Thermodynamic reassessment of the Au–Te system

The Au–Te binary system has been thermodynamically reassessed using the CALPHALD method. The excess Gibbs energy of the liquid phase was formulated with the Redlich–Kister expression and the AuTe2 intermetallic phase was treated as a stoichiometric compound. A set of self-consistent thermodynamic parameters for each phase has been obtained. Good agreement is reached between the calculated and experimental results. Additionally, the standard formation enthalpy and enthalpy of fusion of AuTe2 intermetallic phase have also been calculated

Thermodynamic modeling of the ternary Ce–Fe–Sb system: Assessment of the Ce–Sb and Ce–Fe systems

Abstract The two Ce–Sb and Ce–Fe binary systems have been evaluated using the calculation of phase diagram method (CALPHAD). All of the binary compounds are treated as stoichiometric compounds. Solution phases are described with an ordinary substitutional solution model. The model parameters were derived from an optimization procedure using all available experimental data. The reproduction of the thermochemical and phase diagram information is reported in a series of figures and tables

Optimization of periodic maintenance for wind turbines based on stochastic degradation model

The degradation process of wind turbines is greatly affected by external factors. Wind turbine maintenance costs are high. The regular maintenance of wind turbines can easily lead to over and insufficient maintenance. To solve the above problems, a stochastic degradation model (SDE, stochastic differential equation) is proposed to simulate the change of the state of the wind turbine. First, the average degradation trend is obtained by analyzing the properties of the stochastic degradation model. Then the average degradation model is used to describe the predictive degradation model. Then analyze the change trend between the actual degradation state and the predicted state of the wind turbine. Secondly, according to the update process theory, the effect of maintenance on the state of wind turbines is comprehensively analyzed to obtain the availability. Then based on the average degradation process, the optimal maintenance period of the wind turbine is obtained. The optimal maintenance time of wind turbines is obtained by optimizing the maintenance cycle through availability constraints. Finally, an onshore wind turbine is used as an example to verification. Based on the historical fault data of wind turbines, the optimized maintenance decision is obtained by analyzing the reliability and maintenance cost of wind turbines under periodic and non-equal cycle conditions. The research results show that maintenance based on this model can effectively improve the performance of wind turbines and reduce maintenance costs

Condition Maintenance Decision of Wind Turbine Gearbox Based on Stochastic Differential Equation

Maintenance decision analysis is necessary to ensure the safe and stable operation of wind turbine equipment. To address gearboxes with a high failure rate in wind turbines, this paper establishes a new stochastic differential equation model of gearbox state transition to maximize the utilization of gearboxes. This model divides the state of the gearbox into two parts: internal degradation and external random interference. Weibull distribution and polynomial approximation were used to construct the internal degradation model of the gearbox. The external random interference is simulated by Brownian motion. On the basis of the analysis of monitoring data, the parameters of the gearbox state model were solved using the Newton–Raphson iterative method and entropy method. The state change of the gearbox was simulated in MATLAB, and the residual value between the predicted state and the real state was calculated. Compared with the state transformation model constructed by the traditional ordinary differential equation and the gamma distribution, the Weibull polynomial approximation stochastic model can better reflect the state of the device. With reliability set as the decision goal, the maintenance time of the gearbox is predicted, and the validity of the model is verified through case analysis

Eutectic Reaction and Microstructure Stability in CoCrFeNiNb_x High-Entropy Alloys

Seven arc-melted and then annealed CoCrFeNiNbx (x = 0.3–0.6) alloys are experimentally and thermodynamically investigated in the present work. All the as-cast and 1000 °C annealed CoCrFeNiNbx alloys are composed of face-centered cubic (FCC) and C14 Laves phases. Nb content in the C14 phase stays at around 24.5 at.%, and the Liquid → FCC + C14 eutectic reaction occurred at around 10.8 at.% Nb in a narrow temperature range. It is found that the microstructure in the CoCrFeNiNbx alloys is dramatically affected by the cooling rate and annealing treatment. The C14 phase easily spheroidizes and coarsens under high temperature, which indicates that the interface energy between FCC and C14 is very large. Moreover, the solubility of Nb in the FCC phase decreases with decreasing temperature. After annealing at 800 °C, a needle-like nano Mg3Cd-type τ phase precipitates from the pro-eutectic FCC phase and increases alloy hardness for ~100 HV. This should be a method to strengthen alloys

Eutectic Reaction and Microstructure Stability in CoCrFeNiNbx High-Entropy Alloys

Seven arc-melted and then annealed CoCrFeNiNbx (x = 0.3–0.6) alloys are experimentally and thermodynamically investigated in the present work. All the as-cast and 1000 °C annealed CoCrFeNiNbx alloys are composed of face-centered cubic (FCC) and C14 Laves phases. Nb content in the C14 phase stays at around 24.5 at.%, and the Liquid → FCC + C14 eutectic reaction occurred at around 10.8 at.% Nb in a narrow temperature range. It is found that the microstructure in the CoCrFeNiNbx alloys is dramatically affected by the cooling rate and annealing treatment. The C14 phase easily spheroidizes and coarsens under high temperature, which indicates that the interface energy between FCC and C14 is very large. Moreover, the solubility of Nb in the FCC phase decreases with decreasing temperature. After annealing at 800 °C, a needle-like nano Mg3Cd-type τ phase precipitates from the pro-eutectic FCC phase and increases alloy hardness for ~100 HV. This should be a method to strengthen alloys

Study on Microstructure and Mechanical Properties of Hypereutectic Al–18Si Alloy Modified with Al–3B

An hypereutectic Al–18Si alloy was modified via an Al–3B master alloy. The effect of the added Al–3B and the modification temperature on the microstructure, tensile fracture morphologies, and mechanical properties of the alloy were investigated using an optical microscope, Image–Pro Plus 6.0, a scanning electron microscope, and a universal testing machine. The results show that the size of the primary Si and its fraction decreased at first, and then increased as an additional amount of Al–3B was added. When the added Al–3B reached 0.2 wt %, the fraction of the primary Si in the Al–18Si alloy decreased with an increase in temperature. Compared with the unmodified Al–18Si alloy, the tensile strength and elongation of the alloy modified at 850 °C with 0.2 wt % Al–3B increased by 25% and 81%, respectively. The tensile fracture of the modified Al–18Si alloy exhibited partial ductile fracture characteristics, but there were more areas with ductile characteristics compared with that of the unmodified Al–18Si alloy

A thermodynamic assessment of the Dy–Sn system

International audienceThe Dy–Sn binary system has been optimized using the available experimental information on the phase diagram and thermodynamics based on the CALPHAD approach. The system contains seven intermetallic compounds: Dy5Sn3, Dy5Sn4, Dy11Sn10, DySn, Dy4Sn5, DySn2 and DySn3. They were treated as stoichiometric compounds. The thermodynamic descriptions for all the stable phase in this system were obtained. The calculated phase diagram and thermodynamic quantities agree well with the experiment values

Performance of Large Area n-TOPCon Solar Cells with Selective Poly-Si Based Passivating Contacts Prepared by PECVD Method

Selective emitter (SE) technology significantly influences the passivation and contact properties of n-TOPCon solar cells. In this study, three mask layers (SiOx, SiNx, and SiOxNy) were employed to fabricate n-TOPCon solar cells with phosphorus (P)-SE structures on the rear side using a three-step method. Additionally, phosphosilicon glass (PSG) was used to prepare n-TOPCon solar cells with P-SE structure on the rear side using four-step method, and the comparative analysis of electrical properties were studied. The SiOx mask with a laser power of 20 W (O2 group) achieved the highest solar cell efficiency (Eff, 24.85%), The open-circuit voltage (Voc) is 2.4 mV higher than that of the H1 group, and the fill factor (FF) is 1.88% higher than that of the L1 group. Furthermore, the final Eff of solar cell is 0.17% higher than that of the L1 group and 0.20% higher than that of the H1 group. In contrast, using the four-step method and a laser power of 20 W (P2 group), a maximum Eff of 24.82% was achieved. Moreover, it exhibited an Voc, which is elevated by 3.2 mV compared to the H1 group, and FF increased by 1.49% compared to the L1 group. Furthermore, the overall Eff of the P2 group outperforms both the L1 and H1 groups by approximately 0.14% and 0.17%, respectively. In the four-step groups, the Eff of each laser condition group was improved compared with the L1 group and H1 group, The stability observed within the four-step method surpassed that of the three-step groups. However, in terms of full-scale electrical properties, the three-step method can achieve comparable results as those obtained from the four-step method. This research holds significant guiding implications for upgrading the n-TOPCon solar cell rear-side technology during mass production