Planetary Mill Research Articles

Facile Solid-State Synthesis of Supported Ptm-Nps for the Oxygen Reduction Reaction

Supported bimetallic catalysts composed of platinum and transition metals are highly investigated electrocatalysts for the oxygen reduction reaction (ORR) because of their enhanced activity and stability. However, common routes to synthesize these materials are often laborious and not scalable, employing organic solvents or uneconomical metal deposition methods [1-2]. Here, we present a mechanochemistry-assisted, dry and scalable synthesis route towards supported bimetallic catalysts, which consists of only two steps: First, metal salts are dispersed on a carbon support in a planetary mill without further additives. Following, the powder is reduced with hydrogen and annealed to yield alloyed catalysts. With this process, we are able to synthesize PtM/C catalysts where M was Ni, Co or Ru. Both metal loading and ratio could be adjusted by changing the amount of metal salt. The average size of the PtM-NPs was similarly controlled by changing the annealing temperature.With X-ray diffraction (XRD), we show that no metal or salt reflexes are present after milling and that the XRD pattern matches the carbon support. After reduction and annealing, clear reflexes of the targeted alloy composition are visible. The latter was confirmed by scanning transmission electron microscopy coupled with energy dispersive X-ray spectroscopy (STEM-EDX). After milling, ionic metal species are present as sub-nanometer clusters evenly dispersed over the carbon support. After reduction and annealing, PtM nanoparticles have formed. Neither by XRD nor by STEM-EDX was the presence of unalloyed Pt or M detected. Optical emission spectrometry was used to confirm the targeted loading and bulk composition of the catalysts.Due to the known high activity for catalyzing the ORR, PtNi/C and PtCo/C were subjected to electrochemical evaluation in a rotating disc electrode setup [2]. In both cases, specific activities surpassing 1 mA/cm2 Pt at 0.9 V were reached. The electrochemically active surface area (ECSA) and mass activity were also in the range expected for the composition and particle size. To assess the stability, the catalysts were cycled from 0.4 to 1.0 V (RHE) with a scan rate of 1 V/s for 10800 cycles. The loss in ECSA of approximately 5 % was also in line with expectations. Since iron impurities are known to reduce the lifetime of a proton exchange membrane fuel cell, the milling process was adapted to a Si3N4-mill instead of a steel mill, again demonstrating the flexibility of this synthesis route [3].To conclude, the reported solid-state procedure allows the dry synthesis of supported bimetallic catalysts over a wide range of compositions. The materials show high activity and stability catalyzing the ORR. Due to its simplicity and flexibility, we expect this synthesis approach to be applied in other fields of catalysis within a short period of time.

Lithium oxide loss of lithium niobate nanocrystals during high-energy ball-milling

Congruent lithium niobate (LiNbO 3 ) prepared by sintering was ground under wet conditions in a planetary mill in order to produce nanocrystals. By using gradually lower sizes of the balls in the mill, the final particle size of the crystals could be reduced to about 12–15 nm. The particle size achieved as well as the lithium oxide (Li 2 O) loss of the lithium niobate particles were followed as a function of the grinding time. Lithium oxide was found to be released throughout the entire milling procedure, even in the case when the particle size no longer changed upon the grinding with a particular ball size. About 12% and 20% Li 2 O loss was detected upon grinding with 3 mm and 0.5 mm balls, respectively. X-ray diffractometry revealed the formation of a lithium-deficient phase, LiNb 3 O 8 , the presence of which was confirmed by means of Raman spectroscopy. The LiNb 3 O 8 :LiNbO 3 volume ratio achieved for 70 nm particle size as calculated from both the diffractograms and the lithium oxide loss determined by coulometric titration was assessed to be 0.39 (± 0.03). Correlation was revealed between the composition change of the nanopowder and the total surface area of the particle assembly calculated from dynamic light scattering measurements. • Lithium niobate nanopowders were produced with the help of a planetary mill. • The loss of lithium oxide and formation of LiNb 3 O 8 were observed upon milling. • The lithium loss during the wet grinding process was quantitatively characterized. • Particle size determined by SEM and DLS were in good agreement. • The surface area increase of the particle assembly correlated with the Li 2 O release.

Modification of Natural Peat for Removal of Copper Ions from Aqueous Solutions

This study aimed at estimating peat adsorption properties for copper ion removal from aqueous solutions during peat modification. Two peat modifications have been studied using batch tests and quantitatively reproduced with instrumental analysis by using spectrometric, potentiometric, and thermodynamic modeling methods. The first variation—mechanical activation—was carried out in a planetary mill; for the second one—mechanochemical activation—dry sodium percarbonate (Na2CO3·1.5H2O2) was added. The adsorption of copper ions was studied in the concentration range from 10–150 mg/L with an interaction time from 0.25–12 h. Both modifications led to significant changes in the interaction energy in the adsorption layer; thus, the acceptor properties of macromolecules were enhanced from natural peat to mechanically activated peat and mechanochemically activated peat. FTIR spectra, specific surface area characteristics, and sorption experiments show the predominantly chemical nature of copper sorption. Maximum adsorption capacity was determined to be 24.1, 42.1, and 16.0 mg/g for natural peat, mechanically activated peat, and mechanochemically activated peat, respectively. The example of peat mechanochemically oxidized with Na2CO3·1.5H2O2 shows that the improvement in the physicochemical properties (CBET and specific surface area) plays a smaller role in the sorption capacity in relation to copper ions than the presence of phenolic and carboxyl groups, the content of which decreases during oxidation.

Radar-absorbing composite materials based on ferrite powders

The paper studies the effect of particle sizes of hexagonal ferrite powders on their electrodynamic properties. SrTi0.2Co0.2Fe11.6O19 and BaSc0.2Fe11.8O19 hexaferrites were used as the objects of research. Grinding in a high-energy planetary mill for up to 60 minutes made it possible to obtain hexaferrite powder particles with the average size successively decreasing from 1.5–2 μm to 0.05–0.15 μm. A scanning electron microscope was used for the analysis. Samples were prepared in a mixture with a polymer binder (70% ferrite + 30% polymer), and their electromagnetic radiation (EMR) absorbing capacity was studied in the microwave range from 30 to 50 GHz. It was shown that there is practically no peak corresponding to ferrimagnetic resonance in the composite with ferrite, with a decrease in the average particle size of BaSc0.2Fe11.8O19 hexaferrite powders to 50–150 nm. The dependences of the real and imaginary parts of the magnetic permeability and dielectric constant are given in the frequency range from 107 to 109 Hz. There was no domain wall resonance in the frequency dependence of magnetic losses for a ferrite-based composite mechanically activated for 60 min. SrTi0.2Co0.2Fe11.6O19 ferrite was milled in a bead mill to particles with an average size of 150–300 nm, and then to drying, pressing, sintering at 1360 °С and subsequent grinding to a size of 200–500 μm to obtain similar composites in a bond with a polymer. It was found that the properties of compositions change significantly with a change in the magnetic component synthesis technology: no resonant pattern of EMR absorption was observed. The Curie temperature was measured using the Faraday method. It was shown that it is ~340 °С for the studied material. Therefore, the effect of precursor milling on changes in magnetocrystalline anisotropy was identified.

Adsorption of heхavalent chromium on mechanically activated graphite

Mechanical activation of spectrally pure graphite was carried out in a high-energy planetary mill. Changes in the structure and physicochemical properties caused by this modification are shown by SEM, XRD, Raman spectroscopy, XPS, N2 adsorption-desorption, and inert gas fusion methods. Because of the mechanical activation, a decrease in crystallite size of the graphite and the oxidation occurred; it began to exhibit sorption properties with respect to Cr(VI) ions. The optimal conditions were found for removing more than 99% of Cr(VI) from the 50 mg∙l−1 aqueous solutions. In an acetate buffer solution with pH 6.3 after 1 h of heating at 90°C, the Langmuir adsorption capacity for chromium on this sorbent is 14.7 mg∙g−1. Thermodynamic characteristics of the adsorption were determined; they show that the process is spontaneous and endothermic. It was found that only incomplete desorption of chromium from the surface of the modified graphite is possible using concentrated NaOH solutions. An assumption was made about a mixed mechanism of chromium adsorption, including partial reduction of Cr(VI) to Cr(III), anionic adsorption of Cr(VI) ions through electrostatic interaction, and the formation of an insoluble chemical compound of Cr(III) on the surface of the mechanically activated graphite. The sorbent was tested on a real sample of wastewater from bichromate production, after adsorption hexavalent chromium was not detected in the water.

Effect of Mechanical Activation and Carbon Coating on Electrochemistry of TiNb2O7 Anodes for Lithium-Ion Batteries

TiNb2O7 anode material with a Wadsley–Roth crystallographic shear structure was prepared by solid-state synthesis at a relatively low temperature (1000 °C) and a short calcination time (4 h) using preliminary mechanical activation of the reagent mixture. The as-prepared final product was then ball milled in a planetary mill with and without carbon black. The crystal structure and morphology of the samples were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Electrochemical performance was studied in a galvanostatic mode in varied voltage intervals and at different cycling rates in combination with in situ electrochemical impedance spectroscopy (EIS) measurements. The resistance measured using in situ EIS had the highest values at the end of the discharge and the lowest when charging. The lithium diffusion coefficient, determined by galvanostatic intermittent titration technique (GITT), in samples milled with and without carbon black was an order of magnitude higher than that for the pristine sample. It was shown that improved electrochemical performance of the carbon composite TiNb2O7/C (reversible capacity of 250 mAh g−1 at C/10 with Coulomb efficiency of ~99%) was associated with improved conductivity due to the formation of a conductive carbon matrix and uniform distribution of submicron particles by size.

Melt Synthesis of Lithium Manganese Iron Phosphate: Part II. Particle Size, Electrochemical Performance, and Solid-State Lithium Diffusion

Melt synthesis is a fast and simple process to make dense LiMnyFe1−yPO4 (LMFP with 0 ≤ y ≤ 1) from all-dry, low-cost precursors with zero waste. Part one of this study confirmed that highly crystalline and phase pure LMFP materials can be made by melt synthesis. This part shows that planetary milling can reduce the primary particle size of melt LMFP (0%–75% Mn) to ∼200 nm, which is smaller than the primary particles in commercial LFP reference material (0% Mn). However, further particle size reduction is needed to reach particle sizes below 70 nm observed in reference LMFP (79% Mn). Melt LFP shows almost identical specific capacity and charge/discharge voltage as reference LFP. Melt LMFP materials show a high voltage Mn plateau at ∼4 V associated with the Mn2+/3+ redox, the length of which scales with Mn content. The Mn plateau raises the average discharge voltage of LMFP; hence a minimum specific discharge capacity between 160 mAh g−1 (0% Mn) and 145 mAh g−1 (80% Mn) is sufficient to match the volumetric energy density of LFP. The Atlung Method for Intercalant Diffusion shows that the lithium diffusion coefficient in LMFP is ∼1 order of magnitude higher in the voltage region of the Fe2+/3+ redox couple (3.75–3.1 V vs Li+/Li) than in the voltage region of the Mn2+/3+ redox couple (4.3–3.75 V vs Li+/Li). This emphasizes the need for very small primary particles when making LMFP with relatively high Mn content.

Melt Synthesis of Lithium Manganese Iron Phosphate: Part I. Composition, Physical Properties, Structural Analysis, and Charge/Discharge Cycling

Melt synthesis is a fast and simple process to make dense LiMnyFe1-yPO4 (LMFP with 0 ≤ y ≤ 1) from all-dry, low-cost precursors with zero waste. This study characterizes melt LMFP materials with 0%–100% Mn after particle size reduction by planetary milling and carbon coating with glucose. The melt LMFP samples show higher electrical conductivity at similar pellet density than LFP (0% Mn) and LMFP (79% Mn) reference samples made by traditional methods. The melt LMFP samples exhibit higher crystallinity than the reference samples and show no crystalline impurities. Their unit cell volume and crystallographic density scale with Mn content; the percentage of Fe and/or Mn in Li positions is below 1.5%, which is comparable to reference samples. Crystallite sizes of at least 100 to 175 nm are observed for melt LMFP, which is larger than the fine ∼50 nm crystallites of reference LMFP. Melt LFP shows specific discharge capacity and cycling stability comparable to reference LFP, but the melt LMFP samples with 25%–100% Mn shows worse performance than reference LMFP (79% Mn). Part two of this study will quantify the solid-state lithium diffusion coefficient in melt LMFP materials and correlate it to their electrochemical performance.

ДИНАМИЧЕСКАЯ МОДЕЛЬ ГОРИЗОНТАЛЬНОЙ ПЛАНЕТАРНОЙ МЕЛЬНИЦЫ

Issues are considered that are associated with the determination of dynamic loads encountered in moving units of the planetary mill. A horizontal planetary mill was chosen for compiling a dynamic model, as it has a great potential for organizing a closed grinding cycle with continuous loading and unloading of material. Calculation schemes were drawn up in moving units at the moments of the beginning of its operation and the steady movement of the grinding drums. Using the d’Alembert principle, taking into account the geometric parameters of the grinding unit, the reduced moments of inertia and moments of forces, as well as the acceleration time from a state of rest until the carrier reached a steady angular velocity, were determined. From the condition of equality of the power of the reduced moment of forces acting on the link of reduction, and the power of all forces and moments applied to the links of the planetary mill, the initial torque applied to the carrier was determined, which is necessary in the future to determine the power expended both at the moment of starting the mill, and at the time of its stable operation. It is shown that the initial torque depends on the value of the initial angular acceleration, which, in turn, can be different depending on the accepted law for changing the angular acceleration and the acceleration time to the required angular velocity of steady motion. It is also indicated that during the start-up period, the power supplied to the mill is spent on accelerating the rotation of the leading link and on overcoming various resistances such as friction forces in the units of the carrier and grinding drums.

Optimized purification procedure for Iranian calcium bentonite for producing montmorillonite nanosheets

AbstractIn polymer composites, montmorillonite nanosheets are crucial as fire retardants, reinforcers, anti-corrosives, detoxifying agents and ultraviolet-protection agents. However, the quality of montmorillonite nanosheets can be improved by optimizing the raw bentonite purification process in which undesirable phases are removed. Optimization of Iranian calcium bentonite purification for nanomontmorillonite synthesis considering various parameters based on various physical approaches to dispersion and ultrasonication was investigated; the calcium bentonite purification was performed using sodium hexametaphosphate followed by either sedimentation or centrifugation, and the nanomontmorillonite synthesis was performed using ultrasonic treatment. The effects of suspension concentration, milling type, pH and centrifugation duration and speed on the separation of various impure phases were evaluated qualitatively and optimized. The raw and purified bentonite and the synthesized nanomontmorillonite were characterized using X-ray powder diffraction, X-ray fluorescence spectroscopy, Fourier-transform infrared spectroscopy and scanning electron microscopy. The cation-exchange capacity was also measured in the raw and purified samples. Optimal experimental conditions in the dispersed samples were achieved at a 2.5 wt.% concentration of bentonite suspension and planetary milling at pH 7. While the ultrasonic treatment was more effective than the dispersion approach for cristobalite elimination, a smaller lateral size of the montmorillonite sheets, optimized at 0.5 wt.% concentration of the suspension, was achieved. The increased cation-exchange capacity after the purification improved the exfoliation and delamination of montmorillonite nanosheets in the presence of cetyltrimethylammonium bromide as the surfactant. The interplanar spacing of (001) planes of 15 Å in raw bentonite shifted to 21 Å and 19 Å in purified and non-purified samples, respectively, after synthesis.

Decreased porosity and improved corrosion resistance of B4C-filled Al slabs via hot cross-rolling

The study aims to describe the effect of the hot cross-rolling process on the physical and corrosion properties of hot-pressed Al/30 wt%B4C composite. The starting powders were milled by planetary mill machine and then were sintered by a hot pressing machine at 600 °C for 1 h under 50 MPa pressure in a vacuum. Hot cross-rolling was carried out in 8 and 16 passes after soaking at 773 K (500 °C) for 20 min. Sample characterization takes place through electrochemical corrosion tests, X-ray diffraction, scanning electron microscope and density. The results showed that performing the hot cross-rolling process on the samples leads to an increase in corrosion resistance and density. The 50% hot cross rolled sample had the highest corrosion resistance and density value. The corrosion resistance of the samples was reduced in H3BO3, NaCl and NaOH solutions, respectively. In H3BO3 solution, the continuity of the protective oxide layer is largely preserved, which leads to higher corrosion resistance in this solution than other solutions.

Statistical Analysis of Dry Grinding of Mica in Planetary Mill

A huge amount of energy can be used for fine particle breakage using the planetary mill resulting in high-cost consumption. Understanding how these operating parameters could affect the dry grinding mechanism in a planetary mill is still not sufficiently discussed. The effect of different operating parameters of planetary mills in the dry grinding of mica was investigated using statistical analysis. A laboratory scale of the planetary mill was used by varying the operating parameters such as grinding time (minutes), rotational speed (rpm), and percentage of grinding media (%). A full factorial design was used involving 48 experiments, and the grinding process’ efficiency was evaluated using the cut size of particles (d50) obtained from the particle size distribution analysis. The analysis was supported by morphological analysis by SEM image and structural distortion by XRD test. The statistical analysis showed a good correlation with the R2 value of 0.874 with the standard deviation of 0.852. It was found that the optimum parameters for grinding time, grinding speed, and grinding media were 20 minutes, 400 rpm, and 30% media charged, respectively, with the d50 value of 7.44 μm. This study provides further insight into the mica breakage operating parameters in a planetary mill.

High Densification of Tungsten via Hot Pressing at 1300 °C in Carbon Presence

A reactive sintering technique with a small addition of carbon (up to 1.9 wt.%) has been used for tungsten powder consolidation. The process allowed procurement of the nonporous and fully densified material at 1300 °C and 30 MPa in 12 min. The SEM and EDX analysis showed that the milling of 5 μm tungsten powder with 0.6, 1.3, and 1.9 wt.% of carbon in a planetary mill led to the formation of the nanostructured mix, which appears to be W-C nanopowder surrounding tungsten grains. X-Ray Diffractometry data indicated tungsten hemicarbide (W2C) nucleation during the hot pressing of the milled powders. The exothermic reaction 2W + C → W2C occurs during the sintering process and promotes charge densification. The Vickers hardness and indentation toughness of W-1.3 wt.%C composition reached 5.7 GPa and 12.6 MPa∙m1/2, respectively. High toughness and high material densification allow proposing the W-WC2 for use as a plasma-facing material in fusion applications.

Исследование структуры и свойств механоактивированного титаната самария

The relevance of the work is explained by the need to improve the quality of metal raw materials for the production of products with special properties, for example, in mining when leaching metals from ores, allowing to increase the extraction of components with a higher content in concentrates while minimizing the content of impurities. The purpose of the work. Substantiation of the possibility of changing the structure and properties of samarium titanate powder by processing in a spherical planetary mill "Activator 2S" due to the need to increase the purity of powders. Research methods: systematization, generalization and analysis of theoretical and experimental studies. To study the properties of samarium titanate, the following methods were used: scanning electron microscopy, X-ray phase, chemical, low-temperature nitrogen adsorption, X-ray phase analysis, spectral and atomic absorption with the processing of the results by methods of mathematical statistics. Results. The results of the study of the structure and properties of samarium titanate powders obtained by mechanochemical synthesis using a spherical planetary mill are presented. It is shown that the elemental composition of the mechanochemically synthesized charge corresponds to the stoichiometric content of titanium oxide and samarium. Quantitative values of activation parameters are given. The time of transformation of the initial oxides into nanocrystalline samarium titanate has been determined. The phases of the transformation of samarium titanate from an amorphous state to a crystalline state under the influence of temperature are differentiated. The properties of the samarium titanate powder obtained by mechanosynthesis are given. The possibility of obtaining nanoamorphic powder of samarium titanate by mechanochemical treatment of samarium and titanium oxides of the desired condition is proved.

Effect of chromium addition on the copper binder structure, properties and adhesion to diamond

The study covers the effect of chromium on the structure, mechanical properties, and adhesion of alloys used as a binder for metal-diamond composites. Cu–Cr powder mixtures were obtained by high-energy ball milling in a planetary centrifugal mill. This process was used to obtain two-phase Cu–Cr powders with uniformly distributed submicron Cr particles. Cu–Х%Cr compact samples (where Х = 10, 30 and 50 %) were obtained by hot pressing. It was found that Cu–30%Cr compact samples showed the best mechanical properties (9 times higher as compared to pure copper). These alloys feature a hardening mechanism based on the Hall–Petch law. The resulting alloys have a homogenous ultrafine structure, which results in high ultimate bending strength (2330 MPa). Chromium addition to the copper binder considerably increases its adhesion to diamond in metal-diamond composites due to chemical interaction between chromium included into the binder and diamond carbon with Cr3C2 carbide formation.

Влияние механической активации порошка вольфрама на структуру и свойства спеченного материала SN-CU-CO-W

Introduction. One of the methods for improving the properties of sintered materials is mechanical activation of powders. It ensures milling the powders, changing its energy state, intensifying the sintering of powder materials, and forming a fine-grained structure in it. When tungsten powders are mechanically activated in planetary centrifugal mills, nanoparticles can be formed, which have a high reactive power. The objective of the paper is to study the effect of mechanical activation of tungsten particles on the structure and properties of the sintered Sn-Cu-Co-W powder material. Research technique: Mechanical activation of W16,5 grade tungsten powder is carried out in a planetary centrifugal ball mill AGO-2U for 5…120 minutes with carrier speeds of 400…1,000 rpm. The mixture of tungsten, tin, copper, and cobalt powders are compacted by static pressing in molds and then sintered in vacuum at 820 °C. The morphology and size of powder particles, as well as the structure of the sintered samples, are studied by scanning electronic microscopy, X-ray microanalysis, and optical metallography. Porosity of the sintered samples is identified by the gravimetric method. Microhardness of the structural constituents and macrohardness of the sintered materials are measured, too. Results: in the modes under study, mechanical activation is accompanied by the formation of tungsten nanoparticles with the minimum size of 25 nm. Alongside this, the powder is exposed to cold working, which hinders further milling. Tungsten nanoparticles, characterized by high surface energy, have a significant effect on the dissolution-precipitation of cobalt during liquid-phase sintering of Sn-Cu-Co-W powder material. Addition of nanodispersed tungsten into the material slows down the growth of cobalt particles during sintering and contributes to the formation of a fine-grained structure. The sintered Sn-Cu-Co-W material, containing mechanically activated tungsten, features higher hardness of 105…107 HRB, which is explained by cold working of tungsten particles and dispersion hardening. The results can be applied for improving mechanical properties of Sn-Cu-Co-W alloys used as metallic binders in diamond abrasive tools.

Development of composite filters from biochars for wastewater treatment

ABSTRACT The aim of this research is to develop a bio-nanocomposite filter from locally sourced agro-wastes to treat waste and effluent water. The filters were formulated from coconut and peanut shell biochars, with kaolin as the binding agent and rice husk as the pore-creating agent within nanometric size range using planetary balling milling. The batch composition of the filters was carried out in 10 groups and labelled F1 to F10. The parameters for comparison include linear shrinkage, apparent porosity, water absorption, hardness test, bulk density, and modulus of rupture. The results indicate that the filter F7 showed more resistance to indention with a hardness value of 29.4 than the control with a hardness value of 26.6 and also the flow rate in F7 was noted to be 23.07 ml/h, whereas F9 recorded the least flow rate of 1.03 ml/h. It was also observed that filter F8 had a higher bulk density value of 2.587 g cm-3 due to its high degree of compaction, while the control had a lesser bulk density value of 1.9990 g cm-3. However, the control proved to have a higher apparent porosity of 50%, which was slightly higher than filter F10 with 49.46% apparent porosity.

Studies on the mechanochemically induced chromene-annulation of meso-tetrakis(pentafluorophenyl)-2,3-dihydroxychlorin: Non-innocence of the grinding aids

The modification of chlorins to fine-tune their optical properties is important for their application in medical and technical fields. The solution phase, base-induced formation of a chromene-annulated chlorin from the corresponding meso-tetrakis(pentafluorophenyl)-2,3-dihydroxychlorin by intramolecular S[Formula: see text]Ar displacement of an [Formula: see text]-F atom of a meso-aryl group by an adjacent hydroxy group is well-known. Organic transformations performed by grinding the dry reagents together promise to be a much greener and possibly simpler method compared to traditional solution-based reactions. However, the use of such mechanochemical approaches to accomplish porphyrinoid chromophore modifications are virtually unexplored. We report here the translation of the solution-based base-induced formation of a chromene-annulated chlorin to a solid state mechanochemical reaction in a planetary powder mill. The factors determining the success (and failure) of the reaction are delineated. While this report shows that porphyrinoid framework modifications can principally be induced mechanochemically, the mechanochemical reaction is not (yet) competitive with the solution state reaction. The outcome of the reaction is very sensitive to the particular milling conditions, specifically-and importantly as it is unexpected – the grinding aids used. What we previously believed to be inert or merely basic aids affected a significant degradation of the chlorins under the milling conditions, a finding that might generally limit mechanochemical approaches in porphyrinoid chemistry, or at least require careful adjustments.

A promising strategy for mechanically modified wheat flour by milling of wheat endosperm

A planetary mill was used to grind pure endosperm granule flour using both low-temperature control and normal modes. Particle size distribution, microstructure, pasting characteristics, water absorption indexes, solubility indexes, in vitro digestibility, and thermal characteristics were determined for samples ground for different lengths of time. The resulting flour had D50 below 30 μm and crushed starch content of 8%. Better dispersion of protein and starch was achieved for low temperature grinding and increased grinding time. Independently of temperature, milling decreased peak viscosity, trough viscosity (from 2339 to 1896 cp), and final viscosity (from 3947 to 3535 cp). The water solubility also decreased. There was also a decrease in the enthalpy (ΔH) of gelatinization, and the enthalpy (ΔH) of gelatinization at low temperature was higher at normal temperature. The rapidly digestible starch content was lower and slowly digestible starch content was higher in flour compared with raw material, and the changes in the low and normal modes showed opposite trends, probably influenced by the starch granules surface-protein and starch amorphous regions. The above results suggest that the functional properties of wheat flour were significantly altered by planetary ball milling at low speed and short duration (<200 rpm, <30 min), suggesting potential strategies to expand the flour food applications.

The use of self-fluxing alloys as a source of alloying elements in producing powder products of construction purpose from low-alloyed iron

Background. One of the problems in the production of powder structural materials based on iron alloyed with a small amount of alloying elements (0.5 - 5.0 wt.%) is obtaining a homogeneous alloy in the final material. The distribution uniformity of the alloying elements largely determines the final properties of the material. The use of a mixture of powders constituting the alloy to obtain such alloys, in manycases, does not solve the problem of obtaining homogeneous alloys. Promising in this respect is the use of alloy powders containing alloying elements as sources of alloying elements.Objective. The purpose of the paper is to study the formation regularities of the material’s structure and properties based on iron alloys obtained using self-fluxing alloys (SFA) as a source of alloying elements.Methods. To solve the problem posed in the work, the methods of mixing-grinding in planetary mills, the study of the processes of wetting with SFA iron melts and the interaction between them by the method of a lying drop, scanning microscopy for studying the structureof materials and the distribution of elements in them, measuring mechanical properties (hardness) were used.Results. The principles of determining the optimal conditions for obtaining materials - grinding-mixing time (4 min.), compacting pressure of the original workpieces (600 MPa), sintering temperature (1200 °C), sintering time (more than 80 min.) were established.Their use contributes to the production of products with almost one hundred percent material density and a high degree of homogeneity.Conclusions. As a result of the work carried out, it was found that the use of SFA as alloying elements sources and the preparation of the initial mixture by grinding-mixing methods in a planetary mill promotes the production of materials with a high degree of homogeneity due to the intensification of homogenization and sintering processes and, as a consequence, an increase in their mechanical characteristics.