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In recent years, amorphous bioglass is used to improve the bioactivity of HA (Ca10(PO4)6(OH)2). Nevertheless, bioglass crystallizes and reacts with the matrix to form a complex phase composition during sintering, resulting in an unclear mechanism for tailoring the properties of HA bioceramics. In this work, TPMS structural HA ceramics fabricated by digital light processing (DLP) were doped by akermanite (Ca2MgSi2O7) to better tailor the porosity, bioactivity and mechanical strength. After sintering above 1000 °C, Mg2+ ions from akermanite substitute Ca2+ ions in HA, leading to the decomposition of HA into β-TCP. This process increases the porosity of bioceramics. Additionally, liquid phases sintering caused by akermanite gives rise to the densification and enhancement of grain bonding, thereby reinforcing the mechanical strength of scaffolds. For in vitro bioactivity, as the content of akermanite increases from 0 wt.% to 20 wt.%, carbonated hydroxyapatite firstly deposits onto the surfaces of scaffolds and then disappears, because excessive Mg2+ prevent the hydroxyapatite crystallization. Finally, bioceramics with 5 wt.% and 10 wt.% of akermanite and sintering at 1100 °C exhibit a high porosity of over 80% and an appropriate compressive strength of over 2 MPa, while achieving an enhanced in vitro bioactivity and good biocompatibility. After optimization, this kind of porous scaffolds can be well applied to the repair of cancellous bone defect.

Porous ceramic microspheres are a desirable substance for bone tissue reconstruction and delivery applications. This study focuses on Mg–Ca silicate microspheres encapsulated in biodegradable poly (lactic-co-glycolic acid) (PLGA) to serve as a biocompatible carrier for the controlled release of vancomycin hydrochloride. In this regard, diopside (MgCaSi2O6), bredigite (MgCa7Si4O16), and akermanite (MgCa2Si2O7) powders were synthesized by sol-gel and subsequent calcination methods. Then, porous akermanite, diopside and bredigite microspheres of 700–1000 μm in diameter were fabricated by using carbon porogen, droplet extrusion and sintering, then loaded with the drug and eventually coated with PLGA. The bare microspheres showed a considerable burst release mode of the drug into a physiological medium, whereas PLGA coating of the microspheres reduced the burst release level. To investigate effective mechanisms governing in the drug release from the carriers, the contribution of burst, degradation, and diffusion was analyzed by the sequential quadratic programming algorithm method. It was found that the relative contribution of diffusion to bioresorption is ranked as diopside > akermanite > bredigite, whereas PLGA coating dominates the diffusion mechanism. The dental pulp stem cells cytocompatibility MTT assay of the microspheres also showed that the drug loading deteriorates but PLGA coating improves the cell biocompatibility significantly. Comparatively, the biocompatibility of the PLGA-coated microspheres was ranked as akermanite > diopside > bredigite, as a result of a compromise between the release of the constituting ions of the ceramic carriers and vancomycin molecules. It was eventually concluded that PLGA-coated Mg–Ca silicate microspheres are promising candidates for drug-delivery bone tissue engineering and dental bone grafting applications.

Many bioactive inorganic ions such as calcium (Ca), magnesium (Mg) and silicon (Si) have been confirmed to take part in bone regeneration through promoting the secretion of osteogenesis-related growth factors. However, it is not clear about the effective concentration range and action mechanism of ion combinations on synergistically facilitating osteogenesis. Besides, it is of great significance to design a novel bioceramic that could continuously release these effective inorganic ions to match the need for bone tissue repair. Thus, in this work, the concentration level of combined Ca, Mg, Si ions beneficial to osteogenesis of bone marrow-derived mesenchymal stem cells (BMSCs) was explored by orthogonal experimental design (OED) firstly. Meanwhile, eight single-phase ceramics in CaO-MgO-SiO2 system were synthesized, and the influences of their inherent properties on ion dissolution behaviors were systematically investigated. Finally, based on the above results, three multiphase bioceramics (named C1, C2 and C3) containing calcium silicate, diopside and akermanite as crystalline phase were designed and synthesized. It was found that the ionic extracts of bioceramic C1 were just within the above effective concentration range, displaying a predetermined ability of stimulating osteogenic differentiation of BMSCs through enhancing the expression of bone morphogenetic protein-2 (BMP-2) and vascular endothelial growth factor (VEGF). All the results indicated that this novel multiphase bioceramic with adjustable ion dissolution behavior has a great application potential in bone tissue engineering.

The development of biodegradable Fe-based bone implants has rapidly progressed in recent years. Most of the challenges encountered in developing such implants have been tackled individually or in combination using additive manufacturing technologies. Yet not all the challenges have been overcome. Herein, we present porous FeMn-akermanite composite scaffolds fabricated by extrusion-based 3D printing to address the unmet clinical needs associated with Fe-based biomaterials for bone regeneration, including low biodegradation rate, MRI-incompatibility, mechanical properties, and limited bioactivity. In this research, we developed inks containing Fe, 35 wt% Mn, and 20 or 30 vol% akermanite powder mixtures. 3D printing was optimized together with the debinding and sintering steps to obtain scaffolds with interconnected porosity of 69%. The Fe-matrix in the composites contained the γ-FeMn phase as well as nesosilicate phases. The former made the composites paramagnetic and, thus, MRI-friendly. The in vitro biodegradation rates of the composites with 20 and 30 vol% akermanite were respectively 0.24 and 0.27 mm/y, falling within the ideal range of biodegradation rates for bone substitution. The yield strengths of the porous composites stayed within the range of the values of the trabecular bone, despite in vitro biodegradation for 28 d. All the composite scaffolds favored the adhesion, proliferation, and osteogenic differentiation of preosteoblasts, as revealed by Runx2 assay. Moreover, osteopontin was detected in the extracellular matrix of cells on the scaffolds. Altogether, these results demonstrate the remarkable potential of these composites in fulfilling the requirements of porous biodegradable bone substitutes, motivating future in vivo research. Statement of significance: We developed FeMn-akermanite composite scaffolds by taking advantage of the multi-material capacity of extrusion-based 3D printing. Our results demonstrated that the FeMn-akermanite scaffolds showed an exceptional performance in fulfilling all the requirements for bone substitution in vitro, i.e., a sufficient biodegradation rate, having mechanical properties in the range of trabecular bone even after 4 weeks biodegradation, paramagnetic, cytocompatible and most importantly osteogenic. Our results encourage further research on Fe-based bone implants in in vivo.

The effects of cobalt (Co) substitution on the structural, physico-mechanical properties, as well as the in vitro bioactivity and biodegradability of akermanite (Ca2MgSi2O7) are studied. The XRD patterns showed that the Co substitution did not change the Ca2MgSi2O7 phase. The FESEM micrographs revealed that the partial substitution of Co increased the shrinkage and density of Ca2MgSi2O7 and reduced the grain size. The Co substitution showing the highest mechanical response was 2 mol%. However, the mechanical properties decreased beyond 2 mol% due to the larger grain size. The in vitro degradation test showed that Co substitution altered the degradation profile of Ca2MgSi2O7. However, the degradation rate of Co-substituted Ca2MgSi2O7 was found to be low (1.2%) compared to that of Ca2MgSi2O7 (18%) and led to an alkaline microenvironment. Additionally, an in vitro bioactivity assessment supported the apatite-forming ability of Co-substituted Ca2MgSi2O7 disks after soaking in a SBF solution for 7 and 14 days. Finally, the concentration of Co2+ ions released from the 2 mol% disks was found to be in the non-toxic range. However, a further in vitro and in vivo test needs to be conducted.

The present work reports the synthesis and characterization of polycaprolactone fibers loaded with particulate calcium magnesium silicates, to form composite materials with bioresorbable and bioactive properties. The inorganic powders were achieved through a sol–gel method, starting from the compositions of diopside, akermanite, and merwinite, three mineral phases with suitable features for the field of hard tissue engineering. The fibrous composites were fabricated by electrospinning polymeric solutions with a content of 16% polycaprolactone and 5 or 10% inorganic powder. The physico-chemical evaluation from compositional and morphological points of view was followed by the biological assessment of powder bioactivity and scaffold biocompatibility. SEM investigation highlighted a significant reduction in fiber diameter, from around 3 μm to less than 100 nm after the loading stage, while EDX and FTIR spectra confirmed the existence of embedded mineral entities. The silicate phases were found be highly bioactive after 4 weeks of immersion in SBF, enriching the potential of the polymeric host that provides only biocompatibility and bioresorbability. Moreover, the cellular tests indicated a slight decrease in cell viability over the short-term, a compromise that can be accepted if the overall benefits of such multifunctional composites are considered.

Fiber production from inorganic industrial solid wastes is an effective waste management strategy. Because of cost considerations, most enterprises generally use local solid wastes as raw materials to produce fibers. In this study, we explored the feasibility of producing fibers using fly ash and magnesium slag. The results show that the melting temperature of the blends composed of fly ash, magnesium slag, and a small amount of calcined dolomite first decreased and then increased with an increase in acidity coefficient (Mk) from 1.0 to 2.4. The samples could form a eutectic system in the Mk range of 1.4–1.8, and therefore have a relatively low melting temperature in this Mk range. Fly ash could react with magnesium slag and calcined dolomite to form akermanite, gehlenite-magnesium, and anorthite at temperatures close to the melting temperature; therefore, these crystalline phases were the main reaction products formed in the samples with Mk values lower than 1.80. Anorthite reacted further with some Na-containing and Si-containing spieces to produce labradorite. Thus, the content of anorthite and labradorite rapidly increased and they became the major crystal phases in the blend samples with Mk values greater than 1.80. MAS-NMR spectroscopic analysis revealed that the network structure of the melts depended on the ratio of bridging oxygen to non-bridging oxygen; a high ratio of bridging oxygen to non-bridging oxygen could lead to the formation of a dense network structure in the melt. The blends of fly ash and magnesium slag can be used to produce wool fibers and continuous fibers. In addition, the suitable temperature ranges for the production of both types of fibers were determined. The drawing temperature for continuous fiber production depended on the degree of polymerization and structure of the melt.

We report the in-situ oxygen isotopic distributions corresponding to the petrographic-mineralogical observation on a compact Type A (CTA) Ca-Al-rich inclusion (CAI), KU-N-02, from a reduced CV3 chondrite, Northwest Africa 7865. The CTA has an igneous texture and mainly consists of spinel, melilite, and Al-Ti-rich clinopyroxene (fassaite). Oxygen isotopic compositions of the constituent minerals plot along the carbonaceous chondrite anhydrous mineral line. The spinel grains are poikilitically enclosed in the melilite and fassaite and are uniformly 16O-rich (Δ17O = approximately − 23‰). The fassaite is texturally classified into two types: blocky fassaite and intergranular fassaite. The blocky fassaite crystals exhibit growth zoning as they change from Ti-rich to Ti-poor along the inferred directions of crystal growth from core to rim, while the oxygen isotopic compositions change from 16O-poor (Δ17O = approximately − 6‰) to 16O-rich (Δ17O = approximately − 23‰) with crystal growth. The intergranular fassaite crystals exist between the melilite crystals and exhibit variable Ti abundance and oxygen isotopic compositions. Additionally, their relationships between Ti contents and oxygen isotopic composition are similar to those of the blocky fassaite. The melilite grains are homogeneously 16O-poor (Δ17O = approximately − 2‰), irrespective of their akermanite (Ak) content. Each melilite grain generally exhibits growth zoning with increasing Ak contents from core to rim, although the melilite contains Ak-rich patches within single crystal. Ak-rich patches often include two types of fassaite: small blebby crystals attached to spinel crystals and round crystals. The oxygen isotopic compositions of the Ak-rich patch and blebby fassaite are 16O-poor (Δ17O = approximately − 2‰), similar to that of the host melilite. On the other hand, the round fassaite exhibits significant variation in oxygen isotopic compositions ranging from Δ17O = −23‰ to − 4‰, which are different from those of the host melilite. These petrographic textures and oxygen isotopic variations indicate the presence of a solid precursor with variable oxygen isotopic compositions for the CTA. The spinel and round fassaite grains are relicts of the precursor that melted in the 16O-poor nebular gas, resulting in the crystallization of the host melilite from the 16O-poor melt. The Ak-rich patches and blebby fassaite crystallized from melts trapped by the growing host melilite crystals. The blocky and intergranular fassaite crystallized after the melilite did, and the oxygen isotopic composition of the melt changed to 16O-rich during the crystallization process, suggesting that the oxygen isotopic composition of the surrounding nebular gas could be varied. The inferred oxygen isotopic evolution for CTA is consistent with those inferred for Type B CAIs, suggesting that coarse-grained igneous CAIs formed in a similar nebular environment regardless of precursor chemistry.

This study reports on microstructural, mechanical, and bioactive properties of the chitosan based composite scaffolds reinforced by akermanite. Firstly, the synthesis of akermanite powders was investigated by three different methods as sol-gel, ball-milling, and spray drying, with additional heat treatments. The morphological and microstructural characterizations revealed that the akermanite powders with the homogeneous and narrow particle size distributions were successfully obtained by spray drying and following heat treatment methods. Secondly, the chitosan/akermanite composite scaffolds were produced by the combination of 3D-bioprinting and lyophilization methods. SEM analyses of produced composite scaffolds indicated the interconnected and open-pore structures. The mechanical test results showed that the increasing akermanite addition enhanced the strength of composite scaffolds significantly. The bioactivity test results presented that the composite scaffolds had good in vitro bioactivity based on their good apatite-formation abilities on their surfaces and in simulated body fluid. According to the results, the bioactive 3D-printed scaffold with improved mechanical properties promises the good potential for bone tissue engineering applications.

A thermodynamic model is formulated for (Ca,Na)2(Mg,Fe2+,Al,Fe3+)T1 (Al,Fe3+,Si ) 2 T2 O7 melilites. It employs the compositional vertices: akermanite (Ca2MgSi2O7, 1), gehlenite (Ca2Al2SiO7, 2), iron akermanite (Ca2Fe2+Si2O7, 3), ferrigehlenite (Ca2 Fe 2 3 + SiO7, 4), sodium melilite (NaCaAlSi2O7, 5), and the convergent ordering variables: s = X Al 3 + T2a – X Al 3+ T2b and t = X Fe 3 + T2a – X Fe 3 + T2b to describe the distribution of Al3+, Fe3+ and Si4+ between T2 subsites T2a and T2b. It is calibrated for akermanite–gehlenite melilites based on the calorimetric data of Charlu and others (1981), the assumption that the synthetic samples of Charlu and others approached “equilibrium” states of Al-Si tetrahedral ordering at 970 K, and analogy with the Al2(MgSi) − 1 substitution in CaMgSi2O6 – CaMg1/2 Ti 1 / 2 AlSiO6 – CaAl2SiO6 fassaites (for example, Sack and Ghiorso, 2017). In this model gehlenite has a disordered Al-Si distribution on T2 sites above 1443 K (1170 °C), consistent with the crystallographic data on c/a ratios of lattice parameters as a function of annealing temperature (Woodhead and Waldbaum, 1974) and the high-temperature heat capacities inferred from drop calorimetric data (Pankratz and Kelley,1964). However, above this critical temperature a partially ordered Al-Si distribution persists between T2a and T2b sites in akermanite – gehlenite solid solutions with intermediate X2 (for example, 0.19 X 2 Δ H ¯ f 298.15 o AK and Δ H ¯ f 298.15 o GEHL , consistent with the experimental brackets on decarbonation equilibria of Walter (1963), Hoschek (1974), and Shmulovich (1974), the thermodynamic model for akermanite-gehlenite melilites developed here, the thermodynamic properties of the other phases in these reactions tabulated by Berman (1988), and the revised estimates for C ¯ p and S ¯ 298.15 o of diopside of Sack and Ghiorso (2017), are roughly 1 and 3 (kJ/gfw) more positive than those estimated by Berman (1988). More positive standard enthalpies of formation of both endmembers, together with a decrease in the vibrational heat capacity of gehlenite and less negative deviations from ideal mixing compared with previous calibrations, all contribute to reducing the stability of melilites in this model. Together these effects will decrease the predicted temperature of condensation of melilite from nebular vapors, bringing calculated temperatures of melilite condensation into closer alignment with those of MgAl2O4 spinel than the 80 to 100 K separating their appearances in previous calculations (for example, Yoneda and Grossman, 1995; Petaev and Wood,1998; Ebel and Grossman,2000). These effects, together with a possible increase in spinel stability due to non-negligible solubility of Al8/3O4 alumina component, may allow equilibrium models to match the observed condensation sequence of spinel before melilite in calcium-aluminum inclusions (CAIs) in carbonaceous chondrites, without the need to invoke kinetic effects.

This study aimed to investigate extensively the full phase formation mechanism from the lowest temperature to form the phases to the optimum temperature to crystallize akermanite. The effects of various milling speeds and sintering temperatures on physico-mechanical properties of akermanite prepared using high-energy planetary milling method were also investigated. The minimum formation temperature of akermanite phase (above 800°C) was determined by X-Ray diffraction (XRD) and differential thermal analysis. XRD analysis revealed akermanite had formed through gradual phase development with the increase in temperature. Below 700C, akermanite was structurally unstable while multiple transient compounds (low clinoenstatite, wollastonite, monticellite, and diopside) coexisted, as indicated by low peak intensities. Single phase akermanite was obtained by heat-treating at 1100C. Physical studies suggested the densest akermanite ceramic feature, with tensile strength range of 25.26 ± 1.41 MPa32.10 ± 2.13 MPa and Vickers microhardness range of 1.39 ± 0.04 GPa4.94 ± 0.26 GPa could be obtained at 1250°C.

In the present study, a bioactive silicate-phosphate glass-ceramic scaffold was fabricated via the polymer-derived ceramics (PDC) method. K2HPO4 phosphate salt was used as the P2O5 precursor in this method. The effect of K2HPO4 wt% and heat treatment temperatures (900–1100 °C) was evaluated. It was observed that although increasing the wt% of K2HPO4 led to the formation of scaffolds with higher densities and strengths, it could also increase the formation of the calcium phase, which could result in improper release behavior of scaffolds. On the other hand, higher heat treatment temperatures enhanced the strength of the scaffolds but eliminated the bioactive octacalcium phosphate (OCP) phase. X-ray diffraction (XRD) analysis showed that the dissolution of the OCP phase in simulated body fluid (SBF) resulted in precipitation of hydroxyapatite (HA) on the scaffold surface which enhanced the bioactivity. Furthermore, based on microstructural studies by Scanning Electron Microscopy (SEM), the fabricated scaffold possessed a wide range of pore sizes, appropriate for osteointegration and bone formation. The optimum wt% of phosphate salt was less than 6 wt% and the optimum heat treatment temperature was 1000 °C. After the optimization of compositions and processing, Alamar Blue Assay was used to evaluate HOb cell cultures, showing a continuous proliferation for the optimized samples.

Pure nanocrystalline akermanite was successfully synthesized by mechanical activation and heat treatment of talc, calcium carbonate, and silicate. Powders were characterized by thermogravimetric analysis (TGA), x-ray diffractometry (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The formation mechanism was studied in depth. These results showed that akermanite was produced by the formation and consumption of transitionary compounds such as enstatite, wollastonite, larnite, and merwinite. Pure akermanite was synthesized with a crystalline size of 34 nm after ball milling for 20 h and subsequent heat treatment at 900 °C for 1 h.

With the aging population worldwide, osteoporosis, as an age-related bone metabolic disease, is becoming a hot issue in public health. However, it is still a great challenge to realize osteoporotic bone healing due to the alteration of the bone microenvironment in osteoporosis patients. In this study, a nano-structured akermanite (nAK) coating was in situ constructed on Ti–6Al–4V implants to improve osteoporotic bone repair. In vitro studies indicated that both the surface nano-topography and bioactive ions released from the nAK coatings promoted the proliferation, osteogenesis, angiogenesis and inhibited osteoclastogenesis of ovariectomy rabbit-derived bone marrow mesenchymal stem cells (OVX-rBMSCs). Furthermore, the nAK-coated Ti–6Al–4V implants improved new bone formation and osseointegration in an osteoporosis rabbit model in vivo. These results indicated that the AK coating with a nano-structured surface on the Ti–6Al–4V implant could synergistically promote bone formation and osseointegration for osteoporosis patients. This may be a promising strategy to improve the bone regeneration and osseointegration capability of orthopedic implants under osteoporosis conditions.

Bioceramic porous microspheres are promising substances for dental and orthopedic bone void filling, tissue engineering and drug delivery applications. In this research, the structure and cytocompatibility of bioactive magnesium-calcium silicate macroporous microspheres loaded with vancomycin hydrochloride, an antibiotic drug, were studied. In this regard, bredigite (Ca7MgSi4O16), akermanite (Ca2MgSi2O7) and diopside (CaMgSi2O6) carriers were fabricated through a sequence of sol-gel, calcination, droplet extrusion and sintering processes, followed by impregnated with vancomycin. X-ray diffraction (XRD) and scanning electron microscopy verified the formation of the desired ceramic crystalline phases and macroporous characteristics of the carriers, respectively. Based on the MTT assay, the antibiotic-loaded bredigite, akermanite and diopside devices comparatively exhibited the lowest, intermediate and highest levels of human bone marrow mesenchymal stem cells (hBM-MSCs) viability and proliferation, respectively. It was concluded that the role of the carrier bioresorption kinetics prevails over the drug delivery kinetics in determining the cell biocompatibility of the devices.

In this study, Poly Lactic Acid (PLA) scaffolds containing different amounts of akermanite (Ak) particles were prepared using the fused filament fabrication (FFF) technology. Ak particles were fabricated using sol–gel method. Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM) images revealed that the size of the synthesized Ak particles was 100 ± 20 nm. The structure of the 3D printed scaffolds was investigated by Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD). Distribution of the particles was characterized by Energy Dispersive Spectroscopy (EDS: map), showing the uniform distribution of particles through the PLA matrix. The results of the compression test showed that the strength (plateau stress) of the scaffolds was considerably improved by increasing the Ak particles from 27 ± 2 MPa for the neat polymer scaffold to 45 ± 3 MPa for PLA-30% Ak scaffold, which is near to the values of human cortical bone. The results of the bioactivity test (immersing the scaffolds in the Simulated Body Fluid (SBF) for 7, 14, 21 and 28 days) also indicated the enhanced formation of hydroxyapatite crystals on the scaffold surface upon increasing the immersion time and the Ak particles. While, the increment of Ak particles up to 20 wt.% had no significant effect on printability of scaffolds, and after that, reduced the scaffold printability, so the PLA-Ak 20 wt.% scaffold can be considered as a promising candidate for bone tissue engineering.

Kaolin has an excellent structure formed via a wide range of firing temperature. The correlation between the mineralogy and reactivity of individual elements is extremely complex in a sintered geopolymer material. The main objective of this work is to elucidate the influence of the chemical composition of the raw materials used post-sintering on the kaolin-ground granulated blast furnace slag (GGBS) geopolymer. The samples were cured at room temperature for 5 days before being sintered. The ratio of solid-to-liquid were 1:1, 1.5:1, and 2:1. The addition of the GGBS to the kaolin geopolymer slurry did not only hasten the hardening process during geopolymerization, the presence of SiO2, Al2O3, CaO, and MgO in GGBS had accelerated the formation of nepheline, gehlenite, akermanite, and albite phase after sintering based on the result from x-ray diffraction and fourier-transform infrared spectroscopy On top of the phase transformation, a high ratio of solid-to-liquid (SL 2) had improved the pore distribution from irregular size to well defined formation and increased the densification of the sintered materials. Elemental distribution from micro-XRF investigation prove the high concentration of Ca in localized area and uniformly distribution of Si aligned with the phase of akermanite in SL 2. The main chemical composition of kaolin and GGBS which are SiO2, Al2O3, CaO and MgO had contributed in phase transformation of sintered kaolin-GGBS geopolymer.

Iron oxides are the essential coloring oxides in traditional ceramic glazes. However, when Fe is involved in the coloration in the form of ions or colloids in glazes with low Fe content, it is difficult to identify the iron oxide phases. Generally, in many these glazes, Ca-rich minerals are observed by X-ray diffraction (XRD) or microscopic images, owing to their devitrification by the high Ca content. This study attempts to elucidate the correlation between the crystalline structure and coloration in the glazes while mainly focusing on neoformed Ca-rich minerals and Fe content. An experimental firing was carried out to produce tree ash glazes, with pine tree ash and Buyeo feldspar. In the case of oxidation glazes, the scanning electron microscopy (SEM) images and XRD patterns did not exhibit any Ca-rich crystals, and all the visible light reflectance spectra lines exhibited a similar shape. In contrast, the reduction glazes divided into blue glazes and other colored glazes according to the shapes of their reflectance spectra. It was confirmed that the influence of Ca-rich minerals on the glaze color was more pronounced than the blue color of the reduction glazes when the Ca and feldspar contents were sufficiently high and low, respectively, to form wollastonite. As the Ca content increased and the elemental composition of the reduction glazes changed, the neoformation of the Ca-rich minerals, such as wollastonite, anorthite, diopside, and akermanite was sequentially observed.

This study deals with the corrosion and bioactivity behavior of biodegradable friction-welded CP-Ti/AZ31 joints. The investigations were carried out on the bare, PCL-coated and PCL–akermanite (AKT)-coated joints immersed in simulated body fluid. The samples were subjected to polarization and impedance corrosion tests, weight loss and pH monitoring and cytotoxicity investigations as well as cell adhesion test. The results of corrosion tests and weight loss measurements indicated that whereas the bare alloy shows the highest corrosion rate through 7 days (15.945 mm/y), the PCL–AKT-coated sample presented significantly improved results, even when the soaking period was prolonged to 30 days. The PCL–AKT-coated sample also showed the best biocompatibility, as the cell viability was measured to be 97.52%. The Ca/P ratio was also measured to be about 1.64 for PCL–AKT-coated sample, indicating favorable osteogenic behavior. The results of alizarin red cell staining and absorption spectrum as well as alkaline phosphatase activity confirmed superior osteogenic behavior of the PCL–AKT-coated sample. It was found that the CP-Ti/AZ31 samples coated with PCL–AKT obtained suitable corrosion resistance and cellular response, thus presenting a good potential to be used in orthopedic applications.

This paper reports on the influence of substituting barium (Ba2+) ions on the structural, mechanical and in vitro biological properties of akermanite prepared via high-energy wet planetary ball milling and sintering. The results obtained showed that the properties of the prepared bioceramics are highly dependent on Ba2+ content. It was found that Ba2+ resulted in improved densification (≥90%), and better apatite-forming ability of akermanite ceramic, without altering phase composition. Herein, the enhancement in diametral tensile strength (DTS), Vickers microhardness (HV) and fracture toughness (KIC) for Ba2+-doped akermanite bioceramics are reported for the first time. It was also found that after 21 days of immersion in simulated body fluid (SBF) solution, the doped ceramic surface was completely covered with apatite crystals, indicating Ba2+ encouraged apatite crystals deposition. Therefore, Ba2+-doped akermanite bioceramic could be an attractive alternative bioresorbable material for bone tissue engineering applications.

A series of glass was produced to investigate the effect of MgO/SrO replacement on the crystallization characteristics and properties of phosphosilicate glasses containing high SrO content. The glass samples were synthesized by conventional melting technique based on 5CaO-(40-X)SrO-X MgO– 43SiO2–7P2O5–5CaF2 (where; X = 10, 20, 30 and 40 mol%). The influence of MgO/SrO replacement on phase assemblages, microcrystalline structures, thermal expansion, and mechanical properties was examined as a function of basic chemical compositions and crystallization parameters. Predominant strontium meta-silicates together with strontium fluoroapatite phases are crystallized from the base glass free of magnesium. The substitution of strontium by magnesium up to 50% led to formation strontium akermanite phase Sr2MgSi2O7 at the expense of SrSiO3 phase. Whereas the increase of the MgO/SrO of more than 50%, which led to the crystallization of the clino-enstatite MgSiO3 as a predominant phase. The results show that the α-values of the glass-ceramics are ranged in 94–125 × 10−6 K−1 over the temperature range (25–500 °C). On the other hand, MgO/SrO replacements led to enhancing the microhardness of the resultant crystalline materials from 4713 Mpa to 6744 Mpa. As a result of the designed glass compositions, promising crystalline phases were obtained as well as good thermal and mechanical properties for the resultant glass-ceramics. Therefore, the designed glass-ceramics can be strongly used as biomaterials especially for bone reconstruction applications.

The ceramics in the system CaO–MgO–SiO2 has recently attracted a great deal of attention because they display a good in vitro bioactivity and have potential use as bone implants. Biphasic calcium-magnesium-silicate ceramics were prepared by a sol-gel method. The dried gel with chemical composition 3CaO.MgO.2SiO2 was thermally treated at 1200 °C for 2 hrs. The structural behavior of the synthesized ceramics was examined by means of X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). Merwinite crystalline phase and akermanite phase were recognized. Then, porous akermanite/merwinite scaffolds were prepared to utilize polymer sponge method and evaluated by employing SEM. Furthermore, bone marrow stromal cells (BMSC) adhesion and proliferation on the scaffolds were evaluated by MTT assay test. Differentiation of the cells was assessed by measuring alkaline phosphatase (ALP) activity. The results demonstrated that BMSC adhered and spread well on akermanite scaffolds and proliferated with the increase in the culture time, and the differentiation rate of osteoblasts on scaffolds was comparable to that on blank culture plate control. Thus, the obtained results presented that the akermanite/merwinite scaffolds deserve attention for bone tissue engineering applications.

The crystallization behavior of blast-furnace slag under isothermal and continuous-cooling conditions was studied using the single hot thermocouple technique. The crystallization phases were obtained using FactSage software and X-ray diffractometry. The crystallization kinetic parameters were calculated by combining these results with the Johnson–Mehl–Avrami model. Under isothermal conditions, the shortest crystallization incubation time was 24 and 18 s when the temperatures were 1300 and 1150 °C, and the corresponding critical cooling rates were 4.5 and 14.3 °C/s, respectively. At 1270 °C, the slag was difficult to crystallize and the fiber-forming rate improved. When the continuous-cooling rate was 6.5 °C/s, the slag solidified into a glassy state. The main crystallization phases, gehlenite, akermanite, anorthite, and melangite, were most easily precipitated. The growth factors of melangite and anorthite were approximately 1.63 and 1.68, respectively, which indicated that the crystals nucleated on the surface and grew in two dimensions.

In this work, sol-gel derived bredigite (MgCa7Si4O16), akermanite (MgCa2Si2O7), and diopside (MgCaSi2O6) porous microspheres were loaded with vancomycin, and the release kinetics of this drug from them was evaluated. In this regard, mathematical models of Higuchi, Peppas, Baker-Lonsdale, Hixson-Crowell, first order, and zero order were considered in terms of linear and nonlinear regression analyses. Using the goodness of fitting correlation coefficients, the number of release stages was determined, and then diffusion- and degradation-controlled mechanisms were assigned to each stage. It was found that the diopside microspheres presented a two-step diffusional drug delivery. For akermanite and bredigite, an initial burst diffusion-controlled release followed by a sustained mixed-mode release mechanism of diffusion and degradation was identified, with the domination of the latter especially for bredigite.

The present study illustrates the manufacturing method of hierarchically porous 3D scaffolds based on åkermanite as a promising bioceramic for stereolithography. The macroporosity was designed by implementing 3D models corresponding to different lattice structures (cubic, diamond, Kelvin, and Kagome). To obtain micro-scale porosity, flame synthesized glass microbeads with 10 wt% of silicone resins were utilized to fabricate green scaffolds, later converted into targeted bioceramic phase by firing at 1100 °C in air. No chemical reaction between the glass microspheres, crystallizing into åkermanite, and silica deriving from silicone oxidation was observed upon heat treatment. Silica acted as a binder between the adjacent microspheres, enhancing the creation of microporosity, as documented by XRD, and SEM coupled with EDX analysis. The formation of ‘spongy’ struts was confirmed by infiltration with Rhodamine B solution. The compressive strength of the sintered porous scaffolds was up to 0.7 MPa with the porosity of 68–84%.