Concentration Of Mn Ions Research Articles

Supercapacitor devices based on multiphase MgTiO3 perovskites doped with Mn2+ ions

Recently, perovskites have become a hotspot for researchers attempting to exploit metal and oxygen vacancies in structures of the form MTiO3, facilitating the convenient electron/hole migration, thus displaying interesting properties. Magnesium Titanate (MgTiO3) is a prominent part of the perovskite class, exhibiting remarkable electrical, thermal, and chemical properties. Undoped and Mn-doped MgTiO3 samples were obtained using a solid-state reaction starting from previously synthesized MgO and TiO2 powders, which were separately doped with different Mn ion concentrations. The resulting multiphase materials with a major MgTiO3 phase were thoroughly morpho-structurally analyzed employing XRD, STEM, Raman, PL, XPS, and EPR spectroscopy. The electrochemical results indicate that they show superior performance when used as electrode materials for supercapacitor application due to the high defect concentration as shown in EPR and PL spectroscopy and the ferroelectric behavior observed in XPS and XRD. When used in symmetric and asymmetric supercapacitor devices, they show promising results, with specific capacity values reaching up to 109 F/g for the symmetric and 609 F/g for the asymmetric devices, while energy and power density values reached 84.7 Wh/kg and 90.8 kW/kg respectively, proving a great potential in the energy storage field.

The effect of magnesium impurities on the optical and spectral characteristics of calcium orthovanadate single crystals doped with chromium and manganese

The effect of magnesium co-doping on growth conditions, crystal composition, optical and spectral properties of manganese or chromium-doped Ca3(VO4)2 (CVO) crystal was studied. The single crystals were grown by the Czochralski method. Effective segregation coefficients of manganese and chromium in the CVO matrix with magnesium co-doping were calculated. A redistribution of the absorption lines intensities was observed in the absorption spectra of CVO:Mn:Mg and CVO:Cr:Mg. Low (15 K) temperature fluorescence measurements confirmed that co-doping CVO crystal with Mg ions leads to the redistribution of Mn ions concentration in different valence states, but does not cause changes in their spectral properties. In the presence of magnesium, additional annealing of the materials resulted in a slower reduction of the valence state of doping ions and a noticeable change in crystal coloration. All investigated impurities have practically no effect on the specific ferroelectric domain structure of CVO.

Polymer and micellar catalysis in d-fructose oxidation by imidazolium fluorochromate: A kinetic and mechanistic study

This work investigated the oxidation of d-fructose using imidazolium fluorochromate (IFC) as an oxidant and analyzed how sodium dodecyl sulfate (SDS) and polyethylene glycol (PEG-400) affected the reaction kinetics. The process exhibited a unit-order dependence on IFC, d-fructose, and perchloric acid concentration. Perchloric acid was the primary source of hydrogen ions in the reaction mixture. The stoichiometry of the reaction indicated that 3 mol of d-fructose requires 4 mol of IFC. Acrylonitrile, a radical-generating species, did not impact the reaction rate, indicating the absence of a free radical intermediate. The reaction rate decreases as the Mn (II) ions concentration increases, suggesting the involvement of Cr (IV) species in the reaction. The dielectric value of the reaction medium (D) had an inverse effect on the rate, and the outcomes were consistent with the Amis (log k1 and 1/D) and Kirkwood plots (log k1 and (D-1/2D+1)), indicating the presence of dipole-dipole interactions in the process. SDS and PEG-400 catalyzed the reaction. The reaction showed significant catalysis before reaching the critical micelle concentration (CMC). However, the observed rate constants stabilized at higher SDS concentrations exceeding the CMC. Piszkiewicz's cooperativity model was employed to describe the surfactant catalysis, while the Benesi-Hildebrand equation was utilized to explain polymer catalysis. The activation parameters are ΔH† = 44.3 ± 1.3 kJ mol−1, and ΔS† = −133.4 ± 4.3 J K−1 mol−1. The products of the reaction have been identified by spectral analysis as d-arabinoniclactone and formic acid. The formation of an ester complex followed by its decomposition was proposed as the rate-limiting step in the proposed mechanistic reaction pathway.

Impact of Mn ions concentration on the structural, optical and insulating properties of (Y/Mn) merged codoped TiO2 polymorphs synthesized by hydrothermal decomposition technique

Impact of Mn ions concentration on the structural, optical and insulating properties of (Y/Mn) merged codoped TiO2 polymorphs synthesized by hydrothermal decomposition technique

Unraveling the sources of major, trace and rare earth elements in the waters of a high latitude proglacial environment: Weathering vs. atmospheric signature in Northern Patagonia

Glaciers are important water reservoirs and are extremely sensitive to the effects of climate change. The Manso River basin, in Northwest Patagonia, Argentina, is a typical hydrological system with actively retreating glaciers. In this article, the proglacial environment was examined to assess the sources and the geochemical processes responsible for the chemical signatures of the following water subsystems: 1) clean glacial meltwaters (supraglacial influence, fed by “clean ice” glaciers); 2) dirty glacial meltwaters (subglacial influence, fed by “dirty ice” debris-covered glacier); and 3) proglacial runoff (river). Results indicated that clean glacial meltwaters present high dissolved immobile and nonmobile trace elements, derived from atmospheric input with an anthropogenic component in Pb, Cu, V, and Ni. Dissolved concentrations of Sr, Mn, Rb, and major ions are the result of carbonation and hydrolysis processes. The dirty glacial meltwater presents the highest dissolved load due to the highest water-rock interaction. The proglacial runoff presents intermediate physicochemical characteristics. At the site where the clean and dirty glacial meltwaters mix, the cation denudation rate is 2075 meq+ m−2 y−1. Downstream, geochemical inverse modeling indicates that the Manso Superior River system produces, by weathering reactions, a rate of dissolved load of 2.67 108 mol year−1, along with a CO2 sequestration of 2.05 108 mol year−1, denoting that proglacial environments are an important scenario in the CO2 cycle. The results of this work provide a baseline for future studies in proglacial environments and highlight the importance of assessing metal concentrations and mobilization within the Andean cryosphere.

Preparation of Low-Defect Manganese-Based Prussian Blue Cathode Materials with Cubic Structure for Sodium-Ion Batteries via Coprecipitation Method.

Sodium-ion batteries have important application prospects in large-scale energy storage due to their advantages, such as safety, affordability, and abundant resources. Prussian blue analogs (PBAs) have a stable and open framework structure, making them a very promising cathode material. However, high-performance manganese-based Prussian blue cathode materials for sodium-ion batteries still suffer from significant challenges due to several key issues, such as a high number of vacancy defects and a high crystal water content. This article investigates the effects of the Fe-Mn molar ratio, Mn ion concentration, and reaction time on the electrochemical performance of MnHCF during the coprecipitation process. When Fe:Mn = 1:2, c(Mn2+) = 0.02 mol/L, and the reaction time is 12 h, the content of interstitial water molecules in the sample is low, and the Fe(CN)6 defects are few. At 0.1 C, the prepared electrode has a high initial discharge specific capacity (121.9 mAh g-1), and after 100 cycles at 0.2 C, the capacity retention rate is 65% (~76.2 mAh g-1). Meanwhile, the sample electrode exhibits excellent reversibility. The discharge capacity can still be maintained at around 75% when the magnification is restored from 5 C to 0.1 C. The improvement in performance is mainly attributed to two aspects: On the one hand, reducing the Fe(CN)6 defects and crystal water content is conducive to the diffusion and stable structure of N. On the other hand, reducing the reaction rate can significantly delay the crystallization of materials and optimize the nucleation process.

EVALUATING SUITABLE CHELATING AGENTS FOR Q STAGE IN TCF BLEACHING OF WHEAT STRAW ALKALINE PULPS

The aim of this study was to determine an appropriate chelating agent for Q stage in the TCF bleaching sequence of soda-oxygen, soda, soda-anthraquinone and alkaline-sulfite wheat straw pulps prior to P bleaching stage. In order to study the possible effect of chelating agents, three different chelating agents (EDTA, DTPA and DTMPA) were used. To evaluate the impact of transition metal ions on P stage, the residual Mn, Fe and Cu ion concentrations were determined with atomic absorption spectrometry. Ash and silica contents of pulps have been determined for each chelating agent, separately. FTIR-ATR spectroscopy was used to demonstrate the bleaching effect. The results showed that the most appropriate chelating agents varied depending on the type of pulp. The best chelating effect was achieved with DTMPA for soda-oxygen pulp, EDTA for both soda and alkaline-sulfite pulps, and DTPA for soda-anthraquinone pulp.

SrMn1-xFexO3-δ (x = 0–1) black ceramic pigment: Synthesis, color properties, and application

In this work, SrMn1-xFexO3-δ (x = 0–1) black ceramic pigments were synthesized by the solid-state method. The research explores the influence of calcination temperature and iron ion doping on the color properties of the pigments. Furthermore, the potential applications of SrMn1-xFexO3-δ pigments in ceramic glaze and heat-absorbing materials are also discussed. The findings reveal that the synthesized SrMnO3 pigment exhibits the lowest L*-value (22.30) at 1100 °C, although it displays a slight blue hue. To optimize the color properties of the SrMnO3 pigment, iron ion doping is employed. When the doping level of iron ions is 50 mol.% (i.e., x = 0.5), the L*-value of the SrMn0.5Fe0.5O3-δ pigment calcined at 1000 °C significantly decreases to 19.77, while the a*- and b*-values approach 0, resulting in a pure black color. This is attributed to the high surface roughness, low band gap energy, and substantial oxygen vacancies present in the SrMn0.5Fe0.5O3-δ pigment. The tinting mechanism of the SrMn1-xFexO3-δ pigment in the ceramic glaze is classified as "ion tinting", wherein the glaze color relies on the concentrations of Mn and Fe ions. When the pigment content reaches 36 wt%, the L*-value of the glaze drops to 4.94, showing a deep black shade. Additionally, the SrMn0.5Fe0.5O3-δ pigment exhibits excellent sunlight absorption capabilities, with a near-infrared reflectance (R*) of only 5.04%. This research presents a black ceramic pigment with various advantages, such as simplified processing, affordability, environmental friendliness, and exceptional color performance.

Acid functionalized polypropylene derivatives to adsorb Mn (II) from aqueous solutions: equilibrium, kinetics, and thermodynamic modeling

Polypropylene wastes were used to prepare carboxylated (CPP) and sulfonated (SPP) microparticles for the adsorption of Mn (II) from aqueous media. The microparticles derivatized with nitric or sulfuric acid were characterized in terms of their physico-chemical properties. The generated functional groups on CPP (–COOH and –NO2) and SPP (–COOH, –SO3H, and C = C) enhanced the adsorption of metal ions. The adsorption behavior of Mn (II) ions on the derivatized microparticles was studied under different conditions: Solution pH, polymer dose, contact time, initial concentration of Mn (II) ions, and temperature. Application of kinetics and equilibrium models to the data revealed that the adsorption processes followed pseudo-second order reactions and the Langmuir isotherm. SPP achieved a higher maximum adsorption capacity (9.15 mg g−1) than CPPs (5.51 mg g−1). Therefore, sulfonation was considered the most efficient approach to produce a suitable surface functionality for the removal of metal ions from aqueous solutions. However, thermodynamic studies showed that all adsorption processes are spontaneous and feasible (ΔG = − 1.32 and − 1.46 kJ mol−1 at 20 °C for CPP and SPP, respectively), which ensure the possibility of employing acid-derivatized PP microparticles for metal removal.Graphical abstract

Geometrical and Electronic Structure Analysis of Mn‐Doped CaMO3 (M = Ti, Zr, and Sn)

The geometrical and electronic structures of Mn‐doped CaTiO3, CaZrO3, and CaSnO3 deep‐red emission phosphors are investigated both experimentally and theoretically. All the samples are synthesized with solid‐state reaction method by changing the concentration of the doped Mn ions. Crystal structures of the fabricated samples are examined with the powder X‐ray diffraction technique and valence states of the doped Mn ions are determined by measuring the Mn‐L3 X‐ray absorption near‐edge structure (XANES) spectra. Diffuse reflectance spectra are observed to study the change in electronic structures due to the Mn doping. First‐principles calculations are also carried out to investigate geometrical and electronic structures of Mn‐doped CaMO3, in which different types of electron–electron correlation functionals are employed.

Decreasing of Mangan (II) in The Water Using Membrane of Moringa Seed Powder-TiO2 with Variation of Mass TiO2

Mn (II) is a metal ion commonly used in steel alloys, pigment industries, welding, fertilizers, pesticides, ceramics, and electronics. According to the Regulation of the Minister of Health No. 32 of 2017, the permissible content of Manganese in dug well water is 0.5 mg/L. The purpose of this study was to determine the concentration of Mn (II) ions in water before and after passing through a Moringa Seeds Powder (MSP)-TiO2 membrane 20:1; 20:3; 20:5; 20:7; 20:9 and measure the percentage decrease in the concentration of Mn (II) ions in water after through the MSP-TiO2 membrane. The object of this research is a 55 ppm Mn (II) ion artificial sample at a flow rate of 0.56 mL/minute for 90 minutes with 90-watt radiation UV. The concentration of Mn (II) ion was measured by visible spectrophotometric method, the morphology of MSP, TiO2, and MSP-TiO2 membranes was characterized by SEM-EDX, and its diffraction spectra by X-Ray diffraction. The results obtained that the initial Mn(II) was 55.06 ± 0.031 ppm, the concentration of Mn (II) ions with the MSP-TiO2 membrane of mass MSP-TiO2 were 20:1; 20:3; 20:5; 20:7; 20:9 respectively 36.47±0.00; 44.16±1.15; 44.31±1.04; 44.94±0.94; 42.27±2.61 ppm. The percentage of decrease concentration of Mn (II) ion are 34.19±0.44%; 21.37±0.43%; 20.94±0.85%; 19.24±0.86%; and 19.66±0.86%. The highest percentage decrease in Mn (II) ion concentration was 34.15±0.44% in the variation of mass MSP-TiO2 20:1. This study concludes that the MSP-TiO2 membrane has the potential to reduce the concentration of Mn (II) ions in water.

Activity of photosystem II in spring barley leaves under the action of manganese ions

The influence of manganese ions (30, 60 and 90 mg/l) on the functioning of the photosystem II (PSII) in leaves was assessed on plants of six spring barley cultivars (Belgorodsky 100, st.). The plants were grown on a complete Knop medium without (control) and with the addition of manganese ions (experiment) under natural light conditions. On 14-day-old leaves, parameters of chlorophyll's rapid fluorescence were recorded using a Fluor Pen FP 110/S fluorometer. The sensitivity of the different structural parts of PSII was found to vary depending on the concentration of Mn ions and the genotype used. Thus, absorbed energy flows increased in the cv. Boyarin at 30 and 60 mg/l Mn (by 7.9 and 14.1 %), in cv. Farmer at 60 and 90 mg/l (by 15.8 and 16.1 %), but decreased in cv. Dobryak at 30 and 90 mg/l (by 9.7 and 9.0 %), Farmer at 30 mg/l (by 15.8 %) and Bionic at 60 and 90 mg/l (by 8.0 and 6.8 %). The flow of energy stored in primary photochemical reactions in the cv. Bionic increased at 30 mg/l of manganese (by 6.3 %), but decreased at 60 (by 6.8 %) and 90 mg/l (by 5.3 %); increased in the cv. Boyarin at 30 mg/l of Mn (by 6.4 %), but decreased in the cv. Forward (by 11.7 %). Electronic transport leading to CO2 fixation increased in cv. Farmer at all Mn concentrations (by 8.1...12.6 %), and in cv. Bionic it increased at 30 mg/l (by 7.2 %), but decreased at 90 mg/l (by 7.4 %). The electron flux leading to the oxidation of the finile acceptor of PSI in the studied cultivars did not change under the influence of the stressor. However, the integral parameters of PSII activity (PIABS and PIABS_total indices) under stressful conditions were determined by the plant genotype. This indicates, firstly, the need for targeted selection (to a specific level of the stress factor); secondly, on the possibility of pyramidation of the integral level of resistance to the stressor by selecting parents who differ in the level of change in individual functional reactions of photosynthesis.

Peroxymonosulfate activation by β-cyclodextrin modified amorphous manganese oxides for a high-efficiency bisphenol A degradation

Manganese oxide activated peroxymonosulfate (PMS) has gradually become one of the research focuses in the field of advanced oxidation. In this work, β-cyclodextrin (β-CD) modified amorphous manganese oxide (CD-AM) catalyst was obtained from a mild reaction condition (80 °C oil bath), high temperature crystallization is avoided in the synthesis process, which reduces the difficulty of catalyst preparation process and energy consumption. β-CD is involved in the formation of manganese oxides. Amorphous manganese oxides have larger specific surface area and better PMS activation effect than crystalline manganese oxides, which is different from previous studies. The enrichment of cyclodextrin on BPA can improve the removal activity of amorphous manganese oxide/PMS system on BPA. The introduction of β-CD increased the bisphenol A (BPA) degradation efficiency from 33.1% to 99.4%, and brought the kinetic constant to its 14.9 times. The 94% BPA degradation efficiency was obtained under neutral conditions that is more favorable for the actual process. During the degradation process, 1O2 and ·OH were the main ROS in CD-AM/PMS system, and O·- 2 not only promoted the conversion of O·- 2 to 1O2 but also accelerated the cycle of Mn (III)/Mn (IV). In addition, a simpler material recovery process for application was achieved by transforming CD-AM into the “supported membrane” (AMSM), and better performance and lower Mn ion leaching concentration were accessible. With the utilization of AMSM, Mn ion concentration in the filtrate after first filtration was about 1.2 mg/L, which was only 37% of the Mn ion concentration firstly detected in CD-AM. And after four cycles, the BPA degradation efficiency was 96.9%. When AMSM/PMS system was used to treat BPA in river water, the final degradation efficiency reached 94.8%. CD-AM as a catalyst for activating PMS shows great application potential in actual water.

Исследования магнитных наночастиц Mn-=SUB=-x-=/SUB=-Fe-=SUB=-3-x-=/SUB=-O-=SUB=-4-=/SUB=-@OA (0≤ x≤ 1.0) функционализированных олеиновой кислотой (ОА) для биомедицинских применений

Functionalization (or coverage) MNF is a unique tool for creating particles with the properties required for biomedical applications. Therefore, the study of the magnetic properties of coated MNCs is the most important task of our time. The effect of changes in the concentration of Mn ions on the properties of MnxFe3-xO4 nanoparticles coated with oleic acid (OA) MnxFe3-xO4@OA (where x = 0, 0.25, 0.5, 0.75 and 1.0) to create stabilized magnetic fluids for various applications is investigated. The synthesis of MnxFe3-xO4@OA MNPs was carried out by thermal decomposition using manganese-oleate and iron oleate. The properties and phase states of the obtained MNPs were studied by X-ray diffraction (XRD) and Mossbauer spectroscopy. To understand the behavior of MNCs in small magnetic fields during hyperthermic treatment, Mossbauer studies of MnxFe3-xO4@OA particles were carried out when a magnetic field with a strength of 1.7 kOe was applied. It is established that the thermal decomposition method makes it possible to obtain single-phase superparamagnetic particles promising for biomedical applications

Assessment of Cyprinus carpio Scales as a Low-Cost and Effective Biosorbent for the Removal of Heavy Metals from the Acidic Mine Drainage Generated at Rosia Montana Gold Mine (Romania)

In the present study, the biosorptive potential of Cyprinus carpio scales for the removal of Fe, Mn, and Zn ions from real acidic mine drainage (AMD) generated at the Rosia Montana gold mine (Romania) was explored for the first time. The collected AMD solution is very acidic, and the concentrations of Fe, Mn, and Zn ions exceed more than 34 to 56 times the disposal standards imposed by legislation. Batch adsorption experiments were carried out to study the effect of the sorbent dosage, sorbent particle size, pH, and contact time on the adsorption performance of the fish scales. Before and after the adsorption process, the biosorbent was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, and energy-dispersive X-ray spectroscopy (SEM-EDX). In the investigated experimental conditions, about 100%, 87.1%, and 100% of Fe, Mn, and Zn ions were removed from the AMD after 240 min of contact with the finest-grained Cyprinus carpio scale samples using a solid:liquid ratio of 20:1 (g:L). The adsorption data were analyzed using the pseudo-first order, pseudo-second order, intraparticle diffusion rate, and Elovich equations. The adsorption process was found to follow the pseudo-second-order kinetic model. The maximum adsorption capacities of the fish scales were about 2.46 mg/g for Mn and 0.85 mg/g for Zn ions, respectively. Aside from their significant efficiency in the removal of metals from AMD, Cyprinus carpio scales also have the potential to neutralize the acidic wastewater. Thus, the removal process of metal ions from AMD is ruled by a complex mechanism, including adsorption and iron precipitation. The recycled scales are still able to remove the metal ions from AMD with a better performance during the first regeneration cycle. Based on the obtained results, it might be assessed that the low-cost biowaste of Cyprinus carpio scales have great potential and could be effectively used for the remediation of real acidic mine drainage from a sustainable perspective.

Toxic Metals in Some Decorative Cosmetics and Nail Products

Cosmetic marketing is one of the most profitable and fast increasing markets in Kurdistan Region of Iraq. In recent years, the use of cosmetics has witnessed a rapid increase, especially with the emergence of social media and its impact on this trade. The market is full of different cosmetic brands and nail products. Moderate and low-quality brands of cosmetic samples that available in the local markets were selected to investigate their heavy metals and chemical composition. Samples from face foundation, eye shadow, and nail polish products were taken and examined to evaluate the concentration of metals, that is, Hg, Pb, Cd, As, Mn, Cr, Ni, Co, Fe, Zn, Cu, and Al ions, using X-ray diffraction and X-ray fluorescence techniques. The examination results show high concentrations of Fe and Al metals in the lipstick samples whereas the Hg, Cd, Cr, and Ni were out of detection limit. Moreover, the results show contamination of Hg heavy metal in one of the examined nail polishes brands, whereas the rest of foundation and eye shadow samples show a higher concentration of Al and Fe. Curcumin, as a natural bio-friendly chelate, has been used to deplete metal ions using ultraviolet-visible Spectrophotometer.

Influence of Manganese Doping on Optical Properties of Barium Ferrites Nanoparticles

The barium hexaferrite magnetic materials Mn-doped BaZn1+x Mnx Fe12-2x O19 (x = 0.4, 0.8, 1.2, 1.6, and 2) were prepared using the ceramic method. The powder samples ferrite were subjected to XRD, FT-IR, and UV-Vis to investigate the nanoparticles' structural changes. UV–Vis spectroscopy is used to obtain the samples' absorption spectrum and calculate the band gap energy. X-ray diffraction patterns and FT-IR investigations confirmed the formation of a single-phase M-type hexagonal structure. The grain size was measured from Scherrer's equation, and it is found in the range of 43-56 nm, with increasing the concentration of Mn ions, which shows the enhancement in the degree of crystallinity and increase in the size of grain size. UV-vis spectroscopy was used to confirm the formation of the BaZn1+x Mnx Fe12-2x O19 nanoparticles. The transmission was found to increase slowly in the 200-290 nm wavelength and then decreased to 332 nm after that increase until the maximum for all samples was about 99% in 480-800 nm wavelengths. The highest transmission will be exclusively used for window layers in solar cells. The band gap energy increased gradually with a rise in Mn ions and a decrease in Zn ion concentration. The refractive index, dielectric constant, and optical dielectric constant decreased with an increase in Mn ions and a decrease in Zn ions concentration.

Experimental study on the effects of different factors on the crystallization rate and products of Mn-Ca co-crystallization.

Calcium and manganese are common ions that pollute drinking water and, therefore, ingestion may seriously harm human health. However, despite its importance, few studies into the synergistic removal of calcium and manganese have been reported. Calcium and manganese have similar chemical properties and, consequently, can be removed by co-crystallization, as the exact crystalline phase formed by this process and the process rate depend on the pH, the dissolved oxygen (DO) content, and the concentrations of the component ions. In this work, we experimentally studied the co-crystallization of Mn and Ca using an automatic potentiometric titrator. We found that the concentration of Mn2+ can be reduced from 3.0 to <0.1 mg/L by the co-crystallization of Mn and Ca at pH 10.5 and a DO content of 8.5 mg/L. In addition, the crystallizations of Ca and Mn are mutually inhibitory; the crystallization process of Mn is obviously divided into two stages: crystal nucleation and crystal growth. Increasing the pH, decreasing the DO content, and decreasing the Mn ion concentration increase the rate of CaCO3 crystallization, whereas the opposite changes increase the rate of Mn crystallization. Furthermore, Mn-Ca co-crystallization leads to the formation of various substances, including single crystals (CaCO3/MnCO3), mixed crystals (CaMnCO3), and Mn oxides (MnxOy/Mn(OH)O). Our findings regarding the effects, precipitation rates, and precipitation mechanisms of Mn-Ca co-crystallization serve as an important guide for the optimization and control of Mn-Ca co-crystallization processes.

Mn ions‐activated Gd3(Al,Ga)5O12 garnet solid‐solution ceramics: Cation substitution for dual wavelength red‐emission

AbstractRed‐emitting color‐convertors have attracted considerable attention for promising applications in solid‐state lighting (SSL) to improve color rendition. However, the current nitride and fluoride phosphor powders have encountered several challenges, such as high cost, narrow emission bands, and insufficient stability during operation, which limit the development of high‐power full‐spectrum SSL. In this study, thermally robust Gd3(Al,Ga)5O12:Mn (GAGG:Mn) solid‐solution ceramics (SSCs) with dual wavelength red‐emission bands were prepared via an oxygen solid‐state sintering reaction. The doped Mn ions occupied octahedral Al3+ and Ga3+ sites to generate Mn4+ luminescent centers with pronounced deep‐red emissions peaking at 698 nm (2E → 4A2), and Mn2+ luminescent centers with broad red emissions at 628 nm (4T1 → 6A1). Because the cationic radius matching effect induced the regulation of valence state of Mn, the photoluminescence of the GAGG:Mn SSCs can be tailored by the substitution of Al3+ with Ga3+. Moreover, the Mn3+ also existed in the GAGG lattice host, and their concentration decreased with increasing Ga3+ contents owing to the mismatch of ionic radius between Mn3+ and Ga3+ ions. With the optimization of Al/Ga ratio and concentration of Mn ions, a broad emission band ranging from 550 to 800 nm (bandwidth = 250 nm) was achieved from Gd3Al3Ga2O12:0.3%Mn SSCs upon 465‐nm excitation. Moreover, the GAGG:Mn SSC has over 17‐fold enhanced thermal conductivity compared with the corresponding phosphor powder. This paper opens a door of regulating the valence state of luminescence centers with cation substitution and the application of oxide red‐emitting color‐convertors.

Effect of SiO2/Al2O3 Ratio on the Crystallization and Heavy Metal Immobilization of Glass Ceramics Derived from Stainless Steel Slag

This study investigated the effects of the SiO2/Al2O3 mass ratio on the glass stability, crystallization and heavy metal immobilization of glass ceramics derived from stainless steel slag (SSS). When the SiO2/Al2O3 mass ratio decreased from 11.2 to 4.2, the glass stability and the depolymerization degree of the parent glass increased from 2.13 to 2.40 and subsequently decreased to 2.31. The predominant crystal phase of the resulting glass–ceramics changed from pyroxene and diopside to wollastonite, pyroxene, and diopside as the crystallization temperature of samples increased from 800°C to 860°C. The heavy metals, Cr and Mn, from SSS cured in the spinel of glass–ceramics, whereas the hazardous metal Ni was primarily found in pyroxene (CaNiSi2O6). In addition, the leached concentrations of hazardous metals, Ni, Mn, and Cr ions, in glass-ceramics were far below the national standard. The results showed that it is possible and safe to turn SSS into eco-friendly glass-ceramic.