Surface modification of polyester by oxygen‐ and nitrogen‐plasma treatment

In this paper, we present a study on the surface modification of polyethyleneterephthalate (PET) polymer by plasma treatment. The samples were treated by nitrogen and oxygen plasma for different time periods between 3 and 90 s. The plasma was created by a radio frequency (RF) generator. The gas pressure was fixed at 75 Pa and the discharge power was set to 200 W. The samples were treated in the glow region, where the electrons temperature was about 4 eV, the positive ions density was about 2 × 10¹⁵ m^?3, and the neutral atom density was about 4 × 10²¹ m^?3 for oxygen and 1 × 10²¹ m^?3 for nitrogen. The changes in surface morphology were observed by using atomic force microscopy (AFM). Surface wettability was determined by water contact angle measurements while the chemical composition of the surface was analyzed using XPS. The stability of functional groups on the polymer surface treated with plasma was monitored by XPS and wettability measurements in different time intervals. The oxygen‐plasma‐treated samples showed much more pronounced changes in the surface topography compared to those treated by nitrogen plasma. The contact angle of a water drop decreased from 75° for the untreated sample to 20° for oxygen and 25° for nitrogen‐plasma‐treated samples for 3 s. It kept decreasing with treatment time for both plasmas and reached about 10° for nitrogen plasma after 1 min of plasma treatment. For oxygen plasma, however, the contact angle kept decreasing even after a minute of plasma treatment and eventually fell below a few degrees. We found that the water contact angle increased linearly with the O/C ratio or N/C ratio in the case of oxygen or nitrogen plasma, respectively. Ageing effects of the plasma‐treated surface were more pronounced in the first 3 days; however, the surface hydrophilicity was rather stable later. Copyright © 2008 John Wiley & Sons, Ltd.     

Pyrolysis of N-doped organic aerogels with relation to sorption properties

Resorcinol–formaldehyde aerogels (five samples, three of them with addition of nitrogen containing precursors—3-hydroxypyridine, 3-aminophenol and melamine) have been prepared by sol–gel polycondensation, subcritical drying and pyrolysis. The pyrolysis of prepared organic aerogels has been studied by non-isothermal TG at constant heating rate. The process of pyrolysis has been found to consist of three steps with the total mass loss 40.2–61.7% (room temperature—1,000 °C). The resulted carbon aerogels have been tested as sorbents of Ni(II), Pb(II) and Cu(II) ions from aqueous solutions. Various relations have been found among the results obtained from the pyrolysis experiments and properties affecting adsorption. Besides the expected correlation between the mass loss gained from TG (isothermal step at 500 °C was applied) and from heating in the laboratory oven, the relationship between the mass loss during pyrolysis and sorption capacities for all three metal ions has been found. Other relations among pyrolysis behaviour, surface area and content of nitrogen have been also examined. Batch adsorption experiments show (with an exception of one sample) that N-doped samples have higher adsorption capacity for metal ions. In addition, changing of nitrogen functionalities during the pyrolysis has been considered and pyridinic-N (N-6) functionality has been contemplated as a suitable structure for the adsorption process.     

Partial oxidation of high-boiling hydrocarbon mixtures in the pilot unit

The reason for this investigation into the partial oxidation (POX) of high-boiling hydrocarbons with oxygen in the presence of water vapour was to ensure increased demand on hydrogen, which is essential for the deeper hydrorefining of petroleum oils to ensure better quality of motor fuels. The tests demonstrated the good performance of the pilot plant unit and also the reproducibility of the experiment. The investigation detected a significant impact of water vapour on the selectivity of the partial oxidation of high boiling-point hydrocarbons with regard to the composition of the exhaust gas. In addition, it was noted that the hydrogen content in the reaction product of the partial oxidation of the mixture of visbreaking distillate and residue diluted with pyrolysis fuel oil, achieved 50 %. The content of components in the gaseous product accorded well with a synthesis gas composition produced by the plant unit of the UNIPETROL RPA Co., designed and built under licence from the Shell Petroleum Co.     

Time resolved measurements of the energy distribution in unstable plasma II. Measurement in the ionization waves

A sampling technique described in Part I has been used, for measurement of the electron distribution function. Two groups of electrons and changes of the distribution function along the ionization waves of small amplitude have been found.The authors wish to acknowledge the support afforded them by Professor Dr. V. Kunzl.     

Photometric microtitrations. II

Summary A photometric titration method of microgram concentrations of zinc with dithizone as metallochromic indicator is described. The shape of the titration curve is most favourable for linear end-point extrapolation, if zinc is determined in a 50% ethanolic solution buffered with hexamethylenetetramine to ph 4.8–5.0. The optimum wavelength for the titration is 590 nm. For the concentration range of 2–20g of Zn²⁺ the relative error is ±1–2%. Interfering metals such as cadmium and lead may be masked by hydroxyethyldithiocarbamate.

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Zusammenfassung Eine photometrische Titrationsmethode zur Bestimmung von Mikrogrammengen Zink mit Dithizon als metallochromer Indikator wurde beschrieben. Der Knick der Titrationskurve ist für die lineare Extrapolation des Endpunktes sehr günstig, wenn das Zink in 50%iger äthanolischer Lösung bestimmt wird, deren ph mit Hexamethylentetramin auf 4,8 bis 5,0 gepuffert wird. Die beste Wellenlänge für die Titration ist 590 nm. Für den Konzentrationsbereich 2 bis 20g Zn beträgt der relative Fehler ±1 bis 2%. Störende Metalle wie Cadmium und Blei lassen sich mit Hydroxyäthyldithiocarbamat maskieren.

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Résumé On décrit une méthode de titrage photométrique du zinc en concentration de l'ordre du microgramme, par la dithizone, avec un indicateur métallochromique. La forme de la courbe de titrage se montre très favorable pour l'obtention par extrapolation linéaire du point équivalent, si l'on dose le zinc en solution éthanolique à 50%, tamponnée par l'hexaméthylènetétramine à ph 4,8–5,0. La longueur d'onde optimale pour le dosage est 590 nm. Pour les concentrations de l'ordre de 2–20g de Zn²⁺, l'erreur relative est de ±1–2%. Les métaux qui interfèrent, comme le cadmium et le plomb, peuvent être masqués par l'hydroxyéthyldithiocarbamate.

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Dedicated to Prof. DSc.M. Jureek on the occasion of his 60th birthday.     

Cleaning of Porous Aluminium Titanate by Oxygen Plasma

The removal of organic contaminants from porous Al₂TiO₅ during treatment in oxygen plasma was studied by optical emission spectroscopy (OES). The samples of Al₂TiO₅ were immersed into water emulsion of mineral oil for 3 h to get soaked. Then, they were thoroughly cleaned in ultrasound to remove oil from the surface. Samples were later exposed to RF oxygen plasma at the pressure of 75 Pa. The plasma density was about 2 × 10¹⁶ m⁻³, the electron temperature was about 6 eV and the density of neutral oxygen atoms was about 2 × 10²¹ m⁻³. Optical emission spectra between 200 and 1,000 nm were measured continuously during plasma treatment. The CO peak resulting from oil oxidation reached a well-pronounced maximum between 100 and 150 s of plasma treatment. The maximum in CO corresponded well with a minimum in O peaks. Concentration of oil in the samples was estimated by energy dispersion X-ray analysis. Initially the samples showed high concentration of carbon (about 38 at.%), while after plasma treatment the carbon concentration decreased below the detection limit. The cleaning efficiency was explained by diffusion of oil towards the surface where it was removed by oxidation with oxygen radicals.     

Extractions with long-chain amines-I Extraction of some metal-xylenol orange complexes into methyltrioctylammonium chloride (aliquat 336-S)

The extraction of traces of metals forming intensely coloured complexes with Xylenol Orange in acidic medium (pH 0-3) has been studied. For such extractions in the presence of sulphates, chlorides and nitrates, a solution of methyltrioctylammonium chloride (Aliquat 336-S) in chloroform has been used. It is shown that it is possible to detect small amounts of gallium in indium and vice versa, and titanium or zirconium in thorium. These reactions should be capable of adaption to spectrophotometric determinations. The principle of the extraction of metals as their complexes with various metallochrornic indicators is briefly discussed.     

Contributions to the basic problems of complexometry-XX Determination of calcium and magnesium

A new method for the determination of magnesium in the presence of calcium is described. Calcium is masked with EGTA whilst magnesium is titrated with DCTA with Methylthymol Blue as the indicator. Calcium can be determined in the same solution by back-titration of the excess EGTA with calcium chloride solution. The usual masking agents for iron, aluminium and other heavy metals can be used.     

Enantioselective Synthesis of Spiro Heterocyclic Compounds Using a Combination of Organocatalysis and Transition-Metal Catalysis

Over the last ten years, the combination of organocatalysis with transition metal (TM) catalysis has become one of the most important toolboxes used for synthesizing optically pure compounds containing chiral quaternary centers, including spiro heterocyclic molecules. The dominant method in the enantioselective synthesis of spiro heterocyclic compounds based on synergistic catalysis includes chiral aminocatalysis and NHC catalysis, as already established covalent organocatalytic strategies. Another area of organocatalysis widely combined with TM catalysis producing enantiomerically enriched spiro heterocyclic compounds is non-covalent catalysis, dominated by chiral phosphoric acids, thiourea, and squaramide derivatives. This review article aims to summarize enantioselective methods used for constructing spirocyclic heterocycles based on a combination of organocatalysis and transition metal catalysis.