Investigation of sonochemical treatment of heavy hydrocarbon by ultrasound-assisted cavitation

A highly viscous nature of heavy oil poses challenges to transportation leading to costly operation and difficult processing. Traditional methods of upgrading unconventional hydrocarbon sources involve catalytic and thermal upgrading and these methods require high temperature and pressure. In the present study, partial upgrading of heavy hydrocarbon is studied by using cavitation and the stimulator. Cavitation is a phenomenon comprising of formation, growth and collapse of bubbles in a liquid medium. The most well-known disruptive effect of cavitation occurs during the collapse phase of bubbles. Method of inducing cavitation involves transmitting 20 kHz of ultrasound through an ultrasonic horn. A model molecule used in this study is n-hexadecane (C16). The experiments were carried out at 230 °C, atmospheric pressure and 60 min time scale. The results indicated that the conversion of n-hexadecane into R1 fraction (<C16) and R2 fraction (>C16) was 4.46% for the cavitation-assisted cracking with the stimulator. The selectivity to R1 and R2 fractions were 71% and 29%, respectively. Adding 5 vol% decalin as hydrogen donor into the cracking process yielded 9.18% conversion of n-hexadecane into R1 and R2 fractions. In addition, the selectivity to R1 and R2 fractions were 87% and 13%. This study focuses on less energy intensive process for heavy hydrocarbon by utilizing cavitation and the stimulator and how ultrasound-assisted cracking with the stimulator could be a viable alternative to treat heavy hydrocarbon at the low temperature.     

Predicting nitrogen release during coal tar decomposition

This paper develops a detailed phenomenological reaction mechanism for N-species transformations throughout tar decomposition, including tar-N sequestration into soot. It expands the previously validated mechanism for tar decomposition based on FLASHCHAIN^® theory to cover N-transformations during pulverized fuel firing. Tar-N transformations are described by two distinctive features: (1) An elimination reaction that produces HCN governs the decay in the average moles of nitrogen per aromatic nucleus throughout tar decomposition; and (2) Empirical observations determine the fraction of tar-N incorporated into soot. Validation cases represent heating rates of at least several thousand degrees per second; temperatures from 600 to 1100 °C; tar contact times from 75?ms through 2?s; and coal ranks from subbituminous through low volatile bituminous. The predicted partitioning of coal-N into tar-N, HCN, soot-N, and char-N was within measurement uncertainties for all coals for simulated p. f. firing conditions, including the variation in fractional char-N levels from 0.4 to 0.8 across this domain. Since primary tar-N levels are directly proportional to fractional primary tar yields, and since ultimate soot-N levels account for one-third of tar-N with any coal type, the ultimate coal-N partitioning for CFD furnace simulations can be accurately described with two analyses: (1) A primary devolatilization mechanism to predict primary tar yields under rapid heating conditions; and (2) A submechanism to predict HCN release from char throughout devolatilization up to the point of char ignition. Dynamics may be resolved with either global reactions or the full tar decomposition mechanism, depending on the impact of the lag between tar decomposition and soot production in the subject application.     

Comparison of the Mechanical Properties and the Ballistic Behavior in Heracron®/Phenol Composite after Plasma Treatment

In this study, aramid, Heracron^®, which was purchased from Kolon Inc., Korea, and phenol composites were prepared by plasma treatment and the influence of this plasma treatment on their mechanical properties and ballistic behavior were ascertained. By measurement of water contact angle and XPS analysis, we find that the plasma treatment may help the incorporation of functional oxygen groups on the surface of the Heracron^® fabrics. Additionally, the surface roughness of Heracron^® fiber may be proportional to the plasma treatment times. By SEM and mechanical tests, it was shown that plasma-treated Heracron^®/phenol composites exhibited higher mechanical properties compared with plasma-untreated Heracron^®/phenol composites. Based on this finding, we can conclude that plasma-treatment can promote the interfacial adhesion between Heracron^® and phenol, resulting in the superior mechanical properties of their composites. However, the ballistic behavior conflicted with the mechanical properties. That is to say, a helmet, manufactured from the plasma-treated Heracron^®/phenol composites, exhibited lower ballistic properties than that of the plasma-untreated Heracron^®/phenol composites. As a result, we demonstrated that for ballistic application, somewhat weak fiber–matrix adhesion leads to the improved ballistic behavior. However, it becomes apparent that the optimum strength condition for the composite interphase depends on the particular application, thus increased fiber–matrix adhesion may be more appropriate.     

Polyelectrolyte Nanocomposite Membranes Using Surface Modified Nanosilica for Fuel Cell Applications

The preparation and characterization of a new type of nanocomposite polyelectrolyte membrane (PEM), based on Nafion® (E. I. du Pont de Nemours and Co., Ltd., for its copolymer of tetrafluoroethylene and perfluorinated vinyl ether) and sulfonic acid (-SO₃H) or phosphotungstic acid (PWA) modified nanosilica (Si-SO₃H or Si-PWA, respectively), for direct methanol fuel cell (DMFC) applications are described. Physical characteristics of these manufactured nanocomposite membranes were investigated by scanning electron microscopy (SEM), water uptake, methanol permeability and ion exchange capacity, as well as proton conductivity. The Nafion®/Si-PWA and Nafion®/Si-SO₃H membranes showed higher proton conductivity, lower methanol permeability and, as a consequence, a higher selectivity parameter, in comparison to the neat Nafion® or Nafion®/pristine nanosilica membranes. The obtained results indicated that both the Nafion®/Si-PWA and Nafion®/Si-SO₃H membranes could be utilized as promising polyelectrolyte membranes for direct methanol fuel cell applications.     

Polyelectrolyte Nanocomposite Membranes with Imidazole-Functionalized Multi-Walled Carbon Nanotubes for Use in Fuel Cell Applications

The preparation and characterization of a new type of nanocomposite polyelectrolyte membrane (PEM), based on Nafion® and imidazole modified multi-walled carbon nanotubes (MWCNT-Im), for direct methanol fuel cell (DMFC) applications is described. Related to the interactions between the protonated imidazole groups, grafted on the surface of multi-walled carbon nanotubes (MWCNT), and the negatively charged sulfonic acid groups of Nafion®, new electrostatic interactions can be formed in the interface of the Nafion® and MWCNT-Im which result in both lower methanol permeability and also higher proton conductivity. The physical characteristics of these manufactured nanocomposite membranes were investigated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), water uptake, methanol permeability and ion exchange capacity, as well as proton conductivity. The Nafion®/MWCNT-Im membranes showed higher proton conductivity, lower methanol permeability and, as a consequence, a higher selectivity parameter in comparison to neat Nafion® or Nafion® containing –OH functionalized multi-walled carbon nanotubes (MWCNT-OH) membranes. The obtained results indicated that the Nafion®/MWCNT-Im membranes could be utilized as efficient polyelectrolyte membranes for direct methanol fuel cell applications.     

173Lu和174gLu衰变数据的测量

175Lu（n;2n）174m,gLu（n;2n）173Lu反应在高能中子通量监测中具有重要作用,其产物的放射性活度通常用HPGe探测器测量,这就需要174m,gLu和173Lu的半衰期和γ射线发射率等衰变数据必须准确无误。在主要的评价核数据库中,只有ENDF/B 7.1和JEFF 3.1.1数据库给出了173Lu和174Lu的半衰期和γ射线的发射几率等衰变数据,其中173Lu的射线发射几率ENDF/B 7.1库比JEFF 3.1.1库总体偏高,其他评价数据两个数据库非常一致。在中国原子能研究院的串列加速器上用20 MeV质子辐照金属Yb靶生产了含有173Lu,174m,gLu的放射性溶液,用激光共振电离质谱（LRIMS）和热表面电离质谱（TIMS）两种同位素稀释法测定了该溶液中173Lu和174m,gLu核素浓度,然后制备测量源在HPGe探测器上进行了近7年的跟踪测量,发现173Lu的半衰期为1.45 a,比目前评价的数据1.37 a高6.1%,636.1 keV射线发射几率的偏差最大,比ENDF/B 7.1的评价数据偏高7%。174gLu半衰期的测量结果3.37 a175Lu（n;2n）174m,gLu（n;2n）173Lu反应在高能中子通量监测中具有重要作用,其产物的放射性活度通常用HPGe探测器测量,这就需要174m,gLu和173Lu的半衰期和γ射线发射率等衰变数据必须准确无误。在主要的评价核数据库中,只有ENDF/B 7.1和JEFF 3.1.1数据库给出了173Lu和174Lu的半衰期和射线的发射几率等衰变数据,其中173Lu的射线发射几率ENDF/B 7.1库比JEFF 3.1.1库总体偏高,其他评价数据两个数据库非常一致。在中国原子能研究院的串列加速器上用20 MeV质子辐照金属Yb靶生产了含有173Lu,174m,gLu的放射性溶液,用激光共振电离质谱（LRIMS）和热表面电离质谱（TIMS）两种同位素稀释法测定了该溶液中173Lu和174m,gLu核素浓度,然后制备测量源在HPGe探测器上进行了近7年的跟踪测量,发现173Lu的半衰期为1.45 a,比目前评价的数据1.37 a高6.1%,636.1 keV γ射线发射几率的偏差最大,比ENDF/B 7.1的评价数据偏高7%。174gLu半衰期的测量结果3.37 a,比评价数据3.31 a高约1.8%,174gLu 76.5 keV和1 241.8 keV γ射线的发射几率比ENDF/B 7.1的评价数据分别低1.87%和12.8%。175Lu(n,2n)174m,gLu(n,2n)173Lu are important neutron reactions to monitor the high energy neutron fluxes and the residual nuclei, 174m,gLu and 173Lu, are usually measured by a HPGe spectrometer conveniently so that the decay data such as half lives and gamma-ray emission probabilities of 174m,gLu and 173Lu must be accurate. There are evaluated decay data only in ENDF/B 7.1 and JEFF 3.1.1 among the major evaluated nuclear data libraries, where the most data are almost same besides the gamma-ray emission probabilities of 173Lu are higher in ENDF/B 7.1 than that in JEFF 3.1.1. Yb metal as a target was irradiated by 20 MeV proton beams on a tandem accelerator in CIAE to produce 174m,gLu and 173Lu, and 176Lu isotopic dilution methods based upon a laser resonance ionization mass spectrometer (LRIMS) and a thermal surface ionization mass spectrometer (TIMS) were employed to determine the numbers of nuclides of 174Lu and 173Lu in a solution containing the irradiated target. Several radioactive sources made from the solution had been measured by a HPGe detector during the past 7 years and the peak intensities of the characteristic gamma-rays from 174gLu and 173Lu were analyzed to determine the half lives and gamma-ray emission probabilities. According to the measurements, the half life of 173Lu is 1.45 a, which is about 6.1% longer than the evaluated 1.37 a, and the gamma-ray emission probabilities of 173Lu is also different from the evaluated data, especially the emission probability of 636.1 keV gamma-ray of 173Lu is 7% higher than the value in ENDF/B 7.1. The half life of 174gLu is 3.37 a, about 1.8% longer than the evaluated 3.31 a, and the emission probabilities of 76.5 keV and 1 241.8 keV gamma-rays of 174Lu are 1.87% and 12.8% lower than the evaluated data in ENDF/B 7.1, respectively.     

Water States in Perfluorosulfonic Acid Membranes Using Differential Scanning Calorimetry

The water states in perfluorosulfonic acid membranes (Nafion®) were evaluated using low temperature differential scanning calorimetry (DSC) on both vapor and liquid penetrants. At low sorption levels, water sorbed in Nafion existed in the nonfreezable bound state until a critical value was reached. The critical, nonfreezable water content corresponded to 4.8 water molecules per sulfonate group. Beyond that critical value, additional sorbed water was partitioned between freezable and nonfreezable bound states. The freezable water was in intermediate or freezable bound water state with subzero fussion temperatures. The observed water fusion enthalpy for every additional gram of sorbed water was less than that of pure water. The partition coefficient (K) between the nonfreezable bound state and the freezable state water was estimated as 0.755. The critical nonfreezable water content (W _c ) and the partition coefficient for vapor permeate in Nafion were similar to those of liquid water penetrant. These findings allow one to estimate the bound and freezable water distribution in Nafion. The K value, in conjunction with the critical water content (W _c ), can be used as a quantitative indicator to characterize water states in ionomers. This model may serve as the basis to account for water transport, ionic conductivity, and proton transfer changes in various solid electrolyte membranes.     

Does power ultrasound affect Nafion® dispersions?

The effect of low frequency power ultrasound on Nafion® ionomer used for fabricating proton exchange membrane fuel cell (PEMFC) and water electrolyzer (PEMWE) catalyst inks was investigated. In this study, a series of Nafion® dispersions having three concentrations (10, 5, and 2.5% w/v) were studied under various irradiation durations (t_us), at fixed ultrasonic frequency (f = 42 kHz) and ultrasonic power (P > 2 W), under either controlled or unregulated bulk solution temperature conditions using a laboratory ultrasonic cleaning bath. Viscosity (η), thermal degradation, and glass transition temperature (T_g) for all Nafion® dispersion samples was measured and compared to untreated Nafion® samples. In our conditions, it was found that power ultrasound lowered the viscosity of all tested Nafion® dispersion samples; whilst thermogravimetric and differential scanning calorimetry analyses showed that for all ultrasonically irradiated samples, a negligible overall polymer degradation and no obvious change in T_g was observed under controlled and unregulated bulk temperature conditions. It was found that it is possible that acoustic cavitation causes depolymerisation followed by a polymerisation initiation step during ultrasonication. By comparing the ultrasonically treated and high-shear mixed samples, it was also observed that acoustic and hydrodynamic cavitation played an important role in the reduction of dispersion viscosity.     

Ballistic behavior of Heracron®-based composites: effect of fiber density and fabrication method

In this study, a Heracron^® aramid fiber-based helmet was made, and its ballistic properties were investigated. The effect of fiber density was studied in depth. For the same weight and number of plies, a helmet manufactured from the HT-2820-based composite showed improved ballistic properties compared with one made from the HT-15000-based composite. This result suggested that fiber density may strongly affect the ballistic properties of armor. HT-2820, containing more multifilament fibers, provides more efficient energy absorption and dissipation. The influence of fabrication method on the ballistic behavior of a helmet was studied. The V₅₀ of a helmet made by the film laminating method was 10% better than that for a helmet made by the resin dipping approach. Based on these findings, the film laminating method, which forms the composite by directly attaching aramid fabric to the matrix film, may be a good candidate for improving the ballistic behavior. The required composite interfacial strength will be application-dependent. Greater fiber-matrix adhesion may be advantageous in certain cases.     

Ultrasonic free fatty acids esterification in tobacco and canola oil

Ultrasound accelerates the free fatty acids esterification rate by reducing the mass transfer resistance between methanol in the liquid phase and absorbed organic species on Amberlyst®46 catalyst. The reaction rates of canola oil is three times greater than for tobacco seed oil but half the reaction rate of pure oleic acid as measured in a batch reactor. The beneficial effects of ultrasound vs. the conventional approach are more pronounced at lower temperatures (20 °C and 40 °C vs. 63 °C): at 20 °C, the free fatty acids conversion reaches 68% vs. 23% with conventional mechanical stirring. The increased conversion is attributed to acoustic cavitation that increases mass transfer in the vicinity of the active sites. The Eley–Rideal kinetic model in which the concentration of the reacting species is expressed taking into account the mass transfer between the phases is in excellent agreement with the experimental data. Ultrasound increases the mass transfer coefficient in the tobacco oil 6 and 4.1 fold at 20 °C and 40 °C, respectively.     

Yielding behavior of glassy polymers. I. Free-volume model

Rigid, glassy polymers show a diversity of tensile behavior-ranging from apparently brittle to ductile. To delineate some of the factors that control the toughness or impact resistance of these polymers, the yielding behavior of poly (methyl methacrylate) (PMMA) was studied. Results of other workers have shown that the cold flow exhibited by many glassy polymers can be explained qualitatively by a free-volume model. The treatment assumes that molecular flow is permitted when the free volume increase, resulting from the dilatational component of the applied stress, is sufficient to bring the total free volume to that characteristic of the polymer liquid. The present study refines this approach by introducing an “effective temperature,” defined as that hypothetical temperature at which the glass would have an equilibrium free volume equal to the total free volume of the nonequilibrium glass at temperature T. Equations are derived which more satisfactorily describe the temperature and strain-rate dependences of the tensile yield strain of PMMA glass from -10° to 90°C at rates between 0.015 and 120%/sec.     

Frequency-dependent linear and non-linear response properties of single carrier quantum dots: Role of effective mass and anharmonicity in the confinement potential

We explore the pattern of frequency-dependent linear and non-linear optical (NLO) response of one electron quantum dots harmonically confined in two dimensions. For some fixed values of transverse magnetic field strength (ω_c), and harmonic confinement potential (ω₀), the influence of effective mass (m^*) of the system and the symmetry breaking anharmonic interaction on the frequency-dependent linear (α), and the first (β), and second (γ) NLO responses of the dot is computed through linear variational route. The investigation reveals interesting roles played by the anharmonic interaction and effective mass in modulating the response properties.