina/zirconia functionally graded material prepared by electrophoretic deposition

Mechanical properties of a symmetrical planar functionally graded material (FGM) of Al2O3 + 10% ZrO2/Al2O3 + 30% ZrO2/Al2O3 + 10% ZrO2 prepared by electrophoretic deposition (EPD) and pressureless sintering were studied. Hardness and fracture toughness were measured using indentation methods on cross sections of samples. From the difference between lengths of cracks parallel and perpendicular to layers the residual stresses (arisen due to the thermal expansion coefficient mismatch) were calculated. Thermal shock resistance of particular layers was studied using indentation-quench method. The results were compared to those obtained from a reference non-layered composite material, prepared by the same fabrication technique.status: publishe

Strain Mapping of Indented Zr-Based Bulk Metallic Glass Using Nano-Diffraction

The state-of-the-art nano-diffraction technique available at the P06 beamline of the synchrotron radiation source PETRA III was used to observe the strain distribution induced within bulk metallic glass by nano-indentation. Bulk metallic glass (BMG) with nominal composition Zr$_{52.5}$Ti$_{5}$Cu$_{17.9}$Ni$_{14.6}$Al$_{10}$ at.% was prepared by conventional copper mold injection casting. Using the Berkovich indenter a series of indents forming a line was introduced on to the polished surface of the BMG sample. It has been shown that spatially resolved matrix scans with a nanometer sized beam (600 × 600 nm$^{2}$) can identify positions of the indents and quantitatively describe the strain state after nano-indentation