Spherical Granules Research Articles

Effect of the particle shape on the particle dynamics in a spheronization process

Spherical granules with a narrow size distribution are widely used in many pharmaceutical applications. Extrusion-spheronization is a well-established process to produce such pharmaceutical pellets. The cylindrical extrudates from the extrusion step are rounded in the spheronizer. The formation mechanisms inside of a spheronizer depend strongly on the particle dynamics. To describe the complex particle flow and interactions, the Discrete Element Method can be used. In our previous works the spherical particles during the last part of the spheronization process were studied. Since the pellets have a cylindrical shape at the beginning and undergo different stages of deformation during the rounding process, the objective of this study was the description of the influence of the particle shape on the particle dynamics. To predict the interactions of the pellets, their dominant plastic behaviour was described with an appropriate contact model and the material parameters were calibrated with compression and impact tests.

Studies of Spherical Granules of the CuO-Fe2O3-Al2O3 Catalyst Prepared by Drop Molding for the Process of Fluidized Bed Burning of Brown Coal

A method of drop molding was suggested for preparation of spherical granules of CuO-Fe 2 O 3 -Al 2 O 3 catalysts. The catalysts were characterized using a set of physicochemical methods and tested for fluidized bed burning of brown coal. The influence of thermal treatment (700 and 800 °C) on the activity, strength and physicochemical properties of the spherical CuO-Fe 2 O 3 -Al 2 O 3 catalyst were studied. The prepared catalyst was shown highly active to oxidation of CO (competitive to that of the currently used industrial catalyst), high crushing and attrition mechanical strength (ca. 10–14 MPa of the minimal crushing strength and 15–23 MPa in average; attrition loss 0.8 % according to ASTM D-4058). Testing of the CuO-Fe 2 O 3 -Al 2 O 3 catalyst for the fluidized bed burning of brown coal demonstrated the attainability of high coal burnout (95 %) characteristic of the industrial catalysts (Shchkz-1, IC-12-73, IC-12-74A), the CO content in flue gas being 600 ppm that was lower of that observed with the industrial iron-containing catalyst IC-12-74A 3,000 ppm) and comparable with the catalyst IC-12-73 (700 ppm).

H2S Resistant Bifunctional Catalyst for Steam Reforming of Methane: Activity and Structural Evolution

Results of studying an iron-nickel catalyst for steam reforming of methane, which was prepared by epitaxial deposition of the coat on the surface of spherical granules of commercial γ-Al 2 O 3 , are discussed. The catalyst was shown to be resistant to the presence of hydrogen sulfide in the steam gas mixture. The methane conversion was close to equilibrium at 2.0 MPa, 800 °C, H 2 O : CH 4 = 2 : 1, feed flow rate 6000 h –1 , 30 ppm of H 2 S. XRD, transmission electron spectroscopy (TEM) and Moessbauer spectroscopy were used to study the structure evolution and phase state of the active components of the system. The formation of paramagnetic iron oxide clusters strongly bound to the support structure and iron-nickel alloy FeNi3 particles on the catalyst surface determined the polyfunctional behavior of the catalyst, which is highly active to the steam reforming of methane and to oxidative decomposition of hydrogen sulfide to elemental sulfur.

A new allomorph distribution of C-type starch from root tuber of Apios fortunei

Starch was isolated from root tuber of Apios fortunei. Its morphology, thermal properties, and crystalline structure were investigated in this study. The results showed that the starch had spherical, polygonal, and ellipsoidal granule shapes with central hila, showed two separate gelatinization peaks, and exhibited C-type crystallinity. Hot stage microscope observation showed that starch could be divided into two groups of granules with low and high gelatinization temperatures, and the Group 1 and 2 granules accounted for 45.5% and 54.5% of the total granule number, respectively. The gelatinization peak temperatures of Group 1 and 2 starch granules changed from 68.3 to 66.6 °C and from 75.4 to 82.7 °C with the increase of KCl concentration in water from 0 to 2 M. The Group 2 starch granules were further separated from starch through gelatinizing Group 1 granules at 78 °C in 2 M KCl, and displayed intact granular shape, A-type crystallinity, and single gelatinization peak. The Group 1 and 2 starch granules corresponded to B- and A-type starches, respectively, but had no differences in morphology, size, and amylose content. The above results showed that the A- and B-type allomorphs of C-type starch from A. fortunei were distributed in the different starch granules.

Properties of starch from root tuber of Stephania epigaea in comparison with potato and maize starches

ABSTRACTThe dry root tuber of Stephania epigaea contained 36.5% starch, indicating a good starch source. In this study, starch was isolated from S. epigaea. Its morphology, physicochemical, and functional properties were investigated and compared with potato and maize starches. S. epigaea starch had small spherical granules with centric hila and large ellipsoidal granules with eccentric hila, and granule sizes varied from 7 to 40 μm. The starch had 33.9% amylose content and B-type crystallinity. The gelatinization onset, peak, and final temperatures were 59.4, 62.3, and 66.2°C, respectively, and were lower than those of potato and maize starches, but the enthalpy (16.3 J/g) was higher than that of potato and maize starches. The peak, hot, final, and breakdown viscosities were 2227, 1623, 2149, and 594 dPa s, respectively, and were significantly higher than those of maize starch and lower than those of potato starch. S. epigaea starch was more susceptible to amylase hydrolysis and in vitro digestion than potato starch and less than maize starch. This study would be useful for the applications of starch from S. epigaea in the food and non-food industries.

Effects of additives on the synthesis of spherical aluminum nitride granules by carbothermal reduction-nitridation process

In this work, the effects of various additives on the AlN conversion fraction, weight loss, phase compositions and surface morphology during the carbothermal synthesis of spherical AlN granules were investigated in detail. The results inferred that additives played an important role in the improvement of nitridation rate, the formation of spherical morphology and the growth of particle size. The simultaneous addition of CaF2 and YF3 resulted in the highest nitridation rate in all samples, while excessive CaF2 appeared to retard the nitridation process at a particular temperature. However, Ca-aluminates forming in the synthesis process tended to be reduced and further volatilized at high temperature. Furthermore, by analyzing the weight loss during the carbothermal reduction-nitridation process, the reaction mechanisms in the systems using different additives were also attentively disclosed.

Shedding light on cell compartmentation in the candidate phylum Poribacteria by high resolution visualisation and transcriptional profiling.

Assigning functions to uncultivated environmental microorganisms continues to be a challenging endeavour. Here, we present a new microscopy protocol for fluorescence in situ hybridisation-correlative light and electron microscopy (FISH-CLEM) that enabled, to our knowledge for the first time, the identification of single cells within their complex microenvironment at electron microscopy resolution. Members of the candidate phylum Poribacteria, common and uncultivated symbionts of marine sponges, were used towards this goal. Cellular 3D reconstructions revealed bipolar, spherical granules of low electron density, which likely represent carbon reserves. Poribacterial activity profiles were retrieved from prokaryotic enriched sponge metatranscriptomes using simulation-based optimised mapping. We observed high transcriptional activity for proteins related to bacterial microcompartments (BMC) and we resolved their subcellular localisation by combining FISH-CLEM with immunohistochemistry (IHC) on ultra-thin sponge tissue sections. In terms of functional relevance, we propose that the BMC-A region may be involved in 1,2-propanediol degradation. The FISH-IHC-CLEM approach was proven an effective toolkit to combine -omics approaches with functional studies and it should be widely applicable in environmental microbiology.

Preparation of dense spherical AlN fillers by aqueous granulation and post-sintering process

Herein, an innovative two-step method was proposed to prepare dense spherical aluminum nitride (AlN) fillers for the application of insulating encapsulants, involving spray granulation from AlN-based suspensions and subsequent sintering process to achieve full density. According to investigations on the dispersing ability of powders, the AlN-based aqueous suspensions with various solid loading were firstly prepared for spray granulation. It was indicated that a low-viscosity and high-concentration suspension could enhance the sphericity and uniformity of green granules and simultaneously facilitate the high green density. The spherical AlN green granules were further sintered with boron nitride (BN) powders, which played a role as the interval material to retain the spherical morphology and hinder the agglomerations of AlN granules. The distinct impacts of BN powders, sintering temperatures and additive species on the overall properties of resultant AlN fillers were further studied and rationally uncovered. Based on these results, spherical AlN granules with superior dispersion, low porosity and an average particle size of more than 40µm were successfully fabricated via the newly-developed two-step method, showing promising potentiality for the application as thermal-conductive fillers.

Tunable Wave Propagation in Granular Crystals by Altering Lattice Network Topology

We develop a framework for wave tailoring by altering the lattice network topology of a granular crystal consisting of spherical granules in contact. The lattice topology can alternate between two stable configurations, with the spherical granules of the lattice held in stable equilibrium in each configuration by gravity. Under impact, the first configuration results in a wave with rapidly decaying amplitude as it propagates along a primary chain, while the second configuration results in a solitary wave propagating along the primary chain with no decay. The mechanism to achieve such tunability is by having energy diverted to the granules adjacent to the primary chain in the first case but not the second. The tunable design of the proposed network is validated using both numerical simulations and experiments. In terms of potential applications, the proposed bistable lattice network can be viewed either as a wave attenuator or as a device that allows higher amplitude wave propagation in one direction than in the opposite direction. The lattice is analogous to a crystal phase transformation due to the change in atomic configurations, leading to the change in properties at the macroscale.

Preparation of Granule Powders for Thermal Spray Coating by Utilization of Pyrophyllite Minerals

Pyrophyllite granule powders for thermal spray coating were successfully prepared through spray drying process. To produce a stable slurry, commercial pyrophyllite powder of 45μm in size was ball-milled for reduction of the size to 2 ~ 3 ㎛ and a dispersant was added to control the viscosity. Dense and spherical granules (average granule size : 59 ㎛) were prepared under conditions of 12,500 rpm for rotation velocity of the atomizer and 100 cps for slurry viscosity. The granules were then heat treated at 1,200℃ for proper handling strength and flow properties. The final granules had an apparent density of 0.725 g/㎤ and a flow rate of 2.5 g/sec, which represent excellent properties to be used as the granule powder for thermal spray coatings.

Suzuki-Miyaura cross-coupling of phenylboronic acid with aryl halides catalyzed by palladium and nickel species supported on alumina-based oxides

Two different kinds of Al2O3-ZrO2 have been prepared by the alkoxide sol-gel process: bulky-shaped and formed into spherical granules with the diameter of 2–3 mm. The catalysts have been obtained either by impregnating the support with the metal precursor (Pd or Ni salt solution) or by simultaneous addition of the precursor during synthesis of the support (the co-precipitation technique). The catalysts have been characterized structurally with scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption-desorption studies and successfully applied in the Suzuki-Miyaura cross-coupling of phenylboronic acid with different kinds of aryl halides (2-bromotoluene, 4-bromotoluene, 4-bromoanisole or 4-iodoanisole). Our experiments have shown that nickel species supported on Al2O3-ZrO2 can be successfully employed as the catalyst in the Suzuki-Miyaura process.

Different activation signals induce distinct mast cell degranulation strategies.

Mast cells (MCs) influence intercellular communication during inflammation by secreting cytoplasmic granules that contain diverse mediators. Here, we have demonstrated that MCs decode different activation stimuli into spatially and temporally distinct patterns of granule secretion. Certain signals, including substance P, the complement anaphylatoxins C3a and C5a, and endothelin 1, induced human MCs rapidly to secrete small and relatively spherical granule structures, a pattern consistent with the secretion of individual granules. Conversely, activating MCs with anti-IgE increased the time partition between signaling and secretion, which was associated with a period of sustained elevation of intracellular calcium and formation of larger and more heterogeneously shaped granule structures that underwent prolonged exteriorization. Pharmacological inhibition of IKK-β during IgE-dependent stimulation strongly reduced the time partition between signaling and secretion, inhibited SNAP23/STX4 complex formation, and switched the degranulation pattern into one that resembled degranulation induced by substance P. IgE-dependent and substance P-dependent activation in vivo also induced different patterns of mouse MC degranulation that were associated with distinct local and systemic pathophysiological responses. These findings show that cytoplasmic granule secretion from MCs that occurs in response to different activating stimuli can exhibit distinct dynamics and features that are associated with distinct patterns of MC-dependent inflammation.

Gelatinizing technology combined with gas foaming to fabricate porous spherical hydroxyapatite bioceramic granules

This study fabricated porous spherical hydroxyapatite (HA) bioceramic granules via a novel method by combining the ionotropic gelation of sodium alginate with H2O2 gas-foaming. Firstly, HA powder was dispersed in sodium alginate solution; then, the bubbly slurry prepared by H2O2 gas-foaming was dripped into CaCl2 solution to form hydrogel spheres; finally, these hydrogel spheres were washed, dried and sintered to obtain the HA bioceramic granules. SEM images revealed that the obtained HA granules exhibited spherical shape and interconnected porous structure. XRD, FT-IR and ICP-OES tests confirmed the phase composition and the purity of the HA spherical granules. Compared with commercialized HA irregular granules (BAM® P2040), the HA spherical granules had smaller grain size, more micropores, larger specific surface area and stronger protein adsorption ability. Therefore, the porous spherical HA bioceramic granules shows potential to be a good candidate for bone defect filling materials.

Statistical analysis and comparison of a continuous high shear granulator with a twin screw granulator: Effect of process parameters on critical granule attributes and granulation mechanisms

This study is concerned with identifying the design space of two different continuous granulators and their respective granulation mechanisms. Performance of a continuous high shear granulator and a twin screw granulator with paracetamol formulations were examined by face-centered cubic design, which focused on investigating key performance metrics, namely, granule size, porosity, flowability and particle morphology of granules as a function of essential input process parameters (liquid content, throughput and rotation speed). Liquid and residence time distribution tests were also performed to gain insights into the liquid-powder mixing and flow behavior. The results indicated that continuous high shear granulation was more sensitive to process variation and produced spherical granules with monomodal size distribution and distinct internal structure and strength variation. Twin screw granulation with such a particular screw configuration showed narrower design space and granules were featured with multimodal size distribution, irregular shape, less detectible porosity difference and tighter range of strength. Granulation mechanisms explored on the basis of nucleation and growth regime maps revealed that for most cases liquid binder was uniformly distributed with fast droplet penetration into the powder bed and that granule consolidation and coalescence mainly took place in the nucleation, steady growth and rapid growth regimes.

Physicochemical properties and in vitro digestibility of legume starches

The physicochemical properties and in vitro digestibility of starches from different cultivars (genus) of legumes, namely, black eye bean, baby lima bean, lentil, chick pea, small red bean, and mung bean, were analyzed. All legume starches had oval and spherical granules, with an average diameter of 18.6–27.8 μm. Baby lima bean starch, with high amylose content, high molecular weight (Mw) of amylopection, and low short amylopection branch chains (DP 6–12), showed high gelatinization temperature, gelatinization enthalpy (△H), final viscosity, setback viscosity, and pasting temperature. By contrast, chick pea starch, with low amylose content and Mw of amylopection as well as high short amylopection branch chains, exhibited low gelatinization temperature, △H, peak viscosity, breakdown viscosity, and pasting temperature. Baby lima bean starch was highly resistant to enzyme digestion. The contents of slowly digestible and resistant starches of cooked small red bean were significantly higher than those of other cooked starches.

홍삼의 지용성 성분을 이용한 발효홍삼 농축액 알갱이의 흡습방지 효과

홍삼의 지용성 성분을 이용한 발효홍삼 농축액 알갱이의 흡습방지 효과

Size-induced segregation during pharmaceutical particle die filling assessed by response surface methodology using discrete element method

Discrete element method (DEM) combined with response surface methodology (RSM) was carried out for investigating the segregation behaviour of binary particles during die filling of the pharmaceutical tableting machine, which comprised a horizontally moving die equipped with a vertically moving bottom punch. To achieve accurate particle flow simulations, parameters of the pharmaceutical spherical granules were calibrated using experimental bounced height, rolling distance and angle of repose. These parameters were implemented in the DEM simulations and compared with experimental high-speed camera observations and measurements of the filling ratio. Simulations and experimental results showed reasonable qualitative and quantitative agreement, validating the simulation model. The validated model was employed to evaluate the segregation of binary particle mixtures and RSM was used for analysing the DEM results of the segregation. The RSM revealed that, unlike the die velocity, small particle size, horizontal position and vertical position affected the segregation index significantly. The segregation resulted from percolation of small particles between large particles in the feed shoe and bottom back corner of the die. DEM combined with RSM approach will become significantly efficient method to understand the process for implementing the quality by design approach.

Effect of temperature on the wetting behavior of hydroxypropyl methylcellulose in a twin-screw granulator

Temperature has rarely been examined in twin-screw wet granulation despite the obvious capabilities of the extruder for operating at elevated temperatures. The present work investigates the wetting behavior of a mixture of powders with different sorption characteristics at various temperatures to explain the unique granulation behavior witnessed with high molecular weight hydroxypropyl methylcellulose in a twin-screw extruder. The work studies the twin-screw granulation of a controlled release formulation at three different temperatures, namely 30°C, 55°C and 80°C and attempts to interpret the granular properties of collected samples relative to characterized moisture sorption isotherms measured for the individual ingredients as well as the mixtures. A result of higher temperature processing was reduced coarse particles and a final product with more spherical granules. Increasing temperature was found to reduce water absorption capacity among the ingredients, especially hydroxypropyl methyl cellulose and microcrystalline cellulose, leaving more of the added water for particle bridging. The gel layer of hydroxypropyl methyl cellulose particles was diminished by the higher temperatures which did not appear to impact the strength of the particle bridges formed. Inclusion of a more hydrophobic ingredient like acetaminophen complicates the distribution of water in a granule.

Corrosion and Tribocorrosion Behavior of Ti-Alumina Composites

This work focuses in the corrosion and wear properties of titanium reinforced with 1% wt. alumina particles, produced by a combination of colloidal techniques and powder metallurgy. The alumina particles were added to control the grain growth of titanium during sintering, and simultaneously to increase hardness and wear resistance. Colloidal techniques permitted a homogeneous dispersion of alumina particles on the surface of fine Ti particles by the formulation of stable aqueous suspensions that were further processed by spray-dry to obtain spherical granules with improved compressibility. Ti-alumina samples were produced by uniaxial pressing of granules and vacuum sintering leading to materials with homogeneous microstructure, a reduction of grain size higher than 50 % with respect to pure titanium, and a sensible increase in hardness. But the addition of ceramic particles can also have an influence on the corrosion behavior that is one of the most interesting properties of titanium alloys, and on wear resistance, that is one of the drawbacks of Ti. Moreover, the study of simultaneous action of wear and corrosion (tribocorrosion) is an area of highest interest in applications like biomedical or automotive. The corrosion behavior was evaluated by Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Polarization (PP) in NaCl at two concentrations (0.9 % and 3.5 %) and temperatures (37 oC, and room temperature). Tribocorrosion tests were performed using a reciprocating ball-on-plate tribometer where a 10 mm diameter alumina ball was used as counter material, and 10 N normal load was applied during 30 min in the same concentrations and temperatures of NaCl as in the static corrosion tests. The results showed a clear improvement of wear resistance on the composite without reducing the corrosion behavior in both conditions.

Spray-freeze-dried nanosized silicon carbide containing granules: Properties, compaction behaviour and sintering

Spherical granules comprising silicon carbide nanoparticles have been produced with the help of spray-freeze-drying (SFD) technique. The effect of solid loading of slurries on rheological properties, flowability and morphology of the resulting SFD granules has been studied. Further, a systematic study has been performed to investigate the effect of applied pressures and granule density on the relative densities and microstructures of the green compacts. A marginal increase in viscosity is noted as the solid content of slurries increases from 5 to 15 vol% with significant increase in viscosity being observed in case of 18 vol% slurry. The granules prepared from SiC slurries are spherical in shape with their mean size, density, gravimetric flow rate, and yield strength increasing with the increase in solid content. The mechanical properties of sintered SiC produced from SFD granules are found relatively superior to that made from commercially available spray-dried (SD) granules.