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Materials, Volume 11, Issue 8 (August 2018)

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Cover Story (view full-size image) Inspired by the problems associated with osteochondral defects, we fabricated cytocompatible, [...] Read more.
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Open AccessArticle Some Considerations about the Use of Contact and Confocal Microscopy Methods in Surface Texture Measurement
Materials 2018, 11(8), 1484; https://doi.org/10.3390/ma11081484
Received: 1 July 2018 / Revised: 17 August 2018 / Accepted: 18 August 2018 / Published: 20 August 2018
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Abstract
Surface metrology employs various measurement techniques, among which there has been an increase of noteworthy research into non-contact optical and contact stylus methods. However, some deeper considerations about their differentiation and compatibility are still lacking and necessary. This work compares the measurement characteristics
[...] Read more.
Surface metrology employs various measurement techniques, among which there has been an increase of noteworthy research into non-contact optical and contact stylus methods. However, some deeper considerations about their differentiation and compatibility are still lacking and necessary. This work compares the measurement characteristics of the confocal microscope with the portable stylus profilometer instrumentation, from a metrological point of view (measurement precision and accuracy, and complexity of algorithms for data processing) and an operational view (measuring ranges, measurement speed, environmental and operational requirements, and cost). Mathematical models and algorithms for roughness parameters calculation and their associated uncertainties evaluation are developed and validated. The experimental results demonstrate that the stylus profilometer presents the most reliable measurement with the highest measurement speed and the least complex algorithms, while the image confocal method takes advantage of higher vertical and horizontal resolution when compared with the employed stylus profilometer. Full article
(This article belongs to the Special Issue Special Issue of the Manufacturing Engineering Society (MES))
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Open AccessArticle Silver-Based Chemical Device as an Adjunct of Domestic Oral Hygiene: A Study on Periodontal Patients
Materials 2018, 11(8), 1483; https://doi.org/10.3390/ma11081483
Received: 3 July 2018 / Revised: 14 August 2018 / Accepted: 14 August 2018 / Published: 20 August 2018
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Abstract
The use of chemical devices for periodontitis treatment has led to new strategies aiming primarily to control infections. Over the last few years, new chemical devices have been subjected to many scientific and medical studies. The purpose of the present study was to
[...] Read more.
The use of chemical devices for periodontitis treatment has led to new strategies aiming primarily to control infections. Over the last few years, new chemical devices have been subjected to many scientific and medical studies. The purpose of the present study was to assess the effect of a new silver based chemical devices gel named “Hydrosilver Plus Gel”, abbreviated here as Hydrosilver, on the pathogenic microorganisms, using Polymerase Chain Reaction (PCR) for microbiological analysis. Materials and methods: Ten patients with a diagnosis of chronic periodontitis in the age group >25 years were selected. None of these patients had received any surgical or non-surgical periodontal therapy, and demonstrated radiographic evidence of moderate bone loss. After scaling and root planning, patients received Hydrosilver to be used at home. Four non-adjacent sites in separate quadrants were selected in each patient for monitoring, based on criteria that the sites localise chronic periodontitis. Microbial analysis was analysed at baseline and at Day 15. SPSS program was used for statistical purposes and a paired samples correlation was performed at the end of the observation period. Results: Mean amounts of bacterial loading before and after Hydrosilver treatment reduced statistically significantly (p = 0.002). Conclusions: The present study demonstrated that Hydrosilver has a good impact on oral biofilm. Additional studies are needed to detect the efficacy of this chemical device. Full article
Open AccessArticle In-Situ High Resolution Dynamic X-ray Microtomographic Imaging of Olive Oil Removal in Kitchen Sponges by Squeezing and Rinsing
Materials 2018, 11(8), 1482; https://doi.org/10.3390/ma11081482 (registering DOI)
Received: 30 July 2018 / Revised: 17 August 2018 / Accepted: 17 August 2018 / Published: 20 August 2018
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Abstract
Recent advances in high resolution X-ray tomography (μCT) technology have enabled in-situ dynamic μCT imaging (4D-μCT) of time-dependent processes inside 3D structures, non-destructively and non-invasively. This paper illustrates the application of 4D-μCT for visualizing the removal of fatty liquids from kitchen sponges made
[...] Read more.
Recent advances in high resolution X-ray tomography (μCT) technology have enabled in-situ dynamic μCT imaging (4D-μCT) of time-dependent processes inside 3D structures, non-destructively and non-invasively. This paper illustrates the application of 4D-μCT for visualizing the removal of fatty liquids from kitchen sponges made of polyurethane after rinsing (absorption), squeezing (desorption) and cleaning (adding detergents). For the first time, time-dependent imaging of this type of system was established with sufficiently large contrast gradient between water (with/without detergent) and olive oil (model fat) by the application of suitable fat-sensitive X-ray contrast agents. Thus, contrasted olive oil filled sponges were rinsed and squeezed in a unique laboratory loading device with a fluid flow channel designed to fit inside a rotating gantry-based X-ray μCT system. Results suggest the use of brominated vegetable oil as a preferred contrast agent over magnetite powder for enhancing the attenuation coefficient of olive oil in a multi fluid filled kitchen sponge. The contrast agent (brominated vegetable oil) and olive oil were mixed and subsequently added on to the sponge. There was no disintegration seen in the mixture of contrast agent and olive oil during the cleaning process by detergents. The application of contrast agents also helped in accurately tracking the movement and volume changes of soils in compressed open cell structures. With the in house-built cleaning device, it was quantified that almost 99% of cleaning was possible for contrasted olive oil (brominated vegetable oil with olive oil) dispersed in the sponge. This novel approach allowed for realistic mimicking of the cleaning process and provided closer evaluation of the effectiveness of cleaning by detergents to minimize bacterial growth. Full article
(This article belongs to the Special Issue In-Situ X-Ray Tomographic Study of Materials)
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Open AccessArticle Feasibility Evaluation of Preparing Asphalt Mixture with Low-Grade Aggregate, Rubber Asphalt and Desulphurization Gypsum Residues
Materials 2018, 11(8), 1481; https://doi.org/10.3390/ma11081481
Received: 30 July 2018 / Revised: 14 August 2018 / Accepted: 15 August 2018 / Published: 20 August 2018
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Abstract
Road construction consumes great amounts of high-grade natural resources. Using low-grade natural rocks or some solid wastes as substitute materials is a hot topic. Considering this, the feasibility of using low-grade granite aggregate, solid waste-based filler (desulphurization gypsum residues, DGR) and binder (waste
[...] Read more.
Road construction consumes great amounts of high-grade natural resources. Using low-grade natural rocks or some solid wastes as substitute materials is a hot topic. Considering this, the feasibility of using low-grade granite aggregate, solid waste-based filler (desulphurization gypsum residues, DGR) and binder (waste tire rubber modified asphalt, RMA) simultaneously in asphalt mixtures has been fully investigated in this research. The commonly used base asphalt and limestone powder (LP) filler were control groups. Material characteristics of raw materials mainly including micro-morphology, functional group, mineral phase, chemical composition and thermal stability were first evaluated in order to recognize them. Four asphalt mixtures (two asphalt binder and two filler) were then designed by standard Superpave method. Finally, a detailed investigation into the pavement performance of asphalt mixtures was carried out. The moisture damage resistance and low-temperature crack resistance were detected by the changing rules of stability, strength and fracture energy, and the high-temperature stability and fatigue performance were determined by wheel tracking test and indirect tensile (IDT) fatigue test, respectively. Results suggested that RMA and DGR both showed positive effects on the low-temperature crack resistance and fatigue property of the granite asphalt mixture. DGR also strengthened moisture stability. The contribution of RMA on high-temperature deformation resistance of the granite asphalt mixture was compelling. It can offset the insufficiency in high-temperature stability made by DGR. A conclusion can be made that asphalt mixture prepared with granite, DGR and RMA possesses satisfactory pavement performances. Full article
(This article belongs to the Special Issue Environment-Friendly Construction Materials)
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Open AccessArticle Estimation of Residual Stress in Selective Laser Melting of a Zr-Based Amorphous Alloy
Materials 2018, 11(8), 1480; https://doi.org/10.3390/ma11081480
Received: 19 July 2018 / Revised: 11 August 2018 / Accepted: 17 August 2018 / Published: 20 August 2018
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Abstract
An accurate estimation of residual stresses is crucial to ensure dimensional accuracy and prevent premature fatigue failure of 3D printed components. Different from their crystalline counterparts, the effect of residual stress would be worse for amorphous alloys owing to their intrinsic brittleness with
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An accurate estimation of residual stresses is crucial to ensure dimensional accuracy and prevent premature fatigue failure of 3D printed components. Different from their crystalline counterparts, the effect of residual stress would be worse for amorphous alloys owing to their intrinsic brittleness with low fracture toughness. However, the generation of residual stress and its performance in 3D printed amorphous alloy components still remain unclear. Here, a finite element method combined with experiments and theoretical analyses was introduced to estimate the residual stress in selective laser melting of a Zr-based amorphous alloy. The results revealed that XY cross scanning strategy exhibits relatively low residual stress by comparison with X and Y strategies, and the residual stress becomes serious with increasing bar thickness. The residual stress, on the other hand, could be tuning by annealing or preheating the substrate. The above scenario is thoroughly understood according to the temperature gradient mechanism and its effect on microstructure evaluation. Full article
(This article belongs to the Special Issue Additive Manufacturing: Alloy Design and Process Innovations)
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Open AccessArticle Single-Step Metal-Free Grafting of Cationic Polymer Brushes on Fluorescent Nanodiamonds
Materials 2018, 11(8), 1479; https://doi.org/10.3390/ma11081479
Received: 20 July 2018 / Revised: 10 August 2018 / Accepted: 16 August 2018 / Published: 20 August 2018
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Abstract
Cationic polymers are often employed in conjugation with nanomaterials, and the resultant hybrids are useful for various bioapplications. Here, a single-step metal-free method for the synthesis of fluorescent nanodiamonds (FNDs) conjugated with cationic polymer brushes is reported. Distinct from the common methods such
[...] Read more.
Cationic polymers are often employed in conjugation with nanomaterials, and the resultant hybrids are useful for various bioapplications. Here, a single-step metal-free method for the synthesis of fluorescent nanodiamonds (FNDs) conjugated with cationic polymer brushes is reported. Distinct from the common methods such as atom transfer radical polymerization and reversible addition fragmentation chain transfer, our ring-opening-polymerization-based method is simple and less time consuming and hazardous. Infrared spectroscopy, thermogravimetric analysis, zeta potential, and dynamic light scattering confirmed the synthesis. The produced FND-polymer brushes showed markedly higher cell labeling and internalization efficiency without noticeable cytotoxicity. Our method is general and applicable to other nanoparticles as well for uses in diverse research areas. Full article
(This article belongs to the Special Issue Nanodiamond Particles: Properties and Applications)
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Open AccessReview Nanoscale and Macroscale Scaffolds with Controlled-Release Polymeric Systems for Dental Craniomaxillofacial Tissue Engineering
Materials 2018, 11(8), 1478; https://doi.org/10.3390/ma11081478
Received: 12 July 2018 / Revised: 3 August 2018 / Accepted: 10 August 2018 / Published: 20 August 2018
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Abstract
Tremendous progress in stem cell biology has resulted in a major current focus on effective modalities to promote directed cellular behavior for clinical therapy. The fundamental principles of tissue engineering are aimed at providing soluble and insoluble biological cues to promote these directed
[...] Read more.
Tremendous progress in stem cell biology has resulted in a major current focus on effective modalities to promote directed cellular behavior for clinical therapy. The fundamental principles of tissue engineering are aimed at providing soluble and insoluble biological cues to promote these directed biological responses. Better understanding of extracellular matrix functions is ensuring optimal adhesive substrates to promote cell mobility and a suitable physical niche to direct stem cell responses. Further, appreciation of the roles of matrix constituents as morphogen cues, termed matrikines or matricryptins, are also now being directly exploited in biomaterial design. These insoluble topological cues can be presented at both micro- and nanoscales with specific fabrication techniques. Progress in development and molecular biology has described key roles for a range of biological molecules, such as proteins, lipids, and nucleic acids, to serve as morphogens promoting directed behavior in stem cells. Controlled-release systems involving encapsulation of bioactive agents within polymeric carriers are enabling utilization of soluble cues. Using our efforts at dental craniofacial tissue engineering, this narrative review focuses on outlining specific biomaterial fabrication techniques, such as electrospinning, gas foaming, and 3D printing used in combination with polymeric nano- or microspheres. These avenues are providing unprecedented therapeutic opportunities for precision bioengineering for regenerative applications. Full article
(This article belongs to the Special Issue Polymeric Materials for Medical Applications)
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Open AccessArticle Al2O3-Cu Substrate with Co-Continuous Phases Made by Powder Sintering Process
Materials 2018, 11(8), 1477; https://doi.org/10.3390/ma11081477
Received: 2 August 2018 / Revised: 14 August 2018 / Accepted: 18 August 2018 / Published: 20 August 2018
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Abstract
Ceramic-Al substrates with co-continuous ceramic and metal phases, which exhibit high thermal conductivity and compatible coefficient of thermal expansion (CTE), have been widely investigated through the process of die-casting. In this research, a kind of powder sintering process was proposed for fabricating ceramic-Cu
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Ceramic-Al substrates with co-continuous ceramic and metal phases, which exhibit high thermal conductivity and compatible coefficient of thermal expansion (CTE), have been widely investigated through the process of die-casting. In this research, a kind of powder sintering process was proposed for fabricating ceramic-Cu composite substrates with co-continuous phases. Copper fiber (Cuf) has excellent thermal conductivity and large aspect ratio, making it an ideal material to form bridging network structures in the ceramic-Cu composite. To maintain the large aspect ratio of Cuf, and densify the composite substrate, ZnO-SiO2-CaO glass was introduced as a sintering additive. Both Al2O3/glass/Cuf and Al2O3/30glass/Cup composite substrates were hot-pressed at 850 °C under 25 MPa. Experimental results showed that the thermal conductivity of Al2O3/30glass/30Cuf composite substrate was as high as 38.9 W/mK, which was about 6 times that of Al2O3/30glass; in contrast, the thermal conductivity of Al2O3/30glass/30Cup composite substrate was only 25.9 W/mK. Microstructure observation showed that, influenced by hot press and corrosion of molten ZnO-SiO2-CaO glass, the copper fibers were deformed under hot-pressing, and some local melting-like phenomena occurred on the surface of copper fiber at 850 °C under 25 MPa. The molten phase originating from surface of Cuf welded the overlapping node of copper fibers during cooling process. Finally, the interconnecting metal bridging in ceramic matrix was formed and behaved as a rapid heat-dissipating channel, which is similar to substrates prepared through die-casting process by porous ceramic and melted Al. Full article
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Open AccessArticle Effect of Rejuvenator Containing Dodecyl Benzene Sulfonic Acid (DBSA) on Physical Properties, Chemical Components, Colloidal Structure and Micro-Morphology of Aged Bitumen
Materials 2018, 11(8), 1476; https://doi.org/10.3390/ma11081476
Received: 24 July 2018 / Revised: 4 August 2018 / Accepted: 14 August 2018 / Published: 20 August 2018
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Abstract
DBSA was used as a solubilizer together with conventional rejuvenator (CR) to produce a solubilized rejuvenator (SR), two kinds of aged bitumen involving TFOT aged bitumen and PAV aged bitumen were obtained by thin film oven test (TFOT) and pressurized aging vessel (PAV),
[...] Read more.
DBSA was used as a solubilizer together with conventional rejuvenator (CR) to produce a solubilized rejuvenator (SR), two kinds of aged bitumen involving TFOT aged bitumen and PAV aged bitumen were obtained by thin film oven test (TFOT) and pressurized aging vessel (PAV), respectively. Effects of CR and SR on the physical properties, chemical components, colloidal structure and micro-morphology of TFOT aged bitumen and PAV aged bitumen were investigated. Testing results of physical properties and chemical components indicated that CR and SR can replenish aged bitumen with necessary aromatics, TFOT aged bitumen that chemical component variation deteriorates its physical properties. With regard to PAV aged bitumen, of which the performance attenuation lies in chemical components variation and colloidal structure transformation, even if the content of CR reached up to 10 wt %, the regenerated bitumen cannot meet the regeneration requirement yet due to its definite influence on colloidal structure transformation, comparatively, sulfonic group in SR can react with the superficial atoms of asphaltenes to reform a solvation layer to facilitate the colloidal structure transformation of PAV aged bitumen, performance and beelike structure of regenerated PAV aged with bitumen with 10 wt % SR were approximated to that of virgin bitumen. Full article
(This article belongs to the Special Issue Environment-Friendly Construction Materials)
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Open AccessArticle Electrical Conductivity and Optical Properties of Pulsed Laser Deposited LaNi5 Nanoscale Films
Materials 2018, 11(8), 1475; https://doi.org/10.3390/ma11081475
Received: 15 June 2018 / Revised: 14 August 2018 / Accepted: 17 August 2018 / Published: 19 August 2018
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Abstract
This work presents pulsed laser deposition as a method to obtain unoxidized LaNi5 nanoscale films and describes their temperature and thickness dependent electrical conductivity and the spectral dispersions of some optical properties. AB5-type rare earth element (REE)-nickel compounds are currently
[...] Read more.
This work presents pulsed laser deposition as a method to obtain unoxidized LaNi5 nanoscale films and describes their temperature and thickness dependent electrical conductivity and the spectral dispersions of some optical properties. AB5-type rare earth element (REE)-nickel compounds are currently studied from both theoretical and practical points of view. Special challenges are posed during the preparation of these nanomaterials, which can be overcome using finely tuned parameters in a preparation process that always involves the use of high energies. Film deposition was made by laser—induced vaporization, with short and modulated impulses and electro–optical tuning of the quality factor, mainly on glass and one SiO2 substrate. Deposition geometry dependent linear thickness increase, between 1.5–2.5 nm per laser burst, was achieved. Film structures and phase compositions were determined using XRD and discussed in comparison with films obtained by similar deposition procedures. Temperature and scale dependent properties were determined by studying electrical conductivity and optical properties. Electrical conductivity was measured using the four-probe method. The observed semiconductor-like conductivity for film thicknesses up to 110 nm can be explained by thermal activation of electrons followed by inter-insular hopping or quantum tunneling, which, on the other hand, modulates the material’s native metallic conductance. Films with thicknesses above this value can be considered essentially metallic and bulk-like. The spectral behaviors of the refractive index and absorption coefficient were deduced from differential reflectance spectroscopy data acquired on a broad ultraviolet, visible, near- and mid-infrared (UV-VIS-NIR-MIR) domain, processed using the Kramers-Krönig formalism. Their study led to the identification of the allowed interband transitions. Electronic behavior in the energy bands near the Fermi level and in the surface and interface-states was described, discussing the differences between experimental data and the classical free-electron theoretical model applied for the bulk intermetallic alloy, in correlation with theoretical optical properties or experimental X-ray photoelectron spectroscopy (XPS) results from references. However, the dielectric-like shape of the reflectance of the thinnest film was in accordance with the Lorentz–Drude model. Full article
(This article belongs to the Special Issue Nanomaterials and Materials for Translational Research)
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Open AccessArticle Excellent Carbonation Behavior of Rankinite Prepared by Calcining the C-S-H: Potential Recycling of Waste Concrete Powders for Prefabricated Building Products
Materials 2018, 11(8), 1474; https://doi.org/10.3390/ma11081474
Received: 23 July 2018 / Revised: 13 August 2018 / Accepted: 16 August 2018 / Published: 19 August 2018
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Abstract
Pure rankinite (C3S2) was prepared by calcining a C-S-H gel precursor at a temperature of 1300 °C. The carbonation hardening behavior of the resulting rankinite was revealed by X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, thermogravimetry and differential thermal
[...] Read more.
Pure rankinite (C3S2) was prepared by calcining a C-S-H gel precursor at a temperature of 1300 °C. The carbonation hardening behavior of the resulting rankinite was revealed by X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, thermogravimetry and differential thermal analysis (TG/DTA), and scanning electron microscope (SEM) coupled with energy dispersive spectrum (EDS). The results indicate that the pure rankinite can be easily prepared at a lower temperature. The cubic compressive strengths of the resulting rankinite samples reach a value of 62.5 MPa after 24 h of carbonation curing. The main carbonation products formed during the carbonation process are crystalline calcite, vaterite and highly polymerized amorphous silica gels. The formed carbonation products fill the pores and bind to each other, creating a dense microstructure, which contributes to the excellent mechanical strength. These results provide a novel insight into potential recycling of waste concrete powders for prefabricated building products with lower CO2 emissions. Full article
(This article belongs to the Special Issue Environment-Friendly Construction Materials)
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Open AccessArticle Annealing Behaviour of Pt and PtNi Nanowires for Proton Exchange Membrane Fuel Cells
Materials 2018, 11(8), 1473; https://doi.org/10.3390/ma11081473
Received: 20 July 2018 / Revised: 11 August 2018 / Accepted: 14 August 2018 / Published: 19 August 2018
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Abstract
PtNi alloy and hybrid structures have shown impressive catalytic activities toward the cathodic oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). However, such promise does not often translate into improved electrode performances in PEMFC devices. In this contribution, a Ni
[...] Read more.
PtNi alloy and hybrid structures have shown impressive catalytic activities toward the cathodic oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). However, such promise does not often translate into improved electrode performances in PEMFC devices. In this contribution, a Ni impregnation and subsequent annealing method, translatable to vertically aligned nanowire gas diffusion electrodes (GDEs), is shown in thin-film rotating disk electrode measurements (TFRDE) to enhance the ORR mass activity of Pt nanowires (NWs) supported on carbon (Pt NWs/C) by around 1.78 times. Physical characterisation results indicate that this improvement can be attributed to a combination of Ni alloying of the nanowires with retention of the morphology, while demonstrating that Ni can also help improve the thermal stability of Pt NWs. These catalysts are then tested in single PEMFCs. Lower power performances are achieved for PtNi NWs/C than Pt NWs/C. A further investigation confirms the different surface behaviour between Pt NWs and PtNi NWs when in contact with electrolyte ionomer in the electrodes in PEMFC operation. Indications are that this interaction exacerbates reactant mass transport limitations not seen with TFRDE measurements. Full article
(This article belongs to the Special Issue Metallic Nanowires and Their Applications)
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Open AccessArticle Multi Jet Fusion PA12 Manufacturing Parameters for Watertightness, Strength and Tolerances
Materials 2018, 11(8), 1472; https://doi.org/10.3390/ma11081472
Received: 16 July 2018 / Revised: 15 August 2018 / Accepted: 16 August 2018 / Published: 18 August 2018
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Abstract
The aim of this paper is to explore the watertightness behaviour for high pressure applications using Multi Jet Fusion technology and polyamide 12 as a material. We report an efficient solution for manufacturing functional prototypes and final parts for water pressure applications and
[...] Read more.
The aim of this paper is to explore the watertightness behaviour for high pressure applications using Multi Jet Fusion technology and polyamide 12 as a material. We report an efficient solution for manufacturing functional prototypes and final parts for water pressure applications and provide manufacturing rules for engineers in the pressurized product development process for up to 10 MPa of nominal pressure. The research findings show manufacturers the possibility of using additive manufacturing as an alternative to traditional manufacturing. Water leakage was studied using different printing orientations and wall thicknesses for a range of pressure values. An industrial ball valve was printed and validated with the ISO 9393 standard as also meeting tolerance requirements. This paper is a pioneering approach to the additive manufacturing of high-performance fluid handling components. This approach solves the problem of leakage caused by porosity in additive manufacturing technologies. Full article
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Open AccessArticle The Effect of Alloying Elements on the Structural Stability, Mechanical Properties, and Debye Temperature of Al3Li: A First-Principles Study
Materials 2018, 11(8), 1471; https://doi.org/10.3390/ma11081471
Received: 26 June 2018 / Revised: 11 August 2018 / Accepted: 14 August 2018 / Published: 18 August 2018
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Abstract
The structural stability, mechanical properties, and Debye temperature of alloying elements X (X = Sc, Ti, Co, Cu, Zn, Zr, Nb, and Mo) doped Al3Li were systematically investigated by first-principles methods. A negative enthalpy of formation ΔHf is predicted
[...] Read more.
The structural stability, mechanical properties, and Debye temperature of alloying elements X (X = Sc, Ti, Co, Cu, Zn, Zr, Nb, and Mo) doped Al3Li were systematically investigated by first-principles methods. A negative enthalpy of formation ΔHf is predicted for all Al3Li doped species which has consequences for its structural stability. The Sc, Ti, Zr, Nb, and Mo are preferentially occupying the Li sites in Al3Li while the Co, Cu, and Zn prefer to occupy the Al sites. The Al–Li–X systems are mechanically stable at 0 K as elastic constants Cij has satisfied the stability criteria. The values of bulk modulus B for Al–Li–X (X = Sc, Ti, Co, Cu, Zr, Nb, and Mo) alloys (excluding Al–Li–Zn) increase with the increase of doping concentration and are larger than that for pure Al3Li. The Al6LiSc has the highest shear modulus G and Young’s modulus E which indicates that it has stronger shear deformation resistance and stiffness. The predicted universal anisotropy index AU for pure and doped Al3Li is higher than 0, implying the anisotropy of Al–Li–X alloy. The Debye temperature ΘD of Al12Li3Ti is highest among the Al–Li–X system which predicts the existence of strong covalent bonds and thermal conductivity compared to that of other systems. Full article
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Open AccessArticle Characterization of a New Dry Drill-Milling Process of Carbon Fibre Reinforced Polymer Laminates
Materials 2018, 11(8), 1470; https://doi.org/10.3390/ma11081470
Received: 2 July 2018 / Revised: 7 August 2018 / Accepted: 13 August 2018 / Published: 18 August 2018
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Abstract
Carbon Fibre Reinforced Polymer (CFRP) composites are widely used in aerospace applications that require severe quality parameters. To simplify the assembly operations and reduce the associated costs, the current trend in industry is to optimize the drilling processes. However, the machining of CFRP
[...] Read more.
Carbon Fibre Reinforced Polymer (CFRP) composites are widely used in aerospace applications that require severe quality parameters. To simplify the assembly operations and reduce the associated costs, the current trend in industry is to optimize the drilling processes. However, the machining of CFRP composites is very challenging compared with metals, and several defect types can be generated by drilling. The emerging process of orbital drilling can greatly reduce the defects associated with the traditional drilling of CFRP, but it is a more complex process requiring careful process parameters selection and it does not allow for the complete elimination of the thrust force responsible for delamination damage. As an alternative to traditional and orbital drilling, this work presents a new hole making process, where the hole is realized by a combination of drilling and peripheral milling performed using the same cutting tool following a novel tool path strategy. An original tool design principle is proposed to realize a new drill-milling tool, made of a first drilling and a subsequent milling portion. Two different tool configurations are experimentally tested to evaluate the performance of the newly-conceived combined drill-milling process. This process is quick and easy, and the experimental results show an improvement in the drilled hole quality. Full article
(This article belongs to the Special Issue Special Issue of the Manufacturing Engineering Society (MES))
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Open AccessArticle Product Lifecycle Management as Data Repository for Manufacturing Problem Solving
Materials 2018, 11(8), 1469; https://doi.org/10.3390/ma11081469
Received: 2 July 2018 / Revised: 9 August 2018 / Accepted: 14 August 2018 / Published: 18 August 2018
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Abstract
Fault diagnosis presents a considerable difficulty to human operators in supervisory control of manufacturing systems. Implementing Internet of Things (IoT) technologies in existing manufacturing facilities implies an investment, since it requires upgrading them with sensors, connectivity capabilities, and IoT software platforms. Aligned with
[...] Read more.
Fault diagnosis presents a considerable difficulty to human operators in supervisory control of manufacturing systems. Implementing Internet of Things (IoT) technologies in existing manufacturing facilities implies an investment, since it requires upgrading them with sensors, connectivity capabilities, and IoT software platforms. Aligned with the technological vision of Industry 4.0 and based on currently existing information databases in the industry, this work proposes a lower-investment alternative solution for fault diagnosis and problem solving. This paper presents the details of the information and communication models of an application prototype oriented to production. It aims at assisting shop-floor actors during a Manufacturing Problem Solving (MPS) process. It captures and shares knowledge, taking existing Process Failure Mode and Effect Analysis (PFMEA) documents as an initial source of information related to potential manufacturing problems. It uses a Product Lifecycle Management (PLM) system as source of manufacturing context information related to the problems under investigation and integrates Case-Based Reasoning (CBR) technology to provide information about similar manufacturing problems. Full article
(This article belongs to the Special Issue Special Issue of the Manufacturing Engineering Society (MES))
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Open AccessArticle Hydrothermal Synthesis of Co-Doped NiSe2 Nanowire for High-Performance Asymmetric Supercapacitors
Materials 2018, 11(8), 1468; https://doi.org/10.3390/ma11081468
Received: 20 June 2018 / Revised: 11 July 2018 / Accepted: 15 August 2018 / Published: 18 August 2018
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Abstract
Co@NiSe2 electrode materials were synthesized via a simple hydrothermal method by using nickel foam in situ as the backbone and subsequently characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and a specific surface area analyzer. Results show that the
[...] Read more.
Co@NiSe2 electrode materials were synthesized via a simple hydrothermal method by using nickel foam in situ as the backbone and subsequently characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and a specific surface area analyzer. Results show that the Co@NiSe2 electrode exhibits a nanowire structure and grows uniformly on the nickel foam base. These features make the electrode show a relatively high specific surface area and electrical conductivity, and thus exhibit excellent electrochemical performance. The obtained electrode has a high specific capacitance of 3167.6 F·g−1 at a current density of 1 A·g−1. To enlarge the potential window and increase the energy density, an asymmetric supercapacitor was assembled by using a Co@NiSe2 electrode and activated carbon acting as positive and negative electrodes, respectively. The prepared asymmetrical supercapacitor functions stably under the potential window of 0–1.6 V. The asymmetric supercapacitor can deliver a high energy density of 50.0 Wh·kg−1 at a power density of 779.0 W·kg−1. Moreover, the prepared asymmetric supercapacitor exhibits a good rate performance and cycle stability. Full article
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Open AccessArticle Microstructures, Mechanical and Corrosion Properties of the Extruded AZ31-xCaO Alloys
Materials 2018, 11(8), 1467; https://doi.org/10.3390/ma11081467
Received: 18 July 2018 / Revised: 9 August 2018 / Accepted: 12 August 2018 / Published: 18 August 2018
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Abstract
The effects of the extrusion process and CaO addition amount on microstructure, mechanical, and corrosion properties of AZ31 alloys were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), standard tensile testing, and so on. The grain
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The effects of the extrusion process and CaO addition amount on microstructure, mechanical, and corrosion properties of AZ31 alloys were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), standard tensile testing, and so on. The grain size of AZ31 or AZ31-1%CaO alloy becomes larger with increasing extrusion temperature. The grain size of AZ31-1%CaO alloy is much smaller than that of AZ31 alloy at the same extrusion temperature. In addition, the formation of the Al2Ca phase caused by CaO addition refines the grain size, and the recrystallization of AZ31-1%CaO alloy is improved significantly. The recrystallization grains distribute more uniformly as the increase of extrusion ratio, and the completely recrystallized grains distribute uniformly in the form of equiaxed crystals with an extrusion ratio of 9. Tensile testing results show that extruded AZ31-1%CaO alloy at the extrusion temperature of 300 °C and an extrusion ratio of 9 exhibits the best mechanical properties. While corrosion properties of AZ31 alloys decreases due to the addition of CaO. Full article
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Open AccessArticle Experimental Study of Macro and Microgeometric Defects in Drilled Carbon Fiber Reinforced Plastics by Laser Beam Machining
Materials 2018, 11(8), 1466; https://doi.org/10.3390/ma11081466
Received: 1 July 2018 / Revised: 13 August 2018 / Accepted: 13 August 2018 / Published: 18 August 2018
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Abstract
Plastic matrix composite materials are an excellent choice for structural applications where high strength-weight and stiffness-weight ratios are required. These materials are being increasingly used in diverse industrial sectors, particularly in aerospace. Due to the strict tolerances required, they are usually machined with
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Plastic matrix composite materials are an excellent choice for structural applications where high strength-weight and stiffness-weight ratios are required. These materials are being increasingly used in diverse industrial sectors, particularly in aerospace. Due to the strict tolerances required, they are usually machined with drilling cycles due to the type of mounting through rivets. In this sense, laser beam drilling is presented as an alternative to conventional drilling due to the absence of tool wear, cutting forces, or vibrations during the cutting process. However, the process carries with it other problems that compromise the integrity of the material. One of these is caused by the high temperatures generated during the interaction between the laser and the material. In this work, variance analysis is used to study the influence of scanning speed and frequency on macro geometric parameters, surface quality, and defects (taper and heat affected zone). Also, in order to identify problems in the wall of the drill, stereoscopic optical microscopy (SOM) and scanning electron microscopy (SEM) techniques are used. This experimental procedure reveals the conditions that minimize deviations, defects, and damage in machining holes. Full article
(This article belongs to the Special Issue Special Issue of the Manufacturing Engineering Society (MES))
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Open AccessArticle Biological Compatibility of a Polylactic Acid Composite Reinforced with Natural Chitosan Obtained from Shrimp Waste
Materials 2018, 11(8), 1465; https://doi.org/10.3390/ma11081465
Received: 14 May 2018 / Revised: 1 June 2018 / Accepted: 1 June 2018 / Published: 18 August 2018
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Abstract
The aim of this work is to evaluate the effect of chitosan content (1, 3 and 5 wt %) dispersed in polylactic acid (PLA) on the structure and properties of composites. Also, the hydrolytic degradation, and the cell viability and adhesion of human
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The aim of this work is to evaluate the effect of chitosan content (1, 3 and 5 wt %) dispersed in polylactic acid (PLA) on the structure and properties of composites. Also, the hydrolytic degradation, and the cell viability and adhesion of human MG-63 osteoblasts are analyzed to determine the composites’ suitability for use in tissue engineering. For the manufacture of the materials, natural chitosan was extracted chemically from shrimp exoskeleton. The composites were fabricated by extrusion, because it is a low-cost process, it is reproducible, and it does not compromise the biocompatibility of the materials. FT-IR and XRD show that the chitosan does not change the polymer structure, and interactions between the composite components are discarded. In vitro degradation tests show that the composites do not induce significant pH changes in phosphate buffer solution due to their low susceptibility to hydrolytic degradation. The adhesion and morphological characteristics of the osteoblasts are evaluated using confocal microscopy and scanning electron microscopy. The cell viability is determined by the MTT assay. Osteoblasts adhesion is observed on the surface of PLA and composites. A higher amount of chitosan, higher number of cells with osteoblastic morphology, and mineralized nodules are observed on the composite surface. The highest metabolic activity is evidenced at 21 days. The results suggest that the Polylactic acid/chitosan composites are potentially suitable for use as a biomaterial. Full article
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Open AccessArticle Effects of Cr and Zr Addition on Microstructures, Compressive Properties, and Abrasive Wear Behaviors of In Situ TiB2/Cu Cermets
Materials 2018, 11(8), 1464; https://doi.org/10.3390/ma11081464
Received: 13 July 2018 / Revised: 12 August 2018 / Accepted: 14 August 2018 / Published: 17 August 2018
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Abstract
In situ micro-TiB2/Cu cermets with a different TiB2 content (40, 50, and 60 vol %) were successfully fabricated by combustion synthesis (CS) and hot press consolidation in Cu-Ti-B systems. In addition, different contents of Cr and Zr were added to
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In situ micro-TiB2/Cu cermets with a different TiB2 content (40, 50, and 60 vol %) were successfully fabricated by combustion synthesis (CS) and hot press consolidation in Cu-Ti-B systems. In addition, different contents of Cr and Zr were added to the Cu-Ti-B systems. The microstructure, mechanical properties, and abrasive wear properties of the TiB2/Cu cermets were investigated. As the ceramic content increased, the yield strength and compressive strength of the cermets were found to increase, while the strain decreased. An increase in load and abrasive particle size caused the wear volume loss of the TiB2/Cu cermets to increase. When the ceramic content was 60 vol %, the wear resistance of the TiB2/Cu cermets was 3.3 times higher than that of pure copper. The addition of the alloying elements Zr and Cr had a significant effect on the mechanical properties of the cermets. When the Cr content was 5 wt %, the yield strength, ultimate compressive strength, and microhardness of the cermets reached a maximum of 997 MPa, 1183 MPa, and 491 Hv, respectively. Correspondingly, when the Zr content was 5 wt %, those three values reached 1764 MPa, 1967 MPa, and 655 Hv, respectively, which are 871 MPa, 919 MPa, and 223 Hv higher than those of the unalloyed cermets. The wear mechanism of the in-situ TiB2/Cu cermets, and the mechanisms by which the strength and wear resistance were enhanced by the addition of Zr, were preliminarily revealed. Full article
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Open AccessArticle Fused Filament Fabrication of Small Ceramic Components
Materials 2018, 11(8), 1463; https://doi.org/10.3390/ma11081463
Received: 16 July 2018 / Revised: 8 August 2018 / Accepted: 15 August 2018 / Published: 17 August 2018
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Abstract
With respect to rapid prototyping of ceramic components, there are known only a few processes (stereo lithography, binder jetting). In this work, a new process chain is described in detail, showing that ceramics can be printed in a very cost-efficient way. We developed
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With respect to rapid prototyping of ceramic components, there are known only a few processes (stereo lithography, binder jetting). In this work, a new process chain is described in detail, showing that ceramics can be printed in a very cost-efficient way. We developed a ceramic–polymer composite as filament material that can be printed on a low-cost fused filament fabrication (FFF) desktop printer, even with very small nozzle sizes enabling very small geometric feature sizes. The thermal post-processing, with debinding and sintering, is very close to the ceramic injection molding (CIM) process chain. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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Open AccessArticle Corrosion Behaviors of Q345R Steel at the Initial Stage in an Oxygen-Containing Aqueous Environment: Experiment and Modeling
Materials 2018, 11(8), 1462; https://doi.org/10.3390/ma11081462
Received: 31 May 2018 / Revised: 3 August 2018 / Accepted: 10 August 2018 / Published: 17 August 2018
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Abstract
The ingress of oxygen into pressure vessels used in oil & gas production and transportation could easily result in serious corrosion. In this work, the corrosion behaviors of Q345R steel at the initial stage in 1 wt.% NaCl solution were investigated using electrochemical
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The ingress of oxygen into pressure vessels used in oil & gas production and transportation could easily result in serious corrosion. In this work, the corrosion behaviors of Q345R steel at the initial stage in 1 wt.% NaCl solution were investigated using electrochemical techniques. The effects of oxygen concentration, temperature and pH on corrosion behaviors were discussed. Simultaneously, a numerical model based on the mixed potential theory was proposed. The results show that the proposed model accords well with the experimental data in the pH range from 9.0 to 5.0. In this pH range, the oxygen reduction reaction, H+ reduction, water reduction, and iron oxidation can be quantitatively analyzed using this model. However, this model shows a disagreement with the experimental data at lower pH. This can be attributed to the fact that actual area of reaction on the electrode is much smaller than the preset area due to the block effect resulted from hydrogen bubbles adsorbed on the electrode surface. Full article
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Open AccessArticle Analysis of Surface Extraction Methods Based on Gradient Operators for Computed Tomography in Metrology Applications
Materials 2018, 11(8), 1461; https://doi.org/10.3390/ma11081461
Received: 6 July 2018 / Revised: 13 August 2018 / Accepted: 14 August 2018 / Published: 17 August 2018
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Abstract
Among the multiple factors influencing the accuracy of Computed Tomography measurements, the surface extraction process is a significant contributor. The location of the surface for metrological applications is generally based on the definition of a gray value as a characteristic of similarity to
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Among the multiple factors influencing the accuracy of Computed Tomography measurements, the surface extraction process is a significant contributor. The location of the surface for metrological applications is generally based on the definition of a gray value as a characteristic of similarity to define the regions of interest. A different approach is to perform the detection or location of the surface based on the discontinuity or gradient. In this paper, an adapted 3D Deriche algorithm based on gradient information is presented and compared with a previously developed adapted Canny algorithm for different surface types. Both algorithms have been applied to nine calibrated workpieces with different geometries and materials. Both the systematic error and measurement uncertainty have been determined. The results show a significant reduction of the deviations obtained with the Deriche-based algorithm in the dimensions defined by flat surfaces. Full article
(This article belongs to the Special Issue Special Issue of the Manufacturing Engineering Society (MES))
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Open AccessArticle Fabrication of Polymer Microstructures of Various Angles via Synchrotron X-Ray Lithography Using Simple Dimensional Transformation
Materials 2018, 11(8), 1460; https://doi.org/10.3390/ma11081460
Received: 7 July 2018 / Revised: 6 August 2018 / Accepted: 15 August 2018 / Published: 17 August 2018
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Abstract
In this paper, we developed a method of fabricating polymer microstructures at various angles on a single substrate via synchrotron X-ray lithography coupled with simple dimensional transformations. Earlier efforts to create various three-dimensional (3D) features on flat substrates focused on the exposure technology,
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In this paper, we developed a method of fabricating polymer microstructures at various angles on a single substrate via synchrotron X-ray lithography coupled with simple dimensional transformations. Earlier efforts to create various three-dimensional (3D) features on flat substrates focused on the exposure technology, material properties, and light sources. A few research groups have sought to create microstructures on curved substrates. We created tilted microstructures of various angles by simply deforming the substrate from 3D to two-dimensional (2D). The microstructural inclination angles changed depending on the angles of the support at particular positions. We used convex, concave, and S-shaped supports to fabricate microstructures with high aspect ratios (1:11) and high inclination angles (to 79°). The method is simple and can be extended to various 3D microstructural applications; for example, the fabrication of microarrays for optical components, and tilted micro/nanochannels for biological applications. Full article
(This article belongs to the Special Issue Special Issue of the Manufacturing Engineering Society (MES))
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Open AccessCommunication CVD Synthesis of Monodisperse Graphene/Cu Microparticles with High Corrosion Resistance in Cu Etchant
Materials 2018, 11(8), 1459; https://doi.org/10.3390/ma11081459
Received: 27 June 2018 / Revised: 27 July 2018 / Accepted: 2 August 2018 / Published: 17 August 2018
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Abstract
Copper powder has broad applications in the powder metallurgy, heat exchanger, and electronic industries due to its intrinsically high electrical and thermal conductivities. However, the ease of formation of surface oxide or patina layer raises difficulty of storage and handling of copper powder,
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Copper powder has broad applications in the powder metallurgy, heat exchanger, and electronic industries due to its intrinsically high electrical and thermal conductivities. However, the ease of formation of surface oxide or patina layer raises difficulty of storage and handling of copper powder, particularly in the case of Cu microparticles. Here, we developed a thermal chemical vapor deposition chemical vapor deposition (CVD) process for large-scale synthesis of graphene coatings on Cu microparticles, which importantly can remain monodisperse without aggregation after graphene growth at high temperature by using removal spacers. Compared to other protective coating methods, the intrinsic electrical and thermal properties of Cu powder would not be degraded by uniform growth of low defect few-layer graphene on each particle surface. As a result, when the anticorrosion performance test was carried out by immersing the samples in Cu etchant, the corrosion rate of graphene/Cu microparticles was significantly improved (ca three times slower) compared to that of pristine Cu powder, also showing a comparable anticorrosion ability to commercial CuZn30 alloy. Full article
(This article belongs to the Special Issue Recent Advances in 2D Nanomaterials)
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Open AccessArticle Virtual Extensometer Analysis of Martensite Band Nucleation, Growth, and Strain Softening in Pseudoelastic NiTi Subjected to Different Load Cases
Materials 2018, 11(8), 1458; https://doi.org/10.3390/ma11081458
Received: 27 June 2018 / Revised: 6 August 2018 / Accepted: 14 August 2018 / Published: 17 August 2018
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Abstract
Pseudoelastic NiTi shape memory alloys exhibit different stress–strain curves and modes of deformation in tension vs. compression. We have recently shown that under a combination of compression and shear, heterogeneous deformation can occur. In the present study, we use digital image correlation to
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Pseudoelastic NiTi shape memory alloys exhibit different stress–strain curves and modes of deformation in tension vs. compression. We have recently shown that under a combination of compression and shear, heterogeneous deformation can occur. In the present study, we use digital image correlation to systematically analyze how characteristic features of the nominally uniaxial engineering stress–strain curves (particularly the martensite nucleation peak and the plateau length) are affected by extensometer parameters in tension, compression, and the novel load case of shear-compression. By post-experimental analysis of full surface strain field data, the effect of the placement of various virtual extensometers at different locations (with respect to the nucleation site of martensite bands or inhomogeneously deforming regions) and with different gauge lengths is documented. By positioning an extensometer directly on the region corresponding to the nucleating martensite band, we, for the first time, directly record the strain-softening nature of the material—a specific softening behavior that is, for instance, important for the modeling community. Our results show that the stress–strain curves, which are often used as a basis for constitutive modeling, are affected considerably by the choice of extensometer, particularly under tensile loading, that leads to a distinct mode of localized deformation/transformation. Under compression-shear loading, inhomogeneous deformation (without lateral growth of martensite bands) is observed. The effects of extensometer gauge length are thus less pronounced than in tension, yet systematic—they are rationalized by considering the relative impact of differently deforming regions. Full article
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Open AccessFeature PaperArticle Sinus Membrane Elevation with Heterologous Cortical Lamina: A Randomized Study of a New Surgical Technique for Maxillary Sinus Floor Augmentation without Bone Graft
Materials 2018, 11(8), 1457; https://doi.org/10.3390/ma11081457
Received: 19 July 2018 / Revised: 8 August 2018 / Accepted: 14 August 2018 / Published: 17 August 2018
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Abstract
Background: The aim of this randomized controlled clinical trial was to compare the efficacy of two different techniques for maxillary sinus augmentation using a lateral window approach: Heterologous cortical lamina without any grafting material versus 100% collagenated granular collagen porcine bone. Methods: Twenty-three
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Background: The aim of this randomized controlled clinical trial was to compare the efficacy of two different techniques for maxillary sinus augmentation using a lateral window approach: Heterologous cortical lamina without any grafting material versus 100% collagenated granular collagen porcine bone. Methods: Twenty-three healthy patients with not relevant past medical history (14 women and 9 men, non-smokers, mean age 52 years, range 48–65 years) were included. In Group I, the sinus was filled with collagen porcine bone (Geno-os, OsteoBiol, Turin, Italy) and a collagen membrane (Evolution, OsteoBiol, Turin, Italy) was used to close the lateral window of the sinus. In Group II, the sinus was treated with heterologous cortical lamina only (Lamina, OsteoBiol, Turin, Italy). Results: There was a statistically significant difference in the surgical time required to complete the augmentation procedures: 18.3 ± 2.1 min for lamina treated sites versus 12.5 ± 3.1 min for porcine bone treated sites. In Group I, the mean volume of the graft was 3101 ± 321 mm3 in the immediate postoperative examination (5–7 days), while after a six-month healing period it was 2716.7 ± 432 mm3. Conclusion: This study demonstrates that the use of heterologous cortical lamina is a valid technique for the mechanical support of sinus membranes resulting in only bone tissue formation and not mixed with the graft. The graft material was biocompatible and not completely resorbed after six months, although the remains were integrated into the bone. Full article
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Open AccessArticle Effects of Loading Frequency and Loading Type on High-Cycle and Very-High-Cycle Fatigue of a High-Strength Steel
Materials 2018, 11(8), 1456; https://doi.org/10.3390/ma11081456
Received: 24 July 2018 / Revised: 14 August 2018 / Accepted: 14 August 2018 / Published: 16 August 2018
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Abstract
High-cycle and very-high-cycle fatigue tests via rotary bending (52.5 Hz), electromagnetic resonance (120 Hz) axial cycling, and ultrasonic (20 kHz) axial cycling were performed for a high-strength steel with three heat treatment conditions, and the effects of loading frequency and loading type on
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High-cycle and very-high-cycle fatigue tests via rotary bending (52.5 Hz), electromagnetic resonance (120 Hz) axial cycling, and ultrasonic (20 kHz) axial cycling were performed for a high-strength steel with three heat treatment conditions, and the effects of loading frequency and loading type on fatigue strength and fatigue life were investigated. The results revealed that the loading frequency effect is caused by the combined response of strain rate increase and induced temperature rise. A parameter η was proposed to judge the occurrence of loading frequency effect, and the calculated results were in agreement with the experimental data. In addition, a statistical method based on the control volume was used to reconcile the effect of loading type, and the predicted data were consistent with the experimental results. Full article
(This article belongs to the Special Issue Deformation, Fatigue and Fracture of Materials)
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Open AccessArticle Mechanical Properties Study of Fe-Mn-Si Shape Memory Alloys Welding Seam Formed by Laser Welding with Filler Powder
Materials 2018, 11(8), 1454; https://doi.org/10.3390/ma11081454
Received: 11 July 2018 / Revised: 1 August 2018 / Accepted: 13 August 2018 / Published: 16 August 2018
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Abstract
To reduce the residual stress and improve the fatigue property of the laser weldment by using the stress self-accommodation characteristic of Fe-Mn-Si shape memory alloys (SMAs), a Fe15Mn5Si12Cr6Ni memory alloy welding seam was formed inside 304 stainless steel by laser welding with filler
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To reduce the residual stress and improve the fatigue property of the laser weldment by using the stress self-accommodation characteristic of Fe-Mn-Si shape memory alloys (SMAs), a Fe15Mn5Si12Cr6Ni memory alloy welding seam was formed inside 304 stainless steel by laser welding with filler powder. The combination of the hole-drilling method and the ANSYS software was used to research the distribution law of residual stress inside the laser welding specimen. The fatigue strength of the laser welded specimens with the Fe-Mn-Si SMAs welding seam (experimental materials) and 304 stainless steel welding seam (comparative materials) was measured by cycle bending fatigue test. The microhardness of the welding specimens was measured by the microhardness tester. The thermodynamic model of the laser welding process and the phase transition crystallography of Fe-Mn-Si SMAs were evaluated to analyze the strengthening mechanism of the mechanical properties in the experimental materials. The results show that the distribution law for residual stress in the experiment and simulation are consistent. The experimental materials possess low residual stress, high fatigue strength and high microhardness. The strengthening mechanism for mechanical properties is the welding residual stress-induced γ→ε martensitic transformation inside the experimental materials, which causes the tensile plastic strain of the welding seam to resist residual compression strain, and the residual stress, as the transition driving force, is released in shear processing. Full article
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