Effects of pigmentation on siloxane–polyurethane coatings and their performance as fouling-release marine coatings

Siloxane–polyurethane paints were formulated and characterized for coating properties and performance as fouling-release (FR) marine coatings. Paints were formulated at 20 and 30 pigment volume concentrations with titanium dioxide, and aminopropyl-terminated poly(dimethylsiloxane) (APT-PDMS) loadings were varied from 0 to 30% based on binder mass. The coatings were characterized for water contact angle, surface energy (SE), gloss, and pseudobarnacle (PB) adhesion. The assessment of the FR performance compared with polyurethane (PU) and silicone standards through the use of laboratory biological assays was also performed. Biofilm retention and adhesion were conducted with the marine bacterium Cellulophaga lytica, and the microalgae diatom Navicula incerta. Live adult barnacle reattachment using Amphibalanus amphitrite was also performed. The pigmented coatings were found to have properties and FR performance similar to those prepared without pigment. However, a higher loading of PDMS was required, in some cases, to obtain the same properties as coatings prepared without pigment. These coatings rely on a self-stratification mechanism to bring the PDMS to the coating surface. The slight reduction in water contact angle (WCA) and increase in pseudobarnacle release force with pigmentation suggests that pigmentation slowed or interfered with the self-stratification mechanism. However, increasing the PDMS loading is an apparent method for overcoming this issue, allowing for coatings having similar properties as those of clear coatings and FR performance similar to those of silicone standard coatings.     

An integrated converter model and enhanced control approach for torque ripple minimisation of switched reluctance motor: a CMFG-RNN technique

ABSTRACT

In this paper, a control mechanism for speed control of switched reluctance motor (SRM) with torque ripple reduction utilising moth flame optimisation algorithm and genetic algorithm with recurrent neural network (CMFG-RNN) is presented. The control mechanism comprises of FOPID speed controller in the external loop and current controller in the internal loop along with control of turn-on and turn-off angles for the SRM. The issue of getting the ideal estimations of proportional, integral and derivative gains for both speed and current controller along with the turn-on and turn-off angles is considered as a multi-objective optimisation problem with the goals of limiting the Integral Squared Error of speed and torque ripple. Simulations of CMFG-RNN-based control of SRM are done utilising SIMULINK/MATLAB software. With a specific end goal to assess the strong execution of CMFG-RNN, the comparison of current, speed, flux and torque under different techniques are considered. The outcomes got by CMFG-RNN are contrasted and validated with ALO and NSGA-II techniques. The outcomes uncover that CMFG-RNN-based controllers give better execution as far as lesser torque ripple and quick settling time because of its systematic random search capabilities, thereby enhancing the dynamic execution of SRM drive.     

Microbial desulphurization of coal containing pyritic sulphur in a continuously operated bench scale coal slurry reactor

Pre-combustion microbial desulphurization of coal containing total sulphur (3.90%) and pyritic sulphur (2.80%) has been evaluated in a coal slurry reactor. The coal slurry reactor operated at hydraulic retention time (HRT) of 96 h with a coal pulp density of 15 percent and remove 79 percent of pyritic sulphur and 76 percent of ash with an increase in the calorific value of coal from 4400 to 6800 kcal kg⁻¹ at a pyritic load of 1.9 kg pyritic sulphur kg⁻¹ MLSS d⁻¹. The treated coal yield is 72 percent. The biochemical kinetic coefficients, viz. yield coefficient (Y) and decay coefficient (K_d) in the coal slurry reactor system are 0.178 and 0.007 d⁻¹, respectively, while maximum growth rate (μ_max) and half saturation rate constant (K_s) are 0.025 h⁻¹ and 0.220 g l⁻¹ as pyrite, respectively.     

EVBlocks: A Blockchain-Based Secure Energy Trading Scheme for Electric Vehicles underlying 5G-V2X Ecosystems

Wireless Personal Communications - In this paper, the authors propose a secure and trusted energy trading (ET) scheme for electric vehicles (EVs) for vehicle-to-anything (V2X) ecosystems. The...     

Recovery of phosphorus and aluminium from sewage sludge ash by a new wet chemical elution process (SESAL-Phos-recovery process)

The potential of a new wet chemical process for phosphorus and aluminium recovery from sewage sludge ash by sequential elution with acidic and alkaline solutions has been investigated: SESAL-Phos (sequential elution of sewage sludge ash for aluminium and phosphorus recovery). Its most innovative aspect is an acidic pre-treatment step in which calcium is leached from the sewage sludge ash. Thus the percentage of alkaline soluble aluminium phosphates is increased from 20 to 67%. This aluminium phosphate is then dissolved in alkali. Subsequently, the dissolved phosphorus is precipitated as calcium phosphate with low heavy metal content and recovered from the alkaline solution. Dissolved aluminium is recovered and may be reused as a precipitant in wastewater treatment plants.     

The effect of formulation variables on fouling-release performance of stratified siloxane–polyurethane coatings

The effects of formulation variables, such as type of polyol, solvent type and solvent content, and coating application method, on the surface properties of siloxane–polyurethane fouling-release coatings were explored. Fouling-release coatings allow the easy removal of marine organisms from a ship’s hull via the application of a shear force to the surface. Self-stratified siloxane–polyurethane coatings are a new approach to a tough fouling-release coating system. Combinatorial High Throughput Experimentation was employed to formulate and characterize 24 different siloxane–polyurethane coatings applied using drawdown and drop-casting methods. The resulting coatings were tested for surface energy using contact angle measurements. The fouling-release performance of the coatings was tested using a number of diverse marine organisms including bacteria (Halomonas pacifica and Cytophaga lytica), sporelings (young plants) of the green macroalga (Ulva linza), diatom ((microalga) Navicula incerta), and barnacle (Amphibalanus amphitrite). The performance of the majority of the coatings was found to be better than the silicone standards, Intersleek^® and Silastic^® T2. An increase in solvent content in the formulations increased the surface roughness of the coatings. Coatings made with polycaprolactone polyol appeared to be somewhat rougher compared to coatings made with the acrylic polyol. The adhesion strength of sporelings of Ulva increased with an increase in solvent content and increase in surface roughness. The adhesion strengths of Ulva sporelings, C. lytica, and N. incerta were independent of application method (cast or drawdown) in contrast to H. pacifica adhesion, which was dependent on the application method.