Investigation of the effect of the grain sizes on the dynamic strength of the fine-grained alumina ceramics obtained by Spark Plasma Sintering

The results of dynamic strength tests of the alumina ceramics with various grain sizes are presented. The ceramics were obtained by Spark Plasma Sintering (SPS) of industrial submicron and fine Al2O3 powders. The heating up was performed with the rate of 10 oC/min; the grain sizes in the ceramics was controlled by varying the SPS temperature and the heating rate as well as by varying the initial sizes of the Al2O3 particles in the powders. The ceramics had a high density (over 98%) and a uniform fine-grained microstructure (the mean grain sizes varied from 0.8 to 13.4 mkm). The dynamic compressing tests were carried out by modified Kolsky method with using split Hopkinson pressure bar. The tests were performed at room temperature using a 20-mm PG-20 gas gun with the strain rate of ~10^3 s-1. The dependence of the dynamic ultimate strength of alumina on the grain size was found for the first time to have a non-monotonous character (with a maximum). The maximum value of the dynamic ultimate compression strength (SY = 1060 MPa) was provided at the mean grain size of ~2.9-3 mkm. The reduction of SY for alumina in the range of submicron grain sizes was shown to originate from the reduction of the relative density of the ceramics sintered at lower SPS temperatures.Comment: 16 pages, 1 table, 6 figures, 28 reference

African swine fever in the Primorsky Krai: disease situation and molecular and biological properties of the isolate recovered from a wild boar long bone

It is necessary to continue the analysis of the situation and molecular and biological properties of the current African swine fever virus isolates, recovered in the Russian border territories to cover the following tasks: eradication of African swine fever; development of effective disease surveillance and control programs; search for promising genome markers for the vaccine development; implementation of the differentiation strategy between vaccinated and non-vaccinated animals; and clustering of the isolates. The post-hoc analysis of some ASF epidemiological data and comparative genetic analysis of isolates circulating in the Far East Federal District suggested the agent introduction and spread routes, as well as the seasonality of the infection occurrence in the Primorsky Krai. It was established, that two ASFV subgenotypes (IGR-I и IGR-II), differentiated by intergenic region I73R/I329L, circulated in the region under study during the first months post infection. Analysis of biological properties of ASFV/Primorsky 19/WB-6723 isolate recovered from the long bone of a dead wild boar in the Primorsky Krai suggested that the isolate is highly virulent, able to cause peracute to subacute disease and up to 100% mortality among infected animals. The incubation period and duration of the disease course in experimentally infected pigs were 4–6 and 3–5 days post infection, respectively. The ASFV genome was detected in blood samples collected from infected pigs on 5–8 days post infection by real-time polymerase chain reaction. Specific antibodies in blood samples were not detected. The need in further research of molecular and biological properties of current ASFV isolates was reaffirmed. To prevent the continuation of the epizooty and deterioration of the current situation the approaches to the disease surveillance and control need to be modified

Techniques of blood sampling for detection of African swine fever virus in wild boar and domestic pigs in the field conditions

It is thought that due to the high virulence of the African swine fever virus its circulation in the Russian Federation is accompanied by a low seroprevalence. However taking into account a long-term ASF unfavourable situation, the introduction of the virus into the wild boar population, and the occurrence of attenuated viral variants, the significance of serological testing aimed at the detection of viral antibodies is increasing. To collect field samples of biological material from animals for molecular genetic, virological, and serological tests, filter paper, as well as swabs, can be used. The specificity and sensitivity of enzyme-linked immunosorbent assay when testing blood absorbed by filter paper are worse than those shown when testing sera, but they allow effective detection of African swine fever virus antibodies. It was demonstrated that blood absorbed on filter paper can be used for the immunoblot analysis, but the optimum performance could be achieved when the immunoperoxidase technique in combination with samples, taken by swabs was used. When comparing results of enzyme-linked immunosorbent assay performed on sera collected from domestic pigs (infected with ASFV isolates Antonovo 07/14 and Sobinka 07/15), and blood from ear veins absorbed on filter paper the sensitivity was 88.9%, specificity – 90.6%. However, the use of the immunoperoxidase technique for testing blood from swabs showed 100% coincidence with ELISA, while testing of sera with immunoperoxidase technique was superior to ELISA in sensitivity. This means blood sampling using swabs may be recommended for tests after proper validation. This technique can be especially useful for collecting data about infected wild boars because effective eradication strategies are impossible without such data

Effect of grain boundary state and grain size on the microstructure and mechanical properties of alumina obtained by SPS: A case of the amorphous layer on particle surface

The effect of temperature modes and heating rates (Vh) on the shrinkage kinetics of submicron and fine aluminum oxide powders has been studied. The objects of research comprised (i) submicron alfa-Al2O3 powder, (ii) submicron alfa-Al2O3 powder with an amorphous layer on particle surface, (iii) fine alfa-Al2O3 powder. The alumina ceramic specimens were produced by Spark Plasma Sintering (SPS). Equally fine powders (i) and (ii) were used to analyze the effect of an amorphous layer on sintering kinetics. Powders (i) and (iii) were used to analyze the effect of the initial particle size on shrinkage kinetics. Shrinkage curves were analyzed using the Young-Cutler and Coble models. It has been shown that sintering kinetics is determined by the intensity of grain boundary diffusion for submicron powders and by simultaneous lattice and grain boundary diffusion for fine powders. It has been determined that an amorphous layer on the surface of submicron alfa-Al2O3 powder affects grain boundary migration rate and the Coble equation parameters at SPS final stages. It has been suggested that abnormal characteristics of the alumina ceramics sintered from a submicron powder with an amorphous layer on the particle surface are associated with an increased concentration of defects at grain boundaries that were formed during crystallization of the amorphous layer.Comment: 62 pages, 20 figures, 5 tables, 67 reference

Effect of pig serum storage conditions on detection of anti-ASFV antibodies by ELISA

One of the measures used to control and prevent African swine fever spread in the Russian Federation involves testing pig and boar sera using inter alia serological tools based on enzyme-linked immunosorbent assay (ELISA) for anti-viral antibody detection. However, there is no unified regulatory document specifying storage conditions for sera used in the ELISA for anti-ASFV antibody detection. There are also lack of published data on the maximum admissible shelf life of the pig sera, and the effect of storage conditions on the serological status of the pig sera as for ASF is understudied. The paper demonstrates results of the experiment aimed at the determination of the effect of storage temperatures and shelf life on the serological status of ASFV seropositive and seronegative pig sera when tested by INgezim PPA Compac (Ingenasa, Spain) ELISA as well as on the possibility of false results. During the experiment and analysis of its results, the new data were obtained, and they indicated from none to non-significant effect of the simulated storage conditions on the serological status of sera used for ASFV detection, while hemolyzed sera demonstrated more significant changes proportional to hemolysis degree and storage duration. Although the results of detection of antibodies against the agents of some diseases cannot be used in case of other pathogens, this study has a substantial applied significance as it allows to specify the dependence of the valid results of ASF serodiagnosis on the storage conditions of the samples

Effect of Sc, Hf, and Yb Additions on Superplasticity of a Fine-Grained Al-0.4%Zr Alloy

This research was undertaken to study the way deformation behaves in ultrafine-grained (UFG)-conducting Al-Zr alloys doped with Sc, Hf, and Yb. All in all, eight alloys were studied with zirconium partially replaced by Sc, Hf, and/or Yb. Doping elements (X = Zr, Sc, Hf, Yb) in the alloys totaled 0.4 wt.%. The choice of doping elements was conditioned by the possible precipitation of Al3X particles with L12 structure in the course of annealing these alloys. Such particles provide higher thermal stability of a nonequilibrium UFG microstructure. Initial coarse-grained samples were obtained by induction casting. A UFG microstructure in the alloys was formed by equal-channel angular pressing (ECAP) at 225 °C. Superplasticity tests were carried out at temperatures ranging from 300 to 500 °C and strain rates varying between 3.3 × 10−4 and 3.3 × 10−1 s−1. The highest values of elongation to failure are observed in Sc-doped alloys. A UFG Al-0.2%Zr-0.1%Sc-0.1%Hf alloy has maximum ductility: at 450 °C and a strain rate of 3.3 × 10−3 s−1, relative elongation to failure reaches 765%. At the onset of superplasticity, stress (σ)–strain (ε) curves are characterized by a stage of homogeneous (uniform) strain and a long stage of localized plastic flow. The dependence of homogeneous (uniform) strain (εeq) on test temperature in UFG Sc-doped alloys is increasing uniformly, which is not the case for other UFG alloys, with εeq(T) dependence peaking at 350–400 °C. The strain rate sensitivity coefficient of flow stress m is small and does not exceed 0.26–0.3 at 400–500 °C. In UFG alloys containing no Sc, the m coefficient is observed to go down to 0.12–0.18 at 500 °C. It has been suggested that lower m values are driven by intensive grain growth and pore formation in large Al3X particles, which develop specifically at an ingot crystallization stage