Formation Of Different Phases Research Articles

Spark Plasma Sintering of Pure Titanium: Microstructure and Mechanical Characteristics.

The versatility of titanium (Ti) allows it to be employed in various industries, from aerospace engineering to medical technology, highlighting its significance in modern manufacturing and engineering processes. Spark plasma sintering (SPS) is currently being explored to enhance its properties further and broaden its application range. The current study focuses on exploring and optimizing the effect of SPS temperature (800, 900, 1000, 1100, 1200, and 1400 °C) on pure Ti sintered at 60 MPa in a controlled argon environment with a dwell time of 5 min. All the prepared samples were highly dense with a relative density above 99%, but exhibited significant variations in grain size (10 to 57 µm), tensile yield strength (488 to 700 MPa), ultimate tensile strength (597 to 792 MPa), and ductility (4 to 7%). A microstructural investigation was performed using XRD, SEM, and EDS to predict the influence of sintering temperature on the formation of different phases. The XRD patterns of all sintered samples showed the presence of single-phase α-Ti with hexagonally close-packed Ti. This work is a step forward in optimizing SPS-processed Ti's physical and mechanical properties for enhanced structural and biomedical applications.

Shape-controlled electro-synthesis of pyrrhotite

Recently, iron sulfide nanomaterials have drawn increased interest, due to their novel properties and extensive applications depending on their structure. To date, various methods have been employed for the synthesis of iron sulfide nanostructures with different shapes and morphologies. The synthesis method of iron sulfide nanomaterial is a challenge, as a small variation in sulfur content can lead to formation of different phases of iron sulfide. In this study, iron sulfide nanostructures were synthesized using our fast, simple, efficient, economical and environmentally friendly method in an electrochemical cell containing two iron sheets as electrodes in an aqueous solution of sodium sulfide. This method, with many advantages such as low-toxicity, low cost and easy handling, helps to control the properties of the products through the synthesis by tuning the growth conditions. Here, the influence of applied voltage ranging from 5 V to 25 V and annealing temperatures of 200 °C and 800 °C on the structure and magnetic properties of the products were studied. The samples were analyzed by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). XRD patterns confirmed the formation of monoclinic and hexagonal pyrrhotite at 200 °C and 800 °C, respectively. Based on SEM images, pyrrhotite in different shapes, such as quasi-spherical, feathers, sheets and flower-like structures, are formed depending on the applied voltage and annealing temperature. According to VSM results, all samples annealed at 200 °C are magnetically soft with only a little hysteresis, but the magnetization increases from 2.3 emu/g to 10.1 emu/g when applied voltage varies from 5 V to 25 V. All samples annealed at 800 °C exhibit an antiferromagnetic behavior. With increasing the applied voltage, the value of remanence magnetization and coercivity increases up to ∼2000 Oe and ∼0.14 emu/g, respectively.

A sustainable and energy efficient approach for development of electrically conductive materials and their characterizations

In this study, composite castings of electrically conductive materials were prepared using electromagnetic energy of frequency 2.45 GHz. Three separate sets of castings were produced inside the domestic microwave applicator cavity, with reinforced compositions of up to 15% in steps of 5% for each composite cast (copper (Cu) + 5% molybdenum (Mo), Cu + 10% Mo, and Cu + 15% Mo). A microwave radiation exposure time of 12 min was required for the complete melting of pure copper powder. However, the addition of Mo reinforcement caused a reduction in exposure time to 11.33 min (min) for the Cu-15% Mo composite cast. The formation of different phases was revealed by the X-ray diffraction analysis of the cast samples. Only a 0.92% copper oxide phase was detected in the pure copper cast samples. The composite cast samples exhibited peaks corresponding to Cu64O, Cu6Mo5O18, and MoO2. Microstructure analysis demonstrated that the grains grew in an equiaxed manner with a uniform dispersion of the reinforcements. The maximum microhardness achieved is 99.2 ± 4.99 Hv for Cu + 15% Mo which is 1.66 times better than microwave-cast copper sample.

Wettability and microstructural evolution of copper filler in W and EUROFER brazed joints

In terms of wettability, active systems are characterized by a reduction in interfacial energy as the time at specific conditions is increased. This article aims to investigate the evolution of wettability and microstructure, which undergoes a critical transformation at temperatures and dwell times near brazing conditions due to their significant impact on resultant mechanical properties. The objective is to enhance wettability and prevent the formation of different phases that can occur rapidly within the brazing window conditions. Up to 1105 °C, complete fusion of the filler does not occur. However, once it happens, the expansion of the copper filler in EUROFER increases up to 400%, and the contact angle reduces from 100° to 10°, indicating an active wetting behavior. On the other hand, when copper is used with tungsten, an inert behavior is observed, maintaining the contact angle around 70°. Brazed joints carried out under the most promising wetting conditions demonstrated that at 1110 °C-1 min, various phenomena began to occur. This includes solid-state diffusion of copper in the EUROFER, following the austenitic grain boundaries, and partial dissolution of Fe in the copper braze. Increasing the brazing time from 2 to 5 min achieved high interfacial adhesion properties and controlled the diffusion layer and Fe-rich band formed at the W-braze interface, resulting in the best mechanical results (295 MPa).

Rare-Earth Ion Loss of Er- or Yb-Doped LiNbO3 Crystals Due to Mechanical Destructive Effect of High-Energy Ball Milling

Structural changes of Er- or Yb-ion doped LiNbO3 (LN) nanocrystals were studied in relation to the high-energy ball milling process. The evolution of the size of the particles and the formation of different phases were followed by dynamic light scattering and X-ray diffraction measurements, while the electronic transitions of rare-earth (RE) ions were investigated by absorption spectroscopy in the infrared spectral range. During the milling process, RE ions left the crystal lattice and an RE2O3 phase appeared to an increasing extent next to the LN. The change in the absorption spectra and the phases formed during the grinding process were found to be very similar for both investigated RE ions and were independent of their original concentration in the starting crystal samples. The extent of the RE loss was found to be 90% after 100 min of wet grinding.

Synthesis, characterization, and enhanced photoluminescence of ZrO2:Dy3+ phosphors by incorporating Li+, Na+ and K+ ions for LED applications

ZrO2:(0.01)Dy3+:xA+ (A = Li+, Na+ and K+) phosphors were prepared by one step solution combustion method. X-ray diffraction (XRD), reveal formation of different phases. Functional group presence and its vibrations are assigned from FTIR measurements. Influence of alkali metal ions (A+) on surface morphology were realized from SEM micrograph. XPS study was carried out to confirm the presence of Li+ ions. Photoluminescence (PL) spectra of the samples excited at 350 nm exhibited two strong emission peaks at 480 nm and 580 nm, which are characteristic transitions of Dy3+ ions. However, the relative intensity between these peaks varies considerably due to the variation of the co-dopant/compensator (Li+, Na+, K+) concentration, representing the variation of the crystal field. Effects of different charge compensators (A+) and their concentration on the structural and luminescence properties of ZrO2:(0.01)Dy3+:xA+ phosphors were thoroughly investigated. Further, Judd-Ofelt parameters were calculated. Total emission colour (TEC) concentration of ZrO2:(0.01)Dy3+ phosphors were improved remarkably with the addition of charge compensators (A+), which would promote their applications in solid state lighting. The effective blue emission of the phosphors was changing with different co-dopant incorporation. Implying possible use of this material as a blue emitting phosphor as a blue emitting component in three-component white light-emitting diodes (WLEDs).

The influence of Ho doping on the morphology and magnetic properties of M-type strontium ferrite with different Fe/Sr

Ho-doped strontium ferrite powder samples with different Fe/Sr ratio were successfully prepared by sol-gel auto-combustion method. Different Fe/Sr ratios (Sr1-xHoxFe12O19, Sr1-x/2HoxFe12-x/2O19, SrHoxFe12-xO19, Sr1+xHoxFe12-xO19, Sr1+xHoxFe12-2xO19) were designed to study the influence of Ho doping on the morphology and magnetic properties of M-type strontium ferrite. XRD analysis revealed a relative change in the content of the secondary phases Fe2O3, HoFeO3, and SrFeO3-x in Ho-doped samples as the Fe/Sr ratio varies. The excess of Sr and Fe in the internal environment resulted in such changes in the phase. SEM analysis confirmed that Ho doping led to an increase in grain size. Different doping methods could lead to significant difference in the size of crystal grain. XPS results indicated that the secondary phases caused by Ho doping led to a change in the oxidation state of the iron element. It was inferred from FTIR and Raman spectra that Ho doping into the lattice might occupy both 2b and 4f1 sites. The VSM showed that under the SrHoxFe12-xO19 doping mode (x = 0.05–0.2), the obtained samples showed a decrease in coercivity (Hc) with increasing Ho doping level (from 5.26 to 4.78 kOe), and the saturation magnetization (Ms) also decreased (from 76.73 to 73.28 emu/g). As the Fe/Sr ratio gradually increases, the saturation magnetization of the sample shows a trend of first increasing and then decreasing, while the coercivity shows a trend of first decreasing and then increasing. The intermediate ionic radius of Ho3+ (0.89 Å) among the rare earth elements results in its unique occupancy behavior, which also influences the formation of different phases, resulting in corresponding changes in coercivity and saturation magnetization.

Effect of laser energy densities on the phase composition change in laser-cladded AlCoCrNbMo high-entropy alloy coatings

This work designed a new high-entropy alloy (HEA), namely, AlCoCrNbMo, and prepared it by using laser cladding (LC). The effects of different values of laser energy density (Es) on the phase composition, microstructure, mechanical properties and corrosion resistance of the HEA coating were investigated via X-ray diffractometry; scanning electron microscopy; energy dispersive spectrometry and microhardness, friction wear and electrochemical tests. Results indicate that increasing Es (Es = 35, 55, 75 J/mm2) leads to the formation of different phases, including bcc1, bcc1 +bcc2 and bcc1 +bcc2 +Al3Nb, in the coating. The bcc1 phase is rich in Co and Cr elements, whereas the bcc2 phase is rich in Nb and Mo elements. As Es increases, the HEA coating shows increasing hardness and wear resistance but decreasing corrosion resistance. Moreover, the AlCoCrNbMo alloy prepared through vacuum arc melting does not conform to the form of HEAs but is instead composed of various intermetallic compounds, reflecting the unique advantage of LC. This paper discusses the influence of LC process parameters on the microstructure of HEAs and the unique advantages of LC for HEA preparation.

Thermodynamic and Microstructural Analysis of Lead-Free Machining Aluminium Alloys with Indium and Bismuth Additions.

The present study comprises an investigation involving thermodynamic analysis, microstructural characterisation, and a comparative examination of the solidification sequence in two different aluminium alloys: EN AW 6026 and EN AW 1370. These alloys were modified through the addition of pure indium and a master alloy consisting of indium and bismuth. The aim of this experiment was to evaluate the potential suitability of indium, either alone or in combination with bismuth, as a substitute for toxic lead in free-machining aluminium alloys. Thermodynamic analysis was carried out using Thermo-Calc TCAL-6 software, supplemented by differential scanning calorimetry (DSC) experiments. The microstructure of these modified alloys was characterised using SEM-EDS analysis. The results provide valuable insights into the formation of different phases and eutectics within the alloys studied. The results represent an important contribution to the development of innovative, lead-free aluminium alloys suitable for machining processes, especially for use in automatic CNC cutting machines. One of the most important findings of this research is the promising suitability of indium as a viable alternative to lead. This potential stems from indium's ability to avoid interactions with other alloying elements and its tendency to solidify as homogeneously distributed particles with a low melting point. In contrast, the addition of bismuth does not improve the machinability of magnesium-containing aluminium alloys. This is primarily due to their interaction, which leads to the formation of the Mg3Bi2 phase, which solidifies as a eutectic with a high melting point. Consequently, the presence of bismuth appears to have a detrimental effect on the machining properties of the alloy when magnesium is present in the composition.

Intercalation in 2H-TaSe[formula omitted] for modulation of electronic properties and electrochemical energy storage

Two-dimensional transition metal dichalcogenides (TMDs) exhibit an extensive variety of novel electronic properties, such as charge density wave quantum spin Hall phenomena, superconductivity, and Dirac and Weyl semi-metallic properties. The diverse properties of TMDs suggest that structural transformation can be employed to switch between different electronic properties. Intercalation and zero valence doping of molecules and atoms into the van der Waals gap of TMDs have emerged as effective approaches to modify the charge order states of the material. This eventually leads to phase transition or the formation of different phases, thus expanding the electronic, thermoelectric and optical applications of these materials. In this study, electronic and electrochemical energy storage properties of such an intercalated TMD, namely, 2H-TaSe2 via intercalation of lithium (Li), sodium (Na) and potassium (K) have been investigated. The intercalation of these ions into the dichalcogenide resulted in a modified band structure and novel structural effects, leading to the emergence of a 1 eV band gap. Possibility of electrochemical energy storage application is also explored in this study. Furthermore, the importance of multi orbital electron–electron correlations in intercalated TaSe2 is also investigated via dynamical-mean-field theory with local density approximation.

Plasma-Synthesis of MOF-Derived Nanoporous Copper Oxides for Solar Thermal Application

Nanoporous Metal oxides (P-MOx) have attracted great attention because of their enhanced performances in e.g., energy storage, catalysis, sensors, solar technology, and biomedicine due to large surface area coupled with good thermal and chemical stability. Existing synthesis techniques of P-MOx suffer from major drawbacks such as longer time and limitation in material choices. Plasma assisted synthesis of metal organic framework (MOF) derived P-MOx can be a rapid and sustainable one-step process and allow a higher degree of flexibility in controlling porosity, pore size distribution and surface properties. Herein, synthesis of nanoporous copper oxides (P-CuOx) was carried out by plasma treating copper-based MOF as a precursor. A systematic study of the transformation of MOF to derived P-CuOx has been carried out by varying the plasma treatment time also the formation of different phases of CuO and Cu2O was investigated. Additionally, a comparative study of properties was done between the plasma-synthesised P-CuOx and pyrolytically synthesised P-CuOx. Transformation process of MOF to P-CuOx was studied using x-ray diffraction (XRD) and Raman analysis. Moreover, morphological properties were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Finally detail optical characterization and solar thermal conversion properties of P-CuOx based nanofluid were studied to test its applicability in solar thermal energy harvesting.

Piezo-Enhanced Photocatalytic Performance of Bismuth Ferrite-Based Thin Film for Organic Pollutants Degradation

This work addresses the global sustainable development concerns by investigating the enhancement of piezo-photocatalytic efficiency in bismuth ferrite-based thin films synthesized using reactive high-power impulse magnetron sputtering. The influence of substrate type and Cr addition on structural, optical and ferroelectric properties of bismuth ferrite (BFO) based thin films was investigated. X-ray diffraction measurements showed the formation of different phases depending on the substrate used for sample growth. Compared to the BFO film deposited on FTO (F-SnO2), the Cr-doped BFO (BFCO) sample on SrTiO3 (STO) exhibits higher photodegradation efficiency (52.3% vs. 27.8%). The enhanced photocatalytic activity of BFCO is associated with a lower energy band gap (1.62 eV vs. 1.77 eV). The application of ultrasonic-wave vibrations simultaneously with visible light improved 2.85 times and 1.86 times the photocatalytic degradation efficiencies of BFO/FTO and BFCO/STO catalysts, respectively. The piezoresponse force microscopy (PFM) measurements showed that both catalysts exhibit ferroelectric behavior, but a higher piezoelectric potential was evidenced in the case of the BFO/FTO thin film. The enhancement of piezo-photodegradation efficiency was mainly attributed to the piezoelectric-driven separation and transport of photo-generated carriers toward the surface of the photocatalyst.

Phase-Dependent Dual Discrimination of MoSe2/MoO3 Composites Toward N,N-Dimethylformamide and Triethylamine at Room Temperature.

Herein, we present, a chemiresistive-type gas sensor composed of two-dimensional 1T-2H phase MoSe2 and MoO3. Mixed phase MoSe2 and MoSe2/MoO3 composites were synthesized via a facile hydrothermal method. The structure analysis using X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy revealed the formation of different phases of MoSe2 at different temperatures. With increase in synthesis temperature from 180 to 200 °C, the relative percentage of 1T and 2H-MoSe2 phases changed from 80 to 48%. On the other hand, at 220 °C, 2H-MoSe2 was obtained as a major component. The gas sensing properties of individual MoSe2 and composites were investigated at room temperature toward various analytes. The obtained results revealed that composites possess improved sensing features as compared with individual MoSe2 or MoO3. Data also revealed that the composite with dominating 1T-phase exhibits relatively higher response (10%, at 10 ppm) for dimethylformamide (DMF) compared to triethylamine (TEA) (3%, at 10 ppm). In contrast, the composite with larger 2H-phase exhibited affinity toward TEA and had a relative response of about 2%. Therefore, selectivity of a sensor device can be tuned by an appropriately designed MoSe2/MoO3 composite. These results signify the importance of MoO3-based composites with dual-phase MoSe2 for successfully discriminating between DMF and TEA at room-temperature.

Synthesis and characterization of visible-light-driven novel CuTa2O6 as a promising practical photocatalyst.

In this work, the novel CuTa2O6 phase was successfully synthesized by the hydrothermal and followed by the calcination process. The X-ray diffraction pattern confirms the formation of different phases. At a low temperature, CuTa2O6 exhibits the orthorhombic phase, whereas, at a higher temperature, it underwent a phase transition to a cubic crystal structure. X-ray photoelectron spectroscopic results suggest the presence of all the elements (Cu, Ta, and O). The optical studies were carried out using a UV-Vis DRS spectrophotometer. FESEM images confirm the spherical-shaped particles for the sample annealed at a high temperature. The local atomic and electronic structures around Cu and the contribution of the Cu oxidation state in the CuTa2O6 system were determined by X-ray absorption spectroscopy. To investigate the effective usage of CuTa2O6 in treating wastewater, its photocatalytic activity was investigated by evaluating its use in the photodegradation of MO dye under visible light irradiation. Moreover, the prepared CuTa2O6 photocatalyst exhibits significant photocatalytic activity in the degradation of MO dye and shows excellent stability; it is therefore a promising material for potential use in a practical photocatalyst. The CuTa2O6 photocatalyst suggests an alternative avenue of research into effective photo-catalysts for solar hydrogen water splitting.

Integrated hydrothermal-green approach to synthesize Fe, Ag doped copper sulfide nanopowders and investigations of their thermoelectric properties

Copper sulfide and Fe, Ag doped copper sulfide nanopowders were synthesized by integrated hydrothermal-green approach, using Urtica dioica leaf extract as a solvent. With Fe and Ag doping, covellite as the major phase was sustained but reduction in crystallite size and change in morphology was observed. Decrease in electrical conductivity from ∼186.24 Scm−1 for undoped copper sulfide to ∼34.97 Scm−1 and ∼23.26 Scm−1 on doping Fe and Ag, respectively, at 300 K, was witnessed due to formation of different phases of copper sulfide and incorporation/segregation of Ag/Fe into copper sulfide lattice. Conversely, Seebeck coefficient showed enhanced values on doping Fe and Ag. The maximum power factor of ∼22.22 μW/mK2 was found for undoped copper sulfide. Thus, the incorporation/segregation of Fe/Ag ions in copper sulfide lattice and grain boundaries was found to alter the thermoelectric performance of copper sulfide.

Alkaline-Activation Technique to Produce Low-Temperature Sintering Activated-HAp Ceramic

The fabrication of hydroxyapatite (HAp) ceramics prepared by existing conventional sintering requires high-temperature sintering of 1250 °C to 1300 °C. In this paper, the activated metakaolin (MK)/HAp specimens were prepared from varied mix design inputs, which were varied solid mixtures (different amounts of MK loading in HAp) and liquid-to-solid (L/S) ratios, before being pressed and sintered at 900 °C. Phase analysis, thermal analysis, surface morphology, and tensile strength of the specimens were investigated to study the influences of the Al, Si, Fe, Na, and K composition on the formation of the hydroxyapatite phase and its tensile strength. XRD analysis results show the formation of different phases was obtained from the different mix design inputs HAp (hexagonal and monoclinic), calcium phosphate, sodium calcium phosphate silicate and calcium hydrogen phosphate hydrate. Interestingly, the specimen with the addition of 30 g MK prepared at a 1.25 L/S ratio showed the formation of a monoclinic hydroxyapatite phase, resulting in the highest diametrical tensile strength of 12.52 MPa. Moreover, the increment in the MK amount in the specimens promotes better densification when sintered at 900 °C, which was highlighted in the microstructure study. This may be attributed to the Fe2O3, Na2O, and K2O contents in the MK and alkaline activator, which acted as a self-fluxing agent and contributed to the lower sintering temperature. Therefore, the research revealed that the addition of MK in the activated-HAp system could achieve a stable hydroxyapatite phase and better tensile strength at a low sintering temperature.

Microstructure and high temperature tribological behaviour of self-lubricating Ti-TiBx composite doped with Ni[sbnd]Bi

It is a well-established fact, that the tribological performance of titanium and its alloys at high temperatures is poor, especially for self-mated titanium‑titanium pairs. Previous work has shown a significant improvement in mechanical and high temperature tribological behaviour (700–900 °C) for pure Ti sintered with TiB2 ceramic, occasioned by the in-situ formed boric acid lubricant. The current work explores the possibility to extend the lubrication temperature range (below 700 °C) of Ti-TiB2 composites through the incorporation of a nickel‑bismuth mixture (NiBi) as a solid lubricant using laser melting. To this end, phase equilibrium diagrams have been calculated for the Ti-B-NiBi quaternary system using the CALPHAD method to evaluate the possibility of the formation of different phases due to dilution between the substrate and deposit, as well as their possible interactions. The self-lubricating NiBi samples feature a formation of Bi-Ni-Ti-TiBx functional surface. The functional surface demonstrates a compact and unique microstructure of a hard B-rich phase encapsulated inside a lubricous Bi-rich phase. A two-fold increase in hardness of the surface in comparison to the underlying substrate was noted for NiBi laser-melted samples. Further, the NiBi samples were studied under a reciprocating sliding configuration against a Ti-alloy flat-pin counterbody at temperatures including RT, 400 and 600 °C. The resulting wear scars were analysed utilizing SEM, XRD and 3D profilometry to understand the prevalent wear mechanisms. A significant decrease in coefficient of friction and wear rate was observed for the NiBi laser-melted samples sliding at 400 °C and 600 °C due to the formation of a self-lubricating tribo-oxide layer rich in Bi-compounds. The results are reported in comparison to the unmodified reference Ti-TiB2 composite.

Phase Control in the Modulated Self‐Assembly of Lanthanide MOFs of a Flexible Tetratopic Bis‐Amide Linker

The targeted synthesis of phase-pure metal-organic frameworks (MOFs) is often complicated by the fact that a number of different products can result from the same metal-ligand combination. The self-assembly of lanthanide-based MOFs can be particularly challenging due to the versatile coordination chemistry of the f-block allowing for diverse coordination spheres with irregular geometries driven by steric effects. Herein we show that modulated self-assembly – the addition of small molecules to solvothermal synthesis in order to control pH and coordination equilibria – can control phase formation when preparing lanthanide MOFs from the tetratopic bis-(3,5-dicarboxyphenyl)terephthalamide ligand. We report 27 new MOFs, of which 21 are characterised by single crystal X-ray diffraction, that can be categorised into six structure types. The formation of different phases is largely driven by the contraction in ionic radius across the lanthanide series, but we show how careful choice of both solvent and modulator can influence reaction outcome. As an example, phase pure samples of three Gd MOFs of the same ligand can be selected by simply changing the modulator – acetic acid, benzoic acid, or nitric acid – used in closely related syntheses. These results show that modulation can control phase in f-block MOFs, just as it can in d-block MOFs, and provide design rules for uncovering structural diversity by carefully exploring the chemical parameter space of lanthanide MOFs in single ligand systems.

Preferentially oriented growth of diamond films on silicon with nickel interlayer

A multistep deposition technique is developed to produce highly oriented diamond films by hot filament chemical vapor deposition (HFCVD) on Si (111) substrates. The orientation is produced by use of a thin, 5–20 nm, Ni interlayer. Annealing studies demonstrate diffusion of Ni into Si to form nickel silicides with crystal structure depending on temperature. The HFCVD diamond film with Ni interlayer results in reduced non-diamond carbon, low surface roughness, high diamond crystal quality, and increased texturing relative to growth on bare silicon wafers. X-ray diffraction results show that the diamond film grown with 10 nm Ni interlayer yielded 92.5% of the diamond grains oriented along the (110) crystal planes with ~ 2.5 µm thickness and large average grain size ~ 1.45 µm based on scanning electron microscopy. Texture is also observed to develop for ~ 300 nm thick diamond films with ~ 89.0% of the grains oriented along the (110) crystal plane direction. These results are significantly better than diamond grown on Si (111) without Ni layer with the same HFCVD conditions. The oriented growth of diamond film on Ni interlayers is explained by a proposed model wherein the nano-diamond seeds becoming oriented relative to the β1-Ni3Si that forms during the diamond nucleation period. The model also explains the silicidation and diamond growth processes.Article HighlightsHigh quality diamond film with minimum surface roughness and ~93% oriented grains along (110) crystallographic direction is grown on Si substrate using a thin 5 to 20 nm nickel layer.A detailed report on the formation of different phases of nickel silicide, its stability with different temperature, and its role for diamond film texturing at HFCVD growth condition is presented.A diamond growth model on Si substrate with Ni interlayer to grow high quality-oriented diamond film is established.

Prevention, Mitigation and Correlative Acoustic Spectroscopy of Lithium-Ion Battery Thermal Runaway

Scrutiny of lithium-ion battery failure has seen heavy regulations and restrictions with well-reported headlines of catastrophic thermal runaway of commercial electronic devices and electric vehicles. Thermal runaway occurs at a critical temperature when the rate of heat generation exceeds that of dissipation, highly exothermic decomposition reactions occur and temperatures in excess of 600 ᵒC can be measured 1. These concerns continue to grow with applications of greater energy density and capacity, such as the proliferation of electric vehicles.Isolation of electronically conductive components within the electrode assembly to prevent short circuit has shown promise to prevent the onset of thermal runaway within lithium-ion cells. Here 2, the authors present a metal-coated polymer current collector (PCC) and thermally stable separator (TSS) to prevent and mitigate thermal runaway. 2.10 Ah capacity 18650-geometry cells were subject to thermal, internal short circuit and nail penetration abuse techniques with these materials and their commercial counterparts for individual comparison of the PCCs and TSS. Reductions in cell mass were observed on the order of 5%, due to the majority of the PCC consisting of the polymer substrate rather than pure aluminium and copper in commercial current collectors. High speed synchrotron facilities provided insights into the function of the polymer current collectors with post- mortem X-ray computed tomography. During mitigation testing, cells were taken to failure with thermal and with an internal short circuit device (ISCD) within a Fraction Thermal Runaway Calorimeter (FTRC) to measure the reduction in calorific output. This highlighted the difficulty that exists with detecting gas-induced and internal structural degradation within lithium-ion batteries, especially outside specialized diagnostic laboratories to characterize these rapid changes with elapse within seconds. Attenuation and wave velocity determined by the propagative properties of ultrasound through different phases, prominently highlights structural, temperature and formation of different phases which occur during thermal runaway. Such analysis provided by acoustic spectroscopy are characterised by variations in the attenuation and signal peak shifts. Further information which can be derived from spatial mapping using acoustic spectroscopy 3,4 include: state of charge, state of health, electrochemical performance.Cells made with the aluminium-coated PCC demonstrated 100% success in prevention of thermal runaway during nail penetration, retaining a voltage above 4.00 V. Cells manufactured with the PCC, both PCC and TSS, exhibited a reduction in total energy output on average of 19.4% and 41.3% respectively during thermal abuse. ISCD triggered thermal runaways also observed reductions of 24.6% and 30.3% with these respective cell material configurations. Prevention of thermal runaway is a transformative advancement in improving lithium-ion battery safety, especially in the cylindrical 18650-format cell. Additionally, significant reductions in the calorific output during failure were measured. These safety innovations provides efficacy of these materials independent of cell chemistry (provided they are stable in the operating environment) while also increasing the energy density and be assimilated into existing manufacturing technology.Furthermore, the authors demonstrate correlative high-speed acoustic spectroscopy during routine cycling of a commercial 210 mAh lithium-ion pouch cell and during thermal abuse 5. Mechanical deformation such as gas-induced delaminations, which have been linked to degradation in electrochemical performance, capacity retention, cell state of health and impending thermal runaway, were detected. This degradation was observed with characteristic acoustic spectroscopy signal peaks changes during cycling due to cell manufacturing defects and during induced thermal abuse, were corroborated with high speed synchrotron X-ray imaging. This analysis can be observed immediately after application of the acoustic probe which emphasises the rapid diagnostics insights provided by acoustic spectroscopy as a robust field deployable technique. Thus, integration into battery management systems, second-life evaluation/recycling or as in-line cell metrology during manufacturing would provide real time direct insight into these metrics. Finegan DP, Darcy E, Keyser M, et al. Identifying the Cause of Rupture of Li-Ion Batteries during Thermal Runaway. Adv Sci. 2018. doi:10.1002/advs.201700369Pham MTM, Darst JJ, Walker WQ, et al. Prevention of lithium-ion battery thermal runaway using polymer-substrate current collectors. Cell Reports Phys Sci. 2021. doi:10.1016/j.xcrp.2021.100360Robinson JB, Pham M, Kok MDR, Heenan TMM, Brett DJL, Shearing PR. Examining the Cycling Behaviour of Li-Ion Batteries Using Ultrasonic Time-of-Flight Measurements. J Power Sources. 2019;444.Robinson JB, Maier M, Compton T, Alster G, Brett DJL, Shearing PR. Spatially resolved ultrasound diagnostics of Li-ion battery electrodes. Phys Chem Chem Phys. 2018. doi:10.1039/c8cp07098aPham MTM, Darst JJ, Finegan DP, et al. Correlative acoustic time-of-flight spectroscopy and X-ray imaging to investigate gas-induced delamination in lithium-ion pouch cells during thermal runaway. J Power Sources. 2020;470:228039. doi:10.1016/j.jpowsour.2020.228039