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Effect of Doping of Organic and In-organic Acids on Polyaniline/ Mn3O4 Composite for NTC & Conductivity Behavior
No full textThe paper deals with the study of TCR and conductivity behaviour of the PANI/Mn3 O4 composite in its emeraldine salt state doped with different acids like H3PO4, H2SO4, HClO4, CH3COOH and CH2=CHCOOH. The conductivity results have also been compared with pure emeraldine salt doped with same acid. The characterisation of each composite sample and emeraldine salt was done using XRD, FT-IR, and TGA. From the TCR studies it has been observed that PANI/Mn3O4 composite doped with acetic acid and acrylic acid have negative temperature co-efficient (NTC) behaviour in the temperature range 20-110 and 20-160°C, respectively. Thermistors constant (B) values calculated from the data are 3625 K-1 for composite doped with acetic acid and 3745 K-1 for acrylic acid. Composite samples doped with H3PO4, H2SO4 and HClO4 acid did not show NTC behaviour, as the thermistor constant values in these composites are found to be on lower side. The results of the conductivity behaviour for the composite doped with CH3COOH and HClO4 are of the same order as that of doped emeraldine salt, whereas in other three composite samples the conductivity is much lower in comparison to emeraldine salt samples. XRD studies reveal that crystalline PANI/Mn3O4 composite has been transformed into amorphous phase during doping. From FT-IR spectra, it can be concluded that adsorbed acids anion on the oxide surface work as the charge compensator for positive charge on PANI. TG curves of composite suggest that the thermal degradation process of PANI/Mn3O4 composite proceeds in three steps and thermal stability of the composite depend on the dopant acid. The improvement in the thermal stability of composite is attributed to the interaction between a specific acid and PANI/Mn3O4 composite which may restrict the thermal motion of the PANI chain and shield the degradation of PANI in the composite. From the above study it can be concluded that the PANI/Mn3O4 composite doped with organic acids has the potential to act as NTC material for thermistor applications. Due to variation in the conductivity behaviour of doped composites and PANI, it may find application as sensing material
Humidity Sensing Using Polyaniline/Mn3O4 Composite Doped with Organic/Inorganic Acid
No full textThe polyanlline/Mn3Ο4 composite doped with perchloric acid, sulphuric acid, ortho-phosphoric acid, acetic acid and acrylic acid have been characterized as sensing materials to determine relative humidity in the range of 20-90%. Each composite sample has been used in the form of pellet. Relative humidity measurement has been related with the change in resistance of doped composite samples. Each acid doped polyaniline/Mn3Ο4 showed an increase in resistance as relative humidity increases, however the sensitivity is found to dependent on the type of dopant anions. The response of each composite is found to be almost linear with the humidity but the composites doped with organic acids have found to be more sensitive than those with inorganic dopants. However polyaniline samples doped with these acids under similar conditions showed reverse behaviour that is the resistance decreases with the increase in relative humidity but with lower sensitivity. The anomalous behaviour of the acid doped composite samples may be due to lowering of p-type nature of the polymer chains in the composites with an increase of humidity. Due to the linear increase in resistance of composites doped with organic acids can act as humidity sensor
Schlieren Interferometric Concealed Coded Security Holograms
Get PDFA method has been described to create concealed codes in security holograms. The codes are in the form of pure phase patterns and require an interferometric scheme to convert these invisible phase variations into detectable amplitude/intensity variations. An interferometrically encoded reference beam from the key hologram captures a phase modulated object beam to form the security hologram. In the final reading process, a moiré-like fringe pattern gets generated in the observation plane when the same reference beam illuminates security hologram. This moiré pattern is helpful in verifying the genuineness of the hologram and also facilitates in repositioning of security hologram. In the null mode moiré position, true object wavefront gets reconstructed but the information of concealed codes still remains invisible. Use of schlieren technique is proposed as a simple way to reveal the concealed codes for security hologram authentication. These concealed codes can be used as an anti-counterfeiting feature in embossed security holograms
Direct Visualization of Young’s Boundary Diffraction Wave
No full textExperimental investigations on Young’s boundary diffraction wave are presented where a wavefront division interferometric scheme is used on diffracted wavefront to generate two-beam interference fringes in the geometrically shadow region. These fringes have good visibility and are observable in the whole space, strongly advocating the physical existence of Young’s boundary diffraction wave as a separate entity. Analysis of these fringes may provide vital information about the structure and nature of boundary diffraction wave e.g. existence in whole space, dependence of amplitude on obliquity factor etc
Phase knife-edge Laser Schlieren Diffraction Interferometry with Boundry Diffraction Wave Theory.
No full textWithin the framework of boundary diffraction wave theory it has been shown that the first bright fringe on either side of the central dark fringe of the phase knife-edge Fresnel diffraction pattern could be broadened to cover the whole field of view. Broadening of the first diffraction fringe, instead of conventionally modifying the spatial frequency spectrum, enhances the sensitivity of the Schlieren system. The use of phase knife-edge as viewing diaphragm in Schlieren diffraction interferometry not only enhances the fringe contrast but also avoids the loss in phase information as it lets through light from all parts of the test object and its thin interfacing makes the method suitable even for studying weak disturbances
Measuring Nano Newton Forces with an Indigenous Atomic Force Microscope
No full textThe Atomic Force Microscope (AFM) is a versatile tool in experimental research. The principle of operation
of the AFM is based on the measurement of force fields between an atomically sharp tip and surface atoms
of metals or insulators. In this note, we demonstrate the ability and limitation of an indigenous AFM, designed
and fabricated by us, for various measurements. In particular, short- and long-range interactions between
two surfaces, of different geometrical configurations, have been measured and analysed. Our results
indicate the reliability of our instrument for measuring forces in the nanonewton scale
Low temperature sensing capability of polyaniline and Mn3O4 composite as NTC material
No full textThe paper deals with the synthesis of composite of polyaniline with Mn3O4 via oxidative polymerization of monomer by ammonium persulphate in presence of finely graded (45 μM) Mn3O4. The characterization of composite was done by FT-IR, XRD, TGA, conductivity and TCR. The composite possesses the resistance in the range of kilo-ohms at ambient temperature, which starts decreasing with the increase in temperature and becomes minimum at 170°C and remains constant up to 200°C, thus behaves like semiconductor with respect to temperature resistance characteristics. The factor responsible for decrease in the resistance values during the temperature range of ambient to 170°C is hopping of electrons between Mn2+/Mn3+ and its enhanced mobility due to polyaniline chain. After 200 °C the resistance values of composite again increases slowly, because of waning interaction ofMn3 Ο4 and PANI. Above 300 °C the resistance values increases significantly due to complete decomposition of polyaniline which has been confirmed by thermal analysis. The blend of polyaniline/Mn3O4 was also prepared in the same ratio, the TG of which shows that the blend is just the physical mixture of the two constituents while in case of composite proper interaction is proved, supported by FT-IR, TG and XRD analysis. Thermal analysis shows that the decomposition of polyaniline and its composite is slow in nitrogen atmosphere as compared to air. The thermistor constant B and temperature become linearly dependent. The study shows the potential of composite to act as negative temperature coefficient (NTC) material for thermistor applications and continuous thermocouple
Fabrication of Continuous Fire Wire Detection Sensor using Negative Coefficient Material
No full textManganese-based spinel semiconducting ceramic was mixed with lanthanum oxide powder
and the mixture was characterised for the reproducible negative temperature coefficient (NTC)
of resistance behaviour. The same mixture was used for the fabrication of 15 m long continuous
thermal detector. The addition of La2O3 leads to decrease in thermistor constant and activation
energy values, thus giving freedom to fabricate thermal sensors for various temperature
applications. A 3 m long continuous thermal detector for application in the temperature range
275 - 350 oC was fabricated and later coupled to form a continuous unit of 15 m length
Quantification of Human Immunoglobulin G Immobilised of Gold Coated Silicon Chip for Biosensing Applications
No full textThe most important aspect of biosensor development with high sensitivity is the oriented immobilization
of antibodies on the solid substrate. Human IgG was immobilized on gold-coated silicon employing protein A, protein
G and neutravidin immobilization procedures. The amount of human IgG immobilized was analyzed by 3, 3ƍ, 4, 4ƍ-
tetramethyl benzidine (TMB) substrate assay and was maximum when protein A immobilization procedure was
followed. Human IgG coated biosensing surface was regenerated by treatment with glycine-HCl buffer (50 mM, pH
2.2). Atomic force microscopy was used to analyze the distribution of biomolecules immobilized on gold-coated
silicon. Our study indicates that human IgG molecules were uniformly bound to gold-coated silicon by protein A
immobilization procedur
Concealed moiré pattern encoded security holograms readable by a key hologram
No full textThis paper describes a novel method of incorporating concealed coding features in security holograms in the form of moiré patterns, which need an encoded key hologram to decode them. These concealed codes in the holograms are in turn recorded with an encoded feature, so that these remain invisible to the counterfeiters thereby enhancing the anti-counterfeiting ability of security holograms. These security features, which are specific kinds of moiré patterns, can only be decoded by using an encoded key hologram in the final reading process. Though these type of security holograms are quite suitable for visual inspection, they possess high degree of anti-counterfeit ability and also do not require expensive reading machines. They can also be used as security codes for better protection against counterfeiting embossed holograms. Two different recording schemes for the formation of such security holograms and typical experimental results have been presented