Hydrogen storage properties of MgH2-Ni system

The effect of pure Ni addition (5 wt.%) in MgH2 powder was investigated mechanochemically for short milling times (15, 30, and 45 min). Obtained MgH2-Ni system was characterized by XRD, SEM-EDS, PSD, DSC, and TPD. Compared to pure MgH2, uniform distribution of nickel reduces the temperature of H2 desorption by more than 100 °C. It is shown that influence of two important processes, grinding and catalysis, may be followed separately. We can conclude that the catalysis of H2 desorption by Ni particles on MgH2 matrix is the dominant effect for the investigated short milling times.Twenty-First Young Researchers’ Conference - Materials Science and Engineering: Program and the Book of Abstracts; November 29 – December 1, 2023, Belgrade, Serbi

Effect of metalic and metal-oxide catalysts on LiAlH4 decomposition

Metal and complex light hydrides are the best fitted materials for hydrogen storage within the concept of hydrogen based economy [1]. They meet the basic application requirements: low-cost, safety and they are environmentally friendly. Beside their benefits, as relatively stable compounds, these materials exhibit also some undesirable properties like sluggish kinetics and high temperature of hydrogen desorption. LiAlH4 has emerged as a potential material for solid-state hydrogen storage because of its high hydrogen gravimetric capacity (10.5 wt%). It decomposes in three steps, according to the reactions [2]: 3LiAlH4 → Li3AlH6 + 2Al + H2 (R1) Li3AlH6 → 3LiH + Al + 3/2H2 (R2) 3LiH+3Al → 3LiAl + 3/2H2 (R3) The temperature of the first reaction is between 150-175°C, of the second between 180-220°C and the third between 400420°C. The first two reactions (R1 and R2) are very important from the hydrogen storage point of view: (i) both take place at a reasonable low temperatures and (ii) overall sum of theirs gravimetric hydrogen capacity is 7.8 wt.%, so the reactions (R1) and (R2) are accessible for practical hydrogen storage. However, the slow dehydrogenation kinetics and irreversibility under moderate condition hinder its imminent application. Particle refinement and catalyst or additive introduction by mechanical milling led to the significant improvement of LiAlH4 hydrogen storage properties [2]. However, during the milling process, the temperature in the milling chamber can significantly increase reaching the temperature of R1 or even R2 leading to the degradation of hydride, change in the hydrogen desorption mechanism (figure 1) and decrease in the hydrogen storage capacity of material [3]. So, in this work the impact of metallic (V, Mn an Cr) and metal oxide (Fe2O3 and Nb2O5) additives on the LiAlH4 hydrogen desorption properties with the emphasis on the hydride degradation process during milling and a consequent hydrogen desorption reaction mechanism was studied. The aim was to improve the hydrogen desorption kinetics without hydrogen capacity deterioration.6th International Symposium on Materials for Energy Storage and Conversion : July 5-8, Bol, island of Brač, Croatia, 2022

Influence of mechanochemical activation on the thermal behavior of pyrophyllite

The effect of mechanical milling on the thermal behavior of pyrophyllite ore from a deposit in Parsovići, Bosnia and Herzegovina, was characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and Particle size distribution. The thermal behavior of the material was followed by thermogravimetric and differential thermal analysis and correlated to its microstructural properties. The Williamson-Hall model was used to calculate the crystallite size and microstrain. Mechanochemical treatment of pyrophyllite ore produced a substantial structural modification, mainly along the c axis, resulting in disorder and partial degradation of the crystal structure of the ore. The particle size diminution, induced defects, and microstrain in the crystal lattice cause decrease in the peak intensity until the final disappearance. As confirmed by scanning electron microscopy and particle-size-distribution analysis, the surface area and the agglomeration is more pronounced as grinding time increases. Dehydroxylation of the minerals in the unmilled ore was realized at 716oC confirm by FTIR analysis. The endothermic peak that corresponds to dehydroxylation is shifted toward lower temperatures and becomes broad giving rise to the formation of amorphous SiO2 as milling time increases

Study of milling time impact on hydrogen desorption from LiAlH4-Fe2O3 composites

LiAlH4 was modified by mechanical milling and with the addition of 5 wt.% Fe2O3 in order to improve its hydrogen desorption properties. The composite was milled for 1, 3, 5, 7 or 15min, and depending on the milling time, various phenomena took place. Up to a milling time of 5min, the particle size of the composite decreases. Further milling leads to the particles agglomeration reaching the size of the starting material after 15min. Moreover, the mechanical milling process leads to the transformation of AlH - 4 to AlH 3 - 6 structure as a result of partial hydrogen desorption. Hydrogen desorption during the milling is the most pronounced in the sample milled for 15min, so this sample has only one hydrogen desorption peak in the temperature-programmed desorption measurements.Mechanical milling with the addition of Fe2O3 for up to 15min improves LiAlH4 hydrogen desorption properties as hydrogen desorption temperature and apparent activation energies decrease

Improvement of sorption properties of natural clay pyrophyllite by ultrasonic treatment

Pyrophyllite, a naturally abundant clay material, exhibits remarkable physicochemical characteristics. Its minimal electrical and thermal conductivity, low expansion rate, strong mechanical properties, and outstanding heat resistance make it a valuable resource across diverse industries. Pyrophyllite finds applications in sectors such as paper and plastic manufacturing, brick production, ceramics, cosmetics, rubber processing, and wastewater treatment. Furthermore, its versatility extends to the production of ceramic membranes for efficient water filtration. This paper presents the characterization of natural pyrophyllite ore subjected to ultrasonic treatment at varying time intervals. The ultrasonic treatment aims to eliminate hard phases such as quartz and calcite within the ore, thereby improving its sorption capabilities. The treated samples were subjected to analysis using SEM and XRD techniques. Morphological and structural analysis revealed that as the duration of ultrasonic treatment increased, the proportion of hard phases in the sample decreased. Additionally, this study evaluated the sorption properties of pyrophyllite. A comparative analysis was conducted between a raw clay sample containing various admixtures and a sample that underwent a 30-minute ultrasonic treatment. The sorption of a methylene blue solution after 24 hours in water was assessed, with UV-Vis analysis revealing that the efficiency of the sonically treated pyrophyllite exceeded 97%, whereas the raw ore exhibited approximately 89% efficiency over the same duration. These findings suggest that the removal of hard phases from pyrophyllite ore enhances its sorption propertiesTwenty-First Young Researchers’ Conference - Materials Science and Engineering: Program and the Book of Abstracts; November 29 – December 1, 2023, Belgrade, Serbi

Mechanochemical activation of LiAlH4-Fe2O3 composites-a method to enhance kinetics of hydrogen desorption

Mechanical milling of pure lithium alanate (LiAlH4) was done with addition of 5 weigh percent of Fe2O3 using different milling time ranging from 1 to 15 minutes [1]. Mechanical milling of composites causes destabilization of LiAlH4 structure as it observed by XRD measurements. Particle size distribution results reveals that composite particle size decrease with milling time up to 3 minutes, and then increase almost to the original size, for 15 min sample. Mechanical mailing cause phase transformation from AlH4- to AlH63-. As a consequence of structural and chemical changes, desorption properties of composites are change kinetic of desorption is improved in comparison to unmilled LiAlH4. The shifting of hydrogen desorption temperature to lower temperatures is observed together with change from multi-step desorption to one-step hydrogen desorption is also observed. This caused decrease in activation energy of composites from Ea = 665 kJ/mol for unmilled LiAlH4, Ea = 279 kJ/mol for 3 min milled composite.Solid-State Science & Research ; 10-11th June 2021, Onlin

Detekcija fungicida karbendazima u vodi primenom elektrode od ugljenične paste modifikovane pirofilitom

Ovaj rad ima za cilj da dizajnira elektrodu od ugljenične paste modifikovanu pirofilitom za potencijalnu upotrebu za detekciju pesticida u vodenim rastvorima. Strukturna i morfološka karakterizacija prirodne gline pirofilit i mehanički modifikovanog pirofilita urađena je rendgenostrukturnom analizom i skenirajućom elektronskom mikroskopijom. Elektrohemijske karakteristike ove elektrode ispitivane su cikličnom voltametrijom u 1 mM K4Fe(CN)6 u 0,1 M KCl i 0,5 M H2SO4 i diferencijalnom pulsnom „striping“ voltametrijom u Briton-Robinsonovom puferu na pH 4. Pokazano je da maksimum na + 0,96 V u odnosu na Ag/AgCl elektrodu potiče od oksidacije karbendazima na pH 4 u Briton-Robinsonovom puferu. Dobru stabilnost i osetljivost pokazala je elektroda koja je sadržala 50% ugljenične paste i 50% pirofilita mehanički modifikovanog 15 minuta u mlinu sa kuglama. Razvijena metoda je linearna u opsegu od 1 ppm do 10 ppm sa r= 0,999 i granicom detekcije od 0,3 ppm.10. Memorijalni naučni skup iz zaštite životne sredine "Docent dr Milena Dalmacija", Mart 30.- 31., Novi Sad, 2023

Pyrophyllite modified carbon-based electrode

The main goal is to develop electrode material for the detection of traces of pesticides in food and water in a wide range of pH values. The leading idea is to use natural clay pyrophyllite to modify carbon paste electrode. SPEX Mixer/Mill 5100 is used for mechanochemical modification. The changes in the structure of pyrophyllite before and after the grinding process were studied by means of PSD, XRD, FTIR, and DTA-TG [1]. The electrochemical behavior of the sensor was followed using differential pulse stripping voltammetry (DPSV). It is shown that obtained material can be used as electrodes in electrochemical sensors for pesticide detection in a wide range of pH.Solid-State Science & Research Meeting : June 28-30, Zagreb, 2023

Kinetic behavior of MgH2-transition metal composites: towards hydrogen storage

Hydrogen as an energy vector represents great potential, due to its high gravimetric density and low mass, as well as the fact that combustion does not emit harmful chemical byproducts. Hydrogen has the highest energy density per unit mass compared to any other fuel but a rather low energy density per unit volume. Further, hydrogen storage is a key technology for developing a hydrogen and fuel cell-based economy [1]. Metal hydrides as alternative hydrogen carriers have a wide range of performance parameters such as operating temperature, sorption kinetics, activation conditions, cyclic options, and equilibrium hydrogen pressure. These parameters can be improved or adjusted to meet the technical requirements of different applications. The most commonly used method for hydride destabilization is nanostructuring by mechanical milling which leads to a reduction in the particle and crystallite size of the MgH2 powder. Nanostructuring is often combined with catalyst addition and composite formation [2,3]. The most of research is focused on the morphological, structural, and thermodynamic effects typical for long milling times, while in this work we have followed the changes taking place under short milling times. The thermal stability of magnesium hydride is related to - changes in the crystallites and powder particle size. The analysis also considered the changes in activation energy. MgH2-M composites were prepared by mechanical milling of the as-received MgH2 powder (Alfa Aesar, 98% purity) with the addition of 2 and 5 wt.% of M (M= V, W, Mo). Mechanical milling was performed in s SPEX 5100 Mixer Mill using 8mm diameter milling ball. Samples were milled for 15-45 minutes under the inert atmosphere of argon and a ball-to-powder ratio 10:1 Figure 1. shows the kinetic curves obtained for composites with 5wt% of vanadium. To investigate the desorption process in detail, different models of solid-state kinetics were used as implemented in the code developed in our group. The ratelimiting step of the desorption reaction was determined using the iso-conversional kinetic method due to better accuracy of obtained apparent activation energies. As shown in Table 1 a decrease in apparent activation energies has been observed. It is obvious that the sorption kinetics is affected by material preparation because the reactivity of magnesium with hydrogen is strongly modified by changes in several surface parameters that govern the chemisorption, the dissociation of molecular hydrogen, and hydride nucleation7th MESC-IS 2023 : International Symposium on Materials for Energy Storage and Conversion : 11th INESS : International Conference on Nanomaterials & Adv. Energy Storage Systems : October 7-10, Baku, 2023

Hydrogen Storage in Metal Hydrides: Experimental Approach

The paper deals with the destabilization methods for improving the storage properties of metal hydrides. The experimental approach was used to point out the influence of various types of defects on the structure and stability of hydrides. As a case study, Mg-based hydrides have been investigated. As shown by our research, ion irradiation is the way to introduce a well-defined concentration of defects (Frankel pairs) at the surface and sub-surface layers of a material. Defects at the surface play the main role in sorption reactions since they enhance the dissociation of hydrogen. Further, our research shows that ball-milling introduces defects through the entire sample volume, refines the structure and thus decreases the path for hydrogen diffusion. Surface-modified material demonstrates better thermodynamic and kinetics properties than bulk modified hydride materials.Published in Bulletin of the Chemists and Technologistsof Bosnia and Herzegovina as Special Issue (2024)