Alumina Precursor Research Articles

Effects of Alkali Elements on Copper Indium Gallium Aluminum Selenide Flexible Solar Cells Fabricated on Polyimide Substrates.

Polycrystalline Cu(InGaAl)Se2 (CIGAS) thin films were prepared on polyimide (PI) foils by depositing aluminum (Al) and CIGS precursor layers. Three ceramic CIGS quaternary targets with different sodium (Na) contents were used for investigating the influences of alkali doping at an annealing temperature of 500 °C. The Al concentration was enriched at the front interfaces of absorber films with different Na doping amounts after annealing. Na in the precursor layer diffused to both interfaces during the annealing process, most Na diffused into the Mo layer, and Na existed in the annealed film as compounds Na2Sex and Na2SeO3. An appropriate amount Na element could be beneficial for grain growth in the region beneath the surface. Low Na doping had no significant effect on the crystallization property. High Na doping effected the diffusion of the Cu2-xSe liquid phase and reduced the grain size. On the basis of good crystallization, the passivation effect of Na can effectively improve the performance of cells. A certified power conversion efficiency of 16.19% of a CIGAS flexible solar cell with a 0.54 cm2 active area has been achieved.

Effect of Ga/Al ratio on the luminescent properties of inorganic scintillating GGAG:(4 mol%)Ce ceramic powder

Gadolinium gallium aluminum garnet doped with cerium (GGAG:Ce), a promising ceramic scintillator material, is being excessively explored for its high quality optical properties by the bandgap engineering with different Ga/Al ratio. In this study, GGAG:Ce powders were synthesized using a solvothermal method and sintered at 1300 °C to investigate the impact of the gallium-to-aluminum (Ga/Al) ratio on optical characteristics. The results revealed that a decrease in the Ga/Al ratio led to a decrease in particle size. This observation can be attributed to the different reactivity and growth kinetics of gallium and aluminum precursors during the solvothermal process. Perturbations from the optimized Ga/Al ratio of 1.5–1.77 and 1.27 resulted in substantially enhanced photoluminescence (PL) and radioluminescence (RL) spectra intensities. PL lifetime measurements of various Ga/Al ratio exhibit average PL lifetime between 48 and 57 ns. Specifically, the deviations to 1.77 and 1.27 ratios yielded approximately 125 % and 106 %, respectively, in observed luminescent measurements compared to other ratios. This enhancement in PL and RL intensity suggests that the Ga/Al ratio plays a critical role in modulating the optical properties of GGAG:Ce ceramic powders. The results of this study also highlight the importance of the Ga/Al ratio in tailoring the optical or luminescence characteristics of GGAG:Ce powders.

Atomic Layer Deposition of γ‐Al2O3 on Hexagonal Boron Nitride: A Hybrid Support for Metallocene Catalysts

AbstractHexagonal boron nitride (hBN), also known as white graphene, has recently gained larger attention due to its unique physical and chemical properties. Owing to its excellent thermal conductivity and stability, hBN has been reported as an effective filler in many polymers. This study explores the potential of hBN as a catalyst support and filler for olefin polymerization. We report the atomic layer deposition (ALD) of γ‐Al2O3 on hydroxyl‐functionalized hBN. The alumina precursor, methylaluminoxane, showed high selectivity, depositing Al species only on the B‐OH sites, while B−O‐O−B sites remained unreacted. The hBN/γ‐Al2O3 hybrid was characterized by Fourier transform infrared (FTIR) spectroscopy, X‐Ray diffraction and transmission electron microscopy (TEM). The deposition of the aluminum over the hBN sheets was confirmed. The hBN/γ‐Al2O3 was used as a support for metallocene catalysts. The supported catalyst complex was highly active and produced ethylene‐propylene polymers with molecular weights up to 10 times higher, as demonstrated by gel permeation chromatography (GPC)

Synthesis of monodisperse spherical nano alumina by hydrothermal method and its mechanism study

Ultrafine alumina is widely used in advanced manufacturing industry, and its form, size and dispersion have important effects on its physicochemical properties and application characteristics. However, the superfine monodisperse spherical alumina is difficult to obtain in the actual synthesis process because the alumina precursor grain grows too fast and is easy to agglomerate. In this work, ammonium sulfate was added as the synthetic raw material to improve its dispersity. When the concentration reached 40 % of the aluminum source concentration, the isometric alumina precursor with a particle size of about 35 nm was obtained under the condition of rapid cooling. The influence of ammonium sulfate on the chemical structure of the precursor was determined by Fourier Transform Infrared spectrometer (FTIR) and X-ray photoelectron spectroscopy (XPS). The effects of reactant concentration and reaction temperature on the morphology, particle size and dispersion of the precursor as well as its mechanism were discussed in detail, and the optimal synthesis method of the nano alumina precursor was obtained. Finally, two kinds of precursors were calcined at different temperatures to obtain the equiaxed γ-Al2O3 with a particle size of 20 nm and the monodisperse spherical α-Al2O3 with a particle size of 133 nm, respectively. In this study, nano alumina precursors were synthesized by a simple and reliable method, and monodisperse ultra-fine alumina with different particle size morphologies were obtained, which has great application prospects in precision polishing, special ceramic manufacturing, and 3D printing.

The Effect of Peptizing Agent Concentration on Processing and Properties of Alumina Based Catalyst Support

Gamma alumina (γ-Al2O3) has drawn attention as a support material for heterogeneous catalysts extensively used in the oil and gas industry due to its superior properties. Boehmite (AlOOH) is an industrially accepted and well-known precursor to produce gamma alumina-based support. The process additions such as nitric acid (HNO3) are commonly used in shaping process of alumina to control textural, mechanical and structural properties of final catalyst support. In this work, gamma alumina precursor boehmite was peptized by nitric acid at molar ratio of HNO3/AlOOH ranging from 0 to 0.054. With addition of nitric acid, extrusion paste showed higher plasticity up to 0.017 mole of HNO3/AlOOH. The addition of more than this point led to an inhomogenity of extrusion paste caused by hard and brittle structure caused by the formation of aluminum nitrate salts. Also, higher mechanical strength was observed for samples peptized with lower nitric acid concentration because of effective deagglomeration by peptization. The pore size of catalyst support pellets increased up to an acid/ boehmite molar ratio of 0.017 by peptizing of boehmite. However, beyond this point pore size decreased due to dissolution of boehmite.

Study on Preparation Technology and Heat Conduction Mechanism of High-Purity & Ultra-Fine Alumina Powder from Scrap Aluminum Cans

In view of the increasing scarcity of bauxite resources in China, the high energy consumption and high pollution of electrolytic aluminum, and the requirements for energy conservation and environmental protection, aluminum recycling and high-value utilization of its derivatives have evolved into a crucial development requirement for the aluminum industry in the future. As an important part of the development of recycled aluminum resources, the high-value application of scrap aluminum cans has always been a hot research topic in various recycled aluminum processing enterprises and scientific research units. The traditional regeneration system of waste cans includes a series of complex technological processes such as pretreatment, paint removal, smelting system and casting system, which is difficult to control in the middle of the process. Most of the recycled scrap aluminum cans are cast and downgraded for later use, except for a part of them used as alloy materials for new cans. In this paper, combined with the research on the preparation of metal aluminum alkoxide, combined with recrystallization heat conduction to further study the effective dissolution or adsorption how to remove impurity elements to obtain high-purity aluminum alcohol salt mechanism research, and thermal effect of alcohols with different carbon chains on the synthesis of high-purity aluminum alkoxide was further investigated. Moreover, the changes in morphology and pore size distribution of hydrolyzed alumina precursor materials under different hydrothermal temperature conditions were discussed by means of the alkoxide hydrolysis-sol-gel process. Eventually, the aluminum alkoxide was obtained by the reaction of waste cans with isopropanol and heavy crystal thermal conductivity, and the high-purity aluminum alkoxide was purified by vacuum distillation. Under the hydrothermal condition of 160°C, the high-purity alumina material with a purity of 99.99% and an original crystal size of 200nm was prepared.

Amine-functionalized high-surface-area Al2O3 adsorbent for CO2 capture: Effect of the support calcination conditions

Porous alumina has garnered interest as a substrate in the development of solid amine adsorbents for CO2 capture. However, the calcination conditions of alumina can significantly alter its properties, which in turn affects the adsorption performance of the resulting adsorbents. In this study, high-surface-area alumina was synthesized using a reverse microemulsion method. The impact of the calcination conditions on the pore structure and surface properties of the alumina precursor was examined. Additionally, the porous alumina produced under various calcination conditions served as the support for tetraethylenepentamine (TEPA) loading, and the CO2 capture performance of the resultant adsorbents was assessed. The adsorption kinetics and activation energy were analyzed, emphasizing the cyclic stability when regenerated in a realistic CO2 atmosphere. Our findings indicate that alumina calcined under an air atmosphere with a lid exhibited the highest capture capacity (reaching 89.97 mg/g after a 40 wt% TEPA loading), compared to other alumina samples. The adsorption kinetics corresponded closely with the Avrami model, yielding an activation energy (Ea) of 4.75 kJ/mol. Both alumina samples calcined in air, with and without a lid, demonstrated robust cycling stability and resistance to urea formation. The underlying anti-urea mechanisms were also elucidated in the study.

The Effect of Foaming Agents on the Thermal Behavior of Aluminum Precursors.

Various foaming agents can be used to achieve foaming of the precursors obtained by using the powder metallurgy method. However, the thermal behavior of pure aluminum precursors with different foaming agents has been studied very little in recent times. For the production of aluminum foams with closed cells, 1 wt.% of calcium carbonate (CaCO3), titanium hydride (TiH2), heat-treated TiH2 and zirconium hydride (ZrH2) were used. The foaming capability of the compacted precursors was investigated at temperatures 700, 720 and 750 °C. CaCO3 and TiH2 showed the best foamability at all considered temperatures, while ZrH2 achieved relatively good foaming only at the highest temperature, 750 °C. Due to their low onset temperature of the decomposition compared to the melting point of the unalloyed aluminum, in hydride-based foaming agents the drainage occurred at the bottom part of the foam samples. Among the investigated foaming agents, precursors with heat-treated TiH2 had the worst foaming properties, while CaCO3 showed the best foamability without the occurrence of drainage.

Insights into formation and properties of amorphous mesostructured alumina

Here, using liquid crystals as template, an EISA (evaporation-induced self-assembly) method has been used to synthesize amorphous mesostructured alumina. The effect of the synthesis parameters such as the presence of a chelating agent, the amounts of both porogen agent and alumina precursor on the materials properties have been investigated in details. Under the optimum conditions, after Soxhlet extraction, the obtained Al2O3 presents an HMS (Hexagonal Molecular Sieves) structure and a high specific surface area (≈400 m2/g) with a mesopore size distribution centered around 8.3 nm.Investigation of the thermal stability shows that the crystallization into γ-Al2O3 of the amorphous alumina walls delimiting mesopores begins after heating at 800 °C. We have also demonstrated that half of the carbon present in the as-synthesized material can be removed by washing with water or ethanol at room temperature instead of Soxhlet extraction.On the basis of SAXS, XRD and N2 adsorption-desorption analyses, we have shown that when treated into boiling water or exposed to water vapor the alteration of the mesostructure occurs quickly. Its collapse has been attributed to the crystallization of the amorphous alumina walls into aluminum hydroxides, mainly boehmite, upon the hydration of the alumina.Dual mesoporous alumina have been also obtained from micelles through a cooperative templating mechanism at low P123 amount and in the presence of citric acid. In that case both mesopores networks adopt a wormhole-like mesostructure.

Structure evolution of porous alumina during aging process and its support effect on PtSn/Al2O3 catalyzed propane dehydrogenation

Precise control of porous alumina microstructures is always challenging due to the diversity and complexity of the growth process-related alumina crystalline phase and surface properties. In this work, we established a bottom-up synthesis route with a combination of rapid precipitation at high supersaturation and high-temperature aging in terms of enhancing particle aggregation kinetics. Surprisingly, we discovered that there were two distinct growth stages of alumina precursor (ammonium aluminum carbonate hydroxide) during the aging procedure, that is, oriented attachment at the early stage of crystallization and subsequent Oswald ripening. High-temperature aging can effectively strengthen the aggregation kinetics between the particles and produce large mesoporous (∼16 nm) and a remarkable number of defect sites with the exposure of up to 14 % unsaturated pentacoordinate aluminum ions. Owing to the presence of strong metal-support interactions, the alumina-supported PtSn catalyst exhibited excellent catalytic activity in the propane dehydrogenation reaction with propylene formation with 99 % selectivity and superior stability with a low deactivation rate of 0.007 h−1 over 24 h. These results suggested that it was feasible and instructive to achieve precise control of the structure and surface properties of alumina by manipulating the aggregation process of the initial particles during the aging stage.

(Invited) Small Molecule Inhibitor-Based Approaches for Area-Selective Deposition from First Principles

Atomic layer deposition tackles ever new research questions. Area-selective deposition is one of these recent challenges. Several approaches have been developed to achieve selectivity. One of the most promising is using comparatively small molecules to block the non-growth surface while leaving the growth surface uncovered for the ALD process.This approach requires in-depth knowledge of the surface chemistry of both surfaces involved. In addition, the decomposition pathways of SMI-covered surfaces need to be uncovered to enable stable ALD growth over a maximum number of cycles.These questions are very challenging for lab-based investigations. We present recent progress in the ab initio description of key questions regarding SMI-based ALD processes. At the example of silanol-based SMIs, surface chemistry for Al2O3 growth on Cu while blocking SiO2 will be discussed and compared to experimental findings.[1] Furthermore, the importance of choosing the appropriate surface model will be highlighted. Especially for the challenging question of SMI-layer decomposition.[1 J. Yarbrough, F. Pieck, D. Grigjanis, I.-K. Oh, P. Maue, R. Tonner-Zech, S. F. Bent, "Tuning Molecular Inhibitors and Aluminum Precursors for the Area-Selective Atomic Layer Deposition of Al2O3", Chem. Mater. 2022, 34, 4646-4659.We gratefully acknowledge funding from a Merck KGaA, Darmstadt, Germany 350th Anniversary Research Award. Computations were performed on the CSC Frankfurt, HLR Stuttgart, ZIH Dresden and HPC Regensburg.Figure 1 General structure (a) of the studied SMIs with different reactive and blocking groups (b). Schematic structures of the calculated condensation reactions of the SMIs with OH groups of the SiO2 surface (c). Color code: Si (blue), O (red), and H (white). Figure 1

A Facile Synthesis of Al2O3-Coated LiNi1/3Co1/3Mn1/3O2 with Improved Cycle Life Prepared By a Wet-Chemical Method

Aging of lithium-ion batteries (LIBs) and its prevention has been one of the focal points of LIB research in the recent years. The stability of the well-established anode material graphite far surpasses the stability of emerging high energy cathodes (NCM Ni83, Li- and Mn-rich NCM)1,2. Additionally, the degradation of the solid electrolyte interphase (SEI) on the anode side mainly originates from dissolved TM species of the cathode material3. Thus, to bring the high energy LIBs to market, the main focus has been on the mitigation of cathode degradation. Application of protective coatings is an excellent method for stability improvement and is often preferred over doping and structural modifications4. Nevertheless, a pressing need remains for a more sustainable, cost-effective, and easily scalable method to synthesize coatings on cathode materials.In this work, we study LiNi1/3Co1/3Mn1/3O2 (NCM 111) as a model material and coat it with Al2O3 via a wet-chemical process. Wet-chemical processes have in the past often used toxic precursors or solvents, rendering the sustainability of these methods questionable5,6. Thus, here a wet-chemical coating process is developed based on a green solvent (ethanol) and a non-toxic raw material (aluminium isopropoxide). The coating is based on hydrogen bond formation between a hydrolyzed precursor (Al(OH)3) and the oxygen groups on the surface of the commercially sourced active material (NCM111) to form a uniform coating of Al(OH)3 which is converted to Al2O3 after a sintering step in air at 500°C. In addition to characterizing the effects of coating on the cathode active material, we also investigated how the coating procedure alone, without adding the aluminium precursor, affects the active material. This is done to separate the effects of solution washing and sintering from those of the coating formation on the active material. The pristine, coated, and washed and sintered NCM powders were investigated by SEM, EDS, XPS, XRD, and TEM methods, and electrochemical tests in half cells.The capacity of the uncoated NCM decreases to 80% of initial capacity during the first 200 cycles at 1 C rate. A significant improvement in both capacity retention and rate capability is observed for both the washed and coated samples. Although coated samples display further cycle life improvements, most of the improvements can be attributed to the ethanol washing away residual lithium compounds (RLCs) such as LiCO3, LiOH and LiO, which are left on the particle surface after the synthesis or formed during the storage in ambient atmosphere. RLCs can either accelerate electrolyte and electrode decomposition via several reaction pathways7 or participate in cathode-electrolyte interphase formation, resulting in increased impedance and decreased cycle life. Further improvements in the Al2O3-coated samples due to the coating serving as a protective layer that helps to prevent unwanted reactions between the cathode and the electrolyte.This study demonstrates Al2O3-coated NCM 111 with improved electrochemical performance. Al2O3 is deposited via a facile and environmentally friendly wet-chemical coating process. The study also highlights the importance of washing the active material to remove residual lithium compounds, which can have a significant impact on cycle life and performance.Authors acknowledge the support of M-Era.net project "Inert Coatings for Prevention of Ageing of NMC Cathode for Lithium-Ion Batteries” (InCoatBat).

Chemical dealcoholation of MgCl2·EtOH adduct by Al compounds and its effect on the performance of Ziegler–Natta catalysts

MgCl2·nEtOH adducts play a major role in the industrial production of polyethylenes. Their chemical dealcoholation, usually accomplished during the catalyst synthesis step, has had a pronounced impact on the microstructure of the final Ziegler–Natta pre‐catalysts and the properties of the resulting polymers. Due to the industrial and academic importance of this issue, different aluminum‐based compounds including triethylaluminum (TEAL), triisobutylaluminum (TIBA), and ethylaluminumdichloride (EADC) were used in this research in the chemical dealcoholation of a MgCl2·1.5EtOH adduct, to provide the target catalysts. According to the analytical results, the catalysts synthesized using aluminum compounds (especially TEAL and EADC) generally had a more fractured structure, a smaller particle size and a vast surface area. Aluminum precursors bind to the catalyst structure together with TiCl4, which is manifested from their higher adsorption energies obtained by DFT calculations, and the presence of Al atom in the elemental analysis. Varying the chemical structure and physical properties of the catalysts, established using Al compounds, caused significant variation in the ethylene polymerization kinetic curves, their related rate constants, and the flow characteristic of the final polymers. The overall results outstandingly affirm that by appropriate choice of the Lewis acid compound, during the chemical dealcoholation of the adduct, various Ziegler–Natta catalysts can be achieved for different polyethylene grades.

Influence of Process Parameters in Three-Stage Purification of Aluminate Solution and Aluminum Hydroxide

The influence of process parameters in the three-stage purification of aluminate solution from the Bayer process and aluminum hydroxide was considered in this paper. One of the ways of purification is treating the aluminate solution in order to reduce the concentrations in the starting raw material (solution) and then treating the aluminum hydroxide at a certain temperature and time in order to obtain an alumina precursor of adequate quality. The purification process itself is divided into three phases. The first phase involves the treatment of sodium aluminate with lime in order to primarily remove Ca2+ and (SiO3)2− impurities. Phase II aims to remove impurities of Zn2+, Fe2+, and Cu2+ by treatment with controlled precipitation using specially prepared crystallization centers. In Phase III, Na+ is removed by the process of hydrothermal washing of Al2O3 ∙ 3H2O. In this work, parameters such as temperature (T), reaction time (t), and concentration of lime (c) were studied in order to remove the mentioned impurities and obtain the purest possible product that would be an adequate precursor for special types of alumina.

Accessibility and Mechanical Stability of Nanoporous Zinc Oxide and Aluminum Oxide Coatings Synthesized via Infiltration of Polymer Templates.

The conformal nanoporous inorganic coatings with accessible pores that are stable under applied thermal and mechanical stresses represent an important class of materials used in the design of sensors, optical coatings, and biomedical systems. Here, we synthesize porous AlOx and ZnO coatings by the sequential infiltration synthesis (SIS) of two types of polymers that enable the design of porous conformal coatings-polymers of intrinsic microporosity (PIM) and block co-polymer (BCP) templates. Using quartz crystal microbalance (QCM), we show that alumina precursors infiltrate both polymer templates four times more efficiently than zinc oxide precursors. Using the quartz crystal microbalance (QCM) technique, we provide a comprehensive study on the room temperature accessibility to water and ethanol of pores in block copolymers (BCPs) and porous polymer templates using polystyrene-block-poly-4-vinyl pyridine (PS75-b-P4VP25) and polymers of intrinsic microporosity (PIM-1), polymer templates modified by swelling, and porous inorganic coatings such as AlOx and ZnO synthesized by SIS using such templates. Importantly, we demonstrate that no structural damage occurs in inorganic nanoporous AlOx and ZnO coatings synthesized via infiltration of the polymer templates during the water freezing/melting cycling tests, suggesting excellent mechanical stability of the coatings, even though the hardness of the inorganic nanoporous coating is affected by the polymer and precursor selections. We show that the hardness of the coatings is further improved by their annealing at 900 °C for 1 h, though for all the cases except ZnO obtained using the BCP template, this annealing has a negligible effect on the porosity of the material, as is confirmed by the consistency in the optical characteristics. These findings unravel new potential for the materials being used across various environment and temperature conditions.

Influence of pseudoboehmite properties on characteristics of CoMo/ASA-Al2O3 catalysts for selective hydrotreating of FCC gasoline

The influence of alumina precursor (pseudoboehmites) in CoMo/ASA + Al2O3 catalysts on catalytic activity in FCC gasoline hydrotreating has been studied. Pseudoboehmites prepared by alcoholate, precipitate and hydrothermal technologies were used. Parent powders, supports and catalysts were characterized by low-temperature N2 adsorption, TPD of ammonia, STEM, HRTEM, UV–vis spectroscopy. Catalysts were tested in hydrotreating of the model FCC gasoline feedstock. It is shown that the choice of pseudoboehmite has significant effect on textural, acid and mechanical properties of supports and catalysts, as well as dispersity of the active phase. The type of pseudoboehmite affects the amount of tetrahedral cobalt in catalysts that changes surface activity per 1 g of the catalyst. The linear dependence between the ratio of the medium and weak acid sites and catalyst selectivity was found. It is established that isomerizing activity is higher than the hydrogenating one, when medium/weak acid sites ratio in the catalyst is lower than 1.85.

Shaping Y-Zeolites using in situ formation of alumina and AlPO binders: Coke-resistant catalysts for the cracking of methylcyclohexane

Endothermic catalytic cracking of hydrocarbon fuels over solid acid catalysts has been considered a potential heat sink to offset the thermal loads on high-speed flight vehicles, thus maintaining their catalyst stability and activity. Which is essential as an effective heat sink and produce fuels for sustained flight. The present work demonstrates a novel approach of dispersing zeolite in a catalyst matrix containing inorganic binders such as alumina and aluminum phosphate (ALPO) to improve the thermal, mechanical stability as well as the coke-resistance of Y-zeolites during catalytic cracking of endothermic fuels. Synthesis of such binders modified zeolite was achieved by adding Y-zeolite to pseudo boehmite, an alumina precursor followed by its hydrolysis in the presence of either nitric acid or phosphoric acid, which led to the formation of Alumina or ALPO modified zeolites. During this process, partial removal of alumina from the zeolite framework functions as seed for the growth of alumina and AlPO binders which together form a catalyst matrix consisting of zeolite and binder. Three different Y-Zeolites of varying Si/Al ratios were modified with alumina and ALPO binders using the afore-mentioned process. N2 sorption isotherms, Ammonia TPD, Solid state NMR and SEM imaging showed that these two binders modified the textural, structural, and acidic sites of the zeolites. Catalytic cracking of methylcyclohexane (model endothermic fuel) over these binder modified zeolites was carried out to study their performance and determine the conversion of methylcyclohexane, catalyst stability, product selectivity and coke deposition. Alumina and AlPO binders were observed to have differential binding with the zeolite acid sites, therefore the resultant catalyst activity, product activity and coking behavior were also found to be different. The alumina modified zeolites showed a slight decrease in the catalytic activity but promoted the formation of coke which can be easily oxidized and the selectivity towards cracked products than their isomers. In contrast, AlPO modified zeolites exhibited decreased catalytic activity but also decreased the coking considerably. Spent catalysts characterization clearly demonstrated that the binder modification of zeolites improved the catalyst stability, products selectivity, coke deposition, nature of coke and the amount of coke deposition.

3D porous alumina/graphene hybrids prepared by atomic layer deposition and their performance for water treatment

Metal / carbon hybrids have impressive potential of applications in many fields: catalysis, energy conversion and storage, environmental. However, further efforts are needed to achieve a better control of homogeneity of the metal oxide deposit on the carbon surface to provide reliable synthesis approaches of metal / carbon hybrids. In this work, atomic layer deposition is used to prepare 3D porous alumina / reduced graphene oxide hybrid monoliths. We show that atomic layer deposition, even though rarely reported to prepare metal oxide / carbon hybrids, allows a conformal coating onto the graphene nanosheet surface. In-depth advanced characterization have been performed thanks to a coupled approach consisting of the preparation of lamellas of the porous hybrid by means of focused ion beam and their analysis by transmission electron microscopy. A good accessibility of the alumina precursors to the internal surface of the prepared 3D porous carbon monoliths was evidenced. The alumina / graphene hybrid prepared with 50 cycles of ALD deposit has a surface as high as 284 m2/g. As a proof-of-concept for the interest of the designed hybrids, they are tested for the removal of Congo red, a standard organic dye pollutant. 87 and 98 % of Congo red removal were reached at the first and the second step of adsorption proving the good adsorption performance and reusability ability of the de designed hybrid adsorbents. We believe that such multi-porous 3D alumina / graphene macrostructures that offers a favorable accessibility to the adsorption sites open interesting potentialities for pollution remediation applications.

Adsorption of methylene blue and metachromasy over analcime zeolites synthesized by using different Al precursors

Pure crystalline Analcime (ANA) zeolite samples were successfully synthesized using various aluminum precursors such as aluminum nitrate (ANA-nit), aluminum sulfate (ANA-sul), aluminum isopropoxide (ANA-isop), sodium aluminate (ANA-sodalu) and aluminum chloride (ANA-chl) to study the influence of various anions on the physicochemical properties of ANA zeolite structure. The physicochemical properties of the samples have been studied using elemental analysis, X-ray diffraction, Fourier-transformed infrared spectroscopy, scanning electron microscope, N2-physisorption, X-ray photon spectroscopy, and diffuse reflectance UV–vis measurements. The synthesized analcime samples exhibited highly crystalline ANA structure; however, the anions present in the Al precursor influenced the crystallite and particle sizes. All the samples possessed a band gap energy of around 3.8 eV. The metachromasy phenomenon of methylene blue (MB) over synthesized Analcime samples was investigated under UV irradiation. The UV–vis absorption spectra of MB solution show a transformation from mono-MB to H-aggregated MB species due to the metachromasy phenomenon occurring over the surface of synthesized analcime samples. The formation of H-aggregated MB species differs for the synthesized ANA samples, which depends on the presence of active species on the ANA surface. The ANA-nit sample exhibited a fast metachromatic phenomenon due to more surface basic sites (e.g., O2−, O−) distributed over different (micro-, meso- and macro-) pores.

Formation of Paramagnetic Defects in the Synthesis of Silicon Carbide.

Silicon carbide (SiC) is a very promising platform for quantum information processing, as it can host room temperature solid state defect quantum bits. These room temperature quantum bits are realized by paramagnetic silicon vacancy and divacancy defects in SiC that are typically introduced by irradiation techniques. However, irradiation techniques often introduce unwanted defects near the target quantum bit defects that can be detrimental for the operation of quantum bits. Here, we demonstrate that by adding aluminum precursor to the silicon and carbon sources, quantum bit defects are created in the synthesis of SiC without any post treatments. We optimized the synthesis parameters to maximize the paramagnetic defect concentrations-including already established defect quantum bits-monitored by electron spin resonance spectroscopy.