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By investigating the responding behavior of Li modified (K,Na)NbO3 ceramics under external electrical field, a coincidence phenomenon had been observed. It was found that the amplitude of piezoelectricity enhancement for these ceramics with pure orthorhombic, coexistence and tetragonal phase were consistent with the variation amplitude for the transition temperature from orthorhombic to tetragonal (TO-T). The interpretation of the remnant polarization (Pr) had rationally demonstrated the enhancement of piezoelectricity for these three kinds of ceramics. The residual polarization energy induced by remnant polarization (Pr) was about to affect the thermodynamic equilibrium state of these ceramics and accordingly ΔTO-T varied with these poled ceramics.

To examine the feasibility of using a computer tool for stratifying the severity of Coronavirus Disease 2019 (COVID-19) based on computed tomography (CT) images. We retrospectively examined 44 confirmed COVID-19 cases. All cases were evaluated separately by radiologists (visually) and through an in-house computer software. The degree of lesions was visually scored by the radiologist, as follows, for each of the 5 lung lobes: 0, no lesion present; 1, 1/3 and 2/3 involvement. Lesion density was assessed based on the proportion of ground-glass opacity (GGO), consolidation and fibrosis of the lesions. The parameters obtained using the computer tool included lung volume (mL), lesion volume (mL), lesion percentage (%), and mean lesion density (HU) of the whole lung, right lung, left lung, and each lobe. The scores obtained by the radiologists and quantitative results generated by the computer software were tested for correlation. A Chi-square test was used to test the consistency of radiologist- and computer-derived lesion percentage in the right/left lung, upper/lower lobe, and each of the 5 lobes. The results showed a strong to moderate correlation between lesion percentage scores obtained by radiologists and the computer software (r ranged from 0.7679 to 0.8373, P, Graphical abstract Image 1, Highlights • Lesion percentage calculated by computer and radiologist are highly correlated. • Lesion density quantifiedby computer was correlated with the visually scored proportion of ground glass opacity and consolidation. • The computer tool could reliably and accurately assess the distribution of pneumonia.

Herein we proposed an approach to quantitatively evaluate the individual contribution of orthorhombic and tetragonal phase in the polymorphic phase transition (PPT) region of Li modified (K,Na)NbO3 during the poling process. Through investigating the feature of domain switching in orthorhombic and tetragonal phase, it found that the essence for the switching of polarization vectors 〈110〉 in orthorhombic phase and 〈001〉 in tetragonal phase was tiny ion displacement. With the increase of Li content the volume ratio of tetragonal phase in the coexistence phase at room temperature went up as well as the value of ion displacement and X-ray diffraction results could clearly elaborate the validity of the above statement.

The temperature dependent properties of (K,Na)NbO3-based piezoelectric materials enlightened us that the combination of compositions gradient could remedy the fluctuation of the electrical properties induced by the temperature variation. Then Li modified (K,Na)NbO3 ceramics was chosen as target materials and a multi-layered structure containing a series of composition gradient layers was prepared via a conventional solid state reaction. The results of relative permittivity against temperature demonstrated that the as-called relaxor feature was observed in this proposed multi-layered structure and the change rate of the dielectric anomaly peak got evidently reduced. Besides, the field-induced strain varying less than 10% from the room temperature to 100 °C was also achieved in this layered-structure ceramics. Moreover, the investigation here could render us an important reference for designing ferroelectric materials to satisfy the diversified requirements in the functional device.

Application products moving from small-sized devices to large-scale energy storage systems have pushed the development of lithium-ion batteries towards high-energy densities, high-power densities, and long cycle life. Germanium-based anode materials with high theoretical capacities are expected as promising anode candidates to fulfill those requirements, but suffer from the huge volume expansion upon lithiation, leading to serious material pulverization and capacity fading. Herein, a convenient and cost-effective strategy was conceived focusing on construction of dually-protected Zn 2 GeO 4 /graphene composites. The rationally designed composite was composed of hollowed Zn 2 GeO 4 nanostructures and flexible graphene layers, which acted as two functional nanoframes to synergistically alleviate the volume change during lithiation/delithiation. As a result, the Zn 2 GeO 4 /graphene composite exhibited high specific capacities, excellent cycling stability and desirable rate capability. Specifically, the Zn 2 GeO 4 /graphene composite electrode delivered specific capacity of 702 mA h g −1 at 300 mA g −1 after 600 cycles with capacity retention of 85%. In addition, a high reversible capacity of 600 mA h g −1 was retained over 1000 cycles at a high current density of 800 mA g −1 . Those achieved-results suggested that rational design of electrode nanostructures offers an effective insight for obtaining high-performance batteries.

Novel two-dimensional materials with a layered structure are of special interest for a variety of promising applications. Herein, MoS 2 and MoS 2 /Graphene nanocomposite with hierarchical nanostructure were successfully synthesized employing a one-step hydrothermal method. Photo-degradation of methylene blue (MB) and rhodamine (RHB) were adopted to assess the photo-degradation ability of the products. Comparing with bare MoS 2 , the hierarchical MoS 2 /Graphene nanocomposite achieved relatively higher degradation rate of 99% in 28 min for MB as well in 50 min for RHB. These results verified that this proposed hierarchical nanocomposite is a good photo-degradation semiconductor. The excellent performance was mainly ascribed to the synergistic effect of MoS 2 and graphene layers. The MoS 2 possessing a band gap of 1.9 eV would provide abundant electron-hole pairs. The graphene layers with excellent electro-conductivity could realize the quick transport of electrons via its extended π-conjugation structure, consequently benefiting the separation of photo-generated carriers. These findings indicate that the graphene layer is a promising candidate as a co-catalyst for MoS 2 photo-catalyst, and also provide useful information for understanding the observed enhanced photocatalytic mechanism in experiments.

Rare earth doped perovskite oxides have attracted much attention due to their multifunctional properties (such as photoluminescence, ferro-/piezoelectricity and so forth). In the current work, Er3+-doped (Li,K,Na)NbO3 nano-ceramics were successfully synthesized by spark plasma sintering and as-obtained ceramics exhibited excellent up-conversion photoluminescence (UC PL) behavior. The influences of the doping of Er3+ on the phase structure, microstructure, and UC PL properties were systematically investigated. The XRD and Raman analysis demonstrated that Er3+ ion entered into A site of (Li,K,Na)NbO3 perovskite structure. The most obvious enhancement of UC PL emission was achieved in the ceramics with 0.25 mol% of Er3+ doped, and the intensity of UC PL emission dropped with the further increase of Er3+ doping. Moreover, it found that two photons contributed to this observed UC PL behavior. These findings here rendered potential application of Er3+ doped (Li,K,Na)NbO3 smart materials in novel multifunctional devices.

Lead-free (K 0.49 Na 0.51 )(Nb 1−x Sb x )O 3 piezoelectric ceramics were prepared via the conventional sintering method and the effect of the substitution of Nb with Sb on the phase structure, microstructure and electrical properties of the prepared (K 0.49 Na 0.51 )(Nb 1−x Sb x )O 3 ceramics was systematically investigated. The prepared ceramics exhibited a single-phase perovskite structure which changed from a standard orthorhombic structure to a pseudocubic structure as x was increased from 0 to 0.1. X-ray diffraction patterns and Raman spectra obtained for the prepared ceramics clearly revealed that the degree of structural symmetry increased with x . Substituting an appropriate amount of Sb 5+ for Nb 5+ was found to improve the microstructure and thereby enhance the piezoelectric/ferroelectric properties. Further increasing the Sb content resulted in a decrease of the average grain size and a deterioration of the performance. The peak values of the piezoelectric constant d 33 (182 pC/N) and the electromechanical coupling coefficient k p (41%) were obtained for the ceramic with x =0.06.

Constructing hybrids of transition metal oxides with different kinds of carbon based materials has attracted a lot of attention recently. However, scalable synthesis of homogeneous hybrids with active controllable of microstructure remains great challenge. Here, we proposed a convenient and efficient strategy named freeze-drying process for scalable production of 3D NiO/graphene hybrids. With a controllable procedure, NiO microflowers and graphene layers could preserve uniform configuration from fully mixed solvent to final hybrids materials. The mechanical stability and electrical conductivity of NiO microflowers was increased by graphene. NiO microflowers as spacers intercalated into graphene layers and effectively prevented it from aggregation or restacking, leading to a high specific surface area in hybrids. The NiO/graphene exhibited enhanced cycle stability and rate performance when evaluated as an anode for lithium ion batteries. It rendered high specific capacities about 1000 mA h g−1 after 70 cycles, and 770 mA h g−1 after 100 cycles at 300 mA g−1. Excellent electrochemical properties were probably ascribed to the synergistic effect of NiO microflowers and graphene layers, as a result of smart structure design by a freeze-drying route. This strategy with merits of rational construction and scalable production could establish new aspects for diverse hybrid towards industrialization.

Morphologies and sizes of V 2 O 5 had crucial effect on their optic and catalytic performance. Diverse dimensional V 2 O 5 were successfully synthesized by the combination of a hydrothermal and post heat treatment method. The as-obtained samples were characterized by X-ray power diffraction, scanning electron microscopy, transmission electron microscopy and Raman spectra. Moreover, the optic properties of diverse dimensional V 2 O 5 were examined by Fourier transform imaging spectrometer and UV–vis-spectrophotometer. It showed that the IR transmittance of nanowire (at 1019 cm −1 is 85%) and UV absorbance of microflowers (at 480 nm) were high. Furthermore, the catalytic properties of diverse dimensional V 2 O 5 on the thermal decomposition of ammonium perchlorate were evaluated and compared by Thermo-Gravimetric Analysis and Differential Scanning Calorimetry. Moreover, the best catalytic performance was obtained with the morphology of nanowire. It showed the thermal decomposition temperatures of AP with nanowire, microflowers and microsphere were reduced to 373 °C, 382 °C and 376 °C (decreased by 52 °C, 43 °C and 49 °C).

A series of Co 2+ doped NiO materials (Ni 1 −x Co x O with x = 0, 0.125, 0.25 and 0.5) were synthesized using a facile hydrothermal method followed by a calcination process. The effects of Co 2+ doping on the structural, morphological, magnetic and catalytic properties of NiO were systematically investigated. The results indicated that Co 2+ doping would bring about a series influence to the as-obtained NiO product. The XRD results indicated that within the region of 0 ≤ x ≤ 0.25 the doped products revealed a pure NiO phase. The elementary unit for the hierarchy NiO gradually transformed from nanosheets to nanoneedles with the increase of Co 2+ doping content. As-obtained Co 2+ doped NiO products showed ferromagnetism at room temperature and the magnetization value was increased with the increase of Co 2+ doping content. The catalytic properties of NiO concerning the thermal decomposition of ammonium perchlorate (AP) were significantly improved via the introduction of Co 2+ . The Ni 1 −x Co x O products with x = 0.25 showed the best catalytic performance to AP, which could decrease the beginning and ending decomposition temperature of AP by 44 and 108 °C. The change of morphology, enhancement of electrical conductivity and the synergistic effect between Co 2+ and NiO were the main factors responsible for the improvement of physicochemical behaviors.

Multifunctional luminescent materials based on rare earth doped ferro-/piezoelectrics have attracted much attention due to their potential applications in novel multifunctional devices. Herein, we choose Li modified (K 0.49 Na 0.51 )NbO 3 system benefitting from both of the effect of morphotropic phase boundary and polymorphic phase transition as the target materials, and systematically studied the influence of the doping of Er 3+ on the phase structure, composition, up-conversion photoluminescence property and so forth. A significantly enhanced ferro-/piezoelectric behavior had been achieved in 0.5% Er 2 O 3 doped (Li,K,Na)NbO 3 ceramic. Our results reveal that in addition to the admirable intrinsic piezoelectric properties of (Li,K,Na)NbO 3 ceramic, the donor doping behavior of Er 3+ could enhance the ferro-/piezoelectric properties and obviously improve the up-conversion photoluminescence property of the matrix materials. These findings show great potential of Er 3+ doped (Li,K,Na)NbO 3 materials a future application in novel multifunctional devices.

Owing to scientific importance associated with highly reactive surfaces, the research concerning inorganic single crystals with a large percentage of exposed high-index facets has attracted much attention. In current research, α-Fe2O3 nanocubes exposed with (012) active facet was firstly synthesized via a hydrothermal method. And then a freeze-drying approach was utilized to construct nanostructured Fe2O3/graphene composite. The as-obtained composite exhibited s higher BET surface area than that of bare α-Fe2O3 nanocubes. When evaluated for lithium storage properties, the Fe2O3/graphene rendered remarkable electrochemical cycle stability and high rate performance. At the rate of 300 mA g−1, a high reversible discharge capacity of 1136 mAh g−1 was obtained up to 200 cycles. In addition, the excellent rate performance was also achieved. Excellent electrochemical properties are probably ascribed to the synergistic effect of α-Fe2O3 nanocubes and graphene sheets, as a result of smart structure design via a freeze-drying route. This strategy with merits of rational construction and scalable production could establish new perspective for diverse composites towards commercial application.

Er 3+ doped (K 0.52 Na 0.48 ) 1− x Li x NbO 3 ceramics had been prepared through a conventional solid state reaction routine and their phase structure, ferroelectric, piezoelectric, and photoluminescence properties were systematically investigated. X-ray diffraction results clearly illustrated a phase transition from the orthorhombic to coexistence and further to tetragonal phase with the increase of Li content. Via measuring the ferroelectric and piezoelectric properties of the ceramics, it found that the polymorphic phase transition (PPT) effect contributed the obvious enhancement in electrical properties of the Er 3+ doped (K 0.52 Na 0.48 ) 0.94 Li 0.06 NbO 3 ceramic which lay in the composition region of coexistence phase structure. The up-conversion photoluminescence intensity of green emission and red emission first increased as x increase from 0 to 0.06 and then decreased for x = 0.08. The most obvious enhancement in the up-conversion photoluminescence intensity was also achieved in the composition lying in the vicinity of PPT region. And the above circumstance caused the consideration that here the essence of the coexistence phase may be a phase structure with lower crystal symmetry instead of just physical combination of orthorhombic and tetragonal phase.

The specific heat (CP), thermal diffusivity (η), thermal conductivity (κ), magnetization, resistivity (ρ), and magnetocaloric effect (MCE) were studied in fast-quenched ribbon samples of the Ni50Mn37-xAlxSn13 alloy (x = 2, 4). Anomalies are observed in the form of a jump for the temperature-dependent η(T) and κ(T) near the magnetic and magnetostructural phase transitions, which are associated with critical scattering of heat carriers by distortions of the crystal structure, fluctuations of the order parameter, or structural/magnetic inhomogeneities. The transition to the martensitic phase is found to be accompanied by a sharp increase in the resistivity, suggesting an increase in the electron relaxation rate due to structural distortions inherent in martensite. The value of the magnetoresistive effect at 1.8 T near the martensitic transition reaches ∼40%. The temperature hysteresis was investigated in terms of ρ(T) near TC, which is explained based on the coexistence of the magnetic two-phase state of FM + AFM and the structural magnetic heterogeneity of the samples with dominant austenitic phase. For a sample with x = 2, the electron and phonon components of thermal conductivity were estimated (κph » κe).

The flower-like Co 3 O 4 assembled with nano-leaves could be obtained through annealing the cobalt hydroxide carbonate precursor, which was first synthesized via one-pot hydrothermal route. X-ray diffraction and TEM analysis demonstrated the transition from the precursor of amorphous state to Co 3 O 4 with cubic phase structure. XRD results indicated the increase in the calcination temperature from 300 to 400 °C for the precursor would bring about the increase in the crystallinity degree and ferromagnetic property of the products. The TG analysis demonstrated that as prepared Co 3 O 4 samples for different calcination temperature had significant effect on the thermal decomposition of ammonium perchlorate. And the decomposition temperature region of ammonium perchlorate could be decreased from 303–454 °C to 256–356 °C by the catalysis of Co 3 O 4 .

Er 2 O 3 doped (K,Na)NbO 3 (KNN) ceramics with the composition around the morphotropic phase boundary was synthesized by the conventional solid state reaction. Compared to pure KNN ceramics, KNN doped Er 3+ ceramics exhibited enhanced ferroelectric, piezoelectric properties owing to the donor doping effect. And the maximum value of d 33 =132 pC/N and k p=0.44 were obtained for the ceramics with the addition of 0.5 mol% Er 2 O 3 . Meantime, the intensity of absorb spectra and photoluminescence were obviously enhanced in this kind of sample owing to the lattice distortion induced by the polarization reorientation during poling process. The present work indicated the proposed system exhibited potential application in multifunctional integration device.

Microsphere, micro-net-sphere, hexagon plate and sandwich-like cobalt particle were successfully synthesized via a facile, environmentally friendly and one-step solvothermal method. Subtle control over the reaction conditions could easily achieve these different morphologies with certain crystal structures. Solvothermal method utilized here is pollution free, without surface-active agent and facile to perform. The effects of alkali and Co 2+ content as well as the reaction temperature on the size, morphology and microstructure were investigated individually. Moreover, the catalytic properties concerning the catalytic thermal decomposition of ammonium perchlorate (AP) and magnetic properties of these selected samples were evaluated. It finds that the alteration trend of related properties correspond well with the variation of these samples’ microstructure and morphology. In addition, comparing with the other morphology, Co particles with the morphology of hexagon sheet exhibits outstanding catalytic performance, implying significant practical application in the development of energy-efficient rocket solid propellant recipes.

BaTiO 3 , PbTiO 3 , SrTiO 3 , and Pb(Zr,Ti)O 3 microspheres with uniform size and narrow size distribution have been successfully synthesized by a novel hydrothermal and annealing approach. In this approach, the chemical reaction and crystallization process of the ABO 3 perovskite oxides were separated in two steps. Spherical particles containing the B-site ions were obtained first via a controlled hydrolysis and aging process. Then, during hydrothermal treatment, the A-site ions were incorporated in situ into the microspheres to form amorphous perovskite microspheres. The particles were further crystallized with preserved spherical morphology under subsequent annealing treatment. The BET surface areas of the TiO 2 gel particles, the amorphous PbTiO 3 and the as-annealed PbTiO 3 microspheres were 245.7 m 2 /g, 41.67 m 2 /g and 4.53 m 2 /g, respectively, showing a significant change of the surface feature in the preparation process. This approach also allowed the microspheres diameters to be manipulated from 100 nm to 1500 nm in a controlled manner. Most of the microspheres were composed by closely packed nano-sized particles. Furthermore, the Pb(Zr,Ti)O 3 microspheres with an average diameter of 200 nm exhibited single crystal features, indicating highly oriented growth in the crystallization process. The microspheres were very stable, and still maintained spherical shape after higher temperature calcination.

Li0.05(Na0.51K0.49)0.95(Nb0.95Ta0.05)O3 (abbreviated as KNNLT) with addition of La2O3, CeO2, respectively, were prepared by a conventional ceramic fabrication technique. X-ray diffraction pattern shows that the coexistence of orthorhombic and tetragonal phase structure for KNNLT was not changed by adding La2O3 or CeO2. SEM observation indicates that these two kind dopants have a remarkable effect on the microstructure of KNNLT ceramics. The To–t (temperature for the orthorhombic to tetragonal phase) was shifted toward lower temperature by the addition of rare earth oxide and typical relaxor ferroelectric is demonstrated especially for KNNLT with high content of La2O3. An addition of 0.5% CeO2 could strengthen the piezoelectric and dielectric constant of KNNLT ceramics to some extent. KNNLT ceramics with 0.5% CeO2 obtain optimum electrical properties: d33=272 pC/N, kp=45%, er=784 and tan δ=1.4%.

The influence of sintering temperature and poling processing on the room temperature phase structure and piezoelectric properties of Li0.058(Na0.51K0.49)0.942NbO3 ceramics were systematically investigated. An approach was proposed to roughly determine the ratio of tetragonal and orthorhombic phase in the as-sintered samples. The result of temperature dependence of the dielectric constant proves this method feasible. The best piezoelectric properties of d33 = 255 pC/N was obtained in specimens sintered at 1040 °C. The dense microstructure and high percentage of 90° domains reorientation during poling processing could explain the best performance of samples for 1040 °C. The loose microstructure and low density for the samples of 980 and 1080 °C are responsible for the worse piezoelectric properties comparing with that of sample for 1040 °C. Meanwhile, the segregation also plays an important role in the deteriorate properties for the sample sintered at 1080 °C.

In the present work, lead-free K 0.48 Na 0.52 NbO 3 (KNN) ceramics were synthesized by conventional ceramics processes. The excess 3.3 mol% Na 2 CO 3 and 1.1 mol% K 2 CO 3 were added to decrease the sintering temperature to 990 °C and effectively promote the densification of KNN ceramics. X-ray diffraction results indicated that the excess Na 2 CO 3 and K 2 CO 3 would induce the formation of the A-site riched secondary phase with the sintering temperature. Compositional segregation phenomenon enhanced by different sintering temperature, spurs the formation of secondary phase in KNN-AEe ceramics. In addition, the difference between ferroelectric domain structure of the poled and as-sintered KNN-AEe samples for 990 °C was investigated. Via XRD analysis and SEM observation, it was found that the domain orientation was urged during the poling process.

In this paper, lead-free (Na 0.474 K 0.474 Li 0.052 )(Nb 0.948 Sb 0.052 )O 3 ceramics were synthesized by a conventional solid-state reaction route. The effects of sintering temperature on the crystal structure, microstructure, densification, dielectric properties, and ferroelectric properties of the KNNLS ceramics were addressed. X-ray diffraction patterns and Raman spectrum indicated a transition from orthorhombic to tetragonal phase during the sintering temperature region. This transition is attributed to the migration of Li between the matrix grain and grain boundary. Scanning electron microscopy study revealed increased grain size and enhanced densification with increasing sintering temperature. The density of the ceramics sintered at 1080 °C reached a maximum value of 4.22 g/cm 3 . KNNLS ceramics sintered at an optimum temperature of 1080 °C exhibited high piezoelectric properties, that is 242 pC/N for d 33 , 0.42 for k p and 18.2 μC/cm 2 for P r .

Several kinds of phase structure change behavior in Li 0.058 (Na 0.51 K 0.49 ) 0.942 NbO 3 (KNNLN) ceramics were presented in this work. XPS measurement was employed to determine Na volatilization in the KNNLN samples, and this result explains the difference of the phase structure between the surface and interior of the samples. The phase structure of lead-free KNNLN piezoceramics are studied based on the measurements of the analysis of X-ray diffraction pattern and dielectric properties. The poled samples exhibit orthorhombic structure whereas the surface and interior for unpoled samples exhibit tetragonal and tetragonal-orthorhombic coexistent structures, respectively. An explanation to the mechanism of the structure transformation during poling processing was proposed.

In present work, a simple and direct method was proposed, which could be applied for quantitatively calculating the percentage of 90° domain reorientation in the tetragonal phase of KNNLN ceramics. The relationship between 90° domain reorientation and poling field was established through the X-ray diffraction analysis. Experimental results indicate that the poling field of 5 kV/mm is sufficient for the reorientation of 90° domain and while the percentage of 90° domain reorientation 37.9% and piezoelectric constant 232 pC/N are obtained. The general trend of piezoelectric properties corresponds well with that of the percentage of 90° domain reorientation.

Zr doped Ba0.6Sr0.4TiO3 ceramic was sintered by spark plasma sintering (SPS) and thermal treatment. Sintering behavior, microstructure and dielectric properties of the BST ceramics were investigated by XRD, SEM and impedance analyzer. High dense Ba0.6Sr0.4(Zr0.2Ti0.8)O3 ceramic with 98.2% of the theoretical density was fabricated at 1270 °C for 5 min. The dielectric constant of this sample reduced to 850 at 100 kHz, the tunability of the ceramic increased to 57% (1.5 kV/mm, 298 K) and the figure of merit (FOM) value increased to 475, which is promising material for tunable devices application.

The phase structure of lead-free Li 0.058 (Na 0.51 K 0.49 ) 0.942 NbO 3 (KNNLN) ceramics can be affected by the stress as well as the external electric field. A high piezoelectric constant was obtained in KNNLN ceramics by adjusting the cooling-down speed of the sintering. The {2 0 0} reflection X-ray diffraction lines were measured to accurately identify the room-temperature crystal structure of the as-sintered samples. Dielectric measurements were performed to observe the differences in the phase structure of KNNLN ceramics before and after poling.

In this study, Fe 2 O 3 and TiO 2 codoped Li 0.05 (Na 0.5 K 0.5 ) 0.95 (Nb 0.975 Sb 0.025 )O 3 [(1 − x ) Li 0.05 (Na 0.5 K 0.5 ) 0.95 (Nb 0.975 Sb 0.025 )O 3 – x (Fe 2 O 3 –2TiO 2 ) ( x = 0–0.008)] ceramics were prepared by conventional solid state reaction method, and the microstructure and electrical properties of these samples were investigated. The X-ray diffraction and Raman scattering results show the phase structure of the ceramics undergoes with the increase of Fe 2 O 3 –2TiO 2 content. The grain size distribution of non-doped Li 0.05 (Na 0.5 K 0.5 ) 0.95 (Nb 0.975 Sb 0.025 )O 3 ceramics was relatively wide. The microstructure was composed of grains ranging 0.2–3.0 μm in size. However, with increasing Fe 2 O 3 –2TiO 2 content, the grain size distribution became relatively narrow. Meanwhile, the piezoelectric coefficient ( d 33 ) and electromechanical coupling coefficient ( k p ) showed peak values of 252 pC/N, and 0.424, respectively, which were achieved in the sample with x = 0.002 sintered at 1020 °C.

The effects of sintering temperature and the addition of CuO on the microstructure and piezoelectric properties of 0.95(K0.5Na0.5)NbO3–0.05Li(Nb0.5Sb0.5)O3 were investigated. The KNN-5LNS ceramics doped with CuO were well sintered even at 940 °C. A small amount of Cu2+ was incorporated into the KNN-5LNS matrix ceramics and XRD patterns suggested that the Cu2+ ion could enter the A or B site of the perovskite unit cell and replace the Nb5+ or Li+ simultaneously. The study also showed that the introduction of CuO effectively reduced the sintering temperature and improved the electrical properties of KNN-5LNS. The high piezoelectric properties of d33 = 263 pC/N, kp = 0.42, Qm = 143 and tan δ = 0.024 were obtained from the 0.4 mol% CuO doped KNN-5LNS ceramics sintered at 980 °C for 2 h.

Lead-free (K0.462Na0.48Li0.058)1+xNbO3(0 ≤ x ≤ 0.03) ceramics with excessive alkaline elements were synthesized by conventional ceramics processes as functions of sintering temperatures and quantities of excess alkaline elements. X-ray diffraction results reveal a transformation from tetragonal phase to orthorhombic phase with increasing the contents of excessive alkaline elements. The grain size and the piezoelectric properties were enhanced when a certain amount of excessive alkaline elements were added. Further elevation in the amount of alkaline elements added resulted in excessive liquid phase in the ceramics and deteriorated the piezoelectric properties. With x = 0.01, the ceramics sintered at 1050 °C show better properties of planar electromechanical coupling factor kp = 43.4%, piezoelectric constant d33 = 204 pC/N, dielectric constant e 33 T / e 0 = 704.4 , and loss tangent tan δ = 2.8%.

Plate-like Bi 5 Nb 3 O 15 (B5N3) particles and rectangular KNb 5 Bi 2 O 16 (KN5B2) particles were synthesized by the molten salt process and topochemical microcrystal conversion (TMC), respectively. The effects of the synthesis parameters on the phase structure and morphology of B5N3 precursor and KN5B2 were investigated. Results indicated that the retro-synthesis process of the as-synthesized KN5B2 retained the morphology and structural feature of the B5N3 precursor. The prepared KN5B2 particles with high aspect ratio of 20–30 are promising templates for texturing bismuth-layer and alkali niobate based ceramics by (reactive) templated grain growth method. The same method can be applied to other perovskite-structured templates.

By coupling strong and weak exothermic reactions, (TiC + SiC) composite powders have been prepared by combustion synthesis. The reaction temperature and heating rate strongly depend on the Ti/Si ratios in the reactant powder mixture. The phase assemblage and microstructure of the products can be manipulated by varying the starting compositions. According to SEM observation, the reaction procedure and formation mechanism of TiC and SiC are discussed. It is proposed that the presence of metallic melt phases is important for the formation of the carbide phases.

Co-doped ceria electrolytes of Ce 0.8 Gd 0.2− x Y x O 1.9 ( x = 0.0–0.20) fine powders were prepared with glycine–nitrate method. The results of X-ray diffraction showed that all powders crystallite calcined at 873 K were single phase with cubic fluorite structure. The average crystallite sizes calculated by the Scherrer formula were between 21 and 23 nm, which was in good agreement with the results of TEM and particle size distribution measurements. The thermal expansion curves of Ce 0.8 Gd 0.2− x Y x O 1.9 were measured and the thermal expansion coefficients between 373 and 1123 K were calculated. The SEM results exhibited that electrolyte pellets sintered at 1523 K were dense, and the relative densities of these pellets were over 96%. The impedance spectra analysis of these electrolytes has been performed at 623–1023 K. The results showed that co-doped ceria exhibited higher ionic conductivity and lower activation energy than the singly doped ceria with the same dopant concentration at the temperature range of 773–1023 K, and the electrolytic domain boundary of co-doped ceria was smaller than that of singly doped ceria at 873–973 K. It suggested that co-doping with appropriate ratio gadolinium and yttrium could further improve the electrochemical performance of ceria-based electrolytes. These co-doped samples are ideal electrolyte materials of intermediate temperature solid oxide fuel cells.

Co-doped ceria of Ce{sub 1-x}Gd{sub x-y}Y{sub y}O{sub 2-0.5x}, wherein x = 0.15 and 0.2, 0 {

α-SiAlON powders consisting of one-dimensional rod-like microcrystals were prepared by combustion synthesis in large scales. No obvious negative effect on reaction products was noticed by the increase of sample size, and α-SiAlON was synthesized as predominant phase in all the samples, even in CS-CL with the weight of 1000 g. These results showed good repeatability of combustion synthesis and its great potential in industrial production of α-SiAlON powders in large quantities. According to the phase composition of intermediate product, the reaction procedure in combustion synthesis of Ca α-SiAlON was proposed. At the same time, the strong influence of different starting compositions on the grain morphology of Yb α-SiAlON products was explained with the consideration of reaction temperature and grain growth character.

Bi0.5(Na0.8 K0.2)0.5TiO3 (abbreviated as BNKT) piezoelectric ceramics with extensive texture were prepared by the reactive templated grain growth (RTGG), using plate-like Bi4Ti3O12 (BiT) particles as the templates. Through the analysis of X-ray diffraction pattern of the obtained materials, extensive crystallographic texture was evaluated with a relatively high Lotgering factor (f ≥ 0.9), and the incorporated (Bi0.5 K0.5)TiO3 diffused into the (Bi0.5Na0.5)TiO3 lattice to form a single solid solution. The scanning electron microscopy showed that the in-situ reaction started at the vicinity of BiT surface and proceeded with heat treatment time toward the inner part of the BiT. The high textured BNKT piezoelectric ceramics demonstrated good piezoelectric performance without decreasing the depolarization temperature when they were sintered at 1200 °C for 10 h.

Consolidated Ca α-SiAlON ceramics with gradually varying microstructure and property was prepared by hot-forging. The shape deformation as well as texture development of the sample during forging was studied in detail. It was found that the forging process promoted the growth of elongated α-SiAlON grains and enhanced their preferred orientation with the longitude perpendicular to the pressing force. The strong texture offered the hot-forged sample an increased fracture toughness of 7.9 MPa m 1/2 , which was primarily attributed to the pull-out and debonding behaviors of elongated grains.

To investigate the effects of maternal infection on the offspring's inflammatory response, pups born to LPS- or saline-treated dams were stimulated with LPS or saline, and the expression of cytokines and chemokines was examined. We found that at P21, pups born to LPS-treated dams exhibited diminished serum levels of TNF-alpha, IL-1beta, and IL-6, and inhibited mRNA levels of cytokines, including TNF-alpha, IL-1beta, and IL-6, and chemokines, including MIP-1beta, MIP-2, and KC, in the brain, as compared to pups born to saline-treated dams at 2 h following LPS stimulation. Our results suggest that maternal infection suppresses the offspring's inflammatory response to LPS.

Al-27 and Si-29 solid-state NMR spectra and X-ray diffraction (XRD) patterns were obtained for alpha-SiA1ON powders prepared by combustion synthesis, according to which the phase transformation and structure evolution of ot-SiAlON were studied. It was found that in alpha-SiA1ON Si-29 chemical shift values (-48 < delta(Si) < -47) were close to those in beta-Si3N4 and alpha-Si3N4, indicating that Si atoms kept SiN4 coordination to a large extent in alpha-SiA1ON despite the presence of 0 atoms. Dissimilarly, Al-27 chemical shift values in alpha-SiA1ON deviated clearly from that corresponding to AlN4 coordination (delta(Al) similar to 112) and occurred in a range from 3Al 95.5 to 99.9, which should be assigned to tetrahedral AIQN4-, (0 < x < 4) coordination. The broadening effect of AlOxN4-x, peaks was noticed, which was suggested to induced by slight dispersion of alpha-SiAlON compositions. 27 Al resonances assigned to AlO4 or AlO6 were also observed, revealing the existence of glassy phase in combustion products. By comparing the intensities of AlO4 and AlO6 resonance peaks, it was found that the composition and structure of the co-existing liquid assisting alpha-SiAlON formation were not constant but varied with temperature in combustion synthesis. In addition, with CaF, used as Ca-source alpha-SiAlON with low oxygen contents (n < m/2) were prepared, and it was found that there was a low threshold of oxygen content only beyond which alpha-SiAlON could be formed. (c) 2006 Elsevier B.V. All rights reserved.

With the assistance of mechanical activation, yttrium-stabilized a-SiAlON was prepared by combustion synthesis in air, instead of high-pressure N2 atmosphere for the first time. The reaction activity of metallic particles was remarkably enhanced by mechanical activation, which conduced the reduction of grain size, increased the total surface area and formation of fresh surface. The formation of a-SiAlON by combustion synthesis in air was explained by a kinetically induced reaction mechanism, in which both initial formation of a-SiAlON and following avoidance of oxidation were fulfilled by the retardation of O2infiltration owing to the short reaction period and fast cooling rate. # 2006 Elsevier Ltd. All rights reserved.

(Nd,Dy)-containing SiAlON powders were prepared by combustion synthesis, where it was proved that the phase assemblage and grain morphology of final products could be tailored by controlling the relative contents of the two rare-earth elements. When the molar ratio of Dy/(Nd + Dy) was increased, the phase content of α-SiAlON was promoted and β-SiAlON was reduced. At the same time, the grain morphology of combustion products varied from elongated prismatic crystals to fine isotropic grains. It was also found that the lattice parameters of both α- and β-SiAlON were affected by Dy/(Nd + Dy) ratios. The experimental results were discussed by considering the different ability of Dy 3+ and Nd 3+ to stabilize α-SiAlON structure.

In Ti–Al–C system two ternary carbides of Ti 2 AlC and Ti 3 AlC 2 were prepared by combustion synthesis. Laminated grain morphology and a terraced structure consisting of several parallel laminated layers were observed. On the basis of SEM and TEM results, a layered growth mechanism was proposed to describe the formation of the terraced structure. In this mechanism, the ternary carbide grains will undergo a preferential growth, i.e. each layer grows fast and expands quickly in the basal plane and all the layers are successively stacked along the normal direction identical to the c -axis in the hexagonal structure. This preferential growth characterized by the terraced structure was widely observed in this study and hence may be a common behavior during the growth of Ti 2 AlC and Ti 3 AlC 2 crystals in combustion synthesis.

Novel β-SiAlON micropalings consisting of nanorods have been prepared by combustion synthesis with proper additives. According to TEM images associated with SAD pattern, the preferred growth direction of the nanorods is proved to be [0 0 1]. An epitaxial nucleation and anisotropic growth mechanism is proposed to explain the formation of those micropalings. By this mechanism, new fine crystals are formed on the side faces of coarse crystals and each coarse prismatic β-SiAlON crystal is surrounded by parallel nanorods.

In this paper in situ toughened Yb α-SiAlON ceramics with elongated grains were prepared by two-step hot-pressing. The phase transformation and microstructure development of the samples during the two-step sintering were discussed in detail. It was found that at low temperatures, the formation of intermediate phases reduced the amount of liquid phase and thus slowed down the dissolution and mass transportation processes. In this way, the grain growth was depressed and fine grains were obtained. At the elevated temperature, the intermediate phases would be dissolved, resulting in abundant liquid phase and fast anisotropic grain growth. By the two-step sintering procedure, the nucleation and grain growth could be well manipulated and coarse elongated grains could be produced. These elongated grains improved the fracture toughness of the sintered ceramics via the mechanisms such as grain pull-out and debonding, which were clearly observed by SEM. In addition, the preferred orientation of the elongated α-SiAlON grains was also studied in the light of their growth habit.

Yttrium- and ytterbium-stabilized α-SiAlON powders consisting of rod-like microcrystals were prepared by combustion synthesis. A quenching method was used to investigate the phase formation and microstructure evolution during the combustion synthesis of α-SiAlON. Three reaction stages were proposed for the formation of α-SiAlON as follows: nitridation of metal powders, formation of the co-existing liquid phase, and precipitation of α-SiAlON with the dissolution of nitrides. Different nucleation and growth modes of rod-like α-SiAlON crystals were observed: crystallization from liquid phase, or nucleation and growth based on the surface of as-existed large crystals.

In this paper, (Ca + Yb)- and (Ca + Sr)-stabilized α-SiAlON powders were fabricated by combustion synthesis. The influence of Ca 2+ incorporation on the phase composition and grain morphology of combustion products was discussed. The experimental results showed that with the incorporation of Ca 2+ well-developed rod-like (Ca + Yb) α-SiAlON crystals could be produced. It was also found that, when only Sr 2+ was used as stabilizing cation, the reaction product was (α + β)-SiAlON composite, in which β-SiAlON was the predominant phase and the relative content of α-SiAlON was low. With the incorporation of Ca 2+ , however, both the relative content and the lattice parameters of α-SiAlON were clearly increased. These results indicated that the incorporation of Ca 2+ could assist Sr 2+ into the α-SiAlON lattice structure.

Ca α-SiAlON powders with rod-like crystals were prepared by combustion synthesis from different starting compositions. The growth mechanism of the rod-like Ca α-SiAlON crystals was investigated and two growth modes were observed. One is liquid phase precipitation, and the other is nucleation and growth on smooth surfaces of the as-developed large crystals. During the development of the rod-like Ca α-SiAlON crystals, anisotropic growth occurred with the [0 0 1] direction being the fast growth direction.

By combustion synthesis, Y (α + β)-SiAlON ceramic powders consisting of rod-like crystals were prepared. Effect of starting composition on the phase assemblage of combustion products was studied. It was found that with the increase of oxygen content, the phase assemblage of products varied from single-phase α-SiAlON to β-SiAlON gradually. Novel β-SiAlON whiskers were also observed in the combustion products. From the whisker morphology, it was suggested that both VLS and VS mechanisms operated here. It was also noticed that the whiskers could nucleate either on the basal face or on the side faces of as-existed prismatic rod-like crystals.

In this paper, Yb α-SiAlON crystalline powders with elongated grains were prepared by combustion synthesis. The effects of diluents and NH 4 F additive on the phase composition and microstructure of combustion products were discussed in detail. It is found that proper diluents are helpful to weaken the agglomeration, improve the infiltration of N 2 , and hence facilitate the nitridation reaction. Single-phase α-SiAlON with elongated grains could be fabricated with advisable addition of diluents. Furthermore, adding proper amounts of NH 4 F additive was also beneficial to the nitridation of Si and the development of elongated grains. However, excessive addition of α-Si 3 N 4 diluents or NH 4 F additive will result in β-SiAlON in final phase composition.

By applying SPS technique, new Yb α-SiAlON ceramics in situ toughened by rod-like grains were prepared at a relatively low temperature of 1600 °C, with combustion synthesized seed crystals added. The effects of sintering temperature, heating rate, and the addition of seed crystals on the densification process, phase transformation, microstructure development, and mechanical properties of the samples were discussed in detail. The experimental results showed that Yb α-SiAlON ceramics could be almost fully densified quickly by SPS, and the fast heating rate was helpful to reduce the amount of intermediate phases. Higher sintering temperature and appropriate holding time were beneficial to the promotion of phase transformation and grain growth. It was also demonstrated that the added seed crystals played an important role in enhancing the phase transformation and facilitating the growth of rod-like grains. Being toughened by the rod-like grains via the mechanisms such as grain pull-out and debonding, the fracture toughness of as-sintered Yb α-SiAlON ceramics with additive seed crystals was remarkably improved.