Damage analysis of retrieved BioloxⓇdelta components used in hard and soft bearings.

This retrieval study included 43 Biolox delta explants (18 CoC, 25 CoP). Implants were examined macroscopically, whereby damage was evaluated using a semi quantitative scoring system. Confocal microscopy was used to examine wear related damage patterns of the articulating surfaces. Scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS) was used to analyze wear marks on the implant surface and wear debris in periprosthetic tissue samples. Raman spectroscopy and X-ray diffraction (XRD) were used to quantify monoclinic zirconia fractions. On all components, in vivo wear resulted predominantly in different damage patterns caused by metal transfer. In CoC bearings stripe wear was additionally detected, and some implants underwent severe damage due to component breakage. The wear scores were higher for CoC components, with no differences between the scores for CoC heads and liners. Wear features caused comparable roughening on implants from CoC and CoP bearings. SEM studies demonstrated that most wear marks were caused by metal debris released from implant components. Grain pull-out was observed in stripe wear regions. Monoclinic phase shift was observed in a similar quantity on components from CoP and CoC bearings. The increase of monoclinic zirconia content around metal deposits was minimal and was more pronounced in areas of stripe wear. The results of this study indicate, that ZTA components in general undergo minimal wear in both, CoC and CoP bearings, however, it is more pronounced in the former. Metal deposits, as the most common wear feature, have no significant effect on monoclinic phase transition. STATEMENT OF SIGNIFICANCE: In this paper, we classify all damage patterns macroscopically according to an established scoring system and assess them regarding surface roughness (confocal microscopy) and monoclinic phase content (Raman spectroscopy) in order to derive the severity for patients. We compare hard-hard and hard-soft bearings and relate damage patterns with metal transfer based on SEM/EDS examinations. Furthermore, we work out correlations between patient-specific data, cause of revision and the physical condition of each individual sample Our cohort consists of 43 Biolox delta retrievals, a comparatively large quantity. In addition, we address current topics such as metal transfer and, based on the classification of damage patterns, provide incentives and/or meaningful focal points for further research.

Manufacturing of Open-Cell Aluminium Foams: Comparing the Sponge Replication Technique and Its Combination with the Freezing Method.

The manufacturing of aluminium foams with a total porosity of 87% using the sponge replication method and a combination of the sponge replication and freezing technique is presented. Foams with different cell counts were prepared from polyurethane (PU) templates with a pore count per inch (ppi) of 10, 20 and 30; consolidation of the foams was performed in an argon atmosphere at 650 °C. The additional freezing steps resulted in lamellar pores in the foam struts. The formation of lamellar pores increased the specific surface area by a factor of 1.9 compared to foams prepared by the sponge replication method without freezing steps. The formation of additional lamellar pores improved the mechanical properties but reduced the thermal conductivity of the foams. Varying the pore cell sizes of the PU template showed that-compared to foams with dense struts-the highest increase (~7 times) in the specific surface area was observed in foams made from 10 ppi PU templates. The effect of the cell size on the mechanical and thermal properties of aluminium foams was also investigated.

Missing Piece in the Crystal Chemistry of Zn-Sb Secondary Phases in ZnO-Sb2O3-Bi2O3 Varistor Ceramics: Orthorhombic ß-Zn7Sb2O12. An Experimental and Theoretical Study of the Crystal Structure and Its Thermal and Vibrational Spectroscopic Characterization.

The ternary Zn-Sb oxide ß-Zn7Sb2O12 was prepared by solid state synthesis from ZnO and Sb2O3 at 1250 °C and a reaction time of 168 h. The crystal structure of ß-Zn7Sb2O12 was solved from powder diffraction data by direct-space methods and was refined by the Rietveld technique. The title compound ß-Zn7Sb2O12 crystallizes in the orthorhombic space group Cmme with a = 1210.6(1) pm, b = 1856.7(1) pm, c = 852.2(1) pm, V = 1.9154(1) nm3, and eight formula units per unit cell. The structure can be described as a distorted cubic closest packing of oxide ions with Zn2+ and Sb5+ in the tetrahedral and octahedral interstitial sites. According to group-subgroup relations, the anion packing is directly derived from the spinel structure of α-Zn7Sb2O12; however, the occupation pattern of the interstitials is completely different than in the spinel structure type. The most prominent structural feature in ß-Zn7Sb2O12 is the clustering of all [ZnO4] polyhedra into a [Zn7O20] moiety representing an excerpt from the sphalerite structure. The structural model is corroborated by vibrational spectroscopy as well as density functional theory calculations. Thermal analysis reveals an irreversible phase transition of ß-Zn7Sb2O12 into the α-polymorph at 1330 °C.

Refractory Metal Coated Alumina Foams as Support Material for Stem Cell and Fibroblasts Cultivation.

Ceramics are widely used as implant materials; however, they are brittle and may emit particles when used in these applications. To overcome this disadvantage, alumina foams, which represent a 3D cellular structure comparable to that of human trabecular bone structures, were sputter coated with platinum, tantalum or titanium and modified with fibronectin or collagen type I, components of the extracellular matrix (ECM). To proof the cell material interaction, the unmodified and modified materials were cultured with (a) mesenchymal stem cells being a perfect indicator for biocompatibility and releasing important cytokines of the stem cell niche and (b) with fibroblasts characterized as mediators of inflammation and therefore an important cellular component of the foreign body reaction and inflammation after implantation. To optimize and compare the influence of metal surfaces on cellular behavior, planar glass substrates have been used. Identified biocompatible metal surface of platinum, titanium and tantalum were sputtered on ceramic foams modified with the above-mentioned ECM components to investigate cellular behavior in a 3D environment. The cellular alumina support was characterized with respect to its cellular/porous structure and niche accessibility and coating thickness of the refractory metals; the average cell size was 2.3 mm, the average size of the cell windows was 1.8 mm, and the total foam porosity was 91.4%. The Pt, Ti and Ta coatings were completely dense covering the entire alumina foam surface. The metals titanium and tantalum were colonized very well by the stem cells without a coating of ECM components, whereas the fibroblasts preferred components of the ECM on the alumina foam surface.

Open-Cellular Alumina Foams with Hierarchical Strut Porosity by Ice Templating: A Thickening Agent Study.

Alumina replica foams were manufactured by the Schwartzwalder sponge replication technique and were provided with an additional strut porosity by a freeze-drying/ice-templating step prior to thermal processing. A variety of thickeners in combination with different alumina solid loads in the dispersion used for polyurethane foam template coating were studied. An additional strut porosity as generated by freeze-drying was found to be in the order of ~20%, and the spacings between the strut pores generated by ice-templating were in the range between 20 µm and 32 µm. In spite of the lamellar strut pore structure and a total porosity exceeding 90%, the compressive strength was found to be up to 1.3 MPa. Combining the replica process with freeze-drying proves to be a suitable method to enhance foams with respect to their surface area accessible for active coatings while preserving the advantageous flow properties of the cellular structure. A two-to-threefold object surface-to-object volume ratio of 55 to 77 mm-1 was achieved for samples with 30 vol% solid load compared to 26 mm-1 for non-freeze-dried samples. The freeze-drying technique allows the control of the proportion and properties of the introduced pores in an uncomplicated and predictable way by adjusting the process parameters. Nevertheless, the present article demonstrates that a suitable thickener in the dispersion used for the Schwartzwalder process is inevitable to obtain ceramic foams with sufficient mechanical strength due to the necessarily increased water content of the ceramic dispersion used for foam manufacturing.

An In Vitro Hemodynamic Loop Model to Investigate the Hemocytocompatibility and Host Cell Activation of Vascular Medical Devices.

In this study, the hemocompatibility of tubes with an inner diameter of 5 mm made of polyvinyl chloride (PVC) and coated with different bioactive conjugates was compared to uncoated PVC tubes, latex tubes, and a stent for intravascular application that was placed inside the PVC tubes. Evaluation of hemocompatibility was done using an in vitro hemodynamic loop model that is recommended by the ISO standard 10993-4. The tubes were cut into segments of identical length and closed to form loops avoiding any gap at the splice, then filled with human blood and rotated in a water bath at 37 °C for 3 hours. Thereafter, the blood inside the tubes was collected for the analysis of whole blood cell count, hemolysis (free plasma hemoglobin), complement system (sC5b-9), coagulation system (fibrinopeptide A), and leukocyte activation (polymorphonuclear elastase, tumor necrosis factor and interleukin-6). Host cell activation was determined for platelet activation, leukocyte integrin status and monocyte platelet aggregates using flow cytometry. The effect of inaccurate loop closure was examined with x-ray microtomography and scanning electron microscopy, that showed thrombus formation at the splice. Latex tubes showed the strongest activation of both plasma and cellular components of the blood, indicating a poor hemocompatibility, followed by the stent group and uncoated PVC tubes. The coated PVC tubes did not show a significant decrease in platelet activation status, but showed an increased in complement and coagulation cascade compared to uncoated PVC tubes. The loop model itself did not lead to the activation of cells or soluble factors, and the hemolysis level was low. Therefore, the presented in vitro hemodynamic loop model avoids excessive activation of blood components by mechanical forces and serves as a method to investigate in vitro interactions between donor blood and vascular medical devices.

Microstructure and Compression Properties of VSS­V3B2 Eutectic Alloys in the V-Si-B System.

The present study reports on the microstructural evolution and room temperature plasticity of V(­Si)­B alloys with respect to the V solid solution (VSS)­V3B2 phase region. To investigate the occurring effects systematically, different binary V­B and ternary V­Si­B alloys were produced by conventional arc melting. Scanning electron microscope (SEM) analyses and X-ray diffraction (XRD) measurements were used to characterize the resulting as-cast microstructures. For the first time, the eutectic composition was systematically traced from the binary V­B domain to the ternary V­Si­B system. The observations discover that the binary eutectic trough (VSS­V3B2) seems to reach into the ternary system up to an alloy composition of V­5Si­9B. Room temperature compression tests were carried out in order to study the impact of single-phase and multi-phase microstructures on the strength and plasticity of binary and ternary alloys. The results indicate that the VSS phase controls the plastic deformability in the VSS­V3B2 eutectic microstructure whereas the intermetallic V3B2 acts as a strong hardening phase.

Cellular Nickel-Yttria/Zirconia (Ni-YSZ) Cermet Foams: Manufacturing, Microstructure and Properties.

Open-celled ceramic composite foams were prepared from NiO and yttria-stabilized zirconia (YSZ) powders by the polymer sponge replication (Schwartzwalder) technique using the respective aqueous dispersions. Mechanically stable NiO-YSZ foams with an average porosity of 93 vol.% were obtained. After chemical reduction of the NiO phase with hydrogen, cellular Ni-YSZ cermet structures were obtained. They are characterized by an electric conductivity up to 19∙103 S∙m-1 which can be adjusted by both, the Ni volume fraction, and the sintering/reduction procedure. The NiO-YSZ ceramic foams, as well as the cellular Ni-YSZ cermets prepared therefrom, were characterized with respect to their microstructure by scanning electron microscopy, confocal Raman microscopy and X-ray diffraction with Rietveld analysis. In addition, the compressive strength, the electric conductivity and the thermal conductivity were determined. The collected data were then correlated to the sample microstructure and porosity and were also applied for modelling of the mechanical and electric properties of the bulk Ni-YSZ strut material.

Phase Evolution, Filler-Matrix Interactions, and Piezoelectric Properties in Lead Zirconate Titanate (PZT)-Filled Polymer-Derived Ceramics (PDCs).

PZT-silsesquioxane-based 0-3 hybrid materials are prepared by mixing lead zirconate titanate (Pb(Zr,Ti)O3; PZT) powder with a [R-SiO3/2]n (R = H, CH3, CH=CH2, C6H5) silsequioxane preceramic polymer. A PZT load up to 55 vol.% can be reached in the final composite. The piezoelectric and mechanical properties are investigated as a function of the filler content and are compared with theoretical models and reference samples made of the pure preceramic polymer or PZT filler. The piezoelectric response of the composites, as expressed by the relative permittivity and the piezoelectric coefficients d33 and g33, increases with an increasing PZT content. The bending strength of the composites ranges between 15 MPa and 31 MPa without a clear correlation to the filler content. The thermal conductivity increases significantly from 0.14 W∙m-1∙K-1 for the pure polymer-derived ceramic (PDC) matrix to 0.30 W∙m-1∙K-1 for a sample containing 55 vol.% PZT filler. From X-ray diffraction experiments (XRD), specific interactions between the filler and matrix are observed; the crystallization of the PDC matrix in the presence of the PZT filler is inhibited; conversely, the PDC matrix results in a pronounced decomposition of the filler compared to the pure PZT material.

Open-Cell Aluminum Foams by the Sponge Replication Technique.

Open-cell aluminum foams were manufactured by a sponge replication technique having a total porosity of ~90%. The influence of the thermal processing conditions such as atmosphere and temperature on the cellular structure, phase composition porosity, thermal conductivity, and compressive strength of the foams was studied. It was found that the thermal processing of aluminum foams in Ar at temperatures up to 800 °C led to aluminum foams with a reduced strut porosity, a lower amount of aluminum oxide, a higher thermal conductivity, and a higher compression strength, compared to foams thermally processed in air. These results were explained by the lower amount of aluminum oxide after thermal processing of the foams.

Refitting of Zirconia Toughening into Open-Cellular Alumina Foams by Infiltration with Zirconyl Nitrate.

The present work describes the combination of the well-established dispersion infiltration of the hollow struts in reticulated porous ceramics (RPCs) and the salt solution infiltration of the remaining strut porosity. This approach is applied on alumina foams, which are loaded subsequently with a dispersion of sub-micrometer alumina particles and a ZrO(NO3)2 solution. The zirconyl nitrate is converted into a ZrO2 transformation toughening phase during the final sintering step. As a consequence of the complex microstructure evolution during the consecutive infiltration cycles, the reinforcement phase concentrates selectively at the weak spots of RPC structures-namely, the hollow strut cavities and longitudinal cracks along the struts. As a consequence, a severe improvement of the compressive strength is observed: The average compressive strength, normalized to a porosity of 91.6 vol.%, is 1.47 MPa for the Al2O3/ZrO2 infiltrated foams, which is an improvement by 40% with respect to alumina-only loaded foams (1.05 MPa) or by 206% compared to uninfiltrated alumina RPCs (0.48 MPa). The compressive strength results are correlated to infiltration parameters and the properties of the infiltration fluids, for example the rheological behavior and the size of the Zr solute species in the respective ZrO(NO3)2 solution.

Improving the Strength of ZTA Foams with Different Strategies: Immersion Infiltration and Recoating.

The combination of high strength and toughness, excellent wear resistance and moderate density makes zirconia-toughened alumina (ZTA) a favorable ceramic, and the foam version of it may also exhibit excellent properties. Here, ZTA foams were prepared by the polymer sponge replication method. We developed an immersion infiltration approach with simple equipment and operations to fill the hollow struts in as-prepared ZTA foams, and also adopted a multiple recoating method (up to four cycles) to strengthen them. The solid load of the slurry imposed a significant influence on the properties of the ZTA foams. Immersion infiltration gave ZTA foams an improvement of 1.5 MPa in compressive strength to 2.6 MPa at 87% porosity, only resulting in a moderate reduction of porosity (2-3%). The Weibull modulus of the infiltrated foams was in the range of 6-9. The recoating method generated an increase in compression strength to 3.3-11.4 MPa with the reduced porosity of 58-83%. The recoating cycle dependency of porosity and compression strength is nearly linear. The immersion infiltration strategy is comparable to the industrially-established recoating method and can be applied to other reticulated porous ceramics (RPCs).

Methanesulfonates of high-valent metals: syntheses and structural features of MoO2(CH3SO3)2, UO2(CH3SO3)2, ReO3(CH3SO3), VO(CH3SO3)2, and V2O3(CH3SO3)4 and their thermal decomposition under N2 and O2 atmosphere.

Oxide methanesulfonates of Mo, U, Re, and V have been prepared by reaction of MoO(3), UO(2)(CH(3)COO)(2)·2H(2)O, Re(2)O(7)(H(2)O)(2), and V(2)O(5) with CH(3)SO(3)H or mixtures thereof with its anhydride. These compounds are the first examples of solvent-free oxide methanesulfonates of these elements. MoO(2)(CH(3)SO(3))(2) (Pbca, a=1487.05(4), b=752.55(2), c=1549.61(5) pm, V=1.73414(9) nm(3), Z=8) contains [MoO(2)] moieties connected by [CH(3)SO(3)] ions to form layers parallel to (100). UO(2)(CH(3)SO(3))(2) (P2(1)/c, a=1320.4(1), b=1014.41(6), c=1533.7(1) pm, ß=112.80(1)°, V=1.8937(3) nm(3), Z=8) consists of linear UO(2)(2+) ions coordinated by five [CH(3)SO(3)] ions, forming a layer structure. VO(CH(3)SO(3))(2) (P2(1)/c, a=1136.5(1), b=869.87(7), c=915.5(1) pm, ß=113.66(1)°, V=0.8290(2) nm(3), Z=4) contains [VO] units connected by methanesulfonate anions to form corrugated layers parallel to (100). In ReO(3)(CH(3)SO(3)) (P1, a=574.0(1), b=1279.6(3), c=1641.9(3) pm, α=102.08(2), ß=96.11(2), γ=99.04(2)°, V=1.1523(4) nm(3), Z=8) a chain structure exhibiting infinite O-[ReO(2)]-O-[ReO(2)]-O chains is formed. Each [ReO(2)]-O-[ReO(2)] unit is coordinated by two bidentate [CH(3)SO(3)] ions. V(2)O(3)(CH(3)SO(3))(4) (I2/a, a=1645.2(3), b=583.1(1), c=1670.2(3) pm, ß=102.58(3), V=1.5637(5) pm(3), Z=4) adopts a chain structure, too, but contains discrete [VO]-O-[VO] moieties, each coordinated by two bidentate [CH(3)SO(3)] ligands. Additional methanesulfonate ions connect the [V(2)O(3)] groups along [001]. Thermal decomposition of the compounds was monitored under N(2) and O(2) atmosphere by thermogravimetric/differential thermal analysis and XRD measurements. Under N(2) the decomposition proceeds with reduction of the metal leading to the oxides MoO(2), U(3)O(7), V(4)O(7), and VO(2); for MoO(2)(CH(3)SO(3))(2), a small amount of MoS(2) is formed. If the thermal decomposition is carried out in a atmosphere of O(2) the oxides MoO(3) and V(2)O(5) are formed.

Sulfates of the refractory metals: crystal structure and thermal behavior of Nb2O2(SO4)3, MoO2(SO4), WO(SO4)2, and two modifications of Re2O5(SO4)2.

The sulfates Nb(2)O(2)(SO(4))(3), MoO(2)(SO(4)), WO(SO(4))(2,) and two modifications of Re(2)O(5)(SO(4))(2) have been synthesized by the solvothermal reaction of NbCl(5), WOCl(4), Re(2)O(7)(H(2)O)(2), and MoO(3) with sulfuric acid/SO(3) mixtures at temperatures between 200 and 300 °C. Besides the X-ray crystal structure determination of all compounds, the thermal behavior was investigated using thermogravimetric studies. WO(SO(4))(2) (monoclinic, P2(1)/n, a = 7.453(1) Å, b = 11.8232(8) Å, c = 7.881(1) Å, ß = 107.92(2)°, V = 660.7(1) Å(3), Z = 4) and both modifications of Re(2)O(5)(SO(4))(2) (I: orthorhombic, Pba2, a = 9.649(1) Å, b = 8.4260(8) Å, c = 5.9075(7) Å, V = 480.27(9) Å(3), Z = 2; II: orthorhombic, Pbcm, a = 7.1544(3) Å, b = 7.1619(3) Å, c = 16.8551(7) Å, V = 863.64(6) Å(3), Z = 4) are the first structurally characterized examples of tungsten and rhenium oxide sulfates. Their crystal structure contains layers of sulfate connected [W═O] moieties or [Re(2)O(5)] units, respectively. The cohesion between layers is realized through weak M-O contacts (343-380 pm). Nb(2)O(2)(SO(4))(3) (orthorhombic, Pna2(1), a = 9.9589(7) Å, b = 11.7983(7) Å, c = 8.6065(5) Å, V = 1011.3(1) Å(3), Z = 4) represents a new sulfate-richer niobium oxide sulfate. The crystal structure contains a three-dimensional network of sulfate connected [Nb═O] moieties. In MoO(2)(SO(4)) (monoclinic, I2/a, a = 8.5922(6) Å, b = 12.2951(6) Å, c = 25.671(2) Å, ß = 94.567(9)°, V = 2703.4(3) Å(3), Z = 24) [MoO(2)] units are connected through sulfate ions to a three-dimensional network, which is pervaded by channels along [100] accommodating the terminal oxide ligands. In all compounds except WO(SO(4))(2), the metal ions are octahedrally coordinated by monodentate sulfate ions and oxide ligands forming short M═O bonds. In WO(SO(4))(2), the oxide ligand and two monodentate and two bidentate sulfate ions build a pentagonal bipyramid around W. The thermal stability of the sulfates decreases in the order Nb > Mo > W > Re; the residues formed during the decomposition are the corresponding oxides.