Fouling tendency of ash resulting from burning mixtures of biofuels. Part 1: Deposition rates

Specified mixtures of peat with bark and peat with straw were burned in a lab-scale entrained flow reactor that simulates conditions in the superheater region of a conventional biomass-fired boiler. The deposition rates were recorded on an air-cooled probe that was inserted into the reactor at the outlet. For both mixtures, the deposition behaviour followed a non-linear pattern, which suggests that physico-chemical interaction between the types of ash has taken place. Peat seems to act as a cleansing agent in all mixtures with straw, while it acts as a cleansing agent in mixtures with bark only up to a share of 50 wt% bark. Between 50 and 100 wt% bark, it seems that peat adds to the deposition. The results indicate that it is possible to burn up to 30 wt% bark (renewable biofuel and pulp mill waste) and up to 70 wt% straw (renewable biofuel and agricultural waste) in mixtures with peat (CO₂-neutral fossil fuel) without encountering increased deposition rates.     

Enhanced field emission from nano-graphite coated carbon nanotubes

An effective method by low energy carbonhydrogen ion treatment to enhance field emission of the carbon nanotubes (CNTs) is demonstrated. Comparing with control, field emission (FE) currents of the CNTs by carbonhydrogen ion irradiation increased, and the turn-on field and the threshold field decreased significantly. The structure characteristic revealed by transmission electron microscopy demonstrates that CNTs are coated by nano-graphite particles after being treated with low energy carbonhydrogen ion and that there are large quantities of defects and grain boundaries in the coated layer. It is considered that the coating layer can decrease the effective surface work function of CNTs and correspondingly increase field emission. In addition, the defects, the grain boundaries and the C-H dipoles forming in the process of the low energy ions irradiation can effectively enhance the field emission.     

Co3O4/Bi2O3纳米粒子气相光催化降解甲苯的研究

采用微乳法及化学沉淀法制备了复合氧化物Co3O4/Bi2O3纳米粒子，结果表明，微乳法制备的复合氧化物Co3O4/Bi2O3粒子光催化活性更好；活性的提高程度与n（Co）：n（Bi）有关，其最佳配比为0．02：1；随着焙烧温度的增加，光催化活性提高，750℃焙烧的样品催化活性最好。以甲苯为目标反应物，考察了光照强度、甲苯的初始浓度、气相氧浓度、水蒸气含量对甲苯光催化降解反应速率的影响。     

Enhanced emission and improved thermal stability of BaMgAl10O17:Eu2+ phosphor via additional Mg2+ doping

BaMgAl₁₀O₁₇:Eu²⁺ doped with 0–6% additional Mg²⁺ were synthesized by co-precipitation method. Their photoluminescence and thermal stability were investigated under ultraviolet (UV) and vacuum ultraviolet (VUV) excitation. The additional Mg²⁺-doped samples exhibited stronger emission intensity and better thermal stability than the sample without additional Mg²⁺ under 254 or 147 nm excitation. After thermal degradation, the 4% additional Mg²⁺-doped sample had the highest emission intensity which was 12.7% and 16.6% stronger than that of the sample without additional Mg²⁺ under 254 and 147 nm excitation, respectively. Moreover, the improvement mechanisms on emission intensity and thermal stability were discussed.     

Predicting mechanical strength loss of natural stones after freeze–thaw in cold regions

Natural stones are generally used as building materials for construction and decoration. Determining the deteriorations of stones after freeze–thaw cycles is important subject for natural building stones used in cold regions exposed excessive freezing and thawing during the year. Freeze–thaw test is conducted for determining the deteriorations of stones due to freeze–thaw cycling. The percentage loss in uniaxial compression strength is an important parameter indicating these deteriorations. However, it is extremely laborious and time consuming tests. Because of this, predicting the percentage loss values in uniaxial compression strengths from intact rock properties was the purpose of this paper. Freeze–thaw tests were applied on nine limestone samples selected from different cold regions of Turkey. All of them except two samples were found to be suitable for use in cold regions. A statistical model was developed for predicting the percentage loss values in uniaxial compression strength from intact tests of impact strength, modulus of elasticity and water absorption. This model equation is very reliable (R² = 0.95) and can be very useful for predetermination of uniaxial compression strengths of limestones after freeze–thaw test without testing.     

Effect of method of preparation on properties of temperature and pH-sensitive gels: Chemical crosslinking versus irradiation with e-beam

Two problems that have impeded a broader application of polyelectrolytic smart polymers are their low speed of response and their faulty behavior in the presence of salts. To contribute to the solution of those problems we prepared two series of gels based on N-isopropylacrylamide (NIPAAm) containing ampholytic units using chemical crosslinking methods and electron beam irradiation. In the first method, the gels prepared contain NIPAAm, N-N′-dimethylaminoethylmethacrylate (DMAEM) and a methacrylate of the ortho-, meta- or para-benzoic acid, respectively, to impart amphoteric behavior. They were crosslinked using N-N′-methylenebisacrylamide (BIS) as crosslinker by standard free-radical techniques. In the second method aqueous solutions containing mixtures of polyNIPAAm and charge balanced copolymers of DMAEM with the methacrylates of the ortho-, meta- and para-benzoic acid, respectively, prepared previously, were irradiated by e-beam. Both series were characterized by DSC, mechanical compression and swelling–shrinking tests in deionized water, buffers solutions at different pH-values and in water having different salt concentrations. The results show that the gels prepared by irradiation have a swelling degree up to four times higher than that of the gels prepared by chemical crosslinking, furthermore, their shrinking velocity is up to twenty times higher than that of gels prepared by chemical crosslinking. The results also showed that the gels prepared by chemical crosslinking using monomers show only polyelectrolyte behavior, while those prepared by e-beam irradiation of polymer solutions show in fact amphoteric behavior; while all gels retained their temperature sensitivity between 32 and 39 °C.     

Inhibition effect of 2-amino-4-methylpyridine on mild steel corrosion: Experimental and theoretical investigation

The effect of 2-amino-4-methylpyridine (AMP) on the corrosion behavior of mild steel (MS) in 0.5 M HCl is investigated with electrochemical methods and theoretical calculations. The electrochemical tests show that the polarization resistance of MS increasing the presence of AMP in acid solution. Adsorption of AMP on MS surface is a physical and obeys the Langmuir isotherm. The quantum parameters signaled adsorption occurs on amine and methyl substituents of AMP. The inhibition efficiency is related to frontier orbital’s energy band gap of AMP, which are 5.357 and 6.490 eV for neutral and protonated molecules in aqueous solution, respectively.     

Mesoporous yolk-shell structure Bi2MoO6 microspheres with enhanced visible light photocatalytic activity

Mesoporous yolk-shell structure Bi₂MoO₆ (BMO-YS) microspheres were successfully synthesized via a facile solvothermal route in Bi₂MoO₆ precursor solution. The morphology, structure and photocatalytic performance of the BMO-YS in the degradation of Rhodamine B (RhB) were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, nitrogen adsorption–desorption, UV–vis absorption spectroscopy and electrochemical impedance spectra, respectively. The as-prepared BMO-YS mainly consists of microspheres with diameters of about 1.5 μm. The photocatalytic studies reveal that the BMO-YS not only exhibits optimum photocatalytic performance, which may be attributed to the excellent charge separation characteristics and the enhanced light absorption offered by its unique yolk-shell structure, but also possesses excellent recyclability for photocatalysis.