Carbon Aluminum Research Articles

Zirconia Nanoparticles Uniformly Supported on Mesoporous Alumina–Carbon as a Highly Efficient Catalyst for the Direct Ethanol-to-Butadiene Reaction

Zirconia Nanoparticles Uniformly Supported on Mesoporous Alumina–Carbon as a Highly Efficient Catalyst for the Direct Ethanol-to-Butadiene Reaction

Study on the Mechanical Performance, Durability, and Microscopic Mechanism of Cement Mortar Modified by a Composite of Graphene Oxide and Nano-Calcium Carbonate

Nano-calcium carbonate (NC) is a novel ultrafine solid powder material that possesses quantum size effects, small size effects, surface effects, and macroscopic quantum effects that ordinary calcium carbonate lacks. As a nanomaterial with superior properties, graphene oxide (GO) has been studied extensively in the field of construction. In microscopic characterization, the reaction between NC and tricalcium aluminate (C3A) formed a new hydration product, hydrated calcium aluminum carbonate (C3A·CaCO3·11H2O), which enhanced the arrangement of hydration products and optimized the distribution of pore size in the mortar. Regarding the mechanical properties, the addition of GO and NC significantly enhanced the early-age mechanical performance of the mortar. In terms of durability, the incorporation of GO and NC significantly improved the water permeability, chloride ion permeability, and resistance to sulfate attack of the cement mortar. In this study, it was found that adding 1 wt% NC and 0.02 wt% GO not only improves the mechanical and durability properties but also promotes the hydration reaction according to the microstructure analysis. With the help of NC, compared with other studies, the amount of GO is reduced, while the cost is reduced, and the application of GO in the field of cement-based materials is promoted.

Selective production of high-value fuel via catalytic upgrading of bio-oil over nitrogen-doped carbon-alumina hybrid supported cobalt catalysts

Bio-oil derived from biomass fast pyrolysis can be upgraded to gasoline and diesel alternatives by catalytic hydrodeoxygenation (HDO). Here, the novel nitrogen-doped carbon–alumina hybrid supported cobalt (Co/NCAn, n = 1, 2.5, 5) catalyst is established by a coagulation bath technique. The optimized Co/NCA2.5 catalyst presented 100 % conversion of guaiacol, high selectivity to cyclohexane (93.6 %), and extremely high deoxygenation degree (97.3 %), respectively. Therein, the formation of cyclohexanol was facilitated by stronger binding energy and greater charge transfer between Co and NC which was unraveled by density functional theory calculations. In addition, the appropriate amount of Lewis acid sites enhanced the cleavage of the C–O bond in cyclohexanol, finally resulting in a remarkable selectivity for cyclohexane. Finally, the Co/NCA2.5 catalyst also exhibited excellent selectivity (93.1 %) for high heating value hydrocarbon fuel in crude bio-oil HDO. This work provides a theoretical basis on N dopants collaborating alumina hybrid catalysts for efficient HDO reaction.

A new strategy to prepare ammonium aluminum carbonate hydroxide using plasma electrolytic oxidation in electrolyte containing carbon nanotubes

In this work, a plasma electrolytic oxidation (PEO) technique was used to prepare ammonium aluminum carbonate hydroxide (AACH) in an electrolyte containing carbon nanotubes (CNTs). CNTs were also involved in the composite coating on the surface of 6063 aluminum alloy. The formation mechanism of AACH and effects of CNTs on the microstructure and corrosion behavior of the PEO coatings were investigated. The surface morphology, pore distribution, phase composition, functional groups and electrochemical characteristics of the PEO composite coatings were examined using scanning electron microscopy (SEM), Image Pro software, X-ray diffractometer (XRD), Fourier transform infrared spectrometer (FT-IR) and electrochemical workstations, respectively. Results showed that the rod-like AACH was generated around the discharge channel by reacting between ammonia, carbon dioxide and AlOOH under transient high temperature and high pressure environment with the presence of CNTs. The surface micropores of the composite coatings were enlarged due to the excellent electrical conductivity of CNTs. With the by addition of CNTs of 1.5 g/L, the self-corrosion current of the coating was the smallest, and the polarization resistance Rp was larger than that of 1.0 g/L and 2.0 g/L CNTs.

Efficacy evaluation and exploratory analysis of influencing factors of Banxia Houpu Decoction in the treatment of refractory gastroesophageal reflux disease.

Approximately 10% to 40% of patients with gastroesophageal reflux disease (GERD) exhibit poor response to proton pump inhibitors (PPIs), indicating refractory GERD (RGERD). Banxia Houpu Decoction is a traditional Chinese medicine formula used for treating GERD, particularly for atypical symptoms. This study aimed to investigate the improvement of different symptoms in RGERD patients treated with Banxia Houpu Decoction and identify relevant factors influencing its efficacy. From November 2021 to November 2022, a total of 89 RGERD patients voluntarily participated in this clinical study at our hospital. They were randomly assigned to 2 treatment groups: the Banxia Houpu Decoction group and the Western medicine group. The former received standard-dose Banxia Houpu Decoction, while the latter had a switch in PPI type with double-dose maintenance and the addition of magnesium aluminum carbonate as an acid suppressant. The improvement of different symptoms was compared between the 2 groups. Clinical data, including age, gender, gastric mucosal status, and esophagitis severity, were collected. Univariate analysis was performed to explore factors influencing the therapeutic effect of Banxia Houpu Decoction. Both treatment groups showed significant improvement in Frequency Scale for the Symptoms of GERD (FSSG) scores. The Banxia Houpu Decoction group exhibited the most significant efficacy in relieving throat burning sensation (P = .003) and frequent hiccups (P = .003). It also demonstrated improvement in swallowing difficulty (P = .048) and postprandial abdominal distension (P = .041), surpassing the Western medicine group. The Western medicine group had the most significant improvement in heartburn sensation (P = .008) and showed significant improvement in gastric burning sensation (P = .022), surpassing Banxia Houpu Decoction. Age (P = .025) and gastroesophageal flap valve (GEFV) grade (P = .014) were identified as factors influencing the efficacy of Banxia Houpu Decoction. Banxia Houpu Decoction exhibits superior efficacy compared to double-dose PPI combined with acid suppressants in relieving symptoms such as throat burning sensation, swallowing difficulty, and frequent hiccups. It shows significant efficacy in patients under 60 years of age and with GEFV grades I-II.

PH-dependent growth of alumina nanorods with a high aspect ratio for enhanced propane dehydrogenation performance

Controllable synthesis of porous alumina is always challenging due to the diversity of precursors and the complexity of the growth process. In this work, alumina nanorods with adjustable aspect ratios were synthesized by precipitation to investigate the morphology evolution mechanism related to aging pH, and the structure–activity relationship of alumina. The evolution path of precursors ammonium aluminum carbonate hydroxide (NH4Al(OH)2CO3, AACH) was established by tracking the variation in electrical charges and nitrate concentration during the growth process. It was revealed that the anisotropic adsorption of ions on the AACH crystal facets can modulate the axial and radial growth rates of the microcrystalline rods, regulating the one-dimensional oriented assembly of AACH. Alumina synthesized at pH 9.5 exhibited more exposition of (100) facets due to its higher aspect ratio, resulting in an aluminum content of up to 30% in the five-coordinated state. Due to the presence of strong metal-support interactions, the corresponding PtSn/Al2O3 catalyst demonstrated good propane dehydrogenation activity and stability, with propylene formation with 99% selectivity within 30 h of reaction. This study highlighted the significance of pH regulation in the growth environment of AACH, enabling the selective exposure of crystal facets in the alumina support, and providing an effective pathway to obtain highly active and stable catalysts.

Pozzolanic activity of FCC catalyst waste slag (CWS) for cement and geopolymer production

Catalyst waste slag (CWS) is generated in large amounts when fabricating the catalyst required in the fluid cracking catalyst (FCC) process used for oil refining. Currently, CWS is landfilled. This paper characterizes the CWS and measures its pozzolanic activity. It determines whether the CWS can be used as partial Portland cement (PC) replacement for the first time in the literature. CWS is primarily composed of Al2O3 and CaO. It contains a negligible quantity of heavy metals that can be immobilised in a matrix. The raw CWS is totally amorphous and extremely reactive which results in flash set. Calcination is an effective method to control the reactivity of CWS. Reactivity increased when CWS was calcined between 300 and 600 °C and it peaked at 500 °C, but this caused flash set. Calcination at 800 °C lowers reactivity (as the highly disordered aluminium phases achieve a greater order) which allows for proper handling. Temperatures over 800 °C caused partial crystallization significantly lowering reactivity.The 800°C-calcined CWS reached high mechanical index (6.25), comparable to other pozzolans such as fly ash and red mud, and greater than alum sludge. CWS combines lime profusely and develops more abundant cementing hydrates than similar pozzolans such as calcined alum sludge. The pozzolanic reaction of the 800°C-calcined CWS provides abundant cementing minerals including AFt and AFm phases, calcium aluminium carbonate hydrates and calcium aluminium hydrates.The high reactivity of CWS and its prolific production of cementing phases in pozzolanic reactions indicate that it can be used as a supplementary cementitious material in PC and lime systems; and that it can be used as a precursor to produce low-carbon and geopolymer cements. CWS constitutes a reactive aluminium source which, in a PC system, participates in hydration reactions and can enhance the properties of the resultant materials.

Carbon Racing Wheelchair Frames: Trespassing Technological Unfairness?

This study aimed to compare the performance at World Marathon Majors of three types of racing wheelchair frame materials: Aluminum (Alu), mixed Carbon-Aluminum (CA), and carbon (Carb). Three elite wheelchair athletes (wheelers) (1 male and 2 females) were chosen for the performance analysis, which was conducted on 117 marathons (Alu, n = 49; AC, n = 25; Carb, n = 43). Compared to Alu and CA, Carb was significantly faster (249.18 ± 168.39 s or 4.07%; p = 0.001; Effect size = 0.89) and (388.60 ± 224.06 s or 6.34%; p = 0.0001; Effect size = 0.93), respectively. In addition, no interactions were observed (p > 0.05) between the material of the frame and i) the course profile, ii) the steadiness of intensity, iii) the elevation gained from the start to the finish line, and iv) the surface quality. However, Carb frames behavior in Majors, in which there are remarkable descent sections were 6.9% faster or 412.4 s (effect size = 0.64) relative to Alu, showing an even greater advantage with CA (7.6% or 455.4 s; effect size = 0.63). In conclusion and considering the remarkable advantage in terms of performance that Carb frames confer to elite-wheelers compared to those who use Alu and CA frames, as also the unaffordable price of Carb racing wheelchairs for most elite-wheelers, we advocate for consideration of strict regulations (i.e., do not allow the use of Carb frames at sanctioned marathons) by the government body of this sport IPC Athletics.

Effect of nano-carbon black content on wetting phenomenon of molten steel and alumina–carbon ceramic filter substrates

Effect of nano-carbon black content on wetting phenomenon of molten steel and alumina–carbon ceramic filter substrates

PENGUJIAN KEAUSAN ALUMUNIUM MATRIX KOMPOSIT DIPERKUAT DENGAN KARBON NANOTUBE

Wear testing of engineering materials is an important aspect in evaluating their performance and durability. This study aims to investigate the wear-resistant ability of aluminum composites reinforced with carbon nanotubes (CNTs). The composite manufacturing process was carried out by infiltrating CNTs into the aluminum matrix through powder metallurgy method. Tests were conducted using two methods, namely pressing and sintering with temperature variations of 0oC (non sintering), 400oC, 500oC, 600oC and 700oC. The results showed that the specific wear value on the specimen obtained the best value at a sintering temperature of 400oC with a value of 0.003632850 mm3/kg.m and the highest value at a sintering temperature of 700oC with a value of 0.042771207 mm3/kg.m. And the wear rate on the specimen obtained the best value at a sintering temperature of 400oC with a value of 0.447887285 mm3/s and the highest value at a sintering temperature of 700oC with a value of 1.155387594 mm3/s. This shows that the addition of temperatures greater than 400oC has a major influence on the specific wear value and wear rate of sintering products. In addition, this method is also a reference for further researchers in developing aluminum carbon nanotube technology to obtain optimal results.

PENGARUH VARIASI SUHU SINTERING ALUMUNIUM MATRIK YANG DIPERKUAT KARBON NANOTUBE TERHADAP NILAI KEKERASAN

This study examines the effect of sintering temperature variations on density values and Vickers hardness values on Aluminum Carbon Nanotubes. Tests were conducted using five temperature variations, namely sintering 400°C, 500°C, 600°C, 700°C, and unsintered. The results showed that the 400°C sintering temperature variation produced higher hardness values than the 500°C, 600°C, 700°C, and unsintered sintering temperature variations. AlCNT specimens at a sintering temperature of 400°C have an average hardness value of 46.92 VHN, while at a sintering temperature of 500°C have an average hardness value of 30.48 VHN, while at a sintering temperature of 600°C have an average hardness value of 29.04 VHN, while at a sintering temperature of 700°C have an average hardness value of 26.17 VHN, while at a sintering temperature of 0°C have an average hardness value of 39.79 VHN. Therefore, it is found that the best sintering temperature variation for AlCNT specimens is 400°C for the application of sintering to aluminum carbon nanotubes. In addition, this research can be a reference for further researchers in developing manufacturing methods and characterization of aluminum reinforced with carbon nanotubes to obtain optimal results.

Prediction of SO2 emission concentration in industrial flue gas based on deep learning: The ammonia desulfurization system of the Yunnan aluminum carbon plant as the research object

The desulfurization efficiency of flue gas desulfurization (FGD) systems is affected by many operation parameters, and predicting SO2 emission concentration through mechanism models requires a significant number of resources, limiting the process optimization of the overall desulfurization efficiency. Taking the desulfurization system of Yunnan aluminum carbon plant as the research object, based on the inlet flue gas, process control parameters, and pollutants of the discharged flue gas, we constructed the NARX (nonlinear auto-regressive model with external inputs) neural network and TCN (temporal convolutional network) models. Predicted the concentration of SO2 in the discharged flue gas in the next moment from the above three types of historical data, optimized the industrial control parameters, and reduced the concentration of the discharged SO2. The results show that both TCN and NARX models have strong nonlinear dynamic descriptive ability, and both are capable of accurately predicting the SO2 concentration in the emitted flue gas. The TCN neural network model can control the mean absolute percentage error and root mean square error of the dataset within 1.46% and 1.86, respectively. The response relationship established by the model has an important role in guiding the regulation of SO2 emission and process operation parameters, such as reducing the flue gas pressure of the absorber tower inlet or increasing the pressure of the concentration section of the absorber tower, which can effectively improve the desulfurization rate.

Study on the Effect of Ultra-fine Limestone Powder on the Resistance of Cement-slag Powder System to Chloride Ion Permeability

The effect of different limestone powder fineness on the chloride ion migration coefficient of the cement paste was tested using the Rapid Chloride Migration (RCM) method. The changes in the phase composition and pore structure of the paste were studied using hydration kinetics analysis, XRD and pore structure analysis. The results showed that before the chloride ion erosion, the limestone powder mainly exhibited filling effect, microcrystalline nucleation effect, and chemical activity effect. It reacted with the hydration products of cement to form calcium aluminate carbonate, which improved the strength of the hardened paste. After chloride ion erosion, the diffraction peak of calcium aluminate carbonate weakened, and Friedel’s salt was formed. With the increase of the specific surface area of limestone powder, the chemical activity of the powder became more obvious, and the generation of Friedel’s salt increased, leading to stronger resistance to chloride ion penetration. Limestone powder can reduce the porosity of the hardened paste and optimize the pore structure. When the particle size of the powder increased from 800 to 5000 mesh, the total porosity of the hardened paste decreased from 20.7% to 14.7%, and the most probable pore size decreased from 450nm to 75nm. Limestone powder with a particle size larger than 1500 mesh can fully exert its activity and play a role in solidifying chloride ions, thus improving the resistance to chloride ion penetration of limestone powder cement-based materials.

Interaction of Al–C Atoms at the Aluminum–Carbon Nanoparticle Interface

Interaction of Al–C Atoms at the Aluminum–Carbon Nanoparticle Interface

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.

Precursor-oriented design of nano-alumina for efficient removal of antibiotics

Rapid and efficient removal of environmental antibiotics is vital to curb bacterial resistance. Through rational precursors-oriented design, we attain the best Al2O3 absorbent by 500 °C calcination of ammonium aluminium carbonate hydroxide (AACH) precursor from NH4HCO3 route (AACH-NH4HCO3-500) for fast and efficient removal of tetracycline (TC) and other antibiotics from environmental waters including high-salinity wastewater. AACH-NH4HCO3-500 (0.25 g·L−1) can remove (69.92 ± 1.78)% of aqueous TC (0.025 g·L−1) within 5 min and (97.62 ± 2.75)% within 2 h, and the adsorption capacity is 444.4 mg·g−1, which is the highest qmax of TC for the 2 h-adsorptions among numerous adsorbents. AACH-NH4HCO3-500 has fine tolerance to the coexisting substances, and can be easily regenerated and reused, and has no harm even discarded. The relations among the synthetic methods, the structural features, and the adsorption functions of Al2O3 are disclosed through a systematic comparison of the commercial Al2O3 and different Al2O3 nanomaterials attained from three precursors produced by five different routes. The reasons behind the exceptional adsorption performance are discussed throughout. Our findings would facilitate the development of excellent adsorbents for removal of other pollutants.

Development, Analytical Characterization, and Bioactivity Evaluation of Boswellia serrata Extract-Layered Double Hydroxide Hybrid Composites.

Boswellia serrata Roxb. extract (BSE), rich in boswellic acids, is well known as a potent anti-inflammatory natural drug. However, due to its limited aqueous solubility, BSE inclusion into an appropriate carrier, capable of improving its release in the biological target, would be highly desirable. Starting with this requirement, new hybrid composites based on the inclusion of BSE in a lamellar solid layered double hydroxide (LDH), i.e., magnesium aluminum carbonate, were developed and characterized in the present work. The adopted LDH exhibited a layered crystal structure, comprising positively charged hydroxide layers and interlayers composed of carbonate anions and water molecules; thus, it was expected to embed negatively charged boswellic acids. In the present case, a calcination process was also adopted on the LDH to increase organic acid loading, based on the replacement of the original inorganic anions. An accurate investigation was carried out by TGA, PXRD, FT-IR/ATR, XPS, SEM, and LC-MS to ascertain the nature, interaction, and quantification of the active molecules of the vegetal extract loaded in the developed hybrid materials. As a result, the significant disruption of the original layered structure was observed in the LDH subjected to calcination (LDHc), and this material was able to include a higher amount of organic acids when its composite with BSE was prepared. However, in vitro tests on the composites' bioactivity, expressed in terms of antimicrobial and anti-inflammatory activity, evidenced LDH-BSE as a better material compared to BSE and to LDHc-BSE, thus suggesting that, although the embedded organic acid amount was lower, they could be more available since they were not firmly bound to the clay. The composite was able to significantly decrease the number of viable pathogens such as Escherichia coli and Staphylococcus aureus, as well as the internalization of toxic active species into human cells imposing oxidative stress, in comparison to the BSE.

Anhydrous Aluminum Carbonates and Isostructural Compounds.

We synthesized the inorganic anhydrous aluminum carbonates Al2[C2O5][CO3]2 and Al2[CO3]3 by reacting Al2O3 with CO2 at high pressures and temperatures and characterized them by Raman spectroscopy. Their structures were solved by X-ray diffraction. Al2[CO3]3 forms at around 24-28 GPa, while Al2[C2O5][CO3]2 forms above 38(3) GPa. The distinguishing feature of the new Al2[C2O5][CO3]2-structure type is the presence of pyrocarbonate [C2O5]2--groups, trigonal [CO3]2─groups, and octahedrally coordinated trivalent cations. Al2[CO3]3 has isolated [CO3]2--groups. Both Al-carbonates can be recovered under ambient conditions. Density functional theory calculations predict that CO2 will react with Fe2O3, Ti2O3, Ga2O3, In2O3, and MgSiO3 at high pressures to form compounds which are isostructural to Al2[C2O5][CO3]2. MgSi[C2O5][CO3]2 is predicted to be stable at pressures relative to abundant mantle minerals in the presence of CO2. This structure type allows the incorporation of four elements (Mg, Si, Fe, and Al) abundant in the Earth's mantle in octahedral coordination and provides an alternative phase with novel carbon speciation for carbon storage in the deep Earth.

Preparation of α-Al2O3 by low-temperature calcining γ-Al2O3 with α-phase seed in-situ obtained by ball milling

Due to the high activation energy barrier and the sporadic nature of nucleation, the temperature required for the transition from cubic dense γ-Al2O3 to tripartite α-Al2O3 is as high as 1100–1200 °C. In this work, a two-step strategy was employed to reduce the phase transformation temperature, and prepare α-Al2O3 particles with good dispersion. As the first step, 10 nm sheet γ-Al2O3 was obtained by ammonium aluminum carbonate (AACH) decomposition, which was more favorable to the crystal transformation in the next ball-milling processing. In the second step, γ-Al2O3 powder with partial α-Al2O3 produced in situ by ball-milling γ-Al2O3 was calcined, and α-Al2O3 nanoparticles were obtained at just 850 °C. The content of the α-Al2O3 is determined by the Rietveld Refine method. The relationship between ball-milling time and α-Al2O3 content was clarified, and the effect of α-Al2O3 content on the transformation temperature and morphology of γ-Al2O3 was discussed. The results showed that the α-Al2O3 content rises with the increase of ball milling time, and spherical α-Al2O3 nanoparticles can be obtained when the α-Al2O3 content is 5 %. The addition of α-Al2O3 seeds reduces the phase transition temperature but agglomeration exists. Our proposed two-step low-temperature calcination strategy is an important method for the preparation of alumina nanoparticles

Investigation of the Wear Behavior of Dual-Matrix Aluminum–(Aluminum–Carbon Nanotube) Composites

Aluminum (Al)–aluminum–carbon nanotube (Al–CNT) dual-matrix (DM) composites are a novel class of nanocomposite materials that combine the ductility of the Al matrix with the hardness and wear resistance of the Al–CNT composite and thus can offer a unique combination of properties that make them suitable for a wide range of wear applications such as cutting tools, bearings, brake pads, wear-resistant coatings, etc. However, the specific properties of the DM Al–(Al–CNT) composite will depend on several factors related to the material’s composition and the friction conditions. This study investigates the wear behavior of DM Al–(Al–CNT) composites consisting of a primary matrix of soft aluminum in which milled hard particles of (Al–CNT) are dispersed as affected by five parameters: (1) wt.% CNT in the reinforcement particles, (2) mixing ratio between the reinforcement particles and the soft Al matrix, (3) sliding speed, (4) applied load, and (5) distance. The experimental design used a Taguchi fractional factorial orthogonal array (OA) L27 to reduce the number of experiments, and analysis of variance (ANOVA) was used to determine the significance and to model the effect of each control parameter. Results showed that the wear rate could be reduced by up to 80% by tailoring the composition and controlling the friction conditions. It was found that the mixing ratio significantly impacts the wear behavior of DM Al–(Al–CNT) composites. A mixing ratio of 50% and a CNT content of 3 wt.% at the lowest applied load gave the lowest wear rate and coefficient of friction. Scanning electron microscopy investigations showed fragmentations in the reinforced matrix at higher loads and mixing ratios, which negatively impacted the wear behavior. Our findings confirm that DM Al–(Al–CNT) composites are promising for wear applications. However, the wear behavior depends on the composition and microstructural design of the composite, which needs to be carefully studied and understood.