A review of in-situ high-temperature characterizations for understanding the processes in metallurgical engineering

For the rational manipulation of the production quality of high-temperature metallurgical engineering,there are many challenges in understanding the processes involved because of the black box chemical/electrochemical reactors.To overcome this issue,various in-situ characterization methods have been recently developed to analyze the interactions between the composition,microstructure,and solid-liquid interface of high-temperature electrochemical electrodes and molten salts.In this review,recent progress of in-situ hightemperature characterization techniques is discussed to summarize the advances in understanding the processes in metallurgical engineering.In-situ high-temperature technologies and analytical methods mainly include synchrotron X-ray diffraction(s-XRD),laser scanning confocal microscopy,and X-ray computed microtomography(X-rayμ-CT),which are important platforms for analyzing the structure and morphology of the electrodes to reveal the complexity and variability of their interfaces.In addition,laser-induced breakdown spectroscopy,high-temperature Raman spectroscopy,and ultraviolet-visible absorption spectroscopy provide microscale characterizations of the composition and structure of molten salts.More importantly,the combination of X-rayμ-CT and s-XRD techniques enables the investigation of the chemical reaction mechanisms at the two-phase interface.Therefore,these in-situ methods are essential for analyzing the chemical/electrochemical kinetics of high-temperature reaction processes and establishing the theoretical principles for the efficient and stable operation of chemical/electrochemical metallurgical processes.

Effect of long reaction distance on gas composition from organic-rich shale pyrolysis under high-temperature steam environment

When high-temperature steam is used as a medium to pyrolyze organic-rich shale,water steam not only acts as heat transfer but also participates in the chemical reaction of organic matter pyrolysis,thus affecting the generation law and release characteristics of gas products.In this study,based on a long-distance reaction system of organic-rich shale pyrolysis via steam injection,the effects of steam temperature and reaction distance on gas product composition are analyzed in depth and compared with other pyrolysis processes.The advantages of organic-rich shale pyrolysis via steam injection are then evaluated.The volume concentration of hydrogen in the gas product obtained via the steam injection pyrolysis of organic-rich shale is the highest,which is more than 60%.The hydrogen content increases as the reaction distance is extended;however,the rate of increase changes gradually.Increasing the reaction distance from 800 to 4000 mm increases the hydrogen content from 34.91%to 69.68%and from 63.13%to 78.61%when the steam temperature is 500℃ and 555℃,respectively.However,the higher the heat injection temperature,the smaller the reaction distance required to form a high concentration hydrogen pyrolysis environment(hydrogen concentration>60%).When the steam pyrolysis temperature is increased from 500℃ to 555℃,the reaction distance required to form a high concentration of hydrogen is reduced from 3800 to 800 mm.Compared with the direct retorting process,the volume concentration of hydrogen obtained from high-temperature steam pyrolysis of organic-rich shale is 8.82 and 10.72 times that of the commonly used Fushun and Kivite furnaces,respectively.The pyrolysis of organic-rich shale via steam injection is a pyrolysis process in a hydrogen-rich environment.

Effects of temperature, particle size, and air humidity on sensibility of typical high-energetic explosives

The production and utilization of high-energetic explosives often pose a range of safety hazards,with sensitivity being a key factor in evaluating these risks.To investigate how temperature,particle size,and air humidity affect the responsiveness of commonly used high-energetic explosives,a series of BAM(Bundesanstalt für Materialforschung und-prüfung)impact and friction sensitivity tests were carried out to determine the critical impact energy and critical load pressure of four representative high-energetic explosives(RDX,HMX,PETN and CL-20)under different temperatures,particle sizes,and air humidity conditions.The experimental findings facilitated an examination of temperature and particle size affecting the sensitivity of high-energetic explosives,along with an assessment of the influence of air humidity on sensitivity testing.The results clearly indicate that high-energetic explosives display a substantial decline in critical reaction energy when subjected to micrometre-sized particles and an air humidity level of 45%at a temperature of 90℃.Furthermore,it was noted that the critical reaction energy of high-energetic explosives diminishes with an increase in temperature within 25℃−90℃.In the same vein,as the particle sizes of high-energetic explosives increase,so does the critical reaction energy for micrometre-sized particles.High air humidity significantly affects the sensitivity testing of high-energetic explosives,emphasizing the importance of refraining from conducting sensitivity tests in such conditions.

Interfacial built-in electric field and crosslinking pathways enabling WS_(2)/Ti_(3)C_(2)T_(x) heterojunction with robust sodium storage at low temperature

Developing efficient energy storage for sodium-ion batteries(SIBs)by creating high-performance heterojunctions and understanding their interfacial interaction at the atomic/molecular level holds promise but is also challenging.Besides,sluggish reaction kinetics at low temperatures restrict the operation of SIBs in cold climates.Herein,cross-linking nanoarchitectonics of WS_(2)/Ti_(3)C_(2)T_(x) heterojunction,featuring built-in electric field(BIEF),have been developed,employing as a model to reveal the positive effect of heterojunction design and BIEF for modifying the reaction kinetics and electrochemical activity.Particularly,the theoretical analysis manifests the discrepancy in work functions leads to the electronic flow from the electron-rich Ti_(3)C_(2)T_(x) to layered WS_(2),spontaneously forming the BIEF and“ion reservoir”at the heterogeneous interface.Besides,the generation of cross-linking pathways further promotes the transportation of electrons/ions,which guarantees rapid diffusion kinetics and excellent structure coupling.Consequently,superior sodium storage performance is obtained for the WS_(2)/Ti_(3)C_(2)T_(x) heterojunction,with only 0.2%decay per cycle at 5.0 A g^(-1)(25℃)up to 1000 cycles and a high capacity of 293.5 mA h g^(-1)(0.1A g^(-1)after 100 cycles)even at-20℃.Importantly,the spontaneously formed BIEF,accompanied by“ion reservoir”,in heterojunction provides deep understandings of the correlation between structure fabricated and performance obtained.

Effects of temperature on fracture behavior of Al-based in-situ composites reinforced with Mg_2Si and Si particles fabricated by centrifugal casting

An aluminum-based in-situ composites reinforced with Mg2Si and Si particles were produced by centrifugal casting A1-20Si-5Mg alloy. The microstructure of the composites was examined, and the effects of temperature on fracture behavior of the composite were investigated. The results show that the average fraction of primary Si and Mg2Si particles in the composites is as high as 38%, and ultimate tensile strengths （UTS） of the composites first increase then decrease with the increase of test temperature. Microstructures of broken specimens show that both the particle fracture and the interface debonding affect the fracture behavior of the composites, and the interface debonding becomes the dominant fracture mechanism with increasing test temperature. Comparative results indicate that rich particles in the composites and excellent interface strength play great roles in enhancing tensile property by preventing the movement of dislocations.

Kinetic Implication from Temperature Effect on Hydrogen Evolution Reaction at Ag Electrode

Hydrogen evolution reaction （HER） at polycrystalline silver electrode in 0.1 mol/L HClO4 solution is investigated by cyclic voltammetry in the temperature range of 278-333 K. We found that at electrode potential φa,app decreases with φ, while pre-exponential factor A remains nearly unchanged,which conforms well the prediction from Butler-Volmer equation. In contrast, with φ nega-tive shifts from the onset potential for HER to the potential of zero charge （PZC≈-0.4 V）, both Ea,app and A for HER increase （e.g., Ea,app increases from 24 kJ/mol to 32 kJ/mol）. The increase in Ea,app and A with negative shift in φ from -0.25 V to PZC is explained by the increases of both internal energy change and entropy change from reactants to the transition states, which is correlated with the change in the hydrogen bond network during HER. The positive entropy effects overcompensate the adverse effect from the increase in the activation energy, which leads to a net increase in HER current with the activation energy negative shift from the onset potential of HER to PZC. It is pointed out that entropy change may contribute greatly to the kinetics for electrode reaction which involves the transfer of electron and proton, such as HER.

Preparation of nano-sized cerium and titanium pyrophosphates via solid-state reaction at room temperature

Nano-sized cerium-titanium pyrophosphates Ce1-xTixP2O7 （with x = 0, 0.2, 0.5, 0.7, 0.9, and 1.0） were obtained by grinding a mixture of Ce（SO4）2·4H2O, Ti（SO4）2, and Na4P2O7·10H2O in the presence of surfactant PEG-400 at room temperature, washing the mixture with water to remove soluble inorganic salts, and drying at 100℃. The products and their calcined samples were characterized using ultraviolet-visible spectroscopy （UV-vis）, thermogravimetry and differential thermal analyses （TG/DTA）, X-ray powder diffraction （XRD）, and transmission electron microscopy （TEM）. The results show that nano-sized Ce1-xTixP2O7 behave as an excellent UV-shielding material. Thereinto, the CeP2O7 has the most excellent UV-shielding effect, and the amorphous state of Ce0.8Ti0.2P2O7 can keep at a higher temperature than CeP2O7. Therefore, the stabilization of the amorphous state of the cerium pyrophosphates was carded out by doping titanium. This stabilization is a significant improvement, which enables to apply these amorphous pyrophosphates not only to cosmetics and paints, but also plastics and films.

Temperature Effect on Hydrogen Evolution Reaction at Au Electrode

The temperature dependence of hydrogen evolution reaction （HER） at a quasi-single crystalline gold electrode in both 0.1 mol/L HCl04 and 0.1 mol/L KOH solutions was investigated by cyclic voltammetry. HER current displays a clear increase with reaction overpotential （η） and temperature from 278-333 K. In 0.1 mol/L HClO4 the Tafel slopes are found to increases slightly with temperature from 118 mV/dec to 146 mV/dec, while in 0.1 mol/L KOH it is ca. 153±15 mV/dec without clear temperature-dependent trend. The apparent activation energy （Ea） for HER at equilibrium potential is ca. 48 and 34 kJ/mol in 0.1 mol/L HC104 and 0.1 mol/L KOH, respectively. In acid solution, Ea decreases with increase in η, from Ea-37 kJ/mol （η=0.2 V） to 30 kJ/mol （η=0.35 V）. In contrast, in 0.1 mol/L KOH, Ea does not show obvious change with U. The pre-exponential factor （A） in 0.1 mol/L HC104 is ca. 1 order higher than that in 0.1 mol/L KOH. Toward more negative potential, in 0.1 mol/L HC104 A changes little with potential, while in 0.1 mol/L KOH it displays a monotonic increase with U. The change trends of the potential-dependent kinetic parameters for HER at Au electrode in 0.1 mol/L HClO4 and that in 0.1 mol/L KOH are discussed.

Thermodynamic study and methanothermal temperature-programmed reaction synthesis of molybdenum carbide

Nanostructured molybdenum carbide （Mo2C） was successfully prepared from molybdenum trioxide （MoO3） using methanothermal temperature-programmed reaction. Thermodynamic analysis indicated that in presence of methane, the formation of Mo2C from MoO3 occurs through the path of MoO3 → MoO2→ Mo2C. The carburized MoO3 was characterized using X-ray diffraction （XRD）, CHNS/O analysis, Brunauer-Emmett-Teller （BET） analysis, and field-emission scanning electron microscopy （FESEM）. At final carburization temperatures of 700 and 800℃ and at methane contents ranging from 5vol% to 20vol%, Mo2C was the only solid product observed in the XRD patterns. The re- suits indicated that the effect of methane content on the formation of the carbide phase is substantial compared with the effect of carburization time. Elemental analysis showed that at a final temperature of 700℃, the carbon content of carburized MoO3 is very close to the theoretical carbon mass percentage in Mo2C. At higher carburization temperatures, excess carbon was deposited onto the surface of Mo2C. High-surface-area Mo2C was obtained at extremely low heating rates; this high-surface-area material is a potential electrocatalyst.

Preparing Nano-ZnS by Solid State Reaction at Room Temperature

ZnS nanoparticles were prepared by using solid-state reaction method at room temperature in agate mortar for the first time. The average particle size was about 20nm. This reaction is affected by the structure of reactant, crystal water and defects.

Substitution Reactions by Azide and Thiocyanide Anions in Room Temperature Ionic Liquids

Conducted in the ionic liquids, activated and inactivated halides, acyl chlorides, tosylate, and bezotriazolyl acylates were converted to corresponding azide and thiocyanide compounds in high yields under mild conditions.

Synthesis of Mesoporous Chromium Aluminophosphate (CrAlPO) via Solid State Reaction at Low Temperature

Mesoporous chromium aluminophosphate （CrAIPO） was successfully synthesized via solid state reaction （SSR） route at low temperature in the presence of a cationic surfactant cetyltrimethyl ammonium bromide （CTAB） and inorganic sources such as A1C13 · 6H20, CrCI3 · 6H20 and NaH2PO4 · 2H20. Characterizations by means of powder X-ray diffraction （XRD）, N2 adsorption- desorption, high resolution transmission electron microscopy （HR-TEM）, scanning electron micrography （SEM）, energy dispersion spectroscopy （EDS）, thermo-gravimetry （TG）, Fourier transform infrared spectroscopy （FT-IR）, and ultraviolet visible light spectroscopy （UV-Vis） were carried out to understand both the pore characteristics and electron transition route of these obtained materials. The experimental results show that the meso-CrA1PO materials with various Cr/A1 molar ratios possess a mesostructure and a specific surface area of 193 to 310 m2/g corresponding to an average pore size of 5.5 to 2.2 rim, respectively. The maxium content of Cr in meso-CrA1PO materials synthesized via SSR route can achieve 16.7wt%, being significantly higher than that of the meso-CrA1PO prepared via a conventional sol-gel route. Meanwhile, the formation mechanism of the meso-CrA1PO was also proposed.

High Temperature Chemical Reaction of La_2O_3 in H_3BO_3-C System

The high temperature chemical reaction process of La2O3 in H3BO3-C system was studied by means of XRD and TG-DTA.The results showed that dehydration reaction of H3BO3 occurred in the temperature range of 82～390 ℃;La2O3 and B2O3 reacted to form LaB3O6,LaBO3,and B4C in the temperature range of 836～1400℃;at 1450 ℃,B4C and LaBO3 further reacted to form LaB4,and partial LaB4 and B reacted to form LaB6;at 1500 ℃,LaB4 and B reacting into LaB6 was the main reaction,and the content of LaB6 increased with prolonging time.

Thermokinetic Behaviour Degenerated from Limit Cycle Oscillation of Isothermal B-Z Reaction System due to Temperature Controlling of Heat Compensation Type

The thermokinetic behavior of the B-Z reaction system was influenced by both the chemical reaction-heat conduction coupling and the temperature undulation due to temperature controlling of heat compensation type. Quantitative research indicated that this kind of temperature fluctuation will lead to limit cycle degeneration and the periodic or quasi-periodic response behavior of the focus near a supercritical Hopf bifurcation .

Microstructure and mechanical properties of Fe/NbC composite layer prepared by in-situ reaction

NbC ceramic surface-reinforced steel matrix composites were prepared by an in-situ reaction method at different temperatures(1,050℃,1,100℃and 1,150℃)for different times(1 h,2 h and 3 h).The phase constitution,microstructure and fracture morphology of NbC ceramic surface-reinforced steel matrix composites were analyzed by XRD,SEM and EDS,and the effects of the in-situ reaction temperature and time on the mechanical properties were systematically studied.The results indicate that the NbC reinforcement layer is formed through the reaction between Nb atoms and carbon atoms diffused from the steel matrix to the Nb plate.The thickness of this reinforcement layer increases as the reaction time prolongs.Additionally,an increase in reaction temperature results in a thicker reinforcement layer,although the rate of increase gradually decreases.The relationship among the thickness of the Nb C reinforcement layer,the reaction time and temperature was established by data fitting.The optimal tensile performance is achieved at 1,100℃for 1 h,with a tensile strength of 228 MPa.It is also found that the defects between the reinforcement layer and the steel matrix are related to reaction temperature.At 1,100℃,these defects are minimal.Fracture mostly occurs in the NbC reinforced layer of the composites,and the fracture mode is characterized by typical intergranular brittle fracture.

Eutectic Solution Enables Powerful Click Reaction for In-Situ Construction of Advanced Gel Electrolytes

Thiol-ene click reaction is an intriguing strategy for preparing polymer electrolytes due to its high activity,atom economy and less side reaction.However,the explosive reaction rate and the use of non-electrolytic amine catalyst hamper its application in in-situ batteries.Herein,a nitrogen-containing eutectic solution is designed as both the catalyst of the thiol-ene reaction and the plasticizer to in-situ synthesize the gel polymer electrolytes,realizing a mild in-situ gelation process and the preparation of high-performance gel electrolytes.The obtained gel polymer electrolytes exhibit a high ionic conductivity of 4×10^(−4)S cm^(−1)and lithium-ion transference number(t_(Li)^(+))of 0.51 at 60°C.The as-assembled Li/LiFePO_(4)(LFP)cell delivers a high initial discharge capacity of 155.9 mAh g^(-1),and a favorable cycling stability with the capacity retention of 82%after 800 cycles at 1 C is also obtained.In addition,this eutectic solution significantly improves the rate performance of the LFP cell with high specific capacity of 141.5 and 126.8 mAh g^(-1)at 5 C and 10 C,respectively,and the cell can steadily work at various charge–discharge rate for 200 cycles.This powerful and efficient strategy may provide a novel way for in-situ preparing gel polymer electrolytes with desirable comprehensive performances.

Doping effect of cations(Zr^(4+),Al^(3+),and Si^(4+)) on MnO_x/CeO_2 nano-rod catalyst for NH_3-SCR reaction at low temperature

Thermally stable Zr4+, Al3+, and Si4+ cations were incorporated into the lattice of CeO2 nano‐rods (i.e., CeO2‐NR) in order to improve the specific surface area. The undoped and Zr4+, Al3+, and Si4+ doped nano‐rods were used as supports to prepare MnOx/CeO2‐NR, MnOx/CZ‐NR, MnOx/CA‐NR, and MnOx/CS‐NR catalysts, respectively. The prepared supports and catalysts were comprehensively characterized by transmission electron microscopy (TEM), high‐resolution TEM, X‐ray diffraction, Raman and N2‐physisorption analyses, hydrogen temperature‐programmed reduction, ammonia temperature‐programmed desorption, in situ diffuse reflectance infrared Fourier‐transform spectroscopic analysis of the NH3 adsorption, and X‐ray photoelectron spectroscopy. Moreover, the catalytic performance and H2O+SO2 tolerance of these samples were evaluated through NH3‐selective catalytic reduction (NH3‐SCR) in the absence or presence of H2O and SO2. The obtained results show that the MnOx/CS‐NR catalyst exhibits the highest NOx conversion and the lowest N2O concentration, which result from the largest number of oxygen vacancies and acid sites, the highest Mn4+ content, and the lowest redox ability. The MnOx/CS‐NR catalyst also presents excellent resistance to H2O and SO2. All of these phenomena suggest that Si4+ is the optimal dopant for the MnOx/CeO2‐NR catalyst.

Analysis on the Governing Reactions in Coal Oxidation at Temperatures up to 400°C

The present study aims to further understanding of the principal reactions that occur during coal oxidation at moderate temperatures. Mass change and heat evolution of a sample were monitored by thermo-gravimetric analysis coupled with differential thermal analysis (TGA/DTA). Gaseous and solid products were traced using online or in situ Fourier trans- form infrared spectroscopy (FTIR). Measurements were conducted by heating the samples up to 400?C, with the O2 concentration in the reaction medium set at 0, 10, 21, and 40 vol%, respectively. It was observed that the mass increase of a sample between 150?C and ~275oC was a result of the accumulation of C=O containing species in the coal structure, whereas substantial mass loss and heat evolution of a sample at ~400oC can be attributed to the significant involvement of the direct “burn-off” reaction. Enrichment of O2 inthe reaction medium leads to the acceleration in oxygen chemi- sorption, formation and decomposition of the solid oxygenated complexes, as well as the “burn-off” reaction. With the temperature increasing, the oxidation process governed by oxygen chemisorption gradually shifts to that by significant decomposition reactions, and eventually to that by the direct “burn-off” reaction. Temperature boundaries of these stages can be determined using parameters defined based on a set of TG/DTA data. Shift in the governing reactions is essentially due to the diverse requirements of reactants of the reactions and their energy barriers to be overcome. In en- gineering practice, the phenomena of self-heating and spontaneous combustion of coal correspond to chemisorption and the direct “burn-off” reaction, respectively.

Feedforward Variable Structural Proportional-Integral-Derivative for Temperature Control of Polymerase Chain Reaction

To track the rapidly changing temperature profiles of thermal cycling of polymerase chain reaction （PCR） accurately, an innovative feedforward variable structural proportional-integral-derivative （FVSPID） controller was developed. Based on the step response test data of the heat block, a reduced first order model was estabfished at different operating points. Based on the reduced model, the FVSPID controller combined a feedforward path with the variable structural proportional-integral-derivative （PID） control. The modified feedforward action provided directly the optimal predictive power for the desired setpoint to speed up the dynamic response. To cooperate with the feedforward action, a variable structural PID was applied, where the P mode was used in the case of the largest errors to speed up response, whereas the PD mode was used in the case of larger errors to suppress overshoot, and finally the PID mode was applied for small error conditions to eliminate the steady state offset. Experimental results illustrated that compared to the conventional PID controller, the FVSPID controller can not only reduce the time taken to complete a standard PCR protocol, but also improve the accuracy of gene amplification.

In-situ ultrasonic calibrations of pressure and temperature in a hinge-type double-stage cubic large volume press

Here,simultaneous in-situ calibration of pressures and temperatures was performed in a hinge-type second-stage cubic large volume press(LVP)up to 15 GPa and 1400 K by an acoustic travel-time approach.Based on the recently reported P-tSand P-T-tP-tSequations for Al2O3buffer rod,the cell pressures and temperatures in the chamber of LVP were insitu determined,in comparison with those by conventional off-line(or fixed-points)pressure calibration method and direct thermocouple measurement,respectively.It is found that the cell pressures of the LVP chamber are significantly reduced after annealing at simultaneous high pressures and high temperatures,owing to the stress relaxation as accumulate in the LVP chamber.This acoustic travel-time method is verified to be a good way for precise determination of thermal(cell)pressures at high temperature conditions,and is of great importance and necessity to conduct in-situ physical property measurements under extreme high P-T conditions,especially when the precious synchrotron x-ray/neutron diffraction beams are not available.