-
Xifan WANG, Gabriela MERA, Koji MORITA, Emanuel IONESCU
2016 Volume 124 Issue 10 Pages
981-988
Published: October 01, 2016
Released on J-STAGE: October 01, 2016
JOURNAL
FREE ACCESS
Within the present work, reduced-graphene oxide (rGO)/silicon nitride (Si
3N
4) nanocomposites were prepared upon pyrolysis of a graphene oxide (GO)-filled polysilazane. The novel preparative approach consists in the synthesis of the polysilazane in the presence of different concentrations of GO, yielding a homogeneous GO/polysilazane composite which was subsequently thermally converted in Ar atmosphere into rGO/Si
3N
4 nanocomposites. Hot-pressing of the obtained nanocomposite powders delivered monolithic rGO/Si
3N
4. All prepared samples exhibited the presence of homogeneously dispersed rGO phase within an amorphous or crystalline silicon nitride matrix, as for the as-prepared and hot-pressed samples, respectively. An increasing amount of rGO in the nanocomposites was found to gradually suppress the crystallization of the silicon nitride matrix into α-Si
3N
4. Moreover, depending on the volume fraction of the graphene phase in the ceramic nanocomposites, different dielectric properties were observed, indicating a facile preparative method to produce materials with tunable electromagnetic waves (EMW) behavior.
View full abstract
-
Zineb MOULINE, Kota ASAI, Yusuke DAIKO, Sawao HONDA, Samuel BERNARD, Y ...
2016 Volume 124 Issue 10 Pages
989-995
Published: October 01, 2016
Released on J-STAGE: October 01, 2016
JOURNAL
FREE ACCESS
Amorphous silica-based alkylamine-functionalized hybrid membrane materials were synthesized through polymer-derived ceramics (PDCs) route, in order to selectively transport CO
2. Commercially available perhydropolysilazane (PHPS) was chemically modified with primary and secondary amino silane derivatives, and subsequently oxidized in air at room temperature to afford alkylamine-functionalized amorphous silica materials. CO
2 uptake by the powdered samples was investigated by the thermogravimetric analysis under CO
2 atmosphere, in-situ diffuse reflectance infrared fourier transform spectroscopic analysis and measurement of CO
2 sorption isotherm. In the case of alkylamine-functionalized silica samples, CO
2 uptake mechanism involved chemisorption at very low partial pressures and physisorption at higher partial pressures, demonstrated by the temperature dependence of CO
2 isotherms. The reaction paths and sorption mechanisms related to the nature of the functionalized amino groups were discussed from a viewpoint to develop CO
2-selective facilitated transport ceramic-based membranes.
View full abstract
-
Aitana TAMAYO, Raquel PEÑA-ALONSO, Maria Alejandra MAZO, Fausto ...
2016 Volume 124 Issue 10 Pages
996-1002
Published: October 01, 2016
Released on J-STAGE: October 01, 2016
JOURNAL
FREE ACCESS
Two sets of sol–gel derived glass materials have been prepared and subjected to different thermal treatments. Pyrolysis in inert atmosphere lead to the formation of amorphous Si(B)CO ceramics whereas if the inert atmosphere is changed to NH
3 once the carbon substituents of the preceramic hybrid material transform to a glassy network, the nitrogen is incorporated efficiently while the carbon is retained into the structure, as revealed by
29Si NMR analysis. Raman spectra show a less graphitized structure in the case of B-rich materials because of the reduced mobility of the C atoms due to the formation of mixed (B)CN bonds.
View full abstract
-
Martin SEIFERT, Mateus Lenz LEITE, Günter MOTZ
2016 Volume 124 Issue 10 Pages
1003-1005
Published: October 01, 2016
Released on J-STAGE: October 01, 2016
JOURNAL
FREE ACCESS
The present study deals with the synthesis of Mg
2SiO
4 (Forsterite) applying the route of polymer derived ceramics (PDCs). The liquid, inorganic perhydropolysilazane (PHPS) was used because it is very reactive during pyrolysis in air and forms amorphous SiNO ceramic containing a tremendous amount of SiO
2. Both facts are crucial for the reaction with MgO in order to synthesize Mg-silicates. The results of this study demonstrate, that the Mg-orthosilicate phase is formed at the MgO/SiNO interface via solid state reaction at comparably low temperatures of 1100°C during pyrolysis in air for 2 h. Furthermore the high reactivity of the polysilazane leads to an almost full conversion of the MgO to Mg
2SiO
4 under the used conditions.
View full abstract
-
Christina STABLER, Christoph SEEMÜLLER, Ahmad CHOUDHARY, Martin H ...
2016 Volume 124 Issue 10 Pages
1006-1012
Published: October 01, 2016
Released on J-STAGE: October 01, 2016
JOURNAL
FREE ACCESS
In this work, a lutetium-modified silicon oxycarbide (SiOC) glass ceramic was prepared from a single-source precursor via pyrolysis and subsequent hot pressing. It is shown that the main crystalline phase in the hot-pressed SiLuOC is Lu
2Si
2O
7. The high-temperature (HT) creep behavior of SiLuOC was assessed by compression creep experiments performed between 1100 and 1300°C at constant true stresses between 25 and 75 MPa. The calculated viscosity values of SiLuOC were found to be significantly higher as compared to those of SiRE(Al,Mg)ON glasses (RE = rare earth elements). Thus, the presented SiLuOC-based glasses might be used as alternative sintering aids for the liquid-phase sintering of HT creep resistant Si
3N
4 monolithic samples.
View full abstract
-
Taishi HORIBE, Keiji KUSABA, Ken NIWA, Masashi HASEGAWA, Keisuke YASUD ...
2016 Volume 124 Issue 10 Pages
1013-1016
Published: October 01, 2016
Released on J-STAGE: October 01, 2016
JOURNAL
FREE ACCESS
Graphite-like carbon nitride inorganic compounds were synthesized from molecular 1,2,4-triazole C
2N
3H
3 in high pressure and temperature conditions using a DIA-type multianvil large press. It was found that the N/C content ratio of the carbon nitrides can be systematically controlled by changing the heating temperature at 5 GPa. The substitution of nitrogen for carbon in graphene layers results in the low crystallinity of the synthesized C–N compounds. It should be noted that the
c-axis which is equivalent of the distance between two graphene layers, decreases monotonously with increasing N/C content ratio. This is attributed to both of the smaller atomic size of nitrogen than that of carbon and Van der Waals attraction between C–N graphene layers because of the different electronegativity between nitrogen and carbon.
View full abstract
-
Elisabeth REITZ, Karl Günter SCHELL, Ethel Claudia BUCHARSKY, Rai ...
2016 Volume 124 Issue 10 Pages
1017-1022
Published: October 01, 2016
Released on J-STAGE: October 01, 2016
JOURNAL
FREE ACCESS
In this study precursor derived SiOC/MoSi
2 composites were evaluated with respect to their potential for the application as glow plug material. In a first step, fully dense composite materials with different fractions of electrical conductive MoSi
2 were fabricated by field-assisted sintering technique (FAST). The percolation threshold, where the electrical properties change from insulating to a suitable level of conduction depends on the microstructure, which can be controlled by the initial particle size of the used SiOC particles. It becomes principally possible to fabricate both, the insulating part and the heater material with the same MoSi
2 content and therefore without thermal mismatch. Room temperature properties, high temperature strength, oxidation and creep behaviour depend strongly on the MoSi
2 volume fraction. MoSi
2 contents beyond the percolation threshold lead to significantly enhanced creep rates. At high temperatures, reactions between SiOC and MoSi
2 can be observed, which differ at the air exposed surface and in the interior of the samples. From these findings, an upper limit for the application temperature can be derived.
View full abstract
-
Gian Domenico SORARU, Renzo CAMPOSTRINI, Awoke Asmamaw EJIGU, Emanuele ...
2016 Volume 124 Issue 10 Pages
1023-1029
Published: October 01, 2016
Released on J-STAGE: October 01, 2016
JOURNAL
FREE ACCESS
A simple process for synthesizing SiOC foams with low density (45–115 kg/m
3) and high porosity (95–98%) is reported here. The process involves the impregnation of a flexible polyurethane foam with a preceramic polymer solution and pyrolysis in the inert atmosphere. SEM analysis showed that the resultant SiOC foam had a fully open interconnected porous structure with dense struts. N
2 adsorption test performed on the as-pyrolyzed SiOC foams showed very low surface area, which can be increased by leaching out the SiO
2-rich network by HF, leaving behind a mesoporous C-rich SiOC foam. The remarkably high surface area up to 147 m
2/g (7350 m
2/liter) has been reached after 24 h etching. HF etching leads to a decrease of the compressive strength. However, a good combination of compressive strength (∼80 kPa), porosity (95%) and surface area (7315 m
2/liter) of the foam has been obtained and it makes the SiOC foam a potential candidate for specific applications.
View full abstract
-
Thomas KONEGGER, Thomas PROCHASKA, Richard OBMANN
2016 Volume 124 Issue 10 Pages
1030-1034
Published: October 01, 2016
Released on J-STAGE: October 01, 2016
JOURNAL
FREE ACCESS
A processing technique for the preparation of porous, silicon carbonitride-based ceramics in tubular geometry derived from a liquid polysilazane precursor is presented. After casting of polysilazane/polymer-microbead dispersions, cross-linking, and subsequent pyrolytic conversion and selective removal of polymer templates, specimens with an inner and outer diameter of 6 and 10 mm, respectively, and a length of up to 65 mm were obtained. Porosity was controlled by sacrificial template content and reached values up to 48% after pyrolytic conversion, at average pore opening radii of 1 µm. The tubular specimens exhibited diametral compression strengths (C-ring test) between 24 ± 6 and 36 ± 4 MPa. Darcian permeability constants of up to 1.7·10
−14 m
2 were found by gas permeability testing. The results demonstrate that this methodology facilitates the straightforward generation of complex-shaped porous specimens, further allowing for a control of strength and permeability in a specific range. Potential applications for the tubular, porous structures developed can be anticipated in the fields of separation or catalysis.
View full abstract
-
Bernd MAINZER, Martin FRIEß, Raouf JEMMALI, Dietmar KOCH
2016 Volume 124 Issue 10 Pages
1035-1041
Published: October 01, 2016
Released on J-STAGE: October 01, 2016
JOURNAL
FREE ACCESS
A damage tolerant weak matrix SiC fiber reinforced composite was developed by utilising a polyvinylsilazane in the polymer infiltration and pyrolysis (PIP) process. The polysilazane was infiltrated via resin transfer moulding in a layup of SA3 fabrics, thermally cured and pyrolyzed. This process was repeated until a residual open porosity of below 5% was reached. During pyrolysis the polyvinylsilazane converts to an amorphous SiCN matrix. In combination with the high modulus Tyranno SA3 SiC fibers a weak matrix composite is created. To protect the composite in oxidative environment at high temperatures, an exterior SiC coating by means of chemical vapour deposition was applied. The polyvinylsilazane was investigated in terms of differential scanning calorimetry and measurement of viscosity to find the ideal temperatures for the polymer infiltration step. Specimens of the precursor were cured and pyrolyzed. The densification during pyrolysis was investigated in terms of He gas pycnometry and X-ray diffraction. The composite was characterized by SEM, µCT and mercury intrusion porosimetry. To determine the suitability of the SiC/SiCN composite for high temperature applications, samples were oxidized and tested by means of 3-point bending.
View full abstract
-
Felix ROTH, Philipp WALESKA, Christian HESS, Emanuel IONESCU, Norbert ...
2016 Volume 124 Issue 10 Pages
1042-1045
Published: October 01, 2016
Released on J-STAGE: October 01, 2016
JOURNAL
FREE ACCESS
Polymer-derived silicon oxycarbides exhibiting ≤1 and 10 vol.% of segregated carbon finely dispersed within a glassy Si
xO
yC
z matrix have been investigated by UV Raman spectroscopy using a laser excitation of 4.8 eV (λ = 256.7 nm). Carbon exists as amorphous sp
2–sp
3 bonded component in SiOC/C (≤1 vol.%) pyrolyzed at 1100°C in H
2, including C–C single bonds, polymeric chains and small polycyclic aromatic hydrocarbons (PAHs). The formation of nanocrystalline carbon at T > 1400°C is seen in the Raman spectra of SiOC/C (≤1 vol.%) and SiOC/C (10 vol.%) by the appearance of the G band of graphite. Tempering at 1600°C increases the degree of order within the carbon phase. However, the slight narrowing of the G peak with processing temperature (by about 5%) indicates still not well-crystallized carbon: the Raman results can be best explained by turbostratic carbon (with a lateral size L
a of ≈2 nm) and do not support the model description in literature as a network of single layer graphene.
View full abstract
-
Han ZOU, Jie REN, Xiao WU, Yu DAI, Da-Wei SHA, Yan-Ze WU, Jian-Mei PAN ...
2016 Volume 124 Issue 10 Pages
1046-1051
Published: October 01, 2016
Released on J-STAGE: October 01, 2016
JOURNAL
FREE ACCESS
Modified graphitic C
3N
4 was synthesized by the ionothermal copolymerization method and composited with BiOBr by water-bath heating. The microstructure, specific surface area, photocatalytic activity and optical property of the resulting hybrid photocatalysts were characterized. The results showed that layered BiOBr was formed on the surface of modified graphitic C
3N
4 nanoparticles. The modified graphitic C
3N
4/BiOBr hybrid photocatalysts had a higher specific surface area than that of BiOBr and show a broad response range under visible light. The synergetic effect between the two semiconductors was more favorable for the separation of electron–hole pairs. Rhodamine B solution can be effectively degraded using the hybrid photocatalysts. When the weight ratio of modified graphitic C
3N
4 in the hybrid photocatalyst was up to 50%, the photocatalyst showed the best activity. Photocurrent testing indicated that the recombination of photo-generated electron–hole pairs was inhibited. The photocatalyst showed a good stability by a cycling experiment.
View full abstract
-
Mirabbos HOJAMBERDIEV, Isabel GONZALO-JUAN
2016 Volume 124 Issue 10 Pages
1052-1055
Published: October 01, 2016
Released on J-STAGE: October 01, 2016
JOURNAL
FREE ACCESS
The visible-light-induced photocatalytic water oxidation activity without cocatalyst has been demonstrated for the first time on tantalum (oxy)nitride nanocrystals synthesized by a Ca-assisted nitrogen-rich molecular approach. Monodisperse TaON and Ta
3N
5 nanocrystals were synthesized by using suitable urea/Ta ratios in the presence of Ca
2+ ions. The as-synthesized (oxy)nitrides are in the form of spherically-shaped and well-defined nanocrystals with an average diameter of ca. 7 nm. Both nanocrystals showed absorption edges in the visible region. The band gap energies of TaON and Ta
3N
5 nanocrystals were determined from the Tauc’s plots of the UV–Vis diffuse reflectance spectra to be 2.27 and 2.08 eV for indirect allowed transitions, respectively. The O
2 evolution rate was increased and reached the maximum in the following order: 2.01, 3.32, and 4.66 µmol·h
−1 for the samples synthesized with Ca
2+/urea molar ratio of 0.10, 0.50, and 0.25, respectively, due to the decrease in the optical band gap.
View full abstract
-
Esther ORISAKWE, Rémi MARCHAL, Bruno FONTAINE, Régis GAU ...
2016 Volume 124 Issue 10 Pages
1056-1062
Published: October 01, 2016
Released on J-STAGE: October 01, 2016
JOURNAL
FREE ACCESS
Supplementary material
Metal oxynitrides with perovskite
AMO
3−xN
x structure have been shown to exhibit promising optical, dielectric, magnetoresistive or photocatalytic properties. They are formally obtained from perovskite oxides via substitution of oxygen by nitrogen. However, due to the stability of the
M–O bond, only a limited number of nitrogen-doped perovskites
AMO
3−xN
x and stoichiometric oxynitrides (
AMO
2N and
AMON
2) has been synthesized and studied so far. Different case studies revealed that the oxidation states of the cations, the O/N ratio, as well as the anion ordering can significantly affect their properties. With the aid of density functional theory calculations, the effect of O/N anion ordering was investigated for a series of different metallic perovskite phases
AMO
2N (
A = Rb, Sr, Y and
M = Cr, Mo, W). Results indicate that well-defined
cis-MO
4N
2 octahedra in the structures are energetically preferred over
trans-MO
4N
2 octahedra, leading to zigzag
M–N chains in the materials.
View full abstract
-
Teak Dagan BOYKO, Alexander MOEWES
2016 Volume 124 Issue 10 Pages
1063-1066
Published: October 01, 2016
Released on J-STAGE: October 01, 2016
JOURNAL
FREE ACCESS
The hypothetical spinel carbon nitride (γ-C
3N
4) has received a large amount of attention due to its predicted hardness being comparable to that of diamond. The group 14 spinel binary nitrides that have been synthesized are limited so far to: γ-Si
3N
4, γ-Ge
3N
4 and γ-Sn
3N
4. However, there still remains significant interest in γ-C
3N
4 in the hope that it will eventually be synthesized, but there are no successful reports, thus making the study of γ-C
3N4 strictly theoretical. Through an empirical relationship that correlates hardness, crystal structure and the electronic band gap, we examine a series of group 14 spinel nitrides: γ-C
3N4 γ-Si
3N
4, γ-Ge
3N
4 and γ-Sn
3N
4, as well as their ternary compounds. The hardness and electronic band gap of these materials are calculated using ab initio density functional theory. These results show that in the case of the solid solutions, γ-(Si,Ge)
3N
4 and γ-(Ge,Sn)
3N
4, the tetrahedral site is filled first by the larger cation, Ge and Sn, respectively. Furthermore, the deviation of carbon containing group 14 spinel nitrides from the expected hardness and bandgap trend suggests that γ-Si
3N
4 may remain the hardest known group 14 spinel nitride. Additionally, an improved method to calculate the hardness using the nitrogen bonding tetrahedron provides more unambiguous results and the trend of the hardness agrees with experimental measurements.
View full abstract
-
Sara ZAVAREH, André HILGER, Kathrin HIRSELANDT, Oliver GOERKE, ...
2016 Volume 124 Issue 10 Pages
1067-1071
Published: October 01, 2016
Released on J-STAGE: October 01, 2016
JOURNAL
FREE ACCESS
Highly porous lamellar and cellular cathodes for Li-ion batteries were fabricated from additive-stabilized aqueous suspensions of lithium iron phosphate and carbon black by the unidirectional freeze-casting method and characterized by optical microscopy, scanning electron microscopy, mercury porosimetry, helium pycnometry and X-ray microtomography. The size and orientation of the pores in the specimens were controlled through the variation of the freezing parameters. The diameters of the pores, which are in the range from 0.7 to 30 µm, as well as the wall thickness, decrease as the cooling rate increases. Pore volume and total porosity increase while the solid content of the suspension decreases. The specimen’s structure was changed from lamellar to cellular by increasing the gelatin concentration and solid content in the suspensions. The lamellar specimens demonstrate higher porosity (82–84%) than the cellular samples. Cathodes with lamellar structure possess higher specific capacity and less loss of energy density in comparison to those having cellular structure.
View full abstract
-
Damian M. CUPID, Dajian LI, Christoph GEBERT, Alexandra REIF, Hans FLA ...
2016 Volume 124 Issue 10 Pages
1072-1082
Published: October 01, 2016
Released on J-STAGE: October 01, 2016
JOURNAL
FREE ACCESS
The enthalpy of formation of Li
2MnO
3 was measured by high temperature oxide solution calorimetry in a sodium molybdate solvent and the heat capacity of the compound was determined using differential scanning calorimetry. The enthalpy of formation of Li
2MnO
3 from the elements is slightly less exothermic than that of the orthorhombic and monoclinic modifications of LiMnO
2 but more exothermic than that of LiNiO
2, LiCoO
2, the LiNi
1−xCo
xO
2 solid solutions and the Li
1+xMn
2−xO
4 spinels. The heat capacity of Li
2MnO
3 is also slightly lower than the estimated heat capacity based on stoichiometric amounts of Li
2O and MnO
2 according to the Neumann-Kopp approximation. The slight differences in heat capacities are attributed to the differences in the bonding environments of Li
+ ions in Li
2MnO
3 and the constituent binary oxide Li
2O. The thermochemical data presented here are essential for the advanced thermodynamic modeling of multicomponent electrode materials based on the promising
xLi
2MnO
3·(1 −
x)LiMO
2 nano-composite cathode system.
View full abstract
-
Frank KERN, Rainer GADOW
2016 Volume 124 Issue 10 Pages
1083-1089
Published: October 01, 2016
Released on J-STAGE: October 01, 2016
JOURNAL
FREE ACCESS
Tetragonal zirconia polycrystals (TZP) are ceramics combining high strength and fracture resistance which are applied in biomedical and engineering applications. In this study, a nanoscale monoclinic zirconia nanopowder was coated with 3 mol-% ytterbia via a wet chemical route. The powders obtained after calcination and milling were consolidated into dense samples by hot pressing at 1275–1500°C for 1 h at 50 MPa axial pressure. Microstructure phase composition and mechanical properties were determined. The materials were initially very fine grained and showed grain growth starting at sintering temperatures exceeding 1350°C. At low sintering temperatures bending strength values of 1000–1100 MPa were recorded along with high fracture resistance of >10 MPa√m. In the sintering temperature range between 1350–1375°C, a steep decline of toughness to a level of 6 MPa√m was observed. This decline in fracture resistance is accompanied by a drop in transformability of the tetragonal phase and grain growth. While TZP from coprecipitated powders tend to become tougher with sintering temperature and increasing grain size, materials from stabilizer coated powders showed an adverse tendency. The tough to brittle transition in the 3Yb-TZP studied was attributed to the elimination of the initial stabilizer concentration gradient in the tetragonal grains.
View full abstract
-
Xianrui ZHAO, Dunwen ZUO, Mengxian ZHANG, Feng XU, Shangshen FENG
2016 Volume 124 Issue 10 Pages
1116-1122
Published: October 01, 2016
Released on J-STAGE: October 01, 2016
JOURNAL
FREE ACCESS
This study investigates the influence of sintering pressure on the microstructure and properties of Ti(C,N)–TiB
2–Co cermets prepared by reactive hot processing from a Co–Ti–C–BN system. With increasing sintering pressure, the apparent relative density, fracture toughness and hardness first increase, and then decrease. Cermets with low densities are produced at low applied pressures because liquid cannot infiltrate into the pores, whereas the decomposition of Ti(C,N) and extrusion of cobalt at high pressure produce nano-sized pores that reduce the relative density and mechanical properties. Sintering at 34 MPa produces the optimum combination of high apparent relative density (99.8%) with a fine grain size and few crystal defects, which result in a fracture toughness, hardness, and wear groove depth of 6.71 MPa·m
1/2, 19.01 GPa, and 2.2 µm, respectively.
View full abstract
-
Saowanee SINGSAROTHAI, Vishnu RACHPHET, Sutham NIYOMWAS
2016 Volume 124 Issue 10 Pages
1123-1126
Published: October 01, 2016
Released on J-STAGE: October 01, 2016
JOURNAL
FREE ACCESS
In this study, Fe–W
2B-based composite coating on the inner surface of a steel pipe was produced by centrifugal- Self-propagating high-temperature synthesis (SHS) process. There were FeWO
4, B
2O
3, and Al powders as the major reactants. The effects of coupled additives X(Fe
2O
3–Al) of X = 1, 3, and 5 molar ratio on morphology, composition and micro-hardness of the obtained composite coatings were investigated. The results showed that the system of X = 1 mole was the optimum condition due to its reasonable smoothness (6.5 µm) and hardest (727.90 and 1170.71 HV on alloy and ceramic layers, respectively).
View full abstract
-
Shinya KONDO, Tomoaki YAMADA, Masahito YOSHINO, Tadashi SHIOTA, Kazuo ...
2016 Volume 124 Issue 10 Pages
1127-1131
Published: October 01, 2016
Released on J-STAGE: October 01, 2016
JOURNAL
FREE ACCESS
(001)-epitaxial (Pb
0.91La
0.09)(Zr
0.65Ti
0.35)O
3 (PLZT) ferroelectric thin films were fabricated on SrTiO
3 and MgO substrates, with an SrRuO
3 bottom electrode layer, using pulsed laser deposition. When films were deposited in a single step at a high temperature conventionally used for epitaxial growth, island growth was observed. To suppress the island growth, we used a two-step growth technique. First, a thin initial layer was deposited at a low temperature to promote rapid strain relaxation from the lattice mismatch. Consequently, the island growth was suppressed and when a second layer was deposited at high temperature, a remarkably flatter surface was achieved as compared with that of conventional one-step-grown films. The two-step-grown PLZT films are promising for use in ferroelectric thin film-based plasmonic electro-optic devices.
View full abstract
-
Dae Won JI, Sang-Joo KIM
2016 Volume 124 Issue 10 Pages
1132-1140
Published: October 01, 2016
Released on J-STAGE: October 01, 2016
JOURNAL
FREE ACCESS
A poled lead titanate zirconate rectangular parallelepiped is subjected to compressive stress-induced switching at room and high temperatures. From measured electric displacement and strains, piezoelectric and elastic compliance coefficients are estimated and plotted versus remnant state variables. Then a set of modeling equations is proposed to predict the high temperature behavior of the material reported in one of the authors' previous work. The equations are applied to the present work to calculate the evolutions of reference remnant state variables during mechanical depolarization. Finally, the high temperature behavior of the material during mechanical depolarization is compared with the behavior during electric field-induced polarization reversal in terms of reference remnant state variables.
View full abstract
-
Byung-Nam KIM, Apurv DASH, Young-Wook KIM, Koji MORITA, Hidehiro YOSHI ...
2016 Volume 124 Issue 10 Pages
1141-1145
Published: October 01, 2016
Released on J-STAGE: October 01, 2016
JOURNAL
FREE ACCESS
Fully dense transparent alumina is obtained after spark plasma sintering at 1000°C by using the electrically conductive SiC molding set. Compared to the conventional graphite set, the new mold material lowered the sintering temperature by 150°C for full densification. The SiC set has a lower electrical conductivity than that of the graphite set, which resulted in higher electric field during heating. The enhanced densification is attributed to the high electric field. In this study, the effects of the electric field and the heating rate on the densification of alumina are examined with the SiC molding set, and compared to the results with the graphite set.
View full abstract
-
Lijing DI, Hua YANG, Tao XIAN, Yashan HUO
2016 Volume 124 Issue 10 Pages
1146-1151
Published: October 01, 2016
Released on J-STAGE: October 01, 2016
JOURNAL
FREE ACCESS
In this work, the sonocatalytic property of CaTiO
3 nanoparticles synthesized via a polyacrylamide gel route was investigated by degrading rhodamine B (RhB), methyl orange (MO) and methylene blue (MB) under ultrasonic irradiation. It is revealed that CaTiO
3 particles exhibit an excellent sonocatalytic activity toward the dye degradation. The influence of various experimental parameters [reaction solution temperature, catalyst dosage, initial dye concentration, pH value, and inorganic anions (including NO
3−, SO
42−, H
2PO
4−, and HCO
3−)] on the sonocatalytic efficiency was systematically investigated. Hydroxyl (•OH) radicals were detected by fluorimetry using terephthalic acid as a probe molecule and are found to be produced over the ultrasonic-irradiated CaTiO
3 particles. The addition of ethanol, which acts as a •OH scavenger, leads to a quenching of •OH radicals and a simultaneous decrease in the dye degradation. This suggests that •OH radicals are the dominant active species in the present sonocatalytic reaction. In addition, the recycling sonocatalytic experiment reveals that CaTiO
3 particles exhibit a good stability in their sonocatalytic activity and crystal structure.
View full abstract
-
Shuang ZENG, Jun YANG, Xiaoyan QIU, Zhiyu LIANG, Yuanming ZHANG
2016 Volume 124 Issue 10 Pages
1152-1156
Published: October 01, 2016
Released on J-STAGE: October 01, 2016
JOURNAL
FREE ACCESS
The magnetically recyclable MnFe
2O
4/Polyaniline (PANI) composite was successfully synthesized by a combination of a salt-assisted solution combustion method and an in situ oxidative polymerization method. X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–vis diffuse reflectance spectroscopy (DRS) were employed to characterize the physical and chemical properties of the samples. The results showed that MnFe
2O
4/PANI composite exhibited higher photocatalytic activity and stability than pure PANI and MnFe
2O
4 nanoparticles toward the degradation of rhodamine B (RhB) under visible light irradiation, suggesting the existence of a synergic effect between PANI and MnFe
2O
4. The excited state electrons in the lowest unoccupied molecular orbital (LUMO) of PANI can readily migrate into conduction band (CB) of MnFe
2O
4, while the holes in the valence band (VB) of MnFe
2O
4 migrate to the π-orbital of PANI because of the enjoined electric fields of the two materials, which can further improve the separation of the photoinduced electron–hole pairs.
View full abstract
-
Phonthep NUALKAEW, Anukorn PHURUANGRAT, Phattranit DUMRONGROJTHANATH, ...
2016 Volume 124 Issue 10 Pages
1157-1160
Published: October 01, 2016
Released on J-STAGE: October 01, 2016
JOURNAL
FREE ACCESS
Ag
3VO
4/Bi
2MoO
6 nanocomposites were successfully synthesized by sonochemical method. The as-synthesized products were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), selected area electron diffraction (SAED), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). The results revealed the formation of heterostructure Ag
3VO
4/Bi
2MoO
6 nanocomposites. Photocatalytic activity of the nanocomposites was evaluated through the degradation of rhodamine B (RhB) dye under visible white light irradiation. Among them, heterostructure 10.0 wt% Ag
3VO
4/Bi
2MoO
6 nanocomposites exhibited the highest photocatalytic activity up to 56.26% for the degradation of RhB dye under visible white light within 240 min.
View full abstract