Steelcasting nozzles of calcined dunite

Conclusions Dunite steelcasting nozzles were subjected to testing with melts of the entire range of steel grades produced by the Nizhne-Tagil Metallurgical Combine.The nozzles gave normal casting and no difference was noted in the behavior and wear of unfired dunite and magnesite nozzles with channel diameters of 30 and 70 mm. The quality of rail steel in terms of surface flaws was the same for both nozzle types.In casting wheel and tire steels the experimental nozzles proved to be superior. Dunite nozzles are less susceptible to channel constriction but more susceptible to burn-through by oxygen.Channel encrustation was more prevalent in fired than in unfired dunite nozzles but less prevalent than in unfired magnesite nozzles, in addition to which wear was more rapid in the case of the latter.Translated from Ogneupory, No. 4, pp. 3–7, April, 1975.     

Crystallization of Precursors to Forsterite and Chromium-Doped Forsterite

The pyrolysis and crystallization of poly(methacrylate) precursors and xerogels of forsterite and chromium-doped forsterite were studied by in situ high-temperature, dynamic X-ray diffraction and thermal analysis. For both types of precursor, crystallization of forsterite occurred at lower temperature when doped with chromium. Also, exotherms above 700°C occurred 50°C lower when chromium was present. When residual carbon in the xerogels was more than ∼1%, an unidentified crystalline intermediate phase formed at ∼800°C. Conversion of the intermediate phase to forsterite was faster than amorphous material. Thus, full crystallinity was attained at a lower temperature when the xerogels had some residual carbon.     

煅烧磷石膏对蒸压硅酸盐制品水化过程的影响

磷石膏经高温煅烧改性后与粉煤灰、砂粉、石灰及水泥熟料等制备蒸压硅酸盐制品,研究了不同温度煅烧的磷石膏对蒸压硅酸盐制品水化过程的影响,用蒸压制品中未反应的Ca(OH)₂量及结合水量分析它们的反应速率,用XRD测定蒸压硅酸盐制品的水化产物,并结合SEM分析,结果表明,经煅烧的磷石膏对蒸压硅酸盐制品的水化有明显的促进作用,托勃莫来石与C-S-H(1)等水化产物的迅速生长而形成密实的水化产物结构是其增强蒸压硅酸盐制品的根本原因。     

利用硼泥制备镁橄榄石质多孔陶瓷

利用硼泥废渣、钾长石、羧甲基纤维素钠等原料在950～1200℃不同烧结温度下制备了具有一定强度和气孔率的多孔陶瓷样品。利用TG,DTA,XRD、气孔率、抗弯强度和抗压强度等方法对陶瓷样品进行测试分析。优选获得了抗弯强度达10～33MPa,抗压强度为10～40MPa,气孔率达30％的镁橄榄石质多孔陶瓷。     

以焙烧膨润土为原料合成白榴石工艺研究

以焙烧膨润土为原料,添加一定量的硫酸钾和硫酸铝,利用熔盐法合成了白榴石晶体。采用正交试验分析法,研究了钾硅物质的量比、煅烧温度和保温时间对白榴石合成过程的影响,并确定了合成白榴石的优化工艺条件。采用热重-差示扫描量热分析（TG-DSC）、X射线衍射分析（XRD）和扫描电子显微镜（SEM）对样品进行了表征,进而提出白榴石合成机理。     

用纯橄岩制备硫酸镁的工艺研究

介绍了以纯橄岩为原料,采用酸浸法制备七水硫酸镁的工艺方法.研究并讨论了硫酸浓度、酸浸温度、酸浸时间、矿粉粒度、搅拌速度等因素对纯橄岩分解和七水硫酸镁制备的影响.具体制备方法及工艺条件:将纯橄岩在700 ℃煅烧4 h,用4 mol/L的硫酸溶液于100 ℃处理2 h,过滤,滤液经双氧水氧化,用氨水调pH=7.0～8.0,过滤除杂得到滤液,滤液经冷却结晶,在40～45 ℃烘干2 h后得粗硫酸镁晶体;粗硫酸镁晶体经重结晶,得高纯七水硫酸镁晶体.在此工艺条件下镁的浸出率可达97.86%,产品纯度为99.1%.产品符合HG/T 2680-1995工业七水硫酸镁的要求.     

Zn-Al水滑石及其焙烧产物对水中磷的吸附研究

用水热法制备了不同尿素浓度下的Zn-Al水滑石,焙烧后制得焙烧态水滑石,用XRD、SEM 、BET、FTIR等方法对样品进行了表征,考察了水滑石及焙烧产物对水中磷酸盐的吸附性能.结果表明:水滑石对磷酸盐的吸附基本符合假二级动力学方程和Langmuir吸附等温式,当尿素浓度为0.6 mol/L,150℃水热24h,300...     

Forsterite refractories from the dunites of the Kytlym deposits

Conclusions Kytlym dunites consist mainly of olivine. Their calcination loss is low and their density and strength after firing are adequate.The physicochemical properties of the refractories produced from dunite not fired beforehand are better than those of the refractories produced from fired dunite.All refractories produced from Kytlym dunites satisfy the requirements of GOST 14832-69.Translated from Ogneupory, No. 5, pp. 27–32, May, 1977.     

水滑石及其焙烧产物对水中苯甲酸根的吸附研究

为了脱除水中的苯甲酸根,以苯甲酸作为吸附质,研究了水滑石及其焙烧产物的吸附作用。考察了吸附剂的镁铝摩尔比、初始pH值、苯甲酸浓度、吸附剂添加量、吸附时间和温度对吸附效果的影响,并对比考察水滑石和焙烧水滑石对苯甲酸的吸附。结果表明,水滑石及其焙烧产物对苯甲酸的最优吸附条件均为酸性环境下,镁铝摩尔比3∶1,吸附质浓度220 mg/L,吸附剂的量0.06 g;水滑石吸附时间20 h,吸附温度为60℃时,对苯甲酸的去除效果最好;而焙烧水滑石在室温下吸附苯甲酸8 h达到最高去除率;在同样条件下,水滑石焙烧产物比水滑石对苯甲酸的吸附大得多。     

Engineered morphologies of layered double hydroxide nanoarchitectured shell microspheres and their calcined products

CoFe^IIFe^III-layered double hydroxide (LDH) hollow spheres with two distinctly different hierarchical morphologies—flower-like and raspberry-like, involving edge-on and face-on oriented LDH platelets as building blocks, respectively—can be fabricated by tuning the rate of addition of NaOH solution in a coprecipitation process with sulfonated polystyrene spheres as a template. Ex situ pH-dependent microscopic observations of the formation of the flower-like LDH shells shows the details of non-classic nucleation and growth underlying the edge-on orientation. After calcination, the resulting CoFe₂O₄ materials retain the hierarchical morphology of the corresponding LDH precursor. The hollow CoFe₂O₄ spheres with raspberry-like morphology exhibit magnetic properties comparable to a reference material obtained by calcination of a conventional LDH powder precursor. Similar materials with tunable magnetic properties can be prepared by virtue of the flexibility in LDH layer composition. The CoFe^IIFe^III-LDH spheres with a raspberry-like morphology may be also be prepared by using a scalable procedure involving separate ultra-rapid nucleation and aging steps in a modified colloid mill reactor. The results reported here may open up the possibility of producing shell structures with controllable morphologies and properties on a large scale.     

Forsterite refractory brick produced by talc and magnesite from Thailand

This research focuses on refractory material synthesized from precursors of talc and magnesite in Thailand. They were mixed at a molar ratio of 1:5 with mechanical activation at 5 h and calcined at 1300 °C for 1 h to create forsterite. The resulting forsterite crystals were round with less than 1-μm particle size. Synthetic forsterite refractory was formed into refractory bricks and studied at various sintering temperatures of 1200, 1300, and 1400 °C with a dwell time of 2 h. The characteristics and properties of refractory samples were tested in physical properties, cold crushing strength, thermal conductivity, thermal shock, and corrosion resistance from various substances. The results showed that increasing the sintering temperature increases the physical properties and cold crushing strength values. Also, the sintering temperature increases will increase thermal conductivity. The best condition of forsterite refractory brick sintering was 1400 °C for 2 h (FB-14), which showed the following desirable properties: firing shrinkage of 18%, bulk density of 3.03 g/cm³, the apparent density of 3.26 g/cm³, both apparent porous and water absorption values of zero, and cold crushing strength of 72.18 MPa. The FB-14 brick has excellent resistance to corrosion and penetration from lead silicate frit and copper slag. There was minor weight loss from the corrosion of the chemical solutions used in sodium hexametaphosphate production, whereby weight loss will begin on the 18^th cycle. Consequently, the FB-14 brick can be used for blast furnace walls to slow down corrosion, which will allow the blast furnace to have a longer life cycle.     

Synthesis and characterization of Cu–Co–Fe hydrotalcites and their calcined products

A series of new Cu–Co–Fe compounds with the general formula Cu _x Co_2−x Fe₁HT (x = 0, 0.5, 1, 1.5 and 2) has been prepared by hydrotalcite coprecipitation method. The presence of hydrotalcite phase is revealed by XRD analysis for x values of 0, 0.5 and 1. When the copper quantity is higher than 1, the malachite phase is preferentially formed. These results are confirmed by TG-DTA, FT-IR and XPS analysis. After calcination at 500 °C in air of all samples, XRD analysis reveals the presence of spinel phases such as Co₃O₄, CoFe₂O₄, CuFe₂O₄, Cu _x Co _y O₄ in the solids, monoclinic CuO phase when the copper content is greater or equal to 1 and haematite phase for the sample where x is equal to 2. The presence of these phases is also confirmed by XPS results. For comparison, a Co₂Fe₁OH sample has been synthesized by classical coprecipitation method and although Co₂Fe₁HT sample and Co₂Fe₁OH form a similar phase after calcination at 500 °C, Co₂Fe₁HT500 presents a higher BET value than Co₂Fe₁OH500 sample.     

Defluoridation of drinking water by Mg/Al hydrotalcite-like compounds and their calcined products

Fluorosis, developed in the population who depends on water with high concentrations of fluoride for their daily drinking usage, is one of the most frequently occurring endemic diseases. To search for effective defluoridation agents, we studied F⁻ adsorption by synthetic Mg/Al–CO₃ hydrotalcite-like compounds (HT) and their calcined products (HTC). The adsorption experiments were carried out as a function of time, pH, and the adsorbate concentration. The affecting factors to fluoride sorption were found to be solution pH and the crystallinity of the HT. The results from our adsorption experiments indicated that F⁻ uptake by HTC was much stronger than their precursors HT. It was further observed that the maximal adsorption takes place within the first 15 min. HTs and HTCs exhibit a reversed trend in F⁻ uptake with regard to temperature of the hydrothermal treatment to HT. At any specific initial F⁻ concentration, the removal efficiency of F⁻ increases with the temperature for HTC, but decreases for HT. The removal efficiency is inversely related to the initial fluoride concentration for HTC obtained from HT synthesized at 130 °C (HTC130, the most efficient adsorbent seen in this study). The adsorption isotherm at pH 7 for HTC130 was linear and did not follow Langmuir equation; the K value (slope of the line) was calculated to be 0.46 L/g. HTC130 was shown to be able to bring F⁻ concentration from 5 mg/L down to less than 1 mg/L in aqueous solution, suggesting that this material may be a possible candidate for F⁻ removal.     

Monticellite and Forsterite Crystalline Solutions

New data for monticellite crystalline solutions confirm that monticellite (CaMgSiO₄ is unstable at atmospheric pressure. On the join forsterite-monticellite, the estimated range of stable monticellite crystalline solutions is 89 to 93 mol% monticellite at 1200°C and 75 to 92 mol% at 1490°C. The range of forsterite crystalline solution is 93 to 100 mol% forsterite at 1200°C and 81 t0 100 mol% at 1490°C. These results can be applied to the proportions of phases present in impure periclase refractories at service temperatures.