Microstructure and superelastic properties of free forged Ti–Ni shape-memory alloy

Elemental titanium (Ti) and nickel (Ni) powders were consolidated by spark plasma sintering (SPS) to fabricate Ti–51%Ni (mole fraction) shape-memory alloys (SMAs). The objective of this study is to enhance the superelasticity of SPS produced Ti–Ni alloy using free forging as a secondary process. Products from two processes (with and without free forging) were compared in terms of microstructure, transformation temperature and superelasticity. The results showed that, free forging effectively improved the tensile and shape-memory properties. Ductility increased from 6.8% to 9.2% after forging. The maximum strain during superelasticity increased from 5% to 7.5% and the strain recovery rate increased from 72% to 92%. The microstructure of produced Ti–51%Ni SMA consists of the cubic austenite (B2) matrix, monoclinic martensite (B19′), secondary phases (Ti₃Ni₄, Ti₂Ni and TiNi₃) and oxides (Ti₄Ni₂O and Ti₃O₅). There was a shift towards higher temperatures in the martensitic transformation of free forged specimen (aged at 500 °C) due to the decrease in Ni content of B2 matrix. This is related to the presence of Ti₃Ni₄ precipitates, which were observed using transmission electron microscope (TEM). In conclusion, free forging could improve superelasticity and mechanical properties of Ti–51%Ni SMA.     

自由锻Ti-Ni形状记忆合金的显微组织和超弹性（英文）

采用放电等离子烧结(SPS)法将元素钛粉和镍粉制备成Ti-51%Ni形状记忆合金(SMAs)。研究目的是采用自由锻二次加工以提高SPS合金的性能。对自由锻前后合金的显微组织、相变温度和超弹性进行比较。结果表明,自由锻可以显著提高Ti-Ni形状记忆合金的拉伸强度和形状记忆性能,自由锻后合金的韧性从6.8%提高到了9.2%,超弹性的应变范围从5%增加到7.5%,应变恢复速率从72%提高到92%。Ti-51%Ni合金显微组织中含有立方奥氏体相(B2)基体、单斜马氏体相(B19′)、第二相(Ti_3Ni_4,Ti_2Ni和TiNi_3)和氧化物相(Ti_4Ni_2O,Ti_3O_5)。自由锻后再经500°C时效处理的最终样品的马氏体相变温度向高温方向偏移,这是由于Ti_3Ni_4相(透射电镜下可以观察到)的析出而导致基体中Ni含量的减少。总之,自由锻可以提高Ti-51%Ni形状记忆合金的超弹性和力学性能。     

Role of Metal Oxide Nanomaterials on Thermal Stability of 1,3,6‐Trinitrocarbazole

The thermal behaviour of 1,3,6‐trinitrocarbazole (TENT) in the form of pure and nanocomposite explosives was examined by differential scanning calorimetry (DSC) and thermogravimetry (TG). Thermoanalytical data revealed that thermal decomposition of pure TENT is significantly different from the investigated nanocomposites. The results confirmed that pure TENT decomposed completely in a single stage in the temperature range 400–450 °C. Though, addition of the nanoparticles to the TENT powder leads to higher thermal stability in comparison with the pure TENT. Decomposition kinetics of the pure TENT and the nanocomposites were studied by non‐isothermal DSC at diverse heating rates. The resulted thermokinetic and thermodynamic parameters for the thermal decomposition of pure TENT were compared with the nanocomposites.     

Fabrication by Electrophoretic Deposition of Nano-Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> and Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@SiO<Subscript>2</Subscript> 3D Structure on Carbon Fibers as Supercapacitor Materials

Core–shell nanostructured magnetic Fe₃O₄@SiO₂ with particle size ranging from 3 nm to 40 nm has been synthesized via a facile precipitation method. Tetraethyl orthosilicate was employed as surfactant to prepare core–shell structures from Fe₃O₄ nanoparticles synthesized from pomegranate peel extract using a green method. X-ray diffraction analysis, Fourier-transform infrared and ultraviolet–visible (UV–Vis) spectroscopies, transmission electron microscopy, and scanning electron microscopy with energy-dispersive spectroscopy were employed to characterize the samples. The prepared Fe₃O₄ nanoparticles were approximately 12 nm in size, and the thickness of the SiO₂ shell was?~?4 nm. Evaluation of the magnetic properties indicated lower saturation magnetization for Fe₃O₄@SiO₂ powder (~?11.26 emu/g) compared with Fe₃O₄ powder (~?13.30 emu/g), supporting successful wrapping of the Fe₃O₄ nanoparticles by SiO₂. As-prepared powders were deposited on carbon fibers (CFs) using electrophoretic deposition and their electrochemical behavior investigated. The rectangular-shaped cyclic voltagrams of Fe₃O₄@CF and Fe₃O₄@C@CF samples indicated electrochemical double-layer capacitor (EDLC) behavior. The higher specific capacitance of 477 F/g for Fe₃O₄@C@CF (at scan rate of 0.05 V/s in the potential range of ??1.13 to 0.45 V) compared with 205 F/g for Fe₃O₄@CF (at the same scan rate in the potential range of?~???1.04 to 0.24 V) makes the former a superior candidate for use in energy storage applications.     

A new approach for the synthesis of polyaniline microstructures with a unique tetragonal star-like morphology

Shape-controllable polyaniline (PANI) microstructures with a unique tetragonal star-like morphology were synthesized by a rapid initiated strategy with glycine (Gly) as dopant. The results demonstrate that the morphology of PANI microstructures is significantly influenced by the molar ratio of aniline to glycine. The PANI prepared in this study exhibits nanofiber-like morphology with exceptionally high crystallinity. These nanofibers can self-assemble into tetragonal star-like microstructures with a unique alignment. The chemistry, morphology, and crystal structure of glycine doped star-like microstructures were studied using SEM, UV–vis, FT-IR, XRD and cyclic voltammetry (CV).     

Optimum placement of condensing units of split-type air-conditioners by numerical simulation

Split-type air-conditioners used in residential or office buildings often have the outdoor condensing units installed at the sidewalls or on the roofs. Installation distance from the supporting wall for the first group and the height of installation for the second group are two factors that affect the condenser efficiency. In this study, a CFD code is used to calculate the effect of distance from the supporting wall on the entrance air temperature and on the on-coil temperature of condenser installed between two walls. In the case of condenser installed on the roof, the effect of installation height of the condenser from the finished roof on on-coil temperature is investigated and the minimum recommended height of installation is determined.     

Cause-selecting control charts based on Huber’s M-estimator

Cause-selecting chart (CSC) is effective in monitoring and diagnosing multistage processes. It discriminates between the overall and specific qualities by establishing the relationship between input and output measurements. In practice, the model relating the input and output variables must be estimated. To this end, historical data are used, which often contain outliers. The presence of outliers has a deleterious effect on the control charting procedure. To alleviate the encountered problem, a robust monitoring approach based on Huber’s M-estimator is proposed. Subsequently, the performance of the robust and non-robust CSCs is investigated using the average run length criterion while conducting a simulation study. The results reveal that the Huber-based CSC is superior to the traditional CSC due to its prompt detection of out-of-control conditions.     

pH-sensitive nanogels based on Boltorn H40 and poly(vinylpyridine) using mini-emulsion polymerization for delivery of hydrophobic anticancer drugs

In this study, we describe the synthesis of a new structure of pH-sensitive H40 based nanogel by click reaction through mini-emulsion polymerization. The nanogels were synthesized by cross coupling of H40-poly(ε-caprolactone) (H40-PCL) dendrimers as cores and poly(vinylpyridine) (PVP) as a pH sensitive crosslinker. The poly(ethylene glycol) (PEG) pendant group was introduced at the middle of PVP chains as hydrophilic segment to act as hydrophilic shell at final nanogel for better dispersity. Folic acid that is conjugated at the end of some of PEG through the free carboxyl group was used for targeting cancer cells that overexpress folate receptors.