Preparation, Structure, and Electrical Properties of Cobalt-Modified Bi(Sc3/4In1/4)O3–PbTiO3–Pb(Mg1/3Nb2/3)O3 High-Temperature Piezoelectric Ceramics

Cobalt-modified 0.40Bi(Sc3/4In1/4)O3–0.58PbTiO3–0.02Pb(Mg1/3Nb2/3)O3 ceramics (abbreviated as BSI–PT–PMN–xCo) were produced by conventional two-step solid-state processing. The phase structure, micro structure morphology, and electrical properties of BSI–PT–PMN–xCo were systematically studied. The introduction of Co ions exerted a significant influence on the structure and electrical properties. The experiment results demonstrated that Co ions entered the B-sites of the lattice, resulting in slight lattice distortion and a smaller lattice constant. The average grain size increased from ~1.94 μm to ~2.68 μm with the increasing Co content. The optimized comprehensive electrical properties were obtained with proper Co-modified content 0.2 wt.%. The Curie temperature (Tc) was 412 °C, the piezoelectric constant (d33) was 370 pC/N, the remnant polarization (Pr) was 29.2 μC/cm2, the relatively dielectric constant (εr) was 1450, the planar electromechanical coupling coefficient (kp) was 46.5, and the dielectric loss (tanδ) was 0.051. Together with the enhanced DC resistivity of 109 Ω cm under 300 °C and good thermal stability, BSI–PT–PMN–0.2Co ceramic is a promising candidate material for high-temperature piezoelectric applications.

Review on Manufacturing of Metal Foams

Metal foams possess excellent physical and mechanical properties. This paper reviews the common manufacturing process of metal foams. Various ways used to produce metal foams based on metal properties are described. The manufacturing process follows four primary routes: liquid state, solid state, ion or vapour processing. Liquid-state processing produces porosity to liquid or semi-liquid metals, and solid-state foaming produces metal foams with metal powder as starting material. For ion and vapour processing methods, metals are electro-deposited onto a polymer precursor. The polymer precursor is removed by chemical or heat treatment to produce metal foams. The advantages and limitations of each manufacturing process are also described.

Structural Aspects and Characterization of Structure in the Processing of Titanium Grade4 Different Chips

This study presents the structural aspects of the solid-state processing of various titanium chips. The structural characterization of: (1) commercial pure Ti in the as-received state, (2) manufactured chips, and (3) products of the chip processing are presented. Pure single-phase titanium Grade4 (Ti Gr4) was processed which, among all grades of pure titanium, is characterized by the lowest possible purity and the highest possible strength at the same time. Four geometries of chips were processed, i.e., chips after turning (thin and coarse), and chips after milling (thin and coarse). An unconventional plastic working method was applied to transform a dispersed form (chips) into solid, bulk metal in the form of rods without re-melting. The rods with a diameter of Ø8 mm and a length of about 500 mm were manufactured. Based on computer tomography and Archimedes measurements, it was found that the manufactured rods were consolidated and near fully dense. In turn, microscopy investigations proved that conventional, polycrystalline, grained structures were obtained. Only an insignificantly small number of internal defects were revealed, meaning that the obtained rods exhibited a proper structure typical for commercial titanium. Obtained materials, except of small surface inclusions, were fee of impurities. Whereas the results of the compression tests proved that the manufactured rods are characterized by new interatomic bonds, cohesion and plasticity analogous to those of titanium in the as-received state.

Process Parameter Influence on Tensile Property of Friction Stir Processed Al/Ni-Fe Composite

Friction stir processing (FSP) is a solid-state processing technique that has proven to be an efficient surface modification process for producing aluminium matrix composites (AMCs). However, practical challenges still occur during the processing of AMCs even though extensive progress has been made in recent years. In the present study, the influence of FSP process parameters on the tensile property of Al-Ni-Fe composite has been investigated. The process parameters studied were rotational speed and advancing speed. The rotational speed varied between 600 and 1000 rpm while the advancing speed varied between 70 and 210 mm/min. The rotational speed was kept constant at each setting and the advancing speed varied. Other processing parameters were kept constant throughout the experiments. The results were compared with those of the base metal (Al). The results showed that the tensile strength decreased as the advancing speed increased. The highest tensile strength was obtained at a rotational speed of 1000 rpm and an advancing speed of 70 mm/min.

Pengaruh Temperatur Cetakan terhadap Kualitas Produk Komposit Aluminium - Multiwall Karbon Nanotube yang Dipabrikasi dengan Proses Stir Casting

Penelitian ini bertujuan menyelidiki pengaruh temperatur cetakan terhadap kualitas produk komposit aluminium – multiwall karbon nanotube yang dipabrikasi dengan methode liquid state processing (stir casting). Komposisi campuran aluminium dengan multiwall karbon nanotube adalah 98:2 persen berat. Proses peleburan bahan komposit menggunakan rangkaian pemanas induksi. Temperatur peleburan dipertahankan pada 700 oC selama 10 menit dan kecepatan pengaduk (stirrer) 200 rpm. Leburan komposit dituangkan pada cetakan logam (steel) berbentuk silinder dengan temperatur cetakan bervariasi, 25, 50, 75, 100, 125, dan 150 oC. Hasil produk komposit pada awalnya diamati secara visual, untuk selanjutnya dilakukan beberapa pengujian, antara lain : uji densitas, porositas, dan kekerasan komposit di Lab Metalurgi Jurusan Teknik Mesin Universitas Udayana, dan morfologi/struktur mikro menggunakan alat uji SEM-EDS di Lab. SEM Teknik Mesin ITS. Dari pengamatan diperoleh beberapa kesimpulan, antara lain : semakin tinggi temperatur cetakan, massa jenis komposit aluminium – multiwall karbon nanotube semakin meningkat, namun porositasnya semakin menurun. Sementara semakin tinggi temperatur cetakan, kekerasan komposit aluminium – multiwall karbon nanotube semakin meningkat.

ICOSAHEDRAL PHASE OF Al65Cu25Fe15

The present work aimed to characterize the microstructure of the icosahedral phase (quasicrystalline phase-ϕ) of the system with stoichiometric composition of the quasicrystal Al65Cu25Fe15 . The ternary alloy with nominal composition of Al63Cu25Fe12 was processed by mechanical alloying (MA) as a viable solid state processing method for producing various metastable and stable quasicrystalline phases. The structural characterization of the obtained samples was performed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), while the elemental composition was determined by dispersive energy spectroscopy (DES). The diffraction patterns of Al65Cu25Fe15 showed the presence of ω-Al7Cu2Fe , β-Al(Fe, Cu) and λ-Al13Fe4 phases that coexist with the thermodynamic quasicrystalline phase-ϕ. Finally, elemental analysis indicates that during alloy synthesis there is little variation of the ideal composition. The results indicate that alloys with high percentage of icosahedral phase can be obtained by casting in the air.