An Advanced Centrifugal Technique to Characterize the Sticking Properties of Tomato Pulp during Drying

An advanced centrifugal technique was developed to characterize the stickiness of tomato pulp at various moisture contents and temperatures. To provide tomato pulp samples with different moisture contents, tomato powder produced by a laboratory spray dryer was wetted to six different moisture levels. By noting the rotational speed for a tomato pulp droplet detachment and weighing the mass of the droplet remaining on the surface it is possible to gauge the approximate attachment forces holding the droplet to the substrate. The effects of droplet mass and centrifugation time after reaching the desired rotor speed on the detachment rate were also studied. The detachment force was found to increase at the beginning and then started decreasing as the moisture content decreased presenting a maximum at moisture content of about 34%. In addition, the higher the droplet temperature, the higher the attachment force.     

An Advanced Centrifugal Technique to Characterize the Sticking Properties of Tomato Pulp during Drying

An advanced centrifugal technique was developed to characterize the stickiness of tomato pulp at various moisture contents and temperatures. To provide tomato pulp samples with different moisture contents, tomato powder produced by a laboratory spray dryer was wetted to six different moisture levels. By noting the rotational speed for a tomato pulp droplet detachment and weighing the mass of the droplet remaining on the surface it is possible to gauge the approximate attachment forces holding the droplet to the substrate. The effects of droplet mass and centrifugation time after reaching the desired rotor speed on the detachment rate were also studied. The detachment force was found to increase at the beginning and then started decreasing as the moisture content decreased presenting a maximum at moisture content of about 34%. In addition, the higher the droplet temperature, the higher the attachment force.     

耐火材料的机械冲击疲劳

研究了在周期性机械冲击下耐火材料的性能，并且基于此项研究，提出了一个新的疲劳理论。这个新理论易于改进人们对耐火材料在交替荷载下的复杂断裂性能的理解，实验结果可以用来证实这一理论。以该理论为基础计算出的结果和通过实验确定的数据之间有很好的一致性。     

Advanced research at the Eastern Institute of Refractories

Results of fundamental research conducted at the Eastern Institute of Refractories in recent years are presented. The work has been aimed at meeting the needs of metallurgical enterprises, GAZPROM corporation, power engineering, machine-building, and other branches of industry. Translated from Ogneupory i Tekhnicheskaya Keramika, Nos. 1–2, pp. 3–5, January–February, 1999.     

Mechanical Properties of Weldbonded Joints of Advanced High Strength Steels

In lightweight car body shell mass production, due to requirements on vehicle weight reduction and carbon dioxide emissions, joining of advanced high strength steels (AHSS) with different joining procedures and especially hybrid bonding techniques is becoming more and more important. One of these hybrid bonding techniques is the combination of resistance spot welding and adhesive bonding called weldbonding. One of the important advantages of weldbonded joints in comparison to resistance spot welded joints are the enhanced mechanical properties. To guarantee sufficiently high quality conditions regarding the strength of the weldbonded joints, the influences of the applied adhesive systems and of different base metal combinations are studied. This is carried out for both non-corrosive and corrosive environments and for the choice of different joining parameters settings. In particular, the mechanical behaviour of the weldbonded joints is investigated under quasi-static, impact and fatigue loads. Furthermore, the energy absorption of the weldbonded joints for both non-corrosive and corrosive environments is studied. It is shown that the weldbonded joints possess higher mechanical strengths in all load cases (quasi-static, impact and fatigue). Corrosive attack affects weldbonded joints, and the quasi-static strength is reduced. Resistance spot welded joints are not affected by the corrosive attack, but even after several weeks of corrosive attack, the quasi-static strength of weldbonded joints remains higher than that of resistance spot welded joints.     

Thermodynamic Properties of Non-Oxide Composite Refractories

For initiative application of non-oxides in refractories, it is essential to study thermodynamic properties of non-oxides. The stability and stable order of non-ox- ides under oxidized atmosphere are analyzed firstly and then a new process, “converse reaction sintering”, is proposed. The results of study on oxidation mechanism of silicon and aluminum nitrides indicate that the gaseous suboxides can be produced observably when the oxygen partial pressure is lower than “conversion oxygen partial pressure”. The suboxides can be deposited near the surface of composite to become a compact layer. This causes the material possessing a performance of “self-impedient oxidation”. Metal Si and Al are the better additives for increasing the density and width of compact layer and increasing the ability of anti-oxidation and anti-corrosion. The study on Si3 N4-Al2O3, Si3N4-MgO, Si3 N4-SiC systems is also enumerated as examples in the paper. The experimental results show that the converse reaction sintering is able to make high performance composites and metal Si and Al not only can promote the sintering but also increase the density and width of compact layer.     

Dynamic and Static Tests for Mechanical Properties of Fired Plastic Refractories and Other More Resilient Materials

An apparatus for loading brick-sized specimens and a sensitive deflectometer are described. For a resilient material, the dynamic test, the static shear-free transverse test, and the static shear-corrected transverse test gave the same modulus of elasticity. The resilient materials were dense firebrick, glass, steel, and plaster. The elementary shear correction was satisfactory for the correction of the deflections of transverse test specimens having length-to-depth ratios ranging from 3.2 to 7.2. The dynamic modulus of elasticity, the static secant modulus of elasticity, and the static modulus of rupture were obtained for nine brands of heat-treated plastic refractories. The load-deflection curves obtained from static tests on these materials indicated plastic deformations ranging from nil to 19% of the truly elastic deformations calculated from the results obtained by the dynamic method of test. The differences in the extensibilities calculated from the static and dynamic methods of test were equivalent to these plastic deformations. For studies of thermal spalling, the static extensibilities were preferred because they approximated the strain at rupture.     

烧成MgO-CaO质耐火材料的结构和性能研究

本文以22％和55％ CaO的镁钙砂作主要原料,三种配比的细粉作为基质相,石蜡做结合剂制备烧成镁钙质耐火材料.研究了烧成温度、基质组成和镁钙砂中CaO含量对MgO-CaO材料常温物理性能和荷重软化温度的影响.结果表明:(1)随着烧成温度的升高,MgO-CaO材料气孔率降低,体积密度和耐压强度增大.(2)增加基质相中镁砂粉添加量,颗粒和基质结合良好,耐压强度和荷重软化温度提高.(3)在1550℃到1650℃烧成温度范围内,高钙镁钙质材料的最佳烧成温度为1650℃,低钙镁钙质材料在1600℃烧成综合性能最好.     

Effect of Interface Structure on Mechanical Properties of Advanced Composite Materials

This paper deals with the effect of interface structures on the mechanical properties of fiber reinforced composite materials. First, the background of research, development and applications on hybrid composite materials is introduced. Second, metal/polymer composite bonded structures are discussed. Then, the rationale is given for nanostructuring the interface in composite materials and structures by introducing nanoscale features such as nanopores and nanofibers. The effects of modifying matrices and nano-architecturing interfaces on the mechanical properties of nanocomposite materials are examined. A nonlinear damage model for characterizing the deformation behavior of polymeric nanocomposites is presented and the application of this model to carbon nanotube-reinforced and reactive graphite nanotube-reinforced epoxy composite materials is shown.     

硅酸盐结合碳化硅质耐火材料的性能

以莫来石和硅线石作为碳化硅的结合剂,通过反应结合制备了硅酸盐结合的碳化硅质耐火材料。硅酸盐结合剂的比例在15％～30％(质量)之间。二硅化钼(4％)已作为碳化硅耐火材料的浸渗剂,这种耐火材料的断裂模数随着二硅化钼的添加而提高,它们的热膨胀系数在32.8×10~(-6)～4.1×10~(-6)·(℃)~(-1)之间。该耐火材料对于非铁金属具有抗侵蚀性,但易被熔融盐所侵蚀。     

Influence of Chemical Reactions in Magnesia-Graphite Refractories: I, Effects on Texture and High-Temperature Mechanical Properties

Four formulations of magnesia-graphite-aluminum metal (antioxidant) bricks were prepared from the same raw materials, using the standard commercial practices. Chemical analysis and determination of room-temperature modulus of rupture and Young's modulus, as well as a complete microstructural characterization of the as-received materials, were performed. For high-temperature modulus-of-rupture and Young's modulus data, test samples of the four brick compositions were heated to 1000°, 1200°, and 1450°C in flowing argon (<1000 ppm oxygen at 1000°C) and then loaded mechanically in flexure. Modulus-of-elasticity values ranged from 3.7 to 16.2 GPa and reflected strong effects of aluminum-metal concentration and treatment temperature. Young's modulus evolution with temperature was determined by the evolution of the microstructure in the bulk of the specimens. Modulus-of-rupture values ranged from 6 to 21 MPa, and their evolution with temperature was determined by the evolution of the microstructure in the bulk of the specimens at the lower testing temperatures ( T lessthan equal to 1200°C) and by phase assemblages in the surface regions of the specimens-essentially by the presence of the dense MgO zone-at 1450°C.     

Influence of Glass Dust on Properties of Alumina-carbon Refractories

In order to improve the properties of alumina-carbon refractories, specimens were prepared using white fused corundum, zirconia-mullite and flake graphite as the raw materials, phenolic resin as the binder, adding different mass fractions(1.5%, 2.0%, and 2.5%, respectively) of glass dust, cold isostatic pressing by 120 MPa, drying and firing at 900 ℃ for 3 h. Effects of the glass dust addition on the apparent porosity, bulk density, cold modulus of rupture, hot modulus of rupture and thermal shock resistance were studied. The results show that the cold modulus of rupture of the specimens is improved significantly as the results of glass dust accelerating sintering. However, the hot modulus of rupture decreases. As the glass phase buffers the strain produced by thermal shock, the thermal shock resistance of alumina-carbon specimens is improved, especially for low carbon alumina-carbon materials.     

成型方向对MgO-C质耐火材料性能的影响

为研究不同成型方向对镁碳质耐火材料性能的影响,选取97级电熔镁砂和-195鳞片状石墨为主要原料,以热固性酚醛树脂为结合剂,在1 300 t摩擦压砖机上分别以平打平砌法(成型方向为砌筑层高方向)和侧打平砌法(成型方向垂直于砌筑层高方向)生产指定尺寸的楔形镁碳砖.按规定取样规则制样,分别检测其显气孔率、体积密度、常温耐压强度和1 400℃×0.5h高温抗折强度.结果 表明,当成型方向为砌筑层高方向时,楔形镁碳砖从小头到大头的各项性能均稳定;当成型方向垂直于砌筑层高方向时,楔形镁碳砖从小头到大头的显气孔率不断升高,体积密度、常温耐压强度和高温抗折强度不断降低并随其稍度增大而愈加明显.采用平打平砌法能获得性能稳定的楔形镁碳砖,可为生产制度的制定提供合理依据.     

SiC质耐火材料的碳化氮化制备及性能

以Si粉和SiC颗粒为原料,采用碳化-氮化反应在1 400℃和1 500℃制备了SiC质耐火材料.采用X射线衍射仪、扫描电子显微镜和能谱仪等对试样的物相组成、显微结构和微区成分进行了分析,研究了原料组成和烧成温度对材料烧结性能、力学性能和抗热震性能的影响,并对原料组成和烧成温度进行了优化.结果表明:所制备的SiC质耐火...     

工业窑炉新型耐火材料热物理性能的研究

选择常用的耐火材料,模拟工业窑炉(主要是陶瓷窑炉)实际工况的温度分布特点,在各种温度下对材料试样进行导热系数的测试,最后利用数学方法对测试数据进行分析整理,得出与温度的关系表达式或图表。     

Development, Technology and Physicochemical Properties of New-Generation Refractories

Techniques of cold expansion and high-temperature synthesis of high-melting inorganic compounds (carbides, borides, oxides, etc.) in the combustion wave (self-propagating high-temperature synthesis) based on chemical interactions in a condensed phase are discussed. A specific feature of these techniques is high exothermicity which provides energy to the technological needs virtually without borrowing from outside sources. The effect of physical and chemical factors on the reactions involved is analyzed. Properties of new light-weight cellular castables reinforced with protective coatings capable of sustaining temperatures up to 1400°C are reported.     

Fractographic and Fracture Mechanical Investigations of Refractories under Different Loading Conditions

Crack initiation and propagation have been investigated under tensile and shear loading in ceramically and carbon bonded refractories.A wedge splitting test procedure and a modified shear test have been applied.Test results have been used for material characterization especially with respect to brittleness.Furthermore a microscopic fractographic test procedure was developed and applied on fractured test specimens.In order to explain brittleness dependence on structure properties correlation of fractographic and fracture mechanical results has been evaluated.Frequently brittleness reduction is achieved by a lower amount of transgranular crack propagation associated with a strength decrease while maintaining specific fracture energy unchanged.Deviations from pure linear fracture mechanics increase with decreasing brittleness and contribute to specific fracture energy.Shear specimens may show two generations of cracks,a first one initiated by tensile loads （stable propagation） and a second one by shear loads （unstable propagation）.