Research

13 pages, 36127 KiB

Open AccessArticle

Formation of Bimetallic Fe/Au Submicron Particles with Ultrasonic Spray Pyrolysis

by Peter Majerič, Darja Jenko, Bernd Friedrich and Rebeka Rudolf

Metals 2018, 8(4), 278; https://doi.org/10.3390/met8040278 - 18 Apr 2018

Cited by 11 | Viewed by 4354

This article studies the synthesis of bimetallic Fe/Au submicron particles with Ultrasonic Spray Pyrolysis (USP). The combination of Fe oxide particles’ ferromagnetism with Au nanoparticles’ (AuNPs) surface plasmon resonance has gained high interest in biomedical and various other applications. Initial investigations for producing [...] Read more.

This article studies the synthesis of bimetallic Fe/Au submicron particles with Ultrasonic Spray Pyrolysis (USP). The combination of Fe oxide particles’ ferromagnetism with Au nanoparticles’ (AuNPs) surface plasmon resonance has gained high interest in biomedical and various other applications. Initial investigations for producing Fe/Au particles with USP were carried out in order to study the particle formation mechanisms. Firstly, three precursor salt solutions (Fe acetate, Fe nitrate and Fe chloride) were used to produce Fe oxide particles and to study their effect on particle morphology through characterization by Scanning and Transmission Electron Microscopy (SEM and TEM) with Energy Dispersive X-ray spectroscopy (EDX). These precursor salts produce three types of submicron particles, a mesh of primary nanoparticles, spherical particles and irregular particles, respectively. Next, different solution combinations of precursor salts of Fe and Au were used with the USP. The obtained particles were characterized, and similarities were then examined in the particle formation of pure Fe oxide and Fe/Au particles. The effects of using different salts were analyzed for the formation of favorable morphologies of Fe/Au particles. The combinations of Fe chloride/Au chloride and Fe chloride/Au nitrate in the precursor solution indicate potential in synthesizing bimetallic Fe/Au submicron particles with the USP process. Full article

(This article belongs to the Special Issue Powder Synthesis and Processing)

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12 pages, 18170 KiB

Open AccessArticle

Internal Friction Angle of Metal Powders

by Jiri Zegzulka, Daniel Gelnar, Lucie Jezerska, Alvaro Ramirez-Gomez, Jan Necas and Jiri Rozbroj

Metals 2018, 8(4), 255; https://doi.org/10.3390/met8040255 - 10 Apr 2018

Cited by 18 | Viewed by 7737

Abstract

Metal powders are components with multidisciplinary usage as their application is very broad. Their consistent characterization across all disciplines is important for ensuring repeatable and trouble-free processes. Ten metal powders were tested in the study. In all cases, the particle size distribution and [...] Read more.

Metal powders are components with multidisciplinary usage as their application is very broad. Their consistent characterization across all disciplines is important for ensuring repeatable and trouble-free processes. Ten metal powders were tested in the study. In all cases, the particle size distribution and morphology (scanning electron microscope—SEM photos) were determined. The aim of this work was to inspect the flow behavior of metal powders through another measured characteristic, namely the angle of internal friction. The measured values of the effective internal friction angle in the range 28.6–32.9°, together with the spherical particle shape and the particle size distribution, revealed the likely dominant mode of the metal particle transfer mechanism for stainless steel 316L, zinc and aluminum powder. This third piston flow mechanism is described and illustrated in detail. The angle of internal friction is mentioned as another suitable parameter for the characterization of metal powders, not only for the relative simplicity of the determination but also for gaining insight into the method of the movement of individual particles during the flow. Full article

(This article belongs to the Special Issue Powder Synthesis and Processing)

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13 pages, 5687 KiB

Open AccessArticle

Effects of Porosity on Mechanical Properties and Corrosion Resistances of PM-Fabricated Porous Ti-10Mo Alloy

by Wei Xu, Xin Lu, Bing Zhang, Chengcheng Liu, Shaomin Lv, Shidi Yang and Xuanhui Qu

Metals 2018, 8(3), 188; https://doi.org/10.3390/met8030188 - 15 Mar 2018

Cited by 47 | Viewed by 7393

Abstract

Porous binary Ti-10Mo alloys were prepared using non-spherical titanium, molybdenum powders by the powder metallurgy (PM) space holder technique. Based on the three-dimensional analysis of porosity characteristics, a detailed assessment of the effects of porosity on mechanical properties and corrosion resistances in phosphate-buffered [...] Read more.

Porous binary Ti-10Mo alloys were prepared using non-spherical titanium, molybdenum powders by the powder metallurgy (PM) space holder technique. Based on the three-dimensional analysis of porosity characteristics, a detailed assessment of the effects of porosity on mechanical properties and corrosion resistances in phosphate-buffered saline (PBS) was carried out. For comparison, PM-fabricated CP-Ti with 50.5% porosity sintered at 1200 °C for 2 h and dense Ti-10Mo alloy sintered at 1450 °C for 2 h (relative density is 97.2% and porosity is 2.8%) were studied simultaneously. The results show that with the space-holder volume contents rising from 63 to 79%, the open porosity and average pore size (d₅₀) increase remarkably, while the pore size distribution (d₁₀–d₉₀) tends to be stable at about 100 μm. The average pore sizes (d₅₀) of porous Ti-10Mo alloy can be controlled in the range of 70–380 μm. The PM-fabricated porous Ti-10Mo alloy can achieve a wide range of mechanical properties, with yield compression strength of 248.2–76.9 MPa, and elastic modulus of 6.4–1.7 GPa. In addition, the yield compression strength and the elastic modulus meet the linear regression and exponential formula, respectively. With the porosity of Ti-10Mo alloy increasing from 2.8 to 66.9%, the corrosion rate rises exponentially from 1.6 g/m²·day to 17.1 g/m²·day. In comparison to CP Ti with nearly the same porosity, Ti-10Mo alloy shows significantly higher corrosion resistance. As a result, the relationships between porosity and mechanical properties, corrosion resistances of Ti-10Mo alloys were established, which can be used as a design reference in material selection for orthopedic applications. Full article

(This article belongs to the Special Issue Powder Synthesis and Processing)

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14 pages, 16668 KiB

Open AccessArticle

Metal Injection Moulding of High Nb-Containing TiAl Alloy and Its Oxidation Behaviour at 900 °C

by Chengcheng Liu, Xin Lu, Fei Yang, Wei Xu, Zhe Wang and Xuanhui Qu

Metals 2018, 8(3), 163; https://doi.org/10.3390/met8030163 - 07 Mar 2018

Cited by 6 | Viewed by 4085

Abstract

High Nb-containing TiAl alloy with a nominal composition of Ti-45Al-8.5Nb-0.2W-0.2B-0.02Y (at %) was fabricated by metal injection moulding (MIM) technology with an improved wax-based binder. The critical powder loading and feedstock rheological behaviour were determined. The influence of sintering temperature on microstructures and [...] Read more.

High Nb-containing TiAl alloy with a nominal composition of Ti-45Al-8.5Nb-0.2W-0.2B-0.02Y (at %) was fabricated by metal injection moulding (MIM) technology with an improved wax-based binder. The critical powder loading and feedstock rheological behaviour were determined. The influence of sintering temperature on microstructures and mechanical properties of the sintered samples and their oxidation behaviour were also investigated. Results showed that a feedstock, with a powder loading of 68 vol % and good flowability, could be obtained by using the improved binder, and oxygen pick-up was lower than that of the sample prepared by using a traditional binder. The ultimate tensile strength (UTS) and plastic elongation of the sample sintered at 1480 °C for 2 h were 412 MPa and 0.33%, at room temperature, respectively. The 1480 °C-sintered sample consisted of γ/α₂ lamellar microstructure with the average colony size of about 70 µm, and its porosity was about 4%. The sintered alloy showed better oxidation resistance than that of the cast alloy counterpart. Full article

(This article belongs to the Special Issue Powder Synthesis and Processing)

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5976 KiB

Open AccessArticle

The Effect of Rolling Temperature on the Microstructure and Mechanical Properties of Surface-Densified Powder Metallurgy Fe-Based Gears Prepared by the Surface Rolling Process

by Di Chen, Dekai Li, Jingguang Peng, Taolei Wang, Biao Yan and Wei Lu

Metals 2017, 7(10), 420; https://doi.org/10.3390/met7100420 - 10 Oct 2017

Cited by 4 | Viewed by 4276

Abstract

In this investigation, the surface-rolling process was performed to improve the performance of PM (powder metallurgy) parts. Different rolling temperatures were applied and the effect of rolling temperature on the microstructure and mechanical properties of the surface dense layers in the samples were [...] Read more.

In this investigation, the surface-rolling process was performed to improve the performance of PM (powder metallurgy) parts. Different rolling temperatures were applied and the effect of rolling temperature on the microstructure and mechanical properties of the surface dense layers in the samples were investigated. In the study, room temperature and temperatures of 100 °C, 200 °C, 300 °C were studied during the rolling process. The results confirmed that the sample prepared with a pre-heated temperature of 200 °C had the lowest porosity at the surface area. It also exhibited the highest surface hardness and wear resistance. The optimum rolling temperature was determined to be 200 °C and the related mechanism was discussed. Full article

(This article belongs to the Special Issue Powder Synthesis and Processing)

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21707 KiB

Open AccessArticle

Tensile Properties and Fracture Behavior of a Powder-Thixoformed 2024Al/SiC_p Composite at Elevated Temperatures

by Pubo Li and Tijun Chen

Metals 2017, 7(10), 408; https://doi.org/10.3390/met7100408 - 01 Oct 2017

Cited by 7 | Viewed by 3929

Abstract

In the present work, the tensile properties and fracture behavior of a 2024Al composite reinforced with 10 vol % SiC_p and fabricated via powder thixoforming (PT) were studied at temperatures ranging from 25 °C to 300 °C with a strain rate of [...] Read more.

In the present work, the tensile properties and fracture behavior of a 2024Al composite reinforced with 10 vol % SiC_p and fabricated via powder thixoforming (PT) were studied at temperatures ranging from 25 °C to 300 °C with a strain rate of 0.05 s⁻¹, as well as the PT 2024 alloy. The results indicated that the tensile strengths of both the PT materials were all decreased with increasing the temperature, but the decrease rate of the composite was smaller than that of the 2024 alloy, and the composite exhibited higher tensile strength than that of the 2024 alloy at all of the employed testing temperatures due to the strengthening role of SiC_p. Increasing temperature was beneficial for enhancing the ductility of materials, and the maximum elongation was reached at 250 °C. The elongation decrease over 250 °C was attributed to the cavity formation due to the debonding of the SiC_p/Al interface and the fracturing of the matrix between SiC_p. The fracture of the composite at room temperature initiated from the fracture of SiC_p and the debonding of the SiC_p/Al interface, but that at high temperatures was dominated by void nucleation and growth in the matrix besides the interface debonding. Full article

(This article belongs to the Special Issue Powder Synthesis and Processing)

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4957 KiB

Open AccessArticle

Structure and Formation Model of Ag/TiO₂ and Au/TiO₂ Nanoparticles Synthesized through Ultrasonic Spray Pyrolysis

by Gözde Alkan, Rebeka Rudolf, Jelena Bogovic, Darja Jenko and Bernd Friedrich

Metals 2017, 7(10), 389; https://doi.org/10.3390/met7100389 - 25 Sep 2017

Cited by 18 | Viewed by 4946

Abstract

This article explains the mechanism of the metal/oxide core-shell Ag/TiO₂ and Au/TiO₂ nanoparticle formation via one-step ultrasonic spray pyrolysis (USP) by establishing a new model. The general knowledge on the standard “droplet-to-particle” (DTP) mechanism, nucleation, and growth processes of noble metals, [...] Read more.

This article explains the mechanism of the metal/oxide core-shell Ag/TiO₂ and Au/TiO₂ nanoparticle formation via one-step ultrasonic spray pyrolysis (USP) by establishing a new model. The general knowledge on the standard “droplet-to-particle” (DTP) mechanism, nucleation, and growth processes of noble metals, as well as physical and chemical properties of core and shell materials and experimental knowledge, were utilized with the purpose of the construction of this new model. This hypothesis was assessed on silver (Ag)/titanium oxide (TiO₂) and gold (Au) TiO₂ binary complex nanoparticles’ experimental findings revealed by scanning electron microscopy (SEM), focused ion beam (FIB), high-resolution transmission electron microscopy (HRTEM), and simulation of crystal lattices. It was seen that two mechanisms run as proposed in the new model. However, there were some variations in size, morphology, and distribution of Ag and Au through the TiO₂ core particle and these variations could be explained by the inherent physical and chemical property differences of Ag and Au. Full article

(This article belongs to the Special Issue Powder Synthesis and Processing)

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4107 KiB

Open AccessFeature PaperArticle

The Fabrication of All-Solid-State Lithium-Ion Batteries via Spark Plasma Sintering

by Xialu Wei, Jack Rechtin and Eugene A. Olevsky

Metals 2017, 7(9), 372; https://doi.org/10.3390/met7090372 - 14 Sep 2017

Cited by 28 | Viewed by 6330

Abstract

Spark plasma sintering (SPS) has been successfully used to produce all-solid-state lithium-ion batteries (ASSLibs). Both regular and functionally graded electrodes are implemented into novel three-layer and five-layer battery designs together with solid-state composite electrolyte. The electrical capacities and the conductivities of the SPS-processed [...] Read more.

Spark plasma sintering (SPS) has been successfully used to produce all-solid-state lithium-ion batteries (ASSLibs). Both regular and functionally graded electrodes are implemented into novel three-layer and five-layer battery designs together with solid-state composite electrolyte. The electrical capacities and the conductivities of the SPS-processed ASSLibs are evaluated using the galvanostatic charge-discharge test. Experimental results have shown that, compared to the three-layer battery, the five-layer battery is able to improve energy and power densities. Scanning electron microscopy (SEM) is employed to examine the microstructures of the batteries especially at the electrode–electrolyte interfaces. It reveals that the functionally graded structure can eliminate the delamination effect at the electrode–electrolyte interface and, therefore, retains better performance. Full article

(This article belongs to the Special Issue Powder Synthesis and Processing)

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10364 KiB

Open AccessArticle

Influence of Powder Surface Contamination in the Ni-Based Superalloy Alloy718 Fabricated by Selective Laser Melting and Hot Isostatic Pressing

by Yen-Ling Kuo and Koji Kakehi

Metals 2017, 7(9), 367; https://doi.org/10.3390/met7090367 - 13 Sep 2017

Cited by 32 | Viewed by 6694

Abstract

The aim of this study was to gain a deep understanding of the microstructure-mechanical relationship between solid-state sintering and full-melting processes. The IN718 superalloy was fabricated by hot isostatic pressing (HIP) and selective laser melting (SLM). Continuous precipitates were clearly localized along the [...] Read more.

The aim of this study was to gain a deep understanding of the microstructure-mechanical relationship between solid-state sintering and full-melting processes. The IN718 superalloy was fabricated by hot isostatic pressing (HIP) and selective laser melting (SLM). Continuous precipitates were clearly localized along the prior particle boundary (PPB) in the HIP materials, while SLM materials showed a microstructure free of PPB. The mechanical properties of specimens that underwent SLM + solution treatment and aging were comparable to those of conventional wrought specimens both at room temperature and 650 °C. However, a drop was observed in the ductility of HIP material at 650 °C. The brittle particles along the PPB were found to affect the HIP materials’ creep life and ductility during solid-state sintering. Full article

(This article belongs to the Special Issue Powder Synthesis and Processing)

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