Enhanced bone regeneration of 3D printed β-Ca2SiO4 scaffolds by aluminum ions solid solution

Bioceramics are widely recognized as suitable biomaterials in bone tissue engineering for their osteogenic properties. In this study, 3D printed dicalcium silicate with aluminum ions solid solution (Al–C2S) scaffolds were produced effectively using the compound of preceramic resin, CaCO₃, and Al₂O₃ active powders. The scaffolds exhibited symmetrical and well-proportioned macropores (ca. 400 μm). The proliferation and osteogenic genetic expression levels (osteocalcin, osteopontin, Collagen type I, and Runx2) of rat bone mesenchymal stem cells (rBMSCs) could be enhanced by aluminum ions solid solution in dicalcium silicate scaffolds (C2S), and Al–C2S emerged as a better osteoconductive ability in vivo tests. Therefore, 3D printed Al–C2S scaffold is a promising biomaterial to be applied in bone regeneration.     

Effect of different CaSO4 contents on CaSiO3-CaSO4 porous composite bone scaffolds by 3D gel-printing

Porous CaSiO₃-CaSO₄ composite scaffolds were successfully prepared by 3D gel-printing (3DGP) technology in this study. In order to further improve the degradation performance of pure CaSiO₃ scaffolds, the effect of different CaSO₄ doping contents on CaSiO₃-CaSO₄ composite scaffolds was studied. The results show that when the porous composite scaffolds were placed in simulated body fluid (SBF) for 5 weeks, the weight loss rate was 2.41% (CaSiO₃-1%CaSO₄), 3.97% (CaSiO₃-3%CaSO₄), 4.18% (CaSiO₃-5%CaSO₄), 6.87% (CaSiO₃-7%CaSO₄), and 12.93% (CaSiO₃-9%CaSO₄), respectively, which could be concluded that CaSO₄ doping has a significant effect on improving the biodegradability of CaSiO₃ scaffolds. And CaSO₄ doping can also effectively improve the compressive strength of composite scaffolds and that of CaSiO₃-3%CaSO₄ composite scaffolds was tested as 54.67 MPa, and the shrinkage rate of porous composite scaffolds was nearly 11.4%, which meets the application requirements of bone repairing engineering.     

Effect of PCL concentration on PCL/CaSiO3 porous composite scaffolds for bone engineering

Porous polycaprolactone (PCL)-coated calcium silicate (CaSiO₃) composite scaffolds were successfully prepared by 3D gel-printing (3DGP) and vacuum impregnation technology in this study. The effect of different PCL concentration on porous CaSiO₃ scaffolds prepared by 3DGP technology was studied. The composition and morphological characteristics of PCL/CaSiO₃ scaffolds were tested by using fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and energy dispersive spectrometer (EDS) analysis. PCL coating amount on the scaffolds surface was calculated by thermogravimetric analysis (TGA). Compressive strength was tested by a universal testing machine, and degradability was tested by immersing the scaffolds in a simulated body fluid (SBF). The results show that PCL coating thickness increased from 7.29 μm to 12.2 μm, and the compressive strength of the corresponding composite scaffolds increased from 17.15 MPa to 24.12 MPa following with PCL concentration increasing from 7.5% to 12.5%. When the porous composite scaffolds were immersed in SBF for 28 days, the degradation ratio was 1.06% (CaSiO₃), 1.63% (CaSiO₃-7.5PCL), 1.81% (CaSiO₃-10PCL) and 1.55% (CaSiO₃-12.5PCL), respectively. It is obviously that PCL/CaSiO₃ composite scaffolds, which are suitable for bone growth in bone repair engineering, are beneficial to improve the mechanical properties and biodegradability of pure CaSiO₃ scaffolds.     

Formation of hydroxyapatite on CaSiO3 powders in simulated body fluid

CaSiO₃ powders were prepared from ethanol solutions of Ca(NO₃)₂·4H₂O and Si(OC₂H₅)₄ using NaOH as a precipitant. The resultant powders were heated at three different temperature regimes, (1) 500°C, (2) 500 and 1000^oC and (3) 500 and 1400°C, to obtain the amorphous phase (amorphous-CS), low temperature phase (β-CS), and high temperature phase (α-CS) of CaSiO₃, respectively. The different amorphous and crystalline phases exhibited different microtextures and specific surface areas of the powders. The rough, porous particles of amorphous-CS and β-CS have higher specific surface areas than the smooth, dense particles of α-CS. These CaSiO₃ powders were soaked in a simulated body fluid (SBF) at 36.5°C for 2 h to 30 days. Formation of hydroxyapatite (HAp) was observed on the surfaces of all samples, but the formation behavior and microstructures were different, resulting the differences in microstructure and crystal structure of the starting powders as well as particle size and specific surface area. The HAp formed on the amorphous-CS was a loose porous layer consisting of uniformly-sized tiny ball-like agglomerated particles, while that formed on the β-CS and α-CS was a dense layer consisting of larger ball-like agglomerated particles.     

Effect of different dopants on porous calcium silicate composite bone scaffolds by 3D gel-printing

Porous CaSiO₃ composite scaffolds with different dopants, such as MgSiO₃, MgCl₂ and CaSO₄, were successfully prepared by 3D gel-printing (3DGP). (m, n) is proposed to describe the filament geometry features. The results show that doping can improve the strength of porous composite scaffolds and MgCl₂-doped composite scaffolds had the highest modulus of elasticity of 1241 MPa. The shrinkage rate range of the composite scaffolds was 11.44–13.16%, and their porosity was all about 60%. When porous composite scaffolds were soaked in SBF for 28 days at 37°С, the degradation rate was 2.7% (pure), 0.3% (MgSiO₃), 0.2% (MgCl₂), 5.27% (CaSO₄), respectively. It explains that MgSiO₃ and MgCl₂ inhibited the in vitro degradation of CaSiO₃, while CaSO₄ promoted. It is obviously that doped MgCl₂ can improve the mechanical properties of porous scaffolds, and doped CaSO₄ can improve the degradation of scaffolds, which play an important role in bone repair engineering.     

Robocasting of controlled porous CaSiO3–SiO2 structures: Architecture – Strength relationship and material catalytic behavior

Wollastonite (CaSiO₃) based porous structures are useful in a wide range of applications including catalysis. Furthermore, the use of additive manufacturing techniques for the production of on-demand structures with controlled porosity are widely used for numerous materials. In the present work, CaSiO₃ was synthesized by co-precipitation method resulting in a fine CaSiO₃–SiO₂ powder, which was processed to fabricate regular porous structures using the robocasting technique. Cylindrical structures of 10 mm in diameter and 10 mm in height were robocast following two different arrangement patterns, i.e., orthogonal and honeycomb with two different pore sizes (350 and 500 μm). In general, the orthogonal structures showed better geometrical and dimensional accuracy than honeycomb ones. The compression test showed that orthogonal structures were more reliable, while the honeycomb structures exhibited higher compressive strength. The reasons are on the differences in porosity and pore architecture between them. Additionally, the catalytic properties of the CaSiO₃–SiO₂ powder were studied by the decomposition of isopropyl alcohol. The CaSiO₃–SiO₂ showed strong selective basic catalytic properties, leading on the dehydrogenation of the alcohol producing acetone with a yield up to 92% at 350 °C. In summary, the CaSiO₃–SiO₂ robocast structures have a significant potential for self-supporting catalytic reactors.     

Ultraviolet and visible upconversion in Yb/Er-CaSiO3 β-wollastonite phosphors

Wollastonite (CaSiO₃) is a well-known rock-forming mineral and an important constituent in ceramics and cement industries due to its outstanding mechanical, chemical, and thermal stabilities. Despite technological importance, functional properties such as photon upconversion in CaSiO₃ wollastonite ceramics have not been studied. In this contribution, Yb- and Er-doped CaSiO₃ (Yb/Er–CaSiO₃) wollastonite ceramics were synthesized via microwave hydrothermal technique followed up by heat-treatment in an air environment. X-ray diffraction and transmission electron microscopy studies confirmed the β-wollastonite (2M) phase in the synthesized samples heat-treated at 1050 °C. X-ray photoelectron spectroscopy analysis has shown that the binding energy of Ca 2p orbitals decreases after doping, indicating a change in the crystal environment of Ca in the CaSiO₃ and hence a successful incorporation of Yb³⁺ and Er³⁺ ions in the lattice. The 980 nm excitation resulted in ultraviolet, violet and strong green and red upconversion emissions as well as downshifting infrared emissions due to the energy transfer between Yb³⁺ and Er³⁺ ions. An absolute upconversion quantum yield in the 400–800 nm range is 0.04%. The most intense phonon band was observed at 969 cm^?1 in the Yb/Er–CaSiO₃ system. This study demonstrates that the β-wollastonite can be developed as a new kind of efficient upconversion phosphor material.     

Preparation and in vitro assessment of economic bio-scaffolds modified with wollastonite (CaSiO3)

Porous bioceramic scaffolds are the preferred option for substituting spongy bone. Therefore, this study evaluates the use of carbonate associated with apatite rocks at Hamadat mines (referred to as calcite) as a source of low-cost bioactive material useful for biomedical applications. In this study, the depositional environment and mineralogical, and petrographic behavior of such depositions were studied. Furthermore, the possibility of producing highly porous, low-cost bioceramic scaffolds using the freeze-drying technique was demonstrated. The bioactivity of the produced scaffolds was enhanced by adding different ratios of wollastonite (25, 50 and 75 wt %) to the scaffold’s batches. However, the scaffolds were coated with ZnCl₂ to enhance their antimicrobial susceptibility. The physical and mechanical properties as well as the phase composition and microstructure of the prepared scaffolds were investigated. The X-ray diffraction results revealed the formation of pure phase of α-wollastonite after 3 h of sintering at 1200 °C. To estimate the scaffolds’ biodegradability, the pH and the weight change were measured. The results were confirmed using the inductively coupled plasma measurements for the scaffolds deposited in a simulated body fluid (SBF) solution for 28 days. Results showed that the scaffolds had excellent bioactivity, which was demonstrated by the appearance of apatite particles on their surface after being immersed in the SBF. The antimicrobial activity test revealed that Zn²⁺, NPs and CaSiO₃ had positive effects due to their oxidative stress process. Zn²⁺, Ca²⁺, and Si⁴⁺ cations can be adsorbed on bacterial surface membranes, interacting with the respiratory microbial enzymes, inhibiting their actions, and damaging the cell, thereby causing the bacterial cell decomposition.     

Large Scale Preparation of β‐CaSiO3 Nanostructures by Solid‐State Reaction in NaCl–H2O(v) System at Lower Temperature

An environmentally friendly NaCl–H₂O(v) system was developed to prepare β‐CaSiO₃ nanostructures from commercially available raw materials, CaCO₃ and amorphous SiO₂ (α‐SiO₂), by a one‐step solid‐state reaction at 575°C for 2 h. The formation of β‐CaSiO₃ was accelerated by NaCl–H₂O(v) system. The results demonstrated that both NaCl and H₂O(v) played vital roles in the formation of β‐CaSiO₃ nanostructures at a lower temperature. NaCl is considered to enhance the diffusivity of starting materials and the rate of solid‐state reactions, and promote the crystallization at lower temperature. Water vapor can accelerate the decomposition of CaCO₃, and absorbed water on the surface of solid materials can dissolve NaCl to form an aqueous ionic liquid composed of Na and Cl ions, which is similar to a hydrothermal process, and will further increase the diffusivity of components and reduce the reaction temperature.     

A novel Gd3+ and Yb3+ co-doped ceria-sulphate composite electrolyte for intermediate-temperature fuel cells

In this study, Yb³⁺ and Gd³⁺ co-doped CeO₂ and the corresponding (Li/K)₂SO₄ composite electrolyte were prepared. The structures and morphologies of Ce_0.8Yb_0.1Gd_0.1O_2-α and Ce_0.8Yb_0.1Gd_0.1O_2-α-Li₂SO₄–K₂SO₄ were investigated using X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM). The conductivity of Ce_0.8Yb_0.1Gd_0.1O_2-α (1550 °C) as a function of time during humidification in a nitrogen atmosphere at 700 °C was investigated. The log(σT) vs. 1000T⁻¹ plots, logσ vs. log(pO₂) curves, and fuel cell performances of Ce_0.8Yb_0.1Gd_0.1O_2-α (1550 °C) and Ce_0.8Yb_0.1Gd_0.1O_2-α-Li₂SO₄–K₂SO₄ (1550 °C) were investigated. At 700 °C, Ce_0.8Yb_0.1Gd_0.1O_2-α-Li₂SO₄–K₂SO₄ (1550 °C) showed a power density of 197 mW cm⁻², which is five times higher than that of Ce_0.8Yb_0.1Gd_0.1O_2-α (1550 °C).     

Metal-free synthesis of carbon nanotubes filled with calcium silicate

A new metal-free catalyst CaSiO₃ was developed to grow carbon nanotubes (CNTs) on a pyrolytic graphite paper tape by an ethanol catalytic chemical vapor deposition method at 1200–1400 °C. The prepared CNTs with a droplet tip had a multi-walled structure and were filled with amorphous CaSiO₃. Temperature, determining the melting of CaSiO₃, was critical for the growth of the CNTs. This new catalyst is suggested to follow the similar roles of transition metals in the growth of CNTs by a molten state to absorb carbon and form CNTs after reaching saturation.     

Crystallization behavior of CMAS and NaVO3+CMAS mixture and its potential effect to thermal barrier coatings corrosion

Calcium-magnesium-alumina-silicate (CMAS) and molten salt corrosion pose great threats to thermal barrier coatings (TBCs), and recently, a coupling effect of CMAS and molten salt has been found to cause even severer corrosion to TBCs. In this study, the crystallization behavior of CMAS and CMAS+NaVO₃ is investigated for potentially clarifying their corrosion mechanisms to TBCs. Results indicated that at 1000 °C and 1100 °C, CMAS was crystallized to form CaMgSi₂O₆, while at 1200 °C, the crystallization products were CaMgSi₂O₆, CaSiO₃ and CaAl₂Si₂O₈. The introduction of NaVO₃ in CMAS reduced the crystallization ability, and as the NaVO₃ content increased, glass crystallization occurred at a lower temperature, with crystallization products mainly consisting of CaAl₂Si₂O₈ and CaMgSi₂O₆. At 1200 °C, CMAS+10 wt% NaVO₃ was in a molten state without any crystallization, which suggested that NaVO₃ addition in CMAS could reduce its melting point, indicating enhanced penetration ability in TBCs and thus increased corrosiveness.     

Effect of Fe3O4 concentration on 3D gel-printed Fe3O4/CaSiO3 composite scaffolds for bone engineering

In this study, porous calcium silicate (CaSiO₃) scaffolds were prepared by 3D gel-printing (3DGP) method and Fe₃O₄ water-based magnetic fluids (WMFs) were prepared by phacoemulsification compound chemical coprecipitation method. Fe₃O₄ WMFs were coated on CaSiO₃ scaffolds surface to prepare Fe₃O₄/CaSiO₃ composite scaffolds. The effect of WMFs with different Fe₃O₄ concentrations on porous CaSiO₃ scaffolds was studied. The composition and morphological characteristics of porous scaffolds were analyzed by using scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) analysis. The magnetic properties were tested by vibrating sample magnetometer (VSM). The stability of Fe₃O₄ WMFs coatings and the degradability of composite scaffolds were tested by immersing them in simulated body fluid (SBF). The results show that when Fe₃O₄ concentration was 5.4% (w/v), the composite scaffolds had the highest saturation magnetization of 69.6 emu/g and the best stability in dynamic SBF. It is obviously that Fe₃O₄ WMFs coatings can be used for bone tissue engineering scaffolds repairing.     

Single-source-precursor synthesis of soft magnetic Fe3Si- and Fe5Si3-containing SiOC ceramic nanocomposites

We present here the single-source-precursor synthesis of Fe₃Si and Fe₅Si₃-containing SiOC ceramic nanocomposites and investigation of their magnetic properties. The materials were prepared upon chemical modification of a hydroxy- and ethoxy-substituted polymethylsilsesquioxane with iron (III) acetylacetonate (Fe(acac)₃) in different amounts (5, 15, 30 and 50 wt%), followed by cross-linking at 180 °C and pyrolysis in argon at temperatures ranging from 1000 °C to 1500 °C. The polymer-to-ceramic transformation of the iron-modified polysilsesquioxane and the evolution at high temperatures of the synthesized SiFeOC-based nanocomposite were studied by means of thermogravimetric analysis (TGA) coupled with evolved gas analysis (EGA) as well as X-ray diffraction (XRD). Upon pyrolysis at 1100 °C, the non-modified polysilsesquioxane converts into an amorphous SiOC ceramic; whereas the iron-modified precursors lead to Fe₃Si/SiOC nanocomposites. Annealing of Fe₃Si/SiOC at temperatures exceeding 1300 °C induced the crystallization of Fe₅Si₃ and β-SiC. The crystallization of the different iron-containing phases at different temperatures is considered to be a consequence of the in situ generation of a Fe–C–Si alloy within the materials during pyrolysis. Depending on the Fe and Si content in the alloy, either Fe₃Si and graphitic carbon (at 1000–1200 °C) or Fe₅Si₃ and β-SiC (at T > 1300 °C) crystallize. All SiFeOC-based ceramic samples were found to exhibit soft magnetic properties. Magnetization versus applied field measurements of the samples show a saturation magnetization up to 26.0 emu/g, depending on the Fe content within the SiFeOC-based samples as well as on the crystalline iron silicide phases formed during pyrolysis.     

Composite bioceramic scaffolds with controllable photothermal performance fabricated by digital light processing and vacuum infiltration

Photothermal scaffolds can help clear bone tumor cells after resection. In this work, hydroxyapatite-akermanite-Fe₃O₄ (HA-AK-FE) bioceramic scaffolds were fabricated by infiltrating digital light processing (DLP)-printed HA-AK scaffolds in nano-Fe₃O₄ solution. The prepared HA-AK-FE samples exhibited excellent and controllable photothermal performance under the irradiation of 808 nm near-infrared light. By controlling nano-Fe₃O₄ concentration, irradiation power and infiltration time, temperature of HA-AK-FE samples could be regulated in a wide range from room temperature to 150 °C within 15 s. Photothermal temperature remained stable after 4 times repeated irradiations. In SBF solution and under subcutaneous tissue, the heating rate and photothermal temperature decreased obviously compared with in air, but they could still meet the needs of killing tumors (41–48 °C). The Fe release concentration of wafers after immersing in SBF for 1 day was 0.037 mg/L and non-venomous. These results confirm the feasibility and controllability of fabricating photothermal scaffolds by coating nano-Fe₃O₄ with vacuum infiltration, and the prepared HA-AK-FE scaffolds are hopeful to be used in photothermal therapy of bone tumors.     

Fabrication of Si3N4-based composite containing needle-like TiN synthesized using NH3 nitridation of TiO2 nanofiber

A Si₃N₄ composite containing needle-like TiN particles (7 vol%) was fabricated. Needle-like TiN particles several micrometers long were synthesized using NH₃ nitridation of TiO₂ nanofiber, which was obtained using hydrothermal treatment. A mixed powder of α-Si₃N₄ and the needle-like TiN particles with additives was hot pressed at 24 MPa and 1850 °C for 1 h in N₂ atmosphere. Mechanical properties of the composite were compared with those of a composite containing rounded TiN particles and a monolithic β-Si₃N₄ ceramic. The Si₃N₄ matrix of the composites containing TiN was mainly a-phase, suggesting that the α–β phase transformation of Si₃N₄ was inhibited by the presence of TiN. Although fracture strength of the composites was lower, fracture toughness was comparable to that of monolithic β-Si₃N₄ ceramics. Hardness of the composites was about 19 GPa and was greater than that of the monolithic β-Si₃N₄ ceramic.     

3D printing of porous scaffolds BaTiO3 piezoelectric ceramics and regulation of their mechanical and electrical properties

A series of porous scaffolds of piezoelectric ceramic barium titanate (BaTiO₃) were successfully fabricated by Digital Light Processing (DLP) 3D printing technology in this work. To obtain a high-precision and high-purity sample, the debinding sintering profile was explored and the optimal parameters were determined as 1425 °C for 2h. With the increase of scaffolds porosity from 10% to 90%, the compressive strength and piezoelectric coefficient (d₃₃) decreased gradually. The empirical formulas about the mechanical and piezoelectric properties were obtained by adjusting BaTiO₃ ceramics with different porosity. In addition, the distribution of potential and stress under 100 MPa pressure were studied by the finite element method (FEM).     

Photothermal effect of 3D printed hydroxyapatite composite scaffolds incorporated with graphene nanoplatelets

Porous scaffolds with photothermal effect could be used in the treatment of malignant bone tumors. Herein, graphene nanoplatelets were incorporated into the apatite/gelatin composites to construct porous scaffolds by 3D printing. Under near infrared laser irradiation, the composite scaffolds demonstrated high photothermal conversion efficiency. The temperature of scaffolds could be heated to 43 °C by controlling time and power of the laser irradiation, and then cooled to room temperature subsequently. Mild photothermal treatment (40–43 °C) was applied on MC3T3-E1 cells cultured on the scaffolds. It was found that after 3 cycles of treatment, the proliferation of MC3T3-E1 cells was significantly accelerated. It was suggested that the incorporation of graphene nanoplatelets into 3D printed hydroxyapatite composite scaffolds have the potential to accelerate bone regeneration after photothermal treatment for malignant bone tumors.     

Influence of hydrogen on growth and microstructure of boron nitride coatings obtained from BCl3–NH3–H2 system by chemical vapor infiltration

Hexagonal boron nitride (h-BN) interfacial coatings were prepared by chemical vapor infiltration (CVI) process from BCl₃–NH₃–H₂ system with different hydrogen contents for improving the toughness of ceramic matrix composites. In this study, the yield of BN was found to be 94.90% without hydrogen present in the reactant system as calculated via FactSage, while it reached 99.95% at the [H₂]/[BCl₃] ratio of 10 and the [NH₃]/[BCl₃] ratio of 1, when chemical equilibrium was reached. BN interfacial coatings containing mixture of hexagonal and turbostratic phases were obtained. The deposition rate of coating increased from 18.2 ± 0.4 nm min⁻¹ (β = 0) to 23.0 ± 0.4 nm min⁻¹ (β = 5) with the increase of hydrogen content in reactants, then it significantly decreased when β was 10. Owing to different nucleation amounts on the surface of fibers, samples S2 (β = 2) and S3 (β = 5) exhibited particles with circular shapes and smooth surfaces, while the other coatings presented particles with polygonal shapes and rough surfaces. Moreover, the onset temperature of weight gain of sample S2 was 102 °C higher than that of sample S4, thus indicating the enhancement of the high-temperature oxidation resistance of BN coating.     

The NaxMnO2 materials prepared by a glycine-nitrate method as advanced cathode materials for aqueous sodium-ion rechargeable batteries

Cathodic material for sodium-ion rechargeable batteries based on Na_xMnO₂ were synthesized by glycine nitrate method and subsequent annealing at high temperatures. Different crystal structures with different morphologies were obtained depending on the annealing temperature: hexagonal layeredα-Na_0.7MnO_2.05 nanoplates were obtained at 850 °C, while 3-D tunnel structured Na_0·4MnO₂ and Na_0·44MnO₂, both with rod-like morphology, were obtained at 800 °C and 900 °C, respectively. The investigations of the electrochemical behavior of obtained cathodic materials in aqueous NaNO₃ solution have shown that Na_0·44MnO₂ obtained at 900 °C has shown the best battery performance. Its initial discharge capacities are 123.5 mA h/g, 113.2 mA h/g, and 102.0 mA h/g at the high current densities of 1000, 2000 and 5000 mA/g, respectively.