Role of lamellar structures in the change in strength properties of a wurstite boron nitride-base polycrystalline material

1989 ◽  
Vol 28 (1) ◽  
pp. 36-39 ◽  
Author(s):  
V. M. Volkogin
Keyword(s):  
Boron Nitride ◽  
Polycrystalline Material ◽  
Strength Properties ◽  
Lamellar Structures

SEM Study of Tension Wood Fiber Morphology and its Effect on Paper Properties

1977 ◽  
Vol 35 ◽  
pp. 308-309
Author(s):  
K. W. Robinson
Keyword(s):  
Tension Wood ◽  
Wood Fiber ◽  
Strength Properties ◽  
Fiber Morphology ◽  
Paper Properties ◽  
Pure Cellulose ◽  
Short Rotation ◽  
Hardwood Trees ◽  
Sem Study

Tension wood (TW) is an abnormal tissue of hardwood trees; although it has been isolated from most parts of the tree, it is frequently found on the upper side of branches and leaning stems. TW has been classically associated with geotropic alignment, but more recently it has been associated with fast growth. Paper made from TW is generally lower in strength properties. Consequently, the paper industries' growing dependence on fast growing, short- rotation trees will result in higher amounts of TW in the final product and a corresponding reduction in strength.Relatively few studies have dealt with the role of TW in the structure of paper. It was suggested that the lower strength properties of TW were due to a combination of factors, namely, its unique morphology, compression failures in the cell wall, and lower hemicellulose content. Central to the unique morphology of the TW fiber is the thick gelatinous layer (G-layer) composed almost entirely of pure cellulose.

Structural relationships in the synthesis of cubic boron nitride thin films by ion-assisted deposition

1994 ◽  
Vol 52 ◽  
pp. 638-639
Author(s):  
D. L. Medlin ◽  
T. A. Friedmann ◽  
P. B. Mirkarimi ◽  
M. J. Mills ◽  
K. F. McCarty
Keyword(s):  
Boron Nitride ◽  
Ion Irradiation ◽  
Cubic Boron Nitride ◽  
Film Stress ◽  
Bonded Phases ◽  
Structural Relationships ◽  
Precursor Material ◽  
Pressure Synthesis ◽  
Microstructure Of The Material

The allotropes of boron nitride include two sp2-bonded phases with hexagonal and rhombohedral structures (hBN and rBN) and two sp3-bonded phases with cubic (zincblende) and hexagonal (wurtzitic) structures (cBN and wBN) (Fig. 1). Although cBN is synthesized in bulk form by conversion of hBN at high temperatures and pressures, low-pressure synthesis of cBN as a thin film is more difficult and succeeds only when the growing film is simultaneously irradiated with a high flux of ions. Only sp2-bonded material, which generally has a disordered, turbostratic microstructure (tBN), will form in the absence of ion-irradiation. The mechanistic role of the irradiation is not well understood, but recent work suggests that ion-induced compressive film stress may induce the transformation to cBN.Typically, BN films are deposited at temperatures less than 1000°C, a regime for which the structure of the sp2-bonded precursor material dictates the phase and microstructure of the material that forms from conventional (bulk) high pressure treatment.

Influence of the Aggregate Type on the Properties of Dolomitic Lime-Based Mortars

2016 ◽  
Vol 722 ◽  
pp. 343-350 ◽  
Author(s):  
Martin Vyšvařil ◽  
Tomáš Žižlavský ◽  
Patrik Bayer
Keyword(s):  
Positive Impact ◽  
Total Porosity ◽  
Strength Properties ◽  
Carbonation Reaction ◽  
Dolomitic Lime ◽  
Limestone Aggregate ◽  
Lime Mortars ◽  
Restoration Work ◽  
Limestone Fines

Considering the requirement of numerous restoration work on historical buildings with dolomitic lime-based mortars, a research of the applicability and suitability of various types of plasters for repairing the historical plasters have been developed. This work presents the applicability of limestone aggregate and limestone fines to dolomitic lime-based mortars. The role of aggregates on the properties of dolomitic lime mortars was examined by comparing pure quartz sand and limestone aggregate and its quantity in the mortar. Limestone aggregate and limestone fines accelerated the carbonation reaction in the mortars, but the positive impact of limestone aggregates to strength properties of mortars was not observed. Mortars with limestone aggregate showed higher total porosity and water absorption than those with quartz aggregate. Similar results was obtained for mortars with limestone fines. It was found that limestone aggregate and limestone fines, used in this work, is not so suitable and applicable to the dolomitic lime-based mortar as to the aerial lime-based mortars.

Role of size of hexagonal boron nitride particles on tribo-performance of nano and micro oils

2018 ◽  
Vol 30 (8) ◽  
pp. 441-456 ◽  
Author(s):  
Manoj Kumar Gupta ◽  
Jayashree Bijwe ◽  
Meghashree Padhan
Keyword(s):  
Boron Nitride ◽  
Hexagonal Boron Nitride

scholarly journals Эффективные кристаллы Bi-Sb для термоэлектрического охлаждения при температурах T≲180 K

2019 ◽  
Vol 53 (5) ◽  
pp. 693
Author(s):  
Н.А. Сидоренко ◽  
З.М. Дашевский
Keyword(s):  
Hydrostatic Pressure ◽  
Single Crystals ◽  
High Hydrostatic Pressure ◽  
Polycrystalline Material ◽  
High Strength ◽  
Strength Properties ◽  
Experimental Equipment ◽  
Liquid Environment

Methods of extrusion are widely used in technology of thermoelectric (TE) materials manufacturing with high strength and good TE properties at temperatures above 200 K. The method of extrusion of Bi - Sb single crystals in the liquid environment under high hydrostatic pressure is considered. The construction of experimental equipment is presented. It was shown that presented method of extrusion allows preparing of polycrystalline material with high TE and improved strength properties at temperatures below 180 K.

scholarly journals The role of organic matter in formation of the properties of a shale deposit

2019 ◽  
Vol 484 (2) ◽  
pp. 220-223
Author(s):  
И. Ф. Юсупова
Keyword(s):  
Organic Matter ◽  
Carbonate Rocks ◽  
Strength Properties ◽  
Low Density ◽  
Lower Strength ◽  
Reduction Processes ◽  
Local Areas ◽  
Oil Shales ◽  
Mosaic Distribution

Baltic oil shales — kukersites were studied as an example of rocks with rock-forming organic matter (OM). The volumetric significance of their OM is shown (due to the low density) in the volume and thickness of the shale layers. A higher OM content is responsible for a lower strength of the shales relative to the carbonate rocks of the deposit. The variable OM contents and other heterogeneities of the shale layers (structure, nodules, etc.) are factors of the mosaic distribution of areas with different density–strength properties and, as a result, of uneven reduction of layers and their deformation in the case of OM loss (full or partial). It is concluded that the intercalation of kukersite and limestone layers leads to density and strength anisotropy of the shale deposit. Episodic loss of OM and carbonates by the shales is considered for the local areas of the deposit: here, kukersites contain only a terrigenous component with clasts of limestones, shales, and epigenetic sulfides. The loss of OM is explained by sulfate-reduction processes in the underground hydrosphere.

Role of Grain Boundary Segregation in Austenite Decomposition of Low-Alloyed Steel

2007 ◽  
Vol 558-559 ◽  
pp. 965-970 ◽  
Author(s):  
Shigeru Suzuki ◽  
M. Tanino
Keyword(s):  
Boron Nitride ◽  
Grain Boundaries ◽  
Boundary Segregation ◽  
Austenite Decomposition ◽  
Microstructure Observation ◽  
Austenite Grain ◽  
Auger Spectra ◽  
Low Alloyed Steel ◽  
Manganese Steels

The influence of addition of small amounts of boron and nitrogen on the microstructure formed by austenite decomposition in low-alloyed manganese steels was investigated. In order to understand microstructural changes by addition of boron and nitrogen, Auger electron spectroscopy was used for analyzing prior austenite grain boundaries in steels doped with phosphorus, boron and nitrogen. The results by microstructure observation showed that the formation of Widmanstätten ferrite was suppressed by addition of a small amount of boron in the steels, whereas Widmanstätten ferrite appears to be formed again by addition of boron and nitrogen. The Auger spectra showed that small particles of boron nitride were detected on grain boundaries in steel doped with boron and nitrogen, while boron was segregated at grain boundaries in steel with boron. This indicates that segregation of boron at grain boundaries and/or sub-boundaries may suppress the formation of Widmanstätten ferrite, while the formation of boron nitride seems to be ineffective to suppression of the formation of Widmanstätten ferrite in steels doped with boron and nitrogen.

Sign in / Sign up

Export Citation Format

Share Document