Composites and coatings based on the Si‒B4C‒ZrB2 glass-forming system modified with carbon-containing materials

2021 ◽  
Vol 1 (7) ◽  
pp. 50-56
Author(s):  
A. N. Nikolaev ◽  
I. B. Ban’kovskaya ◽  
N. N. Rozhkova
Keyword(s):  
Phase Composition ◽  
Surface Morphology ◽  
Thermal Resistance ◽  
High Temperatures ◽  
Glass Forming ◽  
Carbon Additives ◽  
Resistance Tests ◽  
Shungite Carbon ◽  
Properties Of Composites

The paper studies the effect of carbon-containing materials (graphite, shungite carbon and acetylene soot) on the properties of composites and coatings based on the Si‒ B4C‒ZrB2 glass-forming system. Thermogravimetric and differential thermal analyzes, thermal resistance tests were carried out, the phase composition was determined, and the surface morphology of the coatings was also studied. It is shown that with the introduction of carbon additives, the area of the vitrified surface of the coating increases, in connection with this, the resistance of the material to high temperatures and other aggressive media improves.

Microbial-Induced Mineralization of Zinc Ions Based on the Degradation of Toluene and Its Characterization

2021 ◽  
Vol 13 (4) ◽  
pp. 656-661
Author(s):  
Yiyan Lv ◽  
Qiwei Zhan ◽  
Xiaoniu Yu
Keyword(s):  
Particle Size ◽  
Phase Composition ◽  
Surface Morphology ◽  
Organic Compounds ◽  
Low Cost ◽  
Zinc Ion ◽  
Zinc Ions ◽  
Quick Response ◽  
Zinc Carbonate ◽  
Carbonate Ions

Microbial-induced degradation of aromatic organic compounds and mineralization of zinc ions have attracted much attention because of its low cost, simple operation and quick response. This research, toluene was decomposed and made the concentration of carbonate ions increased accordingly by the enzymatic pressing of microorganisms, meanwhile carbonate ions mineralized zinc ions into carbonate precipitations. The composition and microstructure were analyzed systematically. The analysis results indicated that carbonate precipitations, basic zinc carbonate, could be successfully prepared by microbial method. The particle size of basic zinc carbonate was nanometer, and its shape was near-spherical. Furthermore, the phase composition, functional groups and surface morphology of the precipitations prepared by different methods were basically the same. This work provided a new method for remediation of zinc ion pollution based on the degradation of toluene.

Structure, phase composition and mechanical properties of composites based on ZrO2 and multi-walled carbon nanotubes

2020 ◽  
Vol 10 ◽  
pp. 56-68
Author(s):  
A. A. Leonov ◽  
◽  
E. V. Abdulmenova ◽  
M. P. Kalashnikov ◽  
◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Phase Composition ◽  
Zirconium Carbide ◽  
Cubic Phase ◽  
Plasma Sintering ◽  
Multi Walled Carbon Nanotubes ◽  
Spark Plasma ◽  
Walled Carbon Nanotubes ◽  
Tetragonal Phase Transition ◽  
Properties Of Composites

In this work, composites based on yttria-stabilized zirconia (3Y-TZP), with additives of 1, 5 and 10 wt. % multi-walled carbon nanotubes (MWCNTs) were investigated. Samples were obtained by spark plasma sintering at a temperature of 1500 °C. It was found that MWCNTs retain their structure after high-temperature sintering, they are located along the grain boundaries of ZrO2, forming a network structure. Found that the addition of 1 wt. % MWCNTs increase the relative density of the composite from 98.3 % to 99.0 %. It is noted that nanotubes can significantly affect the phase composition of composites. Additive 5 wt. % MWCNT partially limits the monoclinic-tetragonal phase transition of ZrO2, and the addition of 10 wt. % MWCNTs leads to the formation of a cubic phase of zirconium carbide. It was found that the fracture toughness of the composite with 10 wt. % MWCNTs increases from 4.0 to 5.7 MPa·m1/2.

Effect of Al2O3 nanofibers on compaction, phase composition, and mechanical properties of ZrO2-based composites obtained by vacuum pressureless sintering

2021 ◽  
pp. 132-143
Author(s):  
A. A. Leonov ◽  
E. V. Abdulmenova ◽  
M. P. Kalashnikov ◽  
Jing Li
Keyword(s):  
Mechanical Properties ◽  
Phase Composition ◽  
Crack Resistance ◽  
Physicomechanical Properties ◽  
Relative Content ◽  
Pressureless Sintering ◽  
Vacuum Sintering ◽  
Tetragonal Modification ◽  
Different Content ◽  
Properties Of Composites

This work studies the effect of the relative content of Al2O3 nanofibers on the compaction, phase composition, and physicomechanical properties of composites based on ZrO2 obtained by free vacuum sintering. It was found that in the process of manufacturing composites, nanofibers are sintered into Al2O3 grains of complex, elongated shape, which form a solid, frame-reinforcing structure. The relative density of composites with 5 wt. % and 10 wt. % of nanofibers, decreases up to 95%. It is shown that in all sintered samples the tetragonal modification of ZrO2 acts as the main phase, and the different content of nanofibers affects the amount of cubic and monoclinic modifications of ZrO2. It was found that addition of 5 wt. % and 10 wt. % of Al2O3 nanofibers increases the microhardness of the composite by 11% and crack resistance by 46%.

scholarly journals Thermal Resistance and Gene Expression of both Desiccation-Adapted and Rehydrated Salmonella enterica Serovar Typhimurium Cells in Aged Broiler Litter

2017 ◽  
Vol 83 (12) ◽  
Author(s):  
Zhao Chen ◽  
Xiuping Jiang
Keyword(s):  
Gene Expression ◽  
Heat Treatment ◽  
Thermal Resistance ◽  
High Temperatures ◽  
Human Pathogens ◽  
Wild Type ◽  
Broiler Litter ◽  
Content Type ◽  
Serovar Typhimurium ◽  
Trehalose Synthesis

ABSTRACT The objective of this study was to investigate the thermal resistance and gene expression of both desiccation-adapted and rehydrated Salmonella enterica serovar Typhimurium cells in aged broiler litter. S. Typhimurium was desiccation adapted in aged broiler litter with a 20% moisture content (water activity [aw], 0.81) for 1, 2, 3, 12, or 24 h at room temperature and then rehydrated for 3 h. As analyzed by quantitative real-time reverse transcriptase PCR (qRT-PCR), the rpoS, proV, dnaK, and grpE genes were upregulated (P < 0.05) under desiccation stress and could be induced after 1 h but in less than 2 h. Following rehydration, fold changes in the levels of these four genes became significantly lower (P < 0.05). The desiccation-adapted ΔrpoS mutant was less heat resistant at 75°C than was the desiccation-adapted wild type (P < 0.05), whereas there were no differences in heat resistance between desiccation-adapted mutants in two nonregulated genes (otsA and PagfD) and the desiccation-adapted wild type (P > 0.05). Survival characteristics of the desiccation-adapted ΔPagfD (rdar [red, dry, and rough] morphotype) and ΔagfD (saw [smooth and white] morphotype) mutants were similar (P > 0.05). Trehalose synthesis in the desiccation-adapted wild type was not induced compared to a nonadapted control (P > 0.05). Our results demonstrated the importance of the rpoS, proV, dnaK, and grpE genes in the desiccation survival of S. Typhimurium. By using an ΔrpoS mutant, we found that the rpoS gene was involved in the cross-protection of desiccation-adapted S. Typhimurium against high temperatures, while trehalose synthesis or rdar morphology did not play a significant role in this phenomenon. In summary, S. Typhimurium could respond rapidly to low-aw conditions in aged broiler litter while developing cross-protection against high temperatures, but this process could be reversed upon rehydration. IMPORTANCE Physical heat treatment is effective in eliminating human pathogens from poultry litter used as biological soil amendments. However, prior to physical heat treatment, some populations of microorganisms may be adapted to the stressful conditions in poultry litter during composting or stockpiling, which may cross-protect them against subsequent high temperatures. Our previous study demonstrated that desiccation-adapted S. enterica cells in aged broiler litter exhibited enhanced thermal resistance. However, there is limited research on the underlying mechanisms of the extended survival of pathogens under desiccation conditions in animal wastes and cross-tolerance to subsequent heat treatment. Moreover, no information is available about the thermal resistance of desiccation-adapted microorganisms in response to rehydration. Therefore, in the present study, we investigated the gene expression and thermal resistance of both desiccation-adapted and rehydrated S. Typhimurium in aged broiler litter. This work will guide future research efforts to control human pathogens in animal wastes used as biological soil amendments.

The Heat Resistance of Spores of Clostridium botulinum 213B Heated at 121–130°C in Acidified Mushroom Extract

1992 ◽  
Vol 55 (11) ◽  
pp. 913-915 ◽  
Author(s):  
K. L. BROWN ◽  
A. MARTINEZ
Keyword(s):  
Citric Acid ◽  
Thermal Resistance ◽  
Heat Resistance ◽  
High Temperatures ◽  
Clostridium Botulinum ◽  
Mushroom Extract ◽  
D Values

Spores of Clostridium botulinum 213B were heated in mushroom extract acidified to pH 6 with citric acid or glucono-deltalactone at temperatures of 121.1, 125, and 130°C using a thermoresistometer. Decimal reduction times were similar in acidified and natural pH (6.7) mushroom extract. At 121.1, 125, and 130°C, D values were in the range 2.44 – 2.55 s, 0.91–1.45 s, and 0.51–0.75 s, respectively. There was no evidence that mild acidification reduced thermal resistance at high temperatures.

Structure and Corrosion Resistance of Iron Coatings Containing Silicon Powders

2011 ◽  
Vol 399-401 ◽  
pp. 1926-1931 ◽  
Author(s):  
Yi Wang ◽  
Gang Chen ◽  
Wei Dong Liu ◽  
Qiong Yu Zhou ◽  
Qing Dong Zhong
Keyword(s):  
Corrosion Resistance ◽  
Phase Composition ◽  
Thermal Treatment ◽  
Surface Morphology ◽  
Electrochemical Impedance ◽  
Electrochemical Corrosion ◽  
Active Surface ◽  
Active Surface Area ◽  
Two Phase ◽  
Electrochemical Corrosion Resistance

Fe + Si coatings were prepared by iron deposition from a bath containing a suspension of silicon powders. These coatings were obtained at galvanostatic conditions, at the current density of jdep=−0.020 A cm−2 and at the temperature of 338 K. For determination of the influence of phase composition and surface morphology of these coatings on changes in the corrosion resistance, these coatings were modified in an argon atmosphere by thermal treatment at 873 K for 2h. A scanning electron microscope was used for surface morphology characterization of the coatings. The chemical composition of the coatings was determined by EDS and phase composition investigations were conducted by X-ray diffraction. It was found that the as-deposited coatings consist of a two-phase structure, i.e., iron and silicon. The phase composition for the Fe + Si coatings after thermal treatment is markedly different. The main peaks corresponding to Fe and Si coexist with the new phases: FeSi. Electrochemical corrosion resistance investigations were carried out in 3.5wt% NaCl, using potentiodynamic and electrochemical impedance spectroscopy (EIS) methods. On the basis of these investigations it was found that the Fe + Si coatings after thermal treatment are more corrosion resistant in 3.5wt% NaCl solution than the as-deposited coatings. The reasons for this are a reduction in the amount of free iron and silicon, the presence of new phases (in particular silicides), and a decrease of the active surface area of the coatings after thermal treatment.

Sign in / Sign up

Export Citation Format

Share Document