The IR spectra of humins formed during the acid-catalyzed conversion of glucose, fructose, and 5-hydroxymethylfurfuraldehyde were compared. The spectra are quite similar except for three groups of features that can be attributed to furan rings and carbonyl groups conjugated with carbon–carbon double bonds. IR spectroscopy further revealed that benzyl groups could be added to the humins as they formed or in a separate aldol addition/condensation reaction after they had been recovered. The IR spectra are consistent with a model where each of the three reactants must first be converted to 2,5-dioxo-6-hydroxyhexanal (DHH) before humins can form via subsequent aldol addition and condensation. The differences in the IR spectral features can then be explained by variations in the concentrations of other aldehydes and ketones that can react with DHH.

Comparison of Structural Features of Humins Formed Catalytically from Glucose, Fructose, and 5-Hydroxymethylfurfuraldehyde

This letter reports a high energy density piezoelectric material in the system given as: Pb[(Zr0.52Ti0.48)O3]1−x[(Zn1∕3Nb2∕3)O3]x+yMnCO3, where x=0.1 and y varies from 0.5to0.9wt%. A piezoelectric material with high energy density is characterized by a high product of piezoelectric voltage constant (g) and piezoelectric strain constant (d). The condition for obtaining large magnitude of g constant was derived to be as ∣d∣=en, where e is the permittivity of the material and n is constant having lower bound of 0.5. It was found that for all practical polycrystalline piezoelectric ceramic materials the magnitude of n lies in the range of 1.1–1.30 and as the magnitude of n decreases towards unity a giant enhancement in the magnitude of g was obtained. A two step sintering process was developed to optimize a polycrystalline ceramic composition with low magnitude of n. For the optimized composition the value of g33 and d33 was found to be 55.56×10−3m2∕C and 291×10−12C∕N, respectively, yielding the magnitude pro...

Realization of high-energy density polycrystalline piezoelectric ceramics

Five Ba(Co 1/3 Nb 2/3 )O 3 samples sintered at different temperatures (form 1350 to 1550 °C), one Ba(Mg 1/3 Ta 2/3 )O 3 and a Ba(Mg 1/3 Nb 2/3 )O 3 sample were examined by Raman scattering to reveal the correlation of the 1:2 ordered perovskite structure with the microwave properties, such as dielectric constant and Q factors. The Ba(Co 1/3 Nb 2/3 )O 3 sample sintered at 1400 °C, which possesses the highest microwave Q value and the lowest dielectric constant among five Ba(Co 1/3 Nb 2/3 )O 3 samples, has the narrowest width and the highest frequency of the stretch mode of oxygen octahedron (i.e. A 1g (O) near 800 cm −1 ). We found that the dielectric constant is strongly correlated with the Raman shift of A 1g (O) stretch modes, and the width of A 1g (O) stretch mode reflects the quality factor Q  ×  f value in the 1:2 ordered perovskite materials. This concludes that the oxygen octahedron play an important role of the material's microwave performance. Based on the results of Q  ×  f values and the lineshapes of A 1g (O) stretch mode, we found that the propagation of microwave energy in Ba(Mg 1/3 Ta 2/3 )O 3 and Ba(Mg 1/3 Nb 2/3 )O 3 shows weak damping behavior, however, Ba(Co 1/3 Nb 2/3 )O 3 samples sintered at different temperature exhibit heavily damped behavior.

Microwave properties of Ba(Mg1/3Ta2/3)O3, Ba(Mg1/3Nb2/3)O3 and Ba(Co1/3Nb2/3)O3 ceramics revealed by Raman scattering

0.8 Pb(Zr0.52Ti0.48)O3–0.2 Pb(Zn1/3Nb2/3)O3 (PZT–PZN) and 2 mol% Mn-doped PZT–PZN ceramics were investigated to deterministically identify the presence and effect of the secondary phase in controlling electrical properties. On the basis of the X-ray diffraction and energy dispersive spectroscopy analysis, we show that secondary phase in Mn-doped PZT–PZN is not MnO2 precipitate, but it is related to the formation of ZnO. This result was found to be consistent with the grain growth observed in the Mn-doped sintered ceramics and changes in ferroelectric behavior. We propose that Mn3+ substitution on Ti and Zr site induces hardening effect, whereas Mn2+ substitution on Zn-site stabilizes the perovskite phase in synthesis of PZT–PZN.

Identification and Effect of Secondary Phase in MnO2-Doped 0.8Pb(Zr0.52Ti0.48)O3–0.2Pb(Zn1/3Nb2/3)O3 Piezoelectric Ceramics

Structure/property regulation is widely investigated for providing theoretical foundations and guidance for designing microwave dielectric ceramics. P–V–L bond theory targets the provision of detailed structural parameters of crystals and fundamental chemical bond characteristics, such as bond ionicity, bond covalency and bond susceptibility. In this review, the concept of P–V–L bond theory, the binary bonding formula theory of complex polycrystalline and the usage of P–V–L bond theory regarding the structural effects on dielectric properties in various crystal structures are introduced. And the bond traits provided via P–V–L bond theory in several ion-doping modification systems are generalized with structural evolution and dielectric properties. Furthermore, conjectures about the development and application directions of P–V–L bond theory in the study of structure/properties of microwave dielectric ceramics are put forward.

Usage of P–V–L bond theory in studying the structural/property regulation of microwave dielectric ceramics: a review

Ba(Co1/3Nb2/3)O3(BCN) has a 1:2 ordered hexagonal structure. A large amount of the liquid phase, which contains high concentrations of Ba and Nb ions was found in the BCN ceramics. Q-values of BCN increased with increasing sintering temperature; however, it significantly decreased when the sintering temperature exceeded 1400 °C. The presence of a large amount of liquid phase could be responsible for the decrease of the Q-value. For (1−x)Ba(Co1/3Nb2/3)O3–xBa(Zn1/3Nb2/3)O3 [(1−x)BCN–xBZN] ceramics, the 1:2 ordered hexagonal structure was observed in the specimens with x⩽0.3 and the BaNb6O16 second phase was found in the specimens with x⩾0.6. Grain growth, which is related to the BaNb6O16 second phase occurred in the specimens with x⩾0.5. In this work, the excellent microwave dielectric properties of τf=0.0 ppm/°C, er=34.5 and Q×f=97,000 GHz were obtained for the 0.7BCN–0.3BZN ceramics sintered at 1400 °C for 20 h.

Effects of microstructure on the microwave dielectric properties of Ba(Co1/3Nb2/3)O3 and (1−x)Ba(Co1/3Nb2/3)O3–xBa(Zn1/3Nb2/3)O3 ceramics

This letter reports a Pb(Zr05Ti05)O3 (PZT) based composition, which provides high piezoelectric and electromechanical properties The general form of the composition is Pb(Zn1/3Nb2/3)x(B1/3I′B2/3II′)y(Zr05Ti05)1−x−yO3+05 wt % MnO2 (x+y=02) Four compositions corresponding to the earlier formulation were studied For the composition corresponding to y=0, the radial mode coupling factor (kp) of 058, longitudinal mode piezoelectric constant (d33) of 277 pC/N, dielectric constant (e33/e0) of 946, and mechanical quality factor (Qm) of 1402 are obtained X-ray diffraction, dielectric, and polarization-electric field measurements were done to investigate the origin for this high performance It was found that high soft properties are obtained due to the shifting of PZT composition towards morphotropic phase boundary and high hard properties are obtained due to the generation of dipolar defects which pin the polarization

Induction of combinatory characteristics by relaxor modification of Pb(Zr0.5Ti0.5)O3

The microstructure and microwave dielectric properties of (1-x)Ba(Co1/3Nb2/3)O3–xBa(Zn1/3Nb2/3)O3 [(1-x)BCN–xBZN] ceramics with 0.0≤x≤1.0 were investigated. When the sintering temperature was 1400°C, a homogeneous phase with a 1:2 ordered structure was found in the specimens with x≤0.3 but for the specimens with x≥0.6, a disordered structure and BaNb6O16 second phase were found. The grain growth related to the BaNb6O16 second phase occurred in the specimens with x≥0.5. The temperature coefficient of the resonant frequency (τf) increased with increasing x, and the specimens with 0.3≤x≤0.4 have zero τf. Dielectric constant (er) increased with the increase in x and was about 34.5 when x=0.3. For the specimens with x≤0.3, the Q×f value was high but decreased as x exceeded 0.3. The maximum Q×f value, 97,000 GHz, was obtained for 0.7BCN–0.3BZN ceramics sintered at 1400°C for 20 h.

Microstructure and Microwave Dielectric Properties of (1-x)Ba(Co1/3Nb2/3)O3–xBa(Zn1/3Nb2/3)O3 Ceramics

A glass-like carbon was fabricated using furan resin. The influence of heat treatment temperature during fabrication process on the chemical and micro-structural changes was studied by various analytical and spectroscopic methods including TGA, FT-IR, CHN, TEM and XRD. The chemical resistance properties of the fabricated glasslike carbon were also investigated. It has been found that the heat-treated samples at higher temperature up to 2600 °C in N2 atmosphere had little weight loss, small amounts of functional groups, and high carbon content. The fabricated glass-like carbons upon heat treatment at 2600 °C showed an amorphous stage without any grain growth and/or reconstruction of structure. The glass-like carbon had much better chemical resistance than the artificial graphite, and exhibited a high chemical resistance due to its low surface areas, minimum impurities, and low graphite crystallites.

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Chemical and Micro-Structural Changes in Glass-Like Carbon during High Temperature Heat Treatment

The crystal structure of (Ba1−x
La
 x
 )[Mg(1 + x)/3Nb(2−x)/3]O3 (BLMN) ceramics with 0 ≤ x ≤ 1 was investigated using X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). When the La content, x, was above 0.1, the 1:2 ordered hexagonal structure found in Ba(Mg1/3Nb2/3)O3 (BMN) was transformed into the 1:1 ordered cubic structure. The 1:1 ordered cubic structure was maintained up to x = 0.7. When x exceeded 0.7, however, BLMN exhibited a 1:1 ordered monoclinic structure, rather than a 1:1 ordered cubic structure. La(Mg2/3Nb1/3)O3 (LMN) has a 1:1 ordered monoclinic P21/n structure with a = 5.6004 A, b = 5.6414 A, c = 7.9346 A, and β = 89.9819°. The monoclinic LMN has the in-phase and the anti-phase tilt of oxygen octahedra. The anti-parallel shift of A-site cations was also found in LMN.

Sahn Nahm

Papers

Effects of microstructure on the microwave dielectric properties of Ba(Co1/3Nb2/3)O3 and (1−x)Ba(Co1/3Nb2/3)O3–xBa(Zn1/3Nb2/3)O3 ceramics

Induction of combinatory characteristics by relaxor modification of Pb(Zr0.5Ti0.5)O3

Microstructure and Microwave Dielectric Properties of (1-x)Ba(Co1/3Nb2/3)O3–xBa(Zn1/3Nb2/3)O3 Ceramics

Chemical and Micro-Structural Changes in Glass-Like Carbon during High Temperature Heat Treatment

Crystal structure of (Ba1−xLax) [Mg(1 + x)/3Nb(2−x)/3]O3 ceramics