Polymers
·
2016
·Vol. 8
·期 2
·55
·
IF 2.944
Baijun Liu,Yajun Wang,Mingyao Zhang,Huixuan Zhang
Particle coagulation is a facile approach to produce large-scale polymer latex particles. This approach has been widely used in academic and industrial research owing to its higher polymerization rate and one-step polymerization process. Our work was motivated to control the extent (or time) of particle coagulation. Depending on reaction parameters, particle coagulation is also able to produce narrowly dispersed latex particles. In this study, a series of experiments were performed to investigate the role of the initiator system in determining particle coagulation and particle size distribution. Under the optimal initiation conditions, such as cationic initiator systems or higher reaction temperature, the time of particle coagulation would be advanced to particle nucleation period, leading to the narrowly dispersed polymer latex particles. By using a combination of the Smoluchowski equation and the electrostatic stability theory, the relationship between the particle size distribution and particle coagulation was established: the earlier the particle coagulation, the narrower the particle size distribution, while the larger the extent of particle coagulation, the larger the average particle size. Combined with the results of previous studies, a systematic method controlling the particle size distribution in the presence of particle coagulation was developed.Keywords:emulsion polymerization;particle size distribution;coagulation;initiator
研究领域:
化学工程
·
材料科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Science of Advanced Materials
·
2016
·Vol. 8
·期 6
·1200-1207
·
IF 1.812
Zhao Lili,Guo Daidong,Kang Xueliang,Liang Longyue,Yang Zhiyuan,Sang Yuanhua,Liu Hong
Barium titanate (BaTiO3) nanopowders with various morphologies and crystallinities were successfully prepared by three methods. For each of them, the sintering kinetics of the BaTiO3 ceramics tuned by morphology were correlated to exposed crystal facets, crystallinity,
interface curvature and particle size distribution. A highly crystalline particle with flat interface results in a low sintering driving force, and the grain growth proceeds along predetermined growth direction. By contrast, spherical particles with small curvature radius and low crystallinity
possess a high sintering driving force, and growth occurs rapidly in all directions. In this latter case, the resulting ceramic presents a large shrinkage and the highest rate of densification. Small particle size with homogeneous size distribution contributes to the ceramic sintering as well.
The understanding of the morphology tuned sintering kinetic of BaTiO3 ceramics provides a basis for the fabrication of BaTiO3 transparent ferroelectric ceramics in the future.
研究领域:
材料科学
·
陶瓷工程
✓ 已验证
DOI
高影响因子
CHEMISTRY OF MATERIALS
·
2015
·
IF 8.354
Mingxia Jiao,Jianfeng Zeng,Lihong Jing,Chunyan Liu,Mingyuan Gao
PEGylated Fe3O4 nanoparticles were prepared through flow synthesis upon the pyrolysis of ferric acetylacetonate (Fe(acac)3) in anisole at 250 °C under pressure of 33 bar, in the presence of α,ω-dicarboxyl-terminated polyethylene glycol (HOOC–PEG–COOH) and oleylamine. In combination with theoretical analysis, the effects of linear velocity, residence time, and reactor dimension on particle size distribution were systematically investigated. In addition, the impact of Ostwald ripening on particle size distribution was also revealed. In particular, the impacts of monomer concentration distributions along both axial and radial directions of the tube reactor on the particle size distribution were carefully investigated. Under optimized conditions, PEGylated Fe3O4 nanoparticles with the relative standard deviation of particle size down to 10.6% were thus obtained. The resulting 4.6 nm particles exhibited excellent colloidal stability and high longitudinal relaxivity (r1) up to 11.1 mM–1·s–1, which manifested the reliability of flow synthesis in preparing PEGylated Fe3O4 nanoparticles as contrast agents for magnetic resonance imaging applications.
研究领域:
材料科学
·
医学影像
·
纳米技术
✓ 已验证
产品关联
DOI
高影响因子
Materials Research Express
·
2020
·Vol. 7
·期 11
·115302
·
IF 1.929
Furong Li,Qingqing Zhang,Shouzheng Jiao,Zhicheng Sun,Jinyue Wen,Xiaoyang Du,Ruping Liu,Luhai Li
Thermal expansion microcapsules (TEMs) are widely used in various fields due to their unique structures. In recent years, TEMs have attracted much attention and have broad market application prospects. In this study, thermally expandable microcapsules with a core–shell structure were prepared by suspension polymerization using acrylonitrile (AN), methyl methacrylate (MMA), and methyl acrylate (MA) as monomers and low-boiling alkane as the core material. Through particle size analysis, morphology test, thermal analysis and other methods, the effects of core material types, single core material and mixed core material, dispersion system on the microcapsule structure, particle size distribution, and expansion properties were compared. Moreover, the core material with a content of 35% can make the expansion ratio of the microcapsules up to 4 times. The expansion performance of the microcapsules with a mixture of isopentane and isooctane (ratio 1:1) as the core material was increased by 27% compared with that of a single core material. In addition, comparing with colloidal SO2/PVP dispersant, the expansion ratio of the microcapsules with magnesium hydroxide as the dispersant was increased by 20%. Finally, the optimized method for preparing thermally expandable microcapsules was obtained.
研究领域:
材料科学
·
化学工程
✓ 已验证
DOI
高影响因子
PROPELLANTS EXPLOSIVES PYROTECHNICS
·
2023
·Vol. 48
·期 9
·e202300048
·
IF 1.8
Yunyan Guo,Jinqiang Zhou,Shujie Liu,Chongwei An,Jingyu Wang,Bidong Wu
Passive micromixers are widely used in the preparation of ultrafine explosives because of their efficient mixing and necessary safety. A novel passive micromixer was designed to prepare nano-TATB. Computational fluid dynamics (CFD) is used to simulate the opening width (K), fluid velocity and mixing performance of the micromixer. The results show that the proposed micromixer has good mixing performance in the Reynolds number (Re) range of 0.1~100, and its pressure drop less than 28204 Pa at Re=100. A microfluidic recrystallization system was established and nano-TATB was prepared by a new micromixer. The results show that the average particle size of the prepared TATB is 93.12 nm, and the particle size distribution ranges from 43 nm to 151.4 nm. The SEM test shows that TATB has better morphological characteristics. XRD results show that the crystal structure of TATB is consistent with that of raw materials. This study proves that the new micromixer has good mixing effect and the feasibility of preparing nano TATB. It also provides reference for the design of micromixer and refinement of other energetic materials.
研究领域:
化学工程
·
爆炸物合成
·
计算流体力学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
·
2020
·
IF 4.65
Shengzeng Lin,Zhen Wang,Tianxing Lu,Haojie Wang,Pei Li,Fang Yang,Zhimeng Guo
The electrochemical properties and microstructure of Li-rich cathode materials Li 1.2 Mn 0.54 Co 0.13 Ni 0.13 O 2 synthesized in one-step were studied. The sample (s-g) was composed of single crystal particles (1–2 μm) with regular and smooth surface, and the particle size distribution was concentrated. Compared with the sample (cop) prepared by traditional coprecipitation method, the discharge specific capacity of sample s-g increased from 79.9 mAh g −1 to 114.5 mAh g −1 at 10C. After 100 cycles at the rate of 0.1C and 0.2C, the capacity retention rates of sample s-g were 99.48% and 105.36%, while those of sample cop were 66.23% and 71.55%, respectively. Homogeneous single crystal structure and good grain size control greatly released the capacity potential of Li-rich cathode materials and solved the problem of poor rate performance and fast capacity decay.
研究领域:
材料科学
·
电化学
✓ 已验证
DOI
高影响因子
NEW JOURNAL OF CHEMISTRY
·
2023
·Vol. 47
·期 36
·17186-17193
·
IF 3.3
Yue Bai,Dongyang Shen,Guowang Yu,Jie Wang,Shuai Lyu,Yuhua Zhang,Guanghui Wang,Jinlin Li,Lin Li
The manufacture of high metal loading catalysts is of great interest in heterogeneous catalysis; however, there are challenges in the construction of the catalytic structure, including particle size, dispersion, and accessibility. Herein, we fabricate a high Ni loading catalyst by the carbonization–oxidation–reduction (COR) strategy for low-temperature dry reforming of methane. The carbon coating obtained by carbonizing organic ligands protects Ni nanoparticles from agglomeration and sintering. Subsequent oxidation–reduction treatment sacrifices carbon and causes Ni redispersion, resulting in dual particle size distribution. The sacrifice of carbon enhances the metal–support interaction and the resistance of metal sintering. 30% Ni/MCF-COR exhibits higher and more stable catalytic activity at relatively low reaction temperature compared with 30% Ni/MCF-H2. COR pretreatment is promising in the manufacture of high metal loading catalysts for the conversion of greenhouse gasses.
研究领域:
催化化学
·
材料科学
✓ 已验证
DOI
高影响因子
CHEMOSPHERE
·
2018
·
IF 4.427
Zongping Wang,Ying Wan,Pengchao Xie,Aijiao Zhou,Jiaqi Ding,Jingwen Wang,Li Zhang,Songlin Wang,Tian C. Zhang
The effects of ultraviolet/persulfate (UV/PS) pretreatment on ultrafiltration (UF) membrane fouling caused by typical natural organic matter (NOM) fractions including humic acid (HA), sodium alginate (SA), and bovine serum albumin (BSA) were investigated. UF membrane fouling during the filtration of different NOM fractions after UV/PS pretreatment was compared through the evaluation of normalized membrane flux decline and membrane fouling reversibility. The fouling mitigation mechanisms were investigated through the characterization of ultraviolet absorbance (UV 254 ), dissolved organic matter , zeta potential , particle size distribution , fluorescence excitation-emission matrix spectra, and fitness of four classic fouling models. Furthermore, the fouled membranes were characterized by Fourier-transform infrared spectroscopy and scanning electron microscopy. The results showed that UV/PS pretreatment significantly alleviated membrane fouling caused by HA, SA, and HA-SA-BSA mixture, and the fouling control performance improved at high PS doses. However, either UV alone or UV/PS pretreatment at low PS dose (10 mg/L) significantly aggravated BSA fouling with the normalized flux at the end of first filtration cycle being 8% and 15%, respectively. The increased particle size of BSA after UV/PS pretreatment was attributed to the formation of aggregates, which mainly accumulated in membrane pores and aggravated membrane fouling. Modeling results suggest that the mitigation of membrane fouling derived from SA and mixed organic fractions was primarily ascribed to the control of cake filtration, while the mitigation of HA fouling was attributed to the declined contribution of standard blocking.
研究领域:
环境科学
·
水处理工程
·
膜技术
✓ 已验证
DOI
PubMed
高影响因子
PROPELLANTS EXPLOSIVES PYROTECHNICS
·
2016
·Vol. 41
·期 5
·899-905
·
IF 1.578
Nan Zhou,Peng Zhu,Yi Rong,Huanming Xia,Ruiqi Shen,Yinghua Ye,Shenglin Lv
Size-controlled and morphologically homogeneous lead trinitroresorcinate (LTNR) particles were synthesized in aqueous solutions using segmented flow. The experimental setup consisted of syringe pumps connected with silicone tubing to a segmented flow microfluidic platform made of polymethyl methacrylate (PMMA) containing silicone-based microchannels immersed in a thermostatted bath. As a starting point for the optimization of the experimental conditions, LTNR particles were first synthesized through conventional batch synthesis. The optimized batch conditions were adapted to segmented flow arrangements. Characterization studies on LTNR formed through batch and segmented flow methods were carried out, and it was found that in the latter LTNR particles exhibited superior particle morphology and narrower particle size distribution. In addition, the heat release of LTNR prepared by segmented flow increased by 353.52 J g −1 in comparison to that formed through batch synthesis. Finally, it was found demonstrated that segmented flow methods result in a 13 % increase in yield for the synthesis of LTNR. This study demonstrated the feasibility of synthesising primary explosives using a segmented flow microfluidic platform.
研究领域:
化学工程
·
材料科学
·
炸药科学
✓ 已验证
产品关联
DOI
高影响因子
Journal of Environmental Sciences
·
2019
·
IF 3.556
Hongyan Sun,Ruyuan Jiao,Hui Xu,Guangyu An,Dongsheng Wang
In order to evaluate the influence of particle size and particle concentration on the coagulation process, two kinds of particle suspensions, nanoparticles and microparticles , were employed to investigate the effect of particle size on coagulation mechanisms with varying coagulation parameters. Results showed that it is easier for nanoparticles to cause self-aggregation because of Brownian motion, while interception and sedimentation are the mainly physical processes affecting particle transport for microparticles, so they are more stable and disperse more easily. The particle size distribution and particle concentration had distinct influence on the coagulation mechanisms. Under neutral conditions, as the amount of coagulant increased, the coagulation mechanism for nanoparticles changed from charge neutralization to sweep flocculation and the nanoparticles became destabilized, re-stabilized and again destabilized. For microparticles, although the coagulation mechanism was the same as that of nanoparticles, the increased rate of aluminum hydroxide precipitation exceeded the adsorption of incipiently formed soluble alum species, resulting in the disappearance of the re-stabilization zone. Under acidic conditions, Brownian motion dominates for nanoparticles at low particle concentrations, while sweep flocculation is predominant at high particle concentrations. As for microparticles, charge neutralization and sweep flocculation are the mechanisms for low and high particle concentrations respectively. Under alkaline condition, although the mechanisms for both nano- and microparticles are the same, the morphology of flocs and the kinetics of floc formation are different. At low particle concentrations, nanoparticles have larger growth rate and final size of flocs, while at high particle concentrations, nanoparticles have higher fractal dimension and recovery factors.
研究领域:
环境科学
·
化学工程
·
胶体与表面化学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
FUEL
·
2024
·
IF 6.7
Mengjie Cao,Shuangde Li,Shikun Wang,Weichen Xu,Xin Zhou,Guangxin Ma,Xiaoze Wang,Linfeng Nie,Yunfa Chen
Designing nickel-based methane cracking catalysts with excellent catalytic activity and surveying their transition during the catalytic process with varied reaction condition have been challenge. In this paper, NiAl catalysts were prepared by reduced hydrotalcite precursor for efficient catalytic methane cracking to produce hydrogen. The catalysts were characterized by XRD, N 2 physisorption, XPS, SEM, TEM, Raman and TGA. The effects of preparation method, Ni/Al ratio and reaction temperature on methane cracking performance were revealed and the transformation for the Ni particles during the reaction process was analyzed. The results indicated that the catalyst performance of hydrotalcite-derived NiAl catalysts is superior to Ni/Al 2 O 3 catalysts prepared by the conventional impregnation method, which maybe due to the better Ni dispersion and uniform average particle size distribution with around 12.7 nm compared with the agglomeration of the Ni/Al 2 O 3 particles for up to 53.2 nm. The catalyst with a Ni/Al molar ratio of 3 exhibited the optimal catalytic activity with a stability for 75 min at nearly 90 % hydrogen yield at 700 °C. The reaction temperature also suggested a positive correlation between the hydrogen yield and the reaction temperature from 600 °C to 800 °C. Moreover, based on the investigation of the catalysts during the reaction transition state, Ni particles sintered rapidly from 10.2 nm to 31.2 nm at the beginning reaction time with the high hydrogen yield and then tended to be stable, which may be correlated well with the degree of graphitization of the deposited carbon. This paper provides a valuable design for efficient methane cracking catalysts.
研究领域:
催化
·
化学工程
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
·
2019
·
IF 3.131
Yiye Wang,Xueyan Luo,Ye Han,Baijun Liu,Yiwei Hu,Xiangchi Liu
Styrene emulsion polymerizations using sodium dodecyl sulfate as an anionic surfactant and in the presence of cationic initiators 2, 2′- Azobis (2-methylpropionamidine) dihydrochloride (AIBA) and 2,2′-azobis(N,N′-dimethyleneisobutyramidine) dihydrochloride (ADIBA) were studied. In this work, an explanation for in situ charge neutralization is proposed, and the effect of in situ charge neutralization on the particle size distribution of the ultimate polymer particles is discussed. Charges of cationic radicals from initiator decomposition shield the anionic charges of surfactant molecules adsorbed on the particle surface and induce particle coagulation during the early particle formation period. As the occurrence of in situ charge neutralization, the particle number decreases and the rate of micelle capture for the initiator radical is enhanced. Thus, the particle nucleation period is shortened, and monodisperse polymer particles with a diameter of ～200−300 nm are prepared using this simple emulsion polymerization process. In addition, hydrolysis of the initiator AIBA at different pH conditions is used to control particle size and stability. Compared to conventional emulsion polymerization theories, the emulsion polymerization in the presence of in situ charge neutralization presents unique kinetics.
研究领域:
高分子化学
·
材料科学
·
胶体科学
✓ 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）