Effect of melting temperature on microstructural evolutions,behavior and corrosion morphology of Hadfield austenitic manganese steel in the casting process

In this study, the effect of melting temperature on the microstructural evolutions, behavior, and corrosion morphology of Hadfield steel in the casting process is investigated. The mold was prepared by the sodium silicate/CO₂ method, using a blind riser, and then the desired molten steel was obtained using a coreless induction furnace. The casting was performed at melting temperatures of 1350, 1400, 1450, and 1500℃, and the cast blocks were immediately quenched in water. Optical microscopy was used to analyze the microstructure, and scanning electron microscopy (SEM) and X-ray diffractrometry (XRD) were used to analyze the corrosion morphology and phase formation in the microstructure, respectively. The corrosion behavior of the samples was analyzed using a potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS) in 3.5wt% NaCl. The optical microscopy observations and XRD patterns show that the increase in melting temperature led to a decrease of carbides and an increase in the austenite grain size in the Hadfield steel microstructure. The corrosion tests results show that with increasing melting temperature in the casting process, Hadfield steel shows a higher corrosion resistance. The SEM images of the corrosion morphologies show that the reduction of melting temperature in the Hadfield steel casting process induced micro-galvanic corrosion conditions.     

Perusing Piezoelectric Head Performance in a New 3-D Printing Design

Rapid prototyping (RP) is a computerized fabrication technology that additively builds highly complex three-dimensional physical objects layer by layer using data generated by computer, for example CAD or digital graphic. Three-dimensional printing (3DP) is one of such technologies that employ ink-jet printing technology for processing powder materials. During fabrication, a printer head is used to print a liquid on to thin layers of powder following the object's profile as generated by the system computer. This work looks at redesigning 3DP machine, using piezoelectric demand-mode technology head in order to improve accuracy, surface finishing and color quality of constructed models. The layers created with aforesaid system are between 25 to 150 μm (steps of 25 μm).     

Effect of Y2O3 on the crystallization kinetics of TiO2 nucleated LAS glass for the production of nanocrystalline transparent glass ceramics

Crystallization kinetics of metastable β-quartz solid solution as a desirable phase for the production of transparent lithium aluminosilicate (LAS) glass ceramics was investigated in the presence of Y₂O₃. Accordingly, differential thermal analysis scans were performed thoroughly to study the mechanism of crystallization kinetics. The aim of this investigation is to discover the complicated mechanism of crystallization process in the presence of co-additives and accordingly find a way for increasing the transparency of glass ceramics. It is shown that the bulk (3D) growth is intensively increased by the enhancement of Y₂O₃. Then again, reducing nucleation and increasing growth mechanisms were recognized for the LAS system in the presence of Y₂O₃. Results of the investigation illustrate that when co-additives are added to glasses, it is necessary to nucleate the optical component separately before the growth process.     

Influence of catalyst on structural and morphological properties of TiO2 nanostructured films prepared by sol–gel on glass

Transparent TiO2 thin films have been prepared by the sol-gel method using titanium alkoxides as precursors.Thin films were deposited on glass supports by the dip-coating technique.The TiO2 layer acts as a self-cleaning coating generated from its photocatalysis and photoinduced superhydrophilicity.The crystalline structure of TiO2 films was dominantly identified as the anatase phase,consisted of uniform spherical particles of about 14-50 nm in size,which strongly depends upon catalyst-type and heat treatment temperature.Increasing heat treating temperature can lead to an increase in crystalline size.The results indicated that the sample S.S(sample derived from sol containing sulfuric acid as catalyst) exhibits superhydrophilic nature and better photocatalytic activity,which can be attributed to its higher anatase content and lower crystalline size.Morphological studies,carried out using Atomic Force Microscopy(AFM),confirm the presence of crystalline phase with such a grain size and low surface roughness.Thus,the applied films exhibiting high photocatalytic activity,superhydrophilic behavior,and low surface roughness can be used as an efficient self-cleaning coating on glass and other optical applications.     

Design and Manufacture of a Wax Injection Tool for Investment Casting Using Rapid Tooling

A rapid wax injection tool of a gearbox shift fork was designed, simulated, and manufactured using rapid prototyping and rapid tooling technology to save time and cost of producing wax models used for the investment casting process. CAE simulation softwares, in particular, MoldFlow, are used to get wax injection moulding parameters such as filling parameters, temperature profiles, freeze time, speed, and pressure. The results of this research were compared with conventional wax model production methods. The criteria of such comparison were based upon parameters such as time, cost, and other related characteristics, which resulted in saving of 50% in time and 60% in cost. In this research, design, assembly, and wax injection operation of the wax tool took 10 days. Considering the fact that wax melting temperature is as low as 70℃ and injection pressure of 0.5 MPa, the tool suffers no damage due to the thermal and pressure stresses, leading to the mass production of wax models.     

Production of ultra-transparent glass-ceramics via controlled crystallization of nanocrystals in the glassy matrix of LAST

Microstructural variation in glass-ceramics encompasses the range from nanocrystalline transparent materials to microcrystalline tough materials. In this investigation, the crystallization process was controlled for the development of ultra transparent Li₂O-Al₂O₃-SiO₂ glass-ceramics containing TiO₂ as a nucleating agent (LAST). Results of UV-Vis absorption spectra were compared with the expected theoretical values calculated by the Rayleigh scattering method for the determination of ultra transparency. Results of the investigation illustrate that the control of crystallization increases the range of ultra transparency by the reduction of crystal size and their uniformity in the glassy matrix. Last but not the least, the optimized samples are ultra transparent approximately in the whole light wavelengths.     

Systematic variation of the stellar initial mass function in early-type galaxies

Much of our knowledge of galaxies comes from analysing the radiation emitted by their stars, which depends on the present number of each type of star in the galaxy. The present number depends on the stellar initial mass function (IMF), which describes the distribution of stellar masses when the population formed, and knowledge of it is critical to almost every aspect of galaxy evolution. More than 50 years after the first IMF determination, no consensus has emerged on whether it is universal among different types of galaxies. Previous studies indicated that the IMF and the dark matter fraction in galaxy centres cannot both be universal, but they could not convincingly discriminate between the two possibilities. Only recently were indications found that massive elliptical galaxies may not have the same IMF as the Milky Way. Here we report a study of the two-dimensional stellar kinematics for the large representative ATLAS(3D) sample of nearby early-type galaxies spanning two orders of magnitude in stellar mass, using detailed dynamical models. We find a strong systematic variation in IMF in early-type galaxies as a function of their stellar mass-to-light ratios, producing differences of a factor of up to three in galactic stellar mass. This implies that a galaxy's IMF depends intimately on the galaxy's formation history.     

Fabrication,microstructure, and optical properties of nanocrystalline transparent LAST glass ceramics containing CeO2

In the present research, the effect of CeO2 dopant on the fabrication of transparent lithium aluminosilicate titanate （LAST） glass ceramics was investigated. Nanocrystallineβ-quartz solid solution （s.s.） was observed to be the main phase crystallized in this system. Com-parable refractive indices of the glassy matrix andβ-quartz s.s., as well as the incorporation of very fine grains size were determined as the main reasons for retaining the transparency of the glass ceramics. CeO2 was introduced as a suitable optical agent, playing a role as a network modifier in the glass ceramics, because it does not accelerate the growth process and retards the extended growth of crystals. Optical investi-gations indicate that the Fermi energy level, direct and indirect band gaps, and Urbach energy decrease with increasing nanocrystal content in the glassy matrix of specimens, which can be related to the expansion of conduction band, the enhancement of ionic bonds in the crystal lat-tice, and the enhancement of structural arrangement degree, respectively.     

Perusing Piezoelectric Head Performance in a New 3-D Printing Design

Rapid prototyping (RP) is a computerized fabrication technology that additively builds highly complex three-dimensional physical objects layer by layer using data generated by computer, for example CAD or digital graphic. Three-dimensional printing (3DP) is one of such technologies that employ ink-jet printing technology for processing powder materials. During fabrication, a printer head is used to print a liquid on to thin layers of powder following the object’s profile as generated by the system computer. This work looks at redesigning 3DP machine, using piezoelectric demand-mode technology head in order to improve accuracy, surface finishing and color quality of constructed models. The layers created with aforesaid system are between 25 to 150 μm (steps of 25 μm).     

Suppression of star formation in early-type galaxies by feedback from supermassive black holes

Detailed high-resolution observations of the innermost regions of nearby galaxies have revealed the presence of supermassive black holes. These black holes may interact with their host galaxies by means of 'feedback' in the form of energy and material jets; this feedback affects the evolution of the host and gives rise to observed relations between the black hole and the host. Here we report observations of the ultraviolet emissions of massive early-type galaxies. We derive an empirical relation for a critical black-hole mass (as a function of velocity dispersion) above which the outflows from these black holes suppress star formation in their hosts by heating and expelling all available cold gas. Supermassive black holes are negligible in mass compared to their hosts but nevertheless seem to play a critical role in the star formation history of galaxies.