Al Source Research Articles

TEAOH-assisted cost-effective preparation of SSZ-13 using L zeolite as Al source

Developing an economical and high-efficiency synthesis pathway of SSZ-13 zeolite is of great significance for the ammonia selective catalytic reduction of nitrogen oxides (NH3-SCR of NOx) reactions. Herein, SSZ-13 zeolite were synthesized using L zeolite as the aluminum source in the presence of a mixed structure directing agent (SDA) composed of N,N,N, trimethtyl-1-adamantammonium hydroxide (TMAdaOH) and tetraethylammonium hydroxide (TEAOH). This synthesis strategy aims to accelerate the crystallization rate through interzeolite transformation, while less expensive TEAOH can play a cooperative structure-directing role, thus reducing the consumption of expensive TMAdaOH template. The results showed that pure SSZ-13 zeolites with high crystallinity can be obtained from L zeolite within 12 h at 160 ℃ under low TMAdaOH/SiO2 ratio of 0.05 (too low to carry out the synthesis on its own in the current synthesis system) in the presence of TEAOH. Moreover, the crystallization mechanism was also investigated by XRD, FT-IR, SEM and TG-DTG techniques. It was proposed that the crystallization of SSZ-13 occurs through the formation of SSZ-13 nuclei under the direction of TMAdaOH and promotion of TEAOH, subsequently TMAdaOH was incorporated in the framework to further induce the crystal growth of SSZ-13. Especially, the zeolite crystal size can be modulated by the amount of TEAOH added. In addition, After Cu2+ exchange, the obtained Cu-SSZ-13 sample exhibits superior catalysis performance in the NH3-SCR of NOx reaction, and the NOx conversion rate remained over 90 % across a broad range from 200 to 600 °C, demonstrating its significant application potentials in NOx removal from diesel vehicle exhausts.

Adjusting Al location in the framework of ITH zeolites for catalytic conversion of methanol to olefins

Adjusting location and distribution of Al sites in the zeolite framework is critical for catalysis, and typical strategies include using zeolites as starting Al source. However, this approach is still challenging for aluminosilicate ITH zeolite. Herein, the distribution of Al species in the framework of ITH was efficiently regulated by implementing LTA zeolite as the aluminum source added in the starting gels (LTA-ITH). The obtained LTA-ITH zeolites have similar nanosheet morphology, textual parameters, and acidic properties to those of conventional ITH synthesized from boehmite (C-ITH), while the results of 27Al MAS NMR spectra and 1-hexene cracking indicate that they have a different Al distribution. The use of LTA zeolite in starting gel is favorable for the formation of more Al species in sinusoidal and straight channels, compared with the C-ITH. Catalytic tests in the conversion of methanol to light olefin showed that LTA-ITH exhibited enhanced catalyst lifetime and propene selectivity compared with the C-ITH, which is reasonably attributed to the different locations of Al species in their respective ITH frameworks.

High-performance Al-doped Cu/ZnO catalysts for CO2 hydrogenation to methanol: MIL-53(Al) source-enabled oxygen vacancy engineering and related promoting mechanisms

Innovative catalyst design and in-depth mechanism understanding are imperative for industrialization of CO2 hydrogenation to methanol. Herein, Al-doped Cu/ZnO catalysts, Cu/Al-ZnO-x (x = 1/32, 1/16 and 1/8, denoting Al/Zn molar ratio), were creatively synthesized using MIL-53(Al) as Al sources and reactive templates. The Cu/Al-ZnO-1/16 catalyst exhibited the highest methanol production rate among the Cu/Al-ZnO-x catalysts, which was 1.93 times as active as the conventional Cu/Al-ZnO-1/16-C catalyst using Al(NO3)3·9H2O as Al source. Structural characterizations reveal that the use of MIL-53(Al) led to higher SBET, more uniform Al distribution, more abundant oxygen vacancies, more appropriate metal-support interactions and larger amount of medium basic sites. Mechanism studies demonstrate that Al doping would markedly induce oxygen vacancy formation on Cu-ZnO interfaces and thus significantly boost methanol synthesis activity. This work offers a facile approach to develop efficient methanol synthesis catalysts and provides new insights into the nature of Al promotion in Cu/ZnO-based catalysts.

In Situ Growth of MOF-303 Membranes onto Porous Anodic Aluminum Oxide Substrates for Harvesting Salinity-Gradient Energy.

As an emerging metal-organic framework (MOF) material in recent years, the MOF-303 membrane has shown great potential applications in seawater desalination, dehydration, and atmospheric water harvesting. Herein, we report on a dense and uniform MOF-303 membrane fabricated by a facile in situ hydrothermal synthesis approach in the presence of an anodized aluminum oxide (AAO) channel membrane acting as the only Al source and substrate. Interestingly, the MOF-303 isomer can be obtained due to an insufficient amount of organic ligand caused by the less hydrophilic and larger pore size of the AAO substrate. The MOF-based composite membranes possessed surface-charge-governed ionic transport behavior. Moreover, the MOF-303/AAO membrane yielded an output power density of 1.87 W/m2 under a 50-fold KCl concentration gradient. Under a 50-fold gradient of artificial seawater and river water, a maximum power density of 1.46 W/m2 can be obtained. After 30 days of stability testing, the composite membrane still maintained the power output, and the power density was higher than 1.20 W/m2. This work provides a facile and effective strategy for constructing Al-based MOF composite membranes and boosts their applications in harvesting salinity-gradient energy.

Accelerated Synthesis of Nanolayered MWW Zeolite by Interzeolite Transformation.

Hierarchical zeolites can offer substantial benefits over bulk zeolites in catalysis. A drawback towards practical implementation is their lengthy synthesis, often requiring complex organic templates. This work describes an accelerated synthesis of nanolayered MWW zeolite based on the combination of interzeolite transformation (IZT) with a dual-templating strategy. FAU zeolite, hexamethyleneimine (HMI), and cetyltrimethylammonium bromide (CTAB) were respectively employed as Al source and primary zeolite, structure directing agent, and exfoliating agent. This approach allowed to reduce the synthesis of nanolayered MWW to 48 h, which is a considerable advance over the state of the art. Tracking structural, textural, morphological, and chemical properties during crystallization showed that 4-membered-ring (4MR) units derived from the FAU precursor are involved in the faster formation of MWW in comparison to a synthesis procedure from amorphous precursor. CTAB restricts the growth of the zeolite in the c-direction, resulting in nanolayered MWW. Moreover, we show that this approach can speed up the synthesis of nanolayered FER. The merits of nanolayered MWW zeolites are demonstrated in terms of improved catalytic performance in the Diels-Alder cycloaddition of 2,5-dimethylfuran and ethylene to p-xylene compared to bulk reference MWW sample.

Dielectric performance of aluminum cation modified graphene oxide membrane: Influence of Al source

This study demonstrates a facile and effective strategy for modifying the dielectric properties of graphene oxide membranes for applications in advanced energy storage devices. The high dielectric constant and low dielectric loss of graphene oxide (GO) make GO-based materials good dielectric separators for developing thin and flexible devices. Controllable tailoring of the dielectric properties of GO membranes is crucial to advance its applications as a dielectric material. Metal cation modification represents one tailoring strategy, but the effects of cation modification are difficult to compare due to its dependence on the metal cation source and the specific physicochemical conditions. In this study, we explore the dielectric properties of GO membranes modified by the introduction of Al3+ from different chemical sources. The dielectric constant and dielectric loss of an unmodified GO membrane and three Al3+ modified GO (AGO) membranes were measured in the frequency range from 1 Hz to 106 Hz, and the performance of a dielectric capacitor fabricated by sandwiching the GO (AGO) membrane between carbon paper electrodes was evaluated by cyclic voltammetry. Results demonstrate that the three different sources of Al3+ differently impact the dielectric properties of GO membranes and thus the performance of as-fabricated dielectric capacitors. Our results advance the fundamental understanding of how metal cation modification impacts the dielectric properties of GO membranes and demonstrate the possibility of designing membranes with controllable dielectric performance.

Synthetic Control of the Defect Structure and Hierarchical Extra-Large-/Small-Pore Microporosity in Aluminosilicate Zeolite SWY.

The SWY-type aluminosilicate zeolite, STA-30, has been synthesized via different routes to understand its defect chemistry and solid acidity. The synthetic parameters varied were the gel aging, the Al source, and the organic structure directing agent. All syntheses give crystalline materials with similar Si/Al ratios (6-7) that are stable in the activated K,H-form and closely similar by powder X-ray diffraction. However, they exhibit major differences in the crystal morphology and in their intracrystalline porosity and silanol concentrations. The diDABCO-C82+ (1,1'-(octane-1,8-diyl)bis(1,4-diazabicyclo[2.2.2]octan)-1-ium)-templated STA-30 samples (but not those templated by bisquinuclidinium octane, diQuin-C82+) possess hierarchical microporosity, consisting of noncrystallographic extra-large micropores (13 Å) that connect with the characteristic swy and gme cages of the SWY structure. This results in pore volumes up to 30% greater than those measured in activated diQuin-C8_STA-30 as well as higher concentrations of silanols and fewer Brønsted acid sites (BASs). The hierarchical porosity is demonstrated by isopentane adsorption and the FTIR of adsorbed pyridine, which shows that up to 77% of the BASs are accessible (remarkable for a zeolite that has a small-pore crystal structure). A structural model of single can/d6r column vacancies is proposed for the extra-large micropores, which is revealed unambiguously by high-resolution scanning transmission electron microscopy. STA-30 can therefore be prepared as a hierarchically porous zeolite via direct synthesis. The additional noncrystallographic porosity and, subsequently, the amount of SiOHs in the zeolites can be enhanced or strongly reduced by the choice of crystallization conditions.

Aluminium extraction from a calcium aluminate slag using sodium carbonate based on the critical examination of the patented industrial Pedersen process

The extraction of aluminium from calcium aluminate phases by leaching with Na2CO3 solutions has been researched intermittently for more than a hundred years. In the 21st century, this process has gained a renewed interest for the design of novel metallurgical methods. The Pedersen Process has been the only known successful industrial scale application of calcium aluminate leaching to date. The engineering principles that ensured plant operations remained, until recently, unknown. These principles are critically assessed for the first time, based on recently retrieved patents submitted at the time the Pedersen process was in operation. The findings of the previous analysis were used for an experimental study with the two goals: (i) to validate the principles applied in the industrial Pedersen process and (ii) to apply these principles in designing an optimized leaching process for calcium aluminate slags originating from alternative Al sources. The calcium aluminate slag used in this study is the by-product of an aluminothermic reduction process for Si production along with an 8% (w/w) Na2CO3 aqueous solution. Results confirmed the majority of the assumed principles. All the tested leaching conditions produced Al extraction in the range of 75% - 95% (w/w).

Quasi‐synchronous solid‐state reaction for cordierite powder synthesis

AbstractThis study investigates a quasi‐synchronous solid‐state reaction for synthesizing cordierite powder using talc, kaolinite, and Al2O3 mineral powders as starting materials. The thermal reaction proceeded with two different stages according to the Al sources provided by: (1) Al2O3 powders—the first stage starting at temperatures that were considerably lower than 1150°C and (2) kaolinite (mullite)—the second stage starting at temperatures that were higher than 1150°C. The goal is to shift the temperature of the first stage to coincide with that of the second stage by mixing α‐cordierite powder with the starting constituents. Exceeding the authentic reduction amounts of Al2O3 on talc particles leads to a rise in the temperature required to initiate the first‐stage reaction to 1200°C. However, this also eliminates the presence of β‐cordierite and spinel that occur in the first stage and allows for the early fulfilment of α‐cordierite formation in the second stage. The excess SiO2 released by the second stage compensates for the insufficient SiO2 required by the first stage, allowing for a smooth processing reaction. Also, a quasi‐synchronous solid‐state reaction for synthesizing cordierite occurs.

Green synthesis and characterization of aluminum oxide nanoparticles using Phoenix dactylifera seed extract along with antimicrobial activity, phytotoxicity, and cytological effects on Vicia faba seeds

AbstractThe present study assessed the green synthesis of aluminum oxide nanoparticles (Al2O3-NPs) by using aluminum (Al) foil waste as an Al source and date palm seed extract as a reducing and stabilizing agent. Several methodologies were employed to investigate Al2O3-NPs, encompassing X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray (EDX) analysis. The UV–visible spectroscopy analysis revealed the presence of an absorption peak at a wavelength of 264 nm, providing evidence for the successful green synthesis of the Al2O3-NPs. The XRD analysis revealed that the average size of the Al2O3-NPs was 32 ± 2.57 nm and had a rhombohedral structure. The EDX facilitated the identification of the elemental composition of the sample, which was found to consist of 40.37% Al and 31.56% O, confirming the high purity of the Al2O3-NPs powder. Furthermore, it was noted that the Al2O3-NPs exhibited the greatest antibacterial efficacy against Candida albicans (21 ± 1.85 mm), but no discernible antimicrobial effect was recorded against Klebsiella pneumoniae at higher concentrations of Al2O3-NPs. No significant variation in the germination of faba bean seeds was observed upon treatment with Al2O3-NPs. The observed mitotic index in the treatment group was determined to be significantly lower compared to the control cells, based on the duration and dosage of Al2O3-NP exposure. In contrast, for micronuclei (MN) and the prevalence of chromosomal abnormalities, there is a noticeable upward trajectory in this phenomenon. Finally, Al2O3-NPs are employed in a variety of applications, such as biomedical and agriculture.

Deposition of layered double hydroxide on non‐pretreated carbon cloth using lactate salts as raw materials

AbstractThis study presented the successful deposition of layered double hydroxide (LDH) onto non‐pretreated carbon cloth (CC) using lactate salts as raw materials. Specifically, under the hydrothermal condition using urea hydrolysis and lactate salts as the source of Mg and Al, MgAl‐LDH was deposited onto the CC surface, which is typically treated with organic solvents and acids to enhance its hydrophilicity prior to LDH deposition. X‐ray diffraction patterns, field‐emission electron microscope images, and elemental analyses revealed the deposition and coating of hexagonal platy particles of a carbonate‐type MgAl‐LDH with pseudo hexagonal phase and Mg/Al molar ratio of 1 onto CC. This LDH coating was not achieved when using chlorides and nitrates, which commonly used Mg and Al sources. These results demonstrated the effectiveness of the proposed method for facile LDH deposition on hydrophobic surfaces.

Impact of Aluminum Modification on the Dielectric Properties of Graphene Oxide Membrane: Different Al Source

The high dielectric constant and low dielectric loss of Graphene oxide (GO) membranes made them good dielectric separator membranes for both dielectric capacitors and planar micro-supercapacitors. A GO membrane, which is GO sheets laminated in the form of “brick-and-mortar” stacking configuration, is an orthotropic material. This means that GO will have different dielectric properties parallel to the GO sheets (in-plane) and perpendicular to the GO sheets (through-plane). Tailoring strategies applied to the membrane will impact its in-plane and through-plane dielectric property differently. Better understanding and ability to tailor the dielectric properties of the GO membrane is crucial for its dielectric applications. The Al3+ has the potential to interact with OFGs of GO sheets on the edge (carboxyl groups), which mainly impacts in-plane properties, or on the basal plane (hydroxyl, carbonyl, and carboxyl groups), which mainly impacts through-plane properties. The uneven interaction of Al3+ with the functional group on the edge and basal plane of GO sheets could lead to different modification effects of the in-plane and through-plane dielectric properties of the GO membrane. It was reported before that Al3+ from different sources will bond with the GO sheet differently, thus it has the potential to impact the through-plane and in-plane dielectric properties of the GO membrane differently. Here, the Al3+-modification to the GO membrane from three different Al source, Al metal foil, chloride salt, and alumina, were applied to tailor the through-plane and in-plane dielectric properties of as-fabricated GO membranes in the frequency range from 0.01 Hz to 105 Hz. Plane-to-plane and edge-to-edge coordination of Al3+ with the functional group on the basal plane or edge of the GO sheets were proposed to understand the different impact of Al3+ on the through-plane and in-plane dielectric properties of the GO membranes. This study provides a facile route to impact the dielectric property of GO membrane through interaction with the oxygenated functional group on the edge and basal plane of the GO sheet, and demonstrate the possibility of designing dielectric GO membrane with controllable dielectric performance.

Ultrafast Synthesis and Regulating Al Status of Mesoporous ZSM-48 Zeolite via a Pretreated-Seed-Solution-Assisted Strategy

Ultrafast synthesis of nanocrystal assembled mesoporous ZSM-48 zeolite spheres of highly crystalline was achieved within 1.5 h by using pretreated-seed-solution-assisted strategy. Interestingly, by altering the introducing sequence of aluminum source (in the pretreated seed solution or in the synthesis gel), the obtained ZSM-48 with similar particle size and total acid sites exhibited quite different crystallization behavior and acid property in terms of Al distribution and acid strength, because of the distinct local microenvironment (Al-rich or Al-free) in the pretreated seed solution. The HZ48-Al-pre (introduce an Al source to the pretreated seed solution) had more framework Al(IV) content and stronger acid strength than that of the HZ48-Al-post (synthesized by the Al-free pretreated seed solution). The corresponding Pt supported catalysts showed a great difference in the n-C12 hydroisomerization reation. The Pt/HZ48-Al-pre catalyst had a very low selectivity (41.1%), and the maximum iso-yield was only 35.5%. However, the ultrafast synthesizedPt/HZ48-Al-post-1.5h catalyst exhibited a superior selectivity (90.1%) with a total i-C12 yield of 82.3% at 330 °C, which was a high level in the exist literature reports.

Enhanced lithium storage capability of Ni-rich LiNi0.9CoxMn0.1−xO2(0 ≤ x ≤ 0.1) cathode by co-operation of Al-doping and V-coating

The Nickel-rich layer materials LiNixCoyMn1−x−yO2 (x ≥ 0.9) are usually accompanied by structural instability and inevitable capacity loss due to surface degradation during long cycles. The Al-V dual-modification is used in this research to enhance the stability of the structure and the electrochemical capacity of LiNi0.9Co0.05Mn0.05O2 (NCM). First, Al source was added during the co-precipitation synthesis of the precursors. Then, the Al-doped precursors were treated at 720 ℃ for 10 h with slight excess lithium to prevent volatilization of lithium during the sintering process. Finally, Al-doped LiNi0.9Co0.04Mn0.03Al0.03O2 (NCMA) materials were treated with V2O5 at 450 ℃ for 4 h. During calcination, Li3VO4-coated LiNi0.9Co0.04Mn0.03Al0.03O2 materials (NCMAV) were generated by employing residual lithium. Meantime, the Al-V dual-modification helps reduce the mingling degree of Ni2+/Li+ and promotes the diffusion of Li+. Hence, the Al-V dual-modified NCMAV displays a superior rate capability of 162.2 mAh g−1 at 5 C, remaining predominant capability retention of 90.5% after 100 cycles at 4.3 V. Compared with NCMAV, the discharge capability of pure NCM is 140.3 mAh g−1 and its capability retention is 81.6% at 5 C. This dual-modification strategy provides a facile and scalable method to achieve massive application of NCM LIBs with high density and excellent cycling stability.

Convert waste to MOF: Nitro-MIL-53(Al) synthesized from waste acid leachate for highly efficient capture of p-nitrophenol

As inspired by the sustainable concept of “turning waste into materials”, a feasible "killing three birds with one stone" strategy was proposed to design and synthesize Al-based MOF material from Al-rich acid leachate of natural kaolinite for capture of p-nitrophenol (PNP). The acid leachate neutralized with aluminum compound, as Al sources and reaction medium, was directly reacted with nitroterephthalic acid (NTPA) to form Al-MOF (named Nitro-MIL-53(Al)), so that the harmless disposal of acidic wastewater, the recovery of valuable metal, and the synthesis of new materials were achieved simultaneously. The porous Nitro-MIL-53(Al) adsorbent has superb adsorption capacity (173.01 mg/g) and removal efficiency (95.76 %, at 400 mg/L) towards PNP, and can be regenerated and reused more than 4 times. It still maintains higher adsorption capability of 117.76–153.21 mg/g for PNP in the waters containing different amounts of co-existing ions, respectively. The comprehensive analyses on structures and adsorption behaviors revealed that PNP was adsorbed onto Nitro-MIL-53(Al) by a chemisorption process, and π-π interaction, hydrogen bonds, and electrostatic attraction synergically contribute to the adsorption of PNP. This research provides a sustainable way to achieve simultaneously harmless disposal of waste liquid and development of new adsorption materials.

Impact of Aluminum Modification on the Dielectric Properties of Graphene Oxide Membrane: Different Al Source

The high dielectric constant and low dielectric loss of Graphene oxide (GO) membranes made them good dielectric separator membranes for developing high performance energy storage and transfer devices. Better understanding and be able to tailor the dielectric properties of the GO membrane is crucial for its dielectric applications. The interaction variation of Al3+ from different source with the functional group on the GO sheets could lead to different modification effects on the dielectric properties of GO membranes. Here, the Al3+-modification, where aluminum metal foil, chloride salt, and alumina serve as different Al3+ source, are applied to tailor the dielectric properties of GO membranes. The dielectric constant and dielectric loss of GO and Al3+ modified GO(AGO) in the frequency range from 0.01 Hz to 105 Hz is studied. The capacitance of a simple dielectric capacitor fabricated by sandwich the GO and AGO membrane in between carbon paper are evaluated to estimate the effect of dielectric separator membrane variation on the electrochemical performance of the capacitor. This study provides a facile and effective strategy to tailor the dielectric property of GO membrane and demonstrate the possibility of designing dielectric GO membrane with controllable dielectric performance.

Synthesis of nanosized IM-5 zeolite and its CH4/N2 adsorption and separation

Reduction of zeolite crystal size from the micron scale to the nanoscale leads to a significant increase in specific surface area, favoring mass-transfer pathways. Here, we have prepared nanoscale (ca. 30–80 nm) IM-5@100 zeolite (IMF type) by a facile strategy of regulating the amount of Al source in the starting gel, and have investigated its CH4/N2 adsorption and separation properties. We found that on decreasing the amount of Al source, the crystal size of the product changed significantly, decreasing from strips of length about 1 μm to irregular nanocrystals. Compared with micron-sized IM-5@50, the mesopore volume of IM-5@100 was increased fourfold from 0.12 cm3/g to 0.49 cm3/g, its external surface area was increased from 38 m2/g to 118 m2/g, and its DFT pore size distribution based on N2 adsorption/desorption showed a mesopore distribution in the range 5–10 nm. Adsorption kinetics tests showed that nano-IM-5@100 can achieve adsorption equilibrium more swiftly and exhibits better mass-transfer performance. Moreover, IM-5@100 showed good adsorption capacity for CH4 (17.8 cm3/g) and high IAST selectivity (4.7) for CH4/N2 (50:50, v/v). Breakthrough experiments have indicated that IM-5@100 permits efficient practical separation of CH4/N2.

Direct Observation of Al Migration Enhancement by Changing the Al and N Source Relative Position in the Molecular Beam Epitaxy of AlGaN Nanowires

Aluminum (Al)-containing nitrides, including AlN, AlScN, and AlGaN, are emerging material platforms for future-generation photonic, electronic, ferroelectric, and multifunctional semiconductor devices. Nonetheless, the low Al migration mobility in a nitrogen environment is a notorious hindrance to obtaining high-quality Al-containing nitride epilayers. This is particularly the case for the epitaxy of Al-containing nitrides with radio frequency (RF) plasma-assisted molecular beam epitaxy (MBE), due to the use of relatively low substrate temperatures. As such, various approaches have been employed in promoting Al migration such as metal-modulated epitaxy (MME). Despite the progress, the effect of the relative position of the Al and N sources on the Al migration mobility has remained unclear. In this study, we show that MBE-grown AlGaN nanowires can be an effective probe to examine the effect of the Al and N source relative position on the Al migration mobility and demonstrate clearly that Al adatoms appear to be more mobile from the Al source that is far away from the N source, compared to those from the Al source that is near the N source. This study therefore can potentially impact the development of emerging Al-containing semiconductor devices by MBE. Moreover, the demonstrated correlated Al source dependent morphological and optical properties of AlGaN nanowires can naturally help the development of AlGaN-nanowire-based UV light-emitting diodes (LEDs) and lasers.

Effect of dual phase structure induced by chemical segregation on hot tearing reduction in additive manufacturing

It is of great significance to explore the chemical compositions, which have not been hitherto examined for their suitability for additive manufacturing (AM), so as to broaden AM’s material library. Since solidification cracking is a major impediment in AM of alloys, especially high entropy alloys (HEAs), a detailed study on the cracking issue during AM is imperative. Keeping this in mind, a customized laser powder bed fusion (LPBF) setup is utilized to fabricate a compositionally graded AlxCoCrFeNi (x = 0.04–0.75) HEA, using the equiatomic AlCoCrFeNi and CoCrFeNi powders as feedstock, to examine the compositional range that enables crack-free fabrication. Experimental results show that when x ≤ 0.7, crack-free fabrication is possible. This compositional range exceeds the threshold reported in the recent literature. Microstructural characterization reveals a constant dual phase structure throughout the gradient, which is induced by the chemical segregation. Further analysis shows that both utilizing AlCoCrFeNi powder as Al source and the segregation contribute to the enhanced printability. The results suggest that the dual phase structure introduced by chemical segregation can effectively inhibit the initiation and propagation of hot tearing problem in metal additive manufacturing.

Accelerated Crystallization of LTA Zeolite Using a Combination of High-Silica FAU Zeolite with Low Crystallinity and Additional Al Sources

Synthesis methods and crystallization mechanisms of LTA zeolites have been studied by various approaches such as using alkali metal hydroxides, organic structure-directing agent cations, or fluoride anions, so that the understanding of the crystallization pathway is one of particular interest. As a fundamental research, we succeeded in synthesizing a highly crystalline LTA zeolite by combining dealuminated FAU with low crystallinity and an additional aluminum source (Al(OH)3). The crystallization rate of the LTA zeolite was higher than that from conventional colloidal silica (Ludox HS-40) and Al(OH)3. In addition, there was a large difference in the particle size distribution of the as-made LTA zeolites. Furthermore, when using dealuminated FAU and Al(OH)3, Al-rich aluminosilicate species with four-ring structures were observed in the initial induction period, after which the gradual incorporation of TMA+ cations into sod cages of the LTA zeolite was found. Based on the obtained results, a crystallization scheme for LTA zeolites synthesized using zeolitic sources of dealuminated FAU as starting materials is proposed, which deepens the understanding of the crystallization pathway of LTA zeolite.