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Nickel oxide yttria-stabilized zirconia (NiO–YSZ) anode materials were synthesized via hydrolysis of the corresponding chloride solutions with NH3, NH3+NaOH, and NaOH as precipitation agents. Powder properties such as crystallite size, morphology, and sintering behavior of the final NiO–YSZ materials were also studied. The mechanism of the formation of NiO–YSZ was established for the different co-precipitation techniques by the direct observation of Ni(NH3)n+2 complexes, Ni(OH)2 and NiO at different stages of the synthesis process. A direct relationship between the precipitation agent, the order of calcination from dry sample to final product, the final composition, the crystallite sizes and particle sizes of NiO, and the sinterability of the final products was established. A comparison of the powder and individual component properties indicate that the choice of precipitation agent greatly influences the final characteristics. Ni/YSZ materials prepared by NH3+NaOH precipitation offer higher Ni dispersion and nanocrystallinity of both the Ni and YSZ phases. The conductivity of both prepared materials compares well with mixed-oxide materials of higher Ni content.

Sodium borosilicate porous glasses arising from spinodal phase separation are promising functional materials for separation membranes, enzyme and catalyst supports, and photonic materials. The present paper studied the effect of the additive of ZrO2 on the spinodal phase separation and pore distribution of the sodium borosilicate glasses using 11B nuclear magnetic resonance spectrum, 29Si nuclear magnetic resonance spectrum, mercury measurement, and nitrogen adsorption techniques. The experimental results showed that ZrO2 inhibited both the initiation process in early stage and the coarsening process in later stage of the spinodal phase separation. The pore volume was found to decrease slightly with the addition of ZrO2 at the beginning. However, when ZrO2 content > 7 mass%, the pore volume decreases dramatically with further addition of ZrO2. 65% of the pore volume in the sample without addition of ZrO2 will be lost when the addition amount of ZrO2 increases from 0 to 10 mass%. The inhibition effect on t...

Nuclear magnetic resonance (NMR) spectra have been used to investigate the spinodal phase separation of sodium borosilicate glasses in the early stage, in which the phase separation is induced by r...

The 11B nuclear magnetic resonance (NMR) spectra, together with X-ray diffraction (XRD) and scanning electron microscopy (SEM), have been used to investigate the phase separation in 15Na 2 O–85B 2 O 3 binary glass. Based on the present investigation we suggest that the phase equilibrium in sodium borate glasses is controlled by the rate competition of the nucleation and crystal growth between two immiscible phases rather than those being proposed by the conventional phase diagram. The experimental results show that the sodium-rich phase, after being heat-treated at 500°C, was not Na 2 O.4B 2 O 3 , as indicated by phase diagram. The over-coordination of oxygen atoms in the sodium-rich phase rendered difficulties in the crystallization of the sodium-rich phase with less than 75 mol % sodium oxide. Therefore, the high growth rate of the boron-rich phase can force the residual glass toward much higher concentrations of sodium oxide. According to the NMR measurements, it was found that, after reaching equilibrium, the 15Na 2 O–85B 2 O 3 glass separated into Na 2 O.9B 2 O 3 and 3Na 2 O.B 2 O 3 .

The kinetics of the phase separation in 15Na2O-85B2O3 binary glasses was investigated using 11B nuclear-magnetic-resonance (NMR) spectra, X-ray diffraction (XRD) and scanning electron microscopy (SEM) observation. It was found that the equilibrium of the phase separation took long time due to the growth of a boron-rich phase and the composition fluctuation in Na-rich phase. Although the XRD results showed that the development of the boron-rich phase was through nucleation and growth, the NMR spectra indicated that the sodium-rich phase always occurred as amorphous glasses with fluctuation in composition during the phase separation. This may result from that the over-coordination of oxygen atoms in the sodium-rich phase, which renders difficulties in the crystallization of the sodium-rich phase with less than 75 mol% sodium oxides. It was found that, at 500°C, the 15Na2O-85B2O3 glasses was finally separated into Na2O·9B2O3 and 3Na2O·B2O3 rather than those being proposed by the conventional phase diagram.

The effect of Al2O3 on the structure change and the phase separation in Na2O-B2O3-SiO2 glass was investigated using 11B nuclear magnetic resonance (NMR), 29Si MAS NMR, and 27Al MAS NMR together with infrared absorption spectroscopy and field emission scanning electron microscopy (FE-SEM). The results show that the structure change from the introduction of Al2O3 contributes greatly to the inhibition of phase separation. First, the introduction of Al2O3 imparts an ionic character to the boron-oxygen network, resulting in the formation of B-O-Al-O-Si bonds and thus increases the compatibility of the silicon network with the boron-oxygen network. Second, the addition of Al2O3 causes the sodium ion to transfer from the boron-oxygen network to AlO4 tetradedra, changing a number of four-coordinated borons into three-coordinated borons. As the bond energy of the four-coordinated boron is weaker than that of the three-coordinated boron, the -B-O-Si- bond with the four-coordinated boron in Na2O-B2O3-SiO2 glasses is easily broken and results in severe phase separation during heat treatment. However, the -B-O-Al- bond with the three-coordinated boron formed in Na2O-B2O3-SiO2-Al2O3 glasses is difficult to be broken due to the high bond energy. In addition, the silicon network in Na2O-B2O3-SiO2-Al2O3 glasses is also strengthened by the addition of Al2O3, which prevents [BO] groups from further aggregation. As a result, the tendency of the glass towards phase separation is greatly suppressed in the Na2O-B2O3-SiO2-Al2O3 system.

The distribution of pores, based on spinodal phase separation in sodium borosilicate glasses that were rapidly quenched at different cooling rates, was investigated. The N2 adsorption−desorption behavior of samples shows that the pore is of the micropore type with pore size

The kinetics of phase separation in 15Na 2 O.85B 2 O 3 binary glass was investigated using 11 B nuclear-magnetic-resonance (NMR) spectra together with X-ray diffraction (XRD) and scanning electron microscopy (SEM). The experimental results showed that the product of sodium-rich phase after heat-treated at 500°C was not Na 2 O.4B 2 O 3 as suggested by previous phase diagram. It was found that the high growth rate of boron-rich phase can force residual glass to much higher concentrations of sodium oxide. After reaching equilibrium, a 15Na 2 O.85B 2 O 3 glass was separated into Na 2 O.9B 2 O 3 and 3Na 2 O.B 2 O 3 according to NMR measurement.

An infiltration technique for fabricating B 4 C-matrix composites has been investigated. B 4 C-Al composites prepared by infiltration are well densified and have shrinkage of about 0.15%, but the fracture toughness is low. The addition of AlB 12 has a strong effect in increasing the toughness of B 4 C-matrix composites. The high fracture toughness of B 4 C-AlB 12 -Al composites is caused by residual Al and by the behaviour of metastable stress-induced phase transition of AlB 12 fromβ-phase to α-phase. The highest hardness (1870 kg/mm 2 ) and flexural strength (457 MPa) are obtained in B 4 C-matrix sample with 8% AlB 12 .

Heterogeneous materials composed of conducting YBa 2 Cu 3 O 7−x particles randomly dispersed inside an insulating polyethylene matrix were prepared. The resistivity of the materials was measured as a function of temperature between 293 K and 410 K. A large positive temperature coefficient (PTC) of resistance was observed near 404 K, and was a maximum of 9 orders of magnitude for the specimen containing 30 vol.% YBa 2 Cu 3 O 7−x . The mechanism of the PTC effect in the materials is related to the percolation behaviour of the YBa 2 Cu 3 O 7−x -polyethylene composites and the thermal expansion of the polyethylene matrix.

An infiltration technique for fabricating B 4 C-matrix composites has been investigated. B 4 C-Al composites prepared by infiltration are well densified and have shrinkage of about 0.15%, but the fracture toughness is low. The addition of AlB 12 has a strong effect in increasing the toughness of B 4 C-matrix composites. The high fracture toughness of B 4 C-AlB 12 -Al composites is caused by residual Al and by the behaviour of metastable stress-induced phase transition of AlB 12 fromβ-phase to α-phase. The highest hardness (1870 kg/mm 2 ) and flexural strength (457 MPa) are obtained in B 4 C-matrix sample with 8% AlB 12 .

The characterization of pores arising from spinodal phase separation in quenched sodium borosilicate glasses is investigated. Theory predicts that the wavelength of the initial stage for spinodal phase separation on cooling is ca. 5–10 nm, whereas after acid leaching, the size of the pore based on so-called spinodal decomposition is much smaller with pores formed in quenched sodium borosilicate glass after leaching being of micropore type with radii of

Open single-walled carbon nanotubes (SWNTs) are attractive as potential storage media for hydrogen gas. The present paper investigates the micropore structure of HiPco SWNTs samples, as studied by nitrogen and argon adsorption technique at low pressures. The proportion of open SWNT is estimated with the Horvath−Kawazoe method. The results show that as-prepared samples may contain as much as 40% open SWNTs, whereas the oxidative purification process reduces this amount significantly. X-ray diffraction and Raman spectroscopy show that the Horvath−Kawazoe method is reliable for estimating the diameter of open SWNTs. In addition, the Horvath−Kawazoe method appears to be sensitive to species adsorbed in the outer grooves.