Initial Phase Composition Research Articles

Hydration kinetics of C3A: effect of lithium, copper and sulfur-based mineralizers

AbstractCalcium aluminate phases have a particular effect on the early heat release during setting initiation and have a substantial influence on the further workability of ordinary Portland cement. The nature of the calcium aluminate hydration products and its kinetics strongly depends on sulfate content and humidity. The effect of mineralisers on melt formation and viscosity is well described for calcium silicate systems, but information is still lacking for calcium aluminates. Therefore, the synergistic effect on the crystal structure and hydration mechanism of the tricalcium aluminate phase of the addition of mineralizers, i.e. Li2O, CuO, SO3 to the raw meal is here investigated. Co-doped calcium aluminate structures were formed during high-temperature treatment. Thermal analysis (TG–DTA and heating microscopy) was used to describe the ongoing high-temperature reaction. Resulting phase composition was dependent on the concentration of the mineralizer. While phase pure system was prepared with low mineralizer concentrations, with increasing mineralizer content the secondary phases were formed. Raman spectroscopy and XPS analysis were used to investigate the cation substitution and to help describe the cations bonding in co-doped calcium aluminate system. Prepared powders have been hydrated in a controlled manner at different temperatures (288, 298, 308 K). The resulting calorimetric data have been used to investigate the hydration kinetics and determine the rate constant of hydration reaction. First-order reaction (FOR) model was here applied for the activation energy and frequency factor calculations. The metastable and stable calcium aluminate hydrates were formed according to initial phase composition. In phase pure systems with low S content, the formation of stable and metastable hydrates was depended on the reaction temperature. Conversely, in systems with secondary phases and higher S content, the hydration mechanism resembled that which appears in calcium sulfoaluminates.

The nonlinear analysis of Portevin-Le Chatelier (PLC) effect: An application to medium Mn steel

The instability of plastic flow in medium manganese steel was investigated through uniaxial tensile tests conducted at room temperature across various strain rates. The Portvin-Le Chatelier (PLC) effect was analyzed using statistical methods and a multifractal approach. The findings indicate that the zigzag stress–strain curves associated with instability plastic flow exhibit typical multifractal characteristics. Furthermore, the multifractal analysis quantifies the influence of strain rate and initial phase composition on the instability characteristics of the stress–strain curves. Specifically, it was observed that lower strain rates and austenite content correspond to a chaotic state, whereas higher strain rates and austenite content result in self-organizing critical dynamics. Finally, the underlying physical mechanisms driving these differing modes of behavior are discussed, with a focus on their relationship to strain rate and the initial austenitic phase fraction.

Effect of initial phase composition on the phase composition, microstructure, and mechanical properties of Si3N4 ceramics

AbstractSilicon nitride (Si3N4) ceramics with initial β‐Si3N4 content from 3% to 88% were prepared by spark plasma sintering from 1450 to 1700°C. The effect of initial β‐Si3N4 content on the phase transition, microstructure evolution, and mechanical properties of the Si3N4 ceramics was studied. The existence of initial β‐Si3N4 accelerated the α–β phase transition. When the initial β‐Si3N4 content was 12% and 46%, the aspect ratio of the grains was increased. When the initial β‐Si3N4 content was 88%, the grains were mainly composed of short rod‐like grains. As the initial β‐Si3N4 content increased, the densification process was slowed down. The hardness and fracture toughness of samples reached about 18 GPa and 6 MPa·m1/2. It is proposed that the mechanical properties of samples are connected with the densification process and β‐Si3N4 content.

Combustion synthesis and consolidation of Ti(C,N)–Si3N4–SiC heterophase ceramic with YAG sintering additives

In this comprehensive study, we investigated the macrokinetics of the filtration combustion process of reactive Ti–Si–C mixtures in a nitrogen environment. It was observed that an increase in nitrogen pressure resulted in a rise in combustion temperature (150–600 °C) and combustion rate (2–8 times) due to the improved availability of nitrogen in the combustion front. Combustion yielded Ti(C,N)–Si3N4–SiC ceramic powders with polyhedral-shaped composite particles and a narrow particle size distribution. The hot pressing (HP) of as-synthesized ceramics significantly altered their phase composition due to Si3N4 dissociation. Introduced as a counter-measure, the YAG sintering additives (5–10 %) not only facilitated the preservation of the phase composition during HP but also considerably reduced the porosity of consolidated ceramics from 25-28 % to 0.6–4.8 %. The samples consolidated using the optimized conditions had a dense and uniform microstructure, retained their initial phase composition, and exhibited hardness values up to 13.4 GPa, flexural strength up to 397 MPa, and fracture toughness up to 5.3 MPa × m1/2.

Astrochemical models of interstellar ices: History matters

Context. Ice is ubiquitous in the interstellar medium. As soon as it becomes slightly opaque in the visible, it can be seen for visual extinctions (AV) above ~1.5. The James Webb Space Telescope (JWST) will observe the ice composition toward hundreds of lines of sight, covering a broad range of physical conditions in these extinct regions. Aims. We model the formation of the main constituents of interstellar ices, including H2O, CO2, CO, and CH3OH. We strive to understand what physical or chemical parameters influence the final composition of the ice and how they benchmark to what has already been observed, with the aim of applying these models to the preparation and analysis of JWST observations. Methods. We used the Nautilus gas-grain model, which computes the gas and ice composition as a function of time for a set of physical conditions, starting from an initial gas phase composition. All important processes (gas-phase reactions, gas-grain interactions, and grain surface processes) are included and solved with the rate equation approximation. Results. We first ran an astrochemical code for fixed conditions of temperature and density mapped in the cold core L429-C to benchmark the chemistry. One key parameter was revealed to be the dust temperature. When the dust temperature is higher than 12 K, CO2 will form efficiently at the expense of H2O, while at temperatures below 12 K, it will not form. Whatever hypothesis we assumed for the chemistry (within realistic conditions), the static simulations failed to reproduce the observed trends of interstellar ices in our target core. In a second step, we simulated the chemical evolution of parcels of gas undergoing different physical and chemical situations throughout the molecular cloud evolution and starting a few 107 yr prior to the core formation (dynamical simulations). We obtained a large sample of possible ice compositions. The ratio of the different ice components seems to be approximately constant for AV > 5, and in good agreement with the observations. Interestingly, we find that grain temperature and low AV conditions significantly affect the production of ice, especially for CO2, which shows the highest variability. Conclusions. Our dynamical simulations satisfactorily reproduce the main trends already observed for interstellar ices. Moreover, we predict that the apparent constant ratio of CO2/H2O observed to date is probably not true for regions of low AV, and that the history of the evolution of clouds plays an essential role, even prior to their formation.

Study on the deformation mechanism of Ti–10Mo–1Fe solid-solution alloys with different cooling rates

The phase composition before deformation is an important factor affecting the deformation mechanism of titanium alloy at room-temperature. In practical production, the initial phase composition can be greatly controlled by changing the solution cooling mode of the alloy, thus affecting the deformation mechanism and mechanical properties of the alloy to a certain extent. Therefore, the study of the effect of solution cooling rate on the deformation mechanism at room-temperature plays an important role in regulating the properties of the alloy. Through room-temperature compression experiments, the microstructure evolution and room-temperature plastic deformation mechanism of Ti–10Mo–1Fe near β-type alloys with different cooling rates after solution treatment at 870 °C were studied in this paper. The results show that the main room-temperature deformation mechanism of the Ti–10Mo–1Fe alloy under rapid cooling conditions (water-cooled) was the {332}<113> twins and stress-induced orthorhombic martensite α″ phase. In addition, a few {112}<111> twins were observed. The plastic deformation mechanism at room temperature under moderate cooling conditions (air-cooled) was primarily {332}<113> twins and dislocation slip. Small numbers of {112}<111> twins were also observed. Under slow cooling conditions (furnace cooling), no new phases are formed during the deformation process, and the plastic deformation mechanism at room temperature is dislocation slip.

Effect of Ti content and annealing on microstructure and mechanical performance of plasma sprayed Ti–Al–C based composite coatings

In the work, Ti–Al–C composite coatings have been produced by plasma spraying graphite @ Ti–Al agglomerates with different Ti content and then Ar-annealed at 800 °C. The microstructure change, phase formation mechanism and mechanical performance of the coatings have been studied. Results displayed that these coatings mainly consisted of (Ti, Al)C, TiC, a small amount of Ti2AlC/Ti3AlC2 and residual Al. These phases were alternatively arranged to form a lamellar structure. After annealing, the Ti2AlC/Ti3AlC2 phase increased with the consumption of (Ti, Al)C and residual Al. Owing to the difference of initial phase composition affected by Ti content, post-annealing generated (Ti, Al)C/TiC–Ti2AlC and (Ti, Al)C/TiC–Ti3AlC2 composite coatings inT2.5AC800 and T1.0AC800 coating, respectively. The laminated structure was hardly changed by annealing. The T2.5AC (970 HV) coating showed higher hardness than the T1.0AC coating (464 HV). After annealing, the hardness of the former coating increased while the latter coating decreased. Both of phase structure and uniformity determined the coating hardness.

Impact of the Initial Phase Composition of Alloys on the Effects Manifested by Yield Sites That Occur on Sheet Aluminum Alloys Subjected to Impact-Oscillatory Loading

The impact of the initial phase composition of alloys was evaluated, in particular, the content of Cu, Mn, and Mg in aluminum alloys D16ChATW, 2024-T351 and aluminum alloy T, which in its physical and mechanical characteristics is close to alloy 6013. The impact was evaluated on the effects manifested by yield sites that occur on aluminum alloys that were subject to the dynamic non-equilibrium processes (DNPs) at the expense of impact-oscillatory loading of different intensities under conditions of static tensioning, The one-time DNP, to which the investigated aluminum alloys were subjected at the pre-set levels of elastic strain followed by static tensioning, was found to cause yield sites formation. This is due to self-organization of the alloy structure, which contributes to alloy plasticization. The initial phase alloys composition impact on the yield sites, which occurs when impulse energy of a different intensity is applied to the alloys, was analyzed. The specimens from the aluminum alloys undergoing DNPs of the same level were compared. This made it possible to conclude that alloys D16ChATW and 2024-T351, which have a higher content of Cu, Mn, and Mg, have longer yield sites upon subsequent static tensioning. On the basis of the experimental results, in particular, physical studies, the authors derived a physical and mathematical model of the yield sites that appear after DNPs.

Working mechanism of calcium nitrate as an accelerator for Portland cement hydration

AbstractPrecast concrete, cold weather concreting, and the emerging technique of concrete additive manufacturing are applications in which the acceleration of cement hydration plays a critical role. To allow precise control of early cement hydration in these applications, a thorough understanding of the working mechanisms of cement hydration accelerators is required. This study contributes to the understanding of the mechanism by which calcium nitrate (Ca(NO3)2) influences early cement hydration. The influence of Ca(NO3)2 on the hydration of an ordinary Portland cement has been followed by isothermal calorimetry, in situ X‐ray diffraction (XRD), quantitative XRD, compressive strength testing, and the analysis of the pore solution composition. Further, the initial pore solution, the initial phase composition, and the phase composition in the fully hydrated cement have been estimated by thermodynamic calculations to corroborate the experimentally obtained results. The results indicate that Ca(NO3)2, especially at the highest analyzed dosage of 5 wt.%, enhances the formation of ettringite and a nitrate‐containing AFm phase. Furthermore, Ca(NO3)2 accelerates alite hydration. Besides the increased Ca concentration in solution, it has been found that a reduction of the Al concentration in the initial pore solution by Ca(NO3)2 possibly contributes to the accelerating effect of Ca(NO3)2 on alite hydration.

Influence of chemical composition and thermomechanical treatment of low-carbon steels on the microstructure and mechanical properties of their laser welded joints

The paper reports microstructures (revealed by transmission electron microscopy) in various zones of laser welds of the X70 and X80 low-carbon steels with different initial microstructures, as well as chemical and phase compositions. In the X70 steels with 0.13% C, the microstructure refinement has been achieved through helical rolling at temperatures of 920 °C and 850 °C (designated as X70-920 and X70-850, respectively). For all studied cases, both initial steel microstructures and phase compositions have determined the formation of different microstructures with various microhardness levels in the weld metal and heat-affected zones. For the X70-850 steel with a more dispersed and homogeneous microstructure (dF = 3.3 μm), a lower microhardness level of 340 HV has been observed in the weld metal, compared with the X70-920 one (dF = 5.5 μm, 370 HV). The reason has been the formation of both bainite and martensite laths in the X70-850 weld metal, while only lath and lamellar martensite has formed in the X70-920 one. For the X80 steel (0.55% C), lowering the carbon content and additional microalloying with chromium, molybdenum and nickel have enabled to decrease the microhardness level down to 295 HV in the weld metal due to the degenerate upper bainite formation and the carbon level reduction in martensite. The dispersed and homogeneous initial microstructures of the X70-850 and X80 steels has provided the formation of granular ferrite-bainite microstructures in the intercritical heat-affected zone. They have possessed a lower proportion of residual austenite regions and small sizes of twinned martensite areas. The welded X80 steel specimen has been characterized by higher ductile properties compared to both X70 ones.

Influence of cooling rate on ω phase precipitation and deformation mechanism of a novel metastable β titanium alloy

This work investigated the effect of cooling rate (water quenching and air cooling) on the precipitation of ω phase after solution treatment in β-phase region, and its effect on the mechanical properties in a novel metastable β titanium alloy (Ti–5Mo–3Cr–Fe–3Zr). The initial microstructures, phase composition and deformation-induced microstructures have been investigated using SEM, EBSD, XRD, and TEM. The phase composition of water-quenched alloy and air-cooled alloy are β, α", and ω phase. The size and volume fraction of ω phase of air-cooled alloy are larger than that of water-quenched alloy, resulting in an increase in tensile strength and a decrease in ductility. Deformation mechanisms of Ti–5Mo–3Cr–Fe–3Zr alloy with different cooling rate change from stress-induced ω phase transformation and dislocation slip to only dislocation slip. The stress-induced ω lamellas parallel to [1-11]β direction along the [0001]ω1 direction, which is formed by {112}β<111>β slip. Dislocations can cut through the encountered ω phase to form ω-free deformation bands, which accounts for the ductility.

Improved cytocompatibility and antibacterial properties of zinc-substituted brushite bone cement based on \u03b2-tricalcium phosphate

For bone replacement materials, osteoconductive, osteoinductive, and osteogenic properties are desired. The bacterial resistance and the need for new antibacterial strategies stand among the most challenging tasks of the modern medicine. In this work, brushite cements based on powders of Zinc (Zn) (1.4 wt%) substituted tricalcium phosphate (β-TCP) and non-substituted β-TCP were prepared and investigated. Their initial and final phase composition, time of setting, morphology, pH evolution, and compressive strength are reported. After soaking for 60 days in physiological solution, the cements transformed into a mixture of brushite and hydroxyapatite. Antibacterial activity of the cements against Enterococcus faecium, Escherichia coli, and Pseudomonas aeruginosa bacteria strains was attested. The absence of cytotoxicity of cements was proved for murine fibroblast NCTC L929 cells. Moreover, the cell viability on the β-TCP cement containing Zn2+ ions was 10% higher compared to the β-TCP cement without zinc. The developed cements are perspective for applications in orthopedics and traumatology.

Synthesis of Fe1-xS Nanoparticles with Various Superstructures by a Simple Thermal Decomposition Route and Their Magnetic Properties

Pyrrhotite nanoparticles with 5C and 3C superstructures were synthesized via a simple one-step thermal decomposition method in which hexadecylamine was used as a solvent at various reaction temperatures (TR). Structural analysis showed that at TR = 360 °C, almost uniform in size and shape Fe7S8 nanoparticles with 3C superstructure are formed, and an increase in the reaction temperature leads to the formation of Fe9S10 nanoparticles (5C superstructure), herewith a significant increase in the size of nanoparticles is observed. High-temperature magnetic measurements in 5 repeated heating-cooling cycles revealed that after the first heating branch in the Fe9S10 samples, the λ—Peak transition disappears, and the magnetization has a Weiss-type behavior characteristic of the Fe7S8 sample. The change in the behavior of magnetization can be explained by the redistribution of iron vacancies, which changes the initial phase composition of nanoparticles.

Understanding reaction-induced restructuring of well-defined FexOyCz compositions and its effect on CO2 hydrogenation

Herein, we provide fundamentals relevant for the development of Fe-based catalysts for CO2hydrogenation to higher hydrocarbons. It was possible owing to preparation of well-defined FexOyCz compositions through controlled decomposition of iron oxalate, determination of their composition under CO2-FT reaction and catalytic tests in a broad range of CO2 conversion. Such steady-state composition changes along the catalyst bed. The changes and their strength depend on the initial phase composition. In addition to the reaction-induced catalyst restructuring, reaction pathways leading from CO2 to CO, CH4 and higher hydrocarbons were elucidated. A correlation between them and the steady-state composition was established and offers the possibility for tailored catalyst design and preparation. Our best performing promoter-free Fe-based catalyst shows the selectivity to CH4 below 10 %, while the selectivity to C2+-hydrocarbons is about 50 % at CO2 conversion of about 25 % and 300 °C. The olefin to paraffin ratio among C2-C4 hydrocarbons is 5.5.

Laser modification of the microstructure and mechanical properties of (Cr3C2-25(Ni20Cr))-5(Ni25C) cermet coatings containing a solid lubricant

This paper presents a study on the effect of laser surface treatment on the microstructure and mechanical characteristics of cold sprayed Cr3C2-25(Ni20Cr)-(Ni-graphite) cermet coatings. The as-sprayed deposits retained the initial powder phase composition. The Cr3C2 particles were homogeneously distributed within the deformed nickel-chromium matrix phase. Moreover, the carbide particles were heavily fragmented due to a high-velocity impact on the substrate or particles already embedded. The solid lubricant (graphite) was mostly distributed between crushed Cr3C2 particles or deformed nickel-chromium matrix. The surface of the as-deposited coatings was laser-treated using a CO2 laser. With the higher applied power of the laser beam, the changes in the coating microstructure and surface topography were more significant. The refinement of the deposit structure and formation of new phases such as Cr7C3 and Cr2O3 were observed. All coatings, both those cold sprayed and those laser-treated, revealed compressive residual stresses, which increased with higher laser power. The post-deposition laser modification of the coating surfaces improved their mechanical properties by almost half.

Structure sensitivity of iron oxide catalyst for CO2 hydrogenation

A series of iron oxide catalysts prepared from ferric/ferrous mixed salts were studied to explore the structure–performance relationship for CO2 hydrogenation. The high selectivity to C5+ hydrocarbons (47 %) at a high CO2 conversion (34 %) could be maintained when the initial Fe3+/Fe2+ ratio in preparation varies from 2/1 to 2.5/0.5, while both the CO2 conversion and selectivity to C5+ hydrocarbons show an obvious decline as the ratio deviates from the range. Combined with various characterization results, the volcano-like evolution of CO2 conversion and selectivity to C5+ hydrocarbons is related to the structure and phase transition of the iron oxide catalysts. With the increase of Fe3+/Fe2+ ratio, the catalyst composition gradually changes from Fe3O4 nanoparticles to β-FeOOH nanorods, meanwhile, the size of Fe3O4 nanoparticles decreases. The smaller Fe3O4 nanoparticles could provide higher active surface area for improved reducibility and CO2 adsorption capacity, whereas the presence of β-FeOOH nanorods is not favorable for the reduction and carburization of catalysts. Consequently, the variation of initial phase composition and structure would affect the formation of Hägg iron carbide (χ-Fe5C2) phase during reaction, which has decisive effect on higher hydrocarbons synthesis from CO2 hydrogenation.

Formation of the ω Phase in the Titanium—Iron System under Shear Deformation

The effect of the phase composition on the α/β-Ti(Fe)→ω-Ti(Fe) transformation in the Ti-4 wt % Fe alloy under shear strain with high-pressure torsion (HPT) has been studied. For shear deformation by means of HPT, two initial states of the alloy were used, which significantly differed in the morphology of the phases and the concentration of iron atoms in the β phase. During HPT, a stationary state occurred in both sample series, which is characterized by the presence of a single ω phase containing 4 wt % Fe and by a grain size of about 200 nm. Thus, the HPT state is equifinal and independent of the initial phase composition of the samples. It was found that under the influence of HPT in Ti-4 wt % Fe alloys not only martensitic (shear) transformation into the ω phase occurs, but also a significant mass transfer of atoms of the alloying element. An analysis of the change in the torsion torque directly in the HPT process made it possible to estimate the rate of deformation-induced mass transfer. It is 18–19 orders of magnitude higher than the rate of conventional thermal diffusion at the processing temperature THPT = 30°C, while it is close to the diffusivity values at 700–800°C. This is because HPT increases the concentration of lattice defects, which in turn is equivalent to an increase in temperature. A similar combination of accelerated mass transfer during HPT and martensitic (shear) transformation was previously observed in copper-based shape memory alloys, but for the first time studied for the formation of ω-phase in titanium alloys.

Effects of grain refinement by HPT processing in carbon steel with various cementite morphology

This article reports on the effect of the initial phase composition (martensitic, patented, spheroidized) of the middle carbon steel C45 (0.45 wt.% C) on grain refinement during high-pressure torsion (HPT) at elevated temperature. It is established that the cementite dissolution and the final grain size after HPT strongly depend on the processing regime, as well as on the cementite morphology in the initial state of the steel. As result of this study, new approaches to obtain a very high-strength state in carbon steels have been proposed.

Phase Equilibria and Lithiation of Industrially Produced Heterogeneous Tin Sulphide Anode Materials for Lithium Ion Batteries

Due to its theoretical capacity of 960 mAh/g, which is approximately two and a half times that of carbon (372 mAh/g), as well as its natural abundance, Sn has been considered as an interesting anode active material to replace the currently used graphite in lithium ion batteries. Despite their high theoretical capacities, Sn-based anodes have not yet been commercialized because they suffer from prohibitively large volume expansions during lithiation via formation of LixSn alloys (>185 % for full lithiation to Li17Sn4). These volume changes lead to extensive crack formation, loss of electrical contact between particles, pulverization of the electrode during cycling, lithium trapping, and the growth of an unstable SEI. One way to take advantage of the high capacity of Sn and simultaneously overcome the detrimental effects associated with its volume expansion is to use Sn-based chalcogenide compounds as anode active materials. In this respect, tin sulfides such as SnS, Sn2S3 and SnS2 are an interesting class of materials due to the formation of a rigid, Li2S matrix phase upon discharge, which can serve to restrict the volume expansion of Sn during subsequent alloying reactions. During the conversion reaction, which can be written as 2b∙Li+SnaSb → b∙Li2S + a∙Sn and occurs at potentials between 1 and 1.6 V vs Li+/Li, a composite electrode structure consisting of Sn particles distributed in a rigid Li2S matrix is produced in-situ. Once pure Sn is formed, additional lithium can be stored via alloying reactions to produce Li17Sn4 encapsulated in the Li2S matrix. According to the mechanism, the capacities of the alloying reactions are 782, 706, and 644 mAh/g for SnS, Sn2S3 and SnS2, respectively. Heterogeneous (mixed-phase) tin sulfides can be readily produced industrially via the thermal reaction of tin and sulphur in closed vessels. However, additional processing steps may be required to produce phase pure materials on the industrial scale. Since these steps may be costly, thereby driving up the price of electrode active material production, it is worthwhile to consider heterogeneous tin sulfides as anode active materials. This is further rooted in the fact that unlike intercalation reactions, where a stable host structure is required for the reversible intercalation/extraction of lithium, the tin sulfide crystal structure is destroyed in the first conversion reaction and does not readily form again on subsequent cycling if the voltage cutoff is limited to below 2V vs Li+/Li. Therefore, in this work, industrially produced heterogeneous tin sulfides were investigated in order to assess their structure-property-performance relationships as anode active materials for lithium ion batteries (LiBs). Firstly, the heterogeneous tin sulfides were subjected to an extensive physio-chemical characterization to determine their chemical compositions (XRF), phase compositions (powder X-ray diffraction), specific surface areas (BET method), particle size distributions (laser diffraction), and morphologies (SEM). Following this, galvanostatic cycling under potential limitation (GCPL), cyclic-voltammetry (CV), and galvanostatic titration intermittent technique (GITT) experiments vs Li+/Li were conducted in order to correlate the electrochemical reaction mechanisms to the initial phase and chemical compositions of the heterogeneous tin sulfide electrode materials. In addition to the physico-chemical characterization and electrochemical investigations, a thermodynamic modelling and simulation approach was also selected to elucidate the complex reaction mechanisms of the heterogeneous tin sulfides. In this regard, calculated phase and property diagrams are essential tools, since they can be used to predict the compositional changes and phase transformations of the electrode materials during lithiation/de-lithiation. Therefore, a CALPHAD (CALculation of PHAse Diagrams)-based thermodynamic description for the multi-component Li-Sn-S system was developed using analytic Gibbs free energy expressions for the phases in the Li-Sn1, Sn-S2, and Li-S3 binary systems which are available in the literature. The ternary Li-Sn-S description was then used to simulate the phase formation and coulometric titration curves for the pure and heterogeneous tin sulphides. Additionally, ambient temperature phase diagrams were calculated, and all phase and property diagrams were used in conjunction with the electrochemical results to elucidate the electrochemical reaction mechanisms for the lithiation of the heterogeneous tin sulphides.

TiN-Nanoparticulate-Reinforced ZrO2 for Electrical Discharge Machining.

This study presents a fabrication route for an electrically conductive ZrO2–TiN ceramic nanocomposite with a nanoscale TiN phase occupying ≤30 vol% to improve the mechanical reinforcement of the zirconia matrix, and at the same time provide electrical conductivity to facilitate electro-discharge machining (EDM). The TiN nanoparticles were incorporated into a 3 mol% yttria-stabilized tetragonal zirconia (Y-TZP) powder, either by admixing a TiN nanopowder (MCP) or by using in-situ synthesis (ISS) via the forced hydrolysis of a titanyl sulphate aqueous solution and the direct nitriding of as-synthesized titania nanoparticles, followed by consolidation and rapid sintering in a spark plasma sintering (SPS) system. The initial phase composition and crystal structure of the as-synthesized powders and the sintered samples were characterized by transmission electron microscopy (TEM) and X-ray difraction (XRD). The influence of the different fabrication routes on the microstructural evolution, electrical and mechanical properties, and affinity for EDM were assessed using TEM, focused ion beam scanning electron microscopy (FIB-SEM, Vickers indentation, electrical conductivity measurements, and profilometry. The MCP synthesis route resulted in finer microstructures that are less prone to microstructural inhomogeneities; however, using the ISS route, it was possible to fabricate electrically conductive Y-TZP nanocomposites containing only 15 vol% of the TiN nanoparticulate phase. Both synthesis routes resulted in an increase of the fracture toughness with an increase of the TiN phase due to the nanoparticulate TiN reinforcement of the Y-TZP ceramic matrix via crack-bridging toughening mechanisms. As both synthesis routes yielded Y-TZP nanocomposites capable of successful EDM machining at a TiN content of ≥30 vol% for the MCP and ≥ 15 vol% TiN for the ISS, a possible mechanism was developed based on the microstructure evolution and grain growth.