Influence of Aluminium and Autoclaving Temperature on the Properties of Autoclaved Aerated Concrete

Autoclaved aerated concrete (AAC) prepared by the mixing of ordinary Portland cement, lime powder, sand, aluminium powder and water. This study covers the variation of physical, mechanical and functional properties of autoclaved aerated concrete with autoclaving temperature and aluminium content and compared with that of normal weight cement mortar sample. In this work, two dosage of aluminium content of 0.4% and 0.8% of the dry weight of ordinary Portland cement and three different autoclaving temperature of 160oC, 180oC and 200oC were used. AAC sample with 0.8% aluminium and 160oC temperature had unit weight of 1490kg/m3 which was lowest among all samples including the control or normal weight cement blocks. Weight reduction of AAC sample was 31.53%. AAC sample with 0.4% aluminium and 200oC autoclaving temperature gave maximum compressive and tensile strength of 19.4MPa and 1.81MPa respectively which were close to that of normal weight concrete and strength of AAC increased with autoclaving temperature and decreased with aluminium content. In this research, the functional propertiesof AAC, absorption capacity was much higher than normal weight concrete and this capacity was increased with aluminium content and with decreasing autoclaving temperature and unit weight of AAC. For AAC with 0.8% aluminium and 160oC temperature gave maximum water absorption capacity (=9.93%). Again, surface absorption rate was higher for first 12hours and with time it would be constant because of its saturated position. Journal of Engineering Science 12(3), 2021, 11-17

Pengaruh priming terhadap vigor benih kedelai (Glycine max (L.) Merril.) yang dikecambahkan pada media dengan cekaman alumunium

Kandungan aluminium yang tinggi pada tanah Ultisol merupakan salah satu masalah utama dalam budidaya tanaman kedelai mulai dari fase perkecambahan hingga pertumbuhan tanaman. Perlakuan priming pada benih diyakini mampu memperbaiki perkecambahan pada lingkungan yang kurang menguntungkan. Penelitian dilakukan untuk mengetahui pengaruh priming pada perkecambahan benih kedelai yang dikecambahkan dalam media masam dan mengandung aluminium. Penelitian disusun dalam Rancangan Acak Lengkap (RAL) pola faktorial. Faktor pertama adalah jenis priming : tanpa priming, H2O (air), KNO3 1%, KNO3 2%, GA3 50 ppm, GA3 100 ppm, dan PEG 6000 7,5%. Faktor kedua adalah varietas kedelai yaitu: Anjasmoro, Burangrang, dan Grobogan. Data dianalisis sidik ragamnya dan dilanjutkan dengan uji Beda Nyata Jujur (BNJ) 5% menggunakan program statistika R Studio. Hasil penelitian menunjukkan priming PEG 7,5% dan varietas Burangrang secara mandiri merupakan perlakuan terbaik untuk meningkatkan vigor benih kedelai berdasarkan variabel waktu muncul kecambah, kecepatan perkecambahan, dan panjang hipokotil. Implikasi penelitian ini adalah PEG 7,5% dapat digunakan untuk perbaikan perkecambahan pada tanah masam dengan kandungan aluminium yang relatif tinggi. High aluminium content in Ultisol is the main problem in soybean cultivation from germination to planting growth phases.Priming treatment is believed to improve seed germination in a poor-growing environment. This study aimed to determine the effect of priming of soybean seeds germinated under acid medium and aluminium stress. The experimental design used was Completely Randomized Design (CRD) with factorial pattern. The first factor was priming type : no priming, H2O (water), 1% KNO3, 2% KNO3, 50 ppm GA3, 100 ppm GA3, and 7.5% PEG 6000. The second factor was soybean variety : Anjasmoro, Burangrang, and Grobogan. The data obtained were analyzed using the R Studio statistic program with a 5% HSD test. The study resulted that each PEG 7.5% priming and Burangrang variety independently was the best in increasing soybean seed vigor based on sprout time emergence, germination speed and hypocotyl length. This research implicates that PEG 7.5% can be used to improve seed germination on acid soils with high aluminium content.

Effect of Inhomogeneous Broadening in Ultraviolet III-Nitride Light-Emitting Diodes

In the past years, light-emitting diodes (LED) made of GaN and its related ternary compounds with indium and aluminium have become an enabling technology in all areas of lighting. Visible LEDs have yet matured, but research on deep ultraviolet (UV) LEDs is still in progress. The polarisation in the anisotropic wurtzite lattice and the low free hole density in p-doped III-nitride compounds with high aluminium content make the design for high efficiency a critical step. The growth kinetics of the rather thin active quantum wells in III-nitride LEDs makes them prone to inhomogeneous broadening (IHB). Physical modelling of the active region of III-nitride LEDs supports the optimisation by revealing the opaque active region physics. In this work, we analyse the impact of the IHB on the luminescence and carrier transport III-nitride LEDs with multi-quantum well (MQW) active regions by numerical simulations comparing them to experimental results. The IHB is modelled with a statistical model that enables efficient and deterministic simulations. We analyse how the lumped electronic characteristics including the quantum efficiency and the diode ideality factor are related to the IHB and discuss how they can be used in the optimisation process.

Effect of reinforcements on graphite/titania/aluminium nanohybrid composites

Aluminium alloys and their composites are often used in aerospace, automobile and biomedical applications. However, mechanical and surface properties of those alloys have not reached up to the expectation. This investigation focused to improve the wear resistance properties along with mechanical and surface properties of aluminium matrix composites. Here, novel aluminium matrix nanohybrid composites were developed using titanium oxide and graphite as reinforced via powder metallurgical route. The sintered samples were analysed by different tests such as, hardness, surface roughness, wear tests and other structural analyses. The obtained results showed that some new compounds formed during sintering were responsible for improved mechanical and surface properties for different applications. The wear test showed that there was rapid worn out of graphite from the composites having aluminium content more than 50 wt% due to the higher content of graphite (10 and 20 wt%, respectively). In addition, due to the increase of porosity in the different hybrid composites, there was an increase in coefficient of friction observed in some materials. The aluminium nanohybrid composite having 40 wt% titania and 10 wt% graphite showed best results compared with others. Therefore, the optimized hybrid composites with proper sintering condition would significantly help to get suitable structural, mechanical as well as tribological properties for many advanced applications.

The Influence of Varying Aluminium and Manganese Content on the Corrosion Resistance and Mechanical Properties of High Strength Steels

The aim of this paper is to evaluate the influence of small variations in chemical composition on the corrosion resistance and mechanical properties of low-manganese and medium manganese high strength steels. Six different steels with manganese content varying from 1.5 to 4.0 wt.% and aluminium from 0.008 to 6.5 wt.% were subjected to the analysis. The other subjects for evaluation included the effect of aluminium as a replacement for silicon, niobium microalloying and the effect of heat treatment. The effect of non-metallic inclusions on localized corrosion initiation and propagation was also documented. Using potentiodynamic testing, exposure testing, tensile and impact testing, it was found that the improvement in corrosion resistance associated with increasing aluminium content is accompanied by a significant deterioration of the mechanical properties. Niobium microalloying and heat treatment was found to have no quantifiable impact on the anti-corrosion properties. The effect of aluminium content proved to be superior to the effect of nonmetallic inclusions in terms of determining the overall corrosion resistance of the experimental steels.

Investigating the growth of AlGaN/AlN heterostructure by modulating the substrate temperature of AlN buffer layer

We have investigated the impact of AlN buffer layer growth parameters for developing highly single crystalline AlGaN films. The low mobility of Al adatoms and high temperature for compound formation are amongst the major causes that affects the growth quality of AlGaN films. Thus, proper optimization need to be carried out for achieving high quality AlGaN due to an augmented tendency of defect generation compared to GaN films. Thus, growth conditions need to be amended to maximize the incorporation ability of adatoms and minimize defect density. So, this study elaborates the growth optimization of AlGaN/AlN/Si (111) heterostructure with varied AlN buffer growth temperature (760 to 800 °C). It was observed that the remnant Al in low temperature growth of AlN buffer layer resist the growth quality of AlGaN epitaxial films. A highly single crystalline AlGaN film with comparatively lowest rocking curve FWHM value (~ 0.61°) and smooth surface morphology with least surface defect states was witnessed when AlN buffer was grown at 780 °C. From the Vegard’s law, the photoluminescence analysis unveils Aluminium composition of 31.5% with significantly reduced defect band/NBE band ratio to 0.3. The study demonstrates good crystalline quality AlGaN film growth with Aluminium content variation between ~ 30–39% in AlGaN/AlN heterostructure on Si(111) substrate leading to a bandgap range which is suitable for next-generation solar-blind photodetection applications.

Investigation on the Microstructure of ECAP-Processed Iron-Aluminium Alloys

The present work deals with adjusting a fine-grained microstructure in iron-rich iron-aluminium alloys using the ECAP-process (Equal Channel Angular Pressing). Due to the limited formability of Fe-Al alloys with increased aluminium content, high forming temperatures and low forming speeds are required. Therefore, tool temperatures above 1100 °C are permanently needed to prevent cooling of the work pieces, which makes the design of the ECAP-process challenging. For the investigation, the Fe-Al work pieces were heated to the respective hot forming temperature in a chamber furnace and then formed in the ECAP tool at a constant punch speed of 5 mm/s. Besides the chemical composition (Fe9Al, Fe28Al and Fe38Al (at.%—Al)), the influences of a subsequent heat treatment and the holding time on the microstructure development were investigated. For this purpose, the average grain size of the microstructure was measured using the AGI (Average Grain Intercept) method and correlated with the aforementioned parameters. The results show that no significant grain refinement could be achieved with the parameters used, which is largely due to the high forming temperature significantly promoting grain growth. The holding times in the examined area do not have any influence on the grain refinement.