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"In general, the Nd-Fe-B as-cast ingot is homogenized for a long time before the hydrogenation, disproportionation, desorption and recombination (HDDR) process, to produce good magnetic properties. Since the homogenizing process is expensive, this work examined the possibility of replacing it with a water quenching process for Nd-Fe-B magnetic powder. The magnetic powders were soaked at 1100oC for 4 hours, followed by water quenching prior to HDDR. The resulting powder had magnetic properties that were almost similar to magnetic powder that was homogenized prior to HDDR. The remanence values of the water-quenched alloy and the homogenized alloy were 7.8 KG and 8.9 KG, respectively, while the coercivity values were 12.6 KOe and 10.3 KOe, respectively. In general, the magnetic properties of both samples were not much different. The microstructure of Nd2Fe14B phase combined with a very slight Nd rich phase in micro grain boundary likely caused the coercivity enhancement."

"Barium hexaferrite telah lama dikenal sebagai magnet permanent dan dikenal pula sebagai bahan yang memiliki struktur keramik dengan komponen utamanya adalah oksida. Oleh karena senyawa oksida memiliki resistivitas yang besar sedangkan Barium hgexaferrite sendiri ?memiliki tingkat kemagnetan yang besar maka bahan ini cukup-potensial untuk dikembagkan sebagai penyerap gelombang elektromagnetik. Dalam Studi ini atom Fe secara parsial disubstitusi oleh Mn dan Ti untuk membentuk fase (Fe, MnTi)2O;, Kemudian Fe|,15(TiMn)o,;5 03 ini dipadukan dengan BaCO3 dan SrCO3 dalam high energy vibration ball mill dan disinter untuk mendapatkan fase(Ba, Sr}0. 6 (Pe, MnTi)203. Ditemukan bahwa fase (Fe, MnTi)2O3 akan diperoleh setelah disinter pada temperature I300°C dan demikian pula halnya dengan fase (Ba, Sr)O. 6 (Fe.MnTi);O3 Hasil pemeriksaan sifat magnet menunjukkan penurunan nilai Ms 2 dari 0.267 emu/g (Bang, Sr0_g,) Fe|2O19 s/d 0.22 emu/g (Bam Sr0_7) Fe12O19,penurunan Hc : dari 15.1 Oc (Bam Sr0;,) Fe|;O|9 s/d 10.5 Oe (Ba0_3 Sm?) Fe|2O19 dan penurunan Mr : dari 0.267 emu/g '(Ba0_1 Sr0_3) F?|2019 s/d 0.22 emu/g (Bam Sr0_-1) Fe,;0;9. Terlihat dengan bertambahnya komposisi Barium (juga artinya penurunan kandungan Sr) malga nilai,_coercivitas membesar, tingkat saturasi kemagnetan membesar dan nilai remanfence juga memvbesar. Hal ini disebabkan sifat dasar Barium lebih bersitat hard magnet. Sehinggadapat disimpulkan bahwa Srontium (Sr) mengubah Ba-hcxaferrite dari hard magnet ke soft magnet.

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Barium Hexaferrtite is well known as a permanent magnet material. It is a ceramic based which has oxides as its main component . Because oxides have a large resistivity and Barium Hexaferrite has a large magnetization, so this material is potentials for high frequency electromagnetic wave absorbers. In this study, Fe in Fe2O`3 was ,partially co-substituted by Manganese and Titanium to form Fe1-,5(TiMn)0.25 O3.Together with other alloys component, the Fe|.75(TiMn)0.25 03.was on milled with Ba C03and SrCO3 under high energy vibration ball mill apparatus. All component are mechanically milled and subsequently sintered to fomi the absorber material, (Ba, Sr)O. 6 (Fe, Mn'l`i)2O3. lt was found that the fiaction of (Fe, MnTi)2O3 wass obtained after sintering at 1300°C for 4 hours. The same condition also applied-for (Ba, Sr)O.6 (Fe.MnTi)2O3. 'l`he investigation on magnetic properties showed a decrease of Ms value from 267 emu/g(Ba0_1 Srog) Fe, 2()|9 s/d 0.22 emu/g (Bang Sr¢1) Fc|2O;9, an increase of Hc value fiom 15.1 Oc (Bam Sras) Fe12O|9 s/d l0.5` Oe (Bam Sr0,)' Fe12O,9 and a decrease of Mr value 0.267 emu/g (Bam Sr0.3) Fe|2O19 s/d 0.22 emu/gf (Bam Sr0.7) Fe;2O;9 This indicates that the substitution of Ba replaced Sr by has changed some basic properties of BaFe=> (MnTi)1.5O|9 from hard magnet to soft magnet"

"In this research, analysis of the magnetic properties of the nanoscale ferromagnetic material barium strontium hexaferrite with the composition of Ba(0.7)Sr(0.3)O6(Fe2O3) or written as B7S3HF is conducted. The material was prepared by the ball mill method, followed by reducing the particle sizes of the material to reach a result in nanometers with a high pressure ultrasonic for 12 hours. In the compacting process, a parameter was given from the outside of the 50 mT magnetic field to determine the cause of the anisotropy phenomenon of the material. To identify the phase of material, changes in the magnetic properties and measurement of the Particle Size of the B7S3HF material were taken. The equipment used was X-Ray Diffraction (XRD), Permagraph (an automatic computer-contolled measuring system) and Particle Size Analyzer (PSA). The results of XRD were seen in their influence against the Buffered Hydrofluoric (BHF) acid, which were caused by the effects of the Strontium (Sr) substitution and by increasing the size of the material volume. Changes in the magnetic properties of the B7S3HF material, due to an induced magnetic field from the outside, were caused in contrast with the remanent value ranging from 0.18 T up to 0.249 T, respectively. This process did not occur, since the coersivity value was fixed at 275.54 kAm-1. Changes in the value of the remanent material rose by 0.069 T or (6.9%). This phenomenon shows the anisotropy influence in the B7S3HF material in an external magnetic induction of 50 mT. The results of the ultrasonic measurements were performed using Particle Size Analyzer (PSA) equipment, which gained a 43.5 nm particle size."

"Barium Heksaferit telah diketahui memiliki nilai saturasi (Ms) yang tinggi, temperature Curie (Tc) yang tinggi, serta resistivitas yang besar yang membuat material tersebut dipandang sangat baik dalam pengaplikasian material RAM (Radar Absorbing Material). Investigasi terbaru telah ditemukan pada SrFe11.9In0.1O19 yang disubtitusi Indium memiliki nilai remanence to saturation ratio yang lebih besar dari 0.5. Namun, nilai koersivitas masih relatif lebih tinggi seiring dengan meningkatnya nilai remanen magnet. Oleh karena itu, penelitian ini bertujuan untuk memperoleh material penyerap gelombang elektromagnetik yang optimum dengan memodifikasi Barium Heksaferit yang disubtitusi In, Mn, dan Ti terhadap BaFe11,9In0,1Mnx/2Tix/2O19. Semua sampel dievaluasi dengan permagraph. Loop hysteresis sampel yang diperoleh dari evaluasi permagraph menunjukkan terjadi penurunan nilai koersivitas seiring dengan peningkatan fraksi ion Mn-Ti. Rata-rata rasio remanen terhadap saturasi mendekati 0,5 dengan magnetisasi saturasi tertinggi sebesar 0,32 T diperoleh dari sampel dengan komposisi x = 0. Hasil XRD menunjukkan bahwa semua sampel yang disintesis adalah material satu fasa. Kapasitas penyerapan terbesar hingga 98,48% dicapai dari sampel dengan komposisi x = 3,0. Sampel tersebut memiliki nilai koersivitas terendah yaitu sebesar 18,40 kA/m.

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Barium Hexaferrite has been known to have a high magnetization saturation value (Ms), a high Curie temperature (Tc), and a large resistivity that makes the material considered as the application of RAM (Radar Absorbing Material). Recent investigations have been carried out that SrFe11.9In0.1O19 substituted with In ions has a remanence to saturation ratio greater than 0.5. However, the value of coercivity was found still relatively higher as the magnetic remanence value increased. Therefore, this study aims to obtain the optimum electromagnetic wave absorbing material by modifying Barium Hexaferrite with the substituted of In, Mn, and Ti for BaFe11,9In0,1Mnx/2Tix/2O19. All samples were evaluated by Permagraph. The Hysteresis Loop of the samples were obtained from the Permagraph evaluation showed a decrease in coercivity value along with the increase in the Mn-Ti ion fraction. The average remanence to saturation ratio is close to 0.5 with the highest saturation magnetization of 0,32 T obtained from samples with composition x = 0. XRD results show that all samples synthesized are single-phase materials. The largest absorption capacity of up to 98,48% was achieved from the sample with the composition x = 3,0. The sample has the lowest coercivity value of 18,40 kA/m."

"Material magnet NdFeB banyak diketahui sebagai magnet permanen yang memiliki sifat magnetik yang superior ditandai dengan tingginya nilai saturasi magnetik dari bahan magnet tersebut. Namun pada bahan NdFeB memiliki nilai koersivitas yang dapat dipengaruhi fasa dari bahan, sehingga material NdFeB berpotensi digunakan sebagai material penyerap gelombang radar jika nilai koersivitas nya sekecil mungkin. Pada penelitian ini dibuat material Nd15-xFe77+xB8 (X= 0, 2 dan 5) dengan perbedaan waktu milling pada material selama 1, 3, 5 jam dan pemberian perlakuan panas terkontrol agar terjadi oksidasi parsial. Pasca pemberian perlakuan panas terkontrol, diperoleh hasil bahwa material Nd15-xFe77+xB8 dengan nilai x = 0, 2 dan 5 memiliki fasa campuran antara fasa magnetik Nd2Fe14B dan -Fe. , pada bahan yang telah diberikan perlakuan panas mengalami dekomposisi ditandai pada hasil XRD terdapat banyak unsur besi. Fasa tersebut sangat berpengaruh pada daya absorbsi bahan, untuk bahan sebelum diberi perlakuan panas akan menyerap gelombang radar sangat baik dengan nilai reflection loss maksimum sebesar 25,10 dB yaitu 94,44% gelombang radar diserap oleh bahan sedangkan pada bahan yang telah mengalami perlakuan panas menyerap gelombang radar sebesar 12,60 dB atau 76,56% gelombang radar diserap oleh bahan. Selain pada fasa semakin lama waktu milling membuat daya serap menjadi semakin baik. Maka dapat disimpulkan bahwa material NdFeB memiliki potensi untuk menjadi material penyerap gelombang radar.

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NdFeB magnetic material is widely known as a permanent magnet which has superior magnetic properties characterized by the high magnetic saturation value. However, NdFeB material has a coercivity value that can be influenced by phase of the material, so that NdFeB material has the potential to be used as a radar wave absorbing material if the coercivity value is as small as possible. In this study, the material Nd15-xFe77+xB8 (X= 0, 2 and 5) was made with a difference in milling time of 1, 3, 5 hours and controlled heat treatment to allow partial oxidation to occur. After giving controlled heat treatment, it was found that the material Nd15-xFe77+xB8 with values of x = 0, 2 and 5 had a mixed phase between the magnetic phase of Nd2Fe14B and α-Fe. , the material that has been given heat treatment experience decomposition marked on the XRD results there are lots of iron elements. This phase greatly affects the absorption of the material, for the material before being heat treated it will absorb radar waves very well with a maximum reflection loss value of 25.10 dB, which is 94.44% of the radar waves are absorbed by the material, while the material that has undergone heat treatment absorbs 12.60 dB or 76.56% of radar waves are absorbed by the material. In addition to the phase, the longer the milling time makes the absorption better. So it can be concluded that the NdFeB material has the potential to become a radar wave absorbing material."