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The present study deals with investigations on the AB5-type MmNi4.6Fe0.4 hydrogen storage alloy with improved storage capacity of ∼1.7 wt % . The as-synthesized MmNi4.6Fe0.4 intermetallic alloy has a storage capacity of ∼1.5 wt % with kinetics ≈25 cm 3 / min / g . In search of effects, which may lead to improvement of storage capacity and kinetics, we have carried out several possible material modifications including substitution of 3d-transition elements such as Fe, Co, Mn, etc. at Ni sites, surface treatment and ball-milling. It has been found that the last material modification, i.e. ball-milling technique gives optimum results. The ball-milling technique parameters like speed, time duration, ball to powder ratio and medium of milling has been optimized. The maximum storage capacity of ∼1.7 wt % with kinetics of ≈35 cm 3 / min / g is obtained when pulverization of the as-synthesized (RF melted) material employing an attritor mill. By varying the medium, duration and speed of ball milling, it was found that the optimum conditions and estimates correspond to medium: hexane, duration: 10 min, speed: 200 rpm. The PCT evaluation was carried out using Sievert's type apparatus. The structural and microstructural characterizations were explored using XRD and SEM. XRD explorations revealed that full-width at half-maximum (FWHM) before and after pulverizations are 0.20 and 0.25°, i.e. there is a broadening of ∼25% in the width of the peaks after pulverization. The microstructural investigations revealed that the average particle size of MmNi4.6Fe0.4 after pulverization was ∼2.5 times less than that of the as-synthesized alloy. Smaller particles together with fresh surfaces are the most likely cause of enhanced hydrogenation (storage capacity and kinetics) behaviour.

A spray pyrolysis technique has been employed to prepare Ag added La0.67Ca0.33MnO3 (Ag-LCMO) polycrystalline film and its properties are compared with those of the La0.67Ca0.33MnO3 (LCMO) film prepared under similar conditions. The addition of silver in LCMO films improves surface morphology and reduces the lattice constant. During the synthesis process, the silver in the Ag-LCMO film melts and segregates at the grain boundaries. The semiconductor-metal transition temperature (Tp) increases by 10 K and normalized voltage noise reduces by more than one order of magnitude. Improvement in surface morphology and better oxygenation of the film due to the presence of silver leads to improvement in the properties of polycrystalline LCMO film.

In the present investigation, we have investigated the effect of external voltage (field) on the alignment of graphitic nanotubes as a result of applied electric field. The details of alignment effect embodying variation of applied electric field corresponding to applied voltage between 2 to 10 volts, the variation of length and diameter of the tubes have been studied. It has been found that both the degree of alignment and optimum length (∼12 μm), diameter (∼60 nm) of the tubes are obtained for the applied electrical field corresponding to 6 volts. The applied electrical field for 6 volts has been estimated to be ≈1889 volts cm −1 . A feasible model for the effect of tube alignment due to the external electric field has been described and discussed.

Synthesis of Hg(Tl)Ba 2Ca2Cu3O8+δ superconducting tapes have been accomplished by annealing the precursor tape, Ba2Ca2Cu3Oy (fabricated by doctor blade tape casting technique) in an environment of Hg(Tl) vapour. Characterization of superconducting HTSC tape sample was carried out through XRD, TEM, SEM and R-T measurements. Surface morphological investigations of the as -synthesized Hg(Tl)Ba2Ca2Cu3O8+δ HTSC tapes by scanning electron microscope have shown the occurrence of curious growth characteristics resembling spiral like features. These growth spirals encompass nearly the whole grain suggesting that spiral growth led to the formation of small crystal like grains of superconducti ng material Hg(Tl)Ba2Ca2Cu3O8+δ. The likely mechanism for the generation of these screw dislocations has been elucidated in terms of incoherent coalescence of growth fronts formed from Hg(Tl):1223 and Hg(Tl):1234 nuclei.

The present paper deals with the synthesis and hydrogenation behaviour of graphitic nanofibres. The GNF were grown by thermal cracking of hydrocarbon gases (ethylene, acetylene) at a temperature of 600°C for a time duration of 2 h. The structural characterizations have been evaluated by X-ray diffraction and transmission as well as scanning electron microscopy. It was found that the as grown graphitic nanofibres, unlike graphite, have preferred orientations corresponding to (101). The hydrogenation behaviour was studied through charging at a pressure of 120 atm. and then discharging at a pressure up to 1 atm. The P–C–T curve drawn based on several dehydrogenation runs has revealed the GNF to have hydrogen storage capacity of ∼10 wt%.

In the present study, photo-electrochemical and hydrogen evolution characteristics of a new type of TiO 2 (ns) and TiO 2 (ns)–In 2 O 3 /Ti septum based semiconductor-septum photo-electrochemical (SC-SEP, PEC) solar cell has been studied. The SC-SEP cell in the configuration of SCE/1 M NaOH/TiO 2 (ns)/Ti/H 2 SO 4 +K 2 SO 4 /Pt CE , Pt WE showed the photo-voltage and photo-current of 0.72 V and 8.6 mA/cm 2 , whereas the SC-SEP cell employing In 2 O 3 admixed TiO 2 (ns) photo-electrode and having the configuration: SCE/1 M NaOH/TiO 2 (ns)–In 2 O 3 /Ti/H 2 SO 4 +K 2 SO 4 /Pt CE , Pt WE , showed the photo-voltage and photo-current of 0.92 V and 14.6 mA/cm 2 , respectively. The hydrogen gas evolution for the SC-SEP cell based on TiO 2 (ns)/Ti photo-electrode was found to be 8.2 l/h m 2 , on the other hand the In 2 O 3 modified TiO 2 (ns) exhibited a higher hydrogen gas evolution rate of 11.8 l/h m 2 . Evidence and arguments have been put forward to show that the presence of In 2 O 3 over TiO 2 makes the system posses the advantages of a colloidal photochemical system. The better performance of the new photo-electrode is thought to be due to improved spectral response and catalytic activity of In 2 O 3 in regard to the hydrogen gas evolution kinetics.

The deteriorating quality of air due to exhaust emissions and the increasing number of motor vehicles in the world, is sending alarming waves throughout the world to try to do something to cut off or significantly reduce these emissions in order to save our planet. Scientists have found that hydrogen presents the best and unprecedented solution to this problem, for its superior combustion qualities and availability. This paper discusses analytically one aspect of combustion i.e. combustion duration and how it is affected by an engine’s operating parameters like compression ratio, equivalence ratio, spark plug location, spark timing and engine speed, and how it affects an engine’s performance parameters like brake specific fuel consumption, brake mean effective pressure, thermal efficiency, as well as emission characteristics.

The present paper describes the fabrication and solar hydrogen production studies employing a new semiconductor-septum (SC-SEP) photoelectrode ns-TiO2–In2O3 admixed/Ti based photoelectrochemical solar cell. The current-voltage characteristics of the above SC-SEP cell revealed that an enhancement in short-circuit current (ISC) up to three times (5∼18.6 mA cm−2). The rate of hydrogen production was found to change with variation in the concentration of the electrolyte in the dark compartment; e.g. for 1 M H2SO4 it is 6.0 lh−1 m−2 and for 6 M it is 14.6 lh−1 m−2. The optimum hydrogen production rate was found to be 14.6 lh−1 m−2 for 6 M H2SO4 and with a further increase in H2SO4 concentration, the hydrogen production rate was found to be invariant. In yet another part of our study instead of using new SC-SEP solar cell design, we used a new material form such as ns-TiO2–VO2. The VO2 admixed ns-TiO2 exhibited a high photo-current and photo-voltage of 19.2 mA cm−2, 680 mV, respectively. The ns-TiO2–VO2 electrode exhibited a higher hydrogen gas evolution rate of 16 l/h1/m2. Evidences and arguments are put forward to show that, whereas for the bare ns-TiO2 electrode, the improvement in the performance of this photo-electrode compared with its original form was due to the higher quantum yield. In the case of ns-TiO2–In2O3 and ns-TiO2–VO2 photo-electrodes, the improvement is due to the improved spectral response resulting from decrease of energy band gap.

The magnetoresistive behaviour of La0.67 Ca0.33 MnO3 thin films deposited by ultrasonic spray pyrolysis on YSZ substrate has been investigated at low applied dc magnetic fields. The highest magneto-resistance ratio (MR ) of -17.75% has been observed at 77 K for applied dc magnetic field, Hdc = 3 kG. The variation of the MR with temperature has been investigated and it has been observed that at lower temperatures the increase in MR is very rapid. This MR -T behaviour shows that the magneto-resistance has its origin in the grain boundaries. The variation of the MR with Hdc shows a faster increase in the MR at lower applied dc fields. Surface morphological explorations employing scanning electron microscopy show the presence of microcracks throughout the films surface and also that these films are micro-crystalline, having an average grain size of ~125 nm.

We report the formation and characterization of nanoparticles and their assemblage to form a threadlike microstructure of silicon, germanium and tin, by the process of thermal deposition in helium ambient under varied conditions of pressure. The structural characterization of the nanoparticles was done by transmission electron microscope (Philips CM12). Resistance versus temperature (R -T ) measurements, on the thin films embodying nanothreads, exhibited anomalous behaviour embodying erratic changes in R -T variations. This was suggestive of variation of nanoparticle distribution with increase in temperature.

In this paper we have shown that polycrystalline films corresponding to Tl-2223 phase can be grown by employing high thalliation temperatures and short thalliation times. Ultrasonically deposited precursor films corresponding to Ba2Ca2.2Cu3.3Ox(Agy) have been thalliated under high vacuum (∼ 10-5 torr) at 890°C to obtain single phase Tl-2223 films. An off-stoichiometric and unreacted pellet of composition Tl2.05Ba2Ca2Cu3Oz has been used as source of Tl. We have shown that oxygen ambient is not necessary for the growth of Tl-2223 phase. The as-thalliated films have Tc’s in the range 123 K ±0.70 K. TheT c has been found to be independent of the addition of AgNO3 to the precursor. The zero field transportJ c has been observed to be > 1.2 X 105 A/cm2 at 77 K. NearT c (110 K-122 K),J c has been observed to follow the power lawJ c ∞ (1-T/T c )p,p 2. A power law withp tt 1.4 has been observed for the temperature range 70 K-110 K. An optimum doping of Ag has been observed to induce about 25% increase inJ c and it also leads to uniform and enlarged grain growth. The surface morphology of Ag free samples contains plate like grains having arbitrary shapes. In contrast to this 0.35 Ag doped sample exhibits nearly rectangular plate like grains

The present study deals with the investigations on the synthesis, structural/microstructural characteristics and hydrogenation/dehydrogenation behaviour of Mg-bearing composite materials Mg- x wt.% CFMmNi 5 prepared through mechanical alloying. The composite materials Mg- x wt.% CFMmNi 5 have been successfully synthesized through ball-milling (mechanical alloying) by employing a high energy attritor mill. The mechanical alloying has been carried out in hexane medium by varying the milling parameters say, speed (revolutions per minute) and milling duration. The as-milled composite materials have been activated at 400±10°C under a hydrogen pressure of ∼35–40 kg cm −2 . These composite materials exhibit high hydrogen storage capacity and fast absorption/desorption kinetics in comparison to the thermally melted counterparts. It has been found that the highest storage capacity material (∼5.4 wt.% at 350°C) corresponds to Mg-30 wt.% CFMmNi 5 . The composite material also exhibits fast desorption kinetics (about 90 cm 3 min −1 ), which is at least two times faster than conventionally prepared (RF melting) alloys. The highest hydrogen storage capacity and fast kinetics were obtained for the mechanically alloyed samples with the optimized milling conditions, i.e. speed ∼400 rev min −1 and time duration of 5 h. The hydriding rate and the improved hydrogen storage capacity of these composite materials have been found to be strongly correlated with structural and microstructural characteristics as brought out through XRD and SEM techniques. The uniform particle size distribution and interfacial grain boundaries explored from the SEM investigations paves the way for better hydrogen storage capacity and fast absorption and desorption kinetics.

The present study is aimed at investigations on the structural and microstructural characterization and hydrogenation behaviour of Zr substituted Fe 1− x Zr x Ti 1.3 ( x = 0.2) alloys. This storage alloy has been synthesized using R.F.induction melting under an argon atmosphere in a previously outgassed graphite crucible. The structural characterization (XRD) has revealed that the as-synthesized sample is multiphasic in nature and embodies the phases FeTi, Fe 2 Ti, FeTi 2 and Ti. Microstructural evaluations (SEM) exhibited the presence of interfaces and cracking. The P–C isotherm was determined and it showed the storage capacity of ∼1.20 wt.% at 200°C. The activation as well as desorption kinetics (75% desorption of H 2 in 6 min) were found to be better for Zr-substituted alloy (Fe 0.8 Zr 0.2 Ti 1.3 ) as compared to FeTi 1.3 . The improved activation and desorption kinetics are thought to be due to presence of several interfaces e.g. Fe(Zr)Ti⧸ Fe(Zr)Ti 2 , Fe(Zr)Ti⧸{Fe(Zr)} 2 Ti and volume expansion induced cracking of Ti.

Alloys with general formula Mg–x wt.% MmNi4.6Fe0.4 have been successfully synthesized through ball milling employing a high energy attritor mill. The ball milling has been done in hexane medium; various time durations and speeds (rev./min) have been employed. The hydrogenation and dehydrogenation behaviour of these new composite materials have been extensively investigated. The as-prepared (ball milled: mechanically alloyed) composite materials have been activated at 400±10°C under a hydrogen pressure of ∼40 kg cm−2. These composite materials have been found to possess one of the highest known storage capacities. It has been found that the highest storage capacity material (∼5.0 wt.% at 350°C) corresponds to Mg–30 wt.% MmNi4.6Fe0.4. The said alloy exhibits fast absorption–desorption kinetics (about 80 cm3 min−1). It is also established that the optimum mechanically alloyed samples for hydrogen storage were obtained with milling at 400 rev./min speed and time duration of ∼5 h. The hydriding rate and the improved hydrogen storage capacity of these composite materials have been found to be strongly correlated with the structural and microstructural characteristics as brought out through XRD and SEM techniques. For example, the ball milled samples having optimum hydrogenation characteristics exhibited highly uniform particle size distribution.

A new photoelectrode system TiO2(ns)–VO2 for photoassisted electrolysis of water is described. The nanostructured TiO2 photoelectrode was prepared by the hydrolysis of titanium-tetraisopropoxide followed by deposition of thin film by spin coating. To prepare the TiO2(ns)–VO2 photoelectrode, vanadium film was deposited on the TiO2(ns) film and subsequently oxidized in O2 ambient. The TiO2(ns)–VO2 photoelectrode exhibited enhanced photovoltage and photocurrent of 680 mV and 11.0 mA cm−2, respectively, whereas the TiO2(ns) presented 540 mV and 3.2 mA cm−2, respectively. X-ray and S.E.M studies were carried out to monitor the surface and bulk characteristics of the TiO2(ns)–VO2 photoelectrode. The rate of hydrogen production under photoelectrolysis was found to be 6 l h−1 m−2 for the TiO2(ns) and ∼13.0 l h−1 m−2 for the TiO2(ns)–VO2 photoelectrode. The TiO2(ns) photoelectrode shows the improvement in the PEC characteristics due to higher quantum yield resulting from the structured nature of the material. The PEC improvement in the TiO2(ns)–VO2 photoelectrode is due to the increase of range of absorption and the decrease of energy gap. © 1999 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.

The present study deals with investigations into the composite hydrogen storage materials LaNi 5 /La 2 Ni 7 , LaNi 3 , for improved hydrogenation characteristics. To achieve this goal, extensive investigations were carried out to study the effect of the presence of secondary phases on the main phase LaNi 5 , with reference to hydrogenation behaviour, including incubation time, p – c isotherms, desorption kinetics, hysteresis factor, cyclic stability and thermodynamic behaviour. Alloys were synthesized through melt-casting with varying concentrations of secondary phases like La 2 Ni 7 , LaNi 3 , Ni (minor phases), i.e. 55%, 30%, 5% and 0%, using a special technique of pellet encapsulation. Structural characterization using the XRD technique confirmed the formation of secondary phases together with major phase LaNi 5 . Microstructural evaluations through SEM revealed that secondary phases suppressed pulverization. Investigations on the hydrogenation behaviour of these alloys showed that the presence of secondary phases in small quantities resulted in a much lower incubation time (lower by 63%), in comparison to singular LaNi 5 alloy. The hydrogen storage capacity and desorption kinetics did not decrease for minor concentrations of secondary phases, but a decrease was found for the alloys having higher concentrations of secondary phases. The hysteresis factor has also been found to be less for the multiphasic alloy. The cyclic stability test with regard to storage capacity degradation, showed a higher stability of the alloy having a small concentration of secondary phases. Thermodynamic parameters have been found to be: Δ H (change in enthalpy), −9.05 and −7.03 kcal mol −1 , and Δ S (change in entropy), 31.92 and 23.64 cal mol −1 K −1 , for the alloys with 5% and 0% secondary concentrations.

Pb-doped Hg-1223 HTSC tapes have been synthesized by annealing the precursor tape (fabricated by doctor blade tape casting technique) in the environment of Hg(Pb) vapor in an evacuated sealed quartz tube at 870°C for 8 h. The HTSC tapes with x ranging between 0.1 and 0.5 exhibit high temperature superconductivity at temperature falling in the range from 110–119 K. The tape sample with optimum doping of Pb 0.35 has a highest T c and J c of ∼119 K and 5.1×10 3 A/cm 2 . With the slight addition of Ag into optimally Pb-doped Hg-1223 tape sample, T c has been found to increase slightly but there is significant enhancement of J c up to a optimum concentration of Ag. The highest T c of ∼123 K and highest J c of ∼2.5×10 4 A/cm 2 is obtained for the tape sample having Ag concentration of 0.2, i.e., (Ag 0.2 ), being an order of magnitude higher than the J c of Ag free optimally Pb-doped Hg-1223 tape samples. J c has been observed to decrease with Ag content higher than 0.2. This decrease in J c has been attributed to the formation of Ag–Hg amalgam, due to the reaction of Hg with Ag.

The quasicrystals being based on quasiperiodic order other than crystal like periodic translational order and embodying self similarity, present unique condensed matter phases. In addition to their curious structural characteristics the paucity of translational periodicity leads to drastic deviations in their electronic behaviour as compared to crystalline counterparts. This paper describes and discusses some new developments in regard to structural and electronic aspects of quasicrystalline materials. In regard to the structural aspects, two comparatively newer features will be described. One of them relates to the observation of variable strain approximants (VSA) first found in Ti68Fe26NiSi5, qc alloys; the other relates to the structure of decagonal phases. The variable strain approximants correspond to qc phases exhibiting variable strain for the different diffraction spots for the same reciprocal lattice row (possessing linear shifts). The VSA is thought to result from variable phason strain mode locking; this in contrast to RAS which results due to linear phason mode locking. The results obtained in our laboratory on VSA will be described and discussed. Another interesting structural feature emanating in the last few years relate to the development of structural models for the decagonal phases which have nearly answered the question ‘Where are the atoms?’ for this qc variant. High resolution electron microscopy has revealed the existence of two types of atom cluster columns with a diameter of 20A; a pentagonal cluster column and a decagonal one. The decagonal quasicrystals can be classified into three types of structures according to the space groups and symmetries and arrangements of the cluster columns. These three deca structures have been typified by: deca Al-Co-Cu, deca Al-Mn and deca Al-Fe-Pd types. Some basic features on the structures of decagonal phases as obtained recently will be outlined.

The present study deals with investigations on the composite hydrogen storage materials LaNi 5 /La 2 Ni 7 , LaNi 3 , for efficient, high energy density Ni–MH batteries. To achieve this goal extensive investigations were carried out to study the effect of presence of secondary phases on the main phase LaNi 5 with reference to hydrogenation behaviour and structural-microstructural characterizations using XRD, TEM and SEM techniques. Alloys were synthesized through melt-casting with varying concentrations of secondary phases like La 2 Ni 7 , LaNi 3 , Ni (minor phases), i.e., 55%, 30%, 5% and 0% by a special technique of pellet encapsulation. Structural characterizations using the XRD technique confirmed the formation of secondary phases together with the major phase LaNi 5 . The diffraction patterns after hydrogenation did not exhibit secondary phase diffraction peaks, instead the resulting phase was found to be single phasic, exhibiting LaNi 5 like diffraction patterns with an unusual intensity distribution. TEM investigations showed the presence of two types of modulated phases; one of which corresponds to a ≈1.5 a o , c ≈ c o and the other to a ≈1.3 a o , c ≈ c o , together with the parent phase (LaNi 5 ), in the as-synthesized and hydrogenated/dehydrogenated versions, corresponding to alloy with secondary phase concentration upto 30%, ( a o and c o being lattice constants of the parent LaNi 5 structure). The signature of the modulated phases were not present in XRD patterns, but could be seen in the selected area electron diffraction patterns, suggesting that modulation has taken place in local areas of the basal plane, due to ordering of hydrogen atoms. These modulated unit cells can be modeled in terms of the original lattice of LaNi 5 , by inserting and ordering of hydrogen atoms at viable interstitial sites. Microstructural evaluations through SEM revealed that secondary phases suppressed pulverization. Investigations of the hydrogenation behaviour of these alloys showed that hydrogen storage capacity and desorption kinetics did not decrease for minor concentrations of secondary phases, but a decrease was found for the alloys having higher concentrations of secondary phases. Similar results were obtained for alloy MmNi 5 , where secondary phases corresponded to Mm 2 Ni 7 and MmNi.

Unlike the rutile; the anatase phase of TiO2 has not been extensively employed for fabrication of PEC cells primarily due to the difficulty in the synthesis of a stable anatase structural variant. The present investigation is focused on the synthesis of the anatase phase and its use as a photoelectrode of high efficiency PEC Solar Cells. TiO2, in the nanostructured form, has been prepared by the hydrolysis of Titanium (IV) isopropoxide solution. The nanostructured TiO2 (anatase) stable phase has been synthesised by sintering the synthesised film at ∼500°C with a heating rate of 1°C/min for a duration of 3 h in argon. The films of nanostructured TiO2 anatase phase have been used as photoelectrodes in PEC solar cells. An improvement in TiO2(ns) anatase phase photoelectrode carried out in the present work corresponds to admixing In2O3 to improve the spectral response. It has been found that admixing In2O3 with TiO2(ns) anatase phase improves the solar spectral response. The structural, microstructural, optical, and photoelectrochemical properties of the TiO2(ns) anatase phase and TiO2(ns) anatase-In2O3 photoelectrode have been studied. The response of TiO2(ns) anatase phase bearing photoelectrode based PEC solar cell corresponds to VOC ≈ 460 mV, ISC ≈ 2.4 mA/cm2 and for its In2O3 doped version, these are VOC ≈ 640 mV and ISC ≈ 10.4 mA/cm2.

In the present study, photoelectrochemical and hydrogen evolution characteristics of CdSe Ti and TiO 2 Ti based semiconductor-septum photoelectrochemical (SC-SEP, PEC) solar cell have been studied. The SC-SEP cell in the configuration of SCE, l M 3S//CdSe/Ti//5 M H 2 SO 4 , Pt(W), Pt(C), gave power output of 0.62 V and 11 mA cm −2 , whereas the conventional Pt, 1 M 3S//CdSe/Ti, PEC cell gives power output of 0.64 V and 6 mA cm −2 . The hydrogen evolution characteristics of SCE, l M 3S//CdSe/Ti//5 M H 2 SO 4 , Pt(W), Pt(C), exhibited a rate of 1.0 to 1.5 1 h −1 m −2 under an illumination intensity of 80 mW cm −2 . The TiO 2 Ti septum based SC-SEP solar cell in the configuration of SCE, 1 M NaOH//TiO 2 /Ti//5 M H 2 SO 4 , Pt(W), Pt(C), gives power output of 0.74 V and 14.5 mA cm −2 whereas the conventional Pt, 1 M NaOH//TiO 2 /Ti, PEC solar cell gives power output of 0.7 V and 5 mA cm −2 . The hydrogen evolution characteristics of TiO 2 /Ti based SC-SEP cell measured in the configuration of SCE, 1 M NaOH//TiO 2 /Ti//5 M H 2 SO 4 , Pt(W), Pt(C), gave a hydrogen evolution rate of 10–15 1 h −1 m −2 under an illumination intensity of 450 mW cm −2 . It has been shown in the present investigation that TiO 2 Ti based SC-SEP solar cell is more stable and gives higher rate of hydrogen production compared to the CdSe Ti based SC-SEP cell. Further studies to optimize the stability and other conditions for the production of solar hydrogen using these SC-SEP solar cells have been outlined.

The generation of higher harmonics in Hg(Tl)BaCaCuO high- T c thin film is reported, when an ac magnetic field is applied to it. The film has been prepared by the spray pyrolysis technique using two step process and exhibits T c ( R =0)=123 K. Application of an ac magnetic field ( H ac > H c1 ) on the film leads to generation of higher odd harmonics. Further, application of the dc field ( H dc ) in addition to the ac field causes generation of even harmonics also. Variations of amplitude of these harmonics as a function of H ac , H dc and temperature are studied. The variation of second and third harmonic amplitudes with H dc shows the hysteresis effect.

The Tl-doped Hg-based HTSC bulk materials corresponding to Hg 1− x Tl x Ba 2 Ca 2 Cu 3 O 8+ δ with x =0.2, 0.4, 0.5, 0.6, and 0.8 have been synthesized using the precursor route. A clear cut variation of T c ( R =0) with increase in Tl concentration and hence from the underdoped to overdoped regions has been demonstrated. These variations correspond to T c variation from ∼106 to ∼133 K for underdoped samples and from ∼106 to ∼129 K for overdoped samples. The crossover from underdoped to overdoped regions is found to take place between x =0.5 and x =0.6 X-ray diffraction (XRD) and TEM studies have revealed the samples to be multiphasic with the presence of Hg, Tl:1223 as the dominant phase. Microstructural investigations reveal the presence of ordered and/or disordered stacking faults and the accompanying polytype like regions.

A new photoelectrode system (for photoelectrolysis of water) employing nanostructured TiO2 has been synthesized. In addition to using a bare TiO2(ns) electrode, a system with an improved electrode obtained through admixing In2O3 into TiO2(ns) has been synthesized and studied. The TiO2(ns) photoelectrode has been prepared by the hydrolysis of Ti[OCH(CH3)2]4 followed by deposition of thin film by a spin-on method. It has been shown that the TiO2(ns) photoelectrode-bearing cell exhibits higher photoelectrochemical output. Possible causes for this are described and discussed. Another improvement in the TiO2(ns) photoelectrode carried out in the present work comprised admixing with In2O3. The In2O3-admixed TiO2(ns) exhibited a much higher photocurrent of 14mA cm−2. The hydrogen gas evolution under photoelectrolysis employing a TiO2(ns) photoelectrode was found to be 61h−1 over a 1 m2 electrode area. The TiO2(ns)-In2O3 electrode exhibited a higher hydrogen gas evolution rate of 10.51 h−1 over a 1 m2 electrode area. Evidence and arguments are put forward to show that, whereas for the bare TiO2(ns) electrode the improvement in the performance of this photoelectrode compared with its original form was due to the higher quantum yield resulting from the nanostructured microstructural feature, for the TiO2(ns)-In2O3 photoanode the improvement is due to improved spectral response, decrease of energy gap and availability of increased photoactive surface area.

Cd doped Tl-2223 thin films (∼ 1 μm) have been grown by annealing B 2 Ca 2 Cd x Cu 3 O y ( x = 0.0, 0.1, 0.2, 0.3) precursor films, deposited on MgO (100) by ultrasonic spray pyrolysis, in Tl 2 O ambient in an evacuated (> 10 −5 Torr) sealed quartz tube at 890°C for 2 h. Doping by Cd has been found to induce the growth of 2223 phase and an enhancement in T c . The T c of the as-grown thin films samples are 118 K, 120 K, 124 K and 121 K respectively for Cd contents x = 0.0, 0.1, 0.2 and 0.3. The observed T c = 124 K for x = 0.2 is higher than the previously observed highest T c of 122 K for Tl-2223 thin films. A distinguishing feature of the present synthesis route is the fact that oxygen has not been used at all in the entire synthesis process. The transport J c of the 0.2 Cd doped films is 1.12 × 10 5 A/cm 2 (77 K, 0 T). The surface morphology of these films shows a very dense growth of platelet-like grains.

The present study deals with investigations on the synthesis and characterisation of negative electrode material for high energy density Ni-MH battery. The hydrogen storage material (MH) has been synthesised through normal casting and melt-spinning techniques. In LaNi 5 /MmNi 5 family various substitutions like Al, Mn, Co have been studied. The substitution of metalloid like Si is known to be very helpful in improving several hydrogenation properties. In the present study, the Si substituted versions of AB 5 -type storage materials typified by LaNi 5− x Si x ( x =0.1,0.3,0.5) have been investigated. A comparison between the present material and the conventional AB 5 -type material MmNi 4.3 Al 0.3 Mn 0.4 has also been made which has been previously studied. The main features revealed by XRD characterisations are the existence of the free Ni and Si together with AB 5 material for all the three compositions. These free Ni and Si were found to disappear and yield, giving rise to a singular material after hydrogenation. The melt-spun version of the material was found to grow invariably in a direction perpendicular to the c -axis. The kinetics and activation process was better for the melt-spun version of the LaNi 4.7 Si 0.3 alloy than its thermally-melted counterpart (bulk) as well as to the alloy MmNi 4.3 Al 0.3 Mn 0.4 . For example, the kinetics of the melt-spun version of LaNi 4.7 Si 0.3 is 60% faster than its bulk version and 70% faster than the melt-spun version of MmNi 4.3 Al 0.3 Mn 0.4 . Similarly, the melt-spun version of the alloy LaNi 4.7 Si 0.3 gets activated in the 2nd cycle itself where as the alloy MmNi 4.3 Al 0.3 Mn 0.4 attains this stage only in the 6th cycle.

The HTSC material Y:124 has the advantage of oxygen stability over its most common counterpart Y:123. However, synthesis of Y 1 Ba 2 Cu 4 O 8 is difficult and requires high oxygen pressure or the presence of oxygen enhancer catalyst. For being useful in various applications, Y:124 has to be not only synthesised but also optimised for its T c and J c values. Thus, for the optimisation of Y:124, three different processing steps, namely oxygen enhancement, hole optimisation and grain boundary passivation, need to be carried out. The present paper describes and discusses the possible mode of synthesis and the optimisation of Y:124 prepared through spray pyrolysis in a simplified way involving two different material processing steps instead of three. The oxygen enhancement and grain boundary passivation required for the J c optimisation both have been achieved by admixing single ingredient AgNO 3 . The optimisation of the hole concentration helpful in T c enhancement has been done through Ca doping. The optimised HTSC films thus formed correspond to Y 0.9 Ca 0.1 Ba 2 Cu 4 O 8 (Ag 0.1 ). Representative T c and J c values obtained for the present HTSC films are ∼80 K and ∼4.2×10 4 A/cm 2 respectively.

(x = 0.1, 0.2, 0.3, 0.5 and 0.8) HTSC tapes have been synthesized through the reaction of a mixture of Hg-Tl vapour with the precursor tapes (fabricated by the doctor blade tape casting technique) in an evacuated sealed quartz tube at for 12 h. The Hg(Tl) tape having composition is found to possess and transport current density (20 K). The observed and seem to be the highest reported so far for Hg(Tl)-Ba-Ca-Cu-O HTSC tapes. SEM explorations of the surface have revealed the occurrence of layered spiral growth features for the Hg(Tl) HTSC tapes.

In the case of Hg-bearing cuprate high temperature superconductors, the great flexibility of rock salt layers permits the introduction of suitable cations to substitute for Hg in the Hg-O layers. In the present investigations, we have studied the structural transitions effected through substitution of Tl and Pb in the Hg-O layers. It has been found that for the doped compositions corresponding to Hg0.50Tl0.50-x Pb x Ba2Ca2 Cu3O8+δ (x = 0.05, 0.10 and 0.20; the samples with these concentrations have been designated as sample A, B and C respectively), curious long period polytype-like structures get formed. Some of the long-period polytypes (LPP) observed in the present investigation were found to possess c-periodicities of ∼31.58 A, ∼63.16 A, ∼107 A, ∼139 A for sample A; ∼228 A, ∼246 A for sample B; and ∼189 A for sample C. It is shown that, in addition to the intergrowth of short period basic structures, a new mechanism elucidated in the present study involving ordering of TI, Pb atoms at Hg site...

The present study deals with investigations on the synthesis and characterization of negative electrode material for high energy density Ni-MH battery. The hydrogen storage material (MH) has been synthesized through thermal and spin melting techniques. A comparative study of materials synthesized by these two techniques with emphasis on the characteristics relevant to battery electrode applications has been carried out. In the present study, the modified composition of AB5-type corresponds to the spin as well as thermal melted versions of MmNi4.3Al0.3Mn0.4 and MmNi4.0Al0.3Mn0.4Si0.3. Structural characterization has revealed that, whereas for the spin melted MmNi4.3Al0.3Mn0.4 the dominant growth is perpendicular to the c-axis, it is parallel to the c-axis for MmNi4.0Al0.3Mn0.4Si0.3. The hydrogenation behaviour of these materials has been monitored through P-C-T and kinetic curves. Attempts have been made to establish a correlation between the structure and hydrogenation behaviour. The spin melted material (MmNi4.3Al0.3Mn0.4) exhibits reduced pulverization and hence is expected to have increased cycle life. This version of the material also exhibits higher storage capacity, faster kinetics and faster activation as compared to the conventionally prepared bulk form. The bulk version of the alloy with silicon has been found to undergo easy activation (2nd cycle) as compared to the bulk version of the alloy without silicon (6th cycle). The spin melted version of the material with silicon leads to smaller (finer) particle size material compared to the alloy form without silicon.

We report the formation and characterization of C films on glass 60 (amorphous) and mica (crystalline) substrates by a spray deposition technique. The deposited films were characterized by X-ray diffractometry, transmission electron microscopy and scanning electron microscopy. The C60 films on glass were found to be polycrystalline and those on mica were textured. The value of (d) = 9.23 A, being close (d)= 10.02 A, seems to be the main cause 010 mica 110 C60 of texturing in the films of C . Redeposited films on mica exhibited enhanced 60 110, 220, etc. X-ray diffraction peaks, demonstrating clearly the textured nature of the film.

The hydrogen absorption characteristics of TiFe partially substituted with small amount of Ni for Fe and corresponding to Fe0.8Ti1.3Ni0.2 has been synthesised through RF melting. The XRD and TEM characterization of Fe0.8Ti1.3Ni0.2 revealed the occurrence of curious structural phases; namely, a superlattice with “a” periodicity of 5.93 A (which is double that of the 2.98 A FeTi1.3 phase) and a modulated phase having a modulation period of 4 times along [110] as compared to d110 of the superlattice phase. The Fe0.8Ti1.3Ni0.2 phase has been found to have faster hydrogen desorption kinetics (30–40 cc/min) which is about 2–3 times higher than that of the parent phase FeTi1.3. It has been suggested that the faster desorption kinetics are due to the Ni substitution leading to the material Fe0.8Ti1.3Ni0.2. This material is biphasic in nature and embodies built-in interfaces and has faster crack propagation on hydrogenation.

The present study is based on improving the intergranular connectivity of Tl HTSC tapes by passivation of grain boundaries through the addition of silver. HTSC tapes to which silver had been added were fabricated by the diffusion of Tl vapour in the precursor tape to which silver had been added. The tapes were cast by using a doctor-blade tape-casting machine. These tapes having Tl:2223 as the majority phase were found to possess in the range 107 - 113 K. The critical current density of the Tl HTSC tapes was found to scale with the silver content and optimum (20 K) and (77 K) were obtained for HTSC tapes. SEM of pure (without silver) and Ag-admixed Tl:2223 tapes revealed that, as the silver content increased, the grain size and intergranular connectivity increased. With an optimum concentration of Ag (y = 0.40), a well-oriented platelet-like grain structure became stabilized, leading to an improvement in . The most curious microstructural feature, observed for the first time in the present study, was the occurrence of sequential layer growth features resembling spiral characteristics. The influence of these microstructural features on the superconducting properties, in particular the transport critical current density, is described and discussed.

The present paper describes the fabrication and solar hydrogen production studies employing a new semiconductor-septum (SC-SEP) photoelectrode n- TiO 2 Ti based photoelectrochemical solar cell with the configuration SCE/1 M NaOH/TiO2/Ti/H2SO4 + K 2 SO 4 Pt CE , PtWE. The monitoring of the current-voltage characteristics of the above SC-SEP cell revealed an enhancement in short-circuit current (ISC) up to three times (5− ~ 15 mAcm−2) that of its single compartment PEC cell counterpart based on the n-TiO2 photoelectrode. The rate of hydrogen production was found to change with variation in the concentration of the electrolyte in the dark compartment; e.g. for 1 M H2SO4 it is 6.31 1 h−1 m−2 and for 5 M it is 13.15 1 h−1 m−2. The optimum hydrogen production rate was found to be 13.151 h−1 m−1 for 5 M H2SO4. With a further increase in H2SO4 concentration, the hydrogen production rate was found to be invariant. The hydrogen production rate of TiO 2 Ti based SC-SEP cells when compared with the only other known SC-SEP cell based on n- CdSe Ti and corresponding to the configuration SCE/polysulfide +0.1 M selenium solute/n-CdSe/Ti/5 M H2SO4/PtCE, PtWE exhibits a hydrogen production rate higher by about 10 times.

HTSC films have been synthesized by reacting Ba - Ca - Cu - O precursor films deposited by spray pyrolysis with Hg - Pb vapour in an evacuated sealed quartz tube at for 4 h. The films with x ranging from 0.1 to 0.3 exhibit high-temperature superconductivity at temperatures falling in the range from 115 to 125 K. The sample with optimum doping of Pb of x = 0.2 shows the highest . Ag admixing at low concentrations has been found to improve . Thus for , i.e. , decreased minimally from 125 K to 124 K and the critical current density has been found to increase to from . However, higher Ag concentrations, e.g. (y > 0.05), in contrast to the case of other HTSC cuprates, have been found to be detrimental to superconducting properties, particularly . The microstructural details as revealed through scanning electron microscopy exhibit the curious characteristic of the existence of spiral-like growth features for lower Ag concentrations, which are found to disappear for higher Ag concentrations.

The Ag doped Hg(Tl):1223 films have been synthesised by annealing Ba 2 Ca 2.2 Cu 3.3 O z (Ag y ); y = 0, 0.25, 0.5, 0.75, 1.0 precursors deposited by spray pyrolysis on single crystal MgO and ZrO 2 substrates, in controlled Hg-Tl vapour ambient in an evacuated sealed quartz tube at 860°C for 720 minutes. The transition temperature ( T c ), dc transport critical current density ( J c ) and microstructure of the films have been found sensitive to Ag content. The microstructural details as revealed through scanning electron microscopy exhibit the curious characteristics of the existence of spiral like growth feature which is found to deteriorate with increasing Ag concentration. The maximum T c = 126 K of the as synthesized Ag doped film with Ag = 0.50 is nearly the same as the T c = 127 K of oxygen annealed Ag-free films, suggesting in itu oxygenation. The transition temperature has been found to decrease for higher Ag contents (0.50 y J c has been observed to decrease steadily with increase in silver content, being highest (7.2 x 10 4 A/cm 2 , 20 K) in Ag-free case. This decrease in J c has been accounted for in term of formation of Ag(Hg) amalgam due to the reaction of Ag with Hg already present in the grain boundary region.

An rf-SQUID has been fabricated on Hg 0.8 Tl 0.2 Ba 2 Ca 2 Cu 3 O 8+ δ thin film using natural grain boundary weak links. The film was prepared by the spray pyrolysis technique and had T c = 123 K. Voltage-flux modulation of the SQUID has been obsrved up to 117.5 K. The flux noise density, √S Ф of the rf-SQUID is ≈ 2.5 × 10 −3 Ф 0 /√ Hz at 1 Hz and 77 K. Th value of √S Ф remains almost the same when the operating temperature is increased from 77 to 112 K, and its value becomes ≈ 4 × 10 −3 Ф 0 /√ Hz at 114 K.

Amongst the non-aluminium based quasicrystalline alloys, investigations of titanium containing alloys in regard to the occurrence and stability of quasicrystalline phases have aroused considerable interest in recent years. Employing X-ray and TEM techniques a systematic investigation of the influence of substitution for Fe by Si and Ni on the stability of icosahedral phase in rapidly quenched Fe-Ti alloy has been carried out. The occurrence of metastable phases including commensurately modulated phase and the decagonal phase in Fe-Ti-Si system have been found. In addition, the occurrence ofstructural disorder manifested by arcs of diffuse scattering in diffraction patterns and anisotropy in the shape of idffraction spots has also been pointed out. It has been observed that 6 at.% of Si in Fe-Ti-Si system results in the formation of single-phase icosahedral quasicrystals. We have shown that contrary to some earlier reported results on Ti2Ni, Ti2Ni(Si) and Ti56Ni23Fe5Si16 alloys do not possess the icosahedral phase. In Ti68Fe26−xNixSi6 alloy system, icosahedral phase formation ability is limited to the value of x

In the present work investigations on the effect of stoichiometric variations on the occurrence and stabilization of quasicrystalline (qc) and related phases have been carried out. Based on the explorations of several Al-deficient and Al-rich versions of the ideal nominal composition i.e. Al 65 Cu 20 Cr 15 , it has been found that the alloy compositions corresponding to Al 62 Cu 23 Cr 15 (Al-deficient) and Al 68 Cu 17 Cr 15 (Al-rich) exhibit several structural subtletics. The Al-deficient alloy, has been found to exhibit crystalline bcc and fcc phases with a = 8.90 A and a = 17.98 A respectively. In addition to these phases, a new crystalline bcc variant (a = 15.42 A) originating from the bcc (a = 8.90 A) phase has been found. Also a curious superstructure of the fcc (a = 17.98 A) has been observed. The Al-rich alloy typified by Al 68 Cu 17 Cr 15 , on the other hand, docs not exhibit any structural variants, instead it shows nearly pure i-phase.

The quasicrystalline and recently discovered carbon bearing exotic solids- the fullerenes (e.g. C60) and their tubule relatives Nano-tubules have a common linkage in the sense that they have built in icosahedral symmetry either at the level of lattice — as in QC materials, or motif e.g. in fullerene or tubule (caps). It is, therefore, of interest to explore the structural features and properties (e.g. electronic behaviour) of the solids on a comparative basis. The basic theme of this paper centres around this aspect. We have discussed and described the structural/microstructural characteristics and properties (with emphasis on electronic behaviour) of the QC, C60 and Nano-tubule. Attempts have then been made to bring out their comparisons for these type of icosahedron bearing solids. The case of comparison of structural behaviours and grass root electronic characteristic e.g. Brillouin zones and density of states of the QC and C60 solid — the special carbon bearing material — have been taken first. Thereafter, the case of tubule-solids which are related to C60 have been taken up. Then inter-relationship between tubule and C60 and the exotic electronic characteristics of the tubules have been discussed and described. Finally the similarities and dissimilarities of the three types of solids in regard to their structural and electronic behaviours have been outlined.

In the present investigation, Tl substituted Hg bearing cuprate high temperature superconductors corresponding to Hg 1−x Tl x Ba 2 Ca 2 Cu 3 O 8+δ with x=0.2, 0.4, 0.5, 0.6, 0.7 and 0.8, have been synthesized. The as synthesized phases characterized through XRD and TEM have been found to possess Hg:1223 as the dominant structural phase. These superconductors, with increasing Tl concentration have been found to pass from the underdoped through optimally doped to the overdoped regimes. The Tc for the underdoped regime (x=0.2) corresponds to ~117 K, for the overdoped regime (x=0.8), it is ~119 K. An interesting result emanating from the present study relates to the fact that an optimum Tc of ~122 K is obtained through oxygenation (annealing in oxygen) of the underdoped regime, reduction (annealing in Ar+H2) of overdoped regime, or else through optimum hole doping by suitable adjustment of substituted Tl concentration (x=0.6).

Alloys with general formula Mg- x wt.% CFMmNi 2 , (10, 10, 30, 40 and 50) have been successfully synthesized. The hydrogenation behaviour of these alloy has been extensively investigated. The as-synthesized composite materials have been activated at 550 ± 10 C under a hydrogen pressure of approximately 34 kg cm and their hydrogen storage capacities and desorption kinetics have been evaluated. The new composite hydrogen storage materials, in contrast to the native ingredient CFMmNi 5 (cerium-free misch-metal pentanickellide), have been found to posses much higher storage capacity and to exhibit favourable absorption-desorption kinetics. It has been found that the composite material Mg-30 wt.% CFMmNi 5 has an optimum storage capacity of approximately 5.6 wt.% at the optimum temperature of around 500°C. This is one of the highest reported storage capacities for any known hydrogen storage material. The composite materials Mg- x wt.% CFMmNi 5 also exhibit fast kinetics, represented by the rate of desorption of about 140 cm 1 min 1 which is about three to four times that of CFMmNi 5 alone. Another important hydrogenation behaviour, hysteresis, has been explored through the evaluation of(1/2 RT )In( P t / P d ). The free energy loss due to the hysteresis effect has been found to vary between 1566 J mol 1 at T = 673K and 3299 J mol 1 at T = 773K. The thermodynamic parametersδHandδS for the present optimum composite storage material have been evaluated and found to be 29.00 kJ mol 1 H, and −112.14 J mol 1 H 2 K 1 respectively. The hydriding rate and the improved hydrogen storage capacity of these composite alloys have been found to be strongly correlated with the structural and microstructural characteristics as brought out through XRD, SEM and EDAX techniques. Based on the observed structural and microstructural characteristics, details of the hydrogenation behaviour have been outlined in terms of multiphasic nature and availability of free nickel on the surface. The present composite materials correspond to a new hydrogen storage material with one of the highest storage capacities (around 5.6 wt.%), suitable desorption kinetics and other amenable hydrogenation features, e.g. hysteresis and thermodynamic (δHandδS) parameters.

The present review focusses on the prospectives and perspectives of high conversion efficiency photoelectrochemical (PEC) solar cells. The PEC solar cells score over their solid state counterparts on several points. Some of these axe ease of fabrication and inbuilt storage capability. In order to make PEC solar cells viable, their conversion efficiencies need to be enhanced so as to reach optimum values. Several feasible efficiency enhancement processes for PEC cells such as electrode surface modification, photoetching, electrolyte modification etc. have been described and discussed in this article. The case of efficiency enhancement of n-GaAs based PEC solar cell through the modification of GaAs by Os3+ or Ru3+ ions leading to efficiency enhancement from 9 to 15% has been described and discussed. In regard to efficiency enhancement through electrolyte modification, the example of n-CdSe based PEC cell where the electrolyte (K3 Fe(CN)6K4 Fe(CN)6) is modified through KCN has been dealt with. The efficiency obtained in this cell is upto ~ 16%. For the PEC solar cells embodying the d-d phototransition, MX2 type layered materials, the most dramatic conversion efficiency enhancements come through photoetching of electrode surfaces. We have described and discussed in detail the efficiency enhancements in n-WSe2I3−, I-Pt solar cells through photoetching of n-WSe2 photoelectrodes in 0.1 M aquaregia. High efficiencies upto ~ 17% have been obtained for those solar cells. Yet another route of fabricating viable PEC solar cells giving high power output corresponds to the development of newer PEC cell designs. One example of the newer cell designs which has been described and discussed in this article corresponds to semiconductor-septum (SC-SEP) PEC solar cell. The SC-SEP, PEC solar cells have been found to yield higher power outputs (Voc and Isc) than the conventional single compartment PEC cells. For example, n-CdSeTi septum based PEC solar cell with configuration — Pt, 1 M-3S//n-CdSe/ Ti//0.1M AgN03, Pt has been found to give higher power output (1.42 V and 20 mA/cm2), as compared to n-CdSe based conventional PEC cell (0.64 V and 6 mA/cm2). Similarly, n-TiO2Ti septum electrode based SC-SEP, cell — Pt, l M NaOH/n-TiO2/Ti/0.1M AgNO3, Pt also gives higher power output (1.2 V and 15 mA/cm2). The case of another new PEC cell design incorporating nanostructured TiO2 photoelectrode overlaid with special dye (Ruthenium trinuclear cyanide complex) and exhibiting efficiencies of 7% (under usual solar illumination) and 12% (in diffuse solar light) has also been outlined.

A new synthesis route for the formation of HTSC films of on a viable substrate e.g. MgO by spray pyrolysis has been found through the addition of in appropriate solution mixture. The works as a rate enhancer catalyst which on dissociation during the film processing at supplies active oxygen necessary for the synthesis of HTSC . The transition for the present film was found to be K for an Ag concentration of 0.10. The observed is comparable with values of film prepared through other routes. In addition through dissociation also provides Ag, which enters the grain boundaries, leading to their passivation. The silver also appears to act as a surfactant, resulting in an enlargement of grain size (e.g. 1.0 to 5.0 m for Ag concentrations of 0.05 and 0.10 respectively). Both these effects ensuing from Ag lead to an enhancement of critical current density, . The optimum of at 16 K has been found for the Ag concentration of 0.10. Thus in the present synthesis of films, both the supply of oxygen required for development of HTSC phase and enhancement of critical current density based on grain boundary passivation and enlargement of grain sizes (decrease of grain boundary density) have been obtained by the singular process of addition of an appropriate concentration of .

The Tl doped HgBaCaCuO HTSC films have been synthesised by reacting BaCaCuO precursor films deposited by spray pyrolysis with a mixture of HgTl vapour in an evacuated sealed quartz tube. These films (∼ 3 μm in thickness) having 1223 as the majority phase are found to possess Tc (R = 0)'s of 127 K and 122 K on MgO (100) and ZrO2 (100) single-crystal substrates, respectively, and Jc ∼ 105 A/cm2 (both MgO and ZrO2 have 20 K). The observed Tc(R = 0) of 127 K is the highest reported so far for Tl doped HgBaCaCuO films. Surface morphological investigations reveal the occurrence of layered spiral-like growth features.

We have investigated the synthesis, structural characterisation and hydrogenation behaviour of the composite alloy Mg- x wt% CFMmNi 5 . It has been found that the composite material corresponding to Mg-30 wt% CFMmNi 5 has a storage capacity of ~5.6 wt% at ~500 °C; this storage capacity is one of the highest reported for any known hydrogen storage material. The composite material also exhibits fast hydriding kinetics (~140 cm 3 /min). Explorations of structural/microstructural characteristics of the as-synthesized and hydrogenated materials reveal that the improved storage capacity and rate of desorption may be due to its multi-phasic nature and the availability of free nickel at the surface.