Phase equilibria of slag systems“FeO”−SiO_(2)−CaO−Al_(2)O_(3)and“FeO”−SiO_(2)−CaO−MgO at 1200℃and p(O_(2))of 10^(−7)kPa

High-temperature experiments were carried out for the slag systems of“FeO”−SiO_(2)−CaO−Al_(2)O_(3)and“FeO”−SiO_(2)−CaO−MgO at 1200℃and p(O_(2))of 10^(−7)kPa.The equilibrated samples were quenched,and the phase compositions were measured by electron probe microanalysis(EPMA).A series of pseudo-ternary and pseudo-binary phase diagrams are constructed to demonstrate their applications in copper smelting process and evaluation of the thermodynamic database.Spinel and tridymite are identified to be the major primary phases in the composition range related to the copper smelting slags.It is found that the operating window of the smelting slag is primarily determined by w_(Fe)/w_(SiO_(2))ratio in the slag.Both MgO and Al_(2)O_(3)in the slag reduce the operating window which requires extra fluxing agent to keep the slag to be fully liquid.Complex spinel solid solutions cause inaccurate predictions of the current thermodynamic database.

Mechanical properties and electronic structures of MgCu_2, Mg_2Ca and MgZn_2 Laves phases by first principles calculations

Mechanical properties and electronic structure of MgCu2, Mg2 Ca and MgZn2 phases were investigated by means of first principles calculations from CASTEP program based on density functional theory（DFT）. The calculated lattice parameters are in good agreement with the experimental and literature values. The calculated heat of formation and cohesive energies showed that MgCu2 has the strongest alloying ability and structural stability. Elastic constants of MgCu2, Mg2 Ca and MgZn2 were calculated, and the bulk moduli, shear moduli, elastic moduli and Poisson ratio were derived. The calculated results show that MgCu2, Mg2 Ca and MgZn2 are all ductile phases. Among the three phases, MgCu2 has the strongest stiffness and the plasticity of MgZn2 phase is the best. Melting points of the three phases were predicted using cohesive energy and elastic constants. Density of states（DOS）, Mulliken population, electron occupation number and charge density difference were discussed. Finally, Debye temperature was calculated and discussed.

Crystal structure,phase transitions,and thermodynamic properties of magnesium metavanadate(MgV_(2)O_(6))

As a promising anode material for magnesium ion rechargeable batteries,magnesium metavanadate(MgV_(2)O_(6))has attracted considerable research interest in recent years.A MgV_(2)O_(6)sample was synthesized via a facile solid-state reaction by multistep-firing stoichiometric mixtures of MgO and V2O5 powder under an air atmosphere.The solid-state phase transition fromα-MgV_(2)O_(6)toβ-MgV_(2)O_(6)occurred at 841 K and the enthalpy change was 4.37±0.04 kJ/mol.The endothermic effect at 1014 K and the enthalpy change was 26.54±0.26 kJ/mol,which is related to the incongruent melting ofβ-MgV_(2)O_(6).In situ XRD was performed to investigate phase transition of the as-prepared MgV_(2)O_(6)at high temperatures.The cell parameters obtained by Rietveld refinement indicated that it crystallizes in a monoclinic system with the C2/m space group,and the lattice parameters of a=9.280 A°,b=3.501 A°,c=6.731 A°,β=111.76°.The solid-state phase transition fromα-MgV_(2)O_(6)toβ-MgV_(2)O_(6)was further studied by thermal kinetics,indicating that this process is controlled first by a fibril-like mechanism and then by a spherulitic-type mechanism with an increasing heating rate.Additionally,the enthalpy change of MgV_(2)O_(6)at high temperatures was measured utilizing the drop calorimetry,heat capacity was calculated and given as:Cp=208.3+0.03583T-4809000T^(−2)(298-923 K)(J mol^(−1)K^(−1)),the high-temperature heat capacity can be used to calculate Gibbs free energy of MgV_(2)O_(6)at high temperatures.

Phase2接触单元在岩土工程接触分析中的应用

接触分析是工程中岩土体与结构、岩体内部的节理裂隙相互作用时面对的关键问题之一。文章基于Phase2软件接触单元模型,介绍了接触单元的滑移准则,提出了法向刚度和切向刚度这两个参数的估算方法。结果表明:接触单元可以较好地模拟接触面之间的黏接、脱开、相对滑动这三种状态,强度折减安全系数法的计算结果与Goodman-Bray法计算结果基本一致;接触单元对不同材料之间的接触面模拟有较好的效果,同时接触单元也可选择是否考虑接触面内的孔隙水压力。

The precipitation behavior of MgZn_(2) and Mg_(4)Zn_(7) phase in Mg-6Zn(wt.%)alloy during equal-channel angular pressing

As-extruded Mg-6Zn(wt.%)Alloy was subjected to severe plastic deformation(SPD)by the equal-channel angular pressing(ECAP)at 160 ℃.The results of tensile tests at room temperature showed that two passes ECAP resulted in a remarkable improvement of strength,yield strength from 200 to 265 MPa and ultimate tensile strength from 260 to 340 MPa.However,with the deformation increasing,the samples processed by ECAP for four or six passes had insignificant difference than that processed by two-pass ECAP.Massive precipitates were observed in all the Mg-6Zn alloys specimens processed by ECAP.Transmission electron microscope and X-ray diffraction results indicated that ECAP treatment induced the precipitation of laves MgZn_(2) phase and transition Mg_(4)Zn_(7) phase.The spherical MgZn_(2) particles and irregular shape Mg_(4)Zn_(7) particles coexist in the microstructure of Mg-6Zn alloy after six pass ECAP.

Optimal parameter space for stabilizing the ferroelectric phase of Hf_(0.5)Zr_(0.5)O_(2) thin films under strain and electric fields

Hafnia-based ferroelectric materials, like Hf_(0.5)Zr_(0.5)O_(2)(HZO), have received tremendous attention owing to their potentials for building ultra-thin ferroelectric devices. The orthorhombic(O)-phase of HZO is ferroelectric but metastable in its bulk form under ambient conditions, which poses a considerable challenge to maintaining the operation performance of HZO-based ferroelectric devices. Here, we theoretically addressed this issue that provides parameter spaces for stabilizing the O-phase of HZO thin-films under various conditions. Three mechanisms were found to be capable of lowering the relative energy of the O-phase, namely, more significant surface-bulk portion of(111) surfaces, compressive c-axis strain,and positive electric fields. Considering these mechanisms, we plotted two ternary phase diagrams for HZO thin-films where the strain was applied along the in-plane uniaxial and biaxial, respectively. These diagrams indicate the O-phase could be stabilized by solely shrinking the film-thickness below 12.26 nm, ascribed to its lower surface energies. All these results shed considerable light on designing more robust and higher-performance ferroelectric devices.

采用PHASE2软件的隧洞一次支护数值模拟与分析

处于V类围岩的隧洞施工时,通常要采取一次支护以保证围岩稳定。采用PHASE2岩土工程弹塑性有限元分析软件,对某引调水工程中处于V类围岩的隧洞围岩位移与塑性区分布进行模拟分析。结果表明:在不采取支护措施情况下,隧洞施工时将发生坍塌破坏,具有极大的安全隐患;在采取拟定措施后,围岩总位移满足规范要求,且未发生塑性破坏,因此支护后隧洞达到稳定且安全的状态,验证支护措施的有效性。但为保证工程安全,建议施工期间做好排水措施,并缩短施工开挖、一次支护措施之间的施工间隔,使支护尽早发挥作用。

低腐蚀、高效相变吸收体系CO_(2)捕集性能及机理研究

液-液相变吸收剂作为碳捕集领域最具节能潜力的新兴吸收剂仍存在CO_(2)容量有限、腐蚀性强等缺点。以富含氨基的聚酰胺-胺树状大分子(PAMAM)为阳离子、具有含N杂环的2-甲基咪唑(2-MI)为阴离子合成离子液体(ILs),并与水和二乙二醇丁醚(DGBE)构建液-液相变吸收剂。以多氨基协同吸收的方式大幅度提升CO_(2)吸收性能,其CO_(2)容量可达4.98 mol CO_(2)/mol ILs,富CO_(2)相体积分数仅为28.7%,且腐蚀性仅为单乙醇胺(MEA)溶液的13.87%。^(13)CNMR分析结果表明,吸收机理遵循两性离子机理及碱性水合机制。用Kamlet-Taft法量化极性发现,相分离现象的发生与极性、密度、黏度变化密切相关。

A 27 GHz,simple 2-bit 1×8 phased array

This study demonstrates a simple 2-bit phased array operating at 27 GHz that supports one-dimensional beam scanning with left-handed circular polarization(LHCP).The antenna is constructed using a compact four-layer printed circuit board(PCB)structure,consisting of a 90°phase shifter layer with microstrip structures,a ground(GND)layer,a direct current(DC)control layer,and a circularly polarized annular radiation patch layer with 1-bit phase shifting.Based on the proposed unit structure,a 1×8 array with half-wavelength inter-element spacing was designed and validated.Experimental results show that the array achieves a peak gain of 10.23 dBi and is capable of beam scanning within±50°.

Durable hierarchical phosphorus‐doped biphase MoS_(2)electrocatalysts with enhanced H^(*)adsorption

Phase engineering is an efficient strategy for enhancing the kinetics of electrocatalytic reactions.Herein,phase engineering was employed to prepare high‐performance phosphorous‐doped biphase(1T/2H)MoS_(2)(P‐BMS)nanoflakes for hydrogen evolution reaction(HER).The doping of MoS_(2)with P atoms modifies its electronic structure and optimizes its electrocatalytic reaction kinetics,which significantly enhances its electrical conductivity and structural stability,which are verified by various characterization tools,including X‐ray photoelectron spectroscopy,high‐resolution transmission electron microscopy,X‐ray absorption near‐edge spectroscopy,and extended X‐ray absorption fine structure.Moreover,the hierarchically formed flakes of P‐BMS provide numerous catalytic surface‐active sites,which remarkably enhance its HER activity.The optimized P‐BMS electrocatalysts exhibit low overpotentials(60 and 72 mV at 10 mA cm^(−2))in H_(2)SO_(4)(0.5 M)and KOH(1.0 M),respectively.The mechanism of improving the HER activity of the material was systematically studied using density functional theory calculations and various electrochemical characterization techniques.This study has shown that phase engineering is a promising strategy for enhancing the H*adsorption of metal sulfides.

Regulating crystal phase of TiO_(2) to enhance catalytic activity of Ni/TiO_(2) for solar-driven dry reforming of methane

Ni/TiO_(2) catalyst is widely employed for photo-driven DRM reaction while the influence of crystal structure of TiO_(2) remains unclear.In this work,the rutile/anatase ratio in supports was successfully controlled by varying the calcination temperature of anatase-TiO_(2).Structural characterizations revealed that a distinct TiO_(x) coating on the Ni nanoparticles(NPs)was evident for Ni/TiO_(2)-700 catalyst due to strong metal-support interaction.It is observed that the TiOx overlayer gradually disappeared as the ratio of rutile/anatase increased,thereby enhancing the exposure of Ni active sites.The exposed Ni sites enhanced visible light absorption and boosted the dissociation capability of CH4,which led to the much elevated catalytic activity for Ni/TiO_(2)-950 in which rutile dominated.Therefore,the catalytic activity of solar-driven DRM reaction was significantly influenced by the rutile/anatase ratio.Ni/TiO_(2)-950,characterized by a predominant rutile phase,exhibited the highest DRM reactivity,with remarkable H_(2) and CO production rates reaching as high as 87.4 and 220.2 mmol/(g·h),respectively.These rates were approximately 257 and 130 times higher,respectively,compared to those obtained on Ni/TiO_(2)-700 with anatase.This study suggests that the optimization of crystal structure of TiO_(2) support can effectively enhance the performance of photothermal DRM reaction.

First-principles study on the interfacial bonding strength and segregation at Mg/MgZn_(2)matrix interface

To understand the interface characteristics between the precipitateβ2and the Mg matrix,and thus guide the development of new Mg-Zn alloys,we investigated the atomic interface structure,work of adhesion(Wad),and interfacial energy(γ)of Mg(0001)/β2’(MgZn_(2))(0001)interface,as well as the effect of segregation behavior of the introduced transition metal atoms(3d,4d and 5d)on interfacial bonding strength.The calculated works of adhesion and interfacial energies dementated that the Zn2-terminated MT+HCP configuration is the most stable structure for all considered models.Take the Zn2-MT+HCP interface as the research object,estimated segregated energies(Eseg)reveal that added transition metal atoms prefer to segregate at Mg-I and Mg-II sites.The predicted Wad and charge density difference results reveal that the segregation of alloying additives employed may all strengthen Mg(0001)/MgZn_(2)(0001)interface,with the enhancement effect of Os,Re,Tc,W,and Ru at the Mg-II site being the most pronounced.

Generalized Mechanism for the Solid Phase Transition of M_(2)O_(3)(M=Al,Ga)Featuring Single Cation Migration and Martensitic Lattice Transformation

Al_(2)O_(3)and Ga_(2)O_(3)exhibit numerous crystal phases with distinct stabilities and materialproperties.However,the phase transitions among thosematerialsare typicallyundesirable in industrial applications,making it imperative to elucidate the transition mechanisms between these phases.The configurational similarities between Al_(2)O_(3)and Ga_(2)O_(3)allow for the replication of phase transition pathways between these materials.In this study,we investigate the potential phase transition pathway of alumina from the 0-phase to the α-phase using stochastic surface walking global optimization based on global neural network potentials,while extending an existing Ga_(2)O_(3)phase transition path.Through this exploration,we identify a novel single-atom migration pseudomartensitic mechanism,which combines martensitic transformation with single-atom diffusion.This discovery offers valuable insights for experimental endeavors aimed at stabilizing alumina in transitional phases.

Calculating the number of radial cracks around a wellbore fractured by liquid CO_(2) phase transition blasting technology

Integrating liquid CO_(2)phase transition blasting(LCPTB)technology with hydraulic fracturing(HF)methods can help reduce wellbore damage,create multiple radial fractures,and establish a complex fracture network.This approach significantly increases the recovery efficiency of low-permeability oil and gas fields.Accurately calculating the number of fractures caused by LCPTB is necessary to predict production enhancement effects and optimize subsequent HF designs.However,few studies are reported on large-scale physical model experiments in terms of a method for calculating the fracture number.This study analyzed the initiation and propagation of cracks under LCPTB,derived a calculation formula for crack propagation radius under stress waves,and then proposed a new,fast,and accurate method for calculating the fracture number using the principle of mass conservation.Through ten rock-breaking tests using LCPTB,the study confirmed the effectiveness of the proposed calculation approach and elucidated the variation rule of explosion pressure,rock-breaking scenario,and the impact of varying parameters on fracture number.The results show that the new calculation method is suitable for fracturing technologies with high pressure rates.Recommendations include enlarging the diameter of the fracturing tube and increasing the liquid CO_(2) mass in the tube to enhance fracture effectiveness.Moreover,the method can be applied to other fracturing technologies,such as explosive fracturing(EF)within HF formations,indicating its broader applicability and potential impact on optimizing unconventional resource extraction technologies.

两相CO_(2)喷射器混合室长度和扩压室角度影响研究

利用已验证的CFD模型研究不同工况下混合室长度和扩压室锥半角对喷射器升压性能的影响。结果表明:在给定工况下,存在最优的混合室长度和扩压室角度参数组合使喷射器的升压性能最高。两者对喷射器性能的影响具有强相关性:当混合室足够长时,掺混较为充分,混合流扩压时不易发生流动分离,扩压室锥半角在0.5°~3°变化对喷射器性能的影响相对较小;而混合室较短时,扩压室壁面附近容易产生湍流损失,扩压室角度的影响较大。此外,最优结构参数受到运行工况的影响,随喷嘴入口压力和温度降低,最优混合室长度增加,最优扩压室角度减小。在研究工况和喷嘴配置下,喷射器最优混合室长度约为38 mm,最优扩压室锥半角为1°~1.5°。

Microstructure and mechanical properties of transient liquid phase bonding Ti_(3)SiC_(2) ceramic to SUS430 steel using an Al interlayer

Ti_(3)SiC_(2) ceramic and SUS430 ferritic stainless steel were welded by the transient liquid phase(TLP)diffusion bonding method using an Al interlayer at 850-1050℃ in vacuum.The evolution of phase and morphology at the interface and bonding strength were systematically investigated.The results show that Ti_(3)SiC_(2) and SUS430 were well bonded at 900-950℃.Three reaction zones were observed at the interface.At the joint interface area adjacent to alloy,the alloy completely reacted with liquid Al to form Al_(86)Fe_(14).At Ti_(3)SiC_(2)/Al interface,Ti and Si diffused outward from Ti_(3)SiC_(2) into the molten Al to form Fe_(3)Al+Al_(5)FeSi+TiAl_(3) zone.Adjacent to Ti_(3)SiC_(2) matrix,Ti_(3)Si(Al)C_(2)+TiCx zone was formed by the loss of Si.The evolution mechanism of TLP-bonded joints was discussed based on the interface microstructure and product phases.In addition,the tensile strength of the joint increased with increasing bonding temperature.The corresponding maximum value of 59.7 MPa was obtained from SUS430/Al(10μm)/Ti_(3)SiC_(2) joint prepared at 950℃.

月桂酸-石蜡二元共晶和纳米SiO_(2)气凝胶新型建筑储能材料的研制和性能表征

以月桂酸(LA)和石蜡(PS)为原料制备了月桂酸-石蜡(LA-PS)二元共晶混合物,通过真空吸附法将二元共晶混合物吸附到纳米SiO_(2)气凝胶中形成复合相变材料月桂酸-石蜡/纳米SiO_(2)气凝胶。泄漏实验表明,纳米SiO_(2)气凝胶对LA-PS的最大吸附率为70%;傅里叶红外光谱的结果显示,LA-PS/纳米SiO_(2)气凝胶具有优异的化学相容性;DSC测试结果显示,LA-PS/纳米SiO_(2)气凝胶的相变温度为35.19℃,相变潜热为115.89J/g。此外,LA-PS/纳米SiO_(2)气凝胶的储能效率为98.99%,说明LA-PS/纳米SiO_(2)气凝胶具有良好的蓄热性能。因此,制备的复合相变材料在玻璃窗透明围护结构利用方面,具有合适的相变温度、较高的相变潜热和较好的热稳定性和耐久性,从而具有较好的应用前景。

B2-CuZr reinforced amorphous alloy matrix composites:A review

B2-CuZr phase reinforced amorphous alloy matrix composites has become one of the research hotspots in the field of materials science due to the“transformation-induced plasticity”phenomenon,which makes the composites show better macroscopic plastic deformability and obvious work-hardening behavior compared to the conventional amorphous alloy matrix composites reinforced with ductile phases.However,the in-situ metastable B2-CuZr phase tends to undergo eutectoid decomposition during solidification,and the volume fraction,size,and distribution of B2-CuZr phase are difficult to control,which limits the development and application of these materials.To date,much efforts have been made to solve the above problems through composition optimization,casting parameter tailoring,and post-processing technique.In this study,a review was given based on relevant studies,focusing on the predictive approach,reinforcing mechanism,and microstructure tailoring methods of B2-CuZr phase reinforced amorphous alloy matrix composites.The research focus and future prospects were also given for the future development of the present composite system.

超临界CO_(2)管道停输过程温压及相态变化规律预测

不同于原油、天然气管道,超临界CO_(2)管道在停输过程中,需要关注温度和压力共同作用下的CO_(2)相态变化。掌握停输过程管道各位置流体温压变化关系、初始气化工况点和气化程度,对实现管道安全状态预判具有重要意义。基于中国石油天然气股份有限公司新疆油田分公司百万吨级超临界CO_(2)管道示范工程KB CO_(2)管道,建立了管道水力热力模型并求解,获得了管道停输后全线压力、温度、密度、持液率及相态变化规律,发现流体密度值与单位温降对应的压降值存在正相关性。基于Peng-Robinson状态方程,得到流体气化前压力、温度和密度变化的函数表达式,该温压关系在CO_(2)相图中为相态迁移路径线的斜率值。该值主要受流体密度影响,流体密度500 kg/m^(3)、650 kg/m^(3)和800 kg/m^(3)对应的斜率值分别为0.213、0.325和0.473。同时,给出了流体初始气化时的温压计算公式和气化后持液率变化预测公式。CO_(2)相图中相态迁移路径线与气液平衡线的交点即为流体初始气化压力和温度点。CO_(2)流体气化后,压力和温度状态点将沿着气液平衡线移动,直到温度降至管道周围土壤环境温度。采用OLGA软件对推导出的计算公式进行了验证,计算值与模拟值的误差在±4.00%以内,说明公式具有较高的准确性。最后应用公式对示范工程停输过程安全状态进行了预测,发现管道起点发生气化时的压力最高,为避免管道任意点发生气化,需在管道压力降至7.0 MPa前进行再启动操作。

一种基于TDLAS的激光CO_(2)传感器设计和应用

针对煤矿井下CO_(2)传感器易受水汽干扰、可靠性低等问题,在红外CO_(2)传感器的基础上,设计了一种基于TDLAS的激光CO_(2)传感器,详细介绍了传感器技术原理和软硬件设计。该传感器通过提取气体吸收后的光谱信号的二次谐波,计算信号衰减的幅度,依据公式推导出待测气体的浓度。实验结果表明,激光CO_(2)传感器相比红外传感器具有更高的可靠性、更强的抗干扰能力,能够有效地避免水汽干扰,具有广泛的应用前景和经济效益。