Ferroelectric KNbO 3 (KN) ceramics were first fabricated in the 1950s, however, their use in commercial technical applications has been hampered by inherently challenging processing difficulties. In the early 1990s, the interest in KN ceramics was revived by the pursuit of Pb-free piezoceramics. More recently the search for inexpensive photovoltaic materials alternative to Si prompted bandgap engineering studies in KN-based solid solutions. If the ferroelectric and piezoelectric properties of KN-based ceramics are now well established, the understanding of chemical doping on the bandgap of KNbased ceramics is still in its infancy. Here we provide a brief review on the current understanding of the structure-property relationships in this class of materials, which successively covers crystal structures, structural phase transitions, lattice dynamics, polarization, solid solutions and bandgap engineering of KN.
Bi3+ with a stereochemically active lone-pair of electrons induces severe lattice strain in BaTiO3 as revealed by a significant Raman shift of the mode associated with the O–Ti–O bonds.
A hybrid composite materialsare one of the types to provide good suspension in wheeled vehicles application.By reducing weight of suspension systems, lowers total fuel exhaustion and costs.One of the most common approaches is to replace steel components with composite materials.To improve safety, comfort, and durability, composite have been introduced. Composite materials are corrosion resistant, have a good strength-to-weight ratio, and can store a lot of elastic strain. The aim of this study is to look into the structural properties of a hybrid compositematerials made of 95 percent Epoxy, 5% rubber, 5% glass fiber, and 5% hybrid composite of rubber and glass fiber. Since it has advantages over other approaches, hand layup was used in the fabrication. The mechanical experiments were used to determine the efficacy of the proposed composite leaf spring. We performed tensile, impact, hardness tests. When reinforcing fibers were used, the experimental results showed an improvement in hardness, impact, tensile strength. after the reinforcing fibers have been added, the best mechanical test results were obtained when hybrid reinforcement was used.
In this work, the mechanical properties of three types of dough rubber NR, NR/BR, and NR/SBR have been investigated using five percentages of materials fill (30, 40, 50, 60, and 70) pphr. Carbon black was used as a filler material. The tensile test was achieved with 300% elongation and strain rates of (100, 200, 300, 400, and 500) mm/min. The tensile strength results indicate that the maximum value of tensile strength for NR Dough carbon black 60 pphr reaches 23.2 MPa; the maximum tensile strain of NR dough (carbon black 50 pphr) reaches 805.5%, and the modulus of elasticity with carbon black 70 pphr reaches 4.3 MPa. It was found that the compression strength decreases with increasing the carbon black, and the maximum value of compression set at NR dough (carbon black 30 pphr) reaches 29.3%. Fatigue crack growth was achieved according to ASTM D 813 for rubber testing. The minimum value of fatigue strength dough (carbon black 70 pphr) reaches 68 (IRHD). For NR dough (carbon black 30,40,50 pphr) reaches 3.5 mm at the number of cycles 15000 cycle. Finally, the maximum hardness of NR.
The aim of this study is to simultaneously establish the processability and physical properties of Lithium aluminosilicate-based (LAS) glass for dental restorations. An eventual outcome is the production of glass-ceramic matching both the aesthetics and mechanical properties of natural tooth. The two LASbased glass compositions, refer to as LAS1 glass and LAS2 glass, are investigated using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), Raman Spectroscopy (RS), Ultrasonic Testing (UT), Vickers Hardness and threepoint bending flexural testing. ICP-OES analyses reveal LAS1 glass and LAS2 glass to be compositionally similar, however LAS2 glass contains traces of vanadium. XRD analyses reveal the presence of Li3PO4 and Li2SiO3 crystals in LAS1 glass, which apparently are not detected in LAS2 glass, however RS analyses obviously show vestiges of these phases in LAS2 glass. DSC reveals LAS1 glass and LAS2 glass to exhibit similar thermal behaviour. LAS1 glass shows a glass transition temperature of ~500°C, two major thermal exothermic events at 615°C and 705°C, which are followed by two minor thermal exothermic events at 750°C and 790°C, and finally a major endothermic event at 910°C. Based on In-situ XRD analyses carried out between 540°C to 790°C, the first exothermic event centred at ~615°C can be associated with the successive crystallisation of Li2SiO3, Li0.25Al0.25Si0.75O2 and LiAlSi4O10, whereas the second peak centred at ~705°C can be associated with the crystallisation of LiAlSi2O6 and Li2Si2O5. Similar results are obtained for isothermal treatments of 30 minutes in the temperature range of 610°C and 870°C, as shown by combined ex-situ by XRD and RS analyses. The incorporation of a nucleation step of 300 minutes at 550°C, reduces the crystallisation temperature of LiAlSi4O10 and Li0.25Al0.25Si0.75O2 by ~20°C, but also leads to increase of the crystallite sizes. Following this initial evaluation of the impact of isothermal heat treatments, other heat treatments are strategically carried out at temperatures below and above the exothermic events in order to evaluate again their impact on both phase assemblage and physical properties, such as hardness, elastic modulus, fracture toughness and colour. Hence, based on the DSC data, nucleation is carried out at a temperature of 550°C for 300 minutes, and crystallisations are carried out at 670°C, 780°C, 800°C, 830°C and 850°C, for different time lengths. XRD results reveal LiAlSi2O6 to be the dominant crystalline phase, followed by Li2Si2O5 and Li2SiO3 for both LAS1 glass and LAS2 glass. Both LAS1 and LAS2 glassceramics exhibit high values of mechanical properties when the heat treatment is at 550°C for 300min,780°C for 120min and 830°C-850°C for 120 min. Moreover, LAS1 glass and LAS2 glass heat treated above 770°C are both aesthetically suitable for dental restorations. Regarding the LAS1 glass, the colour is white, whereas LAS2 glass colour is identical to several standard shades including D2, C1 and B2, depending on the heat treatment temperature
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