Freeze Granulation Research Articles

TABLET GRANULATION: CURRENT SCENARIO AND RECENT ADVANCES

Granulation is a size enlargement process, in fine or coarse particles converted into physically stronger and larger agglomerates having good flow property, better compression characteristics and uniformity, prevent segregation of the blend components, improve content uniformity, and eliminate excessive amounts of fine particles. Size of granules has a size range of 0.2 to 4.0 mm, depending on their subsequent use. Size of the granules depends on the quantity and feeding rate of granulating liquid. The selection of process to prepare granules requires thorough knowledge of physicochemical properties of the drug, excipients, required flow and release properties, to name a few. At current scenario available technologies includes, spray drying, roller compaction, high shear mixing, and fluid bed granulation etc. The objective of present work is to focus on the commonly used and novel granulation technologies like such as pneumatic dry granulation, steam granulation, moisture-activated dry granulation, thermal adhesion granulation, freeze granulation, and foamed binder or foam granulation. Peer Review History: Received 1 September 2017; Revised 5 October; Accepted 4 November, Available online 15 November 2017 Academic Editor: Dr. Sally A. El-Zahaby, Pharos University in Alexandria, Egypt, sally.elzahaby@yahoo.com Received file: Reviewer's Comments: Average Peer review marks at initial stage: 3.5/10 Average Peer review marks at publication stage: 7.0/10 Reviewer(s) detail: Dr. Francis Adou Yapo, Felix Houphouet Boigny, University of Abidjan, Ivory Coast, fyapo@yahoo.fr Dr. Hebatalla Ibrahim Ahmed Abdel Hameed, Al-Azhar University, Faculty of Pharmacy (Girls), Nasr City, Cairo, Egypt, hebatalla123@yahoo.com Similar Articles: IN VITRO-IN VIVO BIO-EQUIVALENCE CORRELATION STUDY OF ATENOLOL, AND ITS BRANDS OF IMMEDIATE RELEASE TABLET UNDER BIO-WAIVER CONDITIONS

Microstructure of Plasma Sprayed Al2O3-3wt%TiO2 Coating Using Freeze Granulated Powder

This study is aiming at controlling the microstructure of plasma sprayed Al2O3-TiO2 composite coatings using freeze granulated powders. As sprayed and sintered Al2O3 + 3wt%TiO2 powders were air plasma sprayed with industry process parameters and compared with a commercial powder. The resulting coatings were investigated with respect to powder flowability, porosity and microstructure of the granules. The results showed that microstructure and melting fraction in the coatings could be tailored with the freeze granulation process and heat treatment conditions.

Preparation of transparent neodymium-doped yttrium aluminate garnet (Nd:YAG) ceramics with the use of freeze granulation

This paper presents the results of the application of freeze granulation to the production of transparent neodymium-doped yttrium–aluminum garnet ceramics. Aqueous suspensions of aluminium oxide, yttrium oxide and neodymium oxide powders were prepared based on nanometric or submicronic powders which were either commercially available or prepared by precipitation. The relations between the composition of suspension, the properties of granulate and the final properties of ceramics (microstructure, optical transmission and emission spectra) were studied.

Injectability of calcium phosphate pastes: Effects of particle size and state of aggregation of β-tricalcium phosphate powders

The present study discloses a systematic study about the influence of some relevant experimental variables on injectability of calcium phosphate cements. Non-reactive and reactive pastes were prepared, based on tricalcium phosphate doped with 5mol% (Sr-TCP) that was synthesised by co-precipitation. The varied experimental parameters included: (i) the heat treatment temperature within the range of 800–1100°C; (ii) different milling extents of calcined powders; (iii) the liquid-to-powder ratio (LPR); (iv) the use of powder blends with different particle sizes (PS) and particle size distributions (PSD); (v) the partial replacement of fine powders by large spherical dense granules prepared via freeze granulation method to simulate coarse individual particles. The aim was contributing to better understanding of the effects of PS, PSD, morphology and state of aggregation of the starting powders on injectability of pastes produced thereof. Powders heat treated at 800 and 1000°C with different morphologies but with similar apparent PSD curves obtained by milling/blending originated completely injectable reactive cement pastes at low LPR. This contrasted with non-reactive systems prepared thereof under the same conditions. Hypotheses were put forward to explain why the injectability results collected upon extruding non-reactive pastes cannot be directly transposed to reactive systems. The results obtained underline the interdependent roles of the different powder features and ionic strength in the liquid media on determining the flow and injectability behaviours.

Spray freeze granulation of submicron alumina and its sintering behavior via spark plasma sintering

Spray freeze granulation is an improved method based on spray granulation, solving many limitations of spray granulation. In this work, spray freeze granulation of submicron alumina is performed to explore the possibility of industrial-scale production of dense alumina via spark plasma sintering. Powder pretreatment such as sedimentation and the selection of granules with the appropriate size are employed for the maximum use of the high qualified as-prepared granules and granule sliding, which would provide a guidance for the industrial-scale production. Debound granules were densified via SPS and the corresponding sintering behaviors such as the recorded shrinkage and shrinkage rate were discussed. The comparison of sintering behaviors between granulated and as-received powder are conducted to identify the role of spray freeze granulation in sinterability for dense alumina. The Vickers hardness (Hv) and the fracture toughness (KIC) of the freeze granulated body are higher than the corresponding properties of the as-received body due to the more homogenous microstructure with little agglomeration in the particle packing after freeze granulation.

Granulation techniques and technologies: recent progresses.

Granulation, the process of particle enlargement by agglomeration technique, is one of the most significant unit operations in the production of pharmaceutical dosage forms, mostly tablets and capsules. Granulation process transforms fine powders into free-flowing, dust-free granules that are easy to compress. Nevertheless, granulation poses numerous challenges due to high quality requirement of the formed granules in terms of content uniformity and physicochemical properties such as granule size, bulk density, porosity, hardness, moisture, compressibility, etc. together with physical and chemical stability of the drug. Granulation process can be divided into two types: wet granulation that utilize a liquid in the process and dry granulation that requires no liquid. The type of process selection requires thorough knowledge of physicochemical properties of the drug, excipients, required flow and release properties, to name a few. Among currently available technologies, spray drying, roller compaction, high shear mixing, and fluid bed granulation are worth of note. Like any other scientific field, pharmaceutical granulation technology also continues to change, and arrival of novel and innovative technologies are inevitable. This review focuses on the recent progress in the granulation techniques and technologies such as pneumatic dry granulation, reverse wet granulation, steam granulation, moisture-activated dry granulation, thermal adhesion granulation, freeze granulation, and foamed binder or foam granulation. This review gives an overview of these with a short description about each development along with its significance and limitations.

改良型超臨界凍結造粒法の開発と粉末吸入製剤への応用

改良型超臨界凍結造粒法の開発と粉末吸入製剤への応用

Comparison of Large‐Scale Production Methods of Fe2O3/Al2O3 Oxygen Carriers for Chemical‐Looping Combustion

AbstractOxygen carrier (OC) particles for chemical‐looping combustion (CLC) may be produced in large scale by a number of methods such as freeze granulation, spray drying, impregnation, and mechanical mixing methods. To select the most appropriate technology for large‐scale preparation, the four preparation methods were adopted to prepare Fe2O3/Al2O3 OCs and compared with each other in terms of productivity, preparation period, physical and chemical characterization, and reactivity in CLC of lignite. Freeze granulation and spray drying methods were found to be more suitable for large‐scale production of OCs for CLC. The results of the comparative studies may provide guidelines for selecting appropriate methods for preparing OCs on industrial scale.

Colloidal Processing and Yield Stress Modeling Towards Dry Pressed Green Bodies for Transparent Polycrystalline Alumina

Colloidal processing is a key aspect in modern ceramic processing but most formulations are found empirically. The need for a better knowledge based design of suspension formulation can be achieved by using interparticle potential modelling linked to rheological models. Here we look at the details behind slurry formulation for freeze granulation of doped alumina powders for use in the production of transparent polycrystalline alumina. The degree of complexation of the dopant ions with the dispersant, polyacrylic acid, has been investigated and shows the effect of both lowering the ionic strength and modifying the adsorption conformation. These insights into the subtleties of colloidal processing are discussed to provide a better basis for future formulation development.

Impedance analysis of 0.5Ba(Zr0.2Ti0.8)O3–0.5(Ba0.7Ca0.3)TiO3 ceramics consolidated from micro-granules

This work aims to contribute new data on the dielectric relaxation behavior of the lead-free piezoelectric 0.5Ba(Zr0.2Ti0.8)O3–0.5(Ba0.7Ca0.3)TiO3 (BZT–BCT) material processed in aqueous media. To obtain a BZT–BCT ceramic with high density, an aqueous suspension of BZT–BCT material was successfully transferred to spherical granules via freeze granulation, followed by sintering of a consolidated high green dens compact at 1350°C for 4h. The dielectric relaxation behavior in the temperature range 300–600°C over the frequency range of 0.1Hz–1MHz has been carried out to display the characteristic of dielectric relaxation behavior of the BZT–BCT ceramic. Two distinct temperature dependent peaks at characteristic frequencies were observed, which shift towards the high frequency end with increasing temperature, depicting a thermally activated relaxation phenomena in the BZT–BCT ceramic. The dependences of dielectric parameters by fitting data with Cole–Cole equations (Nyquist plot) on temperature have been discussed in detail. Relaxation time was found to decrease with increasing temperature and to obey the Arrhenius relationship. The values of calculated resistances were found to be of same order for bulk (Rb) and grain boundary (Rgb) contributions, whereas capacitance values calculated for bulk (Cb) were found to be 2 orders more than that of capacitance values calculated for grain boundaries (Cgb).

Mechanical and functional properties of Al2O3–ZrO2–MWCNTs nanocomposites

Abstract Multi-walled carbon nanotubes (MWCNTs) are often reported as additives improving mechanical and functional properties of ceramic composites. However, despite tremendous efforts in the field in the past 20 years, the results are still inconclusive. This paper studies room temperature properties of the composites with polycrystalline alumina matrix reinforced with 0.5–2 vol.% MWCNTs (composites AC) and zirconia toughened alumina with 5 vol.% of yttria partially stabilised zirconia (3Y-PSZ) containing 0.5–2 vol.% of MWCNTs (composites AZC). Dense composites were prepared through wet mixing of the respective powders with functionalised MWCNTs, followed by freeze granulation, and hot-pressing of granulated powders. Room temperature bending strength, Young's modulus, indentation fracture toughness, thermal and electrical conductivity of the composites were studied, and related to their composition and microstructure. Slight increase of Young's modulus, indentation fracture toughness, bending strength, and thermal conductivity was observed at the MWCNTs contents ≤1 vol.%. At higher MWCNTs contents the properties were impaired by agglomeration of the MWCNTs. The DC electrical conductivity increased with increasing volume fraction of the MWCNTs.

Comparison of preparation methods for iron–alumina oxygen carrier and its reduction kinetics with hydrogen in chemical looping combustion

ABSTRACTSeven preparation methods, namely sol‐gel, co‐precipitation, hydrothermal synthesis, low heating solid‐state reaction, freeze granulation, combustion synthesis, and mechanical mixing, were used to synthesize Fe2O3/Al2O3 oxygen carrier for chemical looping combustion. A comprehensive physicochemical characterization (i.e. productivity, crushing strength, crystalline characteristics, microstructure, and chemical reactivity with hydrogen) was carried out, and the effects of preparation methods and processes on the oxygen carrier performance were explored. Taking into consideration various physicochemical indices, the sol‐gel method and the freeze granulation method were preferred for oxygen carrier preparation. Following that, a critical chemical reaction in in situ gasification chemical looping combustion, the reduction reaction between oxygen carrier and hydrogen, was clarified in terms of reaction kinetics through the non‐isothermal kinetics analysis and the double extrapolation method. Temperature programmed reduction experiments of the sol‐gel‐derived Fe2O3/Al2O3 particle and hydrogen were performed using a chemisorption analyzer. The reduction mechanisms and kinetics parameters for the two‐stage reaction (reduced from Fe2O3 to Fe3O4 and then from Fe3O4 to FeAl2O4) were determined. In the first stage, the reduction reaction is described by the surface reaction model with an order of 2; on the other hand, the conversion from Fe3O4 to FeAl2O4 is dominated by the nucleation and nuclei growth process. © 2014 Curtin University of Technology and John Wiley & Sons, Ltd.

Fostering the properties of Zr0.8Sn0.2TiO4 (ZST) ceramics via freeze granulation without sintering additives

Freeze granulation fosters the properties of Zr0.8Sn0.2TiO4 ceramics with maximum density in the complete absence of sintering additives.

Structural, mechanical and dielectric properties of Ba0.6Sr0.4TiO3—The benefits of a colloidal processing approach

This paper reports on the benefits gathered from a proper colloidal dispersion/deagglomeration of a Ba0.6Sr0.4TiO3 (BST) powder in water followed by spraying the aqueous suspension against liquid nitrogen to obtain homogeneous granules. The density of green compacts derived from the freeze granulated (FG) powder was compared with that of compacts prepared from the same starting BST powder but non-granulated (NG). The sintering ability of the greens and the density, mechanical and functional properties of the obtained ceramics sintered at various temperatures properties were shown to be strongly enhanced by the freeze granulation step. Freeze granulation enabled decreasing the optimal sintering temperature for 50°C, and enhanced all the relevant measured properties, which showed a good correlation with sintered density. Maximum values of dielectric constant (εrmax=5087) and dielectric loss (tanδ=0.009) were measured at the phase transition temperature (Tc=−3°C) and at a constant frequency of 10kHz for the FG BST ceramics sintered at 1250°C, which also showed a flatter temperature-dependent dielectric profile.

Combined Cu/Mn Oxides as an Oxygen Carrier in Chemical Looping with Oxygen Uncoupling (CLOU)

This study investigates the O2 uncoupling properties of five different oxygen carrier particles, consisting of combined oxides of CuO and Mn3O4. The oxygen carriers were produced by freeze granulation followed by calcination at 950 °C for 6 h. Particles with 5, 10, 20, 31, and 61 wt % CuO were examined in both an inert (pure N2) atmosphere and in the presence of solid fuel (wood char) at 750 °C. At this relatively low temperature during fluidization with N2, the samples were capable of releasing gas-phase O2 in concentrations up to 1%. During reduction with wood char in 15 g of oxygen carriers, some materials could release gaseous O2 equal to 1.4% of their total mass. When the crushing strength and attrition index were measured with a customized jet cup, the mechanical stability of these samples was compared. These measurements showed that, in general, samples with a higher CuO content were more mechanically stable. On the basis of XRD analysis of the oxygen carriers, the major phase transitions were Mn2O3 ↔ Mn3O4 and combined spinel (Cu,Mn)3O4 ↔ CuMnO2. These transitions both provide a considerable amount of O2. It is concluded that the Cu–Mn–O system has considerable potential to be used as a oxygen carrier in chemical-looping applications at lower temperatures, perhaps interesting for biofuel combustion.

Hydrolysis Control of AlN Powders for the Aqueous Processing of Spherical AlN Granules

Spherical granules of aluminum nitride (AlN) with an average particle size of about 50 μm were produced from aqueous suspensions using an AlN powder surface treated against hydrolysis with aluminum dihydrogenphosphate [Al(H2PO4)3]. Two different amounts of Al(H2PO4)3 were tested and the effects of surface treatment and aging time were evaluated by various techniques (XRD, TG‐DTA, zeta potential and pH measurements). The treated powder exhibited antihydrolytic property and good dispersing behavior, enabling the preparation of low‐viscosity and high‐concentration aqueous AlN slurries for freeze granulation. The spherical AlN granules were sintered in a boron nitride (BN) powder bed followed by ultrasonic washing of the AlN granulates/BN mixture to remove BN. The sintered spherical AlN granules present excellent crystallinity and high sphericity as observed from SEM micrographs.

Evaluation of CuAl2O4 as an Oxygen Carrier in Chemical-Looping Combustion

The chemical-looping combustion (CLC) process is a novel solution for efficient combustion with intrinsic separation of carbon dioxide. The process uses a metal oxide as an oxygen carrier to transfer oxygen from an air to a fuel reactor where the fuel, or gasification products of the fuel, reacts with the solid oxygen carrier. In this work, copper(II) aluminate (CuAl2O4) was assessed as a potential oxygen carrier using methane as fuel. The carrier particles were produced by freeze–granulation and calcined at 1050 °C for a duration of 6 h. The chemical-looping characteristics were evaluated in a laboratory-scale fluidized-bed reactor in the temperature range of 900–950 °C during 45 alternating redox cycles. The oxygen carrier exhibited reproducible and stable reactivity behavior in this temperature range. Neither agglomeration nor defluidization was noticed in any of the cycles carried out at 900–925 °C. However, after reactivity tests at 950 °C, soft agglomeration and particle fragmentation were observed. Systematic phase analysis of the Cu–Al–O system during the redox cycle was carried out as a function of duration of reduction and oxygen concentration during the oxidation period. It was found that the CuAl2O4 is reduced to copper(I) aluminate (CuAlO2; delafossite), Cu2O, and elemental Cu. The CuAlO2 phase is characterized by slow kinetics for oxidation into CuO and CuAl2O4. Despite this kinetic limitation, complete conversion of methane with reproducible reactivity of the oxygen carrier is achieved. Thus, CuAl2O4 could be a potential oxygen carrier for chemical-looping combustion.

Yield stress modelling of doped alumina suspensions for applications in freeze granulation: towards dry pressed transparent ceramics

Rheology of powder suspensions is a key factor in many processing routes, and better understanding of the parameters that control the rheology improves technical progress by reducing the empirical factors in the formulation of powder slurries. The strict requirements for the production of transparent polycrystalline alumina demand a fundamental understanding of powder handling and processing steps. The use of dopants (Mg, Y, La) has proven useful, but produces noticeable effects on suspension rheology and influences the choice of the processing route. With the prospect of spray granulation of such slurries, the rheological behaviour of doped alumina suspensions was investigated from a fundamental approach taking into account slurry and particle characteristics, and computing the interparticle potentials. This information was then used in a yield stress model which successfully predicted the rheological behaviour of the doped alumina slurries. A strategy for improved slurry formulation is presented.

Influence of Porosity on Performance of Freeze-granulated Fe2O3/Al2O3 Oxygen Carriers Used for Chemical Looping Combustion

Chemical looping combustion (CLC) is a promising solution for the next coal-fired power generation technology with inherent CO2 separation capability. One of the critical aspects for the development of the CLC process is to develop suitable oxygen carrier (OC) particles to transfer oxygen to the fuel in the absence of air. Relevant studies have focused on active material screening, thermodynamic analysis and operational tests. This investigation was conducted on the microstructural property of OCs, to be specific, the particle porosity effect on the performance of iron-based OCs. Fe2O3, supported on Al2O3 was used as the oxygen carrier. The effect of water content of the spray slurry used to produce the OC was varied to determine the influence of OC porosity on reactivity, oxygen transfer capacity and mechanical durability. A preliminary test was done to establish the minimum and maximum water percentage needed to make slurry. A process that included freeze granulation (FG), freeze drying, and calcination was used to prepare four samples of iron oxide/alumina with various water-to-solid phase ratios. A scanning electron microscope (SEM) was used to characterize the porosity of FG Fe2O3/Al2O3 particles. A direct relationship was observed. A Shimpo FGE-10X force gauge was used to measure the crushing strength of selected samples. A thermogravimetric analyzer (TGA) coupled with a mass spectrometer (MS) was used to study the change in reaction rates through multiple reduction-oxidation cycles of the samples. Crystallinity of the OCs in reduced and oxidized forms were confirmed by XRD analysis.

Water based processing of LiFePO4/C cathode material for Li-ion batteries utilizing freeze granulation

A water based solid state synthesis of LiFePO4 has been conducted by utilizing freeze granulation. Various processing conditions were tested and achieved powder properties were characterized by density, XRD, specific surface area, carbon content, conductivity and SEM. Freeze granulation, a novel method for precursor preparation was shown to be an effective method to provide high degree of homogeneity prior to calcination and high ultimate yield of pure LiFePO4. Cathodes were manufactured by water based as well as NMP system based tape casting. A commercial LiFePO4/C powder was also characterized and used to manufacture cathodes as comparison in this study. Charge cycling tests showed promising results with high capacity and long term stability, well in the range of what the commercial powder provided. Post-milling of calcined powder prior to paste preparation for tape casting tended, however, to retard the capacity owing to disturbed carbon distribution and loss of conductivity of the LiFePO4/C. In comparison with the solvent system for cathode manufacturing, the water based system gave similar cell performance, illustrating the possibility to apply a more environmentally sustainable processing of Li-battery cells.