Research

Jump to: Review

10 pages, 2769 KiB

Open AccessArticle

Fabrication of SiC Porous Ceramics by Foaming Method

by Jing Zhao, Xiaoqi Ban, Yifan Yang, Zhigang Yuan, Hongqiang Ru and Desheng Su

Materials 2023, 16(4), 1342; https://doi.org/10.3390/ma16041342 - 04 Feb 2023

Cited by 3 | Viewed by 1789

In this work, hierarchically porous SiC ceramics were prepared via the foaming method. Porous ceramics with tunable, uniform, and bimodal pore structures were successfully fabricated in a facile way. The formation mechanisms of the 1st and 2nd modal macropores are the H₂ [...] Read more.

In this work, hierarchically porous SiC ceramics were prepared via the foaming method. Porous ceramics with tunable, uniform, and bimodal pore structures were successfully fabricated in a facile way. The formation mechanisms of the 1st and 2nd modal macropores are the H₂O₂ foaming process and SiC particle overlap, respectively. The effect of pore-foaming agent amount, foaming temperature, and surfactant was investigated. According to the results, with increasing H₂O₂ amount, the porosity, pore size, and interconnectivity of the 1st modal pores increased, whereas bulk density and strength decreased. The porosity increased while the strength decreased as the foaming temperature increased. Surfactants increased pore interconnectivity and porosity. When the foaming temperature was 85 °C, and the addition of H₂O₂ was 5 wt.%, the porosity, bulk density, flexural strength, and compressive strength were 56.32%, 2.8301 g/cm³, 11.94 MPa, and 24.32 MPa, respectively. Moreover, SiC porous ceramics exhibited excellent corrosion resistance to acids and alkalis. Full article

(This article belongs to the Special Issue Porous Materials and Advanced Manufacturing Technologies)

► Show Figures

Figure 1

24 pages, 12036 KiB

Open AccessArticle

Modeling Materials Coextrusion in Polymers Additive Manufacturing

by Riccardo Sponchiado, Stefano Rosso, Pierandrea Dal Fabbro, Luca Grigolato, Hamada Elsayed, Enrico Bernardo, Mattia Maltauro, Francesca Uccheddu, Roberto Meneghello, Gianmaria Concheri and Gianpaolo Savio

Materials 2023, 16(2), 820; https://doi.org/10.3390/ma16020820 - 14 Jan 2023

Cited by 4 | Viewed by 1820

Abstract

Material extrusion additive manufacturing enables us to combine more materials in the same nozzle during the deposition process. This technology, called material coextrusion, generates an expanded range of material properties, which can gradually change in the design domain, ensuring blending or higher bonding/interlocking [...] Read more.

Material extrusion additive manufacturing enables us to combine more materials in the same nozzle during the deposition process. This technology, called material coextrusion, generates an expanded range of material properties, which can gradually change in the design domain, ensuring blending or higher bonding/interlocking among the different materials. To exploit the opportunities offered by these technologies, it is necessary to know the behavior of the combined materials according to the materials fractions. In this work, two compatible pairs of materials, namely Polylactic Acid (PLA)-Thermoplastic Polyurethane (TPU) and Acrylonitrile Styrene Acrylate (ASA)-TPU, were investigated by changing the material fractions in the coextrusion process. An original model describing the distribution of the materials is proposed. Based on this, the mechanical properties were investigated by analytical and numerical approaches. The analytical model was developed on the simplified assumption that the coextruded materials are a set of rods, whereas the more realistic numerical model is based on homogenization theory, adopting the finite element analysis of a representative volume element. To verify the deposition model, a specific experimental test was developed, and the modeled material deposition was superimposed and qualitatively compared with the actual microscope images regarding the different deposition directions and material fractions. The analytical and numerical models show similar trends, and it can be assumed that the finite element model has a more realistic behavior due to the higher accuracy of the model description. The elastic moduli obtained by the models was verified in experimental tensile tests. The tensile tests show Young’s moduli of 3425 MPa for PLA, 1812 MPa for ASA, and 162 MPa for TPU. At the intermediate material fraction, the Young’s modulus shows an almost linear trend between PLA and TPU and between ASA and TPU. The ultimate tensile strength values are 63.9 MPa for PLA, 35.7 MPa for ASA, and 63.5 MPa for TPU, whereas at the intermediate material fraction, they assume lower values. In this initial work, the results show a good agreement between models and experiments, providing useful tools for designers and contributing to a new branch in additive manufacturing research. Full article

(This article belongs to the Special Issue Porous Materials and Advanced Manufacturing Technologies)

► Show Figures

Figure 1

13 pages, 5376 KiB

Open AccessArticle

Superrepellent Porous Polymer Surfaces by Replication from Wrinkled Polydimethylsiloxane/Parylene F

by Fadoua Mayoussi, Ali Usama, Kiana Karimi, Niloofar Nekoonam, Andreas Goralczyk, Pang Zhu, Dorothea Helmer and Bastian E. Rapp

Materials 2022, 15(22), 7903; https://doi.org/10.3390/ma15227903 - 09 Nov 2022

Cited by 1 | Viewed by 1865

Abstract

Superrepellent surfaces, such as micro/nanostructured surfaces, are of key importance in both academia and industry for emerging applications in areas such as self-cleaning, drag reduction, and oil repellence. Engineering these surfaces is achieved through the combination of the required surface topography, such as [...] Read more.

Superrepellent surfaces, such as micro/nanostructured surfaces, are of key importance in both academia and industry for emerging applications in areas such as self-cleaning, drag reduction, and oil repellence. Engineering these surfaces is achieved through the combination of the required surface topography, such as porosity, with low-surface-energy materials. The surface topography is crucial for achieving high liquid repellence and low roll-off angles. In general, the combination of micro- and nanostructures is most promising in achieving high repellence. In this work, we report the enhancement of wetting properties of porous polymers by replication from wrinkled Parylene F (PF)-coated polydimethylsiloxane (PDMS). Fluorinated polymer foam “Fluoropor” serves as the low-surface-energy polymer. The wrinkled molds are achieved via the deposition of a thin PF layer onto the soft PDMS substrates. Through consecutive supercritical drying, superrepellent surfaces with a high surface porosity and a high water contact angle (CA) of >165° are achieved. The replicated surfaces show low roll-off angles (ROA) <10° for water and <21° for ethylene glycol. Moreover, the introduction of the micro-wrinkles to Fluoropor not only enhances its liquid repellence for water and ethylene glycol but also for liquids with low surface tension, such as n-hexadecane. Full article

(This article belongs to the Special Issue Porous Materials and Advanced Manufacturing Technologies)

► Show Figures

Figure 1

10 pages, 4124 KiB

Open AccessArticle

Permeability and Load Capacity of Iron Porous Bearings with the Addition of Hexagonal Boron Nitride

by Krzysztof Gocman, Tadeusz Kałdoński, Bolesław Giemza and Artur Król

Materials 2022, 15(15), 5112; https://doi.org/10.3390/ma15155112 - 22 Jul 2022

Viewed by 1058

Abstract

Due to their properties, porous sliding bearings are considered to be maintenance-free, which means that no lubrication is required during operation. Their design enables operation at low rotational speeds with high load. Another effect of this bearing design is the lubrication continuity in [...] Read more.

Due to their properties, porous sliding bearings are considered to be maintenance-free, which means that no lubrication is required during operation. Their design enables operation at low rotational speeds with high load. Another effect of this bearing design is the lubrication continuity in the tribological pair. In this study, the selected tribological properties (such as load capacity and permeability) of new-generation iron porous bearings with boron nitride powder were experimentally investigated. Tests were carried out under various conditions, using unique test apparatus. The addition of 3% (weight) of hexagonal boron nitride (hBN) significantly increased the load capacity of tested porous bearings in comparison to the same standard bearings containing 2.5% copper. The obtained p_gr·v rating reached almost 7 MPa, which is a value almost three times higher than the requirements for this type of bearing. It is worth emphasizing that such a result was obtained despite a noticeable deterioration in the air and oil permeability of the bearing. Full article

(This article belongs to the Special Issue Porous Materials and Advanced Manufacturing Technologies)

► Show Figures

Figure 1

16 pages, 7203 KiB

Open AccessArticle

A Low-Cost Porous Polymer Membrane for Gas Permeation

by Selim Haouari and Denis Rodrigue

Materials 2022, 15(10), 3537; https://doi.org/10.3390/ma15103537 - 14 May 2022

Cited by 3 | Viewed by 1715

Abstract

In this work, an efficient technique was used to produce porous membranes for different applications. Polyethylene (PE) was selected for the matrix, while corn starch (CS) was used to create the porous structure via leaching. The membranes were produced by continuous extrusion (blending)–calendering [...] Read more.

In this work, an efficient technique was used to produce porous membranes for different applications. Polyethylene (PE) was selected for the matrix, while corn starch (CS) was used to create the porous structure via leaching. The membranes were produced by continuous extrusion (blending)–calendering (forming) followed by CS leaching in a 20% aqueous acetic acid solution at 80 °C. A complete characterization of the resulting membranes was performed including morphological and mechanical properties. After process optimization, the gas transport properties through the membranes were determined on the basis of pure gas permeation including CH₄, CO₂, O₂, and N₂ for two specific applications: biogas sweetening (CH₄/CO₂) and oxygen-enriched air (O₂/N₂). The gas separation results for ideal permeability and selectivity at 25 °C and 1.17 bar (17 psi) show that these membranes are a good starting point for industrial applications since they are low-cost, easy to produce, and can be further optimized. Full article

(This article belongs to the Special Issue Porous Materials and Advanced Manufacturing Technologies)

► Show Figures

Figure 1

9 pages, 2022 KiB

Open AccessCommunication

Porous Glass Microspheres from Alkali-Activated Fiber Glass Waste

by Mokhtar Mahmoud, Jozef Kraxner, Hana Kaňková, Miroslava Hujová, Si Chen, Dušan Galusek and Enrico Bernardo

Materials 2022, 15(3), 1043; https://doi.org/10.3390/ma15031043 - 28 Jan 2022

Cited by 9 | Viewed by 2791

Abstract

Fiber glass waste (FGW) was subjected to alkali activation in an aqueous solution with different concentrations of sodium/potassium hydroxide. The activated materials were fed into a methane–oxygen flame with a temperature of around 1600 °C. X-ray diffraction analysis confirmed the formation of several [...] Read more.

Fiber glass waste (FGW) was subjected to alkali activation in an aqueous solution with different concentrations of sodium/potassium hydroxide. The activated materials were fed into a methane–oxygen flame with a temperature of around 1600 °C. X-ray diffraction analysis confirmed the formation of several hydrated compounds, which decomposed upon flame synthesis, leading to porous glass microspheres (PGMs). Pore formation was favored by using highly concentrated activating alkali solutions. The highest homogeneity and yield of PGMs corresponded to the activation with 9 M KOH aqueous solution. Full article

(This article belongs to the Special Issue Porous Materials and Advanced Manufacturing Technologies)

► Show Figures

Figure 1

22 pages, 10288 KiB

Open AccessArticle

High Mechanic Enhancement of Chopped Carbon Fiber Reinforced-Low-Density Unsaturated Polyester Resin Composite at Low Preparation Temperature with Facile Polymerization

by Jian Zhang, Xiaojun Wang and Xinjun Fu

Materials 2021, 14(15), 4273; https://doi.org/10.3390/ma14154273 - 30 Jul 2021

Cited by 4 | Viewed by 1847

Abstract

Chopped carbon fiber-reinforced low-density unsaturated polyester resin (CCFR-LDUPR) composite materials with light weight and high mechanical properties were prepared at low temperature and under the synergistic action of methyl ethyl ketone peroxide (MEKP-II) and cobalt naphthenate. Optimal preparation conditions were obtained through an [...] Read more.

Chopped carbon fiber-reinforced low-density unsaturated polyester resin (CCFR-LDUPR) composite materials with light weight and high mechanical properties were prepared at low temperature and under the synergistic action of methyl ethyl ketone peroxide (MEKP-II) and cobalt naphthenate. Optimal preparation conditions were obtained through an orthogonal experiment, which were preparation temperature at 58.0 °C, 2.00 parts per hundred of resin (phr) of NH₄HCO₃, 4.00 phr of chopped carbon fibers (CCFs) in a length of 6.0 mm, 1.25 phr of initiator and 0.08 phr of cobalt naphthenate. CCFR-LDUPR composite sample presented its optimal properties for which the density (ρ) was 0.58 ± 0.02 g·cm⁻³ and the specific compressive strength (P_s) was 53.56 ± 0.83 MPa·g⁻¹·cm³, which is 38.9% higher than that of chopped glass fiber-reinforced low-density unsaturated polyester resin (CGFR-LDUPR) composite materials. Synergistic effects of initiator and accelerator accelerated the specific polymerization of resin in facile preparation at low temperature. Unique “dimples”, “plate microstructure” and “surface defect” fabricated the specific microstructure of the matrix of CCFR-LDUPR composite samples, which was different from that of cured unsaturated polyester resin (UPR) with “body defect” or that of CGFR-LDUPR with coexistence of “surface defect” and “body defect”. Full article

(This article belongs to the Special Issue Porous Materials and Advanced Manufacturing Technologies)

► Show Figures

Figure 1

9 pages, 2554 KiB

Open AccessArticle

Improved Biological Responses of Titanium Coating Using Laser-Aided Direct Metal Fabrication on SUS316L Stainless Steel

by Tae-In Kim, Se-Won Lee, Woo-Lam Jo, Yong-Sik Kim, Seung-Chan Kim, Soon-Yong Kwon and Young-Wook Lim

Materials 2021, 14(14), 3947; https://doi.org/10.3390/ma14143947 - 14 Jul 2021

Cited by 3 | Viewed by 1655

Abstract

Direct metal fabrication (DMF) coatings have the advantage of a more uniform porous structure and superior mechanical properties compared to coatings provided by other methods. We applied pure titanium metal powders to SUS316L stainless steel using laser-aided DMF coating technology with 3D printing. [...] Read more.

Direct metal fabrication (DMF) coatings have the advantage of a more uniform porous structure and superior mechanical properties compared to coatings provided by other methods. We applied pure titanium metal powders to SUS316L stainless steel using laser-aided DMF coating technology with 3D printing. The purpose of this study was to determine the efficacy of this surface modification of stainless steel. The capacity of cells to adhere to DMF-coated SUS316L stainless steel was compared with machined SUS316L stainless steel in vitro and in vivo. Morphological in vitro response to human osteoblast cell lines was evaluated using scanning electron microscopy. Separate specimens were inserted into the medulla of distal femurs of rabbits for in vivo study. The distal femurs were harvested after 3 months, and were then subjected to push-out test and histomorphometrical analyses. The DMF group exhibited a distinct surface chemical composition, showing higher peaks of titanium compared to the machined stainless steel. The surface of the DMF group had a more distinct porous structure, which showed more extensive coverage with lamellipodia from osteoblasts than the machined surface. In the in vivo test, the DMF group showed better results than the machined group in the push-out test (3.39 vs. 1.35 MPa, respectively, p = 0.001). In the histomorphometric analyses, the mean bone-to-implant contact percentage of the DMF group was about 1.5 times greater than that of the machined group (65.4 ± 7.1% vs. 41.9 ± 5.6%, respectively; p < 0.001). The porous titanium coating on SUS316L stainless steel produced using DMF with 3D printing showed better surface characteristics and biomechanical properties than the machined SUS316L. Full article

(This article belongs to the Special Issue Porous Materials and Advanced Manufacturing Technologies)

► Show Figures

Figure 1

19 pages, 7132 KiB

Open AccessArticle

A Micro-Computed Tomography Comparison of the Porosity in Additively Fabricated CuCr1 Alloy Parts Using Virgin and Surface-Modified Powders

by Mirko Sinico, Suraj Dinkar Jadhav, Ann Witvrouw, Kim Vanmeensel and Wim Dewulf

Materials 2021, 14(8), 1995; https://doi.org/10.3390/ma14081995 - 16 Apr 2021

Cited by 8 | Viewed by 3797

Abstract

Recently, the use of novel CuCr1 surface-modified powder for reliable laser powder-bed fusion (LPBF) manufacturing has been proposed, enabling a broader LPBF processing window and longer powder storage life. Nevertheless, virgin CuCr1 powder is also LPBF processable, on the condition that a high-energy [...] Read more.

Recently, the use of novel CuCr1 surface-modified powder for reliable laser powder-bed fusion (LPBF) manufacturing has been proposed, enabling a broader LPBF processing window and longer powder storage life. Nevertheless, virgin CuCr1 powder is also LPBF processable, on the condition that a high-energy density is employed. In this work, we compare two dense specimens produced from virgin and surface-modified CuCr1 powder. Furthermore, a third sample fabricated from surface-modified powder is characterized to understand an abnormal porosity content initially detected through Archimedes testing. Utilizing high-resolution micro-CT scans, the nature of the defects present in the different samples is revealed. Pores are analyzed in terms of size, morphology and spatial distribution. The micro-CT data reveal that the virgin CuCr1 dense specimen displays keyhole pores plus pit cavities spanning multiple layer thicknesses. On the other hand, the sample fabricated with the surface-modified CuCr1 powder mainly contains small and spherical equi-distributed metallurgical defects. Finally, the CT analysis of the third specimen reveals the presence of a W contamination, favoring lack-of-fusion pores between subsequent LPBF layers. The LPBF melting mode (keyhole or conductive), the properties of the material, and the potential presence of contaminants are connected to the different porosity types and discussed. Full article

(This article belongs to the Special Issue Porous Materials and Advanced Manufacturing Technologies)

► Show Figures

Figure 1

17 pages, 3308 KiB

Open AccessArticle

Prediction Models Based on Regression and Artificial Neural Network for Moduli of Layers Constituted by Open-Graded Aggregates

by Yunje Lee, Yongjin Choi, Donghyun Ahn and Jaehun Ahn

Materials 2021, 14(5), 1199; https://doi.org/10.3390/ma14051199 - 04 Mar 2021

Cited by 2 | Viewed by 1464

Abstract

The impermeable cover in urban area has been growing due to rapid urbanization, which prevents stormwater from being naturally infiltrated into the ground. There is a higher chance of flooding in urban area covered with conventional concretes and asphalts. The permeable pavement is [...] Read more.

The impermeable cover in urban area has been growing due to rapid urbanization, which prevents stormwater from being naturally infiltrated into the ground. There is a higher chance of flooding in urban area covered with conventional concretes and asphalts. The permeable pavement is one of Low-Impact Development (LID) technologies that can reduce surface runoff and water pollution by allowing stormwater into pavement systems. Unlike traditional pavements, permeable pavement bases employ open-graded aggregates (OGAs) with highly uniform particle sizes. There is very little information on the engineering properties of compacted OGAs. In this study, the moduli of open-graded aggregates under various compaction energies are investigated based on the Plate Load Test (PLT) and Light-Weight Deflectometer (LWD). Artificial Neural Network (ANN) and Linear Regression (LR) models are employed for estimation of the moduli of the aggregates based on the material type and level of compaction. Overall, the moduli from PLT and LWD steeply increase until the number of roller passes reaches 4, and they gradually increase until the number of roller passes becomes 8. A set of simple linear equations are proposed to evaluate the moduli of open-graded aggregates from PLT and LWD based on the material type and the number of roller passes. Full article

(This article belongs to the Special Issue Porous Materials and Advanced Manufacturing Technologies)

► Show Figures

Figure 1

14 pages, 9638 KiB

Open AccessArticle

Effect of Internal Microstructure Distribution on Quasi-Static Compression Behavior and Energy Absorption of Hollow Truss Structures

by Huilan Ren, Haiting Shen and Jianguo Ning

Materials 2020, 13(22), 5094; https://doi.org/10.3390/ma13225094 - 12 Nov 2020

Cited by 5 | Viewed by 1422

Abstract

In this work, hollow truss structures with different internal microstructure distributions, i.e., basic hollow truss structure (specimen HT), hollow truss structure with internal microstructure at joints (specimen HTSJ), and hollow truss structure with internal microstructure on tube walls (specimen HTSW), were designed and [...] Read more.

In this work, hollow truss structures with different internal microstructure distributions, i.e., basic hollow truss structure (specimen HT), hollow truss structure with internal microstructure at joints (specimen HTSJ), and hollow truss structure with internal microstructure on tube walls (specimen HTSW), were designed and manufactured using a selective laser melting technique. The effect of internal microstructure distribution on quasi-static compressive behavior and energy absorption was investigated by experimental tests and numerical simulations. The experimental results show that compressive strength and specific compressive strength of specimen HTSW increase by nearly 50% and 14% compared to specimen HT, and its energy absorption per volume and mass also increase by 52% and 15% at a strain of 0.5, respectively. However, the parameters of specimen HTSJ exhibit limited improvement or even a decrease in different degrees in comparison to specimen HT. The numerical simulation indicates that internal microstructures change the bearing capacity and structural weaknesses of the cells, resulting in the different mechanical properties and energy absorptions of the specimens. Based on the internal microstructure design in this study, adding microstructures into the internal weaknesses of the cells parallel to the loading direction is an effective way to improve the compressive properties, energy absorption and compressive stability of hollow truss structures. Full article

(This article belongs to the Special Issue Porous Materials and Advanced Manufacturing Technologies)

► Show Figures

Graphical abstract

11 pages, 6290 KiB

Open AccessArticle

Acoustical and Optical Determination of Mechanical Properties of Inorganically-Bound Foundry Core Materials

by Philipp Lechner, Georg Fuchs, Christoph Hartmann, Florian Steinlehner, Florian Ettemeyer and Wolfram Volk

Materials 2020, 13(11), 2531; https://doi.org/10.3390/ma13112531 - 03 Jun 2020

Cited by 10 | Viewed by 2194

Abstract

Inorganically-bound sand cores are used in many light-metal foundries to form cavities in the cast part, which cannot be realised by the mould itself. To enable FEM simulations with core materials, their mechanical properties have to be measured. In this article, we adapt [...] Read more.

Inorganically-bound sand cores are used in many light-metal foundries to form cavities in the cast part, which cannot be realised by the mould itself. To enable FEM simulations with core materials, their mechanical properties have to be measured. In this article, we adapt methods to determine the Young’s and shear modulus, the Poisson ratio and the fracture strain of sand cores. This allows us to fully parametrise an ideal brittle FEM model. We found that the Young’s and shear modulus can be obtained acoustically via the impulse excitation technique. The fracture strain was measured with a high-speed camera and a digital image correlation algorithm. Full article

(This article belongs to the Special Issue Porous Materials and Advanced Manufacturing Technologies)

► Show Figures

Figure 1

Review

Jump to: Research

17 pages, 9134 KiB

Open AccessReview

Additive Manufacturing as a Solution to Challenges Associated with Heat Pipe Production

by Pawel Szymanski and Dariusz Mikielewicz

Materials 2022, 15(4), 1609; https://doi.org/10.3390/ma15041609 - 21 Feb 2022

Cited by 12 | Viewed by 2562

Abstract

The aim of this review is to present the recent developments in heat pipe production, which respond to the current technical problems related to the wide implementation of this technology. A novel approach in HP manufacturing is to utilise hi-tech additive manufacturing techniques [...] Read more.

The aim of this review is to present the recent developments in heat pipe production, which respond to the current technical problems related to the wide implementation of this technology. A novel approach in HP manufacturing is to utilise hi-tech additive manufacturing techniques where the most complicated geometries are fabricated layer-by-layer directly from a digital file. This technology might be a solution to various challenges that exist in HP production, i.e., (1) manufacturing of complex or unusual geometries HPs; (2) manufacturing complicated and efficient homogenous wick structures with desired porosity, uniform pore sizes, permeability, thickness and where the pores are evenly distributed; (3) manufacturing a gravity friendly wick structures; (4) high customisation and production time; (5) high costs; (6) difficulties in the integration of the HP into a unit chassis that enables direct thermal management of heated element and decrease its total thermal resistance; (7) high weight and material use of the part; (8) difficulties in sealing; (9) deformation of the flat shape HPs caused by the high pressure and uneven distribution of stress in the casing, among others. Full article

(This article belongs to the Special Issue Porous Materials and Advanced Manufacturing Technologies)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Porous Materials and Advanced Manufacturing Technologies

Share This Special Issue

Special Issue Editor

Special Issue Information

Keywords

Published Papers (13 papers)

Research

Review

Further Information

Guidelines

MDPI Initiatives

Follow MDPI