Microstructure evolution and phase transformation of ZrB2-45MoSi2-10Al coating at high temperature

The ZrB2-45MoSi2-10Al coating was prepared by a Robotic complex for detonation spraying of coatings equipped with a multi-chamber detonation accelerator on surface of carbon/carbon composites without adhesion sublayer. The coating has a lamella-type structure typical for gas-thermal coatings, well connected with C/C composite substrate without sublayer, and composed of m-ZrO2, t-ZrO2, t-MoSi2, some h-ZrB2, and c-Al phases. Heat treatment of the samples at 1500 °C for 1, 3 and 6 h was carried out in air. The effect of heat treatment on the microstructure and phase composition of the ZrB2-45MoSi2-10Al coating was investigated by X-ray diffraction and scanning electron microscopy. The c-ZrO2 and h-(α-Al2O3) were formed after oxidation at 1500 °C for 6 h. The uniform distribution of ZrO2 ceramic particles and the formation of a-Al2O3 enhanced the thermal stability of the coating. The coating after heat treatment (1, 3 and 6 h) exhibited structure without cracks and low porosity. The dense microstructure of the coating contributed to its good oxidation-resistant property at high temperature.

Assessing the Nutrient Quality of Biofertilizer Produced from Organic Waste Using Lysinibacillus Macroides and Alcaligens Faecalis

Biofertilizers are ecofriendly fertilizers that are produced via degradation of wastes by microorganisms. The efficiency of Lynsibacillus macroides and Alcaligens faecalis in the production of fertilizer from organic wastes was evaluated. The bacterial isolates were isolated from soil samples collected from fallow patch of land in the Rivers State University farm using standard microbiological methods. The test bacteria were identified by conventional and molecular techniques. Organic wastes including cassava peels, elephant grass and poultry droppings used in this study were collected from the Rivers State University Farm. Three experimental treatments were used in this study; treatment 1 contains 300g of the composite substrate without any organisms and served as control, treatment 2 contains 300g of the composite substrate and 200ml of Lynsibacillus macroides while treatment 3 contains 300g of the composite substrate and 200ml of Alcaligenes faecalis. The treatments were allowed to degrade for 10 days. The pH, temperature, nitrogen, phosphorus, potassium and total organic carbon were determined using standard analytical method. Means of physicochemical parameters in treatment 1, 2 and 3, respectively were: pH 8.3±0.7, 8.6±0.4 and 9.0±0.3; Nitrogen: 2.63±0.08, 1.97±0.03 and 1.51±0.01; phosphorus: 4.71±0.01, 4.43±0.01 and 3.52±0.02; potassium: 604.10±2.12, 591.00±1.41421 and 504.20±2.83; total organic carbon: 31.75±0.78, 23.04±0.04 and 17.56±0.01 mg/kg. The treatment which was supplemented with Lysinbacillus macroides produced more nitrogen, phosphorus, potassium and total organic carbon than treatment which was supplemented with A. faecalis. Statistical analysis showed that there was no significant difference (P≤ 0.05) between the quantity of nitrogen produced by L. macroides and A. faecalis. Although the amount of nitrogen produced by both organisms were significantly different from the control. More so, statistical analysis showed that the quantity of phosphorus, potassium and total organic carbon produced by L. macroides was significantly higher (P≤ 0.05) than those produced by A. faecalis and the control. Thus, Lynsibacillus macroides is a better biofertilizer producer than A. faecalis.

Functional Coatings for Damage Detection in Aerospace Structures

The future of aerospace structures is highly dependent on the advancement of reliable and high-performance materials, such as composite materials and metals. Innovation in high resolution non-invasive evaluation of these materials is needed for their qualification and monitoring for structural integrity. Aluminum oxide (or α-alumina) nanoparticles present photoluminescent properties that allow stress and damage sensing via photoluminescence piezospectroscopy. This work describes how these nanoparticles are added into a polymer matrix to create functional coatings that monitor the damage of the underlying composite or metallic substrates. Different volume fractions of α-alumina nanoparticles in the piezospectroscopic coatings were studied for determining the sensitivity of the coatings and successful damage detection was demonstrated for an open-hole tension composite substrate as well as 2024 aluminum tensile substrates with a subsurface notch.