Effects of structural changes on thermal properties and pyrolysis of modified cotton fibres

The changes resulting in the supramolecular structure of cotton fibres after mercerization at different temperatures were investigated by means of X-ray diffraction, sorption measurements and determination of the degree of polymerization. For comparison, corresponding measurements were also carried out after liquid ammonia treatment. Pyrolysis of the mercerized cotton samples showed that the levoglucosan yield of NaOH-treated samples is less than that of untreated or NH₃-treated samples. Comparisons were made of the thermal stability of the modified cotton samples, as indicated by DTA and TG.A decrease in the percentage crystallinity was found to lower the onset and peak temperatures of the major decomposition reactions. An NH₃-treated sample (acetone) was less thermally stable than untreated or mercerized samples.

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Zusammenfassung Mittels Röntgendiffraktionsuntersuchungen, Sorptionsmessungen und Bestimmung deas Polymerisationsgrades wurden die Veränderungen untersucht, die durch die Merzerisierung bei verschiedenen Temperaturen in der supramolekularen Struktur von Baumwollfasern verursacht werden. Zum Vergleich wurden ähnliche Untersuchungen nach Behandlung mit flüssigem Ammoniak durchgeführt. Die Pyrolyse der merzerisierten Baumwollproben zeigt, daß die Levoglukosanausbeute bei NaOH-behandelten Proben geringer ist als bei unbehandelten oder NH₃-behandelten Proben. Auf Grundlage von DTA und TG wurden vergleichende Betrachtungen zur Wärmebeständigkeit der modifizierten Baumwollproben angestellt. Eine Abnahme de prozentualen Kristallinität senkt die Temperatur für Beginn und Peak der hauptsächlichsten Zersetzungsreaktionen. NH₃-behandelte Proben (Azeton) sind thermisch unbeständiger als unbehandelte oder merzerisierte Proben.

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Effect of ionizing radiation on the spectral and electrical properties of clean NH3-mercerized cotton fabric strips

Three different types of ion exchangers namely Dowex-50 WX8, AG-2X8 and Chelex-100 are used to study the sorption behavior of Th(IV) and U(VI) from solutions of Arsenazo-I. The sorption behavior of Arsenazo-I itself is also studied. Possible species sorbed on these resins or present in solutions of U(VI)-and Th(IV)-Arsenazo-I at different concentrations and at different hydrogen ion concentrations are identified. From the obtained data, optimal conditions for separating the two elements are recommended. The possibility of individual concentration of Th(IV) and U(VI) as coloured Arsenazo-I complexes on AG-2X8 is evaluated.     

High efficiency ultra-deep dyeing of cotton via mercerization and cationization

A potentially environmentally responsible dyeing procedure for ultra-deep shades on cotton was developed using a cationization method in combination with mercerization. The effects of both treatments on dyeing performance and colorfastness properties of cotton fabrics dyed with reactive dyes were analyzed individually and in combination. Both mercerization and cationization have been proved to be effective in increasing the depth of shade on cotton. The colorfastness properties, except colorfastness to wet crocking, of mercerized–cationized cotton fabrics dyed without salt were much better than untreated cotton dyed using a conventional dyeing procedure. Unlike untreated cotton fabrics, the concentration of Na₂CO₃ in the dyeing process of mercerized–cationized cotton fabrics was lowered from 20 to 5 g/L without compromising dye fixation and colorfastness properties. With low concentrations of dyes and Na₂CO₃ and no electrolyte in the dye bath effluent, the dyeing procedure of mercerized–cationized cotton fabrics for ultra-deep shades is potentially a more environmentally benign method than conventional dyeing with reactive dyes.     

Influence of changes in fine structure on thermal properties of cotton fibres

Examinations of the structural changes of mercerized cottons in sodium hydroxide or liquid ammonia were followed by determination of the degree of polymerization, sorption ratio and X-ray percentage crystallinity. Comparisons were made of the thermal stability, as indicated by differential thermal analysis and thermogravimetric analysis of the mercerized cottons. A decrease in the percentage crystallinity was found to lower then onset and peak temperatures of the major decomposition reaction. It was also found that the temperature where the major weight loss began increased in the sequence: cellulose III, cellulose II, and cellulose I. Samples in cellulose III crystals form were less thermally stable than samples of cellulose I and cellulose II. It will be noted however that the difference between cellulose II and cellulose III was small. Cotton cellulose II gave a lower yield of levoglucosan than either cotton cellulose I or II.

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Zusammenfassung Strukturelle Veränderungen von merzerisierter Baumwolle in Natriumhydroxid oder flüssigem Ammoniak wurden durch Bestimmung des Polymerisationsgrades, des Sorptionsverhältnisses und der röntgen-Kristallinität verfolgt. Die differentialthermoanalytisch und thermogravimetrisch bestimmte thermische Stabilität der merzerisierten Baumwollen wird verglichen. Eine Verminderung der Kristallinität hat eine Abnahme der Temperaturen zur Folge, bei der die Hauptzersetzungsreaktion einsetzt bzw. mit maximaler Geschwindigkeit verläuft. Es wurde ebenfalls festgestellt, daß die Temperatur, bei der der Hauptgewichtsverlust einsetzt, in der Reihenfolge Cellulose III-Cellulose II-Cellulose I ansteigt. Proben in der Kristallform Cellulose III sind thermisch weniger stabil als die in der Celluloseform I und II. Baumwollcellulose II ergab geringere Ausbeuten an Levoglucosan als Baumwollcellulose I oder III.

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Effect of mercerization and gamma irradiation on the dyeing behaviour of cotton using stilbene based direct dye

The dyeing behaviour of mercerized and gamma irradiated cotton fabric using stilbene based direct dye has been investigated. The fabric was treated with different concentrations of alkali to optimize the mercerization. The optimum mercerized cotton fabric was irradiated to absorbed doses of 2, 4, 6, 8 and 10 kGy using Cs-137 gamma irradiator. Dyeing was performed using irradiated and un-irradiated cotton with dye solutions. The dyeing parameters such as temperature, time of dyeing, pH of dyeing solutions and salt concentration were optimized. The colour strength values of dyed fabrics were evaluated by comparing irradiated and un-irradiated cotton in CIE Lab system using Spectra flash SF650. Methods suggested by International Standard Organization (ISO) were employed to study the effect of gamma irradiation on the colourfastness properties of dyed fabric. It was found that mercerized and irradiated cotton have not only improved the colour strength but enhanced the rating of fastness properties also.     

Effects of substituent and solvent on the structure and spectral properties of maleimide derivatives

The maximum absorption wavelength , emission wavelength (λ_em) and the related oscillator strength (f) of the maleimides in the ground and first excited states were calculated by using the DFT, CIS and the time-dependent density functional theory (TD-DFT) methods, where the molecular structures were optimized by DFT/B3LYP/6-31G^* calculation. Solvent effects on the maleimides were examined using the PCM simulation at DFT/B3LYP level with the 6-31G^* basis set. For N-substituted maleimide, the substituent gives only a slight influence on the maleimide chromophore, while planar conformation of PhMLH leads to the improvement in π-delocalization from substituent to maleimide unit. For 3,4-substituted maleimide, the steric repulsion between substituent and maleimide chromophore influences the extent of π-delocalization and the molecular conformation. The calculated and λ_em of maleimides are in good agreement with the experimental data. In the gas phase, both absorption and emission peaks are red-shift as compared to the non-substituted maleimide. Under solvent environment, the more planar conformation of PhMLH shows a blue-shift in the calculated and λ_em as compared with other N-substituted maleimides. For 3,4-substituted maleimides, the effect of substitution produces the most significant spectral red-shift as compared to other maleimides.     

The influence of storage time on the temperature dependence of the dc electrical conductivity of horn keratin

The direct current electrical conductivity of horn keratin was measured as a function of temperature, in the temperature range 290-480 K, with a constant heating rate, for samples stored for periods of 2-3 weeks and 5 months. The activation energy of charge conducting process was calculated. The longer storage time reduced the water content, and the electrical conductivity, but increased the activation energy at 290-320 K.     

Effects of water contamination on the electrical properties of 18650 lithium-ion batteries

Effects of water on the voltage, internal resistance, initial capacity and cycling behavior of 18650-type lithium-ion batteries are studied. The voltage curves of the first charging can be used to judge whether cells are contaminated by water, because the voltage growth rates of cells are obviously different (>100 mV) between water-free batteries and containing water batteries at the first charging period of 10–50 min. The self-discharging performances of water contamination cells are also larger, because water-related side effects happen continuously during aging at high voltage of 4.2 V. Besides, HF corrosion on the cathode materials and Co ion dissolved out from lithium nickel cobalt manganese oxides lead to rapid capacity fading from >90% (100 cycles) to <80% (300 cycles, 0.5 C charging/0.5 C discharging).     

Effects of dopant concentration and aging on the electrical properties of Y-doped ceria electrolytes

High purity cerium oxide and yttrium oxide were used to form ceria-based solid solution (Ce_1−xY_xO_2−δ, 0.05x0.4) via a conventional mixed-oxide method. All the samples used were aged at 1000 °C in air for 8 days. Crystal structure and microstructure were characterized by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The ionic conductivity (i.e., grain interior (GI) grain boundary (GB) and total conductivities) in this system were systematically studied as a function of dopant content over the temperature range of 250–850 °C in air using an impedance spectroscopy. The lattice parameter decreased with increasing the Y content, but it did not obey Vegard's law. The Y doping had no significant effect on densification behavior and final sintered density, but leading to a significant decrease in grain size as compared to the undoped ceria. The composition x0.1 had a maximum GI conductivity, while a maximum total conductivity was observed at x0.15. A significant high-temperature aging effect was also found for the samples with higher Y doping levels. 10% and 15% decreases in the GI and GB conductivities, respectively, were detected in the aged Ce_0.7Y_0.3O_2−δ ceramic.     

Surface chemical analysis of raw cotton fibres and associated materials

The surface chemical composition of raw unscoured cotton was successfully investigated by the surface analytical techniques X-ray Photoelectron Spectroscopy (XPS) and Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS). The presence of non-cellulosic material at the fibre surface was established and determined to be a complex mixture of fatty acids, alcohols, alkanes, esters and glycerides. The effect of scouring and bleaching was to reduce the surface concentration of these materials but even after aqueous processing some non-cellulosic material residue was still detected at the fibre surface.     

Comparing different protocols of temperature selection in the parallel tempering method

Parallel tempering Monte Carlo simulations have been applied to a variety of systems presenting rugged free-energy landscapes. Despite this, its efficiency depends strongly on the temperature set. With this query in mind, we present a comparative study among different temperature selection schemes in three lattice-gas models. We focus our attention in the constant entropy method (CEM), proposed by Sabo et al. In the CEM, the temperature is chosen by the fixed difference of entropy between adjacent replicas. We consider a method to determine the entropy which avoids numerical integrations of the specific heat and other thermodynamic quantities. Different analyses for first- and second-order phase transitions have been undertaken, revealing that the CEM may be an useful criterion for selecting the temperatures in the parallel tempering.     

Effects of interfacial modifications on electrical properties of laminar composite dielectrics

The reported work highlights that both polarizibility and quasi-DC conductivity, the two most important parameters for high energy density materials, can be influenced by the surface polarity of an oxide and interfacial surface tension between the oxide and polymer in a laminar composite. Surface modification of laminar composites, composed of thermally grown silica and vapor phase grown Parylene C thin films using organosilanes, was used to control silica surface polarity and interfacial surface tension. Surface polarity of thermally grown silica was found to control the interfacial dipolar energy states.     

Studies on the growth, optical, electrical and spectral properties of potassium pentaborate (KB5) single crystals

The bulk single crystals of nonlinear optical material potassium pentaborate (KB5) have been grown by slow evaporation solution growth technique using water as solvent. The grown crystal was confirmed by single crystal X-ray diffraction studies. The structural perfection of the grown crystals has been analyzed by high resolution X-ray diffraction (HRXRD) studies by recording rocking curve. The photoluminescence (PL), UV-vis spectral studies were performed and the optical bandgap of the material was calculated. FTIR and FT-Raman measurements enumerate the functional groups present in the compound. The factor group analysis on KB5 reveals that there are 117 vibrational optical modes. The dielectric behavior of KB5 was investigated with different frequencies and temperatures.     

Effects of temperature and holding time during torrefaction on the pyrolysis behaviors of woody biomass

Torrefaction is the thermal treatment techniques performed at relatively low temperature (<300 °C) in an inert atmosphere, which aims to improve the fuel properties attractively. In this study, woody biomass (Leucaena leucocephala) was torrefied at various temperatures and holding times and the pyrolysis behaviors of the torrefied wood were examined in detail by using TG-MS technique. It was found that the carbon content and the calorific value of the torrefied leucaena increased significantly when temperature and holding time during the torrefaction increased. From the TG-MS analysis, the pyrolysis behaviors of the torrefied leucaena were significantly different from those of the raw leucaena. The char yield at 800 °C for the torrefied leucaena was increased when increasing the holding time during the torrefaction. On the other hand, the tar yield during the pyrolysis decreased significantly with the increase in the holding time during the torrefaction. Through the results from the TG-MS analysis, it was concluded that the structure of leucaena was changed by the torrefaction at temperature below 275 °C and the cross-linking reactions occurred during the pyrolysis resulting in increase in char yields and decrease in tar yields. It was also suggested that the longer the holding time during the torrefaction, the more the cross-linking reactions proceed during the pyrolysis. The results obtained from the study provide the basic information for the pyrolyser and/or gasifier design by using torrefied biomass as a fuel.     

Effects of the ancillary ligands of polypyridyl cobalt(II) complexes on pH-induced spectral properties and DNA binding properties

Abstract  

Two new Co(II) complexes [Co(ipH)₂(bdipH)]²⁺ and [Co(8-HQ)₂(bdipH)] (ipH = imidazo[4,5-f][1,10]phenanthroline, bdipH = 2-(benzo[d][1,3]dioxol-4-yl)-1H-imidazo[4,5-f][1,10]phenanthroline, 8-HQ = 8-hydroxyquinoline) were synthesized and characterized in detail by elemental analysis, IR, and UV–Vis spectroscopic techniques. The effects of pH on the UV–Vis absorption and emission spectra of the complex were studied. The interaction of the two complexes with calf thymus DNA was explored by using viscosity measurements, electronic absorption titration, competitive binding experiments, and cyclic voltammetry. The experimental results show that complex [Co(ipH)₂(bdipH)]²⁺ exhibits pH-sensitive emission, the two complexes can bind to DNA in an intercalation mode, and the DNA binding affinity of complex [Co(ipH)₂(bdipH)]²⁺ (K _b = 2.11 × 10⁵ M⁻¹) is greater than that of complex [Co(8-HQ)₂(bdipH)] (K _b = 1.76 × 10⁵ M⁻¹). The results show that the size and shape of the ancillary ligand have significant effects on the binding affinity of DNA and complexes.     

Effect of temperature and60Co γ-radiation damage on the electrical and structural properties of BaZrO3 ceramics

Well-sintered barium zirconate ceramic bodies have been prepared and identified. Extensive measurements have been made on these specimens, including X-ray diffraction, and DC-electrical conductivity as a function of temperature before and after exposure to a gamma-radiation dose and after various periods (radiation decay time) following removal of the specimens, from the radiation field. The resistivityvs. temperature curve showed an abrupt change at around 60°, in the reverse direction, indicative of a probable transition from ann- to ap-type semiconduction mechanism. Finally, all the results are discussed in detail and correlated on the basis of the interactions of temperature, ionizing radiation damage and radiation annihilation with the barium zirconate lattice.

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Zusammenfassung Gut gesinterte Bariumzirkonatkörper wurden hergestellt und identifiziert. An diesen Proben wurden umfassende Messungen vorgenommen, einschließlich röntgendiffraktometrische und die der elektrischen Gleichstromleitfähigkeit in Abhängigkeit von der Temperatur vor und nach Bestrahlung mit Gamma-Strahien und in Abhängigkeit von der nach der Bestrahlung vergangenen Zeit (Abklingzeit). Die Kurve des Widerstandes in Abhängigkeit von der Temperatur weist bei etwa 60° eine abrupte Änderung in entgegengesetzte Richtung auf, was auf einen wahrscheinlichen Übergang des halbleitungsmechanismus vomn- zump-Typ hinweist. Die in Einzelheiten diskutierten Ergebnisse sind miteinander in Übereinstimmung und werden mit der Wirkung der Temperatur und der durch Bestrahlung verursachten Schädigung und Annihilation des Bariumzirkonatgitters in Zusammenhang gebracht.

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Effects of temperature on conduction mechanism,ac electrical and dielectric properties of NdFe0.9Ni0.1O3 by employing impedance spectroscopy

Journal of Solid State Electrochemistry - In the present work, the effects of temperature and frequency on the ac electrical and dielectric properties of polycrystalline NdFe0.9Ni0.1O3, prepared by...     

Effects of glass-transition temperature on properties of photorefractive polymer composite

In this study, photorefractive polymer composites were developed in which polycarbonate was doped with a dual-function dopant and a photocharge generation sensitizer. The dual-function dopant has the function of providing both charge transport and optical nonlinearity. The composites' photoconductivity and electrooptic coefficient were investigated experimentally. The effects of the glass-transition temperature (T_g), dual-function dopant content, and electric field on the composites' photorefractive properties were studied as well. The results show that the composites' photorefractive properties are enhanced with decreasing T_g, increasing dual-function dopant content, and increasing electric field. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 3302–3306, 1999