| 1. |
|
|
| 2. |
- Chen, Shujing, et al.
(author)
-
Manufacturing Graphene-Encapsulated Copper Particles by Chemical Vapor Deposition in a Cold Wall Reactor
- 2019
-
In: ChemistryOpen. - : Wiley. - 2191-1363. ; 8:1, s. 58-63
-
Journal article (peer-reviewed)abstract
- Functional fillers, such as Ag, are commonly employed for effectively improving the thermal or electrical conductivity in polymer composites. However, a disadvantage of such a strategy is that the cost and performance cannot be balanced simultaneously. Therefore, the drive to find a material with both a cost efficient fabrication process and excellent performance attracts intense research interest. In this work, inspired by the core-shell structure, we developed a facile manufacturing method to prepare graphene-encapsulated Cu nanoparticles (GCPs) through utilizing an improved chemical vapor deposition (CVD) system with a cold wall reactor. The obtained GCPs could retain their spherical shape and exhibited an outstanding thermal stability up to 179 degrees C. Owing to the superior thermal conductivity of graphene and excellent oxidation resistance of GCPs, the produced GCPs are practically used in a thermally conductive adhesive (TCA), which commonly consists of Ag as the functional filler. Measurement shows a substantial 74.6 % improvement by partial replacement of Ag with GCPs.
|
|
| 3. |
- Dai, Zhengxing, et al.
(author)
-
Prediction and verification of heat capacities for pure ionic liquids
- 2021
-
In: Chinese Journal of Chemical Engineering. - : Elsevier. - 1004-9541 .- 2210-321X. ; 31, s. 169-176
-
Journal article (peer-reviewed)abstract
- The heat capacity of ionic liquids is an important physical property, and experimental measuring is usually used as a common method to obtain them. Owing to the huge number of ionic liquids that can be potentially synthesized, it is desirable to acquire theoretical predictions. In this work, the Conductor-like Screening Model for Real Solvents (COSMO-RS) was used to predict the heat capacity of pure ionic liquids, and an intensive literature survey was conducted for providing a database to verify the prediction of COSMO-RS. The survey shows that the heat capacity is available for 117 ionic liquids at temperatures ranging 77.66-520 K since 2004, and the 4025 data points in total with the values from 76.37 to 1484 J·mol-1·K-1 have been reported. The prediction of heat capacity with COSMO-RS can only be conducted at two temperatures (298 and 323 K). The comparison with the experimental data proves the prediction reliability of COSMO-RS, and the average relative deviation (ARD) is 8.54%. Based on the predictions at two temperatures, a linear equation was obtained for each ionic liquid, and the heat capacities at other temperatures were then estimated via interpolation and extrapolation. The acquired heat capacities at other temperatures were then compared with the experimental data, and the ARD is only 9.50%. This evidences that the heat capacity of a pure ionic liquid follows a linear equation within the temperature range of study, and COSMO-RS can be used to predict the heat capacity of ionic liquids reliably.
|
|
| 4. |
- Zhang, Maomao, et al.
(author)
-
Effect of pressure during graphitization on mechanical properties of graphene films
- 2019
-
In: 2019 20th International Conference on Electronic Packaging Technology, ICEPT 2019.
-
Conference paper (peer-reviewed)abstract
- Graphene films (GFs) can be used in the field of electronics cooling, owing to many outstanding properties. In the present paper, GFs samples were graphitized at different pressures to study their effect on the mechanical properties. The elastic modulus and hardness of GFs were measured by nanoindentation and the tensile strength of GFs were obtained by stretching GFs in a tensile tester. Meanwhile, GFs were characterized by X-ray diffraction(XRD), Scanning electron microscopy (SEM) and Raman spectroscopy. The results show that the modulus, hardness and tensile strength of GFs were strongly influenced by the defect and wrinkles among other things.
|
|
| 5. |
- Chen, Jun, et al.
(author)
-
Collaborative validation of GlobeLand30 : Methodology and practices
- 2021
-
In: GEO-SPATIAL INFORMATION SCIENCE. - : TAYLOR & FRANCIS LTD. - 1009-5020 .- 1993-5153. ; 24:1, s. 134-144
-
Journal article (peer-reviewed)abstract
- 30-m Global Land Cover (GLC) data products permit the detection of land cover changes at the scale of most human land activities, and are therefore used as fundamental information for sustainable development, environmental change studies, and many other societal benefit areas. In the past few years, increasing efforts have been devoted to the accuracy assessment of GlobeLand30 and other finer-resolution GLC data products. However, most of them were conducted either within a limited percentage of map sheets selected from a global scale or in some individual countries (areas), and there are still many areas where the uncertainty of 30-m resolution GLC data products remains to be validated and documented. In order to promote a comprehensive and collaborative validation of 30-m GLC data products, the GEO Global Land Cover Community Activity had organized a project from 2015 to 2017, to examine and explore its major problems, including the lack of international agreed validation guidelines and on-line tools for facilitating collaborative validation activities. With the joint effort of experts and users from 30 GEO member countries or participating organizations, a technical specification for 30-m GLC validation was developed based on the findings and experiences. An on-line validation tool, GLCVal, was developed by integrating land cover validation procedures with the service computing technologies. About 20 countries (regions) have completed the accuracy assessment of GlobeLand30 for their territories with the guidance of the technical specification and the support of GLCVal.
|
|
| 6. |
- Chen, Jingjing, et al.
(author)
-
Designing heat exchanger for enhancing heat transfer of slurries in biogas plants
- 2019
-
In: Innovative Solutions for Energy Transitions. - : Elsevier. ; , s. 1288-1293
-
Conference paper (peer-reviewed)abstract
- Heat transfer geometries with enhanced performance for the slurries with high viscosity can improve the net raw biogas production in bio-methane process. In this study, the rheological properties of different slurries were tested, correlated and implemented to computational fluid dynamics (CFD). CFD was then used to screen a new geometry based on the twisted tube combined with mechanism study, and experimental testing was conducted for verification. It shows that the twisted hexagonal tube (THT) has the highest performance. The mechanism for enhancing the heat transfer with THT was mainly due to the effective shear rate. Furthermore, the waste-heat recovery with the THT heat exchanger in biogas production was estimated quantitatively and compared with the normal heat exchanger and scraped-surface heat exchanger (SSHE). Compared to the normal heat exchanger, for THT, the increase of net raw biogas production δNRBP can be up to 17%, while it is only up to 8.53% for SSHE. Besides, the external heating up processes with THT and normal heat exchanger were studied to estimate the heating time for different temperature fluctuations and power requirements of boiler. It is found that the process with THT can save 25-38% heating time for the anaerobic reactor compared to the normal heat exchanger. Therefore, designed THT heat exchanger is promising, and the developed methods can also be beneficial for studying other heat transfer processes.
|
|
| 7. |
- Chen, Yifeng, et al.
(author)
-
Thermodynamic Study for Gas Absorption in Choline-2-pyrrolidine-carboxylic Acid + Polyethylene Glycol
- 2016
-
In: Journal of Chemical and Engineering Data. - : American Chemical Society (ACS). - 0021-9568 .- 1520-5134. ; 61:10, s. 3428-3437
-
Journal article (peer-reviewed)abstract
- The solubility of pure CO2, CH4, and N2 in the mixture of choline-2-pyrrolidine carboxylic acid ([Cho][Pro]) and polyethylene glycol (PEG200) (mass ratio = 1:2) was measured experimentally at temperatures from 308.15 to 338.15 K and pressures up to 28 bar, in which [Cho][Pro] is an ionic liquid and PEG200 is a cosolvent with the purpose to decrease the viscosity. It was found that [Cho][Pro]/PEG200 showed a good selectivity for CO2/CH4 and CO2/N2 separation. The measured experimental data points from this work and others were further used to estimate the thermodynamic properties including the Henry's law constants for the gases in [Cho][Pro]/PEG200, the equilibrium constant for the reaction between CO2 and [Cho][Pro], the CO2 absorption enthalpy in [Cho][Pro]/PEG200, and so forth. The consistent results of the CO2 absorption enthalpy at infinite dilution prove the reliability of the thermodynamic properties obtained in this work. The thermodynamic properties of [Cho][Pro]/PEG200 were further compared with other three typical absorbents, and the absorption enthalpy is nearly half of that for 30 wt % MEA aqueous solution. At the same time, the theoretical amount of absorbents needed for [Cho][Pro]/PEG200 is much lower than that of H2O scrubbing. This shows that [Cho][Pro]/PEG200 is a promising absorbent
|
|
| 8. |
- Fan, Tengteng, et al.
(author)
-
CO2/N2 separation using supported ionic liquid membranes with green and cost-effective [Choline][Pro]/PEG200 mixtures
- 2016
-
In: Chinese Journal of Chemical Engineering. - : Elsevier BV. - 1004-9541 .- 2210-321X. ; 24:11, s. 1513-1521
-
Journal article (peer-reviewed)abstract
- The high price and toxicity of ionic liquids (ILs) have limited the design and application of supported ionic liquid membranes (SILMs) for CO2 separation in both academic and industrial fields. In this work, [Choline][Pro]/polyethylene glycol 200 (PEG200) mixtures were selected to prepare novel SILMs because of their green and cost-effective characterization, and the CO2/N2 separation with the prepared SILMs was investigated experimentally at temperatures from 308.15 to 343.15 K. The temperature effect on the permeability, solubility and diffusivity of CO2 was modeled with the Arrhenius equation. A competitive performance of the prepared SILMs was observed with high CO2 permeability ranged in 343.3-1798.6 barrer and high CO2/N2 selectivity from 7.9 to 34.8. It was also found that the CO2 permeability increased 3 times by decreasing the viscosity of liquids from 370 to 38 mPa·s. In addition, the inherent mechanism behind the significant permeability enhancement was revealed based on the diffusion-reaction theory, i.e. with the addition of PEG200, the overall resistance was substantially decreased and the SILMs process was switched from diffusion-control to reaction-control.
|
|
| 9. |
- He, Hanbing, et al.
(author)
-
Kinetics for Preparation of K2Ti2O5 Using TiO2 Microparticles and Nanoparticles as Precursors
- 2014
-
In: Chinese Journal of Chemical Engineering. - : Elsevier BV. - 1004-9541 .- 2210-321X. ; 22:10, s. 1105-1110
-
Journal article (peer-reviewed)abstract
- The formation mechanism of K2Ti2O5 was investigated with TiO2 microparticles and nanoparticles as precursors by thermogravimetric (TG) technique. A method of direct multivariate non-linear regression was applied for simultaneous calculation of solid-state reaction kinetic parameters from TG curves. TG results show more regular decrease from initial reaction temperature with TiO2 nanoparticles as raw material compared with TiO2 microparticles, while mass losses finish at similar temperatures under the experimental conditions. From the mechanism and kinetic parameters, the reactions with the two materials are complex consecutive processes, and reaction rate constants increase with temperature and decrease with conversion. The reaction proceedings could be significantly hindered when the diffusion process of reactant species becomes rate-limiting in the later stage of reaction process. The reaction active sites on initial TiO2 particles and formation of product layers may be responsible to the changes of reaction rate constant. The calculated results are in good agreement with experimental ones.
|
|
| 10. |
- He, Ming, et al.
(author)
-
A controllable approach for the synthesis of titanate derivatives of potassium tetratitanate fiber
- 2004
-
In: Journal of Materials Science. - 0022-2461 .- 1573-4803. ; 39, s. 3745-3750
-
Journal article (peer-reviewed)abstract
- Three types titanate derivatives, K2Ti6O13 fiber, K2Ti8O17 fiber and anatase TiO2 fiber, were synthesized by ion-exchange reaction from potassium tetratitanate fiber (K2Ti4O9) based on the hydrate conditions predicted by a thermodynamic model. These products were formed by a heat treatment of the corresponding hydrate intermediates K1.33H0.67Ti4O9·H2O, KHTi4O9·0.5H2O and H2Ti4O9·1.2H2O which were quantitatively obtained by controlling the pH value and the equilibrium concentration of potassium ion. The mole ratio of Ti/K in solid phase (R) of the target products was taken as the controlling aim in the hydrate process. The temperature for heat treatment of hydrate intermediates was determined by thermogravimetry (TG) and differential scanning calorimetry (DSC). All products retained fibrous morphology similar to that of K2Ti4O9 used as the starting material.
|
|
