A review on the multi-scaled structures and mechanical/thermal properties of tool steels fabricated by laser powder bed fusion additive manufacturing

The laser powder bed fusion(LPBF) process can integrally form geometrically complex and high-performance metallic parts that have attracted much interest,especially in the molds industry.The appearance of the LPBF makes it possible to design and produce complex conformal cooling channel systems in molds.Thus,LPBF-processed tool steels have attracted more and more attention.The complex thermal history in the LPBF process makes the microstructural characteristics and properties different from those of conventional manufactured tool steels.This paper provides an overview of LPBF-processed tool steels by describing the physical phenomena,the microstructural characteristics,and the mechanical/thermal properties,including tensile properties,wear resistance,and thermal properties.The microstructural characteristics are presented through a multiscale perspective,ranging from densification,meso-structure,microstructure,substructure in grains,to nanoprecipitates.Finally,a summary of tool steels and their challenges and outlooks are introduced.

Advances in Liquid Crystal Epoxy:Molecular Structures,Thermal Conductivity,and Promising Applications in Thermal Management

Traditional heat conductive epoxy composites often fall short in meeting the escalating heat dissipation demands of large-power,high-frequency,and highvoltage insulating packaging applications,due to the challenge of achieving high thermal conductivity(k),desirable dielectric performance,and robust thermomechanical properties simultaneously.Liquid crystal epoxy(LCE)emerges as a unique epoxy,exhibiting inherently high k achieved through the self-assembly of mesogenic units into ordered structures.This characteristic enables liquid crystal epoxy to retain all the beneficial physical properties of pristine epoxy,while demonstrating a prominently enhanced k.As such,liquid crystal epoxy materials represent a promising solution for thermal management,with potential to tackle the critical issues and technical bottlenecks impeding the increasing miniaturization of microelectronic devices and electrical equipment.This article provides a comprehensive review on recent advances in liquid crystal epoxy,emphasizing the correlation between liquid crystal epoxy’s microscopic arrangement,organized mesoscopic domain,k,and relevant physical properties.The impacts of LC units and curing agents on the development of ordered structure are discussed,alongside the consequent effects on the k,dielectric,thermal,and other properties.External processing factors such as temperature and pressure and their influence on the formation and organization of structured domains are also evaluated.Finally,potential applications that could benefit from the emergence of liquid crystal epoxy are reviewed.

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.

Atomistic simulation of thermal effects and defect structures during nanomachining of copper

Molecular dynamics （MD） simulations of monocrystalline copper （100） surface during nanomachining process were performed based on a new 3D simulation model. The material removal mechanism and system temperature distribution were discussed. The simulation results indicate that the system temperature distribution presents a roughly concentric shape, a steep temperature gradient is observed in diamond cutting tool, and the highest temperature is located in chip. Centrosymmetry parameter method was used to monitor defect structures. Dislocations and vacancies are the two principal types of defect structures. Residual defect structures impose a major change on the workpiece physical properties and machined surface quality. The defect structures in workpiece are temperature dependent. As the temperature increases, the dislocations are mainly mediated from the workpiece surface, while the others are dissociated into point defects. The relatively high cutting speed used in nanomachining results in less defect structures, beneficial to obtain highly machined surface quality.

Meso-Cenozoic lithospheric thermal structure in the Bohai Bay Basin,eastern North China Craton

The Bohai Bay Basin is a region where part of the North China Craton has been thinned and destroyed. It has experienced two periods of crustal thinning that occurred during the Cretaceous and Paleogene, but investigations of its Mesozoic and Cenozoic lithospheric thermal structure are limited. Therefore, in this study,the distributions of mantle heat flow, crustal heat flow, and Moho temperatures during the Meso-Cenozoic are calculated based on analyses of the thermal history of the Bohai Bay Basin. The results indicate that the ratio of mantle heat flow to surface heat flow peaked during the late stages of the early Cretaceous and during the middle to late Paleogene. The corresponding mantle heat flow was more than 65% of the surface heat flow. Moho temperatures reached three peaks: 900-1100℃ in the late stages of the early Cretaceous;820-900℃ in the middle to late Paleogene; and(in the Linqing Depression, Cangxian Uplift, and Jizhong Depression) 770-810℃ during the early Neogene. These results reveal that the Bohai Bay Basin experienced significant geological change during the Cretaceous, including the transformation of lithospheric thermal structure from "cold mantle and hot crust" before the Cretaceous to "hot mantle and cold crust" after the Cretaceous. The results also indicate that the basin experienced two large-scale rifting events.Therefore, this work may provide the thermal parameters for further investigations of the geodynamic evolution of eastern China.

Syntheses,Crystal Structures and Kinetic Mechanisms of Thermal Decomposition of Rare Earth Complexes with Schiff Base Derived from o-Vanillin and p-Toluidine

Three complexes, [Pr（NO3）3（HL）2] （1）, [Nd（NO3）3（HL）2] （2） and [Er（NO3）3（HL）2] ·0.5H2O （3）, were synthesized from the reaction of a Schiff base ligand 2-[ （4-methylphenylimino）methyl ]-6-methoxyphenol （C15 H15 NO2, HL） with Ln（NO3）3·6H2O （Ln = Pr, Nd, Er）. Characterization by single-crystal X-ray diffraction technique, elemental analysis, molar conductance, FT-IR, UV-Vis, ^1H NMR and thermal analysis shows the title complexes are neutral molecules where the central Ln（ Ⅲ） ion is ten-coordinated in biapical anti-hexahedron prism geometry, with four oxygen atoms of the phenolic hydroxy and methoxy groups in the two bidentate Schiff base ligands and six oxygen atoms provided by the three bidentate NO3 - anions. Additionally, the kinetic mechanism of thermal decomposition of complex 3 was determined with a TG-DTG curves by both integral and differential methods. The functions of thermal decomposition reaction mechanism and the equation of kinetic compensation effect were obtained.

Structure and Thermal Properties of Transition Metal Imidazole Chloride

The X-ray single-crystal structure analyses have been determined for two metal imidazole chlorides: [Fe(Im)6]Cl24H2O 1 and [CuCl(Im)4]Cl 2 (Im = imidazole). The red crystal of compound 1 is of triclinic, space group Pi with Mr = 607.31 (C18H32Cl2FeN12O4), a = 8.797(2), b = 9.068(2), c = 10.581(2) ? a = 75.35(3), ?= 83.20(3), ? = 61.85(3)o, V = 720.0(2) 3, Z = 1, Dc = 1.401 g/cm3, F(000) = 316, = 0.755 mm-1, R = 0.0353 and wR = 0.1227. The blue crystal of compound 2 belongs to monoclinic, space group P21/c with Mr = 406.77 (C12H16Cl2CuN8), a = 13.909(3), b = 8.8933(18), c = 15.086(7) ? ?= 118.32(2), V = 1642.7(9) 3, Z = 4, Dc = 1.645 g/cm3, F(000) = 828, = 1.666 mm-1, R = 0.0609 and wR = 0.1726. In solid state, both 1 and 2 form three-dimensional hydrogen bond networks to stabilize the structures which were also characterized by TG and elemental analyses. The thermal gravity (TG) data indicate that the residues are Fe and Cu for 1 and 2, respectively.

Hydrothermal Synthesis and Crystal Structure of a New Three-dimensional Heterometallic Coordination Polymer

A new 3d-4fheterometallic polymer {[Sm2Cu（PDC）2（SO4）2（H20）6]·2H2O}n 1 has been synthesized by Sm2O3, Cu（SO4）2·5H2O and pyridine-3,5-dicarboxylic acid under hydrothermal conditions. The compound crystallizes in triclinic system, space group Pi, with a = 6.352（7）, b = 10.040（10）, c = 10.315（11） A, α = 94.958（14）, β = 95.556（7）, γ = 99.747（14）°, V = 641.7（12）A3, Z = 1, M, = 1030.63, Dc= 2.651 Mg/m3,μ = 5.615 mm-1, F（000） = 491, the final R = 0.0491 and wR = 0.1345 for 2098 observed reflections with I 〉 2σ（I）. The compound is a three-dimensional network structure in which infinite lanthanide-carboxylate chains are linked by [Cu（$04）2]2- metalloligands to form a mixed-metal coordination network.

Hydrothermal Synthesis,Crystal Structure and Thermal Stability of a Binuclear Copper(Ⅱ) Complex with 3-(Pyridin-2-yl)-1,2,4-triazole

One novel binuclear copper（Ⅱ） complex [Cu 2 （Hpt） 2 （CO 3） 2 （H 2 O） 2 ]·H 2 O with copper carbonate and 3-（pyridin-2-yl）-1,2,4-triazole （Hpt） was hydrothermally synthesized and characterized by IR and X-ray diffraction analysis.The complex crystallizes in triclinic,space group P2 1 /n with a=0.6862（1）,b=0.7805（1）,c=1.1983（2） nm,α=72.03（2）,β=107.72（3）,γ=75.28（2）o,V=0.5884 nm 3,D c=2.105 g/cm 3,Z=1,F（000）=357,GOOF=1.041,the final R=0.01859 and wR=0.04348.The whole molecule is composed of two cooper ions,two Hpt molecules,two carbonate and three water molecules,forming a binuclear structure.The crystal structure shows that the cooper ion is coordinated with three nitrogen atoms from two Hpt molecules,two oxygen atoms from one carbonic acid and one water molecule,forming a distorted square pyramidal geometry.The TG analysis result shows that the title complex is stable under 131.0 ℃.

Synthesis,Crystal Structure and Thermal Decomposition of a New Energetic Potassium Salt of Bis(dinitromethyl)difurazanyl Ether

A new energetic organic potassium salt bis（dinitromethyl）difurazanyl ether potas- sium salt [K2（BDFE）] was synthesized, and structurally characterized by elemental analysis, IR spectra, t3C NMR and single-crystal X-ray diffraction. K2（BDFE） crystallizes in monoclinic system, space group C2/c with a = 17.342（3）, b = 12.6943（17）, c = 8.0972（11） A, β = 110.630（2）°, V = 1668.3（4） A3, Z = 4, Dc = 2.000 g/cm3, F（000） = 1000,μ= 0.675 mm-1, S = 1.058, the final R = 0.0499 and wR = 0.1452. The K ion is eight-coordinated with eight O atoms from one water molecule and four bis（dinitromethyl）difurazanyl ethers （BDFE）, forming a distorted dodecahedral structure. Thermal decomposition of the title complex was studied by using DSC and TG-DTG. There are primarily two exothermic decomposition processes between 200 and 370 ℃.

Comparative Study of Magmatism in East Pacific Rise Versus Nearby Seamounts:Constraints on Magma Supply and Thermal Structure Beneath Mid-ocean Ridge

Major elements of 2202 basalts from the East Pacific Rise （EPR） and 888 basalts from near- EPR seamounts are used to investigate their differences in magma crystallization pressures and mantle melting conditions. Crystallization pressure calculation from basalts with 5.0wt%〈MgO〈8.0wt % shows that magma crystallization pressures beneath near-EPR seamounts are positively and negatively correlated with Nas and Fes, respectively. However, these correlations are indistinct in axial lavas, which can be explained by chemical homogenization induced by extensive mixing processes. In each segment divided by major transforms and over-lapping spreading centers （OSCs）, near-EPR seamount lavas have higher magma crystallization pressures, higher Fes and lower Nas than the EPR lavas, which indicate cooler lithosphere, lower degrees and shallower melting depths beneath near-EPR seamounts than the EPR. The correlations between magma crystallization pressures and melting conditions beneath near-EPR seamounts imply that the source thermal state controls the melting degree and melt flux, and then melting process controls the shallow lithosphere temperature and magma crystallization depth （pressure）. The cooler mantle sources beneath near-EPR seamounts produce a lower degree of melting and a less robust magma supply, which results in a deep thermal equilibrium level and high magma crystallization pressure. The magma crystallization pressure decreases significantly as spreading rate of the EPR increases from ~80 mm/year in the north （16~N） to ~160 mm/year in the south （19~S）, while this trend is unobvious in near-EPR seamounts. This suggests that the magma supply controlled by spreading rate dominates the ridge crust temperature and magma crystallization depth, while the near-EPR seamount magma supply is not dominated by the axial spreading rate. Because most seamounts form and gain most of their volume within a narrow zone of 5-15 km from ridge axis, they provide good constraint on magma supply and thermal structure beneath the EPR. High magma crystallization pressures in seamounts indicate dramatic temperature decrease from the EPR. The crystallization pressures of seamount lavas are well correlated with mantle melting parameters but in a blurry relationship with axial spreading rate. Despite the adjacency of the EPR and nearby seamounts, the thermal structure beneath the near-EPR seamounts are controlled by their own magma supply and conductive cooling, chemically and thermally unaffected by magmatism beneath the ridge axis.

Synthesis,Crystal Structure, Thermal Decomposition and Sensitivity Properties of (AIM)(HTNR) and (AIM)(PA)

Two new energetic compounds （AIM）（HTNR） and （AIM）（PA）（AIM=2-azidoimidazole, TNR=2,4,6-trini troresorcinol, PA=picric acid） have been prepared by AIM（2-azidoimidazolium） and TNR（2,4,6-trinitroresorcinol） or PA（picric acid） and characterized by elemental analysis and FTIR spectrum. Their crystal structures were determined by X-ray single-crystal diffraction analysis. The obtained results show that （AIM）（HTNR） crystal belongs to monoc linic, P21/c space group, a=1.1306（2） nm, b=0.70305（14） nm, c=1.7398（4） nm, β=106.91°, V=1.3231（5） nm3, Dc=1.778 g/cm3, Z=4, R1=0.0524, wR2[I 〉2σ（I）]=0.1067 and S=1.092 and （AIM）（PA） crystal belongs to monoclinic P21/c space group, a=0.80303（16） nm, b=0.81395（16） nm, c=2.0471（4） nm, β=93.93（3）°, V=1.3349（5） nm3, Dc=1.683 g/cm3, Z=4, R1=0.0784, wR2[I〉2σ（I）]=0.1814 and S=1.098. Both the compounds have electrostatic attraction and hy drogen bonds, which contribute to making the constructions more stable. The decomposition of the two compounds was studied via differential scanning calorimetry（DSC） and thermogravimetry-derivative thermogravimetry（TG-DTG） techniques at a heating rate of 10 oC/min, and the results show that both the compounds underwent one intensive exothermic decomposition stage. Sensitivity tests reveal that the title compounds were insensitive to friction and im pact and sensitive to flame and could be applied in potential pyrotechnics.

Synthesis,Crystal Structure and Thermal Stability of a One-dimensional Chain Cobalt Coordination Polymer [Co(4,4'-bipy)(2,4,6-TMBA)_2(CH_3CH_2OH)_2]_n

A one-dimensional chain cobalt（Ⅱ） coordination polymer with 2,4,6-trimethyl- benzoic acid, 4,4′-bipyridine and cobalt perchlorate anhydrous has been synthesized and characterized in the mixture solvent of water and alcohol. Crystal data for this complex： monoclinic, space group C2/c, a = 2.3805（8）, b = 1.1464（4）, c = 1.5807（5） nm, y = 128.435（4）°, V= 3.3791（18） nm^3, Dc = 1.246 g/cm^3, Z = 4, F（000） = 1340, final GooF = 1.009, R = 0.0504 and wR = 0.1287. Structural analysis shows that the cobalt ion is coordinated with two nitrogen atoms of one 4,4′- bipyridine molecule and four oxygen atoms from two 2,4,6-trimethylbenzoic acid molecules and two alcohol molecules, giving a distorted octahedral coordination geometry. The result of TG analysis indicates that the title complex is stable till 200 ℃.

THERMAL STRUCTURE OF LITHOSPHERE IN THE QAIDAM BASIN, NORTHEAST QINGHAI-TIBET PLATEAU

The Qaidam Basin is a petroleum province in Northeastern Qinghai—Tibetan plateau, China. The Basin is bounded by the Aljin Mountains to the Northwest, the Qilian Mountains to the Northeast, the Qimantager Mountains to the Southeast and East Kunlun Mountains to the Southwest. The average elevation of the basin and these mountains are 2700m and 3000～ 5000 m respect to the sea level, respectively. The basin was developed on the pre\|Mesozoic basement. Thickness of Tertiary system is more than 10000m in the basin,but Quaternary is mainly in the eastern basin with thickness more than 3000m. The lithology in Mesozoic and Cenozoic of the basin are mainly sandstone, shale, calcic rocks and the interlayers of sandstone and shale.

The Upper Ocean Thermal Structure and the Genesis Locations of Tropical Cyclones in the South China Sea

The relationship between the upper ocean thermal structure and the genesis locations of tropical cyclones (TCs) in the South China Sea (SCS) is investigated by using the Joint Typhoon Warning Center (JTWC) best-track archives and high resolution (1/4 degree) temperature analyses of the world's oceans in this paper. In the monthly mean genesis positions of TCs from 1945 to 2005 in the SCS, the mean sea surface temperature (SST) was 28.8℃ and the mean depth of 26℃ water was 53.1 m. From the monthly distribution maps of genesis positions of TCs, SST and the depth of 26℃ water in the SCS, we discovered that there existed regions with SST exceeding 26℃ and 26℃ water depth exceeding 50 m where no tropical cyclones formed from 1945 to 2005 in the SCS, which suggests that there were other factors unfavorable for TC formation in these regions.

Synthesis, Crystal Structure and Thermal Stability of a Nickel(Ⅱ) Complex with Bicycle[2.2.1]-2-hepten-5,6-dicarboxylic Acid

The nickel complex {Ni（2,2-bipy）（H2O）3[C8H11O2（COO）]}（H2O）3 with bicycle-[2.2.1]-2-hepten-5,6-dicarboxylic acid [C7H8（COOH）2] and 2,2＇-bipyridine （bipy） as ligands has been synthesized and characterized. It crystallizes in monoclinic, space group P , with a = 0.74975（3）, b = 1.20309（4）, c = 1.30593（4） nm, α = 109.861（2）, β = 98.519（2）, γ = 90.575（2）o, V = 1.09337（7） nm3, Dc = 1.552 g/cm3, Z = 2, F（000） = 524, the final GOOF = 1.064, R = 0.0397 and wR = 0.1171. The crystal structure shows that the nickel ion is coordinated with four oxygen atoms from one bicycle[2.2.1]-2-hepten-5,6-dicarboxylic acid molecule and three water molecules and two nitrogen atoms from the 2,2′-bipyridine molecule, forming a distorted octahedral coordination geometry. The result of TG analysis shows that the title complex is stable under 200.0 ℃.

Synthesis,Crystal Structure and Thermal Analysis of N-(2,3-Dimethyl-phenyl)-N'-(methoxyl formyl)thiourea

N-（2,3-Dimethyl-phenyl）-N＇-（methoxyl formyl）thiourea was synthesized by the reacting of 2,3-dimethylaniline,potassium thiocyanate（KSCN） and methyl chloroformate（ClCOOCH 3）.Single crystal was obtained by slowly evaporation solvent at room temperature.The structure was characterized by elemental analysis,IR and X-ray crystalography.The compound crystallized：a triclinic system with space group Pī,a=0.83440（12） nm,b=0.89113（13） nm,c=0.93015（13） nm,α=76.548（2） o,β=63.906（2） o,γ=82.538（2） o,V=0.60379（15） nm 3,Z=2,D c =1.311 mg/m 3,F（000）=252,μ=0.256 mm-1,R 1 =0.0379,wR 2 =0.0919.The specific heat capacity of the title compound was determined by a Micro-DSC method,and the specific heat capacity was 1.25 J·g-1 ·K-1 at 298.15 K.Thermodynamic functions,relative to those at the standard temperature of 298.15 K,were calculated via thermodynamic relationship.The thermal behavior of the title compound under a non-isothermal condition was studied by differential scanning calorimetry/thermogravimetric（DSC/TG） method.There was an obvious endothermic peak in the DSC curve,the peak temperature was 479.43 K.The compound mass loss was 89.94% observed from the TG curve.

Crystal structure and thermal expansion of perovskites containing uranium(VI) and rare-earth elements

By the method of high-temperature reactions in solid phase, compounds with the general formula MⅡ（AⅢ2/3U1/3）O3（MⅡ=Sr, AⅢ=Sc, In;MⅡ=Ba, AⅢ=Sc, In, Y, Nd-Lu） were synthesized.Their structures（space groups Fm 3 m and Pnma） were refined by the Rietveld method and morphotropic transition in Ba（Ln2/3U1/3）O3 on the border of Gd-Tb was discovered.By means of high-temperature X-ray diffraction, phase transitions were studied and thermal expansion coefficients were determined.

Hydrothermal Synthesis, Crystal Structure,Thermal Stability and Photophysical Property of a Novel Zinc Complex with Mixed Ligands

A novel metal-organic coordination complex [Zn（CHIP）（AIC）]n （1, CHIP = 2-（4- chlorophenyl）-lH-imidazo[4,5-f][1,10]phenanthroline, A1C = 5-amino-isophthalic acid） has been synthesized by hydrothermal reactions and characterized by elemental analysis, thermogravimetric （TG） analysis, infrared spectrum （IR） and single-crystal X-ray diffraction. Complex 1 crystallizes in monoclinic, space group C2/c with a = 18.259（5）, b = 17.191（4）, c = 16.371（4） A, V= 4717（2） A3, C27H16C1NsOnZn, Mr= 575.29, Dc = 1.620 g/cm3, p（MoKa） = 1.202 mm-1, F（000） = 2335, Z = 8, the final R = 0.032 and wR = 0.074 for 4723 observed reflections （I 〉 2σ（I））. Single-crystal X-ray diffraction reveals that 1 exhibits one-dimensional （1D） double chains, which are linked by H-bond intersections into a 2D structure. TG analysis shows clear weight loss due to the decomposition of different ligands. The luminescent properties for the ligand and complex 1 were also studied.

Hydrothermal Synthesis,Crystal Structure and Thermal Analysis of a Dinuclear Complex Cd_2(3,5-Dinitrobenzoate)_4(pyridine)_4

A dinuclear complex Cd2（dnba）4（pyridine）4 （dnba = 3,5-dinitrobenzoate） has been synthesized by hydrothermal method and characterized by X-ray single-crystal diffraction, elemental analysis, FT-IR spectroscopy, DSC and TG-DTG techniques. The complex with empirical formula C48H32Cd2NI2024 （Mr = 692.83） crystallizes in monoclinic, space group P21/n with a - 12.0344（14）, b = 10.5752（13）, c = 21.578（3） A, β = 104.150（2）°, V = 2662.8（6） A^3, Z = 2, D, = 1.728 g/cm^3,μ（MoKa） = 0.897 mm^-1, F（000） = 1384, S = 1.016 and （△/σ）max = 0.001. R = 0.0638 and wR = 0.0737 for all data; the final R = 0.0337 and wR = 0.0644. In this complex, four carboxylates are bidentate-or chelate-coordinated with the Cd（Ⅱ） centers to give the dinuclear structure. The other coordination positions of Cd（Ⅱ） are occupied by the lone pair electrons from N of four pyridines. Thermal analyses DSC and TG-DTG have been used to determine the thermal decomposition mechanism of the title complex.