Highly efficient two-stage ring-opening of epichlorohydrin with carboxylic acid in a microreaction system

Ring-opening of epoxides with carboxylic acids has been widely used to prepare many high value intermediates in the polymer and pharmaceutical industries. Most of conventional processes proceeded in batch stirred reactors. As such they always suffer from low productivity and selectivity. Here we developed an advanced technology to perform the ring-opening reaction of epichlorohydrin with neodecanoic acid (NDA) for continuous production of 3-chloro-2-hydroxypropyl neodecanoate in a more efficient and safer way. A microreaction system where a microreactor connected to a stirred reactor was established. When the conversion of NDA rapidly reaching around 90% in a microreactor at 110°C, the reaction solution was transferred to a stirred reactor at 90°C. This two-stage operating mode can reduce the reaction time and improve the selectivity through free switching of temperature in the consecutive two reactors, thus substantially reducing the consumption of energy and materials.     

Tetragonal tungsten bronze phase potential in increasing the piezoelectricity of sol-gel synthesized (K0.5Na0.5)1-xLixNbO3 ceramics

(K,Na)NbO₃ (KNN)-based ceramics have been proven to be formidable candidates among lead-free piezoelectric materials, yet poor reproducibility always hinders their progress. In the present study, the effects of low lithium substitution on the electrical properties and microstructure of (K_0.5Na_0.5)_1-xLi_xNbO₃ (KNLN) ceramics were investigated. All samples were synthesized by the sol-gel method. The Curie temperature (T_C) of the ceramics shifted to higher temperature and gradually decreased the monoclinic-tetragonal (T_M-T) phase transition. Li⁺ substitution had a prominent effect on the ferroelectric properties and improved the piezoelectric coefficient (d₃₃) up to 181 pC/N. X-Ray Diffraction (XRD) studies and Field Emission Scanning Electron Microscopy (FESEM) images revealed an inevitable tetragonal tungsten bronze (TTB) secondary phase, which was formed during the preparation process. It was demonstrated that the volatilization of Li⁺ cations facilitated TTB growth. The coexistence of two different phase structures proved to enhance the KNN piezoelectric performance.     

Probing the effect of R-cation radii on structural,vibrational, optical,and dielectric properties of rare earth (R=La,Pr, Nd) aluminates

The present study correlates the effect of R-cation radii on structural, vibrational, optical, and dielectric properties of rhombohedral rare earth aluminates RAlO₃ (R = La, Pr, Nd). The polycrystalline samples of RAlO₃ have been synthesized using sol-gel synthesis technique. Pure rhombohedral phase of RAlO₃ samples has been confirmed with X-ray diffraction. Systematic decrements in the lattice parameter, bond length, and bond angle have been observed, giving rise to structural distortion due to decrease in ionic radii of R-cation. The phononic properties of RAlO₃ have been investigated through Raman spectroscopy, where the degree of distortion of AlO₆ octahedra can be analyzed with the peak position of E_g and A_1g modes. An increase in the energy bandgap with decreasing R-cation radii shows an interconnection with the decrease in Al–O bond length. Interestingly, the decreasing dielectric constant with decreasing ionic radii of R-cation has been correlated with the difference in electronegativity of cation(R³⁺)-anion(O^2?) pair. Also, a positive linear relationship between dielectric constant and energy bandgap has been investigated using Penn model.     

Reaction behavior of quartz in gibbsite-boehmite bauxite in Bayer digestion and its effect on caustic consumption and alumina recovery

A high content of quartz is usually present in Australian gibbsite-boehmite bauxite. The reaction between quartz and sodium aluminate solution at high temperatures in the Bayer process can lead to loss of alumina and sodium oxide. Therefore, to improve alumina recovery, the reaction of quartz needs to be avoided. The digestion behavior of Australian gibbsite-boehmite bauxite and pure quartz in the Bayer process at 230–250 °C was systematically studied in this paper. The mineral composition and morphology of the reaction products were characterized and the kinetics of the quartz dissolution process was studied in detail. It was shown that boehmite in gibbsite-boehmite bauxite can be completely digested at high temperature (250 °C) with a short digestion time (5 min). A short digestion time results in a low reaction rate of quartz in bauxite, and is ideal for alumina recovery at high temperatures. The quartz reaction rate rapidly increases with longer digestion times. The apparent activation energy of the dissolution of quartz in bauxite in the caustic solution is 151.9 kJ mol^?1, and the rate-controlling step of this reaction process is the interfacial chemical reaction. By controlling the particle size of bauxite, the digestion temperature, and the digestion time, the reaction rate of quartz in bauxite can be inhibited, which is beneficial for improving alumina recovery and reducing caustic consumption. Therefore, based on the above theoretical research, a process for digesting gibbsite-boehmite bauxite is proposed using high digestion temperature (250 °C), short digestion time (5 min) and large mineral size. An economic benefit of about US$101.9 million for a refinery with the annual output of 2 million tons of alumina can be created by the proposed process.     

Orthorhombic to tetragonal polymorphic transformation of YTa3O9 and its inhibition through the design of high-entropy (Y0.2La0.2Ce0.2Nd0.2Gd0.2)Ta3O9

To explore the mechanism of phase transformation, YTa₃O₉ was prepared by an integrated one-step synthesis and sintering method at 1500 °C using Y₂O₃ and Ta₂O₅ powders as starting materials. High-temperature XRD patterns and Raman spectra showed that a phase transformation from orthorhombic to tetragonal took place in YTa₃O₉ through the bond length and angle changes at 300–400 °C, which caused a thermal conductivity rise. To inhibit the phase transformation, a high-entropy (Y_0.2La_0.2Ce_0.2Nd_0.2Gd_0.2)Ta₃O₉ (HE RETa₃O₉) was designed and synthesized at 1550 °C using the integrated solid-state synthesis and sintering method. In tetragonal structured HE RETa₃O₉, phase transformation was inhibited by the high-entropy effect. Furthermore, HE RETa₃O₉ exhibited low thermal conductivity, and its tendency to increase with temperature was alleviated (1.69 W/m·K, 1073 K). Good phase stability, low thermal conductivity and comparable fracture toughness to YSZ make HE RETa₃O₉ promising as a new thermal barrier coating material.     

Evolution of core–rim structures and phase transformations in infra-red transmitting Y-α-SiAlON ceramics

Core–rim structures were observed as common features in Y-α-SiAlON ceramics hot-pressed between 1550?1950 °C. We found most dopants were taken into α’-rims, and a transition layer grown first on α-cores from liquid-phase over-saturated with metal solutes. Elongated β’-grain were formed as minor phase with α’- or AlN-cores thus only after the α’ matrix had consumed up all Y solutes, revealing that the α’ → β’ transformation is controlled by the transient liquid-phase and similar defects and dangling bonds could be detected in both SiAlON phases by cathodoluminescence. Quantitative assessment of Y_m/3Si_12?(m+n)Al_m+nO_nN_16?n demonstrates the multiphase evolution, initiated by over-saturation of Y solutes at low temperatures thus retaining α-phase as cores to lower the infra-red transmittance, dictated by homogenization of Al solutes at higher temperature. The elimination of those phase boundaries leads to better dopant and sintering design for achieving transparent and high-performance SiAlON ceramics.     

An integrated model for analysing the effects of ultrasonic vibration on tool torque and thermal processes in friction stir welding

An integrated model of ultrasonic vibration enhanced friction stir welding (UVeFSW) is developed by integrating the thermal-fluid model with the ultrasonic field model and tool torque model. The tool torque and the heat generation rate at tool/workpiece contact interfaces are coupled with the interfacial temperature, strain rate and ultrasonic energy density. The model is used in quantitatively analysing the effects of ultrasonic vibration on tool torque and thermal processes in friction stir welding (FSW). The results show that ultrasonic vibration reduces the flow stress, which results in a decreasing of tool torque, interfacial heat generation rate and interfacial temperature. The complicated interaction of ultrasonic energy with the thermal processes in FSW leads to a gentle thermal gradient and an enhanced plastic material flow in UVeFSW. The model is validated by a comparison of the calculated thermal cycles and tool torque at various welding parameters with the experimentally measured ones.     

Generalized linear model based monitoring methods for high-yield processes

Emerge in technology brought well-organized manufacturing systems to produce high-quality items. Therefore, monitoring and control of products have become a challenging task for quality inspectors. From these highly efficient processes, produced items are mostly zero-defect and modeled based on zero-inflated distributions. The zero-inflated Poisson (ZIP) and zero-inflated Negative Binomial (ZINB) distributions are the most common distributions, used to model the high-yield and rare health-related processes. Therefore, data-based control charts under ZIP and ZINB distributions (i.e., Y-ZIP and Y-ZINB) are proposed for the monitoring of high-quality processes. Usually, with the defect counts, few covariates are also measured in the process, and the generalized linear model based on the ZIP and ZINB distributions are used to estimate their parameters. In this study, we have designed monitoring structures (i.e., PR-ZIP and PR-ZINB) based on the ZIP and ZINB regression models which will provide the monitoring of defect counts by accounting the single covariate. Further, proposed model-based charts are compared with the existing data-based charts. The simulation study is designed to access the performance of monitoring methods in terms of run length properties and a case study on the number of flight delays between Atlanta and Orlando during 2012–2014 is also provided to highlight the importance of the stated research.     

基于信任链的骚扰电话预判技术研究

当前,骚扰电话乱象屡禁不止,严重影响了人民群众的正常生活,甚至威胁到个人财产安全,因此简单有效地识别骚扰电话技术成为亟待解决的问题。区别于现有的对电话号码进行黑白名单标记、大数据分析等识别方法,提出基于信任链的骚扰电话预判技术,从可信度量的角度计算来电号码的可靠程度,并针对高危受害群体的典型应用场景进行分析,通过对骚扰电话的预判,降低其受到电话骚扰甚至电话诈骗的可能性。     

Thermodynamic assessment of the Ga–Se–Te system

In this study, the Ga–Te binary system was reassessed by means of the CALPHAD method using a modified lattice stability parameter for Te as well as experimental data for this binary system. The two-sublattice ionic solution model was applied for the liquid phase, and the intermediate phases were described by the sublattice model. A set of self-consistent thermodynamic parameters was optimized for all the phases in the Ga–Te binary system, which reproduced the phase diagram and the thermodynamic properties well. Using the reevaluated Ga–Te system, previously assessed Ga–Se system, and modified Se–Te system, a critical evaluation of the Ga–Se–Te ternary system was performed. The calculated vertical sections, isothermal sections, and liquidus projection agreed reasonably well with the experimental data. Immiscibility in the liquid phase was observed, and the origin of this behavior is discussed from a thermodynamic perspective.