Editorial

3 pages, 189 KiB

Open AccessEditorial

Obtaining and Characterization of New Materials

by Andrei Victor Sandu

Materials 2021, 14(21), 6606; https://doi.org/10.3390/ma14216606 - 03 Nov 2021

Cited by 6 | Viewed by 1426

The main objective of this Special Issue was to publish outstanding papers presenting cutting-edge research in the field of new materials and their understanding [...] Full article

(This article belongs to the Special Issue Obtaining and Characterization of New Materials)

Research

Jump to: Editorial

13 pages, 3818 KiB

Open AccessFeature PaperArticle

Influence of TiO₂ Nanoparticles on the Resistance of Cementitious Composite Materials to the Action of Bacteria

by Andreea Hegyi, Adrian-Victor Lăzărescu, Henriette Szilagyi, Elvira Grebenişan, Jana Goia and Andreea Mircea

Materials 2021, 14(5), 1074; https://doi.org/10.3390/ma14051074 - 25 Feb 2021

Cited by 5 | Viewed by 1775

Abstract

The formation of biofilms on cementitious building surfaces can cause visible discoloration and premature deterioration, and it can also represent a potential health threat to building occupants. The use of embedded biofilm-resistant photoactivated TiO₂ nanoparticles at low concentrations in the cementitious composite [...] Read more.

The formation of biofilms on cementitious building surfaces can cause visible discoloration and premature deterioration, and it can also represent a potential health threat to building occupants. The use of embedded biofilm-resistant photoactivated TiO₂ nanoparticles at low concentrations in the cementitious composite matrix is an effective method to increase material durability and reduce maintenance costs. Zone of inhibition studies of TiO₂-infused cementitious samples showed efficacy toward both Gram-negative and Gram-positive bacteria. Full article

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19 pages, 17343 KiB

Open AccessArticle

Performance of Sn-3.0Ag-0.5Cu Composite Solder with Kaolin Geopolymer Ceramic Reinforcement on Microstructure and Mechanical Properties under Isothermal Ageing

by Nur Syahirah Mohamad Zaimi, Mohd Arif Anuar Mohd Salleh, Andrei Victor Sandu, Mohd Mustafa Al Bakri Abdullah, Norainiza Saud, Shayfull Zamree Abd Rahim, Petrica Vizureanu, Rita Mohd Said and Mohd Izrul Izwan Ramli

Materials 2021, 14(4), 776; https://doi.org/10.3390/ma14040776 - 07 Feb 2021

Cited by 7 | Viewed by 2429

Abstract

This paper elucidates the effect of isothermal ageing at temperature of 85 °C, 125 °C and 150 °C for 100, 500 and 1000 h on Sn-3.0Ag-0.5Cu (SAC305) lead-free solder with the addition of 1 wt% kaolin geopolymer ceramic (KGC) reinforcement particles. SAC305-KGC composite [...] Read more.

This paper elucidates the effect of isothermal ageing at temperature of 85 °C, 125 °C and 150 °C for 100, 500 and 1000 h on Sn-3.0Ag-0.5Cu (SAC305) lead-free solder with the addition of 1 wt% kaolin geopolymer ceramic (KGC) reinforcement particles. SAC305-KGC composite solders were fabricated through powder metallurgy using a hybrid microwave sintering method and reflowed on copper substrate printed circuit board with an organic solderability preservative surface finish. The results revealed that, the addition of KGC was beneficial in improving the total thickness of interfacial intermetallic compound (IMC) layer. At higher isothermal ageing of 150 °C and 1000 h, the IMC layer in SAC305-KGC composite solder was towards a planar-type morphology. Moreover, the growth of total interfacial IMC layer and Cu₃Sn layer during isothermal ageing was found to be controlled by bulk diffusion and grain-boundary process, respectively. The activation energy possessed by SAC305-KGC composite solder for total interfacial IMC layer and Cu₃Sn IMC was 74 kJ/mol and 104 kJ/mol, respectively. Based on a lap shear test, the shear strength of SAC305-KGC composite solder exhibited higher shear strength than non-reinforced SAC305 solder. Meanwhile, the solder joints failure mode after shear testing was a combination of brittle and ductile modes at higher ageing temperature and time for SAC305-KGC composite solder. Full article

(This article belongs to the Special Issue Obtaining and Characterization of New Materials)

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15 pages, 7225 KiB

Open AccessArticle

Effect of Ni on the Suppression of Sn Whisker Formation in Sn-0.7Cu Solder Joint

by Aimi Noorliyana Hashim, Mohd Arif Anuar Mohd Salleh, Andrei Victor Sandu, Muhammad Mahyiddin Ramli, Khor Chu Yee, Noor Zaimah Mohd Mokhtar and Jitrin Chaiprapa

Materials 2021, 14(4), 738; https://doi.org/10.3390/ma14040738 - 05 Feb 2021

Cited by 5 | Viewed by 1967

Abstract

The evolution of internal compressive stress from the intermetallic compound (IMC) Cu₆Sn₅ growth is commonly acknowledged as the key inducement initiating the nucleation and growth of tin (Sn) whisker. This study investigates the effect of Sn-0.7Cu-0.05Ni on the nucleation and [...] Read more.

The evolution of internal compressive stress from the intermetallic compound (IMC) Cu₆Sn₅ growth is commonly acknowledged as the key inducement initiating the nucleation and growth of tin (Sn) whisker. This study investigates the effect of Sn-0.7Cu-0.05Ni on the nucleation and growth of Sn whisker under continuous mechanical stress induced. The Sn-0.7Cu-0.05Ni solder joint has a noticeable effect of suppression by diminishing the susceptibility of nucleation and growth of Sn whisker. By using a synchrotron micro X-ray fluorescence (µ-XRF) spectroscopy, it was found that a small amount of Ni alters the microstructure of Cu₆Sn₅ to form a (Cu,Ni)₆Sn₅ intermetallic layer. The morphology structure of the (Cu,Ni)₆Sn₅ interfacial intermetallic layer and Sn whisker growth were investigated by scanning electron microscope (SEM) in secondary and backscattered electron imaging mode, which showed that there is a strong correlation between the formation of Sn whisker and the composition of solder alloy. The thickness of the (Cu,Ni)₆Sn₅ IMC interfacial layer was relatively thinner and more refined, with a continuous fine scallop-shaped IMC interfacial layer, and consequently enhanced a greater incubation period for the nucleation and growth of the Sn whisker. These verification outcomes proposes a scientifically foundation to mitigate Sn whisker growth in lead-free solder joint. Full article

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24 pages, 7726 KiB

Open AccessFeature PaperArticle

Experimental Research on the Cutting of Metal Materials by Electrical Discharge Machining with Contact Breaking with Metal Band as Transfer Object

by Aurel Mihail Țîțu, Petrică Vizureanu, Ștefan Țîțu, Andrei Victor Sandu, Alina Bianca Pop, Viorel Bucur, Costel Ceocea and Alexandru Boroiu

Materials 2020, 13(22), 5257; https://doi.org/10.3390/ma13225257 - 20 Nov 2020

Cited by 2 | Viewed by 1568

Abstract

The scientific paper presents practical research carried out by a mixed team of Romanian researchers from universities and the business environment. The research consists in applying the process of cutting metallic materials through electrical discharge machining with contact breaking using a metal band [...] Read more.

The scientific paper presents practical research carried out by a mixed team of Romanian researchers from universities and the business environment. The research consists in applying the process of cutting metallic materials through electrical discharge machining with contact breaking using a metal band as a transfer object. The research was implemented with the help of a specially designed installation in the laboratory and subsequently all the necessary steps were taken to obtain the patent for it. Various metallic materials were cut using this process, but first of all, high alloy steels. In the global research conducted by the authors, active experimental programs and classic experimental programs were used. The composite central factorial experiment was the method that led to the most effective results in terms of interpretations and conclusions. The research as a whole includes unique elements from an engineering point of view and here we can highlight the use of a metal band as a transfer object for this type of process as well as the designed, realized, and subsequently patented installation. Full article

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10 pages, 2833 KiB

Open AccessArticle

Third-Generation Cephalosporin-Loaded Chitosan Used to Limit Microorganisms Resistance

by Letiția Doina Duceac, Gabriela Calin, Lucian Eva, Constantin Marcu, Elena Roxana Bogdan Goroftei, Marius Gabriel Dabija, Geta Mitrea, Alina Costina Luca, Elena Hanganu, Cristian Gutu, Liviu Stafie, Elena Ariela Banu, Carmen Grierosu and Alin Constantin Iordache

Materials 2020, 13(21), 4792; https://doi.org/10.3390/ma13214792 - 27 Oct 2020

Cited by 10 | Viewed by 4161

Abstract

From their discovery, antibiotics have significantly improved clinical treatments of infections, thus leading to diminishing morbidity and mortality in critical care patients, as well as surgical, transplant and other types of medical procedures. In contemporary medicine, a significant debate regarding the development of [...] Read more.

From their discovery, antibiotics have significantly improved clinical treatments of infections, thus leading to diminishing morbidity and mortality in critical care patients, as well as surgical, transplant and other types of medical procedures. In contemporary medicine, a significant debate regarding the development of multi-drug resistance involves all types of pathogens, especially in acute care hospitals due to suboptimal or inappropriate therapy. The possibility of nanotechnology using nanoparticles as matrices to encapsulate a lot of active molecules should increase drug efficacy, limit adverse effects and be an alternative helping to combat antibiotic resistance. The major aim of this study was to obtain and to analyze physico-chemical features of chitosan used as a drug-delivery system in order to stop the antibiotic resistance of different pathogens. It is well known that World Health Organization stated that multidrug resistance is one of the most important health threats worldwide. In last few years, nano-medicine emerged as an improved therapy to combat antibiotic-resistant infections agents. This work relies on enhancement of the antimicrobial efficiency of ceftriaxone against gram(+) and gram(−) bacteria by antibiotic encapsulation into chitosan nanoparticles. Physicochemical features of ceftriaxone-loaded polymer nanoparticles were investigated by particle size distribution and zeta potential, Fourier-transform infrared spectroscopy (FTIR), Thermal Gravimetric Analysis (TG/TGA), Scanning Electron Microscopy (SEM) characteristics techniques. The obtained results revealed an average particle size of 250 nm and a zeta potential value of 38.5 mV. The release profile indicates an incipient drug deliverance of almost 15%, after 2 h of approximately 83%, followed by a slowed drug release up to 24 h. Characteristics peaks of chitosan were confirmed by FTIR spectra indicating a similar structure in the case of ceftriaxone-loaded chitosan nanoparticles. A good encapsulation of the antibiotic into chitosan nanoparticles was also provided by thermo-gravimetric analysis. Morphological characteristics shown by SEM micrographs exhibit spherical nanoparticles of 30–250 nm in size with agglomerated architectures. Chitosan, a natural polymer which is used to load different drugs, provides sustained and prolonged release of antibiotics at a specific target by possessing antimicrobial activity against gram(+) and gram(−) bacteria. In this research, ceftriaxone-loaded chitosan nanoparticles were investigated as a carrier in antibiotic delivery. Full article

(This article belongs to the Special Issue Obtaining and Characterization of New Materials)

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17 pages, 5213 KiB

Open AccessArticle

The Comparative Study of the State of Conservation of Two Medieval Documents on Parchment from Different Historical Periods

by Maria Boutiuc (Haulică), Oana Florescu, Viorica Vasilache and Ion Sandu

Materials 2020, 13(21), 4766; https://doi.org/10.3390/ma13214766 - 26 Oct 2020

Cited by 9 | Viewed by 2096

Abstract

The paper explores the potentiality of an experimental multianalytic protocol with appropriate methodology for determining the chemical and morphostructural characteristics of two old documents on parchment support. Such a protocol can authenticate and assess the state of conservation under the influence of environmental [...] Read more.

The paper explores the potentiality of an experimental multianalytic protocol with appropriate methodology for determining the chemical and morphostructural characteristics of two old documents on parchment support. Such a protocol can authenticate and assess the state of conservation under the influence of environmental factors during storage and archival documentation, thus advancing preventive and prophylactic measures in “treasure” deposits such as the National Archives of Romania, where these documents are kept. The work methodology consisted of three stages. The first stage consists of visual observation for identifying deteriorations and degradations, alongside the selection of representatives’ areas from where micro-samples were collected. The second stage involves Scanning Electron Microscopy coupled by Energy Dispersive X-ray Spectrometry (SEM-EDX) analysis, for highlighting the morphology and determining the elemental composition; lastly, the Fourier-transform infrared (FTIR) analysis and correlation of results establish the chemical and morphostructural changes. The use of this gradual system of analyses allowed determining the differences between these two documents in terms of the materials used for producing them, their manufacturing technologies, the writing and ornamentation, and the overall state of conservation. The results provided the first accurate picture of the chemical nature and manufacturing of the two parchment documents by determining the main characteristics of the collagen and of the finishing, writing, and decoration materials, in view of the natural aging through the oxidative and gelatinization processes of the collagen. The SEM-EDX results revealed the morphological changes of the parchment that occurred at various levels in the collagen fibrous mesh and established the state of conservation of the support, writing, and decorations. Full article

(This article belongs to the Special Issue Obtaining and Characterization of New Materials)

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18 pages, 6196 KiB

Open AccessArticle

Microstructure and Optical Properties of E-Beam Evaporated Zinc Oxide Films—Effects of Decomposition and Surface Desorption

by Lukasz Skowronski, Arkadiusz Ciesielski, Aleksandra Olszewska, Robert Szczesny, Mieczyslaw Naparty, Marek Trzcinski and Antoni Bukaluk

Materials 2020, 13(16), 3510; https://doi.org/10.3390/ma13163510 - 09 Aug 2020

Cited by 6 | Viewed by 2084

Abstract

Zinc oxide films have been fabricated by the electron beam physical vapour deposition (PVD) technique. The effect of substrate temperature during fabrication and annealing temperature (carried out in ultra high vacuum conditions) has been investigated by means of atomic force microscopy, scanning electron [...] Read more.

Zinc oxide films have been fabricated by the electron beam physical vapour deposition (PVD) technique. The effect of substrate temperature during fabrication and annealing temperature (carried out in ultra high vacuum conditions) has been investigated by means of atomic force microscopy, scanning electron microscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy and spectroscopic ellipsometry. It was found that the layer deposited at room temperature is composed of Zn and ZnO crystallites with a number of orientations, whereas those grown at 100 and 200

^{\circ}

C consist of ZnO grains and exhibit privileged growth direction. Presented results clearly show the influence of ZnO decomposition and segregation of Zn atoms during evaporation and post-deposition annealing on microstructure and optical properties of zinc oxide films. Full article

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17 pages, 4873 KiB

Open AccessArticle

Electrochemical Analysis and In Vitro Assay of Mg-0.5Ca-xY Biodegradable Alloys

by Bogdan Istrate, Corneliu Munteanu, Stefan Lupescu, Romeu Chelariu, Maria Daniela Vlad and Petrică Vizureanu

Materials 2020, 13(14), 3082; https://doi.org/10.3390/ma13143082 - 10 Jul 2020

Cited by 15 | Viewed by 2183

Abstract

In recent years, biodegradable Mg-based materials have been increasingly studied to be used in the medical industry and beyond. A way to improve biodegradability rate in sync with the healing process of the natural human bone is to alloy Mg with other biocompatible [...] Read more.

In recent years, biodegradable Mg-based materials have been increasingly studied to be used in the medical industry and beyond. A way to improve biodegradability rate in sync with the healing process of the natural human bone is to alloy Mg with other biocompatible elements. The aim of this research was to improve biodegradability rate and biocompatibility of Mg-0.5Ca alloy through addition of Y in 0.5/1.0/1.5/2.0/3.0wt.%. To characterize the chemical composition and microstructure of experimental Mg alloys, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), light microscopy (LM), and X-ray diffraction (XRD) were used. The linear polarization resistance (LPR) method was used to calculate corrosion rate as a measure of biodegradability rate. The cytocompatibility was evaluated by MTT assay (3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide) and fluorescence microscopy. Depending on chemical composition, the dendritic α-Mg solid solution, as well as lamellar Mg₂Ca and Mg₂₄Y₅ intermetallic compounds were found. The lower biodegradability rates were found for Mg-0.5Ca-2.0Y and Mg-0.5Ca-3.0Y which have correlated with values of cell viability. The addition of 2–3 wt.%Y in the Mg-0.5Ca alloy improved both the biodegradability rate and cytocompatibility behavior. Full article

(This article belongs to the Special Issue Obtaining and Characterization of New Materials)

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13 pages, 2676 KiB

Open AccessArticle

Comparative Analysis of the Thermal Insulation of Multi-Layer Thermal Inserts in a Protective Jacket

by Dubravko Rogale, Goran Majstorović and Snježana Firšt Rogale

Materials 2020, 13(12), 2672; https://doi.org/10.3390/ma13122672 - 12 Jun 2020

Cited by 8 | Viewed by 2601

Abstract

This paper presents the measurement results of the thermal insulation of the outer shell, thermal inserts, and clothing systems, as well as a comparative analysis of the thermal insulation of multi-layer thermal inserts in a thermal jacket intended for professional services in cold [...] Read more.

This paper presents the measurement results of the thermal insulation of the outer shell, thermal inserts, and clothing systems, as well as a comparative analysis of the thermal insulation of multi-layer thermal inserts in a thermal jacket intended for professional services in cold weather. Detachable thermal inserts are made of double-faced, diamond-shaped quilted lining with different masses per unit area, and together with the jacket, they form clothing systems with different thermal properties. Tests of the thermal properties of clothing were performed on a thermal manikin. They showed that an increase in the mass of thermal insulation textile materials contributes to an increase in the thermal insulation properties of clothing and are insufficient for a complete analysis of the thermal properties of clothing. Therefore, for the first time, three new parameters of integration efficiency of the thermal insert, thermal insulation efficiency parameters, and efficiency parameters of the integration of the textile material integrated into the clothing system were introduced. Based on these parameters, it is possible to perform an effective and accurate comparative analysis of the thermal insulation of multi-layer thermal inserts in clothing. This makes it possible to apply exact scientific methods largely in the technical design of the thermal properties of integrated textile materials, instead of experience-based methods as in the past. Full article

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11 pages, 9399 KiB

Open AccessArticle

Phase Formation and High-Temperature Stability of Very Thin Co-Sputtered Ti-Al and Multilayered Ti/Al Films on Thermally Oxidized Si Substrates

by Marietta Seifert, Eric Lattner, Siegfried B. Menzel, Steffen Oswald and Thomas Gemming

Materials 2020, 13(9), 2039; https://doi.org/10.3390/ma13092039 - 27 Apr 2020

Cited by 7 | Viewed by 1967

Abstract

Ti-Al thin films with a thickness of 200 nm were prepared either by co-sputtering from elemental Ti and Al targets or as Ti/Al multilayers with 10 and 20 nm individual layer thickness on thermally oxidized Si substrates. Some of the films were covered [...] Read more.

Ti-Al thin films with a thickness of 200 nm were prepared either by co-sputtering from elemental Ti and Al targets or as Ti/Al multilayers with 10 and 20 nm individual layer thickness on thermally oxidized Si substrates. Some of the films were covered with a 20-nm-thick SiO

_{2}

layer, which was used as an oxidation protection against the ambient atmosphere. The films were annealed at up to 800 °C in high vacuum for 10 h, and the phase formation as well as the film architecture was analyzed by X-ray diffraction, cross section, and transmission electron microscopy, as well as Auger electron and X-ray photoelectron spectroscopy. The results reveal that the co-sputtered films remained amorphous after annealing at 600 °C independent on the presence of the SiO

_{2}

cover layer. In contrast to this, the

γ

-TiAl phase was formed in the multilayer films at this temperature. After annealing at 800 °C, all films were degraded completely despite the presence of the cover layer. In addition, a strong chemical reaction between the Ti and SiO

_{2}

of the cover layer and the substrate took place, resulting in the formation of Ti silicide. In the multilayer samples, this reaction already started at 600 °C. Full article

(This article belongs to the Special Issue Obtaining and Characterization of New Materials)

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20 pages, 16869 KiB

Open AccessArticle

High Temperature Behavior of RuAl Thin Films on Piezoelectric CTGS and LGS Substrates

by Marietta Seifert

Materials 2020, 13(7), 1605; https://doi.org/10.3390/ma13071605 - 01 Apr 2020

Cited by 14 | Viewed by 1962

Abstract

This paper reports on a significant further improvement of the high temperature stability of RuAl thin films (110 nm) on the piezoelectric Ca

_{3}

TaGa

_{3}

Si

_{2}

O

_{14}

(CTGS) and La

_{3}

Ga

_{5}

SiO

_{14}

(LGS) substrates. RuAl thin films [...] Read more.

This paper reports on a significant further improvement of the high temperature stability of RuAl thin films (110 nm) on the piezoelectric Ca

_{3}

TaGa

_{3}

Si

_{2}

O

_{14}

(CTGS) and La

_{3}

Ga

_{5}

SiO

_{14}

(LGS) substrates. RuAl thin films with AlN or SiO

_{2}

cover layers and barriers to the substrate (each 20 nm), as well as a combination of both were prepared on thermally oxidized Si substrates, which serve as a reference for fundamental studies, and the piezoelectric CTGS, as well as LGS substrates. In some films, additional Al layers were added. To study their high temperature stability, the samples were annealed in air and in high vacuum up to 900 °C, and subsequently their cross-sections, phase formation, film chemistry, and electrical resistivity were analyzed. It was shown that on thermally oxidized Si substrates, all films were stable after annealing in air up to 800 °C and in high vacuum up to 900 °C. The high temperature stability of RuAl thin films on CTGS substrates was improved up to 900 °C in high vacuum by the application of a combined AlN/SiO

_{2}

barrier layer and up to 800 °C in air using a SiO

_{2}

barrier. On LGS, the films were only stable up to 600 °C in air; however, a single SiO

_{2}

barrier layer was sufficient to prevent oxidation during annealing at 900 °C in high vacuum. Full article

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11 pages, 2979 KiB

Open AccessArticle

Failure Analysis of Retrieved Osteosynthesis Implants

by Mihai Nica, Bogdan Cretu, Dragos Ene, Iulian Antoniac, Daniela Gheorghita and Razvan Ene

Materials 2020, 13(5), 1201; https://doi.org/10.3390/ma13051201 - 07 Mar 2020

Cited by 17 | Viewed by 2994

Abstract

Failure of osteosynthesis implants is an intricate matter with challenging management that calls for efficient investigation and prevention. Using implant retrieval analysis combined with standard radiological examination, we evaluated the main causes for osteosynthesis implant breakdown and the relations among them for a [...] Read more.

Failure of osteosynthesis implants is an intricate matter with challenging management that calls for efficient investigation and prevention. Using implant retrieval analysis combined with standard radiological examination, we evaluated the main causes for osteosynthesis implant breakdown and the relations among them for a series of cases. Twenty-one patients diagnosed with implant failure were assessed for this work. For metallurgical analysis, microscopy techniques such as scanning electron microscopy (SEM), stereomicroscopy, and optical microscopy were employed. The results showed that material structural deficiencies (nine patients) and faulty surgical techniques (eight patients) were the main causes for failure. An important number of patients presented with material structural deficiencies superimposed on an imperfect osteosynthesis technique (six patients). Consequently, the importance of failure retrieval analysis should not be overlooked, and in combination with other investigational techniques, must provide information for both implant manufacturing and design improvement, as well as osteosynthesis technique optimization. Full article

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16 pages, 2671 KiB

Open AccessArticle

Strength Development and Elemental Distribution of Dolomite/Fly Ash Geopolymer Composite under Elevated Temperature

by Emy Aizat Azimi, Mohd Mustafa Al Bakri Abdullah, Petrica Vizureanu, Mohd Arif Anuar Mohd Salleh, Andrei Victor Sandu, Jitrin Chaiprapa, Sorachon Yoriya, Kamarudin Hussin and Ikmal Hakem Aziz

Materials 2020, 13(4), 1015; https://doi.org/10.3390/ma13041015 - 24 Feb 2020

Cited by 40 | Viewed by 3898

Abstract

A geopolymer has been reckoned as a rising technology with huge potential for application across the globe. Dolomite refers to a material that can be used raw in producing geopolymers. Nevertheless, dolomite has slow strength development due to its low reactivity as a [...] Read more.

A geopolymer has been reckoned as a rising technology with huge potential for application across the globe. Dolomite refers to a material that can be used raw in producing geopolymers. Nevertheless, dolomite has slow strength development due to its low reactivity as a geopolymer. In this study, dolomite/fly ash (DFA) geopolymer composites were produced with dolomite, fly ash, sodium hydroxide, and liquid sodium silicate. A compression test was carried out on DFA geopolymers to determine the strength of the composite, while a synchrotron Micro-Xray Fluorescence (Micro-XRF) test was performed to assess the elemental distribution in the geopolymer composite. The temperature applied in this study generated promising properties of DFA geopolymers, especially in strength, which displayed increments up to 74.48 MPa as the optimum value. Heat seemed to enhance the strength development of DFA geopolymer composites. The elemental distribution analysis revealed exceptional outcomes for the composites, particularly exposure up to 400 °C, which signified the homogeneity of the DFA composites. Temperatures exceeding 400 °C accelerated the strength development, thus increasing the strength of the DFA composites. This appears to be unique because the strength of ordinary Portland Cement (OPC) and other geopolymers composed of other raw materials is typically either maintained or decreases due to increased heat. Full article

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13 pages, 5602 KiB

Open AccessArticle

Innovative Use of Sheep Wool for Obtaining Materials with Improved Sound-Absorbing Properties

by Simona Ioana Borlea (Mureşan), Ancuţa-Elena Tiuc, Ovidiu Nemeş, Horaţiu Vermeşan and Ovidiu Vasile

Materials 2020, 13(3), 694; https://doi.org/10.3390/ma13030694 - 04 Feb 2020

Cited by 32 | Viewed by 5892

Abstract

In recent years, natural materials are becoming a valid alternative to traditional sound absorbers due to reduced production costs and environmental protection. This study explores alternative usage of sheep wool as a construction material with improved sound absorbing properties beyond its traditional application [...] Read more.

In recent years, natural materials are becoming a valid alternative to traditional sound absorbers due to reduced production costs and environmental protection. This study explores alternative usage of sheep wool as a construction material with improved sound absorbing properties beyond its traditional application as a sound absorber in textile industry or using of waste wool in the textile industry as a raw material. The aim of this study was to obtain materials with improved sound-absorbing properties using sheep wool as a raw material. Seven materials were obtained by hot pressing (60 ÷ 80 °C and 0.05 ÷ 6 MPa) of wool fibers and one by cold pressing. Results showed that by simply hot pressing the wool, a different product was obtained, which could be processed and easily manipulated. The obtained materials had very good sound absorption properties, with acoustic absorption coefficient values of over 0.7 for the frequency range of 800 ÷ 3150 Hz. The results prove that sheep wool has a comparable sound absorption performance to mineral wool or recycled polyurethane foam. Full article

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18 pages, 4739 KiB

Open AccessArticle

XRD and TG-DTA Study of New Alkali Activated Materials Based on Fly Ash with Sand and Glass Powder

by Dumitru Doru Burduhos Nergis, Mohd Mustafa Al Bakri Abdullah, Andrei Victor Sandu and Petrică Vizureanu

Materials 2020, 13(2), 343; https://doi.org/10.3390/ma13020343 - 11 Jan 2020

Cited by 72 | Viewed by 6497

Abstract

In this paper, the effect on thermal behavior and compounds mineralogy of replacing different percentages of fly ash with compact particles was studied. A total of 30% of fly ash was replaced with mass powder glass (PG), 70% with mass natural aggregates (S), [...] Read more.

In this paper, the effect on thermal behavior and compounds mineralogy of replacing different percentages of fly ash with compact particles was studied. A total of 30% of fly ash was replaced with mass powder glass (PG), 70% with mass natural aggregates (S), and 85% with mass PG and S. According to this study, the obtained fly ash based geopolymer exhibits a 20% mass loss in the 25–300 °C temperature range due to the free or physically bound water removal. However, the mass loss is closely related to the particle percentage. Multiple endothermic peaks exhibit the dihydroxylation of β-FeOOH (goethite) at close to 320 °C, the Ca(OH)₂ (Portlandite) transformation to CaCO₃ (calcite) occurs at close to 490 °C, and Al(OH)₃ decomposition occurs at close to 570 °C. Moreover, above 600 °C, the curves show only very small peaks which may correspond to Ti or Mg hydroxides decomposition. Also, the X-ray diffraction (XRD) pattern confirms the presence of sodalite after fly ash alkaline activation, whose content highly depends on the compact particles percentage. These results highlight the thermal stability of geopolymers in the 25–1000 °C temperature range through the use of thermogravimetric analysis, differential thermal analysis, and XRD. Full article

(This article belongs to the Special Issue Obtaining and Characterization of New Materials)

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11 pages, 2345 KiB

Open AccessArticle

Characterization of the Acid-Base Character of Burned Clay Ceramics Used for Water Decontamination

by Andrei Victor Sandu, Viorica Vasilache, Ioan Gabriel Sandu, Joseph M. Sieliechi, Innocent Kouassi Kouame, Petre Daniel Matasaru and Ion Sandu

Materials 2019, 12(23), 3836; https://doi.org/10.3390/ma12233836 - 21 Nov 2019

Cited by 5 | Viewed by 1642

Abstract

The paper presents the results of ample investigations performed on industrial and traditional ceramics of fired clay used in processes of water potabilization in the last stage of filtration, after that of active charcoal. Using the data obtained through the scanning electron microscope [...] Read more.

The paper presents the results of ample investigations performed on industrial and traditional ceramics of fired clay used in processes of water potabilization in the last stage of filtration, after that of active charcoal. Using the data obtained through the scanning electron microscope coupled with energy dispersive X-ray analysis (SEM-EDX) and pH analyses, on the basis of the atomic composition and free concentration of hydronium ions, the normal caustic (Si/Al) and summative [(Si+Ti+FeIII+Cl)/(Al+Ca+Mg+Na+K)] modules were assessed, which were correlated with the free acidity and, respectively, the capacity of absorption and ionic exchange of the Fe³⁺ and Al³⁺ ions. The study allowed the selection, on the basis of the caustic module, of the ceramics with high capacity for ionic exchange. Full article

(This article belongs to the Special Issue Obtaining and Characterization of New Materials)

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