Preparation and characterization of CaO-MgO-SiO2 ceramics from silver mine tailings

Silver mine tailings are generated during the exploitation and extraction of silver. Immense amounts of silver mine tailings accumulated in the tailing ponds or backfilled in the mine have resulted in serious dust pollution and heavy metal pollution etc. In this study, ceramics were prepared by using the measure of one step sintering with the mixtures of silver mine tailings, talc and wollastonite, and the impact of silver mine tailings and wollastonite contents on the structure and properties of ceramics were investigated. Moreover, the phase, structure and morphology of ceramics were characterized by methods of XRD, FTIR and SEM. In addition, the apparent porosity, water absorption, volume density, flexural strength and coefficient of thermal expansion of ceramics were tested. The experimental results showed that the optimum performances of ceramics occurred when sintered at 1 200℃ and with raw material consisting of 50 wt% of silver mine tailings, 20 wt% of wollastonite and 30 wt% of talc. The ceramics exhibited excellent properties, with flexural strength of 77.78±8.78 MPa, apparent porosity of(0.4±0.06)%, water absorption of(0.21±0.05)% and a bulk density of 1.93±0.02 g/cm^3. A simple, efficient and economical preparation method of ceramics is presented in this article, which is an effective approach to value-added utilization of silver mine tailings.

U-Pb dating of monazite in the Bainiuchang silver polymetallic deposit,Yunnan Province,and its limitation on Mesozoic mineralization

1.Objective The Gejiu-Bozhushan-Laojunshan tin-tungsten polymetallic metallogenic belt is located in southeastern Yunnan.It is bounded by the Mile-Shizong Fault and the Yangzi Plate to the north and west,respectively,while the Honghe Fault represents its southwestern boundary.It is adjacent to the Ailaoshan Fault,and extends to Guangxi and Vietnam to the southeast(Fig.1a;Liu JP et al.,2021).

A Large Silver Mine Discovered in Henan

Henan,which boasts China’s largest silver mine and second largest gold mine,recently found a large silver mine in the southern part of Xiaoqinling,with an estimated 1,027 tons of silver.The silver mine,located in the south of Xiaoqinling,Henan Province。

Preparation and Characterization of Poly(melamine-urea-formaldehyde) Tetradecanol Microcapsules Coated with Silver Particles

A novel type of microencapsulated phase change materials(microPCMs)based on 1-tetradecanol(TD)core and silver-coated poly(melamine-urea-formaldehyde)(MUF)shell was successfully synthesized by in situ polymerization method followed by silver reduction.Fourier-transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),scanning electron microscopy with energy dispersive X-ray spectrometry(SEM/EDS),thermogravimetric analysis(TGA)and differential scanning calorimetry(DSC)were used to characterize the chemical structure,morphology and thermal properties of the as-prepared silver-coated microPCMs.FTIR analysis confirmed the successful encapsulation of TD with MUF wall materials.The SEM and EDS results indicated that the prepared silver-coated MUF microPCMs exhibited uniform spherical shape with a perfect silver outer layer.From XRD analysis,the Ag metal dispersed on the surface of microcapsules presented the form of elementary substance.The deposition weight of silver particles on the microcapsule surface increased with increasing the amount of silver nitrate,as indicated by EDS tests.The DSC results indicated that the melting temperature and the melting latent heat of microPCMs modified with 0.7g of silver nitrate in 150mL aqueous solution were 39.2°C and 126.6J·g^-1,respectively.Supercooling of the microPCMs coated with silver particles was effectively suppressed,compared with that of microPCMs without Ag.Thus,the encapsulation of TD with silver-coated MUF shell developed by this work can be an effective method to prepare the microPCMs with enhanced thermal transfer performance and phase change properties.

Luminescence intensification of lanthanide complexes by silver nanoparticles incorporated in sol-gel matrix

We present how the luminescence of europium RR-2-P-oxides complexes can be increased by interaction of electronic levels of the complex with the radiation field of silver nanoparticles （NPs）. The procedure by which silver NPs are formed in a sol-gel polyurethane matrix precursor was elaborated. The formed Ag NPs were combined with Eu complex incorporated in ormocer matrix. The emission spectra of the complexes without silver NPs were compared with spectra of the same complexes with addition of silver NPs. As the result of the interaction of the electronic levels of lanthaaide ligands with silver plasmons, dramatic increase of luminescence was observed.

Structure and Luminescence Property of a Hexanuclear Silver(Ⅰ) Cluster Containing Benzaldehyde Thiosemicarbazone

A new hexanuclear silver （I） compound 2 containing thiosemicarbazone with the group of benzene was synthesized and structurally characterized by single-crystal X-ray diffraction, elemental analysis and fluorescence spectrum. The title compound crystallizes in triclinic, space group P with a = 11.611（3）, b = 15.610（5）, c = 15.624（7） , α = 113.942（6）, β = 104.520（6）, γ = 104.230（4）°, V = 2304.1（14） 3, C60H77Ag6N22O4.5S6, Mr = 2018.02, Dc = 1.454 g/cm3, μ（MoKα） = 1.435 mm-1, F（000） = 1005, Z = 1, the final R = 0.0468 and wR = 0.1474 for 6608 observed reflections （I 2σ（I））. In the structure, the S atom of the ligand L2 （L2 = benzaldehyde thiosemicarbazone） served as a triply bridged chelator to connect the six silver atoms into a Ag6L26 cluster. The luminescence property of compound 2 was investigated at room temperature.

Structure and Luminescence Property of a Hexanuclear Thiosemicarbazone Silver(I) Cluster

A new hexanuclear silver（I） compound containing thiosemicarbazones with groups of 1-naphthalene was synthesized and structurally characterized by single-crystal X-ray diffraction, elemental analysis and fluorescence spectrum. The title compound crystallizes in monoclinic, space group P21/c with a = 16.101（4）, b = 24.855（7）, c = 14.492（4） A, β = 109.730（5）, V = 5459（3） A3, C90H102Ag6N2406S6, Mr= 2455.54, Dc= 1.494 g/cm3,μ（MoKa） = 1.228 mm^-1, F（000） = 2472, Z = 2, the final R = 0.0761 and wR = 0.1507 for 5258 observed reflections （I〉 2α（I））. In the structure, the S atom of ligand L serves as a triply bridged chelator to connect the six silver atoms into a Ag6L6 cluster. Luminescence investigation reveals that the compound exhibits two ligand-independent cluster-centered electron transfer bands and one ligand-dependent charge transfer band.

Structure and Luminescent Property of a Tetrahedral Silver(Ⅰ) Cluster Complex Based on Phosphor and Sulphur Mixed-ligand System

A tetrahedral silver(I) cluster complex {Ag4[HC(PPh2)3](S2PPh2)3}ClO4(1,HC(PPh2)3 = 1,1,1-tris(triphenylphosphino)methane, S2PPh2 = diphenyldithiophosphinate) was synthesized by assembling silver ion with phosphor and sulphur mixed-ligand system. The complex was characterized by single-crystal X-ray crystallography, high-resolution mass spectroscopy and thermal analysis. In the crystal structure, an inverted tetrahedron was constructed from Ag4 metal skeleton. The Ag4 cage was stabilized by three diphenyldithiophosphinate ligands and one 1,1,1-tris(triphenylphosphino)methane ligand. 1 exhibits luminescent properties in solid state. A bright yellow-green emission centered at 533 nm has been observed in solid state. Large Stokes' shifts with long range of emissive lifetime indicate that the emission likely originates from a triplet state parentage.

Synthesis, Crystal Structure and Photoluminescent Property of a Novel Silver(I) Compound {[Ag(bpp)]_2(Hphth)(NO_3)·(H_2O)_2}_n

Self-assembly of Ag（I） nitrate, 1,3-bis（4-pyridyl）propane （bpp） and phthalic acid monopotassium salt （KHphth） in CH3OH-H2O solution produced the title complex, {[Ag（bpp）]2（Hphth）（NO3）-（H2O）2}n, which was characterized by single-crystal X-ray diffraction, elemental analysis, IR spectrum, and photoluminescent spectrum. Single-crystal X-ray analysis revealed that the complex crystallizes in a monoclinic system, space group P2dc, with a = 15.4174（5）, b = 8.6398（2）, c = 25.2466（8）A, β = 91.072（1）^o, V = 3362.34（17）A3, Z = 4, C34H37N5O9Ag2, Mr = 875.43, De = 1.729 g/cm^3, u = 1.228 mm^-1, F（000） = 1768, the final R = 0.0749 and wR = 0.1580 for 5754 reflections with I 〉 2o（I）. The Ag atom is coordinated by two N atoms from two bpp molecules in an approximately linear geometry. The Ag（I） ions are linked by the bpp molecules to form one-dimensional zigzag chains propagating along the c axis. The Hphth- and nitrate counter-ions are bridged by solvent water molecules through hydrogen bonds to generate a one-dimensional chain extending along the b axis. Electrostatic interactions between cations and anions, extensive hydrogen bonds and re-re interactions are responsible for the three-dimensional supramolecular structure. In the solid state, the compound exhibits blue photoluminescence with the maximum at 436 nm upon excitation at 344 nm.

Synthesis,Crystal Structure and Luminescence of a Novel One-dimensional Silver(Ⅰ)Sulfonate Complex with Pyrazine Ligand

The title complex,[Ag 2 （L1） 2 （Pyr）·2.5H 2 O] 1 （L1=6-amino-1-naphthalenesulfonate anion,Pyr=pyrazine）,has been synthesized and characterized by single-crystal X-ray diffraction analysis.It crystallizes in triclinic,space group P1,with a=7.339（5）,b=13.105（5）,c=14.097（5）,α=84.377（5）,β=76.921（5）,γ=79.628（5）°,V=1296.7（11） 3,C 48 H 50 Ag 4 N 8 O 17 S 4,M r=1570.68,Z=1,D c=2.011 g/cm 3,μ=1.732 mm-1,F（000）=782,S=1.148,the final R=0.0436 and wR=0.1181 for 4130 observer reflections （I 2σ（Ⅰ））.Compound 1 shows a rare one-dimensional （1D） double chain,and the chains are further connected through secondary bonding,hydrogen bonds,and π-π interactions to generate a three-dimensional （3D） supramolecular structure.The luminescent property of 1 was also studied in the solid state at room temperture.

A Silver Complex of 6,7-Dicyanodipyridoquinoxaline:π-Stacking Interactions and Luminescence

The reaction of 6,7-dicyanodipyridoquinoxaline （DICNQ） with AgNO3 in a 1：1 molar ratio by solution method gave a new complex [Ag（DICNQ）2]NO3 1. Single-crystal X-ray diffraction analysis reveals that the complex crystallizes in the space group Ibca of orthorhombic system with eight formula units in a cell. Crystal data for 1： a = 15.7055（17）, b = 18.411（2）, c = 20.680（2）A, V = 5979.7（11）A3, Z = 8, C32Hl2AgN13O3, Mr = 734.42, Dc = 1.632 g/cm3, μ= 0.734 mm-1, F（000） = 2928, S = 1.023 and T= 293（2） K. The final R = 0.0659 and wR = 0.1927 for 2118 observed reflections with I 〉 2σ（I）, and R = 0.0801 and wR = 0.2196 for all data. The complex builds up a packing structure by π-π stacking interactions and shows a luminescent feature.

Mineralogical Characterization of a Polymetallic Sulfide Ore to Improve Silver Recovery

Based on the mineralogical characterization for the polymetallic sulfide ore, the way to improve silver recovery was studied. The results showed that silver was the most valuable metal whose grade was 448.82 g/t Ag, while 0.118% Cu, 1.65% Pb and 1.06% Zn may be comprehensively utilizated. The main silver-bearing minerals were argent and aregentite which accounted for 87.18% of total silver. Argentite and other metal minerals were distributed in the gangue minerals in complex forms. Argentite grains of 33.76% minus 50 μm indicated that a fine grinding scheme was necessary to enhance the degree of dissociation, and meanwhile selective grinding must be considered to prevent a complete grinding of coarse grains. The optimum regrinding fineness in the Cu flotation was determined as 73% minus 37 μm, while grains of 68.5% minus 74 μm in one-stage grinding remained unchanged as much as possible. Consequently, silver recovery increased to 2.68%, as well as the content of Pb simultaneously decreased from 7.26% to 2.68% in the Cu concentrate. From the lead pyrometallurgical point of view, recovering larger amounts of silver and lead at the expense of decreasing the grade of lead to a suitable level is not only economically viable for the plant, but also convenient for subsequent processing. Silver and lead recovery increased to 13.18% and 12.58%, respectively, while the Pb grade decreased from 53.1% to 46.12% for the Pb concentrate.

Impact Analysis of Microscopic Defect Types on the Macroscopic Crack Propagation in Sintered Silver Nanoparticles

Sintered silver nanoparticles(AgNPs)arewidely used in high-power electronics due to their exceptional properties.However,the material reliability is significantly affected by various microscopic defects.In this work,the three primary micro-defect types at potential stress concentrations in sintered AgNPs are identified,categorized,and quantified.Molecular dynamics(MD)simulations are employed to observe the failure evolution of different microscopic defects.The dominant mechanisms responsible for this evolution are dislocation nucleation and dislocation motion.At the same time,this paper clarifies the quantitative relationship between the tensile strain amount and the failure mechanism transitions of the three defect types by defining key strain points.The impact of defect types on the failure process is also discussed.Furthermore,traction-separation curves extracted from microscopic defect evolutions serve as a bridge to connect the macro-scale model.The validity of the crack propagation model is confirmed through tensile tests.Finally,we thoroughly analyze how micro-defect types influence macro-crack propagation and attempt to find supporting evidence from the MD model.Our findings provide a multi-perspective reference for the reliability analysis of sintered AgNPs.

Silver-catalyzed three-component reaction of phenyldiazoacetate with arylamine and imine

A new method was developed to diastereoselectively synthesize polysubstituted 1,2‐diamine compounds from the reaction of diazoesters with arylamines and diaryl imines by using the dioxazoline ligand L2‐ligated silver catalyst.The Lewis acidity of the silver catalyst affected the different types of substrate diastereoselectivities;It also led to the formation of amine‐exchange side products.

Coordination Triangular Prism of Bisilver Complex with Triply-bridged of Bis(diphenylphosphino)amine

The binuclear complex [Ag2(m-Ph2PNHPPh2)3](ClO4)2CH2Cl2CH3OH (Ph2PNHP- Ph2 = bis(diphenylphosphino)amine) was prepared from the reaction of AgClO4 with bis- (diphenylphosphino)amine in equimolar ratio through self-assembly. The coordination cation affords a triply-bridging [Ag2L3]-type coordination moiety. The silver atom is in a trigonal planar environment with P3 coordination chromophore. The complex (C74H69Cl4N3O9P6Ag2) crystallizes in monoclinic, space group Cc with a = 18.3738(1), b = 20.0207(4), c = 20.5422(4) ? b = 95.829(1), V = 7517.5(2) 3, Z = 4, Mr = 1687.68, Dc = 1.491 g/cm3, F(000) = 3432, m = 0.848 mm-1, the final R = 0.0460 and wR = 0.0935 for 7005 observed reflections with I > 2s(I).

MECHANISM OF ELECTROCHEMILUMINESCENCE OF THE NEW REAGENT 6-(2-HYDROXY-DIETHYLAMINOPHENYLAZO)-2, 3-DIHYDRO-1, 4-PHTHALAZINE-1, 4-DIONE CATALYZED BY SILVER (Ⅰ)

The electrochemi luminescence <ecl> of a new reagent 6-<2-hydroxy-4-diethylaminophenylazo>-2, 3-dihydro-1, 4-phthatazine-1, 4-dione <HDEA> in basic aqueous solution was studied. Trace amount of silver showed significant effect on the efficiency of light emission of HDEA during a positive trigonometrical wave pulse was exerted on the electrodes In the present paper, the ecl spectra of HDEA have been measured. λ_(max) is 410 nm. The reaction of HDEA chemiluminescence and the circular voltammetry, ultraviolet-visible spectrometry for the system have been investigated. The possible mechanism of the ecl of HDEA-KCL-KOH-Ag(I) system has been proposed.

A STUDY ON VOLTAMMETRIC BEHAVIOR OF INDIGO CARMINE AND ITS MIXTURE WITH AMARANTH AT MERCURY FILM ELECTRODE ON SILVER SUBSTRATE

The voltammetric behavior of indigo carmine at mercury film electrode on a silver substrate (MFES) was studied in this paper. It was found that indigo carmine gave a sensitive reduction peak at a potential (Vp) of -0.11 V at pH 4.0 in aqueous solution. The MFES gave good reproducibility and life time. The peak currents (ip) depended lipearly on the concentrations of indigo carmine free 0 to 100 ng/ml. The Vp and Ip of indigo carmine at MFES were independent of the concentrations of amaranth at pH 4.0, the Vp of amaranth was -0.24 V at this pH. The differences of Vp between both colorants enabled to distinguish indigo carmine free amaranth.

Determination of Trace Silver( Ⅰ ) in Basic Aqueous Solution by Electrochemiluminescence of a New Reagent 6-(2-Hydroxy-4-Diethylaminophenylazo)-2,3-Dihydro-1,4-Phthalazine-1,4-Dione

The electrochemiluminescence (ECL) of a new reagent 6- (2-hydroxy- 4 diethy laminophenylazo)-2,3-dihydro-1 ,4-phthalazine-1,4-dione (HDEA) in a basic aqueous so lution was studied by using the apparatus designed by ourselves. Trace amounts of silver ( Ⅰ ) shows a significant effect on the efficiency of light emission of HDEA during a positive trigonometrical wave pulse was exerted on the solution. The linear relationship between the light intensity and the concentration of silver( Ⅰ ) occurs in the range of 5. 0×10-8 to 3. 0×10-8 mol/L Ag(Ⅰ ) in a medium of KOH-KCl-HDEA (pH= 12. 8). The detection limit of the method is 2. 0×10-8 mol/LAg( Ⅰ ), and the r. s. d. for 1.0×10-7 mo)/L Ag ( Ⅰ ) is 5%. Of 21 metal ions concerned, only nickel( Ⅱ ), cerium( Ⅳ ) and cobalt( Ⅱ ) interfere the silver detection seriously; Ⅰ and Br also have some interference.

Synthesis and Crystal Structure of a Tetranuclear Silver Complex with Bis(diphenylphosphino) amine-dioxide as a Tridentate Ligand

The tetranuclear complex[Ag4（μ-Ph2PNHPPh2）2（μ-OPh2PNPPh2O）2] （PF6）2·CH3COCH3 containing bis（diphenylphosphino）amine （Ph2PNHPPh2） and deprotonated bis- （diphenylphosphino）amine-dioxide （OPh2PNPPh2O） was isolated and characterized by X-ray crystallography. The deprotonated OPh2PNPPh2O acts as a tridentate ligand in a chelating and bridging mode. Two of the four Ag atoms are in a trigonal planar environment composed of PO2 chromophore, whereas the other two are coordinated with PN donors in a distorted linear arrangement. The title complex （C51H47Ag2F6N2O3P5） crystallizes in triclinic, space group P1^- with a = 12.9552 （2）, b = 14.1691（3）, c = 15.8110（3）A°, α = 68.7500（10）, β= 86.8840（10）, γ = 75.6170（10）°, V= 2618.16 （8） A°^3, Mr= 1220.50, Z = 2, Dc= 1.548 g/cm^3, F（000） = 1228 and μ（MoKα） = 0.965 mm^-1. The final refinements converged at R = 0.0679 and wR = 0.1528 for 7001 observed reflections （I〉 2σ（I））.

Syntheses,Structures,and Luminescent Properties of Zinc(Ⅱ)and Silver(Ⅰ)Complexes Based on 1-(4′-Carboxylatobenzyl)-3-(pyrazin-2-yl)pyrazole

Two novel coordination compounds, [Zn（CBPP）2（H2O）2]·3H2O（1） and[Ag（CBPP）·2H2O]（2）（HCBPP = 1-（4？-carboxylatobenzyl）-3-（pyrazin-2-yl）pyrazole）, were hydrothermally synthesized and characterized. Compound 1 crystallizes in monoclinic, space group C2 with a = 26.221（4）, b = 8.4211（7）, c = 14.295（3）A, β = 114.561（8）°, V = 2705.9（2） A3, Dc = 1.587 g/cm3, C28H28Cl2N8O9 Zn, Mr = 685.97 F（000） = 1416, μ（Mo Kα） = 0.926 mm-1, Z = 4, R = 0.0287, w R = 0.1076 for 2818 observed reflections（I 〉 2σ（I））, and R = 0.0300, w R = 0.1110 for all data. In 1, each deprotonated CBPP-ligand with a bidentate coordination mode connects two Zn（II） atoms to generate a 1D helical chain along the b axis. The adjacent chains intersect with each other through hinged Zn（II） ions to build up an interesting two-dimensional network. Compound 2 crystallizes in monoclinic, space group P21/n with a = 6.3544（1）, b = 11.7195（3）, c = 19.3188（4）A, β = 94.297（2）°, V = 1434.64（5） A3, Dc = 1.894 g/cm3, C14H13 Ag N4O4, Mr = 409.15 F（000） = 816, μ（Mo Kα） = 11.536 mm-1, Z = 4, R = 0.0456 and w R = 0.1184 for 2402 observed reflections（I 〉 2σ（I））, and R = 0.0517, w R = 0.1275 for all data. In 2, each ligand binds two Ag（I） atoms in a tridentate coordination mode to form an infinite zigzag chain. Their thermal and photoluminescent properties were also investigated.