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In this present study, synthetic tobermorites are prepared using bio-waste (snail shell) and municipal waste (container glasses) as lime and silica precursors respectively. Six batch compositions were formulated with varying combination of soda-lime glass and snail shell ash. The bodies were sintered at 950 °C for a holding period of 2 h in an electric muffle furnace. Analyses such as scanning electron microscopy (SEM/EDS), Fourier Transform Infra-red Spectroscopy (FT-IR), X-ray diffractometry (XRD) were used to assess the microstructure, functional groups and the phase composition of the prepared tobermorites respectively. The results of the morphology shows that the tobermorites possess irregular but spherical shaped grain with coated water films while the EDS shows the presence of Ca and Si with small amount of Al confirming tobermorite. The FT-IR indicates Ca–O–Si and Si–O–Si as main functional groups while the phase composition investigated by XRD indicate low intensity peaks of calcium silicate (CaSiO3).

Electrical conductivity and structure of the CaO-SiO2-based mold flux melts with various Al2O3 contents were investigated. The results show that the electrical conductivity increases with the addition of Al2O3 from 2 wt% to 4 wt%, but decreases with the further increase of Al2O3 from 4 wt% to 8 wt%. Correspondingly, the apparent activation energy reduces firstly from 55.12 ± 1.20 kJ mol to 41.09± 0.38 kJ mol, and then increases from 41.09 ± 0.38 kJ mol to 98.99 ± 1.42 kJ mol. The structure analyses suggest that complex structural units, such as Si-O-Al, Al-O0, Si-O-Si and Q3(Si), reduce first, but increase with the further addition of Al2O3. Conversely, these simple structural units, such as Al-O-, Q0(Si), Q1(Si) and Q2(Si) vary in the opposite way with the change of Al2O3 content. From the variations of electrical conductivity, activation energy and structural units, it can be found that when Al2O3 works as network breaker to simplify the melt structure, the energy barrier for transportation of conducting ions/ionic reduce, which results in the increase of electrical conductivity; while when Al2O3 becomes into network former, the conductivity increases, correspondingly.

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.

Calcium silicate (CS) composite materials are widely applied in cementitious materials and bone tissue engineering. Extensive studies focused on the traditional organic templates (e.g., surfactant)...

The scaffold of bone repair needs a variety of material combinations to meet its intended performance; a typical single material such as zirconia has excellent mechanical properties, while hydroxyapatite and calcium silicate are bioactive materials with different degradation rates. In this paper, porous zirconia scaffolds were fabricated using 3D printing technology. The surface of the scaffold was coated by dipping with different contents of calcium silicate and hydroxyapatite to improve the biological activity and mechanical properties. Mechanical tests show that the coating material can effectively fill the pores of the porous scaffold, increasing its compressive strength by an average of 55%. The simulated body fluid (SBF) test showed that the higher calcium silicate in the coating increased the degradation rate. Cell experiments showed that the coated scaffolds exhibited good cytocompatibility and were beneficial to the proliferation and differentiation of cells. In conclusion, coated scaffolds have potential applications in the field of bone repair.

β-tricalcium phosphate bioceramics suffer from a drawback of poor mechanical strength and a scarcity of capacity to regulate biological performances. In the current study, the overall performances of β-tricalcium phosphate (TCP) bioceramics were improved by incorporating calcium silicate (CS) and magnesium-strontium phosphate (MSP). During the sintering process, the MSP stabilized the β phase of TCP, and the formation of MSP melt ensured effective liquid-sintering of TCP, thus conducing to lower porosity of TCP/MSP and TCP/CS/MSP bioceramics. In comparison with the TCP bioceramics, the TCP/CS and TCP/MSP bioceramics showed lower compressive strength, while the TCP/CS/MSP bioceramics attained noticeably higher compressive strength. Due to the sustained release of therapeutical ions, the TCP/CS bioceramics enhanced in vitro early-stage osteoblastic differentiation, but compromised cell proliferation; both the TCP/MSP and TCP/CS/MSP bioceramics enhanced cell proliferation and osteoblastic differentiation, and restrained osteoclastic activities. Collectively, the TCP/CS/MSP bioceramics with optimal overall performances are promising for efficaciously treating the defects of osteoporotic bone.

Color stability of pulp-capping material is considered vital to the final aesthetic result since the material is placed in the coronal area. The purpose of this study was to compare the color stability of various pulp-capping materials by analyzing color change of tooth over time. A cavity was formed in the crown of the extracted premolar, and 4 types of pulp-capping materials were filled. Color assessment was performed with a spectrophotometer at different intervals: before placement; immediately after material placement; 1 day, 1 week, 2 weeks, 4 weeks, 8 weeks, 12 weeks, and 16 weeks after placement. Proroot white MTA® and TheraCal LC® showed a significant decrease in the L* value and an increase in the ΔE* value over time. In contrast, Biodentine® and Well-Root™ PT showed no significant change in the L* value and maintained a steady ΔE* value. The application of pulp-capping materials containing bismuth oxide as a radiopacifier may result in a color change of teeth. Long-term color stability of pulp-capping materials should be considered when treating teeth with thin enamel thickness or in aesthetically important area.

In this work, we have synthesised a mixture consisting of sodium calcium silicate and calcium silicate nanostructures in the presence and absence of the hydrothermal method. The synthesised products were identified utilising many techniques such as XRD, EDS, FT-IR, HR-TEM, and FE-SEM. The XRD demonstrated that the mean crystallite size of the product, which was synthesised in the absence of the hydrothermal method, is 72.71 nm. The average crystallite size of the products, which were synthesised using the hydrothermal method at 160℃ for 4, 8, and 16 h, are 44.85, 34.89, and 37.38 nm, respectively. HR-TEM confirmed that all the products consist of irregular and rod shapes. The product, which was synthesised after 8 h of hydrothermal treatment, was operated as an adsorbent for the efficient removal of toxic ions (Cd(II) and Hg(II)) from aqueous media. The maximum adsorption capacity of the adsorbent towards Hg(II) and Cd(II) ions are 177.94 and 199.20 mg/g, respectively. The removal process of the studied ions was fitted well with the pseudo-second-order kinetic model and Langmuir equilibrium isotherm. Thermodynamic parameters confirmed that the removal process of the studied ions was spontaneous, chemical, and endothermic.

The mineral formation-transition mechanism, microstructure morphology evolution, pulverization property and chemical reactivity of calcium sulpho-aluminate with sodium dopant are systematically studied with the molar ratio of CaO to Al2O3 is 0.8, the molar ratio of CaO to SiO2 is 1.5, the mass ratio of Al2O3 to SiO2 is 2.0, and the SO3 accounts for 4%. The results show that sodium dopant could promote 3CaO·3Al2O3·CaSO4, CaO·2Al2O3 and 2CaO·Al2O3·SiO2 transform into 2CaO·SiO2, CaO·Al2O3, 12CaO·7Al2O3 and 2Na2O·3CaO·5Al2O3, and it also can decrease the decomposition temperature of reactive materials and the initial phases formation temperature significantly. Sodium diffusion can destroy the clear grain boundary of calcium aluminate and calcium silicate phases, change the macro-microstructure morphology, improve the crystalline degree of the samples, and then improve the pulverization and alumina leaching property. However, excessive sodium dopant can decrease the melting temperature, inhibit the transformation process of 2CaO·SiO2 from β to γ, and then deteriorate the pulverization property significantly again.

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.

In the composition range of x= 0-15 mol%, glasses in the system 24.5Na2O.24.5CaO.6P2O5.xSrO.(45-x)SiO2 have been studied. The glasses are transparent and have an amorphous network structure when they are as prepared. Heat treated glasses, on the other hand, are transformed into opaque white glass ceramics with a highly crystalline network structure. The main well-formed crystalline species in material bioactivity were apatite (calcium phosphate, Ca3(PO4)2, wollastonite (calcium silicate, CaSiO3), and strontium calcium phosphate [Ca2Sr(PO4)2. Increasing SrO improves material crystallite and increases the host glass matrix's hardness. The modification of the apatit Ca(PO3)2 to involve Sr ions inducing Ca2Sr (PO4)2 apatite one is thought to be the cause of the change in XRD spectra, 31P NMR chemical shift, and hardness number as SrO increases. These species help to improve material properties and hardness.

Calcium silicate based materials have gained popularity in recent years due to their resemblance to mineral trioxide aggregate (MTA) and their applicability in cases where MTA is indicated. “Biodentine” is a calcium silicate based product which became commercially available (Septodont) and that was specifically designed as a “dentine replacement” material. The material is actually formulated using the MTA-based cement technology, with the improvement of some material properties. Biodentine™ is a second generation hydraulic calcium silicate material that is composed mainly of tricalcium silicate and it also contains zirconium oxide radiopacifier and some additives. It is scientifically engineered for a specific purpose to be used as a dentine replacement material. The enhanced physical and biologic properties of Biodentine™ could be attributed to the presence of finer particle size, use of zirconium oxide as radiopacifier, purity of tricalcium silicate, absence of dicalcium silicate, and the addition of calcium chloride and hydrosoluble polymer. This article is aimed to review the properties of Biodentine by exploring the research work done in this field so far.

Among the CaCO3 polymorphs, aragonite demonstrates a better performance as a filler material in the paper and plastic industries. Despite being ideal from the environmental protection perspective, the production of aragonite particles via CO2 mineralization of rocks is hindered by the difficulty in achieving high production efficiencies and purities, which, however, can be mitigated by exploiting the potential ability of chelating agents on metal ions extraction and carbonation controlling. Herein, chelating agent N,N-dicarboxymethyl glutamic acid (GLDA) was used to enhance the extraction of Ca from calcium silicate and facilitate the production of aragonite particles during the subsequent Ca carbonation. CO2 mineralization was promoted in the presence of 0.01–0.1 M GLDA at ≤ 80 °C, with the maximal CaCO3 production efficiency reached 308 g/kg of calcium silicate in 60 min using 0.03 M GLDA, which is 15.5 times higher than that without GLDA. In addition, GLDA showed excellent effects on promoting aragonite precipitation, e.g., the content of aragonite was only 5.1% in the absence of GLDA at 50 °C, whereas highly pure (> 90%, increased by a factor of 18) and morphologically uniform aragonite was obtained using ≥ 0.05 M GLDA under identical conditions. Aragonite particle morphologies could also be controlled by varying the GLDA concentration and carbonation temperature. This study proposed a carbon-negative aragonite production method, demonstrated the possibility of enhanced and controlled aragonite particle production during the CO2 mineralization of calcium silicates in the presence of chelating agents.

Calcium silicate (CS) composite bone tissue engineering scaffolds were three-dimensionally printed using titanium metallic powders as the second strengthening phase for overcoming the inherent brittleness and fast degradability. In order to promote the sintering process of all composite scaffolds, mesoporous structure was further introduced into sol-gel-derived CS powders obtaining mesoporous CS (MCS) with larger surface area. The influences of mesoporous structure, sintering temperature and Ti content have been investigated through comparisons of the final scaffold composition, microstructure, compressive strength and in vitro stability. Results showed that CS matrix materials reacted with Ti could form less degradable CaTiO3 and TiC ceramic phases under 1200 °C sintering. The MCS-Ti scaffolds presented significantly improved density and homogeneity compared to CS-Ti. Therefore, MCS-Ti3 scaffolds with the highest 30% Ti addition, possessed the biggest compressive strength of 4.11 ± 0.39 MPa. Moreover, in vitro degradation analyzations demonstrated that MCS-Ti scaffolds enhanced ability of control over the weight losses and pH values of surrounding medium, indicating promising use as an alternative composite for bone repair.

Bioceramic materials currently applied in bone repairing mainly base on calcium phosphate compounds like hydroxyapatite (HA), however, issues including slow degradation rate and insufficient bioactivity limit their efficiency in promoting bone regeneration. Calcium silicate (CS) is a promising alternative for the purpose thanks to its degradability and bioactive Si4+ release ability, while its fast degradation rate will cause pH problem and does not match the rhythm of osteogenesis. Herein, 3D composite bioceramic scaffolds were fabricated by blending different weight fractions (1:0, 3:1, 1:1, 1:3 or 0:1) of CS nanofibers (CSNFs) and HA nanowires (HANWs) via steps of fiber-dispersing, freeze-drying and sintering. With subsequent polymer coating, the porous structure and mechanical properties of the CSNF/HANW scaffolds were improved and scaffold performances were further regulated in dependence on the hydrophobicity/hydrophilicity and degradation rates of the polymers. Poly( l -lactide) (PLLA), poly(lactide-co-caprolactone) (PLCL) and gelatin were applied as the polymer coating. It was found that PLLA- and PLCL-coating would slow down the scaffold degradation and ion release rate compared to the gelatin-coating, while the increasing fraction of CSNFs would accelerate these events to increase medium pH due to the alkalinity of the bioceramic material. Finally, proliferation and osteogenic differentiation of bone marrow mesenchymal stromal cells (BMSCs) achieved desirable outcomes on gelatin-coated CSNF/HANW scaffolds with their fractions of 1:1 and 1:3, strongly suggesting the potential of these scaffolds for bone regeneration.

The deinking effect of printing paper filled with CaSiO3 and CaSiO3/French chalk was investigated. As a result, it shows that the two kinds of paper samples have better deinking effect, and the whiteness of the former is slightly higher than that of the latter. However, the strength index of the former is slightly lower than that of the latter. The adhesive removal effect of the paper sample filled with CaSiO3 is better than that of the paper filled with CaSiO3/ French chalk powder.

Silicon nanotubes (SNTs) are very attractive in the fields of energy, catalysis, and sensors, but a facile template- and/or catalyst-free preparation method is still absent. Herein, we study a controllable and cost-effective approach for preparing SNTs by electrochemically reducing layer-structured calcium silicate (CaSiO3) in molten CaCl2/NaCl without any template and catalyst. The underlying mechanism of the SNT formation is uncovered: the layer-structured CaSiO3 is first electrochemically exfoliated into SiOx (0 < x < 2) sheets while releasing CaO into the molten salts, and then the SiOx sheets are electrochemically reduced and simultaneously crimped into SNTs. The diameter (120-312 nm) and wall thickness (∼40 nm) of the SNTs can be tailorable by manipulating the reduction potential between -1.28 and -1.48 V (vs Ag/AgCl). Lastly, the electrolytic SNTs show a high lithium storage capacity of 3737 mAh g-1 at 0.2 A g-1, a high rate capability of 1371 mA h g-1 at 10 A g-1, and stable cycling with a capacity of 974 mAh g-1 after 600 cycles at 1 A g-1. Overall, the template- and catalyst-free electrochemical method provides a straightforward and facile way to prepare SNTs with a brand-new mechanism that can be applied to other tubular structure materials.

The production of phosphoric acid for use in fertilizer generates toxic fluorosilicic acid as by-product, which can have, when disposed in ocean, negative effects on the maritime ecosystem. With the objective of developing a process for the treatment and valorization of this industrial waste, we study a route starting with a reaction between fluorosilicic acid and sodium chloride that produces a hydrochloric acid solution and sodium fluorosilicate powder. In the present work, we focused on the conversion step of sodium fluorosilicate, consisting of a caustification reaction in an aqueous solvent, with the purpose of obtaining valuable products. We identified a reaction scheme based on a preliminary thermodynamic study using the PHREEQC geochemical software. Experimental tests were then carried out in a 2 L stirred batch reactor, with various characterization techniques of the products (ICP-OES, XRD, TGA) allowing to establish mass balances. We propose two new steps in the conversion process, consisting of the aqueous reaction of CaO with Na2SiF6 at 50 °C, with an intermediate filtration for a molar ratio (CaO/Na2SiF6) of 2.77. This process generates two solid products: (i) pure CaF2, which can be used as an additive in various pyrometallurgical processes and (ii) a mixture of calcium silicate hydrates with low content of CaF2, which constitutes a promising resource for construction and building materials.

The removal of boron from silicon is a crucial step for silicon purification by the metallurgical route. The mechanism of boron removal was investigated by a combined method of using calcium silicate slag containing CaCl2 and O2 gas blowing. It is proved both experimentally and theoretically that the combined refining method is favorable for boron removal from silicon and shows a significantly enhanced boron removal. Thermodynamic calculations show that in addition to borate, a gaseous BOCl species is generated during the processing by the combined refining technique. Ab initio molecular dynamics simulations of BOCl gaseous species formation show that the Si-B bond breaks and a new Si–O–B structure is formed when the oxygen is introduced into the Si–B lattice plane. The existence of chloride further leads to the breaking of the Si–O bond and ultimately generates the O–B–Cl structure that escapes from the Si lattice plane in the form of free boride BOCl.

Aim This study compared biointeractivity (pH of soaking water and calcium ions), porosity, water sorption, solubility, compressive strength, lap shear strength, as well as the apatite forming ability of three calcium silicate-based capping materials: Mineral trioxide aggregate (MTA), Biodentine (BD) and Tech Biosealer capping (BS). Methods One hundred and five discs of the tested materials were prepared in compliance with the manufacturer’s instructions. The materials' pastes were placed in Teflon molds and allowed to set before testing. The pH and Ca+2 ions were measured by a potentiometric method. Porosity, water sorption, and solubility were calculated through the measurement of initial mass, mass, saturated mass and dry mass. Apatite forming ability was measured by an Environmental Scanning Electron Microscope that was connected to a secondary electron detector for energy dispersive X-ray analysis. Meanwhile compressive strength was measured by a computer controlled universal testing machine. Lap shear strength was measured by computer software on the testing machine. All data were statistically analyzed. Results The tested materials showed Ca ions release and alkalization, which decreased with soaking time. The BD exhibited a very high Ca release at both short (3 h) and long times (28 days). Significant high values of open and apparent porosities, water sorption, and solubility were measured for BS, which was followed by the MTA then BD (P

In this article, the first aerogels synthesis through cross-linked polyacrylamide (PAAm) hydrogel was reported through the use of gamma irradiation technique. Hydrogel obtained from gamma irradiation of acrylamide monomer dissolved in a solution of sodium silicate as a silicon precursor. Various irradiation doses (10 up to 60 kGy) and various acrylamide (AAm) contents (6.25, 9.37, 12.5, and 30%) were utilized in the polymerization process. The polyacrylamide (PAAm) hydrogel loaded with sodium silicate inside is soaked in a solution of CaCl2 and then heated at a temperature of 250 °C for 2 h to provide Ca-silicate aerogels with density around 0.16–0.095 gm/cm3 and porosity of 84–94.8%. Almost all samples of the obtained (Ca-Si) aerogels have porosity >80% and low thermal conductivity (thermal conductivity value around 0.114 and 0.096 W/m.K) at ambient condition. This work discusses the effects of preparation conditions like the gamma-irradiation doses and the total solids content (wt%) of PAAm on the formation of Ca-silicate aerogels. It was found that PAAm plays a crucial role in the thermal conductivity and porosity (%) of the obtained Ca-Si aerogel samples. The increasing of PAAm content (wt%) from 6.25 to 30% increased the pores (v%) from 84 to 90.5% and reduced the thermal conductivity from 0.114 to 0.096 W/(m.K). This is because the presence of PAAm at higher concentrations increases the free volume and reduces interfacial interactions to give a high-porous structure of the Ca-Si aerogel.

In the present paper, the issues of studying the influence of complex activation of grouting fluid on the structure and properties of the hardened cement paste and concrete are considered. The problem is relevant for manufacturing of building materials. In the paper, there was used the method of applying in the concrete mix composition of the elementary chemical substances undergone special physical treatment by means of mechanomagnetic activation. For more profound study of the structure formation processes in the hardened cement paste, the method of differential thermo gravimetric analysis has been used. As the research results have shown, the concrete samples on the activated electrolyte solutions are characterized by improved strength. In addition, on the base of differential thermo gravimetric analysis, it was proven that in the studied samples of the hardened cement paste on the electrolyte solutions activated by the method of mechanomagnetic treatment, the less calcium hydroxide and the more hydrated calcium silicate with amorphous and fine crystalline is formed. The obtained results for cement composites could be applied when manufacturing effective binder for concretes and mortars in the production of building materials and structures.

This work aims to investigate the coexistence of the poly(phospho-siloxo) networks and calcium phosphates on the compressive strengths of the acid-based geopolymers obtained at room temperature. Waste fired brick and phosphoric acid were used as an aluminosilicate and chemical reagent, respectively. Calcium aluminate hydrate was prepared by mixing calcium hydroxide from the calcined eggshell and calcined bauxite. Calcium silicate hydrate was obtained by the mixture of rice husk ash and calcium hydroxide. The molar ratios CaO/Al2O3 and CaO/SiO2 in the calcium aluminate and calcium silicate hydrates are equals to 1.0. The X-ray patterns of the acid-based geopolymers indicate the broad hump structure between 18 and 38°(2θ). In addition to this broad band, those from the mixture of calcium sources show the reflection peaks of monetite and brushite. The compressive strength of the reference is 56.43 MPa. Those obtained with the addition of 10, 20, 40 and 50 g of calcined eggshell are 30.15, 22.85, 21.16 and 13.47 MPa, respectively. The ones from calcium aluminate hydrate are 32.62, 31.58, 17.83 and 16.33 MPa, respectively. Whereas those containing calcium silicate hydrate are 44.02, 42.71, 40.19 and 18.59 MPa, respectively. This work demonstrates that the formation of calcium phosphates in the structure of the acid-based geopolymers decreases the poly(phospho-siloxo) chains and therefore reduces their compressive strengths. The moderate addition of calcium silicate hydrate reduces slightly the compressive strengths of the acid-based geopolymers which can be comparable to the one of CEM II 42.5R.

The effects of the P2O5 and CaF2 contents and the basicity on the viscosity of CaO–SiO2–Al2O3–La2O3 slag systems were investigated using the rotating cylinder method during the continuous cooling process. The structural characteristics of the quenched slag samples were clarified by Fourier transform infrared and Raman spectroscopies. The results showed that the slag viscosity and break temperature gradually increased with increasing P2O5 content from 0 and 2.5 to 5 wt% at each basicity of 0.87, 1.0 or 1.17; meanwhile, the viscosity increased as the P2O5 content increased at a greater level at low basicity. The addition of CaF2 obviously reduced the viscosity and break temperature of slag. The increase in the basicity from 0.87 and 1.0 to 1.17 decreased the viscosity of the slags under the present composition range, but raised the break temperature. The maximum viscosity reduction by the basicity occurred in the slag containing 5 wt% P2O5, while the minimum occurred in the slag containing 5 wt% CaF2. P2O5 acted as a network former in the molten slag and increased the polymerization of the silicate and phosphate complex anions, corresponding to an increase in the slag viscosity. CaF2 played a major role in the depolymerization of the silicate and phosphate complex anions in this study.Kindly check and confirm the edit made in the title.The title was no problem.

Endodontic calcium silicate-based cement is the most used materials in root-end filling and/or repairing perforations. However, the relatively high cost associated with these cement is a drawback that necessitates improvements in their manufacturing process through the development of alternatives. This study used differential scanning calorimetry (DSC) and high-temperature X-ray powder diffraction observations of the tricalcium silicate (C3S) crystalline phase to identify and quantify important parameters of hydration reactions such as the degree of hydration. A C3S reference was prepared with pure chemical reagents to develop a novel biomaterial variety of calcium silicate-based cement which was predefined to preserve the significant properties and clinical applications typical of calcium silicates. A methodology of cycled synthesis was used to obtain almost pure, highly crystalline C3S phase. With temperatures that can reach 1450–1500 °C, the thermal processing of the mixture of raw materials gives rise to thermochemical reactions of the formation of the main phases: 2CaO·SiO2 (C2S), 3CaO·SiO2 (C3S), and 3CaO·Al2O3 (C3A). The formation of the C3S phase is aided by the fusion of calcium aluminates (C3A). The use of Al2O3 and MgO as liquid phase-forming agents and the stabilization of the phases in cooling, allowed the liquid phase to provide the greatest precipitation of the C3S solid phase of interest. The X-ray diffraction confirmed the formation of the highly C3S crystalline phase in the material after cooling at the end of the five thermal cycles. The results obtained indicated that such a material could be derived through bottom-up synthesis routes that aim to attain the proper balance between the C3S phase and the use of other cementitious materials.

The present investigation aimed at developing core–shell structured partially etherified fenugreek seed mucilage (EFSM)-sodium alginate (SA) based microhybrids for controlled delivery of flurbiprofen (FLU) by combined gastroretentive bioadhesion and floating approaches. In this milieu, EFSM (degree of carboxymethyl substitution, 0.71) was firstly synthesized and analyzed through 1H NMR and SEM studies. FLU-loaded EFSM-SA core hybrids were subsequently afforded by Ca2+-induced gelation protocol with and without incorporating low-density additives (such as, sunflower oil and calcium silicate) in the formulations. The core matrices were then coated by bioadhesive guar gum (GG)-SA gel membrane utilizing interfacial complexation technique. The developed microhybrids portrayed outstanding drug entrapping efficiency (DEE, 45–89%) and delayed drug eluting behaviour (Q8h, 56–85%). These attributes were significantly influenced by various formulation variables like polymer-blend (EFSM:SA) ratios, low-density additive types and GG-SA coating inclusion. The drug dissolution profile of the core–shell structured microhybrids (F-7) obeyed zero-order kinetic model and its drug transport was driven by case-II mechanism. The formulation (F-7) also demonstrated excellent gastroretentive characteristics and biodegradability. The molar mass ( $$\overline{\mathrm{M}}$$ c) between crosslinks of microhybrids (F-7) calculated utilizing Flory-Rehner equation was decreased with temperature. Furthermore, the microhybrids were characterized for drug-excipients compatibility, thermal behaviour, drug crystallinity and surface morphology. These novel composite matrices were thus evidenced to be appropriate for controlled intragastric delivery of FLU for inflammation and arthritis management.

Silicate micro- and nano-additives are multifunctional in relation to cement systems. Their application can solve a wide range of technological problems while maintaining the economic efficiency of technical solutions. The effect of silicate additives and fillers is determined by their level of dispersion, due to which the technologies for producing nano- and submicro-sized dispersed materials are being developed. The combination of mechanochemical synthesis of modified calcium hydrosilicates with subsequent thermolysis makes it possible to produce calcium silicate dispersions (SCD), which differ in polymodality of the fractional composition including submicro (10–7–10–6 m) and microdimensional (≥10–6 m) modes. The main element of the technology is the use of modifying carbohydrate, which acts as a stabilizer of hydrated phases of silicates. A comparative study of SCD produced using sucrose (sSCD) and lactose (lSCD) revealed the effect of these carbohydrates on the properties of sSCD and lSCD, as well as their effectiveness as a component of cementitious composite binder. It was found that the level of adsorption of modifying carbohydrate determines the physical properties of SCD (granulometry, specific surface area). The relatively high residual content of free sucrose (0.24%) in the composition of sSCD prevents the consolidation of silicates nanoparticles formed during the thermolysis, causes a high content of submicro sized fractions and a high specific surface area with sSCD (26.3 ± 0.7 m2/g). Lactose is absorbed by the silicate phase; the residual content of free lactose does not exceed 0.028% of lSCD. The low content of stabilizing carbohydrate contributes to the development of nanoparticle consolidation, a decrease in the specific surface area of lSCD to 13.0 ± 0.2 m2/g and content of submicrosized fractions. The residual content of free carbohydrates and particle size characteristics of sSCD and lSCD determine the nature of their influence on Cement-SCD-based concrete setting and hardening. The presence of residual sucrose in the composition of sSCD and fine fractions determines the competitive nature of the processes of retardation of hardening and acceleration of hardening of the cement system due to the nucleation effect, as a result of which the curve of the setting time is extreme. In addition, the inhibitory effect of sucrose reduces the strength of concrete on the 7th day. By the 28th day, the inhibitory effect of sucrose has been overcome, and concrete samples demonstrate an 18% increase in compressive strength with a sSCD content of 30%. The low content of residual free lactose in the composition of lSCD causes the nucleation effect. As a result, there is a monotonous reduction in the setting time of concrete mix with an increase in the content of lSCD in the composition of HF, as well as a significant increase in concrete strength (up to 127%) on the 7th day. At the same time, on the 28th day the strength of concrete increases slightly

Glasses in the system 24.5Na2O·24.5CaO·6P2O5·xSrO·(45-x)SiO2 have been studied in the composition region of x = 0 - 15 mol%. The as prepared glasses are transparent and have an amorphous network structure. On the otherhand, heat treated glasses are transformed to opaque white glass ceramic characterized by their highly crystalline network structure. Crystalline apatite (calcium phosphate, Ca3(PO4)2, wollastonite (calcium silicate, CaSiO3), and strontium calcium phosphate Ca2Sr(PO4)2 are the main well-formed crystalline species played the major role in material bioactivity. Increasing SrO leads to enhancing material crystallite and enhances the hardness of the host glass matrix. The change of XRD spectra, 31P NMR chemical shift and hardness number upon increasing SrO are considered due to modification of the apatit Ca(PO3)2 to involve Sr ions inducing Ca2Sr (PO4)2 apatite one. Such species play the role in enhancing material properties and hardness.

The paper studies the matrix formation of the concrete mix modified by nonstandard particles introduced in the concentration of 0 ≤ k ≤ 0.5 in the initial composition of the dispersed phase. The development of the spatial functional groups in concrete dispersions is identified, which are filled with nonstandard particles with varying degrees. The addition of nonstandard particles to the concrete matrix composition leads to the formation of strong structural bonds due to the particle contacting via the adsorption and diffusion layers appearing during the formation of sub-microcrystalline gel surrounded by newly-formed dispersions (calcium silicate hydrates). This is because the high FeO content in the initial composition of nonstandard particles, which affects the particle adhesion in the dispersed phase. The latter possess the high electrostatic and electromagnetic attraction that generates crystallization centers on the contact surface of interphase boundaries.

This study focuses on organically modifying a layered calcium silicate with two types of organic functional groups to control chemical stability. Solvothermal processing was used to prepare organically modified layered calcium silicates with different contents of aminopropyl and phenyl groups. By-products of polyhedral oligomeric silsesquioxanes derived from organosilanes (Rn-SiO1.5n) were also formed in the sample powders upon preparation with a high initial fraction of phenyltriethoxysilane. The formation of layered calcium silicates modified with both organic groups was confirmed by X-ray diffractometry, nuclear magnetic resonance spectroscopy, Fourier-transform infrared spectroscopy, and Raman spectroscopy. The contents of these organic groups in the samples reflected the molar fractions of silanes in the starting materials. Although all samples readily released calcium and silicate ions into a buffer solution of pH = 7.4 after soaking for 24 h, the amounts of released silicate and calcium ions tended to decrease as the initial molar fraction of phenyl groups was increased up to 75 mol%. The chemical stability of the layered calcium silicates increased with the increase of the hydrophobic functional groups incorporated into their structure. These results indicate the potential for applying these modifications in biomaterials with tunable solubility for the purpose of bone reconstruction.

Author(s): Viseshchitra, P; Ercius, P; Monteiro, PJM; Scott, M; Ushizima, D; Li, J; Xu, K; Wenk, HR | Abstract: © 2020 American Ceramic Society (ACERS) Calcium silicate hydrate (C-S-H), is the principal hydration product of Portland cement that mainly contributes to the physical and mechanical properties of concrete. This paper aims to investigate the three-dimensional structure of C-S-H with Ca/Si ratios of 1.0 and 1.6 at the nanoscale using electron tomography. The 3D reconstructions and selected region of interest analysis confirm that the morphology of both C-S-H materials are foil-like structures. The difference between the two materials is the density of elongated structures. C-S-H with Ca/Si ratio 1.6 is clearly composed of denser particles compared to the other C-S-H material due to overlapping of the foil-like structure. Pore analysis shows that C-S-H 1.0 and C-S-H 1.6 have porosities 69.2% and 49.8% respectively. Pore size distribution also reveals that C-S-H 1.0 has pore size range between 0-250nnm and C-S-H 1.6 between 0-100nnm. The pore network's size of C-S-H 1.0 is significantly larger than 1.6. This study illustrates the capability of using electron tomography to determine the 3D nanoscale structure of cementitious products and to distinguish between C-S-H 1.0 and 1.6.

Development and testing of catalytic filters for partial oxidation of methane to increase hydrogen production in a biomass gasification process constitute the subject of the present study. Nickel, iron and lanthanum were coated on calcium silicate filters via co-impregnation technique, and catalytic filters were characterized by ICP-MS, XPS, XRD, TEM, TGA, TPR and BET techniques. The influences of varying reaction temperature and addition of Fe or La to Ni-based catalytic filters on methane conversion, and hydrogen selectivity have been investigated in view of preliminary results obtained from reactions with 6% methane-nitrogen mixture, and catalytic filters were tested with model biogas mixtures at optimum reaction temperature of each filter which were 750 °C or 850 °C. Approximately 93% methane conversion was observed with nearly 6% methane-nitrogen mixture, and 97.5% methane conversion was obtained with model biogas containing CH4 which is 6%, CO2, CO, and N2 at 750 °C. These results indicate that calcium silicate provides a suitable base material for catalytic filters for partial oxidation of methane and biogas containing methane.

The research presented here investigates the reaction mechanism of wollastonite in situ mineral carbonation for carbon dioxide (CO2) sequestration. Because wollastonite contains high calcium (Ca) content, it was considered as a suitable feedstock in the mineral carbonation process. To evaluate the reaction mechanism of wollastonite for geological CO2 sequestration (GCS), a series of carbonation experiments were performed at a range of temperatures from 35 to 90 °C, pressures from 1500 to 4000 psi, and salinities from 0 to 90,000 mg/L NaCl. The kinetics batch modeling results were validated with carbonation experiments at the specific pressure and temperature of 1500 psi and 65 °C, respectively. The results showed that the dissolution of calcium increases with increment in pressure and salinity from 1500 to 4000 psi and 0 to 90000 mg/L NaCl, respectively. However, the calcium concentration decreases by 49%, as the reaction temperature increases from 35 to 90 °C. Besides, it is clear from the findings that the carbonation efficiency only shows a small difference (i.e., ±2%) for changing the pressure and salinity, whereas the carbonation efficiency was shown to be enhanced by 62% with increment in the reaction temperature. These findings can provide information about CO2 mineralization of calcium silicate at the GCS condition, which may enable us to predict the fate of the injected CO2, and its subsurface geochemical evolution during the CO2-fluid-rock interaction.

Mechanical properties and durability of cement-based materials are largely affected by pore structures. This paper provides an overview of several experimental techniques to characterize pore size distribution and specific surface area, with focus on pores in calcium silicate hydrates. The reviewed experimental techniques are nitrogen and water vapor sorption isotherm, proton nuclear magnetic resonance (1H-NMR) and small-angle scattering (SAS). Different pretreatment methods are compared for sorption measurements. Pore size distribution and specific surface area are analyzed using data from different methods to understand difference and consistency of these methods. It is found that pore size distribution calculated from sorption isotherm is very sensitive to adsorption model. Though specific surface areas from different techniques are quite different from each other, they are all able to detect the microstructural alteration due to long-term drying.

The evolution of calcium silicate based cements in the field of dentistry has been rewarding. It offers a plethora of advantages with respect to physicochemical and biological properties. How-ever, the extended setting time and limited antibacterial activity in these cements is quite a concern. This study aimed to develop a fast-setting nanoparticle incorporated root-end filling material for use after periapical surgeries. With the incorporation of the silver nanoparticles, and using calcium chloride as the liquid component, the desirable study outcome was achieved. The set-ting time was significantly reduced when compared to the commercially available root-end filling material

The harm caused by mine tailings has become increasingly problematic in recent years, so efforts are needed to dispose of or reutilize them in environmentally friendly ways. The objective of the present study was to find out if the hydration properties of muscovite contained in mine tailings are suitable for it to be used as a pozzolan in cement, after undergoing mechanical activation. Aqueous suspensions of mechanically activated muscovite were blended with 10, 20, or 30 wt.% calcium oxide and then allowed to harden. The hardened paste samples were analyzed by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS) techniques. The results revealed that the mechanically activated muscovite exhibited pozzolanic reaction activity in the alkaline environment provided by calcium oxide, and the activated muscovite possessed a capacity to react with calcium hydroxide to form hydration products. The calcium oxide content affected significantly the quantities and kinds of hydration products, non-evaporable water content, and the compressive strength development of the paste samples. The hydration products of the 10% calcium oxide-activated, mechanically activated muscovite pastes were Al-containing hydrated calcium silicate (C-A-S-H) gel, stratlingite, and, upon addition of 20% and 30% calcium oxide, Ca-Al hydrotalcite-like (Ht) phases. The present study was helpful in evaluating the hydration properties of the mechanically activated muscovite and also provided a research basis for evaluating the hydration properties of mine tailings containing muscovite after mechanical activation. The results provided a theoretical basis for muscovite-containing mine tailings to be used as a cement additive, and was conducive to the large-scale utilization of mine tailings.

Bioceramics have been widely used for many years to restore and replace hard tissues including bones, teeth and mineralized matrices such as calcified cartilages at osteochondral interfaces, mainly because of their physicochemical similarity with these tissues. Calcium silicate based bioceramics have been shown to possess high bioactivity due to having high apatite-forming ability and stimulating cell proliferation, as well as biodegradability at rates appropriate to hard tissue regeneration. The outstanding biological properties of these ceramics have made them the most studied hard tissue engineering biomaterials along with calcium phosphates and bioactive glasses. Baghdadite is a calcium silicate containing zirconium ions which promotes the proliferation and differentiation of human osteoblasts and consequently increases mineral metabolism and ossification. Recently, it has attracted considerable attention in academic community and widely studied in the form of porous scaffolds, coatings, bone cement and void fillers, microspheres and nanoparticles mostly in orthopedic, dental and maxillofacial applications. This review paper is aimed to summarize and discuss the most relevant studies on the mechanical properties, apatite formation ability, dissolution behavior, and in vitro and in vivo biological properties of baghdadite as a biomaterial for hard tissue regeneration applications.

The effects of magnesium carbonate on the setting time and compressive strength of Portland cement paste were studied when the content of magnesium carbonate was 0wt%, 0.5wt%, 1wt%, 2wt%, and 3wt% by the weight of cement. The influence mechanism was analyzed through combining with the tests of hydration heat, X-ray diffraction (XRD), differential thermal analysis-thermogravimetric analysis (DTA-TG), and scanning electron microscope (SEM). The results show that magnesium carbonate makes the setting time of cement paste shorten, and makes the compressive strengths of cement paste increase at 1 day and 7 days, but decrease at 28 days. The testing results of the heat of hydration, XRD, SEM, and DTA-TG show that magnesium carbonate promotes the formation of Ettringite (AFt) and the hydration of calcium silicate in the early stage when its content is less than 1wt%, but the addition of magnesium carbonate is unfavorable to the later hydration of Portland cement. Based on the above analysis, it is suggested that the content of magnesium carbonate is not more than 1wt%, which has good reference value for using magnesium carbonate to prepare early strength agent for cement paste.

Novel tamarind gum (TG) or carboxymethyl tamarind gum (CMTG) blended diethanolamine-functionalized pectin (DFP) based hydrogels reinforced with calcium silicate (CS) were developed for sustained delivery of rutin (RUT). The DFP (DA, 48.7%) and CMTG (DS, 50.0%) were initially synthesized and analyzed through 1H-NMR, FTIR, XRD and DSC studies. RUT-loaded hybrid hydrogels were subsequently afforded by Ca2+-induced gelation protocol. The hydrogels portrayed acceptable RUT entrapping efficiency (DEE, 29–43%), delayed eluting behaviour (Q6h, 65–100%) and variable swelling at 6 h (16–172%), which were significantly influenced by formulation variables. The RUT dissolution profile of the optimized hydrogels (F-5) obeyed Korsmeyer–Peppas kinetic model with anomalous transport driven mechanism. These matrices also demonstrated excellent mucoadhesion property and biodegradability. Furthermore, the hydrogels revealed their smooth but distorted surface morphology and drug-carrier compatibility with attenuated RUT crystallinity. These hydrogels matrices were thus evidenced to be appropriate for the delivery of hydrophobic RUT in its solubilised form.

Sol-gel processing pathways allow us to develop materials with specific chemical compositions, structures, and microstructures starting from small molecule precursors in the solution phase. In thes...

A new synthetic procedure is described for the synthesis of calcium silicate derivatives, using natural resources such as eggshell (ES) for calcium and oil palm leaves (OPL) for silica, which do not require prepurification. The reaction is performed by directly converting two weight ratio of the precursors, ES:3OPL and ES:6OPL, to dried-powder form by heat treatment at 900 °C for two hours. The results demonstrate that the concentration of the precursors has an effect on the morphology and crystallinity of the calcium silicate derivatives, mainly Ca2SiO4 and CaSiO3. X-ray diffraction results reveal that the reaction product obtained using a 1:3 ratio is quite pure, and mainly consisted of calcium silicate in the form of Ca2SiO4. The CaSiO3 was also identified in ES:6OPL, together with a small amount of excess non-reacted crystalline silica. Furthermore, a scanning electron microscopy analysis shows that both reaction products have a coarse surface. Copyright © 2020 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

The formation and transition of calcium aluminate and calcium silicate compounds from pre-synthesized mullite in low-calcium system were systematically studied by solid-state reaction at 1350–1500 °C using XRF, XRD, FTIR, SEM and PSD methods. Ca3Al2O6, Ca12Al14O33, CaAl2O4, Ca2SiO4 and Ca2Al2SiO7 can form via direct reaction of mullite with CaO at the beginning of the reactions, then Ca12Al14O33 and Ca3Al2O6 react with mullite to form CaAl2O4 and Ca2SiO4, and finally Ca2Al2SiO7 reacts with CaO to generate Ca2SiO4 and calcium aluminate compounds as the sintering process proceeds. Elevating the sintering temperature is in favor of the formation of Ca12Al14O33, Ca3Al2O6 and Ca2Al2SiO7 at the initial reaction stage, but Ca2Al2SiO7 cannot totally transform to calcium silicate and calcium aluminate compounds in the low-calcium system, which deteriorates the pulverization performance of the final products. Increasing the calcium dosage accelerates the transformation of Ca2Al2SiO7 to Ca12Al14O33, CaAl2O4 and Ca2SiO4, which enhances the pulverization performance. If the CaO/Al2O3 molar ratio exceeds 1.4, Ca3Al2O6 will generate by the reactions of pre-formed CaAl2O4 and Ca12Al14O33 with excessive CaO.

Ferrous calcium silicate (FCS) slags are reported to have high potential for use in the copper converting process. However, no phase equilibrium study has been carried out under a simulated converting gas atmosphere in the presence of SO2. In this study, under accurately controlled P(SO2) 0.4 atm and P(O2) 10−6 atm, the phase equilibria of FCS slags in a liquid/spinel/white metal/gas system were investigated for the copper converting process. The liquidus temperatures of slags in the Fe-Ca-Cu-Si-S-O system were quantified as well as the solid solubilities of Cu2O in the spinel phase. The experimental results were compared with the FactSage predictions, which provided clues for further improvement of the thermodynamic modelling. The applications of the FCS slags were further discussed and compared with iron silicate slags. The results obtained will contribute to slag development for converting operations and thermodynamic calculations.

Most porous materials with high specific surface area and diverse internal structures possess good adsorption ability. In this work, a tremella-like mesoporous calcium silicate hydrate (CSH) with high adsorption capacity was successfully prepared via a facile hydrothermal method. The adsorption effect and adsorption mechanism of the as-prepared calcium silicate hydrate (AP-CSH) towards formaldehyde from water were investigated systematically. Results indicate that AP-CSH has high Ca/Si ratio (1.95), large specific surface area (122.83 m2 g−1) and exhibits excellent adsorption capacity. The results of batch adsorption experiments show that AP-CSH can remove formaldehyde from water rapidly and effectively with the maximum removal efficiency of 98.94%. The adsorption process agrees well with the pseudo-second-order and Freundlich isotherm model. Furthermore, regeneration can be achieved by simply immersing AP-CSH in absolute ethanol and the removal efficiency can still reach about 99.50% after five cycles. The adsorption mechanism was also studied by experimental analyses and molecular dynamics simulation. Both experimental results and theoretical simulation support that formaldehyde adsorption over AP-CSH belongs to chemical adsorption.