ANALYSIS OF FLUID FIELD OF LIQUID METAL IN ELECTROMAGNETIC CENTRIFUGAL CASTING

Navier-Stokes equation and Lorentz force equation are used to calculate the fluid field of liquid metal of electromagnetic centrifugal casting (EMCC) in this paper. A field equation is given, which shows the azimuthal velocity closely relates to electrical conductivity, magnetic density, viscosity of liquid metal and radius of casting. The results show that the stationary magnetic field can effectively restrain the fluid flow and the relative velocity between liquid metal and casting mould and the velocity gradient at solid / liquid interface increases with rising magnetic density, which has a great effect on the solidification of liquid metal and crystal growth characteristics.

An experimental study on metal precipitation driven by fluid mixing: implications for genesis of carbonate-hosted lead–zinc ore deposits

A type of carbonate-hosted lead–zinc(Pb–Zn)ore deposits, known as Mississippi Valley Type(MVT)deposits, constitutes an important category of lead–zinc ore deposits. Previous studies proposed a fluid-mixing model to account for metal precipitation mechanism of the MVT ore deposits, in which fluids with metal-chloride complexes happen to mix with fluids with reduced sulfur, producing metal sulfide deposition. In this hypothesis, however, the detailed chemical kinetic process of mixing reactions, and especially the controlling factors on the metal precipitation are not yet clearly stated. In this paper, a series of mixing experiments under ambient temperature and pressure conditions were conducted to simulate the fluid mixing process, by titrating the metal-chloride solutions, doping withor without dolomite, and using NaHS solution. Experimental results, combined with the thermodynamic calculations, suggest that H_2S, rather than HS^-or S^(2-),dominated the reactions of Pb and/or Zn precipitation during the fluid mixing process, in which metal precipitation was influenced by the stability of metal complexes and the pH. Given the constant concentrations of metal and total S in fluids, the pH was a primary factor controlling the Pb and/or Zn metal precipitation. This is because neutralizing or neutralized processes for the ore-forming fluids can cause instabilities of Pb and/or Zn chloride complexes and re-distribution of sulfur species, and thus can facilitate the hydrolysis of Pb and Zn ions and precipitation of sulfides. Therefore, a weakly acidic to neutral fluid environment is most favorable for the precipitation of Pb and Zn sulfides associated with the carbonate-hosted Pb–Zn deposits.

Fluid Inclusion Geochemistry of Metallic Ore Deposits in the South- Central Sector of theDa Hinggan Mountains in China

Physicochemical parameters of mineralization such as temperature, pressure, salinity, density, composition and boiling of ore fluids as well as pH, Eh, fo2 and reducing parameter in theprocess of mineralization of major ore deposits in the study district have been obtained by the authors through systematic observation and determination of characteristics and phase changes of fluid inclusions at different temperatures and analysis of gaseous and liquid phase compositions of the inclusions, thus providing a scientific basis for the division of mineralization-alteration stages, types of mineral deposits and minerogenetic series and the deepening of the knowledge about the ore-forming processes and mechanisms of mineral deposits. It is indicated that the deposits of the same type have similar fluid inclusion geochemical features and physicochemical parameters though they belong to different minerogenetic series, while the compositions of inclusions are not conditioned by deposit types but closely related to the minerogenetic series of deposits.

Simultaneous Removal of Surfactant Template from MCM-41 and Implantation of Transition Metal Complexes into Mesopores with Supercritical Fluid

The simultaneous removal of up to 92% of the surfactant template and chemical implantation of transition metal complexes into mesopores has been successfully achieved by treating as-synthesized pure siliceous MCM-41 with supercritical CO2 modified with CH2Cl2/MeOH mixture, resulting in the formation of functionalized material with uniform pore structure.

Tribological Properties and Machining Performance of Vegetable Oil Based Metal Working Fluids—A Review

Lubricants are playing an important role in world industrial and economic development, mainly by reducing friction and wear in mechanical contacts. The outlook for eco-friendly MWFs for the next decade is 15% of global volume share. Due to ever increasing demand for environmentally acceptable products suitable for use as MWFs, vegetable oil-based MWFs are drawing the attention of researchers across the globe. Owing to the desirable properties of vegetable oils as cutting fluids, vegetable oil-based cutting fluids play an important role in conserving the environment by means of sustainability. This paper focuses on various vegetable oil being developed to promote biodegradable MWFs across the world. The performance of vegetable oils with respect to cutting and thrust force, tool wear, temperature, surface roughness in turning, drilling, milling and grinding a wide variety of materials are studied and reported. The review also throws light on the tribological behavior of vegetable oils that influence the lubricity in Metal working process. The review reveals that vegetable oils offer an alternative, eco-friendly and sustainable MFWs for the future of manufacturing.

Flow Field of Metallic Fluid Acted by Electromagnetic and Centrifugal Force

According to the principle of electromagnetism and hydrodynamics,a mathematical model of flow field for metallic fluid acted by electromagnetic and centrifugal forces was established.The calculation results showed that the relative velocity between metallic fluid layers rises and the absolute rotational velocity of metallic fluid falls with the increase of magnetic induction intensity.The increase of centrifugal revolution hardly affects the relative velocity between metallic fluid layers,but can enhance the absolute rotational velocity of metallic fluid.

Lumen apposing metal stents for pancreatic fluid collections:Recognition and management of complications

For patients recovering from acute pancreatitis,the development of a pancreatic fluid collection (PFC) predicts a more complex course of recovery,and introduces difficult management decisions with regard to when,whether,and how the collection should be drained.Most PFCs resolve spontaneously and drainage is indicated only in pseudocysts and walled-off pancreatic necrosis when the collections are causing symptoms and/or local complications such as biliary obstruction.Historical approaches to PFC drainage have included surgical (open or laparoscopic cystgastrostomy or pancreatic debridement),and the placement of percutaneous drains.Endoscopic drainage techniques have emerged in the last several years as the preferred approach for most patients,when local expertise is available.Lumen-apposing metal stents(LAMS) have recently been developed as a tool to facilitate potentially safer and easier endoscopic drainage of pancreatic fluid collections,and less commonly,for other indications,such as gallbladder drainage.Physicians considering LAMS placement must be aware of the complications most commonly associated with LAMS including bleeding,migration,buried stent,stent occlusion,and perforation.Because of the patient complexity associated with severe pancreatitis,management of pancreatic fluid collections can be a complex and multidisciplinary endeavor.Successful and safe use of LAMS for patients with pancreatic fluid collections requires that the endoscopist have a full understanding of the potential complications of LAMS techniques,including how to recognize and manage expected complications.

Reversible adsorption of metalworking fluids (MWFs) on Cu-BTC metal organic framework

Metalworking fluids(MWFs) are classified as hazardous substances. Due to the characteristics of the stable oil–water emulsions, it requires more costly and complicate treatment techniques to remove oil from spent MWFs. Metal organic frameworks(MOFs) are a porous network material used to remove contaminants from environment. One of the most prominent of MOFs is HKUST-1 or Cu-BTC. In this study, the Cu-BTCs were prepared by solvothermal method in various conditions and used as absorbent for removing oil micelles in MWF emulsion. The particle size of all synthesized Cu-BTCs ranged from ≈80 to 400 nm. The ability of all synthesized Cu-BTCs to remove oil micelle was greater than 95% in 60 min, while the capacity of GAC was obtained the result for only 6.8%. The maximum adsorption capacity(q _(max)) of oil micelles on Cu-BTCs was 1666.7 mg·g^(-1). The highest removal capacity of oil micelles in MWF emulsion is greater than 99% in 24 h by using Cu-BTCs washed with either butanol or ethanol.

The Morphology of Patterning with Pseudoplastic Metal Nanoparticle Fluids during Heat Treatment

A pseudoplastic metal nanoparticle fluid （PMNF） is used in nanoimprint to fabricate semiconductors and func- tional devices. The evaporation of the solvent and the sintering of the Au PMNF are investigated. The key parameters, which influence the morphology of patterning, such as the radius of metal particles, the concentra- tion of metal particles, the Hamaker constant of the solvent, viscosity of the fluids and the evaporation velocity, are analyzed. Based on a two-sphere sintering model, the equations are derived, which represent the relationships between the relative shrinkage and radius of the metal particles, sintering temperature and time. The optimal parameters for the heat treatment are provided in nanoimprint.

Tectonic Dynamic Metallization of Silver-GoldHydrothermal Fluids in Proterozoic GneissTerrene Shear Zones, Suichang, Zhejiang, China

The Suichang mine is the largest silicified vein-type silver-gold mineralization system in Southeast China, whose ore bodies are controlled by shear zones developing in Lower Proterozoic gneiss terrene with initial migmatization, which is covered by Upper Jurassic and Lower Cretaceous volcanic rock system and cut by acidic igneous veins of Jurassic and Cretaceous. The conclusions are as follows: (1) The ore-forming fluid is defined as superhigh tectonic-metamorphic fluid on the base of : 1 (D)-(18O) values 2 fluid inclusions;3 trace elements of pyrite from ores. (2) The shear zone silicified orebod-ies occurred in proterozoic, Jurassic and Cretaceous, which have been transforms in part by ore-bearing comb quartz vein of volcanism.

Study on a New Method of Extraction of Metal Ions from SolidMatrices by Supercritical Fluid

8-Hydroxyquinoline, methanol and Triton-100 were first used together in the extraction of metal ions by supercritical CO2. In the new system, the effects of pressure, temperature and the volume of CO2 on the efficiency of supercritical fluid extraction (SFE) were systematically investigated. The recovery under the optimum condition was only 11.38%, but if suitable concentration of methanol (v/v=5%) was added to the supercritical CO2, the recovery was increased significantly (83.60%, RSD=4.37%, n=5). In order to further enhance the recovery Triton X-100 was added to the samples, and the results were satisfactory (96.62%, RSD=2.85%, n=5).

Geology, Mineralization, Fluid Inclusion and Stable Isotope of the Early Cretaceous Sn and Associated Metal Deposits in the Southern Great Xing’an Range, NE China: A Review

The Southern Great Xing’an Range(SGXR) hosts a number of Early Cretaceous Sn and associated metal deposits, which can be divided into three principal types according to their geological characteristics: skarn type deposits, porphyry type deposits and hydrothermal vein type deposits. Fluid inclusion assemblages of different types of deposits are quite different, which represent the complexities of metallogenic process and formation mechanism. CH4 and CO2 have been detected in fluid inclusions from some of deposits, indicating that the ore-forming fluids are affected by materials of Permian strata. Hydrogen and oxygen isotope data from ore minerals and associated gangue minerals indicate that the initial ore fluids were dominated by magmatic waters, some of which had clearly exchanged oxygen with wall rocks during their passage through the strata. The narrow range for the δ34S values presumably reflects the corresponding uniformity of the ore forming fluids, and these δ34S values have been interpreted to reflect magmatic sources for the sulfur. The comparation between lead isotope ratios of ore minerals and different geological units’ also reveals that deeply seated magma has been a significant source of lead in the ores.

Investigation on the Arc Ignition Characteristics and Energy Absorption of Liquid Metal Current Limiter Based on Self-Pinch Effect

The GaInSn liquid metal current limiter based on the fluid pinch effect has broad application prospects due to its particular properties. However, the limited rated current and abil- ity of power dissipation are the critical problems for its wide application. Firstly, the temperature distribution of the liquid metal current limiter （LMCL） was obtained by experiments with a rated current of 1 kA and the arc ignition phenomenon was observed with 1.5 kA, which indicates that the rated current is mainly limited by the arc rather than the high temperature compared to the traditional switchgears. Furthermore, an improved method is proposed by adding the paralleled pure resistance, impedance or another LMCL element to protect the setup from the fault energy concentration in the setup. The problem of a slower arc voltage increasing rate can be solved by adding a paralleled impedance with suitable parameters. Finally, the current limiting properties based on the improved method were investigated and the alternating oscillating current was found between two paralleled LMCL elements owing to their deviation of arc ignition in reality.

Fluid Characteristics and Evolution of the Zhawulong Granitic Pegmatite Lithium Deposit in the Ganzi-Songpan Region, Southwestern China

The Zhawulong granitic pegmatite lithium deposit is located in the Ganzi-Songpan orogenic belt.Fluid inclusions in spodumene and coexisting quartz were studied to understand the cooling path and evolution of fluid within albite–spodumene pegmatite.There are three distinguishable types of fluid inclusions:crystal-rich,CO2–NaCl–H2 O,and NaCl–H2 O.At more than 500°C and 350~480 MPa,crystal-rich fluid inclusions were captured during the pegmatitic magma-hydrothermal transition stage,characterized by a dense hydrous alkali borosilicate fluid with a carbonate component.Between 412°C and 278°C,CO2–Na Cl–H2 Ofluid inclusions developed in spodumene(I)and quartz(II)with a low salinity(3.3–11.9 wt%NaCl equivalent)and a high volatile content,which represent the boundary between the transition stage and the hydrothermal stage.The subsequentNaCl–H2 Ofluid inclusions from the hydrothermal stage,between 189°C and 302°C,have a low salinity(1.1–13.9 wt%NaCl equivalent).The various types of fluid inclusions reveal the P–T conditions of pegmatite formation,which marks the transition process from magmatic to hydrothermal.The oreforming fluids from the Zhawulong deposit have many of the same characteristics as those from the Jiajika lithium deposit.The ore-forming fluid provided not only materials for crystallization of rare metal minerals,such as spodumene and beryl,but also the ideal conditions forthe growth of ore minerals.Therefore,this area has favorable conditions for lithium enrichment and excellent prospecting potential.

REE Geochemistry of Sulfides from the Huize Zn-Pb Ore Field, Yunnan Province: Implication for the Sources of Ore-forming Metals

REE abundances in sulfides from the Huize Zn-Pb ore field were determined with the ICPMS after preconcentration. The REE abundances in 26 sulfide samples （including pyrite, galena and sphalerite） are very low, with the ~REE ranging from 1.6×10^-9 to 166.8×10^-9. Their LREE/HREE ratios range from 7.6 to 98, showing LREE enrichment relatively. The JEu values are below 1, indicating that they were deposited from an Eu-depleted and reducing fluid-system. Similar to the ore-hosting carbonate strata, calcite separates from carbonate veinlets filling in the fractures or faults crosscutting the carbonate strata also show clear Eu-depletion. This indicates that the carbonate veinlets and their parent fluid was possibly sourced from the strata and inherited the REE geochemical features of the strata. Therefore, REE-geochemical characteristics of both the sulfides and calcites, which were deposited from an ore-forming hydrothermal system, are similar to those of carbonate strata, and strongly suggest that the ore metals were mainly sourced from carbonate strata.

Conjugate Heat Transfer Analysis of an Ultrasonic Molten Metal Treatment System

In piezoceramic ultrasonic devices,the piezoceramic stacks may fail permanently or function improperly if their working temperatures overstep the Curie temperature of the piezoceramic material.While the end of the horn usually serves near the melting point of the molten metal and is enclosed in an airtight chamber,so that it is difficult to experimentally measure the temperature of the transducer and its variation with time,which bring heavy difficulty to the design of the ultrasonic molten metal treatment system.To find a way out,conjugate heat transfer analysis of an ultrasonic molten metal treatment system is performed with coupled fluid and heat transfer finite element method.In modeling of the system,the RNG model and the SIMPLE algorithm are adopted for turbulence and nonlinear coupling between the momentum equation and the energy equation.Forced air cooling as well as natural air cooling is analyzed to compare the difference of temperature evolution.Numerical results show that,after about 350 s of working time,temperatures in the surface of the ceramic stacks in forced air cooling drop about 7 K compared with that in natural cooling.At 240 s,The molten metal surface emits heat radiation with a maximum rate of about 19 036 W/m2,while the heat insulation disc absorbs heat radiation at a maximum rate of about 7922 W/m2,which indicates the effectiveness of heat insulation of the asbestos pad.Transient heat transfer film coefficient and its distribution,which are difficult to be measured experimentally are also obtained through numerical simulation.At 240 s,the heat transfer film coefficient in the surface of the transducer ranges from–17.86 to 20.17 W/（m2？K）.Compared with the trial and error method based on the test,the proposed research provides a more effective way in the design and analysis of the temperature control of the molten metal treatment system.

Effect of groove angle and preheating temperature on temperature profile and fluid velocity in weld pool

The three dimensiotud transient weld pool dynamics are numerically analyzed ,for Forcearc welding, which is a new gas metal arc welding technology to get deep fusion penetration with smaller angle sf V groove to enhance welding efficiency significantly. The influence of groove angle and preheatin,g temperature on heat and .fluid .flow is studied and compared to get an optimal welding parameter. Good agreement is shown between the predicted and experimental results, such as weld bead cross-section and thermal cycles. It can he seen that an apprpriate groove angle could be used to replace high preheating temperature to get inproced penetration and thermal cycles.

Inhalation Bioaccessibility of Potentially Toxic Metals in Tobacco Snuff and Related Exposure Risks

This study determined the concentrations and inhalation bioaccessibility of cadmium, chromium, nickel and zinc in some foreign and locally available tobacco snuff and leaves. For the determination of the heavy metals concentration, the samples were ashed and washed with hydrochloric acid according to standard method. The bioaccessibility test employed the Stimulated Epithelial Lung Fluid (SELF). The total concentration of heavy metals in the four samples investigated ranged between 9.7 - 14.9 μg/g, 24.1 - 37.0 μg/g, 41 - 69 μg/g and 153 - 183 μg/g for cadmium, chromium, nickel and zinc respectively. The percentage inhalation bioaccessibility fraction of the four samples investigated ranged between 20.8% - 59.8%, 3.3% - 8.1%, 21.7% - 48.8% and 7.6% - 12.5% for cadmium, chromium, nickel, and zinc respectively. Statistical analyses using SPSS 21, revealed significant differences in the total concentration of heavy metals in the samples investigated except for Zinc. Risk assessment based on daily consumption of 10 g of the tobacco snuff employing total concentration of the heavy metals suggests that excluding nickel, all other metals investigated indicated daily intake values above WHO permissible levels. However, with the bioaccessible fractions, only cadmium, a known carcinogen indicated levels above WHO limits. From the results of this study, it can be deduced that consumption of tobacco snuff may induce negative health effects such as cancer and its attendant complications, the risk analysis based on bioaccessible concentration suggests lower health risk than analysis based on total heavy metal concentration;hence the assumption that snuff is a safe alternative to tobacco smoking may be erroneous.

Analysis of Molten Metal Distribution in the Mold of a Horizontal Centrifugal Casting

It is numerically studied the influence of the angular velocity, the molten metal viscosity, and the mold wall roughness on the molten metal distribution in the mold of a horizontal centrifugal casting process. The undesirable raining phenomenon sometimes arises in horizontal centrifugal casting. It occurs when the molten metal rains or falls from the top of the mold to the bottom while the mold is rotating. Using Computational Fluid Dynamics simulations, the conditions for the emergence of the raining phenomenon were explored in this work. For the system considered, angular velocities less than 77 rad/s cause the emergence of the raining phenomenon and accumulation of the molten metal in the lower part of the mold, whereas angular velocities greater than 77 rad/s produce a constant thickness of the molten metal and prevent raining.

微通道内单一/混合流体强化传热研究进展

介绍了近年来微通道换热器内冷却介质强化换热的研究进展。阐述了纳米流体、液态金属以及潜热型功能热流体强化传热的机理;探讨了影响纳米流体传热性能的因素,包括纳米颗粒的种类、体积分数和温度等;讨论了增大液态金属传热系数的方法;分析了微胶囊壁材、相变材料和微胶囊的质量分数等对潜热型功能热流体热容的影响。指出了3种冷却介质目前尚存在的缺陷及相应的改善措施,对高热流密度设备散热问题中冷却介质的选取具有一定的指导意义。