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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 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.

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.

It is common to improve the relevant performance in the field of energy storage materials or catalytic materials by regulating the number of defects. However, there are few studies on the biomaterials containing defects for tissue engineering. Herein, a new type of defect-rich scaffolds, black akermanite (B-AKT) bioceramic scaffolds with micro/nanostructure, the thickness of which is from 0.14 to 1.94 µm, is fabricated through introducing defects on the surface of bioceramic scaffolds. The B-AKT scaffolds have advantages on the degradation rate and the osteogenic capacity over the AKT (Ca2 MgSi2 O7 ) scaffolds due to the surface defects which stimulate the osteogenic differentiation of rabbit bone mesenchymal stem cells via activating bone morphogenetic protein 2 （BMP2） signaling pathway and further promote bone formation in vivo. In addition, the prepared B-AKT scaffolds, the temperature of which can be over 100 °C under the near infrared （NIR） irradiation (0.66 W cm-2 ), possess excellent performance on photothermal and antitumor effects. The work develops an introducing-defect strategy for regulating the biological performance of bioceramic scaffolds, which is expected to be applied in the next generation of bioceramic scaffolds for regenerative medicine.

In this study, a series of Er3+/Yb3+ co-doped Ca–Mg–Si glasses were prepared via the containerless processing. Phase composition and luminescent properties of the prepared materials were investigated through XRD and spectrometry, and bioactivity, biocompatibility and cytotoxicity were evaluated. The XRD patterns indicated that akermanite (AKT) ceramic powders were completely transformed into the glassy phase (AKT-G, EYA) through the containerless processing, which exhibit upconversion luminescence, and the luminescence intensity increased with the increase of the doping amount of Er3+ and Yb3+. High amount of Yb3+ doping and existence of Ca2+ in glasses resulted in more intensive red-light emission. The SEM observation, combined with EDS analysis, and cell culture experiments showed that the as-prepared glasses were nontoxic, biocompatible and bioactive. All these results demonstrated that the containerless processing is a facile method for preparing homogeneous luminescent bioactive glasses. Furthermore, this luminescent Ca–Mg–Si glasses may be used as bone implant materials to study the in vivo distribution of degradation products of bone implants, which may be of great significance for the development and clinical application of new bone grafting materials.

The present investigation is dedicated to the manufacturing of reticulated three-dimensional akermanite scaffolds, developed by direct reaction between silica, from the oxidation of a commercial silicone resin and oxide fillers, forming pastes for direct ink writing. Crack-free scaffolds, with dense and regular struts, were due to the use of CaCO3 (micro) and MgO nano-particles as reactive fillers. An excellent phase purity was obtained, with the help of the liquid phase provided by anhydrous sodium borate (Na2B4O7), upon firing. The structure of the scaffolds, finally, was successfully modified by using Mg(OH)2 and hydrated sodium borate: besides macroporosity from direct ink writing, the new scaffolds exhibited homogenous ‘spongy’ struts (owing to water vapor release in the heating step), with no crack. Both types of scaffolds (with dense or porous struts) exhibited remarkable strength-to-density ratios.

Electrospinning, as an effective method for preparation of scaffolds for cell growth templates, has attracted great attention. In this study electrospinning was used to prepare poly (vinyl ...

Glass ceramics with different Al/Na molar ratio from blast furnace slag were prepared using conventional melting-casting method. The structure and properties of glasses or glass ceramics were investigated by DSC, Raman, MAS NMR, XRD, and SEM. The DSC results indicated that the thermal stability (ΔT = Tc-Tg) and crystallization temperature (Tc) of the parent glass firstly increased and then decreased when Al/Na exceeded 1.21. The Raman and 27Al MAS NMR spectra analysis revealed that [AlO6] increased positively with Al2O3/Na2O. The calculation of Qn ([SiO4] units with bridging oxygen atoms number of n) suggested an obvious decline of (Q0+Q2)/(Q1+Q3) and that [SiO4] mainly existed in the form of Q1 when Al/Na exceeded 1.21, which accorded closely with Tc variation. The crystallization results determined by XRD showed that as Al/Na increased, the main crystal phase was transformed from akermanite to gehlenite and nepheline disappeared. Glass ceramics with Al/Na of 1.48 nucleated at 780 °C for 2 h and crystallized at 880 °C for 3 h exhibited the maximum value of flexural strength. Orthogonal experiment (L9(34)) were carried out to investigated the optimum heat treatment of glass ceramics with a Al/Na of 1.48. The analyses indicated that nucleation time variation has little influence on the flexural strength, and the optimum heat treatment was determined as 760 °C – 1 h–900 °C – 1 h and the flexural strength was characterized as 81.310 MPa.

Pure nanocrystalline akermanite powder was synthesized using calcium carbonate, magnesium carbonate, and silicate as the base materials. Base powders were mechanically activated and then heat treated at various temperatures. The produced powders were evaluated by simultaneous thermal analysis (STA), x-ray diffraction (XRD), and scanning electron microscopy (SEM) characterization techniques. The results showed that pure nanocrystalline akermanite was synthesized from powder mechanically activated for 50 h with subsequent annealing at 900 °C for 1 h. Nanostructured akermanite had a crystalline size of 67 nm. The formation mechanism of akermanite was scrutinized. It was found that akermanite forms through the formation of several transition compounds such as enstatite, wollastonite, larnite, and merwinite.

Ceramic scaffolds were prepared starting from a sol–gel powder, which was mixed with glucose as a pore-generating substance and subsequently thermally treated at different temperatures and for different periods in order to ensure the formation of a resistance structure. The final materials were characterized in terms of structure, morphology, and biological properties by employing X-ray diffraction, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, immersion in simulated body fluid, and specific cellular tests on mesenchymal stem cells (optical microscopy, MTT, and GSH assays). The results showed the occurrence of akermanite as the main crystalline phase in all scaffolds. The porosity and compression strength of these 3D architectures can be adjusted through the thermal treatment parameters. Moreover, the biological evaluation indicated an excellent bioactivity and a good biocompatibility at short term for all samples.

Akermanite (Ca2MgSi2O7) has attracted attention in the biomaterial research due to its excellent in vitro and in vivo bioactivity. Mechanical properties such as microhardness and fracture toughness are of great importance for bioactive materials to predict their performance before failure and thus determine the potential biomedical application. In previous work, sintered akermanite prepared by solid-state sintering at 1200°C showed in vitro apatite formation in simulated body fluid (SBF) solution, but having high porosity (more than 20%). In the present study, bulk akermanite bioceramics was fabricated and evaluated the mechanical properties i.e. microhardness and fracture toughness. The akermanite Sr-doped akermanite were synthesised by solid-state sintering at 1225°C for 4 h. Results indicated that the substitution of Sr enhanced the microhardness and fracture toughness which is attributed to the controlled grain size, improved density as well as better sinterability. However, by further increase in amount of dopant beyond 5 mol%, both hardness and fracture toughness decreased due to the larger grain size. akermanite at 1225°C led to a microhardness and fracture toughness of 2.42±0.24 GPa and 1.48±0.03 MPa.m1/2, respectively which makes it a suitable material for non-load bearing application such as, bone filler material.

Glass ceramics from modified molten blast furnace (BF) slag were prepared. The crystallization behavior of the modified BF slag was characterized using differential thermal analysis (DTA), X-ray diffraction (XRD), and field emission scanning electron microscope (FESEM). The crystallization kinetics results indicated that the crystallization activation energy initially decreased and subsequently increased with increasing CaO/SiO2. The crystallization temperature and the crystallization index (n) decreased from 916 to 867 °C, and 5.66–1.13, respectively. The crystallization mechanism transformed from bulk crystallization to surface crystallization. By XRD analyzing, Melilite was developed as the main crystal phase, and the transformation of crystal from akermanite to gehlenite was observed. The rapid surface crystallization was beneficial for maintaining the shape of glass ceramics. The complex replacement in melilite crystals resulted in the micro cracks in glass ceramics, therefore led to the decrease of flexural strength of glass ceramics

Tissue integration of orbital implants, following orbital enucleation treatment, represents a challenge for rapid fibrovascularization, long-time stability, anti-infection, and even induction of vascule regeneration. The objective of this study was to develop porous calcium-magnesium silicate materials, with good stability, bioactivity, and antibacterial potential as new orbital fillers. Three-dimensional (3D) diopside scaffolds (low dissolvability) were fabricated by direct ceramic ink writing assembly and then followed by one-step sintering at 1150 °C for 3 h. The pore wall of the scaffold was modified by another calcium-magnesium silicate, such as bredigite or akermanite, which dissolves quickly but shows greater angiogenic potential. These two Ca-Mg-silicates can be coated onto the pore strut, and the coating layers were observed to slowly dissolve in Tris buffer. The vascularization-favorable Cu ions, which had been doped into the bredigite or akermanite coating, could also be measured in the immersion medium. A primary angiogenic test in a panniculus carnosus muscle model in rabbit indicated that the Cu-doped bredigite and akermanite coatings were significantly beneficial for the neovascularization in the early stages. These results suggest that the diopside-based porous materials modified with functional coatings hold great potential for application in orbital reconstruction.

Owing to their lower carbon footprint and efficient performance compared to portland cement (PC), alkali-activated binders (AAB) show promising potential as an alternative to PC. The present paper investigates the high-temperature performance of AAB concrete through compressive and bond strength tests. Four different AAB concrete mixes with varying proportions of fly ash: slag (100:0, 70:30, 60:40, and 50:50) cured under ambient conditions are exposed to elevated temperatures. The mechanical performance of AAB concrete is corroborated with microstructural changes. The results show that AAB concrete with fly ash: slag ratio of 70:30 exhibits the best mechanical performance after exposure to elevated temperatures. This behaviour is attributed to the growth of new crystalline phases of akermanite and gehlenite as observed from the X-ray diffraction patterns. This study shows that there is an optimum proportion of slag content beyond which the mechanical performance of AAB concrete significantly deteriorates when exposed to elevated temperatures. The failure pattern of AAB concrete during the bond strength test varies with the precursor proportion and the exposure condition.

In vitro activity is important when considering the choice of a multiphasic bioceramic scaffold as phases can dissolve or transform at different rates. The aim of this study is focused on the synthesis and in vitro analysis of multiphasic ceramics obtained from the melt by directional solidification. Depending on the growth rate of the new composition different bioactive phases coexist in the same sample: akermanite, monticellite, tricalcium phosphate and Nurse's A phase, all of them with potential in the medical area as implant for bone or dental repair. With the knowledge of what and how phases dissolve first, it was possible to design materials to get porous scaffolds or more stable ceramics., The authors would like to acknowledge the use of Servicio General de Apoyo en la Investigación- SAI, Universidad de Zaragoza. BMM wants to acknowledge the financial support awarded by the Spanish Ministry of Science and Innovation through the grant PID2019-103847RJ-I00, as well as the one provided by the Regional government of the ‘Junta de Andalucía’ through the project P18-RTJ-1972.

Pure nanocrystalline akermanite (Ca2MgSi2O7) powder was synthesized by mechanical activation with subsequent annealing of talc, calcium carbonate, and silicate powders as the initial materials. Powder samples were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM) techniques. The results showed that pure nanocrystalline akermanite with a crystalline size of 35 nm was synthesized after ball milling the initial powders for 20 h with subsequent annealing at 900 &deg, C for 1 h. Mechanical properties of bulk akermanite samples were studied as well. The results showed that the produced akermanite tablets sintered at 1200 &deg, C for 5 h had a Young&rsquo, s modulus of 3800 MPa, an ultimate compressive strength of 24.7 MPa, and a density of 2.489 g/cm3. The in-vitro behavior of the produced akermanite was evaluated by soaking the samples in an SBF solution. The results showed that the produced akermanite had the apatite formation ability on its surface and can be a good candidate for bone tissue engineering applications.

New analogs of åkermanite: Sr(2)CuSi(2)O(7) and Sr(2)CdSi(2)O(7) as well as many previously synthesized analogs were obtained by a simple technique consisting of heating in air of precipitated gels of the right composition. X-ray data revealed an anomaly of the Cu(2+) and (to a lesser extent) Fe(2+) åkermanites which is explained by a simple geometric argument in terms of a small (~3°) angular distortion of the oxygen tetrahedron surrounding the smaller divalent cation. This interpretation is consistent with previous theoretical discussions and Mössbauer data on the iron analog prepared for this study. Single crystals of cobalt åkermanites can be grown from a sodium tungstate flux.

Bioresorbable composites based on hybrid phosphate-silicate coatings and Mg0.8Ca alloy were obtained using the MAO method in the electrolyte containing the powders of wollastonite and β-TCP. The coating morphology and elemental composition were studied with the help of the scanning electron microscopy and energy-dispersive X-ray spectroscopy. Elongated particles of wollastonite and isometric particles of TCP were evenly distributed on the coatings surface. The crystalline phases of wollastonite, α-TCP, akermanite, diopside and forsterite were found in the coatings. After the 16 days of the immersion in 0.9% NaCl solution the mass loss of bare Mg0.8Ca alloy and the coated samples was 9.2% and 1.5% respectively.

The effect of particle size and phosphorous content in biomineralization media on in vitro bioactivity of monticellite based ceramic powders was investigated. Monticellite based ceramic powder was synthesized at 800 °C for 4 h using boron derivative waste. Monticellite based ceramic powder, comprising monticellite, akermanite, diopside, calcium magnesium borate and zeolite LTA crystalline phases, was crushed and then ball-milled for optimized time to obtain lowest average particle size and the narrowest particle size distribution. In vitro bioactivity of both coarse (d10: 0.5 μm, d50: 3.0 μm, d90: 42 μm) and fine (d10: 0.5 μm, d50: 1.4 μm, d90: 4.8 μm) wafers was determined by incubation in Lactated Ringer's Solution and Human Blood Plasma for 1, 3, 5, 7, 14, 21 and 28 days at 36.5 ± 0.5 °C. The obtained results exhibited that calcite (CaCO3) layer after immersion in Lactated Ringer's Solution and bone-like apatite layer after immersion in Human Blood Plasma were formed on the surface of coarse and fine wafers. The presence of phosphorus in biomineralization media is necessary for apatite formation. The increment of surface roughness favors homogeneous nucleation, and fasten nucleation and growth kinetics of precipitation. As a result, the bioactive characteristic of monticellite based ceramic powder could be governed by the particle size. Resumen: Se investigó el efecto del tamaño de partícula y el contenido de fósforo en los medios de biomineralización sobre la bioactividad in vitro de polvos cerámicos a base de monticellita. El polvo cerámico a base de monticellita se sintetizó a 800 °C durante 4 h utilizando residuos de derivados de boro. El polvo cerámico a base de monticellita, que comprende monticellita, akermanita, diópsido, borato de calcio y magnesio y fases cristalinas de zeolita LTA se trituró, y luego se molió con bola durante un tiempo optimizado para obtener el tamaño de partícula promedio más bajo y la distribución de tamaño de partícula más estrecha. La bioactividad in vitro de obleas gruesas (d10: 0.5 μm, d50: 3.0 μm, d90: 42 μm) y finas (d10: 0.5 μm, d50: 1.4 μm, d90: 4.8 μm) se determinó mediante incubación en solución de Ringer lactato y plasma sanguíneo humano durante 1, 3, 5, 7, 14, 21 y 28 días a 36,5 ± 0,5 °C. Los resultados obtenidos mostraron que la capa de calcita (CaCO3) después de la inmersión en la solución de Ringer lactato y la capa de apatita similar a un hueso después de la inmersión en plasma sanguíneo humano se formaron en la superficie de obleas gruesas y finas. La presencia de fósforo en los medios de biomineralización es necesaria para la formación de apatita. El incremento de la rugosidad de la superficie favorece la nucleación homogénea y fija la cinética de nucleación y crecimiento de la precipitación. Como resultado, la característica bioactiva del polvo cerámico a base de monticellita podría estar gobernada por el tamaño de partícula.

Monticellite is a calcium-magnesium based material with better bioactivity, high mechanical strength, cytocompatibility and osteointegration. Sol-gel assisted combustion technique was adopted to prepare pure monticellite phase by using three different fuels (citric acid, glycine and urea). The influence of different fuels on material properties of monticellite was analyzed with the aid of XRD, SEM, TEM and AFM techniques. The XRD patterns revealed that among the three fuels examined, glycine and urea resulted in pure monticellite phase at 1200°C while citric acid derived monticellite showed akermanite as secondary phase. Morphological analysis such as SEM and TEM micrographs of monticellite showed spherical beads like structure with agglomeration of particles and the particle size lies in the micron regime. Atomic force microscope image shows high surface roughness for the monticellite prepared by using urea as a fuel.

The dosage of blast furnace slag (BFS) in cement is limited on account of relative low reaction rate and low early strength. Improving the early age activity of BFS is the fundamental solution for high volume BFS cementitious materials. Generally, mechanical activation is one of the main techniques to accelerate the early reaction of mineral admixtures. In this study, wet-milling and dry-separation are respectively used to prepare ultrafine BFS to improve its early reactivity. The early hydration characteristics, mechanical property, hydration products of ultrahigh volume BFS cementitious materials are analyzed to assess the efficiency of ultrafine BFS on the properties of BFS cement paste. The results show that the initial and final setting time both gradually decrease as the dry-separation BFS (GS) dosage increases, while the wet-milling BFS (WS) series present the opposite tendency. The electrical resistivity of WS specimens develops at a faster rate than that of GS specimens. Mixes containing WS, at a maximum dosage of 90%, have higher mechanical property than those with GS, resulting in an enhancement of strength. The hydration products mainly include calcium hydroxide, hydrotalcite, hydrotalcite-like phase, calcium carbonate, stratlingite, C-S-H, C-A-S-H, and akermanite.

Background The idea of mixing different grades of diatomite ores with certain ratios to obtain blends with tailored minerals constitution that can help on improving their thermal insulation applicability is introduced in this study. In this respect, three diatomite samples were collected for investigation from El-Masakheet, Kasr El-Sagha, and Demia deposits, El-Fayoum, Egypt. Complete chemical and phase analyses of these samples were carried out. The analyses showed that El-Masakheet sample was of low-grade diatomite with excess calcite content. In addition, Kasr El-Sagha and Demia samples were of high-grade diatomite with minor calcite contents. By firing the dried Kasr El Sagha and Demia yellow samples specimens at different temperatures for 1 h, they showed complete destruction at 900 °C. Different amounts of El-Masakheet sample was blended with Kasr El-Sagha and Demia yellow samples. The specimens were subjected to firing at different temperatures for 1 h. The physical properties of the fired mixed specimens were followed up. Results Results showed that by blending El-Masakheet sample with 50% mass ratio with Kasr El-Sagha or Demia yellow samples, a pronounced increase in the thermal applicability of the fired blends from 900 to 1100 °C was achieved. In addition, a notable increase in their open porosity was recorded. This improvement was attributed to the change in the minerals constitution ratios in the blends due to the increase in their calcite contents after El Masakheet addition, especially the Ca/Si and Ca/(Al + Si) atom ratios. This change served in forming high melting points minerals like α-wollastonite and akermanite on firing the blends specimens instead of low melting point minerals like cristobalite and alkali aluminosilicate which were formed on firing the high-grade ores alone. Consequently, an increasing in the porosity and the thermal applicability of the new specimens from 900 to 1100 °C was achieved. Conclusions The idea of mixing different grades of diatomite ores with certain ratios to obtain blends with tailored minerals constitution can help on improving their thermal insulation applicability and their open porosity. Besides, this concept gave a good solution to get use of the unexploited low-grade diatomite ores, especially of high calcite content.

Solid-state synthesis of monticellite based ceramic powders from boron derivative waste in an eco-friendly route and the investigation of phase transformation mechanisms were studied. The heat-treatment of boron derivative waste, mainly composed of dolomite, calcite and quartz, was systematically carried out at 650 degrees C and 800 degrees C for various dwell times between 1 min and 4 h. The heat-treatment temperatures were selected considering TG-DTA curves of waste and Delta G - T diagrams obtained using FactSage Thermochemical Software. XRF, XRD, FTIR, TG-DTA and SEM analysis, particle size measurement and crystallite size determination carried out extensively. The obtained results showed that monticellite based ceramic powder synthesized at 800 degrees C for 4 h was composed of monticellite, akermanite, diopside, calcium magnesium borate and zeolite. The calcination of dolomite was completed both at 650 degrees C for 1 h and up to 800 degrees C, and calcite was decomposed at 800 degrees C for 30 min. Both diopside and monticellite were firstly detected at 650 degrees C for 30 min and at 800 degrees C for 1 min. Also, akermanite was presented at 800 degrees C for 1 min. The presented method offers the lowest temperature (800 degrees C) in literature for synthesis of monticellite and akermanite which reduces the energy consumption during heat-treatment. (C) 2018 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

The simulation of blast furnace slag was prepared by pure chemical reagents. Test methods like DSC, XRD and SEM were used to study the effect of Al2O3 and MgO content on crystallization of blast furnace slag during fiber formation. The results show that as Al2O3 and MgO contents in the sample changed, blast furnace slag was crystallized at the average temperature below 1232 K. When the ratio of Mg/Al in the samples is 0.6 calculated by Kissinger equation, crystallization activation energy is at the maximum value and the system is in the most stable condition. The sample crystallization phases are mainly calcium akermanite (2CaO·MgO·2SiO2) and gehlenite (2CaO·Al2O3·SiO2). Secondary crystallization phases are anorthite (CaAl2Si2O8), wollastonite minerals (WOLLA) and pyroxene minerals (cPyrA). Meanwhile, the principal crystallization phases of the samples are different types and have different contents, and the microstructures of the sample sections are different due to the difference between MgO/Al2O3 ratio.

There is increasing interest in biodegradable ceramic scaffolds for bone tissue engineering capable of in situ delivery of ionic species favoring bone formation. Strontium has been shown to be osteogenic, but strontium-containing drugs such as strontium ranelate, used in Europe for the treatment of osteoporosis, are now restricted due to clinical evidence of systemic effects. By doping fluorapatite-based glasses with strontium, we developed ceramic scaffolds with fully interconnected macroporosity and cell size similar to that of cancellous bone, that are also capable of releasing strontium. The crystallization behavior, investigated by XRD and SEM, revealed the formation of akermanite and fluorapatite at the surface of strontium-free glass-ceramic scaffolds, and strontium-substituted fluorapatite at the surface of the strontium-doped scaffolds. At 8 weeks after implantation in a rat calvarial critical size defect, scaffolds doped with the highest amount of strontium led to the highest mineral apposition rate. A significantly higher amount of newly-formed bone was found with the strontium-free glass-ceramic scaffold, and possibly linked to the presence of akermanite at the scaffold surface. We demonstrate by energy dispersive XRF analyses of skull sections that strontium was present in newly formed bone with the strontium-doped scaffolds, while a significant amount of fluorine was incorporated in newly formed bone, regardless of composition or crystallization state. Statement of Significance The present work demonstrates the in vivo action of strontium-containing glass-ceramic scaffolds. These bone graft substitutes are targeted at non load-bearing bone defects. Results show that strontium is successfully incorporated in newly formed bone. This is associated with a significantly higher Mineral Apposition Rate. The benefits of in situ release of strontium are demonstrated. The broader scientific impact of this works builds on the concept of resorbable ceramic scaffolds as reservoirs of ionic species capable of enhancing bone regeneration.

Although great strides have been made in medical technology, low back/neck pain and intervertebral disc degeneration initiated from disc degenerative disease remains a clinical challenge. Within the field of regenerative medicine therapy, we have sought to improve the biomechanical transformation of spinal fusion procedures conducted using biodegradable porous implants. Specifically, we have focused on developing mechanically strong bioceramic cages for spinal fusion and functional recovery. Herein, we fabricated the akermanite (AKE) ceramic-based porous cages using low-melting bioactive glass (BG) and 3D printing technology. The osteogenic cell adhesion on the cages was evaluated in vitro, and the spinal fusion was tested in the intervertebral disc trauma model. The results indicated that incorporation of 15% or 30% BG into AKE (i.e., AKE/BG15 and AKE/BG30) could enhance the compressive strength of bioceramic cages by 2- or 5-fold higher than the pure AKE cages (AKE/BG0). In comparison with porous β-tricalcium phosphate cages, the surface of AKE/BG15 and AKE/BG30 cages greatly promoted the growth and alkaline phosphatase expression of osteogenic cells. Histological and biomechanical analysis showed that the AKE/BG15 and AKE/BG30 readily stimulated the new bone tissue growth and improved the spinal biomechanics recovery. In the AKE/BG15 and AKE/BG30 cage groups, 4-6 of the rabbits demonstrated a successful fusion. In contrast, only 0-1 of the initial seeded AKE/BG0 and tricalcium phosphate cages resulted in fusion at 12 weeks post-operatively. In summary, the akermanite-based cages showed an increased bone regenerative effect within an intervertebral disc trauma model, and thus, provided a promising candidate for improving spinal fusion surgery.

The high hydration potential of CaO and MgO phases restricted the application of Mag-Dol refractory composites. In this study, the impact of nano-silica (SiO 2 ) addition on the physical, mechanical, thermo-mechanical as well as microstructure of Mag-Dol refractory composites is investigated. Mag-Dol compositions were prepared by using calcined dolomite and magnesite particles (micron, 0–1, 1–3, 3–5, and 5–8 mm), liquid resin, and 0, 0.5, 1, 1.5, 2, and 2.5 wt% nano SiO 2 as additives. Specimens were heated up to 1650 °C for the 3 h soaking period. Fired specimens were characterized by physical (apparent porosity, bulk density, and hydration resistance), mechanical (cold crushing strength), and thermo-mechanical (flexural strength at 1200 °C) measurements. XRD and SEM/EDS analysis were done to study phases and microstructure analysis of the fired samples, respectively. Results showed that by adding up to 2.5 wt% nano-SiO 2 , due to the formation of CaO·MgO·2SiO 2 (Diopside), 2CaO·MgO·2SiO 2 (Akermanite), and CaO·MgO·SiO 2 (Monticellite) phases, physical and mechanical properties were enhanced. But the highest flexural strength value is achieved for 1 wt% nano-SiO 2 containing sample.

Bioceramics based on the CaO-MgO-SiO2 system, are frequently applied to stimulate bone regeneration due to their bioactivity, controlled bioresorbability rate, biocompatibility, and improved mechanical properties. In this contribution, bioceramic materials; diopside (CaMgSi2O6), akermanite (Ca2MgSi2O7), and merwinite (Ca3MgSi2O8) were synthesized through solution combustion method using glycine as a fuel. Scanning electron microscopy (SEM), Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), N2 physisorption, and energy-dispersive X-ray spectroscopy (EDX) were utilized for characterization. The proposed synthetic method produced highly-pure phases of the bioceramics after calcination at 1000 °C. The bioceramics are characterized by crystalline sizes ranged from 37 to 44 nm and specific surface areas in the range of 26 m2 g−1 to 53 m2 g−1. The in-vitro biomineralization activity and the mechanical properties of the bioceramic scaffolds were investigated by immersing them in simulated body fluid (SBF) for 3, 6, and 9 days. Interestingly, XRD, FT-IR, and SEM results demonstrated that the surface of scaffolds is covered by the hydroxyapatite (HAp) layer after immersing in SBF for 9 days. The rate of HAp deposition is extremely high for merwinite compared to akermanite and diopside, following the same trend of the CaO content. Furthermore, the mechanical properties of the fabricated scaffolds are excellent, as indicated by Young's modulus compressive strength analyses, and the mechanical strength improves with increasing the CaO content. The antibacterial activity of the bioceramics was tested against S. epidermidis, S. aureus, E.coli, and P. aeruginosa. Merwinite exhibits a superior antibacterial activity even at lower concentrations compared to diopside and akermanite. Collectively, the multifunctional properties of the synthesized bioceramics make them auspicious candidates for potential biomedical applications including bone tissue repair.