CERAMICS INTERNATIONAL
·
2020
·
IF 3.83
Mithun Nath,Shengqiang Song,Ning Liao,Tengteng Xu,Hang Liu,Himansu Sekhar Tripathi,Yawei Li
Obtaining a stable Cr 3+ phase at higher temperatures in the presence of hydraulic calcium aluminates (the phases found in calcium aluminate cement, CAC) in the Al 2 O 3 –CaO–Cr 2 O 3 system remains a significant challenge in many application areas, as the formation of toxic, carcinogenic, and water-soluble Cr 6+ compounds often occur. To address the issue, recently, we synthesized a high-temperature stable Cr 3+ ternary compound (CaAl 2 Cr 2 O 7 ) with space group P3 (143). In the present work, we investigated the formation-stability of CaAl 2 Cr 2 O 7 with in-situ calcium aluminate phases at 1500 °C under the CO 2 atmosphere in the Al 2 O 3 –CaO–Cr 2 O 3 system through solid-oxide reactions route varying Cr 2 O 3 content (at constant Al 2 O 3 :CaO ratio). It co-existed with hydraulic calcium aluminates and other phases over the full investigated composition range of 2.76–68.3 mol% Cr 2 O 3 (5–80 wt%). Apart from CAC phases (CaAl 2 O 4 , CaAl 4 O 7 ), major Cr 3+ -phases are CaAl 2 Cr 2 O 7 and (Al,Cr) 2 O 3 while (α,β)-CaCr 2 O 4 and Ca(Al,Cr) 12 O 19 formed as minor phases. At a constant Al 2 O 3 :CaO ratio of 5.6:4.4 mol% (7:3 wt%), the formation of the CaAl 2 Cr 2 O 7 phase increases with Cr 2 O 3 content (up to the investigated composition of 26.43 mol%) and then decreases gradually. The solid solubility of Al and Cr in the CaAl 2 Cr 2 O 7 phase limited over a narrow range, and presumably dependent more on heat treatment condition rather than composition as reflected from the lattice parameter calculations. Though XRD revealed the presence of only Cr 3+ -phases in the partial CO 2 atmosphere, however, traces of Cr 6+ could be detected using XPS and leaching tests. However, leachable Cr 6+ content (0.095–1.252 mg/L) were much below the United States Environmental Protection Agency (US-EPA) permissible limit of 5 mg/L. The formation mechanism of the CaAl 2 Cr 2 O 7 and other phases with plausible reactions were also discussed.
研究领域:
材料科学
·
环境科学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
·
2021
·
IF 5.302
Bingrong Li,Yaowu Wei,Junfeng Chen,Nan Li
C 3 A-containing CaO specimen was prepared and the evolution of its microstructure during hydration process was investigated to clarify the protective mechanism of tricalcium aluminate (C 3 A) on hydration resistance of CaO specimen. The slit-shaped micropores were formed on the grain boundary of CaO due to the stacking of lamellar C 4 AH 13 formed by the hydration of C 3 A. The contact area of residual C 3 A with the moisture was reduced by the porous C 4 AH 13 layer at the original site, which resulted in a slower dissolution rate of C 3 A grain through the porous layer. In addition, the crack propagation and the formation of macropores were inhibited by the pinning effect of C 4 AH 13 , which was beneficial to the improvement of hydration resistance.
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2019
·
IF 3.45
Hang Liu,Shengqiang Song,Andrie M. Garbers-Craig,Zhengliang Xue
Cr 2 O 3 is a well-known corrosion resistant oxide used in refractory applications. However, it can oxidize into toxic and water-soluble Cr(VI) compounds upon reaction with calcium aluminate cement phases in the presence of oxygen, which subsequently causes disposal problems after use. This study describes the extent to which chromium in the spinel Mg(Al,Cr) 2 O 4 phase can be oxidized to Cr(VI) when it reacts with the calcium aluminate cement phases C 12 A 7 , CA, CA 2 and free CaO at 1300 °C in air, using XRD, XPS and leaching tests (TRGS 613 standard) as analytical tools. On reaction with CaO, the Mg(Al,Cr III ) 2 O 4 spinel mainly transformed into hauyne (Ca 4 Al 6 Cr VI O 16 ) and Ca 5 Cr 3 O 12 which contains both Cr(IV) and Cr(VI). The reaction of C 12 A 7 and CA with the spinel phase also resulted in the formation of Ca 4 Al 6 CrO 16 . Conversely, the reaction of Mg(Al,Cr III ) 2 O 4 spinel with CA 2 resulted in the formation of only a trace amount of Cr(VI). Water-soluble Cr(VI) leached in large quantities (>100 mg/L) from samples where the Mg(Al,Cr III ) 2 O 4 reacted with either C 12 A 7 or CA. Almost no Cr(VI) leached from the sample when Mg(Al,Cr III ) 2 O 4 reacted with CaO, using the standard TRGS 613 leach test, but a significant amount of Cr(VI) was released into solution when leached with a HCl solution for 12 h. Both Cr(IV) and Cr(VI) present in the Ca 5 Cr 3 O 12 dissolved into acidic solution. Only a small amount of Cr(VI) leached from the sample that resulted when spinel was reacted with CA 2 , even after a prolonged HCl leach. Cr(III) in spinel Mg(Al,Cr) 2 O 4 is very stable and does not leach in either distilled water or acidic solution.
研究领域:
材料科学
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环境科学
✓ 已验证
产品关联
DOI
高影响因子
CEMENT AND CONCRETE RESEARCH
·
2022
·
IF 11.958
Fang Sun,Xueyu Pang,Shiho Kawashima,Guodong Cheng,Shenglai Guo,Yuhuan Bu
In order to study the abnormal viscosity evolution behavior of oil well cement slurries containing tartaric acid, the influence of tartaric acid on the early-age hydration of oil well cement at high temperatures was investigated by isothermal calorimetry (IC), thermogravimetric analysis (TGA) and quantitative XRD (QXRD) analysis in the temperature range of 60 °C to 89 °C. Results show that, a high dosage of tartaric acid can fundamentally change the typical shape of the cement hydration heat flow curve - two additional exothermic peaks associated with aluminate phase hydration (C 3 A and C 4 AF) appear before the main hydration peak. The unsynchronized hydration of the aluminate phases and the silicate phases was found to be the cause of premature setting. Additionally, long-term curing study (up to 28 d) showed that increasing the dosage of tartaric acid decreased the ultimate hydration extent of C 2 S while it increased the ultimate hydration extent of C 4 AF.
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
CEMENT AND CONCRETE RESEARCH
·
2023
·
IF 11.4
Yamei Cai,Yong Tao,Dongxing Xuan,Xiaohong Zhu,Chi Sun Poon
This work examines the micromechanical properties of AFm phases formed in seawater and deionized water. As the interlayer SO 4 2− in the AFm phase is gradually replaced by Cl − in seawater, the basal spacing of the AFm crystal narrows, which promotes the packing density of nanocrystals and their indentation modulus and hardness, i.e. , Cl-AFm (Friedel's salt) > SO 4 -Cl-AFm (Kuzel's salt) > SO 4 -AFm (monosulphate). It is found that Friedel's salt formed in seawater feature multiple structural and compositional defects. First, the anions (Cl − , OH − , SO 4 2− ) are bound in the interlayer of Friedel's salt, and the bound OH − contents have negative relations with the Cl − concentration in the seawater. Second, the incorporation of Mg ions in the Friedel's salt barely changes its micromechanical properties based on the experimental data and molecular dynamics simulations. Third, when portlandite is present in the seawater, some Ca vacancies would be formed in the Friedel's salt, which would decrease its Young's modulus significantly. This accounts for the decrease in the indentation modulus of Friedel's salt as observed in the experiments. These findings enable us to better understand and control the micromechanical properties of Cl-containing AFm phase formed in seawater-mixed cementitious materials .
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
Nanoscale
·
2021
·Vol. 13
·期 18
·8514-8523
·
IF 7.79
Xiaodan Huang,Xiaojun Wei,Yan Zeng,Lihong Jing,Haoran Ning,Xiaodan Sun,Yingying Li,Di Li,Yuanping Yi,Mingyuan Gao
Spinel oxide nanocrystals are appealing hosts for Cr3+ for forming persistent luminescent nanomaterials due to their suitable fundamental bandgaps. Benefiting from their antisite defect-tolerant nature, zinc gallate doped with Cr3+ ions has become the most studied near-infrared (NIR) persistent luminescent material. However, it remains challenging to achieve persistent luminescence from its inexpensive analogs, e.g., zinc aluminate (ZnAl2O4). Because the radius difference of the cations in the latter system is bigger, it is intrinsically unfavorable for ZnAl2O4 to form Zn–Al antisite defects under mild conditions. Herein, we report a wet-chemical synthetic route for preparing Cr3+-doped ZnAl2O4 nanoparticles with long NIR persistent luminescence. It was demonstrated that methanol (MeOH) as an important component of the mixed solvent played a critical role in tailoring the morphology of the resulting ZnAl2O4:Cr nanocrystals. It could particularly drive the formation of antisite defects in the resulting coral-like nanoparticles bearing zinc-rich cores and zinc gradient peripheries. To disclose the effects of MeOH on the formation of antisite defects as well as particle morphologies, small molecules released during the pyrolysis of metal acetylacetonate precursors were analyzed by using gas chromatography-mass spectrometry. In combination with density functional theory (DFT) calculations, it was found that MeOH can effectively catalyze the thermolysis of metal acetylacetonate precursors, in particular Zn(acac)2. Therefore, MeOH exhibits remarkable effects on the formation of antisite defects by balancing the decomposition rates of Zn(acac)2 and Al(acac)3 through its volume fraction in the reaction system. This work thus constitutes a hitherto less common strategy for achieving NIR persistent luminescence from Cr3+-doped ZnAl2O4 nanoparticles by engineering the cation defects under mild conditions.
研究领域:
材料科学
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化学工程
✓ 已验证
DOI
高影响因子
JOURNAL OF HAZARDOUS MATERIALS
·
2024
·
IF 12.2
Qian Zhao,Xin Li,Guangyuan Chen,Zeru Wang,Chuan Tan,Cheng Liu,Hao Zou,Jing Ma,Lin Zhu,Tao Duan
Effective capture of radioactive iodine from nuclear fuel reprocessing is of great importance for public safety as well as the secure utility of nuclear energy. In this work, a hydrophobic nanosheet silicalite-1 (NSL-1) zeolite with an adjustable size was developed for efficient iodine (I 2 ) and methyl iodide (CH 3 I) adsorption. The optimized all-silica zeolite NSL-1 exhibits an excellent I 2 uptake capacity of 553 mg/g within 45 min and a CH 3 I uptake capacity of 262 mg/g within 1 h. Benefiting from the reduced thickness and enhanced porosity, microporous NSL-1 possesses enhanced iodine adsorption capacity and fast adsorption kinetics , which is a considerable high value among inorganic materials . Unexpectedly, the remarkable characters of high hydrophobicity , acid-resistance and anti-oxidation endow it a higher iodine uptake capacity than traditional aluminosilicate zeolites. More importantly, the high uptake selectivity toward I 2 possessed by NSL-1 owing to its hydrophobic skeleton under simulated dynamic conditions. The low cost, facile and scalable synthesis of NSL-1 further highlights great prospects for applications in the nuclear industry. This work provides useful insights for designing efficient adsorbents for iodine capture .
研究领域:
材料科学
·
核能工程
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环境科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Materials
·
2022
·Vol. 15
·期 22
·8079
·
IF 3.748
Zhanqiang Li,Junfeng Zheng,Wenjuan Zhang,Yong Zheng,Weijun Zhao,Liyan Xue,Fan Yang,Heng Chen
YSZ has been widely used as a TBC material, but its phase change at high temperatures limits its development, thus the need for developing new thermal barrier materials resistant to high temperatures. Rare-earth aluminate ceramics with a garnet structure (Yb3Al5O12) have been considered as a potential thermal barrier material. The melting point of Yb3Al5O12is 2000 °C, which has a potential high temperature application prospect. However, Yb3Al5O12has lower thermal expansion and higher thermal conductivity than YSZ, which is a widely employed thermal barrier coating (TBC) material. To overcome these obstacles, (Y0.2Dy0.2Ho0.2Er0.2Yb0.2)3Al5O12, a high-entropy ceramic, was prepared by a solid-state reaction and pressureless sintering. The thermal conductivity of the (Y0.2Dy0.2Ho0.2Er0.2Yb0.2)3Al5O12was 3.48 W/(m·K) at 300 K, approximately 25.48% lower than that of the Yb3Al5O12 (4.67 W/(m·K)). The thermal expansion coefficient of the (Y0.2Dy0.2Ho0.2Er0.2Yb0.2)3Al5O12was 9.28 × 10−6K−1at 673-1273 K, approximately 18.52% higher than that of the Yb3Al5O12(7.83 × 10−6K−1, 673-1273 K). When the (Y0.2Dy0.2Ho0.2Er0.2Yb0.2)3Al5O12was annealed at 1550 °C for 7 days, its average grain size only increased from 0.7 μm to 1.3 μm. Moreover, the (Y0.2Dy0.2Ho0.2Er0.2Yb0.2)3Al5O12exhibited better chemical stability and a lower grain growth rate than the Yb3Al5O12. This study reveals that (Y0.2Dy0.2Ho0.2Er0.2Yb0.2)3Al5O12is a promising candidate for the future generation of thermal barrier materials.Keywords:rare-earth aluminates;high-entropy ceramics;thermal barrier material;chemical stability
研究领域:
材料科学
·
高温材料
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Nanomaterials
·
2024
·Vol. 14
·期 7
·608
·
IF 4.4
Wei Liu,Yang Zou,Yuang Chen,Zijian Lei,Lili Zhao,Lixin Song
This work involves the introduction of niobium oxide into lanthanum aluminate (LaAlO3) via a conventional solid-state reaction technique to yield LaAlO3:Nb (LaNbxAl1−xO3+δ) samples with Nb5+doping levels ranging from 0.00 to 0.25 mol%. This study presents a comprehensive investigation of the effects of niobium doping on the phase evolution, defect control, and reflectance of LaNbxAl1−xO3+δpowder. Powder X-ray diffraction (XRD) analysis confirms the perovskite structure in all powders, and XRD and transmission electron microscopy (TEM) reveal successful doping of Nb5+into LaNbxAl1−xO3+δ. The surface morphology was analyzed by scanning electron microscopy (SEM), and the results show that increasing the doping concentration of niobium leads to fewer microstructural defects. Oxygen vacancy defects in different compositions are analyzed at 300 K, and as the doping level increases, a clear trend of defect reduction is observed. Notably, LaNbxAl1−xO3+δwith 0.15 mol% Nb5+exhibits excellent reflectance properties, with a maximum infrared reflectance of 99.7%. This study shows that LaNbxAl1−xO3+δpowder materials have wide application potential in the field of high reflectivity coating materials due to their extremely low microstructural defects and oxygen vacancy defects.
研究领域:
材料科学
·
光学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
JOURNAL OF LUMINESCENCE
·
2024
·
IF 3.3
Yibiao Ma,Weifang Liao,Beibei Quan,Zihui Kong,Maxim S. Molokeev,Andrey Zolotov,Ming Cheng,Xiaoyan Chen,Zhi Zhou,Mao Xia
Lead-free non-rare earth oxide phosphors have attracted wide attention due to their environmental protection, sustainability, and potential to replace halides and fluorides in the field of plant lighting. Among them, the Cr 3+ -excited aluminate phosphor exhibits high brightness, high thermal stability, and far red to near-infrared (NIR) emission due to the influence of the crystal field strength (CFS). This property gives rise to a variety of strategies used to modulate the CFS, for example, single ion substitution, chemical unit co-substitution, etc. Here, we chose the substitution of a single ion, with [BaO6] gradually replacing [SrO6] to form a solid solution. Their structural characteristics and the local structure of Cr 3+ are studied and discussed. The device is packaged to evaluate the feasibility of the material for practical application. The prepared phosphor had a bright far-red light emission of 693 nm under blue light excitation, and this spectrum strongly matched the absorption of plant phytochrome P FR . This work provides the design principle of far red light emission activated by Cr 3+ aluminate solid solution, which can inspire further research on pc-LED lights for plant lighting.
研究领域:
材料科学
·
植物学
✓ 已验证
产品关联
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2024
·
IF 5.1
Xuewei Luo,Shuo Huang,Ruiqi Huang,Jianhe Hong,Shuoguo Yuan,Zhu Shu,Ling Zhao,Cheng Lu,Hongyun Jin
By applying the high-entropy strategy, one can develop stable mixed oxide by populating a single sublattice with many distinct cations. Two kinds of rare-earth high-entropy hexaaluminates (La 1/5 Nd 1/5 Sm 1/5 Eu 1/5 Gd 1/5 )MAl 11 O 19 (M = Mg and Zn) were successfully synthesized, and their mechanical and thermal properties were analyzed. We highlight that the Zn-containing sample displays a significant increase in fracture toughness (2.48 MPa m 1/2 ) and a decrease in thermal conductivity (1500 °C, 1.2 W m −1 K −1 ) as compared to the Mg-containing sample. The diffusion of fine grains in platelet-like grains observed only in the Zn-containing sample is considered to be responsible for its outstanding mechanical properties. This work demonstrates the excellent thermal-mechanical properties of the Zn-containing sample and indicates the promising use of high-entropy hexaaluminate in the aerospace field acting as thermal barrier coating materials.
研究领域:
材料科学
·
航空航天工程
✓ 已验证
产品关联
DOI
高影响因子
MATERIALS AND STRUCTURES
·
2024
·Vol. 57
·期 5
·1-12
·
IF 3.4
Zhang Wan,Wu Zhihong,Huang Wang,Liu Jiayuan,Zhou Huafeng,Qiu Junlong
It is insufficient to enhance the strength of shotcrete by simply relying on the early strength component aluminum sulfate in the liquid accelerator. The introduction of organic additives can effectively compensate for this deficiency. In this study, three different structures of organic ethers, 18-crown-6 (ECS), tetraethylene glycol monomethyl ether (Tg), and ethylene glycol monomethyl ether (Eg), were added to an aluminum sulfate alkali-free liquid accelerator, and their effects were comprehensively investigated. The results revealed that these organic ethers were capable of bolstering the strength of the mortar after 28 d. The efficiency of these ether organics on the strength of cement mixed with the accelerator followed the order: ECS > Tg > Eg. Specifically, when the ECS content reached 0.3%, the compressive strength of the mortar at 1 d was measured at 8.07 MPa. In addition, changes in the phase composition and micromorphology were scrutinized through X-ray diffraction and scanning electron microscopy, culminating in the establishment of a mechanistic model elucidating the hydration process of organic ether accelerator cement.
研究领域:
建筑材料学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）