Controllable large-scale processing of temperature regulating sheath-core fibers with high-enthalpy for thermal management

Temperature regulating fibers(TRF_(s)) with high enthalpy and high form stability are the key factors for thermal management. However, the enthalpies of most TRFsare not high, and the preparation methods are still at the laboratory scale. It remains a great challenge to use industrial spinning equipment to achieve continuous processing of TRF_(s) with excellent thermal and mechanical properties. Here, polyamide 6(PA6) based TRF_(s) with a sheath-core structure were prepared by bicomponent melt-spinning. The sheath-core TRF(TRF_(sc)) are composed of PA6 as sheath and functional PA6 as core, which are filled with the shape stable phase change materials(ssPCM),dendritic silica@polyethylene glycol(SiO_(2)@PEG). With the aid of the sheath structure, the filling content of SiO_(2)@PEG can reach 30 %, so that the enthalpy of the TRF_(s) can be as high as 21.3 J/g. The ultra-high enthalpy guarantees the temperature regulation ability during the alternating process of cooling and heating. In hot environment, the temperature regulation time is 6.59 min, and the temperature difference is 12.93℃. In addition, the mechanical strength of the prepared TRF_(sc) reaches 2.26 cN/dtex, which can fully meet its application in the field of thermal management textiles and devices to manage the temperature regulation of the human body or precision equipment, etc.

Exploring the effect of cooling rate on non-isothermal crystallization of copolymer polypropylene by fast scanning calorimetry

Polypropylene is commonly used as a binder for ceramic injection molding,and rapid cooling is often encountered during processing.However,the crystallization behavior of polypropylene shows a strong dependence on cooling rate due to its semi-crystalline characteristics.Therefore,the influence of cooling rate on the quality of final product cannot be ignored.In this study,the fast differential scanning calorimetry(FSC)test was performed to study the influence of cooling rate on the non-isothermal crystallization behavior and non-isothermal crystallization kinetics of a copolymer polypropylene(PP BC03B).The results show that the crystallization temperatures and crystallinity decrease as the cooling rate increases.In addition,two exothermic peaks occur when cooling rate ranges from 30 to 300 K·s^(-1),indicating the formation of another crystal phase.Avrami,Ozawa and Mo equations were used to explore the non-isothermal crystallization kinetics,and it can be concluded that the Mo method is suitable for this study.

The Effects of Thickness and Location of PCMon the Building’s Passive Temperature-Control–A Numerical Study

Building energy consumption and building carbon emissions both account for more than 20%of their total national values in China.Building employing phase change material(PCM)for passive temperature control shows a promising prospect in meeting the comfort demand and reducing energy consumption simultaneously.However,there is a lack of more detailed research on the interaction between the location and thickness of PCM and indoor natural convection,as well as indoor temperature distribution.In this study,the numerical model of a passive temperature-controlled building integrating the developed PCM module is established with the help of ANSYS.In which,the actual weather condition of Beijing city is set as the boundary conditions and the indoor natural convection is simulated with the consideration of radiation model.The effects of PCM’s thickness and location on the internal temperature field are analyzed and discussed.The results show that the room could maintain within the human comfort temperature range with the longest ratio of 94.10%and the shortest ratio of 51.04%as integrating PCM.In comparison,the value is only 26.70%without PCM.The room’s maximum temperature fluctuation can also be improved;it could be lowered by 64.4%compared to the normal condition.When the quantity of PCM is sufficient,further increasing the PCM amount results in a temperature fluctuation reduction of less than 0.1°C and does not increase the comfort time.Placing PCM on the wall induces an apparent variation in indoor temperature along the vertical direction.Conversely,placing PCM on the roof can lead to a heat transfer rate difference of up to seven times.The optimal placement of PCM depends on the difference between the environmental and phase change temperatures.If the difference is positive,placing PCM on the roof is more effective;conversely,the opposite holds.According to the results over the entire cycle,PCM application on vertical walls yields better performance.The significant difference in natural convection caused by the same thickness of PCM but different application positions,coupled with the influence of air movement on the melting and solidification of PCM,further impacts indoor temperature fluctuations and comfort.This study can provide guidance for the application location and thickness of PCM,especially for scenarios where temperature regulation is required at a specific time.

The Crystallization Behavior and Stability of Chromite Synthesized in Chromium-Containing Wastewater at Room Temperature

The ferrite process can not only purify wastewater containing heavy metal ions but also recycle valuable metals from wastewater. Therefore, it is considered a promising technology to treat chromiumcontaining wastewater. However, the process has not been extensively applied in industry due to its high synthesis temperature. In this paper, the feasibility of chromite synthesis at room temperature was comprehensively studied. The effects of critical factors on the effluent quality and the crystallization behavior and stability of the synthetic products were investigated. Results showed that the removal ratio of chromium from wastewater was over 99.0%, and the chromium concentration in the supernatant reached the sewage discharge standard after undergoing the ferrite process at room temperature. Increases in the aeration rate, stirring rate, and reaction time were favorable for the formation of stable chromite. The particles obtained by the ferrite process at room temperature were characterized by a compact structure, and the maximum size of the particles reached 52 μm. Chromium gradually entered the spinel crystal structure during the synthesis process, and the molecular formula of the synthetic chromite might be Fe3-xCrxO4, in which x was approximately 0.30. The path of the microscopic reaction was proposed to illuminate the synthesis mechanism of chromite under room temperature conditions. The present study has laid the foundation for the industrial application of the ferrite process in the purification and utilization of chromium-containing wastewater.

Influence of High Temperature Treatment on the Performance of Nickel-Induced Laterally Crystallized Thin Film Transistors

Well known for their good performance,thin film transistors (TFTs) with active layers which were nickel induced laterally crystallized,are fabricated by conventional process of dual gate CMOS.The influence of pre high temperature treatment of device fabrication on the performance of TFTs is also investigated.The experiment shows that the high temperature treatment affects the performance of the devices strongly.The best performance is obtained by adopting pre treatment of 1000℃.The mobility of 314cm 2/(V·s) is obtained at NMOS TFTs with pre treatment of 1000℃,which is 10% and 22% higher than that treated at 1100℃ and without pre high temperature treatment,respectively.A maximum on/off current ratio of 3×10 8 is also obtained at 1000℃.Further investigation of uniformity verifies that the result is reliable.

Crystallization Temperature and Crystallization Ratio of Mold Flux

The factors influencing the crystallization ratio of mold flux were researched by rapid cooling technolo gy, and the factors affecting crystallization temperature were studied by single thermocouple technique. The results showed that the crystallization ratio of mold flux increases with the basicity and the content of Na2O, CaF2, Li2O and NaF, and decreases with the increase of the content of Al2O3, MgO, BaO, MnO and B2O3. However, the crystallization temperature of mold flux rises with the basicity and the content of NaF, Na2O and CaF2, and reduces with the increase of the content of Al2O3, MgO, BaO, MnO and B2O3. But for Li2O, crystallization temperature decreases firstly to a minimum value at 2%, and then increases gradually with the increase of Li2O.

Effect of sintering temperature on the microstructure and properties of foamed glass-ceramics prepared from high-titanium blast furnace slag and waste glass

Foamed glass-ceramics were prepared via a single-step sintering method using high-titanium blast furnace slag and waste glass as the main raw materials The influence of sintering temperature(900–1060℃) on the microstructure and properties of foamed glass-ceramics was studied. The results show that the crystal shape changed from grainy to rod-shaped and finally turned to multiple shapes as the sintering temperature was increased from 900 to 1060℃. With increasing sintering temperature, the average pore size of the foamed glass-ceramics increased and subsequently decreased. By contrast, the compressive strength and the bulk density decreased and subsequently increased. An excessively high temperature, however, induced the coalescence of pores and decreased the compressive strength. The optimal properties, including the highest compressive strength(16.64 MPa) among the investigated samples and a relatively low bulk density(0.83 g/cm^3), were attained in the case of the foamed glass-ceramics sintered at 1000℃.

Inclusions in large diamond single crystals at different temperatures of synthesis

The inclusions in large diamond single crystals have effects on its ultimate performance, which restricts its industrial applications to a great extent. Therefore, it is necessary to study the inclusions systematically. In this paper, large diamond single crystals with different content values of inclusions are synthesized along the(100) surface by the temperature gradient method(TGM) under 5.6 GPa at different temperatures. With the synthetic temperature changing from 1200?C to 1270?C,the shapes of diamonds change from plate to low tower, to high tower, even to steeple. From the microscopic photographs of the diamond samples, it can be observed that with the shapes of the samples changing at different temperatures, the content values of inclusions in diamonds become zero, a little, much and most, correspondingly. Consequently, with the temperature growing from low to high, the content values of inclusions in crystals increase. The origin of inclusions is explained by the difference in growth rate between diamond crystal and its surface. The content values of inclusions in diamond samples are quantitatively calculated by testing the densities of diamond samples. And the composition and inclusion content are analyzed by energy dispersive spectroscopy(EDS) and x-ray diffraction(XRD). From contrasting scanning electron microscopy(SEM) photographs, it can be found that the more the inclusions in diamond, the more imperfect the diamond surface is.

FEM simulations and experimental studies of the temperature field in a large diamond crystal growth cell

We investigate the temperature field variation in the growth region of a diamond crystal in a sealed cell during the whole process of crystal growth by using the temperature gradient method （TGM） at high pressure and high temperature （HPHT）. We employ both the finite element method （FEM） and in situ experiments. Simulation results show that the temperature in the center area of the growth cell continues to decrease during the process of large diamond crystal growth. These results are in good agreement with our experimental data, which demonstrates that the finite element model can successfully predict the temperature field variations in the growth cell. The FEM simulation will be useful to grow larger high-quality diamond crystal by using the TGM. Furthermore, this method will be helpful in designing better cells and improving the growth process of gem-quality diamond crystal.

Influence of temperature on the properties of one-dimensional piezoelectric phononic crystals

The current study investigates the influence of temperature on a one-dimensional piezoelectric phononic crystal using tunable resonant frequencies. Analytical and numerical examples are introduced to emphasize the influence of temperature on the piezoelectric phononic crystals. It was observed that the transmission spectrum of a one-dimensional phononic crystal containing a piezoelectric material（0.7 PMN-0.3 PT） can be changed drastically by an increase in temperature.The resonant peak can be shifted toward high or low frequencies by an increase or decrease in temperature, respectively.Therefore, we deduced that temperature can exhibit a large tuning in the phononic band gaps and in the local resonant frequencies depending on the presence of a piezoelectric material. Such result can enhance the harvesting energy from piezoelectric materials, especially those that are confined in a phononic crystal.

Effects of Annealing Process on Crystallization and Low Temperature Resistance Properties of PP-R Composites

The effects of the annealing process on the mechanical properties and crystallization behaviors of polypropylene random copolymer（PP-R） composites were investigated using differential scanning calorimetry（DSC）, wide-angle X-ray diffraction（WAXD）, and dynamic mechanical analysis（DMA）, and scanning electron microscopy（SEM）. The experimental results indicated that the annealing process significantly influenced the comprehensive properties of PP-R composites. At temperatures below 23 ℃, the impact strength of the PP-R composites annealed at 120 ℃ for 6 h was relatively high at 74.73 k J/m^2, which was 16.8% higher than that of the samples annealed at 80 ℃ for 6 h. At low temperatures（-30-0 ℃）, the impact strength ranged from approximately 13.31 k J/m^2 to 54.4 k J/m^2. In addition, the annealing process conducted at 120 ℃ for 6 h improved the crystalline structure and low-temperature toughness of the PP-R composites and induced α-form to β-form crystal transformation. The work provides a possible method to reinforce and toughen the semicrystalline polymer at low temperatures（-30-0 ℃） by annealing.

Electron temperature diagnostics of aluminium plasma in a z-pinch experiment at the "QiangGuang-1" facility

Two curved crystal spectrometers are set up on the ＂QiangGuang-1＂ generator to measure the z-pinch plasma spectra emitted from planar aluminum wire array loads. Kodak Biomax-MS film and an IRD AXUVHS5# array are employed to record time-integrated and time-resolved free-bound radiation, respectively. The photon energy recorded by each detector is ascertained by using the L-shell lines of molybdenum plasma. Based on the exponential relation between the continuum power and photon energies, the aluminum plasma electron temperatures are measured. For the time-integrated diagnosis, several ＂bright spots＂ indicate electron temperatures between （450 eV- 520 eV） ± 35%. And for the time-resolved ones, the result shows that the electron temperature reaches about 800 eV±30% at peak power. The system satisfies the demand of z-pinch plasma electron temperature diagnosis on a - 1 MA facility.

Embedding Perovskite in Polymer Matrix Achieved Positive Temperature Response with Inversed Temperature Crystallization

Organic perovskites are promising semiconductor materials for advanced photoelectric applications.Their fluorescence typically shows a negative temperature coefficient due to bandgap change and structural instability.In this study,a novel perovskite-based composite with positive sensitivity to temperature was designed and obtained based on its inverse temperature crystallization,demonstrating good flexibility and solution processability.The supercritical drying method was used to address the limitations of annealing drying in preparing high-performance perovskite.Optimizing the precursor composition proved to be an effective approach for achieving high fluorescence and structural integrity in the perovskite material.This perovskite-based composite exhibited a positive temperature sensitivity of 28.563%℃^(-1)for intensity change and excellent temperature cycling reversibility in the range of 25-40℃in an ambient environment.This made it suitable for use as a smart window with rapid response.Furthermore,the perovskite composite was found to offer temperature-sensing photoluminescence and flexible processability due to its components of perovskite-based compounds and polyethylene oxide.The organic precursor solvent could be a promising candidate for use as ink to print or write on various substrates for optoelectronic devices responding to temperature.

Predictive modeling of critical temperatures in magnesium compounds using transfer learning

This study presents a transfer learning approach for discovering potential Mg-based superconductors utilizing a comprehensive target dataset.Initially,a large source dataset(Bandgap dataset)comprising approximately∼75k compounds is utilized for pretraining,followed by fine-tuning with a smaller Critical Temperature(T_(c))dataset containing∼300 compounds.Comparatively,there is a significant improvement in the performance of the transfer learning model over the traditional deep learning(DL)model in predicting Tc.Subsequently,the transfer learning model is applied to predict the properties of approximately 150k compounds.Predictions are validated computationally using density functional theory(DFT)calculations based on lattice dynamics-related theory.Moreover,to demonstrate the extended predictive capability of the transfer learning model for new materials,a pool of virtual compounds derived from prototype crystal structures from the Materials Project(MP)database is generated.T_(c) predictions are obtained for∼3600 virtual compounds,which underwent screening for electroneutrality and thermodynamic stability.An Extra Trees-based model is trained to utilize E_(hull)values to obtain thermodynamically stable materials,employing a dataset containing Ehull values for approximately 150k materials for training.Materials with Ehull values exceeding 5 meV/atom were filtered out,resulting in a refined list of potential Mg-based superconductors.This study showcases the effectiveness of transfer learning in predicting superconducting properties and highlights its potential for accelerating the discovery of Mg-based materials in the field of superconductivity.

Stability analysis of a liquid crystal elastomer self-oscillator under a linear temperature field

Self-oscillating systems abound in the natural world and offer substantial potential for applications in controllers,micro-motors,medical equipments,and so on.Currently,numerical methods have been widely utilized for obtaining the characteristics of self-oscillation including amplitude and frequency.However,numerical methods are burdened by intricate computations and limited precision,hindering comprehensive investigations into self-oscillating systems.In this paper,the stability of a liquid crystal elastomer fiber self-oscillating system under a linear temperature field is studied,and analytical solutions for the amplitude and frequency are determined.Initially,we establish the governing equations of self-oscillation,elucidate two motion regimes,and reveal the underlying mechanism.Subsequently,we conduct a stability analysis and employ a multi-scale method to obtain the analytical solutions for the amplitude and frequency.The results show agreement between the multi-scale and numerical methods.This research contributes to the examination of diverse self-oscillating systems and advances the theoretical analysis of self-oscillating systems rooted in active materials.

Surface recrystallization of a Ni_3Al based single crystal superalloy at different annealing temperatures and blasting pressure

The effects of annealing temperature and grit blasting pressure on the recrystallization behavior of a Ni3Al based single crystal superalloy were studied in this work. The results show that the precipitation of the Y-NiMo phase occurs at 900 and 1000 °C, which precedes recrystallization. The initial recrystallization temperature was between 1000 and 1100 °C. Cellular recrystallization was formed at 1100 and 1200 °C, which consisted of large columnar γ′ and fine γ + γ′. The dendrite arm closed to the interdendritic region may act as nucleation sites during initial recrystallization by a particle simulated nucleation mechanism at 1280 °C. The size of the grains first turned large and then became small upon the pressure while the recrystallization depth increased all the time.

Synthesis of large diamond crystals containing high-nitrogen concentration at high pressure and high temperature using Ni-based solvent by temperature gradient method

This paper reprots that with Ni-based catalyst/solvent and with a dopant of NAN3, large green single crystal diamonds with perfect shape are successfully synthesized by temperature gradient method under high pressure and high temperature in a China-type cubic anvil high-pressure apparatus （SPD-6 × 1200）, and the highest nitrogen concentration reaches approximately 121-1257 ppm calculated by infrared absorption spectra. The synthesis conditions are about 5.5 CPa and 1240-1300 ℃. The growth behaviour of diamond with high-nitrogen concentration is investigated in detail. The results show that, with increasing the content of NaN3 added in synthesis system, the width of synthesis temperature region for growth high-quality diamonds becomes narrower, and the morphology of diamond crystal is changed from cube-octahedral to octahedral at same temperature and pressure, the crystal growth rate is slowed down, nevertheless, the nitrogen concentration doped in synthetic diamond increases.

Synthesis and Characterization of Liquid Crystal with Lower Temperature of Phase Change of meso-tetra-(4-n-lauroyloxyphenyl)porphyrin

The synthesis and characterization of meso-tetra (4-n-lauroyloxy phenyl) porphyrin with long ester chains are reported. The domains of stability and the structure of the liquid crystalline phases are determined by optical microscopy and differential scanning calorimerials (DSC).

Effect of initial crystallization temperature and surface diffusion on formation of GaAs multiple concentric nanoring structures by droplet epitaxy

GaAs multiple concentric nano-ring structures(CNRs)are prepared with multistep crystallization procedures by droplets epitaxy on GaAs(001)to explore the influence of different initial crystallization temperatures on CNRs morphology.Atomic force microscope(AFM)images show that GaAs nanostructures are more likely to form elliptical rings due to diffusion anisotropy.Meanwhile,with the increase of initial crystallization temperature,the inner ring height and density of CNRs are increased,and outer rings are harder to form.In addition,the mechanism of formation of CNRs is discussed by classical nucleation theory and diffusion theory.The method can be used to calculate the diffusion activation energy of gallium atoms(0.7±0.1 eV)on the GaAs(001)surface conveniently.

Combined use of fly ash and silica to prevent the long-term strength retrogression of oil well cement set and cured at HPHT conditions

The long-term strength retrogression of silica-enriched oil well cement poses a significant threat to wellbore integrity in deep and ultra-deep wells, which is a major obstacle for deep petroleum and geothermal energy development. Previous attempts to address this problem has been unsatisfactory because they can only reduce the strength decline rate. This study presents a new solution to this problem by incorporating fly ash to the traditional silica-cement systems. The influences of fly ash and silica on the strength retrogression behavior of oil well cement systems directly set and cured under the condition of 200°C and 50 MPa are investigated. Test results indicate that the slurries containing only silica or fly ash experience severe strength retrogression from 2 to 30 d curing, while the slurries containing both fly ash and silica experience strength enhancement from 2 to 90 d. The strength test results are corroborated by further evidences from permeability tests as well as microstructure analysis of set cement. Composition of set cement evaluated by quantitative X-ray diffraction analyses with partial or no known crystal structure(PONKCS) method and thermogravimetry analyses revealed that the conversion of amorphous C-(A)-S-H to crystalline phases is the primary cause of long-term strength retrogression.The addition of fly ash can reduce the initial amount of C-(A)-S-H in the set cement, and its combined use with silica can prevent the crystallization of C-(A)-S-H, which is believed to be the working mechanism of this new admixture in improving long-term strength stability of oil well cement systems.