Powder Density Research Articles

Grinding characteristics and energy consumption in cryogenic and ambient grinding of ajwain seeds at varied moisture contents

The study on cryogenic and ambient grinding of ajwain seeds was envisaged to understand the energy consumption pattern during different grinding processes as a function of moisture content 8, 12, 16 and 20% (db) for AA-1, AA-2 and AA-93 varieties of ajwain seeds. The grinding time was found to increase from 57.6 ± 0.01 to 180 ± 0.08 s, whereas feed rate was found to decrease from 6.25 ± 0.07 to 2.00 ± 0.12 kg h−1 with the increasing moisture content. This resulted in more power consumption ranging from 0.012 ± 0.08 to 0.037 ± 0.007 kW h−1 in all the ajwain varieties for the selected moisture range under cryogenic and ambient grinding conditions. But the specific energy consumption was found to be higher in case of ambient grinding conditions. Also, the various energy models such as Kick's, Rittinger's and Bond's work index were found to increase significantly (p < 0.05) with increasing moisture content ranging from 1.02 to 13.22 kJ kg−1, 0.55 to 21.92 kJ kg−1 and 15.31 to 195.31 kJ kg−1, respectively. The cryogenic grinding was found to be more energy efficient than ambient grinding. Moreover, cryogenic grinding results in more yield and good quality product with uniform particle size distribution and lower powder density. This study will help the food processing industries while grinding spices and for designing of appropriate grinder specifically for grinding ajwain seeds.

Production of Oscillatoria sp. BTA‐170 biomass in photobioreactor: Analysis of composition, drying behavior, sorption isotherm, and powder flow characteristics

AbstractIn this study, Oscillatoria sp. BTA‐170 was grown in a photobioreactor for 15 days, yielding 3.1 g/L of biomass. During the composition analysis of biomass, the moisture, protein, carbohydrate, lipid, and ash contents were found to be 83.27, 6.36, 5.48, 3.79, and 1.1% on a wet basis (w.b), respectively. The tray drying properties of cyanobacterial biomass were investigated at temperatures of 40, 60, and 80°C with constant air velocity of 0.6 m/s. To reduce the moisture content of biomass from 83.27% to &lt;10%, drying time required 2, 12, and 30 hr at 80, 60, and 40°C, respectively. The calculated effective moisture diffusivity of biomass was 5.10 × 10−9, 6.34 × 10−8, and 2.30 × 10−7 m2/s at 40, 60, and 80°C, respectively, and the activation energy was found to be 28.01, 31.04, and 33.27 kJ/mol at 40, 60, and 80°C, respectively. The logarithmic and Henderson and Pabis models showed the highest R2 values of 0.997 and 0.996 at 80°C, respectively, and were thus employed to explain biomass drying characteristics. The drying constant value grew with increasing temperature, with the highest value obtained using the logarithmic model at 80°C being 0.523 (hr−1). The bulk density of biomass powder dried at 80°C was 598.21 kg/m3 and the tapped density was 652.80 kg/m3, with Hausner ratio and Carr index of 1.091 and 8.363, respectively, showing that biomass powder had excellent flow qualities. The dried cyanobacterial biomass is a great source of protein, according to FTIR measurements. Similarly, after selecting four models based on the sorption isotherm, the GAB model was shown to be the best fit to represent the sorption behavior of Oscillatoria sp. BTA‐170 powder.Practical ApplicationsThe drying characteristics of Oscillatoria sp. BTA‐170 biomass were evaluated using thin‐layer drying models. The primary goal of drying biomass is to remove water from the solids to a point where microorganisms and degradation chemical processes are considerably reduced. The analysis of drying properties aids in the development of a cost‐effective dryer. By hastening the manufacture of biomass powder, the effective design of the drying process helps to decrease time and processing costs. After the drying process, an FTIR analysis can be used to determine the presence of macromolecules. Similarly, sorption isotherm studies were performed to evaluate the safe moisture content of items and to estimate shelf life at a specific temperature and relative humidity.

Calcium-Reduced Micellar Casein Concentrate-Physicochemical Properties of Powders and Functional Properties of the Dispersions.

This study aimed to examine the physicochemical properties of 30% calcium (Ca)-reduced micellar casein 80% protein powders (RC-MCC) and the functional properties of the resultant dispersions. The calcium reduction in the micellar casein (MCC) powder was achieved by subjecting the liquid micellular casein obtained from the microfiltration of pasteurized skim milk to carbon dioxide (CO2) treatment before and during ultrafiltration. The CO2 injection was controlled to obtain a 0 and 30% reduction in calcium in the C-MCC (control) and RC-MCC powders, respectively. The MCC powders were tested for physicochemical properties such as chemical composition, particle size distribution, and bulk density. The MCC powders were reconstituted in deionized water to test the functional properties of the dispersions, i.e., solubility, viscosity, heat stability, emulsifying capacity, emulsion stability, foam capacity, and foam stability. The CO2 injection did not result in any significant differences in the composition except mineral contents, particularly calcium. The particle size and bulk density of RC-MCC powders were significantly (p < 0.05) lower than control powders. The RC-MCC powder dispersions showed increased heat stability compared to control, whereas no significant changes in viscosity and emulsification capacity were observed between the two dispersions. However, the emulsion stability and foam stability of RC-MCC dispersions were significantly lower than C-MCC dispersions. This study showed that by utilizing a novel microfiltration–CO2 injection–ultrafiltration process, 30% calcium-reduced MCC powder was commercially feasible. This research also provides a detailed understanding of the effect of calcium reduction on the functional properties of resultant MCC dispersions. It showed that calcium reduction could improve the solubility of the powders and heat stability and foam capacity of the dispersions.

Effect of powder variability on laser powder bed fusion processing and properties of 316L

To date, the effects of powder properties, both physical and chemical, on the printed properties of as-built components is still a topic that is poorly understood. A contributing factor is the lack of relevant methods for evaluating the rheological properties of powder, or flowability. This study presents a review of different 316 L powder grades that were produced using various atomization techniques. The physical powder properties were evaluated using powder metallurgical techniques, a powder rheometer (FT4) and a rotating drum analyser (RPA). The results indicate that both the FT4 and RPA are suitable for powder characterization. However, the parameter selection for evaluation must be done keeping in mind the application, in this case thin layer powder spreading. It was found that all bulk powder density measurements, basic flow energy and the break energy were able to both differentiate between powder grades and predict how suitable the powder will be for the laser-based powder-bed fusion process. Despite some printability challenges of the water atomized grades at higher layer thicknesses, it was found that both gas atomized grades performed similarly despite minor differences in particle size distribution. Furthermore, powder variability did not show any detrimental effects on the resulting mechanical properties.

Densification behavior of tungsten alloy powders during hot isostatic pressing

To investigate the densification behavior of tungsten alloy powders during hot isostatic pressing (HIP), the Shima yielding criterion of MSC.Marc was applied to simulate the densification behavior of 93 W-Ni-Fe during HIP. The densification process of tungsten alloy powders and the equivalent stress distribution of capsule during HIP were systematically analyzed. The results show that the densification of tungsten alloy powders during HIP can be divided into several main processes: the first step is expansion, then followed by shrinking, and finally densification with uniform distribution. The density of tungsten alloy reached 93.68% after HIP at 1400 ℃, 140 MPa. Meanwhile, in order to evaluate the quality of the simulation, the HIP experiments were conducted. The deformation of the capsule and the density and mechanical property of tungsten alloy were tested and then compared with simulation results. The results indicate that the maximum relative error of simulation was 1.62% in axial direction and 5.6% in radial direction, and the average relative error of density was only 1.4%. Besides that, by comparing two groups of HIP experiments at different temperatures, the results show that the relative density increased by 2.3% with the temperature increased by 100 ℃.

Raman Spectroscopic Investigation and Electronic State Calculation for Ca2(Mn,Ti)O4 Black Pigments with High Near-Infrared (NIR) Reflectivity.

Layered perovskite A2BO4 compounds were studied by a combination of X-ray powder diffraction (XRD) analysis, Raman spectroscopy, and density functional theory (DFT) calculations. Ti4+-doped Ca2MnO4 ceramics with high near-infrared (NIR) reflectivity were selected as a test case. After elucidating their crystal structures (I41/acd) by XRD analysis, Raman spectroscopy was applied. Raman peaks were observed at approximately 178, 290, 330, 463, 500, and 562 cm-1, which were confirmed by DFT calculations, and were in modes identical to those reported for Sr2IrO4 in the same space group. An additional peak was observed at approximately 780 cm-1 for the Ti4+-doped samples, indicating that a silent A2g mode was activated by doping with Ti4+, similar to the A1g (breathing) mode found in B-site-substituted simple perovskite and B-site-ordered double perovskite structures. The XRD patterns of the doped samples did not exhibit any additional X-ray reflections, except for the pattern typical of nondoped Ca2MnO4. Thus, these results were attributed to the presence of the Ti-Ti correlation with a certain distance. The calculated band gap energies of Ca2MnO4 and Ca2Mn0.75Ti0.25O4 were approximately 1.8 eV, which was in reasonable agreement with the experimental value. The DFT calculations also revealed that one of the factors contributing to the enhancement of NIR reflectivity upon introduction of Ti4+ ions is the reduced density of states (DOS) near the Fermi level.

A Ternary Model for Particle Packing Optimization

Powder packing in metal powders is an important aspect of additive manufacturing (otherwise known as 3-D printing), as it directly impacts the physical and mechanical properties of materials. Improving the packing density of powder directly impacts the microstructure of the finished 3D-printed part and ultimately enhances the surface finish. To obtain the most efficient packing of a given powder, different powder blends of that material must be mixed to minimize the number of voids, irrespective of the irregularities in the particle morphology and flowability, thereby increasing the density of the powder. To achieve this, a methodology for mixing powder must be developed, for each powder type, to obtain the maximum packing density. This paper presents a model that adequately predicts the volumetric fraction of the powder grades necessary for obtaining the maximum packing density for a given powder sample. The model factors in the disparity between theoretical assumptions and the experimental outcome by introducing a volume reduction factor. We outline the model development steps in this paper, testing it with a real-world powder system.

Electrophoretic Deposited Quartz Powder-Assisted Growth of Multicrystalline Silicon

Ingot multicrystalline silicon (Mc-Si) needs to be improved in quality and reduced in cost compared with Czochralski monocrystalline silicon. A uniform and dense quartz nucleation layer was obtained by the electrophoretic deposition of quartz powder on the surface of the silicon wafer. The deposited silicon wafer was annealed at 600 °C for 1 h, and one side of the silicon wafer with the quartz layer was glued to the crucible. During the growth of Mc-Si crystal, the dense quartz powder can play a nucleation role. The results show that the average lifetime of the minority carriers a of quartz-assisted silicon ingot is 7.4 μs. The overall dislocation density of an electrophoretic deposition quartz-assisted silica ingot is low, and the defect density in the middle of the silica ingot is 1.5%, which is significantly lower than that of spray quartz (3.1%) and silicon particle (4.2%). Moreover, electrophoretic deposited quartz-assisted mc-Si can obtain oriented grains, which offers a potential to apply alkaline texturing on mc-Si wafers.

Process Parameter Optimization on Selective Laser Melting of CuSn10 Powders Based on Response Surface Methodology

Abstract A shaping test of CuSn10 powders was carried out by using the selective laser melting (SLM) technology to study influences of process parameters of SLM on compactness of specimens. Meanwhile, process parameters were optimized based on the response surface methodology. Meanwhile, phase composition and microstructure of formed part were analyzed by XRD and OM. Results demonstrated that as the energy density of laser body increases from 146.7 J·mm-3 to 181.3 J·mm-3, pores of samples decrease and the compactness increases from 98.97% to about 99.7%. Subsequently, the compactness begins to decrease with the continuous increase of laser energy density. The incomplete melting of powder under low energy density and gasification of powders under high energy density are major factors that influence the compactness. Over low or high laser energy density is disadvantageous for the improvement of compactness. A mathematical model of interaction between three factors (laser power, laser scanning speed and scanning space) and response value (compactness) was built up by using the BBD principle design test of response surface methodology. The degree of fitting (R2) and correction coefficient (R2 adj) of the model were 0.9952 and 0.9866, which agree well with the fitting degree of experimental tests. Among three factors, influences of laser power and scanning speed on compactness are equivalent and more significant than scanning space. The optimal process parameters which were predicted by the model were laser power=331.471 W, scanning speed=648.045 mm·s-1, scanning space=69.9302 μm. Under this circumstance, the compactness of CuSn10 powders after SLM is 99.75%. According to experimental verification, the practical value of compactness is 99.74%, showing a very small relative error. This proves that the BBD model is reliable. The shaped part is mainly composed of α-Cu phase and metastable phase β’-Cu13.7Sn. Compared with the original powders, the content of metastable phase β’ increases significantly, while the δ-Cu41Sn11 phase disappears.

Structural Phase Transitions in closo-Dicarbadodecaboranes C2B10H12.

The crystal structures of three thermal polymorphs (I, II, and III) for each isomer of closo-dicarbadodecaboranes C2B10H12 (ortho, meta, and para) have been determined by combining synchrotron radiation X-ray powder diffraction and density functional theory calculations. The structures are in agreement with previous calorimetric and spectroscopic studies. The difference between rotatory phases (plastic crystals) I and II lies in isotropic rotations in the former and anisotropic rotations of the icosahedral clusters in the latter. Phase I is the cubic close packing (ccp) of rotating closo-molecules C2B10H12 in the space group Fm3̅. Phase II is the ccp of rotating closo-molecules C2B10H12 in the cubic space group Pa3̅. The preferred rotational axis in II varies with the isomer. The ordered phases III are orthorhombic (meta) or monoclinic (ortho and para) deformations of the cubic unit cell of the disordered phases I and II. The ordering in the phase III of the ortho-isomer carrying the biggest electrical dipole moment creates a twofold superstructure w.r.t. the cubic unit cell. The thermal polymorphism for C2B10H12 and related metal salts can be explained by division of the cohesive intercluster interactions into two categories (i) dispersive cohesive interaction with additional Coulombic components in the metal salts and (ii) anisotropic local interaction resulting from nonuniform charge distribution around icosahedral clusters. The local interactions are averaged out by thermally activated cluster dynamics (rotations and rotational jumps) which effectively increase the symmetry of the cluster. The C2B10H12 molecules resist at least as well as the CB11H12– anion to the oxidation, and both clusters form easily a mixed compound. This allows designing solid electrolytes such as Nax(CB11H12)x(C2B10H12)1–x, where the cation content may be varied and the temperature of transition into the disordered conducting phase is decreased.

Physical properties and prebiotic activity of white dragon fruit (Hylocereus undatus) powders produced using different wall materials

The aim of the present work was to investigate the spray-dried characteristics such as physical properties, morphologies, glass transition temperatures (Tg), and prebiotic activity of white dragon fruit (WDF) powders produced using different wall materials, namely resistant maltodextrin (RMD) and maltodextrin (MD), at optimum spray drying conditions. Results showed that RMD decreased water activity and moisture content, and increased bulk density and true density of powder more than MD. In addition, the particle size of RMD-coated powder (WRMD) was smaller than that of MD-coated powder (WMD), and the morphology of the WRMD powder showed that it had a smooth surface as compared to WMD powder, where shrinkage and dent surfaces were observed. The Tg of WMD powder had higher value, but both types of powders were not significantly (p &gt; 0.05) different. Then, both powders were further investigated for their ability to support the growth of Bifidobacterium longum BB536 and Lactobacillus casei Shirota. The growth of the anaerobic bacteria was determined every 6 h for 24 h at 37°C in six modified MRS media containing glucose, RMD, MD, WRMD powder, WMD powder, and fructooligosaccharides (FOS) as the substrates. Results indicated that all substrates significantly (p &lt; 0.05) increased the growth of the probiotic bacteria, with WRMD powder yielding the highest bacterial count. Based on the findings, WRMD powder can be considerably used as a new prebiotic source for the functional food industry.

Relaxor nature and superior energy storage performance of Sr2Ag0.2Na0.8Nb5O15-based tungsten bronze ceramics through B-site substitution

• The relationship among structure, relaxor behavior and properties is discussed. • Switching from ferroelectric to relaxor is realized through Sb doping in B-sites. • The ceramics possesses a superior W rec of 2.27 J/cm 3 and an ultrahigh η of 93.3%. • x = 0.3 sample displays a high C D (1166.56 A/cm 2 ) and a large P D (118.54 MW/cm 3 ). A series of Sr 2 Ag 0.2 Na 0.8 Nb 5- x Sb x O 15 (SANNS) tungsten bronze ceramics were synthesized by traditional solid-phase methods to investigate the impact of Sb replacement on the structure, relaxor nature, and energy storage properties. The study on the relationship between structure and relaxor behavior revealed two main conclusions: (1) as the Sb 5+ content increased, the crystal structure transformed from an orthorhombic Im 2 a phase to Bbm 2, and then to a tetragonal paraelectric P 4 /mbm phase, accompanied by a decrease in both the cell volume V and the tetragonality of c / a ; (2) switching from ferroelectric to relaxor behavior at room temperature was realized through the doping of B-sites, which could be attributed to incommensurate local structural modulations caused by orthogonal distortion of the P 4 bm structure. Finally, we obtained a superior recoverable energy storage density (2.27 J/cm 3 ) and an ultrahigh efficiency (93.3%) in Sr 2 Na 0.8 Ag 0.2 Nb 4.7 Sb 0.3 O 15 . The charging-discharging performance was also evaluated: a high current density (1166.56 A/cm 2 ) and a large powder density (118.54 MW/cm 3 ) were achieved simultaneously.

Densification mechanism during hot-pressing of single-phase zirconium boride powders with different dislocation density

ZrB2 powders with different dislocation density were synthesised by the self-propagating high-temperature synthesis (SHS) and carbothermal reduction (CTR) method. The defect structure was analysed by transmission electron microscopy (TEM), and the dislocation density was determined though the convolutional multiple whole profile fitting (CMWP-fit). The SHS process exhibited a very high rate of heating and cooling, which introduces a higher dislocation density (8.68 × 1015 m-2) due to thermal stresses caused by the volume change of crystal, and the crystal grew spirally. Comparably, the CTR process depicted a low rate of heating and cooling. The time was sufficient for crystal nucleation and growth, thus the dislocation density of crystal was lower (6.49 × 1011 m-2), and the crystal grew layer-by-layer. By mixing with the SHS and CTR powders, 5 kinds of powders with different dislocation density were prepared, followed by hot-pressing densification. The dislocation density of powder was calculated and result shows that with the increasing of the content of SHS powder from 0 to 1 the dislocation density increases from 6.49 × 1011 m-2 to 8.68 × 1015 m-2, meanwhile the relative density of ZrB2 ceramics increased from 82.1% to 98.1%. The hot-pressing densification can be divided into two stages. In the pre-sintering stage, with increasing of dislocation density of the powders, the densification mechanism changes from bulk diffusion to grain boundary diffusion, and all are of the dislocation-climb mechanism in the post-sintering stage.

A Combination of Calcination and the Spark Plasma Sintering Method in Multiferroic Ceramic Composite Technology: Effects of Process Temperature and Dwell Time.

This study reports a combined technological process that includes synthesis by the calcination powder route and sintering by the Spark Plasma Sintering (SPS) method for multiferroic ceramic composites in order to find the optimal sintering conditions. The effects of temperature on the SPS process and dwell time on the microstructure and dielectric properties of the PF composites were discussed. Research has shown that using the SPS method in the technological process of the multiferroic composites favors the correct densification of powders and allows for obtaining a fine-grained microstructure with good properties and electrophysical parameters in the composite material. The optimal set of parameters and properties is demonstrated by the sample obtained at the temperature of 900 °C for 3 min, i.e., resistivity (6.4 × 108 Ωm), values of the dielectric loss factor (0.016), permittivity at room temperature (753) and permittivity at the phase transition temperature (3290). Moreover, due to the high homogeneity of the microstructure, the strength of the material against electric breakdown increases (when examining the ferroelectric hysteresis loop, the application of a high electric field (3—3.5 kV/mm) is also possible at higher temperatures). In the case of the composite material tested, both the lower and higher temperatures as well as the shorter and longer dwell times (compared to the optimal SPS process conditions) did not contribute to the improvement of the microstructure or the set of usable parameters of the composite materials. The strength of the ceramic samples against electric breakdown has also diminished, while the phenomenon of leakage current increased.

Si-HfO2 composite powders fabricated by freeze drying for bond layer of environmental barrier coatings

Hafnia-doping is expected to improve the performance of silicon bond layer of EBC system for SiC-based CMC. However, obtaining a compositional uniform Si-HfO2 composite coating is still a challenge due to the big difference of their melting point, density and fluidity of powders. Fabrication of evenly distributed Si-HfO2 composite powders with good fluidity and activity is a promising strategy. Freeze drying, a cost-effective and green method, was applied to make Si-HfO2 composite powders for the first time. Highly active nano-sized Si and HfO2 powders were mixed uniformly into a slurry, which was frozen and dried into solid lamellar structure. After crushing down and sieving, composite powders with controllable particle size and good fluidity were achieved, which inherited the uniformity of the slurry. Thickness of the lamellar structure determines the size and shape of the final composite powders, which can be controlled by simply varying the freezing temperatures. Compact and smooth bond coatings with evenly distributed Si and HfO2 were successfully fabricated from these composite powders by plasma spraying. We hope this work could excite the whole society to focus more on the structural design of powders and coatings as well as material selection to further boost the performance of EBCs.

A Density-Dependent Modified Doraivelu Model for the Cold Compaction of Poly (Ether Ketone Ketone) Powders.

The cold compaction of poly (ether ketone ketone) (PEKK) powder was studied by experiments and simulations based on the modified Doraivelu model. Although this model can successfully predict the compaction behavior of metal powders, discussion of the prediction of polymer powders is lacking. Based on the mechanical theory of metal plasticity, the modified Doraivelu model was established by introducing the material parameters m and n. The modified model can predict the compaction density of PEKK powder during cold compaction. A sub-increment method for this constitutive model was then established and implemented into a finite-element model by using the user-defined material subroutine UMAT in ABAQUS/Standard. Consequently, the material parameters of the modified Doraivelu model were identified by an inverse method using the experimental data and simulation results. It was found that when m = 0, n = 4, and the initial relative density was 0.4485, the simulation results were the closest to the experimental ones.

Evolution of Microstructure and Mechanical Properties of a Stainless-Steel Powder/Wire Mesh Composite Porous Strip for Powder Densification

Evolution of Microstructure and Mechanical Properties of a Stainless-Steel Powder/Wire Mesh Composite Porous Strip for Powder Densification

Preparation of nanostructural oxide dispersion strengthened (ODS) Mo alloy by mechanical alloying and spark plasma sintering, and its characterization

The nanostructural oxide dispersion strengthened (ODS) Mo alloy was successfully fabricated by mechanical alloying (MA) and spark plasma sintering (SPS). In this study, the MA and SPS conditions were systematically studied, and the characteristics of oxide particles were investigated. The results show that the MA process can refine the powder and promote the dissolution of interstitial atoms, but introduce the ZrO2 and excess O impurities. To recycle ZrO2 impurity as a source of active element Zr for alloy preparation, the content of Zr and O with milling time was quantitatively evaluated. In the SPS process, the precipitation of oxide particles retard the densification of as-MA Mo powders. Based on the calculated linear shrinkage, the densification behavior is controlled by sintering temperature, which is driven by grain boundary or dislocation climbing. A high relative density of 99.28% in ODS Mo alloy is achieved using the optimized MA (250 rpm/18 h) and SPS (1400 °C/5 min) parameters. Additionally, the ultrafine Mo grain structure (300 nm) and uniformly dispersed nanoscale Y-Zr-O oxide particles (20.32 nm) inside grains greatly improve the mechanical properties (569.63 ± 28.08 HV0.3) of ODS Mo alloys. Non-stoichiometric Y-Zr-O particles, with different Y/Zr ratios (Y/Zr <1), possess a special fluorite crystal structure.

Development and characterization of a spray-dried inhalable ciprofloxacin-quercetin co-amorphous system

Spray drying is an increasingly used particle engineering technique for the production of dry powders for inhalation. However, the amorphous nature of most spray-dried particles remains a big challenge affecting both the chemical and the physical stability of the dried particles. Here, we study the possibility of producing co-amorphous ciprofloxacin-quercetin inhalable particles with improved amorphous stability compared to the individual amorphous drugs. Ciprofloxacin (CIP), a broad-spectrum antibiotic, was co-spray dried with quercetin (QUE), a compound with antibiofilm properties, from an ethanol–water co-solvent system at 2:1, 1:1 and 1:2 M ratios to investigate the formation of co-amorphous CIP-QUE particles. Differential scanning colorimetry (DSC) and X-ray powder diffraction (XRPD) were used for solid-state characterization; dynamic vapor sorption (DVS) was used for investigating the moisture sorption behaviour. The intermolecular interaction was studied via solution-state nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy; the miscibility of the drugs was predicted via free energy calculations based on the Flory–Huggins interaction parameter (χ). A next generation impactor (NGI) was used to study the in vitro aerosol performance of the spray-dried powders. The physicochemical characteristics such as particle size, density, morphology, cohesion, water content and saturation solubility of the spray-dried powders were also studied. The co-spray-dried CIP-QUE powders prepared at the three molar ratios were predominantly amorphous. However, differences were observed between sample types. It was found that at a molar ratio of 1:1, CIP and QUE form a single co-amorphous system. However, increasing the molar ratio of either drug results in the formation of an additional amorphous phase, formed from the excess of the corresponding drug. Despite these differences, DVS showed that elevated humidity had a much lower influence on all three co-amorphous systems compared with the individual amorphous drugs. In vitro aerosolization study showed co-deposition of the two drugs from CIP-QUE powders with a desirable aerosol performance (ED ∼ 72–94%; FPF ∼ 48–65%) whereas QUE-only amorphous powder had an ED of 36% and a FPF of 22%. In summary, spray-dried CIP-QUE combinations resulted in co-amorphous systems with boosted stability and improved aerosol performance with the 1:1 M ratio exhibiting the greatest improvement.

Preparation and characterization of tea oil powder with high water solubility using Pickering emulsion template and vacuum freeze-drying

In this study, tea oil powder was firstly prepared using Pickering emulsion template coupled vacuum freeze-drying with maltodextrin (MD) as wall material. The effect of MD content on the rheological properties of the Pickering emulsion was investigated. The solubility, moisture content, bulk density, encapsulation efficiency, and microstructure of the tea oil powder were evaluated when different concentration of xanthan gum/lysozyme nanoparticles (XG/Ly NPs) were used. The results showed that increasing NPs and MD substantially enhanced the viscoelasticity of Pickering emulsion. The prepared tea oil powder herein had a milky white appearance with water content less than 3.45% ± 0.09%. Its bulk density was 0.34 ± 0.06 g/cm3, and solubility could be as high as 87.13% ± 0.86%. The highest tea oil encapsulation rate reached 66.41% ± 0.01% when 50% MD and 4% XG/Ly NPs was used. The surface of tea oil powder showed a relatively smooth porous microstructure, while the addition of MD made its surface became irregular with porosity and puckering. Additionally, oxidation stability of tea oil powder could be regulated MD and NPs. The results demonstrated that tea oil powder with high water solubility and controlled oxidation stability could be prepared by Pickering emulsion template coupled with vacuum freeze-drying technology.