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

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

Ondrej HanzelRichard SedlákJaroslav SedláčekValéria BizovskáRoman BystrickýVladimír GirmanAlexandra KovalčíkováJán DuszaPavol 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 nanoplateletsGraphene oxideSilicon carbideFunctional propertiesAnisotropy

 

Machinability analysis of multi walled carbon nanotubes filled alumina composites in wire electrical discharge machining process

Machinability analysis of multi walled carbon nanotubes filled alumina composites in wire electrical discharge machining process

Meinam Annebushan Singh, Deba Kumar SarmaOndrej Hanzel, Jaroslav Sedláček, Pavol Šajgalík

Abstract

The approach of machining ceramics with electrical discharge machining process is a great challenge till date due to its low electrical conductivity. Machining is made possible by reinforcing with a conductive phase which increases the overall electrical conductivity. Present work focuses on machining of multi walled carbon nanotubes filled alumina composites. Samples with concentrations ranging from 2.5 to 12.5 vol.% are considered for machining. At lower concentration of 2.5 vol.%, effective machining is not possible. Wire lag phenomena is observed during machining at 5 vol.% sample concentration. Proper machinability is observed with concentration of 7.5 vol.% or more. Also, long micro-cracks are obtained during machining that leads to the workpiece breakage. Spalling effect is observed as the most dominating material removal mechanism. A comparison between alumina composites and conducting metallic alloys were carried out for surface characteristics.

Keywords

AluminaMWCNTWire EDMMRRRa

 

 

 

Microstructure of plasma sprayed Al2O3-3wt% TiO2 coating using freeze granulated powder

Microstructure of plasma sprayed Al2O3-3wt% TiO2 coating using freeze granulated powder

Yiming Yao, Ola Lyckfeldt, Aurélien Tricoire, Dennis Lundström, Uta Klement

Abstract

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.

Keywords

Al2O3-TiO2, Freeze Granulation, Plasma Spray, Microstructure

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

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

Ha-Neul Kim, Jin-Myung Kim, Mi-Ju Kim, Jae-Woong Ko, Young-Jo Park, Kisu Lee, Doo Hyun Choi

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 MgAl2O4 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 MgAl2O4 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.

Keywords

Transparent; MgAl2O4; Spray freeze drying; Freeze granulation; Microfluidization

Large porous particles for respiratory drug delivery. Glycine-based formulations

Large porous particles for respiratory drug delivery. Glycine-based formulations

A.G. Ogienko, E.G. Bogdanova, N.A. Trofimov, S.A. Myz, A.A. Ogienko, B.A. Kolesov, A.S. Yunoshev, N.V. Zubikov, A.Yu. Manakov, V.V. Boldyrev, E.V. Boldyreva

Abstract

Large porous particles are becoming increasingly popular as carriers for pulmonary drug delivery with both local and systemic applications. These particles have high geometric diameters (5–30 μm) but low bulk density (~ 0.1 g/cm3 or less) such that the aerodynamic diameter remains low (1–5 μm). In this study salbutamol and budesonide serve as model inhalable drugs with poor water solubility. A novel method is proposed for the production of dry powder inhaler formulations with enhanced aerosol performance (e.g. for salbutamol-glycine formulation the fine particle fraction (FPF ≤ 4.7 μm) value is 67.0 ± 1.3%) from substances that are poorly soluble in water. To overcome the problems related to extremely poor aqueous solubility of the APIs, not individual solvents are used for spray freeze-drying of API solutions, but organic-water mixtures, which can form clathrate hydrates at low temperatures and release APIs or their complexes as fine powders, which form large porous particles after the clathrates are removed by sublimation. Zwitterionic glycine has been used as an additive to API directly in solutions prior to spray freeze-drying, in order to prevent aggregation of powders, to enhance their dispersibility and improve air-flow properties. The clathrate-forming spray freeze-drying process in the multi-component system was optimized using low-temperature powder X-ray diffraction and thermal analysis.

Keywords

Spray freeze-drying, salbutamol, budesonide, glycine, clathrate hydrates, dry powder inhaler formulation, large porous particles

Review on novel granulation techniques

Review on novel granulation techniques

Nayan Patil, S. C. Khadse, P. P. Ige

Abstract

Tablets are the generally use dosage form, suitable to long-suffering observance, stretch in dose routine as well as design of dosage form. Pharmaceutical tablets be process every one in excess of the humanity use direct-compression, wet and dry granulation. The process choose depends on the ingredient entity description also aptitude towards surge suitably, compact, throw out with collapse. Selecting correct granulation way require systematic study of every component into the method, mixture of ingredient and their interaction. Exhaustive research is going on different novel granulation techniques that are able of replacing traditional granulation techniques as they have advantages of being cost-effective and high yielding. The object of their article is towards centre of attention lying on the novel granulation tools similar to pneumatic dry granulation, freeze granulation, Granurex® technology and so on.

KEYWORDS

Pneumatic dry granulation, melt granulation, nucleation, Granurex®.

Novel Budesonide Particles for Dry Powder Inhalation Prepared Using a Microfluidic Reactor Coupled With Ultrasonic Spray Freeze Drying.

Novel Budesonide Particles for Dry Powder Inhalation Prepared Using a Microfluidic Reactor Coupled With Ultrasonic Spray Freeze Drying.

Saboti D, Maver U, Chan HK, Planinšek O

Abstract

Budesonide (BDS) is a potent active pharmaceutical ingredient, often administered using respiratory devices such as metered dose inhalers, nebulizers, and dry powder inhalers. Inhalable drug particles are conventionally produced by crystallization followed by milling. This approach tends to generate partially amorphous materials that require post-processing to improve the formulations’ stability. Other methods involve homogenization or precipitation and often require the use of stabilizers, mostly surfactants. The purpose of this study was therefore to develop a novel method for preparation of fine BDS particles using a microfluidic reactor coupled with ultrasonic spray freeze drying, and hence avoiding the need of additional homogenization or stabilizer use. A T-junction microfluidic reactor was employed to produce particle suspension (using an ethanol-water, methanol-water, and an acetone-water system), which was directly fed into an ultrasonic atomization probe, followed by direct feeding to liquid nitrogen. Freeze drying was the final preparation step. The result was fine crystalline BDS powders which, when blended with lactose and dispersed in an Aerolizer at 100 L/min, generated fine particle fraction in the range 47.6% ± 2.8% to 54.9% ± 1.8%, thus exhibiting a good aerosol performance. Subsequent sample analysis confirmed the suitability of the developed method to produce inhalable drug particles without additional homogenization or stabilizers. The developed method provides a viable solution for particle isolation in microfluidics in general.

KEYWORDS

DPI; aerosol; budesonide; dry powder inhalation; formulation; microfluidic reactor; particle isolation; powder technology; pulmonary drug delivery; ultrasonic spray freeze drying

Effect of the solvent composition and annealing process on the preparation of spray freeze-dried acetaminophen powder

Effect of the solvent composition and annealing process on the preparation of spray freeze-dried acetaminophen powder

Jae-Young Her, Kwang-Geun Lee

Abstract

The analgesic and physical properties of acetaminophen powder suitable as an inhaled drug produced by spray freeze-drying (SFD) were compared with those of raw acetaminophen. A laser particle size analyzer and scanning electron microscopy (SEM) were applied to estimate physical structure and properties of the particles. A cyclooxygenase (COX) inhibitor screening assay was used to compare the antipyretic and analgesic activity of raw and SFD acetaminophen. According to SEM, SFD acetaminophen particles had various shapes and sizes with porous structures. The optimized conditions for solvent, annealing temperature, and annealing time were water/ethanol mixture (60% water and 40% ethanol), −40°C, and 7 h, respectively. The diameter of optimized acetaminophen powder was 7.33 µm, and the aerodynamic particle size was 3.38 µm. The antipyretic and analgesic activities of acetaminophen after SFD were from 84.3 to 97.1% for COX-1 and from 91.6 to 102.9% for COX-2 compared to those of raw acetaminophen, respectively.

Keywords

Acetaminophen, inhaled drug, optimized solvent, powder process, spray freeze-drying

Spray freeze granulation of submicrometre α-alumina using ultrasonicati

Spray freeze granulation of submicrometre α-alumina using ultrasonicati

S. Ghanizadeh, P. Ramanujam, B. Vaidhyanathan, J. Binner

Abstract

Granulation is a key factor towards improvement of the flowability of fine ceramic powders to make them suitable for industrial dry pressing. Controlled granulation of fine alumina particles with a primary particle size of ∼ 150 nm was carried out using spray-freeze drying, which led to the production of flowable granules with high crushability. The fracture surface of uniaxially die-pressed green bodies made from granules with density values of ≥ 50 % of theoretical showed a uniform microstructure. Sintering experiments were performed using conventional single- and two-stage radiant heating methods followed by density and grain size measurement and characterisation of the final dense compacts to study the efficiency of two-stage sintering in grain growth elimination. The results have been compared with those of alumina bodies prepared using similar suspension by the slip-casting route.

Keywords

Alumina, granulation, spray-freeze drying, two-stage sintering

Effect of freeze-drying treatment on the optical properties of SPS-sintered alumina

Effect of freeze-drying treatment on the optical properties of SPS-sintered alumina

M. Suárez, A. Fernández, J.L. Menéndez, M. Nygren, R. Torrecillas, Z. Zhao

Abstract

This study looks at the influence of alumina powder processing on the preparation of transparent alumina by Spark Plasma Sintering (SPS). Zeta potential measurements were carried out on alumina suspensions in order to determine the best dispersion conditions. Stable slurries were submitted to a spray freeze drying process and their sintering behavior was compared with the corresponding non spray freeze dried powders. Transparent alumina samples were successfully prepared from alumina powders by Spark Plasma Sintering. An optical model considering pore and grain size distributions has been developed to obtain information about porosity in dense materials. It was found that the final density and, accordingly, the optical properties were improved when spray freeze dried starting powder was used.

Keywords

A. Sintering; C. Optical properties; D. Al2O3