Phase Modification Research Articles

Observation of Si 2p Core‐Level Shift in Si/High‐κ Dielectric Interfaces Containing a Negative Charge

AbstractNegative static charge and induced internal electric field have often been observed in the interfaces between silicon and high‐κ dielectrics, for example Al2O3 and HfO2. The electric field provides either beneficial (e.g., field‐effect passivation) or harmful (e.g., voltage instability) effect depending on the application. Different intrinsic and extrinsic defects in the dielectric film and interface have been suggested to cause the static charge but this issue is still unresolved. Here spectroscopic evidence is presented for a structural change in the interfaces where static charge is present. The observed correlation between the Si core‐level shift and static negative charge reveals the role of Si bonding environment modification in the SiO2 phase. The result is in good agreement with recent theoretical models, which relate the static charge formation to interfacial atomic transformations together with the resulting acceptor doping of SiO2.

Modification of the third phase in the framework for vertebrate species persistence in urban mosaic environments.

Urbanisation is rapidly transforming natural landscapes with consequences for biodiversity. Little is documented on the response of African wildlife to urbanisation. We reviewed case studies of vertebrate species' responses to urbanisation in KwaZulu-Natal, South Africa to determine trends. Connected habitat mosaics of natural and anthropogenic green spaces are critical for urban wildlife persistence. We present a novel modification to the final of three phases of the framework described by Evans et al. (2010), which documents this sequence for vertebrate species persistence, based on the perspective of our research. Species in suburbia exhibit an initial phase where behavioural and ecological flexibility, life-history traits and phenotypic plasticity either contribute to their success, or they stay at low numbers. Where successful, the next phase is a rapid increase in populations and distribution; anthropogenic food resources and alternate breeding sites are effectively exploited. The modified third phase either continues to spread, plateau or decline.

Non‐Volatile Reconfigurable Integrated Photonics Enabled by Broadband Low‐Loss Phase Change Material

AbstractPhase change materials (PCMs) have long been used as a storage medium in rewritable compact disk and later in random access memory. In recent years, integration of PCMs with nanophotonic structures has introduced a new paradigm for non‐volatile reconfigurable optics. However, the high loss of the archetypal PCM Ge2Sb2Te5 in both visible and telecommunication wavelengths has fundamentally limited its applications. Sb2S3 has recently emerged as a wide‐bandgap PCM with transparency windows ranging from 610 nm to near‐IR. In this paper, the strong optical phase modulation and low optical loss of Sb2S3 are experimentally demonstrated for the first time in integrated photonic platforms at both 750 and 1550 nm. As opposed to silicon, the thermo‐optic coefficient of Sb2S3 is shown to be negative, making the Sb2S3–Si hybrid platform less sensitive to thermal fluctuation. Finally, a Sb2S3 integrated non‐volatile microring switch is demonstrated which can be tuned electrically between a high and low transmission state with a contrast over 30 dB. This work experimentally verifies prominent phase modification and low loss of Sb2S3 in wavelength ranges relevant for both solid‐state quantum emitter and telecommunication, enabling potential applications such as optical field programmable gate array, post‐fabrication trimming, and large‐scale integrated quantum photonic network.

Effect of Glow Discharge Treatment on the Depth and Degree of Structural Phase Modification of Tool Steel Products

The structure and phase composition of 1.1625, 1.2080 and 1.3343 tool steels (DIN) were studied and the research results are presented. The glow discharge treatment is shown to lead to dissolution and redistribution of the carbide phase, a change in the degree of crystal lattice distortion of the matrix phase, and a decrease in the residual austenite in the surface layer to a depth of 80 μm, which results in a 15% to 30% increase in the microhardness of the surface layers of materials.

Operational modifications of a full-scale experimental vertical flow constructed wetland with effluent recirculation to optimize total nitrogen removal

A full-scale Vertical Flow Constructed Wetland (VFCW) was designed, built, and put into operation in Oman to provide a sustainable wastewater treatment solution within the Middle Eastern context. The VFCW had two stages (vertical flow 1 and 2; called VF1 and VF2, respectively) with a total treatment area of 995 m2 and was planted with common reeds (Phragmites australis), while the treated effluent was recirculated to an anoxic tank. The VFCW was continuously fed with high-strength domestic wastewater for 1.5 years (January 2017–June 2018). The study was divided into two phases: the first phase (Baseline) aimed at evaluating the treatment performance, and the second phase (Modification) aimed at testing different operational modifications to optimize the total nitrogen removal and deal with the nitrified treated effluent. Samples were collected at the inlet buffer tank and VF2 outlet daily during the first phase and weekly during the second phase. Overall, high removal rates obtained for total suspended solids (99.6%), biological oxygen demand (98.7%), chemical oxygen demand (97.8%), ammonia nitrogen (99.5%), total phosphorus (97.2%), and pathogens (99.9%) complied with the Oman Irrigation Standard A. However, limited denitrification was the main challenge since the effluent’s total nitrogen value (25 mg/L) remained above the legal limit. Therefore, several operational modifications were tested, such as increasing the hydraulic retention time in the anoxic tank, increasing the saturation in VF2 beds, the step-feeding of raw wastewater, and the addition of an external carbon source. The step-feeding with artificial carbon dosing resulted in the desired nitrate reduction, i.e., below 11.3 mg/L according to the irrigation standard. This research study is among the first VFCW carried out on a full-scale to optimize its performance under a hot and arid climate.

Robust color image watermarking by elliptical phase modification based on Walsh Hadamard Transform and Triangular Vertex Transform

Robust color image watermarking by elliptical phase modification based on Walsh Hadamard Transform and Triangular Vertex Transform

Extraction of Selected Metal Ions with Mixtures of N,N,N’,N’-tetra-n-octyldiglycolamide and 4,4′(5′)-di-t-butylcyclohexano 18-crown-6

ABSTRACT Previous work has shown that solvent extraction (SX) and extraction chromatography (EXC) systems containing mixtures of extractants can be utilized to impart selectivity and improved physical characteristics that were not achievable with a single extractant. In an effort to discover EXC materials with unique selectivity and improved physical properties, we studied the extraction of selected metal ions from nitric acid and hydrochloric acid by EXC resins prepared from mixtures of N,N,N’,N’-tetra-n-octyldiglycolamide (TODGA) and 4,4′(5′)-di-t-butylcyclohexano 18-crown-6 (dtBCH18C6). Except for enhanced extraction of Ra and Ba from dilute HNO3, the EXC resins essentially exhibited the metal ion extraction properties expected from materials prepared with the individual extractants. The origin of the Ra/Ba enhancement was studied by solvent extraction variation studies in 1-octanol and n-dodecane and on extraction chromatography resins, indicating that the enhancement may not be a true synergistic interaction between the extractants, but a phase modification by the TODGA related to the co-extraction of HNO3 and water. Additionally, the influence of alkyl substituents on the DGA extractant and potential applications of the mixed extractant system in analytical chemistry and nuclear medicine were explored with extraction chromatography resins prepared from the extractant mixtures.

Improvement of Microstructure and Mechanical Properties of Near‐Eutectic Al–Mg2Si Alloys by Eu Addition

To modify the microstructure and improve the tensile properties of Al–Mg2Si alloys, different contents of Eu are added into near‐eutectic Al–Mg2Si alloys by melting. Results show that the near‐eutectic Al–Mg2Si alloys consist of primary α‐Al, the first eutectic and second eutectic (Al + Mg2Si) phases, and a few Fe‐containing phase. When the addition of Eu reaches 0.05%, the first eutectic structure is refined, and the first eutectic Mg2Si phase transforms from platelet into fiber. Meanwhile, the second eutectic phase increases, even that the alloy is almost the second eutectic phase when the Eu content is 0.3%. These changes are induced by the modification of Eu. Tensile testing shows that the ductility and the strength are improved to 8.6% and 178 MPa from 1% and 145 MPa when the Eu content is 0.05%, and fracture mode is also changed. This improvement is caused by the modification of the eutectic structure. The tensile properties are decreased or even deteriorated with further increasing the Eu content, which is induced by over‐modification of Eu addition. It is concluded that the modification of eutectic Mg2Si phase by Eu addition contributes to the enhancement of mechanical properties of the near‐eutectic Al–Mg2Si alloys.

Amorphous zircon at high pressure

The high-pressure behavior of a very low-density amorphous zircon model having Zr (Si) coordination of 5.6 (4.02) is explored by ab initio simulations. Two consecutive pressure-induced phase modifications are proposed for this material. The first transition is from a very low-density amorphous state to a dense amorphous state having Zr (Si) coordination of 7.3 (4.5). The second one is from the dense phase to a high-density amorphous structure with Zr and Si coordination numbers of about 8 and 5.5, correspondingly. Both phase changes proceed progressively. The first phase transformation is irreversible whist the second one is reversible.The Voronoi polyhedron analysis reveals the presence of polyhedron of the zircon crystal (<0,4,4,0>), the zirconia baddaliyette phase (<1,3,3,0>) and the zirconia cotunnite state (<0,3,6,0>) around Zr atoms in the amorphous states formed on both compression and decompression, meaning that the amorphous configurations consist of a mixed state of them.

Simulation Model for Drivability Assessment and Optimization of Hybrid Drive Trains

The growing electrification of vehicle drive trains is increasing their complexity significantly. The interactions between the different drive train components should not be noticed negatively by the occupants, which is considered as good drivability and thus contributes to increasing customer acceptance. Today’s development processes of hybrid- and electric driven cars consider energy management in earlier development phases as drivability optimization. In these early development phases, fuel- and energy consumption are optimized on the basis of standardized driving cycles. Drivability aspects and influences of real driving operation are not integrated until the prototype phase. In this way, modifications of drivability-relevant aspects phase are limited, which restricts the potential to find optimal solutions. In this context, the submitted paper presents an approach for assessment and optimization of the drivability of hybrid drive trains in the virtual development process. The created simulation model is exemplarily based on the P2-hybrid drive train of a VW Passat GTE. For the validation of the drive train model and the assessment of drivability, defined maneuvers were carried out on a test track and compared with the results of maneuver simulations. By simulating different driving maneuvers, the resulting acceleration oscillations, which affect the passenger, are calculated and evaluated from the aspect of drivability. The assessment method is derived from a VDI directive dealing with the effects of vibrations on the wellbeing and human health. In order to identify the influencing factors of different maneuvers and parameters of the drive train components, both were varied in the study. It turned out that change of gears and closing of the clutch had the greatest influence on the drivability and thus has the greatest potential for optimizing design and control strategy of hybrid drive trains. In this way, the presented approach enables the assessment and optimization of drivability of hybrid drive trains in the early development phase and thus reduces the gap between virtual development and prototype phase.

Environmental testing of hydrophobic fluorosilane-modified substrates

Surface wettability is one of the key properties in coating science. Development of non-wettable (superhydrophobic) materials is a promising field of study, leading to many potential applications such as anti-icing, drag reduction, anti-corrosive or foul-proof materials. Different approaches to this problem led to several solutions, among which vapor phase modification seems very promising. The effects of such modification were investigated on glass and silica substrates to define changes in surface wettability. The surface was cleaned and activated by low pressure plasma and modified with fluorosilanes. Chosen modifiers were PFOTS and PFDTS. Samples were also tested in different environmental conditions in climate chamber. Obtained materials were characterized by water contact angle (WCA), surface free energy (SFE, van Oss-Good method), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) measurements. The results allowed to define surface wettability, and the impact of temperature and humidity on modified surfaces. Moreover, XPS results enabled to determine chemical composition of surface and AFM was used to analyse substrate roughness change after modification. Conducted studies allow for better understanding of surface properties modelling and also put a light on environmental durability of modified materials like nanocomposites or coatings.

Designing lightweight diesel engine alternator support bracket with topology optimization methodology

Decreasing fuel consumption and tailpipe emissions have been an important issue nowadays for automotive industry after new regulations. Fuel consumption is also an important parameter that highly affects the customers’ choice. Reduction of total vehicle weight with optimization is one of the common methods to improve fuel consumption and emissions. There are a lot of studies on body, interior, and engine components of the vehicle to improve fuel efficiency and emissions including design modifications, using alternative material and architectural optimizations. In this article, the optimization of an aluminum support bracket that carry alternator and hydraulic steering pump is studied. First, design space is determined with layout analysis defining constraints and fixing points. Then, topology optimization method is applied in order to explore the load carrying path of the component. Final design is frozen through computational analysis verifications and industrialization phase modifications. A comparison of the new design with the actual production showed that the mass of the current design could be reduced by 37%, while all product expectations were met.

Phase analysis of tungsten and phonon behavior of beryllium layers in W/Be periodic multilayers.

In periodic W/Be multilayers, thickness-dependent microstructural and phase modifications were investigated in W and Be layers. In X-ray diffraction, α-W was predominant for the ultrathin layer of W, while β-W evolved along with the α-W phase for higher film thickness. For the thicker layers, the thermodynamically metastable β-W vanished and a single well-defined preferably oriented stable α-W phase was observed. The lattice spacing revealed that these phases exist in the tensile stressed condition. With the increase in thickness of Be layers, the blueshift and narrow linewidth of the transverse optical (TO) phonon mode was observed in Raman scattering studies. However, the TO mode was redshifted and the linewidth was further narrowed consistently with an increase in the thermal annealing temperature of the multilayers. The investigation has quantified an increase in compressive strain and reduction of defects with an increase in thickness of the Be layers. However, for thermally annealed samples, the compressive strain in the Be layers was relaxed and crystalline quality was improved.

UHPLC Coupled with Charged Aerosol Detector for Rapid Separation of Steviol Glycosides in Commercial Sweeteners and Extract of Stevia Rebaudiana

Natural sweeteners are in high demand as a part of a healthy lifestyle. Among them, sweeteners with decreased caloric value and suitability for diabetes patients are most requested. Extension in their consumption extends the need for their quality control. A fast gradient UHPLC coupled with charged aerosol detection enabling quantitation of stevioside, rebaudioside A-D, and steviolbioside in commercial sweeteners and Stevia rebaudiana plant extracts has been developed. The method was developed to achieve high efficiency, simplicity, versatility, and low solvent consumption. All steviol glycosides were baseline-separated in less than 4 min with a total run time of 7 min. Buffer-free eluents were used in the separations and only 2.45 mL solvent were needed per analysis. The state of the art column Luna Omega Polar featuring polar modification of C18 stationary phase was used for the excellent separation of polar steviol glycosides. Critical pair of glycosides, stevioside and rebaudioside A, were baseline separated with a resolution of 2.41. The universal charged aerosol detector allowed quantitation of steviol glycosides with a limit of detection and quantitation 0.15 and 0.5 µg/mL, respectively. Method intra-day precision was less than 2% (RSD), and the recovery was 89.6-105.0% and 93.8-111.4% for plant material and sweetener tablets, respectively. The quantity of steviol glycosides in three out of four commercial sweeteners was 3.0-12.3% higher than declared. The content was about 12.4% less than declared in one sample. The most abundant glycoside detected in sweeteners was stevioside followed by rebaudioside A. A leaf-to-stem ratio describing the dominant accumulation of steviol glycosides in leaves affected the differences in the amount of steviol glycosides among plant samples.

Organic and inorganic mixed phase modification of a silver surface for functionalization with biomolecules and stabilization of electromotive force

A solid-state potentiometric biosensor based on the organic and inorganic mixed phase modification of a silver surface is proposed. Stabilization of the electromotive force and functionalization with biomolecules on the sensing surface were simultaneously achieved using silver chloride chemically deposited with 1,3-diaminopropanetetraacetic acid ferric ammonium salt monohydrate and a self-assembled monolayer with oligonucleotide probes, respectively. The formation of silver chloride and adsorption of alkanethiol on the silver surface were confirmed with X-ray photoelectron spectroscopy. The resulting modified surface reduced the nonspecific binding of interfering biomolecules and achieved a high signal to noise ratio. The electromotive forces of the modified silver thin film electrodes were stable under constant chloride ion concentrations. Hybridization assays were performed to detect microRNA 146. The lower limit of detection was 0.1 pM because of the small standard deviation. The proposed biosensor could be useful as a disposable single-use sensor in medical fields such as liquid biopsies.

Modification of primary and eutectic phases in Al-33.2Cu and Al-20Mg2Si alloys by nano-treating

In this work, an Al-Al2O3-ZrB2 master alloy was applied to nano-treat eutectic Al-33.2Cu and hypereutectic Al-20Mg2Si alloys. The (Al2O3 + ZrB2) particle clusters were detected in these alloys. The Al2Cu eutectics inside of the particle clusters are much coarser than the lamella shaped Al2Cu in the initial alloy. The primary Mg2Si and labyrinthic eutectics have been transformed into fragmentary and intermittent, respectively. The confined space inside of the particle clusters are supposed responsible for the nano-treating performance through affecting the solute diffusion process and phase growth procedure.

7Li NMR Studies of Short-Range and Long-Range Lithium Ion Dynamics in a Heat-Treated Lithium Iodide-Doped Lithium Thiophosphate Glass Featuring High Ion Conductivity

We combine 7Li field-cycling relaxometry with 7Li field-gradient diffusometry to study both short-range and long-range lithium ion dynamics in a heat-treated 0.33 LiI + 0.67 Li3PS4 glass, which exhibits a high ionic conductivity of 6.5 mS/cm. 7Li field-cycling relaxometry, which provides access to the spin–lattice relaxation time T1 over broad frequency and temperature ranges, allows us to determine the activation energy distribution g(Ea) of the local jumps in a model-free way. We find that g(Ea) has a Gaussian form and is characterized by the mean energy Em = 0.40 eV and the standard deviation σ = 0.08 eV. 7Li field-gradient studies indicate free diffusion and yield self-diffusion coefficients of D ∼ 10–12 m2/s at ambient temperatures. Comparing our results for the short-range and long-range ion dynamics and considering previous knowledge about ionic conductivity, we show that the local jumps characterized by the Gaussian distribution g(Ea) determine the macroscopic transport. We conclude that the high ionic conductivity of the heat-treated glass does not result from the formation of minor crystalline regions during the annealing process but rather from a modification of the predominant amorphous phase.

Advances in polymer-based dendrimer-grafted chromatographic separation materials

With the continuous developments in stationary phase preparation technology and materials science, numerous modification methods and new materials have been employed for the functional modification of the polymer stationary phases in solid-phase extraction, high performance liquid chromatography and ion chromatography. In particular, because of their unique structure and properties, poly(amidoamine) (PAMAM) dendrimers play an important role in improving the structure and performance of chromatographic separation materials. In this paper, the application of PAMAM to the modification of polymer-based chromatographic separation materials is reviewed, and further developments are prospected.

Spontaneous morphology and phase modification driven by sequence of deposition in superconducting Ni–Bi bilayers

We report how the sequence of deposition of Ni and Bi affects the final morphology of Ni–Bi bilayers. Two samples have been prepared by sputtering with the same thickness of Ni (4 nm) and Bi (40 nm) but reversed sequence of deposition. The sample with Bi deposited first formed a smooth layer of NiBi3 intermetallic, while the sample Ni deposited first formed mainly NiBi3 nanoparticles with its out-of-plane dimensions bigger than the thickness of the total deposited bilayer. The NiBi3 phase in the two samples results from differing nucleation and growth processes leading to differing morphologies. The volume of NiBi3 is smaller than the pure Bi volume needed for the reaction and this volume contraction is a thermodynamic factor that favors the NiBi3 formation. Both samples are superconducting with the critical temperature Tc of ~4.0 K. The Ni–Bi system offers an example of the formation of a superconducting compound under a volume contraction of its constituents, thus being of interest for both researchers in physics and material sciences.

Metallothermal synthesis of the Laves phase TaCr2 from oxide raw materials

The refractory Laves phase TaCr2 of two compositions (series) was synthesized by the metallothermal (hydride-calcium) method from oxide raw materials (Cr2O3 + Ta2O5). The synthesis temperature was 1200 oC, while the excess of the reducing agent CaH2 was varied relative to the theoretically required for the complete reduction of oxides. It is shown that regardless of the excess of the reducing agent or in its complete absence, the resulting&nbsp; powders have the required chemical composition (composition 1: calculated Cr content &mdash; 37.38% (wt.), actual &mdash; 37.50&plusmn;0.85% (wt.); composition 2: calculated Cr content &mdash; 35.30% (wt.), actual &mdash; 35.38&plusmn;0.31% (wt.)). No significant losses of Cr and Ta were observed during the synthesis of the Laves phase under the conditions of hydride-calcium reduction of Cr2O3 and Ta2O5. All prepared powders contained ~ 0.25% (wt.) oxygen and 0.025% (wt.) calcium. This is a good result for experimental batches first obtained by this method. Powders of the first series (composition 1), regardless of the excess of CaH2, contained no less than 85% (wt.) of the TaCr2 phase of the С15 type and ~ 10% (wt.) of the Cr(Ta) solid solution. However, when the excess of the reducing agent was &gt;50 wt%, a high-temperature modification of the TaCr2 phase with a C14-type hexagonal lattice came in sight. The same picture was observed in the second series of experiments (composition 2). In all cases, the amount of the C14 type TaCr2 phase did not exceed 5% (wt.). Powders of composition 2 contained no less than 90% (wt.) of the C15 type TaCr2 phase or 95% (wt.), if there were two modifications C15 + C14. Depending on the excess of the CaH2 reductant, the alloys contained small amounts of Cr(Ta) or Ta2H hydride. In both series, the powder particles had a finely dispersed spongy structure; large particles of regular shape were present in an insignificant amount. This work was carried out with financial support of the government of the&nbsp;Tula region (grant for work in the field of science and technology No. DS / 161&nbsp;dated October 29, 2020).