Mechanically excellent nacre-inspired protective steel-concrete composite against hypervelocity impacts

Steel–concrete (SC) composite widely used in military defensive project is due to its impressive mechanical properties, long-lived service, and low cost. However, the growing use of hypervelocity kinetic weapons in the present war puts forward higher requirements for the anti-explosion and penetration performance of military protection engineering. Here, inspired by the special ‘brick-and-mortar’ (BM) structural feature of natural nacre, we successfully construct a nacre-inspired steel–concrete (NISC) engineering composite with 2510 kg/m3, possessing nacre-like lamellar architecture via a bottom-up assembling technique. The NISC engineering composite exhibits nacreous BM structural similarity, high compressive strength of 68.5 MPa, compress modulus of 42.0 GPa, Mohs hardness of 5.5, Young’s modulus of 41.5 GPa, and shear modulus of 18.4 GPa, higher than pure concrete. More interestingly, the hypervelocity impact tests reveal the penetration capability of our NISC target material is obviously stronger than that of pure concrete, enhanced up to about 46.8% at the striking velocity of 1 km/s and approximately 30.9% at the striking velocity of 2 km/s, respectively, by examining the damages of targets, the trajectories, penetration depths, and residual projectiles. This mechanically integrated enhancement can be attributed to the nacre-like BM structural architecture derived from assembling the special steel-bar array frame-reinforced concrete platelets. This study highlights a key role of nacre-like structure design in promoting the enhanced hypervelocity impact resistance of steel–concrete composites.

Mechanically Excellent Nacre-inspired Protective Steel-Concrete Composite against Hypervelocity Impacts

Steel-concrete (SC) composite widely used in military defensive project is due to its impressive mechanical properties, long-lived service, and low cost. However, the growing use of hypervelocity kinetic weapons in the present war puts forward higher requirements for the anti-explosion and penetration performance of military protection engineering. Here, inspired by the special ‘brick-and-mortar’ (BM) structural feature of natural nacre, we firstly construct a nacre-inspired steel-concrete (NISC) engineering composite with 2510 kg/m3, possessing nacre-like lamellar architecture via a bottom-up assembling technique. The NISC engineering composite exhibits nacreous BM structural similarity, high compressive strength of 68.5 MPa, compress modulus of 42.0 GPa, Mohs hardness of 5.5, Young’s modulus of 41.5 GPa, and shear modulus of 18.4 GPa, higher than pure concrete. More interestingly, the hypervelocity impact tests reveal the penetration capability of our NISC target material is obviously stronger than that of pure concrete, enhanced up to about 46.8% at the striking velocity of 1 km/s and approximately 30.9% at the striking velocity of 2 km/s, respectively, by examining the damages of targets, the trajectories, penetration depths, and residual projectiles. This mechanically integrated enhancement can be attributed to nacre-like BM structural architecture derived from assembling the special steel-bar framework-reinforced concrete platelets. This study highlights a key role of nacre-like structure design in promoting the enhanced hypervelocity impact resistance of steel-concrete composites.

Ferrobobfergusonite, □Na2Fe2+5Fe3+Al(PO4)6, a New Mineral of the Bobfergusonite Group from the Victory Mine, Custer County, South Dakota, USA

ABSTRACT A new mineral species, ferrobobfergusonite, ideally □Na2Fe2+5Fe3+Al(PO4)6, has been found in the Victory Mine, Custer County, South Dakota, USA. It is massive and associated with ferrowyllieite, schorl, fillowite, arrojadite, quartz, and muscovite. Broken pieces of ferrobobfergusonite are blocky or tabular with single crystals up to 0.9 × 0.7 × 0.4 mm. No twinning or parting is observed macroscopically. The mineral is deep green-brown and transparent with a pale green-yellow streak and vitreous luster. It is brittle and has a Mohs hardness of ∼5, with perfect cleavage on {010}. The measured and calculated densities are 3.68(1) and 3.69 g/cm3, respectively. Optically, ferrobobfergusonite is biaxial (+), with α = 1.698 (2), β = 1.705 (2), γ = 1.727 (2) (white light), 2V (meas.) = 65(2)°, 2V (calc.) = 60°, with orientation of the optic axes α ∧ X = 16°, β = Y, with X = yellowish brown, Y = brown, and Z = deep brown. The dispersion is very strong with r > v. The calculated compatibility index based on the empirical formula is 0.017 (superior). An electron microprobe analysis yielded an empirical formula (based on 24 O apfu) of (Na1.72□1.28)Σ3.00(Fe2+3.50Mn0.89Mg0.44Ca0.13)Σ4.96(Fe3+0.77Al0.23)Σ1.00Al(PO4)6. Ferrobobfergusonite is isostructural with bobfergusonite, a member of the alluaudite supergroup. It is monoclinic, with space group P21/n and unit-cell parameters a = 12.7156(3), b = 12.3808(3), c = 10.9347(3) Å, β = 97.3320(10)°, and V = 1707.37(7) Å3. The crystal structure of ferrobobfergusonite contains six octahedral M (= Fe2+, Mg, Mn2+, Al, Fe3+) sites and five X (= Na, Mn2+, Ca) sites with coordination numbers between 6 and 8. The six MO6 octahedra share edges to form two types of kinked chains extending along [101], with one consisting of M1–M4–M5 linkages and the other of M2–M3–M6 linkages. These chains are joined by PO4 tetrahedra to form sheets parallel to (010), which are linked together through corner-sharing between PO4 tetrahedra and MO6 octahedra in the adjacent sheets, leaving open channels parallel to a, where the large X cations are situated. The M cations are strongly ordered over the six sites, with M1, M2, M3, and M4 being dominantly occupied by Fe2+, and M5 and M6 by Fe3+ and Al, respectively. Among the five X sites, the X1 site is filled with Mn2+ and Ca, whereas the X2–X5 sites are partially occupied by Na.

Allantoin and Natrosulfatourea, Two New Bat-Guano Minerals from the Rowley Mine, Maricopa County, Arizona, USA

ABSTRACT The new minerals allantoin (IMA2020–004a), C4H6N4O3, and natrosulfatourea (IMA2019–134), Na2(SO4)[CO(NH2)2], were found in the Rowley mine, Maricopa County, Arizona, USA, where they occur together in bat guano in association with aphthitalite and urea. Allantoin properties: colorless, transparent, untwinned blades to 0.3 mm; white streak; vitreous luster; brittle; Mohs hardness 1½; conchoidal fracture; good {100} cleavage; 1.72(2) g/cm3 density; biaxial (+) with α = 1.558(2), β = 1.593(2), γ = 1.715(3); 2V = 60(1)°; slight r > v dispersion; optical orientation: Y = b, Z ^ a = 30° in obtuse β. Natrosulfatourea properties: colorless, transparent, untwinned prisms to 0.3 mm; white streak; vitreous luster; brittle; Mohs hardness 1½; irregular fracture; perfect {100} cleavage; 1.97(2) g/cm3 density; biaxial (+) with α = 1.456(2), β = 1.464(5), γ = 1.524(2); 2V = 42(1)°; no dispersion; optical orientation: X = a, Y = c, Z = b. Quantitative chemical analyses could not be obtained for allantoin. Electron microprobe analyses provided the empirical formula Na2.02(S0.98O4)[CO(NH2)2] for natrosulfatourea. Allantoin is monoclinic, P21/c, a = 8.0304(9), b = 5.1596(5), c = 14.8011(18) Å, β = 93.017(7)°, V = 612.41(11) Å3, and Z = 4. Natrosufatourea is orthorhombic, Pbcn, a = 5.5918(4), b = 18.1814(14), c = 6.7179(5) Å, V = 682.98(9) Å3, and Z = 4. The crystal structure of allantoin (R1 = 0.0432 for 1073 I > 2σI) is the same as that reported for the equivalent organic compound. In the structure of natrosulfatourea (R1 = 0.0413 for 785 I > 2σI) NaO6 polyhedra and SO4 tetrahedra form polyhedral layers. The O atom of the CO(NH2)2 (urea) group ligates to two Na atoms and projects into the space between polyhedral layers, linking adjacent layers through hydrogen bonds.

Liudongshengite, Zn4Cr2(OH)12(CO3)·3H2O, a new mineral of the hydrotalcite supergroup, from the 79 mine, Gila County, Arizona, USA

ABSTRACT A new mineral species, liudongshengite, ideally Zn4Cr2(OH)12(CO3)·3H2O, has been found in the 79 mine, Gila County, Arizona, USA. It occurs as micaceous aggregates or hexagonal platy crystals (up to 0.10 × 0.10 × 0.01 mm). The mineral is pinkish and transparent with white streak and vitreous luster. It is brittle and has a Mohs hardness of ∼1.5, with perfect cleavage on (001). No twinning or parting is observed macroscopically. The measured and calculated densities are 2.95 (3) and 3.00 g/cm3, respectively. Optically, liudongshengite is uniaxial (−), with ω = 1.720 (8), ε = 1.660 (7) (white light). An electron microprobe analysis, combined with the carbon content measured using an elemental combustion system equipped with mass spectrometry, yielded the empirical formula (Zn3.25Mg0.17Cr2.58)Σ6.00(OH)12(CO3)1.29·3H2O, based on (M2+ + M3+) = 6 apfu, where M2+ and M3+ are divalent and trivalent cations, respectively. Liudongshengite belongs to the quintinite group within the hydrotalcite supergroup and is the Cr-analogue of zaccagnaite-3R, Zn4Al2(OH)12(CO3)·3H2O. It is trigonal, with space group Rm and unit-cell parameters a = 3.1111(4), c = 22.682(3) Å, and V = 190.12(4) Å3. The crystal structure of liudongshengite is composed of positively charged brucite-like layers, [M2+1–xM3+x(OH)2]x+, alternating with negatively charged layers of (CO3)2–·3H2O. Compared to other minerals in the quintinite group, liudongshengite is remarkably enriched in M3+, with an M2+:M3+ ratio of 1.33:1. Like zaccagnaite-3R and many other hydrotalcite-type minerals, liudongshengite may also possess polytypes, as a series of synthetic hydrotalcite-type compounds with a general chemical formula [Zn4Cr2(OH)12]X2·4H2O, where X = Cl–, NO3–, or ½ SO42–, but with unit-cell parameters different from those for liudongshengite, have been reported previously.

Ferro-fluoro-edenite, a new amphibole endmember from Vulcano Island (Sicily, Italy)

ABSTRACT Ferro-fluoro-edenite, ideally NaCa2Fe2+5(Si7Al)O22F2, was found as prismatic crystals up to 1.00 mm inside cavities in ejecta of the 1873 eruption at La Fossa crater, Vulcano Island, Aeolian Archipelago, Sicily, Italy. It is associated with quartz, magnetite, and vonsenite. Crystals are dark brown to black, transparent or semitransparent with vitreous luster, and non fluorescent. The Mohs hardness is 5–6. Cleavage is fair on {110} and fracture is uneven. Density (calc.) is 3.358 g cm–3 using the empirical formula and single-crystal cell data. The mineral is biaxial negative, α = 1.629(2), β = 1.659(2), γ = 1.667(2), 2V (calc.) = –53.8°, Y = b. Dispersion is weak to very weak, r < v, pleochroism not visible. Ferro-fluoro-edenite is monoclinic, space group C2/m, a = 9.9132(10), b = 18.1736(19), c = 5.2943(6) Å, β = 104.85(1)°, V = 922.0(2) Å3, Z = 2. The strongest X-ray diffraction peaks in the powder pattern are [d(I, hkl)]: 8.54(100, 1 1 0), 4.506(16, 0 4 0), 3.154(52, 3 1 0), 2.833(43, 3 3 0), 2.057(14, 2 0 2), 1.910(12, 5 1 0), 1.662(15, 4 6 1). The FTIR spectrum shows a broad band at about 950 cm–1 and no bands in the OH stretching region. The structure refinement led to a final R = 0.0210 for 1444 observed reflections with I > 2σ(I) and allowed cation site assignment and ordering. Microprobe analysis gave the following empirical formula calculated on the basis of 24 (O + F + Cl) apfu: (Na0.69K0.23□0.08)(Ca1.69Mg0.16Mn0.10Na0.05)Σ2(Fe2+2.86Mg2.04Ti0.10)Σ5(Si6.93Al1.05Ti0.02)Σ8O22(F1.89Cl0.09OH0.02)Σ2.

Mineral Identification Based on Deep Learning That Combines Image and Mohs Hardness

Mineral identification is an important part of geological analysis. Traditional identification methods rely on either the experience of the appraisers or the various measuring instruments, and the methods are either easily influenced by appraisers’ experience or require too much work. To solve the above problems, there are studies using image recognition and intelligent algorithms to identify minerals. However, current studies cannot identify many minerals, and the accuracy is low. To increase the number of identified minerals and accuracy, we propose a method that uses both mineral photo images and the Mohs hardness in deep neural networks to identify the minerals. The experimental results showed that the method can reach 90.6% top-1 accuracy and 99.6% top-5 accuracy for 36 common minerals. An app based on the model was implemented on smartphones with no need for accessing the internet and communication signals. Tested on 73 real mineral samples, the app achieved top-1 accuracy of 89% when the mineral image and hardness are both used and 71.2% when only the mineral image is used.

Taniajacoite and Strontioruizite, Two New Minerals Isostructural with Ruizite from the N'Chwaning III Mine, Kalahari Manganese Field, South Africa

ABSTRACT Two new mineral species, taniajacoite and strontioruizite, ideally SrCaMn3+2Si4O11(OH)4·2H2O and Sr2Mn3+2Si4O11(OH)4·2H2O, respectively, have been identified from the N'Chwaning III mine, Kalahari manganese field, South Africa. Both minerals occur as brown radiating groups or aggregates of acicular or prismatic crystals, with individual crystals up to 0.15 × 0.04 × 0.02 mm for taniajacoite and 1.3 × 0.2 × 0.2 mm for strontioruizite. Minerals associated with taniajacoite include sugilite, aegirine, pectolite, richterite, potassic-ferri-leakeite, and lipuite, whereas those associated with strontioruizite include sugilite, potassic-magnesio-arfvedsonite, and lipuite. Both taniajacoite and strontioruizite are brown in transmitted light, transparent with very light brown streak and vitreous luster. They are brittle and have a Mohs hardness of 5–5.5; cleavage is good on {010} and no parting or twinning is observed macroscopically. The measured and calculated densities are 3.05(2) and 3.09 g/cm3, respectively, for taniajacoite and 3.20(2) and 3.16 g/cm3 for strontioruizite. Optically, both taniajacoite and strontioruizite are biaxial (–), with α = 1.686(2), β = 1.729(2), γ = 1.746(2) (white light), 2V (meas.) = 63.7(5)°, 2V (calc.) = 62.5° for the former and α = 1.692(2), β = 1.734(2), γ = 1.747(2) (white light), 2V (meas.) = 59.1(5)°, 2V (calc.) = 56.6° for the latter. The calculated compatibility index based on the empirical formula is 0.008 for taniajacoite and 0.015 for strontioruizite. An electron microprobe analysis yielded an empirical formula (based on 17 O apfu) of Sr(Ca0.81Sr0.19)Σ1.00(Mn3+1.90Fe3+0.15Al0.01)Σ2.06Si3.96O11(OH)4·2H2O for taniajacoite and (Sr1.61Ca0.42)Σ2.03(Mn3+1.95Fe3+0.05)Σ2.00Si3.98O11(OH)4·2H2O for strontioruizite. Taniajacoite and strontioruizite are isostructural with ruizite. Strontioruizite, like ruizite, is monoclinic with space group C2 and unit-cell parameters a = 9.1575(4), b = 6.2857(4), c = 12.0431(6) Å, β = 91.744(4)°, and V = 692.90(6) Å3, whereas taniajacoite is triclinic, with space group C1 and a = 9.1386(5), b = 6.2566(3), c = 12.0043(6) Å, α = 90.019(4), β = 91.643(4), γ = 89.900(4)°, and V = 686.08(6) Å3. Their structures are characterized by chains of edge-sharing MnO6 octahedra extended along [010], which are linked together by corner-shared SiO4 tetrahedra in four-membered [Si4O11(OH)2] linear clusters, giving rise to a so-called “hetero-polyhedral framework”. The large cations Sr2+ and Ca2+ occupy the seven-coordinated interstices. Unlike monoclinic ruizite and strontioruizite, taniajacoite with Sr:Ca ≈ 1:1 is triclinic, owing to the ordering of Sr2+ and Ca2+ into two crystallographically distinct sites, indicating an incomplete solid solution between Ca and Sr endmembers. The unit-cell volumes for ruizite, taniajacoite, and strontioruizite appear to vary linearly with the Sr/(Ca + Sr) ratio.

Effect of Calcium Carbonate Particle Size on the Scratch Resistance of Rapid Alkyd-Based Wood Coatings

Polymer-based wood coatings are used for aesthetic purposes as well as to protect wood surfaces, especially under external conditions. High-hardness mineral fillers are thought to enhance the resistance of these polymer coatings to wear and scratching. However, recent studies suggest that the relatively low-hardness mineral calcite (CaCO3, Mohs hardness of 3) performs similarly to harder minerals under external conditions. It can replace more expensive hard minerals, thus driving research interest in its use. In this study, CaCO3 powders with different grain sizes were applied to rapid alkyd-based coating formulations, and the effect of CaCO3 particle size on the scratch behavior of the coatings was investigated under identical test conditions. The scratch morphologies, scratch hardness, and roughness values of the scratched surfaces indicated that the surfaces of the rapid alkyd-based wood coatings including finer-grained CaCO3 experienced plastic plowing-type deformation in the form of regular, narrow, and shallow scratches, showing high scratch resistance. Coatings using coarser-grained CaCO3 experienced more extensive plastic deformation of the plowing–tearing type owing to the weaker filler–polymer interface and the breakage of larger coating pieces from the coating surface.

Dioskouriite, CaCu4Cl6(OH)4∙4H2O: A New Mineral Description, Crystal Chemistry and Polytypism

A new mineral, dioskouriite, CaCu4Cl6(OH)4∙4H2O, represented by two polytypes, monoclinic (2M) and orthorhombic (2O), which occur together, was found in moderately hot zones of two active fumaroles, Glavnaya Tenoritovaya and Arsenatnaya, at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. Dioskouriite seems to be a product of the interactions involving high-temperature sublimate minerals, fumarolic gas and atmospheric water vapor at temperatures not higher than 150 °C. It is associated with avdoninite, belloite, chlorothionite, eriochalcite, sylvite, halite, carnallite, mitscherlichite, chrysothallite, sanguite, romanorlovite, feodosiyite, mellizinkalite, flinteite, kainite, gypsum, sellaite and earlier hematite, tenorite and chalcocyanite in Glavnaya Tenoritovaya and with avdoninite and earlier hematite, tenorite, fluorophlogopite, diopside, clinoenstatite, sanidine, halite, aphthitalite-group sulfates, anhydrite, pseudobrookite, powellite and baryte in Arsenatnaya. Dioskouriite forms tabular, lamellar or flattened prismatic, typically sword-like crystals up to 0.01 mm × 0.04 mm × 0.1 mm combined in groups or crusts up to 1 × 2 mm2 in area. The mineral is transparent, bright green with vitreous luster. It is brittle; cleavage is distinct. The Mohs hardness is ca. 3. Dmeas is 2.75(1) and Dcalc is 2.765 for dioskouriite-2O and 2.820 g cm−3 for dioskouriite-2M. Dioskouriite-2O is optically biaxial (+), α = 1.695(4), β = 1.715(8), γ = 1.750(6) and 2Vmeas. = 70(10)°. The Raman spectrum is reported. The chemical composition (wt%, electron microprobe data, H2O calculated by total difference; dioskouriite-2O/dioskouriite-2M) is: K2O 0.03/0.21; MgO 0.08/0.47; CaO 8.99/8.60; CuO 49.24/49.06; Cl 32.53/32.66; H2O(calc.) 16.48/16.38; -O=Cl −7.35/−7.38; total 100/100. The empirical formulae based on 14 O + Cl apfu are: dioskouriite-2O: Ca1.04(Cu4.02Mg0.01)Σ4.03[Cl5.96(OH)3.90O0.14]Σ10∙4H2O; dioskouriite-2M: (Ca1.00K0.03)Σ4.03(Cu4.01Mg0.08)Σ4.09[Cl5.99(OH)3.83O0.18]Σ10∙4H2O. Dioskouriite-2M has the space group P21/c, a = 7.2792(8), b = 10.3000(7), c = 20.758(2) Å, β = 100.238(11)°, V = 1531.6(2) Å3 and Z = 4; dioskouriite-2O: P212121, a = 7.3193(7), b = 10.3710(10), c = 20.560(3) Å, V = 1560.6(3) Å3 and Z = 4. The crystal structure (solved from single-crystal XRD data, R = 0.104 and 0.081 for dioskouriite-2M and -2O, respectively) is unique. The structures of both polytypes are based upon identical BAB layers parallel to (001) and composed from Cu2+-centered polyhedra. The core of each layer is formed by a sheet A of edge-sharing mixed-ligand octahedra centered by Cu(1), Cu(2), Cu(3), Cu(5) and Cu(6) atoms, whereas distorted Cu(4)(OH)2Cl3 tetragonal pyramids are attached to the A sheet on both sides, along with the Ca(OH)2(H2O)4Cl2 eight-cornered polyhedra, which provide the linkage of the two adjacent layers via long Ca−Cl bonds. The Cu(4) and Ca polyhedra form the B sheet. The difference between the 2M and 2O polytypes arises as a result of different stacking of layers along the c axis. The cation array of the layer corresponds to the capped kagomé lattice that is also observed in several other natural Cu hydroxychlorides: atacamite, clinoatacamite, bobkingite and avdoninite. The mineral is named after Dioskouri, the famous inseparable twin brothers of ancient Greek mythology, Castor and Polydeuces, the same in face but different in exercises and achievements; the name is given in allusion to the existence of two polytypes that are indistinguishable in appearance but different in symmetry, unit cell configuration and XRD pattern.