Recently, enormous efforts have been done within the development of Li-ion batteries for use in portable electric devices from small scale applications such as mobile phones, digital cameras, laptop computers, to large scale applications like electrical vehicles (EVs) and hybrid electric vehicles (HEVs). LiFePO4 as an active material in cathode materials in Li-ion batteries has shown outstanding advantages compare to other cathode materials such as low cost, low toxicity and environmental compatibility, good thermal stability, high theoretical specific capacity of 170 mAh/g and operating reversibility at 3.4V. Still, it is a need to develop the manufacture of the cathode material to achieve improved performance reliability by using environmental sustainable processes in order to meet future demands in large scale production and uses of Li-ion batteries. The aim of this work was to develop a non-toxic, cheap, efficient and environmentally friendly process for synthesis of high quality active cathode material based on LiFePO4 for Li-ion batteries. Water based suspensions/solutions containing various reactant constituents have been homogenized, granulated and calcined. Freeze granulation was applied as the key tool for the synthesis of LiFePO4 with integrated carbon in order to produce granules with high degree of homogeneity prior to calcination. The resulting powder materials have been evaluated by XRD, carbon and conductivity measurements and characterization of other physical properties such as density and specific surface area. The promising version was used for manufacture of cathode material by tape casting, cell assembling and evaluation of the performance by charge/discharge cycling of the cells. For the best sample in our experiment the XRD results revealed a high degree of purity, homogeneity and crystallinity of LiFePO4. The produced LiFePO4/C composite also had a high specific surface area and, therefore, considered as a promising material for cathode manufacturing and cell assembly. A discharge capacity of 155 and 140 mAh/g was achieved at the fifth cycle at 0.1C rate at room temperature for the cathodes which were made with NMP (solvent based) and water system, respectively. The long-term stability test indicated good result with no loss in capacity for at least 390 cycles. The satisfactory discharge capacity should be attributed to the homogenous nano-sized particles with a conductive porous carbon structure that was provided by the freeze granulation process and adapted calcination process.
Keywords: Li-ion batteries, LiFePO4, cathode active material, specific capacity, freeze granulation, calcination, LiFePO4/C composite, cell assembly.
Use of freeze granulated powders is successfully used as an industrially viable alternative to loose powder sintering for transparent polycrystalline alumina (PCA). Freeze granulation with narrow granule size distribution was realized after suspension condition optimization, with very good ﬂowability and regular spherical shapes. The key factors are low viscosity slurries linked to the complex interactions between the organic processing additives and their interaction with dopant ions in solution. Real in-line transmittances (RITs) of 52% were achieved by pulsed electric current sintering (PECS) of dry pressed green bodies from doped granulated powders. This is the ﬁrst example of a high RIT (>50%) alumina produced from simple dry pressing of a granulated powder. The results indicate that higher granule solid loads and lower organic additive concentrations give better RITs after PECS. Aging of the powder slurry before freeze granulation proves a crucial step for the optical performance of the ﬁnal transparent PCA.
In the present study the freeze granulation technique is applied in the manufacturing process of Mn-Zn power ferrites.The powders are prepared by the solid state reaction method and a comparison between the standard industrially used spray-drying method and the freeze granulation process with subsequent freeze drying has been carried out, in terms of granulate morphology, compaction behavior and pore size distribution, sintering behavior and magnetic performance. It apeared that the freeze granulation process enables the formation of homogeneous green compact microstructures and finally leads to sintered products of good magnetic quality. Consequently, Mn-Zn ferrites with low losses of 287 mW/cm3 (at measuring conditions f=100 kHz, B=200 mT and T=1000C) are manufactured.
Granulation is one of the most important unit operations in the production of pharmaceutical oral dosage forms. Granulation process will improve flow and compression characteristics, reduce segregation, improve content uniformity, and eliminate excessive amounts of fine particles. The results will be improved yields, reduced tablet defects, increased productivity, and reduced down time. Pharmaceutical products are processed all over the world using the direct-compressing, wet-granulation, or dry granulation methods. Which method is chosen depends on the ingredients individual characteristics and ability to properly flow, compresses, eject, and disintegrate. Choosing a method requires thorough investigation of each ingredient in the formula, the combination of ingredients, and how they work with each other. Then the proper granulation process can be applied. The objective of present article was to focus on the novel granulation technology.
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.
Keywords: chemical looping combustion (CLC), oxygen carrier, porosity
Today influenza vaccine powder for pulmonary delivery are being made by Freeze Granulation resulting in a homogeneous product. The immunogenic properties of the vaccine will be maintained under the storage condition.
Freeze Granulation is a wet granulation method where the powders, chemicals and binders are first mixed and dispersed in a solvent. In the next step the homogeneous slurry is pumped and sprayed through a nozzle to form droplets, which are sprayed into liquid nitrogen for instant freezing. In the final step the frozen granulate is moved to a freeze dryer where the solvent is sublimated leaving spherical, dust-free and homogeneous granules. The solvent could be water or organic solvents with a freezing point close to zero degree, like cyclohexane.