The self-fabrication of materials in nature offers an alternate and powerful solution towards the grand challenge of designing advanced structural materials, where strength and toughness are always mutually exclusive. Crossed-lamellar structures are the most common microstructures in mollusks that are composed of aragonites and a small amount of organic materials. Such a distinctive composite structure has a fracture toughness being much higher than that of pure carbonate mineral. These structures exhibiting complex hierarchical microarchitectures that span several sub-level lamellae from microscale down to nanoscale, can be grouped into two types, i.e., platelet-like and fiber-like crossed-lamellar structures based on the shapes of basic building blocks. It has been demonstrated that these structures have a great potential to strengthen themselves during deformation. The observed underlying toughening mechanisms include microcracking, channel cracking, interlocking, uncracked-ligament bridging, aragonite fiber bridging, crack deflection and zig-zag, etc., which play vital roles in enhancing the fracture resistance of shells with the crossed-lamellar structures. The exploration and utilization of these important toughening mechanisms have attracted keen interests of materials scientists since they pave the way for the development of bio-inspired advanced composite materials for load-bearing structural applications. This article is aimed to review the characteristics of hierarchical structures and the mechanical properties of two kinds of crossed-lamellar structures, and further summarize the latest advances and biomimetic applications based on the unique crossed-lamellar structures.

•Two diamond allotropes with 5–8-membered rings (PHODs) are semiconductors•PHODs are ~ 20% softer in hardness and weaker in tensile strength than diamond•PHODs are ~ 10% lighter in mass densities than diamond•PHODs are light-weight superhard carbon materials•Tuning ring topology balances mechanical property and density of carbon materialsRing topology (RT) is defined as minimal closed rings to characterize the connection features of given atoms so that RT can identify beyond the nearest neighbors the structures of allotropes bearing the same local bonding features, e.g. four-fold coordination in diamond-related materials. Two diamond allotropes with less common 5–8 membered ring topologies were studied by the first-principles calculations in this work. These orthorhombic carbon structures, denoted as L-PHOD and Z-PHOD carbons, respectively, are three dimensional networks connected solely via sp3 hybridized CC bonds but their atoms are arranged in a non-hexagonal ring topology different from the conventional diamond. They can be constructed by superimposing Octagon-Pentagon Graphene monolayer consisting of (5–8)-membered rings connected along a straight or a zigzag path. The L-PHOD and Z-PHOD carbons are predicted to be semiconductors with indirect band gaps ~ 4–5 eV. Compared with diamond the postulated L-PHOD and Z-PHOD carbons are ~ 20% softer in hardness and weaker in tensile strength but ~ 10% lighter in mass densities due to their larger internal channels associated with the octagon rings, implying their potential applications as light-weight superhard materials. Our work suggest that tuning the ring topology of diamond-related materials provides a design strategy to balance the mechanical properties and densities often required in the development of light-weight structure materials.Download high-res image (199KB)Download full-size image

Perovskite oxides LaxSr1–xCo0.9Sb0.1O3–δ (LSCSbx, x=0.0–0.8) are investigated as IT–SOFC cathodes supported with La0.9Sr0.1Ga0.8Mg0.2O3–δ (LSGM) electrolyte. All LSCSbx oxides have a tetragonal distorted perovskite structure with s.g. P4/mmm, while a La2Co2O5 impurity phase was observed within La doping levels at x=0.6–0.8. The LSCSb0.4 has a good chemical compatibility with LSGM electrolyte for temperatures up to 1050 °C. XPS examinations indicate the existence of Co3+/Co4+ mixed valence states in LSCSbx. The conductivity increases with La doping and the LSCSbx with x=0.4 exhibits the highest electrical conductivity (e.g., 673–1637 S cm−1 at 300–850 °C). The thermal expansion coefficient (TEC) decreases from 25.89×10–6 K–1 for x=0.0 to 18.5×10–6 K–1 for x=0.6 at 30–900 °C. Among the LSCSbx compositions, the LSCSb0.2 exhibits the lowest polarization resistance (Rp), which is merely 0.069 Ω cm2 at 700 °C. The maximum power density of the cell with LSCSb0.2 cathode on 300 µm thick LSGM electrolyte attains 564 mW cm–2 at 850 °C, which is higher than that of SrCo0.9Sb0.1O3–δ (SCSb) cathode. All of the results indicate that LSCSb0.2 is a promising material for application in IT–SOFCs cathodes.

To explore the effect of cyclic pre-deformation on static mechanical behavior of materials with different stacking fault energies (SFEs), polycrystalline Cu-16 at. pct Al alloy with a low SFE is selected as the target material in the present work, and the strengthening micro-mechanisms induced by cyclic pre-deformation are compared with the previous studies on pure Al with a high SFE and Cu with an intermediate SFE. The results show that the movement of dislocations exhibits a high slip planarity during cyclic pre-deformation at different total strain amplitudes Δεt/2, and some nano-sized deformation twins are formed after subsequent tension. The cyclic pre-deformation at an appropriate Δεt/2 of 1.0 × 10−3 promotes a significant increase in ultimate tensile strength σUTS nearly without loss of tensile ductility, which primarily stems from the introduction of many mobile planar slip dislocations by cyclic pre-deformation as well as the formation of nano-sized deformation twins during subsequent tension. Based on the comparison of the strengthening micro-mechanisms induced by cyclic pre-deformation in Al, Cu, and Cu-16 at. pct Al alloy, it is deduced that a low-cycle cyclic pre-deformation at an appropriate condition is expected to cause a better strengthening effect on the static tensile properties of low SFE metals.

Uniaxial tensile tests were conducted to investigate the plastic deformation behavior and deformation microstructures of coarse-grained Cu-Ni alloys containing a wide range of Ni contents (5–20 at%), which possess higher stacking fault energies (SFE) than pure Cu. The mechanical testing results show that, with increasing Ni content, i.e., jointly increasing SFE and degree of short range clustering (SRC), the ultimate tensile strength increases, but the ductility keeps almost unchanged; meanwhile, there exists an obvious increasing stage (or “bump”) in the strain-hardening rate curves at around 3% engineering strain. Microstructural examinations demonstrate that dislocations are apt to slip on primary slip planes at the initial stage of deformation (e.g., 3% engineering strain) to form planar slip bands, indicating that the existence of SRCs in Cu-Ni alloys is beneficial to the promotion of planar slip, leading to the occurrence of a “bump” phenomenon in the strain-hardening rate curves. With increasing deformation amount to a certain degree, wavy slip becomes the major deformation mode under the joint influence of high SFE and diminution of SRCs, and the final deformation microstructures transform from dislocation cells and cell blocks into extended dislocation walls with increasing Ni content. Both the cell block structures and extended dislocation walls subdivide the coarse grains uniformly to disperse local strain concentration, thus enabling the Cu-Ni alloys to maintain a high ductility with an increased tensile strength with increasing Ni content. In a word, the plastic deformation behavior of Cu-Ni alloys is actually governed by the competitive influence of SRC and SFE.

Compared with graphene, graphyne and its derivatives possess more diversified atomic configurations and richer electronic structures including Dirac cones (DCs) and metallic features depending on the parity of the number of sp carbon atoms of graphynes. This report described conceptually the process of DC formation of α-graphyne within a tight-binding framework parameterized from density functional calculations. We propose a “triple coupling” mechanism elucidating the DC formation and some flat bands of α-graphynes where the couplings among the three sp carbon chain atoms are critical. The extension of this mechanism further explains the origins of DCs of silagraphynes and the parity dependent electronic structures of α-graphyne derivatives with extended sp carbon chains. Understanding these origins helps in tuning electronic properties in the design of C or C–Si based nanoelectronic devices.

•A maximum fraction of low ΣCSL boundaries can reach 83.3% in GBCD optimized HNASS.•Only Σ3 boundaries can be termed as “effective special boundaries” in HNASS.•Σ3 boundaries effectively interrupt GB connectivity, thus improving IGC resistance.Grain boundary character distribution (GBCD) and the effect of GBCD optimization on the intergranular corrosion (IGC) of a cold rolled and subsequently annealed nickel-free and manganese-bearing high-nitrogen austenitic stainless steel were investigated. The results show that the fraction of low Σ coincidence site lattice boundaries increases from 47.3% for the solid solution treated specimen to 83.3% for the specimen cold-rolled by 7% and then annealed at 1423 K for 10 min. Σ3 boundaries of high fraction effectively interrupt the connectivity of non-corrosion-resisting boundaries (special boundaries like Σ9, Σ27, etc. and general high angle boundaries) network, thus improving the IGC resistance.

To explore the effect of strain rate on the high temperature deformation characteristics of ultrafine-grained materials, the deformation and damage features as well as microstructures of ECAP-treated pure Al at different temperatures T and strain rates were systematically studied through compression tests and microscopic observations. The increase in eliminates strain softening at T≤473 K, and largely enhances the yield strength and flow stress at 473–573 K. The shear deformation dominates the plastic deformation of ECAP-treated Al. Many cracks along shear bands (SBs) are formed at T≥473 K and secondary SBs basically disappear at 1×10−3 s−1; however, at 1×10−2 s−1, cracks are only observed at temperature below 473 K, and secondary SBs become clearer at T≥473 K. The microstructures of ECAP-treated Al mainly consist of sub-grains (SGs). The increase in inhibits the SG growth, thus leading to the increases both in yield strength and flow stress at high temperatures.

The tension-tension fatigue behavior of Fe-18Cr-18Mn-0.63N high nitrogen austenitic stainless steel was investigated focusing on the effect of the imposed stress amplitude on the deformation and damage characteristics. It was found that the S-N curve of the fatigue life vs. the stress amplitude meets a specific bilinear Basquin relationship. With the increase in stress amplitude, the distinctive damage features on the specimen surface change from slip cracking into intergranular cracking. The internal microstructure is mainly composed of planar single-slip dislocation arrangements at low stress amplitudes. In contrast, at high stress amplitudes, the microstructures primarily comprise planar multiple-slip dislocation structures, deformation twins, twin-like bands together with a few wavy slip dislocation arrangements. Such a variation in deformation micromechanisms with the applied stress amplitude is believed to be the major reason for the occurrence of a specific bilinear Basquin relationship in the S-N curve.

To explore the coupled effect of temperature T and strain rate \(\dot{\varepsilon }\) on the deformation features of AZ31 Mg alloy, mechanical behaviors and microstructural evolutions as well as surface deformation and damage features were systematically examined under uniaxial tension at T spanning from 298 to 523 K and \(\dot{\varepsilon }\) from 10−4 to 10−2 s−1. The increase in T or the decrease in \(\dot{\varepsilon }\) leads to the marked decrease in flow stress, the appearance of a stress quasi-plateau after an initially rapid strain hardening, and even to the occurrence of successive strain softening. Correspondingly, the plastic deformation modes of AZ31 Mg alloy transform from the predominant twinning and a limited amount of dislocation slip into the enhanced non-basal slip and the dynamic recrystallization (DRX) together with the weakened twinning. Meanwhile, the cracking modes also change from along grain boundaries (GBs) and at twin boundaries (TBs) or the end of twins into nearby GBs where the DRX has occurred. The appearance of a stress quasi-plateau, the formation of large-sized cracks nearby GBs, and the occurrence of continuous strain softening, are intimately related to the enhancement of the non-basal slip and the DRX.

To explore the temperature dependence of deformation behavior of BCC structural materials and the relevant effect of pre-annealing, commercially pure iron (CP Fe) produced by equal-channel angular pressing (ECAP) is selected as the experimental material. The influences of deformation temperature T and pre-annealing on deformation behavior, surface deformation characteristics and substructures of ECAP Fe were systematically studied. The results show that ECAP Fe undergoes a remarkable strain softening stage after a rapid strain hardening during uniaxial compression, and the softening degree and the yield strength σYS first decrease and then increase with raising temperature. Pre-annealing at 400 °C effectively weakens the strain softening degree and increases σYS. To understand the influence of deformation temperature on deformation behavior, as well as the relevant pre-annealing effect, deformation and damage characteristics and dislocation structures are studied in detail. In a word, the strain softening of ECAP Fe is associated not only with internal structural instability, but also with temperature, and pre-annealing at 400 °C improves high-temperature mechanical properties of ECAP Fe.

The formation of Dirac cones in electronic band structures via isomorphous transformation is demonstrated in 2D planar SiC sheets. Our combined density functional and tight-binding calculations show that 2D SiC featuring C–C and Si–Si atom pairs possesses Dirac cones (DCs), whereas an alternative arrangement of C and Si leads to a finite band gap. The origin of Dirac points is attributed to bare interactions between Si–Si bonding states (valence bands, VBs) and C–C antibonding states (conduction bands, CBs), while the VB–CB coupling opens up band gaps elsewhere. A mechanism of atom pair coupling is proposed, and the conditions required for DC formation are discussed, enabling one to design a class of 2D binary Dirac fermion systems on the basis of DF calculations solely for pure and alternative binary structures.

Magnesium has been recently recognized as a biodegradable metal for bone substitute applications. In order to improve the biocompatibility and osteointegration of pure Mg, two kinds of coatings, i.e., the Ca–P coating and bioglass ceramic cement (BGCC)/Ca–P coating, were prepared on the pure Mg ribbons in the present work. The Ca–P coating was obtained by aqueous solution method. Subsequently, Ca–P coated Mg was immersed into the BGCC slurry, which was prepared by the mix of SiO2–CaO–P2O5 bioglass ceramic (BGC) powders and phosphate liquid with a liquid-to-solid ratio (L/S) of 1.6, to obtain BGCC/Ca–P coating by a dipping–pulling method. The microstructures, morphologies, and compositions of these coatings have been characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS). The effect of these coatings on the mineralization activity of pure Mg has been investigated. The results indicated that both the Ca–P coating and BGCC/Ca–P coating could promote the nucleation of osteoconductive minerals, i.e., bone-like apatite, and the hydroxyapatite (HA) layer formed on the surface of the BGCC/Ca–P coating is obviously more dense, thick, and stable than that formed on the Ca–P coating after immersion in SBF solution for 15 days. The potentiodynamic polarization test indicated that the corrosion current density of the BGCC/Ca–P coated Mg is obviously lower than that of the Ca–P coating and 10 times lower than that of uncoated Mg. These results demonstrated that the BGCC/Ca–P coating can increase significantly the corrosion resistance of Mg and introduce a high biocompatibility of the bone–Mg substrate interface. In summary, the newly developed BGCC/Ca–P coated Mg has a good potential for biomedical applications.Keywords: BGCC; Ca−P; coating; corrosion; magnesium; mineralization;

Dislocation structures in \( [\overline{1} 12] \) Cu-7 at. pct Al alloy single crystals cyclically deformed at different plastic strain amplitudes were investigated by transmission electron microscope (TEM) and compared with the results of \( [\overline{1} 12] \) Cu single crystals. It is found that the plastic strain amplitude γpl has an obvious effect on the slip deformation mode, and consequently on the cyclic hardening behavior of \( [\overline{1} 12] \) Cu-7 at. pct Al alloy single crystals with an intermediate stacking fault energy. For instance, a high slip planarity (i.e., only formation of planar-slip bands) contributes to the occurrence of a gentle cyclic hardening with a much lower saturation stress at a low γpl of 4.5 × 10−4. A mixed planar/wavy-slip mode (e.g., persistent Lüder’s bands/wall-like microstructures) at an intermediate γpl of 2.2 × 10−3 causes an obvious cyclic hardening up to a comparable saturation stress to that for the \( [\overline{1} 12] \) Cu single crystal. In contrast, the deformation mode is dominated by wavy slip (e.g., ill-defined dislocation cells and walls) at the highest γpl of 7.2 × 10−3, causing that its cyclic hardening curve is quite similar to that for the \( [\overline{1} 12] \) Cu single crystal; in this case, a slightly higher saturation stress level than that for the Cu single crystal is reached due to the additional solid solution strengthening.

•A novel porous Mg was produced by a fiber deposition hot pressing technology.•The porous Mg has a 3D interconnected network structure with a porosity of 33-54%.•Mechanical properties of the porous Mg are comparable to those of cancellous bone.Porous magnesium has been recently recognized as a biodegradable metal for bone substitute applications. A novel porous Mg scaffold with three-dimensional (3D) interconnected pores and with a porosity of 33–54% was produced by the fiber deposition hot pressing (FDHP) technology. The microstructure and morphologies of the porous Mg scaffold were characterized by scanning electron microscopy (SEM), and the effects of porosities on the microstructure and mechanical properties of the porous Mg were investigated. Experimental results indicate that the measured Young's modulus and compressive strength of the Mg scaffold are ranged in 0.10–0.37 GPa, and 11.1–30.3 MPa, respectively, which are fairly comparable to those of cancellous bone. Such a porous Mg scaffold having a 3D interconnected network structure has the potential to be used in bone tissue engineering.

A novel magnesium based scaffold with a two-layer structure was synthesized by powder metallurgical process using salt particles as space holder. The outer layer of the scaffold shows an interconnected porous structure and the inner layer presents a compact structure reinforced by the salt particles. Such a specific structure is introduced primarily for the purpose of a better combination of biocompatibility and mechanical compatibility. Experimental results demonstrate that the structural features and mechanical properties of the magnesium based scaffold with a salt content of 30 wt% prepared by the current method are quite compatible with the cancellous bone. Such a novel Mg-based scaffold has the potential to act as degradable implants for bone substitute application.

The effect of cyclic predeformation at different plastic strain amplitudes γpl on the uniaxial tensile behavior of the [017] critical double-slip-oriented copper single crystal was investigated. A cyclic predeformation at a low γpl of 7.0 × 10−4 was found able to enhance the tensile strength of the [017] crystal at nearly no expense of the decrease in plasticity. However, as the γpl for the prefatigue increases to a higher value of 3.0 × 10−3, the tensile strength of the prefatigued [017] crystal decreases to be slightly less than that of the unfatigued crystal, and simultaneously its tensile plasticity decreases markedly. Therefore, a cyclic predeformation at an appropriate plastic strain amplitude might bring about an obvious strengthening effect for metallic single crystals.

Grain boundary engineering (GBE) is a practice of improving resistance to grain boundary failure of the material through increasing the proportion of low Σ coincidence site lattice (CSL) grain boundaries (special grain boundaries) in the grain boundary character distribution (GBCD). The GBCD in a cold rolled and annealed Fe-18Cr-18Mn-0.63N high-nitrogen austenitic stainless steel was analyzed by electron back scatter diffraction (EBSD). The results show that the optimization process of GBE in the conventional austenitic stainless steel cannot be well applied to this high-nitrogen austenitic stainless steel. The percentage of low ΣCSL grain boundaries could increase from 47.3% for the solid solution treated high-nitrogen austenitic stainless steel specimen to 82.0% for the specimen after 5% cold rolling reduction and then annealing at 1423 K for 10 min. These special boundaries of high proportion effectively interrupt the connectivity of conventional high angle grain boundary network and thus achieve the GBCD optimization for the high-nitrogen austenitic stainless steel.

The dislocation structures induced by the cyclic deformation of a \( [\bar{1}49] \) single-slip-oriented Fe-35 wt pct Cr alloy single crystals containing fine Cr-rich precipitates have been studied by transmission electron microscopy (TEM) over the plastic strain amplitude εpl range of 5 × 10−4 to 5 × 10−3. Persistent slip bands (PSBs) with different structures, such as ladder-like structure, irregular ladders, elongated cells, etc., were observed to form at plastic strain amplitudes ranging from 5.0 × 10−4 to 2.5 × 10−3, and the volume fraction of PSBs increases with increasing εpl. As εpl is as high as 5.0 × 10−3, dislocation cells dominate the microstructure, even though a small amount of irregular PSB ladder structures still exists and they tend to evolve as labyrinth-like structures. The instability of Cr-rich precipitates during cyclic straining was believed to facilitate the formation of PSBs and thus promote some similarities of cyclic deformation characteristics between the current body-centered cubic (bcc) Fe-Cr single crystals and face-centered cubic (fcc) metal crystals. Whatever the internal structure of PSBs is, they could always carry the majority of the plastic strain in the course of cyclic deformation, thus causing the occurrence of a stress plateau region in the cyclic stress–strain (CSS) curve of Fe-Cr alloy single crystals.

The effect of short-term pre-annealing treatment on the compressive deformation and damage behavior of ultrafine-grained (UFG) copper produced by equal channel angular pressing (ECAP) has been studied by mechanical tests and microstructural observations. It is found that a controlled 10-min pre-annealing treatment on the UFG copper below the recrystallization temperature can result obviously in a higher strength (higher flow stress level) and a higher flow stability (lower stress softening rate) under uniaxial compression, as compared to the case of as-ECAPed sample. Observations of surface and interior deformation damage features indicate that, compared to the as-ECAPed copper sample, the pre-annealed ECAPed copper at less than recrystallization temperature may exhibit a better compressive plastic deformation capacity, namely, the destructive deformation morphology of large-scale shear bands normally observed in compressed as-produced UFG copper sample would not appear in compressed pre-annealed sample, except for a relatively smooth surface morphology featuring some ‘step’ reliefs with a few discontinuous shear bands and non-propagation voids. Finally, the deformation mechanism of different kinds of severe plastic deformation (SPD) processed UFG materials as well as their pre-annealing effects are further discussed, and a general rule is summarized as follows: an appropriate selection of pre-annealing temperature and annealing time is needed for improving both strength and ductility of SPDed materials with a microstructure comprising equiaxed grains and well-defined grain boundaries.Highlights► Appropriate pre-annealing treatment can improve compressive properties of UFG Cu. ► The pre-annealed UFG copper exhibits a better plastic deformation capacity. ► Pre-annealing effect on deformation mechanism of SPDed materials is discussed.

Fracture surface features of the AL6XN super-austenitic stainless steel fatigued at different stress amplitudes were observed by SEM and quantitatively analyzed by a fractal method. It was found that the morphologies corresponding to three characteristic zones of fracture surface, i.e., fatigue crack source (or initiation) zone, crack growth zone and final rapid fracture area, are more or less related with the applied stress amplitude Δσ/2. A quantitative relationship between the total fatigue life and the average fractal dimension of scanning profile of fracture surface was experimentally established. The lower the fractal dimension, the longer the fatigue life is. A similar change of fractal dimension with the applied Δσ/2 in the fatigue crack source and growth zones suggests that crack initiation and propagation lives might contribute comparably to the resulting total fatigue life of the AL6XN super-austenitic stainless steel tested under constant stress amplitude control.

The microstructures of the Saxidomus purpuratus shell were observed. It was found that the inner and middle layers of the shell are composed of crossed lamellae, while the outer layer exhibits porous structures. With the characteristic structure of each layer, the hardness of inner layer with narrow domains in crossed lamellar structure is the highest, and that of middle layer with wide domains is lower, while the outer layer has the lowest hardness. The damage morphologies of the indentations change a lot, depending not only upon the magnitude of the indentation load, but also upon the orientation between the indentation direction and the crossed lamellae in the microstructure of the shell, which illustrates the anisotropy in mechanical properties of such shells.

To investigate the effect of the spacers of “V”-type dipyridylamide and dicarboxylic ligands on the structural diversity of CoII coordination polymers, [Co(L1)(5-CH3-1,3-bdc)]·2H2O (1) [Co(L2)(5-CH3-1,3-bdc)(H2O)]·H2O (2) [Co(L2)(5-NO2-1,3-bdc)(H2O)]·H2O (3) [Co(L2)(1,3-bdc)(H2O)]·H2O (4) [Co(L2)(4,4′-oba)]·3H2O (5) and L2·2H2O (6) [L1 = N,N′-bis(pyridine-3-yl)pyridine-2,6-dicarboxamide, L2 = N,N′-bis(pyridine-3-yl)-5-methylisophthalic dicarboxamide, 5-CH3-1,3-H2bdc = 5-methylisophthalic acid, 5-NO2-1,3-H2bdc = 5-nitroisophthalic acid, 1,3-H2bdc = 1,3-benzenedicarboxylic acid, 4,4′-H2oba = 4,4′-oxybis(benzoic acid)] have been hydrothermally synthesized. Complexes 1–5 were characterized by IR spectroscopy, thermal analysis, TG and X-ray single-crystal diffraction. Complex 1 is a 2D structure based on (4,4)-connected [Co(5-CH3-1,3-bdc)] network and [Co(L1)] helixes. Complexes 2–4 feature isostructural 2D networks derived from Co-dicarboxylate linear chains and [Co(L2)] helixes. Complex 5 show 1D tubular structure constructed by two parrelled [Co(4,4′-oba)] linear chains and [Co(L2)] loops. Compound 6 is a 3D supramolecular structure extended by L2 ligands and water molecules. The effect of the spacers of “V”-type dipyridylamide and dicarboxylic ligands on the structures of the title compounds were discussed. The magnetic property of 1, the fluorescent behaviors of 1–6 and photocatalytic properties of 1–5 under UV irradiation were studied.Six “V”-type dipyridylamide-based compounds have been hydrothermally synthesized and structural directed by spacers, which show different fluorescent, magnetic and photocatalytic properties.