International Journal of Applied Ceramic Technology
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2022
·Vol. 20
·期 1
·527-533
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IF 2.328
Mengwen Zhang,Lutong Yang,Zhaosheng Li,Binyang Jiang
Al 2 O 3 –cBN has received considerable attention in the field of ceramic cutting tools due to its high hardness, high wear resistance, and low cost, but poor interfacial bonding affects the performance of the composite. In this study, a novel hot-forging process was used to prepare high-performance Al 2 O 3 –cBN composites using Ti(C,N) as a binder. The evolution of the morphology, phase, and microstructure of the hot-forged Al 2 O 3 –Ti(C,N)–cBN composites was determined, and the mechanical properties were measured. The relative density of the composites increases significantly after hot forging, and the deformation of the composites increases with the hot-forging temperature. The highest performing Al 2 O 3 –Ti(C,N)–cBN composite was prepared by hot forging at 1600°C and has a hardness of 20 GPa, a bending strength of 647 MPa and a fracture toughness of 5.37 MPa m 1/2 , which are superior to those of a directly hot-pressed sintered composite. However, at hot-forging temperatures higher than 1700°C, Al 5 O 6 N and TiB 2 are formed in the composite. In the composite hot forged at 1800°C, serrated grain boundaries promote the strength and toughness of the composite to 877 MPa and 6.76 MPa m 1/2 , respectively. Therefore, the novel hot-forging process is expected to enhance material properties.
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高影响因子
CERAMICS INTERNATIONAL
·
2023
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IF 5.2
Hang Liu,Shengqiang Song,Rundong Jing,Mithun Nath
Recently, in the Al 2 O 3 –CaO–Cr 2 O 3 system, a Cr 3+ ternary phase named wuboraite (CaAl 2 Cr 2 O 7 ) was synthesized for the first time in an air atmosphere, which later showed an undetermined hint of solid solubility between Cr 3+ and Al 3+ in different atmosphere. In the present investigation, the solubility limits (or x values) of the CaAl 2± x Cr 2± x O 7 were determined by conducting high-temperature equilibrium experiments in both air and N 2 atmospheres with the various proportionate mixtures of CaO, Al 2 O 3 , and Cr 2 O 3 , and subsequently using powder X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) analysis. In the air atmosphere, the Cr richest end-member of the Wuboraite solid solution phase is CaAl 1.77 Cr 2.23 O 7 (or x = 0.23), while that of Al richest end-member is CaAl 2.18 Cr 1.82 O 7 (or x = 0.18). Whereas, in the N 2 atmosphere, the Cr richest end-member of the wuboraite solid solution phase is CaAl 1.77 Cr 2.23 O 7 (or x = 0.23), while that of Al richest end-member is CaAl 2.15 Cr 1.85 O 7 (or x = 0.15).
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JOURNAL OF THE AMERICAN CERAMIC SOCIETY
·
2023
·
IF 3.9
Wen Yan,Zhe Chen,Guangqiang Li,Shaosong Hong,Nan Li
In present work, the novel Al 2 O 3 -C ceramic filter fabricated by using microporous corundum-spinel powder instead of dense Al 2 O 3 powder and reinforced by SiC whiskers is proposed. The effects of Si powder content (0, 3, 6, and 9 wt. %) on the microstructures and mechanical properties of the filters were studied. After replacing the α-Al 2 O 3 micro-powder with microporous corundum-spinel powder, the in situ spinel whiskers were formed inside the filter skeleton under the reducing atmosphere. The rough surface structure of the microporous powder increased the interface contact area with the small-sized carbon particles, resulting in a compact interface bonding in the filter skeleton and a higher cold compressive strength of the filter. When the Si powder content increased to 6–9 wt. %, the in-situ SiC whiskers were formed not only between the microporous powder, but also inside the pores near the surface of it by vapor-solid reaction mechanism in the filter skeleton. The SiC whiskers synergized with the microporous powder to form a more compact interface structure, thus remarkably enhancing their cold compressive strength and thermal shock resistance. Overall, the mechanical properties of the filters were significantly improved by the addition of 9 wt. % Si powder. The filter skeleton had an apparent porosity of 36.2% and a bulk density of 1.93 g/cm 3 . The filter also exhibited a high cold compressive strength of 1.59 MPa and a superior thermal shock resistance. It has the potential for better purification efficiency on molten steel in the future due to a rougher skeleton surface structure compared to existing Al 2 O 3 -C filters.
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CERAMICS INTERNATIONAL
·
2023
·
IF 5.2
Lizheng Zhang,Yong Zeng,Haihua Yao,Zhaoyao Shi,Jimin Chen
To date, overcoming the trade-off between high solid loading and print accuracy and strength , achieving high-performance and fine ZrO 2 micro-ceramic components through vat photopolymerization 3D printing remains challenging. In this study, the effects of dispersant, particle size and solid content on the dispersion, rheological behavior and stability of ZrO 2 ceramic slurry were systematically studied, and complex, fine and high-performance ZrO 2 micro-ceramic gears were successfully prepared. Then, the microstructure, mechanical properties, tribological properties and surface quality were evaluated. The results show that the rheological behavior of the slurry is the best when the optimal dispersant content is 3.5 wt%. With the increase of solid content, the sintering shrinkage of ZrO 2 (3Y)/Al 2 O 3 ceramics decreased, while the relative density, compressive strength , flexural strength , fracture toughness and hardness increased. The prepared micro-ceramic gears not only have fine structure, but also have dense microstructure and good mechanical properties. The relative density, compressive strength, flexural strength, fracture toughness and hardness strength of ZrO 2 (3Y)/Al 2 O 3 ceramics can reach 98.53 %, 1900 MPa, 648 MPa, 6.4 MPa × m 1/2 and 13.40 GPa, respectively. In particular, this study couples the printing accuracy and strength with the solid load. By adjusting the relationship between the fixed load and the shrinkage rate, the printing of samples with different sizes is realized, which breaks through the accuracy limit of the printing equipment and provides a new idea for the preparation of micro-ceramic gears.
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Molecular Catalysis
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2023
·
IF 4.6
Xiaozhong Wang,Jiali Hu,Cai Xu,Yingqi Chen,Liyan Dai
Herein, a series of NiCu/Al 2 O 3 catalysts were prepared by impregnation method and subsequent thermal treatment under different reduction temperatures. The catalysts exhibited excellent catalytic activity for the amination of diethylene glycol (DEG), and satisfactory yield of tertiarybutylaminoethoxyethanol (TBEE) could be obtained. XRD, N 2 adsorption-desorption, SEM, TEM, XPS, and H 2 -TPR were employed to characterize the catalysts, the interaction between Ni and Cu on the catalytic activity was studied. It was found that NiCu alloy was formed after catalyst reduction, which strengthened the reduction ability of NiO and increased the number of Ni 0 active center, contributing to the enhanced catalytic activity. Moreover, the effects of reaction parameters on catalytic activity were explored. There was no need for a solvent, only 3 molar equivalents of tert‑butylamine (TBA) and 1 wt.% catalyst was required. After 7 h of reaction at 220 °C, satisfactory conversion (89.6%) and selectivity (84.6%) were obtained over the prepared catalyst. Cycle experiment demonstrated that the prepared catalyst retained excellent stability and reusability after six runs without significant loss of catalytic activity. This work provided an efficient catalyst for the catalytic amination of diethylene glycol with tert‑butylamine to TBEE.
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JOM
·
2023
·Vol. 75
·期 12
·5167-5175
·
IF 2.6
Li Guanghui,Huang Jiahao,Sun Hu,Mang Changye,Hou Yanrui,Luo Jun
The novel one-step oxidation–volatilization process for separating MoO 3 from pelletized MoS 2 concentrate supported on a porous Al 2 O 3 -SiO 2 skeleton has been demonstrated to have superior diffusion efficiency compared to the traditional two-step oxidative roasting-sublimation approach. Optimal control of pellet phase and micro-structure evolutions is crucial for maintaining a stable and breathable pellet bed throughout the roasting process, which is essential for industrial application of the new process. This work determined the phase transformations of MoS 2 concentrate pellets during roasting, revealed the formation mechanisms of mullite whiskers from MoS 2 -Al 2 O 3 -SiO 2 system and thus achieved toughening control of roasted MoS 2 concentrate pellets with temperature programmed roasting (TPR). It is found that the intermediate product Al 2 (MoO 4 ) 3 can induce the low-temperature formation of mullite whisker. With TPR, the volatilization rate of molybdenum is 97.2%, and the compressive strength of mullite pellets reach 124.8 N. This study puts forward a feasible route with industrial significance.
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JOURNAL OF CATALYSIS
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2023
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IF 7.3
Qiangqiang Wu,Hanke Li,Guangxing Yang,Yonghai Cao,Hongjuan Wang,Feng Peng,Hao Yu
A variety of adsorbed intermediates have been extensively assigned during CO 2 hydrogenation on Pt/γ-Al 2 O 3 . However, the surface sites where the surface species reside have not been well resolved, which are extremely important to depict the reaction pathways of CO 2 hydrogenation. In the current work, surface species adsorbed on three regions were distinguished by in situ diffuse-reflectance infrared Fourier transform spectroscopy, i.e., contiguous Pt region of Pt nanoparticle, interfacial Pt int -O-Al int region between Pt nanoparticle and γ-Al 2 O 3 , and surface region of γ-Al 2 O 3 away from Pt nanoparticle. The dynamics of adsorbed H species, carbonyl species, bicarbonates, formate species, and adsorbed CO 2 , were identified at different sites, proving that the reaction occurs at the Pt/γ-Al 2 O 3 interface. We found that only the C-containing species at the Pt perimeter are directly active intermediates for the reaction. Such spatial analysis bridges the gap between the hydrogen activation and CO 2 activation, providing a deep understanding of CO 2 hydrogenation. In addition, the interface structure with oxygen vacancy is important for CO 2 activation, driving the reaction through carboxylate (*HOCO) pathway to form CO at the interface rather than formate (*HCOO) pathway and then be hydrogenated at the Pt surface.
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ChemCatChem
·
2023
·Vol. 15
·期 7
·e202300194
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IF 4.5
Tao Li,Mengling Dong,Jiacheng Xu,Tiantian Zhang,Yan Sun,Ning Li,Zuliang Wu,Jing Li,Erhao Gao,Jiali Zhu,Shuiliang Yao,Yong Huang
Graphical CeO 2 /γ-Al 2 O 3 , Pd/CeO 2 , and Pd/CeO 2 /γ-Al 2 O 3 were used for catalyzing low-concentration CH 4 oxidation . γ-Al 2 O 3 can efficiently promote CH 4 oxidation on Pd/CeO 2 and the formation of bicarbonate that is easily gasified to CO 2 . CeO 2 /γ-Al 2 O 3 , Pd/CeO 2 , and Pd/CeO 2 /γ-Al 2 O 3 were used for catalyzing low-concentration CH 4 oxidation. It was found that nano-sized Pd could obviously promote CH 4 oxidation on CeO 2 /γ-Al 2 O 3 . The interaction between Pd and CeO 2 on γ-Al 2 O 3 resulted in higher ratios of Ce 3+ /(Ce 3+ +Ce 4+ ), Pd 2+ /(Pd 2+ +Pd δ+ ), and O ads /(O ads +O latt ), those benefited the formation of more oxygen vacancies and surface reactive oxygen species for CH 4 oxidation. γ-Al 2 O 3 not only supplied a high surface area and enhanced Pd/CeO 2 dispersion on γ-Al 2 O 3 , but also simulated the formation of bicarbonate, where bicarbonate is easier to gasify to CO 2 than bidentate carbonate that formed on Pd/CeO 2 . Operando diffuse reflectance infrared Fourier transform spectroscopy-mass spectrometer analysis results showed that CH 4 oxidation could occur at a temperature as low as 180 °C due to the reaction with surface reactive OH, this reaction was also accompanied by the formation of bicarbonate. The mechanism of CH 4 oxidation promoted by bicarbonate formation on γ-Al 2 O 3 was proposed.
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ACS Sustainable Chemistry & Engineering
·
2023
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IF 8.4
Jiayu Feng,Ping Ning,Kai Li,Xin Sun,Chi Wang,Lijuan Jia,Maohong Fan
The conventional Haber–Bosch NH3 synthesis process requires high temperatures and pressures, resulting in a high carbon footprint and the need to develop alternative NH3 synthesis methods. Accordingly, plasma-based and γ-Al2O3-catalyzed NH3 synthesis from H2O (a hydrogen source) and air/N2 (a nitrogen source) was studied under low temperature and low pressure conditions. The experimental results show that NH3 can be synthesized with air/N2 and H2O, although byproducts such as NO and N2O are also formed. The NH3 formation rate resulting from the use of N2 and H2O is higher than that of air and H2O. Increasing specific energy input (SEI) can increase the NH3 formation rate. Nevertheless, the energy efficiency of NH3 synthesis technology first increases and then decreases with SEI. An NH3 formation rate of 2.92 μmol h–1 g–1 was achieved with an SEI of 11.68 J mL–1 and energy efficiency of 5.10 mg kW–1 h–1 (1.28 mg kWh–1g–1), when wet air at a flow rate of 200 mL min–1 was introduced into the dielectric barrier discharge (DBD) reactor, which was lower than that (4.30 μmol h–1 g–1) attained with N2 + H2O under an SEI of 11.50 J mL–1 and energy efficiency of 7.63 mg kW–1 h–1 (1.91 mg kWh–1g–1). Additionally, the γ-Al2O3 catalyst exhibited good stability. Different results show that plasma-based and γ-Al2O3 catalyzed NH3 synthesis technology is promising.
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Crystals
·
2023
·Vol. 13
·期 1
·107
·
IF 2.7
Shaocong He,Yehua Li,Xiao Zong,Shanghua Wu
In this work, Al2O3-AlN composite ceramics with high bending strength and thermal conductivity were fabricated by Digital Light Processing (DLP). The influence of AlN content on the rheological and cure behavior of Al2O3-AlN suspensions, as well as the microstructure, thermal conductivity, and bending strength of Al2O3-AlN ceramics, were systematically investigated. The result shows that the viscosity and cure ability of the suspensions were decreased with the increase of AlN content, which are beneficial to the spreading and printing accuracy of the suspensions. Besides, the bending strength of ceramics can be improved due to the residual stress by the introduction of AlN. Approaches were employed to minimize the formation of AlON in Al2O3-AlN ceramics by optimizing the amount of AlN and the sintering temperature. The thermal conductivity and bending strength of Al2O3-AlN ceramics were 31.72 ± 0.45 W/(m·K) and 572.73 ± 59.40 MPa, respectively, which are much higher than those of Al2O3ceramics fabricated under the same condition. Finally, complex-shaped Al2O3-AlN ceramics components have been successfully fabricated by DLP, which may provide an opportunity to broaden the application of Al2O3-AlN composite ceramics in heat dissipation components.Keywords:Al2O3-AlN composite ceramics;Digital Light Processing;mechanical properties;thermal conductivity
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ENERGY & FUELS
·
2018
·
IF 3.024
Tingting Huang,Jingyao Chang,Shuisen He,Chenglong Wen,Yu Fan
This paper proposes a novel one-step hydrothermal polyoxometalate (POM) dispersion method for synthesizing NiMo/Al2O3 hydrodesulfurization (HDS) catalysts with high Ni/Mo atomic ratios. The proposed method disperses Mo12O30(μ2-OH)10H2[Ni(H2O)3]4 on the surface of Al2O3 under a hydrothermal environment, which promotes the formation of highly dispersed MoS2 slabs with increased stacking. The proximity between Ni and Mo in POM improves the decoration of MoS2 slabs by Ni, and the high Ni/Mo ratio of POM synthesized by the one-step method ensures that the corresponding catalyst possesses a high concentration of active NiMoS phases. The as-prepared POM-based NiMo/Al2O3 catalyst possesses much better activity in 4,6-dimethyldibenzothiophene HDS than its counterparts synthesized via the traditional incipient wetness impregnation method.
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INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
·
2019
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IF 3.375
Haifeng Li,Sheng Su,Yan Peng,Linkang Wu,Kai Xu,Lijun Liu,Mengxia Qing,Song Hu,Yi Wang,Jun Xiang
High temperature sorbents for removing H2S comprising manganese oxide and Al2O3 support modified with La loadings were prepared with wet impregnation. The removal of H2S and the regeneration of sorbents were conducted at 850 °C to investigate the effect of the support modified with La on the desulfurization ability and durability of the Mn/La/Al2O3 sorbents. The fresh sorbent, first sulfide sorbent, and fourth regenerated sorbent were characterized by nitrogen isothermal adsorption, X-ray power diffraction, scanning electron microscopy, and H2 temperature-programmed reduction. The results showed that the highest initial breakthrough sulfur capacity (BSC) was obtained with Mn/0.78%La/Al2O3(M/0.78L), and the initial BSC decreased with increased La loadings due to the inhibiting of excessive La on the reaction between MnO and H2S. The BSC of sorbents with lower La loadings suffered more serious deactivation than MnxOy/Al2O3 during successive desulfurization–regeneration cycles, and the BSC durability of sorbents increased with an increase in La loadings and calcination temperature of La/Al2O3. Mn/4.83%La/Al2O3 with La/Al2O3 calcined at 900 °C (M/4.83H) had the best BSC durability, which was better than the BSC durability of MnxOy/Al2O3 (M) during several desulfurization–regeneration cycles. The characterization results showed that the structure of the M/4.83H sorbent was more stable than other sorbents. The M/4.83H sorbent derived the La(AlO3) phase, which could maintain the structural stability of the sorbent during several desulfurization–regeneration cycles. The formation of the LaAlO3 phase may inhibit MnxOy from dissolving into Al2O3, which was beneficial for the durability of sorbents during several successive desulfurization–regeneration cycles.
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