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Determining number of sites on ceria stabilizing single atoms via metal nanoparticle redispersion 被引量:4
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作者 Aisulu Aitbekova Cody JWrasman +2 位作者 Andrew RRiscoe Larissa YKunz Matteo Cargnello 《Chinese Journal of Catalysis》 SCIE EI CAS CSCD 北大核心 2020年第6期998-1005,共8页
Single atom catalysts have recently attracted interest due to their maximization of the utilization of expensive noble metals as well as their unique catalytic properties. Based on its surface atomic properties, CeO2 ... Single atom catalysts have recently attracted interest due to their maximization of the utilization of expensive noble metals as well as their unique catalytic properties. Based on its surface atomic properties, CeO2 is one of the most common supports for stabilizing single metal atoms. Many single atom catalysts are limited in their metal contents by the formation of metal nanoparticles once the catalyst support capacity for single atoms has been exceeded. Currently, there are no direct measurements to determine the capacity of a support to stabilize single atoms. In this work we develop a nanoparticle-based technique that allows for quantification of that capacity by redispersing Ru nanoparticles into single atoms and taking advantage of the different catalytic properties of Ru single atoms and nanoparticles in the CO2 hydrogenation reaction. This method avoids complications in metal loading caused by counterions in incipient wetness impregnation and can eventually be applied to a variety of different metals. Results using this technique follow trends in oxygen vacancy concentration and surface oxygen content and show promise as a new method for quantifying support single atom stabilization capacity. 展开更多
关键词 CERIA Single-atom catalyst Oxygen vacancies CO2 hydrogenation redispersion
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A dense graphene monolith with poloxamer prefunctionalization enabling aqueous redispersion to obtain solubilized graphene sheets
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作者 Chen Ye Fan Zhang +13 位作者 Xue Tan Huifang Sun Wen Dai Ke Yang Minghui Yang Shiyu Du Dan Dai Jinhong Yu Nan Jiang Weitao Su Li Fu He Li Jing Kong Cheng-Te Lin 《Chinese Chemical Letters》 SCIE CAS CSCD 2020年第9期2507-2511,共5页
The realization of good aqueous dispersibility of commercial graphene products composed of exfoliated graphene sheets is of significance for downstream applications.However,the tap density of commercial graphene powde... The realization of good aqueous dispersibility of commercial graphene products composed of exfoliated graphene sheets is of significance for downstream applications.However,the tap density of commercial graphene powder is quite low(0.03-0.1 kg/m3),meaning that 1 kg graphene powder occupies about 10-30 m3 in volume during transportation.And,the available content of commercial graphene dispersion/slurry in aqueous medium cannot exceed 5 wt%,although the density is high(≈1050 kg/m3).In this work,a graphene monolith was prepared by oven-drying of graphene sheets prefunctionalized with poloxamer surfactants.Our graphene monoliths not only have a high density(1500 kg/m^3) and high graphene content(≈10 wt%),but also a full capability to be completely redispersed(≈100%) in water by bath sonication to obtain solubilized graphene sheets,whose lateral size and thickness are unchanged compared to as-exfoliated ones.Moreover,a simple empirical method was proposed to predict the redispersion capability of graphene monoliths using different poloxamers by contact angle measurements.Our results provide a universal approach to make exfoliated graphene-based products with better downstream availability and lower transportation cost. 展开更多
关键词 Dense monolith Graphene sheets POLOXAMER Aqueous redispersion Surface functionalization
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Enhanced Redispersibility of Cellulose Nanocrystals in Water via Surface Adsorption of Hydrolyzed Sugars from Corresponding Cellulose Nanocrystal Fabrication
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作者 Yongqi Zhang Yongjian Xu +4 位作者 Chun Liu Ling Yang Jianmin Hu Ruixia Zhang Xiuqiong Guan 《Paper And Biomaterials》 CAS 2022年第2期10-17,共8页
Generally,hydrogen bonds are formed between cellulose nanocrystals(CNCs)during their water removal and drying,leading to the irreversible aggregation of CNCs,and thus a poor water-redispersibility.The present study de... Generally,hydrogen bonds are formed between cellulose nanocrystals(CNCs)during their water removal and drying,leading to the irreversible aggregation of CNCs,and thus a poor water-redispersibility.The present study demonstrated a novel approach that involved using hydrolyzed sugars generated from the corresponding CNC production as redispersing agents to enhance the redispersibility of CNCs.Experimental data indicated that hydrolyzed sugars can be adsorbed onto CNCs through ethanol precipitation.The oven-dried CNCs onto which hydrolyzed sugars were adsorbed via ethanol precipitation were homogeneously redispersed in water.The redispersed CNCs showed the particle size distribution,Zeta potential,and thermal decomposition properties similar to those of the CNCs without drying.This method may improve the use of hydrolyzed sugars obtained in the hydrolysate from the corresponding CNC production,as well as facilitate the transportation and storage of CNCs. 展开更多
关键词 water redispersion cellulose nanocrystals(CNCs) hydrolyzed sugars ethanol precipitation
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Effect of Polyvinyl Alcohol with a Thiol End Group on the Properties of Polyacrylic Dispersions and Spray-dried Powder 被引量:1
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作者 林劲冬 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2007年第2期261-265,共5页
The emulsion polymerization of highly shear-stable copolymer dispersions of methyl methacrylate and butyl acrylate were carried out using poly (vinyl alcohol) with a thiol end group (PVA-SH) as protective colloid.... The emulsion polymerization of highly shear-stable copolymer dispersions of methyl methacrylate and butyl acrylate were carried out using poly (vinyl alcohol) with a thiol end group (PVA-SH) as protective colloid. The dispersions can be transformed into corresponding redispersible powder via a spray dryingcooling process. On-line FT-IR monitoring shows that grafting polymer of PVA-g-PMMA was formed mainly at the stage-1 of the emulsion polymerization. TEM images show, the PVA-SH shell was fragmentary when adding SDS at initial stage and integrated when adding at particle growing or final stage. The particle size turns to be smaller when delayed adding SDS surfactant. Triethanolamine, a co-regulator of PVA-SH, controlled the M to 50 000-70 000 and reduced the PDI to 1.5-1.7. The acrylic dispersions with 0.8wt%-1.5wt% PVA-SH1 can be spray-dried into super dispersible polymer powder (SDPP), which can easily disperse in water and form recon- stituted dispersions with an average particle size smaller than 1 micron. 展开更多
关键词 thiol poly (vinyl alcohol) polymeric emulsifier emulsion polymerization redispersible powder
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Effect of CF and RPP on the Mechanical and Electrical Properties of Smart Aggregate 被引量:2
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作者 王海峰 MEI Zhen 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2018年第2期437-444,共8页
By using redispersible polymer powder(RPP) and carbon fiber(CF) to adjust the flexibility and electrical properties of the smart aggregate, a new kind of smart aggregate with Z type structure was proposed. The stu... By using redispersible polymer powder(RPP) and carbon fiber(CF) to adjust the flexibility and electrical properties of the smart aggregate, a new kind of smart aggregate with Z type structure was proposed. The study shows that Z type aggregate is more sensitive to the feedback of external force than the prism aggregate in the same loading environment, and it indicates that Z type aggregate is more suitable for the research and application of concrete health monitoring. Although the incorporation of RPP would cause the compressive strength of the aggregates and the elastic modulus of hardened cement mortar to reduce slightly within the dosage of RPP by 2.25% because of the polymer film formed in the internal system, this would improve the deformability of the aggregates. In the early loading stage(in the first 60 seconds), the intelligent concrete specimens implanted with Z type smart aggregate do not show higher sensitivity as expected, although the resistance change rate changes a little bit more, the overall of it is still in balance. Adding RPP could improve the flexibility of smart aggregates exactly, and it plays an active role in prolonging the life of the smart aggregates. By implanting Z type aggregates the damage and failure of the concrete structure could be predicted accurately in this study. The results of this paper will help to promote further research and application of intelligent concrete. 展开更多
关键词 carbon fiber(CF) redispersible polymer powder(RPP) mechanical and electrical properties smart aggregate intelligent concrete
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Effect of Curing Regime on Bonding Strength of EVA Modified Mortar to Tile
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作者 何代华 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2010年第2期346-348,共3页
Ethylene-Vinyl Acetate (EVA) redispersible powder and latex were used to modify mortar. Three kinds of curing regimes: standard curing, high temperature curing and freeze-thaw circle curing were adopted to cure the... Ethylene-Vinyl Acetate (EVA) redispersible powder and latex were used to modify mortar. Three kinds of curing regimes: standard curing, high temperature curing and freeze-thaw circle curing were adopted to cure the bonded samples. Bonding strength of EVA modified mortar was tested at 28 days. The development of bonding strengths under all three curing regimes were discussed and compared. The experimental results show that bonding strength increases with the increase of EVA content in mortar. The curing regime used within 28 days is critical according to the bonding strengths values under three curing regimes for different ages. The reasons of that the EVA can improve the bonding strength were analyzed. 展开更多
关键词 EVA redispersible powder LATEX bonding strength curing regime
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Comprehensive comparison of cellulose nanocrystal (CNC) drying using multi-frequency ultrasonic technology with selected conventional drying technologies
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作者 Junli Liu Amir Malvandi Hao Feng 《Journal of Bioresources and Bioproducts》 EI CSCD 2024年第4期465-485,共21页
Cellulose nanocrystals(CNCs)have garnered increased attention due to their renewable nature,abundant feedstock availbility,and good mechanical properties.However,one of the bottlenecks for its commercial production is... Cellulose nanocrystals(CNCs)have garnered increased attention due to their renewable nature,abundant feedstock availbility,and good mechanical properties.However,one of the bottlenecks for its commercial production is the drying process.Because of the low CNC concentrations in suspension after isolation,CNC drying requires the removal of a large amount of water to obtain dry products for the following utilization and saving shipping costs.A novel multi-frequency,multimode,modulated ultrasonic drying technology was developed for CNC drying to improve product quality,reduce energy consumption,and increase production rate.CNCs dried with dif-ferent drying technologies were characterized by Fourier transform infrared(FT-IR)spectra anal-ysis,X-ray diffraction(XRD)analysis,thermogravimetric analysis(TGA),differential scanning calorimetry(DSC),and redispersibility to measure the quality and property changes.Under the same temperature and airflow rate,ultrasonic drying enhanced drying rates,resulting in at least a 50%reduction in drying time compared to hot air drying.The mean particle sizes of CNC from ultrasonic drying changed little with settling time,indicating good redispersibility.In addition,ultrasonic dried CNCs exhibited good stability in aqueous solutions,with the zeta potentials rang-ing from-35 to-65 mV.Specific energy consumption and CO_(2) emissions of various CNC drying technologies were evaluated.Energy consumption of ultrasonic drying is significantly reduced compared to other drying technologies.Moreover,the potential CO_(2) emissions of the fully elec-trified ultrasonic drying could be net zero if renewable electricity is used. 展开更多
关键词 Cellulose nanocrystals Ultrasound Drying kinetics Drying energy Energy-efficient CO_(2)reduction Redispersibility Carbon sequestration
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Dynamic dispersion stability of graphene oxide with metal ions 被引量:2
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作者 Yinghui He Yingjun Liu +6 位作者 Fan Guo Kai Pang Bo Fang Ya Wang Dan Chang Zhen Xu Chao Gao 《Chinese Chemical Letters》 SCIE CAS CSCD 2020年第6期1625-1629,共5页
Graphene oxide(GO),an important chemical precursor of graphene,can stably disperse in aqueous surrounding and undergo aggregation as metal cations introduced.The usual instability of GO with ions is caused by the shie... Graphene oxide(GO),an important chemical precursor of graphene,can stably disperse in aqueous surrounding and undergo aggregation as metal cations introduced.The usual instability of GO with ions is caused by the shielding effect of ions and crosslinking between GO and ions.However,the dynamic stability of GO under ions exchange still remains unclear.Here,we investigated the dynamic dispersion stability of GO with metal ions and observed a redispersion behavior in concentrated Fe3+solution,other than permanent aggregation.The exchange with Fe3+ions drives the reversion of zeta(ζ)potential and enables the redispersion to individual GO-Fe3+complex sheets,following a dynamic electric double layer(EDL)mechanism.It is found that the specifically strong electrostatic shielding effect and coordination attraction between Fe3+and functional oxygen groups allows the selective redispersion of GO in concentrated Fe3+solution.The revealed dynamic dispersion stability complements our understanding on the dispersive stability of GO and can be utilized to fabricate graphene-metal hybrids for rich applications. 展开更多
关键词 Graphene oxide Metal ions redispersion Ion exchange Electric double layer Electrostatic shielding effect COORDINATION
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Dynamic flowsheet simulation of re-entrainment from particle layers formed inside electrostatic precipitators 被引量:2
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作者 Soren Sander Udo Fritsching 《Particuology》 SCIE EI CAS CSCD 2020年第6期41-47,共7页
Electrostatic precipitators clean away the particulate matter of exhaust gases in manifold industrial processes.Parameter studies of particle separation in the size range of several 100 nm to 25μm is of particular in... Electrostatic precipitators clean away the particulate matter of exhaust gases in manifold industrial processes.Parameter studies of particle separation in the size range of several 100 nm to 25μm is of particular interest for the prediction of precipitation efficiencies and emissions.Models typically cover the transport of particles towards walls of the precipitator.However,no model yet covers the possible re-entrainment of particles from layers formed at the walls back into the gas flow.This study presents the implementation of a new time-resolving model for electrostatic precipitation utilizing a re-entrainment model.Experimental data support the results of modelling.The model uses a statistical approach based on properties of the particulate layer forming at the precipitator walls.The model is used for the analysis of the redispersion of particles in a laboratory-scale electrostatic precipitator(Sander,Gawor,&Fritsching,2018).Results show reduced precipitation efficiencies for particles larger than 5μm as particles have higher kinetic impact energies and lower bounding energy at the layer surface.Time dynamics reveal a steady-state behavior of the separation for CaCO3(limestone,trademark"Ulmer WeissR")while Al2O3(trademark"Pural NFR")precipitation is affected by layer buildup at the walls increasing over several minutes. 展开更多
关键词 Electrostatic precipitator Flow sheet model redispersion and re-entrainment Gas cleaning Particle layer
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Redispersible and stable amorphous calcium phosphate nanoparticles functionalized by an organic bisphosphate 被引量:5
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作者 Rong-Hui Lai Ping-Jiang Dong +1 位作者 Yong-Li Wang Jian-Bin Luo 《Chinese Chemical Letters》 SCIE CAS CSCD 2014年第2期295-298,共4页
Although much effort has been focused on the preparation of stable amorphous calcium phosphate (ACP) nanoparticles in aqueous solution, the redispersibility and long-term stability of ACP nanoparticles in aqueous so... Although much effort has been focused on the preparation of stable amorphous calcium phosphate (ACP) nanoparticles in aqueous solution, the redispersibility and long-term stability of ACP nanoparticles in aqueous solution remains an unresolved problem. In this work, stable colloidal ACPs were prepared by using an organic bisphosphonate (BP) as a sterically hindered agent in aqueous solution. The harvested calcium phosphate nanoparticles were characterized by inductively coupled plasma atomic emission spectrometry (ICP-AES), Fourier transform infrared (FTIR), X-ray diffraction (XRD), dynamic light scattering (DLS) and transmission electron microscopy (TEM). ICP-AES, FTIR and XRD results suggested the particles were ACP. DLS and TEM results indicated that the size of the ACP nanoparticles were in the range of 60 nm with a spherical morphology. The resulting calcium phosphate nanoparticles retained its amorphous nature in aqueous solution for at least 6 months at room temperature due to the stabilizing effect of the organic bisphosphonate. Moreover, the surface of the ACP nanoparticles adsorbed with the organic bisphosphate used showed good redispersibility and high colloid stability both in organic and aqueous solutions. 展开更多
关键词 Amorphous calcium phosphate Bisphosphate NANOPARTICLE Redispersibility Stability
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