Preparation of mesoporous silica fiber matrix for VOC removal

A novel method for the preparation of the mesoporous silica fiber matrix was introduced for a removal of volatile organic compounds (VOCs). Paper making technology was applied to make a sheet of mesoporous silica fiber matrix. Reinforcing the mesoporous silica fiber with the ceramic fibers (50 wt.%) increased the mechanical strength of the matrix. Mesoporous silica fibers using TMOS (tetramethoxysilane) as a silica source and CTAC (cetyltrimethyl-ammoniumchloride) as a surfactant were drawn by the spinning method. The spinning process increased both the crystallinity and the fraction of mesopores (1.9 nm) of the fiber. As the spinning rate was increased both the crystallinity and the specific area of the mesoporous silica fiber increased, but the diameter of fiber decreased. We could control the size and morphology of mesoporous silica fiber matrix by changing the shape of substrates. This leads to easy fabrication of honeycomb-structured adsorbent which can be used for the VOC removal.     

On the use of hyperbolic function to describe fatigue <Emphasis Type="Italic">S-N</Emphasis> curve

We analyze the peculiarities of hyperbolic functions describing S-N curves as applied to a welded joint of mild and alloyed steels. We have demonstrated that the parameter σ_u used in σ-N equation does not generally correspond to the ultimate strength of the material, as it is commonly assumed. Methods for calculating the parameters of hyperbolic equations of S-N curves are proposed for cases, where the endurance limits are unknown or experimentally determined. __________ Translated from Problemy Prochnosti, No. 4, pp. 77–89, July–August, 2007.     

Novel hybrid ultrahard material

A novel hybrid ultrahard polycrystalline composite material has been produced by the reinforcement of the polycrystalline diamond composite thermostable material with a CVD grown polycrystalline diamond. It has been found that a thermal treatment of a polycrystalline diamond grown at high pressure ensures an increase of the CVD diamond hardness from 77 to 140 GPa. Tests of drilling tools have shown that in turning granite of the XI drillability index the wear intensity of rock destruction elements of the hybrid ultrahard material is lower than that of rock destruction elements of polycrystalline diamond composite thermostable material by a factor of 14.     

Computer modeling of the jump-like deformation of AMg6 alloy

We describe a procedure for modeling the structural inhomogeneity of a material by the finite element method. We consider the material as a composite consisting of an elastoplastic matrix and brittle inclusions (dispersoids). The finite element model is based on experimental data on the concentration of inclusions and their geometrical sizes. The proposed finite element model describes well the jump-like deformation of AMg6 alloy. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 44, No. 1, pp. 41–44, January–February, 2008.     

Safe restarting of blast furnaces after major repair without preliminary hot-metal discharge from the well

Attention focuses on safety problems with blast-furnace housings that arise on restarting after major repair without preliminary hot-metal discharge from the well’s wear pits. A method of determining the threshold stress corresponding to industrial safety in different stages of furnace startup and operation is proposed. The identification of threshold stresses at which measures must be taken to improve the stress-strain state of the furnace housing at startup is discussed. For the example of blast furnace 7 at OAO ArcelorMittal Krivoi Rog, the dynamics of the stress-strain state in the metal framework of the furnace housing is considered, in the period from startup to the resumption of normal operating conditions.     

Hardness of superhard polycrystalline materials and its temperature dependence

Data on the hardness and fracture toughness of diamond and cubic boron nitride-based polycrystalline superhard materials and the temperature dependence of these materials’ hardness have been considered. It has been found that the temperature dependence of hardness of polycrystals, based on diamond and boron nitride, produced from powders having various dispersions, shows a decrease in hardness of all the materials and difference in the materials thermostability.     

Fem prediction of the influence of warm prestressing on fracture toughness of heat-resistant steel

We present a procedure of prediction of the influence of warm prestressing combined with cycling on the brittle strength of steel 15Kh2MFA. Using a finite-element method, the effect of the combined warm prestressing on the stress-strain state at a fatigue crack tip is studied in an elastic-plastic statement. Electron microscopic observations of fracture surfaces have revealed that fracture is initiated at some distance from the fatigue crack front. Based on the pattern of influence of the plastic prestrain level on the cleavage stress of steel 15Kh2MFA and the experimental CID value, a method is put forward for finite-element modeling of the stress-strain state at a crack tip during the specimen fracture. Using the results of the finite-element modeling, the relevant curves have been plotted and an approximating formula has been proposed to represent the influence of the combined warm prestress level on the fracture toughness of steel 15Kh2MFA.     

Formation of Polycrystalline Boron Carbide B4C with Elevated Fracture Toughness

We have studied the processes of formation of high-density polycrystalline boron carbide B₄C during sintering under high pressure (5.5 GPa) and at high temperature (2200 K). Study of the structure by transmission electron microscopy showed that under the indicated conditions for sintering B₄C powders with original particle size range 2–80 µm, processes of primary recrystallization occur, as a result of which interlayers of nanodispersed grains (10–50 nm) are formed in the near-surface regions of the original coarse grains. The microhardness of such material is 41 GPa, and the fracture toughness is 7.2 MPa · m^1/2.__________Translated from Poroshkovaya Metallurgiya, Nos. 1–2(441), pp. 90–101, January–February, 2005.     

Deposits of excess carbonitride phase in microalloyed steel coils and sheet with different cooling conditions

Deposits of the carbonitrides (Ti, Nb)(C, N), Nb(C, N), and (Nb, V)(C, N) in the austenite and ferrite phases of X70 steel sheet after thermomechanical treatment are investigated. Nb(C, N) particles measuring up to 10 nm are seen in austenite in the final stage of rolling and after its conclusion prior to accelerated cooling of thick sheet. After intense accelerated cooling, most of the niobium and vanadium is retained in the solid solution, as confirmed by the vigorous deposition of (Nb, V)(C, N) particles measuring ∼2–4 nm in ferrite after tempering at 600°C. In coil production, the particles observed may be the result of general deposition or interphase deposition, depending on the cooling of the strip on the output roller conveyer of the continuous broad-strip mill. Carbonitride particles measuring 2–8 nm are deposited at winding temperatures of 550–570°C in steel with niobium and vanadium and at 590°C in steel without vanadium.     

Changes in the properties of a citrate electrolyte used to manufacture cobalt-tungsten coatings

The study of the electroconductivity of a citrate solution that contains cobalt sulfate (0.2 M) and sodium wolframate (0.2 M) used to obtain cobalt-tungsten coatings is carried out. A significant decrease in the conductivity in time of this solution as compared to aqueous and citrate complexes of cobalt was registered. It was shown that the observed changes occurred due to the generation of a mixed heteronuclear complex (probably polymeric) in the solution. The fractioning of the solution by gel filtration showed that all the changes resulted from the conversion of the substance with a high molecular weight.