Commercially pure titanium is less expensive, generally more corrosion resistant and lower in strength than its alloys, and is not heat-treatable. The use of Ti and its alloys as construction materials under severe friction and wear conditions is limited due to their poor tribological properties. Nevertheless, proper addition of hard ceramic particles into Ti and its alloys has proved to be an efficient way to enhance their mechanical and wear properties. Our purpose in this work was to analyze the corrosion, tribocorrosion, mechanical and morphological effects of combining titanium carbide with titanium metal, to create a unique composite via spark plasma sintering technique (SPS). Composites with different mass percentage (1, 5, 10, 15 and 20 wt %) of ceramic phase were produced. The samples of pure Ti and Ti-6Al-4V alloy were also tested, as a reference. These composites were examined for mechanical properties and corrosion resistance in an environment similar to the human body (Ringer’s solution). Open circuit potential (OPC) and anodic polarization measurements were performed. The properties of titanium composites reinforced with micro- and nanocrystalline TiC powders were compared. It was stated that wear properties were significantly improved with increasing amount of TiC in matrix, especially in the case of nanocrystalline reinforcement. In terms of corrosion resistance, the composites showed slightly worse properties compared to pure titanium and Ti-6Al-4V alloy.
The Mn-Zn ferrite powders prepared by high energy ball milling were heat-treated, subsequently compacted and sintered by spark plasma sintering (SPS). Based on the observation of microstructure, the characteristics of samples after SPS were investigated and compared with ones after conventional sintering. The size of initial powders was approximately 650 nm and decreased to 230 nm after milling at 300 rpm for 3 h. After heat treatment at 973K for 1h, the milled powders became larger to approximately 550 nm in size again and the peaks of Mn2O3 disappeared in XRD patterns. In the samples after SPS, the Fe2O3 and MnZnFe2O4 phases decomposed at the higher temperatures than 1173K and 1373K, respectively, while only MnZnFe2O4 phase was detected in the samples conventionally sintered at 1273~1673K. As the sintering temperature increased, the relative density after SPS increased more quickly than that after conventional sintering. In particular, it reached approximately 99% after SPS at 1473K.
In the present paper several species of moss-mites (Acari, Oribatida), including a species new for science (Halozetes impeditus sp. nov.) caught in the vicinity of the Polish "H. Arctowski" Station on King George Island (South Shetlands) are discussed.
Two methods were evaluated in terms of manufacturing of MAX phase preforms characterized with open porosity: microwave-assisted self-propagating high-temperature synthesis (SHS) and spark plasma sintering (SPS). The main purpose of fabrication of such open-porous preforms is that they can be successfully applied as a reinforcement in metal matrix composite (MMC) materials. In order to simulate the most similar conditions to microwave-assisted SHS, the sintering time of SPS was significantly reduced and the pressure was maintained at a minimum value. The chosen approach allows these two methods to be compared in terms of structure homogeneity, complete reactive charge conversion and energy effectivity. Study was performed in Ti-Al-C system, in which the samples were compacted from elemental powders of Ti, Al, C in molar ratio of 2:1:1. Manufactured materials after syntheses were subjected to SEM, XRD and STEM analyses in order to investigate their microstructures and chemical compositions. As was concluded, only microwave-assisted SHS synthesis allows the creation of MAX phases in the studied system. SPS technique led only to the formation of intermetallic secondary phases. The fabrication of MAX phases’ foams by microwave-assisted SHS presents some interesting advantages compared to conventional manufacturing methods. This work presents the characterization of foams obtained by microwave-assisted SHS comparing the results with materials produced by SPS. The analysis of SPS products for different sintering temperatures provided the better insight into the synthesis of MAX phases, supporting the established mechanism. Dissimilarities in the heating mechanisms that lead to the differing synthesis products were also discussed.
In the paper the multiferroic (ferroelectric-ferromagnetic) composites based on ferroelectromagnetic/ferroelectric (BaFe1/2Nb1/2O3 (BFN)) powder and ferrite powder (zinc-nickel ferrite) were obtained by two technological methods. In the composite samples the ratio of the ferroelectromagnetic/ferroelectric powder to the magnetic powder was equal to 90:10. The ceramic powders were synthesized by the classical technological method using powder calcination/solid state synthesis, while densification of the composite powders (sintering) was carried by two different methods: (i) Free Sintering method (FS), and (ii) Spark Plasma Sintering (SPS).
At the work, a comparison of measurement results for composite samples obtained by two sintering methods was made. The studies included the following analysis: DTA, XRD, SEM, DC electrical conductivity, electric permittivity and magnetic properties. The result of measurements presented in the work revealed that the ceramic composite obtained by two different technological sintering method (classical technology – Free Sintering method and Spark Plasma Sintering technique) can be promising lead-free materials for functional applications, for example in sensors for magnetic and electric field.
Coexisting microorganisms are abundant in nature. Plant growth promoting rhizobacteria (PGPR) is a group of beneficial microorganism living around the roots of plants which are able to confer beneficial effects on plant growth. Streptomyces sp. is a gram-positive bacteria as PGPR that can promote plant growth and enhance tolerance in adverse environment. This research was aimed to study the effects of plant growth promotion and stress tolerance of Streptomyces sp. in Arabidopsis and Brassica sp. The amount of indole-acetic acid (IAA) and phosphate solubility were assessed from isolated bacterial. Plant growth promotion was examined in 10-days old seedling with three independent experiments. Our results showed that Streptomyces sp. produced moderate levels of IAA and it was able to solubilize phosphate. Inoculation of Streptomyces sp. enhanced lateral root number, fresh weight and chlorophyll content in Arabidopsis thaliana. Moreover, the inoculation of Streptomyces sp. significantly increased vegetative growth on Arabidopsis and Brassica sp. by producing higher fresh weight and chlorophyll content. Streptomyces sp. also enhanced tolerance to abiotic stress in Arabidopsis and Brassica sp. by increasing fresh weight under condition of salt and heat stress. Under salt stress, inoculation of Streptomyces sp. in Arabidopsis induced activity of catalase enzyme and decreased hydrogen peroxide (H2O2) and malondialdehyde (MDA) production. In the molecular levels, Streptomyces sp. induced protein accumulations in Arabidopsis including nitrogen assimilation (GS1), carbohydrate metabolism (cFBPase), and the light-harvesting chlorophyll (Lhcb1) protein.
A lichenicolous fungus, Dactylospora dobrowolskii Olech et Alstrup, new to science is described. The paper reports on 9 species of lichens and lichenicolous fungi collected in the Bunger Oasis (East Antarctica).