The slowing down of the group velocity of light at the edges of the photonic band gap is one of the important optical effects observed in photonic crystals. In particular, the “slow light” effect is used in photocatalysis to increase the photocatalytic activity of semiconductors. In this work, anatase photonic crystals with different spectral positions of the photonic band gap (390–1283 nm, measured in water) were obtained. It is shown that if one of the photonic band gaps is located near the absorption edge of the semiconductor (410 nm), photonic crystal exhibits high photocatalytic activity in the photodegradation of methylene blue. At the same time, the photocatalytic activity of anatase photonic crystal increases by 30% when the photonic band gap of the third order rather than the first order is located near the absorption edge of the semiconductor.

Aluminum anodizing in electrolytes comprising mixtures of several acids opens way to manufacture porous films of anodic aluminum oxide (AAO) with a widely tunable structure period. Study of thermal transformations in AAO films produced in mixed electrolytes is a separate task, as a complex chemical composition of the material can give rise to some specifics in subsequent annealing. Impurity oxalate and sulfate ions were detected in the AAO produced by aluminum anodizing in sulfuric acid/oxalic acid mixed electrolytes. The sulfate weight fraction appears about one order of magnitude higher than the oxalate weight fraction, and it increases as the concentration ratio of sulfuric acid to oxalic acid in the electrolyte increases. In the same way, the crystallization temperature of amorphous AAO to a mixture of low-temperature Al 2 O 3 polymorphs increases in response to increasing concentration ratio of sulfuric acid and oxalic acid. Thus, the component ratio in the mixed electrolyte used influences the composition and thermal transformations of AAO.

Anodic titanium oxide (ATO) one-dimensional photonic crystals (PhCs) are materials with uniaxial periodic modulation of porosity. A periodic change of an effective refractive index caused by porosity modulation results in the formation of photonic band gaps (PBGs). The non-uniform dissolution of ATO cell walls during the fabrication process hampers the obtaining of a strict optical periodicity of ATO PhCs. Recently it was found that the dissolution of ATO cell walls is accelerated by anodic polarization. However, the main factor controlling the accelerated dissolution of ATO cell walls during anodizing remains unclear. In this study, the correlation between ATO PhC porosity and the charge density is discussed. The dependencies of the spectral photonic band gap (PBG) position and PBG reflectance on the charge density are studied experimentally. The findings open a pathway to the synthesis of ATO PhCs with flawless optical periodicity and high PBG reflectance.

Ceramics consisting of anhydrous calcium sulfate, CaSO4, after firing in the range 800–1000°C have been prepared from calcium sulfate dihydrate (CaSO4⋅2H2O) powder synthesized using aqueous 1 M calcium nitrate (Ca(NO3)2) and ammonium sulfate ((NH4)2SO4) solutions. In the preparation of the powder, the precipitate was washed four times with distilled water to remove ammonium nitrate, NH4NO3, a reaction by-product and, after drying, the powder was disaggregated in acetone. The synthesized CaSO4⋅2H2O powder particles had an elongated prismatic shape both before and after disaggregation. After firing at 800, 900, and 1000°C, the microstructure of the ceramics based on the synthesized CaSO4⋅2H2O powder free of reaction by-products contained sintered elongated polycrystalline structures, confirming that the ceramics inherited the microstructure of the starting powder. Ceramics consisting of anhydrous calcium sulfate, CaSO4, can be recommended for the fabrication of implants for bone tissue defect repair by regenerative medicine methods because they are biocompatible and bioresorbable.

— Ceramics consisting of anhydrous calcium sulfate, CaSO 4 , after firing in the range 800–1000°C have been prepared from calcium sulfate dihydrate (CaSO 4 ⋅2H 2 O) powder synthesized using aqueous 1 M calcium nitrate (Ca(NO 3 ) 2 ) and ammonium sulfate ((NH 4 ) 2 SO 4 ) solutions. In the preparation of the powder, the precipitate was washed four times with distilled water to remove ammonium nitrate, NH 4 NO 3 , a reaction by-product and, after drying, the powder was disaggregated in acetone. The synthesized CaSO 4 ⋅2H 2 O powder particles had an elongated prismatic shape both before and after disaggregation. After firing at 800, 900, and 1000°C, the microstructure of the ceramics based on the synthesized CaSO 4 ⋅2H 2 O powder free of reaction by-products contained sintered elongated polycrystalline structures, confirming that the ceramics inherited the microstructure of the starting powder. Ceramics consisting of anhydrous calcium sulfate, CaSO 4 , can be recommended for the fabrication of implants for bone tissue defect repair by regenerative medicine methods because they are biocompatible and bioresorbable.

Ceramics consisting of anhydrous calcium sulfate, CaSO4, after firing in the range 800-1000 degrees C have been prepared from calcium sulfate dihydrate (CaSO4 center dot 2H(2)O) powder synthesized using aqueous 1 M calcium nitrate (Ca(NO3)(2)) and ammonium sulfate ((NH4)(2)SO4) solutions. In the preparation of the powder, the precipitate was washed four times with distilled water to remove ammonium nitrate, NH4NO3, a reaction by-product and, after drying, the powder was disaggregated in acetone. The synthesized CaSO4 center dot 2H(2)O powder particles had an elongated prismatic shape both before and after disaggregation. After firing at 800, 900, and 1000 degrees C, the microstructure of the ceramics based on the synthesized CaSO4 center dot 2H(2)O powder free of reaction by-products contained sintered elongated polycrystalline structures, confirming that the ceramics inherited the microstructure of the starting powder. Ceramics consisting of anhydrous calcium sulfate, CaSO4, can be recommended for the fabrication of implants for bone tissue defect repair by regenerative medicine methods because they are biocompatible and bioresorbable.