On the Refinement Mechanism of Silicon in Al-Si-Cu-Zn Alloy with Addition of Bismuth

Obtained results of micro and nano studies reveal that bismuth refines the silicon in which the flake silicon changed to lamellar structure with reduction in twin spacing from 160 to 75 nm. Bismuth segregates towards the inter-dendritic regions and decreases the Al-Si contact angle resulting in suppression of the silicon growth causing refinement of the eutectic structure. Increased recalescence temperature and time confirmed that the refinement effect is attributed to the growth stage.     

EFFECT OF HIGH PRESSURE ON THE ACCUMULATION OF IMP AND ON THE STABILITY OF AMP DEAMINASE IN RABBIT SKELETAL MUSCLE

This study evaluated the effect of high pressure on rabbit skeletal muscle, specifically on the production of inosinic acid (IMP), one of “umami” components, and on the activity of adenosine triphosphate (AMP) deaminase, which plays a role in the conversion of AMP to IMP. By increasing the pressure (0.1 to 300 MPa), nucleotide analysis showed that IMP content in muscle increased instantly with a concomitant decrease in ATP content. The IMP content of muscle at 300 MPa was approximately 15% higher than with lower pressures (0.1–200 MPa) when stored for 1 week at 4C after pressurization. These results suggested that the metabolism of nucleotides in muscle was not significantly impaired by pressure treatment. At 300 MPa, AMP deaminase maintained approximately 70% of the activity at 0.1 MPa. In contrast, the activity of purified AMP deaminase was completely lost at 200 MPa, and irreversible conformational changes were observed by in situ fluorescence spectroscopy. These results indicated that purified AMP deaminase was irreversibly denatured under pressure as high as 300–400 MPa.     

Development and antibacterial performance of silver nanoparticles incorporated polydopamine–polyester-knitted fabric

Metallization is one of the finishing processes in textile treatment that can produce multifunctional effects. The present study dealt with the development of an antibacterial polyester-knitted fabric via facile and green impregnation of silver nanoparticles (SNPs). This was done by applying a polymeric foundation on the polyester-knitted fabric by simply dip-coating in the aqueous solution of dopamine. Then the SNPs were in situ fabricated and impregnated on the surface of polydopamine-modified polyester-knitted fabric in an aqueous solution of AgNO₃ at room temperature. Thus, a multi-functional finishing of polyester-knitted fabric was done. The Fourier transform infrared spectroscopy was done to confirm the polymer attachment. Scanning electron microscopy equipped with energy dispersive X-ray was done to confirm the presence of SNPs on treated fabric. The crystallography of the treated surface was examined by X-ray diffraction. The antibacterial properties of treated fabrics against broad spectrum bacterial strains were investigated and found significant.     

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 bismuth on solidification,microstructure and mechanical properties of a near eutectic Al-Si alloys

Computer aided thermal analysis and microstructural observation showed that addition of bismuth (Bi) within the range of 0.25 and 2 wt% produced a greater effect on the Al-Si eutectic phase than on primary aluminium and Al₂Cu phases. Results showed that with addition of 1 wt% Bi the eutectic silicon structure was refined from flake-like morphology into lamellar. Bi refines rather than modifies the Si structure and increases the Al-Si eutectic fraction solid and more significantly there was no fading even up to 180 min of melt holding. Transmission electron microscopy study showed that the Si twin spacing decreased from 160 to 75 nm which is likely attributed to the refining effect of Bi. It was also found that addition of 1 wt% Bi increased the tensile strength, elongation and the absorbed energy for fracture due to the refined eutectic silicon structure.