Excess Aluminum Research Articles

Laser welding of copper to aluminum with spiral trajectory and identification of excessive aluminum melting

Laser welding of copper and aluminum is challenging due to the formation of complex intermetallic phases. Only a defined amount of Al and Cu can be melted because of the limited solubility of Al–Cu systems. Finding the optimum melting is critical for a strong joint. Optical emission during the welding process contains the metal vapor of Al metal that is being welded. This is a good indicator for monitoring the welding process. This research paper focuses on the optical emission of Al from the bottom sheet during welding of Cu (top) and Al (bottom) in overlapped configuration for a spiral trajectory. The emitted signal in the range of 395 nm (±3 nm) from the bottom sheet of aluminum is used to identify excessive Cu–Al welding. The tensile shear strength, microstructure, and welding signal in the time domain for optimum and excessive weld conditions are investigated. In this study, a technique using a photodiode is shown to identify the excessive melting of Al during the welding process in real time.

Excess aluminum tolerance of the common water-hyacinth (Eichhornia crassipes) under greenhouse conditions

Aluminum is a heavy metal toxic to living organisms and is released into soils with a strong acidic composition. The floating aquatic weed Eichhornia crassipes (Mart.) Solms is reported as the most widespread invasive vascular plant in the world and is distributed all over Colombia ranging from sea level to the cold Andean highlands. As a consequence of the solubility of Al3+ in soils, it flows into fresh water sources where E. crassipes grows as an invasive plant. A greenhouse study was conducted in Tunja, Colombia, with the objective of evaluating the growth of aquatic weed in an aqueous substrate with Al3+ content similar to those recorded in lakes (0.0, 0.2, 0.4, 0.6, and 0.8 mg L-1 Al3+). Biomass production, leaf area, evapotranspiration, water use efficiency, and other allometric variables were evaluated. An increase of 18.2% in the transpiration rate and a reduction between 9.7%-41.8% in the leaf area were found. The latter reduced the value of variables such as the specific leaf area between 9.9%-34.6% and leaf area ratio between 16.7%-40.4%. However, the total dry weight, DM partitioning, root to shoot ratio, leaf weight ratio, and the absolute and relative growth rates did not show significantly different values between treatments. Therefore, Al content found in water sources in Colombia, despite being in the ranges reported as toxic for some aquatic plants, did not significantly affect the growth of E. crassipes due to its phenotypic plasticity and anthropic alteration of water sources but rather favor its growth.

Transcriptome Profiling Reveals the Effects of Nitric Oxide on the Growth and Physiological Characteristics of Watermelon under Aluminum Stress.

Excessive aluminum ions (Al3+) in acidic soil can have a toxic effect on watermelons, restricting plant growth and reducing yield and quality. In this study, we found that exogenous application of nitric oxide (NO) could increase the photochemical efficiency of watermelon leaves under aluminum stress by promoting closure of leaf stomata, reducing malondialdehyde and superoxide anion in leaves, and increasing POD and CAT activity. These findings showed that the exogenous application of NO improved the ability of watermelon to withstand aluminum stress. To further reveal the mitigation mechanism of NO on watermelons under aluminum stress, the differences following different types of treatments—normal growth, Al, and Al + NO—were shown using de novo sequencing of transcriptomes. In total, 511 differentially expressed genes (DEGs) were identified between the Al + NO and Al treatment groups. Significantly enriched biological processes included nitrogen metabolism, phenylpropane metabolism, and photosynthesis. We selected 23 genes related to antioxidant enzymes and phenylpropane metabolism for qRT-PCR validation. The results showed that after exogenous application of NO, the expression of genes encoding POD and CAT increased, consistent with the results of the physiological indicators. The expression patterns of genes involved in phenylpropanoid metabolism were consistent with the transcriptome expression abundance. These results indicate that aluminum stress was involved in the inhibition of the photosynthetic pathway, and NO could activate the antioxidant enzyme defense system and phenylpropane metabolism to protect cells and scavenge reactive oxygen species. This study improves our current understanding by comprehensively analyzing the molecular mechanisms underlying NO-induced aluminum stress alleviation in watermelons.

ROS-mediated mitophagy and apoptosis are involved in aluminum-induced femoral impairment in mice

The problem of excessive aluminum (Al) content in food is widespread. After Al enters the body, it can cause mineral metabolism imbalance and reactive oxygen species (ROS) overproduction, which ultimately leads to bone impairment. ROS is mainly produced in mitochondria and acts on mitochondria. Mitochondrial damage is closely related to mitophagy and apoptosis. In order to clarify whether ROS-mediated mitophagy and apoptosis are involved in Al-induced femoral impairment, forty-eight male C57BL/6 N mice were exposed to AlCl3 (179.3 mg/kg) and/or NAC (100 mg/kg) for 90 days. Our results showed that NAC inhibited the mitophagy and apoptosis, and alleviated growth inhibition, mineral metabolism imbalance, structural damage, decreased bone mineral density and decreased bone formation factor expressions in the femora of Al-treated mice. These results suggest that ROS-mediated mitophagy and apoptosis are involved in Al-induced femoral impairment in mice, exogenous ROS clearance is a potential strategy for the treatment of Al-induced bone impairment.

A readily available neutral nickel catalyst for accessing linear ultrahigh molecular weight polyethylene in a living manner

It is of great importance and is highly desired in the olefin polymerization catalysis that a simple catalyst derived from cheap starting materials and short synthetic pathways exhibits superior catalytic property towards a polymerization reaction. In this contribution, starting from commercially available and cheap materials, by using a short and simple three-step reaction route we report a readily available neutral phenoxy-imine nickel catalyst, which significantly enables the formation of linear ultrahigh molecular weight polyethylene (~5 brs/1000C, Mn = 1531 kDa) in a living polymerization (PDI = 1.08–1.11). An enhancement of 77 times on the polymer molecular weight occurs compared to the classical 2,6-diisopropyl substituted phenoxy-imine nickel catalyst. This avoids a tedious synthetic procedure and the use of an excess aluminum reagent as the activator and the scavenger.

Modified MAX Phase Synthesis for Environmentally Stable and Highly Conductive Ti3C2 MXene.

One of the primary factors limiting further research and commercial use of the two-dimensional (2D) titanium carbide MXene Ti3C2, as well as MXenes in general, is the rate at which freshly made samples oxidize and degrade when stored as aqueous suspensions. Here, we show that including excess aluminum during synthesis of the Ti3AlC2 MAX phase precursor leads to Ti3AlC2 grains with improved crystallinity and carbon stoichiometry (termed Al-Ti3AlC2). MXene nanosheets (Al-Ti3C2) produced from this precursor are of higher quality, as evidenced by their increased resistance to oxidation and an increase in their electronic conductivity up to 20 000 S/cm. Aqueous suspensions of stoichiometric single- to few-layer Al-Ti3C2 flakes produced from the modified Al-Ti3AlC2 have a shelf life of over ten months, compared to 1 to 2 weeks for previously published Ti3C2, even when stored in ambient conditions. Freestanding films made from Al-Ti3C2 suspensions stored for ten months show minimal decreases in electrical conductivity and negligible oxidation. Furthermore, oxidation of the improved Al-Ti3C2 in air initiates at temperatures that are 100-150 °C higher than that of conventional Ti3C2. The observed improvements in both the shelf life and properties of Al-Ti3C2 will facilitate the widespread use of this material.

Chemistry of rock-forming silicate and sulfide minerals in the granitoids and volcanic rocks of the Zefreh porphyry Cu–Mo deposit, central Iran: Implications for crystallization, alteration, and mineralization potential

Abstract Cu–Mo mineralization and associated hydrothermal alteration zones in the Zefreh porphyry Cu–Mo deposit are a result of the emplacement of the early Miocene granodioritic-to-granitic porphyritic intrusions into the Eocene volcanic rocks (dacites, pyroclastic rocks, and andesitic lavas) during active subduction along the Urumieh–Dokhtar Magmatic Belt (UDMB) of Iran. The compositions of rock-forming minerals, such as plagioclase, amphibole, and biotite, in the granitoids of the Zefreh magmatic suite are used to determine temperature and oxygen fugacity in the magma during crystallization and emplacement. Plagioclase is locally unaltered and ranges widely in composition with reverse, normal, and oscillatory zoning, but there is no evidence of excess aluminum. Primary calcic amphiboles in the granodiorite porphyry are mainly magnesio-hornblende with high Mg#’s. The crystallization temperature of the granodiorite is in the range of 765–867 °C (average 821 ± 28 °C for amphibole–plagioclase geothermometer) and 706–861 °C (average 808 ± 35 °C for amphibole alone). Whereas, the zircon saturation temperature for the Zefreh granodiorite is lower and ranges from 724° to 733 °C (average 729 ± 4 °C). Biotites in the least-altered granodiorite and in the potassic alteration are Mg-rich and Ti-poor, and mainly fall within the fields of phlogopite and re-equilibrated primary biotite, because of their low TiO2 contents (2.7–4.5 wt%, average 3.5 wt%). Copper and molybdenum in the Zefreh porphyry deposit appear to have been transported by Cl-rich hydrothermal fluids as chloride complexes, based on the calculated halogen fugacity ratios of the fluid in equilibrium with hydrothermal biotite that range from 5.0 to 5.4 for log (ƒH2O)/(ƒHF), 4.3 to 4.8 for log (ƒH2O)/(ƒHCl), and –2.0 to –1.4 for log (ƒHF)/(ƒHCl). The calculated fugacity ratios indicate that the biotites equilibrated with hydrothermal fluids that varied in composition, including oxygen, sulfur, and halogen fugacities. The intercept values for biotites from the Zefreh porphyry Cu–Mo deposit [IV(F) = 1.9 to 2.2 and IV(Cl) = –4.8 to –4.3] correspond to those from other well-known porphyry Cu–(Mo–Au) deposits worldwide [IV(F) = 1.5 to 2.8 and IV(Cl) = –5.0 to –3.5]. On the other hand, hydrothermal chlorite and epidote in the propylitically altered granodiorite of the Zefreh deposit are more Fe-rich and Mn-poor than those in some mineralized porphyry systems. The calculated temperatures of chlorite formation by the geothermometer of Cathelineau (1988) are all similar (300–330 °C), suggesting the potassically altered granodiorite was also affected by later, cooler hydrothermal fluids associated with the distal propylitic alteration zone. Disseminated chalcopyrite in the matrix of the potassically and propylitically altered granodiorite hosts as much as 1.3 wt% Zn and 0.1 wt% As. Based on whole-rock and mineral compositions, we conclude that the Zefreh magmatic system is similar in many regards to subduction-related ore systems, but it is unlikely to host a major porphyry Cu–Mo deposit.

Pre-aggregation of Al13 in optimizing coagulation for removal of humic acid

The effective removal of humic acid (HA) by coagulation has been extensively investigated for water treatments. However, the limitations of pH variation and excessive residual aluminum issues were still factors needed to be considered. In this study, to investigate the coagulation mechanism for removing HA by Al13 and optimize Al13 operation for removing HA, Al13 and preformed Al13 aggregates (Al13agg) were applied to remove HA at different pH conditions. The results showed that preformed Al13agg exhibited superior HA removal performance than Al13 due to its wide pH range and low residual Al level. During coagulation, Al13 and Al13agg interacted with HA in their original status, but the DSlope325-375 difference implied that the complexation capacity between HA and Al13agg was stronger than Al13. The new peaks of HPSEC representing larger molecular weight substances were formed under acidic and neutral conditions, which indicated that HA firstly aggregated into larger complexed molecules by interacting with Al13 or its hydrolysates and was subsequently removed by forming large flocs which was completely different from Al13agg situation. Therefore, the different coagulation mechanisms played the roles in HA removal for Al13 and Al13agg which were studied in this paper. It was believed that the complexation and charge neutralization effects dominated coagulation process for Al13 while sweep flocculation and adsorption coagulation were main driving force for Al13agg in HA removing. This work provides significant understanding of HA removal by Al13 and Al13agg coagulation, which can help to design and optimize the high efficiency coagulant based on Al polycations.

Prevention of Hydrosphere’s Pollution by Aluminium

The environmental hazard is the transport of toxic ions and aluminium oxides entering the hydrosphere. In addition to solving global issues of maintaining environmental wellbeing through sustainable development, it is necessary to solve the technological problems of cleaning water bodies from excessive aluminium. One of the effective measures to solve such problems is the use of phytoremediation - a set of methods for treating wastewater and water bodies with the help of aquatic plants. The study of aquatic organisms (hydrobionts) ecology shows how do they affect the physical and chemical parameters of the environment, including the hydrosphere. Our study in measuring the concentration and toxicity of aluminium ions in the aquatic environment based on the results of experiments with aquatic plants (macrophytes) Ceratophyllum and Chara fragilis, as well as with the higher aquatic plant Callitriche palustris Linne showed the possibility in initiating self-purification processes of hydrosphere objects from mentioned pollutants. Another option in preventing hydrosphere pollution by aluminium compounds should be based on implementation the noospheric transformation of the educational system for national economy specialists in accordance with proposals, given in the paper.

Lodo gerado em Estação de Tratamento de Água: Avaliação preliminar da toxicidade em plantas de milho

O lodo é o principal resíduo gerado em Estação de Tratamento de Água (ETA), é oriundo do processo de potabilização da água, apresenta grande concentração de sólidos e, elementos químicos como o alumínio e ferro. Por esse motivo, o mesmo não pode ser descartado nos mananciais, necessitando de alternativas ambientalmente seguras para uma destinação adequada. O objetivo com esta pesquisa foi avaliar a toxicidade do lodo gerado em ETA associado ao bagaço e vinhaça de cana-de-açúcar na germinação e crescimento inicial de Zea mays L. A compostagem do lodo foi realizada por 60 dias, com uma mistura de bagaço e vinhaça inoculado com Pleurotus sajor-caju. O composto foi incorporado ao solo nas doses de 0; 1; 10 e 100 de composto/solo (g kg-1). Foram semeadas 10 sementes de Z. mays híbrido 2B433Hx da Dow Agrosciences, após sete dias foi realizado o desbaste deixando cinco plântulas em cada vaso. O delineamento experimental utilizado foi o inteiramente casualizado com quatro repetições. Após 21 dias de cultivo foram avaliadas: porcentagem de emergência; índice de velocidade de emergência; comprimento e massa seca de raízes e parte aérea. A dose de 100 g kg-1 promoveu reduções no comprimento de parte aérea e sintomas de deficiência nutricional ocasionados pelo excesso de alumínio, ferro e sódio no lodo. Para o uso seguro, recomendamos a dose de 10 g kg-1 do composto de lodo de ETA.

Кинетика низкотемпературного алюминотермического восстановления танталата железа

The kinetics of low-temperature (900 – 1180 °C) reduction of iron tantalate (98.2 wt % FeTa2O6, 1.8 wt % Ta2O5, particle size < 0.1 mm) by excess aluminum (particle size < 0.14 mm) at the molar ratio Al:FeTa2O6 = 6 was studied. According to differential scanning calorimetry and X-ray powder diffraction, reduction is almost completed at 1180 °C, the metal products are TaFeAl, TaAl3, and Ta17Al12. Based on the results of thermokinetic calculations (Ozawa – Flynn – Wall and nonlinear regression methods), the formal mechanism of the process is represented by the Bna → CnC model, which includes two consecutive steps controlled by autocatalytically activated reactions. Kinetic parameters of the steps are: 1) Е1 = 429 kJ·mol–1, A1 = 1015.3 s–1; 2) Е2 = 176 kJ·mol–1, A2 = 103.9 s–1 (Ej is the activation energy, Aj is the preexponential factor). Prediction in the Bna → CnC model frames indicates the possibility of obtaining a reaction mixture containing ≥ 98 mol. % the final formal reduction product, with isothermal exposure in the temperature range of 1040 – 1120 °C during 1.5 – 5 minutes. The proposed model can be used to develop scientific foundations and substantiate technological modes for obtaining tantalum alloys from mineral and technogenic raw materials.

ВЛИЯНИЕ ЭЛЕМЕНТНОГО ПОРОШКОВОГО СЫРЬЯ НА ФОРМИРОВАНИЕ ПОРИСТОГО КАРКАСА МАХ-ФАЗЫ Ti3AlC2 ПРИ ПОЛУЧЕНИИ МЕТОДОМ СВС

The ternary carbide compound Ti3AlC2 belongs to the so-called MAX-phases – a new type of ceramic materials with unique properties. A simple energy-saving method of self-propagating high-temperature synthesis (SHS) based on combustion is one of the promising methods for the production of this MAX-phase. The application of the SHS technology is to produce a Ti3AlC2 MAX-phase porous frame with the homogeneous porous structure without such defects as large pores, laminations, and cracks is of great interest. The paper investigates the possibility of producing such a porous frame with the maximum content of the Ti3AlC2 MAX-phase using powders of Ti, Al, and C elements of various grades different in particle sizes and carbon forms (soot or graphite) as initial components. Porous frame samples were produced by the open-air burning of pressed briquettes of charge of the initial powders of the selected grades without applying external pressure. The authors studied the macro- and microstructure of the obtained samples, their density, and phase composition. The study shows that using the finest titanium and carbon powders leads to the excessively active combustion with gas evolution and the synthesis of the defective porous samples with the charge briquette shape distortion, large pores, laminations, and cracks. Besides the titanium carbide by-phase, the highest values for the MAX-phase amount in the SHS-product were obtained using the titanium powder of the largest-size fraction together with the graphite powder, rather than soot. The excess aluminum powder addition to the stoichiometric ratio to the initial charge leads to an increase in the MAX-phase amount in the SHS product, compensating for the loss of aluminum due to evaporation. An increase in the sample volume (scale factor) also leads to an increase in the MAX-phase amount in the SHS product due to the slower cooling of the product after the reaction.

Synthesis, Characterization and Investigation of Hydrogen Evolution Activity of Ni‐Mo/Al2O3 Composite

AbstractIn the present study, the hydrogen evolution activity of the Ni−Mo/Al2O3 catalyst was investigated. This catalyst was produced by milling of oxide precursors of nickel oxide (NiO) and molybdenum trioxide (MoO3) with aluminum as a reducing agent. So that oxide precursors with 100 % excess aluminum on stoichiometric composition at different times were milled to perform complete reduction operations. Subsequently, X‐ray diffraction (XRD) analysis was performed for phase analysis and scanning electron microscopy (SEM) was used to investigate the microstructure. It was found that oxide precursors with 100 % excess aluminum on stoichiometric composition were reduced after 50 h of milling and nickel molybdenum/alumina composite was produced. On the other hand, to compare the activity of Ni−Mo/Al2O3 two different catalysts (57 NiMo, 80 NiMo) were also produced by the milling method. The specimens were transformed into pills of 10 mm in diameter and 3 mm in height at 900 MPa pressure. A furnace under an argon atmosphere at a temperature of 1400 °C was used to sinter the produced pills. Finally, the hydrogen evolution activity of this sample was investigated by linear polarization tests and impedance spectroscopy in 1 M KOH solution. The sample reduced with 100 % excess aluminum showed higher activity than the stoichiometric combination, with −62 mV cathodic‐Tafel slope, −70 mV over‐potential at a current density of −10 mA cm−2 and a charge transfer resistance of 126.6 ohms.

Paradoxical Filler Size Effect on Composite Wear: Filler–Matrix Interaction and Its Tribochemical Consequences

The addition of 0.2–5% nanoscale (40–80 nm) α-phase or microscale (40 μm) γ-phase Al2O3 particles in PTFE effectively reduce the matrix wear rate by 99.99%, whereas microscale (> 0.5 μm) α-Al2O3 or nanoscale (40–80 nm) γ-Al2O3 only reduce PTFE wear by ~ 90% under identical loading, dispersion and testing conditions. This paradoxical material system best illustrates the complexity of tribology and the importance of filler–matrix interactions at small scales. We studied the independent effect of the Al2O3/PTFE interface area and alumina structure by systematically varying the particle size over two orders of magnitude for both α- and γ-Al2O3/PTFE composites. Detailed characterizations of filler size, surface area and tribofilm’s chemical composition were conducted. The results found: (1) DLS median particle sizes conformed reasonably to vendor reported values and percentages of microscale filler aggregates correlated weakly with wear rates, (2) electron microscopy of the as-worn composite surface suggested a strong relation between the characteristic size of ‘unreinforced’ polymer domain and composite wear rate, (3) third bodies (i.e., transfer films, debris) played an important role in counterface abrasion, (4) wear rate correlated strongly with filler’s specific surface area and ultralow wear was only maintained ~ 0.3–10 m2/g nominal specific filler–matrix area values, (5) ultralow wear coincided with perfluorinated carboxylic salt rich tribofilms which supported a previously proposed wear reduction mechanism that mechanochemically degraded PTFE chelate with alumina and cause crosslinked and wear-resistant tribofilms, (6) tribofilm Al-F bond signal increased with filler surface area and high wear coincided with excessive tribofilm Al-F signal for γ-Al2O3/PTFE systems. Based on these results and literature hypothesis, we proposed that (1) the 1 μm α-Al2O3 provided the least filler–matrix interface and largest unreinforced polymer domain in PTFE, which lead to the least crosslinked and compartmentalized tribofilms; (2) in γ-alumina filled composites, Al-F bond forms as a product of mechanochemically degraded PTFE but also blocks chelation between the degraded PTFE and alumina fillers, (3) the 20 nm γ-Al2O3 provided the most filler–matrix interface which leads to excessive aluminum fluoride that blocked the filler–matrix chelation, prevented the tribofilm crosslinking and lead to high wear rates. This hypothesis was additionally supported by small molecule experiments in this study. However, this study provides no direct insight into how sensitive the filler–matrix tribochemical interaction is to filler phase or aggregate strength (strong, weak or fully dense).

Novel 2‐hydroxynaphthalene‐based fluorescent turn‐on sensor for highly sensitive and selective detection of Al3+ and its application in imaging in vitro and in vivo

Excessive aluminum exposure in the human body has been held responsible for multiple adverse effects, and existing data underscore the significance of aluminum detection in environmental and biological systems. Developing high‐performance Al3+ fluorescent chemosensors can revolutionize our understanding of the physiological and pathological processes of Al3+ ions. Herein, we reported a highly sensitive and selective Schiff base fluorescence sensor, bis‐NAPPD (1,1'‐((1E,1'E)‐(pyridine‐2,3‐diylbis(azanylylidene))bis(methanylylidene))bis(naphthalen‐2‐ol)), which can recognize Al3+ ions and exhibits a remarkable turn‐on dual emission response (by ~23 fold) with a low nanomolar level detection limit (1.67 × 10−8 M) in methanol. Furthermore, the binding behavior and the turn‐on fluorescence probing mechanism of bis‐NAPPD were illustrated in detail by UV–vis titration, 1H NMR, and ESI‐MS spectroscopy as well as density functional theory calculations. Notably, bis‐NAPPD showed great potential for tracing Al3+ distribution in cells and living zebrafish larvae, and can also be applied in the fluorimetric detection of aluminum in sucralfate tablets with good precision and satisfactory accuracy, which may represent a promising Al3+ probe in bioimaging and biomedical applications.

Reduced doping efficiency of aluminium in Al-doped ZnO film: role of excess aluminium and deposition rate

This work addresses the role of excess Al and deposition rate in reducing the doping efficiency of Al+3 cations in Al-doped ZnO (AZO) films. In this regard, AZO films were deposited on the soda lime glass substrates using co-sputtering from ceramic AZO/ZnO and metallic Al targets. Whereas power to ZnO/AZO target was kept constant, power to Al target was varied to see the effect of varying Al concentration (and deposition rate) on its doping efficiency. Here, Al doping efficiency in ZnO is found to increase initially with increasing deposition rate and Al content, beyond which it decreased because of the formation of higher AlxOy in combination with increased trapped Al in the amorphous regions of these films. Moreover, a detailed discussion on the mechanism of the deposition rate and thereby induced variation in Al doping efficiency is discussed and then related to the optoelectronic properties of these films.

Impact of MWCNT/Al on the combustion behavior of hydroxyl ammonium nitrate (HAN)-based electrically controlled solid propellant

In the controllable combustion field, hydroxyl ammonium nitrate (HAN)-based electrically controlled solid propellants (ECSPs) is of growing interest in green fuels with safety, throttle- ability and at-will on-off capability. However, the current research is confined to the ignition characteristics and ablation process of basic ECSP formulations (75 wt% HAN ionic liquid oxidizer, 5 wt% ammonium nitrate co-oxidizer and 20 wt% polyvinyl alcohol binder), rather than working in functional additives. Herein, multiwall carbon nanotubes (MWCNT) and nano/micro aluminum powders were introduced in ECSPs, facilitating electrical conductivity and energy release. It indicates that the homogeneous dispersed MWCNT in polyvinyl alcohol (PVA) microspheres, preparing by the micro-segmented flow method, results in a 9.8% increase in electrical conductivity of the ECSPs. At 0.5 MPa, ECSPs containing 1%, 3% and 5% 5 µm aluminum powder reinforce the burning rate by 38.0%, 186.3%, 214.7% and mass ablation by 10.7%, 95.2%, 175.6% at 200 V, yet the large heat release by excess aluminum powder shifts the non-self-sustaining combustion of ECSPs to self-sustaining combustion at high pressure (above 0.8 MPa). The mechanism of promoting ECSPs combustion by liberating aluminum-nitric acid (released by HAN ionization) reaction were proposed.

Mechanism of fluoride removal by AlCl3 and Al13: The role of aluminum speciation

Coagulation is an important defluorination process. However, because of the poor sedimentation properties, conventional coagulants often result in limited defluorination performance and excessive residual aluminum. In this study, AlCl3 and the highly-positively-charged molecule [AlO4Al12(OH)24(H2O)12]7+ (Al13) was utilized to treat fluoride-containing water. By comparison, the role of aluminum speciation in fluoride removal was elucidated. Under initial pH of 6.0, 7.0 and 8.0, the highest defluorination efficiencies of high-fluoride water ([F−]0 = 8.0 mg/L) were 78.2%, 71.6% and 83.2% at Al13 dosage of 20 mg/L, 40 mg/L and 50 mg/L. Combined with detailed investigations of the chemical compositions of flocs, along with electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) analysis of residual aluminum, the defluorination mechanisms of both coagulants were discussed. In acidic conditions, both coagulants hydrolyzed and formed various Al clusters, among which transient Al (Alts) was the intermediate of the other clusters. The coprecipitation of high-polymerized Al and F− contributed most of the defluorination rate. While under neutral and alkaline conditions, hydrogen bonding and ion exchange together with coprecipitation were the main roles for Al13. The effects of AlCl3 were merely physical actions, and were affected by the decreased pH. This work provides new insights into the coagulation and defluorination process.

Carbothermal Reduction Nitridation of Fly Ash, Diatomite and Raw Illite: Formation of Nitride Powders with Different Morphology and Photoluminescence Properties

Rare-earth-doped SiAlON and Si3N4 materials from aluminosilicate starting materials have been reported to show superior photoluminescence (PL) properties. Three different starting materials, including pulverized coal furnace fly ash, diatomite and raw illite, were used for synthesis of nitride materials. The phase and morphology evolution of these products were carefully monitored at the low temperature range of 1350 °C to 1450 °C by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and Fourier-transform infrared spectroscopy (FT-IR). The PL properties of Eu-doped nitride products were also comparatively characterized. The results show that the type of starting material affects the phase composition and the photoluminescence properties of products. The existence of aluminum and alkali metals could effectively promote nitridation reactions. Aluminum in the starting materials led to the formation of different aluminum-rich nitride phases. Thus, β-SiAlON could be achieved at a much lower temperature (1350 °C) using raw illite or fly ash containing the proper amount of aluminum. Additionally, excess aluminum led to the formation of corundum and 15R-SiAlON. The products from pulverized coal furnace fly ash had more prismatic particles, and the products from diatomite had more fibrous particles. With the progress of the nitridation process, the fibers were increased, becoming longer and straighter, and the prismatic particles were more obvious. The presence of aluminum in the starting materials led to a blue shift in the photoluminescence spectrum.

High-performance mesoporous (AlN/Al2O3) for enhanced NH3 yield during chemical looping ammonia generation technology

Chemical looping ammonia generation (CLAG), including the N-sorption/desorption steps of the N-carrier, is increasingly important due to the high demand for formation of carbon-free fuel. The N-sorption step, the synthesis of aluminum nitride (AlN) by the carbothermal reduction, has been widely studied for improving the purity and stability of aluminum nitride. However, there are few studies on how to enhance the porosity and thus N-desorption reactivity of AlN, one of the key issues for the CLAG. Therefore, in this paper, a supported Al-based nitrogen carrier (AlN/Al2O3) with mesoporous structure, in which 5% of Y2O3 was added as a catalyst, was developed with excess aluminum oxide (γ-Al2O3) and the corresponding N-desorption of the generated N-carrier was studied with a stationary bed reactor, X-ray diffraction (XRD), Brunner-Emmet-Teller (BET) measurements, Raman spectra and scanning electron microscope (SEM). The results showed that using the excess aluminum oxide in N-sorption step significantly led to the significant improvement in N-carrier's porosity and thus N-desorption reactivity, which did not vary with change in carbon types. Also, the N-sorption performance of γ-Al2O3 with carbon black was better than that with graphite due to their different carbon crystal structures. In addition, the effect of other parameters including the mole ratio of Al2O3:C, reaction temperature on the N-sorption performance of the N-carrier were studied. It was found that the specific surface area of the mesoporous structured Al-based AlN, synthesized with mole ratio of Al2O3: C being 3:3 at 1200 °C, reached to>70 m2/g, which was the best one for good NH3 synthesis performance.