Solid-state Processing Method Research Articles

Effect of nano-TiO2 particles addition on dissimilar AA2024 and AA2014 based composite developed by friction stir process technique

Aluminum composite materials have gained immense popularity in the construction and aerospace industries as these materials are lightweight, durable, and exhibit a high strength-to-weight ratio. The present study aims to develop dissimilar AA2024 and AA2014-based composite materials using nano-TiO2 reinforcement particles via Friction Stir Processing (FSP) techniques. The FSP technique is a solid-state processing method that is used to modify the properties of metal alloys without altering their chemical composition. The samples were prepared by placing a nano-TiO2over AA2024 and AA2014 aluminum alloys sheet and subjected to FSP process parameters. The microstructure, hardness, and tensile properties of the composite samples were assessed using scanning electron microscopy (SEM), Vickers hardness tester, and tensile testing machine respectively. The results showed that the FSP technique led to the formation of a homogeneous and fine-grained microstructure in the composite samples. The nano-TiO2 reinforcement also provided additional strengthening to the AA2024 and AA2014 aluminum alloys matrix resulting in improved hardness and tensile properties of the composites. The resulting composites exhibited enhanced wear resistance properties. The FSP method presented in this study has implications for extending the properties of other metal alloys, opening up new avenues for research in the field of materials science.

Electrodeposited NiFeCo-(Mo,W) high-entropy alloys with nanocrystalline and amorphous structures

High-entropy alloy (HEA) design is an emerging methodology that stabilizes nanocrystalline materials, which themselves are highly sought after due to their high strength and hardness resulting from grain boundary hardening. In the past decade, studies have examined the synthesis and performance of such materials made primarily from vapour- and solid-state processing methods, which offer little flexibility in scalability. By contrast, electrodeposition is a relatively low-cost, highly scalable fabrication route for nanocrystalline materials that can be applied to almost any substrate shape or material, which also has industrial-scale infrastructure already in place. Here, we report the first comprehensive study on the synthesis and characterization of electrodeposited HEAs made from aqueous electrolytes, building on the groundwork of past work on electrodeposited medium-entropy alloys. High-quality alloys of NiFeCo-W, NiFeCo-Mo, and NiFeCo-MoW were deposited onto Cu substrates at thicknesses in the range 31–44 µm. W-containing alloys took on banded structures with underlaying growth-oriented features that are postulated to be nanoglass domains. NiFeCo-Mo exhibited the highest hardness-to-density ratio among these alloys, owing to its laminated nanocrystalline-amorphous structure. We also revealed an inverse Hall-Petch relationship in NiFeCo-W, as well as a linear dependence of hardness on Ni content in the alloys. Our study continues to build a framework for electrodeposition of HEAs, paving the way for developing new high-strength, thermally stable, and scalable nanostructured materials.

Polylactic Acid Chemical Foaming Assisted by Solid-State Processing: Solid-State Shear Pulverization and Cryogenic Milling.

A chemical foaming process of polylactic acid (PLA) was developed via the solid-state processing methods of solid-state shear pulverization (SSSP) and cryogenic milling. Based on the ability of solid-state processing to enhance the crystallization kinetics of PLA, chemical foaming agents (CFA) are first compounded before foaming via compression molding. Specifically, the effects of the pre-foaming solid-state processing method and CFA concentration were investigated. Density reduction, mechanical properties, thermal behavior, and cell density of PLA foams are characterized. Solid-state processing of PLA before foaming greatly increases the extent of PLA foaming by achieving void fractions approximately twice that of the control foams. PLA's improved ability to crystallize is displayed through both dynamic mechanical analysis and differential scanning calorimetry. The solid-state-processed foams display superior mechanical robustness and undergo low stress relaxation. The cell density of the PLA foams also increases with solid-state processing, especially through SSSP. Additionally, crosslinking of PLA during the pre-foaming processing step is found to result in the greatest enhancement of crystallization but decreased void fraction and foam effectiveness. Overall, SSSP and cryogenic milling show significant promise in improving chemical foaming in alternative biopolymers.

Characterization in the icosahedral phase of the system Al63Cu25Fe12

The present work aimed to characterize the microstructure of the icosahedral phase (ɸ-quasicrystalline phase) of the system with stoichiometric composition of the quasicrystal Al63Cu25Fe12. The ternary alloy with nominal composition of Al63Cu25Fe12 was processed by Mechanical Alloying (MA) as a viable solid state processing method for producing various metastable and stable quasicrystalline phases. The structural characterization of the obtained samples was performed by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM), while the elemental composition of the chemical elements Al, Fe and Cu were determined by the technique of X-ray spectroscopy by dispersive energy (EDS). According to the results of XRD, the diffraction patterns of Al63Cu25Fe12 showed the presence of β-Al (Fe, Cu) and λ-Al13Fe4 phases coexist with the thermodynamic ɸ-phase quasicrystalline. Finally, elemental analysis indicates that during alloy synthesis there is little variation of the ideal composition. The results indicate that alloys with high percentage of icosahedral phase can be obtained by casting in the air.

Structural and mechanical properties of a novel Al-Al2O3-WS2 hybrid composites

A solid-state processing method has been adopted to fabricate an advanced aluminum-based hybrid composite with two-dimensional WS2 reinforcement. The structural and mechanical properties of the newly developed Al-based hybrid composites were evaluated. The density of the hybrid composites increases from 2.73 g/cm3 to 2.86 g/cm3 and the average hardness from 33.3 ± 1.359 HV to 52.2 ± 0.729 HV with an increase in WS2 wt% in the matrix phase. The effect of WS2 reinforcement on structural and mechanical properties was discussed to optimize the composition of the developed hybrid composite.

ICOSAHEDRAL PHASE OF Al65Cu25Fe15

The present work aimed to characterize the microstructure of the icosahedral phase (quasicrystalline phase-ϕ) of the system with stoichiometric composition of the quasicrystal Al65Cu25Fe15 . The ternary alloy with nominal composition of Al63Cu25Fe12 was processed by mechanical alloying (MA) as a viable solid state processing method for producing various metastable and stable quasicrystalline phases. The structural characterization of the obtained samples was performed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), while the elemental composition was determined by dispersive energy spectroscopy (DES). The diffraction patterns of Al65Cu25Fe15 showed the presence of ω-Al7Cu2Fe , β-Al(Fe, Cu) and λ-Al13Fe4 phases that coexist with the thermodynamic quasicrystalline phase-ϕ. Finally, elemental analysis indicates that during alloy synthesis there is little variation of the ideal composition. The results indicate that alloys with high percentage of icosahedral phase can be obtained by casting in the air.

Influence of Boron Carbide Addition on Particle Size of Copper Zinc Alloys Synthesized by Powder Metallurgy

Material systems with the combination of metals and non-metals forming an alloy systems has numerous advantages when compared with the monolithic materials. Synthesizing such materials systems can easily be done by many solid state processing methods. Copper Zinc (Cu-Zn) forms a ductile material system finding its applications in various conductive and tribological applications. Nano composites finds lot more applications due to the high specific area occupied by the particles. Focus of the current project is on the study of influence of Boron Carbide (B4C) powders addition into the Cu-Zn matrix while synthesizing them through high energy ball milling. B4C powders are added to the matrix at 10 % by volume. Particle size of the powder are determined by Scherer and Williamson-Hall synthesis methods after characterizing the milled powders by X-Ray diffraction (XRD). As the B4C powders are brittle, maximum volume fraction of these powders are expected to influence particle size of Cu-Zn alloy powders. Powder morphology is analysed by scanning electron microscopy (SEM). Influence of B4C powder particles upon grain size of Cu-Zn alloy powder blends was very minimum due to the tendency of particles to get saturated with respect to particle size after repeated milling.

Fabrication of a novel hydroxyapatite/polyether ether ketone surface nanocomposite via friction stir processing for orthopedic and dental applications.

There is increasing interest in the use of polyether ether ketone (PEEK) for orthopedic and dental implant applications due to its elastic modulus (close to that of bone), biocompatibility and radiolucent properties. However, PEEK is still categorized as bioinert owing to its low integration with surrounding tissues. Methods such as depositing hydroxyapatite (HA) onto the PEEK surface could increase its bioactivity. However, depositing HA without damaging the PEEK substrate is still required further investigation. Friction stir processing is a solid-state processing method that is widely used for composite substrate fabrication. In this study, a pinless tool was used to fabricate a HA/PEEK surface nanocomposite for orthopedic and dental applications. Microscopical images of the modified substrate confirmed homogenous distribution of the HA on the surface of the PEEK. The resultant HA/PEEK surface nanocomposites demonstrated improved surface hydrophilicity coupled with better apatite formation capacity (as shown in the simulated body fluid) in comparison to the pristine PEEK, making the newly developed material more suitable for biomedical application. This surface deposition method that is carried out at low temperature would not damage the PEEK substrate and thus could be a good alternative for existing commercial methods for PEEK surface modification.

THE ICOSAHEDRAL PHASE OF Al63Cu25Fe12 SYSTEM

The present work aimed to characterize the microstructure of the icosahedral phase (quasicrystalline phase-ϕ) of the system with stoichiometric composition of the quasicrystal Al63Cu25Fe12. The ternary alloy with nominal composition of Al63Cu25Fe12 was processed by mechanical alloying (MA) as a viable solid state processing method for producing various metastable and stable quasicrystalline phases. The structural characterization of the obtained samples was performed by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM), while the elemental composition of the chemical elements Al, Fe and Cu were determined by X-ray spectroscopy technique of dispersive energy (EDS). According to the results of XRD, the diffraction patterns of Al63Cu25Fe12 showed the presence of β-Al(Fe, Cu) and λ-Al13Fe4 phases coexist with the thermodynamic ϕ-phase quasicrystalline. Finally, elemental analysis indicates that during alloy synthesis there is little variation of the ideal composition. The results indicate that alloys with high percentage of icosahedral phase can be obtained by casting in the air.

Correlating Directly Recycled Cathode Performance to Aging Conditions

Traditional recycling of lithium-ion battery cathode materials draws the most attention currently due to the valuable metal elements contained, especially cobalt. There are three dominate recycling approaches that may be used to recover useful materials from the aged cathode powders: pyrometallurgical, hydrometallurgical and direct physical.(1-3) The former two methods are already operating at scale. However, they suffer from significant energy input and complex chemical process respectively, which makes the recycled products less environmental-friendly and economically competitive. Recently, processing methods have been developed with less energy and cost input by making directly recycling the cathode material for reuse in a new battery. This is appealing in cases where there is a large amount of identical or very similar cathode materials in use. (2, 4) In this work, we show “direct recycled” products of differently cycled Li(NixCoyAlz)O2 cathode via a solid-state processing method with different parameters. We assess the materials product performance in terms of electrochemical specific capacity, phase purity and consistency. Furthermore, we correlated interaction among aged conditions of cathode, solid-state process parameters and recycled product performance. Figure 1 shows that when treated with the same solid-state process parameters, the recycled cathode materials show different electrochemical performance depending on conditions of the aged cathode materials. In this talk, we will discuss our approach and results, as well as suggest a technical path forward for the implementation of large-scale direct recycling of cathode materials from aged lithium-ion batteries. Reference: L. Gaines, Sustain Mater Techno, 17 (2018).H. Wang, S. Frisco, E. Gottlieb, R. Yuan and J. F. Whitacre, J Power Sources, 426, 67 (2019).R. E. Ciez and J. F. Whitacre, Nat Sustain, 2, 148 (2019).H. Wang and J. F. Whitacre, Energy Technol-Ger, 6, 2429 (2018). Figure 1

Characterization in the Icosahedral Phase of Al63Cu25Fe12 System

The present work aimed to characterize the microstructure of the icosahedral phase (quasicrystalline phase-ϕ) of the system with stoichiometric composition of the quasicrystal Al 63 Cu 25 Fe 12 . The ternary alloy with nominal composition of Al 63 Cu 25 Fe 12 was processed by mechanical alloying (MA) as a viable solid state processing method for producing various metastable and stable quasicrystalline phases. The structural characterization of the obtained samples was performed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), while the elemental composition was determined by dispersive energy spectroscopy (DES). The diffraction patterns of Al 63 Cu 25 Fe 12 showed the presence of quasicrystalline phase-ϕ, ω-Al 7 Cu 2 Fe, β-Al(Fe, Cu) and λ-Al 13 Fe 4 phases that coexist with the thermodynamic quasicrystalline phase-ϕ. In icosahedral phase oxidation of aluminum forms a dense layer on the passivating outer most surface of the quasicrystal which causes depletion in both copper and iron. It was observed not only the presence of alumina, γ-Al 2 O 3 , but also the formation of hematite and copper oxide in the dense layer. Finally, elemental analysis indicates that during alloy synthesis there is little variation of the ideal composition. The results indicate that alloys with high percentage of icosahedral phase can be obtained by casting in the air. DOI: http://dx.doi.org/10.17807/orbital.v11i3.1381

Quasicrystalline Phase Formation of the Al67Cu26Fe15 Alloy

O presente trabalho teve como objetivo caracterizar a microestrutura da fase icosaedral (f-fase quasicristalina) do sistema com composição estequiométrica do quasicristal Al67Cu26Fe15. A liga ternária com composição nominal de Al67Cu26Fe15 foi processada por Moagem Mecânica de Alta Energia, como um método viável de processamento no estado sólido para a produção de várias fases quasicristalinas metaestáveis e estáveis. A caracterização estrutural das amostras obtidas foi realizada por difração de raios-X (DRX) e Microscopia Eletrônica de Varredura (MEV), enquanto a composição elementar dos elementos químicos Al, Fe e Cu foram determinados pela técnica de Espectroscopia de raios X por energia dispersiva (EDS). Na superfície da liga quasicristalina, podemos observar no SEM a presença da alumina g-Al2O3, que contribui para as propriedades texturais de suporte catalítico deviso a sua atividade catalítica, visando maior desempenho em reações de oxidação do metanol. De acordo com os resultados de XRD, os padrões de difração da liga Al67Cu26Fe15 mostraram a presença das fases w-Al7Cu2Fe, b-Al(Fe;Cu) e l-Al13Fe4 coexistem com a f-fase quasicristalina em regime termodinâmico. Finalmente, a análise elementar indica que durante a síntese da liga existe pequena variação da composição ideal. Os resultados indicam que ligas com alto percentual de fase icosaedral podem ser obtidas por fundição ao ar.

Recycling Potential for Finely Divided Ferrous Metallic Scrap Using Powder Technology

Enormous amount of scrap is generated on the shopfloor during manufacturing. Energy needed to melt increasing quantities of scrap will be ever increasing, and so will be the loss of metal during melting. Hence, conversion of scrap directly into marketable products by solid state processing methods is economical due to a lower energy requirement and a greater yield compared to the melting route. This makes the process more environmentally friendly. However, not all materials can be recycled in a solid state, with equal ease. One therefore needs to quantitatively assess the recyclability of a given kind of scrap. In the present work, a procedure to assess the recyclability of finely divided ferrous metallic scrap generated on the shopfloor is demonstrated. Recyclability includes material and the process used for recycling. For instance, a given material might be more recyclable using one process compared to the other. In the present study, the potential of powder technology (powder metallurgy (PM) and metal injection molding (MIM) based processes are compared for solid-state conversion of scrap directly into usable products. Grinding sludge collected in the shopfloor was pulverized and used as raw material. Properties of sintered parts were found to be significantly better due to in-situ reduction and densification during sintering. A quantitative measure of recyclability, namely, the Recyclability Index (RI) was defined to compare the manufacturability of different products. Recycled ferrous parts manufactured by PM route are found to have a greater RI (superior recyclability) than those manufactured by the MIM route. Complex reduction and sintering mechanisms in MIM parts, particularly, the kinetics of diffusion and volumetric shrinkage, limit suitability of MIM for recycling. In contrast, few industrial parts were developed and manufactured by conventional PM based approach to demonstrate the suitability of this novel recycling process especially for manufacture of porous parts.

Electrochemical Performance of LixMn2-YFeyO4-ZClz Synthesized through in Situ Glycine Nitrate Combustion

Background: Lithium manganese oxide spinel is a potential candidate for lithium-ion battery cathodes due to its 3D network of lithium pathways within the structure, low toxicity, reasonable capacity, and low cost. However, this spinel suffers from capacity fading due to fracturing of the structure either through the Jahn-Teller distortion, alternative phase formation via non-stoichiometry, or loss of crystallinity. Historically, cycle life enhancements have been achieved through stabilization of the spinel structure via transition metal doping on the B-site of the lattice. Iron as a dopant is of interest due partly to its low toxicity but primarily its low cost. By adding the redox couple of this transition metal, this spinel can satisfy higher voltage (5.0 V) applications should compatible electrolytes be produced. While B-site doping has proven effective, this effort proposes to observe if cycle life can be even further enhanced in LixMn2-yFeyO4 (LMFO) by also substituting anion dopants. Previously our group has incorporated chlorine and fluorine into the base LiMn2O4 material using solid state processing methods and demonstrated cyclability to 32 cycles as a result of weakening the Li-O bond for easier extraction from the lattice. Others have also added chlorine and more commonly fluorine and demonstrated performance enhancements. However rather than incorporating the halide into the lattice, most studies focus on surface modification of the spinel. The present study intends to look more into the cycle life benefits of the less-studied chlorine incorporation into the bulk of an iron-doped spinel via in situ combustion synthesis of the material. Experimental: A glycine nitrate combustion method was used to synthesize iron doped chlorinated lithium manganese oxide spinel (LMFO-Cl). Stoichiometric amounts of Li(NO­3­), Mn(NO­3)2∙4H2O, FeCl3, and NH2CH2COOH (glycine, Alfa Aesar) in a 1:1 metal to glycine ratio were dissolved into the aqueous solution. The solution was heated to evaporate the water and form a gel, which was heated further to 250 °C when auto ignition occurs. The resultant ash was fired at 600 °C for two to six hours to achieve the desired phase. Material characterization was performed using X-ray diffraction, X-ray fluorescence, BET surface area analysis, thermogravimetric analysis, and scanning electron microscopy. Cathode materials were mixed with carbon black and Teflon in a ratio of 85:10:5 of active to carbon to Teflon binder and calendared to 0.04 cm, punched into disks and pressed onto aluminum mesh opposite a Li metal anode. 2025 button cells were filled with 1 molar LiPF6 in a proportional mixture of diethyl carbonate, dimethyl carbonate, and ethylene carbonate. Electrochemical characterization was performed using electrochemical impedance spectroscopy (Solartron 1260) and cycling on an ARBIN MSTAT4 battery cycler system. Results and Conclusion: A nanoscale LixMn2-yFeyO4-zClz material was synthesized in three different compositions of y and z and desirable phase and morphological properties were achieved. The x-ray diffraction pattern indicated no presence of impurities while the x-ray fluorescence showed maintenance of the chlorine within the material after calcination. BET surface area analysis determined the surface area to be 8.48 m2/g with a highly desirable large pore size for ion transfer (14nm). The material was demonstrated to repeatedly achieve minimal capacity loss with short term cycling in all compositions and yielded 98% of the original discharge capacity at the 250th cycle for the case where y = 0.195 and z = 0.028. Figure 1 shows the cycling behavior out to 250 cycles demonstrating the capacity retention of this composition, LixMn1.805Fe0.195O3.972Cl0.028. Discharging below the 4.1 V plateau to 2.25 V did not immediately impact the cells as the reaction was reversible for all three compositions synthesized in this study. The primary limitations for these experimental cells were the inadequacy of the electrolyte preventing access to the higher voltage plateau at 5.0 V where more capacity could be achieved. Differential capacity curves across the 300 cycles (not shown here) demonstrate typical electrolyte degradation behavior. However the cathode chemistry appears to withstand advanced cycling and further work with electrolyte improvements could emphasize the extent of its performance capabilities. Figure 1

Cycle Life Analysis of LiMn2O4-DCld Made Via in Situ Combustion Synthesis and Reduced-Time Solid State Processing

Lithium manganese oxide spinels exhibit promising electrochemical performance and good thermodynamic and kinetic stability when used as a cathode in lithium and lithium-ion electrochemical systems. This can be attributed to its inherent three-dimensional structure that allows lithium ions to easily flow in and out of the lattice. A common disadvantage of this chemistry is its limited cyclability as a result of the energy barriers for removing lithium from the octahedral sites. Additionally, the dissolution of manganese ions into the electrolyte causes both capacity fading and cycle life degradation in an electrochemical system. CERDEC has previously demonstrated enhanced electrochemical performance at both low and high voltage ranges, with the reversible region occurring between 2.0 V to 4.75 V. This material incorporates chlorine into the lithium manganese spinel structure using a reduced-time solid state processing method, where the material is calcined in air at 600 °C for 2 hours. This method drastically reduces the processing time and calcining temperature in comparison to the traditional hydrothermal fabrication method or the standard solid state method for lithiated manganese spinels. The general formula for the halogenated lithium manganese spinel material is LixMn2O4-dXd, where x ≈ 1 and d ranges from 0.005 to 0.3. This work focuses on further evaluating the cycle life performance of electrochemical cells utilizing this LiMn2O4-dCldcathode material in the high voltage operating range. Additionally, an alternative processing method is analyzed for halogenated lithium manganese spinel, where the material is made via in situ combustion synthesis in order to further promote lithium deinsertion from octahedral sites. Incorporating chlorine into the lithium manganese spinel structure further stabilizes the lattice to prevent manganese dissolution into the electrolyte when utilized in an electrochemical cell. The alternative processing method involves using a glycine nitrate combustion process, where the ash is collected and calcined in air at 600 °C for 2 hours. Material analysis was performed using X-ray diffraction, X-ray fluorescence, thermogravimetric analysis, BET surface area analysis, and scanning electron microscopy to evaluate and verify the composition and structure of the chlorinated spinel material, as well as its particle morphology. This alternative processing method allows for a more uniform structure in the desired spinel phase with higher surface area. Electrochemical coin cells were fabricated utilizing LiMn2O4-dCld against a lithium anode, where the cathode material was synthesized using both processing methods. Test cells were cycled between 3.5 V and 4.75 V at 0.5-1 mA/cm2 to determine cycle life capability and capacity degradation processes. A comparative performance evaluation was also performed by incorporating undoped cathode material into electrochemical coin cells and conducting galvanostatic testing under the same test regime. A cycle life graph is shown displaying the capacity retention of electrochemical coin cells incorporating an undoped lithium manganese spinel, LiMn2O4-dCld synthesized using a glycine nitrate combustion process (GNP), and LiMn2O4-dCld synthesized using the reduced time solid state process (RTP). These cells were cycled between 3.5 V and 4.75 V at 0.5 mA/cm2. The data shows increased capacity retention, above 95% at 130 cycles, using the alternative processing method, GNP. Additionally, a clear degradation and recovery of capacity of the undoped lithium manganese spinel cell is shown, which is attributed to the cell being cycled at a voltage range that is higher than optimal. Figure 1

Different strategies of secondary phase incorporation into metallic sheets by friction stir processing in developing surface composites

Friction stir processing (FSP) is a solid-state processing method, which recently gained wide popularity to modify the microstructure of metallic surfaces and to produce surface composites. For the past decade, composites of different materials such as aluminum, copper, magnesium, titanium, and their alloys were successfully produced by FSP. The amount of secondary phase that is dispersed at the surface of the workpiece during FSP and the level of dispersion depend on many factors such as tool design, processing parameters, and type of material. Recently, the method of secondary phase incorporation into the surface metals was also considered as an important factor in developing surface composites by FSP. A few strategies such as groove filling, holes filling, sandwich method, direct method, and surface coating followed by FSP methods have been developed as promising ways of secondary phase incorporation into the surface of the materials during FSP. The aim of this review paper is to give a comprehensive summary of different methods developed to disperse the secondary phase into the surface of the workpiece during FSP to produce surface composites. The strategies have been explained, compared, and discussed to suggest an appropriate method based on the requirement to adopt in developing surface composites.

Microwave Synthesis and Sintering Methods for Reversible Solid Oxide Fuel Cell Fabrication

The primary focus of our work has been on the development of a stable mixed ionic and electronic conducting (MIEC) oxide electrode that is catalytic for application as an air electrode in reversible solid oxide fuel cells (RSOFCs). For this purpose, our recently developed La0.3Sr0.7Fe0.7Cr0.3O3-δ (LSFCr) material [1], shown to be active as both an anode and cathode material in symmetrical SOFCs, has been modified by replacing the Sr in the A site with Ca, producing La0.3Ca0.7Fe0.7Cr0.3O3- δ (LCFCr), which has been shown to be a very promising oxygen and fuel electrode for reversible SOFCs [2-4]. In the present work, we are working towards a solid oxide fuel cell/electrolysis cell that is fabricated entirely with the use of MW techniques, starting with the synthesis of the electrode/electrolyte powders and including the sintering of the full cell. We have already demonstrated that the LCFCr material can be produced from the precursor salts by microwave (MW) methods, showing that the pure phase can be obtained at a much lower synthesis temperature (300 oC) and that the synthesis time can be cut down by ca. 50% as compared to conventional solid-state processing methods [5]. Another outcome is that there is a significant increase in its surface area (10.4 m2 g-1) vs. what is obtained using standard methods, i.e., 0.89 m2 g-1 ) [5].More recently, we have developed an effective method for the MW co-sintering of the anode-electrolyte-cathode combination in one simple step. This approach, in which sintering temperatures as high as 1000 oC can be achieved in just a few minutes, would have a significant impact on both lowering material and cell manufacturing costs and on further enhancing the performance of these cells. In this work, the LCFCr perovskite powders were first formed using MW methods and were then screen-printed on both sides of a gadolinia-doped ceria (GDC) electrolyte, followed by MW-assisted sintering of the cell. It is worth noting that there were no MW susceptors added in any of the fabrication steps and the normal pre-sintering steps used in conventional furnaces were also not needed. We show that these LCFCr/GDC/LCFCr cells, sintered using only MW methods, gave performances that were very similar to cells fabricated using normal ceramic processing methods. However, the time required to achieve this was decreased by ca. ten times, thus translating to significant savings in manufacturing costs.

Quantitative phase separation in multiferroic Bi0.88Sm0.12FeO3 ceramics via piezoresponse force microscopy

BiFeO3 (BFO) is a classical multiferroic material with both ferroelectric and magnetic ordering at room temperature. Doping of this material with rare-earth oxides was found to be an efficient way to enhance the otherwise low piezoelectric response of unmodified BFO ceramics. In this work, we studied two types of bulk Sm-modified BFO ceramics with compositions close to the morphotropic phase boundary (MPB) prepared by different solid-state processing methods. In both samples, coexistence of polar R3c and antipolar Pbam phases was detected by conventional X-ray diffraction (XRD); the non-polar Pnma or Pbnm phase also has potential to be present due to the compositional proximity to the polar-to-non-polar phase boundary. Two approaches to separate the phases based on the piezoresponse force microscopy measurements have been proposed. The obtained fractions of the polar and non-polar/anti-polar phases were close to those determined by quantitative XRD analysis. The results thus reveal a useful method for quantitative determination of the phase composition in multi-phase ceramic systems, including the technologically most important MPB systems.

Aluminium Metal Matrix Composite – An Insight into Solid State and Liquid State Processes

Aluminium metal matrix composites (AMMCs) are being considered as a group of superior material for its lightness, strength, high specific modulus, low coefficient of thermal expansion and good wear resistance properties. Solid state and liquid state processing methods are used to fabricate AMMCs. Achieving a uniform distribution of reinforcement within the matrix is one such challenge, which affects directly on the properties and quality of composite material. Powder metallurgy route, one of the solid state processing methods can be effectively used to get uniform dispersion of reinforcements with aluminium metal matrix. This paper presents the summary of the ball milling and stir casting processes to fabricate the AMMCs and its applications. Major issues like ball milling time, dispersion of reinforcements, grain size, the stirring time and speed are discussed. Also the effect of different reinforcement for AMMCs on the mechanical properties is discussed in detail.

High Performance Na-Ion Batteries Based on Novel O3 Layered Oxide Cathode Materials

Sodium-ion (Na-ion) batteries represent an attractive alternative to their lithium-ion counterparts, and are expected to offer some significant commercial advantages such as lower active material costs and improved safety characteristics [1,2]. In these systems Na-based layered oxides, NaxMO2(M = transition metal) have emerged recently as high performance and low cost cathode materials [3,4]. These oxide materials may be categorized into three main structural types using the classification proposed by Delmas and co-workers – i.e. O3, P2 and P3 types, where the alkali ions occupy either octahedral (O) or prismatic sites (P), respectively [5].In this study single-phase O3-NaaNi(1-x-y-z)MnxMgyTixO2 materials have been prepared using conventional solid-state processing methods. In these as-made compositions nickel and magnesium are included as M2+ while manganese and titanium are present as M4+. Special attention was given to the product composition, precursor mixing and synthesis conditions to ensure no unwanted NiO impurity content. Figure 1 shows the XRD pattern for a typical O3-Na layered oxide composition and confirms that the material is essentially phase pure.The electrochemical performance of the experimental O3-NaaNi(1-x-y-z)MnxMgyTixO2 phases was evaluated in full Na-ion test cells where the cathode materials were capacity balanced to a commercial hard carbon anode material. The electrolyte used was 0.5 M NaClO4 in propylene carbonate and testing was carried out at 30 oC.In Figure 2 we depict the low rate (C/10) voltage profile derived from a typical constant current charge-discharge cycle. The cathode active material cycles reversibly at a specific capacity of 163 mAh/g and the Na-ion cell generates an average discharge voltage of around 3.0 V. The specific energy performance for the cathode is comparable to commercial Li-ion electrode materials.Figure 3 shows a typical cycle life plot for a representative Na-ion cell. These data were collected at a C/10 charge/discharge rate using voltage limits of 4.2 and 1.0 V. Following 300 cycles the cell has retained over 70 % of the original discharge capacity. Most of this capacity loss is recoverable at lower discharge rates indicating importantly that the fade mechanism is associated with cell impedance changes rather than irreversible loss of active Na. Further performance data for the Na-ion system will be presented.