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news13eueuMicroscopyandAnalysis | July/August 2017above Canadian flag etched into a pennyMcMaster Universityleft Maple leaf demonstrates the technique of building structures atom by atom via STMAlberta UniversityResearchers have been busy celebrating Canada's 150th birthday by showing the world exactly what they can do in the laboratory.Research engineer, Travis Casagrande, from the Canadian Centre for Electron Microscopy at McMaster University used a focused ion beam microscope – the Zeiss NVision40 FIB – to etch a Canadian flag onto the face of a penny.Claiming to have made the world's smallest 3D Canadian flag, Casagrande first milled a tiny hole into the penny, leaving a flagpole standing within the centre.He then fabricated the maple leaf flag from the penny's surface, placing and securing it onto the flagpole with a deposited metal layer.The entire process took around six hours, and according to Casagrande, the trickiest part was forming the shape of the flag.Meanwhile, in a further tiny act of patriotism, researchers from the University of Alberta used scanning tunnelling microscopy to fabricate a maple leaf from 32 hydrogen atoms.Only ten nanometres wide, the leaf is roughly 100 times smaller than the world's smallest national flag, created at the University of Waterloo in September 2016.Researcher Roshan Achal, from the laboratory of Professor Robert Wolkow at the National Institute for Nanotechnology, patterned the leaf onto a silicon wafer using a tungsten STM tip that tapers down to the thickness of a single atom." It's super cool and super Canadian, and demonstrates our strength and skill in this niche of nanotechnology," says Achal." Almost no one else in the world can do it this well."Canada researchers celebrate 150 years with microscopyResearchers at Sweden-based Linköping University and the University of California in Berkeley, US, have observed the migration of atoms between the layers of a thin film.Using high resolution scanning transmission electron microscopy, they imaged the positions of individual atoms in the material.The specimen they studied was a thin film in which layers of a metal, hafnium nitride (HfN), around 5 nm thick, alternated with layers of a semiconductor, scandium nitride (ScN), suitable for use in microelectronics.As the researchers point out, the layers of metal and semiconductor shouldn't mix as problems arise if the atoms diffuse across an interlayer forming a closed bridge between the layers in the film, similar to an electric short circuit.To study the phenomenon, Magnus Garbrecht from the Department of Physics, Chemistry and Biology at Linköping University, heated HfN/ScN to 950°C, and noticed that the hafnium was diffusing down into the underlying layers.Further analysis revealed that a defect was present in the material where this phenomenon arose.He and colleagues heated the material several times and subsequently examined it using STEM, measuring the distance that individual atoms moved."The values we measured agree well with those from previous experiments using indirect methods and with the theoretical models, and this makes us confident that what we are seeing is dislocation-pipe diffusion," says Garbrecht.Research is published in Scientific Reports.STEM captures elusive atomic motionUsing STEM to capture diffusion in thin films Linköping Universitet

Characterization of metal-carbon nanotube composites14eueuJuly/August 2017 | MicroscopyandAnalysisINTRODUCTIONThe hunt for finding a material which can perform under adverse environmental conditions is never ending since the birth of mankind. This has encouraged researchers to take up challenges to find new materials having desired properties and applications. At present metal matrix composites (MMCs) have generated a wide interest because of their high strength, stiffness and fracture toughness1-3. Beside this they can also resist elevated temperatures in corrosive atmospheres. In MMCs the metal, the alloys used as matrices and the reinforcement need to be stable over a range of temperature whilst being non-reactive. The choice of the reinforcement depends on the matrix material and the application of the MMC. The strength-to-weight ratios of resulting composites can be higher than most of the metals and alloys4, 5. Several factors such as melting point, physical and mechanical properties of the composites at various temperatures determine the service temperature of the composites6, 7.Copper (Cu) shows high formability, high resistance to oxidation and corrosion and has a special place among all metals because of its high electrical (5.96×107 S/m) and thermal conductivity (401 W/mK). So, the most universal application of Cu is where high electrical and thermal conductivity are desired. There has been considerable interest in academia as well as industry in the use of Cu-based metal matrix composites in past few decades. Cu is an outstanding material for electrical applications whose competence can be enhanced by refining its mechanical properties8.Carbon nanotubes have emerged as promising reinforcement for a variety of nanocomposites because of their geometry, mechanical strength, chemical stability and electrical conductivity since their discovery in the early 1990s. Single walled carbon nanotubes (SWCNTs) consist of a single layer graphene sheet wrapped to form a tube structure having diameters at nanoscale.Several experiments and simulations reported that CNTs have surprising mechanical properties as illustrated by an elastic modulus of 0.3-1TPa, tensile strength of the order of 10-60 GPa and thermal conductivity of up to 3000 W/mK. Carbon nanotubes come in two principal forms, single walled carbon nanotubes (SWCNT) and multiwalled carbon nanotubes (MWCNT)9-12. The density of multiwalled carbon nanotubes (MWCNTs) is 2.60 g/cc and their specific surface area is about 200-400 m2/g. Cu-based metal matrix composites having carbon nanotubes as reinforcement are used for structural applications and functional materials because of their high strength and excellent electrical and thermal conductivity.It has been reported in literature that with the addition of carbon nanotubes the bulk properties of Cu can be improved. The Cu-based MMCs reinforced with CNTs have superior mechanical properties and are more thermally stable compared to pure Cu13, 14. Carbon nanotubes act as a filler material which reduces the thermal expansion coefficient of the Cu matrix. With the addition of CNTs the bulk electrical conductivity of the Cu composites can also be modified. Here we have used MWCNTs Synthesis of multiwalled carbon nanotubes (MWCNT) and development of Cu-MWCNT compositesHarshpreet Singh1, Lailesh Kumar2, Syed Nasimul Alam21 Department of Chemical and Materials Engineering, University of Auckland, New Zealand, 2 Department of Metallurgical and Materials Engineering, National Institute of Technology, RourkelaFigure 1 (a, b) Schematic of a typical CVD furnace setup used for the synthesis of MWCNTsFIGure 2 X-ray diffraction plot of MWCNTsab