Materials

15 pages, 8599 KiB

Open AccessArticle

The Effect of Processing Route on Properties of HfNbTaTiZr High Entropy Alloy

by Jaroslav Málek, Jiří Zýka, František Lukáč, Monika Vilémová, Tomáš Vlasák, Jakub Čížek, Oksana Melikhova, Adéla Macháčková and Hyoung-Seop Kim

Materials 2019, 12(23), 4022; https://doi.org/10.3390/ma12234022 - 3 Dec 2019

Cited by 25 | Viewed by 5266

Abstract

High entropy alloys (HEA) have been one of the most attractive groups of materials for researchers in the last several years. Since HEAs are potential candidates for many (e.g., refractory, cryogenic, medical) applications, their properties are studied intensively. The most frequent method of [...] Read more.

High entropy alloys (HEA) have been one of the most attractive groups of materials for researchers in the last several years. Since HEAs are potential candidates for many (e.g., refractory, cryogenic, medical) applications, their properties are studied intensively. The most frequent method of HEA synthesis is arc or induction melting. Powder metallurgy is a perspective technique of alloy synthesis and therefore in this work the possibilities of synthesis of HfNbTaTiZr HEA from powders were studied. Blended elemental powders were sintered, hot isostatically pressed, and subsequently swaged using a special technique of swaging where the sample is enveloped by a titanium alloy. This method does not result in a full density alloy due to cracking during swaging. Spark plasma sintering (SPS) of mechanically alloyed powders resulted in a fully dense but brittle specimen. The most promising result was obtained by SPS treatment of gas atomized powder with low oxygen content. The microstructure of HfNbTaTiZr specimen prepared this way can be refined by high pressure torsion deformation resulting in a high hardness of 410 HV10 and very fine microstructure with grain size well below 500 nm. Full article

(This article belongs to the Special Issue Mechanical Properties in Progressive Mechanically Processed Metallic Materials)

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20 pages, 4372 KiB

Open AccessArticle

New Pre-reacted Glass Containing Dental Composites (giomers) with Improved Fluoride Release and Biocompatibility

by Loredana Colceriu Burtea, Cristina Prejmerean, Doina Prodan, Ioana Baldea, Mihaela Vlassa, Miuta Filip, Marioara Moldovan, Madalina-Anca Lazar (Moldovan), Aurora Antoniac, Vasile Prejmerean and Ioana Ambrosie

Materials 2019, 12(23), 4021; https://doi.org/10.3390/ma12234021 - 3 Dec 2019

Cited by 24 | Viewed by 4598

Abstract

The aim of the present work was to prepare a series of novel restorative giomers and investigate the morphology, the physico-chemical properties (residual monomer, fluoride release), and the cytotoxicity of the new materials. The experimental giomers were prepared as light-cured pastes by blending [...] Read more.

The aim of the present work was to prepare a series of novel restorative giomers and investigate the morphology, the physico-chemical properties (residual monomer, fluoride release), and the cytotoxicity of the new materials. The experimental giomers were prepared as light-cured pastes by blending different resin matrices comprising aromatic/aliphatic/urethane (di) methacrylates, with hybrid fillers containing pre-reacted glasses (PRGs), a radiopaque glass, and nano fluorhydroxyapatite. Polyalkenoic acids based on acrylic acid/itaconic acid/N-acryloyl -L-leucine modified or not with methacrylic groups, together with a superficially active glass, were used to prepare the PRGs. The fluoride ion release of the experimental giomers was investigated within a period of 60 days of storage in bidistilled water while using a fluoride ion selective electrode. Beautifil II commercial product was used as a reference. Cell cytotoxicity tests were done in vitro, in accordance with ISO 10993-122012 proceedings. Human dermal fibroblasts and umbilical endothelial vein cultures were used. The values that were obtained for cumulative fluoride release for all experimental giomers were higher than for the Beautifil II product, being more than twice the ones that were obtained for the commercial product after 60 days of storage in bidistilled water. The experimental biomaterials showed similar and/or better results when compared to the commercial one; this effect was maintained in all tested conditions. Full article

(This article belongs to the Special Issue Selected Papers from BIOMMEDD 2018 Conference—Biomaterials)

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18 pages, 6553 KiB

Open AccessArticle

Composite Eco-Friendly Sound Absorbing Materials Made of Recycled Textile Waste and Biopolymers

by Chiara Rubino, Marilés Bonet Aracil, Jaime Gisbert-Payá, Stefania Liuzzi, Pietro Stefanizzi, Manuel Zamorano Cantó and Francesco Martellotta

Materials 2019, 12(23), 4020; https://doi.org/10.3390/ma12234020 - 3 Dec 2019

Cited by 54 | Viewed by 7022

Abstract

In recent years, the interest in reusing recycled fibers as building materials has been growing as a consequence of their ability to reduce the production of waste and the use of virgin resources, taking advantage of the potential that fibrous materials may offer [...] Read more.

In recent years, the interest in reusing recycled fibers as building materials has been growing as a consequence of their ability to reduce the production of waste and the use of virgin resources, taking advantage of the potential that fibrous materials may offer to improve thermal and acoustic comfort. Composite panels, made of 100% wool waste fibers and bound by means of either a chitosan solution and a gum Arabic solution, were tested and characterized in terms of acoustic and non-acoustic properties. Samples with a 5 cm thickness and different density values were made to investigate the influence of flow resistivity on the final performance. Experimental results demonstrated that the samples had thermal conductivity ranging between 0.049 and 0.060 W/(m K), well comparable to conventional building materials. Similarly, acoustic results were very promising, showing absorption coefficients that, for the given thickness, were generally higher than 0.5 from 500 Hz on, and higher than 0.9 from 1 kHz on. Finally, the effects of the non-acoustic properties and of the air gap behind the samples on the acoustic behavior were also analyzed, proving that the agreement with absorption values predicted by empirical models was also very good. Full article

(This article belongs to the Special Issue Innovative Composite Materials for Sound Absorption and Insulation)

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10 pages, 2055 KiB

Open AccessArticle

The Enhanced and Tunable Sustained Release of Pesticides Using Activated Carbon as a Carrier

by Jun Yang, Wanyu Zang, Zheng Zhang, Peng Wang and Qing Yang

Materials 2019, 12(23), 4019; https://doi.org/10.3390/ma12234019 - 3 Dec 2019

Cited by 16 | Viewed by 3484

Abstract

The sustained release of pesticides improves drug utilization efficiency and reduces their adverse effects. Activated carbon (AC) is an excellent adsorbent and promising soil conditioner. It has a rich, porous structure and thus can store and gradually release drugs. In this study, three [...] Read more.

The sustained release of pesticides improves drug utilization efficiency and reduces their adverse effects. Activated carbon (AC) is an excellent adsorbent and promising soil conditioner. It has a rich, porous structure and thus can store and gradually release drugs. In this study, three AC materials with surface areas ranging from 800–2000 m²/g were used and two types of modified activated carbons were prepared, and their capacity as drug carriers was evaluated by using 2,4-Dichlorophenoxyacetic acid sodium (2,4-D sodium) as the model pesticide. The preparations were characterized by scanning electron microscopy, nitrogen physical analysis, and zeta potential. The five preparations showed an enhanced and tunable sustained release of drugs. AC1, with the highest specific surface area, possesses the best drug-loading capacity, reaching 679.18 mg/g, but the lowest drug release rate of 32.31% in 96 h. PDA-AC3 has the lowest specific surface area, showing limited drug-loading ability, 82.94 mg/g, but 100% drug release within 72 h. This study suggests that activated carbon has potent applications in agricultural pest control as an inexpensive, effective, controllable, and safe pesticide carrier. Full article

(This article belongs to the Section Carbon Materials)

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17 pages, 8339 KiB

Open AccessArticle

Effect of Relative Density on Compressive Load Response of Crumpled Aluminium Foil Mesh

by David Hughes, Emeka H. Amalu, Tannaz Pak and Ryan Kennedy

Materials 2019, 12(23), 4018; https://doi.org/10.3390/ma12234018 - 3 Dec 2019

Cited by 4 | Viewed by 2893

Abstract

In recent years, a large number of metal foams and porous metals have been developed. Due to the high cost of these materials alternative manufacturing methods for cellular metallic materials are being explored. Crumpled metallic foil meshes, manufactured via die compression techniques, are [...] Read more.

In recent years, a large number of metal foams and porous metals have been developed. Due to the high cost of these materials alternative manufacturing methods for cellular metallic materials are being explored. Crumpled metallic foil meshes, manufactured via die compression techniques, are evolving as a potential alternative method. However, the non-availability of sufficient data on their load response is limiting their uptake. Uniaxial compressive load response of crumpled aluminium foil meshes (CAFMs) of varying densities, forged by open and closed die compression, are studied. A 0.05 mm thick aluminium sheet mesh, manufactured by the expanded metal process is used. X-ray computed micro-tomography is employed to image the CAFM’s internal cellular structure. The stress-strain relation demonstrates that the CAFMs produce identical load response profile irrespective of their relative density. Power law functions

E_{R} = 17110 ρ_{r}^{3.6547}

and

σ_{Y, E} = 53.092 ρ_{r}^{2.2249}

define the relationships between real Young’s Modulus

E_{R}

and effective yield strength,

σ_{Y, E}

. The study provides new knowledge on the effect of relative density on the compressive properties of CAFMs which have applications across lightweight structural design. Full article

(This article belongs to the Section Porous Materials)

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13 pages, 7317 KiB

Open AccessArticle

Development of Antibacterial Ti-Cu_x Alloys for Dental Applications: Effects of Ageing for Alloys with Up to 10 wt% Cu

by Lee Fowler, Nomsombuluko Masia, Lesley A. Cornish, Lesley H. Chown, Håkan Engqvist, Susanne Norgren and Caroline Öhman-Mägi

Materials 2019, 12(23), 4017; https://doi.org/10.3390/ma12234017 - 3 Dec 2019

Cited by 28 | Viewed by 3831

Abstract

Peri-implantitis, a disease caused by bacteria, affects dental implants in patients. It is widely treated with antibiotics, however, with growing antibiotic resistance new strategies are required. Titanium-copper alloys are prospective antibacterial biomaterials, with the potential to be a remedy against peri-implantitis and antibiotic [...] Read more.

Peri-implantitis, a disease caused by bacteria, affects dental implants in patients. It is widely treated with antibiotics, however, with growing antibiotic resistance new strategies are required. Titanium-copper alloys are prospective antibacterial biomaterials, with the potential to be a remedy against peri-implantitis and antibiotic resistance. The aim of this study was to investigate Ti-Cu_x alloys, exploring how Cu content (up to 10 wt%) and ageing affect the material properties. Electron microscopy, X-ray diffraction, hardness testing, bacteriological culture, and electrochemical testing were employed to characterize the materials. It was found that alloys with above 3 wt% Cu had two phases and ageing increased the volume fraction of Ti₂Cu. An un-aged alloy of 5 wt% Cu showed what could be Ti₃Cu, in addition to the α-Ti phase. The hardness gradually increased with increased Cu additions, while ageing only affected the alloy with 10 wt% Cu (due to changes in microstructure). Ageing resulted in faster passivation of the alloys. After two hours the aged 10 wt% Cu alloy was the only material with an antibacterial effect, while after six hours, bacteria killing occurred in all alloys with above 5 wt% Cu. In conclusion, it was possible to tune the material and antibacterial properties of Ti-Cu_x alloys by changing the Cu concentration and ageing, which makes further optimization towards an antibacterial material promising. Full article

(This article belongs to the Special Issue Ti-Based Biomaterials: Synthesis, Properties and Applications)

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22 pages, 2801 KiB

Open AccessReview

Construction and Demolition Waste as Recycled Aggregates in Alkali-Activated Concretes

by Zahra Abdollahnejad, Mohammad Mastali, Mahroo Falah, Tero Luukkonen, Mehran Mazari and Mirja Illikainen

Materials 2019, 12(23), 4016; https://doi.org/10.3390/ma12234016 - 3 Dec 2019

Cited by 44 | Viewed by 5654

Abstract

The growth of global construction has contributed to an inevitable increase in the amount of construction and demolition (C&D) waste, and the recycling of C&D waste as aggregates in concrete is receiving increased interest, resulting in less demand for normal aggregates and bringing [...] Read more.

The growth of global construction has contributed to an inevitable increase in the amount of construction and demolition (C&D) waste, and the recycling of C&D waste as aggregates in concrete is receiving increased interest, resulting in less demand for normal aggregates and bringing a potential solution for the landfilling of wastes. Recently, several studies have focused on the use of C&D waste in alkali-activated concrete to move one step closer to sustainable concretes. This paper focuses on the main mechanisms of using C&D waste in the resulting physical, mechanical, and durability properties of alkali-activated concrete in fresh and hardened state properties. The main difficulties observed with recycled aggregates (RA) in concrete, such as high levels of water demand, porous structure, and low mechanical strength, occur in RA alkali-activated concretes. These are associated with the highly porous nature and defects of RA. However, the high calcium concentration of RA affects the binder gel products, accelerates the hardening rate of the concrete, and reduces the flowability of alkali-activated concretes. For this reason, several techniques have been investigated for modifying the water content and workability of the fresh matrix and for treating RA and RA/alkali-activated binder interactions to produce more sustainable alkali-activated concretes. Full article

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14 pages, 6356 KiB

Open AccessArticle

Study of Strain-Hardening Behaviour of Fibre-Reinforced Alkali-Activated Fly Ash Cement

by Hyuk Lee, Vanissorn Vimonsatit, Priyan Mendis and Ayman Nassif

Materials 2019, 12(23), 4015; https://doi.org/10.3390/ma12234015 - 3 Dec 2019

Cited by 2 | Viewed by 2734

Abstract

This paper presents a study of parameters affecting the fibre pull out capacity and strain-hardening behaviour of fibre-reinforced alkali-activated cement composite (AAC). Fly ash is a common aluminosilicate source in AAC and was used in this study to create fly ash based AAC. [...] Read more.

This paper presents a study of parameters affecting the fibre pull out capacity and strain-hardening behaviour of fibre-reinforced alkali-activated cement composite (AAC). Fly ash is a common aluminosilicate source in AAC and was used in this study to create fly ash based AAC. Based on a numerical study using Taguchi’s design of experiment (DOE) approach, the effect of parameters on the fibre pull out capacity was identified. The fibre pull out force between the AAC matrix and the fibre depends greatly on the fibre diameter and embedded length. The fibre pull out test was conducted on alkali-activated cement with a capacity in a range of 0.8 to 1.0 MPa. The strain-hardening behaviour of alkali-activated cement was determined based on its compressive and flexural strengths. While achieving the strain-hardening behaviour of the AAC composite, the compressive strength decreases, and fine materials in the composite contribute to decreasing in the flexural strength and strain capacity. The composite critical energy release rate in AAC matrix was determined to be approximately 0.01 kJ/m

^{2}

based on a nanoindentation approach. The results of the flexural performance indicate that the critical energy release rate of alkali-activated cement matrix should be less than 0.01 kJ/m

^{2}

to achieve the strain-hardening behaviour. Full article

(This article belongs to the Special Issue Supplementary Cementitious Materials in Concrete)

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24 pages, 5153 KiB

Open AccessArticle

Prediction of the Ultra-Low-Cycle Fatigue Damage of Q345qC Steel and its Weld Joint

by Qin Tian, Hanqing Zhuge and Xu Xie

Materials 2019, 12(23), 4014; https://doi.org/10.3390/ma12234014 - 3 Dec 2019

Cited by 9 | Viewed by 3096

Abstract

Based on the continuum damage mechanics model (CDM) for monotonic tension, a new CDM for ultra-low-cycle fatigue (ULCF) is put forward to predict ULCF damage of steel and its weld joint under strong earthquakes. The base metal, heat-affected zone and weld metal of [...] Read more.

Based on the continuum damage mechanics model (CDM) for monotonic tension, a new CDM for ultra-low-cycle fatigue (ULCF) is put forward to predict ULCF damage of steel and its weld joint under strong earthquakes. The base metal, heat-affected zone and weld metal of Q345qC steel were considered as research objects, and the uniaxial plastic strain threshold of the CDM model was calibrated via tensile testing combined with finite element analysis of notched round bar specimens. ULCF tests of the base metal and weld specimens were carried out to analyse their fatigue life, fracture life and post-fracture path. Based on the calibrated uniaxial plastic strain threshold, the finite element models of base metal and weld specimens suitable for CDM model were established by ABAQUS. The calibration results of material parameters show that the weld metal has the lowest plastic strain threshold and the largest dispersion coefficient at the plastic strain threshold. Prediction results under cyclic loading with a large strain were compared with experimental values, and results showed that the predicted crack initiation and fracture lives of the base metal and weld specimens are lower than their corresponding experimental values. The predicted errors of crack initiation life and fracture life decrease with increasing strain level. The development law of the damage variable reveals exponential growth combined with a stepped pattern. The CDM model can also accurately predict the number of cycles to initial damage. Taking the results together, the CDM of the ULCF of the base metal and weld specimens could successfully predict post-fracture paths. Full article

(This article belongs to the Section Construction and Building Materials)

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17 pages, 5483 KiB

Open AccessArticle

Influence of Granulometry on Thermal and Mechanical Properties of Cement Mortars Containing Expanded Perlite as a Lightweight Aggregate

by Matías Leyton-Vergara, Alexis Pérez-Fargallo, Jesús Pulido-Arcas, Galo Cárdenas-Triviño and Jeremy Piggot-Navarrete

Materials 2019, 12(23), 4013; https://doi.org/10.3390/ma12234013 - 3 Dec 2019

Cited by 19 | Viewed by 3570

Abstract

This research aims at clarifying the influence of the granulometry of expanded perlite, on the thermal conductivity, structural strength, density, and water absorption of lightweight mortars. Three original perlite gradations have been obtained and three pairs of twin test mortars have been tested [...] Read more.

This research aims at clarifying the influence of the granulometry of expanded perlite, on the thermal conductivity, structural strength, density, and water absorption of lightweight mortars. Three original perlite gradations have been obtained and three pairs of twin test mortars have been tested with those gradations. SEM tests have also been run to clarify the interaction, at a microscopic level, between the expanded perlite and the cement grouting. The results indicate that the mere manipulation of the granulometry may have a considerable and very beneficial effect on the mixture’s properties, such as thermal conductivity and water absorption. Full article

(This article belongs to the Special Issue Testing of Cement-Based Materials)

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11 pages, 7691 KiB

Open AccessArticle

Prepregs for Temperature Resistant Composites

by Eliška Haincová, Pavlína Hájková and Jan Kohout

Materials 2019, 12(23), 4012; https://doi.org/10.3390/ma12234012 - 3 Dec 2019

Cited by 11 | Viewed by 3479

Abstract

In this paper, carbon fabric reinforced inorganic matrix composites were prepared. The inorganic matrix based on alkali activated aluminosilicate was used because of its resistance to fire and the temperatures up to 1000 °C. Influence of heat treatment of fabric, high temperature treatment [...] Read more.

In this paper, carbon fabric reinforced inorganic matrix composites were prepared. The inorganic matrix based on alkali activated aluminosilicate was used because of its resistance to fire and the temperatures up to 1000 °C. Influence of heat treatment of fabric, high temperature treatment of composite and preparation method on the mechanical properties and morphology of the composites were studied. The preparation of composites with the subsequent steps of impregnation, layering and curing of the composites was compared with the prepreg preparation method, which separates the impregnation of the reinforcement from the production of the composite. The SEM photographs show no differences in morphology between composites prepared from heat treated fabric and composites prepared from original fabrics. All four series of samples were comparatively saturated with matrix. Despite this, tensile properties of heat-treated fabric composites were negatively affected. While composites with heat-treated fabric reached the tensile strength up to 274 MPa, composites prepared without heat-treated fabric exhibited strengths higher than 336 MPa. Samples exposed to temperatures reaching 600 °C retained up to 40% of their original strength. The effect of composite preparation method on the tensile properties of the composites has not been proved. Full article

(This article belongs to the Collection Manufacturing Engineering and Mechanical Properties of Composite Materials)

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Graphical abstract

15 pages, 4212 KiB

Open AccessArticle

A Double-Switch Temperature-Sensitive Controlled Release Antioxidant Film Embedded with Lyophilized Nanoliposomes Encapsulating Rosemary Essential Oils for Solid Food

by Xi Chen, Qing Long, Lei Zhu, Li-Xin Lu, Li-Nan Sun, Liao Pan, Li-Jing Lu and Wei-Rong Yao

Materials 2019, 12(23), 4011; https://doi.org/10.3390/ma12234011 - 3 Dec 2019

Cited by 9 | Viewed by 2890

Abstract

In order to match the solid food oxidation during logistics and storage process under severe high temperature, a double-switch temperature-sensitive controlled release antioxidant film embedded with lyophilized nanoliposomes encapsulating rosemary essential oils (REOs) was prepared. The double switch temperature at 35.26 and 56.98 [...] Read more.

In order to match the solid food oxidation during logistics and storage process under severe high temperature, a double-switch temperature-sensitive controlled release antioxidant film embedded with lyophilized nanoliposomes encapsulating rosemary essential oils (REOs) was prepared. The double switch temperature at 35.26 and 56.98 °C was achieved by development of a temperature sensitive polyurethane (TSPU) film. With biaxially oriented polyethylene terephthalate (BOPET) as a barrier layer, the intelligent complex film was prepared via coating the TSPU embedded with lyophilized nanoliposomes encapsulating REOs on BOPET. The results indicate that the REO is well encapsulated in nanoliposomes with encapsulation efficiency (EE) of 67.3%, high stability and lasting antioxidant effect during 60 days. The incorporation of lyophilized nanoliposomes containing REOs into TSPU remains the double-switch temperature-sensitive characteristic of the prepared TSPU. In agreement with porosity and WVTR results, the diffusion coefficient (D) of the antioxidant complex film sharply increases respectively at two switching temperatures, indicating that the intelligent double-switch temperature-sensitive controlled release property is functioning. Furthermore, compared with films directly added with REO, the lower Ds of films added with lyophilized nanoliposomes encapsulating REOs provides a longer-lasting antioxidant activity. Thus, the acquired controlled release antioxidant film sensitive to temperature at 39.56 and 56.00 °C can be potentially applied for protection of solid food during distribution and storage process under severe high temperatures. Full article

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12 pages, 3160 KiB

Open AccessArticle

Tailoring Confining Jacket for Concrete Column Using Ultra High Performance-Fiber Reinforced Cementitious Composites (UHP-FRCC) with High Volume Fly Ash (HVFA)

by Alessandro P. Fantilli, Lucia Paternesi Meloni, Tomoya Nishiwaki and Go Igarashi

Materials 2019, 12(23), 4010; https://doi.org/10.3390/ma12234010 - 3 Dec 2019

Cited by 7 | Viewed by 2842

Abstract

Ultra-High Performance Fibre-Reinforced Cementitious Composites (UHP-FRCC) show excellent mechanical performances in terms of strength, ductility, and durability. Therefore, these cementitious materials have been successfully used for repairing, strengthening, and seismic retrofitting of old structures. However, UHP-FRCCs are not always environmental friendly products, especially [...] Read more.

Ultra-High Performance Fibre-Reinforced Cementitious Composites (UHP-FRCC) show excellent mechanical performances in terms of strength, ductility, and durability. Therefore, these cementitious materials have been successfully used for repairing, strengthening, and seismic retrofitting of old structures. However, UHP-FRCCs are not always environmental friendly products, especially in terms of the initial cost, due to the large quantity of cement that is contained in the mixture. Different rates of fly ash substitute herein part of the cement, and the new UHP-FRCCs are used to retrofit concrete columns to overcome this problem. To simulate the mechanical response of these columns, cylindrical specimens, which are made of normal concrete and reinforced with different UHP-FRCC jackets, are tested in uniaxial compression. Relationships between the size of the jacket, the percentage of cement replaced by fly ash, and the strength of the columns are measured and analyzed by means of the eco-mechanical approach. As a result, a replacement of approximately 50% of cement with fly ash, and a suitable thickness of the UHP-FRCC jacket, might ensure the lowest environmental impact without compromising the mechanical performances. Full article

(This article belongs to the Special Issue Supplementary Cementitious Materials in Concrete)

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11 pages, 5513 KiB

Open AccessArticle

Effects of Temperature on the Tribological Properties of NM600 under Sliding Wear

by Yingchao Pei, Dianxiu Xia, Shouren Wang, Liang Cong, Xuelin Wang and Dongyue Wang

Materials 2019, 12(23), 4009; https://doi.org/10.3390/ma12234009 - 3 Dec 2019

Cited by 11 | Viewed by 2883

Abstract

An investigation on the tribological properties of GCr15 sliding against NM600 was carried out using a high-temperature friction and wear tester. As the temperature rose from room temperature to 300 °C, the average friction coefficient of NM600 increased rapidly, then decreased rapidly, and [...] Read more.

An investigation on the tribological properties of GCr15 sliding against NM600 was carried out using a high-temperature friction and wear tester. As the temperature rose from room temperature to 300 °C, the average friction coefficient of NM600 increased rapidly, then decreased rapidly, and then became stable. The wear volume and specific wear rate of NM600 increased rapidly, then decreased rapidly, and then increased slowly. The wear mechanism and matrix properties of the tested steel at different temperatures are the main reasons for the above results. At 20–50 °C, the main wear mechanism was adhesive wear, fatigue wear, and abrasive wear. At 100–150 ℃, the wear mechanism was mainly adhesive wear, fatigue wear, abrasive wear, and oxidation wear. At 200–300 °C, the wear mechanism was mainly oxidation wear and abrasive wear. Full article

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12 pages, 3089 KiB

Open AccessArticle

Mode Conversion of the Edge Modes in the Graphene Double-Ribbon Bend

by Lanlan Zhang, Binghan Xue and Yueke Wang

Materials 2019, 12(23), 4008; https://doi.org/10.3390/ma12234008 - 3 Dec 2019

Cited by 1 | Viewed by 2265

Abstract

In this paper, a new kind of graphene double-ribbon bend structure, which can support two edge graphene surface plasmons (EGSPs) modes, is proposed. In this double-ribbon bend, one edge mode can be partly converted into another one. We attribute the mode conversion mechanism [...] Read more.

In this paper, a new kind of graphene double-ribbon bend structure, which can support two edge graphene surface plasmons (EGSPs) modes, is proposed. In this double-ribbon bend, one edge mode can be partly converted into another one. We attribute the mode conversion mechanism to the interference between the two edge plasmonic modes. Based on the finite element method (FEM), we calculate the transmission and loss of EGSPs propagating along this graphene double-ribbon bend in the mid-infrared range under different parameters. Full article

(This article belongs to the Section Optical and Photonic Materials)

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13 pages, 2225 KiB

Open AccessArticle

Effect of Silica Fume and Fly Ash Admixtures on the Corrosion Behavior of AISI 304 Embedded in Concrete Exposed in 3.5% NaCl Solution

by Miguel Angel Baltazar-Zamora, David M. Bastidas, Griselda Santiago-Hurtado, José Manuel Mendoza-Rangel, Citlalli Gaona-Tiburcio, José M. Bastidas and Facundo Almeraya-Calderón

Materials 2019, 12(23), 4007; https://doi.org/10.3390/ma12234007 - 3 Dec 2019

Cited by 38 | Viewed by 4226

Abstract

The use of supplementary cementitious materials such as fly ash, slag, and silica fume improve reinforced concrete corrosion performance, while decreasing cost and reducing environmental impact compared to ordinary Portland cement. In this study, the corrosion behavior of AISI 1018 carbon steel (CS) [...] Read more.

The use of supplementary cementitious materials such as fly ash, slag, and silica fume improve reinforced concrete corrosion performance, while decreasing cost and reducing environmental impact compared to ordinary Portland cement. In this study, the corrosion behavior of AISI 1018 carbon steel (CS) and AISI 304 stainless steel (SS) reinforcements was studied for 365 days. Three different concrete mixtures were tested: 100% CPC (composite Portland cement), 80% CPC and 20% silica fume (SF), and 80% CPC and 20% fly ash (FA). The concrete mixtures were designed according to the ACI 211.1 standard. The reinforced concrete specimens were immersed in a 3.5 wt.% NaCl test solution to simulate a marine environment. Corrosion monitoring was evaluated using the corrosion potential (E_corr) according to ASTM C876 and the linear polarization resistance (LPR) according to ASTM G59. The results show that AISI 304 SS reinforcements yielded the best corrosion behavior, with E_corr values mainly pertaining to the region of 10% probability of corrosion, and corrosion current density (i_corr) values indicating passivity after 105 days of experimentation and low probability of corrosion for the remainder of the test period. Full article

(This article belongs to the Special Issue Concrete and Construction Materials)

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10 pages, 3204 KiB

Open AccessArticle

Calculation of Volume Fractions of In Situ TiB and Residual Stress Distributions in Functionally Graded Composite of Ti–TiB–TiB₂

by Youfeng Zhang, Shasha He, Wanwan Yang, Jiangwei Ren and Haijuan Kong

Materials 2019, 12(23), 4006; https://doi.org/10.3390/ma12234006 - 3 Dec 2019

Cited by 3 | Viewed by 2988

Abstract

Ti matrix composite with a polylaminate structure was successfully fabricated via spark plasma sintering (SPS) process. A temperature gradient field (TGF) was obtained during the sintering to form functionally graded material (FGM) in a vacuum under 40 MPa for 5 min. The actual [...] Read more.

Ti matrix composite with a polylaminate structure was successfully fabricated via spark plasma sintering (SPS) process. A temperature gradient field (TGF) was obtained during the sintering to form functionally graded material (FGM) in a vacuum under 40 MPa for 5 min. The actual volume fractions of TiB in the matrix were calculated based on the X-ray diffraction pattern. The target volume fractions of TiB were 0%, 20%, 40%, 60%, 80% and 100%. The calculated TiB volume fractions were slightly higher than the target volume fractions in layers 2–4 and lower than the target volume fractions in layers 5–6 and the deviations in layers 4 and 5 were less than 5% of the target volume. Based on the elastic axial symmetry model, the residual stress distributions in the Ti matrix composite with a polylaminate structure were simulated, indicating a relatively low thermal residual stress in the FGM. Full article

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20 pages, 1477 KiB

Open AccessReview

Cell Bioprinting: The 3D-Bioplotter™ Case

by David Angelats Lobo and Paola Ginestra

Materials 2019, 12(23), 4005; https://doi.org/10.3390/ma12234005 - 2 Dec 2019

Cited by 25 | Viewed by 6385

Abstract

The classic cell culture involves the use of support in two dimensions, such as a well plate or a Petri dish, that allows the culture of different types of cells. However, this technique does not mimic the natural microenvironment where the cells are [...] Read more.

The classic cell culture involves the use of support in two dimensions, such as a well plate or a Petri dish, that allows the culture of different types of cells. However, this technique does not mimic the natural microenvironment where the cells are exposed to. To solve that, three-dimensional bioprinting techniques were implemented, which involves the use of biopolymers and/or synthetic materials and cells. Because of a lack of information between data sources, the objective of this review paper is, to sum up, all the available information on the topic of bioprinting and to help researchers with the problematics with 3D bioprinters, such as the 3D-Bioplotter™. The 3D-Bioplotter™ has been used in the pre-clinical field since 2000 and could allow the printing of more than one material at the same time, and therefore to increase the complexity of the 3D structure manufactured. It is also very precise with maximum flexibility and a user-friendly and stable software that allows the optimization of the bioprinting process on the technological point of view. Different applications have resulted from the research on this field, mainly focused on regenerative medicine, but the lack of information and/or the possible misunderstandings between papers makes the reproducibility of the tests difficult. Nowadays, the 3D Bioprinting is evolving into another technology called 4D Bioprinting, which promises to be the next step in the bioprinting field and might promote great applications in the future. Full article

(This article belongs to the Special Issue Additive Manufacturing towards the Design of 3D Advanced Scaffolds for Tissue Engineering)

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15 pages, 11453 KiB

Open AccessArticle

Sensor-Assisted Assessment of the Tribological Behavioral Patterns of Al–SiCp Composites under Various Environmental Temperature Conditions

by Manivannan S, Senthil Kumaran S, Srinivasan Narayanan, Kathiravan Srinivasan and Alex Noel Joseph Raj

Materials 2019, 12(23), 4004; https://doi.org/10.3390/ma12234004 - 2 Dec 2019

Cited by 5 | Viewed by 2624

Abstract

Currently, the use of sensors and supporting technologies has become indispensable in the assessment of tribological behavioral patterns of composites. Furthermore, the current investigation focused on the assessment of the tribological behavior of the Al–SiCp composite for high-temperature applications. Moreover, the Al–SiCp composite [...] Read more.

Currently, the use of sensors and supporting technologies has become indispensable in the assessment of tribological behavioral patterns of composites. Furthermore, the current investigation focused on the assessment of the tribological behavior of the Al–SiCp composite for high-temperature applications. Moreover, the Al–SiCp composite was fabricated by adapting the liquid metallurgy route with varying weight percentages of SiC_p (x = 3, 6, and 9). Density, hardness, and high-temperature wear tests were performed to evaluate the hardness and tribological characteristics and properties of modern-day advanced composites. Moreover, the inclusion of SiC_p enhanced the advanced composite materials hardness from 60 HV to 110 HV due to a high degree of refinement of the α-phase. Subsequently, the fabricated samples’ wear behavior was assessed by varying the wear parameter viz. the applied load (20 N and 30 N) and sliding distance (250 m, 500 m, 750 m, and 1000 m) with the constant sliding velocity (0.45 m/s) for various temperatures (40 °C, 150 °C, and 250 °C). Moreover, the results revealed that the enhancement in the reinforcement percentage improves the wear resistance. Consequently, the wear rate decreased at 250 °C, possibly owing to the development of the oxide layers. Therefore, the occurrence of delamination and plastic deformation were evidenced in the wear-out surface, thereby depicting the prevalence of delamination and the abrasive wear-mechanism. Full article

(This article belongs to the Special Issue Tribology: Friction and Wear of Engineering Materials)

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23 pages, 41728 KiB

Open AccessArticle

Experimental Assessment of the Fire Resistance Mechanisms of Timber–Steel Composites

by Truong Di Ha Le and Meng-Ting Tsai

Materials 2019, 12(23), 4003; https://doi.org/10.3390/ma12234003 - 2 Dec 2019

Cited by 13 | Viewed by 8454

Abstract

Hybrid structures known as timber–steel composites (TSCs) have been extensively studied due to their potential use as alternative construction materials that can satisfy demands related to sustainability. In addition to load capacity, fire resistance is a major consideration regarding the extensive use of [...] Read more.

Hybrid structures known as timber–steel composites (TSCs) have been extensively studied due to their potential use as alternative construction materials that can satisfy demands related to sustainability. In addition to load capacity, fire resistance is a major consideration regarding the extensive use of TSCs. In this study, 12 specimens were tested using a glulam timber material covering cold-formed steel at the center. Specifically, the TSCs were fabricated from two timber blocks and an I-shaped steel core assembled using dowels or glue as a major structure. In order to use additional timber as a fire protection layer to protect a major structure by its charcoal produced after being burned, an additional timber with 5 cm in thickness was used to cover the major structure. The 1-h fire testing of TSC following the ISO 834-1 standard was applied, in order to achieve the potential application for a 4-story timber building. The results showed that temperatures at the steel flange increased by more than 300 °C for the final 5 min in 10 out of the 12 TSC specimens, indicating that the fire protection provided by the timber structure was not sufficient. The charcoal layer surpassing the extra timber was originally set and entered the steel structure of the TSC, which was expected to retain its physical qualities after a fire. Methods for evaluating the charring properties, based on the conventional method for wood and the standard specification set by Eurocode 5, were used to assess the structural degradation of TSCs. The conventional assessments showed a divergence from the actual performance of TSCs. Such variations demonstrated the limitations of models for conventional wood in assessing the structure of a TSC. A realistic assessment was conducted to expand knowledge related to this composite under destructive processes and provide fire reference values for the practical implementation of TSCs. Full article

(This article belongs to the Section Construction and Building Materials)

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16 pages, 2267 KiB

Open AccessFeature PaperReview

PMMA-Based Bone Cements and the Problem of Joint Arthroplasty Infections: Status and New Perspectives

by Alessandro Bistolfi, Riccardo Ferracini, Carlo Albanese, Enrica Vernè and Marta Miola

Materials 2019, 12(23), 4002; https://doi.org/10.3390/ma12234002 - 2 Dec 2019

Cited by 77 | Viewed by 8500

Abstract

Polymethyl methacrylate (PMMA)-based bone cement is a biomaterial that has been used over the last 50 years to stabilize hip and knee implants or as a bone filler. Although PMMA-based bone cement is widely used and allows a fast-primary fixation to the bone, [...] Read more.

Polymethyl methacrylate (PMMA)-based bone cement is a biomaterial that has been used over the last 50 years to stabilize hip and knee implants or as a bone filler. Although PMMA-based bone cement is widely used and allows a fast-primary fixation to the bone, it does not guarantee a mechanically and biologically stable interface with bone, and most of all it is prone to bacteria adhesion and infection development. In the 1970s, antibiotic-loaded bone cements were introduced to reduce the infection rate in arthroplasty; however, the efficiency of antibiotic-containing bone cement is still a debated issue. For these reasons, in recent years, the scientific community has investigated new approaches to impart antibacterial properties to PMMA bone cement. The aim of this review is to summarize the current status regarding antibiotic-loaded PMMA-based bone cements, fill the gap regarding the lack of data on antibacterial bone cement, and explore the progress of antibacterial bone cement formulations, focusing attention on the new perspectives. In particular, this review highlights the innovative study of composite bone cements containing inorganic antibacterial and bioactive phases, which are a fascinating alternative that can impart both osteointegration and antibacterial properties to PMMA-based bone cement. Full article

(This article belongs to the Special Issue Multifunctional Materials in Tissue Regeneration)

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13 pages, 2480 KiB

Open AccessArticle

Influence of Dental Composite Viscosity in Attachment Reproduction: An Experimental in Vitro Study

by Vincenzo D’Antò, Simone Muraglie, Beatrice Castellano, Ettore Candida, Maria Francesca Sfondrini, Andrea Scribante and Cristina Grippaudo

Materials 2019, 12(23), 4001; https://doi.org/10.3390/ma12234001 - 2 Dec 2019

Cited by 27 | Viewed by 5171

Abstract

Background: Attachments are composite auxiliaries that are used during a clear aligner orthodontic therapy to achieve difficult tooth movements. Two important factors are the planned configuration and the actual position of these auxiliary elements to obtain the desired force system. The aim of [...] Read more.

Background: Attachments are composite auxiliaries that are used during a clear aligner orthodontic therapy to achieve difficult tooth movements. Two important factors are the planned configuration and the actual position of these auxiliary elements to obtain the desired force system. The aim of the present study was to evaluate the role of different composite materials in the correct reproduction of attachment shape and position. Methods: The materials that were considered in the study were a flowable resin, a dental restorative material, and an orthodontic composite. The attachments were created on three models of extracted teeth. Once the impressions were performed, 25 attachments of different shapes were added onto each virtual model to obtain the necessary templates to make the attachments. Each tested material was used to create a set of 25 attachments that were then scanned with an accuracy of 10μm. The resultant STL (stereolithography) files were superimposed onto the ones from the initial virtual plan, through Geomagic software, and the aligned scans were then compared while using a color map. The parameters that were calculated to make a comparison between the created attachments and the ideal ones were the maximum deviation in defect and in excess, the overflow, and the volume’s difference. In addition to these measurements comparing the three above-mentioned groups, the difference in volume between all the ideal and realized samples were analyzed. To test for differences among the three groups, a one-way Analysis of variance (ANOVA) was used with a Bonferroni post-hoc test. The level of significance was set at p < 0.05. Results: No statistically significant results were found between the three groups regarding the maximum value in defect, the maximum value in excess, and the minimum value as control, while a statistically significant difference was found between the overflow of orthodontic resin when compared to the flowable composite. Conclusions: The three materials that were used in this study were appropriate for attachment fabrication. The fidelity of attachment reproduction was similar when using the three different composites. The orthodontic composite showed more overflow when compared with the flowable one. Full article

(This article belongs to the Special Issue Orthodontic Materials and Adhesive Interfaces)

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16 pages, 8887 KiB

Open AccessArticle

Experimental Investigation on the Impact Resistance of Carbon Fibers Reinforced Coral Concrete

by Bing Liu, Jingkai Zhou, Xiaoyan Wen, Jianhua Guo, Xuanyu Zhang, Zhiheng Deng and Huailiang Wang

Materials 2019, 12(23), 4000; https://doi.org/10.3390/ma12234000 - 2 Dec 2019

Cited by 32 | Viewed by 3463

Abstract

In this study, the impact resistance of coral concrete with different carbon fiber (CF) dosages subjected to drop-weight impact test was investigated. For this purpose, three concrete strength grades (C20, C30, C40) and six CF dosages (0.0%, 0.3%, 0.6%, 1.0%, 1.5%, and 2.0% [...] Read more.

In this study, the impact resistance of coral concrete with different carbon fiber (CF) dosages subjected to drop-weight impact test was investigated. For this purpose, three concrete strength grades (C20, C30, C40) and six CF dosages (0.0%, 0.3%, 0.6%, 1.0%, 1.5%, and 2.0% by weight of the binder) were considered, and a total of 18 groups of carbon fibers reinforced coral concrete (CFRCC) were cast. For each group, eight specimens were tested following the drop-weight impact test suggested by CECS 13. Then, the two-parameter Weibull distribution theory was adopted to statistically analyze the variations in experimental results. The results indicated that the addition of CFs could transform the failure pattern from obvious brittleness to relatively good ductility and improve the impact resistance of coral concrete. Moreover, the impact resistance of CFRCC increases with the CF dosage increasing. The statistical analysis showed that the probability distribution of the blow numbers at the initial crack and final failure of CFRCC approximately follows the two-parameter Weibull distribution. Full article

(This article belongs to the Section Construction and Building Materials)

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19 pages, 14109 KiB

Open AccessArticle

Thermophysical Measurements in Liquid Alloys and Phase Diagram Studies

by Yuri Kirshon, Shir Ben Shalom, Moran Emuna, Yaron Greenberg, Joonho Lee, Guy Makov and Eyal Yahel

Materials 2019, 12(23), 3999; https://doi.org/10.3390/ma12233999 - 2 Dec 2019

Cited by 6 | Viewed by 3423

Abstract

Towards the construction of pressure-dependent phase diagrams of binary alloy systems, both thermophysical measurements and thermodynamic modeling are employed. High-accuracy measurements of sound velocity, density, and electrical resistivity were performed for selected metallic elements from columns III to V and their alloys in [...] Read more.

Towards the construction of pressure-dependent phase diagrams of binary alloy systems, both thermophysical measurements and thermodynamic modeling are employed. High-accuracy measurements of sound velocity, density, and electrical resistivity were performed for selected metallic elements from columns III to V and their alloys in the liquid phase. Sound velocity measurements were made using ultrasonic techniques, density measurements using the gamma radiation attenuation method, and electrical resistivity measurements were performed using the four probe method. Sound velocity and density data, measured at ambient pressure, were incorporated into a thermodynamic model to calculate the pressure dependence of binary phase diagrams. Electrical resistivity measurements were performed on binary systems to study phase separation and identify phase transitions in the liquid state. Full article

(This article belongs to the Special Issue Thermal Analysis of Materials)

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13 pages, 3810 KiB

Open AccessArticle

Mechanical and Functional Properties of a Novel Apatite-Ionomer Cement for Prevention and Remineralization of Dental Caries

by Rie Imataki, Yukari Shinonaga, Takako Nishimura, Yoko Abe and Kenji Arita

Materials 2019, 12(23), 3998; https://doi.org/10.3390/ma12233998 - 2 Dec 2019

Cited by 17 | Viewed by 3628

Abstract

Especially in pediatric dentistry, prevention by the control of initial lesions prior to cavitation is very important, and application of a pit and fissure sealant is essential to achieve this. Numerous reports have suggested that resin-based sealants are inferior to sealants based on [...] Read more.

Especially in pediatric dentistry, prevention by the control of initial lesions prior to cavitation is very important, and application of a pit and fissure sealant is essential to achieve this. Numerous reports have suggested that resin-based sealants are inferior to sealants based on glass-ionomer cement (GIC), because of GIC’s many advantages, such as fluoride ion release properties and its good adhesion to tooth structures. However, the use of GIC is impeded due to its low flexural strength and fracture toughness. In this paper, we developed and characterized an apatite-ionomer cement (AIC) that incorporates hydroxyapatite (HAp) into the GIC; this development was aimed at not only reinforcing the flexural and compressive strength but also improving some functional properties for the creation of the material suitable for sealant. We examined the influence of differences in the compounding conditions of GIC powder, liquid, and HAp on flexural and compressive strengths, fracture toughness, fluoride ion release property, shear bond strength to bovine enamel, surface pH of setting cements, and acid buffer capability. These methods were aimed at elucidating the reaction mechanism of porous spherical-shaped HAp (HApS) in AIC. The following observations were deduced. (1) HAp can improve the mechanical strengths of AIC by strengthening the cement matrix. (2) The functional properties of AIC, such as acid buffer capability, improved by increasing the releasing amounts of various ions including fluoride ions. The novel AIC developed in this study is a clinically effective dental material for prevention and remineralization of tooth and initial carious lesion. Full article

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16 pages, 6852 KiB

Open AccessArticle

Fabrication and Histological Evaluation of Porous Carbonate Apatite Block from Gypsum Block Containing Spherical Phenol Resin as a Porogen

by Yuta Sakemi, Koichiro Hayashi, Akira Tsuchiya, Yasuharu Nakashima and Kunio Ishikawa

Materials 2019, 12(23), 3997; https://doi.org/10.3390/ma12233997 - 2 Dec 2019

Cited by 7 | Viewed by 3231

Abstract

The utility of carbonate apatite (CO₃Ap) as a bone substitute has been demonstrated. The feasibility of fabricating macroporous CO₃Ap was evaluated through a two-step dissolution–precipitation reaction using gypsum as the precursor and spherical phenol resin as the porogen. Porogen-containing [...] Read more.

The utility of carbonate apatite (CO₃Ap) as a bone substitute has been demonstrated. The feasibility of fabricating macroporous CO₃Ap was evaluated through a two-step dissolution–precipitation reaction using gypsum as the precursor and spherical phenol resin as the porogen. Porogen-containing gypsum was heated to burn out the porogen and to fabricate macroporous structures. Gypsum transformed into CaCO₃ upon immersion in a sodium carbonate solution, while maintaining its macroporous structure. Next, CaCO₃ transformed into CO₃Ap upon immersion in a Na₂HPO₄ solution while maintaining its macroporous structure. The utility of the macroporous CO₃Ap for histologically reconstructing bone defects was evaluated in rabbit femurs. After 4 weeks, a much larger bone was formed inside the macroporous CO₃Ap than that inside non-macroporous CO₃Ap and macroporous hydroxyapatite (HAp). A larger amount of bone was observed inside non-macroporous CO₃Ap than inside macroporous HAp. The bone defects were completely reconstructed within 12 weeks using macroporous CO₃Ap. In conclusion, macroporous CO₃Ap has good potential as an ideal bone substitute. Full article

(This article belongs to the Section Biomaterials)

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23 pages, 9118 KiB

Open AccessArticle

Detection of Delamination with Various Width-to-depth Ratios in Concrete Bridge Deck Using Passive IRT: Limits and Applicability

by Van Ha Mac, Quang Huy Tran, Jungwon Huh, Nhu Son Doan, Choonghyun Kang and Dongyeob Han

Materials 2019, 12(23), 3996; https://doi.org/10.3390/ma12233996 - 2 Dec 2019

Cited by 34 | Viewed by 6152

Abstract

In bridge structures, concrete decks have a higher risk of damage than other components owing to the direct impact of traffic. This study aims to develop a comprehensive system for bridge inspection using passive infrared thermography (IRT). Experiments were conducted on a concrete [...] Read more.

In bridge structures, concrete decks have a higher risk of damage than other components owing to the direct impact of traffic. This study aims to develop a comprehensive system for bridge inspection using passive infrared thermography (IRT). Experiments were conducted on a concrete specimen (assumed as the surface of the bridge deck) embedded artificial delaminations with different width-to-depth ratios (WTDRs). Both professional handheld IR camera (H-IRC) and a UAV mounted with an IR camera (UAV-IRC) were employed simultaneously to capture the surface temperature of the structure. The present work indicates that the passive IRT technique with an H-IRC can be used to detect delaminations located at depths of 4 cm or less from the structure surface if the WTDRs are not lesser than 1.9 for daytime and 2.5 for nighttime when testing on a sunny day. In addition, the larger the WTDR, the higher the temperature difference can be produced, thus delaminations could be observed more clearly. Furthermore, our study suggests that the concrete bridge deck inspection using passive IRT can produce appropriate results if the inspection is performed from 10:00 to 15:00 or from 19:30 to approximately 2:00 on a sunny day. Good agreement between the results obtained from tests using H-IRC and UAV-IRC was observed, which validates the application of UAV-IRC in real structure inspection. Full article

(This article belongs to the Special Issue Non-Destructive Testing of Structures)

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21 pages, 8682 KiB

Open AccessArticle

The Influence of A Cross-Channel Extrusion Process on The Microstructure and Properties of Copper

by Radosław Łyszkowski, Magdalena Łazińska and Dariusz Zasada

Materials 2019, 12(23), 3995; https://doi.org/10.3390/ma12233995 - 2 Dec 2019

Cited by 3 | Viewed by 3146

Abstract

A new cross-channel extrusion (CCE) method with the application of a back pressure (BP) is proposed and experimentally tested. The introduction of pressure blocks the free flow of material by using an additional set of pistons, which prevents the loss of consistency. The [...] Read more.

A new cross-channel extrusion (CCE) method with the application of a back pressure (BP) is proposed and experimentally tested. The introduction of pressure blocks the free flow of material by using an additional set of pistons, which prevents the loss of consistency. The paper presents results of experimental trials of CCE process. Between one and eight passes of CCE with and without a BP were applied to pure copper billets to refine their initial coarse-grained microstructure at room temperature. It was found that processing by CCE results in the formation of a lamellar structure along the extruded axis and the fine-grained structure in the remaining volume. The material exhibited dynamic recrystallization, which results in the formation of 0.5- to 2-μm grains after one pass and 2- to 8-μm grains after four CCE passes. The fine-grained material had YS of 390-415 MPa. An increase in the microhardness from 70 to 130 HV02 after one pass and then a decrease after four passes were observed. This might indicate that secondary recrystallization and selective grain growth occur, because an exothermic peak (158.5 °C, 53 ± 2.1 J/mol) was observed during DSC (differential scanning calorimetry) testing. The resistivity of the once deformed copper significantly decreases, while its further processing causes the resistivity to increase. Full article

(This article belongs to the Special Issue High Performance Nonferrous Alloys: Composition, Microstructure and Properties)

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14 pages, 6294 KiB

Open AccessArticle

Native Osseous CaP Biomineral Coating on a Biomimetic Multi-Spiked Connecting Scaffold Prototype for Cementless Resurfacing Arthroplasty Achieved by Combined Electrochemical Deposition

by Ryszard Uklejewski, Mariusz Winiecki, Piotr Krawczyk and Renata Tokłowicz

Materials 2019, 12(23), 3994; https://doi.org/10.3390/ma12233994 - 2 Dec 2019

Cited by 6 | Viewed by 3191

Abstract

The multi-spiked connecting scaffold (MSC-Scaffold) prototype with spikes mimicking the interdigitations of articular subchondral bone is an essential innovation in surgically initiated fixation of resurfacing arthroplasty (RA) endoprosthesis components. This paper aimed to present a determination of the suitable range of conditions for [...] Read more.

The multi-spiked connecting scaffold (MSC-Scaffold) prototype with spikes mimicking the interdigitations of articular subchondral bone is an essential innovation in surgically initiated fixation of resurfacing arthroplasty (RA) endoprosthesis components. This paper aimed to present a determination of the suitable range of conditions for the calcium phosphate (CaP) potentiostatic electrochemical deposition (ECD_V=const) on the MSC-Scaffold prototype spikes to achieve a biomineral coating with a native Ca/P ratio. The CaP ECD_V=const process on the MSC-Scaffold Ti4Al6V pre-prototypes was investigated for potential V_ECDfrom −9 to −3 V, and followed by 48 h immersion in a simulated body fluid. An acid–alkaline pretreatment (AAT) was applied for a portion of the pre-prototypes. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) studies of deposited coatings together with coatings weight measurements were performed. Themost suitable V_ECD range, from −5.25 to −4.75 V, was determined as the native biomineral Ca/P ratio of coatings was achieved. AAT increases the weight of deposited coatings (44% for V_ECD = −5.25 V, 9% for V_ECD = −5.00 V and 15% for V_ECD = −4.75 V) and the coverage degree of the lateral spike surfaces (40% for V_ECD = −5.25 V, 14% for V_ECD = −5.00 V and 100% for V_ECD = −4.75 V). XRD confirmed that the multiphasic CaP coating containing crystalline octacalcium phosphate is produced on the lateral surface of the spikes of the MSC-Scaffold. ECD_V=const preceded by AAT prevents micro-cracks on the bone-contacting surfaces of the MSC-Scaffold prototype, increases its spikes’ lateral surface coverage, and results in the best modification effect at V_ECD = −5.00 V. To conclude, the biomimetic MSC-Scaffold prototype with desired biomineral coating of native Ca/P ratio was obtained for cementless RA endoprostheses. Full article

(This article belongs to the Special Issue Bio-Inspired Materials for Biomedical Applications)

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17 pages, 4088 KiB

Open AccessArticle

Biologization of Collagen-Based Biomaterials Using Liquid-Platelet-Rich Fibrin: New Insights into Clinically Applicable Tissue Engineering

by Sarah Al-Maawi, Carlos Herrera-Vizcaíno, Anna Orlowska, Ines Willershausen, Robert Sader, Richard J Miron, Joseph Choukroun and Shahram Ghanaati

Materials 2019, 12(23), 3993; https://doi.org/10.3390/ma12233993 - 2 Dec 2019

Cited by 34 | Viewed by 4533

Abstract

Platelet-rich fibrin (PRF) is a blood concentrate derived from venous blood that is processed without anticoagulants by a one-step centrifugation process. This three-dimensional scaffold contains inflammatory cells and plasma proteins entrapped in a fibrin matrix. Liquid-PRF was developed based on the previously described [...] Read more.

Platelet-rich fibrin (PRF) is a blood concentrate derived from venous blood that is processed without anticoagulants by a one-step centrifugation process. This three-dimensional scaffold contains inflammatory cells and plasma proteins entrapped in a fibrin matrix. Liquid-PRF was developed based on the previously described low-speed centrifuge concept (LSCC), which allowed the introduction of a liquid-PRF formulation of fibrinogen and thrombin prior to its conversion to fibrin. Liquid-PRF was introduced to meet the clinical demand for combination with biomaterials in a clinically applicable and easy-to-use way. The aim of the present study was to evaluate, ex vivo, the interaction of the liquid-PRF constituents with five different collagen biomaterials by histological analyses. The results first demonstrated that large variability existed between the biomaterials investigated. Liquid-PRF was able to completely invade Mucograft^® (MG; Geistlich Biomaterials, Wolhusen, Switzerland) and to partly invade Bio-Gide^® (BG; Geistlich Biomaterials, Wolhusen, Switzerland) and Mucoderm^® (MD; Botiss Biomaterials, Berlin, Germany), and Collprotect^® (CP; Botiss Biomaterials, Berlin, Germany) showed only a superficial interaction. The BEGO^® collagen membrane (BCM; BEGO Implant Systems) appeared to be completely free of liquid-PRF. These results were confirmed by the different cellular penetration and liquid-PRF absorption coefficient (PAC) values of the evaluated membranes. The present study demonstrates a system for loading biomaterials with a complex autologous cell system (liquid-PRF) in a relatively short period of time and in a clinically relevant manner. The combination of biomaterials with liquid-PRF may be clinically utilized to enhance the bioactivity of collagen-based biomaterials and may act as a biomaterial-based growth factor delivery system. Full article

(This article belongs to the Special Issue Advances in Platelet-rich Fibrin for Bone Tissue Engineering)

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Materials, Volume 12, Issue 23 (December-1 2019) – 218 articles

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