Extractive Metallurgy and National Policy

Hydrometallurgical technology offers a unique possibility for developing countries to exploit their mineral resources locally instead of shipping them as concentrates. Production plants may start on a small scale with small capital investment then increase productivity later when the economy permits without financial penalty. This is in contract to smelting operations which necessitates large scale production from the start with high capital investment that may not be available locally.

Polyurea coating for foamed concrete panel:An efficient way to resist explosion

Autoclaved aerated concrete(AAC) panels have ultra-light weight,excellent thermal insulation and energy absorption,so it is an ideal building material for protective structures.To improve the blast resistance of the AAC panels,three schemes are applied to strengthen the AAC panels through spraying 4 mm thick polyurea coating from top,bottom and double-sides.In three-point bending tests,the polyurea-coated AAC panels have much higher ultimate loads than the un-coated panels,but slightly lower than those strengthened by the carbon fiber reinforced plastics(CEFRPs).Close-in explosion experiments reveal the dynamic strengthening effect of the polyurea coating.Critical scaled distances of the strengthened AAC panels are acquired,which are valuable for the engineering application of the AAC panels in the extreme loading conditions.Polyurea coatings efficiently enhance the blast resistance of the bottom and double-sided polyurea-coated AAC panels.It is interesting that the polyurea-coated AAC panels have much more excellent blast resistance than the CFRP reinforced AAC panels,although the latter have better static mechanical properties.

Methods for Improving Volume Stability of Steel Slag as Fine Aggregate

Suitable methods for enhancing the volume stability of steel slag utilized as fine aggregate were determined. The effects of steam treatment at 100 ℃ and autoclave treatment under 2.0 MPa on the soundness of steel slag sand were investigated by means of powder ratio, linear expansion, compressive and flexural strength. DTA, EDX, XRD and ethylene glycol methods were employed to analyze both the treated slags and susceptible expansion grains. Experimental results indicate that powder ratio, content of free lime and rate of linear expansion can express the improvement in volume stability of different treated methods. Steam treatment process cannot ultimately prevent specimens from cracking and decrease of strength, but mortar made from autoclave treated slag keeps integration subjected to hot water of 80℃ until 28 d and its strength do not show significant decrement. The hydration of over-burn free lime and periclase phase are the main cause for the disintegration or crack of untreated and steam treated steel slag＇s specimens. Autoclave treatment process is more effective than steam treatment process on enhancement of volume stability of steel slag.

Synthesis and Microstructure Analysis of Autoclaved Aerated Concrete with Carbide Slag Addition

Synthesis of autoclaved aerated concrete （AAC） has been carried out with carbide slag addition, and the carbide slag could be used as a main material to produce the AAC with the compressive strength about 2 MPa and the density below 0.6 g.cm-3. In this study, quartz sand acted as frame structure phase in the matrix, and quartz addition also influenced the Si/Ca of starting material. Tobermorite and CSH gel were formed readily at 62%, which seemed to enhance the compressive strength of samples. Curing time seemed to affect the morphology of phase produced, and specimen with the plate-like tobermorite formed at 10 h appeared to have a better compressive strength development than the fiber-like one at 18 h. The higher curing temperature seemed to favor the tobermorite and CSH gel formation, which also exerted a significant effect on the strength development of the samples. On the micro-scale, the formed CSH gel was filled in the interface of the matrix, and the tobermorite appeared to grow in internal-surface of the pores and interstices. The tobermorite or/and CSH formation seemed to densify the matrix, and therefore enhanced the strength of the samples.

Leaching of a copper flotation concentrate with ammonium persulfate in an autoclave system

The leaching behavior of a copper flotation concentrate was investigated using ammonium persulfate （APS） in an autoclave systee. The decomposition products of APS, active oxygen, and acidic medium were used to extract metals from the concentrate. Leaching experiments were performed to compare the availability of APS as an oxidizing agent for leaching of the concentrate under atmospheric conditions and in an autoclave system. Leaching temperature and APS concentration were found to be important parameters in both leaching systems. Atmospheric leaching studies showed that the metal extractions increased with the increase in APS concentration and temperature （up to 333 K）. A similar tendency was determined in the autoclave studies up to 423 K. It was also determined that the metal extractions decreased at temperatures above 423 K due to the passivation of the particle surface by molten elemental sulfur. The results showed that higher copper extractions could be achieved using an autoclave system.

Effects of sterilization treatments on the analysis of TOC in water samples

Decomposition experiments conducted with and without microbial processes are commonly used to study the effects of environmental microorganisms on the degradation of organic pollutants.However,the effects of biological pretreatment （sterilization） on organic matter often have a negative impact on such experiments.Based on the principle of water total organic carbon （TOC） analysis,the effects of physical sterilization treatments on determination of TOC and other water quality parameters were investigated.The results revealed that two conventional physical sterilization treatments,autoclaving and 60 Co γ-radiation sterilization,led to the direct decomposition of some organic pollutants,resulting in remarkable errors in the analysis of TOC in water samples.Furthermore,the extent of the errors varied with the intensity and the duration of sterilization treatments.Accordingly,a novel sterilization method for water samples,0.45 μm micro-filtration coupled with ultraviolet radiation （MCUR）,was developed in the present study.The results indicated that the MCUR method was capable of exerting a high bactericidal effect on the water sample while significantly decreasing the negative impact on the analysis of TOC and other water quality parameters.Before and after sterilization treatments,the relative errors of TOC determination could be controlled to lower than 3% for water samples with different categories and concentrations of organic pollutants by using MCUR.

Variation law of gas holdup in an autoclave during the pressure leaching process by using a mixed-flow agitator

The multiphase reaction process of pressure leaching is mainly carried out in the liquid phase. Therefore, gas holdup is essential for the gas–liquid–solid phase reaction and the extraction rate of valuable metals. In this paper, a transparent quartz autoclave, a six blades disc turbine-type agitator, and a high-speed camera were used to investigate the gas holdup of the pressure leaching process. Furthermore, experiments determining the effects of agitation rate, temperature, and oxygen partial pressure on gas holdup were carried out. The results showed that when the agitation rate increased from 350 to 600 r/min, the gas holdup increased from 0.10% to 0.64%. When the temperature increased from 363 to 423 K, the gas holdup increased from 0.14% to 0.20%. When the oxygen partial pressure increased from 0.1 to 0.8 MPa, the gas holdup increased from 0.13% to 0.19%. A similar criteria relationship was established by Homogeneous Principle and Buckingham's theorem. Comprehensively, empirical equation of gas holdup was deduced on the basis of experimental data and the similarity theory, where the criterion equation was determined as ε=4.54×10^(-11)n^(3.65)T^(2.08)P_g^(0.18). It can be seen from the formula that agitation rate made the most important impact on gas holdup in the pressure leaching process using the mixed-flow agitator.

A Review on the Utilization of Waste Material for Autoclaved Aerated Concrete Production

Autoclaved aerated concrete(AAC)has become more attractive due to its excellent and environmental-friendly properties in building construction.AAC is relatively lightweight,possesses lower thermal conductivity,higher heat resistance,lower shrinkage,and fasten construction than normal concrete.AAC is a combination of silica sand,cement,gypsum,lime,water,and an expansion agent.To improve its physical and mechanical properties and reduce its production cost,tremendous innovations where waste materials were utilized as partial replacement of AAC materials were done.This paper is intended to present the literature on the utilization of waste materials as a means of a partial replacement in AAC materials to enhance its physical and mechanical properties and thermal performance.The physical properties such as microstructure and mechanical properties such as density,compressive strength,water absorption are presented to classify the investigation that has been done in such innovations.Apart from that,the discussion on innovations to improve its thermal performance was also presented.Based on the review,an increase of AAC application causes much waste at construction sites and recycling concrete waste powder into wall concrete;particularly,an AAC was not frequently practiced in construction.

Preparation of Copper Phthalocyanine Crystals Using Solvothermal Synthesis

A novel solvothermal synthesis method for the direct growth of B-form crystals of copper phthalocyanine（CuPc） is presented in this article. With quinoline as solvent, crystals were grown after cooling the reaction mixture of 1,3-diiminoisoindoline and copper oxide, heated for 9 h at 270 ℃, to room temperature in an autoclave. These high quality crystals were suitable for characterization measurements. The single-crystal diffraction data show a monoclinic system unit cell： a=1.4668（3） nm, b=0.48109（10） nm, c=1.9515（7） nm, a=90°, B=121.04（2）°, r=90°, where the corresponding cell volume is 1.17991 nm^3. Needle-like single crystals of CuPc up to 10.5 mm in length were obtained. The influences of different temperatures, reaction time and solvent volume on the crystal yields were also discussed. Optimum reaction conditions were 10 mL of quinoline, at 270 ℃ for 8 h.

Extraction of agar from Eucheuma cottonii and Gelidium amansii seaweeds with sonication pretreatment using autoclaving method

The effect of sonication pretreatment condition on Eucheuma cottonii and Gelidium amansii seaweed towards agar extraction wae studied.Four parameters were changed during sonication to investigate the effects on agar yield and quality.These parameters include the time interval,concentration ratio,frequency,and intensity.The highest amount of agar extracted from Eucheuma cottonii species could be obtained from the time interval of 30min,seaweed weight to solvent volume ratio of 1:20,the frequency of 35Hz,and the sonication power intensity of 30%.For Gelidium amansii species,the best agar yield also could be obtained from the time interval of 30 min,1:20 of seaweed weight to water volume ratio,the frequency of 35Hz,and power intensity of 30%.From the experiment,sonication pretreatment signifi cantly influenced the yield and properties of extracted agar.The sonication with autoclaved seaweed produced agar containing less sulfate content,which is an excellent chemical property for gel electrophoresis applications.The gelstrength of sonication with autoclaving for both seaweeds,Eucheuma and Gelidium species was the highest among those by sonication with direct heating,which proved that sonication pretreatment with autoclaving could enhance the physical properties of the agar.

Development of in-situ Micro-Raman spectroscopy system for autoclave experimental apparatus

We developed a set of in-situ Micro-Raman spectroscopy system for autoclave experimental apparatus because of the scientific significance of in-situ Micro-Raman spectroscopy system under the high-pressure hydrothermal condition.We used this system to measure the Raman spectrum of water-fluid and quartz crystal at the temperature ranging from 125 to 420℃.The signal-tonoise ratio of the Raman signal is good.

Impermeability Research of Autoclaved Propylene Oxide Sludge Shell-aggregate Concrete

We aimed to reuse the propylene oxide sludge(POS).Propylene oxide sludge shell-aggregate(POSS-A)and propylene oxide sludge gradient shell-aggregate(POSGS-A)whose main hydrated phase is tobermorite were successfully manufactured by the hydrothermal synthesis of POS and silica materials under the condition of autoclaved(180℃,1.0 MPa)curing.Influences of pre-wetting time of coarse aggregate and pressure application mode on the different concretes were investigated.The experimental results show that the concrete with POSS-A as coarse aggregate(POSS-A concrete),the concrete with POS gradient shell-aggregate as coarse aggregate(POSGS-A concrete),sintered aggregate concrete and common concrete,all have excellent impermeability performance whatever the pre-wetting time of coarse aggregate is 0.5 h or 24 h,and the pre-wetting time of coarse aggregate has a negligible influence on the concrete.The influence degree of pressure application mode on the impermeability performance of the sintered aggregate concrete is the greatest among three kinds of concrete,which has a negligible influence on impermeability performance of the other concretes.POSGS-A can be used as a green building light aggregate in hydraulic concrete.

Effects of Cure Pressure Induced Voids on the Mechanical Strength of Carbon/Epoxy Laminates

This work aims at designing a set of curing pressure routes to produce laminates with various void contents. The effects of various consolidation pressures resulting in different void contents on mechanical strength of carbon/epoxy laminates have been examined. Characterization of the voids, in terms of void volume fraction, void distribution, size, and shape, was performed by standard test, ultrasonic inspection and metallographic analysis. The interlaminar shear strength was measured by the short-beam method. An empirical model was used to predict the strength vs porosity. The predicted strengths conform well with the experimental data and voids were found to be uniformly distributed throughout the laminate.

Cu^2+-catalyzed mechanism in oxygen-pressure acid leaching of artificial sphalerite

The potential autoclave was used to study the catalytic mechanism of Cu^2+during the oxygen pressure leaching process of artificial sphalerite.By studying the potential change of the system at different temperatures and the SEM–EDS difference of the leaching residues,it was found that in the temperature range of 363–423 K,the internal Cu^2+formed a Cu S deposit on the surface of sphalerite,which hindered the leaching reaction,resulting in a zinc leaching rate of only 51.04%.When the temperature exceeds 463 K,the system potential increases steadily.The increase in temperature leads to the dissolution of the CuS,which is beneficial to the circulation catalysis of Cu^2+.At this time,the leaching rate of Zn exceeds 95%.In addition,the leaching kinetics equations at 363–423 and 423–483 K were established.The activation energy of zinc leaching at 363–423 and 423–483 K is 38.66 and 36.25 kJ/mol,respectively,and the leaching process is controlled by surface chemical reactions.

An experimental study of interaction between pure water and alkaline feldspar at high temperatures and pressures

Due to the important scientific significance of the interaction between alkaline feldspar and high-temperature and high-pressure fluids. We have conducted a series of autoclave experiments of feldspar dissolution and secondary mineral precipitation in conditions of 250–500℃, 8-50 MPa, and pH = 3.0 and 5.5. Based on the interaction experiments between alkaline feldspar and fluid of high-temperatures and high-pressures, we get the main results as follows:(1) The law that people have grasped below the critical point about the influence of temperature, pressure, and pH value on the alkaline feldspar dissolution behavior is still held above the critical point.(2) Due to the experimental techniques of autoclave flip 180°—sharp quenching and based on electron microprobe analysis of mineral new formed, theoretical analysis has determined that the new altered minerals distributed on the island dissolution surface of feldspar are products of precipitation on a feldspar surface after saturation of the relative ion concentration in water fluid.

Rapid and Simple Extraction Method for Volatile N-Nitrosamines in Meat Products

A new methodology for extraction, pre-concentration and analysis of volatile nitrosamines in meat-derived products was developed and compared with conventional methods (Distillation and two-step solid-phase extraction). The samples (canned sausages, cured meat, luncheon and smoked meat) were treated with an aqueous sodium hydroxide (NaOH) by autoclaving at 121°C for 10 min and extracted by liquid-liquid extraction with dichloromethane, then the nitrosamines were pre-concentrated using activated silica. Then, gas chromatography coupled with flame ionization detector was used for the separation and determination of the different nitrosamines contained in a real sample and gas chromatography with mass spectrometry detection was used as the confirmation technique. The newly invented autoclaving method allowed the determination of nitrosamine compounds at trace levels with limit of detection ranged from 0.077 to 0.18 ppb and quantitation limits were from 0.26 to 0.6 ppb for all nitrosamines, and found to be superior to the conventional ones, yielding approximately about 10%-20% increasing in the recovery compared with the mean recovery obtained when applying conventional methods.

Thermal Insulation and Strength of Autoclaved Light Concrete

The primary objective of this study was to develop an autoclaved light concrete （ALC） material with ultra-thermal insulation property and to investigate the relationship between its physical characteristics and mechanical properties. Through tests of dry bulk density and compressive strength, relationship of physical characteristics and mechanical properties of samples were studied, resulting in a material with ultra-thermal insulation property. Scanning electron microscope （SEM） and energy-dispersive X-ray spectroscopy （EDX） were applied to analyze the micro-morphology and elemental composition of samples. To identify the product phases, X-ray diffraction （XRD） was engaged. The test results showed that compressive strength and thermal coefficient were reduced with the increasing of aluminum powder within the mixtures. As a result the optimal thermal coefficient and compressive strength of samples were improved to 0.061 W/（m·k） and 1.2 MPa, respectively. SEM, EDX and XRD analyses showed that calcium silicate hydrate and tobermorite crystal were main resultant phases.

A Computer-aided Design System for Framed-mould in Autoclave Processing

The general computer-aided design （CAD） software cannot meet the mould design requirement of the autoclave process for composites, because many parameters such as temperature and pressure should be considered in the mould design process, in addition to the material and geometry of the part. A framed-mould computer-aided design system （FMCAD） used in the autoclave moulding process is proposed in this paper. A function model of the software is presented, in which influence factors such as part structure, mould structure, and process parameters are considered; a design model of the software is established using object oriented （O-O） technology to integrate the stiffness calculation, temperature field calculation, and deformation field calculation of mould in the design, and in the design model, a hybrid model of mould based on calculation feature and form feature is presented to support those calculations. A prototype system is developed, in which a mould design process wizard is built to integrate the input information, calculation, analysis, data storage, display, and design results of mould design. Finally, three design examples are used to verify the prototype.

Preparation of New Cementitious System using Fly Ash and Dehydrated Autoclaved Aerated Concrete

We experimentally studied the interaction between pozzolanic material（fly ash） and dehydrated autoclaved aerated concrete（DAAC）. The DAAC powder was obtained by grinding aerated concrete waste to particles fi ner than 75μm and was then heated to temperatures up to 900 ℃. New cementitious material was prepared by proportioning fly ash and DAAC, named as AF. X-ray diffraction（XRD） was employed to identify the crystalline phases of DAAC before and after rehydration. The hydration process of AF was analyzed by the heat of hydration and non-evaporable water content（Wn）. The experimental results show that the highest reactivity of DAAC can be obtained by calcining the powder at 700 ℃ and the dehydrated products are mainly β-C2 S and CaO. The cumulative heat of hydration and Wn was found to be strongly dependent on the replacement level of fl y ash, increasing the replacement level of fl y ash lowered them in AF. The strength contribution rates on pozzolanic effect of fl y ash in AF are always negative, showing a contrary tendency of that of cement-fl y ash system.

Determination of Seven Volatile N-Nitrosamines in Fast Food

In this study, various fast food samples, including raw meat, cured meat, grilled meat, fried meat, smoked meat and canned meat products, were analyzed for the determination of the seven volatile N-nitrosamines. The samples were treated with an aqueous sodium hydroxide (NaOH) by autoclaving at 121°C for 10 min and extracted by liquid-liquid extraction with dichloromethane, and then the nitrosamines were pre-concentrated by using activated silica. Then, gas chromatography coupled with flame ionization detector was used for the separation and determination of the different nitrosamines contained in a real sample. The applied method allowed the determination of nitrosamine compounds at trace levels with limit of detection ranging from 0.077 to 0.18 ppb, and quantitation limits were from 0.26 to 0.60 ppb for all nitrosamines. The total concentrations of the seven nitrosamines in the studied meat samples ranged from 2.60 to 13.28 μg/kg.