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Advances in Ultrasonic Spray Pyrolysis Processing of Materials

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Manufacturing Processes and Systems".

Deadline for manuscript submissions: closed (30 June 2020) | Viewed by 20403

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Dr. Rebeka Rudolf

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Faculty of Mechanical Engineering, University of Maribor, Smetanova Ulica 17, 2000 Maribor, Slovenia
Interests: production technology; nanomaterials; gold nanoparticles; characterization; innovation
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Special Issue Information

Dear Colleagues,

The scope of the Special Issue “Advances in Ultrasonic Spray Pyrolysis Processing of Materials” is to present new technological advances, trends, and the latest scientific results of the bottom–up method called Ultrasonic Spray Pyrolysis (USP) in comparison with other similar processes. The USP method has a good potential for removing the main problematic technological issues in nanotechnology, which are the (i) production of small quantities of nanomaterials and (ii) variations in the shapes and sizes of nanomaterials from one batch to another. Based on this, it is highly recommended to present your research using novel approaches to solve the above mentioned problems by: (i) describing the influential USP processing parameters, (ii) representing the nano-, micro-, and metastable or multicomponent materials synthesized through USP and similar processes; and (iii) introducing the characterization of conventional and functional properties in direct connection to their formatted structure. Submitted papers are expected to follow different approaches of USP and similar processes, including synthesis of different nano-, micro-, and multicomponent or metastable materials, by defining the physical, chemical, and other properties with the focus of functional properties` identification and an explanation of the formation mechanism. The papers should provide comprehensive insight into USP and similar processes, nano-, micro-, and metastable and multicomponent materials, their characterization, properties, structure, with emphasis on enhanced functional performance for different new applications.

The present Special Issue focuses on the Advances in Ultrasonic Spray Pyrolysis Processing of Materials for getting a new improved solution, not only in nanotechnology, but also in a wide range of materials’ synthesis, including micro- and metastable or multicomponent forms to increase their transition for special application in different engineering areas.

Prof. Dr. Rebeka Rudolf
Guest Editor

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Keywords

Bottom–up nanotechnology
Ultrasonic spray pyrolysis
Technological advances
Nano and micro-materials
Metastable and multicomponent materials
Characterization
Structure
Functional properties

Published Papers (7 papers)

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Research

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14 pages, 2546 KiB

Open AccessArticle

Microstructure Characterisation and Identification of the Mechanical and Functional Properties of a New PMMA-ZnO Composite

by Rebeka Rudolf, Danica Popović, Sergej Tomić, Rajko Bobovnik, Vojkan Lazić, Peter Majerič, Ivan Anžel and Miodrag Čolić

Materials 2020, 13(12), 2717; https://doi.org/10.3390/ma13122717 - 15 Jun 2020

Cited by 11 | Viewed by 2453

Abstract

In this research work, we synthesised poly(methyl methacrylate) (PMMA) enriched with 2 wt.% zinc oxide nanoparticles (ZnO) through conventional heat polymerisation and characterised its microstructure. It was found that the distribution of ZnO nanoparticles was homogeneous through the volume of the PMMA. The mechanical testing of the PMMA-ZnO composite primarily included the determination of the compressive properties on real dentures, while density measurements were performed using a pycnometer. The testing of functional properties involved the identification of the colour of the new PMMA-ZnO composite, where pure PMMA acted as a control. In the second step, the PMMA-ZnO cytotoxicity assays were measured in vitro, which were shown to be similar to the control PMMA. Based on this, it could be concluded that the newly formed PMMA-ZnO composite did not induce direct or indirect cytotoxic effects in L929 cell cultures; therefore, according to ISO/DIN 10993-5:2009, this composite was categorised as non-cytotoxic. Full article

(This article belongs to the Special Issue Advances in Ultrasonic Spray Pyrolysis Processing of Materials)

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13 pages, 5036 KiB

Open AccessArticle

Novel Approach of Nanostructured Bainitic Steels’ Production with Improved Toughness and Strength

by Peter Kirbiš, Ivan Anžel, Rebeka Rudolf and Mihael Brunčko

Materials 2020, 13(5), 1220; https://doi.org/10.3390/ma13051220 - 09 Mar 2020

Cited by 5 | Viewed by 2110

Abstract

The tendencies of development within the field of engineering materials show a persistent trend towards the increase of strength and toughness. This pressure is particularly pronounced in the field of steels, since they compete with light alloys and composite materials in many applications. The improvement of steels’ mechanical properties is sought to be achieved with the formation of exceptionally fine microstructures ranging well into the nanoscale, which enable a substantial increase in strength without being detrimental to toughness. The preferred route by which such a structure can be produced is not by applying the external plastic deformation, but by controlling the phase transformation from austenite into ferrite at low temperatures. The formation of bainite in steels at temperatures lower than about 200 °C enables the obtainment of the bulk nanostructured materials purely by heat treatment. This offers the advantages of high productivity, as well as few constraints in regard to the shape and size of the workpiece when compared with other methods for the production of nanostructured metals. The development of novel bainitic steels was based on high Si or high Al alloys. These groups of steels distinguish a very fine microstructure, comprised predominantly of bainitic ferrite plates, and a small fraction of retained austenite, as well as carbides. The very fine structure, within which the thickness of individual bainitic ferrite plates can be as thin as 5 nm, is obtained purely by quenching and natural ageing, without the use of isothermal transformation, which is characteristic for most bainitic steels. By virtue of their fine structure and low retained austenite content, this group of steels can develop a very high hardness of up to 65 HRC, while retaining a considerable level of impact toughness. The mechanical properties were evaluated by hardness measurements, impact testing of notched and unnotched specimens, as well as compression and tensile tests. Additionally, the steels’ microstructures were characterised using light microscopy, field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM). The obtained results confirmed that the strong refinement of the microstructural elements in the steels results in a combination of extremely high strength and very good toughness. Full article

(This article belongs to the Special Issue Advances in Ultrasonic Spray Pyrolysis Processing of Materials)

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10 pages, 2898 KiB

Open AccessArticle

New Proposal for Size and Size-Distribution Evaluation of Nanoparticles Synthesized via Ultrasonic Spray Pyrolysis Using Search Algorithm Based on Image-Processing Technique

by Elif Emil Kaya, Ozan Kaya, Gözde Alkan, Sebahattin Gürmen, Srecko Stopic and Bernd Friedrich

Materials 2020, 13(1), 38; https://doi.org/10.3390/ma13010038 - 20 Dec 2019

Cited by 25 | Viewed by 2924

Abstract

Nanoparticle properties are correlated to their size, size distribution, and shape; it is essential to accurately measure these features in the field of nanoscience. In this study, silver nanoparticles (AgNPs) were synthesized with the ultrasonic-spray-pyrolysis (USP) method from a water solution of silver nitrate. The synthesized AgNPs were characterized by Dynamic Light Scattering (DLS) analysis and Scanning Electron Microscopy (SEM) to reveal their size and size distribution. A search algorithm based on an image-processing technique to obtain particle size and particle-size distribution from SEM micrographs is proposed. In order to obtain more quantitative information and data with respect to the morphology of particles synthesized under different process parameters, SEM micrographs with a nonhomogeneous background contrast were examined via image-processing techniques in MATLAB. Due to the inhomogeneous contrast of SEM micrographs, defining an overall threshold value was insufficient in the detection of whole nanoparticles. Thus, subimages were directly created according to the maximum and minimum particle size specified by the user to determine local threshold values. The obtained results were automatically combined to represent both particle dimension and location in the SEM micrographs. We confirmed that the results of our DLS analysis, theoretical calculation, and image-processing technique were correlated with our expected results. Full article

(This article belongs to the Special Issue Advances in Ultrasonic Spray Pyrolysis Processing of Materials)

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15 pages, 2517 KiB

Open AccessArticle

The Effect of Stabilisation Agents on the Immunomodulatory Properties of Gold Nanoparticles Obtained by Ultrasonic Spray Pyrolysis

by Marina Bekić, Sergej Tomić, Rebeka Rudolf, Marijana Milanović, Dragana Vučević, Ivan Anžel and Miodrag Čolić

Materials 2019, 12(24), 4121; https://doi.org/10.3390/ma12244121 - 09 Dec 2019

Cited by 9 | Viewed by 2307

Abstract

Gold nanoparticles (GNPs) have been investigated extensively as drug carriers in tumour immunotherapy in combination with photothermal therapy. For this purpose, GNPs should be stabilised in biological fluids. The goal of this study was to examine how stabilisation agents influence cytotoxicity and immune response in vitro. Spherical GNPs, 20 nm in size, were prepared by ultrasonic spray pyrolysis (USP). Three types of stabilising agents were used: sodium citrate (SC), polyvinyl-pyrrolidone (PVP), and poly-ethylene glycol (PEG). Pristine, non-stabilised GNPs were used as a control. The culture models were mouse L929 cells, B16F10 melanoma cells and human peripheral blood mononuclear cells (PBMNCs), obtained from healthy donors. Control SC- and PEG-GNPs were non-cytotoxic at concentrations (range 1–100 µg/mL), in contrast to PVP-GNPs, which were cytotoxic at higher concentrations. Control GNPs inhibited the production of IFN-ϒ slightly, and augmented the production of IL-10 by PHA-stimulated PBMNC cultures. PEG-GNPs inhibited the production of pro-inflammatory cytokines (IL-1, IL-6, IL-8, TNF-α) and Th1-related cytokines (IFN-ϒ and IL-12p70), and increased the production of Th2 cytokines (IL-4 and IL-5). SC-PEG inhibited the production of IL-8 and IL-17A. In contrast, PVP-GNPs stimulated the production of pro-inflammatory cytokines, Th1 cytokines, and IL-17A, but also IL-10. When uptake of GNPs by monocytes/macrophages in PBMNC cultures was analysed, the ingestion of PEG- GNPs was significantly lower compared to SC- and PVP-GNPs. In conclusion, stabilisation agents modulate biocompatibility and immune response significantly, so their adequate choice for preparation of GNPs is an important factor when considering the use of GNPs for application in vivo. Full article

(This article belongs to the Special Issue Advances in Ultrasonic Spray Pyrolysis Processing of Materials)

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17 pages, 3314 KiB

Open AccessArticle

Synthesis of Colloidal Au Nanoparticles through Ultrasonic Spray Pyrolysis and Their Use in the Preparation of Polyacrylate-AuNPs’ Composites

by Doris Golub, Andrej Ivanič, Peter Majerič, Hanuma Reddy Tiyyagura, Ivan Anžel and Rebeka Rudolf

Materials 2019, 12(22), 3775; https://doi.org/10.3390/ma12223775 - 17 Nov 2019

Cited by 16 | Viewed by 2867

Abstract

Colloidal gold nanoparticles (AuNPs) were prepared from two different liquid precursors (gold (III) acetate and gold (III) chloride), using the Ultrasonic Spray Pyrolysis (USP) process. The STEM characterisation showed that the AuNPs from gold chloride are spherical, with average diameters of 57.2 and 69.4 nm, while the AuNPs from gold acetate are ellipsoidal, with average diameters of 84.2 and 134.3 nm, according to Dynamic Light Scattering (DLS) measurements. UV/VIS spectroscopy revealed the maximum absorbance band of AuNPs between 532 and 560 nm, which indicates a stable state. Colloidal AuNPs were used as starting material and were mixed together with acrylic acid (AA) and acrylamide (Am) for the free radical polymerization of polyacrylate-AuNPs’ composites, with the purpose of using them for temporary cavity fillings in the dental industry. SEM characterisation of polyacrylate-AuNPs’ composites revealed a uniform distribution of AuNPs through the polymer matrix, revealing that the AuNPs remained stable during the polymerization process. The density measurements revealed that colloidal AuNPs increase the densities of the prepared polyacrylate-AuNPs’ composites; the densities were increased up to 40% in comparison with the densities of the control samples. A compressive test showed that polyacrylate-AuNPs’ composites exhibited lower compressive strength compared to the control samples, while their toughness increased. At 50% compression deformation some of the samples fracture, suggesting that incorporation of colloidal AuNPs do not improve their compressive strength, but increase their toughness significantly. This increased toughness is the measured property which makes prepared polyacrylate-AuNPs potentially useful in dentistry. Full article

(This article belongs to the Special Issue Advances in Ultrasonic Spray Pyrolysis Processing of Materials)

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10 pages, 11365 KiB

Open AccessArticle

Morphology of Composite Fe@Au Submicron Particles, Produced with Ultrasonic Spray Pyrolysis and Potential for Synthesis of Fe@Au Core–Shell Particles

by Peter Majerič, Darja Feizpour, Bernd Friedrich, Žiga Jelen, Ivan Anžel and Rebeka Rudolf

Materials 2019, 12(20), 3326; https://doi.org/10.3390/ma12203326 - 12 Oct 2019

Cited by 6 | Viewed by 2127

Abstract

Iron core–gold shell (Fe@Au) nanoparticles are prominent for their magnetic and optical properties, which are especially beneficial for biomedical uses. Some experiments were carried out to produce Fe@Au particles with a one-step synthesis method, Ultrasonic Spray Pyrolysis (USP), which is able to produce the particles in a continuous process. The Fe@Au particles were produced with USP from a precursor solution with dissolved Iron (III) chloride and Gold (III) chloride, with Fe/Au concentration ratios ranging from 0.1 to 4. The resulting products are larger Fe oxide particles (mostly maghemite Fe₂O₃), with mean sizes of about 260–390 nm, decorated with Au nanoparticles (AuNPs) with mean sizes of around 24–67 nm. The Fe oxide core particles are mostly spherical in all of the experiments, while the AuNPs become increasingly irregular and more heavily agglomerated with lower Fe/Au concentration ratios in the precursor solution. The resulting particle morphology from these experiments is caused by surface chemistry and particle to solvent interactions during particle formation inside the USP system. Full article

(This article belongs to the Special Issue Advances in Ultrasonic Spray Pyrolysis Processing of Materials)

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Review

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28 pages, 7694 KiB

Open AccessReview

Advances in Ultrasonic Spray Pyrolysis Processing of Noble Metal Nanoparticles—Review

by Peter Majerič and Rebeka Rudolf

Materials 2020, 13(16), 3485; https://doi.org/10.3390/ma13163485 - 07 Aug 2020

Cited by 43 | Viewed by 4711

Abstract

In the field of synthesis and processing of noble metal nanoparticles, the study of the bottom-up method, called Ultrasonic Spray Pyrolysis (USP), is becoming increasingly important. This review analyses briefly the features of USP, to underline the physical, chemical and technological characteristics for producing nanoparticles and nanoparticle composites with Au and Ag. The main aim is to understand USP parameters, which are responsible for nanoparticle formation. There are two nanoparticle formation mechanisms in USP: Droplet-To-Particle (DTP) and Gas-To-Particle (GTP). This review shows how the USP process is able to produce Au, Ag/TiO₂, Au/TiO₂, Au/Fe₂O₃ and Ag/(Y_0.95 Eu_0.05)₂O₃ nanoparticles, and presents the mechanisms of formation for a particular type of nanoparticle. Namely, the presented Au and Ag nanoparticles are intended for use in nanomedicine, sensing applications, electrochemical devices and catalysis, in order to benefit from their properties, which cannot be achieved with identical bulk materials. The development of new noble metal nanoparticles with USP is a constant goal in Nanotechnology, with the objective to obtain increasingly predictable final properties of nanoparticles. Full article

(This article belongs to the Special Issue Advances in Ultrasonic Spray Pyrolysis Processing of Materials)

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