Relative Low Temperature Research Articles

Sustainable sorbent derived from discarded cigarette butts for elimination of tobacco specific nitrosamines carcinogen

In order to control the increasingly serious pollutions of tobacco specific nitrosamines (TSNA) and discarded cigarette butts (DCB) that caused by smoking, new sustainable carbonaceous sorbent was prepared to follow the new idea of “cleaning environment with recycle of waste”. For this propose, DCB was used as the carbon source and aluminum nitrate as the pore-forming agent to form the sorbent with a developed porosity and the well-exposed metal oxides. One-pot synthesis was adopted without template and washing, in order to recycle waste with a sustainable technology. New sorbent could selectively capture 25% of TSNA among hundreds of components in tobacco extract solution or 35 mg g − 1 of 4-methylnitrosamino-1-3-pyridyl-1-butanone (NNK) in aqueous solution, quite better than activated carbon and zeolite NaZSM-5. In addition, the sorbent was able to catalyze the degradation of the adsorbed NNK in 472–584 K to eliminate the environment carcinogen at relative low temperature. Moreover, cell test demonstrates that the sorbent derived from DCB was cell-safe and therefore widely available. The application of this new sorbent will control both pollutions of TSNA and DCB at the same time, which will protect environment and public health effectively. • Recycle of waste to clean environment was demonstrated in this paper. • Using discarded cigarette butts as the raw material to prepare new sorbent. • One-pot synthesis of the alumina doped carbon without template and washing. • Sustainable sorbent effectively capture tobacco specific nitrosamines carcinogen. • New sorbent is cell-safe and therefore widely available.

Thermal physical processes during forming of biocompatible Ca-P coatings by detonation spraying

Carbon-carbon composites with calcium phosphate (Ca-P) coatings (with a thickness up to of ≈100 μm) are considering as prospective grafts for defect bone substitution. Detonation spraying of Ca-P layers allows to fulfil a deposition mode with relative low temperature loads (up to a temperature of the processed surface of ≈850…1100 K) under a pulsed pressure of ≈2…6 bar. Such deposition conditions could promote to minimal thermal decomposition of feedstock HAp.

High Temperature Deformation Behavior and Microstructure Evolution of Low-Density Steel Fe30Mn11Al1C Micro-Alloyed with Nb and V.

The thermal processing parameters is very important to the hot rolling and forging process for producing grain refinement in lightweight high-manganese and aluminum steels. In this work, the high temperature deformation behaviors of a low-density steel of Fe30Mn11Al1C alloyed with 0.1Nb and 0.1V were studied by isothermal hot compression tests at temperatures of 850–1150 °C and strain rates between 0.01 s−1 and 10 s−1. It was found that the flow stress constitutive model could be effectively established by the Arrhenius based hyperbolic sine equation with an activation energy of about 389.1 kJ/mol. The thermal processing maps were developed based on the dynamic material model at different strains. It’s shown that the safe region for high temperatures in a very broad range of both deformation temperature and deformation strain and only a small unstable high deformation region, located at low temperatures lower than 950 °C. The deformation microstructures were found to be fully recrystallized microstructure in the safe deformation region and the grain size decreases along with decreasing temperature and increasing strain rate. Whereas the deformation microstructures is composed by grain refinement-recrystallized grains and a small fraction of non-recrystallized microstructure in the unstable deformation region, indicating that the deformation behaviors controlled by continuous dynamic recrystallization. The Hall Petch relationship between microhardness and the grain size of the high temperature deformed materials indicates that high strength low-density steel could be developed by a relative low temperature deformation and high strain rate.

Throwing power and service life of galvanic cathodic protection with embedded discrete anodes for steel reinforcement in chloride contaminated concrete

The design of a galvanic cathodic protection (GCP) system with embedded discrete anodes for chloride contaminated reinforced concrete is greatly affected by the throwing power of the system. In this research, the influence of environmental conditions and corrosion activity of the steel reinforcement on the throwing power was investigated by means of depolarization measurements.Results show that the throwing power is highest in periods with rainfall, high relative humidity and low temperature and that it decreases with increasing chloride content in the concrete. Generally, GCP with discrete anodes is most effective when installed at the moment of corrosion initiation.

Drying dynamics of meat highlighting areas of relevance to dry‐aging of beef

Drying of foods is a processing step, which has a variety of outcomes from improving shelf life and product stability, to reducing weight, or to achieving a targeted product eating quality. Drying is key step in the manufacturing of some dried meat products, such as jerky. It is also a major event that occurs when beef is dry-aged, where beef is exposed to air under defined conditions for an extended aging period. Although the conditions typically used to produce dried meat products are significantly different from those that prevail during dry-aging, both involve a gradual removal of water from muscle. As there is a paucity of research on the kinetics of the dehydration process occurring during dry-aging of beef, this paper comprehensively reviews models used to describe drying kinetics in other beef products, in order to gain insights regarding the key factors that impact water removal from meat. Consideration is given as to how the specific conditions during dry-aging such as air flows used (approximately 2m/s), high air relative humidity, low temperature, and meat geometry will influence the kinetics of the drying. With regard to modeling, equations derived from Fick's second law of diffusion (e.g., thin-layer models) have been used to describe the drying kinetics of small-sized meat products. However, to apply Fick's law to dry-aging, some different considerations may need to be evaluated such as: tridimensional geometry (i.e., whole muscle); uniform initial moisture content; isotropic diffusion; negligible shrinkage;and a combination of internal and external resistances.

Urban atmospheric particle size distribution in Santiago, Chile

A monitoring campaign of the atmospheric particulate matter (PM) size distribution (between 0.25 and 10 μm in diameter (Dp)) in an urban area with high levels of air pollution between June 2018 and May, 2019 is presented. The relative contribution of 24 size fractions to the total number and mass concentration of PM was analyzed using an aerosol spectrometer. Local meteorological parameters and their effect on the PM concentrations were also evaluated. The size-fractionated particle mass concentrations showed the accumulation (Dp < 1 μm) and coarse (1 μm < Dp < 10 μm) modes. The highest contribution of the accumulation mode was observed during autumn and winter (reaching 99.7 % and 35.2 % of the total number and mass concentrations, respectively). High relative humidity and low temperatures were strongly correlated with high concentrations for the smaller PM fractions, which can be connected to the increase of residential emissions of PM derived from wood burning sources in winter months. The larger PM fractions showed higher concentrations during the spring and summer months, potentially because of dust resuspension due to the high vehicular traffic in the vicinity. High PM concentrations of the larger fractions were favored by the lack of precipitation events and stronger winds during this time of the year. The results showed the importance of the PM1 fraction to improve the source apportionment studies in urban areas and provide information about the potential health effects associated to high PM concentration events.

Accelerated sintering of high-performance oxide dispersion strengthened alloy at low temperature

Powder metallurgy generally is a preferred method to consolidate and prepare some refractory metals considering their high melting temperatures. However, sintering such materials to high density while maintaining fine grain structure is challenging, and generally require ultrahigh temperature or need to be assisted by external pressure. Especially, the preparation of nanostructured oxide dispersion strengthened (ODS) refractory metals at low temperature is more difficult because grain coarsening and densification are simultaneously hindered by the common oxide addition. Thus, it is of great sense to explore a kind of oxide that can be used as both strengthening phase and sintering accelerator. In this work, after extensive theoretical calculation and experimental observation, it is found that the accelerated sintering at low temperature can be achieved in W-HfO2 system. In the absence of external pressure or activator, this system can be rapidly densified without undesirable grain coarsening at a relative low temperature of only 1480 ˚C. Through kinetic analysis and density functional theory (DFT) calculation, it was confirmed that the intergranular HfO2 particles provide a rapid diffusion transport pathway for W atoms in support of densification at temperature of interest. As a result, this alloy exhibits a homogeneous microstructure with ∼97% relative density and ∼200 nm grain size, which renders our alloy with an ultrahigh compressive strength of ∼3 GPa, much higher than the reported values. We believe that the accelerated sintering mechanism found in our W-HfO2 system can be applicable to other refractory metals to prepare high-density nanocrystalline alloys with excellent properties.

Dual photochromics-contained photoswitchable multistate fluorescent polymers for advanced optical data storage, encryption, and photowritable pattern

Stimuli-responsive fluorescent materials that can alternate their emission states on-demand are always desired in many applications. In this study, novel photoswitchable multistate fluorescent polymer (PMFP) was prepared via simple free-radical copolymerization of butyl acrylate (BA) and styrene (St) with two photochromic fluorescent monomers, i.e. sulfonyl diarylethylene-linked 4-hydroxybutyl acrylate (SDTE) and spiropyran-linked methacrylate (SP8). The PMFP displays excellent processability, due to its rational feed ratio of BA and St which result in the relative low glass transition temperature. By changing irradiation light, the non-fluorescent ring-closed spiropyran units and ring-opened diarylethylene moieties in PMFP can be selectively converted into their corresponding luminescence states. Furthermore, as a result of the controllable fluorescence resonance energy transfer (FRET) from the excited diarylethylene to the spiropyran moieties, the emission of the polymer in solution or film can be reversibly switched among distinguishable no-emission, red, and green fluorescence states. Moreover, the PMFP exhibits high brightness, high contrast, rapid photoresponse, and excellent photoreversibility. We also demonstrated that PMFP can be directly used for advanced high-density data storage, multilevel information encryption, and multicolor photorewritable pattern, as well as high-level anticounterfeiting.

Sn doping effect on NiO hollow nanofibers based gas sensors about the humidity dependence for triethylamine detection

• Hollow Sn-doped NiO nanofibers are synthesized through a facile electrospinning approach. • The Sn-doped NiO sensor with suitable Sn content (6 at%) shows the highest gas response to triethylamine. • Sn doping concentrations can significantly influence the resistance of sensors in air and in target gas under different RH. • The resistances of the sensor change slightly in target gas under different RH with suitable Sn doping content (6 at%). High stable triethylamine gas sensors under different relative humidity are highly desirable in order to correctly detect the concentrations of target gas. In this study, a series of Sn-doped NiO hollow nanofibers were prepared through a facile electrospinning process followed by heat treatment. Sn doping could inhibit the crystal growth, and the crystal sizes would decrease with the increase of Sn doping concentration. Gas sensing investigation indicates that Sn doping could significantly enhance the gas response towards triethylamine at a relative low temperature. Especially, the gas sensor exhibits the highest response to triethylamine when the doping content of Sn reaches to 6 at%. The response value is about 16.6–100 ppm triethylamine, and it is ∼9.2 times higher than that of pure NiO nanofibers at the same operating temperature. In addition, the resistances of the gas sensors with different doping contents of Sn would change differently in air or in target gas under variable relative humidity. The resistances in target gas are almost unchanged with the increase of relative humidity with the Sn doping content of 6 at%. It is reasonable to speculate that Sn doping can heavily alter the surface state of NiO nanofibers, which is beneficial for the improvement of the gas response and humidity dependence properties.

Fe2O3-sensitized SnO2 nanosheets via atomic layer deposition for sensitive formaldehyde detection

Metal oxide semiconductor (MOS) nanostructures have been widely explored for formaldehyde sensors. The low surface chemical and electronic properties of pure MOS, however, greatly limits the sensor functions. In this work, Fe2O3-sensitized SnO2 nanosheets are designed via atomic layer deposition (ALD) to realize high performance formaldehyde detection. By varying the ALD cycles, the influence of different Fe2O3 loading on the sensing performance of SnO2 nanosheets is revealed. It is found that Fe2O3 ALD can greatly boost the sensing performance and the SnO2 nanosheets with 20 Fe2O3 ALD cycles exhibits the best response (Ra/Rg = 4.5) and fast response and recovery dynamics (9 and 34 s) to 20 ppm formaldehyde at a relative low temperature of 220 °C. The sensor based on SnO2/Fe2O3 also displays good selectivity to formaldehyde as well as the reliable stability and low limit of detection (LOD). This work will shed some light to design efficient MOS heterostructures for detection of formaldehyde.

Fast triethylamine gas sensing performance based on In2O3 nanocuboids

A simple solvent thermal method and subsequent annealing process were adopted in the successful synthesis of In2O3 nanocuboids. Outstanding sensing performance is demonstrated in the prepared In2O3-based sensor including relative low working temperature (180 °C) and high response value ∼30 toward 20 ppm triethylamine. Excellent triethylamine sensor performance is due to the unique configuration of nanocuboids and a large number of oxygen vacancies in In2O3 nanocrystals, thus improving gas sensitivity. Furthermore, the triethylamine sensing mechanism and potential growth mechanism are also studied.

Novel Si/SiGe fin on insulator fabrication on bulk-Si substrate

In this paper, novel Si/SiGe fin on insulator (FOI) structure fabrication on bulk-Si substrate is systematically explored. A notched Si/SiGe fin etching is first achieved by using a novel three-step etching after a high-quality of SiGe layer epitaxially grown is realized on a Si substrate by optimizing the epitaxial process. To fabricate the Si/SiGe FOI structure, isolation of upper Si/SiGe fin above the notch is investigated by a direct rapid thermal anneal (RTA) oxidation scheme, spike anneal post SiGe fin reveal scheme, and SiN spacer protection scheme. It is found that all these three schemes can achieve the upper Si/SiGe isolation at the notch location, but the direct RTA oxidation scheme suffers the issue of serious oxidation of SiGe fin because SiGe is more easily oxidized than Si in O2 ambient. Furthermore, compared with the direct oxidation scheme, the spike anneal post SiGe fin reveal scheme can attain an obvious better SiGe fin profile. However, there is still a minor lateral loss of SiGe fin caused by the oxidation of SiGe fin due to the residual O2 in N2 ambient. The SiN film covering the revealed SiGe fin before spike anneal treatment may be an effective solution to avoid the oxidation of SiGe fin. Meanwhile, SiN spacer protection scheme by employing a SiN spacer post the step-I etching of the three-step etching can realize the Si/SiGe FOI structure and protect the upper SiGe fin from oxidation during the low-temperature RTA oxidation process. Therefore, using the SiN film or spacer to protect SiGe from oxidation is a necessary way to fabricate the Si/SiGe FOI structure. Meanwhile, the SiN spacer protection scheme with a relative low temperature RTA isolation oxidation is a prefer choice compared with the spike anneal post SiGe fin reveal scheme.

Selective ppb-level ozone gas sensor based on hierarchical branch-like In2O3 nanostructure

• The branch-like In 2 O 3 (B-In 2 O 3 ) with uniform size was synthesized by a surfactant-assistant co-precipitation method. • B-In 2 O 3 with a large specific surface area possessed abundant active sites of chemically adsorbed oxygen. • The response of B-In 2 O 3 based sensor was higher than that of commercial In 2 O 3 (C-In 2 O 3 ) particles. • The limit of detection of B-In 2 O 3 based sensor was down to 30 ppb. For realizing high-performance ozone (O 3 ) sensing, hierarchical branch-like In 2 O 3 (B-In 2 O 3 ) nanomaterials were designed and prepared via a facile co-precipitation method. The unique In 2 O 3 structure consists of abundant nano-rods with the length of ca. 450 nm enabling effective adsorption and diffusion of oxygen and O 3 molecules. The sensors based on B-In 2 O 3 showed sensitive O 3 sensing performances at a relative low working temperature. The response of B-In 2 O 3 based sensors to 100 ppb of O 3 is 44 at 70 °C, which is 4.9-fold higher than the commercial In 2 O 3 (C-In 2 O 3 ) particles. The limit of O 3 detection was as low as 30 ppb. Moreover, the gas sensor exhibited excellent selectivity and device stability. The great sensing behavior is proved to be closely related to the oxygen-chemisorbed ability and large specific surface area of In 2 O 3 materials. Taken together, this work provides a potential sensing platform for highly sensitive and ppb-level O 3 detection.

A novel high-sensitive optical thermometer based on the multi-color emission in Pr3+ doped LiLaMgWO6 phosphors

Nowadays, optical thermometric materials with high sensing sensitivity in a wide temperature interval are urgently required due to the appealing prospect in the field of sensing technology. Herein, the double perovskite Pr3+: LiLaMgWO6 phosphors are successfully prepared via a high-temperature solid-state reaction method, and their concentration/temperature-dependent luminescence properties are discussed systematically. Upon UV excitation, the samples emit blue (3P0→3H4), green (3P0,1 → 3H5) and red emissions (1D2→3H4, 3P0→3F2) from Pr3+ ions. The different changing tendencies in relation to temperature are observed for the emissions from 3P0 and 1D2 multiplets, which are attributed to the effects of cross-over process to Pr3+-W6+ intervalence charge transfer (IVCT) state, cross relaxation process and multiphonon relaxation process. When the fluorescence intensity ratio (FIR) between 3P0→3F2 (654 nm) and 1D2→3H4 (616 nm) transitions is applied for temperature sensing, 0.5%Pr3+: LiLaMgWO6 displays a maximum absolute sensing sensitivity of 2421 × 10−4 K−1 at 573 K. Moreover, it can keep a comparatively high relative sensitivity (1%~3.25% K−1) and low temperature uncertainty (0.15–0.5 K) over a wide temperature range (~280 K), which are superior to those of many luminescence materials reported previously. The present study may provide useful design information to develop high-sensitive luminescent thermometers with a wide applicable temperature range.

In-situ synthesis of nano SiC particles in Al–Si–C system at 750 °C

Abstract For SiCp/Al matrix composites, nano SiC particles (SiCp) show more obvious strengthening effect than micro ones. In general, nano SiCp are added into Al matrix by ex-situ method, during which interfacial and agglomerating problems often generate. In-situ method is considered an effective way to solve above problems, but the in-situ synthesis of nano SiCp hasn't been reported. In this research, nano SiCp were in-situ synthesized in Al–Si–C system via a liquid–solid reaction method at relative low temperature (750 °C). Microstructure observation shows that the obtained nano SiCp have 3C polytype and show hexagonal plate morphology, with average size under 100 nm. In order to lower its surface energy, nano SiCp tend to connect with each other and form a coherent interface with stacking faults. Further research reveals that nano SiCp are formed via a two-step reaction. Nano SiCp can be introduced into Al–Si alloy and elevate its strength both at room and high temperature.

NiO/κ-CeZrO4 functional oxygen carriers with Niδ+ and oxygen vacancy synergy for chemical looping partial oxidation reforming of methane

Chemical looping partial oxidation reforming (CLPOR) technology is an economically attractive, sustainable, and environmental-friendly process strategy of CH4 conversion. In this study, NiO-promoted κ-CeZrO4 functional oxygen carriers (OCs) were designed and synthesized for the CLPOR of methane, with excellent lattice oxygen (LO) transmission performance and structural stability, aiming to reduce the energy penalty and temperature required for methane conversion. The crystalline phase, reaction performance, surface properties and reaction mechanism of the OC were systematically analyzed. In-situ CH4-XPS analysis was further carried out to reveal the internal mechanism with NiO/κ-CeZrO4 and the reason for higher CO selectivity at a low temperature. The methane conversion rate (≥ 80%) and syngas selectivity (≥ 93%) can be obtained under the most of reported reaction conditions (over 850 °C). More importantly, a higher methane conversion rate (52–72%) with syngas selectivity (88–92%) was even able to be achieved at a relative low temperature range 700–800 °C. The excellent performance was attributed to the reducing transmission temperature of the LO and a synergetic effect of Niδ+ and the oxygen vacancies (existed on the surface), thereby inhibiting carbon deposition caused by the excessively fast methane cracking rate under high temperature atmosphere.

Space Charge Measurements in Thin Bilayer BOPP Films by Thermal Pulse Method

In this paper, space charge accumulation in bilayer dielectrics composed of two metalized biaxially oriented polypropylene (BOPP) films thermally coupled by thin heat transfer oil (dibenzyltoluene, DBT) is investigated by thermal pulse method. An improved thermal pulse method for in-situ double-sided measurements is proposed to achieve higher spatial resolution. The accumulation and decay of the injected space charge is monitored after the laminated films being subjected to DC applied field of 150 V/μm at various temperatures from 25°C to 70 °C. Experimental results show that both charge injection rate and migration are sensitive to the operated temperature. Bipolar space charge injection is the rule, but negative charge becomes dominant as the injection rate asymmetry enhances with the elevated temperature. The interface between the films acts as a potential barrier to space charge transport at relative low temperature and the effect of the potential barrier appears weaken as the temperature rises. Therefore, the maximum electrical field by accumulated space charge is approximately 80 V/μm and the internal interface has little impact at 70°C.

High energy product of isotropic bulk Sm-Co/α-Fe(Co) nanocomposite magnet with multiple hard phases and nanoscale grains

Nanocomposite magnets consisting of hard and soft magnetic phases have potential applications to be the next generation of permanent magnets with very high energy product and less expensive rare-earth elements. But it is still a big challenge to obtain bulk magnets with ideal microstructure and high performance. In this work, two - step warm processing at relative low temperatures had been adopted to obtain nearly theoretical density bulk nanocomposite magnets from amorphous/nanocrystalline powder precursors. Novel nanostructures consisting of multiple Sm-Co hard phases (SmCo5 as main phase, SmCo3, SmCo7, Sm2Co17 as minor phases) and 25 wt% α-Fe(Co) soft phase, nanoscale grain size below 20 nm for both the hard phase and soft phase, and the diffusion of Fe and Co compositions had been obtained in bulk isotropic magnets. Besides the ideal nanostructures, a high coercivity of 5.9 kOe, Mr/Ms value of 0.78 and a high square degree of demagnetization curve S = 0.47 were obtained. All of these factors together brought a new record-high energy product (BH)max of 23.6 MGOe. These results make an important step toward fabricating novel nanostructure with high performance.

Study on optical performance and 532 nm laser damage of rapidly grown KDP crystals

Type II samples were obtained from the adjacent positions of pyramidal sector and prismatic sector in the same potassium dihydrogen phosphate (KDP) single crystal grown by the “point seed” technique under different temperature range and supersaturation. Some samples were annealed at 160 °C for 24 h. The UV–Vis spectra, especially in the ultraviolet region, show the optimal transmitting ability for the KDP crystal which was grown under relative low temperature range. The structural analysis performed by means of Fourier transformed infrared spectroscopy (FTIR) suggests that the crystal lattice of the KDP grown under relative small supersaturation become compact at the molecular level. The results of photoluminescence (PL) emission spectra show that the PL intensity increases with the rise of supersaturation and growth temperature range, which indicates that the concentration of all the detected micro defects in the KDP is abundant. The damage threshold conducted using 532 nm ns laser pulses shows the same trend with the results of PL spectra. The laser-induced damage threshold (LIDT) has been improved with the decrease of growth temperature range and supersaturation, and its variation has the highest correlation with the concentration of hydrogen vacancy defect. In addition, thermal annealing can effectively reduce the concentration of all the detected micro defects in the sample, and LIDT of the samples can be enhanced further after laser sub-threshold annealing. • KDP single crystals were obtained using the “point seed” rapid growth technique. • The relationship between laser-induced damage threshold and the concentration of micro defects is established. • The synergistic effect of thermal annealing and laser sub-threshold annealing is confirmed. • Enhanced laser-induced damage competence and laser-induced damage mechanism of the samples has been discussed.

Numerical simulation and experimental verification on the diffusion behavior of tritium in zirconium alloy cladding materials

The research on the diffusion behavior of tritium in zirconium alloy is a crucial problem for nuclear power plant radiation safety evaluation. Based on the basic model of tritium diffusion, a one-dimensional simulation program for the behavior of tritium diffusion was established in this work. The simulation program was verified by typical experiments, and the simulation results were in good agreement with the experimental results. The effects of different concentration and temperature distribution of tritium on the diffusion behavior of tritium in zirconium alloy cladding materials were analyzed. The results show that the increase of tritium concentration in P-C gap lead to the increase of tritium diffusion flux and permeability flux in and out of cladding. Due to the relatively low diffusion coefficient of the coated oxide layer, the existence of the coated oxide layer limits the tritium permeability greatly. The effect of temperature on the diffusion rate of tritium is exponential. The higher the temperature is, the faster the diffusion rate is. The relative low temperature of the oxide layer on the outer surface of zirconium alloy limits the rate of tritium permeation out of the cladding tube. Thermally induced diffusion due to temperature gradient is beneficial to limit the permeation flux of tritium diffusing out of the zirconium cladding.