Improved Strength Properties Research Articles

Effect of Composition, Structural State, and Manufacturing Technology on Service Properties of High-Strength Low-Carbon Steel Main Bimetal Layer

The effect of composition, structural state, excess phase precipitation, and manufacturing technology parameters on service property indices of high-strength, low-carbon steel of a main bimetal layer is studied in detail. For the low-carbon, high-strength steels developed primary importance is attached to strengthening mechanisms, connected with formation of different size carbonitride precipitates with different fineness, and secondary importance applies to the presence of strong structural components. A simultaneous improvement in strength properties and preparation of good steel weldability may be achieved by some increase in carbon content using a balanced microalloying system with a reduction in concentration of manganese, chromium, nickel, and copper, and effective alloying with boron. It is shown that the possibility of achieving high strength properties for the low-carbon steel developed with relatively slow cooling rates creates favorable conditions for obtaining a clad rolled product with a good and stable set of mechanical and other service properties, and quality indices.

Methacrylate compositions modified by oligosilsesquioxanes with methacryl and cyclotriphosphazene substituents

Triethoxysilylphosphazenes have been synthesized via hydrosilylation of cyclotriphosphazenes with various contents of 4-allyl-2-methoxyphenoxy groups by triethoxysilane at an equimolar phosphazene–silane ratio. Hydrolytic copolycondensation of the latter compounds with ?-methacryloxypropyltrimethoxysilane resulted in oligosiloxanes involving functional methacrylic and phosphazene fragments. The oligomers have been used as additives to a dental composition based on bisphenol A-diglycidyl methacrylate and triethylene glycol dimethacrylate. The modified filled compositions are characterized by reduced (4-fold) sensitivity to external illumination and improved strength properties and microhardness.

Nano-AlN particle reinforced Mg composites: microstructural and mechanical properties

In this study, nano-AlN particles were introduced into pure Mg matrix through the powder metallurgy technique incorporating microwave assisted two-directional sintering followed by hot extrusion. The effect of varying volume fraction of nano-AlN addition on the microstructural and mechanical properties of pure Mg was investigated. Microstructural characterisation revealed marginal grain refinement due to the fairly uniform distribution of AlN nano-particulates. X-ray diffraction results indicated basal texture weakening in Mg/0·2AlN composite. Tensile property measurements revealed an overall increase in strength properties and ductility. Among the developed composites, Mg/0·8AlN displayed superior strength (∼30% improvement) and Mg/0·2AlN showed enhanced ductility (∼80% enhancement). Under compressive loading, the developed Mg/AlN nanocomposite formulations exhibited improved strength properties without significant effect on compressibility.

Structure and Properties of Chitin Whisker Reinforced Papers for Food Packaging Application

In recent years, concerns about environmental waste caused by petroleum-derived chemicals as well as the consumer's demand for high quality food products, have prompted people to pay more attention to developing biodegradable food packaging materials using natural resources such as cellulose fibers and chitin derivatives. In this study, chitin whiskers have been successfully generated by hydrolyzing the α-chitin sample. Then the synthesized nano-sized chitin whiskers were used at ratios from 0.1% to 2% (wt%) for improving strength properties of paper sheets by the dip-coating method. Transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE-SEM) were used to investigate the morphology of chitin whiskers and cellulose fiber compounds. The results showed that coating with chitin whiskers brought about an increase in tear strength, burst strength, and wet and dry tensile strength, with a decrease in Zeta-potential value.

Study of Principles for Creating Steel in Order to Prepare High-Strength Reliable Objects by Hot Stamping

Principles for creating a new generation of steels for preparation of objects by hot stamping with an improvement of strength properties (ultimate strength up to 2200 MPa) by a factor of three are analyzed. It is shown that first of all they should be aimed at simultaneous provision of good steel hot ductility indices, quenchability, and hardenability. It is established that boron-containing steels, and also steels of the alloy and microalloy systems Mn–Cr, Mn–Mo–Nb, Mn–Cr–Ni–(Mo–Nb–V) with an attempt to reduce carbon content are most promising for this purpose. With the aim of verifying results obtained experiments are performed for the effect of cooling rate on steel strength properties of the alloy systems selected. Adequacy of the main conclusions and the promise of using boron for alloying, and also alloying and microalloying additions C–Mn–Cr–Ni–Nb–V systems in order to create new low-alloy weldable steels for preparation of objects by hot stamping are confirmed.

Surface modification of natural fibers by plasma for improving strength properties of paper sheets

Abstract Fibers of aspen chemi-thermomechanical pulp (CTMP), spruce CTMP, bleached kraft pulp (BKP), and kraft pulp were treated by low-temperature plasma (air) aiming at the detection of the relationship between chemical components on the surface and the properties of sheets. The effects of plasma treatment were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, and atomic force microscopy. The results show that the strength properties of sheets, especially the wet-tensile strength, were significantly improved, while optical properties were scarcely affected. Aspen and spruce CTMPs with abundant lignin and extractives were sensitive to plasma treatment in that the O/C ratio increased and lignin or extractive contents decreased. However, the crystallinity of BKP evidently decreased after plasma treatment owing to carbohydrate enrichment on the surface. Compared to the partial removal of noncarbohydrates through a laccase/mediator system, plasma treatment did not remove them in large amounts but created more carboxyl and hydroxyl groups, which improved the strength properties of paper sheets.

Strength Characterization of Sand-Bentonite Mixtures and the Effect of Cement Additives

This article studies the strength properties of compacted sand-bentonite landfill barrier material with and without cement addition at different periods of aging. Test results indicated that strength values, both in compression and tension, increased up to threefold in cement added samples, as well as enhancing the ductile behavior. Cubic modulus, described as the slope of the elastic portion of the cubic compressive stress versus strain curves, is determined along with initial and flexural moduli, and all the strength and moduli values were correlated with each other. Finally, it is concluded that there is a marked improvement in strength properties and moduli with cement inclusion and that the effect of aging has been very effective.

Effective Use of Waste Plastic as Bitumen Strength Modifier

Type of shopping bag that are made from various kinds of plastic mainly from low & high density Polypropylene are carrier bags, shopping bags or plastic grocery bags. These are often called single-use bags as these are used to carrying stuff from a store to a home. The uses of these bags are increasing day by day due to rapid increase in population and growth in urban area. Plastic bags not only clog drainage systems but also contribute to flooding. Infrastructure of trash collection is less developed in Pakistan which causes a serious problem of littering. Plastics are friendly to consumer but are not environmental friendly due to their biodegradability. General methods to disposed waste plastic are either by incineration of materials or by way of land filling which are hazardous for human health and environment. This paper covers a new method to utilize waste plastic bags in modification of bitumen not to just effectively utilize waste plastics but also to improve strength properties of bitumen concrete mix of flexible pavement.

Effect of Beating on Paper Physical Strength of OCC

This paper mainly discuss the effect of beating on OCC pulp fiber morphology and paper physical Strength. After the treatment with PFI, the beating degree were ranged from 25 ° SR rises from 56 °SR, the fiber morphologies were greatly changed, and appeared splitting and brooming. Physical results showed that beating can improve strength properties of OCC pulp in the proper degree, 46°SR was the best result in this study.

Palm rachis microfibrillated cellulose and oxidized-microfibrillated cellulose for improving paper sheets properties of unbeaten softwood and bagasse pulps

Bleached palm rachis pulp, pretreated with xylanase enzymes, was used for isolation of microfibrillated cellulose (MFC) and TEMPO-oxidized MFC (TMFC) by ultrafine grinding. The isolated MFC and TMFC were used at ratios from 2.5% to 20% for improving strength properties of paper sheets prepared from unbeaten softwood and bagasse pulps. The retention of microfibrillated cellulose in paper sheets was also estimated. The results showed that MFC or TMFC brought about an increase in density, wet and dry tensile strength, tear resistance, and a decrease in air permeability of paper sheets prepared from unbeaten softwood or bagasse. However, usual beating of softwood fibers was much more effective in improving strength properties of softwood paper sheets than addition of microfibrillated cellulose. On the other hand, the improvement in strength properties of bagasse paper sheets as a result of MFC or TMFC addition was generally higher than that resulted from beating of bagasse pulp. Use of TMFC with unbeaten softwood or bagasse fibers resulted generally in better improvement in tensile strength (wet and dry) than in case of using MFC.

Prospective Production Ways of New Heat-Resisting Materials Based on Polyimides

Abstract. The article is devoted to production and study of materials based on differentkinds of industrially manufactured polyimides, including chemical modification of reactivity ofmultifunctional compounds. The presence of reactive carboxyl, amide and amino groups,capable to interact with multifunctional monomeric and oligomeric modifiers, in macromoleculesof polyamide acids, gives the chance of receiving the polyimide materials possessing propertiesof polymers. As a result, we observe improvement of strength properties and thermalcharacteristics of new polymeric materials for practical aims.Key words: polyimide, geometrical parameters, structural characteristics, properties,modification, block copolyimides.Introduction. Entire prehistory of heat-resistant polymer investigations led to the beliefthat the most successful structure can beconsidered a rigid structure consisting of abenzene ring firmly connected to two five-membered nitrogen-containing rings. Polymers ofthis kind have one common name of aromaticpolyimides (PI).For the past 60 years the polymers of thisclass are the most commonly used heat-resistant polymers due to the complex of uniquecharacteristics. They firmly hold the primacyamong the materials being a source of a hugerange of products for all branches of scienceand technology. The production of the tapes,fibers, coatings, paints, plastics, membranes,composites, bonding, foamed and othermaterials is based on polyimides. Each of themcan work in extremely high thermic conditions[2; 4; 11; 16; 23].

Co-cooking nonwoods with hardwoods

Agricultural residues and energy crops are promising resources that can be utilized in the pulp and paper industry. This study examines the potential of co-cooking nonwood materials with hardwoods as means to incorporate nonwood material into a paper furnish. Specifically, miscanthus, switchgrass, and corn stover were substituted for poplar hardwood chips in the amounts of 10 wt %, 20 wt %, and 30 wt %, and the blends were subjected to kraft pulping experiments. The pulps were then bleached with an OD(EP)D sequence and then refined and formed into handsheets to characterize their physical properties. Surprisingly, all three co-cooked pulps showed improved strength properties (up to 35%). Sugar measurement of the pulps by high-performance liquid chromatography suggested that the strength increase correlated with enriched xylan content.

Paper strength improvement by inclusion of nano-lignocellulose to Chemi-thermomechanical pulp

Abstract So far, chemical pulp fibres have been utilized as conventional stock materials for nanocellulose production. The main aim of this work is to use stock materials from mechanical or chemi-thermomechanical pulping process to produce lignin containing nanofibres, which are referred to as nano-ligno-cellulose (NLC) in this study. The present study shows the influence on handsheets of chemi-thermomechanical pulp (CTMP) fibres blended with NLC. For comparison reasons, nanocellulose (NC) from bleached kraft pulp (BKP) was produced in a similar approach as NLC. Both the NLC and the NC were blended with their respective pulp fibres and their corresponding handsheets properties were evaluated with respect to sheet density. It was found that the handsheets of pulp fibres blended with NLC/NC improved the mechanical properties of handsheets with only a slight effect in relation to the sheet density. Improvements in strength properties of handsheets such as z-strength, tensile index, tear index, burst index, Emodulus, strain at break, tensile stiffness, air resistance were observed.

Comparing the rheological properties of novel nanofibrillar cellulose-formulated pigment coating colours with those using traditional thickener

Abstract Nanocellulose containing materials, such as micro-fibrillated cellulose (MFC) and nanofibrillated cellulose (NFC), are potential additives which could improve strength properties of coated paper and board surfaces and thus substitute natural and synthetic cobinders, such as carboxymethyl cellulose (CMC) and polyacrylic thickeners, in pigmented coating formulations. The aim of this study is to evaluate whether MFC/NFC can be used in coating colours as sole co-binder. In this investigation, the change of rheological and dewatering behaviour of coating colours, having a single blend of pigments (ground calcium carbonate and kaolin clay) together with a latex emulsion binder, is studied when CMC is used as sole co-binder and during its partial and finally total replacement with MFC/NFC. The findings suggest that even though all coatings show viscoelasticity, MFC/NFC is seen to relate to the gel-like nature of the nanoparticles in the coating colour whereas the viscoelastic behaviour in the case of CMC is induced by differential flocculation amongst the pigment and latex binder. The flocculation mechanism is predicted to be necessary in order to provide the link between water retention and elastic structure recovery where anti-sagging is a prerequisite, such as in the coating of rough substrates, e.g. for board and packaging.

Effect of PCC Pretreatment with Pulp Powder on the Paper Properties

Various approaches have been tried to reduce the emission of carbon dioxide in paper industry. One of important approaches is to use PCC manufactured from emission gas as a filler. However, it was recognized that PCC is inferior to other fillers in the paper strength properties of view. Therefore, pretreatment of PCC with pulp powder was tried to mitigate the strength reduction of paper. Pretreatment of PCC with pulp powder improved the bulk(7.4~12.9%) and air permeability(24.8~42.98%), but there is no significant change in opacity. Tensile index, burst index and stiffness were decreased by the use of pretreated PCC with pulp powder. Anionic and cationic PAM were used as a additive for PCC pretreatment in order to improve strength properties. There was no significant change in bulk in all kinds of PAM used in this study. Most strength properties were improved by the pretreatment of PCC with the anionic and cationic PAM and pulp powder, although the opacity and stiffness were more or less decreased.

Development of advanced P/M Ni-base superalloys for turbine disks

In the process of evolution of powder metallurgy in Russia the task permanently formulated was the following: to improve strength properties of P/M superalloys without application of additional complex HIPed blanks deformation operation. On the other hand development of a turbine disk material structure to ensure an improvement in aircraft engine performance requires the use of special HIP and heat treatment conditions. To ensure maximum strength properties of disk materials it is necessary to form a structure which would have optimum size of solid solution grains, γ′-phases and carbides. Along with that heating of the material up to a temperature determined by solvus of an alloy ensures a stable and reproducible level of mechanical properties of the disks. The above-said can be illustrated by successful mastering of new complex-alloyed VVP-class superalloys with the use of powder size − 100 μm. Application of special HIP and heat treatment conditions for these superalloys to obtain the desired grain size and the strengthening γ′-phase precipitates allowed a noticeable improvement in ultimate tensile strength and yield strength up to ≥1600 MPa and ≥1200 MPa respectively. 100 hrs rupture strength at 650 ∘ C and 750 ∘ C was improved up to 1140 MPa and 750 MPa respectively. P/M VVP nickel-base superalloys offer higher characteristics in comparison with many superalloys designed for the same purposes. HIPed disc compacts manufactured from PREP-powder have a homogeneous micro- and macrostructure, a stable level of mechanical properties.

Variable Density Cellular Concrete

There is mentioned some methods of creation variable density cellular concrete, offered original technique. There are presented some properties of the developed material in comparison with the analogue. Variable density cellular concrete can be described as the material with equal variation of density from its periphery to the center. Potentially it will help to improve strength properties and at the same time to maintain low thermal conductivity value of the variable density units.

Fabrication and Mechanical and Thermal Behaviour of Graphene oxide/Epoxy Nanocomposites

Bulk amount of graphite oxide was prepared by oxidation of graphite using the modified Hummers method and its ultrasonication in organic solvents yielded graphene oxide (GO). X-ray diffraction (XRD) pattern, X-ray photoelectron (XPS), Raman and Fourier transform infrared (FTIR) spectroscopy indicated the successful preparation of GO. XPS survey spectrum of GO revealed the presence of 66.6 at% C and 30.4 at% O. Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) images of the graphene oxide showed that they consist of a large amount of graphene oxide platelets with a curled morphology containing of a thin wrinkled sheet like structure. AFM image of the exfoliated GO signified that the average thickness of GO sheets is ~1.0 nm which is very similar to GO monolayer. GO/epoxy nanocomposites were prepared by typical solution mixing technique and influence of GO on mechanical and thermal properties of nanocomposites were investigated. As for the mechanical behaviour of GO/epoxy nanocomposites, 0.5 wt% GO in the nanocomposite achieved the maximum increase in the elastic modulus (~35%) and tensile strength (~7%). The TEM analysis provided clear image of microstructure with homogeneous dispersion of GO in the polymer matrix. The improved strength properties of GO/epoxy nanocomposites can be attributed to inherent strength of GO, the good dispersion and the strong interfacial interactions between the GO sheets and the polymer matrix. However, incorporation of GO showed significant negative effect on composite glass transition temperature (Tg). This may arise due to the interference of GO on curing reaction of epoxy.

Micro Filler Effects of Silica-Fume on the Setting and Hardened Properties of Concrete

The use of supplementary cementitious material is gaining much attention owing to its high pozzolanic property and further improvement in strength properties. Silica-fume is one among the widely used pozzolanic material which exhibits high cementing efficiency due to high silica content. This study presents comprehends a detailed insight on the hydration properties of silica fume with cement. Silica fume consists of very fine particle size and contains silica content more than 90%. The cement hydration results in the formation of calcium hydroxide and this is consumed with the addition of silica fume and results in additional calcium silicate hydrate. This compound primarily envisages the strength and improved microstructure of concrete. Addition of silica-fume fills in the spaces between cement grains. The test results showed that higher compressive strength of concrete is obtained by using 8.0% of silica-fume at 7 and 28 days was 48.25 and 55.83 MPa, respectively. This phenomenon is frequently referred to as particle packing or micro-filling. Even if silica fume did not react chemically, the micro-filler effect would lead to significant improvements in the microstructure of concrete. A comprehensive review has been carried out in this study to give a good understanding on the advantages of pozzolanic properties of silica fume in cement concrete.

Properties of porous concrete from waste crushed concrete (recycled aggregate)

The purpose of this study was to develop porous concrete with acceptable permeability and strength using recycled aggregate from waste crushed concrete. The optimum mix proportions were employed to prepare porous concretes using normal and recycled aggregates. Tests carried out on porous concrete were: void ratio, coefficient of permeability, compressive and flexural strengths. The effect of recycled aggregate on total void ratio, strength and permeability was examined. Styrene butadiene rubber-based redispersible polymer powder and latex were introduced to mixtures to improve strength properties. The total void ratio of porous concrete incorporating recycled aggregate was larger than that of porous concrete with normal aggregate. The addition of polymer modification resulted in a slight decrease in total void ratio regardless of type of aggregate. The compressive strength of porous concrete using recycled aggregate was lower the one using normal aggregate. However, the compressive strengths of porous concretes using normal and recycled aggregates were significantly improved by 57% and 79% respectively, due to polymer modification. The use of recycled aggregate along with optimum content of polymer could produce acceptable porous concrete with both enough drainage and strength properties.