Search

The ceramic composites were designed through the regulation of the composition and temperature in the in-situ oxidized SiC/Al–Mg–Si composites process. The evolutions of the phase and microstructure were studied by X-ray Diffraction(XRD), Scanning Electron Microscope (SEM), and Transmission Electron Microscope(TEM) in different alloy addition and heating temperature. The products of in-situ oxidized SiC/Al–Mg–Si composites showed similar compositions due to high oxidation resistance on SiC since the heated temperature was below 1500 °C. Alloy addition dislodges the oxide shell on SiC. It promoted the oxidation of SiC, providing the sustained-release Si source to form the cordierite, mullite, and forsterite. Moissanite/spinel, mullite/spinel, and cordierite/spinel were obtained by controlling temperature or adding alloy. The mullite rods formed in 20% alloy addition samples at 1350 °C was detected. The step-like microstructure revealed that grains abide by a layer growth mechanism. The bending strength was enhanced from 13.83 ± 3.6 MPa to 22.32 ± 4.3 MPa by eutectic melting, which increased with the alloy addition and elevated temperature. [ABSTRACT FROM AUTHOR]

Al2O3/TiAl in situ composites doped with Cr and V2O5 were successfully prepared from Ti, Al, TiO2, Cr and V2O5 by hot pressing. The effect of in situ formed Al2O3 content on the phase composition, microstructure and mechanical properties of Al2O3/TiAl composites were investigated. The results show that the as-synthesized composites mainly consisted of γ-TiAl/α2-Ti3Al matrix and dispersive Al2O3 reinforcing phases. The in situ formed fine Al2O3 ceramic particles mainly disperse on the grain boundaries of TiAl, resulting in refinement of TiAl matrix, which improves the mechanical properties of the Al2O3/TiAl in situ composite. The composite with 7.54 at.% Al2O3 possesses the maximum flexural strength and fracture toughness of 335.38 MPa and 5.39 MPa m1/2, respectively. The strengthening mechanism was also discussed in detail.

The Linfen kiln complex, one of the most representative of Shanxi kilns, is famous for its oil spotted glazed ware production. In this work, micro‐Raman spectroscopy was applied to analyze the nature of the rusty oil spot pattern of a bowl fragment from Linfen kilns. Crystals of polygonal shape found in the spots at the glaze surface and around bubbles in the cross‐section of the glaze were identified as hematite. Their distribution in the glaze suggests that nucleation seeds and small crystals are carried toward the surface by the rise of bubbles during the heating step of the firing. Raman spectra combined with energy‐dispersive spectrometry (EDS) measurements also suggest that Fe ions in hematite crystals are partially substituted, causing the variation of band position and full width at half maximum (FWHM) of the spectra. Dendritic ε‐Fe2O3 was identified in brown areas of the black glaze, as well as pseudobrookite crystals of tens of microns in the cross‐section of the glaze. The degree of the glaze polymerization (A500/A1000) was calculated at 1.85, indicating a firing temperature lower than 1300°C, consistent with the archaeological data. [ABSTRACT FROM AUTHOR]

The SiC/Al–Mg–Si composite was obtained by in-situ synthesis, and the effects of Mg addition were investigated in this process. Mechanism of in situ SiC growth in the Resin–Al–Mg–Si system was investigated by fabricating and characterizing a SiC/Al–Mg–Si composite under moderate conditions. X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) were used to analyze the phase and its microstructure, with the aim of investigating the evolvement of grains in the alloy matrix. Mg 2 Si formed under higher Mg added conditions, which decreased the molten liquid and Si solute concentrations. Tiny amounts of MgO and MgAl 2 O 4 proved that the pyrolysis gas of resin reacts slightly with the matrix. The key conditions of in-situ synthesis SiC were found that the Mg addition and the Si concentration in the molten alloy were 3%–5% and over 17. 27 % respectively. Ostwald ripening was used to explain the decrease in tiny SiC grains at elevated temperatures. In situ SiC growth is controlled by the interfacial reaction-diffusion mixed model through two different routes in the molten alloy. Two modes of in-situ synthesis were suggested. The intermediate product and template for in situ SiC growth are Al 4 C 3 , and Si was shown to diffuse into its particles gradually. Flowing Si in molten alloy reacted with pyrolysis C directly. Specimens validated the peak bending strength with a rise in temperature. The maximal bending strength was 251.89 MPa. [ABSTRACT FROM AUTHOR]

Abstract This work was aimed to explore the relationship between phosphorus and coloring of copper glaze under oxidizing atmosphere. The phase, microstructure and chemical state of the samples were investigated by X-ray diffraction, Scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The results indicated that the addition of phosphorus broke up the silica network and decreased the viscosity of glaze melt, and then promoted the formation of discrete droplet phase-separated structures. Thus, blue opalescence was formed by the Rayleigh scattering on the sky-blue copper glaze surface. In addition, the reversed polarization of P5+ acted on the Cu–O bond and decreased the ratio of Cu2+ and Cu+. It increased the number of non-bridging oxygens and the spatial density of oxygen atoms around Cu2+, which was the essence of the copper blue glaze. Coupling of the structural color and the chemical color made the sky-blue copper glaze get more vivid. [ABSTRACT FROM AUTHOR]

Abstract Herein, we develop a fluoride-free hydrothermal etching approach using the small amounts of water-assisted potassium hydroxide as ingenious etching agents to produce novel two-dimensional Ti 3 C 2 (OH) 2 -MXene nanoribbons (Ti 3 C 2 (OH) 2 NRs). The as-produced Ti 3 C 2 (OH) 2 NRs possess less Al atoms, more abundant hydroxyl functional groups on their surface, and more open structure features compared with their pristine counterparts and the other etching products. Simultaneously, the resulting Ti 3 C 2 (OH) 2 NRs show significantly enhanced Li ions storage capabilities with outstanding specific capacity of 143.4 mA h g−1 obtained at 100 mA g−1 after 250 cycles, excellent cycling stability, and good rate property, being significantly superior than the parent Ti 3 AlC 2 phases and the sugarcane-like transitional etching products. The superior electrochemical properties of Ti 3 C 2 (OH) 2 NRs could be ascribed to the unique nanoribbon architectures with rich hydroxyl terminal groups and few Al atoms, which facilitates the adsorption and storage of a growing number of Li ions on the surface active sites of Ti 3 C 2 (OH) 2 NRs and the transport of electrons and ions effectively. What's more, this study provides a simple, effective, green, and nontoxic fluoride-free etching procedure to synthesize other more MXenes nanoribbons including but not limited to Ti 3 C 2 (OH) 2 NRs as promising anode candidates for advanced lithium-ion batteries. [ABSTRACT FROM AUTHOR]

The composition, microstructure and corrosion behavior of Al Mg Ga In Sn alloy in cast and heat-treatment were investigated by XRD (X-ray diffraction), SEM (scanning electron microscope) and EDS (energy dispersive spectrometer). The hydrogen evolution parameters, and the electrochemical properties based on different heat-treatment parameters conditions and immersion temperature were also tested. As the heat-treated temperature increased, the second phases were found to be spheroidizing or ellipsoidal shape due to the diffusion and solid solution. The reaction can be divided into three stages: i) the amalgamation initial stage; ii) the micro-galvanic reaction for propagation corrosion; iii) the dissolution-precipitation reaction for uniform corrosion. The hydrolysis rate reached the maximum value when the sample was annealed at temperature of 500 °C for 9 h. The hydrogen generation rate and the open electrochemical potential of the activated aluminum under water are both depending on heat treatment time, heat treatment temperature, and reaction temperature. A corrosion mechanism was also proposed in which Mg 2 Sn and eutectic phase acted as the induction reaction stage during hydrolysis reaction. [ABSTRACT FROM AUTHOR]

(Ti,Mo)Al/Al2O3 composites were successfully synthesized utilizing in situ reactive hot pressing method with Ti, Al, and MoO3 powders as starting materials. A possible synthesis mechanism was proposed to explain the formation of (Ti,Mo)Al/Al2O3 composites. The investigation results indicate a probable reaction process that molten Al reacted with MoO3 to form Al2O3 and Mo, and the TiAl matrix grains were refined increasingly by Al2O3 with the addition of MoO3 increased, accompanying with a small quantity of Mo containing phase AlMoTi2 formed in the fabricated composites. Meanwhile, the microstructure and mechanical properties of the (Ti,Mo)Al/Al2O3 composites were characterized. The as-synthesized composites exhibited lamellar structure of TiAl intermetallic compound and the in situ formed fine Al2O3 particles dispersed at the stratified TiAl matrix grain boundaries hindering the growth of the grain size of the matrix. And the Rockwell hardness, flexural strength, and fracture toughness of the as-prepared (Ti,Mo)Al/Al2O3 composite were 44.08 HRC, 684 MPa, 7.63 MPa·m1/2, which improved by 57.4%, 107.3%, and 38.7% compared to monolithic TiAl, respectively. The reinforcing mechanism of the material was also discussed. [ABSTRACT FROM PUBLISHER]

ZnO-based linear resistance ceramics were synthesized from ZnO-MgO-AlO-LaO-SiO-FeO at 1320 °C for 3 h by the conventional ceramics method in air. The microstructure and the crystal characteristics were investigated by scanning electron microscope equipped with energy dispersive spectrometer and X-ray diffraction respectively. The influence of FeO content on the linear current-voltage ( I- V) characteristic and dielectric characteristics have been systematically investigated in detail. The results indicated that the main phase of samples doped by FeO was hexagonal wurtzite structure of ZnO with the second phase of ZnAlO. The optimum result of linear I- V characteristic was obtained with nonlinear coefficient of 1.08, when the content of FeO was 0.50 mol%. With the increasing of dopant FeO contents, the dielectric constant and resistivity of ZnO-based linear resistance ceramics were influenced significantly, moreover, the resistance-temperature characteristics presented the negative temperature coefficient effects. [ABSTRACT FROM AUTHOR]

The separative-phase fancy glaze was successfully prepared by using the iron ore residue as the ceramic colorant. A possible coloring mechanism was proposed to explain the variation of glaze colors and patterns with the increasing of firing temperature. Effects of the firing temperature on the chromaticity, precipitated phase and microstructure of separative-phase fancy glaze were investigated. The results indicated that with increasing the firing temperature, the content of whitlockite decreased while the size of phase separation droplets in glazes increased. The residual whitlockite weakened coloring of Fe 2 O 3 and formed glaze patterns. In addition, the increased size of phase separation droplets weakened the structural color, which increased the L * and b * value of glazes. Therefore, the color of separative-phase fancy glaze got more yellow and brown gradually. [ABSTRACT FROM AUTHOR]

The moon-white glaze was successfully reproduced with the addition of 0.02 wt% silicon carbide (SiC) for supplying carbon (C) and reducing iron oxide (Fe 2 O 3 ) at 1250 °C. Effects of the SiC contents on the chromaticity, precipitated phase and microstructure of moon-white glaze were investigated. Based on the analysis of colorimeter, XRD, XPS, FT-IR, SEM and TG–DSC, a possible coloring mechanism was proposed to explain the variation of glaze colors with the increasing of SiC content. The results indicated that the addition of SiC contributed to increasing the content of C and the size of phase separation droplets in glazes. The formation of C increased the ratio of Fe 2+ to Fe 3+ and the increased size of phase separation droplets weakened the structural color, which increased the L* and b* value of glazes. Therefore, the color of moon-white glaze got more blue and white gradually. [ABSTRACT FROM AUTHOR]

Al 2 O 3 particle-reinforced Cr 2 AlC in situ composites were successfully fabricated from powder mixtures of Cr 3 C 2 , Cr, Al, and Cr 2 O 3 by a reactive hot-pressing method at 1400 °C. A possible synthesis mechanism was proposed to explain the formation of the composites in which Al 2 O 3 was formed by the aluminothermic reaction between Al and Cr 2 O 3 , meanwhile, Cr 3 C 2 , Al, together with Cr reacted to form Cr 2 AlC in a shortened reaction route. The effect of Al 2 O 3 addition on the microstructure and mechanical properties of Cr 2 AlC/Al 2 O 3 composites was investigated. The results indicated that the as-sintered products consisted of Cr 2 AlC matrix and Al 2 O 3 reinforcement, and the in situ formed fine Al 2 O 3 particles dispersed at the matrix grain boundaries. The flexural strength and Vickers hardness of the composites increased gradually with increasing Al 2 O 3 content. But the fracture toughness peaked at 6.0 MPa m 1/2 when the Al 2 O 3 content reached 11 vol.%. The strengthening and toughening mechanism was also discussed. [ABSTRACT FROM AUTHOR]

The ZnO-based linear resistance ceramics doped with rare-earth oxides (YO, LaO) have been prepared by the conventional ceramics method. The effect of the different doping amounts of rare-earth oxides on the microstructure, electrical properties and aging behavior were investigated in detail. The electrical properties analysis shows that the LaO addition on ZnO-based linear resistance ceramics has more obviously influence than the addition of YO. The samples with the LaO content of 0.25 mol% sintered at 1,320 °C exhibits excellent electrical properties with the resistivity of 253.5 Ω cm and the resistance temperature coefficient of 3.62 × 10/ °C, which are improved by 60 and 90 %, respectively. The nonlinear coefficient of voltage decreases to 1.16, decreases by 4.3 % and the stability of −1.2 % in the variation rate of the resistivity for aging temperature. [ABSTRACT FROM AUTHOR]

Nearly dense and almost single-phase bulk (Cr1–xVx)2AlC (x = 0, 0.25, 0.5, 0.75, and 1.0) ceramics were successfully fabricated by in situ hot-pressing method using Cr, V, Al, and C powders as raw materials. A possible synthesis mechanism was proposed to explain the formation of (Cr1–xVx)2AlC solid solutions. The lattice parameters, microstructure, and mechanical properties of the (Cr1–xVx)2AlC ceramics were investigated in detail. The results indicated that the lattice parameters increased with the substitution of Cr by V and the aspect ratio of the grain changed from 1.4 to 3.2. The dependence of the mechanical properties on the V content was a single-peak type. The (Cr0.5V0.5)2AlC ceramic possessed the optimal mechanical performance and its Vickers hardness, flexural strength, and fracture toughness reached the maximum values of 5.18 GPa, 402 MPa, 5.91 MPa m1/2, respectively, due to the solid solution effect. The energy-consuming mechanisms of the material were also discussed. [ABSTRACT FROM PUBLISHER]

The ZnO-based linear resistance ceramics were fabricated from ZnO-AlO-MgO-TiO at 1,340 °C. The effect of the different doping amounts of MgO on the microstructure and electrical properties were investigated in detail. The optimal sample with the MgO concentration of 7 wt% possesses an energy density of 812 J/cm and a resistance temperature coefficient reaches 0.4 × 10/°C, which are improved by 8 and 103 %, respectively. Spontaneously, the nonlinear coefficient maintains about 1.15 and the resistivity reaches to 778 Ω cm, increased by 33 %. [ABSTRACT FROM AUTHOR]

The ZnO-based linear resistance ceramics were fabricated from ZnO-AlO-MgO-NiO at 1,340 °C. The effect of the different doping amounts of NiO on the microstructure and electrical properties were investigated in detail. Appropriate amount of NiO addition can reduces the nonlinear property and improves the resistance temperature coefficient of the ZnO-based linear resistance ceramics obviously. The samples with the NiO concentration of 15 mol% possess an energy density of 496 J/cm and a resistance temperature coefficient 1.15 × 10/°C, which are improved by 10 and 79 %, respectively. Moreover, the nonlinear coefficient of voltage decrease to 1.14, decreased by 11 % and the resistivity reaches to 43.53 Ω cm, increased by 76 %. [ABSTRACT FROM AUTHOR]

The effect of MgO addition on the properties of (Co, Nb, Cr)-doped SnO varistors was investigated. The samples with different MgO concentrations were fabricated by the conventional ceramic method and sintered at 1,250, 1,300, 1,350 and 1,400 °C for 2 h. It was found that the nonlinear coefficient presented a peak value of 28 and lowest leakage current density of 7 μA/cm when 0.5 mol% MgO was added. The breakdown electrical field increased from 174 to 531 V/mm with increasing MgO from 0.0 to 2.0 mol%. The relative dielectric constant decreased with increasing MgO from 0.0 to 0.5 mol%, but increased with more MgO added. The dielectric loss decreased obviously in the case of low frequency with MgO added, and it had the lowest value when 0.5 mol% MgO added. The optimal samples were obtained by doping MgO with 0.5 mol% and sintering at 1,350 °C. [ABSTRACT FROM AUTHOR]

Al 2O 3/TiAl composites are successfully fabricated by the in-situ hot pressing method from the elemental powders of Ti, Al, TiO 2, and V 2O 5. The effect of V 2O 5 addition on the microstructure and mechanical properties of the Al 2O 3/TiAl in-situ composites is investigated in detail. It is found that the as-synthesized composites mainly consist of V-dissolved γ-TiAl, α 2-Ti 3Al, and Al 2O 3 particles along with a small amount of V 3Al phase, and the in-situ-formed fine Al 2O 3 particles tend to disperse on the grain boundaries of TiAl matrix. With increasing V 2O 5 content, the density and Vickers hardness of the resulting composites gradually increase, whereas the fracture toughness and flexural strength first increase and then decrease with the increase of V 2O 5 content. The composite with 3.5 wt.% V 2O 5 has the maximum value of 9.35 MPa m 1/2 and 713.36 MPa for the fracture toughness and flexural strength, respectively. The toughening mechanism is also discussed in detail. [ABSTRACT FROM AUTHOR]

Fully dense (Ti,Mo)2AlC/Al2O3 in situ composites with high purity were successfully synthesized at 1350 °C by reactive hot pressing of the Ti, Al, TiC, and MoO3 powder mixtures. The effect of MoO3 content on the phase composition, microstructure, and mechanical properties was investigated in detail. The introduction of the Al–MoO3 displacement reaction into the Ti–Al–TiC system resulted in a submicron grain size and a homogeneously distributed matrix phase of (Ti,Mo)2AlC with a secondary Al2O3 phase. The matrix grain size was significantly refined with increasing the Al2O3 content. Compared with the sample without MoO3 addition, the addition of 13.81 wt% MoO3 (corresponding to 10 wt% Al2O3 formation) evidently enhanced the hardness, flexural strength, and fracture toughness by 25%, 69%, and 146%, respectively. The strengthening and toughening mechanisms for the (Ti,Mo)2AlC/Al2O3 composites were also investigated. [ABSTRACT FROM AUTHOR]

Highlights: [•] TiAl based composites were synthesized by hot-press assisted reactive sintering. [•] Cr2O3 addition enables refining the microstructures of the composites. [•] The suitable amount of Cr2O3 in the TiAl based composites is 4.47wt.%. [•] Toughening effect arising from combination of Cr solid solution and in situ Al2O3. [Copyright &y& Elsevier]

(Ti,Mn)Al/Al2O3 composites were successfully synthesized by reactive hot pressing from Ti–Al–TiO2–MnO2 system. The effect of Mn coming from the Al–MnO2 reaction on the microstructure and mechanical properties of (Ti,Mn)Al/Al2O3 in situ composites was investigated in detail. The results show that the as-prepared products are mainly composed of (Ti,Mn)Al matrix (including a little of Ti3Al) and Al2O3 particles, together with a few amount of Al77.5Mn22.5 phases. The (Ti,Mn)Al matrix is refined and the in situ generated Al2O3 particles distribute uniformly on the boundaries of (Ti,Mn)Al by incorporation of Mn. The (Ti,Mn)Al/Al2O3 composite with 1.92 wt% Mn possesses the best mechanical properties. Compared with Mn-free samples obtained from Ti–Al–TiO2 system, the hardness, flexural strength, and fracture toughness are enhanced by 53.46%, 76.49%, and 64.21%, respectively. The strengthening and toughening mechanisms were also discussed specifically. [ABSTRACT FROM AUTHOR]

Abstract: (Ti,Nb)2AlC/Al2O3 in-situ solid solution composites were successfully synthesized from the elemental powder mixtures of Nb2O5, Ti, Al and carbon black using hot-press-aided reaction synthesis. The reaction path was investigated by differential scanning calorimetry (DSC) and X-ray diffractometry (XRD), and a possible reaction mechanism was proposed to explain the formation of (Ti,Nb)2AlC/Al2O3 composites in which the thermite reaction between Al and Nb2O5 formed Al2O3 and Nb, and the latter together with TiAl and TiC reacted to form (Ti,Nb)2AlC. The synthesized composites show plate-like grains packed in a laminated structure typical of Ti2AlC, and the fine Al2O3 particles formed in-situ tend to disperse on the matrix grain boundaries. Compared with the monolithic Ti2AlC synthesized using an identical process, the Vickers hardness, maximum compressive stress, flexural strength and fracture toughness of (Ti0.96,Nb0.04)2AlC/5wt% Al2O3 were enhanced by 33.8%, 12.1%, 118.4% and 111.8%, respectively. The mechanisms by which Al2O3 increases the strength and toughness of the material were also discussed. [Copyright &y& Elsevier]

Abstract: Al2O3 particle-reinforced Ti2AlC composites are successfully synthesized from the powder mixture of Ti, TiC, Al and TiO2 by in situ hot-pressing method. The effect of Al2O3 addition on the microstructure and mechanical properties of the Ti2AlC/Al2O3 composites is investigated in detail. It is found that the as-sintered products are mainly composed of Ti2AlC matrix and Al2O3 reinforcement, and the in situ formed fine Al2O3 particles tend to disperse on the matrix grain boundaries. With increasing the Al2O3 content, the Rockwell hardness, compressive and flexural strength of Ti2AlC/Al2O3 composites gradually increase. But the fracture toughness of the composites increases first then decreases with the increase in the Al2O3 and the Ti2AlC/12wt% Al2O3 sample possesses the maximum value of 5.37MPam1/2, which is improved by 19.3%. [Copyright &y& Elsevier]

Abstract: In situ composites of TiAl reinforced with Al2O3 particles are successfully synthesized from an elemental powder mixture of Ti, Al and Nb2O5 by the hot-press-assisted reaction synthesis (HPRS) method. The as-prepared composites are mainly composed of TiAl, Al2O3, NbAl3, as well as small amounts of the Ti3Al phase. The in situ formed fine Al2O3 particles tend to disperse on the matrix grain boundaries of TiAl resulting in an excellent combination of matrix grain refinement and uniform Al2O3 distribution in the composites. The Rockwell hardness and densities of TiAl based composites increase gradually with increasing Nb2O5 content, and the flexural strength and fracture toughness of the composites have the maximum values of 634MPa and 9.78MPam1/2, respectively, when the Nb2O5 content reaches 6.62wt.%. The strengthening mechanism was also discussed. [Copyright &y& Elsevier]

Abstract: Fully dense and single-phase Ti2AlC ceramic was successfully synthesized by a high energy milling and hot pressing using Ti, C and Al as starting materials. The effects of composition of the initial elemental powders and sintering temperatures on the purity and formation of Ti2AlC were examined. The formation mechanism for the single-phase Ti2AlC ceramics was investigated by XRD in details, which could be described as follows: the most of initial elements reacted to form TiC and Ti–Al intermetallics; the intermetallics and the residual Ti and Al transformed to TiAl phase; and finally the TiAl intermetallics and the TiC reacted to yield Ti2AlC. [Copyright &y& Elsevier]

HoAl-Al2O3/TiAl composites were fabricated by in-situ reaction synthesis using Al, Ti, TiO2 and Ho2O3 powders as raw materials. The effects of Ho2O3 content on the microstructure and mechanical properties of the composites were investigated. The phase constitution and microstructure of the composites were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results indicate that the ultimate phases of the composite are composed of TiAl and Ti3Al (matrix phases), and Al2O3 and HoAl (reinforced phases). Doping Ho2O3 alters the ratio of TiAl and T3Al and the microstructure of the composites, and the properties of the materials were changed accordingly. The mechanical property tests show that the addition of Ho2O3 can improve the properties of composites significantly the bending strength reaches 594 MPa and Vickers hardness reaches 4.76 GPa with 6 wt% Ho2O3. [ABSTRACT FROM AUTHOR]

The persimmon-red glazed wares, characterized by a reddish-brown appearance with high gloss, were one of the main varieties of glazes manufactured in Jian kilns (Fujian province, China) during the Song Dynasty. Densely packed dendritic ε-Fe 2 O 3 crystals in microns size composed of several branches were observed in the glazes surfaces of Jian persimmon-red wares. The branches, consisting of well-arranged rod-like crystals with offset around 110 or 220 nm, could serve as sub-micron mirrors to improve the glaze gloss. A number of Al and few Ti and Mn ions were detected to substitute Fe ions in ε-Fe 2 O 3 crystals. The Al substitution could play a dual role in ε-Fe 2 O 3 structure: (1) stabilizes the structure through increasing of cationic disorder and (2) makes the appearance less dark, which could account for the nice persimmon-red appearance of Jian wares. Besides, zircon, quartz, hematite, jacobsite and mullite were also observed in the glaze surfaces. • Dendritic ε-Fe 2 O 3 crystals in microns size composed of several branches were observed in the glazes surfaces of Jian persimmon-red wares. • The branches consisting of well-arranged rod-like crystals with offset ~110 or 220 nm could serve as sub-micron mirrors to improve glaze gloss. • Al substitutions in ε-Fe 2 O 3 crystals could play a dual role of acting as stabilizers to increase cationic disorder and making appearance less dark. • A few impurity crystals including zircon, quartz, hematite, jacobsite and mullite were detected in the glazes surfaces. [ABSTRACT FROM AUTHOR]

ZnO-based conductive ceramic materials doping ZrO 2 were prepared at 1320 °C by the conventional solid-state sintering method in air, and the influence of comprehensive properties with different ZrO 2 -doped content were studied carefully. Microstructure and crystals of the samples were investigated by SEM and XRD respectively. As a donor, Zr4+ increases the carrier concentration and decreases the resistivity of grain and grain boundary. As-prepared samples shown excellent linear V–I characteristics and were suitable for high frequency electric field. With the increasing of dopant ZrO 2 contents, the dielectric constant and resistivity of ZnO-based conductive ceramics were influenced significantly, moreover, the resistance-temperature characteristics presents the negative temperature coefficient effects. ZnO-based conductive ceramics exhibited excellent comprehensive electrical performance with 0.30 mol% ZrO 2 -doping, in which the nonlinear coefficient is 1.01, the grain boundary barrier height is 0.014 eV, and the resistance temperature coefficient is −2.6×10−3/°C. [ABSTRACT FROM AUTHOR]

Yohen Tenmoku, a masterpiece of Jian kiln with bright blue rendering effect under different incident light, is lack research as only three intact pieces exist in the world. Herein, this study was fortunate to work with Jianxing Sun to conduct technical characterization and material analysis of the imitation Yohen Tenmoku (Song). Black oil spots are composed of magnetite (10–25 µm) and Al doping in hematite (1–3 µm) precipitated on the glaze surface. Brilliant blue color a combination of the bright blue structural color resulting from the coherent scattering of amorphous photonic crystals composed of spherical phase separation structures of 130 nm and the coloring of iron ions produced in a weak reducing atmosphere by the addition of high iron glazes with composite alkali (CaO and MgO). Continuous refraction and reflection of the structural color between the blue glass phases gives the glaze a shiny and dazzling blue color. [ABSTRACT FROM AUTHOR]

ZnO-ZnAl 2 O 4 -SiO 2 -Y 2 O 3 -MgO conductive ceramics were fabricated with different amount of ZnAl 2 O 4 content. The effects of ZnAl 2 O 4 on the microstructures and electrical properties of ZnO-based compound conductive ceramics were investigated. Results showed that the continuously adjustable resistivity could be obtained under the percolation threshold through increasing ZnAl 2 O 4 content and improving the preparing technology. It was found that ZnAl 2 O 4 grain would be encased in the major ZnO grains, with less than 5.0 mol%. When more ZnAl 2 O 4 doping in the samples, it acted as a barrier blocking ZnO grain growth. Interestingly, the dielectric properties indicate that the Maxwell-Wagner interfacial polarization and the threshold effect exists in the matrixes. At the same time, the resistance-temperature ( R-T ) characteristics verify that the conduction mechanism of ZnO-based conductive compound ceramics is a thermally activated progress and the grain-boundary effect is negligible. The improvement of the microstructures and electrical properties has a potential application in the high frequency electrical fields. [ABSTRACT FROM AUTHOR]

In this paper, we report a simple one-step method to prepare shape-controlled flower-like ZnO microstructure. The different morphologies of ZnO flowers, including spindle-based, flake-based and rod-based, were synthesized by simply adjusting the Zn 2+ in alkaline solution. The photocatalytic activities of the variously structural ZnO were investigated under UV-light irradiation, and the results showed that the flake-based ZnO displayed better in catalytic degradation of dyes than the other two structures. Since the flake-based ZnO featured with small grain size, enormous interface area and abundant mesopores due to its special structures. In brief, the present study provides an efficient method for the enhancement of photocatalytic activity by designing the shape-controlled ZnO flowers, especially the flake-based ZnO. These nanoflakes-assembled ZnO with superior photocatalytic performance are also expected to be used in other application such as gas-sensing. [ABSTRACT FROM AUTHOR]

Abstract: ZnO varistors were synthesized using Pr6O11 doped ZnO–Bi2O3 system as raw materials by ball milling. The effects of intensive milling on the microstructure and electrical properties of the varistors were investigated in detail. The results show the intensive milling decreases the particle size and distribution of the powders for ZnO varistors. The optimal samples obtained from the powders milled for 10h have average crystalline grain size of about 4μm and the gradient voltage of 565V/mm, the leakage current of 0.45μA, and the nonlinear coefficient of 75. [Copyright &y& Elsevier]

Sauce glaze is one of the main varieties of glazes produced in the Yaozhou kilns during the Song Dynasty. It is famous for its reddish-brown color and high gloss. In this work, the elemental composition, morphology, structure, and light reflectivity of glazes of archeological sherds were systematically studied. A large number of ε-Fe 2 O 3 dendritic crystals were observed in the glazes. Alkali etching was implemented to remove the glassy matrix surrounding these crystals to further investigate their microstructure. SEM observations emphasize that they are composed of well-arranged parallel branches separated by about 230 nm, each of which consisting of offset stacks of many small flake-shaped crystals, with the offset ranging from 100 to 110 nm. Based on these results, the origin of the reddish-brown color and high gloss was discussed. In addition, cordierite crystals were observed for the first time in the sauce glaze from Yaozhou kilns. [ABSTRACT FROM AUTHOR]

Abstract: Al2O3/TiAl composites were successfully fabricated from powder mixtures of Ti, Al, TiO2 and Cr2O3 by a hot-press-assisted exothermic dispersion method. The effect of the Cr2O3 addition on the microstructures and mechanical properties of Al2O3/TiAl composites was characterized, and the results showed that the Rockwell hardness, flexural strength and fracture toughness of the composites increased as the Cr2O3 content increased. When the Cr2O3 content was 2.5wt%, the flexural strength and the fracture toughness attained peak values of 925MPa and 8.55MPam1/2, respectively. This improvement of mechanical properties was due to the more homogeneous and finer microstructure developed from the addition of Cr2O3 and an increase in the ratio of α2-Ti3Al to γ-TiAl matrix phases. [Copyright &y& Elsevier]

The Yaozhou kiln complex (Shaanxi, China) is a famous black-to-brown ceramic production center due to its significant volume of production, long manufacturing history (from Tang Dynasty to Yuan Dynasty) and variety of decorations. In this work, four representative types of black-to-brown ware from the Yaozhou kilns were selected to study the morphology, structure and distribution of the precipitated crystals in the glazes using a series of imaging and analytical techniques (optical microscopy, XRF, SEM-EDS, TEM-EDS, μRS and UV–vis-IR). The results show that the rare metastable ε-Fe 2 O 3 phase, already observed in typical sauce glaze, was also detected in other types of brown glaze decorations, such as light brown stripes on a darker background or irregular brown spots on a black background. Cross-section analyses also showed a three well-separated layered crystalline distribution in the glazes of lighter brown colors as it has been noted in glazes from Qilizhen kilns. Raman analyses revealed that the crystals contained in third layer are of varying nature: ε-Fe 2 O 3 in the sauce glaze and magnetite in the light brown stripes. The peak shifts and line broadenings observed in the Raman spectra of ε-Fe 2 O 3 crystals were also investigated. They are the result of Al, Ti and Mg substitutions, which were identified using TEM-EDS. Such ionic substitutions would stabilize the metastable ε-Fe 2 O 3 crystals by increasing the cationic disorder. In addition, Mg-, Ca- and Fe-rich spinel crystals were observed for the first time in a black glaze of Yaozhou wares. [ABSTRACT FROM AUTHOR]

This work takes the Five dynasty celadon body of Yaozhou kiln as the major study objects. Based on the analysis of XRF, XRD, SEM/EDS, UV/Vis/NIR spectrophotometers and XPS, the chemical compositions, microstructure and optical quality of the white and black bodies have been investigated. The results indicates that the Five dynasty celadon body has lower SiO 2 content than that of the other dynasties, which provides an evidence for dating research on ancient celadon. Furthermore, the high Fe 2 O 3 and TiO 2 contents enhance the formation of F e 2 3 + T i 4 + O 5 , F e 2 + T i 2 4 + O 5 and Ti 2 O 3 in the black body and deepen the coloring of Fe 2 O 3 . As a result, its color is darker than the white body. In addition, there are more crystal boundaries and residual micropores appeared in the black body. They serve as optical scattering centers and decrease the transmittance of incidence light. Therefore, the black body has much worse transmittance than that of the white body. [ABSTRACT FROM AUTHOR]

(Ti,Mo)Al/Al 2 O 3 composites were successfully synthesized by hot pressing based on the Ti–Al–TiO 2 –MoO 3 system. Effect of MoO 3 content on the microstructure and mechanical properties of (Ti,Mo)Al/Al 2 O 3 composites was investigated in detail. It was found that the as-fabricated samples contain TiAl, Ti 3 Al, and Al 2 O 3 , together with a small amount of Ti 2 AlMo phase reinforcement phase. The fine Al 2 O 3 particles dispersed on the TiAl matrix grain boundaries as a network structure and resulted in the improvement of room mechanical properties of the composites. With increasing of MoO 3 contents, the flexural strength and fracture toughness of (Ti,Mo)Al/Al 2 O 3 composites gradually increase, and with 1.0 at% MoO 3 , doped the products possess the maximum value of 702 MPa and 8.3 MPa m 1/2 for the flexural strength and fracture toughness, respectively. [ABSTRACT FROM AUTHOR]

Abstract: (1− x)Ba(Fe0.5Nb0.5)O3–xBaTiO3 ceramics with giant dielectric constants and low losses were prepared by the conventional solid-state method. The phase structure, microstructures, electrical properties of the ceramics were investigated. The results show that the ceramics are of monoclinic structure and possess dense and fine microstructures. The incorporation of BaTiO3 can significantly reduce the dielectric loss and improve the frequency and temperature stability of the electrical properties of Ba(Fe0.5Nb0.5)O3. [Copyright &y& Elsevier]