Large Polycrystalline Research Articles

Capping Agents Enable Well-Dispersed and Colloidally Stable Metallic Magnesium Nanoparticles.

Mg nanoparticles are an emerging plasmonic material due to Mg's abundance and ability to sustain size- and shape-dependent localized surface plasmon resonances across a broad range of wavelengths from the ultraviolet to the near infrared. However, Mg nanoparticles are colloidally unstable due to their tendency to aggregate and sediment. Nanoparticle aggregation can be inhibited by the addition of capping agents that impart surface charges or steric repulsion. Here, we report that the common capping agents poly(vinyl) pyrrolidone (PVP), polyethylene glycol (PEG), cetyltrimethylammonium bromide (CTAB), and sodium dodecyl sulfate (SDS) interact differently and have varied effects on the aggregation and colloidal stability of Mg nanoparticles. Nanoparticles synthesized in the presence of PVP showed improvements in colloidal stability and reduced aggregation, as observed by electron microscopy and optical spectroscopy. The binding of PVP was confirmed through infrared and X-ray photoelectron spectroscopy. The influence of PVP on the reduction of di-n-butyl magnesium was evaluated through analysis of particle size distribution and Mg yield as a function of reaction time, reducing agent, and temperature. Furthermore, the presence of PVP drastically changes the growth pattern of metallic Mg structures obtained from the reduction of the Grignard reagents butylmagnesium chloride and phenylmagnesium chloride by lithium naphthalenide: large polycrystalline aggregates and well-separated faceted nanoparticles grow without and with PVP, respectively. This study provides new synthetic routes that generate colloidally stable and well-dispersed Mg nanoparticles for plasmonic and other applications.

Amphoteric Chelating Ultrasmall Colloids for FAPbI3 Nanodomains Enable Efficient Near-Infrared Light-Emitting Diodes.

Perovskite light-emitting diodes (PeLEDs) are the next promising display technologies because of their high color purity and wide color gamut, while two classical emitter forms, i.e., polycrystalline domains and quantum dots, are encountering bottlenecks. Weak carrier confinement of large polycrystalline domains leads to inadequate radiative recombination, and surface ligands on quantum dots are the main annihilation sites for injected carriers. Here, pinpointing these issues, we screened out an amphoteric agent, namely, 2-(2-aminobenzoyl)benzoic acid (2-BA), to precisely control the in situ growth of FAPbI3 (FA: formamidine) nanodomains with enhanced space confinement, preferred crystal orientation, and passivated trap states on the transport-layer substrate. The amphoteric 2-BA performs bidentate chelating functions on the formation of ultrasmall perovskite colloids (<1 nm) in the precursor, resulting in a smoother FAPbI3 emitting layer. Based on monodispersed and homogeneous nanodomain films, a near-infrared PeLED device with a champion efficiency of >22% plus enhanced T80 operational stability was achieved. The proposed perovskite nanodomain film tends to be a mainstream emitter toward the performance breakthrough of PeLED devices covering visible wavelengths beyond infrared.

Blue-white electroluminescence of diamond/WS2 quantum dot composite films

Two kinds of diamond films with completely different morphologies were prepared on N-type heavily doped silicon wafers by microwave plasma chemical vapor deposition (MPCVD) method, namely, micron-scale large grain polycrystalline diamond film dominated by (220) crystal plane (220DF) and nano-scale small grain polycrystalline diamond film dominated by (111) crystal plane (111DF). And WS2 quantum dot powder was obtained by aqueous liquid phase ultrasonic method. Then, the 111DF/WS2 quantum dot composite structure film (111DWSF) and 220DF/WS2 quantum dot composite structure film (220DWSF) were prepared by applying WS2 quantum dot powder uniformly on diamond film substrate. The results of electroluminescence (EL) detection show that the 220DWSF device emits visible blue light, and the main peak of EL spectrum is located at 443 nm in the blue region. The 111DWSF device emits white light, and the corresponding EL spectra show strong emission peaks in the blue region (454 nm), green region (536 nm) and red region (632 nm) respectively, meanwhile, the luminous intensity of 111DWSF device is much higher than that of 220DWSF device. In addition, it is also found that the 220DWSF EL device does not show obvious rectification characteristics, while the 111DWSF EL device has obvious rectification characteristics. After FN fitting of the IV characteristic curve of 111DWSF EL device, the tunneling characteristics of electrons are found in the region of high electric field intensity.

(Invited) Processing of Perovskite Materials for Optoelectronic Devices

Among materials used for thin film technologies, perovskite materials have emerged as one of the rising stars for optoelectronic applications. They show great promise for several applications like e.g. photovoltaics, lasers, light emitting diodes or X-ray detectors. Their success is founded on the feature of some perovskite materials to be largely tolerant to the formation of defects, which enables functional layer deposition from liquid precursor inks. In order to exploit the extraordinary optoelectronic properties, it is necessary to adapt the material processing to the requirements of the application. For a large spectrum of devices, homogeneous, high quality, large grain poly-crystalline perovskite layers are required. Accordingly, our work strives to cover the whole spectrum of the layer formation ranging from the perovskite precursor ink chemistry, the deposition process to post-processing and re-crystallization.Regarding the precursor ink, we spotlight the complex formation of the lead halide species by nuclear magnetic resonance and electrical conductivity measurements. We found a strong and systematic impact of the choice of (Lewis base) solvent on the formation of lead complexes in the precursor solution. Surprisingly, a strong difference in the complex formation, not necessarily translates to notable differences in the resulting layers. Indeed, the difference observed in solvation and coordination appears to become less for increased concentrations of the precursor ink. As such we assume, that throughout the drying process, the impact of lead-solvent complexes observed in the ink might diminish. To add another parameter, we also included Lewis-base additives into our investigations, that evidently modify the shape and size of the crystallites in the resulting layers. Despite their far higher donor number, we found the additive to only marginally impact on the lead core in the liquid precursor. Rather, by in-situ GIWAXS characterization, we could show that the intake of thermal energy during the annealing process proves crutial for changes in the crystal formation. After a gas-quenching process, where the perovskite phase is already present, the formation process with and without additive did not show notable differences. Subsequent thermal annealing of the deposited layers on the other hand allows the coordination between lead and the additive and affords a re-organization of the perovskite phase. During the deposition process, anyhow, the process technology (like gas quenching) is still important to form a homogeneous and pinhole-free initial film, which then can reorganize to form a high-quality perovskite layer.In the second part of the presentation, we will show, that the strategy of thermally assisted reorganization is not limited to the initial annealing step. By using a thermal hot-pressing process, we are also able to trigger the perovskite re-organization and re-crystallization even if the perovskite deposition and formation process is already finished. We performed post-processing by providing thermal energy, while simultaneously limiting the available space where potential perovskite decomposition products could leak, by pressing it with a flat stamp. As a result, the perovskite recrystallizes and forms extremely smooth layers that comprise large grains and express remarkable optical quality. We show this strategy to be applicable to a large variety of different hybrid as well as all-inorganic perovskite materials. Employing patterned stamps, we also utilize this strategy to directly imprint photonic nanostructures (e.g. Bragg gratings) into the perovskite layers.We will show how additive driven reorganization and thermal imprint enable a variety of optoelectronic devices ranging from light harvesting (single-junction and tandem perovskite based solar cells) to stimulated light emission (perovskite lasers).

Triple junction disclinations in severely deformed Cu–0.4%Mg alloys

Stress fields arising from triple junction disclinations (TJDs) play a significant role in the microstructure evolution during the plastic deformation of metals. The calculation of TJD strengths from grain orientation data was developed by Bollmann more than 50 years ago, but so far applied only to collections of a few grains. Developed here is a new methodology for calculating TJD strengths and the associated stress fields in large polycrystalline assemblies using experimental electron back-scattered diffraction (EBSD) maps. The methodology combines Bollmann’s approach with a representation of materials as cell complexes. It is computationally efficient and allows for obtaining the spatial distribution of TJD strengths from EBSD images containing thousands of grains. Analysed are the fraction, distribution, and strengths of TJDs within statistically representative microstructures of Cu–0.4%Mg alloy subjected to severe plastic deformation (SPD) by equal channel angular pressing. It is shown that the formation of low-angle grain boundaries (dislocation walls) during SPD leads to an increasing number of TJDs, whose spatial distribution is progressively more uniform and whose strength distribution remains nearly constant. This result suggests that the SPD reduces the internal stresses associated with disclinations in large regions of the material, as closely situated disclinations screen each other’s fields. Regions with high local stresses can be expected between sparsely distributed TJDs with the highest strengths. The average distance between such TJDs could be considered as a natural length scale in a material.

Temperature effects on elastic constants and related properties of apatites

The application of apatites, a class of naturally occurring calcium phosphate minerals with the most common forms being hydroxyapatite (HAP), fluorapatite (FAP) and chlorapatite (ClAP), range from primary production of phosphorus, to bone and dental implants, to potential usage in carbon sequestration and nuclear waste immobilization including those that involve exposure to high temperatures. Due to their hexagonal structure, apatites have five independent elastic constants: nevertheless, experimental studies commonly report isotropic properties, and limited computational results available in the literature exhibit a large scatter. Moreover, investigation of temperature dependence of apatite elastic properties which would be essential for designing future applications is yet to be addressed in the current state of the art. In this work, we evaluate the single crystal elastic constants of the three apatite structures using stress–strain relationships: first from density functional theory (DFT) using ultrasoft pseudopotential with PBEsol exchange–correlation functional under generalized gradient approximation (GGA) on a single unit cell , and then with molecular dynamics (MD) with a 5×5×5 unit cell using a core–shell based potential model at temperatures varying from 10K to 1500K. In this temperature range, apatites exhibit the highest stiffness along the ‘c’ axis, and their elastic constants noticeably decrease with increasing temperature. At very high temperatures, C33 becomes greater than C11 for both FAP and ClAP. It is noteworthy that our DFT study exhibits better conformity with experimental findings when compared to other DFT studies reported in literature. Additionally, MD studies have demonstrated favorable consistency in predicting elastic constants, potentially as a result of fitting potential parameters to experimental data. We also calculate various effective isotropic elastic properties from our single crystal MD results and study their temperature dependence as a substitute for first principles modeling of large polycrystalline systems. All the apatites have very comparable bulk, shear, and elastic moduli, but FAP has slightly higher values, and interestingly, HAP’s Poisson’s ratio shows no variation with temperature. This study sets the baseline with which any future studies on high-temperature applications of apatites (such as carbonate or radionuclide rich apatites) can be compared.

Character and Distribution of Geometrically Necessary Dislocations in Polycrystalline Tantalum.

Geometrically necessary dislocations (GNDs) play a key role in accommodating strain incompatibility between neighboring grains in polycrystalline materials. One critical step toward accurately capturing GNDs in deformation models involves studying the microstructural features that promote GND accumulation and the resulting character of GND fields. This study utilizes high-resolution electron backscatter diffraction to map GND populations in a large polycrystalline sample of pure tantalum, under simple tension. A total of 1,989 grains, 3,518 grain boundaries (GBs), and 3,207 triple junctions (TJs) were examined in a subsurface region of the sample. Correlations between GND density and GB character, and to some extent, TJ character, are investigated. Statistical geometrical relationships between these entities are quantified, and also visualized, using a novel application of two-point statistics. The nature of GNDs across the sample is also visualized and assessed using a recently developed method of mapping the local net Burgers vectors. The different approaches to characterizing GND distribution are compared in terms of how they quantify the size of near boundary gradient zones.

The surface chemistry of ionic liquid-treated CsPbBr3 quantum dots.

The power conversion efficiencies of lead halide perovskite thin film solar cells have surged in the short time since their inception. Compounds, such as ionic liquids (ILs), have been explored as chemical additives and interface modifiers in perovskite solar cells, contributing to the rapid increase in cell efficiencies. However, due to the small surface area-to-volume ratio of the large grained polycrystalline halide perovskite films, an atomistic understanding of the interaction between ILs and perovskite surfaces is limited. Here, we use quantum dots (QDs) to study the coordinative surface interaction between phosphonium-based ILs and CsPbBr3. When native oleylammonium oleate ligands are exchanged off the QD surface with the phosphonium cation as well as the IL anion, a threefold increase in photoluminescent quantum yield of as-synthesized QDs is observed. The CsPbBr3 QD structure, shape, and size remain unchanged after ligand exchange, indicating only a surface ligand interaction at approximately equimolar additions of the IL. Increased concentrations of the IL lead to a disadvantageous phase change and a concomitant decrease in photoluminescent quantum yields. Valuable information regarding the coordinative interaction between certain ILs and lead halide perovskites has been elucidated and can be used for informed pairing of beneficial combinations of IL cations and anions.

Effects of processing parameters on the morphologies of complex sesquioxide thin films

Controlling and predicting the morphology of lanthanide sesquioxides in thin film form is vital to their use in current applications. In the present study, single and codeposited Sm2O3, Er2O3, and Lu2O3 thin films were grown on yttria-stabilized zirconia (8%) substrates by radio frequency magnetron sputtering at room temperature and 500 °C. The effect of two different substrate temperatures and altering the oxide cation on the structural and morphological properties of the films was analyzed. The thin films were characterized by profilometry, scanning electron microscopy, transmission electron microscopy, and x-ray diffraction. The single-component Lu2O3 and Sm2O3 films obtained were of the cubic phase, and the Er2O3 was a mix of cubic and monoclinic phases. It was observed for both the Er2O3 and Lu2O3 films that increasing the substrate temperature to 500 °C resulted in larger grained polycrystalline films. In contrast, large grained polycrystalline films were obtained at both room temperature and 500 °C for Sm2O3 and uneven granularity increased as temperature increased. Codeposition of Lu2O3 and Sm2O3, and Lu2O3 and Er2O3 resulted in a cubic bixbyite phase (the C phase of the lanthanide sesquioxide) solid solution. It was observed that the structure and morphology of the films can be controlled by manipulating deposition parameters. Both substrate temperature and altering the oxide cation contributed to changes in crystallinity and grain structure, which can modify the chemical and physical properties of the films for their applications.

Influence of the cooling rate in annealing post-treatment on small molecule with siloxane side chains for solution-processed organic field-effect transistors

In this study, a donor-acceptor-type small molecule possessing a narrow bandgap with siloxane-terminated side chains, namely, S-LBG, was synthesized and characterized to be used as a semiconducting layer in organic field-effect transistors (OFETs). The diketopyrrolopyrrole (DPP)-based small molecule contains silaindacenodithiophene as an electron-donor core and 2-(1,1-dicyanomethylene)rhodanine as an electron-accepting end group. S-LBG films show highly crystalline structures after thermal annealing treatment owing to the strong intermolecular interactions between its siloxane side chains; furthermore, a smooth-surface film with a large polycrystalline grain size can be fabricated by controlling the cooling rate after annealing. Solution-processed OFETs using cooled S-LBG films at a rate of 1 °C/min and exhibits a high hole mobility of 0.102 cm2 V−1 s−1 with a π–π stacking distance of 0.659 nm.

Rapid in-situ phosphorus injection synthesis of large quantity InP polycrystalline

In this paper, a large quantity rapid in-suit phosphorus injection synthesis technology of InP polycrystalline is presented. 20 Kg high-purity InP melt has been synthesized in 170 min, which is the fastest and largest synthesis of InP polycrystalline reported so far. Melt temperature and phosphorus injection rate are two key parameters affecting the synthesis result. Synthesis experiments were carried out under various melt temperatures, the optimal synthesis temperatures of two synthesis processes were determined. The phosphorus injection rate was controlled by adjusting the injector heating power. The injector heating power curves were optimized through experiments. The synthesized InP polycrystalline were characterized by Hall effect measurement and glow discharge mass spectrometer. The results show that the carrier concentration and mobility of synthesized 20 Kg stoichiometric InP polycrystalline were <2.0E15 cm−3 and> 4600 cm2 V−1 s−1, respectively. The results also show that high melt temperature, increase of synthesis time and deviation from stoichiometry will increase the concentration of impurities and reduce the purity of synthesized polycrystalline. It was found that synthesis rate increases with synthesis quantity. With the increase of synthesis quantity, the carrier mobility of polycrystalline increases, the carrier concentration decreases, and the polycrystalline quality can be improved.

The novel and facile electrolysis method for removing the cobalt binder phase from large diameter polycrystalline diamond compacts

The thermal stability, wear resistance and impact toughness of polycrystalline diamond compact (PDC) are the primary determining variables in determining the performance. The cobalt binder contributes significantly to the PDC's thermal stability and wear resistance. To increase the thermal stability of the PDC, this paper used electrolysis to remove the cobalt binder from the polycrystalline diamond (PCD) layer of the PDC with a diameter of 62 mm. The optimal process parameters for cobalt removal via electrolysis were determined by examining the electrolyte concentration, the electrolytic voltage, and the electrolytic time. The cobalt removal impact was evaluated using a scanning electron microscope (SEM), an energy dispersive spectrometer (EDS), an X-ray diffraction (XRD), and thermogravimetric analysis-differential thermal analysis (TG-DTA). In addition, the abrasion ratio of the PDC samples were tested. The experimental results indicated that the optimal electrolysis parameters for cobalt removal were obtained when the concentration of cobalt sulphate was 4 g/100 mL, the electrolysis voltage was 2.5 V, and the electrolysis time was 10 h; in this case, the cobalt removal rate from the PCD layer exceeded 80%, and the cobalt removal depth was 372 μm. TG-DTA analysis revealed that the thermal stability of PDC was significantly enhanced as a result of the initial graphitization temperature of the cobalt removal sample being increased from 1071 °C to 1113 °C, but the abrasion ratio rose by more than 20%. It was discovered that electrolysis may efficiently remove the cobalt binder phase from the PCD layer, therefore improving the thermal stability and wear resistance of PDC.

Growth and characterization of crystalline Bi2Se3 thin films on flexible metal foils by magnetron sputtering system

We report the large area thin film deposition of Bi2Se3 on flexible thin molybdenum (Mo) and titanium (Ti) metal foils using magnetron sputtering technique at temperature of 400 °C. The crystallinity of post-selenized thin film was investigated using x-ray diffraction and high intense peaks of Bi2Se3 (0006) along other planes was obtained which showed the preferred orientation along c-axis on these polycrystalline substrates. Raman spectroscopy showed three main characteristic Raman peaks i.e. A11g, E2g, and A21g which revealed the formation of pure hexagonal phase of the Bi2Se3. Field emission scanning electron microscopy studied showed hexagonal nanoflakes shape Bi2Se3 films with large granular sizes ranging from 200 to 450 nm and stoichiometry of Bi2Se3 thin film was confirmed by energy dispersive x-ray analysis. The growth of crystalline hexagonal phase of Bi2Se3 thin films on large area polycrystalline low cost flexible metal foils using magnetron sputtering system pave the way for futuristics flexible energy devices.

Dissolution of Kidney Stones; Nano and Micro Morphologies Developed During Remelting

We have synthesized calcium oxide and calcium oxalate based kidney stones and investigated remelting to understand the process of dissolution. The dissolution morphology and remelting process in water was observed for the pure and intensely impurity doped oxalateurate stones grown at lower pH to study effect of acidity, and pH near actual pH of the stomach. Direct observation showed different melting morphologies. We observed needles, plates, dendrites, and lamella depending on the pH level and impurities. Remelting studies indicated that during breaking of large polycrystalline bunched stones grown at lower pH break into faceted small crystals which dissolve into the solvent depending on the acidity pH and impurities. High purity stones grown near stomach pH (6.4-7.5) tends to grow in needles morphology which dissolve slowly and fragment into smaller needles. A comparison was made with real kidney stones observed at Herring laboratory and similarity was observed with impurity doped stones. There was significant difference in decomposition of pure and impurity doped stones. Thermal analysis (DTA) showed that sugar doped oxides decompose continuously.

High Resolution Residual Strain/Stress Measurements on Three Axis Neutron Diffractometer

Focusing 3-axis diffractometer set-up equipped with bent perfect crystal (BPC) monochromator and analyzer offers the sensitivity in determination of strains Dd/d &lt; 10-4 in polycrystalline materials which is about one order of magnitude higher with respect to that of conventional 2-axis neutron scanners. It also offers possibility of line profile analysis for reasonable sample volumes and counting times. In this paper, the feasibility of using the 3-axis set-up even for measurements of rather large bulk polycrystalline samples with an acceptable resolution is presented. As the 3-axis set-up exploits focusing in real and momentum space, by a proper adjustment of the curvature of the analyzer, a high-resolution determination of the lattice changes can also be achieved even on large irradiated gauge volumes, though with a slightly relaxed resolution. It can be successfully exploited namely, in the strain/stress measurements on samples exposed to an external load, e.g. in tension/compression rig, in aging machine etc. In addition to the original performance where the analysis is carried out by rocking the BPC analyzer and the neutron signal registered by a point detector, a new alternative is offered which uses a fixed rocking angle position of the analyzer and the detector signal is registered by a one-dimensional position sensitive detector (PSD). This trick makes possible in some cases the elastic strain/stress measurements considerably faster and thus reduces the drawback of the time consuming step-by-step analysis.

Bioengineering, characterization, and biological activities of C@CuO@Cu nanocomposite based-mediated the Vicia faba seeds aqueous extract

Vicia faba seeds are a rich source of polyphenolic, and flavonoid compounds that have high antioxidant activity. The aqueous extract of V. faba seeds has been used for the biosynthesis of a nanocomposite (NC) consisting of three different types of nanoparticles that are deposited onto each other as [email protected]2[email protected]. Physicochemical, optical, electrical, and morphological properties of the as-biofabricated [email protected]2[email protected] NC were characterized using different analytical techniques as X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), Ultraviolet–visible spectroscopy (UV–Vis), Photoluminescence (PL), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDX), Raman, Zeta-potential, and water/moisture content). Results confirmed that V. faba seeds aqueous extract mediated the fabrication of [email protected]2[email protected] NC at high and pure crystalline nature. The nano-formulation had a face center cubic crystallographic system at the nano-scale range using Debye–Scherrer's equation (13.8 nm) in XRD analysis and (20.9 ± 6.2 nm) using TEM analysis. The crystallinity index (1.6) with a large surface area and polycrystalline nature were being investigated. In addition, the biological activity of the synthesized NC was analyzed. [email protected]2[email protected] NC showed high anti-inflammatory activity compared with diclofenac potassium with IC50 = 213.3 μg/mL. Moreover, the nano-formulation had a potent antibacterial activity, particularly against Gram-negative bacteria. Cytotoxicity of the [email protected]2[email protected] NC against MCF7, HCT116, and HepG2 cell lines showed efficient cytotoxic impact with IC50 = 84.8, 116.1, and 120.5 μg/mL, respectively. So, the nanocomposite [email protected]2[email protected] may provide a promising platform for the effective treatment of different types of cancer.

Unveiling a critical thickness in photocatalytic TiO2 thin films grown by plasma-enhanced chemical vapor deposition using real time in situ spectroscopic ellipsometry

TiO2 thin films of various thicknesses have been deposited on silicon at low-temperature by PECVD operating in continuous mode (T < 130 °C) and pulsed mode (T < 80 °C) using oxygen/titanium isopropoxide low-pressure inductively coupled plasma. The study of the crystallinity and microstructure of the films by atomic force microscopy, scanning electron microscopy and x-ray diffraction allowed showing that the roughness and amount of anatase are closely related to the film thickness. The coalescence of large polycrystalline columns emerging from an assembly of thin columns was found to happen at a critical thickness, at about 150 nm in the continuous mode and 250 nm in the pulsed mode. Real time in situ spectroscopic ellipsometry study allowed to monitor the growth and to determine this critical thickness for both plasma modes. The change of morphology type to large columnar structure is associated with an important increase in the photocatalytic activity. The determination of this coalescence thickness by ellipsometry may provide an interesting method to evaluate the impact of process parameters on TiO2 thin films characteristics.

Performance of CVD diamond detectors for single ion beam-tagging applications in hadrontherapy monitoring

In the context of online ion range verification in particle therapy, the CLaRyS collaboration is developing Prompt-Gamma (PG) detection systems. The originality in the CLaRyS approach is to use a beam-tagging hodoscope in coincidence with the gamma detectors to provide both temporal and spatial information of the incoming ions. The ion range sensitivity of such PG detection systems could be improved by detecting single ions with a 100ps (σ) time resolution, through a quality assurance procedure at low beam intensity at the beginning of the treatment session. This work presents the investigations that led to assessment of the Chemical Vapor Deposition (CVD) diamond detectors performance to fulfill these requirements. A 90Sr beta source, 68MeV protons, 95 MeV/u carbon ions and a synchrotron X-ray pulsed beam were used to measure the time resolution, single ion detection efficiency and proton counting capability of various CVD diamond samples. An offline technique, based on double-sided readout with fast current preamplifiers used to improve the signal-to-noise ratio, is also presented. The different tests highlighted Time-Of-Flight resolutions ranging from 13ps (σ) to 250ps (σ), depending on the diamond crystal quality and the particle type and energy. The single 68MeV proton detection efficiency of various large area polycrystalline (pCVD) samples was measured to be >96% using coincidence measurements with a single-crystal reference detector. Single-crystal CVD (sCVD) diamond proved to be able to count a discrete number of simultaneous protons while it was not achievable with a polycrystalline sample. Considering the results of the present study, two diamond hodoscope demonstrators are under development: one based on sCVD, and one of larger size based on pCVD. They will be used for the purpose of single ion as well as ion bunches detection, either at reduced or clinical beam intensities.

Optimizing the cellular automata finite element model for additive manufacturing to simulate large microstructures

This study proposes an implementation of the cellular automata finite element (CAFE) model in order to optimize its performance for simulating the solidification of additively manufactured (AM) materials. The translating melt pool in AM leads to a highly localized region of activity at any given time. The time scale associated with the evolving temperature field is much larger than the time scale associated with grain solidification. A separation of temporal scales is proposed such that solidification analysis is treated independently as sub-cycles within each discrete time step of the scanning laser. At each laser time step, all of the domain is idle except a small portion, which is the region where the material is undercooled but has yet to be solidified. This region is identified, and a second partition of the computational resources is established such that the solidification computations are evenly balanced. Numerical studies demonstrate that the proposed implementation achieves dramatic improvement in parallel scalability than previously reported and thus advances the state-of-the-art of CAFE modeling for AM in terms of computational efficiency. This improved computational performance is necessary to simulate the large 3D polycrystalline microstructures required to evaluate texture and grain morphology, and two of such simulations are presented. The model is validated for laser powder bed fusion 316L stainless steel, where the polycrystalline grain morphology and crystallographic texture of the simulated microstructure closely match experimental characterization data. A second simulation is performed for a different scan pattern in order to highlight and evaluate its effect on microstructural features.

Electrochemo‐Mechanical Effects on Structural Integrity of Ni‐Rich Cathodes with Different Microstructures in All Solid‐State Batteries

AbstractThe electrochemo‐mechanical effects on the structural integrity of electrode materials during cycling is a non‐negligible factor that affects the cyclability and rate performance of all solid‐state batteries (ASSBs). Herein, combined with in situ electrochemical impedance spectroscopy (EIS), focused ion beam (FIB)–scanning electron microscope (SEM), and solid state nuclear magnetic resonance (ssNMR) techniques, the electrochemical performance and electrochemo‐mechanical behavior are compared of conventional polycrystalline NCM811 (LiNi0.8Co0.1Mn0.1O2), small‐size polycrystalline NCM811 and single‐crystal (S‐) NCM811 in Li10SnP2S12 based ASSBs during long charge–discharge cycles. The results show that the deteriorating performance of both large and small polycrystalline NCM811 originates from their inherent structural instability at &gt;4.15 V, induced by the visible voids between the randomly oriented grains and microcracks due to the electrode pressing process and severe anisotropic volume change during cycling, rather than lithium ion transport in the primary particle. In contrast, S‐NCM811 with good microstructural integrity show remarkably high capacity (187 mAh g−1, 18 mA g−1), stable cyclability (100 cycles, retention of 64.5%), and exceptional rate capability (102 mAh g−1 at 180 mA g−1) in ASSBs even without surface modification. Moreover, 1 wt% LiNbO3@S‐NCM811 further demonstrates excellent initial discharge capacity and capacity retention. This work highlights the critical role of electrochemo‐mechanical integrity and offers an promising path towards mechanically‐reliable cathode materials for ASSBs.