Designing structures that have minimal or zero coefficients of thermal expansion (CTE) are useful in many engineering applications. Zero thermal expansion is achievable with the design of porous materials. The behavior is primarily stretch-dominated, resulting in favorable stiffness. Two and three-dimensional lattices are designed using ribs consisting of straight tubes containing two nested shells of differing materials. Differential Poisson contraction counteracts thermal elongation. Tubular ribs provide superior buckling strength. Zero expansion is achieved using positive expansion isotropic materials provided axial deformation is decoupled by lubrication or segmentation. Anisotropic materials allow more design freedom. Properties of two-dimensional zero expansion lattices, of several designs, are compared with those of triangular and hexagonal honeycomb nonzero expansion lattices in a modulus-density map. A three-dimensional, zero expansion, octet-truss lattice is also analyzed. Analysis of relative density, mechanical stiffness, and Euler buckling strength reveals high stiffness in stretch-dominated lattices and enhanced strength due to tubular ribs.

The effect of Al doping on the reflective properties of TiO2 nanoparticles, synthesized by sol–gel method, has been investigated. It has been observed that with Al doping, the phase transition temperature for anatase to rutile phase increases; however, no change in morphology has been observed. No additional absorption edge was found in the absorption spectra, but a weak luminescent peak was noticed in the photoluminescence spectra. TiO2nanoparticles with 0.1% Al doping show higher photostability with practically no change in reflectance. A coating material has been prepared by dispersing these synthesized nanoparticles in water solution of organic binder. Coating material parameters such as pigment to binder weight ratio, solvent ratio, pH of solution have been taken into care to make the coating material flowable with good ability to adhere. Their coating was applied on a plastic substrate with different coating thicknesses to design light reflectors. These reflectors have been found to have diffuse reflectance of 98.17–98.29% for the 0.25-mm-thick coating.

In this study, a powder blend representing 6061 Al-alloy was first mixed with Al2O3 ceramic particles and then foamed by using the powder compact melting method. 6061-Al2O3 foams and control specimens 6061 foams (without ceramic reinforcement) were produced. The effects of both different ratios of Al2O3 particle addition and different kinds of heat treatment on hardenability, structure and mechanical behavior of the final foams were investigated. Foams that were fully heat treated had the highest hardness values, and they performed best with an increase in collapse strength up to 100% over the untreated samples. Improved cell structure and decreased drainage were obtained when the Al2O3 addition was not more than 5 vol%. The compression test results were interpreted in terms of the foam’s microstructure, and correlations were made relating to the unloading modulus and compression strength of the foams to the relative density.

Ti-6Al-4V alloy with attractive properties such as corrosion resistance and high specific strength has a broad impact on daily life in the field of aerospace and medicine. The addition of TiC to Ti-6Al-4V is to further improve abrasion resistance and hardness. To have a low processing cost and precise control of the TiC volume fraction and distribution, the composite is densified with a blend of Ti-6Al-4V and TiC powders through a powder metallurgy route. The densification kinetics of the blend is studied for uniaxial die pressing (i) under isothermal conditions at 1020 °C, where β-Ti-6Al-4V deforms by creep and (ii) upon thermal cycling from 860 to 1020 °C, where the α-β transformation leads to transformation superplasticity. Densification curves for both isothermal and thermal cycling for various applied stresses and TiC fractions are in general agreement with predictions from continuum models and finite element simulation models performed at the powder level.

Observation of room temperature ferromagnetism (RTFM) is reported in polycrystalline thin films of Ti1−xMnxO2 (x = 0.10 and 0.15) synthesized by spray pyrolysis technique on fused quartz substrates. Our experimental results clearly suggest partial incorporation of manganese (Mn) in titanium dioxide (TiO2) lattice up to certain extent and rest of the Mn ions are consumed to form secondary Mn-related phase such as manganese oxide (Mn3O4). The observed weak ferromagnetic ordering at room temperature in the films is established to be due to incorporation of Mn in TiO2matrix rather than the presence of other secondary phases since none of the Mn or Ti/Mn oxide phase is ferromagnetic at room temperature. Bound magnetic polaron model is invoked to explain the observed ferromagnetism in these highly resistive films.

We report on the photovoltaic properties of polymer solar cells with an inverted structure wherein the electron-collecting electrode comprises an indium tin oxide (ITO) electrode coated with titanium dioxide (TiO2) nanoparticles dispersed into poly(N-vinylpyrrolidone) (PVP). The optimization of performance of polymer solar cells in which the TiO2 concentration in PVP was varied is presented. Pristine solar cells with the TiO2:PVP-coated ITO electrodes showed S-shape current-voltage characteristics. The S-shaped feature disappeared after the continuous exposure of the solar cells to light from an AM 1.5G solar simulator, leading to an improved device performance compared with solar cells that use an ITO or ITO/TiO2 electron-collecting electrodes.

LM13 Al-alloy—cenosphere hybrid foam (HF) was made by foaming LM13 alloy–cenosphere mixture through a stir casting technique using CaCO3 as a foaming agent. In the melt mixture, 35 vol% of cenosphere was used and the foaming temperature was varied (660 and 690 °C). The foam contains microporosities as well as macroporosities and hence these are referred as HFs. The age-hardening characteristics and thereof deformation behavior of these foams have been examined using both microhardness and plateau stress measurements. It is further noted that energy absorption and plateau stress are maximum, and densification strain is minimum under peak-aged condition irrespective of the density of HF. Empirical relations are proposed to predict plateau stress, densification strain, and energy absorption as a function of aging time and relative density.

The development of porous metals has led to the need for an accurate prediction of the physical and mechanical properties of the many possible fabricated structures. For applications where yield stress needs to be reduced, while maintaining a high conductivity, the optimization of the pore dimensions, volume fraction, and pore spacing is required. A finite element model has been developed to simulate the effects of these factors on the electromechanical behavior of porous copper. This model was validated against samples of copper with mechanically induced pores as well as a copper GASAR sample. Good agreement (within an error of ±3%) was shown between the model and experimental data for the resistivity and effective modulus for both the mechanically induced pore and the GASAR samples, although the low ductility of the samples was not predicted and restricts the application of the simulation.

Heat transfer coefficients of porous copper samples with single- and double-layer structures, fabricated by the lost carbonate sintering process, were measured under forced convection conditions using water as the coolant. Compared with the empty channel, introducing a porous copper sample enhanced the heat transfer coefficient 5–8 times. The porous copper samples with double layers of porosities of 60% and 80% often had lower heat transfer coefficients than their single layer counterparts with the same overall porosities because the coolant flowed predominantly through the high-porosity layer. For the same double-layer structure, the order of the double layer had a large effect on the heat transfer coefficient. Placing the high-porosity layer next to the heat source was more efficient than the other way around. The predictions of a segment model developed for the heat transfer coefficient of multilayer structures agreed well with the experimental results.