Zulkarnain Jalil

The use of Silica from beach sand as catalyst in Magnesium based hydrides for Hydrogen storage materials

Magnesium (Mg) as one of the potential candidate material for absorbing hydrogen, because theoretically has the ability to absorb large quantities of hydrogen 7,6 wt%. However, the kinetic reaction of Mg is very slow. Its takes 60 minutes to adsorp hydrogen with the operating temperature (adsorb/desorb) high of 350°C. Therefore, in this study discusses the hydrogen storage materials based on MgH2-SiO2. The purpose of this study to improve desorption temperature of hydrogen storage system based on MgH2. The main material is MgH2 combined with inserting SiO2 catalyst was successfully extracted from quartz sand with coprecipitation method. As for the material preparation process is done with the technique of mechanical alloying. Milling MgH2+SiO2 samples using a ball milling for 5 hours, with the ratio of ball to powder 10:1 and a speed of 400 rpm. By variation of the catalyst insertion of 1 wt%, 3 wt%, and 5 wt% of SiO2. The results of XRD measurement known that the sample was reduced to scale nanocrystal. Phase arising from the result of XRD observation are MgH2 phase as the main phase, and SiO2 phase as a minor phase. DSC testing results show that the lowest desorption temperature obtained on the sample with the addition of inserts weight of the catalyst 5 wt% SiO2 has milling for 5 hours which is equal 307,11°C.

MgH2-SiC based hydrogen storage material prepared by reactive mechanical alloying method

Hydrogen storage in metal hydrides, compared to conventional methods, is regarded as one of the best solutions due to the higher volumetric storage capacity and safety. Magnesium and magnesium-based alloys are promising candidates for hydrogen storage. The hydrogen storage capacity of magnesium in the form of MgH2 amounts to 7.6 wt%. Unfortunately, Mg has a high thermodynamic stability and therefore, relatively slow desorption kinetics, which are the major drawbacks for the application as a hydrogen storage material. Various techniques are developed to improve the sorption characteristics by accelerating the aforesaid processes. In this work we success to synthesis and investigate the catalytic effect of SiC and Ni (in nanostructure scale) on MgH2 using reactive mechanical alloying method in 10 bar H2. At first step, using SiC catalyst the sorption properties can be improved. The most promising step by using double catalysts of SiC and Ni (MgH2-5wt%SiC-5wt%Ni) which absorp 5.7 wt% hydrogen and at the same time decrease the desorption temperature to 250°C. Compared to T onset of pure MgH2 -which desorp at 380° C. To the best of our knowledge, this is the best result so far for MgH2-SiC system.

The role of nano-Ni catalyst in MgH2 obtained by reactive mechanical milling method for solid hydrogen storage application

Magnesium (Mg) is regarded as one of the candidate material for absorbing hydrogen, because theoretically, has the ability to absorb hydrogen in the large quantities (7.6 wt%). However, Mg has shortage, namely its kinetic reaction is very slow, it takes time to absorb hydrogen at least 60 minutes with very high operating temperatures (300-400°C). The aim of this study is to improve the hydrogen desorption temperature of Mg-based hydrogen storage material. In this work, we used nano-nickel (Ni) as catalyst in MgH2 and obtained by reactive mechanical milling method. The duration of milling was done in 2 hours (soft milling) with the 2 mol% Ni catalyst and milled under hydrogen atmosphere (10 bar). As the results, small amount of 2 mol% Ni in nanometer scale acts as a suitable catalyst for improvement the kinetics of MgH2 which could absorp 5.5 wt% of hydrogen within 10 minutes at 300°C. It is obvious that small amount has much better as catalyst in nanoparticle size and at the same time allowed to reduce th...

Magnetic behavior of natural magnetite (Fe3O4) extracted from beach sand obtained by mechanical alloying method

Investigation on the iron sand characteristic of Syiah Kuala beach in Banda Aceh coastal region has been performed. Samples were prepared by mechanical alloying method using a planetary type high energy ball milling. As shown by XRF results, the results indicate that the iron sand is dominated by magnetite up to 85.80 %. The XRD test showed that the Fe3O4 (magnetite) appears as the majority phase. Furthermore, the magnetic properties observation found that the magnetization saturation (Ms) and remanent (Br) are decreasing with the increasing of the coercivity (Hc). These results inform us that the mechanical alloying method is a very attractive technique to reduce the beach sand particle into nanometer scale.Investigation on the iron sand characteristic of Syiah Kuala beach in Banda Aceh coastal region has been performed. Samples were prepared by mechanical alloying method using a planetary type high energy ball milling. As shown by XRF results, the results indicate that the iron sand is dominated by magnetite up to 85.80 %. The XRD test showed that the Fe3O4 (magnetite) appears as the majority phase. Furthermore, the magnetic properties observation found that the magnetization saturation (Ms) and remanent (Br) are decreasing with the increasing of the coercivity (Hc). These results inform us that the mechanical alloying method is a very attractive technique to reduce the beach sand particle into nanometer scale.

The effect of thickness on microwave absorbing properties of barium ferrite powder

We have investigated the effect of thickness on microwave absorbing properties of barium ferrite (BaFe12O19) powder prepared by a solid-state reaction method with a sintering temperature of 1100°C for 5 hours. The sample was analyzed using XRD, SEM, PERMAGRAPH, and vector network analyzer (VNA). The microwave absorbing properties were measured at the frequency in the range of 8.2 – 12.4 GHz. Permeability, permittivity and reflection loss (RL) were calculated at a given thickness based on transmit line theory. The results show the optimal RL of −23.07 dB can be obtained at 10.72 GHz with a thickness of 3.0 mm, bandwidth with RL less than −5 dB and −10 dB can reach 1.2 GHz (10.4−11.6 GHz) and 0.8 GHz (10.6−11.4 GHz), respectively.

Pengamatan In-Situ Tekanan dan Temperatur pada Pembentukan MgH2/Ni melalui Metode Reactive Mechanical Alloying (RMA) untuk Aplikasi Material Penyimpan Hidrogen

The observation on reactive mechanical alloying (RMA) process had been done to form MgH2 material with adding Ni nanoparticles as catalist for hydrogen storage material applications. Pressure and temperature of material forming were recorded by microcontroller set for 30 minutes. Mg with adding Ni 5 wt % was milled by High Energy Ball Mill (HEBM) at H2 atmosphere in 1 atm of pressure. The measurement results showed that the pressure had been changed and temperature also changes up to 38oC. This process proves that the alloying betwen Mg and H2 had been formed. The X-ray diffraction pattern identify MgH2 phase. SEM image showed the morphology of MgH2 particles.

Dampak Penggantian Fe3O4 secara Parsial dengan Abu Sekam Padi (ASP) terhadap Porositas dan Kuat Tekan Keramik Komposit Clay-Fe3O4

Berdasarkan kajian pendahuluan diketahui bahwa penggunaan pasir laut dan penggantiannya dengan abu sekam padi (ASP) hingga pada fraksi berat tertentu dalam pembentukan keramik komposit clay belum mampu menunjukkan kuat tekan seperti yang diinginkan. Ditambah lagi karena kandungan Cl-dan SO4- yang bersifat korosif, penggunaan pasir laut tersebut tidak lagi direkomendasikan. Mineral utama dari pasir besi yaitu Fe3O4selanjutnya diajukan sebagai penggantinya untuk memproduksi keramik komposit clay baru. Karena pasir besi merupakan sumber daya alam yang tidak dapat diperbaharui, maka penggunaan mineral Fe3O4 tersebut perlu dibatasi. Selanjutnya, ASP masih dipilih untuk menggantikan Fe3O4secara parsial demi keberlanjutan produksi dari material-material keramik tersebut. Keramik dari komposit clay-Fe3O4/ASP tersebut selanjutnya diperkenalkan dalam makalah ini dan nantinya dirancang sebagai material bagi komponen-komponen yang menerima pembebanan berupa tekan dan juga termal. Dua tipe ASPlalu disiapkan dan selanjutnya dikarakterisasimenggunakan spektrometer X-ray fluorescence (XRF). Tidak terdapat perbedaan yang signifikan pada komposisi kimia dari keduanya. Namun, keduanya memiliki bulk density yang berbeda. Hasil pengujian porositas terhadap material keramik komposit tersebut menunjukkan bahwa penggantian Fe3O4dengan ASP meningkatkan porositas material. Hasilpengujian tekan menunjukkan bahwa meningkatnya berat fraksi dari ASP diikuti oleh penurunan kuat tekan material. Analisis X-ray diffraction (XRD) terhadap material baru tersebut menunjukkan bahwa sebagian besar dari Fe3O4 telah bertransformasi menjadi Fe2O3 dan transformasi tersebut selanjutnya dapat menentukan besarnya porositas dan juga kuat tekan dari material tersebut.

Magnetic Behavior of Natural Fe2O3 from Lhoong Iron Ore Mining Area, Aceh Province, Indonesia

The mineral composition and magnetic behavior of nano-Fe2O3 of iron ore from Lhoong mining area, Aceh province, were studied. The iron ore was prepared by mechanical milling method. The mineral and chemical compositions of samples were investigated by XRD and XRF analysis tests. The XRF test showed that the Lhoong iron ore contains Fe2O3 (93.88%) in association with other isomorphous impurities, such as SiO2, MnO, and Al2O3, in varying proportions. Compared to XRD results, it was consistent with XRF; the phase compositions of iron ore were mainly hematite (Fe2O3). The XRD revealed that hematite was the major mineral component in the Lhoong iron ores. SEM observation showed fine crystalline structure of Lhoong iron ore after the milling process. The main mineral morphology was microcrystalline in agglomerate forms. The magnetic properties of the samples after milling showed the increasing in the remanent (Br) and coercivity (Hc). This increasing can be explained that nano-Fe2O3 phase after milling for 20 hours plays an important role in the magnetic behavior of Lhoong iron ore. It is understood that the longer milling time is sufficient to complete the transformation of hematite (Fe2O3) to magnetite (Fe3O4).