Добірка наукової літератури з теми "Polycrystalline material synthesis"

Single-crystal Er3+:YAG has long been used as a laser material, and recent work has shown polycrystalline ceramic Er3+:YAG to be a suitable laser material, with benefits of lower cost and easier production. However, relatively little work has been done with the synthesis and spectroscopic characterization of Er3+:YAG nanocrystals. In this work, we present the synthesis of nanocrystalline Er3+:YAG and the results of comparative spectroscopic characterization with single-crystal and polycrystalline ceramic counterparts. The results show good agreement between the optical properties of the three hosts, with the nanocrystals demonstrating relatively higher intensity in the 1.53 μm emission. These results demonstrate the viability of Er3+:YAG nanocrystals as a potential laser material.

AbstractMetal-organic frameworks (MOFs) have emerged as a class of promising membrane materials. UiO-66 is a prototypical and stable MOF material with a number of analogues. In this article, we review five approaches for fabricating UiO-66 polycrystalline membranes including in situ synthesis, secondary synthesis, biphase synthesis, gas-phase deposition and electrochemical deposition, as well as their applications in gas separation, pervaporation, nanofiltration and ion separation. On this basis, we propose possible methods for scalable synthesis of UiO-66 membranes and their potential separation applications in the future.

Hydrothermal synthesis produces polycrystalline NaBi(Ti_1−xZr_x)O₆ with small composition range; densified x = 0.01 material shows favourable piezoelectric coefficient and permittivity.

Gram scale multi-layer graphene grown on polycrystalline SiC microspheres were prepared by continuously preparation method in argon through chemical vapor deposition process using liquid polysilacarbosilane as raw material. The observation of products obtained at different temperature confirmed the growth is temperature dependent process. The method could be developed to synthesis hybrid nanostructures based on multi-layer graphene grown on polycrystalline SiC microspheres.

ABSTRACTThe recently discovered orthorhombic allotrope of silicon, Si24, is an exciting prospective material for the future of solar energy due to a quasi-direct bandgap near 1.3 eV, coupled with the abundance and environmental stability of silicon. Synthesized via precursor Na4Si24at high temperature and pressure (∼850 °C, 9 GPa), typical synthesis results have yielded polycrystalline samples with crystallites on the order of 20 μm. Several approaches to increase the crystal size have yielded success, including in-situ thermal spikes and refined selection of the starting materials. Microstructural analysis suggests that coherency exists between diamond silicon (d-Si) and Na4Si24. This hypothesis has led to the successful attempts at single crystal synthesis by selecting large crystals of d-Si along with metallic Na as the precursors rather than powdered and mixed precursor material. The new synthesis approach has yielded single crystals of Na4Si24greater than 100 μm. These results represent a breakthrough in synthesis that enables further characterization and utility. The promise of Si24for the future of solar energy generation and efficient electronics is strengthened through these advances in synthesis.

AbstractThe first labortory synthesis and characterization of the mineral Nadorite, PbSbO2Cl, is reported. The material was synthesized by combining PbCl2, PbO and Sb2O3. Powder X-ray diffraction data on the polycrystalline product is consistent with the previously reported crystal structure on the mineral. Infrared and thermogravimetric data are also present.

The propagation of redox reactions governs the electrochemical properties of battery materials and their critical performance metrics in battery cells. The recent research progress, especially aided by advanced analytical techniques, has revealed that incomplete and heterogeneous redox reactions prevail in many electrode materials. Advanced high-capacity cathode materials are mostly polycrystalline materials that exhibit complex charge distribution (the valence state distribution of the redox-active cations) due to the presence of numerous constituting grains and grain boundaries. The redox reactions in individual grains typically do not proceed concurrently due to their distinct geometric locations in polycrystalline particles. As a result, these unsynchronized local redox events collectively induce heterogeneous and anisotropic charge distribution, building up intergranular and intragranular stress. Therefore, these polycrystalline materials may exhibit weak mechanical stability, leading to undesired chemomechanical breakdown during battery operation. Grain engineering in polycrystalline materials provides a large playground to modulate the materials properties beyond controlling the chemical composition, and electronic and crystal structures. In particular, the anisotropic ion-conducting pathways in layered oxides make the grain crystallographic orientation a critical factor in determining the modality of the redox reactions in these materials. This presentation will discuss our recent progress in the design, synthesis, and characterization of cathode microstructures in lithium batteries. First, we will discuss how the charge distribution is guided by grain crystallographic orientations in polycrystalline battery materials. We elucidate the spatially resolved charge distribution in lithium layered oxides with different grain crystallographic arrangements and establish a model to quantify their charge distributions. While the holistic “surface-to-bulk” charge distribution prevails in polycrystalline particles, the crystallographic orientation-guided redox reaction governs the charge distribution in the local charged nanodomains. Compared to the randomly oriented grains, the radially aligned grains exhibit a lower cell polarization and higher capacity retention upon battery cycling. The radially aligned grains create less tortuous lithium-ion pathways, thus improving the charge homogeneity as statistically quantified from over 20 million nanodomains in polycrystalline particles. This study provides an improved understanding of the charge distribution and chemomechanical properties of polycrystalline battery materials. Second, we will discuss how the grain arrangement affects the thermal stability of polycrystalline cathode materials in rechargeable batteries. We performed a systematic in situ study on the Ni-rich polycrystalline cathode materials to investigate the fundamental degradation mechanism of charged cathodes at elevated temperatures, which is essential for tailoring material properties and improving performance. Using multiple microscopy, scattering, thermal, and electrochemical probes, we decoupled the major contributors to the thermal instability from intertwined factors. Based on our findings, the cathode grain microstructure has a forgotten yet important role in the thermal stability of polycrystalline rechargeable batteries. Oxygen release, as an important process during the thermal runaway, can be regulated through engineering grain arrangements. The grain arrangement can modulate the macroscopic crystallographic transformation pattern and oxygen diffusion length in layered cathodes to offer more possibilities for cathode material design and synthesis. Third, we will discuss our new understanding of particle behaviors in composite cathodes. We capture and quantify the particle motion during the solidification of battery electrodes and reveal the statistics of the dynamically evolving motion in the drying process, which has been challenging to resolve. We discover that the particle motion exhibits a strong dependence on its geometric location within a drying electrode. Our results also imply that the final electrode quality can be controlled by balancing the solvent evaporation rate and the particle mobility in the region close to the drying surface. We formulate a network evolution model to interpret the regulation and equilibration between electrochemical activity and mechanical damage of these particles. Through statistical analysis of thousands of particles using x-ray phase-contrast holotomography in a Ni-rich cathode, we found that the local network heterogeneity results in asynchronous activities in the early cycles, and subsequently the particle assemblies move toward a synchronous behavior. Our study pinpoints the chemomechanical behavior of individual particles and enables better designs of the conductive network to optimize the utility of all the particles during operation.

Taking earthy graphite and electrolytic powder as raw materials, copper/graphite raw material is prepared by power metallurgy and then polycrystalline diamond powder is prepared by shock wave synthesis. Impaction on yield and abrasion resistance from copper content, particle size of graphite powder, heat treatment and re-pressing process has been researched. As result, yield of polycrystalline diamond powder is decreasing as decreasing copper content. It is decreased dramatically when the copper content is less than 90%. It is increased and then decreased as increasing the particle size of graphite powder, and the better particle size of graphite powder is 70μm. It is increased slightly and then decreased dramatically as increasing heat treatment temperature before re-pressing. The higher the heat treatment temperature, the more the yield after re-pressing. Impaction on the abrasion resistance of polycrystalline diamond powder from the preparing process of copper/graphite is smaller.

We report on the synthesis of activated carbon-semi-polycrystalline polyaniline (SPani-AC) composite material using in-situ oxidative polymerization of aniline on the carbon surface in an aqueous HCl medium at an elevated temperature of 60 °C. The electroactive polymeric composite material exhibits a uniformly distributed spindle-shaped morphology in scanning electron microscopy (SEM) and well-defined crystallographic lattices in the high-resolution transmission electron microscopy (TEM) images. The X-ray diffraction (XRD) spectrum reveals sharp peaks characteristic of crystalline polyaniline. The characteristic chemical properties of polyaniline are recorded using laser Raman spectroscopy. The cyclic voltammetry curves exhibit features of surface-redox pseudocapacitance. The specific capacitance calculated for the material is 507 F g−1 at the scan rate of 10 mV s−1. The symmetrical two-electrodes device exhibits a specific capacitance of 45 F g−1 at a current density of 5 A g−1. The capacitive retention calculated was found to be 96% up to 4500 continuous charge–discharge cycles and observed to be gradually declining at the end of 10,000 cycles. On the other hand, Coulombic efficiency was observed to be retained up to 85% until 4500 continuous charge–discharge cycles which declines up to 72% at the end of 10000 cycles. The article also presents a detailed description of material synthesis, the formation of polyaniline (Pani) chains, and the role of material architecture in the performance as surface redox supercapacitor electrode.

Recent theoretical calculations have predicted that ZnO doped with Mn exhibits room-temperature ferromagnetism. This has attracted intensive interest, because of its prospective applications in spintronic devices. However, experimental studies on Mndoped ZnO materials have revealed that their magnetic properties vary from the ferromagnetic through antiferromagnetic and spin-glass to the paramagnetic. This makes the question of the origin of ferromagnetism in Mn-ZnO materials become more complicated.

Parts made out of titanium alloys demonstrate anisotropic mechanical properties when manufactured by electron beam melting, an emerging additive manufacturing technique. Understanding the process history dependent heterogeneous microstructure, and its effect on mechanical properties is crucial in determining the performance of additively manufactured titanium alloys as the mechanical behavior heavily relies on the underlying microstructural features. This thesis work focuses on combined experimental and computational techniques for microstructure characterization, synthetic microstructure generation, mechanical property measurement, and mechanical behavior modeling of polycrystalline materials, with special focus on dual phase titanium alloys. Macroscopic mechanical property measurements and multi-modal microstructure characterizations (high energy X-ray diffraction, computed tomography and optical microscopy) are performed on additively manufactured Ti-6Al-4V parts, revealing the heterogeneity of the microstructure and properties with respect to the build height. Because characterizing and testing every location within a build is not practical, a computational methodology is established in order to reduce the time and cost spent on microstructure-property database creation. First a statistical volume element size is determined for the Fast Fourier Transform based micromechanical modeling technique through a sensitivity study performed on an experimental Ni-based superalloy and syntheticW, Cu, Ni and Ti structures, showing that as the contrast of properties (e.g., texture, field localization, anisotropy, rate-sensitivity) increases, so does the minimum simulation domain size requirement. In all deformation regimes a minimum volume element is defined for both single and dual phase materials. The database is then expanded by generating statistically representative Ti structures which are modified for features of interest, e.g., lath thickness, grain size and orientation distribution, to be used in spectral full-field micromechanical modeling. The relative effect of the chosen microstructural features is quantified through comparisons of average and local field distributions. Fast Fourier transform based technique, being a spectral, full-field deformation modeling tool, is shown to be capable of capturing the relative contribution from varying microstructural features such as phase fractions, grain morphology/ size and texture on the overall mechanical properties as the results indicate that the mean field behavior is predominantly controlled by the alpha phase fraction and the prior beta phase orientation.

In recent days, the need for device miniaturization has led to immense research activities in the field of material science. It has become essential to discover and design new materials or to modify the existing materials to meet the ever-increasing demand of new multifunctional materials in the industry. In this regard, complex oxides stand out as one of the most promising material classes. In particular, multiferroic materials simultaneously possessing two or more primary ferroic orders (ferromagnetism/antiferromagnetism, ferroelectricity, ferroelasticity) offer advantages over other materials. In this research work, comprehensive studies on polycrystalline material synthesis, thin film growth and characterization pertaining to few such promising multiferroic materials are reported. Among different types of multiferroics, hexagonal (h) rare-earth manganites (h-RMnO3, R = Dy-Lu, Sc, Y) form a unique class of materials which exhibit ferroelectricity at room temperature and above by virtue of non-centrosymmetric P63cm crystal structure. The magnetic structure compatible with the hexagonal crystal symmetry is relatively complex and unique. It consists of triangular non-collinear lattice of Mn atoms in the ab basal plane which are magnetically frustrated and results in significantly lower magnetization and magnetic ordering temperatures (TN in the range of 70-130 K). Below TN, magnetic and ferroelectric orderings coexist in h-RMnO3 with evidences of magnetoelectric coupling due to which these materials gained lot of research interest. But, despite their room-temperature ferroelectric behaviour, the h-RMnO3 series of compounds are not suitable for practical multiferroic applications because their magnetic ordering temperatures are significantly lower than the room temperature. In this context, we have chosen two compounds h-LuMnO3 and h-ScMnO3 both possessing high magnetic ordering temperature among the h-RMnO3 series. Our primary motivation was on increasing the strength of magnetic interactions and the magnetic ordering temperature by doping at either A or B-site while maintaining the polar P63cm crystal symmetry intact, which yields room temperature ferroelectric properties (as in hexagonal RMnO3). Interestingly, in addition to the improved multiferroic properties of these doped h-RMnO3 samples, we observed emergence of new phenomena as a result of doping. Moreover, we found that the substrate induced epitaxial stain in the thin films of doped h-RMnO3 compounds resulted in new properties which were not discernible in bulk. Present thesis works can be broadly divided in three parts. The ‘first part’ is on 50% Fe doped LuMnO3 (i.e. LuMn0.5Fe0.5O3) compound. Due to higher magnetic moment of Fe3+ compared to Mn3+, the compound LuMn0.5Fe0.5O3 possesses improved magnetic nature compared to parent compound LuMnO3 while holding the polar P63cm crystal symmetry of LuMnO3. LuMn0.5Fe0.5O3 samples were synthesized both in polycrystalline bulk and epitaxial thin film form. Three different types of studied were performed on these samples the results of which are presented in chapters three, four, and five. In the ‘second part’ tetravalent Zr4+ ion was used for doping at the Sc3+ site in ScMnO3. This resulted in electron doping in the system. Thorough investigations relating to the effect of electron doping in multiferroic behaviour of ScMnO3 and detailed studies of the emerging new phenomena are given in chapters six and seven. The A-site tetravalent ion doping in ScMnO3 reduces the magnetic frustration; it induces ferromagnetic behaviour while preserving the polar P63cm crystal structure. The ‘third part’ of the thesis work is on thin film samples of 50% Ni doped LuMnO3. In contrast to Fe doping, 50% Ni doping in place of Mn changes the crystal symmetry of LuMnO3 to monoclinic P21/n crystal symmetry. The chemical formula of the resultant compound can be written as Lu2MnNiO6 as the compound falls under the category of double perovskites. Due to the change in crystal symmetry, the magnetic and other physical properties are found to be completely different in Lu2MnNiO6 than that in LuMnO3. These results are documented in chapter eight. A brief chapter-wise outline of the thesis is given below: Chapter 1 gives a general introduction to the physics of multiferroics and related phenomena. Brief descriptions of few relevant topics such as anti-phase boundary type crystal growth defects, exchange bias phenomenon, spin-glass, etc are also provided. Motivation for the present research work is included at the end of this chapter. Chapter 2 summarizes various experimental techniques used in this thesis and their basic working principles. It describes bulk sample preparation processes and thin film growth technique adopted. Chapter 3 presents detailed experimental characterization of the compound LuMn0.5Fe0.5O3 (LMFO) with special reference to its multiferroic magnetoelectric properties. X-ray photoemission (XPS) spectra are collected which confirmed the valence state of Mn and Fe to be +3, only. The compound stabilizes in polar hexagonal (P63cm) crystal symmetry and exhibits long-range antiferromagnetic ordering below TN = 103 K. Additionally, in the magnetization vs. temperature (M-T) data, an extra hump-type anomaly was noticed close to room temperature. This is an unseen feature in the related RMnO3 compounds. By inspection of prevalent magnetic exchange paths existing in the P63cm crystal symmetry, we have argued that its origin lies in the intraplane short range spin ordering. Heat capacity of LMFO is also measured and analysed to elucidate the magnetic entropy. This further supports the existence of intraplane spin ordering at higher temperature beyond TN. Indication of magnetoelectric coupling is obtained from dielectric anomaly at TN. Room-temperature ferroelectric behaviour is unambiguously probed by Piezo response force microscopy (PFM) and measurement of standard and remnant ferroelectric hysteresis loops. Further, from high-temperature dielectric data, the occurrence of ferroelectric transition above 900 K and relaxation due to Maxwell-Wagner interfacial polarization between grain and grain boundaries is ascertained. Chapter 4 deals with antiphase boundary (APB) defect induced anomalous weak ferromagnetism, exchange bias effect and large vertical hysteretic shift in the single-phase antiferromagnetic system LuMn0.5Fe0.5O3 (LMFO). Presence of APB-type defects in LMFO has been probed using 57Fe Mössbauer spectroscopy measurement and high-resolution transmission electron microscopy (HRTEM) technique. At the APB, the bulk super exchange interaction is modified, and the APB spin interaction gives rise to a separate component in Mössbauer spectra having unusually low internal field. From the magnetization measurements, we find that the new APB-induced magnetic interaction persists up to T*= 330 K whereas the intrinsic long-range antiferromagnetic ordering temperature is TN =103 K. Upon field cooling strong pinning effect of the APB spins lead to large vertical hysteretic shift in LMFO. Finally, post annealing the optimally sintered LMFO sample helps to understand the evolution of defects and their influence on weak ferromagnetism and exchange bias properties. It is observed that the ferromagnetic nature of LMFO becomes more pronounced as the defect content increases and also exchange bias properties of LMFO change accordingly. Chapter 5 details the results of multiferroic characterization of LuMn0.5Fe0.5O3 (LMFO) epitaxial thin film grown by pulsed laser deposition (PLD) technique on cubic (001)-SrTiO3 (STO) substrate. The films exhibit orthorhombic (Pnma) crystal symmetry and show both (0k0) and (h0h) out-of-plane orientations. In addition, HRTEM image revealed that the unit cell of LMFO also has slight monoclinic distortion. The LMFO/STO films are compressively strained along the [100] direction and tensile strained along the [010] and [001] directions. Films display weak-ferromagnetic nature along with the dominant antiferromagnetic interaction. The observed ferromagnetism has been attributed to the substrate-induced epitaxial strain in the film. Interdigitated gold electrodes were patterned using photolithography and lift-off procedures and in-plane ferroelectric hysteresis loops are measured. PFM measurements are also carried out. Interestingly, the films exhibit room-temperature ferroelectric behaviour which is likely due to the slight monoclinic tilt of the orthorhombic unit cell of LMFO in the epitaxial film. Chapter 6 reports on multiferroic properties of a series of electron doped multiferroic compound Sc1-xZrxMnO3 (x = 0, 0.05, 0.1, and 0.2). All the doped samples stabilize in P63cm structure and, as a result of Zr4+ doping, Mn2+ is generated at the expense of Mn3+. Detailed analysis of XPS spectra are carried out to confirm the presence of Mn3+, Mn2+, and Zr4+ cations. The parent compound ScMnO3 exhibits long-range antiferromagnetic ordering below TN = 130 K. As Zr4+ concentration increases in the doped systems, antiferromagnetic ordering gradually diminishes while shifting to low temperatures and additional ferromagnetic interaction gradually develops. The 20% doped sample showed significant hysteresis with greatly enhanced magnetization. Interestingly, even with zero magnetic moment of Sc3+, a Schottky-like anomaly is observed at 5 K in the heat capacity data of samples with x = 0.1 and 0.2. This we attribute to the highly resistive nature of doped samples. While measuring ferroelectric hysteresis loops, we found that the leakage current contribution is significantly reduced in case of x = 0.2 compound compared to ScMnO3. Additionally, the compound x = 0.2 shows improved dielectric and ferroelectric behaviour. It is proposed that doping of Zr4+ compensates for the cation deficiency and consequently eliminates the inherent oxygen vacancies by charge compensation. Chapter 7 explores electron-doping induced exchange bias effect and cluster glass magnetism in multiferroic Sc0.8Zr0.2MnO3 bulk material. Scanning electron microscopy (SEM) images were collected and microstructure of the sample was investigated which suggested that grain boundaries do not have any significant role in the emergence of exchange bias effect and ferromagnetism in Sc0.8Zr0.2MnO3. Detailed investigations have been carried out to study the influence of temperature, cooling field and training effect on exchange bias parameters so as to obtain insights into the real nature of the observed exchange bias. A comparison of exchange bias properties of Sc0.8Zr0.2MnO3 to the typical phase-separated exchange bias system is presented. We found compelling evidence of cluster glass magnetic nature of Sc0.8Zr0.2MnO3 by dc field dependent magnetic measurements, ac susceptibility measurements, magnetization relaxation experiments and memory tests. Chapter 8 discusses growth of epitaxial thin films of Lu2MnNiO6 (LMNO) by PLD technique on two different substrates (001)-LaAlO3 (LAO) and (001)-SrTiO3 (STO) and compares the structural and magnetic properties of these films. Evidences of simultaneous presence of both (001) and (110) oriented out-of-plane domains are obtained in the epitaxial film of LMNO. We have performed detailed investigation using X-ray diffraction, reciprocal space mapping (RSM) and HRTEM technique and found that there are total six monoclinic twin variants in the film from the (110) and (001) oriented out-of-plane domains. Both films, LMNO/LAO and LMNO/STO showed ferromagnetic behaviour. Due to very good lattice match with LAO substrate, the LMNO/LAO film grows as well-ordered film and the value of saturation magnetization is very close to what has been reported for bulk LMNO with ordered double perovskite structure. Large lattice mismatch with STO substrate resulted in disordered LMNO/STO films. It is found that the magnetic moment (MS, at maximum field of 70 kOe) is significantly reduced in disordered LMNO/STO (MS = 2.4 μB/f.u. at 70 kOe) compared to the ordered LMNO/LAO (MS = 4.0 μB/f.u. at 70 kOe). Moreover, along with the dominant ferromagnetic interactions, glassy magnetic interactions are observed in both of the films below their ferromagnetic ordering temperatures. Chapter 9 provides highlights of major findings in this thesis work and a conclusion to this study. Future prospects are briefly outlined.

Single crystals with composition Lu3Al5O12 were synthesized using Czochralski and micro-pulling-down melt growth techniques. Polycrystalline ceramics of the same composition were synthesized by vacuum annealing of powders prereacted using a citrate-nitrate combustion technique and by spark-plasma-sintering of powders prereacted using a flame-spray-pyrolysis technique. Single crystals and polycrystalline ceramics are activated with Ce3+ or Pr3+ or doubly activated with Ce3+ and Tb3+ ions. Cerium-doped Czochralski-grown single crystals were compared to cerium-terbium codoped Czochralski-grown and micro-pulling down single crystals. Cerium-terbium codoped single crystals are also compared to similarly-activated polycrystalline ceramics sintered under vacuum using combustion-synthesized prereacted powders. X-ray diffraction analysis and fluorescence characterization were used to determine successful formation of single-phase LuAG and successful incorporation of doping species. Absorbance, fluorescence, radioluminescence, and scintillation decay analyses were used to compare synthesis processes and activator selection.

An investigation into the effect of nanofluid minimum quantity lubrication (MQL) on the temperatures in surface grinding is presented and discussed. Six types of nanoparticles, namely molybdenum disulfide (MoS2), zirconium dioxide (ZrO2), carbon nanotube (CNT), polycrystalline diamond, aluminum oxide (Al2O3), and silica dioxide (SiO2), are considered to mix individually with a pollution-free palm oil in preparing the nanofluids. A commonly used Ni-based alloy was chosen as the workpiece material. It is shown that CNT nanofluid results in the lowest grinding temperature of 110.7°C and the associated energy proportionality coefficient of 40.1%. The relevant physical properties of the nanofluids such as the coefficient of thermal conductivity, viscosity, surface tension, and the contact state between the droplets and workpiece surface (contact angle) were discussed to shine a light on their effect on the cooling performance. A mathematical model for convective heat transfer coefficient was then developed based on the boundary layer theories.

The synthesis of polycrystalline powder is a key step for materials sciences. In this chapter, we present the well-known methods of preparation of powders such as: solid-state reaction, sol–gel, hydrothermal, combustion, co-precipitation. Moreover, synthesis methods by arc furnace, by heating in a “high frequency” induction furnace and by high energy grinding are presented. The obtained powders could be defined by their purity, gain size, crystallinity, and morphology, which are influenced by the synthesis method. In addition, each method is dependent on some parameters like pH, concentration and temperature.

A citrate pyrolysis technique is a unique route to prepare reactive precursor mixtures through an ignition process of concentrated aqueous solution. This procedure enables to synthesize highly homogeneous and fine powders for functional materials. The double-chain based superconductor Pr2Ba4Cu7O15−δ and double perovskite photocatalytic semiconductor Ba2Tb(Bi,Sb)O6 were synthesized by using the citrate pyrolysis technique. For the present sample with a reduction treatment for 72 h, a sharp superconducting transition appeared at an onset temperature Tc,on=26 K accompanied by a zero-resistance state at Tc,zero=22 K. The superconducting volume fraction estimated from the magnetization measurement showed an excellent value of ∼58%. Both reduction treatment in a vacuum and subsequent quenching procedure are needed to realize higher superconductivity due to further oxygen defects. The polycrystalline samples for Ba2Tb(Bi1−x,Sbx)O6 (x=0 and 0.5) were formed in the monoclinic and cubic crystal structures. We conducted the gaseous 2-propanol (IPA) and methylene blue (MB) degradation experiments under a visible light irradiation, to evaluate photocatalytic activities of the powder samples. For the Sb50% substituted sample, the highest performance of MB degradation was observed. The effect of Sb-substitution on the photocatalytic degradation of MB is in direct contrast to that on the IPA decomposition under visible light irradiation. The enhanced photocatalytic properties in the citrate samples are attributed to their morphology, where fine particles are homogeneously distributed with a submicron order.

Egyptian blue was first used as a pigment on tomb paintings in Egypt from around 2300 BC, and during the subsequent 3,000 years, its use both as a pigment and in the production of small objects spread throughout the Near East and Eastern Mediterranean and to the limits of the Roman Empire. During the Roman period, Egyptian blue was distributed in the form of balls of pigment up to about 15mm across, and appears to have been the most common blue pigment to be used on wall paintings throughout the Empire. Egyptian blue was both the first synthetic pigment, and one of the first materials from antiquity to be examined by modern scientific methods. A small pot containing the pigment that was found during the excavations at Pompeii in 1814 was examined by Sir Humphrey Davy. Subsequently, x-ray diffraction analysis was used to identify the compound as the calcium-copper tetrasilicate C_aC_uSi₄O₁₀, and to establish that Egyptian blue and the rare natural mineral cuprorivaite are the same material. Examination of Egyptian blue samples in cross-section in a scanning electron microscope (SEM) revealed that they consist of an intimate mixture of Egyptian blue crystals (i.e. C_aC_uSi₄O₁₀) and partially reacted quartz particles together with varying amounts of glass phase (Tite, Bimson, and Cowell 1984). At this stage it should be emphasized that, in the literature, the term Egyptian blue tends to be used to describe both crystals of calcium-copper tetrasilicate and the bulk polycrystalline material that is used as the pigment and is sometimes referred to as frit. In this chapter, the suffix ‘crystal’ or ‘mineral’ will be added when the former meaning applies, and the suffix ‘pigment’, ‘sample’, or ‘frit’ will be added when the latter meaning applies. For the current study, a small group of Roman Egyptian blue samples were examined using scanning electron microscopy (SEM) with attached analytical facilities. Using the chemical compositions of the samples, together with the description of the manufacture of Egyptian blue given by Vitruvius (Morgan 1960) at the beginning of the first century BC in his Ten Books on Architecture, an attempt is made to identify the raw materials used in the production of Roman Egyptian blue.

Electrodeposition techniques is used for the deposition of nickel oxide thin film electrodes. In the present work, we report electrodeposition of nickel oxide thin film on the conducting stainless steel (SS) substrates for the application of electrochemical supercapacitor. X-ray diffraction confirms simple cubic crystal structure with polycrystalline nature of the deposited NiO sample that exhibits hydrophilic nature confirmed from the wettability study. The Scanning Electron Microscope (SEM) observed dense with cracky morphology. UV spectrum exhibits 3.55eV band gap of samples. The capacitive characteristics of the deposited thin film are investigated in 1M KOH electrolyte using cyclic voltammetry (CV). The supercapacitive properties of NiO are strongly affected by the scan rate. The maximum specific capacitance obtained is 162 F/g at 2 mV/s scan rate.

Laser ablation has emerged as a novel method to synthesize a large variety of nanomaterials.1-7 Currently, most works merely focus on the material synthesis using laser ablation technique with little attention to the correlation of the ablated substrates with the synthesized materials. This work is aimed at filling this gap and giving new insights based on laser ablation of single crystal diamond-cubic (dc) (400) Si in air. Polycrystallization is a ubiquitous phenomenon occurring during laser ablation of Si. The polycrystallization rate of the ablated areas increases with increasing the laser powers, which well explains the polycrystalline instinct of the synthesized nanomaterials. Faster cooling rates of the laser-generated molten Si layers over their nucleation rates result in the surface amorphoization. With the aid of laser-generated shock waves, the molten layers together with the newly formed polycrystalline Si materials will be pushed upward in air to solidify amorphous SiOx encapsulated polycrystalline Si composites. This work tends to remind the researchers to pay more attention to the relationship between the ablated surfaces and the collected nanomaterials no matter where the laser ablation is implemented, in either air or liquids or vacuum.

The controlled synthesis of nanostructured particles with uniform size, shape, composition, and preferred orientation is a formidable task. Some conventional techniques have been demonstrated with limited success; however, reproducible processing schemes for heterogeneous multifunctional materials are still not satisfactory. To realize the advantageous technical applications of nanostructured materials, self-assembly or self-organizing methods are currently under investigation. Our results show that the matrix or template used for directed growth of nanoparticles (Fe, Ni) significantly affects the resultant mechanical properties of the multilayered structure. For example, a crystalline material like TiN, which grows epitaxially on silicon, results in embedded epitaxial nanoparticles. Conversely, an amorphous template like Al2O3 results in polycrystalline magnetic particles. In this work, we will discuss the effect of matrix type, specifically yttria stabilized zirconia (YSZ), on the orientation of nanoparticle assemblies. The resultant mechanical and magnetic properties of the multilayer structures will be discussed in the oral presentation.

Abstract Since the late 1970's, research on the efficiency and cutting life of polycrystalline diamond compact (PDC) cutters identified elevated temperature due to frictional heating as one of the primary accelerants of wear to the diamond cutting edge. Temperatures as low as 700 °C activate the back-conversion process, whereby diamond transforms into graphite, due to the presence of catalytic metal in the diamond structure. The Oil and Gas industry responded by investing years developing technologies to reduce the temperatures that PDC's experience in application via improved hydraulics for cooling, higher quality surface finishes to reduce friction, and improved thermal stability via material structure and chemical treatments. PDC cutter technology has progressed substantially in the last 30+ years, but the challenge of synthesizing a perfectly thermally stable PDC still remains unmet until now. Recently, Zhan (2018, 2020, 2021a and 2021b) first developed a new strategy to synthesize ultrastrong and catalyst-free polycrystalline diamond (CFPCD) or binderless PDC cutters with a new world record as the hardest and tough diamond material and the highest thermal stability up to 1,400°C via his invented ultra-high pressure and ultra-high temperature (UHPHT) technology, which is three to seven times higher than conventional PDC cutters used in the industry. An initial laboratory study of a new catalyst-free extreme high pressure, high temperature CFPCD material provides the first instance of a catalyst metal free polycrystalline diamond structure that actually boosts rock cutting performance above and beyond that of the current state-of-the-art PDCs. Proof of concept CFPCD specimens were evaluated against commercial, state-of-the-art non-leached (NL) and deep leached (DL) PDC cutters in the lab. Two CFPCD grades, A & B, were run through a series of tests to evaluate their potential for rock cutting and, ultimately, for use in oil & gas drilling applications. Laboratory testing was conducted on vertical borer wear tests, KIC fracture toughness tests, and thermal degradation monitoring tests. Lab results reveal a threshold that must be exceeded in the synthesis of catalyst-free CFPCDs to achieve sufficient diamond intergrowth and structural integrity to surpass the current state-of-the-art DL PDCs. CFPCD grade A wore equivalently to a commercially available NL cutter and exhibited a toughness comparable to that of commercially available DL PDC material. Grade B, synthesized at a significantly higher pressure than grade A, cut 5.7 times the distance of a commercial NL PDC for an equivalent wearscar volume, and exhibited a 160 % reduction in wear volume comparing volume of diamond worn to volume of rock cut (or G ratios) to DL PDC after cutting the equivalent of roughly 50 miles of rock. The wearscar surface of Grade B also exhibited excellent integrity with no cracking or chipping damage compared to Grade A and commercial PDC grades. This is the first documented instance of a catalyst-free PDC achieving the best wear performance and integrity (fracture toughness) than the current PDC cutters offering on the market. Thermal stability limits of PDC cutters has greatly improved in the past 20 years, but the best commercial PDC's still rely on extending leach depths with certain performance limits. For the first time in the industry, there is a PDC material than shifts this boundary without the use of catalysts and leaching technology, producing a truly differentiable PDC cutter.

In this work, an experimental heat transfer investigation was carried out to investigate the combined influence of both amorphous carbon (a-C) layer thickness and carbon nanofibers (CNFs) on the convective heat transfer behavior. Synthesis of these carbon nano structures was achieved using catalytic chemical vapor deposition process (CCVD) on a 50 μm nickel wire at 650°C. Due to their extremely high thermal conductivity, CNFs are used to augment/modify heat transfer surface. However, the inevitable layer of a-C that occurs during the synthesis of the CNFs layer exhibit low thermal conductivity which may result in insulating the surface. In contrast, the amorphous layer helps in supporting and mechanical stabilizing of the CNFs layer attachment to the polycrystalline nickel (Ni270) substrate material. To better understand the influences of these two layer on heat transfer, the growth mechanism of the CNFs layer and the layer of carbon is investigated and growth model is proposed. The combined impact of both a-C and CNFs layer on heat transfer performance is studied on three different samples which were synthesized by varying the deposition period (16 min, 23min and 30 min). The micro wire samples covered with CNF layers were subjected to a uniform flow from a nozzle. Heat transfer measurement was achieved by a controlled heat dissipation through the micro wire to attain a constant temperature during the flow. This measurement technique is adopted from hot wire anemometry calibration method. Maximum heat transfer enhancement of 18% was achieved. This enhancement is mainly attributed to the surface roughness and surface area increase of the samples with moderate CNFs surface area coverage on the sample.

Two-dimensional (2D) materials such as transition metal dichalcogenides (TMDCs) have recently emerged as an exciting class of quantum materials that can enable technological advancement in various fields, including electronics, optoelectronics, and photonics. Therefore, there is a significant demand for high-quality crystal growth and wafer-scale integration methods to transition their exciting properties from lab to fab. Here, I will discuss some of the laser-based synthesis techniques we have developed to control the growth of both single-crystalline 2D flakes and large-scale polycrystalline 2D films for wafer-scale electronics. I will report the synthesis of the highest-quality single-crystalline monolayers using the laser-assisted vapor phase growth method directly from stoichiometric powders. I will particularly highlight our condensed phase growth approach compatible with direct laser writing as well as the conventional lithography and device integration technologies. Patterned integration of 2D materials on both flexible and rigid substrates will be demonstrated. The crystal structures, quality, and device performance will also be discussed and compared with the common growth methods. These laser-based approaches provide unique synthesis and processing opportunities that are not easily accessible through conventional methods.

ZnO is a well-known traditional industrial material which has high potential to become one of the key components for the next generation of future electronics, LED emitters, visible light photocatalysis and others. In its pristine form ZnO has relatively wide band gap of approximately 3.4 eV, but a lot of emerging applications requires some level of electronic structure engineering and structure optimisation. Studies show that ZnO properties strongly depend on the intrinsic defects type and concentrations. Both characteristics usually are depending on the synthesis method. Accordingly, there is great interest to develop new methods which would allow to obtain ZnO with optimised band gap and other properties. In current, study ZnO films were deposited using reactive magnetron sputtering with unconventional Ar-O2 gas mixture supply control: Ar flow was controlled to maintain total gas pressure at 1x10-2 mbar, whereas O2 flow rate was actively adjusted to maintain the selected intensity of optical zinc emission from the working cathode zone. Applying such ZnO formation method it was possible to stabilise reactive magnetron sputtering process over wide range of conditions. Elemental composition analysis by XPS revealed that despite large variations in Zn emission peak intensity within tested experimental conditions all films had nearly identical Zn:O ratios but at the same time their structural and optical properties differed significantly. The colour of the films varied from highly transparent yellowish-greenish, to intense orange, to opaque black. XRD analysis showed that films consisted of single polycrystalline wurtzite phase with varying orientations. PL spectroscopy analysis revealed that films had a lot of various defects including oxygen and zinc vacancies, interstitials and surface defects. Wide variation of ZnO properties obtained by different reactive sputtering conditions demonstrates the potential of the proposed method to control the formation of various intrinsic defects and to tailor their concentration.

Abstract Polycrystalline diamond compact (PDC) bits have been increasing their application drilling many formations in the past 20+ years. However, their performance in drilling very hard, abrasive and interbedded formations still needs improvement. The main weak point comes from their primary cutting elements, PDC cutters, which still need improvements of wear resistance, impact resistance, and thermal stability. During the traditional manufacturing of the PDC cutters, cobalt catalyst has to be used to lower the pressure and temperature. In this study, we developed an ultra high pressure and high temperature (UHPHT) technology to make the PDC cutters without metallic catalyst into reality. Through this development, we can generate pressures of 14 GPa-35 GPa, which is three to seven times of that in the traditional PDC cutter manufacturing technology. In addition, the extreme high temperatures ranging from 1,900 °C to 2,300 °C are achieved, which is 500-900 °C higher than that in traditional process. Using this UHPHT technology, we successfully processed ultra-strong and catalyst-free PDC materials with two high pressures at 14 GPa and 16 GPa, respectively, to study the different responses of the material properties from different processing parameters. The new process applied industry available micro-sized synthetic diamond powders as starting material to eliminate the large volume shrinkage in phase transformation from graphite to diamond which is typically experienced in traditional manufacturing process. The hardness of the 14-GPa CFPCD materials reaches the top limit of the single crystal diamond, more than double that of the traditional PDC cutters. The material also possesses the near-metallic fracture toughness – more than two times of the traditional PDC cutters. Furthermore, the 16-GPa CFPCD material breaks all four single crystal diamond indenters in Vickers hardness tester, an indication of the world's hardest material in the family of diamonds. As a result, the material exhibits industry-recorded wear resistance and thermal stability. The combination of these breakthrough properties of the new CFPCD materials activates the goal in the effort of "One-Run-To-TD" in drilling operation, after the implementation of CFPCD materials as PDC cutters for PDC drill bits.