Ceramic Granules Research Articles

Effect of nozzle inlet parameters on the dry granulation atomization process of Si3N4 ceramic bearing balls

In this paper, the atomization characteristics of Si3N4 ceramic dry granulation affect the performance of Si3N4 ceramic bearing balls. In order to improve the dry granulation characteristics and the comprehensive performance of Si3N4 ceramic bearing balls, the atomization mechanism of the spinning nozzle used for Si3N4 dry granulation was studied in detail. The interaction between air and binder in the pressure-swirl nozzle is analyzed based on VOF method, the modified realizable [Formula: see text] turbulence model is used to simulate the flow field inside and outside the pressure-swirl nozzle, the effects of nozzle inlet parameters including the number of tangential inlets and the deflection angle of tangential inlets on the binder volume fraction, velocity distribution and pressure distribution are analyzed. The results show that when the number of tangential inlets increases from 1 to 4, the swirl strength of gas–liquid two-phase in the nozzle increases, the mean diameter of air core increases from 1.51[Formula: see text]mm to 2.01[Formula: see text]mm, and the spray cone angle increases from 18.5[Formula: see text] to 26.4[Formula: see text]. Besides, when the deflection angle of tangential inlet increases from 0[Formula: see text] to 15[Formula: see text], the swirl strength of gas–liquid two-phase in the nozzle with the deflection angle of tangential inlet of 10[Formula: see text] is the largest, and the mean diameter of air core and spray cone angle is 3.04[Formula: see text]mm and 30.7[Formula: see text], respectively. Based on the atomization experiment platform of the electric control fuel system, the mean diameter of air core and spray cone angle are measured, the micromorphology of Si3N4 particles is observed, which verifies the correctness of numerical simulation. When the Si3N4 particles are prepared by dry granulation, taking the atomization performance of nozzle into consideration, the pressure-swirl nozzle with 4 tangential inlets and 10[Formula: see text] deflection angle should be selected.

Investigation of the Properties of Heat-Protective Coatings to Improve the Performance of Products

The heat-loaded part of the combustion chamber of a liquid rocket engine are Considered. The proposed coating has several layers: an internal metal coating that contacts the part or substrate, and an external coating made of a mixture of ceramic granules and metal powder. At the same time, to obtain the initial surface for coating with the required surface layer roughness, it is proposed to use the method of sand blasting. The article analyzes possible mechanisms of material formation for "base-coating" transition zones, as well as the influence of their chemical composition on the adhesive strength of layers.. The choice of brand and combination of materials used for coating is justified. Technological modes that have been tested in production conditions when applying heat-resistant coatings to parts of modern rocket engines are proposed. The influence of technological parameters of the initial surface preparation process and the geometry of the resulting micro-relief of the substrate on the adhesion characteristics of a multilayer coating made of heat-protective materials operating in the high-temperature zone of the combustion chamber of liquid rocket engines is revealed.

Increasing the titanium alloys durability due to modifications by vibro-abrasive processing of the strengthened surface layer

It is shown that vibroabrasive treatment of hardened titanium alloy specimens contributes to an increase in their durability. This effect is explained by the removal of a defective surface layer containing microcracks and subject to the influence of residual tensile stresses. It is shown that the proposed stage of vibro-abrasive processing with ceramic granules makes it possible to almost completely remove iron introduced after vibro-impact surface hardening, which makes it possible to exclude the operation of etching in nitric acid from the technological process. The current state of research on durability in world science is briefly presented.

Active cooling systems for the hot zone of heat engines

Various types of hot zone cooling systems for liquid rocket engines are considered. The analysis of systems for external and internal cooling of the hot zone of the combustion chamber and the jet co-PLA is performed. The area of primary use of external and internal impact of components on the combustion chamber and the jet nozzle of a temporary product with a high thermal load on the material is given. Recommendations on the choice of technological methods for processing heat-protective coatings were developed, where the advantages of combined electroabrasive treatment were revealed. In this case, the possibility of finishing the transition sections of the path from areas that are difficult to access for the tool, which have coatings with ceramic granules that have been used in the latest products of aerospace technology, is shown. The mechanism of heat transfer by the cooling medium from the areas of the greatest heating, as a rule, to the flow of the liquid fuel component of the fuel is shown. Examples of implementation of modern cooling systems on typical designs of combustion chambers of modern rocket engines are considered. It is shown that the cooling efficiency will be higher the more belts of the cooling medium curtain are located along the length of the combustion chamber. At the same time, it should be taken into account that the use of an excessively large number of belts means a significant complication of the camera design, its manufacturing technology, and an increase in the cost of the product.

Study on adsorption of lead and cadmium by non-burning ceramic granules from waterworks residual sludge

In this experiment, the unburned ceramiste water treatment residuals (UCWTR) was prepared by the burning-free method to study its adsorption performance on Pb and Cd. Adsorption experiments show that the quality of ceramsite improved with the height of the filler layer in the reaction column, and its penetration and depletion time are prolonged. On the contrary, the driving force of mass transfer increases with the initial concentration of water in the reaction column, and the penetration and exhaustion time is shortened. The dynamic adsorption process of Pb and Cd by UCWTR is more consistent with the Thomas model and Yoon-Nelson model, and the correlation coefficient R2 is greater than 0.9. Under the condition that the initial flow rate v is 10 mL/min, the height of the packing layer h is 10 cm, and the initial concentration C0 is 150 mg/g, the fitted dynamic saturated adsorption capacities of UCWTR for lead and cadmium are 9.22 mg/g, 11.52 mg/g, the static adsorption capacity of lead and cadmium are 1.48 times and 155 times respectively. kT decreases as the height of the filler layer and the initial concentration increase; kYN decreases as the height of the filler layer increases, and increases as the initial concentration increases; the time t required to penetrate 50% of the adsorbent increases with the height of the filler layer and decreases with the increase of the initial concentration, which indicated that the solution did not reach full contact with UCWTR during the dynamic adsorption process.

Effect of sintering temperature on sorption properties and compressive strength of calcium phosphate ceramic granules

In this study we determined sintering temperature effect on bovine serum albumin (BSA) adsorption and compressive strength of calcium phosphate ceramic granules. Hydroxyapatite (HAp) and biphasic calcium phosphate (BCP) with HAp and β-tricalcium phosphate ratio 50:50 granules were prepared by sintering at 1000, 1100, 1150 and 1200 °C. HAp granules showed higher compressive strength than BCP, at 1200 °C reaching 7.1 ± 0.2 MPa and 5.4 ± 0.4 MPa, respectively. For samples sintered at higher temperatures the adsorption capacity in mg/g and mg/ml (adsorbed BSA per bulk volume of granules) decreases whereas the capacity in mg/m2 (adsorbed BSA per one square meter of granules surface area) increases. BSA adsorption capacity in current research is compared with other results presented in literature, concluding that for samples with lower specific surface area the adsorption capacity in mg/m2 is increased.

Building Osteogenic Microenvironments With Strontium-Substituted Calcium Phosphate Ceramics.

Bioceramics have experienced great development over the past 50 years. Modern bioceramics are designed to integrate bioactive ions within ceramic granules to trigger living tissue regeneration. Preclinical and clinical studies have shown that strontium is a safe and effective divalent metal ion for preventing osteoporosis, which has led to its incorporation in calcium phosphate-based ceramics. The local release of strontium ions during degradation results in moderate concentrations that trigger osteogenesis with few systemic side effects. Moreover, strontium has been proven to generate a favorable immune environment and promote early angiogenesis at the implantation site. Herein, the important aspects of strontium-enriched calcium phosphate bioceramics (Sr-CaPs), and how Sr-CaPs affect the osteogenic microenvironment, are described.

METHODS FOR COOLING THE HOT ZONE OF HEAT ENGINES AND TECHNOLOGICAL TECHNIQUES FOR IMPLEMENTING THE METHODS

Various types of hot zone cooling systems for liquid rocket engines are considered. The analysis of systems for external and internal cooling of the hot zone of the combustion chamber and the jet co-PLA is performed. The area of primary use of external and internal impact of components on the combustion chamber and the jet nozzle of a temporary product with a high thermal load on the material is given. Recommendations on the choice of technological methods for processing heat-protective coatings were developed, where the advantages of combined electroabrasive treatment were revealed. In this case, the possibility of finishing the transition sections of the path from areas that are difficult to access for the tool, which have coatings with ceramic granules that have been used in the latest products of aerospace technology, is shown. The mechanism of heat transfer by the cooling medium from the areas of the greatest heating, as a rule, to the flow of the liquid fuel component of the fuel is shown. Examples of implementation of modern cooling systems on typical designs of combustion chambers of modern rocket engines are considered. It is shown that the cooling efficiency will be higher the more belts of the cooling medium curtain are located along the length of the combustion chamber. At the same time, it should be taken into account that the use of an excessively large number of belts means a significant complication of the camera design, its manufacturing technology, and an increase in the cost of the product.

Influence of Flowability of Ceramic Tile Granule Powders on Sintering Behavior of Relief Ceramic Tile

Used in the ceramic tile market as a representative building material, relief ceramic tile is showing increased demand recently. Since ceramic tiles are manufactured through a sintering process at over 1,000 oC after uniaxial compression molding by loading granule powders into a mold, it is very important to secure the flowability of granular powders in a mold having a relief pattern. In this study, kaolin, silica, and feldspar are used as starting materials to prepare granule powders by a spray dryer process; the surface of the granule powders is subject to hydrophobic treatment with various concentrations of stearic acid. The effect on the flowability of the granular powder according to the change of stearic acid concentration is confirmed by measuring the angle of repose, tap density, and compressibility, and the occurrence of cracks in the green body produced in the mold with the relief pattern is observed. Then, the green body is sintered by a fast firing process, and the water absorption, flexural strength, and durability are evaluated. The surface treatment of the granule powders with stearic acid improves the flowability of the granule powders, leading to a dense microstructure of the sintered body. Finally, the hydrophobic treatment of the granule powders makes it possible to manufacture relief ceramic tiles having a flexural strength of 292 N/cm, a water absorption of 0.91 %, and excellent mechanical durability

Structural integrity of calcium hydroxide granule bulks for thermochemical energy storage

Thermochemical energy storage using the gas-solid reaction of calcium oxide with water vapour is a promising approach especially for high-capacity applications such as CSP. Current research is mainly concerned with lowering reactor cost and therefore concentrating on dynamic systems with granules instead of powder as solid storage material. As stresses affecting the structural integrity of the granules increase with increasing bulk size, small samples as used for thermogravimetric analysis (TGA) might underestimate their impact on granule stability. This work complements existing literature on granule stability by experiments at bulk scale: two shaped granule samples and two ceramic encapsulated granule samples as well as a reference powder were cycled in a lab-scale reactor as well as within a TGA apparatus. Even though preservation of the granule structure was observed after cycling within the TGA apparatus, crushing strength measurements already indicated a decrease of mechanical stability of 81–88% for the shaped granules and 6–11% for the encapsulated granules. As a consequence, structural integrity of the granule bulk was only preserved in case of partial hydration. Given high reactivity, the granule structure – shaped and encapsulated – was destroyed after the first hydration causing a bulk volume expansion of up to a factor of 2.5. Reaction behaviour of the reference powder was consistent despite formation of cm-sized agglomerates. This work confirms that reaction conditions within a bulk are more challenging regarding structural integrity of storage material granules due to greater stresses acting on the single granule. These stresses can be significantly reduced by partial hydration.

Radiographic, macromorphological and hematological evaluation of hydroxyapatite ceramics with diff erent physicochemical properties

Treatments of fragmentary fractures in case of loss regenerative potential of bone tissue require usingdiff erent composite materials. Among all of them, ceramics based on synthetic hydroxyapatite and tricalcium phosphate are considered promising. The reparative osteogenesis in spongy and compact rabbit’s bone tissueusing 3 composite materials with diff erent physicochemical propertieswas studied. A reparative osteogenesiscontrolled by monitoring clinical, radiologic and macromorphologic parameters. Composite materials infl uence on the organism was studied by determining the dynamics of hematological parameters throughout the study period. To realize this scheme was formed a 3 experimental groups and one control group of rabbits. The created defects of animals of fi rst experimental group were fi lled out with GT + α-TKF-500, thedefects of second oneanimals group fi lled out with GTlKl-2, and defects ofthird oneanimals group fi lled out with GTlKg-700. The GTlKl-700materials were doped with silicon. In control animals, bone defects were allowed to heal under a blood clot. During the studies, all animals were located in the same environment conditions. A blood samples for hematological investigation was taken from the external jugular vein before anesthesia and at the 3rd, 7th, 14th, 21st and 42nd day after surgery. X-ray examination was performed on 14th, 21st, and 42nddays.The animals were removed from the experiment on 21stand 42nd days. The samples were examined by macromorphologic method. By radiologic examination was found that composite materials had osteoconductive properties except the silicondoped example which hadosteoinductive properties. The samples of compact bone tissue of 1st and 3rd experimental groups characterized by formation of punctate osteosclerosis with a compacted contour of the periosteumon the 42nd day. But the bone samples of 2nd experimental group had compacted contours of the periosteum only. However, in the cancellous bone tissue on the 42nd day in the animals of the 1st experimental group developed point osteosclerosis, which visualized as individual granules of the composite.But in the animals of 2nd group thewhite spot which was outlined shape and homogeneous structure at the defect was found. The bone samples of 3rd animals group shoved a clearly limited point osteosclerosisforming were was found ceramic granules. In case using ofGT + α-TKF-500, a strong connection of granules from the formed bone tissue and without any periosteal growthswas noted. Using GTlKl-2 places of defects were identical to not injured sites of radial bones. Using GTlKg-700 shows that bone defect is fi lled to the level of the plane of the bone surface and covered with a periosteum without visible growths. The granules of the composite are evenly distributed in the regenerate and associated with bone tissue. The analysis of hematological parameters did not reveal any fundamental diff erences, but the use of hydroxyapatite implants is not accompanied, in contrast to spontaneous reparative osteogenesis, the development of leukocytosis, which indicates a moderate course of its infl ammatory reaction. But the latter is accompanied by a platelet reaction, the most pronounced when using implants, which is probably due to the infl uence of platelet factors and is indirect evidence of early osteoblastic reaction. Key words: fractures, rabbits, erythrocytes, leukocytes, platelets, hemoglobin.

Morphology and structure characterization of ceramic granules

For the production of brittle materials like technical ceramics it is important to prohibit big defects in the material to achieve high mechanical strength. Due to that already the granule properties are important because they can cause defects in the final product. Characterization and quantification of the granule properties are important steps for improving the production process and properties of the granules for further processing. In this work a novel method for the characterization and quantification of granule morphology, especially sphericity, and internal structure like the ratio of macro pores is provided via digital microscopy. The new quantitative characterization method can be done in an academic and industrial field with appropriate effort. Differences between granules can be characterized, quantified and be used for further development.

Cold compression of ceramic spray-dried granules: Role of the spatial distribution of the binder

We report an experimental study of the compaction behaviour of zirconia granules formed by a spray drying process. Using two different binders that were fully characterized, we have investigated the influence of the binder spatial distribution in the granules on compaction of a granule packing. Spatial distributions were modified by tuning binder adsorption on the ceramic nanoparticles in the spray dried suspensions. Granule powders with binder either located between nanoparticles only, or partly concentrated within a segregated layer at the surfaces of granules were thus obtained. We have found the role of the segregated layer is fully negligible during granule compression, and we justify that result by providing estimates of the theoretical compression energies of segregated layers and polymer bridges. We discuss the role of the binder bridges between nanoparticles, and we suggest a picture accounting for the experimental influence of binder mechanical properties and concentration on the compaction behaviour of spray-dried granules.

New Insight on Deformation of Walnut/Ceramic Proppant Pack under Closure Stress in Hydraulic Fracture: Numerical Investigation

This study is an attempt to investigate the mechanical behavior of proppant packs deforming under compression loading. A generalized confined compression test (CCT) was simulated in the present study to investigate the deformation of walnut/ceramic proppants against compression. In this way, the CCT was simulated using ABAQUS explicit code. Unlike ordinary CCT, we obtained permeability of compressed packs through image processing of deformed packs. It was observed that a pack with small particles could markedly withstand deformation, however, at the expense of having lower permeability. Also, selecting a proper proppant pack strongly depends on the prevailing stress regime, where at low stress ( 40 Mpa), the pack with more ceramic is the best choice. Mixtures of walnut and ceramic proppants showed greatly strength improvement compared to similar cases with pure walnut granules. As a result, making use of such packing is highly recommended due to significant mechanical stability and also being of lower price compared to packs of pure ceramic granules.

Dispersion of ceramic granules within human fractionated adipose tissue to enhance endochondral bone formation

Engineering of materials consisting of hypertrophic cartilage, as physiological template for de novo bone formation through endochondral ossification (ECO), holds promise as a new class of biological bone substitutes. Here, we assessed the efficiency and reproducibility of bone formation induced by the combination of ceramic granules with fractionated human adipose tissue (“nanofat”), followed by in vitro priming to hypertrophic cartilage. Human nanofat was mixed with different volumetric ratios of ceramic granules (0.2-1 mm) and cultured to sequentially induce proliferation (3 weeks), chondrogenesis (4 weeks), and hypertrophy (2 weeks). The resulting engineered constructs were implanted ectopically in nude mouse. The presence of ceramic granules regulated tissue formation, both in vitro and in vivo. In particular, their dispersion in nanofat at a ratio of 1:16 led to significantly increased cell number and glycosaminoglycan accumulation in vitro, as well as amount and inter-donor reproducibility of bone formation in vivo. Our findings outline a strategy for efficient utilization of nanofat for bone regeneration in an autologous setting, which should now be tested at an orthotopic site. Statement of significanceIn this study, we assessed the efficiency and reproducibility of bone formation by a combination of ceramic granules and fractionated human adipose tissue, also known as nanofat, in vitro primed into hypertrophic cartilage. The resulting engineered cartilaginous constructs, when implanted ectopically in nude mouse, resulted in bone and bone marrow formation, more reproducibly and strongly that nanofat alone. This project evaluates the impact of ceramic granules on the functionality and chondrogenic differentiation of mesenchymal progenitors inside their native adipose tissue niche and outlines a novel strategy for an efficient application of nanofat for bone regeneration in an autologous setting.

A Simple Method to Evaluate the Purity of Synthetic Hydroxyapatite Granules

Using a method based on the spectrophotometric analysis of the liquids remaining after washing ceramic granules, the type of impurity was determined, the wavelength for measuring the impurity was established, and the type of cuvette (polystyrene or quartz) was analyzed. The absorbance of the samples was measured at wavelengths between 190 and 1100 nm. The results showed that both cuvette types are useful; however, the greatest absorbances were detected using quartz ones at low wavelengths around 190 nm. The comparison of absorption spectra from the samples, centrifuged and noncentrifuged, enabled us to define the impurities as small apatite particles.

Pelletisation by tumbling as an alternative method of agglomerating nanometric particles for use as feedstock in bi-modal structured flame-sprayed ceramic coatings

This paper is focused on the physical evaluation of ceramic granules of Al2O3, Al2O3-13 wt% TiO2 (AT-13) and TiO2 obtained from alumina and titania nanoparticles by pelletisation in a rotating drum. The results were compared with those of both sintered and non-sintered granules of similar chemical compositions and particle size distributions which were spray dried, as well as with those of TiO2 pelletised granules blended with atomised alumina particles. The results obtained indicated that the physical characteristics of the pelletised granules conferred them a free-flowing behavior which was similar to that of the spray-dried granules. However, the TiO2 pelletised granules blended with harder atomised alumina particles disintegrated and, therefore, exhibited a poor flowability. Additionally, it was evident that the ceramic coatings fabricated from pelletised granules displayed a structure which was as or more compact than those of the granules obtained from agglomerated powders by spray drying with or without sintering, apart from being more compact than that of the coatings deposited from TiO2 pelletised granules blended with atomised alumina particles. The above findings indicate that the alternative pelletising method is potentially useful for the use of agglomerated nanoparticles as feedstock in the fabrication of bi-modal structured flame-sprayed ceramic coatings.

Effect of Hydrophobic Surface Coating on Flowability of Ceramic Tile Granule Powders

Effect of Hydrophobic Surface Coating on Flowability of Ceramic Tile Granule Powders

General Influence of Biphasic Calcium Phosphate on Osteoporotic Bone Density

Abstract Bone density of the femur body of rabbit was determined in vivo. Experimental osteoporosis was induced by ovariectomy and subsequent injections of methylprednisolone. In the greater trochanter region of right femur, defects were created and filled with granules of hydroxyapatite and tricalcium phosphate (HAP/TCP 70/30) or HAP/TCP 70/30 together with 5% strontium. After three months, the animals were euthanized. The bone mass density of the right and left body of femur was measured by cone beam computed tomography (CT) scan. The results of the study showed that the right femur of the rabbit, where biomaterials had been implanted, and the left femur, where no biomaterial implantation occurred, became denser after filling the defect with HAP/TCP 70/30 ceramic granules or 5% Sr modified HAP/TCP ceramic granules. There was no difference between operated and non-operated legs and HAP/TCP and HAP/TCP with 5% strontium groups.

Numerical analysis on gas-solid mixing in ceramic dry granulation room with baffles

In order to investigate the influence of baffles on the mixing effect of particles during ceramic dry granulation process.Air-particles interaction was analyzed by euler gas-solid two phases flow model, the granulation area was simplified.The three dimensional physical model of particles mixing process was constructed, granulation room rotary motion was simulated by sliding grid method and multiple reference frame method, turbulent motion was analyzed by modified RNG discrete model. The influence of different baffles on particles mixing was investigated according to the volume fraction distribution and velocity field, changed the position of the baffle can increase the blending effect by about 22%.The results showed: when there were no baffles, wall baffles and middle baffles in the granulation room, the average volume fraction of powder was about 0.22, 0.18 and 0.26 respectively. The average speed of powder was about 0.6m/s, 0.9m/s and 0.4m/s respectively. The wall baffle made the powder have significant axial movement, the experimental data showed: when granulation room had wall baffles, the content of active particles accounted for about 73%. It is helpful to improve the understanding of gas-solid two phase flow field in ceramic drying granulation room and provide some theoretical guidance for the design and optimization of the baffle.