Mineralogy and physico-chemical properties of alluvial clays from Sanaga valley (Center,Cameroon): Suitability for ceramic application

Alluvial clays from four localities along the Sanaga River (Center Cameroon) were studied by physico-chemical, mineralogical and technological characterization in order to assess their suitability as ceramic raw materials. The chemical compositions indicated that SiO₂ (65–70%) and Al₂O₃ (12–15%) are major elements while Fe₂O₃ is less (4–7%). Kaolinite, quartz and feldspar are the main minerals. Particle size distribution and chemical composition are indicative of “plastic red clays” belonging to heavy sandy clays group. Their medium to high plasticity is suitable for fired earth and fine ceramics products. Pressed samples were fired at temperatures ranging between 900 and 1100 °C for coarse ceramic products. Linear shrinkage, flexural strength and water absorption indicated that the clays from one site (Mbandjock) are good for brick making. Clays from the three other localities present poor technological properties (higher shrinkage and cracks), they need degreasers before use as ceramic raw materials. Although water absorption and flexural strength parameters are good for all the studied samples, firing shrinkage needs to be improved.     

氧化锆活性对烧结性能的影响

分别以化学法和电熔法制备的氧化锆及二者混合共磨粉为原料,通过造粒、成型、干燥、烧成制得样品,对烧成样品物理性能和微观结构进行分析,研究原料活性对烧结性能的影响.研究结果表明:在加入同样稳定剂的条件下,电熔氧化锆活性较差,烧结后气孔率较高,化学氧化锆烧结后收缩大,开裂严重,两者都无法满足作为制备氧化锆质定径水口基质原料要求,当二者的混合比例为1:1时,试样的烧结温度合适,气孔率、烧成收缩、耐压强度等各项理化指标较好,满足用作制备氧化锆质定径水口基质要求.     

AN INVESTIGATION OF TWENTY-ONE SASKATCHEWAN BALL CLAYS1

Twenty-one Saskatchewan ball clays have been investigated; the study covers in a general way their chemical, raw, and fired properties. The information presented will no doubt prove of immediate interest to the ball clay trade and especially to the Saskatchewan shippers and exporters. In general, the more outstanding properties of the clays studied are raw strength, fired color, craze resistance, and rate of vitrification. Their raw strength is remarkably high, greater than that of any similar clay on the market at the present time. One clay developed the exceptional raw strength, though diluted with 50% potters’ flint, of over 1000 lbs. per square inch, a second one 938 lbs., while the average of the eleven highest is 812.8 lbs.; clays of such high strength should prove of interest to the trade where it is desirable to reduce losses in the raw and bisque state. A number of the clays tested are outstanding as ball clays in that they fire white or nearly so up to and including cone 12, the purity of whiteness being equal to that of white firing china clays. The porosity and fired volume shrinkage of the Saskatchewan clays correspond more nearly to those of the English ball clays than do the Tennessee-Kentucky clays as studied by Sortwell.     

拉伸速率对尼龙6力学性能和颈缩区结晶度的影响

以己内酰胺为原料,通过开环聚合法制备了尼龙6材料。利用电子万能试验机对尼龙6材料进行了10,20,50 mm/min三种不同速率的拉伸实验,结果表明,随着拉伸速率的增加,尼龙6的屈服强度略有增加,而断裂伸长率和断裂能则大为减少。利用差示扫描量热仪对拉伸后试件的结晶度进行了测试,结果表明,在颈缩区有新的晶型生成;随着拉伸速率的增加,结晶度也随之增大,当拉伸速率为50 mm/min时,其颈缩区结晶度比初始结晶度提高了27.5%。     

Influence of mineralogical composition of applied ball clays on properties of porcelain tiles

Relations between quality of ball clays applied in raw materials batches for manufacture of porcelain tiles, and physical properties and microstructure of obtained tiles, were investigated. Studied clays constituted 35% of the batch, while the other components were unchangeable. Stoch index, new IR 3620/3700 index and XRIR index (Stoch index multiplied by IR 3620/3700 index), were proposed to take into account crystallinity of kaolinite and contents of illite and smectites in studied clays. Relationship between XRIR index value of clay, and water absorption and abrasion resistance of the obtained ceramic material, was found. Water absorption of the tile is also correlated with grain size distribution and bending strength of used clay. Optimal ball clay for porcelain tile production should exhibit: Stoch index - min. 4.3; IR 3620/3700 index - min. 1.2; XRIR index - min. 4.8; grain size median - max. 0.27 μm; bending strength after drying - min. 8.0 MPa.     

Biodegradable PLA based nanocomposites for packaging applications: The effects of organo-modified bentonite concentration

The effects of concentration and surface modification of two Brazilian bentonite clays on nanocomposites' properties based on polylactic acid – (PLA) were investigated. The samples were prepared by the extrusion/injection method to obtain biodegradable packaging plastics. The raw materials and their bionanocomposites were characterized by various techniques. Natural clay samples presented a size of around 2 μm while the modified ones' size was 5–6 μm, probably due to the presence of cetyltrimethylammonium bromide in the interlayer space. The particle size and the contact angle increased with the treatment and the clay's density decreased. The organoclays were homogeneously dispersed in PLA, which can be associated with the interactions between PLA chains' carbonyl groups and the organoclays. The bionanocomposites present modified clay particles axis aligned to the flow direction of the extruder/injector. Chocolate organoclay acts as a nucleating agent to PLA crystal growth, increasing the sample's crystallinity, while Bofe organoclay interferes with the amorphous chain's mobility and diminishes the sample's crystallization. The addition of both organoclays to PLA diminished the sample's elongation at break and strength, although the organoclays increased the sample's Young modulus, even though Bofe organoclay is more active in PLA amorphous phase and Chocolate organoclay on the crystalline one.     

粉煤灰为基制备耐火材料的研究

以粉煤灰为主要原材料,煤矸石和工业氧化铝为辅料,通过控制物料比例制备了不同Al2O3含量在不同烧结温度下的耐火材料.对所制备材料进行结构性能测试,并借助X射线衍射和扫描电镜对材料进行微观分析.实验结果表明:不同的烧结温度及氧化铝含量对耐火制品的致密性、力学性能、耐火度和晶型状态都有影响.制品在1350 ℃、Al2O3的含量为45%时,其性能指标为:体积密度2.47 g/cm3、常温耐压41 MPa、耐火度1450 ℃、晶型状态以莫来石相和刚玉相为主.该制品的力学性能和使用性能较好,可为进一步利用粉煤灰制备高附加值材料奠定基础.     

Effect of the plant waste onto the properties of use and the microstructure of phyllosilicates based ceramics

The present study aimed at using plant waste (Musa Paradisiaca) for manufacturing clay-based ceramics in order to promote lower sintering temperature while preserving the properties of use. Two kaolinic-illitic clays (NZ1 and KO) from Central African Republic were used mixed with 1 to 10 mass% of the plant waste (MP). The clays and the waste exhibited accessory phases: quartz and iron oxides, and K₂O respectively. MP was collected, dried and sieved (<100 μm) previously to its mixture with clays. According to the sintering behavior of KO and NZ1 derived from thermodilatometry, the densification was obtained after firing at 1200°C. Results showed that open porosity decreased from 35% to 17% with increasing temperature in the range 900 to 1200°C for KO and NZ1. This porosity remained in the range 30%-40% while increasing the MP content (firing at 1000°C for 1h.). The optimized MP content was 3 and 5 mass% for KO and NZ1 clay materials respectively. The compressive strength and thermal conductivities were improved compared to clay samples without MP fired at 1200°C. Moreover a significant decrease in the sintering temperature was achieved, leading to energy saving in line with sustainability issues.     

铝矾土-伊利石-高岭土体系陶瓷材料制备工艺的研究

以生铝矾土、高岭土和伊利石为主要原料,采用传统陶瓷工艺方法,制备了铝矾土-伊利石-高岭土体系陶瓷材料。以Al2O3质量分数在60～65%范围的坯料为研究对象,研究了原料配比和坯料细度等因素与试样的烧成温度及抗弯强度的关系。利用XRD、SEM等分析手段对材料的物相组成和显微结构进行了表征。结果表明:铝矾土-伊利石-高岭土体系陶瓷材料,在1320～1360℃烧结范围内能够制备抗弯强度110～140MPa的高强度陶瓷材料;提高铝矾土的含量和原料的细度均有利于强度的提高;添加适量的滑石有助于强度的提高以及烧结温度的降低;在原料配比相同的条件下,烧结范围下限附近烧成的试样强度较高。     

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。     

一种新型3D打印成型-脱脂-烧结工艺

基于316L不锈钢粉末与高分子材料配方,首先利用开炼机对配方材料进行充分混炼,粉碎、干燥后,制备出大小相对均匀的物料混合物颗粒。然后利用自主研制的粉体喂料3D打印机,对金属坯体进行3D打印,随后采用溶剂脱脂法对金属胚体进行脱脂,最后对其进行烧结实验,研究在不同烧结工艺条件下所得试样的物理机械性能,由此分析确定最佳的烧结工艺。结果表明,随烧结温度升高,烧结制品的致密化程度逐步增加,各项物理机械性能也逐步提高,在1370℃烧结工艺条件下,所得金属制品各项物理机械性能最佳,且和传统粉末冶金制品相接近,其烧结密度达7.43 g/cm3,抗拉强度达501.2 MPa,冲击位移达4.54 mm,延伸率达27.1%,抗弯曲力达16.54 KN ,硬度达80.74 HRB。同时,通过微观对比、机理分析及实验验证,印证了1370℃为最佳的烧结工艺,烧结制品具有成分均匀、组织细小和性能稳定等优点。     

非厌氧消化与厌氧消化污泥制备烧结保温材料性能研究

利用几种不同污泥制备烧结保温墙体材料,对比非厌氧消化污泥与厌氧消化污泥制备烧结保温墙体材料的性能。首先分析研究原料的物理、化学性能,结果表明,重庆地区的页岩适宜作为制备污泥砖的掺配料,最佳烧成温度为950℃;污泥具有高含水率,高发热量和高烧失量等特点。其次,选择综合性能较好1#污泥和4#污泥脱水后加入页岩,进行成型烧结,测定制品的成型含水率、干燥收缩率和抗压强度等。结果表明：4#污泥制品的综合性能高于1#污泥。当非厌氧消化污泥掺量为15%,烧成温度为950℃时,试样抗压强度等级达到MU7.5,导热系数为0.3001 W/(m·K),比纯页岩降低了33.33%;当厌氧消化污泥掺量为20%,烧成温度为950℃时,试样抗压强度等级达到MU7.5,导热系数为0.2600 W/(m·K),比纯页岩降低了42.22%。分析可知,在保证强度不变的情况下,厌氧消化污泥可有效提高污泥制砖掺量。     

Use of semiacid clay of the Kuznetsk Basin

Conclusions Izhmorsk clays can be classed as kaolinite-hydrated micaceous raw materials (monothermite) with a large impurity-content of quartz. The properties of these clays are similar to those of Barzassk clays, and the two materials can be mineralogically classed as the same type.The Izhmorsk clays were used to obtain specimens of semiacid products with an apparent porosity of 18–23%, having a finely porous structure, and a compressive strength of 300–500 kg/cm².Since they are similar to the Barzassk semiacid clays that were studied in industrial conditions at KMK, we can consider Izhmorsk clays to be suitable for producing refractories.The basic condition for producing semiacid refractories, when employing the method normally used for firebrick, is careful observation of the firing cycle, which will ensure completion of mullite formation, while maintaining the quartz in the crystalline phase and the production of finely porous structures in the materials.Industrial testing of semiacid refractories in various conditions should be organized as a means of extending the application, and of solving the problem of using, semiacid products.An all-round exploitation of the Barzassk source of fireclays and the Izhmorsk source of sands is required in conjunction with the use of the large resources of semiacid raw materials with the basic refractory clays and sands.Translated from Ogneupory, No.3, pp. 11–17, March, 1968.     

Mineralogy of clay raw material from Burkina Faso and Niger used for ceramic wares

Some clay deposits in West Africa provide raw materials for the local and traditional manufacture of ceramic products. We selected three clays in Burkina Faso, with the references ROG, GRI and POT and a fourth one, AKN1 in Niger. These clays have been mined for many years. There is growing demand for such materials and the reserves are sufficient to meet this demand. The ROG and GRI clays are used as construction materials in both fired and unfired bricks. The POT and AKN1 clays are used for producing the porous ware of fired pottery. A study was carried out to look at some of the physico–chemical characteristics of these raw materials in order to enhance their use. This is a preliminary study which will be followed by further investigations into the production of different ceramic wares. An analysis of the chemical and mineralogical composition of the materials and some investigations of their fired properties during a firing cycle up to 1000°C has demonstrated that, taken as a whole, they possess satisfactory characteristics for the described applications.     

Synthesis and properties of new fluoroelastomer nanocomposites from tailored anionic layered magnesium silicates (hectorite)

In the field of polymer clay nanocomposites, naturally occurring smectite group of clays are the most commonly used nanofillers. In the present work, smectite group clay, hectorite was synthesized in the laboratory with an intention to understand the structure–property relationship of polymer nanocomposites, with special reference to the characteristics of the nanoclays. The nanocomposites were prepared using these synthetic clays and fluoroelastomer by a solution mixing process. The clays and their nanocomposites were characterized by using X‐ray diffraction, X‐ray fluorescence, infra‐red spectroscopy, and transmission electron microscopy. It was observed that clay formation was a function of the concentration of the constituent materials. The gallery spacings and surface areas of synthetic clays are higher than those of the natural clay. Mechanical, dynamic mechanical, swelling, and thermal properties of these nanocomposites were also studied. The properties of these nanocomposites were compared with the nanocomposites obtained from natural clays, available commercially. Synthetic clay filled samples showed better properties than the natural clay filled samples, e.g., synthetic hectorite filled sample exhibited 75% increment in tensile strength and 24% improvement in 100% modulus compared with the natural hectorite based system. The results were explained with the help of thermodynamics and morphology. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

低成本大孔陶瓷膜支撑体的制备与表征(英文)

以高岭土和白云石为主要原料,通过反应烧结法制备低成本大孔陶瓷膜支撑体,对制备的支撑体进行了结构和性能表征.结果表明:在高岭土中引入质量分数为20%的白云石,可显著抑制高岭土的高温烧结;加入白云石后制备的支撑体在1 150~1 300℃保温1h后,主晶相为莫来石、堇青石和钙长石,平均孔径和抗弯强度随烧成温度升高而增大,而水通量和孔隙率降低;加入20%白云石并在1 250℃保温1 h制各的大孔支撑体的孔隙率和平均孔径分别为44.6%和4.7μm,抗弯强度和纯净水通量分别达到47.6MPa和10.76m3/(m2·h·bar).     

High-toughness mullite ceramics fabricated by hot-press sintering of pyrophyllite and AlOOH at low temperatures

High-toughness mullite ceramics were fabricated through hot-press sintering (HPS) of pyrophyllite and AlOOH, which were wet-milled and well mixed using a planetary ball mill. The impacts of sintering temperatures and contents of AlOOH on mullite phase formation, densification, microstructure and mechanical properties in ceramic materials were investigated through XRD, SEM and mechanical properties determination. The results indicated that high-toughness mullite ceramics could be successfully prepared by HPS at temperatures higher than 1200°C for 120 min. Increasing the sintering temperature from 1000 to 1300°C significantly enhanced the flexural strength and fracture toughness of samples. The highest flexural strength of 297.97±25.32 MPa and fracture toughness of 4.64±0.11 MPa⋅m^1/2 were obtained for samples sintered at 1300°C. Further increase of temperature to 1400°C resulted in slight decrease of flexural strength and fracture toughness. Compared with the mullite ceramics prepared only using pyrophyllite as raw material, incorporation of AlOOH into raw material significantly increased the mechanical properties of final mullite ceramics. And stoichiometric AlOOH and pyrophyllite as starting material gave the best performance in fracture toughness. The high-toughness of mullite ceramics were ascribed to the high mullite phase content, fine mullite whiskers and in situ formed, intertwined three-dimensional network structure obtained through HPS at a low temperature of 1300°C.     

Synthesis of high-performance mullite ceramics based on associated rare-earth kaolin

The objective of this work was to prepare high-purity, high-strength mullite ceramics from low-cost, associated rare-earth kaolin (AREK). A reaction sintering process using calcined AREK and γ-Al₂O₃ powders was used to synthesize high-performance mullite ceramics. Mineralogical, morphological, and chemical characteristics of AREK were given. The effects of associated REEs in kaolin and sintering temperature on the microstructural evolution, phase transformation, and physical properties of mullite were studied. The results showed that the mullite contents were 98.8%, the maximum aspect ratio was 8.22 μm, the relative density was 93.04%, and the micro-Vickers hardness and flexural strength were 10.63 GPa and 184.24 MPa, after sintering at 1500°C for 4 h. For comparison, calcined without rare-earth kaolin was also employed as a raw material to synthesize mullite ceramics, and the mullite content prepared by sintering the two kaolin clays at 1320–1480°C for 4 h was quite similar. However, mullite prepared using AREK forms secondary mullite in the temperature range of 1480–1500°C with a significantly higher mullite content, and therefore, the advantages of preparing mullite based on AREK as the raw material are high purity, low mullitization temperature, and high strength.     

SiC/β-Sialon装甲陶瓷的制备及性能

采用无压烧结工艺制备高比强度SiC/β-sialon复相陶瓷。研究了原料组成和第一阶段反应温度对合成β-sialon相的影响,分析了氧化物添加剂和第二阶段烧结温度对材料烧结性能和力学性能的影响。利用X射线衍射仪、扫描电子显微镜以及万能试验机表征样品的物相组成、微观结构和力学性能。结果表明：用10%（质量分数,下同）的苏州土部分替代Al2O3和SiO2能有效促进β-sialon相的生成,在1500℃保温2h合成出无杂相的β-sialon相;复合添加5%ZrO2和5%Y2O3可促进样品的烧结致密化。当温度为1650℃时,样品的体积密度为2.90g/cm3,抗弯强度和断裂韧性分别达到375MPa和3.24（MPa·m1/2）,弯曲比强度为1.29×105（N·m）/kg,比Al2O3提高了40%以上。     

金属硫化物陶瓷摩擦材料的制备与性能研究

以硫粉、锡粉、三硫化二锑为烧结剂,再加入其他辅助原料,利用金属硫化物的低熔点烧结制备陶瓷摩擦材料。研究了原料的不同配比对金属硫化物陶瓷摩擦材料的体积密度、气孔率、力学性能、摩擦性能以及显微结构的影响。硫含量对金属硫化物陶瓷摩擦材料性能有很重要的影响,通过对比寻求较为理想的原料配比,并对其实际应用的可行性进行探讨。