Morphology,mechanical, and dielectric breakdown properties of PBT/PET/TPE,PBT/PET/PA66, PBT/PET/LMPE,and PBT/PET/TiO2 blends

The morphology and thermal behavior of tertiary blends of poly(butylene terephthalate) [PBT]/poly(ethylene terephthalate) [PET] alloy resin (Alloy)/thermoplastic elastomer (TPE), Alloy/nylon 66 (PA66), Alloy/low molecular weight polyester (LMPE), and Alloy/titanium dioxide (TiO₂) have been investigated by scanning electron microscopy, differential scanning calorimetry, and thermogravimetry (TG). In case of TPE and LMPE containing blends did not show any morphological change compared with Alloy whereas for PA66 containing blends, the size of the dispersed phase increased with the increase the PA66 contents. The crystallization peak of Alloy/TPE blends became undetectable with an increasing TPE content. In contrast, the crystallization temperature (T_c1) of Alloy/PA66, Alloy/LMPE, Alloy/TiO₂ blends increased significantly as the PA66, LMPE, and TiO₂ content increases. TG traces show a significant shift of the weight loss towards higher temperature for Alloy/TiO₂ blend whereas Alloy/TPE, Alloy/PA66 and Alloy/LMPE blends slightly decreases in thermal stability than Alloy. To investigate the applicability for insulation material, the prepared blend samples were extruded an electric wire and the breakdown voltage (BDV) of wires was investigated. The melt flow rate of Alloy increased as the amount of TPE increased, and a contrary trend was found when the increase of the amount of TiO₂. The dielectric breakdown test applies a voltage that is greater than the product's rated operating voltage for a specific period of time during which dielectric breakdown must not occur. The BDV of Alloy/TPE and Alloy/PA66 blends is higher than other blends before and after thermal aging 225°C for 30 min. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Thermochemistry of Charge-Coupled Substitutions in Silicate Glasses: The Systems Ml/nn+ AlO2-SiO2 (M = Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Pb)

Enthalpies of solution of framework aluminosilicate glasses x M_{l/ n} ^{n +} AlO₂-(1- x )SiO₂ (M = Cs, Rb, K, Na, Li, Ba, Pb, Sr, Ca, Mg) in molten 2PbO.B₂O₃ near 973 K were measured. The sequence above represents increasing ability of the nonframework cation M to bond to the bridging oxygen. In that sequence, the enthalpy of the substitution Si⁴⁺→+ Al³⁺+ 1/ n M ^{n +} in the glass becomes less exothermic, the enthalpy of vitrification increases, and the tendency toward glass-glass immiscibility becomes more pronounced. These parameters correlate smoothly with the ionic potential, z/r , of the substituting cation.     

Microwave Dielectric Properties of Sr(B'1/2Nb1/2)O3 [B'=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Er, Yb, and In] Ceramics

Sr(B'_1/2Nb_1/2)O₃ [B'=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Er, Yb, and In] ceramics were prepared by the conventional solid-state ceramic route. The crystal structure and microstructure of the ceramics were characterized by X-ray diffraction and scanning electron microscopic methods, and the dielectric properties were measured in the microwave range. Addition of a small amount of CeO₂ as a sintering aid improved the densification and dielectric properties of the ceramics. The effects of cation substitution and glass addition on the microwave dielectric properties of the ceramics were also investigated. Glass addition resulted in the lowering of the processing temperature of the materials without much affecting the dielectric properties, whereas cation substitution resulted in the variation of the temperature coefficient of resonant frequencies. A correlation of dielectric properties with the tolerance factor and ionic radii of B'-site elements of the ceramics has been observed.     

Crystalline Solution in the System MgO-Mg,SiO4,-MgAl2,O4,

Crystalline solubility relations in the system MgO-Mg₂SiO₄MgAl₂O₄ (periclase-forsterite-spinel) were studied using coprecipitated gels as starting materials. The substitution 2Al = Mg + Si was investigated along the join Mg₂SiO₄-Mg-Al₂O₄,. At 1720°C the maximum crystalline solution in forsterite is about 0.5 mole % MgAI₂O₄, and in spinel it is slightly more than 5.0 mole % Mg₂SiO₄. The solubility of MgO in forsterite was 0.5 mole % at 1860°C, whereas more than 11 mole % Mg₂SiO₄ can be dissolved in the periclase structure at this temperature. Ternary crystalline solution exists in the periclase structure to a composition of Mg_0.853Al_0.063Si_0.026O at 1710°C.     

Dense Perovskite, La1-xA'xFe1-yCoyO3-δ (A'= Ba, Sr, Ca), Membrane Synthesis, Applications, and Characterization

La_{1- x} A' _x Fe_0.8Co_0.2O_3-δ (A'= Ca, Sr, Ba) perovskite powders were synthesized to attain the desired properties of high O₂ flux and stability under reducing conditions. Steady-state oxygen permeation rates for La_{1- x} A' _x Fe_0.8-Co_0.2O_3-δ perovskite membranes in nonreacting experiments with air on one side and helium on the other side of the membrane were in the order A' _x = Ba_0.8 > Ba_0.6 > Ca_0.6 > Sr_0.6. Partial oxidation of methane to syngas (CO + H₂) was performed in a dense La_0.2Ba_0.8Fe_0.8Co_0.2O_3-δ membrane reactor at 850°C in which oxygen was separated from air and simultaneously fed into the methane stream. The reducing atmosphere affected the membrane reaction-side surface while barium enrichment occurred on the air-side surface. Oxygen continuously transported from the air side appeared to stabilize the membrane interior, and the reactor was operated for up to 850 h.     

Phase Equilibria in the Systems NiO-Cr2,O3,-O2, MgO-Cr2O3−O2, and CdO-Cr2,O3,-O2, at High Oxygen Pressures

Phase equilibria were determined for the systems NiO-Cr₂O₃−O₂, MgO-Cr₂O₃,-O₂, and CdO-Cr₂O₃−O₂ from 450° to above 850° C and at oxygen pressures of from 2 to 3500 atm. Only two intermediate phases were found in the nickel system: NiCrO., (CrVO₄ structure) and the spinel NiCr₂O₄. The magnesium and cadmium systems are similar in that they have three analogous phases: the low-temperature α-MgCrO₄ and α-CdCrO₄ (both with the CrVO₄ structure), the high-temperature β-MgCrO₄ and β-CdCrO₄ (both with the α-MnMoO₄ structure), and the spinels MgCr₂O₄ and CdCr₂O₄. The cadmium system contains an additional phase, Cd₂CrO₅, which is primitive monoclinic.     

Wilson parameters for the system H2, N2, CO,CO2, CH4, H2S,CH3OH,and H2O

Parameters for the Wilson equation have been determined for 24 of the 28 binary pairs in the system: H₂, N₂, CO, CO₂, CH₄, H₂S, CH₃OH, and H₂O. The data for eleven pairs were fit using the symmetric convention, with the remaining pairs satisfying the unsymmetric convention. Coefficients for the missing pairs could be estimated from Henry's Law constants. References have been included for the heat capacities of liquid methanol and carbon dioxide. Heats of mixing were also found in the literature. This information, plus readily available gas heat capacities, provides sufficient information to calculate multicomponent material and energy balances for the columns used in the separation of H₂S and CO₂ by cold methanol absorption.     

The Effect of Dopants on the Dielectric Properties of Ba(B'1/2Ta1/2)O3 (B'=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Yb, and In) Microwave Ceramics

Low-loss dielectric ceramics based on Ba(B'_1/2Ta_1/2)O₃ (B'=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Yb, and In) complex perovskites have been prepared by the solid-state ceramic route. The dielectric properties (ɛ_r, Q _u, and τ_f) of the ceramics have been measured in the frequency range 4–6 GHz by the resonance method. The resonators have a relatively high dielectric constant and high quality factor. Most of the compounds have a low coefficient of temperature variation of the resonant frequencies. The microwave dielectric properties have been improved by the addition of dopants and by solid solution formation. The solid solution Ba[(Y_{1− x} Pr _x )_1/2Ta_1/2]O₃ has x =0.15, with ɛ_r=33.2, Q _u× f =51,500 GHz, and τ_f≈0. The microwave dielectric properties of Ba(B'_1/2Ta_1/2)O₃ ceramics are found to depend on the tolerance factor ( t ), ionic radius, and ionization energy.     

Novel synthesis of Poly(N1’,N3’- diacryloylmalonohydrazide): characterization, complexation, ion selectivity, thermogravimetry, swelling, morphology and biological activity

N ^1’ ,N ^3’ - Diacryloylmalonohydrazide was obtained upon treating malonohydrazide with acryloyl chloride. The obtained acrlyoyl derivative was transferred to the corresponding polymer through treating with AIBN at 75°C. The obtained products were characterized using elemental analysis and spectral data. Ion selectivity, complex formation, TGA, EDS and morphology were studied.     

Thermal Expansion of Al2O3, BeO, MgO, B4C, SiC, and TiC Above 1000°C.

Thermal-expansion data on Al₂O₃, BeO, MgO, B₄C, SiC, and TiC were obtained to the temperatures where permanent deformation begins, due to sintering or other causes. The thermal expansion for these materials was found to be approximately linear over the measured temperature range. But as a linear extrapolation to room temperature was not possible, the coefficient of thermal expansion is not a constant over this temperature range. The results are compared with the latest published data for each material. The average coefficients of linear thermal expansion are given as follows:

All BeO specimens which were heated to above 2050°C. had a very large expansion. Visual examination of the cooled specimens revealed that they had bent and cracked, the physical dimensions had enlarged, and the color had changed to a bright milky white. A brief discussion of the probable reasons for these changes is given. In the attempt to extend the expansion measurements, the melting point of BeO was obtained. A specimen of hot-pressed BeO melted at 2450°± 30°C., whereas a slip-cast BeO specimen melted at 2470°± 20° C.     

Sintering, Microstructure, Hardness, and Fracture Toughness Behavior of Y2O3-CeO2-ZrO2

A wet-chemical approach is applied to derive fine powders with compositions 11 mol% CeO₂-ZrO₂, 1 mol% YO_1.5-10 mol% CeO₂-ZrO₂, 12 mol% CeO₂-ZrO₂, and 2 mol% YO_1.5-10 mol% CeO₂-ZrO₂ by the coprecipitation method. The characteristics of the as-derived powders are evaluated through thermal analysis and electron microscopy. The sintering behavior of the calcined powders is carried out at 1400° and 1500°C for 1 to 10 h. Sintered density higher than 98% of theoretical is achieved for sintering at 1400°C for several hours. The as-sintered density dependence on the sintering condition is related to the extent of tetragonal-to-monoclinic phase transformation as well as the associated microcracks. Partial substitution by Y₂O₃ in CeO₂-ZrO₂ results in reduced grain size and tends to stabilize the tetragonal structure. Y₂O₃ is more effective than CeO₂ with respect to the grain size refinement and tetragonal stability. In addition, Y₂O₃ substitution in CeO₂-ZrO₂ increases the hardness, while it decreases the fracture toughness.     

Phase Stability of Ln2BaCuO5 (Ln = Dy, Er, Eu, Gd, Ho, Sm, Yb)

Phase stability of a series of Ln₂BaCuO₅ (Ln=Dy, Er, Eu, Gd, Ho, Sm, Yb) has been studied as a function of oxygen partial pressure and temperature by X-ray diffraction, thermal gravimetric, and differential thermal analyses. Above the critical temperature T_d, phase decomposition with a decrease in sample weight took place. In the case of Ln=Dy, Er, Ho, and Yb, the Ln₂BaCuO₅ was decomposed into Ln₂O₃BaCuO₃ and BaCuO₂. The critical temperature T_d (K) was changed depending heavily on the oxygen partial pressure P (Pa) and the effective ionic radius R (0.1-nm unit) of the Ln atom which was sevenfold coordinated by oxygen atoms. The observed T_d values for all of the systems, together with those of Y₂BaCuO₅ reported previously, closely followed the relation T_d=−17493R²+ 34582R − 15489 + 239.47 In P with a reliability index R_p=0.5%. [Key words: superconductors, barium, phases, X-ray diffraction, differential thermal analysis.]     

Studies of Silica-Structure Phases: I, GaPO4, GaAsO4, and GaSbO4

In the course of work on all compositions which would probably yield silica-structure phases, a detailed study was made of the A³⁺B⁵⁺O₄-type compounds with gallium as the trivalent element. Two forms of GaPO₄ exist corresponding to quartz and cristobalite; the quartz form has a thermal expansion of the low-quartz type and no stable α-β transition is found in this phase. It inverts stably to the cristobalite form at 933°± 4°C. The cristobalite form melts at 1670°C. and the liquid cannot be made to form a glass. The cristobalite form also has a metastable displacive transition at 616°± 2°C. GaAsO₄ exists only in a form corresponding to the lowquartz structure. It disproportionates into Ga₂O₃ and As₂O₅ at about 1000°C. GaSbO₄ could only be prepared in one form corresponding to the rutile structure. The influence of such phases on SiO₂ was determined by studying a few mixtures in the system SiO₂-GaPO₄. The SiO₂ end member appears to admit about 25% GaPO₄ into solid solution in the cristobalite phase at the highest temperature. Even under hydrothennal conditions, however, equilibrium cannot be easily attained at the lower temperatures in a few hundred hours. The results are presented in a not-impossible diagram for the system GaPO₄-SiO₂.     

Lattice Parameters, Ionic Conductivities, and Solubility Limits in Fluorite-Structure MO2 Oxide [M = Hf4+, Zr4+, Ce4+, Th4+, U4+] Solid Solutions

Changes in the lattice parameters of fluorite type MO₂ oxides (M = Hf⁴⁺, Zr⁴⁺, Ce⁴⁺, Th⁴⁺, U⁴⁺) due to the formation of solid solutions can be predicted by proposed empirical equations. The equations show the generalized relationship between dopant size and ionic conductivity in the binary systems of these oxides, illustrating that the smaller the difference between the dopant ionic radius and the critical dopant radius, the higher the conductivity. The solubility limit of the same periodic group elements in fluorite-structure MO₂ oxides decreaes linearly with the square of Vegard's slope for each solute as determined from the proposed equations.     

Nonlinear Optical Properties of TeO2-Based Glasses: MOx-TeO2 (M = Sc, Ti, V, Nb, Mo, Ta, and W) Binary Glasses

The third-order nonlinear optical susceptibilities, X⁽³⁾, of TeO₂-based glasses containing transition metal oxides (M = Sc₂O₃, TiO₂, V₂O₅, Nb₂O₅, MoO₃, Ta₂O₅, and WO₃) glasses have been measured by the third harmonic generation (THG) method in order to investigate the effect of the empty d-orbital contributions to the third-order nonlinear optical susceptibilities. It is found that the addition of TiO₂, Nb₂O₅, and WO₃ to TeO₂ glass increases the X⁽³⁾ value as well as the refractive index, while others decrease both of them. The positive effect of the TiO₂, Nb₂O₅, or WO₃, on the X⁽³⁾ of TeO₂ glass was interpreted in terms of the cationic empty d-orbital contribution. There is an almost linear relation between the X⁽³⁾ and the term (n²_ω+ 2)³.(n²_ω -1).E_d/E²₀ containing three measurable parameters only, irrespective of the kinds of MO, which was derived based on the bond orbital theory developed by M. E. Lines. The largest X⁽³⁾ value obtained is 1.69 × 10⁻¹² esu for 30NbO_2.5.70TeO₂ glass, about 60 times larger than that of pure fused silica glass.     

Processing and Dielectric Properties of Sillenite Compounds Bi12MO20−δ (M = Si, Ge, Ti, Pb, Mn, B1/2P1/2)

Six sillenite compounds Bi₁₂MO_20-δ (M = Si, Ge, Ti, Pb, Mn, B_1/2P_1/2) were synthesized, and the resulting single-phase powders were then sintered to obtain ∼97% dense ceramics. An analysis of their microwave dielectric properties, performed at ∼5.5 GHz, revealed a permittivity of ∼40 for all six compounds. The temperature coefficient of resonant frequency was the lowest for the Pb analogue (−84 ppm/K) and was found to increase with increasing ionic radius of the B-site ion to a value of −20 ppm/K for the Bi₁₂SiO₂₀ and Bi₁₂(B_1/2P_1/2)O₂₀ compounds. The Q × f value is a maximum for Bi₁₂SiO₂₀ and Bi₁₂GeO₂₀ with 8100 and 7800 GHz, respectively. The dielectric properties of the sillenites have been correlated with the structure of the oxygen network of the sillenite crystal lattice. As a result of its low sintering temperature (850°C), chemical compatibility with silver, low dielectric losses, and temperature-stable permittivity, the Bi₁₂SiO₂₀ compound is a suitable material for applications in low-temperature cofiring ceramic (LTCC) technology.     

Structural,vibrational, optical,magnetic and dielectric properties of Bi1−xBaxFeO3 nanoparticles

Bi_1−xBa_xFeO₃ (x=0.05, 0.10 and 0.15) nanoparticles were synthesized by the sol–gel method. X-ray diffraction and Raman spectroscopy results showed the presence of distorted rhombohedral structure of Bi_1−xBa_xFeO₃ nanoparticles. Rietveld refinement and Williamson–Hall plot of the x-ray diffraction patterns showed the increase in lattice parameters, unit cell volume and the particle size. Infrared spectroscopy and Raman analysis revealed the shifting of phonon modes towards the higher wavenumber side with increasing Ba concentration. These samples exhibited the optical band gap in the visible region (2.47–2.02 eV) indicating their ability to absorb visible light. Magnetic measurement showed room temperature ferromagnetic behavior, which may be attributed to the antiferromagnetic core and the ferromagnetic surface of the nanoparticles, together with the structural distortion caused by Ba substitution. The magnetoelectric coupling was evidenced by the observation of the dielectric anomaly in the dielectric constant and the dielectric loss near antiferromagnetic Neel temperature in all the samples.