Pulse Plasma Sintering of NiAl-Al2O3 Composite Powder Produced by Mechanical Alloying with Contribution of Nanometric Al2O3 Powder

NiAl-Al₂O₃ composites, fabricated from the prepared composite powders by mechanical alloying and then consolidated by pulse plasma sintering, were presented. The use of nanometric alumina powder for reinforcement of a synthetized intermetallic matrix was the innovative concept of this work. Moreover, this is the first reported attempt to use the Pulse Plasma Sintering (PPS) method to consolidate composite powder with the contribution of nanometric alumina powder. The composite powders consisting of the intermetallic phase NiAl and Al₂O₃ were prepared by mechanical alloying from powder mixtures containing Ni-50at.%Al with the contribution of 10 wt.% or 20 wt.% nanometric aluminum oxide. A nanocrystalline NiAl matrix was formed, with uniformly distributed Al₂O₃ inclusions as reinforcement. The PPS method successfully consolidated NiAl-Al₂O₃ composite powders with limited grain growth in the NiAl matrix. The appropriate sintering temperature for composite powder was selected based on analysis of the grain growth and hardness of Al₂O₃ subjected to PPS consolidation at various temperatures. As a result of these tests, sintering of the NiAl-Al₂O₃ powders was carried out at temperatures of 1200 °C, 1300 °C, and 1400 °C. The microstructure and properties of the initial powders, composite powders, and consolidated bulk composite materials were characterized by SEM, EDS, XRD, density, and hardness measurements. The hardness of the ultrafine-grained NiAl-Al₂O₃ composites obtained via PPS depends on the Al₂O₃ content in the composite, as well as the sintering temperature applied. The highest values of the hardness of the composites were obtained after sintering at the lowest temperature (1200 °C), reaching 7.2 ± 0.29 GPa and 8.4 ± 0.07 GPa for 10 wt.% Al₂O₃ and 20 wt.% Al₂O₃, respectively, and exceeding the hardness values reported in the literature. From a technological point of view, the possibility to use sintering temperatures as low as 1200 °C is crucial for the production of fully dense, ultrafine-grained composites with high hardness.     

Synthesis and Characterization of Fluorite-Type La2Ce2O7 Plasma Sprayable Powder for TBCs Application

This work focuses on the fabrication of lanthanum cerate (La₂Ce₂O₇, LC) powders via two chemical routes: modified Pechini sol-gel method and solid-state synthesis. The synthesized LC powders were heat treated in the temperature range of 1000–1400 °C for 6 h and investigated as a material for thermal barrier coating (TBC) applications. For this purpose, the powder morphology, chemical composition, crystal structure and thermal stability were studied. Scanning electron microscopy (SEM) of the synthesized powders revealed an agglomerated structure consisting of fine and uniformly distributed grains. Energy-dispersive X-ray spectroscopy (EDXS) indicated that the chemical compositions of the LC powders were similar to the stoichiometric ratio of La₂Ce₂O₇. A cubic fluorite structure was observed by X-ray diffraction analysis (XRD) after calcining the LC powder prepared by solid-state synthesis at 1300 °C. In contrast, there was always a fluorite structure in the LC powder synthesized by the Pechini sol-gel method after heat treatment over the entire temperature range. The thermal behavior of the LC powders was analyzed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TG) in the temperature range of 25–1300 °C. Neither an obvious mass change nor a visible energy change was observed within the tested temperature range, indicating high phase stability of the LC powder and its suitability for TBC applications. Spheroidization on the prepared LC powders was also investigated, revealing that powder size and morphology had a significant impact on the spheroidization efficiency.     

The Preparation of Dense Materials in the MgO–ZrO2 System by the Application of Nanometric Powders

Crystallization under hydrothermal conditions allowed us to prepare nanometric powders in the MgO–ZrO₂ system of different magnesia concentrations. Sintering runs of these powder compacts studied using dilatometry measurements during heating and cooling revealed essential differences in their behavior. The microstructure of the resulting polycrystal is strongly related to the magnesia content in the starting powder, which strongly influences the phase composition of the resulting material and its mechanical properties. It should be emphasized that the novel processing method of such materials differs from the usual applied technology and leads to magnesia–zirconia materials of a different microstructure than that of “classical” materials of this kind.     

Elaboration of Alumina-Zirconia Composites: Role of the Zirconia Content on the Microstructure and Mechanical Properties

Alumina-zirconia (AZ) composites are attractive structural materials, which combine the high hardness and Young’s modulus of the alumina matrix with additional toughening effects, due to the zirconia dispersion. In this study, AZ composites containing different amounts of zirconia (in the range 5–20 vol %) were prepared by a wet chemical method, consisting on the surface coating of alumina powders by mixing them with zirconium salt aqueous solutions. After spray-drying, powders were calcined at 600 °C for 1 h. Green bodies were then prepared by two methods: uniaxial pressing of spray-dried granules and slip casting of slurries, obtained by re-dispersing the spray dried granulates. After pressureless sintering at 1500 °C for 1 h, the slip cast samples gave rise to fully dense materials, characterized by a quite homogeneous distribution of ZrO₂ grains in the alumina matrix. The microstructure, phase composition, tetragonal to monoclinic transformation behavior and mechanical properties were investigated and are here discussed as a function of the ZrO₂ content. The material containing 10 vol % ZrO₂ presented a relevant hardness and exhibited the maximum value of K_I0, mainly imputable to the t → m transformation at the crack tip.     

Red Y2O3:Eu-Based Electroluminescent Device Prepared by Atomic Layer Deposition for Transparent Display Applications

Y₂O_3:Eu is a promising red-emitting phosphor owing to its high luminance efficiency, chemical stability, and non-toxicity. Although Y₂O₃:Eu thin films can be prepared by various deposition methods, most of them require high processing temperatures in order to obtain a crystalline structure. In this work, we report on the fabrication of red Y₂O₃:Eu thin film phosphors and multilayer structure Y₂O₃:Eu-based electroluminescent devices by atomic layer deposition at 300 °C. The structural and optical properties of the phosphor films were investigated using X-ray diffraction and photoluminescence measurements, respectively, whereas the performance of the fabricated device was evaluated using electroluminescence measurements. X-ray diffraction measurements show a polycrystalline structure of the films whereas photoluminescence shows emission above 570 nm. Red electroluminescent devices with a luminance up to 40 cd/m² at a driving frequency of 1 kHz and an efficiency of 0.28 Lm/W were achieved.     

Synthesis of Ni/Y2O3 Nanocomposite through USP and Lyophilisation for Possible Use as Coating

The Ni/Y₂O₃ catalyst showed high catalytic activity. Based on this, the aim of this study was to create Ni/Y₂O₃ nanocomposites powder with two innovative technologies, Ultrasonic Spray Pyrolysis (USP) and lyophilisation. In the USP process, thermal decomposition of the generated aerosols in an N₂/H₂ reduction atmosphere caused a complete decomposition of the nickel (II) nitrate to elemental Ni, which became trapped on the formed Y₂O₃ nanoparticles. The Ni/Y₂O₃ nanocomposite particles were captured via gas washing in an aqueous solution of polyvinylpyrrolidone (PVP) in collection bottles. PVP was chosen for its ability to stabilise nano-suspensions and as an effective cryoprotectant. Consequently, there was no loss or agglomeration of Ni/Y₂O₃ nanocomposite material during the lyophilisation process. The Ni/Y₂O₃ nanocomposite powder was analysed using ICP-MS, SEM-EDX, and XPS, which showed the impact of different precursor concentrations on the final Ni/Y₂O₃ nanocomposite particle composition. In a final step, highly concentrated Ni/Y₂O₃ nanocomposite ink (Ni/Y₂O₃ > 0.140 g/mL) and test coatings from this ink were prepared by applying them on a white matte photo paper sheet. The reflection curve of the prepared Ni/Y₂O₃ nanocomposite coating showed a local maximum at 440 nm with a value of 39% reflection. Given that Ni is located on the surface of the Ni/Y₂O₃ nanocomposite in the elemental state and according to the identified properties, tests of the catalytic properties of this coating will be performed in the future.     

Characterization of Al2O3 Matrix Composites Fabricated via the Slip Casting Method Using NiAl-Al2O3 Composite Powder

This work aimed to characterize Al₂O₃ matrix composites fabricated by the slip casting method using NiAl-Al₂O₃ composite powder as the initial powder. The composite powder, consisting of NiAl + 30 wt.% Al₂O₃, was obtained by mechanical alloying of Al₂O₃, Al, and Ni powders. The composite powder was added to the Al₂O₃ powder to prepare the final powder for the slip casting method. The stained composite samples presented high density. EDX and XRD analyses showed that the sintering process of the samples in an air atmosphere caused the formation of the NiAl₂O₄ spinel phase. Finally, the phase composition of the composites changed from the initial phases of Al₂O₃ and NiAl to Al₂O₃, Ni, and NiAl₂O₄. However, in the area of Ni, fine Al₂O₃ particles remaining from the initial composite powder were visible. It can be concluded that after slip casting, after starting with Al₂O₃ and the composite powder (NiAl-Al₂O₃) and upon sintering in air, ceramic matrix composites with Ni and NiAl₂O₄ phases, complex structures, high-quality sintered samples, and favorable mechanical properties were obtained.     

Characterization of Al2O3 Samples and NiAl–Al2O3 Composite Consolidated by Pulse Plasma Sintering

The paper describes an investigation of Al₂O₃ samples and NiAl–Al₂O₃ composites consolidated by pulse plasma sintering (PPS). In the experiment, several methods were used to determine the properties and microstructure of the raw Al₂O₃ powder, NiAl–Al₂O₃ powder after mechanical alloying, and samples obtained via the PPS. The microstructural investigation of the alumina and composite properties involves scanning electron microscopy (SEM) analysis and X-ray diffraction (XRD). The relative densities were investigated with helium pycnometer and Archimedes method measurements. Microhardness analysis with fracture toughness (K_IC) measures was applied to estimate the mechanical properties of the investigated materials. Using the PPS technique allows the production of bulk Al₂O₃ samples and intermetallic ceramic composites from the NiAl–Al₂O₃ system. To produce by PPS method the NiAl–Al₂O₃ bulk materials initially, the composite powder NiAl–Al₂O₃ was obtained by mechanical alloying. As initial powders, Ni, Al, and Al₂O₃ were used. After the PPS process, the final composite materials consist of two phases: Al₂O₃ located within the NiAl matrix. The intermetallic ceramic composites have relative densities: for composites with 10 wt.% Al₂O₃ 97.9% and samples containing 20 wt.% Al₂O₃ close to 100%. The hardness of both composites is equal to 5.8 GPa. Moreover, after PPS consolidation, NiAl–Al₂O₃ composites were characterized by high plasticity. The presented results are promising for the subsequent study of consolidation composite NiAl–Al₂O₃ powder with various initial contributions of ceramics (Al₂O₃) and a mixture of intermetallic–ceramic composite powders with the addition of ceramics to fabricate composites with complex microstructures and properties. In composites with complex microstructures that belong to the new class of composites, in particular, the synergistic effect of various mechanisms of improving the fracture toughness will be operated.     

Structural Features of Y2O2SO4 via DFT Calculations of Electronic and Vibrational Properties

The traditional way for determination of molecular groups structure in crystals is the X-Ray diffraction analysis and it is based on an estimation of the interatomic distances. Here, we report the analysis of structural units in Y₂O₂SO₄ using density functional theory calculations of electronic properties, lattice dynamics and experimental vibrational spectroscopy. The Y₂O₂SO₄ powder was successfully synthesized by decomposition of Y₂(SO₄)₃ at high temperature. According to the electronic band structure calculations, yttrium oxysulfate is a dielectric material. The difference between the oxygen–sulfur and oxygen–yttrium bond nature in Y₂O₂OS₄ was shown based on partial density of states calculations. Vibrational modes of sulfur ions and [Y₂O₂²⁺] chains were obtained theoretically and corresponding spectral lines observed in experimental Infrared and Raman spectra.     

Hydrothermal Aging of ATZ Composites Based on Zirconia Made of Powders with Different Yttria Content

The presented work concerns the development and investigation of three different grades of ZrO₂ materials containing Al₂O₃ particles (ATZ-Alumina Toughened Zirconia ceramics with 2.3–20 vol.% of alumina). The zirconia powders containing 3 mol.% of yttria were synthesized by a precipitation/calcination method and fabricated from two different zirconia powders with different yttria content. Then, the selected ATZ composites (ATZ-B, ATZ-10 and ATZ-20) were prepared by means of conventional mixing, compacting and sintering at 1450 °C for 1.5 h. The phase composition, microstructure, relative density and basic mechanical properties were determined. Uniform microstructures with relative densities over 99% of theoretical density, hardness values between 12.0–13.8 GPa, flexural strength up to 1 GPa and outstanding fracture toughness of 12.7 MPa⋅m^1/2 were obtained. The aging susceptibility of alumina toughened zirconia materials, as a consequence of hydrothermal treatment, was investigated. The aim of this study was to determine the influence of LTD (low temperature degradation) on the tetragonal to monoclinic phase transitions and on the flexural strength of hydrothermally aged specimens. The results were compared to those obtained for commercially available tetragonal zirconia-based materials containing 3 mol.% of yttria. This research shows that ATZ composites that have excellent mechanical properties and sufficient hydrothermal aging resistance can be attained and later used in technical and biomedical applications.     

Sol-Gel Synthesis and Antioxidant Properties of Yttrium Oxide Nanocrystallites Incorporating P-123

Yttrium oxide (Y₂O₃) nanocrystallites were synthesized by mean of a sol-gel method using two different precursors. Raw materials used were yttrium nitrate and yttrium chloride, in methanol. In order to promote oxygen vacancies, P-123 poloxamer was incorporated. Synthesized systems were heat-treated at temperatures from 700 °C to 900 °C. Systems at 900 °C were prepared in the presence and absence of P-123 using different molar ratios (P-123:Y = 1:1 and 2:1). Fourier transform infrared spectroscopy (FTIR) results revealed a characteristic absorption band of Y–O vibrations typical of Y₂O₃ matrix. The structural phase was analyzed by X-ray diffraction (XRD), showing the characteristic cubic phase in all systems. The diffraction peak that presented the major intensity corresponded to the sample prepared from yttrium chloride incorporating P-123 in a molar ratio of P-123:Y = 2:1 at 900 °C. Crystallites sizes were determined by Scherrer equation as between 21 nm and 32 nm. Antioxidant properties were estimated by 2,2-diphenyl-1-picrylhydrazyl (DPPH•) assays; the results are discussed.     

Preparation and Characterization of Cu and Ni on Alumina Supports and Their Use in the Synthesis of Low-Temperature Metal-Phthalocyanine Using a Parallel-Plate Reactor

Ni- and Cu/alumina powders were prepared and characterized by X-ray diffraction (XRD), scanning electronic microscope (SEM), and N₂ physisorption isotherms were also determined. The Ni/Al₂O₃ sample reveled agglomerated (1 μm) of nanoparticles of Ni (30–80 nm) however, NiO particles were also identified, probably for the low temperature during the H₂ reduction treatment (350 °C), the Cu/Al₂O₃ sample presented agglomerates (1–1.5 μm) of nanoparticles (70–150 nm), but only of pure copper. Both surface morphologies were different, but resulted in mesoporous material, with a higher specificity for the Ni sample. The surfaces were used in a new proposal for producing copper and nickel phthalocyanines using a parallel-plate reactor. Phthalonitrile was used and metallic particles were deposited on alumina in ethanol solution with CH₃ONa at low temperatures; ≤60 °C. The mass-transfer was evaluated in reaction testing with a recent three-resistance model. The kinetics were studied with a Langmuir-Hinshelwood model. The activation energy and Thiele modulus revealed a slow surface reaction. The nickel sample was the most active, influenced by the NiO morphology and phthalonitrile adsorption.     

Hydrothermal Synthesis of Nanocrystalline ZrO2-8Y2O3-xLn2O3 Powders (Ln = La,Gd, Nd,Sm): Crystalline Structure,Thermal and Dielectric Properties

Zirconium dioxide (ZrO₂) is one of the ceramic materials with high potential in many areas of modern technologies. ZrO₂ doped with 8 wt.% (~4.5 mol%) Y₂O₃ is a commercial powder used for obtaining stabilized zirconia materials (8 wt.% YSZ) with high temperature resistance and good ionic conductivity. During recent years it was reported the co-doping with multiple rare earth elements has a significant influence on the thermal, mechanical and ionic conductivity of zirconia, due complex grain size segregation and enhanced oxygen vacancies mobility. Different methods have been proposed to synthesize these materials. Here, we present the hydrothermal synthesis of 8 wt.% (~4.5 mol%) YSZ co-doped with 4, 6 and 8 wt.% La₂O₃, Nd₂O₃, Sm₂O₃ and Gd₂O₃ respectively. The crystalline phases formed during their thermal treatment in a large temperature range were analyzed by X-ray diffraction. The evolution of phase composition vs. thermal treatment temperatures shows as a major trend the formation at temperatures >1000 °C of a cubic solid solutions enriched in the rare earth oxide used for co-doping as major phase. The first results on the thermal conductivities and impedance measurements on sintered pellets obtained from powders co-doped with 8 wt.% Y and 6% Ln (Ln = La, Nd, Sm and Gd) and the corresponding activation energies are presented and discussed. The lowest thermal conductivity was obtained for La co-doped 8 wt.% YSZ while the lowest activation energy for ionic conduction for Gd co-doped 8 wt.% YSZ materials.     

Novel Microwave-Assisted Method of Y2Ti2O7 Powder Synthesis

In the paper, a novel technique for highly dispersed pyrochlore Y₂Ti₂O₇ is proposed. The experimental results proved that the application of microwave irradiation at a certain stage of calcination allowed synthesizing of Y₂Ti₂O₇ in much shorter time, which ensured substantial energy savings. An increase up to 98 wt.% in the content of the preferred phase with a pyrochlore-type structure Y₂Ti₂O₇ was obtained after 25 h of yttrium and titanium oxides calcination at a relatively low temperature of 1150 °C, while the microwave-supported process took only 9 h and provided 99 wt.% of pyrochlore. The proposed technology is suitable for industrial applications, enabling the fabrication of large industrial amounts of pyrochlore without solvent chemistry and high-energy mills. It reduced the cost of both equipment and energy and made the process more environmentally friendly. The particle size and morphology did not change significantly; therefore, the microwave-assisted method can fully replace the traditional one.     

The Effect of Yttria Content on Microstructure,Strength, and Fracture Behavior of Yttria-Stabilized Zirconia

Yttria-stabilized zirconia (YSZ) is well-known as a material with perfect mechanical, thermal, and electrical properties. It is used for manufacturing various high-temperature components for aerospace and energy generation, as well as wear- and corrosion-resistant devices in medicine. This work investigated the effect of a Y₂O₃ addition to ZrO₂ on the microstructure and mechanical properties of YSZ ceramics produced by one sintering schedule. ZrO₂ ceramics doped with 3, 4, 5, 6, 7, and 8 mol% Y₂O₃ (designated 3YSZ through to 8YSZ) were prepared by using conventional sintering at 1550 °C for 2 h in argon. The effect of yttria content was analyzed with respect to grain size, morphology of the microstructural features, phase composition, parameters of fracture surface, and flexural strength. The 7YSZ ceramics sintered at 1550 °C for 2 h showed the highest level of flexural strength due to the formation of the fine-grained microstructure containing mainly the monoclinic and tetragonal zirconia phases. The fracture micromechanism in the studied YSZ ceramics is discussed.     

Structural,Electromagnetic and Microwave Properties of Magnetite Extracted from Mill Scale Waste via Conventional Ball Milling and Mechanical Alloying Techniques

This study presents the utilization of mill scale waste, which has attracted much attention due to its high content of magnetite (Fe₃O₄). This work focuses on the extraction of Fe₃O₄ from mill scale waste via magnetic separation, and ball milling was used to fabricate a microwave absorber. The extracted magnetic powder was ground-milled using two different techniques: (i) a conventional milling technique (CM) and (ii) mechanical alloying (MM) process. The Fe₃O₄/CM samples were prepared by a conventional milling process using steel pot ball milling, while the Fe₃O₄/MM samples were prepared using a high-energy ball milling (HEBM) method. The effect of milling time on the structural, phase composition, and electromagnetic properties were examined using X-ray diffraction (XRD) and a vector network analyzer (VNA). XRD confirmed the formation of magnetite after both the magnetic separation and milling processes. The results revealed that Fe₃O₄ exhibited excellent microwave absorption properties because of the synergistic characteristics of its dielectric and magnetic loss. The results showed that the Fe₃O₄/CM particle powder had a greater absorption power (reflection loss: <−10 dB) with 99.9% absorption, a minimum reflection loss of −30.83 dB, and an effective bandwidth of 2.30 GHz for 2 mm thick samples. The results revealed the Fe₃O₄/MM powders had higher absorption properties, including a higher RL of −20.59 dB and a broader bandwidth of 2.43 GHz at a matching thickness of only 1 mm. The higher microwave absorption performance was attributed to the better impedance matching property caused by the porous microstructure. Furthermore, the magnetite, Fe₃O₄ showed superior microwave absorption characteristics because of the lower value of permittivity, which resulted in better impedance matching. This study presents a low-cost approach method by reutilizing mill scale waste to fabricate a high purity crystalline Fe₃O₄ with the best potential for designing magnetic nano-sized based microwave absorbers.     

Microstructural and Optical Properties of MgAl2O4 Spinel: Effects of Mechanical Activation,Y2O3 and Graphene Additions

Magnesium aluminate and other alumina-based spinels attract attention due to their high hardness, high mechanical strength, and low dielectric constant. MgAl₂O₄ was produced by a solid-state reaction between MgO and α-Al₂O₃ powders. Mechanical activation for 30 min in a planetary ball mill was used to increase the reactivity of powders. Yttrium oxide and graphene were added to prevent abnormal grain growth during sintering. Samples were sintered by hot pressing under vacuum at 1450 °C. Phase composition and microstructure of sintered specimens were characterized by X-ray powder diffraction and scanning electron microscopy. Rietveld analysis revealed 100% pure spinel phase in all sintered specimens, and a decrease in crystallite size with the addition of yttria or graphene. Density measurements indicated that the mechanically activated specimen reached 99.6% relative density. Furthermore, the highest solar absorbance and highest spectral selectivity as a function of temperature were detected for the mechanically activated specimen with graphene addition. Mechanical activation is an efficient method to improve densification of MgAl₂O₄ prepared from mixed oxide powders, while additives improve microstructure and optical properties.     

Chemical Vapour Deposition of Scandia-Stabilised Zirconia Layers on Tubular Substrates at Low Temperatures

The paper presents results of investigation on synthesis of non-porous ZrO₂-Sc₂O₂ layers on tubular substrates by MOCVD (metalorganic chemical vapor deposition) method using Sc(tmhd)₃ (Tris(2,2,6,6-tetramethyl-3,5-heptanedionato)scandium(III), 99%) and Zr(tmhd)₄ (Tetrakis(2,2,6,6-tetramethyl-3,5-heptanedionato)zirconium)(IV), 99.9+%) as basic reactants. The molar content of Sc(tmhd)₃ in the gas mixture was as follows: 14, 28%. The synthesis temperature was in the range of 600–700 °C. The value of extended Gr_x/Re_x² expression (Gr-Grashof number, Re-Reynolds number and x-the distance from the gas inflow point) was less than 0.01. The layers were deposited under reduced pressure or close to atmospheric pressure. The layers obtained were tested using scanning electron microscope (SEM) with an energy dispersive X-ray spectroscope (EDS) microanalyzer, X-ray diffractometer and UV-Vis spectrophotometer. The layers deposited were non-porous, amorphous or nanocrystalline with controlled chemical composition. The layers synthesized at 700 °C were nanocrystalline. ZrO₂-Sc₂O₃ layers with 14 mol.% Sc₂O₃ content had a rhombohedral structure.     

Microstructure Evolution and Properties of an In-Situ Nano-Gd2O3/Cu Composite by Powder Metallurgy

Gadolinia (Gd₂O₃) is potentially attractive as a dispersive phase for copper matrix composites due to its excellent thermodynamic stability. In this paper, a series of 1.5 vol% nano-Gd₂O₃/Cu composites were prepared via an internal oxidation method followed by powder metallurgy in the temperature range of 1123–1223 K with a holding time of 5–60 min. The effects of processing parameters on the microstructure and properties of the composites were analyzed. The results showed that the tensile strength and conductivity of the nano-Gd₂O₃/Cu composite have a strong link with the microporosity and grain size, while the microstructure of the composite was determined by the sintering temperature and holding time. The optimal sintering temperature and holding time for the composite were 1173 K and 30 min, respectively, under which a maximum ultimate tensile strength of 317 MPa was obtained, and the conductivity was 96.8% IACS. Transmission electron microscopy observations indicated that nano-Gd₂O₃ particles with a mean size of 76 nm formed a semi-coherent interface with the copper matrix. In the nano-Gd₂O₃/Cu composite, grain-boundary strengthening, Orowan strengthening, thermal mismatch strengthening, and load transfer strengthening mechanisms occurred simultaneously.     

Quasi-Continuous Network Structure Greatly Improved the Anti-Arc-Erosion Capability of Ag/Y2O3 Electrical Contacts

Ag/Y₂O₃ has excellent potential to replace Ag/CdO as the environmentally friendly electrical contact material. Using spherical Y₂O₃ as the starting material, Ag/Y₂O₃ contacts with a quasi-continuous network structure were successfully fabricated by a low-energy ball milling treatment. The mean size of Y₂O₃ used ranged from 243 to 980 nm. Due to the differences in the size of Y₂O₃, Ag/Y₂O₃ contacts had different primitive microstructures, thereby exhibiting distinctive anti-arc-erosion capabilities. Ag/Y₂O₃ contact prepared using 243 nm Y₂O₃ showed the best anti-arc-erosion capability and the most outstanding electrical performance measures, such as low contact resistance, less mass transfer, and no failure up to 10⁵ cycle times. The quasi-continuous network structure formed in the micro-scale was responsible for the excellent electrical performance. The short distance between Y₂O₃ particles in the network promoted the cathode arc motion, and thus alleviated the localized erosion. The results obtained herein may inspire further attempts to design electrical contacts rationally.