The mechanical properties of porous ceramics are greatly influenced by their microstructure. Therefore, mechanical behavior of highly porous ceramics is different from that of dense ceramics. In this work, we evaluate different mechanical testing methods such as static compression, Brazilian disc test and 3-point bending on their suitability for comparison of highly porous ceramic materials. It is shown that 3-point bending is more suitable than static compression or Brazilian disc testing, as the material exhibits no critical crack propagation under compressive loading. With 3-point bending tests, a quantitative comparison of the mechanical properties of foams with different microstructures and porosities is possible. Under cyclic compression the foams exhibit a very high degree of crack tolerance in combination with preservation of their structural integrity even at high strains of 10%.

In this study, we are reporting the time- and temperature-dependence of the electrical resistivity and temperature-dependence of the Hall voltage in neodymium nickelate thin films. The films were deposited on a lanthanum aluminate substrate [LaAlO3 (001)] by a pulsed laser deposition technique, with thicknesses ranging from 0.6 to 120 nm. Time-dependent electrical transport measurements indicated the formation of a kinetically stable metallic glassy phase rather than a stable insulating phase on cooling below the transition temperature, TM-I. Comparisons of the low-temperature behavior with that of common insulators further supported this claim. Hall effect measurements on the 1.2-nm sample showed a local maximum in the carrier concentration just below the TM-I on both the heating and cooling cycles. This again confirmed the proposed low-temperature structure, in that, for the 1.2-nm sample, there was a minimal degree of supercooling before transitioning to a kinetically stable glassy phase.

Four-layer multiwalled carbon nanotube (MWNT) thin films were deposited via dropcasting (1 mg/mL MWNTs and 10 mg/mL SDBS) onto filter papers that vary in pore size (1, 5, 25, and 40 µm) to determine the effect of the underlying substrate structure on the in-plane properties of the films. The films (<100 nm thick) were dried using vacuum filtration, and drying in a 65 °C heater with and without a ceramic heating board. DC resistance of the films ranged from 6 × 103 to 9.3 × 109 Ω. Impedance spectroscopy analysis revealed a low and a high frequency inductive response and two parallel R–C circuits for the more conducting thin films. High resistance films were fit by a single RC circuit with a constant-phase element. The differences in the in-plane electrical responses of the different MWNT films can be explained by the degree of carbon nanotube surface coverage, obtained as a result of using different pore size filter papers. The drying method utilized also affected the CNT network formation and its resultant electrical properties.

Er3+-doped oxyfluoride transparent glass and glass-ceramics (GCs) containing SrF2 nanocrystals were prepared and their spectroscopic properties were investigated. The formation of SrF2 nanocrystals in GCs has been confirmed by x-ray diffraction (XRD) and transmission electron microscopy. The Judd-Ofelt (JO) parameters have been evaluated from absorption spectra of the Er3+-doped glass and GCs, which are used to predict radiative properties for some important luminescence levels of Er3+ ions in glass and GCs. The XRD and JO parameters suggest that the Er3+ ions are progressively incorporated into the SrF2 nanocrystals in the GCs compared with glass. The up-conversion luminescence intensity increases significantly in GCs with increase in time of thermal treatment. The lifetime of the 4S3/2 level of the Er3+ ions in GCs is found to be slightly higher than that in the glass due to the incorporation of Er3+ ions into the lower phonon energy of SrF2 nanocrystals in the GCs.

Properties of entangled materials, made of fibers, depend on the number and the nature of contacts between fibers and fibers orientation. Nonsintered and sintered steel wools have been characterized by x-ray tomography to extract structural information such as fibers orientation and number of contacts before and during compression. Image analysis techniques were developed on tomography images and validated on virtual materials, generated and deformed by numerical simulation based on molecular dynamic equations. The structural parameters measured during the structural characterization were finally used to link the structure of the studied material with the measured mechanical properties. To do this link, an analytical model usually used for this kind of material was modified to describe the evolution of mechanical properties in compression.

Fully dense (Ti,Mo)2AlC/Al2O3 in situ composites with high purity were successfully synthesized at 1350 °C by reactive hot pressing of the Ti, Al, TiC, and MoO3 powder mixtures. The effect of MoO3 content on the phase composition, microstructure, and mechanical properties was investigated in detail. The introduction of the Al–MoO3 displacement reaction into the Ti–Al–TiC system resulted in a submicron grain size and a homogeneously distributed matrix phase of (Ti,Mo)2AlC with a secondary Al2O3 phase. The matrix grain size was significantly refined with increasing the Al2O3 content. Compared with the sample without MoO3 addition, the addition of 13.81 wt% MoO3 (corresponding to 10 wt% Al2O3 formation) evidently enhanced the hardness, flexural strength, and fracture toughness by 25%, 69%, and 146%, respectively. The strengthening and toughening mechanisms for the (Ti,Mo)2AlC/Al2O3 composites were also investigated.

We introduce a novel method for producing polystyrene (PS)-grafted multiwalled carbon nanotubes (MWCNTs), which provides a direct route to composites where carbon nanotubes (CNTs) are the major component. Infrared and Raman spectroscopies confirmed that the MWCNTs were functionalized with PS. Thermogravimetric analysis showed that CNTs increase thermal stability of the composite up to a critical loading (∼40 wt%) beyond which high nanotube loadings decrease the polymer degradation temperature, as a consequence of the thermal properties of CNTs and the composite morphology. Even at loadings as high as 80 wt% MWCNTs, the composite is an effective masterbatch material for both solution- and melt-processing. These results show that in situ polymerizations can be flexible and robust techniques for nanocomposite processing, overcoming limitations of conventional processing techniques to produce nanocomposites with very high nanotube loadings, not achieved hitherto.

A simple stochastic model is developed to determine the pop-in load and maximum shear stress at pop-in in nanoindentation experiments conducted with spherical indenters that accounts for recent experimental observations of a dependence of these parameters on the indenter radius. The model incorporates two separate mechanisms: pop-in due to nucleation of dislocations in dislocation-free regions and pop-in by activation of preexisting dislocations. Two different types of randomness are used to model the stochastic behavior, which include randomness in the spatial location of the dislocations beneath the indenter and randomness in the orientation of the dislocations, i.e., randomness in the stress needed to activate them. In addition to correctly predicting the experimentally observed average maximum shear stress at pop-in, the model also correctly describes the scatter in pop-in loads and how it varies with indenter radius. Monte Carlo simulations are used to validate the model and visualize the scatter expected for a limited number of tests.

Structured lead zirconium titanate (PZT)–epoxy composites are prepared by dielectrophoresis. The piezoelectric and dielectric properties of the composites as a function of PZT volume fraction are investigated and compared with the corresponding unstructured composites. The effect of poling voltage on piezoelectric properties of the composites is studied for various volume fractions of PZT composites. The experimentally observed piezoelectric and dielectric properties have been compared with theoretical models. Dielectrophoretically structured composites exhibit higher piezoelectric voltage coefficients compared to 0–3 composites. Structured composites with 0.1 volume fraction of PZT have the highest piezoelectric voltage coefficient. The flexural strength and bending modulus of the structured and random composites were analyzed using three-point bending tests.

In the present work, it has been suggested that the gene expression programing is a good tool for determination of hardness of metal matrix nanocomposite produced by mechanical alloying (MA). For example, we studied the Al matrix nanocomposite, and to build the models, 35 input-target data were gathered from the literature, randomly divided into 28 and 7 data sets and then were respectively trained and tested by the proposed models. The differences between the models were in their gene number, chromosomes, and head size. The amount of reinforcement, ball to powder ratio, compaction pressure, milling time, reinforcement hardness, sintering temperature, sintering time, and vial speed were 8 independent input parameters. The output parameter was mean hardness of nanocomposites. The results indicate that gene expression programing is a powerful tool for predicting the hardness of the nanocomposite produced by MA.

In this work, we have studied the superhydrophobicity and buoyancy of two types of nanostructured surfaces: the cabbage leaf and a vertically aligned carbon nanotubes (VACNTs) carpet. The wettability of these surfaces were characterized by contact angle, tilting angle, sliding volume and sliding speed measurements. The results were correlated to the related surface topologies, which were investigated by scanning electron microscopy. Buoyancy of different surfaces has been investigated through measurements of the forces acting on the surface. Finally, we demonstrate that cabbage leaves and VACNT carpets have some common features with the water strider’s leg, better understanding the mechanisms of buoyancy related to the structural shape and size of natural or artificial nanostructures.

This work reports the preparation of iron-doped alumino-phosphate glass using microwave (MW) radiation at 1723 K in comparision with a conventional resistance heating furnace at the same temperature. X-ray diffraction analysis of the sample prepared in an MW furnace has confirmed glass formation which is similar to that of glass prepared in an electric furnace. Glass transition temperatures (Tg) for MW and conventional melted glass samples were observed to be 866 and 873 K, respectively. Higher Fe2+/(Fe3+ + Fe2+) ratio was reported in glass prepared in the MW furnace compared with the conventional furnace. The Fourier transform infrared spectra for both the samples indicate identical nature. It was observed that the maximum power required for melting glass in MW heating was 0.85 kW, which is around 25–30% of the power consumed by the conventional resistance heating furnace. In addition, the time needed to melt the glass in the MW furnace was found to be 3–4-fold lesser than the time required in the resistance heating furnace.

The microstructure and thermoelectric properties of InSb–NiSb composite system are investigated. NiSb, ranging from micro- to nanoscale, is introduced as a nonsoluble second phase in the InSb matrix by using the water quenching method. The morphology of the second phase is adjusted by varying the composition from hypoeutectic to hypereutectic alloys. The eutectic composite with a semiconducting InSb matrix and a metallic NiSb fiber on the order of 100-nm diameter is obtained. Melt spinning (MS) is applied to the eutectic composition to change the NiSb dispersion phase to around 200-nm diameter sphere. Transport properties, including Seebeck coefficient, resistivity, Hall coefficient, and thermal conductivity, are measured from 80 to 630 K. Compared to the water quenched (WQ) eutectic sample, the MS process results in a slight increase in the carrier concentration but a remarkable reduction in the mobility and thermal conductivity. Compared to the InSb matrix, ZT of the samples with the NiSb second phase is lower. For the eutectic samples, ZT is significantly reduced after the MS process because of the loss in mobility. ZT of the WQ InSb matrix is the highest in all the samples, ∼0.5 at 600 K.

A quasicrystal (QC)- based alloy composite was made by copper mold casting under a low-vacuum level condition at the bulk metallic glass (BMG)- forming composition (Zr65Cu15Al10Ni10)90Nb10. The QC alloy consisted of a majority of icosahedral quasicrystal phase and a small amount Zr-rich glassy phase. Under uniaxial compression at room temperature, the BMG alloy exhibits a certain plastic strain; the QC alloy is much stronger but brittle. The icosahedral glass model was used to describe the I-phase structure. The structure–property relations of the BMG and QC alloys are discussed assuming the common preferential icosahedral atomic structure in both cases and the existence of local glue structure in the BMG structure.

High quality CdSe nanocrystals (NCs) were synthesized via a nonorganometallic precursor and extracted in different solvents. The difference in the influence of the nature of the solvent namely ethanol, N,N-dimethyl formamide (DMF), and acetonitrile on extraction of the same type of NCs was studied with respect to quality and stability of NCs. Characterization by x-ray diffraction technique, absorption–emission spectroscopy, scanning, transmission, and atomic force microscopy demonstrated the formation of NCs of good optical property and surface composition from the synthesis method used. Different polarities of the solvent strongly influence photoluminescence (PL), surface defects, concentrations of NCs extracted, particle sizes, and surface passivation. Ethanol extraction results in small-sized NCs and good particle size distribution. DMF extraction causes lesser interfacial defects and hence prevents radiative recombinations. PL quenching was observed in all the three solvents, and this necessitates further stabilization of NCs. The stability of the so-extracted NCs was evaluated for change in their properties with respect to aging. Aging substantiated the adverse effects of acetonitrile to extract the lesser surface passivated NCs leading to Ostwald ripening and island formation. The phase and structure of NCs remain unaffected with aging or by the nature of solvent used.

Porous silicon (PSi) microparticles are designed as tunable delivery carriers for the model anticancer drug, mitoxantrone dihydrochloride (MTX). The surface of the native nanostructured PSi particles was chemically modified by grafting dodecyl and undecanoic acid via thermal hydrosilylation with 1-dodecene and undecylenic acid, respectively. Attenuated total reflectance Fourier transform infrared spectroscopy and nitrogen adsorption–desorption measurements were used to characterize the physiochemical properties of the native and chemically modified PSi microparticles. MTX was loaded by physical adsorption to the native and dodecyl-terminated PSi or by covalent attachment to the undecanoic acid-terminated microparticles. Both drug release profile and the Si erosion of the carriers were significantly affected by the surface chemistry of the PSi microparticles and the drug loading method. The MTX release spans over a period of several hours to weeks, as dictated by these parameters. In vitro cytotoxicity studies on human breast carcinoma (MDA-MB-231) cells revealed that the released MTX maintains its cytotoxic functionality, in comparison to the very low toxicity of all PSi microparticles.

A new low-cost synthesis of brookite TiO2nanoparticles using isopropanol as both the solvent and ligand is described here. Other ligands can be bound to the titania surface during or postsynthesis to tailor the particles’ functionality. The often extremely rapid hydrolysis of titanium isopropoxide has been successfully controlled so that nanoparticle growth is achieved. The resulting 4-nm particles are nonagglomerated, stable in solution, and have a low polydispersity. The synthesis is scalable and enables the simple fabrication of large amounts of titania nanoparticles that do not scatter visible light and are highly suited for incorporation into optical composites.

Metal matrix composites manufactured by the powder metallurgy route often exhibit different tensile strength due to particle geometrical reasons. The tensile strength tendency was studied in 2024 Al/30% SiCp composites as a function of relative particle size (RPS) ratio between the matrix and reinforcement particles. Dry blended composite powders, with different RPS ratios, were hot-pressed in vacuum, their microstructures were observed, and their tensile properties were measured. It was found that a decrease in RPS ratio resulted in a decrease in tensile strength, as a result of improved distribution of the SiCp. Despite their low density and heterogeneous distribution, 3-μm SiCp-reinforced composites had maximum tensile strength. The main reasons were due to the few fracture for small SiCp and the strengthening of the matrix microstructure from small particle effects. Solution treatment plus aging of the composites with the RPS ratio of 10:3 resulted in a significant improvement (42%) in strength due to the smaller diffusion path length for the alloying element.

When supported by suitable metal oxides such as ceria, platinum often displays increased catalytic activity and selectivity. A chemical vapor infiltration technique was used to impregnate Pt nanoparticles into an ordered mesoporous gadolinium-doped ceria (OMG), which was templated from KIT-6 silica. High Pt loading, up to 38 vol% of OMG, was achieved. This synthesis method is highly scalable and offers easy control over catalyst–support geometry. A detailed study of the OMG structure was conducted by controlling the synthesis parameters of the KIT-6 silica template. Formation mechanism and thermal stability of the OMG/Pt–OMG composite were also studied. The mesostructure composites were found to sustain until 750 and 650 °C, respectively. The highly structural composite holds the promise of increased activity, selectivity, and stability for applications in heterogeneous catalysis.