Effect of plasma nitriding of austenitic stainless steel produced by direct metal laser sintering

A special additive manufacturing (AM), called as Direct Metal Laser Sintering (DMLS), is a technology that produces 3D workpieces using a wide range of different metals as raw materials. The aim of current research is to investigate the plasma nitriding effect on the DMLS produced samples. The direct current plasma nitriding treatment was achieved at 440 °C for 4 hours with 75%N2 – 25%H2 gas mixture. Before the treatment, the 316L austenitic stainless steels samples were ground with different methods to modify the surface roughness. Scanning electron microscope (SEM), X-ray diffractometer, glow discharge optical electron spectroscopy, Vickers microhardness tester and potentiodynamic corrosion test were used for the characterization of surface properties. The results demonstrated that the surface roughness did not affect the outcome of the plasma nitriding, but the corrosion resistance increases with the decrease of the surface roughness compared to the untreated 3D sample.

Review on the Lymphatic Vessels in the Dental Pulp

Despite many studies, opinions on the lymphatic system of the teeth are still incompatible. Studies using light and electron microscopy and directly using methods such as a radioisotope (radionuclide) scan and interstitial fluid pressure measurement reported incomplete results. Immunohistochemistry (IHC) plays the main role in investigating presence of the lymphatic system in dental tissues. This method uses labeled antibodies against antigens typical of lymphatic vessels. The use of appropriate staining enables the detection of antigen-antibody reaction products using a light (optical), electron or fluorescence microscope. However, these studies do not show the system of vessels, their histologic structure under physiological conditions and inflammation as well as the lymphangiogenesis process in the dental pulp. Unfortunately, there is a lack of studies associating the presence of lymphatic vessels in the dental pulp with local lymphatic nodes or large vessels outside the tooth. In the scientific and research environment, the evaluation of the lymphatic system of the teeth is problematic because it is quite difficult to clearly distinguish lymphatic vessels from small blood vessels. Despite many indications of the presence of lymphatic vessels in the pulp chamber, this problem remains open and needs further research.

Controlling the Emission Properties of Quantum Rods via Multiscale 3D Ordered Organization

A specific organization of optically active nanoscale objects can greatly affect the optical response of a system. Here, we report the controlled modification of the fluorescent emission by the assembly of water-soluble quantum rods (QRs). Our study combines optical, electron microcopy, and X-ray scattering characterizations to reveal a correlation between the self-assembly behavior of QRs into ordered 3D-arrays and the optical properties (luminescence) of formed assemblies, where the observed optical response is highly dependent on the QR aspect ratio. Specifically, shorter, 18 nm long QRs (QR18), exhibiting a well-defined smectic packing, demonstrate an enhancement of the emission intensity accompanied by a red shift and a lifetime reduction. In contrast, 40 nm long QRs (QR40), forming a columnar phase, does not show these optical properties.

Effect of Grain Refiner on Fracture Toughness of 7050 Ingot and Plate

In this paper, two types of grain refining alloys, Al-3Ti-0.15C and Al-5Ti-0.2B, were used to cast two types of 7050 rolling ingots. The effect of Al-3Ti-0.15C and Al-5Ti-0.2B grain refiners on fracture toughness in different directions for 7050 ingots after heat treatment and 7050-T7651 plates was investigated using optical electron microscopy (OEM) and scanning electron microscopy (SEM). Mechanical properties testing included both tensile and plane strain fracture toughness (KIC). The grain size was measured from the surface to the center of the 7050 ingots with two different grain refiners. The fracture surface was analyzed by SEM and energy dispersive spectrometer (EDS). The experiments showed the grain size from edge to center was reduced in 7050 ingots with both the TiC and TiB refiners, and the grain size was larger for ingots with the Al-3Ti-0.15C grain refiner at the same position. The tensile properties of 7050 ingots after heat treatment with Al-3Ti-0.15C grain refiner were 1–2 MPa lower than the ingot with the Al-5Ti-0.2B grain refiner. For the 7050-T7651 100 mm thick plate with the Al-3Ti-0.15C grain refiner, for the L direction, the tensile properties were lower by about 10~15 MPa; for the plate with the Al-3Ti-0.15C refiner than plate with Al-5Ti-0.2B refiner, for the LT direction, the tensile properties were lower by about 13–18 MPa; and for the ST direction, they were lower by about 8–10 MPa compared to that of Al-5Ti-0.2B refiner. The fracture toughness of the 7050-T7651 plate produced using the Al-3Ti-0.15C ingot was approximately 2–6 MPa · m higher than the plate produced from the Al-5Ti-0.2B ingot. Fractography of the failed fracture toughness specimens revealed that the path of crack propagation of the 7050 ingot after heat treatment produced from the Al-3Ti-0.15C grain refiner was more tortuous than in the ingot produced from the Al-5Ti-0.2B, which resulted in higher fracture toughness.

Formation of core-shell droplets for the encapsulation of liquid contents

Accurate control of monodisperse core-shell droplets generated in a microfluidic device has a broad range of applications in research and industry. This paper reports the experimental investigation of flow-focusing microfluidic devices capable of producing size-tuneable and monodisperse core-shell droplets. The dimension of the core-shell droplets was controlled passively by the channel geometry and the flow rate of the liquid phases. The results indicate that microchannel geometry is more significant than flow rates. The highly controllable core-shell droplets could be subsequently employed as a template for generating core-shell micropaticles with liquid core. Optical, electron microscopy and X-ray computed microtomography showed that the geometry of the core-shell droplets remains unchanged after solidification, drying and collection. The present study also looks at the thermal stability of core-shell particles depending on the particle size. The larger core-shell partcles with a thicker shell provide a higher resistance to heating at elevated temperature. The high degree of control with a flow-focusing microfluidic device makes this a promising approach for the encapsulation, storage, and delivery of lipophilic contents.

A novel multinuclear solid state NMR approach for the characterization of kidney stones

The spectroscopic study of pathological calcifications (including kidney stones) is extremely rich and helps to improve the understanding of the physical and chemical processes associated with their formation. While FTIR imaging and optical/electron microscopies are routine techniques in hospitals, there has been a dearth of solid state NMR studies introduced into this area of medical research, probably due to the scarcity of this analytical technique in hospital facilities. This work introduces effective multinuclear and multi-dimensional solid state NMR methodologies to study the complex chemical and structural properties characterising kidney stone composition. As a basis for comparison three hydrates (n = 1, 2 and 3) of calcium oxalate are examined along with nine representative kidney stones. The multinuclear MAS NMR approach adopted investigates the 1H, 13C, 31P and 43Ca nuclei, with the 1H and 13C MAS NMR data able to be readily deconvoluted into the constituent elements associated with the different oxalates and organics present. For the first time, the full interpretation of highly resolved 1H NMR spectra is presented for the three hydrates, based on structure and local dynamics. The corresponding 31P MAS NMR data indicates the presence of low-level inorganic phosphate species, however the complexity of these data make the precise identification of the phases difficult to assign. This work provides physicians, urologists and nephrologists with additional avenues of spectroscopic investigation to interrogate this complex medical dilemma that requires real multi technique approaches to generate effective outcomes.

Addressable Graphene Encapsulation of Wet Specimens on a Chip for Optical, Electron, Infrared, and X-ray based Spectromicroscopy Studies

Label-free spectromicroscopy methods offer the capability to examine complex cellular phenomena. Electron and X-ray-based spectromicroscopy methods, though powerful, have been hard to implement with hydrated objects due to the vacuum...

Focused Ion Beam Exposure of Ultrathin Electron-Beam Resist for Nanoscale Field-Effect Transistor Contacts Formation

The lithographic methods are used to form contacts for nanostructures smaller than 100 nm , in part, e-beam lithography and focused ion beam lithography with the use of electron-sensitive resist. Focused ion beam lithography is characterized by greater susceptibility to resist, high value of backward scattering, proximity effect, and best ratio of speed performance and contrast to exposed elements’ minimal size, compared to e-beam lithography. In this work, a method of ultrathin resist exposure by focused ion beam is developed. Electron-sensitive resist thickness dependence on increase of its toluene dilution was established. It was shown that electron-sensitive resist thinning down to 30 μm based on α-chloro-methacrylate with α-methylstyrene allows the 500-nm gapped metal contacts formation over a span of 30 μm. Silicon nanostructures within metallic nanoscale gap on dielectric substrate have been obtained. The geometry of obtained nanostructures was studied by optical, electron, ion, and probe microscopy. It has been established that it is possible to not use additional alignment keys when nanoscale field-effect transistors are created based on silicon nanostructures.

Low-noise GaAs quantum dots for quantum photonics

Quantum dots are both excellent single-photon sources and hosts for single spins. This combination enables the deterministic generation of Raman-photons—bandwidth-matched to an atomic quantum-memory—and the generation of photon cluster states, a resource in quantum communication and measurement-based quantum computing. GaAs quantum dots in AlGaAs can be matched in frequency to a rubidium-based photon memory, and have potentially improved electron spin coherence compared to the widely used InGaAs quantum dots. However, their charge stability and optical linewidths are typically much worse than for their InGaAs counterparts. Here, we embed GaAs quantum dots into an n-i-p-diode specially designed for low-temperature operation. We demonstrate ultra-low noise behaviour: charge control via Coulomb blockade, close-to lifetime-limited linewidths, and no blinking. We observe high-fidelity optical electron-spin initialisation and long electron-spin lifetimes for these quantum dots. Our work establishes a materials platform for low-noise quantum photonics close to the red part of the spectrum.