The solution synthesis of colloidal semiconductor quantum dots (QDs), such as CdSe QDs, has developed tremendously in the last two decades. Such QDs exhibit excellent optical properties, such as size dependent optical gaps and efficient carrier multiplication, because of the quantum confinement effect. Colloidal QDs have potential in various optical and optoelectronic devices, such as light emitting devices, solar cells and wavelength converters for displays. The use of toxic cadmium materials in light emitting devices and wavelength converters is currently unavoidable for achieving full color visible emission. Less toxic alternatives are required. Safe facile procedures for synthesizing narrow gap arsenide QDs are also required for QD-solar cells, which exploit low threshold energies of carrier multiplication. This article reviews recent advances in the synthesis and properties of colloidal QDs. Their applications are reviewed in terms of cadmium-free QD-phosphors, and safe and facile syntheses of arsenide QDs for solar cells. Our group’s research on the synthesis of the ternary chalcopyrite I-III-VI₂ semiconductors, ZnO and InAs QDs, and fabrication of electroluminescent devices using ZnO QDs is discussed.

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Investigation to obtain the high quality (Bi,Na)TiO₃ (BNT) single crystals and polycrystalline ceramics and to reveal the polarization mechanism of rhombohedral BNT were performed. BNT single crystals were grown by the high-Po₂ flux method and their polarization and piezoelectric properties were investigated along [100]_c, [110]_c and [111]_c, where “c” denote cubic notation used. Strain measurements of rhombohedral BNT crystals suggest that the polarization reversal along [111]_c is achieved by non-180° spontaneous polarization (P_s) rotation. The values of remanent polarization (P_r) obtained along these three directions provided a value of P_s of 55–60 µC/cm² at 25°C for rhombohedral BNT. The aerosol deposition (AD) method with use of heat treatment supplied fully dense self-supported BNT polycrystalline films detached from substrates. The annealed self-supported BNT polycrystalline films indicated a superior low leakage current density (J) of approximately 10⁻⁸ A/cm² at 150 kV/cm, which was lower than that of sintered bulks. Also well-saturated hysteresis loops with a large P_r of 40 µC/cm² were confirmed, which was near value of maxmum P_r (48–52 µC/cm²) estimated from the P_s of high quality BNT single crystals. The high-Po₂ flux method and use of the AD method have been demonstrated to be effective for the obtaining high quality BNT single crystals and polycrystalline ceramics.

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The goals of bone tissue engineering are to apply biomaterial scaffolds with adhered cells, such as osteoblasts, bone marrow stromal stem cells, or chondrocytes, to repair, regenerate, and restore the functions of damaged bone tissue or to replace those tissues with porous engineered biomaterials. Over recent decades, a diverse class of biomaterials has been applied in bone tissue engineering field. Porous hydroxyapatite bioceramic is currently receiving significant attention as a bone tissue engineering substitute because of its biological characteristics, including biocompatibility, bioactivity, osteoconduction, and vasculogenesis. This biomaterial has a three-dimensional structure with interconnected spherical pores of uniform size, which encourages bone ingrowth and achieves good integration of the material and the host bone over time. However, the compressive strength and elastic modulus of porous hydroxyapatite scaffolds generally weaken as the porosity increases, in both in vitro and in vivo testing. Zirconia can be used to toughen hydroxyapatite materials for bone repair and replacement because of its unique biomechanical properties, including compressive strength and fracture toughness. Additionally, a zirconia chitosan hybrid containing bone morphogenetic protein-2 and mesenchymal stem cells derived from induced pluripotent stem cells has been used as a coating material adhered to surface of scaffolds to promote bone regeneration and repair. Here, we provide a succinct review of zirconia toughened hydroxyapatite biomaterial scaffolds that incorporate bone morphogenetic protein-2 and mesenchymal stem cells for bone tissue engineering and describe the biomaterials that are currently being investigated based on the recent literature and our own data.

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Ultrafine-grained Si₂N₂O–Si₃N₄ composites are fabricated by hot press sintering of amorphous nanosized silicon nitride powders at 1600, 1650, and 1700°C, with nanosized Al₂O₃ and Y₂O₃ as additives. Sintered materials of increasing average grain sizes of 280, 360, and 480 nm were obtained with increasing sintering temperature. The nanoindentation hardness, microhardness and macroscopic Vickers hardness are tested using nanoindentation, microhardness tester, and macroscopic Vickers hardness tester. The hardness is found to decrease with increasing sintering temperature and average grain size. The results of the nanoindentation hardness and microhardness tests obviously reflect the effect of loading. The nanoindentation hardness is related to the ratio of the indentation maximum contact cross-sectional area A and the average grain cross-sectional area S. As the ratio of A and S decreases, the fine-grain strengthening effect becomes less evident. The comparative analysis of nanoindentation hardness and microhardness revealed that the microhardness test is considered more suitable for estimating the hardness of the ultrafine-grained Si₂N₂O–Si₃N₄ composites.

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New composite ceramics consisting of spinel-type LiFe_1−xMn_xSiO₄ nanocrystals and glassy phase were synthesized by a quenching of melts with the compositions of 25Li₂O–(25 − y)Fe₂O₃–2yMnO₂–50SiO₂ (y = 0–25, mol %) and their electrochemical performance as cathode materials for Li⁺ ion secondary batteries (LIBs) was examined. In the melt-quenched samples with y = 0–7.5, the formation of LiFe_1−xMn_xSiO₄ nanocrystals with a diameter of ∼30 nm was confirmed together with the presence of the glassy phase from XRD, STEM-EDX, and HRTEM measurements. The electrical conductivity (σ) of the melt-quenched samples (composites) at room temperature decreased rapidly with increasing MnO₂ content, i.e., σ = 2.0 × 10⁻³ Scm⁻¹ for the sample with y = 0 and σ = 5.7 × 10⁻⁹ Scm⁻¹ for the sample with y = 7.5, and the activation energy (E_a) of σ was 0.2–0.3 eV. From the electrochemical charge and discharge curves, it was clarified that the melt-quenched samples work as cathode materials for LIBs. The sample with LiFe_0.7Mn_0.3SiO₄ nanocrystals showed a large discharge capacity of 361 mAhg⁻¹ at the first cycle, although a large decrease in the discharge capacity with cycling was observed. The melt-quenched samples with y = 10–25 were glasses with no crystals, but they also showed Li⁺ ion battery performance.

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Fabrication, microstructure and properties of in situ formation of strengthened eutectic composites, consisting of a matrix (B₄C, and B₄C–NbB₂ composite) and also containing regularly distributed whiskers of NbB₂ by spark plasma sintering (SPS) is reported. It has shown that pressure and the temperature at which pressure is decreased during SPS may be used as a means of controlling the eutectic formation and composites microstructure. The microstructure-property relations were determined for composites of NbB₂–B₄C eutectic composition as a function of NbB₂ content, eutectic inclusion rod size and NbB₂–NbB₂ spacing distance. It was found that the composites with the eutectic composition of 30–35 mol.% NbB₂ obtained by SPS exhibit a high Vickers hardness (26–27 GPa) and a maximum in indentation fracture toughness (~7 MPa·m^1/2) in case of interlamelar spacing distance of 0.8 ± 0.4 µm.

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5 V cathode material LiNi_0.5Mn_1.5O₄ was synthetized by a simple wet chemical reaction using acetates as precursor’s materials. Cathode active materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and Inductively Coupled Plasma (ICP). Electrochemical properties of active materials were evaluated through charge–discharge tests with operation voltage between 3.5 to 4.9 V at 0.3 C. The synthetized sample with high amount of Mn/Ni precursor (LMNO-1) shows a higher first discharge capacity but a faster degradation after 3 cycles. This behavior should be due to the lack of Mn substitute by Ni and therefore more significant Jahn–Teller effect as shown by Raman, ICP and XPS results.

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The channel lining of Inner Mongolia hetao irrigation is set in the research background, which was used by natural pumice concrete as the raw material. In the present study, based on the existing research and analysis methods of air entraining natural pumice concrete freeze-thaw damage, a nuclear magnetic resonance detection technique was introduced. From the research of essence of freeze-thaw coupling-induced concrete damage in saline solution, natural pumice concrete porosity and transversal relaxation time T₂ spectral parameters were used as criteria. Nuclear magnetic resonance imaging (NMRI) technology, an intuitive method, was used to quantitatively determine the freeze-thaw damage. Furthermore, the nuclear magnetic resonance results were compared and demonstrated, combined with ultrasonic testing methods and the capillary water absorption test. Based on the study results, it may be concluded that four peaks were present in the T₂ distribution of air entraining natural lightweight aggregate concrete after 200 cycles of freezing and thawing, the porosity increased with the increase of the air-entraining agent, and T₂ spectrum area increased. The freeze-thaw cycle of frost resistance was improved by a moderate quantity of air entraining agent. An excess of the air-entraining agent caused large pores, which accelerated the freeze-thaw damage. NMRI was used to analyze the pore damage propagation characteristics of the air-entraining concrete, which provides information for freezing thawing damage analysis of concrete, and also represents the unique advantages of NMR techniques.

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A poled lead titanate zirconate rectangular parallelepiped is subjected to an electric field at a room temperature called reference temperature to reach a specific value of polarization. Then the temperature of specimen is raised at the specific value of polarization under no electric field, measuring polarization and strain changes in the specimen. Pyroelectric and thermal expansion coefficients are estimated from measured responses. A set of modeling equations is proposed to predict the dependence of the thermal moduli on remnant state variables and the relations between remnant state variables at high temperatures.

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The effect of initial setting temperature on the compressive strength of calcium phosphate cements prepared using Ca₄(PO₄)₂O and CaHPO₄ was examined. The strength of the initial setting bodies increased with increasing temperatures: the strength of the body heated at 100°C was ~14 MPa, which was ~7 times higher than that heated at 37°C. When the setting bodies were soaked in simulated body fluid at 37°C for 24 h, they showed enhanced strength properties owing to the interlocking structure originating from hydroxyapatite formation. The extent of this effect increased with decreasing setting temperatures: the strength of the body heated at 37°C was ~50 MPa, which was ~3 times higher than that heated at 100°C. This was due to the rapid formation of hydroxyapatite following initial setting of the bodies treated at higher temperatures and the delayed hydration reaction following soaking in simulated body fluid.

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Sintering behaviour as dependence of water absorption, flexural strength and firing shrinkage of dry pressed test samples made from three different types of feldspar rocks on the firing temperature (1120–1300°C) was determined. Potassium, potassium-sodium and sodium-calcium industrially milled feldspars with similar granulometry according to equivalent mean spherical diameter of the grains d(0.5) in the range of 16.6–20.8 µm were used. The sintering process was described according to changes in mineralogical composition of the fired test samples too. During the sintering process, feldspars gradually disappear in phases–first of all alkali feldspars (albite, microcline); anorthite (calcium feldspar) is more resistant to melting thanks to its higher melting temperature and it increases the sintering temperature of feldspar. Sodium-potassium feldspar Z43NaK50 with the lowest content of alkalis (3.35% of K₂O and 2.67% of Na₂O) and the highest equivalent mean spherical diameter d(0.5) showed the most intensive sintering activity. An explanation of this unexpected fact can be found in the equilibrium phase diagrams and in the formation of low melting eutectic mixtures.

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