Preparation Of Powders Research Articles

Chemical changes of aloe vera gel during the preparation of instant powder and its antioxidant activity

Aloe vera contains flavonoid compounds with high antioxidant activity in powder form, which is usually affected by the encapsulating agent. Maltodextrin is currently used as an encapsulating agent because of its high solubility, while gum arabic is a viscous substance that increases oxidation resistance. Therefore, this study aimed to produce aloe vera instant powder with a mixture of maltodextrin and gum arabic as an encapsulating agent and evaluate the chemical changes during the preparation of powder with high antioxidant activity. The powder was processed by mixing aloe vera gel with an encapsulating agent of maltodextrin and gum arabic mixture in a ratio of 1/1 with variations of 5%, 10% and 15%. Each sample was dried using a drum dryer at 120°C, 130°C and 140°C. During preparation, the samples were analyzed for their moisture content, phenolic content, flavonoid content and antioxidant activity expressed as DPPH radical scavenging activity. The results showed that the addition of encapsulating agents decreased the moisture content, phenolic content, and flavonoid content of aloe vera gel, however no significant effect (p>0.05) on antioxidant activity. Drying at a higher temperature will produce aloe vera powder with higher antioxidant activity. The aloe vera instant powder which was produced with a 5% encapsulating agent at the drying temperature of 130°C had high antioxidant activity of 26.21±7.58%.

Synthesis of nano- and ultra-fine refractory carbide powders by low-temperature calcium-carbothermic process and their grain growth during sintering

Metal carbides are widely used in various applications as catalysts, components of composite materials, cutting tools, and abrasive materials where the particle/grain size has a great impact on target properties. Here, we report a facile way to synthesize nano- and ultra-fine carbides of IVb-Vb groups, including high-entropy carbides, which are of interest nowadays due to their superior properties, by the combination of calcium-hydride reduction of metal oxides and the direct reaction of the reduced metals with carbon in one production step. By tailoring the synthesis parameters, it is possible to obtain the carbide powders of a size in the range of 50–1500 nm with high crystallinity. The average particle size is found to be dependent on the homologous synthesis temperature and follows a power law. We have also shown the possibility of obtaining ultrafine-grained bulk carbides (d = 0.24–0.9 μm) via spark-plasma sintering at a temperature of 1500–1650 °C with a relative density >95 % without using additives. The HEC (Ti,Zr,Nb,Hf,Ta)C has a higher activation energy of grain growth (collective recrystallization) compared to binary TaCx (x = 0.8 and 1), which confirms the effect of lattice distortion on diffusion coefficients. The suggested fabrication route can be widely used for nano and ultrafine carbide powder preparation on the industrial scale.

The microstructural evolution and densification process of titanium or tin doped indium zinc oxide ceramic targets

Herein, titanium or thin doped indium zinc oxide (IZO) ceramic targets, composed of TiO2/SnO2, In2O3 and ZnO were prepared. The preparation of composite powders, microstructure evolution, densification and photoelectric properties of these ceramic targets were systematically in detail. The results indicated that doping of SnO2 was more conducive to the density of IZO targets than the doping of TiO2, while they all were beneficial for optimizing electrical performance of IZO ceramic targets due to the solid solution of TiO2/SnO2 in phases, thus the doped IZO ceramic targets had lower resistivity than nondoped IZO targets. In addition, 1wt% SnO2 doped in IZO ceramic targets performed the best (relative density > 99%, resistivity < 1.1 mΩ·cm, average grain size < 2 µm).

Influences of oxygen partial pressure on the phase composition of the (Bi, Pb)-2212 precursor powder

Bi-2223 tapes, synthesized through the two-powder method, exhibit distinctive features such as high current density and a controllable secondary phase. Traditionally, the two-powder method involves the separate preparation of Bi-2212 and CaCuO powders followed by their mixing. However, during this process, it is necessary to dope the Bi-2212 powder with an appropriate Pb content to achieve a stable lattice structure in the Bi-2223 phase. The alteration of ion valences between Pb2+ and Pb4+ influences the oxygen content, thereby affecting the phase formation of (Bi, Pb)-2212 and, consequently, the final properties of Bi-2223 tapes. Surprisingly, limited research has explored the impact of the heat treatment process on (Bi, Pb)-2212. Consequently, this study investigates the phase composition and microstructure of (Bi, Pb)-2212 under various oxygen partial pressures to deepen our understanding of the effect of Pb on the composition of (Bi, Pb)-2212. Simultaneously, the behavior of Pb in the lattice of Bi-2212 is analyzed. Ultimately, the findings reveal that low oxygen conditions are advantageous for fabricating (Bi, Pb)-2212 powder with a high main phase content and a reduced secondary phase, thereby demonstrating excellent current-carrying performance in Bi-2223 tapes.

Selection and purification of Li2CO3 precursor for bolometric double beta decay experiments

This paper describes the preparation of radiopure lithium carbonate powder for the needs of low-background research, in particular, AMoRE-II, the second phase of a search for the neutrinoless double-beta decay (0νDBD) of the 100Mo isotope using over 100 kg of 100Mo contained in 200 kg of ultra-pure Li2100MoO4 bolometric crystals. About 150 kg of pure Li2CO3 powder is required to synthesize the crystals. The desired radiopurity for the lithium powder is 40K below 100 mBq/kg, and Th/U and Ra are at a few mBq/kg. Several commercially available powders were tested with ICP-MS and HPGe detectors at the Center for Underground Physics (CUP) of the Institute for Basic Science in Korea. The lowest purity of the tested products was 99.99%. The results of the powders’ radioassay at CUP showed that none of the tested products were suited for the 0νDBD search application. A special purification technology had to be developed to remove the original contamination of the powder with potassium (K), thorium (Th), uranium (U), and radium (Ra). Lithium carbonate crystallization via carbonization technique was inefficient in removing radiochemical impurities. Lithium formate fractional recrystallization effectively removed Ra, K, and Th, but the synthesis of the final lithium carbonate product had a low yield and required the introduction of additional chemicals. The analysis results of raw and purified powders, the decontamination efficiency, and plans are described in the article.

Mechano-chemical hydrothermal synthesis of NH4NiPO4·H2O and its transformation to LiNiPO4

Powder preparation of materials that can be used in production cathodes can be simplified by development of mechanical synthesis. In this paper, we report a novel approach using mechano-chemical hydrothermal synthesis of NH4NiPO4·H2O (Ammonium Nickel Phosphate Hydrate – ANP) was investigated. This method is easily scalable and is characterized with great repeatability. It uses inexpensive raw materials: NH4H2PO4 and NiCO3·Ni(OH)2·4H2O for one step synthesis without external source of heating. Reaction between substrates was conducted in water environment by planetary ball milling. As a result of high attrition inside milling chamber, both temperature and pressure is rising. By modification of conditions morphology of obtained powders can be modified. The produced ANP powders with phase purity up to 94.3 vol% (XRD measurement), were transformed to LiNiPO4 (Lithium Nickel Phosphate - LNP) by mixing with finely grinded Li2CO3 and calcination at 500 °C for 2 h. It resulted in LNP content of up to 91.2 vol% in final samples (XRD measurement). The mechano-chemical hydrothermal method was proved to be successful in terms of obtaining LNP using a dissolution – precipitation mechanism during wet milling at room temperature.

Preparation of Si3N4 powder by carbothermal reduction and nitridation of glucose and water glass

Herein, Si3N4 powders were successfully synthesized via carbothermal reduction nitridation of glucose and water glass as starting materials. The effects of synthesis temperature, glucose-to-water glass molar ratio, and Si3N4 seeding on the production were investigated. The results show that the reduction rate of silica increases with increasing temperature. The highest Si3N4 yield of 98.5 % was observed at 1450 °C after 400 min. The conversion of amorphous silica to Si3N4 was increased when the molar ratio of glucose/water glass was from 3.6 to 9.0 and is slightly affected when this ratio is greater than 9.0. Moreover, the maximum nitrogen content (N wt%) was 39.1 % when Si3N4/water glass molar ratio was 0.05. In the early stage of the reduction process, SiO2 is mainly reduced to SiC which is then converted to Si3N4.

A quality-by-design strategic approach for the development of bedaquiline-pretomanid nanoparticles as inhalable dry powders for TB treatment

Tuberculosis (TB) is caused by Mycobacterium tuberculosis (M.tb) and is the second leading cause of death from an infectious disease globally. The disease mainly affects the lungs and forms granulomatous lesions that encapsulate the bacteria, making treating TB challenging. The current treatment includes oral administration of bedaquiline (BDQ) and pretomanid (PTD); however, patients suffer from severe systemic toxicities, low lung drug concentration, and non-adherence. In this study, we developed BDQ-PTD loaded nanoparticles as inhalable dry powders for pulmonary TB treatment using a Quality-by-Design (QbD) approach. The BDQ-PTD combination showed an additive/synergistic effect for M.tb inhibition in vitro, and the optimized drug ratio (1:4) was successfully loaded into polymeric nanoparticles (PLGA NPs). The QbD approach was implemented by identifying the quality target product profile (QTPPs), critical quality attributes (CQAs), and critical process parameters (CPPs) to develop efficient design space for dry powder preparation using spray drying. The three-factorial and three-level Box-Behnken Design was used to assess the effect of process parameters (CPPs) on product quality (CQAs). The Design of Experiments (DoE) analysis showed different regression models for product quality responses and helped optimize process parameters to meet QTPPs. The optimized dry powder showed excellent yield (72 ± 2 % w/w), high drug (BDQ-PTD) loading, low moisture content (<1% w/w), and spherical morphology. Further, aerosolization performance revealed the suitability of powder for deposition in the respiratory airways of the lungs (MMAD 2.4 µm and FPF > 75 %). In conclusion, the QbD approach helped optimize process parameters and develop dry powder with a suitable quality profile for inhalation delivery in TB patients.

Preparation of red jujube powder with high content of Amadori compounds and higher antioxidant activity by controlling the Maillard reaction.

Amadori compounds (ACs) are stable compounds produced in the early stage of the Maillard reaction (MR) with health benefits such as immunomodulatory, antithrombosis, and tumor-preventive effects. Jujube is a medicinal and edible fruit in China. It is rich in free amino acids and reducing sugar, but traditionally, little attention was paid to the formation of ACs when jujube was processed, neither the influence of ACs on health effects. In this paper, we aimed to increase ACs through controlling the MR during different heating processes of jujube powder with adjusted water content and find the most effective AC that contributed to the antioxidant effects of jujube powder. The optimal dry-heating conditions to produce ACs were as follows: The water activity was 0.294, the heating temperature was 90°C, and the time was 120min. After processing, the ACs content of jujube powder was 18.55±0.19mg/g dry weight (DW), which was more than 100 times of those in the unheated jujube powder (0.153±0.003mg/g DW). Besides, the antioxidant activity of jujube powder after dry-heating process was higher than that of unheated one. As the most abundant AC in the dry-heated jujube powder (12.90±0.75mg/g DW), N-(1-deoxy-d-fructose-1-yl) proline (Fru-Pro) showed the highest antioxidant activity (62% of equivalent l-ascorbic acid) among 12 ACs in ferric reducing antioxidant power assay. This result provided a method to produce jujube product with high content of ACs and confirmed the positive contribution of Fru-Pro to the antioxidant activity of the jujube powder.

Study on Preparation of High-Performance Flake Silver Powder by Liquid Phase Reduction

Flake silver powder was prepared by liquid phase reduction method with silver nitrate as silver source, ferrous sulfate heptahydrate as reducing agent, citric acid and gum acacia as surfactants. The effects of reducing agent dosage, citric acid dosage, gum acacia dosage, silver nitrate dosage and reaction temperature on the properties of silver powder were studied. The results show that when the dosage of silver nitrate is 0.08 mol·L−1, the molar ratio of silver nitrate to ferrous sulfate heptahydrate is 1:2, the oxidizing solution is added to the reducing solution at the rate of 100 ml·min−1, the citric acid is added to the oxidizing solution at 7.5% of the mass of silver nitrate, the gum acacia is added equally dispersed to the oxidizing solution and the reducing solution, the addition amount is 20% of the mass of silver nitrate and the reaction temperature is 30 °C, the silver powder obtained is flake with good dispersion and narrow particle size distribution.

Optimization of cryoprotectant formulation to enhance the viability of Lactiplantibacillus plantarum NBC99 isolated from human origin

Freeze drying has been well applied in the preparation of high-efficiency viability probiotic powders. However, the process is generally accompanied by probiotic viability deficiency, which poses a problem for further application. In this study, various kinds of cryoprotectant formulations (skim milk, maltodextrin, and sucrose) were tested to enhance the survival of Lactiplantibacillus plantarum NBC99 after freezing and freeze-drying. An I-optimal experimental design-oriented optimization model was presented to optimize the cryoprotective medium, and the highest cell survival was observed with 25% skim milk, 8.71% maltodextrin, and 1.13% sucrose cryoprotectant as the optimum condition. L. plantarum NBC99 has been a good potential strain for the manufacture of an industrial probiotic, and this research has aimed to investigate the long-term protective effects of optimum cryoprotectant formulations on the viability of bacteria. The results showed the potential value of freeze-dried probiotic L. plantarum NBC99 culture for commercialization.

Evaluation and standarisation of Shatavaryadi Churna

Introduction-The Ayurvedic medical system has recently got a lot of medical and healthcare services in India. To evaluate the quality, safety, and effectiveness of the medicine, standards and purity of herbal formulation are crucial. However, pharmacopoeia testing is the protocol that all medicines must follow in order to be accepted globally. A compound herbal formulation called Shatvaryadi Churna is suggested for the treatment of a number of diseases. For the treatment of Timira Vyadhi, patal vyadhi, kancha vyadhi and many other raktaj vikara the formulation was documented in the Ayurvedic classic Yoga Ratnakar. Materials &amp; methods- Shatavaryadi Churna was made by using the standard procedure with all aseptic precautions and as described in the Ayurvedic Pharmacopoeia for Churna Kalpana (Powder Preparation). The manufactured medication has been standardised by adhering to the approved pharmacopeial protocol for quality control procedures. Results- Organoleptic parameters, physiochemical evaluation, and microbiological load test was done these analytical values were within the expected limits.

Preparation of ultrafine tungsten powder by fluidized bed hydrogen reduction of WO3-Co3O4

This article investigated the preparation of ultrafine W powder by fluidized bed hydrogen reduction, and the apparent activation energy was determined for various reduction stages by using temperature programmed reduction with hydrogen. The results demonstrate that the introduction of Co3O4 significantly enhances the reduction process of WO3.High Co3O4 content can lead to the formation of CoWO4 in the initial stage and obtain products with high content of Co3W. An increase in the Co3O4 content correlates with a gradual decrease in the particle size of the product. The apparent activation energy for the WO3 → WO2 and WO2 → W processes decreases as the Co3O4 content increases. It can be decreased from 105.59 kJ /mol to 78.72 kJ/mol for the WO3 → WO2 stage, and from 107.38 kJ/mol to 78.38 kJ/mol for the WO2 → W stage, respectively.

Effects of gelatin type and concentration on the preparation and properties of freeze-dried fish oil powders

The effects of gelatin type (porcine skin gelatin, PSG; bovine skin gelatin, BSG; fish gelatin, FG; or cold-water fish skin gelatin, CFG) and concentration on the preparation and properties of fish oil powders were investigated in this work. The oil powders were prepared using the combination method of gelatin-sodium hexametaphosphate complex coacervation with starch sodium octenyl succinate (SSOS)-aided freeze-drying. Compared with the other gelatins, CFG—with an unobvious isoelectric point, a lower molecular weight, more hydrogen bonds, and longer gel formation time—could not form complex coacervates, which are necessary to prepare oil powders. For oil powders obtained from the other gelatins, gelatin type and concentration did not have obvious effects on microscale morphologies; they did, however, have significant effects on physicochemical properties. The highest peroxide values of the oil powders were mainly dependent on the gelatins, expressed in the following manner: PSG (153 ± 5 – 168 ± 3 meq/Kg oil) < BSG (176 ± 5 – 188 ± 1 meq/Kg oil) < FG (196 ± 11 – 201 ± 22 meq/Kg oil). Acidic and neutral pH could not dissolve the complex coacervates. However, the oil powders could be quickly dissolved to form emulsion droplets in the gastric phase, and that SSOS increased coacervate stability and promoted oil digestion during the in vitro gastrointestinal process. In sum, this study contributes fundamental information to understanding the development of fish oil solid encapsulation preparations.

Intelligent material classification of traditional Chinese medicine based on semantic analysis

A method for material classification of traditional Chinese medicines based on the physical properties of powder has been established by our research group. This method involves pre-treatment of traditional Chinese medicine decoction pieces, powder preparation, and determination of physical properties, being cumbersome. In this study, the word segmentation logic of semantic analysis was adopted to establish the thesaurus and local standardized semantic word segmentation database with the macroscopic and microscopic characteristics of 36 model traditional Chinese medicines as the basic data. The physical properties of these medicines have been determined and the classification of these medicines is clear in the cluster analysis. A total of 55 keywords for powdery, fibrous, sugary, oily, and brittle materials were screened by association rules and the set inclusion and exclusion criteria, and the weights of the keywords were calculated. Furthermore, the algorithms of the keyword matching scores and the computation rules of the single or multiple material classification were established for building the intelligent model of semantic analysis for the material classification. The semantic classification results of the other 35 TCMs except Pseudostellariae Radix(multi-material medicine) agreed with the clustering results based on the physical properties of the powder, with an agreement rate of 97.22%. In model validation, the prediction results of semantic classification of traditional Chinese medicines were consistent with the clustering results based on the physical properties of powder, with an agreement rate of 83.33%. The results showed that the method of material classification based on semantic analysis was feasible, which laid a foundation for the development of intelligent decision-making technology for personalized traditional Chinese medicine preparations.

Synthesis of nanocrystalline W[sbnd]Cu powders via freeze-drying and hydrogen reduction

The preparation of nanocrystalline WCu powders plays a significant role in the production of high-performance WCu composites. The chemical reduction method is a promising approach for industrial nano-powder synthesis. However, the influence of various reduction parameters on the morphology and grain size of the reduced powders, as well as their underlying mechanisms, have remained unclear. In this study, we investigated the effects of reduction steps, temperature, duration, hydrogen inflow rate, and copper content on the grain size of the composite powders and disclosed the related mechanisms. Through optimization of reaction parameters, WCu powders with grain sizes below 50 nm were obtained. Moreover, the utilization of the synthesized nanocrystalline WCu powders as raw materials yielded a bulk W20Cu composite with an ultrahigh hardness of 600 HV30.

Preparation of quaternary spherical TiO2-B4C-C-Cu composite powder for laser cladding

Powder preparation is the key step in producing laser cladding coatings with desired properties. In this paper, quaternary TiO2-B4C-C-Cu composite powder with high sphericity and good densification has been successfully prepared by a powder fabrication process combining spray granulation with densification sintering. The effects of slurry characteristics, spray granulation process parameters, and densification sintering temperature on particle morphology and performance were studied. The formation mechanism of quaternary spherical TiO2-B4C-C-Cu composite powder was revealed by analyzing the process of heat transfer and water transfer in the droplets, and the optimization direction of the powder preparation was indicated. The optimized process parameters for the quaternary spherical TiO2-B4C-C-Cu composite powder are: slurry solid content of 52 wt%, dispersant content of 1.25 wt%, binder content of 2 wt%, inlet temperature of 180 °C, the airflow rate of 310 L/h, slurry feed rate of 4.5 ml/min, and the two-stage temperatures of densification sintering are 500 ℃ and 900 ℃ for 1 h, in turn. Under the optimized process, the fluidity of the powder reaches 112 s/50 g, the apparent density reaches 1.2 g/ml, and more than 70% of the particles are between 15–53 µm. The powder has been verified by laser cladding to prepare in-situ synthesized TiB2-TiC-Cu composite coatings, which could have a better prospect for potential application.

Coupling of tape casting and in situ solid-state reaction for manufacturing La0.9Sr0.1Ga0.8Mg0.2O3 electrolyte of efficient solid oxide cells

Perovskite oxide La0.9Sr0.1Ga0.8Mg0.2O3 (LSGM) is an intermedium-temperature solid oxide cell electrolyte material with extraordinary oxygen-ion conductivity. However, the manufacturing procedures of LSGM discs are complex involving multiple steps of powder preparation, forming, and sintering at high temperatures. Herein, thin LSGM electrolyte discs are prepared by coupling of tape casting and in situ solid-state reaction using oxides/carbonates as the feedstock. A pure-phase LSGM electrolyte disc with uniform elemental distribution is obtained by sintering at 1450 °C, and it possesses an ionic conductivity of 0.105 S cm1 at 800 °C, a thermal expansion coefficient of 12.2 × 106 K1, and a bending strength of 156 MPa A 170 µm thick LSGM electrolyte-supported single cell delivers a peak power density of 0.96 W cm2 at 800 °C and an electrolysis current density of 1.82 A cm2 at 1.5 V with no noticeable degradation for 200 h. The findings of this research provide a cost-effective approach for manufacturing the LSGM electrolytes of efficient and durable solid oxide cells.

Influence of guide vane on dispersion of aggregates near the guide vane in a turbo air classifier

Ultra-fine particles are prone to agglomeration, limiting the preparation of ultra-fine powder. The aggregates' disaggregation mechanism is studied, and the proposal of improving the guide vane of a turbo air classifier is contributed to strengthen powder disaggregation based on CFD-DEM coupling and the novel local fluid domain extraction method. The results show the cylindrical tail of guide vane is conducive to the disaggregation, and the powder dispersion near the guide vane is improved. When the inlet air velocity vin is <18 m·s−1, the cylindrical tail of guide vane can significantly improve the powder dispersion. When the cylinder diameter is larger than or equal to 2 mm, the effect of the increase of the cylinder diameter on powder dispersion is significant. However, the increase of cylinder diameter will lead to the increase of energy consumption, so the cylinder diameter should not be too large.

The characteristics of H6 against Microcystis aeruginosa.

Algal bloom caused by Microcystis aeruginosa has always been the focus of attention; microbial algal control has the advantages of significant effect, low investment cost, and environmental friendliness; the use of microbial technology to inhibit the bloom has a broad prospect for development. In this study, a strain of Enterobacterium algicidal bacteria screened from a river was used to study the algicidal characteristics against Microcystis aeruginosa using SEM, 3-D EEM and zeta potential. The results showed that the optimal dosage (v/v) of the strain was 5% and the removal rate of algal cells was 70% after 7 days. When the algal density was OD680nm = 0.3, the removal rate of algal cells reached 83% after 7 days. In the pH range of 5 ~ 11, the removal rate of algal cells was 70 ~ 80% after 7 days. Algicidal bacteria H6 is mainly indirect algae lysis and is supplemented by direct algae lysis. Algicidal bacteria H6 removes algicidal substances by secreting high temperature resistant algicidal substances and algicidal products are humic acids. Algicidal bacterium H6 was a strain of Enterobacterium with good algicidal effect in a wide pH range, which enriched the bacterial resources in the control of cyanobacteria bloom in water. The high temperature resistance of the algae-soluble substance secreted by the algae-soluble substance provided convenience for the subsequent preparation and application of bacterial powder.