Unstable Phase Research Articles

Phase Control of Multivalent Vanadium Oxides VOx by Ion‐Beam Sputter‐Deposition

Vanadium–oxygen materials are of interest for various applications and fields of solid‐state physics owing to the unequaled plethora of different phases. The wealth of phases and complexity of its phase diagram infer a strong sensitivity on the growth parameters for each phase. Thus, the reproducible growth of vanadium‐oxide thin‐films of defined phases by nonequilibrium techniques is challenging. Here, it is shown that ion‐beam sputter‐deposition (IBSD) is a powerful tool to reproducibly deposit defined polycrystalline vanadium oxide films by precisely controlling oxygen flux and substrate temperature in the growth process. Hence, it is demonstrated that IBSD has the potential to reliably produce binary phases (including unstable phases) from the vanadium–oxygen phase space. X‐ray diffraction (XRD) and Raman spectroscopy are used to establish a map of the different crystalline phases dependent on the growth parameters. In particular, it is proved that thin‐film V3O7 can be realized by IBSD and its Raman fingerprint is unambiguously identified.

A quantum corrected R–N–AdS black hole and it’s thermodynamics of phase transition

To investigate the quantum gravity effects on the black hole thermodynamics, we studied the phase transition in a quantum corrected R–N–AdS black holes. First, based on the work of Kazakov and Solodukhin, the spherically symmetric quantum fluctuation is applied to R–N–AdS black hole, and the metric is given. Next, we investigate the basic thermodynamic quantity and Smarr formula, and then propose that the quantum correction parameter a should also be treated as a variable to ensure the establishment of the new Smarr formula. Finally, the P–V diagram and phase transition for the quantum corrected R–N–AdS black hole are studied. Compared with the existing research on R–N–AdS black hole, some effects by quantum fluctuation are analyzed and presented. First, the quantum correction will weaken the charge effect of the black hole. Second, the P–V curve of the quantum corrected black hole is no longer analogous to that of Van Der Waals (VDW) gas exactly. Third, the black hole has two more phase states than R–N–AdS black hole. One is a remnant phase state, the other is an unstable phase state. And both are derived from the quantum corrections of the black hole.

Electronic gap stability of two-dimensional tin monosulfide phases: Towards optimal structures for electronic device applications

It is well known that tin monosulfide is a potential environment-friendly solar cell material that maximizes light-energy conversion efficiency, given its band gap at the peak of the solar emission spectrum. However, the presence of Sn and S vacancies at the surface of SnS hinders the performance of these solar cells. In the present work, we have prepared tin sulfide platelets on graphite using vapor phase deposition under a known temperature gradient. Remarkably, we observe two types of growth modes: (i) a dominant one with platelet-like flat crystals and (ii) a less favorable one, formed by spiral terraces. Both structures present a chemical composition compatible with SnS. Using scanning tunneling microscopy (STM) and spectroscopy (STS), we observe that, whereas flat SnS platelets exhibit fluctuations in the band gap and doping, spiral platelets exhibit stable, homogeneous band gap, and negative doping. Using selected area electron diffraction (SAED), we determine that, whereas the platelets of the unstable phase are associated with the common orthorhombic structure of SnS, the minor stable spiral platelets are polycrystalline and are in the metastable cubic phase. The production of this less favorable phase on large surface areas is of potential interest for the production of more efficient tin sulfide-based solar cells. In addition, our analysis of solar cell materials using STM/STS and SAED provides a framework for the rapid determination of the suitability and applicability of 2D materials for other potential optoelectronic applications.

Hubungan Conformity dengan Motivasi Belajar Siswa Kelas X SMKN 2 Kota Solok

Education is the main thing in life. Every human being has the right to obtain education as development and progress in itself. Education is always associated with learning and directly proportional to study habits. The success of the learning process depends on students' motivation and enthusiasm for learning. Student motivation is also influenced by conformism. In adolescence, conformity is very influential on consideration in making decisions. Furthermore, adolescence is an unstable phase and is very sensitive to conformity. This study aims to analyze the relationship between compliance and learning motivation of students in class X of SMKN 2 Kota Solok. The population in this study was Class X, Department of Light Vehicle Engineering, SMKN 2 Kota Solok, for the 2020/2021 academic year, there were 120 students. The sample for this study consisted of 48 students from SMKN 2 Kota Solok. The sampling technique in this study used a random sampling technique. The results of this study indicate the value of rcount > rtable which indicates the validity and the Cronbach alpha > 0.6 which indicates the reliability of the research data. After analyzing the correlation test, it was found that the high level of compliance in class X resulted in the inhibition of students' motivation to learn. Students who perform well tend to be noticed by their peers and have higher motivation than students who perform well and tend to be ostracized by their peers.

Gravitational-Scalar Instability of a Two-Component Degenerate System of Scalarly Charged Fermions with Asymmetric Higgs Interaction

Based on the previously formulated mathematical model of a statistical system with scalar interaction of fermions and the theory of gravitational-scalar instability of a cosmological model based on a two-component statistical system of scalar-charged degenerate fermions, a numerical model of the cosmological evolution of gravitational-scalar perturbations is constructed and specific examples of the development of instability are given. Some features of the instability's development are investigated depending on the nature of the behavior of the unperturbed cosmological model. It is shown that unstable modes can appear at very early stages of cosmological expansion or contraction, and the duration of the unstable phase is comparable to tens of Planck scales. In this case, however, a very significant increase in unstable modes is possible due to the redistribution of energy between the components of the scalar doublet.

Stabilization of ferric arsenate sludge with ZVI intensive corrosion and enhancement of long-term arsenic immobilization via resin encapsulation

In this study, a novel stabilization/solidification (S/S) method, achieved by mechanochemically activated zero-valent iron (ZVI) intensive corrosion and resin encapsulation, was investigated for arsenic sludge disposal. The results showed that arsenic stabilization was enhanced by intensive corrosion process, with arsenic leaching concentration decreasing from 128.75 mg/L to 0.35 mg/L after stabilization treatment under optimized conditions. The residual state arsenic was increased from 96.32 wt% to 99.13 wt% after stabilization. The subsequent resin encapsulation solidification scheme has a significant effect on the low arsenic leachability of the stabilized sludge. The arsenic concentration of resin solidification matrix was 0.47 mg/L, which was significantly lower than that of cement solidification matrix (1.77 mg/L), as a control group. It also can be seen that resin curing showed much lower cumulative release rate (0.009 wt%) than cement curing (0.54 wt%) at the end of leaching test, under a 60-day long-term leaching test, indicating that resin curing has higher long-term arsenic stability. Resin curing can maintain the structure of the stabilized As-Fe phase by resin encapsulation, while the traditional cement curing would destroy the original stable As-Fe phase, and produce unstable As-Ca phase, resulting in the risk of arsenic pollution. Moreover, the matrix based on ZVI intensive corrosion and resin encapsulation scheme has great advantages in low compatibilization ratio and resistance to pH impact.

Variational Analysis of the Speed of Propagating Fronts in Superconductors

A new approach has taken to determine the speed of the superconducting-normal interface (front) propagating from a stable superconducting phase to the unstable normal phase by means of a variational method. In this process a trial function g(x) is introduced which has a relation with the superconducting order parameter F. Starting from the time-dependent Ginzburg-Landau (TDGL) equations an expression is derived for the front speed in terms of GL parameter κ. The Chittagong Univ. J. Sci. 43(1): 41-50, 2021

Specific therapy needs of young adults with chronic pain : Results of a qualitative interview study

Young adults find themselves in an unstable phase of life with relationship breaks, falling structures and great challenges in life. Chronic pain makes it difficult to cope with this stage of life due to functional, emotional and social limitations. For this age group there are hardly any target group-specific treatment programs. The aim of the study was to find out what needs the patient group of young adults with chronic pain have with regard to inpatient pain therapy and what need is indicated for aseparate therapy concept for this age group. Within the framework of aqualitative research approach, specific needs of young adults with regard to inpatient pain therapy were surveyed via guideline-based interviews. Atotal of 66interviews were conducted with patients and practitioners. The evaluation was carried out using the method of structuring qualitative content analysis. Five main categories regarding the specific treatment needs of young adult pain patients were identified: respect, belonging, special circumstances, locating the pain and specific elements of therapy. Special living conditions and arespectful treatment attitude are of particular importance. Agreater number of activation offers, ahigher proportion of life counseling and perspective-creating aspects as well as psychotherapeutic offers are anecessity for an efficient therapy. Acceptance and commitment therapy techniques and the positive benefits of peer groups can expand the treatment approach for young adults. Young adults could benefit from atarget group-specific and needs-adapted care structure.

Mitigating Jahn–Teller Effects by Fast Electrode Kinetics Inducing Charge Redistribution

AbstractManganese hexacyanomanganates have attracted significant attention as promising cathode materials for sodium‐ion batteries owing to the high theoretical capacity and low cost of Mn resources. Because of the strong Jahn–Teller effect, causing unstable local phase transition and distortion, the redox reactions of the high‐spin state of Mn(III) are considered to be a conundrum. Herein, it is reported that the charge‐redistribution mechanism of low‐spin MnIII + high‐spin MnIII → low‐spin MnII + high‐spin MnIV in manganese hexacyanomanganates can decrease unstable high‐spin MnIII, leading to the mitigation of Jahn–Teller distortion. X‐ray absorption near‐edge spectroscopy and X‐ray photoelectron spectroscopy suggest that the fast reaction rate activates charge redistribution. Moreover, different crystal structures, reported using post‐mortem synchrotron X‐ray diffraction analysis, confirm a large orthorhombic structure, thus verifying the presence of charge redistribution based on the superexchange rule. These results demonstrate that manganese hexacyanomanganate in an aqueous electrolyte can achieve long‐term cyclability, thus paving the way for high‐performance batteries.

The influence of cryogenic treatment on titanium alloys mechanical properties

One of the most promising applications of cryogenic therapy is its ability to transform a wide range of materials. In this study, Titanium alloy (Ti6Al4V) was subjected to both deep and shallow cryogenic treatment. In addition to the anti-aging treatment, a deep cryogenic treatment was administered to the patient. Tensile tests were used to examine how cryogenic treatment affected the mechanical characteristics and ductility of Ti6Al4 alloy. According to this studies, cryogenic treatment expands flexibility of Ti6Al4V alloy. After 24 and 36 h, the deep cryo-treated samples had Uniform Plastic Deformation Region (UPDR) that were 5.3% and 8.3% greater than the untreated ones. However, after 36 h of cryogenic treatment, the yield strength of the material decreased by 2%. When subjected to a 36-hour period of severe cryogenic treatment, the alloy's phase ratio decreased from 8.1% to 5.6%, resulting in structural changes within the material. The unstable a phase gave rise to both stable and unstable phases. Experiments have shown that cryogenic treatment raises the flexibility and durability of Ti6AI4V alloy while also controlling the microstructure and lowering residual stress when performed at room temperature.

Ambient pressure synthesis of unstable bulk phases of strongly correlated rare-earth nickelates

An ambient pressure synthesis recipe of SmNiO3 for well-defined metal–insulator transitions.

DESIGN OF CUBIC Ni-BASED ALLOYS FOR USE AS COATING IN PETROCHEMICAL INDUSTRY – A FIRST PRINCIPLES APPROACH

This work presents the structural stability and mechanical properties of ordered face-centred cubic (FCC) Ni-Cr binary and ternary alloys. The effects of alloying on these properties have been evaluated using the first principles density functional theory (DFT) within generalised gradient approximation (GGA). The calculated heats of formation show that the introduction of third elements (Al, Ti, Mo, Sn) improved the thermodynamic stability of the usually unstable L12 Ni3Cr phase. Unsurprisingly, ternary alloys that yielded higher mechanical properties were those alloyed with Al and Ti owing to their ability to form a very stable L12 phase with Ni. Therefore, the theoretical technique has been successfully employed to identify promising high-strength cubic Ni-based ternary intermetallic alloys that can be used as coatings.

Hexavalent chromium mobility in a high amorphous phase Chromite Ore Processing Residue (COPR) in the perspective of a chromium remediation treatment

The mineralogical and chemical composition of chromite ore processing residue (COPR) from a site in the north of France (Lille) was investigated. The mineralogical composition was obtained by X-ray diffraction and Rietveld analysis. Geochemical characteristics were established based on elemental analysis, acid leaching, sequential extraction and a chemical equilibrium experiment. Remarkably, this COPR material is composed of 65% silica-rich amorphous phases. Another noticeable result is the presence of about 11% of quartz. Content in toxic Cr(VI) is about 4.9 g/kg, occurring in the solution phase or fixed in unstable crystalline cement phases. Literature data on most studied COPR materials allowed establishing a classification of the materials into (1) high calcium/low silica, (2) intermediate and (3) low calcium/high silica categories. This calcium–silica relation is indicative of the quality of the original ore and the geochemical changes having occurred in a COPR deposit over time, compared with fresh COPR produced from pure ore, and possibly the post-deposit admixture of other waste materials. The Lille material belongs to the third category. The high silica content has influenced the phase associations and their stabilities and favours Cr(VI) mobility. Extraction of leachable Cr(VI) from COPR induces formation of a new chemical equilibrium in the material with a recharge in mobile chromium due to dissolution of cement phases. However, the rate of equilibration is very slow. Four hundred days were needed for the high amorphous phase material in this study. Extraction of leachable Cr(VI) is not a suitable remediation method because it will not allow to withdraw the solid bound Cr(VI) from the material in a single treatment.

Increasing the rating performance of paraffin up to 5000 cycles for active latent heat storage by adding high-density polyethylene to form shape-stabilized phase change material

The unstable phase transition of pure paraffin limits its application, particularly for active latent heat storage (ALHS). In passive latent heat storage, the addition of high-density polyethylene (HDPE) can decrease paraffin's leakage rate, which is associated with unstable phase transition and increase its durability after a large thermal number. This study aims to discover the possibility to use HDPE as a shape-stabilizer to increase the paraffin's performance for the ALHS system. Pure paraffin and composite paraffin/HDPE (80:20 wt%) are prepared as the reference material. The evaluation is focused on thermal properties, stability and performance during charging and discharging under different thermal cycles. Thermal cycle treatment uses temperature as a working boundary where the sample is heated from 30°C to 150°C, then cooled back to 30°C and repeated until 5000 cycles. Three different cycle references are chosen (1, 1000 and 5000 cycles) for each evaluation. The melting temperature of paraffin is decreased from 61.6°C to 59.8°C after 5000 cycles where Paraffin/HDPE slightly decreased from 60.4°C to 60.1°C. The heat fusion is decreased by 8.7% and 2.9% for paraffin and Paraffin/HDPE, respectively. The isothermal phase change is observed for paraffin/HDPE even after 5000 cycles with a higher rating performance by 30% faster to complete one cycle than pure paraffin. The other thermal performance is discussed in detail within the article, including the phase transition model during charging and discharging for the sample.

Response of ferrite, bainite, martensite, and retained austenite to a fire cycle in a fire-resistant steel

Understanding the kinetics of microstructural degradation during the event of a fire is of major relevance to future optimization of fire-resistant steels (FRS). In this work, we use in situ synchrotron X-ray diffraction to assess the rapid thermally-assisted degradation of different starting microstructures, such as (i) ferrite + pearlite; (ii) bainite + retained austenite, and (iii) martensite + retained austenite, during the simulation of a fire cycle in a Fe-0.13C-0.11Cr-0.38Mo-0.04V FRS. Our results show that retained austenite is the most unstable phase, especially when generated by faster cooling rates, decomposing at temperatures as low as 180 °C during fire simulations. Bainite and martensite are both unstable and undergo recovery and carbon desaturation via secondary precipitation of cementite. However, bainite is comparatively more stable than martensite since its decomposition starts at 400 °C, while for martensite it occurs at 320 °C. We also present a methodology to deconvolute the effect of temperature on the increased background and signal intensities of the X-ray spectra, allowing the direct observation of the kinetics of secondary cementite precipitation. • Different starting microstructures were submitted to a simulated fire cycle. • The kinetics of microstructural decomposition was studied using synchrotron X-ray diffraction. • Bainite, martensite and retained austenite underwent carbon desaturation during heating. • The kinetics of secondary precipitation of cementite was revealed for each microstructure .

Stability of large complex systems with heterogeneous relaxation dynamics

We study the probability of stability of a large complex system of size N within the framework of a generalized May model, which assumes a linear dynamics of each population size n i (with respect to its equilibrium value): . The a i > 0’s are the intrinsic decay rates, J ij is a real symmetric (N × N) Gaussian random matrix and measures the strength of pairwise interaction between different species. Our goal is to study how inhomogeneities in the intrinsic damping rates a i affect the stability of this dynamical system. As the interaction strength T increases, the system undergoes a phase transition from a stable phase to an unstable phase at a critical value T = T c. We reinterpret the probability of stability in terms of the hitting time of the level b = 0 of an associated Dyson Brownian motion (DBM), starting at the initial position a i and evolving in ‘time’ T. In the large N → ∞ limit, using this DBM picture, we are able to completely characterize T c for arbitrary density μ(a) of the a i ’s. For a specific flat configuration , we obtain an explicit parametric solution for the limiting (as N → ∞) spectral density for arbitrary T and σ. For finite but large N, we also compute the large deviation properties of the probability of stability on the stable side T < T c using a Coulomb gas representation.

A Dynamic Holding Approach to Stabilizing a Bus Line Based on the Q-Learning Algorithm with Multistage Look-Ahead

The unreliable service and the unstable operation of a high-frequency bus line are shown as bus bunching and the uneven distribution of headways along the bus line. Although many control strategies, such as the static and dynamic holding strategies, have been proposed to solve the above problems, many of them take on some oversimplified assumptions about the real bus line operation. So it is hard for them to continuously adapt to the evolving complex system. In view of this dynamic setting, we present an adaptive holding method that combines the classic approximate dynamic programming (ADP) with the multistage look-ahead mechanism. The holding time, the only control means used in this study, will be determined by estimating its impact on the operation stability of the bus line system in the remaining observation period. The multistage look-ahead mechanism introduced into the classic Q-learning algorithm of the ADP model makes it easy that the algorithm gets through its earlier unstable phase more quickly and easily. During the implementation of the new holding approach, the past experiences of holding operations can be cumulated effectively into an artificial neural network used to approximate the unavailable Q-factor. The use of a detailed simulation system in the new approach makes it possible to take into account most of the possible causes of instability. The numerical experiments show that the new holding approach can stabilize the system by producing evenly distributed headway and removing bus bunching thoroughly. Compared with the terminal station holding strategies, the new method brings a more reliable bus line with shorter waiting times for passengers.

Unified complex coefficient PID controller tuning for complex coefficient system

Generally, controllers are tuned to meet the desired time and frequency domain specifications for integer/fractional order real coefficient systems whose frequency response is symmetric about the origin of the complex frequency plane. These controllers are tuned through analytical/numerical approaches. On the contrary, the frequency responses of the complex coefficient systems are unsymmetrical, and hence tuning of controllers should consider both positive and negative frequencies. In this article, tuning of complex coefficient proportional integral derivative controller is proposed for such systems to meet the desired gain and phase margin specifications in positive and negative frequencies. For illustration, the simulation results are presented for stable, unstable, and non-minimal phase systems with the proposed tuning method.

Prediction of low-temperature fracture resistance curves of unmodified and crumb rubber modified hot mix asphalt mixtures using a machine learning approach

Fracture resistance curves (R-curves) provide a robust tool for a comprehensive insight into the crack propagation regime in engineering materials. In this paper, an extensive research program is conducted to determine R-curves for hot mix asphalt (HMA) mixtures with varying properties. The experimental results are then used to develop R-curve prediction models following a machine learning approach. Three-point single-edge notched beam (SE(B)) experiments were conducted on HMA mixtures incorporating 0%, 5%, 10%, 15%, and 20% crumb rubber at low temperatures. The temperature ranged from + 5 °C to −20 °C while limestone and siliceous aggregate with two gradations were used in developing mixtures with two base bitumen having performance grades of PG58-22 and PG64-22. It was observed that as the temperature is declined to −20 °C, the stable crack growth region is significantly diminished in the R-curves, and the mixtures undergo a brittle fracture with abrupt failure of the specimen. A temperature of −15 °C could be determined where the transition from quasi-brittle to brittle fracture occurs. Mixtures fabricated incorporating 20% crumb rubber exhibited a progressively rising R-curve at the lowest test temperature (−20 °C) even in the unstable crack propagation phase, which is a desirable material characteristic. Two prediction models were developed for R-curves. Artificial neural networks (ANN) were used in the first model resulting in an R-square value of 0.965. Due to the black-box nature of the ANN, the multi-gene genetic programming approach was also applied in the prediction of the R-curves to derive a mathematical equation between the input data and the outputs. The R-square equaled 0.870 in this method. R-curves could successfully be predicted by both methods considering the negligible to fair errors.

Desorption and Transport of Temperature-Pressure Effect on Adsorbed Gas in Coal Samples from Zhangxiaolou Mine, China

Abstract The development of coal seam fissures and gas migration process caused by mining disturbance has an extremely important influence on gas control and roadway stability. In this study, the desorption, diffusion, and migration tests of adsorbed gas under the coupling effect of temperature and uniaxial compression were conducted on four coal samples from Zhangxiaolou mine, using the temperature and pressure coupling test system of deep coal rocks. The test confirms that the higher the temperature, the faster the desorption and emission of the adsorbed gases in the coal, and the larger the volume of the emitted gases. Meanwhile, it is found that the adsorbed gases in the coal samples of Zhangxiaolou mine are carbon dioxide and methane in the order of content. It is found that during the uniaxial compression process, several large negative values of the pressure of the emitted gas occur during the stable growth stage of the crack. This indicates that the crack expansion makes a new negative pressure space inside the coal sample, and the negative pressure values increase continuously during the unstable growth phase of the crack until the coal sample is destroyed. And after the axial pressure is removed, the escaped gas pressure shows a large positive value due to the rebound of the coal matrix and the continuous desorption of a large amount of adsorbed gas from the new crack location, which has a significant hysteresis with respect to the occurrence of the peak stress. Meanwhile, the SEM images of the coal samples before and after the test are analyzed to confirm the cause of the negative pressure generation.