Electrophysical properties of a porous silicon carbide ceramic

The electrical resistance and thermal electromotive force have been measured for porous silicon carbide resistance materials. It has been established that the range of controlled variation in the electrical resistance is 5·10^–2 to 1·10⁴ · cm, and that the composition of the conducting SiC phase and the concentration of added dielectric constituents have a decisive influence on the electrical characteristics examined.Material Science Problems Institute, Academy of Sciences of the Ukraine, Kiev. Translated from Poroshkovaya Metallurgiya, No. 4(364), pp. 85–89, April, 1993.     

Formation of highly porous ceramic based on silicon nitride

The formation of the structure of a porous ceramic based on Si₃N₄ has been investigated. It has been found that the structure can be controlled over a wide range of porosities. Materials based on a consisting of a single fraction silicon nitride of grain size 3–5 μm, with the addition of a fine-grained pore agent have most uniform, hard, and developed porous structure. A comparative evaluation of the properties of material based on SiC and Si₃N₄ showed that silicon nitride materials of the same porosity are stronger and that small micropores can be formed in them. That is of fundamental importance in the development of materials—catalyst carriers for chemical production and various kinds of filtering devices. With the results of the investigations general technological recommendations can be made for producing ceramics with specific structures.     

多孔陶瓷过滤制品渗透率的研究

渗透率是多孔陶瓷过滤制品的一个重要性能,直接关系到制品的结构和使用性能.以不同形状不同材料多孔陶瓷过滤试样为例,研究了其渗透率的评定方法,讨论了渗透率与厚度的关系,提出了在评定渗透率时应注意的问题.     

Resin-modified glass ionomers for luting posterior ceramic restorations

OBJECTIVES: Until recently, esthetic inlay restorations in posterior teeth have been limited to cavities surrounded by enamel. Dentin adhesive systems in combination with luting composites and light-cured resin-modified glass ionomer cements offer a possibility for bonding ceramic inlays to cavities when the cervical margin is in dentin. This study was designed to compare in vitro marginal integrity of ceramic inlays bonded to dentin to restorations placed in cavities with margins located entirely in the enamel. METHODS: In the present in vitro study, the sealing abilities of a dentin bonding agent/luting composite combination (Syntac/Dual Cement, Vivadent) and resin-modified glass ionomers (Photac Fil, Photac Bond, ESPE; Dyract, De Trey Dentsply; Fuji II LC, GC Dental Industrial Corp.; and Vitremer, 3M Dental Products) used as luting agents in cavities extending beyond the cemento-enamel junction, were compared to the sealing abilities of a conventional luting composite (Vita Cerec Duo Cement, Vita) in cavities within sound enamel. SEM analysis and dye penetration were performed to evaluate marginal integrity at the cervical cavity margins. RESULTS: The dentin bonding agent/luting composite combination (Syntac/Dual Cement) rendered a marginal seal within the dentin similar to the quality obtained with the conventional luting procedures within sound enamel. When three out of the five resin-modified glass ionomers were used as luting agents (Dyract, Fuji II LC and Vitremer), the results were comparable to those reported for the dentin bonding agents and the conventional method. SIGNIFICANCE: Light-cured resin-modified glass ionomer cements may be considered as an alternative to dentin bonding agents when the cavity margins of ceramic inlay restorations are within the dentin. However, further studies, e.g., wear resistance, must be performed.     

石英孔梯度陶瓷材料的孔结构控制工艺研究

以长江沿岸低品位石英砂为主要原料,采用真空烧结制备石英孔梯度多孔陶瓷材料,为新型保温材料的开发提供参考。结果表明:当水料比为1.0时,石英孔梯度陶瓷坯体的成形性及气孔分布较好;石英孔梯度陶瓷的气孔率随烧结温度的升高而先变大后变小,其最佳烧结温度为1 100℃;烧结材料的密度为1.343 g/cm3,气孔率为48.7%,抗压强度为7.071MPa,孔梯度结构过渡均匀。     

烧结温度对过滤用SiO_2多孔陶瓷性能的影响

以石英砂、废玻璃和高岭土为主要原料,采用压制成形法制备过滤用SiO2多孔陶瓷。确定了造孔剂的反应温度,探讨了烧结温度对多孔陶瓷吸水率、气孔率、抗弯强度及显微组织的影响。结果表明:造孔剂在300~450℃快速反应;随烧结温度升高,多孔陶瓷的吸水率、显气孔率和液体渗透率逐渐降低,抗弯强度和致密度逐渐提高,最佳烧结温度为1030℃。     

A novel sort of porous ceramic foam ball with modified surface for arsenic removal from aqueous solution

A sort of lightweight porous ceramic foam ball that can float on the water was recently made from the nat-ural zeolite.The diameters of porous ball and its macroscopic pores are around 5 and 1 mm, respectively. Such ball surface could be modified to activate in different ways, i.e.loading the active alumina or desili-cating the ball.Both of modified products have been investigated to adsorb the toxic ion of arsenic (As) in water effectively.This kind of porous ceramic ball was prepared by powder sintering, using natural clinop-tilolite powder as the primary raw material.An active-alumina-loaded porous ceramic product was genera-ted by sol-gel method with pseudoboehmite (AlOOH) as the main composition.The active Al atom on the porous ball surface could also be achieved by desilicating the ceramic ball in the NaOH solution. Such a desilicated product exhibited a good activity to adsorb the arsenic ion although carrying no ac-tive alumina.With this effective porous structure, the present products can be expected to become practically advantageous.     

Treatment with rhG-CSF for osteomyelitis in a patient with p47-phox-deficient chronic granulomatous disease

A 24-year-old woman with osteomyelitis was diagnosed as having p47-phox-deficient chronic granulomatous disease (CGD). The patient showed a marked deficiency of p47-phox, which is very rare in Japan. As the clinical response to various antibiotics including sulfamethoxazole-trimethoprim was not satisfactory, we added recombinant human granulocyte colony-stimulating factor (rhG-CSF) to the treatment protocol. We report the beneficial clinical course of the patient, together with the effect of rhG-CSF on the granulocyte function, and the present report indicates that rhG-CSF is useful for the treatment of antibiotic-resistant infection in the variant type of p47-phox-defective CGD.