Journal of Materials Research and Technology-JMR&T
·
2023
·
IF 6.4
Pengfei Li,Ruiming Yin,Yunfei Bai,Yanhong Ding,Xiaofeng Zeng,Yongquan Li
To reduce the lattice oxygen content of Si 3 N 4 green bodies, samples were prepared using an N,N-dimethylacrylamide (DMAA) system. The endothermic and exothermic peaks are related to the decomposition of organic matter and the reaction between pyrolytic carbon and impurity oxides in the sintering process. Multi-step heat preservation during the thermal degreasing process reduced the carbon content and defects. The α→β phase transformation and aspect ratio of grains changed from 89.2% to 4.84:1 at 1640 °C to 96.3% and 7.80:1 at 1700 °C, respectively. The relative density, hardness, fracture toughness, and thermal conductivity of the Si 3 N 4 samples reached 98.5%, 1353 HV, 8.51 MPa·m 1/2 , and 97.1 W·m −1 ·K −1 , respectively. Pyrolytic carbon can react with SiO 2 , which reduces the content of the glass phase in the green body and affects the dissolution and precipitation process and lattice oxygen content. In the structure of the Si 3 N 4 sample, carbon particles with sizes of 100–500 nm and near-spherical shapes were observed. Intergranular-phase YMgSi 2 O 5 N was formed during the sintering process, which was conducive to improving the thermal conductivity. This article uses lower temperature and no pressure conditions to prepare Si 3 N 4 ceramics, which can provide reference for batch and low-cost production.
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高影响因子
IRANIAN POLYMER JOURNAL
·
2021
·Vol. 30
·期 4
·331-342
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IF 1.899
An Kai,Guan Lianxiong,Kang Huiting,Tian Dating
Zipper-like thermosensitive molecularly imprinted polymers (MIPs) based on konjac glucomannan (KGM) for metformin hydrochloride were prepared using KGM, a natural polysaccharide, as the matrix, acrylamide (AM) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) as the comonomers, N, N′ -methylenebis(acrylamide) as the cross-linking agent, ceric ammonium nitrate as the initiator, and metformin hydrochloride as the template molecule. The resultant MIPs were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectrometry (XPS), X-ray diffractometry (XRD), thermal gravimetric analyzing (TGA), and scanning electron microscopy (SEM). The interpolymer interactions between poly (AM) and poly (AMPS) were demonstrated by the results of ultraviolet spectrometry (UV), indicating that MIPs with zipper-like structure could be fabricated. The thermo-responsive MIPs with on/off-switchable characteristic were evaluated by the method of cyclic voltammetry (CV). The adsorption experiment showed that the target molecules could be controlled to be adsorbed/desorbed by changing the external temperature. The adsorption capacity at high temperature was higher than that at low temperature. Moreover, the adsorption capacity of MIPs was much higher than that of NIPs. The results of adsorption experiments showed that the MIPs could specifically recognize and adsorb metformin with excellent selectivity, repeatability, and stability. Langmuir equation and Freundlich equation were applied to fit the adsorption isotherms of MIPs and the results showed that the Langmuir equation fitted better than the Freundlich equation. The product is expected to serve as a novel adsorption and separation material.
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高影响因子
CERAMICS INTERNATIONAL
·
2021
·
IF 4.527
Shuang Yin,Dongliang Mao,Limei Pan,Xia Fang,Yang Wang,Tai Qiu,Jian Yang
The porous SiC–Si 3 N 4 composite ceramics with good EMW absorption properties were prepared by combination of gelcasting and carbothermal reduction. The pre-oxidation of Si 3 N 4 powders significantly improved the rheological properties of slurries (0.06 Pa s at 103.92 s −1 ) and also suppressed the generation of NH 3 and N 2 from Si 3 N 4 hydrolysis and reaction between Si 3 N 4 and initiator APS, thereby reducing the pore defects in green bodies and enhancing mechanical properties with a maximum value of 42.88 MPa. With the extension of oxidation time from 0 h to 10 h, the porosity and pore size of porous SiC–Si 3 N 4 composite ceramics increased from approximately 41.86% and 1.0–1.5 μm to 46.33% and ~200 μm due to the production of CO, N 2 and gaseous SiO, while the sintering shrinkage decreased from 16.24% to 10.50%. With oxidation time of 2 h, the Si 2 N 2 O fibers formed in situ by the reaction of Si 3 N 4 and amorphous SiO 2 effectively enhanced the mechanical properties , achieving the highest flexural strength of 129.37 MPa and fracture toughness of 4.25 MPa m 1/2 . Compared with monolithic Si 3 N 4 ceramics, the electrical conductivity , relative permittivity and dielectric loss were significantly improved by the in-situ introduced PyC from the pyrolysis of three-dimensional network DMAA-MBAM gel in green bodies and the SiC from the carbothermal reduction reaction between PyC and SiO 2 and Si 3 N 4 . The porous SiC–Si 3 N 4 composite ceramics prepared by the unoxidized Si 3 N 4 powders demonstrated the optimal EMW absorption properties with reflection loss of −22.35 dB at 8.37 GHz and 2 mm thickness, corresponding to the effective bandwidth of 8.20–9.29 GHz, displaying great application potential in EMW absorption fields.
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RSC Advances
·
2019
·Vol. 9
·期 47
·27305-27317
·
IF 3.049
Jing Li,Jindi Huang,Ruiming Yin
This work aims to develop an effective method for investigating the multistage debinding kinetics and reaction mechanisms of removing N,N-dimethylacrylamide/N,N′-methylenebisacrylamide (DMAA/MBAM) polymer from gelcast ceramic parts. Thermogravimetry (TG) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) experiments were performed to investigate the thermal degradation characteristics and the main compounds produced during the pyrolysis of DMAA/MBAM polymer within green components. A multi-stage parallel reaction model (M-PRM) was proposed to separate the overlapping peaks in the dα/dT curves. The kinetic parameters (activation energy E and pre-exponential factor k0) of each substage were calculated using model-free methods (Flynn–Wall–Ozawa, Starink, Friedman and Kissinger–Akahira–Sunose) and an activation energy variable model. In addition, the most appropriate kinetic mechanism function f(α) of each substage was analyzed and discussed via Málek's procedure and the Šesták–Berggren (SB) model. The results showed that the DMAA/MBAM polymer burnout in green components can be divided into three substages through a three-stage parallel reaction model (3-PRM). The values of E (Friedman method) for substages 1 to 3 were E(α) = 139.862 − 110.481α + 156.161α2 − 88.714α3 kJ mol−1, E(α) = 160.791 + 152.496α − 236.906α2 + 163.724α3 kJ mol−1 and E(α) = 72.132 + 452.830α − 669.039α2 + 507.015α3 kJ mol−1, respectively. The average values of E showed an increasing tendency from substages 1 to 3, and a kinetic compensation effect was also observed between the E and k0 in each substage. The kinetic mechanism analysis revealed that the reaction mechanisms for substages 1 to 3 were f(α) = (1 − α)0.668α3.049(−ln(1 − α))−3.874, f(α) = (1 − α)0.700α3.177(−ln(1 − α))−3.962 and f(α) = (1 − α)1.049α−0.161(−ln(1 − α))0.518, respectively. It is expected that the research results can be extended to investigate the multiplex debinding of binders or polymers for various colloidal molding techniques.
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PubMed
高影响因子
CERAMICS INTERNATIONAL
·
2019
·
IF 3.45
Jing Li,Chuanfu Zhang,Ruiming Yin,Wenhai Zhang
Thermal debinding is an important step in a gelcasting process, and the proper selection of the debinding technique is crucial for the quality of a green body. In this work, the pyrolysis characteristics of an N,N-dimethylacrylamide/N,N′-methylenebisacrylamide gel system in a thermal debinding process of a gelcast SiAlON green body were investigated through nonisothermal thermogravimetric analysis and a thermogravimetric analyzer coupled with Fourier transform infrared spectroscopy analysis. In addition, the pyrolysis kinetics of the thermal debinding process of the gelcast SiAlON green body were described by using a three-parallel-distributed activation energy model. The results showed that the conversion (α) and reaction rate (dα/dT) curves predicted by the kinetic model agreed well with the experimental data. The kinetic parameters ( E 0, i , k 0, i , and σ i ) of the global thermal debinding process were 116.0–158.0 kJ/mol, 9.31 × 10 8 s −1 and 2.19–20.52 kJ/mol, respectively. Finally, a solid–fluid–thermal–mechanical coupling numerical model of the thermal debinding process was established through finite element methods on the basis of theories of the porous medium seepage and thermodynamics. The distributions of the residual content of the gel polymer , the temperature, the pressure, and the stress in the green body throughout the entire thermal debinding process were evaluated using this model. It was shown that a high heating rate leads to a high temperature gradient and von Mises stress inside the green body. Moreover, a reasonable debinding technique was proposed to effectively prevent and eliminate defects caused by excessive stress or a temperature gradient inside the green body. In a given DMAA/MBAM gel system, the strongest stress peak can be effectively eliminated by holding at 310 °C for no less than 2 h at a heating rate of 1 °C/min. This work aims to provide a theoretical basis for studying thermal debinding kinetics and optimizing debinding techniques for the gelcasting of various materials.
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高影响因子
International Journal of Applied Ceramic Technology
·
2024
·
IF 1.8
Heng Zhang,Dongxu Yao,Yongfeng Xia,Yu-Ping Zeng
Porous Si 3 N 4 ceramics were prepared using the low-toxicity monomer HEMA (2-hydroxyethyl methacrylate) via a modified gel casting method. The rheological properties of Si 3 N 4 slurries were investigated. Triethanolamine with high activity was used as a catalyst and modifier for gelation reactions, effectively improving the curing rate and suppressing the inherent surface oxygen inhibition in such process systems. With an increase in solid loading of the slurry, the drying shrinkage (12.3% to 5.4%) significantly decreased, while the green body density (44.0%–49.0%) and flexural strength (9.65–16.46 MPa) increased, demonstrating an excellent mechanical strength. After sintering at 1700°C, the porous Si 3 N 4 ceramics prepared with 24–36 vol% solid loading slurry exhibited a flexural strength of 144.39–193.66 MPa and a porosity of 55.8% to 49.0%. The dielectric constant and loss tangent at 30 GHz ranged from 2.88 to 3.38 and 1.17–1.56 × 10 −3 , respectively. These ceramics show promising potential applications in high-performance structural ceramics and high-temperature wave-transparent materials.
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高影响因子
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
·
2025
·
IF 6.2
Heng Zhang,Dongxu Yao,Ming Zhu,Yongfeng Xia,Jun Zhao,Yu-Ping Zeng
Porous Si 3 N 4 ceramics hold great promise for high-temperature wave-transparent materials, but it is a significant challenge to achieve both a low dielectric constant and high mechanical strength. This study explores a method combining in-situ pre-gel casting and non-directional freeze-drying to produce high-porosity, uniform microstructure Si 3 N 4 ceramics. By adjusting gel concentration and pre-gelation time, ice crystal growth effectively restricted, resulting in a uniform pore structure. The resulting porous Si 3 N 4 ceramics exhibited low drying shrinkage (1.50 %) and high porosity (59.13 %), with a flexural strength of 119.48 MPa, surpassing porous ones produced by other wet forming processes. At 30 GHz, the dielectric constant was 2.45, and the dielectric loss was 5.65 × 10 −3 .
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ACS Nano
·
2025
·
IF 16
Shuo Wang,Yuequan Wang,Yantong Li,Xiaoxue Lai,Miao Hu,Meng Chen,Cong Li,Xinrong Liu,Yanzhi Song,Yihui Deng
Inflammation-related immune cell subsets with abnormal activation, impaired tolerance, and complex intercellular interactions drive the progression and incurability of autoimmune diseases (AIDs). Here, we present an antigen-free nanovaccine-enabled holo-immunotherapy that comprehensively modulates inflammation, innate immunity, and adaptive immunity. The nanovaccine, composed of dual NF-κB inhibitors (budesonide and bortezomib) and comodified with sialic acid (SA) and enzyme-cleavable polyethylene glycol (PEG), leverages the SA-Siglec axis for targeted delivery to inflammation-related macrophage, dendritic cell, and CD4+ T cell subsets. By bridging innate and adaptive immunity, this multitargeted strategy synergistically reshapes the inflammatory microenvironment, establishes robust memory immune tolerance, and promotes immune homeostasis restoration, leading to sustained efficacy and delayed relapse in the collagen-induced arthritis (CIA) mouse model. Unlike traditional vaccines, the antigen-free design eliminates reliance on exogenous antigens, minimizes off-target immune risks, and holds promise for broader clinical applicability. The nanovaccine outperforms anti-TNF-α antibodies in treating models of CIA, adjuvant-induced arthritis, and chronic ulcerative colitis, highlighting its potential as a universal vaccine platform for AID therapy. Overall, this work provides a strategy to address AID challenges through precise immune regulation and durable therapeutic benefits.
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PubMed
高影响因子
CERAMICS INTERNATIONAL
·
2025
·
IF 5.6
Xianggang Liu,Hui Chen,Yuxin Zhao,Jingjie Zhang,Xianglong Meng,Guangchun Xiao,Zhaoqiang Chen,Mingdong Yi,Wenyu Liu,Chonghai Xu
Al 2 O 3 /CaF 2 self-lubricating ceramic materials were prepared using a low-toxicity methylacrylamide gelcasting system. The rheological properties of the Al 2 O 3 slurry were analyzed to study the effects of dispersant content, solid loading, and pH on its flowability. Optimal results were achieved with a dispersant content of 0.5 wt%, a solid loading of 54 vol%, and a pH of 9. The relative density of the resulting green body was 56 %, with a strength of 18.2 MPa. After sintering for 2 h in a vacuum furnace at 1650 °C, the material exhibited a hardness exceeding 750 HV and a bending strength above 300 MPa when the CaF 2 content was less than 10 vol%. Additionally, the tribological properties of Al 2 O 3 /CaF 2 under various conditions were investigated, revealing optimal performance at a CaF 2 content of 10 vol%. The average friction coefficient and wear rate were 0.245 and 2.96 × 10 −5 mm 3 /N⋅m, respectively, representing reductions of 48 % and 54 % compared to pure Al 2 O 3 materials. These findings demonstrate that gelcasting is an effective method for preparing self-lubricating ceramic materials, offering a new approach for fabricating complex-shaped self-lubricating ceramic components.
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