Dispersion Of Powders Research Articles

Highly dispersed chromium(III) molybdate powders obtained by solid phase synthesis

Objectives. To obtain highly dispersed powders of chromium(III) molybdate Cr2(MoO4)3 by solid phase synthesis and to study their porous structure.Methods. After stirring in water, a mixture of Cr2O3 and MoO3 oxide powders was dried in air and subjected to heat treatment in the temperature range of 600–800°C. After heat treatment, the products were identified by X-ray phase and sedimentation analysis. The specific surface area was measured using the Brunauer–Emmett–Teller static adsorption method. Porosity parameters were measured using the Barrett–Joyner–Halenda (BJH) method.Results. The Gibbs free energy ΔG of the reaction between chromium and molybdenum oxides was calculated and it was shown that the process is characterized by a significant negative value of ΔG. Concurrently, the Gibbs energy exhibits a relatively weak dependence on temperature. The highly dispersed chromium(III) molybdate powders with specific surface area of 15.3–29.7 m2·g−1 obtained in this way were pure according to X-ray diffraction analysis. A study of the volume, diameter, and pore size distribution was conducted through the utilization of nitrogen adsorption–desorption isotherms in accordance with the BJH model.Conclusions. It was demonstrated that Cr2(MoO4)3 powders possess a mesoporous structure and are distinguished by a bimodal pore system comprising small pores with a diameter of 2–3 nm and larger pores with a diameter ranging from 15 to 30 nm.

Metal Powder Production by Atomization of Free-Falling Melt Streams Using Pulsed Gaseous Shock and Detonation Waves

A new method of producing metal powders for additive manufacturing by the atomization of free-falling melt streams using pulsed cross-flow gaseous shock or detonation waves is proposed. The method allows the control of shock/detonation wave intensity (from Mach number 4 to about 7), as well as the composition and temperature of the detonation products by choosing proper fuels and oxidizers. The method is implemented in laboratory and industrial setups and preliminarily tested for melts of three materials, namely zinc, aluminum alloy AlMg5, and stainless steel AISI 304, possessing significantly different properties in terms of density, surface tension, and viscosity. Pulsed shock and detonation waves used for the atomization of free-falling melt streams are generated by the pulsed detonation gun (PDG) operating on the stoichiometric mixture of liquid hydrocarbon fuel and gaseous oxygen. The analysis of solidified particles and particle size distribution in the powder is studied by sifting on sieves, optical microscopy, laser diffraction wet dispersion method (WDM), and atomic force microscopy (AFM). The operation process is visualized by a video camera. The minimal size of the powders obtained by the method is shown to be as low as 0.1 to 1 μm, while the maximum size of particles exceeds 400–800 μm. The latter is explained by the deficit of energy in the shock-induced cross-flow for the complete atomization of the melt stream, in particular dense and thick (8 mm) streams of the stainless-steel melt. The mass share of particles with a fraction of 0–10 μm can be at least 20%. The shape of the particles of the finest fractions (0–30 and 30–70 μm) is close to spherical (zinc, aluminum) or perfectly spherical (stainless steel). The shape of particles of coarser fractions (70–140 μm and larger) is more irregular. Zinc and aluminum powders contain agglomerates in the form of particles with fine satellites. The content of agglomerates in stainless-steel powders is very low. In general, the preliminary experiments show that the proposed method for the production of finely dispersed metal powders demonstrates potential in terms of powder characteristics.

Performance evaluation of dispersibility of submicron powder by jet mill and clarification of dispersion mechanism by addition of aid

Performance evaluation of dispersibility of submicron powder by jet mill and clarification of dispersion mechanism by addition of aid

Additive manufacturing of high-performance aluminium nitride ceramics using high solid loading and low viscosity slurry

ABSTRACT In this study, the complex aluminium nitride (AlN) components with performance comparable to those produced by conventional methods were fabricated through an improved additive manufacturing technique. The use of a novel surfactant (KMT3331) improved the dispersion of AlN powder in resin, enhancing the compatibility between the powder and the resin, resulting in a low-viscosity slurry with solid loading exceeding 60 vol.%. This approach improved the density and homogeneity of the green bodies, resulting in dense and microstructurally homogeneous AlN ceramics, as well as reduced the sintering shrinkage and grain size. Finally, by controlling oxygen impurities introduced from the debinding process, complex-shaped AlN ceramics with high thermal conductivity (184.56 ± 2.77 W·m−1·K−1), outstanding mechanical properties (bending strength of 458.09 ± 36.03 MPa, fracture toughness of 3.95 ± 0.26 MPa·m1/2) and high reliability (Weibull modulus of 14.89) were obtained, greatly broadening the prospect of AlN ceramics in advanced thermal management applications.

Analysis of the results of research and testing of geomodifiers of friction

The practice of maintenance of any equipment can be significantly supplemented by nontraditional tribotechnics for the indiscriminate restoration of worn friction interfaces and the prevention of new equipment with GMT technology. The predecessor of this direction were solid lubricants, solid lubricants and hard lubricants. They entered the special engineering of the space age and nuclear energy. But for ordinary equipment, it is more appropriate to use non-traditional tribotechnics with running-in, preventive and especially with repair and restoration tribocompositions in-troduced into units during technical service. This analysis is devoted to the analysis of the features of this direction with one of the types of tribostats — namely, with friction geomodifiers made of highly dispersed powders of serpentine minerals — hydrosilicates Mg, Al, Ni, Fe.

Research in the area of obtaining of activated alumina. Part 7. Production of reactive alumina with controlled particle size distribution

The key technological factors determining the formation of granulometric composition of highly dispersed alpha-alumina powders in the process of thermal treatment of feedstock have been researched. The decisive influence of temperature modes of synthesis and concentration of Cr2O3 additive on phase transformations and structural and morphological characteristics of reactive alumina is shown. The fact of formation of thermodynamically stable primary crystals of alpha aluminum oxide with a characteristic mode of 0.5 μm has been established for the first time. Technological principles of thermal synthesis of reactive alpha-alumina with predictable particle size distribution have been developed.

Derivative spectrophotometry allows quantitative determination of essential oils in dispersible powders of spray-dried nanocapsules

This study aimed to develop and validate an analytical methodology based on derivative spectrophotometry to determine the true concentration of ginger (ZEO) and rosemary (REO) essential oils in nanocapsule redispersible powder formulations. Second-order derivative spectrophotometry made it possible to nullify the interference of nanocapsule components at 240 and 245 nm wavelengths for ZEO and REO, respectively. The validated method was linear in the range 0.01-0.04 mg mL−1 for ZEO and 0.6-0.96 mg mL−1 for REO. It is also accurate with RSD of 1.82 and 1.44 for ZEO and REO respectively, and shows recovery rates close to 100% in both essential oils when assessing accuracy. The methodology used allowed the determination of the essential oils in the presence of the formulation components, simply and quickly, showing to be an option to be used for quantification of OEs in these nanometric systems.

Quantifying dispersion and light emission for aluminum powder suspensions with varied surface energy

The dust combustion of aluminum (Al) particles post ballistic impact was studied bi-spectrally in the visible (VIS) and near-infrared (NIR) using high-speed imaging. Powders were delivered loosely via a novel sabot design into a chamber and impacted an anvil at speeds of 1050 m/s. Two identically sized Al powders were studied, one was untreated (UN), the other processed using a thermal annealing and quenching treatment called superquenched (SQ). The SQ Al powder had reduced surface energy compared to UN Al powder, which was induced by the annealing–quenching treatment. Particle dispersion and emission during reaction was quantified by introducing a field emission fraction metric that characterizes the burning powder cloud and relates to particle combustibility. In the case of SQ Al, VIS light emission from dispersed powder decays slower compared to UN Al. High-speed NIR imaging shows UN Al agglomerates resulting in high concentrations of unreacted Al. The differences in powder dispersion and emission were attributed to different combustion regimes and further confirmed by x-ray diffraction analysis of post-burn products, which demonstrated different residue phase compositions. This study demonstrates that a field emission fraction is a quantitative analysis tool to simultaneously evaluate dispersion and emission of dust combustion.

Methods for the synthesis of highly dispersed alumomagnesial spinel powders for structural and optically transparent ceramic materials (Review)

Methods for the synthesis of highly dispersed alumomagnesial spinel powders for structural and optically transparent ceramic materials (Review)

3D characterisation of metal powders for additive manufacturing using Nano-CT and deep learning

ABSTRACT The geometrical properties of metal powders, the main raw material in additive manufacturing processes, can have a significant impact on the quality of the parts produced. Therefore, it is essential to characterise these powders effectively. Nano-computed tomography (Nano-CT) technology, with its high-resolution 3D measurement capability, is ideally suited to measure the geometrical characteristics of tiny powders. However, the current CT testing methods for metal powders has two main drawbacks. Firstly, it does not take into account the effect of particle adhesion. Second, it cannot achieve high-precision measurements of the internal pores of powders. To address these limitations, we propose a novel testing method for metal powders that utilises Nano-CT technology. The method first obtains highly dispersed powder samples through a specially sample preparation technique. Then, an improved U-shape networks with multi-level supervision are proposed to achieve high-precision segmentation of the internal pores of the powder. Ultimately, this paper achieves high-precision 3D characterisation of metal powders.

Highly Monodisperse Stable Gold Nanorod Powder for Optical Sensor.

Gold nanorods (GNRs) as plasmonic metal nanoparticles are valuable for optical applications due to their tunable plasmonic properties. However, conventional colloidal GNRs face significant optical instability during storage, which limits their practical use. In this work, we developed a highly dispersible GNR powder using an octadecyl trimethylammonium bromide (C18TAB)-assisted freeze-drying method, preserving the optical and chemical sensing properties of GNRs for over 4 months. Compared with C16TAB, C18TAB significantly enhances the GNRs dispersibility even at lower concentrations. Our study demonstrates that C18TAB forms a sponge-like crystal structure that prevents aggregation during the freeze-drying process. The resulting GNR powder retains its plasmonic features and water dispersibility, achieving near-identical optical properties to those of fresh GNR solutions. This stability enabled creation of a liquid-free colorimetric test kit with a long shelf life. This work marks a significant step forward in the use of GNRs as standard analytical reagents, opening new avenues for real-world applications.

Synchrotron computed tomography combined with AI-based image analysis for the advanced characterization of spray dried amorphous solid dispersion particles

Particle engineering aims to design particles with specific properties. A deeper understanding of how particle formation relates to material attributes and process conditions are critical to strengthen knowledge on powder properties and enhance modeling capabilities. New, alternative powder characterization techniques can offer novel and more accurate measures for particle properties, giving more advanced characterization information. In this context, a case study is presented in which spray dried amorphous solid dispersion powders produced by modifying process conditions were characterized by both well-established compendial methods (i.e., laser light diffraction, SEM image analysis, bulk and tapped density, and gas adsorption), as well as a new method combining synchrotron computed tomography (SyncCT) with AI-based image analysis. SyncCT was used to classify and quantify the spray dried particles as hollow spheres and solid particles, giving a more detailed quality measure of the particle shape, as they impact downstream processing differently. Moreover, hollow particle wall thicknesses, as well as internal and external particle surface areas were measured by SyncCT. Altogether, powder characterization data from SyncCT show similar trends to that obtained from compendial techniques and giving additional quality measure regarding particle shape, showing promise of this new and advanced characterization method.

Characterisation of AZ31/TiC composites fabricated via ultrasonic vibration assisted friction stir processing

In this study, the effect of ultrasonic vibration during Friction Stir Vibration Processing (FSVP) on the microstructure and mechanical behaviour of AZ31/TiC surface composites was investigated. Specifically, Titanium Carbide (TiC) particles were introduced as a reinforcement (15 vol%) into the magnesium alloy AZ31 using both Friction Stir Processing (FSP) and FSVP. Comprehensive examinations were carried out to analyse the microstructure, hardness, and tensile behaviour of the resulting composites. The study revealed significant improvements in mechanical properties due to the application of ultrasonic vibration during FSP. Firstly, the stir zone region was found to be free from voids, enhancing material flow and promoting even dispersion of TiC powders within the matrix. Secondly, refinement of grains was observed due to dynamic recrystallization and the pinning effect imposed by TiC particles, leading to the formation of more dislocations in the composite and indicating a considerable alteration in the material’s structure. Importantly, the vibration during FSP introduced an auxiliary energy source, resulting in a remarkable enhancement in both hardness and tensile strength. Compared to the AZ31/15 vol% TiC FSP composite, the composites produced via FSVP exhibited a grain size reduction of about 64% and improvements in hardness and ultimate tensile strength (UTS) of about 55% and 21%, respectively. Notably, these improvements were achieved without compromising the ductility of the composite, which remained at appreciable levels.

High Resolution X-ray Diffraction Studies of the Natural Minerals of Gas Hydrates and Occurrence of Mixed Phases

The types and concentrations of gas hydrates collected from four different geological sites were analyzed using high-resolution angular dispersive X-ray powder diffraction, with synchrotron radiation as the source. Measurements were taken across a temperature range of 80 to 300 K and a pressure range of 0.1 to 80 MPa. All four gas hydrate samples showed the presence of three mixed crystal structures: structures I, II, and H. Additionally, the ice Ih structure was inherently present in all the natural gas hydrate minerals. The variation in the types and concentrations of gas hydrates can be attributed to the diversity of natural gases at different geographic locations.

Prediction of mechanical properties of manufactured sand polymer-modified mortar based on swarm intelligence algorithm

Because polymer-modified mortar (PMM) exhibits a complex and diverse composition, there is a complex nonlinear relationship between its mechanical properties and mix proportions that is challenging for conventional mechanical performance prediction methods to accurately predict. Consequently, in this study, a predictive model utilizing a backpropagation neural network (BPNN) was formulated, featuring a structure of 6–14-2. Simultaneously, three swarm intelligence algorithms were integrated—the ant colony optimization algorithm, grey wolf optimization algorithm, and bat optimization algorithm (BAT)—to collectively refine the optimization process of the BPNN prediction model. The model's input layer included cement (OPC), cellulose ether (CE), dispersible polymer powder (DPP), antifoam (AF), fly ash (FA), and tuff stone powder (SP), and the output layer consisted of the compressive and bond strengths. The model dataset comprised 520 samples (260 × 2), with 60 % (312) used for model establishment and 40 % (208) used for validation. Correlation matrix and principal component analyses were conducted on the dataset, along with a comparative analysis of the factors influencing the mechanical performance evaluation indicators. The results indicate that at 7 and 28 d, there was a positive correlation between the DPP and AF with the development of PMM mechanical properties. At 7 d, the SP and FA were negatively correlated with the compressive and flexural strength, whereas the CE was positively correlated with the bond strength. At 28 d, the OPC was negatively correlated with the compressive, bond, and flexural strengths, and positively correlated with the SP and FA. C3 represents the optimal mix proportion for the PMM, and considering the influence of all raw materials, F3 was identified as the comprehensive optimal mix proportion. The predictive performance evaluation indicators of the BAT–BPNN for the compressive and bond strengths were R2 = 0.980 and 0.942, MAE = 5.967 and 1.958, MAPE = 0.071 and 0.041, and RMSE = 4.686 and 1.594, respectively. BAT significantly improves the predictive accuracy of the BPNN model, enabling the prediction of PMM mechanical properties and providing a scientific basis for its mix proportion design.

The Effect of Sodium Hexametaphosphate on the Dispersion and Polishing Performance of Lanthanum-Cerium-Based Slurry.

A lanthanum-cerium-based abrasive composed of CeO2, LaOF, and LaF3 was commercially obtained. The effect of sodium hexametaphosphate (SHMP) on powder dispersion behavior was systematically investigated using the combined techniques of liquid contact angle, turbidity, zeta potential (ZP), scanning electron microscopy (SEM), powder X-ray diffraction (XRD) combined with Rietveld refinements, X-ray photoelectron spectroscopy (XPS), and polishing tests. The results indicated that the addition of 0.5 wt.% SHMP dispersant to the 5 wt.% lanthanum-cerium-based slurry produced the most stable suspension with a high turbidity of 2715 NTU and a low wetting angle of 45°. The as-obtained slurry displayed good surface polishing quality for K9 glass, with low surface roughness (Ra) of 0.642 and 0.515 nm (in the range of 979 × 979 μm2) at pH = 6 and 11, respectively, which corresponds to the fact that it has local maximum absolute values of ZP at these two pH values. SEM images demonstrated that after appropriate grafting of SHMP, the particle aggregation was reduced and the slurry's dispersion stability was improved. In addition, the dispersion mechanism was explained based on the principle of complexation reaction, which reveals that the dispersant SHMP can increase the interparticle steric hindrance and electrostatic repulsions. In an acidic environment, steric hindrance dominates, while electrostatic repulsion prevails under alkaline conditions. As expected, this polishing slurry may find potential applications in manufacturing optical devices and integrated circuits.

Development of water dispersible powder (WDP) formulation for management of snails

Development of water dispersible powder (WDP) formulation for management of snails

Self-propagating high-temperature synthesis of AlN–TiC powder composition using sodium azide and C2F4 fluoroplastic

Producing powder compositions using conventional processing technology can lead to the formation of large agglomerates and, therefore, makes it difficult to obtain a uniform microstructure. The production of composites by self-propagating high-temperature synthesis can reduce costs and the number of technological stages, as well as lead to obtaining composites that are more homogeneous. Synthesis by the combustion of mixtures of powder reagents of sodium azide (NaN3), fluoroplastic (C2F4), aluminum and titanium with different ratios of reagents in a nitrogen gas atmosphere at a pressure of 4MPa was used for the production of a highly dispersed powder ceramic AlN–TiC composition. Thermodynamic calculations have confirmed the possibility of synthesis of AlN–TiC compositions of different formulations in combustion mode. The dependences of temperature and combustion rate on the composition of the initial mixtures of reagents were experimentally determined for all stoichiometric reaction equations. The study have shown that the experimentally found dependences of combustion parameters on the ratio of the initial components correspond to the theoretical results of thermodynamic calculations. The formulation of the synthesized composition differs from the theoretical composition by a lower content of target phases and the formation of Al2O3, Na3AlF6 and TiO2 side phases. The powder composition consists of aluminum nitride fibers with a diameter of 100–250nm and ultradisperse particles of predominantly equiaxed and lamellar shapes with a particle size of 200–600nm. As the combustion temperature increases to produce the largest amount of titanium carbide phase, the particle size increases to the micron level.

Dual admixtures for cement-based composites comprising steel slag powder and residual lignin-based liquor

Steel slag is a by-product of the steel industry that can be used as an aggregate and/or mineral admixture, conferring physical and mechanical benefits to cement-based composites. In parallel, sugarcane bagasse is a by-product of the sugar/alcohol industry used in biorefineries to produce bioethanol. The delignification processes, employed as a pretreatment in biorefineries, generate residual liquors that contain lignin. Lignin is a natural polymer with plasticizing properties when incorporated into cement mixtures. Given this scenario, this work sought to produce and evaluate dual admixtures containing a residual lignin-based liquor and a steel slag powder. The proposed dual admixtures were prepared from two strategies and incorporated in cement pastes and mortars at different dosages. Mixtures containing a commercial silica suspension and a reference mixture (without admixtures) were also evaluated. The flow test showed that the dual admixtures promoted higher spreading than the silica suspension in all the proposed dosages. Also, the mortars containing the dual admixtures had significantly higher compressive strengths and more refined pore structures than the reference mortar. The residual lignin-based liquor enhanced the workability of the composites and favored the dispersion of the steel slag powder into the matrix. The liquor's plasticizing and set-retarding capacities were attributed to its anionic functional groups and sugar content, respectively. Additionally, the high-efficiency grinding of the steel slag powder contributed to improving its specific surface area and fineness parameters, justifying its performance as a filler and a supplementary cementitious material. This study presents a new route for developing more eco-efficient cement-based composites. It also complies with the principles of circular economy by offering a feasible strategy for valorizing large-scale industrial wastes in civil construction.

AuNPs@MoS2 functionalized copper metal organic framework for boosting electrocatalytic glucose oxidation

A novel non-enzyme glucose sensor based on functionalized copper metal–organic framework composite material, AuNPs@MoS2/Cu-MOF, was developed for rapid glucose analysis. Cu-MOF nanomaterial was prepared via a hydrothermal method, followed by the surface loading of core–shell structured AuNPs@MoS2 to synthesize AuNPs@MoS2/Cu-MOF composite material. Consequently, a novel gold nanoparticle @ molybdenum disulfide/copper metal–organic framework (AuNPs@MoS2/Cu-MOF/GCE) non-enzyme glucose sensor was constructed. Scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray powder Diffraction (XRD) was used to verify that the non-enzyme glucose sensor had been constructed effectively. Traditional electrochemical characterization methods were employed to study the electrocatalytic performance of the AuNPs@MoS2/Cu-MOF/GCE sensor and its catalytic oxidation of glucose. The experimental results demonstrated a good linear correlation between the concentration of glucose and the peak current within the range of 0.05–14.85 mM, with a detection limit of 16.7 μM. The AuNPs@MoS2/Cu-MOF/GCE sensor exhibited rapid electrochemical response to glucose (within 0.5 s), along with long-term stability and excellent selectivity. This is because Cu(II) in Cu-MOF can serve as active sites for the electrocatalytic oxidation of glucose, while the core–shell structure of AuNPs@MoS2 with excellent conductivity can lower the energy barrier in the reaction, further accelerating this catalytic reaction. The AuNPs@MoS2/Cu-MOF/GCE sensor is cost-effective, easy to operate, and suitable for accurate rapid quantification of glucose.