JOURNAL OF THE AMERICAN CERAMIC SOCIETY
·
2023
·Vol. 107
·期 2
·1033-1041
·
IF 3.9
Xiaoyu Li,Hongye Wang,Xinwei Xu,Naichao Chen,Biao Guo,Jin Cheng,Xianqiang Chen,Hong Wang
The MgO-MoO 3 system shows significant potential for applications in microwave dielectric ceramics. However, the formation mechanism, crystal structures, and microwave dielectric properties of this system have not been systematically investigated. This work aims to comprehensively study the crystal structures, phase transitions, and microwave dielectric properties of compounds in the MgO-MoO 3 system. In particular, the research delves into the unexplored transformation mechanism from β-MgMo 2 O 7 to α-MgMo 2 O 7 and MgMoO 4 . As a result, the three compounds exhibiting favorable microwave dielectric properties have been successfully fabricated. These compounds can be effectively sintered at temperatures ranging from 685 to 900°C and exhibited dielectric constants (ε r ) ranging from 5.41 to 6.89, as well as Qf values ranging from 100 000 to 130 000 GHz. Additionally, prototype microstrip antennas are designed and fabricated using β-MgMo 2 O 7 and MgMoO 4 ceramics as substrates. The obtained antenna's performance is excellent, with S 11 values below −30 dB and a gain exceeding 6 dB at 5.8 GHz, highlighting the potential of the developed ceramics for practical applications in microwave devices.
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高影响因子
Biomaterials Advances
·
2023
·
IF 0
Mengxing Ge,Deqiao Xie,Youwen Yang,Huixin Liang,Jiasen Gu,Qiuwei Zhang,Jianling Xie,Zongjun Tian
Recent advancements in medical technology and increased interdisciplinary research have facilitated the development of the field of medical engineering. Specifically, in bone repair, researchers and potential users have placed greater demands on orthopedic implants regarding their biocompatibility, degradation rates, antibacterial properties, and other aspects. In response, our team developed composite ceramic samples using degradable materials calcium phosphate and magnesium oxide through the vat photopolymerization (VP) technique. The calcium phosphate content in each sample was, respectively, 80 %, 60 %, 40 %, and 20 %. To explore the relationship between the biocompatibility, antibacterial activity, and MgO content of the samples, we cultured them with osteoblasts (MC3T3-E1), Escherichia coli (a gram-negative bacterium), and Staphylococcus aureus (a gram-positive bacterium). Our results demonstrate that as the MgO content of the sample increases, its biocompatibility improves but its antibacterial activity decreases. Regarding the composite material samples, the 20 % calcium phosphate content group exhibited the best biocompatibility. However, after 0.5 h of co-cultivation, the antibacterial rates of all groups except the 20 % calcium phosphate content group co-cultured with S. aureus exceed 80 %. Furthermore, after 3 h, the antibacterial rates against E. coli exceed 95 % in all groups. This is because higher levels of MgO correspond to lower pH values and Mg 2+ concentrations in the cell and bacterial culture solutions, which ultimately promote cell and bacterial proliferation. This elevates the biocompatibility of the samples, albeit at the expense of their antimicrobial efficacy. Thus, modulating the MgO content in the composite ceramic samples provides a strategy to develop gradient composite scaffolds for better control of their biocompatibility and antibacterial performance during different stages of bone regeneration.
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PubMed
MATERIALS CHEMISTRY AND PHYSICS
·
2023
·
IF 4.6
Qi Yuan,Yutong Meng,Sen Wang,Gaobin Liu,Qiyao Wang,Kuoming Song,He Zhao,Shuai Yan,Xin Li
The effects of different contents of B 2 O 3 -Bi 2 O 3 on the sintering temperature and dielectric properties of MgO-12%TiO 2 (w) ceramics were investigated. B 2 O 3 -Bi 2 O 3 addition effectively reduced the sintering temperature and improved the dielectric properties of ceramic samples; however, an excessive amount of B 2 O 3 -Bi 2 O 3 led to the deterioration of dielectric properties. This is because Bi 2 O 3 participated in the chemical reaction between MgO and TiO 2 and generated a high-dielectric-loss Bi 2 Ti 2 O 7 phase, resulting in an increased dielectric loss in the ceramic samples. In contrast, B 2 O 3 formed a liquid phase to fill the grain gaps and pores during sintering, improving the densities of the ceramic samples. An appropriate amount of B 2 O 3 -Bi 2 O 3 accelerated the reaction between MgO and TiO 2 and formed ultralow-dielectric-loss phases—MgTiO 3 and Mg 2 TiO 4 , and the dielectric losses of the ceramic samples decreased to an order of 10 −5 .
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RSC Advances
·
2021
·Vol. 11
·期 21
·12532-12542
·
IF 3.361
HanShuang Liu,KaiJun Wang,XiaoYan Cao,JiaXin Su,Zhenggui Gu
In this study, different magnesium, copper, lanthanide single metal, and composite multimetal oxide catalysts were prepared via the coprecipitation route for the aerobic oxidation of cumene into cumene hydroperoxide. All catalysts were characterized using several analytical techniques, including XRD, SEM, EDS, FT-IR, BET, CO2-TPD, XPS, and TG-DTG. La2O3–CuO–MgO shows higher oxidation activity and yield than other catalysts. The results of XRD and SEM studies show that the copper and magnesium particles in the catalyst are smaller in size and have a distribution over a larger area due to the introduction of the lanthanum element. The CO2-TPD results confirmed that the catalyst has more alkali density and alkali strength, which can excite active sites and prevent the decomposition of cumene hydroperoxide. XPS results show that due to the promotional effect of La2O3, there are more lattice and active oxygen species in the catalyst, which can effectively utilize the lattice defects under the strong interaction between metal oxides for rapid adsorption and activation, thus improving the oxidation performance. Besides, La2O3–CuO–MgO exhibits good stability and crystalline structure due to its high oxygen mobility inhibiting coking during the cycle stability test. Finally, the possible reaction pathway and promotional mechanism on La2O3–CuO–MgO in cumene oxidation are proposed. We expect this study to shed more light on the nature of the surface-active site(s) of La2O3–CuO–MgO catalyst for cumene oxidation and the development of heterogeneous catalysts with high activity in a wide range of applications.
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高影响因子
Journal of Materiomics
·
2020
·
IF 5.797
Chi Zhang,Ying Chen,Xin Li,Haishen Ren,Genshui Wang,Xianlin Dong
Glass-free MgO-based microwave dielectric ceramics (1-x) wt% (0.98 MgO-0.02 Al 2 O 3 )-x wt% LiF (x = 0.5, 1, 2, 3, 4) were synthesized where LiF and Al 2 O 3 were utilized as sintering additive and reinforcement phase in MgO matrix respectively. It was found that ion substitution is apt to occur between LiF and MgO, leading to the formation of oxygen vacancies and MgF 2 . Nevertheless, different from ordinary liquid-phase sintering, morphologies of ceramics were distinctly altered with grains changing from polyhedron to sphere-like shape and densities underwent obvious decrease when excessive amount of LiF was introduced and we call it excessive liquid-phase sintering. Grain boundary weakening caused by this circumstance would exert an adverse effect on physical properties. Moreover, LiF addition dramatically reduced dielectric breakdown strength and altered the dielectric breakdown behavior of MgO-based ceramics, which is dominated by electrical breakdown mechanism. Combination of good properties were achieved in 1 wt% LiF modified MgO-based ceramics sintered at 950 °C which exhibited superior microwave properties (ε r = 9.56, tanδ = 9.2 × 10 −5 , Qf = 124,600 GHz), high flexural strength (184.5 MPa), high thermal conductivity (21.3 W/(m⋅K)), high coefficient of thermal expansion (∼12 ppm/°C) and moderate electrical properties (E b = 35.9 kV/mm, ρ = 4.9 × 10 12 Ω cm).
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APPLIED CATALYSIS A-GENERAL
·
2020
·
IF 5.006
Xuefei Wang,Yong Men,Jinguo Wang,Shuang Liu,Qiaoling Song,Mei Yang
Catalytic transformation of ethanol has been studied over a series of MgO-SiO 2 composite catalysts with different ZnO loadings. Vast differences in product selectivity are obtained by varying ZnO loadings in enabling the control over product distribution. Our results reveal that MgO-SiO 2 composite catalysts with low ZnO loadings tend to show an enhanced efficiency for C C bond coupling and exceptionally high selectivity to 1,3-butadiene whereas the high ZnO loadings favor the formation of acetaldehyde via dehydrogenation. Thorough analysis of characterization results via XRD, BET, IR, TPD, and 29 Si MAS NMR indicates that ZnO loading influences the extent of MgO and SiO 2 interaction during preparation, and the surface acid-base chemistry, which were both found to correlate with the catalytic performance. This study proposes that the Mg O Si interfacial structure formed by the strong MgO and SiO 2 interaction at low ZnO loadings is of prime importance for the formation of 1,3-butadiene, benefiting from the desirable properties of balanced dehydrogenation and C C bond coupling while excess ZnO loadings destroy the Mg O Si interfacial bonds over the MgO-SiO 2 composite catalysts, which are the key structures required for C C bond growth.
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Environmental Science-Nano
·
2021
·Vol. 8
·期 9
·2569-2583
·
IF 8.131
Siyang Li,Shujuan Zhan,Jingxiang Sun,Lingai Yao,Jinzhu Zhu,Jinxi Feng,Ya Xiong,Shuanghong Tian
Highly reactive nanoclusters of metal oxides are extremely difficult to synthesize due to their thermodynamic instability. For the first time, MgO nanoclusters supported on sewage sludge-derived hierarchical porous carbon (MgO nanoclusters/SC) were successfully prepared by grafting 1.31 ± 0.03 mmol g−1 acidic groups on the SC, then dynamically controlling the chemisorption of Mg2+ on the modified SC within 20 s, and finally transforming the fixed Mg2+ into MgO nanoclusters with a size of less than 2.4 nm via thermal treatment. Moreover, the cluster size could be facilely tailored by controlling the dynamic adsorption time and initial aqueous Mg2+ concentration. The resulting five MgO nanoclusters/SC-20 s samples with 0.43–1.12% (mass percentage) Mg have a turnover frequency of 0.038 towards the catalytic ozonation of 4-chlorophenol, much higher than those of the bigger nanoclusters and nanocrystals (i.e. MgO/SC-20 s with 1.43% Mg, MgO/SC-3 min with 0.85–2.0% Mg). The pseudo-first-order reaction constant of MgO nanoclusters/SC with 1.12% Mg is 0.0126 min−1, 6.0 and 4.1 times that of SC and bulky MgO/SC, respectively. The presence of MgO nanoclusters/SC also enhanced the removal of cephalexin, florfenicol and sulfamethoxazole by 54.3%, 45.5%, and 57.4%, respectively. The high activity can be ascribed to the rich and highly under-coordinated Mg in the smaller MgO nanoclusters and the unblocked hierarchical pores of the SC support. Finally, DFT calculations revealed at the atomic level that the under-coordinated Mg in MgO nanoclusters could directly or indirectly activate ozone through the protonated hydroxyl or just hydroxyl bonded to the under-coordinated Mg. Except for (MgO)2, the smaller the nanocluster, the higher the activity. This work shed a light on the design and preparation of highly reactive nanoclusters of metal oxide catalysts for catalytic ozonation of refractory organic pollutants.
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JOURNAL OF THE AMERICAN CERAMIC SOCIETY
·
2018
·Vol. 102
·期 5
·2415-2425
·
IF 2.956
Jingyuan Chu,Yue Zhao,Guangyu Jiang,Wei Wu,Zhiwei Zhang,Zhiyong Hong,Zhijian Jin
Tuning substrate properties is an effective methodology to modulate the texture development of MgO films deposited by ion beam-assisted deposition (IBAD) process for epitaxial oxide films. Herein, a solution deposition planarization (SDP) technique is employed to deposit Gd-Zr-O layer for engineering surface properties of the flexible metal substrate. The correlation between the Gd-Zr-O thin film microstructure and the IBAD-MgO texture is investigated. The coordinated study on atomic force microscopy (AFM) and reflection high-energy electron diffraction (RHEED) reveal that the grain coarsening during high-temperature sintering negatively influences the texture formation of IBAD-MgO. Moreover, the chemical environment of the atoms on the surface of Gd-Zr-O seed layer also plays a critical role, which is normally overlooked. The X-ray photoelectron spectroscopy (XPS) analysis indicates that the carbon residue and intermediate phase result in the poor texture of the IBAD-MgO. This phenomenon is related to the partial decomposition and synthesis reactions due to the lower sintering temperature or reduced surface to volume ratio. We demonstrate the high-quality texture of IBAD-MgO layer, deposited on mono-coated thick Gd-Zr-O film, by using optimal heat-treatment conditions. The cross-sectional TEM images present the dense Gd-Zr-O film with Gd 2 Zr 2 O 7 nanograins. The multifunctionalities, such as planarization, a barrier layer, and seed layer, of Gd-Zr-O layers are realized in full-stacked CeO 2 /LaMnO 3 /IBAD-MgO/SDP-Gd-Zr-O/C276 samples. This work demonstrates a route for simplifying the architecture of 2G-HTS using Gd-Zr-O layer and explores the effect of the surface properties on texture formation in IBAD-MgO layer.
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JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
·
2019
·
IF 4.029
Chen-Hua Lou,An-Nan Chen,Lu Lu,Jia-Min Wu,Li-Jin Cheng,Rong-Zhen Liu,Shuang Chen,Ying Chen,Yu-Sheng Shi,Chen-Hui Li
MgO-doped Ba 0.67 Sr 0.33 TiO 3 (BST) ceramics with uniform microstructure and enhanced dielectric loss were prepared by direct coagulation casting via high valence counter ions (DCC-HVCI) method. MgO was utilized as acceptor dopant as well as coagulating agent to release Mg 2+ solidifying ceramic suspensions. Effect of sintering temperature and MgO doping content on microstructure and dielectric properties of BST ceramics was investigated. It was found that the loss tangent value (tan δ) decreased remarkably from 0.025 to 0.004 with increasing MgO concentration from 0.5 to 1.5 mol%. The 1.5 mol% MgO-doped BST ceramics processed high density of 99.5% and tan δ of 0.004 which is improved by 150% compared with that of dry-pressed samples. This improvement can be attributed to the ubiquitous distribution of MgO in BST ceramic matrix leading to the enhanced inhibitive effect. This paper provides a novel facial route to prepare high-performance functional ceramics with high reliability and low cost.
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高影响因子
ACS Omega
·
2018
·
IF 0
Qiangying Zhang,Man He,Beibei Chen,Bin Hu
In this paper, magnetic mesoporous carbon composites were prepared by calcination of the mixture of magnesium citrate and Fe3O4@SiO2 in an inert atmosphere. A high content of Fe3O4@SiO2 and MgO was in situ embedded in a carbon matrix. After removing the MgO template by diluted acid, the resulting material (Fe3O4@SiO2@mC) was subjected to further H2O2 oxidation treatment. The formed oxygen-containing functional groups on the products provided plenty of active sites for the adsorption of analytes of interest. The obtained composites (Fe3O4@SiO2@mC-H2O2) exhibited a mesoporous structure with a high specific surface area of 731 m2 g–1. The adsorption capacities of Fe3O4@SiO2@mC-H2O2 for Cu(II) and Pb(II) were calculated to be 86.5 and 156 mg g–1, respectively. Under optimal conditions, the adsorption isotherm of Cu(II) and Pb(II) onto Fe3O4@SiO2@mC-H2O2 fitted the Langmuir model and the adsorption kinetic was well-correlated with the pseudo-second-order model. Besides, Fe3O4@SiO2@mC-H2O2 exhibited fast removal dynamics (within less than 1 min) for Cu(II) and Pb(II), demonstrating great application potential in wastewater treatment.
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PubMed
CERAMICS INTERNATIONAL
·
2013
·
IF 1.789
Huiwen Yuan,Yu Shi,Zhongzi Xu,Chunhua Lu,Yaru Ni,Xianghui Lan
Thermal and mechanical properties of high temperature aluminate cementitious thermal energy storage materials enriched with nano-MgO (NM) are investigated. According to the development of thermal storage materials and their application environment requirement in solar thermal power, the specimens were subjected to heating at 105, 350, and 900 °C. It was observed that the addition of NM provided a great improvement on the thermal properties of the composite pastes which were heated principally at 350 and 900 °C. When the NM content was 1 wt%, the thermal conductivities are 34.8% and 23.6% higher than that of pure paste at 350 and 900 °C, respectively. Meanwhile, at 2 wt% NM particles loading, the optimum value of volume heat capacity is obtained, which are 19.8% and 40.8% higher than that of pure paste at 350 and 900 °C, respectively. Moreover, compressive strength of the composite paste with 1 wt% NM presents approximately 30.5%, 27.8%, and 23.8% higher than that of pure paste at 105, 350, and 900 °C, respectively. XRD , TG-DSC, SEM, and MIP were used to characterize the phases, mass/heat changes, microstructure and pore distribution of the hardened cement pastes , respectively.
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GREEN CHEMISTRY
·
2014
·Vol. 16
·期 9
·4371-4377
·
IF 6.852
Mingming Li,Xuan Xu,Yutong Gong,Zhongzhe Wei,Zhaoyin Hou,Haoran Li,Yong Wang
A novel and sustainable synthesis of a Pd/CN@MgO catalyst is presented here, offering a bifunctional catalyst with high catalytic activity towards a tandem aldol condensation–hydrogenation reaction of furfural with acetone in a one-pot reactor. The incorporation of biomass based hydrophilic N-containing carbon (CN) in the catalyst provides a subtle but elegant method to control the good water dispersibility, the reaction stability, and the ultrafine dispersion of palladium particles (2.2 nm in average size) in the bifunctional catalyst Pd/CN@MgO. With such improved features, an impressive 99% furfural conversion and 95% selectivity for the hydrogenated products (saturated ketones) was obtained by using Pd/CN@MgO as a novel bifunctional catalyst in the reported tandem reaction. This catalyst design strategy and the high efficiency of the catalyst in the reported system offer potential for the preparation of bi/multifunctional catalysts and the one-pot synthesis of bioderived intermediates.
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