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Micro/Nano Materials for Clean Energy and Environment

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

Deadline for manuscript submissions: closed (31 March 2019) | Viewed by 46816

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Special Issue Editors

Prof. Dr. Zhongchao Tan

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Guest Editor

1. Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON, 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, Collections and Topics in MDPI journals

Assoc. Prof. Dr. Qinghai Li

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Guest Editor

1. Director, Tsinghua University-University of Waterloo Joint Research Center for Micro/Nano Energy & Environment Technology, Beijing, China
2. 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 Therefore, through this Special Issue, I am seeking your original, unpublished works that describe recent advances in micro/nano materials in relation to clean energy and the environment.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

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

micro/nanomaterials
energy
environment

Published Papers (11 papers)

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Research

Jump to: Review

20 pages, 2444 KiB

Open AccessArticle

Improved Method for Measuring the Permeability of Nanoporous Material and Its Application to Shale Matrix with Ultra-Low Permeability

by Taojie Lu, Ruina Xu, Bo Zhou, Yichuan Wang, Fuzhen Zhang and Peixue Jiang

Materials 2019, 12(9), 1567; https://doi.org/10.3390/ma12091567 - 13 May 2019

Cited by 18 | Viewed by 3418

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 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

(This article belongs to the Special Issue Micro/Nano Materials for Clean Energy and Environment)

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12 pages, 4182 KiB

Open AccessArticle

Colorimetric Detection of Mercury Ions in Water with Capped Silver Nanoprisms

by Fouzia Tanvir, Atif Yaqub, Shazia Tanvir, Ran An and William A. Anderson

Materials 2019, 12(9), 1533; https://doi.org/10.3390/ma12091533 - 10 May 2019

Cited by 37 | Viewed by 3975

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 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

(This article belongs to the Special Issue Micro/Nano Materials for Clean Energy and Environment)

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17 pages, 3369 KiB

Open AccessArticle

Effects of the Limestone Particle Size on the Sulfation Reactivity at Low SO₂ Concentrations Using a LC-TGA

by Runxia Cai, Yiqun Huang, Yiran Li, Yuxin Wu, Hai Zhang, Man Zhang, Hairui Yang and Junfu Lyu

Materials 2019, 12(9), 1496; https://doi.org/10.3390/ma12091496 - 08 May 2019

Cited by 11 | Viewed by 2759

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 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

(This article belongs to the Special Issue Micro/Nano Materials for Clean Energy and Environment)

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12 pages, 10620 KiB

Open AccessArticle

Numerical Assessment on Rotation Effect of the Stagnation Surface on Nanoparticle Deposition in Flame Synthesis

by Lilin Hu, Zhu Miao, Yang Zhang, Hai Zhang and Hairui Yang

Materials 2019, 12(9), 1361; https://doi.org/10.3390/ma12091361 - 26 Apr 2019

Cited by 3 | Viewed by 2204

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 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

(This article belongs to the Special Issue Micro/Nano Materials for Clean Energy and Environment)

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18 pages, 9855 KiB

Open AccessArticle

A Multiscale Model of Oxidation Kinetics for Cu-Based Oxygen Carrier in Chemical Looping with Oxygen Uncoupling

by Hui Wang, Zhenshan Li and Ningsheng Cai

Materials 2019, 12(7), 1170; https://doi.org/10.3390/ma12071170 - 10 Apr 2019

Cited by 19 | Viewed by 3463

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 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

(This article belongs to the Special Issue Micro/Nano Materials for Clean Energy and Environment)

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13 pages, 23791 KiB

Open AccessArticle

Theoretical Study of As₂O₃ Adsorption Mechanisms on CaO surface

by Yaming Fan, Qiyu Weng, Yuqun Zhuo, Songtao Dong, Pengbo Hu and Duanle Li

Materials 2019, 12(4), 677; https://doi.org/10.3390/ma12040677 - 25 Feb 2019

Cited by 29 | Viewed by 3989

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. 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

(This article belongs to the Special Issue Micro/Nano Materials for Clean Energy and Environment)

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21 pages, 5520 KiB

Open AccessArticle

Study on Adsorption Mechanism and Failure Characteristics of CO₂ Adsorption by Potassium-Based Adsorbents with Different Supports

by Bao-guo Fan, Li Jia, Yan-lin Wang, Rui Zhao, Xue-song Mei, Yan-yan Liu and Yan Jin

Materials 2018, 11(12), 2424; https://doi.org/10.3390/ma11122424 - 30 Nov 2018

Cited by 9 | Viewed by 3769

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 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

(This article belongs to the Special Issue Micro/Nano Materials for Clean Energy and Environment)

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17 pages, 6666 KiB

Open AccessArticle

Dust Loading Performance of a Novel Submicro-Fiber Composite Filter Medium for Engine

by Jin Long, Min Tang, Zhaoxia Sun, Yun Liang and Jian Hu

Materials 2018, 11(10), 2038; https://doi.org/10.3390/ma11102038 - 19 Oct 2018

Cited by 26 | Viewed by 4678

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 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

(This article belongs to the Special Issue Micro/Nano Materials for Clean Energy and Environment)

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16 pages, 4511 KiB

Open AccessArticle

Preparation of Fibrillated Cellulose Nanofiber from Lyocell Fiber and Its Application in Air Filtration

by Jin Long, Min Tang, Yun Liang and Jian Hu

Materials 2018, 11(8), 1313; https://doi.org/10.3390/ma11081313 - 29 Jul 2018

Cited by 20 | Viewed by 6131

Abstract

Ambient particulate matter less than 2.5 μm (PM_2.5) 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 PM_2.5 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

(This article belongs to the Special Issue Micro/Nano Materials for Clean Energy and Environment)

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14 pages, 3004 KiB

Open AccessArticle

Filtration of Sub-3.3 nm Tungsten Oxide Particles Using Nanofibrous Filters

by Raheleh Givehchi, Qinghai Li and Zhongchao Tan

Materials 2018, 11(8), 1277; https://doi.org/10.3390/ma11081277 - 25 Jul 2018

Cited by 6 | Viewed by 3521

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 (WO_x) 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

(This article belongs to the Special Issue Micro/Nano Materials for Clean Energy and Environment)

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Review

Jump to: Research

25 pages, 3218 KiB

Open AccessReview

Phase Change Materials for Energy Efficiency in Buildings and Their Use in Mortars

by Mariaenrica Frigione, Mariateresa Lettieri and Antonella Sarcinella

Materials 2019, 12(8), 1260; https://doi.org/10.3390/ma12081260 - 17 Apr 2019

Cited by 105 | Viewed by 7824

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 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

(This article belongs to the Special Issue Micro/Nano Materials for Clean Energy and Environment)

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