Main factors affecting the thermal stability of aluminosilicate refractories

It is shown that the partial pressure of oxygen and thermocycling in variable gas media are the main factors characterizing the thermal stability of aluminosilicate refractories. The obtained functional dependences of the variation of the properties of the refractories are described by equations.     

A mixture of buffing dust and chrome shavings as a filler for nitrile rubbers

The incorporation of biopolymers, such as chrome shavings and buffing dust, into rubber blends makes it possible to obtain biodecomposable collagen–elastomer materials with good utility properties. It is the presence of a biopolymer in multicomponent polymeric materials that facilitates enzymatic hydrolysis and results in biodecomposition through the loss of cohesiveness and polymer scattering. The undertaking of such original studies was justified by the benefits resulting from a new generation of polymeric materials and the need for a solution to the problem of growing amounts of wastes by waste management in the tanning industry. In this study, the effect of a mixture of chrome shavings and buffing dust on the properties of nitrile rubbers was examined. The dust and shavings, in a 1:1 proportion, were mixed with 5 parts by weight of zinc oxide and, in this form, was added to the rubber blends. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

添加物对高铬耐火材料结构与性能的影响

研究了Al2 O3和ZrO2 对水煤浆加压气化炉用高铬耐火材料结构与性能的影响。结果表明 :Al2 O3能有效提高高铬材料的致密化程度 ;适量的ZrO2 能够明显地改善高铬耐火材料的抗热震性能。颗粒与基质比较紧密的结合 ,粒状和环状(Cr,Al) 2 O3固溶体的共存 ,以及增韧相ZrO2 均匀分布的显微结构特征 ,都是高铬耐火材料具有较好综合性能的内在因素。     

Study of factors affecting the formation of a gradient structure in acrylate copolymer/fluoro-copolymer blends

The effects of the solution concentration and the rate of solvent evaporation on the formation of gradient structures were examined for poly(2-ethylhexyl acrylate-co-acrylic acid-co-vinyl acetate) [P(2EHA-AA-VAc)]/poly(vinylidene fluoride-co-hexafluoro-acetone) [P(VDF-HFA)] blends. When the 30/70 P(2EHA-AA-VAc)/P(VDF-HFA) blend was prepared from 10 wt% THF solution, a gradient structure was not formed. When the 70/30, 50/50, and 30/70 P(2EHA-AA-VAc)/P(VDF-HFA) blends were prepared by casting from 5 wt% tetrahydrofuran (THF) solution onto poly(tetrafluoroethylene) (PTFE), the chemical compositions of the surface and bottom sides of the blends were different depending on the blend ratio and rate of solvent evaporation. Therefore, it was concluded that the formation of a gradient structure is strongly influenced by the solution concentration and the rate of solvent evaporation.     

不同气氛中高铬材料的抗煤熔渣性研究

采用静态坩埚法,分别在空气、氩气和埋炭3种气氛中对高铬材料进行了抗煤渣试验,采用直接观察、SEM观察、EDS分析等手段,对比分析了煤渣的侵蚀深度和渗透深度。结果表明:1)试验气氛主要影响煤熔渣对高铬砖的侵蚀程度,而对煤熔渣在高铬砖中的渗透程度影响较小;2)在空气气氛中,煤熔渣对高铬砖的侵蚀和渗透程度均比在氩气和埋炭气氛中的小;3)在氩气和埋炭气氛中,溶解在煤熔渣中的Cr2O3被还原成单质Cr并从煤熔渣中析出,使高铬材料中Cr2O3在煤熔渣中的溶解-还原-析出循环不断进行,高铬材料被熔渣严重侵蚀;4)综合比较,在氩气气氛中进行的静态坩埚抗渣试验是实验室评价高铬材料较为理想的抗渣试验方法。     

Effect of filler fibres on structure formation in cation-exchange membranes

Conclusions -- An attempt has been made to replace the inert reinforcing filler in ion-exchange membranes with an active material — man-made fibres.-- The membranes prepared conform fully to the requirements imposed on cation-exchange membranes.Saratov Polytechnic Institute. Translated from Khimicheskie Volokna, No. 5, pp. 29–32, September–October, 1992.     

Effect of the grain composition of the batch on the structure and properties of periclase refractories

Conclusions The structure and properties of periclase articles have been studied as a function of the quality of the powders and the grain composition of the batch. The possibility of obtaining periclase refractories with a high density (open porosity 8–12%) and heat resistance (11–16 heat cycles into water) is shown. In order to obtain strong dense articles with an enhanced heat resistance, it is recommended that dense powders with a fine-crystal structure be used; additional recrystallization during the high-temperature firing helps to strengthen the articles.The addition of 1% ZrO₂ improves the properties of the articles, which is the result of the strengthening of the diffusion processes capable of forming strong direct bonds between the periclase crystals in the aggregates and the bonding material.Deceased.Translated from Ogneupory, No. 2, pp. 52–57, February, 1979.     

普通填料对POE性能的影响

以普通填料（CaCO3、炭黑、石蜡油）填充茂金属聚烯烃弹性体（POE），研究了填充体系的力学性能随填料含量变化的规律。结果表明：碳酸钙的加入使POE的强度和伸长率下降，硬度提高；炭黑的加入使其拉伸强度和扯断伸长率下降，硬度和撕裂强度上升，当炭黑用量为40份时，综合性能较佳；而石蜡油的加入则使其强度和硬度下降，扯断伸长率提高。     

Some factors affecting delayed ettringite formation in heat-cured mortars

Although more than 10 years of studies on delayed ettringite formation (DEF) have led to consensus in numerous areas of past disagreements, some questions remain experimental work is needed to complete the knowledge of this pathology. Following this objective, this paper studies the influence of pre-existing microcracking, wetting/drying cycles and the type of sulfated addition on DEF in steam cured mortars. The mortar specimens were prepared using an Ordinary Portland Cement and two types of sulfate were added to the mixtures: calcium sulfate (CaSO₄) or sodium sulfate (Na₂SO₄). The results confirm the well-known effect of temperature: no expansion was observed in any of the mixtures cured at room temperature. Moreover, no expansion was observed after 800 days for the reference mortar or for the mortar containing calcium sulfate but all the specimens of heat-cured mortars containing sodium sulfate expanded markedly after about 50 days whatever the supplementary treatments applied (thermal shrinkage or wetting/drying cycles). These results show the significant role played by alkalis in the occurrence of delayed ettringite. The supplementary treatments intended to cause prelimiray microcracking of the specimens did not promote expansion but contributed to a slight acceleration of the reaction. The ultimate values of expansion were similar to those obtained with sound mortars.     

Physicochemical factors affecting the formation of the biological response modifier scleroglucan

The use of phosphate as the limiting nutrient for scleroglucan formation by Sclerotium glucanicum led to stimulation of glucan formation. Final exopolysaccharide concentrations achieved in phosphate-limited (18·9 kg m^?3) cultures were much higher than in the usual nitrogen-limited fermentations (11·4 kg m^?3). The mechanism by which phosphate limitation engendered glucan formation may be largely non-specific, involving a generalised diversion of the carbon source away from biomass formation and towards glucan synthesis. The effect of stirrer speed was examined in a fermenter fitted with a 6-bladed Rushton turbine impeller of 0·5 vessel diameter. It was noted that biomass and scleroglucan formation showed different optima. This may have been due to the markedly different oxygen requirements of the two processes.     

Dispersity and phase composition of some ultradisperse ZrO2-bearing powders

Results of an electron-microscopic study (including microdiflraction) and a x-ray laser microanalyzer study of the dispersity of powders in the ZrO₂-A1₂O₃ system containing from 94.9 to 29.6% ZrO₂ and obtained by plasmachemical synthesis are presented. The features of the crystalline and morphological structure of the powder particles are considered. It is inferred that the crystal structure and the morphology of the powder particles affect the properties of the powders in the manufacturing process.     

纳米Fe2O3对镁铬耐火材料烧结及力学性能的影响

在镁铬耐火材料中添加纳米Fe2O3,研究了它对镁铬耐火材料烧结性能与常温力学性能的影响.结果发现,在相同的工艺条件下,加入1%(外加)的纳米Fe2O3即可使镁铬砖的烧成温度降低150℃左右,并在相同烧成温度下能使试样的常温抗折强度和耐压强度大幅度提高.分析认为,在镁铬耐火材料中添加少量纳米级Fe2O3,可促进MgO-FeO固溶体中Cr3+和Al3+含量的提高,增强镁铬砖的直接结合程度,从而提高其力学性能.