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Considerable progress toward the development of electronic devices that rely on organic semiconductors as the active material component has been made in recent years. The key step for realization of the advanced organic electronic, or optical, device is the ability to micropattern different kinds of electronic materials, such as organic semiconductor/conducting materials, over large areas with micrometer-sized resolution. Here we demonstrate a simple and direct method for micropatterning small-molecule microcrystalline films using an epoxy stamp. The "hot lift off" method is highly selective, creating patterns with high resolution and relies on straightforwardly tailoring the adhesive properties between the epoxy and the film. This process is well suited for patterning many types of materials.

is concerned, the present finding bears essential implications for applying the superplastic forming of ceramics into a costeffective industrial production of complex shaped silicon nitride-based components, and for production of other polycrystalline materials that are sintered to full density via a liquid-phase sintering process. ExperimentalThe starting powders were Si 3 N 4 (Ube, SN-E10), AlN (HC Starck, Grade C), Al 2 O 3 , Y 2 O 3 , and Yb 2 O 3 (Johnson Matthey Chemicals Ltd.). When calculating the compositions, corrections were made for the small amounts of oxygen present in the Si 3 N 4 and AlN precursor powders. The starting materials, in batches of 50 g, were ball milled in water-free propanol for 24 h, using sialon milling media. The dried powders were consolidated in vacuum in an SPS apparatus, Dr. Sinter 2050 (Sumitomo Coal Mining Co. Ltd., Japan). The powder precursors were loaded in cylindrical carbon dies with an inner diameter of 12 mm. The samples were heated via a pulsed direct current that passed through the pressure die, i.e., the pressure die also acted as a heating source. The temperature was automatically raised to 600 C over a period of 3 min, and from this point on it was monitored and regulated by an optical pyrometer focused on the surface of the die. A heating rate of 200 C min ±1 was used, and a uniaxal pressure of 50 MPa was applied from the start to the end of the sintering cycle. The set-up allowed a cooling rate of~400 C min ±1 in the temperature range 1800±1000 C.The compressive deformation tests were carried out both in the SPS apparatus and in a conventional HP chamber heated by surrounding graphite heating elements. The fully densified cylindrical samples, with a diameter of 12 mm and a height of~6 mm, were loaded in a graphite die with an inner diameter of 20 mm, and deformed by applying a compressive stress through the oppositely moving graphite punches.The crystalline phase assemblies present in the sintered ceramics were determined from Guinier±Hägg X-ray powder diffraction patterns, using monochromatic Cu Ka radiation and Si as an internal standard. Both fractured and polished surfaces of the samples were examined in a scanning electron microscope (Jeol JSM 880) equipped with an energy-dispersive spectrometer (EDS, LINK ISIS). In order to obtain the best contrast between different phases, the microscopy images were recorded in back-scattered electron mode, where the a-sialon and Yb/Y-enriched intergranular glassy phases show medium gray and bright contrasts, respectively, whereas b-sialon, if present, appears with in dark (black) contrast. The amounts of intergranular glassy phase were evaluated with an image-analyzing package supplied with the LINK ISIS system. The contrast difference between the a/b-sialon grains and the Yb/Y-containing glassy phase was used to estimate the phase content in vol.-%, which was assumed valid for the whole sample volume. The estimated minimum and maximum amounts of glassy phase gave an error of ± 1 %.

We conducted a combined anion photoelectron spectroscopy and density functional theory study on the structural evolution of copper-doped silicon clusters, CuSi(n)(-) (n = 4-18). Based on the comparison between the experiments and theoretical calculations, CuSi(12)(-) is suggested to be the smallest fully endohedral cluster. The low-lying isomers of CuSi(n)(-) with n ≥ 12 are dominated by endohedral structures, those of CuSi(n)(-) with n < 12 are dominated by exohedral structures. The most stable structure of CuSi(12)(-) is a double-chair endohedral structure with the copper atom sandwiched between two chair-style Si(6) rings or, in another word, encapsulated in a distorted Si(12) hexagonal prism cage. CuSi(14)(-) has an interesting C(3h) symmetry structure, in which the Si(14) cage is composed by three four-membered rings and six five-membered rings.

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Auxetic materials have numerous promising engineering applications such as fracture resistance and energy storage due to their negative Poisson's ratios (NPRs). However, compared to materials possessing positive Poisson's ratios (PPRs), auxetic materials are rare. In this paper, by employing first principles calculations, we found a high NPR two-dimensional (2D) material, tungsten carbide (W2C), in the transition metal carbides (MXenes). Our results of the relatively moderate Young's modulus and fracture strength as well as the critical strain showed that the 2D monolayer W2C is an extraordinary flexible material. Our DFT results also demonstrated that W2C possesses high NPRs while Hf2C and Ta2C have PPRs. Furthermore, the mechanically induced deformation mechanism and the NPR formation mechanism of W2C have been proposed. Such an intrinsic NPR in W2C is attributed to the strong coupling between the C-p and W-d orbitals in the pyramid structural unit. The mechanically induced deformation mechanism and the PPR formation mechanism of Hf2C have also been determined. The intrinsic NPR for W2C transforms to PPR upon the surface functionalization induced. The behavior occurs due to the W-C interaction weakening. The excellent NPR in the 2D MXene material combined with other outstanding properties such as the metallic state would bring about its promising engineering prospects, ranging from the metal-ion battery, to automobiles and aircraft.

By employing molecular dynamics simulations, a family of graphyne heterojunctions (GYHJs) made by two different graphynes (GYs) have been designed and prepared. The dependence of tunable properties of GYHJs, such as thermal conductivity, mechanical properties, interfacial thermal resistance and rectification, on the composition and type of GYHJs is determined. Upon changing the composition of a GYHJ, one can keep a constant value of its fracture strength (and/or Young's modulus), while tuning its thermal conductivity. The thermal conductivities of GYHJs in the zigzag direction are larger than those in the armchair direction, indicating GYHJs are anisotropic. By decreasing the percentage of γ-GY, the thermal conductivities of GYHJs γ-GY/6,6,12-GY/γ-GY and γ-GY/14-GY/γ-GY decrease linearly in the armchair direction, whereas they undergo three stages (first decrease, then keep a constant value, and finally increase) in the zigzag direction. Regarding the mechanical response, by increasing the percentage of the graphyne in the GYHJ which possesses smaller Young's modulus, the Young's modulus of the GYHJ decreases. These findings would provide significant insights into the potential applications of graphyne-family materials in nanodevices.

Understanding the effect of defects on mechanical responses and failure behaviors of a graphene membrane is important for its applications. As examples, in this paper, a family of graphene with various 5–8–5 defects are designed and their mechanical responses are investigated by employing molecular dynamics simulations. The dependence of fracture strength and strain as well as Young’s moduli on the nearest neighbor distance and defect types is examined. By introducing the 5–8–5 defects into graphene, the fracture strength and strain become smaller. However, the Young’s moduli of DL (Linear arrangement of repeat unit 5–8–5 defect along zigzag-direction of graphene), DS (a Slope angle between repeat unit 5–8–5 defect and zigzag direction of graphene) and DZ (Zigzag-like 5–8–5 defects) defects in the zigzag direction become larger than those in the pristine graphene in the same direction. A maximum increase of 11.8% of Young’s modulus is obtained. Furthermore, the brittle cracking mechanism is proposed for the graphene with 5–8–5 defects. The present work may provide insights in controlling the mechanical properties by preparing defects in the graphene, and give a full picture for the applications of graphene with defects in flexible electronics and nanodevices.