Colouration Process Research Articles

Enhancement of gasochromic response to hydrogen of WO3 thin films by post-process modification and catalyst selection

The gasochromic properties of WO3 thin films deposited by electron beam evaporation were investigated, focusing on their structural, morphology and optical changes caused by heat treatment. Moreover, the influence of the thickness and type of catalyst on the gasochromic properties of WO3 was examined. X-ray diffraction measurements revealed that WO3 thin films annealed up to 473 K remained amorphous, whereas annealing at 673 K and above, initiated crystallization into a monoclinic structure. Gasochromic behaviour was observed in response to hydrogen exposure, with the most significant changes occurring in films annealed at 673 K with a thin adlayer of palladium catalyst. A gasochromic response of 1.84 was achieved for H2 concentration as low as 25 ppm. The process of gasochromic colouration was correlated with the changes of free charge carrier concentration calculated based on Drude free electron theory. XPS analysis confirms WO3 reduction under hydrogen exposure, validating proposed colouration mechanisms. These comprehensive findings offer insights into optimizing gasochromic thin films for various sensing applications.

Colouration of Polyester Using Bio-Shell Microcapsules: Efficient Resource and Waste Water Management

The present work aimed at efficient utilization of resources viz., water, dyes and chemicals (without using any supportive chemical) for colouration of polyester. The method of complex coacervation was attempted for obtaining the microcapsules. Bio-shelled (gelatin and gum acacia) microcapsules of disperse dyes were analysed for their resource efficient auxiliary chemicals free colouration on polyester (PET) over conventionally dyed one. The remnant liquor recovered from colouration of polyester was recycled for subsequent three colouration cycles (without treatment) showing negligible shade difference and the fastness rating. The effluent of fourth colouration cycles treated with primary water treatments and was found to be translucent, neutral in pH and low effluent load (TDS >231 ppm, BOD >114 mg/l, and COD > 469 mg/l). The solids recovered from bath were analyzed and found to be nontoxic (LD50 > 8000) as well. Cost of disperse dye microcapsules was calculated to be USD $ 4.17 /kg. Cost involved in microencapsulated colouration is much lower (USD $ 2.19) than conventional process of colouration (USD $ 3.93) due to absence of auxiliary chemicals, post treatment, much lower electrical energy consumption. Thus, microencapsulated colouration is easily adoptable in existing process line of polyester colouration, which leads to small liquid discharge of low effluent load.

New Approaches for Textile Colouration and Surface Pattern Using Enzyme-based Biotechnology

The research presented in this paper gives an overview of a study which was undertaken to investigate the potential offered by the enzyme laccase (EC.1.10.3.2) as a creative design tool for innovative colouration and decorative surface pattern of textiles with a focus on providing sustainable alternatives to conventional processes used in industry. Research was conducted in two parts. The control (scientific) phase explored laccases potential for transforming a range of colourless aromatic compounds into coloured polymeric products via its reaction mechanism, and its ability to facilitate the colouration of most commonly used textile fibre types. Reaction processing parameters such as temperature, pH values, aromatic compound concentrations, and reaction times were investigated to achieve a diverse colour palette, ranging from light–medium to dark shades of blue, green, pink, purple, and yellow hues. Wool and nylon fibre types were found to be most suitable for laccase-catalyzed colouration. The creative phase investigated the design potential offered by the enzymatic colouration process developed; different and contrasting substantivity properties offered by various fibre types were exploited to produce shadow, reserve, and contrasting coloured effects on specially woven jacquard fabrics. The research demonstrates the potential offered by laccase as a transformative tool to replace conventional industrial colouration and surface pattern design processes with biological systems, which offer important advantages of simpler processing using milder conditions that eliminate additional chemical use and reduce energy consumption. The adoption of enzyme-based biotechnologies could help the textile industry transition towards a sustainable future.

Major Development in Cotton Coloration: A Review

Most cotton fabrics are dyed with reactive dyes because they produce a full range of bright fashion colours with a high degree of wash fastness.Reactive dyes are frequently considered as king of dyes for cotton owing to their simple application techniques. However, reactive dyes are anionic and cotton fibers gain anionic surface charge in water, the charge repulsion adversely affects the dye bath exhaustion. Large quantity of electrolyte is added to overcome this problem. Some problems such as low dye utilization, high degree of salt utilization and colored effluent due to unexhausted, unfixed, and hydrolyzed dyestuffs, and high volume of waste water discharged, always exist in the application of reactive dyes.These electrolytes are neither exhausted nor destroyed and hence remain in the discharge dye liquor which leads to enormous environmental problem. Due to these problems this class of dyes is the most unfavorable one from the ecological point of view, these effluents produced gives high values of BOD/COD and increases salinity of the rivers affects the delicate biochemistry of aquatic life.A number of more environmentally sustainable approaches for reactive dyeing of cotton have been proposed to overcome the polluted effluent problem. This paper reviews options to improve the sustainability of the colouration process through development in dye structure, modification of dyeing machinery and processes, chemical modification of cotton fibre prior to dyeing, and use of organic compounds in place of inorganic chemicals.

Realisation of Solid-State Electrochromic Devices Based on Gel Electrolyte.

Background: In the last decade, there has been much interest in the area of solid polymer electrolyte (SPE) to address the issues of electrolyte leakage and evaporation in electrochromic devices (ECD). ECD is a state-of-the-art technology having the ability to change from transparent state to opaque state under the influence of a small applied voltage for energy saving applications. Methods: In this work, tungsten oxide (WO 3) films were fabricated via the sol-gel spin-coating method. Subsequently, ECDs were assembled based on SPE and liquid polymer electrolyte (LPE), respectively using indium doped tin oxide (ITO) coated glass as conducting electrodes and WO 3 films as working electrode. Results: Cyclic voltammetry (CV) results revealed reduced ionic conductivity of conducting ions in SPE based ECD (SECD) owing to increased viscosity by addition of PMMA. However, lesser time was required for the colouration process. LPE based ECD (LECD) showed higher colouration efficiency (CE) compared to its SECD counterpart. This is attributed to its larger optical modulation. Conclusions: This work presents a comparison between the performance of LECD and SECD in terms of electrochromic (EC) and optical properties. They were analysed through CV, chronoamperometry (CA) and ultraviolet-visible (UV-Vis) spectrophotometer. Furthermore, this work provides an insight on the employment of solid-state electrolytes in ECDs in view of the persistent leakage and evaporation problems in ECD implementation.

Realisation of Solid-State Electrochromic Devices Based on Gel Electrolyte

Background: In the last decade, there has been much interest in the area of solid polymer electrolyte (SPE) to address the issues of electrolyte leakage and evaporation in electrochromic devices (ECD). ECD is a state-of-the-art technology having the ability to change from transparent state to opaque state under the influence of a small applied voltage for energy saving applications. Methods: In this work, tungsten oxide (WO 3) films were fabricated via the sol-gel spin-coating method. Subsequently, ECDs were assembled based on SPE and liquid polymer electrolyte (LPE), respectively using indium doped tin oxide (ITO) coated glass as conducting electrodes and WO 3 films as working electrode. Results: Cyclic voltammetry (CV) results revealed reduced ionic conductivity of conducting ions in SPE based ECD (SECD) owing to increased viscosity by addition of PMMA. However, lesser time was required for the colouration process. LPE based ECD (LECD) showed higher colouration efficiency (CE) compared to its SECD counterpart. This is attributed to its larger optical modulation. Conclusions: This work presents a comparison between the performance of LECD and SECD in terms of electrochromic (EC) and optical properties. They were analysed through CV, chronoamperometry (CA) and ultraviolet-visible (UV-Vis) spectrophotometer. Furthermore, this work provides an insight on the employment of solid-state electrolytes in ECDs in view of the persistent leakage and evaporation problems in ECD implementation.

Realisation of Solid-State Electrochromic Devices Based on Gel Electrolyte.

Background: In the last decade, there has been much interest in the area of solid polymer electrolyte (SPE) to address the issues of electrolyte leakage and evaporation in electrochromic devices (ECD). ECD is a state-of-the-art technology having the ability to change from transparent state to opaque state under the influence of a small applied voltage for energy saving applications. Methods: In this work, tungsten oxide (WO 3) films were fabricated via the sol-gel spin-coating method. Subsequently, ECDs were assembled based on SPE and liquid polymer electrolyte (LPE), respectively using indium doped tin oxide (ITO) coated glass as conducting electrodes and WO 3 films as working electrode. Results: Cyclic voltammetry (CV) results revealed reduced ionic conductivity of conducting ions in SPE based ECD (SECD) owing to increased viscosity by addition of PMMA. However, lesser time was required for the colouration process. LPE based ECD (LECD) showed higher colouration efficiency (CE) compared to its SECD counterpart. This is attributed to its larger optical modulation. Conclusions: This work presents a comparison between the performance of LECD and SECD in terms of electrochromic (EC) and optical properties. They were analysed through CV, chronoamperometry (CA) and ultraviolet-visible (UV-Vis) spectrophotometer. Furthermore, this work provides an insight on the employment of solid-state electrolytes in ECDs in view of the persistent leakage and evaporation problems in ECD implementation.

DESIGN AND FABRICATION OF REPROMASTER DYEING MACHINE

Dyeing is a process of complete colouration of textiles, and this can be achieved by the type and the extent of pre-treatment imputed to produce an excellent absorbency and whiteness. Quality dyeing depends on factors such as pH, form of textile, type of fibre, formulation of dyeing recipe, initial preparation of dye solution, liquor mixture ratio, and selection of machinery mixing speed. This research work illustrates basic design and fabrication concepts of repromaster dyeing machine and also to achieve effective implementation of the ideal technology of dyeing. This machine was designed and fabricated to carry out textile dyeing for mass production. Although selection of machine depends on type of process to be carried out, which are batch, semi-continuous or continuous dyeing process. This repromaster dyeing is a continous process machine with an excellent dye output, it is faster, require less skill to operate and cost effective. This research work concept provides some firsthand information on some basic dyeing processes. KEYWORDS: Repromaster, machine, dyeing, working principle, continuous, fibre, colouration.

Development, testing and evaluation of energy savings potentials of photovoltachromic windows in office buildings. A perspective study for Australian climates

PhotoVoltaChromic (PVC) cells are among the emerging smart windows technologies with an interesting potential of building integration. PVC technology combines ElectroChromic materials with Dye Sensitized Solar cells in order to have a self-powered adaptive transparent film. The main advantage of this technology is to have an automatic control – potentially manually overridden – of colouration process, depending on levels of solar irradiance. Moreover, a PVC window can operate, at the same time, as a photovoltaic cell, producing energy exceeding the amount required for the colouring process. In the current study, for the first time, the full potential of PVC windows in office buildings is assessed. For this analysis, a PVC cell with a Visible Light Transmittance (VLT) variable between 16.9% and 31.5% has been selected. Australia has been considered as reference location, due to the presence, in its territory, of different climatic regions, ranging from tropical/subtropical climates to the temperate ones. The results show a strong dependence of potential energy savings on Window-to-Wall Ratio (WWR) and solar irradiance on windows. In cooling dominated climates, the adoption of PVC windows has been demonstrated to be always beneficial, even with very low WWR and/or non-optimal exposures, achieving overall energy savings of up to 20%. In heating dominated climates, adoption of PVC windows should be carefully considered, as it is highly beneficial when large glazed surfaces are present. In this case annual total energy savings up to the 32% can be predicted in comparison with buildings equipped with standard clear windows.

Structural colouration of textiles with high colour contrast based on melanin-like nanospheres

The striking structural colour originated from photonic crystals (PCs) self-assembled with specific nanospheres has been applied in various industries. Structural chromogen with lifelike manifestations is also expected to become a novel colouration technology for textiles. However, the contrast of structural colour is usually affected by scattered light generated from nanospheres. In order to obtain high contrast structural colour on fabric substrates, the melanin-like nanospheres were prepared and applied to fabricate PCs on white fabric surface. The melanin-like PS@PDA nanospheres showed smooth surface and perfect sphericity, which assured the self-assembly of melanin-like nanospheres to form well-organized face-centred cubic and regularly close-packed arrays to exhibit brilliant structural colour. In addition, the phenomenon of double-sides structural colouration of fabric was explained via analysing the driving force of self-assembly of nanospheres in dispersion solution. It is found that the melanin-like nanospheres can replace black substrate to achieve high contrast structural colour on white fabric substrate and simplify the process of structural colouration of textiles because the dyeing process of fabric can be omitted. The feasible technique would promote the practical application of structural colour in textile field.

Toxicity and environmental impacts approached in the dyeing of polyamide, polyester and cotton knits

Three colouration process was analyzed, in which consumption of water, the spent of electrical and thermal energy, emission of carbon dioxide besides effluent toxicity of dyeing of polyamide, cotton and polyester knits were approached. the dyeing of polyamide knit presented lowest consumption of electrical energy, the dyeing of polyester knit presented the lowest consumption of thermal energy and emission of co2 molecules into atmosphere, and the effluent of cotton dyeing presented lowest acute toxicity (CE50) to Daphnia similis.

In situ colouration of wool

In nature, enzymes catalyse the oxidation of phenols to produce quinonic compounds which are deeply coloured. In this study, the same process was mimicked for colouration of wool. Oxidative polymerisation of catechol was carried out in situ by combining fresh potato juice (enzyme source) with catechol (phenol) to synthesise a range of fast colours. Effect of process variables, namely concentration, time and temperature of treatment on colour value was studied. The unique property of this process is that besides colouration, it improves the mechanical properties and imparts value added properties such as antioxidant and improved moisture management to wool. As the process is based on use of unrefined plant juice instead of purified enzymes it is more economical and ecofriendly. The study opens up an area for exploration of local plant sources for a clean process of colouration.

De Colorando Auro: Medieval colouring techniques researched using modern analytical techniques

The visual appearance of gold and gilding can be influenced in many ways, such as by changing the composition of the gold alloy or the nature of the gilded substrate. A less known medieval technique, reported in historical treatises, is the chemical treatment of the gilded surface itself, after application and burnishing of the gilding. We reporte here results regarding the study of the Holy Lady Shrine of Huy (13th c AD Mosan, Belgium) on which a possible artificial colouration of the gildings was detected. This led to many questions regarding applicable conservation-restoration treatments. Here is an overview of the results obtained, along with a discussion of the methodology that was developed to study this colouration process, also highlighting the necessary complementarity between laboratory and synchrotron-based analytical approaches. The 3-steps methodology proposed in this paper is generic for most cultural heritage problems where the application of ancient surface modification recipes is suspected but where the scarcity of the historical samples does not allow a direct study of such samples.

Luminescent Properties of Cerium Doped Potassium Iodide Single Crystals in Response to γ-irradiation.

Potassium iodide doped with cerium ions were prepared by Bridgemann Stockbarger technique and investigated by optical absorption, Photoluminescence(PL), Thermoluminescence(TL), Photostimulated Luminescence(PSL) and TL emission. The optical absorption measurement indicates that F and V centers are formed in the crystals during the γ-ray irradiation process. Optical absorption and Photoluminescence studies confirm the presence of cerium ions in the trivalent state. Spectral distribution under the Thermoluminescence Emission(TLE) and Optically Stimulated Luminescence(OSL) support the idea that the defect annihilation process to be due to thermal release of F-electron in KI:Ce(3+) crystals. Both Ce(3+) and Ce(2+) emissions were observed in the Thermoluminescence emission of the crystals. Thermoluminescence(TL) has been identified to be due to thermal release of electron produced during colouration process.

Effects of bleaching on absorbency and strength of jute-cotton union furnishing fabrics

Bleaching of jute-cotton union fabric has been carried out using different chemicals and methods. It was found that the Sample L bleached with sodium silicate and H 2 O 2 sequentially at 85°C for one hour then at room temperature for another hour and the sample M bleached at RT with a sequential combination of chemicals produce acceptable level of whiteness and efficient to carry out the colouration process successfully and these processes are energy saving, economical and also minimize damage in fabric strength. The absorbency property of these samples was very satisfactory, hence, efficient to carry out the colouration process successfully besides, these processes are energy saving, economical and also minimize damage to fabric tearing and bursting strengths. Moreover, the increase in absorbency of these materials, particularly for sample M was at par with conventional kier-boiled and bleached sample N. Conventional bleaching process produces a pure white colour but there was substantial loss in fabric strength and weight.

On the Origin of the Green Colour of Archaeological Bone Artefacts of the Gallo‐Roman Period

Recent findings in the city of Reims have lead to the discovery of manufactured bone objects coloured in green throughout their entire volume. In order to discover the intentional nature of the colouration and to propose a colouration mechanism, modern ox bones have been coloured in the laboratory. Bones with a hue similar to that of the archaeological artefacts have been obtained by boiling in an acidic brine in a copper vessel. A combination of infrared spectroscopy, X‐ray diffraction and transmission electron microscope observations did not reveal the speciation of copper, but allowed us to validate the colouration process and to discuss the intentional origin of the colouration.

Colouration process of colloidal tungsten oxide nanoparticles in the presence of hydrogen gas

In this study, tungsten oxide nanoparticles were fabricated by pulsed laser ablation (PLA) of tungsten target using the first harmonic of a Nd:YAG laser (1064nm) in deionized water. After ablation, a 0.2g/lit PdCl2 solution was added to activate the solution against the hydrogen gas. Dynamic light scattering and X-ray photoelectron spectroscopy were used to measure the average size and the surface chemical composition of the synthesized nanoparticles, respectively. The aim is to investigate the influence of hydrogen exposure time on colouration process of colloidal nanoparticles. According to optical measurements, hydrogen bubbling into the produced colloidal Pd–WO3 led to formation of several absorption peaks at ∼1.26, ∼1.6 and ∼1.97eV. We observed the appearance and growth of a peak at 1.6eV at the initial stages of hydrogen exposure. However, two other peaks became dominant at long exposure times. The coloration process is reversible in the presence of oxygen gas.

Prerequisites for evolution: variation and selection in yellow autumn birch leaves

Prerequisites for evolution: variation and selection in yellow autumn birch leaves

Thermoluminescence and optical studies on X-irradiated terbium-doped potassium bromide crystals

This paper reports the thermoluminescence (TL) and other optical studies made on terbium-doped KBr crystals X-irradiated at room temperature. Photoluminescence studies confirm the presence of terbium ions in the KBr matrix in their trivalent form. Formation of Z 1 centres on F-bleaching of X-irradiated crystals is observed. The characteristic emission due to Tb 3+ ions in the spectral distribution under optically stimulated emission and thermoluminescence emission confirm the participation of the Tb ions in the recombination process. TL process has been identified to be due to the thermal mobilization of electrons produced during the colouration process.

Importance of olfactory and visual signals of autumn leaves in the coevolution of aphids and trees

Deciduous trees remobilize the nitrogen in senescing leaves during the process of autumn colouration, which in many species is associated with increased concentrations of anthocyanins. Archetti and Hamilton and Brown observed that autumn colouration is stronger in tree species facing a high diversity of specialist aphids. They proposed a coevolution theory that the bright colours in autumn might provide an honest signal of defence commitment, thus deterring migrant aphids from settling on the leaves. So far, there have been very few experimental results to support the hypothesis, and tree commitment to phenolics-based defences has not shown direct protection against aphids. Predators and parasitoids have been found to be the major controllers of arboreal aphids. Indirect defences involve the emission of attractive volatile compounds that enhance the effectiveness of carnivorous enemies. The indirect defence hypothesis is presented to explain low aphid diversity on tree species that are green during autumn. The hypothesis suggests that green foliage can continue to produce herbivore-inducible plant volatiles and maintain volatile-based indirect plant defences against aphids until leaf abscission.