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Materials, Volume 11, Issue 3 (March 2018) – 128 articles

Cover Story (view full-size image): Complex plasmonic nanocomposites have a great potential in a wide range of applications ranging from photonics and photovoltaics, to catalysis for environmental issues such as water remediation. Indeed, the evolution of nanofabrication techniques, which have radically improved in the past decades, allows the synthesis of ever more advanced structures presenting very complex geometries. However, accurately modeling the optical properties of such systems, which are often beyond the capabilities of exact numerical methods, can still be challenging. In this context, we propose an original, semi-analytical approach that combines RCWA (rigorous coupled wave analysis) with advanced effective medium theory to address the problem. To validate our approach, we test it using experimental measurements realized on plasmonic nanoparticles periodically distributed in structured polymer thin films. In particular, we [...] Read more.
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18 pages, 7036 KiB  
Review
Metal-Insulator-Metal-Based Plasmonic Metamaterial Absorbers at Visible and Infrared Wavelengths: A Review
by Shinpei Ogawa and Masafumi Kimata
Materials 2018, 11(3), 458; https://doi.org/10.3390/ma11030458 - 20 Mar 2018
Cited by 167 | Viewed by 17631
Abstract
Electromagnetic wave absorbers have been investigated for many years with the aim of achieving high absorbance and tunability of both the absorption wavelength and the operation mode by geometrical control, small and thin absorber volume, and simple fabrication. There is particular interest in [...] Read more.
Electromagnetic wave absorbers have been investigated for many years with the aim of achieving high absorbance and tunability of both the absorption wavelength and the operation mode by geometrical control, small and thin absorber volume, and simple fabrication. There is particular interest in metal-insulator-metal-based plasmonic metamaterial absorbers (MIM-PMAs) due to their complete fulfillment of these demands. MIM-PMAs consist of top periodic micropatches, a middle dielectric layer, and a bottom reflector layer to generate strong localized surface plasmon resonance at absorption wavelengths. In particular, in the visible and infrared (IR) wavelength regions, a wide range of applications is expected, such as solar cells, refractive index sensors, optical camouflage, cloaking, optical switches, color pixels, thermal IR sensors, IR microscopy and gas sensing. The promising properties of MIM-PMAs are attributed to the simple plasmonic resonance localized at the top micropatch resonators formed by the MIMs. Here, various types of MIM-PMAs are reviewed in terms of their historical background, basic physics, operation mode design, and future challenges to clarify their underlying basic design principles and introduce various applications. The principles presented in this review paper can be applied to other wavelength regions such as the ultraviolet, terahertz, and microwave regions. Full article
(This article belongs to the Special Issue New Horizon of Plasmonics and Metamaterials)
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9 pages, 4554 KiB  
Article
Evaluation of Fracture Strength of Ceramics Containing Small Surface Defects Introduced by Focused Ion Beam
by Nanako Sato and Koji Takahashi
Materials 2018, 11(3), 457; https://doi.org/10.3390/ma11030457 - 20 Mar 2018
Cited by 16 | Viewed by 4648
Abstract
The aim of this study was to clarify the effects of micro surface defects introduced by the focused ion beam (FIB) technique on the fracture strength of ceramics. Three-point bending tests on alumina-silicon carbide (Al2O3/SiC) ceramic composites containing crack-like [...] Read more.
The aim of this study was to clarify the effects of micro surface defects introduced by the focused ion beam (FIB) technique on the fracture strength of ceramics. Three-point bending tests on alumina-silicon carbide (Al2O3/SiC) ceramic composites containing crack-like surface defects introduced by FIB were carried out. A surface defect with a r e a in the range 19 to 35 µm was introduced at the center of each specimen. Test results showed that the fracture strengths of the FIB-defect specimens depended on a r e a . The test results were evaluated using the evaluation equation of fracture strength based on the process zone size failure criterion and the a r e a parameter model. The experimental results indicate that FIB-induced defects can be used as small initial cracks for the fracture strength evaluation of ceramics. Moreover, the proposed equation was useful for the fracture strength evaluation of ceramics containing micro surface defects introduced by FIB. Full article
(This article belongs to the Section Advanced Materials Characterization)
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10 pages, 11682 KiB  
Article
Study on Microstructure and Mechanical Properties of Hypereutectic Al–18Si Alloy Modified with Al–3B
by Chunjie Gong, Hao Tu, Changjun Wu, Jianhua Wang and Xuping Su
Materials 2018, 11(3), 456; https://doi.org/10.3390/ma11030456 - 20 Mar 2018
Cited by 22 | Viewed by 4297
Abstract
An hypereutectic Al–18Si alloy was modified via an Al–3B master alloy. The effect of the added Al–3B and the modification temperature on the microstructure, tensile fracture morphologies, and mechanical properties of the alloy were investigated using an optical microscope, Image–Pro Plus 6.0, a [...] Read more.
An hypereutectic Al–18Si alloy was modified via an Al–3B master alloy. The effect of the added Al–3B and the modification temperature on the microstructure, tensile fracture morphologies, and mechanical properties of the alloy were investigated using an optical microscope, Image–Pro Plus 6.0, a scanning electron microscope, and a universal testing machine. The results show that the size of the primary Si and its fraction decreased at first, and then increased as an additional amount of Al–3B was added. When the added Al–3B reached 0.2 wt %, the fraction of the primary Si in the Al–18Si alloy decreased with an increase in temperature. Compared with the unmodified Al–18Si alloy, the tensile strength and elongation of the alloy modified at 850 °C with 0.2 wt % Al–3B increased by 25% and 81%, respectively. The tensile fracture of the modified Al–18Si alloy exhibited partial ductile fracture characteristics, but there were more areas with ductile characteristics compared with that of the unmodified Al–18Si alloy. Full article
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15 pages, 10346 KiB  
Article
Fabrication and Characteristics of Sintered Cutting Stainless Steel Fiber Felt with Internal Channels and an Al2O3 Coating
by Shufeng Huang, Zhenping Wan and Shuiping Zou
Materials 2018, 11(3), 455; https://doi.org/10.3390/ma11030455 - 20 Mar 2018
Cited by 2 | Viewed by 4796
Abstract
A novel sintered cutting stainless steel fiber felt with internal channels (SCSSFFC) composed of a stainless-steel fiber skeleton, three-dimensional interconnected porous structure and multiple circular microchannels is developed. SCSSFFC has a jagged and rough surface morphology and possesses a high specific surface area, [...] Read more.
A novel sintered cutting stainless steel fiber felt with internal channels (SCSSFFC) composed of a stainless-steel fiber skeleton, three-dimensional interconnected porous structure and multiple circular microchannels is developed. SCSSFFC has a jagged and rough surface morphology and possesses a high specific surface area, which is approximately 2.4 times larger than that of the sintered bundle-drawing stainless steel fiber felt with internal channels (SBDSSFFC) and is expected to enhance adhesive strength. The sol-gel and wet impregnation methods are adopted to prepare SCSSFFC with an Al2O3 coating (SCSSFFC/Al2O3). The adhesive strength of SCSSFFC/Al2O3 is investigated using ultrasonic vibration and thermal shock tests. The experimental results indicate that the weight loss rate of the Al2O3 coating has a 4.2% and 8.42% reduction compared with those of SBDSSFFCs based on ultrasonic vibration and thermal shock tests. In addition, the permeability of SCSSFFC/Al2O3 is investigated based on forced liquid flow tests. The experimental results show that the permeability and inertial coefficients of SCSSFFC/Al2O3 are mainly affected by the coating rate, porosity and open ratio; however, the internal microchannel diameter has little influence. It is also found that SCSSFFC/Al2O3 yields superior permeability, as well as inertial coefficients compared with those of other porous materials reported in the literature. Full article
(This article belongs to the Section Porous Materials)
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22 pages, 20226 KiB  
Article
3D Printability of Alginate-Carboxymethyl Cellulose Hydrogel
by Ahasan Habib, Venkatachalem Sathish, Sanku Mallik and Bashir Khoda
Materials 2018, 11(3), 454; https://doi.org/10.3390/ma11030454 - 20 Mar 2018
Cited by 250 | Viewed by 19987
Abstract
Three-dimensional (3D) bio-printing is a revolutionary technology to reproduce a 3D functional living tissue scaffold in-vitro through controlled layer-by-layer deposition of biomaterials along with high precision positioning of cells. Due to its bio-compatibility, natural hydrogels are commonly considered as the scaffold material. However, [...] Read more.
Three-dimensional (3D) bio-printing is a revolutionary technology to reproduce a 3D functional living tissue scaffold in-vitro through controlled layer-by-layer deposition of biomaterials along with high precision positioning of cells. Due to its bio-compatibility, natural hydrogels are commonly considered as the scaffold material. However, the mechanical integrity of a hydrogel material, especially in 3D scaffold architecture, is an issue. In this research, a novel hybrid hydrogel, that is, sodium alginate with carboxymethyl cellulose (CMC) is developed and systematic quantitative characterization tests are conducted to validate its printability, shape fidelity and cell viability. The outcome of the rheological and mechanical test, filament collapse and fusion test demonstrate the favorable shape fidelity. Three-dimensional scaffold structures are fabricated with the pancreatic cancer cell, BxPC3 and the 86% cell viability is recorded after 23 days. This hybrid hydrogel can be a potential biomaterial in 3D bioprinting process and the outlined characterization techniques open an avenue directing reproducible printability and shape fidelity. Full article
(This article belongs to the Special Issue NextGen Materials for 3D Printing)
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27 pages, 21464 KiB  
Article
Wastes as Aggregates, Binders or Additions in Mortars: Selecting Their Role Based on Characterization
by Catarina Brazão Farinha, Jorge De Brito, Rosário Veiga, J. M. Fernández, J. R. Jiménez and A. R. Esquinas
Materials 2018, 11(3), 453; https://doi.org/10.3390/ma11030453 - 20 Mar 2018
Cited by 18 | Viewed by 4617
Abstract
The production of waste has increased over the years and, lacking a recycle or recovery solution, it is forwarded to landfill. The incorporation of wastes in cement-based materials is a solution to reduce waste deposition. In this regard, some researchers have been studying [...] Read more.
The production of waste has increased over the years and, lacking a recycle or recovery solution, it is forwarded to landfill. The incorporation of wastes in cement-based materials is a solution to reduce waste deposition. In this regard, some researchers have been studying the incorporation of wastes with different functions: aggregate, binder and addition. The incorporation of wastes should take advantage of their characteristics. It requires a judicious analysis of their particles. This research involves the analysis of seven industrial wastes: biomass ashes, glass fibre, reinforced polymer dust, sanitary ware, fluid catalytic cracking, acrylic fibre, textile fibre and glass fibre. The main characteristics and advantages of each waste are enunciated and the best type of introduction in mortars is discussed. The characterization of the wastes as particles is necessary to identify the most suitable incorporation in mortars. In this research, some wastes are studied with a view to their re-use or recycling in mortars. Thus, this research focuses on the chemical, physical and mechanical characterization of industrial wastes and identification of the potentially most advantageous type of incorporation. Full article
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18 pages, 5847 KiB  
Article
Gradient Nanostructured Tantalum by Thermal-Mechanical Ultrasonic Impact Energy
by Jong-Min Chae, Keun-Oh Lee and Auezhan Amanov
Materials 2018, 11(3), 452; https://doi.org/10.3390/ma11030452 - 20 Mar 2018
Cited by 17 | Viewed by 5431
Abstract
Microstructural evolution and wear performance of Tantalum (Ta) treated by ultrasonic nanocrystalline surface modification (UNSM) at 25 and 1000 °C were reported. The UNSM treatment modified a surface along with subsurface layer with a thickness in the range of 20 to 150 µm, [...] Read more.
Microstructural evolution and wear performance of Tantalum (Ta) treated by ultrasonic nanocrystalline surface modification (UNSM) at 25 and 1000 °C were reported. The UNSM treatment modified a surface along with subsurface layer with a thickness in the range of 20 to 150 µm, which depends on the UNSM treatment temperature, via the surface severe plastic deformation (S2PD) method. The cross-sectional microstructure of the specimens was observed by electron backscattered diffraction (EBSD) in order to confirm the microstructural alteration in terms of effective depth and refined grain size. The surface hardness measurement results, including depth profile, revealed that the hardness of the UNSM-treated specimens at both temperatures was increased in comparison with those of the untreated ones. The increase in UNSM treatment temperature led to a further increase in hardness. Moreover, both the UNSM-treated specimens with an increased hardness resulted in a higher resistance to wear in comparison with those of the untreated ones under dry conditions. The increase in hardness and induced compressive residual stress that depend on the formation of severe plastically deformed layer with the refined nano-grains are responsible for the enhancement in wear resistance. The findings of this study may be implemented in response to various industries that are related to strength improvement and wear enhancement issues of Ta. Full article
(This article belongs to the Special Issue Surface Modification to Improve Properties of Materials)
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12 pages, 8354 KiB  
Article
The Effect of Poly (Glycerol Sebacate) Incorporation within Hybrid Chitin–Lignin Sol–Gel Nanofibrous Scaffolds
by Turdimuhammad Abdullah, Lassaad Gzara, Giovanna Simonetti, Ahmed Alshahrie, Numan Salah, Pierfrancesco Morganti, Angelo Chianese, Afsoon Fallahi, Ali Tamayol, Sidi A. Bencherif and Adnan Memic
Materials 2018, 11(3), 451; https://doi.org/10.3390/ma11030451 - 19 Mar 2018
Cited by 21 | Viewed by 6686
Abstract
Chitin and lignin primarily accumulate as bio-waste resulting from byproducts of crustacean crusts and plant biomass. Recently, their use has been proposed for diverse and unique bioengineering applications, amongst others. However, their weak mechanical properties need to be improved in order to facilitate [...] Read more.
Chitin and lignin primarily accumulate as bio-waste resulting from byproducts of crustacean crusts and plant biomass. Recently, their use has been proposed for diverse and unique bioengineering applications, amongst others. However, their weak mechanical properties need to be improved in order to facilitate their industrial utilization. In this paper, we fabricated hybrid fibers composed of a chitin–lignin (CL)-based sol–gel mixture and elastomeric poly (glycerol sebacate) (PGS) using a standard electrospinning approach. Obtained results showed that PGS could be coherently blended with the sol–gel mixture to form a nanofibrous scaffold exhibiting remarkable mechanical performance and improved antibacterial and antifungal activity. The developed hybrid fibers showed promising potential in advanced biomedical applications such as wound care products. Ultimately, recycling these sustainable biopolymers and other bio-wastes alike could propel a “greener” economy. Full article
(This article belongs to the Special Issue Polymeric Materials for Medical Applications)
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12 pages, 3844 KiB  
Article
The Preparation of TiO2 Film by the Sol-Gel Method and Evaluation of Its Self-Cleaning Property
by Yu Liang, Sijia Sun, Tongrong Deng, Hao Ding, Wanting Chen and Ying Chen
Materials 2018, 11(3), 450; https://doi.org/10.3390/ma11030450 - 19 Mar 2018
Cited by 69 | Viewed by 7367
Abstract
TiO2 sol was produced by the sol-gel method through the hydrolysis and the aging of tetrabutyl titanate and the TiO2 film was obtained by dipping and uniform lifting of the acid-treated and ultrasound-treated clean glass slides into the TiO2 sol [...] Read more.
TiO2 sol was produced by the sol-gel method through the hydrolysis and the aging of tetrabutyl titanate and the TiO2 film was obtained by dipping and uniform lifting of the acid-treated and ultrasound-treated clean glass slides into the TiO2 sol followed by aging, drying, and calcination. The effect of the hydrolysis control agents to the formed sol was researched and the crystalline state, the morphology, and the photocatalytic properties of the products after calcination were characterized. The structural morphology, the contact angles before and after illumination, and the self-cleaning properties of the TiO2 film were characterized as well. The results showed that by using acetylacetone as the hydrolysis control agent, the formed TiO2 sol had relatively high stability. The product after the calcination of the TiO2 sol was of single anatase type with crystalline size of 18–20 nm and it could degrade nearly 100% of methylene blue after 90 min illumination. The formed TiO2 film is compact, continuous, smooth, and had the properties of super-hydrophilicity (after 30 min illumination due to its contact angle decreasing from 21° to nearly 0°) and anti-fogging capability, which indicated its excellent self-cleaning property. Full article
(This article belongs to the Special Issue Photocatalytic Materials for Energy and Environmental Applications)
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12 pages, 2290 KiB  
Article
Electronic, Optical, and Lattice Dynamical Properties of Tetracalcium Trialuminate (Ca4Al6O13)
by Huayue Mei, Yuhan Zhong, Peida Wang, Zhenyuan Jia, Chunmei Li and Nanpu Cheng
Materials 2018, 11(3), 449; https://doi.org/10.3390/ma11030449 - 19 Mar 2018
Cited by 10 | Viewed by 4670
Abstract
The electronic, optical, and lattice dynamical properties of tetracalcium trialuminate (Ca4Al6O13) with a special sodalite cage structure were calculated based on the density functional theory. Theoretical results show that Ca4Al6O13 is ductile [...] Read more.
The electronic, optical, and lattice dynamical properties of tetracalcium trialuminate (Ca4Al6O13) with a special sodalite cage structure were calculated based on the density functional theory. Theoretical results show that Ca4Al6O13 is ductile and weakly anisotropic. The calculated Young’s modulus and Poisson ratio are 34.18 GPa and 0.32, respectively. Ca4Al6O13 is an indirect-gap semiconductor with a band gap of 5.41 eV. The top of the valence band derives from O 2p states, and the bottom of conduction band consists of Ca 3d states. Transitions from O 2p, 2s states to empty Ca 4s, 3d and Al 3s, 3p states constitute the major peaks of the imaginary part of the dielectric function. Ca4Al6O13 is a good UV absorber for photoelectric devices due to the high absorption coefficient and low reflectivity. The lattice vibration analysis reveals that O atoms contribute to the high-frequency portions of the phonon spectra, while Ca and Al atoms make important contributions to the middle- and low-frequency portions. At the center of the first Brillouin zone, lattice vibrations include the Raman active modes (E, A1), infrared active mode (T2), and silentmodes (T1, A2). Typical atomic displacement patterns were also investigated to understand the vibration modes more intuitively. Full article
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13 pages, 1989 KiB  
Review
Overview of Piezoelectric Biosensors, Immunosensors and DNA Sensors and Their Applications
by Miroslav Pohanka
Materials 2018, 11(3), 448; https://doi.org/10.3390/ma11030448 - 19 Mar 2018
Cited by 261 | Viewed by 17502
Abstract
Piezoelectric biosensors are a group of analytical devices working on a principle of affinity interaction recording. A piezoelectric platform or piezoelectric crystal is a sensor part working on the principle of oscillations change due to a mass bound on the piezoelectric crystal surface. [...] Read more.
Piezoelectric biosensors are a group of analytical devices working on a principle of affinity interaction recording. A piezoelectric platform or piezoelectric crystal is a sensor part working on the principle of oscillations change due to a mass bound on the piezoelectric crystal surface. In this review, biosensors having their surface modified with an antibody or antigen, with a molecularly imprinted polymer, with genetic information like single stranded DNA, and biosensors with bound receptors of organic of biochemical origin, are presented and discussed. The mentioned recognition parts are frequently combined with use of nanoparticles and applications in this way are also introduced. An overview of the current literature is given and the methods presented are commented upon. Full article
(This article belongs to the Special Issue Piezoelectric Materials and Devices)
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10 pages, 5367 KiB  
Article
Bismuth Oxysulfide and Its Polymer Nanocomposites for Efficient Purification
by Yidong Luo, Lina Qiao, Huanchun Wang, Shun Lan, Yang Shen, Yuanhua Lin and Cewen Nan
Materials 2018, 11(3), 447; https://doi.org/10.3390/ma11030447 - 19 Mar 2018
Cited by 3 | Viewed by 4325
Abstract
The danger of toxic organic pollutants in both aquatic and air environments calls for high-efficiency purification material. Herein, layered bismuth copper oxychalcogenides, BiCuSO, nanosheets of high photocatalytic activity were introduced to the PVDF (Polyvinylidene Fluoride). The fibrous membranes provide an easy, efficient, and [...] Read more.
The danger of toxic organic pollutants in both aquatic and air environments calls for high-efficiency purification material. Herein, layered bismuth copper oxychalcogenides, BiCuSO, nanosheets of high photocatalytic activity were introduced to the PVDF (Polyvinylidene Fluoride). The fibrous membranes provide an easy, efficient, and recyclable way to purify organic pollutant. The physical and photophysical properties of the BiCuSO and its polymer composite were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), ultraviolet-visible diffuse reflection spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), electron spin resonance (EPR). Photocatalysis of Congo Red reveals that the BiCuSO/PVDF shows a superior photocatalytic activity of a 55% degradation rate in 70 min at visible light. The high photocatalytic activity is attributed to the exposed active {101} facets and the triple vacant associates V B i ‴ V O • • V B i ‴ . By engineering the intrinsic defects on the surface of bismuth oxysulfide, high solar-driven photocatalytic activity can be approached. The successful fabrication of the bismuth oxysulfide and its polymer nanocomposites provides an easy and general approach for high-performance purification materials for various applications. Full article
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14 pages, 5956 KiB  
Article
Facile Fabrication of Cu2O Nanobelts in Ethanol on Nanoporous Cu and Their Photodegradation of Methyl Orange
by Zhenhua Dan, Yulin Yang, Fengxiang Qin, Hao Wang and Hui Chang
Materials 2018, 11(3), 446; https://doi.org/10.3390/ma11030446 - 19 Mar 2018
Cited by 65 | Viewed by 6193
Abstract
Thin cupric oxide (Cu2O) nanobelts with width of few tens of nanometers to few hundreds of nanometers were fabricated in anhydrous ethanol on nanoporous copper templates that was prepared via dealloying amorphous Ti40Cu60 ribbons in hydrofluoric acid solutions [...] Read more.
Thin cupric oxide (Cu2O) nanobelts with width of few tens of nanometers to few hundreds of nanometers were fabricated in anhydrous ethanol on nanoporous copper templates that was prepared via dealloying amorphous Ti40Cu60 ribbons in hydrofluoric acid solutions at 348 K. The Cu2O octahedral particles preferentially form in the water, and nanobelts readily undergo the growth along the lengthwise and widthwise in the anhydrous ethanol. The ethanol molecules serve as stabilizing or capping reagents, and play a key role of the formation of two-dimensional Cu2O nanobelts. Cu atoms at weak sites (i.e., twin boundary) on the nanoporous Cu ligaments are ionized to form Cu2+ cations, and then react with OH− to form Cu2O and H2O. The two-dimensional growth of Cu2O nanostructure is preferred in anhydrous ethanol due to the suppression of random growth of Cu2O nanoarchitectures by ethanol. Cu2O nanobelts have superior photodegradation performance of methyl orange, three times higher than nanoporous Cu. Full article
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9 pages, 1792 KiB  
Article
Light Trapping with Silicon Light Funnel Arrays
by Ashish Prajapati, Yuval Nissan, Tamir Gabay and Gil Shalev
Materials 2018, 11(3), 445; https://doi.org/10.3390/ma11030445 - 19 Mar 2018
Cited by 14 | Viewed by 5327
Abstract
Silicon light funnels are three-dimensional subwavelength structures in the shape of inverted cones with respect to the incoming illumination. Light funnel (LF) arrays can serve as efficient absorbing layers on account of their light trapping capabilities, which are associated with the presence of [...] Read more.
Silicon light funnels are three-dimensional subwavelength structures in the shape of inverted cones with respect to the incoming illumination. Light funnel (LF) arrays can serve as efficient absorbing layers on account of their light trapping capabilities, which are associated with the presence of high-density complex Mie modes. Specifically, light funnel arrays exhibit broadband absorption enhancement of the solar spectrum. In the current study, we numerically explore the optical coupling between surface light funnel arrays and the underlying substrates. We show that the absorption in the LF array-substrate complex is higher than the absorption in LF arrays of the same height (~10% increase). This, we suggest, implies that a LF array serves as an efficient surface element that imparts additional momentum components to the impinging illumination, and hence optically excites the substrate by near-field light concentration, excitation of traveling guided modes in the substrate, and mode hybridization. Full article
(This article belongs to the Special Issue Latest Nanotechnology Research Output 2017—Select papers from Applied Nanotechnology and Nanoscience International Conference—ANNIC 2017)
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11 pages, 3229 KiB  
Article
Laser Direct Metal Deposition of 2024 Al Alloy: Trace Geometry Prediction via Machine Learning
by Fabrizia Caiazzo and Alessandra Caggiano
Materials 2018, 11(3), 444; https://doi.org/10.3390/ma11030444 - 19 Mar 2018
Cited by 138 | Viewed by 10124
Abstract
Laser direct metal deposition is an advanced additive manufacturing technology suitably applicable in maintenance, repair, and overhaul of high-cost products, allowing for minimal distortion of the workpiece, reduced heat affected zones, and superior surface quality. Special interest is growing for the repair and [...] Read more.
Laser direct metal deposition is an advanced additive manufacturing technology suitably applicable in maintenance, repair, and overhaul of high-cost products, allowing for minimal distortion of the workpiece, reduced heat affected zones, and superior surface quality. Special interest is growing for the repair and coating of 2024 aluminum alloy parts, extensively utilized for a wide range of applications in the automotive, military, and aerospace sectors due to its excellent plasticity, corrosion resistance, electric conductivity, and strength-to-weight ratio. A critical issue in the laser direct metal deposition process is related to the geometrical parameters of the cross-section of the deposited metal trace that should be controlled to meet the part specifications. In this research, a machine learning approach based on artificial neural networks is developed to find the correlation between the laser metal deposition process parameters and the output geometrical parameters of the deposited metal trace produced by laser direct metal deposition on 5-mm-thick 2024 aluminum alloy plates. The results show that the neural network-based machine learning paradigm is able to accurately estimate the appropriate process parameters required to obtain a specified geometry for the deposited metal trace. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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12 pages, 3891 KiB  
Article
Poly(vinylidene Fluoride-Hexafluoropropylene) Porous Membrane with Controllable Structure and Applications in Efficient Oil/Water Separation
by Xinya Wang, Changfa Xiao, Hailiang Liu, Qinglin Huang, Junqiang Hao and Hao Fu
Materials 2018, 11(3), 443; https://doi.org/10.3390/ma11030443 - 18 Mar 2018
Cited by 35 | Viewed by 6651
Abstract
Poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) porous membranes are fabricated via thermally induced phase separation (TIPS) with mixed diluent (dibutyl phthalate (DBP)/dioctyl phthalate (DOP)). The effects of mixed diluent are discussed in detail in term of morphology, mean pore size, selective wettability, etc. The results show [...] Read more.
Poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) porous membranes are fabricated via thermally induced phase separation (TIPS) with mixed diluent (dibutyl phthalate (DBP)/dioctyl phthalate (DOP)). The effects of mixed diluent are discussed in detail in term of morphology, mean pore size, selective wettability, etc. The results show that the membrane structure changes from spherulitic to bicontinuous with the change of DBP/DOP ratio. It is also found that the degree of crystallization decreases with the decrease of DBP/DOP ratio in mixed diluent. When liquid–liquid (L-L) phase separation precedes solid–liquid (S-L) phase separation, the obtained membranes have outstanding hydrophobicity and lipophilicity, excellent mechanical property. Additionally, the PVDF-HFP hybrid membranes are prepared with silica (SiO2) particles and the effect of SiO2 content on structure and properties is discussed. It is found that the PVDF-HFP hybrid membrane with 2 wt % SiO2 (M3-S2) has better properties and higher filtration rate and separation efficiency for surfactant-stabilized water-in-oil emulsion separation. Moreover, the membrane M3-S2 also exhibits excellent antifouling performance for long-running. Full article
(This article belongs to the Section Thin Films and Interfaces)
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20 pages, 1265 KiB  
Review
Machining of Fibre Reinforced Plastic Composite Materials
by Alessandra Caggiano
Materials 2018, 11(3), 442; https://doi.org/10.3390/ma11030442 - 18 Mar 2018
Cited by 88 | Viewed by 9017
Abstract
Fibre reinforced plastic composite materials are difficult to machine because of the anisotropy and inhomogeneity characterizing their microstructure and the abrasiveness of their reinforcement components. During machining, very rapid cutting tool wear development is experienced, and surface integrity damage is often produced in [...] Read more.
Fibre reinforced plastic composite materials are difficult to machine because of the anisotropy and inhomogeneity characterizing their microstructure and the abrasiveness of their reinforcement components. During machining, very rapid cutting tool wear development is experienced, and surface integrity damage is often produced in the machined parts. An accurate selection of the proper tool and machining conditions is therefore required, taking into account that the phenomena responsible for material removal in cutting of fibre reinforced plastic composite materials are fundamentally different from those of conventional metals and their alloys. To date, composite materials are increasingly used in several manufacturing sectors, such as the aerospace and automotive industry, and several research efforts have been spent to improve their machining processes. In the present review, the key issues that are concerning the machining of fibre reinforced plastic composite materials are discussed with reference to the main recent research works in the field, while considering both conventional and unconventional machining processes and reporting the more recent research achievements. For the different machining processes, the main results characterizing the recent research works and the trends for process developments are presented. Full article
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23 pages, 10645 KiB  
Article
Modelling and Optimization of Polycaprolactone Ultrafine-Fibres Electrospinning Process Using Response Surface Methodology
by Adhi Anindyajati, Philip Boughton and Andrew J. Ruys
Materials 2018, 11(3), 441; https://doi.org/10.3390/ma11030441 - 17 Mar 2018
Cited by 18 | Viewed by 4461
Abstract
Electrospun fibres have gained broad interest in biomedical applications, including tissue engineering scaffolds, due to their potential in mimicking extracellular matrix and producing structures favourable for cell and tissue growth. The development of scaffolds often involves multivariate production parameters and multiple output characteristics [...] Read more.
Electrospun fibres have gained broad interest in biomedical applications, including tissue engineering scaffolds, due to their potential in mimicking extracellular matrix and producing structures favourable for cell and tissue growth. The development of scaffolds often involves multivariate production parameters and multiple output characteristics to define product quality. In this study on electrospinning of polycaprolactone (PCL), response surface methodology (RSM) was applied to investigate the determining parameters and find optimal settings to achieve the desired properties of fibrous scaffold for acetabular labrum implant. The results showed that solution concentration influenced fibre diameter, while elastic modulus was determined by solution concentration, flow rate, temperature, collector rotation speed, and interaction between concentration and temperature. Relationships between these variables and outputs were modelled, followed by an optimization procedure. Using the optimized setting (solution concentration of 10% w/v, flow rate of 4.5 mL/h, temperature of 45 °C, and collector rotation speed of 1500 RPM), a target elastic modulus of 25 MPa could be achieved at a minimum possible fibre diameter (1.39 ± 0.20 µm). This work demonstrated that multivariate factors of production parameters and multiple responses can be investigated, modelled, and optimized using RSM. Full article
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24 pages, 5182 KiB  
Article
Optical Aggregation of Gold Nanoparticles for SERS Detection of Proteins and Toxins in Liquid Environment: Towards Ultrasensitive and Selective Detection
by Antonino Foti, Cristiano D’Andrea, Valentina Villari, Norberto Micali, Maria Grazia Donato, Barbara Fazio, Onofrio M. Maragò, Raymond Gillibert, Marc Lamy de la Chapelle and Pietro G. Gucciardi
Materials 2018, 11(3), 440; https://doi.org/10.3390/ma11030440 - 17 Mar 2018
Cited by 50 | Viewed by 7732
Abstract
Optical forces are used to aggregate plasmonic nanoparticles and create SERS–active hot spots in liquid. When biomolecules are added to the nanoparticles, high sensitivity SERS detection can be accomplished. Here, we pursue studies on Bovine Serum Albumin (BSA) detection, investigating the BSA–nanorod aggregations [...] Read more.
Optical forces are used to aggregate plasmonic nanoparticles and create SERS–active hot spots in liquid. When biomolecules are added to the nanoparticles, high sensitivity SERS detection can be accomplished. Here, we pursue studies on Bovine Serum Albumin (BSA) detection, investigating the BSA–nanorod aggregations in a range from 100 µM to 50 nM by combining light scattering, plasmon resonance and SERS, and correlating the SERS signal with the concentration. Experimental data are fitted with a simple model describing the optical aggregation process. We show that BSA–nanorod complexes can be optically printed on non-functionalized glass surfaces, designing custom patterns stable with time. Furthermore, we demonstrate that this methodology can be used to detect catalase and hemoglobin, two Raman resonant biomolecules, at concentrations of 10 nM and 1 pM, respectively, i.e., well beyond the limit of detection of BSA. Finally, we show that nanorods functionalized with specific aptamers can be used to capture and detect Ochratoxin A, a fungal toxin found in food commodities and wine. This experiment represents the first step towards the addition of molecular specificity to this novel biosensor strategy. Full article
(This article belongs to the Special Issue SERS-Active Substrates)
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20 pages, 6298 KiB  
Article
Effect of Target Composition and Sputtering Deposition Parameters on the Functional Properties of Nitrogenized Ag-Permalloy Flexible Thin Films Deposited on Polymer Substrates
by Waheed Khan, Qun Wang and Xin Jin
Materials 2018, 11(3), 439; https://doi.org/10.3390/ma11030439 - 17 Mar 2018
Cited by 16 | Viewed by 5725
Abstract
We report the first results of functional properties of nitrogenized silver-permalloy thin films deposited on polyethylene terephthalic ester {PETE (C10H8O4)n} flexible substrates by magnetron sputtering. These new soft magnetic thin films have magnetization that is [...] Read more.
We report the first results of functional properties of nitrogenized silver-permalloy thin films deposited on polyethylene terephthalic ester {PETE (C10H8O4)n} flexible substrates by magnetron sputtering. These new soft magnetic thin films have magnetization that is comparable to pure Ni81Fe19 permalloy films. Two target compositions (Ni76Fe19Ag5 and Ni72Fe18Ag10) were used to study the effect of compositional variation and sputtering parameters, including nitrogen flow rate on the phase evolution and surface properties. Aggregate flow rate and total pressure of Ar+N2 mixture was 60 sccm and 0.55 Pa, respectively. The distance between target and the substrate was kept at 100 mm, while using sputtering power from 100–130 W. Average film deposition rate was confirmed at around 2.05 nm/min for argon atmosphere and was reduced to 1.8 nm/min in reactive nitrogen atmosphere. X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, vibrating sample magnetometer, and contact angle measurements were used to characterize the functional properties. Nano sized character of films was confirmed by XRD and SEM. It is found that the grain size was reduced by the formation of nitride phase, which in turns enhanced the magnetization and lowers the coercivity. Magnetic field coupling efficiency limit was determined from 1.6–2 GHz frequency limit. The results of comparable magnetic performance, lowest magnetic loss, and highest surface free energy, confirming that 15 sccm nitrogen flow rate at 115 W is optimal for producing Ag-doped permalloy flexible thin films having excellent magnetic field coupling efficiency. Full article
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15 pages, 2308 KiB  
Article
Optical and Electrical Characterization of Biocompatible Polymeric Lines for Hemodialysis Applications
by Enrico Ravagli and Stefano Severi
Materials 2018, 11(3), 438; https://doi.org/10.3390/ma11030438 - 16 Mar 2018
Cited by 4 | Viewed by 5337
Abstract
During hemodialysis (HD), blood is circulated through an extracorporeal tubing system (bloodline) made of medical-grade polymeric material. Sensors of various types that do not come into contact with blood (optical, electromagnetic, etc.) are applied directly across the bloodline for clinical purposes and for [...] Read more.
During hemodialysis (HD), blood is circulated through an extracorporeal tubing system (bloodline) made of medical-grade polymeric material. Sensors of various types that do not come into contact with blood (optical, electromagnetic, etc.) are applied directly across the bloodline for clinical purposes and for therapy customization. Thus, a detailed knowledge of the bloodline’s physical properties is useful for the development of next-generation HD sensors. In this work, we performed a novel comparative analysis of the materials used by the manufacturers of the bloodlines. We focused on signals and characterization techniques matching those of the abovementioned sensors; consequently, this is an application-specific study of the optical and electrical characterization of bloodline material. Such properties are analyzed and compared for bloodlines from seven different manufacturers by optical absorbance spectroscopy and electrical impedance spectroscopy (EIS). Absorbance spectrum measurements are carried out in the VIS-NIR range. Absorbance spectra are pre-processed and data from both types of analyses are normalized with respect to sample thickness. Optical analysis shows that all bloodlines except one have similarly shaped spectra with slight quantitative differences. In all optical spectra, we find a decreasing trend of specific absorption from 0.14 mm−1 at 400 nm to 0.06 mm−1 at 1000 nm, with an absorption peak at 915 nm. In one case, a large absorption peak centered at ≃600 nm is found. Electrical analysis shows that all bloodlines have the electrical properties of a constant-phase element (CPE), with statistically significant differences in parameters’ values. Estimation of electrical CPE parameters for all bloodline returns a range of 0.942–0.957 for parameter n and a range of 12.41–16.64 for parameter Q0’. In conclusion, we find that, although some statistically significant differences are present, bloodlines from a representative group of manufacturers share similar electrical and optical properties. Therefore, contactless sensing devices developed for HD will work on different bloodlines if a simple recalibration is performed. Full article
(This article belongs to the Special Issue Polymeric Materials for Medical Applications)
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12 pages, 7004 KiB  
Article
Experimental Study on the Fire Performance of Tubular Steel Columns with Membrane Protections for Prefabricated and Modular Steel Construction
by Xin Zhang, Lei Peng, Zhao-peng Ni, Tian-xiao Ni, Yi-liang Huang and Yang Zhou
Materials 2018, 11(3), 437; https://doi.org/10.3390/ma11030437 - 16 Mar 2018
Cited by 7 | Viewed by 6098
Abstract
Experimental research was conducted to study the fire resistance of steel tubular columns used in prefabricated and modular construction. In order to achieve high-efficient prefabrication and fast on-site installation, membrane protections using board products and thermal insulation blankets are adopted as the favorable [...] Read more.
Experimental research was conducted to study the fire resistance of steel tubular columns used in prefabricated and modular construction. In order to achieve high-efficient prefabrication and fast on-site installation, membrane protections using board products and thermal insulation blankets are adopted as the favorable protection method. Three protected tubular columns were tested in a full-scale column furnace with axial load applied. The study variables were different membranes, including fiber reinforced calcium silicate (FRCS) boards, rock wool and aluminum silica (Fiberfrax) insulations. The results suggest that one layer of 12 mm FRCS board with rock wool insulation has insufficient fire protection. However, steel columns protected with two layers of 12 mm FRCS boards with insulation appeared to have good fire resistances and could achieve a fire resistance rating as high as 2.5~3.0 h. Full article
(This article belongs to the Section Advanced Materials Characterization)
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25 pages, 11752 KiB  
Article
Investigation of Polyaniline and a Functionalised Derivative as Antimicrobial Additives to Create Contamination Resistant Surfaces
by Julia Robertson, Marija Gizdavic-Nikolaidis and Simon Swift
Materials 2018, 11(3), 436; https://doi.org/10.3390/ma11030436 - 16 Mar 2018
Cited by 20 | Viewed by 4779
Abstract
Antimicrobial surfaces can be applied to break transmission pathways in hospitals. Polyaniline (PANI) and poly(3-aminobenzoic acid) (P3ABA) are novel antimicrobial agents with potential as non-leaching additives to provide contamination resistant surfaces. The activity of PANI and P3ABA were investigated in suspension and as [...] Read more.
Antimicrobial surfaces can be applied to break transmission pathways in hospitals. Polyaniline (PANI) and poly(3-aminobenzoic acid) (P3ABA) are novel antimicrobial agents with potential as non-leaching additives to provide contamination resistant surfaces. The activity of PANI and P3ABA were investigated in suspension and as part of absorbent and non-absorbent surfaces. The effect of inoculum size and the presence of organic matter on surface activity was determined. PANI and P3ABA both demonstrated bactericidal activity against Escherichia coli and Staphylococcus aureus in suspension and as part of an absorbent surface. Only P3ABA showed antimicrobial activity in non-absorbent films. The results that are presented in this work support the use of P3ABA to create contamination resistant surfaces. Full article
(This article belongs to the Special Issue Conductive Polymers: Materials and Applications)
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15 pages, 48828 KiB  
Article
Laser-Aided Directed Energy Deposition of Steel Powder over Flat Surfaces and Edges
by Fabrizia Caiazzo and Vittorio Alfieri
Materials 2018, 11(3), 435; https://doi.org/10.3390/ma11030435 - 16 Mar 2018
Cited by 21 | Viewed by 4685
Abstract
In the framework of Additive Manufacturing of metals, Directed Energy Deposition of steel powder over flat surfaces and edges has been investigated in this paper. The aims are the repair and overhaul of actual, worn-out, high price sensitive metal components. A full-factorial experimental [...] Read more.
In the framework of Additive Manufacturing of metals, Directed Energy Deposition of steel powder over flat surfaces and edges has been investigated in this paper. The aims are the repair and overhaul of actual, worn-out, high price sensitive metal components. A full-factorial experimental plan has been arranged, the results have been discussed in terms of geometry, microhardness and thermal affection as functions of the main governing parameters, laser power, scanning speed and mass flow rate; dilution and catching efficiency have been evaluated as well to compare quality and effectiveness of the process under conditions of both flat and edge depositions. Convincing results are presented to give grounds for shifting the process to actual applications: namely, no cracks or pores have been found in random cross-sections of the samples in the processing window. Interestingly an effect of the scanning conditions has been proven on the resulting hardness in the fusion zone; therefore, the mechanical characteristics are expected to depend on the processing parameters. Full article
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15 pages, 33472 KiB  
Article
Hot Deformation Behavior and a Two-Stage Constitutive Model of 20Mn5 Solid Steel Ingot during Hot Compression
by Min Liu, Qing-Xian Ma and Jian-Bin Luo
Materials 2018, 11(3), 434; https://doi.org/10.3390/ma11030434 - 16 Mar 2018
Cited by 4 | Viewed by 4121
Abstract
20Mn5 steel is widely used in the manufacture of heavy hydro-generator shaft forging due to its strength, toughness, and wear resistance. However, the hot deformation and recrystallization behaviors of 20Mn5 steel compressed under a high temperature were not studied. For this article, hot [...] Read more.
20Mn5 steel is widely used in the manufacture of heavy hydro-generator shaft forging due to its strength, toughness, and wear resistance. However, the hot deformation and recrystallization behaviors of 20Mn5 steel compressed under a high temperature were not studied. For this article, hot compression experiments under temperatures of 850–1200 °C and strain rates of 0.01 s−1–1 s−1 were conducted using a Gleeble-1500D thermo-mechanical simulator. Flow stress-strain curves and microstructure after hot compression were obtained. Effects of temperature and strain rate on microstructure are analyzed. Based on the classical stress-dislocation relationship and the kinetics of dynamic recrystallization, a two-stage constitutive model is developed to predict the flow stress of 20Mn5 steel. Comparisons between experimental flow stress and predicted flow stress show that the predicted flow stress values are in good agreement with the experimental flow stress values, which indicates that the proposed constitutive model is reliable and can be used for numerical simulation of hot forging of 20Mn5 solid steel ingot. Full article
(This article belongs to the Special Issue Materials: 10th Anniversary)
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13 pages, 15653 KiB  
Article
Wear Behaviours and Oxidation Effects on Different UHMWPE Acetabular Cups Using a Hip Joint Simulator
by Saverio Affatato, Alessandro Ruggiero, Sami Abdel Jaber, Massimiliano Merola and Pierangiola Bracco
Materials 2018, 11(3), 433; https://doi.org/10.3390/ma11030433 - 16 Mar 2018
Cited by 23 | Viewed by 4250
Abstract
Given the long-term problem of polyethylene wear, medical interest in the new improved cross-linked polyethylene (XLPE), with or without the adding of vitamin E, has risen. The main aim of this study is to gain further insights into the mutual effects of radiation [...] Read more.
Given the long-term problem of polyethylene wear, medical interest in the new improved cross-linked polyethylene (XLPE), with or without the adding of vitamin E, has risen. The main aim of this study is to gain further insights into the mutual effects of radiation cross-linking and addition of vitamin E on the wear performance of ultra-high-molecular-weight polyethylene (UHMWPE). We tested four different batches of polyethylene (namely, a standard one, a vitamin E-stabilized, and two cross-linked) in a hip joint simulator for five million cycles where bovine calf serum was used as lubricant. The acetabular cups were then analyzed using a confocal profilometer to characterize the surface topography. Moreover; the cups were analyzed by using Fourier Transformed Infrared Spectroscopy and Differential Scanning Calorimetry in order to assess the chemical characteristics of the pristine materials. Comparing the different cups’ configuration, mass loss was found to be higher for standard polyethylene than for the other combinations. Mass loss negatively correlated to the cross-link density of the polyethylenes. None of the tested formulations showed evidence of oxidative degradation. We found no correlation between roughness parameters and wear. Furthermore, we found significantly differences in the wear behavior of all the acetabular cups. XLPEs exhibited lower weight loss, which has potential for reduced wear and decreased osteolysis. However, surface topography revealed smoother surfaces of the standard and vitamin E stabilized polyethylene than on the cross-linked samples. This observation suggests incipient crack generations on the rough and scratched surfaces of the cross-linked polyethylene liners. Full article
(This article belongs to the Special Issue Advanced Biomaterials for Orthopaedic Application: The Challenge of New Composites and Alloys Used as Medical Devices)
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12 pages, 986 KiB  
Article
Anisotropic-Cyclicgraphene: A New Two-Dimensional Semiconducting Carbon Allotrope
by Marcin Maździarz, Adam Mrozek, Wacław Kuś and Tadeusz Burczyński
Materials 2018, 11(3), 432; https://doi.org/10.3390/ma11030432 - 16 Mar 2018
Cited by 12 | Viewed by 5022
Abstract
A potentially new, single-atom thick semiconducting 2D-graphene-like material, called Anisotropic-cyclicgraphene , has been generated by the two stage searching strategy linking molecular and ab initio approach. The candidate was derived from the evolutionary-based algorithm and molecular simulations was then profoundly analysed [...] Read more.
A potentially new, single-atom thick semiconducting 2D-graphene-like material, called Anisotropic-cyclicgraphene , has been generated by the two stage searching strategy linking molecular and ab initio approach. The candidate was derived from the evolutionary-based algorithm and molecular simulations was then profoundly analysed using first-principles density functional theory from the structural, mechanical, phonon, and electronic properties point of view. The proposed polymorph of graphene (rP16-P1m1) is mechanically, dynamically, and thermally stable and can achieve semiconducting with a direct band gap of 0.829 eV. Full article
(This article belongs to the Section Carbon Materials)
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18 pages, 6535 KiB  
Article
Optoelectronic Properties of X-Doped (X = O, S, Te) Photovoltaic CSe with Puckered Structure
by Qiang Zhang, Tianyuan Xin, Xiaoke Lu and Yuexia Wang
Materials 2018, 11(3), 431; https://doi.org/10.3390/ma11030431 - 16 Mar 2018
Cited by 13 | Viewed by 4801
Abstract
We exploited novel two-dimensional (2D) carbon selenide (CSe) with a structure analogous to phosphorene, and probed its electronics and optoelectronics. Calculating phonon spectra using the density functional perturbation theory (DFPT) method indicated that 2D CSe possesses dynamic stability, which made it possible to [...] Read more.
We exploited novel two-dimensional (2D) carbon selenide (CSe) with a structure analogous to phosphorene, and probed its electronics and optoelectronics. Calculating phonon spectra using the density functional perturbation theory (DFPT) method indicated that 2D CSe possesses dynamic stability, which made it possible to tune and equip CSe with outstanding properties by way of X-doping (X = O, S, Te), i.e., X substituting Se atoms. Then systematic investigation on the structural, electronic, and optical properties of pristine and X-doped monolayer CSe was carried out using the density functional theory (DFT) method. It was found that the bonding feature of C-X is intimately associated with the electronegativity and radius of the doping atoms, which leads to diverse electronic and optical properties for doping different group VI elements. All the systems possess direct gaps, except for O-doping. Substituting O for Se atoms in monolayer CSe brings about a transition from a direct Γ-Γ band gap to an indirect Γ-Y band gap. Moreover, the value of the band gap decreases with increased doping concentration and radius of doping atoms. A red shift in absorption spectra occurs toward the visible range of radiation after doping, and the red-shift phenomenon becomes more obvious with increased radius and concentration of doping atoms. The results can be useful for filtering doping atoms according to their radius or electronegativity in order to tailor optical spectra efficiently. Full article
(This article belongs to the Special Issue Density Functional Theory (DFT) Calculation of Materials Properties)
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9 pages, 1737 KiB  
Article
Two-Dimensional MX2 Semiconductors for Sub-5 nm Junctionless Field Effect Transistors
by Bin Peng, Wei Zheng, Jiantao Qin and Wanli Zhang
Materials 2018, 11(3), 430; https://doi.org/10.3390/ma11030430 - 15 Mar 2018
Cited by 6 | Viewed by 3985
Abstract
Two-dimensional transitional metal dichalcogenide (TMDC) field-effect transistors (FETs) are proposed to be promising for devices scaling beyond silicon-based devices. We explore the different effective mass and bandgap of the channel materials and figure out the possible candidates for high-performance devices with the gate [...] Read more.
Two-dimensional transitional metal dichalcogenide (TMDC) field-effect transistors (FETs) are proposed to be promising for devices scaling beyond silicon-based devices. We explore the different effective mass and bandgap of the channel materials and figure out the possible candidates for high-performance devices with the gate length at 5 nm and below by solving the quantum transport equation self-constantly with the Poisson equation. We find that out of the 14 compounds, MoS2, MoSe2, and MoTe2 may be used in the devices to achieve a good subthreshold swing and a reasonable current ON-OFF ratio and delay. Our work points out the direction of further device optimization for experiments. Full article
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12 pages, 8767 KiB  
Article
Effect of Multiwalled Carbon Nanotubes on the Mechanical Properties of Carbon Fiber-Reinforced Polyamide-6/Polypropylene Composites for Lightweight Automotive Parts
by Huu-Duc Nguyen-Tran, Van-Tho Hoang, Van-Ta Do, Doo-Man Chun and Young-Jin Yum
Materials 2018, 11(3), 429; https://doi.org/10.3390/ma11030429 - 15 Mar 2018
Cited by 71 | Viewed by 7864
Abstract
The development of lightweight automotive parts is an important issue for improving the efficiency of vehicles. Polymer composites have been widely applied to reduce weight and improve mechanical properties by mixing polymers with carbon fibers, glass fibers, and carbon nanotubes. Polypropylene (PP) has [...] Read more.
The development of lightweight automotive parts is an important issue for improving the efficiency of vehicles. Polymer composites have been widely applied to reduce weight and improve mechanical properties by mixing polymers with carbon fibers, glass fibers, and carbon nanotubes. Polypropylene (PP) has been added to carbon fiber-reinforced nylon-6 (CF/PA6) composite to achieve further weight reduction and water resistance. However, the mechanical properties were reduced by the addition of PP. In this research, multiwalled carbon nanotubes (CNTs) were added to compensate for the reduced mechanical properties experienced when adding PP. Tensile testing and bending tests were carried out to evaluate the mechanical properties. A small amount of CNTs improved the mechanical properties of carbon fiber-reinforced PA6/PP composites. For example, the density of CF/PA6 was reduced from 1.214 to 1.131 g/cm3 (6.8%) by adding 30 wt % PP, and the tensile strength of 30 wt % PP composite was improved from 168 to 173 MPa (3.0%) by adding 0.5 wt % CNTs with small increase of density (1.135 g/cm3). The developed composite will be widely used for lightweight automotive parts with improved mechanical properties. Full article
(This article belongs to the Section Advanced Composites)
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