Ludwigite is the main available boron-bearing resource in China. In order to enrich the theory system and optimize its utilization processes, this paper study the mechanism and kinetics on non-isothermal decomposition of ludwigite in inert atmosphere by means of thermal analysis. Results show that, the decomposition of serpentine and szajbelyite is the main cause of mass loss in the process. At the end of decomposition, hortonolite and ludwigite are the two main phases in the sample. The average E value of structural water decomposition is 277.97 kJ/mol based on FWO method (277.17 kJ/mol based on KAS method). The results is proved to be accurate and reliable. The mechanism model function of structural water decomposition is confirmed by Satava method and Popescu method. The form of the most probable model function is G(α) = (1 – α)–1 – 1 (integral form) and f (α) = (1 – α)2 (differential form), and its mechanism is chemical reaction. This is verified by the criterion based on activation energy of model-free kinetics analysis.
This paper shows the possibility that the mineral coal existing in the mining basins of northern Spain have a high added value. This would facilitate its future use in different fields such as new materials, nanotechnology, energy use in situ, coal bed methane, enhanced coal bed methane and coalmine methane.
An analytical study of mineral coal samples is carried out. The samples come from two deposits located in coal basins of the Cantabrian Mountains. The duly prepared samples are subjected to an activation process. Within this transformation, different treatments are applied to different sub-samples. Some of the sub-samples suffer a previous demineralization by successive attacks with acids, followed by oxidation and pyrolysis. Finally, all of them are activated with CO2 and H2O(steam).
The carbonaceous products resulting from each treatment are characterised. The results show that all the pre-treatments used were positive for the textural development of the materials. Likewise, proper management of the processes and of the different operating variables allows the procurement of carbonaceous materials with a “tailor-made” structural development of the coal type. This material receives the name “activated” and can be employed in specific processes.
Passive noise reduction methods require thick and heavy barriers to be effective for low frequencies and those clasical ones are thus not suitable for reduction of low frequency noise generated by devices. Active noise-cancelling casings, where casing walls vibrations are actively controlled, are an interesting alternative that can provide much higher low-frequency noise reduction. Such systems, compared to classical ANC systems, can provide not only local, but also global noise reduction, which is highly expected for most applications. For effective control of casing vibrations a large number of actuators is required. Additionally, a high number of error sensors, usually microphones that measure noise emission from the device, is also required. All actuators have an effect on all error sensors, and the control system must take into account all paths, from each actuator to each error sensor. The Multiple Error FXLMS has very high computational requirements. To reduce it a Switched-Error FXLMS, where only one error signal is used at the given time, have been proposed. This, however, significantly reduces convergence rate. In this paper an algorithm that uses multiple errors at once, but not all, is proposed. The performance of various algorithm variants is compared using simulations with the models obtained from real active-noise cancelling casing.
Tires play an important role in the automobile industry. However, their disposal when worn out has adverse effects on the environment. The main aim of this study was to prepare activated carbon from waste tire pyrolysis char by impregnating KOH onto pyrolytic char. Adsorption studies on lead onto chemically activated carbon were carried out using response surface methodology. The effect of process parameters such as temperature (°C), adsorbent dosage (g/100 ml), pH, contact time (minutes) and initial lead concentration (mg/l) on the adsorption capacity were investigated. It was found out that the adsorption capacity increased with an increase in adsorbent dosage, contact time, pH, and decreased with an increase in lead concentration and temperature. Optimization of the process variables was done using a numerical optimization method. Fourier Transform Infrared Spectra (FTIR) analysis, X-ray Diffraction (XRD), Thermogravimetric analysis (TGA) and scanning electron microscope were used to characterize the pyrolytic carbon char before and after activation. The numerical optimization analysis results showed that the maximum adsorption capacity of
93.176 mg/g was obtained at adsorbent dosage of 0.97 g/100 ml, pH 7, contact time of 115.27 min, initial metal concentration of 100 mg/and temperature of 25°C. FTIR and TGA analysis showed the presence of oxygen containing functional groups on the surface of the activated carbon produced and that the weight loss during the activation step was negligible.
The five-layer Aurivillius type structures with the general chemical formula Bi5Fe2-xMnxTi3O18, where x = 0, 0.6, 1.2 have been synthesized and tested. The SEM studies showed a significant increase in grain size in the manganese-modified Aurivillius type ceramic material (for x = 1.2). The increase in the amount of manganese ions (Mn3+) affects the decrease in the temperature at which the relaxation processes take place. Namely from 525 K (1 kHz) and 725 K (1 MHz) for BFT sample (x = 0) to 355 K (1 kHz) and 565 K (1 MHz) for BFM12T sample (x = 1.2). Using the Arrhenius’s law and the Vogel-Fulcher’s relationship the activation energy (Ea) and the relaxation time have been calculated. The value of Ea increases with the increase of the Mn amount from 0.737 eV (for x = 0) to 0.915 eV (for x = 1.2).
Nil strength temperature of 1062°C and nil ductility temperature of 1040°C were experimentally set for CuFe2 alloy. The highest formability at approx. 1020°C is unusable due to massive grain coarsening. The local minimum of ductility around the temperature 910°C is probably due to minor formation of γ-iron. In the forming temperatures interval 650-950°C and strain rate 0.1-10 s–1 the flow stress curves were obtained and after their analysis hot deformation activation energy of 380 kJ·mol–1 was achieved. Peak stress and corresponding peak strain values were mathematically described with good accuracy by equations depending on Zener-Hollomon parameter.
In the current study, the hot deformation of medium carbon V-Ti micro-alloyed steel was surveyed in the temperature range of 950 to 1150°C and strain rate range of 0.001 to 1 s–1 after preheating up to 1200°C with a compression test. In all cases of hot deformation, dynamic recrystallization took place. The influence of strain rate and deformation temperature on flow stress was analyzed. An increase in the strain rate and decrease in the deformation temperature postponed the dynamic recrystallization and increased the flow stress. The material constants of micro-alloyed steel were calculated based on the constitutive equations and Zener-Hollomon parameters. The activation energy of hot deformation was determined to be 458.75 kJ/mol, which is higher than austenite lattice self-diffusion activation energy. To study the influence of precipitation on dynamic recrystallization, the stress relaxation test was carried out in a temperature range of 950 to 1150°C after preheating up to 1200°C. The results showed no a stress drop while representing the interaction of particles with dynamic recrystallization.
This paper aims to show the effect of activation method of tyre pyrolysis char (TPC) on adsorption of bisphenol A (BPA) from aqueous solutions. The TPC was produced from end-of-life-tyres (ELT) feedstock in a pilot plant at 773 K. Activation was accomplished using two classical methods: physical activation withCO2 and chemical activation withKOH. The two produced adsorbents had pores ranging from micro- to macropores. Distinct differences in the BET surface areas and pore volumes between the adsorbents were displayed showing better performance of the chemically activated adsorbent for adsorption of BPA from water.
The results of the kinetic studies showed that the adsorption of BPA followed pseudo-second-order kinetic model. The Freundlich, Langmuir, Langmuir–Freundlich and Redlich–Peterson isotherm equations were used for description of the adsorption data. The Langmuir–Freundlich isotherm model best fits the experimental data for the BPA adsorption on both adsorbents. The Langmuir–Freundlich monolayer adsorption capacity, qmLF, obtained for the CO2-activated tyre pyrolysis char (AP-CO2) and KOH-activated tyre pyrolysis char (AP-KOH) were 0.473 and 0.969 mmol g��1, respectively.
A. B. Dobrowolski, a member of the Belgian expedition in Belgica to West Antarctica (1897-1899), after his return home became a strong supporter of Polish scientific activity in the Polar countries. His patronage - called by him the "Polar Action", was especially well marked during organization of three Polish expeditions to the Svalbard archipelago: to Bear Island during the 2nd Polar Year, 1932-33 and to Spitsbergen in 1934 and 1938. Apart from his scientific achievements in Antarctica, Dobrowolski was also widely known as an author of popular-scientific books on history of discovery and exploration in the Arctic and the Antarctic.