High Al Content Research Articles

Numerical and experimental investigations of micro Al particle additive on the performances of HTPB hybrid rocket motors

The hybrid rocket motor (HRM) emerges as a promising propulsion system offering thrust adjustment at a low cost. Prior research has indicated that the inclusion of micro Al additives enhances HRM performance, yet a comprehensive investigation remains absent. Thus, this study aims to explore the impact of Al particle additive content and size variation on the characteristics of hybrid rocket motors (HRMs) through experiments and simulations. Firing tests are conducted on HRMs employing unadulterated HTPB, 38 % additive Al (2 μm), and 58 % Al (2 μm). Experimental findings reveal enhancements of 12.6 % and 33.9 % in regression rate, and 2.5 % and 8.0 % in specific impulse for the 38 % Al and 58 % Al fuel configurations, respectively, compared to the base case. Subsequently, a numerical two-phase combustion model is built to analyze the inner flow field characteristics. The high consistency between experimental and simulation results validates the efficacy of the numerical approach employed. Following this, a series of simulations covering Al content ranging from 0 % to 58 % and Al particle sizes from 0.4 μm to 75 μm is conducted. Simulation outcomes indicate that specific impulse and combustion efficiency enhancements correlate with the increase in Al mass fraction for particles with diameters under 35 μm. However, high Al content proves detrimental to specific impulse and combustion efficiency when particle diameter exceeds 35 μm. Additionally, regression rate and thrust demonstrate an increase with Al content, albeit the rate of increment diminishes with larger Al particles. This study comprehensively examines the influence of Al particle addition on HRM performance and elucidates the underlying mechanisms, thereby offering insights into HRM design and manufacture.

Effect of composition on the thermal properties and structure of M-Al-Si-O-N glasses, M = Na, Mg, Ca

The primary objective of this study is to explore the relationship between the composition, structure, and thermal characteristics of M-Al-Si-O-N glasses, with M representing sodium (Na), magnesium (Mg), or calcium (Ca). The glasses were prepared by melting in a quartz crucible at 1650 °C and AlN precursor (powder) was utilized as a nitrogen source. The measured thermal properties studied were glass transition temperature (Tg), crystallization temperature (Tc), glass stability, viscosity, and thermal expansion coefficient (α). The findings indicate that increasing the aluminum content leads to higher glass transition, crystallization temperatures, and viscosities. In contrast, fragility values increase with the Al contents, while modifier elements and silicon content influence thermal expansion coefficient values. FTIR analysis revealed that in all glasses, the dominant IR bands are attributed to the presence of Q2 and Q3 silicate units. The effect of Al is observed as a progressive polymerization of the silicate network resulting from the glass-forming role of Al2O3. In most samples, the Q4 silicate mode was also observed, strongly related to the high Al content. Overall, the study shows that the complexity of composition-property correlations where the structural changes affect the properties of Mg/Ca-based oxynitride glasses has potential implications for their use in various technological fields.

Investigation of MBE grown high Al concentration AlGaN ohmic contact

Investigation of MBE grown high Al concentration AlGaN ohmic contact

Do aluminum (Al)-hyperaccumulator and phosphorus (P)-solubilising species assist neighbouring plants sensitive to Al toxicity and P deficiency?

We aimed to evaluate the facilitation effects of an aluminum (Al) hyperaccumulator species bearing cluster roots, Gevuina avellana, on the seedling growth and performance of an Al-intolerant and phosphorus (P)-deficient-sensitive plant, Vaccinium corymbosum. For this, seedlings of G. avellana and V. corymbosum were grown alone or together as follows: i) two G. avellana seedlings, ii) one G. avellana + one V. corymbosum and iii) two V. corymbosum, in soil supplemented with Al (as Al2(SO4)3) and in the control (without Al supplementation). We determined relative growth rate (RGR), photosynthetic rate, chlorophyll concentration, lipid peroxidation and Al and nutrient concentration [Nitrogen (N), P, potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), and sulfur (S)] in leaves and roots of both species. The results showed that, in general, G. avellana did not assist V. corymbosum to enhance its RGR nor reduce its Al uptake. However, G. avellana assisted V. corymbosum in enhanced N acquisition and, consequently, to increase its chlorophyll concentration and photosynthetic rate. Besides, V. corymbosum had lower lipid peroxidation in leaves when grown in the soil with high Al supplementation in association with G. avellana. Our results suggest a facilitating effect of G. avellana to V. corymbosum when grown in soils with high Al concentration, by enhancing chlorophyll concentrations and photosynthetic rate, and decreasing the oxidative damage to lipids.

A marine incursion during the onset of T-OAE in Sichuan Basin, China: Evidence from green clay minerals and carbonate concretions

A high-amplitude global sea level rose rapidly during the early Toarcian (Early Jurassic), making the transgression deposits potential stratigraphic correlation markers of marine and terrestrial successions. Green clay minerals (i.e., glauconite and chamosite), carbonate concretions, and geochemical database associated with the early Toarcian global transgression are archived in the Lower Jurassic Da'anzhai Member (the Early Toarcian age) in the Sichuan Basin of China, a mega lake along the Tethys Ocean. The fine-grained glauconites with high Al and low Si contents suggested that they were transported from offshore to the lake by marine incursion and were oxidized during the transport processes. The green authigenic chamosite cement and redeposited chamosite grains with high Mg/Fe and low Al/Si ratios were diagenetically transformed from berthierine formed in the brackish water caused by marine incursion. The chemically impure siderite concretions with low 87Sr/86Sr ratios and high δ13C values suggested that the lake water and sediment pore waters were mixed with seawater. Coeval calcareous concretions have low 87Sr/86Sr ratios and high δ13C values, indicating the mixing of lake water with seawater. Combining the stratigraphic low 87Sr/86Sr values, we suggested that there was a marine incursion into the Sichuan Basin. According to the organic carbon isotopic stratigraphy correlation, the marine incursion occurred during the onset of T-OAE. The rapid and high-amplitude global sea-level rise may have caused this marine incursion.

Complexation mechanism of Pb2+ on Al-substituted hematite: A modeling study and theoretical calculation

Hematite nanoparticles commonly undergoes isomorphic substitution of Al3+ in nature, while how the Al-substitution-induced morphological change, defective structure and newly generated Al–OH sites affect the adsorption behavior of hematite for contaminants remains poorly understood. Herein, the interfacial reactions between Al-substituted hematite and Pb2+ was investigated via CD-MUSIC modeling and DFT calculations. As the Al content increased from 0% to 9.4%, Al-substitution promoted the proportion of (001) facets and caused Fe vacancies on hematite, which increased the total active site density of hematite from 5.60 to 17.60 sites/nm2. The surface positive charge of hematite significantly increased from 0.096 to 0.418 C/m2 at pH 5.0 due to the increases in site density and proton affinity (logKH) of hematite under Al-substitution. The adsorption amount of hematite for Pb2+ increased from 3.92 to 9.74 mmol/kg at pH 5.0 and 20 μmol/L initial Pb2+ concentration with increasing Al content. More Fe vacancies may lead to a weaker adsorption energy (Ead) of hematite for Pb2+, while the Ead was enhanced at higher Al content. The adsorption affinity (logKPb) of bidentate Pb complexes slightly increased while that of tridentate Pb complexes decreased with increasing Al content due to the presence of ≡ AlOH−0.5 and ≡ Fe2AlO−0.5 sites. Tridentate Pb complexes were dominant species on the surface of pure hematite, while bidentate ones became more dominant with increasing Al content. The obtained model parameters and molecular scale information are of great importance for better describing and predicting the environmental fate of toxic heavy metals in terrestrial and aquatic environments.

Influence of Cr + Si content variation on cutting behavior of TiAlCrSiN HPPMS coatings

As high power pulse magnetron sputtering (HPPMS) technology is becoming popular in cutting tool industry, the development of nanocomposite coating systems such as TiAlCrSiN with this technology presents a new research avenue. Here, the combined effect of Cr and Si contents on properties and cutting behavior of high Al content TiAlCrSiN HPPMS coatings needs further investigation. For this purpose, three HPPMS coatings with Al/Ti ratio x = 1.4–1.5 and varying Cr + Si content, namely (Ti28Al40Cr16Si16)N, (Ti30Al43Cr17Si10)N and (Ti36Al54Cr5Si5)N, were deposited on cemented carbide substrates. In addition to basic characterization, the fracture behavior of the coatings was characterized by scratch tests. The cutting behavior of the coated inserts was exemplarily investigated during dry cutting of normalized medium carbon steel C45 with cutting speed vc = 80 m/min, feed rate f = 0.12 mm and cutting depth ap = 0.8 mm. The tool damage over the cutting time of tc = 35–40 min, as per the tool condition, was observed using light microscopy. Moreover, the damage mechanisms were analyzed in detail at the end of the cutting test using scanning electron microscopy. All coatings showed comparable indentation hardness HIT and indentation modulus EIT. However, an increased Cr + Si content amplified the brittle fracture of the coating under sliding load of scratch test. Moreover, the workpiece material C45 showed a higher adhesion tendency to cutting insert with high Cr + Si content TiAlCrSiN coatings during cutting tests. The tool wear and built-up edge formation increased due to the combined effect of workpiece adhesions and amplified brittle fracture of the coating at considered cutting speed. On the other hand, the inserts with low Cr + Si content coating exhibited better cutting performance and reduced built-up edge formation based on the improved fracture behavior of the coating and lower adhesion tendency of workpiece material to the corresponding coated insert.

Expanding the applications of the wear-resistant titanium aluminum nitride thin-film to include temperature sensing

This study investigates an approach to temperature sensing by integrating Titanium Aluminum Nitride (TiAlN), originally engineered for wear and corrosion applications, as a temperature sensor within a multilayered thin film system. A nitride multilayer system was developed by physical vapor deposition (PVD) using a single four-target magnetron sputtering chamber; intermediate vacuum interruption steps were employed for masking procedures. The multilayer architecture design aimed to provide the sensor layer with mechanical protection and electrical shielding. Structural and electrical characterization of the TiAlN single layer revealed semiconductor behavior and stable electrical resistance up to 750 °C, with minimal signal stabilization requirements. Despite the higher Al content, the TiAlN temperature sensor exhibited a cubic crystal structure characterized by diffuse nanolayers, resulting from a two-fold rotational deposition and target configuration. A detailed examination of the multilayer system cross-section containing the TiAlN sensor was conducted using scanning transmission electron microscopy (STEM). The analysis revealed its columnar morphology with the presence of typical PVD growth defects, including voids and droplets. While the presence of these defects may impact the electrical characteristics of the sensor, the selected experimental conditions effectively maintained the structural integrity of the multilayer system despite the vacuum interruptions caused by masking procedures. Validation experiments confirmed the functionality of the multilayer system for temperature measurements up to 400 °C. The signal acquisition system addressed room temperature resistance variations and low sensitivity (thermistor coefficient ∼100 K), resulting in a measured error of approximately 6%. This study demonstrates promising results of TiAlN as a temperature sensor within a multilayered system, expanding its range of potential applications.

Factors affecting reduction efficiency in industrial retorts for Mg production by aluminothermic process

Industrial experiments were carried out for Mg production by aluminothermic process in industrial retorts and the factors affecting the reduction efficiency were analyzed. The results show that the main factors reducing the reduction ratio are oxidation and combustion of crystallized magnesium and uneven mixing of raw materials. The latter could result in raw material regions with low Al concentration and MgO redundance, which can promote the formation of 12CaO·7Al2O3 and CaO·Al2O3. For raw material regions with higher Al concentration, both MgO and CaO can be reduced to form the Mg2Ca phase. Radiation and chemical reaction heat are the key factors affecting the reaction rate. Increasing the heating temperature can rapidly increase the bed temperature and obtain sufficient reaction ratio. The higher the magnesium content in the pellets is, the longer the reduction time is required.

Paleoclimate changes across the Cenomanian–Santonian transition at the southern Neo-Tethys margin (SW Iran): An integrated approach

The Cenomanian–Santonian (C–S) carbonate successions include valuable petroleum reservoirs in the Zagros Basin. They also provide important information on the paleogeographic setting, paleoclimatic conditions, and tectonic evolution of the southern Neo-Tethys margin. This study focuses on the paleoclimatic changes across the C–S transition using the petrographical, petrophysical, paleontological, major and trace element and isotope geochemical data from three subsurface sections selected from the southern Dezful Embayment and northwestern part of the Persian Gulf. Remarkable differences in allochemical (skeletal and non-skeletal) elements indicate dissimilar paleoclimatic conditions during the Cenomanian–Turonian and Santonian. Paleoexposure events are related to diagenetic processes such as extensive meteoric dissolution (karstification) and the development of bauxitic–lateritic paleosols with high Fe, Al, and kaolinite concentrations indicating warm and humid (tropical) conditions. Increased values of Fe, Al, Rb, and 87Sr/86Sr isotopic ratios and depletion of Ca, Sr, δ18O, and δ13C considered together indicate meteoric diagenetic effects under this paleoclimatic condition. Spectral gamma measurements are used to investigate paleoclimatic conditions. Low content of Uranium (U) throughout the transgressive systems tract (TST) and high concentration in the regressive systems tract (RST) along with low contents of kaolinite within the Santonian sequence denote the predominance of arid conditions. The major fall in U concentrations at the Cenomanian–Turonian interface (CT-Exposure Surface) could be regarded as an outcome of the fall in the relative sea-level and a proxy of oxidizing conditions (Th/U > 7) that could be the consequence of a change in paleoclimate from humid/semi-humid to humid. Evidence for a 3–4 °C decrease in paleo-temperature and increase in aridity are recorded during the Cenomanian–Santonian transition in the Zagros Basin, which is in close agreement with global trends. This cooling pattern is attributed to a decline in atmospheric CO2 levels and alterations in oceanic circulation, specifically an increase in meridional circulation.

External aluminium supply regulates photosynthesis and carbon partitioning in the Al-accumulating tropical shrub Melastoma malabathricum.

Aluminium (Al) is toxic to most plants, but recent research has suggested that Al addition may stimulate growth and nutrient uptake in some species capable of accumulating high tissue Al concentrations. The physiological basis of this growth response is unknown, but it may be associated with processes linked to the regulation of carbon assimilation and partitioning by Al supply. To test alternative hypotheses for the physiological mechanism explaining this response, we examined the effects of increasing Al concentrations in the growth medium on tissue nutrient concentrations and carbon assimilation in two populations of the Al-accumulator Melastoma malabathricum. Compared to seedlings grown in a control nutrient solution containing no Al, mean rates of photosynthesis and respiration increased by 46% and 27%, respectively, total non-structural carbohydrate concentrations increased by 45%, and lignin concentration in roots decreased by 26% when seedlings were grown in a nutrient solution containing 2.0 mM Al. The concentrations of P, Ca and Mg in leaves and stems increased by 31%, 22%, and 26%, respectively, in response to an increase in nutrient solution Al concentration from 0 to 2.0 mM. Elemental concentrations in roots increased for P (114%), Mg (61%) and K (5%) in response to this increase in Al concentration in the nutrient solution. Plants derived from an inherently faster-growing population had a greater relative increase in final dry mass, net photosynthetic and respiration rates and total non-structural carbohydrate concentrations in response to higher external Al supply. We conclude that growth stimulation by Al supply is associated with increases in photosynthetic and respiration rates and enhanced production of non-structural carbohydrates that are differentially allocated to roots, as well as stimulation of nutrient uptake. These responses suggest that internal carbon assimilation is up-regulated to provide the necessary resources of non-structural carbohydrates for uptake, transport and storage of Al in Melastoma malabathricum. This physiological mechanism has only been recorded previously in one other plant species, Camellia sinensis, which last shared a common ancestor with M. malabathricum more than 120 million years ago.

Control of Aluminum and Titanium Contents in the Electroslag Remelting of ATI 718PlusTM Alloy.

The burning loss of Al and Ti elements in superalloys during electroslag remelting has become a prevalent issue. And the existing slag system is not suitable for smelting the ATI 718PlusTM alloy. Therefore, it is imperative to develop a new slag system for smelting the ATI 718PlusTM alloy. To mitigate this issue, a thermodynamic model of the oxidation reaction of Al and Ti at the slag and alloy interface was established based on the ion and molecule coexistence theory (IMCT). The thermodynamic model was used to investigate the correlation between the equilibrium content of Al and Ti, slag composition, smelting temperature, and initial Al and Ti content of the electrode. The results indicate that while increasing the smelting temperature can effectively inhibit the burning loss of Al, it will exacerbate the burning loss of Ti. Increasing CaO and Al2O3 contents can inhibit the Al burning loss, while an increase in the TiO2 content can inhibit the Ti burning loss. Although an increase in the MgO content results in the burning loss of Al, its impact on the Al is minimal. The burning loss of Al and Ti was not affected by the change in the CaF2 content. The high Al content in ATI 718PlusTM makes it prone to burning loss of Al during the electroslag remelting. The combustion loss of Al can be reduced by increasing the Ti content in the electrode or adding a suitable amount of aluminum powder to the slag system. The accuracy of the model had been validated through experimental verification.

Effect of compositional minor adjustment on localized lamellar structure coarsening of TiAl alloys with different solidification modes

Possible lamellar coarsening in the as-cast microstructure of TiAl alloys significantly affects the subsequent processing of ingot metallurgy, and a systematic study of it is necessary. In this paper, two TiAl alloys with different solidification modes (TNM-45Al alloy and TNM-0.3Si-0.7 C alloy) were obtained by compositional minor adjustment basing on TNM alloy. The effect of different adjustment routes on the localized lamellar structure coarseing behaviour and the resulting differences in the uniformity of the nanohardness distribution were investigated by comparing with TNM alloy. It is found that increasing the Al content of the TNM alloy while keeping the solidification mode as β-solidification unchanged leads to severe localised lamellar coarsening in the S-segregation zone of TNM-45Al alloy, including continuous coarsening (CC) and discontinuous coarsening (DC). In contrast, the solidification mode of the TNM-0.3Si-0.7 C alloy with the addition of the strong α stabilizer elements Si and C is transformed into hypoperitectic solidification with severe peritectic segregation, but the lamellar structure exhibits surprising full-domain stability. The results show that the thermodynamic tendency caused by high Al content and the absence of net-like β-segregation leads to severe localised lamellar coarsening in TNM-45Al alloy. CC can be accomplished through the migration of interface defects. DC is formed by the nucleation and expansion of γ-phase Shockley incomplete dislocations, and the interfaces consist of the α2 /γ interface and the first discovered γ /γ twin interface. The lamellar coarsening of TNM-0.3Si-0.7 C alloy can be effectively suppressed by the solid solution of Si/C atoms and the near net-like β-segregation in the primary β-phase region. As a result, the distribution uniformity of the nanohardness of the lamellar structure in TNM-0.3Si-0.7 C alloy is excellent, with the variance decreasing from ±0.24 of TNM alloy to ±0.20, while it increases to ±0.37 for the TNM-45Al alloy.

Evolution of static recrystallization microstructure caused by residual strain of an Al-richen Ni-based single crystal superalloy

Recrystallization has a devastating effect on the service process of single crystal superalloys (SX). This study mainly investigated the static recrystallization (SRX) behavior of an as-cast high Al content nickel-based SX under local or global deformation at room temperature, as well as heat treatment at various temperatures. The microstructural evolution was observed under different conditions using electron back scatter diffraction (EBSD), which was employed to determine the SRX threshold. The results indicated that the critical SRX temperature exceeds 1260 °C, and the critical plastic strain is greater than 5 %. In particular, the characteristic of the higher SRX tendency in the interdendritic region (IDR) of the as-cast SX was discovered, which was attributed to the phenomenon that the IDR with lower deformation resistance was prone to significant plastic accumulation and the bulk γ' could be the nucleation substrate of the SRX. Furthermore, with the increase in heat treatment temperature, there are certain changes in the morphology characteristics of re-precipitated γ' in the vicinity of the SRX grain boundary with a higher migration rate. This is mainly attributed to the decrease in the internal subcooling of the bulk γ' phase and the increase in the concentration of γ' forming elements at the grain boundary front.

Effects of high Al content on the steel–slag reaction and inclusion formation in molten steel

Three groups of refining experiments using the slags with different CaO/Al2O3 mass ratio (C/A = 0, 1.32 and 2.52 for No. 1 [without slag], No. 2 and No. 3) were carried out. The experiment results show that the increase of C/A led to the decrease of Al content. The steel–slag–inclusion multiphase reactions (SSIMR) model under high Al content conditions was constructed by the effective equilibrium reaction zone and FactSage 8.2 software. The modeling predictions of changes of [Al], [Ca] and [Mg] and SiO2, MgO and CaO in the slag are consistent with the experimental results. The SSIMR modeling suggested that the reactivity of [Al] and SiO2 in slag decreased with the increase of C/A, while the reactivity of [Al] and CaO in slag increased with the increase of C/A. The increase of C/A has little effect on the reaction between [Al] and MgO in slag. Inclusion observations in the No. 2 and No. 3 experiments show that inclusions change from Al2O3 and MgAl2O4 in early stages to CaO-MgO-Al2O3-SiO2 inclusions in the late stages. This study may help predict steel–slag reaction and inclusion formation under high Al content conditions.

Exploring the effect of polyacrylamide/graphene oxide composite hydrogel on the synthesis and application of ZSM-5 molecular sieves

Herein, we demonstrate the synthesis of coffin-shaped ZSM-5 molecular sieves in polyacrylamide (PAM)/graphene oxide (GO) composite hydrogel using the hydrothermal method. The as-synthesized products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS), and Thermogravimetry analyses (TGA). The effect of PAM and GO addition on the morphology and structure of ZSM-5 was investigated. The results indicated that the introduction of PAM and GO promoted the growth of the ZSM-5 (101) plane. Moreover, samples synthesized in the PAM/GO hydrogel exhibited a longer c-axis and a more pronounced coffin-shaped morphology compared to samples synthesized solely in PAM hydrogel. The Si/Al ratio decreased with the addition of GO, possibly due to interface effects leading to the formation of ZSM-5 precursors with a higher Al content. TG, FT-IR, and XPS characterization revealed hydrogen bonding interactions between PAM and GO, and the addition of GO likely restricted the movement of polymers, improving cross-linking between monomers and forming a more uniform network structure. The sample G-15 (P-5) exhibited higher mesopore volume and average pore diameter, contributing to enhanced catalytic performance. However, with increasing GO content, the average pore diameter decreased, potentially due to functional groups on the surfaces of graphene oxide and polyacrylamide forming a more uniform and structurally stable three-dimensional network structure. This allowed for controlled modulation of the molecular sieve morphology and pore size. The introduction of PAM/GO hydrogel resulted in a moderate amount of weak acid and an increased amount of strong acid, both shifting to lower temperatures. The ZSM-5 molecular sieves synthesized in the PAM/GO composite hydrogel demonstrated outstanding MTO catalytic performance, exhibiting high selectivity for light olefins and an extended catalytic lifespan. This work is expected to provide new ideas and methods for developing efficient ZSM-5 catalysts.

Disordered medium-pore zeolite PST-24 as an efficient low-temperature isobutanol dehydration catalyst

The disordered medium-pore zeolite PST-24 was found to be an efficient catalyst for low-temperature dehydration of bio-based isobutanol to isobutene.

Muddy sediments are an important potential source of silicon in coastal and continental margin zones

The dissolution of silicate minerals on the seafloor releases an important amount of dissolved silicon (dSi), which is necessary for maintaining high diatom production in Coastal and Continental Margin Zones (CCMZs). However, the dissolution of silicate minerals along the continental shelves is variable, which hinders our understanding of the marine Si cycle on both a regional and global scale. To understand the discrepancy of silicon (Si) released in different sediment matrices and its potential controlling factors, we investigated surface sediments of typical CCMZs of the Chinese marginal Seas using a continuous alkaline extraction technique, grain size and chemical (carbon and total nitrogen) analysis as well as a qualitative measurement of clay mineral composition by X-ray diffraction. The results showed that the amount of Si and aluminum (Al) leached from muddy sediments were 2 times greater than those released from sandy sediments. High dissolution rates (> 0.20 mg-SiO2 g−1 min−1) of silicate minerals are caused by a large sediment-specific surface area. Further, our data showed that biogenic silica (bSi) with high Al content (Si:Al < 40) has low reactivity and that the source of Al incorporated in bSi is silicate minerals undergoing dissolution. We show that although the dissolution of silicate minerals is less active than that of bSi, it still potentially releases more bio-available Si and Al to seawater due to its dominant presence on the seafloor (70.3% − 99.0%wt). This study highlights silicate minerals as an important potential marine Si source and emphasizes the need for a better understanding of the roles of silicate minerals in the Si cycle of marginal seas in future studies.

Assessment of the concentration of toxic metals (aluminum, cadmium and manganese) in the soil and evergreen plant species at the Sastavci surface mine and its vicinity

The study aims to determine the concentration of Al+3, Cd+2 and Mn+2 in the soil and parts of evergreen plant species - juniper and white pine - at the surface mine Sastavci (Badanj) and its vicinity in order to determine the possibility of using evergreen plants as an ecological indicator or for phytoremediation. Globally, as a result of various anthropogenic activities such as traffic, agricultural activities, waste incineration, industrial production, mining, etc., it represents a serious problem leading to pollution with toxic and potentially toxic metal cations. One of the more innovative techniques used for the remediation of mining areas is phytoremediation. By applying phytoremediation, certain plant species in polluted areas have the ability to act as accumulators or hyperaccumulators, absorbing toxic metals from the soil through the plant roots and transporting them to the upper parts. This research has been conducted to determine the concentration of Al+3, Cd+2 and Mn+2 at the surface mine itself and its surroundings, as well as to monitor the distribution of metal cations in the system of roots, branches, needles, and fruits of the evergreen plant species - white pine and juniper. The results showed that the sampled soil was contaminated with Cd in zones I and II for both plant species, since the concentrations exceeded the limit values, while the concentration of Cd in zone III as well as in the control zone was below the determination limits for both plant species. The concentration of Mn in the soil from the white pine and juniper zone was above the world average in all three zones, as well as in the control zone itself. The soil was most enriched with the analyzed elements in the surface mine of zone I and zone II. According to the analysis of elements in the parts of white pine, roots, branches, needles and fruits, the highest concentration of Al was detected in the root in zone I, while the lowest concentration was recorded in the fruit (cones) in the control zone, an increased concentration of Cd was recorded in the branches in zones I and II, and the highest concentration of Mn was recorded in needles in zone II. The highest Al concentration was recorded in the juniper root in zone I and the lowest in the juniper fruit in the control zone, the Cd concentration was the highest in the juniper root zone I, and the lowest in the juniper fruit and the highest Mn concentration was recorded in the juniper needles in zone I. Based on the obtained values of the coefficient of biological absorption, it can be concluded that white pine is not suitable for phytoextraction or phytostabilization of the tested elements. The analysis of biological factors (bioconcentration, translocation and bioaccumulation factor) indicated possible usage of juniper in phytoextraction only for Cd.

Electrical characteristics of Al/AlGaAs/GaAs diode with high-Al concentration at the interface

Electrical characteristics of Al/AlGaAs/GaAs diode with high-Al concentration at the interface