The technology age of terahertz (THz) frequency is coming, with tremendous features and astonishing applications in various fields of science. Using THz time domain spectroscopy, we demonstrate experimentally, for the first time, the fingerprint absorption peaks and the complex dielectric response trends in a 0.1-3 THz frequency waveband, on intentionally synthesized and processed chemical vapor deposition polycrystalline and single-crystal diamond films with systematic quality difference. The two absorption signatures within the 0.1-3 THz frequency band, in which the atomic vibration is material-independent, are attributed to the sp(2) phonon vibration modes of as-grown graphitic phases and/or defects. Regarding the complex dielectric responses of diamond in the THz waveband, the scattering effect resulting from the extended grain boundaries associated with concomitant pores (even gaps) (and/or extended crystal cleavage faults associated with amorphous carbon), as well as intrinsic lattice absorption resulting from increased sp(2) impurities, have been taken into account. Especially the defect size comparable with the wavelength is also found to have a significant effect on the loss at a higher-frequency electromagnetic wave. These findings are expected to promote not only ultra-sensitive quality diagnosis for diamond but also verification of an ideal transmission material for THz waveband applications.

Thermoelectrics can recover waste heat, environmental heat or heats from different sources and convert it to electricity.

Ba0.5Sr0.5Ce0.6Zr0.2Gd0.1Y0.1O3−δ (BSCZGY) proton conducting electrolyte material for intermediate temperature solid oxide fuel cells (IT-SOFCs) has been synthesized by a sol-gel modified Pechini process and its sinterability, thermal expansion, microstructure, ionic conductivity and chemical stability have been investigated. Ionic conductivity at 700°C was measured to be ~8×10−3Scm−1 in wet 5vol.% H2/Ar atmospheres. Chemical stability test in pure CO2 up to 1200°C shows that the material is highly stable; better than the stability of BaZr0.3Ce0.5Y0.1Yb0.1O3−δ.

Single phase polycrystalline BaZr 0.3 Ce 0.5 Y 0.1 Yb 0.1 O 3 - δ electrolyte material was prepared by solid state reaction route. Rietveld analysis of the XRD data confirms the tetragonal symmetry in the I4/mcm space group with unit cell parameters of a = b = 6.0567(3) Å and c = 8.5831(5) Å. The addition of ZnO as a sintering additive was found to reduce the sintering temperature and enhance both overall sinterability and grain growth. Sintering temperature was reduced by 200–300 °C, and a very high relative density of about 98% was achieved at 1400 °C. Impedance spectroscopy in humidified 5% H 2 /Ar atmosphere shows that the protonic conductivity at 600 °C was 8.60 × 10 −3 S cm −1 . Thermal analysis performed in pure CO 2 atmosphere shows very good chemical stability up to 1200 °C. Good biaxial flexure strength of 100–200 MPa was reported which makes this material a promising electrolyte material for intermediate temperature solid oxide fuel cells (IT-SOFCs).

A straightforward electrochemical dissolution-precipitation approach has been developed to synthesize nanostructured β-Ni(OH)2 powders (particle size 10-100 nm, specific surface area ∼100 m(2) g(-1)) from Ni metal anodes. The approach differs from existing electrochemical synthesis methods in that it predominantly results in bulk precipitation of nanoparticles, without significant film growth on either of the electrodes. Heat treatment of the as-synthesized β-Ni(OH)2 afforded NiO with mostly preserved nanostructure and very high specific surface area (≤100 m(2) g(-1), depending on calcination temperature). The as-synthesized β-Ni(OH)2 was found to be an excellent catalyst for the oxygen evolution reaction (OER) in the technologically important water electrolysis process, apparently contradicting recent reports that the α polymorph is required for such high activity. With catalyst loadings <0.1 mg cm(-2), OER current densities of 10 mA cm(-2) were sustained at overpotentials as low as 340 mV, with Tafel slopes of only ∼38 mV/decade. The catalyst was highly stable in alkaline media over the course of electrolysis experiments lasting for several hours. This performance surpasses that of many previously reported earth-abundant OER catalysts and is comparable to that obtained with state-of-the-art RuO2 and IrO2 catalysts.

Most cathodes for SOFCs such as LSM, LSC, LSCF contain lanthanum oxide. In this study, cathode materials free from lanthanum oxide have been prepared. Compositions in the BaO-Y2O3-Fe2O3 and BaO-Y2O3-Co2O3-Fe2O3 have been obtained. Selected compositions with high electrical conductivities up to 60Scm-1 have been composited with GDC10 to form composite cathode with matching thermal expansion to GDC10. Symmetrical cells with GDC10 between the experimental cathodes, and small SOFCs with GDC10 as electrolyte, GDC10.NiO as anode and composite cathode have been constructed and evaluated up to 800oC. The electrical conductivity, thermal expansion, impedance and power densities have been studied. Power densities between 400-800oC have been obtained. The results are discussed in relation to the processing, microstructures, properties and performance of the solid oxide fuel cells.

A Composite oxide ionic conductor consisting of La10Si6O27 (LASIO) and Ce0.9Gd0.1O1.95 (GDC) was synthesized by a modified sol-gel method. The La10Si6O27 powders prepared by modified sol-gel synthesis were coated with GDC gel and latter calcined to form a La10Si6O27 - Ce0.9Gd0.1O1.95 composite material. The structural and microstructural properties of the composite were investigated using powder XRD, SEM and TMA. EIS was conducted in air on the sintered pellets to evaluate the electrochemical performance of the pellets. The conductivity of the composite electrolyte at 973 K was 26 mS /cm which is two orders of magnitudes higher than that for the pure LASIO but lower than that of the GDC (30 mS/cm). The thermal expansion of the composite electrolyte is similar to that obtained for the LASIO.

A Composite oxide ionic conductor consisting of La 10 Si 6 O 27 (LASIO) and Ce 0.9 Gd 0.1 O 1.95 (GDC) was synthesized by a modified sol-gel method. The La 10 Si 6 O 27 powders prepared by modified sol-gel synthesis were coated with GDC gel and latter calcined to form a La 10 Si 6 O 27 - Ce 0.9 Gd 0.1 O 1.95 composite material. The structural and microstructural properties of the composite were investigated using powder XRD, SEM and TMA. EIS was conducted in air on the sintered pellets to evaluate the electrochemical performance of the pellets. The conductivity of the composite electrolyte at 973 K was 26 mS /cm which is two orders of magnitudes higher than that for the pure LASIO but lower than that of the GDC (30 mS/cm). The thermal expansion of the composite electrolyte is similar to that obtained for the LASIO.

Achieving high densification at low sintering temperatures for lanthanum silicate apatites is a major technological hurdle to enable this class of materials to be evaluated as electrolytes for solid oxide fuel cells. Using sol-gel process, materials close to 97% of theoretical density have been obtained at a low sintering temperature of 1773 K for both doped and undoped samples. The effect of varying concentrations of Zn2+ doping on the sinterability, electrical, thermal and microstructural properties of 0.2 mol Mg2+ doped La10Si6O27 were investigated.Ionic conductivity of the samples was measured using electrochemical impedance spectroscopy in the temperature range of 573 K-1073 K. A total ionic conductivity of 1.7 x 10(-2) Scm(-1) with a corresponding activation energy of 0.33 eV at 1073 K were measured for the composition La10Zn0.2(SiO4)(5.8)O-2.5 which is higher than 9 x 10(-3) Scm(-1) for the undoped composition La-10(SiO4)(6)O-3. The composition La(10)oMg(0.2)Zn(0.4)(SiO4)(5.4)O-4.8 has the lowest thermal expansion coefficient of 8.470 x 10(-6) K-1 of all the samples investigated. (C) 2015 Elsevier Masson SAS. All rights reserved.

Barium calcium aluminium boro-silicate glass (BCABS) is used as a sealant for Solid Oxide Fuel Cells (SOFCs) at 800 degrees C. One major problem is the reaction of this glass with barium oxide and other materials in the composition such as Ba-Y-Co-Fe (BYCF) and Ba-Sr-Co-Fe (BSCF) used in the fuel cell components, leading to the formation and spreading of barium aluminosilicate glass on the surface of the fuel cells. This investigation found that adding 0.4 mol% ZrO2 to BCABS prevents the formation of barium aluminosilicate glass. The resistivity of the mixture is 4 MO, while the thermal expansion coefficient (TEC) is 12.40x10(-6)/degrees C. Therefore, BCABS glass with 0.4mol%ZrO2 generated a novel composite for SOFCs.

Anatase is the preferred phase of TiO2 in dye-sensitized solar cells (DSSCs) because of its lower charge recombination than other phases. However, for small diameter nanotubes before detached from the Ti foil, rutile rather than anatase appears upon a pre-treatment annealing at 400 degrees C or above. Here we have fabricated highly ordered free-standing small diameter (50 nm) TiO2 nanotube membranes which were pre-treated at 300 degrees C to maintain pure anatase phase. The free-standing nanotube membranes were used to fabricate the photoanodes and were further calcined at 500 degrees C to achieve full crystallization of the nanotubes. It was shown that the electron lifetime is much longer in the 300 degrees C-pre-treated nanotubes than those pre-treated at 400 or 500 degrees C, leading to a significantly improved power conversion efficiency of 4.59% (enhanced by similar to 50%). (C) 2014 Elsevier B.V. All rights reserved.

Ba0.95FeY0.05O2.81 was prepared by solid state reaction method to study its structure, conductivity and thermal expansion coefficients. X-ray powder diffraction at elevated temperatures showed the pure phase at 100 - 600 °C, then the phase changed at 700 - 800 °C. Electrical conductivity measurements at different temperatures showed that the conductivity increased with an increasing amount of Co2O3. The highest conductivity was observed for 10 wt%Ba0.95FeY0.05O2.81 + 90 wt%Co2O3. Thermal expansion coefficients were measured for different compositions to determine the compatibility with Ce0.9Gd0.1O1.95 electrolyte. Results showed that the conductivity and thermal expansion coefficient were sensitive to the composition. The optimum composition was 10 wt%BFY532 + 90 wt%Co2O3, which gave the highest conductivity at 600 - 800 °C. The thermal expansion coefficient was 12.79×10 -6 o C -1 at 40 - 800 °C, which is compatible with the Ce0.9Gd0.1O1.95 electrolyte.

A new model is presented to describe the quantum confinement and surface passivation effects of nanoclusters. The quantum well depth (phi) and the band gap width (E-g) of nanoclusters are independent concepts, because the phi depends on the surface electron density while the E-g is a function of the crystal field of the solid. The phi and E-g can be correlated with the joint physical and chemical effects, which are quite simple but have rarely been noticed. It is suggested that the bond contraction at the surface and the rise in the surface-to-volume ratio (gamma), as well as the cluster interaction, enhance intrinsically the crystal field and hence the band gap E-g. Reaction with electronegative elements, such as oxygen and nitrogen, widens extrinsically the E-g by producing holes below the Fermi level [Appl. Phys. Lett. 72, 1706 (1998)]. The formulation agrees well with experimental observations on the band gap enlargement by reducing particle size.

Percolation theory deals with the behaviour of connected clusters in a system. Originally developed for studying the flow of liquid in a porous body, the percolation theory has been extended to quantum computation and communication, entanglement percolation in quantum networks, cosmology, chaotic situations, properties of disordered solids, pandemics, petroleum industry, finance, control of traffic and so on. In this paper, the application of various models of the percolation theory to predict and explain the properties of a specially developed family of dense sintered and highly refractory Al2O3-W composites for potential application in high intensity discharge light sources such as high pressure sodium lamps and ceramic metal halide lamps are presented and discussed. The low cost, core-shell concept can be extended to develop functional composite materials with unusual dielectric, electrical, magnetic, superconducting, and piezoelectric properties starting from a classical insulator. The core shell concept can also be applied to develop catalysts with high specific surface areas with minimal amount of expensive platinium, palladium or rare earth nano structured materials for light harvesting, replicating natural photosynthesis, in synthetic zeolite composites for the cracking and separation of crude oil. There is also possibility of developing micron and nanosize Faraday cages for quantum devices, nano electronics and spintronics. The possibilities are limitless.

There are now new legislations emerging or being contemplated to restrict the use of Pb in electronic devices. This development has provided the impetus for the development of Pb- free solder alloys and efforts are now geared towards characterizing their operational and functional properties. The most common alloys being recommended and investigated are those primarily based on the Sn-Ag-Cu (SAC) system. These SAC alloys generally have higher melting points than conventional Pb-Sn alloy. Additionally they are susceptible to microstructural evolution of inter-metallic compounds that have been implicated in thermal fatigue life, mechanical strength and fracture toughness of the soldered joints. We have studied the Sn rich corner of the Sn-Ag-Cu system with minor additions aimed at minimizing detrimental microstructural development and improving the solderability and the mechanical strength of soldered joints. Some of the SAC alloys with minor additions showed some interesting properties. Their shear strength measured ranged from 30 – 60 MPa. The combined properties of strength and conductivity recorded compared favorably with that of traditional Pb-Sn solders.

The paper presents some preliminary investigations on the sintering of alumina ceramics to translucency in a low thermal mass furnace. It is found that extremely fast sintering occurs in a forming gas atmosphere. Rapid densification occurs in minutes rather than hours normally encountered in conventional sintering of ceramics.

The following sections are included:PART I. DEVELOPMENT OF SUSTAINABLE LIGHTING FROM GASEOUS DISCHARGEIntroductionLighting from the dawn of civilization to the 21st centuryNeed for energy conservation and sustainabilityHow Radiation is GeneratedThe Development of Compact Fluorescent LampsThe Development of PhosphorsPhosphors in cathode ray tubes (CRT)Phosphors for general lighting applicationsConversion UV to Visible Using PhosphorsCompact Fluorescent Lamps (CFLs)Energy Conservation and Sustainable Development in LightingAdvanced Ceramics and Composites for High Intensity Discharge LampsDevelopment of Alumina to TranslucencyCeramic-Metal (Cermets) Composites for High Intensity Discharge LampsDevelopment of Glass Ceramic Sealing Materials for the Ceramic Halide LampsDevelopment of Compact White Light High Pressure Sodium LampsDevelopment of Seals for the Ceramic Metal Halide (CMH) LampsMaterials Systems Investigated to Produce Refractory and Metal Halide Resistant Glass SealsConclusionsPART II. DEVELOPMENT OF SUSTAINABLE SOLID STATE LIGHTINGIntroductionOrganic Light Emitting Diodes (OLEDs)Basic Principle of Solid State Lamps Obtained from Light Emitting DiodesMaterials Used for LEDsInternal Efficiency of LEDsVarious Colors of LED and White LEDsDiscussionConclusionPART III. SUSTAINABLE DISPERSED COMBINED MICRO POWER AND HEAT GENERATIONIntroductionRationale for combined dispersed power and heat generationTechnologies being developed to support micro dispersed power generationApplication of solid oxide fuel cell for dispersed micro power generationDispersed micro power without grid interconnectionReview of Fuel Cell TechnologiesPrinciple of fuel cellMaterials developmentThermodynamic Efficiency and EMF of Fuel CellsTypes of Fuel CellsPEM fuel cellsAlkaline fuel cellMolten carbonate fuel cell (MCFC)Phosphoric acid fuel cell (PAFC)Direct methanol fuel cell (DMFC)Solid oxide fuel cell (SOFC)Design of Solid Oxide Fuel CellsReactions Occurring at the Interfaces of the Anode, Cathode and ElectrolyteCurrent Development of Intermediate Temperature Solid Oxide Fuel Cells (ITSOFCs)Current Status of Research in Solid Oxide Fuel Cells WorldwideResearch Carried Out by the Author and His GroupDiscussionSummary