Effect of electrochemical modification of titanium hydride fraction on oxygen content in surface and deep layers

The paper presents a study of the microstructure and oxygen concentration in the surface and deep layers of fractions of unmodified titanium hydride and titanium hydride modified by electrodeposited layers of Ti and Cu at temperatures of 300-900 ° C. The composition of the oxide layer and the concentration of titanium and oxygen atoms are estimated. It is shown that an increase in the thickness and compaction of the oxide layer with increasing temperature prevents the penetration of oxygen into the deep layers of the unmodified fraction of titanium hydride. Modification of titanium hydride by electrochemical deposition of metallic titanium at a temperature of 700 °C reduces the oxygen concentration in titanium hydride at a layer depth of 50 μm from 35 wt% to 12.5 wt%. Electrodeposition of coatings based on titanium and copper at 700 °C reduces the oxygen concentration to 9.2 wt%, which may be due to the protective mechanism of the formed copper titanate layer. At 900 °C, in the modification layer based on titanium and copper, due to the eutectoid transformation of the β-phase of titanium, the process of contact melting occurs and a multiphase zone is formed. The oxygen concentration at a layer depth of 50 μm is no more than 12.4 wt%.

Surface Modification of Titanium Orthodontic Implants

Orthodontic miniscrews have had a considerable impact on modern orthodontic treatment, not only by providing a new source of anchors for anchorage-demanding cases, but also for force management and control. Whilst miniscrews need to be mechanically stable during treatment to provide sufficient anchorage and predictable force control, as temporary anchorage devices they need also be easy to remove after orthodontic treatment. These requirements differentiate orthodontic miniscrews from dental implants - which once placed, are not to be removed - and dictate the approach as to how their clinical performance can be optimized. Over the past decade, various titanium surface modifications and improvements in implant surface topography have shown to enhance osseointegration of endosseous dental implants. Some of these techniques have helped provide a similar enhancement of the biomechanical potential of orthodontic miniscrews as well. In this perspective, we present a brief discussion on all such reported techniques followed by a detailed account of the most recently proposed ultraviolet photofunctionalization technique - a novel chair-side surface modification method.

Research of the structure and mechanical properties of gas-thermal coatings after induction heat treatment

In this article the process of induction-thermal modification of titanium coatings formed by electroplasma spraying was considered. The influence of the inductor current on the temperature of processed samples was experimentally established. The research results showed that thermal treatment of the samples with titanium coatings at a temperature of 750–1200 °C and a duration of 300 s led to an increase in porosity from 56±2 to 61±1 % and in microhardness from 1035–1532 to 1825–1883 HV0,98, the sprayed layer thickness decreased from 320±30 to 114±15 μm as well. A change of nanoscale structural elements shape was also observed.

PHOTOCATALYTIC TREATMENT OF WATERS, POLLUTED WITH PHENOLS

The analysis of the environmental and human health threats imposed by phenols was conducted to show the need for further improvement of methods of their destruction. Being toxic in their initial composition and precursor to toxic metabolites in human body, phenols should be controlled in natural water and waste waters. They are listed as priority pollutants in most national regulation around the world and are the initial compounds for the formation of persistent organic pollutants in the environment, polluted with other active radicals. A variety of physical and chemical methods were offered for the destructive or non-destructive removal of phenols and their derivatives from water. The comparative study of possible methods, described in research papers, was conducted in terms of their efficiency and complexity to define benefits and drawbacks. The analysis showed the need for development of low energy consuming method, which needs minimal equipment and can be run under industrial condition for phenol contaminated wastewaters. Among the possible methods which meet the mentioned criteria photocatalytic destruction of phenols was showed to be perspective. A series of experiments was conducted using a range of water solution of phenol and different dosage of catalysts. The catalysts used in experiments were made of 6 modification of titanium oxide and bismuth ferrite. The initial and residual concentration of phenol was controlled by the means of high-performance liquid chromatography. The duration of the exposure and the type of light were other independent variables. The results of the whole sequence of experiments demonstrated higher efficiency of rutile under visible light and one hour of exposure. The tested photocatalytic system is simple and therefore technically and economically feasible.

Research Progress of Adsorption and Photocatalysis of Formaldehyde on TiO2/AC

Based on the increasingly serious formaldehyde pollution, effective degradation of formaldehyde has become a practical problem that humans urgently need to solve. Among many treatment methods, activated carbon has the advantages of large specific surface area, high adsorption efficiency, and uniform pore size distribution. As a kind of clean photocatalytic material for formaldehyde degradation, titanium dioxide supported by activated carbon has become a research hotspot to develop adsorption-catalytic materials for formaldehyde degradation. In this paper, the research progress of activated carbon and its modification, the photocatalytic principle and modification of titanium dioxide, and TiO2/AC materials are reviewed. The results show that the pore size distribution gradient and acidic oxygen-containing functional groups of activated carbon play key roles in the formaldehyde adsorption process. TiO2 doped with metal ions and nonmetal ions can significantly improve the photocatalytic activity. The TiO2/AC material can greatly improve the photocatalytic rate and achieve the technical goal of efficient and clean degradation for formaldehyde.

Interaction of Various Variants of the Nanostructured Surface of Titanium with MSCs Isolated from Adipose Tissue

Titanium has been successfully used in dental implantology for a long time. Due to the osseointegration process, titanium implants are able to withstand the chewing load. This article is devoted to the study of surface treatment methods of titanium alloys and the study of their interaction with mesenchymal stem cells (MSCs). The surface microrelief can influence MSC differentiation in different ways, which subsequently gives it osteogenic potential. The paper proposes modes of surface modification of titanium alloys on Grade 4 and Grade 1 by chemical and electrochemical (anodizing) etching. The possibility of modifying the surface of titanium alloys using the synthesis of graphene layers has been proposed in this paper for the first time. The osteogenic potential of a particular surface was assessed by the number of mesenchymal stem cells cultured on them under identical conditions.

Influence of yttrium and niobium oxides modifiers on physicochemical and photocatalytic properties of titanium (IV) oxide

The photocatalytic and physicochemical properties of titanium (IV) oxide modified by yttrium and niobium oxides were studied. It is shown that modification is a powerful way to increase the efficiency of catalysts' photocatalytic properties and improve the photocatalytic process as a whole. Commercial and laboratory-synthesized titanium (IV) oxides were used as catalysts for modification. Modification of titanium (IV) oxide powders in an amount of 1 wt. % by appropriate modifiers was performed by the hydrothermal method, after which they were characterized by diffraction and X-ray fluorescence methods. The structural characteristics of modified and non-modified titanium (IV) oxide samples by the method of low-temperature nitrogen adsorption-desorption have been studied. A slight increase in the specific surface area was found: from 61 m2/g to 70 m2/g for the commercial sample and from 172 m2/g to 180 m2/g for the synthesized one in this work. Similar dependencies are observed when studying the optical properties by the spectrophotometric method. Determination of surface properties (surface acidity) of modified and non-modified photocatalysts based on TiO2 showed different effects of modifiers on TiO2 acidity: in the modification by yttrium oxide, the acidity decreases, and in the case of niobium oxide – increases. Studies of photocatalytic and sorption activities with respect to dyes of different nature are not the same – the photocatalytic activity after modification increases, the sorption capacity with the cationic dye decreases, anionic – increases. Additional studies on dye destruction are in full accordance with photocatalytic and sorption experiments.