Study of the gradual degradation of ZnSe-containing multilayer nanostructures—active elements of electron-beam and optical pumping lasers

The gradual degradation of green-range pulse lasers based on ZnSe-containing quantum-well structures with optical and electron-beam pumping has been investigated. The operation of the lasers over several hours without decreasing the output power (with the active elements at room temperature and a pulse repetition rate of 50 Hz) has been shown.     

Irradiation effect on the activation energy of thermal decomposition of polymers

The present work looks into the aspect of thermal modifications induced in polymers by proton irradiation. The kinetics of thermal decomposition of polymers is investigated by using the thermogravimetric (TG) technique. It has been observed that the degradation of polymers is a multi-step process that involves sequential and competing processes, and obeys the Arrhenius kinetics which allows us to connect the rate constant with the absolute temperature and the activation energy. The activation energy of thermal decomposition has been calculated from the TG curves, and its variation with different irradiation doses has been derived.     

聚丙烯/抗老化剂复合体系的γ-射线辐照降解研究

研究了聚丙烯(PP)及含有受阻酚类抗氧剂和受阻胺类光稳定剂复合体系的PP复合物经过γ-射线辐照后发生的结构变化及抗老化剂所起作用。实验利用红外光谱(FTIR)和示差扫描量热法(DSC)对PP的结构变化进行了系统表征。研究结果表明,当辐照剂量较小(50 kGy)时,纯PP及其复合物体系均未发生明显降解;当辐照剂量较大(≥50 kGy)时,PP及其复合物的羰基指数迅速提高,二者的结晶温度和熔融温度大幅度降低,说明PP发生了严重降解。在相同γ-射线辐照剂量条件下(≥50 kGy),PP复合物的羰基指数高于纯PP,而结晶温度以及熔融温度低于纯PP,表明高辐照剂量下抗老化剂复合物的存在不但没有阻止聚丙烯的降解,反而加快了降解的速率。     

Ultrasonic degradation of poly(vinyl alcohol) in aqueous solution

Solution of poly(vinyl alcohol) in water with different concentrations (by weight 1%, 1.5%, 2%) and different volumes (50, 75 and 100 ml) were subjected to ultrasonic degradation. A method of viscometry was used to study the degradation behavior and kinetic model was developed to estimate the degradation rate constant. The degradation rate constant was correlated with the power input due to ultrasonic irradiation and reaction volume. It was found that rate constant decreases as the reaction volume and concentration increases. The proportionality index of the relation between rate constant, power input and reaction volume was found to be nearly equal for all concentrations studied. The proportionality constant was found to be approximately equal for 1% and 1.5% solution and for 2% solution it was approximately half the value for that of 1% and 1.5% solutions. The decrease in rate constant and proportionality constant is attributed to the fact that at higher concentration and at higher volume, the intensity of cavitation phenomenon is depressed and therefore the extent of polymer chain breaking decreases. The difference in the values of limiting viscosities (constant solution viscosity which does not decrease by further ultrasonic irradiation) for 50, 75 and 100 ml solutions for each of 1% and 1.5% concentration was negligible. But 2% solution at 100 ml volume showed slightly higher value of limiting viscosity than that for 50 and 75 ml.     

Crystalline structure and its effects on the degradation of linear calcium polyphosphate bone substitute

Calcium polyphosphate (CPP) bone substitutes were prepared by gravity sintering crystal transformations. The crystalline structure of CPP was analyzed by Raman spectroscopy and in situ variable temperature XRD. In addition, the variation of CPP in SBF considering as degradation was characterized by monitoring the changes of its compressive strength and weight loss. The results revealed that CPP was inorganic condensed phosphate with linear long chain structure. Amorphous CPP (a-CPP) was initially transformed to crystalline γ-CPP, then crystalline β-CPP with the increase of sintering temperature. The transformation of γ-CPP to β-CPP occurred from 650 to 670 °C. Compressive strength decreased quickly at initial stage for all specimens after immersed in SBF, and thereafter, continued to decrease at a slower rate subsequently. After immersion for 15 and 30 days, the compressive strength of γ-CPP decreased from 13.5 to 7.6 and 4.8 MPa, while β-CPP decreased from 16 to 12 and 8 MPa, respectively. The degradation rate of a-CPP, γ-CPP and β-CPP decreased with time after immersed in SBF. a-CPP had highest degradation rate, which would have been completely degraded in 10 days, and the weight loss ratio of γ-CPP was 28% for 15 days and 35% for 30 days, but the weight loss of β-CPP was only 11% for 30 days. The results therefore revealed that CPPs with different degradation rates could be obtained by controlling crystalline structure.     

Effect of phase noise on optical minimum-shift keying transmission systems

Phase-modulated (PM) signals have recently been used in long-haul lightwave communication systems to reach record distances. Added directly to the signal phase, linear and nonlinear phase noise cause performance degradation in PM systems. Minimum-shift keying (MSK), as a special format of PM signals, presents some different features of phase noise tolerance. This paper investigates the effect of phase noise on the performance degradation in the 10 Gb/s optical MSK systems and analyzes the contribution of phase noise to the bit error rate (BER), compared with the conventional PM format, 50% duty cycle optical return-to-zero differential phase-shift keying (RZ-DPSK) signals, in several typical local fiber dispersion transmission systems. The effect of intensity noise on the performance degradation in the corresponding transmission systems is also investigated.     

A study of the activation energy of thermal decomposition of irradiated polymers

The ion irradiation of polymeric solids induces numerous modifications in the polymer properties thus increasing their applicability in various fields. The present work looks into the aspect of thermal modifications induced in the irradiated polymers. The kinetics of thermal decomposition of polymers is investigated by using the thermogravimetric (TG) technique. It has been observed that the degradation of polymers is a multi-step process that involves sequential and competing processes, and obeys the Arrhenius kinetics which allows us to connect the rate constant with the absolute temperature and the activation energy. The activation energy of thermal decomposition has been calculated from the TG curves, and its variation with different irradiation doses has been derived.     

Sonolytic degradation of endocrine disrupting chemical 4-cumylphenol in water

The sonolytic degradation of endocrine disrupting compound 4-cumylphenol (4-CyP) in aqueous solution was investigated. The influence of operating parameters for sonication process such as 4-CyP initial concentration, frequency, power, pH, temperature and saturating gas was examined. The extent of degradation was inversely proportional to the initial substrate concentration. The rate of 4-CyP degradation was frequency dependent. The degradation rate increased proportionally with increasing ultrasonic power from 20 to 100 W and temperature in the range of 20-50°C. The most favorable degradation pH was acidic media. Destruction in the presence of saturating gas follows the order: argon>air>nitrogen. The 4-CyP degradation was inhibited in the presence of nitrogen gas owing to the free radical scavenging effect in vapor phase within the bubbles of cavitation. The ultrasonic degradation of 4-CyP was clearly promoted in the presence of bromide anions and the promoting effect on degradation increased with increasing bromide concentration. At low 4-CyP concentration (0.05 mg L(-1)), bicarbonate ion drastically enhanced the rate of 4-CyP degradation. Experiments conducted using pure and natural water demonstrated that the sonolytic treatment was more efficient in the natural water compared to pure water.     

Sonocatalytic degradation of methyl parathion in the presence of nanometer and ordinary anatase titanium dioxide catalysts and comparison of their sonocatalytic abilities

The degradation of methyl parathion (O,O-dimethyl-O-(4-nitrophenyl)-phosphorothioate) using anatase titanium dioxide (TiO₂) powder as heterogeneous sonocatalysts is reported. The influences of reaction parameters such as the species of TiO₂ sonocatalysts, methyl parathion concentrations, TiO₂ adding amount, pH, ultrasonic intensity, ultrasonic frequency and temperature have been investigated and the optimal conditions for eliminating methyl parathion have been identified. The efficiencies of sonocatalytic degradation in both nanometer and ordinary anatase systems are compared and the results indicate that the sonocatalytic activity of nanometer anatase TiO₂ powder is better than that of ordinary anatase TiO₂ powder. The primary degradation and the total mineralization of methyl parathion have been monitored by high performance liquid chromatography (HPLC) and UV–vis spectra, respectively. Methyl parathion got destroyed to some extent in both nanometer and ordinary anatase systems under ultrasonic irradiation. The kinetics for the degradation process of methyl parathion follows the first-order reaction. The degradation ratio of methyl parathion surpassed 90% within 50 min in the optimal experiment conditions.     

Comparison of ultrasonic degradation rates constants of methylene blue at 22.8 kHz, 127 kHz, and 490 kHz

Techniques such as solvent extraction, incineration, chemical dehalogenation, and biodegradation have been investigated for the degradation of hazardous organic compounds. We found ultrasound to be an attractive technology for the degradation of hazardous organic compounds in water. However, the effects of ultrasonic frequency on degradation rate constants were not investigated quantitatively. In this study, the degradation process of a model for hazardous organic compound methylene blue was investigated using ultrasonic irradiation. The study focused on the effects of ultrasonic frequency and ultrasonic power on the degradation rate constant. The apparent degradation rate constants were estimated based on time dependence of methylene blue concentration assuming pseudo-first-order kinetics for the decomposition. A linear relationship between the apparent degradation rate constant and ultrasonic power was identified. In addition, the apparent degradation rate constants at frequencies of 127 and 490 kHz were much larger than those at 22.8 kHz. A relationship between the apparent degradation rate constant and the sonochemical efficiency value (SE value) was also found. Based on these results, a simple model for estimating the apparent degradation rate constant of methylene blue based on the ultrasonic power and the SE value is proposed in this study.     

Chain Degradation under Low-Intensity Sonication of Polymer Solutions in the Presence of Filler: Mechanism of Ultrasonic Degradation of Flexible Chain Macromolecules

Routine dispersion of fillers in polymer solutions in a usual ultrasonic cleaning bath has been shown to lead to chain degradation. It is the filler presence, only, that has been demonstrated to provoke chain degradation under low-intensity sonication. A critical analysis of the literature concerned with the effects arising from propagation of acoustic waves in a liquid and an experimental study of ultrasonic degradation of polymers in solution were carried out. Based on these results, the mechanisms of chain degradation were discussed. Our previously proposed universal mechanism of chain degradation in inhomogeneous hydrodynamic fields has been shown to explain the basic facts repeatedly confirmed over the years of studying the ultrasonic degradation: (i) the existence of a limiting molecular weight such that macromolecules with lower molecular weights are not subject to degradation and (ii) the dependences of degradation rate on polymer molecular weight, polymer concentration, and temperature.     

Degradation of reactive,acid and basic textile dyes in the presence of ultrasound and rare earths [Lanthanum and Praseodymium]

Degradation of five textile dyes, namely Reactive Red 141 (RR 141), Reactive Blue 21 (RB 21), Acid Red 114 (AR 114), Acid Blue 113 (AB 113) and Basic Violet 16 (BV 16) in aqueous solution has been carried out with ultrasound (US) and in combination with rare earth ions (La³⁺ and Pr³⁺). Kinetic analysis of the data showed a pseudo-first order degradation reaction for all the dyes. The rate constant (k), half life (t_1/2) and the process efficiency (φ) for various processes in degradation of dyes under different experimental conditions have been calculated. The influence of concentrations of dyes (16–40 mg/L), pH (5, 7 and 9) and rare earth ion concentration (4, 12 and 20 mg/L) on the degradation of dyes have also been studied. The degradation percentage increased with increasing rare earth amount and decreased with increasing concentration of dyes. Both horn and bath type sonicators were used at 20 kHz and 250 W for degradation. The sonochemical degradation rate of dyes in the presence of rare earths was related to the type of chromophoric groups in the dye molecule. Degradation sequence of dyes was further examined through LCMS and Raman spectroscopic techniques, which confirmed the sonochemical degradation of dyes to non-toxic end products.     

Effect of geometry of hydrodynamically cavitating device on degradation of orange-G

In this research work, we have carried out geometric optimization of different cavitating devices using degradation of orange-G dye [OG] as a model pollutant. Three different cavitating devices viz. orifice plate, circular venturi and slit venturi were optimized and the degradation of orange-G dye was studied. The optimization of all three cavitating devices was done in terms of fluid inlet pressure to the cavitating devices and cavitation number. The effect of pH and initial concentration of the dye on the degradation rate was also studied. The geometry of cavitating device (flow cross sectional area, perimeter, shape, etc.) was found to be an important parameter in getting the maximum cavitational effect using hydrodynamic cavitation. The cavitational yield of all three cavitating devices were compared on the basis of mg of total organic carbon (TOC) reduction per unit energy supplied. The slit venturi gives almost 50% higher degradation rate and cavitational yield among all three cavitating devices studied for the same amount of energy supplied.     

Hydrodynamic cavitation for micropollutant degradation in water – Correlation of bisphenol A degradation with fluid mechanical properties

The present work addresses the correlation of bisphenol A (BPA) degradation by hydrodynamic cavitation with the fluid mechanical properties of the cavitating jet in the reactor. The effects of inlet pressure and two orifices were investigated. The fluid mechanics conditions during the reaction were evaluated by optical measurements to determine the jet length, bubble volume, number of bubbles, and bubble size distribution. In addition, chemiluminescence of luminol is used to localize chemically active bubbles due to the generation of hydroxyl radicals in the reactor chamber. The correlation between the rate constants of BPA degradation and the mechanical properties of the liquid is discussed. Here, linear dependencies between the degradation of BPA and the volume expansion of the bubble volume and chemiluminescence are found, allowing prediction of the rate constants and the hydroxyl radicals generated. BPA degradation of 50% was achieved in 30 min with the 1.7 mm nozzle at 25 bar. However, the 1 mm nozzle has been demonstrated to be more energetically efficient, achieving 10% degradation with 30% less power per 100 passes. There is a tendency for the number of small bubbles in the reactor to increase with smaller nozzle and increasing pressure difference.     

Exploring the effects of pulsed ultrasound at 205 and 616 kHz on the sonochemical degradation of octylbenzene sulfonate

Compared to continuous wave (CW) ultrasound, pulsed wave (PW) ultrasound has been shown to result in enhanced sonochemical degradation of octylbenzene sulfonate (OBS). However, pulsed ultrasound was investigated under limited pulsing conditions. In this study, pulse-enhanced degradation of OBS was investigated over a broad range of pulsing conditions and at two ultrasonic frequencies (616 and 205 kHz). The rate of OBS degradation was compared to the rate of formation of 2-hydroxyterephthalic acid (HTA) following sonolysis of aqueous terephthalic acid (TA) solutions. This study shows that sonication mode and ultrasound frequency affect both OBS degradation and HTA formation rates, but not necessarily in the same way. Unlike TA, OBS, being a surface active solute, alters the cavitation bubble field by adsorbing to the gas/solution interface of cavitation bubbles. Enhanced OBS degradation rates during pulsing are attributed to this adsorption process. However, negative or smaller pulse enhancements compared to enhanced HTA formation rates are attributed to a decrease in the high-energy stable bubble population and a corresponding increase in the transient bubble population. Therefore, sonochemical activity as determined from TA sonolysis cannot be used as a measure of the effect of pulsing on the rate of degradation of surfactants in water. Over relatively long sonolysis times, a decrease in the rate of OBS degradation was observed under CW, but not under PW conditions. We propose that the generation and accumulation of surface active and volatile byproducts on the surface and inside of cavitation bubbles, respectively, during CW sonolysis is a contributing factor to this effect. This result suggests that there are practical applications to the use of pulsed ultrasound as a method to degrade surface active contaminants in water.     

Ultrasonic waste-water treatment: incidence of ultrasonic frequency on the rate of phenol and carbon tetrachloride degradation

Organic compounds in aqueous solution submitted to an ultrasonic irradiation behave differently according to their physical and chemical properties. In this work, hydrogen peroxide formation and the degradation rate of phenol and carbon tetrachloride have been studied at different frequencies: 20, 200, 500 and 800 kHz. Whatever the frequency, it is easier to decompose CCl₄ than phenol by means of ultrasonic wave. It is shown that the rates of reactions involving hydroxyl radicals (hydrogen peroxide formation and phenol degradation) have a maximum value at 200 kHz. The best yield observed at 200 kHz for the phenol degradation may be the result of better HO radicals availability outside of the bubble of cavitation. The degradation rate for carbon tetrachloride which decomposes into the bubble of cavitation increases with frequency. Calculating the reaction rate for one ultrasonic period shows that the efficiency of one ultrasonic cycle decreases as frequency increases.     

聚丙烯/有机改性蒙脱土纳米复合材料的光氧化降解研究

研究了聚丙烯/有机改性蒙脱土(OMMT)纳米复合材料在365 nm紫外光辐照下的光氧化降解过程中的结构变化。主要利用红外光谱方法进行表征。在辐照初期(紫外光辐照时间小于11 h),复合体系的光氧化降解速率大于纯聚丙烯体系;随着辐照时间的延长(大于11 h),复合体系的光氧化降解速率小于纯聚丙烯体系。主要原因是蒙脱土既有光屏蔽作用,又有加速光氧化降解的作用,这两种作用共存,但在辐照初期,催化光降解作用占主导地位,随着辐照时间延长,光屏蔽作用占主导。蒙脱土的含量对聚丙烯的光氧化降解速率也存在影响。另外,蒙脱土的加入对聚丙烯光氧化降解产物也产生影响,羧酸类及酸酐类产物增多,酯类产物减少。     

Analysis on the capacity degradation mechanism of a series lithium-ion power battery pack based on inconsistency of capacity

The lithium-ion battery has been widely used as an energy source. Charge rate, discharge rate, and operating tem- perature are very important factors for the capacity degradations of power batteries and battery packs. Firstly, in this paper we make use of an accelerated life test and a statistical analysis method to establish the capacity accelerated degradation model under three constant stress parameters according to the degradation data, which are charge rate, discharge rate, and operating temperature, and then we propose a capacity degradation model according to the current residual capacity of a Li-ion cell under dynamic stress parameters. Secondly, we analyze the charge and discharge process of a series power battery pack and interpret the correlation between the capacity degradations of the battery pack and its charge/discharge rate. According to this cycling condition, we establish a capacity degradation model of a series power battery pack under inconsistent capacity of cells, and analyze the degradation mechanism with capacity variance and operating temperature difference. The comparative analysis of test results shows that the inconsistent operating temperatures of cells in the series power battery pack are the main cause of its degradation; when the difference between inconsistent temperatures is narrowed by 5 ℃, the cycle life can be improved by more than 50%. Therefore, it effectively improves the cycle life of the series battery pack to reasonably assemble the batteries according to their capacities and to narrow the differences in operating temperature among cells.     

Study of the sonophotocatalytic degradation of basic blue 9 industrial textile dye over slurry titanium dioxide and influencing factors

The sonophotocatalytic degradation of basic blue 9 industrial textile dye has been studied in the presence of ultrasound (20 kHz) over a TiO(2) slurry employing an UV lamp (15 W, 352 nm). It was observed that the color removal efficiency was influenced by the pH of the solution, initial dye concentration and TiO(2) amount. It was found that the dye degradation followed apparent first order kinetics. The rate constant increased by decreasing dye concentration and was affected by the pH of the solution with the highest degradation obtained at pH 7. The first order rate constants obtained with sonophotocatalysis were twofold and tenfold than those obtained under photocatalysis and sonolysis, respectively. The chemical oxygen demand was abated over 80%.