bluuebunny/crossref_metadata_2025 huggingface dataset:
Educação infantil e políticas educacionais: do passado ao presente na busca do futuro
Authors: Castro Elisangela Aparecida de , Sá Michele Aparecida de , Camargo Pedro Luiz Teixeira de
Published: August 2017

Este artigo objetiva apresentar uma explanação histórica da educação no país e discutir as políticas que regem a Educação Infantil entre 1988, com a promulgação da Constituição Federal, até a publicação da lei nº 12.796, de 4 de abril de 2013, que alterou a LDB/1996, apresentando alguns desafios como o acesso, a permanência e a formação professoral, entre outros, que a sociedade defronta para aquisição do direito à instrução formal. A metodologia utilizada foi documental e bibliográfica, de maneira a fundamentar a temática proposta. Neste estudo, conclui-se que ainda existe uma distância entre a prática e o que está disposto em lei. Verificou-se como um dos maiores desafios para se efetivar a emenda Lei nº 12.796 a questão do acesso à educação formal, pois cerca de 56 % das crianças brasileiras com idade para frequentar a primeira etapa de ensino ainda estão fora do ambiente escolar. Para superar essa fragilidade, sugere-se um sistema educacional que prossiga com as políticas públicas educacionais já estabelecidas.
Onde termina o público e começa o privado? Análise da privatização da cultura na Praça da Liberdade em Belo Horizonte
Authors: Correia Gabriel Farias Alves , Colares André Felipe Vieira , Saraiva Luiz Alex Silva
Published: August 2017

Observar as práticas culturais e os investimentos privados realizados pode resultar em descobertas das transformações sociais que estão vinculadas às políticas de cultura empresarial. Por meio da análise dos discursos produzidos pelo Circuito Praça da Liberdade de Belo Horizonte, este trabalho busca examinar de que forma o público e o privado se misturam em processos de concessão de espaços públicos realizados pelo Estado; enfocando espaços culturais. Essa discussão torna-se pertinente ao observar o interesse de uma coletividade sendo suplantado pelos interesses privados e do capital. A coleta de dados foi realizada por meio da abordagem qualitativa e a análise dos dados foi realizada a partir da análise francesa do discurso. Foi verificada a existência de discursos de exaltação do próprio espaço com a finalidade de transparecer uma imagem social comprometida com o bem público e a presença da lógica mercadológica de que as atividades privadas atendem a interesses específicos de lucratividade.
Encontros de narrativas entre Oswald de Andrade e Walter Benjamin
Authors: Silva Cristina Maria da
Published: August 2017

Adentramos nos mosaicos da condição humana que perpassam a obra de Oswald de Andrade (1890-1954) e Walter Benjamin (1892-1940). Propiciamos nos labirintos de nossas escrituras encontros (im) possíveis entre os dois escritores, em suas concepções de crítica, leitura, escrita e de uma reeducação do olhar diante da vida. Em ambos, nenhuma certeza consoladora, em seus relatos o ensaio constante diante da vida e as reservas diante dos sentidos arbitrários das palavras.
Percepções sobre qualidade de vida entre idosos que participam de uma Universidade Aberta para Maturidade
Authors: Peixoto Nádia , Lima Lara Carvalho Vilela , Bittar Cléria Maria Lobo
Published: August 2017

O envelhecimento populacional é um fenômeno mundial atrelado ao aumento da esperança de vida. O objetivo deste estudo foi avaliar as percepções de qualidade de vida (QV) de idosos que frequentavam a Universidade Aberta para Maturidade - UNABEM, na Universidade do Estado de Minas Gerais, Unidade de Passos. A amostra foi constituída por 90 idosos que frequentavam assiduamente o projeto; foram utilizados os questionários WHOQOL-BREF e OLD para avaliar as percepções de QV. Observou-se que, dentre os participantes, a maior parte da amostra era do sexo feminino, na faixa etária entre 60|69 anos, casada, com ensino médio completo, morava em domicílio multigeracional, com renda entre um e dois salários mínimos, e católica. A maioria percebeu sua QV como ‘muito boa’ e ‘boa’ e estava satisfeita com sua saúde. Quanto à percepção da QV, os domínios e facetas relações sociais e participação social foram os que alcançaram maior escore, respectivamente. O domínio meio ambiente e a faceta morte e morrer obtiveram menor escore. Pode-se concluir que idosos que participam de atividades como as ofertadas na UNABEM são capazes de ter melhor percepção de QV global, principalmente com relação ao convívio social, aspecto relevante que influencia positivamente nessa etapa da vida.
Influence of Proposed Hardening Process on Hardness and Toughness of Martensitic Stainless Steel
Authors: Saikaew Charnnarong , Sawatwor Worakarn
Published: August 2017

Many researchers have studied the effects of heat treating processes on mechanical properties, corrosion and wear resistance of various martensitic stainless steels. It is crucial to comprehensively understand the role of heat treating processes on the mechanical properties of the steels with a systematic approach. In this work, the specimens were heat treated by preheating in two steps before continuing the heating to the quench temperature. The first preheating was performed in the furnace maintained at 400 °C for 5 min. The second step was done in the furnace kept at 800 °C for 5 min. Then the specimens were heated directly to the hardening temperature, 1030 °C. The specimens reached 1030 °C for a sufficient time of 30 min to form austenite and to allow enough of the carbides to be dissolved to ensure the desired combination of hardness and toughness. After hardening time was over, the specimens were quenched in water to form martensite for 2-8 s and holding in the air for 4 s, followed with water quenching for 2-8 s and cooling to room temperature. Data was collected in order to perform one-way analysis of variance (ANOVA). In this study, the ANOVA consisted of four levels of soaking time of 2, 4, 6 and 8 s and holding time of 4 s. All heat-treated specimens were then used to perform hardness and Charpy-V-Notch impact tests. The results showed that the hardness values increased with increasing of soaking time. The impact energy value slightly decreased with the soaking time range of 2-4 s whereas it rapidly decreased with the soaking time range of 4-6 s and slightly increased with the range of 6-8 s. However, the results from ANOVA showed that the soaking time did not significantly affect the averages hardness and impact energy at the level of significance of 0.05.
Effect of Ti Addition on Corrosion Properties of As-Cast and Hot-Rolled AM60 Magnesium Alloys
Authors: Sun Yavuz , Aydın Nazif Ugur , Turen Yunus , Ahlatci Hayrettin , Zengin Huseyin
Published: August 2017

This study investigates the effect of Ti addition (0, 0.2, 0.5, 1wt%) on corrosion resistance of as-cast and hot rolled AM60 magnesium alloy. Corrosion behaviors were investigated by immersion tests and electrochemical analysis. The results showed that Ti addition altered the microstructure of as-cast AM60 magnesium alloy by decreasing the amount of β-Mg17Al12 eutectic phase. Homogenization treatment resulted in the dissolution of the most of the β-Mg17Al12 phases. Homogenized samples exhibited the lowest corrosion rate in immersion test while the best corrosion resistance was found for hot-rolled samples in electrochemical test. In hot-rolled state, Ti addition led to a slight change in the corrosion resistance of AM60 magnesium alloy.
Effect of Sn Addition on Corrosion Properties of As-Cast and Hot-Rolled AZ31 Magnesium Alloys
Authors: Turen Yunus , Güzel Didem , Zengin Huseyin , Sun Yavuz , Ahlatci Hayrettin
Published: August 2017

In this study, the effect of Sn addition on corrosion resistance of as-cast and hot rolled AZ31 magnesium alloy was investigated. Sn additions were made by 0.2 wt%, 0.5 wt% and 1 wt%. An electric resistance furnace was used to produce alloys. Hot rolling process was performed at 350 °C by 40% thickness reduction at one rolling pass. Microstructure characterizations were performed by optical (OM) and scanning electron microscope (SEM). Immersion tests and electrochemical analyses were performed to investigate the corrosion resistance of the alloys. A 3.5% NaCl working solution at room temperature was used in both corrosion tests. The results showed that Sn addition decreased the primary dentrite size and restricted the growth of secondary dentritic arm. The as-cast structures transformed to dynamically recrystallized grain structures after hot-rolling process in all the alloys. Corrosion resistance of AZ31 magnesium alloy tended to decrease with Sn addition. This decrease was more clear in homogenized and hot-rolled states while there were some flactuations in as-cast states.
Design and Processing of FGCM Materials for Applications Subjected to Intensive Abrasive Wear
Authors: Badoi Ion , Constantinescu Dan Mihai , Vlasceanu Daniel
Published: August 2017

The present work shows the design criteria of FGCM, respectively selection criteria of PM (Powder Metallurgy) matrix, and use of reinforcement particles in correlation with the mechanical stresses resulting in moulds and punches used for steel cold extrusion, powder compaction, sheet metal stamping and series production of parts processed with these tools. Therefore, sintered and repressed state are analysed, and the microstructural and mechanical properties of steel powders used for matrices development, grade High Speed Steels (HSS), AISI M2 and AISI M4, and low alloyed steel powders Ancorsteel 2000 and Ancorsteel 4600 V are defined. Also there are analysed the physical and mechanical properties of the reinforcement particles TiC, WC, Al2O3, B4C, SiC, etc. Are presented the manufacturing methods, the technological parameters for development of functionally graded materials in vertical and horizontal plans, compacting to 500-600 MPa,, sintering temperature to 1050 °C for SiC reinforcement and 1100-1150 °C for matrix reinforced with Al2O3 , repressing to 600 MPa/1100 °C of sintered preforms, heat treatment and wear properties of FGCM materials as Ancorsteel 2000 and Ancorsteel 4600 reinforced with Al2O3 and SiC particles
Damping Capacity of Metallic Materials for Automotive Industry
Authors: Crăciun Radu Cristian , Stanciu Sergiu , Cimpoeşu Nicanor , Cimpoeşu Ramona , Manole Vasile
Published: August 2017

New requests from the automotive industry suppose to apply new materials with mechanical resistance to heat and vibrations and also with low weight. In order to replace plastic materials with high damping capacity a viable solution can be the metallic materials with sufficient internal friction to transform the external mechanical energy in thermal energy without affecting the microstructure or the mechanical properties of the metallic materials. In automotive applications an important role, especially in low velocity impacts, are the bumper elements. In this article possibility of copper-based shape memory alloys to fulfill the damping necessity of metallic materials is analyzed. Dynamic - mechanical analyze of few copper based shape memory alloys is realized and the results compared to proposed a better solution of Cu-based shape memory alloy for damping materials applications. The damping capacity difference between martensite and austenite like phases is also analyzed.
Study on Degradation Mechanisms of the Inner Surface of Fire-Arms
Authors: Petre Ivona , Bratu Vasile , Enescu Maria Cristiana , Stoian Elena Valentina , Anghelina Florina Violeta
Published: August 2017

This paper presents a study on the behavior of the inner surface of the gun barrel. The service life of the gun barrel of the cylinder is given by the state of their inner surface to which is necessary to know the phenimena leading to its degradation The study aims knowledge and analysis of phenomena taking place inside the cylinder pipe before and after a number of withdrawals and phenomena occurring dragging bullet pipe. Multiple requests at the same time acting corrosion may damage the pipe gun. The amount of wear by oxidation has been studied using the model parameters Quinn correlate the intensity of the action of various oxidation wear.The results showed that the pipes which have been treated electrochemically with a hard chromium layer exhibits a longer life than the untreated ones.
Aspects of the Structure and Corrosion Resistance of Materials Used in Tongue Piercings
Authors: Buzea Corina Mona , Csáki Ioana , Cotruț Mihai Cosmin
Published: August 2017

For centuries, piercing was an expression of art around the world and constituted a significant part of the culture and rituals of many different civilizations. This study evaluated the microstructure and the corrosion resistance in artificial saliva of two newly implantable devices used in tongue piercing. We investigated materials microstructure by optical microscopy and scanning electron microscopy (SEM), followed by an energy-dispersive X-ray spectroscopy (EDX) analysis in order to determine elemental composition. The corrosion resistance was determined by linear polarization technique. The corrosion tests were performed in artificial saliva Fusayama Meyer (composition: 0.4 gl-1NaCl, 0.9 gl-1 KCl, 1 gl-1 urea, 0.69 gl-1 NaH2PO4, 0.795 gl-1 CaCl * 2H2O) with a pH = 5.2 at temperature of 37 ± 0.5°C. The materials used for these types of implants were identified as Ti-6Al-4V alloy (sample 1) and austenitic stainless steel (sample 2). From corrosion resistance evaluation point of view, sample 1 showed the most electropositive value and hence better corrosion behavior compared to sample 2, having the Ecor potential -398.24 mV but this is clearly according the chemical composition of these two metallic biomaterials.
Pressure Influence on the AlCrFeNiMn/Graphite High Entropy Composite Microhardness
Authors: Popescu Gabriela , Branzei Mihai , Popescu Cristian Aurelian , Matei Alecs Andrei , Trusca Roxana , Csáki Ioana
Published: August 2017

During the last years, mechanical alloying technique for high entropy alloys (HEAs) has been more often approached due to the good homogenous chemical distribution and near net shape technology provided by the respectively process. A new composite material having the matrix as HEA reinforced with graphite particles was designed. The graphite particles addition in the high entropy matrix (AlCrFeNiMn) improves the particles weldability during mechanical alloying and assures a good creep behavior for the final product. The aim of this paper is to investigate the pressure influence on the microhardness as dependence of sintering parameters which can be reflected also on the microstructure. The high entropy composite was completely alloyed after 40 hours of milling. The obtained composite was pressed using different pressures values in order to investigate the pressure influence on the microhardness and microstructure. The samples were investigated using optical microscopy, scanning electron microscopy, X-rays diffraction and microhardness tests. The microhardness values for all the samples were between 300 – 700 HV.
Characterization of Cr2O3 Adhesion Properties by Destructive Testing in Accordance with the APS Metal Spraying Process Parameters
Authors: Gheța Roxana Alexandra , Goran Mariana , Bușaru Alina Elena , Bichir Laurenția , Dumitru Gabriel Marius
Published: August 2017

This paper aims to study the correlation between some parameters of the metalspraying by APS process and the level of chromium oxide (Cr2O3) adhesion to the base material. Among the properties of the layers deposited by APS are those of wear resistance. In the context of evaluating the coatings properties and understanding aspects related to the coat structure phenomena, the purpose of the experiment presented here is to characterize the adherence of thermal sprayed coating Cr2O3. Because, the main problem of metalspraying layers is adhesion to the base material, there were subjected to tensile testing 2 samples made by 1C45 steel, which were previously bonded with an epoxy glue. The adhesion of the deposited layer on the basic material is important for ensuring the quality of products. The results show that the quality of surfaces and the existence of accidental defects at the interface lead to a decrease of adherence.
Improvement of Structural, Morphological and Mechanical Properties of CrNx Sputtered Thin Films by Vacuum Annealing Process
Authors: Nualkham Intira , Sakdanuphab Rachsak , Sakulkalavek Aparporn
Published: August 2017

In this study, CrNx thin films were prepared on 304 stainless steel substrate by DC reactive magnetron sputtering technique. Different N2 gas partial pressure from 10 to 30% was employed in the sputtering process while sputtering power, sputtering pressure and total film thickness were kept constant. In order to improve structural, morphological, and mechanical properties, vacuum annealing process was adopted on the CrNx thin films at the temperature of 400 oC. The standard characterization techniques such as X-ray diffraction, scanning electron microscope, atomic force microscope and hardness (load force of HV0.1) were used to reveal the properties of as-deposited and annealing films. The as-deposited films show two-phase crystal structure of Cr2N and CrN depending on N2 gas partial pressure. After the annealing process, the films effectively enhance the crystal structure and found the phases change from Cr2N to CrN for the film deposited at low N2 partial pressure. The surface roughness of the films was between 5 - 20 nm, and as expected the annealing films shows smoother surface than the as-deposited films. Hardness of the CrNx films is in the range of 7 to 10 GPa. The mechanism of improvement in structural and mechanical properties of annealing films is introduced based on strain relaxation.
Fastenerless-Riveting Utilizing Friction Stir Forming for Dissimilar Materials Joining
Authors: Ohashi Takahiro , Tabatabaei Hamed Mofidi , Nishihara Tadashi
Published: August 2017

This paper proposes a new joining approach for dissimilar materials, called ‘the fastenerless-riveting,’ employing the friction stir forming (FSF). The FSF is a friction stir process invented by Nishihara in 2002. In FSF, a substrate material was put on a die firstly. Next, friction stirring was conducted on the back surface of the material. The material then deformed and precisely filled the cavity of the die due to high pressure and heat caused by the friction stirring. The authors utilized the FSF approach to generate rivet like joints as followings. First, a substrate which is capable for friction stirring, i.e. an aluminum alloy plate, was put on a dissimilar material plate having holes, i.e. a steel plate. The authors call the former ‘the host member,’ the latter ‘a joined member.’ These members were put on a die having the cavity to fabricate the head of the rivet-like structure. Then FSF was conducted to form the stems and heads of the structure. Joint members are able to be stacked within the forming limit. In the study, the authors firstly conducted the proof of the concept (PoC) tests to generate rivet-like structure between steel and aluminum alloy plate and between CFRP and aluminum alloy plate, then investigated the forming conditions, i.e. tool feed rate, tool pass and the corresponding results, including the volume of the generated stem and head of the individual rivet-like structure. 3mm-thick A5083P-O aluminum alloy plates was utilized as the host member, and a 0.7mm-thick SPCE steel plate and a 0.8mm-thick CFRP plate as the joined members.
Influence of Scanning Parameters on X-Ray Diffraction Peaks of Copper
Authors: Chakartnarodom Parinya , Kongkajun Nuntaporn , Laitila Edward A.
Published: August 2017

The aim of this work is to study the influence of x-ray diffractometer scanning parameters on the integrated intensity and full-width at half maximum (FWHM) of copper powder x-ray diffraction peaks by using statistical analysis methods. X-ray diffraction (XRD) analysis of the copper powder was accomplished using step scan mode with step sizes of 0.03o and 0.05o 2q, and preset time changes from 0.1-3.5 s. Integrated intensity of an x-ray peak was calculated by the numerical method. FWHM was measured as the width of Pearson VII model of the x-ray peak at the half-maximum intensity. The statistical analysis methods including linear regression and statistical hypothesis test were used to analyze the correlation between the preset time and the error on integrated intensity calculation, and the FWHM of a peak on the XRD pattern. The results from statistical analysis show that increasing the preset time from 0.1 s to 3.5 s does not affect the FWHM of an x-ray peak, but it reduces the relative error in integrated intensity calculation. Moreover, using the preset time greater than 1 s will minimize the relative error in integrated intensity calculation of an x-ray peak. While step size did not affect both the relative error in integrated intensity calculation or FWHM, the smaller step size would provide more data points for better accurate model of an x-ray peak.
The Investigation of Ultrasonic Energy Attenuation in AISI 316 Stainless Steel Weld Joint
Authors: Noipitak Mai , Khwansri Boonhlua
Published: August 2017

This research aims to study and describe the effect of microstructure on shape of distance amplitude correction (DAC) curve and ultrasonic inspectability of stainless steel weld joint. Two calibration blocks (side drilled hole block) were prepared from AISI 316 stainless steel plate according with ASME section V version 2013. One calibration block was varied the grain size by annealing process. The annealing temperature and holding time were 1,200 °C and 4 hours, respectively and then cooled down in furnace. AISI 316 Butt joint welding specimens were prepared to establish the artificial discontinuities. Lack of fusion and drill hole, diameter 1 and 2.5 mm, were selected to establish as discontinuities. Specimens were welded by gas tungsten arc welding and shielded metal arc welding process. Then, the gain size and microstructure of two calibration blocks were analyzed by microscope. The macrostructure, gain size and microstructure of weld joint were determined by microscope. Longitudinal and transverse wave with probe frequency 2.25 and 4 MHz and angle probe 45, 60 and 70 degrees were used to describe the effect of microstructure on shape of DAC curve and investigate the ultrasonic inspectability in stainless steel weld. The experiment results found that the ultrasonic energy of longitudinal and transverse wave in calibration blocks decreased as the gain size increased. The attenuation due to gain size affected to the shape of DAC curve. The grain size in heat effected zone (HAZ) of weld specimen is larger than base material and the ultrasonic transverse wave can detect lack of fusion and drill hole diameter 2.5 mm but cannot detect drill hole diameter 1 mm. The usefulness of this research is utilizable for searching the discontinuities in the weld zone of stainless steel by ultrasonic. The attenuation of ultrasonic energy in the weld zone of AISI 316 is usually high and the amplitude displayed at the screen is very low. This reason can be made the operator wrong result interpretation, if they did not consider about the attenuation from microstructure.
Influence of Molecular Weight on the Non-Isothermal Melt Crystallization of Biodegradable Poly(D-Lactide)
Authors: Limwanich Wanich , Phetsuk Sawarot , Meepowpan Puttinan , Kungwan Nawee , Punyodom Winita
Published: August 2017

The influence of molecular weight of poly (D-lactide) (PDL) on the melt crystallization was successfully investigated by non-isothermal differential scanning calorimetry (DSC) technique. The synthesized PDLs with three different number average molecular weights (Mn) of 2.39×105 (PDL1), 1.09×105 (PDL2) and 0.61×105 (PDL3) were utilized in this study. From DSC kinetics analysis, it was found that the rate of PDLs crystallization increased with increasing cooling rate. Furthermore, the crystallization rate of PDLs was dependent on molecular weight and determined to be in the following order: PDL3 > PDL2 > PDL1. The crystallization mechanism was analyzed by the Avrami, Ozawa and Liu models. The mechanism of all PDLs crystallization was nucleation with three dimensional growths. Furthermore, the molecular weight of PDLs affected not only the crystallization rate but also the thermal property. As the molecular weight of PDLs increased, the melting temperature (Tm) increased but the heat of melting (∆Hm) decreased.
Medicated Pressure Sensitive Adhesive Patches from STR-5L Block Rubber: Effect of Preparation Process
Authors: Kalkornsurapranee Ekwipoo , Waiprib Rungtiwa , Pichayakorn Wiwat
Published: August 2017

STR-5L is a high quality block rubber in Thailand that is interesting to apply in medical and pharmaceutical products because it has very low impurity but high uniformity. In this study, medicated pressure sensitive adhesive (PSA) patches were developed by melt blending technique using hydroxyethyl cellulose (HEC) as tackifier and paraffinic oil as softener. Two rolls mill was used to blend all ingredients and the thin PSA patches were rolled out. Various preparation parameters were studied such as initial viscosity of rubber (60 or 80 Mooney viscosity; MV), mastication time (5-20 minutes), step of mixing, mixing time (35-80 minutes) and gap between rollers (0.1-0.4 mm). The suitable processing conditions were optimized. It was found that the rubber having initial viscosity of 80 MV provided better physical properties, for example, higher force T-peel, lap shear strength and shear holding time. Longer mastication time increased the shear holding time of patches. At 70 minutes of mixing time, the patches showed the highest shear holding time and did not leave any residue on the testing equipment surface. Moreover, the shear holding time decreased when the gap between rollers was expanded. Mixing method with the sequential addition of STR-5L, HEC and then paraffinic oil, provided good PSA patches. However, preparation process did not affect the plasticity retention index of PSA patches due to there were not significant change of values when those all parameters were varied. Next, lidocaine or its hydrochloride salt in powder form could be blended into this PSA to be the homogeneous patches. This lidocaine PSA patches for local anesthetics application on the skin would be evaluated in further study.
Properties of Sintered Bronze-Graphite Containing Calcium Sulfate Derived from Waste Plaster Molds
Authors: Auechalitanukul Chiraporn , McCuiston Ryan C. , Bunlangsup Benjawan , Naikorn Chanattha , Tapanaun Sudachuan
Published: August 2017

This study examined the effect of calcium sulfate additions on the microstructure and frictional properties of a 95bronze-5graphite material, commonly used for frictional applications. The samples were prepared using a powder metallurgy process. The calcium sulfate powder was obtained from recycled plaster molds previously used for ceramic slip casting. The plaster molds were cleaned, crushed and ball milled to obtain powder, which was calcined at 400 °C for 4 hours and screened. 2 to 8 weight percent calcium sulfate powder was added to a premixed powder composed of copper and tin and mixed before the graphite was added. The powder mixture was compacted into a disc shape under a pressure of 500 MPa. The compacted samples were sintered at 750 °C for 30 minutes in a reducing atmosphere. It was found that the green density of the samples decreased with increased amounts of calcium sulfate. After sintering, the densities were found to have decreased due to sample expansion. A finer microstructure was observed in the samples containing calcium sulfate powder, possibly due to a grain boundary pinning effect. The addition of calcium sulfate resulted in the reduction of both the measured friction coefficient and wear of the bronze-graphite samples. However, the addition of calcium sulfate powder above 6 weight percent appeared to show decreasing effects.
Simulation of Irradiation-Based Processing System for Natural Rubber Vulcanization
Authors: Kosaentor Kittiya , Kongmon Ekkachai , Thongbai Chitrlada , Rimjaem Sakhorn
Published: August 2017

Natural rubber is an important export product of Thailand, which presently contributes about 40% of global production and export. In order to make the natural rubber latex to be durable material, the proper vulcanization process is needed. In typical vulcanization process, chemical substances are added to improve the rubber properties. This may cause some problems e.g. toxicity, blooming effects and unpresented smell due to the additive substances. Vulcanization using an accelerated electron beam does not need to add possibly toxic chemical compounds, especially sulfur. Thus, it was proved to be an alternative method for high quality natural rubber vulcanization. This paper presents about simulation of electron beam irradiation for natural rubber vulcanization with variable electron beam energy and current of 0.5-4 MeV and 10-100 mA, respectively. These ranges of the electron beam energy and current will give adjustable absorb dose, which is the most important parameter for electron beam processing. The absorb energy and its distribution in the natural rubber latex are simulated by using a Monte Carlo method program, GEometry ANd Tracking 4 (GEANT4), with the aim to find the optimal conditions of electron beam properties for sufficient natural rubber vulcanization. Study results of the energy distribution for electron beam penetration in the natural rubber latex are presented and discussed in this paper.
Effect of Poly(D-Lactic Acid)-co-Polyethylene Glycol on the Crystallization of Poly(L-Lactic Acid)
Authors: Kaewlamyai Ployrawee , Lertworasirikul Amornrat
Published: August 2017

Poly (lactic acid) (PLA) is a biopolymer derived from renewable resources and can be disposed of without creating harm to the environment. PLA can be formed by thermoplastic processes and has good mechanical properties. However, its disadvantages are a high crystallization temperature, slow crystallization rate, poor heat stability and low ductility. In the past, it was found that poly (D-lactic acid) (PDLA) can form complexes with poly (L-lactic acid) (PLLA) and the complexes could accelerate the crystallization and increase the degree of crystallinity of the PLA, but decrease the ductility. It is known that polyethylene glycol (PEG) can improve the ductility of PLLA. In this research, PDLA was copolymerized with PEG in an attempt to improve both crystallization behavior and ductility of PLLA. Poly (D-lactic acid)-co-polyethylene glycol (PDEG) was synthesized by ring opening polymerization using D-lactide and PEG at a D-lactide:PEG weight ratio of 10:3. The PDEG was blended with PLLA with a PDEG content of 0wt% to 50wt% by melt blending process. Fourier transform infrared spectrometry (FT-IR) and X-Ray diffractometry (XRD) confirmed the stereocomplex formation between PDEG and PLLA. Characterization by differential scanning calorimetry (DSC) revealed that crystallization temperatures of the blends were decreased in the presence of PDEG. Storage moduli and tan of the blends obtained from dynamic mechanical analysis (DMA) decreased as PDEG content increased. Polarized optical microscopy (POM) micrographs of blends with PDEG content of 1wt% to 5wt% obviously showed that crystallization rate was increased. PDEG has the potential to be an effective nucleating agent and efficient plasticizer for PLLA.
The Thermal-Aging Effect on the Microstructure Evolution and Shear Strength of the Sn-Rich Au-Sn Soldering between Altic and Si Substrate in Microelectronics
Authors: Athichalinthorn Panaaek , Darayen Jidsucha , Puttichaem Wachira , Techapiesancharoenkij Ratchatee , Lohwongwatana Boonrat
Published: August 2017

The Au-Sn soldering alloys are commonly used in microsoldering process for microelectronic industry due to fluxless process and relatively low melting temperature with good eutectic microstructures. This study investigated the microstructures of Au-Sn soldering between AlTiC and Si substrates with Ti/Pt/Au under bump metallization (UBM). The microstructures of the solder samples under three conditions: before bonding, after bonding and after thermal-cycle aging, were investigated. The shear strength values of pre-aging and post-aging soldering were compared. The thermal-cycling temperatures were ranged from -40 to 125 °C for 300 cycles. The intermetallic compounds (IMCs) of the AuSn solders consist of AuSn, AuSn2, and AuSn4. After thermal-cycle aging, the bonding strength was increased due to the improved IMC bonding between solders and UBM; the shear surfaces were rougher due to the growth of AuSn and AuSn2.
Degradation of Silica-Reinforced Natural Rubber by UV Radiation and Humidity in Soil
Authors: Reowdecha Manuchet , Sukthaworn Chalermchat , Dittanet Peerapan , Moonprasith Nantina , Lampang Thipjak Na , Loykulnant Surapich , Prapainainar Paweena
Published: August 2017

In this research study, the degradation of natural rubber was applied for applications in agriculture products such as rubber mulch. This work included the synthesis of 20% wt silica/ natural rubber composites from high ammonia concentrate latex (HA) and fresh latex (FL). They were casted by film casting. The experimental study of rubber composite degradation was done by putting the samples underground and above the soil surface under accelerated degradation test box equipped with a solar simulator lamp for a period of 50 days. Samples were characterized by scanning electron microscopy (SEM) to examine the dispersion on cross-sectional area between natural rubber and silica. Thermogravimetric analysis (TGA) was used to analyze the thermal stability of the composites. Tensile strength (MPa), modulus at 100% elongation (MPa), and elongation at break (%) of the samples after aging were tested by focusing on. It was found that thermal degradation of natural rubber compounds consisted of one step of mass loss between 341°C and 455°C. The SEM result showed good dispersion of Si in the rubber samples. Moreover, it was found that before aging, the composite samples had higher tensile strength than that of the rubber. After aging, the composite samples had lower tensile strength than that of the rubber. Elongation @ break value of HA/Si and FL/Si after aging were decreased obviously.
Mechanical and Thermal Properties of PLA Melt Blended with High Molecular Weight PEG Modified with Peroxide and Organo-Clay
Authors: Thongpina Chanchai , Tippuwanan Chaiwat , Buaksuntear Kwanchai , Chuawittayawuta Teerani
Published: August 2017

The thermal and mechanical properties of poly (lactic acid) blended with high molecular weight PEG, i.e. PEG1000 and PEG6000 were compared. The contents of PEG added were 10, 12.5 and 15 % by weight, with respect to PLA. The PLA/PEG blends were modified by addition of organic peroxide in order to induced crosslinking. Addition of organic modified montmorrillonite (Cloisite 30B, C30B) was also performed in order to modify mechanical performance of PLA/PEG blends. C30B was prepared via master batch in PLA. Morphology, crystallization, thermal stability and mechanical properties of the blends were investigated using SEM, DSC, TGA and universal testing macine, respectively. Morphology of cryogenic fracture surface showed smooth brittle surface. PEG1000 well plasticized PLA where as PEG6000 shows better thermal stability and mechanical properties. The presence of PEG induced PLA to perform cold crystallization. Tm in PLA was slightly changed whereas degree of crystallinity of PLA was improved by PEG but slightly decreased by peroxide. The thermal stability of PLA was enhanced with the addtion of PEG6000. The toughening of PLA was confirmed by the increment of elongation at break. The exfoliation of C30B was interfered by the crosslink PLA. Then tensile strength of PLA/PEG/C30B/Luperox101 was then suppressed. The optimum properties, in term of toughening and thermal stability, were found at PEG content of 10 % rather than 15% by weight, for both PEG1000 and PEG6000.
Poly(Lactic Acid)-Polybutylene Succinate-Activated Carbon Composite Foams
Authors: Ketkul Kittimasak , Threepopnatkul Poonsub , Aussawasathien Darunee , Hrimchum Kittipong
Published: August 2017

Polymer blends of poly (lactic acid) (PLA) and polybutylene succinate (PBS) containing activated carbon (AC) were foamed by using Azodicarbonamide (ADC) through an extrusion process. The composite foams containing 5 phr of AC had lower density than those without AC loading for PLA:PBS ratios of 90:10, 80:20, 70:30, and 60:40. The incident of higher void fraction was the consequences of more foaming nucleation centers which were induced by adding AC in the composite foam. Maximum reduction of density by 50% with the void fraction of 50% was achieved when both ADC and AC were applied at 5 phr with the PLA:PBS ratio of 80:20. The addition of AC in composite foams enhanced the crystallization in PBS phase but had no effects on PLA crystallinity. The thermal stability of composite foams with and without AC dosages for each PLA:PBS proportion was slightly changed. For PLA-PBS blend foams, the more PLA loading there was the more tensile strength and modulus there would be. For PLA-PBS-AC composite foams, AC could improve the modulus and tensile strength of composite foams in PBS-rich samples whereas no effect on PLA-rich samples.
Slip Degassing to Improve the Properties of Slip Cast and Reaction Bonded Si3N4
Authors: Somton Kritkaew , Rodchom Mana , Wonglom Thassanee , Dateraksa Kannigar , McCuiston Ryan C.
Published: August 2017

The effect of slip degassing on the microstructure and mechanical properties of slip cast and reaction bonded Si3N4 was studied. The slip was prepared by aqueous ball milling of silicon (Si) powder. Hydrogen bubbles, a result of Si oxidation during milling, were degassed from the slip using a combination of vacuum and heat. The slip was then cast into a plaster mould to obtain rectangular green bodies. The Si green samples were sintered in a nitrogen atmosphere at 1500°C to convert the Si to Si3N4. After that the nitrided samples were polished to dimensions of 3 x 4 x 30 mm. The density, porosity, flexural strength, phase content and microstructure of the sintered samples were studied. The results showed that the degassing process increased the slip density. After casting and subsequent nitridation, it was found that the average apparent density of the samples increased from 2.89 to 2.95 g/cm3, the porosity decreased from 52.9 to 49.5 %, and the flexural strength increased from 8.1 to 9.3 MPa, when the degassed slip was used. A microstructural examination showed that the pores in the samples were filled with whiskers, which most likely resulted from a vapor phase growth mechanism. The samples produced from the degassed slip tended to have fewer whiskers, due to the reduced pore size and volume. A comparison of the XRD patterns showed no phase differences between the samples. The appearance of Si2N2O, and SiC likely resulted from the reactions between O2 and C impurities with Si3N4.
Synthesis of Nanocrystalline Cobalt Ferrite by the Sonochemical Method in Highly Basic Aqueous Solution
Authors: Pasupong Patchara , Choojun Kittisak , Vittayakorn Naratip , Seeharaj Panpailin
Published: August 2017

This study reported the preparation of nanocrystalline CoFe2O4 in single step by the sonochemical method in highly basic aqueous solution without requiring of high temperature calcination process. To prepare nanocrystalline CoFe2O4, the mixed solution of the required molar ratio of cobalt nitrate hexahydrate (Co (NO3).6H2O) and ferric nitrate nonahydrate (Fe (NO3).9H2O) was precipitated in high concentration of sodium hydroxide medium solution (NaOH) under high intensity ultrasonic irradiation (20 kHz, 150 W/cm2). The effect of NaOH concentration (5, 10, 15 and 20 M) on phase formation, microstructure and magnetic property of CoFe2O4 was investigated. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) results showed that the as-prepared powders were single phase CoFe2O4 with cubic spinel structure. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) study showed that nanocrystalline CoFe2O4 had monosized distorted spherical morphology and an agglomeration of the nanocrystalline CoFe2O4 into nanoparticles was observed when increasing the NaOH concentration. The nanocrystalline CoFe2O4 exhibited superparamagnetic property and the saturation magnetization (Ms) obtained from vibrating sample magnetometry (VSM) was found to correlate with the crystallite size and varied from 39-45 emu/g.
The Effect of Zirconium Oxide on Properties and Crystallization of Soda-Lime Silicate Glass
Authors: Meechoowas Ekarat , Suriyoporn Surisa , Pantulap Usanee , Tapasa Kanit
Published: August 2017

In this study, the properties and crystallization of re-melted soda-lime silicate glass cullet added with Al2O3, CaCO3 and ZrO2 were investigated in order to study the potential usage as a parent glass for glass-ceramics. Al2O3, CaCO3 and ZrO2 were added into the 71SiO2-10Na2O-6K2O-5CaO-4MgO-2SrO-ZrO2-Al2O3 glass cullet to increase the crystallization of the glass. The glass batches (%wt) of (65-x) Cullet:13Al2O3:22CaCO3:xZrO2 (x = 0, 1, 2, 4, 6 and 8) were melted at 1500°C for 3 hours. The crystallization was investigated by Differential Scanning Colorimetry technique (DSC) and it was found that the glasses with 6 and 8 %wt of ZrO2 crystallized rapidly. It means that ZrO2 acted as the nucleating agent in this glass system. The major crystallines determined by X-ray diffraction technique (XRD) were silica (SiO2), wollastonite (CaSiO3) potassium silicate (K6Si3O9) and zirconium oxide (ZrO2). The thermal expansion of glasses determined by dilatometric method indicated the characteristic of glass-ceramics and the effect of ZrO2 on the thermal properties of glass. In conclusion, modifying the composition of soda-lime silicate cullet with Al2O3 CaCO3 and ZrO2 had potential to produce glass-ceramics.
Structure, Magnetic Property and Energy Band Gap of Fe-Doped NiO Nanoparticles Prepared by Co-Precipitation Method
Authors: Toboonsung Buppachat
Published: August 2017

Fe-doped NiO nanoparticles was prepared by the co-precipitation method. The precipitation solution were used the concentration of FeSO4 mixing NiCl2 for 0.5 M. The precipitation process was used a magnetic stirrer of 1100 rpm, a temperature of 30-60 OC for 0.5 h and the dropping a NaOH of 0.5 M in the mixing solution. The precipitate product was dried at the temperature of 120 OC for 9 h and calcined in a furnace at the temperature of 400 OC for 4 h in air atmosphere. The powder product was analyzed a crystal structure by a x-rays diffractometer, calculated an energy band gap by UV-VIS spectrophotometer, measured a magnetic properties by a vibrating sample magnetometer and explained morphology by a scanning electron microscope. It was found that the crystal structure was shown face center cubic. The nanoparticles in the range of 30-100 nm was observed the morphology of the optimum product. However, the coercive, the magnetic moment and the energy band gap was found the optimum at the doping Fe of 8 wt% at the precipitation temperature of 40 OC.
Chemical Composition-Microstructure-Dielectric Constant Relations of Mg-Doped Calcium Titanate Synthesized by Solid State Reaction Technique
Authors: Jongprateep Oratai , Sato Nicha , Palomas Jednupong , Jantaratana Pongsakorn
Published: August 2017

It has been generally accepted that doping of dielectric materials could significantly contribute to compositional and microstructural evolution, which consequently lead to alteration in dielectric properties. In this study, the effects of adding magnesium (Mg) at 5,10 and 20at% on the chemical composition, microstructure and dielectric constant of calcium titanate (CaTiO3) synthesized by solid state reaction was assessed. Chemical composition analysis using an X-ray diffraction technique CaTiO3 doped with 5 at% Mg has been found to contain a single phase whereas samples doped with 10 and 20 at% Mg both exhibited apparent secondary phase (MgO). Microstructural examination however, revealed that no significant variation in particle size, grain size and density were evident among the samples of different Mg contents. Average dielectric constants obtained from the entire samples ranged from 245.9 to 387.6 (at 1 MHz) and the sample with the highest dielectric constant was that doped with 5 at% Mg. Enhancement of dielectric constant in the samples with the lowest level of Mg doping has been attributed largely to the homogeneity of its chemical composition.
Development of Glass-Ceramics from Soda Lime Silica Glass Waste by Direct Sintering Method for Opal Imitation
Authors: Bootkul Duangkhae , Intarasiri Sawet
Published: August 2017

Natural opal, an amorphous, hydrous form of silica (SiO2-n-H2O), has been one of the favored precious gemstones for many centuries. Though beautiful, opal is very fragile and is damaged quite easily. Thus, opals of all varieties have been synthesized experimentally and commercially. The objective of this project was to synthesize and to compare crystalline opals. In this work, the development of powder sintered glass ceramics process based on soda lime silica glass waste with metal oxide powder enable jewelry applications. The substantial viscous flow of the glass led to dense products for rapid treatments at relatively low temperatures (900–1,000°C), whereas glass/metal powder interactions resulted in the formation of color agent crystals, provide enhancing optical properties. Several techniques were applied for characterization of the ingots. The chemical analysis was performed by Energy Dispersive X-ray Fluorescence (ED-XRF). The mineralogical compositions of the samples were determined by X-ray diffraction analysis. Raman spectroscopy was applied for optical characterization. The results were compared with a natural common opal. The present investigation demonstrated that the common opal with both color and colorless appearance can be synthesized by the technique, as the crystalline phase of opal structure was identified by XRD measurement. There is a great potential for such materials with novel functionalities for artificial gemstone application, i.e. opal forming.
Effects of Aluminium Contents and Consolidation Techniques on Chemical Composition, Microstructure and Dielectric Properties of Strontium Titanate
Authors: Palomas Jednupong , Jongprateep Oratai
Published: August 2017

It has been accepted that compositions and microstructures significantly affected
dielectric properties of materials. In general, chemical compositions were influenced by additive
contents, while consolidation techniques controlled microstructure of the materials to have
appropriate grain sizes. This study, therefore, aimed at examining effects of aluminium contents and
consolidation techniques on chemical compositions and microstructures of the strontium titanate.
Experimental results revealed that at higher aluminium contents, only small quantities of TiO 2
secondary phase were present, while grain sizes generally decreased. The results also indicated that
the cold isostatic pressing technique led to high sintered density. The greatest dielectric constant
(281.5 at 1 MHz) obtained in this study was achieved in strontium titanate sample with 30 at% of
Al addition, pressed by cold isostatic pressing. Enhancement of dielectric constant of the sample
was attributed to low secondary phase, fine grain sizes and high sintered density.