C | December 2017 - Browse Articles

1643 KiB

Open AccessReview

A Review of Smart Materials in Tactile Actuators for Information Delivery

by Xin Xie, Sanwei Liu, Chenye Yang, Zhengyu Yang, Tian Liu, Juncai Xu, Cheng Zhang and Xianglin Zhai

C 2017, 3(4), 38; https://doi.org/10.3390/c3040038 - 8 Dec 2017

Cited by 14 | Viewed by 13389

Abstract

As the largest organ in the human body, the skin provides the important sensory channel for humans to receive external stimulations based on touch. By the information perceived through touch, people can feel and guess the properties of objects, like weight, temperature, textures, [...] Read more.

As the largest organ in the human body, the skin provides the important sensory channel for humans to receive external stimulations based on touch. By the information perceived through touch, people can feel and guess the properties of objects, like weight, temperature, textures, and motion, etc. In fact, those properties are nerve stimuli to our brain received by different kinds of receptors in the skin. Mechanical, electrical, and thermal stimuli can stimulate these receptors and cause different information to be conveyed through the nerves. Technologies for actuators to provide mechanical, electrical or thermal stimuli have been developed. These include static or vibrational actuation, electrostatic stimulation, focused ultrasound, and more. Smart materials, such as piezoelectric materials, carbon nanotubes, and shape memory alloys, play important roles in providing actuation for tactile sensation. This paper aims to review the background biological knowledge of human tactile sensing, to give an understanding of how we sense and interact with the world through the sense of touch, as well as the conventional and state-of-the-art technologies of tactile actuators for tactile feedback delivery. Full article

(This article belongs to the Special Issue Wearable Electronics)

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2639 KiB

Open AccessArticle

Efficient Air Desulfurization Catalysts Derived from Pig Manure Liquefaction Char

by Rajiv Wallace, Sundaramurthy Suresh, Elham H. Fini and Teresa J. Bandosz

C 2017, 3(4), 37; https://doi.org/10.3390/c3040037 - 20 Nov 2017

Cited by 6 | Viewed by 4693

Abstract

Biochar from the liquefaction of pig manure was used as a precursor of H₂S desulfurization adsorbents. In its inorganic matter, it contains marked quantities of calcium, magnesium and iron, which are known as hydrogen sulfide oxidation catalysts. The char was used [...] Read more.

Biochar from the liquefaction of pig manure was used as a precursor of H₂S desulfurization adsorbents. In its inorganic matter, it contains marked quantities of calcium, magnesium and iron, which are known as hydrogen sulfide oxidation catalysts. The char was used either as-received or mixed with 10% nanographite. The latter was added to increase both the content of the carbon phase and conductivity. ZnCl₂ in two different ratios of char to an activation agent (1:1 and 1:2) was used to create the porosity in the carbon phase. The content of the later was between 18–45%. The activated samples adsorbed 144 mg/g H₂S. Sulfur was the predominant product of reactive adsorption. Its deposition in the pore system and blockage of the most active pores ceased the materials’ activity. The presence of the catalytic phase was necessary but not sufficient to guarantee good performance. The developed porosity, which can store oxidation products in the resulting composite, is essential for the good performance of the desulfurization process. The surface of the composite with nanographite showed the highest catalytic activity, similar to that of the commercial Midas^® carbon catalyst. The results obtained indicate that a high quality reactive adsorbent/catalyst for H₂S removal can be obtained from pig manure liquefaction wastes. Full article

(This article belongs to the Special Issue Smart Carbon Materials in Catalysis)

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2405 KiB

Open AccessArticle

The Role of Carbon on Copper–Carbon Composites for the Electrooxidation of Alcohols in an Alkaline Medium

by Leticia García-Cruz, Conchi O. Ania, Ana Paula Carvalho, Teresa J. Bandosz, Vicente Montiel and Jesús Iniesta

C 2017, 3(4), 36; https://doi.org/10.3390/c3040036 - 20 Nov 2017

Cited by 7 | Viewed by 5600

Abstract

Copper–carbon composites were prepared following various different synthetic routes and using various carbon precursors (i.e., lignocellulose and graphite oxide), and were used as electrocatalysts for the oxidation of propargyl alcohol (PGA) in an alkaline medium. The electrochemical response of the copper-based catalysts was [...] Read more.

Copper–carbon composites were prepared following various different synthetic routes and using various carbon precursors (i.e., lignocellulose and graphite oxide), and were used as electrocatalysts for the oxidation of propargyl alcohol (PGA) in an alkaline medium. The electrochemical response of the copper-based catalysts was analyzed in terms of the influence of the metallic species, the carbon matrix incorporated in the composites, and the chemical structure of the ionomers—Nafion and poly (4-vinylpyridine) cross-linked methyl chloride quaternary salt resin (4VP)—used in the fabrication of the electrodes. Data has shown that the incorporation of reduced graphene oxide sheets between the copper metallic particles increased the performance due to the increased conductivity provided by the carbonaceous phase. Catalytic inks with ca. 40 wt.% Nafion and 12 wt.% 4VP as ionomers provided the best electrochemical response and cohesion of the catalysts, minimizing the losses in the electroactivity of the copper species. Full article

(This article belongs to the Special Issue Smart Carbon Materials in Catalysis)

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11812 KiB

Open AccessArticle

Thermal Treatment of Melt-Spun Fibers Based on High Density PolyEthylene and Lignin

by Panagiotis Goulis, Giorgos Konstantopoulos, Ioannis A. Kartsonakis, Konstantinos Mpalias, Stavros Anagnou, Dimitrios Dragatogiannis and Costas Charitidis

C 2017, 3(4), 35; https://doi.org/10.3390/c3040035 - 13 Nov 2017

Cited by 6 | Viewed by 5366

Abstract

The purpose of this study was the synthesis of novel low-cost carbon fibers along with the investigation of the optimal parameters of temperature and time for the stabilization of hybrid high-density polyethylene (HDPE) and lignin melt-spun fibers. These fibers were manufactured by physical [...] Read more.

The purpose of this study was the synthesis of novel low-cost carbon fibers along with the investigation of the optimal parameters of temperature and time for the stabilization of hybrid high-density polyethylene (HDPE) and lignin melt-spun fibers. These fibers were manufactured by physical compounding of HDPE and chemically-modified softwood kraft lignin (SKL) in order to produce green fiber precursors for carbon fiber synthesis. Stabilization tests were performed with respect to thermal treatment (physical method) and sulfonation treatment (chemical method). The results revealed that only chemical methods induce the desired thermal process-ability to the composite fibers in order to manufacture carbon fibers by using a simple method. This investigation shed light on the stabilization techniques of polymeric fibers in the absence of any cyclic groups in terms of environmentally-friendly mass production of carbon fibers using low-cost and green raw materials. This study facilitates incorporation of softwood lignin in homegrown polymeric fibers by a low-cost production process via melt-spinning of composite fibers, which were successfully stabilized using a facile chemical method and carbonized. Additionally, a comprehensive investigation of the thermal behavior of the samples was accomplished, by examining several ways and aspects of fiber thermal treating. The properties of all studied fibers are presented, compared, and discussed. Full article

(This article belongs to the Special Issue Chemical Bond Formation for Nanocarbon-Based Composites)

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1821 KiB

Open AccessArticle

Acyclic Arylamine-Based Ionophores as Potentiometric Sensors for Zn²⁺ and Ni²⁺ Ions

by Harpreet Kaur, Manmohan Chhibber and Susheel K. Mittal

C 2017, 3(4), 34; https://doi.org/10.3390/c3040034 - 7 Nov 2017

Cited by 5 | Viewed by 3913

Abstract

Two receptor molecules N-(2-nitrophenyl)benzene-1,2-diamine (DPA) and N,N-bis(2-nitrophenyl)benzene-1,2-diamine (TPA) are proposed as Zn²⁺ and Ni²⁺-selective electrodes, respectively. The two electrodes respond to Zn²⁺ and Ni²⁺ ions with the detection limits of 1.3 × 10⁻⁶ [...] Read more.

Two receptor molecules N-(2-nitrophenyl)benzene-1,2-diamine (DPA) and N,N-bis(2-nitrophenyl)benzene-1,2-diamine (TPA) are proposed as Zn²⁺ and Ni²⁺-selective electrodes, respectively. The two electrodes respond to Zn²⁺ and Ni²⁺ ions with the detection limits of 1.3 × 10⁻⁶ M and 2.8 × 10⁻⁶ M, respectively. Both the electrodes have a life time of four months and respond within 15 s and 20 s, respectively, for Zn²⁺ and Ni²⁺ over a wide pH range (3–9). The electrodes show very good selectivity towards the primary ions in presence of some alkali, alkaline earth, and transition metal ions. Full article

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2506 KiB

Open AccessArticle

MoS₂ Decorated Carbon Nanofibers as Efficient and Durable Electrocatalyst for Hydrogen Evolution Reaction

by C. Zhang, Z. Wang, S. Bhoyate, T. Morey, Brooks L. Neria, Venkata Vasiraju, Gautam Gupta, Soubantika Palchoudhury, P. K. Kahol, S. R. Mishra, Felio Perez and Ram K. Gupta

C 2017, 3(4), 33; https://doi.org/10.3390/c3040033 - 30 Oct 2017

Cited by 61 | Viewed by 11739

Abstract

Hydrogen is an efficient fuel which can be generated via water splitting, however hydrogen evolution occurs at high overpotential, and efficient hydrogen evolution catalysts are desired to replace state-of-the-art catalysts such as platinum. Here, we report an advanced electrocatalyst that has low overpotential, [...] Read more.

Hydrogen is an efficient fuel which can be generated via water splitting, however hydrogen evolution occurs at high overpotential, and efficient hydrogen evolution catalysts are desired to replace state-of-the-art catalysts such as platinum. Here, we report an advanced electrocatalyst that has low overpotential, efficient charge transfers kinetics, low Tafel slope and durable. Carbon nanofibers (CNFs), obtained by carbonizing electrospun fibers, were decorated with MoS₂ using a facile hydrothermal method. The imaging of catalyst reveals a flower like morphology that allows for exposure of edge sulfur sites to maximize the HER process. HER activity of MoS₂ decorated over CNFs was compared with MoS₂ without CNFs and with commercial MoS₂. MoS₂ grown over CNFs and MoS₂-synthesized produced about 374 and 98 times higher current density at −0.30 V (vs. Reversible Hydrogen Electrode, RHE) compared with the MoS₂-commercial sample, respectively. MoS₂-commercial, MoS₂-synthesized and MoS₂ grown over CNFs showed a Tafel slope of 165, 79 and 60 mV/decade, capacitance of 0.99, 5.87 and 15.66 mF/cm², and turnover frequency of 0.013, 0.025 and 0.54 s⁻¹, respectively. The enhanced performance of MoS₂-CNFs is due to large electroactive surface area, more exposure of edge sulfur to the electrolyte, and easy charge transfer from MoS₂ to the electrode through conducting CNFs. Full article

(This article belongs to the Special Issue Smart Carbon Materials in Catalysis)

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3601 KiB

Open AccessArticle

An Atomistic Carbide-Derived Carbon Model Generated Using ReaxFF-Based Quenched Molecular Dynamics

by Matthew W. Thompson, Boris Dyatkin, Hsiu-Wen Wang, C. Heath Turner, Xiahan Sang, Raymond R. Unocic, Christopher R. Iacovella, Yury Gogotsi, Adri C. T. Van Duin and Peter T. Cummings

C 2017, 3(4), 32; https://doi.org/10.3390/c3040032 - 23 Oct 2017

Cited by 18 | Viewed by 7533

Abstract

We report a novel atomistic model of carbide-derived carbons (CDCs), which are nanoporous carbons with high specific surface areas, synthesis-dependent degrees of graphitization, and well-ordered, tunable porosities. These properties make CDCs viable substrates in several energy-relevant applications, such as gas storage media, electrochemical [...] Read more.

We report a novel atomistic model of carbide-derived carbons (CDCs), which are nanoporous carbons with high specific surface areas, synthesis-dependent degrees of graphitization, and well-ordered, tunable porosities. These properties make CDCs viable substrates in several energy-relevant applications, such as gas storage media, electrochemical capacitors, and catalytic supports. These materials are heterogenous, non-ideal structures and include several important parameters that govern their performance. Therefore, a realistic model of the CDC structure is needed in order to study these systems and their nanoscale and macroscale properties with molecular simulation. We report the use of the ReaxFF reactive force field in a quenched molecular dynamics routine to generate atomistic CDC models. The pair distribution function, pore size distribution, and adsorptive properties of this model are reported and corroborated with experimental data. Simulations demonstrate that compressing the system after quenching changes the pore size distribution to better match the experimental target. Ring size distributions of this model demonstrate the prevalence of non-hexagonal carbon rings in CDCs. These effects may contrast the properties of CDCs against those of activated carbons with similar pore size distributions and explain higher energy densities of CDC-based supercapacitors. Full article

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2079 KiB

Open AccessReview

Nitrogen-Doped Activated Carbon as Metal-Free Catalysts Having Various Functions

by Shin-Ichiro Fujita, Hiroshi Yoshida and Masahiko Arai

C 2017, 3(4), 31; https://doi.org/10.3390/c3040031 - 18 Oct 2017

Cited by 10 | Viewed by 6629

Abstract

Nitrogen-doped carbon materials have been gaining increasing interest as metal-free catalysts. In this article, the authors have briefly introduced their recent studies on the utilization of nitrogen-doped activated carbon (N-AC) for several organic synthesis reactions, which include base catalyzed reactions of Knoevenagel condensation [...] Read more.

Nitrogen-doped carbon materials have been gaining increasing interest as metal-free catalysts. In this article, the authors have briefly introduced their recent studies on the utilization of nitrogen-doped activated carbon (N-AC) for several organic synthesis reactions, which include base catalyzed reactions of Knoevenagel condensation and transesterification, aerobic oxidation of xanthene and alcohols, and transfer hydrogenation of nitrobenzene, 3-nitrostyrene, styrene, and phenylacetylene with hydrazine. Doped-nitrogen species existed on the AC surface in different structures. For example, pyridine-type nitrogen species appear to be involved in the active sites for Knoevenagel condensation and for the oxidation of xanthene, while graphite-type nitrogen species appear to be involved for the oxidation of alcohols. Being different from these reactions, both surface nitrogen and oxygen species are involved in the active sites for the hydrogenation of nitrobenzene. N-AC was practically inactive for the transfer hydrogenation of vinyl and ethynyl groups, but it can catalyze those hydrogenation reactions assisted by co-existing nitrobenzene. Comparison of N-AC with conventional catalysts shows that N-AC can alternate with conventional solid base catalysts and supported metal catalysts for the Knoevenagel condensation and oxidation reactions. Full article

(This article belongs to the Special Issue Smart Carbon Materials in Catalysis)

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4092 KiB

Open AccessArticle

Physico-Mechanical, Dielectric, and Piezoelectric Properties of PVDF Electrospun Mats Containing Silver Nanoparticles

by Ahmed A. Issa, Mariam A. Al-Maadeed, Adriaan S. Luyt, Deepalekshmi Ponnamma and Mohammad K. Hassan

C 2017, 3(4), 30; https://doi.org/10.3390/c3040030 - 16 Oct 2017

Cited by 83 | Viewed by 8494

Abstract

Poly(vinylidene fluoride) (PVDF) is a piezoelectric material with outstanding physical and mechanical properties. The piezoelectric properties depend on the β-phase content of this polymer, while the physical and mechanical properties depend on the morphology and degree of crystallinity of the material. Silver [...] Read more.

Poly(vinylidene fluoride) (PVDF) is a piezoelectric material with outstanding physical and mechanical properties. The piezoelectric properties depend on the β-phase content of this polymer, while the physical and mechanical properties depend on the morphology and degree of crystallinity of the material. Silver has antibacterial effects, and silver nanoparticles (Ag-NPs) have large surface areas rich in electrons. In this paper, we produced electrospun PVDF fibrous mats that contained different contents of Ag-NPs between 0% and 1.0%. The β-content in PVDF was found to increase by about 8% for Ag-NPs content of 0.4–0.6%. The electrospun fiber mats had a higher β-crystalline content, nano-pores were visible on the fiber surfaces, and the tensile strength and thermal stability were improved. Dielectric analysis indicated weak interfacial adhesion between the PVDF and Ag-NPs. Good piezoelectric response was observed in the electrospun fibers containing 0.4% AgNPs, which shows a good correlation between the β-crystalline phase content of the composites and its energy-harvesting application. Full article

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1839 KiB

Open AccessReview

Graphene–Noble Metal Nano-Composites and Applications for Hydrogen Sensors

by Sukumar Basu and Surajit Kumar Hazra

C 2017, 3(4), 29; https://doi.org/10.3390/c3040029 - 13 Oct 2017

Cited by 20 | Viewed by 6617

Abstract

Graphene based nano-composites are relatively new materials with excellent mechanical, electrical, electronic and chemical properties for applications in the fields of electrical and electronic devices, mechanical appliances and chemical gadgets. For all these applications, the structural features associated with chemical bonding that involve [...] Read more.

Graphene based nano-composites are relatively new materials with excellent mechanical, electrical, electronic and chemical properties for applications in the fields of electrical and electronic devices, mechanical appliances and chemical gadgets. For all these applications, the structural features associated with chemical bonding that involve other components at the interface need in-depth investigation. Metals, polymers, inorganic fibers and other components improve the properties of graphene when they form a kind of composite structure in the nano-dimensions. Intensive investigations have been carried out globally in this area of research and development. In this article, some salient features of graphene–noble metal interactions and composite formation which improve hydrogen gas sensing properties—like higher and fast response, quick recovery, cross sensitivity, repeatability and long term stability of the sensor devices—are presented. Mostly noble metals are effective for enhancing the sensing performance of the graphene–metal hybrid sensors, due to their superior catalytic activities. The experimental evidence for atomic bonding between metal nano-structures and graphene has been reported in the literature and it is theoretically verified by density functional theory (DFT). Multilayer graphene influences gas sensing performance via intercalation of metal and non-metal atoms through atomic bonding. Full article

(This article belongs to the Special Issue Chemical Bond Formation for Nanocarbon-Based Composites)

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