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Basem M A Abdo, Saqib Anwar, Abdulaziz M El-Tamimi, Emad Abouel Nasr
Fabrication of precise micro-features in bioceramic materials is still a challenging task. This is because of the inherent properties of bioceramics, such as low fracture toughness, high hardness, and brittleness. This paper places an emphasis on investigating the multi-objective optimization of fabrication of microchannels in alumina (Al₂O₃) bioceramics by using rotary ultrasonic machining (RUM). The influence of five major input parameters, namely vibration frequency, vibration amplitude, spindle speed, depth of cut, and feed rate on the surface quality, edge chipping, and dimensional accuracy of the milled microchannels was analyzed...
February 18, 2019: Materials
Bishwajeet Singh Bhardwaj, Takeshi Sugiyama, Naoko Namba, Takayuki Umakoshi, Takafumi Uemura, Tsuyoshi Sekitani, Prabhat Verma
The application of dinaphthothienothiophene (DNTT) molecules, a novel organic semiconductor material, has recently increased due to its high charge carrier mobility and thermal stability. Since the structural properties of DNTT molecules, such as the molecular density distribution and molecular orientations, significantly affect their charge carrier mobility in organic field-effect transistors devices, investigating these properties would be important. Here, we report Raman spectroscopic studies on DNTT in a transistor device, which was further analyzed by the density functional theory...
February 18, 2019: Materials
Jinrong Lu, Jinshan Hu, Yinghua Liang, Wenquan Cui
Ursolic acid (UA) as a natural ursane-triterpenoid has rich pharmacological activities. We have found that it possesses aggregation properties and could self-assemble into organogels. Based on the aggregation property of ursolic acid in suitable solvents, its derivative appended with aromatic rings by amide groups was synthesized. The property of self-assembly into organogel was studied in this paper. The results revealed that this derivative could form supramolecular gel in halogenated benzene and also gelate chloroform in the presence of toluene or p -xylene...
February 18, 2019: Materials
Yajian Wang, Yuyou Yang, Mingjiang Tao
Understanding the underlying processes associated with the viscoelasticity performance of ethylene-propylene-diene monomer (EPDM) during its service life is essential for assessing and predicting its waterproofing performance in underground infrastructure. The viscoelasticity of the polymer is closely related to its free volume, and both of these properties depend on multiple factors, such as temperature, stress magnitude, and strain level. To explore the fundamental viscoelastic behavior of EPDM using free volume as a proxy for viscoelasticity, this article investigates the influence of temperature, stress magnitude, and strain level, as well as their combined effect, on the free volume through molecular dynamics (MD) simulations...
February 18, 2019: Materials
Enrique Sodupe Ortega, Andres Sanz-Garcia, Alpha Pernia-Espinoza, Carmen Escobedo-Lucea
Hybrid constructs represent substantial progress in tissue engineering (TE) towards producing implants of a clinically relevant size that recapitulate the structure and multicellular complexity of the native tissue. They are created by interlacing printed scaffolds, sacrificial materials, and cell-laden hydrogels. A suitable biomaterial is a polycaprolactone (PCL); however, due to the higher viscosity of this biopolymer, three-dimensional (3D) printing of PCL is slow, so reducing PCL print times remains a challenge...
February 18, 2019: Materials
Li He, Yan Wang, Jinghui Gao, Jianhong Wang, Tongxin Zhao, Zhixin He, Zuting Zhong, Xingmin Zhang, Lisheng Zhong
Recently, tricritical ferroelectrics have been drawn tremendous attention, owing to their ultrahigh dielectric permittivities of up to εr > 5 × 10⁴, and their consideration for prototype materials in the development of high-performance energy storage devices. Nevertheless, such a materials system suffers from the disadvantage of low breakdown strength, which makes its energy density far from the satisfactory level for practical application. In this paper, a material-modification approach has been reported, for improving the dielectric strength for tricritical ferroelectric materials Ba(Ti1- x Sn x )O₃ (BTS) through doping with Bi1...
February 18, 2019: Materials
Michał Sarnowski, Karol J Kowalski, Jan B Król, Piotr Radziszewski
In the course of manufacturing, transport and installation, road bitumens and asphalt mixtures can be exposed to the impact of elevated process temperatures exceeding 240 °C. This mainly applies to the mixtures used for road pavements and bridge deck insulation during adverse weather conditions. The heating process should not change the basic and rheological properties of binders and the asphalt mixtures that to a degree cause the degradation of asphalt pavement durability. The work involved analyzing the properties of non-modified bitumens and SBS polymer modified bitumens, heated at temperatures of 200 °C, 250 °C and 300 °C for 1 h...
February 18, 2019: Materials
Mohanraj Murugesan, Dong Won Jung
Consistent and reasonable characterization of the material behavior under the coupled effects of strain, strain rate and temperature on the material flow stress is remarkably crucial in order to design as well as optimize the process parameters in the metal forming industrial practice. The objective of this work was to formulate an appropriate flow stress model to characterize the flow behavior of AISI-1045 medium carbon steel over a practical range of deformation temperatures (650⁻950 ∘ C) and strain rates (0...
February 18, 2019: Materials
Fei Li, Hongjun Ni, Lixiang Yang, Yi Jiang, Donghong Wang, Baode Sun
The interaction between alloy melt and mold facecoats is the main factor affecting the surface quality of investment casting nickel-based superalloys. An investigation was undertaken to develop suitable refractories as facecoat materials for the directionally solidified blades of DZ22B nickel-based superalloys in order to avoid a sand-burning defect. The wettability and interface reactions between alloy melt and various facecoats were studied by using a sessile drop experiment and the real investment casting method, respectively...
February 18, 2019: Materials
Weizhe Hao, Xuejun Zhang, Yanhong Tian
Poly(p-phenylene benzobisoxazole) (PBO) fiber shows fascinating properties including excellent mechanical performance, high crystallinity, and fairly good heat resistance as a kind of polymer fiber. Its properties make it a possible candidate as a precursor of carbon fiber. This paper mainly investigates the possibility of yielding carbon fiber from PBO by direct carbonization using a continuous process and multiple properties of yielded fiber treated under different heat treatment temperature (HTT). The results show that PBO fiber was able to sustain an HTT as high as 1400 °C under the inert atmosphere and that the shape of fiber was still preserved without failure...
February 18, 2019: Materials
Wenhan Lyu, Xianmei Wu, Weijiang Xu
The nonlinear spring model combined with dislocation dipole theory was applied to describe the acoustic nonlinearity during the fatigue process in metals. The spring stiffness changes with fatigue degree. For the early stage, spring stiffness approaches infinity, and the heavier nonlinearity mainly results from the increase of dislocation density. Further fatigue leads to the occurrence of micro-cracks, during which spring stiffness begins to decrease. Abundant micro-crack sprouting accelerates the crack's expansion, and spring stiffness drops quickly, which causes the obvious decline in the transmitted harmonic amplitudes...
February 18, 2019: Materials
Zhuangzhuang Liu, Xiaonan Huang, Aimin Sha, Hao Wang, Jiaqi Chen, Cheng Li
The adhesion bonding between asphalt and aggregate significantly influences field performance and durability of asphalt pavement. Adhesion promoters are typically used to improve asphalt-aggregate bonding and minimize moisture-related pavement damage, such as cracking and raveling. This study evaluated the effectiveness of plant ash byproduct as adhesion promoter to improve asphalt-aggregate adhesion performance. Three commonly used aggregate types (granite, basic rock, and limestone) and two asphalt binder types were used in laboratory testing...
February 18, 2019: Materials
Wenyue Li, Nazifah Islam, Guofeng Ren, Shiqi Li, Zhaoyang Fan
There is strong interest in developing high-frequency (HF) supercapacitors or electrochemical capacitors (ECs), which can work at the hundreds to kilo hertz range for line-frequency alternating current (AC) filtering in the substitution of bulky aluminum electrolytic capacitors, with broad applications in the power and electronic fields. Although great progress has been achieved in the studies of electrode materials for ECs, most of them are not suitable to work in this high frequency range because of the slow electrochemical processes involved...
February 18, 2019: Materials
Yuxia Liu, Kai Jiang, Shuting Yang
A novel integrated electrode structure was designed and synthesized by direct electrodepositing of Cu⁻Sn alloy anode materials on the Celgard 2400 separator (Cel-CS electrode). The integrated structure of the Cel-CS electrode not only greatly simplifies the battery fabrication process and increases the energy density of the whole electrode, but also buffers the mechanical stress caused by volume expansion of Cu⁻Sn alloy active material; thus, effectively preventing active material falling off from the substrate and improving the cycle stability of the electrode...
February 18, 2019: Materials
Xin Zhao, Minshu Du, Feng Liu
As the sole metal that could reduce CO₂ to substantial amounts of hydrocarbons, Cu plays an important role in electrochemical CO₂ reduction, despite its low energy efficiency. Surface morphology modification is an effective method to improve its reaction activity and selectivity. Different from the pretreated modification method, in which the catalysts self-reconstruction process was ignored, we present operando synthesis by simultaneous electro-dissolution and electro-redeposition of copper during the CO₂ electroreduction process...
February 17, 2019: Materials
Tatyana Elkin, Stacy M Copp, Ryan L Hamblin, Jennifer S Martinez, Gabriel A Montaño, Reginaldo C Rocha
Polystyrene- b -polyethylene glycol (PS- b -PEG) amphiphilic block copolymers featuring a terminal tridentate N,N,N -ligand (terpyridine) were synthesized for the first time through an efficient route. In this approach, telechelic chain-end modified polystyrenes were produced via reversible addition-fragmentation chain-transfer (RAFT) polymerization by using terpyridine trithiocarbonate as the chain-transfer agent, after which the hydrophilic polyethylene glycol (PEG) block was incorporated into the hydrophobic polystyrene (PS) block in high yields via a thiol-ene process...
February 17, 2019: Materials
Faisal I Shalabi, Javed Mazher, Kaffayatullah Khan, Mohammed Alsuliman, Ibrahim Almustafa, Ward Mahmoud, Naif Alomran
In this study, cement-treated waste sand as a by-product material produced from Al-Ahsa quarries (Saudi Arabia) was experimentally tested and investigated as a base course material for the foundation of structures and roads. The study aimed to use the waste sand as a construction material by improving its strength, bearing capacity, and stiffness. The waste sand was mixed with different percentages of Portland cement content (0, 2, 4, 6, and 8%) at the maximum dry density and optimum water content of the standard Proctor compaction conditions of a non-treated sample...
February 17, 2019: Materials
Tong Tang, Xiufang Chen, Bo Zhang, Xianmiao Liu, Benhua Fei
In this study, the effects of tung oil heat treatment on the physico-mechanical properties of moso bamboo were investigated. Here, heat treatment in tung oil at 100⁻200 °C was used to modify natural bamboo materials. The changes in the nanostructures of cell walls in bamboo caused by oil heat treatment, like density, chemical compositions, and cellulose crystalline, were evaluated to study their correlation with mechanical properties. Results showed that the mechanical performance of bamboo, such as ultimate stress, modulus of elasticity (MOE), and modulus of rupture (MOR), didn't reduce after heat treatment below 200 °C, compared with the untreated bamboo, which was mainly due to the tung oil uptake, stable cellulose content, and the increment of cellulose crystalline...
February 17, 2019: Materials
Hoang-Nam Nguyen, Tan-Y Nguyen, Ke Van Tran, Thanh Trung Tran, Truong-Thinh Nguyen, Van-Duc Phan, Thom Van Do
Triple-layered composite plates are created by joining three composite layers using shear connectors. These layers, which are assumed to be always in contact and able to move relatively to each other during deformation, could be the same or different in geometric dimensions and material. They are applied in various engineering fields such as ship-building, aircraft wing manufacturing, etc. However, there are only a few publications regarding the calculation of this kind of plate. This paper proposes novel equations, which utilize Mindlin's theory and finite element modelling to simulate the forced vibration of triple-layered composite plates with layers connected by shear connectors subjected to a moving load...
February 16, 2019: Materials
Marco Tatullo, Gianrico Spagnuolo, Bruna Codispoti, Fausto Zamparini, Anqi Zhang, Micaela Degli Esposti, Conrado Aparicio, Carlo Rengo, Manuel Nuzzolese, Lucia Manzoli, Fabio Fava, Carlo Prati, Paola Fabbri, Maria Giovanna Gandolfi
Human periapical cyst mesenchymal stem cells (hPCy-MSCs) are a newly discovered cell population innovatively collected from inflammatory periapical cysts. The use of this biological waste guarantees a source of stem cells without any impact on the surrounding healthy tissues, presenting a valuable potential in tissue engineering and regenerative medicine applications. In the present study, hPCy-MSCs were collected, isolated, and seeded on three experimental mineral-doped porous scaffolds produced by the thermally-induced phase-separation (TIPS) technique...
February 16, 2019: Materials
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