Metal Core Recession and Head Stain Studies of MIG Heads Sliding against Cobalt-Doped Gamma Iron Oxide and Metal Particle Tapes

Metal-in-gap (MIG) heads are commonly used for high-density magnetic recording. Metal core recession and head stains increase the gap between the tape and the head, resulting in signal loss. In this study, accelerated sliding wear tests of Co-γFe₂O₃, and metal particle (MP) tapes against MIC heads made of three different amorphous and, nanocrystalline metals were conducted under various operating conditions. Metal core recess and propensity for head staining were measured. The degree of tape contact with a recessed core was also measured by pressing the tape against a glass slide with Cr grids and using an optical interference technique. The authors found that the core recess was about the same for all three core metals. Core recess by MP tape was larger than that, by oxide tape. The tape speed appeared to have little effect on the recess value. The authors also found that significant recess may occur during initial contouring of the head surface; however, after sliding for about 250 km, core recess reaches a steady-stale value which may be either higher or lower than the initial values. The mechanism of core recession was studied. The authors believe that core recession occurs as a consequence of the debris trapped, between the tape and the core, in addition to that caused by some tape contact. Formation of head stains was observed in all combinations. The stains fanned on the metal cores were heaviest for CoNbZr metal, followed by CoTaZr and FeTaC. Co-γFe₂O₃ tape produced a more severe stain than the MP tape. The apparent roughening of head rubbing surface observed for CoNbZr heads sliding against Co-γFe₂O₃, tape was due to the formation of stains.     

Failure Mechanisms of Advanced Metal Evaporated Tape in an Advanced Linear Tape Drive

Demand for increased data storage has resulted in the development of various types of magnetic tape. To achieve higher recording density, tape manufacturers are developing thin-film tapes, such as advanced metal evaporated (AME) tape, for use in linear tape drives. The structure of AME tape is fundamentally different from metal particulate (MP) tape. The goal of this study was to determine the methods and mechanisms associated with failure of AME tapes as well as to investigate the effect of tape cupping and initial edge quality on tape durability in an advanced linear tape drive. It is shown that AME tape exhibits a slightly lower coefficient of friction than the MP. The negatively cupped AME tape demonstrated a greater value of lateral tape motion peak-to-peak amplitude than both of the positively cupped AME samples as well as the MP tape sample. It was found that poor initial tape edge condition plays a large role in debris generation. For these reasons, positively cupped AME tapes with good initial relative edge contour are recommended for use in linear tape drives. The dominant mechanism of failure for the AME samples is adhesive wear resulting in removal of the DLC overcoats and sublayers.

     

Head/Tape Spacing Measurements for Digital Linear Tape Drives Using Three-Color Interferometry

The spacing of the head/tape interface in a digital linear tape (DLT) drive was measured using replica glass heads and three-color interferometry. A modified load-unload method was used to calibrate the light intensity. Class heads with different island widths and zero and nine degree skew angle were used to investigate the effect of head contour on the head/tape spacing. In addition, thin and thick metal particle tapes were evaluated to study the effect of tape compliance, tape speed and tape tension. “Tape tenting” was observed for heads with a narrow center island.     

Tribology of videotapes

Increased recording density in magnetic recording has been achieved by introducing newly developed magnetic tapes, such as metal particulate tapes and metal-evaporated tapes. As a loss in magnetic recording increases with spacing between a magnetic tape and a magnetic head, these are obliged to contact each other. A tape also rubs tape-transportation elements in videotape recorders (VTRs), such as the stationary drum and guide posts. Thus it is not too much to say that the development of new magnetic tapes for practical application depends on tribological research.

In this paper, tribological analyses for the improvements of durability and runnability of metal particulate tapes and metal-evaporated videotapes are reviewed.     

Effects of Different Magnetic Tapes and Operating Parameters on Lateral Tape Motion in a Linear Tape Drive

The need for increased storage capacity in today's data storage technology has created a continuing need to study the tribological performance of magnetic tape. Lateral tape motion (LTM) is one important area of ongoing tribological research. The objective of the study presented in this article is to determine the effects different magnetic tapes and operating parameters have on LTM. Specifically, the research focuses on LTM in five different tape samples and the effects the varying operating parameters have on LTM. The tapes studied include metal particulate (MP), thin MP, and three advanced metal evaporated (AME) tapes, as well as MP tapes with different edge quality and tapes from staggered packs. The operating parameters studied include tension, speed, and head and bearing setup. Experimental methods used to collect and analyze the LTM data are discussed and the findings are presented.     

Wear Behavior of Thin Film Heads for VCR in Sliding with Metal Evaporated Tapes

In order to apply thin film heads to digital video cassette recorders, wear behavior, machinability of head materials, and level difference of the heads were evaluated. The tests, performed with metal evaporated tapes, were divided into two stages. First, wear rate and machinability of individual materials were evaluated. It was found that adhesive wear was dominant for every material. Wear damage was especially-severe for metal magnetic films. Machinability was satisfactory for most bulk materials except for those with a hardness of more than 1000 kgf/mm², ZrO₂ ceramics and devitalized glass. Secondly, wear damage and level difference were evaluated using model heads. After the test, a number of flows were formed on sliding surfaces, mainly on the film surfaces, indicating that abrasive wear occurred. With bulk material of larger wear rate, the level difference reached the final value faster and its deviation was smaller. With Co-Zr-Nb magnetic metal and an Al₂O₃ protective layer, the level difference was less than 20 nm using CaTiO₃ or ZrO₂-Ta₂O₅, bulk substrates.     

Effect of temperature,humidity and crystal directions on wear of rotary heads

In the advanced tape drive systems which achieve a higher recording density, the wear of rotary heads should be decreased to obtain a higher reproduced output signal by decreasing the ‘Gap depth’ of heads, keeping enough life time. By using the heads made by two kinds of crystal directions of Mn–Zn ferrite and metal evaporated tapes with DLC coating, temperature and humidity dependences of head wear are investigated. The wear rates of both crystal direction heads increase with the decrease in temperature. The wear rate of a (110) head increases very quickly at low temperature, compared with a (100) head. These temperature dependences of head wear are caused by the temperature dependence of the elastic modulus of the tape and the temperature dependence of the friction coefficient between the tape and the head.     

Investigations of nano- and macro-wear of magnetic tape head materials

The nano- and macro-wear characteristics of calcium titanate, single crystal ferrite and polycrystalline ferrite were investigated using nano-scratch testing and wear bar testing. Nano- and micro-indentations were made to determine nano- and micro-hardness, and nano-scratch testing was used to evaluate relative wear rates on the nano-scale. The macro-wear characteristics of the various head materials against metal particle tapes was investigated as a function of tape speed using wear bars mounted in a DLT tape drive. The micro-indentation method was used to investigate wear of the head/tape interface in a linear tape drive. The results from nano- and macro-wear tests were analysed and correlated with the microstructure of the materials.     

两种高聚物薄带的沙尘磨损特性研究

首次开展了ATM(Auto TellerMachine)高聚物部件在沙尘环境中的磨损研究。在实验室模拟降尘环境中使用ATM中的Tape-scraper摩擦系统,对PI(聚酰亚胺)和PEN(聚萘二甲酸乙二酯)两种高聚物薄带的磨损行为进行了研究,并利用扫描电镜对薄带的磨损表面进行了分析。实验采用了采集自沙漠的自然沙尘。实验结果表明:PI薄带比PEN薄带表现出更优良的耐沙尘磨损性能。PEN薄带的微观磨损机理主要是纤维组织的塑性流动和拉断,而PI薄带的微观磨损机理为裂纹的萌生、扩张和块状剥落。用材料的机械变形因子可以很好地解释两种聚合物薄带的磨损特性差异。     

The measurement of in-situ wear of video heads

A method of measuring in-situ wear of video heads which determines the variation in wear along the surface of the video head is described. Knoop diamond indentations are positioned along the head, either side of the magnetic gap, enabling wear rate to be monitored at several positions. Virgin tape is run over the heads in the form of standard E180 cassettes and the wear occurring at each indentation position is derived from the reduction in length of the main diagonal. Wear rate is plotted against the position of the indentations. This describes the variation in wear along the head and therefore the conformation of the tape to the head. The technique has been used to study the wear of video heads with three types of tape sample: two iron-oxide-based formulations, with either Al₂O₃ or Cr₂O₃ added as head cleaning agents, and one chromium-dioxide-based tape. Little difference was found between the performances of the iron oxide tape samples. The chromium dioxide sample, however, produced wear some five to six times greater than the iron oxide tapes.     

Tribology of metal evaporated tapes—for improvement of recording density

Increased recording density in video tape recorders and tape drives for data storage has been achieved by the increase in areal recording density and the decrease in tape thickness. Areal recording density can be increased by introducing high performance tapes, like metal evaporated tapes, with superior magnetic characteristics and smooth magnetic surfaces to reduce the spacing loss. However smoother surfaces often produce a higher friction coefficient, which could result in tape damage by the scanning heads and unstable runnability of tapes in VTRs or tape drives. Also thinner tapes show lower mechanical stiffness in general, which could result in damage of the tape edges during tape transportation. Superior durability and runnability are thus required of high performance tape in addition to magnetic characteristics, in spite of the trend towards smoother surface and thinner tapes. Therefore the development of practical new magnetic tapes requires research into their tribology. It was found that the durability and runnability of metal evaporated tapes with smoother surfaces can be improved by DLC coating, and that the edge damage of thinner tapes can be eliminated by decreasing the static friction coefficient, but not the kinetic one. Though the durability and the runnability of metal evaporated tapes themselves have been improved from the tape design point of view, as mentioned above, further improvement may be expected by integrating tape design with that of the VTR/tribo-elements tape drive design and thus further increasing recording density in the future.     

Wear of tribe-elements of video tape recorders

The helical scan magnetic recording equipment, like the video tape recorders (VTR), consist of many tribe-elements. The wear of these tribe-elements is an essential problem affecting the reliability of the equipment. The rotating magnetic head in high-speed rubbing with the magnetic tape needs a self-cleaning effect by mild wear. A simple trial of reducing the head wear often brings partial recession, friction polymer and brown stain. The summary of the current study of head wear is given by dividing it into the head factors, the tape factors, the system factors and the atmosphere factors. The computational analysis of head contour change caused by wear is compared with the experimental results. The outline of the tribology of motor, capstan and tape path in the VTR is introduced.     

Flexible media — recent developments from the tribology point of view

With the increase in the recording density of hard disk systems, the demand on the increase in the data recording capacity of tape drive systems as back-up systems is increasing. One of the advantages of the tape drive systems is high volumetric recording density, which is obtained by high areal recording density and thin tapes. The areal recording density can be increased by introducing high performance tapes, such as metal evaporated tapes, with superior magnetic characteristics and smooth magnetic surface to reduce the spacing loss. However, a smoother surface often produces a higher friction coefficient, which could cause tape damage by rotary heads and unstable tape runnability in the tape drives. Adoption of MR heads to tape drive systems is also effective in increasing the areal recording density. However, the wear allowance of the MR heads (shield type) is much smaller than that of the inductive heads. Thinner tapes show lower mechanical stiffness in general, which could cause damage to tape edges easily during tape transportation. In the second or later generation of tape drive systems, a thinner tape is often introduced. These thinner tapes should also have the interchangeability of the original thickness tape. New materials for a base film, such as PEN (polyethylene naphthalate) or aramid in which the elastic moduli are larger than those of PET, are required for thinner tapes. It was found that these side effects by the increase in the volumetric recording density can be improved by tribology. The tribological improvements from the drive design side is very important, as well as from the tape design side.     

Investigation of tape edge wear of magnetic recording tapes

Tape edge wear is studied for polyethylene naphthalate-based magnetic tape as a function of tape speed, tape tension, and tape guide surface roughness. The results show that tape edge wear is on the order of 0.04 nm per cycle at a constant force of 45 mN and that edge wear increases with increasing tape speed, tape tension and tape guide surface roughness. In addition, tape edge wear of three coated tapes with polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polyaramid (PA) substrate is studied. It is found that edge wear of polyaramid based tape is similar to that of PET-based and PEN-based tapes.     

Role of zirconium diboride particles on microstructure and wear behaviour of AA7075 in situ aluminium matrix composites at elevated temperature

ABSTRACT

The present research work examines the impact of temperature on the dry sliding wear behaviour of AA7075 aluminium strengthened zirconium diboride (ZrB₂) particulate composite (0, 3, 6, 9 and 12?wt.%). The dry sliding wear behaviour of the AMCs was inspected utilizing a pin-on-disc machine at differing temperatures (40, 60, 120, 180 and 240°C). The wear resistance of AMCs improved with the increased substance of ZrB₂ particulates at all test temperatures. The worn surface of the AMC pins was described utilizing FESEM. It was found from the SEM micrographs of worn surface, that at different temperatures, adhesion and metal flow were the prime wear process of the AA7075 composites, while for in situ formed AMCs, metal stream and oxidation were the factors affecting the wear process. The worn surface of the AMCs showed that there was a modification in wear component from abrasive wear to metal flow.     

Analysis of the stains produced by metal particle tapes on helical scan heads in data recording applications

The increasing demand for high capacity data storage requires decreasing the head-to-tape gap and reducing the track width. A problem very often encountered is the development of adhesive debris on the heads at low humidity and high temperatures. The debris lead to an increase of space between the head and media, and thus a decrease in the playback signal. In this study on stains, samples of ferrite used in DDS (Digital Data Storage) heads in conjunction with MP (metal particulate) tapes have been subjected to a series of experiments including staining using a loop tester and high humidities, and their surface analysed using XPS (X-ray Photon Spectroscopy). The results confirm that stains form at low humidity. Chemical analysis shows that they contain iron particles and polymeric binder transferred from the MP tape. The chemical anchors in the binder used to grip the iron particles now react with the ferrite surface to create strong chemical bonds. At high humidity, a thin layer of iron oxyhydroxide forms on the surface of the ferrite. This soft material increases the wear rate and so reduces the amount of stain present on the heads.     

横纹槽管内插扭带复合强化传热的试验研究*

不同强化传热方式的复合会产生不同的传热效果,通过试验将不同扭率的扭带与同一规格横纹槽管复合强化传热的效果进行对比。试验以高黏度的导热油为工质,在500<Re<7 000、50<Pr<180的参数范围内,研究复合强化管的Nu数和阻力系数f随着Re数的变化情况,通过多元线性回归得到Nu数和f的关联式,并以强化传热性能评价指标(Performance evaluation criteria,PEC)值为标准评价其综合换热性能。结果表明：相同扭率下,复合强化管的阻力系数是光管内插扭带阻力系数的2~5倍,Nu数是光管内插连续扭带的1~4倍。随着Re数的增加,扭率Y对复合强化管的Nu数值影响越来越小。层流工况下,复合强化管的综合换热性能指标PEC值随Re数的增加而增加,且与扭率Y成负相关;过渡流工况下,复合强化管的PEC值都随Re数的增加而减小,扭率Y为5.21时的复合强化管综合换热效果最好。     

The tribology of flexible magnetic recording media—the influence of wear on signal performance

The tribology of magnetic recording systems is different to conventional tribology in many important aspects and an understanding of this branch of the science is still in its infancy. This paper presents a review of one specific aspect of the tribology of flexible tape storage systems, that is wear of heads and media and the effect on signal performance. Based on the work of this author's group and others and with reference to classical tribological principles, the various mechanisms of wear have been identified in particulate media, metal evaporated media and various recording head types and have been discussed in terms of the effect of signal degradation and error or drop out production. From this review, the wear mechanisms and surface and subsurface parameters which should have the most influence on the future development of media and systems are identified.     

A study of the durability of flexible magnetic media in a linear tape system

Travan™ linear tape drives (with the head removed) and custom-made tape cyclers were used for sample generation in a preliminary study of the durability of experimental particulate media. The first tester cycled short (1 m) closed loops of tape, whereas the second cycled cartridge loaded media for an identical number of passes (0, 100, 250, 500, 1000, 5000, 10 000). X-ray photoelectron spectroscopy was used to identify chemical changes to the media surface and in the case of the Travan tester, these changes were compared to dropout growth through the use of a dedicated Travan drive. The results show binder depletion and an increase in surface lubricant with increasing number of cycles, irrespective of the type of tester used. The tapes exhibited good durability since the surface changes did not have a detrimental effect on the dropout characteristics.     

水基流延法制备低温共烧陶瓷生带材料新工艺

为实现硼硅酸盐玻璃陶瓷基低温共烧陶瓷生带材料的低成本、安全无毒化生产,采用以水性乳胶作为粘结剂的水基流延工艺进行制备;采用数字旋转黏度计分别对分散剂、固相、粘结剂含量对浆料黏度的影响进行了研究,利用扫描电镜对烧结前后生带材料的微观形貌进行了分析.结果表明:利用硼硅酸盐玻璃+Al<,2>O<,3>粉体作为固相,苯丙乳液作为粘结剂,苯丙烯酸铵作为分散剂,甘油作为增塑剂,成功制备出了固含量高、稳定性好、干燥快的水基流延浆料;制备的生带材料表面光滑、强度高,容易在室温下叠层,经过850℃×30 min烧结,其致密度可以达到96.45%.