Template-Assisted Iron Nanowire Formation at Different Electrolyte Temperatures.

We studied the morphology, structure, and magnetic properties of Fe nanowires that were electrodeposited as a function of the electrolyte temperature. The nucleation mechanism followed instantaneous growth. At low temperatures, we observed an increase of the total charge reduced into the templates, thus suggesting a significant increase in the degree of pore filling. Scanning electron microscopy images revealed smooth nanowires without any characteristic features that would differentiate their morphology as a function of the electrolyte temperature. X-ray photoelectron spectroscopy studies indicated the presence of a polycarbonate coating that covered the nanowires and protected them against oxidation. The X-ray diffraction measurements showed peaks coming from the polycrystalline Fe bcc structure without any traces of the oxide phases. The crystallite size decreased with an increasing electrolyte temperature. The transmission electron microscopy measurements proved the fine-crystalline structure and revealed elongated crystallite shapes with a columnar arrangement along the nanowire. Mössbauer studies indicated a deviation in the magnetization vector from the normal direction, which agrees with the SQUID measurements. An increase in the electrolyte temperature caused a rise in the out of the membrane plane coercivity. The studies showed the oxidation resistance of the Fe nanowires deposited at elevated electrolyte temperatures.

Towards Automatic Detection of Precipitates in Inconel 625 Superalloy Additively Manufactured by the L-PBF Method.

In our study, the comparison of the automatically detected precipitates in L-PBF Inconel 625, with experimentally detected phases and with the results of the thermodynamic modeling was used to test their compliance. The combination of the complementary electron microscopy techniques with the microanalysis of chemical composition allowed us to examine the structure and chemical composition of related features. The possibility of automatic detection and identification of precipitated phases based on the STEM-EDS data was presented and discussed. The automatic segmentation of images and identifying of distinguishing regions are based on the processing of STEM-EDS data as multispectral images. Image processing methods and statistical tools are applied to maximize an information gain from data with low signal-to-noise ratio, keeping human interactions on a minimal level. The proposed algorithm allowed for automatic detection of precipitates and identification of interesting regions in the Inconel 625, while significantly reducing the processing time with acceptable quality of results.

Microstructure and Properties of Electrodeposited Nanocrystalline Ni-Co-Fe Coatings.

Materials based on Ni-Co-Fe alloys, due to their excellent magnetic properties, attract great attention in nanotechnology, especially as candidates for high-density magnetic recording media and other applications from spintronic to consumer electronics. In this study, Ni-Co-Fe nanocrystalline coatings were electrodeposited from citrate-sulfate baths with the Ni2+:Co2+:Fe2+ ion concentration ratios equal to 15:1:1, 15:2:1, and 15:4:1. The effect of the composition of the bath on the morphology, microstructure, chemical composition, microhardness, and magnetic properties of the coatings was examined. Scanning (SEM) and transmission (TEM) electron microscopy, X-ray diffractometry (XRD), and energy dispersive X-ray spectroscopy (EDS) were used to study surface morphology, microstructure, chemical, and phase composition. Isothermal cross-sections of the Ni-Co-Fe ternary equilibrium system for the temperature of 50 °C and 600 °C were generated using the FactSage package. Magnetic properties were analyzed by a superconducting quantum interference device magnetometer (SQUID). All the coatings were composed of a single phase being face-centered cubic (fcc) solid solution. They were characterized by a smooth surface with globular morphology and a nanocrystalline structure of grain diameter below 30 nm. It was determined that Ni-Co-Fe coatings exhibit high hardness above 4.2 GPa. The measurements of hysteresis loops showed a significant value of magnetization saturation and small coercivity. The microstructure and properties of the obtained nanocrystalline coatings are interesting in terms of their future use in micromechanical devices (MEMS).

Microstructure, Micro-Mechanical and Tribocorrosion Behavior of Oxygen Hardened Ti-13Nb-13Zr Alloy.

In the present work, an oxygen hardening of near-ß phase Ti-13Nb-13Zr alloy in plasma glow discharge at 700-1000 °C was studied. The influence of the surface treatment on the alloy microstructure, tribological and micromechanical properties, and corrosion resistance is presented. A strong influence of the treatment on the hardened zone thickness, refinement of the α' laths and grain size of the bulk alloy were found. The outer hardened zone contained mainly an oxygen-rich Ti α' (O) solid solution. The microhardness and elastic modulus of the hardened zone decreased with increasing hardening temperature. The hardened zone thickness, size of the α' laths, and grain size of the bulk alloy increased with increasing treatment temperature. The wear resistance of the alloy oxygen-hardened at 1000 °C was about two hundred times, and at 700 °C, even five hundred times greater than that of the base alloy. Oxygen hardening also slightly improved the corrosion resistance. Tribocorrosion tests revealed that the alloy hardened at 700 °C was wear-resistant in a corrosive environment, and when the friction process was completed, the passive film was quickly restored. The results show that glow discharge plasma oxidation is a simple and effective method to enhance the micromechanical and tribological performance of the Ti-13Nb-13Zr alloy.

Precipitates in Additively Manufactured Inconel 625 Superalloy.

Laser-based additive manufacturing processes are increasingly used for fabricating components made of nickel-based superalloys. The microstructure development, and in particular the precipitation of secondary phases, is of great importance for the properties of additively manufactured nickel-based superalloys. This paper summarizes the literature data on the microstructure of Inconel 625 superalloy manufactured using laser-based powder-bed fusion and directed energy deposition processes, with particular emphasis on the phase identification of precipitates. The microstructure of Inconel 625 manufactured by laser-based directed energy deposition in as-built condition is investigated by means of light microscopy and transmission electron microscopy. Phase analysis of precipitates is performed by the combination of selected area electron diffraction and microanalysis of chemical composition. Precipitates present in the interdendritic areas of as-built Inconel 625 are identified as MC and M23C6 carbides as well as the Laves phase.

Influence of polyetheretherketone coatings on the Ti-13Nb-13Zr titanium alloy's bio-tribological properties and corrosion resistance.

Polyetheretherketone (PEEK) coatings of 70-90µm thick were electrophoretically deposited from a suspension of PEEK powder in ethanol on near-ß Ti-13Nb-13Zr titanium alloy. In order to produce good quality coatings, the composition of the suspension (pH) and optimized deposition parameters (applied voltage and time) were experimentally selected. The as-deposited coatings exhibited the uniform distribution of PEEK powders on the substrate. The subsequent annealing at a temperature above the PEEK melting point enabled homogeneous, semi-crystalline coatings with spherulitic morphology to be produced. A micro-scratch test showed that the coatings exhibited very good adhesion to the titanium alloy substrate. Coating delamination was not observed even up to a maximal load of 30N. The PEEK coatings significantly improved the tribological properties of the Ti-13Nb-13Zr alloy. The coefficient of friction was reduced from 0.55 for an uncoated alloy to 0.40 and 0.12 for a coated alloy in a dry sliding and sliding in Ringer's solution, respectively. The PEEK coatings exhibited excellent wear resistance in both contact conditions. Their wear rate was more than 200 times smaller compared with the wear rate of the uncoated Ti-13Nb-13Zr alloy. The obtained results indicate that electrophoretically deposited PEEK coatings on the near-ß titanium alloy exhibit very useful properties for their prospective tribological applications in medicine.

Real-time atomic scale imaging of nanostructural evolution in aluminum alloys.

We present a new approach to study the three-dimensional compositional and structural evolution of metal alloys during heat treatments such as commonly used for improving overall material properties. It relies on in situ heating in a high-resolution scanning transmission electron microscope (STEM). The approach is demonstrated using a commercial Al alloy AA2024 at 100-240 °C, showing in unparalleled detail where and how precipitates nucleate, grow, or dissolve. The observed size evolution of individual precipitates enables a separation between nucleation and growth phenomena, necessary for the development of refined growth models. We conclude that the in situ heating STEM approach opens a route to a much faster determination of the interplay between local compositions, heat treatments, microstructure, and mechanical properties of new alloys.

Electromagnetic energy sources in surgery.

The biophysics, mechanism of actions, applications, benefits and complications of electromagnetic (EM) energy-based surgical instruments, and their current use are reviewed. Understanding the mechanism of action, tissue effects, and appropriate applications of EM devices is critical to achieving an optimal surgical outcome. Although a more diverse range of EM devices are used in human medicine, current use in veterinary medicine is limited to conventional electrosurgery and CO(2) lasers.

Can harmonic focus curved shear effectively seal the pancreatic ducts and prevent pancreatic leak? Feasibility evaluation and testing in ex vivo and in vivo porcine models.

BACKGROUND: The purpose of this study was to evaluate the ability of Harmonic energy technology to transect and seal the pancreatic duct compared with the standard monopolar electrosurgery transection and oversew technique in a porcine distal pancreatectomy survival model. Harmonic energy technology is as effective as standard oversew technique for preventing pancreatic leak after distal pancreatectomy. METHODS: The animal protocol used for this study was approved by the Institutional Animal Care and Use Committee (IACUC) prior to the conduct of the study. Spleen-preserving distal pancreatectomy was performed in seven pigs (80-100 lb) by the same surgeon. In four animals, the pancreas was divided with the Harmonic Focus Curved Shears (test group) with no additional suturing for control of hemostasis or leak. In three animals, the pancreas was divided using monopolar electrosurgery (30 W coagulation) and the cut end of the pancreas was oversewn with a locking suture (control group). A previously worked out standard operative technique was used in all procedures. Operating end points included surgery time and blood loss. Animals were euthanized and necropsied at 7 to 8 d following surgery. Survival endpoints included clinical response to surgery, serum chemistry profiles before surgery and at necropsy, and histology of the pancreas transection site. RESULTS: Mean operative time for pancreatic resection was 15min in the control group and 10min in the test group. No significant blood loss was noted in either group. The median size of the resected pancreas was 4.3 cm. Three animals in the control group and three in the test group completed the study without complications. One animal in the test group failed to eat, appeared dehydrated, and was taken off study on POD#2. In this animal, there was a doubling of serum lipase at euthanasia and gross evidence of ileus, which was attributed to a pancreatic leak. Histologic examination of the residual pancreas in both groups at necropsy revealed a 2-5 mm band of necrotic tissue associated with neutrophilic infiltration in the control group, and less than a 1mm band of necrotic tissue in the test group. CONCLUSION: The Harmonic Focus Curved Shears, using Harmonic energy technology, appears to seal the pancreatic ducts and prevent pancreatic leak at 75% (3/4) efficiency in this survival model. However, the survival leak rate, 25% (1/4) was higher in the Harmonic Focus Curved Shears test group compared with the control oversewn group 0% (0/3). This feasibility study shows potential for Harmonic technology to be used to seal the pancreatic ducts, but additional testing and optimization of surgical techniques are needed.

Prognosis for acute nontraumatic hemoperitoneum in the dog: a retrospective analysis of 60 cases (2003-2006).

The complete medical records of 60 dogs with hemoabdomen were reviewed. All dogs underwent exploratory laparotomy and had a diagnosis established by a veterinary pathologist. Final diagnoses were hemangiosarcoma in 38 (63.3%) dogs, splenic hematoma in 16 (26.6%) dogs, splenic torsion in three (5%) dogs, hepatocellular carcinoma in two (3.3%) dogs, and carcinomatosis in one (1.6%) dog. Twenty-four (63.1%) dogs with hemangiosarcoma, 14 (87.5%) dogs with splenic hematoma, three (100%) dogs with splenic torsion, and two (100%) dogs with hepatocellular carcinoma were discharged from the hospital. Dogs with hemangiosarcoma were given a poor prognosis, while dogs with splenic hematoma, splenic torsion, and hepatocellular carcinoma were given a fair to good prognosis.