Hot stamping is a well-established technology for producing safety relevant car components. The use of hot stamped components in modern car bodies offers the possibility of improving crash ...performance due to their high strength while simultaneously decreasing the fuel consumption by reducing sheet thicknesses and thus weight. Hot stamped components are mainly produced using the boron-manganese-alloyed steel 22MnB5. To prevent formation of oxide layer during heat treatment and subsequent forming process, AlSi-coatings are applied on the workpiece surface. Since hot stamped parts are formed at temperatures between 600 °C and 800 °C, no suitable lubricants have been found yet. Thus, severe wear and high friction occur during the forming process affecting final part quality as well as life-time of hot stamping tools. Consequently, measures for reducing tribological load during the forming operation have to be found in order to improve part quality and increase efficiency of industrial hot stamping applications. Within this study, the impact of the tool material on friction and wear is analyzed by comparing the tribological behavior of the newly developed high thermal conductivity hot work tool steel Thermodur 2383 Supercool with the reference material 1.2367. Both are characterized by means of flat strip drawing experiments under hot stamping conditions. The experiments are performed with different hardness values for each of the two tool materials. Furthermore, wear behavior is analyzed using scanning electron microscope and confocal microscope measurements of workpiece and tool. Hereby, fundamental wear and friction mechanisms within hot stamping applications are identified. The results of this study help to increase the process understanding regarding the tribological conditions during hot stamping. In future research work tool-side measures for increasing the life-time of hot stamping tools will be developed.
•Improved resistance against adhesive wear with increasing tool hardness revealed.•Material transfer, ploughing and flattening identified as main friction mechanisms.•New hot stamping tool steel with high thermal conductivity has been presented.
Molecular Graph Paper Lindner, Marcin; Valášek, Michal; Mayor, Marcel ...
Angewandte Chemie International Edition,
July 3, 2017, Letnik:
56, Številka:
28
Journal Article
Recenzirano
Odprti dostop
We present a self‐assembled template that consists of tetraphenylmethane derivatives and adopts a periodic lateral arrangement on a Au(111) surface with acetyl groups sticking out of the molecular ...film. By using the tip of a scanning tunneling microscope, these acetyl groups can be removed in a spatially controlled way without significantly affecting the remaining molecular assembly. The chemically modified molecules can be readily distinguished from the original ones such that information can be engraved in the molecular film. Both the modified nature of an individual molecule and the order of the molecular film are shown to persist at room temperature. The mesh size of this molecular graph paper can be tuned by varying the length of the molecular spacer so that writing and reading information on the nanoscale with variable letter sizes becomes possible.
Tetraphenylmethane derivatives adopt a periodic lateral arrangement on gold(111) surfaces with acetyl groups sticking out of the molecular film. These acetyl groups can be removed by using the tip of a scanning tunneling microscope in a spatially controlled way without significantly affecting the remaining molecular assembly. This approach can be used for writing and reading on the nanoscale.
•A mixture of hydrated salts were adopted as phase change materials.•Phase segregation of the hydrated salts was inhibited.•Subcooling was slightly mitigated.•Thermal cycling performance was greatly ...improved after PVP coating.
A novel shape-stabilized phase change material composite was prepared by impregnating the mixture of hydrated salts (Na2SO4·10H2O–Na2HPO4·12H2O) into porous silica matrix obtained by sol–gel process and further coated with polyvinylpyrrolidone (PVP) to improve the thermal cycling performance. The chemical compatibility, morphology and phase change properties were investigated by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), hot-stage polarizing optical microscope (HS-POM) and differential scanning calorimetry (DSC). Confined in the silica matrix, phase segregation of the hydrated salts was inhibited and subcooling was slightly mitigated. No leakage was observed during the solid–liquid phase transition even when the mass ratio of hydrated salts to silica was as high as 70:30. Results showed that the melting enthalpy of the composite can reach 106.2kJ/kg with the melting temperature at 30.13°C and there was no significant enthalpy loss after 30 thermal cycles.
Information on the liverworts family Plagiochilaceae in Taman Eden 100 Natural Tourist Park North Sumatra has never been reported. This study aims to invent the spesies of Plagiochilaceae at Taman ...Eden 100 Natural Park, North Sumatra to complete the liverworts data of Sumatra. Samples were collected by exploring and surveying accessible path within the research site. The observation was done in the laboratory based on morphological characters under the binocular microscope. Identification of the species used some existing literature that contains key identification, description or illustration of Plagiochilaceae. Sixteen species of Plagiochilaceae were found in this area, including three genera: Pedinophyllum (1 species), Plagiochilion (1 species), and Plagiochila (14 species). The most common species found in the study was Plagiochila arbuscula, while the uncommon species found were Plagiochila frondescens, P. sumatrana, and Pedinophyllum sp.
Abstract
Natural radioactivity is common in the environment. As well as in geological formations such as soil, rock, air, water and plants. Which required extensive researches in many countries are ...due to the global interest in exposure to natural radioactivity. Ten different samples of milk collected from Iraqi markets were evaluated for concentration of alpha radioactivity (uranium concentration, effective radium content and radon concentrations) using CR-39. After exposure, the detectors were etched in a (NaOH) solution of normality (6.25 N) at a temperature of 70 °C for 8 hours. The tracks were calculated by the microscope track-counting system. At a rate of 0.171 ppm, uranium concentrations ranged between 0.079 – 0.263 ppm. While, the effective radium content varied from 53.724 - 178.47 mBq/kg with an arithmetic rate of 116.096 mBq/kg. The variation of the radon exhalation values for the mass unit and for the area unit was also observed between 0.406 - 1.349 m
Bq
/kg.h and 3.076 -10.217 m
Bq/m
2
.h, at a mean rate of 0.943 mBq/kg.h and 6.646 mBq/m
2
.h, respectively. The average of annual average internal effective dose (AAIED) due to ingestion of 222Rn in milk samples in children and adults has been found 0.60 nSv/y and 0.2 nSv/y respectively, there are excellent correlation between radium concentrations and radon exhalation rate and uranium concentration(R
2
=1). Thus, the results of this study do not constitute a health hazard to the lives of people because they are within the limits allowed internationally.
Nowadays, the research in conservation science is focused on developing advanced portable analytical techniques able to achieve subsurface data in situ and in a non‐invasive way. Micro‐spatially ...offset Raman spectroscopy (micro‐SORS) is an emerging analytical technique developed to address the need of non‐invasively retrieving the molecular composition of the subsurface compounds; however, so far, micro‐SORS studies of artworks have been carried out only with benchtop Raman microscopes, precluding the non‐invasive analysis of large objects and artworks in situ. Here, for the first time, portable micro‐SORS was used for non‐invasive and in situ investigation of art objects. The potential of portable micro‐SORS is demonstrated through the reconstruction of the layer sequences in selected areas of two 16th century panel paintings, providing unequivocal information about the preparation layer spread over the panels and the pigments used in the painted layers and supplying essential information on the artist's technique.
For the first time, portable micro‐spatially offset Raman spectroscopy (micro‐SORS) was used for non‐invasive and in situ investigation of art objects. Micro‐SORS measurements permitted the reconstruction of the layer sequences in selected areas of two 16th century panel paintings, providing unequivocal information about the preparation layer spread over the panels and the pigments used in the painted layers.
This study is focused on investigating the role of bismuth oxide (Bi2O3) nanoparticles to improve structural, optical, electrical, and mechanical properties of low‐density polyethylene (LDPE). For ...this purpose, Bi2O3 nanoparticles were synthesized by using the solvothermal method and examined by transmission electron microscopes (TEM), x‐ray diffraction (XRD), Fourier transformed infrared (FTIR) spectroscopy, and ultraviolet–visible (UV–Vis) light absorption methods. LDPE‐based nanocomposites were prepared by changing the nanoparticle additive ratio in the composite from 0% to 2% by weight. The composites were analyzed in the context of their FTIR spectra, atomic force microscope (AFM) images, UV–Vis light absorption spectra, stress–strain curves, and energy storage abilities. While the AFM findings indicate a smoother surface for the composites, the optical band gap analysis reveals a slightly decreased direct optical band gap energy. The analyses based on dielectric spectroscopy also highlight the LDPE/0.5% n‐Bi2O3 composite in terms of the best energy storage capability. Additionally, the highest Young's modulus, toughness, stress at break, and percentage of strain at break were also recorded for the LDPE/0.5% n‐Bi2O3 composite. In this context, the LDPE/0.5% n‐Bi2O3 composite with improved dielectric and mechanical properties can be suggested as a new promising LDPE‐based nanocomposite with better properties for industrial purposes.
The physical, electrical, and mechanical properties of LDPE/Bi2O3 nanocomposites.
Accurate chromosome segregation is necessary so that genetic material is equally shared among daughter cells. However, maturing mammalian oocytes are particularly prone to chromosome segregation ...errors, making them a valuable tool for identifying the causes of mis-segregation. Factors such as aging, cohesion loss, DNA damage, and the roles of a plethora of kinetochore and cell cycle-related proteins are involved. To study chromosome segregation in oocytes in a live setting is an imaging challenge that requires advanced techniques. Here we describe a method for examining chromosomes in live oocytes in detail as they undergo maturation. Our method is based on tracking the "center of brightness" of fluorescently labeled chromosomes. Here we describe how to set up our software and run experiments on a Leica TCS SP8 confocal microscope, but the method would be transferable to other microscopes with computer-aided microscopy.
The translation of stacking techniques used in capillary electrophoresis (CE) to microchip CE (MCE) in order to improve concentration sensitivity is an important area of study. The success in ...stacking relies on the generation and control of the stacking boundaries which is a challenge in MCE because the manipulation of solutions is not as straightforward as in CE with a single channel. Here, a simple and rapid online sample concentration (stacking strategy) in a battery operated nonaqueous MCE device with a commercially available double T-junction glass chip is presented. A multistacking approach was developed in order to circumvent the issues for stacking in nonaqueous MCE. The cationic analytes from the two loading channels were injected under field-enhanced conditions and were focused by micelle-to-solvent stacking. This was achieved by the application of high electric fields along the two loading channels and a low electric field in the separation channel, with one ground electrode in the reservoir closest to the junction. At the junction, the stacked zones were restacked under field-enhanced conditions and then injected into the separation channels. The multistacking was verified under a fluorescence microscope using Rhodamine 6G as the analyte, revealing a sensitivity enhancement factor (SEF) of 110. The stacking approach was also implemented in the nonaqueous MCE with contactless conductivity detection of the anticancer drug tamoxifen as well as its metabolites. The multistacking and analysis time was 40 and 110 s, respectively, the limit of detections was from 10 to 35 ng/mL and the SEFs were 20 to 50. The method was able to quantify the target analytes from breast cancer patients.
In this work, SiC/C aerogels with a high specific surface area (>1000 m2*g−1) and high porosity (>90%) synthesized through carbothermal reduction of biphenylene-bridged polysilsesquioxane (BP)/clay ...mineral nanocomposite aerogels. BP/clay mineral nanocomposite aerogels first prepared via sol-gel method followed by supercritical CO2 (ScCO2) drying process, then used to form SiC/C aerogels by intermolecular carbothermal reduction. The exfoliated BP/clay mineral nanocomposite aerogel caused the growth of several millimeters long SiC nanowires (NWs) with a diameter in the range of 30–90 nm on the surface of SiC/C monolith aerogel and worm-like SiC nanostructures in the interior of SiC/C aerogel. Digital microscope, XRD, FE-SEM, FT-IR, TEM, HRTEM, SAED, HAADF-STEM, EDS, BET, and mercury porosimetry techniques employed to fully characterize the obtained products. Al2O3-assisted vapor-solid (VS) mechanism proposed for the growth mechanism of SiC NWs on the surface of aerogels.
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