Preparation of spray-dried microparticles using Gelucire 44/14 and porous calcium silicate or spherical microcrystalline cellulose to enhance transport of water-insoluble pranlukast hemihydrate across Caco-2 monolayers

The aim of this work was to prepare spray-dried microparticles using Gelucire®44/14 (GLC) and porous calcium silicate (FLR) or spherical crystalline cellulose (M06) to enhance transport of poorly water-soluble pranlukast hemihydrate (PLH) across Caco-2 monolayers. FLR or M06 were added to the PLH–GLC aqueous mixture prepared by adding distilled water at 60 °C to a melted mixture of PLH/GLC (1/1) at a PLH–GLC/carrier ratio of 1/1 or 1/17. Spray-dried FLR microparticles have the PLH–GLC solid dispersion (SD) in their pores and spray-dried M06 microparticles have the PLH–GLC SD on their surface. The dissolutions of PLH from the spray-dried FLR (SD/FLR = 1/1), spray-dried M06 (SD/M06 = 1/1), and spray-dried M06 (SD/M06 = 1/17) microparticles in Tween 80 aqueous solution were markedly fast. The transport of PLH from the spray-dried FLR (SD/FLR = 1/1) across Caco-2 monolayers was hardly observed. The transport of PLH across Caco-2 monolayers from the spray-dried M06 (SD/M06 = 1/17) increased with time, and the transport was significantly higher compared to that from PLH powder. The addition of polyethylene glycol 1500 into GLC of the spray-dried M06 was effective to increase the transport of PLH across Caco-2 monolayers. Spray-dried microparticles of PLH using GLC and M06 are a feasible means of enhancing transport across Caco-2 monolayers.     

Rheological properties and spray-drying behaviors of nano-SiC based aqueous slurry

The nano-SiC based aqueous slurry with 25 wt% solid content was prepared by using β-SiC nanopowder as matrix phase, TiN nanopowder as toughening phase, and Y₃Al₅O₁₂ sol as dispersion medium. The rheological properties and spray-drying behaviors of the aqueous slurry were investigated. The nano-SiC based aqueous slurry had better stability, dispersion and rheological property with a typically shear thinning. The SiC and TiN nanoparticles were “parceled” or “fixed” by the Y₃Al₅O₁₂ sol with network structure, which constructed a stable dispersing system. After spray-drying of this slurry, the nano-SiC based spray-dried granules had high loose density, low repose angle and homogenous compositions distribution. It was beneficial for preparing SiC-based ceramic nanocomposite.     

The hydration and microstructure of ultra high-strength concrete with cement–silica fume–slag binder

This study investigated the flowability, compressive strength, heat of hydration, porosity and calcium hydroxide content of ultra-high-strength concrete (UHSC) with cement–silica fume–slag binder at 20 °C. The composition of the binder was designed using seven-batch factorial design method. The relationships between the binder composition and the properties were expressed in contours. Results showed that proper silica fume content could improve the flowability and compressive strength of UHSC, reduce the porosity and calcium hydroxide content of UHSC. Slag reduced the flowability, compressive strength, porosity, and calcium hydroxide content of UHSC to certain extent. The silica fume and slag demonstrated positive synergistic effects on the flowability and 3 d compressive strength, but have negative synergistic effects on the total heat of hydration, hydration heat when the time is infinitely long(P₀), 56 d compressive strength, porosity and calcium hydroxide content of UHSC.     

Compressive strength and microstructural characteristics of class C fly ash geopolymer

Geopolymers prepared from a class C fly ash (CFA) and a mixed alkali activator of sodium hydroxide and sodium silicate solution were investigated. A high compressive strength was obtained when the modulus of the activator viz., molar ratio of SiO₂/Na₂O was 1.5, and the proper content of this activator as evaluated by the mass proportion of Na₂O to CFA was 10%. The compressive strength of these samples was 63.4 MPa when they were cured at 75 °C for 8 h followed by curing at 23 °C for 28 d. In FTIR spectroscopy, the main peaks at 1036 and 1400 cm^?1 have been attributed to asymmetric stretching of Al–O/Si–O bonds, while those at 747 cm^?1 are due to the Si–O–Si/Si–O–Al bending band. The main geopolymeric gel and calcium silicate hydrate (C–S–H) gel co-exist and bond some remaining unreacted CFA spheres as observed in XRD and SEM–EXDA. The presence of gismondine (zeolite) was also observed in the XRD pattern.     

Synthesis and characterization of anatase photocatalyst powder from sodium titanate compounds

The synthesis of anatase photocatalyst powder from sodium titanate compounds prepared from rutile and sodium carbonate powder was studied. The sodium titanate compounds were derived from the solid-state reactions of three different (1:4, 1:1.58 and 1:0.73) (m/m) ratios of TiO₂:Na₂CO₃ at 850 °C. Then, the powder was dissolved in 5 M H₂SO₄ solution, filtered, washed, dried and calcined at 400, 500 or 600 °C for 2 h. The effects of processing parameters on the resultant phase structure, crystallite size, morphology and the surface area of the synthesized powders were investigated. It was found that the anatase powder with a crystallite size of about 102 nm and a specific surface area of 16.7 m²/g synthesized from sodium titanate compounds with a 1:1.58 (m/m) ratio of TiO₂:Na₂CO₃ and calcined at 600 °C showed the best photocatalytic activity to degrade of methylene blue in aqueous solution under UV irradiation.     

Investigation of UV-photon induced hydrophilicity of titanium ion-implanted soda-lime silicate glasses

The UV-induced wetting effect on titanium oxide surface is well-known; however, the UV-induced hydrophilicity of titanium implanted soda-lime silicate glass has not been investigated. Hence the contact angle of water droplet under the indoor fluorescent lights on titanium-ion implanted soda-lime silicate glasses was investigated. The silicate glasses were implanted by MEVVA ion implanter by 40 keV titanium ions with a fluence of 10¹⁵ ions cm^?2. The contact angle, the chemical bonding environment, and surface morphologies were examined. Results show the formation of TiO₂, the increase of surface roughness, and the reduction of the contact angle after the ion implantation. Further enhancement of hydrophilicity after the 254 nm pre-UV irradiation for 1 h on the implanted sample surface was observed. The enhancement of the wetting effect after ion implantation could be attributed to rougher TiO₂ content surface. However, according to the mechanisms of UV photo-induced hydrophilicity on TiO₂ proposed previously, the enhancement of hydrophilicity of titanium implanted surface with and without 254 nm pre-photon radiation can be attributed to not only the reduction of hydrocarbon on surface during the UV radiation but also to the oxygen vacancies produced by 254 nm UV photon irradiation.     

Conversion of high silicon fly ash to Na-P1 zeolite: Alkaline fusion followed by hydrothermal crystallization

In this research, we converted high silicon fly ash to a high ion-exchange capacity zeolite using a two stages conversion process. Alkaline fusion was applied to collapse the fly ash crystalline phases and release Si content. Then Si/Al ratio of the synthesis sol adjusted with appropriate amount of industrial grade materials. A synthesis solution with the molar ratio of 2.2 SiO₂:Al₂O₃:5.28 Na₂O:106 H₂O was hydrothermally crystallized to Na-P1 zeolite at 120 °C for 4 h. The as-synthesized zeolite characterized by means of X-ray diffraction, infrared spectroscopy, scanning electron microscopy and thermal analysis. Cation exchange capacity of the zeolite was determined using ammonium acetate method. The zeolitization remarkably improved the cation exchange capacity of the final product (e.g. 3.23 meq/g in comparison to the raw fly ash ～0.005–0.02 meq/g).Due to the high CEC and sufficient whiteness of the final product, we suggest that the as-synthesized zeolitic powder is a potential candidate as a detergent builder.     

Fabrication and characterization of Ag/calcium silicate core-shell nanocomposites

The Ag/calcium silicate nanocomposite with core-shell nanostructure has been successfully synthesized using Ag solution, Ca(NO₃)₂·4H₂O and Na₂SiO₃·9H₂O in ethanol/water mixed solvents at room temperature for 48 h. Ag solution was previously prepared by microwave-assisted method in ethylene glycol (EG) at 150 °C for 10 min. The nanocomposites consisted of Ag core and an amorphous calcium silicate shell. The XRD and EDS results confirmed that the product was the Ag/calcium silicate nanocomposite. The TEM micrographs indicated that the Ag/calcium silicate nanocomposite was core-shell nanoparticles. The effects of Ca(NO₃)₂·4H₂O and Na₂SiO₃·9H₂O concentration on the shells of Ag/calcium silicate nanocomposite were investigated. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and energy-dispersive X-ray spectra (EDS). This method is simple, fast and may be extended to the synthesis of the other kinds of core-shell nanocomposites.     

A facile method for production of high-purity silica xerogels from bagasse ash

In this paper, we systematically report the synthesis of mesoporous silica xerogels in high purity from bagasse ash. The bagasse ash was chosen as the raw material due to its availability and low-price, and environmental considerations also were important. Silica was extracted as sodium silicate from bagasse ash using NaOH solution. The sodium silicate was then reacted with HCl to produce silica gel. To produce high-purity silica xerogels, three different purification methods were investigated, i.e., acid treatment, ion exchange treatment, and washing with de-mineralized water. We were able to produce high-purity silica (>99 wt.%) by washing the produced gels with either de-mineralized water or with ion exchange resin. The specific surface area of the prepared silica xerogels ranged from 69 to 152 m² g^?1 and the pore volume ranged from 0.059 to 0.137 cm³ g^?1. The pore radii were 3.2–3.4 nm, which indicated that the silica xerogels was mesoporous. From the adsorption characterization, it was obvious that adsorptive capacity was better for high-purity silica xerogels compared with low-purity. The maximum adsorption capacity by high-purity silica xerogel was 0.18 g-H₂O/g-SiO₂. Finally, we demonstrate the potential of bagasse ash for mesoporous silica production with its excellent adsorptive capacity that makes it beneficial as an environmental solution.     

Alkali-activated complex binders from class C fly ash and Ca-containing admixtures

Processes that maximize utilization of industrial solid wastes are greatly needed. Sodium hydroxide and sodium silicate solution were used to create alkali-activated complex binders (AACBs) from class C fly ash (CFA) and other Ca-containing admixtures including Portland cement (PC), flue gas desulfurization gypsum (FGDG), and water treatment residual (WTR). Specimens made only from CFA (CFA100), or the same fly ash mixed with 40 wt% PC (CFA60–PC40), with 10 wt% FGDG (CFA90–FGDG10), or with 10 wt% WTR (CFA90–WTR10) had better mechanical performance compared to binders using other mix ratios. The maximum compressive strength of specimens reached 80.0 MPa. Geopolymeric gel, sodium polysilicate zeolite, and hydrated products coexist when AACB reactions occur. Ca from CFA, PC, and WTR precipitated as Ca(OH)₂, bonded in geopolymers to obtain charge balance, or reacted with dissolved silicate and aluminate species to form calcium silicate hydrate (C-S-H) gel. However, Ca from FGDG probably reacted with dissolved silicate and aluminate species to form ettringite. Utilization of CFA and Ca-containing admixtures in AACB is feasible. These binders may be widely utilized in various applications such as in building materials and for solidification/stabilization of other wastes, thus making the wastes more environmentally benign.     

Facile route to obtain a highly bioactive SiO2–CaO–Na2O–P2O5 crystalline powder

This work describes a facile method to obtain highly bioactive crystalline powders of the SiO₂–CaO–Na₂O–P₂O₅ system using a simple route: solid state reaction. Success in obtaining the highly bioactive crystal phase of interest (sodium calcium silicate Na₂Ca₂Si₃O₉ containing phosphorus) involves heating the starting reactant powder mixture under an oxidizing atmosphere for 480 min in the temperature range 950–1000 °C. Despite a significant loss of phosphorus at heat treatment temperatures above 950 °C, the resulting Na₂Ca₂Si₃O₉ crystal phase is thermally stable up to 1100 °C. Longer treatment times favor the formation of a secondary phase (sodium calcium phosphate NaCaPO₄), which, according to recent studies, further increases the bioactivity of a similar material. Finally, in vitro bioactivity tests in acellular simulated body fluid (SBF) of a powder containing only the Na₂Ca₂Si₃O₉ phase has shown behavior similar to that of Biosilicate® — an ~ 99.5% crystalline glass–ceramic whose outstanding characteristics of interaction with living tissue have already been reported in the literature.     

Influence of raw powder preparation routes on properties of hydroxyapatite fabricated by 3D printing technique

A comparison between two routes of raw powder preparation, namely spray drying and grinding, for 3D printing of hydroxyapatite was carried out. Hydroxyapatite particles prepared by the spray drying technique were spherical in shape whereas the grinding route gave irregular-shaped agglomerates. Spray-dried powders had higher tap density than milled powders, however milled powders yielded 3DP specimens with greater green density and strength. After sintering at 1300 °C for 1 and 5 h, samples fabricated from milled powders showed a 32% higher in sintered density, a 20% lower in porosity and approximately two times higher flexural modulus and strength than samples fabricated from spray-dried powders. This difference was related to the better packing characteristics of milled powders which promoted improved inter- and intra-particle densification during high temperature sintering compared to the spray-dried powders which yielded only high intra-particle densification, but lower inter-particle densification.     

Porous β-NaCaPO4 containing borate glass-ceramic scaffolds

A novel β-NaCaPO₄ containing borate glass-ceramic is prepared. Two porous glass-ceramic scaffolds are prepared by binding particles with the size of 200–300 μm by 5 wt.% sodium silicate solution and 2 wt.% chitosan solutions, respectively. The reaction of the scaffolds in the SBF solution is characterized by weight loss analysis, XRD, FTIR, and SEM. The same is done to the 45S5 glass scaffolds as comparison. XRD and FTIR indicate that the carbonate hydroxyapatite has formed more rapidly on the borate glass-ceramic scaffolds. The carbonated hydroxyapatite depositing on chitosan binding scaffolds has lower crystallization degree than that on sodium silicate binding scaffolds and is similar to that of the human bone, which makes the chitosan binding scaffolds a good potential prospect in the field of tissue engineering.     

Characteristics of Inconel Powders for Powder-Bed Additive Manufacturing

In this study, the flow characteristics and behaviors of virgin and recycled Inconel powder for powder-bed additive manufacturing (AM) were studied using different powder characterization techniques. The results revealed that the particle size distribution (PSD) for the selective laser melting (SLM) process is typically in the range from 15 μm to 63 μm. The flow rate of virgin Inconel powder is around 28 s·(50 g)⁻¹. In addition, the packing density was found to be 60%. The rheological test results indicate that the virgin powder has reasonably good flowability compared with the recycled powder. The inter-relation between the powder characteristics is discussed herein. A propeller was successfully printed using the powder. The results suggest that Inconel powder is suitable for AM and can be a good reference for researchers who attempt to produce AM powders.     

Workability and strength of coarse high calcium fly ash geopolymer

In this paper, the basic properties viz., workability and strength of geopolymer mortar made from coarse lignite high calcium fly ash were investigated. The geopolymer was activated with sodium hydroxide (NaOH), sodium silicate and heat. The results revealed that the workable flow of geopolymer mortar was in the range of 110 ± 5%–135 ± 5% and was dependent on the ratio by mass of sodium silicate to NaOH and the concentration of NaOH. The obtained compressive strength was in the range of 10–65 MPa. The optimum sodium silicate to NaOH ratio to produce high strength geopolymer was 0.67–1.0. The concentration variation of NaOH between 10 M and 20 M was found to have a small effect on the strength. The geopolymer samples with high strength were obtained with the following practices: the delay time after moulding and before subjecting the sample to heat was 1 h and the optimum curing temperature in the oven was 75 °C with the curing duration of not less than two days.     

Recovery of high surface area mesoporous silica from waste hexafluorosilicic acid (H2SiF6) of fertilizer industry

In this article we report recovery of mesoporous silica from the waste material (hexafluorosilicic acid) of phosphate fertilizer industry. The process involves the reaction of hexafluorosilicic acid (50 ml, 24 wt% H₂SiF₆) and 100 ml, 0.297 M Na₂CO₃ to generate the alkaline aqueous slurry. Silica was separated from the slurry by filtration and the sodium fluoride was extracted from the aqueous solution by evaporation method. The obtained mesoporous silica was characterized by N₂ absorption/desorption (BET), thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscope (SEM), and EDS. The results confirm that the separation of silica and NaF was successful and the final products have high purity. The silica product was found to have an average pore diameter of 4.14 nm and a high surface area (up to 800 m²/g). The process reported in this study may significantly reduce the release of hazardous materials into the environment and it might confer economic benefits to the responsible industries.     

Combustion synthesis of WC powder in the presence of alkali salts

This paper deals with the formation of tungsten carbide sub-micrometer powders from WO₃ + Mg + C + sodium salts (NaCl, Na₂CO₃) system by combustion synthesis technique. The powders were characterized by XRD and FESEM. X-ray data demonstrate the superiority of the NaCl + Na₂CO₃ combined mixture in the WC formation process. Single phase, sub-micrometer WC powders were synthesized at temperatures as low as 1600 °C. The roles of sodium salts in combustion process were discussed and chemical mechanism of WC formation was proposed. WC powder produced by salt-assisted combustion synthesis technique has a size 0.2–3 μm, crystalline shape and low agglomeration degree.     

Sulfate resistance of cement-reduced eco-friendly concretes

Two newly developed cement-reduced eco-friendly concretes with high limestone powder content and low water/powder ratio were tested for sulfate resistance. Mortar samples with a paste composition of eco- as well as conventional concretes were immersed in 30 g l⁻¹ Na₂SO₄ and saturated Ca(OH)₂ reference solutions for 200 days at 8 °C. To evaluate the reaction mechanisms of progressing sulfate attack a combined approach of mechanical, mineralogical, and microstructural methods was applied.Gypsum and bassanite neo-formations related linearly to the expansion during sulfate exposure, except for one sample where ettringite co-precipitated. Thaumasite formation was not observed in spite of potentially favorable conditions. This is considered to be related to the evolution of the experimental solutions, kinetic effects, and the competing formation of CaCO₃ polymorphs triggered by the usage of superplasticizer. Both eco-friendly mixes exhibited a better sulfate resistance than their corresponding reference samples and are therefore suggested to be applicable in low sulfate-loaded environments according to DIN EN 206-1. Eco-friendly concrete based on CEM III/B performed superior against sulfate attack and is expected to withstand even severe sulfate exposure despite a much higher water/cement ratio than required by the standard.     

Improving core bond strength and dimensional stability of particleboard using polymer powder in core layer

Low density polyethylene powder (LDPE) was used as polymer binder in the core layer of three layer particleboard. In the first phase, six levels of the LDPE powder (5–30 wt.%) based on the composition by weight, were mixed with the core particles with 8 wt.% urea–formaldehyde (UF) resin. In the second phase, the LDPE powder content was kept constant at 10 wt.% in all treatments and the UF resin content applied to the core layer was decreased gradually from 8 to 4 wt.%. Thickness swelling and water absorption of the particleboards significantly decreased with increasing the LDPE content in the core layer. Similarly, incorporation of the LDPE powder into the core layer of the particleboard greatly improved internal bond strength. The flexural properties of the particleboards, the modulus of rupture (MOR) and modulus of elasticity (MOE), were positively affected by increasing LDPE content up to 10 wt.% but the further increment of the LDPE decreased the MOR and MOE. The UF resin content can be reduced in the core layer of the particleboard as a function of increasing the LDPE powder.     

Anomalous dissolution property enhancement of naringenin from spray-dried particles with α-glucosylhesperidin

Spray-dried particles were prepared with α-glucosyl hesperidin (Hsp-G), a hesperidin derivative with enhanced water solubility, to improve the solubility profile of naringenin (NRG). Naringenin was used as a model hydrophobic polyphenol. The spray-dried sample of NRG in the presence of Hsp-G formed 3–4 μm spherical particles. Those particles showed a halo pattern in powder X-ray diffractometry, indicating the amorphous state of NRG in the solid dispersion with Hsp-G. Interestingly, the obtained powders dissolved immediately into the aqueous media and demonstrated dramatically high apparent solubility, over 60-fold greater than NRG crystals, when the loading ratio of NRG/Hsp-G was 1/20. The apparent solubility of NRG increased in proportion to the amount of Hsp-G loaded (R² > 0.99). These results suggested that a specific molecular interaction, a micelle-like structure in which NRG was incorporated with Hsp-G molecules, was formed in spray-dried particles, resulting in the anomalous enhancement in the solubility of NRG.