I’ve long been suspicious about attempts to see energy as the overwhelmingly central item setting both options and criteria for design in nature. Indeed, when I tried to create a conceptual framework for teaching biology to college students, I ended up putting energy distinctly second to information. Where energy rules, one can find some analog of voltage potential. But in nature, who eats whom boils down to the design and operation of one’s particular teeth and other equipment. I once set up an electrical analog of an ecosystem, but it gave an unreasonable picture until I added ad hoc diodes to keep the trees from eating the caterpillars at night and other such misbehavior. (Steve Vogel, Duke University, 2007)

In materials processing, Nature replaces the massive use of energy (for example high temperatures or harsh chemical reactions) with the use of information (which equates with structure at all levels, molecule to ecosystem). Indeed, most of the exceptional functionality of biological materials is due to their complex structure, driven by their chemical composition and morphology derived from DNA. It is here that the most important aspect of biomimetics emerges, and it has the power to redesign engineering.

Herein we compare the lattice parameters, room temperature shear and Young’s moduli, and phonon thermal conductivities of Ti2AlC0.5N0.5 and Ti3Al(C0.5, N0.5)2 solid solutions with those of their end members, namely Ti2AlC, Ti2AlN, Ti3AlC2, and Ti4AlN2.9. In general, the replacement of C by N decreases the unit cell volumes and increases the elastic moduli and phonon thermal conductivities. The increase in the latter two properties, however, is sensitive to the concentrations of defects, most likely vacancies on one or more of the sublattices.

While nanowires and nanotubes have been shown to be electrically sensitive to various chemicals, not enough is known about the underlying mechanisms to control or tailor this sensitivity. By limiting the chemically sensitive region of a nanostructure to a single binding site, single molecule precision can be obtained to study the chemoresistive response. We have developed techniques using single-walled- carbon-nanotube (SWCNT) circuits that enable single-site experimentation and illuminate the dynamics of chemical interactions. Discrete changes in the circuit conductance reveal chemical processes happening in real-time and allow SWCNT sidewalls to be deterministically broken, reformed, and conjugated to target species.

Based on microindentation experiments of three different metals, Guelorget et al. [J. Mater. Res. 22, 1512 (2007)] have compared the performance of five different indentation methods on extracting material plastic properties—among them, three papers were proposed by Cao and Lu [Acta Mater.52, 4023 (2004); J. Mater. Res.20, 1194 (2005); J. Mech. Phys. Solids53, 49 (2005)] and two papers were published by our group [Ogasawara et al., Scripta Mater.54, 65 (2006); Zhao et al. Acta Mater.54, 23 (2006)]. They argued that the performances of our techniques in [Ogasawara et al., Scripta Mater.54, 65 (2006); Zhao et al. Acta Mater.54, 23 (2006)] were quite poor. Here we show that Guelorget et al. [J. Mater. Res. 22, 1512 (2007)] have made quite a few mistakes and problematic steps when they handled the experiment data and performed reverse analysis. Indeed, the material plastic properties extracted from the correct procedures based on our papers [Ogasawara et al., Scripta Mater.54, 65 (2006); Zhao et al. Acta Mater.54, 23 (2006)] are much better and more stable than that reported in Guelorget et al. [J. Mater. Res. 22, 1512 (2007)]. Several general issues related to interpreting microindentation data and reverse analysis are also discussed, which may serve as important guidelines for similar studies in the future.

Water-soluble PbSe semiconductor quantum dots (QDs) with near-infrared absorption of 1100–2520 nm (corresponding to a diameter of 3–13 nm) were synthesized using 2-aminoethanthiol (AET). The oleic acid-stabilizing ligands used in the traditional synthesis of PbSe were exchanged with the 2-AET ligands, which promoted the solubilization of the QDs in an aqueous medium. This occurred due to the attraction of the surrounding water molecules to the exposed amino group, thus allowing the particles to reside in the water environment. The water-soluble PbSe QDs have very narrow size distribution (σ ≈ 4.5–5.5%). Transmission electron microscopy, spectrophotometric measurements, and Fourier transform infrared spectroscopy indicate that the morphology, size, size distribution, and chemical composition of the PbSe QDs remained unchanged during the transfer to an aqueous medium. In conclusion, the ability to synthesize water-soluble PbSe QDs with stable properties and uniform size distribution will allow them to have substantial advantages for biological applications such as biosensors and drug delivery.

Differential thermal analysis, as the main means of measurement, was used to prepare bulk MgB2 samples and monitor the sintering reaction process. Combined with microstructure observation by scanning electron microscopy and x-ray diffraction analysis, the formation process of MgB2 phase at the temperature before Mg melting was summarized. Additionally, a new kinetic analysis (a variant on the Flynn–Wall–Ozawa) method under nonisothermal conditions was used to determine that the reaction between Mg and B powders involves random nucleation followed by an instantaneous growth of nuclei (Avrami–Erofeev equation, n = 2), which can properly explain the in situ formation process of bulk MgB2 at the temperature before Mg melting. The value of activation energy E and the function of conversion f(α) are obtained independently, and thereby the determination of mechanism function is not affected by the value of E. The values of E decrease from 175.418 to 160.395 kJ mol−1 with the increase of the conversion degrees (α) from 0.1 to 0.8. However, as the conversion degrees approach 0.9, the value of E increases to 222.647 kJ mol−1, and the corresponding pre-exponential factor A is about three orders of magnitude larger than the previous ones.

The microstructure and residual stress of sputter-deposited yttria-stabilized zirconia (YSZ) films are presented as a function of thickness (5–1000 nm), deposition pressure (5–100 mTorr), and post-deposition temperature. The as-deposited residual stress of YSZ ranges from −1.4 GPa to 100 MPa with variations in sputtering conditions. Transitions from compressive to tensile stress are identified with variations in working pressure and film thickness. The origins and variations in as-deposited stress are determined to be from tensile stress due to grain coalescence/growth, and compressive stresses are due to forward sputtering/“atomic peening” of target atoms. The evolution of residual stress with post-deposition annealing shows a tensile stress hysteresis of up to 1 GPa for films deposited at low working pressures. This hysteresis is believed to be due to crystallization and the diffusive relief of compressive stresses initially generated by atomic peening during deposition. Discussion and evaluation of other common residual stress mechanisms are presented throughout.

A novel vapor-transport-assisted wet chemistry process was developed to fabricate oxide nanodot arrays from soft polymer templates. The feasibility and wide applicability of the proposed process was demonstrated with creation of high-density oxide nanodot arrays of TiO2, ZnO, and Co3O4. The present process not only avoids the over-growth problem inevitable in wet chemistry processes but also enables formation of oxide nanodots at low temperatures. The process can be readily extended to other compound systems in which the products can be formed through reactions of two reactants, one in liquid phase and the other in vapor phase.

Dense β-Si4Al2O2N6 and β-Si4Al2O2N6-0.5SiO2 ceramics were obtained from α-Si3N4, α-Al2O3, AlN, and Y2O3 upon sintering green bodies consolidated by aqueous gel casting. For comparison purposes, a β-Si4Al2O2N6 was also prepared by the conventional dry-powder processing route. In the case of gel-cast β-Si4Al2O2N6, the as-purchased AlN powder was treated with H3PO4 and Al(H2PO4)3 prior to use along with α-Si3N4, α-Al2O3, and Y2O3. The gel-cast β-Si4Al2O2N6 exhibited superior hardness (1423 ± 6 Hv), fracture toughness (3.95 ± 0.3 MPa⋅m1/2), and coefficient of thermal expansion (CTE) (3.798 × 10−6/°C between 30 and 1000 °C) in comparison to the ceramic consolidated by conventional dry pressing, which exhibited only 1317 ± 5 Hv, 3.30 ± 0.2 MPa⋅m1/2, and 3.532 × 10−6/°C between 30 and 700 °C. The in situ-generated ∼9 wt% SiO2 has considerably reduced the dielectric constant and CTE of β-Si4Al2O2N6 from 7.30 to 6.32 and from 3.798 × 10−6/°C to 3.519 × 10−6/°C, respectively. The loss tangent property of the investigated materials was little influenced by the variation of chemical composition and processing route.

Electrical conductivity of open-cell metallic foam calculated by Dharmasena and Wadley using the tetrakaidecahedral cell-based model with ligaments of constant or varying triangular cross sections along the cell edges was mistakenly concluded to strongly overestimate measured electrical conductivities of the open-cell aluminum foams (ERG Duocel). Accurate analysis shows that the model with triangular ligaments on the contrary underestimates the experimental results. A tetrakaidecahedral cell-based model that takes into account the particular ligament geometry, which is determined by constant mean curvature of ligament surfaces, is shown to explain the experimental data of electrical conductivity of the Duocel foams ranging in relative density from 4% to 12%.

The Pb(ZrxTi1–x)O3(PZT) films sputter deposited on LaNiO3(LNO)/Si(100) substrates were recrystallized to highly (l00)-oriented perovskite structure by high oxygen-pressure processing (HOPP) and high argon-pressure processing (HAPP), which were performed at a relatively low temperature 400 °C compared to the normally required temperature condition above 600 °C. Ferroelectricity of PZT films was investigated by a measurement of P-E hysteresis loop. The P-E hysteresis loops of the PZT(52/48) and PZT(30/70) films after HOPP showed better squareness and larger remnant polarization than those of as-sputtered ones prepared at a high temperature of 600 °C. Although the PZT films with HAPP also showed a high (l00)-oriented perovskite structure and obvious ferroelectricity, their P-E loops suggested relatively poor ferroelectricity compared to those of the PZT films with HOPP. This means that a further optimization for HAPP is needed to improve ferroelectricity of PZT films.

ZnO grown on α-Al2O3(0001) generally possesses an orientation such that α-Al2O3(0001) is parallel to ZnO(0001) and two in-plane domains nucleate, so that α-Al2O3[11¯20] is parallel to ZnO[11¯20] and/or α-Al2O3[11¯20] is parallel to ZnO[10¯10]. In this paper, we report a new growth mode for ZnO grown on α-Al2O3(0001) using metalorganic chemical vapor deposition (MOCVD). We find that α-Al2O3[11¯20] is parallel to ZnO[10¯10], but the (0001) plane of ZnO is tilted relative to the (0001) plane of α-Al2O3 such that ZnO(0001) is almost parallel to the α-Al2O3(¯1104) plane. This orientation reduces the extent of lattice mismatch. The interface between ZnO and α-Al2O3 is abrupt and possesses periodic dislocations.

There is increasing observational evidence for an implication of the order of interfacial water layers in biology, for instance in processes of cellular recognition and during first contact events, where cells decide to survive or enter apoptosis. Experimental methods that allow access to the order of interfacial water layers are thus crucial in biomedical engineering. In this study, we show that interfacial water structures can be nondestructively analyzed on the nanocrystalline diamond. Results open the gate to a new chapter in the design of biomaterials inspired by biomimetic principles.

In this study, the effects of electromigration (EM) on the growth of Cu–Sn intermetallic compounds (IMCs) in Cu/SnBi/Cu solder joints under 5 × 103 A/cm2 direct current stressing at 308, 328, and 348 K were investigated. For each Cu/SnBi/Cu solder joint under current stressing, the IMCs at the cathode side grew faster than that at the anode side. The growth of these IMCs at the anode side and the cathode side were enhanced by electric current. The growth of these IMCs at the cathode followed a parabolic growth law. The kinetics parameters of the growth of the IMCs were calculated from the thickness data of the IMCs at the cathode side at different ambient temperatures. The calculated intrinsic diffusivity (D0) of the Cu–Sn IMCs was 9.91 × 10−5 m2/s, and the activation energy of the growth of the total Cu–Sn IMC layer was 89.2 kJ/mol (0.92 eV).

We conducted an investigation into the thermodynamic properties of two stoichiometric CaCu3Ti4O12(CCTO) samples prepared by solid-state reaction and soft chemistry methods to probe the stability of the material relative to simpler oxide constituents (e.g., CaO, CuO, and TiO2) over a wide temperature range. Thermodynamic functions (i.e., heat capacity, formation enthalpies, entropies, and Gibbs free energies) have been measured from near absolute zero to 1100 K using calorimetric methods, including drop solution, low-temperature adiabatic relaxation, and differential scanning calorimetry. In addition, the thermodynamic characteristics of the magnetic-phase transition from the antiferromagnetic to the paramagnetic state are reported. It has been shown that CCTO is very stable relative to constituent oxides and calcium titanate at room temperature and higher, independent of the synthesis route. The enthalpic factor is dominant in the thermodynamics of CCTO, with the entropic factor having almost no effect on the stability of the compound relative to other oxide assemblages. The recommended values for the standard molar enthalpy of formation from constituent oxides and from elements at 298.15 K are −122.1 ± 4.5 and −4155.7 ± 5.2 kJ/mol−1, respectively. The mean of the third law entropy at 298.15 K is 368.4 ± 0.1 J/mol−1/K−1. Based on the thermodynamic data reported, the study confirms the possibility of CCTO decomposition in a reducing atmosphere or CO2 under conditions recently observed in experiments.

The ultrafast dynamic reflectivity of vanadium pentoxide is measured using 40 fs pulses from a self-mode-locked Ti:sapphire laser. The laser pulses excite acoustic vibrations at wave numbers of 145 and 103 cm−1. The amplitudes of the induced oscillations depend strongly on the orientation between the linear polarization of the laser pulses and the crystal axes, with the largest oscillations observed for an orientation of 45°. The higher-frequency oscillation is induced immediately upon arrival of the laser pulse, while the lower-frequency oscillation appears a few picoseconds later. The oscillations persist for approximately 10 ps after the arrival of the pulse. The oscillations are attributed to transverse acoustic modes propagating along the a-axis of the crystal.

A stable nano body-centered cubic (bcc) CoFe2 alloy was isolated by employing a combination of N2H4.H2O reduction and sonochemical route under basic conditions. This alloy has proved to be a potential precursor for CoFe2O4 production. X-ray diffraction and transmission electron microscopy confirms the formation of a bcc phase CoFe2 alloy with particle size <10 nm and spherical morphology. Thermogravimetric analysis confirmed the oxidation of the alloy composition showing a weight gain between 200 and 500 °C, which corresponds to fully oxidized CoFe2O4. A significant increase in the saturation magnetization (Ms = 230 emu/g) for the nano CoFe2 alloy was observed in comparison with that of the theoretical bulk value (200 emu/g) at 300 K.

Magnesium alloys are potential biodegradable biomaterials in hard tissue implants. However, the fast degradation rate in the biological environment has hampered widespread applications. We propose to use a ZrO2 coating in conjunction with a Zr transition layer to improve the corrosion resistance of AZ91 magnesium alloy. X-ray photoelectron spectroscopy discloses that the coating is composed of ZrO2. The Vickers hardness measurement demonstrates that the surface hardness of the alloy is significantly enhanced. The electrochemical behavior of the coated sample is systematically evaluated by means of potentiodynamic polarization, open-circuit potential evolution, and electrochemical impedance spectroscopy. The electrochemical results indicate that the corrosion resistance of the coated alloy is enhanced significantly, and the electrode-controlled processes in a coated alloy–solution system are discussed.

In this paper, the growth of thin and dense films of vertically aligned carbon nanotubes (CNTs) on Fe–Co/TiN/Si(100) substrates is reported. Special attention is held to the preparation of the TiN buffer layers. This layer is deposited by pulse laser deposition at high temperature with a high texturation according to [TiN(100)//Si(100)]. Further ammonia heat treatment is performed at 623 K to control a Ti:N stoichiometry and remove oxygen impurity. Fe and Co as catalysts are subsequently deposited at high temperature (923 K) at the monolayer level with two ultrahigh vacuum evaporator cells. The growth of CNTs is performed by a direct-current plasma-enhanced and hot filaments-assisted catalytic chemical vapor deposition (dc HF CCVD) process. Highly dense films of CNTs, are obtained with only 0.5 nm Fe(Co) evaporated. Observations by transmission electron microscopy show that most of the CNTs display sizes in the 2.5–6 nm range, most of them with a double-wall (DW). This is in agreement with spectral features of the Raman radial breathing modes (RBM) in the 70–130 cm−1 range. Generally, these large-diameter DWCNTs display a high defect density with morphologies partially collapsed into flattened twisted shapes.

In this article, we describe oxidation of molten Sn–0.07 wt% P alloy exposed in air at 280 °C. Although oxidation can be effectively reduced by the addition of trace phosphorus, the oxide film has a poor protection for the molten alloy with a high P concentration. The oxide film was analyzed by x-ray photoelectron spectroscopy. Comparing the results with the low P sample, there was a high phosphorous content in the film and a new Sn–P compound on the surface of the high P sample. It is assumed that the poor protection against oxidation of the film could be due to volatility of phosphorus in the Sn–P alloy at the temperature.