Browsing by Author "Ali, Azam"
Now showing 1 - 10 of 10
Results Per Page
Sort Options
- ItemCopper electroless plating of cotton fabrics after surface activation with deposition of silver and copper nanoparticles(Elsevier Ltd, 2020-02) Ali, Azam; Baheti, Vijay; Vik, Michal; Militký, JiříIn this work, surface metallization of cotton fabrics was performed by electroless plating using a shorter route than is conventional. The fabric surface was activated by deposition of silver and copper nanoparticles, and then a thin layer of copper was coated using electroless plating. The performance of coated fabrics was compared in terms of electrical conductivity, electromagnetic interference (EMI) shielding, Joule heating and antibacterial properties with another sample coated with conventional electroless plating. The orthogonal array testing strategy was adopted to optimize the various factors of the electroless plating bath. The samples prepared by electroless plating of copper showed greater performance for the fabric first deposited with silver particles than those first deposited with copper particles or conventionally treated. Samples of copper electroplating over silver had surface resistivity of 20 Ω, EMI shielding of 75.53 dB and Joule heating of 83.1 °C. Moreover, samples with modified electroless plating showed better attachment of the metal layer and therefore longer durability.
- ItemDevelopment of electrically conductive composites based on recycled resources(2019-07) Ali, Azam; Baheti, Vijay; Khan, Muhammad Zaman; Ashraf, Munir; Militký, JiříThe current study was focused on the development of electrically conductive composites of carbon particle filled cotton fabric/epoxy systems. The carbon particles were refined to the scale of micro/nanoparticles using ball milling and morphological properties were studied by Malvern zetasizer and SEM. The influence of different concentrations of carbon particles in green epoxy resin for electrical conductivity was studied. Additionally, the electrical conductivity and electromagnetic shielding ability of conductive composites were analyzed. Waveguide method at high frequency (i.e. at 2.45 GHz) was used to investigate the EMI shielding. Similarly, the effect of different concentrations of carbon particles in composites was also studied for mechanical strength (tensile and flexural). A comprehensive study showed the improvements in electrical and mechanical properties with increase in the concentration of carbon particles and their even distribution in resin. The composites with higher carbon filler concentration showed maximum electrical conductivity (1.0E-02), shielding effectiveness 23.13 dB and mechanical properties.
- ItemElectrical Conductivity of PLA Films Reinforced With Carbon Nano Particles from Waste Acrylic Fibers(2018) Naeem, Salman; Gilani, Syed Qummer Zia; Baheti, Vijay; Wiener, Jakub; Militký, Jiří; Javed, Saima; Ali, Azam; Javed, Zafar; ul Hassan, Syed ZameerThe acrylic fibrous waste was effectively transformed into activated carbon through physical activation in single stage carbonization under charcoal using at different carbonization temperatures 800, 1000 and 1200 degrees C. The characterization of carbonized fibers was performed with the help of XRD and EDX in order to find out the degree of crystallinity and proportion of different elements in carbonized fibres prepared at different temperatures. Later on, the carbonized fibers were pulverized in dry conditions by high energy planetary ball milling to get activated carbon micro/nano particles. In addition to refinement of size, the electrical conductivity of pulverized carbon particles was found to increase with increase in milling time. Subsequently, the particles were incorporated into poly lactic acid (PLA) in different loadings from 1 to 10% to develop conductive green composite films The composite films were then characterized for electrical, thermo-mechanical and thermal properties.
- ItemEnergy harvesting performance of silver electroplated fabrics(ELSEVIER SCIENCE SA, PO BOX 564, 1001 LAUSANNE, SWITZERLAND, 2019-06-01) Ali, Azam; Baheti, Vijay; Militký, JiříThe objective of present study was to make electrically conductive multifunctional fabrics and their further use as electrodes for the development of triboelectric generator (TrEG). The conductive fabrics were made by the coating of thin copper layer and then electroplating of silver layer. The surface structure, electrical conductivity, hydrophobicity, and antibacterial properties of coated fabrics were examined to know their multifunctional properties. After silver electroplating, the fabrics depicted the electrical resistivity of 2 Omega mm as compared to 70 Omega mm electrical resistivity reported for the copper coating alone. Later, the energy harvesting performance of conductive fabric electrodes was studied by combining with oppositely charged triboelectric materials such as silicon rubber and rabbit fur. The fabricated TrEG was found to produce 21 V and 3.5 mu A current under the stretching action whereas 33 V and 6 mu A current under the pressing action. Furthermore, it charged the 1 mu F capacitor to 17 mV in 5 s. When its energy harvesting performance was investigated under the mechanical actions of human body, it generated about 10 V from elbow movements and about 40 V from foot movements.
- ItemInvestigation of Mechanical and Thermomechanical Properties of Nanocellulose Coated Jute/Green Epoxy Composites(2018) Jabbar, Abdul; Militký, Jiří; Ali, Azam; Javed, Muhammad UsmanThe present study was aimed to investigate the effect of nanocellulose coating on the mechanical and thermomechanical properties of jute/green epoxy composites. Cellulose was purified from waste jute fibers, converted to nanocellulose by acid hydrolysis and subsequently 3, 5 and 10 wt% of nanocellulose suspensions were coated over woven jute reinforcement. The composites were prepared by hand layup and compression molding technique. The surface topologies of treated jute fibers, jute cellulose nanofibrils (CNF), nanocellulose coated jute fabrics and fractured surfaces of composites were characterized by scanning electron microscopy (SEM). The prepared composites were evaluated for tensile, flexural, fatigue, fracture toughness and dynamic mechanical properties. The results revealed the improvement in tensile modulus, flexural strength, flexural modulus, fatigue life and fracture toughness of composites with the increase in concentration of nanocellulose coating over jute reinforcement except the decrease in tensile strength. Dynamic mechanical analysis (DMA) results also showed the increase in storage modulus and reduction in tangent delta peak height of nanocellulose coated jute composites.
- ItemMetal Coating on Ultrafine Polyester Non-woven Fabrics and Their Ageing Properties(2019-07) Ali, Azam; Baheti, Vijay; Militký, Jiří; Khan, Zaman; Zhu, GuochengThe presented research work proposed a simple technique to metalize the milife fabric (very fine thickness) with silver coating. The polyester fabrics were firstly sensitized with copper, and then silver plating was performed on the surface. The presence of silver over the fabric was observed by scanning electron microscope and respective EDX spectra. The change in the electrical conductivity, electromagnetic shielding and joule heating properties were examined for different electroplating time. The electrically conductive fabrics showed low electrical resistance with high EMI shielding over frequency range of 30 MHz to 1.5 GHz. To have an idea about the durability of electrical conductivity under stretch load, the 75 cycles of stretch and release were carried out. Furthermore, the heating performance of silver plated fabric was studied through measuring the change in temperature at the surface of the fabric while applying a voltage difference across the fabric. Lastly, the effect of ageing parameters like washing, oxidation and sulfidation were examined on the functional and comfort properties (i.e. thermal conductivity and stiffness) of conductive fabric.
- ItemMultifunctional polylactic acid composites filled with activated carbon particles obtained from acrylic fibrous wastes(2019-02) Naeem, Salman; Baheti, Vijay; Militký, Jiří; Ali, AzamThe objective of this work was to explore the potentials of porous and electrically conductive activated carbon particles for possible enhancement of multifunctional properties of PLA. The activated carbon was inexpensively prepared from acrylic fibrous wastes by novel single stage carbonization and physical activation. The influence of 800 degrees C, 1,000 degrees C, and 1,200 degrees C carbonization temperature on physical, morphological, and electrical properties was studied from EDX, X-ray diffraction, SEM, and BET analysis. Later, the carbonized acrylic fibrous waste was pulverized in dry conditions by high energy planetary ball milling to get activated carbon particles. The particles were then incorporated into PLA under 1, 5 and 10 wt% loading to prepare composite films by solvent casting, and their electrical conductivity, EMI shielding, thermo-mechanical, and thermal stability properties were investigated.
- ItemPovrchové ukládání kovů na textilní strukturyAli, Azam; ; Militký Jiří, prof. Ing. CSc. Skolitel : 55135Tato disertační práce se zabývá vývojem elektricky vodivých, multifunkčních textilií chránících proti elektromagnetickému záření v širokém rozsahu frekvencí (EMI). V první části práce byly připraveny vodivé textilie pomocí in-situ povrchové depozice částic mědi. Pro studium morfologie nanesených částic mědi byl použit skenovací elektronový mikroskop a rentgenové difrakční techniky. Funkčnost vodivých tkanin byla analyzována hodnocením účinnosti elektromagnetického stínění v kmitočtovém rozsahu 30 MHz až 1,5 GHz. Bylo zjištěno, že stínění elektromagnetického rušení se zvyšuje se zvyšujícím se počtem dílčích nánosů, což přímo souvisí se zvýšeným odrazem elektromagnetického záření jako důsledek tvorby husté (za perkolačním prahem) rovnoměrnější povrchové vrstvy vodivých částic mědi. Dále byla zkoumán vliv povrchové vrstvy částic mědi na antibakteriální odolnost proti patogenním bakteriím, jako je Staphylococcus aureus a Escherichia coli. Textilie s povrchovou vrstvou částic mědi vykazovaly dobrou odolnost v praní, což bylo prokázáno jak mikroskopickým zkoumáním mikrostruktury, tak malou ztrátou elektrické vodivosti po praní.Cílem druhé části disertační práce bylo vyvinout multifunkční tkané vodivé textilie v plátnové vazbě s přijatelnou elektrickou vodivostí pomocí in-situ nanášení částic stříbra. Byl zkoumán vliv koncentrace soli stříbra a počtu dílčích nánosů na změnu elektrické vodivosti, elektromagnetického stínění (EMI) a antimikrobiálních vlastností těchto multifunkčních tkanin. Pro studium morfologie uložených částic stříbra byla použita SEM analýza. Bylo zjištěno, že elektromagnetické stínění se zvyšuje se zvyšováním obsahu částic stříbra.Stříbrné částice byly také nanášeny na elastické pleteniny pomocí stejného způsobu in-situ nanášení. Cílem byla příprava elastických (vratně deformovatelných) vodivých pletenin pro možné aplikace v elektroterapii. Výhodnost těchto pletenin byla hodnocena na základě řady vlastností, jako je elektrická vodivost v normálním a deformovaném stavu, antibakteriální schopnosti a trvanlivost. Do 80% ní tahové deformace byla pozorována velmi malá změna elektrické vodivosti. Po 90% ní tahové deformaci bylo zjištěno, že se elektrický odpor významně zvyšuje. Bylo simulováno chování vodivých pletenin (elektrod) při různých pohybech lidského těla pomocí změn elektrického odporu při opakovaných cyklech prodlužování a odlehčování. Bylo zjištěno, že elektrický odpor zůstává konstantní při více než 100 cyklech prodlužování a odlehčování. Dlouhodobé působení konstantního elektrického proudu nevýznamně změnilo elektrický odpor elastických vodivých pletenin. Tyto elastické vodivé pleteniny textilií bude možno použít jako flexibilní textilní elektrody v elektroterapii transkutánní elektrické stimulace nervů.Třetí část disertační práce je zaměřena na návrh jednoduchého způsobu povrchového ukládání částic kovů na bavlněné tkaniny bez použití elektrického pole zkráceným. Povrch tkaniny byl aktivován nanesením nanočástic stříbra a mědi a následně byla vytvořena tenká vrstva částic mědi bez elektrickým pokovováním. Funkčnost povrchově pokovených tkanin byla hodnocena pomocí elektrické vodivosti, elektromagnetického stínění, teploty odporového ohřevu a bakteriální odolnosti. Textilie, kde byla provedena aktivace nanesením částic stříbra s následným bezproudovým pokovováním mědí, vykazovaly vyšší účinnost ve srovnání s textiliemi, kde byla provedena aktivace nanesením částic mědi s následným bezproudovým pokovováním mědí. Textilie aktivované nanesením částic stříbra s elektrolytickým pokovením mědi měly povrchový odpor 20 ?, elektromagnetického stínění 75,53 dB a teplotu 119 ° C při ohřevu pomocí stejnosměrného napětí 10 V při konstantním proudu 1 A (10 wattů). Kromě toho tyto textilie vykazovaly delší trvanlivost efektů.Cílem čtvrté části disertační práce bylo připravit elektricky vodivé multifunkční textilie využitelné jako elektrody pro triboelektrický generátor (TrEG). Vodivé textilie byly vyrobeny depozicí
- ItemSuperhydrophobicity, UV protection and oil/water separation properties of fly ash/Trimethoxy(octadecyl)silane coated cotton fabrics(Fiber Society, 2019) Khan, Muhammad Zaman; Baheti, Vijay; Militký, Jiří; Ali, Azam; Viková, MartinaThe presented study proposed simple and low-cost approach for improvement in UV protection and superhydrophobic properties of cotton fabrics by coating of mechanically activated fly ash particles. The maximum UV blocking was observed for 3 wt% fly ash, where UV transmittance decreased from 14.19% of untreated fabric to 0.11% of coated fabric. After subsequent treatment of Trimethoxy(octadecyl)silane (OTMS) on fly ash coated fabrics, the water contact angle was increased to 143° 147° and 153° for fly ash concentration of 1, 2 and 3 wt% respectively. From Cassie-Baxter theories, the unwetted fraction of air pockets were estimated to be 43%, 55% and 67% respectively for 1, 2 and 3 wt% of fly ash particles. Furthermore, the coated fabrics showed great potentials for separation of floating oil layer, underwater oil droplet or oil/water mixture. The separation efficiency of 98%, 96%, 97% and 95% was obtained for selected model oils toluene, n-hexane, chloroform and petro ether, respectively.
- ItemSynthesis and applications of nano-TiO2: a review(SPRINGER HEIDELBERG, TIERGARTENSTRASSE 17, D-69121 HEIDELBERG, GERMANY, 2019-02) Noman, Muhammad Tayyab; Ashraf, Muhammad Azeem; Ali, AzamTiO2-based nanomaterials have attracted prodigious attention as a photocatalysts in numerous fields of applications. In this thematic issue, the mechanism behind the photocatalytic activity of nano-TiO2 as well as the critical properties have been reviewed in details. The synthesis routes and the variables that affect the size and crystallinity of nano-TiO2 have also been discussed in detail. Moreover, a newly emerged class of color TiO2, TiO2 in aerogel form, nanotubes form, doped and undoped form, and other forms of TiO2 have been discussed in details. Photocatalytic and photovoltaic applications and the type of nano-TiO2 that is more suitable for these applications have been discussed in this review.