Porous Granules Research Articles

Study of Moulding Sands to Create Three-Layer Magnesium Concrete

Abstract The article is devoted to the problem of creating energy-efficient building materials for enclosing structures. The aim of the research is to develop a recipe and a method for moulding sands placing to create heat-insulating concrete of a multilayer structure. The three-layer magnesium concrete containing layers of different densities is an object of a scientific research. Compositions of moulding sands for concrete’s central and surface layers have been developed and studied. Materials specially developed were used as raw materials for moulding sands; they are as follows: composite magnesial binder and porous filler obtained by low-temperature firing of a granular mixture based on sodium liquid glass and thermal energy waste (fly ash from thermal power plants, aluminosilicate microsphere). Possibility of regulating moulding sand’s properties for concrete’s central layer by varying the content and fractional composition of porous granules has been shown. There has been proposed the moulding sand for surface layers of three-layer magnesium concrete containing crushed porous sand. The related composition of moulding sands favours with adhesion of concrete’s different layers. Various technological methods for producing magnesium concrete of a complex structure have been studied. The research reveals technological and operational characteristics of three-layer magnesium concrete obtained by horizontal and vertical deposition of moulding sands.

Influence of Process Parameters on the Electrochemical Properties of Hierarchically Structured Na3V2(PO4)3/C Composites

AbstractSodium vanadium phosphate Na3V2(PO4)3 (NVP) is a promising next‐generation cathode material for sodium‐ion batteries (SIB) but the practical application as a cathode active material for SIBs is hindered by its poor electronic conductivity. To overcome this limitation and to improve the electrochemical performance in terms of rate capability and cycling stability, carbon coatings are a viable approach. In this work, we utilized a spray‐drying synthesis process and systematically varied the processing parameters to optimize the electrochemical performance of NVP/carbon composite materials. The spray‐drying process yields spherical, porous granules of NVP particles embedded in a carbon matrix, which is formed by the thermal decomposition of polyacrylic acid or β‐lactose.

Recombinant bone matrix maintains the graft space, induces vascularized bone regeneration and preserves canine tooth extraction socket structure.

Recombinant bone matrix (RBM) is a newly conceived and engineered porous bone graft granule of average size 600 μm composed of purified recombinant collagen peptide. We sought to examine the behaviour with time of RBM that was grafted in the canine tooth extraction socket. The canine tooth extraction socket of the hemisectioned mandibular third premolar distal root was grafted with RBM granules, whereas the opposite side extraction socket served as non-grafted control. The mandibular samples were harvested at 1, 3 and 6 months of healing and subjected to micro-CT imaging and decalcified paraffin-embedded histology. Separately, the effect of RBM was compared with that of deproteinized cancellous bovine bone (DCBB) and bovine atelocollagen plug (BACP) in the canine tooth extraction model at 3 months of healing. RBM maintained the grafted space in the socket and the gingival connective tissue until new bone was formed within its porous space. The regenerated bone was highly vascularized and continued to mature, while RBM was completely bioresorbed by 6 months. The buccal and lingual alveolar ridge heights of the RBM-grafted extraction socket was better preserved than those of non-grafted control sockets. The degree of socket preservation by RBM was equivalent to that by DCBB, although their healing mechanisms were different. This study demonstrated that RBM induced controlled active bone regeneration and preserved the extraction socket structure in a canine model. Bioresorbable RBM engineered without animal or human source materials presents a novel bone graft category with robust bone regenerative property.

Реверс воздушного потока в изолирующем самоспасателе на химически связанном кислороде

The advantages of the chemical method of reserving oxygen in an insulating breathing apparatus are the high density of its packaging and the automatic feed rate determined by the stoichiometry of the binding reaction of exhaled carbon dioxide. Nevertheless, according to the experimental data and theoretical estimates, the protective resource of the regenerative cartridge is not used efficiently enough. The reason is the uneven distribution of exothermic heat sources in the regenerative cartridge, which effects the pore structure of the chemisorbent and slows down the sorption kinetics. In addition, in devices with a short period of protective action, the proportion of the dead sorbent layer is large, unused by the time of the critical CO2 slip through the regenerative cartridge. The integrated approach to eliminating these causes consists in moving the sources of exothermic heat into the dead layer of the sorbent, which is achieved by reversing the regenerated air flow. The formalism is proposed that alows to simulate the operation of an insulating self-rescuer on chemically bound oxygen with a circular circuit of the air duct after the reverse of the air flow. Recommendations are formulated on the choice of breathing apparatus in which reverse is advisable, and the moment of changing the direction of filtration of exhaled air through the regenerative cartridge. It is shown that the reverse ensures a more uniform distribution of exothermic heat sources in the regenerative cartridge to prevent sintering of porous granules of an oxygen-containing product made on the basis of potassium peroxide. This increases the efficiency of using the protective resource of the breathing apparatus.

Bacteria-based self-healing concrete− A life cycle assessment perspective

A life cycle assessment (LCA) was utilised to evaluate the environmental impact of bacteria-based self-healing concretes (BBSHCs), where non-ureolytic bacterial endospores are encapsulated in porous calcium silicate granules. Findings reveal that 1 m3 of BBSHC has an overall 85% higher environmental impact than equivalent conventional concrete, primarily due to calcium nitrate and polyvinyl acetate. Furthermore, BBSHC has a 36% larger embodied carbon footprint (120 kg CO2 eq) and a 51% larger water footprint (260 L). However, by selectively incorporating BBSHC in specific areas of reinforced concrete structures, leveraging its inherent self-healing properties to deliberately allow wider crack widths, and consequently, reduce the amount of non-structural steel needed to control early-age cracking, sustainability improvements ranging from 12% to 50% can be achieved depending on the impact category. In this regard, a BBSHC-structure can potentially save up to 51 kg CO2 eq per m3.

Comparison of osteogenic capability of 3D-printed bioceramic scaffolds and granules with different porosities for clinical translation.

Pore parameters, structural stability, and filler morphology of artificial implants are key factors influencing the process of bone tissue repair. However, the extent to which each of these factors contributes to bone formation in the preparation of porous bioceramics is currently unclear, with the two often being coupled. Herein, we prepared magnesium-doped wollastonite (Mg-CSi) scaffolds with 57% and 70% porosity (57-S and 70-S) via a 3D printing technique. Meanwhile, the bioceramic granules (57-G and 70-G) with curved pore topography (IWP) were prepared by physically disrupting the 57-S and 70-S scaffolds, respectively, and compared for in vivo osteogenesis at 4, 10, and 16weeks. The pore parameters and the mechanical and biodegradable properties of different porous bioceramics were characterized systematically. The four groups of porous scaffolds and granules were then implanted into a rabbit femoral defect model to evaluate the osteogenic behavior in vivo. 2D/3D reconstruction and histological analysis showed that significant bone tissue production was visible in the central zone of porous granule groups at the early stage but bone tissue ingrowth was slower in the porous scaffold groups. The bone tissue regeneration and reconstruction capacity were stronger after 10weeks, and the porous architecture of the 57-S scaffold was maintained stably at 16weeks. These experimental results demonstrated that the structure-collapsed porous bioceramic is favorable for early-stage osteoconduction and that the 3D topological scaffolds may provide more structural stability for bone tissue growth for a long-term stage. These findings provide new ideas for the selection of different types of porous bioceramics for clinical bone repair.

Effects of Processing Conditions on the Properties of Porous Diatomite Granules Prepared by Sodium Alginate Gelation

The proper application of millimeter-sized spherical porous ceramic supports in catalytic operations relies on their ease of handling, convenient separation, recyclability, high-catalyst-solid loading, and the optimum mass transfer of reactants and products. However, common granulation techniques of spherical carriers entail complex liquid-phase-based processes under severe conditions and the use of toxic or expensive reagents. The present study discusses the manufacturing of porous ceramic granules derived from an inexpensive silica source (diatomite, solid network) and a biopolymer cross-linked by ion exchange (sodium alginate, patterning structure). The results indicated that, with fixed granulation conditions, porous diatomite granules with a sphericity of approximately 0.9 could be successfully obtained by optimization of the diatomite/sodium alginate dispersion to a 30.07 wt.% solid content and 1560 mPa·s viscosity (at ~0.3 s−1). Moreover, the described manufacturing process was proven effective in developing hierarchically porous diatomite granules that were heat-treated at 1200 °C with high sphericity (~0.9), acceptable compressive strength (5.17 ± 0.31 MPa), and porosity features (total porosity: 69.0 ± 2.9%, macropore size: 2.777 μm, mesopore size: 35.34 nm), establishing them as well-matched support materials for either catalytic or adsorption applications.

Behavioural responses of bone-like cells on dense and porous dicalcium phosphate dihydrate-coated β-tricalcium phosphate granules

Behavioural responses of bone-like cells on dense and porous dicalcium phosphate dihydrate-coated β-tricalcium phosphate granules

Functionalization of Octacalcium Phosphate Bone Graft with Cisplatin and Zoledronic Acid: Physicochemical and Bioactive Properties.

Bones are the fourth most frequent site of metastasis from malignant tumors, including breast cancer, prostate cancer, melanoma, etc. The bioavailability of bone tissue for chemotherapy drugs is extremely low. This requires a search for new approaches of targeted drug delivery to the tumor growth zone after surgery treatment. The aim of this work was to develop a method for octacalcium phosphate (OCP) bone graft functionalization with the cytostatic drug cisplatin to provide the local release of its therapeutic concentrations into the bone defect. OCP porous ceramic granules (OCP ceramics) were used as a platform for functionalization, and bisphosphonate zoledronic acid was used to mediate the interaction between cisplatin and OCP and enhance their binding strength. The obtained OCP materials were studied using scanning electron and light microscopy, high-performance liquid chromatography, atomic emission spectroscopy, and real-time PCR. In vitro and in vivo studies were performed on normal and tumor cell lines and small laboratory animals. The bioactivity of initial OCP ceramics was explored and the efficiency of OCP functionalization with cisplatin, zoledronic acid, and their combination was evaluated. The kinetics of drug release and changes in ceramics properties after functionalization were studied. It was established that zoledronic acid changed the physicochemical and bioactive properties of OCP ceramics and prolonged cisplatin release from the ceramics. In vitro and in vivo experiments confirmed the biocompatibility, osteoconductivity, and osteoinductivity, as well as cytostatic and antitumor properties of the obtained materials. The use of OCP ceramics functionalized with a cytostatic via the described method seems to be promising in clinics when primary or metastatic tumors of the bone tissue are removed.

Cylindrical granules in the development of mesalazine solid formulations (Ⅰ): Physical properties, compression behaviors, and tableting performances

Cylindrical granules have been employed in the pharmaceutical industry. However, to our knowledge, the study on the compressibility and tabletability of cylindrical granules has not been reported. This study aimed to explore the effects of the physical properties of cylindrical granules on the compression behaviors and the tableting performances, with mesalazine (MSZ) as a model drug. First, the six formulations of MSZ cylindrical granules were extruded by changing the ethanol proportion in the binder. Then, the physical characteristics of MSZ cylindrical granules were systematically studied. Subsequently, the compressibility and tabletability were evaluated using different mathematic models. It was worth noting that highly porous cylindrical granules possessed favorable compressibility and good tabletability due to the increased pore volume, reduced density, and decreased fracture forces. Finally, dissolution tests were conducted and highly porous granules showed higher dissolution rates than the less porous ones, but an opposite trend was observed for the corresponding tablets. This study proved the importance of physical properties in the tableting process of cylindrical granules and provided strategies to improve their compressibility and tabletability.

Obtaining and study of physical-chemical properties of porous materials based on kaolin

The object of research is kaolin from the Hlukhovetsky deposit (Ukraine). On its basis, granulated sorbent materials were obtained with the addition of various amounts of cellulose as a pore former. After forming the samples, they were dried and fired at a temperature of 800 °C. The obtained granules with a size of 8–9 mm were modified with zero-valent iron. The physicochemical, including sorption properties of granular composites were studied. Using scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), the morphology of the obtained samples was investigated and the presence of zero-valent iron particles on the surface and in the pores of the sorbents was confirmed. Based on desorption experiments, it was determined by chemical analysis that the Fe0 content in modified samples with increased pore former content increases from 0.01 g/g of granules for a sample containing 1% cellulose to 0.016 g/g for a carrier with 3 % pore former. The specific surface area and pore volume of the samples were determined by the method of low-temperature adsorption-desorption of nitrogen. Thus, with an increase in the content of the pore former in the ceramic mass, the specific surface of both unmodified and modified samples slightly decreases. Thus, with a cellulose content of 1 %, it is 20 m2/g and 17 m2/g, respectively. When the pore former is increased to 3%, these values are 15 m2/g and 12 m2/g. After applying a layer of zero-valent iron on porous granules, the volume of pores decreases, which is due to the formation of agglomerates of iron particles during synthesis. The study of the sorption capacity of the obtained sorbents with respect to Cr(VI) from model solutions containing a mixture of metal cations (copper, cadmium, cobalt, zinc) showed that granular materials exhibit sorption capacity for metal anions, even in the presence of cations. The amount of chromium sorption naturally increases for modified samples with an increase in the cellulose content in them. However, for model solutions that do not additionally contain metal cations, the sorption value is somewhat higher. Thus, for a sample with a 3 % pore former content, the sorption value is 0.7 mg/g and 0.9 mg/g, respectively, at an initial chromium(VI) concentration of 10 mg/g. The obtained experimental data indicate that the obtained porous granular sorbents based on kaolin can be used in the further treatment of wastewater from electroplating enterprises, which contain a mixture of pollutants in both anionic and cationic forms.

Discrete element simulation of the breakage behavior of porous granules utilizing bond models

AbstractIn the development of ships, the aspect of collision safety plays a major role. In this paper, the approach to improve the crashworthiness of ships is to fill the already existing double hull with a granular material. For this purpose, the material used is to be investigated numerically. A discrete element approach is applied for this in the paper presented. Since the breakage behavior of the particles is of particular interest, the discrete element method is used together with a bonded particle method. This approach is extended by a model which is able to take into account the micro-cracks occurring in the material and the energy dissipation caused by them. Using this and other models of the bonded particle method, simulations are carried out and compared with corresponding experiments. A particular focus is on uniaxial compression tests with single particles and particle systems. The single-particle tests are used to determine various simulation parameters relevant to individual particles in terms of geometry and material. In addition, the multi-particle tests provide insight into the behavior of several particles, their interaction and dynamics. These simulations can be used to test the extent to which it is possible to represent porous particles and their fracture behavior by numerical means.

球状多孔質β型リン酸三カルシウム顆粒を用いたセメントの作製と評価

Calcium phosphate cements (CPCs) with macropores and micropores for high bone regeneration ability are desired. CPCs with macropores and micropores which were prepared by combining porous granules have been reported. In this study, the cement system composed of β-tricalcium phosphate (β-TCP) granules and phosphoric acid solution was selected, and the effects of the characteristics of granules on the microstructures and properties of the cements were examined. The spherical porous β-TCP granules with high porosity and irregular porous β-TCP granules with low porosity were prepared, and they were mixed with a phosphoric acid solution. When the spherical porous granules with high porosity were used, the granules were packed uniformly in the cement, and the size distribution of the macropores formed among the granules was narrower than that of the cement prepared using the irregular porous β-TCP granules with low porosity. The cement with high porosity can be obtained from the spherical porous granules with high porosity. The cement prepared using the spherical granules with high porosity showed lower compressive strength and higher dissolution rate than the cement prepared using irregular granules with low porosity.

Sol-gel fabrication of porous ceria microspheres for thermochemical carbon dioxide (CO2) splitting

Porous CeO2 has been of great interest recently, due to its great catalytic efficiency in splitting CO2 into CO and O2. Porous CeO2 microspheres are the key to scaling up such reactions in the fluidized-bed solar thermochemical reactors. In this paper, we report the processing and CO2 splitting performance of porous ceria microspheres. To fabricate the porous ceria microspheres, homogenous cerium-based sol-gel precursors were synthesized from cerium acetate. The acrylamide (AM) was used as both solidification and pore-generation agent. The polymerization of acrylamide facilitated the conversion of liquid droplets to solid gel microspheres. The optimal AM content was around 20 wt%, ensuring both sufficient porosity and the integrity of the ceria microspheres after thermal decomposition. After heat treatment at 1500 °C for 1 h, porous CeO2 microspheres were obtained, with an average diameter of ∼800 μm and surface area of 2.9 m2/g. These microspheres had high porosity and good sphericity. The CO2 splitting performances of these microspheres were characterized using thermogravimetric analysis (TGA). During the thermal cycles between 1000 and 1400 °C, the O2 yield of porous ceria microspheres was 49 μmol/g, and the CO yield was 88 μmol/g. Compared with porous ceria granules of particle size of ∼800 μm, the porous ceria microspheres exhibited higher O2 and CO production yields. After thermochemical cycles, the microspheres were not sintered together, and the surface area was slightly reduced to 2.7 m2/g.

Bonded particle models for discrete element simulation of porous granules

AbstractThe growing interest in granular materials used in mechanical applications, for example as crash absorbers in ship collisions, leads to an increased need for numerical models to simulate such granules. Since, in the case of an application as a crash absorber, the fracture behaviour of the granules is of particular interest, the numerical models must be able to simulate the breakage and predict, for example, the energy dissipation during fracture. For this purpose, a discrete element method is used together with a bonded particle model. Since the bond model mainly affects the fracture of particles, this work focuses on new models and their influence on the breaking behaviour of granules.

Combined granulation–alkali activation–direct foaming process: A novel route to porous geopolymer granules with enhanced adsorption properties

High-value applications, such as adsorbents, have drawn attention to geopolymers. In several of those applications, having the geopolymer as porous spherical particles is beneficial. This study presents a novel process for fabricating porous metakaolin-based geopolymer granules using a combination of direct foaming, one-part alkali activation, and granulation. In short, the precursor (e.g., metakaolin) and solid activator (e.g., sodium silicate) are loaded in a granulator, in which an aqueous blowing agent (e.g., H2O2) is added while the granulator is running, and the obtained granules are cured at 60 °C. Characterization of the granules for physico-chemical and morphological properties indicated an increase in overall porosity, especially in the µm-scale pores. Also specific surface area (+50%) and nanoscale pore volume (+102%) increased when using more concentrated H2O2 (20 or 30%) compared to nonporous granules. The use of porous granules was also demonstrated in dynamic adsorption experiments for ammonium (NH4+) uptake, which showed up to ∼126% increase in cumulative adsorption amount compared to nonporous granules. The highest NH4+ uptake was obtained with 10% H2O2 solution as the granulation fluid. The results confirmed the feasibility of the method for introducing porosity to geopolymer granules, which enhances the adsorption properties of the granules.

Osteoblast-Mediated Resorption of Porous Bioactive SCPC Granules Enhances Bone Regeneration in Human Extraction Sockets

Bone graft materials are widely used in orthopedic and maxillofacial surgeries. The controlled resorbability of the graft material is essential for bone regeneration. Hydroxyapatite and biphasic calcium phosphate bone grafts have poor resorption and limited bone conductive effects. Histology analyses of bone biopsy from SCPC grafted human extraction sockets showed complete bone regeneration and graft resorption in absence of osteoclasts and macrophages. The hypothesis of the present study is that bioactive SCPC inhibits osteoclast’s activity due to the presence of resorbable silica phase in the material. Our objective is to analyze the effect of SCPC dissolution products on the resorption activity of osteoclasts. The conditioned medium was prepared by immersion of SCPC resorbable bioactive SCPC porous granules (Shefabone, Inc, USA) in cell culture medium at various ratios at 37°C for 3 days. The concentration of Si ions released from the SCPC granules into cell culture medium was measured using ICP-OES. Osteoclast precursors derived from human bone marrow were seeded on bone slices and cultured in the conditioned medium containing 10% FBS and osteoclast induction factors. Osteoclast differentiation and resorption were evaluated by TRAP staining and measurement of the volume of resorption pits on the bone slices. Mature multinuclear giant TRAP-positive osteoclasts were observed on the bone substrates after 14 days incubation in control medium containing osteoclast induction factors. In conditioned medium, the number of multinuclear TRAP-positive cells was significantly decreased as the concentration of SCPC dissolved silica increased. The dissolution of silica from SCPC into the culture medium correlates well with down regulation of osteoclast differentiation and the rapid bone regeneration in human bone defects.

Preparation and evaluation of osteoinductive porous biphasic calcium phosphate granules obtained from eggshell for bone tissue engineering

The synthetic bone graft substitutes currently used clinically are osteoconductive but not osteoinductive; their low success rate is thus their biggest disadvantage. The use of biomass raw materials for synthesizing calcium phosphate has gradually attracted increased research attention. In this study, hydroxyapatite powder was prepared through liquid-phase precipitation from eggshell, and porous biphasic calcium phosphate granules (EBGs) were then obtained using a pore former and sintering procedure. The EBGs were discovered to have high biocompatibility and no cytotoxicity. The results of animal experiments showed that the area of new bone growth was high, numerous Haversiancanals could be observed, and almost all EBGs were surrounded by new bone tissue, which proved that the EBGs had excellent osteoinductivity. By contrast, numerous fat cells were found in the femoral defect area when a commercial bone graft was employed. Various biological inorganic ions (Mg, Sr, Na, and Fe) originally in the eggshell raw materials were incorporated into the EBGs, and the EBGs exhibited excellent osteogenic abilities. The developed approach provides an economical and feasible solution for the treatment of bone defects.

Comparative Efficiency of Gene-Activated Matrices Based on Chitosan Hydrogel and PRP Impregnated with BMP2 Polyplexes for Bone Regeneration

Gene therapy is one of the most promising approaches in regenerative medicine. Gene-activated matrices provide stable gene expression and the production of osteogenic proteins in situ to stimulate osteogenesis and bone repair. In this study, we developed new gene-activated matrices based on polylactide granules (PLA) impregnated with BMP2 polyplexes and included in chitosan hydrogel or PRP-based fibrin hydrogel. The matrices showed high biocompatibility both in vitro with mesenchymal stem cells and in vivo when implanted intramuscularly in rats. The use of porous PLA granules allowed the inclusion of a high concentration of polyplexes, and the introduction of the granules into hydrogel provided the gradual release of the plasmid constructs. All gene-activated matrices showed transfecting ability and ensured long-term gene expression and the production of target proteins in vitro. At the same time, the achieved concentration of BMP-2 was sufficient to induce osteogenic differentiation of MSCs. When implanted into critical-size calvarial defects in rats, all matrices with BMP2 polyplexes led to new bone formation. The most significant effect on osteoinduction was observed for the PLA/PRP matrices. Thus, the developed gene-activated matrices were shown to be safe and effective osteoplastic materials. PLA granules and PRP-based fibrin hydrogel containing BMP2 polyplexes were shown to be the most promising for future applications in bone regeneration.

Effects of cooling conditions and chitosan coating on the properties of porous calcium phosphate granules produced from hard clam shells

• Clam shell was used to synthesize CaP granules by gas foaming technique. • Samples under furnace cooling condition were biphasic CaP granules (HA/β-TCP). • Samples under air cooling condition were triphasic CaP granules (HA/β-TCP/α-TCP). • Samples air-cooled and chitosan-coated had maximum compressive strength. The main inorganic components of clam shells are calcium carbonate and trace elements of magnesium, strontium, and zinc. Clam shells can be used as a calcium source to synthesize calcium phosphates, and these trace elements promote the growth of bone tissue and improve the performance of bioceramics. In this study, hydroxyapatite (HA) powders were synthesized from clam shells, and porous calcium phosphate granules were prepared through the gas foaming technique. In addition, the effects of a chitosan coating and cooling conditions on the strength of the porous granules were investigated. The results indicated that the samples produced under the furnace cooling condition were biphasic hydroxyapatite/β-tricalcium phosphate granules (HA/β-TCP), whereas the samples produced under the air-cooling condition were triphasic hydroxyapatite/β-tricalcium phosphate/α-tricalcium phosphate granules (HA/β-TCP/α-TCP). The compressive strength of the porous granules prepared through air cooling was 79% higher than that of the granules produced through furnace cooling. The compressive strength of the air-cooled sample after the subsequent application of the chitosan coating further increased by 21%. A degradability test revealed that the weight loss rate of the air-cooled samples was greater than that of the furnace-cooled samples, which was due to the presence of high-solubility α-TCP in the air-cooled samples.