Densification Temperature Research Articles

Highly sensitive temperature sensor based on a liquid crystal selectively infiltrated two-core photonic crystal fiber

This article proposes a temperature sensor based on liquid crystal selectively filled two-core photonic crystal fiber featuring high sensitivity and compact structure. In order to achieve the purpose of compact structure and temperature sensing, we consider to combine the temperature-sensitive material liquid crystal (LC) E7 and photonic crystal fiber to study the performance of temperature sensing. Since the applied electric field and temperature have great influence on the arrangement of liquid crystal molecules, LC as a temperature sensitive material can improve the sensing performance. An air hole filled with LC isolates the two horizontal cores, where the two horizontal cores act as two separate waveguides and the LC core is used to regulate the mode coupling of the two horizontal cores. In the process of transferring light energy from one core to another, the position of the transmission spectrum of the sensor is changed by optimizing the diameter of LC core and horizontal two-core, and then a sensor with high sensitivity and stable performance is designed. The coupling length and transmission spectrum of the sensor are analyzed by using full vector finite element method. By analyzing the wavelength dips of the transmission spectrum, the maximum sensitivity of the proposed temperature sensor can be reached −6.69 nm/℃ at 30 ℃ for Y-polarized (Y-Pol) direction. The main advantages of the sensor proposed in this paper are simple structure and easy to manufacture, high sensitivity and high fitting coefficient.

To Study the Mixing and Compaction Temperatures of Organophilic Nanoclay Modified Asphalt Binder

Abstract: The use of modified asphalt binders in hot-mix asphalt has steadily increased over the past several decades. Mixing and compaction temperatures of an asphalt binder plays a vital role in the production and placement of asphalt mixes but there are no standards for mixing and compaction temperatures for modified asphalt binder especially with Organophilic nanoclay. In this study the effect of nanoclay modified binder on mixing and compaction temperatures of asphalt mixture was observed using conventional test for asphalt mixture-softening point test, penetration test and rotational viscometer test. Five different percentages i-e 3, 3.5, 4, 4.5 and 5% of Nanoclay (modifier) are selected for three different binders (ARL 60/70, ARL 80/100 & NRL 60/70). Six different samples for each binder are prepared and conventional testing is carried out using standard procedures. With an increase in the percentage of Nanoclay the softening point values and viscosity values increases, similarly the penetration values decrease. The mixing temperature range is 155-165°C and compaction temperature range is 135-145 °C to achieve maximum density in the field

Appraising bitumen coverage, workability, and production temperatures of warm asphalt-aggregate blends

ABSTRACT In this study, temperature-dependent high and low shear-rate workability indices (WIs) proposed from a developed workability tester, were employed respectively to determine suitable mixing and compaction temperatures for 12 warm mix blends. An automated procedure was also developed to determine the percentage of coated aggregates using a computer analysis code and set additional possible mixing temperatures for the blends. Two base binders, three representative warm asphalt technologies, and two gradations of basaltic aggregate were involved in the experimental work. Additionally, a framework of WI was introduced. The warm mixed blends were coated at lower temperatures compared to hot mixes. The workability of mixture is not controlled by binder viscosity only; rather it is dominated by the interwoven characteristics of asphalt-aggregate components. The proposed methodology helped in determination of reduced production temperatures for warm mix blends, and the reduction degree is affected by technology type and rate, and binder grade.

Ultra-compact hybrid silicon:chalcogenide waveguide temperature sensor.

We demonstrate a real-time, reusable, and reversible integrated optical sensor for temperature monitoring within harsh environments. The sensor architecture combines the phase change property of chalcogenide glasses (ChG) with the high-density integration advantages of high index silicon waveguides. To demonstrate sensor feasibility, ChG composition Ge40S60, which is characterized by a sharp phase transition from amorphous to crystalline phase around 415 °C, is deposited over a 50 µm section of a single mode optical waveguide. The phase transition changes the behavior of Ge40S60 from a low loss to high loss material, thus significantly affecting the hybrid waveguide loss around the phase transition temperature. A transmission power drop of over 40dB in the crystalline phase compared to the amorphous phase is experimentally measured. Moreover, we recover the amorphous phase through the application of an electrical pulse, thus showing the reversible nature of our compact temperature sensor. Through integrating multiple compositions of ChG with well-defined phases transition temperatures over a silicon waveguide array, it is possible to determine, in real-time, the temperature evolution within a harsh environment, such as within a nuclear reactor cladding.

Pyroelectric metamaterial millimeter-wave detector

We present experimental demonstration of a multi-functional metamaterial absorber, which operates as an efficient detector of millimeter wave radiation at room temperature. Intimate integration of a pyroelectric crystal directly within the metamaterial unit cell enables an efficient large area sensing element made up of repeating unit cells that are nearly ten times smaller than the operational wavelength. An un-amplified intrinsic responsivity of 3.90 V/W is demonstrated at 91.5 GHz, which is close to the peak of the spectral absorption at 97.8 GHz. Numerical full-wave electromagnetic simulations match well to experiments and clarify the underlying absorption mechanism, while thermal simulations permit optimization of the responsivity. The demonstrated results show that the monolithic pyroelectric metamaterial geometry well functions as a detector and represents an ideal device platform for realization of novel and compact room temperature millimeter wave sensing and imaging components.

Characterization of Garnet-Type Li6SrLa2Bi2O12 Solid Electrolyte for LiCoO2 Cathode Composite in All-Solid-State Battery

Together with the development of inorganic solid lithium (Li) ion conducting materials for the use as solid electrolytes, the formation of intimate solid-solid interface between electrode active material and solid electrolyte is pivotal for realizing high performance all-solid-state Li-ion batteries (LiBs) with high safety and reliability. Oxide-based solid electrolytes have the advantages of good chemical stability and ease of handling, but for many of them, the high temperature processing is required for the densification, which may cause undesired side reactions with electrode active materials during the processing.Although garnet-type oxide solid electrolyte Li6SrLa2Bi2O12 (LSLBO) has lower ionic conductivity than widely studied garnet-type Li7La3Zr2O12 (LLZO), LSLBO can be sintered at much lower temperatures than LLZO [1,2]. Therefore, there is a possibility to suppress the side reaction with electrode active materials during high-temperature sintering for fabricating oxide-based all-solid-state LiBs.In this study, we prepared dense LSLBO or composites of LiCoO2 (LCO) cathode and LSLBO by hot pressing (HP). LSLBO densified at 750 °C for 1 hour showed high relative density of 95%. The densification temperature of LSLBO by HP confirmed in this work is 100–150 °C lower than Bi-doped LLZO with the formula of Li6La3ZrBiO12 (LLZBO) [3, 4]. Bulk and total (bulk + grain conductivity) ionic conductivity of LSLBO fabricated by HP attained to 2.1 × 10-4 and 1.1 × 10-4 S/cm at room temperature, which is much higher than LSLBO prepared by a conventional furnace sintering (FS) [1] and spark plasma sintering (SPS) [2]. The electrochemical stability of LSLBO at an electrical potential from 3 to 6 V vs. Li/Li+ was also confirmed by measuring the cyclic voltammogram.From XRD analysis of mixed LSLBO and LCO powders after annealing, LSLBO and LCO were found to be thermally compatible at temperature below 800 °C and LCO-LSLBO composite densified at 700 °C for 1 hour by HP showed mixed conducting properties with both electronic and ionic conductivity of 10-5-10-4 S/cm at room temperature. From galvanostatic charge and discharge testing of sintered LCO-LSLBO composite sheet, we found that electrochemical performance of LCO is not degraded by co-sintering with LSLBO. These results suggest that LSLBO solid electrolyte can be applied for LCO cathode composite in oxide-based all-solid-state LiBs.

Characterization of Na2M2TeO6 (M = Ni, Zn) for Oxide-Based All-Solid-State Sodium-Ion Batteries

All-solid-state sodium (Na) ion batteries (SiBs) are promising high-safety and low cost alternatives to current lithium (Li) ion batteries (LiBs), particularly suitable for the application to large-scale electrical energy storage systems. Development of inorganic solid Na-ion conducting materials used for solid electrolyte is most critical issue to realize all-solid-state SiBs. The solid electrolyte materials should have not only high Na-ion conductivity at room temperature but also chemical and electrochemical stabilities against both cathode and anode active materials. Oxide based solid electrolytes have lower conductivity and poorer deformability than sulfide based one, but they have other advantages such as their chemical stability in air and easiness for handling.Na2M2TeO6 (M = Zn, Mg, Ni, Co, etc.) with a P2-type honeycomb layered structure has been reported as a fast Na-ion conducting oxide [1]. Particularly, Na2Zn2TeO6 (NZTO) is an attractive candidate for a solid electrolyte material because of the high ionic conductivity well above 10-4 S cm-1 at room temperature, wide electrochemical potential window and lower densification temperature than other oxide-based Na-ion conductors such as NASICON and Na-β alumina [2–4]. On the other hand, Na2Ni2TeO6 (NNTO) has been investigated as a cathode active material for SiB operating at 3–4 V vs Na/Na+ [5,6]. Because of the similarity in their crystal structure and constituent elements, NNTO cathode and NZTO as solid electrolyte may be co-sintered without forming undesired secondary phases to fabricate all-solid-state SiBs.In this work, we investigated firstly the reactivity between NNTO and NZTO powders at annealing temperature between 500 ºC and 800 ºC in air. From XRD measurements, it was found that the reaction between NNTO and NZTO is negligible at annealing temperature below 700 ºC while when annealed at 800 ºC, they forms a solid-solution phase without forming any secondary phases. Based on this result, we fabricated NNTO-NZTO laminate via co-sintering NNTO and NZTO pellets at 700 ºC in air. Thicknesses of NNTO and NZTO layers in the laminate were set to 1 mm.From impedance measurements, apparent ionic conductivity of the NNTO-NZTO laminate was estimated to be approximately 0.1 mS cm-1 at 27 ºC, which is close to the prediction with taking into account only the conductivity of individually sintered NNTO (= 0.04 mS cm-1) and NZTO (= 0.36 mS cm-1) at 700 ºC. This indicates that the interfacial resistance between NNTO and NZTO layers is not so large. In addition, using the NNTO-NZTO laminate with NNTO layer thickness of 80 µm, electrochemical Na extraction reaction from NNTO layer through NZTO solid electrolyte was demonstrated via galvanostatic testing at room temperature. Obtained results are very fundamental but can be applied to fabricate all-solid-state SiBs with NNTO cathode and NZTO solid electrolyte via simple co-sintering process in future.

Evaluating the test protocols to determine the mixing and compaction temperatures of modified bitumen

Evaluating the test protocols to determine the mixing and compaction temperatures of modified bitumen

Effect of Chemical Warm Mix Additive on the Properties and Mechanical Performance of Recycled Asphalt Mixtures

Newer technologies such as warm mix asphalt (WMA) and reclaimed asphalt pavement (RAP) have gained international approval and have been considered as appropriate solutions that support the sustainability goals of the highway sector. However, both technologies present some shortcomings. The lower mixing and compaction temperatures of WMA reduce the binder aging and the bond between the aggregates and the coating binder, thus resulting in less rutting resistance and higher moisture susceptibility. On the other hand, RAP mixes tend to be stiffer and more brittle than conventional hot mix asphalt (HMA) due to the effect of aged binder. This tends to increase the crack propagation distresses. In an attempt to overcome their individual shortcomings, this study investigated the new concept of a combined WMA-RAP technology. The chemical WMA additive Rediset LQ1102CE was utilized with mixtures incorporating low (15%), medium (25%), and high (45%) RAP contents. Dynamic modulus (DM) and flow number (FN) tests were conducted to investigate the effect of Rediset on the behavior of RAP mixtures. The dynamic modulus |E*| mastercurves were developed using the sigmoidal model and Franken model was used to fit the accumulated permanent deformation curve. The results of this study showed that Rediset addition improved the cracking resistance of RAP mixtures. However, the rutting resistance was reduced but kept within the acceptable range except for mixtures containing low RAP content.

Production of Bitumen Modified with Low-Molecular Organic Compounds from Petroleum Residues. 5. Use of Maleic Anhydride for Foaming Bitumens

The possibility of using maleic anhydride as a foaming agent to produce foamed bitumen was investigated. The optimal content of maleic anhydride was determined according to the indicators of the growth of the binder volume and the half-life of the foam. With use of maleic anhydride as a foaming agent, foamed bitumen was obtained, and later was used to obtain two samples of stone mastic asphalt, which differed in mixing and compaction temperatures of stone mastic asphalt mix. For comparison, the composition of stone mastic asphalt mix was designed using non-foamed (BND 70/100 and BND 70/100 modified with maleic anhydride) and foamed bitumen (BND 70/100 foamed with maleic anhydride at two different temperatures). Stone mastic asphalt specimens were formed and tested

A 0.6V–1.8V Compact Temperature Sensor With 0.24 °C Resolution, ±1.4 °C Inaccuracy and 1.06nJ per Conversion

This paper presents a fully-integrated CMOS temperature sensor for densely-distributed thermal monitoring in systems on chip supporting dynamic voltage and frequency scaling. The sensor front-end exploits a sub-threshold PMOS-based circuit to convert the local temperature into two biasing currents. These are then used to define two oscillation frequencies, whose ratio is proportional to absolute-temperature. Finally, the sensor back-end translates such frequency ratio into the digital temperature code. Thanks to its low-complexity architecture, the proposed design achieves a very compact footprint along with low-power consumption and high accuracy in a wide temperature range. Moreover, thanks to a simple embedded line regulation mechanism, our sensor supports voltage-scalability. The design was prototyped in a 180nm CMOS technology with a 0{\deg}C $-$ 100{\deg}C temperature detection range, a very wide supply voltage operating range from 0.6V up to 1.8V and very small silicon area occupation of just 0.021$mm^2$. Experimental measurements performed on 20 test chips have shown very competitive figures of merit, including a resolution of 0.24{\deg}C, an inaccuracy of $\pm$1.4{\deg}C, a sampling rate of about 1.5kHz and an energy per conversion of 1.06nJ at 30{\deg}C.

Low temperature coefficient of resistance and high conductivity: Enhanced Cu–substituted LaCo0.4Ni0.6O3 ceramics for functional material

The LaCo0.4Ni0.6-yCuyO3 (LCNCu, y = 0.02–0.08) ceramics were prepared and their possibility as a cheap alternative functional material for thick film resistors was studied. Scanning electron microscopy, differential–thermal and thermomechanical analyses showed that the incorporation of Cu2+ lowered the densification temperature and enhanced the compactness of LCNCu ceramics. All of the samples revealed relatively high conductivity. When y < 0.05, both Cu2+ substitution and sintering temperature showed a strong influence on the conductivity of LCNCu ceramics. However, the simulation results indicated that the density of states almost did not change after Cu2+ substitution despite the weakened electron transport. The temperature coefficient of resistance (TCR) gradually decreased with the addition of Cu2+. Low TCR values (absolute values < 300 ppm/°C) and high conductivity were realized for the samples with y ≤ 0.04 sintered at 1200 °C and y = 0.02 sintered at 1225 °C. Consequently, the improved LaCo0.4Ni0.6-yCuyO3 ceramics may be a potential economical functional material for thick film resistors.

Chemical modification of porcelain tile surface to optimize flexural strength and Weibull modulus through the ion exchange process

The goal of this research was to improve the ion exchange mechanism in porcelain tiles by modifying the tile surface chemically. Ion exchange, also known as chemical tempering, is a procedure for improving the mechanical qualities of porcelain tiles. So, solutions comprising alkaline and alkaline earth metals with a low ionic radius were sprayed on the surfaces of pressed unfired porcelain tiles (lithium, calcium, and magnesium). Subsequently, the porcelain tiles were sintered at the maximum densification temperature (1200 °C). The ion exchange process was carried out at 480 °C for 25 min in a eutectic mixture of molten salts with 73 wt% KNO3 and 27 wt% Ba(NO3)2. The results show that the flexural strength of the Li+/Mg+2 surface-enriched samples was 75 ± 4 MPa, representing an increase of 32% in relation to non-treated porcelain tiles and an increase of 17% in relation to the chemically tempered samples without prior modification. A significantly larger Weibull modulus (15–20) were found for the chemically modified tiles in comparison with the value for the unmodified porcelain tiles (7–8). These findings demonstrated that chemical modification of the porcelain surface can optimize the ion exchange process, resulting in increased breaking force and, as a result, flexural strength and Young's modulus. This approach can help reduce the thickness of ceramic tiles while maintaining mechanical properties. This would result in lower raw material usage and energy expenditure during production, as well as lower carbon emissions associated with the production of porcelain tiles.

Unraveling the Innermost Jet Structure of OJ 287 with the First GMVA + ALMA Observations

We present the first very long baseline interferometric (VLBI) observations of the blazar OJ 287 carried out jointly with the Global Millimeter VLBI Array (GMVA) and the phased Atacama Large Millimeter/submillimeter Array (ALMA) at 3.5 mm on 2017 April 2. The participation of phased ALMA has not only improved the GMVA north–south resolution by a factor of ∼3, but has also enabled fringe detections with signal-to-noise ratios up to 300 at baselines longer than 2 Gλ. The high sensitivity has motivated us to image the data with newly developed regularized maximum likelihood imaging methods, revealing the innermost jet structure with unprecedentedly high angular resolution. Our images reveal a compact and twisted jet extending along the northwest direction, with two bends within the inner 200 μas, resembling a precessing jet in projection. The component at the southeastern end shows a compact morphology and high brightness temperature, and is identified as the VLBI core. An extended jet feature that lies at ∼200 μas northwest of the core shows a conical shape, in both total and linearly polarized intensity, and a bimodal distribution of the linear polarization electric vector position angle. We discuss the nature of this feature by comparing our observations with models and simulations of oblique and recollimation shocks with various magnetic field configurations. Our high-fidelity images also enabled us to search for possible jet features from the secondary supermassive black hole (SMBH) and test the SMBH binary hypothesis proposed for this source.

Effects of water-foaming and liquid warm mix additive on the properties and chemical composition of asphalt binders in terms of short term ageing process

This study investigated the effects of water-foaming of asphalt binders containing liquid warm mix additives as an intention to produce warm-mix asphalt with enhanced performance in scope of compaction and moisture resistance. Two paving grade bitumen were used as a base material – a 35/50 and 50/70 paving grade bitumen binders. The investigation involved subjecting the asphalt binders to short-term ageing using rolling thin-film oven test protocol in temperatures ranging from 123 °C to 163 °C to simulate the effects of lowered processing temperatures in warm mix asphalt techniques. The testing methods included standard classification tests, basic evaluation of foaming performance, dynamic viscosity testing, evaluation of high temperature stiffness and non-recoverable compliance using a dynamic shear rheometer as well as evaluation of changes in chemical composition of the binders using Fourier transform infrared spectroscopy. The results have shown that water-foaming of asphalt binders incorporating the liquid warm mix additive led to an additional, significant drop in their dynamic viscosity in the mixing and compaction temperature range, while no significant effects to the performance-related characteristics of the binders were observed. It was found that the small changes in asphalt binder rheology caused by water-foaming were reverted in the course of laboratory short-term ageing. The process of water foaming has induced measurable changes in the chemical structure of the investigated binders associated traditionally with oxidative ageing, however these did not affect the results after the short-term laboratory ageing using the rolling thin-film oven test protocol. Based on the conducted work it was concluded that the simultaneous use of water-foaming and the liquid warm mix additive should not have permanent effects on the performance of the investigated asphalt binders, while enabling enhanced coating and workability of the asphalt mixtures produced in lowered temperatures.

Phase composition, microstructure and dielectric properties of middle-fired LiF-doped MgTi(1− x )Zr x O3 ceramics

LiF-doped MgTi(1− x )Zr x O3 (0.05 ≤ x ≤ 0.20) ceramics were fabricated via a conventional solid-state reaction route. All samples displayed MgTiO3 phase accompanying with a little of ZrO2 and Mg2TiO4 as the second phase. The lattice constant increased with increasing x due to the substitution of Zr4+ for Ti4+. The densification temperatures were reduced to the range of 1100–1150 °C due to LiF-doping. The microwave dielectric property of MgTi(1− x )Zr x O3 ceramics depended on the substitution content of Zr4+. Typical, MgTi0.90Zr0.10O3 ceramic exhibited microwave dielectric properties of εr = 18.7, tanδ = 2.8 × 10−4, and Q × f = 34300 GHz.

Assessment of metal leaching from rediset-polymer modified asphalt binder on groundwater and soil contamination

Road pavement is a structure that expose to various climate conditions. To make it more durable, modification of asphalt binder with polymer is a popular option. However, to maintain the environmental sustainability, the mixing and compaction temperature needs to be reduced. Warm Mix Asphalt additive had been widely used for this purpose. In this research, the impact of a polymer modified asphalt binder, PG76 together with a chemical WMA additive, Rediset on groundwater and soil contamination was investigated. The effect of Rediset on PG76 in terms of viscosity and activation energy was also studied via the rotational viscosity test. Even though it was found that Rediset might affect the viscosity of PG76, the activation energy shows independent values. ATR-FTIR was employed to understand the reaction between these two substance. It was found that there had been no chemical reaction between PG76 and Rediset. As a complementary, AFM was utilised to observe the surface characteristics at micro-scale. It appeared that Rediset did contribute to the binder’s surface morphology. Finally, the modified tank leaching test together with analysis by ICP-MS, discovered that after 64 days submerged under flood, Rediset-PG76 had no effect on the adjacent water source and soil.

High‐entropy boride–carbide ceramics by sequential boro/carbothermal synthesis

AbstractA dual‐phase high‐entropy boride (HEB)/carbide (HEC) ceramic with a fine grain size was synthesized by a sequential boro/carbothermal process. In the first step, an Hf–Nb–Ta–Ti–Zr‐containing carbide was synthesized by a carbothermal reduction of oxides followed by the reaction of the carbide with B4C and ZrH2 to convert part of the carbide to boride. The resulting composition was ∼29 vol% HEB with an average grain size of ∼1.1 μm. Solid solution formation occurred at the densification temperature of 1900°C resulting in a relative density higher than 99%. The Vickers hardness was 26.5 ± 1.4 GPa. This is the first report of synthesizing dual‐phase boride–carbide high‐entropy ceramics from carbothermally synthesized, HEC powders.

Low-temperature densification of high-entropy (Ti,Zr,Nb,Ta,Mo)C\u2014Co composites with high hardness and high toughness

In order to prepare high toughness (Ti,Zr,Nb,Ta,Mo)C ceramics at low temperatures while maintaining high hardness, a liquid-phase sintering process combined with Co-based liquid-phase extrusion strategy was adopted in this study. The densification temperature can be lowered to 1350 °C, which is much lower than the solid-state sintering temperature (∼2000 °C) generally employed for high-entropy carbide ceramics. When sintered at 1550 °C and 30 MPa applied pressure, part of the Co-based liquid-phase was squeezed out of the graphite mold, such that only ∼3.21 vol% of Co remained in the high-entropy ceramic. Compared to the Co-free solid-state sintered (Ti,Zr,Nb,Ta,Mo)C ceramics, prepared at 2000 °C and 35 MPa, the hardness was slightly decreased from 25.06±0.32 to 24.11±0.75 GPa, but the toughness was increased from 2.25±0.22 to 4.07±0.13 MPa·m1/2. This work provides a new strategy for low-temperature densification of high-entropy carbides with both high hardness and high toughness.

A novel epoxy-terminated polyethylene modified asphalt with low-viscosity and high storage stability

The storage stability of polyethylene (PE) modified asphalt is a major constraint to its wide application. In addition, PE raises the mixing and compaction temperature of asphalt, causing environmental pollution. The effective synthesis of stable and environmentally friendly PE modifiers is an important and challenging topic. We propose a strategy to reduce the molecular weight of PE while adding functionalized end group to PE. The obtained low molecular weight epoxy-terminated-polyethylene (EPE) for modified asphalt is storage stable, reduces mixing and compaction temperatures of asphalt, and reduces environmental pollution. The difference between the top and bottom softening points of asphalt containing 3 wt% and 5 wt% EPE was 1.25 °C and 0.7 °C, which exceeded most previously reported PE-modified asphalt. In addition, EPE, due to its low molecular weight, reduces the high temperature viscosity of asphalt, achieving lower mixing and compaction temperatures. Besides, dynamic shear rheometer (DSR) and multiple stress creep recovery (MSCR) data showed that the rheological properties of EPE modified asphalt were also significantly improved. This work will provide further guidance for the application of PE in asphalt.