CO_2硬化水玻璃旧砂的湿法再生探索

现代铸造业发展的一个重要目标是绿色铸造。水玻璃砂是最有可能实现绿色制造的型砂,水玻璃旧砂的再生回用是其关键。本文探讨了不同转速、时间、温度条件下湿法再生CO2硬化水玻璃旧砂的效果。结果表明:适宜的参数为转速800 r/min,时间10 min,温度80℃,用水量1∶1,再生砂残留碱约为3%。     

一种减少超细粉的砂加工生产线

设计一种砂加工生产线,在原矿破碎前采用一种滚筒筛对原矿物料进行过滤,减少过磨产生大量的超细粉。该系统主要安装了滚筒筛与配套输送皮带,将不同粒度的物料进行分级处理,合格粒度以下的物料直接进入选矿系统,分级出来的大颗粒物料再利用皮带机经过破碎、碾磨处理,达到可防止过磨产生超细粉,提高工作效率,降低物料损耗的效果。     

固体废弃物在绿色建筑砂浆中应用的研究进展

论述了粉煤灰、矿渣、尾矿砂、钢渣、废玻璃等固体废弃物在绿色建筑砂浆中应用的研究进展。固体废弃物在砂浆组分中的应用主要表现在胶凝材料、砂浆骨料与掺合料等方面,结合文献,分析了固体废弃物掺入对绿色砂浆性能影响,并且指明存在的问题,最后对固体废弃物在绿色砂浆中应用与发展前景提出展望。     

Foundry qualities and applications of local synthetic sand mixtures

Synthetic sand mixtures were compounded from a dredged sand bonded with clays of different plasticity. The foundry qualities of the mixtures were studied for their possible application in synthetic sand moulds for foundries. The clays utilized are fireclay from Enugu and Ogharaki clay from Delta State, Nigeria. Properties studied include: classification characteristics, the green and the dry compressive strengths, the permeability and the shatter index.Results indicate that the more plastic Ogharaki clay is a better binder, at least on the basis of the green strength and the shatter index. Moulds made of fireclay are slightly more permeable at lower moisture content. Apart from these, mixtures of any of the bonding clays developed the best qualities with about 8% binder content and a water content ranging from 3.5 to 4.0%. The study also shows that the synthetic sands would be suitable for steel and general purpose casting considering the low water and the low binder contents of the mixtures.     

沙漠砂制备混凝土研究进展

采取“因地制宜,就地取材”策略,合理地将沙漠砂用于混凝土制备,是缓解西北地区建筑用砂供需矛盾的一种有效途径。本文首先通过文献研究与统计分析相结合的方法,归纳总结了不同地区沙漠砂基本理化特性;其次,梳理了现阶段沙漠砂制备混凝土研究状况,并对其所存在问题进行了总结概括;最后,展望了沙漠砂混凝土未来研究发展方向。研究表明,沙漠砂在一定条件下可替代或部分替代骨料用于制备混凝土,沙漠砂部分代替河砂制备的混凝土的工作性、力学性能及耐久性(抗冻性、抗高温性)能够满足一般的工程要求,部分情况下甚至优于普通混凝土。本研究可为沙漠砂混凝土在实际工程中的应用提供借鉴,并可为实现沙漠砂的绿色开采及资源化利用提供新的模式参考。     

Influence of Mold Material on the Mold Stability for Foundry Use

Silicon - In CO2 molding process, sodium silicate is used as a binder to form a chemical bond to have high strength, good dimensional accuracy, etc. as compared to green sand mold. The mold...     

16.00-20 16PR沙地轮胎的开发

介绍16.00-20 16PR沙地轮胎的开发情况。轮胎模型两胎圈间的距离比设计轮辋宽度增大12.5 mm可改善下胎侧屈挠较大的问题;胎冠部位设置4层缓冲帘布层,胎冠帘线角度取49°,可减小机头直径和宽度,优化胎坯断面高宽比;拱形行驶面和浅而窄的花纹沟设计适合沙地使用。成品轮胎性能符合设计要求。     

油砂沥青超临界水热改质研究进展

油砂沥青超临界水热改质技术作为一种新型的绿色工艺,具有原料转化率高,体系结焦量少,脱硫、脱硝、脱重金属效果明显等优点;但迄今为止学术界对该过程的机理及相态变化情况仍无法进行准确的描述,尤其是对超临界水在体系中的作用仍存在争议。本文总结了油砂沥青超临界水热改质技术的机理,重点分析了超临界水在体系中的作用,简述了供氢剂和催化剂的研究情况,同时从相行为方面提出了提高体系改质效果的方法。分析表明超临界水在体系中的供氢效果并不显著,而更多的是以催化剂的作用存在。固体催化剂在该体系中的应用存在诸多缺陷,供氢剂的开发将成为油砂沥青超临界水热改质技术的发展方向,且供氢剂和自由基引发剂的应用将极大缓和工艺条件、降低设备要求,有利于促进该工艺的工业化。     

真空去水压制成型对机制砂混凝土性能的影响

为顺应当今建筑工业化和固废资源化趋势,工程界提出了采用真空去水压制成型新工艺,以实现机制砂混凝土的高效预制生产。本文研究了真空去水压制成型时间对不同初始水灰比(W/C)机制砂混凝土性能的影响,结果表明：与天然砂混凝土相比,真空去水压制能更显著提升机制砂混凝土的强度,主要是由于在高密实成型条件下,机制砂充分发挥了嵌锁效应,经真空负压-0.07 MPa及压制15 MPa处理100 s后,机制砂混凝土初始W/C从0.58降低至0.32,抗压强度提升了44.6%,延长处理时间性能提升效果减弱,尤其是对W/C较小的混凝土;压汞测孔(MIP)发现真空去水压制后混凝土硬化体孔隙率大幅降低,尤其是大于50 nm的有害孔,与压制前相比,其比例下降均超过70%,孔径分布得到了改善,且水化程度均提高至0.6以上;扫描电子显微镜(SEM)和X射线衍射(XRD)表明,经真空去水压制处理后,混凝土内硬化浆体变得更密实,定向排列的针状钙矾石及片状Ca(OH)₂含量减少,而界面过渡区(ITZ)黏结性能提高。采用真空去水压制成型机制砂混凝土,符合现代预制混凝土构件生产的绿色、节能、环保发展要求。     

透水型泡沫混凝土的制备及其水分保持性能研究

海绵型生态城市是目前我国正在大力推行的城市建设的目标,城市道路、绿地、排水管网等市政设施不但具有快渗快排功能,还应具有一定的水分保持功能.基于传统的泡沫混凝土,采用发泡剂与产气剂协同使用的方法制备了兼具透水和保水功能的泡沫混凝土.并系统研究了水灰比、发泡剂掺量、砂掺量和玻璃纤维掺量对材料透水性的影响规律,在此基础上研究了材料的水分保持性能与透水性能的相关性.结果表明:材料的透水性能随水灰比、发泡剂掺量、砂掺量的提高先增大后减小,并随着玻璃纤维掺量的提高逐渐减小.通过合理控制制备工艺,可获得具有较好透水率和保水性的泡沫混凝土材料,以满足海绵城市的建设的需求.     

Micropatterning of photosensitive glass-ceramic-polymer composite by sand blasting

Abstract

A photosensitive, sandblasted composite was used to achieve a high aspect ratio of barrier ribs. The authors investigated the erosion of the photosensitive composite prepared with two different pastes: normal and photosensitive. The barrier ribs underwent micropatterning with calcium carbonate powder as the sand blasting erodent material. The patterned green barrier ribs were fired in an air atmosphere and the thermal, physical and mechanical properties of the resulting composites were determined by thermal gravimetric analysis, atomic force microscopy, nanoindentation, and peel testing. The photosensitive composite had better adhesion with a dry film resist and showed lower porosity, surface roughness, stiffness and elastic modulus than a normal composite, which was attributed to the remaining polymer. In the process, the developed photosensitive composite and the dry film resist film were able to withstand the impact of the separated particles or clusters. These results support the use of sand blasting to fabricate the micropatterning of barrier ribs with two layers of photosensitive composite.     

工艺参数对石英质多孔材料孔性能的影响

以长江沿岸低品位石英砂为主要原料,采用真空烧结制备了石英质多孔材料。通过实验分析发现:随烧结温度的升高、水料比的增大或发泡剂含量的增加,多孔材料的气孔率增大,抗压强度降低;而随着保温时间的延长,多孔材料的气孔率降低,抗压强度升高。通过优化得出最佳配比为:石英砂60 wt%、高岭土30 wt%、助烧剂9.6 wt%、发泡剂0.4 wt%。按这一最佳配比配料,在水料比为0.9的条件下球磨2 h制浆发泡,而后在1175°C烧结1 h,可以制备得到性能较佳的石英质多孔材料。     

Autofluidization: The fluidization of solid particles by gases evolving from the particles

An experimental procedure was developed to study the autofluidization (i.e. the fluidization of solid particles by gases evolving from the particles) of green coke. It was found that the best method was to heat a 30 cm deep bed of 178 μm quartz sand to 800°C while fluidizing it with air and then adding a small batch of ?1 mm coke particles to the surface of the bed. After allowing the coke to mix with the sand for 20 s, the fluidizing air was reduced to a lower rate. Pressure is then measured as a function of height in the bed and time. The result is a series of pressure measurements which decay smoothly from the fluidized state to a new steady state once all the coke's volatiles have been released. From these measurements it is possible to calculate gas velocities in the bed as well as bed voidage and apparent density. It was found that the upper sections of the bed would remain fluidized for up to nearly 2 min after the coke was added to the sand while the lower parts of the bed were never fluidized. Simple theory, in the form of the Blake-Kozeny equation, does a good job of predicting when autofluidization will occur and what the changes in bed height and pressure are within the bed.     

Condensation and hydrophobicity of the surface hydroxyl groups between organosilane modified water glass and microsilica

As one of the novel green foundry binders, the bonding strength of two-component inorganic binder system (water glass-microsilica) under wet conditions needs to be further improved. In this work, γ-(methacryloxypropyl) trimethoxy silane (MPS) was added to water glass. The effect of MPS on the storage stability of sand core was studied, based on which the mechanisms of condensation and hydrophobicity of water glass-microsilica were discussed. The results showed that the maximum bonding strength of 1.0 wt% MPS modified sand core was increased by 15.5% at 80–85% RH. MPS promoted the dehydration condensation between water glass and microsilica, which will make its three-dimensional network more complex. Moreover, it formed a hydrophobic organosilane layer on the surface of the bonding bridge, which can play a role in shielding hydrophilic Na⁺ and prevent the destruction of bonding film by forming Si–O–R bonds, preventing the external water from damaging.     

改性夯土墙材的强度影响因素相关性研究

夯土建筑是中国传统民居建筑的主要形式之一。它具有就地取材、冬暖夏凉、施工方便、能耗低、绿色环保等优点,应在美丽乡村建设中得到极大的传承和应用。但传统夯土墙材由素土构成,存在强度低、耐水性差等缺点,从而限制了其推广使用。以四川西北地区的素土为原料,选用水泥、砂、碎石、纤维、EFS(易孚森)土体稳定剂为改性材料制备改性夯土墙材,以期提高其抗压强度,并研究改性后各影响因素与抗压强度的相关程度,以及微观改性机理。结果表明,龄期、水泥掺量、砂及碎石总掺量、EFS掺量、纤维种类与抗压强度之间的偏相关系数依次为0.77、0.72、0.68、0.64、0.61。水泥、砂及碎石骨料、EFS土体稳定剂掺量的增加和龄期的增长,均有利于提高试件的抗压强度。通过XRD、IR、SEM分析可知,水泥水化反应产生的胶凝产物与土颗粒之间进行包裹、填充、连接,整体结构间孔隙率减少,形成更致密而稳定的微观结构,从而提高了改性材料的抗压强度。     

The determination of porosity in iron ore green pellets by packing in silica sand

Porosity is a very important property of iron ore green pellets. At LKAB, the mercury porosimeter was replaced some years ago by the GeoPyc instrument, in which the sample volume is measured by packing in silica sand. Some critical features of the GeoPyc measurement are pointed out in this study. The green pellets need to be strengthened by spraying with a fast-drying lacquer before measurement. A system for continuous instrument control is needed to detect any wear on the measuring tools that might lead to erroneous measurement results. The reproducibility measured on steel spheres was ± 1% (2σ), which is equal to the reproducibility given by the instrument manufacturer. The reproducibility measured on lacquer-strengthened green pellets used as in-house reference samples was, however, much better, ± 0.3% (2σ). The calibration error against mercury porosimetry was improved from ± 0.6% to ± 0.2% (2σ) after introducing the changes specified in the text. The GeoPyc instrument is easy to use and the problematic handling of mercury is avoided.     

Synthesis of MgSiO3 ceramics using natural desert sand as SiO2 source

High-quality inorganic minerals are being increasingly consumed in the fabrication of ceramics. In the present work, desert sand was adopted as the source of SiO₂ to synthesize MgSiO₃ and MgSiO₃SiC composite ceramics in an endeavor to economize on mineral resources and improve the desert ecosystem through the industrial application of desert sand. Experimental results show that the use of drift sand enabled the formation of glass phase at lower temperatures, which promoted protoenstatite transformation, prevented sintering cracking, and densified the ceramic bodies. The composites consisted of MgSiO₃ (protoenstatite), SiC, glass phase, and small amounts of forsterite and SiO₂. The addition of SiC particles caused the green bodies to resist densification, but this was improved by increasing the sintering temperature. The composite ceramic containing 30 wt % of SiC and sintered at 1350 °C had the highest bending strength, whereas that containing 50 wt% of SiC and sintered at 1400 °C had the highest hardness and the lowest coefficient of thermal expansion among all the samples.     

Effect of Operating Temperature on Water‐Based Oil Sands Processing

Operating temperature is one of the most important controlling parameters in oil sands processing. Considering the massive energy consumption and green house gas emission, lowering the processing temperature is highly desirable. To achieve such an ambitious goal requires a comprehensive understanding on the role of temperature in oil sands processing. This paper provides an overview of major findings from existing studies related to oil sands processing temperature. The relation between temperature and bitumen recovery is discussed. The effect of temperature on the physiochemical properties of oil sand components, such as bitumen viscosity, bitumen surface tension and surface potentials of bitumen and solids, is analyzed. The interactions between bitumen and solids and between bitumen and gas bubbles as a function of temperature are recounted. Also discussed is the role of chemical additives in oil sand processing. It has been found that temperature affects nearly all properties of oil sands among which bitumen viscosity and bitumen‐solids adhesion impose a prominent impact on bitumen recovery. The use of selected chemical additives can reduce bitumen viscosity and/or the bitumen‐solids adhesion, and thus provide a possible way to process oil sands at a low temperature while maintaining a high bitumen recovery.     

Use of industrial wastes in the formulation of olivine green pigments

This work describes the formulation and synthesis of Ni-olivine green pigments from industrial wastes, namely foundry sand and a sludge resulting from the wastewater treatment of the Ni/Cr galvanising process. This second one is considered as hazardous waste since the leached levels of nickel and chromium are above legal concentrations. Pigments were prepared by the solid state reaction method and Ni₂SiO₄ is formed at only 1050 °C. SiO₂ (in excess) and NiCr₂O₄ are present as secondary phases. By using pure reagents and following similar processing conditions, the Ni-olivine phase is only observed at 1200 °C. The green colour of the pigments is due to spin-allowed transitions of Ni²⁺ in octahedral M1 and M2 positions. The sample prepared from wastes shows a stronger and darker green hue. The colouring performance of ceramic glazes and bodies is also optimal, confirming the potential of the use of such wastes for ceramic pigments production.     

Preparation of high–strength closed–pore foamed ceramics from desalted sea sand at temperatures below 1000 °C

Based on high–temperature sintering with SiC as the foaming agent, the technical potential of preparing foamed ceramics (FCs) from desalted sea sand at temperatures below 1000 °C was studied. Rapid melting of the ceramic bodies at elevated temperatures helped to seal more foaming gas, resulting in a large foaming volume for the FCs. If the interior of the ceramic bodies melted quickly during sintering, the foaming gas was trapped in situ, resulting in a homogenous FC pore structure. By coordinating the borax content and sintering temperature of the green bodies, the melting characteristics of the ceramic bodies could be optimised during sintering, usually producing a large foaming volume and a homogeneous FC pore structure. The FCs sintered from the green bodies with 25–35 wt% of borax at 900–1000 °C obtained high total/closed porosities of (68–75)%/(65–72)%, a relatively dense surface, a homogenous pore structure, and a relatively high compressive strength of 8.1–11.2 MPa.