News on how Freeze Granulation can improve our powder properties

Structured emulsion-templated porous copolymer based on photopolymerization for carbon capture

Dariush Nikjoo, Farid Akhtar

Abstract

Porous hydrogel copolymers of acrylamide (AAM) and acrylic acid (AAC) were structured in the form of monoliths and granules. AAM-co-AAC porous copolymer monoliths were synthesized using high internal phase emulsion (HIPE) as template and photopolymerization. For granulation, photopolymerization was used for the fabrication of the AAM-co-AAC hydrogel, which was subsequently freeze-granulated. The structural analysis (FTIR and XRD) confirmed the successful synthesis of hydrogel copolymers. The CO2 uptake capacity of structured AAM-co-AAC copolymers was evaluated through adsorption and absorption mechanisms by volumetric and gravimetric methods, respectively. The granules exhibited the CO2 adsorption uptake of 0.8 mmol g−1 at 25 kPa and 298 K. The CO2 and N2 adsorption data demonstrated that the hydrogel copolymers were selective for CO2. Furthermore, the granules were capable of capturing CO2 in the presence of water. The results of absorption of CO2 on water-swollen granules demonstrated that CO2-uptake capacity increases with increasing water content up to 1.8 mmol g−1.

Keywords

Porous polymer, Photopolymerization, Adsorption, Absorption, Carbon capture

Phase change and droplet dynamics for a free falling water droplet

K.R. Sultana, K. Pope, L.S. Lam, Y.S. Muzychka

Abstract

This paper numerically examines phase change of free falling droplets in a sub-zero environment. The model is based on the solution of the Navier-Stokes equations coupled with the Volume of Fluid (VOF) methodology for tracking the droplet-air interface. A 2D axisymmetric model is adopted to implement the influential numerical parameters. The phase change phenomenon of fresh and salt water droplets with constant and variable properties are considered in this model. Current results reveal that the internal circulation enhances heat transfer to the surrounding air and increases the nucleation phenomenon. Furthermore, larger sized droplets have a higher nucleation temperature than the smaller sized droplets. The computational results are compared to previously published experimental data for nucleation and droplet dynamics. The results of this paper provide new insights on phase change and droplet dynamics and contribute to the understanding of mechanisms involved with spray freezing applications.

Keywords

Computational fluid dynamics, Droplet, Nucleation, Sub-zero environment, Thermophysical properties

Improving quercetin dissolution and bioaccessibility with reduced crystallite sizes through media milling technique

Muwen Lu, Chi-Tang Ho, Qingrong Huang

Abstract

Quercetin (QC) is a common bioflavonoid with low water solubility, which limits its oral bioavailability and in vivo beneficial functions. To enhance QC bioaccessibility, QC nanoparticles were produced using the media milling technology. Hydrophobically modified starch (HMS) was added with the ratio of 1:1 to QC as a stabilizer to prevent the agglomeration of QC particles. The QC nanodispersions were either spray-dried or freeze-dried after media milling process. Physicochemical characteristics of dried QC powders were measured through dynamic light scattering (DLS), Fourier Transform-Infrared spectroscopy (FTIR), dissolution test and X-ray diffraction (XRD). The detailed crystallite structures were carefully analyzed. The TNO dynamic gastro-intestinal model-1 (TIM-1) was utilized to study the in vitro QC bioaccessibility by simulation of the digestive processes in the upper GI tract. This study suggests that media milling technique combined with spray/freeze-drying treatment is an efficient processing method for the development of crystalline nutraceuticals-based functional food products with reduced crystallite sizes and enhanced metastable equilibrium solubility, dissolution and bioaccessibility.

Keywords

Quercetin, Nanoparticle, Wet milling, Dissolution, Bioaccessibility

Solid state stability of polyphenols from a plant extract after fluid bed atmospheric spray-freeze-drying

Cristiane Cardoso Correia Teixeira, Tatiana Pereira de Freitas Cabral, Luciana, Alves Tacon, Isabel Lemos Villardi, Aurea Donizete Lanchote, Luis Alexandre Pedro deFreitas

Abstract

Dry powder extracts are the most suitable pharmaceutical forms of phytomedicines due to their greater physical and chemical stability in the solid state, in addition to the possibility of easy preparation of tablets and capsules. Recently, Baccharis dracunculifolia D.C. crops have been stimulated in Brazil to obtain the green propolis, which is derived from pollen harvesting of Baccharis by the Apis mellifera, and develop new phytomedicines from this plant. The aim of this work was to obtain stable powdered Baccharis dracunculifolia leaf extracts dried by fluidized-bed atmospheric spray-freeze-drying and study the stability of its chemical markers in the solid state. The drying was performed using D-mannitol, modified corn starch and their mixture as adjuvants. Physical characterization was performed by determining the dried extract powder size, morphology, flow and packing. Their chemical stability was evaluated by high performance liquid chromatography quantification of p-coumaric acid, cinnamic acid, artepillin C and baccharin. The antioxidant activity of the dried extract was determined using the stable free radical 2,2-diphenylpicrylhydrazil. The results showed that the four prenylated compounds are sensitive to drying at freezing temperatures, but D-mannitol could efficiently prevent their loss. The Baccharis spray-freeze-dried extracts showed a high yield, low moisture and excellent pharmacotechnical properties. The stability tests demonstrated a high loss of polyphenols at 40, 60 and 80 °C, especially artepillin C (the main marker) and showed high instability. The kinetics of polyphenols losses were measured, and their rates were used to fit three-dimensional diffusion models and the Arrhenius equation. The results demonstrate that the Baccharis dracunculifolia dried extract, using artepillin C as a reference, could achieve a shelf life as long as 10 years when stored at 4 °C and protected from light. The process of fluid-bed atmospheric spray-freeze-drying was shown to be an attractive alternative for drying of heat-sensitive and high value-added materials such as medicinal plant extracts.

Keywords

Polyphenols, Baccharis dracunculifolia, Fluid bed, Spray-freeze-drying, Degradation

Synthesis of high-performance Li2FeSiO4/C composite powder by spray-freezing/freeze-drying a solution with two carbon sources

Synthesis of high-performance Li₂FeSiO₄/C composite powder by spray-freezing/freeze-drying a solution with two carbon sources

Yukiko Fujita, Hiroaki Iwase, Kenji Shida, Jinsun Liao, Takehisa Fukui, Motohide Matsuda

Abstract

Li₂FeSiO₄ is a promising cathode active material for lithium-ion batteries due to its high theoretical capacity. Spray-freezing/freeze-drying, a practical process reported for the synthesis of various ceramic powders, is applied to the synthesis of Li₂FeSiO₄/C composite powders and high-performance Li₂FeSiO₄/C composite powders are successfully synthesized by using starting solutions containing both Indian ink and glucose as carbon sources followed by heating. The synthesized composite powders have a unique structure, composed of Li₂FeSiO₄ nanoparticles coated with a thin carbon layer formed by the carbonization of glucose and carbon nanoparticles from Indian ink. The carbon layer enhances the electrochemical reactivity of the Li₂FeSiO₄, and the carbon nanoparticles play a role in the formation of electron-conducting paths in the cathode. The composite powders deliver an initial discharge capacity of 195 and 137 mAh g⁻¹ at 0.1 C and 1 C, respectively, without further addition of conductive additive. The discharge capacity at 1 C is 72 mAh g⁻¹ after the 100^th cycle, corresponding to approximately 75% of the capacity at the 2nd cycle.

Keywords

Lithium-ion battery, Cathode material, Li2FeSiO4/C, Spray-freezing/freeze-drying, Nanoparticle, Composite powder

ECerS2017 Fourth Day

Fourth day at the 15th Conference & Exhibition of the European Ceramic Society (ECerS2017), 13th of July, 2017. Discussions on the applications of Freeze Granulation on the processing of high performance ceramics.

ECerS2017 Third day

Third day at ECerS2017 in Budapest with good meetings on how to apply Freeze Granulation for new challenges within processing of Ceramic powders, like diamonds and graphene, and also powder micro encapsulation.

ECerS2017 Second day

Second day at ECerS2017 in Budapest with discussions on applications of Freeze Granulation.

ECerS2017 First day seminar by Ola at PowderPro

On the first day of ECerS2017 in Budapest Ola Lyckfeldt hold a seminar on (klick on the title) – Freeze Granulation – A multi-tool for enhanced ceramic processing.

Anisotropy of functional properties of SiC composites with GNPs, GO and in-situ formed graphene

Ondrej Hanzel, Richard Sedlák, Jaroslav Sedláček, Valéria Bizovská, Roman Bystrický, Vladimír Girman, Alexandra Kovalčíková, Ján Dusza, Pavol Šajgalík

Abstract

This paper reports on anisotropy of functional properties of different silicon carbide-graphene composites due to preferential orientation of graphene layers during sintering. Dense silicon carbide/graphene nanoplatelets (SiC/GNPs) and silicon carbide/graphene oxide (SiC/GO) composites were sintered in the presence of yttria (Y₂O₃) and alumina (Al₂O₃) sintering additives at 1800 °C in vacuum by the rapid hot pressing (RHP) technique. It is found that electrical conductivity of SiC/GNPs and SiC/GO composites increases significantly in the perpendicular direction to the RHP pressing axis, reached up to 1775 S/m in the case of SiC/GO (for 3.15 wt.% of rGO). Also, thermal diffusivity was found to increase slightly by the addition of GNPs in the SiC/GNPs composites in the perpendicular direction to the RHP pressing axis. But, in the parallel direction, the addition of GNPs showed a negative effect. The formation of graphene domains was observed in reference sample SiC-Y₂O₃-Al₂O₃ sintered by RHP, without any addition of graphene. Their presence was confirmed indirectly by increasing electrical conductivity about three orders of magnitude in comparison to the reference sample sintered by conventional hot press (HP). Raman, SEM and TEM analysis were used for direct evidence of presence of graphene domains in RHP reference sample.

Keywords

Graphene nanoplatelets; Graphene oxide; Silicon carbide; Functional properties; Anisotropy