Dynamic surface elasticity of polymer solutions

The surfaces of surfactant solutions exhibit viscoelastic dilational behavior which may be investigated by modern optical and mechanical methods. The present study focuses on the dynamic dilational properties of the polymer solution — gas interface. Linear flexible polymer chains at the surface are considered as consisting of trains, lying on the surface, and loops and tails that protrude into the liquid. The Rouse model is used to describe the inner dynamics of the trains, whereas their motion relative to their neighbors on the surface can be described with the help of the reptation conception. An expression for the complex dynamic dilational surface elasticity has been derived. Although, in general, the relaxation of the surface tension is characterized by an infinite series of relaxation times, it is shown that for many systems the dynamics of the surface layer can be described approximately by only two main relaxation times. The dispersion equation, which was obtained earlier for solutions of conventional surfactants, is shown to be fulfilled for polymer solutions also.     

表面电沉积Ni—La2O3复合镀层的Fe26Cr1Mo不锈钢的氧化行为研究

Ｆｅ２６Ｃｒ１Ｍｏ不锈钢在９００℃氧化时，生成的氧化层在冷却过程中大量剥落，经表面共电沉积ＮｉＬａ２Ｏ３复合镀层后，抗热循环能力明显提高。     

Effect of chemical demineralization on thermal behavior of bituminous coals

Growing environmental concerns and the need for alternatives for oil and natural gas resulted in intensive researches on ultra clean coal (UCC). Therefore, the researches related to practice and application of various methods to produce UCC become more important. Thermal characterization of chemically demineralized coals by thermogravimetric analysis method is presented in this study. The aim of the study is to provide thermal data for HF–HNO₃ leaching system used for the production of UCC. Coal samples were first physically enriched by density separation. Then the enriched portion was chemically demineralized by using HF and HNO3, respectively. Ash content of coal samples were reduced to a range of 0.12–0.41% by chemical demineralization process. The petrographic, ultimate and proximate analyses were carried out to determine main features of samples. Physically and chemically enriched coal samples were then analyzed in a TG by two different techniques separately. The first technique covered thermal characterization of samples under non-isothermal conditions. Characteristic temperatures for each sample were obtained from the TG and DTG data. The second technique involved the determination of reactivity of in situ produced chars of each sample.     

A comparative study on textural characterization: cation-exchange and sorption properties of crystalline alpha-zirconium(IV), tin(IV), and titanium(IV) phosphates

Tetravalent metal phosphates (M=Zr, Ti, and Sn) were prepared and characterized by XRD, surface properties, and TG-DTA. The cation exchange and sorption behavior of these metal phosphates toward transition metal ions such as Cu(2+), Co(2+), and Ni(2+) have been studied comparatively as a function of temperature and concentration. The adsorption process was found to increases with increase in temperature and concentration. The selectivity order for alpha-titanium and alpha-tin phosphates is Cu(2+)>Co(2+)>Ni(2+), whereas for alpha-zirconium phosphate it is Cu(2+)>Ni(2+)>Co(2+). The ion exchange capacity of alpha-titanium phosphate is greater than those of other phosphates, which is explained on the basis of the surface behavior, disorderness of the system, degree of hydrolysis of incoming guest adsorbate metal ions, and structural steric hindrance of the exchangers during adsorption and sorption. The distribution coefficient, Gibbs free energy, enthalpy, and entropy values indicate that the ion-exchange processes are spontaneous.     

Viscoelastic and thermal characterization of crosslinked PVC

Soft PVC is employed for the manufacturing of a wide range of products with different properties and a relatively low cost. The utilization of soft PVC is restricted by the poor thermal, chemical and mechanical resistance properties. Also, plasticizer migration can modify the properties or can make useless the materials for some applications because of toxicity or a general loss of properties. PVC crosslinking is the most effective way to improve mechanical and transport properties of rigid or flexible PVC at high temperatures, but at the same time the thermal stability of PVC may be significantly reduced. In this work, the crosslinking reaction of plasticized poly(vinyl chloride) (PVC) through difunctional amines was studied. The mechanisms involved in the crosslinking reaction were explained by Fourier transform infrared (FTIR) analysis. The thermal activated crosslinking reaction was studied by cone and plate rheometry, analyzing the evolution of viscoelastic properties of the suspension as a function of time and temperature. The effect of the addition of crosslinking agents on the thermal stability of the polymer was studied by thermogravimetric analysis (TGA), which revealed that crosslinking reactions promote thermal degradation phenomena in the polymer matrix. This is attributed to the formation of HCl and other species promoting polymer degradation during crosslinking, thus leading to higher weight loss during thermal treatment with respect to unmodified PVC plastisols. This was also confirmed by an evident yellowing after crosslinking, especially at higher temperatures.     

Small angle X-ray scattering from lamellar phase for β-3,7-dimethyloctylglucoside/water system: comparison with β-n-alkylglucosides

Small angle X-ray scattering (SAXS) is measured for the lamellar phase in aqueous systems of 1-o-β-3,7-dimethyoctyl-D-glucopyranoside (β-Glc(Ger)), which has recently been prepared by us, 1-o-β-decyl-D-glucopyranoside (β-GlcC₁₀), and 1-o-β-octyl-D-glucopyranoside (β-GlcC₈). The repeat distance d obtained from the position of the diffraction peak does not follow the swelling law d = 2δ_hc/_hc, where δ_hc and _hc are the thickness and the volume fraction of the hydrophobic layer, respectively. This may result from the fact that δ_hc increases and, equivalently, the surface area per surfactant molecule (a_s) decreases with increasing concentration. So we calculate δ_hc and a_s from the observed d value at each concentration using the above swelling law. The half-thickness δ_hc increases in the order β-GlcC₈ < β-Glc(Ger) < β-GlcC₁₀ at a fixed concentration. On the other hand, the data on a_s for β-GlcC₁₀ and β-GlcC₈ lie on the same line and the data for β-Glc(Ger) lies above this line. These results suggest that the cross-sectional area of the geranyl chain is larger than that of the glucose headgroup. Existence of water filled defects in bilayer sheets is also discussed based on the SAXS pattern and the concentration dependence of d.     

Anomalous diffusion in a random velocity field

We construct diffusions in random velocity fields which present anomalous superdiffusive behavior. The mean square displacement can be made to have any power lawt for 1<2. Higher moments and characteristic functions are also investigated.     

Hydrothermal synthesis and intercalation behavior of a layered titanium phosphate Ti2(H2PO4)(HPO4)(PO4)2 · 0.5C6N2H16, with an extended γ-phase intercalated into organic amine

With a hydrothermal technique, a layered titanium phosphate with the formula Ti₂(H₂PO₄)(HPO₄)(PO₄)₂ · 0.5C₆N₂H₁₆ (denoted TP-J2) has been prepared by treating the Ti/H₃PO₄/H₂O/1-methylpiperazine system directly. The as-synthesized products were characterized by powder X-ray diffraction, CP-MAS solid-state ³¹P NMR spectroscopy, thermogravimetric and differential thermal analyses (TG-DTA). The structure was solved by single-crystal X-ray diffraction analysis and it presents an extended γ-phase intercalated with organic amine. Crystal data: triclinic, , a = 8.106 (2) Å, b = 8.197 (2) Å, c = 11.658 (2) Å.  = 78.32 (3)°, β = 80.85 (3)°, γ = 77.90 (3)°, Z = 2. Additionally, the intercalation behavior of TP-J2 with n-alkyl monoamine (n = 2, 3, 4, 6, 8, 10 and 12) was investigated. Owing to the strong brønsted base, N,N′-dimethylpiperazine, resides in the interlayer, it presented unusual features of TP-J2 in contrast with that of γ-Tip.     

Zinc ions and zinc sulfide particles in sol-gel zirconium phosphate synthesis, thermal behavior and X-ray characterization

Zinc ions can be exchanged in sol-gel zirconium phosphate by using the batch or hydrothermal method. The zinc materials obtained that undergo thermal treatment after complete dehydration, can rehydrate fully or partially depending on whether half or all the zinc ions are exchanged. At high temperature syntherization is evident. By flowing sulfide acid over the zinc forms, zinc sulfide particles are formed and their amount depends on the length of time of the gas flow and on the state of hydration of the original material. This is not the case in the half exchanged zinc zirconium phosphate material. The decomposition temperature of the ZnS particles depends on their position in the exchanger: whether on the surface or between the layers of the host matrix. The XRD patterns of the materials obtained are similar to those of the sol-gel zirconium phosphate. The presence of ZnS particles is evident.     

Application of ultrasound-assisted acid leaching procedures for major and trace elements determination in edible seaweed by inductively coupled plasma-optical emission spectrometry

A new method using diluted reagents (nitric and hydrochloric acids and oxygen peroxide) and ultrasound energy to assist metals acid leaching with from edible seaweed was optimized. The method uses a first sonication at high temperature with hydrochloric acid as a previous stage to an ultrasound-assisted acid leaching with 7 ml of an acid solution containing nitric acid, hydrochloric acid and hydrogen peroxide at concentrations of 3.7, 3.0 and 3.0 M, respectively. Optimum conditions for the first sonication step were ultrasound energy at 17 kHz, sonication temperature at 65 °C, an acid volume of 2 ml, an hydrochloric acid concentration of 6.0 M and a sonication time of 10 min. It has been found that the first sonication stage at high temperature with hydrochloric acid is necessary to obtain quantitative recoveries for As, Ba, Fe and V. Otherwise quantitative recoveries were reached for the other elements investigated (Ca, K, Na, Mg, Cd, Cr, Cu, Mn, Ni, Pb and Zn). The repeatability of the ultrasound-assisted acid leaching method was around 10% for all elements. Adequate limit of detection and limit of quantification were reached by using inductively coupled plasma-optical emission spectrometry (ICP-OES) for measurements. The method resulted accurate after analysing several seaweed certified reference materials (IAEA-140/TM, NIES-03 and NIES-09). The method was finally applied to the multi-element determination in edible seaweed samples.