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By Orlando Romig

PART I-PREPARATION OP METALLIC SINGLE CRYSTALS WITH ESPECIAL REFERENCE TO SINGLE CRYSTALS OP ZINC? As metals and alloys are composed, of, an aggregate of allotriomorphic crystals or grains, each possessing an individual orientation, the physical characteristics of a metal or an alloy are closely related to the properties of the individual crystals. The preparation and study of single metallic crystals are, therefore, matters of considerable importance. The advent of the X-ray spectrograph as a valuable metallurgical tool has magnified the importance of this subject, because the interpretation of some X-ray spectrographs is difficult unless single crystals are used in these studies. PREVIOUS WORK The first paper, as far as the writer knows, on the behavior or preparation of single crystals of metals is by Baker.1 He describes the behavior of extruded wires of sodium and potassium. These wires, when pulled in tension, instead of I showing the usual conical fracture common to most metals, had a chisel-shaped fracture when they were broken. I and II, Fig. 1, have a similar fracture. Baker checked his results by preparing single crystal wires from molten sodium and potassium and observing their properties. He prepared the wires by filling glass tubes, under oil, with the molten metal. The surfaces of the strained wires showed slip bands of remarkable clearness of which photographs are shown in his paper. He concluded that these wires were single crystals and "that the portions of the metal brought into play are cubes. Such cubes, when placed so that a plane through 'two opposite edges was parallel to the axis of the wire, would allow of lateral contraction by faces gliding over one another in one direction only and not in the direction at right angles."

Jan 1, 1927

By Orlando E. Romig

As metals and alloys are composed of an aggregate of allotriomorphic crystals or grains, each possessing an individual orientation, the physical characteristics of a metal or an alloy are closely related to the properties of the individual crystals. The preparation and study of single metallic crystals are, therefore, matters of considerable importance. The advent of the X-ray spectrograph as a valuable metallurgical tool has magnified the importance of this subject, because the interpretation of some X-ray spectrographs is difficult unless single crystals are used in these studies. Previous Work The first paper, as far as the writer knows, on the behavior or preparation of single crystals of metals is by Baker.' He describes the behavior of extruded wires of sodium and potassium. These wires, when pulled in tension, instead of showing the usual conical fracture common to most metals, had a chisel-shaped fracture when they were broken. I and 11, Fig. 1, have a similar fracture. Baker checked his results by preparing single crystal wires from molten sodium and potassium and observing their properties. He pre- pared the wires by filling glass tubes, under oil, with the molten metal. The surfaces of the strained wires showed slip bands of remarkable clearness of which photographs are shown in his paper. He concluded that these wires were single crystals and "that the portions of the metal brought into play are cubes. Such cubes, when placed so that a plane through two opposite edges was parallel to the axis of the wire, would allow of lateral contraction by faces gliding over one another in one direction only and not in the direction at right angles."

Jan 1, 1927

Preparation of MgO Nano-Particles with Magnesite

Sep 13, 2010

By Yue-yuan Li

China has abundant magnesite resource, but the low-grade and powder ores have always been rejected, which influences the comprehensive utilization of resource and often causes circumstance problems. The present work investigated the preparation of magnesia whisker using magnesite tailings as starting materials by preparation magnesium carbonate whisker as precursor firstly in the route of calcination, hydration, carbonation and pyrolysis, follows by second calcination of the precursor. The influence of pyrolysis conditions and additives on morphology of magnesium carbonate crystal as well as the influence of calcination conditions on morphology of magnesia whisker was investigated. The results showed that thermal decomposition products was MgCO3?3H2O. Magnesium carbonate whisker with length of 10~60 µm and the length-to-diameter ratio of 10~20 was prepared when soluble magnesium salt was added. While temperature was elevated at 1°C?min-1, magnesia whisker with length of 10~60µm was obtained.

Jan 1, 2010

By Xiang-yang Zhou

Keywords: Low-Grade Dolomite, Low CaO Content, High Specific Surface Area, MgO. A low energy consumption preparation technology of magnesium oxide with low calcium oxide content and high specific surface area from low-grade dolomite has been investigated. The optimum technical conditions for the preparation of magnesium oxide are the followings: dolomite is partially calcined at 750-800° for 2 h; the optimum solid-liquid ratio range in calcined dolomite slurry is 20-30 g?l?1; carbonation temperature, carbon dioxide pressure and end point pH value of carbonation are less than 40°, 0.4-0.6 MPa and 7 respectively during carbonation process; decomposition temperature of Mg(HCO3)2 solution is near 100°; calcination temperature of the precursor (i.e. precipitated basic magnesium carbonate) is less than 850°. More than 90% of magnesium can be extracted by the technology. The MgO product (CaO < 0.38%) with a specific surface area of near 50 m2?g?1 also can be obtained by the technology.

Jan 1, 2005

By Johns AS

Comissioning of a new residue disposal tcluding upgraded classification for none backfill preparation, new variable speed pumps and a new residue dam took place in 1¦76. The system is described.

Jan 1, 1978

By Duan Xin-hui, Wang Xin, Peng Jin-hui, C. Srinivasakannan, Zhang Li-bo

The work attempts to optimize the process of preparation of modified semi-coke from semi-coke using phosphoric acid (H3P04) as the activating agent using the response surface methodology (RSM). The influences of three major dependent variables, the impregnation ratio, activation time, and activation temperature were assessed on the independent variables yield and the iodine number. The empirical relationship between the dependent and the independent variables were established using the quadratic response surface models, which were utilized to optimize the process parameters. The significance of each of the parameters and interaction among the parameters on the independent variable was assessed based on analysis of variance (ANOVA). The process variables were varied within the range of impregnation ratio (IR) from 1.5 to 4, activation time from 30 to 90 min and activation temperature from 550 'C to 650 'C. The optimized process conditions were estimated to be an IR of 2.29, activation time of 32 min, and an activation temperature of 605°C respectively using the process optimization tool. The BET surface area of modified semi-coke of the optimized sample was estimated to be 915m2/g, with the pore volume of0.71cm3/g, with an average pore diameter of 3.09 nm, with micropore volume fraction being 52.36%. The scanning electron microscope (SEM) images were utilized to visualize the surface pore structure.

Jan 1, 2013

By Yuezhen Zhou, Zewei Liu, Dachun Liu, Chongfang Yang, Wenlong Jiang, Fansong Liu

A novel process that the combination of vacuum decomposition and acid leaching was proposed. The influence of distillation times, diameter and thickness of the feeding material on the mass fraction of Molybdenum (Mo) and sulphur (S) in residual was investigated. The influence of leaching temperature, leaching time, concentration of hydrochloric acid solution, and ratio of liquid to solid on leaching rates of Mo and S in acid leaching process was also investigated. Due to the fact that SO2 emission happening in the long process of traditional molybdenum metallurgy could be avoided in this novel method, this combination process was environmentally-friendly. Molybdenum powder was obtained through handling molybdenite concentrate under the optimal condition parameters, and the mass fraction of Mo reached 98.29 wt%. So it's feasible to produce molybdenum powder from molybdenite concentrate by using this new method.

Mar 1, 2017

By Qing Bo

In this study, the cobalt oxide precursor was prepared in open-style reactor in the condition of high reactant concentration, and then the precursor was decomposed to obtain the cobalt oxides (Co3O4). The effects of some factors on the cobalt precipitation, the particle size and size distribution, and the micro-morphology were addressed. The factors studied include cobalt concentration, initial pH of solution, temperature and time for the reaction, the charge amount of urea, and the temperature for decomposition. It is determined that the precursor particle is in the chemical composition of Co2(OH)3Cl with fine crystalline. By calcinations under proper conditions, the mono-dispersed cobalt oxide particles were prepared with fine crystalline, about 2 µ m in particle size and regular shape in morphology.

Jan 1, 2006

By Zhang Duomo

A novel homogenous precipitation method, including microwave heating, solution conductivity controlling and freeze drying, was developed for the preparation of US nanoparticles. The effects of the precipitation conditions on the structure and morphology of CdS particles were discussed individually. It was found that under the experimental conditions the particle sizes were controllable in the range of 14nm to 100nm. Blend-type CdS was obtained from nitrate or sulphate solution and the more stable wurtzite-type US was obtained from chloride solution, which was ascribed to the coordination of C1 and Cd2+ altering the supersaturation of the solution as well as the different growth units and their connecting patterns, In the precipitation process the surface of US nanoparticles were surface modified with CH3CHSCOOH. The results demonstrate that the bifunctional thiols of thioglycolic acid modified the surface through Cd-S coordination bonding and the induced counter ion AOT-SO3 as the balance charge further increased the stability and dispersity of US nanoparticles. This surface-modified US nanoparticles had been used to prepare nonlinear optics and self-assemble catalysts.

Jan 1, 2003

By Zhihong Liu

Monodisperse micron size nickel oxalate particles with rhombohedron morphology were prepared from condensed Ni(OH)2 suspension by a novel gel-sol process proposed by one of the authors. Firstly, condensed nickel hydroxide gel was formed by fast adding 1 mol dm-3 NaOH solution into 0.2 mol dm-3 nickel chloride solution, and then oxalic acid solution with a concentration of 0.25 mol dm-3 was dropped into the gel drop wise through a pump equiped with a pH controller under preset pH value, and in this process, Ni(OH)2 gel was converted gradually into monodisperse nickel oxalate sol. The formation of the nickel oxalate particles was found to proceed through a dissolution-recrystallization mechanism from the nickel hydroxide gel. The product particles exhibited rhombohedron like shape with micron size long axis and sub-micron size short axis. The effects of such factors, as temperature, surfactants, et al, were evaluated experimentally on the particles sizes and morphologies.

Jan 1, 2006

By Huang Kai

By adding the solid oxalate acid powder into the solution of nickel chloride or its ammonia coordinated solution, the uniform compound particles were prepared and the precipitated particles were transferred to the mono-dispersed NiO particles by calcination. In this study, the various experimental conditions were investigated, the characteristics of the corresponding obtained particles were analyzed, and the formation mechanism of the particles was elucidated. It was found that the solid oxalate acid provided the solid-solution interface for the precipitation and induced the nucleation and growth of the product particles.

Jan 1, 2005

By M. Kargar Razi

According to the unique properties and many applications of nano silver powder, it was prepared from acid leaching tail solution. The low value residual gold and silver ions were occurred with fellow heavy metals as pollutants (Fe2+, Cu 2+and Zn2+) in acid leaching tail solution in Mouteh gold mine in Iran. Preparation of nano silver particles was achieved in two steps: first, by addition of ammonia as separation step and second by using different reagents as precipitation and extraction steps. Different controlled parameters were including pH, residence time and temperature, mixing time, and reducing reagents to metals molar ratio. Acid leaching process was carried out with sulphuric and nitric acid via suitable reductants. In order to remove copper, zinc, and silver ions from solution, all of the conditions were controlled. The optimum conditions for preparation of nano silver powder with less than 90 nm were pH 10.5, hydrazine/methanol to silver molar ratio of 3 to 4, and reduction time of 5 min in 45 °C. The results were evaluated via SEM, A.A and UV- Vis spectroscopy analytical methods.

Jan 1, 2014

By J. -S. Park, H. -S. Jeon

This study has been carried out to develop a relatively simple hydrometallurgical process for recovering nickel as nickel sulfate from the spent nickel-cadmium battery residue in which cadmium was removed by vacuum distillation. This residue is composed of 36 % nickel, 20 % iron, and other metals such as cobalt. First, crushing and selective classification were performed to separate iron to produce a nickel-rich product (over 40 % nickel). This product was dissolved in sulfuric acid to obtain a nickel sulfate solution. During the dissolution, nitric acid and air were added to the system to enhance the iron oxidation reaction rate. The free acid remaining in the dissolved solution was neutralized by adding nickel carbonate. Iron was precipitated as iron hydroxide and removed from the solution. The nickel sulfate solution was then fed to a vacuum evaporator to concentrate the solution by evaporation of water and crystallized at around 45°C to obtain nickel sulfate hexahydrate. A recrystallization process could remove other impurities such as zinc and manganese.

Jan 1, 2000

Discussion of the paper of S. E. Bretherton, presented at the Butte meeting, August, 1913, and printed in Bulletin No. 80, August, 1913, pp. 1481 to 1487. S. E., BRETHERTON, San Francisco, Cal.:-Since preparing my paper, our chemist, F. L. Wilson, has been experimenting with Leadville, Colo., oxidized zinc ore and Leadville zinc sulphides containing lead, operating upon 40-1b. lots at a time. His results on Leadville sulphides are as follows: The raw ore contained a trace of gold, 5.04 oz. of silver, 19.1 per cent of zinc, and 7.24 per cent of lead. After roasting the ore contained a trace of gold, 5.72 oz. of silver, 0.75 per cent of copper, 21.7 per cent of zinc, and 8.29 per cent of lead. The loss in weight by leaching was 38.8 per cent. The extraction was 42.8 per cent of the copper, 80.6 per cent of the zinc, 7.1 per cent of the lead, 0.64 per cent of the silver, and no gold. The little .silver that is extracted would be thrown down with the copper when precipitating it from the zinc and both thrown hack into the residue to be smelted. There would be no trouble in smelting the residue with nearly all the sulphur eliminated and containing less than 7 per cent. of zinc. On zinc carbonates containing silicates the results are not satisfactory. H. O. HOFMAN, Boston, Mass. (communication to the Secretary*) :¬The paper by Mr. Bretherton upon the application of ammonia and carbonic acid to the recovery of zinc as oxide from roasted sulphide ore is of interest to me, as the first installation of the Schnabel process for the extraction of zinc from a mixture of zinc oxide, lead oxide (with some cupric oxide), and pellets of enriched lead, produced in steaming liquated zinc-silver-lead crust of the Parkes process, was made at Lautenthal, Harz mountains, where I was chemist. In that capacity I carried out numerous experiments on the Schnabel process, was active in the erecting of the plant, and later had charge of it. After the Lautenthal plant had been in operation for some time a similar one was built at Hoboken-les-Anvers, but both have been abandoned, as the wet process could not compete with the distillation of the liquated zinc-silver-lead crust, now used universally in the Parkes process.

Jan 11, 1913

By Y. X. Yang

Porous silica was obtained by acid leaching of chrysotile. The porous silica had been characterized by chemical analysis, powder X-ray diffraction (XRD), Fourier transform infrared spectros-copy (FT-IR), and N2 adsorption-desorption techniques. It is shown in this study that the porous silica retains the nanofibrous morphology of the original chrysotile, and produces a high specific surface area (SBET) of 391. 8 m2/g and total pore volume of 1. 05 mL/g. The increase in SBET and the total pore volume of the porous silica reflect the formation of micropores of 1.2~1.5nm and meso-pores of 3.2~3.8nm in diameter inside the porous structure. The hysteresis loop of N2 adsorption-desorption curve indicates mainly slit-shaped pores. The porous silica is amorphous, but its structure is regular to some extent. The structural unit of silica from chrysotile is a SiO4 tetrahedron and six-member silicon-oxygen rings with the tetrahedral positioned alternately up and down in the six-member rings.

Jan 1, 2014

By Guomin Jiang

Potassium ferrate is an excellent multifunctional reagent for wastewater treatment, but its preparation is crucial. The improved hypochlorite oxidation method was used to prepare potassium ferrate in this study. Iron nitrate, the preferred iron source, was added into hypochlorite solution and then the stabilization agent was added during the purification process of product. The influence of available chlorine content, iron molecular proportion, reaction temperature and reaction time on potassium ferrate preparation was investigated. The optimal condition for potassium ferrate preparation is 15% of available chlorine content , 0.6 of iron molecular proportion , 30i of reaction temperature , 45min of reaction time. The yield of potassium ferrate is about 67% with high purity (> 99%). The structure and performances of the product was characterized by XRD, EDX, SEM, TG and IR and the results show that the prepared product is consistent with the properties of potassium ferrate(VI).

Jan 1, 2010

By Ahmed M. Yousif, Walid M. Abdellah, Galal M. Abdel Wahab, Amal E. Mubark

The present work is concerned with selective dissolution of niobium from Gabal El Faliq concentrate sample by using fluoridefree process. The chemical analysis of concentrate sample revealed the presence of high amount of ZrO2, Nb2O5, Re2O3, and HfO2 assaying 33.6, 1.99, 4.8, and 1.2%w/w respectively. Several economic minerals including zircon, samarskite, fergusonite, and xenotimewere recorded in the studied sample. About 98%of Nb content was selectively dissolved at the optimumconditions of 1:2 concentrate sample: KOH weight ratio, 2.5 h fusion time, and fusion temperature of 550 °C. Organic solvent extraction process using Aliquat 336S in xylene was effectively used for preparing pure Nb2O5 (98.95%).

Oct 22, 2019

By Hyung Sup Choi

The preparation of high-purity zirconyl compounds was studied in order to develop an economical process for obtaining pure zirconium via the caustic fritting of zircon sand. The direct dissolution of caustic frits with concentrated hydrochloric or nitric acid at 80c. followed by the addition of a small amount of acidified gelatin, gave high-purity zirconyl chloride or nitrate. The addition of a small amount of gelatin caused a mutual flocculation between colloidal silica and gelatin. The precipitation of this silica floc markedly lowered the content of silica in the product. The silica content of the compounds (or solution) so produced, generally less than 100 ppm., was sufficiently low for tributyl phosphate extraction for nitrate solutions. It was found that the degree of purification de-pends not only on the procedures employed but also on the nature of the frit itself. Silica was more effectively eliminated from the fritted product produced at higher temperatures, and less silica was present in the com-pound prepared from the frit produced in a shorter heating time. In order to ascertain the nature of the

Jan 1, 1965

By Yuanbo Zhang, Mingjun Rao, Weiguang Tian, Huimin Tang, Guanghui Li, Lei Ye, Guoshen Liang, Zhiwei Peng, Foquan Gu, Tao Jiang

The amount of slag produced from a typical ferronickel smelting pro- cess is 4 to 6 times that of the metal product, and handling this slag is a huge challenge to the ferronickel industry. The feasibility of a technological route for preparing refractory materials from a ferronickel slag was verified in this study. Based on the thermodynamics analysis, the effect of the sintering temperature on the properties of refractory material from the slag was studied in the presence of magnesia. The results of thermodynamics calculation showed that the reaction of MgO with SiO generated forsterite and enstatite, whereas the reaction between 2 MgO and Fe O /Al O produced corresponding magnesia spinels. The experi- 2 3 2 3 mental results showed that a refractory material with refractoriness of 1580 °C, bulk density of 2.88 g/cm3, compressive strength of 106.9 MPa, and apparent porosityof 5.8%was obtained under the conditions ofmagnesia addition of 15 wt %, sintering temperature of 1350 °C and sintering time of 3 h. With increasing sintering temperature, the bulk density and the compressive strength of refractory material increased but the apparent porosity decreased, mainly attributed to the formation of the liquid phase which promoted the densification of the refractory material. (cid:1) (cid:1) (cid:1)

Mar 1, 2018