Reaction sintering of an Fe-6 Wt Pct B-48 Wt Pct Mo alloy in the presence of liquid phases

The mechanism of liquid phase sintering of an Fe-6 wt pct B-48 wt pct Mo alloy was investigated by means of thermal dilatometry, differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). A fine composite microstructure of Mo₂FeB₂ and ferrite was produced from powders of Fe, Mo, and FeB by a reaction sintering process involving two liquid phases. The hard phase Mo₂FeB₂ is produced in the compact prior to liquid formation initially by the reaction 2Mo+2FeB=Mo₂FeB₂+Fe and later by the reaction 2Mo+2Fe₂B=Mo₂FeB₂+ 3Fe. Above 1365K, considerable densification results from the initial stage rearrangement of the solid phases (austenite and Mo₂FeB₂) coexisting with the first formed liquid phase (L₁). Another liquid (L₂) which forms above 1415K, where Mo₂FeB₂ is the only coexisting solid phase, is required for complete densification. L₂, having a high solubility for Mo₂FeB₂, provides for solution/reprecipitation processes which characterize the intermediate stage of liquid phase sintering. The effective separation of the initial and intermediate stages by L₁ and L₂ is considered essential for the control of the sintered microstructure of the ternary alloy. Teiichi Ando, formerly with the Technical Research Laboratory, Toyo Kohan Co., Ltd., is with the Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139.     

NATURAL ZEOLITES IN AIR DRYING

The local clinoptilolite from Bigadis region in Turkiye, was used for air drying in packed column. The effective diffusion coefficient of water in natural zeolite was found as 5×10^-10 m² s^-1 from isothermal uptake measurements. Effects of packing height and airvelocity on breakthrough curves were studied.     

Super-low friction and lightweight hydraulic cylinder using multi-directional forging magnesium alloy and its application to robotic leg

Abstract

One of the most important missions for robots is to operate in severe environments, and these situations require robots to have ‘toughness’ which can overcome large shocks, degraded communication quality, unexpected condition, and other critical accidents. Although there are many kinds of approaches to realize tough robotic systems, developing a tough actuators is one of the key technologies for them. We focus on hydraulic actuators and attempt to develop a tough robotic actuator with greater toughness than the electromagnetic actuators used in conventional robotic systems. In general, hydraulic actuators have enough toughness for severe environments, but their controllability and lightness are insufficient for robot systems. Herein, we propose novel hydraulic actuators that realizes lightweight with a multidirectional-forging magnesium alloy and have high controllability by low friction pistons. Prototypes were developed to examine the fundamental characteristics of the actuators and compare the two approaches for the low-friction pistons: one is based on a packing mechanism using an elastic restoring pressure, and the other utilizes a fluid-bearing technology. After basic experiments, the prototype was applied to a robotic leg to verify their potential in actual robotic systems. The robotic leg successfully jumped 260 mm in height with 21 MPa.     

Determination of FA composition and total trans FA of Turkish margarines by capillary GLC

In this research, FA composition and total trans FA contents of 16 different brands of margarine (8 hard-type and 8 soft-type) sold in Turkey were determined by capillary GLC method. According to the results, the contents of saturated FA, monounsaturated FA, and PUFA were within the ranges of 23.9–32.3, 44.0–61.9, and 14.2–24.1%, respectively, in hard-type margarines, and 27.0–39.9, 21.0–40.9, and 32.0–53.7%, respectively, in soft-type margarines. Hard-type margarines contained total trans FA concentrations of 20.1–34.3%, whereas soft-type margarines contained less than 8.9% total trans FA. C_18∶1 trans acid content was within the range of 18.5–29.8% in hard-type margarines, and it was significantly higher than the range in soft margarines (0.7–8.1%). C_18∶1 trans acid was the major trans FA in all margarines, and C_18∶3 trans acid concentrations were less than 0.2%.     

Injection molding of thermotropic liquid crystal polymers

Thermotropic liquid crystal polymers consist of rod-like molecules and are often called “self reinforcing thermoplastics.” Their rheological behaviors as well as orientation development during processing are often very similar to those of short fiber-filled composites. Without reinforcement, the polymer shows superior mechanical properties to conventional glass fiber-reinforced engineering resins. The orientation distribution in the crosssection as well as flow patterns in the molded thermotropic polymers are clearly visible to the naked eye due to color differences. This makes it particularly convenient to study the orientation distribution as well as the flow patterns of packing, back flow, jetting, flow instabilities, and weld line formation in injection molding. This paper discusses physical properties of a typical ther motropic polymer and their relationship to mold filling process in the injection molding.     

Effect of liquid temperature on spray flash evaporation

To complement the authors' previous experimental study of spray flash evaporation pursued at 60°C jet inlet temperature, an additional experimental study has been made of the effect of liquid temperature on the spray flash evaporation by changing jet inlet temperatures to 40 and 80°C.From the experimental results, a more general empirical equation suitable for predicting the variation of liquid temperature in the center of jet with residence time was deduced, and the recommendable operating conditions were proposed. Furthermore, an expedient method for prediction of the liquid temperature drop along the length of jet was devised for the recommendable operating conditions.It was realized that, even at lower liquid temperatures, the spray flash evaporation still has higher evaporation performance and extremely faster evaporation rate than the flash evaporation occurring in other systems.     

Hydrodynamics of a spouted bed with a porous draft tube containing a small amount of finer particles

A small-size spouted bed with a porous draft tube was employed to obtain hydrodynamic data of binary mixtures of glass beads for a range of operating conditions and design factors. In this case, a small amount of finer particles was added mostly to the large majority of coarser particles. Under this condition, minimum spouting velocity, bed pressure drop, hold-up of solid particles within a draft tube, gas flow rate through the annulus and solids circulation rate were determined by changing the total gas flow rate and the mass fraction of finer particles as operating parameters, and by changing the height of the entrainment zone and the draft tube diameter as geometric parameters. The results show that the gas flow rate through the annulus increases by increasing the distance between the gas inlet nozzle and the bottom of the draft tube, that is, the height of the entrainment zone, but decreases with increasing draft tube diameter and mass fraction of finer particles. The porous draft tube shows a higher gas flow rate through the annulus than the non-porous draft tube, particularly in the case of the low height of the entrainment zone. The solids circulation rate increases with increasing gas velocity, the height of the entrainment zone and the porous draft tube diameter. Moreover, the porous draft tube leads to a higher solids circulation rate than the non-porous draft tube.     

Computational Models in Architecture: Understanding Multi-Dimensionality and Mapping

The aim of this paper is to discuss computational thinking and parametric design and thus “what model is” in the realm of mathematics in architecture. Here we investigate how multi-dimensionality and reference systems should be contemplated, along with what mapping is and how it is related with algorithms in computational design. Set theory and functional relations are re-visited and similarity/similitude concepts and the importance of nondimensional parameters relating different reference systems (interpreted as domain and range relations) are pointed out. In this context, computational design approaches based on modern biomimetic studies in architecture which are beyond metaphors or analogies are considered as the prominent cases of the present inquiry.     

Initiator‐free photopolymerization of common acrylate monomers with 254 nm light

Using an available light source at a wavelength of 254 nm, common acrylate monomers were polymerized without any photoinitiators, which was confirmed using Fourier transform IR (FTIR) spectroscopy, ¹H NMR, gel permeation chromatography and fast atom bombardment mass spectrometric measurements. It was found that phenyl acrylate shows higher conversion than n‐ and t‐butyl acrylates. A trifunctional acrylate was also used for UV curing. The cured films were fabricated successfully on different kinds of substrates by using a batch‐ or conveyor‐type irradiation apparatus. It is indicated from FTIR spectral measurements that ca 40%–50% of acryloyl groups are consumed by the photopolymerization. Oxygen concentration in the sample chamber influences the photopolymerization, indicating that the polymerization proceeds via a radical process. © 2018 Society of Chemical Industry