Effects of Solid-State Reaction Synthesis Processing Parameters on Thermoelectric Properties of Mg_2Si

The Mg_(2)Si-matrix thermoelectric material was synthesized by low temperature solid-state reaction.This paper studies the effects of holding time and reaction temperature on the particle size and the properties of the material,and also studies effects of doping elemental Sb,Te and their doping seqence on the properties of the material.The result shows that excessively high temperature and elongated holding time of solid-state reaction are harmful,there is a range of particle size to ensure optimum properties and the doping sequence of Sb or Te without influencing the properties.

Macroscopic Structural Analysis on a 10 kW Class Lab-Scale Process Heat Exchanger Prototype under a High-Temperature Gas Loop Condition

A PHE (Process Heat Exchanger) is a key component in transferring high-temperature heat generated from a VHTR (Very High Temperature Reactor) to a chemical reaction for the massive production of hydrogen. Last year, a 10 kW class lab-scale PHE prototype made of Hastelloy-X was manufactured at the Korea Atomic Energy Research Institute (KAERI), and a performance test of the PHE prototype is currently underway in a small-scale nitrogen gas loop at KAERI. The PHE prototype is composed of two kinds of flow plates: grooves 1.0 mm in diameter machined into the flow plate for the primary coolant, and waved channels bent into the flow plate for the secondary coolant. Inside the 10 kW class lab-scale PHE prototype, twenty flow plates for the primary and secondary coolants are stacked in turn. In this study, to understand the macroscopic structural behavior of the PHE prototype under the steady-state operating condition of the gas loop, high-temperature structural analyses on the 10 kW class lab-scale PHE prototype were performed for two extreme cases: in the event of contacting the flow plates together, and when not contacting them. The analysis results for the extreme cases were also compared.

Strengthening iron enrichment and dephosphorization of high-phosphorus oolitic hematite using high-temperature pretreatment

The efficient development and utilization of high-phosphorus oolitic hematite is of great strategic significance for the sustainable supply of iron-ore resources in China.In this paper,the mechanism of high-temperature pretreatment for enhancing the effect of iron enrichment and dephosphorization in the magnetization roasting–leaching process was studied by X-ray diffraction(XRD),vibration sample magnetometer(VSM),scanning electron microscopy and energy dispersive spectrometry(SEM–EDS).Compared with the process without high-temperature pretreatment,the iron grade of the magnetic separation concentrate after high-temperature pretreatment had increased by 0.98%,iron recovery rate had increased by 1.33%,and the phosphorus content in the leached residue had decreased by 0.12%.High-temperature pretreatment resulted in the dehydration and decomposition of hydroxyapatite,the dehydration of limonite and the thermal decomposition of siderite,which can produce pores and cracks and weaken the compactness of the ore,improve the magnetization characteristics of roasted ore,and strengthen the iron enrichment and dephosphorization during the magnetization roasting and leaching process.

Micro-analysis of high-temperature oxidation-resistance of a new kind of heat-resistant grid plate in grate-kiln

To further improve the oxidation-resistance of materials and reduce the cost of grid plates in grate-kiln, a new kind of heat-resistant grid plate was developed. The microstructure of this grid plate with a life more than 18 months was studied by XRD, SEM and EDS techniques. The results show that high hardness, high intensity and good impact property make the new kind of heat-resistant grid plate and its oxide film have a higher resistance to deformation and abrasion at 900-1000℃ Besides, small grain size is beneficial to form a complete protective oxide film. The oxide film composed of SiO2 layer, Cr2O3 layer and Fe2O3 layer is rather thin and bonds closely with the backing. The forming of the chemical stable nickel-rich layer increases the density of Cr2O3 layer.

Fabrication of YAG:Ce^(3+) and YAG:Ce^(3+),Sc^(3+) Phosphors by Spark Plasma Sintering Technique

In this study,a single-doped phosphors yttrium aluminum garnet(Y_(3)Al_(5)O_(12),YAG):Ce^(3+),single-doped YAG:Sc^(3+),and double-doped phosphors YAG:Ce^(3+),Sc^(3+) were prepared by spark plasma sintering(SPS)(lower than 1 200℃).The characteristics of synthesized phosphors were determined using scanning electron microscopy(SEM),X-ray diffraction(XRD),and fluorescence spectroscopy.During SPS,the lattice structure of YAG was maintained by the added Ce^(3+) and Sc^(3+).The emission wavelength of YAG:Ce^(3+) prepared from SPS(425-700 nm) was wider compared to that of YAG:Ce^(3+) prepared from high-temperature solid-state reaction(HSSR)(500-700 nm).The incorporation of low-dose Sc^(3+) in YAG:Ce^(3+) moved the emission peak towards the short wavelength.

Effect of Dopant Concentration on Luminescence Properties of KCaPO4:Sm

KCaPO4 doped with different concentrations of Sm was synthesised by a high-temperature solid-state method, and the crystal structure, morphology, TL and OSL properties of Sm-doped KCaPO4 were systematically investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermoluminescence (TL), and optically stimulated luminescence (OSL) techniques. The results show that 0.3 mol% Sm-doped KCaPO4 annealed at 1073 K for 1 h has the highest TL intensity, and thus is expected to be a candidate material for thermoluminescence dosimetry applications.

Impact of fabrication methods on binder distribution and charge transport in composite cathodes of all-solid-state batteries

The manufacturing process of all-solid-state batteries necessitates the use of polymer binders.However,these binders,being ionic insulators by nature,can adversely affect charge transport within composite cathodes,thereby impacting the rate performance of the batteries.In this work,we aim to investigate the impact of fabrication methods,specifically the solvent-free dry process versus the slurry-cast wet process,on binder distribution and charge transport in composite cathodes of solid-state batteries.In the dry process,the binder forms a fibrous network,while the wet process results in binder coverage on the surface of cathode active materials.The difference in microstructure leads to a notable 20-fold increase in ionic conductivity in the dry-processed cathode.Consequently,the cells processed via the dry method exhibit higher capacity retention of 89%and 83%at C/3 and C/2 rates,respectively,in comparison to 68%and 58%for the wet-processed cells at the same rate.These findings provide valuable insights into the influence of fabrication methods on binder distribution and charge transport,contributing to a better understanding of the binder’s role in manufacturing of all-solid-state batteries.

Shock effects on the upper limit of the collision weld process window

The maximum flyer impact velocity based on a dynamic solidification cracking mechanism is proposed to describe the upper limit of collision welding process windows.Thus,the upper limit of the weld window is governed by the evolution of dynamic stresses and temperatures at the weld interface.Current formulations for the upper limit of the collision weld window assume that both the flyer and target are made of the same material and approximate stress propagation velocities using the acoustic velocity or the shear wave velocity of the weld material.However,collision welding fundamentally depends on the impacts that generate shockwaves in weld members,which can dominate the stress propagation velocities in thin weld sections.Therefore,this study proposes an alternative weld window upper limit that approximates stress propagation using shock velocities calculated from modified 1-D Rankine-Hugoniot relations.The shock upper limit is validated against the experimental and simulation data in the collision welding literature,and offers a design tool to rapidly predict more accurate optimal collision weld process limits for similar and dissimilar weld couples compared to existing models without the cost or complexity of high-fidelity simulations.

Mechanism of vanadic titanomagnetite solid-state reduction

The influence mechanism of vanadic titanomagnetite solid-state reduction was studied in this paper.Optical microscopy(OM),scanning electron microscope(SEM),and X-ray diffraction(XRD)were used to characterize the structure and phases of the samples.The results show that the dense structure is not the reason that limits the reducibility of Panxi vanadic titanomagnetite.Metallization rate of 93%was achieved when it was reduced at 1100℃for 100 min.After pre-oxidation,Fe_(9)TiO_(15)and Fe_(2)O_(3)are the main phases of samples.Pre-oxidation could destroy the dense structure of vanadic titanomagnetite and increase the specific surface area of particles.However,reducibility of vanadic titanomagnetite is not improved obviously by pre-oxidation,with metallization rate increasing only 1%under the same reduction conditions,and the generated metallic iron grains are smaller.Phase transformation of vanadic titanomagnetite at different reduction temperatures shows that the presence of FeTi_(2)O_(5)is the main reason that limits the reducibility of Panxi vanadic titanomagnetite.

Advanced Glycation Endproducts in 35 Types of Seafood Products Consumed in Eastern China

Advanced glycation endproducts(AGEs) have been recognized as hazards in processed foods that can induce chronic diseases such as cardiovascular disease, diabetes, and diabetic nephropathy. In this study, we investigated the AGEs contents of 35 types of industrial seafood products that are consumed frequently in eastern China. Total fluorescent AGEs level and Nε-carboxymethyl-lysine(CML) content were evaluated by fluorescence spectrophotometry and gas chromatography-mass spectrometry(GC-MS), respectively. The level of total fluorescent AGEs in seafood samples ranged from 39.37 to 1178.3 AU, and was higher in canned and packaged instant aquatic products that were processed at high temperatures. The CML content in seafood samples ranged from 44.8 to 439.1 mg per kg dried sample, and was higher in roasted seafood samples. The total fluorescent AGEs and CML content increased when seafood underwent high-temperature processing, but did not show an obvious correlation. The present study suggested that commonly consumed seafood contains different levels of AGEs, and the seafood processed at high temperatures always displays a high level of either AGEs or CML.

Synthesis, Crystal Structure and Chemical Bonding of a New Binary Lu-Sn Phase: Lu_(11)Sn_(10)

A new tetragonal phase of LunSnl0 is obtained from high temperature reaction of the pure elements in a welded tantalum tube. Its crystal structure was established by single-crystal X-ray diffraction. Lu11Sn10 crystallizes in the tetragonal space group 14/mmm （No. 139） with a = 11.2953（18）, c = 16.424（4） A, V= 2095.5（7）A3, Z= 4, Mr = 3111.57, Dc = 9.863 g/cm^3, p = 62.897 -1 mm , F（000） = 5124, and the final R = 0.0348 and wR = 0.0894 for 706 observed reflections with 1 〉 2σ（I）. The structure of LullSnl0 may be derived from the HonGel0 structural type. It is isostructural with DyllSn10, featuring a three-dimensional （3D） framework composed of [Sn4] squares and [Sn2] dimers interlinked via Sn-Sn bonds with two types of one-dimensional （1D） tunnels along the c-axis, which are occupied by isolated Sn atoms, [Sn2] dimers and all the Lu atoms Band structure calculation based on density functional theory method indicates that LUllSn10 is metallic.

Microstructural Characteristics of Asphalt Concrete with Different Gradations by X-ray CT

The main objective of this paper is to evaluate the effects of asphalt concrete types on the microstructural characteristics at high-temperature. Suspend-dense structure and Skeleton-dense structure were selected to investigate the deformation of pavement at meso-scale. The internal microstructures of typical asphalt concretes, AC, SUP and SMA, were scanned by X-ray CT device, and microstructural changes before and after high-temperature damage were researched by digital image processing. Adaptive threshold segmentation algorithm（ATSA） based on image radius was developed and utilized to obtain the binary images of aggregates, air-voids and asphalt mastic. Then the shape and distribution of air-voids and aggregates were analyzed. The results show that the ATSA can distinguish the target and background effectively. Gradation and coarse aggregate size of asphalt mixtures have an obvious influence on the distribution of air-voids. The movements of aggregate particles are complex and aggregates with elliptic sharp show great rotation. The effect of gradation on microstructure during high-temperature damage promotes the research about the failure mechanism of asphalt concrete pavement.

Synthesis,Crystal Structure,Physical Properties and Theoretical Studies of the New Ternary Sulfide with Closed Cavities:CsYb_7S_(11)

A novel ternary rare-earth sulfide, CsYb7S（11）, has been successfully synthesized by high-temperature solid-state reaction of an elemental mixture with modified Cs Cl flux. The single-crystal X-ray diffraction data reveal its orthorhombic symmetry in space group Cmca（no. 64） with a = 15.271（3）, b = 13.414（2）, c = 18.869（3） A°, V = 3865.2（2） A°^3, Z = 8, Mr = 1696.85, Dc = 5.832 g/cm^3, μ = 36.538 mm^-1, F（000） = 5768, the final R = 0.0225 and w R = 0.0517 for 2258 observed reflections with I 〉 2σ（I）, 2.67〈θ〈27.48o, w = 1/[σ^2（Fo^2） ＋（0.0443 P）2 ＋ 8.7453 P], where P =（Fo^2 ＋ 2Fc^2）/3, S = 1.036,（Δρ）max = 1.609 and（Δρ）min = –1.922. The remarkable structural feature is the dual tricapped Cs2@S18 cube closed cavities far apart within the three-dimensional [Yb7S（11）]-covalent bonding matrix. Magnetic susceptibility measurements show that the title compound exhibits temperature-dependent（50～300 K） para-magnetism and obey the Curie-Weiss law. Moreover, the optical gap of 2.03 Ev for CsYb7S11 was deduced from the UV/Vis reflectance spectroscopy and DFT study indicates an indirect band gap with an electronic transfer excitation of S-3p to Yb-5d orbital.

Synthesis,Crystal Structure,and Optical Property of Zero-dimensional Quaternary Thioborate：Ba9B3GaS15

A new zero-dimensional（0D） thioborate Ba_9B_3GaS_（15） has been discovered by conventional high-temperature solid-state reaction. The compound crystallizes in orthorhombic space group Pbca with a = 8.4759（8）,b = 22.266（2）,c = 31.426（3） ？,V = 5931（2） ？~3,Z = 8,Mr = 1819.11,Dc = 4.075 g/cm3,μ = 13.684 mm^（-1）,F（000） = 6320,S = 1.034,（Δρ）max = 5.039,（Δρ）min = –5.409 e/？~3,the final R = 0.0362 and w R = 0.1053 for 19243 observed reflections with I 〉 2σ（I）. The structure is constructed by discrete [BS_3]^（3–） trigonal planes and isolated [GaS_4]^（5–） tetrahedra with Ba^（2＋） and isolated S^（2–） filled among them. The UV-Vis-near-IR spectrum reveals a wide band gap of 3.15 eV that agrees with the electronic structure calculation.

Colloidal Alumina-bonded TiB_2 Coating on Cathode Carbon Blocks in Aluminum Cells

Self-propagating high-temperature synthesis (SHS) with reduction process was used to fabricate TiB2 powder from TiO2-B2O3-Mg system. The colloidal alumina-bonded TiB2 paste was prepared and coated on the cathode carbon blocks. Various properties of the baked paste such as the corrosive resistance, thermal expansion and wettability were tested. Experimental results showed that the colloidal alumina-bonded TiB2 coating could be well wetted by liquid aluminum; and the thermal expansion coefficient of the coated material was 5.8x10(-6) degreesC(-1) at 20-1000 degreesC, which was close to that of the traditional anthracite block cathode (4x10(-6) degreesC(-1)); the electrical resistivity was 8 mu Omega (.)m at 900 degreesC when the content of alumina in the coated material was about 9% in mass fraction. In addition, some other good results such as sodium resistance were also reported.

Magnetic properties and crystallization kinetics of Zn_(0.5) Ni_(0.5) Fe_2O_4

Precursor of nanocrystalline Zno.sNio.sFe2O4 was obtained by grinding mixture of ZnSO4.7H2O, NiSO4.6H2O, FeSO4.7H2O, and Na2CO3.10H2O under the condition of suffactant polyethylene glycol （PEG）-400 being present at room temperature, washing the mixture with water to remove soluble inorganic salts and drying it at 373 K. The spinel Zn0.5Ni0.5Fe2O4 was obtained via calcining precursor above 773 K. The precursor and its calcined products were characterized by differential scanning calorimetry （DSC）, Fourier transform infrared （FF-IR）, X-ray diffraction （XRD）, and vibrating sample magnetometer （VSM）. The result showed that Zn0.sNio.sFe204 obtained at 1073 K had a saturation magnetization of 74 A.mLkg-1. Kinetics of the crystallization process of Zn0.5Ni0.5Fe2O4 was studied using DSC technique, and kinetic parameters were determined by Kissinger equation and Moynihan et al. equation. The value of the activation energy associated with the crystallization process of Zr0.5Ni0.5Fe2O4 is 220.89 kJ-mol-1. The average value of the Avrami exponent, n, is equal to 1.59±0.13, which suggests that crystallization process of Zn0.5Ni0.5Fe2O4 is the random nucleation and growth of nuclei reaction.

Selection of Heat Treatment Process and Wear Mechanism of High Wear Resistant Cast Hot-Forging Die Steel

Dry sliding wear tests of a Cr-Mo-V cast hot-forging die steel was carried out within a load range of 50--300 N at 400℃ by a pin-on-disc high temperature wear machine. The effect of heat treatment process on wear resistance was systematically studied in order to select heat treatment processes of the steel with high wear resistance. The morphology, structure and composition were analyzed using scanning electron microscopy （SEM）, X-ray diffraction （XRD） and energy dispersive spectroscopy （EDS） ; wear mechanism was also discussed. Tribo-oxide layer was found to form on worn surfaces to reduce wear under low loads, but appear inside the matrix to increase wear under high loads. The tribo-oxides were mainly consisted of Fe3O4 and Fe2O3, FeO only appeared under a high load. Oxidative mild wear, transition of mild-severe wear in oxidative wear and extrusive wear took turns to operate with increasing the load. The wear resistance strongly depended on the selection of heat treatment processes or microstructures. It was found that bainite presented a better wear resistance than martensite plus bainite duplex structure, martensite structure was of the poorest wear resistance. The wear resistance increased with increasing austenizing temperature in the range of 920 to 1 120 ℃, then decreased at up to 1 220 ℃. As for tempering temperature and microstructure, the wear resistance increased in following order： 700℃ （tempered sorbite）, 200 ℃ （tempered martensite）, 440 to 650 ℃ （tempered troostite）. An appropriate combination of hardness, toughness, microstructural thermal stability was re- quired for a good wear resistance in high-temperature wear. The optimized heat treatment process was suggested for the cast hot-forging steel to be austenized at 1020 to 1 120 ℃, quenched in oil, then tempered at 440 to 650℃ for 2 h.

Current understanding and applications of the cold sintering process

In traditional ceramic processing techniques,high sintering temperature is necessary to achieve fully dense microstructures.But it can cause various problems including warpage,overfiring,element evaporation,and polymorphic transformation.To overcome these drawbacks,a novel processing technique called“tcold sintering process(CSP)”has been explored by Randall et al.CSP enables densification of ceramics at ultra-low temperature(<300℃)with the assistance o f transient aqueous solution and applied pressure.In CSP,the processing conditions including aqueous solution,pressure,temperature,and sintering duration play critical roles in the densification and properties of ceramics,which will be reviewed.The review will also include the applications of CSP in solid-state rechargeable batteries.Finally,the perspectives about CSP is proposed.

Spatial phase structure and oxidation process of Al-W alloy powder with high sphericity

In this study,Al-30W(wt.%)alloy powder was prepared by Aluminothermic reduction and hightemperature gas atomization.We then studied the phase composition,surface morphology,spatial phase structure,and thermal oxidation process using XRD,SEM/EDS,TEM,DSC,and DTA/TG analysis.The results showed that the Al-30W alloy powder exhibited high sphericity,and the interior presented a special spatial phase structure in which the Al/W amorphous alloy phase and the metastable Al/W intermetallic compound phase were distributed in the pure Al matrix.When the Al-30W alloy powder was stabilized in a vacuum tube furnace,the spatial phase structure of the alloy powder changed,and a small amount of pure Al was embedded in the Al_(12)W matrix.The resulting Al-30W alloy powder products,treated in air at different temperatures,were collected in situ and characterized.The results presented that with an increase in temperature,the types and morphologies of the Al/W intermetallic compounds in the Al-30W alloy powder changed.Furthermore,the Al-30W alloy powder began to undergo intense oxidation reactions at about 900℃,accompanied by a concentrated energy release and rapid weight gain.The volatilization of WO_(3)produced in the oxidation process promoted the complete oxidation of the Al-30W alloy powder,and the Al-30W alloy powder was completely oxidized at 1300℃.At this stage,all W atoms were transformed into gaseous WO_(3),and only a large number of small Al_(2)O_(3)fragments remained in the oxidation product.Thus,the Al-30W alloy powder exhibited excellent thermal reactivity and oxidation integrity,and may offer excellent application prospects in the field of energetic materials.