The Influence of the Precursor’s Nature and Drying Conditions on the Structure, Morphology, and Thermal Properties of TiO2 Aerogels

A cost-effective solution for the synthesis of high-porosity TiO2 aerogels, which can be used as a mesoporous perovskite network charge-carrier material during the manufacture of solar cells, is described. The effects of the synthesis parameters (precursor (titanium (IV) isopropoxide (TIP) and tetrabutyl orthotitanate (TBOT)), additional solvent exchange (n-hexane (nH), cyclohexane (CH), and diethyl ether (DE)), subcritical drying (800 mbar vacuum, 70 °C, 8 h), aging, and calcination on the aerogel’s structure have been investigated. Methods of XRD, FT-IR, BET, Raman, STA, SEM, UV–vis, and thermal conductivity measurements were applied to find out the relation between the synthesis conditions and the properties of the synthesized aerogels. Amorphous aerogels are polydispersed systems with the highest probability of pore diameter from 0.5 to 15 nm. An nH-exchanged, aged aerogel synthesized from the precursor TIP shows the highest diameter of pores. After calcination, the aerogels tend to crystallize into an anatase phase and the size of the crystallites depends on the precursor’s nature. Calcination leads to a significant increase in both the apparent and true density of the aerogels, and it also results in an increase in porosity and thermal conductivity

Microstructuring of electrospun mats employing femtosecond laser

Electrospun mats from nano/micro-fibers with control porosity and pore shape may be ideal candidate for tissue engineering scaffolds. In this study three type of poly(vinyl alcohol) (PVA) mats of 48-65 µm thickness with different nano/micro-fibers diameters mostly of 100-200 nm were deposited by electrospinning process. Controlled density porosity in the electrospun mats was introduced by Yb:KGW femtosecond laser micromachining system. The influence of electrospun mat micro structure, the distance between the adjacent laser ablation points, the number of femtosecond laser pulses on quality and structure of laser irradiated holes were investigated. It was demonstrated that the quality of irradiated holes depend on structure of electrospun mats (diameter of nano/micro-fibers, thickness of mats) and femtosecond laser processing parameters. Varying the distance between points and number of applied femtosecond laser pulses it is possible to fabricate electrospun mats with pores of 22-36 μm diameter.DOI: http://dx.doi.org/10.5755/j01.ms.21.1.10249</p

Forestry wastes filled polymer composites for agricultural use

Two kinds of polymer composites were prepared using poly (vinyl alcohol) as binder and forestry or wood processing wastes as fillers. In one kind of the composites pine needle meal was used as filler while the other kind of the composites was filled with pine bark meal. Glycerol and oleic acid were used for the modification of mechanical, sorption properties and solubility of the composites. The films of the composites were fabricated and their mechanical, viscoelastic and antifungal properties as well as water absorption and solubility in water were studied. Mathematical experiment design was used to evaluate influence and importance of both glycerol and oleic acid content on of mechanical properties, solubility and water absorption of the composite films filled with pine bark meal. The second order polynomial models were developed in order to find out optimal content of both glycerol and oleic acid in compositions. Exploitation properties of the composite pots prepared from the composites were studied and vegetation tests were performed. It was shown that evaporation rate of water through the walls of the composite pots was by 45% lower and the temperature of substrate in the composite pots was by 3e4 C higher as compared with the corresponding characteristics of peat pots. Plants cultivated in the composite pots had better developed root system relative to those cultivated in peat potsGamtos tyrimų centrasKauno technologijos universitetasVytauto Didžiojo universitetasŽemės ūkio akademij