NiO Content Research Articles

Effect of concentrations ratios of NiO on the efficiency of solar cell for (CdO)1-x(NiO)x thin films

CdO:NiO/Si solar cell film was fabricated via deposition of CdO:NiO in different concentrations 1%, 3%, and 5% for NiO thin films in R.T and 723K, on n-type silicon substrate with approximately 200 nm thickness using pulse laser deposition. CdO:NiO/n-Si solar cell photovoltaic properties were examined under 60 mW/cm2 intensity illumination. The highest efficiency of the solar cell is 2.4% when the NiO concentration is 0.05 at 723K.

MOF-derived NiO/Ni architecture encapsulated into N-doped carbon nanotubes for advanced asymmetric supercapacitors

In the second step, the Ni-MOF was transformed into Ni-MOF-600 with low NiO content via calcination under nitrogen protection at 600 °C

Exchange-biased hybrid γ-Fe2O3/NiO core-shell nanostructures: three-step synthesis, microstructure, and magnetic properties.

A two-step solvothermal method combining a calcination process was conducted to synthesize γ-Fe2O3/NiO core-shell nanostructures with controlled microstructure. The formation mechanism of this binary system has been discussed, and the influence of microstructures on magnetic properties has been analyzed in detail. Microstructural characterizations reveal that the NiO shells consisted of many irregular nanosheets with disordered orientations and monocrystalline structures, packed on the surface of the γ-Fe2O3 microspheres. Both the grain size and NiO content of nanostructures increase with the increasing calcination temperature from 300 °C to 400 °C, accompanied by an enhancement of the compactness of NiO shells. Magnetic studies indicate that their magnetic properties are determined by four factors: the size effect, NiO phase content, interface microstructure, i.e. contact mode, area, roughness and compactness, and FM-AFM (where FM and AFM denote the ferromagnetic γ-Fe2O3 and the antiferromagnetic NiO components, respectively) coupling effect. At 5 K, the γ-Fe2O3/NiO core-shell nanostructures display certain exchange bias (HE = 60 Oe) and enhanced coercivity (HC = 213 Oe).

The effect of P–T on the reaction between tonalitic melt and mantle lherzolite at 2–4 GPa and implications for evolution of North China Cratonic Lithosphere and generation of High Mg# andesite

To assess the effects of reaction factors (mainly P and T) on the mineral assemblage and chemical composition of residual minerals and reacted melt in the reaction between andesitic melt and mantle peridotite, we conducted experimental reactions between tonalitic melt and mantle lherzolite using a DS-3600 six-anvil apparatus at 2–4 GPa and 1250 °C–1400 °C. The reaction products contain two types of reaction vein: orthopyroxene(r) [r means this mineral generated in melt-peridotite reaction and located at reaction rim] + garnet(r) and orthopyroxene(r). The mineral assemblages of the reaction veins are controlled by the reaction P and T, which can be determined via the empirical discriminant function: Y = 3.33 × 10−6 T2–2.17 × 10−3 T − 0.5 − P (T in °C, P in GPa; Y ≥ 0: Opx veins form; Y < 0: Opx + Grt veins form). These two types of reaction vein match those found in mantle xenoliths in Mesozoic and Cenozoic magmas from the North China Craton (NCC), indicating that they were formed by similar processes. The melt–peridotite reaction (including P and T) also influences the chemical composition of the residual minerals in the experimental products, with the major element variations being similar to those of NCC lithospheric mantle evolution from Palaeozoic to Cenozoic. Based on the experimental results, olivine in xenoliths from depths of ~100 km (~3 GPa) has higher SiO2 and lower NiO and MnO contents than olivine in xenoliths from depths of ~130 km (~4 GPa), and orthopyroxene in xenoliths from depths of ~100 km has higher Mg#, higher CaO content, and lower NiO content than orthopyroxene in xenoliths from depths of ~130 km. The reacted-mantle xenoliths contain clinopyroxene that originated from cold (<1300 °C) and deep (~135 km) lithospheric mantle. The P–T conditions also control the chemical composition of the reacted melt. An increasing reaction pressure increases the SiO2 content, whereas an increasing reaction temperature reduces the SiO2 content. In combination with the varying Na2O and K2O contents of the parental magma, the reacted melt can yield almost all types of intermediate magma with high Mg# (Mg# = mol[Mg/(Mg + ∑Fe)], Mg# > 0.45) character. This variation in major element of the reacted melt agrees with field observations of Mesozoic high-Mg# andesitic rocks from the NCC, indicating similar causes of the variation in the major element contents. With respect to the trace element content of the reacted melt, a garnet content of 15%–20% produces a right deviation of the heavy rare earth element partition curve (chondrite-normalized) and substantially elevates the Sr/Y and LaN/YbN ratios, indicating an adakite-like reacted melt.

Kinetics of the reduction and oxidation of Mg added NiO/Al2O3 for chemical looping combustion

Reduction and oxidation kinetics of Mg added Ni-based oxygen carriers with different types of NiO and Mg contents were investigated for chemical looping combustion (CLC) using thermogravimetric analyzer (TGA) in the temperature range of 825–900°C. The Johnson–Mehl–Avrami (JMA) model was adopted for determination of kinetic parameters of both reduction and oxidation reaction of the three oxygen carriers. It was found that the reduction reaction consists of (1) fast surface reaction in which the reaction rate is independent of both the reaction temperature and the fuel gas concentration, (2) nucleation with short duration, and (3) kinetic controlled reaction under influence of gas diffusion rate. In oxidation reaction, the reaction rates were not heavily dependent on reaction temperature because of the low activation energies. Instead, the concentration of O2 strongly affected the pre-exponential factors, and the reaction rate constant k, consequently. Unlike the reduction reaction, the fast surface reaction was not observed in the oxidation reaction. The type of NiO used for preparation of the oxygen carriers was found to be more important factor than Mg contents for determination of the kinetic parameters for both reduction and oxidation.

The Effects of the Content of NiO on the Microstructure and Photocatalytic Activity of the NiO/TiO2 Composite Film

The NiO/TiO2 composite films with the NiO content of 3 %, 5 %, 10 %, 13 %, 15 % and 20 % were prepared by mechanical coating technology and subsequent oxidation process. The composition and microstructure of the films were analyzed by X-ray Diffraction (XRD), scanning electron microscope (SEM), and energy dispersive spectroscopy (EDS). The photocatalytic activity was evaluated and the effects of the content of NiO on microstructure and photocatalytic activity of the films were studied. The results show that NiO particles are dispersed in the Ti coatings, and the NiO concentration in the inner layer of the coatings is higher than in the outer layer. With the addition of NiO in the NiO/Ti coating, the ductility is deteriorated and the thickness is reduced of the NiO/Ti coatings. The films with NiO/TiO2/Ti composite microstructure are obtained by the oxidation of NiO/Ti coatings. Photocatalytic efficiency of the films is obviously enhanced with the help of the p-n junction heterostructure in the NiO/TiO2 films. The optimum content of NiO is about 13 %, and the degradation rate of methyl orange solution reaches the maximum value of 88.44 %. DOI: http://dx.doi.org/10.5755/j01.ms.24.4.19266

FTIR and Optical Properties of NiO Doped Cr2O3 Nanopar-ticles Synthesis by Hydrothermal Method

Pure and Nickel oxide doped chromium (III) oxide (Cr2O3) nanoparticals are synthesized by hydrothermal technique. The effect of dopant Ni concentration on the structural behavior of Cr2O3 nanoparticles was examined by X-ray diffraction. The average crystallite size of the synthesized nanoparticles was measured from XRD patterns using Scherrer equation and was decreased from 22nm to 12.9 nm with the increasing Nio concentration in Cr2O3 from (0, 0.01, 0.06, and 0.10). Morphologies and compositional elements of the synthesized nanoparticles were observed by the field emission scanning electron microscopy (FESEM) and energy dispersive X-ray (EDX) spectroscopy, respectively. The optical property of the samples was measured by ultraviolet - visible (UV-Vis.) absorption spectroscopy. The observed optical band gap value ranges from 2.3eV to 2.5eV for Ni doped nanoparticles

Development of Nano- $$\hbox {WO}_{3}$$ WO 3 Doped with NiO for Wireless Gas Sensors

\(\hbox {WO}_{3}\) doped with NiO nanopowders with different NiO concentrations were prepared by sol–gel technique. The fabrication of the thin films for gas sensors applications was utilized using thermal vacuum evaporation technique. The morphological structure, crystallinity and optical properties of \(\hbox {WO}_{3}\) and NiO-doped \(\hbox {WO}_{3}\) nanopowders were characterized using scanning electron microscopy, X-ray diffraction and UV–Vis spectrophotometer, respectively. The electrical behaviors of the sensors were determined and measured by the two platinum electrodes sensor’s resistance with different gases at various temperatures. The results show that a great response to \(\hbox {CO}_{2}\) gas was 164% at 5% doping ratio which is applicable for all environmental and industrial fields. GSM module by MAX circuit was applied on gas sensor devices to send a wireless message telling that there is a leakage in the area which the sensor installed.

Decoding of Mantle Processes in the Mersin Ophiolite, Turkey, of End-Member Arc Type: Location of the Boninite Magma Generation

The Mersin ophiolite, Turkey, is of typical arc type based on geochemistry of crustal rocks without any signs of mid-ocean ridge (MOR) affinity. We examined its ultramafic rocks to reveal sub-arc mantle processes. Mantle peridotites, poor in clinopyroxene (&lt;1.0 vol.%), show high Fo content of olivine (90–92) and Cr# [=Cr/(Cr + Al) atomic ratio] (=0.62–0.77) of chromian spinel. NiO content of olivine is occasionally high (up to 0.5 wt.%) in the harzburgite. Moho-transition zone (MTZ) dunite is also highly depleted, i.e., spinel is high Cr# (0.78–0.89), clinopyroxene is poor in HREE, and olivine is high Fo (up to 92), but relatively low in NiO (0.1–0.4 wt.%). The harzburgite is residue after high-degree mantle melting, possibly assisted by slab-derived fluid. The high-Ni character of olivine suggests secondary metasomatic formation of olivine-replacing orthopyroxene although replacement textures are unclear. The MTZ dunite is of replacive origin, resulted from interaction between Mg-rich melt released from harzburgite diapir and another harzburgite at the diapir roof. The MTZ dunite is the very place that produced the boninitic and replacive dunite. The MTZ is thicker (&gt;1 km) in Mersin than in MOR-related ophiolite (mostly &lt; 500 m), and this is one of the features of arc-type ophiolite.

Mineral records of the pyroxenites formed within harzburgites (Ulaş, Sivas, Turkey): implications on petrogenesis and tectonic setting

In this article, the petrological processes of the clinopyroxenite dykes and host peridotites occurring in Ulas District (Sivas, mid-Anatolia, Turkey) are discussed. The new geochemical data from major minerals in the clinopyroxenite dykes and host harzburgites revealed differences to the supra-subduction zone (SSZ)-type pyroxenites and peridotites. In particular, the NiO content of olivines in the host harzburgites showed the signature of the mantle, whereas rare olivines of the clinopyroxenites had a NiO content and Fo number that were inferior to those of mantle peridotites. The high Mg-number of clinopyroxenes in the clinopyroxenites was likely associated with the partial remelting of the host harzburgites. Additionally, the rare earth element pattern of clinopyroxenes from the studied clinopyroxenites exhibited a similar pattern to those of the other SSZ or fore-arc clinopyroxenes. Additionally, the low Mgnumber and relatively high Cr-number of spinels in the clinopyroxenites showed similarity to the subduction-related origin. Based on textural and geochemical evidence, the harzburgites were interpreted as depleted mantle rock, which was modified by melt-peridotite interactions. Consequently, the pyroxenites likely occurred as a crystallizing or cumulative zone of the SSZ-type melt and the minerals were gained from partial melting of the harzburgites through the interaction with such magma.

Melt-dunite interactions at 0.5 and 0.7 GPa: experimental constraints on the origin of olivine-rich troctolites

Olivine-rich troctolites and dunites are diffuse lithologies at crust-mantle transition of the oceanic lithosphere. Disequilibrium textures coupled to mineral compositions indicate that melt-rock reactions play an important role in their origin. The prevailing view is that olivine-rich troctolites are related to extensive melt impregnation of a precursor mantle dunite.In order to provide experimental constraints, we performed reactive dissolution and crystallization experiments by juxtaposing three variably evolved MORB-type glasses with a melt-bearing dunite at 1300 °C and then cooling to 1150 °C at constant pressure (0.5 and 0.7 GPa). Additionally, an isothermal experiment (0.7 GPa, 1250 °C) provides a snapshot of olivine-melt reaction after the high-temperature step.Runs result in glass-bearing gabbro overlain by olivine-rich troctolite (at 0.5 GPa) or dunite (at 0.7 GPa) showing disequilibrium textures comparable with natural occurrences typically related to melt-rock reaction, e.g. embayed and resorbed subhedral olivine with lobate contacts against plagioclase and clinopyroxene, often occurring as large poikiloblasts including rounded olivines. Modal abundance of interstitial phases and mineral chemistry are strongly controlled by the extent of reacting melt infiltrated into the dunite matrix, i.e. the melt/olivine ratio. We found that higher pressure further limits olivine dissolution and results in a lower high-T porosity, decreasing the final abundance of interstitial phases.Olivine composition is mostly buffered by the starting San Carlos olivine, resulting in high XMg (0.88–0.90). NiO content decreases at increasing melt/olivine ratio, matching the composition of olivine in natural samples. Remarkably, at very low melt/olivine ratio, NiO can exceed the starting San Carlos value as a result of the increase of Ni olivine-melt partition coefficient during cooling after olivine assimilation in the reacted melt. This might potentially produce high-Ni, at high XMg, magmatic olivine.Melt composition affects the chemistry of interstitial minerals that show large compositional variability (anorthite in plagioclase, TiO2 in clinopyroxene) as a result of local equilibrium driven by trapped melt. Remarkably, mineral co-variation trends (e.g. anorthite in plagioclase vs. olivine XMg) match those of some natural olivine-rich troctolites occurrences.Experimental results corroborate and constrain the lead role of melt-rock reactions in the origin of olivine-rich rocks at mantle crust transition in the oceanic lithosphere.

Dielectric dispersion, dipolar relaxation and a.c. conduction phenomena of NiO doped lead bismuth silicate glass system

Dielectric properties of heavy metal oxide glass system viz., PbO-Bi2O3-SiO2 mixed with varied concentration of NiO are studied as functions of frequency and temperature. The dielectric parameters viz., ε′, tan δ, σa.c. are observed to increase with NiO content. Electric moduli formalism is adopted for the analysis of dipolar relaxation effects. Impedance plots drawn for the glasses doped with different NiO concentrations pointed out decreasing value of electrical impedance of the glass samples with increase of NiO content. Activation energies for dipoles and for a.c. conductivity are found to decrease, whereas the concentration of defect energy states N(EF) is increased with increase of NiO content. Quantitative analysis of these results along with those of spectroscopic studies indicated that with increase of NiO concentration there is gradual growing presence of Ni2+modifier (Oh) ions in the glass matrix. As modifiers these ions are anticipated to stimulate structural defects by depolymerizing the glass network. The increasing degree of disintegration of the glass network is predicted to facilitate for diffusion of conducting ions in the bulk glasses. Finally, it is concluded that in spite of the fact that the host glass is a heavy dense glass (composed of multi component heavy metal oxides with low mobile charge carriers) which has got plenty of other applications in optically operated devices, it is more conducive even for easy diffusion of Ni2+ions that contribute to ionic conductivity. In view of these observations it is concluded that the studied glass may be considered as ionic conducting material to be used in solid electrolytes.

Controlled synthesis of Nix-Co(1-x) bimetallic nanoparticles using the thermogravimetric method

In the present study, Nix-Co(1-x) (x=0, 0.2, 0.4, 0.6, 0.8, 1) nanoparticles(NPs) were synthesized using the thermogravimetric method. The production of these NPs was carried out through the reduction reaction of nickel and cobalt oxides, as metal precursors, and methane gas, as a reducing agent, under atmospheric pressure. The raw materials and the products were characterized using XRD, FESEM, XRF, EDS and Map analysis. Initially, the duration of the reduction reaction and conversion of NiO and CoO to Ni and Co NPs was predicted using a grain model simulation. The effect of different parameters such as methane volume percentage and reduction temperature on the duration of conversion were investigated by this model in order to properly choose the optimum temperature and volume percentage of methane gas for the experiments. The experimental results demonstrated that the reaction time of nickel and cobalt oxides with 23vol.% methane at 830°C for the production of Ni and Co NPs was 14 and 39min, respectively, which was in good agreement with the predicted results. Investigation of the reaction time for (NiO)x-(Co3O4)(1-x) binary mixture with methane was evaluated by considering the relative compositions of NiO(x=0, 0.2, 0.4, 0.6, 0.8, 1). The results showed that as the content of NiO in the binary mixture increased, the duration of Nix-Co(1-x)‌ NPs production decreased. XRD and EDS analysis confirmed the formation of about 96% of Ni0.6-Co0.4 BNPs and over 97% of Ni and Co NPs. In addition, the effect of methane diffusion into the pellets was investigated on (NiO)0.4-(CoO)0.6 with sintered and non-sintered modes.

Combined effect of pH and H2S on the structure of passive film formed on type 316L stainless steel

The effect of pH on the structure and protectiveness of passive films formed in H2S-containing environment was investigated using potentiodynamic polarization, X-ray photoelectron spectroscopy (XPS) and time of flight secondary ion mass spectrometry (ToF-SIMS). The corrosion resistance of 316L stainless steel decreased with pH under H2S-containing condition. The passive films formed at higher pH contained lower content of Cr and higher content of S. This was responsible for the passive film degradation. Ni was enriched at the film/metal interface, while Cr was enriched in the passive film. The content of NiO in the passive film increased with pH, which resulted in the weakened Ni enrichment at the film/metal interface at higher pH. The results also indicated that H2S and pH had a combined effect on the passive film structure. The oxide films presented a three-layer structure, where the outermost layer was mainly composed of hydroxides, and the intermediate and inner layers were dominated by sulfides and oxides. The presence of H2S could inhibit the formation of iron oxides. Therefore, iron oxides and iron sulfides were enriched in the inner and intermediate layer, respectively.

Facile preparation of a Ni/MgAl2O4 catalyst with high surface area: enhancement in activity and stability for CO methanation

Abstract To enhance the performance of anti-coking and anti-sintering of the Ni-based catalysts during the reaction process of CO methanation, we synthesized a group of catalysts denoted as “Ni-xMgAl2O4” via the modified co-precipitation method utilizing carbon black as hard template. The addition of carbon black could significantly improve the specific surface area of MgAl2O4 to 235.8 m2 g−1. The Ni catalysts supported on high-surface-area MgAl2O4 (Ni-0.25MA) exhibited enhanced catalytic performance and hydrothermal stability in comparison with the conventional Ni-based magnesia alumina spinel catalysts with the same NiO content. In the process of 120-h stability test, the Ni-0.25MA catalyst exhibited remarkable improvement in both anti-sintering and anti-coking. After a series of characterizations, we found that the addition of carbon black could make more pores over MgAl2O4, resulting in the supported Ni particles being anchored in the pore rather than on the outside surface of support. This structure enhanced the dispersion of nickel nanoparticles, thus strengthening the interaction between nickel species and the MgAl2O4 support, which led to the promotion in catalytic activity and stability of high-surface-area Ni/MgAl2O4.

On the relative timing of listwaenite formation and chromian spinel equilibration in serpentinites

Ultramafic rocks exposed at the Earth's surface generally record multiple stages of evolution that may include melt extraction, serpentinization, carbonatization, and metamorphism. When quantitative thermometry based on mineral chemistry is applied to such rocks, it is often unclear what stage of their evolution is being observed. Here, in peridotites with extensive replacement of silicate minerals by carbonates (listwaenites), we present a case study that addresses the timing of carbonate formation relative to closure of exchange reactions among relict primary minerals. Massive and schistose serpentinized peridotites of Neoproterozoic age outcrop at Gabal Sirsir, South Eastern Desert, Egypt (northwestern corner of the Arabian-Nubian Shield or ANS). Petrography, bulk composition, and mineral chemistry are all consistent with a strongly depleted mantle harzburgite protolith for the serpentinites. Bulk compositions are low in Al_2O_3 and CaO and high in Mg# [molar Mg/(Mg+Fe) = 0.89–0.93]. Relict spinel has high Cr# [molar Cr/(Cr+Al)] and low Ti, while relict olivine has high Mg# and NiO contents. Based on compositions of coexisting relict olivine and chromian spinel, the protolith experienced 19 to 21% partial melt extraction. Such high degrees of partial melting indicate a supra-subduction zone environment, possibly a forearc setting. Along thrust faults and shear zones, serpentinites are highly altered to form talc-carbonate rocks and weathering-resistant listwaenites that can be distinguished petrographically into Types I and II. The listwaenitization process took place through two metasomatic stages, associated first with formation of the oceanic crustal section and near-ridge processes (∼750–700 Ma) and subsequently during obduction associated with the collision of East and West Gondwana and escape tectonics (∼650–600 Ma). In the first stage, Mg# of chromian spinel in the serpentinites continuously changed due to subsolidus Mg–Fe^(2+) redistribution, while the Mg# of chromian spinel in the Type I listwaenites was frozen due to the absence of coexisting mafic silicates. During the second stage, the Type II listwaenites formed along shear zones accompanied by oxidation of relict chromian spinel to form ferritchromite and Cr-bearing magnetite in both serpentinites and listwaenites. The high Cr# of chromian spinel relics in both serpentinites and listwaenites preserves primary evidence of protolith melt extraction, but divalent cations are more easily mobilized at low temperature. Hence, relict chromian spinel in listwaenites shows significantly higher Mg# and lower MnO than that in serpentinite, suggesting that nearly complete alteration of ultramafic rocks to form listwaenite took place prior to re-equilibration between chromian spinel and the surrounding mafic minerals in serpentinites. Furthermore, the ferritchromite in the serpentinites has higher Mn content (1.1–2.1 wt%) than that in the listwaenites (0.6–0.9 wt%), indicating its formation after carbonatization since carbonate minerals are a favorable sink for Mn.

The enhanced ethanol sensing properties obtained by the introduction of NiO into ZnO/SnO2 mixed metal oxides

NiO has been introduced into ZnSn-mixed metal oxide composites (MMOCs) with various Ni contents via a simple co-precipitation/sintering route. The influences of introduction of NiO on light absorption and ethanol sensing properties of ZnSn-MMOCs have been investigated. The obtained ternary NiZnSn-MMOCs exhibit extended adsorption to visible light area and lower energy band gap values. Consequently, their sensitivities and responses to ethanol have been enhanced by the introduction of NiO at certain range compared to binary ZnSn-MMOCs, which is attributed to the visible light responsive component of NiO and the p-n heterostructures between NiO and ZnSn-MMOCs. The ternary NiZnSn-MMOCs with the optimal content of NiO reveal high sensitivity of 180–200 ppm of ethanol at 225 °C and quick response time to low concentration of ethanol.

Novel Microwave Absorption Materials of Porous Flower-Like Nickel Oxide@Polyaniline in the X-Band

Porous flower nickel oxide@polyaniline (NiO@PANI) composites as excellent microwave absorption (MA) materials in the X-band were synthesized via a two-step strategy in this work. The porous NiO flower is uniformly dispersed and homogeneous in particle size after Ostwald ripening process. Coating conductive PANI on the surface of porous NiO microspheres could improve interfacial polarization and dielectric loss property that will lead to a great improvement of MA properties. Electromagnetic (EM) parameters of NiO@PANI composites with different NiO contents were investigated by a vector network analyzer and the reflection loss (RL) values with varied thickness were also calculated. The results showed that the effective absorption bandwidths ([Formula: see text][Formula: see text]dB) of all NiO@PANI composites can cover the whole X-band. Especially, the NiO@PANI[Formula: see text] composite is able to attenuate microwave energy in the X-band with the thickness of 2.5[Formula: see text]mm. The NiO@PANI[Formula: see text] has a maximum RL of [Formula: see text][Formula: see text]dB at 10.1[Formula: see text]GHz and the effective absorption bandwidths cover 4.64[Formula: see text]GHz (11.12–15.76[Formula: see text]GHz) at 2.0[Formula: see text]mm. The excellent MA absorption performance may be ascribed to the polarization effect, dielectric loss and structure of porous flower-like NiO@PANI. Our work confirms that the synthesized NiO@PANI composite is an attractive candidate as a highly efficient MA material in the X-band.

Spectroscopic, dielectric dispersion and dc conductivity studies of Sb2O3doped lithium fluoro borophosphate glasses mixed with small concentrations of NiO

Glasses of the composition(20–x) LiF–10 Sb2O3–10 B2O3–60P2O5: x NiO(0 < x < 0.25) were synthesized by conventional rapid melt quenching method. The non–crystalline nature of the samples was confirmed by XRD analysis and the glass forming abilities were analyzed by DTA studies. The compositional dependence of structural aspects of the glasses was analyzed by FT–IR and Raman studies. The DTA, FT–IR and Raman studies suggested an increasing degree of disorder in the glass network with increasing concentration of NiO up to 0.20 mol %. The reversal trend observed beyond 0.20 mol% is attributed to an increasing polymerization of glass network. The optical absorption (OA) and photoluminescence (PL) studies were also carried on these glasses. The results of OA and PL spectral studies suggested that the gradual increase of octahedral Ni2+ ions with the increase in the concentration of NiO up to 0.20 mol%. Electrical properties viz., dielectric dispersion, DC and AC conductivity of the titled glass samples were also performed on titled glass samples. The observed increase in the values of dielectric constant, dielectric loss and AC conductivity (at any frequency and temperature) with the increase in the concentration of NiO up to 0.20 mol%is ascribed to the increasing space charge polarization in the glass network. The results of conductivity studies indicated that there is a mixed conduction (both ionic and polaronic) and the polaron hopping seems to prevail over ionic conduction in the glasses containing less than 0.20 mol% of NiO.

Chrome-diopside Megacryst-bearing Lamprophyre from the Late Cretaceous Mundwara Alkaline Complex, NW India: Petrological and Geodynamic Implications

ABSTRACT The occurrence of a rare mantle-derived chrome-diopside megacryst (∼8 mm), containing inclusions of olivine, in a lamprophyre dyke from the late Cretaceous polychronous (∼100 - 68 Ma) Mundwara alkaline complex of NW India is reported. The olivine inclusions are forsteritic (Fo: 85.23) in composition, and their NiO (0.09 wt%) and CaO (0.13 wt%) contents imply derivation from a peridotitic mantle source. The composition of the chrome diopside (Cr2O3: 0.93 wt ) (Wo45.27 En48.47 Fs5.07 and Ac1.18) megacryst is comparable to that occurring in the garnet peridotite xenoliths found in diamondiferous kimberlites from Archaean cratons. Single pyroxene thermobarometry revealed that this chrome diopside megacryst was derived from a depth range of ∼100 km, which is relatively much deeper than that of the chrome-diopside megacrysts (∼40-50 km) reported in spinel-lherzolite xenoliths from the alkali basalts of Deccan age (ca. 66-67 Ma) from the Kutch, NW India. This study highlights that pre-Deccan lithosphere, below the Mundwara alkaline complex, was at least ∼100 km thick and, likely, similar in composition to that of the cratonic lithosphere.