Defective Grey TiO2 with Minuscule Anatase–Rutile Heterophase Junctions for Hydroxyl Radicals Formation in a Visible Light-Triggered Photocatalysis

The novelty of this work was to prepare a series of defect-rich colored TiO2 nanostructures, using a peroxo solvothermal-assisted, high-pressure nitrogenation method. Among these solids, certain TiO2 materials possessed a trace quantity of anatase–rutile heterojunctions, which are beneficial in obtaining high reaction rates in photocatalytic reactions. In addition, high surface area (above 100 m2/g), even when utilizing a high calcination temperature (500 °C), and absorption of light at higher wavelengths, due to the grey color of the synthesized titania, were observed as an added advantage for photocatalytic hydroxyl radical formation. In this work, we adopted a photoluminescent probe method to monitor the temporal evolution of hydroxyl radicals. As a result, promising hydroxyl radical formations were observed for all the colored samples synthesized at 400 and 500 °C, irrespective of the duration of calcination.

Effect of Annealing Temperature of CoCr2O4 on Structural and Vibrational Properties

CoCr2O4 nanoparticles were prepared by low-temperature sol–gel auto combustion method. In this paper, we have investigated the structural behavior of CoCr2O4 nanoparticles annealed at two different temperatures (600 °C and 800 °C). From the X-ray diffraction (XRD) pattern of CoCr2O4, we have found that there is no change in crystalline structure and it was indexed in the cubic spinel structure with space group Fd3m. It was observed that average crystallite size increases with calcination temperature. High calcination temperature reduced the noise level and enhanced the accuracy of calculated parameters. For both the samples of CoCr2O4, we observed Raman scattering modes at around 471, 516, 539, 561, 590, 626 and 688 cm–1. The additional modes in vibrational spectra appear due to the disorder effect.

Development and Characterization of Hydroxyapatite-Alumina Biocomposites for Orthopedic Implants

Hydroxyapatite-Alumina composite powders, HAP-Al2O3, for biomedical applications were synthesized by neutralization method. Composites with different alumina content were prepared and calcined over the temperature range of 900-1300°C for 3 h. Effects of alumina content and calcination on the structural properties of powders were studied. The as-received powders and ceramics were characterized by various techniques (XRD, IR, SEM, TEM). Compressive strength of ceramics was determined using direct compressing. Results indicate that both crystallinity of the HAp-Al2O3 powders and the compressive strength increased with the temperature of calcination, but depending of the alumina content where the formation of β-TCP phase as secondary phase is detected after heat treatment. We notice that HAp-10Al2O3 offers the best mechanical strengths that can be improved by a high calcination temperature.

PENGARUH TEMPERATUR KALSINASI TERHADAP SIFAT MEKANIK MATERIAL SCAFFOLD HIDROKSIAPATIT DARI TULANG KAMBING

<p><em>In this study, a preliminary study on the preparation of hydroxyapatite (HAp) as bone filler was made from sheep femur bone by calcination method</em><em>. The femur of the sheep is cut into a form of scaffold with dimensions of 5 mm x 5 mm x 5 mm. The calcination process is performed at four variations of temperature (700^oC, 900^oC, 1100^oC, 1300^oC). Characterization of scaffold material done before and after calcination process, it intended to find out the influence and relationship between calcination of temperature on the mechanical properties of SHA material. The results of hardness testing show that the higher calcination temperature then the SHA material hardness value also increased. The optimum hardness value occurs at 1100^oC calcination temperature of 38.23±0.985VHN. Meanwhile, high calcination temperature will also decrease the compressive strength of SHA material. The value of the optimum compressive strength is achieved at 1100^oC calcination temperature of 2.23±0.249 MPa. The morphology of SHA scaffold was analyzed by Scanning Electronic Microscopy (SEM). The observation of SEM shows the occurrence of porous interconnections in all temperature variations. SEM analysis results show that porous interconnect is formed at all temperature variations with diameter size ± 100-500μm. Very high calcination temperature will give the impact of HAp wall is getting thinner and the porous diameter is getting bigger. Porous interconnection damage is also seen at 1300°C which causes the mechanical properties of SHA to decrease.</em></p>

Fabrication, Characterization and Comparison of Nanocrystalline NiMn2O4 and NiZn0.2Mn1.8O4 NTCR Ceramic Thermistor Powders

Here, NiMn2O4 and NiZn0.2Mn1.8O4 nanocrystalline ceramic powders are fabricated, characterized, and compared for thermistor applications. Solution route was used to synthesize the materials. The NiMn2O4 is a spinel single crystal material with the average crystallite size 26.82 nm and a particle size less than 1 μm and has uniform morphology. The EDS results confirmed the composition of NiMn2O4 that consisted of Ni, Mn, and O2 only. The average crystallite size of NiZn0.2Mn1.8O4 is 37.48 nm and the particle size is less than 0.5 μm. There has been observed some agglomeration formation due to high calcination temperature. The β-value of NiMn2O4 is larger than NiZn0.2Mn1.8O4, hence thermistors constructed from NiMn2O4 are more stable and applicable as NTCR thermistor powder.

L-Leucine Templated Biomimetic Assembly of SnO2 Nanoparticles and Their Lithium Storage Properties

SnO2 nanoparticles have been synthesized by a novel route of a sol-gel method assisted with biomimetic assembly using L-leucine as a biotemplate. The microstructure of as-prepared SnO2 nanoparticles was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectra (FT-IR), and Brunner−Emmet−Teller (BET) measurements. The results demonstrated that the growth of SnO2 could be regulated by L-leucine at a high calcination temperature. The electrochemical performance of SnO2 was also measured as anodes for lithium-ion battery. It is a guidance for the growth regulation of SnO2 at high temperature to obtain SnO2/C with nanosized SnO2 coated by a graphitic carbon.

Fabrication of Porous Mullite Ceramics with Different Phase of Alumina for Insulation Materials

This paper reports the effects of γ-Al2O3 and α-Al2O3 on the properties of lightweight insulation materials. The phase compositions, microstructure and mechanical properties of lightweight insulation materials are separately investigated by XRD, SEM and tabulate thermal conductivity apparatus methods. The results indicate that the increasing of the amount of γ-Al2O3 is beneficial to improving the bulk density, compressive strength and acid resistance of the fired specimens. The fact negatively impacts on the increasing of the apparent porosity; however, it has no significant effect on the thermal conductivity of specimens. Meanwhile, the studies highlight that when the content of γ-Al2O3 increases, the nucleation and growth of mullite is accelerated at high calcination temperature, which has positive effect on improving the physicochemical properties of lightweight insulation materials. And the γ-Al2O3-free SiO2 glass phase system is guided by theoretical analysis of reaction conditions for non-catalytic system with Factsage modelling.

Nickel Oxide Catalysts for Partial Oxidation of Methane to Synthesis Gas

<p class="Default">Nickel catalysts supported on different carriers (θ-Al₂O₃, γ-Al₂O₃, HZSM-5 with γ-Al₂O₃, HZSM-5, and NaX) have been investigated for the partial oxidation of methane. All the supported nickel catalysts showed a high activity for the formation of synthesis gas, and γ-Al₂O₃ was the most effective among all the tested carriers. The effect of the heat-treatment temperature of the 3 wt.% Ni/γ-Al₂O₃ catalyst on its catalytic activity was studied, and a considerable decrease in its activity was observed by the heat-treatment of the catalyst at 1000 °C compared with the catalysts prepared by the 300–800 °C – calcination. The XRD analysis suggested the formation of NiAl₂O₄ that is a non-reducible compound at the high calcination temperature. The addition of a modifier (Co, Ce, or La) to the 3 wt.% Ni/γ-Al₂O₃ catalyst increased the selectivity to H₂ and CO with the decreasing selectivity to CO₂, and the highest selectivity to H₂ was obtained by the 5 wt.% NiLa/γ-Al₂O₃. The developed 5 wt.% NiLa/γ-Al₂O₃ catalyst showed a high stability for 30 h for the partial oxidation of methane at 750 °C. The methane conversion reached 95%, selectivity to hydrogen 83% and 52% to carbon monoxide.</p>