Ca-Mg silicates are receiving a growing interest in the field of bioceramics. In a previous study, wollastonite-diopside (WD) glass-ceramics were successfully prepared by a new processing route, ...consisting of the heat treatment of a silicone resin embedding reactive oxide particles and a Ca/Mg-rich glass. The in vitro degradation, bioactivity, and cell response of these new WD glass-ceramics, fired at 900-1100 °C for 1 h, as a function of the Ca/Mg-rich glass content, are the aim of this investigation The results showed that WD glass-ceramics from formulations comprising different glass contents (70-100% at 900 °C, 30% at 1100 °C) exhibit the formation of an apatite-like layer on their surface after immersion in SBF for seven days, thus confirming their surface bioactivity. The XRD results showed that these samples crystallized, mainly forming wollastonite (CaSiO₃) and diopside (CaMgSi₂O₆), but combeite (Na₂Ca₂Si₃O₉) crystalline phase was also detected. Besides in vitro bioactivity, cytotoxicity and osteoblast adhesion and proliferation tests were applied after all characterizations, and the formulation comprising 70% glass was demonstrated to be promising for further in vivo studies.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Additive manufacturing of large scale parts is an innovative, challenging research field, with the potential of producing parts with complex structures, specific functional and structural properties. ...In this study, binder jetting was employed using two different large scale printers to fabricate non-structural parts made of artificial stone. The printing bed was comprised of aggregates (River sand and Poraver expanded glass) and reactive magnesium oxide and potassium phosphate powders, which were activated by selectively depositing water, layer after layer. The exothermic reaction between reactive powders and water generates in situ a hydraulic inorganic binder, that binds the aggregates in the bed. The reaction parameters were controlled to achieve a fast setting, enabling rapid printing at the macro-scale (in the range of tens of centimeters or meters). The influence of the voxel size of the printers on the microstructure and printing quality of the fabricated parts, their physical and mechanical properties as well as the in situ formation of the cement phase were investigated by X-ray microtomography.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Reticulated åkermanite (Ca2MgSi2O7) 3D scaffolds were fabricated by direct ink writing of pastes based on a commercial silicone resin and fillers, such as calcium carbonate (CaCO3) and magnesium ...hydroxide (Mg(OH)2) microparticles, followed by heat treatment at 1100 °C in air. To form liquid phase upon firing and thus promote the ionic interdiffusion, borax (Na2B4O7·10H2O) or hydrated sodium phosphate (Na2HPO4·12H2O) were considered as alternative additives. Although leading to scaffolds with different strength-to-density ratio, the two additives did not lead to substantial differences in terms of biological response. All fabricated ceramics exhibited acellular in-vitro bioactivity upon immersion in simulated-body-fluid (SBF) as well as antibacterial activity against S. aureus and E. coli. Direct contact cell viability test, performed with a stromal-cell line from mouse bone marrow (ST-2 cells), indicated no cytotoxicity of both samples determined by the WST-8 assay.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The focus of the present work is the development of a metallic ink that possesses controlled rheological properties: by keeping printing parameters constant both AISI 316L dense parts and porous ...scaffolds have been produced. Shrinkage, porosity, and mechanical properties have been studied to evaluate the link between the ink rheological properties and the final part. Depending on binder composition, linear shrinkage ranging from 9% to 22% and porosity from 34 to 7 vol% are measured. Tensile strength for specimens sintered at 1240 °C reach the value of 444 MPa and elongation at a break of 12.3%. These values are still far from additively manufactured AISI 316L parts with powder bed fusion technologies, but represent an improvement compared to previously reported data in the literature for AISI 316L parts 3D printed by DIW. Porous scaffolds with a spanning distance of 1.2 mm are printed and sintered. Porosity of 74 vol% and compression strength of 74 MPa are measured for this set of samples showing how the produced ink represents a valuable alternative to pastes already present in the literature.
AISI316L dense and porous parts are 3D printed by direct ink writing (DIW). The ink rheological properties are tuned to control shape retention after printing. The effect of sintering temperature on AISI316L dense parts' mechanical properties is studied.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Printing curved lattice structures is a demanding task due to the current limitations in standard 3-axes printing technologies available in the market: a removable support structure often needs to be ...printed, and printing layer-by-layer to generate an inclined surface causes a significant stair-stepping effect, affecting the surface quality and leading to anisotropy in physical properties. To overcome these limitations, the connection of the printing unit to a >3-axes robotic arm seems to be a feasible solution for printing polymeric based structures, as demonstrated by previous works reported in the literature. In this paper, a method for printing by Direct Ink Writing cylindrical lattice structures is presented: three different materials, SiOC amorphous ceramic, Ti6Al4V-based composite and CaSiO3 bioceramic, are printed by the combination of extrusion of an elastomeric ink and a mandrel connected to a robotic arm. The method shows high potential for printing ceramic and metal cylindrical lattice structures and their combination.
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•Cylindrical lattice structures were successfully printed by the combination of Direct Ink Writing and a robotic arm.•The use of an elastomeric-based ink allowed printing complex geometries that could be easily removed from the support.•By means of a thermal treatment, SiOC glass, Ti6Al4V-composite and CaSiO3 cylindrical lattice structures were fabricated.•The method proposed here shows high potential for printing complex geometries made of multiple materials.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Zirconia-toughened alumina (ZTA)/Al2TiO5 composites were prepared via a sol–gel route. The prepared samples were uniaxially pressed and pressurelessly sintered at 1650–1700 °C for 1 h. The ...microstructure, densification, and X-ray diffraction patterns of the sintered ZTA/Al2TiO5 composites were investigated, and their mechanical properties, thermal coefficient, and shock resistance were characterized. The addition of Al2TiO5 hindered the grain growth of the alumina particles and enhanced the relative density, Vickers hardness, and bending strength of the composites compared with pure ZTA samples. The fracture toughness was improved by 19% upon the addition of 40 wt% Al2TiO5. Moreover, increasing the Al2TiO5 content resulted in an improvement in the thermal shock resistance.
The cooling of a melt corresponding to the eutectic between wollastonite (CaSiO3) and diopside (CaMgSi2O6) determines the synthesis of an interesting example of alkali‐free bioactive glass, easily ...converted into glass‐ceramics featuring two silicate phases, coupled also with åkermanite (Ca2MgSi2O7), by sinter‐crystallization of fine glass powders at 1000°C. The fabrication of scaffolds by digital light processing of glass powders suspended in a photo‐curable, sacrificial binder, is a well‐established technique; the present paper aims at disclosing novel approaches, concerning the topology of scaffolds, offering components with remarkable strength, especially in bending conditions. As an alternative, glass‐ceramic foams were fabricated by the firing of porous precursors derived from the gelation of suspensions of glass powders in alkali‐free basic aqueous solution.
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BFBNIB, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Biosilicate® glass-ceramics are among the most valid alternatives to 45S5 Bioglass. They combine a similar bioactivity and bioresorbability as the 45S5 with superior mechanical strength, owing to the ...crystallization of a Na–Ca silicate phase. This crystallization may be experienced upon viscous flow sintering of fine glass powders, thus configuring a sinter-crystallization process. As crystallization is seldom complete, sintering can also be applied to semicrystalline powders. The sintering/crystallization combination may be exploited for shaping highly porous bodies, to be used as scaffolds for bone tissue engineering, in the form of foams. The present study aims at exploring a gel-casting process, based on the room temperature foaming of powders suspended in a “weakly alkaline” (1 M NaOH) aqueous solution, followed by sintering at 1,000°C. The gelation of suspensions is attributed to the formation of hydrated compounds, later decomposed upon firing. Amorphous powders provided more intense gelation than semicrystalline ones, promoted a more homogeneous foaming, and stimulated a substantial crystallization upon firing. The homogeneity of foamed samples was assessed using micro-tomography and was further improved by casting foamed suspensions (“foam casting”) before setting.
Hardystonite-based (HT) bioceramic foams were easily obtained via thermal treatment of silicone resins and reactive oxide fillers in air. By using a commercial silicone, incorporating strontium oxide ...and magnesium oxide precursors (as well as CaO and ZnO), and treating it at 1100 °C, a complex solid solution (Ca
Sr
Zn
Mg
Si
O
) that has superior biocompatibility and bioactivity properties compared to pure hardystonite (Ca
ZnSi
O
) can be obtained. Proteolytic-resistant adhesive peptide mapped on vitronectin (D2HVP), was selectively grafted to Sr/Mg-doped HT foams using two different strategies. Unfortunately, the first method (via protected peptide) was unsuitable for acid-sensitive materials such as Sr/Mg-doped HT, resulting in the release of cytotoxic levels of Zinc over time, with consequent negative cellular response. To overcome this unexpected result, a novel functionalization strategy requiring aqueous solution and mild conditions was designed. Sr/Mg-doped HT functionalized with this second strategy (via aldehyde peptide) showed a dramatic increase in human osteoblast proliferation at 6 days compared to only silanized or non-functionalized samples. Furthermore, we demonstrated that the functionalization treatment does not induce any cytotoxicity. Functionalized foams enhanced mRNA-specific transcript levels coding
,
,
, and
at 2 days post-seeding. In conclusion, the second functionalization strategy proved to be appropriate for this specific biomaterial and was effective at enhancing the material's bioactivity.
Surface modification of titanium-based implants has been extensively researched as an effective tool to generate a bioactive surface that helps to create a new bone and forms a natural bond at the ...interface between the implants and surrounding bone tissues. The present research is focused on the development of a new methodology to obtain sphene (CaTiSiO5) biocoatings on titanium substrates. Based on previous results, where sphene coatings were obtained by a manual airbrush, the coating system was improved in order to have a full control of the process in terms of uniform morphology of the biocoating. The effectiveness of the coating system and deposition process is supported by microscopic analysis of the produced coatings, by surface roughness measurements of uncoated and coated substrates, and estimation of the adhesion strength between the coatings and the substrate. The results showed that the coatings had crack-free homogenous surfaces with ideal characteristics for orthopedic and dental implants in terms of adhesion strength and surface roughness.
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•An automatic spray coating system was developed in order to deposit sphene precursors on Ti substrates.•The deposition time effect on coating thickness and roughness was studied.•The developed sphene coating was characterized to be a layered and porous.•Even at high overall thickness the coatings was completely crack-free and showed a good adhesion strength to the substrate.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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