Mineralogy and crystal chemistry of a low grade nickel laterite ore

To acquire understanding of Ni enrichment from laterite ore,the mineralogy and crystal chemistry of a low grade limonite type nickel laterite ore sample assaying 0.97% Ni from Indonesia were studied using optical microscopy,X-ray diffraction（XRD）,scanning electron microscopy（SEM） and electron probe microanalysis（EPMA）.According to EPMA results,the mineral includes 80% goethite（（Fe,Ni,Al）O（OH）） with 0.87% Ni,15% silicate minerals with lizardite（（Mg,Fe,Ni）3Si2O5（OH）） and olivine（（Mg,Fe,Ni）2SiO4）,and 1.19% Ni,and other minor phases,such as hematite,maghemite,chromite and quartz,and no Ni was detected.The mineralogy of the laterite ore indicates that due to the complicated association of the various phases and the variable distribution of Ni,this refractory laterite ore can not be upgraded by traditional physical beneficiation processes.

Insights into the floatability between spodumene and albite from crystal chemistry standpoint

Spodumene is a silicate mineral rich in lithium.However,the gangue mineral,albite has similar crystal chemical structure and composition to spodumene.In this work,the density functional theory(DFT)calculation was taken to research the floatability from the perspective of crystal chemistry.And contact angle test and reagent adsorption test were used to support the simulation results.In addition,the weighted total density of broken bonds is proposed for the first time to judge the generation probability of cleavage surface.The DFT calculation results display that the Na and Al sites on the albite surface are the adsorption sites of water molecules.While the water molecules only bond with Al atom on the surface of spodumene and each Al site can adsorb only one water molecule.Thus,the wetting effect of water molecules on the albite surface is stronger than that of spodumene.This is consistent with the result of contact angle.In sodium oleate system,the oleic acid anion is adsorbed on the spodumene surface in form of a multicomponent ring while the albite is a single ring.Theoretically,oleic acid anion can be strongly adsorbed on the surface of spodumene and albite under vacuum.The adsorption strength of spodumene is higher than that of albite.However,on hydrated surface,the adsorption strength of oleic acid anion on mineral surface is greatly reduced due to the interaction between water molecules and metal site on mineral surface.Thus,spodumene and albite are hard to float without external activated ions in sodium oleate system.

Crystal Chemistry Research of Minerals of Nigerite Group and Its Significance

There is a type of complex oxide mineral, composed of many elements such as Sn, Mg, Fe, Zn, Ti, Mn, Al, etc., in the areas of Anhua, Linwu and Shizhuyuan of Hunan Province. These minerals belong to nigerite, Mg-nigerite (pengzhizhongite), etc.. According to the principle of closest packing, the crystal chemical properties of nigerite (brown), pengzhizhongite (buff), Zn-nigerite (fawn), Fe-nigerite, Mn-nigerite (greenish-black) etc. have been analyzed. Their crystal structures may be characterized by O (the layers of cation octahedral coordinations), T_1 (the mixed layers of cation octahedral coordinations and cation tetrahedral coordinations in same directions), T_2 (the mixed layers of cation octahedral coordinations and cation tetrahedral coordination in different directions). The position of layer-O and layer-T is alternate permutation. The crystal structure of pengzhizhongite (6 H ) may be expressed by …OT_2OT_1OT_1…, taaffeite (8 H ), …OT_2OT_1OT_2OT_1…, and nigerite (24 R ), … OT_1OT_2 OT_2OT_1 …×3 etc.. In their structure, there are not only the crystal structure units of spinel … OT_2 OT_2 … but also the units of nolanite … OT_1 OT_1 …. The research of these minerals has important theoretic and practical significance in the fields of minerals, gemology, material science etc..

Crystal chemistry and structural design of iron-based superconductors

The second class of high-temperature superconductors （HTSCs）, iron-based pnictides and chalcogenides, necessarily contain Fe2X2 （＂X＂ refers to a pnictogen or a chalcogen element） layers, just like the first class of HTSCs which possess the essential CuO2 sheets. So far, dozens of iron-based HTSCs, classified into nine groups, have been discovered. In this article, the crystal-chemistry aspects of the known iron-based superconductors are reviewed and summarized by employing ＂hard and soft acids and bases （HSAB）＂ concept. Based on these understandings, we propose an alternative route to exploring new iron-based superconductors via rational structural design.

The crystal chemistry and the compressibility of silicate-carbonate minerals:Spurrite,galuskinite and tilleyite

Spurrite Ca5（SiO4）2（CO3）,galuskinite Ca7（SiO4）3（CO3） and tilleyite Ca5（Si2O7）（CO3）2are three representative minerals formed in high-temperature skarns in the silicate-carbonate system.Their crystal chemistry and compressibility have been investigated using first-principles theoretical simulation.These minerals are structurally described as the combination of interwoven layers constituted by Ca polyhedra and Si polyhedra,with the[CO3]triangles being 'separators' to depolymerize the Si-Ca aggregations.With the effect of pressure,the Si polyhedra and the[CO3]groups present rigid behaviors whereas the Ca-0 bonds undergo considerable compression.Several pressure-induced abnormities in the lattice parameter variations have been identified,revealing the existence of subtle changes in the compression process.Isothermal equations of state parameters are obtained:K0= 71.1（1） GPa,V0= 1003.31（4） A3and K0′ = 5.4（1）for spurrite;K0= 75.0（1） GPa.V0= 1360.30（7） A3,K0’ = 5.4（1） for galuskinite,and K0= 69.7（3） GPa,V0= 1168.90（2） A3and K0’ = 4.0（1） for tilleyite.These compounds have similar K0values to calcite CaCO3but are much more compressible than larnite β-Ca2SiO4.Generally for these minerals,the bulk modulus exhibits a negative correlation with the[CO3]proportion.The structural and compressional properties of silicate-carbonate minerals compared with silicates and carbonates are expected to be a guide for further investigations on Si polyhedra and[CO3]coexistent phases.

Comparative Crystal Chemistry of Rare Earth Minerals

Polyhedral analysis is used to study the geometrical limits of the crystal structure on isomorphic substitution of rare earths.The rare earth sites in the structure may be distinguished into six groups on the basis of mean ionic radii of the substituting cations in each rare earth site:Y,Y+Ca,REE,REE+Ca,Ce+Ca,Ce.The calcula- tion of volumes of 70 rare earth polyhedra indicates that the polyhedral volumes of the heavy rare earth are in a range of 13×10^(-3)～28×10^(-3) nm^3,the volumes of light rare earth polyhedra are in 20×10^(-3)～40×10^(-3) nm^3, and the polyhedral sizes suitable to isomorphic substitution of all REE are about 21×10^(-3)～29×10^(-3) nm^3.The size of REE polyhedra depends on mean ionic radii in REE sites,coordination number and linkage of polyhedra. In structures where exist two kinds of polyhedra,with the change of composition in REE site,both REE polyhedron and anion group polyhedron tend to be more distorted,leading to the change of structural symmetry. The contrary distortion tendencies of both polyhedra favours the stability of the structure.The phenomena may be interpreted by the potential energy distribution or the potential energy compensating mechanism of the crystal.

Compositional Variations and Its Implications of a Bastnaesite Crystal,Mianning County,Sichuan Province

A bastnaesite crystal about 12×20 mm 2 in size collected from a pegmatitic aegirine augite barite bastnaesite vein of the Maoniuping rare earth deposit, Mianning County, Sichuan Province, has been analyzed for La, Ce, Pr and Nd by synchronous radiative X ray fluorescence(SRXRF) technics at the National BEPC Laboratory. The results show an apparent compositional variation along vertical and horizontal sections accross the crystal which may be divided into three compositional zones(A, B and C). Significant difference exists between the inner portion(zone A), averaging at 28 35% La 2O 3, 35 04% CeO 2, 2 01% Pr 6O 11 and 5 44% Nd 2O 3, and the outer portion(zone B), averaging at 32 81% La 2O 3, 42 26% CeO 2 3 30% Pr 6O 11 and 7 08%. Nd 2O 3, of the crystal. Only one analysis is available on the egde of the crystal(zone C) yielding 14 50% La 2O 3, 21 41% CeO 2, 4 19% Pr 6O 11 and 16 71% Nd 2O 3, which demonstrates probably fractionations between LREE and HREE. The La/Ce ratio, however, is nearly constant around 0 84±0 08 among the three zones, while the La/Pr and La/Nd ratios erratically fluctuate due to low and variable contents of Pr and Nd. These results indicate that the REE bearing hydrothermal system underwent a significant compositional change during the stepwise growth of the bastnaesite crystal.

One-pot Synthesis,Characterization and Crystal Structure Determination of Novel 1,4,5-Trisubstituted 1,2,3-Triazole with Two Conformational Isomers:1-Benzyl-5-((4-methoxyphenyl)ethynyl)-4-phenyl-1H-1,2,3-triazole

The title compound l-benzyl-5-（（4-methoxyphenyl）ethynyl）-4-phenyl-1H-1,2,3-triazole（C24H19N3O） was designed and synthesized using one-pot strategy and structural characterization was done by single-crystal X-ray diffraction,NMR,IR and MS.This compound was crystallized out from an ethanolic solution in triclinic system,space group P1 with a =9.9038（9）,b = 10.2928（9）,c = 18.8715（19）A°,α = 103.541（6）,β = 90.507（7）,γ = 97.157（7）°,V =1854.2（3） A°3,Z = 4,crystal size（mm） = 0.25 × 0.1 × 0.1 and R（int） = 0.068.Its asymmetric unit contains two independent molecules.The crystal structure of the title compound is stabilized by intramolecular interactions of types C-H…N and C-H…O.Additionally,X-ray analysis reveals obvious C-H…π,π-π stacking interactions between two adjacent aromatic ring planes.

Preparation and Composition-Structure-Thermal Stability Relation of a Novel Open-framework Vanadium Phosphate(H_3NCH_2CH_2NH_3)_3[(VO)_4(PO_4)_2(HPO_4)_4]

A novel open-framework vanadium(W) phosphate(H_3NCH_2CH_2NH_3)_3[(VO)_4(PP_4)_2(HPO_4)_4] (short for V_2P_3-en) has been prepared. It issynthesized hydrothermally in the presence of ethylenediamine (en) at 170 deg C for 5 days byself-assembly from structurally simple precursors V_2O_5, H_3PO_4 and H_2O. The compound ischaracterized by means of Fourier transform-infrared spectroscopy (FT-IR),Thermogravimetry-differential thermal analysis (TG-DTA), X-ray powder diffraction analysis (XRD) andScanning electron microscopy (SEM). Furthermore, the composition-structure-thermal stabilityrelation of V_2P_3-en is explored in terms of crystal chemistry, and the potential approach to theenhancement of its thermal stability is proposed.

Recent progress,mechanisms,and perspectives for crystal and interface chemistry applying to the Zn metal anodes in aqueous zinc-ion batteries

The need for large-scale electrochemical energy storage devices in the future has spawned several new breeds of batteries in which aqueous zinc ion batteries(AZIBs)have attracted great attention due to their high safety,low cost,and excellent electrochemical performance.In the current research,the dendrite and corrosion caused by aqueous electrolytes are the main problems being studied.However,the research on the zinc metal anode is still in its infancy.We think it really needs to provide clear guidelines about how to reasonably configure the system of AZIBs to realize high-energy density and long cycle life.Therefore,it is worth analyzing the works on the zinc anode,and several strategies are proposed to improve the stability and cycle life of the battery in recent years.Based on the crystal chemistry and interface chemistry,this review reveals the key factors and essential causes that inhibit dendrite growth and side reactions and puts forward the potential prospects for future work in this direction.It is foreseeable that guiding the construction of AZIBs with high-energy density and long cycle life in various systems would be quite possible by following this overview as a roadmap.

Modified RNA with a Phosphate-Methylated Backbone. A Serious Omission in Our (Retracted) Study at HIV-1 RNA Loops and Integrated DNA. Specific Properties of the (Modified) RNA and DNA Dimers

After the recent publication in the Journal of Biophysical Chemistry entitled “Retracted HIV Study Provides New Information about the Status of the in Vitro Inhibition of DNA Replication by Back-bone Methylation”, it is of importance to review the results of Buck’s group on the synthesis and conformation analyses of phosphate-methylated RNAs in order to afford information on the absence of a further investigation with regard to this de facto acceptable approach. In fact these compounds belong to the very first group of RNAs with a modified neutral backbone by phosphatemethylation. In contrast to the corresponding phosphate-methylated DNAs with a frozen B-conformation, the phosphate-methylated RNAs show an A-conformation. The latter is a prerequisite for duplex formation with (complementary) (natural) RNA. A number of experiments support this fundamental statement. After the HIV study was retracted, the overall results concerning the phosphate-methylated RNAs were published without mentioning Buck’s initial proof of concept and his contributions. Generally, the (modified) dimer RNAs and DNAs possess a number of specific biophysical properties. A novel explanation is given for conflicting structural determinations.

Crystal structure guided machine learning for the discovery and design of intrinsically hard materials

In this work,a machine learning(ML)model was created to predict intrinsic hardness of various compounds using their crystal chemistry.For this purpose,an initial dataset,containing the hardness values of 270 compounds and counterpart applied loads,was employed in the learning process.Based on various features generated using crystal information,an ML model,with a high accuracy(R^(2)=0.942),was built using extreme gradient boosting(XGB)algorithm.Experimental validations conducted by hardness measurements of various compounds,including MSi_(2)(M=Nb,Ce,V,and Ta),Al_(2)O_(3),and FeB_(4),showed that the XGB model was able to reproduce load-dependent hardness behaviors of these compounds.In addition,this model was also used to predict the behavior based on prototype crystal structures that are randomly substituted with elements.

Pseudorotaxane Ligand-Induced Formation of Copper(I)lodide Cluster Based Assembly Materials:From Zero to Three Dimensional

Comprehensive Summary In this work,we have successfully obtained a series of novel copper(I)–iodide clusters(CuI NCs)based assembly materials by combining supramolecular pseudorotaxane ligands{[Mebpe^(+)]PF_(6)^(–)@CB[6](CB[6]=cucurbit[6]uril),L’·PF_(6)}and linkers{BPHF@CB[6],[BPHF=C_(14)H_(20)N_(4)(PF_(6))_(2)],L·PF_(6)},including discrete cluster CuI 1 and extended cluster organic frameworks MORF 1 and MORF 2.CuI 1 can be described as a dumbbell-shaped molecule with its body-centered site and two vertexes respectively occupied by one[Cu_(5)I_(6)]^(–)cluster and two CB[6]held together by two L’·PF_(6) ligands.The crystal structures of MORF 1 and MORF 2 are 1D anionic chain and four-fold interpenetrated 3D cationic diamondoid structure,respectively,which all featured intriguing alternating CB[6]and CuI NCs.