Porosity of acoustic wood-wool cement board

Wood-wool cement board (WWCB) is a porous composite material consisting of Portland cement inorganic binder mixed with wood-wool as reinforcement. It is widely used as thermal and acoustic insulator in buildings because of low density, high porosity, good fire resistance and compatibility with other binders and building materials. The maority of composite characteristics, including as density, strength, oung modulus, gas permeability, thermal conductivity, and thermal diffusivity, are dependent on porosity. Aside from density, the other ualities stated, including sound absorption coefficient, are affected by pore sie distribution. The acoustic properties of airWWCB interaction are described through air complex modulus and air complex effective density used in many acoustic models for porous materials. Two techniues for determining porosity are used and compared on samples of wood-wool cement board from normal manufacturing received from FAMAT H d.o.o. Sv. ri arete, Croatia. The Archimedes techniue is utilied to determine the real and apparent density of the bulk WWCB, while image analysis of the surface layer and deeper layers reached by grinding and polishing is used to analye layer by layer porosity and pore sie distribution. The approaches are compared based on their complexity, length of analysis, and the type and uality of information obtained

On the Temperature Corresponding to a = 0.632 in Non-isothermal JMA Kinetics

The expression for rate, da/dT, of the nucleation and growth (NG) process under non-isothermal conditions, as described by the Johnson-Mehl-Avrami (JMA) kinetic model, served as the basis for a detailed study of a class of functions F(m) = (da/dT)Tm, where m ÎÂ. Studies of the fractional conversion, a, of the NG process at the temperature of the maximum of function F(m), T = T(m), have shown that when reduced activation energy, x = E/RT, approaches infinity (x®¥), fractional conversion, a, at the temperature corresponding to the maximum of function F(m), a(m), converges to a = 0.632, for any value of m. It has been further shown that fractional conversion, a, for the NG process is equal to a = 0.632 at the temperature corresponding to the maximum of function F(m) = (da/dT)Tm for the particular value of parameter m from the interval: 1 £ m £ 2

Thermal Properties of Epoxy Resin/Layered Double Hydroxide Intercalated Nanocomposites

Pripravljen je Ca-Al slojeviti hidroksid (LDH) modifi ciran benzoatnim anionima (Ca4Al2(OH)12(C6H5COO)2 · x H2O, LDH-B) modifi ciranom metodom rehidratacije, tj. dodavanjem benzojeve kiseline i CaO u smjesu vode i acetona, kojom se trikalcijev aluminat (Ca3Al2O6) pretvara u konačni slojeviti hidroksid. Interkalacija benzoatnih aniona unutar LDH slojeva potvrđena je rendgenskom difrakcijom (XRD), spektroskopijom u infracrvenom području (FTIR) i termogravimetrijskom analizom (TGA). Interkalirani nanokompoziti na osnovi epoksidne smole i LDHB pripravljeni su in situ polimerizacijom, uz polioksipropilen diamin kao umreživalo. Uzorci s različitim udjelom LDH-B (5, 10 i 15 phr) ispitivani su XRD-om, FTIR-om, TGA-om, razlikovnom pretražnom kalorimetrijom i transmisijskom elektronskom mikroskopijom (TEM). Rendgenska difrakcija pokazala je nastajanje interkaliranih nanokompozita, a TEM analiza potvrdila raspršenje LDH-B unutar matrice i nastajanje interkalirane strukture, uz djelomično raslojavanje u nanokompozitu s 5 phr punila. Toplinska analiza pokazala je smanjenje početne temperature degradacije u usporedbi s nemodifi ciranim epoksidnim polimerom, dok se ostatak pri 1000 °C povećao, posebice kod djelomično raslojenog nanokompozita. Staklište se snizuje u usporedbi s nemodificiranim epoksidnim polimerom, što upućuje na slabije umreživanje epoksidne matrice.Ca-Al layered double hydroxide (LDH) modifi ed by the incorporation of benzoate anions (Ca4Al2(OH)12(C6H5COO)2 · x H2O, LDH-B) was prepared by a variation of the rehydration method, by adding benzoic acid and CaO into a mixture of water and acetone used to convert tricalcium aluminate (Ca3Al2O6) into fi nal layered structure. Intercalation of benzoate anions within LDH layers was confi rmed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Intercalated nanocomposites based on an epoxy resin and LDH-B were prepared by in situ polymerisation, with poly(oxypropylene) diamine as a curing agent. Nanocomposites prepared with different contents of LDH-B (5, 10 and 15 phr) were characterised by XRD, FTIR, TGA, differential scanning calorimetry and transmission electron microscopy (TEM). The XRD results indicated formation of intercalated nanocomposites, and TEM analysis confi rmed that LDH-B was dispersed within the matrix forming an intercalated structure, which becomes partially exfoliated in the nanocomposite with 5 phr fi ller. Results of thermal analysis showed detrimental infl uence on initial degradation temperature in comparison to the neat crosslinked epoxy, while residue at 1,000°C increases, especially for the partially exfoliated nanocomposite. The glass transition temperature decreases in comparison with the neat crosslinked epoxy, indicating poorer crosslinking of the epoxy matrix

Sol-gel Synthesis and Characterization of Lithium and Cerium Codoped Perovskite

Perovskites are an important group of ceramic materials with a structural formula ABO3 and wide array of potential applications in electronics, superconductors, catalysis, etc. CaTiO3, by which the whole group was named for, is particularly significant due to its use in catalysis, but its photocatalytic activity is limited by a large band gap value (~3.5 eV). A possible solution is the substitution of A and B cations with foreign cations which causes the alteration of properties, including photocatalytic efficiency. The aim of this work was the sol-gel synthesis of lithium and cerium codoped CaTiO3, characterization of the prepared gel and ceramics obtained by its thermal treatment. Samples of codoped perovskite, Ca1-xLixCexTiO3, where x = 0, 0.01, 0.02, 0.03 and 0.04, were prepared and characterized using powder X–ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), differential thermal and thermo- gravimetric analysis (DTA-TGA), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Photocatalytic activity was evaluated through the study of methylene blue photocatalytic degradation. XRD analysis showed that the prepared samples consisted of calcium nitrate and titanium chelate. In accordance with the established thermal evolution path, all samples were thermally treated at 500 °C for 2 hours. Beside perovskite, Ca2Ti2O6 appeared as a secondary phase in all thermally treated samples. SEM analysis of thermally treated samples showed the presence of agglomerates of irregular morphology and the decrease of primary particles size with the increase of dopants concentration. The sample with x=0.04 showed an increased photocatalytic activity

Influence of agglomeration and contamination in the course of amorphous powder grinding on structure and microstructure of sintered mullite

The process of grinding of amorphous pre-mullite powder has been investigated. The powder has been obtained by sol-gel process followed by drying, calcination and wet milling in planetary ball mill for various periods. While particle size distributions shifts to finer size distributions as the grinding time increase, the specific surface area dependence on the grinding time shows complex behavior. This was attributed to the agglomeration in the course of calcinations partially promoted by slight re-esterification of the sample surface in the course of grinding. Mill wear debris has been observed in samples grinded for longer periods. The influence of particle size, re-esterification, agglomeration and contamination of samples on the mullite formation process, structure, sintering process and microstructure development, has been further investigated. Slight changes in samples phase composition, as well as mullite structure, and the great decrease of sintered body porosity with the duration of grinding have been observed. (doi: 10.5562/cca1662

Layered double hydroxides as nanofillers for polymers

U posljednjih desetak godina osobitu pozornost privlače slojeviti hidroksidi (e. layered double hydroxides, LDH) kao potencijalna nanopunila za polimere. Osnovni anorganski slojevi LDH pozitivno su nabijeni te predstavljaju komplement negativno nabijenim slojevitim silikatima i omogućuju uvođenje različitih aniona kao modifikatora u strukturu punila. Ve}ina istraženih slojevitih hidroksida sintetskog je podrijetla i stoga visoke čistoće, što im je prednost u usporedbi s prirodnim punilima. Svojstva slojevitih hidroksida mogu se mijenjati u širokom rasponu, prikladnim izborom metalnih kationa i protuaniona. Ovaj rad daje pregled novijih istraživanja slojevitih hidroksida – nanopunila za polimere, uključujući postupke priprave i karakterizacije te načine ugradnje u polimerne matrice.Over the past decade, special attention has been paid to layered double hydroxides (LDH) as potential nanofillers for polymers. Basic inorganic layers of LDHs are positively charged; thus they complement the negatively charged silicate layers and may serve as a route for the introduction of anionic functionalities as modifiers in the filler structure. Most of the investigated LDHs are of synthetic origin and consequently of high purity, which presents an advantage in comparison with naturally occurring fillers. The properties of LDHs may be varied in a wide range by the adequate choice of metal cations and counteranions. This paper gives an overview of the recent investigations into layered double hydroxides as polymer nanofillers, and describes the filler synthesis and characterization procedures as well as procedures for the incorporation of fillers within polymer matrices