Development of Porous Films Based on Polyanionic Cellulose to Form Functional Coatings

New porous films based on polyanionic cellulose with AlOOH nanoparticles have been developed. The morphology of the films has been studied by electron microscopy: the size of the formed pores is 1000-500 microns; the total surface porosity of the films is 30%. Using infrared microscopy, it was shown that during the formation of porous films, their chemical composition remains unchanged. Differential scanning calorimetry was used to determine the threshold for thermal destruction of porous films: 306 С. The possibility of using the obtained materials as antifriction coatings when filling the pores with solid lubricant MoS2 is considered. It is shown that for a steel sample protected by a porous coating with MoS2, the friction coefficient decreases by 50% compared to the friction coefficient for a steel surface under a load of up to 450 MPa.

Evolution of the Surface Structure and Functional Properties of the Electroconducting Polymer Coatings onto Porous Films

Composite systems containing electroconducting polymer coatings (polyaniline and polypyrrole) applied to porous films of semicrystalline polymers (polyethylene, polypropylene, and polyvinylidene fluoride) have been prepared. Porous supports were obtained in the process based on polymer melt extrusion with subsequent annealing, uniaxial extensions, and thermal stabilization. Conducting coatings were formed by the oxidative polymerization of the monomers directly onto the porous supports. The structure (overall porosity, permeability, pore sizes, factor of orientation) and morphology (specific surface and character of the film surface) of the supports were characterized by sorptometry, filtration porosimetry, atomic force microscopy (AFM), and X-ray scattering techniques. It was observed that the porous supports have a strongly developed relief surface which is formed in the pore formation process. It was proven by scanning electron microscopy (SEM) that the porous supports have an oriented structure, and the surface of the composites is defined by the morphology inherent in the conducting component. It was shown that these composites (porous support/conducting coating) demonstrate electric conductivity both along the surface and between surfaces. It was demonstrated that the deposition of conducting coatings leads to an increase in the water wettability of the composites compared with pronounced hydrophobic supports. The composites are characterized by good adhesion between components due to a relief film surface as well as high mechanical strength and elasticity provided by the oriented character of the supports.

Ion-doped mesoporous bioactive glass: preparation, characterization, and applications using the spray pyrolysis method

Bioactive glasses (BAG) are one type of biomaterial that is used in dentistry and orthopedics to repair or replace damaged bone. The spray pyrolysis process is low-cost and one of the most common ways for producing porous films and films with high-density packing and particle homogeneity.

PROMISING COMPOSITE MATERIALS BASED ON NANOSCALE APATITE WITH GELATIN AS A BINDING AGENT

Порошки наноразмерных гидроксиапатита и фторапатита синтезированы методом осаждения из растворов. В качестве связующего вещества использован пищевой желатин. Такая композиция имеет высокую адгезию на материалах различной природы и пористости. Получены также пористые пленки и гранулы с развитой удельной поверхностью. Рассмотрены их микроструктуры. Изучена возможность использования коллоидной суспензии и водной суспензии кристаллического апатита в сочетании с раствором желатина в качестве биоактивного материала, как для создания покрытий, так и получения гранул. Установлено, что использование порошка апатита совместно с желатином позволяет существенно сократить сроки формирования биоактивного покрытия и значительно повысить его адгезионную прочность. Сопоставлены получаемые гранулы апатита по размерам в зависимости от концентрации желатина в водном растворе. На разработанные биоактивные покрытия и гранулированный материал на основе наноразмерного апатита со связующим агентом поданы заявки на патент. Nanoscale hydroxyapatite and fluorapatite powders were synthesized by precipitation from solutions. Food gelatin is used as a binder. This composition has a high adhesion on materials of different nature and porosity. Porous films and granules with a developed specific surface area were also obtained. Their microstructures are considered. The possibility of using a colloidal suspension and an aqueous suspension of crystalline apatite in combination with a gelatin solution as a bioactive material, both for creating coatings and obtaining granules, has been studied. It is established that the use of apatite powder together with gelatin can significantly reduce the time of formation of a bioactive coating and significantly increase its adhesive strength. The obtained apatite granules are compared in size depending on the concentration of gelatin in an aqueous solution. Patent applications have been filed for the developed bioactive coatings and granular material based on nanoscale apatite with a binding agent.

Interrogation of the Selectivity and Electrokinetics of CO2 Reduction by AgSn Films in the Presence of Protic Organic [DBU–H]+ Cations as judged by Impedance Spectroscopy and Distribution of Relaxation Times Analysis

The use of renewable electricity to synthesize high energy and high value chemicals via reduction of CO2 is an attractive strategy for renewable energy storage. Improving our understanding of how heterogeneous CO2 reduction electrocatalysts function is important to designing efficient systems for conversion of CO2 into commodity chemicals such as CO and HCO2H. Both Ag- and Sn-based materials have been previously considered as CO2 reduction catalysts and offer distinct CO2RR selectivities. In this work, we have considered electrodeposited composite film electrodes prepared from electroplating baths with varying ratios of Ag+ and Sn2+ triflates to understand how the performance of such composite materials varies as a function of composition. XPS analysis confirms that for each composite film electrodes, Ag existed in the metallic (Ag0) state, while the Sn was mainly oxidized (Sn2+/4+). The AgSn composite film electrodes studied herein are therefore best considered as AgSnOx cathodes with varying ratios of Ag0:Sn2+/4+. These systems were assessed as CO2RR electrocatalysts and were found to promote the 2e–/2H+ reductions to deliver CO and HCOOH with fast kinetics and high efficiencies from electrolyte solutions containing the protic organic cation [DBU–H]+. While Sn-rich composite films showed poor selectivities for CO versus HCO2H, a significant increase in CO versus HCO2H selectivity (up to 99%) is achieved for composite film electrodes in which the Ag content ranged from 25 - 75%. By tuning the ratio of Ag0 to SnOx we prepared composite film cathode materials that support quantitative current efficiencies for generation of CO with geometric current densities approaching 30 mA/cm2 at applied overpotentials that are less than 750 mV were realized. Additionally, electrochemical impedance spectroscopy (EIS) coupled with analysis of the distribution of relaxation times (DRT) was used to better understand factors important to the composites’ activity under CO2RR conditions. Probing the dynamics with DRT analysis revealed that multiple processes relating to both adsorption and diffusion-controlled events are important to the activity of the electrocatalysts considered in this work. The collection of electroanalytical investigations suggest that synergistic interactions between Ag and SnOx give rise to porous films that support enhanced CO2RR kinetics and that mixing of Ag with SnOx enhances the efficacy of adsorption and stabilization of reduced CO2 intermediates and [DBU–H]+ cations to facilitate CO evolution at the cathode/electrolyte interface.

Molecular Dynamics Simulation of Laser Induced Heating of Silicon Dioxide Thin Films

The full-atomistic classical molecular dynamics simulation of the laser heating of silicon dioxide thin films is performed. Both dense isotropic films and porous anisotropic films are investigated. It is assumed that heating occurs due to nodal structural defects, which are currently considered one of the possible causes of laser induced damage. It is revealed that heating to a temperature of 1000 K insignificantly affects the structure of the films and the concentration of point defects responsible for the radiation absorption. An increase in the heating temperature to 2000 K leads to the growth of the concentration of these defects. For “as deposited” films, this growth is greater in the case of a porous film deposited at a high deposition angle. Annealing of film reduces the difference in the concentration of laser induced defects in dense and porous films. The possible influence of optical active defects arising due to heating on the laser induced damage threshold is discussed.

Fabrication of Highly Porous and Pure Zinc Oxide Films Using Modified DC Magnetron Sputtering and Post-Oxidation

Porous films of metals and metal oxides exhibit larger surface areas and higher reactivities than those of dense films. Therefore, they have gained growing attention as potential materials for use in various applications. This study reports the use of a modified direct current magnetron sputtering method to form porous Zn-ZnO composite films, wherein a subsequent wet post-oxidation process is employed to fabricate pure porous ZnO films. The porous Zn-ZnO composite films were initially formed in clusters, and evaluation of their resulting properties allowed the optimal conditions to be determined. An oxygen ratio of 0.3% in the argon gas flow resulted in the best porosity, while a process pressure of 14 mTorr was optimal. Following deposition, porous ZnO films were obtained through rapid thermal annealing in the presence of water vapor, and the properties and porosities of the obtained films were analyzed. An oxidation temperature of 500 °C was optimal, with an oxidation time of 5 min giving a pure ZnO film with 26% porosity. Due to the fact that the films produced using this method are highly reliable, they could be employed in applications that require large specific surface areas, such as sensors, supercapacitors, and batteries.