Thermal Stability of Rare Earth-Rich Phase in High Temperature Titanium Alloy

The thermal stability of the rare earth rich phase particles in α, α+β and β phase regions of Ti 5Al 4Sn 2Zr 1Mo 0 25Si 1Nd(Ti 55) high temperature titanium alloy heat treated was studied. Under conditions of 600～980 ℃/1～100 h and 1050～1500 ℃/1～10 h, the average particle size ranges from 3 34 to 4 20 μm, the circularity shape factor from 0 619 to 0 759, and the volume fraction from 1 4% to 1 8%. The results show that nearly no change is found for the size, shape, and volume fraction of the particles in the alloy, and the rare earth rich phase particles exhibit thermal stability.

Significantly enhanced thermal stability of HMX by phase-transition lysozyme coating

A new robust bio-inspired route by using lysozyme aqueous solution for surface modification on 1,3,5,7-tetranitro-1,3,5,7-tetrazocane(HMX)was described in this paper.HMX crystals were coated by in situ phase transition of lysozyme(PTL)molecules.The HMX decorated by PTL was characterized by SEM,XRD,FTIR and XPS,demonstrating a dense core-shell coating layer.The coverage of lysozyme on HMX crystal was calculated by the ratio of sulfur content.The surface coverage increased from 60.5% to 93.5% when the content of PTL was changed from 0.5 wt% to 2.0 wt%,indicating efficient coating.The thermal stability of HMX was investigated by in situ XRD and DSC.The thermal phase transition temperature of HMX(β to δ phase)was delayed by 42℃ with 2.0 wt% PTL coating,which prevented HMX from thermal damage and sensitivity by the effect of PTL coating.After heating at 215℃,large cracks appeared in the naked HMX crystal,while the PTL coated HMX still maintained intact,with the impact energy of HMX dropped dramatically from 5 J to 2 J.However,the impact energy of HMX with 1.0 wt% and 2.0 wt% coating content(HMX@PTL-1.0 and HMX@PTL-2.0)was unchanged(5 J).Present results potentially enable large-scale fabrication of polymorphic energetic materials with outstanding thermal stability by novel lysozyme coating.

Construction of core@double-shell structured energetic composites with simultaneously enhanced thermal stability and safety performance

The poor thermal stability and high sensitivity severely hinder the practical application of hexanitrohexaazaisowurtzitane(CL-20).Herein,a kind of novel core@double-shell CL-20 based energetic composites were fabricated to address the above issues.The coordination complexes which consist of natural polyphenol tannic acid(TA) and Fe~Ⅲ were chosen to construct the inner shell,while the graphene sheets were used to build the outer shell.The resulting CL-20/TA-Fe~Ⅲ/graphene composites exhibited simultaneously improved thermal stability and safety performance with only 1 wt% double-shell content,which should be ascribed to the intense physical encapsulation effect from inner shell combined with the desensitization effect of carbon nano-materials from outer shell.The phase transition(ε to γ) temperature increased from 173.70 ℃ of pure CL-20 to 191.87℃ of CL-20/TA-Fe~Ⅲ/graphene composites.Meanwhile,the characteristic drop height(H_(50)) dramatically increased from 14.7 cm of pure CL-20 to112.8 cm of CL-20/TA-Fe~Ⅲ/graphene composites,indicating much superior safety performance after the construction of the double-shell structure.In general,this work has provided an effective and versatile strategy to conquer the thermal stability and safety issues of CL-20 and contributes to the future application of high energy density energetic materials.

Preparation and Thermal Stability of AlMoON Based Solar Selective Absorption Coating

AlMoON based solar selective absorption coatings were deposited on stainless steel substrate by magnetron sputtering.The coatings included infrared reflection layer Mo,absorption layer AlMoN,absorption layer AlMoON and antireflection layer AlMoO from bottom to top.The surface of the deposited coatings is flat without obvious defects.The absorptivity and emissivity are 0.896 and 0.09,respectively,and the quality factor is 9.96.After heat treatment at 500℃-36 h,the surface roughness of the coating increases,a small number of cracks and other defects appear,and the broken part is still attached to the coating surface.A certain degree of element diffusion occurs in the coatings,resulting in the decline of the optical properties of the coatings.The absorptivity and emissivity are 0.883 and 0.131,respectively,the quality factor is 7.06,and the PC value is 0.0335.The coatings do not fail under this condition and have certain thermal stability.

Thermal Stability and Degeneration Behavior of Solar Selective Absorber Based on WTi-Al_(2)O_(3)Cermet

A WTi-Al_(2)O_(3)cermet-based solar selective absorber was prepared to investigate the atomic diffusion induced spectral selectivity degeneration.The as-deposited coating exhibits superior absorptance(0.934)and low thermal emittance(0.098),as well as excellent thermal stability with a selectivity of 0.900/0.07 even after annealing at 923 K for 400 h in Ar ambient.However,the multilayer coating failed after being subjected to annealing at 923 K for 400 h in an air environment,as indicated by a decrease in solar absorptance to 0.912 and an increase in thermal emittance to 0.634.The microstructure characterizations reveal that the annealed coating exhibits a columnar morphology along the vertical direction of the substrate.The presence of abundant grain boundaries in the multilayer coating promotes the outward diffusion of Cr and Mn atoms in the stainless-steel substrate.The Mn atoms,in particular,possess the capability to migrate towards the surface of the coating and undergo an oxidation reaction with oxygen,facilitating the formation of a thick Mn_(2)O_(3)layer.The roughness of the coating surface was significantly increased in this case,adversely affecting solar absorptance due to amplified sunlight reflection.In addition,the rocketing of thermal emittance is attributed to the destabilization of W infrared reflective layer during the annealing.These findings highlight the importance of considering the outward diffusion of Mn and Cr elements in the stainless-steel substrate when optimizing solar selective absorbers.

The Effect of Uncaria gambir on Optical Properties and Thermal Stability of CNF/PVA Biocomposite Films

Cellulose-based film has gained popularity as an alternative to synthetic polymers due to its outstanding properties.Among all types of cellulose materials available,cellulose nanofiber(CNF)has great potential to be utilized in a diverse range of applications,including as a film material.In this study,CNF biocomposite film was prepared by using polyvinyl alcohol(PVA)as a matrix and Uncaria gambir extract as a filler.This study aims to investigate the effect of Uncaria gambir extract on the optical properties and thermal stability of the produced film.The formation of the CNF biocomposite films was confirmed using Fourier Transform Infrared Spectroscopy,their transmittance characteristics were measured using UV-Vis spectroscopy and a transmittance meter,while their reflectance was determined using a reflectance meter.The results revealed that the addition of Uncaria gambir extract to the CNF biocomposite film improved its UV-shielding properties,as indicated by the lower percentage of transmittance in the visible region,10%–70%.In addition,its reflectance increased to 10.6%compared to the CNF film without the addition of Uncaria gambir extract.Furthermore,the thermal stability of the CNF biocomposite film with the addition of Uncaria gambir extract improved to around 400℃–500℃.In conclusion,the results showed that CNF biocomposite film prepared by adding Uncaria gambir extract can be a promising candidate for optical and thermal management materials.

Research progress on classification,source,application of phytosterol esters,and their thermal oxidation stability

Phytosterol esters can effectively decrease serum cholesterol concentration in the human body and prevent cardio-cerebrovascular diseases.It was found that phytosterol esters exhibited better solubility and bioavailability than free phytosterols.In recent years,phytosterol esters have attracted increasing attention.However,during food processing,phytosterol esters are susceptible to degradation at high temperatures,resulting in certain losses and formation of potentially harmful substances for humans.This paper reviews the relevant literatures and updates on the thermal oxidation stability of phytosterol esters in recent years from the following aspects:(i)Sources,physiological activities,and applications of phytosterol esters;(ii)Oxidation mechanism of phytosterol esters;(iii)Effects of phytosterols species,the volume of addition,food matrix,heating temperature and time,and antioxidants on the thermal loss and oxidation stability of phytosterol esters.The research progress on the safety of phytosterol esters is also discussed in detail.Additionally,the prospects for future research are highlighted.

Semitransparent Organic Solar Cells with Superior Thermal/Light Stability and Balanced Efficiency and Transmittance

Semitransparent organic solar cells show attractive potential in the application of building-integrated photovoltaics,agrivoltaics,floating photovoltaics,and wearable electronics,as their multiple functionalities of electric power generation,photopermeability,and color tunability.Design and exploration of semitransparent organic solar cells with optimal and balanced efficiency and average visible light transmittance and simultaneously high stability are in great demand.In this work,based on a layer-by-layer-processed active layer and an ultrathin metal electrode,inverted semitransparent organic solar cells(ITO/AZO/PM6/BTP-eC9/MoO_(3)/Au/Ag)were fabricated.Optimal and balanced efficiency and average visible light transmittance were demonstrated,and simultaneously promising thermal and light stability were achieved for the obtained devices.The power conversion efficiency of 13.78-12.29%and corresponding average visible light transmittance of 14.58-25.80%were recorded for the ST-OSC devices with 25-15 nm thick Ag electrodes,respectively.Superior thermal and light stability with~90%and~85%of initial efficiency retained in 400 h under 85°C thermal stress and AM1.5 solar illumination were demonstrated,respectively.

Further Analysis of Machine Tool Dimensional Accuracy and Thermal Stability under Varying Floor Temperature

Machining is as old as humanity, and changes in temperature in both the machine’s internal and external environments can be of great concern as they affect the machine’s thermal stability and, thus, the machine’s dimensional accuracy. This paper is a continuation of our earlier work, which aimed to analyze the effect of the internal temperature of a machine tool as the machine is put into operation and vary the external temperature, the machine floor temperature. Some experiments are carried out under controlled conditions to study how machine tool components get heated up and how this heating up affects the machine’s accuracy due to thermally induced deviations. Additionally, another angle is added by varying the machine floor temperature. The parameters mentioned above are explored in line with the overall thermal stability of the machine tool and its dimensional accuracy. A Robodrill CNC machine tool is used. The CNC was first soaked with thermal energy by gradually raising the machine floor temperature to a certain level before putting the machine in operation. The machine was monitored, and analytical methods were deplored to evaluate thermal stability. Secondly, the machine was run idle for some time under raised floor temperature before it was put into operation. Data was also collected and analyzed. It is observed that machine thermal stability can be achieved in several ways depending on how the above parameters are joggled. This paper, in conclusion, reinforces the idea of machine tool warm-up process in conjunction with a carefully analyzed and established machine floor temperature variation for the approximation of the machine tool’s thermally stability to map the long-time behavior of the machine tool.

Intrinsic thermal stability of inverted perovskite solar cells based on electrochemical deposited PEDOT

Thermal stability of perovskite materials is an issue impairing the long-term operation of inverted perovskite solar cells(PSCs). Herein, the thermal attenuation mechanism of the MAPb I3films that deposited on two different hole transport layers(HTL), poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)(PEDOT:PSS) and poly(3,4-ethylenedioxythiophene)(PEDOT), is comprehensively studied by applying a heat treatment at 85℃. The thermal stress causes the mutual ions migration of I, Pb and Ag through the device, which leads to the thermal decomposition of perovskite to form Pb I2. Interestingly, we find that I ions tend to migrate more towards electron transport layer(ETL) during heating, which is different with the observation of I ions migration towards HTL when bias pressure is applied. Moreover, the use of electrochemical deposited PEDOT as HTL significantly decreases the defect density of MAPb I3films as compared to PEDOT:PSS supported one. The electrochemical deposition PEDOT has good carrier mobility and low acidity, which avoids the drawbacks of aqueous PEDOT:PSS. Accordingly, the inverted PSCs based on PEDOT show superior durability than that with PEDOT:PSS. Our results reveal detailed degradation routes of a new kind of inverted PSCs which can contribute to the understanding of the failure of thermal-aged inverted PSCs.

Thermal–moisture dynamics and thermal stability of active layer in response to wet/dry conditions in the central region of the Qinghai–Tibet Plateau,China

The amount of rainfall varies unevenly in different regions of the Qinghai-Tibet Plateau, with some regions becoming wetter and others drier. Precipitation has an important impact on the process of surface energy balance and the energy-water transfer within soils. To clarify the thermal-moisture dynamics and thermal stability of the active layer in permafrost regions under wet/dry conditions, the verified water-vapour-heat coupling model was used. Changes in the surface energy balance, energy-water transfer within the soil, and thickness of the active layer were quantitatively analyzed. The results demonstrate that rainfall changes significantly affect the Bowen ratio, which in turn affects surface energy exchange. Under wet/dry conditions, there is a positive correlation between rainfall and liquid water flux under the hydraulic gradient;water vapour migration is the main form under the temperature gradient, which indicates that the influence of water vapour migration on thermalmoisture dynamics of the active layer cannot be neglected. Concurrently, regardless of wet or dry conditions,disturbance of the heat transport by conduction caused by rainfall is stronger than that of convection by liquid water. In addition, when rainfall decreases by 1.5 times(212 mm) and increases by 1.5 times(477 mm), the thickness of the active layer increases by 0.12 m and decreases by 0.21 m, respectively. The results show that dry conditions are not conducive to the preservation of frozen soil;however, wet conditions are conducive to the preservation of frozen soil, although there is a threshold value. When this threshold value is exceeded, rainfall is unfavourable for the development of frozen soil.

Exceptional thermal stability and enhanced hardness in a nanostructured Mg-Gd-Y-Zn-Zr alloy processed by high pressure torsion

A Mg-8.2Gd-3.8Y-1.0Zn-0.4Zr(wt.%) alloy is processed by solution treatment and high pressure torsion(HPT) at room temperature to produce a nanostructured light material with high hardness. The stability of this alloy is subsequently tested through isochronal annealing for 0.5 h at 373 K to 673 K. The results reveal a thermal stability that is vastly superior to that of conventional Mg-based alloys processed by severe plastic deformation: the grain size remains at around 50 nm on heating to 573 K, and as the temperature is increased to 673 K,grain growth is restricted to within 500 nm. The stability of grain refinement of the present alloy/processing combination allowing grain size to be limited to 55 nm after exposure at 573 K, appears to be nearly one order of magnitude better than for the other SPD processed Mg-RE type alloys, and 2 orders of magnitude better than those of SPD processed RE-free Mg alloys. This superior thermal stability is attributed to formation of co-clusters near and segregation at grain boundaries, which cause a thermodynamic stabilization of grain size, as well as formation of β-Mg_(5)RE equilibrium phase at grain boundaries, which impede grain growth by the Zener pinning effect. The hardness of the nanostructured Mg-Gd-Y-Zn-Zr alloy increases with increasing annealing temperature up to 573 K, which is quite different from the other SPD-processed Mg-based alloys. The high hardness of 136 HV after annealing at 573 K is mainly due to solute segregation and solute clustering at or near grain boundaries.

Optimizing the morphology of all-polymer solar cells for enhanced photovoltaic performance and thermal stability

Due to the complicated film formation kinetics, morphology control remains a major challenge for the development of efficient and stable all-polymer solar cells(all-PSCs). To overcome this obstacle, the sequential deposition method is used to fabricate the photoactive layers of all-PSCs comprising a polymer donor PTzBI-oF and a polymer acceptor PS1. The film morphology can be manipulated by incorporating amounts of a dibenzyl ether additive into the PS1 layer. Detailed morphology investigations by grazing incidence wide-angle X-ray scattering and a transmission electron microscope reveal that the combination merits of sequential deposition and DBE additive can render favorable crystalline properties as well as phase separation for PTzBI-oF:PS1 blends. Consequently, the optimized all-PSCs delivered an enhanced power conversion efficiency(PCE) of 15.21%along with improved carrier extraction and suppressed charge recombination. More importantly, the optimized all-PSCs remain over 90% of their initial PCEs under continuous thermal stress at 65 °C for over 500 h. This work validates that control over microstructure morphology via a sequential deposition process is a promising strategy for fabricating highly efficient and stable all-PSCs.

17.13% Efficiency and Superior Thermal Stability of Organic Solar Cells Based on a Comb-Shape Active Blend

With rapid progress,organic solar cells(OSCs)are getting closer to the target of real application.However,the stability issue is still one of the biggest challenges that have to be resolved.Especially,the thermal stability of OSCs is far from meeting the requirements of the application.Here,based on the layer-by-layer(LBL)process and by utilizing the dissolubility nature of solvent and materials,binary inverted OSCs(ITO/AZO/PM6/BTP-eC9/MoO3/Ag)with comb shape active morphology are fabricated.High efficiency of 17.13%and simultaneous superior thermal stability(with 93%of initial efficiency retained in~9:00 h under 85℃in N_(2))are demonstrated,showing superior stability to reference cells.The enhancements are attributed to the formed optimal comb shape of the active layer,which could provide a larger D/A interface,thus more charge carriers,render the active blend a more stable morphology,and protect the electrode by impeding ion's migration and corrosion.To the best of our knowledge,this is the best thermal stability of binary OSCs reported in the literature,especially when considering the high efficiency of over 17%.

Thermal stability analysis of a satellite-borne optical bench based on quasi-kinematic support

Macao Science Satellite-1(known as MSS-1)is a low-inclination mission that will be launched at the beginning of 2023.An optical bench is used for accessing high-precision strength and direction measurements of the magnetic field.In this paper,we present a thermal stability design for the optical bench based on quasi-kinematic support by kinematic hinges on the MSS-1.The change in angles with the finite element method(FEM)model modified by thermal deformation test data is analyzed.The robustness of the structure is also investigated via the Monte Carlo method.Two main results are obtained.First,the peak-to-peak value(Vp-p)of the inter-boresight angle is at most 1.24″,and the Vp-p of the inter-boresight angle modification and analysis is no more than 3.13″,both of which are better than those on the Swarm satellites in orbit.Second,the 90°fibers of the carbon-reinforced arm need to be strictly controlled during the technological process.

High-strength and thermally stable TiB_(2)-modified Al-Mn-Mg-Er-Zr alloy fabricated via selective laser melting

To increase the processability and plasticity of the selective laser melting(SLM)fabricated Al-Mn-Mg-Er-Zr alloys,a novel TiB_(2)-modified Al-Mn-Mg-Er-Zr alloy with a mixture of Al-Mn-Mg-Er-Zr and nano-TiB_(2) powders was fabricated by SLM.The pro-cessability,microstructure,and mechanical properties of the alloy were systematically investigated by density measurement,microstruc-ture characterization,and mechanical properties testing.The alloys fabricated at 250 W displayed higher relative densities due to a uni-formly smooth top surface and appropriate laser energy input.The maximum relative density value of the alloy reached(99.7±0.1)%,demonstrating good processability.The alloy exhibited a duplex grain microstructure consisting of columnar regions primarily and equiaxed regions with TiB_(2),Al6Mn,and Al3Er phases distributed along the grain boundaries.After directly aging treatment at a high tem-perature of 400℃,the strength of the SLM-fabricated TiB_(2)/Al-Mn-Mg-Er-Zr alloy increased due to the precipitation of the secondary Al6Mn phases.The maximum yield strength and ultimate tensile strength of the aging alloy were measured to be(374±1)and(512±13)MPa,respectively.The SLM-fabricated TiB_(2)/Al-Mn-Mg-Er-Zr alloy demonstrates exceptional strength and thermal stability due to the synergistic effects of the inhibition of grain growth,the incorporation of TiB_(2) nanoparticles,and the precipitation of secondary Al6Mn nanoparticles.

Polymer Fiber Rigid Network with High Glass Transition Temperature Reinforces Stability of Organic Photovoltaics

Organic photovoltaics(OPVs)need to overcome limitations such as insufficient thermal stability to be commercialized.The reported approaches to improve stability either rely on the development of new materials or on tailoring the donor/acceptor morphology,however,exhibiting limited applicability.Therefore,it is timely to develop an easy method to enhance thermal stability without having to develop new donor/acceptor materials or donor–acceptor compatibilizers,or by introducing another third component.Herein,a unique approach is presented,based on constructing a polymer fiber rigid network with a high glass transition temperature(T_(g))to impede the movement of acceptor and donor molecules,to immobilize the active layer morphology,and thereby to improve thermal stability.A high-T_(g) one-dimensional aramid nanofiber(ANF)is utilized for network construction.Inverted OPVs with ANF network yield superior thermal stability compared to the ANF-free counterpart.The ANF network-incorporated active layer demonstrates significantly more stable morphology than the ANF-free counterpart,thereby leaving fundamental processes such as charge separation,transport,and collection,determining the device efficiency,largely unaltered.This strategy is also successfully applied to other photovoltaic systems.The strategy of incorporating a polymer fiber rigid network with high T_(g) offers a distinct perspective addressing the challenge of thermal instability with simplicity and universality.

Formation of Natural Melanin/TiO_(2) Nanostructure Hybrids with Enhanced Optical,Thermal and Magnetic Properties as a Soft Material

The natural Melanin/TiO_(2) was synthesized by the use of ultrasonication under UV radiation.The influence of natural melanin on the structural,optical and thermal properties of TiO_(2) nanoparticles was investigated by using Fourier transform infrared spectroscopy,thermogravimetric analysis and UV-Vis spectroscopy.It was observed that incorporating natural melanin on TiO_(2) nanoparticles(TiO_(2)-Mel)occurred at 2.01 eV with a low value of Urbach energy around 100 meV indicating improvement in the crystalline structure.Magnetic measurement at room temperature showed diamagnetic behavior.Furthermore,thermal results showed that TiO_(2)-Mel is stable even at temperatures up to 400℃.According to the results obtained by the thermal stability of melanin with titanium dioxide,it can be a good candidate in many applications such as solar cells and optoelectronics.

Development of Morus alba Reinforced Poly-Lactic Acid with Elevated Mechanical and Thermal Properties

This research investigates the mechanical and thermal properties of Morus alba combined with polylactic acid in comparison with other natural fibers. The study uses three different fiber and PLA compositions - 20%, 30%, and 40% respectively - to produce composite materials. In addition, another composite with the same fiber volume is treated with a 4% NaOH solution to improve mechanical properties. The composites are processed by twin-screw extrusion, granulation, and injection molding. Tensile strength measurements of raw fibers and NaOH-treated fibers were carried out using a single-fiber tensile test with a gauge length of 40 mm. It was observed that the NaOH surface treatment increases the resistance against tensile loading and exhibited improved properties for raw fiber strands. The diameter of the fibers was measured using optical microscopy. During this research, flexural tests, impact tests, differential scanning calorimetry (DSC), and heat deflection temperature measurements (HDT) were conducted to evaluate the mechanical and thermal properties of the developed composite samples. The results indicate that the mechanical properties of NaOH-treated Morus alba-reinforced polylactic acid outperform both virgin PLA samples and untreated Morus alba samples.

Microstructure and interface thermal stability of C/Mo double-coated SiC fiber reinforced γ-TiAl matrix composites

C/Mo duplex coating interfacially modified SiC fiber-reinforced γ-TiAl matrix composite （SiCf/C/Mo/γ-TiA1） was prepared by foil-fiber-foil method to investigate its interfacial modification effect. SiCf/C/TiAl composites were also prepared under the same processing condition for comparision. Both kinds of the composites were thermally exposed in vacuum at 800 and 900℃ for different durations in order to study thermal stability of the interfacial zone. With the aids of scanning electron microscope （SEM） and energy dispersive spectrometer （EDS）, the interracial microstructures of the composites were investigated. The results reveal that, although adding the Mo coating, the interfacial reaction product of the SiCf/C/Mo/TiAl composite is the same with that of the SiCf/C/TiA1 composite, which is TiC/Ti2AlC between the coating and the matrix. However, C/Mo duplex coating is more efficient in hindering interfacial reaction than C single coating at 900 ℃ and below. In addition, a new layer of interfacial reaction product was found between Ti2AlC and the matrix after 900 ℃, 200 h thermal exposure, which is rich in V and close to the chemical composition of B2 phase.