Special Issue "Micro/Nano Materials for Clean Energy and Environment"

A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (31 March 2019).

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Prof. Dr. Zhongchao Tan
E-Mail Website
Guest Editor
1. Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, Ontario, Canada
2. Executive Director, Tsinghua University–University of Waterloo Joint Research Center for Micro/Nano Energy and Environment Technology, Beijing, China
Interests: green energy; air emission control; indoor air quality; aerosol; nanotechnology
Special Issues and Collections in MDPI journals
Assoc. Prof. Dr. Qinghai Li
E-Mail Website
Guest Editor
Director, Tsinghua University-University of Waterloo Joint Research Center for Micro/Nano Energy & Environment Technology, Beijing, China
Department of Energy and Power Engineering, Tsinghua University, Beijing, China
Interests: solar energy utilization; biomass and waste combustion; industrial boiler development

Special Issue Information

Dear Colleagues,

Energy and environment are two interrelated global challenges. Energy resources are depleting while air pollution and greenhouse emissions are deteriorating our only habitat, the planet Earth. New materials are critical to winning the final battle for sustainable living environments and against climate change.  Thanks to countless renowned researchers and engineers all over the world, like you, technologies advance every day. New knowledge has to be synthesized and shared with the international community in a timely and regular way. Therefore, through this Special Issue, I am seeking your original, unpublished works that describe recent advances in micro/nano materials in relation to clean energy and the environment. I extend my warm invitation for research papers from a broad range of topics related to micro/nanostructured materials aiming at future energy resources, low emission energy conversion, energy storage, energy efficiency, air emission control, air monitoring, air cleaning, and many other related applications. High quality manuscripts will be published in the Special Issue after rigorous peer-review. Our team will work hard towards the rapid and wide dissemination of your valuable research results, recent developments, and novel applications in the area of the materials, energy and environment.

This Special Issue is dedicated to the first anniversary of the Tsinghua University–University of Waterloo Joint Research Center for Micro/Nano Energy and Environment Technology. (https://uwaterloo.ca/jcmeet). Full papers, communications, and reviews are all welcome. I look forward to receiving your work.

Prof. Dr. Zhongchao Tan
Assoc. Prof. Dr. Qinghai Li
Guest Editor

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Keywords

  • micro/nanomaterials
  • energy
  • environment

Published Papers (11 papers)

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Research

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Open AccessArticle
Improved Method for Measuring the Permeability of Nanoporous Material and Its Application to Shale Matrix with Ultra-Low Permeability
Materials 2019, 12(9), 1567; https://doi.org/10.3390/ma12091567 - 13 May 2019
Cited by 1
Abstract
Nanoporous materials have a wide range of applications in clean energy and environmental research. The permeability of nanoporous materials is low, which affects the fluid transport behavior inside the nanopores and thus also affects the performance of technologies based on such materials. For [...] Read more.
Nanoporous materials have a wide range of applications in clean energy and environmental research. The permeability of nanoporous materials is low, which affects the fluid transport behavior inside the nanopores and thus also affects the performance of technologies based on such materials. For example, during the development of shale gas resources, the permeability of the shale matrix is normally lower than 10−3 mD and has an important influence on rock parameters. It is challenging to measure small pressure changes accurately under high pressure. Although the pressure decay method provides an effective means for the measurement of low permeability, most apparatuses and experiments have difficulty measuring permeability in high pressure conditions over 1.38 MPa. Here, we propose an improved experimental method for the measurement of low permeability. To overcome the challenge of measuring small changes in pressure at high pressure, a pressure difference sensor is used. By improving the constant temperature accuracy and reducing the helium leakage rate, we measure shale matrix permeabilities ranging from 0.05 to 2 nD at pore pressures of up to 8 MPa, with good repeatability and sample mass irrelevance. The results show that porosity, pore pressure, and moisture conditions influence the matrix permeability. The permeability of moist shale is lower than that of dry shale, since water blocks some of the nanopores. Full article
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Open AccessArticle
Colorimetric Detection of Mercury Ions in Water with Capped Silver Nanoprisms
Materials 2019, 12(9), 1533; https://doi.org/10.3390/ma12091533 - 10 May 2019
Cited by 2
Abstract
The emission of mercury (II) from coal combustion and other industrial processes may have impacts on water resources, and the detection with sensitive but rapid testing methods is desirable for environmental screening. Towards this end, silver nanoprisms were chemically synthesized resulting in a [...] Read more.
The emission of mercury (II) from coal combustion and other industrial processes may have impacts on water resources, and the detection with sensitive but rapid testing methods is desirable for environmental screening. Towards this end, silver nanoprisms were chemically synthesized resulting in a blue reagent solution that transitioned towards red and yellow solutions when exposed to Hg2+ ions at concentrations from 0.5 to 100 µM. A galvanic reduction of Hg2+ onto the surfaces is apparently responsible for a change in nanoprism shape towards spherical nanoparticles, leading to the change in solution color. There were no interferences by other tested mono- and divalent metal cations in solution and pH had minimal influence in the range of 6.5 to 9.8. The silver nanoprism reagent provided a detection limit of approximately 1.5 µM (300 µg/L) for mercury (II), which compared reasonably well with other reported nanoparticle-based techniques. Further optimization may reduce this detection limit, but matrix effects in realistic water samples require further investigation and amelioration. Full article
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Open AccessArticle
Effects of the Limestone Particle Size on the Sulfation Reactivity at Low SO2 Concentrations Using a LC-TGA
Materials 2019, 12(9), 1496; https://doi.org/10.3390/ma12091496 - 08 May 2019
Cited by 1
Abstract
Limestone particle size has a crucial influence on SO2 capture efficiency, however there are few studies on the sulfation reactivity, which covers a broad range of particle sizes at low SO2 concentrations. In this paper, a large-capacity thermogravimetric analyzer (LC-TGA) was [...] Read more.
Limestone particle size has a crucial influence on SO2 capture efficiency, however there are few studies on the sulfation reactivity, which covers a broad range of particle sizes at low SO2 concentrations. In this paper, a large-capacity thermogravimetric analyzer (LC-TGA) was developed to obtain the sulfur removal reaction rate under a wide range of particle sizes (3 μm–600 μm) and SO2 concentrations (250 ppm–2000 ppm), and then compared with the results of a traditional fixed bed reactor and a commercial TGA. The experimental results showed that the LC-TGA can well eliminate the external mass transfer and obtain a better measurement performance. Both the final conversion and the reaction rate reduced with the decreasing of SO2 concentration, but ultrafine limestone particles still showed the good sulfation reactivity even at 250 ppm SO2. An empirical sulfation model was established based on the experimental results, which can well predict the sulfation process of different limestone particle sizes at low SO2 concentrations. The model parameters have a strong negative correlation against the particle size, and the fit of the reaction order of SO2 was found to be about 0.6. The model form is very simple to incorporate it into available fluidized bed combustion models to predict SO2 emission. Full article
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Open AccessArticle
Numerical Assessment on Rotation Effect of the Stagnation Surface on Nanoparticle Deposition in Flame Synthesis
Materials 2019, 12(9), 1361; https://doi.org/10.3390/ma12091361 - 26 Apr 2019
Abstract
The effect of rotation of the stagnation surface on the nanoparticle deposition in the flame stabilizing on a rotating surface (FSRS) configuration was numerically assessed using CFD method. The deposition properties including particle trajectories, deposition time, temperature and surrounding O2 concentration between [...] Read more.
The effect of rotation of the stagnation surface on the nanoparticle deposition in the flame stabilizing on a rotating surface (FSRS) configuration was numerically assessed using CFD method. The deposition properties including particle trajectories, deposition time, temperature and surrounding O2 concentration between the flame and stagnation surface were examined. The results revealed that although flame position is insensitive to the surface rotation, the temperature and velocity fields are remarkably affected, and the deposition properties become asymmetric along the burner centerline when the surface rotates at a fast speed (rotational speed ω ≥ 300 rpm). Particles moving on the windward side have similar deposition properties when the surface rotates slowly, but the off-center particles on the leeward side have remarkable longer deposition time, lower deposition temperature, and lower surrounding O2 concentration, and they even never deposit on the surface when the surface rotates at a high speed. The rotation effect of the stagnation surface can be quantitatively described by an analogous Karlovitz number (Ka’), which is defined as the ratio of characteristic residence time of moving surface to the aerodynamics time induced by flame stretch. For high quality semiconducting metal oxide (SMO) films, it is suggested that Ka’ ≥ 1 should be kept. Full article
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Open AccessArticle
A Multiscale Model of Oxidation Kinetics for Cu-Based Oxygen Carrier in Chemical Looping with Oxygen Uncoupling
Materials 2019, 12(7), 1170; https://doi.org/10.3390/ma12071170 - 10 Apr 2019
Cited by 1
Abstract
Copper oxide is one of the promising oxygen carrier materials in chemical looping with oxygen uncoupling (CLOU) technology, cycling between Cu2O and CuO. In this study, a multiscale model was developed to describe the oxidation kinetics of the Cu-based oxygen carrier [...] Read more.
Copper oxide is one of the promising oxygen carrier materials in chemical looping with oxygen uncoupling (CLOU) technology, cycling between Cu2O and CuO. In this study, a multiscale model was developed to describe the oxidation kinetics of the Cu-based oxygen carrier particle with oxygen, including surface, grain, and particle scale. It was considered that the solid product grows with the morphology of disperse islands on the grain surface, and O2 contacts with two different kinds of grain surfaces in the grain scale model, that is, Cu2O surface (solid reactant surface) and CuO surface (solid product surface). The two-stage behavior of the oxidation reaction of the Cu-based oxygen carrier was predicted successfully using the developed model, and the model results showed good agreement with experimental data in the literature. The effects of oxygen partial pressure, temperature, and particle structure on the oxidation performance were analyzed. The modeling results indicated that the transition of the conversion curve occurs when product islands cover most part of the grain surface. The oxygen partial pressure and particle structure have an obvious influence on the duration time of the fast reaction stage. Furthermore, the influence of the external mass transfer and the change of effectiveness factor during the oxidation reaction process were discussed to investigate the controlling step of the reaction. It was concluded that the external mass transfer step hardly affects the reaction performance under the particle sizes normally used in CLOU. The value of the effectiveness factor increases as the reaction goes by, which means the chemical reaction resistance at grain scale increases resulting from the growing number of product islands on the grain surface. Full article
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Open AccessArticle
Theoretical Study of As2O3 Adsorption Mechanisms on CaO surface
Materials 2019, 12(4), 677; https://doi.org/10.3390/ma12040677 - 25 Feb 2019
Cited by 2
Abstract
Emission of hazardous trace elements, especially arsenic from fossil fuel combustion, have become a major concern. Under an oxidizing atmosphere, most of the arsenic converts to gaseous As2O3. CaO has been proven effective in capturing As2O3 [...] Read more.
Emission of hazardous trace elements, especially arsenic from fossil fuel combustion, have become a major concern. Under an oxidizing atmosphere, most of the arsenic converts to gaseous As2O3. CaO has been proven effective in capturing As2O3. In this study, the mechanisms of As2O3 adsorption on CaO surface under O2 atmosphere were investigated by density functional theory (DFT) calculation. Stable physisorption and chemisorption structures and related reaction paths are determined; arsenite (AsO33−) is proven to be the form of adsorption products. Under the O2 atmosphere, the adsorption product is arsenate (AsO43−), while tricalcium orthoarsenate (Ca3As2O8) and dicalcium pyroarsenate (Ca2As2O7) are formed according to different adsorption structures. Full article
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Open AccessArticle
Study on Adsorption Mechanism and Failure Characteristics of CO2 Adsorption by Potassium-Based Adsorbents with Different Supports
Materials 2018, 11(12), 2424; https://doi.org/10.3390/ma11122424 - 30 Nov 2018
Cited by 1
Abstract
In order to obtain the adsorption mechanism and failure characteristics of CO2 adsorption by potassium-based adsorbents with different supports, five types of supports (circulating fluidized bed boiler fly ash, pulverized coal boiler fly ash, activated carbon, molecular sieve, and alumina) and three [...] Read more.
In order to obtain the adsorption mechanism and failure characteristics of CO2 adsorption by potassium-based adsorbents with different supports, five types of supports (circulating fluidized bed boiler fly ash, pulverized coal boiler fly ash, activated carbon, molecular sieve, and alumina) and three kinds of adsorbents under the modified conditions of K2CO3 theoretical loading (10%, 30%, and 50%) were studied. The effect of the reaction temperature (50 °C, 60 °C, 70 °C, 80 °C, and 90 °C) and CO2 concentration (5%, 7.5%, 10%, 12.5%, and 15%) on the adsorption of CO2 by the adsorbent after loading and the effect of flue gas composition on the failure characteristics of adsorbents were obtained. At the same time, the microscopic characteristics of the adsorbents before and after loading and the reaction were studied by using a specific surface area and porosity analyzer as well as a scanning electron microscope and X-ray diffractometer. Combining its reaction and adsorption kinetics process, the mechanism of influence was explored. The results show that the optimal theoretical loading of the five adsorbents is 30% and the reaction temperature of 70 °C and the concentration of 12.5% CO2 are the best reaction conditions. The actual loading and CO2 adsorption performance of the K2CO3/AC adsorbent are the best while the K2CO3/Al2O3 adsorbent is the worst. During the carbonation reaction of the adsorbent, the cumulative pore volume plays a more important role in the adsorption process than the specific surface area. As the reaction temperature increases, the internal diffusion resistance increases remarkably. K2CO3/AC has the lowest activation energy and the carbonation reaction is the easiest to carry out. SO2 and HCl react with K2CO3 to produce new substances, which leads to the gradual failure of the adsorbents and K2CO3/AC has the best cycle failure performance. Full article
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Open AccessArticle
Dust Loading Performance of a Novel Submicro-Fiber Composite Filter Medium for Engine
Materials 2018, 11(10), 2038; https://doi.org/10.3390/ma11102038 - 19 Oct 2018
Cited by 1
Abstract
Airborne dust can cause engine wear and contribute to engine gas emission. This study developed a novel submicro-fiber filter medium to provide protection to engines against dust. The wet-laid submicro-fiber medium was prepared by a dual-layer paper machine, and its dust loading performance [...] Read more.
Airborne dust can cause engine wear and contribute to engine gas emission. This study developed a novel submicro-fiber filter medium to provide protection to engines against dust. The wet-laid submicro-fiber medium was prepared by a dual-layer paper machine, and its dust loading performance was compared with other filter media during laboratory and field tests. During the laboratory tests, the dust holding capacity of the wet-laid submicro-fiber medium was 48% and 10% higher than that of the standard heavy-duty medium and electrospun submicro-fiber medium, respectively. During the field tests, the pressure drop of the wet-laid submicro-fiber filter was 45% lower than that of the standard heavy-duty filter after 10,000 km of operation. It was found that there were two crucial ways to design a better filter medium for protection against dust. Firstly, the surface loading rather than the depth loading was preferred for dust filtration. The submicro-fiber layer kept large amounts of dust particles from penetrating into the depth of filter medium. Secondly, particles were captured preferably by fibers rather than pores. The unique fibrous structure of the wet-laid submicro-fiber medium made more particle deposition take place on fibers via interception and inertial impaction. Full article
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Open AccessArticle
Preparation of Fibrillated Cellulose Nanofiber from Lyocell Fiber and Its Application in Air Filtration
Materials 2018, 11(8), 1313; https://doi.org/10.3390/ma11081313 - 29 Jul 2018
Cited by 2
Abstract
Ambient particulate matter less than 2.5 μm (PM2.5) can substantially degrade the performance of cars by clogging the air intake filters. The application of nanofibers in air filter paper can achieve dramatic improvement of filtration efficiency with low resistance to air [...] Read more.
Ambient particulate matter less than 2.5 μm (PM2.5) can substantially degrade the performance of cars by clogging the air intake filters. The application of nanofibers in air filter paper can achieve dramatic improvement of filtration efficiency with low resistance to air flow. Cellulose nanofibers have gained increasing attention because of their biodegradability and renewability. In this work, the cellulose nanofiber was prepared by Lyocell fiber nanofibrillation via a PFI-type refiner, and the influence of applying a cellulose nanofiber on filter paper was investigated. It was found that the cellulose nanofibers obtained under 1.00 N/mm and 40,000 revolutions were mainly macrofibrils of Lyocell fiber with average fiber diameter of 0.8 µm. For the filter papers with a different nanofiber fraction, both the pressure drop and fractional efficiency increased with the higher fraction of nanofibers. The results of the figure of merit demonstrated that for particles larger than 0.05 µm, the figure of merit increased substantially with a 5% nanofiber, but decreased when the nanofiber fraction reached 10% and higher. It was concluded that the optimal fraction of the cellulose nanofiber against PM2.5 was 5%. The results of the figure of merit were related to the inhomogeneous distribution of nanofibers in the fibrous structure. The discrepancy of the theoretical and measured pressure drop showed that a higher nanofiber fraction led to a higher degree of fiber inhomogeneity. Full article
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Open AccessArticle
Filtration of Sub-3.3 nm Tungsten Oxide Particles Using Nanofibrous Filters
Materials 2018, 11(8), 1277; https://doi.org/10.3390/ma11081277 - 25 Jul 2018
Cited by 1
Abstract
This work aims to understand the effects of particle concentration on the filtration of nanoparticles using nanofibrous filters. The filtration efficiencies of triple modal tungsten oxide (WOx) nanoparticles were experimentally determined at three different concentrations for the size range of 0.82–3.3 [...] Read more.
This work aims to understand the effects of particle concentration on the filtration of nanoparticles using nanofibrous filters. The filtration efficiencies of triple modal tungsten oxide (WOx) nanoparticles were experimentally determined at three different concentrations for the size range of 0.82–3.3 nm in diameter. All tests were conducted using polyvinyl alcohol (PVA) nano-fibrous filters at an air relative humidity of 2.9%. Results showed that the filtration efficiencies of sub-3.3 nm nanoparticles depended on the upstream particle concentration. The lower the particle concentration was, the higher the filtration efficiency was. Full article
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Review

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Open AccessReview
Phase Change Materials for Energy Efficiency in Buildings and Their Use in Mortars
Materials 2019, 12(8), 1260; https://doi.org/10.3390/ma12081260 - 17 Apr 2019
Cited by 4
Abstract
The construction industry is responsible for consuming large amounts of energy. The development of new materials with the purpose of increasing the thermal efficiency of buildings is, therefore, becoming, imperative. Thus, during the last decades, integration of Phase Change Materials (PCMs) into buildings [...] Read more.
The construction industry is responsible for consuming large amounts of energy. The development of new materials with the purpose of increasing the thermal efficiency of buildings is, therefore, becoming, imperative. Thus, during the last decades, integration of Phase Change Materials (PCMs) into buildings has gained interest. Such materials can reduce the temperature variations, leading to an improvement in human comfort and decreasing at the same time the energy consumption of buildings, due to their capability to absorb and release energy from/in the environment. In the present paper, recent experimental studies dealing with mortars or concrete-containing PCMs, used as passive building systems, have been examined. This review is mainly aimed at providing information on the currently investigated materials and the employed methodologies for their manufacture, as well as at summarizing the results achieved so far on this subject. Full article
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