Spherical Granules Research Articles

Novel colloidal approach for the microstructural improvement in Ti(C,N)/FeNi cermets

In this work, the combination of colloidal and powder metallurgy techniques was proposed as an alternative route to produce Ti(C,N)-based cermets with a 15–20 vol% of Fe/Ni alloy (85/15 wt%) as metal matrix. The novelty of this processing route is based in the mixture of fine powders (1–3 μm) in suspension which promotes the uniformity of the phase distribution and consequently its reactivity, leading to 99.9% dense cermets with 1300 Vickers Hardness (HV30). The preparation of colloidal and chemically stable slurries of non-oxide and metal powders in aqueous media is a key step of the process. Highly concentrated aqueous slurries of Ti(C,N), Fe, Ni and C powders were prepared and mixed. Then bulk pieces were shaped by Slip casting (SC), Slip Casting + Cold Isostatic Pressing (SC-CIP) and Spray-Dry + Uniaxial Pressing of the obtained spherical granules (SDP). The composite formulation and the thermal treatment were optimized to prevent Ni sublimation during sintering as well as to improve liquid phase sintering in terms of wetting and reactivity among well packed particles. The effective dispersion of the slurry and the synergistic effect of combined techniques yielded the preparation of reliable materials by the SDP process with 15 wt% of FeNi with the addition of 0.5 wt% of C. The optimization of the composite formulation and the processing parameters improves both density and hardness of a finer microstructure of the composite after a short sintering treatment (120 min) at 1450 °C in vacuum.

Spherical porous granules in MgO[sbnd]Fe2O3[sbnd]Nb2O5 system: In situ observation of formation behavior using high-temperature confocal laser-scanning microscopy

The pyrolytic reactive granulation process, yielding ceramic spherical porous granules, is simple, consisting of typical ceramic processing methods, viz., wet-ball milling of powders, vacuum drying, granulation via sieving through a screen mesh, and one-step heat treatment for local reactive sintering within each granule. Here, the microstructural development of spherical porous granules was successfully visualized by in situ high-temperature confocal laser-scanning microscopy during the heating up to 1400°C in air. Based on the result of the in situ observation, a simple but powerful size-controlling process of spherical porous granules, viz., multiscreen sieving after the heating was demonstrated. Nearly monodispersed spherical porous granules composed of pseudobrookite-type MgFeNbO5 were easily obtained.

PVB modified spherical granules of β-TCP by spray drying for 3D ceramic printing

Monodispersed and spherical β-TCP granules for 3D printing were prepared by spray drying with the surface modification of PVB. Modifier PVB attached to the particle surface to form the crosslinked network structure and keep them combine with each other into aggregates. The morphology, size, forming performance and crushing behavior of granules as well as the microstructure and density of as-fabricated β-TCP ceramics were used to optimize the PVB contents. Promising results could be expected that PVB contents were 1.0 wt.% and the average particle size of granules was 37.36 μm. The modified granules exhibited excellent forming performance with monodispersed and spherical aggregates for 3D printing. They could be completely crushed under 80 MPa without obvious inter-granules void. These granules with 1.0 wt.% PVB had defined strengths for ceramic forming. The good dispersity and flowability assured the high density and uniform porous structure of β-TCP ceramics, which were used as biological ceramic materials and completely met the standard for bone tissue engineering.

Fabrication of interconnected porous calcium-deficient hydroxyapatite using the setting reaction of α tricalcium phosphate spherical granules

Abstract Interconnected porous calcium-deficient hydroxyapatite (cdHAp) blocks may be an ideal biomaterial to repair bone defects because of their greater similarity to human bone than that of sintered hydroxyapatite (HAp) with respect to calcium content and crystallinity. In particular, the interconnected pores in cdHAp may provide pathways for cell migration and tissue ingrowth. In this study, the feasibility of fabricating interconnected porous cdHAp blocks through the setting reaction of alpha-tricalcium phosphate (αTCP) spherical granules was investigated. It was found that regulation of cdHAp formation was important to fabricate interconnected porous cdHAp blocks. That is, cdHAp needed to precipitate preferentially at the contacting areas between αTCP spherical granules. Exposure of αTCP spherical granules to steam under appropriate pressure was effective for this purpose. When αTCP spherical granules were immersed in water at 100 °C, the setting reaction resulted in dense cdHAp blocks because of the free crystal growth of cdHAp in water. Therefore, steam was used to localize the water at the contacting areas between αTCP spherical granules, which was driven by the surface tension of the water. Without an applied load, no setting reaction was observed when αTCP spherical granules were exposed to steam at 100 °C for 12 h. In contrast, under a load of 20 MPa, cdHAp precipitated to bridge spherical granules, providing an interconnected porous cdHAp block. The porosity and diametral tensile strength of this block were approximately 63% and 1.5 MPa, respectively.

Fabrication of transparent MgAl2O4 spinel via spray freeze drying of microfluidized slurry

Abstract Spherical granules were prepared from a monodispersed slurry by combining the microfluidization (MF) method and the spray freeze-drying (SFD) process. Starting with the prepared granules, transparent MgAl 2 O 4 ceramics were fabricated through pressureless sintering followed by hot isostatic pressing. A comparison with a polydispersed slurry prepared by the ball-milling method showed successful fabrication of a mono-dispersed state by microfluidization method, and 80% visible in-line transmittance was obtained at a 600-nm wavelength from a process starting with a monodispersed slurry of low solid content. Microstructural analysis of the green bodies, the pre-sintered bodies, and the hot isostatic pressed bodies of the prepared MgAl 2 O 4 ceramics revealed that the slurry dispersion should be controlled to a high level in order to suppress scattering sources such as pores and microcracks, which affect the in-line transmittance of visible light.

An experimental study on preparation of vitrified bond diamond grinding wheel with hollow spherical corundum granules as pore former

Hollow spherical corundum granules were introduced into a vitrified bond diamond grinding wheel as pore former. The influences of content and particle size of the hollow spherical corundum granules on porosity, flexural strength, and hardness of the vitrified bond diamond wheel samples were systematically investigated. The grinding performance of the designed vitrified bond diamond cup wheel on sapphire and 6H-silicon carbide (SiC) substrates was examined, and morphological properties of the ground surface were evaluated. Results showed that higher content and smaller size of hollow spherical corundum granules could lead to the increase of the porosity and the decrease of flexural strength and hardness. Sapphire and 6H-SiC substrates could be effectively ground by the vitrified bond diamond cup wheel containing 8% hollow spherical corundum granules. During the grinding, although a brittle mode dominated the material removal of two substrates, more ductile removals and lower surface roughness could be identified from 6H-SiC substrate than from sapphire.

Enhancement of Defluoride Performance of the Spherical $$\hbox {FeOOH}/{\upgamma }\hbox {-Al}_{2}\hbox {O}_{3}$$ FeOOH / γ -Al 2 O 3

Excess fluoride in drinking water hazarded people health, so we have undertaken to develop a nanoscale \(\hbox {FeOOH}/{\upgamma }\hbox {-Al}_{2}\hbox {O}_{3}\) absorbent to remove fluoride in drinking water. The as-prepared nanoscale \(\hbox {FeOOH}/{\upgamma }\hbox {-Al}_{2}\hbox {O}_{3}\) absorbent was characterized by transmission electron microscopy, surface area analyzer, and X-ray diffraction. Herein, we explored the effect of pH of solution, concentration of initial fluoride, contact time, and temperature on defluoride efficiency. The results showed the composite owned to further adherence to defluoride, compared to spherical and mesoporous alumina granules. The experiment data were fit with different models and assessed by regression coefficient \((R^{2})\); the pseudo-second-order model was used to explain the adsorption process. The adsorption mechanism can be explained by a proton shifting mechanism.

Manufacture of NiAl-based rods for plasma centrifugal spraying using mechanochemical synthesis

An alternative technology is proposed for the production of NiAl–Co–Cr–Hf–Al2O3 alloy rods. It includes the fabrication of a powder by mechanochemical synthesis (MCS) followed by hot isostatic pressing in forming tool. The processes of MCS of the intermetallic alloy in a planetary mill and an attritor are studied. The products of synthesis in various mixers are compared. The microstructure and the properties of compacted samples are studied: their ultimate compressive strength is 1390–1480 MPa at a plasticity of 8.5–8.8%. Spherical granules with a target size of 20–200 μm are fabricated by plasma centrifugal spraying of the rod workpiece formed by the proposed technology.

Processing alumina spheres by a colloidal route using silica-polystyrene hybrid nanoparticles

Colloidal granulation of alumina is an original shaping process leading to spherical granules directly in suspension from a diluted system. It is based on a heterocoagulation mechanism where silica added in small amount acts as a binding agent. The role of a submicronic latex of polystyrene was investigated, free, or as a hybrid object covered by silica nanoparticles synthesized by a Pickering emulsion polymerization method. Latex particles were not able to form primary agglomerates despite a high negative zêta potential. An addition of latex in combination with silica improved the state and homogeneity of the final microstructure which could be attributed to a decrease of the internal strains during the processing. Hybrid nanoparticles, by combining the binding agent (silica) and the organic phase, were able to form primary agglomerates, and to finally obtain alumina spheres exhibiting both a spherical morphology and a greater homogeneous microstructure.

Stable Li Plating/Stripping Electrochemistry Realized by a Hybrid Li Reservoir in Spherical Carbon Granules with 3D Conducting Skeletons.

Lithium metal is a promising battery anode. However, inhomogeneous mass and charge transfers across the Li/electrolyte interface result in formation of dendritic Li and "dead" Li, and an unstable solid electrolyte interphase, which incur serious problems to impede its service in rechargeable batteries. Here, we show that the above problems can be mitigated by regulating the interfacial mass/charge transfer. The key to our strategy is hybrid Li storage in onion-like, graphitized spherical C granules wired on a three-dimensional conducting skeleton, which enhances the negativity of surface charge of the C host to contribute to a uniform Li plating while also forming stable Li/C intercalation compounds to offset any irreversible Li loss during cycling. As a result, the anode shows a suppressed dendrite formation and a high Li utilization >95%, enabling a practical Li battery to strike a long lifespan of 1000 cycles at a surplus Li of merely 5%.

Histocytological and histochemical features of the adrenal gland of Adult Egyptian native breeds of chicken (Gallus Gallus domesticus)

BackgroundAvian adrenal gland is one of the most important endocrine glands as it regulates several vital physiological functions. Removal of such gland leads to death of bird. ObjectiveThe present investigation aims to illustrate morphological, histocytological and histochemical features of adrenal gland of Adult Egyptian native breeds of Chicken (Gallus gallus domesticus) by means of gross anatomy, light and transmission electron microscope. Materials and methodsThirty chickens of 6months old were collected from Beni-Suef province, Egypt. Immediately after sacrifying the birds, right and left adrenals were subjected to histomorphological, histochemical and ultrastructural examinations. ResultsGrossly, the adrenal glands were situated cranio-medially to the kidneys with yellowish color. Histologically, they were ensheathed with thin collagenous connective tissue capsule containing many blood vessels and associated with numerous autonomic ganglia. The parenchyma was composed of mixture of cortical and medullary tissues as well as numerous blood sinusoids. The cortical tissues were demarcated in two distinct zones; subcapsular and inner. The cells of subcapsular cortical zone (SCZ) contained more lipid droplets and less mitochondria than the inner cortical cells do. Two types of chromaffin cells were distinguished; epinephrine (E-) and norepinephrine (NE-) producing cells. The former contained spherical moderate electron-dense secretory granules. The latter contained abundant pleomorphic intensely electron-dense secretory granules. ConclusionHigher cortical tissues on the expense of medullary ones may be the need for increased production of adrenal cortical hormones (glucocorticoids and mineralocorticoids) in the chicken that lives in areas which water conservation is important.

Control of Algal Blooms in Eutrophic Water Using Porous Dolomite Granules

The use of aluminum-based coagulants in water pretreatment is being carefully considered because aluminum exposure is a risk factor for the onset of Alzheimer’s disease. Lightly burned-dolomite kiln dust (LB-DKD) was evaluated as an alternative coagulant because it contains high levels of the healthful minerals calcium and magnesium. An organic pore forming agent (OPFA) was incorporated to prepare porous granules after OPFA removal through a thermal decomposition process. A spray drying method was used to produce uniform and reproducible spherical granules with low density, since fine dolomite particles have irregular agglomeration behavior in the hydration reaction. The use of fine dolomite powder and different porosity granules led to a visible color change in raw algae (RA) containing water, from dark green to transparent colorlessness. Also, dolomite powders and granules exhibited a mean removal efficiency of 48.3% in total nitrogen (T-N), a gradual increase in the removal efficiency of total phosphorus (T-P) as granule porosity increased. We demonstrate that porous dolomite granules can improve the settling time and water quality in summer seasons for the emergent treatment of excessive algal blooms in eutrophic water.

An innovative method for the preparation of high API-loaded hollow spherical granules for use in controlled-release formulation

The aim of this study was to prepare controlled-release (CR) granules with suitable particle strength, flowability, particle size distribution (PSD) and density characteristics for blending with other excipients. We also wanted these CR granules to contain large quantities of active pharmaceutical ingredient (API). A high shear mixer was used to mix an API with various polymers at various feed ratios, and the resulting granulated materials were sprayed with solvent. The wet granules were dried using a fluidized bed dryer to give CR granules. The API content of the granules was determined to be 95wt%. The granules were found to be spherical in shape with smooth surfaces by scanning electron microscopy. The inner structure of each granule was determined to be hollow by X-ray computed tomography, highlighting the unusual mechanism of this granulation process. The PSD of the granules was found to be dependent on that of the constituent polymer, and a narrow PSD was obtained by adjusting the PSD of the polymer. The dissolution profile of the granules was also dependent on the constituent polymer. Taken together, these results show that we have successfully developed a new manufacturing technology for the simple and low-cost preparation of ideal CR granules.

Effects of trimethylol propane and AAS salt on properties of waterborne polyurethane with low gloss

Abstract A series of waterborne polyurethane(WPU) dispersions containing different amounts of trimethylol propane(TMP) and/or 2-[(2-aminoethyl)amino]ethanesulfonic acid sodium salt (AAS salt), were synthesized by prepolymer emulsification process. The effects of TMP and AAS salt on properties of WPU dispersions were discussed to find out the appropriate formulation of WPU dispersion with low gloss. The results showed the particle size of WPU increased as the TMP content increased, but a decrease to the gloss and transparency. Spherical granules emerged in the surface morphology of WPU films when the TMP content exceeded beyond 1% by weight via scanning electron microscope (SEM). In contrast, as the AAS salt content increased, the particle size of WPU decreased, and the gloss and transparency increased. It was most worth noting that the dispersion stability of WPU dispersions was enhanced dramatically with the increase of AAS salt content by measuring the Zeta potential of emulsion. Therefore, WPU dispersions with low gloss and high dispersion stability can be prepared successfully with the AAS content of 0.5% by weight and the TMP content of 1%–1.5% by weight when other influence factors were fixed to a suitable condition.

Starch Synthase 4 and Plastidal Phosphorylase Differentially Affect Starch Granule Number and Morphology.

The process of starch granule formation in leaves of Arabidopsis (Arabidopsis thaliana) is obscure. Besides STARCH SYNTHASE4 (SS4), the PLASTIDIAL PHOSPHORYLASE (PHS1) also seems to be involved, since dpe2-1/phs1a double mutants lacking both PHS1 and the cytosolic DISPROPORTIONATING ENZYME2 (DPE2) displayed only one starch granule per chloroplast under normal growth conditions. For further studies, a dpe2-1/phs1a/ss4 triple mutant and various combinations of double mutants were generated and metabolically analyzed with a focus on starch metabolism. The dpe2-1/phs1a/ss4 mutant revealed a massive starch excess phenotype. Furthermore, these plants grown under 12 h of light/12 h of dark harbored a single large and spherical starch granule per plastid. The number of starch granules was constant when the light/dark regime was altered, but this was not observed in the parental lines. With regard to growth, photosynthetic parameters, and metabolic analyses, the triple mutant additionally displayed alterations in comparison with ss4 and dpe2-1/phs1a The results clearly illustrate that PHS1 and SS4 are differently involved in starch granule formation and do not act in series. However, SS4 appears to exert a stronger influence. In connection with the characterized double mutants, we discuss the generation of starch granules and the observed formation of spherical starch granules.

Fills of Co-Sized and Different-Sized Granules as Quasi-Ordered Structures

From the measured data of the packing density γ (and/or porosity ω) of filling media of co-sized or different-sized granules, the authors evaluate the coordination number of a sphere granule N and the acceptable type of cell as a self-sufficient element of a conditionally ordered structure. It is shown that for the expansive class of filling media (of identical spherical granules, nearly identical granules, and also granules differing no more than twice in size), the medium′s structure may be considered to consist of cells close to square-rhombic ones (γ = 0.605 and ω = 0.395) by assuming that N ≈ 8. A filling media with different-sized granules (granule size differs more than twice) may be considered structures with combinations of cells like rhombic, rhombic-diagonal, and square-rhombic diagonal cells, for which γ ≥ 0.7 and ω ≤ 0.3. Here, N is assumed from N ≈ 8 to N ≈ 12 in accordance with the established relationship between N and γ (and/or ω).

Description of Gloeomargarita lithophora gen. nov., sp. nov., a thylakoid-bearing, basal-branching cyanobacterium with intracellular carbonates, and proposal for Gloeomargaritales ord. nov.

A unicellular cyanobacterium, strain Alchichica-D10, was isolated from microbialites of the alkaline Lake Alchichica, Mexico. The cells were short rods (3.9±0.6 µm in length and 1.1±0.1 µm in width) forming biofilms of intense emerald green colour. They exhibited red autofluorescence under UV light excitation. UV-visible absorption spectra revealed that they contain chlorophyll a and phycocyanin, and electron microscopy showed the presence of thylakoids. The strain grew within a temperature range of 15-30 °C. Genomic DNA G+C content was 52.2 mol%. The most remarkable feature of this species was its granular cytoplasm, due to the presence of numerous intracellular spherical granules (16-26 per cell) with an average diameter of 270 nm. These granules, easily visible under scanning electron microscopy, were composed of amorphous carbonate containing Ca, Mg, Ba and Sr. A multi-gene phylogeny based on the analysis of 59 conserved protein markers supported robustly that this strain occupies a deep position in the cyanobacterial tree. Based on its phenotypic characters and phylogenetic position, strain Alchichica-D10 is considered to represent a new genus and novel species of cyanobacteria for which the name Gloeomargarita lithophora gen. nov., sp. nov. is proposed. The type strain is Alchichica-D10 (Culture Collection of Algae and Protozoa CCAP strain 1437/1; Collections de Cyanobactéries et Microalgues Vivantes of the Museum National d'Histoire Naturelle in Paris strain PMC 919.15). Furthermore, a new family, Gloeomargaritaceae, and a new order, Gloeoemargaritales, are proposed to accommodate this species under the International Code of Nomenclature for algae, fungi and plants.

Design of Highly Dispersible PLGA Microparticles in Aqueous Fluid for the Development of Long-Acting Release Injectables.

In this study, we developed highly dispersible polylactic glycolic acid (PLGA) copolymer microparticles (MRPs) in aqueous fluid. A solution containing both dissolved aripiprazole as a model drug and PLGA were spray-dried to make MRPs. The resultant MRPs were further co-processed with water-soluble additives and a surfactant to improve their dispersion behavior. The granules containing MRPs and additives, termed granulated microparticles (G-MRPs) were prepared by a newly established drop freeze-drying technique. The physicochemical properties of MRPs and G-MRPs were evaluated as a long-acting release depot injectable. The MRPs were spherical particles with diameters of approximately 1 to 20 µm and strongly assembled to one another in the aqueous phase, forming large aggregations. In contrast, the G-MRPs were spherical granules with diameters of approximately 200 to 400 µm that displayed a microparticles-in-granule structure in which small MRPs were embedded in the porous matrix inside the granules. When the G-MRPs were placed in water, the porous matrix base was immediately dissolved, and each embedded MRP was individually released, thus inducing monodispersion and significantly improved dispersibility. The excellent dispersibility was attributed to the water-soluble porous network structure mainly composed of D-mannitol and the steric hindrance effects derived from the polymeric molecular chains. These properties may give rise to the excellent passage of PLGA microparticles through needles for use in depot formulation suspensions. A crystalline evaluation of the G-MRPs suggested that the drug and PLGA molecularly interacted and that their thermodynamic stability was improved.

Modeling of the Dynamics of Burning a Granule of Carbonate Mineral

Thermophysical processes occurring during the thermal decarbonization of natural carbonate minerals (limestones, magnesites) have been investigated. A new model of the working process of burning a single spherical carbonate granule in the form of a system of ordinary differential equations has been proposed. This system makes it possible to generalize, in a natural manner, the model to the multidimensional and nonstationary cases where a moving mass of loose material is described. A comparison of the numerical calculations of the decarbonization dynamics and the measurement results obtained under totally controlled laboratory conditions has proved the high accuracy of the proposed model.

Basic properties of solitary waves in granular crystals

We consider a chain of lightly contacting identical spherical elastic granules and provide explicit analytical expressions to fully characterize solitary waves (SWs) that may be generated in the chain by an impact or an applied shock force. These SWs consist of individual packages of linear momentum/energy transmitted across the granules through Hertzian contacts. They are nonlinear translational waves (involving no vibrations) that propagate through the granular chain without distortion, i.e., without any temporal evolution in shape or size. In particular, we focus on a fully-formed SW and provide analytical expressions for the associated peak value as well as the time variation of the granules’ displacement, velocity, acceleration, and compressive contact force acting across any two contacting granules. In addition, by considering a SW as an “effective particle”, we provide explicit analytical expressions for its linear momentum, total energy, equivalent (or effective) mass and effective velocity. All of the above mentioned results are shown to depend only on the peak value of the SW's contact force and the properties of the granules, i.e., their diameter, density, and elastic moduli. Then we provide a simple recipe to calculate the peak value of the SW's contact force in terms of a given shock force. Finally, we check by numerical simulations the accuracy of the analytical predictions.