Calcium Silicate Particles Research Articles

Tribological and mechanical behaviour of dual-particle (nanoclay and CaSiO3)-reinforced E-glass-reinforced epoxy nanocomposites

An E-glass-reinforced epoxy-based nanocomposite containing organomodified nanoclay (15–20 nm) and calcium silicate particles (75–149 μm) was developed through mechanical shearing mixing and hand layup techniques. Three weight fractions (2, 3 and 4%) of nanoclay were selected to study the effects of nanoclay on mechanical and wear behaviour of nanocomposites. Tensile and flexural properties of nanocomposites were evaluated and compared. The wear properties were evaluated for three speed (3.14, 4.19 and 5.24 m s−1) and load (20, 50, and 80 N) conditions based on a design of experiment (L16 matrix) concept. The wear loss results were statistically analysed to study the significance of load, speed and nanoclay content. The morphologies of wear surface and fracture surface were examined with the aid of a scanning electron microscope (SEM) to identify the wear and fracture mechanisms. It was found that the wear loss increases with increasing nanoclay amount due to the particle agglomeration effects. Statistical analysis determines that the load is the most significant parameter affecting the wear resistance of nanocomposites. The mean and S/N ratio analyses rank the parameters significance in affecting wear resistance as follows: load > nanoclay content > speed. The wear mechanisms of nanocomposites are complex due to the observation of multiple features such as fibre thinning, matrix wear and fibre/matrix debonding as against abrasive wear in the pure epoxy. Tensile and flexural test results show that a good dispersion of nanoclay is achieved with 2 wt% amount in epoxy-based nanocomposites. The mechanical properties degrade above 2 wt% due to the excessive reinforcement, uneven distribution and the particle agglomeration effects. Fractography studies of tension-failed samples show that pure epoxy resin fails by multimode gauge explosive mode, whereas nanocomposites fail mainly by the matrix/fibre interface failure and fibre breakages.

In vitro degradation and surface bioactivity of iron-matrix composites containing silicate-based bioceramic

Iron-matrix composites with calcium silicate (CS) bioceramic as the reinforcing phase were fabricated through powder metallurgy processes. The microstructures, mechanical properties, apatite deposition and biodegradation behavior of the Fe-CS composites, as well as cell attachment and proliferation on their surfaces, were characterized. In the range of CS weight percentages selected in this study, the composites possessed compact structures and showed differently decreased bending strengths as compared with pure iron. Immersion tests in simulated body fluid (SBF) revealed substantially enhanced deposition of CaP on the surfaces of the composites as well as enhanced degradation rates as compared with pure iron. In addition, the composite containing 20% CS showed a superior ability to stimulate hBMSCs proliferation when compared to pure iron. Our results suggest that incorporating calcium silicate particles into iron could be an effective approach to developing iron-based biodegradable bone implants with improved biomedical performance.

Feasibility of Carbonation Reactions to Control Permeability in the Deep Subsurface

Abstract Injection and subsequent carbonation of calcium and magnesium silicate particles are proposed here as a novel strategy to grout fractures or pores and decrease fluid conductivity in the deep subsurface by taking advantage of favorable reaction kinetics. This approach could be used to manage legacy environmental risks from energy extraction techniques such as hydraulic fracturing of shale formations. To evaluate this approach, we studied the carbonation of wollastonite (CaSiO3) in the presence of ground shale under temperature and pressure (T/P) conditions broadly representative of the gas-producing regions of the Marcellus formation in the eastern United States. Effect of calcite (CaCO3) precipitation on shale particle morphology and interparticle pore structures was investigated and impacts on permeability were evaluated using batch and column experiments. Formation T/P were positively correlated with extent of carbonation. Side reactions involving calcium ions and passivation by amorphous silic...

Substantial enhancement of corrosion resistance and bioactivity of magnesium by incorporating calcium silicate particles

We discovered that calcium silicate is an effective reinforcement phase to improve the corrosion resistance, mechanical strength and biological performance of Mg or Mg-based alloys to overcome their major drawbacks for orthopedic implant applications.

Human urine-derived stem cells can be induced into osteogenic lineage by silicate bioceramics via activation of the Wnt/β-catenin signaling pathway

Human urine-derived stem cells (USCs) have great application potential for cytotherapy as they can be obtained by non-invasive and simple methods. Silicate bioceramics, including calcium silicate (CS), can stimulate osteogenic differentiation of stem cells. However, the effects of silicate bioceramics on osteogenic differentiation of USCs have not been reported. In this study, at first, we investigated the effects of CS ion extracts on proliferation and osteogenic differentiation of USCs, as well as the related mechanism. CS particles were incorporated into poly (lactic-co-glycolic acid) (PLGA) to obtain PLGA/CS composite scaffolds. USCs were then seeded onto these scaffolds, which were subsequently transplanted into nude mice to analyze the osteogenic differentiation of USCs and mineralization of extracellular matrix formed by USCs in vivo. The results showed that CS ion extracts significantly enhanced cell proliferation, alkaline phosphatase (ALP) activity, calcium deposition, and expression of certain osteoblast-related genes and proteins. In addition, cardamonin, a Wnt/β-catenin signaling inhibitor, reduced the stimulatory effects of CS ion extracts on osteogenic differentiation of USCs, indicating that the observed osteogenic differentiation of USCs induced by CS ion extracts involves Wnt/β-catenin signaling pathway. Furthermore, histological analysis showed that PLGA/CS composite scaffolds significantly enhanced the osteogenic differentiation of USCs in vivo. Taken together, these results suggest the therapeutic potential of combining USCs and PLGA/CS scaffolds in bone tissue regeneration.

Preparation and characterization of mesoporous calcium silicate grafted polypropylene non-woven fabric

Calcium silicate particles containing mesoporous SiO2 (CaSiO3@SiO2) on the surface was grafted onto polypropylene non-woven fabric. First, polyacrylic acid grafted PP non-woven (PP-g-AA) was prepared by UV irradiation graft and sodium polyacrylate PP non-woven (PP-g-COONa) was synthesized after neutralization by NaOH. Then calcium silicate grafted PP non-woven (PP-g-CaSiO3) was synthesized by dipping PP-g-COONa in Na2SiO3 solution and crosslinking by CaCl2. After modification by hydrochloric acid solution, PP non-woven grafted calcium silicate containing mesoporous SiO2 (PP-g-CaSiO3@SiO2) was obtained and characterized by SEM, FTIR, DSC, BET and XRD. The PP-g-CaSiO3@SiO2 was prepared simply without using any organic solvent, and can be used in the fields of organic adsorption, separation, drug release, tissue engineering and catalysis.

Mechanical Properties of High Density Polyethylene/Modified Calcium Silicate Composites

High density polyethylene (HDPE)/calcium silicate (CS) composites containing vinyltriethoxysilane treated calcium silicate contents varying from 0–10 phr were prepared by injection molding. Thus obtained HDPE/CS composites were characterized by the thermal analyses. The mechanical properties were evaluated. It was found that the incorporation of the calcium silicate into high density polyethylene resulted in a slight increase in the yield stress (6.85–11.76 %) as well as tensile strength (7.02–12.84 %). However, the elongation at yield and the elongation at break decreased by 9.23–24.87 % and by 11.03–60.73 %, respectively, with the increasing calcium silicate content. The vinyltriethoxysilane modified CS exhibited the dispersibility in HDPE matrix arising from the compatibility between high density polyethylene matrix and the disperse phase (treated calcium silicate particles) which led to the effect on the mechanical properties of the composites. It could be concluded that the modified calcium silicate played a role in reinforcing the mechanical properties into the high density polyethylene.

Preparation and characterization of protein molecularly imprinted polysiloxane using mesoporous calcium silicate as matrix by sol–gel technology

Calcium silicate particles containing mesoporous SiO2 on the surface (CaSiO3@SiO2) were prepared by acid modification of calcium silicate with diluted hydrochloric acid. Bovine serum albumin (BSA) molecularly imprinted polysiloxane (MIP) was synthesized using silane as the functional monomer, BSA as the template and CaSiO3@SiO2 particles as the matrix in an aqueous phase. SEM, granulometry, FT-IR and BET analysis were used to characterize the protein MIP. Influence factors on the rebinding capacity of the MIP were investigated, such as the pH in treating CaSiO3, eluent type and silane proportion. The mass of BSA loading and rebinding on CaSiO3@SiO2 and MIP was investigated. The adsorption and recognition properties of the MIP were evaluated and the results showed that the MIP exhibited an obvious improvement in terms of rebinding capacity for BSA as compared with non-imprinted polysiloxane (NIP). BSA imprinted polysiloxane could recognize the template protein by using Lys, Ova, Hb, and Glo as control proteins, and the selectivity factor (β) was above 2.3. The rebinding capacity of BSA imprinted polysiloxane for BSA reached 81.31 mg/g, which was 2.25 times of NIP.

Morphology and Property of Calcium Silicate Encapsulated with Alginate Beads

The alginate beads encapsulating calcium silicate were prepared. The morphologies and properties of the encapsulated beads were investigated. The beads were prepared by mixing modified calcium silicate with vinyltriethoxysilane in an alginate solution. The alginate-calcium silicate dispersion was dropped into a calcium chloride solution. The mean particle size of the resulting beads depended on the content of modified calcium silicate in alginate solution. In addition, the shape of the alginate gel was controlled by the viscosity of the alginate solution. The result showed that the calcium silicate particles were well dispersed within the matrix of the alginate. The thermal stability of the alginate beads encapsulating the calcium silicate increased with increasing the content of modified calcium silicate.

Simple preparation and initial characterization of semi-amorphous hollow calcium silicate hydrate nanoparticles by ammonia-hydrothermal-template techniques

Semi-amorphous hollow calcium silicate hydrate nanoparticles (CS10d120Hac) were successfully synthesized via simple ammonia-hydrothermal-template approach (AHT) followed by acid treatment. Results revealed that the newly synthesized samples had homogenous hollow nano-interior wherein the shell wall contained semi-amorphous calcium silicate hydrate. The AHT intensified the formation of a stronger electrostatic interaction (Si–O–Ca) from the weaker electrostatic contact composed of silicate wall-calcium hydroxide interaction (Si–OH–Ca) forming a thin semi-amorphous calcium silicate hydrate shell wall. This is also a convenient way for structural stability of the hollow CS10d120Hac. The CS10d120Hac showed a relatively higher surface area, which is uniquely rare especially if compared with bulk calcium silicate particles. This CS10d120Hac can be selectively functionalized with multiple organic and inorganic groups. Hence, this work may open a new route for the formation of hybrid hollow bio-active particles.

Effect of chemically reactive enamel coating on bonding strength at steel/mortar interface

In this study, 84 mortar cylinders, each with one steel rod embedded at its center, were tested in tension to characterize the bonding strength at the steel/mortar interface. The effects of different enamel coatings on the steel rods and the mortar curing time were investigated. The bond strength between a smooth steel rod and mortar can be increased by as much as seven times when the rod is coated with a mixture of 50% (by weight) enamel and 50% calcium silicate (CS) particles. This increase in bond strength is due to the increased surface roughness of the coating and chemical bonding of the embedded CS particles to the surrounding mortar. Uncoated smooth and roughened steel rods and rods coated with pure enamel could be pulled cleanly out of the mortar cylinders, whereas the cylinders split when rods coated with reactive enamels containing CS particles were removed. The failure loads of rods coated with reactive enamels increase with concrete aging time, with a maximum load reached up to at least 97 days, whereas the failure loads of uncoated rods decreased slightly after 28 days of curing.

Mechanochemical Synthesis of Nano Calcium Silicate Particles at Room Temperature

Nano-sized calcium silicate powders were synthesized at room temperature by the new mechanochemical method using a high energy planetary ball mill. The formation of calcium silicate from its raw materials (calcium carbonate and dehydrated silica gel) was monitored by the XRD analysis with progression of ball milling. It is observed that the synthetic process comes to an end through the following three sequential stages: comminution of raw materials, recombination of comminuted raw materials to final product, and comminution of final product to smaller sizes. The nanostructure of the synthesized powder was realized by the FESEM photomicrograph, TEM image and XRD analyses. These analytical observations have revealed that the nano-sized polycrystalline calcium silicate particles are formed after about 6 h of ball milling and they are spheroidal in shape. The average particle size of the as-generated calcium silicate nanocrystalline powders is found to be around 21 nm which decreases with increasing ball milling but increases with annealing at elevated temperature.

Synthesis of cellulose–calcium silicate nanocomposites in ethanol/water mixed solvents and their characterization

Cellulose–calcium silicate nanocomposites with calcium silicate nanoparticles homogeneously dispersed in the cellulose matrix have been successfully synthesized using cellulose solution, Ca(NO 3) 2·4H 2O and Na 2SiO 3·9H 2O in ethanol/water mixed solvents at room temperature for 24 h. The cellulose solution was previously prepared by the dissolution of cellulose in a solvent system of N, N-dimethylacetamide (DMAc)/lithium chloride (LiCl). The feeding order had an influence on the morphology of the cellulose–calcium silicate nanocomposites and the size of the calcium silicate particles. The cellulose in nanocomposites showed cellulose type II crystalline structure. The products were characterized by X-ray powder diffraction (XRD), thermogravimetric analysis (TG), differential scanning calorimetric analysis (DSC), Fourier transform infrared spectrometry (FT-IR), energy-dispersive X-ray spectra (EDS), and scanning electron microscopy (SEM).

Problems in PFBC boiler (2): characterization of bed materials found in a commercial PFBC boiler at different load levels

Bed materials sampled from a commercial pressurized fluidized bed combustion (PFBC) of coal boiler at different loads of 270 and 285 MW output levels (bed materials; namely BM270 and BM285, respectively) were characterized in term of their morphology, composition, and thermal properties, since the operation at a little higher output suffered the problem of poor fluidization, resulting in a shutdown due to the slagging at the bottom of the boiler. BM270 was uniform grains with diameter around 3–5 mm, consisting principally of CaCO 3 grains, which carried fine calcium aluminosilicate particles on their surface. In contrast, BM285 carried much larger grains among grains similar to BM270. The larger grains were classified into two groups, sintered egg (SE) and agglomerated grain (AG). The former grains were fused as well as adhered fine particles of calcium oxide and aluminosilicate, while the latter grains were adhered ones without extensive fusion. Higher temperature at a particular location occurring in 285 MW output operation may accelerate the calcination of CaCO 3 forming CaO. Yellow particles present dominantly in BM285 adhered each other to form AG. Low viscosity of melted calcium aluminosilicate formed the smooth surface of BM285 yellow particles that carried more numbers of very fine aluminosilicate. CaO particles successively adhered through SO 2 absorption to the half-solidified surface, forming porous surface of CaSO 4 found over AG. AG was degraded into fines particles when saved in the air atmosphere. CaO particles which bridged the BM285 yellow particles in AG may lose their binding force through their hydration into Ca(OH) 2 by absorbing humidity. Bed materials and ash particles are locally heated and softened to form SE through softening and adhesion of powder materials such as very fine calcium oxide, alumina, and silicate particles into a compact grain. Unique properties of very fine particles must be clarified. Unburnt char particles were found among the BM285, providing with another evidence of poor fluidization once larger grains are produced. A little more charge rate of feed at 285 MW output may critically increase the chance of poor heat dispersion at some locations, causing the agglomeration of bed materials and coal ash, which leads to the poorer fluidization first locally and then in the whole boiler.