Research

10 pages, 3284 KiB

Open AccessArticle

Effect of Filler Alignment on Piezo-Resistive and Mechanical Properties of Carbon Nanotube Composites

by Hyunwoo Kim, Soon-Kook Hong, Jae-Kwan Ryu and Sung-Hoon Park

Materials 2020, 13(11), 2598; https://doi.org/10.3390/ma13112598 - 07 Jun 2020

Cited by 13 | Viewed by 2912

Highly aligned multi-walled carbon nanotube (MWCNT) polymer composites were fabricated via a roll-to-roll milling process; the alignment of the MWCNTs could be controlled by varying the speed of the rotating rolls. The effect of MWCNT alignment on the polymer matrix was morphologically observed [...] Read more.

Highly aligned multi-walled carbon nanotube (MWCNT) polymer composites were fabricated via a roll-to-roll milling process; the alignment of the MWCNTs could be controlled by varying the speed of the rotating rolls. The effect of MWCNT alignment on the polymer matrix was morphologically observed and quantitatively characterized using polarized Raman spectroscopy. To provide a more detailed comparison, MWCNT composites with alignment in the transverse direction and random alignment were fabricated and tested. Enhanced mechanical and electrical properties were obtained for the aligned MWCNT composite, which can be attributed to the efficient electrical network and load transfer, respectively. In addition, a cyclic stretching test was conducted to evaluate the piezo-resistive characteristics of the aligned MWCNT composites. The composites with an aligned filler configuration showed an exceptionally high degree of strain sensitivity compared to the other composites. Full article

(This article belongs to the Special Issue Advanced Materials for Energy and Environmental Applications)

► Show Figures

Figure 1

11 pages, 2895 KiB

Open AccessArticle

Strain-Sensing Properties of Multi-Walled Carbon Nanotube/Polydimethylsiloxane Composites with Different Aspect Ratio and Filler Contents

by Oh-Nyoung Hur, Ji-Hwan Ha and Sung-Hoon Park

Materials 2020, 13(11), 2431; https://doi.org/10.3390/ma13112431 - 26 May 2020

Cited by 32 | Viewed by 2752

Abstract

For filler composite systems used in strain sensor applications, piezoresistive effect, strain hysteresis, and repeatability are critical factors, which have to be clearly evaluated and understood. To investigate the effects of the aspect ratio and content of a multi-walled carbon nanotube (MWCNT) on [...] Read more.

For filler composite systems used in strain sensor applications, piezoresistive effect, strain hysteresis, and repeatability are critical factors, which have to be clearly evaluated and understood. To investigate the effects of the aspect ratio and content of a multi-walled carbon nanotube (MWCNT) on the strain sensor properties of the composite, MWCNT/Polydimethylsiloxane (PDMS) composites with varying filler contents and aspect ratios were fabricated. In order to uniformly disperse MWCNTs on the polymer matrix, we used a three-roll milling method to generate high shear force for de-bundling MWCNTs. Mechanical and electrical properties of the MWCNT composites were evaluated for each case. In addition, through the cyclic stretching test, we optimized the strain-sensing properties of the MWCNT composites by considering their piezoresistive effects and strain hysteresis. Full article

(This article belongs to the Special Issue Advanced Materials for Energy and Environmental Applications)

► Show Figures

Figure 1

14 pages, 2323 KiB

Open AccessArticle

Numerical Characterization for Electrical Conductivity of Two-Dimensional Nanocomposite Systems with Conducting Fiber Fillers

by Jungmin Lee, Yesol Yun, Sang Hyun Lee and Jinyoung Hwang

Materials 2020, 13(10), 2410; https://doi.org/10.3390/ma13102410 - 24 May 2020

Cited by 2 | Viewed by 1996

Abstract

Hybrid nanotube composite systems with two different types of fillers attract considerable attention in several applications. The incorporation of secondary fillers exhibits conflicting behaviors of the electrical conductivity, which either increases or decreases according to the dimension of secondary fillers. This paper addresses [...] Read more.

Hybrid nanotube composite systems with two different types of fillers attract considerable attention in several applications. The incorporation of secondary fillers exhibits conflicting behaviors of the electrical conductivity, which either increases or decreases according to the dimension of secondary fillers. This paper addresses quantitative models to predict the electrical performance in the configuration of two dimensional systems with one-dimensional secondary fillers. To characterize these properties, Monte Carlo simulations are conducted for percolating networks with a realistic model with the consideration of the resistance of conducting NWs, which conventional computational approaches mostly lack from the common assumption of zero-resistance or perfect conducting NWs. The simulation results with nonperfect conductor NWs are compared with the previous results of perfect conductors. The variation of the electrical conductivity reduces with the consideration of the resistance as compared to the cases with perfect conducting fillers, where the overall electrical conductivity solely originates from the contact resistance caused by tunneling effects between NWs. In addition, it is observed that the resistance associated with the case of invariant conductivity with respect to the dimension of the secondary fillers increases, resulting in the need for secondary fillers with the increased scale to achieve the same electrical performance. The results offer useful design guidelines for the use of a two-dimensional percolation network for flexible conducting electrodes. Full article

(This article belongs to the Special Issue Advanced Materials for Energy and Environmental Applications)

► Show Figures

Figure 1

12 pages, 3630 KiB

Open AccessArticle

Properties of Iron Bacteria Biofouling on Ni-P-rGO Coating under Flowing Conditions

by Mingyang Sun, Zhiming Xu, Zuodong Liu, Bingbing Wang and Huishuang Di

Materials 2020, 13(3), 764; https://doi.org/10.3390/ma13030764 - 07 Feb 2020

Cited by 2 | Viewed by 1950

Abstract

Biofouling on heat exchange devices can decrease heat transfer efficiency, corrode materials, and even lead safety accidents. Most heat exchange devices are made of carbon steel, which produces biofouling easily. In this paper, nickel-phosphorus-reduced graphene oxide (Ni-P-rGO) coating was prepared on carbon steel [...] Read more.

Biofouling on heat exchange devices can decrease heat transfer efficiency, corrode materials, and even lead safety accidents. Most heat exchange devices are made of carbon steel, which produces biofouling easily. In this paper, nickel-phosphorus-reduced graphene oxide (Ni-P-rGO) coating was prepared on carbon steel by electroless plating as a kind of advanced material to study the properties of iron bacteria biofouling under flowing conditions. The coating was analyzed via scanning electron microscopy and Raman spectroscopy. The properties of iron bacteria biofouling on carbon steel and Ni-P-rGO coating were then compared under flowing conditions. Compared with carbon steel, the asymptotic value of fouling resistance on the Ni-P-rGO coating significantly decreased. Additionally, the induction period and the time of reaching the asymptotic value greatly increased. The inhibition properties of biofouling of advanced materials Ni-P-rGO coating under different temperatures, flow velocities, and initial concentrations was also studied. Full article

(This article belongs to the Special Issue Advanced Materials for Energy and Environmental Applications)

► Show Figures

Graphical abstract

23 pages, 11942 KiB

Open AccessArticle

Effect of Residual CaSO₄ in Clinker on Properties of High Belite Sulfoaluminate Cement Based on Solid Wastes

by Dunlei Su, Qiuyi Li, Yuanxin Guo, Gongbing Yue and Liang Wang

Materials 2020, 13(2), 429; https://doi.org/10.3390/ma13020429 - 16 Jan 2020

Cited by 8 | Viewed by 2348

Abstract

The high belite sulfoaluminate cement (HBSAC) containing CaSO₄, and without CaSO₄, based on solid wastes were successfully prepared from petroleum coke desulfurization slag (PCDS), fly ash (FA), carbide slag (CS), and bauxite (BX). The mineral composition of clinkers after [...] Read more.

The high belite sulfoaluminate cement (HBSAC) containing CaSO₄, and without CaSO₄, based on solid wastes were successfully prepared from petroleum coke desulfurization slag (PCDS), fly ash (FA), carbide slag (CS), and bauxite (BX). The mineral composition of clinkers after different calcination history were investigated by X-ray fluorescence (XRF), X-ray diffraction (XRD)/Quantitative X-ray diffraction (QXRD), and scanning electron microscopy (SEM), so as to determine the calcination temperatures. The difference between residual CaSO₄ and dihydrate gypsum (DG) and the optimal content of residual CaSO₄ were discussed by studying the properties of HBSAC. The results revealed that the residual CaSO₄ in clinker could replace DG to participate in hydration, and showed some advantages in strength and early hydration heat, but meanwhile increased the water requirement of normal consistency and hydration heat at 72 h, and prolonged the setting time. With the increase of residual CaSO₄ content in clinker, the lower limit temperature of clinker formation gradually increased, and the crystal size of clinker minerals became finer and the boundary between crystals became more blurred. However, the optimal calcination temperature (1300 °C) of HBSAC clinker did not change. Considering the effect of residual CaSO₄ content on the water requirement of normal consistency, setting time, hydration heat, strength, and hydration products, the optimal design content of residual CaSO₄ in HBSAC clinker based on solid wastes, such as PCDS and FA, was 15%. Full article

(This article belongs to the Special Issue Advanced Materials for Energy and Environmental Applications)

► Show Figures

Figure 1

12 pages, 2367 KiB

Open AccessArticle

Characterization of Corrosion Behavior of CLF-1 in Liquid Lithium Using Calibration-Free Laser-Induced Breakdown Spectroscopy in Depth Profile Analysis

by Zhi Cao, Yongtao An, Xianglin Wang, Chang’an Chen and Ying Li

Materials 2020, 13(1), 240; https://doi.org/10.3390/ma13010240 - 06 Jan 2020

Cited by 6 | Viewed by 2398

Abstract

It is important to get fast and quantitative compositional depth profiles for the boundary layer of the corroded specimen in order to understand the corrosion process and mechanism due to liquid lithium induced corrosion problems to structural material of fusion reactors. In this [...] Read more.

It is important to get fast and quantitative compositional depth profiles for the boundary layer of the corroded specimen in order to understand the corrosion process and mechanism due to liquid lithium induced corrosion problems to structural material of fusion reactors. In this work, calibration-free laser-induced breakdown spectroscopy (CF-LIBS) is introduced to investigate the compatibility of CLF-1(China low-activation Ferritic steel) exposed in liquid lithium at 500 °C for 500 h. The results show that CF-LIBS constitutes an effective technique to observe the corrosion layer of specimens which are non-uniform and the elements of matrix show gradient distribution from the boundary to the inner layer. The concentration was 82–95 wt.% Fe, 5–12 wt.% Cr, 0.45–0.85 wt.% Mn, 1.6–1.1 wt.% W, 0.11–0.16 wt.% V, and <0.2 wt.% Li along the longitudinal corrosion depth for the corrode CLF-1. The results reveal the quantitative elemental variation trend of CLF-1 in the lithium corrosion process and indicate that the CF-LIBS approach can be applied to the analysis of composition in multi-element materials. Full article

(This article belongs to the Special Issue Advanced Materials for Energy and Environmental Applications)

► Show Figures

Figure 1

11 pages, 4130 KiB

Open AccessArticle

Surface Roughening of Electrolyte Membrane for Pt- and Ru-Sputtered Passive Direct Methanol Fuel Cells

by Wonyeop Jeong, Gu Young Cho, Suk Won Cha and Taehyun Park

Materials 2019, 12(23), 3969; https://doi.org/10.3390/ma12233969 - 29 Nov 2019

Cited by 6 | Viewed by 2213

Abstract

Platinum (Pt) and ruthenium (Ru) were sputtered on an electrolyte membrane and it was used as a membrane-electrode assembly for passive direct methanol fuel cells (DMFCs) operating with high concentration methanol solution (4 M). Thick (Pt of 300 nm and Ru of 150 [...] Read more.

Platinum (Pt) and ruthenium (Ru) were sputtered on an electrolyte membrane and it was used as a membrane-electrode assembly for passive direct methanol fuel cells (DMFCs) operating with high concentration methanol solution (4 M). Thick (Pt of 300 nm and Ru of 150 nm) and thin (Pt of 150 nm and Ru of 75 nm) sputtered catalysts were prepared and their performance was first evaluated to find out the best sputtering conditions showing higher performance. Subsequently, four electrolyte membranes with different surface roughness were prepared to investigate its influence on the performance. As a result, the performance of the passive DMFC showed increasing tendency as the roughness is low, while the performance was decreased as the roughness was high, indicating there exists an optimal roughness of the electrolyte membrane. It was further investigated through morphological study through electron microscopy that such performance variation is attributed to the surface of sputtered Pt–Ru catalyst on the rough electrolyte membrane that adequate roughness induces the increase of reactive area while a too rough surface bears the poor contact of it with gas-diffusion layer. Full article

(This article belongs to the Special Issue Advanced Materials for Energy and Environmental Applications)

► Show Figures

Figure 1

13 pages, 1135 KiB

Open AccessArticle

Maize Straw as a Valuable Energetic Material for Biogas Plant Feeding

by Jakub Mazurkiewicz, Andrzej Marczuk, Patrycja Pochwatka and Sebastian Kujawa

Materials 2019, 12(23), 3848; https://doi.org/10.3390/ma12233848 - 22 Nov 2019

Cited by 54 | Viewed by 6012

Abstract

Maize has great potential, especially as a substrate for biofuels production. The aim of this paper is to analyze the possibility of usage in methane fermentation maize straw harvested in different weather conditions, which had an influence on different physical parameters, mainly the [...] Read more.

Maize has great potential, especially as a substrate for biofuels production. The aim of this paper is to analyze the possibility of usage in methane fermentation maize straw harvested in different weather conditions, which had an influence on different physical parameters, mainly the dry mass content. The research has shown that maize straw harvested in Central-Eastern Europe can have a broad spectrum of dry mass content, which is related to diverse weather conditions during autumn. However, independently from moisture content, maize straw can be a good (for more wet material) or very good (for more dried straw) substrate for the biogas plant. With the methane productivity reaching 201–207 m³/Mg of fresh mass, this material is a significantly better substrate than that typically used in Europe maize silage (approximately 105 m³/Mg FM). It was noted that the retention time for maize straw (36–42 days) is longer than in the case of maize silage (less than 30 days). However, this difference is quite small and can be accepted by the biogas plant operators. Full article

(This article belongs to the Special Issue Advanced Materials for Energy and Environmental Applications)

► Show Figures

Figure 1

8 pages, 2930 KiB

Open AccessArticle

Effect of Dispersion by Three-Roll Milling on Electrical Properties and Filler Length of Carbon Nanotube Composites

by Ji-Hwan Ha, Sang-Eui Lee and Sung-Hoon Park

Materials 2019, 12(23), 3823; https://doi.org/10.3390/ma12233823 - 21 Nov 2019

Cited by 25 | Viewed by 4023

Abstract

For practical use of carbon nanotube (CNT) composites, especially in electronic applications, uniform dispersion of a high concentration of CNTs in a polymer matrix is a critical challenge. Three-roll milling is one of most reliable dispersion techniques. We investigate the effect of three-roll [...] Read more.

For practical use of carbon nanotube (CNT) composites, especially in electronic applications, uniform dispersion of a high concentration of CNTs in a polymer matrix is a critical challenge. Three-roll milling is one of most reliable dispersion techniques. We investigate the effect of three-roll milling time on CNT length and the electrical properties of a CNT/polydimethylsiloxane composite film with 10 wt% CNTs. During the milling process, the CNT length is decreased from 10 to 1–4 μm by mechanical shear forces. The electrical conductivity increases after 1.5 min of milling owing to dispersion of the CNTs but decreases with increasing milling time owing to the decrease in the CNT length. Considering the changes in the electrical conductivity of the CNT composite and CNT length, we determined how to optimize the three-roll milling time to obtain a suitable dispersion state. Full article

(This article belongs to the Special Issue Advanced Materials for Energy and Environmental Applications)

► Show Figures

Figure 1

12 pages, 4468 KiB

Open AccessArticle

Seamless Tube-Type Heater with Uniform Thickness and Temperature Distribution Based on Carbon Nanotubes Aligned by Circumferential Shearing

by Yoonchul Sohn, Dongearn Kim, Sung-Hoon Park and Sang-Eui Lee

Materials 2019, 12(20), 3283; https://doi.org/10.3390/ma12203283 - 09 Oct 2019

Cited by 5 | Viewed by 2638

Abstract

The uniform temperature distribution, one of the requirements for long-term durability, is essential for composite heaters. An analytical model for temperature distribution of a tube-type heater was derived, and it revealed that thickness uniformity is one order more important than intrinsic material properties [...] Read more.

The uniform temperature distribution, one of the requirements for long-term durability, is essential for composite heaters. An analytical model for temperature distribution of a tube-type heater was derived, and it revealed that thickness uniformity is one order more important than intrinsic material properties such as density, heat capacity, and electrical conductivity of the heating tube. We introduced a circumferential shearing process to fabricate a flexible, seamless tube-type heating layer of carbon nanotube/silicone rubber composite with outstanding uniform distribution of thickness and temperature, which may be attributed to a shorter characteristic dimension in the circumferential direction than in the axial direction. The temperature uniformity was experimentally verified at various temperatures under heating. The difference in measured thickness and temperature in circumferential direction was within ±1.3~3.0% (for t_avg = 352.7 μm) and ±1.1% (for T_avg = 138.8 °C), respectively, all over the heating tube. Therefore, the circumferential shearing process can be effective for cylindrical heaters, like a heating layer of a laser printer, which fuse toners onto papers during printing. Full article

(This article belongs to the Special Issue Advanced Materials for Energy and Environmental Applications)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Advanced Materials for Energy and Environmental Applications

Share This Special Issue

Special Issue Editor

Special Issue Information

Keywords

Published Papers (10 papers)

Research

Further Information

Guidelines

MDPI Initiatives

Follow MDPI