Property of resistance to fragmentation of injectable calcium-phosphate cement (CPC) pastes was evaluated. CPC pastes are widely used as bone fillers due to their biocompatibility and osteoconductivity. However, the potential for fractures due to the formation of voids and cracks in the CPC, called “fragmentation,” reduces the biomechanical strength of CPCs. To develop new CPCs that do not exhibit fragmentation, a method for assessing the presence or absence of fragmentation is required. For in vitro evaluation of the fragmentation resistance, the internal structure of cement specimens allowed to stand in pure water or blood was observed using X-ray micro-computed tomography (X-ray µ-CT) method. In the case of cement specimens derived from commercially-available β-tricalcium phosphate powder ball milled and surface modified in 3,000 ppm inositol phosphate solution, no cracks or voids in the internal structure were observed in samples allowed to set in either pure water or blood. For in vivo verification of the fragmentation resistance, the same CPC pastes were implanted into pig thigh muscle and tibiae for 4 and 24 weeks, respectively. The implanted CPC specimens formed a lump without internal voids or cracks. These data showed that the CPC pastes with the fragmentation resistance both in vitro and in vivo and are thus unlikely to generate fractures. Furthermore, the evaluation method using X-ray µ-CT could enables rapid and simple verification of the fragmentation resistance of the injectable CPC pastes. To our knowledge, this is the first report of the use of this method to evaluate resistance to fragmentation of CPC pastes. Furthermore, because of its simplicity and ease of use, the X-ray µ-CT method shows promise as a gold standard.

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Porous alumina with a denser surface layer is fabricated from an alumina/novolac composite body containing hexamethylenetetramine (HMT) that is used as a blowing agent and a curing agent for the novolac resin. A gas blown from HMT leads to the formation of pores up to submillimeter inside the alumina/novolac composite body. On the other hand, the denser surface layer without large pores is formed by the gas released from the surface during blowing. The blowing condition for the alumina/novolac composite body is examined as a function of heat-treatment temperature in order to investigate the formation of the pore and the surface layer. Porous alumina with the denser surface layer is obtained through de-binding and sintering of the body. This paper also describes the microstructure and mechanical strength of the sintered porous alumina, and advantages of the denser surface layer.

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An environmentally friendly tap-hole clay that contains almost no benzo[a]pyrene was developed using resin and pitch as binder. The effects of the pitch addition on the tap-hole clay were investigated through evaluating the physical and chemical properties together with the microstructure, phase compositions and thermal analysis. The plasticity of the tap-hole clay is significantly improved with increasing pitch addition. However, the bulk density of tap-hole clay decreases gradually with increasing pitch content after treatment at different temperatures, while the apparent porosity increases due to the evaporation of pitch components and relatively low solid components. Also, this phenomenon is the main reason for the poor volume stability of tap-hole clay after heat treatment at different temperatures, although mullite formation has negated some of the shrinkage. Mechanical-strength evolution of the tap-hole clay is closely related to the carbonization process of the resin and pitch at high temperatures. Oxidation resistance could be significantly improved with 2 wt % of the pitch, but there is almost no change with much more than 2 wt %. However, the higher pitch content corresponds to better slag resistance. In terms of the comprehensive performance of the tap-hole clay, 4 wt % of the pitch would be better.

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Silver powders are important for the production of silicon solar cells and low-temperature co-fired ceramics. In this study, a silver powder was produced at a rate of 2 kg/min through water atomization with a water pressure of 80 MPa and water flow rate of 220 L/min. Scanning electron microscopy analysis showed that the silver particles produced were aggregated and had various types of morphologies such as spherical, elliptical, and irregular. The volume average particle size and its standard deviation were 8 and 4.1 µm, respectively. Powder X-ray diffraction revealed that the as-prepared silver powder had a single phase with high crystallinity. The oxygen content in the silver powder measured by electron probe micro analysis was 50 ppm. The silver powder was classified to the size of ≤2.5 µm, and the shrinkage of the silver paste was 25.5% at 900°C, comparable to that of the powder obtained by chemical reduction. Electrical measurements revealed that the specific resistivity of the silver paste sintered at 900°C for 60 min was 2.11 × 10⁻⁸ Ω m. The silver paste exhibited lower specific resistivity when the sintering temperature was high and sintering time was long.

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We report the effect of Sr substitution on the structural, electrical, and mechanical properties of Ca₂Al₂SiO₇ (CAS) piezoelectric single crystals for high-temperature pressure sensors. Single crystals of Sr-substituted CAS (Sr-CAS) with a nominal chemical composition of CaSrAl₂SiO₇ were grown by using the Czochralski technique. The single-crystal X-ray structure analysis revealed that Sr atoms were placed in the Ca decahedral sites, which decreased the polyhedral distortion slightly. The piezoelectric modulus d′₃₁ and electrical resistivity of Sr-CAS measured at 23°C were slightly lower than those of CAS, but still sufficient for the satisfactory performance of the produced sensors. The rupture strength of the Sr-CAS crystal was 230 MPa, 1.2 times higher than that of a CAS crystal. The obtained results suggest that Sr-CAS crystals can be candidate materials for high-temperature pressure sensors.

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Cr-doped hexagonal ferrites, with chemical composion Sr_0.35Ca_0.30La_0.35Fe_12.00−xCr_xO₁₉ (where 0.00 ≤ x ≤ 1.05), were synthesized using the traditional ceramic route. An X-ray diffractometer (XRD) and a vibrating sample magnetometer were used to characterize the phase composition and magnetic properties of the magnetic powders, respectively. The XRD data show that when the Cr content (x) ≤ 0.60, non-magnetic phase, α-Fe₂O₃, is obviously observed. When the Cr content (x) ≥ 0.60, the diffraction patterns demonstate that the magnetic powders show the magnetoplumite structure, and only a small trace of α-Fe₂O₃ is observed. The saturation magnetization linearly decreases with the increase of Cr content (x) from 0.00 to 1.05, while the remanent magnetization first increases with Cr content (x) from 0.00 to 0.45, and then keeps constant with Cr content (x) form 0.45 to 0.75, and decreases when Cr content (x) ≥ 0.75. The coercivity initially enhances significantly with the increasing of Cr content (x) until it reaches to the maximum value of 3925 Oe at Cr content (x) = 0.60, and then decreases slowly when Cr content (x) ≥ 0.60.

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In this work, a nitrogen-doping carbon-based catalyst to oxygen reduction reaction (ORR) is fabricated by using ammonia as single nitrogen source. The catalyst is characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The catalytic activity to ORR is tested by electrochemical linear sweep voltammetry. The results show that the cobalt ions are reduced to metallic cobalt by acetylene black at high temperature. The metallic cobalt further facilitates the reaction between ammonia and acetylene black to form pyridinic and pyrollic C-N structures as the active sites of the catalyst to ORR. A better catalyst with an ORR onset potential of 0.69 V (vs. reversible hydrogen electrode) can be obtained at 600°C for 120 min.

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This paper presents a study on coupled deterioration mechanisms, including carbonation and frost attack, on concrete prepared with 0, 50 and 100% by weight coarse recycled concrete aggregates (CRCA) to replace coarse natural aggregate (CNA). Fly ash (FA) was also used as 0, 20 and 40% weight replacements of cement. Carbonation depth, relative dynamic modulus of elasticity (RDME) and residual compressive strength were measured during the tests. Nuclear magnetic resonance analysis was performed on the selected samples to identify pores and cracks formed through coupled deterioration. Results showed that freeze–thaw cycle and carbonation affected each other. On the one hand, carbonation can increase strength and reduce permeability to improve freeze–thaw resistance and form new pores, which accelerate freeze–thaw damage. On the other hand, the depth of carbonated concrete increased as the freeze–thaw deterioration increased; this finding could be due to cracking associated with increased internal deterioration caused by freeze–thaw cycle. In contrast to the findings of the single-factor test, concrete subjected to coupled deterioration by freeze-thaw and carbonation showed lower residual compressive strength and residual RDME but higher carbonation depth.

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Dispersion of AlN precipitates was observed in powder-sintered nitrogen-deficient TiN_1−x–AlN composites at 1400–1600°C. The AlN nano-precipitates presented epitaxial interface with TiN_1−x. The phase development and chemical compositions at the interface of TiN_1−x/AlN diffusion couple indicated that AlN decomposition occurred during sintering, N atoms diffused into TiN_1−x formed stoichiometric TiN, and atoms diffused across TiN gave rise to the precipitate of AlN in TiN_1−x.

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GaN nanowires were synthesized on silicon, nickel nitrate [Ni(NO₃)₂]-dispersed silicon, and a nickel-dispersed alumina (Ni/Al₂O₃) composite under an argon atmosphere containing a low partial pressure of ammonia (P_NH3 = 10 kPa). GaN nanowires were formed on the Ni(NO₃)₂-dispersed silicon and Ni/Al₂O₃ composite substrates. Two kinds of nanowires with different morphologies were observed. Initially, the formation of rough-surfaced nanowires occurred, which was followed by the formation of smooth-surfaced nanowires. In the case of the Ni/Al₂O₃ composite, GaN nanowires with rough surfaces were formed after 15 min at 1000°C, and the number of nanowires increased with the holding time. TEM observations showed that the nanowires grew in the [100] direction, which supported the proposed vapor–liquid–solid growth mechanism.

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Waste soda lime glass powder was hydrothermally treated twice at 150°C, and the resulting powder was mixed with CaCO₃ powder in the weight ratio of 1:3 and heat-treated at 1450°C. The resulting powder was identified as Ca₃SiO₅ as the main phase with small amounts of Ca₃Al₂O₆, which are both common Portland cement sources. The elemental composition of the resulting cements was evaluated and all minor components (Cl, Na, SO₃, etc.) were found to be less than the JIS standard value for eco-cement.

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