Leaching kinetics of colemanite in ammonium hydrogen sulphate solutions

The aim of the study was to investigate the dissolution kinetics of colemanite in ammonium hydrogen sulphate solutions in a mechanical agitation system and to declare an alternative reactant to produce boric acid. Reaction temperature, concentration of ammonium hydrogen sulphate, stirring speed, solid/liquid ratio and particle size were selected as parameters on the dissolution rate of colemanite. The experimental results were successfully correlated by linear regression using Statistica Package Program. Dissolution curves were evaluated in order to test shrinking core models for solid–fluid systems. It was observed that increase in the reaction temperature and decrease in the solid/liquid ratio causes an increase the dissolution rate of colemanite. The dissolution extent is highly increased with increase the stirring speed rate between 100 and 500 rpm and the dissolution extent is slowly increased with increase the stirring speed between 500 and 700 rpm in experimental conditions. The activation energy was found to be 32.66 kJ/mol. The leaching of colemanite was controlled by diffusion through the ash or product layer. The rate expression associated with the dissolution rate of colemanite depending on the parameters chosen may be summarized as follows: 1 ? 3(1 ? X)^2/3 + 2(1 ? X) = 8.99 × C^1.08 × W^1.39 × D^?1.27 × (S/L)^?0.54 × e^(?32.66/RT)t.     

Orthorhombic‐pseudocubic phase transition and piezoelectric properties of (Na0.5K0.5)(Nb1−xSbx)‐SrZrO3 ceramics

0.96(Na_0.5K_0.5)(Nb_1?xSb_x)‐0.04SrZrO₃ ceramics with 0.0≤x≤0.06 were well sintered at 1060°C for 6 hours without a secondary phase. Orthorhombic‐tetragonal transition temperature (T_O‐T) and Curie temperature (T_C) decreased with the addition of Sb₂O₅. The decrease in T_C was considerable compared to that in T_O‐T, and thus the tetragonal phase zone disappeared when x exceeded 0.03. Therefore, a broad peak for orthorhombic‐pseudocubic transition as opposed to that for orthorhombic‐tetragonal transition appeared at 115°C‐78.2°C for specimens with 0.04≤x≤0.06. An orthorhombic structure was observed for specimens with x≤0.03. However, the polymorphic phase boundary structure containing orthorhombic and pseudocubic structures was formed for the specimens 0.04≤x≤0.06. Furthermore, a specimen with x=0.055 exhibited a large piezoelectric strain constant of 325 pC/N, indicating that the coexistence of orthorhombic and pseudocubic structures could improve the piezoelectric properties of (Na_0.5K_0.5)NbO₃‐based lead‐free piezoelectric ceramics.     

纤维缠绕机网格型芯模零件库的建立

利用VC++6.0和Pro/Toolkit结合设计出纤维缠绕机网格型芯模的零件库,在零件库中可以根据实际需要生成相应的网格型芯模,在新生成的模型中建立网格型芯模的尺寸对象和关系式的对话框。使用时通过修改对话框中芯模的尺寸并更新来获得新的网格型芯模模型,同时在对话框中显示芯模的尺寸文本和关系式。通过对话框能够清楚地知道各个尺寸的具体含义,因此能够为纤维缠绕机数控程序的编写提供必要的尺寸参数。     

Crystallization of itaconic anhydride grafted poly(lactic acid) during annealing

The effect of annealing poly(lactic acid) (PLA) and PLA grafted with itaconic anhydride (IA) at different temperatures was studied using differential scanning calorimetry (DSC) and wide angle X‐ray scattering (WAXS). For PLA, two crystal forms were obtained when annealed between 110 and 120 °C, transforming into only the α‐form at 130 °C while a mixture of α′ and α‐form were obtained in grafted PLA. Grafting increased the percentage crystallinity of PLA, but it was mostly unaffected by the degree of grafting. The rate of crystallization was strongly dependent on the degree of grafting; when annealed at 100 °C, the crystallinity increased from 27.7 to 43.1% while the crystallization halftime reduced from 10.7 to 4.4 min at the lowest degree of grafting. It was thought that the increase in crystallization rate was likely due heterogeneous nucleation in the presence of grafted chains. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44614.     

High temperature corrosion behavior of Ni-based alloys

The high temperature corrosion behavior of N07263, N06600, and N06625 in LiCl-Li₂O molten salt was investigated at temperatures ranging from 650 to 850 °C in a glove box. The high temperature corrosion behavior was observed using measurements of the oxide morphology and thickness, the extent of internal corrosion, and the compositional changes in the scale and in the substrate. Corrosion tests were performed, and these demonstrated that the main corrosion products were Fe(Ni,Co)₃, FeNi₃, and LiCrO₂. The internal corrosion of N07263 was localized, while that of N06600 maintained intergranular corrosion throughout the test temperature range. N06625 exhibited uniform intergranular corrosion behaviors at low and high temperatures. N07263 exhibited superior corrosion resistance, as evidenced by its corrosion layer which was more continuous, dense, and adherent when compared with those of N06600 and N06625.     

Tailored blank design and prediction of weld line movement using the backward tracing scheme of finite element method

To achieve weight and cost reductions in component manufacturing, tailored blank is introduced for forming automotive structural skin components. In order to obtain successful application of tailored blanks without necessarily trimming after the forming process, it is critical to design an initial welded blank and to predict the weld line movement, which is usually determined by intuition and experience with the trial-and-error approach. A systematic approach method of the backward tracing scheme, which is confirmed by experiment, is extended to design the initial tailored blank for net-shape production in this study. The optimised tailored blank by the backward tracing scheme appears to be successful in obtaining a net-shape stamping product. This blank also improves the forming condition during stamping process. All simulation results show that the backward tracing scheme can be applied to more general blank design.     

Development of Polymer Network of Phenolic and Epoxies Resins Mixed with Linseed Oil: Pilot Study

Epoxy resin was mixed with phenolic resins in different percentages by weight. Composite 40/60 means the proportion by weight of epoxy resin is 40%. It was found that only composites 50/50 and 40/60 could be cured in ambient conditions. Dynamic mechanical analysis showed that only these two composites form interpenetrating polymer network. The addition of linseed oil to the two resins results also in the formation of interpenetrating network irrespective of proportion by weight of the resins; the mechanical properties will only be better when the percentage by weight of epoxy resin is higher; the aim of reducing cost and at the same time maintaining the mechanical properties cannot be fully achieved because epoxy resin is much more expensive than its counterpart.     

Measurement of excess enthalpies using a high-pressure flow microcalorimeter and determination of binary interaction parameters for thermodynamic models

While an equation of state (EOS) plays a critical role in estimating thermodynamic properties, employing it in the determination of binary interaction parameters is extremely important. In general, these parameters can be determined from phase equilibrium data. However, data collection from experiments is a time-consuming and tedious process. In this study, after measuring the excess enthalpies of binary systems containing CO₂ by high-pressure flow isothermal microcalorimetry (IMC), we determined the EOS binary interaction parameters, specifically, the Peng-Robinson EOS binary interaction parameters. These binary interaction parameters obtained by IMC were compared with those obtained by vapor-liquid equilibrium (VLE) experiments. Hence, high-pressure flow IMC appears to be an effective method for the determination of interaction parameters that are used in the estimation of thermodynamic properties. Further, the Flory-Huggins interaction parameters of a binary mixture CO₂ containing with various mole compositions were also estimated by employing high-pressure IMC.