Crystals

7 pages, 2030 KiB

Open AccessArticle

Investigation of 1/f and Lorentzian Noise in TMAH-treated Normally-Off GaN MISFETs

by Ki-Sik Im, Mallem Siva Pratap Reddy, Yeo Jin Choi, Youngmin Hwang, Sung Jin An and Jea-Seung Roh

Crystals 2020, 10(8), 717; https://doi.org/10.3390/cryst10080717 - 18 Aug 2020

Cited by 3 | Viewed by 2375

Abstract

A tetramethyl ammonium hydroxide (TMAH)-treated normally-off Gallum nitride (GaN) metal-insulator-semiconductor field-effect transistor (MISFET) was fabricated and characterized using low-frequency noise (LFN) measurements in order to find the conduction mechanism and analyze the trapping behavior into the gate insulator as well as the GaN [...] Read more.

A tetramethyl ammonium hydroxide (TMAH)-treated normally-off Gallum nitride (GaN) metal-insulator-semiconductor field-effect transistor (MISFET) was fabricated and characterized using low-frequency noise (LFN) measurements in order to find the conduction mechanism and analyze the trapping behavior into the gate insulator as well as the GaN buffer layer. At the on-state, the noise spectra in the fabricated GaN device were 1/f^γ properties with γ ≈ 1, which is explained by correlated mobility fluctuations (CMF). On the other hand, the device exhibited Lorentzian or generation-recombination (g-r) noises at the off-state due to deep-level trapping/de-trapping into the GaN buffer layer. The trap time constants (τ_i) calculated from the g-r noises became longer when the drain voltage increased up to 5 V, which was attributed to deep-level traps rather than shallow traps. The severe drain lag was also investigated from pulsed I-V measurement, which is supported by the noise behavior observed at the off-state. Full article

(This article belongs to the Special Issue Nano/Micro and Bio-Inspired Materials on Wide-Bandgap-Semiconductor-Based Optoelectronic/Power Devices)

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2 pages, 162 KiB

Open AccessEditorial

Microwave Liquid Crystal Technology

by Holger Maune

Crystals 2020, 10(8), 716; https://doi.org/10.3390/cryst10080716 - 18 Aug 2020

Cited by 5 | Viewed by 1934

Abstract

Information and communication technologies (ICT) are the foundation of growth and development in the modern global economy [...] Full article

(This article belongs to the Special Issue Microwave Liquid Crystal Technology)

29 pages, 6232 KiB

Open AccessReview

The Effects of Size and Shape Dispersity on the Phase Behavior of Nanomesogen Lyotropic Liquid Crystals

by Fatima Hamade, Sadat Kamal Amit, Mackenzie B. Woods and Virginia A. Davis

Crystals 2020, 10(8), 715; https://doi.org/10.3390/cryst10080715 - 18 Aug 2020

Cited by 6 | Viewed by 4614

Abstract

Self-assembly of anisotropic nanomaterials into fluids is a key step in producing bulk, solid materials with controlled architecture and properties. In particular, the ordering of anisotropic nanomaterials in lyotropic liquid crystalline phases facilitates the production of films, fibers, and devices with anisotropic mechanical, [...] Read more.

Self-assembly of anisotropic nanomaterials into fluids is a key step in producing bulk, solid materials with controlled architecture and properties. In particular, the ordering of anisotropic nanomaterials in lyotropic liquid crystalline phases facilitates the production of films, fibers, and devices with anisotropic mechanical, thermal, electrical, and photonic properties. While often considered a new area of research, experimental and theoretical studies of nanoscale mesogens date back to the 1920s. Through modern computational, synthesis, and characterization tools, there are new opportunities to design liquid crystalline phases to achieve complex architectures and enable new applications in opto-electronics, multifunctional textiles, and conductive films. This review article provides a brief review of the liquid crystal phase behavior of one dimensional nanocylinders and two dimensional nanoplatelets, a discussion of investigations on the effects of size and shape dispersity on phase behavior, and outlook for exploiting size and shape dispersity in designing materials with controlled architectures. Full article

(This article belongs to the Special Issue New Trends in Lyotropic Liquid Crystals)

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2 pages, 135 KiB

Open AccessEditorial

New Horizons in Zeolites and Zeolite-Like Materials

by Leonid Kustov

Crystals 2020, 10(8), 714; https://doi.org/10.3390/cryst10080714 - 18 Aug 2020

Cited by 1 | Viewed by 1836

Abstract

Zeolites have been known for about 250 years, though their active life in science and industry started in the late 1960s. [...] Full article

(This article belongs to the Special Issue New Horizons in Zeolites and Zeolite-Like Materials)

15 pages, 5280 KiB

Open AccessArticle

Design, Synthesis, and Evaluation of X-ray Crystal Structure, Biological Activities, DFT Calculations, and Molecular Docking of Phenyl Imidazolidin-2-One Derivatives

by Xile Deng, Can Jin, Yong Xie, Junbo Gao and Xiaomao Zhou

Crystals 2020, 10(8), 713; https://doi.org/10.3390/cryst10080713 - 18 Aug 2020

Cited by 6 | Viewed by 2764

Abstract

Eight phenyl imidazolinone derivatives were synthesized from N²-(2,4-dimethylphenyl)-N¹-methyformamidine (DPMF) via scaffold-hopping method using the ring-closure approach. The prepared compounds were verified using ¹H and ¹³C NMR and HRMS spectroscopies. The structure of compound 3c was confirmed [...] Read more.

Eight phenyl imidazolinone derivatives were synthesized from N²-(2,4-dimethylphenyl)-N¹-methyformamidine (DPMF) via scaffold-hopping method using the ring-closure approach. The prepared compounds were verified using ¹H and ¹³C NMR and HRMS spectroscopies. The structure of compound 3c was confirmed by single-crystal X-ray diffraction analysis. The mean plane of the phenyl and imidazolinone moieties was almost coplanar with an angle of 8.85(4)°. In the crystal, molecules were interlinked with intermolecular hydrogen bonds (N–H···O and C–H···O), generating a network structure. Additionally, compound 3f displayed the highest insecticidal activity (86.7%) against Plutella xylostella at 600 mg/L, which was significantly higher than the insecticidal activity (23.0%) of DPMF. Also, compound 3d displayed good fungicidal activities against Phytophthora capsici, Phytophthora sojae, and Phytophthora infestans. Density functional theory (DFT) calculations were performed to explain the insecticidal and fungicidal activities of phenyl imidazolidin-2-one derivatives, especially potent compounds 3f and 3d. Moreover, the binding modes of compounds 3a–h and DPMF against octopamine receptor of Plutella xylostella were studied by homology modeling and molecular docking. Therefore, a preliminary structure–activity relationship (SAR) was derived and discussed. These results encourage the exploration of novel insecticides and fungicides based on DPMF. Full article

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12 pages, 3829 KiB

Open AccessArticle

The Study of High Breakdown Voltage Vertical GaN-on-GaN p-i-n Diode with Modified Mesa Structure

by Wen-Chieh Ho, Yao-Hsing Liu, Wen-Hsuan Wu, Sung-Wen Huang Chen, Jerry Tzou, Hao-Chung Kuo and Chia-Wei Sun

Crystals 2020, 10(8), 712; https://doi.org/10.3390/cryst10080712 - 18 Aug 2020

Cited by 4 | Viewed by 4558

Abstract

In this paper, we fabricated Gallium Nitride (GaN) vertical p-i-n diodes grown on free-standing GaN (FS-GaN) substrates. This homogeneous epitaxy led to thicker GaN epi-layers grown on the FS-GaN substrate, but a high crystalline quality was maintained. The vertical [...] Read more.

In this paper, we fabricated Gallium Nitride (GaN) vertical p-i-n diodes grown on free-standing GaN (FS-GaN) substrates. This homogeneous epitaxy led to thicker GaN epi-layers grown on the FS-GaN substrate, but a high crystalline quality was maintained. The vertical GaN p-i-n diode showed a low specific on-resistance of 0.85 mΩ-cm² and high breakdown voltage (BV) of 2.98 kV. The high breakdown voltage can be attributed to the thick GaN epi-layer and corresponds to the mesa structure. Improvement of the device characteristics by the mesa structure was investigated using device simulations. We proved that a deeper mesa depth is able to decrease the electric field at the bottom of the mesa structure. Furthermore, a smaller mesa bevel angle will assist the BV up to 2.98 kV at a 60° bevel angle. Our approach demonstrates structural optimization of GaN vertical p-i-n diodes is useful to improve the device performance. Full article

(This article belongs to the Special Issue GaN-Based Optoelectronic Materials and Light Emitting Devices)

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16 pages, 2800 KiB

Open AccessArticle

Fluorinated Tolane Dyads with Alkylene Linkage: Synthesis and Evaluation of Photophysical Characteristics

by Shigeyuki Yamada, Eiji Uto, Tomohiro Agou, Toshio Kubota and Tsutomu Konno

Crystals 2020, 10(8), 711; https://doi.org/10.3390/cryst10080711 - 18 Aug 2020

Cited by 7 | Viewed by 2708

Abstract

Light-emitting materials have received considerable attention because of their broad applications as substrates in bio-imaging and sensing components, light-emitting displays, and lighting devices. Herein, we developed fluorinated tolane and bistolane derivatives containing fluorinated aromatic rings and demonstrated their intense photoluminescence (PL) characteristics in [...] Read more.

Light-emitting materials have received considerable attention because of their broad applications as substrates in bio-imaging and sensing components, light-emitting displays, and lighting devices. Herein, we developed fluorinated tolane and bistolane derivatives containing fluorinated aromatic rings and demonstrated their intense photoluminescence (PL) characteristics in crystalline powder states. We focused on molecules showing varied PL behavior with a change in the molecular aggregated structures. We synthesized novel fluorinated tolane dyads consisting of fluorinated tolane-based π-conjugated scaffolds and flexible alkylene linkages to control both the electron-density distribution and molecular aggregated states. Fluorinated tolane dyads connected with an alkylene linkage showed blue PL in a dilute solution, but the PL efficiency achieved was low. In contrast, the crystalline powder of tolane dyad substrates exhibited dual emission—relatively intense blue to deep blue PL—originating from monomer and aggregate emission. The PL behavior changed significantly with the alkylene linkage and the application of a mechanical stimulus to the crystalline powder sample. The fluorinated tolane dyads developed in this study could serve as stimulus-responsive photoluminescent materials suitable for optical applications. Full article

(This article belongs to the Special Issue Recent Developments in Stimuli-Responsive Luminescent Materials)

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12 pages, 6262 KiB

Open AccessArticle

Engineered Layer-Stacked Interfaces Inside Aurivillius-Type Layered Oxides Enables Superior Ferroelectric Property

by Shujie Sun and Xiaofeng Yin

Crystals 2020, 10(8), 710; https://doi.org/10.3390/cryst10080710 - 18 Aug 2020

Cited by 9 | Viewed by 2519

Abstract

Layer engineering with different layer numbers inside Aurivillius-type layered structure, similar to interface engineering in heterojunctions or superlattices, can give rise to excellent physical properties due to the correlated layer-stacked interfaces of two different layer phases with different strain states. In this work, [...] Read more.

Layer engineering with different layer numbers inside Aurivillius-type layered structure, similar to interface engineering in heterojunctions or superlattices, can give rise to excellent physical properties due to the correlated layer-stacked interfaces of two different layer phases with different strain states. In this work, using the solid-state reactions from Aurivillius-type Bi₃TiNbO₉ (2-layer) and Bi₄Ti₃O₁₂ (3-layer) ferroelectric powder mixtures, single-phase compound of Bi₇Ti₄NbO₂₁ with an intergrowth structure of 2-layer and 3-layer perovskite slabs sandwiched between the Bi-O layers was synthesized and the effects of this layer-engineered strategy on the structure, Raman-vibration and ferroelectric properties were systematically investigated. The mostly-ordered intergrowth phase was observed clearly by utilizing X-ray diffraction and advanced electron micro-techniques. Uniformly dispersions and collaborative vibrations of Ti and Nb ions in the layer-engineered Bi₇Ti₄NbO₂₁ were demonstrated. Remarkably, dielectric and ferroelectric properties were also recorded and an enhanced ferroelectric response was found in the layer-engineered mixed-layer sample with high ferroelectric Curie temperature, compared with the homogeneous 2-layer and 3-layer samples. Analyses of the Raman spectra and atomic structures confirmed that the performance improvement of the layer-engineered sample is intrinsic to the correlated layer-stacked interfaces inside the Aurivillius-type layered oxides, arising from strain-induced lattice distortions at the interfaces. Full article

(This article belongs to the Special Issue Advanced Research on Heterogeneous Materials)

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13 pages, 5042 KiB

Open AccessArticle

Use of Flue Gas Desulfurization Gypsum, Construction and Demolition Waste, and Oil Palm Waste Trunks to Produce Concrete Bricks

by Lalitsuda Phutthimethakul, Park Kumpueng and Nuta Supakata

Crystals 2020, 10(8), 709; https://doi.org/10.3390/cryst10080709 - 18 Aug 2020

Cited by 14 | Viewed by 3271

Abstract

This research aims to study the utilization of waste from power plants, construction and demolition, and agriculture by varying the ratios of flue-gas desulfurization (FGD) gypsum, construction and demolition waste (CDW), and oil palm trunks (OPT) in concrete production. This research used these [...] Read more.

This research aims to study the utilization of waste from power plants, construction and demolition, and agriculture by varying the ratios of flue-gas desulfurization (FGD) gypsum, construction and demolition waste (CDW), and oil palm trunks (OPT) in concrete production. This research used these as the raw materials for the production of concrete bricks of 15 × 15 × 15 cm. There were 12 ratios of concrete brick, fixing 5.5 wt% of FGD gypsum to replace Portland cement and substituting coarse sand with 0 wt%, 25 wt%, 50 wt%, or 75 wt% of CDW, and gravel with 0 wt%, 0.5 wt%, and 1 wt% of OPT. The initial binder:fine aggregate:coarse aggregate ratio was 1:2:4 and the water to cement ratio was 0.5, curing in water at room temperature for 28 days. Then, all concrete brick specimens were tested for compressive strength and water absorption. From the experiment, it was found that the highest compressive strength of concrete brick specimens was 45.18 MPa, which was produced from 5.5% gypsum without CDW and OPT, while 26.84 MPa was the lowest compressive strength obtained from concrete bricks produced from 5.5% FGD gypsum, 75% CDW, and 1% OPT. In terms of usage, all proportions can be applied in construction and building work because the compressive strength and water absorption were compliant with the Thai Industrial Standard TIS 57-2530 and TIS 60-2516. Full article

(This article belongs to the Special Issue Numerical Study of Concrete)

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14 pages, 7272 KiB

Open AccessArticle

Multi-Approach Study Applied to Restoration Monitoring of a 16th Century Wooden Paste Sculpture

by Auxiliadora Gómez-Morón, Pilar Ortiz, Rocio Ortiz, Francesco Colao, Roberta Fantoni, Jacques Castaing and Javier Becerra

Crystals 2020, 10(8), 708; https://doi.org/10.3390/cryst10080708 - 17 Aug 2020

Cited by 1 | Viewed by 2845

Abstract

A multi-approach study has been designed to evaluate the mannerist-style masterpiece of the Christ of the Expiration (Museum Brotherhood, Seville, Spain), a polychrome wooden paste sculpture of the 16th Century that was restored in the Andalusian Historical Heritage Institute (IAPH). During its intervention, [...] Read more.

A multi-approach study has been designed to evaluate the mannerist-style masterpiece of the Christ of the Expiration (Museum Brotherhood, Seville, Spain), a polychrome wooden paste sculpture of the 16th Century that was restored in the Andalusian Historical Heritage Institute (IAPH). During its intervention, a combination of two non-destructive prototypes were used to evaluate the different color in its feet regarding its legs and torso and its cause. A portable equipment that combined X-ray diffraction (XRD) and X-ray fluorescence (XRF) was employed to analyze chemical composition and mineralogical characterization of pigments. This equipment allowed obtaining simultaneously XRF and XRD at the same point without sampling. X-ray techniques identified cerussite, hydrocerussite and barite in different layers. The presence of zinc oxide from a recent restoration was also detected. Additionally, laser induced fluorescence (LIF) was employed to assess the presence of different fluorescent compounds on the surface. This technique showed the use of acrylic products in the feet, loincloth and torso of Christ from previous restoration and allowed to detect spectral difference on the feet and a high ration of the acrylic product on feet, both could be the cause of the differential degradation between the feet and torso. This multi-approach study based on portable and non-destructive techniques allowed restoration monitoring and helped restorers to take decisions without sampling. Full article

(This article belongs to the Special Issue Structural and Optical Properties of Cultural Heritage Crystalline Materials)

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22 pages, 72586 KiB

Open AccessArticle

A Comparative Study on Blast-Resistant Performance of Steel and PVA Fiber-Reinforced Concrete: Experimental and Numerical Analyses

by Le Chen, Weiwei Sun, Bingcheng Chen, Sen Xu, Jianguo Liang, Chufan Ding and Jun Feng

Crystals 2020, 10(8), 707; https://doi.org/10.3390/cryst10080707 - 16 Aug 2020

Cited by 5 | Viewed by 2961

Abstract

This paper deals with the blast-resistant performance of steel fiber-reinforced concrete (SFRC) and polyvinyl alcohol (PVA) fiber-reinforced concrete (PVA-FRC) panels with a contact detonation test both experimentally and numerically. With 2% fiber volumetric content, SFRC and PVA-FRC specimens were prepared and comparatively tested [...] Read more.

This paper deals with the blast-resistant performance of steel fiber-reinforced concrete (SFRC) and polyvinyl alcohol (PVA) fiber-reinforced concrete (PVA-FRC) panels with a contact detonation test both experimentally and numerically. With 2% fiber volumetric content, SFRC and PVA-FRC specimens were prepared and comparatively tested in comparison with plain concrete (PC). SFRC was found to exhibit better blast-resistant performance than PVA-FRC. The dynamic mechanical responses of FRC panels were numerically studied with Lattice Discrete Particle Model-Fiber (LDPM-F) which was recently developed to simulate the meso-structure of quasi-brittle materials. The effect of dispersed fibers was also introduced in this discrete model as a natural extension. Calibration of LDPM-F model parameters was achieved by fitting the compression and bending responses. A numerical model of FRC contact detonation was then validated against the blast test results in terms of damage modes and crater dimensions. Finally, FRC panels with different fiber volumetric fractions (e.g., 0.5%, 1.0% and 1.5%) under blast loadings were further investigated with the validated LDPM-F blast model. The numerical predictions shed some light on the fiber content effect on the FRC blast resistance performance. Full article

(This article belongs to the Special Issue Numerical Study of Concrete)

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10 pages, 573 KiB

Open AccessReview

Potential Influences of Bacterial Cell Surfaces and Nano-Sized Cell Fragments on Struvite Biomineralization

by Robert J. C. McLean and Erin T. Brown

Crystals 2020, 10(8), 706; https://doi.org/10.3390/cryst10080706 - 15 Aug 2020

Cited by 3 | Viewed by 2683

Abstract

Struvite (MgNH₄PO₄·6H₂O) calculi are formed as a result of urinary tract infections by Proteus mirabilis and other urease-producing bacteria. During struvite formation, the bacteria grow as biofilms, and thus crystals are formed in close association with bacterial [...] Read more.

Struvite (MgNH₄PO₄·6H₂O) calculi are formed as a result of urinary tract infections by Proteus mirabilis and other urease-producing bacteria. During struvite formation, the bacteria grow as biofilms, and thus crystals are formed in close association with bacterial cell surfaces and biofilm matrix components. Small nano-sized objects (originally termed “nanobacteria”) have been described in association with urinary calculi including struvite calculi. A much more likely explanation of these nano-structures is outer membrane vesicles (OMVs) that can be produced by P. mirabilis and other Gram-negative bacteria. In this brief review, we describe the association of bacterial cell surfaces and biofilm matrix components with metal binding and the generation of chemical microenvironments during struvite formation; we propose potential mechanisms whereby OMVs can influence struvite crystal growth and biomineralization. Full article

(This article belongs to the Section Biomolecular Crystals)

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8 pages, 2071 KiB

Open AccessArticle

Structural and Electric Properties of MnO₂-Doped KNN-LT Lead-Free Piezoelectric Ceramics

by Yunfeng Deng, Junjun Wang, Chunxiao Zhang, Hui Ma, Chungeng Bai, Danqing Liu, Fengmin Wu and Bin Yang

Crystals 2020, 10(8), 705; https://doi.org/10.3390/cryst10080705 - 15 Aug 2020

Cited by 9 | Viewed by 2732

Abstract

Structural, ferroelectric, dielectric, and piezoelectric properties of K_0.5Na_0.5NbO₃-LiTaO₃-xmol%MnO₂ lead-free piezoelectric ceramics with 0.0 ≤ x ≤ 0.3 were studied. The ceramic samples were synthesized through the conventional solid-state reaction method. The MnO [...] Read more.

Structural, ferroelectric, dielectric, and piezoelectric properties of K_0.5Na_0.5NbO₃-LiTaO₃-xmol%MnO₂ lead-free piezoelectric ceramics with 0.0 ≤ x ≤ 0.3 were studied. The ceramic samples were synthesized through the conventional solid-state reaction method. The MnO₂ addition can reduce the sintering temperature of KNLNT ceramics. Compared with undoped KNLNT ceramic, the piezoelectric measurements showed that piezoelectric properties of K_0.5Na_0.5NbO₃-LiTaO₃-xMnO₂ were improved (d₃₃ = 251 pC/N) when x = 0.1. In addition, KNLNT-xMnO₂ ceramics have larger P_r(20.59~21.97 μC/cm²) and smaller E_c(10.77~6.95 kV/cm), which indicates MnO₂ has excellent softening property, which improves the ferroelectric properties of KNLNT ceramics This work adds relevant information regarding of potassium sodium niobate K_0.5Na_0.5NbO₃ (KNN) when doped Li, Ta, Mn at the B-site. Full article

(This article belongs to the Special Issue Multifunctional Crystal Materials with Non-centrosymmetry: Piezoelectric and Nonlinear Optical Properties and Their Applications)

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2 pages, 139 KiB

Open AccessEditorial

Additive Manufacturing (AM) of Metallic Alloys

by Flaviana Calignano

Crystals 2020, 10(8), 704; https://doi.org/10.3390/cryst10080704 - 15 Aug 2020

Cited by 2 | Viewed by 1672

Abstract

The introduction of metal additive manufacturing (AM) processes in industrial sectors, such as the aerospace, automotive, defense, jewelry, medical and tool-making fields, has led to a significant reduction in waste material and in the lead times of the components, innovative designs with higher [...] Read more.

The introduction of metal additive manufacturing (AM) processes in industrial sectors, such as the aerospace, automotive, defense, jewelry, medical and tool-making fields, has led to a significant reduction in waste material and in the lead times of the components, innovative designs with higher strength, lower weight and fewer potential failure points from joining features [...] Full article

(This article belongs to the Special Issue Additive Manufacturing (AM) of Metallic Alloys)

12 pages, 2682 KiB

Open AccessArticle

Growth of Interface Region in 2D Wet Foam

by Atef F. I. Abdelkader, Elmuez A. Dawi, A. Karim Haj Ismail and Samer H. Zyoud

Crystals 2020, 10(8), 703; https://doi.org/10.3390/cryst10080703 - 14 Aug 2020

Viewed by 2392

Abstract

This study investigates the evolution of different grain boundaries in two-dimensional wet foam (2D) together with the width and the roughness of the interface. The foam around the boundaries coarsened and became disordered. The level of the disorder increased with time over a [...] Read more.

This study investigates the evolution of different grain boundaries in two-dimensional wet foam (2D) together with the width and the roughness of the interface. The foam around the boundaries coarsened and became disordered. The level of the disorder increased with time over a range and is consistent with the results from previous studies on relatively ordered soap froths. Although the misorientation angle comprising the grain boundaries did not affect the evolution of the foam, the nature of the system boundaries had a significant effect on the degree of the disorder along the grain boundaries. This result is in good agreement with earlier published simulation results. Full article

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12 pages, 3059 KiB

Open AccessArticle

Broadband Asymmetric Propagation in Pillared Meta-Plates

by Lin Chen, Wei Wang, Guohua Nie, Yabin Jin, Daniel Torrent and Bahram Djafari-Rouhani

Crystals 2020, 10(8), 702; https://doi.org/10.3390/cryst10080702 - 14 Aug 2020

Cited by 4 | Viewed by 2619

Abstract

The asymmetric propagation of mechanical energy across interfaces is a challenging problem with a wide range of applications. In this work, we present a novel structure presenting the asymmetric propagation of elastic waves in thin plates in a broadband range. The structure consists [...] Read more.

The asymmetric propagation of mechanical energy across interfaces is a challenging problem with a wide range of applications. In this work, we present a novel structure presenting the asymmetric propagation of elastic waves in thin plates in a broadband range. The structure consists of a combination of symmetrically and asymmetrically distributed pillars, so that the former decouple the different Lamb modes and the latter mix all of them. We show that a combination in tandem with these two structures can realize an efficient broadband asymmetric propagation at the subwavelength range and achieve a transmission difference larger than 200 dB between forward and backward directions. The proposed pillared meta-plate brings a new way for subwavelength and broadband wave manipulation in the fields of wave isolation, sensing and communication, among others. Full article

(This article belongs to the Special Issue Emerging Trends in Phononic Crystals)

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21 pages, 4608 KiB

Open AccessArticle

Optical and Geometrical Characterizations of Non-Linear Supramolecular Liquid Crystal Complexes

by Hoda A. Ahmed, Mohamed Hagar, Omaima A. Alhaddad and Ayman A. Zaki

Crystals 2020, 10(8), 701; https://doi.org/10.3390/cryst10080701 - 14 Aug 2020

Cited by 10 | Viewed by 2419

Abstract

Nonlinear architecture liquid crystalline materials of supramolecular 1:1 H-bonded complexes (I/II and I/III) were prepared through a self-assembly intermolecular interaction between azopyridine (I) and 4-n-alkoxybenzoic acid (II) as well as 4-n-alkoxyphenylazo benzoic acid [...] Read more.

Nonlinear architecture liquid crystalline materials of supramolecular 1:1 H-bonded complexes (I/II and I/III) were prepared through a self-assembly intermolecular interaction between azopyridine (I) and 4-n-alkoxybenzoic acid (II) as well as 4-n-alkoxyphenylazo benzoic acid (III). The H-bond formation of the prepared supramolecular hydrogen bonded (SMHB) complexes was confirmed by Fourier-transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC). Optical and mesomorphic behaviors of the prepared complexes were studied by polarized optical microscopy (POM) as well as DSC. Theoretical calculations were performed by the density functional theory (DFT) and used to predict the molecular geometries of the synthesized complexes, and the results were used to explain the experimental mesomorphic and optical properties in terms of their estimated thermal parameters. Ordinary and extraordinary refractive indices as well as birefringence at different temperatures were investigated for each sample using an Abbe refractometer and modified spectrophotometer techniques. Microscopic and macroscopic order parameters were calculated for individual compounds and their supramolecular complexes. Full article

(This article belongs to the Special Issue Optical and Molecular Aspects of Liquid Crystals)

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15 pages, 3313 KiB

Open AccessArticle

Quantitative Structure–Property Relationships from Experiments for CH₄ Storage and Delivery by Metal–Organic Frameworks

by Eyas Mahmoud

Crystals 2020, 10(8), 700; https://doi.org/10.3390/cryst10080700 - 13 Aug 2020

Cited by 3 | Viewed by 2565

Abstract

Quantitative structure–property relationships (QSPRs) can be applied to metal–organic frameworks (MOFs) to allow for reasonable estimates to be made of the CH₄ storage performance. QSPRs are available for CH₄ storage of MOFs, but these were obtained from Grand Canonical Monte Carlo [...] Read more.

Quantitative structure–property relationships (QSPRs) can be applied to metal–organic frameworks (MOFs) to allow for reasonable estimates to be made of the CH₄ storage performance. QSPRs are available for CH₄ storage of MOFs, but these were obtained from Grand Canonical Monte Carlo (GCMC) simulations which have come under scrutiny and of which the accuracy has been questioned. Here, QSPRs were developed from experimental data and insights are provided on how to improve storage and deliverable CH₄ storage capacity based on material properties. Physical properties of MOFs, such as density, pore volume, and largest cavity diameter (LCD), and their significance for CH₄ storage capacity were assessed. One relationship that was found is that CH₄ gravimetric storage capacity is directly proportional to Brunauer–Emmett–Teller (BET) surface area (r² > 90%). The QSPRs demonstrated the effect of van der Waals forces involved in CH₄ adsorption. An assessment was made of the accuracy of QSPRs made by GCMC as compared to QSPRs derived from experimental data. Guidelines are provided for optimal design of MOFs, including density and pore volume. With the recent achievement of the gravimetric 2012 DOE CH₄ storage target, the QSPRs presented here may allow for the prediction of structural descriptors for CH₄ storage capacity and delivery. Full article

(This article belongs to the Special Issue Metal-Organic Frameworks)

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15 pages, 8907 KiB

Open AccessArticle

Crystallographic Texture Analysis of As-Built and Heat-Treated Ti6Al4V (ELI) Produced by Direct Metal Laser Sintering

by Amos Muiruri, Maina Maringa and Willie du Preez

Crystals 2020, 10(8), 699; https://doi.org/10.3390/cryst10080699 - 12 Aug 2020

Cited by 9 | Viewed by 3321

Abstract

This paper reports on an investigation of crystallographic texture of as-built and heat-treated Ti6Al4V (ELI) produced by direct metal laser sintering (DMLS). The texture analyses were conducted using electron backscatter diffraction (EBSD). The β-phase texture from the obtained EBSD data was ascertained based [...] Read more.

This paper reports on an investigation of crystallographic texture of as-built and heat-treated Ti6Al4V (ELI) produced by direct metal laser sintering (DMLS). The texture analyses were conducted using electron backscatter diffraction (EBSD). The β-phase texture from the obtained EBSD data was ascertained based on a reconstruction method using the Automatic Reconstruction of Parent Grain for EBSD data (ARPGE) program. A significant improvement of the maximum intensity of the texture from the pole figure was also noted upon heat treatment. The as-built samples and samples heat-treated just below the α→β transformation temperature showed a stronger fibrous texture of the reconstructed β-grains with the ⟨

100

⟩ directions almost parallel to the build direction. The alignment of the fibrous texture in the build direction disappeared after heat treatment above the α→β-grain transformation temperature. Full article

(This article belongs to the Special Issue Crystallography of Structural Phase Transformations)

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10 pages, 3399 KiB

Open AccessArticle

Spontaneous Growth of CaBi₄Ti₄O₁₅ Piezoelectric Crystal Using Mixed Flux Agents

by Mengdi Fan, Guangda Wu, Fapeng Yu, Lili Li, Yanlu Li, Xiufeng Cheng and Xian Zhao

Crystals 2020, 10(8), 698; https://doi.org/10.3390/cryst10080698 - 12 Aug 2020

Cited by 3 | Viewed by 2460

Abstract

The bismuth layer-structured ferroelectrics (BLSFs) materials have potential for high-temperature piezoelectric applications. Among these piezoelectric materials, the CaBi₄Ti₄O₁₅ (CBT) piezoelectric ceramic with a high decomposition temperature of about 1250 °C attracts a lot of attention. Achieving a CBT [...] Read more.

The bismuth layer-structured ferroelectrics (BLSFs) materials have potential for high-temperature piezoelectric applications. Among these piezoelectric materials, the CaBi₄Ti₄O₁₅ (CBT) piezoelectric ceramic with a high decomposition temperature of about 1250 °C attracts a lot of attention. Achieving a CBT single crystal is a significant way to improve its piezoelectric properties. For this purpose, the flux system for growing CBT crystal was explored in this study. The optimum flux composition ratio was found to be PbO:B₂O₃:CBT = 3:3:1 in mol%, where the PbO–B₂O₃ mixtures were used as a flux system. Millimeter size flake-shaped CBT crystals were obtained using the spontaneous growth process for the first time. The relationship between the crystal structure and flake growth habit was analyzed. In addition, the bandgap was evaluated by the combination of transmittance spectrum and first-principle calculations. Besides, the piezoelectric property was predicted from the perspective of polyhedral distortion, which indicated the potential of CBT crystal for piezoelectric applications. Full article

(This article belongs to the Special Issue Multifunctional Crystal Materials with Non-centrosymmetry: Piezoelectric and Nonlinear Optical Properties and Their Applications)

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29 pages, 3849 KiB

Open AccessArticle

On the Applicability of Stereological Methods for the Modelling of a Local Plastic Deformation in Grained Structure: Mathematical Principles

by Stanislav Minárik and Maroš Martinkovič

Crystals 2020, 10(8), 697; https://doi.org/10.3390/cryst10080697 - 12 Aug 2020

Cited by 3 | Viewed by 2110

Abstract

Analysis of systems and structures from their cross-sectional images finds applications in many branches. Therefore, the question of content, quantity, and accuracy of information obtained from various techniques based on cross-sectional views of structures is particularly important. Application of conventional techniques for two-dimensional [...] Read more.

Analysis of systems and structures from their cross-sectional images finds applications in many branches. Therefore, the question of content, quantity, and accuracy of information obtained from various techniques based on cross-sectional views of structures is particularly important. Application of conventional techniques for two-dimensional imaging on the analysis of structure from a cross-sectional image is limited. The reason for this limitation is the fact that these techniques use a fixed cross-sectional plane and therefore cannot check the 3D structural changes caused by deformation. Geometric orientation of a grained structure must be considered when data, scanned from a cross section, is processed in order to obtain information about local deformation in this structure. The so-called degree of structure orientation in 3D can be estimated experimentally from the cross-sectional image of the structure by the statistical (Saltykov) method of oriented testing lines. Subsequently if the correlation between orientation and deformation were to be known a detailed map of local deformation in the structure could be revealed. Unfortunately, exact theoretical works dealing with the assessment of local deformation by means of change of structure orientation in 3D are still missing. Our work seeks to partially remove this shortcoming. In our work we are interested in how the transformation of the image of a grained structure in a cross-sectional plane reflects structure deformation. An initial shape of grains is assumed which is transformed into a deformed shape by analytic calculation. We present brief mathematical derivations aimed at the problem of single grain-surface area deformation. The main goal of this work led to the design of a computationally low consuming procedure for quantification of local deformation in a grained structure based on the distortion of the image of this structure in a cross-sectional view. Full article

(This article belongs to the Special Issue Crystal Plasticity)

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20 pages, 7485 KiB

Open AccessArticle

Enhanced Performance of Concrete Composites Comprising Waste Metalised Polypropylene Fibres Exposed to Aggressive Environments

by Rayed Alyousef, Hossein Mohammadhosseini, Fahed Alrshoudi, Mahmood Md. Tahir, Hisham Alabduljabbar and Abdeliazim Mustafa Mohamed

Crystals 2020, 10(8), 696; https://doi.org/10.3390/cryst10080696 - 12 Aug 2020

Cited by 14 | Viewed by 3090

Abstract

The utilisation of waste plastic and polymeric-based materials remains a significant option for clean production, waste minimisation, preserving the depletion of natural resources and decreasing the emission of greenhouse gases, thereby contributing to a green environment. This study aims to investigate the resistance [...] Read more.

The utilisation of waste plastic and polymeric-based materials remains a significant option for clean production, waste minimisation, preserving the depletion of natural resources and decreasing the emission of greenhouse gases, thereby contributing to a green environment. This study aims to investigate the resistance of concrete composites reinforced with waste metalised plastic (WMP) fibres to sulphate and acid attacks. The main test variables include visual inspection, mass loss, and residual strength, as well as the microstructural analysis of specimens exposed to aggressive environments. Two sets of concrete mixes with 100% ordinary Portland cement (OPC) and those with 20% palm oil fuel ash (POFA) were made and reinforced with WMP fibres at volume fractions of 0–1.25%. The results revealed that the addition of WMP fibres decreased the workability and water-cured compressive strength of concrete mixes. The outcomes of the study suggest that the rate of sulphate and acid attacks, in terms of mass losses, was controlled significantly by adding WMP fibres and POFA. The mutual effect of WMP fibre and POFA was detected in the improvement in the concrete’s resistance to sulphate and acid attacks by the reduction in crack formation, spalling, and strength losses. Microstructural analysis conducted on the test specimens elucidates the potential use of POFA in improving the performance of concrete in aggressive environments. Full article

(This article belongs to the Special Issue Numerical Study of Concrete)

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8 pages, 1428 KiB

Open AccessArticle

Homogeneous Nucleation of Hydroxyapatite, Ca₅OH(PO₄)₃, at 37 °C

by Hans Erik Lundager Madsen

Crystals 2020, 10(8), 695; https://doi.org/10.3390/cryst10080695 - 11 Aug 2020

Cited by 1 | Viewed by 2340

Abstract

Precipitation of the calcium phosphate hydroxyapatite,

{Ca}_{5} OH {({PO}_{4})}_{3}

, is studied by simple mixing of reagent solutions and measurement of light scattering (turbidimetry) at six different wavelengths from 300 to 800 nm. Measured turbidities are analyzed using [...] Read more.

Precipitation of the calcium phosphate hydroxyapatite,

{Ca}_{5} OH {({PO}_{4})}_{3}

, is studied by simple mixing of reagent solutions and measurement of light scattering (turbidimetry) at six different wavelengths from 300 to 800 nm. Measured turbidities are analyzed using Mie’s theory of light scattering from small particles. Results are interpreted in terms of classical theory of homogeneous nucleation, and from this the surface free energy of crystals is determined. The low value thus found is explained as the effect of protonation of the strongly basic anions hydroxide and phosphate at the crystal surface. Relatively large particles registered by turbidimetry are shown to be not monocrystals, but aggregates of nanocrystals. Full article

(This article belongs to the Section Biomolecular Crystals)

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14 pages, 3823 KiB

Open AccessArticle

CO₂ Capture in A Bubble-Column Scrubber Using MEA/CaCl₂/H₂O Solution—Absorption and Precipitation

by Pao Chi Chen and Shiun Huang Zhuo

Crystals 2020, 10(8), 694; https://doi.org/10.3390/cryst10080694 - 11 Aug 2020

Cited by 4 | Viewed by 2998

Abstract

This study used the solvent monoethylamine (MEA)/CaCl₂/H₂O to investigate CO₂ absorption and CaCO₃ crystallization in a bubble column scrubber. The variables explored were pH, gas flow rate, gas concentration, the liquid flow rate of the solution to [...] Read more.

This study used the solvent monoethylamine (MEA)/CaCl₂/H₂O to investigate CO₂ absorption and CaCO₃ crystallization in a bubble column scrubber. The variables explored were pH, gas flow rate, gas concentration, the liquid flow rate of the solution to absorb CO_2, and CaCO₃ crystallization. Under a continuous mode, the solution of CaCl₂ was fed continuously, and the pH dropped after CO₂ absorption. To maintain the set pH value, there was an automatic input of the MEA solvent into the bubble column. In addition to maintaining the pH, the solution could also absorb CO₂ and produce CaCO₃ crystals, which served two purposes. The results showed that there were mainly vaterite crystals. At different pH values, the lower the pH, the higher the precipitation rate of vaterite (F_p), and vice versa. However, under different gas flow rates, the F_p decreased as the pH value increased. Additionally, the process variables also affected the absorption rate (R_A) and the overall mass-transfer coefficient (K_Ga) generally increased with increasing pH, gas concentration, and gas flow rate. However, it slowed down under operating conditions at high pH and high gas flow rate. Finally, correlation equations for R_A, K_Ga, and F_p were also obtained and discussed in the study. Full article

(This article belongs to the Special Issue Carbonates Volume II)

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8 pages, 2290 KiB

Open AccessArticle

Kinetics of Capability Aging in Ti-13Nb-13Zr Alloy

by Myoungjae Lee, In-Su Kim, Young Hoon Moon, Hyun Sik Yoon, Chan Hee Park and Taekyung Lee

Crystals 2020, 10(8), 693; https://doi.org/10.3390/cryst10080693 - 11 Aug 2020

Cited by 8 | Viewed by 2482

Abstract

Metals for biomedical implant applications require a simultaneous achievement of high strength and low Young’s modulus from the viewpoints of mechanical properties. The American Society for Testing and Materials (ASTM) standards suggest two types of processing methods to confer such a mechanical performance [...] Read more.

Metals for biomedical implant applications require a simultaneous achievement of high strength and low Young’s modulus from the viewpoints of mechanical properties. The American Society for Testing and Materials (ASTM) standards suggest two types of processing methods to confer such a mechanical performance to Ti-13Nb-13Zr alloy: solution treatment (ST) and capability aging (CA). This study elucidated the kinetics of CA process in Ti-13Nb-13Zr alloy. Microstructural evolution and mechanical change were investigated depending on the CA duration from 10 min to 6 h. The initial ST alloy possessed the full α′-martensitic structure, leading to a low strength, low Young’s modulus, and high ductility. Increasing CA duration increased mechanical strength and Young’s modulus in exchange for the reduction of ductility. Such a tendency is attributed to the decomposition of α′ martensite into (α+β) structure, particularly hard α precipitates. Mechanical compatibility (i.e., Young’s modulus compensated with a mechanical strength) of Ti-13Nb-13Zr alloy rarely increased by changing CA duration, suggestive of the intrinsic limit of static heat treatment. Full article

(This article belongs to the Special Issue Crystal Plasticity)

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20 pages, 2144 KiB

Open AccessArticle

Modelling the Anti-Methicillin-Resistant Staphylococcus Aureus (MRSA) Activity of Cannabinoids: A QSAR and Docking Study

by Eliceo Cortes, José Mora and Edgar Márquez

Crystals 2020, 10(8), 692; https://doi.org/10.3390/cryst10080692 - 11 Aug 2020

Cited by 20 | Viewed by 4199

Abstract

Twenty-four cannabinoids active against MRSA SA1199B and XU212 were optimized at WB97XD/6-31G(d,p), and several molecular descriptors were obtained. Using a multiple linear regression method, several mathematical models with statistical significance were obtained. The robustness of the models was validated, employing the leave-one-out cross-validation [...] Read more.

Twenty-four cannabinoids active against MRSA SA1199B and XU212 were optimized at WB97XD/6-31G(d,p), and several molecular descriptors were obtained. Using a multiple linear regression method, several mathematical models with statistical significance were obtained. The robustness of the models was validated, employing the leave-one-out cross-validation and Y-scrambling methods. The entire data set was docked against penicillin-binding protein, iso-tyrosyl tRNA synthetase, and DNA gyrase. The most active cannabinoids had high affinity to penicillin-binding protein (PBP), whereas the least active compounds had low affinities for all of the targets. Among the cannabinoid compounds, Cannabinoid 2 was highlighted due to its suitable combination of both antimicrobial activity and higher scoring values against the selected target; therefore, its docking performance was compared to that of oxacillin, a commercial PBP inhibitor. The 2D figures reveal that both compounds hit the protein in the active site with a similar type of molecular interaction, where the hydroxyl groups in the aromatic ring of cannabinoids play a pivotal role in the biological activity. These results provide some evidence that the anti-Staphylococcus aureus activity of these cannabinoids may be related to the inhibition of the PBP protein; besides, the robustness of the models along with the docking and Quantitative Structure–Activity Relationship (QSAR) results allow the proposal of three new compounds; the predicted activity combined with the scoring values against PBP should encourage future synthesis and experimental testing. Full article

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21 pages, 4362 KiB

Open AccessArticle

Microstructure Characterization in Individual Texture Components by X-Ray Line Profile Analysis: Principles of the X-TEX Method and Practical Application to Tensile-Deformed Textured Ti

by Bertalan Jóni, Éva Ódor, Mia Maric, Wolfgang Pantleon and Tamás Ungár

Crystals 2020, 10(8), 691; https://doi.org/10.3390/cryst10080691 - 10 Aug 2020

Viewed by 3267

Abstract

A novel X-ray diffraction-based method and computer program X-TEX has been developed to determine the microstructure in individual texture components of polycrystalline, textured materials. Two different approaches are presented. In the first one, based on the texture of the specimen, the X-TEX software [...] Read more.

A novel X-ray diffraction-based method and computer program X-TEX has been developed to determine the microstructure in individual texture components of polycrystalline, textured materials. Two different approaches are presented. In the first one, based on the texture of the specimen, the X-TEX software provides optimized specimen orientations for X-ray diffraction experiments in which diffraction peaks consist of intensity contributions stemming from grain populations of separate texture components in the specimen. Texture-specific diffraction patterns can be created by putting such peaks together from different measurements into an artificial pattern for each texture component. In the second one, the X-TEX software can determine the intensity contributions of different texture components to diffraction peaks measured in a particular sample orientation. According to this, peaks belonging mainly to one of the present texture components are identified and grouped into the same quasi-phase during the evaluation procedure. The X-TEX method was applied and tested on tensile-deformed, textured, commercially pure titanium samples. The patterns were evaluated by the convolutional multiple whole profile (CMWP) procedure of line profile analysis for dislocation densities, dipole character, slip systems and subgrain size for three different texture components of the Ti specimens. Significant differences were found in the microstructure evolution in the two major and the random texture components. The dislocation densities were discussed by the Taylor model of work hardening. Full article

(This article belongs to the Special Issue X-ray and neutron Line Profile Analysis of Microstructures)

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10 pages, 3873 KiB

Open AccessArticle

(Ba,K)(Zn,Mn)₂Sb₂: A New Type of Diluted Magnetic Semiconductor

by Shuang Yu, Guoqiang Zhao, Yi Peng, Xiancheng Wang, Qingqing Liu, Runze Yu, Sijia Zhang, Jianfa Zhao, Wenmin Li, Zheng Deng, Yasutomo J. Uemura and Changqing Jin

Crystals 2020, 10(8), 690; https://doi.org/10.3390/cryst10080690 - 10 Aug 2020

Cited by 5 | Viewed by 2257

Abstract

A series of polycrystalline samples of a new diluted magnetic semiconductor (DMS) (Ba,K)(Zn,Mn)₂Sb₂ has been synthesized and systematically studied. The parent phase is the so-called “Zintl compound” BaZn₂Sb₂, a week-degenerate semiconductor with a narrow band gap [...] Read more.

A series of polycrystalline samples of a new diluted magnetic semiconductor (DMS) (Ba,K)(Zn,Mn)₂Sb₂ has been synthesized and systematically studied. The parent phase is the so-called “Zintl compound” BaZn₂Sb₂, a week-degenerate semiconductor with a narrow band gap of 0.2 eV. In (Ba,K)(Zn,Mn)₂Sb_2, the charge is doped by (Ba,K) substitution while the spin is independently doped by (Zn,Mn) substitution. (Ba,K)(Zn,Mn)₂Sb₂ and analogue (Ba,K)(Zn,Mn)₂As₂ have comparable narrow band gaps, carrier and spin concentrations. However, the former establishes a short-range spin-glass order at a very low temperature (<10 K), while the latter forms a long-range ferromagnetic ordering with a Curie temperature up to 230 K. The sharp contrast makes (Ba,K)(Zn,Mn)₂Sb₂ to be a touchstone for DMS theoretical models. Full article

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13 pages, 10437 KiB

Open AccessArticle

High-Temperature Mechanical Properties of IN718 Alloy: Comparison of Additive Manufactured and Wrought Samples

by Trunal Bhujangrao, Fernando Veiga, Alfredo Suárez, Edurne Iriondo and Franck Girot Mata

Crystals 2020, 10(8), 689; https://doi.org/10.3390/cryst10080689 - 09 Aug 2020

Cited by 39 | Viewed by 5479

Abstract

Wire Arc Additive Manufacturing (WAAM) is one of the most appropriate additive manufacturing techniques for producing large-scale metal components with a high deposition rate and low cost. Recently, the manufacture of nickel-based alloy (IN718) using WAAM technology has received increased attention due to [...] Read more.

Wire Arc Additive Manufacturing (WAAM) is one of the most appropriate additive manufacturing techniques for producing large-scale metal components with a high deposition rate and low cost. Recently, the manufacture of nickel-based alloy (IN718) using WAAM technology has received increased attention due to its wide application in industry. However, insufficient information is available on the mechanical properties of WAAM IN718 alloy, for example in high-temperature testing. In this paper, the mechanical properties of IN718 specimens manufactured by the WAAM technique have been investigated by tensile tests and hardness measurements. The specific comparison is also made with the wrought IN718 alloy, while the microstructure was assessed by scanning electron microscopy and X-ray diffraction analysis. Fractographic studies were carried out on the specimens to understand the fracture behavior. It was shown that the yield strength and hardness of WAAM IN718 alloy is higher than that of the wrought alloy IN718, while the ultimate tensile strength of the WAAM alloys is difficult to assess at lower temperatures. The microstructure analysis shows the presence of precipitates (laves phase) in WAAM IN718 alloy. Finally, the effect of precipitation on the mechanical properties of the WAAM IN718 alloy was discussed in detail. Full article

(This article belongs to the Special Issue Recent Advances in Metallurgy and Properties of Superalloys)

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2 pages, 161 KiB

Open AccessEditorial

Photonic Crystals

by Martella Daniele and Sara Nocentini

Crystals 2020, 10(8), 688; https://doi.org/10.3390/cryst10080688 - 08 Aug 2020

Cited by 1 | Viewed by 2098

Abstract

The past and present goal of photonic technology stems in the fine and arbitrary control of light propagation within miniaturized devices that can possibly integrate different functionalities [...] Full article

(This article belongs to the Special Issue Sonic and Photonic Crystals)

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Crystals, Volume 10, Issue 8 (August 2020) – 87 articles

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