Effect of Doping different Percentages of Lithium Fluoride on Some Optical Characteristics of Poly-Methyl Methacrylate Polymer

This study implements the optical characteristics of Poly-Methyl methacrylate (PMMA) polymer before and after doping different percentages of Lithium Fluoride (LiF). Where the specimens were formulated as disk shape with diameter of (2.5 cm) and thickness of (0.148 cm) using Thermal pressing technology. The absorbance and reflectivity spectra were recorded in addition to their coefficients at range (300-1100) nm. Also, the study has included the determination of refraction and real and imaginary part of dielectric constant coefficients.

The Failure Mechanisms of Precast Geopolymer after Water Immersion

Precast geopolymers with lower water/binder (0.14), which mainly consists of alkali solution, fly ash (FA) and steel slag (SS), were manufactured through molding pressing technology. The failure mechanisms of precast geopolymers after water immersion were studied by testing the loss of compressive strength, the pH of the leaching solution, the concentration of ions (Na+, Ca2+, Si4+ and Al3+), the evolution of phases, pore structure and morphology, and further discussion of the regulation evolution was performed. The results show that the harmful pores (>50 nm) of geopolymers progressively decrease from 70% to 50% after 28 days of water immersion when the content of steel slag increases from 0 to 80 wt.%. Compressive strength of geopolymers sharply reduces in the first 3 days and then increases during the water immersion process, but the phase composition varies slightly. Furthermore, increasing the content of steel slag could decrease the total porosity and further prevent the water resistance.

Rice straw and energy reed fibers reinforced phenol formaldehyde resin polymeric biocomposites

Herein, natural fiber (energy reeds and rice straw) reinforced with phenol formaldehyde (PF) polymeric resin biocomposites are developed and reported in this study. The dimensions of energy reeds and rice straws used for this research were 0.5–1.66 mm and 0.1–3.55 mm, respectively. The hot-pressing technology was used for manufacturing the biocomposites. The proportions for mixing of rice straw/energy reed fibers in composite systems were 90/0, 54/36, 36/54, and 0/90 whereas remaining 10% were belong to PF resin. The nominal densities of the biocomposite panels were 680 kg/m3, however the actual densities were 713.655, 725, 742.79, and 764.49 kg/m3. The main objective of this study is to develop hybrid biocomposites from different proportions of energy reeds and rice straw fibers using PF resin and to find the convenient ratio and materials for biocomposites production. The obtained results demonstrate that mechanical properties and stability against the moisture increases with the increase of energy reeds loading in the composite systems. The biocomposite developed from 100% energy reeds provided the higher mechanical properties compared to 100% rice straw. The thermal and morphological properties of the produced biocomposite materials were investigated and found significant. The thermo-mechanical properties of the composite materials increase with the increase in energy reed fiber loading in composite system. Furthermore, the coefficient of variation (R2) also demonstrates a positive attributions of energy reed fibers loading in composite systems. Moreover, the overall performances of the developed biocomposite panels demonstrate them as potential and novel candidate to the composite community in the coming times. Graphical abstract

Rice straw and energy reeds fiber reinforced phenol formaldehyde resin hybrid polymeric composite panels

AbstractHerein, natural fiber (energy reeds and rice straw) reinforced with phenol formaldehyde (PF) polymeric resin hybrid biocomposites are developed and reported in this study. The dimensions of energy reeds and rice straws used for this research were 0.5 to 1.66 mm and 0.1 to 3.55 mm, respectively. The hot-pressing technology was used for manufacturing the biocomposites. The proportions for mixing of rice straw/energy reeds in composite systems were 90/0, 54/36, 36/54, and 0/90, whereas another 10% were PF resin. The nominal densities of the biocomposite panels were 680 kg/m3, however the actual densities were 713.655, 725, 742.79, and 764.49 kg/m3. The main objective of this study is to develop hybrid biocomposites from different proportions of energy reeds and rice straw fibers and to find the convenient ratio and materials for biocomposites production. The obtained results demonstrate that mechanical properties and stability against the moisture increases with the increase of energy reeds loading in the composite systems. However, the biocomposite developed from 100% energy reeds provided the higher mechanical properties compared to 100% rice straw. The mechanical, physical, thermal, and morphological properties of the produced biocomposite materials were investigated. Moreover, the overall thermomechanical performances of the developed biocomposite panels demonstrate a potential and novel materials in the coming times. Furthermore, the coefficient of variation (R2) also demonstrates a positive attributions of energy reed fibers loading inn composite systems.

Applying of Pressing Technology to Forming Finger-Joint Profile for Wood Splicing

Splicing of wood lengthwise is widely used in the manufacture of various products. The basic method of forming the finger joint profile is milling. This method has a number of disadvantages: high cost of the milling tool, necessity of its periodic sharpening; high energy consumption of the milling process, design constraints on the geometric parameters and strength of fingers (tenons). An alternative to milling is a new way of forming such joints elements as mortise and tenons by pressing along the grain. This method allows obtaining mortises in the form of fairly accurate rectangular imprints on the ends of the blanks. The use of a punching tool instead of a cutting one avoids chips and reduces the cost of the aspiration system. Previously, rectangular tenons were used only for L-type box joints. The aim of the study is to prove the possibility of using the cold end pressing technology to form the mortises and tenons profile for end joining that meet regulatory requirements. A series of experiments on pressing the elements of joints profile in the form of multiple tenons has shown that the achieved accuracy and roughness meet the requirements for the manufacture of joints intended for lengthwise splicing. Assessment of the strength of the joints showed their compliance with the regulatory requirements. The conducted research confirms confirms the possibility of using the pressing technology to form the profile of the finger joint for wood splicing.

Effect of hot isostatic pressing technology on structure and properties of products made of VZh159 heat-temperature alloy

The hot isostatic pressing (HIP) technology is considered on the example of making of compacts made of VZh159 powder. It is shown that powders with fractional composition of –70 +25 µm, bulk density of 3.77 g/cm3 , fl uidity of 2.3 g/s, specifi c surface of 446 cm2 /g, and average Fischer particle size of 16 µm are prone to sorbed gases. Gases on the surface of the powder body as result of the HIP cycle can form non-metallic inclusions that reduce the properties of the compact. To effectively remove gases, vacuum heat treatment is used: degassing. It is established that the structure of HIP-compacts after two- or four-stage ageing has fi ner grain (point 9) compared to the cast alloy (point 7).The mechanical properties of the compacts obtained made of VZh159 power exceed the correspointing requirements of the standard process documentation for ultimate strength by 21...22 % and elongation by 36...45 %.

The Effect of Fullerene Soot Nanoparticles on the Microstructure and Properties of Copper-Based Composites

Copper-based composite materials strengthened with nanosized fullerene soot particles were produced by mechanical milling and hot pressing technology with a content of carbon up to 5 wt. %. The microstructure of the composite powders and the compacts prepared using them were examined by light microscopy, SEM, EDS, XRD, and XPS; hardness, heat conductivity, and tribological characteristics were measured. The interesting feature of the observed microstructure was a “marble” pattern formed by a white boundary net. The study shows homogeneous distribution of carbon inside the copper grains and its lower concentration in the grain boundaries. The effect was caused by a reaction of carbon with oxygen adsorbed by the copper particles surface. The maximal hardness of the material is 160 HB for the sample with 0.5 wt. % of fullerene soot; this material has the minimal friction coefficient (0.12) and wear in a dry friction condition. Heat conductivity of the material (Cu-0.5 wt. % C) is 288 W/m*K.