Understanding the influence of petrographic parameters on strength of differently sized shale specimens using XRD and SEM

Ground failure is a major contributor to fatalities in underground mines in the US.Underground coal mines in the Northern Appalachian have weak roof rock composed of shale,which is prone to failure under high horizontal stress.Understanding the relationship among strength,specimen size and rock petrographic parameters is essential for developing an effective ground control plan.Size effect studies have found that rock strength varies with specimen size.This paper attempts to understand this strength variation using three specimen sizes(254-mm,508-mm,and 762-mm).The specimen strength was measured and the major petrographic parameters affecting the strength,namely grain size,grain shape,quartz content,clay content,etc.were analyzed using X-ray diffraction(XRD)and scanning electron microscopy(SEM).The petrographic parameters were then correlated with the strength of the three differently sized specimens.The results showed that 508-mm specimen had the lowest strength.Quartz content of the 508-mm specimen was lower than that of 254-mm and 762-mm specimens.Clay content and average grain size of the 508-mm specimen were higher than those of 254-mm and 762-mm specimens.These results clearly show that grain size,quartz content and clay content contribute to strength variation observed in differently sized shale specimens.

钢渣粉/聚酯纤维沥青混合料水稳定性研究

为了实现钢渣粉在沥青路面中的可持续利用,同时结合河南省冬季冰雪天气下路面的除冰情况,研究了掺有聚酯纤维与钢渣粉沥青混合料的水稳定性。制备4种聚酯纤维掺量(0、0.3%、0.4%、0.5%)AC-13沥青混合料开展复盐(掺量配比为NaCl∶CaCl2∶CH2COONa=1∶1∶2)冻融循环劈裂试验,结果表明聚酯纤维掺量为0.4%时,沥青混合料水稳定最好;在最佳纤维掺量下制备5种替代率(0、25%、50%、75%、100%)钢渣粉沥青混合料,采用冻融劈裂抗拉强度比(freeze-thaw splitting tensile strength ratio,TSR)确定最佳钢渣粉替代率为75%,混合料水稳定性最佳;通过冻融腐蚀因子K评价沥青混合料的抗侵蚀性能,结果表明:聚酯纤维/钢渣粉沥青混合料的抗侵蚀性能最强,聚酯纤维沥青混合料次之,普通石灰岩沥青混合料最弱。通过电镜扫描(scanning electron microscope,SEM)、X射线衍射(X-ray diffraction,XRD)技术探索钢渣粉/聚酯纤维沥青混合料界面黏附作用的改性机理。微观分析表明:掺量为0.4%的聚酯纤维形成的纤维网状结构以及沥青、钢渣粉(75%的替代率)和矿粉三者存在界面能量作用可以很好地改善沥青混合料的水稳定性。

Microstructure characteristics of cement-stabilized sandy soil using nanosilica

An experimental program was conducted to explore the impact of nanosilica on the microstructure and mechanical characteristics of cemented sandy soil.Cement agent included Portland cement type II.Cement content was 6% by weight of the sandy soil.Nanosilica was added in percentages of 0%,4%,8% and 12% by weight of cement.Cylindrical samples were prepared with relative density of 80% and optimum water content and cured for 7 d,28 d and 90 d.Microstructure characteristics of cementnanosilica-sand mixtures after 90 d of curing have been explored using atomic force microscopy(AFM),scanning electron microscopy(SEM) and X-ray diffraction(XRD) tests.Effects of curing time on microstructure properties of cemented sandy soil samples with 0% and 8% nanosilica have been investigated using SEM test.Unconfined compression test(for all curing times) and compaction test were also performed.The SEM and AFM tests results showed that nanosilica contributes to enhancement of cemented sandy soil through yielding denser,more uniform structure.The XRD test demonstrated that the inclusion of nanosilica in the cemented soil increases the intensity of the calcium silicate hydrate(CSH) peak and decreases the intensity of the calcium hydroxide(CH) peak.The results showed that adding optimum percentages of nanosilica to cement-stabilized sandy soil enhances its mechanical and microstructure properties.

Mineral phase and structure changes during roasting of fine-grained carbonaceous gold ores and their effects on gold leaching efficiency

While roasting has been widely applied to reduce the negative effect of carbonaceous matters on gold extraction from fine-grained carbonaceous gold ores, the phase and structure changes of minerals during roasting and their in fluences on the leachi ng rate of gold have not been fully understood. This limits the extraction of carbonaceous gold deposits. The current work examines the oxidation process of a fine-grained carbonaceous gold ore during roasting using a range of techniques including X-ray diffraction (XRD), seanning electron microscopy (SEM), Energy Dispersive Spectrometer (EDS) analysis and pore structure analysis together with gold leaching tests. The results show that during the process of oxidative roasting, the carbonaceous matters (organic carbon and graphitic carbon) and pyrite were completely decomposed at 600 ℃ with the carbonaceous components burned and pyrite oxidized into hematite. At 650 ℃, while dolomite was decomposed into calcia, magnesia, calcium sulfate etc., the calcine structure became loose and porous, leading to a high gold leaching rate from the roasted product. Above 750 ℃, the porous calcite structure started to collapse along with the agglomeration, leading to the secondary encapsulation of gold particles, which contributed to the sharp drop in the gold leaching rate of the roasted product. This study suggests optimum phase and structure changes of minerals during roasting to achieve maximum gold extraction from fine-grained carbonaceous gold deposits.

Electrochemical characterization of Ni-Co and Ni-Co-Fe for oxidation of methyl alcohol fuel with high energetic catalytic surface

Non Pt based metals and alloys as electrode materials for methyl alcohol fuel cells have been investigated w ith an aim of finding high electrocatalytic surface property for the faster electrode reactions.Electrodes w ere fabricated by electrodeposition on pure Al foil,from an electrolyte of Ni,Co,Fe salts.The optimum condition of electrodeposition w ere found out by a series of experiments,varying the chemistry of the electrolyte,pH valve,temperature,current and cell potential.Polarization study of the coated Ni-Co or Ni-CoFe alloy on pure Al w as found to exhibit high exchange current density,indicating an improved electro catalytic surface w ith faster charge-discharge reactions at anode and cathode and low overvoltage.Electrochemical impedance studies on coated and uncoated surface clearly show ed that the polarization resistance and impedance w ere decreased by Ni-Co or Ni-Co-Fe coating.X-ray diffraction(XRD),energy dispersive X-ray spectroscopy(EDX)and atomic absorption spectroscopy(AAS)studies confirmed the presence of alloying elements and constituents of the alloy.The morphology of the deposits from scanning electron microscope(SEM)images indicated that the electrode surface w as a three dimensional space w hich increased the effective surface area for the electrode reactions to take place.

Long-term Hardening Characteristics of Prestressed Anchorage Grout

Grout plays an important role in the transmission and maintenance of anchoring force,and in the protection of anchorage materials against corrosion.Thus,the hardening characteristics of grout directly affect the anchoring effectivity and long-term reliability.We have excavated a prestressed anchorage which has been in service for 20 years,and have tested the grout which has worked for that long period under complicated geological conditions through strength tests and have analyzed its mineral composition using scanning electron microscopy(SEM) and X-ray diffraction(XRD).The results show that the mineral composition of the 12.5 m segment differs from other segments,and corresponds with poor coagulation characteristics of the 12.5 m segment grout.Analysis shows that unhydrated tricalcium silicate may be the reason for the localized poor coagulation.

Properties,Morphology and Structure of BPDA/PPD/TFMB Polyimide Fibers

The mechanical properties of fibers were notably improved by incorporating 2,2＇-bis（trifluoromethyl）benzidine（TFMB） into 3,3＇,4,4＇-biphenyltetracarboxylic dianhydride（s-BPDA） and p-phenylenediamine（PPD） backbone.The best strength and modulus of BPDA/PPD/TFMB polyimide（PI） fiber（diamine molar ratio of PPD/TFMB= 90/10） were 1.60 and 90 GPa,respectively,which was over two times that of BPDA/PPD PI fiber.SEM image showed that the cross-section of fibers at each stage was round and voids free.Besides,the ＂skin-core＂ and microfibrillar structure were not observed.The thermal properties of PI fibers were also investigated.The results showed that the fibers owned excellent thermal stability,moreover,the structural homogeneity of fibers were significantly improved by heat-drawn stage.The T g values were found to be around 300 °C by dynamic mechanical analysis（DMA）.Wide angle X-ray diffraction（WAXD） and small angle X-ray scattering（SAXS） experiments indicated that the order degree of longitudinal and lateral stacks,the molecular orientation and the structural homogeneity of fibers were improved in the preparation process of fibers.

An Experimental Study of the Physicochemical Properties of a Cement Matrix Containing Dredged Materials

Recently, the amount of dredged soil material (DM) has been rapidly increasing in Korea due to four major river maintenance projects and new harbor construction. DM waste is mostly dumped into the ocean, while only a small part of it has been utilized for coastal reclaiming, or as filling and backfilling material. This study carried out physical and chemical tests to map out a specific plan for utilizing DM in a mortar mixture. The compressive strength tests and microstructure analysis using XRD and SEM of cement mortar contained DM were performed as a replacement for fine aggregate or as a filler material of mortar matrix. The study measured the impact of contaminants contained in DM and how silt and clay influenced the compressive strength of the mortar.

Electrodeposition of Cyclic Multilayer Zn-Co Films Using Square Current Pulses and Investigaions on Their Corrosion Behaviors

The cyclic multilayer alloy (CMA) coatings of Zn-Co have been developed galvanostatically on mild steel (MS), using single bath technique. Depositions were carried out using square current pulses. Corrosion behaviors of the coatings were evaluated by potentiodynamic polarization and electrochemical impedance method, supported by dielectric spectroscopy. The cyclic cathode current densities (CCCD’s) and number of layers were optimized for highest corrosion stability of the coatings. The CMA coating developed at 3.0/5.0 A/dm2, having 300 layers, represented as (Zn-Co) 3.0/5.0/300 was found to exhibit ~ 40 times better corrosion resistance compared to monolayer coating, developed from same bath for same time. Substantial improvement in the corrosion resistance of CMA coatings is attributed to layered coating, having alternatively different phase structures, evidenced by XRD study. The formation of multilayer and corrosion mechanism was analyzed using Scanning Electron Microscopy.

Chemical Durability and Structural Proprieties of the Vitreous Part of the System xCaO-(40-x)ZnO-15Na₂O-45P₂O₅

The influence of CaO on the glass forming characteristics and properties of Na2O-CaO-ZnO-P2O5 glasses has been investigated. According to the studies that we performed on phosphate based glass within system xCaO-(40-x)ZnO-15Na2O-45P2O5 (10 ≤ x ≤ 30;mol%), it was found that the increase of CaO and substitution of ZnO can give a good chemical durability. Both Cristallographies X-ray and IR spectroscopy have confirmed the structure change when the CaO content increases in the glass. This change results in the formation of metaphosphate and/or rings of metaphosphate groups at the expense of pyrophosphate. So it indicates the formation of Ca-O-P bonds in the network glass that replaces hydrated P-O-Na and P-O-P bands. The phosphate chains units can be bonded together in rings forming meta-phosphate groups. These rings likely lead to the formation of agglomerates of crystalline phases, which is the main cause of the increase in the chemical durability of the glasses when the CaO content increases. The latter may lead to wider use of these materials, especially in the biomedical field.

Environmental and Mineralogical Studies of the Sabkhas Soil at Ismailia—Suez Roadbed, Southern of Suez Canal District, Egypt

Eight surface sabkha soils samples were collected from Ismailia—Suez roadbed, southwestern of Suez Canal district. Sedimentological and mineralogical analyses were conducted using grain size;X-ray diffraction and Scanning Electron Microscopy (SEM). Grain size analysis indicates high contents of fine sand and mud as well as presence of salts. X-ray diffraction;Scanning Electron Microscopy (SEM) and EDAX tool clarified that the sabkha soils are enriched by quartz, sulfate minerals (gypsum, anhydrite), carbonate minerals (calcite-dolomite-aragonite), chlorides (halite and bischofite), and clay minerals. The results elucidate that the appearance of sabkha deposits and their distribution in the study area are controlled mainly by the content of water soluble salts through parent materials;ground water table;subsurface structural;and physiographic features for instance surface relief or topography;and human activity.

Conditional Optimization of Solution Combustion Synthesis for Pioneered La₂O₃Nanostructures to Application as Future CMOS and NVMS Generations

In the Mediterranean region, climate change will result by 2100 in a tempera-ture increase that most likely will range from 2°C to 2.7°C, while annual precip-itation will most likely reduce in the range of 3% to 10%. This paper uses hy-drological modeling of precipitation and evapotranspiration to evaluate the challenge to aquifer natural recharge considering Palestine as a case study. The study showed that the climate change impacts on aquifer recharge will vary according to the distributions of monthly precipitation and evapotranspiration in the recharge areas. The 2°C to 3°C increase in temperature could result in a reduction of 6% to 13% in aquifer annual recharge. Aquifer recharge was found to be sensitive to changes in precipitation as a reduction of 3% to 10% in annual precipitation could result in a reduction in annual recharge ranging from 3% to 25%. It was observed that aquifers with recharge areas characterized by lower precipitation are more sensitive to precipitation reduction and thus groundwater resources will be negatively impacted more in these areas by climate change. Thus, climate change will reduce water availability in drier areas requiring adaptation measures through improving water management and rehabilitation of water infrastructure.

Production and Characterization of Nano Structured Silicon Carbide by High Energy Ball Milling

The article has been retracted due to the investigation of complaints received against it. The Editorial Board found that substantial portions of the text came from other published paper. Comparing with the paper published in International Journal of Engineering, Science and Technology Vol. 3, No. 4, 2011, pp. 82-88 (www.ijest-ng.com), these two papers have the same contents before Figure 7 and the author added Fig. 8, 9, 10 on the 2012 paper. The scientific community takes a very strong view on this matter, and the Journal of Minerals and Materials Characterization and Engineering (JMMCE) treats all unethical behavior seriously. This paper published in Vol.11 No.5, 529-541, 2012 has been removed from this site.

Reduced Activation Energy of Iron and Copper Ion Doped Mullite which Can Be Used as a Substrate in Electronic Industry

The crystallized mullite composite has been synthesized via sol-gel technique in the presence of transition metal ions such as iron and copper. The electrical resistivity and activation energy of the composites have been measured and their variation with concentration of the metal ion has been investigated. The resistivity of doped mullite decreases rapidly in the shorter temperature range and sharply in the higher temperature range. The decreasing resistivity is due to the 3d orbital electrons and the concentration of metal ions present. X-ray analysis confirms the presence of metal ions in mullite, which entered in the octahedral site. The Fe2+ and Cu2+ ions will substitute Al3+ ion in the octahedral site of mullite structure and most probably will be responsible for reducing the resistivity as well as the activation energy. Transition metal ion doped mullite-based ceramic can be considered as promising material as a substrate in the electronic industry, because of its reasonable atom density, its low activation characteristics, low thermal expansion coefficient and high mechanical strength. The present material we have developed has an activation energy of resistivity/band gap energy, Eg, 1.11 eV at 0.04 M concentration for Cu2+ ion.

Synthesis and Characterization of Copper Substituted Nickel Nano-Ferrites by Citrate-Gel Technique

Mixed Copper substituted Nickel nano-ferrites having the chemical formula Ni1-xCuxFe2O4 (where x = 0, 0.2, 0.4, 0.6, 0.8, 0.9 and 1.0) were synthesized by citrate gel technique. The crystal structure characterization and morphology were investigated by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). An elemental composition of the samples were studied by energy dispersive X-ray Spectroscopy (EDS). Lattice parameter, X-ray density, Volume of the Unit Cell and The values of the hopping length for octahedral (dB) and tetrahedral (dA) sites were calculated. The observed results can be explained on the basis of composition.

Characterization of Chromium Substituted Cobalt Nano Ferrites Synthesized by Citrate-Gel Auto Combustion Method

Co-Cr nano-ferrites, having the chemical formula CoCrxFe2-xO4 (where x = 0.0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0), were synthesized by the Citrate-gel auto combustion method. Synthesized powders were sintered at 500°C for 4 hours in an air and were characterized by XRD, SEM and EDS. XRD analysis showed cubic spinel structure of the ferrites and the crystallite sizes (D) were found in the range of 6 - 12 nm. The values of lattice parameter (a) decreased and X-ray density (dx) increased with the increase of Cr content. Scanning Electron Microscopic (SEM) studies revealed nano crystalline nature of the samples. An elemental composition of the samples was studied by Energy Dispersive Spectroscopy (EDS). The observed results can be explained on the basis of composition and crystal size.

Structural Changes in Human Teeth after Heating up to 1200°C in Argon Atmosphere

The phase transformation of hydroxyapatite (HAP, Ca10(PO4)6(OH)2) to the beta tricalcium phosphate phase (β-TCP, β-Ca3(PO4)2) at 1100°C is well known. However, in the case of human tooth, the HAP phase transformation is still an open area. For example, the CaO phase has sometimes been reported in the set of phases that make up the teeth. In this study, physical changes of human teeth when subjected to heat treatment in inert atmosphere (argon) were studied. The results were compared with those obtained in air atmosphere, from room temperature (25°C) up to 1200°C. Morphological changes were analyzed by light and scanning electron microscopy (SEM). The HAP to β-TCP phase transformation was followed in powder samples by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Heating of teeth results in the removal of organic material and structural water before the HAP to β-TCP phase transformation, the increment in hardness and the induced crystal growth. The percentage of the phases, crystal growth and lattice parameter variations as a function of temperature was quantified by Rietveld analysis. The black color was observed in dentin heated under argon atmosphere. Differences in expansivity produce fractures in dentin at 300°C in argon and at 400°C in air. In dentin, the coexistence of the HAP and β-TCP phases was observed after 800°C in argon and after 600°C in air;in enamel it was observed at 600°C in argon compared with 400°C in air. In general, the role played by the argon atmosphere during the thermal treatment of the teeth is to retard the processes observed in air.

Annealing Effects on Electrical Properties and Interfacial Reactions of Ni/Cu Schottky Rectifiers on n-Type InP

We report on the effect of annealing temperature on electrical, interfacial reactions and surface morphological properties of Ni/Cu Schottky contacts on n-type InP. The extracted barrier height of as-deposited Ni/Cu Schottky contact is 0.59 eV (I-V) respectively. The high-quality Schottky contact with barrier height and ideality factor of 0.65 eV (I-V) and 1.15 respectively, can be obtained after annealing at 300℃ for 1 min in a nitrogen atmosphere. However, annealing at 400℃, results the decrease in the barrier height to 0.54 eV (I-V). From the above observations, it is observed that Ni/Cu Schottky contact exhibited excellent electrical properties after annealing at 300℃. Hence, the optimum annealing temperature for the Ni/Cu Schottky contact is 300℃. Furthermore, Cheung’s functions is used to extract the diode parameters including ideality factor, barrier height and series resistance. According to the XRD analysis, the formation of the indium phases at the Ni/Cu/n-InP interface could be the reason for the increase in the barrier height at annealing temperature 300℃. Further, the degradation of the barrier heights after annealing at 400℃ may be due to the formation of phosphide phases at the Ni/Cu/n-InP interface. Scanning electron microscopy (SEM) results show that the overall surface morphology of the Ni/Cu Schottky contact is reasonably smooth.

Development of Non-Shrinking Soft Ferrite Composition Useful for Microinductors Applications

NiCuZn Ferrites are widely employed for many electronic applications, but can be replaced by MgCuZn ferrites owing to their superior properties like high initial permeability, high resistivity, low magnetostriction, environmental stability and low cost. Three series of NiMgCuZn ferrites were prepared by conventional sintering process. The formation of single phase in these ferrites was confirmed by x-ray diffraction. Initial permeability measurements on these samples were carried out in the temperature range of 30-400℃. The effect of the external applied stress on the open magnetic circuit type coil with these ferrites was studied by applying uniaxial compressive stress parallel to magnetizing direction and the change in the inductance was measured. The variation of ratio of inductance (ΔL/L)% increases upto certain applied compressive stress and there after it decreases, showing different stress sensitivities for different compositions of ferrites studied in the present work. With a view to develop stress insensitive NiMgCuZn ferrite, a low stress sensitivity composition among all the ferrites studied was chosen and different amounts of SiO2 were added to it and a series of ferrite compositions were prepared. The variation of ratio of inductance (ΔL/L)% with external applied compressive stress was examined. These results show that, in a particular composition of 0.05 wt% SiO2added Ni0.3Mg0.3Cu0.1Zn0.3Fe2O4 ferrite exhibited stress insensitivity. It was noticed that addition of SiO2 was found to be effective in reducing the stress sensitivity. This was confirmed from the elastic behaviour studies at room temperature on these ferrite samples. These studies were carried out to develop a ferrite composition for its use as core material for microinductor applications.

Processing and Characterization of Bulk FeSe

We investigated the effect of processing conditions on the structure and physical properties of the polycrystalline samples of Ca0.8Fe2Se2 prepared via solid state reaction. X-ray diffraction showed that the main phase became FeSe when the sintering temperature increased above 350 ℃. The temperature dependence of magnetization （M-T curves） recorded in zero-field-cooled mode by SQUID magnetometer showed some bumps at around 120 K to 140 K. These bumps moved to lower temperatures when the processing temperature increased above 550 ℃. On the other hand, pure FeSe materials produced at 900 ℃ for 24 h showed a sharp superconducting transition Tconset = 8.16 K and the critical current density of 6,252 A/cm2 at 5 K, self-field. SEM results indicated an enhanced grain connectivity.