bluuebunny/crossref_metadata_2025 huggingface dataset:
Hybrid TiO2–Polyaniline Photocatalysts and their Application in Building Gypsum Plasters
Authors: Sulowska Agnieszka , Wysocka Izabela , Pelczarski Daniel , Karczewski Jakub , Zielińska-Jurek Anna
Published: April 2020

Hybrid materials of conjugated polymer and titanium(IV) oxide have attracted considerable attention concerning their potential benefits, including (i) efficient exploitation of visible light, (ii) a high adsorption capacity for organic contaminants, (iii) and effective charge carriers separation. The new class of the photocatalysts is promising for the removal of environmental pollutants in both aqueous and gaseous phases. For the first time, in this study, the polyaniline (PANI)–TiO2 hybrid composite was used for the degradation of phenol in water and toluene in the gas phase. Polyaniline–TiO2 was prepared by the in situ polymerization of aniline on the TiO2 surface. The obtained hybrid material was characterized by diffuse reflectance spectroscopy (DR/UV-Vis), X-ray diffraction (XRD), fast-Fourier transformation spectroscopy (FTIR), photoluminescence (PL) spectroscopy, microscopy analysis (SEM/TEM), and thermogravimetric analysis (TGA). An insight into the mechanism was shown based on the photodegradation analysis of charge carrier scavengers. Polyaniline is an efficient TiO2 photosensitizer for photodegradation in visible light (λ > 420 nm). The trapping experiments revealed that mainly h+ and ˙OH were the reactive oxygen species that were responsible for phenol degradation. Furthermore, the PANI–TiO2 hybrid nanocomposite was used in gypsum plaster to study the self-cleaning properties of the obtained building material. The effect of PANI–TiO2 content on the hydrophilic/hydrophobic properties and crystallographic structure of gypsum was studied. The obtained PANI–TiO2-modified gypsum plaster had improved photocatalytic activity in the reaction of toluene degradation under Vis light.
Nailing of Layers: A Promising Way to Reinforce Concrete 3D Printing Structures
Authors: Perrot A. , Jacquet Y. , Rangeard D. , Courteille E. , Sonebi M.
Published: April 2020

Today, the extrusion-based 3D printing of concrete is a potential breakthrough technology for the construction industry. It is expected that 3D printing will reduce the cost of construction of civil engineering structures (removal of formwork) and lead to a significant reduction in time and improve working environment conditions. Following the use of this additive manufacturing layer-wise process, it is required to change the way concrete structures are designed and reinforced, especially for the parts of the structure under tension loads. Indeed, the extrusion-based concrete 3D printing process does not allow for the production of conventional reinforced concrete, and there is a need to develop other ways of compensating for the low mechanical performances of concrete, particularly in tension. In this study, the reinforcement of printed structures by using steel nails through the deposited layers of fresh concrete was investigated. Additionally, three-layer and 10-layer samples were reinforced with nails with varying inclination and spacing. The results show that inclined nails can be used to provide a flexural strengthening of the printing material in different directions.
Evaluation of Implants with Different Macrostructures in Type I Bone—Pre-Clinical Study in Rabbits
Authors: de Carvalho Silva Leocádio Amanda , Silva Júnior Matusalém , José Pimentel Lopes de Oliveira Guilherme , da Col Santos Pinto Gustavo , Silveira Faeda Rafael , Marques Padovan Luis Eduardo , Marcantonio Júnior Élcio
Published: April 2020

The objective of this study was to assess the primary stability and the osseointegration process in implants with different macrostructures (Cylindrical vs. Hybrid Conical) in rabbit tibiae. Twenty-four (24) rabbits were used, divided into 3 experimental periods (2, 4 and 8 weeks) with 8 animals each. Each animal bilaterally received 2 implants from each group in the tibial metaphysis: Cylindrical Implant (CI) and Hybrid Conical Implant (HCI). All implants were assessed for insertion torque. After the experimental periods, one of the implants in each group was submitted to the removal counter-torque test and descriptive histological analysis while the other implant was used for microtomographic and histometric analysis (%Bone-Implant Contact). HCI implants showed higher insertion torque (32.93 ± 10.61 Ncm vs. 27.99 ± 7.80 Ncm) and higher % of bone-implant contact in the 8-week period (79.08 ± 11.31% vs. 59.72 ± 11.29%) than CI implants. However, CI implants showed higher values of removal counter-torque than HCI implants in the 8-week period (91.05 ± 9.32 Ncm vs. 68.62 ± 13.70 Ncm). There were no differences between groups regarding microtomographic data. It can be concluded that HCI implants showed greater insertion torque and bone-implant contact in relation to CI implants in the period of 8 weeks when installed in cortical bone of rabbits.
Study on Tribological Properties and Mechanisms of Different Morphology WS2 as Lubricant Additives
Authors: Hu Ningning , Zhang Xiuheng , Wang Xianghui , Wu Na , Wang Songquan
Published: April 2020

In the present work, the relationship curve of the coefficient of friction (COF) with varying loads of different morphology WS2 lubricating additives in the friction process at various sliding speeds was studied. On this basis, wear marks and elements on the wear surfaces after friction were analyzed, and then the anti-wear and mechanism effects of WS2 of different forms in the lubrication process were discussed. Meanwhile, the Stribeck curve was used to study the lubrication state of the lubricating oil in the friction process. It was revealed that the COF of lubricating oil containing lamellar WS2 decreased by 29.35% at optimum condition and the minimum COF was concentrated at around 100 N. The COF of lubricating oil containing spherical WS2 decreased by 30.24% and the minimum coefficient was concentrated at 120 N. The extreme pressure property of spherical WS2 was better than that of lamellar WS2, and the wear resistance of spherical WS2 was more stable when the load was over 80 N. The different morphology of WS2 additives can play anti-wear and anti-friction roles within a wide range of sliding speeds.
Modelling the Surface Plasmon Spectra of an ITO Nanoribbon Grating Adjacent to a Liquid Crystal Layer
Authors: Reshetnyak Victor Yu. , Zadorozhnii Victor I. , Pinkevych Igor P. , Bunning Timothy J. , Evans Dean R.
Published: April 2020

The reflection and transmission coefficients of an indium tin oxide (ITO) nanoribbon grating placed between a nematic liquid crystal (LC) layer and an isotropic dielectric medium are calculated in the infrared region. Reflection and transmission spectra in the range of 1–5 μm related to the surface plasmon excitation in the ITO nanoribbons are obtained. Dependence of the peak spectral position on the grating spacing, the ribbon aspect ratio, and the 2D electron concentration in the nanoribbons is studied. It is shown that director reorientation in the LC layer influences the plasmon spectra of the grating, enabling a control of both the reflection and transmission of the system. The data obtained with our model are compared to the results obtained using COMSOL software, giving the similar results.
Hydrochloric Acid Pretreatment of Different Types of Rice Husk Ash Influence on the Properties of Cement Paste
Authors: Liu Jing , Xie Chunyan , Fu Chao , Wei Xiuli , Wu Dake
Published: April 2020

When properly processed, rice husk ash (RHA) comprises a large amount of SiO2, which exhibits a high pozzolanic activity and acts as a good building filler. In this paper, the effects of rice husk ash content, acid pretreatment, and production regions on the compressive and flexural properties and water absorption of a cement paste were studied. The experimental results showed that the compressive strength of the rice husk ash was the highest with a 10% content level, which was about 16.22% higher than that of the control sample. The rice husk after acid pretreatment displayed a higher strength than that of the sample without the acid treatment, and the rice husk from the Inner Mongolia region indicated a higher strength than that from the Guangdong province. However, the flexural strength of each group was not significantly different from that of the blank control group. The trend observed for the water absorption was similar to that of the compressive strength. The variation in the RHA proportions had the greatest influence on the properties of the paste specimens, followed by the acid pretreatments of the rice husks. The production regions of the rice husks indicated the least influence.
Plasmonic Emission of Bullseye Nanoemitters on Bi2Te3 Nanoflakes
Authors: Yan Qigeng , Li Xiaoli , Liang Baolai
Published: April 2020

Topological insulators, such as Bi2Te3, have been confirmed to exhibit plasmon radiation over the entire visible spectral range. Herein, we fabricate bullseye nanoemitters, consisting of a central disk and concentric gratings, on the Bi2Te3 nanoflake. Due to the existence of edge plasmon modes, Bi2Te3 bullseye nanostructures are possible to converge light towards the central disk. Taking advantage of the excellent spatial resolution of cathodoluminescence (CL) characterization, it has been observed that plasmonic behaviors depend on the excitation location. A stronger plasmonic intensity and a wider CL spectral linewidth can be obtained at the edge of the central disk. In order to further improve the focusing ability, a cylindrical Pt nanostructure has been deposited on the central disk. Additionally, the finite element simulation indicates that the electric-field enhancement originates from the coupling process between the plasmonic emission from the Bi2Te3 bullseye and the Pt nanostructure. Finally, we find that enhancement efficiency depends on the thickness of the Pt nanostructure.
Reactive Infiltration and Microstructural Characteristics of Sn-V Active Solder Alloys on Porous Graphite
Authors: Zhang Yubin , Liao Xinjiang , Lin Qiaoli , Mu Dekui , Lu Jing , Huang Hui , Huang Han
Published: April 2020

In this work, the reactive wetting and infiltration behaviors of a newly designed Sn-V binary alloy were comprehensively explored on porous graphite for the first time. It was discovered that 0.5 wt.% addition of V can obviously improve the wettability of liquid Sn on porous graphite and the nominal V contents in Sn-V binary alloys has minor effects on the apparent contact angles wetted at 950 °C. Moreover, the V-containing Sn-V alloys were initiated to spread on porous graphite at ~650 °C and reached a quasi-equilibrium state at ~900 °C. Spreading kinetics of Sn-3V alloy on porous graphite well fitted in the classic product reaction controlled (PRC) model. However, our microstructural characterization demonstrated that, besides vanadium carbide formation, the adsorption of V element at the wetting three-phase contact line spontaneously contributed to the reactive spreading and infiltrating of Sn-V alloys on porous graphite. Meanwhile, the formation of continuous vanadium carbides could completely block the infiltration of Sn-V active solder alloy in porous graphite. Affected by the growth kinetics of vanadium carbides, the infiltration depth of Sn-V alloys in porous graphite decreased at increased isothermal wetting temperatures. This work is believed to provide implicative notions on the fabrication of graphite related materials and devices using novel V-containing bonding alloys.
Chromium Concentrate Recovery from Solid Tannery Waste in a Thermal Process
Authors: Famielec Stanisław
Published: April 2020

Leather processing requires substantial inputs of energy, water and chemicals. Additionally, it generates significant amounts of liquid and solid waste, severely impacting the environment. Processing 1 Mg of raw hides yields up to 600–700 kg of waste, considerable amounts of which are solid tannery waste. Such waste contains chromium (Cr) compounds, which are commonly used as tanning agents. This paper reviews solid tannery waste treatment technologies, with emphasis on waste incineration in a specially designed experimental tunnel incinerator. Three different types of tannery waste were subjected to tests: trimmings, shavings and buffing dust. As the research revealed, the process can be applied to all types of solid tannery waste. Moreover, it enables the reuse of the heat of the process and results in a Cr concentrate in the process residues. The conducted analyses (carbon, hydrogen and nitrogen elemental analysis; inductively coupled plasma optical emission spectroscopy; powder X-ray diffraction) proved that there is no or little organic content in the obtained residual ash, which contains up to 53.1%(w/w) Cr in the form of Cr (III) oxide. Such material may be used as a Cr ore substitute in the chemical or metallurgical industries.
Fabrication of Hollow and Porous Tin-Doped Indium Oxide Nanofibers and Microtubes via a Gas Jet Fiber Spinning Process
Authors: Ghosh Monoj , Jana Sadhan C.
Published: April 2020

We report the morphologies of tin-doped indium oxide (ITO) hollow microtubes and porous nanofibers produced from precursor solutions of polyvinylpyrrolidone (PVP), indium chloride (InCl3), and stannic chloride (SnCl4). The polymer precursor fibers are produced via a facile gas jet fiber (GJF) spinning process and subsequently calcined to produce ITO materials. The morphology shows strong dependence on heating rate in calcination step. Solid porous ITO nanofibers result from slow heating rates while hollow tubular ITO microfibers with porous shells are produced at high heating rates when calcined at a peak temperature of 700 °C. The mechanisms of formation of different morphological forms are proposed. The ITO fibers are characterized using several microscopy tools and thermogravimetric analysis. The concentration of inorganic salts in precursor solution is identified as a key factor in determining the porosity of the shell in hollow fibers. The data presented in this paper show that GJF method may be suitable for fabrication of hollow and multi-tubular metal oxide nanofibers from other inorganic precursor materials.
Minimization of the Influence of Shear-Induced Particle Migration in Determining the Rheological Characteristics of Self-Compacting Mortars and Concretes
Authors: Baumert Christian , Garrecht Harald
Published: April 2020

Determining the exact rheological properties of cementitious materials in fundamental units is a crucial step in concrete science. It is undisputed that before measuring rheological properties in concrete rheometers, it is necessary to pre-shear the fresh mortar or concrete. Due to the migration of the coarse particles into areas with lower shear stress, however, segregation takes place. An experimental set-up was developed to determine the effects on the measured values of the concrete rheometer ICAR. This allows the active homogenization (pre-shearing) of the material before each change of speed. In the tests higher raw values (macroscopic data) could be measured. This clearly influences the calculated rheological Bingham parameters and modified Bingham parameters for a self-compacting concrete (SCC) with a maximum grain size of 16 mm. Therefore, the homogeneity of the material, a main hypothesis of rheological measurements, does not seem to be fulfilled with the coaxial rheometer used. The process of the indispensable pre-shearing therefore requires more attention in the future so that measurement errors can be minimized. Especially in numerical simulation, suitable rheological models and the realistic determination of parameters are crucial. Since the shear-induced particle migration is largely dependent on the maximum grain size, an ultra-high performance concrete (UHPC) with a maximum particle size of only 0.5 mm was also investigated in the laboratory mixer KNIELE KKM-RT. The integrated rheometer enables also the active homogenization of the fresh concrete during pre-shearing but without the danger of over-mixing, as it is the case for the experimental ICAR setup. This article proves that relevant differences can also be identified for such a material.
Model-Based Roentgen Stereophotogrammetric Analysis to Monitor the Head–Taper Junction in Total Hip Arthroplasty in Vivo—And They Do Move
Authors: Xu Jing , Sonntag Robert , Kretzer J. Philippe , Taylor Dominic , Forst Raimund , Seehaus Frank
Published: April 2020

Model-based Roentgen stereophotogrammetric analysis (RSA) using elementary geometrical shape (EGS) models allows migration measurement of implants without the necessity of additional attached implant markers. The aims of this study were: (i) to assess the possibility of measuring potential head–taper movement in THA in vivo using model-based RSA and (ii) to prove the validity of measured head–taper migration data in vitro and in vivo. From a previous RSA study with a 10 years follow-up, retrospectively for n = 45 patients head–taper migration was calculated as the relative migration between femoral ball head and taper of the femoral stem using model-based RSA. A head–taper migration of 0.026 mm/year can be detected with available RSA technology. In vitro validation showed a total migration of 268 ± 11 µm along the taper axis in a similar range to what has been reported using the RSA method. In vivo, a proof for interchangeable applicability of model-based RSA (EGS) and standard marker-based RSA methods was indicated by a significant deviation within the migration result after 12-month follow-up for all translation measurements, which was significantly correlated to the measured head–taper migration (r from 0.40 to 0.67; p < 0.05). The results identified that model-based RSA (EGS) could be used to detect head–taper migration in vivo and the measured movement could be validated in vitro and in vivo as well. Those findings supported the possibility of applying RSA for helping evaluate the head–taper corrosion related failure (trunnionosis).
Improving Dispersion of Recycled Discontinuous Carbon Fibres to Increase Fibre Throughput in the HiPerDiF Process
Authors: Pozegic Thomas R. , Huntley Samantha , Longana Marco L. , He Suihua , Bandara R. M. Indrachapa , King Simon G. , Hamerton Ian
Published: April 2020

In order to increase the material throughput of aligned discontinuous fibre composites using technologies such as HiPerDiF, stability of the carbon fibres in an aqueous solution needs to be achieved. Subsequently, a range of surfactants, typically employed to disperse carbon-based materials, have been assessed to determine the most appropriate for use in this regard. The optimum stability of the discontinuous fibres was observed when using the anionic surfactant, sodium dodecylbenzene sulphonate, which was superior to a range of other non-ionic and anionic surfactants, and single-fibre fragmentation demonstrated that the employment of sodium dodecylbenzene sulphonate did not affect the interfacial adhesion between fibres. Rheometry was used to complement the study, to understand the potential mechanisms of the improved stability of discontinuous fibres in aqueous suspension, and it led to the understanding that the increased viscosity was a significant factor. For the shear rates employed, fibre deformation was neither expected nor observed.
Improved Microstructure and Hardness Properties of Low-Temperature Microwave-Sintered Y2O3 Stabilized ZrO2 Ceramics with Additions of Nano TiO2 Powders
Authors: Weng Min-Hang , Lin Cheng-Xun , Huang Cian-Song , Tsai Chin-Yi , Yang Ru-Yuan
Published: April 2020

This paper reports the improvement of microstructural and hardness properties of 3 mol% yttria-stabilized zirconia (3Y-TZP) ceramics with nano TiO2 powders (with 0, 0.9, 1.8, and 2.7 wt%) added using a low-temperature microwave-assisted sintering of 1250 °C. Even at such a low sintering temperature, all sintered samples had the main phase of tetragonal zirconia (t-ZrO2) without the appearance of the secondary monoclinic phase or TiO2 phase, and had high relative densities, larger than 95%. The grain growth was well developed, and the grain sizes were around 300–600 nm. The Ti and O elements appeared at the grain and grain boundary and increased with the increased nano TiO2 contents identified by the element analysis, although the TiO2 phase did not appear in the X-ray pattern. The Vickers hardness was in the range of 10.5 to 14.5 GPa, which first increased with increasing content till 0.9 wt% and then decreased. With citric acid corrosion treatment for 10 h, the Vickers hardness only decreased from 14.34 GPa to 13.55 GPa with the addition of 0.9 wt% nano TiO2 powder. The experiment results showed that 0.9 wt% nano TiO2 addition can improve the densification as well as the Vickers hardness under a low temperature of microwave-assisted sintering.
What Is the Value of Water Contact Angle on Silicon?
Authors: Bryk Paweł , Korczeniewski Emil , Szymański Grzegorz S. , Kowalczyk Piotr , Terpiłowski Konrad , Terzyk Artur P.
Published: April 2020

Silicon is a widely applied material and the wetting of silicon surface is an important phenomenon. However, contradictions in the literature appear considering the value of the water contact angle (WCA). The purpose of this study is to present a holistic experimental and theoretical approach to the WCA determination. To do this, we checked the chemical composition of the silicon (1,0,0) surface by using the X-ray photoelectron spectroscopy (XPS) method, and next this surface was purified using different cleaning methods. As it was proved that airborne hydrocarbons change a solid wetting properties the WCA values were measured in hydrocarbons atmosphere. Next, molecular dynamics (MD) simulations were performed to determine the mechanism of wetting in this atmosphere and to propose the force field parameters for silica wetting simulation. It is concluded that the best method of surface cleaning is the solvent-reinforced de Gennes method, and the WCA value of silicon covered by SiO2 layer is equal to 20.7° (at room temperature). MD simulation results show that the mechanism of pure silicon wetting is similar to that reported for graphene, and the mechanism of silicon covered by SiO2 layer wetting is similar to this observed recently for a MOF.
Detection of Flaws in Concrete Using Ultrasonic Tomography and Convolutional Neural Networks
Authors: Słoński Marek , Schabowicz Krzysztof , Krawczyk Ewa
Published: April 2020

Non-destructive testing of concrete for defects detection, using acoustic techniques, is currently performed mainly by human inspection of recorded images. The images consist of the inside of the examined elements obtained from testing devices such as the ultrasonic tomograph. However, such an automatic inspection is time-consuming, expensive, and prone to errors. To address some of these problems, this paper aims to evaluate a convolutional neural network (CNN) toward an automated detection of flaws in concrete elements using ultrasonic tomography. There are two main stages in the proposed methodology. In the first stage, an image of the inside of the examined structure is obtained and recorded by performing ultrasonic tomography-based testing. In the second stage, a convolutional neural network model is used for automatic detection of defects and flaws in the recorded image. In this work, a large and pre-trained CNN is used. It was fine-tuned on a small set of images collected during laboratory tests. Lastly, the prepared model was applied for detecting flaws. The obtained model has proven to be able to accurately detect defects in examined concrete elements. The presented approach for automatic detection of flaws is being developed with the potential to not only detect defects of one type but also to classify various types of defects in concrete elements.
Gradient-Modified HfC-SiC Mixed Bi-Interlayers Synthesized under Different TMS Flow Rate Increment for Depositing Diamond Coating onto WC-Co Substrate
Authors: Zheng Ke , Gao Jie , Yu Shengwang , Wang Yongsheng , Hei Hongjun , Ma Yong , Zhou Bing , Tang Bin , Wu Yucheng
Published: April 2020

To deposit well-adhered diamond coating, gradient-modified hafnium carbide-silicon carbide (HfC-SiC) mixed bi-interlayers were prepared on cemented carbides (WC-Co) by plasma surface metallurgy technique under the different tetramethylsiline (TMS) flow rate increment. The effects of the TMS flow rate increment on the composition, microstructure, adhesion, and hardness of the bi-interlayers were investigated. Then, the well-adhered bi-interlayer was chosen for the deposition of the diamond coating. It was found that the HfC-SiC mixed bi-interlayers consisted of a diffusion-modified HfC-riched inner layer and a SiC-riched outer layer. The TMS flow rate increment played a key role in tailoring the surface morphology, thickness, and interface character of the bi-interlayer. The dense nanocrystalline diamond coating was formed on the optimized bi-interlayer at the increment of 0.20 sccm/2 min. The diamond coating showed excellent adhesion, which was benefited from the cobalt (Co) diffusion inhibition, gradient composition distribution, and mechanical interlocking.
Supercritical Phase Inversion: A Powerful Tool for Generating Cellulose Acetate-AgNO3 Antimicrobial Membranes
Authors: Baldino Lucia , Cardea Stefano , Reverchon Ernesto
Published: April 2020

Antimicrobial composite membranes, formed by cellulose acetate loaded with AgNO3 particles, were produced by supercritical phase inversion. Different cellulose acetate concentrations were tested (15%, 20%, 30%(w/w)), whereas the active agent (i.e., silver nitrate) concentration was fixed at 0.1%(w/w) with respect to the quantity of polymer used. To determine the influence of the process parameters on membranes morphology, the pressure and temperature were varied from 150 to 250 bar and from 55 to 35 °C, respectively. In all cases, regularly porous membranes were produced with a uniform AgNO3 distribution in the membrane matrix. Silver release rate depended on membrane pore size, covering a time interval from 8 to 75 h.
Microstructure Influence of SACX0307-TiO2 Composite Solder Joints on Thermal Properties of Power LED Assemblies
Authors: Skwarek Agata , Ptak Przemysław , Górecki Krzysztof , Hurtony Tamás , Illés Balázs
Published: April 2020

The effect of the microstructure of solder joints on the thermal properties of power LEDs is investigated. Solder joints were prepared with different solder pastes, namely 99Sn0.3Ag0.7Cu (as reference solder) and reinforced 99Sn0.3Ag0.7Cu–TiO2 (composite solder). TiO2 ceramic was used at 1 wt.% and with two different primary particle sizes, which were 20 nm (nano) and 200 nm (submicron). The thermal resistance, the electric thermal resistance, and the luminous efficiency of the power LED assemblies were measured. Furthermore, the microstructure of the different solder joints was analyzed on the basis of cross-sections using scanning electron and optical microscopy. It was found that the addition of submicron TiO2 decreased the thermal and electric thermal resistances of the light sources by 20% and 16%, respectively, and it slightly increased the luminous efficiency. Microstructural evaluations showed that the TiO2 particles were incorporated at the Sn grain boundaries and at the interface of the intermetallic layer and the solder bulk. This caused considerable refinement of the Sn grain structure. The precipitated TiO2 particles at the bottom of the solder joint changed the thermodynamics of Cu6Sn5 formation and enhanced the spalling of intermetallic grain to solder bulk, which resulted in a general decrease in the thickness of the intermetallic layer. These phenomena improved the heat paths in the composite solder joints, and resulted in better thermal and electrical properties of power LED assemblies. However, the TiO2 nanoparticles could also cause considerable local IMC (Intermetallic Compounds) growth, which could inhibit thermal and electrical improvements.
The Possibility of Interlocking Nail Fabrication from FFF 3D Printing PLA/PCL/HA Composites Coated by Local Silk Fibroin for Canine Bone Fracture Treatment
Authors: Pitjamit Siwasit , Thunsiri Kittiya , Nakkiew Wasawat , Wongwichai Tunchanok , Pothacharoen Peraphan , Wattanutchariya Wassanai
Published: April 2020

The biomaterials polylactic acid (PLA), polycaprolactone (PCL), and hydroxyapatite (HA) were selected to fabricate composite filaments for 3D printing fused filament fabrication (FFF), which was used to fabricate a composite biomaterial for an interlocking nail for canine diaphyseal fractures instead of metal bioinert materials. Bioactive materials were used to increase biological activities and provide a high possibility for bone regeneration to eliminate the limitations of interlocking nails. HA was added to PLA and PCL granules in three ratios according to the percentage of HA: 0%, 5%, and 15% (PLA/PCL, PLA/PCL/5HA, and PLA/PCL/15HA, respectively), before the filaments were extruded. The test specimens were 3D-printed from the extruded composite filaments using an FFF printer. Then, a group of test specimens was coated by silk fibroin (SF) using the lyophilization technique to increase their biological properties. Mechanical, biological, and chemical characterizations were performed to investigate the properties of the composite biomaterials. The glass transition and melting temperatures of the copolymer were not influenced by the presence of HA in the PLA/PCL filaments. Meanwhile, the presence of HA in the PLA/PCL/15HA group resulted in the highest compressive strength (82.72 ± 1.76 MPa) and the lowest tensile strength (52.05 ± 2.44 MPa). HA provided higher bone cell proliferation, and higher values were observed in the SF coating group. Therefore, FFF 3D-printed filaments using composite materials with bioactive materials have a high potential for use in fabricating an interlocking nail for canine diaphyseal fractures.
Mechanical Characteristics of Cement-Based Grouting Material in High-Geothermal Tunnel
Authors: Wang Mingnian , Hu Yunpeng , Jiang Cheng , Wang Yicheng , Liu Dagang , Tong Jianjun
Published: April 2020

The cement-based grouting materials used for practical purposes in high-geothermal tunnels are inevitably affected by humidity and high temperature, leading to the deterioration of mechanical properties. Based on the characteristics of changing high temperatures and two typical conditions of hot-humid and hot-dry environments in high-geothermal tunnels, many mechanical strength tests were carried out on the grouting material cured under different environmental conditions. The study results indicated that high temperature and low relative humidity were unfavorable to the development of mechanical characteristics of grouting material, but the coupling effect of two factors could improve the strength at early ages and reduce the degradation of long-term strength. As the curing temperature exceeded 56.3 °C, the humidity effect on strength played a more important role in recovering the strength of grouting material damaged by high temperature. Temperature had more significant impact on the relative peak stress while the relative humidity had greater influence on the relative peak strain. A calculation compressive constitutive model was prospered, which considering both temperature and relative humidity. The study results may provide much valuable experimental data and theoretical supporting for the design of compression constitutive of cement-based grouting material in high-geothermal tunnel.
Sustainable Designed Pavement Materials
Authors: Xiao Yue , Erkens Sandra , Li Mingliang , Ma Tao , Liu Xueyan
Published: April 2020

This Special Issue “Sustainable Designed Pavement Materials” has been proposed and organized as a means to present recent developments in the field of environmentally-friendly designed pavement materials. For this reason, articles included in this special issue relate to different aspects of pavement materials, from industry solid waste recycling to pavement materials recycling, from pavement materials modification to asphalt performance characterization, from pavement defect detection to pavement maintenance, and from asphalt pavement to cement concrete pavement, as highlighted in this editorial.
Bone Regeneration and Soft Tissue Enhancement Around Zygomatic Implants: Retrospective Case Series
Authors: Peñarrocha-Diago Miguel , Bernabeu-Mira Juan Carlos , Fernández-Ruíz Alberto , Aparicio Carlos , Peñarrocha-Oltra David
Published: April 2020

Purpose: To present a case series of zygomatic implants combined with bone regeneration and soft tissue enhancement techniques to reduce the risk of biological delayed complications such as maxillary sinusitis and soft tissue recession. Materials and methods: Zygomatic implants placed simultaneously with different bone regeneration techniques (buccal, palatal and buccal-palatal bone regeneration) and soft tissue enhancement techniques (pediculate and free connective tissue graft) were followed for at least 12 months. The following information was collected: patient age and sex, number of zygomatic implants, zygomatic implant success rate, zygomatic implant position according to classification of the Zygomatic Anatomy Guide Approach (ZAGA), sinus membrane perforation, type and outcome of the bone regeneration or the soft tissue enhancement technique, bone gain (width and length along the zygomatic implant) and keratinized buccal mucosa width, duration of follow-up, loading protocol (immediate or delayed) and biological complications (maxillary sinusitis and soft tissue recession). Results: Thirty-one zygomatic implants placed in 19 patients were included. All implants were successful and none of the implants presented biological complications. The bone regeneration technique was successful in 30 of 31 cases with a mean palatal bone width of 3 mm, buccal bone width of 2.65 mm, palatal bone length of 6.5 mm and buccal bone length of 8.3 mm. The success rate of soft tissue enhancement was 100% and it established at least 2 mm of keratinized buccal mucosa width in all implants. Conclusions: Within the limitations of the present study, bone regeneration and soft tissue enhancement techniques were useful to establish more favorable conditions of the peri-implant tissues around zygomatic implants. This could prevent biological complications such as maxillary sinusitis and soft tissue recessions. Prospective and randomized controlled clinical trials with longer follow-up periods are advisable.
High-temperature Mechanical Properties and Their Influence Mechanisms of ZrC-Modified C-SiC Ceramic Matrix Composites up to 1600 °C
Authors: Sha Jianjun , Wang Shouhao , Dai Jixiang , Zu Yufei , Li Wenqiang , Sha Ruyi
Published: April 2020

In order to understand the influence of the mechanisms of ZrC nanoparticles on the high-temperature mechanical properties of C-SiC ceramic matrix composites, the mechanical properties were measured from room temperature (RT) to 1600 °C under vacuum. The microstructures features were characterized by scanning electron microscopy. In comparison with the composites without ZrC nanoparticles, the ZrC-modified composite presented better mechanical properties at all temperatures, indicating that the mechanical properties could be improved by the ZrC nanoparticles. The ZrC nanoparticles could reduce the residual silicon and improve the microstructure integrity of composite. Furthermore, the variation of flexural strength and the flexural modulus showed an asynchronous trend with the increase of temperature. The flexural strength reached the maximum value at 1200 °C, but the highest elastic modulus was obtained at 800 °C. The strength increase was ascribed to the decrease of the thermally-induced residual stresses. The degradation of mechanical properties was observed at 1600 °C because of the microstructure deterioration and the formation of strongly bonded fiber–matrix interface. Therefore, it is concluded that the high temperature mechanical properties under vacuum were related to the consisting phase, the matrix microstructure, and the thermally-induced residual stresses.
Effect of Cereclor as Rejuvenator to Enhance the Aging Resistance of Reclaimed Asphalt Pavement Binder
Authors: Yaseen Ghulam , Hafeez Imran
Published: April 2020

Asphalt is the most commonly used material for pavement construction around the world, and therefore, it is vital to acquaint a practice that restores the reclaimed asphalt pavement (RAP) binder properties to the required level of performance by adding proper rejuvenators. However, a rejuvenator may perform better in the early stages of its application but may not necessarily perform better in the long run. The aim of this study is to assess the rejuvenation effect on the aging resistance of RAP binder in long-life performance through applying artificial aging. In this study, base virgin binder of pen grade 60/70 and RAP binder rejuvenated with Cereclor were subjected to artificial aging to simulate the short- and long-term aging effects. Penetration, softening point, ductility, and viscosity; saturates, aromatics, resins, and asphaltene (SARA) fractionation; and Fourier-transform infrared (FTIR) spectroscopy, bending beam rheometer (BBR), and dynamic shear rheometer (DSR) tests were conducted to evaluate the potential improvements in various properties of RAP binder. The results indicated that the physical, fractional composition, rheological, and aging resistance of RAP binder improved through the rejuvenation mechanism. Therefore, the rejuvenator improved the chemical structure through re-balancing the constituents in the colloidal system, even after long-term re-aging, which proves it to be an aging-resistant binder. Furthermore, it has been concluded that Cereclor has substantial rejuvenation potential even after applying artificial aging, and it can be utilized in pavement recycling to achieve long-life performance. Furthermore, the results depict good correlations between the physical, rheological, and chemical parameters of virgin and RAP binder.
Application of Life-Dependent Material Parameters to Fatigue Life Prediction under Multiaxial and Non-Zero Mean Loading
Authors: Kluger Krzysztof , Karolczuk Aleksander , Derda Szymon
Published: April 2020

This study presents the life-dependent material parameters concept as applied to several well-known fatigue models for the purpose of life prediction under multiaxial and non-zero mean loading. The necessity of replacing the fixed material parameters with life-dependent parameters is demonstrated. The aim of the research here is verification of the life-dependent material parameters concept when applied to multiaxial fatigue loading with non-zero mean stress. The verification is performed with new experimental fatigue test results on a 7075-T651 aluminium alloy and S355 steel subjected to multiaxial cyclic bending and torsion loading under stress ratios equal to R = −0.5 and 0.0, respectively. The received results exhibit the significant effect of the non-zero mean value of shear stress on the fatigue life of S355 steel. The prediction of fatigue life was improved when using the life-dependent material parameters compared to the fixed material parameters.
Fabrication of TiB2–Al1050 Composites with Improved Microstructural and Mechanical Properties by a Liquid Pressing Infiltration Process
Authors: Ko Seongmin , Park Hyeonjae , Lee Yeong-Hwan , Shin Sangmin , Jo Ilguk , Kim Junghwan , Lee Sang-Bok , Kim Yangdo , Lee Sang-Kwan , Cho Seungchan
Published: April 2020

This study was conducted on titanium diboride (TiB2) reinforced Al metal matrix composites (MMCs) with improved properties using a TiB2 and aluminum (Al) 1050 alloy. Al composites reinforced with fine TiB2 at volume ratios of more than 60% were successfully fabricated via the liquid pressing infiltration (LPI) process, which can be used to apply gas pressure at a high temperature. The microstructure of the TiB2–Al composite fabricated at 1000 °C with pressurization of 10 bar for 1 h showed that molten Al effectively infiltrated into the high volume-fraction TiB2 preform due to the improved wettability and external gas pressurization. In addition, the interface of TiB2 and Al not only had no cracks or pores but also had no brittle intermetallic compounds. In conclusion, TiB2–Al composite, which has a sound microstructure without defects, has improved mechanical properties, such as hardness and strength, due to effective load transfer from the Al matrix to the fine TiB2 reinforcement.
Determination of an Objective Criterion for the Assessment of the Feasibility of an Instrumented Indentation Test on Rough Surfaces
Authors: Marteau Julie , Jourani Abdeljalil , Bigerelle Maxence
Published: April 2020

The influence of roughness on the results of indentation testing was investigated using a semianalytical model. This model used simulated surfaces that were described using three standard roughness parameters: the root-mean-square deviation Sq, the wavelength (or cut-off of Gaussian high-pass filter), and the fractal dimension. It was shown that Sq had the largest effect on the determination of the macrohardness, while the surface wavelength and fractal dimension had negligible effects at the scale of investigation. The error of determination of the macrohardness rose with the increase of the ratio Sq/hmax where hmax was the maximum indentation depth: Sq/hmax ratios lower than 0.02 were required to obtain a systematic error of the macrohardness lower than 5%, whatever the examined material mechanical properties (in elasticity and plasticity).
An Amplitude- and Temperature-Dependent Vibration Model of Fiber-Reinforced Composite Thin Plates in a Thermal Environment
Authors: Zu Xudong , Wu Huaishuai , Lv Haiyu , Zheng Yu , Li Hui
Published: April 2020

A thermal environment has a complex influence on the dynamic characteristics of fiber-reinforced composite materials and structures. It is challenging to consider the effects of high temperature and external vibration energy simultaneously on their nonlinear vibration response. In this research, the material nonlinearities, due to both the excitation amplitudes and the high temperatures, are studied for the first time, and a new nonlinear vibration model of fiber-reinforced composite thin plates in a thermal environment is proposed by introducing the nonlinear thermal and amplitude fitting coefficients simultaneously. Then, based on the classical laminated plate theory, the complex modulus approach, and the power function and the Ritz methods, dynamic governing equations in high-temperature environments are derived to solve the nonlinear natural frequencies and vibration responses and damping parameters. Moreover, the three-dimensional fitting curves of the elastic moduli and loss factors, excitation amplitudes, and temperature values are obtained so that the key nonlinear fitting coefficients in the amplitude- and temperature-dependent model can be identified. To validate this model, the experimental tests on CF130 carbon/epoxy composite thin plates are undertaken. It is found that the 3rd and 5th natural frequencies, vibration responses, and damping results obtained from the nonlinear model are consistent with the experimental measurements, and the mechanism of nonlinear thermal vibration behaviour is revealed.
Use of Pyrazole Hydrogen Bonding in Tripodal Complexes to Form Self Assembled Homochiral Dimers
Authors: Brewer Greg , Butcher Raymond J. , Zavalij Peter
Published: April 2020

The 3:1 condensation of 5-methyl-1H-pyrazole-3-carboxaldehyde (MepyrzH) with tris(2-aminoethyl)amine (tren) gives the tripodal ligand tren(MePyrzH)3. Aerial oxidation of a solution of cobalt(II) with this ligand in the presence of base results in the isolation of the insoluble Co(tren)(MePyrz)3. This complex reacts with acids, HCl/NaClO4, NH4ClO4, NH4BF4, and NH4I to give the crystalline compounds Co(tren)(MePyrzH)3(ClO4)3, {[Co(tren)(MePyrzH0.5)3](ClO4)1.5}2 {[Co(tren)(MePyrzH0.5)3](BF4)1.5}2 and [Co(tren)(MePyrzH)3][Co(tren)(MePyrzH)3]I2. The latter three complexes are dimeric, held together by three Npyrazole –H…Npyrazolate hydrogen bonds. The structures and symmetries of these homochiral dimers or pseudodimers are discussed in terms of their space group. Possible applications of these complexes by incorporation into new materials are mentioned.
Thermoplastic Elastomeric Composites Filled with Lignocellulose Bioadditives. Part 1: Morphology, Processing, Thermal and Rheological Properties
Authors: Miedzianowska Justyna , Masłowski Marcin , Strzelec Krzysztof
Published: April 2020

Thermoplastic elastomer blends based on natural rubber (NR) and ethylene-vinyl acetate copolymer (EVA) with different weight ratios (30, 40, 50, 60 and 70 parts per hundred rubber (phr) of NR) and 10, 20 and 30 phr of straw were prepared and characterized. Current environmental problems were the motivation to produce this type of system, namely: the need to replace plastics at least partly with natural materials; increasing the amount of renewable raw materials and managing excess straw production. When using this bioadditive in traditional materials, the high processing temperature can be problematic, leading to the degradation of straw fibers. The solution can be polymer mixtures that are prepared at significantly lower temperatures. Scanning electron microscope (SEM) imaging was used to investigate the particle size of fibers and phase morphology of composites. Moreover, determination of the thermal properties of the filler and composites showed that the processing temperature used in the production of NR/EVA blends reduces the risk of degradation of the natural filler. Differential scanning calorimetry (DSC) was used to determine the thermal behavior of the filled composites. Finally, rheological tests of materials allow the determination of optimal processing parameters and properties of materials in dynamic conditions. The proposed blends exhibit elastic properties, and due to the lack of chemical cross-linking they can be processed and recycled like thermoplastics. In addition, they offset the disadvantages and combine the advantages of natural rubber and ethylene-vinyl acetate copolymer in the form of thermoplastic elastomeric biocomposites.
Green Functions of the First Boundary-Value Problem for a Fractional Diffusion—Wave Equation in Multidimensional Domains
Authors: Pskhu Arsen
Published: April 2020

We construct the Green function of the first boundary-value problem for a diffusion-wave equation with fractional derivative with respect to the time variable. The Green function is sought in terms of a double-layer potential of the equation under consideration. We prove a jump relation and solve an integral equation for an unknown density. Using the Green function, we give a solution of the first boundary-value problem in a multidimensional cylindrical domain. The fractional differentiation is given by the Dzhrbashyan–Nersesyan fractional differentiation operator. In particular, this covers the cases of equations with the Riemann–Liouville and Caputo derivatives.
Clusters in Separated Tubes of Tilted Dipoles
Authors: Armstrong Jeremy R. , Jensen Aksel S. , Volosniev Artem G. , Zinner Nikolaj T.
Published: April 2020

A few-body cluster is a building block of a many-body system in a gas phase provided the temperature at most is of the order of the binding energy of this cluster. Here we illustrate this statement by considering a system of tubes filled with dipolar distinguishable particles. We calculate the partition function, which determines the probability to find a few-body cluster at a given temperature. The input for our calculations—the energies of few-body clusters—is estimated using the harmonic approximation. We first describe and demonstrate the validity of our numerical procedure. Then we discuss the results featuring melting of the zero-temperature many-body state into a gas of free particles and few-body clusters. For temperature higher than its binding energy threshold, the dimers overwhelmingly dominate the ensemble, where the remaining probability is in free particles. At very high temperatures free (harmonic oscillator trap-bound) particle dominance is eventually reached. This structure evolution appears both for one and two particles in each layer providing crucial information about the behavior of ultracold dipolar gases. The investigation addresses the transition region between few- and many-body physics as a function of temperature using a system of ten dipoles in five tubes.