Using double-V-notched specimens of austenitic steel SUS310S with high ductility, creep rupture tests are conducted in tension, torsion and combined tension-torsion stress states at 700°C. Creep fracture surfaces of the ruptured notches as well as longitudinal sections of the un-ruptured notches are observed in detail with scanning electron micrographs. The creep fracture modes and the initiation and growth behaviors of creep voids in the notched specimens under the stress conditions stated above are investigated and discussed, based on the stress distributions in notch cross-sections calculated by finite element method. It is confirmed that the mean stress in a specimen at a multi-axial stress state promotes the brittle creep fracture. It is also suggested that the von Mises effective stress and the mean stress promote the initiation of creep voids and their growth, respectively.

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In order to develop forging process of magnesium alloys without lubrication, frictional behavior of magnesium alloy AZ31B (Mg-3%Al-1%Zn) is evaluated by a tapered plug penetration test under dry condition. The cemented tungsten carbide (WC) plugs polished to be a mirror-like surface are coated with diamond-like carbon (DLC) and TiAlN by physical vapor deposition (PVD). The cylindrical hollow billets of AZ31B are penetrated by the tapered plugs at a temperature of 200°C. The surface roughness of the hole of the billet, the adhesion length of AZ31B on the plug surface and the penetration load are measured. Compared with WC and TiAlN coating, it is found that DLC coating is effective in preventing AZ31B from adhering to the tool surface and reducing the penetration load.

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The effects of power-law plasticity (yield strength σ_y and strain hardening exponent n) on the plastic strain distribution underneath a Vickers indenter was explicitly investigated by recourse to macro- and micro-indentation experiments on heat-treated Al-Zn-Mg alloy. With carefully designed aging profile, Al alloy can achieve similar σ_y with different n, and vice versa. Using the Vickers tip, the samples were macro-indented, sectioned and micro-indented to construct the sub-surface strain distribution. Thus, the effects of σ_y and n on stain distribution underneath Vickers indenter were revealed.

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Fine rounded powders preferable for metal injection moulding (MIM) are expensive. This forces MIM makers to recycle green scraps, for example, the runner system and defected green parts. This is particularly necessary for injection moulded small parts where parts are only a small portion of the injection short size. There is very little published data, although recycling feedstock has been practise throughout the industry. This work aims at investigating the effects of recycled stainless steel 630 feedstock content on the density, mechanical properties, dimensional changes and microstructure. Five batches of compounded virgin and recycled feedstock were studies from 0% to 100% recycled feedstock with the increment of 25%. Homogenously compounded feedstock was injected using the same injection condition. Subsequently, green parts were debinded and sintered at 1325°C for 2 hours in argon atmosphere. The results suggest that the green density increases linearly with increasing percentage of recycled feedstock because the polymeric binder was broken down during previous process. However, the sintered density remains nominally constant. As a result, the mechanical properties and microstructure of sintered parts are independent of recycled feedstock content. However, the volumetric and linear shrinkage decreases linearly with the increase in percentage of recycled feedstock. The difference in shrinkage is vital to dimensional control during commercial production. For example, only 4.5% of recycled feedstock can be added to virgin feedstock if a tolerance of ±0.3 mm is required for a 25 mm MIM part.

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This study presents a steady state and transient solution for a finite width two-lobe bearing operating with a non-Newtonian lubricant, obeying the power law model. A non-linear time-transient analysis is carried out and the orbital stability of journal is ensured by solving the equation of motion by fourth order Runge-Kutta method. Using the expressions for eccentricity ratio of lower and upper lobes and film thickness for each lobe, the modified Reynolds equation is solved separately for each lobe by finite difference technique with a successive over-relaxation scheme. Performance parameters of two-lobe bearing like load carrying capacity, Sommerfeld number, attitude angle; flow and friction parameter are determined and compared with the established results for Newtonian lubricants. Stability parameters are compared with circular bearings. It is found that the non-Newtonian effects are very prominent in the determination of load capacity, flow and friction characteristics of two-lobe bearings. Stability parameters of two-lobe bearings are considerably higher for all eccentricity ratios compared to circular bearings; hence these bearings are better suited for applications where whirl instability limits the speed at which the bearing can be operated.

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Tungsten oxide (WO₃) is recently recognized as one of the most widely studied gas sensitive ceramics. To maintain good thermal stability at moderate operating temperature, the gas sensitive materials were typically heated at several hundreds degree Celsius. Such treatment caused grain growth, resulting to reduction of specific surface area which is considered to be one of the important properties determining gas sensor's performance. In this present work, grain growth of the WO₃ nanoplate was retarded by incorporation of silica (SiO₂) particle. To obtain homogeneous structure, the SiO₂ was incorporated by mixing tetraethyl orthosilicate into the W precursor during precipitation of the tungsten oxide. It was found that the SiO₂ dramatically retarded the particle growth, preserved the nanoplate structure, and resulted to more porous WO₃ powder. The effect was very significant when the powders were calcined at high temperatures.

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Ni²⁺ ions occupy the tetrahedral (4), trigonal bipyramid (5) and octahedral (6) sites in glasses and glass-ceramics. The color changes depending on coordination number, typically pink for tetrahedral site, brown for trigonal bipyramid and tetrahedral sites and green to blue for octahedral site, respectively. The broad near infrared (NIR) emission peaking at around 1220 nm was observed for octahedral Ni²⁺ ions. This emission is due to ³T₂(F)→³A₂(F) transition.

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In situ reinforcing elastomer composites based on Santoprene thermoplastic elastomer, a polymerized polyolefin compound of ethylene-propylene-diene monomer (EPDM)/polypropylene (PP), and a thermotropic liquid crystalline polymer (TLCP), Rodrun LC3000, were prepared using a single-screw extruder. The rheological behavior, morphology, mechanical and thermal properties of the blends containing various LC3000 contents were investigated. All neat components and their blends exhibited shear thinning behavior. With increasing TLCP content, processability became easier because of the decrease in melt viscosity of the blends. Despite the viscosity ratio of dispersed phase to the matrix phase for the blend system is lower than 0.14, most of TLCP domains in the blends containing 5-10 wt% LC3000 appeared as droplets. At 20 wt% LC3000 or more, the domain size of TLCP became larger due to the coalescence of liquid TLCP threads that occurred during extrusion. The addition of LC3000 into the elastomer matrix enhanced the initial tensile modulus considerably whereas the extensibility of the blends remarkably decreased with addition of high TLCP level (>20wt%). The results obtained from thermogravimetric analysis suggested that the incorporation of LC3000 into Santoprene slightly improved the thermal resistance both in nitrogen and in air.

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This article has been found to be a duplicate publication of their article on another journal, and thus retracted by the Editor.

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GTAW process is used for welding of pressure vessels made of hypo-eutectic Al-Cu alloy AA2219 containing 6.3% Cu. As welded Yield strength of the alloy was found to be in the range of 140-150 MPa, using conventional single pass GTAW technique on both AC and DCSP modes. Interestingly, it was also found that weld-strength decreased with increase in thickness of the weld coupons. Welding metallurgy of AA2219 Al alloy was critically reviewed and factors responsible for lower properties were identified. Multipass GTAW on DCSP mode was postulated to improve the weld strength of this alloy. A systematic experimentation using 12 mm thick plates was carried out and YS of 200 MPa has been achieved in the as welded condition. Thorough characterization including optical and electron microscopy was conducted to validate the metallurgical phenomena attributable to improvement in weld strength. This paper presents the conceptual understanding of welding metallurgy of AA2219 alloy and validation by experiments, which could lead to better weld properties using multipass GTAW on DCSP mode.

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This study examined the creep behavior of DiARY^®, a shape-memory polymer (SMP), and the factors influencing the creep behavior. The creep test using the short term method obtained the master curve for the creep compliance, and confirmed the time-temperature superposition principle. Using this method, physical aging has little effect on the results of the creep test. To examine the effects of physical aging, we performed the creep test without using this method, which showed that physical aging alters the energy of activation of DiARY and the time-physical age time dependency at a specific temperature. The aging master curves were obtained as very smooth curves. In addition, the aging shift factors were attained when creating the aging master curves. The effect of physical aging depended on the time and temperature, confirming the time-physical aging time superposition principle, and achieved the effect of physical aging described as the aging shift rate. Using the master curve, time-temperature shift factor, and aging shift rate, it was possible to estimate the creep deformation, including the effect of physical aging on creep behavior.

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Stress distributions beneath the contact surface of ceramic plat in contact with round bar were analyzed by 3-D FEM. On the basis of analytical results, the contact strength was evaluated by considering varied sizes and positions of pre-existing defects from a viewpoint of fracture mechanics. The contact rupture occurs from a surface defect that pre-exists in the vicinity of the edge of the plate. If we posit the premise that a defect size and a distance from contact boundary to its defect, the contact rapture load can be evaluated by using the proposed equation.

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Fixed bed pyrolysis of physic nut waste was conducted to investigate the influence of different operating conditions, such as sample size, final temperature and hold time, on properties of the pyrolyzed chars. The obtained chars were characterized by a thermogravimetric analyzer (TGA) for proximate analyses and by Brunauer-Emmett-Teller (BET) for determination of their accelerated surface area. The surface morphology of char was investigated using scanning electron microscopy (SEM). For chemical characterization, an X-ray diffractometer (XRD) and a Fourier transform infrared spectroscope (FTIR) were used to identify inorganic components and surface organic functional groups of the char. In this work, the FTIR analysis indicated the existence of phosphonate groups, carboxyl groups and amine groups on char surface. The XRD pattern of the surface also verified the presence of graphite as main carbon structure. The conditions yielding char with maximum BET surface area of 249.60 m²·g^-1 and high fixed carbon are final temperature of 800°C, hold time of 15 minutes, and heating rate of 20°C/min for 0.425-0.5 mm particle. Generally, high temperature pyrolysis of raw materials with short hold time results in char with favorable smooth, porous surface with large cavities.

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The optical absorption due to Mn³⁺, Cu²⁺, Ni²⁺ and Co²⁺ ions in industrial soda-lime-silica glass was investigated as a function of the Na₂O concentration in the range of 11-19 mol%. With increasing Na₂O concentration in the experimental glasses, the calculated basicity; Λ_cal, increased. The ²⁹Si NMR spectra showed a high proportion of non-bridging oxygens; NBOs as the basicity of glass was increased. The results are thought to be due to tetrahedral networks; Q⁴ species were disconnected by replacing the bridging oxygens; BOs with NBOs forming Q³ species. These results were confirmed by a shift and broadening of XRD peaks. The redox reactions of the Mn²⁺-Mn³⁺ and Cu⁺-Cu²⁺ couples shifted toward the more oxidized ions due to oxygen partial pressure; p(O₂) during melting and the oxide ion activity; a_O2- where increase with increasing glass basicity. While the Ni²⁺-Ni³⁺ and Co²⁺-Co³⁺ couples were assumed to be presented only the Ni²⁺ and Co²⁺ ions in these glasses, respectively. The optical absorption bands due to Mn³⁺, Cu²⁺, Ni²⁺ and Co²⁺ ions occurred at characteristic wavelengths with different optical densities or intensities as a function of glass basicity. The increase in the intensities of the absorption bands of these absorbing ions depended not only on the ion concentration but also on the increase of polarisability of the oxide (-II) species; α_oxide(-II) surrounding the ions. This value directly affected the extinction coefficients of the ions; ε_ion. The increase of ε_ion is associated with increased intensity of color.

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The powder in PZ-PNN system with formula (1-x)PbZrO₃-xPb(Ni_1/3Nb_2/3)O₃ with x=0.0-0.5, are synthesized via the columbite precursor technique. The formation of the perovskite phase in the calcined powders has been investigated as a function of calcination conditions by TG-DTA and XRD techniques. Moreover, morphology and particle size evolution have been determined via SEM technique, respectively. The complete solid solutions of perovskite phase of PZ-PNN ceramics were obtained over a wide compositional range. It was observed that for the binary system (1-x)PbZrO₃-xPb(Ni_1/3Nb_2/3)O₃, the change in the calcinations temperature is approximately linear with respect to the PNN content in the range x=0.0-0.5. With an increase in x, the calcinations temperature shifts up to high temperatures. It is seen that optimization of calcination conditions can lead to a 100% yield of PZ-PNN in a pseudo-cubic phase.

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In the present study, joining and caulking of a dissimilar material using shot peening was investigated. The availability of the plastic flow, i.e., the peening droop makes the joining of the dissimilar material possible. This method is similar to caulking. In the experiment, two kinds of shot peening machines, air type and centrifugal type, were employed. In order to examine experimentally the influence of working temperature on joinability, equipment with a heating furnace was produced. Firstly, the influences of processing conditions on the joining between the dissimilar material and the cylindrical substrate were examined. The dissimilar materials were joined to the cylindrical substrate. Secondary, the joining of the dissimilar materials using the peening droop was performed. The bond strength was evaluated by tensile test. The dissimilar materials were successfully joined to the substrate by the peening droop. Bond strength increased with increasing kinetic energy of shots and processing temperature. It was found that the present method using the shot peening process was very effective for joining the dissimilar materials.

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In this work, a further study on boronizing using compression method called superplastic boronizing (SPB) was conducted. This process was conducted on duplex stainless steel (DSS) which has been thermo-mechanically treated to obtain fine grain microstructure and exhibit superplasticity. Effort was being put in obtaining ultra hard surface through SPB by focusing on the boron powder particle size. The microstructure, hardness, and layer thickness of the boronized materials were investigated. The formation of hard boride layers were confirmed by XRD analysis. Metallographic studies and scanning electron microscope (SEM) revealed a uniform, dense and smooth morphology of boride layer produced on all the boronized specimens. Comparison using as-received DSS with coarse microstructure also was performed. The overall results from the study showed that the SPB process can produce a very hard surface and significantly improve the surface properties of DSS.

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Among several types of ceramic membrane developed for a half of century, alumina is the most extensive advantage. In this study, many types of alumina with different particle size distributions were used as a starting material for fabrication of support sheet ceramic membrane using extrusion process. The investigation focused on the alumina dough components composed of some organic binders and water. The organic binder of about 12 wt. % was required in order for dough to be easily extruded, while the amount of water added to the dough depended on the particle size of alumina powder. The particle size and size distribution of starting powder showed strong effects on pore size of sintered alumina support. The pore size decreased when smaller particle size of starting powder was used. In addition, the pore volume of the sintered alumina decreased with increasing the sintering temperature due to improvement in densification, while pore size remained the same. The mechanical strength of alumina supports was also influenced by the particle size of starting powder; the finer particle size resulted in the higher mechanical strength. However, in order to obtain a good flux for the membrane, a high mechanical strength of the support along with its effective porosity is critical concerns. In this work, the support sintered at 1450°C provided a proper porosity of approximately 40% with an acceptable mechanical strength of 30-45MPa.

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The interactions between the hydronium ions and the waters in Nafion® polyelectrolyte membrane are relevant in the proton transfer process of fuel cell. To investigate a role of water in the proton transfer mechanism, molecular dynamic simulations have been performed for models of Nafion® side chains cluster with the water molecules and the hydronium ions comparing with dry system. After simulations, the trajectories were analyzed in term of intermolecular distances, potential energy, and radial distribution function.

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This research aims to investigate the functionality of nano-precipitated calcium carbonate (NPCC) as filler in thermoplastic resins based on property enhancement. Three types of thermoplastics were used: polyethylene (PE), polypropylene (PP) and polyvinyl chloride (PVC). The resins were evaluated by determining the effect of different NPCC loading on the chemical structure, thermal and mechanical properties of thermoplastics. Results showed that there was an interfacial bonding with the NPCC surface and the thermoplastics. Change in absorption peak and area were predominant in the PVC filled composite. There was a decreased in crystallinity of the PE and PP with the addition of filler. Tremendous increase on the tensile and impact strength was exhibited by the NPCC filled PVC composites while PE and PP composites maintained a slight increase in their mechanical properties. Nano-sized filler was proven to improve the mechanical properties of thermoplastics compared with micron-sized filler because nano-sized filler has larger interfacial area between the filler and the polymer matrix.

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This paper describes the experimental research of the warpage behavior of a thin-core flexible substrate made of multiple layers of metal and polymer components. The composite substrate was subjected to varied temperatures inside a Shadow Moiré chamber and the warpage behavior was carefully measured at different intervals up to the peak temperature. The maximum displacement was carefully monitored using the principle of Shadow Moiré technique which has been used as a non-contact method in obtaining the 3-D shapes and surface morphologies of materials and allows fine tuning of contours to achieve the best resolution. The same measurement procedures were done during its cool down stage. Different surface profiles were created on the substrate which varies depending on the distribution of the metal and polymer components. It also showed that the magnitude of displacement caused by the warpage gradually changes over temperature. By correlating the observed warpage morphologies of the substrate with that of the temperature load, two warpage mechanisms were observed—one that is largely controlled by the thermo-mechanical properties of the individual layers of the substrate creating a saddle shaped warpage behavior and one that is due to the global response of the bulk properties of the substrate with its surrounding materials.

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Thermally tempered glass is made by cooling rapidly after heating float glass to near a softening point. The compressive residual stresses generated at the surface layer by thermal expansion make strengthen the material. However, the tensile residual stress layer will be also generated in the interior of the material to compensate for the surface compression residual stress. The presence of these residual stress layers in the thermally tempered glass will play an important role from the viewpoint of crack growth in fatigue. In this study, in order to examine the fatigue crack growth behavior of thermally tempered glass in detail, a simple and straight method suggested by Gupta was applied, where the crack size after indentation is measured by microscope directly. As a result, it was found that the surface compressive residual stress in thermally tempered glass not only strengthen but also restrain the crack growth.

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The anti-plane shear crack in a finite thickness plate is analyzed by the continuously distributed dislocations model and the stress intensity factors are calculated. The results are compared with those in an infinite thickness plate. It is found that the larger the ratio of the crack length to the plate thickness is, the larger the stress intensity factor is and that the Mode II component accompanies with the Mode III component, which does never appear in an infinite thickness plate. The Mode II stress intensity factor appears strongly near the plate surfaces and vanishes at the center of the plate in the thickness direction. This indicates the crack surface inclines steeply near the plate surfaces and does not incline at the center.

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Fluorine (F)-doped, antimony (Sb)-doped, fluorine and antimony co-doped tin oxide (SnO₂) thin films were prepared by ultrasonic spray pyrolysis technique using SnCl₂, NH₄F and SbCl₃ as precursors of Sn, F and Sb elements respectively. F and Sb doping concentrations carried out from 1 to 20 wt% and 1 to 4 wt% in F-doped and Sb-doped SnO₂ films respectively. In F and Sb co-doped SnO₂ films, the proportions of F and Sb to Sn in starting solution were 15 and 2 wt% respectively. XRD patterns showed that the preferred orientation of SnO₂:F, SnO₂:Sb and SnO₂:F, Sb is dependent on the doping concentration. The variation of doping concentration and preferred orientation of the films was reflected in their morphology as investigated by SEM. The electrical properties of the films were performed by Hall effect measurements in van der Pauw configuration. The minimum resistivity values of SnO₂:F and SnO₂:Sb were found in the films doped with 15 wt% of F and 2 wt% of Sb. However, The minimum of resistivity value of F and Sb co-doped SnO₂ films is not better than neither the one of F-doped nor the one of Sb-doped SnO₂ films. The optical transmission of SnO₂:F films was found to increase with increasing in F doping concentration. Whereas the optical transmission of SnO₂:Sb was found to decrease with increasing in Sb concentration. The F and Sb co-doped SnO₂ films annealed in three different conditions at 500°C show the lower transmission values than the value obtained in the as-prepared SnO₂:F, Sb films.

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This research compared the corrosion behavior of the Ni plated and the un-plated Hastelloy C-276 and stainless steel 316 EAS coatings in 2M NaOH solution at 25°C using electrochemical technique. The results can be summarized that Ni plating of approximately 10 microns thick as a sealant can improve the corrosion resistance of the EAS coatings. The as sprayed Hastelloy C-276 coating exhibits higher corrosion rate than the as sprayed stainless steel 316 coating. The corrosion behavior can be improved further by smoothening of the EAS coating surface before plating. The corrosion resistance of the smoothened Hastelloy C-276 coatings, both plated and un-plated, are superior to those of the stainless steel 316 coatings.

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A novel initiator, tin(II) hexoxide, has been synthesized for use in the bulk ring-opening polymerization of ε-caprolactone at 140 °C and the kinetics studied using dilatometry. The effectiveness of the new initiator was compared alongside that of the corresponding conventional system, tin(II) octoate / 1-hexanol. The results showed that tin(II) hexoxide, although effective, took time to dissolve in the monomer due to its molecular aggregation, leading to a prolonged induction period. Despite this, first-order kinetics, a high conversion (>90%) and a polycaprolactone (PCL) molecular weight sufficiently high for melt processing were obtained. The small-scale melt spinning of PCL monofilament fibers and the effect of off-line drawing on their tensile properties is also briefly described. This work highlights the potential for the further development of more soluble tin(II) alkoxides for use as initiators which can offer greater reaction control in cyclic ester polymerization.

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